JPH1167201A - Carbon material for lithium ion secondary battery negative electrode and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon material for a lithium ion secondary battery negative electrode with high charge/discharge capacity, high initial charge/ discharge efficiency, high charge/discharge speed, and high charge/discharge cycle characteristics, and its manufacturing method. SOLUTION: In this manufacturing method, a carbonaceous powder material filled in a container, having a filling density of 0.5-1.3 g /cm<3> is heat-treated at temperatures from room temperature to 1,500 deg.C in an atmosphere containing oxygen having an initial concentration of 1×10<-6> to 10×10<-6> mole/cm<3> , then graphitized at 2,400 deg.C or higher in an non-oxidizing, inert gas atmosphere, then cooled to 300 deg.C or lower. The carbon material obtained has such physical properties that the ratio of peak intensity (I1580 ) of a spectrum in a wave band of 1,580±100 cm<-1> to peak intensity (I1360 ) of a spectrum in a wave band of 1,360±100 cm<-1> is less than 0.2 in a laser Raman spectrum, and the intensity ratio of (101) diffraction peak to (100) diffraction peak in X ray diffraction is 1.0 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon material suitable for a negative electrode material for a lithium ion secondary battery and a method for producing the same, and more particularly, to an excellent initial charge / discharge efficiency, high energy density, and The present invention relates to a carbon material for a negative electrode capable of providing a lithium ion secondary battery having excellent charge / discharge cycle characteristics and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, electronic devices have undergone rapid technological development with the aim of miniaturization, weight reduction, and high performance. As a result, portable electronic devices such as cellular phones, PHSs, camcorders, and personal computers have become more widespread. Advanced. With the development of these new devices, nickel-metal hydride batteries and lithium-ion secondary batteries have emerged as new secondary batteries. In particular, a lithium ion secondary battery has many advantages such as a high energy density and a high electromotive force, a wide operating temperature range due to the use of a non-aqueous electrolyte, excellent long-term storage, and light weight and small size. doing. Therefore, such a lithium ion secondary battery is expected to be put to practical use as a high-performance battery for a power source of a portable electronic device, an electric vehicle, a power storage device, and the like. The performance and safety of the lithium ion secondary battery were improved by using a carbon-based material instead of lithium metal for the negative electrode. That is, when the carbon-based material is used for the negative electrode, lithium dendrites are not formed because lithium ions are incorporated into the carbon structure, and safety is dramatically improved. There are two types of carbon-based materials used for the negative electrode. At present, low-crystalline carbonaceous materials such as baked products of furfuryl alcohol, graphitized products of mesocarbon microbeads (MCMB), and natural graphite are available. And other graphitic materials have been put to practical use. Among them, the carbonaceous material is characterized by a large amount of lithium taken in by weight, that is, a large capacity per weight, and far exceeds 372 mAh / g, which is the theoretical capacity of graphite, which is the capacity of C ₆ Li. Various carbon materials exhibiting discharge capacity have been reported. However, these carbonaceous materials have problems such as low initial charge / discharge efficiency (initial discharge capacity / initial charge capacity), poor cycle characteristics, and low density of the carbonaceous material itself. There are various problems that need to be solved when used in a secondary battery.

On the other hand, in the case of the graphitic carbon material, the reaction mechanism consists of a simple reaction of intercalation and deintercalation of lithium between graphite layers, and the initial charge / discharge efficiency is relatively high. In addition, since the density of the graphitic carbon material itself is high, high energy per volume can be obtained, and in this respect, expectations are increasing. However, in the case of natural graphite, the degree of graphitization is high and the chargeable / dischargeable capacity per unit weight is considerably large,
On the other hand, there is a problem in that charge / discharge efficiency and cycle characteristics are reduced when charge / discharge is performed at a high current density. Such a material is used for a negative electrode of a high-load power supply that needs to take out a large current and that is preferably charged at a high current density in order to shorten a charging time, for example, a power supply for a device having a drive motor or the like. Is not suitable. JP-A-5-325967 discloses such a graphitic carbon material.
A carbon fiber obtained by graphitizing carbon fibers using a pitch having a volume content of 70% or more of the mesophase as a raw material is disclosed, and it is pointed out that various battery characteristics are excellent. According to the above publication, the mesophase pitch used as a raw material is not particularly limited as long as it has a high graphitization property, and the spinning conditions and the infusibilizing conditions are not limited at all. However, in the current situation where higher performance negative electrode materials are required, the above-mentioned carbon materials are still not satisfactory in various battery characteristics, and are further manufactured under specific manufacturing conditions using specific raw materials. Production of a high-performance negative electrode material with stable quality by the method described above has been demanded.

