JP2018159059A - Carbon material-resin composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon material-resin composite material having excellent conductivity.SOLUTION: A carbon material-resin composite material contains carbon material and resin, where the carbon material-resin composite material has a BET specific surface area of 50 m/g or more and 2500 m/g or less; when the Raman spectrum of the carbon material-resin composite material is measured by Raman spectroscopy, a peak intensity ratio between D band and G band in the Raman spectrum, D/G ratio, is 0.2 or less.SELECTED DRAWING: None

Description

  The present invention relates to a carbon material / resin composite material including a carbon material and a resin.

  Conventionally, carbon materials have been widely used as conductive materials and heat conductive materials. In recent years, utilization as electrode materials for secondary batteries such as lithium ion secondary batteries and capacitors has been studied. As such a carbon material, graphite, carbon nanotube, graphene, exfoliated graphite, or the like is used. Exfoliated graphite is obtained by exfoliating the original graphite, and is a graphene sheet laminate that is thinner than the original graphite.

  Patent Document 1 below discloses a exfoliated graphite / resin composite material containing exfoliated graphite and a resin. In the method for producing exfoliated graphite / resin composite material of Patent Document 1, first, a composition containing graphite or primary exfoliated graphite and a polymer, wherein the polymer is fixed to graphite or primary exfoliated graphite is prepared. Next, the polymer contained in the prepared composition is thermally decomposed to peel off the graphite or primary exfoliated graphite while leaving a part of the polymer. As a result, exfoliated graphite / resin composite material is produced. Also. Patent Document 1 describes that in the step of preparing the composition, a composition containing a thermally decomposable foaming agent may be prepared.

International Publication No. 2014/034156

  In recent years, there has been a demand for higher performance of secondary batteries, particularly in in-vehicle applications such as hybrid vehicles and electric vehicles. Accordingly, there is a demand for further lower resistance in the electrodes of secondary batteries. Therefore, even when the exfoliated graphite / resin material of Patent Document 1 having high conductivity (low resistance value) is used, it is still not sufficient.

  An object of the present invention is to provide a carbon material / resin composite material having excellent conductivity.

The carbon material / resin composite material according to the first invention of the present application is a carbon material / resin composite material containing a carbon material and a resin, wherein the BET specific surface area of the carbon material / resin composite material is 50 m ² / g or more, or less 2500 m 2 / ^g, as measured Raman spectrum of the carbon material-resin composite material by Raman spectroscopy, the peak intensity ratio of D band and G band of the Raman spectrum D / G The ratio is 0.2 or less.

The carbon material / resin composite material according to the second invention of the present application is a carbon material / resin composite material including a carbon material and a resin, and the BET specific surface area of the carbon material / resin composite material is 50 m ² / g or more, or less 2500 m 2 / ^g, as measured Raman spectrum of the carbon material-resin composite material by Raman spectroscopy, the G-band of the Raman spectrum, the ratio the half width of the peak intensity of 3.0 That's it.

A carbon material / resin composite material according to a third invention of the present application is a carbon material / resin composite material including a carbon material and a resin, and the BET specific surface area of the carbon material / resin composite material is 50 m ² / g or more, or less 2500 m 2 / ^g, as measured Raman spectrum of the carbon material-resin composite material by Raman spectroscopy, the peak intensity ratio of D band and G band of the Raman spectrum D / G The ratio is 0.2 or less, and the ratio of the peak intensity to the full width at half maximum is 3.0 or more in the G band of the Raman spectrum.

  Hereinafter, the first to third inventions of the present application may be collectively referred to as the present invention.

  In a specific aspect of the carbon material / resin composite material according to the present invention, when the Raman spectrum of the carbon material / resin composite material is measured by Raman spectroscopy, the half-width of the peak intensity in the G band of the Raman spectrum is measured. When the ratio is A and the ratio of the peak intensity in the D band of the Raman spectrum to the half width is B, the ratio A / B is 8.0 or more and 100.0 or less.

  In another specific aspect of the carbon material / resin composite material according to the present invention, when the differential thermal analysis of the carbon material / composite material is performed at a heating rate of 10 ° C./min, the temperature is 300 ° C. or higher and 900 ° C. or lower. There are two exothermic peaks in the range.

  In another specific aspect of the carbon material / resin composite material according to the present invention, the carbon material is exfoliated graphite.

  In yet another specific aspect of the carbon material / resin composite material according to the present invention, the carbon material has a graphite structure, and is a partially exfoliated graphite having a structure in which graphite is partially exfoliated. is there.

  In still another specific aspect of the carbon material / resin composite material according to the present invention, the resin is a polyether. The polyether is preferably polyethylene glycol.

  According to the present invention, it is possible to provide a carbon material / resin composite material having excellent conductivity.

It is a disassembled perspective view which shows the structure of the battery for lithium ion secondary battery experiment used by the Example and the comparative example.

  Details of the present invention will be described below.

The carbon material / resin composite material according to the first to third inventions of the present application includes a carbon material and a resin. In the carbon material / resin composite material, the carbon material and the resin are combined. The BET specific surface area of the carbon material / resin composite material is 50 m ² / g or more and 2500 m ² / g or less.

  In the first invention, the D / G ratio, which is the peak intensity ratio between the D band and the G band in the Raman spectrum of the carbon material / resin composite material, is 0.2 or less. The Raman spectrum of the carbon material / resin composite material is measured by Raman spectroscopy.

More specifically, in the present invention, Raman spectra, for example, by high laser Raman ^microscopy, can be obtained in a range of 3100cm ^-1 ~700cm -1. As the high-speed laser Raman microscope, for example, a product number “Raman touch” manufactured by Nanophoton can be used.

The peak of the D band in the Raman spectrum is a peak derived from the defect structure. Peak of the D band is generally observed in the vicinity of ^{1349cm -1 ~1353cm} -1 of the Raman spectrum.

On the other hand, the peak of the G band in the Raman spectrum is a peak derived from in-plane stretching vibration of a six-membered ring structure of carbon atoms. Peak of the G-band is generally observed in the vicinity of ^{1578cm -1 ~1592cm} -1 of the Raman spectrum.

  The D / G ratio, which is the peak intensity ratio between the D band and the G band, serves as an index of the defect amount of the carbon material. The smaller the peak intensity ratio between the D band and G band, the smaller the amount of defects in the carbon material.

  In the first invention, since the D / G ratio in the Raman spectrum of the carbon material / resin composite material is not more than the above upper limit, the amount of defects in the carbon material is small. Therefore, the carbon material / resin composite material of the first invention has a small resistance value and is excellent in conductivity.

  In the second invention, in the G band of the Raman spectrum, the ratio of the peak intensity to the half width (peak intensity / half width) is 3.0 or more. The Raman spectrum of the carbon material / resin composite material is measured by Raman spectroscopy as in the first invention.

  In the second invention, the ratio (peak intensity / full width at half maximum) in the G band of the Raman spectrum of the carbon material / resin composite material is equal to or greater than the above lower limit, so that it is close to a graphite structure having a complete structure with few defects. Can do. Therefore, the carbon material / resin composite material of the second invention has a small resistance value and is excellent in conductivity.

  In the third invention, the D / G ratio in the Raman spectrum of the carbon material / resin composite material is 0.2 or less, and the ratio in the G band of the Raman spectrum of the carbon material / resin composite material (peak intensity / half (Value range) is 3.0 or more. The Raman spectrum of the carbon material / resin composite material is measured by Raman spectroscopy as in the first invention.

  In the third invention, the D / G ratio in the Raman spectrum of the carbon material / resin composite material is not more than the above upper limit, and the ratio (peak intensity / half width) in the G band of the Raman spectrum is not less than the above lower limit. Therefore, the resistance value is small and the conductivity is excellent.

  Thus, the carbon materials / resin composite materials according to the first to third inventions all have small resistance values and are excellent in conductivity. Moreover, in the carbon material / resin composite material according to the first to third inventions, the BET specific surface area is in the above range, and the specific surface area is large, so that it is easy to take a conductive path.

  The carbon material / resin composite material according to the first to third inventions is excellent in conductivity and has a large specific surface area. For example, it can be used as an electrode material for secondary batteries such as lithium ion secondary batteries and capacitors. When used, the capacity can be increased. Therefore, the carbon material / resin composite material according to the first to third inventions can be suitably used for secondary batteries such as lithium ion secondary batteries and capacitor electrode materials.

  Hereinafter, the first to third inventions may be collectively referred to as the present invention.

  In the present invention, the D / G ratio in the Raman spectrum of the carbon material / resin composite material is preferably 0.2 or less, more preferably 0.15 or less, and even more preferably 0.1 or less. When the D / G ratio is not more than the above upper limit, the amount of defects in the carbon material can be further reduced, and the conductivity of the carbon material / resin composite material can be further enhanced. Further, the lower limit value of the D / G ratio is not particularly limited, but may be 0.001, for example.

  In the present invention, in the G band of the Raman spectrum of the carbon material / resin composite material, the ratio of the peak intensity to the half value width (peak intensity / half value width) is preferably 3.0 or more. When the ratio (peak intensity / full width at half maximum) is not less than the above lower limit, it can be made closer to a graphite structure having a complete structure with few defects. Therefore, the conductivity of the carbon material / resin composite material can be further enhanced.

