WO2001001505A1 - Positive electrode material for lithium secondary cell, positive electrode for lithium secondary cell and lithium secondary cell - Google Patents

Abstract

A positive electrode material for a lithium secondary cell containing a manganese oxide and/or a lithium manganese composite oxide as a positive electrode active material and exhibiting a decomposed amount of PF6 anion as measured by the following storage test of 10 νmol or less, the storage test having the procedure that: a) a cell element is assembled which uses a positive electrode having a collector and, crimped thereto, 24 mg of a positive electrode material, a counter electrode comprising Li, and a mixed solution from EC and DMC containing 1.0 mol/l of LiPF6 as an electrolyte, and the cell element is charged with a charge current density of 0.2 mA/cm2 until a high limit of 4.2 V and then destructed; the positive electrode is taken out and immersed b) under an argon gas atmosphere, c) in a dried PTFE container, d) into a mixed solution from EC and DEC containing 1.0 mol/l of LiPF¿6?, and is e) stored for a week at 80°C; and a decomposed amount of PF6 anion is determined through measuring the amounts of PF6 anion in the mixed solution before and after the storage.

Description

 Description Positive electrode material for lithium secondary battery, positive electrode for lithium secondary battery and lithium secondary battery

 The present invention relates to a positive electrode material for a lithium secondary battery, and more particularly to a positive electrode material for improving high temperature characteristics of a lithium secondary battery, and further relates to a positive electrode containing the positive electrode material, and the positive electrode as a constituent element. Battery. Background art

As a cathode active material for a lithium secondary battery is proposed L i M n ₂ 0 ₄ with a Subineru structure is a composite oxide of manganese and lithium, studies that have been conducted actively. It has the advantages of high voltage, high energy density, more reserves than cobalt and nickel, and low cost. In addition, the charge-discharge cycle life at room temperature, which has been a problem, has been improved to the practical stage. However, such a manganese-based lithium secondary battery has a problem that its high-temperature stability is inferior. Therefore, at present, it has not reached a practical level for demands used in a high-temperature environment.

In the past, various studies have been conducted on the improvement of high-temperature stability with the aim of improving cycle characteristics and storage characteristics under high-temperature environments, and reports have been made. For example, in Journal of Power Sources 74 (1998) 228-233, it is proposed that a part of M n is replaced by C o, and in Electrochemical Society Proceedings Volume 97-18.49, a part of M n is proposed. It is disclosed that substituting C with Co or substituting a part of oxygen with F has an effect of improving high-temperature cycle characteristics. In addition, Japanese Patent Application Laid-Open No. Hei 8-264314 discloses providing a coating made of metal fluoride on the surface of the active material, and Japanese Patent Application Laid-Open No. Hei 8-231304 discloses that the active material is The surface properties such as fluorination are modified to improve the storage characteristics at high temperatures. In addition, Japanese Patent Application Laid-Open No. 10-125307 reports that the surface of the positive electrode active material is coated with an organic substance containing an amino group. Further, as an improved example of the spinel-type lithium-manganese composite oxide, a layered lithium-cobalt composite oxide, a layered lithium-nickel composite oxide, and these other metal-substituted materials are converted into a spinel-type lithium-manganese composite oxide. Examples of mixing are known. For example, a spinel-type lithium manganese composite oxide and a layered lithium cobalt composite oxide are mixed to improve cycle characteristics (Japanese Patent No. 27151624), and lithium nickel cobalt aluminum is used. There is known an example in which a composite oxide and a lithium manganese composite oxide are mixed to provide an inexpensive and highly safe battery (Japanese Patent Application Laid-Open No. H11-154120).

 However, a major problem with batteries using manganese-based composite oxides is poor cycle and storage characteristics under high-temperature environments, and it has not been sufficiently discussed whether this improvement can be achieved. There was no discussion on what manganese-based composite oxide and what combination of compounds should be used to improve the cycle characteristics and storage characteristics under high temperature environments.

 With the above-mentioned conventional technology, the cycle characteristics and storage characteristics under a high-temperature environment are still insufficient, and further improvement in high-temperature stability and cycle characteristics under a high-temperature environment has been strongly desired.

 An object of the present invention is to provide a manganese-based compound which is excellent in high-temperature characteristics such as high-temperature stability and high-temperature cycle characteristics and can be used for a lithium ion secondary battery. Disclosure of the invention

The present inventors have result of intensive studies, the positive electrode containing the conventional lithium-manganese composite oxide is more under a high temperature environment, promoting the degradation of L i PF ₆ salt in the electrolytic solution, P 0 ₂ F It was found that _two anions were generated. It was also found that this decomposition reaction depends on the state of the positive electrode and progresses remarkably in the charged end state. Further, lithium secondary batteries decomposition reaction using the positive electrode as a cause significantly in the L i PF ₆ was particularly found that significant performance degradation at high temperatures. Further, the decomposition reaction of L i PF ₆ not only use and composition of the positive electrode of the additive has also been found to be determined by the particle diameter and the like various factors of the positive electrode. Ri above, the present inventors as an index the resulting ease of decomposition reaction of L i PF _6, using a hard positive electrode occurs decomposition of L i PF ₆ It has been found that a lithium secondary battery having excellent high-temperature characteristics can be obtained by doing so, and the present invention has been completed.

 That is, the first gist of the present invention resides in the following (1) to (20).

(1) In a positive electrode material for a lithium secondary battery containing a manganese oxide and / or a lithium manganese composite oxide as a positive electrode active material, a battery element is prepared using the positive electrode material, and the positive electrode material charged with this is used. A positive electrode material for a lithium secondary battery, wherein the amount of PF ₆ anion decomposed measured by the following storage test (I) is 1 xl 0〃mo 1 or less.

Storage test (I)

a 1) A positive electrode formed by molding 24 mg of the positive electrode material into a circular shape with a diameter of 12 mm, and crimping it to a current collector (circular aluminum expanded metal with a diameter of 16 mm). i metal, 1 O mo l / L mixture of Echire Nkabone bets and Jechiruka one Poneto containing L i PF ₆ (volume ratio 3: 7) as the electrolytic solution. assembled battery element was used to charge this After charging to an upper limit voltage of 4.2 V at a current density of 0.2 mA / cm ² , the battery element is then disassembled, and the charged positive electrode is taken out.

b 1) In an argon gas atmosphere with a dew point of —5 ° C or less

c 1) 8 0 ° 3 hours Porite trough Ruo ii ethylene vessel dried at C, d 1) 1. containing O mo l / L of L i PF _6, ethylene force one Poneto 1. 5 ml and Jechiruka Liquid mixture with 3.5 ml of monocarbonate (acid content: 2.0 mmol / L or less, P ₂ F ₂ anion: 0.5 mmol / L or less, and ethanol: 0.01 mg or less) Dipped in

e 1) One week at 80 ° C

Save, PF ₆ The amount of Anion it it measurement (measurement temperature: 2 0 ° C) in the mixture before and after the storage, and obtains the PF ₆ § two on amount of degradation from the difference.

(2) The amount of P 0 ₂ F ₂ ion contained in the solution after storage obtained according to the storage test (I) is less than 110 1111 0 1 at 20 ° (1 ) Cathode materials for lithium secondary batteries.

(3) The cathode according to (1) or (2), wherein the cathode material contains a binder resin. Positive electrode material for aluminum secondary batteries.

(4) The positive electrode material for a lithium secondary battery according to any one of (1) to (3), wherein a PF ₆ anion decomposition inhibitor is dispersed and mixed in the positive electrode material.

(5) In the manganese oxide and / or positive electrode material for lithium secondary batteries containing a lithium-manganese composite oxide having a positive electrode active material and PF ₆ § two on decomposition inhibitor, as the PF ₆ Anion decomposition inhibitor, following A positive electrode material for a lithium secondary battery, characterized in that a material having a decomposition amount of PF 67 2one measured by a storage test (II) of ₆ × 10 jo 1 or less is used.

Storage test (II)

a 2) Li _{1 + x} Mn _{2 x} 〇 ₄ (here, 0 ^ χ ≤ 0.05) A lithium-manganese composite oxide with a spinel structure of the composition extracted from lithium, equivalent to a fully charged state Lithium-manganese composite oxide (0.05 ≤ L 1/1 ^ 11 molar ratio ≤ 0.09)

b 2) In an argon gas atmosphere with a dew point of --75 ° C or less,

c 2) d2) In a polytetrafluoroethylene container dried for 3 hours at 80, d 2) mixed with 160 mg of the above-mentioned PF ₆ -dione decomposition inhibitor,

. e 2) 1 including O mol / L of L i PF _6, ethylene carbonate 2. 4 ml Jechiruka one Boneto 5. mixture of 6 ml (acid content:. 2 O mm ol / L or less, P_〇 ₂ F ₂ Anion: 0.5 mmol / L or less, and Ethanol: 0.0 lmg or less)

f 2) One week at 70 ° C

Save, measure the amount of PF ₆ anion in the mixture before and after storage (measurement temperature: 20 ° C), and determine the amount of PF ₆ anion decomposed.

(6) Storage test The amount of P 0 ₂ F ₂ ion contained in the solution after storage obtained according to (Π) is less than 5 10〃111 0 1 at 20 ° 〇 (5 The positive electrode material for a lithium secondary battery according to).

(7) Storage test When the storage of (II) is extended for another two weeks, the amount of ethanol contained in the solution after storage is lmg or less, and the amount of ethanol described in (5) or (6) Positive electrode material for aluminum secondary batteries.

(8) The positive electrode material for a lithium secondary battery according to any one of (5) to (7), wherein a PF ₆ anion decomposition inhibitor is dispersed and mixed.

(9) The positive electrode material for a lithium secondary battery according to any one of (4) to (8), wherein the PF ₆ anion decomposition inhibitor contains a lithium nickel composite oxide.

(1 0) PF ₆ Anion decomposition inhibitor, 1 group 5 and 1 at least selected from the group consisting of Group 6 containing one element compounds of the Periodic Table of the Elements, at least 2 class in the molecule Compounds having an amino group, compounds having at least a tertiary amino group in the molecule, compounds having at least one amide bond in the molecule, compounds having at least one nitrogen-containing heterocycle in the molecule Or the positive electrode material for a lithium secondary battery according to any one of (4) to (8), containing a compound having at least one hydroxyl group in a molecule.

(11) The addition amount of the PF ₆ anion decomposition inhibitor is in the range of 0.0001 to 80% with respect to the positive electrode active material, which is one of (4) to (10). The positive electrode material for a lithium secondary battery as described above.

(12) The positive electrode material for a lithium secondary battery according to (9), wherein the amount of the PF ₆ anion decomposition inhibitor added is in the range of 1 to 80 wt% with respect to the positive electrode active material.

(13) The positive electrode material for a lithium secondary battery according to (10), wherein the amount of the PF ₆ anion decomposition inhibitor is in the range of 0.001 to 1 Owt% based on the positive electrode active material.

 (14) The manganese oxide and / or lithium manganese composite oxide has a subinel-type structure, and a part of the manganese site is replaced with at least one element selected from typical elements. The positive electrode material for a lithium ion secondary battery according to any one of (1) to (13), which is an oxide.

 (15) The positive electrode material for a lithium ion secondary battery according to (14), wherein the typical element that replaces part of the manganese site is aluminum and / or lithium.

(16) The positive electrode material for a lithium ion secondary battery according to (14) or (15), wherein the substitution amount of the typical element is 0.05 mol or more in 2 mol of manganese. . (17) The positive electrode material contains a lithium manganese composite oxide having a spinel structure and a lithium nickel composite oxide having a layered structure, and a part of the manganese site of the lithium manganese composite oxide is composed of another element. (1) to (9), wherein the average voltage measured by the following measuring method (I) of the substituted element-substituted lithium manganese composite oxide is 4.059 V or more. 9) The positive electrode material for a lithium ion secondary battery according to any one of (11), (12), and (14) to (16).

<Measurement method of average voltage (I)>

(1) The composite oxide is weighed at 75% by weight, acetylene black at 20% by weight, and polytetrafluoroethylene (PTFE) powder at 5% by weight, and mixed to form a thin sheet. After adjusting the total weight to 12.5 mgZcm ² , this sample is further pressed against aluminum expanded metal to form a test electrode. The test electrode is dried for 1 hour at 120 ° C under reduced pressure.

(2) Under an argon atmosphere, a 25 / m porous polyethylene film was used as a separator, lithium metal foil was used as a counter electrode, and a nonaqueous electrolyte solution was used. : with 1 mol / Li Tsu solution obtained by dissolving lithium hexafluorophosphate (L i PF ₆₎ of torr to 7 mixed solvent, to prepare a coin-type battery of CR 2 0 3 2 type.

③ The obtained coin-type battery is subjected to a constant current charge / discharge cycle of 0.5 mA / cm ² (charge upper limit 4.35 V, discharge lower limit 3.2 V) in an environment of 25 ° C. The average voltage V e

 V e = (average charge voltage in the second cycle + average discharge voltage in the second cycle) / 2.

 The average charge voltage or average discharge voltage is calculated by measuring the voltage during charge or discharge at 2-second intervals, and dividing the value obtained by integrating the voltage over time by the time required for charge or discharge.

(18) The lithium-nickel composite oxide has an average voltage of 3.830 V or less when measured by the following measurement method (Π). (14) To lithium ion secondary battery according to any one of (17) to (17). Positive electrode material for secondary batteries.