[0004]

The present invention has been made under such circumstances. That is, the present invention provides a carbon material for a negative electrode of a lithium ion secondary battery having a large charge / discharge capacity, a high initial charge / discharge efficiency, a high charge / discharge rate, and excellent charge / discharge cycle characteristics, and a method for producing the same. The purpose is to provide.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have studied from various angles a method for producing a graphite-based carbon material for a negative electrode of a lithium ion secondary battery. As a result, it was found that only when the carbon material was manufactured under specific manufacturing conditions, it was possible to obtain a graphite-based carbon material for a negative electrode that could achieve the above object, and completed the present invention. Was. That is, the present invention

[0006] Packing density 0.5 to 1.3 g / cm^ThreeIn container
The carbonaceous powder material filled in
At an initial concentration of 1 × 10^-6-10 × 10^-6Mol /
cm ^ThreeAfter heat treatment in an atmosphere containing oxygen
Continuously at 2400 ° C or higher in a non-oxidizing inert gas atmosphere
Graphite at temperature, then cooled to below 300 ° C
Method for producing carbon material for negative electrode of lithium ion secondary battery
And then calcined at a temperature of 400 to 1500 ° C.
That the particle size has been adjusted to an average particle size of 100 μm or less.
Characteristic for the negative electrode of the lithium ion secondary battery described above
Manufacturing method of carbon material, or carbonaceous powder material melt spinning mesophase pitch
And then infusibilized and fired at a temperature of 400-1500C
After crushing, the particle size was adjusted to an average particle size of 100 μm or less.
The lithium ion as described above, characterized in that
A method for producing a carbon material for a secondary battery negative electrode.
And the present invention is 1580 ± 100 cm in laser Raman spectroscopy.^-1
Peak intensity (I₁₅₈₀)
1360 ± 100cm for^-1In the wavelength range of
Peak intensity (I₁₃₆₀) Is less than 0.2 and X-ray times
(101) and (100) diffraction peaks due to fold
Wherein the intensity ratio of the above is not less than 1.0.
A lithium ion secondary battery produced by the method according to any one of
A carbon material for a secondary battery negative electrode.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the present invention, as a carbon material for producing a graphite-based carbon material used for a negative electrode material for a lithium ion secondary battery, an easily graphitizable material in which a graphite structure is easily developed is preferable. For this purpose, it is preferable to promote the orientation of the carbon hexagonal mesh plane by once bringing the easily graphitizable pitch into a molten state, and then calcinate at a temperature of 400 to 1500 ° C. to carbonize. At this time, it is more preferable to forcibly increase the orientation by applying a stress in a molten state. Specifically, it is preferable to form into mesophase pitch-based carbon fibers or mesocarbon microbeads. In the present invention, uniform powder can be obtained by further adjusting the particle size by a method such as pulverization, and stable production can be achieved. And stabilization of quality can be achieved. Generally, when powder is used as a carbonaceous material, a difference occurs between the surface and the internal carbon structure in the graphitization treatment. In other words, the inside of the powder has a relatively developed structure with a graphite structure, but the surface is generally affected by the external environment, and the structure is such that the development of the graphite structure is suppressed, or the graphite structure develops. Even if it does, the basal surface of graphite is usually exposed, and it becomes a structure which is disadvantageous for the entrance and exit of lithium ions in the battery reaction. Furthermore,
Since many active sites and functional groups reacting with the battery electrolyte, the electrolytic solution and lithium ions are present on the surface of the powder, the charge-discharge efficiency and the cycle characteristics are adversely affected. The present inventors have conducted intensive studies to solve these disadvantages,
The present invention has been completed.

