Carbon material resin composite for non-aqueous electrolyte secondary batteries, dispersion for non-aqueous electrolyte secondary batteries using the same, electrodes for non-aqueous electrolyte secondary batteries, and non-aqueous electrolyte secondary batteries

Abstract

To provide a carbon material resin composite which is dispersible by a simple method.SOLUTION: A carbon material resin composite for a non-aqueous electrolyte secondary battery contains a carbon material and a resin material, wherein a 50% cumulative particle diameter (D50) of the carbon material in the resin composite is 0.01-5 μm. There is also provided a carbon material resin composite for a non-aqueous electrolyte secondary battery, wherein a mass ratio of a resin material when the total mass of the carbon material is 1 is within a range of 0.4 to 10.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a carbon material resin composite for a non-aqueous electrolyte secondary battery, a dispersion for a non-aqueous electrolyte secondary battery using the same, an electrode for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery.

Background Art

[0002] In recent years, with the popularization of electric vehicles, the miniaturization, light weight, and high performance of portable devices, there has been a demand for secondary batteries having a high energy density and an increase in their capacity. Under such circumstances, due to the characteristics of high energy density and high voltage, lithium-ion secondary batteries, in particular, are widely used in many devices as non-aqueous electrolyte secondary batteries using non-aqueous electrolytes or solid electrolytes.

[0003] In the field of such secondary batteries, for example, Patent Documents 1 to 3 describe improving the dispersion performance of a dispersion of a conductive material to improve battery characteristics. On the other hand, many carbon materials used as conductive materials are difficult to disperse, and it is common to prepare a dispersion alone as in the above patent documents and then mix it with an active material to prepare a composite slurry. However, when preparing a dispersion alone, in addition to the problem that the dispersion state deteriorates, such as sedimentation, when there is a time gap until the preparation of the composite slurry, in the case of a battery of a type containing an electrolyte in the composite slurry, moisture absorption of the dispersion may become a problem because moisture is disliked. Regarding the above problems, in the case of a carbon material obtained by removing and solidifying the solvent of a dispersion, it is considered that an effective means would be to obtain a material with high reproducibility of dispersion when redispersed. Patent Document 4 describes a method of dissolving a mixture of carbon nanotubes, a nonionic surfactant, and a solid thickener to prepare an aqueous dispersion, then removing water from the aqueous dispersion by a spray drying method, and further redispersing it in water.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] When preparing composite slurry for lithium-ion secondary batteries, dispersion devices that use weak impact and shear forces and suppress cavitation, such as planetary mixers and dispersers, are often used to prevent the active material from being atomized or detached. However, Patent Document 4 requires redispersion using an ultrasonic stirring device or a homogenizer for high viscosity to break down the aggregates formed in the drying process, making it difficult to achieve a dispersion liquid in which the aggregates have been broken down by such a simple method as described above. The problem that this invention aims to solve is to provide a carbon material resin composite that can be dispersed by a simple method in order to solve the above problem. [Means for solving the problem]

[0006] In other words, the present invention relates to a carbon material resin composite for non-aqueous electrolyte secondary batteries, comprising a carbon material and a resin material, wherein the 50% cumulative particle size (D50) of the carbon material in the resin composite is 0.01 to 5 μm.

[0007] The present invention also relates to the carbon material resin composite for non-aqueous electrolyte secondary batteries, wherein the mass ratio of the resin material to the total mass of the carbon material is in the range of 0.4 to 10.

[0008] The present invention also relates to the carbon material resin composite for non-aqueous electrolyte secondary batteries, wherein the weight-average molecular weight of the resin material is 20,000 to 10,000,000.

[0009] The present invention also relates to a dispersion for a non-aqueous electrolyte secondary battery comprising the above-mentioned carbon material resin composite for non-aqueous electrolyte secondary batteries and a solvent, wherein the carbon material resin composite is dispersed in the solvent, and the 50% cumulative particle size (D50) of the carbon material in the solvent is 0.01 to 5 μm.

