WO2020137909A1 - Graphite material for negative electrode of lithium-ion secondary battery - Google Patents

Abstract

This graphite material for a negative electrode of a lithium-ion secondary battery: has an average plane interval d002 of (002) planes of 0.3354-0.3370 nm as determined by X-ray diffraction measurement; shows that the ratio ID/IG between an intensity (ID) of a peak within 1300-1400 cm-1 and an intensity (IG) of a peak within 1580-1620 cm-1 as respectively determined by Raman spectroscopic measurement is 0.09-0.40; has a surface roughness of 6.0-14.0; has optically anisotropic domains, the area of which accounts for 95.0-99.0% with respect to 100.0% of the sum total area of the optically anisotropic domains, optically isotropic domains, and voids; and satisfies (1) 5 μm2≤Da(10)≤20 μm2, (2) 40 μm2≤Da(50)≤250 μm2, and (3) 200 μm2≤Da(90)≤500 μm2, where the area of the largest domain is defined as Da(n) when an integrated value obtained by integrating the areas of the optically anisotropic domains sequentially, starting with the smallest one, reaches n % of the total area of all the optically anisotropic domains.

Description

[Title of invention determined by ISA based on Rule 37.2] Graphite material for negative electrode of lithium-ion secondary battery

The present invention relates to a graphite material for a negative electrode of a lithium ion secondary battery, and a lithium ion secondary battery and an all-solid-state lithium ion secondary battery using the graphite material as a negative electrode material.

▽As a power source for mobile devices, lithium-ion secondary batteries have become the mainstream because of their large energy density and long cycle life. Since the functions of mobile devices are diversified and the power consumption is increased, it is required for lithium ion secondary batteries to further increase the energy density thereof and at the same time improve the charge/discharge cycle characteristics. In addition, recently, there is an increasing demand for high-output and large-capacity secondary batteries for electric tools such as electric drills and hybrid vehicles. Conventionally, lead secondary batteries, nickel-cadmium secondary batteries, and nickel-hydrogen secondary batteries have been mainly used in this field, but expectations for small, lightweight, high energy density lithium ion secondary batteries are high, and large currents are high. A lithium ion secondary battery having excellent load characteristics (rate characteristics) is required.

Particularly, in automobile applications such as battery electric vehicles (BEV) and hybrid electric vehicles (HEV), long-term cycle characteristics for 10 years or more and rate characteristics for driving a high-power motor are mainly required characteristics, Furthermore, a high volumetric energy density is required to extend the cruising range, which is severe compared to mobile applications.

This lithium-ion secondary battery generally uses a metal oxide such as lithium cobalt oxide or lithium manganate or a composite oxide thereof as a positive electrode active material, a lithium salt as an electrolyte solution, and a graphite as a negative electrode active material. Carbonaceous materials are used. As graphite, there are natural graphite and artificial graphite.

-Natural graphite is generally inexpensive and has the advantage of high capacity because it is highly crystalline. However, since it is scaly in shape, when it is made into a paste with a binder and applied to a current collector, natural graphite is oriented in one direction. When charged with such an electrode, the electrode expands in only one direction, and the performance as an electrode such as current characteristics and cycle life is deteriorated. Although spheroidized natural graphite obtained by granulating natural graphite into spheres has been proposed, the spheroidized natural graphite is crushed and oriented by the press during electrode production. Further, as a drawback of high crystallinity, a large amount of gas is generated at the time of initial charging due to the high surface activity of natural graphite, and the initial efficiency is low, which further deteriorates the cycle life. In order to solve these problems, Patent Document 1 proposes a method of coating artificial carbon on the surface of natural graphite processed into a spherical shape. However, although the material produced by this method can meet the high capacity, low current and medium cycle characteristics required for mobile applications, etc., it can meet the requirements for large current and long cycle characteristics of large batteries as described above. Very difficult to meet. In addition, natural graphite has many metal impurities such as iron, which is problematic in terms of quality stability.

▽As artificial graphite, those obtained by graphitizing petroleum, coal pitch, coke, etc. can be obtained at relatively low cost. However, the needle-shaped coke having good crystallinity becomes scaly and is easily oriented. In order to solve this problem, the method described in Patent Document 2 has been successful. In this method, not only fine powder of artificial graphite raw material but also fine powder of natural graphite and the like can be used, and it has high capacity and excellent characteristics as the graphite for small lithium ion secondary batteries to date. However, in order to satisfy the required characteristics for automotive applications, it is essential to improve productivity with an increase in the amount used, reduce manufacturing cost, control impurities, and improve cycle characteristics and storage characteristics.

Further, the negative electrode material using so-called hard carbon or amorphous carbon described in Patent Document 3 has excellent characteristics with respect to a large current, and also has relatively good cycle characteristics. However, the volume energy density is too low and the price is very expensive, so that it is used only for some special large batteries.

Japanese Patent No. 3534391 Japanese Patent No. 3361510 JP-A-7-320740

An object of the present invention is to provide a graphite material for a lithium-ion secondary battery negative electrode, which can be used to manufacture an electrode having both high cycle characteristics, high rate characteristics, and high energy density required for a large battery.

The present invention has the following configurations.
[1] The average spacing d002 of (002) planes measured by X-ray diffraction is 0.3354 nm or more and 0.3370 nm or less,
The ratio ID / IG between peak intensity in the range of 1300 ~ 1400 cm ^-1 by Raman spectroscopic measurement (ID) and the peak intensity in the range of ^{1580 ~ 1620cm -1 (IG) (} R value) 0.09 Is 0.40 or less,
The surface roughness calculated from the ratio of the BET surface area to the sphere-converted area calculated from the particle size distribution (BET surface area/sphere-converted area) is 6.0 to 14.0,
The ratio of the area of the optically anisotropic domain is 95.0% with respect to the total area of the optically anisotropic domain, the optically isotropic domain and the void of 100.0% measured by observing the cross section of the graphite material with a polarization microscope. ~99.0%,
The integrated value when the areas of the optically anisotropic domains are integrated in order from the smallest one is the maximum domain area (μm ² ) when n% of the area (μm ² ) of all the optically anisotropic domains is reached. A graphite material for a negative electrode of a lithium ion secondary battery that satisfies the following conditions (1) to (3) when Da(n) (where n represents a numerical value in the range of 0 to 100) is satisfied.
(1) 5 μm ² ≦Da (10) ≦20 μm ²
(2) 40 μm ² ≦Da (50) ≦250 μm ²
(3) 200 μm ² ≦Da (90) ≦500 μm ²
[2] The ratio of the area of the void is 1.0% or less with respect to the total area of the optically anisotropic domain, the area of the optically isotropic domain and the area of the void of 100.0%. 1. The graphite material for a lithium ion secondary battery negative electrode according to 1.
[3] Db is the maximum domain area (μm ² ) when the total number of optically anisotropic domains arranged in ascending order of area reaches m% of the number of all optically anisotropic domains. (M) (where m represents a numerical value in the range of 0 to 100), the graphite material for a lithium ion secondary battery negative electrode according to the above 1 or 2, which satisfies the following condition (4).
(4) Db(99.5)/Da(100)≦0.75
[4] When the maximum value of the length of the long side of the optically anisotropic domain is Lmax and the 50% particle diameter (D50) in the volume-based particle diameter distribution measured by a laser diffraction method is Lave, 4. The graphite material for a negative electrode of a lithium ion secondary battery according to any one of 1 to 3 above, wherein Lmax/Lave is 1.0 or less.
[5] The 10% particle diameter (D10) in the volume-based particle diameter distribution measured by a laser diffraction method is 1.0 μm or more and 16.0 μm or less, and the 50% particle diameter (D50) is 6.0 μm or more and 30.0 μm. The graphite material for a lithium ion secondary battery electrode according to any one of 1 to 4 above, which has a 90% particle diameter (D90) of 25.0 μm or more and 80.0 μm or less.
[6] The graphite material for a lithium ion secondary battery electrode according to any one of 1 to 5 above, which has a BET specific surface area of 0.5 m ² /g or more and 6.0 m ² /g or less.
[7] The graphite material for a negative electrode of a lithium ion secondary battery according to any one of 1 to 6 above, which has a circularity of 0.89 or more and 0.98 or less.
[8] The graphite material for a lithium ion secondary battery negative electrode according to any one of 1 to 7 above, wherein the uniformity of particle size (D60/D10) is 1.5 or more and 3.0 or less.
[9] The graphite material for a negative electrode of a lithium ion secondary battery according to any one of 1 to 8 above, wherein the surface oxygen content is 0.010 or more and 0.030 or less.
[10] A negative electrode active material containing the graphite material described in any one of 1 to 9 above.
[11] A negative electrode for a lithium ion secondary battery, containing the negative electrode active material as described in 10 above.
[12] A lithium ion secondary battery using the negative electrode described in 11 above.
[13] An all-solid-state lithium ion secondary battery using the negative electrode described in 11 above.

According to the present invention, it is possible to obtain a graphite material for a lithium-ion secondary battery, which can be used to manufacture an electrode having both high cycle characteristics, high rate characteristics, and high energy density required by a large battery.

1 is a schematic diagram showing an example of the configuration of an all-solid-state lithium-ion secondary battery in one embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail.

[1] Graphite Material A graphite material for a negative electrode of a lithium ion secondary battery (hereinafter, also referred to as “graphite material (I)”) in one embodiment of the present invention will be described in detail below.

