WO2022102693A1

WO2022102693A1 - Conductive aid for non-aqueous electrolyte secondary batteries, positive electrode for non-aqueous electrolyte secondary batteries, and non-aqueous electrolyte secondary battery

Info

Publication number: WO2022102693A1
Application number: PCT/JP2021/041478
Authority: WO
Inventors: 優奈國澤; 裕樹澤田; 浩樹増田
Original assignee: 積水化学工業株式会社
Priority date: 2020-11-13
Filing date: 2021-11-11
Publication date: 2022-05-19
Also published as: TW202230858A; JPWO2022102693A1

Abstract

Provided is a conductive aid for non-aqueous electrolyte secondary batteries which is capable of improving safety and suppressing a temperature increase during high-current charging/discharging of a non-aqueous electrolyte secondary battery.　A conductive aid which contains a resin and a carbon material having a graphene layer structure, and is to be used in non-aqueous electrolyte secondary batteries, wherein: a obtained via formula (1) satisfies 3<a≤100 and b obtained via formula (2) satisfies 20≤b≤100 when the amount of resin contained in the conductive aid is x0 wt%, the BET specific surface area of the conductive aid is y0m2/g, the amount of resin contained in the conductive aid after heating said conductive aid for five hours at 600°C is x1 wt%, and the BET specific surface area of the conductive aid after heating said conductive aid for five hours at 600°C is y1m2/g; and the number of particles of the conductive aid in a fluid dispersion is 15 million particles/mgC or higher when obtaining the fluid dispersion by dispersing the conductive aid in N-methyl-2-pyrrolidone.　Formula (1): a=(y0-y1)/(x0-x1). Formula (2): b=y0-(y0-y1)x0/(x0-x1)

Description

Conductive aid for non-aqueous electrolyte secondary batteries, positive electrode for non-aqueous electrolyte secondary batteries, and non-aqueous electrolyte secondary batteries

The present invention relates to a conductive auxiliary agent for a non-aqueous electrolyte secondary battery, and a positive electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery using the conductive auxiliary agent for the non-aqueous electrolyte secondary battery.

In recent years, research and development of non-aqueous electrolyte secondary batteries have been actively carried out for mobile devices, hybrid vehicles, electric vehicles, household power storage applications, etc. In particular, in applications for hybrid automobiles and electric automobiles, charging / discharging with a large current is required.

However, when the non-aqueous electrolyte secondary battery is charged and discharged with a large current, the secondary battery itself may generate heat and ignite. This heat generation may be caused by a large electron resistance or ion diffusion resistance, which are resistances at the positive electrode of the secondary battery. Therefore, for the purpose of reducing the resistance in the positive electrode of the secondary battery, a carbon material such as graphite may be used as the conductive auxiliary agent for the positive electrode of the secondary battery. However, graphite can reduce electron resistance because it exhibits good electron conductivity, but because it is a material having a two-dimensional spread, it inhibits the diffusion of ions such as lithium ions and battery resistance. There is a problem that the number increases.

In this regard, Patent Document 1 below discloses a lithium ion secondary battery provided with an electrode using conductive auxiliary agent particles having voids. Patent Document 1 describes that a sufficient amount of electrolytic solution can be retained in the vicinity of the active material particles by using the conductive auxiliary agent particles having voids.

Japanese Patent No. 5501137

However, even when the conductive auxiliary agent particles as in Patent Document 1 are used, it is difficult to achieve both the improvement of the holding property of the electrolytic solution and the improvement of the electronic conductivity at a high level. Therefore, there is a problem that the battery resistance cannot be sufficiently lowered and heat generation during charging / discharging with a large current cannot be suppressed.

An object of the present invention is a conductive auxiliary agent for a non-aqueous electrolyte secondary battery, which can suppress a temperature rise during charging and discharging of a non-aqueous electrolyte secondary electric current at a large current and can enhance safety. Another object of the present invention is to provide a positive electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery using the conductive auxiliary agent for the non-aqueous electrolyte secondary battery.

The conductive auxiliary agent for a non-aqueous electrolyte secondary battery according to the present invention is a conductive auxiliary agent used for a positive electrode of a non-aqueous electrolyte secondary battery, and contains a carbon material having a graphene laminated structure and a resin, and is said to be conductive. The amount of resin contained in the auxiliary agent is x0% by weight, the BET specific surface area of the conductive auxiliary agent is _y0 ^{m 2} _/ g, and the conductive auxiliary agent is heated at 600 ° C. for 5 hours before becoming the conductive auxiliary agent. When the amount of the resin contained is x ₁ % by weight and the BET specific surface area of the conductive auxiliary agent after heating the conductive auxiliary agent at 600 ° C. for 5 hours is y ₁ m ² / g, the following formula (1) 3 <a ≦ 100 is satisfied, b obtained by the following formula (2) satisfies 20 ≦ b ≦ 100, and the conductive auxiliary agent is dispersed and dispersed in N-methyl-2-pyrrolidone. When the liquid is obtained, the number of particles of the conductive auxiliary agent in the dispersion liquid is 1500 million / mgC or more.

a = (y ₀ -y ₁ ) / (x ₀ -x ₁ ) ... Equation (1)
b = y _0- (y ₀ -y ₁ ) x ₀ / (x ₀ -x ₁ ) ... Equation (2)

In a specific aspect of the conductive auxiliary agent for a non-aqueous electrolyte secondary battery according to the present invention, the x ₀ is 2 or more and 20 or less.

In another specific aspect of the conductive auxiliary agent for a non-aqueous electrolyte secondary battery according to the present invention, the _y0 is 25 or more and 200 or less.

In still another specific aspect of the conductive auxiliary agent for a non-aqueous electrolyte secondary battery according to the present invention, when the conductive auxiliary agent is dispersed in N-methyl-2-pyrrolidone to obtain a dispersion liquid, the dispersion liquid is obtained. Among them, the 50% particle size (D50) in the cumulative particle size distribution based on the volume of the conductive auxiliary agent is 0.1 μm or more and 5 μm or less.

In yet another specific aspect of the conductive auxiliary agent for a non-aqueous electrolyte secondary battery according to the present invention, the carbon material is partially peelable flaky graphite having a structure in which graphite is partially peeled off.

The positive electrode for a non-aqueous electrolyte secondary battery according to the present invention contains a positive electrode active material and a conductive auxiliary agent for a non-aqueous electrolyte secondary battery configured according to the present invention.

The non-aqueous electrolyte secondary battery according to the present invention includes a positive electrode for a non-aqueous electrolyte secondary battery configured according to the present invention.

According to the present invention, a conductive auxiliary agent for a non-aqueous electrolyte secondary battery, which can suppress a temperature rise during charging and discharging of a non-aqueous electrolyte secondary battery with a large current and can improve safety, Further, it is possible to provide a positive electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery using the conductive auxiliary agent for the non-aqueous electrolyte secondary battery.

FIG. 1 is a schematic view showing an example of a resin residual type partially peeled thin-section graphite. FIG. 2 is a schematic diagram showing an example of partially peeled thin-section graphite that has been activated. FIG. 3 is a diagram showing the relationship between the amount of residual resin and the BET specific surface area in the partially peeled thin-section graphite.

Hereinafter, the details of the present invention will be described.

[Conductive aid for non-aqueous electrolyte secondary batteries]
The conductive auxiliary agent for a non-aqueous electrolyte secondary battery of the present invention (hereinafter, also referred to as a conductive auxiliary agent) is a conductive auxiliary agent used for a positive electrode of a non-aqueous electrolyte secondary battery. The conductive auxiliary agent contains a carbon material having a graphene laminated structure and a resin. The conductive auxiliary agent is preferably a composite of a carbon material having a graphene laminated structure and a resin.

In the present invention, in the formula: y = ax + b, a obtained by the following formula (1) satisfies 3 <a ≦ 100, and b obtained by the following formula (2) satisfies 20 ≦ b ≦ 100. ..

In the formulas (1) and (2), the amount of the resin contained in the conductive auxiliary agent is x0% by weight, and the BET specific surface area of the conductive auxiliary agent is _y0 ^{m 2} _/ g. Further, the amount of resin contained in the conductive auxiliary agent after heating the conductive auxiliary agent at 600 ° C. for ₅ hours is x1% by weight, and the BET specific surface area after heating the conductive auxiliary agent at 600 ° C. for 5 hours is y. It shall be ₁ m ² / g. In addition, x ₁ may be 0% by weight.

The amount of resin contained in the conductive auxiliary agent is calculated by measuring the weight change with heating temperature by thermogravimetric analysis (hereinafter referred to as TG) and obtaining the weight change with respect to the weight of the conductive auxiliary agent as a percentage. can do. Further, the BET specific surface area of the conductive auxiliary agent can be measured from the adsorption isotherm of nitrogen in accordance with the BET method. As the measuring device, for example, a product number "ASAP-2000" manufactured by Shimadzu Corporation can be used.

Further, in the present invention, when the above-mentioned conductive auxiliary agent is dispersed in N-methyl-2-pyrrolidone (hereinafter, also referred to as NMP) to obtain a dispersion liquid, the particles of the conductive auxiliary agent in the obtained dispersion liquid are obtained. The number is 1500 million / mgC or more.

