KR101430733B1 - Negative active material for rechargeable lithium battery, method of preparing the same, and rechargeable lithium battery including the same - Google Patents

Abstract

Provided are a negative electrode active material for a lithium secondary battery, a preparing method of the same, and a lithium secondary battery including the same comprising a spherical natural graphite particles containing spherical natural graphite particles assembled with flaky natural graphite fragments which are rolled with pieces in cabbage shapes or random shapes; and non-crystalline or quasi crystalline carbon. A gap between the flaky natural graphite fragments exists on the surface part and the inside of the spherical natural graphite particles. The non-crystal or quasi crystalline carbon is coated on the spherical natural graphite particles and exists in the gap to keep the gaps on the surface part and the inside of the spherical natural graphite particles.

Description

TECHNICAL FIELD The present invention relates to a negative active material for a lithium secondary battery, a method for producing the negative active material, and a lithium secondary battery including the same. [0001] The present invention relates to a negative active material for a lithium secondary battery,

A negative electrode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery comprising the same.

At present, a crystalline graphite material is used as an anode active material of a lithium secondary battery. Crystalline graphite is divided into artificial graphite and natural graphite. Since the artificial graphite is generally obtained by carbonizing the carbon precursor under an inert atmosphere at a high temperature of about 2800 DEG C or higher to remove impurities and graphitizing the carbon precursor, the use of natural graphite is increasing.

When the natural graphite particles are used as the negative electrode active material, the uniformity of the slurry application during electrode production is lowered due to the anisotropic nature of the particle shape, and flaky graphite particles are oriented along the current collector by rolling and press- There is a problem that the characteristics of the semiconductor device are greatly deteriorated. Therefore, natural graphite, which is currently commercialized, is a spherical natural graphite obtained by granulating scaly graphite into a spherical shape. However, in the case of the spherical natural graphite, there is a need to improve the high rate charge / discharge characteristics and cycle life characteristics.

One embodiment of the present invention is to provide a negative electrode active material for a rechargeable lithium battery having excellent high rate charge / discharge characteristics and cycle life characteristics.

Another embodiment is to provide a method for manufacturing the negative electrode active material for a lithium secondary battery.

Another embodiment provides a lithium secondary battery comprising the negative electrode active material for a lithium secondary battery.

One embodiment includes spherical natural graphite particles in which scaly natural graphite pieces are assembled and assembled into a cabbage or random phase; And spherical natural graphite-modified composite particles containing amorphous or quasi-crystalline carbon, wherein a spherical natural graphite particle has a gap therebetween in a surface portion and inside of the graphite natural graphite particles, The quasicrystalline carbon is coated on the surface of the spheroidized natural graphite particles and the amorphous or quasicrystalline carbon is dispersed in the spherical natural graphite particles in such a manner that the spherical natural graphite particles Thereby providing a battery negative electrode active material.

The spherical natural graphite particles may have an average particle diameter (D50) of 5 to 40 mu m.

The amorphous or semi-crystalline carbon may be included in an amount of 1 to 20 parts by weight based on 100 parts by weight of the spherical natural graphite particles.

The spherical natural graphite-modified composite particle may further include a lithium compound including Li ₂ O, Li ₂ CO _3, or a combination thereof, and the lithium compound is coated on the surface of the spherical natural graphite particles, The lithium compound may be present on the surface portion of the spheroidized natural graphite particles and in a gap formed inside.

The lithium compound may be included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the spherical natural graphite particles.

Another embodiment provides a method of manufacturing a graphite sheet, comprising: preparing a solution comprising spheroidized natural graphite particles, amorphous or quasi-crystalline carbon precursor, and a solvent, the scaly graphite pieces being assembled into a cabbage or random phase and assembled; The solution is subjected to ultrasonic treatment to form a gap spreading between the scratched natural graphite slices on the surface portion and inside of the spheroidized natural graphite particles while maintaining the crystallinity of the spheroidized natural graphite particles, The amorphous or quasi-crystalline carbon precursor is coated on the surface of the natural graphite particles and the amorphous or quasi-crystalline carbon precursor is impregnated in the gap existing on the surface portion and inside of the spherical natural graphite particles; Drying the ultrasonic treated solution to obtain spherical natural graphite modified particles; And heat treating the spheroidized natural graphite modified particles to coat amorphous or quasi-crystalline carbon on the surface of the spheroidized natural graphite particles and to inject the amorphous or semi- To produce a spherical natural graphite-modified composite particle in which crystalline carbon is present in the negative electrode active material for lithium secondary batteries.

Another embodiment provides a method of manufacturing a graphite sheet, comprising the steps of: preparing a solution comprising sculptured natural graphite particles assembled and assembled into a cabbage or random phase, spherical natural graphite particles, an amorphous or quasi-crystalline carbon precursor, lithium acetate and a solvent; The solution is subjected to ultrasonic treatment to form a gap spreading between the scratched natural graphite slices on the surface portion and inside of the spheroidized natural graphite particles while maintaining the crystallinity of the spheroidized natural graphite particles, Wherein the amorphous or quasi-crystalline carbon precursor and the lithium acetate are coated on the surface of the natural graphite particles and the open gap existing on the surface portion and inside of the spherical natural graphite particles, ; Drying the ultrasonic treated solution to obtain spherical natural graphite modified particles; And heat treating the spheroidized natural graphite modified particles to form amorphous or semi-crystalline carbon and a lithium compound coated on the surface of the spheroidized natural graphite particles, Comprising the steps of: preparing a spherical natural graphite-modified composite particle in which amorphous or quasi-crystalline carbon and a lithium compound are present, wherein the lithium compound is Li ₂ O, Li ₂ CO ₃ or a combination thereof, Of the present invention.

In another embodiment, there is provided a method of manufacturing a graphite sheet, comprising the steps of: preparing a solution including sculpted natural graphite particles assembled and assembled into a cabbage or random phase, spherical natural graphite particles, amorphous or quasi-crystalline carbon precursor, and a solvent; The solution is subjected to ultrasonic treatment to form a gap spreading between the scratched natural graphite slices on the surface portion and inside of the spheroidized natural graphite particles while maintaining the crystallinity of the spheroidized natural graphite particles, The amorphous or quasi-crystalline carbon precursor is coated on the surface of the natural graphite particles and the amorphous or quasi-crystalline carbon precursor is impregnated in the gap existing on the surface portion and inside of the spherical natural graphite particles; Adding the lithium acetate to the ultrasonic treated solution, and drying the coated graphite particle, wherein the spherical natural graphite particles are coated on the surface of the spherical natural graphite particle with the amorphous or quasi-crystalline carbon precursor and the lithium acetate, Obtaining spherical natural graphite modified particles impregnated with said amorphous or quasi-crystalline carbon precursor and said lithium acetate in said gap; And heat treating the spheroidized natural graphite modified particles to form amorphous or semi-crystalline carbon and a lithium compound coated on the surface of the spheroidized natural graphite particles, Comprising the steps of: preparing a spherical natural graphite-modified composite particle in which amorphous or quasi-crystalline carbon and a lithium compound are present, wherein the lithium compound is Li ₂ O, Li ₂ CO ₃ or a combination thereof, Of the present invention.

