JP6922927B2 - Negative electrode material for lithium ion secondary battery, negative electrode for lithium ion secondary battery and lithium ion secondary battery - Google Patents

Description

The present invention relates to a negative electrode material for a lithium ion secondary battery, a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery.

Lithium-ion secondary batteries are lighter in weight and have higher input / output characteristics than other secondary batteries such as nickel-hydrogen batteries and lead-acid batteries. Therefore, in recent years, high input / output batteries used in electric vehicles, hybrid electric vehicles, etc. It is attracting attention as a power source.
Since the commercialization of lithium-ion secondary batteries in 1991, higher energy density and further improvement of input / output characteristics are still strongly desired. As a means for that purpose, a technique for improving the negative electrode material contained in the negative electrode of the lithium ion secondary battery occupies an important position (see, for example, Patent Document 1 and Patent Document 2).

Japanese Unexamined Patent Publication No. 4-370662 Japanese Unexamined Patent Publication No. 5-307956

As a material for the negative electrode material of a lithium ion secondary battery, a carbon material such as graphite or amorphous carbon is widely used.
Graphite has a structure in which hexagonal network surfaces of carbon atoms are regularly laminated, and lithium ion insertion / desorption reactions proceed from the ends of the laminated network surfaces to charge and discharge.
In addition, amorphous carbon has excellent input / output characteristics because the lithium ion insertion / desorption reaction proceeds on the entire surface because the hexagonal network surface is irregularly laminated or does not have a network structure. Lithium ions are easily obtained. Further, in contrast to graphite, amorphous carbon has low crystallinity, can suppress the reaction with the electrolytic solution to be low, and has excellent life characteristics.

Graphite cannot be said to have sufficient input / output performance because the insertion / removal reaction of lithium ions proceeds only at the end. Further, since the crystallinity is high and the surface reactivity is high, the reactivity with the electrolytic solution may be high, especially at a high temperature, and there is room for improvement in terms of the life characteristics of the lithium ion secondary battery. On the other hand, amorphous carbon has an irregular crystal structure due to its lower crystallinity than graphite, and its energy density cannot be said to be sufficient.

Based on the above-mentioned difference in properties between graphite and amorphous carbon, as a carbon material capable of achieving both high energy density derived from graphite and long life characteristics derived from amorphous carbon, a core material made of graphite is used. A carbon material in which an amorphous carbon layer is formed on the surface has been proposed.

In recent years, there has been an increasing need for higher battery capacity in order to extend the mileage, especially in in-vehicle applications. Therefore, in the case of in-vehicle use as well as in the case of consumer use, high density of electrodes is being studied. Among them, there is a concern that the input / output characteristics may be deteriorated due to the high density of electrodes, and it is an issue to achieve both high capacity and input / output characteristics. In other words, there is a need to tackle problems that are difficult to solve simply by combining graphite and amorphous carbon.

INDUSTRIAL APPLICABILITY The present invention includes a negative electrode material for a lithium ion secondary battery and a negative electrode for a lithium ion secondary battery capable of manufacturing a lithium ion secondary battery excellent in input / output characteristics and life characteristics while maintaining high charge / discharge efficiency, and a negative electrode for the lithium ion secondary battery. It is an object of the present invention to provide a lithium ion secondary battery manufactured using the above.

Means for solving the above problems include the following embodiments.
<1> The average spacing _{d 002} determined by X-ray diffraction method is 0.335Nm～0.339Nm, specific surface area determined from nitrogen adsorption measurements at 77K is 0.5m ² /g~6.0m ² / A negative electrode material for a lithium ion secondary battery, which is g and contains a carbon material satisfying the following (1) and (2).
(1) In the number-based particle size distribution, the particle size when the relative particle amount q0 of the difference is the mode is 11.601 μm or less.
(2) In the particle size distribution based on the number, the ratio (q0A / q0B) of the difference relative particle amount q0A when the particle size is 11.601 μm and the difference relative particle amount q0B when the particle size is 7.806 μm is 1. It is .20 to 3.00.

<2> The average surface spacing d ₀₀₂ obtained by the X-ray diffraction method is 0.335 nm to 0.339 nm, the R value of Raman spectroscopy measurement is 0.1 to 1.0, and the following (1) and ( A negative electrode material for a lithium ion secondary battery containing a carbon material satisfying 2).
(1) In the number-based particle size distribution, the particle size when the relative particle amount q0 of the difference is the mode is 11.601 μm or less.
(2) In the particle size distribution based on the number, the ratio (q0A / q0B) of the difference relative particle amount q0A when the particle size is 11.601 μm and the difference relative particle amount q0B when the particle size is 7.806 μm is 1. It is .20 to 3.00.

<3> The average surface spacing d ₀₀₂ determined by the X-ray diffractometry is 0.335 nm to 0.339 nm, and is arranged on at least a part of the surface of the first carbon phase as the core and the surface of the first carbon phase. A negative electrode material for a lithium ion secondary battery, which comprises a second carbon phase different from the first carbon phase, and also contains a carbon material satisfying the following (1) and (2).
(1) In the number-based particle size distribution, the particle size when the relative particle amount q0 of the difference is the mode is 11.601 μm or less.
(2) In the particle size distribution based on the number, the ratio (q0A / q0B) of the difference relative particle amount q0A when the particle size is 11.601 μm and the difference relative particle amount q0B when the particle size is 7.806 μm is 1. It is .20 to 3.00.

<4> In the volume-based particle size distribution, when the volume cumulative distribution curve is drawn from the small particle size side, the integrated value Q3 when the particle size is 9.516 μm is 4.0% or more of the whole. The negative electrode material for a lithium ion secondary battery according to any one of <1> to <3>.

<5> The carbon material has a particle size (50% D) of 1 μm to 20 μm when the cumulative volume is 50% when a volume cumulative distribution curve is drawn from the small particle size side in the volume-based particle size distribution. The negative electrode material for a lithium ion secondary battery according to any one of <1> to <4>.

<6> The carbon material has a particle size (99.9% D) when the cumulative volume is 99.9% when a volume cumulative distribution curve is drawn from the small particle size side in a volume-based particle size distribution. The negative electrode material for a lithium ion secondary battery according to any one of <1> to <5>, which is 63 μm or less.

<7> The carbon material, a tap density of ^{0.90g / cm 3 ~2.00g / cm 3} <1> ~ <6> negative electrode material for a lithium ion secondary battery according to any one of.

<8> The negative electrode material for a lithium ion secondary battery according to any one of <1> to <7>, wherein the carbon material has a pellet density of 1.55 g / cm ^{3 or less.}

<9> A negative electrode for a lithium ion secondary battery including a negative electrode material layer containing the negative electrode material for a lithium ion secondary battery according to any one of <1> to <8> and a current collector.

<10> The lithium ion secondary battery including the negative electrode for the lithium ion secondary battery, the positive electrode, and the electrolyte according to <9>.

According to the present invention, a negative electrode material for a lithium ion secondary battery and a negative electrode for a lithium ion secondary battery capable of manufacturing a lithium ion secondary battery having excellent input / output characteristics and life characteristics while maintaining high charge / discharge efficiency. In addition, a lithium ion secondary battery manufactured by using the same is provided.

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including element steps and the like) are not essential unless otherwise specified. The same applies to the numerical values and their ranges, and does not limit the present invention.