The dispersion can be obtained, for example, by diluting the conductive auxiliary agent with NMP to adjust the concentration to a concentration of 30 ppm to 50 ppm, and then subjecting it to ultrasonic treatment for 1 hour. Further, the number of particles of the conductive auxiliary agent (carbon material) can be obtained by calculation using the obtained NMP dispersion liquid, for example, from the particle concentration obtained by measuring with a flow particle image analyzer manufactured by Simex. .. When the number of particles is A / mgC, the particle concentration obtained from the measurement is X / μL, the concentration of the diluted conductive auxiliary agent dispersion is Yμg / g, and the specific gravity of NMP is Zg / cc. , The number of particles A / mgC is obtained from the following formula (3). The concentration of the conductive auxiliary agent dispersion liquid is Y μg / g, when the weight of the conductive auxiliary agent contained in the dispersion liquid is Y'μg and the weight of the entire dispersion liquid is Y''g. Obtained from 4). For example, when the concentration of the conductive auxiliary agent is as small as several tens of ppm in the NMP dispersion used in the measurement, an approximation of solution specific density ≈ NMP specific gravity can be used.

A = X / (Y × Z)… Equation (3)
Y = Y'/ Y'' ... Equation (4)

In the conductive auxiliary agent for a non-aqueous electrolyte secondary battery of the present invention, since a in the above formula (1) and b in the above formula (2) are within the above range, BET is used even when a small amount of resin is used. The specific surface area can be increased. Therefore, since the amount of the resin having a large resistance can be reduced, the electron conductivity of the carbon material having the graphene laminated structure is unlikely to decrease. Further, since the BET specific surface area can be increased, the holding property of the electrolytic solution can be enhanced, and the diffusivity of ions such as lithium ions can be enhanced. Further, since the number of particles of the carbon material measured by the above method is at least the above lower limit value, the diffusivity of ions such as lithium ions can be enhanced from this point as well. Therefore, since the conductive auxiliary agent for a non-aqueous electrolyte secondary battery of the present invention is excellent in both electron conductivity and ion diffusivity, the battery resistance of the non-aqueous electrolyte secondary battery can be effectively reduced. Therefore, it is possible to suppress the temperature rise during charging / discharging of the non-aqueous electrolyte secondary electric current with a large current, and it is possible to improve the safety.

In the present invention, a (slope) in the above formula (1) is more than 3, preferably 4 or more, more preferably 5 or more, 100 or less, preferably 80 or less, and more preferably 70 or less. When a in the above formula (1) exceeds the above lower limit value, the BET specific surface area can be further increased, so that the electrolyte retention property can be further improved and the diffusivity of ions such as lithium ions can be further improved. It can be further enhanced. Further, when a in the above formula (1) is not more than the above upper limit value, the decomposition reaction of the non-aqueous electrolyte secondary battery with the electrolytic solution can be made more difficult to occur.

In the present invention, b (intercept) in the above formula (2) is 20 or more, preferably 25 or more, more preferably 30 or more, 100 or less, preferably 90 or less, and more preferably 80 or less. When b in the above formula (2) is at least the above lower limit value, the BET specific surface area can be further increased, so that the electrolyte retention property can be further improved and the diffusivity of ions such as lithium ions can be improved. It can be further enhanced. Further, when b in the above formula (2) is not more than the above upper limit value, the decomposition reaction of the non-aqueous electrolyte secondary battery with the electrolytic solution can be made more difficult to occur.

In the present invention, x ₀ (resin amount) in the above formulas (1) and (2) is preferably 2 (% by weight) or more, more preferably 5 (% by weight) or more, and further preferably 8 (weight). %) Or more, preferably 35 (% by weight) or less, more preferably 30 (% by weight) or less, still more preferably 20 (% by weight) or less. When the above x ₀ is at least the above lower limit value, the electrolyte retention property can be further enhanced, and the diffusivity of ions such as lithium ions can be further enhanced. Further, when the above x ₀ is not more than the above upper limit value, the battery resistance of the non-aqueous electrolyte secondary battery can be further reduced.

In the present invention, y ₀ (BET specific surface area) in the above formulas (1) and (2) is preferably 20 (m ² / g) or more, more preferably 25 (m ² / g) or more, preferably 25 (m 2 / g) or more. Is 500 (m ² / g) or less, more preferably 300 (m ² / g) or less, still more preferably 200 (m ² / g) or less. When the y ₀ is equal to or greater than the lower limit, the electrolyte retention property can be further enhanced, and the diffusivity of ions such as lithium ions can be further enhanced. Further, in this case, the contact point with the active material can be further sufficiently secured. Further, when the y ₀ is not more than the upper limit value, the handleability can be further improved.

In the present invention, the number of particles of the conductive auxiliary agent measured by the above method is preferably 3000 million / mgC or more, more preferably 4000 million / mgC or more, still more preferably 5000 million / mgC or more. Is. In this case, the diffusivity of ions such as lithium ions can be further enhanced. The upper limit of the number of particles of the carbon material measured by the above method is not particularly limited, but is, for example, 50,000 million particles / mgC or less.

Further, the 50% particle size (D50) in the cumulative particle size distribution based on the volume of the conductive auxiliary agent is preferably 0.1 μm or more, more preferably 0.3 μm or more, preferably 5 μm or less, and more preferably 3 μm or less. When the particle size of the conductive auxiliary agent is within the above range, the battery resistance of the non-aqueous electrolyte secondary battery can be further effectively reduced.

The particle size may be measured, for example, by using an NMP dispersion obtained by diluting the conductive auxiliary agent with NMP to adjust the concentration to 800 ppm to 1000 ppm and then applying ultrasonic treatment for 1 hour. can. Further, the particle size can be measured by using the obtained NMP dispersion liquid, for example, by a laser diffraction / scattering type particle size distribution measuring device manufactured by Microtrac Bell.

The conductive auxiliary agent may be added as a powder at the time of producing the positive electrode, or may be added as, for example, an NMP dispersion liquid in order to improve the handling property.

In the present invention, examples of the carbon material having a graphene laminated structure include graphite and flaky graphite. Whether or not it has a graphene laminated structure is determined by a peak near 2θ = 26 ° (derived from the graphene laminated structure) when the X-ray diffraction spectrum of the carbon material is measured using CuKα rays (wavelength 1.541 Å). It can be confirmed by whether or not the peak) is observed. The X-ray diffraction spectrum can be measured by wide-angle X-ray diffraction. As the X-ray diffractometer, for example, SmartLab (manufactured by Rigaku Co., Ltd.) can be used.

The shape of the carbon material is not particularly limited, and examples thereof include a shape that spreads in two dimensions, a spherical shape, a fibrous shape, and an indefinite shape. The shape of the carbon material is preferably a shape that spreads two-dimensionally. Examples of the shape spreading in two dimensions include a scale-like shape or a plate-like shape (flat plate shape). When having such a two-dimensionally expanding shape, electron conductivity can be further enhanced. Above all, the shape of the carbon material is preferably scaly. Since the carbon material is scaly, the electron conductivity can be further enhanced.

Graphite is a laminate of multiple graphene sheets. The number of laminated graphene sheets of graphite is usually about 100,000 to 1,000,000. As the graphite, for example, natural graphite, artificial graphite, expanded graphite or the like can be used. Expanded graphite has a higher ratio of the interlayer distance between graphene layers being larger than that of ordinary graphite, and can be more preferably used as a raw material for flaky graphite.

The flaky graphite is obtained by exfoliating the original graphite, and refers to a graphene sheet laminate thinner than the original graphite. The number of graphene sheets laminated in the flaky graphite may be smaller than that of the original graphite. The flaky graphite may be flaky oxide graphite.

In the flaky graphite, the number of laminated graphene sheets is not particularly limited, but is preferably 2 or more, more preferably 5 or more, preferably 3000 or less, more preferably 1000 or less, still more preferably 500 or less. be. When the number of laminated graphene sheets is at least the above lower limit, the conductivity of the flaky graphite can be further enhanced. When the number of laminated graphene sheets is not more than the above upper limit, the specific surface area of the flaky graphite can be further increased.

Further, the flaky graphite is preferably a partially peelable flaky graphite having a structure in which graphite is partially peeled off.

As an example of the structure in which the graphite is "partially peeled off", in the graphene laminate, the graphene layers are opened from the edge to the inside to some extent, that is, a part of graphite is peeled off at the edge. In the central portion, a structure in which a graphite layer is laminated in the same manner as the original graphite or primary flaky graphite can be mentioned. Therefore, the portion where a part of graphite is peeled off at the edge is connected to the central portion. Further, the partially exfoliated thin-section graphite may include those in which the graphite at the edge is exfoliated and flaked.

In the partially peeled thin-section graphite, the graphite layer is laminated in the central portion in the same manner as the original graphite or the primary thin-section graphite. Therefore, the degree of graphitization is higher than that of conventional graphene oxide or carbon black, and the conductivity is excellent. In addition, it has a structure in which graphite is partially peeled off, so that the specific surface area is large. Therefore, the electrolyte retention property can be further improved.

In the present invention, it is preferable to use a resin residual type partially peelable flaky graphite as the conductive auxiliary agent. Hereinafter, the resin residual type partially peeled thin-section graphite will be described in detail.