The solvent may be selected from the group consisting of water, N-methylpyrrolidone, dimethylformamide, toluene, ethylene, dimethylacetamide, acetone, methyl ethyl ketone, hexane, tetrahydrofuran, decane, ethanol, methanol, isopropanol, . ≪ / RTI >

The amorphous or quasi-crystalline carbon precursor may be selected from the group consisting of citric acid, stearic acid, sucrose, polyvinylidene fluoride, carboxymethylcellulose (CMC), hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, starch, phenolic resin, furan resin, per furyl alcohol, polyacrylic acid, polyacrylic sodium, polyacrylonitrile, polyimide, epoxy resin, Styrene, polyvinyl alcohol, polyvinyl chloride, coal pitch, petroleum pitch, mesophase pitch, low molecular weight heavy oils, glucose, gelatin, sugars or combinations thereof.

The ultrasonic treatment may be performed by irradiating ultrasonic waves at an oscillation frequency of 10 to 35 kHz and an output of 10 to 100 W for 1 minute to 24 hours.

The drying may be carried out by spray drying, rotary spraying, nozzle spraying, ultrasonic spraying or a combination thereof; A drying method using a rotary evaporator; Vacuum drying method; Natural drying method; Or a combination thereof.

The heat treatment may be performed at a temperature of 500 to 2500 ° C.

The amorphous or semi-crystalline carbon precursor may be included in an amount of 2 to 80 parts by weight based on 100 parts by weight of the spherical natural graphite particles.

The lithium acetate may be included in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the spherical natural graphite particles.

Another embodiment includes a negative electrode comprising the negative electrode active material; anode; And a lithium secondary battery comprising the electrolyte.

The details of other embodiments are included in the detailed description below.

It is possible to realize a lithium secondary battery excellent in high rate charge / discharge characteristics and cycle life characteristics.

1 is a schematic cross-sectional view of a negative electrode active material according to one embodiment.
2 and 3 are scanning electron microscope (SEM) photographs of cross sections of the negative electrode active material according to Example 1 and Comparative Example 1, respectively.
4 to 11 are scanning electron microscope (SEM) photographs of the negative electrode active materials according to Examples 1 to 5 and Comparative Examples 1 to 3, respectively.
12 is a transmission electron microscope (TEM) photograph of the cross section of the negative electrode active material according to Example 5. Fig.
13 and 14 are TEM micrographs of high magnification portions of the portions indicated by (a) and (b) in FIG. 12, respectively.
15 is a graph showing load contrast density values of the negative electrode active material according to Examples 1 to 3 and Comparative Examples 1 and 2. FIG.
16 is a graph showing an X-ray diffraction pattern (XRD) of the negative electrode active material according to Examples 3 and 4 and Comparative Example 2. Fig.
FIG. 17 is a graph showing an X-ray diffraction pattern (XRD) obtained by enlarging some 2? Sections in FIG.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

The negative electrode active material according to one embodiment can be explained with reference to FIG.

1 is a schematic cross-sectional view of a negative electrode active material according to one embodiment.

1, the negative electrode active material according to an embodiment is a spherical natural graphite-modified composite particle, wherein the graphite natural graphite-modified composite particle 100 is a natural graphite-modified composite particle in which scaly natural graphite fragments 10 are formed into a cabbage or random phase Spherical natural graphite particles that have been assembled and assembled, and amorphous or semi-crystalline carbon 30. Specifically, the spheroidized natural graphite particles have a gap 20 formed thereon in a surface portion and inside thereof. The gap 20 is formed by a method of manufacturing the negative electrode active material described later, specifically, by ultrasonic treatment of the solution, And the natural graphite pieces 10 can be formed between the natural graphite pieces 10. At this time, the crystallinity of the spheroidized natural graphite particles can be maintained as it is when the gap formed by the ultrasonic treatment of the solution is formed. The amorphous or semicrystalline carbon 30 may be coated on the surface of the spheroidized natural graphite particles as well as on the surface of the spherical natural graphite particles and in the gap 20 existing inside the spherical natural graphite particles. Wherein said amorphous or quasi-crystalline carbon is coated on the surface of said spheroidized natural graphite particles and is present in a gap formed in the surface portion and inside of said spheroidized natural graphite particles, Not only the graphite pieces can be bonded to each other, but also the structure of the gap can be maintained.

In one embodiment, the "gap" possessed by spheroidized natural graphite particles has a different meaning from "voids ". "Gap" means an empty space formed between the scaly natural graphite fragments that are formed during the assembly of the spherical natural graphite particles without changing the crystallinity of the spherical natural graphite particles. On the other hand, "voids or cavities" are voids formed in the interior of crystalline graphite particles including natural graphite by a strong external force, specifically a milling process that gives a stronger external force than ultrasonic treatment, Are formed as structural defects, and thus the crystallinity of the graphite particles is changed.

When the spherical natural graphite-modified composite particle according to one embodiment has the above-described structure, the reactivity with the electrolyte is improved, thereby realizing a lithium secondary battery having excellent high rate charge / discharge characteristics and cycle life characteristics.

Specifically, since the amorphous or quasi-crystalline carbon is coated on the surface of the spherical natural graphite particles and is present in a gap formed in the surface portion and inside of the spherical natural graphite particles, The squeezing phenomenon of the spheroidized natural graphite particles can be suppressed and the gap can be maintained through the ultrasonic treatment. As a result, the reactivity with the electrolyte is excellent, so that the high rate charging / discharging characteristics of the lithium secondary battery can be improved.

Also, since amorphous or quasi-crystalline carbon is coated on the surface of the spherical natural graphite particles and is present in a gap formed between the surface portion of the spherical natural graphite particles and the inside of the spherical natural graphite particles, , It is possible to suppress deterioration of the structural stability of the spherical natural graphite particles which may occur upon repetition of charging and discharging, thereby improving the cycle characteristics.

The amorphous or semicrystalline carbon is present not only in a gap existing in the surface portion of the spherical natural graphite particles but also in a gap existing inside the spherical natural graphite particles. In this case, when present in the internal gap, it may include deep inside, that is, in the vicinity of the center or center of spherical natural graphite particles. Such a structure may improve the structural stability of spherical natural graphite particles Can contribute more.

The spherical natural graphite particles can be formed by the methods disclosed in Korean Patent Publication Nos. 2003-0087986 and 2005-0009245, but are not limited thereto. For example, a step of repeatedly processing the scaly natural graphite having an average particle diameter of 30 탆 or more by using a rotary machine is performed, whereby the friction between the powder and the crushing due to the collision between the inner side of the rotary machine and the scaly natural graphite powder Processing, shearing of powder by shearing stress, and the like, so that the spherical natural graphite particles can be finally produced.

In this way, the spherical natural graphite particles can be formed by assembly of scaly natural graphite fragments into a cabbage or random phase. In addition, the spheroidized natural graphite particles may be spherical as well as circular, or may be spherical having an index of about 0.8 or more, which is calculated by projecting three-dimensional natural graphite particles on a two-dimensional plane.

