JPH10139410A - Production of carbonaceous material and battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce economically a carbonaceous material having high performance as a material for negative electrodes of lithium-ion secondary battery without use of a solvent of troublesome handling, such as quinoline. SOLUTION: This carbonaceous material, which is used as a material for negative electrodes of lithium-ion secondary batteries, is produced by steps of: heat-treating vacuum pitch until its quinoline-insoluble content becomes 50-85wt.% so as to form mesophase pitch; powdering the obtained mesophase pitch to fine particles having an aspect ratio of 2 or less; oxidizing the powder; and carbonizing and graphitizing the oxidized powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a carbonaceous material, and more particularly, to economically provide a high-performance carbonaceous material as a negative electrode material for a lithium ion secondary battery. .

[0002]

2. Description of the Related Art In recent years, miniaturization and weight reduction of electronic devices and communication devices have been rapidly progressing, and there is a strong demand for miniaturization and weight reduction of secondary batteries used as power sources for driving these devices. A lithium ion secondary battery having a high energy density and a high voltage has been proposed.

A lithium ion secondary battery uses, for example, lithium cobalt oxide for a positive electrode, uses a carbonaceous material such as graphite for a negative electrode, occludes lithium ions in the carbonaceous material at the time of charging, and stores these lithium ions at the time of discharge. The ions are released from the negative electrode. Various materials have been proposed as the positive electrode material. At present, lithium cobalt oxide is most widely used. On the other hand, carbon is mainly used as the negative electrode material. It is divided into crystalline materials and carbonaceous amorphous materials.

[0004]

As one of the above-mentioned graphite materials, spherical mesophase pitch fine particles are used as a negative electrode material. These spherical mesophase pitch fine particles are fine particles which are precipitated in the pitch by heating various pitches to a temperature of 350 ° C. to 500 ° C., and have a structure similar to graphite. When the heat treatment of the pitch is continued as it is, the whole eventually changes to coke.In order to obtain the mesophase pitch fine particles, in the process of producing the spherical mesophase pitch fine particles, a solvent is added to the heat-treated pitch to remove only the fine particles. It is necessary to separate them by centrifugation or another method (Japanese Patent Laid-Open No. 4-115458, etc.).

The separation of the above-mentioned spherical mesophase pitch fine particles is complicated because the separation operation is performed from a high-viscosity molten pitch to which a solvent is added. In addition, the amount of the obtained spherical fine particles per 100 parts by weight of the pitch used is About 10
Only about 30 parts by weight, the yield is very low, and there is a problem of recovery of the used solvent. Therefore, not only the operation is complicated, but also the spherical mesophase pitch fine particles obtained from the low yield have a problem that they are extremely expensive as compared with the raw materials used, and the finally obtained lithium ion This is one cause of an increase in the cost of the secondary battery.

As a method for solving the above problems, a so-called “β-isolate” obtained by treating coal tar pitch with quinoline to separate a quinoline-soluble component and further removing a toluene-insoluble component from the quinoline-soluble component is used. A method has been proposed in which a "resin" is prepared, and a mesophase pitch obtained by hydrogenating and heaviering the resin is used as a raw material to provide a carbonaceous material (Japanese Patent Publication No. 64-33186 and Japanese Patent Application Laid-Open No. No. 223808).

According to the above method, although good spherical carbon powder can be obtained, there is a problem that a large amount of quinoline and toluene having a high boiling point and high toxicity are used in a large amount. Many problems remain, and as a result, there is a problem that the cost of the obtained spherical carbon material is significantly increased. Accordingly, an object of the present invention is to economically provide a high-performance carbonaceous material as a negative electrode material or the like for a lithium ion secondary battery without using any complicated solvent such as quinoline.

[0008]

The above object is achieved by the present invention described below. That is, the present invention provides a reduced pressure pitch,
A step of heat-treating the quinoline insoluble matter to 50 to 85% by weight to form a mesophase pitch, a step of pulverizing the obtained mesophase pitch into fine particles having an aspect ratio of 2 or less, a step of oxidizing the pulverized product, and A method for producing a carbonaceous material, comprising a step of carbonizing and graphitizing an oxidized product, and a lithium ion secondary battery using the carbonaceous material as a negative electrode material.