(Remaining resin type partially peeled thin-section graphite)
FIG. 1 is a schematic view showing an example of a resin residual type partially peeled thin-section graphite. As shown in FIG. 1, the resin residual type partially peelable thinned graphite 10 (hereinafter, also simply referred to as simply partially peeled thinned graphite) has a structure in which the edge portion 11 is peeled off. On the other hand, the central portion 12 has a graphite structure similar to that of the original graphite or the primary flaky graphite. Further, in the edge portion 11, the resin 13 is arranged between the graphene layers that have been peeled off. Therefore, the resin residual type partially peeled thinned graphite 10 is a complex of the partially peeled thinned graphite and the resin. The resin 13 may be partially or wholly carbonized.

The number of laminated graphite layers in the partially peeled thin-section graphite is preferably 5 or more and 3000 or less, more preferably 5 or more and 1000 or less, and 5 or more and 500 or less. Is even more preferable.

When the number of laminated graphite layers is within the above range, the battery resistance of the non-aqueous electrolyte secondary battery can be reduced even more effectively.

If the number of laminated graphite layers is too small, it may not be possible to connect the active materials of each positive electrode in the positive electrode for a non-aqueous electrolytic secondary battery, which will be described later. As a result, the electron conduction path in the positive electrode may be interrupted, and the rate characteristics and cycle characteristics may deteriorate. Further, if the number of laminated graphite layers is too large, the size of one partially peeled thinned graphite becomes extremely large, and the distribution of the partially peeled thinned graphite in the positive electrode may be biased. Therefore, the electron conduction path in the positive electrode may be underdeveloped, and the rate characteristics and cycle characteristics may deteriorate.

The method for calculating the number of laminated graphite layers is not particularly limited, but it can be calculated by, for example, visually observing with a transmission electron microscope (TEM) or the like.

The resin residual type partially peelable flake graphite contains, for example, graphite or primary flake graphite and a resin, and a composition in which the resin is grafted or adsorbed to graphite or primary flake graphite is prepared. It can be obtained by thermally decomposing the resin contained in the composition. When the resin is thermally decomposed, it is thermally decomposed while a part of the resin remains.

The partially peelable thinned graphite can be produced, for example, by the same method as the method for producing a thinned graphite / resin composite material described in International Publication No. 2014/034156. That is, for example, it can be produced by going through a step of producing a composition containing graphite or primary flaky graphite and a resin, and a step of thermally decomposing the composition in an open system. However, the present invention differs from the above manufacturing method in that the ranges of a and b in the above formula (1) are adjusted by the method described later.

As the graphite, it is preferable to use expanded graphite because the graphite can be peeled off more easily. Further, the primary flaky graphite broadly includes flaky graphite obtained by exfoliating graphite by various methods. The primary flaky graphite may be a partially peelable flaky graphite. Since the primary flaky graphite is obtained by exfoliating graphite, its specific surface area may be larger than that of graphite.

Further, the graphite or primary flaky graphite used may be one that has been subjected to a thinning treatment. Examples of the device used for the thinning process include a high-pressure emulsifying device, a vacuum emulsifying device, a vacuum bead mill, and a stirring device. From the viewpoint of further increasing the number of particles, a high-pressure emulsifying device and a stirring device are particularly preferable.

The heating temperature in the thermal decomposition of the resin is not particularly limited depending on the type of resin, but can be, for example, 250 ° C to 1000 ° C. The heating time can be, for example, 20 minutes to 5 hours. Since the amount of the remaining resin can be adjusted more easily, the heating temperature is preferably 350 ° C. to 600 ° C., and the heating time is preferably 40 minutes to 3 hours. Further, the heating may be performed in the atmosphere or in an atmosphere of an inert gas such as nitrogen gas. However, from the viewpoint of further enhancing the conductivity of the obtained partially peeled thinned graphite, it is desirable to perform the above heating in an atmosphere of an inert gas such as nitrogen gas. Further, the heating step may be performed a plurality of times.

The resin is not particularly limited, but is preferably a polymer of a radically polymerizable monomer. In this case, it may be a homopolymer of one kind of radically polymerizable monomer or a copolymer of a plurality of kinds of radically polymerizable monomers. The radically polymerizable monomer is not particularly limited as long as it is a monomer having a radically polymerizable functional group.

Examples of the radically polymerizable monomer include styrene, methyl α-ethyl acrylate, methyl α-benzyl acrylate, α- [2,2-bis (carbomethoxy) ethyl] methyl acrylate, dibutyl itaconate, and dimethyl itaconate. , Α-substituted acrylic acid ester consisting of dicyclohexylitaconate, α-methylene-δ-valerolactone, α-methylstyrene, α-acetoxystyrene, glycidylmethacrylate, 3,4-epoxycyclohexylmethylmethacrylate, hydroxyethylmethacrylate, hydroxy Vinyl monomers with glycidyl groups and hydroxyl groups such as ethyl acrylates, hydroxypropyl acrylates and 4-hydroxybutyl methacrylate; vinyl monomers with amino groups such as allylamine, diethylaminoethyl (meth) acrylates and dimethylaminoethyl (meth) acrylates, methacryl Monomers with carboxyl groups such as acid, maleic anhydride, maleic acid, itaconic acid, acrylic acid, crotonic acid, 2-acryloyloxyethyl succinate, 2-methacryloyloxyethyl succinate, 2-methacryloyloxyethyl phthalic acid; Monomer having a phosphate group such as Hosmer (registered trademark) M, Hosmer (registered trademark) CL, Hosmer (registered trademark) PE, Hosmer (registered trademark) MH, Hosmer (registered trademark) PP manufactured by Unichemical Co., Ltd .; Monomers having an alkoxysilyl group such as methoxysilane and 3-methacryloxypropyltrimethoxysilane; (meth) acrylate-based monomers having an alkyl group, a benzyl group and the like can be mentioned.

Examples of the resin used include polyethylene glycol, polypropylene glycol, polyglycidyl methacrylate, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral (butyral resin), poly (meth) acrylate, polystyrene, polyester and the like.

Among the above resins, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, and polyester are particularly preferable because the BET specific surface area can be secured with a smaller amount of residual resin.

The resin type can be appropriately selected in consideration of the affinity with the solvent used.

The content of the resin before thermal decomposition fixed to graphite or primary flake graphite is preferably 0.1 part by weight or more, more preferably 0, with respect to 1 part by weight of graphite or primary flake graphite excluding the resin content. It is 3 parts by weight or more, preferably 30 parts by weight or less, and more preferably 20 parts by weight or less. When the content of the resin before thermal decomposition is within the above range, it is easier to control the content of the residual resin after thermal decomposition. Further, when the content of the resin before thermal decomposition is not more than the above upper limit value, it is more advantageous in terms of cost.

The content of the residual resin after thermal decomposition is preferably 2 parts by weight or more, more preferably 5 parts by weight or more, preferably 50 parts by weight or less, based on 100 parts by weight of the partially peelable flake graphite containing the resin content. It is preferably 20 parts by weight or less. When the content of the residual resin after thermal decomposition is at least the above lower limit value, the BET specific surface area can be further increased. Further, when the content of the residual resin after thermal decomposition is not more than the above upper limit value, the battery resistance can be further lowered.

The resin content before thermal decomposition and the amount of residual resin remaining in the partially peeled thin-section graphite shall be calculated by measuring the weight change with heating temperature by, for example, thermogravimetric analysis (hereinafter referred to as TG). Can be done.

Further, in the case of producing a complex with a positive electrode active material, the amount of resin may be reduced after producing the complex with the positive electrode active material.

As a method for reducing the amount of the resin, a method of heat treatment at a temperature equal to or higher than the decomposition temperature of the resin and lower than the decomposition temperature of the positive electrode active material is preferable. This heat treatment may be performed in the atmosphere, under an inert gas atmosphere, under a low oxygen atmosphere, or under vacuum.

The method for producing partially peeled thin-section graphite may be one in which pores are formed by performing a gas activation treatment in addition to the above-mentioned production method. Examples of gas activation treatment include steam activation, carbon dioxide activation, and oxygen activation. Of these, carbon dioxide activation is more preferable.

Further, the temperature of the gas activation treatment can be, for example, 700 ° C to 950 ° C. The holding time at that temperature can be, for example, 15 minutes to 2 hours. Among them, the temperature of the gas activation treatment is preferably 800 ° C. to 900 ° C., and the holding time at that temperature is preferably 30 minutes to 1 hour.

FIG. 2 is a diagram showing an example of partially peeled thin-section graphite that has been activated. As shown in FIG. 2, it can be seen that in the partially peeled thin-section graphite 20 that has been activated, the pores 24 are formed in the resin 23. When such pores 24 are formed, the electrolytic solution retention property can be further enhanced, and the ion diffusivity of lithium ions and the like can be further enhanced.

Further, the obtained partially peelable flaky graphite can be pulverized or classified by a mill such as a mill mixer, a blender mill, a jet mill or a ball mill, or water, methanol, ethanol, N-methyl-2-pyrrolidone ( It may be used after being placed in an organic solvent typified by NMP) and then subjected to sonication. For example, when crushing with a mixer, the particle size can be adjusted by the crushing time.

In the present invention, the ranges of a in the above formula (1) and b in the above formula (2) are adjusted when producing the partially peelable flaky graphite. The range of a in the above formula (1) and b in the above formula (2) can be adjusted, for example, by adjusting the blending amount of the resin, adjusting the firing temperature and firing time, activating treatment, or pre-thinning treatment. can. As a result, as shown by the solid line in FIG. 3, it is possible to obtain a partially peelable thinned graphite having a large BET specific surface area with respect to the amount of residual resin even when compared with the conventional partially peeled thinned graphite (broken line). can. Therefore, when such a conductive auxiliary agent which is a partially peelable fragmented graphite is used, it is excellent in both electron conductivity and ion diffusivity, so that the battery resistance of the non-aqueous electrolyte secondary battery can be effectively reduced. can.

