WO2012091515A2 - Negative electrode active material for a lithium secondary battery, method for manufacturing same, and lithium secondary battery using same - Google Patents

Negative electrode active material for a lithium secondary battery, method for manufacturing same, and lithium secondary battery using same Download PDF

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WO2012091515A2
WO2012091515A2 PCT/KR2011/010374 KR2011010374W WO2012091515A2 WO 2012091515 A2 WO2012091515 A2 WO 2012091515A2 KR 2011010374 W KR2011010374 W KR 2011010374W WO 2012091515 A2 WO2012091515 A2 WO 2012091515A2
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Prior art keywords
secondary battery
active material
lithium secondary
negative electrode
electrode active
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PCT/KR2011/010374
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French (fr)
Korean (ko)
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WO2012091515A3 (en
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이종혁
최정우
김선아
이종민
이정무
김정곤
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애경유화 주식회사
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Priority to JP2013547363A priority Critical patent/JP5886875B2/en
Priority to CN201180043190.XA priority patent/CN103250283B/en
Priority claimed from KR1020110146964A external-priority patent/KR101375688B1/en
Publication of WO2012091515A2 publication Critical patent/WO2012091515A2/en
Publication of WO2012091515A3 publication Critical patent/WO2012091515A3/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a negative electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery using the same, and more particularly, by preparing a negative electrode active material including a carbonized carbide obtained by heat treatment of a polyurethane resin under an active gas atmosphere.
  • the specific surface area reduces the problem of water adsorption, improves the initial charge and discharge efficiency of the secondary battery, improves the energy density of the battery, and improves battery characteristics such as excellent life characteristics, charge and discharge output, and high temperature storage characteristics.
  • the present invention relates to a negative electrode active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery using the same.
  • the type of vehicle driven by an electric motor may be classified into an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like.
  • the secondary battery is responsible for a power source for driving the motor.
  • automotive secondary batteries require very large output characteristics and lifetime characteristics.
  • lithium secondary batteries have higher energy density to weight and superior output characteristics than nickel-hydrogen batteries, and thus, they are widely used as power sources for driving motors of electric vehicles.
  • Graphite is mostly used as a negative electrode active material of automotive lithium secondary batteries, and exhibits a high discharge voltage of 3.6 V, which is the most widely used for ensuring high energy density of lithium secondary batteries and high life characteristics of secondary batteries with excellent reversibility. .
  • graphite has a problem in that energy input / output characteristics are inferior, and in particular, low temperature output characteristics are insufficient.
  • about 10% of the volume change of graphite occurs during charging and discharging, thereby adversely affecting the bonding strength between the current collector and the mixture layer, thereby degrading the lifespan of the battery.
  • non-graphitizable carbon having fine pores has been proposed and partially used.
  • the non-graphitizable carbon is a structure in which lithium ions are stored and released in numerous pores, and there is almost no volume expansion during charging and discharging of lithium ions, so the battery has excellent life characteristics, and fine lithium pores are present in all directions of particles. It is known to be excellent in output characteristics because it can be stored and released.
  • non-graphitizable carbon has a large specific surface area, the amount of solvents and binders must be increased when manufacturing electrode slurries, and the energy density of the battery is lowered as the amount of binder increases. When the secondary battery is increased, moisture reacts with the electrolyte to form hydrofluoric acid (HF), thereby increasing irreversible capacity and lowering durability.
  • HF hydrofluoric acid
  • Patent Document 1 relates to nano-sized spherical non-graphitizable carbon and a method for manufacturing the same and a lithium secondary battery containing the carbon as a negative electrode active material, nano-sized non-graphite including a surfactant Chemical carbon was prepared, and Korean Unexamined Patent Publication No. 2011-0042840 (Patent Document 2) discloses a negative active material for a lithium secondary battery including spherical graphite and plate-like graphite obtained by coating amorphous carbon on natural graphite and firing the same. A secondary battery was manufactured.
  • the conventional anode active material for lithium secondary batteries using the non-graphitizable carbon and graphite as described above has a small specific surface area and is insufficient to be used as a negative electrode active material by satisfying the requirements of a carbon material having excellent output characteristics.
  • the present invention is to solve the conventional problems, by producing a negative electrode active material comprising a carbonized carbide by heat-treating the polyurethane resin in an active gas atmosphere, the problem of water adsorption is reduced due to the low specific surface area, 2
  • the purpose of the present invention is to provide a negative electrode active material for a lithium secondary battery and a method of manufacturing the same, which improves the energy density of the battery by improving the initial charge and discharge efficiency of the secondary battery and improves battery characteristics such as excellent life characteristics, charge and discharge output, and high temperature storage characteristics. It is done.
  • another object of the present invention is to provide a negative electrode for a lithium secondary battery including the negative electrode active material and a lithium secondary battery comprising the same.
  • the polyurethane resin is heat treated and carbonized under an inert gas atmosphere to smooth out the gas so as not to contaminate the surface of the product due to the tar component, and further carbon coating after carbonization. It is possible to achieve the desired surface properties only by the carbonization process of the present invention so that no post-treatment is required.
  • the polyurethane resin which is a precursor of the negative electrode active material for a lithium secondary battery according to the present invention, may be prepared by the reaction of a polyol and an isocyanate.
  • the polyol is a conventional one used for preparing a polyurethane resin, but is not particularly limited, but specifically, a polyether polyol, a polyester polyol, a polytetramethylene ether glycol polyol, a Polyharnstoff Dispersion (PHD) polyol, Any one or two or more selected from amine-modified polyols, Manmich polyols, and mixtures thereof are preferred, more preferably polyester polyols, amine-modified polyols, Manmich polyols Or mixtures thereof.
  • PLD Polyharnstoff Dispersion
  • the molecular weight of the said polyol is 300-3000, More preferably, it is effective that it is 400-1500. If the molecular weight of the polyol is less than 300, there is a disadvantage in that the thermal stability of the polyurethane resin synthesized by the formation of a monool is reduced and melting occurs in the carbonization process. If the molecular weight of the polyol exceeds 3000, it is amorphous in the polyol structure. Carbon chains increase and the thermal stability of polyurethane resin falls.
  • the number of hydroxyl groups of the polyol is preferably 1.5 to 6.0, more preferably 2.0 to 4.0, and it is effective that the hydroxyl group content present in the polyol is 3 to 15% by weight.
  • the specific surface area becomes excessively large when the polyurethane resin is carbonized, thereby increasing water adsorption, thereby reducing battery efficiency.
  • the isocyanate reacting with the polyol is a conventional one used for preparing a polyurethane resin, but is not particularly limited. Specifically, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 4,4'-dicyclo Hexylmethane diisocyanate (H12MDI), polyethylene polyphenyl isocyanate, toluene diisocyanate (TDI), 2,2'-diphenylmethane diisocyanate (2,2'-MDI), 2,4'-diphenylmethane diisocyanate ( 2,4'-MDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI, monomeric MDI), polymeric diphenylmethane diisocyanate (polymeric MDI), orthotoluidine diisocyanate (TODI), Any one or two or more selected from naphthalene diosocyanate (NDI), is
  • 4,4'-diphenylmethane diisocyanate (4,4'-MDI, monomeric MDI), polymeric diphenylmethane diisocyanate (polymeric MDI) or polyethylene polyphenyl isocyanate is effective.
  • the mixing ratio of the polyol and isocyanate is effective to include 150 to 240 parts by weight of the isocyanate based on 100 parts by weight of the polyol. If the content of isocyanate is less than 150 parts by weight, the formation of isocyanurate bonds that enhance thermal stability is not sufficient, resulting in a problem that the resin is melted similarly to digraphitizable carbon during the carbonization process, and the content of isocyanate is If it is more than 240 parts by weight, isocyanurate bonds are excessively generated, and the specific surface area is increased after the carbonization process, thereby increasing the water adsorption rate, and the element ratio of oxygen to the resulting polyurethane resin is increased to produce a secondary battery. When the problem occurs that the electrical characteristics are deteriorated.
  • a catalyst may be added to induce the reaction of the polyol and the isocyanate to prepare the polyurethane resin.
  • the catalyst is pentamethyldiethylene triamine, dimethyl cyclohexyl amine, bis- (2-dimethyl aminoethyl) ether, triethylene diamine ( (triethylene diamine) potassium octoate (potassium octoate), tris (dimethylaminomethyl) phenol (tris (dimethylaminomethyl) phenol), potassium acetate (potassium acetate) or any one or more selected from them may be used, and
  • the content of the catalyst is preferably added in an amount of 0.1 to 5 parts by weight based on the polyol, and more preferably in an amount of 0.5 to 3 parts by weight, and when the content of the catalyst is 0.1 parts by weight or less, the reaction between the polyol and the isocyanate is too slow.
  • the problem occurs that the production efficiency of the negative electrode active material decreases, and when the content of the catalyst exceeds 5 parts by weight It proceeds too fast and the formed non-uniformly is a polyurethane resin, so that there arises a problem that the physical properties of the negative electrode active material decreases.
  • a foaming agent may be included in order to facilitate the pulverization of the polyurethane resin, and a foam stabilizer may be further added to improve the quality of the polyurethane resin.
  • flame retardants such as Tris (2-ChloroPropyl) Phosphate (TCPP), Tris (2-Chroroethyl) Phosphate (TCEP), Triethyl phosphate (TEP), and Trimethyl phosphate (TMP) are further added to improve the thermal stability of the polyurethane resin. More may be added.
  • the mixing ratio of the polyol and isocyanate may vary depending on the amount of additives such as catalysts, foam stabilizers, blowing agents, flame retardants, etc., but is not limited thereto.
  • the isocyanate contains a large amount of NCO group, as the addition rate of the isocyanate increases, the content of nitrogen and oxygen increases. It is effective that the preferred nitrogen content ranges from 7 to 9% by weight of the total polyurethane resin.
  • the content of nitrogen is more than 9% by weight, the specific surface area of carbon after the carbonization process increases to increase the moisture adsorption in the air to reduce the efficiency of the battery, when the content of nitrogen is less than 7% by weight It is not preferable because the amount of isocyanurate bond is insufficient, so that the thermal stability of the polyurethane resin is reduced and the resin melts like carbonaceous carbon when carbonized.
  • the content of hydrogen is preferably 4 to 6% by weight of the total polyurethane resin
  • the oxygen content is preferably 15 to 22% by weight of the total polyurethane resin.
  • the manufacturing method of the negative electrode active material for lithium secondary batteries is demonstrated in detail.
  • the above-mentioned polyol and isocyanate are reacted to prepare a polyurethane resin, and the carbonized step of heat-treating the prepared polyurethane resin under an inert gas atmosphere.
  • the polyurethane resin may be obtained by exothermic reaction by uniformly mixing the polyol and isocyanate at a constant ratio.
  • a conventional polymer resin mixing method may be used.
  • mixing by an impeller or in-line mixing by high pressure extrusion is effective.
  • the obtained polyurethane resin is in the form of agglomerates, and is preferably pulverized to a suitable size to perform a carbonization step because the density is low due to foaming and the processing yield per hour is lowered.
  • the process is not necessarily performed, and a process of pulverizing the bulk polyurethane resin after the carbonization process is also possible.
  • the cumulative volume of the particles analyzed by the particle size analyzer is 50% after the first crushing through a crusher using a mechanical crushing method.
  • the secondary grinding process is performed such that the average particle size (D50) of the spot is about 100 to 200 ⁇ m.
  • the carbonization step includes a pre-carbonization step and the main carbonization step, the pre-carbonization step is heat-treated for 30 to 120 minutes at 600 to 1000 °C temperature, the main carbonization step is 1000 to 1400 °C temperature It is effective to heat treatment for 30 to 120 minutes at.
  • the pre-carbonization step and the main carbonation step is preferably performed sequentially.
  • the precarbonization step is carried out under an inert gas atmosphere, the inert gas is preferably used helium, nitrogen, argon or a mixture thereof.
  • the precarbonization step is preferably performed at 600 to 1000 ° C, more preferably at 700 to 900 ° C. If the preliminary carbonization is carried out below 600 ° C., the low molecular weight gases are less volatilized and thus remain inside the material, which may reduce the yield of the product, and due to the residual gas generated in the main carbonization step, There is a problem of contaminating the inside of the furnace and the surface of the product.
  • the pre-carbonization step, after the pre-carbonization step or after the main carbonization step may include a fine grinding step of adjusting the particle size to a size suitable for manufacturing as an electrode for a lithium secondary battery.
  • the pulverizing step may be pulverized using a conventional pulverizer using a mechanical pulverization method, and in particular, various pulverizers such as ball mills, pin mills, rotor mills, and jet mills may be used.
  • the jet mill grinding process which is easy to pulverize, has a problem in that it is difficult to reduce the particle size to 60 ⁇ m or less since the specific gravity of the polyurethane resin is low when the pre-carbonization step is performed, thereby limiting the impact between particles.
  • Pin mill and rotor mill processes also have a limit in the rotational force, it is difficult to reduce the particle size due to the low specific gravity of the particles. Therefore, when the fine grinding step is performed using a jet mill, a pin mill and a rotor mill, it is preferable to carry out after the precarbonization step or after the main carbonization step.
  • the fine-pulverization step is performed after the pre-carbonization step because the fine-pulverized particles may aggregate with each other after the pre-carbonization step. Is more effective. Jet mills are most effective when the milling step is carried out after the preliminary carbonization step.
  • the average particle size (D50) of the particles pulverized by the jet mill is preferably 3 to 50 ⁇ m, more preferably 3 to 20 ⁇ m, and most preferably 6 to 15 ⁇ m.
  • the average particle size (D50) is less than 3 ⁇ m, the amount of fine particles generated less than 1 ⁇ m increases, the specific surface area of the particles increases, and the property of adsorbing moisture in the air increases, causing lithium ions and water to react in the battery reaction.
  • the capacity can be increased, and the fine powder increases, the porosity between the particles increases, the filling density of the particles is lowered, and lithium ions inserted into the carbon particles are easily eluted at a high temperature of 65 ° C. or higher during the battery reaction.
  • a problem occurs that the high temperature storage characteristics of the deteriorate.
  • the main carbonization step of heat treatment for 30 to 120 minutes at a temperature of 1000 to 1500 °C.
