TWI752112B - Negative electrode material for lithium ion secondary battery, negative electrode for lithium ion secondary battery, and lithium ion secondary battery - Google Patents

Abstract

A negative electrode material for a lithium ion secondary battery comprising a carbon material, the carbon material having an average plane distance d₀₀₂ as measured by X-ray diffraction of from 0.335 nm to 0.339 nm and a specific surface area as measured by nitrogen adsorption at 77K of from 0.5 m² /g to 6.0 m² /g, and satisfying the following conditions (1) and (2): (1) has a particle size when a differential relative particle amount q0 is the mode value, in a number-based distribution of particle size, of 11.601 μm or less. (2) has a ratio of a differential relative particle amount at 11.601 μm (q0A) to a differential relative particle amount at 7.806 μm (q0B), q0A/q0B, of from 1.20 to 3.00.

Description

Negative electrode material for lithium ion secondary battery, negative electrode for lithium ion secondary battery, and lithium ion secondary battery

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.

Compared with other secondary batteries such as nickel-metal hydride batteries and lead-acid batteries, lithium-ion secondary batteries are lighter in weight and have higher input-output characteristics, so in recent years, they have been used as high-input-output batteries in electric vehicles, hybrid electric vehicles, etc. attention has been paid to the power supply.

Since lithium ion secondary batteries were commercialized in 1991, there has been a strong demand for higher energy density and further improvement in input and output characteristics. As a means to achieve this, a technique of improving the negative electrode material contained in the negative electrode of a lithium ion secondary battery occupies an important position (for example, refer to Patent Document 1 and Patent Document 2).

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 4-370662

[Patent Document 2] Japanese Patent Laid-Open No. 5-307956

As the material of the negative electrode material of the lithium ion secondary battery, carbon materials such as graphite and amorphous carbon can be widely used.

Graphite has a structure in which hexagonal mesh surfaces of carbon atoms are regularly laminated, and lithium ions are inserted from the ends of the laminated mesh surfaces. The reaction is removed to perform charge and discharge.

In addition, the lamination of the hexagonal mesh surface of amorphous carbon is irregular, or does not have a mesh structure, therefore, the insertion of lithium ions. The desorption reaction proceeds over the entire surface, and it is easy to obtain lithium ions excellent in input and output characteristics. In addition, amorphous carbon has characteristics such as low crystallinity, low reaction with electrolyte, and excellent life characteristics compared to graphite.

In graphite, since the intercalation and deintercalation reaction of lithium ions proceeds only at the ends, it cannot be said that the input/output performance is sufficient. Moreover, since crystallinity is high and surface reactivity is high, especially at high temperature, the reactivity with electrolyte solution may become high, and there exists room for improvement in the lifetime characteristic of a lithium ion secondary battery. On the other hand, since the crystallinity of amorphous carbon is lower than that of graphite, the crystal structure is irregular, and it cannot be said that the energy density is sufficient.

According to the difference in the properties of graphite and amorphous carbon, as a carbon material that can achieve both high energy density derived from graphite and long life characteristics derived from amorphous carbon, there is proposed a layer of amorphous carbon formed on a layer containing graphite. The carbon material in the state of the surface of the nuclear material.

In recent years, especially in vehicle-mounted applications, in order to extend the running distance, the demand for higher capacitance of the battery has further increased. Therefore, as with civilian use, Electrode densification is also being studied for automotive applications. Among them, there is a concern that the input/output characteristics may be degraded due to the increase in the density of the electrodes, so that both the increase in capacitance and the input/output characteristics have become a problem. That is, it is required to work on a problem that is difficult to solve only by combining graphite and amorphous carbon.

An object of the present invention is to provide 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 capable of producing a lithium ion secondary battery that maintains high charge-discharge efficiency and has excellent input/output characteristics and life characteristics. The lithium ion secondary battery produced therefrom.

Means for solving the above-mentioned problems include the following embodiments.

<1> A negative electrode material for a lithium ion secondary battery, comprising a carbon material, in which the average interplanar spacing d ₀₀₂ obtained by the X-ray diffraction method is 0.335 nm to 0.339 nm. measurement was nitrogen adsorption specific surface area of 0.5m ² /g~6.0m ² / g, and satisfying the following (1) and (2) :( 1) to a number-based particle size distribution, the difference of the relative particle (2) The relative particle size q0A of the difference when the particle size is 11.601 μm and the difference when the particle size is 7.806 μm in the particle size distribution based on the number The ratio of particle amount q0B (q0A/q0B) is 1.20~3.00.

<2> A negative electrode material for a lithium ion secondary battery, comprising a carbon material, in which the average interplanar spacing d ₀₀₂ obtained by X-ray diffraction is 0.335 nm to 0.339 nm, and the value of the carbon material measured by Raman spectroscopy is The R value is 0.1 to 1.0, and the following (1) and (2) are satisfied: (1) In the particle size distribution based on the number, the particle size when the relative particle amount q0 of the difference becomes the mode value is 11.601 μm or less; ( 2) In the particle size distribution based on the number, the ratio (q0A/q0B) of the relative particle amount q0A of the difference when the particle diameter is 11.601 μm and the relative particle amount q0B of the difference when the particle diameter is 7.806 μm is 1.20 to 3.00.

<3> A negative electrode material for a lithium ion secondary battery, comprising a carbon material in which the average interplanar spacing d002 obtained by the X-ray diffraction method is 0.335 nm to 0.339 nm, and the carbon material includes a first nucleus serving as a nucleus A carbon phase, and a second carbon phase disposed on at least a part of the surface of the first carbon phase and different from the first carbon phase, and satisfying the following (1) and (2): (1) on a number basis In the particle size distribution, the particle size when the relative particle size q0 of the difference is the mode value is 11.601 μm or less; (2) In the particle size distribution based on the number, the relative particle size q0A and the particle size of the difference when the particle size is 11.601 μm The relative particle amount q0B ratio (q0A/q0B) of the difference when it is 7.806 μm is 1.20 to 3.00.

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

<5> The negative electrode material for a lithium ion secondary battery according to any one of <1> to <4>, wherein the carbon material has a particle size distribution on a volume basis ranging from small particles When the cumulative volume distribution curve is drawn from the radial side, the particle size (50%D) when the cumulative volume is 50% is 1 μm to 20 μm.

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

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

<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 particle density of 1.55 g/cm ³ or less.

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

<10> A lithium ion secondary battery comprising the negative electrode for a lithium ion secondary battery according to <9>, a positive electrode, and an electrolyte.

According to the present invention, it is possible to provide 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 capable of producing a lithium ion secondary battery that maintains high charge-discharge efficiency and has excellent input/output characteristics and life characteristics. The lithium ion secondary battery produced therefrom.

Hereinafter, the form for implementing this invention is demonstrated in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps and the like) are not essential unless otherwise specified. The same applies to the numerical value and the range thereof, and does not limit the present invention.

In the term "step" in this specification, except for a step that is independent from other steps, even if it cannot be clearly distinguished from other steps, as long as the purpose of the step is achieved, the step is included.