In the present invention, when the X-ray diffraction spectrum of the mixture of the partially peeled thin section graphite and Si at a weight ratio of 1: 1 is measured, the peak ratio c / d is preferably 0.20 or more, more preferably 0.20 or more. Is 0.25 or more. The peak ratio c / d is preferably 10.0 or less, more preferably 8.0 or less, and even more preferably 5.0 or less. The above c is the height of the highest peak in the range where 2θ is 24 ° or more and less than 28 °. The above d is the height of the highest peak in the range where 2θ is 28 ° or more and less than 30 °. As Si, for example, silicon powder having φ = 100 nm or less can be used.

The X-ray diffraction spectrum can be measured by a wide-angle X-ray diffraction method. As X-rays, CuKα rays (wavelength 1.541 Å) can be used. As the X-ray diffractometer, for example, SmartLab (manufactured by Rigaku Co., Ltd.) can be used.

In the X-ray diffraction spectrum, the peak derived from the graphite structure appears near 2θ = 26.4 °. On the other hand, peaks derived from Si such as silicon powder appear in the vicinity of 2θ = 28.5 °. Therefore, the ratio c / d is the peak ratio between the peak near 2θ = 26.4 ° and the peak near 2θ = 28.5 ° (peak around 2θ = 26.4 ° / around 2θ = 28.5 °). It can be obtained from the peak of).

If the c / d is too small, the formation of the graphite structure in the partially peeled thin-section graphite itself is immature, the electron conductivity is low, and there are defects, so that the resistance value of the positive electrode increases. Battery characteristics may deteriorate.

If the above c / d is too large, the partially peeled thin-section graphite itself becomes rigid, it becomes difficult to disperse it in the positive electrode, and the electron conductivity may decrease.

The partially peeled flake graphite has a D / G ratio of 0.8 or less when the peak intensity ratio between the D band and the G band is the D / G ratio in the Raman spectrum obtained by Raman spectroscopy. It is preferably 0.7 or less, and more preferably 0.7 or less. When the D / G ratio is within this range, the conductivity of the partially peeled thin-section graphite itself can be further increased, and the amount of gas generated can be further reduced. Further, the D / G ratio is preferably 0.05 or more. When the D / G ratio is at least the above lower limit value, the amount of gas generated by the reaction with the decomposition of the electrolytic solution can be further suppressed.

[Positive electrode for non-aqueous electrolyte secondary battery]
The positive electrode for a non-aqueous electrolyte secondary battery of the present invention comprises a positive electrode active material and the above-mentioned conductive auxiliary agent for a non-aqueous electrolyte secondary battery. Therefore, it is possible to suppress the temperature rise during charging / discharging of the non-aqueous electrolyte secondary electric current with a large current, and it is possible to enhance the safety.

The positive electrode for a non-aqueous electrolyte secondary battery of the present invention (hereinafter, also simply referred to as a positive electrode) may have a general positive electrode configuration, composition, and manufacturing method, or may be a composite of a positive electrode active material and a conductive auxiliary agent. May be used.

(Positive electrode active material)
The positive electrode active material used in the present invention may be any one in which the desorption and insertion reactions of ions such as lithium ions proceed, and may be noble than the battery reaction potential of the negative electrode active material. At that time, the battery reaction may involve Group 1 or Group 2 ions. Examples of such ions include H ion, Li ion, Na ion, K ion, Mg ion, Ca ion, or Al ion. Hereinafter, the details of the system in which Li ions are involved in the battery reaction will be illustrated.

In this case, examples of the positive electrode active material include lithium metal oxide, lithium sulfide, and sulfur.

Examples of the lithium metal oxide include those having a spinel structure, a layered rock salt structure, an olivine structure, or a mixture thereof.

Examples of the lithium metal oxide having a spinel structure include lithium manganate.

Examples of the lithium metal oxide having a layered rock salt structure include lithium cobalt oxide, lithium nickel oxide, and a ternary system.

Examples of the lithium metal oxide having an olivine structure include lithium iron phosphate, lithium manganese iron phosphate, and lithium manganese phosphate.

The positive electrode active material may contain a so-called dope element. The positive electrode active material may be used alone or in combination of two or more.

The average particle size of the positive electrode active material is preferably 0.5 μm or more, more preferably 1.0 μm or more, preferably 20 μm or less, and more preferably 10 μm or less. When the average particle size of the positive electrode active material is within the above range, the battery resistance can be lowered more effectively, and the battery capacity can be further increased. The average particle size of the positive electrode active material is a value obtained by measuring the size of each particle from an SEM (scanning electron microscope) and a TEM image and calculating the average particle size. The particles may be primary particles or granulated materials in which the primary particles are aggregated.

The BET specific surface area of the positive electrode active material is preferably 0.1 m ² / g or more, preferably 50 m ² / g or less. In this case, the desired output density can be obtained more easily. The BET specific surface area can be measured by the method described above.

The content of the positive electrode active material is preferably 70% by weight or more, more preferably 75% by weight or more, preferably 98% by weight or less, and more preferably 95% by weight or less with respect to the total amount of the positive electrode material. When the content of the positive electrode active material is within the above range, the battery resistance can be lowered more effectively, and the battery capacity can be further increased.

(Conductive aid)
The conductive auxiliary agent is the above-mentioned conductive auxiliary agent for a non-aqueous electrolyte secondary battery of the present invention. The content of the conductive auxiliary agent is preferably 1.5% by weight or more, more preferably 2% by weight or more, preferably 20% by weight or less, more preferably 15% by weight, based on the total amount of the positive electrode material for the non-aqueous electrolyte secondary battery. % Or less. When the content of the conductive auxiliary agent is within the above range, the battery resistance can be lowered more effectively. Further, when the above-mentioned conductive auxiliary agent for a non-aqueous electrolyte secondary battery of the present invention is used as the first conductive auxiliary agent, a second conductive auxiliary agent different from the first conductive auxiliary agent may be further used. ..

The second conductive auxiliary agent is preferably a carbon material different from the partially peeled thinned graphite. The second conductive auxiliary agent is not particularly limited, and examples thereof include graphene, granular graphite compounds, fibrous graphite compounds, carbon black, and activated carbon. Among them, the second conductive auxiliary agent is preferably carbon black from the viewpoint of further lowering the electrolyte retention.

The graphene may be graphene oxide or reduced graphene oxide.

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

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

As these second conductive aids, one type may be used alone, or a plurality of types may be used in combination.

The BET specific surface area of the second conductive auxiliary agent is preferably 5 m ² / g or more, more preferably 10 m ² / g or more, and further preferably 25 m ² / g or more. When the BET specific surface area of the second conductive auxiliary agent is at least the above lower limit value, the electrolyte retention property of the non-aqueous electrolyte secondary battery can be further enhanced. Further, from the viewpoint of further improving the handleability at the time of producing the positive electrode, the BET specific surface area of the second conductive auxiliary agent is preferably 2500 m ² / g or less.

The first conductive auxiliary agent and the second conductive auxiliary agent can be distinguished from each other by, for example, SEM or TEM.

The second conductive auxiliary agent may have a functional group on its surface. In this case, the positive electrode can be manufactured more easily.

When the weight of the first conductive auxiliary agent is Ag and the weight of the second conductive auxiliary agent is Bg, the ratio A / B is preferably 0.01 ≦ A / B ≦ 100. When the ratio A / B is less than the above lower limit value or larger than the above upper limit value, the resistance of the positive electrode may increase.

The positive electrode for a non-aqueous electrolyte secondary battery of the present invention may be formed of a positive electrode active material, a first conductive auxiliary agent, and a second conductive auxiliary agent, but the positive electrode is made more easily. From the point of view, a binder may be included. A complex of a positive electrode active material, a first conductive auxiliary agent, and a second conductive auxiliary agent may be used.

The solid content concentration of the dispersion liquid of the first conductive auxiliary agent and the second conductive auxiliary agent (hereinafter collectively referred to as the conductive auxiliary agent) is 0.5 when the weight of the conductive auxiliary agent is 1. As mentioned above, it is preferably 1000 or less. From the viewpoint of further improving the handleability, it is more preferably 1 or more and 750 or less. Further, from the viewpoint of further enhancing the dispersibility, it is particularly preferably 2 or more and 500 or less. If the weight of the solvent is less than the above lower limit value, the conductive auxiliary agent may not be able to be dispersed to a desired dispersion state, while if it is larger than the above upper limit value, the manufacturing cost may increase.

(binder)
The positive electrode for a non-aqueous electrolyte secondary battery of the present invention may contain a binder from the viewpoint of forming the positive electrode more easily.

The binder is not particularly limited, and for example, at least one resin selected from the group consisting of polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber, polyimide, and derivatives 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 a positive electrode.

The non-aqueous solvent is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylethylketone, methyl acetate, ethyl acetate, and tetrahydrofuran. A dispersant or a thickener may be added to these.

The amount of the binder contained in the positive electrode is preferably 0.3 parts by weight or more and 30 parts by weight or less, and more preferably 0.5 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the positive electrode active material. be. When the amount of the binder is within the above range, the adhesiveness between the positive electrode active material and the conductive auxiliary agent can be maintained, and the adhesiveness with the current collector can be further enhanced.

