JP2006164570A - Method of manufacturing graphite material for lithium secondary battery anode, and lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing graphite material for a lithium secondary battery anode and a lithium secondary battery capable of easily achieving industrial manufacturing of graphite material for the lithium secondary battery anode having excellent anode characteristics. <P>SOLUTION: The method of manufacturing the graphite material for the lithium secondary battery anode comprises a graphitization treatment process for obtaining a graphite material by putting a carbon material with a boron compound added under a graphitization treatment, and a heat treatment process of heat-treating the graphite material under an oxidizing gas atmosphere at 400 to 700°C. More preferably, a mechanical surface treatment is to be preliminarily applied to the graphitized material in the heat treatment process. The lithium secondary battery of a nonaqueous system uses the obtained graphitizing material as an anode, and is provided with a cathode, and electrolyte solution with electrolyte dissolved in a nonaqueous solvent. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a graphite material for a lithium secondary battery negative electrode and a lithium secondary battery.

A carbon material is generally used as a negative electrode material for a lithium secondary battery in terms of safety and life. Natural graphite, carbon fiber, or mesophase spherules are known to exhibit high performance as a negative electrode material for a lithium secondary battery by themselves or simply by heat treatment at a high temperature (for example, Patent Document 1 and Non-Patent Document 1). 2). However, natural graphite has poor load characteristics due to excessive crystal orientation, and carbon fibers and mesophase spherules have complicated manufacturing processes, resulting in high manufacturing costs.
For this reason, the graphite material which moderately graphitized the coke obtained by calcining the pitch derived from petroleum or coal is used suitably for the negative electrode material of a lithium secondary battery.

  Further, various techniques for adding boron to the graphite material have been studied for the purpose of improving the negative electrode characteristics by graphitizing the graphite material obtained by graphitizing the above coke (for example, Patent Documents 2 and 3). reference.).

  All of the above boron addition techniques have been verified in an experimental furnace, but when these techniques are applied to an industrial furnace such as an Atchison furnace, the overvoltage increases and the discharge capacity decreases. Moreover, a new proposal for improving this has been made together with a report of the knowledge that the initial efficiency is lowered because a side reaction occurs during the first charge (see Patent Document 4).

According to the above findings, in order to realize graphitization in an industrial furnace by operating for a long time in the atmosphere, the inside of the furnace becomes a carbon monoxide and nitrogen atmosphere in the graphitization temperature region, and the surface of the material and the inner wall surface of the fine crack Inevitably, a large amount of insulative boron nitride is produced, which causes (1) an increase in contact resistance between graphite powders when used as a negative electrode and (2) a side reaction. It is said that.
The above proposal based on this finding is a material obtained by graphitizing carbon powder using pitch as a raw material, and the specific crystal structure and boron atom concentration are set to 0. 0 relative to the total atom concentration of boron, carbon and nitrogen. A negative electrode having a specific resistance within a specific range of less than 15 is used for the negative electrode, thereby reducing contact resistance and side reactions between graphite powders mainly by not increasing the boron atom concentration. It can be done.

  In addition, in connection with the above proposal, the purpose is to remove boron nitride covering the surface of the graphite material and the inner wall surface of the fine crack without causing structural change and oxidation consumption of the graphite material itself. There has been proposed a method of decomposing boron nitride by heat-treating the graphite powder after the crystallization treatment at 900 to 1500 ° C. for 1 hour or more in a gas atmosphere containing carbon dioxide (see Patent Document 5). In this proposal, the use of an oxidizing gas instead of carbon dioxide is undesirable because the graphite powder itself is more oxidatively consumed than the decomposition of boron nitride and the yield is significantly reduced.

