JP5447287B2 - Carbon material for lithium ion secondary battery, negative electrode material for lithium ion secondary battery, and lithium ion secondary battery - Google Patents

Description

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

Conventionally, a carbon material has been used for the negative electrode of a lithium ion secondary battery. This is because even if the charge / discharge cycle proceeds, dendritic lithium is hardly deposited on the negative electrode using the carbon material, and safety is guaranteed.
Such a carbon material includes a highly crystalline material such as graphite and an amorphous carbon material called hard carbon. Highly crystalline materials such as graphite have the advantages of small irreversible capacity and high charge / discharge efficiency, but there are limitations on charge capacity and discharge capacity, and there is a problem that it is difficult to increase capacity, Amorphous carbon materials have high charge capacity and discharge capacity, but have a problem of large irreversible capacity and low charge / discharge efficiency. Thus far, materials having both crystalline and amorphous properties have been proposed. Has been studied.
For example, in Patent Document 1, the interplanar spacing is evaluated by a diffraction peak measured using a general-purpose wide-angle X-ray diffractometer, and furthermore, a laminated structure of carbon hexagonal mesh planes (that is, crystal parts) in a carbon material by a Raman spectrum. And the technique which evaluated the ratio of an amorphous carbon component etc. is disclosed. However, in the technique disclosed in Patent Document 1, the crystal structure of graphite contained in an amorphous material cannot be found by wide-angle X-ray diffraction, and the high charge capacity, discharge capacity, and excellent charge / discharge efficiency of the present invention are not found. The technology for coexisting amorphous / crystalline is not disclosed.

JP 2006-236752 A

  The present invention can solve the above-mentioned problems, and according to the present invention, a lithium ion battery having a high charge capacity and discharge capacity and excellent balance of charge capacity, discharge capacity and charge / discharge efficiency is provided. It is possible to provide a carbon material for a lithium ion secondary battery, a negative electrode material for a lithium ion secondary battery, and a lithium ion secondary battery.

The above object is achieved by the following items (1) to (5).

(1) Under the following conditions (A) to (E), the average plane distance d of the (002) plane determined by the wide-angle X-ray diffraction method is 3.60 mm or more and 3.90 mm or less, and the c-axis direction Lithium ions having an amorphous structure with a crystallite size Lc of 8 to 50 mm and a graphite structure with a (002) plane spacing d of 3.25 to 3.40 mm Carbon material for secondary batteries.
(A) Light source: Synchrotron radiation (B) Large Debye-Scherrer camera, camera radius: 286.48 mm
(C) Beam size: Length 0.3mm x width 3.0mm
(D) Detector: Imaging plate (50 μm = 0.01 °)
(E) Incident X-ray: wavelength of 1.0 mm (12.4 keV)

(2) In the carbon material for a lithium ion secondary battery according to item (1),
A carbon material for a lithium ion secondary battery having a specific surface area of 15 m ² / g or less and 1 m ² / g or more by a BET three-point method in nitrogen adsorption.

(3) In the carbon material for a lithium ion secondary battery according to (1) or (2),
A carbon material for a lithium ion secondary battery containing 95 wt% or more of carbon atoms and containing 0.5 wt% or more and 5 wt% or less of nitrogen atoms as elements other than carbon atoms.

(4) A negative electrode material for a lithium ion secondary battery comprising the carbon material for a lithium ion secondary battery according to any one of items (1) to (3).

(5) A lithium ion secondary battery comprising the negative electrode material for a lithium ion secondary battery according to item (4).

  According to the present invention, a carbon material for a lithium ion secondary battery, a negative electrode material for a lithium ion secondary battery, and lithium capable of providing a lithium ion battery having high charge / discharge efficiency and high charge capacity and discharge capacity. An ion secondary battery is provided.

2 is a diffraction pattern of synchrotron radiation in Example 1. FIG. It is a schematic diagram of a lithium ion secondary battery.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Carbon material for lithium ion secondary battery)
First, the outline | summary of the carbon material for lithium ion secondary batteries of this invention (henceforth a carbon material may be demonstrated).
The carbon material for a lithium ion secondary battery of the present invention is
Under the following conditions (A) to (E), the average interplanar spacing d of the (002) plane determined by the wide angle X-ray diffraction method is 3.40 mm or more and 3.90 mm or less, and the crystallites in the c-axis direction For a lithium ion secondary battery having an amorphous structure with a size Lc of 8 to 50 mm and a graphite structure with a (002) plane spacing d of 3.25 to 3.40 mm Carbon material.
(A) Light source: Synchrotron radiation (B) Large Debye-Scherrer camera, camera radius: 286.48 mm
(C) Beam size: Length 0.3mm x width 3.0mm
(D) Detector: Imaging plate (50 μm = 0.01 °)
(E) Incident X-ray: wavelength of 1.0 mm (12.4 keV)