(Method for manufacturing positive electrode)
Examples of the method for producing a positive electrode include a method for producing a positive electrode by forming a mixture of a positive electrode active material, a conductive auxiliary agent, and a binder on a current collector.

From the viewpoint of making the positive electrode even easier, it is preferable to make it as follows. First, a slurry is prepared by adding a binder solution or a dispersion liquid to the positive electrode active material and the conductive auxiliary agent and mixing them. Next, the prepared slurry is applied onto the current collector, and finally the solvent is removed to prepare a positive electrode. Further, the positive electrode may be produced after forming a complex of the positive electrode active material and the conductive auxiliary agent.

As the method for producing the above slurry, an existing method can be used. For example, a method of mixing using a mixer or the like can be mentioned. The mixer used for mixing is not particularly limited, and examples thereof include a planetary mixer, a disper, a thin film swirl type mixer, a jet mixer, and a self-public rotation type mixer.

The solid content concentration of the slurry is preferably 30% by weight or more and 95% by weight or less from the viewpoint of making coating easier. From the viewpoint of further enhancing the storage stability, the solid content concentration of the slurry is more preferably 35% by weight or more and 90% by weight or less. Further, from the viewpoint of further suppressing the production cost, the solid content concentration of the slurry is more preferably 40% by weight or more and 85% by weight or less.

The solid content concentration can be controlled by a diluting solvent. As the diluting solvent, it is preferable to use a binder solution or a solvent of the same type as the dispersion liquid. Further, another solvent may be used as long as it is compatible with the solvent.

The current collector used for the positive electrode is preferably aluminum or an alloy containing aluminum. Aluminum is not particularly limited because it is stable in a 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 is not particularly limited, but is preferably 10 μm or more and 100 μm or less. If the thickness of the current collector is less than 10 μm, it may be difficult to handle from the viewpoint of production. On the other hand, if the thickness of the current collector is thicker than 100 μm, it may be disadvantageous from an economic point of view.

The current collector may be a metal other than aluminum (copper, SUS, nickel, titanium, and alloys thereof) coated with aluminum.

The method of applying the slurry to the current collector is not particularly limited, and for example, a method of applying the slurry with a doctor blade, a die coater, a comma coater, or the like and then removing the solvent, or a method of applying the slurry with a spray and then removing the solvent. Examples thereof include a method and a method of removing the solvent after application by screen printing.

Since the method for removing the solvent is even 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 at which the solvent is removed is higher than 250 ° C., the binder may deteriorate.

The positive electrode may be compressed to a desired thickness and density. The compression is not particularly limited, but can be performed by using, for example, a roll press, a hydraulic press, or the like.

The thickness of the positive electrode after compression is not particularly limited, but is preferably 10 μm or more and 1000 μm or less. If the thickness is less than 10 μm, it may be difficult to obtain the desired capacity. On the other hand, when the thickness is thicker than 1000 μm, it may be difficult to obtain a desired output density.

The density of the positive electrode is preferably 1.0 g / cm ³ or more and 4.0 g / cm ³ or less. If it is less than 1.0 g / cm ³ , the contact with the positive electrode active material and the conductive auxiliary agent may be insufficient and the electronic conductivity may decrease. On the other hand, if it is larger than 4.0 g / cm ³ , it becomes difficult for the electrolytic solution described later to permeate into the positive electrode, and the conductivity of ions such as lithium ions may decrease.

The positive electrode preferably has an electric capacity of 0.5 mAh or more and 10.0 mAh or less per 1 cm ² of the positive electrode. If the electric capacity is less than 0.5 mAh, the size of the battery with the desired capacity may be large. On the other hand, when the electric capacity is larger than 10.0 mAh, it may be difficult to obtain a desired output density. The electric capacity per 1 cm ² of the positive electrode may be calculated by manufacturing a half cell made of lithium metal as a counter electrode after manufacturing the positive electrode and measuring the charge / discharge characteristics.

The electric capacity per 1 cm ² of the positive electrode is not particularly limited, but can be controlled by the weight of the positive electrode formed per unit area of the current collector. For example, it can be controlled by the coating thickness at the time of slurry coating described above.

[Non-water electrolyte secondary battery]
The non-aqueous electrolyte secondary battery of the present invention may be any one using a compound that promotes the insertion and desorption reaction of alkali metal ions or alkaline earth metal ions. Examples of the alkali metal ion include lithium ion, sodium ion, and potassium ion. Examples of the alkaline earth metal ion include calcium ion and magnesium ion. In particular, it can be suitably used for those using lithium ions (lithium ion secondary batteries).

(Positive electrode)
The non-aqueous electrolyte secondary battery of the present invention includes the positive electrode for the non-aqueous electrolyte secondary battery of the present invention. Therefore, it is possible to suppress the temperature rise during charging / discharging of the non-aqueous electrolyte secondary electric current with a large current, and it is possible to improve the safety.

(Negative electrode)
The negative electrode used in the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, but one containing a negative electrode active material such as natural graphite, artificial graphite, hard carbon, metal oxide, lithium titanate, or silicon-based material is used. be able to.

(Separator)
The separator used in the non-aqueous electrolyte secondary battery of the present invention may have a structure that is installed between the positive electrode and the negative electrode and is insulating and can contain the non-aqueous electrolyte described later. Examples of such a separator include nylon, cellulose, polysulfone, polyethylene, polyporopylene, polybutene, polyacrylonitrile, polyimide, polyamide, and polyethylene terephthalate. In addition, woven fabrics, non-woven fabrics, microporous membranes, etc., which are composites of two or more of these, can be mentioned.

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

The thickness of the separator is not particularly limited, but is preferably 5 μm or more and 100 μm or less. If the thickness of the separator is less than 5 μm, the positive electrode and the negative electrode may come into contact with each other. If the thickness of the separator is thicker than 100 μm, the resistance of the battery may increase. From the viewpoint of economy and handleability, it is more preferably 10 μm or more and 50 μm or less.

(Non-water electrolyte)
The non-aqueous electrolyte used in the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and for example, an electrolytic solution in which a solute is dissolved in a non-aqueous solvent can be used. Further, using a gel electrolyte in which a polymer is impregnated with an electrolytic solution in which a solute is dissolved in a non-aqueous solvent, a polymer solid electrolyte such as polyethylene oxide or polypropylene oxide, or an inorganic solid electrolyte such as sulfate glass or oxynitride is used. May be good.

The non-aqueous solvent preferably contains a cyclic aprotic solvent and / or a chain aprotic solvent because the solute described later can be 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, and chain ether.

Further, a solvent generally used as a solvent for a non-aqueous electrolyte 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, sulforane, dioxolane, propion. Methyl acid acid and the like can be used. These solvents may be used alone, or a mixture of two or more kinds of solvents may be used. However, from the viewpoint of more easily dissolving the solute described later and further enhancing the conductivity of lithium ions, it is preferable to use a solvent in which two or more kinds of solvents are mixed.

The solute is not particularly limited, but it is preferable to use LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiCF ₃ SO ₃ , LiBOB (Lithium Bis (Oxalato) Borate), or LiN (SO ₂ CF ₃ ) ₂ . .. In this case, it can be more easily dissolved with a non-aqueous 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, the 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 any more.

Further, the non-aqueous electrolyte may further contain additives such as flame retardants and stabilizers.

(Non-water electrolyte secondary battery)
The positive electrode and the negative electrode of the non-aqueous electrolyte secondary battery of the present invention may have the same electrodes formed on both sides of the current collector, and the positive electrode is formed on one side of the current collector and the negative electrode is formed on the other side of the current collector. That is, it may be a bipolar electrode.

The non-aqueous electrolyte secondary battery may be a battery in which a separator is arranged between the positive electrode side and the negative electrode side, or may be a laminated battery. The positive electrode, negative electrode and separator contain a non-aqueous electrolyte responsible for lithium ion conduction.

The non-aqueous electrolyte secondary battery may be exteriorized with a laminate film after the laminates have been squeezed or laminated, or a square, oval, cylindrical, coin-shaped, button-shaped, or sheet-shaped metal. It may be exteriorized with a can. The exterior may be equipped with a mechanism for releasing the generated gas. The number of laminated bodies is not particularly limited, and the laminated bodies can be laminated until a desired voltage value and battery capacity are exhibited.

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

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples and can be appropriately changed without changing the gist thereof.

(Example 1)
Production Example 1 of Conductive Auxiliary Agent;
First, 7 g of artificial graphite (manufactured by IMERIS, trade name "KS6L"), 22 g of a 1% aqueous solution of carboxymethyl cellulose (manufactured by CMC, Aidrich), and polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., trade name "PEG-600"). ”) 70 g (10 times with respect to graphite) was mixed to prepare a raw material composition.

Next, the above raw material composition was heat-treated with a muffle heating device (manufactured by Motoyama Co., Ltd., product number "MBA-2040D-SP") at 370 ° C. for 1 hour in a nitrogen (N ₂ ) atmosphere for the first time. A fired product (1st fired product) was obtained. Furthermore, the 1st fired product is activated by an activation experimental device (manufactured by Asahi Rika Seisakusho, product number "ARF-50KC") at 800 ° C. for 30 minutes under a carbon dioxide (CO ₂ ) atmosphere (flow rate 0.3 L / min). The activated product was obtained by doing. Finally, after a step of crushing for 3 minutes using a crusher, a conductive auxiliary agent (first conductive auxiliary agent) which is a carbon material (partially peeling type flaky graphite) having a structure in which graphite is partially peeled off. ) Was produced.

