KR101753892B1 - Method for preparing negative electrode composition of lithium secondary battery, and negative electrode and lithium secondary battery prepared by using the same - Google Patents

Abstract

The present invention provides a method for producing a conductive material, comprising the steps of preparing a dispersion by mixing and dispersing a conductive material and a cellulose-based thickener in a solvent, and adding and mixing a negative electrode active material and a binder to the dispersion, A secondary particle having a BET specific surface area of not less than 100 m ² / g and an average particle diameter (D ₅₀ ) of not more than 1 μm, and a process for producing a negative electrode composition for a lithium secondary battery, And a lithium secondary battery comprising the negative electrode.
By the method for producing a composition for forming a negative electrode of the lithium secondary battery, the conductive material having an excellent conductivity increasing effect between the active materials is uniformly dispersed and contained in the composition without adsorption of the binder, so that the electrode resistance in the anode can be reduced, As a result, the output characteristics and life characteristics of the lithium secondary battery can be improved.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for preparing a negative electrode for a lithium secondary battery, a negative electrode for a lithium secondary battery using the same, and a lithium secondary battery using the same. BACKGROUND ART [0002]

The present invention relates to a method for preparing a composition for forming a negative electrode of a lithium secondary battery, and a negative electrode and a lithium secondary battery for a lithium secondary battery manufactured 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. Particularly, as the market extends from small lithium secondary batteries used in portable devices to large secondary batteries used in automobiles, high capacity and high output of negative electrode active materials are required.

As the loading amount of the active material in the electrode increases, more energy can be emitted per unit area. Therefore, in order to satisfy the above-mentioned required characteristics, the loading amount of the active material in the electrode must be increased. However, when the loading amount of the active material is increased, the resistance in the electrode is increased due to the decrease of the conductive material and the binder content relatively, and the adhesive force is decreased to deteriorate the life characteristic of the battery.

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

Particularly, when the conductive material is used as fine particles having a size of several tens of nanometers, the cohesive force is so strong that coagulation between conductive fine particles tends to occur when dispersed in a solvent. Such non-uniform dispersion of the conductive material in the anode active material layer leads to a decrease in conductivity and a deterioration in output characteristics of the battery. In addition, the agglomerate of the simply agglomerated conductive material may deteriorate the conductivity between the active materials because of the low structural retention. In addition, the conductive fine particles have a large specific surface area to adsorb the binder, which results in a non-uniform distribution of the binder in the anode active material layer and consequently a decrease in adhesion.

Accordingly, in order to improve battery performance and lifetime characteristics, it is important to uniformly disperse the constituents in the composition for forming an anode, in addition to the development of a cathode component having excellent properties.

Japanese Patent Laid-Open No. 1996-195201 (published on July 30, 1996)

A first object of the present invention is to provide a method of manufacturing a composition for forming a negative electrode of a lithium secondary battery, in which a conductive material having an excellent conductivity increasing effect between active materials is uniformly dispersed without adsorption of a binder, , And a composition for forming a negative electrode, which is prepared as described above.

A second technical object of the present invention is to provide a negative electrode prepared using the composition for forming a negative electrode, which is produced according to the above-mentioned production method.

A third object of the present invention is to provide a lithium secondary battery including the negative electrode, a battery module, and a battery pack.

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 method of manufacturing a lithium secondary battery, comprising: preparing a dispersion by mixing and dispersing a conductive material and a cellulose-based thickener in a solvent; and adding and mixing a negative electrode active material and a binder to the dispersion, Wherein the conductive material comprises secondary particles in which primary particles are aggregated and the secondary particles have a BET specific surface area of 100 m ² / g or more and an average particle diameter (D ₅₀ ) of 1 μm or less. Of the composition for forming a negative electrode.

According to another embodiment of the present invention, there is provided a composition for forming a negative electrode, which is produced by the above production method.

In addition, the present invention provides a negative electrode for a lithium secondary battery manufactured using the composition for forming a negative electrode.

Furthermore, the present invention provides a lithium secondary battery including the negative electrode, a battery module, and a battery pack.

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

By the method for producing a composition for forming a negative electrode of a lithium secondary battery according to the present invention, a conductive material having an excellent conductivity increasing effect between active materials is uniformly dispersed and contained in the composition without adsorption of the binder, The use of a low content of conductive material can also provide good conductivity. As a result, it is possible to improve the output characteristics and lifetime characteristics of a lithium secondary battery including a negative electrode manufactured using the composition for forming a negative electrode.

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.

A method of preparing a composition for forming a negative electrode of a lithium secondary battery according to an embodiment of the present invention includes the steps of preparing a dispersion by mixing and dispersing a conductive material and a cellulose-based thickener in a solvent (step 1) And a binder (step 2), wherein the conductive material includes secondary particles agglomerated with primary particles, the secondary particles have a BET specific surface area of 100 m ² / g or more, The average particle diameter (D ₅₀ ) is 1 탆 or less.