In this specification, the numerical range indicated by "~" includes the numerical value described before and after the "~" as the minimum value and the maximum value, respectively.

In the numerical range described in stages in this 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 described in another stagewise description of the numerical value range. In addition, in the numerical range described in this specification, the upper limit or the lower limit of this numerical range may be replaced with the value shown in an Example.

In this specification, when there are multiple substances corresponding to each component in the composition, unless otherwise specified, the content rate or content of each component in the composition refers to the total of the multiple substances present in the composition. content or content.

In this specification, when there are plural kinds of particles corresponding to each component in the composition, unless otherwise specified, the particle diameter of each component in the composition refers to the value of the mixture of the plural kinds of particles in the composition. .

In the term "layer" or "film" in this specification, when observing the presence of the layer or film In the case of the area of in addition to the case of being formed in the whole of the area, the case of being formed only in a part of the area is also included.

In this specification, the term "laminated" means that layers are stacked, and two or more layers may be combined, and two or more layers may be detached.

<Anode material for lithium ion secondary battery (1)>

The negative electrode material for a lithium ion secondary battery of the present embodiment (hereinafter, abbreviated as "negative electrode material" in some cases) includes a carbon material, and the average interplanar spacing d ₀₀₂ of the carbon material obtained by the X-ray diffraction method is 0.335 nm ~ 0.339nm, the adsorption of nitrogen at 77K was measured by obtaining the specific surface area of 0.5m ² /g~6.0m ² / g, and satisfying the following (1) and (2).

(1) In the particle size distribution based on the number of objects, the particle size when the relative particle amount q0 of the difference becomes the mode value is 11.601 μm or less.

(2) The ratio of the relative particle amount q0A of the difference when the particle diameter is 11.601 μm to the relative particle amount q0B of the difference when the particle diameter is 7.806 μm in the particle size distribution based on the number of objects (q0A/q0B) is 1.20 to 3.00 .

By using the negative electrode material of the present embodiment, a lithium ion secondary battery that maintains high charge-discharge efficiency and also has excellent input-output characteristics and life-span characteristics can be produced.

The composition of the negative electrode material of the present embodiment is not particularly limited as long as it includes a carbon material that satisfies the above 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 mass % or more, more preferably 80 mass % or more, further preferably 90 mass % or more, and particularly preferably 100% by mass.

(carbon material)

_{The average interplanar spacing d 002} of the carbon material obtained by the X-ray diffraction method was 0.335 nm to 0.339 nm.

Among the values of the average interplanar spacing d ₀₀₂ , 0.3354 nm is a 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 interplanar spacing d ₀₀₂ is within the above-mentioned range, there is a tendency that excellent initial charge-discharge efficiency and energy density of the lithium ion secondary battery can be obtained.

In the present embodiment, the average interplanar spacing d ₀₀₂ of the carbon material can be obtained by irradiating a sample of the carbon material with X-rays (CuKα rays), based on the diffraction distribution obtained by measuring the diffraction rays with a goniometer, and according to the The diffraction peaks corresponding to the carbon 002 surface appearing in the vicinity of the incident angle 2θ=24° to 27° were calculated using Bragg's equation.

From the viewpoint of the energy density of the lithium ion secondary battery, _{the value of the average interplanar spacing d 002} of the carbon material is preferably small. Specifically, for example, it is preferably 0.335 nm to 0.337 nm.

The value of the average interplanar spacing _d002 of the carbon material tends to become smaller by, for example, increasing the temperature of the heat treatment of the carbon material, and therefore, the average interplanar spacing _{d002 can be} adjusted within the above-mentioned range by utilizing this property.

Measured by nitrogen adsorption at 77K and the carbon material to obtain a specific surface area (hereinafter sometimes referred to as N ₂ specific surface area) of 0.5m ² /g~6.0m ² / g.

When the N ₂ specific surface area of the carbon material is within the above-mentioned range, there is a tendency that the balance between the input-output characteristics and the initial charge-discharge efficiency can be favorably maintained.

The N ₂ specific surface area of the carbon material can be determined by the Brunauer-Emmett-Teller (BET) method from the adsorption isotherm obtained by nitrogen adsorption measurement at 77K.

On input-output characteristic of the secondary battery and a lithium ion balance initial charge-discharge efficiency viewpoint, N ₂ specific surface area is preferably 1.0m ² /g~5.0m ² / g.

The N ₂ specific surface area tends to decrease in value by, for example, increasing the volume average particle size of the carbon material, increasing the temperature of the heat treatment of the carbon material, and modifying the surface of the carbon material, so it can be used For this property, the N ₂ specific surface area is set within the above-mentioned range.

In the particle size distribution based on the number of objects of the carbon material, the particle size when the relative particle amount q0 of the difference becomes the mode value is 11.601 μm or less. If the particle diameter at which the relative particle amount q0 of the difference becomes the average value exceeds 11.601 μm, the proportion of the carbon material with a large particle diameter increases, so that the diffusion distance of lithium ions from the particle surface of the carbon material to the inside becomes longer, and the lithium ions The tendency for the input/output characteristics of the secondary battery to decrease.

The particle diameter when the relative particle amount q0 of the difference becomes the average value is preferably 11.601 μm or 9.516 μm, more preferably 11.601 μm.

In the carbon material, the total value of the relative particle amount q0 of the difference when the particle diameter is 11.601 μm and the relative particle amount q0 of the difference when the particle diameter is 9.516 μm is preferably 25 or more, more preferably 30 or more, and still more preferably 32 or more. .

The ratio (q0A/q0B) of the relative particle amount q0A of the difference when the particle diameter is 11.601 μm and the relative particle amount q0B of the difference when the particle diameter is 7.806 μm in the number-based particle size distribution of the carbon material is 1.20 to 3.00 .

If the value of q0A/q0B is less than 1.20, there is a tendency for the input/output characteristics to degrade.

When the value of q0A/q0B exceeds 3.00, the contact between particles of the carbon material deteriorates, and the life characteristics of the lithium ion secondary battery tend to decrease.

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, from the viewpoint of the input/output characteristics and the life characteristics.

The particle size distribution based on the number of objects of the carbon material in this specification can be obtained by dividing the range of particle diameters from 0.1 μm to 2000 μm into 50 pieces by a logarithmic ratio. For example, n=(2000/0.1)^(1/50) can be obtained and the particle size can be obtained from 0.1×n, 0.1×n^2, . . . , 0.1×n^50. The total value of the relative particle amount q0 for each particle diameter 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 together.

In the particle size distribution based on volume of the carbon material, when the cumulative volume distribution curve is drawn from the small particle size side, the cumulative value Q3 when the particle size is 9.516 μm is preferably 4.0% or more of the whole, more preferably 9.0% or more.

When the cumulative value Q3 when the particle size is 9.516 μm is 4.0% or more of the whole, the contact points between the particles can be sufficiently ensured by the fine particles contained in the carbon material, and the life characteristics of the lithium ion secondary battery can be improved. Propensity.