 <Measurement method of average voltage (Π)>

① Lithium-nickel composite oxide 75% by weight, acetylene black 20% by weight-polytetrafluoroethylene powder 5% by weight and mix to form a thin sheet. After adjusting the total weight to 12.5 mg / cm ² , this sheet is further pressed against aluminum expanded metal to form a test electrode. The test electrode is dried for 1 hour at 120 ° C under reduced pressure.

② In an argon atmosphere, a porous polyethylene film of 25 2m was used as the separator, lithium metal foil was used as the counter electrode, and the volume ratio of ethylene carbonate and getyl carbonate was used as the non-aqueous electrolyte solution. 3: 7 six full Uz potash lithium phosphate mixtures 1 mol / Li tree torr solvent (L i PF ₆₎ using a solution obtained by dissolving as to produce a coin-type battery of CR 2 03 2 type .

③ The obtained coin battery was subjected to a constant current charge / discharge cycle with a current density of 0.2 mA / cm ² (charge upper limit 4.2 V, discharge lower limit 3.2 V) at 25 ° C. , The average voltage V e

 V e = (average charge voltage in the second cycle + average discharge voltage in the second cycle) / 2.

 The average charge voltage or average discharge voltage is the value obtained by measuring the voltage during charge or discharge at 2-second intervals and integrating the voltage over time by the time required for charge or discharge.

 (19) The method according to (14) to (18), wherein the weight ratio of the lithium nickel composite oxide to the total weight of the lithium manganese composite oxide and the lithium nickel composite oxide is 0.7 or less. The positive electrode material for a lithium ion secondary battery according to any one of the above.

(2 0) either storage test (I) or ([pi) 8 0% of PF 6 Anion degradation products in the solution after it is P_〇 ₂ F ₂ Anion (1) to (1-9) 1 The positive electrode material for lithium secondary batteries described in (1).

Further, the present inventors have proposed a lithium manganese composite oxide having a spinel structure in which a part of a manganese site has been replaced with a specific element, and a lithium manganese composite oxide having a layered structure. When used in combination with Kel composite oxide, battery characteristics including high-temperature characteristics are remarkably improved, and when lithium manganese composite oxide having spinel structure and lithium nickel composite oxide having layer structure are used together. However, they also found that the use of lithium manganese composite oxides with an average voltage relatively higher than usual significantly improved battery characteristics, including high-temperature characteristics.

 That is, the second gist of the present invention resides in the following (21) to (26).

 (21) A positive electrode material for a lithium ion secondary battery containing a lithium manganese composite oxide having a spinel structure and a lithium nickel composite oxide having a layered structure, wherein the manganese site of the lithium manganese composite oxide A positive electrode material for a lithium ion secondary battery, characterized in that a part of the material is replaced with at least one element selected from typical elements.

 (22) The positive electrode material for a lithium ion secondary battery according to (21), wherein the typical element that substitutes a part of the manganese site is aluminum and / or lithium.

 (23) The positive electrode material for a lithium ion secondary battery according to (21) or (22), wherein the substitution amount of the typical element is 0.05 mol or more in 2 mol of manganese. .

 (24) A positive electrode material for a lithium ion secondary battery, comprising a lithium manganese composite oxide having a spinel structure and a lithium nickel composite oxide having a layered structure, wherein the manganese site of the lithium manganese composite oxide Is partially replaced by another element, and the average voltage of the other element-substituted lithium manganese composite oxide measured by the following measurement method (I) is 4.059 V or more. A positive electrode material for lithium ion secondary batteries.

<Measurement method of average voltage (I)>

(1) The composite oxide is weighed at 75% by weight, acetylene black at 20% by weight, and polytetrafluoroethylene (PTFE) powder at a ratio of 5% by weight, and mixed to form a thin sheet. After adjusting the total weight to be 12.5 mg / cm ² , this sample is further pressed against aluminum expanded metal to form a test electrode. The test electrode is dried for 1 hour at 120 ° C under reduced pressure. (2) Under an argon atmosphere, a porous polyethylene film of 25 m is used as a separator, a lithium metal foil is used as a counter electrode, and a nonaqueous electrolyte solution is used, in which the volume ratio of ethylene carbonate and getyl carbonate is 3: using a solution prepared by dissolving 1 mol / Li tree torr six full Uz lithium phosphate (L i PF ₆₎ 7 mixed solvent, to prepare a coin-type battery of CR 2 03 2 type.

③ The obtained coin-type battery is subjected to a constant current charge / discharge cycle of 0.5 mA / cm ² (charge upper limit 4.35 V, discharge lower limit 3.2 V) in an environment of 25 ° C. The average voltage V e

 V e = (average charge voltage in the second cycle + average discharge voltage in the second cycle) / 2.

 The average charge voltage or average discharge voltage is calculated by measuring the voltage during charge or discharge at 2-second intervals, and dividing the value obtained by integrating the voltage over time by the time required for charge or discharge.

 (25) The lithium-nickel composite oxide is characterized by having an average voltage of 3.830 V or less when measured by the following measurement method (II). (21) The positive electrode material for a lithium ion secondary battery according to any one of claims 24 to 25.

<Measurement method of average voltage (II)>

(1) Mix 75% by weight of lithium nickel composite oxide, 20% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene powder, and form a thin sheet. After adjusting the total weight to 12.5 mgZcm ² , this sheet is further pressed against aluminum expanded metal to form a test electrode. The test electrode is dried for 1 hour at 120 ° C under reduced pressure.

(2) Under an argon atmosphere, a porous polyethylene film of 25〃m is used as a separator, a lithium metal foil is used as a counter electrode, and a volume ratio of ethylene carbonate and getyl carbonate is used as a non-aqueous electrolyte solution. : with 1 mol / Li Tsu solution obtained by dissolving lithium hexafluorophosphate (L i PF ₆₎ of torr to 7 mixed solvent, to prepare a coin-type battery of CR 2 03 2 type.

③ The obtained coin-type battery is subjected to a current density of 0.2 mA / cm ² constant current charge / discharge cycle (charge upper limit: 4.2 V, discharge lower limit: 3.2 V), and average voltage V e

 V e = (average charge voltage in the second cycle + average discharge voltage in the second cycle) / 2.

 The average charge voltage or average discharge voltage is the value obtained by measuring the voltage during charge or discharge at 2-second intervals and integrating the voltage over time by the time required for charge or discharge.

 (26) The weight ratio of the lithium nickel composite oxide to the total weight of the lithium manganese composite oxide and the lithium nickel composite oxide is 0.7 or less (21) to (25). The positive electrode material for a lithium ion secondary battery according to any one of the above.

 Further, as another gist of the present invention, the following (27) to (31) are given.

(27) A positive electrode for a lithium ion secondary battery, wherein an active material layer containing the positive electrode material for a lithium secondary battery according to any one of (1) to (26) is formed on a current collector. .

 (28) A lithium ion secondary battery comprising the positive electrode material for a lithium secondary battery according to any one of (1) to (26) in a positive electrode.

 (29) A lithium comprising: a positive electrode using the positive electrode material for a lithium secondary battery according to any one of (1) to (26); a negative electrode; and an electrolyte obtained by dissolving a lithium salt in a solvent. Rechargeable battery.

 (30) The lithium secondary battery according to (28) or (29), wherein the negative electrode contains a carbon material.

(3 1) lithium salt is L i PF ₆ (2 8) to (3 0) Izure or one for lithium secondary battery according the. BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, the present invention will be described in more detail.

Feature of the present invention is the use of the manganese compound such as to suppress the decomposition of L i PF ₆ in a high temperature environment as the positive electrode of a lithium secondary battery. That is, the present invention There are important points as the positive electrode material is to use a low reactivity to L i PF _6.

Specifically, as a first embodiment, as a positive electrode material for a lithium secondary battery containing a positive electrode active material composed of a manganese oxide or a lithium manganese composite oxide, PF ₆ measured by the storage test (I) described below is used. Use one with a decomposition amount of 1 × 10〃mo 1 or less. If the decomposition amount of this PF ₆ anion is larger than 1 × 10〃mo 1, the high-temperature characteristics such as high-temperature stability and high-temperature cycle characteristics are poor, which is not preferable. For conventional cathode materials, high temperature characteristics not preferred, such as high temperature stability and high-temperature cycle characteristics, degradation of normal above PF ₆ Anion is greater than 1 X 1 0〃Mo 1.

 Storage test (I)

a 1) A positive electrode made by molding 24 mg of the positive electrode material into a circular shape with a diameter of 12 mm, and crimping it to a current collector (expanded circular aluminum metal with a diameter of 16 mm), and Li as the counter electrode metal, 1. as the electrolyte O mo l / L Echire emissions carbonate and Jechiruka one Poneto a mixture containing L i PF ₆ (volume ratio 3: 7) assembled battery element using the charge current so After charging to a maximum voltage of 4.2 V at a density of 0.2 mA / cm ² , the battery element is then disassembled, and the charged positive electrode is taken out.

b 1) Under an argon gas atmosphere with a dew point of less than 75 ° C

c 1) 8 0 ° 3 hours Porite trough Ruo ii ethylene vessel dried at C, d 1) 1. including Omo l / L of L i PF _6, ethylene force one Poneto 1. 5 m l and Jechiruka one Poneto 3. mixed solution of 5 m 1 (acid content: 2. 0 mmo l / L hereinafter, P_〇 ₂ F ₂ 7 two oN: 0. 5mmo l / L or less, and Etano Ichiru: 0. 0 1 mg or less)

e 1) One week at 80 ° C

Store and measure the amount of PF ₆ anion in the mixture before and after storage (measurement temperature:

20 ° C), and determine the amount of PF ₆ dione decomposition from the difference.

In the present invention, the amount of PF ₆ anion decomposed means the amount of PF 6 anion decomposed. PF ₆ anion is decomposed into, for example, P 0 ₂ F ₂ —, P 0 ₃ F ² — It is considered something. In the present invention, the PF ₆ cation decomposition inhibitor means an agent that suppresses the decomposition of PF ₆ cation.

 In the above storage test (I), a circular aluminum expanded metal with a diameter of 16 mm is used as the current collector. The thickness of the current collector is usually 50 to 300 m, and a thickness of about 200 m may be used. In the above storage test (I), the compression of the positive electrode material to the current collector in al) was performed, for example, by stacking the current collector and 24 mg of the positive electrode material formed into a circular shape with a diameter of 12 mm on a tablet molding machine. Just set and press. The pressure for the crimping is usually 80 to 100 MPa, and the crimping may be performed at around 90 MPa.

In the storage test (I), c1) to e1) are performed under the conditions of b1). For el)), it is sufficient that the inside of the ethylene container of c1) in which the positive electrode of a1) is immersed is bl) in the ethylene container of the c1), and it does not affect the immersion of the positive electrode. The exterior of the polyethylene container does not need to be under the conditions of b1). In dl) of the storage test (I) containing L i PF ₆ of "1. Omo l / L, ethylene carbonate 1. 5 m 1 and Jechiruka one Boneto 3. mixed solution of 5 m l (acid content: 2. Ommo lZL or less, P 0 ₂ F ₂ anion: 0.5 mmo l / L or less, and ethanol: 0.0 l mg or less) ”means that“ the following (i) to (iii) Immersed in a mixture that satisfies

(i) The acid content is not more than 2.0 mm 01 / L, the content of P 0 ₂ F ₂ anion is not more than 0.5 mmo 1 / L, and the ethanol content is not more than 0.0 lmg.

(ii) Includes 1.0 m 01 / L of L i PF ₆ .

 (iii) Consists of 1.5 ml of ethylene carbonate and 3.5 ml of getylcapone.

The above condition (i) is based on the condition that the acid content and P 0 ₂ F ₂ ion contained in generally commercially available ethylene carbonate (EC) and ゃ ethyl carbonate (DEC) are decomposed into PF ₆ ion. It is a condition specified to eliminate the influence. Under these conditions, the acid content and the P 0 ₂ F ₂ anion do not affect the decomposition of the PF ₆ anion.

Lithium rechargeable battery using positive electrode material that can decompose Li PF ₆ under high temperature environment The reason for the high-temperature cycle property is deteriorated when used as a positive electrode, yet such is a Tsumabiraka bur, the surface of the positive electrode material that causes the degradation of L i PF ₆ is reacted with the solvent Ya lithium © beam salts of the electrolyte It is speculated that compounds that have an adverse effect on the charging and discharging of the lithium secondary battery may be formed on the surface of the positive electrode. It also has an adverse effect, which is also considered to have an adverse effect on charging and discharging.

As the means for suppressing the decomposition of L i PF ₆ in the storage test (I), but are not limited especially, for example, the presence of PF ₆ § two on decomposition inhibitor in the positive electrode material. Specifically, a method of incorporating a PF ₆ anion decomposition inhibitor such as an inorganic compound, an organic compound, an organometallic compound, or an organic ion into a positive electrode containing manganese oxide and / or lithium manganese composite oxide, Examples thereof include a method of substituting a part of the element of the positive electrode active material with an inorganic ion such as a group 15 to 17 in the periodic table.

When the PF ₆ anion decomposition inhibitor is contained in the positive electrode material, the decomposition amount of the PF ₆ anion measured by the following storage test (II) is 6 x 10 mol or less as the PF ₆ anion decomposition inhibitor. It is preferred to use one. The use of PF ₆ § two on decomposition inhibitor decomposition of PF ₆ Anion is 6 XI 0 uo 1 below as measured by the following storage test (II), the high-temperature properties such as high temperature stability and high-temperature cycle characteristics Can be improved.

