JPWO2017110796A1 - Carbon material for secondary battery negative electrode, active material for secondary battery negative electrode, secondary battery negative electrode and secondary battery - Google Patents

Abstract

The present invention provides a carbon material for a secondary battery negative electrode that realizes a low-resistance secondary battery negative electrode while providing high peel strength between the negative electrode active material layer and the negative electrode current collector, and the carbon material for a secondary battery negative electrode described above. There are provided a secondary battery negative electrode active material produced by containing the secondary battery negative electrode active material, a secondary battery negative electrode configured using the secondary battery negative electrode active material, and a secondary battery using the secondary battery negative electrode. The carbon material for secondary battery negative electrode of the present invention comprises carbon particles whose relative pressure when the normalized water vapor adsorption amount in the standardized water vapor adsorption isotherm is 0.5 is in the range of 0.2 to 0.8. Including.

Description

  The present invention relates to a carbon material for a secondary battery negative electrode, an active material for a secondary battery negative electrode, a secondary battery negative electrode, and a secondary battery.

  In recent years, the use of secondary batteries has been studied in various technical fields ranging from small electrical products such as mobile phones to large machine products such as automobiles. As the secondary battery, various types such as a non-aqueous electrolyte secondary battery using an organic electrolyte solution or the like as an electrolyte or a solid battery using a solid electrolyte have been studied. In any type of secondary battery, a carbon material such as hard carbon or graphite is widely used as the negative electrode active material of the conventional secondary battery.

  For secondary battery negative electrodes, in addition to the negative electrode active material composed of particulate carbon materials, etc., thickeners, binders (binders) and other additives are blended in aqueous solvents and stirred to produce negative electrode slurries. In general, the negative electrode slurry is applied to a negative electrode current collector such as a copper foil and dried. The thickener adjusts the viscosity of the negative electrode slurry as desired, and the binder improves the adhesion between the negative electrode slurry and the negative electrode current collector. Patent Document 1 describes that carboxymethyl cellulose is used as a thickener and styrene-butadiene rubber is used as a binder.

JP-A-11-162451

  By mixing the binder with the negative electrode slurry, the adhesion between the negative electrode slurry and the negative electrode current collector is improved, and the peel strength between the negative electrode active material layer and the negative electrode current collector in the produced secondary battery negative electrode is improved. . Thereby, the physical strength of the secondary battery negative electrode is improved. However, an adhesive elastomer material is generally used for the binder, and since the elastomer material has low conductivity, there is a problem that the electrical resistance of the negative electrode active material layer is increased by blending the binder. .

  The present invention has been made in view of the above problems, and provides a secondary battery negative electrode charcoal that realizes a low battery secondary battery negative electrode while providing high peel strength between the negative electrode active material layer and the negative electrode current collector. The material is provided. The present invention also provides an active material for a secondary battery negative electrode produced by including the carbon material for a secondary battery negative electrode, a secondary battery negative electrode configured using the active material for a secondary battery negative electrode, and the secondary battery negative electrode. A secondary battery using a secondary battery negative electrode is provided.

  According to the study of the present inventors, the hydrophilicity of the carbon particles is within a predetermined range, so that the carbon particles and the binder are well bonded in the presence of the aqueous solvent and applied to the negative electrode current collector. It was found that when the negative electrode slurry was dried, the adhesion between the negative electrode active material layer and the negative electrode current collector was extremely good. Based on the above study, the present inventor has completed the present invention based on the knowledge that the above problem can be solved by setting the normalized water vapor adsorption amount indicating the degree of hydrophilicity of the carbon particles within a predetermined range. It was.

  That is, the carbon material for a secondary battery negative electrode of the present invention is a carbon particle having a relative pressure when the normalized water vapor adsorption amount in the standardized water vapor adsorption isotherm is 0.5 within a range of 0.2 to 0.8. Is included.

  Moreover, the active material for secondary battery negative electrodes of this invention contains the carbon material for secondary battery negative electrodes of this invention. Further, the secondary battery negative electrode of the present invention includes a secondary battery negative electrode active material layer containing the secondary battery negative electrode active material of the present invention, and a negative electrode current collector in which the secondary battery negative electrode active material layer is laminated. And. Moreover, the secondary battery of this invention is equipped with the secondary battery negative electrode of this invention, an electrolysis layer, and a secondary battery positive electrode.

  According to the present invention, high peel strength is realized between the negative electrode active material layer and the negative electrode current collector by setting the normalized water vapor adsorption amount of the carbon particles blended in the aqueous solvent together with the binder within the above range. Is done. For this reason, even if the blending amount of the binder is reduced, the peel strength between the negative electrode active material layer and the negative electrode current collector can be sufficiently obtained, and the resistance of the secondary battery negative electrode can be suppressed. Accordingly, an active material for a secondary battery negative electrode, a secondary battery negative electrode, and a secondary battery that can suppress an increase in electrical resistance during charging / discharging of the secondary battery by using the carbon material for a secondary battery negative electrode of the present invention is provided. can do.

It is a graph showing the normalization water vapor adsorption isotherm of a carbon material. It is a schematic diagram which shows an example of a lithium ion secondary battery provided with the negative electrode manufactured using the carbon material of this invention.

  A secondary battery negative electrode carbon material (hereinafter also simply referred to as a carbon material), a secondary battery negative electrode active material (hereinafter also simply referred to as a negative electrode active material), a secondary battery negative electrode (hereinafter referred to as a negative electrode active material) according to an embodiment of the present invention. The secondary battery will be described in order.

  As the secondary battery in which the carbon material of the present invention, the negative electrode active material, or the negative electrode is used, and the secondary battery of the present invention, for example, an alkali metal secondary such as a lithium ion secondary battery or a sodium ion secondary battery is used. A battery can be mentioned. However, the secondary battery is not limited to this, and includes various types such as a secondary battery that occludes and releases other charge carriers, a non-aqueous electrolyte secondary battery, or a solid secondary battery. In the following description, a lithium ion secondary battery will be described as an example of a secondary battery.

<Carbon material>
The carbon material for a secondary battery negative electrode of the present embodiment is a carbon material that can be used as a material for an active material for a negative electrode. Such a carbon material includes carbon particles having a relative pressure in the range of 0.2 to 0.8 when the normalized water vapor adsorption amount in the standardized water vapor adsorption isotherm is 0.5.

  First, the water vapor adsorption characteristics of the carbon material will be described. FIG. 1 is a graph showing a normalized water vapor adsorption isotherm of a carbon material. More specifically, it is a graph in which normalized water vapor adsorption isotherms obtained by normalizing the adsorption isotherms of carbon materials according to Examples 1 to 3, Reference Examples 1 and 2 and Comparative Example 1 described later are superimposed. The adsorption isotherm can be determined using a commercially available gas adsorption amount measuring device such as BELSORP-max (manufactured by Nippon Bell Co., Ltd.).

