KR20140099988A - Anode active material for lithium secondary battery and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to an anode active material including spherical natural graphite having an amorphous carbon coating layer and a scaly natural graphite having an amorphous carbon coating layer, to an anode including the same, and to a lithium secondary battery. By using the anode active material on the anode of the lithium secondary battery, an electrode having high electric conductivity can be formed and rate properties can be enhanced.

Description

[0001] The present invention relates to a negative electrode active material for a lithium secondary battery, and a lithium secondary battery comprising the same. [0001] The present invention relates to a negative active material for a lithium secondary battery,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative electrode active material including scaly natural graphite on which an amorphous carbon coating layer is formed and scaly natural graphite on which an amorphous carbon coating layer is formed, and a negative electrode and a lithium secondary battery comprising the same.

BACKGROUND ART [0002] With the recent development of the information communication industry, as electronic devices have become smaller, lighter, thinner, and portable, there is a growing demand for higher energy density of batteries used as power sources for such electronic devices. Lithium secondary batteries are the ones that can best meet this demand, and researches thereon are actively being carried out.

Lithium-containing cobalt oxide (LiCoO ₂ ) is mainly used as the positive electrode active material of the lithium secondary battery, and lithium-containing manganese oxide such as LiMn ₂ O _{4 having a} spinel crystal structure and lithium-containing nickel oxide (LiNiO ₂ ) are also used .

The negative electrode active material of the lithium secondary battery mainly uses a carbon-based material, and the carbon-based material includes crystalline carbon and amorphous carbon. Crystalline carbon is represented by graphite carbon such as natural graphite and artificial graphite. Amorphous carbon is a mixture of non-graphitizable carbons (hard carbons) obtained by carbonizing a polymer resin and heat- And graphitizable carbons (soft carbons).

The carbonaceous active material used as the negative electrode active material has a very low discharge potential of about -3 V with respect to the standard hydrogen electrode potential and exhibits a highly reversible charge / discharge behavior due to the uniaxial orientation of the graphite plate layer (graphene layer) Electrode cycle life.

In general, amorphous carbon has a large capacity, but has a disadvantage of large irreversibility in charge and discharge processes. Natural graphite, which is a typical example of the crystalline carbon, has a high theoretical limit capacity of 372 mAh / g, but has a disadvantage that life deterioration is severe. In order to improve this, recently, a method of using artificial graphite having a high specific surface area and improved natural graphite has been attempted. However, hydrophobic artificial graphite has a very low dispersibility in an aqueous slurry other than NMP, making it difficult to obtain the desired physical properties of the battery.

To solve this problem, a method for manufacturing a battery using an anode active material including an artificial graphite-based active material and a carbon-containing compound having a specific surface area of 200 m 2 / g or more and 450 m 2 / g or less has been developed.

However, in the case of the above method, since a large amount of water is required due to a large specific surface area, the solid content of the negative electrode slurry is lowered and a large amount of binder is required. As a result, the adhesive strength of the negative electrode is lowered, It is disadvantageous that the initial efficiency is decreased due to the formation of the SEI layer.

In the case of artificial graphite prepared by graphitization heat treatment at 2800 ℃ or higher, the current efficiency of the initial charging / discharging process was up to 92%. Artificial graphite has to be subjected to heat treatment at 2800 DEG C or higher as described above, which involves a problem that the manufacturing cost is increased and the production cost of the battery is affected.

Therefore, the performance of the artificial graphite material is improved from the viewpoints of the non-capacity of the material and the initial current efficiency, and the production cost is significantly reduced, Development is required.

Disclosure of Invention Technical Problem [8] The present invention provides a negative electrode active material having an electrode having a high electrical conductivity and excellent rate characteristics, and a lithium secondary battery including the negative electrode active material.

In order to solve the above problems, the present invention provides a negative electrode active material comprising spherical natural graphite having an amorphous carbon coating layer and scintillating natural graphite having an amorphous carbon coating layer formed thereon.

Also, the present invention provides a negative electrode active material slurry comprising the negative electrode active material, the binder resin, and the polar solvent.

Furthermore, the present invention provides a current collector and a negative electrode including the negative electrode active material slurry on at least one surface of the current collector.