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

In the particle size distribution based on the volume of the carbon material, when the cumulative volume distribution curve is drawn from the small particle size side, the particle size (50% D, hereinafter, also referred to as the volume average particle size) when the accumulation becomes 50% is preferably 1 μm to 20 μm, more preferably 3 μm to 18 μm, still more preferably 5 μm to 15 μm.

If the volume average particle diameter of the carbon material is 1 μm or more, the specific surface area tends to be suppressed from being excessively large and the initial charge-discharge efficiency of the lithium ion secondary battery is reduced. On the other hand, when 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 interior tends to be long, and the input/output characteristics of the lithium ion secondary battery tend to decrease.

In the particle size distribution based on the volume of the carbon material, when the cumulative volume distribution curve is drawn from the small particle size side, the particle size (99.9% D, hereinafter, also referred to as the maximum particle size) when the accumulation becomes 99.9% is preferably 63 μm Below, it is more preferable that it is 50 micrometers or less, and it is still more preferable that it is 45 micrometers or less.

When the maximum particle diameter of the carbon material is 63 μm or less, the electrode plate tends to be thinned when producing the electrode, and the influence on the input/output characteristics tends to be suppressed.

The volume-based particle size distribution of the carbon material in this specification can be obtained by dividing the range of 0.1 μm to 2000 μm 50 times with a logarithmic ratio, similarly 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.

The particle size distribution of the carbon material in this specification can be measured by a known method. For example, a dispersion liquid prepared by dispersing a sample of carbon material and a surfactant in purified water is put into a sample water tank of a laser diffraction particle size distribution measuring device, and a superfluid is applied while circulating it with a pump. The particle size distribution of the carbon material was obtained by measuring by laser diffraction under the following measurement conditions with sonication for 1 minute. As a laser diffraction particle size distribution analyzer, "SALD-3000J" of Shimadzu Corporation, for example, can be used. Here, you can select "Number" or "Volume" as the output conditions to obtain the particle size distribution based on the number or the particle size distribution based on the volume.

(setting of measurement conditions)

Measurement times: 1 time

Measurement interval: 2 seconds

Average times: 64 times

Measurement range of absorbance: 0.01~0.2

(arbitrary particle size.% table setting)

Range: 0.1μm~2000μm

Number of divisions: 50

The carbon material of the present embodiment can be obtained, for example, by combining two or more carbon materials with different particle sizes.

Examples of such combinations of carbon materials include 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 particle diameter. A combination of carbon materials having a particle size of 15 μm to 17 μm, etc.

As a ratio when two kinds of carbon materials with different particle sizes are combined, for example, the mass ratio is in the range of 7:3 to 3:7, and the mass ratio is in the range of 6:4 to 4:6. Wait.

Knock tightness carbon material is preferably ^{0.90g / cm 3 ~ 2.00g / cm} 3, more preferably ^{1.00g / cm 3 ~ 1.50g / cm} 3, and further is excellent ^{1.05g / cm 3 ~ 1.30g / 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 in the production of 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 favorable.

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-mentioned range by utilizing this property.

The tap density of the entire negative electrode material including the carbon material may be 0.90 g/cm ³ to 3.00 g/cm ³ . As a method of adjusting the tap density of the negative electrode material, a method of including a metal component or the like described later in addition to the carbon material is exemplified.

In the present specification, the tightness or knock carbon material negative electrode material refers to a value as follows (g / cm ^3): A sample powder was slowly put to 100cm ³ measuring cylinder capacity of 100cm ^3, for stoppered graduated cylinder so that the cylinder from The value (g/cm ³ ) was obtained by dividing the mass (g) of the sample powder after that by the volume (cm ^{3 ) by dropping 250 times from a height of 5 cm.}

The particle density of the carbon material is preferably 1.55 g/cm ³ or less, more preferably 1.50 g/cm ³ or less. When the particle density is 1.55 g/cm ³ or less, when the electrode is densified, the voids between the particles of the carbon material are prevented from becoming too small, the ion concentration in the vicinity of the particles decreases, and the input/output characteristics of the lithium ion secondary battery are reduced. Propensity.

The particle density of the carbon material tends to decrease by, for example, reducing the volume average particle diameter of the carbon material, and the particle density can be set within the above-mentioned range by utilizing this property.

The particle density of the entire negative electrode material including the carbon material may be 1.10 g/cm ³ to 2.00 g/cm ³ . As a method of adjusting the particle density of the negative electrode material, a method of controlling the temperature of the heat treatment performed on the carbon material can be cited.

In the present invention, the particle density of the carbon material or the negative electrode material refers to the following value (g/cm ³ ): 1.00 g of the sample powder is put into the molding machine, and the pressure is 1.0 t by the hydraulic press to press ^{The value (g/cm 3} ) is obtained by dividing the obtained volume by the mass (g) of the thickness (cm) and cross-sectional area (cm ^{2 ) of the sample afterward.}

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

R-value is defined as the Raman spectroscopic measurement in the obtained Raman spectrum, the intensity of the maximum peak intensity nearby ^-1 1580cm Ig, and the maximum peak near 1360 cm ^-1 to the intensity Id ratio (Id / Ig). Here, ^{the peak appearing in the vicinity of 1580 cm -1} is usually identified as a peak corresponding to the graphite crystal structure, for example, the peak observed ^{at 1530 cm -1} to 1630 cm ^{-1 .} Further, the so-called peak appearing in the vicinity of 1360cm ^-1, typically identified to 1300cm ^-1 ~ 1400cm ^-1 peak is observed with a peak corresponding to the structure of amorphous carbon, for example, means.

In this specification, the Raman spectrophotometer is used for the Raman spectrophotometer (model: NRS-1000, JASCO Corporation). The sample plate was measured by irradiating argon laser light (excitation wavelength: 532 nm).

Examples of the material of the carbon material include carbon such as graphite (artificial graphite, natural graphite, graphitized mesocarbon, graphitized carbon fiber, etc.), low-crystalline carbon, and mesocarbon. Material. From the viewpoint of increasing the charge and discharge capacity, at least a part of the carbon material is preferably graphite.

The shape of the carbon material is not particularly limited. For example, a scale shape, a spherical shape, a block shape, etc. are mentioned. From the viewpoint of obtaining high knock density, spherical shape is preferable. What is necessary is just to select suitably the carbon material which has the said physical property from these carbon materials. One type of carbon material may be used alone, or two or more types having different materials, shapes, and the like may be used in combination.

The carbon material may be a composite material including a first carbon phase serving as a core, and a second carbon phase different from the first carbon phase and disposed on at least a part of the surface (eg, to coat the core). The carbon material is composed of a plurality of different carbon phases, whereby a carbon material that can more effectively exhibit desired physical properties or properties can be obtained.