Here, it is generally said that the adsorption phenomenon starts from the adsorption of molecules to the surface of the particles, and eventually the adsorption of the molecules suddenly proceeds to the pores inside the particles when the entire particle surface is covered. Yes. On the other hand, in the case of adsorption of water to a hydrophilic and porous material such as carbon particles, it is considered that adsorption of water molecules to the particle surface and adsorption to the inside of the pore proceed. On the other hand, when a binder having a molecular size much larger than that of water is adsorbed on the carbon particles, it is adsorbed exclusively on the surface of the carbon particles. For this reason, it is considered that the quality of the binding of the binder to the carbon particles is governed by the ease of physical adsorption of water on the surface of the carbon particles by eliminating the adsorption of water to the inside of the carbon particles as much as possible.
Regarding the adsorption phenomenon of gas on solids, if the adsorption temperature is constant, the number of gas molecules adsorbed on a solid mass (adsorption number) depends only on the pressure, and if the pressure is increased, the number of adsorption is It is known to increase monotonically. Moreover, adsorption and desorption being in an equilibrium state is called adsorption equilibrium, and the pressure at that time is called adsorption equilibrium pressure. The ratio between the adsorption equilibrium pressure and the saturated vapor pressure is called a relative pressure, and the relative pressure takes a value from 0 to 1. A plot of relative pressure on the horizontal axis and gas adsorption amount (adsorption volume, etc.) on the vertical axis is called an adsorption isotherm. The slope of the adsorption isotherm represents the amount of increase in the amount of gas adsorbed when the relative pressure is slightly increased. In other words, the adsorption isotherm shows the total amount of gas that can be adsorbed on the surface of the solid and the inside of the pores, and the ease of physical adsorption only on the surface of the solid does not appear.
Therefore, the present inventor considered that the adsorption phenomenon of water vapor to the carbon particles first occurs on the surface of the carbon particles and then proceeds to the inside of the pores. It was conceived that the rate of water adsorption on the surface of the carbon particles appears in the slope of the rise. That is, when the adsorbability of the carbon particles on the surface is good, adsorption to the surface occurs at a relatively low relative pressure, so that the rise of the adsorption isotherm is shifted to the low pressure side. On the other hand, if the adsorptivity to the surface of the carbon particles is poor, the adsorption of water occurs exclusively inside the pores, and such adsorption occurs in the vicinity of reaching the adsorption equilibrium. It is considered that the rise of is shifted to the high pressure side.
For this reason, the present inventor does not use the adsorption isotherm itself, but the normalized water vapor in which the vertical axis (gas adsorption amount) in the adsorption isotherm is dimensionless with the gas adsorption amount (maximum adsorption amount) in the adsorption / desorption equilibrium state. We focused on the amount of adsorption. More specifically, in the normalized water vapor adsorption isotherm representing the relationship between the normalized water vapor adsorption amount and the relative pressure, the relative pressure at which half the maximum adsorption amount of gas is adsorbed, that is, the normalized water vapor adsorption amount is 0.5 (see FIG. In the case where the relative pressure of water vapor, which is indicated by a one-dot chain line in FIG. Specifically, when the relative pressure is 0.8 or less (indicated by a two-dot chain line in FIG. 1), the water adsorption on the surface of the carbon particles is sufficiently good and the bond with the binder is increased. It is clear. This will be described in more detail in the examples described later.
In addition, in this specification, the amount of water vapor adsorption refers to that at room temperature (25 ° C.) unless otherwise specified.

  In the carbon material of this embodiment, the preferable lower limit of the relative pressure of water vapor when the normalized water vapor adsorption amount is 0.5 is 0.2. As a result, a carbon material is formed in which a predetermined amount of pores are formed inside and water vapor is adsorbed more than a predetermined amount not only on the surface but also inside the pores. For this reason, by using such a carbon material, it is avoided that the pore volume for alkali metals such as lithium ions to enter in the secondary battery negative electrode becomes too small. From the above viewpoint, the relative pressure of water vapor when the normalized water vapor adsorption amount is 0.5 is preferably 0.4 or more, and more preferably 0.6 or less.

  It is preferable that the normalized water vapor adsorption isotherm of the carbon particles used in the carbon material of the present embodiment has an inflection point in a range of relative pressure of 0.4 to 0.8. In FIG. 1, the approximate position of the inflection point IP is indicated by a cross. More specifically, at the relative pressure below the inflection point, the increase rate indicating the increase in the normalized water vapor adsorption amount with respect to a slight increase in the relative pressure is gradual, and this increase rate is maximum at the inflection point. Further, at the relative pressure above the inflection point, this increase rate decreases again, and the slope of the normalized water vapor adsorption isotherm becomes gentle. And by having the inflection point IP in the range of 0.4 to 0.8, which is an intermediate relative pressure in the normalized water vapor adsorption isotherm, to the surface of the carbon particles mainly generated at a lower relative pressure. It can be said that the adsorption of water vapor occurs satisfactorily. This is presumably because the inclination of the normalized water vapor adsorption isotherm is maximized at an intermediate relative pressure and the inflection point IP is generated because water vapor is favorably adsorbed on the surface of the carbon particles. The inflection point IP of the normalized water vapor adsorption isotherm is more preferably in the range of relative pressure of 0.4 or more and 0.6 or less.

  Further, the carbon particles of the present embodiment preferably have a normalized water vapor adsorption amount within a predetermined upper limit to lower limit range at an intermediate relative pressure. If this lower limit is too small, hydrophilicity to the surface of the carbon particles will be insufficient and sufficient binding with the binder will not be obtained, and if this upper limit is excessive, the pore volume inside the carbon particles will be low. It becomes too small and it becomes difficult to obtain a sufficient amount of charge / discharge of the secondary battery. More specifically, in the carbon particles of the present embodiment, the normalized water vapor adsorption amount when the relative pressure is 0.5 in the normalized water vapor adsorption isotherm is in the range of 0.2 to 0.8 (FIG. 1). Are indicated by double-sided arrows), and more preferably in the range of 0.3 to 0.6.

  The method for obtaining a carbon material containing carbon particles having a relative pressure of water vapor in a preferable range in the normalized water vapor adsorption amount specified in the present embodiment is not particularly limited.

