JP2003128405A - Method of manufacturing carbon composite fine particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing carbon composite fine particles which contain natural graphite having random orientation and high crystallinity and have improved adhesive properties to a pole plate of the natural graphite and are suitable for a negative electrode material in a lithium ion secondary battery. SOLUTION: The method of manufacturing the carbon composite fine particles comprises heating a kneaded material obtained by kneading (1) natural graphite, (2) at least one kind of a spherical carbon component selected from a spherical carbon precursor and a spherical carbon material and (3) a binder at 2,400 to 3,000 deg.C, if necessary after it is subjected to the primary heating at 700 to 1,500 deg.C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing carbon composite powder.

[0002]

2. Description of the Related Art A lithium ion secondary battery has a voltage of 4V.
It is high in weight, light in weight and high in discharge capacity, and is widely used as a power source for portable electronic devices. In order to increase the discharge capacity at such a high voltage, it is essential that the crystallinity of carbon used for the negative electrode is well developed.

The theoretical capacity of graphite crystals is 372 mAh / g, and natural graphite has a capacity close to this value.
However, graphites such as natural graphite that have developed crystallinity are not well compatible with solvents and adhesives, and have poor adhesiveness to the electrode plate. Further, since the shape is flat and they are oriented parallel to each other at the time of application, there is a drawback that it is difficult to take in lithium ions during charging.

Japanese Unexamined Patent Publication (Kokai) No. 6-36760 discloses a method of improving the adhesion of natural graphite to an electrode plate and the orientation of natural graphite by mixing and using natural graphite and coke.
However, in this method, since the coke having low crystallinity is used, the battery capacity stored in the negative electrode is reduced.

Further, in Japanese Patent Laid-Open No. 5-94838,
Although a method of coating the surface of graphite with coke is disclosed, this method has a high cost because the step of coating with coke is complicated, and the effect of improving the orientation of graphite is sufficient. Not really.

Further, JP-A-5-290844 discloses a method of mixing natural graphite and artificial graphite having low crystallinity, and JP-A-8-287952 discloses mixing graphite with a spherical carbon material. A method is disclosed. However, the above-mentioned method of simply mixing artificial graphite having low crystallinity, spherical carbonaceous material, and the like reduces the battery capacity stored in the negative electrode, and cannot sufficiently improve the orientation of graphite.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional state of the art, and its main purpose is to include randomly oriented natural graphite having high crystallinity, Another object of the present invention is to provide a method for producing a carbon composite powder which has improved adhesion of the natural graphite to an electrode plate and which is suitable as a negative electrode material in a lithium ion secondary battery.

[0008]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the above problems. As a result, to natural graphite, a spherical carbonaceous component and a binder were added, and a kneaded product obtained by kneading this was a granular product in which natural graphite was randomly oriented, and by heat-treating the kneaded product,
The carbonaceous component and the binder are graphitized to improve the crystallinity, and at the same time, the natural graphite is purified. As a result, the negative electrode of the lithium-ion secondary battery is high in crystallinity and contains randomly oriented natural graphite. As a result, they have found that a carbon composite powder suitable as a product can be obtained, and have completed the present invention.

That is, the present invention provides the following method for producing a carbon composite powder. 1. (1) natural graphite, (2) at least one spherical carbonaceous component selected from spherical carbon precursor and spherical carbon material,
And (3) the kneaded product obtained by kneading the binder,
A method for producing a carbon composite powder, which comprises heating at 2400 to 3000 ° C. 2. (1) natural graphite, (2) at least one spherical carbonaceous component selected from spherical carbon precursor and spherical carbon material,
And (3) the kneaded product obtained by kneading the binder,
2400-30 after primary heating at 700-1500 ° C
A method for producing a carbon composite powder, which comprises heating at 00 ° C. 3. Natural graphite has a purity of less than 99.9% and an average particle size of 3 to
Item 3. The method for producing a carbon composite powder according to Item 1 or 2, which has a size of 30 µm. 4. The spherical carbonaceous component has an aspect ratio of 3 or less, a circularity of 0.9 or more, and an average particle diameter of 3 to 50 μm.
5. The method for producing a carbon composite powder according to any one of 1. 5. 20 to 90% by weight of natural graphite and spherical carbonaceous component 1
The method for producing a carbon composite powder according to any one of Items 1 to 4, wherein 10 to 70 parts by weight of the binder is used with respect to 100 parts by weight of the material composed of 0 to 80% by weight.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for producing a carbon composite powder of the present invention, natural graphite, spherical carbonaceous component and binder are used as raw materials.

