KR101757964B1 - Composition for preparing positive electrode of lithium secondary battery, and positive electrode and lithium secondary battery prepared by using the same - Google Patents

Abstract

The present invention provides a composition for forming an anode of a lithium secondary battery comprising a cathode active material, a conductive material and a binder, wherein the cathode active material is contained in an amount of 90% by weight or more based on the total weight of the composition, (Conductive material / binder ratio) of from 0.6 to 1.2, and a positive electrode and a lithium electrode prepared using the same. Thereby providing a secondary battery.
[Equation 1]
2.4? (D ₉₀ -D ₁₀ ) / D _50? 3
The composition for forming an anode of a lithium secondary battery according to the present invention is characterized in that the cathode active material, the binder and the conductive material are uniformly dispersed in the composition and the penetration of the binder between the pores of the cathode active material is prevented, And can exhibit improved adhesion.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for forming a positive electrode of a lithium secondary battery, and a positive electrode and a lithium secondary battery manufactured using the same. BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a composition for forming a positive electrode of a lithium secondary battery, and a positive electrode and a lithium secondary battery produced using the same.

As technology development and demand for mobile devices increase, the demand for secondary batteries as energy sources is rapidly increasing. Among such secondary batteries, lithium secondary batteries having a high energy density and voltage, a long cycle life, and a low self-discharge rate are commercially available and widely used.

In the lithium secondary battery, the positive electrode is prepared by applying a composition for positive electrode, which is prepared by collectively mixing a positive electrode active material, a conductive material and a binder with a solvent, onto a positive electrode collector and drying the positive electrode collector. However, since most of the anode components, including the cathode active material and the conductive material, are used in powder form, when they are mixed in a solvent and mixed together, they have low miscibility with the solvent and are dispersed unevenly in the composition. When the positive electrode active material layer is formed by applying the positive electrode current collector in which the positive electrode composition components are dispersed nonuniformly, it is difficult to uniformly coat the positive electrode current collector. As a result, the thickness uniformity is low A cathode active material layer having surface defects is formed to deteriorate performance and lifetime characteristics of the battery.

More specifically, since the conductive material is used as fine particles at a level of several tens of nanometers, the cohesive force is strong, and cohesion between the conductive fine particles tends to occur when the conductive material is dispersed in a solvent. Such non-uniform dispersion of the conductive material in the cathode active material layer causes a decrease in conductivity and a deterioration in output characteristics of the battery.

In addition, uneven dispersion of the binder in the positive electrode active material layer causes unevenness of the bonding strength of the positive electrode active material layer to the positive electrode collector, and as a result, the positive electrode active material layer is separated from the positive electrode collector and peeled off. In this case, not only the performance of the battery itself is remarkably lowered but also the life characteristic of the battery is shortened.

Accordingly, in order to improve battery performance and lifespan characteristics, there is a need to develop a cathode component having excellent properties and a technique for uniformly dispersing the components in the composition for anode formation.

Korean Registered Patent No. 1103198 (registered on December 29, 2011)

A first object of the present invention is to provide a method for forming a cathode active material layer in which a binder is uniformly dispersed in a cathode active material layer and a binder is contained in the cathode active material layer, And a composition for forming a positive electrode of a lithium secondary battery.

A second technical problem to be solved by the present invention is to provide a positive electrode for a lithium secondary battery manufactured using the composition for forming a positive electrode.

In addition, a third technical problem to be solved by the present invention is to provide a lithium secondary battery, a battery module, and a battery pack including the positive electrode.

However, the technical problem to be solved by the present invention is not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

According to an embodiment of the present invention, there is provided a composition for forming an anode of a lithium secondary battery comprising a cathode active material, a conductive material, and a binder, wherein the cathode active material is at least 90 wt% and including, to the conductive material having a particle size meeting the particle size distribution ratio _{((D 90 -D 10) /} D 50) condition according to equation (1), and the conductive material and the binder is a mixture weight ratio of 0.6 to 1.2 (Ratio of conductive material / binder).

[Equation 1]

2.4? (D ₉₀ -D ₁₀ ) / D _50? 3

According to another embodiment of the present invention, there is provided a positive electrode of a lithium secondary battery manufactured using the composition for forming an anode.

According to another embodiment of the present invention, there is provided a lithium secondary battery including the positive electrode, a battery module, and a battery pack.

Other details of the embodiments of the present invention are included in the following detailed description.

The composition for forming a positive electrode of a lithium secondary battery according to the present invention is characterized in that the positive electrode active material, the binder and the conductive material are uniformly dispersed in the positive electrode active material layer and the binder enters the space between the positive electrode active materials to increase the migration resistance of lithium ions It is possible to reduce the internal resistance at the time of manufacturing the positive electrode and to exhibit excellent adhesion. As a result, the output characteristics and lifetime characteristics of the lithium secondary battery including the positive electrode prepared using the positive electrode composition can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
FIG. 1 is a photograph of a distribution of a conductive material on a positive electrode prepared according to Example in Experimental Example 1 using a scanning electron microscope (SEM). FIG.
Fig. 2 is a graph showing the resistance in an electrode of a positive electrode prepared by mixing the conductive material and the binder in various mixing weight ratios in Experimental Example 2. Fig.
Fig. 3 is a graph showing the peel strength measured at the anode prepared by mixing the conductive material and the binder at various mixing weight ratios in Experimental Example 2. Fig.
4A and 4B are SEM photographs of the positive electrode (positive electrode 1-2) prepared by mixing the conductive material and the binder at a mixing weight ratio of 0.8 in Experimental Example 2 at different positions.
5A and 5B are SEM photographs of a positive electrode (anode 1-1) prepared by mixing a conductive material and a binder at a mixing weight ratio of 0.5 in Experimental Example 2 at different positions.
FIG. 6 is a graph showing the electrode resistance of the anode prepared in Experimental Example 2 in the state of not charging / discharging using electrochemical impedance spectroscopy (EIS).
FIG. 7 is a graph showing the resistance in the electrode of the anode prepared using the conductive material having various particle size distributions in Experimental Example 3. FIG.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