In addition, the present invention provides a lithium secondary battery comprising a cathode, a cathode, a separator interposed between the cathode and the anode, and an electrolyte in which a lithium salt is dissolved.

It is possible to form an electrode having high electrical conductivity by including the spherical natural graphite in which the amorphous carbon coating layer is formed and the negative electrode active material including the scaly natural graphite in which the amorphous carbon coating layer is formed, 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.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a form of a negative electrode active material in which scaly natural graphite or a conductive material is formed in a fine space formed between spherical natural graphite particles. FIG.
2 is a view showing the structure of natural graphite particles.
3 is a graph showing the rate characteristics of the lithium secondary batteries of Example 1 and Comparative Example 1 according to Experimental Example 1 of the present invention.

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.

The negative electrode active material of the present invention includes spherical natural graphite in which an amorphous carbon coating layer is formed and scaly natural graphite in which an amorphous carbon coating layer is formed.

 According to an embodiment of the present invention, spherical natural graphite having an amorphous carbon coating layer formed thereon and scintillating natural graphite having an amorphous carbon coating layer formed thereon are mixed with each other so that charging and discharging are progressed to provide excellent conductivity even after the electrode is expanded In addition, it is possible to suppress the side reaction with the electrolyte and to improve the rate characteristics of the lithium secondary battery.

In general, amorphous carbon or crystalline carbon is used as an anode material of a lithium secondary battery, and crystalline carbon is mainly used because of its high capacity. Such crystalline carbon is natural graphite or artificial graphite.

In the case of artificial graphite, charge-discharge efficiency is high, but it is not only costly, but also dispersed very poorly in an aqueous slurry, which makes it difficult to obtain a desired level of physical properties.

On the other hand, natural graphite has a low cost, excellent voltage flatness and a high capacity close to the theoretical capacity, and thus has high utility as an active material. However, since natural graphite exhibits a high crystal plate shape, when it is made of an electrode plate, the active material is flatly compressed with a high density, so that impregnation of the electrolytic solution is not easy and the high rate charge / discharge characteristics may be deteriorated.

That is, when an electrode plate is manufactured using only natural graphite on a high crystal plate, there may be problems such as detachment of active material from the current collector, bending of the electrode plate, difficulty in adjusting the thickness of the electrode plate, low adhesive force between the active material and the current collector, electrolyte impregnation,

Accordingly, the present invention solves the above problems by using natural graphite capable of exhibiting a high capacity and sphering it.

However, when an electrode is formed of spherical natural graphite as a negative electrode active material of a lithium secondary battery, a pore is formed between spherical graphite as shown in Fig. There is a limitation in making such a microspace by making only a conductive pathway of electrons between the anode active material and a conductive material such as point-like carbon black (Fig. 1 (a)).

Thus, according to one embodiment of the present invention, by adding scintillating natural graphite capable of simultaneously acting as a negative active material and a conductive material to spherical natural graphite, scintillating natural graphite is present in a micro space formed between spherical natural graphite (B) in FIG. 1), it is possible to form an electrode having a high electrical conductivity, thereby lowering the resistance of the battery and improving the rate characteristic of the lithium secondary battery .

The spherical natural graphite and the scaly natural graphite used in one embodiment of the present invention each include an amorphous carbon coating layer on its surface. That is, the spherical natural graphite and the scaly natural graphite surface may be coated with an amorphous carbon coating layer, respectively, and then they may be mixed to form a composite body.

According to one embodiment of the present invention, since the amorphous carbon coating layer is formed on the surface of the spherical natural graphite, it is possible to increase the hardness of the spherical natural graphite, to easily maintain the spherical shape even after rolling, A low and stable SEI layer can be formed and high initial efficiency can be obtained. Further, since the amorphous carbon coating layer is formed on the surface of the scratched natural graphite, the specific surface area of the scratched natural graphite is reduced, thereby minimizing the side reaction with the electrolytic solution and improving the stability at high temperatures. Particularly, scaly natural graphite formed with an amorphous carbon coating layer acts as a negative electrode active material and conductive material between spherical natural graphite, and can provide excellent conductivity even after the electrode is expanded as charge / discharge progresses.