 Storage test (II)

a 2) Li _{1 + x} Mn ₂ — _x 〇 ₄ (where 0 _≤ χ ^ 0. 05) Fully-charged lithium extracted from lithium manganese composite oxide having a spinel structure with a composition of Lithium-manganese composite oxide (0.05 ≤ L: 1/11 / molar ratio ≤ 0.09)

b 2) Under an argon gas atmosphere with a dew point of less than 75 ° C,

c 2) In a polyethylene tetrafluoroethylene container dried for 3 hours at 80, d 2) mixed with the PF ₆ anion decomposition inhibitor 16 O mg,

. e 2) 1 O containing mo l / L of L i PF _6, ethylene force one Poneto 2 4 ml Jefferies chill carbonate 5. mixture of 6 m 1 (acid content:.. 2 0 mm ol / L or less, P 0 ₂ F ₂ anion: 0.5 mmo 1 / L or less, and ethanol: 0.01 mg or less)

f 2) One week at 70 ° C

Save, PF ₆ Anion amount measurement (measurement temperature: 2 0 ° C) in the mixture before and after the storage, and obtains the PF ₆ § two on amount of degradation.

The storage test ([pi) of a 2) in the _{"L i 1 + x Mn 2 -} x 0 4 ( here, lithium of the lithium-manganese composite oxide having a spinel structure 0≤ X≤ 0. 0 5) a composition the extracted, lithium manganese composite oxide corresponding to the fully charged state (0. 0 5≤ L i / Mn molar ratio ≤ 0. 0 9) _{"is, L i 1 + x Mn 2} - x 0 4 ( wherein 0 ≦ x ≦ 0.05) It can be obtained by treating a lithium manganese composite oxide having a spinel structure of the following composition with an acid. Specifically, a lithium manganese composite oxide having a spinel structure having a composition of Li _{1 + x} Mn ₂ _ _x 04 (here, 0 ≤ _x ≤ 0.05) is added to water and stirred at room temperature. It is obtained by dropwise addition of acid while the pH is stable at 0.8-1.2. Normally, it may be stabilized at pH1. Sulfuric acid or the like may be used as the acid. Whether pH is stable at 0.8 to 1.2 can be confirmed by continuing stirring for about 6 hours and confirming that there is no fluctuation in pH. If it is confirmed that the pH is stable at 0.8 to 1.2, it can be obtained by repeating water washing several times while performing suction filtration, for example, drying at 90 ° C.

"Lithium equivalent to a fully charged state extracted from lithium of a lithium manganese composite oxide having a Sbinel structure having a composition of Li _{1 + x} Mn _{2 x} 〇 ₄ (where 0≤χ ^ 0.05) The manganese composite oxide (0.05≤L: 1/1 ^ 11 molar ratio≤0.09) "means" L i _Y Mn ₂ — _χ 0 ₄ (where 0≤χ ^ 0. 0 5, 0.1 0 ≤ y ≤ 0.18)

In the storage test (II) a2), the lithium of the lithium manganese composite oxide having a Svinel structure having a composition of Li _{1 + x} Mn _{2 x} 〇 ₄ (here, 0≤x≤0.05) The extracted lithium manganese composite oxide (0.05≤L 丄 / 11 molar ratio≤0.09) corresponding to the fully charged state "is a lithium manganese oxide having a spinel structure used as the positive electrode active material of the present invention. Object (L i _{1 + x} Mn ₂ — _x 0 ₄ (Here, 0≤x≤ 0. 0 5) represents a fully charged state of) deflection of the L i / Mn molar ratio gives the amount of decomposition of PF ₆ § two on the storage test (II) The impact is minimal.

In the storage test (II), c2) to f2) are performed under the conditions of b2). In addition, for 2), the mixture of a lithium manganese composite oxide corresponding to the fully charged state of a 2) and the PF ₆ anion decomposition inhibitor of d 2) was crushed, and the polytetrafluoro of c 2) was crushed. It is sufficient that the inside of the polyethylene container is under the condition of b2), and the outside of the polytetrafluoroethylene container which does not affect the immersion of the positive electrode does not need to be under the condition of b2).

"1. Omo lZL of L i PF ₆ and including, ethylene carbonate 2. 4 m 1 Jechiruka one Poneto 5. mixture of 6 ml (acid content in e 2) of the storage test (II): 2. Ommo l / L or less, P〇 ₂ F ₂ anion: 0.5 mmol / L or less, and ethanol: 0.01 mg or less) ”means that“ (iv) to (vi) Immersed in a mixture that satisfies

(iv) The acid content is 2.0 mm 0 1 ZL or less, and the P 0 ₂ F ₂ anion content is 0.5 mm 01 / L or less, and the ethanol content is 0.5 mg or less.

(V) including the L i PF ₆ of 1. 0 mo 1 / L.

 (vi) Consists of 2.4 ml of ethylene glycol and 5.6 ml of getyl carbonate.

The condition (iv) is for the same reason as described in the above (i). In the present invention, the ability of the PF ₆ anion decomposition inhibitor is not determined by the composition of the substance or the specific physicochemical properties. This is because even the compounds of the same composition have different physicochemical properties such as structure, surface area, acidity, basicity, and average voltage depending on the preparation method, pulverization method, storage method, etc. the strength of the interaction between PF ₆ is different.

Examples of the composition of the PF ₆ dione decomposition inhibitor used in the present invention include inorganic compounds, organic compounds, and organometallic compounds. A plurality of types of PF ₆ anion decomposition inhibitors may be used.

Specific examples of the PF ₆ anion decomposition inhibitor are shown below, but as described above, only the composition It should be noted that whether or not the PF ₆ anion decomposition inhibitor of the present invention is satisfied is not uniquely determined.

Examples of the inorganic compound that can be used as the PF ₆ anion decomposition inhibitor include oxides, composite oxides, nitrides, and sulfides of various metals belonging to Groups 2 to 14 of the periodic table of the elements. These are oxides or composite oxides of various metals belonging to Group 14. As the above-mentioned metal elements, specifically, Sr, Ca, Ba, Mg, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, B, Al, and Sn. Further, a compound capable of reversibly storing and releasing lithium ion can also be suitably used as a PF ₆ dione decomposition inhibitor. Examples thereof include a lithium iron composite oxide, a lithium cobalt composite oxide, and a lithium nickel composite oxide, preferably a lithium nickel composite oxide, and particularly preferably a lithium nickel composite oxide having a layered structure. be able to. Of course, those obtained by substituting some of these metals with other metal elements can also be used.

PF ₆ 7 two on organic compounds can be used as a decomposition inhibitor, it is a organometallic compound, a chelating agent, i.e. include those which have the property of forming (chelating activity) heavy metal complexes. Among them, compounds containing at least one element selected from the group consisting of at least Groups 15 and 16 of the Periodic Table of the Elements are preferred. Specifically, compounds having at least one amino group in the molecule, compounds having at least one amide bond in the molecule, compounds having at least one hydroxyl group in the molecule, or at least one compound in the molecule And compounds having a nitrogen-containing heterocyclic ring. Also, metal salts of these compounds can be suitably used, and the metal element used for the metal salt is at least one selected from the group consisting of Groups 1, 2 and 13 of the periodic table of the elements. One kind of metal element is included. More specifically, bisbenzylidene hydrazide oxalate, bis (cyclohexanone) oxalyldihydrazone, N, N, 1-bis {2- (3- (3,5-di-tert-butyl-14-hydroxyphenyl)) ) Propionyloxyl] ethyl} oxamide, 3- (N-salicyloyl) amino-1,2,4-triazolyl, disalicyloylhydrazine decanedicarboxylate, N, N, 1-bis [3--3,5-] G-t-butyl-41-hydroxyphenyl) propionyl] hydrazine, bis-isophthalate [2-ph Enoxypropionyl hydrazide], pyrrol, pyrazol, imidazole, benzoimidazole, 1, 2, 4-triazole, 3_ (N-salicyloyl) amino-1,2,4-1 Triazoles and their lithium salts, sodium salts, magnesium salts, aluminum salts and the like.

When a compound having an amino group is used as the PF ₆ anion decomposition inhibitor, a compound having a secondary or tertiary amino group is preferable. Particularly, in the case of using the electrolytic solution containing L i PF ₆ This tendency is remarkable. This is considered for the following reasons.

That is, when a compound having an amino group is used as a PF ₆ anion decomposition inhibitor, if a hydrogen atom is bonded to the nitrogen atom of the amino group, this hydrogen atom functions as an active proton. the compound L i PF ₆ react with results acids such as HF are generated, which further reacts with the electrode, it is estimated that there may be lowered performance as a battery. This tendency is remarkable for primary amine having a large amount of active protons. On the other hand, tertiary § Mi emission has a low reactivity with L i PF ₆ for not having an active pro tons, but would not cause deterioration of the battery performance as described above, mutual manganese oxide From the viewpoint of action, generally, primary or secondary amines tend to have stronger interaction. This is because tertiary amines have a weaker interaction with manganese oxides than primary or secondary amines, which can form ionic or covalent bonds with manganese oxides (coordination bonds). Therefore, it seems that the tertiary amine that has interacted once is easily dissociated. Therefore, it is considered that the ability of the PF ₆ anion decomposition inhibitor contained in the positive electrode material is determined by the above two balances. As a result, it is presumed that a compound having a secondary or tertiary amine is more preferable than a primary amine. However, the use of amines having a bulky location substituent, since it is possible to suppression reaction itself and the L i PF _6, can also be used primary § Mi emissions.

The presence state of the PF ₆ anion decomposition inhibitor in the positive electrode material is usually a state in which the surface of the positive electrode active material is uniformly covered, or a state in which the PF ₆ anion decomposition inhibitor is localized or dispersed in the positive electrode material. In the former case, Ru can stop the direct contact of L i PF ₆ and manganese. In the latter case, the positive electrode active material in the coexistence of the L i PF ₆ decomposition inhibitor It can inhibit the interaction of L i PF ₆ with quality. In the presence of L i PF ₆ decomposition inhibitor used in the present invention in the positive electrode material, for example, dispersive mixing, and the like, other deposition or Zorugeruko one tee ring, the O Rikatsu material particle surface to heat treatment L i method of forming a coating of PF ₆ decomposition inhibitor can be employed. However, depending on the type of the PF ₆ anion decomposition inhibitor, coating by heat treatment or the like may cause loss or deterioration of the PF ₆ anion decomposition inhibitor, and may lose the intended effect. On the other hand, dispersion mixing is preferred because it is a simple addition method, is not affected by alteration, and can sufficiently exhibit its original effect. In the present invention, “dispersed mixing” means simply mixing a plurality of substances, and means mixing that does not involve heat treatment at such a high temperature that the mixture is chemically changed. It is preferable that a plurality of substances are mixed to disperse the PF ₆ anion decomposition inhibitor used in the present invention in the positive electrode material, and it is preferable that the PF ₆ anion decomposition inhibitor is uniformly dispersed. Dispersion mixing may be dry mixing or wet mixing. For physical mixing, a mortar, ball mill, jet mill, Loedige mixer, or the like can be used. In order to effectively remain in the positive electrode material, a material that is hardly dissolved in the electrolytic solution is preferable.

As the PF ₆ dione decomposition inhibitor to be used, a compound having low solubility in the electrolytic solution to be used is desirable. In addition, PF ₆ anion decomposition inhibitors do not often pose a major problem when inorganic compounds are used, but their physical or physicochemical tendencies are those with low average voltage, those with large surface area, Compounds having lattice defects are preferred. However, since these are not unique and are determined by the combination of factors, not all compounds follow the above-mentioned individual tendencies.

The content of the PF ₆ anion decomposition inhibitor may be arbitrarily determined, but is usually in the range of 0.001 to 80 wt% based on the positive electrode active material. If the amount is too small, only an insufficient effect can be obtained and the high temperature stabilizing effect is hardly exhibited.On the other hand, if the amount is too large, the resistance may increase, and other characteristics such as a decrease in capacity may be reduced. Come out. As PF ₆ 7 two on decomposition inhibitor, the use of lithium can occluding and releasing compounds, even many amount is advantageous in that the capacity of the positive electrode does not decrease. In this case, the amount of the additive used is based on manganese oxide and lithium manganese oxide. Always at least 1 wt%, preferably at least 5 wt%, more preferably at least 10 wt%, and usually at most 80 wt%, preferably at most 60 wt%, more preferably at most 35 wt%. It is. On the other hand, when a compound containing at least one element selected from the group consisting of Groups 15 and 16 of the Periodic Table of the aforementioned elements and not absorbing and releasing lithium is used. The amount of the additive used is usually at least 0.001 wt%, preferably at least 0.001 wt%, more preferably at least 0.000 wt%, based on manganese oxide and lithium manganese oxide. It is at least lwt%, usually at most 10wt%, preferably at most 5wt%, more preferably at most 1wt%.

In the present invention, the positive electrode active material to be used may be the PF ₆ anion decomposition inhibitor itself. That may be one of the compounds is the positive electrode active material and PF ₆ 7 two on decomposition inhibitor.