Since the conductivity of the positive electrode active material itself is low in the positive electrode composed of the positive electrode active material, the conductive material and the binder, the content of the conductive material is increased to improve the resistance characteristic of the positive electrode. In addition, since the positive electrode active material and the conductive material have no adhesiveness, the content of the binder is increased to increase the adhesive force between the positive electrode active material and the conductive material and the adhesive force between the positive electrode active material layer and the current collector. However, when the content of the conductive material and the binder in the positive electrode active material layer increases, the ratio of the positive electrode active material decreases and the capacity decreases. Also, when the binder is present in an excessively high content in excess of the amount required for connecting the positive electrode active material and the conductive material or for increasing the adhesion to the current collector, the resistance in the anode is increased, whereas when the content of the binder is excessively low The adhesion between the current collector and the cathode active material is increased and the contact between the cathode active material and the conductive material is reduced to increase the resistance in the cathode active material layer. Furthermore, excessive amounts of the binder may enter the pores between the cathode active materials to increase the resistance to diffusion of lithium ions into the pores. Accordingly, in order to reduce the resistance inside the cathode active material layer without deteriorating the capacity characteristics, the physical properties and the mixing ratio of the cathode active material, the conductive material, and the binder constituting the cathode active material layer must be controlled simultaneously.

On the other hand, in the present invention, in the production of a composition for forming an anode which can exhibit excellent capacity characteristics including 90 wt% or more of the positive electrode active material, by controlling the mixing ratio of the conductive material and the binder and the particle size of the conductive material simultaneously, It is possible to uniformly disperse the active material, the conductive material and the binder, and prevent the penetration of the binder into the voids between the cathode active materials. As a result, it is possible to manufacture a positive electrode and a lithium secondary battery for a lithium secondary battery having a reduced internal resistance with excellent adhesion.

That is, the positive electrode forming composition in accordance with one embodiment of the present invention, the positive electrode active material, to a particle size distribution according to equation (1) ratio _{((D 90 -D 10) /} D 50) a conductive material of a particle size that meet the conditions And a binder, wherein the cathode active material is contained in an amount of 90 wt% or more based on the total weight of the composition, and the conductive material and the binder are contained in a mixed weight ratio (ratio of conductive material / binder) of 0.6 to 1.2.

[Equation 1]

2.4? (D ₉₀ -D ₁₀ ) / D _50? 3

Hereinafter, each component constituting the composition for forming an anode will be described in more detail.

In the composition for forming an anode, the cathode active material is a compound capable of reversibly intercalating and deintercalating lithium (ritied intercalation compound), and specifically, a cathode active material such as cobalt, manganese, nickel, or aluminum And may be a lithium transition metal oxide including a transition metal and lithium.

The lithium-transition metal oxide is specifically a lithium-manganese-based oxide (for example, LiMnO ₂ , LiMn ₂ O And the like), lithium-cobalt oxide (e.g., LiCoO ₂ and the like), lithium-nickel-based oxide (for example, LiNiO ₂ and the like), lithium-nickel-manganese-based oxide (for example, LiNi _{1 -Y} Mn Nickel-cobalt-based oxide (e.g., LiNi _{1 - Y 2} O ₃ , where 0 <Y <1), LiMn _{2 -z} Ni _z O _{4 Y} Co _Y O ₂ (where, 0 <Y <1) and the like), lithium-manganese-cobalt oxide (e.g., LiCo _1-Y Mn _Y O ₂ (where, 0 <Y <1), LiMn _{2 -z} Co _z O ₄ (where, 0 <z <2), and the like), lithium-nickel-manganese-cobalt oxide (e.g., Li (Ni Co _{P Q R} Mn) O ₂ (here, 0 <P <1, 0 <Q <1, 0 <R <1, P + Q + R = 1) or _{Li (Ni P Co Q Mn R} ) O 4 ( here, 0 <P <2, 0 <Q <2, 0 <R <2 , P + Q + R = 2) , etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li (Ni _P Co _Q Mn _R M _S) O ₂ (here, M is Al, Fe, V, Cr, Ti, Ta, is selected from the group consisting of Mg, Mo, P, Q, R and S are atoms minutes of each independent element 1, 0 <R <1, 0 <S <1, P + Q + R + S = 1), and these lithium transition metal oxides may be tungsten (W ) Or niobium (Nb).

More specifically, the lithium transition metal oxide may be LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , lithium nickel manganese cobalt oxide (for example, Li (Ni _{0 .6} Mn _{0 .2} Co _{0 .2} ) O ₂ , _{LiNi 0 .5 Mn 0 .3 Co 0} .2 O 2, or _{LiNi 0 .8 Mn 0 .1 Co 0} .1 O 2 and the like), or lithium nickel cobalt aluminum oxide (for example, LiNi _{0 .8} Co _{0 .15} Al _{0 .05} O _2, etc.), and any one or a mixture of two or more thereof may be used.

The above-mentioned cathode active material may be contained in an amount of 90% by weight or more, more specifically 90% by weight to 98% by weight based on the total weight of the composition for forming an anode, based on the solid content. If the content of the cathode active material is less than 90% by weight, there is a fear of a decrease in capacity.

In addition, the positive electrode active material may be one which is a specific surface area measured by the BET (Brunauer-Emmett-Teller) method of 50,000m ² / g to 170,000m ² / g. If the BET specific surface area of the cathode active material is less than 50,000 m ² / g, the dispersibility of the cathode active material is low and the size of the gap between the cathode active materials is large, so that the penetration of the binder can be facilitated. On the other hand, if the BET specific surface area exceeds 170,000 m ² / g, there is a fear that the dispersibility is lowered due to agglomeration between the cathode active material particles.