  • This carbonization step improves the conductivity of carbon after removing the low molecular weight gases generated in the precarbonization step, and optimizes the characteristics as a negative electrode material for secondary batteries by reducing the element ratio (H / C%) of hydrogen and carbon. It is a step for.
  • the main carbonization step is carried out under an inert gas atmosphere, and the inert gas is preferably helium, nitrogen, argon or a mixture thereof.
  • the heat treatment temperature of the carbonization step is preferably 1000 to 1500 ° C, more preferably 1200 to 1400 ° C.
  • the element ratio (H / C%) of hydrogen and carbon is increased to decrease the output characteristics of the battery, and the remaining hydrogen in carbon reacts irreversibly with lithium ions for the first 5 cycles.
  • the carbonization temperature is higher than 1400 ° C, the reversible capacity, which is the storage capacity of lithium ions, decreases, the energy density of the battery is greatly reduced, and the specific surface area increases.
  • the commercial furnace in order to withstand the heat treatment temperature of more than 1500 °C because the material and configuration of the electric furnace must be changed to a heat-resistant material, there arises a problem that the manufacturing cost and process cost increases.
  • the negative active material for a lithium secondary battery that has undergone the preliminary carbonization step, the fine grinding step and the carbonization step according to the present invention has a specific surface area of 2.0 to 5.0 m 2 / g, and as shown in FIG. 6, an average pore size of 1 It is preferable that it is-5 nm.
  • the (002) mean layer spacing (d002) obtained by the X-ray diffraction method (XRD) was 3.7 to 4.0 kPa
  • the crystallite diameter Lc (002) in the C-axis direction was 0.8 to 2 nm
  • the R value was 1.3 to It is preferable that it is 2, and it is preferable that the peak intensity ratio (5 degree peak / 002 peak) is 2-4
  • required by elemental analysis is 0.1 or less, oxygen and It is preferable that the element ratio (O / C%) of carbon is 1.0 or less.
  • the negative electrode active material for a lithium secondary battery manufactured by the manufacturing method of the present invention has physical properties in the above range, the water adsorption rate is reduced, it is formed in a structure that is easy to charge and discharge lithium ions to improve the initial charge and discharge efficiency of the secondary battery You can.
  • the structure of the negative electrode active material for a lithium secondary battery is formed by uniformly and appropriately combining the urethane reaction, urea reaction, and isocyanurate reaction of the polyurethane resin in the structure, and the microstructure close to amorphous is fine and uniform pores. It was confirmed that including the formed.
  • the specific surface area of the negative electrode active material is prepared by preparing a negative electrode active material including a carbonized carbide by heat-treating a polyurethane resin under an active gas atmosphere. It is lowered, prevents the adsorption of water by forming a surface in which the mesopores are not developed, and it is easy to remove moisture in the electrode drying process, thereby improving the initial efficiency, output and life characteristics of the secondary battery.
  • the lithium secondary battery including the negative electrode active material has an advantage that the initial charge and discharge efficiency of the battery is significantly improved.
  • 1 is a graph showing a change in the nitrogen content according to the isocyanate content of the negative electrode active material of the lithium secondary battery according to the present invention.
  • FIG. 2 is a graph showing the change in specific surface area according to the isocyanate content of the negative electrode active material of the lithium secondary battery according to the present invention.
  • FIG 3 is a graph showing a change in the initial charge and discharge efficiency according to the isocyanate content of the negative electrode active material of the lithium secondary battery according to the present invention.
  • FIG 4 is a graph showing a change in the initial charge and discharge efficiency according to the carbonization temperature of the negative electrode active material of the lithium secondary battery according to the present invention.
  • FIG. 5 is a graph analyzing mesopores on the surface of the negative electrode active material of the lithium secondary battery according to the present invention.
  • FIG. 6 is a graph analyzing micropores on the surface of the negative electrode active material of the lithium secondary battery according to the present invention.
  • the R value is defined as the ratio of the intensities of (A) and (B) in 2 ⁇ representing the (002) peak.
  • (A) is the background established by drawing a straight line based on the baselines on both sides of the (002) peak
  • (B) is the intensity at the junction where the background meets the (002) peak in parallel with the (002) peak.
  • Samples were collected according to KS A 0094, KS L ISO 18757 standards, and degassed at 300 ° C for 3 hours through a pretreatment device, followed by nitrogen gas adsorption BET method through surface area and pore size analyzer devices (P / P0) The specific surface area of the sample was measured at 0.05 to 0.3.
  • pores on the surface of the sample were analyzed by nitrogen gas adsorption through a Pore Size Analyzer (Bellsorp mini II).
  • the analysis shows the total volume distribution of the pores (Micropore) having a diameter of 2 nm or less by the HK method, and the total volume distribution of the pores (Mesopore) having a diameter of 2-50 nm by the BJH method. .
  • the prepared carbon was left at a relative humidity of 70% and a temperature of 25 ° C. for 24 hours, and then maintained at 200 ° C. for 5 minutes using Karl fischer moisture measurement equipment to measure the amount of moisture adsorbed on the sample.
  • a slurry was prepared in a ratio of 97: 3 to a negative electrode active material and a binder, coated to a thickness of 100 ⁇ m, dried, perforated in the form of a circular disc of 1 cm 2, and then measured by Karl Fischer for measuring the moisture content of the electrode after 120 hours vacuum drying for 6 hours. The instrument was held at 200 ° C. for 5 minutes to measure the residual moisture content of the electrode.
  • the measuring cell is a coin-type half-cell with lithium metal foil as an electrode and a counter electrode prepared with a cathode active material and a binder in a ratio of 97: 3, and EC / DEC is mixed in a 1: 1 ratio with an organic electrolyte with a separator therebetween. It was prepared in 2016 type coin cell by impregnating 1M LiPF6 dissolved electrolyte solution.
  • Charging was performed by inserting lithium ions into the carbon electrode with a constant current method up to 0.005V at 0.1 C rate, and then inserting lithium ions with a constant current method from 0.005V. When the current reached 0.01 mA, the lithium ion insertion was terminated. In the discharge, lithium ion was detached from the carbon electrode at a constant current method at a rate of 0.1 C with a final voltage of 1.5 V.
  • the output characteristic evaluation is a measure of the output characteristics at the time of lithium ion discharge. After 5 cycles of charging and discharging to 0.1 C at the initial stage, the discharge (lithium ion desorption) C rate is increased step by step and 5 C-rate compared to 0.1 C rate reversible capacity. The retention rate of the reversible capacity was measured.
  • the polyurethane resin was pulverized using a crusher to have a particle diameter of 0.1 to 2 mm, and then the pulverized product was heated to 700 ° C. in a nitrogen gas atmosphere, and maintained at 700 ° C. for 1 hour to carry out preliminary carbonization. A yield of 38% lithium secondary battery negative electrode active material precursor was obtained.
  • the obtained negative electrode active material precursor was pulverized with an average particle size of about 6 ⁇ 12 ⁇ m using a jet mill, the maximum particle size was not to exceed 50 ⁇ m.
  • the pulverized negative electrode active material precursor is placed in a ceramic crucible and heated to 1200 ° C. at a temperature rising rate of 5 ° C./min. Under a nitrogen gas atmosphere, and maintained at 1200 ° C. for 1 hour to undergo a carbonization process.
  • Table 1 below shows the composition ratio and carbonization temperature of the polyol and isocyanate, and the ⁇ evaluation test items> of the anode active material for the lithium secondary battery prepared in Example 1 were measured, and the results are shown in Tables 2 and 3 below. And in Table 4.
  • Example 2 was carried out in the same manner as in Example 1 except that the carbonization temperature was carried out at 1300 °C.
  • Example 2 was carried out in the same manner as in Example 1 except that the carbonization temperature was carried out at 1400 °C.
  • Example 4 was carried out in the same manner as in Example 1 except that the isocyanate content was performed at 194 g.
  • Example 5 was carried out in the same manner as in Example 4 except that the carbonization temperature was carried out at 1300 °C.
  • Example 5 was carried out in the same manner as in Example 4 except that the carbonization temperature was carried out at 1400 °C.
  • Example 7 was carried out in the same manner as in Example 1 except that the isocyanate content was carried out at 210 g.
  • Example 8 was carried out similarly to Example 7, except that the carbonization temperature was performed at 1300 ° C.
  • Example 9 was carried out in the same manner as in Example 7, except that the carbonization temperature was performed at 1400 ° C.
  • Example 10 was carried out in the same manner as in Example 1 except that the isocyanate content was carried out at 225 g.
  • Example 11 was carried out in the same manner as in Example 10 except that the carbonization temperature was performed at 1300 ° C.
  • Example 12 was carried out in the same manner as in Example 10 except that the carbonization temperature was performed at 1400 ° C.
  • Sucrose as a precursor was heated to 1200 °C at a temperature increase rate of 5 °C / min in a nitrogen atmosphere and maintained for 1 hour and carbonized, and then pulverized into particles of an average particle diameter of 12 ⁇ m with a rotary blade cutter mill to prepare carbon.
  • Comparative Example 2 was carried out in the same manner as in Comparative Example 1 except that the carbonization temperature was 1300 °C.
  • the petroleum pitch was melted at 150 ° C. using a precursor, extruded to form granules, and then maintained at 300 ° C. in air for 6 hours to insolubilize. Thereafter, the temperature was raised to 700 ° C. under a nitrogen atmosphere, and preliminary carbonization was performed for 1 hour to obtain a cathode active material precursor having a yield of 68% of carbonization.
  • the obtained negative electrode active material precursor was pulverized with an average particle size of about 6-12 ⁇ m using a jet mill, placed in a crucible made of ceramic material, heated to 1200 ° C. at a temperature increase rate of 5 ° C./min under a nitrogen atmosphere, and maintained for 1 hour.
  • a carbon material usable as a negative electrode active material for a lithium secondary battery was prepared.
  • Comparative Example 4 was carried out in the same manner as in Comparative Example 3 except that the carbonization temperature was 1300 ° C.
  • Comparative Example 5 was carried out in the same manner as in Example 1 except that the carbonization temperature was 900 ° C.
  • Comparative Example 6 was carried out in the same manner as in Example 2, except that the isocyanate content was carried out at 350 g.
  • the negative electrode active materials prepared in Examples and Comparative Examples were used in the negative electrode of the aqueous electrolyte secondary battery, and the charge (lithium insertion) capacity and the discharge (lithium detachment) capacity of the negative electrode active material were precisely independent without being affected by the performance of the counter electrode.
  • a lithium secondary battery was constructed using lithium metal as a counter electrode, and characteristics were evaluated.
  • the lithium secondary battery is a 2016-sized (20 mm diameter, 16 mm thick) coin-type battery assembled in a glove box under an argon atmosphere. A 1 mm thick metal lithium is pressed onto the bottom of a coin-type battery can, and a polypropylene separator is placed thereon. Was formed and the negative electrode was faced with lithium.
  • the electrolyte used was prepared by adding 1.2 M of LiPF6 salt to a solvent prepared by mixing EC (Ethylene Carbonate), DMC (Dimethyl Carbonate) and EMC (Ethyl Methyl Carbonate) in a volume ratio of 1: 1: 1.
  • the lithium secondary battery was assembled by putting it in a doll battery, touching the can cover, and pressing.
  • the amount of electricity supplied at this time divided by the weight of the negative electrode active material of the electrode was called the charging capacity per unit weight of the negative electrode active material (mAh / g).
  • the battery was stopped for 10 minutes and discharged.
  • the discharge was carried out at a constant current until the voltage of the coin-type battery became 1.5V.
  • the value of the discharged electricity divided by the weight of the negative electrode active material of the electrode was the discharge capacity per unit weight of the negative electrode active material (mAh / g). It was.
  • the reversible capacity was defined as the discharge capacity, the irreversible capacity was calculated by subtracting the discharge capacity from the charging capacity, and the efficiency was calculated as the percentage (%) of the discharge capacity.
  • the characteristic value of a basic coin-type battery was shown by averaging the characteristic value of three or more of the same batteries made from the same sample.
  • High rate charge / discharge characteristics analysis of the assembled lithium secondary battery was performed at 25 ° C. by the constant current-constant voltage method (CCCV) as in (c).
  • the high rate charge / discharge characteristics change the current density during charge and discharge, increase the constant current density supplied or discharged by cycle, and represent the capacity (mAh / g) measured and charged at the current density.
  • the specific surface area is reduced, such as reversible capacity and initial charge and discharge efficiency It was confirmed that the characteristic was remarkably improved.
  • the active material for a lithium secondary battery of the present invention does not develop mesopores on the carbon surface, so that the water content is low, and the adsorption amount of the water is also reduced, thereby reducing irreversible capacity and initial charging and discharging efficiency. It can be seen that the electrochemical properties such as increased significantly.

Abstract

The present invention relates to a negative electrode active material for a lithium secondary battery, to a method for manufacturing same, and to a lithium secondary battery using same, in which the negative electrode active material comprises carbides obtained by heat-treating a polyurethane resin in an active-gas atmosphere, and carbonizing the heat-treated resin, thereby reducing the specific surface area and thus relieving problems of moisture adsorption, improving initial charging/discharging efficiency of a secondary battery, and thus improving the energy density of the secondary battery and improving the characteristics of the battery, such as imparting a lengthened lifespan and improved charging/discharging output properties, high-temperature storage characteristics, etc. thereto.

Description

리튬이차전지용 음극 활물질 및 그 제조방법, 이를 이용한 리튬이차전지Anode active material for lithium secondary battery, manufacturing method thereof, and lithium secondary battery using same
본 발명은 리튬이차전지용 음극 활물질 및 그 제조방법, 이를 이용한 리튬이차전지에 관한 것으로, 보다 구체적으로는 폴리우레탄 수지를 활성기체 분위기 하에서 열처리하여 탄소화한 탄화물을 포함하는 음극 활물질을 제조함으로써, 낮은 비표면적으로 인하여 수분 흡착에 대한 문제가 저감되고, 2차 전지의 초기 충방전 효율이 향상되어 전지의 에너지 밀도를 향상시키고, 우수한 수명 특성, 충방전 출력, 고온저장특성 등의 전지 특성을 향상시킨 리튬이차전지용 음극 활물질 및 그 제조방법, 이를 이용한 리튬이차전지에 관한 것이다.The present invention relates to a negative electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery using the same, and more particularly, by preparing a negative electrode active material including a carbonized carbide obtained by heat treatment of a polyurethane resin under an active gas atmosphere. The specific surface area reduces the problem of water adsorption, improves the initial charge and discharge efficiency of the secondary battery, improves the energy density of the battery, and improves battery characteristics such as excellent life characteristics, charge and discharge output, and high temperature storage characteristics. The present invention relates to a negative electrode active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery using the same.