[1-1] d002, Lc
The average interplanar spacing d002 of the (002) planes of the graphite material (I) measured by X-ray diffraction is 0.3354 nm or more. 0.3354 nm is the lower limit value of d002 of the graphite crystal. The d002 is preferably 0.3356 nm or more. When the d002 is 0.3356 nm or more, the graphite crystal structure is not overdeveloped, and the cycle characteristics are excellent. Further, d002 is 0.3370 nm or less, preferably 0.3365 nm or less, more preferably 0.3360 nm or less from the viewpoint that the discharge capacity becomes large and a battery satisfying the energy density required for a large battery can be obtained. is there.

The crystallite size Lc of the (002) diffraction line of the graphite material (I) measured by X-ray diffraction is preferably 80 nm from the viewpoint that the discharge capacity becomes large and a battery satisfying the energy density required for a large battery can be obtained. Or more, more preferably 90 nm or more, and further preferably 100 nm or more. Further, the Lc(002) is preferably 1000 nm or less, more preferably 500 nm or less, still more preferably 300 nm or less, from the viewpoint that the graphite crystal structure does not develop too much and the cycle characteristics are excellent.

The graphite crystal plane spacing d002 and the crystallite size Lc can be measured using a powder X-ray diffraction (XRD) method (see Iwashita et al., Carbon vol. 42 (2004), p. 701-714).

[1-2] Surface Roughness The surface roughness of a graphite material is determined by the ratio of the BET surface area to the sphere-converted area calculated from the particle size distribution (BET surface area/sphere-converted area) (Toshio Oshima et al., Journal of Powder Engineering). , Vol. 30, No. 7, (1993) 496-501).

The surface roughness of the graphite material (I) is 6.0 or more, preferably 7.0 or more, and more preferably 8.0 or more, from the viewpoint that resistance tends to decrease and rate characteristics tend to improve. Further, the surface roughness is 14.0 or less, preferably 13.0 or less, more preferably 12.0 or less from the viewpoint of suppressing side reactions with the electrolytic solution and excellent cycle characteristics.

The BET specific surface area can be determined using a specific surface area meter using a nitrogen gas adsorption method (for example, NOVA-1200 manufactured by Quantachrome).

The sphere-converted area ( _SD ) calculated from the particle size distribution can be calculated by the following formula based on the data of the particle size distribution obtained by using a laser diffraction type particle size distribution measuring device (for example, Mastersizer manufactured by Malvern Instruments Ltd.). it can.

Vi is the relative volume of the particle size category i (average diameter d _i ), ρ is the particle density, and D is the particle size.

[1-3] Optical Structure Evaluation of Graphite Material by Polarization Microscope The optical structure of graphite material can be evaluated by a polarization microscope.

[1-3-1] Area Ratio of Optically Anisotropic Domain A graphite material is a domain that exhibits optical anisotropy (a domain in which crystals have developed and a graphite network plane is arranged. Hereinafter, referred to as an optically anisotropic domain. ) And an optically isotropic domain (a domain in which crystals are undeveloped or in which crystal disorder such as hard carbon is large. Hereinafter referred to as an optically isotropic domain) and voids. Here, the domain means a unit region where optical tissues are continuous. The measuring method is according to the method described in Examples.

In the graphite material (I), the area of the optically anisotropic domain is 95.0% or more, preferably 96% with respect to the total area of the optically anisotropic domains, optically isotropic domains, and voids of 100.0%. It is 0.0% or more. Since the optically anisotropic domain contributes to insertion/desorption of lithium ions and the like, the energy density becomes large when the content is 95.0% or more. Further, the area of the optically anisotropic domain is 99.0% or less, preferably 98.0% or less, from the viewpoint that an optically isotropic domain can be sufficiently secured and cycle characteristics and rate characteristics are excellent.

In the graphite material (I), the area of the optically isotropic domain is 100.0% of the total of the area of the optically anisotropic domain, the area of the optically isotropic domain, and the area of the voids, which is excellent in rate characteristics and cycle characteristics. Therefore, it is preferably 1.0% or more, and more preferably 1.5% or more. The area of the optically isotropic domain is preferably 5.0% or less, and more preferably 4.0% or less, from the viewpoint that the optically anisotropic domain can be sufficiently secured and the energy density is excellent.

In the graphite material (I), the area of the voids is preferably 1.0% or less, more preferably 0% with respect to the total of the area of the optically anisotropic domain, the area of the optically isotropic domain, and the area of the voids of 100.0%. It is 0.5% or less, and more preferably 0.3% or less. Since the voids do not directly contribute to charge and discharge, the energy density becomes high when the void content is 1.0% or less.

[1-3-2] Da
In the graphite material (I), from the viewpoint of the distribution of the size of the optically anisotropic domains, when the areas of the optically anisotropic domains are integrated in the order of increasing area, the integrated value is the total optical anisotropy. When the maximum domain area when n% of the domain area (μm ² ) is reached is Da(n) (where n represents a numerical value in the range of 0 to 100), the following conditions (1) to (3) is satisfied.

(1) 5 μm ² ≦Da (10) ≦20 μm ²
(2) 40 μm ² ≦Da (50) ≦250 μm ²
(3) 200 μm ² ≦Da (90) ≦500 μm ²
When the conditions (1) to (3) are satisfied, discharge capacity, cycle characteristics, and rate characteristics can all be improved.

In the condition (1), Da(10) is preferably 7 μm ² or more, more preferably 8 μm ² or more, and Da(10) is preferably 16 μm ² or less, more preferably 12 μm ² or less.

In the condition (2), Da(50) is preferably 100 μm ² or more, more preferably 150 μm ² or more, and Da(50) is preferably 230 μm ² or less, more preferably 210 μm ² or less.

The condition (3), Da (90) is preferably 250 [mu] m ² or more, more preferably 300 [mu] m ² or more, also, Da (90) is preferably 450 [mu] m ² or less, more preferably 420 [mu] m ² or less.

In addition to the conditions (1) to (3), from the same viewpoint as above, Da(30) is preferably 10 μm ² or more, more preferably 20 μm ² or more, further preferably 30 μm ² or more, and , Da(30) is preferably 90 μm ² or less, more preferably 80 μm ² or less, still more preferably 70 μm ² or less.

[1-3-3] Db/Da
In the graphite material (I), when the optically anisotropic domains are arranged in ascending order of the area from the viewpoint of the distribution of the size of the optically anisotropic domains, the total number thereof is the number of all optically anisotropic domains. When the area value of the maximum domain when it reaches m% is Db(m) (where m represents a numerical value in the range of 0 to 100), the following condition (4) is preferably satisfied.
(4) Db(99.5)/Da(100)≦0.75

When the condition (4) is satisfied, the area of the optical texture domain is sufficiently large and a large discharge capacity can be obtained. From the same viewpoint, Db(99.5)/Da(100) is more preferably 0.65 or less, still more preferably 0.55 or less.

[1-3-4] Lmax/Lave
In the optically anisotropic domain of the graphite material (I), the maximum value of the long side length is Lmax, and the 50% particle diameter (D50) in the volume-based particle diameter distribution of the graphite material (I) by the laser diffraction method. Is Lave, Lmax/Lave is preferably 1.00 or less, and more preferably 0.95 or less. When Lmax/Lave is 1.00 or less, the optically anisotropic domains are not too large, and the orientation of the carbon network in each domain is not oriented in one direction but is oriented in any direction. The expansion and contraction of the crystallite at that time are dispersed, and as a result, the amount of deformation of the electrode becomes small. As a result, the probability of losing electrical contact between particles is reduced even when charging and discharging are repeated, and cycle characteristics are improved. In addition, since the probability that the edges of graphite into and out of ions are present on the electrode surface is increased, the rate characteristic is also advantageous. The measurement of Love can be performed using a laser diffraction type particle size distribution measuring instrument such as Malvern Mastersizer.

[1-3-5] Cmin
The orientation of the optically anisotropic domain can be confirmed from the change in domain interference color when the sample is rotated from 0 to 45 degrees with respect to the analyzer of the polarization microscope. In this case, depending on the orientation of the domain, it can be classified into three types of interference colors of blue, yellow and magenta. Of the total area of each color, the smallest area ratio is represented by Cmin. The orientation is random, which means that the anisotropic structure does not grow significantly, and when the direction is small, the anisotropic structures are aligned and the anisotropic structure grows greatly.

Cmin, which represents the randomness of the orientation of the optically anisotropic domain of the graphite material (I), is preferably 20% or less, more preferably 15% or less, still more preferably 12% or less. If Cmin is 20% or less, the anisotropic structure grows sufficiently and the discharge capacity increases.

[1-4] In the Raman R value graphite material (I), 1580cm ^-1 ~ a peak intensity (ID) in the range of 1300 ~ 1400 cm ^-1 by Raman spectroscopic measurement (near the specifically 1360 cm ^-1) The intensity ratio ID/IG (R value) to the peak intensity (IG) in the range of 1620 cm ⁻¹ is 0.09 or more, preferably 0.10 or more, more preferably 0.12 or more. When ID/IG (R value) is 0.09 or more, the barrier for lithium in/out is lowered, and the current load characteristics are likely to be improved. The ID/IG (R value) is 0.40 or less, preferably 0.30 or less, and more preferably 0 or 20 or less. When ID/IG (R value) is 0.40 or less, excessive exposure of highly active edge portions can be suppressed, and Coulombic efficiency can be increased.