On the other hand, in the present invention, the BET specific surface area of the positive electrode active material can be defined as a value measured by a nitrogen adsorption method. Specifically, it can be measured by the BET 6-point method by a nitrogen gas adsorption / distribution method using a porosimetry analyzer (Bell Japan Inc, Belsorp-II mini).

The cathode active material may have an average particle diameter (D ₅₀ ) of 5 탆 to 10 탆. If the average particle diameter (D ₅₀ ) of the cathode active material is less than 5 탆, there is a fear of degradation of dispersibility due to agglomeration between the cathode active materials. If the average particle diameter exceeds 10 탆, there is a fear that the dispersibility of the cathode active material itself decreases, .

In the present invention, the average particle diameter (D ₅₀ ) of the cathode active material can be defined as an average particle diameter based on 50% of the particle diameter distribution. The average particle size of the cathode active material can be measured using, for example, a laser diffraction method. More specifically, after the cathode active material is dispersed in a solution, a commercially available laser diffraction particle size measurement (Microtrac MT 3000, for example), and an ultrasonic wave of about 28 kHz is irradiated at an output of 60 W, and then an average particle diameter (D ₅₀ ) of 50% of the particle diameter distribution in the measuring apparatus can be calculated.

In addition, in the composition for forming an anode, the conductive material is used for imparting conductivity to the anode, and can be used without particular limitation as long as it does not cause a chemical change in the constituent battery and has electron conductivity. Specific examples thereof include graphite such as natural graphite and artificial graphite; Carbonaceous materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black or carbon fiber; Metal powder or metal fiber such as copper, nickel, aluminum or silver; The conductive whiskers such as zinc oxide whiskers, calcium carbonate whiskers, titanium dioxide whiskers, silicon oxide whiskers, silicon carbide whiskers, aluminum borate whiskers, magnesium borate whiskers, potassium titanate whiskers, silicon nitride whiskers, silicon carbide whiskers, alumina whiskers, (Whisker); Conductive metal oxides such as titanium oxide; And polyphenylene derivatives. These may be used alone or in admixture of two or more.

More specifically, the conductive material may be a carbon-based material in consideration of the remarkable improvement effect of the mixing weight ratio control with the conductive material, and more specifically, carbon black, acetylene black, ketjen black, , A carbon black, a black black, a black black, and a carbon fiber.

The conductive material is an aggregate of secondary particles, that is, tertiary particles formed by aggregating primary particles. The conductive material on the tertiary particle can be confirmed by scanning electron microscope observation of the positive electrode active material layer.

In addition, it can be one having a particle size meeting the particle size distribution ratio _{((D 90 -D 10) /} D 50) according to conditions to the conductive material expression (1).

[Equation 1]

2.4? (D ₉₀ -D ₁₀ ) / D _50? 3

When the particle size distribution ratio of the conductive material is out of the above range and is less than 2.4 or more than 3, the resistance in the electrode is greatly increased.

The particle size distribution ratio of the conductive material may be more specifically 2.4 to 2.7 considering the remarkable improvement effect of the control of the particle size distribution ratio of the conductive material.

In the conductive material, the conductive material on the primary particle has a mean particle diameter (D50) of nanometers but forms a cluster of tertiary particles in the composition for forming an anode. Accordingly, the average particle diameter (D ₅₀ ) of the conductive material contained in the composition for forming an anode may be 1 탆 or less. When the average particle diameter (D ₅₀ ) of the conductive material exceeds 1 탆, the dispersibility in the composition for forming an anode is low, and consequently, the conductive path of the conductive material in the cathode active material is not easily formed. In addition, there is a fear that the energy density of the anode may be lowered due to the bulky structural feature. More specifically, the average particle diameter (D ₅₀ ) of the conductive material may be 0.8 to 1 탆.

In the present invention, the particle diameters of the conductive material, D ₉₀ , D ₁₀ and D ₅₀ , can be respectively defined by particle diameters on the basis of 90%, 10% and 50% of the particle diameter distribution, Means the particle size of the conductive material. The particle diameter of the conductive material can be measured using a laser diffraction method as described above.

The conductive material may be included in an amount of 1 to 20 parts by weight based on 100 parts by weight of the cathode active material. If the content of the conductive material is less than 1 part by weight, there is a possibility that the conductivity improvement and the cycle characteristics improvement effect by the use of the conductive material may be insufficient. If the conductive material is more than 20 parts by weight, the reaction between the conductive material and the electrolyte may increase, . The conductive material may be included in an amount of 1 to 10 parts by weight based on 100 parts by weight of the positive electrode active material, considering the remarkable effect of improving the conductivity and cycle characteristics of the conductive material.

In addition, in the composition for forming an anode, the binder improves the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector, and can be used without any particular limitation, Do. Specifically, the binder may be a fluorine-based polymer such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyhexafluoropropylene, etc., a polyalkylene polymer such as polyethylene, ), Poly (meth) acrylate-based polymers (e.g., polymethyl methacrylate, polyacrylate and the like), and various rubbers (such as styrene butadiene rubber and fluorine rubber) The above mixture may be used.

The binder may be a binder of a fluorine-based polymer, and more specifically, polyvinylidene fluoride, polytetrafluoroethylene, or the like may be used. , Or a binder of a fluorine-based polymer such as polyhexafluoropropylene.

When the binder is a binder of a fluorine-based polymer, the fluorine-based polymer may include a functional group such as a carboxyl group, a hydroxyl group, a sulfonic acid group and a glycidyl group in the molecule, specifically a functional group capable of hydrogen bonding with a hydroxyl group on the surface of the positive electrode active material .