(1) Raw Material Pitch The raw material for producing the carbonaceous powder material is not limited to any of resin-based, petroleum-based, coal-based, and synthetic pitches using a catalyst or the like. However, in the present invention,
It is preferable that the mesophase pitch is easily graphitizable. In particular, the aromatic carbon ratio fa is 0.5 or more, and furthermore,
It is preferably 0.6 or more. Here, the aromatic carbon ratio is a ratio of carbon atoms forming an aromatic ring structure to all carbon atoms, and in the case of all aromatic carbons such as naphthalene, fa = 1. In the present invention, the above fa is 0.
When it is smaller than 5, the planar structure of the aromatic molecules constituting the mesophase is low, and the carbon material obtained from such a pitch is difficult to graphitize even if it is graphitized at a high temperature. In some cases, the charge / discharge capacity of the negative electrode of the secondary battery does not increase.

(2) Carbonaceous Powder Material Since the carbon material used for the negative electrode material for a lithium ion secondary battery is used after being applied in the form of a sheet, it needs to be in a powder form. With regard to the carbon material of the present invention, various methods can be used as a method for forming a powder and a method for adjusting the particle size, but in the present invention, it is preferable to form and pulverize once in a molten state. That is, for example, a method in which a heated and melted pitch is carbonized within a predetermined temperature range without making it infusible, and then physically pulverized, or the mesocarbon microbeads are captured from a state in which the mesophase pitch is melted or melt-dispersed or precipitated. For example, there may be used a method of pulverizing and granulating the mesophase pitch, a method of forming a mesophase pitch into a fiber by a melt spinning method, making it infusible or carbonized, and then pulverizing. A resin obtained by carbonizing a resin insoluble in a solvent, a pitch or a thermosetting resin without passing through a molten state may not show a remarkable effect even when the method of the present invention is used. This is presumably because the graphite crystal is easily oriented inside the powder by passing through the solution or the molten state, and a powder surface layer different from the inside is formed.

(3) Graphitization As a general method of graphitizing a powder, a graphite container is filled with a carbonaceous powder material, and is placed under an inert atmosphere under an inert atmosphere.
A method of performing a heat treatment at a temperature of not less than ° C. Various studies were made on the graphitization conditions when producing a high-performance carbon material suitable for a negative electrode material for a lithium ion secondary battery by graphitization. 1500 ° C, preferably 300 to 1
By bringing the powder into contact with oxygen in the temperature range of 000 ° C, carbon and functional groups that are less likely to have a graphite structure that hinders the intercalation and deintercalation of a small amount of lithium ions in the powder surface layer It was found that a high-capacity, high-efficiency material can be obtained by developing a graphite structure at a temperature of 2400 ° C. or higher and not contacting with oxygen until the temperature reaches 300 ° C. or lower during cooling. .

[0011] The carbonaceous powder material to be graphitized is subjected to a temperature of 400 to 1500 ° C, preferably 600 to 100 ° C, prior to the treatment in order to prevent agglomeration and sticking due to generation of volatiles and tar.
Desirably, it is carbonized by firing at a temperature of 0 ° C. The temperature of carbonization cannot be unconditionally determined because there is a trade-off between time and amount. However, at a temperature lower than 400 ° C., agglomeration and sticking are liable to occur in the graphitized material, resulting in poor powder production yield. Tend to be. If the temperature is higher than 1500 ° C., the amount of powder having exposed basal surface of graphite increases in the pulverization step after carbonization, and the negative electrode characteristics may be impaired.
In addition, the average particle size of the powder is 100 from the viewpoint of sheet density and handleability when producing a negative electrode sheet.
μm or less, more preferably 50 μm or less.

