JPH09251855A - Manufacture of carbon powder for negative electrode of lithium ton secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture graphitic carbon powder having high crystallinity and a small specific surface area and suitable for a negative electrode of a battery by thermally treating tar or pitch so as to prepare a predetermined bulk mesophase, followed by graphitization. SOLUTION: Tar and/or pitch is thermally treated at 430-520 deg.C, thus preparing a bulk mesophase having an optically anisotropic micro structure and a powder residue of 5wt.% or less in a solubility test. The resultant bulk mesophase is pulverized, followed by baking at the non-oxidizing atmosphere as it is, for graphitization. Consequently, it is possible to provide aspheric, graphitic carbon powder having high crystallinity and a small specific surface area.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a graphite carbon powder having a low specific surface area and good crystallinity, which is suitable as a negative electrode active material for a lithium ion secondary battery, and a negative electrode material for this battery.

[0002]

2. Description of the Related Art With the spread of small portable electric and electronic devices, new secondary batteries such as Ni-hydrogen batteries and lithium batteries have been actively developed.

A lithium battery is a battery using lithium as a negative electrode active material and a non-aqueous solution as an electrolytic solution. Since lithium is a very base metal, a large voltage can be taken out and a battery having a high energy density can be obtained. Therefore, it is already used in large quantities as a primary battery. However, when a lithium battery is converted into a secondary battery, lithium in the negative electrode grows in a dendrite state by repeated charging / discharging, and short-circuits with the positive electrode, resulting in a short cycle life of repeated charging / discharging.

Therefore, a lithium ion secondary battery has been proposed in which carbonized or graphitized carbon is used as the negative electrode active material and a non-aqueous solution containing lithium ions is used as an electrolytic solution.
In a lithium ion secondary battery, it is considered that lithium ions from the electrolytic solution are taken into carbon by doping, occlusion, insertion (intercalation), etc., and thus function as a negative electrode. That is, charging and discharging occur due to the incorporation and release of lithium ions into carbon, but the electrode reaction mechanism has not been fully clarified at this time. This type of negative electrode is generally produced by mixing carbon powder with a small amount of a binder and molding the mixture (eg, JP-A-62-62).
-90863 and Japanese Patent Laid-Open No. 5-290848).

[0005]

The graphite carbon powder for the negative electrode of the lithium ion secondary battery is required to have a small specific surface area and high crystallinity. On the surface of this powder, a passivation film that does not contribute to the discharge and is formed of an electrolytic solution or lithium is formed. Usage efficiency deteriorates. On the other hand, if the crystallinity of graphite is high, the amount of lithium ions taken in, for example, in the form of LiC ₆ increases due to the regular insertion of graphite between the layers, and the discharge capacity increases. In addition, it is said that the utilization efficiency of the electrolytic solution and lithium will be increased.

A general method for producing graphitic carbon powder is a method of pulverizing natural graphite or artificial graphite obtained by graphitizing coke to adjust the particle size to a predetermined value. However, in this method, since graphite is a layered material and has a high cleavage property, the powder tends to have a flat shape and an acute fracture surface is generated during pulverization, so that the specific surface area is usually 5 m ² / g or more. It will be a large value.

As a precursor of carbon powder having a small specific surface area, there are mesophase spherules which are spherical particles of optical anisotropy generated in the heating process of pitch. It is also known to use a carbon powder obtained by separating the mesophase microspheres from the pitch and firing and carbonizing or graphitizing the same, as a negative electrode of a lithium ion secondary battery (Japanese Patent Laid-Open No. 4-115458).
(See Japanese Patent Application Laid-Open Nos. 5-234584 and 5-307958).

The mesophase spherules have a particle size of several to several tens of μm, which is suitable for the production of a negative electrode for a lithium ion secondary battery, and the particle size is relatively uniform. It may be carbonized or graphitized. However, the mesophase spherules separated from the pitch have a melting property, and if this is calcinated as it is, it is melted at the time of carbonization and the particles are fused and the shape of the spherule is lost. However, it is necessary to oxidize the surface by heat treatment or the like in air before firing (Japanese Patent Laid-Open No. Hei 5-
(See Japanese Patent No. 234584).