The spherical natural graphite particles may have an average particle diameter (D50) of 5 to 40 mu m, and more specifically, 7 to 30 mu m. D50 means an average diameter of particles having a cumulative volume of 50 vol% in the particle size distribution. When spherical natural graphite particles having an average particle size within the above range are used, scintillation of natural graphite fragments into a cabbage or random phase is facilitated and the electrochemical characteristics can be improved.

The amorphous or semicrystalline carbon may be contained in an amount of 1 to 20 parts by weight, and more specifically 2 to 15 parts by weight, based on 100 parts by weight of the spherical natural graphite particles. When the amorphous or semi-crystalline carbon is coated on the surface of the spherical natural graphite particles within the above-mentioned content range, or when the amorphous or semi-crystalline carbon exists in the surface portion of the spherical natural graphite particles and in the gaps between the spherical natural graphite particles, It is possible to appropriately maintain the gap between the natural graphite pieces formed on the inside thereof.

The spheroidized natural graphite-modified composite particle may further include a sintered natural graphite particle and a lithium compound in addition to the amorphous or semi-crystalline carbon. Specifically, the lithium compound can be coated on the surface of the spherical natural graphite particles together with the amorphous or semi-crystalline carbon, and the amorphous or semi-crystalline carbon can be coated on the surface of the spherical natural graphite particles, Or the lithium compound may be present together with the quasi-crystalline carbon.

The lithium compound may include Li ₂ O, Li ₂ CO _3, or a combination thereof. The lithium compound may be formed by using lithium acetate in the preparation. Specifically, lithium acetate can be decomposed into Li ₂ CO ₃ by heat treatment, and Li ₂ O can be formed when decomposition proceeds further.

On the other hand, spherical natural graphite particles are basically composed of graphite layer plane in the c-axis direction, ABAB ... Hexagonal graphite is a hexagonal graphite structure that is stacked in the order of Type rhombohedral graphite structure. The nongraphical graphite structure is a structural defect, which increases the degree of disorder of the graphite structure, thereby suppressing insertion and desorption of lithium during charging and discharging and inducing an irreversible reaction. Since the superficial graphite structure is less thermodynamically stable than the hexagonal lattice graphite structure, the superficial graphite structure can be removed by heat treatment at a temperature higher than 2000 ° C. However, the heat treatment at such a temperature requires a great deal of cost. According to one embodiment, when the spherical natural graphite-modified composite particle further comprises the lithium compound, the lithium acetate reacts with the spherical natural graphite particles in the heat treatment step during the production of the spherical natural graphite-modified composite particle, Type graphite structure, which is a structural defect, can be easily removed even at a relatively low temperature such as at a relatively low temperature, for example, to improve the charging / discharging initial efficiency and cycle life characteristics.

The lithium compound may be included in an amount of 0.01 to 10 parts by weight, specifically 0.1 to 5 parts by weight, based on 100 parts by weight of the spherical natural graphite particles. When the lithium compound is contained within the above range, the reaction between the lithium acetate used in the production and the scratched natural graphite particles constituting the spherical natural graphite particles sufficiently occurs, By effectively removing the defects, the initial charge-discharge characteristics and the charge-discharge cycle characteristics can be improved.

The above-mentioned negative electrode active material can be produced by the following method.

Preparing a solution containing spheronized natural graphite particles, an amorphous or a quasi-crystalline carbon precursor, and a solvent; subjecting the solution to ultrasonic treatment; drying the ultrasonic treated solution to obtain spherical natural graphite modified particles; The spherical natural graphite modified particles may be heat-treated to produce the spherical natural graphite modified composite particles.

Specifically, as described above, the spherical natural graphite particles may be agglomerated into agglomerated cabbage or random phases, and granulated particles may be used.

The amorphous or quasi-crystalline carbon precursor may be selected from the group consisting of citric acid, stearic acid, sucrose, polyvinylidene fluoride, carboxymethylcellulose (CMC), hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, starch, phenolic resin, furan resin, per furyl alcohol, polyacrylic acid, polyacrylic sodium, polyacrylonitrile, polyimide, epoxy resin, Styrene, polyvinyl alcohol, polyvinyl chloride, coal pitch, petroleum pitch, mesophase pitch, low molecular weight heavy oils, glucose, gelatin, sugars or combinations thereof.

The amorphous or semi-crystalline carbon precursor may be included in an amount of 2 to 80 parts by weight, and more specifically 5 to 50 parts by weight, based on 100 parts by weight of the spherical natural graphite particles. When the amorphous or quasi-crystalline carbon precursor is contained within the above range, the structure of the gap between the natural graphite slices on the surface and inside of the spherical natural graphite particles can be suitably maintained.

The solvent may be selected from the group consisting of water, N-methylpyrrolidone, dimethylformamide, toluene, ethylene, dimethylacetamide, acetone, methyl ethyl ketone, hexane, tetrahydrofuran, decane, ethanol, methanol, isopropanol, . ≪ / RTI >

Through the ultrasonic treatment of the solution, the spherical natural graphite particles are kept in a crystalline state, and the spherical natural graphite particles are separated from the natural graphite particles which are formed during the production of the spherical natural graphite particles. The spherical natural graphite particles are coated with the amorphous or quasicrystalline carbon precursor on the surface of the spherical natural graphite particles and the spherical natural graphite particles are coated on the surface of the spherical natural graphite particles and the gap The amorphous or quasi-crystalline carbon precursor may be impregnated.

The ultrasonic treatment can be performed under the following conditions.

The ultrasonic treatment may be performed by irradiating ultrasonic waves at an oscillation frequency of 10 to 35 kHz and an output of 10 to 100 W for 1 minute to 24 hours. The oscillation frequency may be specifically 20 to 35 kHz, more specifically 20 to 30 kHz, and the output may be specifically 15 to 70 W, more particularly 20 to 60 W, For 5 minutes to 10 hours, more specifically 10 minutes to 2 hours. When ultrasonic waves are irradiated under the above-mentioned range, a gap can be formed between the natural graphite slices on the surface and inside of the spherical natural graphite particles while maintaining the graphite crystallinity of the spherical natural graphite particles. have.

Drying of the ultrasonic treated solution may be accomplished by spray drying, rotary spraying, nozzle spraying, ultrasonic spraying or a combination thereof; A drying method using a rotary evaporator; Vacuum drying method; Natural drying method; Or a combination thereof.

The heat treatment of the spheroidized natural graphite modified particles may be performed at a temperature of 500 to 2500 ° C, specifically, at a temperature of 500 to 2000 ° C, more specifically, at a temperature of 900 to 1500 ° C. When the heat treatment is performed within the above temperature range, the hetero-element corresponding to the impurity can be sufficiently removed during the carbonization process of the amorphous or quasi-crystalline carbon precursor, thereby reducing the irreversible capacity and improving the charge / discharge characteristics.

The heat treatment may be performed in an atmosphere containing nitrogen, argon, hydrogen, or a mixed gas thereof, or under a vacuum.