When the carbon material is a composite material including a first carbon phase serving as a core and a second carbon phase disposed on at least a part of the surface, the combination of the first carbon phase and the second carbon phase includes the first carbon phase. A combination of a carbon phase and a second carbon phase having a crystallinity different from that of the first carbon phase, preferably a first carbon phase and a second carbon having a crystallinity lower than ( _{the value of d 002} is greater than the first carbon phase) the first carbon phase combination of phases.

When the carbon material is a composite material comprising a first carbon phase serving as a nucleus and a second carbon phase having a crystallinity lower than that of the first carbon phase, the material of the first carbon phase serving as a nucleus is preferably selected from the group consisting of: in graphite. In this case, the second carbon phase is preferably selected from those whose crystallinity is lower than that of the first carbon phase (hereinafter, also referred to as a low-crystalline carbon phase).

The material of the second carbon phase whose crystallinity is lower than that of the first carbon phase is not particularly limited, and can be appropriately selected according to desired properties. Preferable examples of the second carbon phase include organic compounds (carbon precursors) that can be changed into carbonaceous materials by heat treatment. obtained carbon phase. Specifically, ethylene heavy end pitch, crude oil pitch, coal tar pitch, asphalt (asphalt) decomposed pitch, and organic compounds such as polyvinyl chloride can be mentioned. Pitch produced by thermal decomposition, synthetic pitch produced by polymerizing naphthalene and the like in the presence of a super acid, and the like. In addition, thermoplastic synthetic polymers such as polyvinyl chloride, polyvinyl alcohol, polyvinyl acetate, and polyvinyl butyraldehyde, and natural polymers such as starch and cellulose can also be used as carbon precursors.

When the carbon material is the composite material, the first carbon phase serving as a nucleus is preferably _{a graphite material having an average interplanar spacing d 002} in the range of 0.335 nm to 0.339 nm from the viewpoint of increasing the charge and discharge capacity. In particular, when using _{a graphite material whose d 002} is in the range of 0.335 nm to 0.338 nm, preferably in the range of 0.335 nm to 0.337 nm, the charge and discharge capacity is large and is 330 mAh/g to 370 mAh/g. the tendency of lithium-ion secondary batteries.

The volume average particle diameter (50% D) of the graphite material serving as the first carbon phase is preferably 1 μm to 20 μm. When the volume average particle diameter of the graphite material is 1 μm or more, the raw material graphite contains an excessive amount of fine powder, and the occurrence of aggregation in the step of attaching the organic compound as a carbon precursor to the core material can be suppressed, and both can be made more uniform. Tendency to mix. When the volume average particle diameter of the graphite material is 20 μm or less, the mixing of coarse particles in the negative electrode material can be suppressed, and the generation of lineation and the like tends to be suppressed when the negative electrode material is applied.

The specific surface area of the graphite material serving as the first carbon phase obtained by nitrogen adsorption measurement at 77K, that is, the BET specific surface area (N ₂ specific surface area) is preferably 0.1 m ² /g to 30 m ² /g, more preferably It is 0.5m ² /g to 25m ² /g, more preferably 0.5m ² /g to 15m ² /g. When the N ₂ specific surface area of the ^{graphite material is 0.1 m 2} /g or more, it tends to be difficult to cause aggregation 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 can be maintained in an appropriate range, and the organic compound tends to adhere more uniformly.

Examples of the shape of the graphite material to be the first carbon phase include a scaly shape, a spherical shape, a block shape, and the like, and a spherical shape is preferred from the viewpoint of increasing the tap density.

As an index showing the degree of spheroidization of the graphite material, the aspect ratio can be mentioned. The aspect ratio of the graphite material in this specification is a value obtained by "maximum length vertical length/maximum length", and the maximum value thereof is 1. Here, the "maximum length" is the maximum value of the distance between two points on the outline of the particles of the graphite material, and the "maximum length vertical length" is perpendicular to the line segment connecting the two points to be the maximum length and connecting the particles. The length of the longest of the line segments connecting the two points on the contour of .

The aspect ratio of the graphite material can be measured, for example, using a flow-type particle image analyzer. As a flow-type particle image analyzer, "FPIA-3000" of Sysmex Co., Ltd., etc. can be mentioned.

The average aspect ratio of the graphite material serving as the first carbon phase is preferably 0.1 or more, more preferably 0.3 or more. When the average aspect ratio of the graphite material is 0.1 or more, the ratio of the flake graphite in the graphite material does not become 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 base surface, in the step of attaching the organic compound as a carbon precursor to the core material, there is a possibility that the organic compound will adhere more by the edge surface. However, if the average aspect ratio If it is 0.1 or more, the organic compound tends to adhere to the core material more uniformly. As a result, the distribution of low-crystalline carbon and crystalline carbon in the obtained carbon material tends to become more uniform.

In addition to the carbon material, the negative electrode material may contain other components as necessary. For example, a metal component may be contained.

Examples of the metal components include powders of metals containing elements that are alloyed with lithium, such as Al, Si, Ga, Ge, In, Sn, Sb, Ag, etc. as necessary, for high capacitance, at least Al, Si, and Ga. , Ge, In, Sn, Sb, Ag and other elements that alloy with lithium, the powder of the multi-element alloy, the powder of the lithium alloy, and the like. A metal component may be used individually by 1 type, and may be used in combination of 2 or more types. In addition, 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 composite state with the carbon material.

When the negative electrode material also contains a metal component in addition to the carbon material, compared with the case where only the carbon material is contained, there is a tendency that the tap density of the entire negative electrode material increases. For example, the tap density of the entire negative electrode material can be set to 0.3 g/cm ³ to 3.0 g/cm ³ . When the tap density of the negative electrode material is large, the charge-discharge reaction can be accelerated, the negative electrode resistance can be reduced, and there is a tendency that favorable input-output characteristics can be obtained.

In the case where the negative electrode material also includes a metal component in addition to the carbon material, the amount is not particularly limited. For example, it may be 1 mass % - 50 mass % of the whole negative electrode material.

<Anode material for lithium ion secondary battery (2)>

The negative electrode material for a lithium ion secondary battery of the present embodiment includes a carbon material in which the average interplanar spacing d ₀₀₂ determined by the X-ray diffraction method is 0.335 nm to 0.339 nm, and the R value measured by Raman spectroscopy is 0.1 to 1.0, and the following (1) and (2) are satisfied.

(1) In the particle size distribution based on the number of objects, the particle size when the relative particle amount q0 of the difference becomes the mode value is 11.601 μm or less.

(2) The ratio of the relative particle amount q0A of the difference when the particle diameter is 11.601 μm to the relative particle amount q0B of the difference when the particle diameter is 7.806 μm in the particle size distribution based on the number of objects (q0A/q0B) is 1.20 to 3.00 .

In the negative electrode material of the present embodiment, the details and preferable aspects of each condition can be referred to the descriptions related to the negative electrode material of the above-mentioned embodiment.