Next, the carbon material for a lithium ion secondary battery will be described in detail.
The raw materials or precursors used for the carbon material for lithium ion secondary batteries are not particularly limited, but the petroleum-based tars and pitches produced as a by-product during ethylene production, coal tars produced during coal dry distillation, and low coal tars are low. Heavy components obtained by distilling off boiling components and pitches, petroleum-based or coal-based tars or pitches such as tars and pitches obtained by liquefaction of coal, and those obtained by crosslinking the tars, pitches, etc., and thermosetting A resin obtained by carbonizing a resin or a resin composition such as an adhesive resin or a thermoplastic resin is preferable, and a resin or a resin composition described below is particularly preferable. However, tar, pitch obtained from the above-mentioned petroleum, coal, etc., or those subjected to a crosslinking treatment thereof are also included in the broadly defined resin or resin composition in the present invention, and these may be used alone or in combination of two or more. Can do.
Further, as will be described later, the resin composition contains the above resin as a main component and can contain a curing agent, an additive and the like.

  Here, the thermosetting resin is not particularly limited. For example, a phenol resin such as a novolac type phenol resin or a resol type phenol resin, an epoxy resin such as a bisphenol type epoxy resin or a novolac type epoxy resin, a melamine resin, a urea resin, or aniline. Examples thereof include resins, cyanate resins, furan resins, ketone resins, unsaturated polyester resins, and urethane resins. In addition, modified products obtained by modifying these with various components can also be used.

  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, Polyamide, polycarbonate, polyacetal, polyphenylene ether, polybutylene terephthalate, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyetherimide, polyamideimide, polyimide, polyphthalamide, and the like can be given.

A thermosetting resin is preferable as the resin as the main component used in the carbon material of the present invention. Thereby, the remaining carbon rate of a carbon material can be raised more.
And among thermosetting resins, those selected from novolak-type phenol resins, resol-type phenol resins, melamine resins, furan resins, aniline resins, and modified products thereof are preferable. Thereby, the freedom degree of design of a carbon material spreads and it can manufacture at low cost.

Moreover, when using a thermosetting resin, the hardening | curing agent can be used together.
Although it does not specifically limit as a hardening | curing agent used here, For example, in the case of a novolak-type phenol resin, a hexamethylene tetramine, a resol type phenol resin, a polyacetal, paraform etc. can be used. In the case of epoxy resins, known as epoxy resins such as polyamine compounds such as aliphatic polyamines and aromatic polyamines, acid anhydrides, imidazole compounds, dicyandiamide, novolac-type phenol resins, bisphenol-type phenol resins, and resol-type phenol resins. Can be used.
In addition, even if it is a thermosetting resin that normally uses a predetermined amount of a curing agent, the resin composition used in the present invention may use a smaller amount than usual or may be used without using a curing agent. You can also

Moreover, in the resin composition used by this invention, an additive can be mix | blended besides this.
Although it does not specifically limit as an additive used here, For example, the carbon material precursor carbonized at 200-800 degreeC, an organic acid, an inorganic acid, a nitrogen-containing compound, an oxygen-containing compound, an aromatic compound, and nonferrous A metal element etc. can be mentioned.
The above additives may be used alone or in combination of two or more depending on the type and properties of the resin used.

  As a resin used for the carbon material of the present invention, nitrogen-containing resins described later may be included as a main component resin. Moreover, when the nitrogen-containing resin is not contained in the main component resin, at least one kind of nitrogen-containing compound may be included as a component other than the main component resin, or the nitrogen-containing resin is included as the main component resin. In addition, a nitrogen-containing compound may be included as a component other than the main component resin. By carbonizing such a resin, a carbon material containing nitrogen can be obtained.

Here, the following can be illustrated as nitrogen-containing resin.
Examples of thermosetting resins include melamine resins, urea resins, aniline resins, cyanate resins, urethane resins, phenol resins modified with nitrogen-containing components such as amines, and epoxy resins.
Examples of the thermoplastic resin include polyacrylonitrile, acrylonitrile-styrene (AS) resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide, polyetherimide, polyamideimide, polyimide, and polyphthalamide.

Moreover, the following can be illustrated as resin other than nitrogen-containing resin.
Examples of the thermosetting resin include phenol resin, epoxy resin, furan resin, and unsaturated polyester resin.