And carbonizing the amorphous or quasi-crystalline carbon precursor existing on the surface of the spheroidized natural graphite through the heat treatment to form a gap between the natural graphite slices and amorphous or quasicrystalline carbon Amorphous or semicrystalline carbon may be present in the gap between the surface of the spherical natural graphite particle and the inside of the spherical natural graphite particle.

When the spherical natural graphite modified composite particle thus prepared is used as an anode active material, the reactivity with the electrolyte is improved, and a lithium secondary battery having excellent high rate charge / discharge characteristics and cycle life characteristics can be realized.

Specifically, when a negative electrode is manufactured using spherical natural graphite particles as a negative electrode active material, compression of spherical natural graphite particles may occur due to a pressing process. Particularly, when the gap is formed between the natural graphite pieces on the scales of the spherical natural graphite particles due to the ultrasonic treatment, the pressing phenomenon due to the pressing process may occur more severely. However, according to one embodiment, an amorphous or quasi-crystalline carbon precursor is impregnated into the gaps between the scintillating natural graphite pieces during ultrasonic treatment, the surface of the spheroidized natural graphite is coated with an amorphous or quasi-crystalline carbon precursor, The amorphous or semi-crystalline carbon is coated on the surface of the spheroidized natural graphite particles, and at the same time, the amorphous or semi-crystalline carbon is present on the surface portion of the spheroidized natural graphite particle and inside the gap formed therein, Can be suppressed to maintain a clear gap formed by the ultrasonic treatment process. As a result, the reactivity with the electrolyte is excellent, so that the high rate charging / discharging characteristics of the lithium secondary battery can be improved.

On the other hand, spherical natural graphite particles are difficult to effectively buffer repeated expansion and contraction of graphite during repeated intercalation and deintercalation of lithium during charging and discharging, The coupling state of the natural graphite section is loosened, and the structural stability of the spherical natural graphite particles may be deteriorated. In one embodiment, the amorphous or semi-crystalline carbon is coated on the surface of the spheroidized natural graphite particles and is present in a gap formed in the surface portion of the spheroidized natural graphite particle and inside thereof, The scaly natural graphite pieces can be bonded to each other. Accordingly, it is possible to suppress deterioration of the structural stability of the spheroidized natural graphite particles, which may be caused by repeated expansion and contraction of the graphite during repeated insertion and desorption of lithium during charging and discharging, so that the cycle characteristics can be improved .

The spherical natural graphite-modified composite particles further comprising the spherical natural graphite particles and the lithium compound in addition to the amorphous or semi-crystalline carbon may be prepared as follows.

The first method comprises preparing a solution comprising spheronized natural graphite particles, an amorphous or semi-crystalline carbon precursor, lithium acetate and a solvent, ultrasonicating the solution, drying the ultrasonic treated solution to form spherical The natural graphite-modified composite particles can be produced by obtaining natural graphite-modified particles and heat-treating the spheroidized natural graphite-modified particles.

Forming a gap between the natural graphite particles on the surface of the spherical natural graphite particle and the natural graphite particles on the inside of the spherical natural graphite particle while maintaining the crystallinity of the spherical natural graphite particle through ultrasonic treatment of the solution, Wherein the amorphous or quasi-crystalline carbon precursor and the lithium acetate are coated on the surface of the spherical natural graphite particles and the amorphous or semicrystalline carbon precursor and the amorphous or quasi-crystalline carbon precursor are coated on the surfaces of the spherical natural graphite particles, Lithium acetate can be impregnated.

Also, through the heat treatment of the spheroidized natural graphite modified particles, not only carbonization of the amorphous or quasi-crystalline carbon precursor existing on the surface of the spherical natural graphite particles and the gaps between the natural graphite slices, Amorphous or quasi-crystalline carbon and a lithium compound are coated on the surface of the spherical natural graphite particles and the amorphous or semi-crystalline carbon and the lithium compound are coated on the surface of the spherical natural graphite particles, Lithium compounds may be present together.

In the method for producing a spherical natural graphite-modified composite particle further comprising the lithium compound, the kind and content of the spherical natural graphite particles and the amorphous or quasi-crystalline carbon precursor, the conditions of the ultrasonic wave, the drying method, The conditions of the heat treatment are all the same as those described above.

The second method comprises preparing a solution containing spherical natural graphite particles, an amorphous or semi-crystalline carbon precursor, and a solvent, ultrasonifying the solution, adding lithium acetate to the ultrasonic treated solution, drying To obtain spherical natural graphite modified particles, and then subjecting the spheroidized natural graphite modified particles to a heat treatment, thereby producing spherical natural graphite modified composite particles.

Forming a gap between the natural graphite particles on the surface of the spherical natural graphite particle and the natural graphite particles on the inside of the spherical natural graphite particle while maintaining the crystallinity of the spherical natural graphite particle through ultrasonic treatment of the solution, The amorphous or quasi-crystalline carbon precursor may be coated on the surface of the spheroidized natural graphite particles, and the amorphous or quasi-crystalline carbon precursor may be impregnated in the gap between the surfaces of the spherical natural graphite particles and the inside thereof.

Adding the lithium acetate to the ultrasonic wave treated solution and drying the spherical natural graphite particles; and applying the amorphous or quasi-crystalline carbon precursor and the lithium acetate on the surface of the spherical natural graphite particles, The amorphous or quasi-crystalline carbon precursor and the lithium acetate may be impregnated into the gap present.

Also, through the heat treatment of the spheroidized natural graphite modified particles, not only carbonization of the amorphous or quasi-crystalline carbon precursor existing on the surface of the spherical natural graphite particles and the gaps between the natural graphite slices, Amorphous or quasi-crystalline carbon and a lithium compound are coated on the surface of the spherical natural graphite particles and the amorphous or semi-crystalline carbon and the lithium compound are coated on the surface of the spherical natural graphite particles, Lithium compounds may be present together.

In the first and second methods, the lithium acetate may be included in an amount of 0.1 to 20 parts by weight, and more specifically 0.1 to 15 parts by weight, based on 100 parts by weight of the spherical natural graphite particles. When the lithium acetate is contained in the above content range, the reaction of the lithium acetate with the scratched natural graphite particles constituting the spherical natural graphite particles sufficiently occurs and the defect of the graphite graphite structure present in the scratched natural graphite particles The initial charge-discharge characteristics and the charge-discharge cycle characteristics can be improved.

Similarly, in the second production method of the spherical natural graphite-modified composite particles further comprising the lithium compound, the kind and content of the spherical natural graphite particles and the amorphous or quasi-crystalline carbon precursor, the condition of the ultrasonic wave, Are the same as those described above.

According to another embodiment, there is provided a lithium secondary battery comprising a negative electrode, a positive electrode and an electrolyte solution including the above-mentioned negative electrode active material.

The lithium secondary battery can be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the type of the separator and the electrolytic solution used. The lithium secondary battery can be classified into a cylindrical shape, a square shape, a coin shape, Depending on the size, it can be divided into bulk type and thin type. The structure and the manufacturing method of these cells are well known in the art, and detailed description thereof will be omitted.