As means for suppressing the decomposition of PF ₆ 7 two on, arbitrary favored method of replacing a part of the elements of the positive electrode active material in 1 5 to 1 7 group or the like of inorganic ions other metal elements and the Periodic Table of the Elements. In this case, as the positive electrode active material, hardly oxygen release at high temperatures, but preferably those having the properties of structural changes with occlusion and release of lattice defects is small or lithium ion is small, and these also, PF ₆ § As in the case of the dione decomposition inhibitor, the degree to which the decomposition of PF ₆ dione is suppressed is not uniquely determined by the factors alone.

In the present invention, the amount of decomposition of PF ₆ Anion when performing the above storage test the (I) is 1 x 1 0 juLm o 1 or less, preferably 6 mo 1 below. However, because it is not realistic even in an effort to reduce the amount of degradation in Ri linseed, the lower limit of the amount of degradation is usually 1 x 1 0- ² mo 1 about. On the other hand, when the above storage test ( ₆ ) was performed, the amount of PF672one decomposed was 6 × 10 mol or less, preferably 55 mol or less, more preferably 5 × 1 mol or less. 0〃mol or less. In this case not feasible even in an effort to reduce the amount of degradation More or is, the lower limit of the amount of degradation is usually about 1 XI 0- ² mo l.

In the present invention, the degradation product of the PF ₆ anion of Li PF _{6 in} the above-mentioned storage test is usually mainly P 0 ₂ F ₂ anion. Therefore, the above storage test (I) In performance and the positive electrode to be evaluated, the performance of the PF ₆ Anion decomposition inhibitor to be evaluated by the storage test ([pi) it can also evaluate child generation amount of produced P 02 F ₂ as a parameter. In the present invention, the amount of P 0 ₂ F ₂ anion contained in the preservation solution at 20 ° C. at the time of performing the above preservation test is usually 1 × 10 〃mol under the storage test conditions (I). Hereinafter, it is preferably 5 mol or less. On the other hand, under the storage test condition (II), it is usually 5 × 10〃mol or less, preferably 4 xl0〃mol or less. Here, the amount is limited to “at 20 ° C.” because the generated P〇 ₂ F ₂ anion is often contained in the precipitate. Therefore, the state of the storage solution at ₂₀ ° C. is a state in which the content of the P 0 ₂ F ₂ anion in the storage solution at ₂₀ ° C. becomes constant regardless of time.

In the present invention, the above storage test (I) or ([pi) the PF ₆ when the Anio down degradant 80% or more, and particularly 9 5% or more is P_〇 ₂ F ₂ Anion good Good.

Further, in the present invention, when a storage test is performed by the method of the storage test (Π), ethanol is generated along with the generation of P ₂ F ₂ anion. The preferred amount of ethanol to be produced is as follows: when the storage in the above-mentioned storage test (II) is extended for another two weeks, that is, when the above-mentioned storage test (II) in which the storage time is three weeks is performed, The amount of ethanol contained in the liquid is 1 mg or less, and even 0.5 mg or less. When a large amount of ethanol is produced in the above storage test (II), the PF ₆ anion decomposition inhibitor cannot achieve sufficient improvement in high-temperature properties. Even in the case of the above storage test (I), the production of ethanol may be confirmed in some cases, but the amount produced is extremely small. The amount of ethanol contained in the preservation solution after the preservation test by the method under the above storage conditions (I) is usually 0.1 mg or less.

The amounts of PF ₆ anion and P 0 ₂ F ₂ anion contained in the above preservation solution can be determined by various known analytical methods. Examples thereof include ion chromatography analysis, F-NMR and P-NMR. This time important, when performing these analyzes, as a blank, under conditions as not to cause the decomposition of the stored previous 1. Omo l / L be a solution containing L i PF ₆ of L i PF ₆ The measurement is to be performed. In addition, especially when the amount of P 0 ₂ F ₂ anion in the preservation solution is small, If necessary, the anion may be analyzed by performing operations such as concentration under conditions that do not change the composition of the anion in the storage solution.

 Ethanol can be measured by various known analytical methods. For example, gas chromatography, liquid chromatography, NMR and the like can be mentioned. Specifically, it can be measured using the measuring method in the embodiment of the present invention.

In the present invention, a manganese oxide and / or a lithium manganese composite oxide is used as an active material. Note that, in the present invention, the active material is a main substance that is the basis of an electromotive reaction of the battery, and means a substance that can occlude and release ions. The manganese oxide and / or lithium manganese composite oxide may be any as long as it can reversibly occlude and release Li as an active material, and is preferably a lithium manganese composite oxide, particularly lithium having a spinel structure. Manganese composite oxides are preferred. The composition of a lithium manganese composite oxide having a spinel structure is generally represented by L i M n ₂ 〇 ₄ , but some of M n have been replaced with other metals, and oxygen deficiency has occurred. It can also be used, and is included in the lithium manganese composite oxide having a spinel structure. Examples of the metal that partially substitutes for Mn include Al, Ti, V, Cr, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, B, Ge and the like.

 As a preferred embodiment of the first embodiment of the present invention and a second embodiment of the present invention, there is provided a lithium-ion secondary battery containing a lithium manganese composite oxide having a suberin-type structure and a lithium nickel composite oxide having a layered structure. A positive electrode material for a lithium ion secondary battery, wherein a part of the manganese site of the lithium-manganese composite oxide is replaced with at least one element selected from typical elements. Is mentioned. In the present invention, a high temperature is achieved by containing a lithium nickel composite oxide having a layered structure, and by substituting at least one element selected from typical elements for a part of the manganese site of the lithium manganese composite oxide. High temperature characteristics such as stability and high temperature cycle characteristics have been improved.

The lithium manganese composite oxide having a spinel structure used above is, for example, a mixture of a lithium compound, a manganese compound, and a compound of at least one or more typical elements that partially replace the manganese site. Baking in or Can be obtained by mixing a lithium compound and a manganese compound, firing the mixture in the air to produce a subinel-type lithium-manganese composite oxide, and then reacting it with at least one compound of a typical element. Such typical elements that substitute for the Mn site include Li, B, Mg, Al, Ca, Zn, Ga, and Ge. Of course, it is possible to replace the manganese site with multiple elements. As the substitution element of the manganese site, Li, Mg, A1, and Ga are preferable, and aluminum and / or lithium are particularly preferable. The substitution amount of a typical element is preferably 0.05 mol or more, more preferably 0.06 mol or more, and most preferably 0.08 mol or more in 2 mol of manganese.

 As a preferred embodiment of the first embodiment of the present invention and a third embodiment of the present invention, a lithium ion secondary battery containing a lithium manganese composite oxide having a suberin-type structure and a lithium nickel composite oxide having a layered structure The lithium manganese composite oxide, wherein a part of the manganese site of the lithium manganese composite oxide is replaced by another element, and the average voltage of the lithium manganese composite oxide measured by the following measurement method (I) is: A positive electrode material for lithium ion secondary batteries, which is characterized by a voltage of 4.059 V or more. Here, the following measurement method (I) is a measurement method for determining a preferable lithium manganese composite oxide used as a positive electrode material. The average voltage measured by the following measurement method (I) is 4.059 V or higher. It is preferable from the viewpoint of improving high temperature characteristics such as characteristics.

 <Measurement method of average voltage (I)>

(1) The composite oxide is weighed at 75% by weight, acetylene black at 20% by weight, and polytetrafluoroethylene (PTFE) powder at 5% by weight and mixed to form a thin sheet. After adjusting the total weight to 12.5 mg / cm ² , this sample is further pressed against aluminum expanded metal to make a test electrode. The test electrode is dried for 1 hour at 120 ° C under reduced pressure.

② Under an argon atmosphere, a porous polyethylene film of 25 2m was used as a separator, lithium metal foil was used as a counter electrode, and a nonaqueous electrolyte solution was used, in which the volume ratio of ethylene carbonate and getyl carbonate was 3: 7 mixed solvent With 1 mol / Li Tsu solution obtained by dissolving lithium hexafluorophosphate (L i PF ₆₎ torr, to produce a coin-type battery of CR 2 03 2 type.

③ The obtained coin-type battery is subjected to a constant current charge / discharge cycle of 0.5 mA / cm ² (charge upper limit 4.35 V, discharge lower limit 3.2 V) in an environment of 25 ° C. The average voltage V e

 V e = (average charge voltage in the second cycle + average discharge voltage in the second cycle) / 2.

 The average charge voltage or average discharge voltage is calculated by measuring the voltage during charge or discharge at 2-second intervals, and dividing the value obtained by integrating the voltage over time by the time required for charge or discharge.

In the above measurement method (I), the sample was pressed onto expanded metal in step (1), for example, in a tableting machine, (1) aluminum expanded metal and (2) 75% by weight of the composite oxide, acetylene black 2 0 wt%, and mixed and weighed at a ratio of Porite Torafuroroechi Ren (PTFE) powder 5% by weight, thin sheet and one preparative shape, overlapping those total weight was adjusted 1 2. 5 mg / cm ² and so as Just set it and press it. The pressure for crimping is usually 80 to 100 MPa, and the pressure may be about 90 MPa.

 The thickness of the expanded metal is usually 50 to 300 3m, and a thickness of about 200〃m may be used.

 The spinel-type lithium manganese composite oxide used as the above active material has an average voltage of 4.059 V or more, preferably an average voltage of 4.060 V or more, and more preferably 4.06 V or more. 5 V or more, most preferably 4.070 V or more. However, the average voltage is usually less than 4.3 V, because of the difficulties in manufacturing high voltage ones. Here, the average voltage is a value measured according to the above ① to ③.

 If the method is strictly defined in this way, the average voltage can be uniquely determined.

The lithium manganese composite oxide having a spinel structure used above and having a part of the manganese site replaced by another element is, for example, a part of the manganese site replaced by at least one or more elements. Can be obtained by: This Examples of the element that replaces the Mn site, such as Al, Ti, V, Cr, Fe, Co, Li, Ni, and Cu, Zn, Mg, Ga, Zr, B, Ge and the like, preferably Li, B, Mg, Al, Ca, Zn, Ga, Ge and the like typical elements No. Of course, it is possible to replace the manganese site with multiple elements. Aluminum and / or lithium are particularly preferable as the manganese site substitution element, since it is possible to increase the average voltage of the spinel-type lithium manganese composite oxide with a small amount.

 In the preferred embodiment of the first embodiment, the second embodiment of the present invention, and the third embodiment of the present invention, a lithium manganese composite oxide having a spinel structure used, hereinafter referred to as “composite oxide (A)” Of the "may be", a preferred one is a general formula L i [M n — ^ A L y L i jO where x, y and z are each 0 or more, and x = y + z. However, y and z are not simultaneously 0. ). Here, y is usually 0.5 or less, preferably 0.25 or less, and usually 0.1 or more. Z is usually 0.1 or less, preferably 0.08 or less, and usually 0.02 or more. If y and z are too small, the high-temperature characteristics may deteriorate, while if too large, the capacity tends to decrease.

In the above description, the oxygen atoms of the composite oxide (A) may have non-stoichiometric properties, and some of the oxygen atoms may be substituted with a halogen element such as fluorine. The lithium nickel composite oxide having a layered structure used in the preferred embodiment of the first embodiment, the second embodiment of the present invention and the third embodiment of the present invention (hereinafter sometimes referred to as “composite oxide (B)” In general, those having a basic composition formula L i N i〇 ₂ are preferred. Among them, those having an average voltage of 3.830 V or less are preferable, and especially those having an average voltage of 3.820 V or less. More preferably, the voltage is 3.810 V or lower, and more preferably, the voltage is 3.80 V. By lowering the average voltage of the composite oxide (B), the potential difference from the composite oxide (A) is reduced. It is expected that the interaction between the composite oxides (A) and (B) will increase as described in the section of action, and as a result, the characteristics at high temperatures can be improved. Usually, the average voltage is more than 3.5 V because the one with too low average voltage is difficult to manufacture.

The method of measuring the average voltage of the composite oxide (B) is the same as that of the composite oxide (A). It is almost the same as the measurement method, except that in step (3), the current density is 0.2 mA / cm ² and the upper limit of charge is 4.2 V.

 Such a composite oxide (B) having a reduced average voltage can be obtained by substituting a part of nickel with another element. Further, it can also be obtained by making the particle size of the composite oxide (B) small, so that lithium can be easily taken in and out.

 Examples of the element capable of partially replacing nickel include metal elements such as B, Al, Fe, Sn, Cr, Cu, Ti, Zn, Co, and Mn. Of course, it is possible to replace the nickel site with multiple elements. Particularly, aluminum and / or cobalt are preferable.

Particularly preferred composite oxide (B) has the general formula _{L i [N i (1 _} x) C o y A l z] 0 2 ( provided that x, y and z is a number which it zero or more, x = y + z, except that y and z are not both 0 at the same time. Here, y and z are each independently usually 0.5 or less, preferably 0.25 or less, and usually 0.1 or more. Z is usually 0.1 or less, preferably 0.08 or less, and usually 0.02 or more. If y and z are too small, the high temperature characteristics tend to be poor, while if too large, the capacity tends to decrease. In the above, the oxygen atoms of the composite oxide (B) may have non-stoichiometric properties, and some of the oxygen atoms may be substituted with a halogen element such as fluorine. In the preferred embodiment of the first embodiment, the second embodiment of the present invention and the third embodiment of the present invention, the composite oxide (A) and the composite oxide (B) are in the form of a mixture thereof. Or a complex involving a chemical bond.