  The ratio (peak intensity / full width at half maximum) in the G band of the Raman spectrum of the carbon material / resin composite material is more preferably 4.0 or more, and even more preferably 5.0 or more. In this case, the conductivity of the carbon material / resin composite material can be further enhanced. The upper limit of the ratio (peak intensity / half width) is not particularly limited, but can be set to 20.0, for example.

  Further, when the ratio of the peak intensity in the G band to the half width (peak intensity / half width) is A and the ratio of the peak intensity in the D band to the half width (peak intensity / half width) is B, the ratio A / B is preferably 8.0 or more and 100.0 or less. The ratio A / B is more preferably 15.0 or more and 80.0 or less, and further preferably 20.0 or more and 70.0 or less. When the ratio A / B is within the above range, the conductivity of the carbon material / resin composite material can be further enhanced.

  In the present invention, when a differential thermal analysis of the carbon material / resin composite material is performed at a temperature rising rate of 10 ° C./min, it is preferable that the temperature range is 300 ° C. or more and 900 ° C. or less and has two exothermic peaks. The two exothermic peaks are an exothermic peak derived from a carbon material and an exothermic peak derived from a resin.

  When the two exothermic peaks are within the above temperature range, the resin is grafted on the carbon material or adsorbed between the carbon material layers, and the thinning of the carbon material proceeds. The conductivity can be further increased by increasing the conductivity.

  When the exothermic peak derived from the resin is below 300 ° C., there is a resin that is not involved in the peeling of the carbon material, and the specific surface area of the carbon material / resin composite material may be lowered. Although it is possible to coexist, it is desirable that there is as little as possible.

  In addition, when a peak derived from graphite exists at a temperature exceeding 900 ° C., sufficient peeling of the carbon material may not proceed, and the specific surface area of the carbon material / resin composite material may be lowered.

  The two exothermic peaks are more preferably in the temperature range of 400 ° C. or higher and 800 ° C. or lower, and more preferably in the temperature range of 430 ° C. or higher and 700 ° C. or lower.

  Differential thermal analysis (DTA) can be measured, for example, in the range of 30 ° C. to 1000 ° C. using a differential thermal analyzer. As the differential thermal analyzer, for example, product number “TG / DTA6300” manufactured by SII can be used.

  Hereinafter, the details of each material constituting the carbon material / resin composite material of the present invention will be described.

[Carbon material]
Examples of the carbon material include graphite, exfoliated graphite, flaky graphite, artificial graphite, and expanded graphite.

  Graphite is a laminate of a plurality of graphene sheets. The number of graphite graphene sheets stacked is usually about 100,000 to 1,000,000 layers. As the graphite, for example, natural graphite, artificial graphite or expanded graphite can be used. Expanded graphite has a larger interlayer between graphene layers than normal graphite. Therefore, it is preferable to use expanded graphite as the graphite.

  Exfoliated graphite is obtained by exfoliating the original graphite, and refers to a graphene sheet laminate that is thinner than the original graphite. The number of graphene sheets laminated in exfoliated graphite should be less than the original graphite.

  In the exfoliated graphite, the number of graphene sheets stacked is preferably 1000 layers or less, more preferably 500 layers or less. When the number of graphene sheets stacked is not more than the above upper limit, the specific surface area of exfoliated graphite can be further increased.

  The exfoliated graphite is preferably a partially exfoliated graphite having a graphite structure and a structure in which the graphite is partially exfoliated.

  More specifically, “partially exfoliated graphite” means that in the graphene laminate, the graphene layer is open from the edge to some extent inside, that is, a part of the graphite is exfoliated at the edge. In the central part, the graphite layer is laminated in the same manner as the original graphite or primary exfoliated graphite. Therefore, the part where the graphite is partially peeled off at the edge is continuous with the central part. Further, the partially exfoliated exfoliated graphite may include one exfoliated and exfoliated from the edge graphite.

  Thus, in the partially exfoliated exfoliated graphite, the graphite layer is laminated at the center side similarly to the original graphite or primary exfoliated graphite. Therefore, the degree of graphitization is higher than that of conventional graphene oxide and carbon black, and the conductivity can be further increased.

  Such partially exfoliated exfoliated graphite includes graphite or primary exfoliated graphite and a polymer, and a composition in which the polymer is fixed to the graphite or primary exfoliated graphite by grafting or adsorption is prepared and thermally decomposed. Can be obtained. In addition, it is preferable that a part of polymer, ie, resin, contained in the composition remains. That is, a resin-retained partially exfoliated graphite is preferable. However, partially exfoliated graphite from which the resin (polymer) has been completely removed may be used.

  As graphite used as a raw material, expanded graphite is preferable. Expanded graphite can be easily peeled off because the interlayer of the graphene layer is larger than that of normal graphite. Therefore, by using expanded graphite as the raw material graphite, it is possible to easily produce a resin-retained partially exfoliated exfoliated graphite.

In the above graphite, the number of graphene layers is about 100,000 to 1,000,000, and the BET specific surface area has a value of 20 m ² / g or less.

On the other hand, in the resin-retained partially exfoliated graphite, the number of graphene layers is preferably 3000 or less. The BET specific surface area of the resin-retained partially exfoliated graphite is preferably 50 m ² / g or more, and more preferably 70 m ² / g or more. The upper limit of the BET specific surface area of the resin-retained partially exfoliated graphite is usually 2500 m ² / g or less.

  As a raw material, primary exfoliated graphite may be used instead of graphite. Examples of primary exfoliated graphite include exfoliated graphite obtained by exfoliating graphite, partially exfoliated exfoliated graphite, and resin-retained partially exfoliated graphite. Moreover, exfoliated graphite obtained by exfoliating graphite by a conventionally known method is widely included. Since primary exfoliated graphite is obtained by exfoliating graphite, the specific surface area may be larger than that of graphite.

  The resin contained in the resin residual type partially exfoliated exfoliated graphite is not particularly limited, and examples thereof include polyether resins such as polypropylene glycol, polyethylene glycol, and polytetramethylene glycol, polyglycidyl methacrylate, polyvinyl acetate, and polybutyral. Polyacrylic acid, polystyrene, poly α-methylstyrene, polyethylene, polypropylene, polyisobutylene and other polyvinyl resins, and polybutadiene, polyisoprene, styrene butadiene rubber and other diene resins. Preferably, a resin that easily generates free radicals by thermal decomposition, such as polypropylene glycol, polyethylene glycol, polyglycidyl methacrylate, polyvinyl acetate, and the like can be used. More preferred are polyethers such as polypropylene glycol, polyethylene glycol, and polytetramethylene glycol. More preferred is polyethylene glycol.

  In the resin-retained partially exfoliated graphite, the interlayer distance between the graphene layers is increased, and the specific surface area is large. Further, the resin-retained partially exfoliated graphite has a structure in which the central portion has a graphite structure and the edge portion is exfoliated, and thus is easier to handle than conventional exfoliated graphite. Resin-retained partially exfoliated graphite has high dispersibility in other resins because it contains a resin. In particular, when the other resin is a resin having a high affinity with the resin contained in the resin residual type exfoliated graphite, the dispersibility of the resin residual type partially exfoliated exfoliated graphite in the other resin is further increased. Will be enhanced. The resin is desirably disposed between the graphene layers of the partially exfoliated graphite. But resin may adhere to the surface and edge part of partially exfoliation type exfoliated graphite. Further, it is desirable that the resin is grafted or adsorbed on the partially exfoliated exfoliated graphite.

  Specifically, the resin-retained partially exfoliated graphite can be obtained by the production method described in the column of an example of the production method described later, and used as it is as an example of the carbon material / resin composite material of the present invention. be able to. However, in the present invention, a carbon material and a resin composite material may be obtained by separately preparing a carbon material and a resin and combining them.

[resin]
The resin is not particularly limited. For example, polyether resins such as polypropylene glycol, polyethylene glycol, polytetramethylene glycol, polyglycidyl methacrylate, polyvinyl acetate, polybutyral, polyacrylic acid, polystyrene, poly α-methylstyrene, polyethylene , Polyvinyl resins such as polypropylene and polyisobutylene, and diene resins such as polybutadiene, polyisoprene and styrene butadiene rubber. Preferably, a resin that easily generates free radicals by thermal decomposition, such as polypropylene glycol, polyethylene glycol, polyglycidyl methacrylate, polyvinyl acetate, and the like can be used. From the viewpoint of further enhancing the conductivity of the carbon material / resin composite material, more preferred are polyethers such as polypropylene glycol, polyethylene glycol, and polytetramethylene glycol. More preferred is polyethylene glycol.

  The resin content in the carbon material / resin composite material is preferably 0.01% by mass to 70.0% by mass. More preferably, it is 1.0 mass%-55.0 mass%, More preferably, it is 5.0 mass%-30.0 mass%. When the resin content is not less than the above lower limit, the dispersibility of the carbon material / resin composite material in other resins can be further enhanced. Moreover, when content of resin is below the said upper limit, the electroconductivity of a carbon material and a resin composite material can be improved further.

[Other ingredients]
The carbon material / resin composite material of the present invention may contain other components as long as the effects of the present invention are not impaired.