If the spherical natural graphite and the scaly natural graphite do not form the amorphous carbon coating layer and form the coating layer together, the scaly natural graphite can not sufficiently fulfill the role as intended in the present invention.

The method of forming the amorphous carbon coating layer on the surfaces of the spherical natural graphite and the scaly natural graphite according to an embodiment of the present invention includes a method of forming the amorphous carbon coating layer on the surface of the natural graphite, Coating with pyrolytic carbon using one or more gas or liquid carbon sources selected from the group consisting of propylene; Or by coating with a liquid or solid phase pitch. For example, the carbon source or pitch and the spherical natural graphite, and the carbon source or pitch and the scaly natural graphite may be respectively put into a firing furnace and fired at a temperature range of, for example, 300 ° C to 1400 ° C. The pitch may be coal-based pitch or petroleum pitch.

The amount of amorphous carbon relative to the spherical natural graphite may be 0.5 to 10 parts by weight based on 100 parts by weight of the spherical natural graphite. If the coating amount of the amorphous carbon is less than 0.5 part by weight, the hardness of the spherical natural graphite may be lowered and the side reaction with the electrolyte may increase. Conversely, if the amorphous carbon coating amount exceeds 10 parts by weight, The resistance may increase, and the surface may become hard and the electrode density can not be increased.

The amount of amorphous carbon to the scaly natural graphite may be 0.5 to 10 parts by weight based on 100 parts by weight of scaly natural graphite. When the coating amount of the amorphous carbon is less than 0.5 part by weight, side reaction with the electrolyte may increase. On the contrary, when the coating amount of amorphous carbon is more than 10 parts by weight, the thickness of the amorphous carbon layer is excessively increased, The resistance may increase, and the surface may become hard and the electrode density can not be increased.

The spherical natural graphite in which the amorphous carbon coating layer is formed according to an embodiment of the present invention may have an average particle diameter of 12 탆 to 18 탆. The average particle size of the spherical natural graphite is advantageous as it minimizes the particle size in order to maximize the degree of disorder in the expansion direction for each particle so as to prevent particle expansion due to charging of lithium ions, If it exceeds 18 탆, the expansion becomes severe and charging and discharging are repeated, so that the interfacial bondability and the bondability between the particles and the current collector are deteriorated, and the cycle characteristics can be greatly reduced. Further, when the particle size is less than 12 탆, the particle size is small, so that the amount of the active material is increased within a unit volume, and a larger amount of binder is required.

Further, the spherical natural graphite according to an embodiment of the present invention has a specific surface area of 3.3 m 2 / g to 5.1 m 2 / g and has a compression density of 1.40 g / cc to 1.85 g / cc under a pressure of 12 mPa to 16 mPa But it is not limited thereto.

According to one embodiment of the present invention, a method of producing natural graphite on a high crystal plate as spherical natural graphite can be achieved by, for example, introducing plate-shaped graphite particles into a sphering device to control rotor speed and rotor time Whereby spherical natural graphite having a desired particle size can be obtained. In addition, commercially available spherical natural graphite can be purchased and used.

In addition, according to one embodiment of the present invention, the scratched natural graphite may be obtained by collecting and classifying the remaining fine particles in the process of manufacturing the spherical natural graphite, for example, in a flake type, , And is not limited thereto.

The average diameter of the scaly natural graphite on which the amorphous carbon coating layer is formed may be from 3 탆 to 11 탆, and preferably from 3 탆 to 8 탆. If the average diameter of the scintillating natural graphite is less than 3 탆, a large amount of binder is required, which may cause problems such as filter clogging in the process. If the average natural graphite exceeds 11 탆, There may be difficulty in mixing.

According to an embodiment of the present invention, the scratched natural graphite preferably has a specific surface area of 3 m 2 / g to 25 m 2 / g, and when the specific surface area exceeds 25 m 2 / g, Can be excessive and stability at high temperatures can be reduced. Further, the scaly natural graphite is preferably a material having a compressive density of 1.40 g / cc to 1.85 g / cc under a pressure of 12 mPa to 16 mPa. If the compression density is less than 1.50 g / cc, the energy density per unit volume decreases, and the surface may have a hard property under the same pressure. Therefore, when the compression density is higher than 1.85 g / cc, It is possible to cause a decrease in initial efficiency and deterioration of high-temperature characteristics due to a large specific surface area, and the adhesion of the electrode may be reduced.