<Anode material for lithium ion secondary battery (3)>

The negative electrode material for a lithium ion secondary battery of the present embodiment includes a carbon material in which the average interplanar spacing d ₀₀₂ determined by the X-ray diffraction method is 0.335 nm to 0.339 nm, and includes the first carbon as a core A phase, and a second carbon phase disposed on at least a part of the surface of the first carbon phase and different from the first carbon phase, and satisfying the following (1) and (2).

(1) In the particle size distribution based on the number of objects, the particle size when the relative particle amount q0 of the difference becomes the mode value is 11.601 μm or less.

(2) The ratio of the relative particle amount q0A of the difference when the particle diameter is 11.601 μm to the relative particle amount q0B of the difference when the particle diameter is 7.806 μm in the particle size distribution based on the number of objects (q0A/q0B) is 1.20 to 3.00 .

In the negative electrode material of the present embodiment, details and preferred aspects of each condition Reference can be made to the description regarding the negative electrode material of the above-described 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 generally used for producing negative electrode materials can be employed.

In the case where the carbon material is a composite material including a first carbon phase serving as a core and a second carbon phase arranged on at least a part of its surface, the production method thereof includes, for example, the following method: After the organic compound is attached to the surface of the core material that becomes the first carbon phase, it is calcined in an inert environment at 750°C to 1200°C to carbonize the carbon precursor. As an organic compound used as a carbon precursor, the organic compound mentioned as an example of a carbon precursor is mentioned.

The method of attaching the carbon precursor to the surface of the first carbon phase is not particularly limited. For example, a wet method in which the core material of the first carbon phase is mixed in a liquid obtained by dissolving or dispersing a carbon precursor in a solvent, and then the solvent is removed, and by separating the core material and the carbon precursor with A dry method in which a mixture obtained by mixing in a solid state is adhered by applying mechanical energy, a gas phase method such as a CVD method, and the like. From the viewpoint of control of the specific surface area of the carbon material, it is preferably performed by a dry method.

The method of attaching the carbon precursor to the surface of the first carbon phase by a dry method is not particularly limited. For example, a container having a structure capable of at least one of mixing and agitation of the contents is filled with a mixture of the first carbon phase and a carbon precursor, and mechanical energy is applied to perform at least one of mixing and agitation, whereby the The carbon precursor is attached to the surface of the first carbon phase. Specifically, it can be performed using, for example, a container provided with devices such as blades and screws. The magnitude of the mechanical energy applied to the mixture is not particularly limited. For example, it is preferably 0.360kJ/kg~36000kJ/kg, more preferably 0.360kJ/kg~7200kJ/kg, and still more preferably 2.50kJ/kg~2000kJ/kg.

Here, the mechanical energy applied to the mixture is a value obtained by multiplying the time (h) by the load (kW) and dividing the value by the mass (kg) of the filled mixture. By setting the mechanical energy applied to the mixture to the above-mentioned range, the presence of the carbon precursor is more uniformly attached to the surface of the first carbon phase, and the distribution of low-crystalline carbon and crystalline carbon in the obtained carbon material becomes more uniform. Propensity.

The state (intermediate product) in which the carbon precursor was adhered to the surface of the first carbon phase was further heated and calcined. The calcination temperature is not particularly limited as long as it is a temperature at which the carbon precursor can be carbonized. For example, it is preferably 750°C to 2000°C, more preferably 800°C to 1800°C, and still more preferably 900°C to 1400°C. When the calcination temperature is 750°C or higher, the charge-discharge efficiency, input-output characteristics, and cycle characteristics of the lithium ion secondary battery tend to be well maintained, and when the calcination temperature is 2000°C or lower, the low-crystalline carbon portion can be suppressed. The crystallinity tends to become too high. As a result, there is a tendency that characteristics such as rapid charging characteristics, low-temperature charging characteristics, and overcharge safety can be well maintained. The environment at the time of firing is not particularly limited as long as it is an environment in which the intermediate product is not easily oxidized. For example, a nitrogen atmosphere, an argon atmosphere, a self-decomposing gas atmosphere, and the like can be applied. The form of the furnace used for calcination is not particularly limited. For example, it is preferable to use at least one of electricity and gas as a heat source, a batch furnace, a continuous furnace, or the like.

<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 including the negative electrode material, and a current collector. Thereby, it is possible to maintain high charge-discharge efficiency In addition, it is a lithium ion secondary battery with excellent input/output characteristics and life characteristics. The negative electrode for a lithium ion secondary battery may contain other constituent elements as needed, in addition to the negative electrode material layer and the current collector containing the negative electrode material described above.

The method of producing the negative electrode for lithium ion secondary batteries is not particularly limited. For example, a method of preparing a slurry by kneading a negative electrode material and an organic binder together with a solvent using a dispersing device such as a stirrer, a ball mill, a super sand mill, and a pressurized kneader can be used. A method of applying the negative electrode material composition to the surface of the current collector to form a negative electrode material layer, preparing a paste-like negative electrode material composition in the same manner as described above, molding it into a shape such as a sheet or pellet, and mixing it with Methods of integrating current collectors, etc.

The organic binder is not particularly limited. For example, styrene-butadiene copolymer, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, (meth)acrylonitrile, hydroxyl (meth)acrylate Ethyl unsaturated carboxylic acid ester such as ethyl ester, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid and other ethylenically unsaturated carboxylic acid, polyvinylidene fluoride, polyethylene oxide Alkane, polyepichlorohydrin, polyphosphazene, polyacrylonitrile and other polymer compounds with high ionic conductivity. (Meth)acrylate means at least one of acrylate and methacrylate.

The amount of the organic binder contained in the negative electrode material composition is not particularly limited, but is preferably 0.5 parts by mass to 20 parts by mass relative to 100 parts by mass of the total of the negative electrode material and the organic binder.

The negative electrode material composition may also include a tackifier for adjusting viscosity. as The thickeners include, for example, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, polyacrylic acid (salt), oxidized starch, phosphorylated starch, casein ( casein) etc.

The negative electrode material composition may also include conductive auxiliary materials. As the conductive auxiliary material, for example, in addition to carbon materials such as carbon black, graphite, and acetylene black, oxides, nitrides, and the like that exhibit conductivity can also be mentioned. The amount of the conductive auxiliary material is not particularly limited, but may be about 0.5 parts by mass to 15 parts 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, metal materials such as aluminum, copper, nickel, titanium, and stainless steel are formed into a foil shape, a perforated foil shape, a mesh shape, and the like. Furthermore, porous materials, such as porous metal (foamed metal), carbon paper, etc. can also be used.

The method of applying the negative electrode material composition to the current collector is not particularly limited. For example, metal mask printing method, electrostatic coating method, dip coating method, spray coating method, roll coating method, doctor blade method, corner wheel coating method, gravure coating method, screen printing method and other coating methods. After the negative electrode material composition is applied to the current collector, it is dried with a hot air dryer, an infrared dryer, or a combination of these to remove the solvent contained in the negative electrode material composition. Furthermore, a calendering process by a flat press, a calender roll, etc. is performed as needed.

