WO2014181925A1

WO2014181925A1 - Electrolyte composition with excellent high-temperature stability and performance and electrochemical element including same

Info

Publication number: WO2014181925A1
Application number: PCT/KR2013/006738
Authority: WO
Inventors: 송현곤; 김영수
Original assignee: 국립대학법인 울산과학기술대학교 산학협력단
Priority date: 2013-05-10
Filing date: 2013-07-26
Publication date: 2014-11-13
Also published as: KR20140133219A

Abstract

An electrolyte composition according to the present invention includes: (i) a solvent; (ii) a lithium salt; and (iii) 0.1 to 5% by weight of a pullulan series polymeric resin based on the total weight of the electrolyte composition, characterized in that the pullulan series polymeric resin is a polymer, oligomer or a mixture thereof containing at least one repeat unit represented by formula 1. The electrolyte composition according to the present invention has excellent durability at room temperature or higher temperature, and prevents generation of a gas due to the breakdown of the electrolyte at high temperature so as to improve the stability of an electrochemical element, thus effectively applied to manufacture the electrochemical element.

Description

Electrolyte composition having excellent high temperature stability and performance and electrochemical device including same Field of the Invention The present invention provides high temperature stability and performance for use in electrochemical device fields such as lithium secondary batteries, capacitors, solar cells, and energy storage devices. The present invention relates to an excellent electrolyte composition, and more particularly, to an electrolyte composition exhibiting excellent life characteristics in phase silver and silver, and improving the safety of electrochemical devices by suppressing gas generation due to decomposition of electrolyte at high temperatures. . Background

As the technology development and demand for mobile devices increase, the demand for secondary batteries as energy sources is increasing rapidly. Among them, many studies have been conducted on lithium secondary batteries having high energy density and high discharge voltage.

A lithium secondary battery may be classified into a lithium ion battery containing a liquid electrolyte as it is, a lithium ion polymer battery containing an electrolyte in a gel-like form, and a lithium polymer battery of a solid electrolyte, depending on the form of the electrolyte.

Lithium ion battery containing liquid electrolyte has a risk of leakage of electrolyte when manufactured in pouch form, and may ignite / explode when exposed to high temperature and / or high pressure. In addition, even if a large current flows within a short time due to overcharging, external short circuit, nail penetration, local crush, etc., there is a risk of fire / explosion while the battery is heated by IR heating.

When the temperature of the battery rises, the reaction between the electrolyte and the electrode is accelerated, and as a result, reaction heat is generated, thereby increasing the silver content of the battery, which in turn accelerates the reaction between the electrolyte and the electrode. As a result, the temperature of the battery rises rapidly, which in turn accelerates the reaction between the electrolyte and the electrode. This vicious cycle turns the battery on A thermal runaway phenomenon occurs when the temperature rises sharply, and when the temperature rises to a certain level or more, the battery may ignite. In addition, as a result of reaction between the electrolyte and the electrode, gas is generated and the internal pressure of the battery increases, and the lithium secondary battery explodes above a certain pressure. The risk of ignition / explosion can be said to be the most fatal drawback of lithium secondary batteries.

Therefore, the capacity of the lithium ion polymer battery which has the advantage that it is low in the possibility of leakage of electrolyte solution, is high, and it is possible to make ultra thin and lightweight the shape of a battery, etc. is increasing. However, a lithium ion polymer battery in which the electrolyte is contained in a gel-like form has a high current discharge due to the high viscosity of the electrolyte, which impedes the migration of lithium silver, resulting in high lithium ion mobility and high resistance in the battery. It is disadvantageous, and has a disadvantage in that the volume energy density is lower than that of a lithium ion battery, and the manufacturing process is relatively complicated, resulting in a high manufacturing cost.

Accordingly, there is a need for the development of an electrolyte composition that can provide excellent battery performance and safety by controlling gas generation due to electrolyte decomposition at high temperature while exhibiting excellent life characteristics at room temperature and high temperature. SUMMARY OF THE INVENTION An object of the present invention is to provide an electrolyte composition which exhibits excellent life characteristics at phase silver and high temperature, and can suppress the generation of gas due to electrolyte decomposition in silver and thereby improve the safety of an electrochemical device.

Still another object of the present invention is to provide an electrochemical device including the electrolyte composition.