Each step will be described in more detail below.

(Step 1)

Step 1 is a step of preparing a dispersion containing a conductive material and a cellulose-based thickener.

In the step 1, the conductive material is used for imparting conductivity to the negative electrode, and can be used without particular limitation as long as it has conductivity and does not cause chemical change in a battery constituted. Specific examples thereof include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black and carbon fiber; Metal powder or metal fibers such as copper, nickel, aluminum and 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. Among these, the conductive material may be a carbon-based material in consideration of the remarkable improvement effect due to the use of the conductive material and the high-temperature drying process in the cathode manufacturing process, and more specifically, carbon black, acetylene black, Carbon black, black black, furnace black, lamp black, thermoplastic black, and carbon fiber.

In addition, the conductive material includes a secondary particle phase in which primary particles are aggregated. The conductive material on the secondary particle can be confirmed by scanning electron microscope observation of the anode active material layer, and the number of particles of the corresponding size can be confirmed through particle size distribution.

Specifically, the conductive material on the secondary particle has an increased BET (Brunauer-Emmett-Teller) specific surface area as compared with the conductive material on the primary particle. Specifically, the conductive material may have a BET specific surface area of 100 m ² / g or more, more specifically 100 to 1000 m ² / g. On the other hand, in the present invention, the BET specific surface area of the conductive 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 conductive material on the secondary particle may have an average particle diameter (D ₅₀ ) of 1 μm or less. If 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 anode active material is not easily formed. In addition, there is a fear that the energy density of the cathode may be lowered due to a 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 average particle diameter (D ₅₀ ) of the conductive material can be defined as a particle diameter based on 50% of the particle diameter distribution, wherein the average particle diameter of the conductive material means the particle size of the conductive material on the secondary particle. Further, the average particle size of the conductive material can be measured using a laser diffraction method. More specifically, the conductive material may be dispersed in a solution, and then a commercially available laser diffraction particle size analyzer (for example, Microtrac MT 3000), and an ultrasonic wave of about 28 kHz was 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.

The conductive material may be included in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the negative electrode active material. If the content of the conductive material is less than 0.1 part by weight, the conductivity and the cycle characteristics are not improved by using the conductive material. If the amount exceeds 5 parts by weight, the reaction between the conductive material and the electrolyte increases due to the increase of the specific surface area of the conductive material. And the cycle characteristics may be lowered. More specifically, the conductive material may be contained in an amount of 0.5 to 3.5 parts by weight, more specifically 1 to 3 parts by weight, based on 100 parts by weight of the negative electrode active material.

The cellulose-based thickening agent which can be used in the preparation of the dispersion in step 1 is not particularly limited as long as it is generally used for improving the dispersibility of the electrode components and controlling the viscosity of the composition during the production of the electrode-forming composition. Specific examples of the cellulose-based thickening agent include carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, alcohol-soluble butyrate of cellulose, cellulose acetate, cellulose acetate butyrate, cellulose butylate, cyanoethylcellulose , Methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, ethylhydroxyethyl cellulose, nitrocellulose, carboxymethyl cellulose, carboxymethyl cellulose sodium, carboxymethyl cellulose ammonium, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethylcellulose Or a sodium salt thereof. These may be used singly or in combination of two or more.

The cellulose-based thickener may be one having a degree of substitution of the carboxyl group in the unit unit of the polymer constituting the cellulose-based compound of 1 to 1.5.

Generally, a cellulose compound used as a binder or a thickener in an electrode-forming composition, for example, carboxymethylcellulose may have a cellulose repeating unit, i.e., 3 or less carboxymethyl groups per unit unit, The average number of carboxymethyl groups or carboxyl groups substituted with hydroxy groups in a unit unit is referred to as degree of substitution (DS). The solubility of cellulose compounds in water varies depending on the degree of substitution. In general, when the cellulose compound has a high degree of substitution, the solubility in water increases, and when the cellulose compound has a low degree of substitution, the solubility in water decreases. The solubility of the cellulose-based compound in water affects the dispersion characteristics of the composition for forming a negative electrode as a result. The better the solubility in water, the better the dispersibility of the components including the negative electrode active material.

In the present invention, as described above, dispersion of a conductive material having a low dispersibility can be promoted by dispersing a cellulose-based thickener having a high degree of substitution of a carboxyl group in a unit unit with a conductive material. The cellulose-based thickener dispersed in the solvent is easily adsorbed on the negative active material to be added to maintain the repulsive force between the negative active materials, thereby uniformly dispersing the negative active material in the composition. In addition, the cellulose-based compound adsorbed on the surface of the negative electrode active material has a larger amount of binder around the negative active material, so that the adhesive force around the negative active material increases compared to other materials. Accordingly, when the negative electrode active material is an active material having a large volume change due to charging and discharging such as silicon or silicon oxide, the volume change of the silicon oxide due to charging and discharging can be minimized, and mechanical detachment and cracks in the electrode can be prevented, The characteristics can be improved.