The method of forming the negative electrode material composition into a shape such as a sheet or pellets and integrating it with the current collector is not particularly limited. For example, rolls, presses, or a combination of these can be used and can be performed by well-known methods. The pressure during integration is preferably 1 MPa~200MPa.

The negative electrode density of the negative electrode for a lithium ion secondary battery is preferably 1.3 g/cm ³ to 1.8 g/cm ³ , more preferably 1.4 g/cm ³ to 1.8 g/cm ³ , and still more ^{preferably 1.5 g/cm 3} to 1.7 g/cm ³ . When the negative electrode density is 1.3 g/cm ³ or more, the resistance value tends not to decrease and the capacitance tends to be maintained high, and when it is 1.8 g/cm ³ or less, the decrease in rate characteristics and cycle characteristics tends to be suppressed.

<Lithium-ion secondary battery>

The lithium ion secondary battery of the present embodiment includes the above-described negative electrode for a lithium ion secondary battery, a positive electrode, and an electrolyte. A lithium ion secondary battery can be obtained, for example, by arranging a negative electrode for a lithium ion secondary battery and a positive electrode in a container so as to face each other through a separator, and dissolving an electrolyte in a solvent to prepare an electrolytic solution. liquid into the container.

The positive electrode can be obtained by forming a positive electrode layer by applying a positive electrode material to the surface of the current collector, similarly to the negative electrode. As the current collector, a belt-shaped one in which a metal material such as aluminum, titanium, and stainless steel is formed 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, metal oxides, metal sulfides, and phosphoric acid compounds that can be doped or inserted into lithium ions, and other materials can be mentioned.

Examples of the positive electrode active material include lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), and lithium cobalt oxide in which at least a part of cobalt is substituted with at least one of nickel and manganese. complex oxides (LiCo _x Ni _y M _z O ₂ , x+y+z=1), complex oxides (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 olivine (olivine) 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 nonwoven fabrics, cloths, microporous films, or combinations of these, which are mainly composed of polyolefins such as polyethylene and polypropylene. Furthermore, in the structure of the lithium ion secondary battery, when the positive electrode and the negative electrode are not in contact with each other, 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 .}

Examples of the solvent for dissolving the electrolyte include ethylene carbonate, fluoroethylene carbonate, chloroethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, cyclopentanone, cyclohexylbenzene, Butane, propane sultone, 3-methylcyclobutane, 2,4-dimethylcyclobutane, 3-methyl-1,3-oxazolidin-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, 1,2-dimethoxy Non-aqueous solvents such as ethyl ethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, methyl acetate, ethyl acetate, trimethyl phosphate, and triethyl phosphate.

The structure of the electrode in a lithium ion secondary battery is not specifically limited. In general, a positive electrode and a negative electrode, and a separator provided between the positive electrode and the negative electrode as needed, can be exemplified. Those in which the plates are overlapped are wound in a swirling state (wound electrode group), and those in which the plates are not wound in a swirl shape (laminated electrode group).

The type of lithium ion secondary battery is not particularly limited. For example, a laminated battery, a paper battery, a button battery, a coin cell, a laminated battery, a cylindrical battery, a prismatic cell, etc. are mentioned.

The negative electrode material of the present embodiment is excellent in charge-discharge input-output characteristics and life characteristics, and thus can be suitably used for lithium ion secondary batteries requiring large capacitance, such as electric vehicles, power tools, and power storage applications. Among them, in electric vehicle (EV), hybrid electric vehicle (HEV), plug-in hybrid electric vehicle (PHEV) and other automotive applications, in order to improve acceleration performance and It is desirable to use the negative electrode material of the present embodiment, which is excellent in input/output characteristics, in order to satisfy the requirement of charging and discharging with a large current due to regenerative braking performance.

[Example]

Hereinafter, the present invention will be further specifically described 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, coal tar pitch (softening point of 98° C., residual carbon rate (carbonization rate) of 50%) 5 parts by mass of the mixture obtained by mixing was put into a cylinder with rotors, and the inner wall of the cylinder and the rotors were rubbed with each other, thereby making the coal tar pitch adhere to the surface of spherical natural graphite. The step of rubbing against each other was performed under a load of 24 kW for 5 minutes (load: 1800 kJ/kg). Next, the temperature was raised to 1000°C at a temperature increase rate of 20°C/hour under nitrogen gas flow, and maintained for 1 hour to carbonize the coal tar pitch. Then, it was decomposed with a cutter mill, sieved with a 300-mesh sieve, and the undersize portion thereof was obtained as a composite material 1 .

100 parts by mass of spherical natural graphite having a volume average particle diameter of 16 μm (d ₀₀₂ =0.336 nm, average aspect ratio = 0.8) was used in place of the spherical natural graphite having a volume average particle diameter of 10 μm, as in Composite Material 1 Obtain composite 2.

The composite material 1 and the composite material 2 were mixed at 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 compaction measurement, and particle density measurement by the methods shown below.

[XRD analysis (measurement of _{average interplanar spacing d 002)]}

The carbon material was filled in the concave part of the sample holder made of quartz and set on the measurement platform. The measurement was performed using a wide-angle X-ray diffraction apparatus (manufactured by Rigaku Co., Ltd.) under the following measurement conditions.

Radiation source: CuKα rays (wavelength=0.15418nm)

Output: 40kV, 20mA

Sampling amplitude: 0.010°

Scanning range: 10°~35°

Scanning speed: 0.5°/min

[N ₂ specific surface area measurement]

For carbon materials, nitrogen adsorption at liquid nitrogen temperature (77K) was measured by a multipoint method using a high-speed specific surface area/pore distribution measuring device (“ASAP2010” from MICROMERITICS, Inc.), and the BET method (relative to pressure range: 0.05~0.2) to calculate the N ₂ specific surface area.

[Particle size distribution measurement]

A solution prepared by dispersing a carbon material and a surfactant in purified water is placed in a sample water tank of a laser diffraction particle size distribution analyzer ("SALD-3000J" from Shimadzu Corporation), while The ultrasonic wave was applied for 1 minute while being circulated by a pump, and the measurement was performed by a laser diffraction method under the following measurement conditions. At this time, the output conditions were set as the number or volume basis, and the values corresponding to the following (1) to (5) were examined.

(setting of measurement conditions)

Measurement times: 1 time

Measurement interval: 2 seconds

Average times: 64 times

Measurement range of absorbance: 0.01~0.2

(arbitrary particle size.% table setting)

Range: 0.1μm~2000μm

Number of divisions: 50

(1) In the particle size distribution based on the number of objects obtained by setting the distribution criteria of the output condition as "number of objects" in the particle size distribution measurement, the particle size when the relative particle amount q0 of the difference becomes the mode is investigated.

(2) Calculation of the distribution criteria for the output conditions in the particle size distribution measurement The ratio of the relative particle amount q0A of the difference when the particle diameter is 11.601 μm and the relative particle amount q0B of the difference when the particle diameter is 7.806 μm in the number-based particle size distribution obtained as “number of objects” (q0A/ q0B).