[1-5] Volume-Based Particle Size Distribution by Laser Diffraction Method The 50% particle size (D50) in the volume-based particle size distribution by the laser diffraction method of the graphite material (I) is preferably 6.0 μm or more, more preferably 10 μm. It is at least 0.0 μm, more preferably at least 15.0 μm. When the D50 is 6.0 μm or more, the coatability is increased, the production efficiency is improved, and the Coulombic efficiency is easily increased. Further, the D50 is preferably 30.0 μm or less, more preferably 29.0 μm or less, and further preferably 27.0 μm or less from the viewpoint of enhancing rate characteristics.

The 10% particle size (D10) in the volume-based particle size distribution of the graphite material (I) measured by the laser diffraction method is preferably 1.0 μm or more, more preferably 4.0 μm or more, and further preferably from the viewpoint of enhancing cycle characteristics. Is 7.0 μm or more. The D10 is preferably 16.0 μm or less. When the D10 is 16.0 μm or less, a thin electrode can be manufactured, which is advantageous for increasing the energy density.

The 90% particle diameter (D90) in the volume-based particle diameter distribution of the graphite material (I) by the laser diffraction method is preferably 25.0 μm or more. Further, the D90 is preferably 80.0 μm or less, more preferably 70.0 μm or less, and further preferably 50.0 μm or less, from the viewpoint that a thin electrode can be manufactured and it is advantageous for increasing the energy density. ..

The volume-based particle size distribution by the laser diffraction method can be measured with a laser scattering diffraction type particle size distribution measuring device (MASTERSIZER manufactured by MALVERN).

[1-6] BET Specific Surface Area The BET specific surface area of the graphite material (I) is preferably 0.5 m ² /g or more, more preferably 0.8 m ² /g or more, further preferably from the viewpoint of enhancing rate characteristics. Is 1.0 m ² /g or more. The BET specific surface area, from the viewpoint that it is possible to increase the coulombic efficiency and cycle characteristics, preferably not more than 6.0 m ² / g, more preferably 4.0 m ² / g or less, more preferably 3.0 m ² / g or less. The BET specific surface area can be measured using the BET specific surface area measuring device described in the examples.

[1-7] Circularity The circularity of the graphite material (I) is preferably 0.89 or more, more preferably 0.90 or more, from the viewpoint that the energy density can be increased. Further, the circularity is preferably 0.98 or less, more preferably 0.96 or less from the viewpoint that the number of particles contact each other and the rate characteristics are improved. The circularity can be measured using the circularity measuring device described in the examples.

[1-8] Uniformity of particle size (D60/D10)
The uniformity of particle size (D60/D10) in the graphite material (I) is preferably 1.5 or more, more preferably 1.8 or more, and further preferably 2.0 or more, from the viewpoint of excellent electrode coatability of the particles. Is. Further, the uniformity of particle size (D60/D10) is preferably 3.0 or less, more preferably 2.8 or less, and further preferably 2.6 or less. When D60/D10 is 3.0 or less, the uniformity is low, that is, the width of the particle size distribution is narrow, and the electrode density can be increased. Here, D60 is a 60% particle size in the volume-based particle size distribution by the laser diffraction method, and D10 is a 10% particle size in the volume-based particle size distribution by the laser diffraction method.

[1-9] Surface oxygen content When the graphite material is graphitized by direct current application to the powder, the surface is appropriately oxidized and stabilized, and side reactions with the electrolytic solution are suppressed.
In the graphite material (I), the amount of surface oxygen between the surface of the particle and 40 nm in the depth direction, measured from the peak intensity of O1s obtained by HAX-PES measurement using hard X-ray of 7940 eV, is: It is preferably 0.010% by mass or more, and more preferably 0.015% by mass. When the amount of surface oxygen is 0.010 mass% or more, Coulomb efficiency is improved due to the effect of oxidation. The amount of surface oxygen is preferably 0.040 mass% or less, more preferably 0.030 mass% or less. When the amount of surface oxygen is 0.040 mass% or less, the conductivity of the graphite material is not adversely affected and the resistance can be suppressed low, so that the rate characteristics can be maintained high.

[2] Method for Producing Graphite Material for Lithium Ion Secondary Battery Electrode A method for producing graphite material (I) according to one embodiment of the present invention (hereinafter, also referred to as “production method (II)”) comprises crushing a carbon material. To obtain carbon particles, and a graphitization step of heat-treating the carbon particles at 2800° C. or more and 3300° C. or less to obtain a graphite material.
[2-1] Carbon material

The carbon material is not limited, for example, petroleum pitch, coal pitch, coal coke, petroleum coke, petroleum-derived bulk mesophase carbon, petroleum-derived mesophase microbeads, coal-derived bulk mesophase carbon, coal-derived mesophase microbeads, and mixtures thereof. It is preferably selected from those that have been heat treated. Among them, petroleum-derived bulk mesophase carbon, petroleum-derived mesophase microbeads, coal-derived bulk mesophase carbon, coal-derived mesophase microbeads, petroleum-derived mesophase pitch, coal-derived mesophase pitch, and petroleum coke are more preferable, and petroleum coke is further preferable. Particularly preferred is petroleum coke obtained from crude oil having a paraffin content of 40% or more. When the paraffin content is preferably 40% by mass or more, more preferably 50% by mass or more, further preferably 60% by mass or more, a graphite material having a large optically anisotropic domain can be obtained, and high energy density and high cycle characteristics can be obtained. It's easy to get a point battery

Paraffin content is obtained from the mass of paraphene component when the total amount of paraffinic component, aromatic component, resin component and asphaltene component of crude oil component is 100% by mass. As a measuring method, the TLC-FID method can be used, and it can be measured by Iotroscan (manufactured by LSI Medience Co., Ltd.).

When the carbon material is heated from 300° C. to 1200° C. in an inert atmosphere, the mass reduction in this temperature range is preferably 0.1% by mass or more. When the mass reduction is 0.1% by mass or more, the particle shape is likely to be agglomerate or spherical at the time of pulverization, the electrode is likely to have a high density, and the side reaction with the electrolytic solution is reduced when used as the negative electrode. .. The reason for this is presumed that the component volatilized by heating from 300° C. to 1200° C. stabilizes the crystal of the exposed edge portion during graphitization. Further, the mass reduction is preferably 3.0 mass% or less from the viewpoint that particles after graphitization are less bound to each other and the yield is good.

The loss on heating can be measured by using a commercially available device capable of simultaneous differential thermal/thermogravimetric measurement (TG-DTA) at a heating rate of 10° C./min. In the example, Seiko Instruments' TGDTAw6300 is used, about 15 mg of a measurement sample is accurately measured, placed on a platinum pan and set in the apparatus, and argon gas is flown at 200 ml/min to 300 at 10° C./min. The temperature is raised from ℃ to 1200 ℃ and measured. As a reference, α-alumina manufactured by Wako Pure Chemical Industries, which has been previously treated at 1500° C. for 3 hours to remove volatile components, is used.

[2-2] Crushing Step Although the method of crushing the carbon material is not limited, it can be carried out using a commercially available crusher such as a jet mill, a hammer mill, a roller mill, a pin mill and a vibration mill. It is also possible to use two or more types of these pulverizers and pulverize in two stages. Carbon particles are obtained by crushing the carbon material.

The maximum thermal history of the carbon material is preferably 600°C or lower. When the maximum heat history is 600° C. or less, the carbon material is not crushed into scales during crushing and a large amount of edge surface is not exposed, and when used as a negative electrode after graphitization, a side reaction with an electrolytic solution occurs. Less.

The carbon particles are preferably heat-treated at 800°C or higher and 1500°C or lower. Heat treatment at 800° C. or higher lowers the resistance value during graphitization and increases productivity. From the same viewpoint, the heat treatment temperature is more preferably 900° C. or higher, further preferably 1000° C. or higher. Further, when the heat treatment temperature is 1500° C. or lower, the volatile components of the carbon material appropriately remain and the surface of the graphite material (I) becomes in an appropriate state. From the same viewpoint, the heat treatment temperature is more preferably 1400° C. or lower, still more preferably 1300° C. or lower. Although the method of heat treatment is not limited, for example, a rotary kiln, a roller hearth kiln, or a batch type baking furnace can be used, and it is preferable to perform the heat treatment in an inert gas atmosphere.

The angle of repose of the carbon particles is preferably 30° or more, more preferably 32° or more. If the angle of repose is less than 30°, the fluidity of the carbon material becomes high, so that the carbon material may scatter during charging into the furnace body or powder may be ejected during energization. Further, the angle of repose is preferably 50° or less, more preferably 45° or less, and further preferably 40° or less. When the angle of repose exceeds 50°, the fluidity of the carbon material decreases, the filling property in the furnace body decreases, the productivity decreases, and the energization resistance of the entire furnace may increase extremely.

-The angle of repose can be measured using a tap denser. Specifically, using KYT-4000 manufactured by Seishin Enterprise Co., Ltd., 50 g of a measurement sample was allowed to freely fall from a dedicated inlet on the upper part of the device, and deposited in a triangular pyramid shape on an attached table, and then the table and the triangular pyramid. The angle of repose can be obtained by measuring the rising angle of the protractor with a protractor.

The compression ratio ((solidified bulk density-relaxed bulk density)/relaxed bulk density) calculated from the loosened bulk density (0 times tapping) and the compacted bulk density (tap density) of the carbon particles is 20% or more and 50% or less. preferable. Within this range, it is possible to obtain an electrode slurry which has good fluidity and is easily applied onto the current collector when preparing an electrode slurry kneaded with a binder and a solvent.