In the present specification, the term "process" includes not only a process independent of other processes but also the process if the purpose of the process is achieved even if the process cannot be clearly distinguished from the other process. Is done.
In the numerical range indicated by using "~" in the present specification, the numerical values before and after "~" are included as the minimum value and the maximum value, respectively.
In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. good. Further, in the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.
In the present specification, the content or content of each component in the composition refers to the content of each component in the composition when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified. It means the total content or content of substances.
In the present specification, the particle size of each component in the composition is a mixture of the plurality of particles existing in the composition unless otherwise specified, when a plurality of particles corresponding to each component are present in the composition. Means a value for.
In the present specification, the term "layer" or "membrane" refers to a part of the region in addition to the case where the layer or the membrane is formed in the entire region when the region where the layer or the membrane exists is observed. The case where only is formed is also included.
As used herein, the term "laminated" refers to stacking layers, and two or more layers may be bonded or the two or more layers may be removable.

<Negative electrode material for lithium ion secondary battery (1)>
The negative electrode material for a lithium ion secondary battery of the present embodiment (hereinafter, may be simply referred to as “negative electrode material”) has an average surface spacing d ₀₀₂ obtained by an X-ray diffraction method of 0.335 nm to 0.339 nm. the specific surface area determined from nitrogen adsorption measurements at 77K is the 0.5m ² /g~6.0m ² / g, and containing a carbon material satisfying the following (1) and (2).
(1) In the number-based particle size distribution, the particle size when the relative particle amount q0 of the difference is the mode is 11.601 μm or less.
(2) In the particle size distribution based on the number, the ratio (q0A / q0B) of the difference relative particle amount q0A when the particle size is 11.601 μm and the difference relative particle amount q0B when the particle size is 7.806 μm is 1. It is .20 to 3.00.

By using the negative electrode material of the present embodiment, it is possible to manufacture a lithium ion secondary battery having excellent input / output characteristics and life characteristics while maintaining high charge / discharge efficiency.

The composition of the negative electrode material of the present embodiment is not particularly limited as long as it contains a carbon material satisfying the above-mentioned conditions. From the viewpoint of obtaining the effect of the present embodiment, the ratio of the carbon material to the entire negative electrode material is preferably 50% by mass or more, more preferably 80% by mass or more, and more preferably 90% by mass or more. It is more preferably 100% by mass, and particularly preferably 100% by mass.

(Carbon material)
_{The average surface spacing d 002} determined by the X-ray diffraction method of the carbon material is 0.335 nm to 0.339 nm.
The value of the average interplanar spacing d ₀₀₂ is 0.3354 nm, which is the theoretical value of graphite crystals, and the closer to this value, the higher the energy density tends to be. When the value of the average surface spacing d ₀₀₂ is within the above range, excellent initial charge / discharge efficiency and energy density of the lithium ion secondary battery tend to be obtained.

In the present embodiment, the average surface spacing d ₀₀₂ of the carbon material is a diffraction angle 2θ = 24 ° from the diffraction profile obtained by irradiating the sample of the carbon material with X-rays (CuKα rays) and measuring the diffraction lines with a goniometer. It can be calculated using Bragg's equation from the diffraction peak corresponding to the carbon 002 plane appearing near ~ 27 °.

The value of the average surface spacing d ₀₀₂ of the carbon material is preferably small from the viewpoint of the energy density of the lithium ion secondary battery. Specifically, for example, it is preferably 0.335 nm to 0.337 nm.
Since the value of the average surface spacing d ₀₀₂ of the carbon material tends to decrease as the temperature of the heat treatment performed on the carbon material is increased, for example, the average surface spacing d ₀₀₂ is kept within the above range by utilizing this property. Can be adjusted to.

The specific surface area determined from nitrogen adsorption measurements at 77K carbon material (hereinafter sometimes referred to as _{N 2} specific surface area) ^is 0.5m ² /g~6.0m 2 / g.
_{When the N 2} specific surface area of the carbon material is within the above range, the balance between the input / output characteristics and the initial efficiency tends to be well maintained.
The N ₂ specific surface area of the carbon material can be determined by using the BET method from the adsorption isotherm obtained from the nitrogen adsorption measurement at 77K.

From the viewpoint of the balance of the input and output characteristics and initial efficiency of the lithium ion secondary battery, it is preferable _{N 2} specific surface area is 1.0m ² /g~5.0m ² / g.
The N ₂ specific surface area tends to be reduced in value by, for example, increasing the volume average particle size of the carbon material, increasing the temperature of the heat treatment performed on the carbon material, or modifying the surface of the carbon material. some reason, the N ₂ specific surface area by using this property can be set within the above range.

The carbon material has a particle size of 11.601 μm or less when the relative particle amount q0 of the difference is the mode in the particle size distribution based on the number. When the particle size at which the relative particle amount q0 of the difference is the most frequent value exceeds 11.601 μm, the proportion of carbon material having a large particle size increases, so that the diffusion distance of lithium ions from the surface of the particles of the carbon material to the inside increases. As it becomes longer, the input / output characteristics of the lithium ion secondary battery tend to deteriorate.

The particle size at which the relative particle amount q0 of the difference is the mode is preferably 11.601 μm or 9.516 μm, and more preferably 11.601 μm.

For the carbon material, the total value of the difference relative particle amount q0 when the particle size is 11.601 μm and the difference relative particle amount q0 when the particle size is 9.516 μm is preferably 25 or more, preferably 30 or more. Is more preferable, and 32 or more is further preferable.

The carbon material has a ratio (q0A / q0B) of the difference relative particle amount q0A when the particle size is 11.601 μm and the difference relative particle amount q0B when the particle size is 7.806 μm in the particle size distribution based on the number. It is 1.20 to 3.00.
If the value of q0A / q0B is less than 1.20, the input / output characteristics tend to deteriorate.
When the value of q0A / q0B exceeds 3.00, the contact between the particles of the carbon material becomes poor, and the life characteristic of the lithium ion secondary battery tends to deteriorate.
From the viewpoint of input / output characteristics and life characteristics, the value of q0A / q0B is preferably in the range of 1.20 to 2.20, and more preferably in the range of 1.25 to 2.10.

In the present specification, the particle size distribution based on the number of carbon materials is obtained by dividing the range of particle diameters of 0.1 μm to 2000 μm into 50 logarithmic ratios. For example, the particle size is obtained from n = (2000 / 0.1) ^ (1/50) and is from 0.1 × n, 0.1 × n ^ 2, ..., 0.1 × n ^ 50. can get. The total value of the relative particle amount q0 for each particle size in the range of 0.1 μm to 2000 μm is 100.
Table 1 shows the value of the relative particle amount q0 and the particle size of the difference based on the number of carbon materials used in Example 2.

For carbon materials, when the volume cumulative distribution curve is drawn from the small particle size side in the volume-based particle size distribution, the integrated value Q3 when the particle size is 9.516 μm is 4.0% or more of the total. It is preferably 9.0% or more, and more preferably 9.0% or more.
When the integrated value Q3 when the particle size is 9.516 μm is 4.0% or more of the whole, the contact points between the particles are sufficiently secured by the minute particles contained in the carbon material, and the lithium ion secondary battery There is a tendency for the life characteristics of the particles to improve.

The upper limit of the integrated value Q3 is not particularly limited, but is preferably 30% or less, and more preferably 20% or less.

The carbon material has a particle size (50% D, hereinafter also referred to as a volume average particle size) when the cumulative volume is 50% when a volume cumulative distribution curve is drawn from the small particle size side in the volume-based particle size distribution. Is preferably 1 μm to 20 μm, more preferably 3 μm to 18 μm, and even more preferably 5 μm to 15 μm.
When the volume average particle size of the carbon material is 1 μm or more, the specific surface area tends to be too large and the decrease in the initial charge / discharge efficiency of the lithium ion secondary battery tends to be suppressed. On the other hand, if the volume average particle size of the carbon material is 20 μm or less, the particle size is too large and the diffusion distance of Li from the particle surface to the inside becomes long, and the input / output characteristics of the lithium ion secondary battery may deteriorate. It tends to be suppressed.