In order to achieve the above object, the present invention

(i) a solvent;

(ii) lithium salts; And

(iii) 0.1 to 5 weight> pullulan based on total weight of electrolyte composition (pullulan) polymer resin

As an electrolyte solution composition comprising:

The pullulan-based polymer resin is a polymer, an oligomer or a mixture thereof containing one or more repeating units represented by the following general formula (1):

In Chemical Formula 1,

Each R is independently H or (CH ^ CN,

1 is an integer of 1-10.

In addition, the present invention provides an electrochemical device comprising the electrolyte composition. 1 is a graph showing the discharge capacity of the battery according to the charge and discharge cycle.

2 is a graph showing the change in thickness with time of the battery left in a high temperature chamber of 80 ^° C. DETAILED DESCRIPTION OF THE INVENTION The electrolyte composition according to the present invention comprises (i) a solvent; (ii) lithium salts; And (Hi) an electrolyte solution composition containing 0.1 to 5 wt% of a pullulan polymer resin based on the total weight of the electrolyte composition, wherein the pullulan polymer resin is represented by Formula 1 below. It is characterized in that the electrolyte composition, characterized in that the polymer, oligomer or a mixture thereof containing at least one repeating unit.

In Chemical Formula 1,

Each R is independently H or (CH iCN,

1 is an integer of 1-10. The pullulan-based polymer resin may have a weight average molecular weight of 1,000 to 10, 000, 000. The solvent is not particularly limited as long as it is an organic solvent used as a non-aqueous solvent of a conventional lithium secondary battery. For example, a carbonate compound, a lactone compound, an ether compound, a sulfolane compound, a dioxolane compound, a ketone compound, a nitrile compound, And halogenated hydrocarbon compounds. More specifically, carbonates, such as dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, ethylene glycol dimethyl carbonate, propylene glycol dimethyl carbonate, ethylene glycol diethyl carbonate, vinylene carbonate , Lactones such as Y-butyrolactone, dimethicethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, ethers of 1,4-dioxane, sulfolane and 3-methylsulfuran Sulfolanes, dioxolanes such as 1,3-dioxolane, ketones such as 4-methyl-2-pentanone, nitriles such as acetonitrile, pyridiononitrile, valeronitrile, benzonitrile, 1,2 Halogenated tower hydrogens such as dichloroethane, other methyl formate, dimethylformamide diethylformamide, dimethyl sulfoxide and imida; Salts, may be mentioned Lee Eun-sung liquid such as a quaternary ammonium salt. They may also be used in combination, preferably cyclic carbonates and linear carbonates may be used in combination. The lithium salt is a material that is readily soluble in the non-aqueous solvent, such as _{LiCl, LiBr, Lil, LiC10 4} , LiBF 4, LiBioCho, LiPF 6, LiCF 3 S0 3, LiCF 3 C0 2, LiAsF 6l LiSbF 6, L iA ! Cl _4l CH ₃ S0 ₃ Li, CF ₃ S0 ₃ Li, (CF ₃ S0 ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic carbonate, lithium tetraphenylborate, imide or combinations thereof can be used have.

Cyanobanunggi of the pullulan-based polymers included in the electrolyte composition of the present invention facilitates the smooth movement of lithium ions at the interface with the electrode, and the hydroxyl (-0H) bandunger is a strong hydrogen bond. By preventing the electrolyte from being denatured or generated gas has the advantage of achieving excellent battery performance and safety at the same time. The pullulan-based polymer resin may include 1 to 5% by weight based on the total weight of the electrolyte composition, and also 0.1 to 4% by weight, 0.1 to 3% by weight, 0.1 to 2.5 based on the total weight of the electrolyte composition Weight 0.1 to 2 weight ¾, 0.2 to 5 weight ¾, 0.2 to 4 weight%, 0.2 to 3 weight ¾, 0.2 to 2.5 weight%, 0.2 to 2 weight%, 0.3 to 5 weight%, 0.3 to 4 weight%, 0.3-3 weight%, 0.3-2.5 weight%, 0.3-2 weight ¾, 0.4-5 weight%, 0.4-4 weight%, 0.4-3 weight%, 0.4-2.5 weight%, 0.4-2 weight%, 0.5- 5 weight%, 0.5 to 4 weight%, 0.5 to 3 weight%, 0.5 to 2.5 weight%, 0.5 to 2 weight% may be included.