최근 친환경 그린카에 대한 관심과 수요가 높아지고 있는 가운데 전기모터로 구동되는 자동차의 등장이 가시화되고 있다. 전기모터로 구동되는 자동차의 종류는 EV(Electric Vehicle), HEV(hybrid Electric Vehicle), PHEV(Plug-in Hybrid Electric Vehicle) 등으로 구분할 수 있고, 모터를 구동시키는 전원은 이차전지가 담당하게 된다. 자동차용 이차전지는 모바일 IT기기에 적용되는 전지와는 다르게 매우 큰 출력 특성과 수명특성 등이 요구되고 있다. 이차전지 중에서도 니켈수소전지 보다는 리튬이차전지가 중량대비 에너지밀도가 높고 출력특성이 우수하여 전기자동차의 구동모터용 전원으로 각광받고 있다. Recently, with the increasing interest and demand for eco-friendly green cars, the emergence of electric motor-driven cars is becoming visible. The type of vehicle driven by an electric motor may be classified into an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like. The secondary battery is responsible for a power source for driving the motor. Unlike secondary batteries applied to mobile IT devices, automotive secondary batteries require very large output characteristics and lifetime characteristics. Among secondary batteries, lithium secondary batteries have higher energy density to weight and superior output characteristics than nickel-hydrogen batteries, and thus, they are widely used as power sources for driving motors of electric vehicles.
현재 자동차용 리튬이차전지의 음극 활물질로써 대부분 흑연이 사용되고 있으며, 3.6V의 높은 방전 전압을 나타내어, 리튬이차전지의 에너지 밀도가 높고, 뛰어난 가역성으로 이차전지의 높은 수명 특성을 보장하여 가장 널리 사용되고 있다. 그러나 흑연은 에너지 입출력 특성이 떨어지는 문제점이 있고, 특히 저온 출력 특성이 미흡한 문제가 있다. 또한, 충방전시 흑연의 부피변화가 약 10% 정도 발생하는데 이에 따라 집전체와 합제층의 결합력에 악영향을 미쳐 전지의 수명특성이 저하되기도 한다. Graphite is mostly used as a negative electrode active material of automotive lithium secondary batteries, and exhibits a high discharge voltage of 3.6 V, which is the most widely used for ensuring high energy density of lithium secondary batteries and high life characteristics of secondary batteries with excellent reversibility. . However, graphite has a problem in that energy input / output characteristics are inferior, and in particular, low temperature output characteristics are insufficient. In addition, about 10% of the volume change of graphite occurs during charging and discharging, thereby adversely affecting the bonding strength between the current collector and the mixture layer, thereby degrading the lifespan of the battery.
이러한 문제를 해결하기 위하여 미세공이 발달된 난흑연화성 탄소가 제안되어 일부 사용되고 있다. 난 흑연화성 탄소는 수많은 기공 내에 리튬이온이 저장되고 방출되는 구조로서 리튬이온 충방전시 부피팽창이 거의 없어 전지의 수명특성이 매우 우수하며, 입자의 전 방향에 존재하는 미세기공을 통해 리튬이온을 저장 방출할 수 있어 출력특성도 우수한 것으로 알려져 있다. 그러나, 난흑연화성 탄소는 비표면적이 커서 전극슬러리 제조시 용매 및 바인더의 사용량이 증가되어야 하고, 바인더의 증가량만큼 전지의 에너지 밀도가 낮아지는 문제가 있으며, 높은 비표면적으로 인하여 대기 중에서 수분 흡착량이 증가하여 이차전지 제조시, 수분이 전해액과 반응하여 불산(HF)을 형성하여 비가역용략을 증가시키고, 내구성을 저하시키는 단점이 있다. In order to solve this problem, non-graphitizable carbon having fine pores has been proposed and partially used. The non-graphitizable carbon is a structure in which lithium ions are stored and released in numerous pores, and there is almost no volume expansion during charging and discharging of lithium ions, so the battery has excellent life characteristics, and fine lithium pores are present in all directions of particles. It is known to be excellent in output characteristics because it can be stored and released. However, since non-graphitizable carbon has a large specific surface area, the amount of solvents and binders must be increased when manufacturing electrode slurries, and the energy density of the battery is lowered as the amount of binder increases. When the secondary battery is increased, moisture reacts with the electrolyte to form hydrofluoric acid (HF), thereby increasing irreversible capacity and lowering durability.
상기 문제를 해결하는 방법으로 열린기공보다 닫힌 기공을 발달시켜 비표면적을 줄이기 위하여 상압/가압 하에서 탄소화를 진행하는 방법이나, 난흑연화성 탄소 표면에 열분해 탄소를 형성시켜 비표면적을 줄이는 방법이 개시된 바 있다. 그러나 원료의 탄화시 타르 성분 등에 의하여 재오염 되거나, 원료 도가니 상부와 하부의 제품의 균일성이 떨어지는 문제점이 있다. In order to solve the above problem, a method of carbonizing under normal pressure / pressurization to reduce specific surface area by developing closed pores rather than open pores, or reducing specific surface area by forming pyrolytic carbon on a non-graphitizable carbon surface is disclosed. There is a bar. However, when the carbonization of the raw material is recontaminated by the tar component or the like, there is a problem that the uniformity of the product of the upper and lower raw crucible is inferior.
대한민국 등록특허 제0450642호(특허문헌 1)에서는 나노크기의 구형 난흑연화성 탄소 및 이의 제조방법 및 상기 탄소를 음극 활물질로 포함하는 리튬이차전지에 관한 것으로, 계면활성제를 포함하여 나노크기의 난흑연화성 탄소를 제조하였으며, 대한민국 공개특허 제 2011-0042840호(특허문헌 2)에서는 천연 흑연에 비정질 카본을 코팅한 후 소성하여 얻어진 구형 흑연과 판상형 흑연을 포함하는 리튬이차전지용 음극 활물질 및 이를 이용한 리튬이차전지를 제조하였다. Republic of Korea Patent No. 0450642 (Patent Document 1) relates to nano-sized spherical non-graphitizable carbon and a method for manufacturing the same and a lithium secondary battery containing the carbon as a negative electrode active material, nano-sized non-graphite including a surfactant Chemical carbon was prepared, and Korean Unexamined Patent Publication No. 2011-0042840 (Patent Document 2) discloses a negative active material for a lithium secondary battery including spherical graphite and plate-like graphite obtained by coating amorphous carbon on natural graphite and firing the same. A secondary battery was manufactured.
상기와 같은 종래의 난흑연화성 탄소 및 흑연을 이용한 리튬이차전지용 음극활물질은 비표면적이 작으며 출력 특성이 우수한 탄소소재의 요건을 충족하여 음극 활물질로 사용되기에는 부족함이 있다. The conventional anode active material for lithium secondary batteries using the non-graphitizable carbon and graphite as described above has a small specific surface area and is insufficient to be used as a negative electrode active material by satisfying the requirements of a carbon material having excellent output characteristics.
본 발명은 종래의 문제점을 해결하기 위한 것으로, 폴리우레탄 수지를 활성기체 분위기 하에서 열처리하여 탄소화한 탄화물을 포함하는 음극 활물질을 제조함으로써, 낮은 비표면적으로 인하여 수분 흡착에 대한 문제가 저감되고, 2차 전지의 초기 충방전 효율이 향상되어 전지의 에너지 밀도를 향상시키고, 우수한 수명 특성, 충방전 출력, 고온저장특성 등의 전지 특성을 향상시킨 리튬이차전지용 음극 활물질 및 그 제조방법을 제공하는 것을 목적으로 한다. The present invention is to solve the conventional problems, by producing a negative electrode active material comprising a carbonized carbide by heat-treating the polyurethane resin in an active gas atmosphere, the problem of water adsorption is reduced due to the low specific surface area, 2 The purpose of the present invention is to provide a negative electrode active material for a lithium secondary battery and a method of manufacturing the same, which improves the energy density of the battery by improving the initial charge and discharge efficiency of the secondary battery and improves battery characteristics such as excellent life characteristics, charge and discharge output, and high temperature storage characteristics. It is done.
또한, 본 발명의 또 다른 목적은 상기 음극 활물질을 포함하는 리튬이차전지용 음극 및 이를 포함하는 리튬이차전지를 제공하는 것을 목적으로 한다. In addition, another object of the present invention is to provide a negative electrode for a lithium secondary battery including the negative electrode active material and a lithium secondary battery comprising the same.
상기와 같은 목적을 달성하기 위한 본 발명에 따르면, According to the present invention for achieving the above object,
리튬이차전지용 음극 활물질을 제조하기 위하여 폴리우레탄 수지를 비활성기체 분위기 하에서 열처리하여 탄소화함으로써, 가스 배출을 원활하게 하여 타르 성분으로 인하여 제품 표면을 오염시키지 않도록 하며, 탄소화 이후 추가의 탄소코팅 등의 후처리가 필요 없을 만큼 본 발명의 탄소화 공정만으로 원하는 표면특성을 달성할 수 있게 되었다. In order to manufacture the negative electrode active material for lithium secondary battery, the polyurethane resin is heat treated and carbonized under an inert gas atmosphere to smooth out the gas so as not to contaminate the surface of the product due to the tar component, and further carbon coating after carbonization. It is possible to achieve the desired surface properties only by the carbonization process of the present invention so that no post-treatment is required.
본 발명에 의한 리튬이차전지용 음극 활물질의 전구체인 폴리우레탄 수지는 폴리올과 이소시아네이트의 반응에 의하여 제조될 수 있다. The polyurethane resin, which is a precursor of the negative electrode active material for a lithium secondary battery according to the present invention, may be prepared by the reaction of a polyol and an isocyanate.
상기 폴리올은 폴리우레탄 수지 제조에 사용되는 통상적인 것으로 특별히 한정하지는 않으나, 구체적으로는 폴리에테르계 폴리올, 폴리에스테르계 폴리올, 폴리테트라메틸렌 에테르 글리콜 폴리올, 피에이치디 폴리올(Polyharnstoff Dispersion(PHD) polyol), 아민(Amine) 변성 폴리올, 만니히(Manmich)폴리올 및 이들의 혼합물 중에서 선택되는 어느 하나 또는 둘 이상이 바람직하며, 보다 바람직하게는 폴리에스테르 폴리올, 아민(Amine) 변성 폴리올, 만니히(Manmich)폴리올 또는 이들의 혼합물이 효과적이다. The polyol is a conventional one used for preparing a polyurethane resin, but is not particularly limited, but specifically, a polyether polyol, a polyester polyol, a polytetramethylene ether glycol polyol, a Polyharnstoff Dispersion (PHD) polyol, Any one or two or more selected from amine-modified polyols, Manmich polyols, and mixtures thereof are preferred, more preferably polyester polyols, amine-modified polyols, Manmich polyols Or mixtures thereof.
상기 폴리올의 분자량은 300 내지 3000인 것이 바람직하고, 보다 바람직하게는 400 내지 1500인 것이 효과적이다. 폴리올의 분자량이 300미만일 경우에는 모노올의 형성으로 합성된 폴리우레탄 수지의 열안정성이 저하되어 탄화공정에서 용융이 발생하는 단점이 있으며, 폴리올의 분자량이 3000을 초과할 경우에는, 폴리올 구조 내에 비정질 탄소사슬이 증가하여 또한 폴리우레탄 수지의 열안정성이 저하된다. 또한, 폴리올의 수산기 수는 1.5 내지 6.0개인 것이 바람직하고, 보다 바람직하게는 2.0 내지 4.0개이며, 폴리올 내에 존재하는 수산기 함량은 3 내지 15중량%인 것이 효과적이다. 이는 최적의 분자량을 가진 폴리올을 최적 함량을 포함하는 폴리우레탄 수지를 탄소화하여 음극 활물질로 제조했을 때, 바람직한 범위의 비표면적 및 표면특성을 가지게 하기 위함이다. 수산기 수 및 수산기 함량이 상기 범위를 초과할 경우에는 폴리우레탄 수지를 탄소화 시켰을 때 비표면적이 과도하게 커짐으로써, 수분흡착이 증가하여 전지효율을 저감시키는 문제가 발생한다. It is preferable that the molecular weight of the said polyol is 300-3000, More preferably, it is effective that it is 400-1500. If the molecular weight of the polyol is less than 300, there is a disadvantage in that the thermal stability of the polyurethane resin synthesized by the formation of a monool is reduced and melting occurs in the carbonization process.If the molecular weight of the polyol exceeds 3000, it is amorphous in the polyol structure. Carbon chains increase and the thermal stability of polyurethane resin falls. In addition, the number of hydroxyl groups of the polyol is preferably 1.5 to 6.0, more preferably 2.0 to 4.0, and it is effective that the hydroxyl group content present in the polyol is 3 to 15% by weight. This is to have a specific surface area and surface characteristics of the preferred range when the polyol having the optimum molecular weight is carbonized polyurethane resin containing the optimum content to prepare a negative electrode active material. When the number of hydroxyl groups and the content of hydroxyl groups exceed the above ranges, the specific surface area becomes excessively large when the polyurethane resin is carbonized, thereby increasing water adsorption, thereby reducing battery efficiency.