In the present invention, further, the average particle size is preferably 100
When the carbonaceous powder material adjusted to a particle size of μm or less is graphitized, the packing density of the graphite material or the like in a heat-resistant container is set to 0.5 to 1.3 g / cm ^3, and from room temperature to 1500 ° C. Is performed in an atmosphere having an initial oxygen concentration of 1 × 10 ⁻⁶ to 10 × 10 ⁻⁶ mol / cm ³ , and then graphitized at a temperature of 2400 ° C. or more in a non-oxidizing inert gas atmosphere. , 3
The object of the present invention is achieved by performing a cooling treatment to a temperature of 00 ° C. or lower. That is, during the heat treatment from room temperature to 1500 ° C., the oxygen at a predetermined initial concentration is mainly consumed by the reaction on the surface of the carbonaceous powder.
The heat treatment such as a cooling treatment is performed in a reduced pressure atmosphere or an inert gas atmosphere such as air from which oxygen has been removed, nitrogen or argon. The heat treatment temperature in the oxygen-containing atmosphere is 1500 ° C.
When the ratio exceeds, the powder is consumed by oxidation to the inside of the powder, and the production yield is extremely lowered, which is not preferable.

Further, the initial oxygen concentration is 1 × 10^-6Mole
/ Cm^ThreeIf lower, the surface of powder particles by oxygen
The reforming effect is not sufficiently exhibited, and the oxygen concentration is 10 ×
10 ^-6Mol / cm^ThreeThe higher the value, the higher the carbonaceous powder material
Decrease in yield due to oxidation consumption of
Oxidation consumption of furnace materials and containers made of steel becomes remarkable and cost
Disadvantageous. In particular, graphitization at a temperature of 2400 ° C or higher
When oxygen is present, the presence of oxygen in the carbonaceous powder material
The yield has been significantly reduced due to
In the present invention, the initial oxygen concentration is controlled
It is important to do it. Furthermore, the capacity of secondary batteries is graphitized.
Tend to increase as the degree of
When the temperature is lower than 2400 ° C., the progress of graphitization is low.
This is not preferable because the battery capacity decreases.

In view of the above, in the present invention, the graphitization treatment is more preferably performed at a temperature of 2400 to 3200 ° C. At a temperature exceeding 3200 ° C., the cost of graphitization becomes extremely high, including maintenance costs. The packing density is largely affected by the particle size, surface area and carbonization temperature.
The average particle size heat treated at a temperature of 00 to 1500 ° C. is 10
0.5 to 1.3 g for a carbonaceous powder material of 0 μm or less
/ Cm ³ , and more preferably 0.8 to 1.2 g / cm ³ . In order to increase the packing density to a value higher than 1.3 g / cm ^3, an operation such as applying a mechanical force is required at the time of filling, which is disadvantageous from the viewpoint of workability and the like. There is a drawback that the quality is not constant due to the occurrence of the problem. On the other hand, if the packing density is less than 0.5 g / cm ³ , the productivity is poor and the cost is high. Also, in the cooling process to a temperature of 300 ° C. or less after the graphitization treatment, if oxygen is present, the yield decreases, the functional groups are formed on the powder surface, and the negative electrode material characteristics considered to be due to the formation of heterogeneous carbon. There is a decrease. That is, the powder removal operation is performed at 300 ° C
It is preferable to carry out after cooling below. Room temperature to 15
Time to contact oxygen with temperature up to 00 ° C, 2400 ° C
The graphitization time and cooling time at the above temperatures are not uniquely determined depending on the properties of the carbonaceous powder material, such as the degree of carbonization and surface area, and are not determined uniquely. It can be appropriately adjusted in consideration of performance.

The graphitic powder material subjected to the graphitization treatment according to the production method of the present invention has a particle size of 15% by laser Raman spectroscopy.
The ratio of the peak intensity (I ₁₃₆₀ ) of the spectrum in the wavelength range of 1360 ± 100 cm ⁻¹ to the peak intensity (I ₁₅₈₀ ) of the spectrum in the wavelength range of 80 ± 100 cm ⁻¹ is
Less than 0.2, preferably 0.18 or less, and X-ray diffraction (XR
The intensity ratio between the (101) diffraction peak and the (100) diffraction peak according to D) is 1.0 or more, preferably 1.15 or more, and exhibits high performance lithium ion secondary battery negative electrode characteristics. . That is, when the peak ratio in the laser Raman spectroscopy is 0.2 or more, the cycle characteristics and the charge / discharge capacity of the battery are poor, and when the peak ratio of XRD is less than 1.0, the charge / discharge capacity is also poor. It will be.