The functional groups contained in the binder may form a hydrogen bond with a hydroxyl group present on the surface of the current collector or the surface of the positive electrode active material to improve the adhesion. In addition, by forming a selective permeable coating of lithium ion on the surface of the positive electrode active material, generation of a lithium compound synthesized by the reaction of the electrolyte solution and lithium ion on the surface of the positive electrode active material at the time of initial discharge can be suppressed. As a result, even if the internal temperature of the battery rises due to a short circuit or the like, a thermally unstable lithium compound is few, decomposition heat generation is suppressed, and reaction of lithium ions and an electrolyte in the positive electrode active material can be suppressed.

More specifically, the binder may contain one or more, more specifically, one to three, functional groups in the molecule.

The binder may be included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the cathode active material. If the content of the binder is less than 1 part by weight, it is difficult to exhibit the necessary adhesion effect in the electrode. If the content of the binder is more than 30 parts by weight, there is a fear of deterioration of capacity characteristics of the battery. More specifically, the binder may be included in an amount of 1 to 10 parts by weight based on 100 parts by weight of the cathode active material.

In the composition for forming an anode according to an embodiment of the present invention, the conductive material and the binder may be contained in a mixed weight ratio (conductive material / binder) of 0.6 to 1.2. If the mixing weight ratio of the conductive material and the binder is less than 0.6, the content of the binder increases to increase the resistance of the lithium ions to diffuse into the pores. If the mixing weight ratio exceeds 1.2, the binder content decreases and the adhesive strength decreases. The conductive material and the binder may be more specifically contained in a mixing weight ratio of 0.8 to 1 in consideration of the remarkable improvement effect of controlling the content of the conductive material and the binder.

More specifically, in the composition for forming an anode according to an embodiment of the present invention, the cathode active material has a BET specific surface area of 50,000 m ² / g to 170,000 m ² / g, (D ₅₀ ) of the conductive material is 1 탆 or less, and the conductive material and the binder are contained in a mixed weight ratio of 0.8 to 1, wherein the conductive material and the binder have a size distribution ratio of 2.4 to 2.7, more specifically 2.5 to 2.7, It is possible to remarkably improve the electrode resistance reducing effect and the adhesion improving effect.

Meanwhile, the composition for forming an anode according to an embodiment of the present invention may further include one or more other additives such as a dispersing agent, a filler, a surfactant, etc. together with the above-described components.

Specifically, the dispersant can act as a thickener for increasing the dispersibility of the components in the composition for forming an anode, particularly, the conductive material, and appropriately controlling the viscosity of the composition for forming an anode.

The dispersing agent can be used without particular limitation as long as it is usually used in a composition for forming an anode. Specific examples of the dispersing agent include a cellulose compound, a polyalkylene oxide, a polyvinyl alcohol, a polyvinyl pyrrolidone, a polyvinyl acetal, a polyvinyl ether, a polyvinyl sulfonic acid, a polyvinyl chloride (PVC), a polyvinylidene fluoride Amide, polyacrylamide, poly-N-isopropyl acrylamide, poly-N, N-dimethyl acrylamide, polyethyleneimine, polyoxyethylene, poly (2-methoxy Styrene / acrylic ester (ASA) polymer, acrylonitrile / styrene / acrylic (meth) acrylate, acrylonitrile / butadiene / styrene (ASA) polymer and propylene carbonate, a styrene / acrylonitrile (SAN) copolymer, or a mixture of methyl methacrylate / acrylonitrile / butadiene / styrene (MABS) poly And the like, and either one of them or a mixture of two or more of them may be used.

The polyalkylene oxide may be polyethylene oxide, polypropylene oxide, or a polyethylene oxide / polypropylene oxide copolymer.

The cellulose-based compound may be selected from the group consisting of carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, alcohol-soluble butyrate of cellulose, cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethylcellulose, methylcellulose , Ethylcellulose, hydroxyethylcellulose, ethylhydroxyethylcellulose, nitrocellulose, carboxymethylcellulose, carboxymethylcellulose sodium, carboxymethylcellulose ammonium, hydroxyethylcellulose, hydroxypropylcellulose or hydroxypropylmethylcellulose .

When the dispersant is a cellulose compound, the weight average molecular weight (Mw) of the cellulose compound may be 2,000,000 g / mol to 3,000,000 g / mol. If the Mw of the cellulose compound is less than 2,000,000 g / mol, the effect of improving the dispersibility may be insignificant. If the Mw is more than 3,000,000 g / mol, there is a fear of difficulty in the process and a decrease in capacity of the composition for forming an anode. In the present invention, the weight average molecular weight (Mw) is a polystyrene reduced weight average molecular weight (Mw) measured by gel permeation chromatography (GPC).

More specifically, the dispersing agent may be carboxymethylcellulose satisfying the weight average molecular weight condition described above.

The dispersant may be used in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the positive electrode active material. If the content of the dispersing agent is less than 0.1 parts by weight, the improvement effect of the use of the dispersing agent is insignificant. If the amount of the dispersing agent is more than 10 parts by weight, the content of the conductive material and the cathode active material becomes relatively low, There is a concern.

The composition for forming an anode having the above-described constitution can be prepared by mixing the above-mentioned cathode active material, conductive binder, and other additives in a solvent. At this time, the types and content of the cathode active material, conductive material, binder, and other additives are the same as those described above.