According to one embodiment of the present invention, the scaly natural graphite has a hexagonal plate structure having a lattice constant of 2.46 Å in the a-axis and 6.73 Å in the c-axis, as shown in FIG. 2 Have.

The average inter-layer distance (d002) of the natural graphite particles is obtained by obtaining a graph of 2? Values measured by X-ray diffractometry and calculating the peak position of the graph by the integral method and calculating by the Bragg formula using the following equation have.

&Quot; (1) "

d ₀₀₂ =? / 2 sin?

In addition, the crystallite size (Lc) of the scaly natural graphite particles can be calculated from the crystallite size Lc (002) in the C axis direction of the particles by the Scherrer equation of the following equation (2).

&Quot; (2) "

K = Scherrer constant (K = 0.9)

β = half width

lambda = wavelength (0.154056 nm)

&thetas; = angle at maximum peak

According to one embodiment of the present invention, the scaly natural graphite may have a crystallite size Lc in the C axis direction of 10 nm to 20 nm when XRD is measured using CuK ?. When the Lc of the natural graphite is within the above range, the electrical conductivity is excellent, the diffusion speed of lithium ions is faster, and insertion and desorption of lithium ions can be more easily performed. If Lc is more than 20 nm, the moving distance of lithium ions may be disturbed to act as a resistor, resulting in degradation of output characteristics. If Lc is less than 10 nm, it may be difficult to express the capacity inherent in graphite.

The mixing ratio of the spherical natural graphite on which the amorphous carbon coating layer is formed and the natural graphite on which the amorphous carbon coating layer is formed may be 9: 1 to 7: 3 by weight. If the amount of the natural graphite is more than the above range, the specific surface area increases, the decomposition reaction of the electrolyte increases, the initial efficiency decreases, and the life characteristic may deteriorate over a long period of time. Since the amount of graphite is insufficient to perform the intended role, resistance can not be reduced and the rate characteristics are not improved and there is a problem that the adhesive strength of the electrode is decreased.

The present invention also provides a negative electrode active material slurry comprising (a) the negative active material, (b) a binder resin, and (c) a polar solvent.

At this time, the negative electrode active material may be about 40 to 97 wt% based on the total weight of the negative electrode active material slurry. When the content of the negative electrode active material is less than 40% by weight, the amount of water is increased, so that the application of the negative electrode active material is not smoothly performed when the electrode is formed, and the trace of vaporization of bubbles on the electrode surface may be left while moisture is evaporated. On the other hand, if it exceeds 97% by weight, the viscosity of the active material slurry becomes high and dispersion of the binder or the like may not be achieved.

The binder resin used in the present invention is not limited as far as it is an aqueous binder resin that can be used in the production of a negative electrode, and examples thereof include rubber binders such as acrylonitrile-butadiene rubber, styrene-butadiene rubber and acrylic rubber, Cellulose, carboxymethyl cellulose and polyunsaturated vinylidene, and carboxymethyl cellulose or styrene-butadiene rubber can be used in particular. The binder resin may include about 20 to 30% by weight based on the total weight of the negative electrode active material slurry.

According to an embodiment of the present invention, the negative electrode active material slurry may further include a conductive material. Examples of the conductive material which can be used include natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black, carbon nanotube, fullerene, carbon fiber, metal fiber, carbon fluoride, Powder, zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivative, or a mixture of two or more thereof, preferably carbon black.

The negative electrode slurry contains a residual amount of a polar solvent, and water may be used as the polar solvent.

The thus-prepared negative electrode active material slurry of the present invention can be manufactured into a negative electrode according to a manufacturing method commonly used in the art.

The negative electrode according to an embodiment of the present invention can be manufactured by applying the negative electrode active material slurry on the negative electrode current collector having an appropriate thickness and length or forming the negative electrode active material slurry into a film shape.

Also, the present invention provides a lithium secondary battery comprising the negative electrode and the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte in which the lithium salt is dissolved.