또한, 상기 폴리올과 반응하는 이소시아네이트는 폴리우레탄 수지 제조에 사용되는 통상적인 것으로 특별히 한정하지는 않으나, 구체적으로는 헥사메틸렌디이소시아네이트(HDI), 이소포론디이소시아네이트(IPDI), 4,4'-디시클로헥실메탄디이소시아네이트(H12MDI), 폴리에틸렌 폴리페닐 이소시아네이트, 톨루엔 디이소시아네이트(TDI), 2,2‘-디페닐메탄 디이소시아네이트(2,2'-MDI), 2,4’-디페닐메탄 디이소시아네이트(2,4'-MDI), 4,4'-디페닐메탄 디이소시아네이트(4,4'-MDI,monomeric MDI), 폴리머릭 디페닐메탄 디이소시아네이트(polymeric MDI), 오르토톨루이딘 디이소시아네이트(TODI), 나프탈렌 디오소시아네이트(NDI), 크실렌 디이소시아네이트(XDI), 라이신디이소시아네이트(LDI) 및 트리페닐메탄 트리이소시아네이트(TPTI) 중에서 선택되는 어느 하나 또는 둘 이상이 바람직하며, 보다 바람직하게는 4,4'-디페닐메탄 디이소시아네이트(4,4'-MDI, monomeric MDI), 폴리머릭 디페닐메탄 디이소시아네이트(polymeric MDI) 또는 폴리에틸렌 폴리페닐 이소시아네이트가 효과적이다. In addition, the isocyanate reacting with the polyol is a conventional one used for preparing a polyurethane resin, but is not particularly limited. Specifically, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 4,4'-dicyclo Hexylmethane diisocyanate (H12MDI), polyethylene polyphenyl isocyanate, toluene diisocyanate (TDI), 2,2'-diphenylmethane diisocyanate (2,2'-MDI), 2,4'-diphenylmethane diisocyanate ( 2,4'-MDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI, monomeric MDI), polymeric diphenylmethane diisocyanate (polymeric MDI), orthotoluidine diisocyanate (TODI), Any one or two or more selected from naphthalene diosocyanate (NDI), xylene diisocyanate (XDI), lysine diisocyanate (LDI) and triphenylmethane triisocyanate (TPTI) are preferred. It said, more preferably 4,4'-diphenylmethane diisocyanate (4,4'-MDI, monomeric MDI), polymeric diphenylmethane diisocyanate (polymeric MDI) or polyethylene polyphenyl isocyanate is effective.
상기 폴리올과 이소시아네이트의 혼합비율은 상기 폴리올 100 중량부에 대하여 상기 이소시아네이트가 150 내지 240 중량부 포함하는 것이 효과적이다. 이소시아네이트의 함량이 150 중량부 미만일 경우에는 열안정성을 높여주는 이소시아누레이트 결합의 형성이 충분하지 못하여, 탄소화 공정시 이흑연화성 탄소와 유사하게 레진이 용융되는 문제가 있으며, 이소시아네이트의 함량이 240 중량부 초과일 경우에는 이소시아누레이트 결합이 과도하게 생성되어, 탄소화 공정 후 비표면적이 증가되고 이에 따라 수분 흡착율이 높아지고, 생성되는 폴리우레탄 수지에 산소의 원소비율이 높아져 이차전지로 제조했을 때 전기적 특성이 저하되는 문제가 발생한다. The mixing ratio of the polyol and isocyanate is effective to include 150 to 240 parts by weight of the isocyanate based on 100 parts by weight of the polyol. If the content of isocyanate is less than 150 parts by weight, the formation of isocyanurate bonds that enhance thermal stability is not sufficient, resulting in a problem that the resin is melted similarly to digraphitizable carbon during the carbonization process, and the content of isocyanate is If it is more than 240 parts by weight, isocyanurate bonds are excessively generated, and the specific surface area is increased after the carbonization process, thereby increasing the water adsorption rate, and the element ratio of oxygen to the resulting polyurethane resin is increased to produce a secondary battery. When the problem occurs that the electrical characteristics are deteriorated.
상기 폴리우레탄 수지를 제조하기 위하여 폴리올과 이소시아네이트의 반응을 유도하기 위해 촉매를 첨가할 수 있다. 상기 촉매는 펜타메틸디에틸렌 트리아민(pentamethyldiethylene triamine), 디메틸 사이클로헥실아민(dimethyl cyclohexyl amine), 비스-(2-디메틸 아미노에틸)에테르(Bis-(2-dimethyl aminoethyl)ether), 트리에틸렌 디아민((triethylene diamine) 포타슘 옥토에이트 (potassium octoate), 트리스(디메틸아미노메틸)페놀(tris(dimethylaminomethyl)phenol), 포타슘 아세테이트(potassium acetate) 또는 이들의 혼합물 중에서 선택된 어느 하나 또는 둘 이상을 사용할 수 있고, 상기 촉매의 함량은 폴리올에 대하여 0.1 내지 5중량부 첨가하는 것이 바람직하며 , 보다 바람직하게 0.5 내지 3 중량부 첨가하는 것이 효과적이다. 촉매의 함량이 0.1중량부 이하일 경우는 폴리올과 이소시아네이트의 반응이 너무 느리게 진행되어 음극활물질 제조효율이 감소하는 문제가 발생하며, 촉매의 함량이 5중량부 초과일 때는 반응이 너무 빠르게 진행되어 폴리우레탄 수지가 불균일하게 형성되고, 이에 따라 음극활물질의 물성이 저하되는 문제가 발생한다. A catalyst may be added to induce the reaction of the polyol and the isocyanate to prepare the polyurethane resin. The catalyst is pentamethyldiethylene triamine, dimethyl cyclohexyl amine, bis- (2-dimethyl aminoethyl) ether, triethylene diamine ( (triethylene diamine) potassium octoate (potassium octoate), tris (dimethylaminomethyl) phenol (tris (dimethylaminomethyl) phenol), potassium acetate (potassium acetate) or any one or more selected from them may be used, and The content of the catalyst is preferably added in an amount of 0.1 to 5 parts by weight based on the polyol, and more preferably in an amount of 0.5 to 3 parts by weight, and when the content of the catalyst is 0.1 parts by weight or less, the reaction between the polyol and the isocyanate is too slow. The problem occurs that the production efficiency of the negative electrode active material decreases, and when the content of the catalyst exceeds 5 parts by weight It proceeds too fast and the formed non-uniformly is a polyurethane resin, so that there arises a problem that the physical properties of the negative electrode active material decreases.
또한, 폴리우레탄 수지의 분쇄를 용이하기 위하여 발포제를 포함할 수 있으며, 폴리우레탄 수지의 품질향상을 위하여 정포제를 추가로 더 포함할 수 있다. In addition, a foaming agent may be included in order to facilitate the pulverization of the polyurethane resin, and a foam stabilizer may be further added to improve the quality of the polyurethane resin.
또한, 폴리우레탄 수지의 열적안정성 향상을 위하여 TCPP(Tris(2-ChloroPropyl) Phosphate), TCEP(Tris(2-Chroroethyl) Phosphate), TEP(triethyl phosphate) 및 TMP(Trimethyl phosphate) 등의 난연제를 추가로 더 첨가할 수 있다.In addition, flame retardants such as Tris (2-ChloroPropyl) Phosphate (TCPP), Tris (2-Chroroethyl) Phosphate (TCEP), Triethyl phosphate (TEP), and Trimethyl phosphate (TMP) are further added to improve the thermal stability of the polyurethane resin. More may be added.
상기 폴리올 및 이소시아네이트의 혼합비율은 촉매, 정포제, 발포제, 난연제 등 첨가제의 함량에 의해 변동될 수 있으므로, 상기 범위에만 한정하는 것은 아니다. The mixing ratio of the polyol and isocyanate may vary depending on the amount of additives such as catalysts, foam stabilizers, blowing agents, flame retardants, etc., but is not limited thereto.
바람직하게는 합성된 폴리우레탄 수지의 원소분석을 통한 산소, 질소 및 수소의 함량을 기준으로 하는 것이 효과적이다. 이소시아네이트에는 다량의 NCO기가 포함되어 있으므로, 이소시아네이트의 첨가 비율이 증가할수록, 질소와 산소의 함량이 증가하게 된다. 바람직한 질소 함량의 범위는 전체 폴리우레탄 수지의 7 내지 9 중량%인 것이 효과적이다. 질소의 함량이 9중량% 초과일 경우, 탄소화 공정 이후 탄소의 비표면적이 증가하여 대기 중의 수분 흡착률이 높아져 전지의 효율을 감소시키는 문제가 발생하며, 질소의 함량이 7중량% 미만일 경우에는 이소시아누레이트 결합의 양이 충분치 않아 폴리우레탄 수지의 열적안정성이 감소하여 탄화시 이흑연화성 탄소와 같이 수지가 용융되므로 바람직하지 않다. Preferably, it is effective to base the content of oxygen, nitrogen and hydrogen through elemental analysis of the synthesized polyurethane resin. Since the isocyanate contains a large amount of NCO group, as the addition rate of the isocyanate increases, the content of nitrogen and oxygen increases. It is effective that the preferred nitrogen content ranges from 7 to 9% by weight of the total polyurethane resin. If the content of nitrogen is more than 9% by weight, the specific surface area of carbon after the carbonization process increases to increase the moisture adsorption in the air to reduce the efficiency of the battery, when the content of nitrogen is less than 7% by weight It is not preferable because the amount of isocyanurate bond is insufficient, so that the thermal stability of the polyurethane resin is reduced and the resin melts like carbonaceous carbon when carbonized.
또한, 수소의 함량은 전체 폴리우레탄 수지의 4 내지 6중량%인 것이 바람직하고, 산소의 함량은 전체 폴리우레탄 수지의 15 내지 22중량%인 것이 바람직하다. 수소 및 산소의 함량이 상기 범위 미만일 경우에는, 이소시아누레이트 구조의 함량이 과다하여 폴리우레탄 수지를 탄소화했을 때 비표면적이 과도하게 커짐으로써, 대기 중의 수분흡착량이 증가하여 전지효율을 저감시키는 문제가 발생한다. 수소 및 산소의 함량이 상기 범위 초과일 경우에는, 폴리우레탄 수지를 탄소화했을 때 최적의 미세구조 개질을 위한 화학반응이 충분치 못하여 폴리우레탄 수지의 용융이 발생하여 리튬이차전지의 음극 활물질에 적합한 하드카본 구조를 발현하지 못한다.In addition, the content of hydrogen is preferably 4 to 6% by weight of the total polyurethane resin, the oxygen content is preferably 15 to 22% by weight of the total polyurethane resin. When the content of hydrogen and oxygen is less than the above range, the specific surface area becomes excessively large when carbonizing the polyurethane resin due to excessive content of the isocyanurate structure, thereby increasing the amount of water adsorption in the air and reducing battery efficiency. A problem arises. When the content of hydrogen and oxygen exceeds the above range, when the carbonized polyurethane resin is carbonized, the chemical reaction for the optimum microstructure modification is not sufficient, so that the polyurethane resin is melted and hardly suitable for the negative electrode active material of the lithium secondary battery. It does not express carbon structure.
다음으로, 리튬이차전지용 음극 활물질의 제조방법에 대하여 상세히 설명한다. 상술한 폴리올과 이소시아네트를 반응시켜 폴리우레탄 수지를 제조하고, 제조된 폴리우레탄 수지를 비활성 기체 분위기 하에서 열처리하는 탄소화 단계를 포함한다. Next, the manufacturing method of the negative electrode active material for lithium secondary batteries is demonstrated in detail. The above-mentioned polyol and isocyanate are reacted to prepare a polyurethane resin, and the carbonized step of heat-treating the prepared polyurethane resin under an inert gas atmosphere.
상기 폴리올과 이소시아네이트의 일정비율로 균일하게 혼합하여 발열반응에 의한 폴리우레탄 수지를 얻을 수 있다. 상기 혼합방법은 통상의 고분자 수지 혼합방법을 사용할 수 있으며, 바람직하게는 임펠러에 의한 혼합 또는 고압압출에 의한 인라인 혼합이 효과적이다. The polyurethane resin may be obtained by exothermic reaction by uniformly mixing the polyol and isocyanate at a constant ratio. As the mixing method, a conventional polymer resin mixing method may be used. Preferably, mixing by an impeller or in-line mixing by high pressure extrusion is effective.
얻어진 폴리우레탄 수지는 덩어리 형태이며, 발포에 의하여 밀도가 낮아 시간당 처리 수율이 떨어지기 때문에 적당한 크기로 분쇄하여 탄소화 단계를 수행하는 것이 바람직하다. 그러나 반드시 수행되어야 하는 공정은 아니며 벌크상태의 폴리우레탄 수지를 탄소화 공정을 거친 후 분쇄하는 공정도 가능하다. 예비탄소화 공정 전, 즉 벌크상태의 폴리우레탄수지의 분쇄단계를 거칠 경우에는 기계적 분쇄방법으로 크러셔(crusher)를 통하여 1차 분쇄한 후 입도분석기에 의해 분석된 입자의 누적체적이 50%가 되는 지점의 평균입자 크기(D50)가 100 내지 200㎛ 정도 되도록 2차 분쇄공정을 수행한다. The obtained polyurethane resin is in the form of agglomerates, and is preferably pulverized to a suitable size to perform a carbonization step because the density is low due to foaming and the processing yield per hour is lowered. However, the process is not necessarily performed, and a process of pulverizing the bulk polyurethane resin after the carbonization process is also possible. Before the pre-carbonization process, that is, when the bulk polyurethane resin is pulverized, the cumulative volume of the particles analyzed by the particle size analyzer is 50% after the first crushing through a crusher using a mechanical crushing method. The secondary grinding process is performed such that the average particle size (D50) of the spot is about 100 to 200 μm.
또한, 상기 탄소화 단계는 예비탄소화 단계 및 본탄소화 단계를 포함하며, 상기 예비탄소화 단계는 600 내지 1000℃ 온도에서 30 내지 120분 동안 열처리하고, 본탄소화 단계는 1000 내지 1400℃ 온도에서 30 내지 120분 동안 열처리하는 것이 효과적이다. 또한, 예비탄소화 단계 및 본탄소화 단계는 순차적으로 진행되는 것이 바람직하다. In addition, the carbonization step includes a pre-carbonization step and the main carbonization step, the pre-carbonization step is heat-treated for 30 to 120 minutes at 600 to 1000 ℃ temperature, the main carbonization step is 1000 to 1400 ℃ temperature It is effective to heat treatment for 30 to 120 minutes at. In addition, the pre-carbonization step and the main carbonation step is preferably performed sequentially.