The amount of resin was calculated using TG (manufactured by Hitachi High-Tech Science Corporation, product number "STA7300") as the amount of resin whose weight was reduced in the range of 350 ° C. to 600 ° C. As a result, it was confirmed that a partially peelable flaky graphite containing 18% by weight of the resin could be produced (resin amount x ₀ = 18% by weight). Further, the BET specific surface area _y0 of the partially peelable flaky graphite was measured using a specific surface area measuring device (manufactured by Shimadzu Corporation, product number "ASAP-2000", nitrogen gas) and found to be 200 m ² / g. ..

Manufacturing example of positive electrode;
The positive electrode of Example 1 was produced as follows.

First, 10 g of N-methyl-2-pyrrolidone (NMP, manufactured by Kishida Chemical Co., Ltd., grade for LiB) was added to 2 g of carbon black as a second conductive auxiliary agent different from the above first conductive auxiliary agent for 5 hours. It was treated with an ultrasonic cleaner (manufactured by AS ONE) to prepare a carbon black dispersion (hereinafter, carbon material dispersion 1 of Example 1).

Next, 3.8 g of NMP was added to 0.2 g of partially peelable thinned graphite as the first conductive auxiliary agent produced in Production Example 1, and the treatment was performed with an ultrasonic cleaner (manufactured by AS ONE) for 5 hours. , A dispersion liquid of partially peelable thinned graphite prepared in Production Example 1 (hereinafter, a dispersion liquid 2 of a carbon material of Example 1) was prepared.

Subsequently, 8.8 g of the positive electrode active material (LiNi _0.5 Mn _0.3 Co _0.2 O ₂ (NMC), manufactured by Nippon Kagaku Co., Ltd.) and a binder (PVdF, solid content concentration 12% by weight, NMP solution) were added. 2.0 g, dispersion liquid 1 4.75 g, and dispersion liquid 2 1.0 g (10 parts by weight) were placed in an ointment container (manufactured by Mano Chemical Co., Ltd., UG 35 mL) at this mixing ratio, and an automatic revolving mixer. (Awatori Rentaro, AR-250, manufactured by Shinky Co., Ltd.) was stirred twice at 2200 rpm / min to prepare an electrode slurry. Subsequently, the electrode slurry is applied onto an Al foil (UACJ, 1N30, single gloss, 20 μm) with an applicator (clearance: 120 μm to 135 μm), dried in a blower oven at 80 ° C./8 minutes, and vacuum oven. The remaining solvent was removed under the conditions of 150 ° C./12 hours. Further, it was pressed by a hot roll press machine. Finally, vacuum drying was performed at 150 ° C. for 12 hours in a vacuum oven installed in a dry room to obtain a positive electrode. The design capacity calculated from the weight of the electrode was 1.00 ± 0.05 mAhcm ^-2 , and the electrode density calculated from the thickness was 2.95 ± 0.10 gcc ^-1 .

Manufacturing example of negative electrode;
The negative electrode was prepared as follows.

First, a binder (PVdF, solid content concentration 12% by weight, NMP solution) was mixed with 100 parts by weight of the negative electrode active material (artificial graphite) so that the solid content was 5 parts by weight to prepare a slurry. Next, the slurry was applied to a copper foil (20 μm), heated in a blower oven at 120 ° C. for 1 hour to remove the solvent, and then vacuum dried at 120 ° C. for 12 hours. Next, the slurry was also applied and dried on the back surface of the copper foil in the same manner.

Finally, a negative electrode was produced by pressing with a roll press machine. The capacity of the negative electrode was calculated from the electrode weight per unit area and the theoretical capacity (350 mAh / g) of the negative electrode active material. As a result, the capacity of the negative electrode (per one side) was 1.5 mAh / cm ² .

Manufacture of non-aqueous electrolyte secondary batteries;
First, the prepared positive electrode (electrode part: 40 mm × 50 mm), negative electrode (electrode part: 45 mm × 55 mm) and separator (polyforme-based microporous film, 25 μm, 50 mm × 60 mm) were subjected to negative electrode / separator / positive electrode / separator /. The electrodes were laminated in this order so that the capacity of the positive electrode was 200 mAh (5 positive electrodes and 6 negative electrodes). Next, aluminum tabs and nickel-plated copper tabs were vibration-welded to the positive and negative electrodes at both ends, and then placed in a bag-shaped aluminum laminate sheet, and three sides were heat-welded to the non-aqueous electrolyte secondary before filling the electrolyte. A battery was made. Further, after vacuum-drying the non-aqueous electrolyte secondary battery before filling with the electrolytic solution at 60 ° C. for 3 hours, 20 g of the non-aqueous electrolyte (ethylene carbonate / dimethyl carbonate = 1/2 volume%, LiPF ₆₁ mol / L) is added. A non-aqueous electrolyte secondary battery was prepared by sealing while reducing the pressure. The steps up to this point were carried out in an atmosphere (dry box) having a dew point of −40 ° C. or lower. Finally, after charging the non-aqueous electrolyte secondary battery to 4.25 V, it is left at 25 ° C. for 100 hours, and the gas generated in an atmosphere (dry box) having a dew point of -40 ° C. or less, and excessive electrolysis. After removing the liquid, the non-aqueous electrolyte secondary battery of Example 1 was prepared by sealing while reducing the pressure again.

(Example 2)
The same as in Example 1 except that the conductive auxiliary agent (partially peelable flake graphite) of Production Example 2 shown below was used instead of the conductive auxiliary agent (partially peelable flake graphite) of Production Example 1. A non-aqueous electrolyte secondary battery was obtained.

Production Example 2 of Conductive Auxiliary;
First, 7 g of artificial graphite (manufactured by IMERIS, trade name "KS6L"), 22 g of 1% aqueous solution of carboxymethyl cellulose (CMC, manufactured by Aidrich), and 56% aqueous solution of polyvinyl acetate (manufactured by Nippon Carbide, product number "Nicazole"). ") 62.5 g (5 times with respect to graphite) was mixed to prepare a raw material composition.

Next, the prepared raw material composition was heat-treated in a muffle heating device (manufactured by Motoyama Co., Ltd., product number "MBA-2040D-SP") at 430 ° C. for 2 hours in an _N2 atmosphere to produce the first fired product. (1st fired product) was obtained. Furthermore, the activated product is obtained by activating the 1st fired product in a CO ₂ atmosphere (flow rate 0.3 L / min) for 30 minutes at 900 ° C. using an activation experimental device (ARF-50KC manufactured by Asahi Rika Seisakusho). rice field. Finally, after a step of crushing for 3 minutes using a crusher, a conductive auxiliary agent (first conductive auxiliary agent) which is a carbon material (partially peeled thin-section graphite) having a structure in which graphite is partially peeled off. ) Was produced.

The amount of resin was calculated using TG (manufactured by Hitachi High-Tech Science Corporation, product number "STA7300") as the amount of resin whose weight was reduced in the range of 350 ° C. to 600 ° C. It was confirmed that a partially peelable flaky graphite containing 3.5% by weight of the total weight could be produced (resin amount x ₀ = 3.5% by weight). Further, the BET specific surface area _y0 of the partially peelable flaky graphite was measured using a specific surface area measuring device (manufactured by Shimadzu Corporation, product number "ASAP-2000", nitrogen gas) and found to be 95 m ² / g. ..

(Example 3)
The same as in Example 1 except that the conductive auxiliary agent (partially peelable thinned graphite) of Production Example 3 shown below was used instead of the conductive auxiliary agent (partially peeled thinned graphite) of Production Example 1. A non-aqueous electrolyte secondary battery was obtained.

Production Example 3 of Conductive Auxiliary Agent;
First, 7 g of artificial graphite (manufactured by IMERIS, trade name "KS6L"), 22 g of a 1% aqueous solution of carboxymethyl cellulose (CMC, manufactured by Aidrich), and a 56% aqueous solution of polyvinyl acetate (manufactured by Nippon Carbide, trade name "". Nikazole ”) 37.5 g (3 times with respect to graphite) was mixed to prepare a raw material composition.

Next, the above raw material composition was heat-treated in a muffle heating device (manufactured by Motoyama Co., Ltd., product number "MBA-2040D-SP") at 430 ° C. for 2 hours in an _N2 atmosphere, whereby the first fired product (1st fired product (manufactured by Motoyama). 1st fired product) was obtained. Further, the 1st fired product was heat-treated at 450 ° C. for 100 minutes in an N ₂ atmosphere containing 5% O ₂ in the same muffle heating device to obtain a second fired product (2nd fired product). Finally, after a step of crushing for 3 minutes using a crusher, a conductive auxiliary agent (first conductive auxiliary agent) which is a carbon material (partially peeled thin-section graphite) having a structure in which graphite is partially peeled off. Was produced.

The amount of resin was calculated using TG (manufactured by Hitachi High-Tech Science Corporation, product number "STA7300") as the amount of resin whose weight was reduced in the range of 350 ° C. to 600 ° C. It was confirmed that a partially peelable flaky graphite containing 10% by weight of resin could be produced with respect to the total weight (resin amount x ₀ = 10% by weight). Further, the BET specific surface area _y0 of the partially peelable flaky graphite was measured using a specific surface area measuring device (manufactured by Shimadzu Corporation, product number "ASAP-2000", nitrogen gas) and found to be 105 m ² / g. ..