[0016]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Example 1 A petroleum catalytic cracking oil having a number average molecular weight of 280 and fa = 0.68 was used as a raw material, and 5 mol of hydrogen fluoride was added to 1 mol of the oil.
In a molar autoclave, the boron fluoride was added to 0.
After supplying 5 mol, heat treatment was performed at 300 ° C. for 3 hours.
Using the obtained mesophase pitch as a raw material, a width of 1.5 mm
Spinning holes with a diameter of 0.2 mm in a row of 40
Using a mouthpiece having zero pieces, heated air was blown out from the slits, and the molten pitch was drawn to produce pitch fibers having an average diameter of 13 μm. The spun fibers are collected on the belt while being sucked from the back of a belt made of stainless steel mesh having a mesh of 15 mesh, and then collected at 170 ° C. in air.
To 300 ° C. at an average temperature rising rate of 7 ° C./min to perform infusibility treatment. The obtained infusibilized yarn is placed under a nitrogen atmosphere,
After firing at 650 ° C., the mixture was pulverized to obtain a carbon fiber powder having an average particle diameter of 20 μm. As described in the obtained mesoface pitch-based carbon fiber powder (CF) and JP-A-60-51612, a boiling point of 200 ° C. from which free carbon was removed.
The above coal tar is heated at a temperature of 400 ° C. and a pressure of 8 kg / cm.
Heat-treated under ² G conditions for 14 hours and centrifuged at 450 ° C. to give carbonized mesocarbon microbeads (MCMB) having an average particle size of 15 μm in a graphite container in which atmosphere gas can be replaced. Is 0.8 g / cm ³
In the atmosphere (oxygen concentration 8.9 × 10 ^-6 mol / cm
^The mixture was filled in ³ ), and the gas inlet valve was closed, and the heat treatment was performed to 1000 ° C. with the outlet sealed with water. Next, the inlet valve is opened and graphitization treatment is performed at 2900 ° C. for 1 hour while flowing a slight amount of nitrogen gas. Then, while increasing the nitrogen gas flow rate to such an extent that gas can be confirmed to flow out from the outlet water seal portion, the mixture is cooled to room temperature and graphite is cooled. A high quality carbon powder was obtained. The physical properties and the negative electrode characteristics of the lithium ion secondary battery of the obtained graphitic carbon powder were measured and evaluated by the following methods. The results are shown below and in Table 1.

CF MCMB Raman peak ratio (R = I ₁₃₆₀ / I ₁₅₈₀ ) ^{* 1} 0.15 0.13 XRD peak ratio [K = (101) / (100)] 1.21 1.22 Initial efficiency (discharge amount) / Charge amount, 1st cycle) (%) 93 91 Discharge amount (5th cycle) (mAH / g) ^{* 2} 319 308 * 1: Argon ion laser light was used as the light source, and Nippon Bunko Kogyo NRS2000 was used as the spectroscope. It measured using. * 2: For measurement, use lithium metal for the anode and reference electrode, and mix perchloric acid as the electrolyte in a mixed carbonate ester solvent in which ethylene carbonate (EC) / dimethyl carbonate (DMC) was adjusted to a volume ratio of 1/1. The charge and discharge capacity characteristics were measured in an electrolytic solution in which lithium (LiClO ₄ ) was dissolved at a concentration of 1 mol. The measurement of the charge / discharge capacity characteristic was performed under a constant current charge / discharge of 100 mA / g, and the measurement potential range was 0 to 1.5 V / Li / Li ⁺ (reference electrode), and the measurement was repeated 10 times.