[0010] The present invention also relates to an electrode for a non-aqueous electrolyte secondary battery, comprising the above-mentioned carbon material resin composite for non-aqueous electrolyte secondary batteries, or the above-mentioned dispersion for non-aqueous electrolyte secondary batteries.

[0011] The present invention also relates to a non-aqueous electrolyte secondary battery comprising the above-mentioned electrodes for a non-aqueous electrolyte secondary battery. [Effects of the Invention]

[0012] The carbon material resin composite for non-aqueous electrolyte secondary batteries of the present invention makes it possible to provide a carbon material resin composite that can be dispersed by a simple method. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows the dispersion (1) of the carbon material resin composite manufactured in the example, after drying and observation by SEM. [Figure 2] This figure shows the dispersion (11) of the carbon material resin composite prepared in the comparative example, after drying and observation by SEM. [Modes for carrying out the invention]

[0014] The carbon material resin composite for non-aqueous electrolyte secondary batteries of the present invention comprises a carbon material and a resin material, characterized in that the secondary particles of the carbon material are dispersed in the resin without aggregation. That is, the resin material can suppress the drying aggregation of carbon materials during the drying process, and the carbon materials can be easily crushed without the need for strong dispersion such as ultrasonic vibration, cavitation, or crushing by media. Therefore, when preparing the composite slurry, high dispersion can be achieved even by simple methods such as homodispersion or a rotating and revolving mixer. Accordingly, the electronic resistance of the electrode can be kept low, and a battery equipped with an electrode using the carbon material resin composite can exhibit excellent battery characteristics. In addition, since the carbon material resin composite of the present invention is in a solid state, problems of dispersion stability such as sedimentation and thickening during the transportation and storage of the dispersion can be solved when preparing the composite slurry. Furthermore, since dehydration by drying is easy, the problem of hygroscopicity can also be solved.

[0015] Hereinafter, the present invention will be described in detail. In this specification, the carbon material resin composite for non-aqueous electrolyte secondary batteries may be referred to as "carbon material composite", the dispersion obtained by dispersing the carbon material composite for non-aqueous electrolyte secondary batteries in a solvent may be referred to as "dispersion", and the electrode for non-aqueous electrolyte secondary batteries may be referred to as "electrode". In the process of manufacturing the carbon material resin composite for non-aqueous electrolyte secondary batteries, the liquid obtained by dispersing the carbon material together with the resin material in a solvent is referred to as "dispersion liquid" to distinguish it from the above-mentioned "dispersion".

[0016] <Carbon material> The carbon material used in the present invention is not particularly limited as long as it is a carbon material having conductivity. For example, carbon black (furnace black, acetylene black, ketjen black, medium thermal carbon black, etc.), activated carbon, graphite, hard carbon, carbon nanotubes, carbon nanofibers, carbon nanohorns, graphene-based carbon materials (graphene, graphene nanoplatelets, etc.), nanoporous carbon, and carbon fibers can be used. These carbon materials may be used alone or in combination of two or more.

[0017] [Carbon black] Examples of the carbon black include furnace black produced by continuously thermally decomposing a gaseous or liquid raw material in a reactor, particularly ketjen black using ethylene heavy oil as a raw material, channel black produced by burning a raw material gas and applying the flame to the bottom surface of channel steel for rapid cooling and precipitation, thermal black obtained by periodically repeating combustion and thermal decomposition using a gas as a raw material, particularly acetylene black using acetylene gas as a raw material. Further, oxidized carbon black or hollow carbon that is commonly used may also be used. These carbon blacks may be used alone or in combination of two or more.