(Example 4)
The same as in Example 1 except that the conductive auxiliary agent (partially peelable flake graphite) of Production Example 4 shown below was used instead of the conductive auxiliary agent (partially peelable flake graphite) of Production Example 1. A non-aqueous electrolyte secondary battery was obtained.

Production Example 4 of Conductive Auxiliary Agent;
First, a graphite dispersion prepared by mixing 30 g of artificial graphite (manufactured by IMERIS, trade name "KS6L"), 90 g of a 1% aqueous solution of carboxymethyl cellulose (manufactured by CMC, Aidrich), and 810 g of ultrapure water was prepared. A graphite pretreated product was prepared by repeating collisions 300 times at a pressure of 200 MPa with a collision-type high-pressure emulsifier.

Subsequently, 233 g of the obtained graphite pretreated product (graphite concentration 3%) and 21 g of polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., trade name "PEG-600") (3 times with respect to graphite) were mixed. A raw material composition was prepared.

Next, the above raw material composition is heat-treated at 370 ° C. for 1 hour in an _N2 atmosphere with a muffle heating device (manufactured by Motoyama Co., Ltd., trade name “MBA-2040D-SP”) to produce a first fired product. (1st fired product) was obtained. Further, the 1st fired product was heat-treated at 390 ° C. for 20 minutes in an N ₂ atmosphere containing 5% O ₂ to obtain a second fired product (2nd fired product). Finally, after a step of crushing for 3 minutes using a crusher, a conductive auxiliary agent (first conductive auxiliary agent) which is a carbon material (partially peeled thin-section graphite) having a structure in which graphite is partially peeled off. Was produced.

The amount of resin was calculated using TG (manufactured by Hitachi High-Tech Science Corporation, product number "STA7300") as the amount of resin whose weight was reduced in the range of 350 ° C. to 600 ° C. It was confirmed that a partially peelable flaky graphite containing 10% by weight of resin could be produced with respect to the total weight (resin amount x ₀ = 10% by weight). Further, the BET specific surface area _y0 of the partially peelable flaky graphite was measured using a specific surface area measuring device (manufactured by Shimadzu Corporation, ASAP-2000, nitrogen gas) and found to be 98 m ² / g.

(Example 5)
The same as in Example 1 except that the conductive auxiliary agent (partially peelable flake graphite) of Production Example 5 shown below was used instead of the conductive auxiliary agent (partially peelable flake graphite) of Production Example 1. A non-aqueous electrolyte secondary battery was obtained.

Production Example 5 of Conductive Auxiliary Agent;
First, a graphite dispersion prepared by mixing 30 g of artificial graphite (manufactured by IMERIS, trade name "KS6L"), 90 g of a 1% aqueous solution of carboxymethyl cellulose (manufactured by CMC, Aidrich), and 810 g of ultrapure water was prepared. A graphite pretreated product was prepared by repeating collisions 300 times at a pressure of 200 MPa with a collision-type high-pressure emulsifier.

Subsequently, 233 g of the above-mentioned graphite pretreated product and 21 g of polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., product number "PEG-600") (3 times with respect to graphite) were mixed to prepare a raw material composition. Next, the above raw material composition is heat-treated at 370 ° C. for 1 hour in an _N2 atmosphere with a muffle heating device (manufactured by Motoyama Co., Ltd., trade name “MBA-2040D-SP”) to produce a first fired product. (1st fired product) was obtained. Further, the 1st fired product was heat-treated at 390 ° C. for 10 minutes in an N ₂ atmosphere containing 5% O ₂ to obtain a second fired product (2nd fired product). Finally, after a step of crushing for 3 minutes using a crusher, a conductive auxiliary agent (first conductive auxiliary agent) which is a carbon material (partially peeled thin-section graphite) having a structure in which graphite is partially peeled off. Was produced.

The amount of resin was calculated using TG (manufactured by Hitachi High-Tech Science Corporation, product number "STA7300") as the amount of resin whose weight was reduced in the range of 350 ° C. to 600 ° C. It was confirmed that a partially peelable flaky graphite containing 20% by weight of resin could be produced with respect to the total weight (resin amount x ₀ = 20% by weight). Further, the BET specific surface area _y0 of the partially peelable flaky graphite was measured using a specific surface area measuring device (manufactured by Shimadzu Corporation, ASAP-2000, nitrogen gas) and found to be 215 m ² / g.

(Comparative Example 1)
The same as in Example 1 except that the conductive auxiliary agent (partially peelable flake graphite) of Production Example 6 shown below was used instead of the conductive auxiliary agent (partially peelable flake graphite) of Production Example 1. A non-aqueous electrolyte secondary battery was obtained.

Production Example 6 of Conductive Auxiliary Agent;
First, 7 g of artificial graphite (manufactured by IMERIS, trade name "KS6L"), 22 g of a 1% aqueous solution of carboxymethyl cellulose (manufactured by CMC, Aidrich), and polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., "PEG-600"). A raw material composition was prepared by mixing with 21 g (3 times with respect to graphite).

Next, the raw material composition was heat-treated in a muffle heating device (manufactured by Motoyama Co., Ltd., trade name "MBA-2040D-SP") at 370 ° C. for 1 hour in an _N2 atmosphere, whereby the first fired product (1st fired product (). 1st fired product) was obtained. Further, the 1st fired product was heat-treated at 390 ° C. for 30 minutes in an N ₂ atmosphere containing 5% O ₂ to obtain a second fired product (2nd fired product). Finally, after a step of crushing for 3 minutes using a crusher, a conductive auxiliary agent (first conductive auxiliary agent) which is a carbon material (partially peeled thin-section graphite) having a structure in which graphite is partially peeled off. Was produced.

The amount of resin was calculated using TG (manufactured by Hitachi High-Tech Science Corporation, product number "STA7300") as the amount of resin whose weight was reduced in the range of 350 ° C. to 600 ° C. It was confirmed that a partially peelable flaky graphite containing 4.2% by weight of resin could be produced with respect to the total weight (resin amount x ₀ = 4.2% by weight). Further, the BET specific surface area _y0 of the partially peelable flaky graphite was measured using a specific surface area measuring device (manufactured by Shimadzu Corporation, ASAP-2000, nitrogen gas) and found to be 34 m ² / g.

(Comparative Example 2)
The same as in Example 1 except that the conductive auxiliary agent (partially peelable thinned graphite) of Production Example 7 shown below was used instead of the conductive auxiliary agent (partially peeled thinned graphite) of Production Example 1. A non-aqueous electrolyte secondary battery was obtained.

Production Example 7 of Conductive Auxiliary Agent;
First, 7 g of artificial graphite (manufactured by IMERIS, trade name "KS6L"), 22 g of a 1% aqueous solution of carboxymethyl cellulose (manufactured by CMC, Aidrich), and 35 g of polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., PEG-600) ( 5 times with respect to graphite) was mixed to prepare a raw material composition.

Next, the obtained raw material composition was heat-treated in a muffle heating device (manufactured by Motoyama Co., Ltd., product number "MBA-2040D-SP") at 370 ° C. for 1 hour in an _N2 atmosphere to perform the first firing. A product (1st fired product) was obtained. Further, the 1st fired product was heat-treated at 390 ° C. for 30 minutes in an N ₂ atmosphere containing 5% O ₂ to obtain a second fired product (2nd fired product). Finally, after a step of crushing for 3 minutes using a crusher, a conductive auxiliary agent (first conductive auxiliary agent) which is a carbon material (partially peeled thin-section graphite) having a structure in which graphite is partially peeled off. Was produced.

The amount of resin was calculated using TG (manufactured by Hitachi High-Tech Science Corporation, product number "STA7300") as the amount of resin whose weight was reduced in the range of 350 ° C. to 600 ° C. It was confirmed that a partially peelable flaky graphite containing 10% by weight of resin could be produced with respect to the total weight (resin amount x ₀ = 10% by weight). Further, the BET specific surface area _y0 of the partially peelable flaky graphite was measured using a specific surface area measuring device (manufactured by Shimadzu Corporation, ASAP-2000, nitrogen gas) and found to be 60 m ² / g.

(Comparative Example 3)
The same as in Example 1 except that the conductive auxiliary agent (partially peelable thinned graphite) of Production Example 8 shown below was used instead of the conductive auxiliary agent (partially peeled thinned graphite) of Production Example 1. A non-aqueous electrolyte secondary battery was obtained.

Production Example 8 of Conductive Auxiliary Agent;
First, 7 g of artificial graphite (manufactured by IMERIS, trade name "KS6L"), 22 g of a 1% aqueous solution of carboxymethyl cellulose (manufactured by CMC, Aidrich), and polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., trade name "PEG-600"). ") 21 g (3 times with respect to graphite) was mixed to prepare a raw material composition.

Next, the obtained raw material composition was heat-treated in a muffle heating device (manufactured by Motoyama Co., Ltd., product number "MBA-2040D-SP") at 370 ° C. for 1 hour in an _N2 atmosphere to perform the first firing. A product (1st fired product) was obtained. Further, the 1st fired product was heat-treated at 390 ° C. for 40 minutes in an N ₂ atmosphere containing 5% O ₂ to obtain a second fired product (2nd fired product). Finally, after a step of crushing for 3 minutes using a crusher, a conductive auxiliary agent (first conductive auxiliary agent) which is a carbon material (partially peeled thin-section graphite) having a structure in which graphite is partially peeled off. Was produced.