As another related technique, based on the premise of manufacturing conditions in which boron nitride is not substantially formed, boron is efficiently converted into graphite with the recognition that boron carbide in the graphite material impedes negative electrode characteristics. For the purpose of removing from the material, the graphite material after the graphitization treatment is oxidized and heat treated to change boron carbide to boron oxide, and then the graphite material is washed to remove boron oxide, in other words, boron compound is removed from the graphite material. A technique for completely removing the image has been proposed (see Patent Document 6).
Boron with the recognition that the negative electrode characteristics can be improved by obtaining a closed structure in which the ends of the c-plane layer of graphite material are connected and closed, for example, because it is difficult for the electrolyte to enter between the layers. The surface of boron-containing graphite powder heat-treated at a high temperature that causes solid solution of the material is surface-treated by heat treatment or the like, the surface of the c-plane layer is scraped off, and the closed structure closed by graphitization is once opened to flatten the end of the c-plane layer. Then, a technique for obtaining a closed structure at the end of the c-plane layer again by heat treatment in an inert gas at a temperature of 800 ° C. or higher has been proposed (see Patent Document 7).
These technologies are different from the above-mentioned two proposals in technical idea and also in the technical configuration.
Japanese Patent Application Laid-Open No. 64-2258 Japanese Patent Laid-Open No. 5-290843 JP-A-8-31422 Japanese Patent Laid-Open No. 11-31507 Japanese Patent Laid-Open No. 2000-12032 JP 2003-77472 A Japanese Patent Laid-Open No. 2001-106518 “Carbon”, Vol. 13, 337 (1975) "J. Electrochem. Soc." 142, 2564 (1995)

  Based on the same recognition as the above-mentioned two proposals, the inventors have increased contact resistance between graphite powders due to the presence of boron nitride and that side reactions during the initial charge have deteriorated the negative electrode characteristics. As a result of examining these two proposals in more detail, the former (Patent Document 4) does not necessarily have a sufficient effect in improving the charge / discharge efficiency, and further improvement is necessary. On the other hand, the latter (Patent Document 5) suffers from problems such as heat treatment at a high temperature in a non-oxidizing atmosphere, although it is easy in the laboratory and not necessarily suitable as an industrially implemented technique. I came up with something.

  The present invention has been made in view of the above problems, and graphite for lithium secondary battery negative electrodes capable of industrially easily producing a graphite material for lithium secondary battery negative electrodes having good negative electrode characteristics. An object of the present invention is to provide a material manufacturing method and a lithium secondary battery.

In order to achieve the above object, a method for producing a graphite material for a lithium secondary battery negative electrode according to the present invention comprises:
A graphitization treatment step of obtaining a graphitized material by graphitizing a carbon material added with a boron compound;
A heat treatment step of heat-treating the graphitized material at a temperature of 400 to 800 ° C. in an oxidizing gas atmosphere;
It is characterized by having.

  The method for producing a graphite material for a negative electrode of a lithium secondary battery according to the present invention is characterized in that the graphitized material is subjected to a mechanical surface treatment in advance in the heat treatment step.

  The lithium secondary battery according to the present invention is a non-aqueous lithium secondary battery comprising a positive electrode, a negative electrode, and an electrolyte solution in which an electrolyte is dissolved in a non-aqueous solvent. A graphite material obtained by a material manufacturing method is used for a negative electrode.

  The method for producing a graphite material for a negative electrode of a lithium secondary battery and a lithium secondary battery according to the present invention are excellent because a graphitized material obtained by adding a boron compound is heat-treated at a temperature of 400 to 800 ° C. in an oxidizing gas atmosphere. A negative electrode having excellent negative electrode characteristics and a lithium secondary battery using the negative electrode can be easily industrially realized.

  Embodiments of the present invention will be described below.

  The method for producing a graphite material for a negative electrode of a lithium secondary battery according to the present invention includes a graphitization treatment step of graphitizing a carbon material added with a boron compound to obtain a graphitized material, and the resulting graphitized material as an oxidizing gas. A heat treatment step of performing heat treatment at a temperature of 400 to 800 ° C. in an atmosphere.

The raw material carbon material (carbon powder) used in the present invention is not particularly limited, but is a material that can easily form an optimal graphite structure (lamination arrangement regularity of the graphite layer) as a carbon powder for a lithium secondary battery negative electrode. For example, carbon fibers using pitch as a raw material, pitch coke and mesophase spherules can be mentioned.
When pitch is used as a raw material, it is essentially important that graphite crystallinity is easily developed by firing, that is, so-called graphitization (easily graphitizable). For example, petroleum pitch, asphalt pitch, coal Examples thereof include tar pitch, naphthalene pitch, crude oil decomposition pitch, petroleum sludge pitch, pitch obtained by thermal decomposition of a polymer, and the like, and these pitches may be subjected to hydrogenation treatment or the like.