The carbon material has a particle size (99.9% D, hereinafter, maximum particle size) when the cumulative volume is 99.9% when a volume cumulative distribution curve is drawn from the small particle size side in the volume-based particle size distribution. (Also referred to as) is preferably 63 μm or less, more preferably 50 μm or less, and further preferably 45 μm or less.
When the maximum particle size of the carbon material is 63 μm or less, the electrode plate is likely to be thinned when the electrode is manufactured, and the influence on the input / output characteristics tends to be suppressed.

In the present specification, the volume-based particle size distribution of the carbon material is obtained by dividing the range of 0.1 μm to 2000 μm into 50 logarithmic ratios, similar to the number-based particle size distribution. The volume-based particle size distribution can be measured in the same manner as the number-based particle size distribution.

In the present specification, the particle size distribution of the carbon material can be measured by a known method. For example, a dispersion prepared by dispersing a sample of a carbon material together with a surfactant in purified water is placed in a sample water tank of a laser diffraction type particle size distribution measuring device, and ultrasonic waves are applied for 1 minute while circulating with a pump. It is obtained by measuring with a laser diffraction method under the measurement conditions of. As the laser diffraction type particle size distribution measuring device, for example, "SALD-3000J" manufactured by Shimadzu Corporation can be used. Here, by selecting "number" or "volume" as the output condition, a number-based particle size distribution or a volume-based particle size distribution can be obtained.

(Setting of measurement conditions)
Number of measurements: 1 measurement interval: 2 seconds Average number of measurements: 64 measurements Absorbance range: 0.01 to 0.2
(Arbitrary particle size /% table setting)
Range: 0.1 μm to 2000 μm
Number of divisions: 50

The carbon material of the present embodiment can be obtained, for example, by combining two or more types of carbon materials having different particle sizes.
Such a combination of carbon materials includes a combination of a carbon material having a volume average particle diameter of 8 μm to 12 μm and a carbon material having a volume average particle diameter of 14 μm to 18 μm, and a carbon material having a volume average particle diameter of 9 μm to 11 μm and a volume average. Examples thereof include a combination of carbon materials having a particle size of 15 μm to 17 μm.
Examples of the ratio when two types of carbon materials having different particle sizes are combined include, for example, a mass ratio in the range of 7: 3 to 3: 7, and a mass ratio in the range of 6: 4 to 4: 6.

Carbon material is preferably a tap density of ^{0.90g / cm 3 ~2.00g / cm 3} , more preferably ^{1.00g / cm 3 ~1.50g / cm 3} , 1.05g / It is more preferably cm ^{3 to} 1.30 g / cm ^3.
When the tap density of the carbon material is 0.90 g / cm ³ or more, the amount of organic substances such as binders used when producing the negative electrode can be reduced, and the energy density of the lithium ion secondary battery tends to increase. .. On the other hand, when the tap density of the carbon material is 2.00 g / cm ³ or less, the input / output characteristics tend to be good.

The tap density of the carbon material tends to increase by increasing the volume average particle size of the carbon material, for example, and the tap density can be set within the above range by utilizing this property.

The tap density of the entire negative electrode material containing a carbon material ^may be ^{0.90g / cm 3 ~3.00g / cm 3} . Examples of the method for adjusting the tap density of the negative electrode material include a method of incorporating a metal component or the like, which will be described later, in addition to the carbon material.

In the present specification, the tap density of the carbon material or the negative electrode material is such that the sample powder 100 cm ^{3 is slowly poured into a graduated cylinder having a capacity of 100 cm 3} , the graduated cylinder is plugged, and the graduated cylinder is dropped 250 times from a height of 5 cm. It means a value (g / cm ³ ) obtained by dividing the mass (g) of the sample powder after the test by the volume (cm ^3).

Carbon material is preferably pellet density of 1.55 g / cm ³ or less, more preferably 1.50 g / cm ³ or less. When the pellet density is 1.55 g / cm ³ or less, when the electrode density is increased, the voids between the particles of the carbon material become too small, and the ion concentration near the particles decreases, so that the lithium ion secondary battery is inserted. Deterioration of output characteristics tends to be suppressed.

The value of the pellet density of the carbon material tends to be lowered by, for example, reducing the volume average particle size of the carbon material, and the pellet density can be set within the above range by utilizing this property.

The pellet density of the entire negative electrode material including the carbon material may be ^{1.10 g / cm 3 to} 2.00 g / cm ^3. Examples of the method of adjusting the pellet density of the negative electrode material include a method of controlling the temperature of the heat treatment performed on the carbon material.

In the present invention, the pellet density of the carbon material or the negative electrode material is the thickness (cm) and the cross-sectional area of the sample after 1.00 g of the sample powder is put into the molding machine and pressed with a pressure of 1.0 t by a hydraulic press. It means a ^{value (g / cm 3} ) obtained by dividing the mass (g) by the volume obtained from ^{cm 2).}

The carbon material preferably has an R value of 0.1 to 1.0, more preferably 0.2 to 0.8, and further preferably 0.3 to 0.7, as measured by Raman spectroscopy. preferable. When the R value is 0.1 or more, graphite lattice defects used for insertion and desorption of lithium ions are sufficiently present, and deterioration of input / output characteristics tends to be suppressed. When the R value is 1.0 or less, the decomposition reaction of the electrolytic solution is sufficiently suppressed, and the decrease in the initial efficiency tends to be suppressed.

R value, in the Raman spectrum obtained in the Raman spectrometry, to define the intensity Ig of the maximum peak in the vicinity of 1580 cm ^-1, the intensity ratio of the intensity Id of the maximum peak around 1360 cm ^-1 and (Id / Ig). Here, the peak appearing near 1580 cm ^-1, generally a peak identified as corresponding to the graphite crystal structure, means a peak observed for example ^{1530cm -1 ~1630cm} -1. The peak appearing in the vicinity of 1360 cm ^-1 is a peak usually identified to correspond to the amorphous structure of carbon, and means, for example, a peak observed in ^{1300 cm -1 to} 1400 cm ^-1.

In the present specification, the Raman spectroscopic measurement is performed by using a laser Raman spectrophotometer (model number: NRS-1000, JASCO Corporation) on a sample plate in which the negative electrode material for a lithium ion secondary battery is set flat. The measurement is performed by irradiating light (excitation wavelength: 532 nm).

Examples of the material of the carbon material include carbon materials such as graphite (artificial graphite, natural graphite, graphitized mesophase carbon, graphitized carbon fiber, etc.), low crystalline carbon, and mesophase carbon. From the viewpoint of increasing the charge / discharge capacity, it is preferable that at least a part of the carbon material is graphite.

The shape of the carbon material is not particularly limited. For example, scaly, spherical, lumpy and the like can be mentioned. From the viewpoint of obtaining a high tap density, it is preferably spherical. From these carbon materials, a carbon material having the above-mentioned physical characteristics may be appropriately selected. As the carbon material, one type may be used alone, or two or more types having different materials, shapes and the like may be used in combination.

The carbon material is a composite material containing a first carbon phase that is the nucleus and a second carbon phase that is different from the first carbon phase that is located on at least a part of the surface thereof (for example, that covers the nucleus). It may be. By composing the carbon material from a plurality of different carbon phases, it is possible to obtain a carbon material capable of more effectively exhibiting desired physical properties or properties.