Although mesophase microspheres are commercially available under the name of mesocarbon microbeads (MCMB),
In this method, the mesophase spherules separated from the pitch by a method such as solvent extraction or sedimentation are subjected to an oxidation treatment to reduce the meltability and improve the fluidity and handleability. Therefore, this commercially available mesophase microsphere is generally already subjected to an oxidation treatment.

However, due to this oxidation treatment before firing,
When the mesophase spherules are graphitized by calcination, the crystallinity of the obtained graphitized carbon powder decreases because the amount of three-dimensional crosslinks in carbon increases. Cross-linking
This is because it hinders the formation of layered graphite crystals. for that reason,
The method of firing mesophase spherules does not give graphitized carbon powder having good crystallinity.

Further, the graphite layer surfaces in the mesophase spherules are not completely parallel to each other, and the edges of the layer surfaces are perpendicular to the surface of the sphere (that is, the interlayer distance is narrow at the center and spreads toward the outer circumference). Takes a distorted crystal structure. From these points, the crystallinity of the mesophase spherules after graphitization is not very good, and even when the graphitized carbon powder obtained by firing the mesophase spherules is used, the lithium ion secondary I can't get the battery.

Japanese Unexamined Patent Publication (Kokai) No. 5-74452 discloses a carbonaceous material having a relatively large specific surface area and a small spherical carbonaceous material having a relatively small specific surface area (eg, one obtained by firing mesophase spherules or spherical phenol resin). ) Is described as a negative electrode material for a lithium ion secondary battery. Also in this case, as the carbon powder having a small specific surface area, a small spherical powder obtained by firing mesophase small spheres is used, and there is a problem similar to the above.

The present invention is intended to develop a method for producing graphitic carbon powder having high crystallinity and small specific surface area, which is suitable for a negative electrode of a lithium ion secondary battery.

[0014]

According to the present invention, tar and / or pitch are heat-treated at 430 to 520 ° C. to have an optically anisotropic microstructure, and the powder remaining amount in a meltability test is 5% by weight or less. Is prepared, pulverized, and then fired as it is in a non-oxidizing atmosphere for graphitization to produce a carbon powder for a negative electrode of a lithium ion secondary battery.

In the present invention, in order to increase the crystallinity of graphite, bulk mesophase is used as a raw material for firing instead of mesophase spherules. When observing with a polarizing microscope while heating tar and pitch, spherical particles (mesophase spheres) with optical anisotropy first appear in the liquid phase after being liquefied by melting. In this state, the amount of the optically anisotropic substance is several percent to several tens percent by weight. Continued heating increases the amount of mesophase microspheres that come into contact and coalesce. When this coalescence progresses, the whole becomes optically anisotropic. Bulk mesophase (also called mesophase pitch) is a state in which the whole is optically anisotropic. Therefore, bulk mesophases were obtained in greater quantities than mesophase microspheres and were required for mesophase microspheres,
It is cheaper than mesophase spherules because it does not require a separation step from the liquid phase such as solvent extraction.

In the present invention, tar or pitch is heat-treated in a specific temperature range to form a bulk mesophase which is substantially entirely composed of an optically anisotropic microstructure and has no substantial meltability. Crush this bulk mesophase,
If it is fired as it is in a non-oxidizing atmosphere and carbonized and graphitized without crushing at all during firing, it has high crystallinity and a small specific surface area. A non-spherical graphitic carbon powder having a measured inter-layer distance (d ₀₀₂ ) of 002 planes of 3.362 Å or less and a specific surface area of 1 m ² / g or less is obtained.

The meltability test for evaluating the meltability of the bulk mesophase was carried out by a powder sample of the bulk mesophase (particle size of about 150 μm) that was passed through a 100-mesh sieve after crushing.
m or less) in a crucible with a lid and an inert gas atmosphere
(Eg, nitrogen or argon) is heated to 1000 ° C. at a heating rate of 100 ° C./hr to carbonize. After cooling, the resulting carbide is 32 mesh (particle size about 500 μm)
Lightly rub the sieve with a spoon and do not pass through the sieve (remains on the sieve) Weight of powder (remaining powder)
Is measured.