According to the present invention, the reduced-pressure pitch is heat-treated until its quinoline-insoluble content becomes 50 to 85% by weight to form a mesophase pitch, and the mesophase pitch is pulverized into fine particles without separation. By oxidizing the pulverized material, the pulverized material changes into a shape close to a sphere, and in this state, carbonization and graphitization are performed, whereby lithium ions of the same or greater size than spherical mesophase pitch fine particles separated from the conventional heat treatment pitch are obtained. It has been found that carbonaceous fine particles having an occlusion ability can be obtained. Therefore, according to the present invention, without using any solvent such as quinoline or toluene, a high-performance carbonaceous material as a negative electrode material or the like for a lithium ion secondary battery can be produced in a simple operation at a high yield and economically. Can be provided.

[0010]

Next, the present invention will be described in more detail with reference to preferred embodiments. The production method of the present invention comprises, as shown in the production process diagram of FIG. 1, a step of heat-treating the reduced-pressure pitch until the quinoline-insoluble content becomes 50 to 85% by weight to form a mesophase pitch. A step of pulverizing into fine particles having an aspect ratio of 2 or less,
Oxidizing the pulverized material, and carbonizing the oxidized material.
It is characterized by comprising a step of graphitizing.

The reduced-pressure pitch used as a raw material in the present invention is a fraction remaining after further distillation under reduced pressure of coal tar from which light components have been removed by atmospheric distillation. Preferably, the coal tar is centrifuged to remove solid impurities present in the coal tar, and steam distilled in an atmospheric distillation tower to remove light components present in the coal tar, and the boiling point is 280 ° C. The above fraction is obtained. This fraction is not specified unconditionally by the type of coal tar used,
Preferably, it is obtained by distillation under normal pressure under the condition that 100 parts by weight of the charged coal tar is 75 parts by weight or less, preferably 70 parts by weight or less.

The vacuum distillation is performed by further distilling the above-mentioned atmospheric distillate under reduced pressure to remove residual light components in the atmospheric distillate. The atmospheric distillate is heated in a heating furnace, and is subjected to vacuum distillation in a short time at a heating temperature of 360 ° C. or less, preferably 300 to 360 ° C., and a reduced pressure of 50 Torr or less, preferably 30 Torr or less. Most of the light components are removed by this vacuum distillation, and pitches having various softening points can be obtained depending on the conditions of the vacuum distillation. In the present invention, the softening point of the obtained vacuum pitch is 100 ° C to 120 ° C.
C., preferably a temperature in the range of 105 to 115.degree. Under reduced pressure distillation conditions in which the softening point exceeds the above range, caulking (carbonization) occurs in the heating furnace tube during reduced pressure distillation, which may hinder stable vacuum distillation operation. The reduced pressure pitch thus obtained can have a narrow and constant molecular weight distribution of the contained components,
Stable properties are obtained when the toluene-insoluble content is 25% by weight or less and the quinoline-insoluble content is 4% by weight or less.

In the method of the present invention, omitting vacuum distillation has the following disadvantages. That is, the softening point is 10
The pitch of 0 to 120 ° C. can be obtained by heat-treating a pitch obtained by distillation under normal pressure, but the obtained heat-treated pitch has a wide molecular weight distribution and polycyclic condensation contained in the mesophase phase in the mesophase pitch. The molecular weight distribution of the aromatic compound also becomes non-uniform, and when it is subsequently carbonized and graphitized and used as a negative electrode material of a lithium battery, there are disadvantages such as a reduced amount of lithium occlusion.

In the present invention, the reduced pressure pitch adjusted as described above is heat-treated. The heat treatment is performed at 420 ° C. or lower, preferably 39 ° C. while blowing a non-oxidizing gas such as nitrogen gas.
Heat treatment is performed at 5 to 400 ° C. By blowing the gas, the uniformity of the temperature of the molten pitch is maintained, uneven distribution of pitch components is prevented, and low-boiling substances present in the pitch are also forcibly removed. The flow rate of the inert gas is set to 0.
05 Nm ³ / pitch kg · hr or more, preferably 0.1
In the case of 5 to 0.20 Nm ³ / pitch kg · hr, the heat treatment time is usually about 3 to 7 hours, preferably about 4 to 6 hours.

Further, a discharge pipe is provided in the reactor so that light components generated during the heat treatment can be removed, and the pressure in the reactor is raised to 9 kg / cm ² · G or less, preferably 5 kg / cm ² during the temperature rise process. ^A pressure regulating valve is provided to keep the pressure at 2.G or less, and light components are continuously discharged. The above heat treatment is carried out until the quinoline-insoluble content of the heat-treated product becomes 50 to 85% by weight, preferably 70 to 95% by weight of toluene-insoluble content together with the quinoline-insoluble content, more preferably 55 to 80% by weight of quinoline-insoluble content The process is continued until a mesophase pitch having a toluene insoluble content of 70 to 90% by weight is obtained.