Example 2 Atmosphere gas was replaced with mesophase pitch-based carbon fiber powder having an average particle size of 20 μm and a carbonized mesocarbon microbead having an average particle size of 15 μm obtained at 1500 ° C. and baked at 1500 ° C. in the same manner as in Example 1. In a graphite container that can be
After filling the container to a packing density of 1.2 g / cm ³ and replacing the inside of the container with nitrogen gas having an oxygen concentration of 2.0 × 10 ⁻⁶ mol / cm ³ , close the gas inlet valve and seal the outlet with water. In this state, heat treatment was performed to 1500 ° C. Next, the inlet valve is opened and graphitization is performed at 2900 ° C. for 1 hour while flowing a small amount of nitrogen gas. Then, while increasing the flow rate of nitrogen gas to such an extent that the gas can be confirmed to flow out from the outlet water seal portion, it is cooled to room temperature and the graphite is cooled. A high quality carbon powder was obtained. The physical properties and the negative electrode characteristics of the lithium ion secondary battery of the obtained graphitic carbon powder were measured and evaluated by the above-mentioned methods. The results are shown below and in Table 1. CF MCMB Raman peak ratio (R = I ₁₃₆₀ / I ₁₅₈₀ ) ^{* 1} 0.09 0.10 XRD peak ratio [K = (101) / (100)] 1.17 1.21 Initial efficiency (discharge amount / charge amount) , 1st cycle) (%) 91 90 Discharge amount (5th cycle) (mAH / g) ^{* 2} 301 294

Example 3 The same carbonaceous powder material as in Example 1 was placed in a graphite container with a lid having airtightness to such an extent that the material was not spilled so that the packing density was 0.8 g / cm ^3. Medium (oxygen concentration 8.9 ×
^10-6 mol / cm ³ ), and the surroundings are covered with coke powder to the extent that new oxygen does not enter during the graphitizing process while maintaining the heat insulating property. The mixture was cooled to near to obtain a graphitic carbon powder. When the oxygen concentration was measured at 1500 ° C. during the temperature rise and inside the container at 500 ° C. during the cooling, no oxygen was detected. The physical properties and the negative electrode characteristics of the lithium ion secondary battery of the obtained graphitic carbon powder were measured and evaluated by the above-mentioned methods. The results are shown below and in Table 1. CF MCMB Raman peak ratio (R = I ₁₃₆₀ / I ₁₅₈₀ ) ^{* 1} 0.13 0.14 XRD peak ratio [K = (101) / (100)] 1.23 1.25 Initial efficiency (discharge amount / charge amount) , 1st cycle) (%) 93 91 Discharge amount (5th cycle) (mAH / g) ^{* 2} 317 311

COMPARATIVE EXAMPLE 1 Except that the atmosphere was replaced with argon until oxygen was no longer detected under the initial conditions of the graphitization treatment, and the argon atmosphere was maintained until the graphitization treatment and the cooling-out to room temperature.
Graphitic carbon powder was obtained in the same manner as in Example 1. The physical properties and the negative electrode characteristics of the lithium ion secondary battery of the obtained graphitic carbon powder were measured and evaluated by the above-mentioned methods. The results are shown below and in Table 1. CF MCMB Raman peak ratio (R = I ₁₃₆₀ / I ₁₅₈₀ ) ^{* 1} 0.22 0.25 XRD peak ratio [K = (101) / (100)] 0.97 0.92 Initial efficiency (discharge amount / charge amount) , 1st cycle) (%) 81 83 Discharge amount (5th cycle) (mAH / g) ^{* 2} 264 253

Comparative Example 2 A graphitic carbon powder was obtained in the same manner as in Example 1 except that the oxygen concentration, which was the initial condition for the graphitization treatment, was 0.8 × 10 ⁻⁶ mol / cm ³ . The physical properties and the negative electrode characteristics of the lithium ion secondary battery of the obtained graphitic carbon powder were measured and evaluated by the above-mentioned methods. The results are shown below and in Table 1. CF MCMB Raman peak ratio (R = I ₁₃₆₀ / I ₁₅₈₀ ) ^{* 1} 0.26 0.23 XRD peak ratio [K = (101) / (100)] 0.94 0.88 Initial efficiency (discharge amount / charge amount) , 1st cycle) (%) 85 85 Discharge amount (5th cycle) (mAH / g) ^{* 2} 281 268