Natural graphite is a scaly or flaky crystalline substance, and the higher the purity, the better. However, when the production method of the present invention is used, it is not necessary to use high-purity natural graphite, and Those less than 99.9% can be used. Further, a material having a purity of less than 95% may be used, but in consideration of fouling of a furnace used for graphitization, a material having a purity of 95% or more is preferably used, and a material having a purity of 98% or more is preferably used. More preferable.

Natural graphite has an average particle size of 3 to 30 μm.
It is preferable to use a crushed product. If the average particle size is smaller than 3 μm, the specific surface area may be too large, and if the average particle size is larger than 30 μm, the surface may not be smooth easily when used for an electrode, which is not preferable.

The average particle size in the present specification is measured by a laser beam particle size distribution measuring device, and the volume ratio of particles is accumulated from the fine powder side, and the accumulated ratio is 50%.
It is the particle size when it becomes.

In the method of the present invention, as the spherical carbonaceous component, at least one component selected from a spherical carbon precursor and a spherical carbon material is used.

By using these spherical carbonaceous components, it is possible to obtain a granular material in which natural graphite is randomly oriented in the kneading step described later.

The spherical carbonaceous component has an aspect ratio of 3 or less,
A circularity of 0.9 or more is preferable, and an aspect ratio of 2 or less and a circularity of 0.95 or more are more preferable. Here, the circularity can be measured using, for example, a flow type particle image analyzer FPIA-2100 manufactured by Sysmex Corporation. Specifically, the circularity means that the particles dispersed in water are imaged by a CCD camera, the particle projected area of the particle image is obtained, and the perimeter of a circle corresponding to the particle projected area is taken as a molecule, and the imaged particles are taken. It is a ratio with the perimeter of the projected image as the denominator, and the closer the particle image is to a perfect circle, the closer the circularity is to one.

Among the components which can be used as the spherical carbonaceous component, the carbon precursor is a carbonization intermediate which is obtained by heating an organic substance and is in a stage before the final carbonized product. Usually, it contains a different element in addition to carbon. Specifically, a carbonized intermediate obtained by heat-treating coal tar, petroleum distillation residue or the like as a raw material at a temperature higher than the temperature in the kneading step described later can be used.

The spherical carbon precursor satisfying the above conditions is not particularly limited, but examples thereof include mesophase spherules and spherical phenol resin.

On the other hand, any spherical carbon material may be used as long as it has the above-mentioned spherical shape, and amorphous carbon, carbonized products, graphitized products and the like can be used. The carbon precursor may be carbonized or graphitized by heat treatment.

As the spherical carbonaceous component, a component selected from the above-mentioned spherical carbon precursor and spherical carbon material can be used alone or in combination of two or more.

The spherical carbonaceous component has an average particle size of 3 to
It is preferable to use one having a thickness of about 50 μm,
It is more preferable to use one having a thickness of about μm. If the average particle size is less than 3 μm, the specific surface area may become too large. Further, if the average particle size is larger than 50 μm, the surface may not be smooth easily when used for an electrode, which is not preferable.

In the method of the present invention, the binder acts as a binder for the natural graphite and the spherical carbonaceous component, having a suitable viscosity during the kneading operation described later, and 2400 to 2400.
Any component that graphitizes when heat-treated at 3000 ° C. may be used, and various pitches, resins, and the like can be used.
Generally, the viscosity of the binder during the kneading operation is preferably about 100 to 10,000 cP at the kneading temperature.