If the quinoline insoluble content is less than 50% by weight, the mesophase pitch fine particles are fused to each other when oxidizing the mesophase pitch fine particles, or the fine particles are hardly graphitized when these fine particles are oxidized. When the quinoline insoluble content exceeds 85% by weight, coking of the reduced pressure pitch proceeds, the heat melting property is lost, and the particles are not rounded during the pulverization of the mesophase pitch. There are problems such as an increase in the aspect ratio, and the toluene-insoluble matter is not preferable because if it is out of the above range, the same problem occurs. In the above heat treatment, the softening point is 280 ° C. or higher, preferably 320 ° C.
The heating temperature, the heating time, the pressure and the like are preferably set so as to be in a range of from about 370 ° C. to 370 ° C., more preferably from 330 ° C. to 365 ° C. Softening point of heat treated product is 280 ℃
If it is less than the above, the amount of mesophase pitch fine particles generated is insufficient. On the other hand, if the softening point of the heat-treated product exceeds 370 ° C., the fluidity of the pitch is lost and handling becomes difficult.

In the above heat treatment, spherical mesophase pitch fine particles are continuously generated and grown in the pitch,
Since the ratio between the optically isotropic component and the optically anisotropic component (spherical mesophase pitch fine particles) in the pitch changes,
During the heat treatment, these quantitative ratios are sampled and confirmed, and the optically anisotropic component becomes 50% by volume or more, preferably about 60 to 95% by volume of the whole, It is preferable to set the heat treatment conditions so that is uniformly dispersed in the optically anisotropic component.

The amount of the optically anisotropic component in the heat-treated product is 50
When the volume is less than the volume%, the infusibilization time for oxidizing the pitch to a predetermined oxygen concentration becomes long, and the crystallinity when the pitch is carbonized and graphitized thereafter is insufficient, and is insufficient. On the other hand, when the amount of the optically anisotropic component in the heat-treated product exceeds about 95% by volume, the aspect ratio of the particles obtained by pulverizing the heat-treated product becomes large, and the shape becomes almost spherical when oxidized. It is not sufficient in that it does not change to

Next, the high softening point pitch is cooled and then pulverized to a particle size of less than 200 mesh. The powder is pulverized to have an average particle size of 50 μm or less, preferably 5 to 30 μm. The pulverizer is not particularly limited, and for example, a pulverizer such as a ball mill, a stirring mill, and a jet pulverizer can be used.

The above pulverized material is subjected to an oxidation treatment. This oxidation treatment may be performed in air at a temperature of 140 to 300 ° C.,
Nitrogen gas is flowed into the oxidation furnace to achieve an oxygen concentration of 16 to 18% by weight.
It is preferable to carry out in a degree. In addition, during oxidation, the oxidation furnace is divided into multiple sections so that temperature control can be accurately performed so that the pulverized particles do not sinter to form molten aggregates, or a fluidized bed can be used so that the pulverized substances do not come into contact with a heat source. It is preferable to carry out the treatment in an oxidizing furnace or to perform the treatment in a thin layer.

In this oxidation treatment, the degree of oxidation is desirably set so that the oxidized product contains about 2 to 10% by weight of oxygen. If the oxygen content is less than the above range, that is, if the oxidation is insufficient, there is a problem that fusion occurs again in the carbonization / graphitization process, and in the finally obtained carbonaceous material of the present invention, the optical structure in the particles is On the other hand, it is not sufficient in that it cannot be retained. On the other hand, if the oxidation is excessive, the amorphous property of the oxidized product increases, the crystallinity deteriorates, and the specific surface area increases. Particles that have been subjected to the above-mentioned pulverization and oxidation treatment lose sharp corners of the particles due to friction energy at the time of pulverization and heat energy of an oxidation reaction, become slightly rounded particles, and have an aspect ratio of 1 to 2. Within the range.

Finally, the oxidized product is carbonized and graphitized according to a conventional method. 700 ° C to 1200 ° C for carbonization
Temperature, and the graphitization is performed at 2500-3000 ° C.
At a temperature of Since each processing time differs depending on the device to be used, an optimum time may be selected depending on the employed device. These carbonization and graphitization treatments can be performed continuously, and various conditions and apparatuses for carbonization and graphitization can be used as they are. In the carbonization / graphitization process, there is no significant change in the shape of the particles, but most of the oxygen contained before the process is eliminated.