The carbon material of the present embodiment preferably has a surface area per unit volume of 10,000 cm ⁻¹ or more. Thereby, the carbon material of this embodiment is excellent in the ability to occlude and release alkali metal ions such as lithium ions, and exhibits the effect of suppressing electrical resistance. The carbon material of the present embodiment has a surface area per unit volume of 16000 cm ⁻¹ or less, and it is preferable that extremely fine carbon material particles are excluded. The surface area per unit volume can be calculated by the following formula (1) using data obtained from a number-based particle size distribution measured by a laser diffraction / scattering particle size distribution analyzer.
Formula (1)
Area per unit volume (cm ⁻¹ ) = total surface area (cm ² ) / total volume (cm ³ ) (1)
The particle size distribution can be measured by a commercially available laser diffraction / scattering particle size distribution measuring device such as LA-920 manufactured by Horiba, Ltd., and the particle size means the particle diameter.

  Further, the “total surface area” is the sum of values obtained by multiplying the surface area when particles of each particle size in the particle size distribution are converted into true spheres by the frequency (%) of particles at each particle size. The “total volume” is the total sum of values obtained by multiplying the volume when the particles of each particle size in the particle size distribution are converted into true spheres by the frequency (%) of the particles at each particle size. “Frequency” is the ratio of particles at each particle size to the total number of particles subjected to measurement.

One of the preferable aspects of the carbon material of the present embodiment is a range in which the true specific gravity of the carbon particles contained in the carbon material is 1.5 g / cm ³ or more and 1.7 g / cm ³ or less. By selecting carbon particles having a true specific gravity of 1.5 g / cm ³ or more, the charge / discharge capacity value can be stabilized. Further, by selecting carbon particles having a true specific gravity of 1.7 g / cm ³ or less, it contributes to the improvement of the life characteristics of the secondary battery in which the carbon material of the present embodiment is used. The true specific gravity can be determined by a true specific gravity measurement method using butanol.

  The method for adjusting the carbon particles contained in the carbon material of the present embodiment to have a true specific gravity in the above preferred range is not particularly limited, but for example, depending on the selection of the carbon material raw material or the heating condition of the carbon material raw material, It is possible to adjust the true specific gravity.

Below, carbon used as the main material of the carbon material of this embodiment is demonstrated.
The carbon material of this embodiment contains carbon as a main material, and may contain components other than carbon as necessary. Here, the term “carbon is a main material” means that carbon is contained in an amount of 80% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more when the carbon material is 100% by mass. Say. Carbon contained in the carbon material in the present embodiment is carbon particles that are substantially granular. The carbon material in the present embodiment may contain the carbon particles and an optional additive, or may be substantially composed only of carbon particles.

  The optional component other than carbon in the carbon material is not particularly limited, and examples thereof include nitrogen and phosphorus. By including nitrogen in the carbon material, electrical characteristics suitable for the carbon material (particularly, carbon material containing hard carbon) can be imparted due to the electronegativity of nitrogen.

  The carbon used as the main material can be appropriately selected and used as long as it is a material for the negative electrode active material and can absorb and release chemical species such as lithium ions. Specific examples include hard carbon and graphite, but are not limited thereto.

  Below, the aspect in which the carbon particle in the carbon material of this embodiment contains hard carbon is demonstrated.

That is, as one preferred aspect of the carbon material of the present embodiment, the carbon particles contained in the carbon material are obtained by an X-ray diffraction method using CuKα rays as a radiation source. Hard carbon whose ₀₀₂ is 0.340 nm or more can be included.

Hard carbon (non-graphitizable carbon) is a carbon material obtained by firing a polymer that does not easily develop a graphite crystal structure, and is an amorphous substance. In other words, the hard carbon is a carbon material that does not have a graphene structure or carbon that only partially has a graphene structure, and has the specific average interplanar spacing d ₀₀₂ . When the average interplanar spacing d ₀₀₂ of hard carbon is 0.340 nm or more, especially 0.360 nm or more, the shrinkage / expansion between layers due to occlusion of lithium ions is difficult to occur. it can. The upper limit of the average interplanar distance d ₀₀₂ is not particularly defined, but can be set to 0.390 nm or less, for example. The average spacing _{d 002} is 0.390nm or less, particularly when it is 0.380nm or less performed smoothly absorbing and releasing lithium ions, it is possible to suppress the deterioration of the charge-discharge efficiency.

  Further, the hard carbon preferably has a crystallite size Lc of 0.8 nm or more and 5 nm or less in the c-axis direction ((002) plane orthogonal direction).

  By setting Lc to 0.8 nm or more, particularly 0.9 nm or more, there is an effect that a space between carbon layers capable of occluding and releasing lithium ions is formed, and a sufficient charge / discharge capacity can be obtained. By setting the thickness to 0.5 nm or less, it is possible to suppress the collapse of the carbon laminate structure due to the occlusion and release of lithium ions and the reductive decomposition of the electrolytic solution, and to suppress the decrease in charge / discharge efficiency and charge / discharge cycleability.

Lc is calculated as follows.
It was determined from the half width of the 002 plane peak and the diffraction angle in the spectrum obtained from the X-ray diffraction measurement using the following Scherrer equation.

Lc = 0.94λ / (βcosθ) (Scherrer equation)
Lc: crystallite size λ: wavelength of characteristic X-ray K _α1 output from the cathode β: half width of peak (radian)
θ: Reflection angle of spectrum

  The X-ray diffraction spectrum of hard carbon can be measured by an X-ray diffractometer “XRD-7000” manufactured by Shimadzu Corporation. The method for measuring the average spacing in hard carbon is as follows.

  From the spectrum obtained from the X-ray diffraction measurement of hard carbon, the average interplanar spacing d can be calculated as follows from the following Bragg equation.

λ = 2 × d _hkl × sin θ (Bragg equation) (d _hkl = d ₀₀₂ )
λ: wavelength of characteristic X-ray K _α1 output from the cathode θ: reflection angle of spectrum

  Carbon particles, which are hard carbon, have the property that lithium ions can be occluded and released over the entire surface. Therefore, the carbon material containing the carbon particles of hard carbon having a surface area per unit volume in the above-described range exhibits a remarkable effect of being excellent in the ability to occlude and release lithium ions by increasing the surface area. That is, the carbon material of the present embodiment that includes carbon particles that are hard carbon sufficiently enjoys the effects produced by the configuration of the present embodiment and exhibits excellent effects.

  From the viewpoint of fully enjoying the effects obtained by including hard carbon in the carbon particles as described above, the carbon particles in the present embodiment may contain 90% by mass or more of hard carbon.