The loosened bulk density is the density obtained by dropping 100 g of a sample from a height of 20 cm into a graduated cylinder and measuring the volume and mass without applying vibration. The solidified bulk density (tap density) is a density obtained by measuring the volume and mass of 100 g of powder tapped 400 times using a Kantachrome auto tap.

These are measurement methods based on ASTM B527 and JIS K5101-12-2, but the drop height of the auto tap in tap density measurement was set to 5 mm.

The circularity of the carbon particles is preferably 0.89 or more, more preferably 0.90 or more, from the viewpoint that the density can be increased and the heat can be uniformly distributed during graphitization. Further, the circularity is preferably 0.98 or less, more preferably 0.96 or less from the viewpoint of increasing contact between particles and increasing heat generation efficiency during graphitization.

The uniformity of the particle size (D60/D10) of the carbon particles is preferably 1.5 or more, more preferably 1.8 or more, and further preferably 2.0 or more. When the D60/D10 is 1.5 or more, the uniformity is low, that is, the width of the particle size distribution is narrow, and the fluidity during graphitization is high and the heat is easily uniformly distributed. Further, D60/D10 is preferably 3.0 or less, more preferably 2.8 or less, still more preferably 2.6 or less from the viewpoint of good fluidity and excellent transportability.

[2-3] Graphitization Step Although the graphitization step in the production method (II) is not limited, it is preferably carried out by directly applying an electric current to the carbon particles to generate heat.

The method of directly passing an electric current through the carbon particles is not limited, but for example, it can be performed using a rectangular parallelepiped furnace body made of ceramic brick and having an open top. When such a furnace body structure is adopted, heat is uniformly applied to the carbon particles, so that there is an advantage that no aggregation occurs during graphitization. Further, since the temperature distribution is uniform and there is no trap portion for impurity volatilization, a graphite material with few impurities can be obtained.

The graphitization treatment is preferably performed in a non-oxidizing atmosphere. For example, a method of performing heat treatment in an atmosphere of an inert gas such as nitrogen gas, or a method of providing a layer for barrier to oxygen on the surface in contact with air can be mentioned. As the barrier layer, for example, a method of separately providing a carbon plate or a carbon powder layer and consuming oxygen can be cited.

The graphitization temperature is preferably 2500° C. or higher, more preferably 2900° C. or higher, even more preferably 3000° C. or higher. The upper limit of the graphitization temperature is preferably 3300° C. or lower from the viewpoint of preventing alteration due to sublimation of the material. It is preferable not to crush or crush the obtained graphite material after the graphitization treatment. By crushing or crushing after graphitization, the edge surface of the surface may be newly exposed and the performance may deteriorate.

In the graphitization treatment, it is preferable to add a graphitization promoter such as a boron compound such as B ₄ C or a silicon compound such as SiC. The blending amount is preferably 10 mass ppm or more and 100000 mass ppm or less in the carbon material. This can increase the heat treatment efficiency and productivity of graphitization.

[3] Negative Electrode Active Material of Lithium Ion Secondary Battery The negative electrode active material of the lithium ion secondary battery in one embodiment of the present invention (hereinafter also referred to as “negative electrode active material (III)”) is the above graphite material (I). Including.

The negative electrode active material (III) is made of the above graphite material (I) or further contains other graphite or carbon material. When containing other graphite or carbon material, it is preferable to add 0.01 to 20.00 parts by mass of the other graphite material or carbon material to 100.00 parts by mass of the graphite material (I). By mixing and using other graphite or carbon materials, a negative electrode active material having excellent characteristics of other graphite or carbon materials while maintaining the excellent characteristics of the graphite material (I) can be obtained. It is possible. From the same viewpoint, it is more preferable to add 0.01 to 10.00 parts by mass. As other graphite or carbon material, spherical natural graphite or artificial graphite is preferable.

Also, it is preferable to mix carbon fiber in the negative electrode active material (III). The amount of carbon fiber blended is preferably 0.01 to 20.00 parts by mass, more preferably 0.500 to 5.00 parts by mass, relative to 100.00 parts by mass of the negative electrode active material (III).

Examples of carbon fibers include PAN-based carbon fibers, pitch-based carbon fibers, organic carbon fibers such as rayon-based carbon fibers, and vapor grown carbon fibers. Of these, vapor grown carbon fiber having high crystallinity and high thermal conductivity is particularly preferable. In the case of adhering carbon fibers to the surface of the composite carbon particles, vapor grown carbon fibers are particularly preferable.

As a device for mixing the composite carbon particles and other materials, a commercially available mixer or stirrer can be used. Specific examples include mixers such as ribbon mixers, V-type mixers, W-type mixers, one-blade mixers and Nauta mixers.

[4] Negative Electrode for Lithium Ion Secondary Battery A negative electrode for a lithium ion secondary battery (hereinafter, also referred to as “negative electrode (IV)”) in one embodiment of the present invention contains the negative electrode active material (III). More specifically, the negative electrode (IV) comprises a current collector and a negative electrode mixture layer formed by applying a negative electrode mixture containing the negative electrode active material (III) and a binder onto the current collector. .. The negative electrode mixture preferably contains a conductive auxiliary agent. Examples of the conductive aid include Denka Black (registered trademark, HS-100), VGCF (registered trademark)-H, and the like.

The current collector may be, for example, aluminum, nickel, copper, stainless steel foil, mesh, or the like. The coating thickness of the negative electrode mixture is preferably 50 to 200 μm. The method of applying the negative electrode mixture is not particularly limited, and examples thereof include a method of applying with a doctor blade or a bar coater and thereafter forming with a roll press or the like.

Examples of the pressure molding method include molding methods such as roll pressing and press pressing. The pressure during pressure molding is preferably 1×10 ³ to 3×10 ³ kg/cm ² .

Examples of the binder include fluorine-based polymers such as polyvinylidene fluoride and polytetrafluoroethylene, and SBR (styrene butadiene rubber).

[5] Lithium Ion Secondary Battery A lithium ion secondary battery has a structure in which a positive electrode and a negative electrode are immersed in an electrolytic solution or an electrolyte. The lithium ion secondary battery in one embodiment of the present invention comprises the above negative electrode (IV).

For a positive electrode of a lithium ion secondary battery, a lithium-containing transition metal oxide is usually used as a positive electrode active material, and preferably at least selected from Ti, V, Cr, Mn, Fe, Co, Ni, Mo and W. An oxide mainly containing one kind of transition metal element and lithium, wherein a compound having a molar ratio of lithium to the transition metal element of 0.3 to 2.2 is used, more preferably V, Cr, Mn, A compound which is an oxide mainly containing at least one transition metal element selected from Fe, Co and Ni and lithium, and whose molar ratio of lithium to the transition metal is 0.3 to 2.2 is used. In addition, you may contain Al, Ga, In, Ge, Sn, Pb, Sb, Bi, Si, P, B etc. in the range less than 30 mol% with respect to the transition metal which exists mainly. Among the above positive electrode active materials, the general formula Li _x MO ₂ (M is at least one of Co, Ni, Fe and Mn, x=0.02 to 1.2) or Li _y N ₂ O ₄ (N Contains at least Mn. It is preferable to use at least one material having a spinel structure represented by y=0.02-2).

In a lithium-ion secondary battery, a separator may be provided between the positive electrode and the negative electrode. Examples of the separator include non-woven fabric containing polyolefin such as polyethylene and polypropylene as a main component, cloth, a microporous film, or a combination thereof.

Known electrolytes, inorganic solid electrolytes, and polymer solid electrolytes can be used as the electrolyte solution and the electrolyte constituting the lithium ion secondary battery in the preferred embodiment of the present invention, but the organic electrolyte solution from the viewpoint of electrical conductivity is preferable.

Note that there are no restrictions on the selection of other necessary members for battery configurations other than the above.

[6] All-solid-state lithium-ion secondary battery The all-solid-state lithium-ion secondary battery has a structure in which the positive electrode and the negative electrode are in contact with the solid electrolyte layer. FIG. 1 is a schematic diagram showing an example of the configuration of an all-solid-state lithium ion secondary battery 1 according to this embodiment. The all-solid-state lithium-ion secondary battery 1 includes a positive electrode layer 11, a solid electrolyte layer 12, and a negative electrode layer 13.

The positive electrode 11 has a positive electrode current collector 111 and a positive electrode mixture layer 112. The positive electrode current collector 111 is connected to a positive electrode lead 111a for exchanging charges with an external circuit. The positive electrode current collector 111 is preferably a metal foil, and an aluminum foil is preferably used as the metal foil.

The positive electrode mixture layer 112 contains a positive electrode active material, and may further contain a solid electrolyte, a conductive additive, a binder, and the like. Examples of the positive electrode active material include rock salt type layered active materials such as LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , and LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , spinel type active materials such as LiMn ₂ O _4. , Olivine type active materials such as LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , LiCuPO ₄ and sulfide active materials such as Li ₂ S can be used. Further, these active materials may be coated with LTO (Lithium Tin Oxide), carbon or the like.

As the solid electrolyte that may be contained in the positive electrode mixture layer 112, the materials mentioned in the solid electrolyte layer 12 described later can be used, but a material different from the material contained in the solid electrolyte layer 12 can be used. You may use. The content of the solid electrolyte in the positive electrode mixture layer 112 is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, and 80 parts by mass or more with respect to 100 parts by mass of the positive electrode active material. Is more preferable. The content of the solid electrolyte in the positive electrode mixture layer 112 is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and 125 parts by mass or less with respect to 100 parts by mass of the positive electrode active material. Is more preferable.