When the carbon material is a composite material containing a first carbon phase as a core and a second carbon phase arranged on at least a part of the surface thereof, a combination of the first carbon phase and the second carbon phase. Examples include a combination of a first carbon phase and a second carbon phase having a different crystallinity from the first carbon phase, which is less crystalline than the first carbon phase and the first carbon phase ( A combination of the second carbon phase (where the value of d _{002 is larger than the first carbon phase) is preferred.}

When the carbon material is a composite material containing a first carbon phase as a core and a second carbon phase having a lower crystallinity than the first carbon phase, the material of the first carbon phase as a core is It is preferably selected from the graphite described above. In this case, the second carbon phase is preferably selected from those having lower crystallinity than the first carbon phase (hereinafter, also referred to as a low crystal carbon phase).

The material of the second carbon phase, which has lower crystallinity than the first carbon phase, is not particularly limited and is appropriately selected according to desired properties. A preferred example of the second carbon phase is a carbon phase obtained from an organic compound (carbon precursor) that can be transformed into a carbonaceous substance by heat treatment. Specifically, it is produced by polymerizing ethylene heavy end pitch, crude oil pitch, coal tar pitch, asphalt decomposition pitch, pitch produced by thermal decomposition of organic compounds such as polyvinyl chloride, naphthalene, etc. in the presence of super strong acid. The synthetic pitch to be performed can be mentioned. Further, thermoplastic synthetic polymers such as polyvinyl chloride, polyvinyl alcohol, polyvinyl acetate and polyvinyl butyral, and natural polymers such as starch and cellulose can also be used as carbon precursors.

When the carbon material is the composite material described above, the first carbon phase as the core is _{a graphite material having an average surface spacing d 002} in the range of 0.335 nm to 0.339 nm from the viewpoint of increasing charge / discharge capacity. Is preferable. In particular, _{when a graphite material having d 002} in the range of 0.335 nm to 0.338 nm, preferably 0.335 nm to 0.337 nm is used, the charge / discharge capacity is as large as 330 mAh / g to 370 mAh / g, which is good lithium ion. Secondary batteries tend to be obtained.

The graphite material to be the first carbon phase preferably has a volume average particle size (50% D) of 1 μm to 20 μm. When the volume average particle size of the graphite material is 1 μm or more, fine powder is contained in the raw material graphite in an appropriate amount, and the occurrence of aggregation in the step of adhering the organic compound as a carbon precursor to the core material is suppressed. Both tend to be mixed more evenly. When the volume average particle size of the graphite material is 20 μm or less, the mixture of coarse particles in the negative electrode material is suppressed, and the occurrence of streaks and the like during coating of the negative electrode material tends to be suppressed.

Graphite material as the first carbon phase is preferably a ratio determined by nitrogen adsorption measurements at 77K surface area, i.e. BET specific surface area _{(N 2} specific surface area) is 0.1m ² / g~30m ² / g , more preferably 0.5m ² / g~25m ² / ^g, further preferably 0.5m ² / g~15m 2 / g. _{When the N 2} specific surface area of the graphite material ^{is 0.1 m 2} / g or more, aggregation tends to be less likely to occur in the step of adhering the organic compound as a carbon precursor to the core material. _{When the N 2} specific surface area of the graphite material ^{is 30 m 2} / g or less, the specific surface area is maintained in an appropriate range, and the organic compounds tend to adhere more evenly.

Examples of the shape of the graphite material serving as the first carbon phase include scaly, spherical, and lumpy shapes, and it is preferable that the graphite material has a spherical shape from the viewpoint of increasing the tap density.

An aspect ratio can be mentioned as an index showing the degree of spheroidization of the graphite material. In the present specification, the aspect ratio of the graphite material is a value obtained by "maximum length vertical length / maximum length", and the maximum value is 1. Here, the "maximum length" is the maximum value of the distance between two points on the contour line of the particles of the graphite material, and the "maximum length vertical length" is perpendicular to the line segment connecting the two points having the maximum length. It is the length of the longest line segment connecting two points on the contour line of the particle.
The aspect ratio of the graphite material can be measured using, for example, a flow-type particle image analyzer. Examples of the flow type particle image analyzer include "FPIA-3000" manufactured by Sysmex Corporation.

The graphite material serving as the first carbon phase preferably has an average aspect ratio of 0.1 or more, and more preferably 0.3 or more. When the average aspect ratio of the graphite material is 0.1 or more, the proportion of scaly graphite in the graphite material is not too large, and the amount of the edge surface of the graphite material can be suppressed within an appropriate range. Since the edge surface is more active than the basal surface, there is a concern that more organic compounds will be attached to the edge surface in the step of attaching the organic compound as a carbon precursor to the core material, but the average aspect ratio is high. If it is 0.1 or more, the organic compound tends to adhere to the core material more evenly. As a result, the distribution of low crystalline carbon and crystalline carbon in the obtained carbon material tends to be more even.

The negative electrode material may contain other components in addition to the carbon material, if necessary. For example, it may contain a metal component.
As the metal component, if necessary for increasing the capacity, a metal powder composed of an element alloying with lithium such as Al, Si, Ga, Ge, In, Sn, Sb, Ag, Al, Si, Ga, etc. Examples thereof include powders of multi-element alloys containing at least elements that alloy with lithium such as Ge, In, Sn, Sb, and Ag, and powders of lithium alloys. As the metal component, one type may be used alone, or two or more types may be used in combination. When the negative electrode material contains a metal component, the metal component may be added separately from the carbon material or may be added in a state of being composited with the carbon material.

When the negative electrode material contains a metal component in addition to the carbon material, the tap density of the entire negative electrode material tends to increase as compared with the case where the negative electrode material contains only the carbon material. For example, it is possible to a tap density of the entire negative electrode material and ^{0.3g / cm 3 ~3.0g / cm 3} . When the tap density of the negative electrode material is large, the charge / discharge reaction is promoted, the negative electrode resistance is reduced, and good input / output characteristics tend to be obtained.

When the negative electrode material contains a metal component in addition to the carbon material, the amount thereof is not particularly limited. For example, the amount may be 1% by mass to 50% by mass of the entire negative electrode material.

<Negative electrode material for lithium ion secondary battery (2)>
In the negative electrode material for a lithium ion secondary battery of the present embodiment, the average surface spacing d ₀₀₂ determined by the X-ray diffraction method is 0.335 nm to 0.339 nm, and the R value of Raman spectroscopy measurement is 0.1 to 1. It contains a carbon material that is 0 and satisfies the following (1) and (2).
(1) In the number-based particle size distribution, the particle size when the relative particle amount q0 of the difference is the mode is 11.601 μm or less.
(2) In the particle size distribution based on the number, the ratio (q0A / q0B) of the difference relative particle amount q0A when the particle size is 11.601 μm and the difference relative particle amount q0B when the particle size is 7.806 μm is 1. It is .20 to 3.00.

In the negative electrode material of the present embodiment, the details of each condition and the preferred embodiment can be referred to the above-described description of the negative electrode material of the embodiment.

<Negative electrode material for lithium ion secondary battery (3)>
The negative electrode material for a lithium ion secondary battery of the present embodiment has an average surface spacing d ₀₀₂ determined by an X-ray diffraction method of 0.335 nm to 0.339 nm, and has a first carbon phase as a core and the first carbon phase. A second carbon phase different from the first carbon phase arranged on at least a part of the surface of the carbon phase of the above, and a carbon material satisfying the following (1) and (2).
(1) In the number-based particle size distribution, the particle size when the relative particle amount q0 of the difference is the mode is 11.601 μm or less.
(2) In the particle size distribution based on the number, the ratio (q0A / q0B) of the difference relative particle amount q0A when the particle size is 11.601 μm and the difference relative particle amount q0B when the particle size is 7.806 μm is 1. It is .20 to 3.00.