  The raw material of the hard carbon is not particularly limited, and examples thereof include a resin material such as a thermosetting resin or a thermoplastic resin. The raw materials include petroleum-based tar or pitch produced as a by-product during ethylene production, coal tar produced during coal dry distillation, heavy component or pitch obtained by distilling off low-boiling components of coal tar, and tar obtained by coal liquefaction. Examples thereof include petroleum-based or coal-based materials such as pitch, and those obtained by crosslinking the above-described petroleum-based or coal-based materials. The hard carbon raw materials described above can be used alone or in combination of two or more. Also, plant materials such as coconut shells can be used as raw materials for hard carbon.

  The thermosetting resin is not particularly limited, and examples thereof include phenolic resins such as novolac type phenolic resin and resol type phenolic resin, epoxy resins such as bisphenol type epoxy resin and novolac type epoxy resin, melamine resin, urea resin, and aniline. Examples thereof include resins, cyanate resins, furan resins, ketone resins, unsaturated polyester resins, and urethane resins. The carbon material may be a modified product obtained by modifying these materials with various components.

  The thermoplastic resin is not particularly limited. For example, polyethylene, polystyrene, polyacrylonitrile, acrylonitrile-styrene (AS) resin, acrylonitrile-butadiene-styrene (ABS) resin, polypropylene, vinyl chloride, methacrylic resin, polyethylene terephthalate, Examples include polyamide, polycarbonate, polyacetal, polyphenylene ether, polybutylene terephthalate, polyphenylene sulfide, polysulfone, polyether sulfone, polyether ether ketone, polyether imide, polyamide imide, polyimide, and polyphthalamide.

  In particular, a thermosetting resin is preferable as the main component resin used for hard carbon. Thereby, the residual carbon rate of hard carbon can be raised more.

  Among thermosetting resins, a resin selected from a novolak-type phenol resin, a resol-type phenol resin, a melamine resin, a furan resin, an aniline resin, or a modified product thereof is preferable as a resin that is a main component of hard carbon. Thereby, the freedom degree of design of a carbon material spreads and it can manufacture at low cost. Further, the stability during cycling and the input / output characteristics of a large current can be further improved.

  Moreover, when using a thermosetting resin, the hardening | curing agent can be used together. The said hardening | curing agent is not specifically limited, A well-known hardening | curing agent can be used. For example, in the case of a novolac type phenol resin, hexamethylenetetramine, resol type phenol resin, polyacetal, paraform or the like can be used as a curing agent. In the case of epoxy resins, use polyamine compounds such as aliphatic polyamines and aromatic polyamines, acid anhydrides, imidazole compounds, dicyandiamide, novolac-type phenol resins, bisphenol-type phenol resins, or resole-type phenol resins as curing agents. Can do.

Next, the aspect in which the carbon particles in the carbon material of the present embodiment include graphite will be described.
Graphite is one of the allotropes of carbon, and is a hexagonal hexagonal plate crystal material that forms a layered lattice made of layers of six-carbon rings. It has a so-called graphene structure. The graphite includes natural graphite and artificial graphite.
Graphite has a desirable property that there is little voltage change from the beginning of discharge to the end of discharge, and can maintain a stable high voltage until the end of discharge. Part or all of the carbon particles contained in the carbon material of the present embodiment may be made of graphite.

The carbon particles in the carbon material of the present embodiment may contain hard carbon and graphite from the viewpoint of providing a well-balanced carbon material by utilizing the advantages of hard carbon and graphite.
The aspect of the present embodiment that includes both hard carbon and graphite as the carbon particles is the case where the hard carbon particles and the graphite particles are individually observed in the microscopic observation, and the two are fused or bound, and the appearance is And the case of being integrally observed.

  The content ratio of hard carbon and graphite in the carbon material of the present embodiment is not particularly limited. However, from the viewpoint of satisfactorily solving the desired problem of the present embodiment by including a large amount of hard carbon having a surface area per unit volume within a predetermined range, the following ratio ranges are preferable. That is, in the carbon material according to the present embodiment including hard carbon and graphite, the mass ratio of both in the carbon material is in the range of hard carbon: graphite = 51 mass%: 49 mass% to 95 mass%: 5 mass%. It is preferable that

Components other than the carbon material blended in the negative electrode slurry will be described. An aqueous solvent may be used for the negative electrode slurry.
As the thickener, carboxymethylcellulose or a salt thereof can be used.
Binders (binders) include organic polymer binders, specifically fluoropolymers such as polyvinylidene fluoride and polytetrafluoroethylene, or rubbery high polymers such as styrene-butadiene rubber, butyl rubber, and butadiene rubber. Molecules can be used. These may be modified by surface modification or the like.

  The binder may be blended at a ratio of 0.01% by mass to 5% by mass, preferably 0.1% by mass to 3% by mass, based on the mass of the carbon material blended in the negative electrode slurry. Since the carbon material of the present embodiment has high hydrophilicity and good binding to the binder, even if the binder is suppressed to the above-mentioned blending ratio, the gap between the negative electrode active material layer and the negative electrode current collector in the electrode Sufficient peel strength can be obtained. Moreover, it is possible to make a negative electrode collector low resistance by suppressing the compounding quantity of a binder.

  Since the thickener and the binder are used by being dispersed in an aqueous solvent, the thickener and the binder are easily adsorbed on the highly hydrophilic carbon material particles. As a result, a negative electrode slurry in which the thickener and the binder are uniformly dispersed can be prepared. The electrode prepared by applying the negative electrode slurry to the negative electrode current collector has the negative electrode active material layer and the negative electrode current collector. Adhesion strength with is improved.

A viscosity modifier and a conductive material may be further added to the negative electrode slurry as necessary.
Examples of the viscosity modifier include N-methyl-2-pyrrolidone, dimethylformamide, and alcohol.
As the conductive material, for example, any one or a combination of acetylene black, ketjen black, vapor grown carbon fiber, and the like can be used. Although the compounding quantity of a electrically conductive material is not specifically limited, For example, 2 mass parts or more and 10 mass parts or less are preferable with respect to 100 mass parts of negative electrode active materials, More preferably, they are 3 mass parts or more and 7 mass parts or less.

  Next, an example of the carbon material manufacturing method of the present embodiment will be described. Here, an example in which the carbon contained in the carbon material is hard carbon will be described as an example, but this does not limit the present embodiment.

  In order to produce the carbon material of the present embodiment, first, a raw material or a composition containing the raw material is prepared. The said raw material is 1 type (s) or 2 or more types selected from resin or plant material etc. which become the raw material of the hard carbon mentioned above. Moreover, the said composition contains the said raw material and arbitrary additives. In the following description, a method for producing a carbon material using the composition will be described in detail. However, the curing treatment, the pulverization treatment of the cured product, and the carbonization treatment described later are substantially performed using only raw materials. The same applies to the case of manufacturing.