[0018] [Carbon nanotube] The carbon nanotube has a shape in which planar graphite is wound into a cylindrical shape, and may be either a single-walled carbon nanotube having a structure in which a single layer of graphite is wound or a multi-walled carbon nanotube having a structure in which two or more layers of graphite are wound, or may be a mixture of single layers and multi-layers. Further, the side wall of the carbon nanotube does not have to be a graphite structure. For example, a carbon nanotube having a side wall with an amorphous structure can also be used.

[0019] The average outer diameter of the carbon nanotube is preferably 3 nm or more and 25 nm or less, more preferably 5 nm or more and 20 nm or less, and even more preferably 5 nm or more and 15 nm or less. When the average outer diameter of the carbon nanotube is within the above range, the surface of the active material described later is easily coated with the carbon nanotube, and the conductivity and adhesion of the electrode film are improved.

[0020] Hard carbon has a disordered arrangement of crystallites and is difficult to have a planar arrangement of crystallites even when sintered at a high temperature, and is also called non-graphitizable carbon. Examples of hard carbon include glassy carbon, cellulose carbon, charcoal, sugar carbon, and coal tar carbon.

[0021] Examples of commercially available carbon blacks include Ketjenblack EC-300J, EC-600JD, and Lionite EC-200L from Lion Specialty Chemicals; Furnace Black #2350, #2600, #3050B, #3030B, #3230B, and #3400B from Mitsubishi Chemical Corporation; and Denka Black Li-400 and FX-35 from Denka Corporation.

[0022] Examples of commercially available carbon nanotubes include VGCF-H and VGCF-X from Showa Denko Corporation; carbon nanotubes from Meijo Nanocarbon Co., Ltd.; NTP3003, NTP3021, NTP3121, NTP8012, NTP8022, NTP9012, NTP9112 from NTP Corporation; 10B and 6A from JEIO Corporation; and TUBALL from OCSiAl Corporation.

[0023] <Resin materials> The resin material of this embodiment includes a resin-type dispersant and / or a binder resin. From the viewpoint of dispersion stability and aggregation suppression of carbon materials, it is preferable to include a resin-type dispersant, and it is more preferable to include both a resin-type dispersant and a binder resin.

[0024] [Resin-type dispersant] The resin-type dispersant of this embodiment stabilizes and disperses carbon materials. Examples of resin-type dispersants include basic resin-type dispersants, which are resins with a weight-average molecular weight of 500 or more and have basic functional groups; acidic resin-type dispersants, which are resins with acidic functional groups; amphoteric resin-type dispersants, which are resins with both basic and acidic functional groups; and nonionic resin-type dispersants, which are nonionic resins.

[0025] Examples of basic resin-type dispersants include resins having cyclic amino groups or quaternary ammonium salts, wherein some or all of the amino groups may be neutralized. Examples of such resin-type dispersants include homopolymers of polymerizable monomers such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, methylethylaminoethyl (meth)acrylate, dimethylaminostyrene, and diethylaminostyrene, or copolymers with other polymerizable monomers, and acid neutralized products thereof.

[0026] Examples of acidic resin-type dispersants include resins having carboxyl groups, sulfo groups, or phosphate groups, and some or all of the above acidic functional groups may be neutralized. Examples of such resin-type dispersants include polymerizable monomers having carboxyl groups such as maleic acid, fumaric acid, itaconic acid, citraconic acid, acrylic acid, methacrylic acid, crotonic acid, and cinnamic acid; polymerizable monomers having sulfo groups such as vinyl sulfonic acid, (meth)allyl sulfonic acid, styrene sulfonic acid, (meth)acryloyloxyethyl sulfonic acid, isoprene sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, and allyloxybenzenesulfonic acid; polymerizable monomers having phosphate groups such as mono(2-acryloyloxyethyl) acid phosphate and mono(2-methacryloyloxyethyl) acid phosphate; homopolymers of these, copolymers with other polymerizable monomers, and alkali-neutralized products thereof.

[0027] Examples of amphoteric resin-type dispersants include those containing both the basic and acidic skeletons, such as copolymers of styrene-maleic acid-N,N-dimethylaminoethyl (meth)acrylate.