In the negative electrode material of the present embodiment, the details of each condition and the preferred embodiment can be referred to the above-described description of the negative electrode material of the embodiment.

<Manufacturing method of negative electrode material>
The method for producing the negative electrode material of the present embodiment is not particularly limited, and a method usually used for producing the negative electrode material can be adopted.

When the carbon material is a composite material containing a first carbon phase as a core and a second carbon phase arranged on at least a part of the surface thereof, a method for producing the carbon material is, for example, a carbon precursor. After adhering the organic compound to the surface of the core material to be the first carbon phase, a method of carbonizing the carbon precursor by firing in an inert atmosphere at 750 ° C. to 1200 ° C. can be mentioned. Examples of the organic compound used as the carbon precursor include the above-mentioned organic compounds as an example of the carbon precursor.

The method of adhering the carbon precursor to the surface of the first carbon phase is not particularly limited. For example, a wet method in which a core material to be the first carbon phase is mixed with a liquid in which a carbon precursor is dissolved or dispersed in a solvent and then the solvent is removed, the core material and the carbon precursor are mixed in a solid state. Examples thereof include a dry method in which the obtained mixture is adhered by applying mechanical energy, a vapor phase method such as a CVD method, and the like. From the viewpoint of controlling the specific surface area of the carbon material, it is preferable to use the dry method.

The method of adhering the carbon precursor to the surface of the first carbon phase by the dry method is not particularly limited. For example, a mixture of the first carbon and a carbon precursor is filled in a container having a structure capable of at least one of mixing and stirring of the contents, and at least one of mixing and stirring is performed while applying mechanical energy. Can be attached by. Specifically, for example, it can be carried out using a container equipped with a device such as a wing or a screw. The amount of mechanical energy applied to the mixture is not particularly limited. For example, it is preferably 0.360 kJ / kg to 36000 kJ / kg, more preferably 0.360 kJ / kg to 7200 kJ / kg, and even more preferably 2.50 kJ / kg to 2000 kJ / kg.

Here, the mechanical energy applied to the mixture is a value obtained by multiplying the load (kW) by the time (h) and dividing by the mass (kg) of the packed mixture. By setting the mechanical energy applied to the mixture in the above range, the carbon precursor adheres more evenly to the surface of the first carbon, and the distribution of low crystalline carbon and crystalline carbon in the obtained carbon material becomes more even. There is a tendency.

The state after the carbon precursor is attached to the surface of the first carbon phase (intermediate product) is further heated and fired. The firing temperature is not particularly limited as long as the carbon precursor can be carbonized. For example, it is preferably 750 ° C. to 2000 ° C., more preferably 800 ° C. to 1800 ° C., and even more preferably 900 ° C. to 1400 ° C. When the firing temperature is 750 ° C. or higher, the charge / discharge efficiency, input / discharge characteristics, and cycle characteristics of the lithium ion secondary battery tend to be maintained well, and when the firing temperature is 2000 ° C. or lower, low crystalline carbon. It tends to be suppressed that the crystallinity of the portion becomes too high. As a result, characteristics such as quick charge characteristics, low temperature charge characteristics, and overcharge safety tend to be maintained satisfactorily. The atmosphere at the time of firing is not particularly limited as long as the intermediate product has an atmosphere in which it is difficult to oxidize. For example, a nitrogen gas atmosphere, an argon gas atmosphere, a self-decomposing gas atmosphere, or the like can be applied. The type of furnace used for firing is not particularly limited. For example, a batch furnace, a continuous furnace, or the like using at least one of electricity and gas as a heat source is preferable.

<Negative electrode for lithium ion secondary battery>
The negative electrode for a lithium ion secondary battery of the present embodiment includes a negative electrode material layer containing the above-mentioned negative electrode material and a current collector. This makes it possible to construct a lithium ion secondary battery having excellent input / output characteristics and life characteristics while maintaining high charge / discharge efficiency. The negative electrode for a lithium ion secondary battery may include, if necessary, other components in addition to the negative electrode material layer and the current collector including the negative electrode material described above.

The method for producing the negative electrode for a lithium ion secondary battery is not particularly limited. For example, a negative electrode material and an organic binder are kneaded together with a solvent using a disperser such as a stirrer, a ball mill, a super sand mill, or a pressure kneader to prepare a slurry negative electrode composition, which is used as a surface of a current collector. A method of forming a negative electrode layer by applying the solvent to the current collector, a method of preparing a paste-like negative electrode composition in the same manner as described above, forming the negative electrode composition into a sheet shape, a pellet shape, or the like, and integrating the negative electrode composition with the current collector. Can be mentioned.

The organic binder is not particularly limited. For example, ethylenically unsaturated carboxylic acid esters such as styrene-butadiene copolymers, methyl (meth) acrylates, ethyl (meth) acrylates, butyl (meth) acrylates, (meth) acrylonitrile, and hydroxyethyl (meth) acrylates, acrylic acids. , Esteric unsaturated carboxylic acids such as methacrylic acid, itaconic acid, fumaric acid, maleic acid, polyvinylidene fluoride, polyethylene oxide, polyepicrohydrin, polyphosphazene, polyacrylonitrile and other polymer compounds with high ionic conductivity. And so on. (Meta) acrylate represents at least one of acrylate and methacrylate.
The amount of the organic binder contained in the negative electrode composition is not particularly limited, but is preferably 0.5 parts by mass to 20 parts by mass with respect to 100 parts by mass in total of the negative electrode material and the organic binder.

The negative electrode composition may contain a thickener for adjusting the viscosity. Examples of the thickener include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, polyacrylic acid (salt), oxidized starch, phosphorylated starch, casein and the like.

The negative electrode composition may include a conductive auxiliary material. Examples of the conductive auxiliary material include carbon materials such as carbon black, graphite, and acetylene black, as well as oxides and nitrides exhibiting conductivity. The amount of the conductive auxiliary agent is not particularly limited, but may be about 0.5% by mass to 15% by mass with respect to 100 parts by mass of the negative electrode material.

The material and shape of the current collector are not particularly limited. For example, a metal material such as aluminum, copper, nickel, titanium, stainless steel, etc., which is formed into a foil shape, a perforated foil shape, a mesh shape, or the like can be mentioned. Furthermore, porous materials such as porous metal (foamed metal), carbon paper, and the like can also be used.

The method of applying the negative electrode composition to the current collector is not particularly limited. Examples thereof include coating methods such as a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, a roll coating method, a doctor blade method, a comma coating method, a gravure coating method, and a screen printing method. After the negative electrode composition is applied to the current collector, it is dried by a hot air dryer, an infrared dryer, or a dryer combining these in order to remove the solvent contained in the negative electrode composition. Further, if necessary, rolling processing is performed by a flat plate press, a calendar roll, or the like.

The method of molding the negative electrode material composition into a sheet shape, a pellet shape, or the like and integrating the negative electrode material composition with the current collector is not particularly limited. For example, it can be carried out by a known method using a roll, a press or a combination thereof. The pressure at the time of integration is preferably about 1 MPa to 200 MPa.

The negative electrode density of the lithium-ion secondary battery negative electrode ^is preferably ^{1.3g / cm 3 ~1.8g / cm 3} , more preferably from 1.4g / cm ³ ~1.8g / cm 3 , further preferably ^{1.5g / cm 3 ~1.7g / cm 3} . When the negative electrode density is 1.3 g / cm ³ or more, the resistance value is unlikely to decrease and the capacity tends to be maintained high, and when it is 1.8 g / cm ³ or less, the decrease in rate characteristics and cycle characteristics is suppressed. Tends to be.