In the preferred embodiment of the first embodiment, the second embodiment of the present invention, and the third embodiment of the present invention, the active material is based on the total amount of the composite oxide (A) and the composite oxide (B) The weight ratio R of the composite oxide (B) is usually 0.7 or less, preferably 0.6 or less, and more preferably 0.3 or less. Further, it is usually at least 0.05, preferably at least 0.1. If the mixing ratio of the lithium-nickel composite oxide is too small, the effect of improving the high-temperature characteristics tends to be small, while if too large, a problem may occur in terms of cost and safety. The particle size of the composite oxide (A) or (B), or a composite of these, is usually at least 0.3 lm, preferably at least 0.3, more preferably at least 0.3 μm, and usually at least 0.3 μm. 0 m or less, preferably 10 m or less, more preferably 5 m or less. The specific surface area by these nitrogen adsorption methods is usually 0.3 m ² / g or more, and usually 15 m ² / g or less. If the particle size is too small or the specific surface area is too large, the cycle deterioration of the battery may increase, or safety problems may occur. If the particle size is too large or the specific surface area is too small, the internal resistance of the battery may be large and output may be difficult to obtain.

 The present invention also relates to a positive electrode and a battery for a lithium ion secondary battery using the positive electrode material for a lithium secondary battery as described above. That is, the positive electrode for a lithium ion secondary battery of the present invention is obtained by forming an active material layer containing the positive electrode material on a current collector.

 The positive electrode is generally formed by forming an active material layer containing an active material and a binder on a current collector. The active material layer can be usually obtained by preparing a slurry containing the above constituent components, applying the slurry on a current collector, and drying.

 The proportion of the active material of the present invention in the active material layer is usually at least 10% by weight, preferably at least 30% by weight, more preferably at least 50% by weight, and usually at most 99.9% by weight, preferably at most 99.9% by weight. Is less than 99% by weight.

Examples of the binder used for the positive electrode include polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, EPDM (ethylene-propylene-diene terpolymer), and SBR (styrene-styrene). Butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluoroelastomer, polyvinyl benzoate, polymethyl methacrylate, polyethylene, nitrocellulose and the like. The proportion of the binder in the active material layer is usually at least 0.1% by weight, preferably at least 1% by weight, more preferably at least 5% by weight, and usually at most 80% by weight, preferably at most 6% by weight. 0% by weight or less, more preferably 40% by weight or less, and most preferably 10% by weight or less. If the ratio of the binder is too low, the active material cannot be sufficiently retained, resulting in insufficient mechanical strength of the positive electrode, which may degrade battery performance such as cycle characteristics. May reduce sex. The active material layer usually contains a conductive agent to increase conductivity. Examples of the conductive agent include carbon materials such as graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle cox. The proportion of the conductive agent in the active material layer is usually at least 0.01% by weight, preferably at least 0.1% by weight, more preferably at least 1% by weight, and usually at most 50% by weight, preferably at most 3% by weight. 0% by weight or less, more preferably 15% by weight or less. If the proportion of the conductive agent is too low, the conductivity may be insufficient, and if it is too high, the battery capacity may decrease.

 As the slurry solvent, an organic solvent that usually dissolves or disperses the binder is used. For example, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N, N-dimethylaminobutyrol pyramine, ethyleneoxy And tetrahydrofuran. In addition, a dispersant, a thickener, and the like can be added to water to form a slurry of the active material with a latex such as SBR.

 The thickness of the active material layer is usually about 10 to 200 m.

 As the material of the current collector used for the positive electrode, aluminum, stainless steel, nickel steel, or the like is used, and aluminum is preferable.

 The active material layer obtained by coating and drying is preferably compacted by a roller press or the like in order to increase the packing density of the active material.

 A lithium ion secondary battery can be obtained using the active material of the present invention and the positive electrode. The lithium ion secondary battery of the present invention contains the active material in the positive electrode, and usually has the positive electrode, the negative electrode, and a non-aqueous electrolyte.

The negative electrode active material used for the negative electrode of the secondary battery of the present invention may be a lithium alloy such as lithium-poly-aluminum alloy, but can store and release lithium with higher safety. Carbon materials are preferred. Examples of the carbon material include natural or artificial graphite, petroleum-based coke, coal-based coke, carbide of petroleum-based pitch, carbide of coal-based pitch, and carbide of resin such as phenolic resin and crystalline cellulose, and the like. Carbon material, furnace black, acetylene bra And carbon black, peach-based carbon fiber, PAN-based carbon fiber, or a mixture of two or more of these.

 The negative electrode is usually formed by forming an active material layer on a current collector as in the case of the positive electrode. At this time, as the binder used and the conductive agent / slurry used as needed, the same solvent as that used for the positive electrode can be used. As the current collector of the negative electrode, copper, nickel, stainless steel, nickel plating steel, or the like is used, and copper is preferably used.

 Examples of the non-aqueous electrolyte solution that can be used in the lithium secondary battery of the present invention include those in which various electrolyte salts are dissolved in a non-aqueous solvent. Non-aqueous solvents include, for example, carbonates, ethers, ketones, sulfolane compounds, lactones, nitriles, halogenated hydrocarbons, amines, esters, amides, phosphate esters Compounds and the like can be used. Typical examples of these are propylene carbonate, ethylene carbonate, and ethylene ethylene oxide—ponate, trifluoropropylene carbonate, getyl carbonate, dimethyl carbonate, ethyl methyl carbonate, vinylene carbonate, and terephthalate. Trahydrofuran, 2—Methylte Trahydrofuran, 1,4-dioxane, 4-methyl-2, pentanone, 1,2—Dimethoxane, 1,2—Jetokishetan, Arptyloractone, 1,3—Dioxolan, 4-methylol 1,3 Dioxolane, Jetylether, Sulfolane, Methylsulfolane, Acetonitrile, Bropionitrile, Benzonitrile, Butyronitrile, Nono, 'Leronitrile, 1,2-Dichloroethane, Dimethylformamide The Chirusuruhokishi de, phosphate preparative Rimechiru, even alone, such as phosphoric acid DOO Ryechiru properly mixed solvent of two or more can be used.

The above-mentioned non-aqueous solvent preferably contains a high dielectric constant solvent for dissociating the electrolyte. Here, the high dielectric constant solvent means a solvent having a relative dielectric constant at 25 ° C. of 20 or more. Among the high dielectric constant solvents, it is preferable that ethylene carbonate, propylene carbonate, and a compound in which hydrogen atoms thereof are replaced with another element such as halogen or an alkyl group are contained in the electrolytic solution. The proportion of the high dielectric constant solvent in the electrolyte is preferably 20% by weight or more, more preferably 3% by weight or more. It is at least 0% by weight, most preferably at least 40% by weight. If the content of the high dielectric constant solvent is small, desired battery characteristics may not be obtained in some cases.

As the electrolyte salt, any conventionally known can be used, L i C L_〇 _{4, L i A s F 6} , L i PF 6, L i BF 4, L i B (C 6 H 5) 4, L i C l, L i B r , L i CH 3 S_〇 _{3 L i, L i CF a} S 0 3. L i N (SO 2 CF 3) had _{L i N (SO 2 C 2} F 5) 2, L i C (SO 2 CF 3 ) 3, L i N (S 0 3 CF 3) lithium salts of _2, and the like.

_{Further, C 0 2, N 2 0} , C_〇, S◦ ₂ like gas or Porisarufuai de S _x ^ -, bi two alkylene carbonate, catechol force one Bonnet one preparative such efficiency Yoi charge and discharge of the lithium ion to the negative electrode surface The additive which produces a good film which enables the above-mentioned process may be added to the above-mentioned solvent alone or in a mixed solvent at an arbitrary ratio.

 Further, a solid polymer electrolyte which is a conductor of an alkali metal cation such as lithium ion can also be used. In this case, a conventionally known polymer can be used as the polymer, but a polymer having high ionic conductivity to lithium ions is preferably used. Examples of such a polymer include polyethylene oxide, polypropylene oxide, polyethylene imide and the like. Usually, the polymer solid electrolyte contains the above-mentioned polymer and the above-mentioned lithium salt, but it is also possible to add the above-mentioned solvent and use it as a gel electrolyte. That is, in this case, the electrolyte solution is made into a matrix by a polymer.

Even when an inorganic solid electrolyte is used, a known crystalline or amorphous solid electrolyte can be used for the inorganic substance. Examples of the crystalline solid electrolyte include L i I, L i ₃ N, L i _{1 + x} M _x T i ₂ — _x (P〇 ₄ ) ₃ (M = A 1, S c, Y, La) _{, L i 0 5 -. 3} x RE. _{. 5 + x T i 0 3} (RE = L a, P r, Nd, Sm) and the like, as the solid electrolyte of the amorphous, for example, 4. 9 L i I - 34. 1 L i 2 O-glass such as 0-6 1 B 205, 33.3 L i 20-6 6.7 S i〇 _{2 and} 0.45 L i I-0.37 L i ₂ S-0.26 B ₂ S ₃ , 0.30 L i I-0.42 L i ₂ S — 0.28 S i S _{2 and} other sulfide glasses. A plurality of these can be used. Normally, a separation is provided between the positive electrode and the negative electrode. For separation, a microporous polymer film is used. A polymer made of a polyolefin-based polymer such as polybutene can be used. Further, a nonwoven fabric filter made of glass fiber or the like, or a composite nonwoven fabric filter made of glass fiber and polymer fiber can also be used. The chemical and electrochemical stability of the separation is an important factor. From this point, a polyolefin polymer is preferable, and it is preferable to be made of polyethylene from the viewpoint of the self-closing temperature, which is one of the purposes of the battery separation.

 In the case of polyethylene separator, it is preferably ultra-high molecular weight polyethylene from the viewpoint of high-temperature shape retention, and the lower limit of the molecular weight is preferably 500,000, more preferably 1,000,000, and most preferably 150,000. It is ten thousand. On the other hand, the upper limit of the molecular weight is preferably 500,000, more preferably 400,000, and most preferably 300,000. If the molecular weight is too large, the fluidity is too low and the pores of the separator may not be closed when heated.

 Hereinafter, the present invention will be described more specifically with reference to examples.

 [Preparation of manganese composite oxide]

Preparation Example _{1 L i [Mn 96 L i} 4] 0 4 Preparation

Subineru type lithium manganese complex oxide _{L i [Μη ^ L i O} . 4] 0 4 was prepared as follows.

Manganese sesquioxide (Mn ₂ 0 ₃₎ and the departure material Lithium hydroxide _{(L i OH 'H 2 0} ), it molar ratio of its compound 1: was blended so that 1.04. Ethanol was added to this formulation and ground well in a mortar to make a homogeneous mixture. The obtained mixture is calcined in the air at 500 ° C (heating rate: 5 ° C / min) for 24 hours, and then in the air at 780 ° C (heating rate: 5 °). (C / min) for 24 hours, then cool to 450 ° C (cooling rate: 0.2 ° C / min), hold for 24 hours, then slowly cool to room temperature by natural cooling and take out Was. Elemental analysis was Toko _{filtration, L i fMrii ge L i 0.} . _4] ● ₄ had been obtained. The resulting spinel type lithium The lithium manganese composite oxide was designated as lithium manganese composite oxide (A). Preparation Example 2 Preparation of LitMn us Alo.HLiojjC

Lithium manganese composite oxide of the spinel-type _{L i [Mnj. 8 5 A} 1 0.! ! _{L i o. O 4] 0} 4 was prepared as follows.

Manganese sesquioxide (Mn ₂ 0 _3), lithium carbonate _{(L i 2 C 0 3)} , and alumina hydrate (A 100H) was used as a starting material, and that of an compound molar ratio is 0.9 4: It was blended so that 1.04: 0.10. Ethanol was added to this formulation and ground well in a mortar to form a uniform mixture. The obtained mixture is heated in the air at 500 ° C (heating rate: 5 ° C / min), 600 ° C (heating rate: 5 ° C / min), 700 ° C (heating rate: 5 ° C / min) and 800 ° C (heating rate: 5 ° C / min) for 6 hours, then 900 ° C in air (heating rate: 5 °) C / min) for 24 hours, then cooled to 300 ° C. at a cooling rate of 0.2 ° C./min, and then slowly cooled down to room temperature by natural cooling. Elemental analysis showed that Li [Mn J. 96 Lio. _4] 0 ₄ was obtained. The obtained spinel-type lithium manganese composite oxide was designated as lithium manganese composite oxide (B).

Preparation of Preparation 3 acid treatment lithium manganese oxide L i _x Mn _y 〇 ₄

In a 300 ml beaker at room temperature under air, the pH of the suspension was added to a suspension of 6.60 g of the above-mentioned lithium manganese composite oxide (A) in distilled water (180 ml). 1.0 0 4. 5 N sulfuric acid until the addition, after stirring for 6 hours, the resulting suspension was filtered to give the crude was i xMn _y 0 ₄ as a dark red-brown powder. This was washed 6 times with distilled water (20 ml), air-dried all day and night, and further dried at 90 ° C under normal pressure for 1 hour to obtain 4.88 full charge after extracting lithium. An acid-treated lithium manganese composite oxide was obtained from which lithium was extracted to an extent equivalent to the state. The L i / Mn molar ratio of this acid-treated lithium manganese composite oxide was 0.07. X-ray diffraction measurement confirmed that the cubic spinel structure was maintained, and IR confirmed that water was not contained.