  As the boron compound used in the present invention, metal boron (boron alone), boron nitride, boron oxide, boron carbide, boric acid or the like can be used as appropriate, and these compounds are used alone or in combination of two or more. Can be used.

  The method of mixing the raw material carbon material and the boron compound is not particularly limited as long as both are uniformly dispersed. For example, a mixing method using a blender or a kneader can be employed. .

  The boron compound is added in an amount of 0.01% by weight <B <10% by weight, preferably 0.01% by weight <B <5% by weight, more preferably 0.8% as boron with respect to the graphitized carbon material. It is 01 mass% <B <3 mass%. If the amount of boron added is too large, it is not preferable because it is expensive and not industrially suitable, and further, sintering of the carbon particles occurs and pulverization or the like is required in the subsequent process.

  The graphitization treatment can be performed using an appropriate industrial furnace. In the present invention, even if boron nitride is produced by graphitizing in the atmosphere, it can be handled by subsequent heat treatment. That is, not only an atmosphere control furnace but also an Atchison furnace or LWG furnace capable of mass heat treatment can be used. After raising the temperature of the carbon material to 2500 ° C. or higher, preferably 2800 ° C. or higher in these industrial furnaces, the graphitized material obtained has a sufficiently high degree of graphitization by cooling and lowering the temperature to near room temperature. The holding time at the maximum temperature is not particularly limited but is preferably 1 hour or longer.

The graphitized material (graphitized carbon powder) thus obtained has a very high graphitization because the ₀₀₂ plane spacing d ₀₀₂ obtained by X-ray diffraction is 0.3359 nm or less due to the catalytic effect of the added boron. Have a degree. However, boron nitride is formed and coated on the material surface and the inner wall of the crack, and when used in a battery as it is, the irreversible capacity becomes large.

In the present invention, the graphitized material obtained by the graphitization treatment is used in an oxidizing gas atmosphere, preferably in the air or in an oxygen atmosphere at a temperature in the range of 400 to 800 ° C. for 10 minutes or more, preferably 30 minutes. More preferably, the heat treatment is performed for 1 hour or longer. When the temperature is lower than 400 ° C., the effects of the present invention described below cannot be sufficiently obtained, and when the temperature exceeds 800 ° C., the oxidation consumption of the graphitized material becomes significant and the product yield is significantly reduced. It is.
If the oxygen concentration is too high, it is not preferable because it leads to a decrease in the product yield described above, and if it is less than 10%, the effect of the present invention described below cannot be obtained sufficiently, or is not desirable from the viewpoint of productivity. . The oxygen concentration is preferably about 20%.
The heating furnace used for the heat treatment is not particularly limited, and can be appropriately selected from a Tamman furnace, a muffle furnace, a calsiner kiln, and the like that are usually used industrially. The heating furnace may be a batch type or a continuous type.

  The heat treatment is an oxidation treatment in a region where boron nitride is thermodynamically stable. Therefore, unlike the conventional mechanism for decomposing and removing boron nitride, the negative electrode characteristics are improved by a mechanism in which the surface structure of the graphitized material is changed to a suitable one as the negative electrode of the battery by performing heat treatment. Can be considered.

In this case, more preferably, the mechanical surface treatment is performed prior to the heat treatment, that is, before the graphitized material is oxidized.
Thereby, the effect of heat treatment is improved by performing oxidation and heat treatment in a state where a new cross section of the graphitized material is previously exposed. Therefore, the mechanical surface treatment is performed lightly as long as this effect can be exhibited.

  An industrially used pulverizer can be used for the mechanical surface treatment. Specific examples include an atomizer, a Raymond mill, an impeller mill, a ball mill, a cutter mill, a jet mill, and a hybridizer, but are not particularly limited thereto.

  Next, the lithium secondary battery of the present invention using the graphite material (graphitized material) obtained by the above-described method for producing a graphite material for a lithium secondary battery negative electrode of the present invention as a negative electrode will be described.

  As a method of forming a negative electrode using the negative electrode material for a lithium secondary battery of the present invention as an active material, the performance of the graphite material for a negative electrode of the lithium secondary battery of the present invention is sufficiently drawn, and the shapeability is high, As long as it is stable chemically and electrochemically, it is not particularly limited. For example, a fluorine-based resin powder such as polyvinylidene fluoride (PVdF) or a water-soluble binder such as styrene butadiene rubber (SBR) or carboxymethylcellulose (CMC) is added to the material for the negative electrode of the lithium secondary battery of the present invention as a carbonaceous binder. Then, a slurry can be prepared by mixing using a solvent such as N-methylpyrrolidone (NPM), dimethylformamide, water, alcohol or the like, and can be formed by applying and drying on a current collector.