<Lithium-ion secondary battery>
The lithium ion secondary battery of the present embodiment includes the above-mentioned negative electrode for a lithium ion secondary battery, a positive electrode, and an electrolyte. In the lithium ion secondary battery, for example, a negative electrode and a positive electrode for a lithium ion secondary battery are arranged in a container so as to face each other via a separator, and an electrolytic solution prepared by dissolving an electrolyte in a solvent is injected into the container. Can be obtained by doing.

The positive electrode can be obtained by applying a positive electrode material to the surface of the current collector to form a positive electrode layer in the same manner as the negative electrode. As the current collector, a strip-shaped current collector obtained by forming a metal material such as aluminum, titanium, or stainless steel into a foil shape, a perforated foil shape, a mesh shape, or the like can be used.

The material used for the positive electrode is not particularly limited. For example, positive electrode active materials such as metal compounds capable of doping or intercalating lithium ions, metal oxides, metal sulfides, and phosphate compounds, and other materials can be mentioned.
As the positive electrode active material, at least a part of cobalt was replaced with at least one of nickel and manganese in _{lithium cobalt oxide (LiCoO 2} ), lithium nickel oxide (LiNiO ₂ ), lithium manganate (LiMnO _{2), and lithium cobalt oxide.} composite oxide _{(LiCo x Ni y Mn z O} 2, x + y + z = 1), mixed oxide of cobalt in these compounds, at least a part of nickel and manganese is substituted with additional element _{M '(LiCo a Ni b Mn} c _M'd O ₂ , a + b + c + d = 1, M': Al, Mg, Ti, Zr or Ge), lithium manganese spinel (LiMn ₂ O ₄ ), lithium vanadium compound, V ₂ O ₅ , V ₆ O ₁₃ , VO ₂ , MnO ₂ , TiO ₂ , MoV ₂ O ₈ , TiS ₂ , V ₂ S ₅ , VS ₂ , MoS ₂ , MoS ₃ , Cr ₃ O ₈ , Cr ₂ O ₅ , and Olivin type LiMPO ₄ (M: Co, Ni) , Mn, Fe).
Examples of other materials include conductive polymers such as polyacetylene, polyaniline, polypyrrole, polythiophene, and polyacene, and porous carbon.

Examples of the separator include non-woven fabrics mainly composed of polyolefins such as polyethylene and polypropylene, cloths, micropore films, and combinations thereof. If the positive electrode and the negative electrode do not come into contact with each other due to the structure of the lithium ion secondary battery, the separator may be omitted.

Examples of the electrolyte include lithium salts such _{as LiClO 4} , LiPF ₆ , LiAsF _{6 , LiBF 4} , and LiSO ₃ CF _3.
Solvents that dissolve the electrolyte include ethylene carbonate, fluoroethylene carbonate, chloroethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, cyclopentanone, cyclohexylbenzene, sulfolane, propanesulton, 3-methylsulfolane, and 2,4-dimethyl. Sulfolane, 3-methyl-1,3-oxazolidine-2-one, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, butyl methyl carbonate, ethyl propyl carbonate, butyl ethyl carbonate, dipropyl carbonate, Examples thereof include non-aqueous solvents such as 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, 1,3-dioxolane, methyl acetate, ethyl acetate, trimethylphosphate and triethylphosphate.

The configuration of the electrodes in the lithium ion secondary battery is not particularly limited. In general, a pile of a positive electrode and a negative electrode and a separator provided between the positive electrode and the negative electrode, if necessary, wound in a spiral shape (swirl type electrode plate group) and a spiral shape. Examples include plate-shaped ones (laminated electrode plate group) that are not wound around.

The type of lithium ion secondary battery is not particularly limited. Examples thereof include laminated batteries, paper batteries, button batteries, coin batteries, laminated batteries, cylindrical batteries, square batteries and the like.

Since the negative electrode material of the present embodiment has excellent input / output characteristics and life characteristics during charging and discharging, a lithium ion secondary material that is required to have a relatively large capacity for electric vehicles, power tools, power storage, etc. Suitable for batteries. In particular, in automobile applications such as electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (PHEV), charging and discharging with a large current is required to improve acceleration performance and brake regeneration performance. In order to satisfy such requirements, it is desirable to use the negative electrode material of the present embodiment having excellent input / output characteristics.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

[Example 1]
_{100 parts by mass of spherical natural graphite (d 002} = 0.336 nm, average aspect ratio = 0.8) with a volume average particle diameter of 10 μm and coal tar pitch (softening point 98 ° C., residual carbonization rate (carbonization rate) 50%) A mixture obtained by mixing 5 parts by mass was placed in a cylinder in which a rotary blade was arranged and rubbed between the inner wall of the cylinder and the rotary blade to adhere a coal tar pitch to the surface of spherical natural graphite. .. The rubbing step was carried out at a load of 24 kW for 5 minutes (load: 1800 kJ / kg). Next, the temperature was raised to 1000 ° C. at a heating rate of 20 ° C./hour under nitrogen flow, and the temperature was maintained for 1 hour to carbonize the coal tar pitch. Then, it was crushed with a cutter mill, sieved with a 300 mesh sieve, and the under-sieve was obtained as composite material 1.

_{Composite material 1 except that 100 parts by mass of spherical natural graphite (d 002} = 0.336 nm, average aspect ratio = 0.8) having a volume average particle diameter of 16 μm was used instead of spherical natural graphite having a volume average particle diameter of 10 μm. The composite material 2 was obtained in the same manner as in the above.

The composite material 1 and the composite material 2 were mixed so as to have a mass ratio of 5: 5 (composite material 1: composite material 2) to prepare a carbon material. The obtained carbon material was subjected to XRD analysis, specific surface area measurement, particle size distribution measurement, tap density measurement, and pellet density measurement by the methods shown below.

[XRD analysis (measurement of _{average surface spacing d 002)]}
The carbon material was filled in the concave portion of the quartz sample holder and set on the measurement stage. The measurement was performed with a wide-angle X-ray diffractometer (manufactured by Rigaku Co., Ltd.) under the following measurement conditions.
Radioactive source: CuKα ray (wavelength = 0.15418 nm)
Output: 40kV, 20mA
Sampling width: 0.010 °
Scanning range: 10 ° to 35 °
Scan speed: 0.5 ° / min

_{[N 2} specific surface area measurement]
For carbon materials, nitrogen adsorption at liquid nitrogen temperature (77K) was measured by the multipoint method using a high-speed specific surface area / pore distribution measuring device (MICROMERITICS'ASAP2010'), and the BET method (relative pressure range: 0). It was calculated from .05-0.2).

[Measurement of particle size distribution]
A solution in which a carbon material is dispersed in purified water together with a surfactant is placed in a sample water tank of a laser diffraction type particle size distribution measuring device (“SALD-3000J” manufactured by Shimadzu Corporation) and circulated by a pump for 1 minute. Was measured by a laser diffraction method under the following measurement conditions. At this time, the output conditions were set based on the number or volume, and the values corresponding to the following (1) to (5) were examined.

(Setting of measurement conditions)
Number of measurements: 1 measurement interval: 2 seconds Average number of measurements: 64 measurements Absorbance range: 0.01 to 0.2
(Arbitrary particle size /% table setting)
Range: 0.1-2000 μm
Number of divisions: 50

(1) In the particle size distribution based on the number obtained by setting the distribution standard of the output condition as "number" in the above particle size distribution measurement, the particle size when the relative particle amount q0 of the difference became the mode was investigated.