In the melting test, the sieve used after carbonization was 32
The mesh and the one with bigger eyes than before carbonization is 10
This is because there is a possibility that a large amount of particles that do not pass through the original 100-mesh sieve may be generated due to particle deformation and weak adhesion during carbonization by heating at 00 ° C. If substantial meltability remains in the bulk mesophase, powder particles will agglomerate during heating to 1000 ° C to form a large agglomerate of several mm or more, so even a 32 mesh sieve will not pass through. The meltability of the bulk mesophase can be evaluated by the above test.

In the present invention, the heat treatment is carried out so that a bulk mesophase having substantially no meltability and having a powder remaining amount of 5% by weight or less measured by the meltability test method is produced.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention will be described in detail below. The raw material is tar, pitch which is a distillation residue of tar, or both. The raw material is preferably coal tar or coal tar pitch rich in aromatics, but petroleum-based ones can also be used. This raw material is heat-treated at 430 to 520 ° C while removing oil (volatile matter) to generate a bulk mesophase which is a carbon precursor. The heat treatment may be carried out in the presence of a small amount of acid (eg nitric acid).

The heat treatment is preferably carried out under reduced pressure of about 10 to 100 torr in order to promote removal of oil and formation of bulk mesophase. Therefore, the heat treatment can be performed using, for example, a vacuum distillation apparatus. When the heat treatment is carried out at atmospheric pressure, it is preferable to carry out the heat treatment under the flow of an inert gas such as nitrogen gas in order to promote the removal of oil and prevent the oxidation during the heat treatment.

By this heat treatment, the aromatic compound in tar or pitch is polymerized, and as described above, bulk mesophase having an optically anisotropic microstructure is generated through the mesophase microspheres. The optically anisotropic microstructure can be confirmed by a polarization microscope. If the tar or pitch is directly heat-treated as described above, a bulk mesophase having a microstructure having a flow structure oriented in one direction along the gas flow generated or flowing can be obtained. on the other hand,
When the heat treatment is carried out in the presence of a small amount of nitric acid, a bulk mesophase having a mosaic pattern of optically anisotropic microstructure is formed. If the microstructure has optical anisotropy, any of these patterns may be used, but a flow pattern in one direction is preferable.

The heat treatment is continued until a bulk mesophase is obtained which has substantially no meltability (that is, the remaining amount of powder in the meltability test is 5% by weight or less). For that purpose, although it depends on the temperature and the degree of pressure reduction during the heat treatment, generally, a heat treatment time of several tens of minutes to several tens of hours is required, and the heat treatment is performed within several hours under a sufficient reduced pressure or an inert gas flow. Is completed.

If the meltability of the bulk mesophase is substantially left, the powder is melted and fused again during the temperature rising process when the powder is crushed after the heat treatment and then baked, and the powder shape collapses. It is necessary to pulverize again in the middle and then continue firing (for example, pulverize after carbonization and then perform graphitization treatment), and only carbon powder having a large specific surface area can be obtained.

If the heat treatment temperature is lower than 430 ° C., it becomes difficult to obtain a bulk mesophase having substantially no meltability even if the degree of reduced pressure is increased. When the heat treatment temperature is higher than 520 ° C., the specific surface area of the carbon powder obtained after graphitization becomes large, as will be described later in detail. The preferable heat treatment temperature is 450 to 520 ° C, more preferably 460 to 500 ° C.

The obtained bulk mesophase having substantially no meltability is pulverized to have a predetermined particle size suitable for producing a negative electrode of a lithium ion secondary battery. The appropriate particle size varies depending on the configuration of the battery, but usually the average particle size is several μm to 50 μm.
m. For crushing, hammer mill, fine mill,
It may be carried out using a conventional fine pulverizer such as an attrition mill or a ball mill. After crushing, if necessary, classification may be performed to make the particle sizes uniform.

The powder of bulk mesophase obtained by pulverization is fired as it is in a non-oxidizing atmosphere to be graphitized. This firing can be performed in the same manner as conventional graphitization, and as is well known, it is generally performed in two steps of carbonization (carbonization) and graphitization.

Prior to this firing, an oxidation treatment for preventing fusion of powder during firing is not carried out as is done in conventional mesophase spherules. In the present invention, the firing raw material mesophase powder has substantially no meltability,
Since the fusion due to the melting of the powder hardly occurs in the temperature rising process of the firing, the powder obtained by the pulverization can be directly fired in the non-oxidizing atmosphere. As a result, a decrease in crystallinity after graphitization due to the oxidation treatment can be avoided.