Although the carbonaceous material of the present invention is useful for various uses, a lithium ion secondary battery as one of the uses will be described. Lithium ion secondary batteries are
For example, the positive and negative electrode plates are formed on a current collector made of a metal foil on which positive and negative active material layers are formed, and a nonaqueous organic solvent is used as an electrolytic solution. Charges and discharges are enabled by the exchange of electrons when lithium ions move.

The active material layer forming the electrode plate is formed from an electrode coating solution comprising at least an active material and a binder. As the negative electrode active material, the carbonaceous material of the present invention is used, and as the positive electrode active material, for example, LiCo
Lithium oxides such as O ₂ , LiMn ₂ O ₄ , TiS ₂ , Mn
By using one of chalcogen compounds such as O ₂ , MoO ₃ , V ₂ O ₅ or a combination thereof, a lithium ion secondary battery having a high discharge voltage of about 4 volts can be obtained. It is preferable that these active materials are uniformly dispersed in the formed coating film. For this purpose, it is preferable to use a powder having an average particle diameter of about 10 μm having a particle diameter in the range of 1 to 100 μm as the positive and negative active materials.

As the binder for the active material layer, for example,
Thermoplastic resins, that is, arbitrarily selected from polyester resins, polyamide resins, polyacrylate resins, polycarbonate resins, polyurethane resins, cellulose resins, polyolefin resins, polyvinyl resins, fluorine resins, polyimide resins, and the like can be used. it can.

The active material layer constituting the electrode plate is formed by the following method. First, an electrode coating solution is prepared by kneading or dispersing and dissolving a binder and a fine powdered active material appropriately selected from the above-mentioned materials using an appropriate dispersion medium. Next, using the obtained coating liquid, coating is performed on the current collector. As a coating method, a method such as gravure, gravure reverse, die coating, and slide coating is used. Thereafter, an active material layer having a desired film thickness is formed through a drying step of drying the applied coating liquid to obtain positive and negative electrode plates.

As the current collector used for the electrode plate, for example, a metal foil such as aluminum and copper is preferably used. The thickness of the metal foil is about 10 to 30 μm. When a lithium ion secondary battery is manufactured using the positive and negative electrode plates manufactured as described above, a non-aqueous electrolyte in which a solute lithium salt is dissolved in an organic solvent is used as an electrolyte. Used.

The organic solvent used at this time includes cyclic esters, chain esters, cyclic ethers, chain ethers and the like. Examples of the cyclic esters include propylene carbonate and the like. , Chain esters include dimethyl carbonate and the like, and cyclic ethers include tetrahydrofuran and the like,
In addition, examples of the chain ethers include 1,2-dimethoxyethane.

The solute lithium salt which forms a non-aqueous electrolyte with the above organic solvent is LiClO ₄ , LiB
Inorganic lithium salts such as F ₄ , LiPF ₆ , LiAsF ₆ , LiCl, and LiBr; and LiB (C ₆ H ₅ ) ₄ and LiN
(SO ₂ CF ₃ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiOSO
₂ CF ₃ , LiOSO ₂ C ₂ F ₅ , LiOSO ₂ C ₃ F ₇ , L
iOSO ₂ C ₄ F ₉ , LiOSO ₂ C ₅ F ₁₁ , LiOSO ₂
Organic lithium salts such as C ₆ F ₁₃ and LiOSO ₂ C ₇ F ₁₅ are used.

[0030]

Next, the present invention will be described more specifically with reference to examples and comparative examples. Example 1 As a raw material, a softening point of 115.0 ° C. and a quinoline insoluble content of 2.3.
A pressure-reduced pitch having a uniform molecular weight distribution of 19.1% by weight, a toluene insoluble content of 19.1% by weight and a number average molecular weight of 494 was used. This raw material was introduced into a reaction vessel preheated to 270 ° C. This reaction vessel has an inert gas blowing nozzle at the bottom preheated to 270 ° C., and is additionally equipped with a mechanical stirring device.
The effective internal capacity is 1.2 m ³ (outer diameter 1,200 mm, height 2,700 mm). Temperature rise rate 10 ° C /
After raising the temperature to 400 ° C. for 0.1 hour, 0.17
Nitrogen gas is blown in under the condition of Nm ³ / pitch kg · hour, the mixture is stirred at 120 rpm, and the pressure in the reaction vessel is 5 kg.
/ Cm ² · G, and heat-treated for 6 hours. During this time,
The liquid in the reaction vessel was in a completely mixed state.