If the content of the pullulan-based polymer resin is less than 0.1 weight ¾, it is not preferable because it does not exert effects such as promoting the movement of lithium ions or preventing electrolyte degeneration, and the content of the pullulan-based polymer resin is more than 5% by weight. In this case, the viscosity of the electrolyte becomes too high and the ion conductivity of the electrolyte drops sharply, which is not preferable because the output characteristics of the battery deteriorate when used in the battery.

In addition, the electrolyte composition of the present invention may have a lithium ion transfer constant (transference numbe r) of 0.5 or more, preferably 0.6 or more, more preferably 0.7 or more. The reason why the electrolyte composition of the present invention has a high lithium ion transfer constant value is due to the interaction between the pullulan-based polymer resin and lithium ions and anions included in the electrolyte composition. For example, in the case of an electrolyte composition containing LiPF ₆ as a lithium salt, the pullulan-based polymer resin and the anion PF are relatively strongly bonded to each other. Due to the high activation energy required for copper, the movement is slow. On the other hand, Li ⁺ has a relatively weak bond, so the movement energy is low and the movement is fast. This relative fastness is represented by the high ion transfer constant of lithium ions.

In addition, the electrolyte composition of the present invention may further include an electrolyte additive other than the pullulan-based polymer resin,

The electrolyte additive may be a polymer, an oligomer or a mixture thereof containing one or more repeating units represented by the following Formula 2.

In Chemical Formula 2

X, Y and Z are each independently H, 0H or (CH ₂ ) _n CN,

Each R ′ is independently H or (C¾) ₀ CN,

At this time, m is an integer of 0-10, n and 0 are each independently an integer of 1-10.

When the electrolyte additive is further included, the electrolyte composition of the present invention is 3

It may cause a physical or chemical gelling reaction at 0 ^° C. or higher, preferably 30 to 80 ^° C., more preferably 45 to 60 ^° C.

In addition, since the temperature is proportional to the function of time, the electrolyte composition further comprising the electrolyte solution additive for a long time at 10 to 30 ^° C, preferably 15 to 25 ^° C, is less than the temperature causing the gelation. In some cases, gelation of the electrolyte composition may be induced.

The gelation refers to the change of the electrolyte composition from the liquid state to the gel state through the interaction between the electrolyte additive itself or the electrolyte additive and the solvent. For example, when the electrolyte additive is a polymer, an oligomer, or a mixture thereof including at least one repeating unit represented by Chemical Formula 1, the electrolyte composition of the present invention may be a liquid through interaction between the electrolyte additive itself or the electrolyte additive and a solvent. It can change from gel state to gel state, and the cyano (black nitrile) reaction of the electrolyte additive contained in the gelled electrolyte composition helps the lithium silver to move smoothly at the interface with the electrode, and hydroxy ( -0H) The reactor prevents the gel from breaking down or deforming due to strong hydrogen bonding.

Therefore, the electrolyte composition of the present invention further comprising the electrolyte additive may have a high ion conductivity even after gelation, even though it is in a gel state.

The amount of the electrolyte additive added is based on the total amount of the electrolyte composition.

0.01 to 15% by weight, 0.01 to 10% by weight, 0.1 to 15% by weight, 0.1 to 10% by weight, 0.1 to 5% by weight, 0.1 to 4% by weight, 0.1 to 3% by weight, 0.1 to 2.5% by weight, 0. 1 to 2 weight%, 0.2 to 10 weight%, 0.2 to 5 weight 0.2 to 4 weight 0.2 to 3 weight%, 0.2 to 2.5 weight%, 0.2 to 2 weight%, 0.3 to 10 weight%, 0.3 to 5 weight% , 0.3 to 4% by weight, 0.3 to 3% by weight, 0.3 to 2.5% by weight, 0.3 to 2% by weight, 0.4 to 10% by weight ᅳ 0.4 to 5% by weight, 0.4 to 4% by weight, 0.4 to 3% by weight, 0.4 to 2.5 weight ¾, 0.4 to 2 weight%, 0.5 to 10 weight ¾>, 0.5 to 5 weight%, 0.5 to 4 weight%, 0.5 to 3 weight%, 0.5 to 2.5 weight ¾, 0.5 to 2 weight% Can be.