Further, the heat treatment temperature for obtaining the bulk mesophase is 520 ° C. or lower, and the carbon powder having a small specific surface area can be obtained by pulverizing and calcination. This is because the powder to be fired has not been subjected to heat treatment at a temperature higher than 520 ° C, so the shrinkage during carbonization / graphitization is relatively large, and this shrinkage causes the open pores on the powder surface to become closed pores or crushed. This is because the surface generated in step 1 is softened and deformed and smoothed, and the specific surface area is reduced.

When heat-treated at a temperature higher than 520 ° C., and then pulverized and fired, the fracture surface having a large specific surface area generated by the pulverization tends to remain as it is, and the effect of reducing the specific surface area due to the above-mentioned shrinkage and smoothing is exerted. Get smaller. In addition, JP-A-5-29
As described in 0848, the effect of reducing the specific surface area is also small when the powder obtained by carbonizing the bulk mesophase and then pulverizing is used. Therefore, it is possible to generate a bulk mesophase by heat treatment at 520 ° C or lower, and after crushing to a predetermined particle size, perform calcination for carbonization and graphitization without crushing at all. Is important to get.

The firing atmosphere during carbonization is an inert gas (eg,
Either a rare gas such as argon, nitrogen, etc. or a reducing gas (eg, hydrogen or hydrogen + inert gas) may be used. If the firing atmosphere during carbonization is oxidative, carbon is partially oxidized, which causes a decrease in crystallinity after graphitization and an increase in specific surface area. Therefore, the concentration of oxidizing gas such as oxygen, water vapor and carbon dioxide in the firing atmosphere should be as low as possible.

The rate of temperature rise during carbonization is preferably about several degrees Celsius / min or less. If the rate of temperature rise at this time is extremely high (for example, when heating in a fluidized bed, etc.
/ Min), the carbon foams to lower the density and increase the specific surface area. In this carbonization stage, heating is usually carried out at a temperature within the range of 700 to 1100 ° C, and this temperature is maintained for about 1 to 10 hours.

The carbonized powder obtained is heated in a graphitizing furnace to a temperature necessary for graphitization, usually 2500 ° C. or higher, preferably 2800 ° C. or higher, for graphitization. The temperature rise rate and the atmosphere for graphitization may be almost the same as those for carbonization, but at the graphitization temperature, reducing gases such as hydrogen and, in some cases, nitrogen may also react with carbon. An atmosphere of active gas is preferred.

In the present invention, after the firing raw material is heated to a temperature higher than 520 ° C., pulverization treatment that does not change the particle diameter of the powder is carried out both after carbonization and after graphitization.
The reason for this is that, as described above, if the pulverization treatment is performed after heating to a temperature higher than 520 ° C., the effect of reducing the specific surface area cannot be obtained, or the specific surface area increases.

Although the powder may be in a lightly adhered state after carbonization or graphitization, such an adhered powder may be forced through a sieve or mixed with a mixer. The method of disintegration may be carried out because it has a very small effect on the specific surface area.

The carbon powder produced by the method of the present invention has a high crystallinity of d ₀₀₂ of 3.362 Å or less because the bulk mesophase is graphitized without oxidation.
Further, since it is crushed before being heated to 520 ° C. and then fired as it is, closed pores and smoothing of the fracture surface occur during the carbonization and graphitization processes, and the specific surface area becomes as small as 1 m ² / g or less. Therefore,
When a lithium ion secondary battery is constructed by using this carbon powder as a negative electrode active material, the use efficiency of the electrolytic solution and lithium is high,
A battery having a large discharge capacity can be obtained.

Further, since the pulverized raw material of bulk mesophase is the raw material for firing, the particle morphology of the powder is non-spherical, unlike the one obtained by firing mesophase microspheres.
Non-spherical particles tend to be packed more densely than spherical particles, and the packing density of the carbon powder of the negative electrode is higher, and therefore the battery capacity per volume is higher. In addition, the bulk mesophase of the raw material is cheaper and can be produced in a larger amount than the mesophase spherules, so that the production cost of the negative electrode is significantly lower than that when the mesophase spherule is used as the raw material. Furthermore, since the mesophase microspheres still have meltability, they are generally used after being subjected to an oxidation treatment, so that a graphitized carbon powder with good crystallinity cannot be obtained, but in the present invention, bulk mesophase is not oxidized. Therefore, the crystallinity is also good.