[0028] Nonionic resin-type dispersants refer to resins other than the basic resin-type dispersants, acidic resin-type dispersants, and amphoteric resin-type dispersants, and are preferably water-soluble resins. Examples of such nonionic resin-type dispersants include polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, polyacrylonitrile, copolymers of butadiene and acrylonitrile, polyacrylamide, poly-N-vinylacetamide, polyalkylene glycol, and cellulose derivatives (cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethylcellulose, ethyl hydroxyethylcellulose, nitrocellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose).

[0029] These resin-type dispersants may be used individually or in combination of two or more types.

[0030] The resin-type dispersant is preferably a nonionic resin-type dispersant, and more preferably polyvinylpyrrolidone, polyacrylonitrile, a copolymer of butadiene and acrylonitrile, or a cellulose derivative.

[0031] The weight-average molecular weight of the resin-type dispersant is preferably 1,000 or more, more preferably 5,000 or more, and even more preferably 20,000 or more. A weight-average molecular weight within the above range is preferable because it leads to improved dispersion stability and battery characteristics.

[0032] [Binder resin] The binder resin of this embodiment primarily has the function of bonding materials such as carbon materials together.

[0033] Examples of binders include polymers or copolymers containing ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, acrylonitrile, styrene, vinyl butyral, vinyl acetal, vinylpyrrolidone, etc. as constituent units; polyurethane resins, polyester resins, phenolic resins, epoxy resins, phenoxy resins, urea resins, melamine resins, alkyd resins, acrylic resins, formaldehyde resins, silicone resins, fluororesins; cellulose resins such as carboxymethylcellulose; rubbers such as styrene-butadiene rubber and fluororubber; and conductive resins such as polyaniline and polyacetylene. Modified forms, mixtures, and copolymers of these resins may also be used.

[0034] The weight-average molecular weight of the binder resin is preferably 50,000 to 10,000,000, and more preferably 100,000 to 5,000,000. A weight-average molecular weight within this range is preferable because it suppresses the aggregation of carbon materials.

[0035] These binder resins may be used individually or in combination of two or more types.

[0036] [Weight-average molecular weight of resin materials] The weight-average molecular weight of resin materials can be measured by determining the polystyrene equivalent value obtained using gel permeation chromatography (GPC) equipped with an RI detector. A device such as the Tosoh HLC-8320GPC can be used. Furthermore, when using a resin-type dispersant and a binder resin in combination, the molecular weight is calculated from the sum of the product of the weight-average molecular weight of each resin material multiplied by its mass percentage.

[0037] The weight-average molecular weight of the resin material contained in the carbon material resin composite is preferably 20,000 or more, more preferably 50,000 or more, and more preferably 100,000 or more. A weight-average molecular weight within this range is preferable because it suppresses aggregation of the carbon material.

[0038] <Carbon material resin composite> The carbon material resin composite for non-aqueous electrolyte secondary batteries of the present invention comprises at least a carbon material and a resin material, characterized in that the 50% cumulative particle size (D50) of the carbon material in the resin composite is 0.01 to 5 μm. In this specification, the 50% cumulative particle size (D50) of the carbon material in the resin composite refers to the particle size (particle size of secondary particles) when the carbon material is dispersed in the resin material or mixed with the resin material and aggregated in some cases occurs, and does not necessarily coincide with the particle size of the primary particles of the carbon material used as a material in the manufacturing process of the resin composite.

[0039] The above 50% cumulative particle size (D50) is more preferably 3 μm or less, even more preferably 1 μm or less, and particularly preferably 0.5 μm or less. By using the above range, carbon materials can be easily broken down and good dispersions can be obtained without using strong dispersion equipment that requires cavitation such as ultrasound or crushing with beads. From the viewpoint of dispersion stability after crushing, the lower limit of the 50% cumulative particle size (D50) is more preferably 0.02 μm or larger, even more preferably 0.03 μm or larger, and particularly preferably 0.05 μm or larger.