The apparatus for preparing the composition is not particularly limited. For example, when the raw material and the additive are melt-mixed, a kneading apparatus such as a kneading roll, a uniaxial or biaxial kneader can be used. In addition, when the raw materials and additives are dissolved and mixed, a mixing device such as a Henschel mixer or a disperser can be used, and when performing pulverization and mixing, for example, a device such as a hammer mill or a jet mill can be used. Can do.
In addition, in order to impart desired characteristics to the carbon material to be produced, metals, pigments, lubricants, antistatic agents are prepared during the preparation of the above composition or after the curing treatment described later and before the carbonization treatment. Additives such as additives and antioxidants may be further added.

  Next, a curing process is performed on the composition prepared as described above. By performing the curing treatment, the raw materials contained in the composition can be cured and infusible. As a result, even when the resin composition is pulverized before the carbonization treatment, the crushed composition or resin is prevented from being re-fused during the carbonization treatment, and carbon particles having a desired particle diameter are efficiently obtained. Can be obtained.

  Although the conditions for the curing treatment are not particularly limited, for example, heating can be performed for 1 hour or more and 10 hours or less at a temperature (for example, 200 ° C. or more and 600 ° C. or less) at which a raw material included in the composition can cause a curing reaction. The heating device used in the curing process is not particularly limited, and a large continuous furnace, a medium batch furnace, or a small furnace can be appropriately selected and used.

  Next, a grinding process is performed. The pulverization process is generally performed after the above-described curing process and before the carbonization process described later. However, in the production of the carbon material of the present embodiment, the curing process is omitted, and after the preparation of the raw material or the composition, the carbonization is performed. A pulverization process can also be performed before a process.

  The pulverization method in the pulverization process is not particularly limited, and for example, an arbitrary pulverizer can be used. Examples of the pulverizer include impact mills such as ball mills, vibrating ball mills, rod mills, and bead mills, and airflow pulverizers such as cyclone mills, jet mills, and dry air pulverizers. It is not limited. In the pulverization treatment, these devices may be used alone or in combination of two or more, or may be used by pulverizing a plurality of times with one device. In the pulverization treatment, in addition to these apparatuses, classification may be appropriately performed using a sieve or a pulverization apparatus having a classification function may be used.

Next, the carbonization process will be described.
In order to produce a carbon material containing hard carbon, the composition or a cured product of the composition is carbonized. The carbonization treatment may be performed once or twice or more. For example, the pre-carbonization treatment may be performed at a relatively low temperature (for example, 200 ° C. or more and less than 800 ° C.), and then the carbonization treatment may be performed at a high temperature (for example, 800 ° C. or more and 3000 ° C. or less). Moreover, you may perform a pre carbonization process and the hardening process mentioned above simultaneously.

  The conditions for the carbonization treatment are not particularly limited. For example, the temperature is raised from normal temperature to a temperature increase rate in the range of 1 ° C./hour to 200 ° C./hour, and the temperature in the range of 800 ° C. to 3000 ° C. is set for 0.1 hour. It can be carried out by holding for not less than 50 hours, preferably not less than 0.5 hours and not more than 10 hours. The atmosphere during the carbonization treatment is not particularly limited. For example, an inert gas atmosphere containing an inert gas such as nitrogen or helium gas, an inert gas atmosphere containing a small amount of oxygen in the additive gas atmosphere, or a reducing gas such as hydrogen. It is preferable to employ a reducing gas atmosphere mainly containing. By selecting such a gas atmosphere, it is possible to suppress thermal decomposition (oxidative decomposition) of raw materials such as a resin and obtain a carbon material containing desired carbon particles.

  With the above manufacturing method, the carbon material of the present embodiment including hard carbon carbon particles can be manufactured. As a modification, the carbon material of this embodiment containing hard carbon and graphite can be produced by preliminarily blending graphite with a composition as a raw material. Further, as a different modification, the carbon material of the present embodiment containing hard carbon and graphite is mixed with the carbon material containing the carbon particles of hard carbon obtained as described above and mixed with graphite pulverized to an appropriate particle size. Can also be manufactured.

  The negative electrode active material of the present embodiment including the carbon material of the present embodiment, the secondary battery negative electrode of the present embodiment including the negative electrode active material layer including the negative electrode active material, and the secondary battery negative electrode The secondary battery of this embodiment provided will be described.

<Active material for negative electrode>
The active material for secondary battery negative electrode of this embodiment contains the carbon material for secondary battery negative electrode of this embodiment mentioned above.
By including the carbon material of the present embodiment that exhibits the above-described electrical resistance suppressing effect, the negative electrode active material of the present embodiment suppresses a significant increase in electrical resistance in a low-temperature environment of the negative electrode, and is excellent in charge. Contributes to the discharge efficiency. In the present embodiment, the negative electrode active material refers to a material that can occlude and release chemical species serving as a charge carrier in a secondary battery negative electrode. Examples of the chemical species include lithium ions or sodium ions in an alkali metal ion secondary battery.

  The negative electrode active material is a substance that can occlude and release chemical species such as alkali metal ions (for example, lithium ions or sodium ions) in a secondary battery such as an alkali metal ion battery. The negative electrode active material described in this specification means a substance containing a carbon material generated using the resin composition of the present embodiment.

  The negative electrode active material may be substantially composed of only the carbon material of the present embodiment, but may further include a material different from the carbon material. Examples of such materials include materials generally known as negative electrode materials such as silicon, silicon monoxide, and other graphite materials.

<Secondary battery negative electrode and secondary battery>
Hereinafter, the secondary battery negative electrode of this embodiment and the secondary battery of this embodiment provided with the said secondary battery negative electrode are demonstrated.

  The secondary battery negative electrode of the present embodiment is a negative electrode collector in which the secondary battery negative electrode active material layer including the above-described secondary battery negative electrode active material and the secondary battery negative electrode active material layer are stacked. And an electric body. Moreover, the secondary battery of this embodiment is comprised including the secondary battery negative electrode of this embodiment mentioned above, an electrolysis layer, and a secondary battery positive electrode.

  The negative electrode of the present embodiment is configured using the negative electrode active material of the present embodiment, so that the negative electrode active material layer and the negative electrode current collector are in good contact with each other with high peel strength, but low resistance. A negative electrode is realized.

  Examples of the secondary battery include, but are not limited to, alkali metal secondary batteries such as lithium ion secondary batteries and sodium ion secondary batteries. The secondary battery includes various types using different electrolytes such as a non-aqueous electrolyte secondary battery and a solid secondary battery. In the following description, a lithium ion secondary battery will be described as an example of a secondary battery.