The negative electrode active material of the present invention can be used in appropriate combination with a positive electrode active material and a non-aqueous electrolyte (for example, an organic solvent-based electrolyte), but these non-aqueous electrolyte and positive electrode active material are used in lithium secondary batteries. There are no particular restrictions on this as long as it can be used normally.
In addition, the lithium secondary battery negative electrode material of the present invention may be used for all of the negative electrode, or may be used for a part of the negative electrode and the remainder may be another negative electrode material.

As the positive electrode active material, for example, a lithium-containing transition metal oxide (LiM (1) xO ₂ where x is a numerical value in the range of 0 ≦ x ≦ 1, where M (1) represents a transition metal, Co , Ni, Mn, Ti, Cr, V, Fe, Zn, Al, Sn, In, or LiM (1) yM (2) z-yO in the formula ₄ , y is 0 ≦ y ≦ 1 Where M (1) and M (2) represent transition metals, and are at least one of Co, Ni, Mn, Ti, Cr, V, Fe, Zn, Al, Sn, and In Transition metal chalcogenides such as Ti, S ₂ and NbSe, vanadium oxides and lithium compounds such as V ₂ O ₅ , V ₆ O ₁₃ , V ₂ O ₄ and V ₃ O ₆ , general formula MxMo ₆ Ch _6-y (wherein x is a numerical value in the range of 0 ≦ x ≦ 4, y is 0 ≦ y ≦ 1, M represents a metal including a transition metal, Ch represents a chalcogen metal), activated carbon, activated carbon fiber, or the like.

  The organic solvent in the non-aqueous electrolyte (for example, organic solvent-based electrolyte) is not particularly limited, and examples thereof include propylene carbonate, ethylene carbonate, butyl carbonate, chloroethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. 1,1-dimethoxyethane, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, Anisole, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, chloronitrile, propionitrile, trimethyl borate, tetramethyl silicate, nitromethane, dimethylformamide, N-methylpyrrolidone, ethyl acetate, trimethyl Rutohorumeto, nitrobenzene, benzoyl chloride, benzoyl bromide, tetrahydrothiophene, dimethyl sulfoxide, 3-methyl-2-oxazolidone, ethylene glycol, sulfite, a single solvent or a mixture of two or more solvents such as dimethyl sulfite may be used.

As the electrolyte, any known ones conventionally can be used, for example _{LiClO 4, LiBF 4, LiPF 6} , LiAsF 6, LiB (C 6 H 5), LiCl, LiBr, LiCF 3 SO 3, Li ( CF ₃ SO ₂ ) ₂ N, Li (CF ₃ SO ₂ ) ₃ C, Li) CF ₃ CH ₂ OSO ₂ ) ₂ N, Li (CF ₃ CF ₂ CH ₂ OSO ₂ ) ₂ N, Li (HCF ₂ CF ₂ One or a mixture of two or more of CH ₂ OSO ₂ ) ₂ N, Li ((CF ₃ ) ₂ CHOSO ₂ ) ₂ N, LiB [C ₆ H ₃ (CF ₃ ) ₂ ] ₄ can be exemplified.

  A lithium secondary battery using the graphite material for a negative electrode of the lithium secondary battery of the present invention as a negative electrode has a large discharge capacity, a small loss during charge and discharge, and excellent press characteristics described later. In addition, the negative electrode material can be produced industrially at low cost.