Specific examples of such a binder include pitches such as coal tar pitch, petroleum pitch and naphthalene pitch, phenol resin, 3,5-dimethylphenol formaldehyde resin, furan resin, polyvinyl chloride and the like.

When the binder is liquid at room temperature, it can be added as it is, and when it is solid at room temperature, the average particle size is, for example, 5 to 30 so as to facilitate the mixing operation.
It is preferable to pulverize it to about 0 μm for use, or to mix it in a molten state.

In the method for producing a carbon composite powder of the present invention, first, the above-mentioned natural graphite, a spherical carbonaceous component and a binder are kneaded to obtain a kneaded product.

Among the raw material components, the blending ratio of the natural graphite and the spherical carbonaceous component is 100% by weight based on the total amount of both.
Natural graphite 20-90% by weight and spherical carbonaceous component 10-8
It is preferably about 0% by weight. If the blending amount of the spherical carbonaceous component is too small, the effect of improving the orientation of the natural graphite is small, while if the blending amount is too large, the crystallinity of the resulting carbon composite powder is significantly reduced, and the cost is also low. It becomes high, which is not preferable.

The amount of the binder blended is preferably about 10 to 70 parts by weight based on 100 parts by weight of the total amount of natural graphite and spherical carbonaceous components. If the blending amount of the binder is too small, it is not preferable because the adhesive performance between the filler components composed of natural graphite and spherical carbonaceous components is lowered, and if the blending amount of the binder is too large, the resulting carbon composite is obtained. It is not preferable because the crystallinity of the powder may decrease.

Further, the amount of the binder used is preferably within a range of the above-mentioned compounding amount, and is about 0.2 to 0.4 times the amount of oil absorption measured by an absorber meter. If the amount of oil absorption is more than 0.4 times, the amount of binder used becomes too much, which may reduce the crystallinity of the obtained carbon composite powder. If less than 0.2 times,
The amount of binder used may be reduced, and the effect of improving the packing density may be impaired.

As a method of kneading a raw material composed of natural graphite, a spherical carbonaceous component and a binder, the raw material components may be mixed and stirred and kneaded while heating at a temperature equal to or higher than the softening point of the binder. The upper limit of the heating temperature is not particularly limited, and may be a temperature having an appropriate viscosity depending on the type of binder, but it is usually preferably about 300 ° C. or lower.

By this kneading, a kneaded product of natural graphite, spherical carbonaceous components and binder is obtained as a granulated product.
As a result, a granulated product having a bead-like shape in which natural graphite is randomly oriented and has low orientation is obtained. By heating this granulated product and using it as a negative electrode of a non-aqueous solvent secondary battery such as a lithium ion secondary battery, the orientation of the negative electrode is relaxed. Also, by granulating, fine powder is reduced,
The specific surface area of the obtained carbon composite powder is reduced, and the irreversible capacity can be reduced when used as the negative electrode of the non-aqueous solvent secondary battery.

Next, after cooling the obtained kneaded product,
If necessary, grind to a predetermined particle size. At this time,
In order to avoid over-milling, it is preferable to use a crushing type mill. The particle size of the crushed material at this time is preferably larger than the particle size of the natural graphite as a starting material. When the particle size is smaller than that of the starting material, the randomly oriented natural graphite granules are broken. In addition, when the primary heating described below is not performed, the granulated product has an average particle size of 5 to 40 μm at this stage.
It is preferable to adjust the particle size to a certain level. This makes it possible to prevent the carbon composite powder obtained after graphitization from having an excessively large specific surface area.

Thereafter, the kneaded product of the natural graphite, the spherical carbonaceous component and the binder is heat-treated at a temperature of about 2400 to 3000 ° C. By this heat treatment, the purity is 99.9%.
Purity of 99.9, even when less than natural graphite is used
It can be purified to a high purity of not less than%. At the same time, the spherical carbonaceous component and the binder can be graphitized. As a result, granular carbon composite powder is obtained. If the heating temperature is lower than 2400 ° C, the above two treatments will not be sufficient. It may be higher than 3000 ° C,
From the point of view of the sublimation of graphite and the safety and cost of the furnace, 3000 ° C or lower is sufficient.