상기 예비탄소화 단계는 비활성 기체 분위기하에서 수행되며, 비활성 기체는 헬륨, 질소, 아르곤 또는 이들의 혼합가스를 사용하는 것이 바람직하다. 예비탄소화 단계는 600 내지 1000℃에서 수행되는 것이 바람직하며, 보다 바람직하게는 700 내지 900℃에서 수행되는 것이 효과적이다. 예비 탄소화를 600℃ 미만에서 수행할 경우, 저분자량 가스들의 휘발이 덜 됨으로써 재료 내부에 잔류하게 되고, 이로 인해 제품의 수득률이 감소될 수 있으며, 본탄소화 단계에서 발생되는 잔여가스로 인하여 전기로 내부와 제품 표면을 오염시키는 문제가 발생한다. 또한, 예비 탄소화를 1000℃ 초과하여 수행할 경우 필요이상의 열량 공급으로 제조비 상승의 원인이 되며, 높은 온도로 인하여 원료에서 배출된 타르 가스의 열분해 생성물로 제품의 오염이 발생하는 문제가 있다. The precarbonization step is carried out under an inert gas atmosphere, the inert gas is preferably used helium, nitrogen, argon or a mixture thereof. The precarbonization step is preferably performed at 600 to 1000 ° C, more preferably at 700 to 900 ° C. If the preliminary carbonization is carried out below 600 ° C., the low molecular weight gases are less volatilized and thus remain inside the material, which may reduce the yield of the product, and due to the residual gas generated in the main carbonization step, There is a problem of contaminating the inside of the furnace and the surface of the product. In addition, when the pre-carbonization is performed in excess of 1000 ℃ causes the production cost increase by supplying more calories than necessary, there is a problem that the contamination of the product with the pyrolysis product of the tar gas discharged from the raw material due to the high temperature.
예비탄소화 단계 이전, 예비탄소화 단계 이후 또는 본탄소화 단계 이후에 리튬이차전지용 전극으로 제조하기 적합한 크기로 입자크기를 조절하는 미분쇄단계를 포함할 수 있다.The pre-carbonization step, after the pre-carbonization step or after the main carbonization step may include a fine grinding step of adjusting the particle size to a size suitable for manufacturing as an electrode for a lithium secondary battery.
상기 미분쇄단계는 기계적 분쇄방법을 사용하는 통상의 분쇄기를 사용하여 분쇄할 수 있으며, 특히 볼밀, 핀밀, 로터밀 및 제트밀 등 다양한 분쇄장치를 사용할 수 있다. 일반적으로 미분쇄에 용이한 제트밀 분쇄공정은 예비탄소화 단계 이전에 실시하는 경우 폴리우레탄 수지의 비중이 낮아 입자간의 충격량을 높이는데 한계가 있어 입자크기를 60㎛이하로 줄이기 어려운 문제가 있으며, 핀밀 및 로터밀 공정도 회전력에 한계가 있고, 입자의 비중이 낮아 입자의 크기를 줄이기 어려운 문제가 발생한다. 따라서, 제트밀, 핀밀 및 로터밀을 사용하여 미분쇄단계를 수행할 경우 예비탄소화 단계 이후 또는 본탄소화 단계 이후에 실시하는 것이 바람직하다. The pulverizing step may be pulverized using a conventional pulverizer using a mechanical pulverization method, and in particular, various pulverizers such as ball mills, pin mills, rotor mills, and jet mills may be used. In general, the jet mill grinding process, which is easy to pulverize, has a problem in that it is difficult to reduce the particle size to 60 µm or less since the specific gravity of the polyurethane resin is low when the pre-carbonization step is performed, thereby limiting the impact between particles. Pin mill and rotor mill processes also have a limit in the rotational force, it is difficult to reduce the particle size due to the low specific gravity of the particles. Therefore, when the fine grinding step is performed using a jet mill, a pin mill and a rotor mill, it is preferable to carry out after the precarbonization step or after the main carbonization step.
또한, 1차 분쇄된 폴리우레탄 입자를 미분쇄하고 예비 탄소화를 진행할 경우, 예비 탄소화단계 이후에 미분쇄된 입자가 서로 응집될 수 있기 때문에 상기 미분쇄단계는 예비탄소화 단계 이후에 수행하는 것이 더욱 효과적이다. 예비 탄소화 단계 이후에 미분쇄 단계를 수행할 경우 제트밀을 이용하는 것이 가장 효과적이다. 제트밀에 의해 분쇄된 입자의 평균입자크기(D50)는 3 내지 50㎛ 인 것이 바람직하며, 보다 바람직하게는 3 내지 20㎛이며, 가장 바람직하게는 6 내지 15㎛인 것이 효과적이다. 평균입자크기(D50)가 3㎛ 미만일 경우에는, 1㎛ 미만의 미분발생량이 증가하여 입자의 비표면적이 증가하여 대기 중의 수분을 흡착하는 성질이 증가함으로써 전지 반응에서 리튬이온과 수분이 반응하여 비가역용량을 증가시킬 수 있는 문제가 있으며, 미분이 증가함으로써, 입자간의 공극률이 증가하여 입자의 충진밀도가 낮아지며, 전지반응시 65℃ 이상의 고온에서 탄소입자 내부에 삽입되어 있는 리튬이온이 쉽게 용출되는 등의 고온저장특성이 저하되는 문제가 발생한다. 또한, 평균입자크기(D50)가 50㎛ 초과일 경우에는 입자의 계면이 작아져 리튬이온의 출입면적이 좁아지므로 전지반응시 리튬이온의 입출력 특성이 저하되는 문제가 발생한다. In addition, when the finely pulverized polyurethane particles are subjected to pre-pulverization and pre-carbonization, the fine-pulverization step is performed after the pre-carbonization step because the fine-pulverized particles may aggregate with each other after the pre-carbonization step. Is more effective. Jet mills are most effective when the milling step is carried out after the preliminary carbonization step. The average particle size (D50) of the particles pulverized by the jet mill is preferably 3 to 50 µm, more preferably 3 to 20 µm, and most preferably 6 to 15 µm. When the average particle size (D50) is less than 3 μm, the amount of fine particles generated less than 1 μm increases, the specific surface area of the particles increases, and the property of adsorbing moisture in the air increases, causing lithium ions and water to react in the battery reaction. There is a problem that the capacity can be increased, and the fine powder increases, the porosity between the particles increases, the filling density of the particles is lowered, and lithium ions inserted into the carbon particles are easily eluted at a high temperature of 65 ° C. or higher during the battery reaction. A problem occurs that the high temperature storage characteristics of the deteriorate. In addition, when the average particle size (D50) is greater than 50㎛, since the interface of the particles becomes small and the entrance and exit area of the lithium ions becomes narrow, there is a problem that the input and output characteristics of the lithium ions during the battery reaction is reduced.
예비 탄소화 단계 및 미분쇄 단계를 거친 후 1000 내지 1500℃ 온도에서 30 내지 120분 동안 열처리하는 본탄소화 단계를 포함한다. 본탄소화 단계는 예비탄소화 단계에서 발생하는 저분자량의 기체들을 제거한 후에 탄소의 전도성을 향상시키고, 수소와 탄소의 원소비(H/C%)를 감소시킴으로써 이차전지용 음극소재로서 특성을 최적화시키기 위한 단계이다. 본탄소화 단계는 비활성기체 분위기 하에서 수행되며, 비활성 기체는 헬륨, 질소, 아르곤 또는 이들의 혼합가스를 사용하는 것이 바람직하다.After the preliminary carbonization step and the fine grinding step, the main carbonization step of heat treatment for 30 to 120 minutes at a temperature of 1000 to 1500 ℃. This carbonization step improves the conductivity of carbon after removing the low molecular weight gases generated in the precarbonization step, and optimizes the characteristics as a negative electrode material for secondary batteries by reducing the element ratio (H / C%) of hydrogen and carbon. It is a step for. The main carbonization step is carried out under an inert gas atmosphere, and the inert gas is preferably helium, nitrogen, argon or a mixture thereof.
본탄소화 단계의 열처리 온도는 1000 내지 1500℃가 바람직하며, 보다 바람직하게는 1200 내지 1400℃가 효과적이다. 1000℃ 미만의 온도에서 탄소화할 경우에는, 수소와 탄소의 원소비(H/C%)가 높아져 전지의 출력특성이 감소하고, 탄소 내의 잔류하는 수소가 리튬이온과 비가역적으로 반응하여 초기 5사이클 정도에서 전지의 용량저하가 발생하는 문제가 있으며, 1400℃ 초과의 온도에서 탄소화할 경우에는, 리튬이온의 저장능력인 가역용량이 감소하여 전지 제조시 에너지밀도가 크게 저하되고, 비표면적이 증가하여 대기 중의 수분을 흡착하는 성질이 증가함으로써, 전지 반응에서 리튬이온과 수분이 반응하여 비가역용량을 증가시킬 수 있는 문제가 발생한다. 또한 상업적인 측면에서도 전기로가 1500℃이상의 열처리 온도를 견디기 위해서는 전기로의 재질 및 구성이 열에 강한 소재로 바뀌어야 하므로 제조비용 및 공정비용이 상승하는 문제가 발생한다. The heat treatment temperature of the carbonization step is preferably 1000 to 1500 ° C, more preferably 1200 to 1400 ° C. When carbonizing at a temperature below 1000 ° C., the element ratio (H / C%) of hydrogen and carbon is increased to decrease the output characteristics of the battery, and the remaining hydrogen in carbon reacts irreversibly with lithium ions for the first 5 cycles. When the carbonization temperature is higher than 1400 ° C, the reversible capacity, which is the storage capacity of lithium ions, decreases, the energy density of the battery is greatly reduced, and the specific surface area increases. As the property of adsorbing moisture in the air increases, there arises a problem that the lithium ion reacts with moisture in the battery reaction, thereby increasing the irreversible capacity. In addition, the commercial furnace in order to withstand the heat treatment temperature of more than 1500 ℃ because the material and configuration of the electric furnace must be changed to a heat-resistant material, there arises a problem that the manufacturing cost and process cost increases.
본 발명의 제조방법에 의한 예비 탄소화 단계, 미분쇄 단계 및 탄소화 단계를 거친 리튬이차전지용 음극 활물질은 비표면적이 2.0 내지 5.0㎡/g 이고, 도 6에 나타난 바와 같이, 평균 기공크기가 1 내지 5nm인 것이 바람직하다. 또한, X선 회절법(XRD)에 의해 구해지는 (002) 평균 층면간격 (d002)가 3.7 내지 4.0Å이고, C축 방향의 결정자 직경 Lc(002)가 0.8 내지 2nm이며, R값이1.3 내지 2인 것이 바람직하고, 피크강도비인(5°피크/002피크)가 2 내지 4인 것이 바람직하며, 원소분석에 의해 구해지는 수소와 탄소의 원소비(H/C %)가 0.1 이하, 산소와 탄소의 원소비(O/C %)가 1.0이하인 것이 바람직하다. The negative active material for a lithium secondary battery that has undergone the preliminary carbonization step, the fine grinding step and the carbonization step according to the present invention has a specific surface area of 2.0 to 5.0 m 2 / g, and as shown in FIG. 6, an average pore size of 1 It is preferable that it is-5 nm. Further, the (002) mean layer spacing (d002) obtained by the X-ray diffraction method (XRD) was 3.7 to 4.0 kPa, the crystallite diameter Lc (002) in the C-axis direction was 0.8 to 2 nm, and the R value was 1.3 to It is preferable that it is 2, and it is preferable that the peak intensity ratio (5 degree peak / 002 peak) is 2-4, The element ratio of hydrogen and carbon (H / C%) calculated | required by elemental analysis is 0.1 or less, oxygen and It is preferable that the element ratio (O / C%) of carbon is 1.0 or less.
이는 본 발명의 제조방법에 의해 제조된 리튬이차전지용 음극 활물질은 상기 범위의 물성을 가짐으로써, 수분 흡착율이 감소되고, 리튬이온 충방전에 용이한 구조로 형성되어 이차전지의 초기충방전효율을 향상시킬 수 있다. 또한, 이러한 리튬이차전지용 음극 활물질의 구조는 폴리우레탄 수지의 우레탄반응, 우레아 반응 및 이소시아누레이트 반응이 조직 내에서 균일하고 적절하게 조합됨으로써 형성되었으며, 비정질에 가까운 미세구조가 미세하고 균일한 기공을 포함하여 형성됨을 확인하였다. This is because the negative electrode active material for a lithium secondary battery manufactured by the manufacturing method of the present invention has physical properties in the above range, the water adsorption rate is reduced, it is formed in a structure that is easy to charge and discharge lithium ions to improve the initial charge and discharge efficiency of the secondary battery You can. In addition, the structure of the negative electrode active material for a lithium secondary battery is formed by uniformly and appropriately combining the urethane reaction, urea reaction, and isocyanurate reaction of the polyurethane resin in the structure, and the microstructure close to amorphous is fine and uniform pores. It was confirmed that including the formed.
본 발명의 리튬이차전지용 음극 활물질 및 그 제조방법, 이를 이용한 리튬이차전지에 따르면, 폴리우레탄 수지를 활성기체 분위기 하에서 열처리하여 탄소화한 탄화물을 포함하는 음극 활물질을 제조함으로써, 음극 활물질의 비표면적이 낮아지고, 메조기공이 발달하지 않은 표면을 형성시켜 수분흡착을 방지하며, 전극 건조공정에서 수분제거가 용이하여 이차전지의 초기효율, 출력 및 수명특성이 현저히 향상시킬 수 있는 장점이 있다. 또한, 상기 음극 활물질을 포함하는 리튬이차전지는 전지의 초기충방전효율이 현저히 향상되는 장점이 있다. According to the negative electrode active material for a lithium secondary battery of the present invention, a method for manufacturing the same, and a lithium secondary battery using the same, the specific surface area of the negative electrode active material is prepared by preparing a negative electrode active material including a carbonized carbide by heat-treating a polyurethane resin under an active gas atmosphere. It is lowered, prevents the adsorption of water by forming a surface in which the mesopores are not developed, and it is easy to remove moisture in the electrode drying process, thereby improving the initial efficiency, output and life characteristics of the secondary battery. In addition, the lithium secondary battery including the negative electrode active material has an advantage that the initial charge and discharge efficiency of the battery is significantly improved.