  Other components include, for example, antioxidants such as phenols, phosphoruss, amines or sulfurs, UV absorbers such as benzotriazoles or hydroxyphenyltriazines, metal damage inhibitors, hexabromobiphenyl ethers or deca Examples include halogenated flame retardants such as bromodiphenyl ether, flame retardants such as ammonium polyphosphate or trimethyl phosphate, additives such as fillers, antistatic agents, stabilizers, pigments, and dyes. These additives may be used alone or in combination.

  Hereinafter, an example of the method for producing the carbon material / resin composite material of the present invention will be described.

[Production method of carbon material / resin composite material]
As an example of a method for producing a carbon material / resin composite material, a method for producing the resin-retained partially exfoliated graphite described above will be described.

(Process of preparing raw material composition)
In the manufacturing method as an example of the carbon material / resin composite material, a composition containing graphite or primary exfoliated graphite and a polymer, and the polymer is fixed to the graphite or primary exfoliated graphite is first prepared. Examples of the step of preparing this composition include the following first and second methods for fixing the polymer to graphite or primary exfoliated graphite by grafting the polymer to graphite or primary exfoliated graphite. . Moreover, you may use the 3rd method of fixing a polymer to graphite or primary exfoliated graphite by making a polymer adsorb | suck to graphite or primary exfoliated graphite.

First method;
In the first method, first, a mixture containing graphite or primary exfoliated graphite and a radical polymerizable monomer is prepared as a raw material. Next, the radically polymerizable monomer contained in the mixture is polymerized. Thereby, a polymer in which the radical polymerizable monomer is polymerized in the mixture is generated, and the polymer is grafted to graphite or primary exfoliated graphite.

  In the first method, first, a composition containing graphite or primary exfoliated graphite and a radical polymerizable monomer is prepared.

  The blending ratio of the graphite and the radical polymerizable monomer is not particularly limited, but is desirably 1: 1 to 1: 100 by mass ratio. By setting the blending ratio in the range, it is possible to effectively exfoliate graphite or primary exfoliated graphite and obtain a carbon material / resin composite material more effectively.

  A method for preparing the composition is not particularly limited, and examples thereof include a method in which a radical polymerizable monomer is used as a dispersion medium and graphite or primary exfoliated graphite is dispersed in the radical polymerizable monomer.

  Next, a step of producing a polymer in which the radical polymerizable monomer is polymerized in the composition is performed by polymerizing the radical polymerizable monomer contained in the composition.

  At this time, the radical polymerizable monomer generates a free radical. As a result, the radical polymerizable monomer undergoes radical polymerization, thereby producing a polymer in which the radical polymerizable monomer is polymerized. On the other hand, the graphite or primary exfoliated graphite contained in the composition has a radical trapping property because it is a laminate of a plurality of graphene layers. Therefore, when a radically polymerizable monomer is co-polymerized in the composition, the free radicals are adsorbed on the edge and surface of the graphene layer of the graphite or primary exfoliated graphite. Therefore, the polymer or radical polymerizable monomer having free radicals generated at the time of polymerization is grafted to the end portion and the surface of the graphene layer of graphite or primary exfoliated graphite.

  Examples of the method for polymerizing the radical polymerizable monomer include a method in which the composition is heated to a temperature higher than the temperature at which the radical polymerizable monomer spontaneously starts polymerization. By heating the composition to the temperature or higher, free radicals can be generated in the radical polymerizable monomer contained in the composition. Thereby, the polymerization and grafting described above can be carried out.

  As described above, when the radical polymerizable monomer is polymerized by heating, both the polymerization of the radical polymerizable monomer and the thermal decomposition of the polymer described later can be performed only by heating the composition. Accordingly, the graphite or primary exfoliated graphite can be more easily separated.

  The heating method is not particularly limited as long as the composition can be heated to the temperature or higher, and the composition can be heated by an appropriate method and apparatus. Moreover, in the case of the said heating, you may heat without sealing, ie, a normal pressure. However, it may be sealed and heated.

  Further, in order to reliably polymerize the radical polymerizable monomer, the temperature may be further maintained for a certain time after heating to a temperature equal to or higher than the temperature at which the radical polymerizable monomer spontaneously starts polymerization. The time for maintaining the temperature near the above temperature is preferably in the range of 0.5 hours to 5 hours, although it depends on the kind and amount of the radical polymerizable monomer to be used.

  After the step of producing the polymer, the composition is heated to the thermal decomposition temperature of the polymer to perform a step of thermally decomposing the polymer while leaving a part of the polymer remaining. Thereby, the polymer contained in the composition, the polymer grafted on the end portion and the surface of the graphene layer of graphite or primary exfoliated graphite, and the like are thermally decomposed. In the present invention, the thermal decomposition temperature of the polymer means a decomposition end point temperature dependent on TGA measurement. For example, if the polymer is polystyrene, the thermal decomposition temperature of the polymer is about 350 ° C.

  At this time, when the polymer or the like grafted on the end portion and the surface of the graphene layer of graphite or primary exfoliated graphite is thermally decomposed, a peeling force is generated between the graphene layers. Therefore, by pyrolyzing a polymer or the like, the graphene layer of graphite or primary exfoliated graphite can be peeled off to obtain exfoliated graphite.

  In addition, a part of the polymer, that is, the resin remains in the composition by this thermal decomposition. The thermal decomposition start temperature and the thermal decomposition end temperature of the resin in the carbon material / resin composite material obtained by thermal decomposition are respectively higher than the thermal decomposition start temperature and the thermal decomposition end temperature of the resin before the composite.

  The heating method is not particularly limited as long as it can be heated to the thermal decomposition temperature of the polymer, and the composition can be heated by an appropriate method and apparatus. Moreover, in the case of the said heating, you may heat without sealing, ie, a normal pressure. Further, it may be sealed and heated. Therefore, exfoliated graphite can be produced inexpensively and easily. Thermal decomposition so that the resin remains can be achieved by adjusting the heating time. That is, the amount of residual resin can be increased by shortening the heating time. Also, the amount of residual resin can be increased by lowering the heating temperature.

  In the second method and the third method described later, the heating temperature and the heating time may be adjusted in the step of heating so as to leave a part of the polymer (resin).

  If the polymer can be thermally decomposed so that a part of the polymer remains while part of the polymer remains in the composition, the temperature is further increased after heating to a temperature equal to or higher than the thermal decomposition temperature of the polymer. You may maintain for a fixed time. The time for maintaining the temperature near the above temperature is preferably in the range of 0.5 hours to 5 hours, although it depends on the kind and amount of the radical polymerizable monomer to be used.

  Further, in the step of producing the polymer, when the radical polymerizable monomer is polymerized by heating, the heat treatment for producing the polymer and the heat treatment for thermally decomposing the polymer are performed by the same method and apparatus. You may carry out continuously.

Second method;
In the second method, the polymer is first grafted to graphite or primary exfoliated graphite by heating the polymer to a temperature in the temperature range of 50 ° C. or higher and 600 ° C. or lower in the presence of graphite or primary exfoliated graphite. Let As described above, in the second method, the polymer obtained in advance is heated to the specific temperature range in the presence of graphite or primary exfoliated graphite. Thereby, polymer radicals generated by thermally decomposing the polymer can be directly grafted to graphite or primary exfoliated graphite. In the first method, a radical polymerizable monomer is polymerized in the presence of graphite or primary exfoliated graphite to produce a polymer, and grafting of the polymer onto graphite or primary exfoliated graphite has been attempted.

  As the polymer of the second method, an appropriate pyrolytic radical generating polymer can be used.

  Most organic polymers generate radicals at the decomposition temperature. Therefore, many organic polymers can be used as the polymer that forms radicals near the decomposition temperature. However, a polymer of a radical polymerizable monomer such as a vinyl monomer is preferably used. Examples of such vinyl monomers, that is, vinyl group-containing monomers, include monomers such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and benzyl acrylate. Preferably, styrene and glycidyl methacrylate are used. Examples of the polymer formed by polymerizing the vinyl group-containing monomer include (meth) acrylic acid alkyl ester, polypropylene, polyvinyl phenol, polyphenylene sulfide, polyphenylene ether, and the like.

  In addition, polymers containing a halogen element such as chlorine, such as polyvinyl chloride, chlorinated vinyl chloride resin, ethylene fluoride resin, vinylidene fluoride resin, and vinylidene chloride resin can also be used. Ethylene vinyl acetate copolymer (EVA), polyvinyl acetal, polyvinyl pyrrolidone and copolymers thereof can also be used. Polymers obtained by cationic polymerization such as polyisobutylene and polyalkylene ether can also be used.

  Polyurethane, epoxy resin, modified silicone resin, silicone resin and the like obtained by crosslinking oligomers can also be used.

  Polyallylamine may be used, in which case the amino group can be grafted to graphite or primary exfoliated graphite. Polyvinylphenol or polyphenols may be used, in which case the phenolic OH can be grafted to graphite or primary exfoliated graphite. Further, when a polymer having a phosphate group is used, the phosphate group can be grafted.

  Further, a condensation polymer such as polyester or polyamide may be used. In that case, the decomposition product is grafted although the radical concentration obtained at the decomposition temperature is low.