The electrolyte composition of the present invention described above may be used in an electrochemical device including a positive electrode and a negative electrode. In the present invention, the electrochemical device includes all the elements for electrochemical reaction, for example, may be any kind of primary, secondary battery, fuel cell, solar cell, capacitor or energy storage device, lithium secondary battery It may be a capacitor or a solar cell, preferably a lithium ion battery, a lithium ion polymer battery, or a lithium polymer battery.

In particular, in the case of a lithium secondary battery, the electrolyte composition of the present invention is injected in a liquid state into an electrode structure composed of a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. To produce a lithium secondary battery. As the positive electrode, the negative electrode, and the separator constituting the electrode structure, all those conventionally used in manufacturing a lithium secondary battery may be used.

The positive electrode is prepared by coating a mixture of a positive electrode active material, a conductive material and a binder on a current collector and then drying it. A positive electrode active material may be preferably a lithium-containing transition metal oxide, for example, lithium cobalt oxide (LiCo0 ₂ ), A layered compound such as litop nickel oxide (LiNi0 ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn ₂ - _x 0 4 (wherein X is 0 to 0.33), LiMn0 ₃ , LiMn ₂ 0 ₃ , LiMn0 _2, and the like; Lithium copper oxide (Li ₂ Cu02); LiV ₃ O _8> LiFe ₃ O ₄₎ Vanadium oxides such as V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; Ni-site type lithium nickel oxide represented by the chemical formula LiNii- _x Mx0 ₂ , wherein M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3; Formula LiMn ₂ - _x M _x 0 ₂ , wherein M = Co, Νί, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1, or Li ₂ Mn ₃ M0 ₈ , where M = Fe, Co, A lithium manganese composite oxide represented by Ni, Cu or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with alkaline earth metal silver; Disulfide compounds; Fe ₂ (Mo0 ₄ ) ₃ and the like.

The conductive material is typically added in an amount of 1 to 50% by weight based on the total weight of the mixture including the positive electrode active material, and is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, natural or artificial alum Abyss; Carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp block and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride, aluminum and nickel powders; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component that assists the bonding of the active material and the conductive material to the current collector, and is generally added in an amount of 1 to 50 weight ¾ based on the total weight of the mixture including the positive electrode active material, for example, polyvinyl fluoride Leadene, polyvinyl alcohol, carboxymethyl salose (CMC), starch, hydroxypropylcellose, regenerated cellrose, polyvinylpyridone, tetrafluoroethylene polyethylene, polypropylene, ethylene- Propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like can be used.

The negative electrode is manufactured by coating and drying the negative electrode material on the negative electrode current collector, and if necessary, the components as described above may be further included.

The negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, carbon, nickel, titanium on the surface of copper or stainless steel , Surface treated with silver or the like, aluminum-cadmium alloy or the like can be used.

As said negative electrode material, For example, Carbon, such as a decoated softened carbon and an inferior carbon; Sn _x Mei-xMe ' _y O _z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, Group 2, Group 3 elements, halogen; 0 <x≤l metal composite oxides such as l <y <3; 1 <ζ <8); Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; _{SnO, Sn0 2) PbO, Pb0} 2, Pb 2 0 3, Pb 3 0 4, Sb 2 0 3l Sb 2 0 4, Sb 2 0 5, GeO, Ge0 2, Bi 2 0 3, Bi 2 0 4, and Oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni system material etc. are mentioned.

The separator is interposed between the cathode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally from 0.01 to 10, the thickness is generally 5 to 300 i / m.

As the separator, for example, olefin polymers such as chemical resistance and hydrophobic polypropylene; Sheets or non-woven fabrics made of glass fibers or polyethylene, etc. may be used.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may have a cylindrical, square, pouch or coin type using a can. In addition, it may be a cable type lithium secondary battery having a structure such as a linear wire.

Hereinafter, the present invention will be described with reference to the following Examples and Comparative Examples, but the present invention is not limited thereto. Example Example 1 Preparation of Electrolyte

To a 1: 2 (volume ratio) organic solvent mixture of ethylene carbonate as a cyclic carbonate and ethyl methyl carbonate as a linear carbonate, LiPF ₆ was added at a concentration of 1 M, and a pullulan-based polymer resin (R = (CH ₂ ) ₂ CN and a weight average molecular weight of 300,000) were added in an amount of 2 wt% based on the total weight of the electrolyte to prepare an electrolyte solution.