As the conduction aid, it is preferable to use a particulate carbonaceous conduction aid or a fibrous carbonaceous conduction aid. As the particulate carbonaceous conductive aid, Denka Black (registered trademark) (manufactured by Denki Kagaku Kogyo Co., Ltd.), Ketjen Black (registered trademark) (manufactured by Lion Corporation), graphite fine powder SFG series (manufactured by Timcal), graphene Particulate carbon such as can be used. As the fibrous carbonaceous conductive additive, vapor grown carbon fibers (VGCF (registered trademark), VGCF (registered trademark)-H (manufactured by Showa Denko KK)), carbon nanotubes, carbon nanohorns and the like can be used. .. Vapor grown carbon fiber "VGCF (registered trademark)-H" (manufactured by Showa Denko KK) is most preferable because it has excellent cycle characteristics. The content of the conductive additive in the positive electrode mixture layer 112 is preferably 0.1 part by mass or more, and more preferably 0.3 part by mass or more, based on 100 parts by mass of the positive electrode active material. The content of the conductive additive in the positive electrode mixture layer 112 is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less with respect to 100 parts by mass of the positive electrode active material.

Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene oxide, polyvinyl acetate, polymethacrylate, polyacrylate, polyacrylonitrile, polyvinyl alcohol, styrene-butadiene rubber, carboxymethyl cellulose and the like.

In the positive electrode mixture layer 112, the content of the binder with respect to 100 parts by mass of the positive electrode active material is preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 1 part by mass or more and 7 parts by mass or less.

The solid electrolyte layer 12 is interposed between the positive electrode layer 11 and the negative electrode layer 13, and serves as a medium for moving lithium ions between the positive electrode layer 11 and the negative electrode layer 13. The solid electrolyte layer 12 preferably contains at least one selected from the group consisting of a sulfide solid electrolyte and an oxide solid electrolyte, and more preferably contains a sulfide solid electrolyte.

Examples of the sulfide solid electrolyte include sulfide glass, sulfide glass ceramics, Thio-LISICON type sulfide, and the like. More specifically, for example, Li ₂ S-P ₂ S ₅ , Li ₂ S-P ₂ S ₅ -LiI, Li ₂ S-P ₂ S ₅ -LiCl, Li ₂ S-P ₂ S ₅ -LiBr, Li ₂ S-P ₂ S ₅ -Li ₂ O, Li ₂ S-P ₂ S ₅ -Li ₂ O-LiI, Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -LiI, Li ₂ S-SiS _{2 -LiBr, Li 2 S-SiS 2} -LiCl, Li 2 S-SiS 2 -B 2 S 3 -LiI, Li 2 S-SiS 2 -P 2 S 5 -LiI, Li 2 S-B 2 S 3, Li ₂ S—P ₂ S ₅ —Z _m S _n (where m and n are positive numbers, Z represents any one of Ge, Zn, and Ga), Li ₂ S—GeS ₂ , and Li ₂ S— SiS ₂ -Li ₃ PO ₄ , Li ₂ S-SiS ₂ -Li _x MO _y (where x and y are positive numbers, M is P, Si, Ge, B, Al, Ga or In) , Li ₁₀ GeP ₂ S ₁₂ , Li _3.25 Ge _0.25 P _0.75 S ₄ , 30Li ₂ S.26B ₂ S ₃ .44LiI, 63Li ₂ S.36SiS ₂ .1Li ₃ PO ₄ , 57Li ₂ S.38SiS ₂ .. 5Li ₄ SiO ₄ , 70Li ₂ S·30P ₂ S ₅ , 50LiS ₂ ·50GeS ₂ , Li ₇ P ₃ S ₁₁ , Li _3.25 P _0.95 S ₄ , Li ₃ PS ₄ , Li ₂ S·P ₂ S ₃ ·P ₂ S ₅ etc. can be mentioned. The sulfide solid electrolyte material may be amorphous, crystalline, or glass ceramics.

Examples of the oxide solid electrolyte include perovskite, garnet, and LISICON type oxide. More specifically, for example, La _0.51 Li _0.34 TiO _2.94 , Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ , Li ₇ La ₃ Zr ₂ O ₁₂ , 50Li ₄ SiO ₄ .50Li ₃ BO ₃ , Li _2.9 PO _{3.3. N 0.46 (LIPON), Li 3.6} Si 0.6 P 0.4 O 4, Li 1.07 Al 0.69 Ti 1.46 (PO 4) 3, Li 1.5 Al 0.5 Ge 1.5 (PO 4) may be mentioned ₃ or the like. The oxide solid electrolyte material may be amorphous, crystalline, or glass ceramics.

The negative electrode layer 13 includes a negative electrode current collector 131 and a negative electrode mixture layer 132. The negative electrode current collector 131 is connected to a negative electrode lead 131a for exchanging charges with an external circuit. The negative electrode current collector 131 is preferably a metal foil, and a stainless foil, a copper foil, or an aluminum foil is preferably used as the metal foil. The surface of the current collector may be coated with carbon or the like.

The negative electrode mixture layer 132 contains a negative electrode active material, and may also contain a solid electrolyte, a binder, a conductive auxiliary agent, and the like. The composite carbon particles are used as the negative electrode active material.

As the solid electrolyte that may be contained in the negative electrode mixture layer 132, the materials mentioned in the solid electrolyte layer 12 may be used, but the solid electrolyte contained in the solid electrolyte layer 12 or the positive electrode mixture layer may be contained. A material different from the existing solid electrolyte may be used. The content of the solid electrolyte in the negative electrode mixture layer 132 is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, and 80 parts by mass or more with respect to 100 parts by mass of the negative electrode active material. Is more preferable. The content of the solid electrolyte in the negative electrode mixture layer 132 is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and 125 parts by mass or less with respect to 100 parts by mass of the negative electrode active material. Is more preferable.

As the conductive auxiliary agent that may be included in the negative electrode mixture layer 132, the conductive auxiliary agents described in the description of the positive electrode mixture layer 112 can be used, but the conductive auxiliary agent included in the positive electrode mixture layer 112 is used. Different materials may be used. The content of the conductive additive in the negative electrode mixture layer 132 is preferably 0.1 part by mass or more, and more preferably 0.3 part by mass or more, with respect to 100 parts by mass of the negative electrode active material. The content of the conductive additive in the negative electrode mixture layer 132 is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less with respect to 100 parts by mass of the negative electrode active material.

As the binder, for example, the materials mentioned in the description of the positive electrode mixture layer 112 can be used, but the binder is not limited to these. In the negative electrode mixture layer 132, the content of the binder based on 100 parts by mass of the negative electrode active material is preferably 0.3 parts by mass or more and 10 parts by mass or less, and 0.5 parts by mass or more and 5 parts by mass or less. More preferable.

Note that there are no restrictions on the selection of other necessary members for battery configurations other than the above.

Hereinafter, examples of the present invention will be specifically described. It should be noted that these are merely examples for explanation and do not limit the present invention.
The methods for evaluating the physical properties of the graphite materials of Examples and Comparative Examples, the methods for producing the batteries, the methods for measuring the characteristics of the batteries, and the graphite materials used in each example are as follows.

[7] Evaluation method of physical properties of graphite material,
[7-1] Surface spacing d002, Lc
Fill a glass sample plate (sample plate window 18×20 mm, depth 0.2 mm) with a mixture of graphite material and standard silicon (made by NIST) in a mass ratio of 9:1. The measurement was performed under the conditions.
XRD device: Rigaku's SmartLab (registered trademark)
X-ray type: Cu-Kα ray Kβ ray removal method: Ni filter X-ray output: 45 kV, 200 mA
Measuring range: 24.0 to 30.0 deg.
Scan speed: 2.0 deg. /Min.
The Gakushin method was applied to the obtained waveforms to determine the values of the surface spacing d002 and Lc. (See Iwashita et al., Carbon vol. 42 (2004), p.701-714).

[7-2] Calculation of Volume-Based Particle Diameter and Sphere-Converted Area by Laser Diffraction Method Particle Size Measuring Device: Mastersizer2000 manufactured by Marvern
A 5 mg sample was placed in a container, water containing 0.04% by mass of a surfactant was added, and ultrasonication was performed for 5 minutes, followed by measurement.

[7-3] BET Specific Surface Area BET Specific Surface Area Measuring Device: Quantrome NOVA 2200e
A 3 g sample was placed in a measurement cell (9 mm×135 mm), dried at 300° C. for 1 hour under vacuum, and then measured. N ₂ was used as the gas for measuring the BET specific surface area.

[7-4] Evaluation of Optical Texture The optical texture of the graphite material was evaluated as follows. (Latest Carbon Material Experimental Technology (Analysis/Analysis) Japan Society of Carbon Materials (2001), Publishing: Cypec Corporation)

[7-4-1] Preparation of Graphite Material A double-sided tape was attached to the bottom of a plastic sample container having an internal volume of 30 cm ³ , and about 2 spatulas (about 2 g) of the observation sample were placed on it. Cold embedding resin (trade name: cold embedding resin #105, manufacturing company: Japan Composite Co., Ltd., sales company: Marumoto Struers Co., Ltd.) with a curing agent (product name: curing agent (M agent), Manufacturing company: NOF CORPORATION, sales company: Marumoto Struers Co., Ltd.) were added and kneaded for 30 seconds. The obtained mixture (about 5 ml) was slowly poured into the sample container until the height became about 1 cm, and the mixture was allowed to stand for 1 day to cure. Next, the cured sample was taken out and the double-sided tape was peeled off. Then, the surface to be measured was polished using a polishing plate rotary type polishing machine.