  As the polymer prepared in advance, a homopolymer of glycidyl methacrylate, polystyrene, polyvinyl acetate, polypropylene glycol, polyethylene glycol, polytetramethylene glycol, polybutyral and the like are preferably used. By using these polymers, graphite or primary exfoliated graphite can be more effectively exfoliated. From the viewpoint of further enhancing the conductivity of the obtained carbon material / resin composite material, more preferred are polyethers such as polypropylene glycol, polyethylene glycol, and polytetramethylene glycol. More preferred is polyethylene glycol.

  In the second method, the blending ratio of graphite or primary exfoliated graphite and polymer is not particularly limited, but it is desirable that the weight ratio is 1: 1 to 1:50. By setting the blending ratio within this range, graphite or primary exfoliated graphite can be exfoliated more effectively, and a carbon material / resin composite material can be obtained effectively.

  Also in the second method, as in the case of the first method, graphite or primary exfoliated graphite can be more effectively exfoliated by heating that causes thermal decomposition of the polymer described later.

  Also in the second method, a specific method for preparing the composition is not limited, and examples thereof include a method in which a polymer and graphite or primary exfoliated graphite are put in an appropriate solvent or dispersion medium and heated. .

  The polymer is grafted onto graphite or primary exfoliated graphite by the heating. About this heating temperature, it is desirable to set it as the range of 50 to 600 degreeC. By setting the temperature within this range, the polymer can be effectively grafted onto the graphite. Thereby, graphite or primary exfoliated graphite can be more effectively exfoliated. The reason for this is considered as follows.

  By heating the polymer obtained by polymerizing the radical polymerizable monomer, a part of the polymer is decomposed and radical trapped in the graphene layer of graphite or primary exfoliated graphite. Therefore, the polymer will be grafted to graphite or primary exfoliated graphite. And if a polymer is decomposed | disassembled and baked in the heating process mentioned later, a big stress will be added to the graft surface currently grafted by the graphite or primary exfoliated graphite of a polymer. Therefore, it is considered that the peeling force acts starting from the graft point, and the graphene layer is effectively expanded.

Third method;
As a third method, a method of dissolving or dispersing graphite and a polymer in an appropriate solvent can be mentioned. As such a solvent, tetrahydrofuran, methyl ethyl ketone, toluene, ethyl acetate, ethanol, water, or the like can be used.

  In the third method, a composition in which a polymer is adsorbed on graphite or primary exfoliated graphite in a solvent is prepared as the above composition. The method for adsorbing the polymer to graphite or primary exfoliated graphite is not particularly limited. Since the polymer has adsorptivity to graphite, a method of mixing graphite or primary exfoliated graphite with the polymer in the above-described solvent can be used.

  The adsorption of the polymer is considered to be due to the interaction between the surface energy of graphite and the polymer.

Exfoliation step of graphite or primary exfoliated graphite by thermal decomposition of polymer;
In any of the first method, the second method, and the third method, after preparing the composition as described above, the polymer contained in the composition is pyrolyzed. Thereby, the graphite or primary exfoliated graphite is peeled off while leaving a part of the polymer, whereby a carbon material / resin composite material can be obtained. In order to achieve thermal decomposition of the polymer in this case, the composition may be heated to a temperature higher than the thermal decomposition temperature of the polymer. More specifically, it is heated to a temperature higher than the thermal decomposition temperature of the polymer, and the polymer is further baked. At this time, it is fired to such an extent that the polymer remains in the composition. Thereby, a carbon material / resin composite material can be obtained. For example, the thermal decomposition temperature of polystyrene is about 380 ° C. to 450 ° C., and the thermal decomposition temperature of polyglycidyl methacrylate is about 400 ° C. to 500 ° C. The thermal decomposition temperature of polybutyral is about 550 ° C. to 600 ° C. in the atmosphere.

  In the present invention, the polymer contained in the composition is pyrolyzed under an inert gas atmosphere. Examples of the inert gas include nitrogen, helium, argon, and carbon dioxide gas, and nitrogen is preferable. The oxygen concentration is preferably less than 2.5%. More preferably, it is 1.0% or less. In this case, defects in the carbon material in the obtained carbon material / resin composite material can be further reduced. Therefore, the conductivity of the carbon material / resin composite material can be further enhanced.

  The reason why the carbon material / resin composite material can be obtained by thermal decomposition of the polymer is considered to be due to the reason described above. That is, it is considered that when the polymer grafted on the graphite is baked, a large stress acts on the graft point, thereby increasing the distance between the graphenes.

  In the first method, it has been explained that the heating for polymerizing the radical polymerizable monomer and the thermal decomposition of the polymer may be carried out continuously in the same heating step. Also in the second method, a heating step for grafting the polymer onto graphite or primary exfoliated graphite and a heating step for thermally decomposing the polymer may be performed continuously.

  Furthermore, it is desirable to carry out a plurality of times in both the first method and the second method. For example, after preparing the composition by the first method, the polymer is pyrolyzed to obtain exfoliated graphite that is substantially free of the polymer. The obtained exfoliated graphite is used as the primary exfoliated graphite of the raw material of the first method. Furthermore, a carbon material / resin composite material having a larger specific surface area may be obtained by repeating the first method one or more times. Similarly, after preparing the composition by the second method, the polymer is pyrolyzed to obtain exfoliated graphite substantially free of polymer. The obtained exfoliated graphite may be used as the primary exfoliated graphite of the raw material in the second method, and the carbon material / resin composite material may be obtained by further performing thermal decomposition of the second method and polymer. Even in these cases, a carbon material / resin composite material having a larger specific surface area can be obtained.

  Further, for example, after preparing the composition by the first method, the polymer is thermally decomposed to obtain a carbon material / resin composite material, and then the carbon material / resin composite material is used as a primary material of the first method. Used as exfoliated graphite. A carbon material / resin composite material having a larger specific surface area may be obtained by repeating the first method one or more times. Similarly, after preparing the composition by the second method, the polymer is thermally decomposed to obtain a carbon material / resin composite material. The obtained carbon material / resin composite material may be used as the primary exfoliated graphite of the raw material in the second method, and the second method and polymer may be further pyrolyzed to obtain the carbon material / resin composite material.

  In addition, the composition prepared by the first method is heated to obtain exfoliated graphite that is substantially free of polymer. The exfoliated graphite may be used as primary exfoliated graphite as a raw material of the second method, and a carbon material / resin composite material may be obtained in the same manner as in the second method. Conversely, the composition obtained by the second method is heated to obtain exfoliated graphite that is substantially free of polymer. The exfoliated graphite is used as the primary exfoliated graphite of the raw material of the first method. Hereinafter, in the same manner as in the first method, a composition is prepared, and the polymer is thermally decomposed by heating to obtain a carbon material / resin composite material. May be obtained. Thus, exfoliated graphite substantially free of polymer obtained by the above thermal decomposition may be further used as primary exfoliated graphite as a raw material. A carbon material / resin composite material having a larger specific surface area can be obtained by repeating the flaking by the production method of the present invention once or more.

  In addition, after heating the composition prepared by the first method and obtaining a carbon material / resin composite material, the carbon material / resin composite material is used as a primary exfoliated graphite as a raw material of the second method, A carbon material / resin composite material may be obtained in the same manner as in the second method. Conversely, the composition obtained by the second method is heated to obtain a carbon material / resin composite material. Thereafter, the carbon material / resin composite material may be used as the primary exfoliated graphite of the raw material of the first method, and the carbon material / resin composite material may be obtained in the same manner as in the first method. In this way, the carbon material / resin composite material is further used as primary exfoliated graphite as a raw material, and the exfoliation by the production method of the present invention is repeated one or more times, so that the carbon material / resin composite having a larger specific surface area is obtained. Material can be obtained.

(Other variations)
In the present invention, the carbon material is obtained by pyrolyzing the polymer in the composition having a structure in which the polymer in which the radical polymerizable monomer is polymerized as described above is grafted to graphite or primary exfoliated graphite. A resin composite material has been obtained. In this invention, you may give the process of exfoliating graphite by another method further. For example, as described above, a carbon material / resin composite material may be used as a raw material, and another conventionally known method for thinning graphite may be further performed. Alternatively, the method for producing a carbon material / resin composite material of the present invention may be carried out using primary exfoliated graphite obtained by another method for exfoliating graphite as a raw material. Even in this case, a carbon material / resin composite material having a larger specific surface area can be obtained. As such another graphite flaking method, for example, a graphite flaking method by electrochemical treatment or an adsorption-pyrolysis method can be used.

  In this production method, no thermally decomposable foaming agent is used during heating, and the polymer (resin) is thermally decomposed in an inert gas atmosphere. Therefore, the amount of defects in the carbon material can be reduced, and the above-described D / G ratio can be reduced. Further, it can be close to a graphite structure having a complete structure with few defects, and the ratio (peak intensity / half width) in the G band of the Raman spectrum can be increased. Since defects of the carbon material can be reduced and the graphite structure having a complete structure can be obtained, the resistance value of the carbon material / resin composite material can be reduced, and the conductivity can be increased.

  The carbon material / resin composite material obtained by this production method as an example is the above-mentioned resin-retained partially exfoliated graphite. However, in the present invention, the carbon material and the resin may be separately prepared, and the carbon material and the resin may be combined by a method such as kneading to obtain the carbon material / resin composite material.