The positive electrode is prepared by applying a positive electrode active material onto a positive electrode collector and then drying the positive electrode active material. The cathode active material may be preferably a lithium-containing transition metal oxide, for example, Li _x CoO ₂ (0.5 <x <1.3), Li _x NiO ₂ (0.5 <x <1.3), Li _x MnO ₂ 0.5 <x <1.3, 0 <a <1, 0 <b <0.5), Li _x Mn ₂ O ₄ (0.5 <x <1.3), Li _x (Ni _a Co _b Mn _c ) O ₂ 1, 0 <c <1, a + b + c = 1), Li x Ni 1 -y Co y O 2 (0.5 <x <1.3, 0 <y <1), Li x Co 1 -y Mn y O _{2 (0.5 <x <1.3,} 0≤y <1), Li x Ni 1 -y Mn y O 2 (0.5 <x <1.3, O≤y <1), Li x (Ni a Co b Mn c) O _{4 (0.5 <x <1.3,} 0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), Li x Mn 2 -z Ni z O 4 (0.5 <x < 1.3, 0 <z <2), Li _x Mn _{2 -z} Co _z O ₄ (0.5 <x <1.3, 0 <z <2), Li _x CoPO ₄ (0.5 <x <1.3) and Li _x FePO ₄ 0.5 <x <1.3), or a mixture of two or more thereof. The lithium-containing transition metal oxide may be coated with a metal such as aluminum (Al) or a metal oxide. In addition to the lithium-containing transition metal oxide, sulfide, selenide and halide may also be used.

As the separator, a conventional porous polymer film conventionally used as a separator, for example, a polyolefin such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer and an ethylene / methacrylate copolymer A porous polymer film made of a high molecular weight polymer may be used alone or in a laminated manner, or a nonwoven fabric made of a conventional porous nonwoven fabric such as a glass fiber having a high melting point, a polyethylene terephthalate fiber or the like may be used. It is not.

The lithium salt that can be used as the electrolyte used in the present invention may be any of those conventionally used in an electrolyte for a lithium secondary battery. For example, the anion of the lithium salt may include F ^- , Cl ^- , Br ^- , I ^{- _{NO 3 -, N (CN)}} 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, ^{_{(CF 3) 5 PF -,}} (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (FSO 2) 2 N -, CF 3 _{CF 2 (CF 3) 2 CO} -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2) 7 SO 3 -, CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^-, and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- .

Examples of the electrolyte used in the present invention 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. no.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape, a square shape, a pouch shape, a coin shape, or the like using a can.

The lithium secondary battery of the present invention can be used as a power source for various electronic products. For example, a portable telephone, a mobile phone, a game machine, a portable television, a notebook computer, a calculator, and the like, but is not limited thereto.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example

EXAMPLES The present invention will be further illustrated by the following examples and experimental examples, but the present invention is not limited by these examples and experimental examples.

&Lt; Preparation Example 1 &

[Production of spherical natural graphite having amorphous carbon layer]

Petroleum pitch and spherical natural graphite were mixed at a ratio of 1:10 wt% and fired in a firing furnace at a temperature of about 1000 캜 to prepare spherical natural graphite coated with amorphous carbon at a content of 2.0 wt% on the surface of spherical natural graphite Respectively.

[Production of amorphous carbon coated flake natural graphite]

A natural graphite having an average diameter of 6 占 퐉, a crystallite size Lc of 18 nm in the C axis direction and a specific surface area of 20 m &lt; 2 &gt; / g and a pitch were mixed and fired at a temperature of about 1000 DEG C, To produce 1.0% by weight of scaly natural graphite coated with amorphous carbon.

&Lt; Example 1 >

[ Preparation of negative active material slurry]

Spherical natural graphite coated with amorphous carbon and scaly natural graphite coated with amorphous carbon prepared in Preparation Example 1 were mixed at a weight ratio of 9: 1 to prepare an anode active material.

Subsequently, 46 g of the prepared negative electrode active material, 20 g of the SBR binder and 2 g of carbon black as a conductive material were mixed and mixed with water (H ₂ O) as a solvent to prepare a uniform negative electrode active material slurry.