The cellulose-based thickener may have a weight average molecular weight (Mw) of 800,000 to 4,000,000 g / mol. If the Mw of the cellulose-based compound is less than 800,000 g / mol, the effect of improving the dispersibility of the cellulose-based thickener may be insignificant. If the Mw is more than 4,000,000 g / mol, there is a difficulty in processing the composition for forming a negative electrode. 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).

In addition, the cellulose thickener may include two kinds of cellulose compounds having different Mw within the above-mentioned Mw range, wherein the two kinds of cellulose compounds may be the same , Or they may be different compounds.

More specifically, the cellulose thickener may include carboxymethylcellulose (CMC) or carboxymethylcellulose sodium salt (CMCNa) that satisfies the above degree of substitution and Mw, and more specifically may be carboxymethylcellulose . In general, carboxymethylcellulose and carboxymethylcellulose sodium salt, especially carboxymethylcellulose, have higher solubility in water and ionization than other cellulosic compounds. In addition, since the composition has a high viscosity, it can impart excellent coating properties to the composition for forming an anode, and is excellent in adhesion, so that the active material can be prevented from falling off from the current collector.

The cellulose-based thickener may be added in a total amount in step 1, or may be separately added in a subsequent step 2 in which the dispersion is mixed with the conductive material and then mixed with the negative electrode active material.

Specifically, when the cellulose compound is added in step 2, the cellulose compound in step 1 may be added in an amount of 60 to 80% by weight based on the total amount of the cellulosic compound used.

Further, in the step 2, the cellulose-based thickener used for each step may be one having an Mw optimized for the kind of the component to be mixed together and the physical property demand. Specifically, the cellulose-based thickener (hereinafter referred to as a first cellulose-based thickener) charged in Step 1 includes a cellulose-based compound satisfying the above-mentioned substituent and having an Mw of 800,000 g / mol to 1,200,000 g / mol, Based thickener (hereinafter referred to as a second cellulose-based thickener) may contain a cellulose-based compound satisfying the above-mentioned substituent and having an Mw of 1,200,000 g / mol to 4,000,000 g / mol. When the second cellulosic compound having a higher Mw is mixed with the negative electrode active material as described above, the second cellulosic compound adhered to the surface of the negative active material retains more binder and increases the adhesion around the negative active material . Also, the change in the volume of the negative electrode active material due to charging and discharging is minimized, thereby preventing the occurrence of mechanical separation and cracks in the negative electrode, thereby improving the lifetime characteristics of the battery.

The cellulose-based thickener may be used in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the negative electrode active material. If the content of the cellulose-based thickener is less than 0.1 parts by weight, the effect of using the thickener is insignificant. When the content of the cellulose-based thickener is more than 10 parts by weight, the content of the conductive material and the negative electrode active material is relatively low, May be deteriorated. More specifically, the cellulose thickener may be used in an amount of 0.5 to 5 parts by weight based on 100 parts by weight of the negative electrode active material.

The solvent which can be used in the preparation of the dispersion in step 1 is not particularly limited as long as it is usually used in a composition for forming a negative 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 organic solvent such as N-methyl-2-pyrrolidone, dimethylsulfoxide, or dimethylformamide; Or an aqueous solvent such as water, isopropyl alcohol, etc., and any one of them or a mixture of two or more of them may be used. More specifically, the solvent can be aqueous-based in view of increasing the dispersibility of the negative electrode active material and the conductive material constituting the negative electrode composition and increasing the solubility of the binder and the cellulose-based thickener.

The solvent may be included in an amount such that the solvent has an appropriate viscosity in consideration of the applicability and processability of the negative electrode composition. Specifically, it may be added in an amount such that the viscosity of the negative electrode composition (B-type viscometer, 25 캜, 12 rpm) is from 1000 cps to 5000 cps. If the viscosity of the composition for forming an anode is less than 1000 cps, the process time may be prolonged. If the viscosity exceeds 5000 cps, the coating property may be deteriorated and the thickness of the negative electrode active material layer may increase. . 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).

The step of mixing and dispersing the conductive material and the cellulose-based thickener in the step 1 may be carried out in the above-mentioned solvent. Specifically, a conductive material and a cellulose-based thickening agent are mixed and dispersed in a solvent, or a cellulosic thickener is first dissolved in a solvent to prepare a cellulose-based thickener-containing solution, and then a conductive material is added to the prepared solution, ≪ / RTI >

The mixing and dispersing process for producing the dispersion may 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 may be carried out by a jet flow of 10,000 to 25,000 rpm for 10 to 20 minutes. 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.