Comparative Example 3 A graphitic carbon powder was obtained in the same manner as in Example 1 except that the oxygen concentration was changed to 15 × 10 ⁻⁶ mol / cm ³ . The physical properties and the negative electrode characteristics of the lithium ion secondary battery of the obtained graphitic carbon powder were measured and evaluated by the above-mentioned methods. The results are shown below and in Table 1. The product yield was reduced by 5%, the coating property and the discharge capacity at the 10th cycle were reduced, and the battery performance such as cycle property was not good. CF MCMB Raman peak ratio (R = I ₁₃₆₀ / I ₁₅₈₀ ) ^{* 1} 0.15 0.13 XRD peak ratio [K = (101) / (100)] 1.21 1.22 Initial efficiency (discharge amount / charge amount) , 1st cycle) (%) 93 91 Discharge amount (5th cycle) (mAH / g) ^{* 2} 300 295 Discharge amount (10th cycle) (mAH / g) ^{* 2} 282 265

COMPARATIVE EXAMPLE 4 Until no oxygen was detected under the initial conditions of the graphitization treatment, the atmosphere was sufficiently replaced with argon, and the mixture was heat-treated to 1600 ° C. and had an oxygen concentration of 1 × 10 ⁻⁶ mol / cm ³ at 1600 ° C. After flowing argon gas for the volume of the graphite container (10 minutes), the process was switched to argon gas again and the same processing as in Example 1 was performed. Regarding the obtained graphitic carbon powder, the battery performance of the product was good, but the product yield was reduced by 8%, and the oxidative consumption of the upper container was remarkable.

Comparative Example 5 Graphitic carbon powder was obtained in the same manner as in Example 1 except that the temperature was changed from 600 ° C. to an air atmosphere and cooled to room temperature after the graphitization. The physical properties and the negative electrode characteristics of the lithium ion secondary battery of the obtained graphitic carbon powder were measured and evaluated by the above-mentioned methods. The results are shown below and in Table 1. CF MCMB Raman peak ratio (R = I ₁₃₆₀ / I ₁₅₈₀ ) ^{* 1} 0.42 0.54 XRD peak ratio [K = (101) / (100)] 1.10 1.16 Initial efficiency (discharge amount / charge amount) , 1st cycle) (%) 82 81 Discharge amount (5th cycle) (mAH / g) ^{* 2} 276 259

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

As described above in detail, according to the manufacturing method of the present invention, lithium having a large charge / discharge capacity, a high initial charge / discharge efficiency, a high charge / discharge rate, and excellent charge / discharge cycle characteristics is obtained. A carbon material for a negative electrode of an ion secondary battery can be obtained.

Claims (4)

[Claims] 1. A packing density of 0.5 to 1.3 g / cm.^ThreeIn the container
From the filled carbonaceous powder material to room temperature to 1500 ° C
At an initial concentration of 1 × 10^-6-10 × 10 ^-6Mol / c
m^ThreeAfter heat treatment in an atmosphere containing oxygen
Subsequently, in a non-oxidizing inert gas atmosphere, a temperature of 2400 ° C. or more
And then cooled to a temperature below 300 ° C.
For producing a carbon material for a negative electrode of a lithium ion secondary battery. 2. The carbonaceous powder material is characterized in that a carbonized material obtained by passing a graphitizable pitch through a molten state and then calcining at a temperature of 400 to 1500 ° C. is adjusted to an average particle diameter of 100 μm or less. The method for producing a carbon material for a negative electrode of a lithium ion secondary battery according to claim 1. 3. The carbonaceous powder material is obtained by melt-spinning a mesophase pitch, then infusibilizing and firing at a temperature of 400 to 1500 ° C., and then pulverizing to adjust the particle size to an average particle size of 100 μm or less. The method for producing a carbon material for a negative electrode of a lithium ion secondary battery according to claim 1. 4. 1580 ± 1 in laser Raman spectroscopy
Ratio is less than 0.2 of the spectrum of the peak intensity at 1360 wavelength range of ± 100 cm ^-1 to the peak intensity of the spectrum (I ₁₅₈₀₎ in the wavelength range of 100 cm ^-1 (I _1360), and by X-ray diffraction (101) diffraction Peak and (10
0) The carbon material for a negative electrode of a lithium ion secondary battery produced by the method according to any one of claims 1 to 3, wherein the intensity ratio of the diffraction peak is 1.0 or more.