[Slurry for electrode formation]
The carbon material / resin composite material of the present invention can be suitably used, for example, as an electrode forming slurry for an electricity storage device. Since the carbon material / resin composite material of the present invention is excellent in conductivity, in an electricity storage device including an electrode formed using an electrode forming slurry containing such a carbon material / resin composite material, output characteristics and the like Battery characteristics can be improved.

  The power storage device is not particularly limited, but a non-aqueous electrolyte primary battery, an aqueous electrolyte primary battery, a non-aqueous electrolyte secondary battery, an aqueous electrolyte secondary battery, an all-solid electrolyte primary battery, an all-solid electrolyte secondary battery, a capacitor, An electric double layer capacitor or a lithium ion capacitor is exemplified.

  The secondary battery as an example of the electricity storage device may be any battery that uses a compound that undergoes insertion and elimination reactions of alkali metal ions or alkaline earth metal ions. Examples of alkali metal ions include lithium ions, sodium ions, and potassium ions. Examples of the alkaline earth metal ions include calcium ions and magnesium ions. In particular, the carbon material / resin composite material of the present invention is highly effective for the positive electrode of a non-aqueous electrolyte secondary battery, and among them, it can be suitably used for a lithium ion secondary battery, that is, a lithium ion secondary battery.

  When producing a slurry used for such an electrode of an electricity storage device, the carbon material / resin composite material may be used as it is, or may be used in the form of a dispersion after being dispersed in a dispersion medium.

(Dispersion medium)
The dispersion medium to be used is not particularly limited, and an aqueous solvent, a non-aqueous solvent, a mixed solvent of an aqueous solvent and a non-aqueous solvent, or a mixed solvent of different non-aqueous solvents is used.

  Although it does not specifically limit as an aqueous solvent, Solvents, such as water, carboxymethylcellulose sodium aqueous solution, carboxymethylcellulose ammonium aqueous solution, can be used.

  The non-aqueous solvent is not particularly limited, but from the viewpoint that the carbon material / resin composite material is more easily dispersed, an alcohol solvent typified by methanol, ethanol, propanol, tetrahydrofuran, N-methyl-2-pyrrolidone, etc. These solvents can be used.

  The method for dispersing the carbon material / resin composite material in the dispersion medium is not particularly limited, and examples thereof include ultrasonic dispersion, mixer dispersion, jet mill dispersion, and stirrer dispersion.

[Slurry for positive electrode]
The carbon material / resin composite material of the present invention can be suitably used as a positive electrode slurry for forming a positive electrode in a non-aqueous electrolyte secondary battery as described above. The positive electrode slurry includes the above-described carbon material / resin composite material, a positive electrode active material, and a binder as necessary.

  Hereinafter, the details of each material constituting the positive electrode slurry will be described.

(Positive electrode active material)
Any positive electrode active material may be used as long as lithium ion desorption and insertion reactions proceed. Examples of the positive electrode active material include a lithium transition metal composite oxide having a layered rock salt structure and a lithium transition metal composite oxide having a spinel structure. A mixture obtained by mixing a plurality of these positive electrode active materials may be used.

  Examples of the lithium transition metal composite oxide having a layered rock salt structure include a compound represented by the following formula (1).

_{Li a Ni b Mn c Co d} X e O 2 ... Equation (1)

  (In formula (1), X is selected from at least B, Mg, Al, Si, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Zr, Nb, Mo, In, and Sn. A, b, c, d and e are 0 <a ≦ 1.2, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1, 0 ≦ d <1, 0 ≦ e ≦ 1, and b + c + d + e = 1.

_{Li a Ni b Mn c Co d} X e O 2 of a is 0 <a ≦ 1.2. When a ≦ 0, it may not function as a positive electrode active material. On the other hand, when a> 1.2, a large amount of impurities such as lithium carbonate may be contained.

_{Li a Ni b Mn c Co d} X e O 2 of b, c, d, and e, respectively, 0 ≦ b ≦ 1,0 ≦ c ≦ 1,0 ≦ d <1,0 ≦ e ≦ 1, b + c + d + e = 1. When b> 1, c> 1, e> 1, or d ≧ 1, the stability of the positive electrode active material may be reduced.

As a lithium transition metal complex oxide having a layered rock salt structure, Li _a Ni _b Mn _c Co _d O ₂ (where 0 <a ≦ 1.2, from the viewpoint of further improving the stability in the positive electrode active material) 0 <b <1, 0 <c <1, 0 <d <1, and b + c + d = 1), Li _a Ni _b Mn _c O ₂ (where 0 <a ≦ 1.2, 0 < b <1,0 <c <1, and b + c = is within 1 _{range), Li a Ni b Co d} Al e O 2 ( where, 0 <a ≦ 1.2,0 <b <1,0 < d <1, 0 <e <1, and b + d + e = 1), Li _a Ni _b X _e O ₂ , where 0 <a ≦ 1.2, 0 <b <1, 0 <e <1, and b + e = is within 1 _{range), Li a Mn c X e} O 2, ( where, 0 <a ≦ 1.2,0 <c <1,0 <e <1 and, + E = is within 1 range), or _{Li a Co d X e O 2} ( where, 0 <a ≦ 1.2,0 <d <1,0 <e <1, and d + e = within 1 range A lithium transition metal composite oxide having a layered rock salt structure represented by

From the viewpoint of further improving the stability of the positive electrode active material itself and further facilitating the production method, LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiNi _0.5 Mn _0.3 Co _0.2 O ₂ , LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.4 Mn _0.4 Co _0.2 O ₂ , LiNi _0.1 Mn _0.1 Co _0.8 O ₂ , LiNi _{0. 8} Co _0.16 Al _0.04 O ₂ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ , LiNi _0.8 Co _0.1 Al _0.1 O ₂ , LiNiO ₂ , LiMnO ₂ , or LiCo More preferred is at least one selected from the group consisting of _d X _e O ₂ (where 0 <d <1, 0 <e <1, and d + e = 1).

  These lithium transition metal composite oxides having a layered rock salt structure may be further doped with the same or different element as X. Further, a so-called lithium rich system in which a is larger than 1 is also included in the present invention.

  Examples of the lithium transition metal composite oxide having a spinel structure include a compound represented by the following formula (2).

_{Li 1 + x M y Mn 2} -x-y O 4 ... formula (2)

  (In the formula (2), x and y are in the range of 0 ≦ x ≦ 0.2 and 0 <y ≦ 0.6, respectively, M is a group 2 to group 13 and the third period. (At least one selected from the group consisting of elements belonging to ˜4 periods (excluding Mn))

  From the viewpoint of further improving the stability of the positive electrode active material itself, the elements belonging to Groups 2 to 13 and belonging to the third to fourth periods are Al, Mg, Zn, Co, Fe, Ti, Cu, Ni, or Cr is preferable, and Al, Mg, Zn, Ti, Ni, or Cr is more preferable. From the viewpoint of further improving the stability of the positive electrode active material itself, the element belonging to Group 2 to Group 13 and belonging to the third period to the fourth period is more preferably Al, Mg, Zn, Ni, or Ti. The elements belonging to Groups 2 to 13 and belonging to the third period to the fourth period may be used alone or in combination of two or more.

X of _{Li 1 + x M y Mn 2} -x-y O 4 is 0 ≦ x ≦ 0.2. When x <0, the capacity of the positive electrode active material may decrease. On the other hand, when x> 0.2, a large amount of impurities such as lithium carbonate may be contained.

Y of _{Li 1 + x M y Mn 2} -x-y O 4 is 0 <y ≦ 0.6. When y = 0, the stability of the positive electrode active material may decrease. On the other hand, when y> 0.6, many impurities such as M oxide may be contained.

Among these lithium transition metal composite oxides having a spinel structure, Li _{1 + x} Al _y Mn _2−xy O ₄ (0 ≦ x ≦ 0.1, 0 <y ≦ 0.1), Li _{1 + x} Mg _y Mn _2-xy O ₄ (0 ≦ x ≦ 0.1, 0 <y ≦ 0.1), Li _{1 + x} Zn _y Mn _2-xy O ₄ (0 ≦ x ≦ 0.1, 0 <y ≦ _{0.1), Li 1 + x Cr} y Mn 2-x-y O 4 (0 ≦ x ≦ 0.1,0 <y ≦ 0.1), and _{Li 1 + x Ni y Mn 2} -x-y O 4 (0 ≦ x ≦ 0.1 and 0 <y ≦ 0.6) are preferred. In this case, in combination with a nonaqueous electrolyte described later, gas generation can be further suppressed, and the effect of increasing the end-of-charge voltage can be further increased. Since the above effect can be further obtained, Li _{1 + x} Al _y Mn _2-xy O ₄ (0 ≦ x ≦ 0.1, 0 <y ≦ 0.1), Li _{1 + x} Mg _y Mn _2-xy O ₄ (0 ≦ x ≦ 0.1, 0 <y ≦ 0.1), or Li _{1 + x} Ni _y Mn _2-xy O ₄ (0 ≦ x ≦ 0.1, 0 <y ≦ 0.6) Is more preferable.