As a result of Step 1 by the above-described process, a dispersion in which the conductive material is uniformly dispersed in the cellulose-based thickener-containing solution is obtained.

(Step 2)

Step 2 is a step of adding a negative electrode active material, a binder and optionally a cellulose compound to the dispersion prepared in Step 1 and mixing the dispersion.

In the step 2, a compound capable of reversibly intercalating and deintercalating lithium may be used as the negative electrode active material. Specific examples thereof include graphite-based materials such as artificial graphite, natural graphite and graphite; Carbonaceous materials such as crystalline or 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 the metallic compound and the carbon compound, and either one of them or a mixture of two or more of them may be used. More specifically, the negative electrode active material may include silicon oxide of SiO _x (0 < x < 2), a graphite based material, or a mixture thereof. In addition, the silicon oxide may be specifically amorphous.

More specifically, the negative electrode active material may include a mixture of the silicon oxide and the graphite based material.

The silicon oxide represented by SiOx (0 < x < 2) has a larger volume change due to charging and discharging than the graphite based material, but the theoretical capacity is larger. Accordingly, when a mixture of the silicon oxide and the graphite based material is included, the battery capacity can be increased as compared with the battery containing only the graphite based material. In the case of silicon oxide, the binding between the anode active materials and the conductive network are liable to be broken when the volume is changed. However, when mixed with a graphite-based material, it is possible to prevent binding between the negative electrode active material and disconnection of the conductive network.

When the negative electrode active material includes a mixture of silicon oxide and graphite-based material, specifically, the silicon oxide and graphite-based material may be mixed in a mixing weight ratio of 1: 9 to 5: 5. If the content of the graphite-based material is too high as compared with the silicon oxide, the charging capacity per unit amount of the anode active material may be decreased, the content of silicon oxide may be excessively high as compared with the graphite-based material, The expansion and contraction of the electrode plate increases with an increase in the content of silicon oxide having a large change in volume due to the increase of the volume of the silicon oxide. As a result, the electrical contact between the silicon oxide and the graphite based material becomes insufficient.

The shape of the negative electrode active material is not particularly limited, and may have various shapes such as a particle shape, a plate shape, and a fibrous shape. The negative electrode active material may be primary particles or secondary particles in which a plurality of primary particles are aggregated. Specifically, the negative electrode active material may be spherical primary particles per se or may be secondary particles agglomerated into a spherical form. For example, when the negative electrode active material is a graphite based material such as artificial graphite or natural graphite, the graphite based material of the primary particles may be a plate-like material, but the aggregated secondary particles may form a spherical particle form.

The graphite-based negative electrode active material having a plate-like shape is oriented in the compression process for improving the filling density in the process of manufacturing the negative electrode so that the ion diffusion rate in the negative electrode active material layer decreases, discharge capacity decreases, Etc. may occur. On the other hand, when the primary particles themselves have a spherical shape or a secondary particle shape in the form of a spherical shape, there is no fear of occurrence of the above-mentioned problem due to orientation in the compression process.

In the present invention, a plate shape is defined as a shape having two flat planes, and includes not only a complete plate shape but also flakes, scales and the like which are similar to plates. Specifically, when a long axis on one of two flat surfaces on a plate is defined as a length and a length between two flat surfaces is defined as a thickness, the graphite has an average length of 0.1 to 5 mu m and an average length of 10 to 500 nm Lt; / RTI &gt;

More specifically, the negative electrode active material may be spherical particles having an average particle diameter (D ₅₀ ) of 2 to 20 μm. In the present invention, the average particle diameter of the negative electrode active material can be defined as a particle diameter on the basis of 50% of the particle diameter distribution of the primary or secondary particles. The average particle size (D ₅₀ ) of the particles can be measured using, for example, a laser diffraction method. More specifically, the negative active material may be dispersed in a solvent, (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.

The negative electrode active material may include 80 to 98% by weight based on the total weight of the composition for forming a negative electrode. When the content of the negative electrode active material is less than 80 wt%, the output characteristics of the battery may be deteriorated. When the amount of the negative electrode active material is more than 98 wt%, there is a fear that the active material detachment due to the decrease in the binding force in the electrode and the peeling phenomenon with the current collector occur.

In addition, in the step 2, the binder improves the adhesion between the anode active material particles and the adhesion between the anode active material and the current collector. The binder can be used without particular limitation as long as it is usually used for a cathode forming composition. 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. More specifically, the binder may be a styrene-butadiene rubber. The styrene-butadiene rubber improves the dispersibility of the negative electrode active material and the conductive material in the composition and has a strong adhesive force, thereby reducing the content of the binder and increasing the content of the negative electrode active material, thereby increasing the capacity of the lithium secondary battery. In addition, it is possible to improve the structural stability of the electrode and improve various characteristics of the battery.