[Production of lithium secondary battery]

The prepared anode active material slurry was coated on one side of the copper current collector to a thickness of 65 μm, dried and rolled, and then punched to a required size to prepare a negative electrode.

Next, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a ratio of 30: ₁ , after coating the anode foil with a lithium cobalt oxide (LiCoO ₂ ) on the Al foil and interposing a polyolefin separator between the anode and the cathode. 70 in a volume ratio of 1 M LiPF ₆ dissolved in a solvent was injected to prepare a coin type half cell.

Comparative Example  One

A coin type lithium secondary battery was prepared in the same manner as in Example 1, except that spherical natural graphite coated with amorphous carbon prepared in Preparation Example 1 was used alone as an anode active material.

Experimental Example  One : Charge / discharge rate  Measure

Each of the coin-type half-cells manufactured in the above-described Example 1 and Comparative Example 1 was evaluated for capacity while varying the charge-discharge rate from 0.1 C to 5 C at a room temperature in a voltage range of 0 V to 1.5 V Respectively. The results are shown in Fig.

As shown in FIG. 3, in the case of Example 1, the capacity is maintained at 800 C or higher at 2.5 C-rate, and at 700 C or higher at 4 C-rate, whereas in Comparative Example 1, the capacity rapidly decreases from 2 C- At the C-rate, it can be seen that it drops to 650 mAh.

From the above, it can be confirmed that the rate characteristics of the lithium secondary battery including the negative electrode active material according to Example 1 of the present invention are far superior to those of Comparative Example 1.

Claims (15)

Spherical natural graphite in which an amorphous carbon coating layer is formed, and scaly natural graphite in which an amorphous carbon coating layer is formed.
The method according to claim 1,
Wherein the scaly natural graphite has a crystallite size Lc in the C-axis direction of 10 nm to 20 nm when XRD is measured.
The method according to claim 1,
Wherein the graphite natural graphite on which the amorphous carbon coating layer is formed has an average diameter of 3 占 퐉 to 11 占 퐉.
The method according to claim 1,
Wherein the spherical natural graphite having the amorphous carbon coating layer formed thereon has an average particle diameter of 12 to 18 占 퐉.
The method according to claim 1,
Wherein the mixing ratio of the spherical natural graphite in which the amorphous carbon coating layer is formed and the scratched natural graphite in which the amorphous carbon coating layer is formed is in a weight ratio of 9: 1 to 7: 3.
The method according to claim 1,
Wherein the amount of the amorphous carbon relative to the spherical natural graphite is 0.5 to 10 parts by weight based on 100 parts by weight of the spherical natural graphite.
The method according to claim 1,
Wherein the amount of the amorphous carbon relative to the scaly natural graphite is 0.5 to 10 parts by weight based on 100 parts by weight of scaly natural graphite.
The method according to claim 1,
Wherein the amorphous carbon coating layer is formed by coating with pyrolytic carbon using one or more gas or liquid carbon sources selected from the group consisting of methane, ethane, ethylene, butane, acetylene, carbon monoxide, propane, polyvinyl alcohol and propylene; Or a coating of a liquid or solid phase pitch.
A negative electrode active material slurry comprising the negative active material, the binder resin and the polar solvent according to claim 1.
10. The method of claim 9,
Wherein the negative electrode active material slurry further comprises a conductive material.
11. The method of claim 10,
The conductive material may be at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, carbon nanotube, fullerene, carbon fiber, metal fiber, carbon fluoride, aluminum, , Zinc oxide, potassium titanate, titanium oxide, and polyphenylene derivative, or a mixture of two or more thereof.
10. The method of claim 9,
The binder resin is any one selected from the group consisting of acrylonitrile-butadiene rubber, styrene-butadiene rubber, acrylic rubber, hydroxyethyl cellulose, carboxymethyl cellulose and polyunsaturated vinylidene or a mixture of two or more thereof As a negative active material slurry.
10. The method of claim 9,
Wherein the binder resin is 20 to 30% by weight based on the total weight of the negative electrode active material slurry.
A negative electrode comprising the current collector and the negative active material slurry of claim 9 formed on at least one side of the current collector.
A lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte in which a lithium salt is dissolved, wherein the negative electrode is the negative electrode according to Claim 14.

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