도 1은 본 발명에 따른 리튬이차전지의 음극 활물질의 이소시아네이트 함량에 따른 질소의 함량변화를 나타낸 그래프이다. 1 is a graph showing a change in the nitrogen content according to the isocyanate content of the negative electrode active material of the lithium secondary battery according to the present invention.
도 2는 본 발명에 따른 리튬이차전지의 음극 활물질의 이소시아네이트 함량에 따른 비표면적 변화를 나타낸 그래프이다.2 is a graph showing the change in specific surface area according to the isocyanate content of the negative electrode active material of the lithium secondary battery according to the present invention.
도 3은 본 발명에 따른 리튬이차전지의 음극 활물질의 이소시아네이트 함량에 따른 초기충방전효율의 변화를 나타낸 그래프이다. 3 is a graph showing a change in the initial charge and discharge efficiency according to the isocyanate content of the negative electrode active material of the lithium secondary battery according to the present invention.
도 4는 본 발명에 따른 리튬이차전지의 음극 활물질의 탄소화온도에 따른 초기충방전효율의 변화를 나타낸 그래프이다.4 is a graph showing a change in the initial charge and discharge efficiency according to the carbonization temperature of the negative electrode active material of the lithium secondary battery according to the present invention.
도 5는 본 발명에 따른 리튬이차전지의 음극활물질 표면의 메조기공을 분석한 그래프이다.5 is a graph analyzing mesopores on the surface of the negative electrode active material of the lithium secondary battery according to the present invention.
도 6는 본 발명에 따른 리튬이차전지의 음극활물질 표면의 마이크로기공을 분석한 그래프이다.6 is a graph analyzing micropores on the surface of the negative electrode active material of the lithium secondary battery according to the present invention.
이하, 본 발명의 리튬이차전지용 음극 활물질 및 그 제조방법에 대하여 바람직한 실시형태 및 평가시험항목을 상세히 설명한다. 본 발명은 하기의 실시예에 의하여 보다 더 잘 이해될 수 있으며, 하기의 실시예는 본 발명의 예시 목적을 위한 것이고, 첨부된 특허 청구범위에 의하여 한정되는 보호범위를 제한하고자 하는 것은 아니다. EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment and evaluation test item are demonstrated in detail about the negative electrode active material for lithium secondary batteries of this invention, and its manufacturing method. The invention can be better understood by the following examples, which are intended for purposes of illustration of the invention and are not intended to limit the scope of protection defined by the appended claims.
<평가 시험 항목><Evaluation test item>
1) 폴리우레탄 수지의 원소분석1) Elemental Analysis of Polyurethane Resin
① C, H, N, S, O 원소분석장비(C, H, N, S(EA1110-FISONS), O(FlashEA 112))에 의해 얻어진 원소비율(%)에 각 원소의 질량을 곱한 총합에서 각 원소의 백분율을 구하여 원소의 질량비율을 구하였다. ① From the sum of the element ratios (%) obtained by C, H, N, S, O elemental analysis equipment (C, H, N, S (EA1110-FISONS), O (FlashEA 112), multiplied by the mass of each element. The percentage of each element was determined to determine the mass ratio of the elements.
② H/C 비율 측정② H / C ratio measurement
원소분석을 통해 얻어진 원소비율(%) 중 수소 및 탄소의 원소비를 H/C ratio= 수소/탄소*100의 수식으로 하여 원소비율을 구하였다. The element ratio of hydrogen and carbon in the element ratio (%) obtained through elemental analysis was calculated by the formula of H / C ratio = hydrogen / carbon * 100.
③O/C 비율 측정③O / C ratio measurement
원소분석을 통해 얻어진 원소비율(%) 중 산소 및 탄소의 원소비를 O/C ratio= 산소/탄소*100의 수식으로 하여 원소비율을 구하였다. The element ratio of oxygen and carbon in the element ratio (%) obtained through elemental analysis was determined by the formula of O / C ratio = oxygen / carbon * 100.
2) XRD 측정2) XRD measurement
① 입자의평균층간거리(d002)분석① Analysis of average interlayer distance (d 002 ) of particles
X-ray 회절법을 이용하여 측정한 2θ값의 그래프를 얻어 그래프의 피크 위치를 적분법에 의해 구하여 Bragg 공식에 의해 d002(d002 = λ/2sinθ)를 계산한다. CuKa선의 파장은 0.15406nm로 하였다. 이때, 측정 범위는 2.5° ~ 80°까지 이며, 측정 속도는 5°/min으로 하였다. Obtain a graph of 2θ values measured by X-ray diffraction method, calculate the peak position of the graph by the integral method, and calculate d002 (d002 = lambda / 2sinθ) by Bragg's formula. The wavelength of the CuKa line was 0.15406 nm. At this time, the measurement range was up to 2.5 ° ~ 80 °, the measurement speed was 5 ° / min.
② 흑연격자결정성비교분석 (R value)② Graphite lattice crystallinity comparison analysis (R value)
: R 값은, (002) peak를 나타내는 2θ에서의 (A)와 (B)의 각 intensity 비로 정의된다. The R value is defined as the ratio of the intensities of (A) and (B) in 2θ representing the (002) peak.
(A) 는 (002) peak의 양 옆의 baseline을 기준으로 직선을 그어 설립되는 background이며, (B) 는 background를 (002) peak로 평행 이동하여 (002) peak와 만나는 접점에서의 intensity이다.(A) is the background established by drawing a straight line based on the baselines on both sides of the (002) peak, and (B) is the intensity at the junction where the background meets the (002) peak in parallel with the (002) peak.
R = B / AR = B / A
[규칙 제91조에 의한 정정 16.01.2012]　 [Revision 16.01.2012 under Rule 91]
③ 입자의 crystalline size 분석③ crystalline size analysis of particles
: Scherrer의 식에 의해 입자의 C축 방향의 결정자 두께 Lc(002)를 계산하였다. : The crystallite thickness Lc (002) in the C-axis direction of the particle was calculated by the Scherrer equation.
Lc(002)= (Scherrer의 식)Lc (002) = (Scherrer's equation)
K = 0.9K = 0.9
λ = wavelength (0.154056nm)λ = wavelength (0.154056 nm)
B = FWHM (Full Width at Half Maximum)B = FWHM (Full Width at Half Maximum)
3) 비표면적 측정3) Specific surface area measurement
KS A 0094, KS L ISO 18757 규격에 따라 시료를 채취하여 전처리 장치를 통해 300℃에서 3시간 탈가스 처리 후 Surface Area, Pore Size Analyzer 장치를 통해 질소가스 기체 흡착 BET법에 의한 압력구간(P/P0) 0.05~0.3에서 시료의 비표면적을 측정하였다.Samples were collected according to KS A 0094, KS L ISO 18757 standards, and degassed at 300 ° C for 3 hours through a pretreatment device, followed by nitrogen gas adsorption BET method through surface area and pore size analyzer devices (P / P0) The specific surface area of the sample was measured at 0.05 to 0.3.
4) 표면기공 분석4) Surface Pore Analysis
전처리 장치를 통해 300℃에서 3시간 동안 탈가스 처리 후 Pore Size Analyzer(Bellsorp mini Ⅱ)를 통해 질소가스 기체 흡착법에 의해 시료 표면의 기공을 분석하였다.After degassing at 300 ° C. for 3 hours through a pretreatment apparatus, pores on the surface of the sample were analyzed by nitrogen gas adsorption through a Pore Size Analyzer (Bellsorp mini II).
분석은 HK method법에 의해 2nm 이하 크기의 직경을 갖는 기공(Micropore)의 전체 부피 분포도로 나타내었으며, BJH method법에 의해 2~50nm 크기의 직경을 갖는 기공(Mesopore)의 전체 부피 분포도로 나타내었다.The analysis shows the total volume distribution of the pores (Micropore) having a diameter of 2 nm or less by the HK method, and the total volume distribution of the pores (Mesopore) having a diameter of 2-50 nm by the BJH method. .
Micropore = ≤ 2nmMicropore = ≤ 2nm
Mesopore = 2 ~ 50nmMesopore = 2 to 50 nm
Macropore = ≥ 50nmMacropore = ≥ 50nm
5) 수분 흡착량 측정5) Moisture adsorption amount measurement
제조된 탄소를 상대습도 70%, 온도 25℃의 조건에서 24시간 방치 후 Karl fischer 수분측정장비를 이용하여 200℃에서 5분간 유지하여 시료에 흡착된 수분의 양을 측정하였다.The prepared carbon was left at a relative humidity of 70% and a temperature of 25 ° C. for 24 hours, and then maintained at 200 ° C. for 5 minutes using Karl fischer moisture measurement equipment to measure the amount of moisture adsorbed on the sample.
6) 잔류 수분량 측정6) Residual moisture content measurement
음극 활물질과 바인더를 97:3의 비율로 슬러리를 제조하여 100 ㎛두께로 코팅후 건조하여 1㎠의 원형디스크 형태로 타공 후 120 ℃ 진공건조를 6시간 행한 후의 전극의 잔류 수분량을 Karl Fischer 수분 측정장비를 이용하여 200℃에서 5분간 유지하여 전극의 잔류 수분량을 측정하였다.A slurry was prepared in a ratio of 97: 3 to a negative electrode active material and a binder, coated to a thickness of 100 μm, dried, perforated in the form of a circular disc of 1 cm 2, and then measured by Karl Fischer for measuring the moisture content of the electrode after 120 hours vacuum drying for 6 hours. The instrument was held at 200 ° C. for 5 minutes to measure the residual moisture content of the electrode.
7) 측정셀의 제조방법 및 충방전 특성평가7) Manufacturing method of measuring cell and evaluation of charge and discharge characteristics
측정셀은 코인형 반쪽전지로서 음극활물질과 바인더를 97:3의 비율로 제조한 전극과 상대전극으로 리튬금속박을 사용하였으며, 분리막을 사이에 두고 유기전해액으로 EC/DEC가 1:1 비율로 혼합되어 있고 1M의 LiPF6가 용해된 전해액을 함침하여 2016 type코인셀로 제조하였다. The measuring cell is a coin-type half-cell with lithium metal foil as an electrode and a counter electrode prepared with a cathode active material and a binder in a ratio of 97: 3, and EC / DEC is mixed in a 1: 1 ratio with an organic electrolyte with a separator therebetween. It was prepared in 2016 type coin cell by impregnating 1M LiPF6 dissolved electrolyte solution.
8) 충방전특성평가8) Charge / discharge characteristic evaluation
충전은 0.1 C rate로 0.005V까지 정전류법으로 탄소전극에 리튬이온을 삽입시키고 0.005V부터 정전류법으로 리튬이온 삽입을 진행시키다가 전류가 0.01mA가 될 때 리튬이온 삽입을 종료하였다. 방전은 0.1C rate로 정전류법으로 종지전압을 1.5V로하여 리튬이온을 탄소전극으로부터 탈리시켰다.Charging was performed by inserting lithium ions into the carbon electrode with a constant current method up to 0.005V at 0.1 C rate, and then inserting lithium ions with a constant current method from 0.005V. When the current reached 0.01 mA, the lithium ion insertion was terminated. In the discharge, lithium ion was detached from the carbon electrode at a constant current method at a rate of 0.1 C with a final voltage of 1.5 V.
9) 출력특성평가9) Output Characteristic Evaluation
출력특성 평가는 리튬이온 방전시의 출력 특성을 측정한 것으로서 초기 0.1 C로 5사이클 충방전 진행 후 이후부터 방전(리튬이온 탈리) C rate만 단계적으로 증가시키면서 0.1C rate 가역용량 대비 5 C-rate 가역용량의 유지율을 측정하였다.The output characteristic evaluation is a measure of the output characteristics at the time of lithium ion discharge. After 5 cycles of charging and discharging to 0.1 C at the initial stage, the discharge (lithium ion desorption) C rate is increased step by step and 5 C-rate compared to 0.1 C rate reversible capacity. The retention rate of the reversible capacity was measured.
[실시예 1]Example 1
음극 활물질용 폴리우레탄 수지의 합성Synthesis of Polyurethane Resin for Negative Electrode Active Material
수산기를 7중량% 포함하는 폴리올(AKP SSP-104) 100g 과 4,4‘-MDI 175g을 4000rpm 속도로 10초간 교반하여 경화된 폴리우레탄 수지를 제조하였다. 상기 폴리우레탄 수지는 파쇄기를 이용하여 입경이 0.1~2 mm가 되도록 분쇄를 한 후, 분쇄물을 질소가스분위기 중 에서 700℃까지 승온시키고, 700℃에서 1시간 유지하여 예비 탄소화를 실시하여 탄화수율 38%의 리튬이차전지 음극활물질 전구체를 얻었다. 얻어진 음극활물질 전구체는 제트밀을 사용하여 평균입경이 약 6~12㎛ 정도로 미분쇄하였으며, 최대입자크기는 50㎛을 넘지 않도록 하였다. 미분쇄된 음극활물질 전구체는 세라믹 재질의 도가니에 넣고 질소가스 분위기 하에서 5℃/min.의 승온속도로 1200℃까지 승온시키고, 1200℃에서 1시간 유지하여 탄소화 공정을 거침으로써 리튬이차전지용 음극활물질로 사용가능한 탄소재를 제조하였다. 이하 표 1에서는 폴리올과 이소시아네이트의 조성비와 탄소화 온도를 나타내었으며, 실시예 1에서 제조된 리튬이차전지용 음극활물질을 상술한 <평가시험항목>을 측정하였으며, 그 결과를 하기의 표 2, 표 3 및 표 4에 나타내었다. 100 g of polyol (AKP SSP-104) containing 7% by weight of hydroxyl group and 175 g of 4,4′-MDI were stirred at 4000 rpm for 10 seconds to prepare a cured polyurethane resin. The polyurethane resin was pulverized using a crusher to have a particle diameter of 0.1 to 2 mm, and then the pulverized product was heated to 700 ° C. in a nitrogen gas atmosphere, and maintained at 700 ° C. for 1 hour to carry out preliminary carbonization. A yield of 38% lithium secondary battery negative electrode active material precursor was obtained. The obtained negative electrode active material precursor was pulverized with an average particle size of about 6 ~ 12㎛ using a jet mill, the maximum particle size was not to exceed 50㎛. The pulverized negative electrode active material precursor is placed in a ceramic crucible and heated to 1200 ° C. at a temperature rising rate of 5 ° C./min. Under a nitrogen gas atmosphere, and maintained at 1200 ° C. for 1 hour to undergo a carbonization process. A carbon material usable as was prepared. Table 1 below shows the composition ratio and carbonization temperature of the polyol and isocyanate, and the <evaluation test items> of the anode active material for the lithium secondary battery prepared in Example 1 were measured, and the results are shown in Tables 2 and 3 below. And in Table 4.