The heat treatment atmosphere is preferably a non-oxidizing atmosphere. The heating time may be the time until the entire heat treatment target reaches a predetermined heating temperature depending on the shape, size, etc. of the heat treatment target.

Prior to the heat treatment at the temperature of about 2400 to 3000 ° C., 700 to 1500 ° C.
Primary heating may be performed at about the same temperature. By performing the primary heating, the volatile components can be removed from the granulated product, and when the secondary heating treatment at 2400 to 3000 ° C. is performed in the graphitization furnace, the heating treatment can be safely performed. Further, carbonization of the spherical carbonaceous component and the binder proceeds by the primary heating, so that the secondary heating can be efficiently performed.

The primary heat treatment may be usually carried out in a non-oxidizing atmosphere using a general baking furnace. The heating time of the primary heat treatment may be the time until the entire heat treatment target reaches a predetermined heating temperature depending on the shape, size, etc. of the heat treatment target.

When performing the primary heating, 2400 to 30
Before performing secondary heating at about 00 ° C., the specific surface area of the carbon composite powder obtained after graphitization is adjusted by sizing the granulated product to a particle size of about 5 to 40 μm in average particle size, if necessary. It can be prevented from becoming excessive.

By heat-treating at about 2400 to 3000 ° C. by the above-mentioned method, the spherical carbonaceous component and the binder are graphitized to improve the crystallinity and a carbon material having a high discharge capacity can be obtained. At the same time, since the purity of the natural graphite is improved and becomes a high-purity natural graphite, the natural graphite can be used without being purified to a high purity in advance.

The spacing (d ₀₀₂ ) of the (002) plane of the obtained carbon composite powder is 0.3361 nm or less, and the crystallite size (Lc) is 60 nm or more. For this reason,
The crystallinity of the obtained carbon composite powder is high. The above-mentioned interplanar spacing and the size of the crystallites are obtained by crushing the sample to be measured with an agate mortar, adding about 15% by weight of X-ray high-purity silicon powder to the sample, mixing them, and packing this in a sample cell. A CuKα ray monochromated with a graphite monochromator is used as a radiation source, and a wide angle X is obtained by a reflection diffractometer method.
It is the value obtained by measuring the line diffraction.

The circularity of the obtained carbon composite powder is
It is preferably 0.9 or more. When an electrode is produced using such a carbon composite powder, the orientation of graphite crystals in the obtained electrode can be made more random.

The obtained carbon composite powder is a highly crystalline carbon composite particle containing randomly oriented natural graphite. The carbon composite particles have improved adhesion to the electrode plate and can exhibit excellent discharge characteristics when used as an electrode material for a non-aqueous solvent secondary battery such as a lithium ion secondary battery. The method for producing the secondary battery electrode may be in accordance with a conventional method, for example, to prepare a slurry liquid by suspending the carbon composite powder in a liquid prepared by dissolving the electrode plate binder in a solvent,
This may be applied to the electrode plate by a predetermined thickness, temporarily dried, and then compressed and dried.

[0041]

According to the method for producing a carbon composite powder of the present invention, a carbon composite powder having high crystallinity and natural graphite randomly oriented can be obtained. The carbon composite powder is
When used as an electrode material for a non-aqueous solvent secondary battery such as a lithium-ion secondary battery, it has good compatibility with solvents and adhesives, good adhesion to the electrode plate, and high crystallinity. , Having a large discharge capacity.

[0042]

EXAMPLES The present invention will be described in more detail with reference to examples.