The negative electrode may be prepared by mixing the above-described negative electrode active material, a binder and optionally a conductive material to prepare a composition for forming a negative electrode active material layer, and then applying the negative electrode active material composition to a negative electrode collector. These negative electrode compositions are well known in the art A detailed description thereof will be omitted.

  Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to the following embodiments.

(Preparation of negative electrode active material)

Example  One

2.5 parts by weight of spherical natural graphite particles (POSCO Chemtech, SNG12) having an average particle size (D50) of 12.5 占 퐉 and 0.23 parts by weight of a petroleum pitch (the yield after carbonization was amorphous or quasicrystalline carbon 5 Weight part) was added to 100 parts by weight of tetrahydrofuran to prepare a mixed solution. The mixed solution was mixed using a magnetic stirrer, and ultrasonic waves were irradiated for 60 minutes at a frequency of 20 kHz and an output of 25 W. Then, 100 parts by weight of distilled water After the tetrahydrofuran was evaporated using a rotary evaporator, spherical natural graphite modified particles were prepared by spin drying at 160 ° C. The spheroidized natural graphite modified particles were heat-treated at 1200 ° C for 1 hour in an argon atmosphere and then subjected to a furnace cooling to prepare spherical natural graphite-modified composite particles having an average particle size (D50) of 16.3 μm.

Example  2

2.5 parts by weight of spherical natural graphite particles (POSCO Chemtech, SNG12) having an average particle size (D50) of 12.5 占 퐉 and 0.23 parts by weight of a petroleum pitch (the yield after carbonization was amorphous or quasicrystalline carbon 5 100 parts by weight of distilled water was added to 100 parts by weight of tetrahydrofuran to prepare a mixed solution. The mixed solution was mixed using a magnetic stirrer and irradiated with ultrasonic waves at a frequency of 20 kHz and an output of 55 W for 10 minutes. After the tetrahydrofuran was evaporated using a rotary evaporator, spherical natural graphite modified particles were prepared by spin drying at 160 ° C. The spheroidized natural graphite modified particles were heat-treated at 1200 ° C for 1 hour in an argon atmosphere, and then subjected to furnace cooling to prepare spherical natural graphite-modified composite particles having an average particle size (D50) of 16 μm.

Example  3

2.5 parts by weight of spherical natural graphite particles having an average particle diameter (D50) of 12.5 占 퐉 (POSCO Chemtech, SNG12) and 0.3 parts by weight of a petroleum pitch (the carbonylation yield was amorphous or quasicrystalline carbon 7 Weight part) was added to 100 parts by weight of tetrahydrofuran to prepare a mixed solution. The mixed solution was mixed using a magnetic stirrer and ultrasonic waves were irradiated for 60 minutes at a frequency of 20 kHz and an output of 55 W. Then, 100 parts by weight of distilled water After the tetrahydrofuran was evaporated using a rotary evaporator, spherical natural graphite modified particles were prepared by spin drying at 160 ° C. The spheroidized natural graphite modified particles were heat-treated at 1200 ° C for 1 hour in an argon atmosphere and then cooled to produce spherical natural graphite-modified composite particles having an average particle size (D50) of 17.2 μm.

Example  4

2.5 parts by weight of spherical natural graphite particles having an average particle diameter (D50) of 12.5 占 퐉 (POSCO Chemtech, SNG12) and 0.3 parts by weight of a petroleum pitch (the carbonylation yield was amorphous or quasicrystalline carbon 7 Weight part) was added to 100 parts by weight of tetrahydrofuran to prepare a mixed solution. The mixed solution was mixed using a magnetic stirrer and ultrasonic waves were irradiated for 60 minutes at a frequency of 20 kHz and an output of 55 W. Then, 100 parts by weight of distilled water After the tetrahydrofuran was evaporated by using a rotary evaporator, 0.125 part by weight of lithium acetate was dissolved therein and spray-dried at 160 ° C to prepare spherical natural graphite modified particles. The spheroidized natural graphite modified particles were heat-treated at 1200 ° C for 1 hour in an argon atmosphere and then furnace cooled to prepare spherical natural graphite-modified composite particles having an average particle size (D50) of 17.1 μm.

Example  5

2.5 parts by weight of spherical natural graphite particles having an average particle diameter (D50) of 16 占 퐉 (POSCO Chemtech, SNG16) and 0.3 parts by weight of a petroleum pitch (the yield after carbonization was amorphous or quasicrystalline carbon 7 Weight part) was added to 100 parts by weight of tetrahydrofuran to prepare a mixed solution. The mixed solution was mixed using a magnetic stirrer and ultrasonic waves were irradiated for 60 minutes at a frequency of 20 kHz and an output of 55 W. Then, 100 parts by weight of distilled water After the tetrahydrofuran was evaporated using a rotary evaporator, spherical natural graphite modified particles were prepared by spin drying at 160 ° C. The spheroidized natural graphite modified particles were heat-treated at 1200 ° C for 1 hour in an argon atmosphere, and then subjected to furnace cooling to prepare spherical natural graphite-modified composite particles having an average particle size (D50) of 19.5 μm.

Comparative Example  One

Spherical natural graphite particles (POSCO Chemtech, SNG12) having an average particle diameter (D50) of 12.5 占 퐉 were used as an anode active material.

Comparative Example  2

2.5 parts by weight of spherical natural graphite particles having an average particle diameter (D50) of 12.5 占 퐉 (POSCO Chemtech, SNG12) and 0.3 parts by weight of a petroleum pitch (the carbonylation yield was amorphous or quasicrystalline carbon 7 Weight part) was added to 100 parts by weight of tetrahydrofuran to prepare a mixed solution. The mixed solution was stirred for 1 hour using a magnetic stirrer, 100 parts by weight of distilled water was added, and tetrahydrofuran was evaporated using a rotary evaporator Followed by spray drying at 160 DEG C to prepare spherical natural graphite modified particles. The spheroidized natural graphite modified particles were heat-treated at 1200 ° C for 1 hour in an argon atmosphere, and then subjected to furnace cooling to prepare spherical natural graphite-modified composite particles having an average particle size (D50) of 16 μm.

Comparative Example  3

2.5 parts by weight of spherical natural graphite particles (POSCO Chemtech, SNG12) having an average particle diameter (D50) of 16 占 퐉 and 0.3 parts by weight of a petroleum pitch (the yield after carbonization was amorphous or quasi-crystalline carbon 7 Weight part) was added to 100 parts by weight of tetrahydrofuran to prepare a mixed solution. The mixed solution was stirred for 1 hour using a magnetic stirrer, 100 parts by weight of distilled water was added, and tetrahydrofuran was evaporated using a rotary evaporator Followed by spray drying at 160 DEG C to prepare spherical natural graphite modified particles. The spheroidized natural graphite modified particles were heat-treated at 1200 ° C for 1 hour in an argon atmosphere and then subjected to furnace cooling to prepare spherical natural graphite-modified composite particles having an average particle size (D50) of 17 μm.