More specifically, the styrene-butadiene rubber may be styrene-butadiene rubber (SBR) having an average particle diameter (D ₅₀ ) of 90 to 150 nm and a tensile strength of 90 to 160 kgf. The styrene butadiene rubber satisfying the above-mentioned particle size and physical properties can exhibit a superior adhesive force. In the present invention, the average particle diameter (D ₅₀ ) of the styrene-butadiene rubber can be defined as the particle diameter on the basis of 50% of the particle diameter distribution, and can be measured using the laser diffraction method have.

The binder may be included in an amount of 1 to 20 parts by weight based on 100 parts by weight of the negative electrode active material. If the content of the binder is less than 1 part by weight, it is difficult to exhibit sufficient adhesion in the negative electrode. If the content of the binder is more than 20 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 negative electrode active material.

In the step 2, a cellulose compound may be added together with the negative electrode active material and the binder.

The cellulosic compound is the same as that described in the above step 1 and may be added in an amount of the remainder of the total amount of the cellulose compound that can be contained in the composition for forming the negative electrode active material, excluding the amount added in step 1.

In the step 2, mixing of the negative electrode active material, the binder, and optionally the usable cellulosic compound may be carried out according to a conventional method as described in the step 1. Specifically, the mixing in step 2 may be carried out one or more times 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 may be conducted at a rotation speed of 1,000 to 5,000 rpm for 10 minutes to 1 hour.

The above-mentioned method for preparing a negative electrode composition is a method for producing a negative electrode, which comprises: mixing a conductive material having excellent dispersibility of a conductive material with a cellulosic thickener and having excellent conductivity increasing effect between active materials, It is possible to uniformly disperse the conductive material and prevent the conductive material from adsorbing the binder with a large specific surface area. As a result, the composition for forming a negative electrode and the negative electrode prepared using the composition described above can exhibit excellent conductivity even when a low content of a conductive material is used, and can exhibit improved adhesion between the negative active material layer and the negative electrode active material layer Lt; / RTI &gt;

Accordingly, according to another embodiment of the present invention, there is provided a composition for forming an anode, which is produced by the above production method.

Specifically, the negative electrode composition includes an anode active material, a conductive material, a binder, and a cellulose-based compound, and the above-mentioned components are uniformly dispersed in a solvent by the optimized production method. Here, the negative electrode active material, the conductive material, the binder, the cellulosic compound, and the solvent are the same as described above.

The viscosity of the negative electrode composition (B-type viscometer, room temperature, 12 rpm) may be 550 cps to 5000 cps.

More specifically, the composition for forming a negative electrode may include 0.1 to 5 parts by weight or 1 to 3 parts by weight of a conductive material per 100 parts by weight of the negative electrode active material; 1 to 20 parts by weight or 1 to 10 parts by weight of a binder; And 0.1 to 10 parts by weight or 0.5 to 5 parts by weight of a cellulose-based thickener, and the solvent contains an amount such that the viscosity of the composition for forming an anode is from 550 cps to 5000 cu, or from 1000 cps to 3000 cps at 25 캜, When the conductive material is a secondary particle-like carbon-based material having primary particles aggregated and having a BET specific surface area of 100 m ² / g or more and an average particle diameter (D ₅₀ ) of 1 μm or less, excellent conductivity and adhesion .

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

Specifically, the negative electrode includes a negative electrode collector and a negative electrode active material layer formed on the negative electrode collector.

In the negative electrode, the negative electrode 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, Or stainless steel surface treated with carbon, nickel, titanium or silver, aluminum-cadmium alloy, or the like. 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.

In the negative electrode, the negative electrode active material layer may be prepared using the above-described negative electrode composition. Specifically, the negative electrode active material layer is coated on at least one surface of the negative electrode collector using a conventional slurry coating method, And optionally rolling.

Examples of the slurry coating method when applying the composition for forming an anode include bar coating, spin coating, roll coating, slot die coating, spray coating, and the like. . 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.

The step of drying the coated film of the negative electrode forming composition formed on the negative electrode current collector after the coating step can remove the moisture contained in the negative electrode as well as evaporate the solvent in the negative electrode forming composition and increase the binding force of the binder Heat treatment at a certain temperature, hot air injection, or the like. Specifically, the drying process may be carried out at a temperature lower than the melting point of the binder, which is higher than the boiling point of the solvent, and 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 above-described composition for forming an anode on a separate support, drying the same to form a film, peeling the formed film from the support, laminating the same on the negative electrode collector, . At this time, the anode composition, anode collector, coating, drying and rolling processes are the same as described above.

The negative electrode prepared by using the composition for forming an anode as described above is uniformly distributed in the negative electrode active material layer without adsorbing the binder with excellent conductivity, thereby improving the conductivity and the adhesive strength to improve the output characteristics and lifetime characteristics of the lithium secondary battery .