Example 1

 Preparation of positive electrode and confirmation of capacity

Commercially available composition Li as an additive to lithium manganese composite oxide (A). ₅ N ΐ o. 80 CO o. 15 A 1 o. ₅層₂ layered lithium nickel oxide (hereinafter sometimes referred to as PF ₆ anion decomposition inhibitor (a)) was added such that the weight ratio of lithium manganese composite oxide (A) / additive = 3/1. And mixed.

 A mixture obtained by weighing 75% by weight of the obtained mixture, 20% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene powder was sufficiently mixed in a mortar to form a positive electrode material. It was punched out with a punch of 12 mm (^. At this time, the total weight was adjusted to be about 18 mg. This was pressed against aluminum expansive metal to form a positive electrode.

Then, the obtained positive electrode of the test electrode, L i metal assembled battery element as a counter electrode, a constant current charge of 0. ² mA / cm 2, i.e. up to desorb reacting L i ions from the positive electrode 4. 2 V Or 4.35 V, and a constant current discharge of 0.2 mA / cm ² , that is, a test to insert Li ions into the positive electrode, was performed at the lower limit of 3.2 V. The initial desorption capacity was Q s (C) mAh / g, and the initial insertion capacity was Q s (D) mAh / g.

 Preparation of negative electrode and capacity confirmation

Graphite powder with an average particle size of about 8 to 10 μm (d002 = 3.35 Å) is used as the negative electrode active material, and this is abbreviated as polyvinylidene fluoride (PVdF). Are mixed in a solution of N-methyl bilolidon (hereinafter may be abbreviated as NMP) at a weight ratio of 92.5: 7.5, and then mixed with the negative electrode mixture slurry. did. This slurry was applied to one side of a copper foil 20 m thick, dried at 120 ° C to evaporate the solvent, punched out 12 mm, and shaken at 0.5 ton / cm ² . After the treatment, the negative electrode was used.

Incidentally, pole test this negative electrode, L i metal assembled battery element as a counter electrode, were tested to insert L i ions in the negative electrode at a constant current of 0. ² m A / cm 2 at the lower limit 0 V, the negative electrode at this time The initial insertion capacity per unit weight of the active material was defined as Q f mAh / g.

 Assembling the battery element

Place the positive electrode on the positive electrode can, place a 25 μm porous polyethylene film as a separator on top of it, press it with a polypropylene gasket, place the negative electrode, and arrange a thickness adjustment space. After placing, place the non-aqueous electrolyte solution (ethylene carbonate Ne one DOO / Jechiruka one Bonnet one DOO = 3/7 mixture solvent 1 liter to dissolve L i PF ₆ 1 mol of) was impregnated sufficiently in addition to the batteries, sealing said battery carrying the negative electrode can Thus, a CR203 type coin-type battery was obtained. At this time, the balance between the weight of the positive electrode active material and the weight of the negative electrode active material is almost

 It was set so that the amount of the positive electrode active material [g] / the amount of the negative electrode active material [g] = (Qf / 1.2) / Qs (C).

 Test method

 The obtained battery element was evaluated as follows. To compare the high temperature characteristics of the batteries obtained in this way,

 First, constant current 0.2 C charge / discharge 2 cycles and constant current 1 C charge / discharge 1 cycle are performed at room temperature, and then constant current 0.2 C charge / discharge 1 cycle is performed at a high temperature of 50 ° C. A cycle test of 100 charge / discharge cycles of C was performed. The upper charging limit was 4.1 V and the lower limit voltage was 3.0 V.

 At this time, the discharge capacity Qh (10 °) at the 100th cycle was compared with the discharge capacity Qh (1) at the 1st cycle in the 1C charge / discharge cycle test at 50 ° C. The ratio is the high-temperature cycle capacity retention ratio P, that is,

 P [%] = {Q h (1 0 0) / Q h (1)} x 1 0 0

This value was used to evaluate the high temperature characteristics of the battery.

 At this time, the one-hour rate current value of the battery, that is, 1 C,

 1 C [mA] = Q s (D) x positive electrode active material amount [g]

Was set.

 Table 1 shows the results.

Example 2

 A battery was prepared and evaluated in the same manner as in Example 1 except that the lithium manganese composite oxide (B) was used instead of the lithium manganese composite oxide (A) as the lithium manganese composite oxide. Table 1 shows the results.

Example 3

Using the lithium manganese composite oxide (B) in place of the lithium manganese composite oxide (A) as the lithium manganese composite oxide; and A battery was fabricated and evaluated in the same manner as in Example 1, except that the weight ratio of the manganese composite oxide to the layered lithium nickel oxide was 9: 1. Table 1 shows the results. Example 4

As the lithium manganese composite oxide, the lithium manganese composite oxide (B) was used in place of the lithium manganese composite oxide (A). Further, instead of the PF ₆ anion decomposition inhibitor ( _a ), those jet mill powder碎in nitrogen in the same manner as in example 1 except for using (hereinafter i PF ₆ decomposition inhibitor may be referred to as (b)), produce a battery was evaluated. Table 1 shows the results. Example 5

As a mixture of lithium-manganese composite oxide and PF ₆ § two on decomposition inhibitor, a lithium-manganese composite oxide (B), as PF ₆ 7 two on decomposition inhibitor 3- (N- salicyloyl) amino-1, 2 , 41-triazole (hereinafter sometimes referred to as PF ₆ -dione decomposition inhibitor (C)) was added in an amount of 0.6 wt% based on the total weight of the lithium manganese composite oxide. A battery was prepared in the same manner as in Example 1, except that the mixture was mixed with ethanol and vacuum-dried at 120 ° C for 1 hour, and the upper limit of charge during the cycle test was set to 4.2 V. , evaluated. Table 1 shows the results.

Example 6

PF as ₆ § two on decomposition inhibitor, Okisarirujihi Dora hydrazone (hereinafter PF ₆ § two on suppressing decomposition for the total amount of the lithium-manganese composite oxide 1. amount corresponding to 6 wt% bis (Kisano down to cyclo) A battery was fabricated and evaluated in the same manner as in Example 5, except that the agent (d) was used. Table 1 shows the results. Comparative Example 1

 The battery was manufactured in the same manner as in Example 1, except that the lithium-manganese composite oxide (A) was used alone as the positive electrode active material, and that the upper limit of charge during the cycle test was set to 4.2 V. Were fabricated and evaluated. Table 1 shows the results.

Comparative Example 2

Except that the lithium manganese composite oxide (B) was used alone as the positive electrode active material and that the upper limit of charge during the cycle test was set to 4.2 V. A battery was fabricated and evaluated in the same manner as in Example 1. Table 1 shows the results. Storage test

 Storage test (I)

In the above example and the comparative example, a 200 mm thick, 16 mm-diameter circular aluminum expanded metal (current collector) and a 12 mm-diameter circular shape were formed on a tablet press. The same positive electrode material as used, 24 mg, was stacked and set, and the positive electrode material was pressed against aluminum expanded metal at a pressure of 90 MPa to form a positive electrode. This was combined with Li metal as a counter electrode. , 1 0 mo 1 / L Echire emissions carbonate and Jechiruka mixed electrolytic solution as one Poneto containing L i PF ₆ (volume ratio 3: 7). a battery was fabricated device had use with. After charging the battery to a charging current density of 0.2 mA / cm ² and an upper limit voltage of 4.2 V, the battery was disassembled so as not to cause a short circuit, and a positive electrode material in a charged state was obtained.

The battery element was a CR203 type coin-type battery. That is, a positive electrode is placed on a positive electrode can, a 25-μm porous polyethylene film is placed on the positive electrode can as a separator, pressed with a polypropylene gasket, and then a counter electrode is placed on the positive electrode can. After placing the sampler, add a mixed solution of ethylene carbonate and getyl carbonate in a volume ratio of 3: 7 with L i PF ₆ concentration of l mol / L as a non-aqueous electrolyte solution in the battery. After soaking, the negative electrode can was placed and the battery was sealed. Charged as above in a sealed polytetrafluoroethylene container with a capacity of approximately 7 ml, dried at 80 ° C for 3 hours in an argon gas atmosphere with a dew point of 75 ° C or less the cathode material as a state, 1. including Omo l / L of L i PF _6, E styrene force one Poneto 1 5 m 1 and Jechiruka one Boneto 3. mixed solution of 5 ml (acid content:. 2. 0mmo l / L or less, P〇 ₂ F ₂ anion: 0.5 mmol / L or less, and ethanol: below the detection limit) and stored at 80 ° C for one week.

Analysis of the amount of PF ₆ anion decomposed, and the content of P ₂ F ₂ anion and ethanol in the preservation solution was performed after the temperature was cooled from 80 ° C to 20 ° C, and the dew point was The storage container was opened under an argon gas atmosphere at a temperature of not more than ° C, and only the solution part was sampled and subjected to the method described later. Table 1 shows the results. The analysis of ethanol was performed after storage at 80 ° C for 3 weeks. Although subjected to the same storage test even storage temperature 2 0 ° C, generation of decomposition and P 0 ₂ F ₂ § two on the PF ₆ § two on the significant difference in this case is not observed, PF ₆ It was confirmed that the formation of anions did not depend on the moisture brought in.

 Storage test (II)

The acid-treated lithium manganese composite was placed in a sealed polytetrafluoroethylene container with a content of about 15 ml, which was dried at 80 ° C for 3 hours in an argon gas atmosphere with a dew point of -75 ° C or less. and oxide 1 ₆ 0 mg, PF 6 and Anion decomposition inhibitor 1 6 0 mg, the content of the acid component and P 0 ₂ F ₂ Anion, it it 2. O mmo l / L or less and 0. 5 mm 0 1 / L or less and ethanol content detection limit (0. 0 1 mg) of the following, 1. 0 mo 1 / L mixture of ethylene carbonate / di Echiruka one Bonnet Ichito containing L i PF ₆ (ethylene The cells were stored at 2.4 ° C. for one week at 2.4 ° C. in 2.4 ml of lipstick and 5.6 ml of getyl liponate.

Analysis of the amount of PF ₆ anion decomposed and the content of P 0 ₂ F ₂ anion and ethanol in the preservation solution showed that after cooling the temperature from ま で 0 ° C to 20 ° C, the dew point was The storage container was opened under an argon gas atmosphere of 75 ° C. or lower, and only the solution part was sampled, and the method was described later. Table 1 shows the results. The analysis of ethanol was performed after storage at 80 ° C for 3 weeks.

Although subjected to the same storage test even storage temperature 2 0 ° C, generation of decomposition and P 0 ₂ F ₂ § two on the PF ₆ Anion significant difference in this case is not observed, PF ₆ § two It was confirmed that the formation of ON was not due to the water carried in.

 [Analysis method]

 Analysis of anion contained in storage solution

After collecting the storage solution under an argon gas atmosphere, the concentrations of PF ₆ anion and P 及 び₂ F ₂ anion in the solution were quantified using a DX-120 ion chromatograph analyzer manufactured by Dionex. Incidentally, as a blank, by measuring 1. O mo l / Anion amount of the electrolytic solution of L i PF ₆ containing L before storage in a similar analysis, the decomposition of L i PF ₆ by this analysis does not take place It was confirmed.

Incidentally, as shown in Table one 1, when stored for one week only electrolyte as a blank test test under 7 0 ° C, any decomposition of significant PF ₆ § two on and P 0 ₂ The formation of F ₂ anion could not be confirmed.

 Analysis of ethanol contained in storage solution

 After collecting the preservation solution in an argon gas atmosphere, only the volatile components are collected under dry nitrogen by a known method (trap to trap condensation), and the amount of ethanol contained in the preservation solution is determined by gas chromatography. did.

As shown in Table 1, as a blank test of the storage test, only the electrolytic solution was stored at 70 ° C for 3 weeks, and no production of ethanol was confirmed in any case.

¾— 1 Example Example Example Example Example Example Example Example Comparative example Comparative example Blanc 1 2 3 4 5 6 1 2 試 験 Test Positive electrode 剂 Lithium manganese composite oxidation (A) (Β) (B) (B) (B ) (B) (A) (13)

 Kind of thing

LiPF ₆ decomposition inhibitor (a) (a) (a) (b) (c) (d)

Storage test method Lithium manganese composite oxide 5 5 5 75 75 99.4 98.4 100 100 1

Composition of (I) sift (wt%)

 τ · / I'll il

LiPF 6 minutes iff- elevation ili ^1] agent a S 25 25 10 25 0.6 1.6 0 0 storage test (I) PF ₆ 7 on the decomposition S 1 v 1 Π q 1 JL vX Ί Π A x 9v 1 Π

 (i mo \)

P〇 ₂ F ₂ Anion amount (imol) 1x10 9 1x10 4 2x10 2x10 Generated EtOH amount (mg) 0.05 0.05 0.05 0.05 0.05 0.05 <0.05 0.1 0.1 <0.05 Storage test (II) PF ₆ Anion degradation 38 17 15 25 240> 1

 (jumol)

P0 ₂ F ₂ anion fl (umo \) 37 17 14 20 198> 0.8 E t OH iS (mg) 0.4 0.3>0.05> 0.05 1.9> 0.01 High temperature cycle capacity f Retention P (%) 81 84 83 89 82 88 68 76

From Table 1, it can be seen that in the examples satisfying the requirements of the present invention, the high-temperature cycle characteristics have been greatly improved.