  Below, an example of the lithium ion secondary battery containing the carbon material of this embodiment is demonstrated using FIG. FIG. 2 is a schematic diagram illustrating an example of the lithium ion secondary battery 100 including the carbon material of the present embodiment. As shown in FIG. 2, the lithium ion secondary battery 100 includes a negative electrode 10, a positive electrode 20, a separator 30, and an electrolytic layer 40.

  As shown in FIG. 2, the negative electrode 10 includes a negative electrode active material layer 12 and a negative electrode current collector 14. The negative electrode active material layer 12 contains the carbon material (not shown) of the present embodiment described above. The negative electrode current collector 14 is not particularly limited, and a current collector that can be used for the negative electrode can be appropriately selected and used. For example, a copper foil or a nickel foil can be used, but is not limited thereto.

The obtained slurry can be formed into a sheet shape, a pellet shape, or the like by compression molding, roll molding, or the like, and the negative electrode active material layer 12 can be obtained. The negative electrode 10 can be obtained by laminating the negative electrode active material layer 12 and the negative electrode current collector 14 thus obtained.
Moreover, the negative electrode 10 can also be manufactured by apply | coating the obtained negative electrode slurry to the negative electrode collector 14, and drying.

  The electrolytic layer 40 fills between the positive electrode 20 and the negative electrode 10, and is a layer in which lithium ions move by charge / discharge. The electrolytic layer 40 can be configured by filling a known electrolyte. As the electrolyte, for example, a nonaqueous electrolytic solution in which a lithium salt serving as an electrolyte is dissolved in a nonaqueous solvent is used.

  Examples of the non-aqueous solvent include cyclic esters such as propylene carbonate, ethylene carbonate, and γ-butyrolactone; chain esters such as dimethyl carbonate and diethyl carbonate; chain ethers such as dimethoxyethane; or a mixture thereof. Can be used.

Is not particularly limited as electrolytes generally be a known electrolyte, for example, it may be used lithium metal salt such as LiClO _4, LiPF _6.

  In the case of a secondary battery other than the non-aqueous electrolyte secondary battery, the electrolytic layer 40 has a gel polymer electrolyte containing a polymer material such as polyethylene oxide or polyacrylonitrile, or a solid such as zirconia. The aspect which has electrolyte is mentioned.

  The separator 30 is not particularly limited, and can be a member that is permeable to chemical species such as lithium ions, and a generally known separator can be used. For example, a porous film constituted by using polyethylene or polypropylene, Nonwoven fabrics can be mentioned.

As illustrated in FIG. 2, the positive electrode 20 includes a positive electrode active material layer 22 and a positive electrode current collector 24.
It does not specifically limit as the positive electrode active material layer 22, Generally, it can form with a well-known positive electrode active material. Is not particularly limited as the cathode active material include lithium cobalt oxide (LiCoO _2), lithium nickel oxide (LiNiO _2), composite oxides such as lithium manganese oxide (LiMn ₂ O _4); polyaniline, polypyrrole, etc. Or the like can be used.
The positive electrode active material contains an organic polymer binder and a conductive material in the same manner as the negative electrode active material described above. The blending amounts of the organic polymer binder and the conductive material in the positive electrode active material are not particularly limited, and may be the same as the negative electrode active material or may be blended in an amount different from the negative electrode active material.

  It does not specifically limit as the positive electrode electrical power collector 24, A generally well-known positive electrode electrical power collector can be used, For example, aluminum foil, stainless steel foil, titanium foil, nickel foil, copper foil etc. can be used. The positive electrode 20 in the present embodiment can be manufactured by a generally known positive electrode manufacturing method.

  The secondary battery can be formed by appropriately disposing the negative electrode 10, the positive electrode 20, the separator 30, and the electrolytic layer 40 in a case suitable for the secondary battery.

  As mentioned above, although embodiment of this embodiment was described, these are illustrations of this invention and various structures other than the above are also employable. For example, in FIG. 2, an example in which the negative electrode active material layer 12 is formed on one surface of the negative electrode current collector 14 and the positive electrode active material layer 22 is formed on one surface of the positive electrode current collector 24. Indicated. As a modification, the negative electrode active material layer 12 is formed on both surfaces of the negative electrode current collector 14, the positive electrode active material layer 22 is formed on both surfaces of the positive electrode current collector 24, and these are interposed via the separator 30 and the electrolytic layer 40. You may comprise a secondary battery by making it oppose.

  Examples of the present invention and comparative examples will be described below. However, the present invention is not limited to the following examples and comparative examples. In Examples, “part” indicates “part by mass”, and “%” indicates “% by mass”.

<Preparation of carbon material for secondary battery negative electrode>
A carbon material for a secondary battery negative electrode (hereinafter, referred to as a carbon material) used in Examples or Comparative Examples was prepared as follows. First, a resin (carbon material raw material) blended in a resin composition used for producing a carbon material was prepared as follows.
(Synthesis of aniline resin)
100 parts of aniline, 697 parts of 37% formaldehyde aqueous solution, and 2 parts of oxalic acid were placed in a three-necked flask equipped with a stirrer and a condenser, reacted at 100 ° C. for 3 hours, and dehydrated to obtain 110 parts of aniline resin.
(Synthesis of novolac type phenolic resin)
100 parts of phenol, 64.5 parts of 37% formaldehyde aqueous solution, and 3 parts of oxalic acid were placed in a three-necked flask equipped with a stirrer and a condenser, reacted at 100 ° C. for 3 hours, dehydrated at elevated temperature, and novolak-type phenolic resin 90 Got a part.