According to another embodiment of the present invention, there is provided a lithium secondary battery including the negative electrode.

Specifically, the lithium secondary battery includes the negative electrode, the positive electrode, the separator interposed between the negative electrode and the positive electrode, and the nonaqueous electrolyte. In the lithium secondary battery, the negative electrode is the same as that described above.

In the lithium secondary battery, the positive electrode includes a positive electrode collector and a positive electrode active material layer formed on the positive electrode collector and including a positive electrode active material.

The positive electrode current collector may be any one of stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum, and may be made of stainless steel, 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.

In the cathode active material layer, a compound capable of reversibly intercalating and deintercalating lithium (lithium intercalation compound) may be used as the cathode active material. Specifically, it may be a lithium-transition metal oxide including lithium and a transition metal such as cobalt, manganese, nickel, or aluminum.

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 cathode active material may be contained in an amount of 80 to 98% by weight based on the total weight of the composition for forming an anode. When the content of the positive electrode active material is less than 80 wt%, the output characteristics of the battery may be deteriorated. When the amount of the positive electrode active material is more than 98 wt%, detachment of the active material and detachment from the current collector may occur.

In addition, the cathode active material layer may further include a conductive material and a binder together with the cathode active material.

At this time, the conductive material is used for imparting conductivity to the anode, and can be used without particular limitation as long as it has conductivity and does not cause chemical change in the battery constituted. Specific examples thereof include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black and carbon fiber; Metal powder or metal fibers such as copper, nickel, aluminum and 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. Among them, a carbon-based material such as carbon black may be more preferable considering the remarkable improvement effect of the use of the conductive material and the high-temperature drying process in the anode manufacturing process.

The conductive material may be included in an amount of 1 to 20 parts by weight, or 1 to 10 parts by weight based on 100 parts by weight of the cathode active material. When the amount of the conductive material is less than 1 part by weight, the amount of the conductive material may be too small to increase the internal resistance of the electrode. If the amount of the conductive material is more than 20 parts by weight, It is possible to reduce the battery capacity due to the reduction of the electrode active material.

In addition, the binder serves to improve the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, There may be mentioned polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluorine rubber or various copolymers thereof. Can be used.

The binder may be included in an amount of 1 to 20 parts by weight, or 1 to 10 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, the adhesive force between the positive electrode active material in the active material layer and the adhesive strength of the active material layer with respect to the positive electrode collector may deteriorate and the performance and life characteristics of the battery may be deteriorated. The relative capacity of the active material may be decreased and the capacity of the battery may deteriorate due to an increase in the resistance of the electrode due to excessive binder.

The positive electrode may be produced by a conventional positive electrode manufacturing method. Specifically, the positive electrode active material may be prepared by dissolving a conductive material and a binder in a solvent together with the positive electrode active material, and then coating the positive electrode current collector on the positive electrode current collector, followed by drying and rolling.

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

Thereafter, the coating, drying and rolling processes for the positive electrode current collector can be carried out in the same manner as described above for the negative electrode manufacturing method.

Alternatively, the positive electrode may be prepared by applying the composition for positive electrode on a separate support, drying the positive electrode active material layer-forming film, peeling the positive electrode active material layer-forming film from the support, and laminating the film on the positive electrode current collector.

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-based liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte that can be used in the production of a lithium secondary battery. But are 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 positive electrode and the negative electrode, positioning the electrode assembly inside the case, and injecting an electrolyte into the case.

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

According to another aspect 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 same.

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 : Preparation of composition for negative electrode formation]

0.48 g of carboxymethylcellulose (degree of substitution of carboxyl group in unit unit: 1.2, Mw = 1,000,000 g / mol) was added to distilled water to prepare a 1% solution of carboxymethylcellulose. Carbon black (secondary particulate, BET specific surface area : 300 m ² / g, and an average particle diameter (D ₅₀ ): 0.81 탆) was added thereto, followed by mixing and dispersing for 15 minutes at a speed of 25,000 rpm using a jet flow generator (clear mixer).

38.4 g of amorphous SiOx (0 <x <1) silicon oxide (average particle diameter (D ₅₀ ): 2 μm) and 50.4 g of spherical natural graphite (average particle diameter (D ₅₀ ): 5 μm) (Average particle diameter (D ₅₀ ): 120 nm, tensile strength: 110 kgf) of carboxymethyl cellulose (degree of substitution of the carboxyl group in the unit unit: 1, Mw = 2,500,000 g / mol) , And then dispersed for 15 minutes at a rotation speed of 1200 rpm using a TK mixer to prepare a composition for forming a negative electrode (viscosity at 25 ° C: 1500 cps).