[0038]

[Examples] Example 1 Coal tar was vacuum-distilled under reduced pressure of 50 torr at 480 ° C.
After heating for 4 hours, a bulk mesophase was obtained. Observation of the obtained bulk mesophase with a polarization microscope revealed that it had a microstructure with 100% optical anisotropy of the flow structure. This bulk mesophase sample was pulverized with a hammer mill for fine pulverization (U-mizer made by Fuji Paudal) at a rotation speed of the pulverization blade of 12,000 rpm, and the powder that passed through a 100-mesh sieve was used to test the meltability ( Heating atmosphere:
The amount of powder remaining on the 32 mesh screen was 0% by weight when examined by nitrogen.

A part of this bulk mesophase was heated in a nitrogen atmosphere in a heating furnace at a heating rate of 10 ° C./hr to 500 ° C.
Heated to 520 ° C, 550 ° C, 700 ° C or 1000 ° C. Further, a part of the material heated to 1000 ° C. was transferred to a graphitization furnace under an argon atmosphere and heated to 2800 ° C. at a temperature rising rate of 10 ° C./min.

These materials (bulk mesophase and its heated sample up to 1000 ° C.) were crushed using the above hammer mill at a rotation speed of 12,000 rpm. Obtained powder 150
The particles were classified with a mesh (about 100 μm) sieve, and the average particle size of the powder that passed through the sieve was measured by a laser scattering method. Transfer the classified powder to 10 in a graphitizing furnace under an argon atmosphere.
It was heated to 2800 ° C at a temperature rising rate of ° C / min and kept at 2800 ° C for 30 minutes for graphitization.

The obtained graphitized carbon powder was first classified with a 32 mesh (about 500 μm) sieve by rubbing a medicinal herb gently, and the powder that passed through this sieve was then filtered through a 150 mesh (about 100 μm) sieve. It was classified in. Average particle size of powder passing through 150 mesh screen (laser scattering method)
, Specific surface area (nitrogen adsorption method), and interlayer distance d ₀₀₂ (X
Line diffraction, Gakushin method) was measured. The results are shown in Table 1 together with the classification results. All of these carbon powders were irregularly shaped non-spherical powders.

[0042]

[Table 1]

It can be seen from Table 1 that carbon powder having a small specific surface area can be obtained if the heating temperature before pulverizing the bulk mesophase is 520 ° C. or lower. Even if the heating temperature before pulverization is 520 ° C or less, if the bulk mesophase is not substantially meltable, the average particle size will increase substantially due to fusion of powder during graphitization treatment after pulverization. I know there isn't. On the other hand, if the temperature is higher than 520 ° C before crushing, only carbon powder with a large specific surface area can be obtained without crushing again during firing after crushing.
When heated to 00 ° C., graphitized and then pulverized, a carbon powder having a very large specific surface area was obtained.

Example 2 Coal tar was charged into the same apparatus as in Example 1 and nitrogen gas was blown into the upper space of the apparatus to prevent oxidation and maintain the liquid temperature at 500 ° C. Time processed. The obtained bulk mesophase had 100% optical anisotropy and a flow-structured microstructure, and the residual powder amount in the meltability test was 0%.

The bulk mesophase was crushed with the hammer mill used in Example 1 at 6,000 rpm and classified with a 150-mesh sieve to obtain a powder having an average particle size of 35.0 μm.
This bulk mesophase powder was heated to 700 ° C at 200 ° C / hr in a heating furnace in an argon atmosphere to carbonize it, kept at this temperature for 2 hours, then transferred to a graphitization furnace and heated in an argon atmosphere at 10 ° C / hr. The temperature was raised to 3000 ° C. at a heating rate of min, and this temperature was maintained for 30 minutes to obtain graphitized carbon powder. This carbon powder is 0% above 500 μm and 100% below 100 μm, has an average particle size of 34.7 μm and a specific surface area of 0.5 m ² / g, d
₀₀₂ was 3.3570Å. The powder had a non-spherical irregular shape.