Examples of the present invention and comparative examples will be described below. These examples and comparative examples are provided to better explain the present invention and do not limit the contents of the present invention.
First, a method for measuring various physical property values in each example will be described below.
The specific surface area was measured by the BET method using nitrogen gas adsorption.
The tap density was measured at a tap density of 20 times and 300 times using a 100 cm ³ resin graduated cylinder with a tap density measuring device manufactured by Seishin Corporation. The measuring method was based on JIS-K1501.
The particle diameter is obtained from the particle size distribution measured by the laser diffraction method. The maximum particle diameter at 10% of the fine powder side with respect to the volume is 10% cumulative particle diameter, the maximum particle diameter at 50% is the average particle diameter, and 90%. Was determined as 90% cumulative particle size.
For the yield of the graphite material, the remaining amount of the graphitized material after heat treatment (oxidation treatment) with respect to the mass of the graphitized material subjected to the graphitization treatment was expressed in%.
Electrode preparation and battery performance evaluation were based on the following methods.
Add 3% by mass of a styrene butadiene rubber / carboxymethyl cellulose mixture as a binder to the carbon powder to be used for the test, knead it with distilled water as a solvent to create a slurry, and apply it uniformly to a copper foil with a thickness of 18 mμ. Thus, a negative electrode foil was obtained. This negative electrode foil was dried and pressed to a predetermined electrode density to prepare an electrode sheet, and a negative electrode was prepared by cutting out from this sheet into a circle having a diameter of 15 mmΦ. In order to evaluate the electrode characteristics of the single electrode of the negative electrode, metallic lithium cut into about 15.5 mmΦ was used for the counter electrode. Using a solution of LiPF ₆ dissolved at a concentration of 1 mol / l in a mixed solvent of ethylene carbonate and diethyl carbonate (volume ratio 1: 1 mixture) as an electrolytic solution, a coin cell was prepared using a porous membrane of propylene as a separator, Charge and discharge test under constant current and constant voltage discharge at constant current of 0.1 mA / cm ^{2 at} a constant temperature of 25 ° C. and a voltage range where the lower limit voltage of terminal voltage is 0 V and the upper limit voltage of discharge is 1.5 V. went.
As for the press characteristics, a 10 mm square was cut out from the negative electrode foil, the thickness and the mass were measured, and then pressed at a predetermined pressure using a uniaxial press. Then, after measuring the thickness again, the active material (carbon powder and binder) was peeled off, and the mass of the copper foil was measured to determine the value of the active material mass, and the density was calculated.

Example 1
Bulk raw coke produced by a delayed coking method using coal-based heavy oil was pulverized by a Raymond mill to obtain an average particle size of 20 μm. This was carbonized at about 800 ° C. using a lead hammer furnace to obtain a carbide. Boron carbide in an amount of 1.5% by mass in terms of boron was added to the carbide, filled in a graphite vessel, and graphitized at about 3000 ° C. in an Atchison furnace. The obtained graphitized material was classified using a sieve having a sieve opening of 75 μm, and particle size adjustment was performed to remove fine powder by air classification. Furthermore, the graphite material was oxidized in the atmosphere at 600 ° C. for 1 hour.
The obtained graphite material has a tap density at 20 taps of 0.86 g / cm ³ , a tap density at 300 taps of 1.14 g / cm ³ , and a BET specific surface area of 1.0 m ² / g.
Met. Further, the 10% cumulative particle size of the graphite material was 14.4 μm, the average particle size was 24.5 μm, and the 90% cumulative particle size was 44.8 μm. Moreover, the yield of the graphite material was 99.5%.
The electrode characteristics of the battery using this material as the negative electrode were an initial charge capacity of 491 mAh / g, an initial discharge capacity of 342 mAh / g, and an initial irreversible capacity of 149 mAh / g.
Moreover, the press characteristic obtained using this material was 1.70 g / cm ³ under a pressure of 1.5 ton / cm ² , which was a value almost equivalent to Comparative Example 1 described later.

(Example 2)
The graphite material was treated in the same manner as in Example 1 except that it was oxidized at 600 ° C. for 5 hours in the atmosphere.
Obtained graphite material is 20 times the tap density of the tap is 0.80 g ^/ cm 3, 300 times the tap density of the tap is 1.10 g ^/ cm 3, BET specific surface area of 1.5 m ² / g
Met. The 10% cumulative particle size of the graphite material was 14.3 μm, the average particle size was 24.3 μm, and the 90% cumulative particle size was 44.2 μm. Moreover, the yield of the graphite material was 99.3%.
The electrode characteristics of the battery using this material as the negative electrode were an initial charge capacity of 381 mAh / g, an initial discharge capacity of 342 mAh / g, and an initial irreversible capacity of 39 mAh / g.
Moreover, the press characteristic obtained using this material was 1.73 g / cm ³ under a pressure of 1.5 ton / cm ² .