(3) Investigate the particle size distribution based on volume obtained by setting the distribution criterion of the output condition as “volume” in the particle size distribution measurement, and when the volume cumulative distribution curve is drawn from the small particle size side, the particle size is 9.516 μm The accumulated value Q3 at the time.

(4) Investigate the particle size distribution based on the volume obtained by setting the distribution criterion of the output condition as “volume” in the particle size distribution measurement, and when the cumulative volume distribution curve is drawn from the small particle size side, when the accumulation becomes 50% particle size (50% D).

(5) Investigate the particle size distribution based on the volume obtained by setting the distribution criterion of the output condition as “volume” in the particle size distribution measurement, when the cumulative volume distribution curve is drawn from the small particle size side, and the accumulation becomes 99.9% particle size (99.9% D).

[Knock tightness determination]

100 cm ^{3 of the} carbon material was slowly put into ^{a measuring cylinder with a capacity of 100 cm 3} , and the measuring cylinder was plugged. This graduated cylinder was dropped 250 times from a height of 5 cm, and the value obtained from the mass and volume of the carbon material thereafter was referred to as the tap tightness.

[Particle Density Measurement]

1.00 g of the carbon material was put into a 13 mm diameter former (13 mm pellet die model 3619 from Carver), and a hydraulic press (“Carver Standard Press” from Carver) was used. Press)") after pressing with a pressure of 1.0 t, the thickness and cross-sectional area of the carbon material after pressing will The value obtained by dividing the obtained volume by the mass of the carbon material was set as the tap compactness.

[average aspect ratio]

The average aspect ratio of the carbon material was obtained using a fluid particle image analyzer (“FPIA-3000” from Sysmex Corporation).

[Measurement of initial charge-discharge efficiency]

With respect to 98 parts by mass of the produced carbon material, CMC (carboxymethyl cellulose, "Serogen (Serogen (Serrogen)" from Daiichi Kogyo Pharmaceutical Co., Ltd. was added as a thickener so as to be 1 part by mass in terms of the solid content of CMC. Serogen) WS-C") in an aqueous solution with a concentration of 2% by mass, and kneaded for 10 minutes. Next, purified water was added so that the solid content concentration (the total of the negative electrode material and CMC) in the kneaded product became 40% by mass to 50% by mass, and the kneading was performed for 10 minutes. Next, an aqueous dispersion having a concentration of 40% by mass of SBR (“BM-400B” from ZEON Co., Ltd.) as a binder was added so that the solid content of SBR would be 1 part by mass, and mixed for 10%. A paste-like negative electrode material composition was produced. 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. Furthermore, it dried at 105 degreeC, and removed the water|moisture content, and produced the sample electrode (negative electrode).

Next, the sample electrode, the separator, and the counter electrode were layered in this order, put into a battery container, and injected to _{dissolve LiPF 6} in ethylene carbonate ( EC) and methyl ethyl carbonate (MEC) (EC and MEC in a volume ratio of 1:3) in a mixed solvent to prepare a coin cell battery. The opposite electrode is made of metallic lithium, and the separator is made of polyethylene microporous membrane with a thickness of 20 μm.

Between the sample electrode and the counter electrode of the obtained coin cell, the battery was ^{charged with a constant current of 0.2 mA/cm 2} to 0 V (Vvs. Li/Li ⁺ ), and then charged with a constant voltage of 0 V until the current reached 0.02 mA until. Next, after a rest time of 30 minutes, a 1-cycle test of discharging to 2.5 V (Vvs. Li/Li ^{+ ) at a constant current of 0.2 mA/cm 2} was performed, 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 referred to as charging, and the case where lithium ions are released from the sample electrode on the contrary is referred to as discharge.

[Evaluation of life characteristics]

A negative electrode prepared by the same method as the negative electrode material composition used for the measurement of the initial charge-discharge efficiency was prepared by using a notch wheel coater with the gap adjusted so that the coating amount per unit area was 9.0 mg/cm ^{2 .} The material composition was coated on an electrolytic copper foil with a thickness of 40 μm. Then, the electrode density was adjusted to 1.5 g/cm ³ with a hand press. This electrode was punched out into a disk shape with a diameter of 14 mm to prepare a sample electrode (negative electrode). A coin cell was produced in the same manner as the measurement of the initial charge-discharge efficiency except that the sample electrode was used.

Using the coin cells produced as described above, the evaluation of life characteristics was performed in the following procedure.

(1) Charge to 0V (Vvs.Li/Li ⁺ ) at a constant current of 0.48mA, and then charge at a constant voltage of 0V until the current reaches 0.048mA.

(2) After a rest time of 30 minutes, ^{a 1-cycle test of discharging to 1.5V (Vvs. Li/Li +} ) at a constant current of 0.48 mA was performed, and the discharge capacitance was measured.

^{(3) Charge to 0V (Vvs.Li/Li +} ) at a constant current of 4.8mA, and charge at a constant voltage of 0V until the current reaches 0.48mA.

(4) After a rest time of 30 minutes, discharge was performed to 1.5V (Vvs.Li/Li ⁺ ) at a constant current of 4.8mA.

(5) The charge-discharge cycle test of the above (3) and (4) was carried out for 50 cycles.

The discharge capacitance retention rate from the first cycle when the cycle was repeated for 50 cycles (=50th cycle discharge capacitance/1st cycle discharge capacitance×100) was measured. The higher the discharge capacity retention ratio, the better the life characteristics can be judged.

(Evaluation of input and output characteristics)

A coin cell battery was produced by the same method as for the life characteristics, and the evaluation of the input and output characteristics was performed in the following procedure.

(1) Charge to 0V (Vvs.Li/Li ⁺ ) at a constant current of 0.96mA, and then perform constant voltage charge at 0V until the current value reaches 0.096mA.

(2) After a rest time of 30 minutes, discharge was performed to 1.5V (Vvs.Li/Li ⁺ ) at a constant current of 0.96mA.

(3) Charge up to half the capacitance 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 this time was confirmed. A rest time of 30 minutes was set during the test at each current value.

ΔV was plotted against each current value, and the slope was defined as a resistance value (Ω). As the value is smaller, it can be judged that the input/output characteristics are excellent.

[Example 2]

A carbon material was produced in the same manner as in Example 1, except that the composite material 1 and the composite material 2 were mixed at a mass ratio of 4:6 (composite material 1:composite material 2), and their properties were investigated. In addition, coin cells were produced and their performance was evaluated. The results are shown in Table 2.

[Example 3]

A carbon material was produced in the same manner as in Example 1, except that the composite material 1 and the composite material 2 were mixed at a mass ratio of 3:7 (composite material 1:composite material 2), and their properties were investigated. In addition, coin cells were produced and their performance was evaluated. The results are shown in Table 2.

[Example 4]

A carbon material was produced in the same manner as in Example 1, except that the composite material 1 and the composite material 2 were mixed at a mass ratio of 6:4 (composite material 1:composite material 2), and their properties were investigated. In addition, coin cells were produced and their performance was evaluated. The results are shown in Table 2.