[실시예 2]Example 2
실시예 2는 탄소화 온도를 1300℃로 실시한 것을 제외하고 실시예 1과 동일하게 실시하였다. Example 2 was carried out in the same manner as in Example 1 except that the carbonization temperature was carried out at 1300 ℃.
[실시예 3]Example 3
실시예 2는 탄소화 온도를 1400℃로 실시한 것을 제외하고 실시예 1과 동일하게 실시하였다. Example 2 was carried out in the same manner as in Example 1 except that the carbonization temperature was carried out at 1400 ℃.
[실시예 4]Example 4
실시예 4는 이소시아네이트 함량을 194g으로 실시한 것을 제외하고 실시예 1과 동일하게 실시하였다. Example 4 was carried out in the same manner as in Example 1 except that the isocyanate content was performed at 194 g.
[실시예 5]Example 5
실시예 5는 탄소화 온도를 1300℃로 실시한 것을 제외하고 실시예 4와 동일하게 실시하였다. Example 5 was carried out in the same manner as in Example 4 except that the carbonization temperature was carried out at 1300 ℃.
[실시예 6]Example 6
실시예 5는 탄소화 온도를 1400℃로 실시한 것을 제외하고 실시예 4와 동일하게 실시하였다. Example 5 was carried out in the same manner as in Example 4 except that the carbonization temperature was carried out at 1400 ℃.
[실시예 7]Example 7
실시예 7은 이소시아네이트 함량을 210g으로 실시한 것을 제외하고 실시예 1과 동일하게 실시하였다. Example 7 was carried out in the same manner as in Example 1 except that the isocyanate content was carried out at 210 g.
[실시예 8]Example 8
실시예 8는 탄소화 온도를 1300℃로 실시한 것을 제외하고 실시예 7과 동일하게 실시하였다. Example 8 was carried out similarly to Example 7, except that the carbonization temperature was performed at 1300 ° C.
[실시예 9]Example 9
실시예 9는 탄소화 온도를 1400℃로 실시한 것을 제외하고 실시예 7과 동일하게 실시하였다. Example 9 was carried out in the same manner as in Example 7, except that the carbonization temperature was performed at 1400 ° C.
[실시예 10]Example 10
실시예 10는 이소시아네이트 함량을 225g로 실시한 것을 제외하고 실시예 1과 동일하게 실시하였다. Example 10 was carried out in the same manner as in Example 1 except that the isocyanate content was carried out at 225 g.
[실시예 11]Example 11
실시예 11은 탄소화 온도를 1300℃로 실시한 것을 제외하고 실시예 10과 동일하게 실시하였다. Example 11 was carried out in the same manner as in Example 10 except that the carbonization temperature was performed at 1300 ° C.
[실시예 12]Example 12
실시예 12는 탄소화 온도를 1400℃로 실시한 것을 제외하고 실시예 10과 동일하게 실시하였다. Example 12 was carried out in the same manner as in Example 10 except that the carbonization temperature was performed at 1400 ° C.
[비교예 1] Comparative Example 1
Sucrose를 전구체로 하여 질소 분위기하에서 5℃/min의 승온속도로 1200℃로 승온한 후 1시간 유지하여 탄소화한 후 회전날 커터밀로 평균입경 12㎛의 입자로 분쇄하여 탄소를 제조하였다.Sucrose as a precursor was heated to 1200 ℃ at a temperature increase rate of 5 ℃ / min in a nitrogen atmosphere and maintained for 1 hour and carbonized, and then pulverized into particles of an average particle diameter of 12 ㎛ with a rotary blade cutter mill to prepare carbon.
[비교예 2]Comparative Example 2
비교예 2는 탄소화온도를 1300℃로 한 것을 제외하고 비교예 1과 동일하게 실시하였다. Comparative Example 2 was carried out in the same manner as in Comparative Example 1 except that the carbonization temperature was 1300 ℃.
[비교예 3]Comparative Example 3
비교예 3은 석유계 Pitch를 전구체를 사용하여 150℃에서 용융을 시킨 후 압출하여 과립을 형성한 후 대기중에서 300℃의 온도로 6시간 유지하여 불용화 처리하였다. 그 후 질소 분위기 하에서 700℃로 승온하고, 1시간 유지하여 예비탄소화를 수행하여, 탄화수율 68%의 음극활물질 전구체를 얻었다. 얻어진 음극활물질 전구체를 제트밀을 사용하여 평균 입자크기가 약 6~12㎛ 정도로 미분쇄하여 세라믹 재질의 도가니에 넣고 질소분위기 하에서 5℃/min 의 승온속도로 1200℃로 승온하고 1시간 유지하여 탄소화 공정을 거침으로써 리튬이차전지용 음극활물질로 사용가능한 탄소재를 제조하였다. In Comparative Example 3, the petroleum pitch was melted at 150 ° C. using a precursor, extruded to form granules, and then maintained at 300 ° C. in air for 6 hours to insolubilize. Thereafter, the temperature was raised to 700 ° C. under a nitrogen atmosphere, and preliminary carbonization was performed for 1 hour to obtain a cathode active material precursor having a yield of 68% of carbonization. The obtained negative electrode active material precursor was pulverized with an average particle size of about 6-12 μm using a jet mill, placed in a crucible made of ceramic material, heated to 1200 ° C. at a temperature increase rate of 5 ° C./min under a nitrogen atmosphere, and maintained for 1 hour. By the carbonization process, a carbon material usable as a negative electrode active material for a lithium secondary battery was prepared.
[비교예 4][Comparative Example 4]
비교예 4는 탄소화 온도를 1300℃로 한 것을 제외하고 비교예 3과 동일하게 실시하였다. Comparative Example 4 was carried out in the same manner as in Comparative Example 3 except that the carbonization temperature was 1300 ° C.
[비교예 5][Comparative Example 5]
비교예 5은 탄소화 온도를 900℃로 한 것을 제외하고 실시예 1과 동일하게 실시하였다.Comparative Example 5 was carried out in the same manner as in Example 1 except that the carbonization temperature was 900 ° C.
[비교예 6]Comparative Example 6
비교예 6은 이소시아네이트 함량을 350g로 실시한 것을 제외하고 실시예 2와 동일하게 실시하였다. Comparative Example 6 was carried out in the same manner as in Example 2, except that the isocyanate content was carried out at 350 g.
이차전지의제조Manufacture of Secondary Battery
(a) 전극 제작(a) Electrode Fabrication
상기 실시예 및 비교예에서 제조된 음극 활물질 97 중량부에 SBR(Stylene Butadiene Rubber) 1.5 중량부, CMC(Carboxyl Methyl Cellulose) 1.5 중량부를 첨가하여 증류수를 첨가하며 슬러지 형태로 균일하게 교반하여 구리 호일 상에 균일하게 코팅하였다. 코팅은 닥터블레이드를 사용하여 110㎛로 균일하게 코팅하였고 60℃ 오븐에서 30분간 건조하여 0.6Mpa의 압력으로 프레스를 시행하였다. 호일상의 전극을 넓이 1cm2의 원형으로 펀칭하여 120℃ 진공오븐에서 12시간 건조하였다.  Add 1.5 parts by weight of SBR (Stylene Butadiene Rubber) and 1.5 parts by weight of CMC (Carboxyl Methyl Cellulose) to 97 parts by weight of the negative electrode active material prepared in Examples and Comparative Examples to add distilled water and stir evenly in the form of sludge to form a copper foil Coated uniformly. The coating was uniformly coated at 110 μm using a doctor blade, dried in an oven at 60 ° C. for 30 minutes, and pressed at a pressure of 0.6 Mpa. The electrode on the foil was punched into a circular shape having a width of 1 cm 2 and dried in a vacuum oven at 120 ° C. for 12 hours.
(b) 시험 전지의 제작(b) Preparation of test cell
상기 실시예 및 비교예에서 제조된 음극 활물질은 수계전해질 이차전지의 음극에 사용하였으며, 음극활물질의 충전(리튬삽입) 용량 및 방전(리튬탈리) 용량이 대극의 성능에 영향을 받지 않고 단독적으로 정밀하게 평가하기 위하여 리튬 금속을 대극으로 사용하여 리튬이차전지를 구성하고, 특성을 평가하였다. The negative electrode active materials prepared in Examples and Comparative Examples were used in the negative electrode of the aqueous electrolyte secondary battery, and the charge (lithium insertion) capacity and the discharge (lithium detachment) capacity of the negative electrode active material were precisely independent without being affected by the performance of the counter electrode. In order to evaluate easily, a lithium secondary battery was constructed using lithium metal as a counter electrode, and characteristics were evaluated.
리튬이차전지는 2016사이즈(직경 20mm, 두께 16mm)의 코인형 전지로 아르곤분위기 하의 글로브 박스 내에서 조립되었으며, 1mm두께의 금속리튬을 코인형 전지캔의 바닥에 압착하였고 그 위에 폴리프로필렌 재질의 분리막을 형성하고, 음극을 리튬과 마주보게 하였다. 이때, 사용된 전해질은 EC(Ethylene Carbonate)와 DMC(Dimethyl Carbonate), EMC(Ethyl Methyl Carbonate)를 부피비 1:1:1로 혼합하여 제조된 용매에 1.2M의 LiPF6 염을 첨가하여 제조된 것으로 코인형 전지에 투입하여 캔 커버를 닿고 압착하여 리튬이차전지를 조립하였다.The lithium secondary battery is a 2016-sized (20 mm diameter, 16 mm thick) coin-type battery assembled in a glove box under an argon atmosphere. A 1 mm thick metal lithium is pressed onto the bottom of a coin-type battery can, and a polypropylene separator is placed thereon. Was formed and the negative electrode was faced with lithium. In this case, the electrolyte used was prepared by adding 1.2 M of LiPF6 salt to a solvent prepared by mixing EC (Ethylene Carbonate), DMC (Dimethyl Carbonate) and EMC (Ethyl Methyl Carbonate) in a volume ratio of 1: 1: 1. The lithium secondary battery was assembled by putting it in a doll battery, touching the can cover, and pressing.
(c) 전지 용량 측정(c) battery capacity measurement
상기 조립된 리튬2차전지에 대한 특성 분석은 TOYO SYSTEM社에서 제조된 TOSCAT-3100 충방전 시험장치를 이용하여 정전류-정전압법(CCCV)에 의해 25℃에서 충방전을 시행하였다. 여기서 '충전'은 음극에 리튬이 삽입되는 반응으로 코인형 전지의 전압이 낮아지는 반응이고, '방전'은 리튬이 음극에서 탈리되어 대극쪽으로 이동하는 반응으로, 코인형 전지의 전압이 높아지는 반응이다. 또한 여기서 정전류-정전압 조건은 코인형 전지의 전압이 0.005V가 될 때까지 일정한 전류밀도(0.1C 기준)로 충전을 행하고, 그 후에 전압을 유지한 채 전류값이 0.05mA가 될 때까지 일정하게 감소시켜 충전을 진행한다. 이 때 공급한 전기량을 전극의 음극활물질의 중량으로 나눈 값을 음극활물질의 단위중량 당 충전용량(mAh/g)이라 하였다. 충전 종료 후, 10분간 전지의 작동을 멈추고 방전을 시행하였다. 방전은 코인형 전지의 전압이 1.5V가 될 때까지 일정한 전류로 시행하였고, 이 때 방전한 전기량을 전극의 음극활물질의 중량으로 나눈 값을 음극활물질의 단위중량 당 방전용량(mAh/g)이라 하였다. 가역용량은 방전용량으로 정의하였으며 비가역용량은 충전용량에서 방전용량을 뺀 용량으로 계산하였고 효율은 충전용량 대비 방전용량을 퍼센트(%)로 계산하였다. 기본적인 코인형 전지의 특성값은 동일시료로 제작한 동일 전지 3개 이상의 특성값을 평균하여 나타내었다.Characterization of the assembled lithium secondary battery was charged and discharged at 25 ℃ by the constant current-constant voltage method (CCCV) using the TOSCAT-3100 charge and discharge test apparatus manufactured by TOYO SYSTEM. Here, 'charging' is a reaction in which the voltage of the coin-type battery decreases due to the insertion of lithium into the negative electrode, and 'discharge' is a reaction in which lithium is detached from the negative electrode and moves toward the counter electrode. . In this case, the constant current-constant voltage condition is charged at a constant current density (0.1C standard) until the voltage of the coin-type battery becomes 0.005V, and then constantly until the current value becomes 0.05mA while maintaining the voltage. Decrease to proceed with charging. The amount of electricity supplied at this time divided by the weight of the negative electrode active material of the electrode was called the charging capacity per unit weight of the negative electrode active material (mAh / g). After the end of charging, the battery was stopped for 10 minutes and discharged. The discharge was carried out at a constant current until the voltage of the coin-type battery became 1.5V. The value of the discharged electricity divided by the weight of the negative electrode active material of the electrode was the discharge capacity per unit weight of the negative electrode active material (mAh / g). It was. The reversible capacity was defined as the discharge capacity, the irreversible capacity was calculated by subtracting the discharge capacity from the charging capacity, and the efficiency was calculated as the percentage (%) of the discharge capacity. The characteristic value of a basic coin-type battery was shown by averaging the characteristic value of three or more of the same batteries made from the same sample.
(d) 고율 충방전 특성 측정(d) Measurement of high rate charge and discharge characteristics
상기 조립된 리튬2차전지에 대한 고율 충방전 특성 분석은 (c)와 동일하게 정전류-정전압법(CCCV)에 의해 25℃에서 시행하였다. 고율 충방전 특성은 충방전시의 전류밀도를 변화시켜,공급 또는 방전되는 일정한 전류밀도를 사이클 별로 증가시켜 그 전류밀도에서 충방전되어 측정되는 용량(mAh/g)으로 나타내었다.High rate charge / discharge characteristics analysis of the assembled lithium secondary battery was performed at 25 ° C. by the constant current-constant voltage method (CCCV) as in (c). The high rate charge / discharge characteristics change the current density during charge and discharge, increase the constant current density supplied or discharged by cycle, and represent the capacity (mAh / g) measured and charged at the current density.