<Example 1>
To 100 parts of the aniline resin, 10 parts of hexamethylenetetramine was blended and pulverized and mixed with a vibration ball mill. The obtained resin composition was heated from room temperature at a heating rate of 100 ° C./hour in a nitrogen atmosphere using a large continuous furnace, and after reaching 550 ° C., the fired state was maintained for 1.5 hours. Then, carbonization was performed (first firing step). Then, after pulverization and particle size adjustment, firing in a large continuous furnace from room temperature to 100 ° C / hour in a nitrogen atmosphere, and after reaching 1180 ° C, the firing state is maintained for 2 hours Then, carbonization was performed (second firing step). The carbon material thus obtained was used as the carbon material of Example 1.
<Example 2>
10 parts of triphenyl phosphate (manufactured by Daihachi Chemical Industry Co., Ltd., trade name: TPP) and 3 parts of hexamethylenetetramine were blended with 100 parts of the above-mentioned novolak type phenol resin, and pulverized and mixed with a vibration ball mill. . The obtained resin composition was heated from room temperature at a heating rate of 100 ° C./hour in a nitrogen atmosphere using a medium-sized batch furnace, and after reaching 550 ° C., the fired state was maintained for 1.5 hours. The curing process was performed. Then, after pulverizing and adjusting the particle size, firing in a small continuous furnace in a nitrogen atmosphere from room temperature to a rate of 100 ° C./hour, and after reaching 1180 ° C., maintaining the firing state for 2 hours Then, carbonization was performed (second firing step). The carbon material thus obtained was used as the carbon material of Example 2.
<Example 3>
A carbon material is produced in the same manner as the method for producing the carbon material of Example 2 except that the temperature increase rate in the second firing step in Example 2 is changed to 80 ° C./hour, and the charcoal of Example 3 is produced. The material.
<Reference Example 1>
After infusibilization treatment of coconut shells, the temperature was raised from room temperature to 100 ° C / hour in a nitrogen atmosphere using a medium-sized batch furnace. After reaching 550 ° C, the firing state was maintained for 1.5 hours Then, a curing process was performed. Thereafter, pulverization was performed to obtain a pulverized product.
About the subsequent process, the carbon material was produced | generated by the method similar to the method of producing | generating the carbon material of Example 2, and it was set as the carbon material of the reference example 1. FIG.
<Reference Example 2>
Pitch tar was added to 100 parts by weight of petroleum coke whose particle size was adjusted to an average particle size of 10 μm, and kneaded at 200 ° C. to form a block shape. The compact was packed in a firing furnace and heat-treated at 1000 ° C. in a nitrogen atmosphere, and then graphitized at 3000 ° C. To 100 parts of graphite obtained by pulverizing this graphitized block and further adjusting the particle size, 150 parts of the novolac-type phenol resin is dispersed using methanol to obtain a mixture solution of graphite particles and phenol resin. Prepared. From this mixture solution, a mixture of graphite particles and phenol resin was collected by filtration, and the collected mixture was dried in vacuum at 120 ° C. for 24 hours. The dried mixture is heated from room temperature to 100 ° C / hour in a nitrogen atmosphere using a medium-sized batch furnace, and after reaching 550 ° C, the fired state is maintained for 1.5 hours to cure. Processed. Thereafter, a pulverization and particle size adjustment step was performed.
Regarding the subsequent steps, a carbon material was produced by the same method as the method for producing the carbon material of Example 2 except that the pulverized material was used, and the carbon material of Reference Example 2 was obtained.
<Comparative Example 1>
Pitch tar was added to 100 parts by weight of petroleum coke whose particle size was adjusted to an average particle size of 10 μm, and kneaded at 200 ° C. to form a block shape. The compact was packed in a firing furnace and heat-treated at 1000 ° C. in a nitrogen atmosphere, and then graphitized at 3000 ° C. The carbon material obtained by pulverizing and adjusting the particle size of this graphitized block was used as the carbon material of Comparative Example 1.

The water vapor adsorption isotherm of the carbon material obtained in each example, each reference example and comparative example was obtained using a gas adsorption amount measuring device (BELSORP-max: manufactured by Nippon Bell Co., Ltd.) (not shown).
As a pretreatment, the carbon material was heat-treated at 300 ° C. for 1 hour and dried. The measurement temperature of the water vapor adsorption isotherm was normal temperature (25 ° C.), and the amount of carbon material in the measurement sample was 0.1 g.
Further, as the adsorption / desorption equilibrium judgment condition, it was judged that the adsorption / desorption equilibrium was reached when the pressure change for 500 seconds was 0.3% or less.
Further, for each example, each reference example, and comparative example, the maximum water vapor adsorption amount, which is the amount of water vapor adsorbed in the adsorption / desorption equilibrium state, is obtained, and the water vapor adsorption amount of each example is normalized using this as the denominator (dimensionless) The normalized water vapor adsorption isotherm shown in FIG. 1 was obtained.

  In the normalized water vapor adsorption isotherm of each example obtained, the relative pressure when the normalized water vapor adsorption amount was 0.5 was calculated. The results are shown in Table 1. In addition, the case where the relative pressure was within the range of 0.2 or more and 0.8 or less was evaluated as “◯”, and the case where the relative pressure was not within the range was evaluated as “X”.

In the normalized water vapor adsorption isotherm of each example, when the inflection point IP was within the range of the relative pressure of 0.2 to 0.8, the relative pressure corresponding to the inflection point IP was calculated. The results are shown in Table 1.
In Example 1, the inflection point IP occurred when the relative pressure was 0.42. In Example 2, the inflection point IP occurred when the relative pressure was 0.5. In Example 3, the inflection point IP occurred at a relative pressure of 0.49. In Reference Example 1, the inflection point IP occurred at a relative pressure of about 0.6. On the other hand, in Reference Example 2 and Comparative Example 1, the inflection point IP did not occur within the range of the relative pressure of 0.2 or more and 0.8 or less.

  In the normalized water vapor adsorption isotherm of each example, the normalized water vapor adsorption amount at a relative pressure of 0.5 was calculated. As the water vapor amount range, the case where the normalized water vapor adsorption amount was within the range of 0.2 to 0.8 was evaluated as “◯”, and the case where it was not within the range was evaluated as “X”.

  On the other hand, with respect to 100 parts of the carbon material obtained in each example, each reference example, and comparative example, 1.5 parts of carboxymethyl cellulose (manufactured by Daicel Finechem Co., Ltd., CMC Daicel 2200), styrene-butadiene rubber (JSR Corporation) Made by TRD-2001), 2 parts acetylene black (Denka Black, Denka Black Co., Ltd.) and 100 parts distilled water are added, and stirred and mixed with a rotating / revolving mixer to prepare a negative electrode slurry. did.

The negative electrode slurry was applied to one side of a 14 μm thick copper foil (Furukawa Electric Co., Ltd., NC-WS), then pre-dried in air at 60 ° C. for 2 hours, and then at 120 ° C. for 15 hours. Vacuum dried. After vacuum drying, the electrode was pressure-formed by a roll press. The basis weight of the negative electrode active material layer after drying was 6.55 mg / cm ² .

  The negative electrode of each example was cut into a strip having a sufficient length, and the adhesion strength between the negative electrode active material layer and the negative electrode current collector was measured. The measurement was performed by sticking an adhesive tape on the surface side where the negative electrode active material layer was provided, pulling it in a 90 ° direction (that is, a direction in which the adhesive tape is erected) at a speed of 50 mm / min, and measuring the peel strength. . The results are shown in Table 1 as electrodeposition adhesion strength.