Polishing was performed by pressing the polishing surface against the rotating surface. The rotation speed of the polishing plate is 1000 rpm. The polishing plate count is #500, #1000, #2000 in this order, and the last is alumina (trade name: Baicalox type 0.3CR, particle size 0.3 μm, manufacturing company: Baikowski, sales company: Baikou It was mirror-polished using (Ski Japan).
The polished sample was fixed on the slide with clay, and 10 spots were randomly observed in a reflection mode using a polarization microscope (BX51, manufactured by OLYMPUS).

[7-4-2] Cross-Section Observation of Graphite Material with Polarization Microscope Images observed with a polarization microscope were taken by connecting a CAMEDIA C-5050 ZOOM digital camera manufactured by OLYMPUS to the polarization microscope with an attachment. The shooting mode was HQ2560×1280, and the shutter time was 1.6 seconds. The photographed data was read in the bmp format using an image analyzer LUZEX AP manufactured by Nireco Corporation. The display format of the color data is IHP color (I indicates luminance, H indicates hue, and P indicates purity). The image was captured at 2560 x 1920 pixels.

A square area (100 μm square) was cut out from the same point at an observation angle of 0° and 45°, and the images of the selected magnifications were subjected to the following analysis for all particles within that range to obtain an average. The magnification used in the analysis was an objective lens×50, 1 pixel=0.05 μm. With respect to the area inside the particle, colors were extracted for blue, yellow, magenta, black, and pure magenta, and the area ratio of each was counted. Although the color of the optically anisotropic domain changes depending on the orientation of the crystallites, the probability of facing straight ahead is extremely low. Therefore, even if magenta is shown, the wavelength is almost different from that of pure magenta. On the other hand, the optically isotropic domain always exhibits a pure magenta wavelength. Therefore, in the present invention, all of pure magenta is identified as an optical isotropic region.

For color extraction, the command of LUZEX AP was used, and the extraction width of each color was set by setting the IHP data as shown in Table 1 below. In order to remove noise, the W-1 command of ELIMINATE1 of the logical filter is used to remove the area of 1 dot or less. For counting, the number of pixels was used to calculate the total number of pixels in the image and the number of pixels of the corresponding color.

As the optically anisotropic domain, the area ratio of the portion where the color changed when the sample was rotated 0°, 45°, and 90° with respect to the analyzer of the polarization microscope was calculated as shown in Table 2.

Particle area (%)=B1+Y1+M1+K1+PM1
Optical isotropic area ratio (%) = PM1
Void area ratio (%) = K1
Optical anisotropic area ratio (%) = 100-(optical isotropic area ratio)-(void area ratio)
Similarly, d45 and d90 were calculated, and the average value of d00, d45, and d90 was taken as the value of the particle.
Here, the voids of the carbon material mean voids in the particles, and voids between particles are not included.

[7-5] Raman spectroscopic analysis Raman spectroscopic device: JASCO Corporation NRS-5100
Excitation wavelength 532.36Nm, entrance slit width 200 [mu] m, the exposure time of 15 seconds, the number of integrations twice, was measured under the conditions of the diffraction grating 600 / mm, the intensity of the peak in the range of 1300 ~ 1400 cm ^-1 and (ID) The intensity ratio of the intensity (IG) of the peak in the range of 1580 to 1620 cm ^-1 was defined as the R value (ID/IG).

[7-6] Circularity Circularity measuring device: Flow type particle image analyzer FPIA-3000 (manufactured by Sysmex Corporation)
The circularity is obtained by dividing the circumference of a circle having the same area as the observed area of a particle image by the circumference of the particle image, and the closer to 1 the closer the circle is to a perfect circle. The circularity can be expressed by the following equation, where S is the area of the particle image and L is the perimeter.
Circularity = (4πS) ^1/2 /L

The graphite material was purified by passing through a filter having an opening of 106 μm, 0.1 g of the sample was added to 20 ml of ion-exchanged water, and 0.1 to 0.5% by mass of a surfactant was added to uniformly disperse the graphite material. A sample solution for measurement was prepared. Dispersion was performed by using an ultrasonic cleaner UT-105S (manufactured by Sharp Manufacturing System) for 5 minutes. The obtained sample solution for measurement was put into an apparatus, and the median of circularity was calculated from the number-based frequency distribution of circularity analyzed for 10,000 particles in the LPF mode.

[7-7] Surface Oxygen Amount The amount of oxygen on the surface of the graphite material was quantified by performing HAX-PES measurement with an incident energy of 7940 eV using a device permanently installed at SPring-8 (beam line BL46XU). Regarding the measurement conditions, in the narrow spectrum of C1s, the energy range of photoelectron Kinetic Energy was measured from 7638 to 7658 eV, and in the narrow spectrum of O1s, the energy range of photoelectron Kinetic Energy was measured from 7396 to 7416 eV. The amount of oxygen on the surface of the graphite material was quantified according to the following method.

[7-7-1] Energy calibration of photoelectron spectrum A plate-shaped Au sample was measured as a standard sample. Kinetic Energy as narrow spectrum of Au4f measures the energy range of 7648 ~ 7859eV, permanent BL46XU by calculating the difference between the theoretical peak position of the peak position and Au4f _7/2 of Au4f _7/2 obtained in the measurement The work function φ value of the device was calculated. Based on the calculated φ value, energy calibration of the narrow spectrum of the graphite material was performed.

[7-7-2] Normalization of photoelectron spectrum intensity The O1s narrow spectrum intensity of the graphite material was normalized based on the arbitrary C1s narrow spectrum intensity and the C1s narrow spectrum intensity obtained by the measurement. The normalized strength x(O1s) was calculated from the following formula 1.
[Formula 1]
Normalized strength x (O1s) = measured strength (O1s) x arbitrary strength (C1s)/measured strength (C1s)

[7-7-3] Quantification of oxygen content on graphite material surface Based on the above, the surface oxygen content of the graphite material was quantified by the following formula 2 from the normalized strength (O1s) of the graphite materials of the examples and comparative examples. Here, the arbitrary intensity (C1s) in Expression 2 is the value used in Expression 1.
[Formula 2]
Graphite material surface oxidation amount a (mol%) = (normalized strength x (O1s)/c arbitrary strength (C1s)) x cumulative number of measurements d (C1s) / cumulative number of measurements e (O1s)

-This measurement integrates information from the surface of the graphite material to a depth of about 40 nm by using synchrotron radiation with extremely high brightness. Therefore, highly accurate measurement results can be obtained with almost no influence of contamination on the surface of the graphite material. Since the proportion of carbon as a main component in a graphite material is overwhelmingly high, it is appropriate to calculate the amount of oxygen by the above method standardized from the C1s narrow spectrum intensity of carbon.

[7-8] Lithium ion secondary battery evaluation [7-8-1] Paste preparation:
To 100 parts by mass of the graphite material, 10 parts by mass of KF polymer L1320 (N-methylpyrrolidone (NMP) solution product containing 12% by mass of polyvinylidene fluoride (PVDF)) manufactured by Kureha Chemical Co., Ltd. was added and kneaded with a planetary mixer. , And the main ingredient stock solution.

[7-8-2] Electrode preparation, electrode density:
After adding NMP to the base material stock solution to adjust the viscosity, it was applied on a high-purity copper foil to a thickness of 250 μm using a doctor blade. This was vacuum dried at 120° C. for 1 hour, punched into 18 mmφ, and the punched electrodes were sandwiched between super steel press plates and pressed against the electrodes at a pressure of ² t/cm ² . Then, it was dried at 120° C. for 12 hours in a vacuum dryer to obtain an evaluation electrode. The mass of the active material at this time was divided by the volume of the active material to obtain the electrode density (g/cm ³ ).

[7-8-3] Battery preparation:
A battery was manufactured as follows. The following operations were carried out in a dry argon atmosphere with a dew point of -80°C or lower.
In a cell with a polypropylene screw-in lid (inner diameter of about 18 mm), a copper foil electrode and a metallic lithium foil prepared in [7-8-2] above were separated with a separator (polypropylene microporous film (Cell Guard 2400)). It was sandwiched and laminated. An electrolytic solution was added to this and a lid was provided to obtain a battery for evaluation. As the electrolytic solution, a mixed solution of 8 parts by mass of EC (ethylene carbonate) and 12 parts by mass of DEC (diethyl carbonate) in which 1 mol/liter of LiPF ₆ was dissolved as an electrolyte was used.

[7-8-4] Discharge capacity, energy density, Coulomb efficiency CC (constant current: constant current) charging was performed from a rest potential to 0.002 V at 0.4 mA in a thermostat set at 25°C. Next, CV (constant volt: constant voltage) charging was switched at 0.002 V, and charging was performed at a cutoff current value of 50.8 μA. Discharge was performed at 0.4 mA in CC mode with an upper limit voltage of 1.5 V.

The discharge capacity was defined as the value obtained by dividing the quantity of electricity during the first discharge by the weight of the graphite material for the negative electrode of the lithium-ion secondary battery. Further, the discharge capacity (0.2 C) was multiplied by the electrode density to obtain the volume energy density. Further, the ratio of the charge capacity at the time of initial charge and the discharge capacity at the time of first discharge, that is, the value obtained by expressing the ratio of initial discharge capacity/initial charge capacity in percentage was taken as the Coulombic efficiency.