  Examples of the thermoplastic resin include polyethylene, polystyrene, polypropylene, vinyl chloride, methacrylic resin, polyethylene terephthalate, polycarbonate, polyacetal, polyphenylene ether, polybutylene terephthalate, polyphenylene sulfide, polysulfone, polyethersulfone, and polyetheretherketone. .

In addition, when a nitrogen-containing compound is used as a component other than the main component resin, the type thereof is not particularly limited. In addition to the aromatic polyamine, dicyandiamide and the like, besides the curing agent component, a compound containing nitrogen such as an amine compound, ammonium salt, nitrate, nitro compound which does not function as a curing agent can be used.
As the nitrogen-containing compound, one type may be used or two or more types may be used in combination, whether or not the main component resin contains nitrogen-containing resins.

Although it does not specifically limit as nitrogen content in the resin composition used for the carbon material of this invention, or resin, It is preferable that it is 5-65 weight%. More preferably, it is 10 to 20% by weight.
By performing the carbonization treatment of such a resin composition or resin, the carbon atom content in the carbon material finally obtained is 95 wt% or more, and the nitrogen atom content is 0.5 to 5 wt%. Is preferred.
Thus, by containing 0.5 wt% or more, particularly 1.0 wt% or more of nitrogen atoms, it is possible to impart electrical characteristics suitable for the carbon material due to the electronegativity of nitrogen. Thereby, occlusion and discharge | release of lithium ion can be accelerated | stimulated and a high charging / discharging characteristic can be provided.

  Further, by setting the nitrogen atom to 5 wt% or less, particularly 3 wt% or less, the electrical characteristics imparted to the carbon material are suppressed from becoming excessively strong, and the occluded lithium ions are electrically connected to the nitrogen atoms. Adsorption is prevented. Thereby, an increase in irreversible capacity can be suppressed and high charge / discharge characteristics can be obtained.

The nitrogen content in the carbon material of the present invention is not limited to the nitrogen content in the resin composition or the resin, but is subjected to a condition for carbonizing the resin composition or the resin, or a curing treatment or a pre-carbonization treatment before the carbonization treatment. In some cases, these conditions can also be adjusted by appropriately setting.
For example, as a method of obtaining the carbon material having the nitrogen content as described above, the nitrogen content in the resin composition or the resin is set as a predetermined value, and conditions for carbonizing the resin composition, particularly the final temperature are adjusted. There are methods.

  The method for preparing the resin composition used for the carbon material of the present invention is not particularly limited. For example, the above main component resin and other components are blended in a predetermined ratio, and these are melt mixed. These components can be prepared by dissolving them in a solvent and mixing them, or by pulverizing and mixing these components.

In the carbon material, the nitrogen content is measured by a thermal conductivity method.
In this method, a measurement sample is converted into a simple gas (CO ₂ , H ₂ O, and N ₂ ) using a combustion method, and then the gasified sample is homogenized and then passed through a column. . Thereby, these gas is isolate | separated in steps and content of carbon, hydrogen, and nitrogen can be measured from each thermal conductivity.
In the present invention, an element analysis measuring device “PE2400” manufactured by PerkinElmer Co., Ltd. was used.

Further, as shown in FIG. 1, the carbon material of the present invention is obtained by the wide angle X-ray diffraction method under the following conditions (A) to (E) (the diffraction pattern measured by the wide angle X-ray diffraction method is (Calculated using the Bragg equation) (002) The average interplanar spacing d is 3.40 mm or more and 3.90 mm or less, and the crystallite size Lc in the c-axis direction is 8 mm or more and 50 mm or less. Lithium ions having a crystalline structure (peak of diffraction pattern) and a graphite structure (peak of (002) plane) having a (002) plane spacing d of 3.25 mm or more and less than 3.40 mm. It is a carbon material for secondary batteries.
(A) Light source: Synchrotron radiation (B) Large Debye-Scherrer camera, camera radius: 286.48 mm
(C) Beam size: Length 0.3mm x width 3.0mm
(D) Detector: Imaging plate (50 μm = 0.01 °)
(E) Incident X-ray: wavelength of 1.0 mm (12.4 keV)
In addition, the surface interval d of the (002) plane is derived from the diffraction angle (spectral reflection angle) θ by a parabolic approximation method, that is, a parabola passing through several arbitrary points in the vicinity of the peak top by the least square method. Is determined by the method using the peak top, and is calculated using the following Bragg equation.
λ = 2d _hkl sinθ Bragg equation (d _hkl = d ₀₀₂ )
λ: incident X-ray wavelength θ: reflection angle of spectrum The carbon material of the present invention has an average interplanar spacing d of (002) plane of 3.40 mm or more and 3.90 mm or less, and the crystallite size in the c-axis direction It has an amorphous structure in which Lc is not less than 8% and not more than 50%, and also has a graphite structure in which the (002) plane spacing d is not less than 3.25 and less than 3.40%. The material has an amorphous structure with an average interplanar spacing that is easy for lithium to enter and exit, so the charge capacity and discharge capacity can be increased, and the amorphous structure has a graphite structure. As a result, the insertion / extraction of lithium ions is performed smoothly, so that the charge / discharge efficiency can be increased while having a high charge capacity and discharge capacity.
The wide-angle X-ray diffraction method is a well-known technique for analyzing the structure of carbon materials. In the present invention, the wide-angle X-ray diffraction method using synchrotron radiation by SPring-8 of the High Brightness Optical Science Research Center is used. By using a measurement method with extremely high resolution, it was possible to identify a graphite structure existing in amorphous carbon, which was not known in the past. The present invention has been able to reach the development of a material capable of realizing high charge capacity and high discharge capacity, which is the main object of the present invention.