Evaluation 1: Scanning electron microscope of negative electrode active material SEM ) Photo analysis

FIGS. 2 and 3 are SEM photographs of cross sections of the negative electrode active material according to Example 1 and Comparative Example 1, respectively. FIGS. 4 to 11 are cross-sectional views of the negative active material according to Examples 1 to 5 and Comparative Examples 1 to 3, It is a scanning electron microscope (SEM) photograph.

Referring to FIGS. 2 and 4 to 8, it can be seen that the negative electrode active material prepared in Examples 1 to 5 has a gap formed between the natural graphite slices on the surface of the spherical natural graphite particles.

Referring to FIGS. 2 and 3 showing the cross section, it can be seen that the negative electrode active material prepared in Example 1 has a gap formed between the natural graphite slices on the inside as well as the surface portion of the spherical natural graphite particles. The spheroidized natural graphite particles of Comparative Example 1 may have some gaps in the interior of the fabric, but the gaps in the surface portion are almost non-existent, and gaps that are partially present in the interior portions are also formed as in the structure of Example 1 through ultrasonic treatment It can be confirmed that this is not a gap.

Evaluation 2: Transmission electron microscope of the anode active material TEM ) Photo analysis

Transmission electron microscope (TEM) photographs of the cross section of the negative electrode active material prepared in Example 5 are shown in Figs. 12 to 14. Fig.

12 is a transmission electron microscope (SEM) image of the cross-section of the negative electrode active material prepared in Example 5, and FIGS. 13 and 14 are transmission electron micrographs of high magnification of the portions shown in FIGS. 12A and 12B, respectively.

Referring to FIGS. 12 to 14, it is confirmed that amorphous or semi-crystalline carbon exists in the gap between the natural graphite slices on the surface and inside of the spherical natural graphite particles formed by the ultrasonic treatment.

Evaluation 3: Analysis of particle size distribution of anode active material

The average particle size (D50) of the negative electrode active material is shown in Table 1, by measuring the particle size distribution of the negative electrode active material prepared in Examples 1 to 5 and Comparative Examples 1 to 3 by a laser diffraction scattering particle size distribution measurement method.

Example Comparative Example One 2 3 4 5 One 2 3 Average particle diameter
(D50) (占 퐉) 16.3 16 17.2 17.1 19.5 12.5 15 17

Referring to Table 1, it can be seen that the average particle size (D50) of the negative electrode active material is increased in Examples 1 to 4 in which the ultrasonic treatment was performed, as compared with the case of Comparative Example 2 in which the ultrasonic treatment was not performed. In addition, it can be seen that the average particle size (D50) of the negative electrode active material is increased in the case of Example 5 in which the ultrasonic treatment is performed, as compared with the case of Comparative Example 3 in which the ultrasonic treatment is not performed. This is due to the formation of gaps between the natural graphite slices on the surface and inside of the spherical natural graphite particles through ultrasonic treatment.

Evaluation 4: Specific surface area  analysis

The specific surface area (BET surface area) of the negative electrode active material prepared in Examples 1 to 5 and Comparative Examples 1 to 3 was measured by gas adsorption / desorption, and the results are shown in Table 2 below.

Example Comparative Example One 2 3 4 5 One 2 3 Negative active material
Specific surface area (m ² / g) 9.5 7 7.5 7.2 6.2 6.7 2.8 2.7

It can be seen from Table 2 that the specific surface area of the negative electrode active material is increased as compared with the case of Comparative Example 2 in which the ultrasonic treatment is applied to the carbon coated electrodes of Examples 1 to 4 without ultrasonic treatment. In addition, the specific surface area of the negative electrode active material is increased in the case of Example 5 in which the ultrasonic treatment is performed, as compared with the case of Comparative Example 3 in which carbon coating is performed without ultrasonic treatment. This is due to the formation of gaps between the natural graphite slices on the surface and inside of the spherical natural graphite particles through ultrasonic treatment.

Evaluation 5: Measurement of the pressing strength of the negative electrode active material

The densities of the pellets produced by increasing the load and pressing the negative active material prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were calculated and the results are shown in FIG.

15 is a graph showing load contrast density values of the negative electrode active material according to Examples 1 to 3 and Comparative Examples 1 and 2. FIG.

Referring to FIG. 15, in Examples 1 to 3, although spherical natural graphite particles were opened by ultrasonic treatment to open gap between natural graphite slices, compared to Comparative Example 1, Is not increased. It can be seen that the pressing strengths of Examples 1 to 3 are similar to those of Comparative Example 2.

Thus, during the ultrasonic treatment, an amorphous or quasi-crystalline carbon precursor is impregnated into the gaps between the scintillating natural graphite pieces, the surface of the spheroidized natural graphite is coated with an amorphous or quasi-crystalline carbon precursor, As the amorphous or quasi-crystalline carbon is coated on the surface of the spheroidized natural graphite particles and is present in the gap formed in the surface portion and the inside of the spheroidized natural graphite particle, the pressing phenomenon of the spheroidized natural graphite particles is suppressed It can be seen that the gaps opened through the ultrasonic treatment process can be maintained.

Evaluation 6: X-ray of anode active material diffraction  Pattern analysis

Crystallinity of the negative active material prepared in Examples 3 and 4 and Comparative Example 2 was measured using an X-ray diffraction pattern analyzer, and the results are shown in FIGS.

FIG. 16 is a graph showing the X-ray diffraction pattern (XRD) of the negative electrode active material according to Examples 3 and 4 and Comparative Example 2. FIG. 17 is a graph showing the XRD pattern (XRD) Fig.

Referring to FIGS. 16 and 17, it can be seen that the peak of the graphite structure of the non-graphite type disappears in the case of Example 4 including lithium acetate. This indicates that the reaction of lithium acetate and spherical natural graphite particles with scintillating natural graphite particles , Which effectively removes defects of the graphite-type graphite present in the scintillating natural graphite particles.

Ray diffraction patterns of the negative electrode active materials prepared in Examples 3 and 4 and Comparative Example 2, that is, La and Lc values were calculated from the results of FIG. 16, and are shown in Table 3 below.

La is the crystallite size in the direction parallel to the base plane (a-axis direction), Lc is the crystallite size in the direction perpendicular to the base plane (c-axis direction) to be.

Example Example 3 4 5 2 3 La (nm) 20.0 20.2 22.8 20.1 22.9 Lc (nm) 25.3 25.5 27.9 25.4 27.8

It can be seen from the above Table 3 that the La and Lc values of Examples 3 and 4 prepared by ultrasonic treatment are not substantially different from those of Comparative Example 2 which is carbon coated without ultrasonic treatment. Also, it can be seen that the La and Lc values of Example 5 prepared by ultrasonic treatment are not significantly different from those of Comparative Example 3, which is carbon coated without ultrasonic treatment. From this, it can be seen that even when subjected to ultrasonic treatment, the crystallinity of spherical natural graphite particles is not affected.

(Preparation of Test Cell)

4 wt% of a binder obtained by mixing 96 wt% of each of the negative electrode active materials prepared in Examples 1 to 5 and Comparative Examples 1 to 3 with CMC / SBR (carboxymethylcellulose / styrene-butadiene rubber) in a weight ratio of 1: To prepare an anode slurry. The negative electrode slurry was coated on a copper foil, followed by drying and pressing to prepare respective negative electrodes.