The solvent is not particularly limited as long as it is used in a composition for forming a positive electrode. Specifically, the solvent may be an aliphatic hydrocarbon-based solvent such as pentane, n-hexane, octane, cyclopentane or cyclohexane; Aromatic hydrocarbon solvents such as benzene, toluene, and xylene; Aldehyde type solvents such as furfural; Ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone or cyclohexanone; Ester solvents such as butyl acetate, ethyl acetate, methyl acetate, butyl propionate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, or 3-methoxybutyl acetate ethylene glycol diacetate; Ether solvents such as tetrahydrofuran, dioxane, or ethylene glycol dimethyl ether; Alcohol solvents such as methanol, ethanol, normal propanol, isopropyl alcohol, butyl alcohol, octyl alcohol, cyclohexanol, allyl alcohol, benzyl alcohol, cresol or furfuryl alcohol; Polyol-based solvents such as glycerol, ethylene glycol, and diethylene glycol; Alcohol ether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether; An aprotic polar solvent such as N-methyl-2-pyrrolidone, dimethylsulfoxide, or dimethylformamide; Or water, and one of these may be used alone, or a mixture of two or more thereof may be used.

In addition, the solvent may be included in an amount sufficient to have an appropriate viscosity, specifically, a viscosity of 1,000 cps to 5,000 cps in consideration of the applicability and processability of the composition for forming a positive electrode of a lithium secondary battery. In the present invention, the viscosity is defined as a value measured at 25 DEG C using a BM type viscometer (VISCOMETER, manufactured by TOKIMEC).

In addition, the mixing can be carried out according to a conventional mixing or dispersing method.

Concretely, it can be carried out by using a mixing or dispersing device such as a homogenizer, a bead mill, a ball mill, a basket mill, an impact mill, a universal stirrer, a clear mixer or a TK mixer. More specifically, the dispersion can be carried out by a jet flow. When the dispersion process is carried out using the jet flow as described above, the uniform dispersion of the above components in the solvent can be promoted.

More specifically, the dispersion may be conducted at least twice at a rotation speed of 1,000 to 5,000 rpm.

The cathode active material, the conductive material, the dispersant, and other additives in the solvent are uniformly dispersed in the solvent by the above-described production method to produce a composition for forming an anode capable of reducing the internal resistance of the battery during the production of the anode and improving the output characteristics .

According to another embodiment of the present invention, there is provided a positive electrode for a lithium secondary battery produced using the composition for forming an anode.

Specifically, the positive electrode includes a positive electrode collector and a positive electrode active material layer on the positive electrode collector, and the positive electrode active material layer may be formed using the composition for forming an anode.

As the positive electrode collector, the positive electrode collector may be used without any particular limitation as long as it has conductivity without causing chemical changes in the battery. Examples of the positive electrode collector include stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum, Surface-treated with carbon, nickel, titanium or silver, or the like may be used.

In addition, the cathode current collector may have a thickness of 3 to 500 탆, and fine unevenness may be formed on the surface of the cathode current collector to increase the adhesive force of the cathode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The positive electrode can be produced by a conventional positive electrode manufacturing method, except that the positive electrode forming composition produced by the above-mentioned production method is used.

Specifically, the composition for anode formation may be coated on the positive electrode current collector, followed by drying and rolling. At this time, the step of coating, drying and rolling the cathode current collector of the anode forming composition may be carried out according to a conventional method.

Specifically, the coating process of the anode forming composition may be applied to one surface of the cathode current collector by a conventional slurry coating method such as bar coating, spin coating, roll coating, slot die coating, or spray coating. The coating method may be carried out by mixing one or more methods.

In applying the composition for forming an anode, it may be preferable to apply the composition for forming an anode to an appropriate thickness in consideration of the loading amount and the thickness of the active material in the finally prepared positive electrode active material layer.

Thereafter, a drying process is performed on the coated film of the composition for forming an anode formed on the positive electrode current collector.

At this time, the drying process may be carried out by evaporation of the solvent in the composition for forming the anode and removal of moisture contained in the anode as much as possible, and at the same time, heat treatment at a temperature capable of increasing the binding force of the binder, hot air injection or the like.

Specifically, the drying step may be carried out at a temperature lower than the melting point of the binder having a boiling point of the solvent, more specifically, at 100 to 150 ° C. More preferably 100 to 120 DEG C and a pressure of 10 torr or less for 1 to 50 hours.

The rolling step after the drying step may be carried out according to a conventional method.

Alternatively, the above-mentioned positive electrode may be produced by peeling the positive electrode active material layer-forming film prepared by coating the above-mentioned composition for forming an anode on a separate support and drying it, and laminating it on the positive electrode collector .

The positive electrode prepared according to the above-described production method can reduce the internal resistance when applying the battery due to the uniform dispersion of the composition for forming the positive electrode, improve the adhesive force, and improve the output characteristics and life characteristics of the battery when the battery is applied .

Accordingly, according to another embodiment of the present invention, a lithium secondary battery including the positive electrode is provided.

Specifically, the lithium secondary battery includes the positive electrode, the negative electrode, the separator interposed between the negative electrode and the positive electrode, and the nonaqueous electrolyte.

In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector. The negative electrode active material layer is formed by applying and drying a composition for forming a negative electrode including a negative electrode active material.

The negative electrode current collector may be used without particular limitation as long as it has high conductivity without causing chemical changes in the battery. Specific examples thereof include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium or silver, aluminum-cadmium alloy, or the like can be used.

The negative electrode current collector may have various shapes, and may be in the form of a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven fabric, or the like.

The negative electrode current collector may preferably have a thickness of 3 to 500 mu m. Further, fine unevenness or a pattern may be formed on the surface of the current collector so as to enhance the bonding force of the negative electrode active material.

The composition for forming an anode may be prepared by dissolving and dispersing an anode active material, a binder, and a conductive material in a solvent.

At this time, as the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber and amorphous carbon; Metal compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys or Al alloys; Or a composite containing a metallic compound and a carbonaceous material, and the like, alone or in a mixture of two or more of them may be used. Also, a metal lithium thin film may be used as the negative electrode active material.

In addition, the binder plays a role of binding between the anode active materials and improving the adhesion between the anode active material and the anode current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinyl alcohol, starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene- (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluorinated rubber, or various copolymers thereof, and one kind or a mixture of two or more thereof may be used .