Further, the carbon material of the present invention may have an average interplanar spacing d of the (002) plane of 3.40 mm or more and 3.90 mm or less, and particularly when it is 3.60 mm or more, occlusion of lithium ions. It is preferable that the shrinkage / expansion between the layers is less likely to occur, and the decrease in charge / discharge cycleability can be further suppressed.
On the other hand, when the average interplanar spacing d of the (002) plane is 3.80 mm or less, it is preferable because occlusion / desorption of lithium ions is performed smoothly and a decrease in charge / discharge efficiency can be further suppressed.
Furthermore, in the carbon material of the present invention, the crystallite size Lc in the c-axis direction (the (002) plane orthogonal direction) is preferably 8 to 50 mm.
By setting Lc to 8 mm or more, particularly 9 mm or more, there is an effect that a carbon interlayer space capable of inserting and extracting lithium ions is formed, and a sufficient charge / discharge capacity can be obtained. By doing so, it is possible to suppress the collapse of the carbon laminate structure due to the insertion / desorption of lithium ions and the reductive decomposition of the electrolytic solution, and to suppress the decrease in charge / discharge efficiency and charge / discharge cycle performance.
Lc is calculated as follows.
It was determined from the half width of the (002) plane peak of the amorphous structure and the diffraction angle (spectral reflection angle) in the spectrum obtained from the wide-angle X-ray diffraction measurement using the following Scherrer equation.
Lc = 0.94λ / (βcosθ) (Scherrer equation)
Lc: crystallite size λ: incident X-ray wavelength β: half width of peak (radian)
θ: Reflection angle of spectrum

Furthermore, the carbon material of the present invention preferably has a specific surface area of 15 m ² / g or less and 1 m ² / g or more according to the BET three-point method in nitrogen adsorption.
Reaction with a carbon material and electrolyte solution can be suppressed because the specific surface area by BET 3 point method in nitrogen adsorption is 15 m < ² > / g or less.
Moreover, there exists an effect that appropriate permeability to the carbon material of electrolyte solution is acquired by making the specific surface area by BET 3 point method in nitrogen adsorption into 1 m < ² > / g or more.
The calculation method of the specific surface area is as follows.
The monomolecular adsorption amount Wm was calculated from the following formula (1), the total surface area Total was calculated from the following formula (2), and the specific surface area S was calculated from the following formula (3).
1 / [W (Po / P-1) = (C-1) / WmC (P / Po) / WmC (1)
In the formula (1), P: pressure of the adsorbate gas in the adsorption equilibrium, Po: saturated vapor pressure of the adsorbate at the adsorption temperature, W: adsorption amount at the adsorption equilibrium pressure P, Wm: monomolecular layer adsorption amount, C : Constant on the magnitude of the interaction between the solid surface and the adsorbate (C = exp {(E1-E2) RT}) [E1: heat of adsorption of the first layer (kJ / mol), E2: measurement temperature of the adsorbate Liquefaction heat (kJ / mol)]
Total = (WmNAcs) M (2)
In formula (2), N: Avogadro number, M: molecular weight, Acs: adsorption cross section S = Total / w (3)
In formula (3), w: sample weight (g)

The carbon material as described above can be manufactured as follows.
First, a resin or resin composition to be carbonized is manufactured.
The apparatus for preparing the resin composition is not particularly limited. For example, when melt mixing is performed, a kneading apparatus such as a kneading roll, a single screw or a twin screw kneader can be used. Moreover, when performing melt | dissolution mixing, mixing apparatuses, such as a Henschel mixer and a disperser, can be used. And when performing pulverization mixing, apparatuses, such as a hammer mill and a jet mill, can be used, for example.
The resin composition thus obtained may be one obtained by physically mixing a plurality of types of components, or is applied during mixing (stirring, kneading, etc.) during preparation of the resin composition. A part of the material may be chemically reacted with mechanical energy and thermal energy converted from the mechanical energy. Specifically, a mechanochemical reaction using mechanical energy or a chemical reaction using thermal energy may be performed.