Comparative Example 1 Coal tar was heat-treated in the same manner as in Example 1 except that the heat treatment temperature was lowered to 410 ° C. The bulk mesophase obtained was 100% optical anisotropy under a polarization microscope observation, and its microstructure had a flow structure, but the powder remaining amount in the meltability test was 98% by weight, and the The sex remained.

This bulk mesophase was pulverized and classified in the same manner as in Example 2 to obtain an average particle size of 36.2 μm.
Of the powder was carbonized and graphitized. Since the powder was fused during carbonization, the carbon powder obtained after graphitization was crushed and classified as above. In this way, the carbon powder regrinded after graphitization was 0% above 500 μm and 100% below 100 μm, with an average particle size of 32.8 μm, a specific surface area of 5.4 m ² / g, d ₀₀₂
Was 3.358Å irregularly shaped powder. When crushed at the end of carbonization and graphitized, more than 500 μm is 100% and 100 μm or less is 100%. The average particle size of carbon powder is 34.0 μm and the specific surface area is 1.8 m ² / g. d ₀₀₂ is 3.3581Å
It became.

Even if the heat treatment temperature before pulverization is 520 ° C. or lower, if the bulk mesophase used for pulverization has meltability, the powder will be fused during carbonization, and it will be necessary to pulverize again before graphitizing. The specific surface area of the obtained carbon powder was very large, and in this case as well, the specific surface area was further increased by graphitizing and then pulverizing.

Comparative Example 2 Commercially available mesophase microspheres (mesocarbon microbeads, average particle size 25 μm) were used as a firing raw material. The mesophase microspheres had already been subjected to an oxidation treatment, and the powder remaining amount in the meltability test was 0% by weight. This was carbonized and graphitized in the same manner as in Example 2.

The obtained graphitized carbon powder was classified in the same manner as in Example 1 using a 32 mesh screen and then a 150 mesh screen. 0% for powders over 500 μm, 100 μm
The following powders were 100%. The average particle size of this powder is 25
μm, the specific surface area was 0.6 m ² / g, and the d ₀₀₂ was 3.365 Å. As a result of microscopic observation, the graphite crystal structure was a structure typical of the above-mentioned mesophase microspheres, and the powder shape was spherical.

Since the mesophase spherules are subjected to the oxidation treatment, the fusion of the powder during the carbonization and graphitization is very unlikely to occur, and the spheroidal particle shape is well maintained even after the firing, so that it is obtained. The specific surface area of carbon powder is small,
It can be seen that the graphite crystallinity (d ₀₀₂ ) is inferior.

[0052]

Industrial Applicability According to the present invention, a graphitized carbon powder having good crystallinity and a small specific surface area can be produced by using bulk mesophase, which is an inexpensive material as compared with mesophase microspheres, as a raw material. Therefore, by using this graphitized carbon powder as a negative electrode active material, it is possible to economically manufacture a lithium ion secondary battery having a high discharge capacity and a small irreversible capacity and a high utilization efficiency of lithium and an electrolytic solution. Be expected.

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[Procedure amendment]

[Submission date] December 4, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Method of producing carbon powder for negative electrode of lithium-ion secondary battery

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction contents]

[0001]

The present invention relates to relates to the production how the carbon powder of the negative electrode active material as a good crystallinity graphite in a suitable low specific surface area of the lithium ion secondary battery.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C10C 3/14 C10C 3/14 H01M 4/02 H01M 4/02 D 4/04 4/04

Claims (2)

[Claims] 1. Tar and / or pitch between 430 and 52
A bulk mesophase having an optically anisotropic microstructure and having a powder remaining amount of 5% by weight or less in a meltability test was prepared by heat treatment at 0 ° C., pulverized, and then calcined in a non-oxidizing atmosphere as it is. And graphitizing the carbon powder for a negative electrode of a lithium-ion secondary battery. 2. A specific surface area of 1 m ² / g or less and an interlayer distance d _002.
A negative electrode material for a lithium-ion secondary battery, which is composed of non-spherical graphitic carbon powder having a particle size of 3.362 Å or less.