  From the results shown in Table 1, the carbon materials of Examples 1 to 3 have a relative water vapor pressure in the range of 0.4 to 0.6 when the normalized water vapor adsorption amount is 0.5. The inflection point IP was in the range of relative pressure 0.4 to 0.6, and the normalized water vapor amount when the relative pressure was 0.5 was in the range of 0.3 to 0.6. As a result, in Example 1 and Example 2, the electrode adhesion strength was the highest value of 6 [N / m], and in Example 3, the electrode adhesion strength was as high as 5 [N / m]. In the graph shown in FIG. 1, the carbon materials of Examples 1 to 3 rise rapidly at a relative pressure of about 0.5, and water vapor adsorption on the surface of the carbon particles occurs well at this relative pressure. I understand that.

  In the carbon material of Reference Example 1, the relative pressure of water vapor when the normalized water vapor adsorption amount was 0.5 was in the range of 0.2 to 0.8, but the inflection point IP was about 0.6. It was generated at a relatively high relative pressure, and the normalized water vapor amount when the relative pressure was 0.5 was 0.2 or less. As a result, the electrode adhesion strength was as low as 2 [N / m]. In the graph shown in FIG. 1, Reference Example 1 shows a more gradual rise than Examples 1 to 3, and it can be seen that the adsorption of water vapor to the surface of the carbon particles is inferior to each example.

  In the carbon material of Reference Example 2, the relative pressure of water vapor when the normalized water vapor adsorption amount was 0.5 was in the range of 0.4 to 0.6, but the relative pressure was 0.2 to 0.8. Inflection point IP did not occur in the range. In Reference Example 2, it was found that the normalized water vapor adsorption amount gradually and monotonically increased as a whole in the graph shown in FIG. From this, it can be seen that the carbon material of Reference Example 2 is inferior to each example in the adsorption of water vapor to the surface of the carbon particles.

  In the carbon material of Comparative Example 1, when the normalized water vapor adsorption amount is 0.5, the relative pressure of water vapor exceeds 0.8, and the adsorption of water vapor occurs only on the internal pores rather than the surface, in other words. It can be seen that the adsorption of water vapor to the surface of the carbon particles is greatly inferior to each example. As a result, the electrode adhesion strength was the lowest value of 1 [N / m].

  From the above results, the carbon materials of Examples 1 to 3 and Reference Examples 1 to 2 have a relative pressure of water vapor in the range of 0.2 to 0.8 when the normalized water vapor adsorption amount is 0.5. Thus, it was found that an electrode adhesion strength higher than that of Comparative Example 1 was obtained. In Examples 1 to 3, the normalized water vapor amount when the relative pressure is 0.5 is 0.3 or more, and the inflection point IP is in the range of the relative pressure of 0.2 to 0.8. Thus, it was found that the material had better hydrophilicity than Reference Examples 1 and 2, the bond with the binder was good, and the electrode adhesion was high.

The above embodiment includes the following technical idea.
(1) A carbon material for a secondary battery negative electrode including carbon particles having a relative pressure in the range of 0.2 to 0.8 when the normalized water vapor adsorption amount in the standardized water vapor adsorption isotherm is 0.5.
(2) The carbon material for a secondary battery negative electrode as described in (1) above, wherein the normalized water vapor adsorption isotherm has an inflection point in a relative pressure range of 0.4 to 0.8. .
(3) The above (1) or (2) comprising carbon particles having a normalized water vapor adsorption amount in the range of 0.2 to 0.8 in the normalized water vapor adsorption isotherm when the relative pressure is 0.5 The carbon material for secondary battery negative electrodes as described in 2.
(4) The secondary battery negative electrode according to any one of (1) to (3), wherein the carbon particles have a true specific gravity in a range of 1.5 g / cm ³ or more and 1.7 g / cm ³ or less. Carbon material.
(5) From the above (1) to (5), the carbon particles include hard carbon having an average interplanar spacing d ₀₀₂ of (002) planes of 0.340 nm or more determined by an X-ray diffraction method using CuKα rays as a radiation source. The carbon material for secondary battery negative electrode as described in any one of 4).
(6) The carbon material for a secondary battery negative electrode according to (5), wherein the carbon particles include 90% by mass or more of the hard carbon.
(7) The carbon material for a secondary battery negative electrode according to (5) or (6), wherein the carbon particles include the hard carbon and graphite.
(8) A secondary battery negative electrode active material containing the carbon material for a secondary battery negative electrode according to any one of (1) to (7) above.
(9) A secondary battery negative electrode active material layer comprising the secondary battery negative electrode active material described in (8) above, and a negative electrode current collector in which the secondary battery negative electrode active material layer is laminated. Secondary battery negative electrode having.
(10) A secondary battery comprising the secondary battery negative electrode described in (9) above, an electrolytic layer, and a secondary battery positive electrode.

DESCRIPTION OF SYMBOLS 10 ... Negative electrode 12 ... Active material layer 14 for negative electrodes ... Negative electrode collector 20 ... Positive electrode 22 ... Positive electrode active material layer 24 ... Positive electrode collector 30 ... Separator 40- ..Electrolytic layer 100 ... lithium ion secondary battery

Claims (10)

  A carbon material for a secondary battery negative electrode, comprising carbon particles having a relative pressure in the range of 0.2 or more and 0.8 or less when the normalized water vapor adsorption amount on a standardized water vapor adsorption isotherm is 0.5.   The carbon material for a secondary battery negative electrode according to claim 1, wherein the normalized water vapor adsorption isotherm has an inflection point in a relative pressure range of 0.4 to 0.8.   3. The secondary battery according to claim 1, comprising carbon particles having a normalized water vapor adsorption amount in a range of 0.2 to 0.8 when the relative pressure is 0.5 in the normalized water vapor adsorption isotherm. Carbon material for negative electrode. 4. The carbon material for a secondary battery negative electrode according to claim 1, wherein the carbon particles have a true specific gravity in a range of 1.5 g / cm ³ or more and 1.7 g / cm ³ or less. 5. The carbon particle according to claim 1, wherein the carbon particles include hard carbon having an average interplanar spacing d ₀₀₂ of (002) plane of 0.340 nm or more, which is obtained by an X-ray diffraction method using CuKα rays as a radiation source. Carbon material for secondary battery negative electrode as described in claim | item.   The carbon material for a secondary battery negative electrode according to claim 5, wherein the carbon particles include 90% by mass or more of the hard carbon.   The carbon material for a secondary battery negative electrode according to claim 5 or 6, wherein the carbon particles include the hard carbon and graphite.   The active material for secondary battery negative electrodes containing the carbon material for secondary battery negative electrodes as described in any one of Claim 1 to 7.   A secondary battery comprising: a secondary battery negative electrode active material layer comprising the secondary battery negative electrode active material according to claim 8; and a negative electrode current collector in which the secondary battery negative electrode active material layer is laminated. Negative electrode.   A secondary battery comprising the secondary battery negative electrode according to claim 9, an electrolytic layer, and a secondary battery positive electrode.

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