The carbon material of the present invention is obtained by carbonizing the above resin composition or resin.
Although it does not specifically limit as conditions for carbonization here, For example, it can carry out by hold | maintaining for 0.1 to 50 hours by temperature rising from normal temperature to 1-200 degreeC / hour, Preferably it can carry out for 0.5 to 10 hours. The atmosphere during the carbonization treatment is an inert atmosphere such as nitrogen or helium gas, or a substantially inert atmosphere where a trace amount of oxygen is present in the inert gas, or a reducing gas atmosphere. Is preferred. By doing in this way, thermal decomposition (oxidative decomposition) of resin can be suppressed and a desired carbon material can be obtained.
Conditions such as temperature and time during the carbonization can be adjusted as appropriate in order to optimize the characteristics of the carbon material.

In addition, before performing the said carbonization process, a pre carbonization process can be performed.
Although it does not specifically limit as conditions of a pre carbonization process here, For example, it can carry out at 200-600 degreeC for 1 to 10 hours. Thus, even if the resin composition or the resin is infusibilized by performing the pre-carbonization treatment before the carbonization treatment, and the resin composition or the resin is pulverized before the carbonization treatment step, the resin composition after the pulverization is performed. It is possible to prevent the object or resin from being re-fused during the carbonization treatment, and to obtain a desired carbon material efficiently.
At this time, the amorphous structure in which the average face spacing d of the (002) plane of the present invention is 3.40 mm or more and 3.90 mm or less and the crystallite size Lc in the c-axis direction is 8 mm or more and 50 mm or less. As an example of a method for obtaining a carbon material for a lithium ion secondary battery having a graphite structure having a (002) plane spacing d of 3.25 mm or more and less than 3.40 mm, a reducing gas, The pre-carbonization treatment can be performed in the absence of an inert gas.

Further, when a thermosetting resin or a polymerizable polymer compound is used as the resin constituting the carbon material, the resin composition or the resin can be cured before the pre-carbonization treatment.
Although it does not specifically limit as a hardening processing method, For example, it can carry out by the method of giving the heat quantity which can perform a hardening reaction to a resin composition, the method of thermosetting, or the method of using resin and a hardening | curing agent together. Thereby, since the pre-carbonization treatment can be performed substantially in the solid phase, the carbonization treatment or the pre-carbonization treatment can be performed in a state in which the resin structure is maintained to some extent, and the structure and characteristics of the carbon material can be controlled. become.

  In addition, when performing the carbonization treatment or the pre-carbonization treatment, a metal, a pigment, a lubricant, an antistatic agent, an antioxidant, or the like is added to the resin composition to impart desired characteristics to the carbon material. You can also.

When the said hardening process and / or pre carbonization process are performed, you may grind | pulverize a processed material after the said carbonization process after that. In such a case, variation in the thermal history during the carbonization treatment can be reduced, and the uniformity of the surface state of the carbon material can be improved. And the handleability of a processed material can be made favorable.
Furthermore, the present invention has an amorphous structure in which the average spacing d of (002) planes is 3.40 mm or more and 3.90 mm or less and the crystallite size Lc in the c-axis direction is 8 mm or more and 50 mm or less. In order to obtain a carbon material for a lithium ion secondary battery having a graphite structure having a (002) plane spacing d of 3.25 mm or more and less than 3.40 mm, in the presence of a reducing gas or an inert gas Then, it is naturally cooled (cooled) to 800 to 500 ° C. and then cooled at 20 ° C./hour or more and 500 ° C./hour or less until it becomes 200 ° C. or less, preferably 100 ° C. or less.
If cooling is performed under conditions within the above range, the cooling rate is faster than that of natural cooling, and a unique structure that appropriately includes a graphite structure in an amorphous structure can be obtained, whereby the carbon material of the present invention can be obtained. Guessed.

(Lithium secondary battery)
Next, an embodiment of a negative electrode material for a secondary battery (hereinafter simply referred to as “negative electrode material”) of the present invention and a lithium secondary battery (hereinafter simply referred to as “secondary battery”) which is an embodiment using the same. explain.

FIG. 2 is a schematic diagram showing the configuration of the embodiment of the secondary battery.
The secondary battery 10 includes a negative electrode 13 composed of a negative electrode material 12 and a negative electrode current collector 14, a positive electrode 21 composed of a positive electrode material 20 and a positive electrode current collector 22, an electrolyte solution 16, and a separator 18. Is included.