  The particle diameters of the lithium transition metal composite oxide having a layered rock salt structure and the lithium transition metal composite oxide having a spinel structure are preferably 0.1 μm or more and 50 μm or less, respectively. From the viewpoint of further improving the handleability, the particle diameter is more preferably 0.5 μm or more and 30 μm or less. The particle diameter here is a value obtained by measuring the size of each particle from the SEM and TEM images and calculating the average particle diameter. The particles may be primary particles or a granulated body obtained by aggregating primary particles.

The specific surface areas of the lithium transition metal composite oxide having a layered rock salt structure and the lithium transition metal composite oxide having a spinel structure are preferably 0.1 m ² / g or more and 50 m ² / g or less, respectively. In this case, a desired power density can be obtained more reliably. The specific surface area can be calculated by measurement using the BET method.

  Only one of the lithium transition metal composite oxide having a layered rock salt structure and the lithium transition metal composite oxide having a spinel structure may be used, or a mixture of both may be used. For example, a mixture of two or more types of lithium transition metal composite oxides having a layered rock salt structure with different compositions and particle sizes (or lithium transition metal composite oxides having a spinel structure) may be used.

(binder)
The binder is not particularly limited, and for example, a resin such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber, polyimide, or a derivative thereof can be used.

  The binder is preferably dissolved or dispersed in a non-aqueous solvent or water from the viewpoint of more easily producing the positive electrode of the secondary battery. The non-aqueous solvent is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, methyl acetate, ethyl acetate, and tetrahydrofuran. A dispersant or a thickener may be added to these binders.

  The amount of the binder contained in the positive electrode slurry is preferably 0.3 parts by weight or more and 30 parts by weight or less, more preferably 0.5 parts by weight or more and 15 parts by weight with respect to 100 parts by weight of the positive electrode active material. It is as follows. When the amount of the binder is within the above range, the adhesion with the current collector can be further enhanced while maintaining the adhesion between the positive electrode active material and the carbon material / resin composite material.

(Second carbon material)
In producing the positive electrode slurry, when the carbon material / resin composite material of the present invention is used as the first carbon material, a second carbon material other than the first carbon material may be included. The second carbon material is a carbon material different from the first carbon material, and is not particularly limited. Examples thereof include graphene, a granular graphite compound, a fibrous graphite compound, and carbon black. These may be used alone or in combination.

  The granular graphite compound is not particularly limited, and examples thereof include natural graphite, artificial graphite, and expanded graphite.

  The fibrous graphite compound is not particularly limited, and examples thereof include carbon nanohorn, carbon nanotube, or carbon fiber.

  The carbon black is not particularly limited, and examples thereof include furnace black, ketjen black, and acetylene black.

From the viewpoint of further enhancing the electrolyte solution retention of the secondary battery, the BET specific surface area of the second carbon material is preferably 5 m ² / g or more. From the viewpoint of further enhancing the electrolyte solution retention of the secondary battery, the BET specific surface area of the second carbon material is more preferably 10 m ² / g or more, and further preferably 25 m ² / g or more. Further, from the viewpoint of further improving the ease of handling during the production of the positive electrode, the BET specific surface area of the second carbon material is preferably 2500 m ² / g or less.

  The phrase “including the first carbon material and the second carbon material” means that, for example, the first carbon material and the second carbon material are present in a positive electrode described later. The method for causing the first carbon material and the second carbon material to exist is not particularly limited, but may be mixed at the time of producing a positive electrode described later, or the first carbon material and the second carbon material in advance. May be mixed.

  When mixing two carbon materials, the ratio A / B is 0.01 or more and 100 or less, where A is the weight of the first carbon material and B is the weight of the second carbon material. It is preferable to be within the range. When the ratio A / B is within the above range, the resistance of the positive electrode in the secondary battery can be further reduced. Therefore, when used in a secondary battery, heat generation during charging / discharging with a large current can be further suppressed.

(Method for producing positive electrode slurry)
The positive electrode slurry can be obtained by mixing the carbon material / resin composite material of the present invention, the positive electrode active material, and a binder solution or dispersion.

  Examples of the method for preparing the positive electrode slurry include a method in which a carbon material / resin composite material and a positive electrode active material are mixed with a mixer and the like, and then a binder solution or dispersion is added. And a binder solution or dispersion, and a method of mixing using a mixer or the like. Although it does not specifically limit as a mixer used for mixing, A planetary mixer, a disper, a thin film swirl-type mixer, a jet mixer, or a self-rotation type mixer etc. are mentioned.

  The solid content concentration of the positive electrode slurry is preferably 30% by weight or more and 95% by weight or less from the viewpoint of more easily performing the coating described below. From the viewpoint of further improving the storage stability, the solid content concentration of the positive electrode slurry is more preferably 35% by weight or more and 90% by weight or less. From the viewpoint of further suppressing production costs, the solid content concentration of the positive electrode slurry is more preferably 40% by weight or more and 85% by weight or less.

  The solid content concentration of the positive electrode slurry can be controlled by a diluting solvent. As the diluting solvent, it is preferable to use the same type of solvent as the binder solution or dispersion. If there is no problem in compatibility, another solvent may be used as a dilution solvent.

[Positive electrode for non-aqueous electrolyte secondary battery]
The positive electrode for a non-aqueous electrolyte secondary battery using the carbon material / resin composite material of the present invention is prepared by, for example, applying a positive electrode slurry on a current collector foil substrate, which is a current collector, prepared by the above-described method, It can manufacture by removing and drying.

  The current collector foil substrate is preferably aluminum or an alloy containing aluminum. Aluminum is not particularly limited because it is stable in the positive electrode reaction atmosphere, but is preferably high-purity aluminum represented by JIS standards 1030, 1050, 1085, 1N90, 1N99, and the like.

  The thickness of the current collector foil substrate is not particularly limited, but is preferably 10 μm or more and 100 μm or less. When the thickness of the current collector foil substrate is less than 10 μm, handling may be difficult from the viewpoint of production. On the other hand, when the thickness of the current collector foil substrate is thicker than 100 μm, it may be disadvantageous from an economic viewpoint.

  The current collector foil substrate may be one in which the surface of a metal other than aluminum (copper, SUS, nickel, titanium, or an alloy thereof) is coated with aluminum.

  The method of applying the positive electrode slurry to the current collector foil substrate is not particularly limited, and examples thereof include a method of removing the solvent after applying the positive electrode slurry with a doctor blade, a die coater, a comma coater or the like. Or the method of removing a solvent after apply | coating by spray, the method of removing a solvent after apply | coating by screen printing, etc. may be used.

  Since the method for removing the solvent is much simpler, drying using a blower oven or a vacuum oven is preferable. Examples of the atmosphere for removing the solvent include an air atmosphere, an inert gas atmosphere, and a vacuum state. The temperature for removing the solvent is not particularly limited, but is preferably 60 ° C. or higher and 250 ° C. or lower. If the temperature at which the solvent is removed is less than 60 ° C., it may take time to remove the solvent. On the other hand, if the temperature for removing the solvent is higher than 250 ° C., the binder may deteriorate.

  The positive electrode for a non-aqueous electrolyte secondary battery using the carbon material / resin composite material of the present invention may be compressed to a desired thickness and density. Although compression is not specifically limited, For example, it can carry out using a roll press, a hydraulic press, etc.

  The thickness of the positive electrode for a nonaqueous electrolyte secondary battery produced using the carbon material / resin composite material of the present invention after compression is not particularly limited, but is preferably 10 μm or more and 1000 μm or less. If it is less than 10 μm, it may be difficult to obtain a desired capacity. On the other hand, when it is thicker than 1000 μm, it may be difficult to obtain a desired output density.

The density of the positive electrode for a non-aqueous electrolyte secondary battery using the carbon material / resin composite material of the present invention is not particularly limited, but is preferably 1.0 g / cm ³ or more and 4.0 g / cm ³ or less. When the density is less than 1.0 g / cm ³ , the contact between the positive electrode active material and the carbon material becomes insufficient, and the electronic conductivity may be lowered. On the other hand, when the density is larger than 4.0 g / cm ³ , an electrolyte solution described later hardly penetrates into the positive electrode, and lithium conductivity may be lowered.

The positive electrode for a non-aqueous electrolyte secondary battery using the carbon material / resin composite material of the present invention preferably has an electric capacity per 1 cm ^{2 of} positive electrode of 0.5 mAh or more and 10.0 mAh or less. When the electric capacity is less than 0.5 mAh, the size of the battery having a desired capacity may increase. When the electric capacity is greater than 10.0 mAh, it may be difficult to obtain a desired output density. The calculation of the electric capacity per 1 cm ² of the positive electrode may be performed by preparing a half cell using lithium metal as a counter electrode after the positive electrode is manufactured, and measuring charge / discharge characteristics.

The electric capacity per 1 cm ^{2 of the} positive electrode of the positive electrode for a nonaqueous electrolyte secondary battery is not particularly limited, but can be controlled by the weight of the positive electrode formed per unit area of the current collector foil substrate. For example, it can control by the coating thickness at the time of the above-mentioned slurry application for positive electrodes.

[Nonaqueous electrolyte secondary battery]
The positive electrode and the negative electrode of the nonaqueous electrolyte secondary battery of the present invention may have a form in which the same electrode is formed on both surfaces of a current collector foil substrate (current collector). It may be a form in which the negative electrode is formed on the surface, that is, a bipolar electrode.