Considering the remarkable improvement effect, it is preferable that the binder is an aqueous binder. In particular, considering the remarkable improvement effect, the adhesive ability of the binder itself, and the high-temperature drying process in the cathode production process, the styrene-butadiene rubber is more preferable can do.

The binder may be contained in the composition for forming an anode in an amount such that the binder is contained in an amount of 10 to 30% by weight based on the total weight of the composition for forming a negative electrode.

The conductive material is the same as that described above for the anode forming composition, and may be contained in an amount of 1 wt% to 15 wt% based on the total weight of the cathode forming composition. If the amount of the conductive material is less than 1 wt%, the performance of the battery may deteriorate due to an increase in the internal resistance of the electrode due to too small an amount of the conductive material. When the amount of the conductive material exceeds 15 wt% It may cause problems such as a decrease in the capacity of the battery due to the reduction of the electrode active material.

Examples of the solvent include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone ) Or water, and either one of them or a mixture of two or more of them may be used.

The composition for forming an anode may further include a thickener together with the above components. Specifically, the thickener may be a cellulose-based compound such as carboxymethylcellulose (CMC). The thickening agent may be contained in the composition for forming an anode in an amount such that it is contained in an amount of 1 to 10% by weight based on the total weight of the composition for forming a negative electrode.

The composition for forming an anode having the above-described structure can be applied to one surface of an anode current collector using a conventional slurry coating method.

Examples of the slurry coating method include bar coating, spin coating, roll coating, slot die coating, spray coating and the like, and one or more of these methods may be mixed.

It may be preferable to apply the composition for forming the negative electrode to an appropriate thickness in consideration of the loading amount and the thickness of the active material in the finally formed negative electrode active material layer upon application of the negative electrode composition.

Thereafter, the coating film of the composition for negative electrode formation formed on the negative electrode current collector is subjected to a drying process.

At this time, the drying process can be performed by evaporation of the solvent in the composition for forming the negative electrode and removal of moisture contained in the negative electrode as much as possible, and at the same time, heat treatment at a temperature at which the binding force of the binder can be increased, hot air injection or the like.

Specifically, the drying step may be carried out at a temperature lower than the melting point of the binder having a boiling point of the solvent, more specifically, at 100 to 150 ° C. More preferably 100 to 120 DEG C and a pressure of 10 torr or less for 1 to 50 hours.

The rolling step after the drying step may be carried out according to a conventional method.

Alternatively, the negative electrode active material layer may be prepared by coating the negative electrode active material composition on a separate support followed by drying to form a film, peeling the formed film from the support, laminating the negative electrode current collector on the negative electrode current collector, &Lt; / RTI &gt;

At this time, the anode composition, anode collector, coating, drying and rolling processes are the same as described above.

Meanwhile, in the lithium secondary battery, the separator is not particularly limited as long as it is used as a separator in a lithium secondary battery. In particular, it is preferable that the separator is low in resistance against ion movement of the electrolyte and excellent in electrolyte wettability. Specifically, porous polymer films such as porous polymer films made of polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers and ethylene / methacrylate copolymers, May be used. Further, a nonwoven fabric made of a conventional porous nonwoven fabric, for example, glass fiber of high melting point, polyethylene terephthalate fiber, or the like may be used.

In the lithium secondary battery, examples of the electrolyte include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte which can be used in the production of a lithium secondary battery. The present invention is not limited thereto.

Specifically, the electrolyte may include an organic solvent and a lithium salt.

The organic solvent may be used without limitation as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate,? -Butyrolactone and? -Caprolactone; Ether solvents such as dibutyl ether or tetrahydrofuran; Ketone solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethyl carbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate PC) and the like can be used.

Among these, a carbonate-based solvent is preferable, and a cyclic carbonate (for example, ethylene carbonate or propylene carbonate) having a high ionic conductivity and a high dielectric constant, for example, such as ethylene carbonate or propylene carbonate, For example, ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferable.

In addition, the lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium _{salt, LiPF 6, LiClO 4, LiAsF} 6, LiBF 4, LiSbF 6, LiAl0 4, LiAlCl 4, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiN (C 2 F 5 SO 3) 2 _{, LiN (C 2 F 5 SO} 2) 2, LiN (CF 3 SO 2) 2. LiCl, LiI, or LiB (C ₂ O ₄ ) ₂ may be used. The lithium salt may be contained in the electrolyte at a concentration of approximately 0.6 mol / l to 2 mol / l.

In addition to the above electrolyte components, the electrolyte may contain, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, and the like for the purpose of improving lifetime characteristics of the battery, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrroles, pyrroles, pyrroles, pyrroles, , 2-methoxyethanol, aluminum trichloride, and the like may be further included. The additive may be included in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.

The lithium secondary battery having the above structure can be manufactured by manufacturing an electrode assembly with a separator interposed between the anode and the cathode, placing the electrode assembly in the case, and injecting the electrolyte into the case.

As described above, since the lithium secondary battery according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it can be used in portable devices such as mobile phones, notebook computers, digital cameras, and electric automobiles such as hybrid electric vehicles .

According to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell and a battery pack including the battery module.

The battery module or the battery pack may include a power tool; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV); Or a power storage system, as shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

 [ Manufacturing example  1: Preparation of composition for positive electrode formation]

Li (Ni Mn _{0 .6 0 0 .2 .2} Co) O ₂ positive active material (mean particle size (D50): 5㎛, BET specific surface area: 160,000m ² / g), average of the carbon black conductive material (tertiary particles particle diameter _{D 10 = 0.48㎛, D 50 =} 1㎛, D a ₉₀ = 2.98㎛) and PVdF binder in a weight ratio from N- methyl pyrrolidone solvent of 90: 5: after mixing in a ratio of 5, using the mixer 25 The mixture was further mixed for 4 minutes at 1500 rpm for 5 minutes to prepare a composition for forming a positive electrode (viscosity: 1500 mPa · s).