  In the negative electrode 13, as the negative electrode current collector 14, for example, a copper foil or a nickel foil can be used. And the negative electrode material 12 uses the carbon material of this invention.

The negative electrode material of the present invention is manufactured, for example, as follows.
1 to 30 parts by weight of an organic polymer binder (fluorine polymer including polyethylene, polypropylene, etc., rubbery polymer such as butyl rubber and butadiene rubber) and an appropriate amount of viscosity with respect to 100 parts by weight of the carbon material. An adjustment solvent (N-methyl-2-pyrrolidone, dimethylformamide, etc.) is added and kneaded, and the paste-like mixture is molded into a sheet or pellet by compression molding, roll molding, etc. 12 can be obtained.
And the negative electrode 13 can be manufactured by laminating | stacking with the negative electrode collector 14. FIG.

  Further, 1 to 30 parts by weight of an organic polymer binder (fluorine polymer including polyethylene, polypropylene, etc., rubbery polymer such as butyl rubber, butadiene rubber, etc.) and an appropriate amount with respect to 100 parts by weight of the carbon material. A viscosity adjusting solvent (N-methyl-2-pyrrolidone, dimethylformamide, etc.) was added and kneaded, and the slurry mixture was used as the negative electrode material 12, and this was applied to the negative electrode current collector 14 and molded. Thus, the negative electrode 13 can also be manufactured.

As the electrolytic solution 16, a solution obtained by dissolving a lithium salt serving as an electrolyte in a non-aqueous solvent is used.
As this non-aqueous solvent, it is possible to use a mixture of cyclic esters such as propylene carbonate, ethylene carbonate and γ-butyrolactone, chain esters such as dimethyl carbonate and diethyl carbonate, and chain ethers such as dimethoxyethane. it can.
As the electrolyte, lithium metal salts such as LiClO ₄ and LiPF ₆ , tetraalkylammonium salts, and the like can be used. Further, the above salts can be mixed with polyethylene oxide, polyacrylonitrile, etc. and used as a solid electrolyte.

  Although it does not specifically limit as the separator 18, For example, porous films, such as polyethylene and a polypropylene, a nonwoven fabric, etc. can be used.

In the cathode 21, and is not particularly limited as cathode material 20, such as lithium cobalt oxide (LiCoO _2), lithium nickel oxide (LiNiO _2), composite oxides such as lithium manganese oxide (LiMn ₂ O _4), Conductive polymers such as polyaniline and polypyrrole can be used.
As the positive electrode current collector 22, for example, an aluminum foil can be used.
And the positive electrode 21 in this embodiment can be manufactured with the manufacturing method of the known positive electrode.

  It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.

Hereinafter, the present invention will be described with reference to examples. However, the present invention is not limited to the examples. In the examples and comparative examples, “parts” represents “parts by weight” and “%” represents “% by weight”.
First, measurement methods in the following examples and comparative examples will be described.

(1. Measurement of the distance (d) of the (002) plane by synchrotron radiation and the size Lc of the crystallite in the c-axis direction)
Wide-angle X-ray diffraction under the following conditions (A) to (E) at the High Synchrotron Radiation Research Center (JASRI) Large Synchrotron Radiation Facility SPring-8, BL19B2 The surface spacing d (002) and the crystallite size (Lc) in the c-axis direction were evaluated. Note that the diffraction angle (spectral reflection angle) θ is obtained by a parabolic approximation method, that is, a method in which a parabola passing through any number of points near the peak top of the spectrum is derived by the least square method and the peak is the peak top. Were determined.
(A) Light source: Synchrotron radiation (B) Large Debye-Scherrer camera, camera radius: 286.48 mm
(C) Beam size: Length 0.3mm x width 3.0mm
(D) Detector: Imaging plate (50 μm = 0.01 °)
(E) Incident X-ray: wavelength of 1.0 mm (12.4 keV)
○ (002) plane spacing d
λ = 2d _hkl sinθ Bragg equation (d _hkl = d ₀₀₂ )
λ: incident X-ray wavelength θ: spectral reflection angle ○ crystallite size Lc in the c-axis direction
It was determined from the half width of the (002) plane peak of the amorphous structure and the diffraction angle (spectral reflection angle) θ of the amorphous structure obtained from the wide-angle X-ray diffraction measurement using the following Scherrer equation.
Lc = 0.94λ / (βcos θ) (Scherrer equation)
Lc: crystallite size λ: incident X-ray wavelength β: half-width of peak (radian)
θ: Reflection angle of spectrum

(2. Measurement of the average spacing d of (002) planes using a conventional lab-scale X-ray diffractometer)
Using a Shimadzu X-ray diffractometer “XRD-7000” (incident X-ray wavelength CuKα1.54Å), the surface spacing d of the (002) plane was measured.