The pitch yield after heat treatment is 67.
At 5% by weight, the softening point was 364 ° C., the content of the optically anisotropic component in the visual count with a polarizing microscope was 74% by volume, and the optically isotropic component was included in the optically anisotropic component. The mesophase pitch was uniformly dispersed. The quinoline-insoluble content of this pitch was 70% by weight, and the toluene-insoluble content was 8%.
It was 3% by weight. The above-mentioned mesophase pitch is pulverized by a jet mill to obtain a fine powder having an aspect ratio of 2 or less, no particles having a particle size of 48 μm or more, and fine particles having a particle size of 2 μm or less and 3% by weight or less having an average particle size of 16 μm. Was. The above fine powder is heated at a rate of 4 ° C./min.
The temperature was raised from 260 ° C. to 260 ° C. and maintained for 20 minutes to perform an oxidation treatment. By performing this oxidation treatment, a fine powder of mesophase pitch having a fixed oxygen content of 5.4% by weight of an optical component having a rounder shape than the fine powder at the time of the pulverization was obtained.

The above fine powder was heated in a nitrogen atmosphere at a heating rate of 3
The temperature was raised to 1,100 ° C. at a rate of ° C./hour, carbonized for 2 hours, and then graphitized again at 3,000 ° C. for 2 hours.
As a result, the yield of the graphitized product was 82% by weight, the crystal lattice constant C ₀ of the obtained graphite particles was 6.73 °, Lc representing the crystallite size was 710 °, and the specific surface area was 0.85 m ^2.
/ G. In the above examples, the yield of the finally obtained carbonaceous material of the present invention based on the initial raw material was 5%.
In contrast, the yield of the conventional method of separating spherical fine particles from the heat-treated mesophase pitch is at most about 24% by weight.

Example 2 Example 1 except that the heat treatment time of the reduced pressure pitch was changed to 5 hours.
The carbonaceous material of the present invention was obtained in the same manner as described above, and was similarly evaluated as an electrode material. The quinoline insoluble content of the heat-treated product was 65%.
% By weight, toluene insoluble content is 76% by weight, softening point is 350
° C, the content of the optically anisotropic component in the visual count with a polarizing microscope was 51% by weight, and the oxygen content of the oxidized product was 5.7.
% By weight.

Comparative Example 1 The pulverized mesophase pitch in which the optically isotropic component of Example 1 was uniformly dispersed in the optically anisotropic component was not subjected to oxidation treatment, and the other carbonization treatment was the same as in Example 1. Was done. At this time, since the fine powders were fused and agglomerated, they were pulverized again, but the aspect ratio of the particles was 3.2. This fine powder was subjected to the same graphitization treatment as in Example 1. Thereafter, a carbonaceous material of a comparative example was obtained in the same manner as in Example 1, and was similarly evaluated as an electrode material.

COMPARATIVE EXAMPLE 2 In place of the reduced pressure pitch of Example 1, a pitch obtained by subjecting coal tar to normal pressure distillation and then heat-treated (heat-treated without vacuum distillation to adjust the softening point to 112.0 ° C.) ) Was used as a raw material, and a carbonaceous material of a comparative example was obtained in the same manner as in Example 1, and was similarly evaluated as an electrode material.

Evaluation as electrode material 95 parts by weight of the carbonaceous fine powder obtained in the above Examples and Comparative Examples and 5 parts by weight of a binder (polytetrafluoroethylene: 33% by weight, acetylene black: 66% by weight, surface activity) The mixture was kneaded well and formed into a pellet having a diameter of 13 mm, and this was sandwiched between nickel nets and pressed at a pressure of 3.8 t / cm ² , and pressed at 150 ° C. for 5 hours.
The electrode was prepared by vacuum drying for an hour. A lithium foil was used as a counter electrode, and an equimolar mixed solvent of ethylene carbonate and diethylene carbonate in which lithium perchlorate was dissolved at a concentration of 1 mol / liter was used as an electrolytic solution. The discharge capacity of the battery was measured under constant current charging and discharging at a current density of 0.1 mA / cm ² . The evaluation results are shown in Table 1 below. From the results in Table 1, it can be seen that the lithium ion secondary battery using the carbonaceous material of the present invention has high capacity and low irreversible capacity.