[Formula 1]

Example 2: Fabrication of Lithium Secondary Battery

95% by weight of LiCo0 ₂ , ₂ % by weight of Super-P (conductor) and 3% by weight of PVdF (binder) were added to the solvent N-methyl-2-pyridone (NMP) as a positive electrode active material. To prepare a, the positive electrode was prepared by coating, drying, and pressing on both sides of the aluminum foil, respectively.

A negative electrode mixture slurry was prepared by adding 97.5 weight ¾ of natural graphite, 1.5 weight% of SBR (Styrene-Butadiene Rubber, binder) and 1 weight ¾ of CMCC CarboxyMethyl Cellulose (thickener and binder) as a negative electrode active material to water as a solvent. The negative electrode was prepared by coating, drying and pressing on both sides of the copper foil.

After the electrode assembly was manufactured by stacking the positive electrode and the negative electrode using NH616 (product name) manufactured by Asahi Corporation, a lithium secondary battery was prepared by injecting the electrolyte solution prepared in Example 1 above. Comparative Example 1: Preparation of Electrolyte

An electrolyte solution was prepared in the same manner as in Example 1, except that the polymer resin was not added. Comparative Example 2: Fabrication of Lithium Secondary Battery

A lithium secondary battery was manufactured in the same manner as in Example 2, except that the electrolyte prepared in Comparative Example 1 was injected as the electrolyte. Experimental Example 1: Evaluation of Life Characteristics

The cells prepared in Example 2 and Comparative Example 2 were placed in a chamber at 23 ^° C., and then charged to a 740 mA current in the range of 3 to 4.2 V in a constant current / constant voltage (CC / CV) mode using a charge / discharger. Charge / discharge was carried out continuously 300 cycles (shown in Figure 1).

Referring to the graph of FIG. 1, the discharge capacity of the battery of Example 2 including the electrolyte solution containing the pullulan polymer resin is improved as compared with the battery of Comparative Example 2 without the pullulan polymer resin in the electrolyte solution. I could confirm that. Experimental Example 2: Evaluation of High Temperature Safety

In order to evaluate the high temperature stability of the battery, the battery prepared in Example 2 and Comparative Example 2 was charged to 4.2 V and placed in a high temperature chamber at 80 ^° C. for 3 days, and the thickness change of the battery was observed at 10 minute intervals. 2 is shown.

As can be seen in Figure 2, the battery of Example 2 containing the electrolytic solution according to the present invention was confirmed that the increase in thickness is less than the battery of Comparative Example 2.

Claims

Scope of claim

1. (i) a solvent;

(ii) lithium salts; And

(iii) 0.1 to 5 weight ¾ pullulan polymer resin based on the total weight of the electrolyte composition

As an electrolyte solution composition comprising,

An electrolyte solution composition, characterized in that the pullulan-based polymer resin is a polymer, an oligomer, or a mixture thereof containing at least one repeating unit represented by Formula 1 below:

In Chemical Formula 1

Each R is independently H or (CH iCN)

1 is an integer of 1-10.

2. The electrolyte solution composition according to item 1, wherein the pullulan polymer resin has a weight average molecular weight of 1 ᅳ 000 to 10,000,000.

3. The electrolyte composition according to claim 1, wherein the electrolyte composition foams the pullulan-based polymer resin in an amount of 0.5 to 2 weight ¾ based on the total weight of the electrolyte composition.

4. The electrolyte solution composition according to item 1, wherein the solvent is a non-aqueous solvent composed of a mixture of a linear carbonate compound and a cyclic carbonate compound.

5. The electrolytic solution composition according to item 1 above. An electrolyte solution composition further comprising an electrolyte additive, wherein the electrolyte additive is a polymer, an oligomer, or a mixture thereof including one or more repeating units represented by Formula 2 below:

[Formula 2]

In Chemical Formula 2,

X, Y and Z are each independently H, 0H or (CH ₂ ) _n CN, and R 'are each independently H or (CH ₂ ) ₀ CN, where m is an integer from 0 to 10, n and 0 is an integer of 1-10 each independently.

6. The electrolyte composition according to claim 5, wherein the electrolyte composition comprises 0.01 to 15% by weight of the electrolyte additive based on the total weight of the electrolyte composition.

7. Electrochemical device comprising the electrolytic solution composition according to any one of items 1 to 6.

8. The method of paragraph 7, The electrochemical device is an electrochemical device, characterized in that the lithium secondary battery, a capacitor or a solar cell.