(Example 3)
The graphite material was treated in the same manner as in Example 1 except that it was oxidized in the atmosphere at 700 ° C. for 1 hour.
The obtained graphite material has a tap density at 20 taps of 0.77 g / cm ³ , a tap density at 300 taps of 1.07 g / cm ³ , and a BET specific surface area of 1.6 m ² / g.
Met. The 10% cumulative particle size of the graphite material was 13.9 μm, the average particle size was 23.7 μm, and the 90% cumulative particle size was 42.6 μm. Moreover, the yield of the graphite material was 98.1%.
The electrode characteristics of the battery using this material for the negative electrode were initial charge capacity of 360 mAh / g, initial discharge capacity of 346 mAh / g, and initial irreversible capacity of 14 mAh / g.
Moreover, the press characteristic obtained using this material was 1.78 g / cm ³ under a pressure of 1.5 ton / cm ² .

Example 4
The graphite material was treated in the same manner as in Example 1 except that it was oxidized at 700 ° C. for 5 hours in the atmosphere.
Obtained graphite material is 20 times the tap density of the tap is 0.74 g ^/ cm 3, a tap density of at 300 taps is 1.03 g ^/ cm 3, BET specific surface area of 1.9m ² / g
Met. Further, the 10% cumulative particle size of the graphite material was 13.8 μm, the average particle size was 23.9 μm, and the 90% cumulative particle size was 43.7 μm. Moreover, the yield of the graphite material was 94.5%.
The electrode characteristics of the battery using this material for the negative electrode were an initial charge capacity of 356 mAh / g, an initial discharge capacity of 346 mAh / g, and an initial irreversible capacity of 10 mAh / g.
Moreover, the press characteristic obtained using this material was 1.81 g / cm ³ under a pressure of 1.5 ton / cm ² .

(Example 5)
Prior to the oxidation treatment, the same treatment as in Example 4 was performed except that the mechanical surface treatment of the graphite material was performed by an atomizer.
The obtained graphite material had a tap density of 0.69 g / cm ³ at 20 taps, a 0.97 g / cm ³ tap density at 300 taps, and a BET specific surface area of 2.4 m ² / g. . The 10% cumulative particle size of the graphite material was 13.6 μm, the average particle size was 23.6 μm, and the 90% cumulative particle size was 42.9 μm. Moreover, the yield of the graphite material was 89.8%.
The electrode characteristics of the battery using this material for the negative electrode were an initial charge capacity of 358 mAh / g, an initial discharge capacity of 344 mAh / g, and an initial irreversible capacity of 14 mAh / g.
Moreover, the press characteristic obtained using this material was 1.76 g / cm ³ under a pressure of 1.5 ton / cm ² .

(Comparative example)
A graphite material was obtained by the same treatment as in Example 1 except that the oxidation treatment was not performed.
The obtained graphite material had a tap density at 20 taps of 0.88 g / cm ³ , a tap density at 300 taps of 1.16 g / cm ³ , and a BET specific surface area of 0.8 m ² / g. . The 10% cumulative particle size of the graphite material was 14.2 μm, the average particle size was 24.2 μm, and the 90% cumulative particle size was 44.5 μm.
The electrode characteristics of the battery using this material as the negative electrode were an initial charge capacity of 531 mAh / g, an initial discharge capacity of 339 mAh / g, and an initial irreversible capacity of 192 mAh / g.
Moreover, the press characteristic obtained using this material was 1.68 g / cm ³ under a pressure of 1.5 ton / cm ² .

Claims (3)

A graphitization treatment step of obtaining a graphitized material by graphitizing a carbon material added with a boron compound;
A heat treatment step of heat-treating the graphitized material at a temperature of 400 to 800 ° C. in an oxidizing gas atmosphere;
A method for producing a graphite material for a negative electrode of a lithium secondary battery, comprising:   2. The method for producing a graphite material for a negative electrode of a lithium secondary battery according to claim 1, wherein the graphitized material is subjected to mechanical surface treatment in advance in the heat treatment step. In a non-aqueous lithium secondary battery comprising an electrolyte in which an electrolyte is dissolved in a positive electrode, a negative electrode, and a non-aqueous solvent,
3. A lithium secondary battery, wherein a graphite material obtained by the method for producing a graphite material for a negative electrode of a lithium secondary battery according to claim 1 or 2 is used for a negative electrode.