Using the respective cathodes and lithium metal as positive electrodes, a separator made of a porous polypropylene film was laminated between the negative electrode and the positive electrode to produce an electrode assembly. Thereafter, an electrolytic solution in which 1 M of LiPF ₆ was dissolved in a mixed solvent of diethyl carbonate (DEC) and ethylene carbonate (EC) (DEC: EC = 1: 1) was added to prepare a test cell.

Evaluation 7: Initial of lithium secondary battery Charging and discharging  Character analysis

The initial charge-discharge characteristics according to Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated by the following method using the test cell prepared above, and the results are shown in Table 4 below.

For the cells prepared according to Examples 1 to 5 and Comparative Examples 1 to 3, charging was carried out in a CC / CV mode with a current density of 70 mA / g, the end voltage was maintained at 0.01 V, the current was 7 mA / (10% current density). The discharge was performed in CC mode with a current density of 70 mA / g and the termination voltage was maintained at 1.5V.

In the following Table 4, the initial charge / discharge efficiency (%) is obtained as a percentage of the initial discharge capacity with respect to the initial charge capacity.

In the case of Examples 1 to 5 using the negative electrode active material prepared by ultrasonic treatment as shown in the following Table 4, it was found through ultrasonic treatment that the gap between the scratched natural graphite slices on the surface portion and inside of the spherical natural graphite particles, It is understood that the initial efficiency is similar to or slightly superior to that of Comparative Example 2 coated with amorphous carbon without ultrasonic treatment.

In Example 4 in which a spherical natural graphite-modified composite particle containing lithium acetate was produced, Examples 1 to 3, which did not contain lithium acetate, and Examples 1 to 3 in which lithium acetate was not included, It can be confirmed that the initial charging and discharging efficiency is improved as compared with the case of the comparative example 2. This is due to the fact that the irreversible capacity between the initial charge and discharge reactions is reduced by effectively removing defects of the graphite structure of the naturally occurring graphite existing on the scaly natural graphite due to the reaction of the lithium acetate with the scaly natural graphite.

Evaluation 8: Analysis of high rate charging characteristics of lithium secondary battery

High-rate charging characteristics according to Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated by the following method using the prepared test cell, and the results are shown in Table 4 below.

For the cells prepared according to Examples 1 to 5 and Comparative Examples 1 to 3, the charging was performed in the CC mode at a current density of 0.2 to 2 C-rate, the end voltage was maintained at 0.01 V, the discharge was 0.2 At the current density of C-rate, it was done in CC mode, and the termination voltage was maintained at 1.5V.

As shown in Table 4, in Examples 1 to 5 using the negative electrode active material prepared by ultrasonic treatment, as compared with Comparative Examples 2 and 3 using the negative electrode active material coated with amorphous carbon without ultrasonic treatment, It can be confirmed that the charging characteristics are excellent. This is because through the above ultrasonic treatment, amorphous or quasi-crystalline carbon exists in the gap between the natural graphite slices on the surface and in the inside of the spherical natural graphite particles and the compression phenomenon of the spherical natural graphite particles And the reactivity with the electrolytic solution is improved.

Evaluation 9: High-rate discharge characteristic analysis of lithium secondary battery

The high-rate discharge characteristics according to Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated by the following method using the test cell prepared above, and the results are shown in Table 4 below.

For the cells prepared according to Examples 1 to 5 and Comparative Examples 1 to 3, the charging was performed in CC / CV mode at a current density of 0.2 C-rate, the termination voltage was maintained at 0.01 V, the current was 0.02 The charge was terminated at the C-rate. Discharge was performed in CC mode at a 0.2 to 10 C-rate range and the termination voltage was maintained at 1.5V.

As shown in Table 4, in Examples 1 to 5 using the negative electrode active material prepared by ultrasonic treatment, as compared with Comparative Examples 2 and 3 using the negative electrode active material coated with amorphous carbon without ultrasonic treatment, It can be confirmed that the discharge characteristics are excellent. This is because through the above ultrasonic treatment, amorphous or quasi-crystalline carbon exists in the gap between the natural graphite slices on the surface and in the inside of the spherical natural graphite particles and the compression phenomenon of the spherical natural graphite particles And the reactivity with the electrolytic solution is improved.

Evaluation 10: Analysis of cycle life characteristics of lithium secondary battery

The cycle life according to Examples 1 to 5 and Comparative Examples 1 to 3 was evaluated using the prepared test cell, and the results are shown in Table 4.

Charging was performed in CC mode with a current density of 0.5 C-rate and the termination voltage was maintained at 0.01V. The discharge was performed in the CC mode at a current density of 0.5 C-rate, and the end voltage was maintained at 1.5 V, and a total of 100 cycles were performed.

In the following Table 4, the capacity retention rate (%) is obtained as a percentage of the discharge capacity after 100 cycles to the discharge capacity of the initial cycle.

As shown in Table 4, in Examples 1 to 5 using the negative electrode active material prepared by ultrasonic treatment, as compared with Comparative Examples 2 and 3 using the negative electrode active material coated with amorphous carbon without ultrasonic treatment, It can be confirmed that the life characteristic is excellent. This is because through the above ultrasonic treatment, amorphous or quasi-crystalline carbon exists in the gap between the natural graphite slices on the surface and in the inside of the spherical natural graphite particles and the compression phenomenon of the spherical natural graphite particles And the reactivity with the electrolytic solution is improved. In addition, amorphous or quasi-crystalline carbon is present on the surface of the spherical natural graphite particles and on the surface portion of the spheroidized natural graphite particles and in the gaps between the spherical natural graphite particles, And deterioration of the structural stability of the spheroidized natural graphite particles, which can be caused by repeated expansion and contraction of the graphite during the repeating of the desorption, can be suppressed.

Early
Charging and discharging
efficiency(%) High rate charging characteristic High rate discharge characteristic Volume
Retention rate
(%) Charging capacity (mAh / g) Discharge capacity (mAh / g) 0.2C 1C 2C 0.2C 1C 2C 5C 10C Example 1 92.7 344 247 147 359 359 357 354 282 92 Example 2 93 337 234 130 355 355 355 352 312 91 Example 3 93.3 331 232 130 356 356 355 354 310 94 Example 4 94 332 230 115 355 355 354 352 302 95 Example 5 92.7 328 229 128 359 359 358 354 298 96 Comparative Example 1 90 338 162 51 359 359 355 304 179 60 Comparative Example 2 93 332 220 79 353 351 350 343 248 70 Comparative Example 3 92.5 325 219 96 360 359 358 332 229 80

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

100: spherical natural graphite-modified composite particles
10: Scattered graphite pieces
20: Clear gap
30: amorphous or quasi-crystalline carbon

Claims (16)