(2) In the particle size distribution based on the number obtained by using the distribution standard of the output condition as the "number" in the above particle size distribution measurement, the relative particle amount q0A of the difference when the particle size is 11.601 μm and the particle size are 7 The ratio (q0A / q0B) of the difference to the relative particle size q0B at .806 μm was calculated.

(3) In the volume-based particle size distribution obtained by setting the distribution standard of the output condition as "volume" in the above particle size distribution measurement, the particle size is 9.516 μm when the volume cumulative distribution curve is drawn from the small particle size side. The integrated value Q3 at the time of was examined.

(4) In the volume-based particle size distribution obtained by setting the distribution standard of the output condition as "volume" in the above particle size distribution measurement, the cumulative volume is 50% when the volume cumulative distribution curve is drawn from the small particle size side. The particle size (50% D) at that time was examined.

(5) In the volume-based particle size distribution obtained by setting the distribution standard of the output condition as "volume" in the above particle size distribution measurement, when the volume cumulative distribution curve is drawn from the small particle size side, the accumulation is 99.9%. The particle size (99.9% D) at that time was examined.

[Tap density measurement]
The carbon material 100 cm ³ was slowly poured into a graduated cylinder having a capacity of 100 cm ^{3, and the graduated cylinder was plugged.} The value obtained from the mass and volume of the carbon material after dropping the graduated cylinder 250 times from a height of 5 cm was defined as the tap density.

[Pellet density measurement]
After putting 1.00 g of carbon material into a 13 mm diameter molding machine (Carver's 13 mm volume die model number 3619) and pressurizing it with a hydraulic press (Carver's "Carver Standard Press") at a pressure of 1.0 t. The value obtained by dividing the volume obtained from the thickness and cross-sectional area of the carbon material by the mass of the carbon material was defined as the pellet density.

[Average aspect ratio]
The average aspect ratio of the carbon material was determined using a flow-type particle image analyzer (“FPIA-3000” of Sysmex Corporation).

[Measurement of initial charge / discharge efficiency]
1 part by mass of an aqueous solution containing 2% by mass of CMC (carboxymethyl cellulose, "Cerogen WS-C" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a thickener with respect to 98 parts by mass of the produced carbon material. And kneaded for 10 minutes. Next, purified water was added so that the solid content concentration in the kneaded product (total of the negative electrode material and the CMC) was 40% by mass to 50% by mass, and kneading was performed for 10 minutes. Next, as a binder, an aqueous dispersion having a concentration of SBR (“BM-400B” of Nippon Zeon Corporation) of 40% by mass was added so as to make up 1 part by mass of the solid content of SBR, and mixed for 10 minutes to paste. A negative electrode material composition in the form of a shape was prepared. This negative electrode material composition was applied to an electrolytic copper foil having a thickness of 40 μm using a mask having a thickness of 200 μm so as to form a circle having a diameter of 9.5 mm. Further, it was dried at 105 ° C. to remove water to prepare a sample electrode (negative electrode).

_{Next, the sample electrode, the separator, and the counter electrode stacked in this order are placed in a battery container, and LiPF 6} is added to a mixed solvent of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) (EC and MEC have a volume ratio of 1: 3). Was injected to a concentration of 1.5 mol / liter, and a coin battery was prepared. Metallic lithium was used for the counter electrode, and a polyethylene micropore membrane having a thickness of 20 μm was used for the separator.

Between the sample electrode of the obtained coin battery and the counter electrode, it is charged to 0 V (Vvs. Li ^{/ Li + ) with a constant current of 0.2 mA / cm 2} , and then the current becomes 0.02 mA at a constant voltage of 0 V. Charged up to. Next, a one-cycle test was conducted in which the battery was discharged to 2.5 V (Vvs. Li ^{/ Li + ) at a constant current of 0.2 mA / cm 2} after a 30-minute rest period, and the initial charge / discharge efficiency was measured. The initial charge / discharge efficiency (%) was calculated as (discharge capacity) / (charge capacity) × 100. Here, the case where lithium ions are occluded in the sample electrode of the negative electrode material is regarded as charging, and conversely, the case where lithium ions are released from the sample electrode is regarded as discharging.

[Evaluation of life characteristics]
The negative electrode material composition prepared by the same method as the negative electrode material composition used for the measurement of the initial charge / discharge efficiency was applied to an electrolytic copper foil having a thickness of 40 μm so that the coating amount per unit area was 9.0 mg / cm ^2. It was coated with a comma coater with adjusted clearance. Then, the electrode density was adjusted to ^{1.5 g / cm 3 by hand pressing.} This electrode was punched into a disk shape having a diameter of 14 mm to prepare a sample electrode (negative electrode). A coin battery was produced in the same manner as in the measurement of the initial charge / discharge efficiency except that this sample electrode was used.

Using the coin battery produced above, the life characteristics were evaluated by the following procedure.
^{(1) The battery was charged to 0 V (Vvs. Li /} Li +) with a constant current of 0.48 mA, and then charged to a current of 0.048 mA with a constant voltage of 0 V.
(2) After a rest time of 30 minutes, ^{a one-cycle test of discharging to 1.5 V (Vvs. Li /} Li +) at a constant current of 0.48 mA was performed, and the discharge capacity was measured.
(3) The battery was charged to 0 V (Vvs. Li ^/ Li +) with a constant current of 4.8 mA, and charged to a current of 0.48 mA with a constant voltage of 0 V.
(4) After a 30-minute rest period, the battery was discharged to ^{1.5 V (Vvs. Li / Li +) with a constant current of 4.8 mA.}
(5) The charge / discharge cycle test of (3) and (4) above was performed for 50 cycles.
When the above cycle was repeated 50 cycles, the discharge capacity retention rate from the first cycle (= 50th cycle discharge capacity / 1st cycle discharge capacity × 100) was measured. It can be determined that the higher the discharge capacity retention rate, the better the life characteristics.

(Evaluation of input / output characteristics)
A coin battery was manufactured by the same method as the life characteristic, and the input / output characteristics were evaluated by the following procedure.
(1) Charging was performed to 0 V (Vvs. Li ^/ Li +) with a constant current of 0.96 mA, and then constant voltage charging was performed at 0 V until the current value reached 0.096 mA.
(2) After a 30-minute rest period, the battery was discharged to ^{1.5 V (Vvs. Li / Li +) with a constant current of 0.96 mA.}
(3) Charging was performed to half the capacity with a constant current of 0.96 mA.
(4) Discharge was performed for 10 seconds at current values of 4.8 mA, 14.4 mA, and 24 mA, and the voltage drop (ΔV) at that time was confirmed. There was a 30 minute rest period between the tests at each current value.
ΔV was plotted for each current value, and the slope was taken as the resistance value (Ω). It can be judged that the smaller this value is, the better the input / output characteristics are.

[Example 2]
A carbon material was prepared in the same manner as in Example 1 except that the composite material 1 and the composite material 2 were mixed so as to have a mass ratio of 4: 6 (composite material 1: composite material 2), and their characteristics were examined. In addition, a coin battery was manufactured and its performance was evaluated. The results are shown in Table 2.

[Example 3]
A carbon material was prepared in the same manner as in Example 1 except that the composite material 1 and the composite material 2 were mixed so as to have a mass ratio of 3: 7 (composite material 1: composite material 2), and their characteristics were examined. In addition, a coin battery was manufactured and its performance was evaluated. The results are shown in Table 2.

[Example 4]
A carbon material was prepared in the same manner as in Example 1 except that the composite material 1 and the composite material 2 were mixed so as to have a mass ratio of 6: 4 (composite material 1: composite material 2), and their characteristics were examined. In addition, a coin battery was manufactured and its performance was evaluated. The results are shown in Table 2.