  The nonaqueous electrolyte secondary battery of the present invention may be one obtained by winding a separator disposed between the positive electrode side and the negative electrode side, or may be a laminate (laminate). The positive electrode, the negative electrode, and the separator contain a nonaqueous electrolyte that is responsible for lithium ion conduction. Accordingly, examples of the nonaqueous electrolyte secondary battery include a lithium ion secondary battery.

  The non-aqueous electrolyte secondary battery of the present invention may be wound or laminated with a laminate film after the laminate is wound, or may be rectangular, elliptical, cylindrical, coin-shaped, button-shaped, or sheet-shaped. It may be packaged with a metal can. The exterior may be provided with a mechanism for releasing the generated gas. The number of stacked layers can be stacked until a desired voltage value and battery capacity are exhibited.

  The nonaqueous electrolyte secondary battery of the present invention can be an assembled battery connected in series or in parallel as appropriate depending on the desired size, capacity, and voltage. In the assembled battery, it is preferable that a control circuit is attached to the assembled battery in order to confirm the state of charge of each battery and improve safety.

(Positive electrode)
The positive electrode for a non-aqueous electrolyte secondary battery described above can be used for the positive electrode. The positive electrode for a nonaqueous electrolyte secondary battery can be obtained by applying a slurry for positive electrode containing the carbon material / resin composite material of the present invention on a current collector foil substrate and drying it. Therefore, the nonaqueous electrolyte secondary battery including such a positive electrode is excellent in battery characteristics such as output characteristics.

(Negative electrode)
Although it does not specifically limit as a negative electrode, The thing containing negative electrode active materials, such as natural graphite, artificial graphite, a metal oxide, lithium titanate, or a silicon type, can be used.

(Separator)
The separator may be any structure as long as it is installed between the positive electrode and the negative electrode described above and can be insulative and include a nonaqueous electrolyte described later. Examples of the material of the separator include nylon, cellulose, polysulfone, polyethylene, polypropylene, polybutene, polyacrylonitrile, polyimide, polyamide, polyethylene terephthalate, or a woven fabric, nonwoven fabric, microporous membrane, etc., which is a combination of two or more of them. Can be mentioned.

  The separator may contain various plasticizers, antioxidants, flame retardants, or may be coated with a metal oxide or the like.

  Although the thickness of a separator is not specifically limited, It is preferable that they are 5 micrometers or more and 100 micrometers or less. When the thickness of the separator is less than 5 μm, the positive electrode and the negative electrode may contact each other. When the thickness of the separator is greater than 100 μm, the resistance of the battery may increase. From the viewpoint of further improving economy and handleability, the thickness of the separator is more preferably 10 μm or more and 50 μm or less.

(Nonaqueous electrolyte)
The non-aqueous electrolyte used in the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, but high electrolytes such as gel electrolyte, polyethylene oxide, and polypropylene oxide impregnated in a polymer with an electrolyte solution in which a solute is dissolved in a non-aqueous solvent are used. Molecular solid electrolytes or inorganic solid electrolytes such as sulfide glass and oxynitride can be used.

  As the non-aqueous solvent, it is preferable to include a cyclic aprotic solvent and / or a chain aprotic solvent because the solute described later is more easily dissolved. Examples of the cyclic aprotic solvent include cyclic carbonates, cyclic esters, cyclic sulfones, and cyclic ethers. Examples of the chain aprotic solvent include chain carbonate, chain carboxylic acid ester, chain ether and the like. In addition to the above, a solvent generally used as a solvent for nonaqueous electrolytes such as acetonitrile may be used. More specifically, dimethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyl lactone, 1,2-dimethoxyethane, sulfolane, dioxolane, propion For example, methyl acid can be used. These solvents may be used alone or in combination of two or more. However, it is preferable to use a solvent in which two or more kinds are mixed from the viewpoint of further easily dissolving a solute described later and further enhancing the conductivity of lithium ions.

The solute is not particularly _limited, it is preferably _{LiClO 4, LiBF 4, LiPF 6} , LiAsF 6, LiCF 3 SO 3, LiBOB (Lithium Bis (Oxalato) Borate), or _LiN (SO 2 _{CF 3)} is ₂ . In this case, it can be dissolved more easily by a solvent.

  The concentration of the solute contained in the electrolytic solution is preferably 0.5 mol / L or more and 2.0 mol / L or less. If the concentration of the solute is less than 0.5 mol / L, desired lithium ion conductivity may not be exhibited. On the other hand, if the concentration of the solute is higher than 2.0 mol / L, the solute may not dissolve further. The nonaqueous electrolyte may contain a trace amount of additives such as a flame retardant and a stabilizer.

  Next, the present invention will be clarified by giving specific examples and comparative examples of the present invention. In addition, this invention is not limited to a following example.

Example 1
Production of carbon materials / resin composite materials;
1 g of expanded graphite (trade name “PF powder 8” manufactured by Toyo Tanso Co., Ltd.), 5 g of polyethylene glycol (trade name “PEG-600” manufactured by Sanyo Kasei Co., Ltd.) and 30 g of pure water were mixed to obtain a mixture. . Next, the mixture was subjected to ultrasonic treatment for 5 minutes in an intensity memory 9 8 times using an ultrasonic crusher (trade name “Astrason XL” manufactured by MISONIX). Ultrasonic treatment refined and dispersed expanded graphite and adsorbed polyethylene glycol (PEG) to expanded graphite. In this way, a composition in which polyethylene glycol was adsorbed on expanded graphite was prepared.

  Next, the composition was heat-dried at a temperature of 150 ° C. for 1.5 hours to obtain a dried product. Thereafter, the obtained dried product was further heated to a temperature of 400 ° C. under a nitrogen atmosphere (oxygen concentration of 0.1% or less) and maintained at a temperature of 400 ° C. for 2 hours. Thereby, the polyethylene glycol in the dried product was pyrolyzed, and the expanded graphite was peeled off. As described above, a carbon material / resin composite material that is a resin-retained partially exfoliated graphite was obtained.

(Example 2)
Production of carbon materials / resin composite materials;
5 g of expanded graphite (trade name “PF powder 8” manufactured by Toyo Tanso Co., Ltd.), 200 g of pure water, and 0.2 g of sodium carboxymethyl cellulose (ALDRICH, weight average molecular weight Mw: 250,000) are mixed, A mixture was obtained. Next, using the ultrasonic crusher (trade name “UH-600SR”, manufactured by SMT Co., Ltd.), the mixture is subjected to ultrasonic treatment for 4 hours at an S value of 6 on the power monitor, and the graphite dispersion liquid. Was made. While stirring the obtained graphite dispersion at 6,000 rpm with a homomixer (manufactured by Special Chemicals Co., Ltd., product number “Homoxar MARKII f-model”), a vinyl acetate emulsion (manufactured by Nippon Carbite Industries, Ltd., trade name “Nicazole CL- 101 ") 100 g was added. After stirring for 30 minutes, the vinyl acetate emulsion was adsorbed on the expanded graphite. In this way, a composition in which the vinyl acetate emulsion was adsorbed on the expanded graphite was prepared.

  Next, the composition was heat-dried at 120 ° C. for 1.5 hours and 150 ° C. for 1.5 hours to obtain a dried product. Thereafter, the obtained dried product was further heated to a temperature of 430 ° C. under a nitrogen atmosphere (oxygen concentration of 0.1% or less) and maintained at a temperature of 430 ° C. for 4 hours. Thereby, the vinyl acetate emulsion in the composition was thermally decomposed, and the expanded graphite was peeled off. Thereby, a carbon material / resin composite material which is a resin-retained partially exfoliated graphite was obtained.

(Comparative Example 1)
160 g of polyvinyl acetate (manufactured by Denki Kagaku Kogyo Co., Ltd., product number “Sacnol SN-04T”, polymerization degree 500-700) was dissolved in tetrahydrofuran to obtain a 33.3% by weight solution of polyvinyl acetate. To this polyvinyl acetate solution, 8 g of expanded graphite (trade name “PF powder 8” manufactured by Toyo Tanso Co., Ltd.) and ADCA (trade name “AC # R-K3” manufactured by Eiwa Kasei Co., Ltd., thermal decomposition temperature: 210 ° C.) 16 g was added to obtain a mixture.

  Next, the mixture was irradiated with ultrasonic waves at 100 W and a transmission frequency of 28 kHz for 5 hours using an ultrasonic treatment device (manufactured by Honda Electronics Co., Ltd.). Thereby, a composition in which the expanded graphite was dispersed in polyvinyl acetate was obtained. The composition was maintained at a temperature of 80 ° C. for 2 hours and then at a temperature of 110 ° C. for 1 hour. Thereafter, it was maintained at a temperature of 150 ° C. for 1 hour to obtain a sheet-like composition in which tetrahydrofuran was dried. Furthermore, the sheet-like composition was coarsely pulverized by a pulverizer to obtain a powdery composition in which polyvinyl acetate was adsorbed on expanded graphite. Thereafter, the temperature was maintained at 230 ° C. for 2 hours. Thereby, the ADCA was thermally decomposed and foamed in the powdery composition.

  Next, the heating process maintained at the temperature of 450 degreeC for 2 hours was implemented, and the carbon material and the resin composite material were obtained.