Above examples, Comparative Examples, since the high-temperature cycle characteristics Using PF ₆ 7 two on decomposition inhibitor to a particular lithium manganese oxide was found to be improved, the present inventors have PF ₆ Anion decomposition Focusing on lithium nickel oxide, which is one of the controls, the following study was further conducted.

 <1. Measurement of average voltage of composite oxide>

① A mixture of 75% by weight of the composite oxide to be measured, 20% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene (PTFE) powder is weighed and mixed well in a mortar to form a thin sheet. It was punched into a circle with a punch. At this time, the total weight was adjusted to 12.5 mgZcm ² in order to keep the thickness almost constant. This sample was further pressed against aluminum expanded metal to form a test electrode. The test electrode was dried at 120 ° C under reduced pressure for lhr.

(2) A CR202 type coin-type battery was created in a dry box in an argon atmosphere. That is, the test electrode was placed on the positive electrode can, a 25 m porous polyethylene film was placed thereon as a separator, pressed with a polypropylene gasket, and a 15 mm0 lithium metal foil was placed as a counter electrode. After placing the thickness adjustment sensor, 1 liter of a mixed solvent of ethylene carbonate (EC) and getyl carbonate (DEC) in a volume ratio of 3: 7 is added to lithium fluoride (1 liter). A solution in which 1 mol of L i PF ₆ ) was dissolved was used as a non-aqueous electrolyte solution, and the solution was added to the inside of the battery and sufficiently permeated. Then, a negative electrode can was placed and the battery was sealed.

③ Under the environment of 25 ° C, in the case of composite oxide (A), charge the battery prepared above at a constant current charge / discharge cycle of 0.5 mA / cm ² (charge upper limit 4.35 V, discharge The lower limit is 3.2 V), and the composite oxide (B) has a constant current charge / discharge cycle of 0.2 mA / cm ² (charge upper limit 4.20 V, discharge lower limit 3.2 V). The average voltage V e was calculated by the following equation.

V e = (Average charge voltage in the second cycle + Average discharge voltage in the second cycle) / 2 The average charge voltage or average discharge voltage in the above formula is obtained by measuring the voltage during charge or discharge at 2 second intervals. The value obtained by integrating the voltage with time is used for charging or discharging. It was calculated by dividing by the time required.

 The initial charge capacity of the composite oxide (A) used in this test was Q c (A) mA h / g, the initial discharge capacity was Q d (A) mA h / g, and the initial charge of the composite oxide (B) was The capacity was defined as Q c (B) mA / g, and the initial discharge capacity was defined as Q d (B) mAh / g.

 <2. High temperature cycle test>

 (Creation of positive electrode)

 A mixture of the composite oxide (A) and the composite oxide (B) is used as a positive electrode active material. A positive electrode was prepared in the same manner as in Example 1 except that the positive electrode was weighed at a ratio of 1.

 (Creation of negative electrode)

 A negative electrode was manufactured in the same manner as in Example 1. As in Example 1, a coin-type battery was assembled using the negative electrode as a test electrode and Li metal as a counter electrode in the same manner as when the average voltage of the composite oxide was measured, and the current was sufficiently low. The initial insertion capacity for the test in which Li ions were inserted (lower limit 0 V) and desorbed (upper limit 1.5 V) into the negative electrode was Q (F) mA h / g.

 (Assembly of battery element)

 A battery element was assembled in the same manner as in Example 1. At this time, the balance between the weight of the positive electrode active material and the weight of the negative electrode active material is determined by the weight of the composite oxide (B) in the mixture of the composite oxide (A) and the composite oxide (B). Calculate the ratio R from the following formula,

 R = (weight of composite oxide (B)) / {(weight of composite oxide (A))

 + (Weight of composite oxide (B))}

Using this, the following equation was set.

 Amount of positive electrode active material [g] / Amount of negative electrode active material [g] =

 Q (F) / {Qc (A) · (1-R) + Qc (B) · R} / 1.2 (Test method)

In order to compare the high temperature characteristics of the obtained batteries, the 1 hour rate current value of the battery, that is, 1 C, was set as the following formula for convenience, and the following test was performed. 1 C [mA] = {Q d (A). (1-R) + Q d (B)-R}

 x (amount of positive electrode active material [g〗]) First, two cycles of constant current 0.2 C charge / discharge and one cycle of constant current 1 C charge / discharge are performed at room temperature, and then constant current 0.2 at a high temperature of 50 ° C. One cycle of C charge / discharge and then 100 cycles of constant current 1 C charge / discharge were tested. The upper charging limit was 4.1 V and the lower limit voltage was 3.0 V.

 At this time, the ratio of the discharge capacity Qh (100) at the 100th cycle to the discharge capacity Qh (1) at the 1C cycle of the 100C test section at 50 ° C The high-temperature cycle capacity retention rate P] was determined by the following equation, and the high-temperature characteristics of the batteries were compared using this value of P.

 P [%] = {Qh (100) / Qh (1)} x l O O (v)

Example 7

As the lithium manganese composite oxide having a spinel structure, L i is Subineru type was 0.04 molar substitution on Mn support wells L i M n ₂ 0 _4, namely L i [Mn was _{9 e} L i. . _4] 0 ₄ was prepared in the same manner as in Preparation Example 1. The average particle size of the obtained lithium manganese composite oxide was 4. The average voltage measured by the above method was 4.060 V.

On the other hand, as the lithium secondary characterizing complex oxide having a layered structure, N i part of site is layered substituted with cobalt and aluminum L i N I_〇 _2, i.e.巿sales of L i [N i. ₈ . C 0. . I ₅ A 1. . ₅ ] 0 ₂ composition (average particle size 6.2

〃M) was used. The average voltage measured by the above method was 3.809 V.

 Next, a positive electrode was prepared by setting the weight mixing ratio R of the composite oxide (B) in the positive electrode active material to 0.5, and a high-temperature cycle test was performed by the above-described method to maintain the capacity after 100 cycles. The rate was determined. The results are shown in Table 1-2.

Example 8

As the lithium manganese composite oxide having a spinel structure, it it 0.04 lithium and aluminum in Mn site, 0.1 1 mol substituted spinel Le type L i Mn ₂ 0 _4, namely L i tMnusA l o. ! _: L i _{0. 04} ] 〇 ₄ It was prepared in the same manner as in Preparation Example 2. The average particle size of the obtained lithium manganese composite oxide was 7.4 zm. The average voltage measured by the above method was 4.071 V.

 The same oxide as in Example 1 was used as the composite oxide (B), and a positive electrode was prepared by setting the weight mixing ratio R of the composite oxide (B) in the positive electrode active material to 0.5. The test was performed. The results are shown in Table 1-2.

Example 9

 A high-temperature cycle test was performed in the same manner as in Example 2 except that the weight mixing ratio R of the composite oxide (B) in the positive electrode active material was set to 0.25. The results are shown in Table 1-2.

Example 10

 The composite oxide (B) used in Examples 7 to 9 was further pulverized in a nitrogen atmosphere, and this was newly used as the composite oxide (B) (average particle diameter 0.55 μm). The average voltage of this composite oxide (B) was 3.786 V.

 The other conditions were the same as in Example 9 to prepare a positive electrode, and a high-temperature cycle test was performed by the method described above. The results are shown in Table 1-2.

Comparative Example 3

 A high-temperature cycle test was performed in the same manner as in Example 7, except that the composite oxide (A) used in Example 7 was used alone as the positive electrode active material. The results are shown in Table 1-2.

Example 11 (Comparative Example 4 for the third aspect of the present invention)

As a lithium manganese composite oxide having a spinel type structure, spinel type LiMn ₂ 〇 ₄ in which lithium and conjugate are substituted at Mn site by 0.04 and 0.10 mol, respectively, that is, LifMnus C o o. L i o. OJC was created by the following method.

Manganese sesquioxide (Mn ₂ 0 _3), lithium carbonate _{(L i 2 C 0 3)} , carbonate cobalt (C o C 0 ₃₎ was used as a starting material, it molar ratio of about 0.5 that of Compound 9 3 : 0.52: 0.10. Ethanol was added to the mixture, and the mixture was ground well in a mortar to form a uniform mixture and then dried. The resulting mixture is airborne at 500 ° C for 6 hours, 600 ° C for 6 hours, 700 ° C for 6 hours, 800 ° C For 6 hours, and then calcined in air at 850 ° C. for 24 hours, and slowly cooled to room temperature at 0.2 ° C./min. The average particle size of the obtained lithium manganese composite oxide was 5.2 zm. The average voltage measured by the above method was 4.081 V.

 The same oxide as in Example 1 was used as the composite oxide (B), and a positive electrode was prepared by setting the weight mixing ratio R of the composite oxide (B) in the positive electrode active material to 0.5. The test was performed. The results are shown in Table 1-2.

Example 12 (Comparative Example 5 for the third embodiment of the present invention)

As the lithium manganese composite oxide having a Subineru structure, commercially available unsubstituted L i M n 204 (elemental _{analysis:... L i ..Mn 2} ..0 4 with measuring the average voltage at said process As a result, it was 4.052 V.

The same oxide as in Example 7 was used as the composite oxide (B), and a positive electrode was prepared with the weight mixing ratio R of the composite oxide (B) in the positive electrode active material being 0.5. The test was performed. The results are shown in Table 1-2.

¾-2 Complex oxide (A) Composition formula Complex oxide (B) Complex oxide (A) Complex oxide (Β) High temperature cycle

M n-site 11 conversion element mole !: Heavy S ratio Average ί¾ pressure Average ¾ pressure maintenance rate

M n A 1 C o L i R V V Ρ Example 7 1.96 0.00 0.00 0.04 0.50 4.060 3.809 85% Example 8 1.85 0.11 0.00 0.04 0.50 4.071 3.809 88%

¾Example 9 1.85 0.12 0.00 0.04 0.25 4.071 3.809 84% Example 1 0 1.85 0.12 0.00 0.04 0.25 4.071 3.786 89% Example 1 1 1.86 0.00 0.10 0.04 0.50 4.041 3.809 79%

 2.00 0.00 0.00 0.00

Example 1 2 0.50 4.052 3.809 74% Comparative Example 3 1.96 0.00 0.00 0.04 0.00 4.060 65%

Example た, in which the composite oxide (A) was a composite oxide in which part of the manganese site was replaced with lithium, exhibited very good high-temperature characteristics with a retention of 85% in a high-temperature 100-cycle test. You can see that. In Example 8, the high-temperature cycle retention rate was further increased by substituting aluminum and using a composite oxide (A) having a high average voltage. Also, when the mixing ratio of the composite oxide (B) is reduced as in Example 9, the high-temperature cycle retention rate slightly decreases, but as in Example 10, the average voltage of the composite oxide (B) is reduced. It can be seen that the use of a material improves the maintenance rate.

When the composite oxide (A) is used alone as in Comparative Example 3, the high-temperature cycle retention is very low. Moreover, the use of PF ₆ Anion decomposition inhibitor as in Example 1 1 and 1 2, PF ₆ good § two turned compared to the comparative example decomposition inhibitor is not added to clearly re-Gu Le retention. However, in Examples 11 and 12, the composite oxide (A) having an average potential lower than 4.059 V was used, so that the composite oxide (A) having an average voltage higher than 4.05 V was used. )), It can be seen that the high-temperature cycle maintenance ratio is slightly lower than those of Examples 7 to 10 using). Industrial applicability

 ADVANTAGE OF THE INVENTION According to this invention, when used as a lithium secondary battery, the positive electrode material with favorable high temperature characteristics can be provided. Further, according to the present invention, a lithium secondary battery having good high-temperature characteristics can be provided. Therefore, since inexpensive material manganese can be used practically as a cathode material, a high-performance, safe and inexpensive lithium secondary battery can be supplied to a wide range of uses, and its industrial value is great.

Claims

The scope of the claims

1. In a positive electrode material for a lithium secondary battery containing a manganese oxide and / or a lithium manganese composite oxide as a positive electrode active material, a battery element is prepared using the positive electrode material, and a positive electrode material charged with the battery element is prepared. the positive electrode material for a lithium secondary battery degradation amount of PF ₆ § two on as determined by the following storage test is a storage test (I) is characterized and this is 1 xl 0〃 mo 1 below.

Storage test (I)

a 1) A positive electrode formed by molding 24 mg of a positive electrode material into a circular shape with a diameter of 12 mm, and crimping it to a current collector (a circular aluminum expanded metal with a diameter of 16 mm). metal, 1 as an electrolyte solution mixture of O mo lZL Echire emissions carbonate and Jechiruka one containing L i PF ₆ of Boneto (volume ratio 3: 7). assembled battery element using the charge current density 0 this After charging to a maximum voltage of 4.2 V at 2 mA / cm ² , the battery element was then disassembled, and the charged positive electrode was taken out.

b 1) Under an argon gas atmosphere with a dew point of 1 Ί5 ° C or less

c 1) In a polytetrafluoroethylene container dried at 80 ° C for 3 hours, d 1) 1.5 ml of ethylene carbonate containing 1.5 mol of L i PF ₆ and G Mixed with 3.5 ml (acid content: 2.0 mmol / L or less, P 0 ₂ F ₂ anion: 0.5 mmol / L or less, and ethanol: 0.01 mg or less) Immersed in

e 1) One week at 80 ° C

Store and measure the amount of PF ₆ dione in the mixed solution before and after storage (measurement temperature: 20 ° C), and calculate the amount of PF ₆ dione decomposition from the difference.