[ Example  : Production of lithium secondary battery]

A lithium secondary battery was prepared using the negative electrode active material prepared in the above Production Example.

Specifically, the composition for anode formation prepared in the above Production Example was coated on a Cu foil with a loading amount of 2.6 mAh / cm ³ , dried by heat treatment at 150 ° C, and rolled to produce a negative electrode.

On the other hand, Li (Ni Mn _{0 .6 0 0 .2 .2} Co) O ₂ positive active material, a carbon black conductive agent, and PVdF binder in a weight ratio from N- methyl pyrrolidone solvent of 90: a mixture in a ratio of 5:05 A composition for forming an anode (viscosity: 5000 mPa.s) was prepared, applied to an aluminum current collector, and then dried and rolled to prepare a positive electrode.

A lithium secondary battery was prepared by preparing an electrode assembly between the positive electrode and the negative electrode prepared above with a separator of porous polyethylene interposed therebetween, placing 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.

[ Comparative Example  1: Production of lithium secondary battery]

Carbon black (secondary particles, BET specific surface area: 50m ² / g, average particle size _{(D 50): 1.45㎛) 1g} , amorphous SiOx (0 <x <1), silicon oxide (average particle diameter (D ₅₀ as the negative electrode active material) ) And 57.6 g of spherical natural graphite (average particle diameter (D ₅₀ ): 5 탆) were mixed and mixed with carboxymethyl cellulose (substitution degree of carboxyl group in the unit unit: 1.2, Mw = 1,000,000 g / mol) And 2.2 g of styrene-butadiene rubber (average particle diameter (D ₅₀ ): 120 nm, tensile strength: 110 kgf) as a binder were mixed in distilled water and dispersed for 15 minutes at a rotation speed of 1200 rpm using a TK mixer, (Viscosity at 25 ° C: 1500 cps) was prepared.

[ Comparative Example  2: Production of lithium secondary battery]

Carbon black (secondary particles, BET specific surface area: 300m ² / g, average particle size _{(D 50): 0.81㎛) 1g} , amorphous SiOx (0 <x <1), silicon oxide (average particle diameter (D ₅₀ as the negative electrode active material) ) And 57.6 g of spherical natural graphite (average particle diameter (D ₅₀ ): 5 탆) were mixed and mixed with carboxymethyl cellulose (substitution degree of carboxyl group in the unit unit: 1.2, Mw = 1,000,000 g / mol) And 2.2 g of styrene-butadiene rubber (average particle diameter (D ₅₀ ): 120 nm, tensile strength: 110 kgf) as a binder were mixed in distilled water and dispersed for 15 minutes at a rotation speed of 1200 rpm using a TK mixer, (Viscosity at 25 ° C: 1500 cps) was prepared.

[ Experimental Example : Evaluation of Battery Characteristics]

The sheet resistance and the adhesive strength of the negative electrode in the lithium secondary battery produced in the above Examples and Comparative Examples were respectively evaluated.

Specifically, the sheet resistance of the negative electrode was measured at a temperature of room temperature (25 占 폚) in a driving voltage range of 2.5 to 3.65 V with respect to the lithium secondary battery manufactured in the above Examples and Comparative Examples under the condition of 0.1 C / Discharge was performed, and then charge / discharge was performed 5 times under the condition of 1C / 1C. Then, the resistance of the lithium secondary battery was measured by filling the battery with a charging depth (SOC) of 50%. The results are shown in Table 1 below.

The adhesive force was measured by using an electrode rudder (15 cm x 1 cm) against the negative electrode manufactured in the above-described manner, punched out by TOP / BACK, Lane, left / middle / right point in the same lane, Was attached to a slide glass attached to each of the samples. 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 a grip of a universal testing machine (UTM) (LF Plus, manufactured by LLOYD) was attached as an electrode adhesive strength measuring instrument, and then a load cell of 5 N was applied to measure the peel strength Respectively.

Example Comparative Example 1 Comparative Example 2 The cathode sheet resistance (m? / Sq) 10 15 12 Peel strength (gf / cm) 12 13 10

As a result of the experiment, the negative electrode of the embodiment prepared by using the negative electrode composition prepared by linearly dispersing the conductive material having the wide specific surface area and the small particle size on the secondary particle with the cellulose type thickening agent had a small secondary specific surface area As compared with the negative electrode of Comparative Example 1 prepared using a conductive material of particulate form and a composition for anode formation prepared without the line dispersion treatment for the conductive material and the cellulose based thickening agent, But showed a significantly reduced sheet resistance in sheet resistance. This is because, in the case of Example 1, the conductive material on the secondary particle having a large specific surface area and a small particle size easily penetrates between the anode active materials and forms a conductive path between the active materials, thereby improving the conductivity.