[7-8-5] Rate characteristic The rate characteristic was measured in a constant temperature bath set at 25°C. For charging (insertion of lithium into graphite), CC (constant current: constant current) charging is performed from a rest potential to 0.002 V at 0.2 mA/cm ² . Next, it was switched to CV (constant volt: constant voltage) charging at 0.002 V, and stopped when the current value dropped to 25.4 μA. For discharge (release from carbon), a constant-current constant-voltage discharge test was performed at current densities of 0.2 C and 3 C, and cutoff was performed at a voltage of 1.5 V. The value of discharge capacity (3C)/discharge capacity (3C) was defined as the discharge rate characteristic.

[7-8-6] Cycle characteristics Charging (insertion of lithium into carbon) in a constant temperature bath set at 60°C CC (constant current: constant current) from rest potential to 0.002 V at 0.2 mA/cm ^2. Charged. Next, it was switched to CV (constant volt: constant voltage) charging at 0.002 V, and stopped when the current value dropped to 25.4 μA.

-Discharge (emission from graphite) was CC discharge at a current density of 1C and cut off at a voltage of 1.5V. The discharge was repeated 200 cycles. The value of the discharge capacity at the 200th cycle/the discharge capacity at the first cycle was defined as the cycle characteristic.

[Example 1]
The petroleum coke obtained by using the delayed coking process on a Chinese crude oil having a paraffin content of 45% by mass was used as a carbon material. This was crushed with a Hosokawa Micron bantam mill, air classified with a Nisshin Engineering turbo classifier to D50 of 17.0 μm, and heat-treated at 1000° C. while flowing nitrogen gas with a Japanese insulator roller hearth kiln to obtain carbon particles 1 Got The physical properties of carbon particles 1 are summarized in Table 3.

A ceramic brick was used to form a furnace with a length of 500 mm, a width of 1000 mm, and a depth of 200 mm, and carbon electrode plates of 450 x 180 mm and a thickness of 20 mm were installed on both inner end surfaces. The carbon particles 1 were packed in the furnace and a lid provided with a nitrogen gas inlet and an exhaust port was provided. A transformer was installed, and heating was performed by passing an electric current between the electrode plates for about 5 hours while flowing a nitrogen gas, and graphitized at a maximum temperature of 3200° C. to obtain a graphite material 1. Table 4 shows various physical properties of the obtained graphite material 1 and evaluation results of the lithium ion battery.

[Example 2]
Carbon particles 2 were obtained by the same production method as in Example 1 except that the carbon material was pulverized and classified so that D50 was 15.0 μm. The physical properties of carbon particles 2 are summarized in Table 3.
Next, a graphite material 2 was obtained in the same manner as in Example 1 except that the obtained carbon particles 2 were used. Table 4 shows various physical properties of the obtained graphite material 2 and evaluation results of the lithium ion battery.

[Example 3]
Carbon particles 3 were obtained by the same production method as in Example 1 except that the carbon material was pulverized and classified so that D50 was 24.0 μm. Table 3 shows the physical properties of the carbon particles 3.
Next, a graphite material 3 was obtained in the same manner as in Example 1 except that the obtained carbon particles 3 were used. Table 4 shows various physical properties of the obtained graphite material 3 and evaluation results of the lithium ion battery.

[Example 4]
Carbon particles 4 were obtained by the same production method as in Example 1 except that the carbon material was pulverized and classified so that D50 was 27.0 μm. Table 3 shows the physical properties of the carbon particles 4.
Next, a graphite material 4 was obtained in the same manner as in Example 1 except that the obtained carbon particles 4 were used. Table 4 shows various physical properties of the obtained graphite material 4 and evaluation results of the lithium ion battery.

[Example 5]
The petroleum coke obtained by using the delayed coking process with respect to Chinese crude oil having a paraffin content of 65% by mass was used as a carbon material. This was crushed with a Hosokawa Micron bantam mill, air-flow classified with a Nisshin Engineering turbo classifier to D50 of 23.0 μm, and heat-treated at 1000° C. while flowing nitrogen gas with a Nippon Insulator roller hearth kiln to produce carbon particles 5 Got Table 3 shows the physical properties of the carbon particles 5.
Next, a graphite material 5 was obtained in the same manner as in Example 1 except that the obtained carbon particles 5 were used. Table 4 shows various physical properties of the obtained graphite material 5 and evaluation results of the lithium ion battery.

[Comparative Example 1]
A petroleum coke obtained by using a delayed coking process for a Venezuelan crude oil having a paraffin content of 27% by mass was used as a carbon material. This was crushed with a Hosokawa Micron bantam mill, air-flow classified with a Nisshin Engineering turbo classifier to D50 of 16.0 μm, and heat-treated at 1000° C. while flowing nitrogen gas with a Japanese insulator roller hearth kiln to produce carbon particles 6 Got Table 3 shows the physical properties of the carbon particles 6.
Next, a graphite material 6 was obtained in the same manner as in Example 1 except that the obtained carbon particles 6 were used. Table 4 shows various physical properties of the obtained graphite material 6 and evaluation results of the lithium ion battery.

[Comparative example 2]
A petroleum coke obtained by using a delayed coking process was used as a carbon material for a Mexican crude oil having a paraffin content of 32% by mass. This was crushed with a Hosokawa Micron bantam mill, air classification was performed with a Nisshin Engineering turbo classifier to D50 of 16.0 μm, and heat treatment was performed at 1000° C. while flowing nitrogen gas with a Japanese insulator roller hearth kiln to obtain carbon particles 7 Got Table 3 shows the physical properties of the carbon particles 7.
Next, a graphite material 7 was obtained in the same manner as in Example 1 except that the obtained carbon particles 7 were used. Table 4 shows various physical properties of the obtained graphite material 7 and evaluation results of the lithium ion battery.

[Comparative Example 3]
The petroleum coke obtained by using the delayed coking process with respect to a California crude oil having a paraffin content of 36% by mass was used as a carbon material. This was crushed with a Hosokawa Micron bantam mill, air-flow classified with a Nisshin Engineering turbo classifier to D50 of 16.0 μm, and heat-treated at 1000° C. while flowing nitrogen gas with a Nippon Insulator roller hearth kiln to obtain carbon particles 8 Got Table 3 shows the physical properties of the carbon particles 8.
Next, a graphite material 8 was obtained in the same manner as in Example 1 except that the obtained carbon particles 8 were used. Table 4 shows various physical properties of the obtained graphite material 8 and evaluation results of the lithium ion battery.

[Comparative Example 4]
A graphite crucible with a screw lid was filled with carbon particles 2, and graphitized at a maximum temperature of 3200° C. using an Acheson furnace to obtain a graphite material 9. Table 4 shows various physical properties of the obtained graphite material 9 and evaluation results of the lithium ion battery.

[Comparative Example 5]
Carbon particles 3 were filled in a graphite crucible with a screw lid and graphitized at a maximum temperature of 3200° C. using an Acheson furnace to obtain a graphite material 10. Table 4 shows various physical properties of the obtained graphite material 10 and evaluation results of the lithium ion battery.

[Comparative Example 6]
600 g of Chinese natural graphite having D50 of 7 μm was put into a hybridizer NHS1 manufactured by Nara Machine Co., Ltd. and treated at a rotor peripheral speed of 60 m/sec for 3 minutes to obtain spherical graphite particles having an average particle diameter of 15 μm. 3 kg of the spherical graphite particles and 1 kg of petroleum-based tar were charged into an M20 type Loedige mixer (internal volume 20 liters) manufactured by Matsubo Co., Ltd. and kneaded. Then, in a nitrogen gas atmosphere, the temperature was raised to 700° C. for detarring treatment, and then the temperature was raised to 1300° C. for heat treatment. The heat-treated product obtained was crushed with a pin mill to obtain a graphite material 11. Table 4 shows various physical properties of the obtained graphite material 11 and evaluation results of the lithium ion battery.

[Comparative Example 7]
MCMB2528 (graphitization temperature: 2800° C.) manufactured by Osaka Gas was used as the graphite material 12. Table 4 shows various physical properties of the graphite material 12 and evaluation results of the lithium ion battery.

[Comparative Example 8]
Coal coke was crushed using a Bantam mill (manufactured by Hosokawa Micron Co., Ltd.), and carbon particles 9 having a D50 of 6 m were obtained by air classification using a turbo classifier (manufactured by Nisshin Engineering Co., Ltd.). Table 3 shows the physical properties of the carbon particles 9.

100 parts by mass of carbon particles 9 and 100 parts by mass of coal-based pitch were mixed and kneaded for 30 minutes while applying heat at 200°C. Then, heat treatment was performed at 3200° C. for 10 minutes in an argon gas stream using an induction heating furnace, and the graphite material 13 was obtained by pulverizing so that D50 was 23.0 μm. Table 4 shows various physical properties of the obtained graphite material 13 and evaluation results of the lithium ion battery.

[8] Preparation of all-solid-state lithium-ion secondary battery A method for preparing an all-solid-state lithium-ion secondary battery using the graphite materials obtained in Examples and Comparative Examples will be described below. Regarding the components of the battery manufactured here, those corresponding to the components with the reference numerals shown in FIG. 1 will be described with the reference symbols of the corresponding components.

[8-1] Preparation of Solid Electrolyte Layer 12 Starting materials Li ₂ S (manufactured by Nippon Kagaku Kogyo Co., Ltd.) and P ₂ S ₅ (manufactured by Sigma-Aldrich Japan GK) in a molar ratio of 75:25 under an argon gas atmosphere. D50 by mechanically milling (rotation speed 400 rpm) for 20 hours using a planetary ball mill (P-5 type, manufactured by Fritsch Japan KK) and zirconia balls (10 mmφ 7 pieces, 3 mmφ 10 pieces). To obtain an amorphous solid electrolyte of Li ₃ PS ₄ of 0.3 μm.
The obtained amorphous solid electrolyte is press-molded by a uniaxial press molding machine using a polyethylene die having an inner diameter of 10 mmφ and a SUS punch to prepare the solid electrolyte layer 12 as a sheet having a thickness of 960 μm. ..