[ Manufacturing example  2: Preparation of composition for positive electrode formation]

Li (Ni Mn _{0 .6 0 0 .2 .2} Co) O ₂ positive active material (mean particle size (D50): 5㎛, BET specific surface area: 160,000m ² / g), average of the titanium conductive material (third particulate oxide particle diameter _{D 10 = 0.48㎛, D 50 =} 1㎛, D a ₉₀ = 2.98㎛) and PVdF binder in a weight ratio from N- methyl pyrrolidone solvent of 90: 5: after mixing in a ratio of 5, using the mixer 25 The mixture was further mixed for 4 minutes at 1500 rpm for 5 minutes to prepare a composition for forming a positive electrode (viscosity: 1500 mPa · s).

[ Example  1 and 2: The lithium secondary battery  Produce]

Lithium secondary batteries were prepared using the cathode active materials prepared in Preparation Examples 1 and 2, respectively.

Specifically, the composition for forming an anode prepared in the above Production Example was coated on Al foil at a loading amount of 2.6 mAh / cm &lt; ³ &gt;, dried by heat treatment at 150 DEG C, and rolled to prepare a positive electrode.

Meanwhile, MCMB (mesocarbon microbead), a carbon black conductive material, and a PVdF binder were mixed in an N-methylpyrrolidone solvent in a weight ratio of 85: 10: 5 as an anode active material to prepare a composition for forming an anode, This was applied to the entire copper collector to prepare a negative electrode.

A lithium secondary battery was fabricated by preparing an electrode assembly between the positive electrode and the negative electrode prepared above through a separator of porous polyethylene, positioning the electrode assembly inside the case, and injecting an electrolyte into the case. The electrolyte solution was prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) at a concentration of 1.15 M in an organic solvent composed of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate (mixed volume ratio of EC / EMC / DEC = 3/4/3) Respectively.

( Experimental Example  One)

An adhesive tape was attached to the positive electrode prepared in Example 1 and peeled to observe a conductive material present in the positive electrode active material layer using a scanning electron microscope (SEM) . The results are shown in Fig.

As shown in FIG. 1, it can be seen that the conductive material in the cathode active material layer exists as a tertiary particle, that is, secondary particles formed by agglomeration of primary particles exist as agglomerates that are re-agglomerated (black circles).

( Experimental Example  2)

The change in resistance and peel strength in the electrode according to the mixing weight ratio of the conductive material and the binder was evaluated.

The composition for forming the positive electrode was prepared in the same manner as in the above Preparation Example, except that the respective materials were used in the amounts shown in the following Table 1 in detail. The prepared anode composition was coated on Al foil at a loading amount of 2.6 mAh / cm &lt; ³ &gt;, dried by heat treatment at 150 [deg.] C and rolled to prepare a positive electrode.

A pouch type unit cell was manufactured using the anode. At this time, a lithium thin film was used as a cathode.

Anode No. 1-1 1-2 1-3 1-4 1-5 Mixing weight ratio of conductive material / binder 0.5 0.8 One 1.25 1.5 Active matter (% by weight) 94 92.8 92 91 90 Binder (% by weight) 4 4 4 4 4 Conductive material (% by weight) 2 3.2 4 5 6 Loading amount (mAh / cm ² ) 2.6 2.6 2.6 2.6 2.6

The battery cell prepared above was initially charged / discharged at a temperature of room temperature (25 ° C) under a driving voltage range of 2.5 to 3.65 V at 0.1 C / 0.1 C, and then charged / discharged at a rate of 1 C / / Discharge. Then, the battery cell was charged with a charge depth (SOC) of 50% to measure the resistance. The results are shown in Fig.

Further, the positive electrode prepared above was punched out by TOP / BACK, Lane, left / middle / right point in the same lane using an electrode rudder (15 cm x 1 cm) And a sample was adhered to a slide glass. For the next sample, the surface of the rubbed electrode was evenly adhered to the double-sided tape using a roller having a load of 2 kg from 13 to 15 times. Thereafter, a sample prepared in the grip of Universal Testing Machine (UTM) (LF Plus, manufactured by LLOYD) was mounted as an electrode adhesive force measuring instrument, and then a load cell of 5 N (1 lbf) was applied The peel strength was measured. The results are shown in Fig.

In FIG. 2, the half-circle represents the film resistance ( R _film ) corresponding to the charge transfer in SEI (solid electrolyte interphase) generated on the surface of the internal electrode. As a charge transfer resistance ( R _ct ) indicative of a reduction reaction. The smaller the X-axis resistance value of the inflection point where the film resistance and the charge transfer resistance meet, the lower the internal resistance. As shown in FIG. 2, the anode having a mixture ratio of the conductive material and the binder of 0.8, 1, and 1.25 exhibited significantly lower internal resistance than that of the cathode having the conductive material and the binder in the mixing ratio of 0.5 or 1.5.

On the other hand, in the case of the peel strength shown in Fig. 3, the peeling strength remarkably deteriorated while the mixing ratio of the conductive material and the binder exceeded 1.

From these results, it can be understood that the content of the conductive material and the binder contained in the composition for forming an anode should be in a mixing weight ratio of 0.8 to 1 in order to obtain a good balance of the adhesion improving effect together with the decrease in the resistance in the anode.

In addition, the positive electrode having a mixture ratio of the conductive material and the binder of 0.8 and 0.5 was processed by ion milling, and the cross-sectional structure of the positive electrode active material layer was observed using a scanning electron microscope (SEM) Respectively. The results are shown in Figs. 4A, 4B, 5A and 5B.

FIGS. 4A and 4B are SEM photographs taken at different positions with respect to the positive electrode (positive electrode 1-2) in which the mixing ratio by weight of the conductive material and the binder is 0.8. FIGS. 5A and 5B are graphs And the anode (positive electrode 1-1) were observed at different positions.