Spherical natural graphite particles assembled into a cabbage phase on the surface portion and a random phase in the central portion, And
Amorphous or quasicrystalline carbon
Modified natural graphite-modified composite particles,
Wherein the spherical natural graphite particles have a gap formed between the natural graphite slices by ultrasonic treatment on the surface portion thereof,
Wherein the amorphous or quasi-crystalline carbon is coated on the surface of the spheroidized natural graphite particles and the amorphous or quasi-crystalline carbon is present on the surface of the spheroidized natural graphite particles
Negative electrode active material for lithium secondary battery. The method according to claim 1,
Wherein the spherical natural graphite particles have an average particle diameter (D50) of 5 to 40 占 퐉. The method according to claim 1,
Wherein the amorphous or semi-crystalline carbon is contained in an amount of 1 to 20 parts by weight based on 100 parts by weight of the spherical natural graphite particles. The method according to claim 1,
Wherein the spherical natural graphite-modified composite particle further comprises a lithium compound including Li ₂ O, Li ₂ CO _3, or a combination thereof,
Wherein the lithium compound is coated on the surface of the spheroidized natural graphite particles and the lithium compound is present in a gap in the surface portion of the spherical natural graphite particles
Negative electrode active material for lithium secondary battery. 5. The method of claim 4,
Wherein the lithium compound is contained in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the spherical natural graphite particles. Preparing a solution comprising scaly graphite natural graphite particles assembled into a cabbage phase on the surface portion and a random phase in the center portion, granulated natural graphite particles, an amorphous or quasi-crystalline carbon precursor, and a solvent;
The solution is subjected to ultrasonic treatment to form a clear gap between the scaly natural graphite slices on the surface of the spherical natural graphite particles while maintaining the crystallinity of the spherical natural graphite particles, Impregnating the amorphous or quasi-crystalline carbon precursor with the amorphous or quasicrystalline carbon precursor on the surface of the particles and the gaps present on the surface of the spherical natural graphite particles;
Drying the ultrasonic treated solution to obtain spherical natural graphite modified particles; And
Wherein the spheroidized natural graphite particles are coated with amorphous or quasi-crystalline carbon and the spherical natural graphite particles are coated with amorphous or quasi-crystalline carbon The step of producing an existing spheroidized natural graphite-modified composite particle
And a negative electrode active material for lithium secondary batteries. Preparing a solution comprising scaly natural graphite particles, agarose natural graphite particles, amorphous or semi-crystalline carbon precursor, lithium acetate and a solvent, which are assembled on the surface portion in the cabbage phase and randomly in the center portion;
The solution is subjected to ultrasonic treatment to form a clear gap between the scaly natural graphite slices on the surface of the spherical natural graphite particles while maintaining the crystallinity of the spherical natural graphite particles, Impregnating the amorphous or quasi-crystalline carbon precursor and the lithium acetate on the surface of the particles with the amorphous or semi-crystalline carbon precursor and the lithium acetate coated on the surface of the spherical natural graphite particles;
Drying the ultrasonic treated solution to obtain spherical natural graphite modified particles; And
Treating the spheroidized natural graphite modified particles with an amorphous or quasi-crystalline carbon and a lithium compound coated on the surface of the spherical natural graphite particles and forming amorphous or semi-crystalline graphite particles on the gap existing on the surface of the spherical natural graphite particles; Crystalline carbon and a lithium compound in the presence of a binder,
Wherein the lithium compound comprises Li ₂ O, Li ₂ CO _3, or a combination thereof
A method for producing a negative electrode active material for lithium secondary batteries. Preparing a solution comprising scaly graphite natural graphite particles assembled into a cabbage phase on the surface portion and a random phase in the center portion, granulated natural graphite particles, an amorphous or quasi-crystalline carbon precursor, and a solvent;
The solution is subjected to ultrasonic treatment to form a clear gap between the scaly natural graphite slices on the surface of the spherical natural graphite particles while maintaining the crystallinity of the spherical natural graphite particles, Impregnating the amorphous or quasi-crystalline carbon precursor with the amorphous or quasicrystalline carbon precursor on the surface of the particles and the gaps present on the surface of the spherical natural graphite particles;
Wherein the graphite particles are coated with the amorphous or quasicrystalline carbon precursor and the lithium acetate on the surface of the spherical natural graphite particles and the graphite particles coated on the surface of the spherical natural graphite particles are coated with lithium acetate, Obtaining spherical natural graphite modified particles impregnated with the amorphous or quasi-crystalline carbon precursor and the lithium acetate in the gap formed; And
Treating the spheroidized natural graphite modified particles with an amorphous or quasi-crystalline carbon and a lithium compound coated on the surface of the spherical natural graphite particles and forming amorphous or semi-crystalline graphite particles on the gap existing on the surface of the spherical natural graphite particles; Crystalline carbon and a lithium compound in the presence of a binder,
Wherein the lithium compound comprises Li ₂ O, Li ₂ CO _3, or a combination thereof
A method for producing a negative electrode active material for lithium secondary batteries. 9. The method according to any one of claims 6 to 8,
The solvent may be selected from the group consisting of water, N-methylpyrrolidone, dimethylformamide, toluene, ethylene, dimethylacetamide, acetone, methyl ethyl ketone, hexane, tetrahydrofuran, decane, ethanol, methanol, isopropanol, And a negative electrode active material for lithium secondary batteries. 9. The method according to any one of claims 6 to 8,
The amorphous or quasi-crystalline carbon precursor may be selected from the group consisting of citric acid, stearic acid, sucrose, polyvinylidene fluoride, carboxymethylcellulose (CMC), hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, starch, phenolic resin, furan resin, per furyl alcohol, polyacrylic acid, polyacrylic sodium, polyacrylonitrile, polyimide, epoxy resin, A process for producing a negative electrode active material for a lithium secondary battery, comprising the steps of: preparing a negative electrode active material for lithium secondary battery, the negative electrode active material comprising styrene, polyvinyl alcohol, polyvinyl chloride, coal pitch, petroleum pitch, mesophase pitch, low molecular weight heavy oil, glucose, gelatin, saccharides, 9. The method according to any one of claims 6 to 8,
The ultrasonic treatment is performed by irradiating ultrasonic waves at an oscillation frequency of 10 to 35 kHz and an output of 10 to 100 W for 1 minute to 24 hours
A method for producing a negative electrode active material for lithium secondary batteries. 9. The method according to any one of claims 6 to 8,
The drying may be carried out by spray drying, rotary spraying, nozzle spraying, ultrasonic spraying or a combination thereof; A drying method using a rotary evaporator; Vacuum drying method; Natural drying method; Or a combination thereof. ≪ / RTI > 9. The method according to any one of claims 6 to 8,
Wherein the heat treatment is performed at a temperature of 500 to 2500 ° C. 9. The method according to any one of claims 6 to 8,
Wherein the amorphous or semi-crystalline carbon precursor is contained in an amount of 2 to 80 parts by weight based on 100 parts by weight of the spherical natural graphite particles. 9. The method according to claim 7 or 8,
Wherein the lithium acetate is contained in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the spherical natural graphite particles. An anode comprising the anode active material of any one of claims 1 to 5;
anode; And
Electrolyte
≪ / RTI >

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