Table 1

Examples 3 to 5 and Comparative Examples 3 to 5 By changing the heat treatment conditions of the reduced pressure pitch in Example 1 as shown in Table 2 below, mesophase pitches having the physical properties shown in Table 2 were obtained.

Table 2 Note) Heat treatment conditions: temperature (° C) / time (Hr) / gas blowing
Amount (Nm^Three/ Pitch kg ・ hr)

Using each mesophase pitch obtained above, carbonaceous materials of the present invention and comparative examples were obtained in the same manner as in Example 1, and evaluated as electrode materials in the same manner as above. Table 3 shows the results. From the results in Table 3, it can be seen that the lithium ion secondary battery using the carbonaceous material of the present invention has high capacity and low irreversible capacity.

Table 3

Examples 6 to 9 and Comparative Examples 6 and 7 Carbon dioxide of the present invention and comparative examples was prepared in the same manner as in Example 1 except that the oxidation conditions were variously changed and the oxygen content of the oxidized product was variously changed. Quality material was obtained and evaluated as an electrode material in the same manner as described above. Table 4 shows the results. From the results in Table 4, it can be seen that the lithium ion secondary battery using the carbonaceous material of the present invention has high capacity and low irreversible capacity.

Table 4

[0044]

According to the present invention as described above, the reduced pressure pitch is heat-treated to a mesophase pitch until the quinoline-insoluble content becomes 50 to 85% by weight, and the mesophase pitch is separated without separating the mesophase pitch. By oxidizing this, the pulverized material changes into a nearly spherical shape, and in this state, by carbonizing and graphitizing, spherical mesophase pitch fine particles separated from the conventional heat-treated pitch or equivalent to the same. It has been found that carbonaceous fine particles having the above-mentioned lithium ion storage capacity can be obtained. Therefore, according to the present invention, without using any solvent such as quinoline or toluene, a high-performance carbonaceous material as a negative electrode material or the like for a lithium ion secondary battery can be produced in a simple operation at a high yield and economically. Can be provided.

[Brief description of the drawings]

FIG. 1 is a process chart of a manufacturing method of the present invention.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H01M 4/02 H01M 4/02 D 4/04 4/04 A 4/58 4/58 10/40 10/40 Z (72) Inventor Komura (2) Inventor Yasuyuki Takigawa 4-Chome Kita-Kita 1-chome, Chiyoda-ku, Tokyo Ad-Chemco Co., Ltd. (72) Inventor Shigeyuki Hirano Tokyo (72) Inventor Tetsuo Shiode 4-chome Kita-kita 4-chome, Chiyoda-ku, Tokyo Ad Chemo Co., Ltd.

Claims (9)

[Claims] 1. The reduced pressure pitch is adjusted to a quinoline insoluble content of 5%.
0 to 85% by weight to form a mesophase pitch, a step of pulverizing the obtained mesophase pitch into fine particles having an aspect ratio of 2 or less, a step of oxidizing the pulverized product, and a step of carbonizing the oxidized product. -A method for producing a carbonaceous material, comprising a step of graphitizing. 2. The method according to claim 1, wherein the quinoline insoluble content of the mesophase pitch is 55 to 80% by weight. 3. The method for producing a carbonaceous material according to claim 1, wherein the quinoline-insoluble content of the mesophase pitch is 55 to 80% by weight and the toluene-insoluble content is 70 to 90% by weight. 4. A pitch heat treatment, wherein the softening point is 280.
The method for producing a carbonaceous material according to claim 1, wherein the method is performed until the temperature becomes higher than or equal to ° C. 5. A heat treatment of the pitch having a softening point of 320
The method for producing a carbonaceous material according to claim 1, wherein the method is performed until the temperature reaches to 370 ° C. 6. The method for producing a carbonaceous material according to claim 1, wherein the heat treatment of the pitch is performed until the optical anisotropy (mesophase) component in the pitch becomes 50% by volume or more. 7. The method for producing a carbonaceous material according to claim 1, wherein the heat treatment of the pitch is performed until the optical anisotropy (mesophase) component in the pitch becomes 60 to 95% by volume. 8. The method for producing a carbonaceous material according to claim 1, wherein the oxidation treatment is performed in a range where the oxygen content of the oxidized product is 2 to 10% by weight. 9. A lithium ion secondary battery using the carbonaceous material according to claim 1 as a negative electrode material.