[표 1]TABLE 1
Figure PCTKR2011010374-appb-I000002
Figure PCTKR2011010374-appb-I000002
[표 2]TABLE 2
Figure PCTKR2011010374-appb-I000003
Figure PCTKR2011010374-appb-I000003
[표 3]TABLE 3
Figure PCTKR2011010374-appb-I000004
Figure PCTKR2011010374-appb-I000004
[표 4]TABLE 4
Figure PCTKR2011010374-appb-I000005
Figure PCTKR2011010374-appb-I000005
상기 표 2 내지 표 4 및 도 1 내지 도 4에 나타난 바와 같이, 리튬이차전지용 음극 활물질 제조시 최적의 함량의 이소시아네이트를 함유할 경우, 비표면적이 감소하고, 가역용량 및 초기충방전효율 등의 전기적 특성이 현저히 향상되는 것을 확인하였다. 탄소화 온도를 최적화함으로써, 불필요한 에너지 손실을 방지하며, 고효율의 전지효율을 나타내는 것을 확인하였다. 또한, 본 발명의 리튬이차전지용 활물질은 도 5에서 나타난 바와 같이, 탄소 표면에 메조기공이 발달하지 않아 수분함량이 적고, 또한 수분의 흡착량도 감소하여 비가역용량이 감소하고, 초기충방전효율이 증가되는 등의 전기화학적 특성도 현저히 향상됨을 알 수 있다. As shown in Table 2 to Table 4 and Figures 1 to 4, when the isocyanate containing the optimum content in the production of a negative active material for a lithium secondary battery, the specific surface area is reduced, such as reversible capacity and initial charge and discharge efficiency It was confirmed that the characteristic was remarkably improved. By optimizing the carbonization temperature, it was confirmed that unnecessary energy loss was prevented and that the cell efficiency was high. In addition, as shown in FIG. 5, the active material for a lithium secondary battery of the present invention does not develop mesopores on the carbon surface, so that the water content is low, and the adsorption amount of the water is also reduced, thereby reducing irreversible capacity and initial charging and discharging efficiency. It can be seen that the electrochemical properties such as increased significantly.
또한, 본 발명의 실시예에 따라 제조된 음극 활물질에 비하여, 비교예 1 및 비교예 2에 나타난 바와 같이 Sucrose를 탄소화하여 음극 활물질을 제조했을 때, 도 5에 나타난 바와 같이 메조기공이 많이 형성되어 수분의 흡착량이 증가하고, 전극의 잔류수분량이 현저히 높아진다. 그 결과 초기 충방전 효율 및 출력특성 등의 전지특성이 떨어져 리튬이차전지용 음극 활물질로 적합하지 않다는 것을 알 수 있으며, 비교예 3 및 비교예 4에 나타난 바와 같이 석유계 Pitch를 사용하여 음극활 물질을 제조했을 때, 초기충방전효율은 양호하나 가역용량 및 출력특성이 현저히 떨어져 리튬이차전지용 음극활물질로 적합하지 않다는 것을 알 수 있다. In addition, compared to the negative electrode active material prepared according to the embodiment of the present invention, as shown in Comparative Example 1 and Comparative Example 2, when the negative active material was prepared by carbonizing Sucrose, as shown in FIG. As a result, the adsorption amount of moisture increases, and the residual moisture content of the electrode is significantly increased. As a result, it can be seen that the battery characteristics such as initial charge and discharge efficiency and output characteristics are not suitable, and thus it is not suitable as a negative electrode active material for lithium secondary batteries.As shown in Comparative Examples 3 and 4, petroleum-based pitches are used to When manufactured, the initial charging and discharging efficiency is good, but the reversible capacity and the output characteristics are remarkably poor, it can be seen that it is not suitable as a negative electrode active material for lithium secondary batteries.
이상에서 본 발명의 바람직한 실시예를 설명하였으나, 본 발명은 다양한 변화와 균등물을 사용할 수 있으며, 상기 실시예를 적절히 변형하여 동일하게 응용할 수 있음이 명확하다. 따라서, 상기 기재 내용은 하기의 특허청구범위의 한계에 의해 정해지는 본 발명의 범위를 한정하는 것이 아니다. Although the preferred embodiment of the present invention has been described above, it is clear that the present invention can use various changes and equivalents, and can be applied in the same manner by appropriately modifying the above embodiment. Accordingly, the above description is not intended to limit the scope of the invention as defined by the following claims.

Claims (16)

  1. 폴리우레탄 수지를 비활성기체 분위기 하에서 열처리하여 탄소화한 탄화물을 포함하는 리튬이차전지용 음극활물질 Cathode active material for lithium secondary battery containing carbide carbonized by heat-treating polyurethane resin under inert gas atmosphere
  2. 제 1항에 있어서, The method of claim 1,
    상기 탄화물의 평균입자크기가 1 내지 50㎛이며, 비표면적이 2.0 내지 5.0㎡/g 이고, 평균 기공크기가 1 내지 5nm인 리튬이차전지용 음극활물질The average particle size of the carbide is 1 to 50㎛, the specific surface area is 2.0 to 5.0㎡ / g, the average pore size is 1 to 5nm negative electrode active material for lithium secondary battery
  3. 제 1항에 있어서, The method of claim 1,
    상기 열처리는 1차 열처리 및 2차 열처리를 포함하고, The heat treatment includes a first heat treatment and a second heat treatment,
    상기 1차 열처리는 600 내지 1400℃ 온도에서 30 내지 120분간 진행하고, The first heat treatment is performed for 30 to 120 minutes at 600 to 1400 ℃ temperature,
    상기 2차 열처리는 1000 내지 1,400℃ 온도에서 30 내지 120분간 진행하며, The secondary heat treatment is performed for 30 to 120 minutes at a temperature of 1000 to 1,400 ℃,
    상기 1차 열처리 및 2차 열처리는 순차적으로 진행되는 리튬이차전지용 음극활물질 The first and second heat treatments are sequentially performed negative electrode active material for lithium secondary battery
  4. 제 1항에 있어서, The method of claim 1,
    상기 리튬이차전지용 음극활물질은 X선 회절법에 의해 구해지는 (002) 평균 층면간격 (d002)가 3.7 내지 4.0Å이고, C축 방향의 결정자 직경 Lc(002)가 0.8 내지 2nm이며, R값이1.3 내지 2이며, 피크강도비인(5°피크/002피크)가 2 내지 4인 리튬이차전지용 음극활물질, The negative electrode active material for a lithium secondary battery has a (002) mean layer spacing (d002) of 3.7 to 4.0 kPa determined by the X-ray diffraction method, a crystallite diameter Lc (002) in the C-axis direction of 0.8 to 2 nm, and an R value of A negative active material for a lithium secondary battery having a 1.3 to 2 and a peak intensity ratio (5 ° peak / 002 peak) of 2 to 4,
  5. 제 1항에 있어서,The method of claim 1,
    상기 리튬이차전지용 음극활물질은 수소와 탄소의 원소비(H/C %)가 0.1 이하, 산소와 탄소의 원소비(O/C %)가 1.0이하인 리튬이차전지용 음극활물질The negative electrode active material for a lithium secondary battery has an element ratio (H / C%) of hydrogen and carbon of 0.1 or less and an element ratio (O / C%) of oxygen and carbon of 1.0 or less.
  6. 제 1항에 있어서,The method of claim 1,
    상기 리튬이차전지용 음극활물질을 포함하는 전극에서 잔류수분량이 100 내지 500 ppm인 리튬이차전지용 음극활물질Lithium secondary battery negative electrode active material having a residual water content of 100 to 500 ppm in the electrode containing the negative electrode active material for lithium secondary battery
  7. 제 1항에 있어서, The method of claim 1,
    상기 폴리우레탄 수지는 산소의 함량이 15 내지 22중량%이고, 질소의 함량이 7 내지 9중량%이며, 수소의 함량이 4 내지 6 중량%인 리튬이차전지용 음극활물질The polyurethane resin has an oxygen content of 15 to 22% by weight, a nitrogen content of 7 to 9% by weight, and a hydrogen content of 4 to 6% by weight of a negative electrode active material for a lithium secondary battery
  8. 제 1항에 있어서, The method of claim 1,
    상기 폴리우레탄 수지는 폴리올 및 이소시아네이트를 포함하며,The polyurethane resin includes polyols and isocyanates,
    상기 폴리올 100 중량부에 대하여, 상기 이소시아네이트가 150 내지 240중량부인 리튬이차전지용 음극활물질The negative active material for lithium secondary battery, wherein the isocyanate is 150 to 240 parts by weight based on 100 parts by weight of the polyol.
  9. 제 8항에 있어서, The method of claim 8,
    상기 폴리올은 폴리에테르계 폴리올, 폴리에스테르계 폴리올, 폴리테트라메틸렌 에테르 글리콜 폴리올, 피에이치디 폴리올(Polyharnstoff Dispersion(PHD) polyol), 아민(Amine) 변성 폴리올, 만니히(Manmich)폴리올 및 이들의 혼합물 중에서 선택되는 어느 하나 또는 둘 이상이고, The polyol may be selected from polyether polyol, polyester polyol, polytetramethylene ether glycol polyol, Polyharnstoff Dispersion (PHD) polyol, amine modified polyol, Manmich polyol and mixtures thereof Any one or more than two,
    상기 이소시아네이트는 헥사메틸렌디이소시아네이트(HDI), 이소포론디이소시아네이트(IPDI), 4,4'-디시클로헥실메탄 디이소시아네이트(H12MDI), 폴리에틸렌 폴리페닐 이소시아네이트, 톨루엔 디이소시아네이트(TDI), 2,2‘-디페닐메탄 디이소시아네이트(2,2'-MDI), 2,4’-디페닐메탄 디이소시아네이트(2,4'-MDI), 4,4'-디페닐메탄 디이소시아네이트(4,4'-MDI,monomeric MDI), 폴리머릭 디페닐메탄 디이소시아네이트(polymeric MDI), 오르토톨루이딘 디이소시아네이트(TODI), 나프탈렌 디오소시아네이트(NDI), 크실렌 디이소시아네이트(XDI), 라이신디이소시아네이트(LDI) 및 트리페닐메탄 트리이소시아네이트(TPTI) 중에서 선택되는 어느 하나 또는 둘 이상인 리튬이차전지용 음극활물질.The isocyanates include hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (H12MDI), polyethylene polyphenyl isocyanate, toluene diisocyanate (TDI), 2,2 ' -Diphenylmethane diisocyanate (2,2'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 4,4'-diphenylmethane diisocyanate (4,4'- MDI, monomeric MDI, polymeric diphenylmethane diisocyanate (polymeric MDI), orthotoluidine diisocyanate (TODI), naphthalene diosocyanate (NDI), xylene diisocyanate (XDI), lysine diisocyanate (LDI) and triphenyl A cathode active material for any one or two or more selected from methane triisocyanate (TPTI).
  10. 제 8항에 있어서,The method of claim 8,
    상기 폴리올의 분자량은 300 내지 3000이고, 상기 폴리올 내에 존재하는 하이드록시 함량은 전체 폴리올의 3 내지 15중량%인 리튬이차전지용 음극활물질. The molecular weight of the polyol is 300 to 3000, the hydroxy content present in the polyol is 3 to 15% by weight of the total polyol of the negative electrode active material for lithium secondary battery.
  11. 제 1항에 있어서, The method of claim 1,
    상기 폴리우레탄 수지는 발포제, 난연제, 촉매 또는 정포제를 추가로 더 포함하는 리튬이차전지용 음극활물질 The polyurethane resin is a negative electrode active material for a lithium secondary battery further comprising a blowing agent, a flame retardant, a catalyst or a foam stabilizer.
  12. 폴리우레탄수지를 비활성기체 분위기 하에서 열처리하는 탄소화 단계를 포함하는 리튬이차전지용 음극활물질의 제조방법.A method for producing a negative electrode active material for a lithium secondary battery comprising a carbonization step of heat-treating the polyurethane resin in an inert gas atmosphere.
  13. 제 12항에 있어서,The method of claim 12,
    상기 탄소화단계는 예비탄소화 단계 및 본탄소화 단계를 포함하며,The carbonization step includes a pre-carbonization step and the main carbonization step,
    상기 예비탄소화단계는 600 내지 1000℃ 온도에서 30 내지 120분 동안 열처리하는 단계이고,The precarbonization step is a heat treatment for 30 to 120 minutes at 600 to 1000 ℃ temperature,
    상기 본탄소화 단계는 1000 내지 1400℃ 온도에서 30 내지 120분 동안 열처리하는 단계를 포함하는 리튬이차전지용 음극활물질의 제조방법.The main carbonization step is a method of manufacturing a negative electrode active material for a lithium secondary battery comprising the heat treatment for 30 to 120 minutes at a temperature of 1000 to 1400 ℃.
  14. 제 12항에 있어서, The method of claim 12,
    상기 리튬이차전지용 음극활물질의 평균 입자크기가 1 내지 50㎛가 되도록 분쇄하는 미분쇄 단계를 추가로 더 포함하는 리튬이차전지용 음극활물질의 제조방법.Method for producing a negative active material for a lithium secondary battery further comprises a fine grinding step of pulverizing so that the average particle size of the negative electrode active material for a lithium secondary battery 1 to 50㎛.
  15. 제 13항에 있어서, The method of claim 13,
    상기 미분쇄단계는 예비탄소화 단계 이전, 예비탄소화 단계 이후 또는 탄소화 단계 이후 중에서 선택되는 1회 또는 2회 이상 진행되는 리튬이차전지용 음극활물질의 제조방법The pulverization step is a method of manufacturing a negative electrode active material for a lithium secondary battery that is carried out one or more times selected from before the pre-carbonization step, after the pre-carbonization step or after the carbonization step.
  16. 제 1항 내지 제 11항 중에서 선택되는 어느 한 항의 리튬이차전지용 음극활물질을 포함하는 리튬이차전지Lithium secondary battery comprising a negative electrode active material for any one of the lithium secondary battery selected from claim 1 to claim 11
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