(3. Measurement of Raman spectrum)
Using an InViaReflex Raman microscope manufactured by RENISHAW, the sample is magnified with a 20x objective lens, irradiated with YAG laser light having a wavelength of 532 nm and 2.5 mW, the number of times of Raman scattering light is integrated five times, and the measurement range is 100 to 2000 cm. ⁻¹ , measured at an exposure time of 100 seconds. The resulting spectral subtract one baseline to the intensity IG of G band from the base line in the range of D band intensity ID and 1560～1650Cm ^-1 in the range of 1300～1400Cm ^-1 of Raman spectrum The R value (ID / IG), which is the intensity ratio, was determined.

(4. Specific surface area)
It measured by the BET 3 point method in nitrogen adsorption | suction using the Yuasa company make Nova-1200 apparatus. A specific calculation method is as described in the above embodiment.

(5. Carbon content, nitrogen content)
The measurement was performed using an elemental analysis measuring device “PE2400” manufactured by PerkinElmer. The measurement sample is converted into CO ₂ , H ₂ O, and N ₂ using a combustion method, and then the gasified sample is homogenized and then passed through the column. Thereby, these gases were separated stepwise, and the contents of carbon, hydrogen, and nitrogen were measured from the respective thermal conductivities.
A) Carbon content rate After carbonizing the obtained carbon material in 110 degreeC / vacuum for 3 hours, the carbon composition ratio was measured using the elemental analysis measuring device.
B) Nitrogen content The obtained carbon material was dried at 110 ° C./vacuum for 3 hours, and then the nitrogen composition ratio was measured using an elemental analyzer.

(6. Charge capacity, discharge capacity, charge / discharge efficiency)
(1) Manufacture of a bipolar coin cell for secondary battery evaluation 10 parts of polyvinylidene fluoride as a binder and N-methyl-2- 2 as a diluting solvent with respect to 100 parts of the carbon material obtained in each example and comparative example A suitable amount of pyrrolidone was added and mixed to prepare a slurry-like negative electrode mixture. The prepared negative electrode slurry-like mixture was applied to both sides of 18 μm copper foil, and then vacuum-dried at 110 ° C. for 1 hour. After vacuum drying, the electrode was pressure-formed by a roll press. This was cut out as a circle having a diameter of 16.156 mm to produce a negative electrode.
The positive electrode was evaluated with a bipolar coin cell using lithium metal. As the electrolytic solution, a solution obtained by dissolving 1 mol / liter of lithium perchlorate in a mixed solution of ethylene carbonate and diethyl carbonate having a volume ratio of 1: 1 was used.

(2) Evaluation of Charging Capacity and Discharging Capacity The charging condition was that charging was stopped at a constant current of 25 mA / g until it reached 1 mV, and then the charging was terminated when the current attenuated to 1.25 mA / g with 1 mV holding. The cut-off potential under discharge conditions was 1.5V.

(3) Evaluation of charge / discharge efficiency Based on the value obtained in the above (2), the charge / discharge efficiency was calculated by the following formula.
Charge / discharge efficiency (%) = [discharge capacity / charge capacity] × 100

Example 1
As a resin composition, phenol resin PR-217 (manufactured by Sumitomo Bakelite Co., Ltd.) was processed in the order of the following steps (a) to (f) to obtain a carbon material.
(A) Temperature reduction from room temperature to 500 ° C. at 100 ° C./hour without any of reducing gas replacement, inert gas replacement, reducing gas flow and inert gas flow (b) Reducing gas replacement and inert gas replacement After degreasing treatment at 500 ° C. for 2 hours without cooling gas flow and inert gas flow, cooling (c) fine pulverization with a vibrating ball mill (d) 1200 ° C. from room temperature under inert gas (nitrogen) substitution and flow (E) Carbonization for 8 hours at 1200 ° C under an inert gas (nitrogen) flow (f) After natural cooling to 600 ° C under an inert gas (nitrogen) flow, Cooling from 600 ° C to 100 ° C at 100 ° C / hour

(Example 2)
In Example 1, an aniline resin (synthesized by the following method) was used instead of the phenol resin.
100 parts of aniline, 697 parts of 37% aqueous formaldehyde, 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. The obtained aniline resin had a weight average molecular weight of about 800.
The resin composition obtained by pulverizing and mixing 100 parts of the aniline resin and 10 parts of hexamethylenetetramine obtained as described above was treated in the same process as in Example 1 to obtain a carbon material.