Example 1 Natural graphite powder (produced in China) was jet milled to have an average particle size of about 1
It was pulverized to 5 μm, and 10 parts by weight of mesophase microspheres having an average particle diameter of 10 μm as a spherical carbon precursor were mixed with 90 parts by weight of this powder. To 100 parts by weight of this mixed powder, 30 parts by weight of coal tar pitch (softening point 80 ° C.) (PKQL manufactured by Kawasaki Steel) was mixed and kneaded for 120 minutes at 200 ° C. using a Z-type kneader. The granulated product, which gradually increased in viscosity and became in a granulated state, was cooled, crushed, put in a graphite crucible, and carbonized at 800 ° C. in a lead hammer type continuous firing furnace.

This was sized to an average particle size of about 25 μm, placed in a graphite crucible, and placed in an Acheson type graphitizing furnace for 3000 times.
Graphitized at ° C.

The following various measurements were performed on the obtained carbon composite powder. The results are shown in Table 1 below. (A) Crystallinity measurement (d ₀₀₂ and Lc) If the sample to be measured is a powder, it is ground as it is, and if it is in the form of fine pieces, it is ground in an agate mortar and about 15% by weight of the sample is a high-purity X-ray silicon powder. Add and mix, fill in a sample cell, and use Cukα rays monochromatized with a graphite monochromator as a radiation source, and use a reflection-type diffractometer method to obtain a wide-angle X-ray.
Crystallinity was measured by measuring line diffraction. (B) Specific surface area: measured by the BET one-point method by nitrogen gas adsorption. (C) Measurement of circularity: Flow type particle image analyzer FPIA-2100 manufactured by Sysmex Corporation was used. [Production of electrode] To measure the discharge capacity and initial efficiency when the carbon composite powder obtained by the above method is used as an electrode,
An electrode was produced by the following method.

PVDF binder (polyvinylidene fluoride binder, manufactured by Kureha Chemical Co., Ltd .: 1100)
Dissolve 0556 g in 1.5 ml of N-methyl-2-pyrrolidone, add 0.5 g of the above carbon composite powder to make a slurry, and apply this to electrolytic copper foil (Fukuda metal foil powder: CF8) with a doctor blade to obtain about 105 μm. Apply to the thickness of 11
It was dried for 5 minutes by a hot air circulation dryer at 0 ° C. The thickness of the carbon layer was compressed to 70 μm by a hard chrome-plating roll press, vacuum dried at 130 ° C. for 12 hours, weighed, and further vacuum dried at 130 ° C. for 24 hours. After that, dew point -7
Electrodes placed in a dry box at 0 ° C or below
The discharge capacity and initial efficiency were measured by the following methods. The results are shown in Table 1 below. [Measurement of Discharge Capacity] A coin-type cell in which a lithium metal electrode was opposed to each other by sandwiching a separator (a polyethylene porous film) impregnated with an electrolytic solution was subjected to a charge / discharge test. For the electrolyte, LiPF 6 was added to a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1.
What melt | dissolved ₆ in the ratio of 1 mol / liter was used. In the charge / discharge test, the current value was 1.54 mA, charging was performed until the potential difference between both electrodes became 0 V, and discharging was performed up to 1.5 V.

Example 2 Natural graphite powder (produced in China) was jet milled to have an average particle size of about 1
The particles were pulverized to 5 μm, and 30 parts by weight of mesophase microspheres having an average particle size of 10 μm as a spherical carbon precursor were mixed with 70 parts by weight of this powder. To 100 parts by weight of this mixed powder, 25 parts by weight of coal tar pitch (softening point 80 ° C.) (Kawasaki Steel Co., Ltd .: PKQL) was mixed and kneaded for 120 minutes at 200 ° C. using a Z-type kneader. Gradually increase the viscosity and cool the granulated product in the granulated state, crush it, put it in a graphite crucible, and put it in a lead hammer type continuous firing furnace.
Carbonized at 00 ° C.

This was sized to an average particle size of about 25 μm, placed in a graphite crucible, and placed in an Acheson type graphitizing furnace for 3000 times.
Graphitized at ° C.

An electrode was prepared based on the method described in Example 1.

The above-mentioned various measurements were performed on these heat-treated products and electrodes. The results are shown in Table 1 below.