[Comparative Example 1]

A carbon material was produced in the same manner as in Example 1, except that the composite material 1 and the composite material 2 were mixed at a mass ratio of 2:8 (composite material 1:composite material 2), and their properties were investigated. In addition, coin cells were produced and their performance was evaluated. The results are shown in Table 2.

[Comparative Example 2]

A carbon material was produced in the same manner as in Example 1 except that only the composite material 2 was used, and investigate its properties. In addition, coin cells were produced and their performance was evaluated. The results are shown in Table 2.

[Comparative Example 3]

A carbon material was produced in the same manner as in Example 1 except that only the composite material 1 was used, and its characteristics were investigated. In addition, coin cells were produced and their performance was evaluated. The results are shown in Table 2.

[Comparative Example 4]

It is the same as composite material 1 except that 100 parts by mass of spherical natural graphite having a volume average particle diameter of 22 μm (d ₀₀₂ =0.336 nm, average aspect ratio=0.7) is used instead of spherical natural graphite having a volume average particle diameter of 10 μm Composite 3 is obtained.

A carbon material was produced in the same manner as in Example 1, except that the composite material 3 and the composite material 2 were mixed at a mass ratio of 5:5 (composite material 3:composite material 2), and their properties were investigated. In addition, coin cells were produced and their 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) with a volume average particle size of 22 μm was passed through a 300-mesh sieve, and the obtained under-sieve portion and the composite material 2 were in a mass ratio of 5:5 (sieve). Lower part: A carbon material was produced in the same manner as in Example 1, except that it was mixed in the manner of composite material 2), and its characteristics were investigated. In addition, coin cells were produced and their performance was evaluated. The results are shown in Table 2.

[Comparative Example 6]

Using an autoclave, the carbonaceous coal tar was heat-treated at 400° C. to obtain crude coke. After pulverizing the coarse coke, it was calcined in an inert atmosphere at 1200° C. to obtain a coke lump. The coke mass was pulverized to an average particle size of 15 μm using an impact pulverizer equipped with a classifier, and then passed through a 200-mesh sieve to obtain a portion under the sieve as carbon particles (d ₀₀₂ =0.342 nm). A composite material was obtained in the same manner as the composite material 1 except that 100 parts by mass of the carbon particles were mixed with 20 parts by mass of polyvinyl alcohol (polymerization degree: 1700, complete saponification type, carbonization rate: 15 mass %) 4.

A carbon material was produced in the same manner as in Example 1, except that the composite material 4 and the composite material 2 were mixed at a mass ratio of 5:5 (composite material 4:composite material 2), and their properties were investigated. In addition, coin cells were produced and their performance was evaluated. The results are shown in Table 2.

[Comparative Example 7]

The spherical natural graphite with a volume average particle size of 10 μm (d ₀₀₂ = 0.336 nm, average aspect ratio = 0.8) and spherical natural graphite with a volume average particle size of 16 μm (d ₀₀₂ = 0.336 nm, average aspect ratio = 0.8) A carbon material was produced in the same manner as in Example 1, except that the mixture was mixed so that the mass ratio was 5:5, and its characteristics were investigated. In addition, coin cells were produced and their 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 agglomerates were pulverized with a pin mill, and then shaped into a block with ^{a density of 1.52 g/cm 3 by a molding press.} After calcining the obtained block at a maximum temperature of 800°C using a muffle furnace, graphitization was performed at 2900°C using an Acheson furnace in a self-decomposing gas atmosphere. Next, the graphitized block was roughly pulverized with a hammer, and then a graphite powder having an average particle diameter of 30 μm was obtained with a pin mill. Furthermore, this graphite powder was subjected to 1000 revolutions/minute (rpm) of pulverization and 7000 revolutions/minute (rpm) of classification using a spheroidizing device (manufactured by Hosokawa Micron, Faculty). Minute treatment to produce spheroidized artificial graphite powder. The spheroidized artificial graphite powder was passed through a 200-mesh sieve to obtain a fraction under the sieve as a carbon material. The properties of this carbon material were investigated in the same manner as in Example 1. In addition, coin cells were produced and their performance was evaluated. The results are shown in Table 2.

[Table 2]

From the results shown in Table 2, it became clear that the lithium ion secondary batteries of Examples 1 to 4 produced using the negative electrode material containing the carbon material of the present embodiment maintained high charge-discharge efficiency, input-output characteristics and lifespan. The characteristics are also excellent.

Claims (10)

A negative electrode material for a lithium ion secondary battery, comprising a carbon material, in which the average interplanar spacing d ₀₀₂ obtained by an X-ray diffraction method is 0.335 nm to 0.339 nm, and the carbon material contains a first carbon phase that becomes a nucleus , and a second carbon phase disposed on at least a part of the surface of the first carbon phase and different from the first carbon phase, and satisfying the following (1) and (2): (1) particle size distribution based on number (2) In the particle size distribution based on the number, the relative particle size q0A of the difference when the particle size is 11.601 μm and the particle size are 7.806 The relative particle amount q0B ratio (q0A/q0B) of the difference in μm is 1.20 to 3.00. The negative electrode material for lithium ion secondary batteries according to claim 1, wherein the R value measured by Raman spectroscopy is 0.1 to 1.0. The patentable scope of the application as a first item a lithium ion secondary battery negative electrode material, wherein the adsorption of nitrogen at 77K was measured and determined by a specific surface area of 0.5m ² /g~6.0m ² / g. The negative electrode material for a lithium ion secondary battery according to any one of claims 1 to 3, wherein the carbon material has a volume cumulative distribution curve drawn from a small particle size side in a volume-based particle size distribution In the case of , the cumulative value Q3 when the particle size is 9.516 μm is 4.0% or more of the whole. The negative electrode material for lithium ion secondary batteries according to any one of claims 1 to 3, wherein the carbon material has a particle size distribution on a volume basis Among them, when the volume cumulative distribution curve is drawn from the small particle diameter side, the particle diameter (50% D) when the accumulation becomes 50% is 1 μm to 20 μm. The negative electrode material for a lithium ion secondary battery according to any one of claims 1 to 3, wherein the carbon material has a volume cumulative distribution curve drawn from a small particle size side in a volume-based particle size distribution In the case of , the particle size (99.9% D) when the accumulation is 99.9% is 63 μm or less. The negative electrode material for a lithium ion secondary battery according to any one of the claims 1 to 3, wherein the carbon material has a tap density of 0.90 g/cm ³ to 2.00 g/cm ³ . The negative electrode material for lithium ion secondary batteries according to any one of claims 1 to 3 of the claimed scope, wherein the carbon material has a particle density of 1.55 g/cm ³ or less. A negative electrode for a lithium ion secondary battery, comprising a negative electrode material layer including the negative electrode material for a lithium ion secondary battery according to any one of claims 1 to 8, and a current collector. A lithium ion secondary battery comprising the negative electrode for a lithium ion secondary battery described in claim 9, a positive electrode, and an electrolyte.