(Evaluation)
Raman measurement;
The carbon material / resin composite material obtained in Examples and Comparative Examples is dispersed in a glass plate, and a high-speed laser Raman microscope (manufactured by Nanophoton, product number “Raman touch”) is used for the region dispersed in fine powder. The imaging Raman was measured under the following measurement conditions.

[Measurement condition]
Laser: 531.8nm, output 100%
Measurement range: 3100 cm ^{−1 to} 700 cm ⁻¹
Objective lens: 100 times Aperture: 50 μm slit Exposure time: 60 seconds / line (measurement time: 1 hour)

  The data obtained above is analyzed at any three locations (range: 2.5 μm × 1.2 μm) for each carbon material / resin composite material using analysis software (Nanophoton, product name “RAMAN Viewer”). Went. Thereby, the intensities of the G band and the D band and the half widths of the G band and the D band were obtained. Further, the D / G ratio, the peak intensity of the G band / the half width of the G band, and A / B were calculated. A is the ratio of the peak intensity in the G band to the full width at half maximum. B is the ratio of the peak intensity in the D band to the full width at half maximum. The average value of the three locations calculated in this manner was used as the value of each carbon material / resin composite material.

TG / DTA measurement;
About 2 mg of the carbon material / resin composite material obtained in Examples and Comparative Examples was weighed on a Pt pan. About the measured carbon material / resin composite material, using a differential heat / thermogravimetric simultaneous measurement device (product number “TG / DTA6300” manufactured by SII), 10 ° C./min from 30 ° C. to 1000 ° C. in an air atmosphere. Measurement was performed under the condition of heating at a speed. In the obtained DTA curve, the number of exothermic peaks existing in the range of 300 ° C. or higher and 900 ° C. or lower was determined.

BET specific surface area measurement;
With respect to 100 mg of the carbon material / resin composite material obtained in Examples and Comparative Examples, the BET specific surface area was measured using a specific surface area measurement device (manufactured by Shimadzu Corporation, product number “ASAP-2000”).

Powder resistance;
About 100 mg of carbon materials / resin composite materials obtained in Examples and Comparative Examples, 4 kN, 8 kN, 12 kN, using a low resistivity meter (product number “Loresta-GX LMCP-T700” manufactured by Mitsubishi Chemical Analytech Co., Ltd.) The volume resistivity of the powder was measured under a load of 16 kN. The volume resistivity obtained in this measurement was plotted on the vertical axis and the density was plotted on the horizontal axis, and an approximate expression was obtained with an exponential function for each sample. From the obtained approximate expression, the volume resistivity (Ω · cm) of each sample at a density of 1 (g / cc) was determined.

Evaluation of dispersibility:
10 mg of the carbon material / resin composite material obtained in Examples and Comparative Examples is put in a container containing 40 g of ethanol, and is used with an ultrasonic treatment device (manufactured by Honda Electronics Co., Ltd.) at 100 W and an oscillation frequency of 28 kHz. Ultrasound was irradiated for minutes. The dispersion state at that time was visually observed, and when no aggregate was present, it was judged that the dispersibility was good (◯).

  The results are shown in Table 1 below.

Evaluation of battery characteristics;
Using the carbon material / resin composite material obtained in Examples 1 and 2 and Comparative Example 1, batteries for lithium ion secondary battery experiments were prepared, and battery characteristics (output characteristics) were evaluated.

(Manufacture of positive electrode)
The carbon material / resin composite material obtained in Examples 1 and 2 and Comparative Example 1 was added to 92 parts by weight of LiCoO ₂ as an active material, respectively, and a binder (PVdF, solid content concentration) was added. 12 wt%, NMP solution) was mixed so that the solid content was 4 parts by weight, and NMP was appropriately added to prepare a positive electrode slurry. As an active material, a product name “Lithium cobalt (III) oxide” manufactured by ALDRICH was used.

  Next, after coating this positive electrode slurry on an aluminum foil (20 μm), the solvent was removed by a blowing oven at 120 ° C. for 1 hour. Then, it vacuum-dried on 120 degreeC and the conditions for 12 hours, and obtained the electrode sheet.

  The obtained electrode sheet was roll-pressed under the condition of a temperature of 25 ° C. by an ultra-small desktop roll press machine manufactured by Hosen Co., Ltd., and then punched out into a circular shape so as to have a diameter of 14 mm. A positive electrode was obtained.

(Electrode density)
The electrode density was determined by the following formula. The results are shown in Table 2 below.

Electrode density (g / cm ³ ) = electrode weight excluding current collector and binder resin (g) / electrode volume excluding current collector (cm ³ )

  Next, using the positive electrode of the sheet-like lithium ion secondary battery obtained above, a battery for lithium ion secondary battery experiment was prepared as follows, and the charge / discharge characteristics were evaluated.

  The positive electrode of the lithium ion secondary battery was dried under vacuum at 110 ° C. for 4 hours. After drying, a lithium ion secondary battery experimental battery was produced using this positive electrode in a glove box sprayed with argon gas.

  The structure of the lithium ion secondary battery experimental battery is schematically shown in an exploded perspective view in FIG.

As shown in FIG. 1, between the negative electrode body 1 and the positive electrode body 2, the negative electrode 3, the separator 4, the electrode guide 5, the positive electrode 6 obtained as described above, the electrode presser 7, A spring 8 was laminated. As the negative electrode 3, a lithium metal piece having a diameter of 16 mm was used. For the separator 4, a resin film (manufactured by Sekisui Chemical Co., Ltd., trade name “Esfino”) was used. Further, as the electrolytic solution, 1 mol / L of _{LiBF 4 (EC: DEC = 1} : 1v / v%) of the electrolyte solution (manufactured by Kishida Chemical Co., Ltd.) was used.

  In the lithium ion secondary battery experimental battery assembled as described above, the voltage was charged from 3.1 V to 4.25 V at a charge rate of 0.05 C. The voltage was maintained for 2 hours after reaching 4.25 V, and then rested for 1 minute. Next, the battery was discharged from 4.25V to 3.1V at a discharge rate of 0.05C. After the discharge, it was paused for 1 minute.

  The cycle consisting of the above charging and discharging was repeated 5 times. Next, the charge / discharge rate was changed to 0.1 C, and charging and discharging were performed for one cycle. Next, the charge / discharge rate was changed to 0.2C, and charging and discharging were performed for one cycle. Subsequently, the charge / discharge rate was changed to 0.5C, 1.0C, and 2.0C, and charging and discharging were performed for one cycle. The output characteristics were calculated from the value of the discharge capacity of 2C, assuming that the value of the discharge capacity at 0.2C at that time was 100%. The results are shown in Table 2 below.

DESCRIPTION OF SYMBOLS 1 ... Negative electrode body 2 ... Positive electrode body 3 ... Negative electrode 4 ... Separator 5 ... Electrode guide 6 ... Positive electrode 7 ... Electrode presser 8 ... Spring

Claims (9)

A carbon material / resin composite material including a carbon material and a resin,
The BET specific surface area of the carbon material / resin composite material is 50 m ² / g or more and 2500 m ² / g or less,
When the Raman spectrum of the carbon material / resin composite material is measured by Raman spectroscopy, the D / G ratio, which is the peak intensity ratio between the D band and G band of the Raman spectrum, is 0.2 or less. Material / resin composite material. A carbon material / resin composite material including a carbon material and a resin,
The BET specific surface area of the carbon material / resin composite material is 50 m ² / g or more and 2500 m ² / g or less,
A carbon material / resin composite material having a ratio of a peak intensity to a half-value width of 3.0 or more in a G band of the Raman spectrum when a Raman spectrum of the carbon material / resin composite material is measured by Raman spectroscopy. A carbon material / resin composite material including a carbon material and a resin,
The BET specific surface area of the carbon material / resin composite material is 50 m ² / g or more and 2500 m ² / g or less,
When the Raman spectrum of the carbon material / resin composite material is measured by Raman spectroscopy, the D / G ratio, which is the peak intensity ratio between the D band and G band of the Raman spectrum, is 0.2 or less,
A carbon material / resin composite material in which the ratio of the peak intensity to the full width at half maximum is 3.0 or more in the G band of the Raman spectrum.   When the Raman spectrum of the carbon material / resin composite material is measured by Raman spectroscopy, the ratio of the peak intensity in the G band of the Raman spectrum to the full width at half maximum is A, and the half width of the peak intensity in the D band of the Raman spectrum. The carbon material / resin composite material according to any one of claims 1 to 3, wherein the ratio A / B is 8.0 or more and 100.0 or less when the ratio to B is B.   The differential heat analysis of the carbon material / composite material at a temperature rising rate of 10 ° C / min has two exothermic peaks in a temperature range of 300 ° C or higher and 900 ° C or lower. Carbon material / resin composite material according to item.   The carbon material / resin composite material according to any one of claims 1 to 5, wherein the carbon material is exfoliated graphite.   The carbon material / resin according to any one of claims 1 to 6, wherein the carbon material is a partially exfoliated exfoliated graphite having a graphite structure and a structure in which graphite is partially exfoliated. Composite material.   The carbon material / resin composite material according to claim 1, wherein the resin is a polyether.   The carbon material / resin composite material according to claim 8, wherein the polyether is polyethylene glycol.

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