The amount of resin was calculated using TG (manufactured by Hitachi High-Tech Science Corporation, product number "STA7300") as the amount of resin whose weight was reduced in the range of 350 ° C. to 600 ° C. It was confirmed that a partially peelable flaky graphite containing 1% by weight of resin could be produced with respect to the total weight (resin amount x ₀ = 1% by weight). Further, the BET specific surface area _y0 of the partially peelable flaky graphite was measured using a specific surface area measuring device (manufactured by Shimadzu Corporation, product number "ASAP-2000", nitrogen gas) and found to be 19 m ² / g. ..

(Comparative Example 4)
The same as in Example 1 except that the conductive auxiliary agent (partially peelable thinned graphite) of Production Example 9 shown below was used instead of the conductive auxiliary agent (partially peeled thinned graphite) of Production Example 1. A non-aqueous electrolyte secondary battery was obtained.

Production Example 9 of Conductive Auxiliary Agent;
First, 7 g of artificial graphite (manufactured by IMERIS, trade name "KS6L"), 22 g of a 1% aqueous solution of carboxymethyl cellulose (manufactured by CMC, Aidrich), and polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., trade name "PEG-600"). ") 21 g (3 times with respect to graphite) was mixed to prepare a raw material composition.

Next, the obtained raw material composition was heat-treated in a muffle heating device (manufactured by Motoyama Co., Ltd., product number "MBA-2040D-SP") at 370 ° C. for 1 hour in an _N2 atmosphere to perform the first firing. A product (1st fired product) was obtained. Further, the 1st fired product was heat-treated at 390 ° C. for 10 minutes in an N ₂ atmosphere containing 5% O ₂ to obtain a second fired product (2nd fired product). Finally, after a step of crushing for 3 minutes using a crusher, a conductive auxiliary agent (first conductive auxiliary agent) which is a carbon material (partially peeled thin-section graphite) having a structure in which graphite is partially peeled off. Was produced.

The amount of resin was calculated using TG (manufactured by Hitachi High-Tech Science Corporation, product number "STA7300") as the amount of resin whose weight was reduced in the range of 350 ° C. to 600 ° C. It was confirmed that a partially peelable flaky graphite containing 24% by weight of resin could be produced with respect to the total weight (resin amount x ₀ = 24% by weight). Further, the BET specific surface area _y0 of the partially peelable flaky graphite was measured using a specific surface area measuring device (manufactured by Shimadzu Corporation, product number "ASAP-2000", nitrogen gas) and found to be 154 m ² / g. ..

<Evaluation>
(Relationship between resin amount and BET specific surface area)
The conductive auxiliaries (first conductive auxiliaries) obtained in Production Examples 1 to 9 were each fired at 600 ° C. for 5 hours, and the amount of resin contained in the conductive auxiliaries after heating x ₁ % by weight. The BET specific surface area y ₁ m ² / g was determined. Further, a was calculated by the following formula (1), and b was calculated by the following formula (2). The resin amount of the conductive auxiliary agent was calculated by the same method as described above using TG, and the BET specific surface area was calculated by the same method as described above using a specific surface area measuring device.

(Number of particles)
The conductive auxiliaries (first conductive auxiliaries) obtained in Production Examples 1 to 9 were diluted with NMP and adjusted to a concentration of 30 ppm to 50 ppm, respectively, and then ultrasonic cleaners (28 kHz, VS-100III, AS ONE). A dispersion was obtained by subjecting it to ultrasonic treatment for 1 hour using (manufactured by the same company). Further, the number of particles of the conductive auxiliary agent was determined by measuring with a flow particle image analyzer (manufactured by Sysmex Corporation) using the obtained NMP dispersion liquid. Specifically, the number of particles is A / mgC, the concentration of particles obtained from the measurement is X / μL, the concentration of the diluted conductive auxiliary agent dispersion is Yμg / g, and the specific gravity of NMP is Zg / μL. As cc, the number of particles A / mgC was calculated from the following formula (3). The concentration of the conductive auxiliary agent dispersion liquid is Y μg / g, where the weight of the conductive auxiliary agent contained in the dispersion liquid is Y'μg and the weight of the entire dispersion liquid is Y''g, from the following formula (4). I asked. Since the NMP dispersion used in the measurement has a small conductive auxiliary agent concentration of several tens of ppm, an approximation of solution specific density ≈ NMP specific gravity was used.

A = X / (Y × Z)… Equation (3)
Y = Y'/ Y'' ... Equation (4)

(Battery resistance evaluation of non-aqueous electrolyte secondary battery)
Battery evaluation was carried out as follows. First, the battery was connected to a charge / discharge tester (manufactured by Toyo System Co., Ltd., trade name "TOSCAT3100"), and left for 12 hours without passing current. Next, 0.2C CCCV charging (charging end voltage: 4.25V, CV STOP: 3 hours or 0.02C, rest time after charging: 1 minute), -0.2C CC discharge (discharging end voltage 2.5V, Post-discharge pause time: 1 minute), charging and discharging were repeated 5 times. Subsequently, resistance measurement was performed. On the discharge side, the voltage values when discharged at 0.5C, 1.0C, and 2.0C for 10 seconds from the fully charged state and 50% discharged at 0.2C (SOD50%) are read, and Ohm's law is used. : The resistance value R was calculated from V = I × R.

As for the battery resistance, when the average value of the discharge resistance value R calculated as described above is less than 0.5Ω, it is regarded as acceptable (〇), and when it is 0.5Ω or more, it is regarded as rejected (×). Table 1 shows the results of the non-aqueous electrolyte secondary batteries prepared in Examples 1 to 5 and Comparative Examples 1 to 4.

(Evaluation of temperature rise during charging and discharging with large current)
The evaluation of the temperature rise during charging and discharging with a large current was carried out as follows. First, the non-aqueous electrolyte secondary batteries produced in Examples 1 to 5 and Comparative Examples 1 to 4 were placed in a constant temperature bath at 25 ° C. and connected to a charging / discharging device (manufactured by Hokuto Denko Co., Ltd., product number "HJ1005SD8"). .. Next, the non-aqueous electrolyte secondary battery was charged with a constant current (current value 0.2C, charge termination voltage 4.25V). Further, after charging, the battery was rested for 1 minute, discharged to 2.5 V at 20 C (large current), and the temperature rise was measured. As for the temperature, a thermocouple (K type) was attached to the central portion of the non-aqueous electrolyte secondary battery with an imide tape, measured with a data logger (Graphtec, GL900APS), and the maximum temperature was recorded. For the temperature rise, the difference between the maximum temperature and 25 ° C. was calculated, and a temperature rise of less than 10 ° C. was regarded as acceptable (◯), and a temperature rise of 10 ° C. or higher was regarded as rejected (×). The results of the non-aqueous electrolyte secondary batteries prepared in Examples 1 to 5 and Comparative Examples 1 to 4 are shown in Table 1 below.

10, 20 ... Partially peelable flaky graphite 11 ... Edge portion 12 ...

Central portion

13, 23 ... Resin 24 ... Pore

Claims

A conductive auxiliary agent used for the positive electrode of a non-aqueous electrolyte secondary battery.
Contains a carbon material having a graphene laminated structure and a resin,
The amount of resin contained in the conductive auxiliary agent is x0% by weight, the BET specific surface area of the conductive auxiliary agent is y0 m 2 / g, and the conductive auxiliary agent is heated at 600 ° C. for 5 hours. When the amount of resin contained in the agent is x 1 % by weight and the BET specific surface area of the conductive auxiliary agent after heating the conductive auxiliary agent at 600 ° C. for 5 hours is y 1 m 2 / g.
A obtained by the following equation (1) satisfies 3 <a≤100, and
B obtained by the following formula (2) satisfies 20 ≦ b ≦ 100, and
When the conductive auxiliary agent is dispersed in N-methyl-2-pyrrolidone to obtain a dispersion liquid, the number of particles of the conductive auxiliary agent in the dispersion liquid is 1500 million particles / mgC or more, which is non-water. Electrolyte A conductive auxiliary agent for secondary batteries.
a = (y 0 -y 1 ) / (x 0 -x 1 ) ... Equation (1)
b = y 0- (y 0 -y 1 ) x 0 / (x 0 -x 1 ) ... Equation (2)
The conductive auxiliary agent for a non-aqueous electrolyte secondary battery according to claim 1, wherein x 0 is 2 or more and 20 or less.
The conductive auxiliary agent for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein y 0 is 25 or more and 200 or less.
When the conductive auxiliary agent was dispersed in N-methyl-2-pyrrolidone to obtain a dispersion liquid, the 50% particle size (D50) in the cumulative particle size distribution based on the volume of the conductive auxiliary agent was obtained in the dispersion liquid. The conductive auxiliary agent for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, which is 0.1 μm or more and 5 μm or less.
The conductive auxiliary agent for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the carbon material is a partially peelable flaky graphite having a structure in which graphite is partially peeled off. ..
A positive electrode for a non-aqueous electrolyte secondary battery containing the positive electrode active material and the conductive auxiliary agent for the non-aqueous electrolyte secondary battery according to any one of claims 1 to 5.
A non-aqueous electrolyte secondary battery comprising the positive electrode for the non-aqueous electrolyte secondary battery according to claim 6.