[Comparative Example 1]
A carbon material was prepared in the same manner as in Example 1 except that the composite material 1 and the composite material 2 were mixed so as to have a mass ratio of 2: 8 (composite material 1: composite material 2), and their characteristics were examined. In addition, a coin battery was manufactured and its performance was evaluated. The results are shown in Table 2.

[Comparative Example 2]
A carbon material was prepared in the same manner as in Example 1 except that only the composite material 2 was used, and its characteristics were examined. In addition, a coin battery was manufactured and its performance was evaluated. The results are shown in Table 2.

[Comparative Example 3]
A carbon material was prepared in the same manner as in Example 1 except that only the composite material 1 was used, and its characteristics were examined. In addition, a coin battery was manufactured and its performance was evaluated. The results are shown in Table 2.

[Comparative Example 4]
_{Composite material 1 except that 100 parts by mass of spherical natural graphite (d 002} = 0.336 nm, average aspect ratio = 0.7) having a volume average particle diameter of 22 μm was used instead of spherical natural graphite having a volume average particle diameter of 10 μm. The composite material 3 was obtained in the same manner as in the above.
A carbon material was prepared in the same manner as in Example 1 except that the composite material 3 and the composite material 2 were mixed so as to have a mass ratio of 5: 5 (composite material 3: composite material 2), and their characteristics were examined. In addition, a coin battery was manufactured and its performance was evaluated. The results are shown in Table 2.

[Comparative Example 5]
_{Spherical natural graphite (d 002} = 0.336 nm, average aspect ratio = 0.7) having a volume average particle diameter of 22 μm is passed through a 300 mesh sieve, and the obtained sieve and composite material 2 have a mass ratio of 5: 5. A carbon material was prepared in the same manner as in Example 1 except that the mixture was mixed so as to be (under a sieve: composite material 2), and its characteristics were examined. In addition, a coin battery was manufactured and its performance was evaluated. The results are shown in Table 2.

[Comparative Example 6]
Coal-based coal tar was heat-treated at 400 ° C. by autoclave to obtain raw coke. After crushing this raw coke, coke was baked in an inert atmosphere at 1200 ° C. to obtain coke lumps. This coke mass was pulverized to an average particle size of 15 μm using an impact crusher equipped with a classifier, and then passed through a 200 mesh sieve _{to obtain carbon particles (d 002} = 0.342 nm) under the sieve. The composite material is the same as the composite material 1 except that a mixture obtained by mixing 100 parts by mass of the carbon particles and 20 parts by mass of polyvinyl alcohol (degree of polymerization 1700, fully saponified type, carbonization rate 15% by mass) is used. I got 4.
A carbon material was prepared in the same manner as in Example 1 except that the composite material 4 and the composite material 2 were mixed so as to have a mass ratio of 5: 5 (composite material 4: composite material 2), and their characteristics were examined. In addition, a coin battery was manufactured and its performance was evaluated. The results are shown in Table 2.

[Comparative Example 7]
Spherical natural graphite with a volume average particle diameter of 10 μm (d ₀₀₂ = 0.336 nm, average aspect ratio = 0.8) and spherical natural graphite with a volume average particle diameter of 16 μm (d ₀₀₂ = 0.336 nm, average aspect ratio = 0.8) ) Was mixed so as to have a mass ratio of 5: 5, and a carbon material was prepared in the same manner as in Example 1 and its characteristics were examined. In addition, a coin battery was manufactured and its performance was evaluated. The results are shown in Table 2.

[Comparative Example 8]
_{100 parts by mass of carbon particles (d 002} = 0.342 nm) prepared in Comparative Example 6, 30 parts by mass of coal tar pitch, and 5 parts by mass of iron oxide powder were mixed at 250 ° C. for 1 hour. The obtained mass was crushed with a pin mill and then molded into a block ^{having a density of 1.52 g / cm 3 by a die-in press.} The obtained block was calcined in a muffle furnace at a maximum temperature of 800 ° C., and then graphitized in an Achison furnace at 2900 ° C. under a self-decomposing gas atmosphere. Then, the graphitized block was roughly crushed with a hammer, and then a graphite powder having an average particle diameter of 30 μm was obtained with a pin mill. Further, this graphite powder is processed for 10 minutes at a crushing rotation speed of 1800 rotations / minute (rpm) and a classification rotation speed of 7000 rotations / minute (rpm) using a spheroidizing processing device (Faculty manufactured by Hosokawa Micron) to form a spherical shape. An artificial graphite powder was prepared. This spherical artificial graphite powder was passed through a 200-mesh sieve to obtain a carbon material under the sieve. The characteristics of this carbon material were investigated in the same manner as in Example 1. In addition, a coin battery was manufactured and its performance was evaluated. The results are shown in Table 2.

As is clear from the results shown in Table 2, the lithium ion secondary batteries of Examples 1 to 4 produced by using the negative electrode material containing the carbon material of the present embodiment input and output while maintaining high charge / discharge efficiency. It was also excellent in characteristics and life characteristics.

Claims (10)

_{The average interplanar spacing d 002} determined by the X-ray diffractometry is 0.335 nm to 0.339 nm, and the graphite material as the first carbon phase as the core and at least a part of the surface of the first carbon phase are covered. A negative electrode material for a lithium ion secondary battery, which comprises amorphous carbon as a second carbon phase to be arranged, and also contains a carbon material satisfying the following (1) and (2).
(1) In the number-based particle size distribution, the particle size when the relative particle amount q0 of the difference is the mode is 11.601 μm or less.
(2) In the particle size distribution based on the number, the ratio (q0A / q0B) of the difference relative particle amount q0A when the particle size is 11.601 μm and the difference relative particle amount q0B when the particle size is 7.806 μm is 1. It is .20 to 3.00. The specific surface area determined from nitrogen adsorption measurements at 77K is 0.5m ² /g~6.0m ² / g, negative for a lithium ion secondary battery according to claim 1 electrode material. The negative electrode material for a lithium ion secondary battery according to claim 1 or 2, wherein the R value of Raman spectroscopy is 0.1 to 1.0. The carbon material is claimed to have an integrated value Q3 of 4.0% or more of the total when the particle size is 9.516 μm when the volume cumulative distribution curve is drawn from the small particle size side in the volume-based particle size distribution. The negative electrode material for a lithium ion secondary battery according to any one of items 1 to 3. A claim that the carbon material has a particle size (50% D) of 1 μm to 20 μm when the cumulative volume is 50% when a volume cumulative distribution curve is drawn from the small particle size side in a volume-based particle size distribution. The negative electrode material for a lithium ion secondary battery according to any one of 1 to 4. The carbon material has a particle size (99.9% D) of 63 μm or less when the cumulative volume is 99.9% when a volume cumulative distribution curve is drawn from the small particle size side in the volume-based particle size distribution. The negative electrode material for a lithium ion secondary battery according to any one of claims 1 to 5. The carbon material, a tap density of 0.90g ^/ cm ³ ~2.00g ^/ cm 3 a is claim 1 negative electrode material for a lithium ion secondary battery according to any one of claims 6. The negative electrode material for a lithium ion secondary battery according to any one of claims 1 to 7, wherein the carbon material has a pellet density of 1.55 g / cm ^{3 or less.} A negative electrode for a lithium ion secondary battery including a negative electrode material layer containing the negative electrode material for a lithium ion secondary battery according to any one of claims 1 to 8 and a current collector. The lithium ion secondary battery including the negative electrode for a lithium ion secondary battery according to claim 9, the positive electrode, and an electrolyte.