Example 3 Natural graphite powder (produced in China) was jet-milled to an average particle size of about 1
After pulverizing to 5 μm, 50 parts by weight of this powder was mixed with 50 parts by weight of mesophase microspheres having an average particle diameter of 10 μm as a spherical carbon precursor. To 100 parts by weight of this mixed powder, 20 parts by weight of coal tar pitch (softening point 80 ° C.) (Kawasaki Steel Co., Ltd .: PKQL) was mixed and kneaded for 120 minutes at 200 ° C. using a Z-type kneader. Gradually increase the viscosity and cool the granulated product in the granulated state, crush it, put it in a graphite crucible, and put it in a lead hammer type continuous firing furnace.
Carbonized at 00 ° C.

This was sized to an average particle size of about 25 μm, placed in a graphite crucible, and placed in an Acheson type graphitizing furnace for 3000 times.
Graphitized at ° C.

An electrode was prepared based on the method described in Example 1.

The above-mentioned various measurements were performed on these heat-treated products and electrodes. The results are shown in Table 1 below.

Example 4 Natural graphite powder (produced in China) was jet-milled to an average particle size of about 1
It was pulverized to 5 μm, and 10 parts by weight of mesophase microspheres having an average particle diameter of 10 μm as a spherical carbon precursor were mixed with 90 parts by weight of this powder. To 100 parts by weight of this mixed powder, 40 parts by weight of coal tar pitch (softening point 80 ° C.) (Kawasaki Steel Co., Ltd .: PKQL) was mixed and kneaded for 120 minutes at 200 ° C. using a Z-type kneader. Gradually increase the viscosity and cool the granulated product in the granulated state, crush it, put it in a graphite crucible, and put it in a lead hammer type continuous firing furnace.
Carbonized at 00 ° C.

This was sized to an average particle size of about 25 μm, placed in a graphite crucible, and placed in an Acheson type graphitization furnace for 3000 times.
Graphitized at ° C.

An electrode was prepared based on the method described in Example 1.

The above-mentioned various measurements were performed on these heat-treated products and electrodes. The results are shown in Table 1 below.

Example 5 Natural graphite powder (produced in China) was jet-milled to an average particle size of about 1
The particles were pulverized to 5 μm, and 30 parts by weight of mesophase microspheres having an average particle size of 10 μm as a spherical carbon precursor were mixed with 70 parts by weight of this powder. To 100 parts by weight of this mixed powder, 35 parts by weight of coal tar pitch (softening point 80 ° C.) (Kawasaki Steel Co., Ltd .: PKQL) was mixed and kneaded for 120 minutes at 200 ° C. using a Z-type kneader. Gradually increase the viscosity and cool the granulated product in the granulated state, crush it, put it in a graphite crucible, and put it in a lead hammer type continuous firing furnace.
Carbonized at 00 ° C.

This was sized to an average particle size of about 25 μm, placed in a graphite crucible, and placed in an Atchison type graphitizing furnace in 3000.
Graphitized at ° C.

An electrode was prepared based on the method described in Example 1.

The above-mentioned various measurements were performed on these heat-treated products and electrodes. The results are shown in Table 1.

Example 6 Natural graphite powder (produced in China) was jet milled to have an average particle size of about 1
After pulverizing to 5 μm, 50 parts by weight of this powder was mixed with 50 parts by weight of mesophase microspheres having an average particle diameter of 10 μm as a spherical carbon precursor. To 100 parts by weight of this mixed powder, 30 parts by weight of coal tar pitch (softening point 80 ° C.) (PKQL manufactured by Kawasaki Steel) was mixed and kneaded for 120 minutes at 200 ° C. using a Z-type kneader. Gradually increase the viscosity and cool the granulated product in the granulated state, crush it, put it in a graphite crucible, and put it in a lead hammer type continuous firing furnace.
Carbonized at 00 ° C.

This was sized to an average particle size of about 25 μm, placed in a graphite crucible, and placed in an Acheson type graphitization furnace for 3000 times.
Graphitized at ° C.