[8-2] Preparation of Negative Electrode Mixture Layer 132 Graphite material 48.5 parts by mass, solid electrolyte (Li ₃ PS ₄ , D50: 8 μm) 48.5 parts by mass, VGCF (registered trademark)-H (Showa Denko) (Manufactured by corporation) 3 parts by mass are mixed. The mixture is homogenized by milling at 100 rpm for 1 hour using a planetary ball mill. The homogenized mixture is press-molded at 400 MPa with a uniaxial press molding machine using a polyethylene die having an inner diameter of 10 mmφ and a SUS punch to prepare the negative electrode mixture layer 132 as a sheet having a thickness of 65 μm.

[8-3] Preparation of Positive Electrode Mixture Layer 112 55 parts by mass of positive electrode active material LiCoO ₂ (D50:10 μm, manufactured by Nippon Kagaku Kogyo Co., Ltd.) and 40 parts by mass of solid electrolyte (Li ₃ PS ₄ , D50:8 μm). , VGCF (registered trademark)-H (manufactured by Showa Denko KK). The mixture is homogenized by milling at 100 rpm for 1 hour using a planetary ball mill. The homogenized mixture is press-molded at 400 MPa using a uniaxial press molding machine using a polyethylene die and an SUS punch, and the positive electrode mixture layer 112 is prepared as a sheet having a thickness of 65 μm.

[8-4] Assembly of All Solid-State Lithium Ion Secondary Battery 1 The negative electrode mixture layer 132, the solid electrolyte layer 12, and the positive electrode mixture layer 112 obtained above were laminated in this order in a polyethylene die having an inner diameter of 10 mmφ. The negative electrode mixture layer 132 side and the positive electrode mixture layer 112 side were sandwiched by a SUS punch at a pressure of 100 MPa (1000 kgf/cm ² ) to form the negative electrode mixture layer 132, the solid electrolyte layer 12, and the positive electrode mixture layer. 112 is joined to obtain a laminated body A.

The obtained layered product A was once taken out from the die, and the negative electrode lead 131a, the copper foil (the negative electrode current collector 131), and the layered product A with the negative electrode mixture layer 132 facing downward from the bottom in the die, aluminum. The foil (positive electrode current collector 111) and the positive electrode lead 111a are stacked in this order, and sandwiched with a pressure of 1 MPa (10 kgf/cm ² ) from both sides of the negative electrode lead 131a side and the positive electrode lead 111a side with a SUS punch, and the negative electrode lead 131a, The copper foil, the laminate A, the aluminum foil, and the positive electrode lead 111a are joined to obtain the all-solid-state lithium ion secondary battery 1.

[8-5] Evaluation of Battery All the following battery evaluations are performed in the atmosphere at 25°C.

[8-5-1] Coulombic efficiency The all-solid-state lithium-ion secondary battery 1 manufactured as described above is charged with constant current at 1.25 mA (0.05 C) from the rest potential to 4.2 V. .. Subsequently, constant voltage charging is performed for 40 hours at a constant voltage of 4.2V. Let the charge capacity (mAh) by constant voltage charge be the initial charge capacity Qc1.

Next, constant current discharge is performed at 1.25 mA (0.05 C) until 2.75 V is reached. The discharge capacity (mAh) by the first constant current discharge is defined as the discharge capacity Qd1. A value obtained by dividing the discharge capacity Qd1 (mAh) by the mass of the composite material in the negative electrode layer is defined as the discharge capacity density (mAh/g).
Further, the ratio of the discharge capacity Qd1 to the charge capacity Qc1 is expressed as a percentage, and 100×Qd1/Qc1 is taken as the Coulombic efficiency (%).

[8-5-2] Rate characteristics After charging in the same procedure as above, discharge capacity Q _2.5 d [mAh] measured by constant current discharge at _2.5 mA (0.1 C) until 2.75 V. To measure. After charging in the same procedure as above, the discharge capacity Q ₇₅ d [mAh] measured by constant current discharge at 75 mA (3.0 C) until 2.75 V is measured. 100×Q ₇₅ d/Q _2.5 d is defined as 3C rate capacity maintenance rate (%) (rate characteristic).

[8-5-3] Cycle characteristics Charge is carried out by constant current charging of 5.0 mA (0.2 C) until it reaches 4.2 V, and then at a constant voltage of 4.2 V, the current value is 1.25 mA (0 C). Constant-voltage charging is performed until it decreases to .05C). The discharge is a constant current discharge of 25 mA (1.0 C) until the voltage reaches 2.75V.
These charges and discharges are performed 100 times, and 100×Qd100/Qd1 is taken as 100 cycle capacity retention rate (%) (cycle characteristics) as the discharge capacity Qd100 at the 100th time.

[Example 6, Comparative Examples 9 to 11]
Table 5 shows the evaluation results of the all-solid-state lithium ion secondary batteries using the graphite materials 1, 6, 9, 11 obtained in the above Examples and Comparative Examples.

DESCRIPTION OF SYMBOLS 1... All-solid-state lithium ion secondary battery 11... Positive electrode layer 12... Solid electrolyte layer 13... Negative electrode layer 111... Positive electrode collector 111a... Positive electrode lead 112... Positive electrode Mixture layer 131... Negative electrode current collector 131a... Negative electrode lead 132... Negative electrode mixture layer

Claims (13)

1. The average spacing d002 of the (002) planes measured by X-ray diffraction is 0.3354 nm or more and 0.3370 nm or less,
   The ratio ID / IG between peak intensity in the range of 1300 ~ 1400 cm ^-1 by Raman spectroscopic measurement (ID) and the peak intensity in the range of ^{1580 ~ 1620cm -1 (IG) (} R value) 0.09 Is 0.40 or less,
   The surface roughness calculated from the ratio of the BET surface area to the sphere-converted area calculated from the particle size distribution (BET surface area/sphere-converted area) is 6.0 to 14.0,
   The ratio of the area of the optically anisotropic domain is 95.0% with respect to the total area of the optically anisotropic domain, the optically isotropic domain and the void of 100.0% measured by observing the cross section of the graphite material with a polarization microscope. ~99.0%,
   The integrated value when the areas of the optically anisotropic domains are integrated in order from the smallest one is the maximum domain area (μm ² ) when n% of the area (μm ² ) of all the optically anisotropic domains is reached. A graphite material for a negative electrode of a lithium ion secondary battery that satisfies the following conditions (1) to (3) when Da(n) (where n represents a numerical value in the range of 0 to 100) is satisfied.
   (1) 5 μm ² ≦Da (10) ≦20 μm ²
   (2) 40 μm ² ≦Da (50) ≦250 μm ²
   (3) 200 μm ² ≦Da (90) ≦500 μm ²
2. The ratio of the area of the void is 1.0% or less with respect to a total of 100.0% of the area of the optically anisotropic domain, the area of the optically isotropic domain, and the area of the void. The graphite material for a negative electrode of the lithium ion secondary battery described.
3. Db(m) is the maximum domain area (μm ² ) when the total number of the optically anisotropic domains arranged in ascending order reaches m% of the number of all optically anisotropic domains. The graphite material for a negative electrode of a lithium ion secondary battery according to claim 1 or 2, wherein the following condition (4) is satisfied, where (m represents a numerical value in the range of 0 to 100).
   (4) Db(99.5)/Da(100)≦0.75
4. In the case where the maximum value of the length of the long side of the optically anisotropic domain is Lmax, and the 50% particle size (D50) in the volume-based particle size distribution of the graphite material measured by a laser diffraction method is Lave. , Lmax/Lave is 1.0 or less, The graphite material for a negative electrode of a lithium ion secondary battery according to any one of claims 1 to 3.
5. The 10% particle diameter (D10) in the volume-based particle diameter distribution measured by a laser diffraction method is 1.0 μm or more and 16.0 μm or less, and the 50% particle diameter (D50) is 6.0 μm or more and 30.0 μm or less. The graphite material for a lithium ion secondary battery electrode according to any one of claims 1 to 4, having a 90% particle diameter (D90) of 25.0 μm or more and 80.0 μm or less.
6. The graphite material for a lithium ion secondary battery electrode according to any one of claims 1 to 5, which has a BET specific surface area of 0.5 m ² /g or more and 6.0 m ² /g or less.
7. The graphite material for a negative electrode of a lithium ion secondary battery according to any one of claims 1 to 6, which has a circularity of 0.89 or more and 0.98 or less.
8. The graphite material for a lithium ion secondary battery negative electrode according to any one of claims 1 to 7, which has a particle size uniformity (D60/D10) of 1.5 or more and 3.0 or less.
9. The graphite material for a negative electrode of a lithium ion secondary battery according to any one of claims 1 to 8, which has a surface oxygen content of 0.010 or more and 0.030 or less.
10. A negative electrode active material containing the graphite material according to any one of claims 1 to 9.
11. A negative electrode for a lithium ion secondary battery, which contains the negative electrode active material according to claim 10.
12. A lithium-ion secondary battery using the negative electrode according to claim 11.
13. All-solid-state lithium-ion secondary battery using the negative electrode according to claim 11.

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