As shown in FIGS. 4A, 4B, 5A and 5B, in the positive electrode (positive electrode 1-1) prepared by mixing the conductive material and the binder at a mixing weight ratio of 0.5, resistance was generated between the positive electrode active materials A binder band was observed. However, in the case of the positive electrode (positive electrode 1-2) prepared by mixing the conductive material and the binder in a mixing weight ratio of 0.8, it was confirmed that the positive electrode active material, the conductive material and the binder were uniformly dispersed and dispersed, and no binder strip was observed .

The EIS resistance, which is an internal resistance of the positive electrode prepared in the above-described manner, was measured by electrochemical impedance spectroscopy (EIS) when the negative electrode was inserted into the gap between the positive and negative electrode active materials without charging / discharging .

Specifically, the impedance was measured at OCV (open circuit voltage) by using AC impedance while changing the frequency of the small voltage of 10 mV to about 10 ⁶ to 10 ^-4 Hz. The results are shown in Fig.

As shown in Fig. 6, in the case of the positive electrode (positive electrode 1-1) in which the mixing ratio by weight of the conductive material and the binder is 0.5, the significantly increased EIS resistance Respectively.

( Experimental Example  3)

In addition, the electrode characteristics according to the particle size distribution ratio of the conductive material contained in the anode forming composition were evaluated.

A positive electrode was prepared in the same manner as in Example 1 except that a conductive material having a particle size distribution ratio as shown in Table 2 was used.

Anode No. Particle size (탆) Particle size distribution ratio
((D ₉₀ -D ₁₀ ) / D ₅₀ ) D ₁₀ D ₅₀ D ₉₀ 2-1 0.63 1.4 3.89 2.32 2-2 0.48 One 2.98 2.5 2-3 0.31 0.81 2.58 2.8

A unit cell was manufactured by the same method as in Experimental Example 1, and the resistance was measured by filling the battery with a charging depth (SOC) of 50%. The results are shown in Fig.

7, even if the mixing weight ratio of the conductive material and the binder contained in the anode forming composition satisfies the condition of 0.8 to 1, the particle size distribution ratio condition (2.4? (D ₉₀ -D ₁₀ ) / D for the positive electrode (anode No. 2-1) does not meet the ₅₀ ≤3), increase in the resistance is sharply than the positive electrode (anode No. 2-2 and 2-3) that meets the conductive material in the particle size distribution ratio condition Respectively.

From these results, it was found that, in order to obtain an effect of simultaneously increasing the adhesion to the positive electrode collector and reducing the internal resistance of the electrode well, the mixing weight ratio of the conductive material and the binder contained in the composition for forming an anode, It can be seen that control must be performed at the same time.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope of the invention.

Claims (21)

Cathode active material,
To a particle size distribution according to equation (1) ratio _{((D 90 -D 10) /} D 50) a conductive material having a grain size that meets the criteria, and
A binder,
The cathode active material is contained in an amount of 90 wt% or more based on the total weight of the composition,
Wherein the conductive material and the binder are contained in a mixed weight ratio of 0.8 to 1 (ratio of conductive material / binder).
[Equation 1]
2.4? (D ₉₀ -D ₁₀ ) / D _50? 3
The method according to claim 1,
Wherein the positive electrode active material has a specific surface area of 50,000 m ² / g to 170,000 m ² / g.
The method according to claim 1,
Wherein the average particle diameter (D ₅₀ ) of the positive electrode active material is 5 탆 to 10 탆.
The method according to claim 1,
Wherein the conductive material has a particle size distribution ratio of 2.4 to 2.7 according to Equation (1).
The method according to claim 1,
Wherein the conductive material is an aggregate of secondary particles formed by aggregation of primary particles.
The method according to claim 1,
Wherein the average particle diameter (D ₅₀ ) of the conductive material is 1 탆 or less.
The method according to claim 1,
Wherein the conductive material is a carbon-based material.
The method according to claim 1,
Wherein the conductive material is a carbon-based material including at least one selected from the group consisting of carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, Composition for forming an anode.
The method according to claim 1,
Wherein the conductive material is contained in an amount of 1 to 20 parts by weight based on 100 parts by weight of the positive electrode active material.
delete The method according to claim 1,
Wherein the binder is a fluorine-based polymer.
The method according to claim 1,
Wherein the binder is a fluoropolymer containing any one or two or more selected from the group consisting of polyvinylidene fluoride, polytetrafluoroethylene, and polyhexafluoropropylene, and a composition for forming an anode of a lithium secondary battery
The method according to claim 1,
Wherein the binder is contained in an amount of 1 to 20 parts by weight based on 100 parts by weight of the positive electrode active material.
The method according to claim 1,
The BET specific surface area of the cathode active material is 50,000 m ² / g to 170,000 m ² / g,
Wherein the conductive material has a particle size distribution ratio of 2.4 to 2.7 according to Equation 1 and an average particle diameter (D ₅₀ ) of the conductive material is 1 탆 or less,
Wherein the conductive material and the binder are contained in a mixing weight ratio of 0.8 to 1. 2. The lithium secondary battery according to claim 1,
The method according to claim 1,
Wherein the lithium secondary battery has a viscosity of 1000 cps to 5000 cps.
A positive electrode for a lithium secondary battery produced by using the composition for forming an anode according to claim 1.
A lithium secondary battery comprising the positive electrode according to claim 16.
A battery module comprising the lithium secondary battery according to claim 17 as a unit cell.
A battery pack comprising the battery module according to claim 18.
20. The method of claim 19,
A battery pack that is used as a power source for mid- to large-sized devices.
21. The method of claim 20,
Wherein the middle- or large-sized device is selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle and a system for power storage.

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