2. The amount of P 0 ₂ F ₂ anion contained in the solution after storage obtained according to the storage test (I) is 1 X 10 1mo 1 or less at 20 ° C. The positive electrode material for a lithium secondary battery according to the above.

3. The positive electrode material for a lithium secondary battery according to claim 1, wherein the positive electrode material contains a binder resin.

4. The positive electrode material for a lithium secondary battery according to any one of claims 1 to 3, wherein a PF ₆ anion decomposition inhibitor is dispersed and mixed in the positive electrode material.

5. Oite manganese oxide and / or a positive electrode active material and a positive electrode material for a lithium secondary battery containing a PF ₆ 7 two on decomposition inhibitor comprising a lithium-manganese composite oxide, as the PF ₆ Anion decomposition inhibitor A positive electrode material for a lithium secondary battery, wherein a material having a decomposition amount of PF ₆ anion measured by the following storage test (II) of ₆ × 10 mo 1 or less is used.

Storage test (Π)

a 2) Li _{1 + x} Mn ₂ _ _x 0 ₄ (where 0 _{≤ x} ≤ 0.05) Lithium-manganese composite oxide with a spinel structure of composition The corresponding lithium-manganese composite oxide (0.05 ≤ L i / Mn molar ratio ≤ 0.09)

b 2) Under an argon gas atmosphere with a dew point of less than 75 ° C,

c 2) In a polytetrafluoroethylene container dried at 80 ° C for 3 hours, d 2) mixed with 160 mg of the above PF ₆ -dione decomposition inhibitor,

e 2) 1. including Omo l / L of L i PF _6, a mixture of ethylene carbonate 2. 4 ml Jefferies chill carbonate 5. 6 m l (acid content: 2. Ommo l / L or less, P_〇 ₂ F ₂ Anion : 0.5mmol / L or less and ethanol: 0.5Olmg or less)

f 2) One week at 70 ° C

Save, measure the amount of PF ₆ anion in the mixture before and after storage (measurement temperature: 20 ° C), and determine the amount of PF ₆ anion decomposed.

6. The method according to claim 5, wherein the amount of P 0 ₂ F ₂ anion contained in the solution after storage obtained according to the storage test (II) is not more than 5 10〃1110 1 in 20 ^. Positive electrode material for lithium secondary batteries.

 7. The lithium secondary battery according to claim 5 or 6, wherein the amount of ethanol contained in the solution after storage is 1 mg or less when the storage test (II) is further extended for 2 weeks. Positive electrode material.

8. PF ₆ 7 two on decomposition inhibitor is any of the claims 5 to 7 are dispersed mixed The positive electrode material for a lithium secondary battery according to any one of the above.

9. The positive electrode material for a lithium secondary battery according to any one of claims 4 to 8, wherein the PF ₆ anion decomposition inhibitor contains a lithium nickel composite oxide.

10. The PF ₆ anion decomposition inhibitor is a compound containing at least one element selected from the group consisting of Groups 15 and 16 of the Periodic Table of the Elements, and at least a secondary amino group in the molecule. Compounds having at least one tertiary amino group in the molecule, compounds having at least one amide bond in the molecule, compounds having at least one nitrogen-containing heterocycle in the molecule, 9. The positive electrode material for a lithium secondary battery according to claim 4, further comprising a compound having at least one hydroxyl group in a molecule.

11. The method according to any one of claims 4 to 10, wherein the amount of the PF ₆ anion decomposition inhibitor added is in the range of 0.001 to 80 wt% with respect to the positive electrode active material. Positive electrode material for lithium secondary batteries.

12. The positive electrode material for a lithium secondary battery according to claim 9, wherein the amount of the PF ₆ anion decomposition inhibitor added is in the range of 1 to 80 wt% based on the positive electrode active material.

13. The positive electrode for a lithium secondary battery according to claim 10, wherein the amount of the PF ₆ anion decomposition inhibitor added is in the range of 0.0001 to 10 wt% with respect to the positive electrode active material. material.

14. Manganese oxide and lithium or lithium manganese composite oxide have a spinel structure, and a part of manganese site is replaced by at least one element selected from typical elements. The positive electrode material for a lithium ion secondary battery according to any one of claims 1 to 13, wherein

 15. The positive electrode material for a lithium ion secondary battery according to claim 14, wherein the typical element that substitutes a part of the manganese site is aluminum and / or lithium.

 16. The positive electrode material for a lithium ion secondary battery according to claim 14 or 15, wherein the substitution amount of the typical element is 0.05 mol or more in 2 mol of manganese.

17. The positive electrode material contains a lithium manganese composite oxide having a spinel structure and a lithium nickel composite oxide having a layered structure, and part of the manganese site of the lithium manganese composite oxide is composed of another element. And the average voltage of the other element-substituted lithium manganese composite oxide measured by the following method (I) is as follows:

The positive electrode material for a lithium ion secondary battery according to any one of claims 1 to 9, 11, 12, and 14 to 16, wherein the positive electrode material has a voltage of 4.059 V or more.

<Measurement method of average voltage (I)>

(1) The composite oxide is weighed at 75% by weight, acetylene black at 20% by weight, and polytetrafluoroethylene (PTFE) powder at 5% by weight and mixed to form a thin sheet. After adjusting the total weight to 12.5 mgZ cm ² , this sample is further pressed against aluminum expanded metal to form a test electrode. The test electrode was under reduced pressure. Dry at C for 1 hour.

② In an argon atmosphere, a porous polyethylene film of 25 2m is used as a separator, lithium metal foil is used as a counter electrode, and a nonaqueous electrolyte solution is used, in which the volume ratio of ethylene carbonate and getylcapone is 3: using a solution prepared by dissolving 1 mol / Li Uz torr of lithium hexafluorophosphate (L i PF ₆₎ 7 mixed solvent, to prepare a coin-type battery of CR 2 03 2 type.

③ The obtained coin-type battery is subjected to a constant current charge / discharge cycle of 0.5 mA / cm ² (charge upper limit 4.35 V, discharge lower limit 3.2 V) in an environment of 25 ° C. The average voltage V e

 V e = (average charge voltage in the second cycle + average discharge voltage in the second cycle) / 2.

 The average charge voltage or average discharge voltage is calculated by measuring the voltage during charge or discharge at 2-second intervals, and dividing the value obtained by integrating the voltage over time by the time required for charge or discharge.

 1 8. The lithium nickel composite oxide having an average voltage of 3.830 V or less when measured by the following measurement method (II).

The positive electrode material for a lithium ion secondary battery according to any one of items 4 to 17.

<Measurement method of average voltage (II)>

(1) A mixture of 75% by weight of lithium nickel composite oxide, 20% by weight of acetylene black, and 5% by weight of borotetrafluoroethylene powder is mixed to form a thin sheet. After adjusting the total weight to 12.5 mg / cm ² , this sheet is further pressed against aluminum expanded metal to form a test electrode. test The electrode is dried under reduced pressure at 120 ° C for 1 hour.

② In an argon atmosphere, a 25〃m porous polyethylene film was used as a separator, lithium metal foil was used as a counter electrode, and a nonaqueous electrolyte solution was used, in which the volume ratio of ethylene carbonate and getyl carbonate was 3: using a solution obtained by dissolving hexafluoride potash lithium phosphate in 1 mol / liter (L i PF ₆₎ 7 mixed solvent, to prepare a coin battery of CR 2 0 3 2 type.

③ The obtained coin-type battery, in an environment of 2 5 ° C, current density 0. 2 m constant current charge and discharge cycles of the A / cm ² (charging upper limit 4. 2 V, the discharge lower limit 3. 2 V ) To change the average voltage V e

V e = (average charge voltage in the second cycle + average discharge voltage in the second cycle) / 2.

 The average charge voltage or average discharge voltage is the value obtained by measuring the voltage during charge or discharge at 2-second intervals and integrating the voltage over time by the time required for charge or discharge.

 19. The lithium according to any one of claims 14 to 18, wherein the weight ratio of the lithium nickel composite oxide to the total amount of the lithium manganese composite oxide and the lithium nickel composite oxide is 0.7 or less. Positive electrode material for ion secondary batteries.

20. Any one of claims 1 to 19, wherein at least 80% of the decomposition product of PF ₆ anion in the liquid after the storage test (I) or (II) is P 0 ₂ F ₂ anion. The positive electrode material for lithium secondary batteries described in (1).

 21. A positive electrode material for a lithium ion secondary battery containing a lithium manganese composite oxide having a spinel type structure and a lithium nickel composite oxide having a layered structure, wherein the manganese site of the lithium manganese composite oxide A positive electrode material for a lithium ion secondary battery, characterized in that a part of the positive electrode material is substituted with at least one element selected from typical elements.

 22. The positive electrode material for a lithium ion secondary battery according to claim 21, wherein the typical element that substitutes a part of the manganese site is aluminum and / or lithium.

23. Claim that the substitution amount of the typical element is 0.05 mol or more in 2 mol of manganese Item 21. The positive electrode material for a lithium ion secondary battery according to Item 21 or 22.

 2 4. A positive electrode material for a lithium ion secondary battery, comprising: a lithium manganese composite oxide having a spinel structure and a lithium nickel composite oxide having a layered structure, wherein the manganese site of the lithium manganese composite oxide is Is partially substituted by another element, and the average voltage of the other element-substituted lithium manganese composite oxide measured by the following measurement method (I) is 4.059 V or more. A positive electrode material for a lithium ion secondary battery.

<Measurement method of average voltage (I)>

(1) The composite oxide is weighed at 75% by weight, acetylene black at 20% by weight, and polytetrafluoroethylene (PTFE) powder at 5% by weight and mixed to form a thin sheet. After adjusting the total weight to be 12.5 mg / cm ² , this sample is further pressed against aluminum expanded metal to form a test electrode. The test electrode is dried for 1 hour at 120 ° C under reduced pressure.

(2) Under an argon atmosphere, a 25 / m porous polyethylene film was used as a separator, lithium metal foil was used as a counter electrode, and a non-aqueous electrolyte solution was used in which the volume ratio of ethylene carbonate to getyl carbonate was 3: 7. using a solution prepared by dissolving 1 mol / Li Tsu six full Uz lithium phosphate torr (L i PF ₆₎ in a mixed solvent of, to prepare a coin-type battery of CR 2 03 2 type.

③ The obtained coin-type battery is charged and discharged at a constant current of 0.5 mA / cm ² at an environment of 25 ° C (charge upper limit 4.35 V, discharge lower limit 3.2 V). And the average voltage V e

 V e = (average charge voltage in the second cycle + average discharge voltage in the second cycle) / 2.

 The average charge voltage or average discharge voltage is calculated by measuring the voltage during charge or discharge at 2-second intervals, and dividing the value obtained by integrating the voltage over time by the time required for charge or discharge.

25. The lithium nickel composite oxide according to any one of claims 21 to 24, wherein the lithium nickel composite oxide has an average voltage of 3.830 V or less when measured by the following measurement method (II). The positive electrode material for a lithium ion secondary battery according to one of the above. Method of measuring average voltage (II)>

(1) Mix 75% by weight of lithium nickel composite oxide, 20% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene powder, and form a thin sheet. After adjusting the total weight to 12.5 mg / cm ² , this sheet is further pressed against aluminum expanded metal to form a test electrode. The test electrode is dried for 1 hour at 120 ° C under reduced pressure.

② In an argon atmosphere, a porous polyethylene film of 25 2m is used as a separator, lithium metal foil is used as a counter electrode, and a nonaqueous electrolyte solution is used, in which the volume ratio of ethylene carbonate and getylcapone is 3: using a solution prepared by dissolving 1 mol / Li tree torr six full Uz lithium phosphate (L i PF ₆₎ 7 mixed solvent, to prepare a coin battery of CR 2 03 2 type.

③ The obtained coin battery was subjected to a constant current charge / discharge cycle with a current density of 0.2 mA / cm ² (charge upper limit 4.2 V, discharge lower limit 3.2 V) at 25 ° C. , The average voltage V e

V e = (average charge voltage in the second cycle + average discharge voltage in the second cycle) / 2.

 The average charge voltage or average discharge voltage is the value obtained by measuring the voltage during charge or discharge at 2-second intervals and integrating the voltage over time by the time required for charge or discharge.

26. The weight ratio of the lithium nickel composite oxide to the total amount of the lithium manganese composite oxide and the lithium nickel composite oxide is 0.7 or less, wherein the weight ratio is 0.7 or less. The positive electrode material for a lithium ion secondary battery according to any one of the above.

 27. A positive electrode for a lithium ion secondary battery, comprising an active material layer containing the positive electrode material for a lithium secondary battery according to claim 1 formed on a current collector.

 28. A lithium ion secondary battery comprising the positive electrode material for a lithium secondary battery according to claim 1 in a positive electrode.

2 9. Lithium comprising a positive electrode using the positive electrode material for a lithium secondary battery according to any one of claims 1 to 26, a negative electrode, and an electrolytic solution obtained by dissolving a lithium salt in a solvent. Rechargeable lithium battery.

 30. The lithium secondary battery according to claim 28 or 29, wherein the negative electrode contains a carbon material.

3 1. The lithium secondary battery according to the lithium salt is one either of claims 2 8 to 3 0 a L i PF _6.