An electrode was prepared based on the method described in Example 1.

The above-mentioned various measurements were performed on these heat-treated products and electrodes. The results are shown in Table 1 below.

Comparative Example 1 Coal tar pitch (softening point 80 ° C.) (Kawasaki Steel Co., Ltd .: PKQL) based on 100 parts by weight of natural graphite powder (made in China) having an average particle size of about 15 μm used in Examples 1 to 6 Was mixed with 30 parts by weight and kneaded for 120 minutes at 200 ° C. using a Z type kneader. The granulated product having a gradually increased viscosity and in a granulated state was cooled, then crushed, put into a graphite crucible, and carbonized at 800 ° C. in a lead hammer type continuous firing furnace.

This was sized to an average particle size of about 25 μm, placed in a graphite crucible, and placed in an Acheson type graphitizing furnace for 3000 times.
Graphitized at ° C.

An electrode was prepared based on the method described in Example 1.

The above-mentioned various measurements were performed on these heat-treated products and electrodes. The results are shown in Table 1.

Comparative Example 2 The natural graphite powder having an average particle size of about 15 μm used in Examples 1 to 6 was put into a graphite crucible and placed in an Acheson type graphitizing furnace.
Heat treatment was performed at 000 ° C. Moreover, an electrode was produced based on the method described in Example 1. The above-mentioned various measurements were performed on these heat-treated products and electrodes. The results are shown in Table 1.

Comparative Example 3 Mesophase small spheres (average particle size of about 20 μm) were placed in a graphite crucible and placed in a lead hammer type continuous firing furnace for 800 times.
It was carbonized at ℃, crushed, put again in a graphite crucible and heat-treated at 3000 ℃ in an Acheson type graphitizing furnace. Moreover, an electrode was produced based on the method described in Example 1. The above-mentioned various measurements were performed on these heat-treated products and electrodes. The results are shown in Table 1.

[0073]

[Table 1]

As is clear from Table 1, the carbon composite powders of Examples 1 to 6 have the same degree of circularity, bulk density, and ratio as the mesocarbon microbeads, while maintaining high crystals of natural graphite and a large discharge capacity. It had a surface area.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koji Kuroda             3-26 Nagano Tanomachi, Fukuchiyama, Kyoto             Ceremony Company SCE Kyoto Factory (72) Inventor Teruhiro Tsurumoto             3-26 Nagano Tanomachi, Fukuchiyama, Kyoto             Ceremony Company SCE Kyoto Factory F-term (reference) 4G046 CA00 CA04 CA07 CB02 CC03                 5H050 AA02 AA07 AA08 BA17 CB07                       CB08 DA11 EA21 EA23 EA26                       FA19 GA02 GA10 HA00 HA01                       HA05 HA14

Claims (5)

[Claims] 1. A kneaded product obtained by kneading (1) natural graphite, (2) at least one spherical carbonaceous component selected from a spherical carbon precursor and a spherical carbon material, and (3) a binder. A method for producing a carbon composite powder, which comprises heating at ˜3000 ° C. 2. A kneaded product obtained by kneading (1) natural graphite, (2) at least one spherical carbonaceous component selected from a spherical carbon precursor and a spherical carbon material, and (3) a binder, After primary heating at ~ 1500 ° C, 2400
A method for producing a carbon composite powder, which comprises heating at ˜3000 ° C. 3. The method for producing a carbon composite powder according to claim 1, wherein the natural graphite has a purity of less than 99.9% and an average particle diameter of 3 to 30 μm. 4. The spherical carbonaceous component has an aspect ratio of 3 or less,
The method for producing a carbon composite powder according to claim 1, wherein the circularity is 0.9 or more and the average particle size is 3 to 50 μm. 5. A binder of 10 to 70 parts by weight is used with respect to 100 parts by weight of a material consisting of 20 to 90% by weight of natural graphite and 10 to 80% by weight of a spherical carbonaceous component.
5. The method for producing a carbon composite powder according to any one of 1.