Compared with the negative electrode of Comparative Example 2, which was produced using the negative electrode composition prepared without the line dispersion process with the cellulose-based thickener, despite the fact that the negative electrode of the above-mentioned example uses the conductive material having the same characteristics, By the treatment, the conductive material was uniformly dispersed in the composition for forming an anode, thereby exhibiting a reduced sheet resistance and an increased peel strength.

The composition for forming a negative electrode of the present invention, in which a conductive material having an average particle size and a specific surface area optimized to improve the conductivity between active materials is used and the conductive material is uniformly dispersed in the composition by dispersing it first with a cellulose type thickener , It can be confirmed that the binder for the conductive material is prevented from adsorbing and the conductive path between the active materials is easily formed, thereby increasing the conductivity and adhesion of the negative electrode.

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 (26)

Preparing a dispersion by mixing and dispersing a conductive material and a cellulose-based thickener in a solvent, and
Adding a negative electrode active material and a binder to the dispersion and mixing the dispersion,
Wherein the conductive material includes secondary particles in which primary particles are aggregated,
Wherein the secondary particles have a BET specific surface area of not less than 100 m ² / g and an average particle diameter (D ₅₀ ) of not more than 1 탆. In the method for producing a composition for forming a negative electrode of a lithium secondary battery ,
The binder is a fluorine-based polymer, a polyalkylene-based polymer, or a variety of rubbers, or a mixture of two or more thereof,
The cellulose-based thickener is a cellulose-based and the degree of substitution of carboxyl groups of the polymer units of the unit 1 to 1.5 constituting the compound, the weight average molecular weight (M _w) of lithium comprises a 800,000 to 4,000,000g / mol of carboxymethylcellulose A method for manufacturing a composition for forming a negative electrode of a secondary battery.
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 contained in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the negative electrode active material.
delete delete delete The method according to claim 1,
The cellulose-based thickener is a lithium secondary cellulose-based and the degree of substitution of carboxyl groups of the polymer units of the unit 1 to 1.5 constituting the compound, the weight average molecular weight (Mw) of 800,000 to comprises 1,200,000g / mol of carboxymethylcellulose A method for producing a composition for forming a negative electrode of a battery.
The method according to claim 1,
Wherein the cellulose-based thickener is contained in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the negative electrode active material.
The method according to claim 1,
Wherein the solvent is an aqueous solvent.
The method according to claim 1,
Wherein the dispersion is prepared by dispersing a cellulose-based thickener-containing solution prepared by dissolving a cellulose-based thickener in a solvent and adding a conductive material to the solution.
The method according to claim 1,
Wherein the dispersion is carried out by a jet flow at a rotation speed of 10,000 to 25,000 rpm.
The method according to claim 1,
Wherein the negative electrode active material comprises a mixture of a silicon oxide negative active material of SiOx (0 <x <2) and a graphite negative active material in a weight ratio of 1: 9 to 5: 5 Gt;
The method according to claim 1,
Wherein the binder is a styrene-butadiene-based rubber.
The method according to claim 1,
Wherein the binder is a styrene-butadiene-based rubber having an average particle diameter (D ₅₀ ) of 90 to 150 nm and a tensile strength of 90 to 160 kgf.
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 negative electrode active material.
The method according to claim 1,
Wherein the negative electrode active material and the binder are added to the dispersion, wherein the cellulose-based thickener is further added.
17. The method of claim 16,
Wherein the cellulosic thickener has a degree of substitution of a carboxyl group in a unit unit of a polymer constituting a cellulose compound of 1 to 1.5 and a weight average molecular weight (Mw) of 1,200,000 g / mol to 4,000,000 g / mol. A method for producing a composition for forming a negative electrode.
A composition for forming a negative electrode of a lithium secondary battery produced by the production method according to claim 1.
19. The method of claim 18,
1 to 3 parts by weight of a conductive material, 1 to 10 parts by weight of a binder, and 0.5 to 5 parts by weight of a cellulose-based thickener, based on 100 parts by weight of an anode active material,
A solvent in an amount such that the viscosity of the composition for forming a negative electrode is from 1000 cps to 5000 cps at 25 캜,
Wherein the conductive material comprises a carbon-based material in the form of a secondary particle having aggregated primary particles and a BET specific surface area of 100 m ² / g or more and an average particle diameter (D ₅₀ ) of 1 μm or less. / RTI &gt;
20. The method of claim 19,
Wherein the cellulose-based thickener comprises a different cellulosic compound having a different weight average molecular weight (Mw).
An anode for a lithium secondary battery produced by using the composition for forming a negative electrode according to claim 18.
A lithium secondary battery comprising a cathode according to claim 21.
23. A battery module comprising the lithium secondary battery according to claim 22 as a unit cell.
A battery pack comprising the battery module according to claim 23.
25. The method of claim 24,
A battery pack that is used as a power source for mid- to large-sized devices.
26. The method of claim 25,
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.