(Comparative Example 1)
A carbon material composed of graphite (mesophase carbon microbeads) was prepared.

(Comparative Example 2)
In Example 1, instead of phenol resin, in place of coal tar pitch (manufactured by JFE Shoji Co., Ltd.), the steps of (d), (e), and (f) were changed as follows. The carbon material was obtained by performing the same process.
(D) Under inert gas (nitrogen) substitution and flow, from room temperature to 1100 ° C, 100 ° C /
(E) Carbonization for 4 hours at 1100 ° C under inert gas (nitrogen) flow (f) Natural cooling to 100 ° C under inert gas (nitrogen) flow

(Comparative Example 3)
In Example 1, the process of (d), (e), (f) was changed as follows, and it processed in the process similar to Example 1, and obtained the carbon material.
(D) Under inert gas (nitrogen) substitution and flow, from room temperature to 1000 ° C, 100 ° C /
(E) Carbonization for 8 hours at 1000 ° C under inert gas (nitrogen) circulation (f) Natural cooling to 100 ° C under inert gas (nitrogen) circulation

  Table 1 shows the evaluation results of the carbon materials obtained in the above Examples and Comparative Examples and the measurement results of the charge capacity, discharge capacity, and charge / discharge efficiency when the carbon materials are used as the negative electrode.

It has an amorphous structure in which the average interplanar spacing d of the (002) plane of the present invention is 3.40 mm or more and 3.90 mm or less, and the crystallite size Lc in the c-axis direction is 8 mm or more and 50 mm or less. In addition, in Examples 1 and 2 which are carbon materials for lithium ion secondary batteries having a graphite structure in which the (002) plane spacing d is 3.25 mm or more and less than 3.40 mm, both the charge capacity and the discharge capacity are High charge and discharge efficiency.
In Comparative Example 1 having no amorphous halo pattern based on the amorphous structure, the efficiency was high, but both the charge capacity and the discharge capacity were low. Further, in the comparative example 2 which has only the amorphous halo pattern based on the amorphous structure and does not have the (002) plane peak of the graphite structure in the wide-angle X-ray diffraction method using synchrotron radiation of the present invention, the charge capacity and discharge capacity are high. The efficiency is lowered, and in Comparative Example 3, the discharge capacity and the efficiency are lower than in the example.
Further, in wide-angle X-ray diffraction using a conventional lab scale apparatus, the interplanar spacing d of the graphite structure that is 3.25 mm or more and less than 3.40 mm in the example was not detected.
Further, the Raman spectra of Examples 1 and 2 and Comparative Examples 2 and 3 based on an amorphous structure are all results that are not significantly different. In the Raman spectrum, amorphous carbon, which is a feature of the material of the present invention, is obtained. It was not possible to identify the crystal structure derived from graphite

DESCRIPTION OF SYMBOLS 10 Secondary battery 12 Negative electrode material 14 Negative electrode collector 13 Negative electrode 20 Positive electrode material 22 Positive electrode collector 21 Positive electrode 16 Electrolytic solution 18 Separator

Claims (5)

Under the following conditions (A) to (E), the average interplanar spacing d of the (002) plane obtained by the wide angle X-ray diffraction method is 3.60 mm or more and 3.90 mm or less, and the crystallites in the c-axis direction For a lithium ion secondary battery having an amorphous structure with a size Lc of 8 to 50 mm and a graphite structure with a (002) plane spacing d of 3.25 to 3.40 mm Carbon material.
(A) Light source: Synchrotron radiation (B) Large Debye-Scherrer camera, camera radius: 286.48 mm
(C) Beam size: Length 0.3mm x width 3.0mm
(D) Detector: Imaging plate (50 μm = 0.01 °)
(E) Incident X-ray: wavelength of 1.0 mm (12.4 keV) The carbon material for a lithium ion secondary battery according to claim 1,
A carbon material for a lithium ion secondary battery having a specific surface area of 15 m ² / g or less and 1 m ² / g or more by a BET three-point method in nitrogen adsorption. The carbon material for a lithium ion secondary battery according to claim 1 or 2,
A carbon material for a lithium ion secondary battery containing 95 wt% or more of carbon atoms and containing 0.5 wt% or more and 5 wt% or less of nitrogen atoms as elements other than carbon atoms.   The negative electrode material for lithium ion secondary batteries containing the carbon material for lithium ion secondary batteries in any one of Claims 1 thru | or 3. The lithium ion secondary battery containing the negative electrode material for lithium ion secondary batteries of Claim 4.