[0040] The 50% cumulative particle size (D50) of the carbon material in the carbon material resin composite described above can be measured by determining the 50% cumulative particle size (D50) from the particle size distribution measurement of the dispersion. This is because the carbon material resin composite of the present invention is easily crushed without applying impact force or cavitation, and therefore the 50% cumulative particle size (D50) in the dispersion maintains the 50% cumulative particle size (D50) of the secondary particles of the carbon material in the carbon material resin composite.

[0041] In this specification, the 50% cumulative particle size (D50) of the dispersion is determined by measurement using a particle size analyzer (NANOTRACWAVE, MT3000, manufactured by Microtrac-Bell Co., Ltd.). The method involves leaving the dispersion in a constant temperature bath at 25°C for at least one hour, thoroughly stirring and diluting the dispersion, and then measuring the 50% cumulative particle size (D50) (by volume) of the dispersion using a particle size analyzer (NANOTRACWAVE, manufactured by Microtrac-Bell Co., Ltd.).

[0042] In the carbon material resin composite for non-aqueous electrolyte secondary batteries of the present invention, a mass ratio of resin material to carbon material in the range of 0.4 to 10 is preferable, as it improves redispersibility and suppresses an increase in resistance when used as a battery. A range of 0.5 to 5 is more preferable, and a range of 1 to 3 is even more preferable.

[0043] <Method for manufacturing carbon material resin composites>

[0044] The carbon material resin composite for non-aqueous electrolyte secondary batteries of the present invention can be manufactured, for example, by preparing a dispersion in which a carbon material is dispersed with a resin material in a solvent, and then vaporizing the solvent from the dispersion.

[0045] [Dispersion] The dispersion apparatus used for the above-mentioned dispersion process is not particularly limited, and a dispersion machine commonly used for pigment dispersion, etc., can be used. For example, mixers such as dispersers and planetary mixers, Rotation and revolution mixers such as the "Awatori Rentaro" manufactured by Shinky Co., Ltd. High-shear mixers such as the Primix "Homomixer Mark II", Rotor / stator type mixers such as the SILVERSON Model AX5, Ultrasonic homogenizers such as "AdvancedDigitalSonifer®" manufactured by BRANSON Corporation, Red Devil paint shakers, ball mills, sand mills (such as Shinmaru Enterprises' "Dino Mill"), attritors, pearl mills (such as Eirich's "DCP Mill"), and media-type dispersers such as Coball Mills. Wet jet mills (Genus PY from Genus Corporation, Starburst from Sugino Machine Co., Ltd., Nanomizer from Nanomizer Co., Ltd., etc.), media-less dispersers such as Micros from Nara Machinery Co., Ltd., Other examples of roll mills include, but are not limited to, these.

[0046] [solvent] Examples of solvents used in preparing the above-mentioned dispersion include alcohols, glycols, cellosolves, amino alcohols, amines, ketones, carboxylic acid amides, phosphate amides, sulfoxides, carboxylic acid esters, phosphate esters, ethers, nitriles, and water.

[0047] The carbon material content in the above dispersion is preferably 0.1 to 40% by mass, and more preferably 0.5 to 20% by mass, based on the total mass of the dispersion.

[0048] The drying method is not particularly limited as long as the solvent can be vaporized, and conventionally known methods can be used. Examples include hot air drying using an oven, spray drying using a spray dryer, reduced-pressure drying using an evaporator, and freeze-drying. From the viewpoint of productivity, hot air drying and spray drying are preferred.

[0049] <Dispersion for non-aqueous electrolyte secondary batteries> The dispersion for non-aqueous electrolyte secondary batteries comprises the carbon material resin composite of the present invention and a solvent, wherein the carbon material resin composite is dispersed in the solvent. In the dispersion, it is preferable that the 50% cumulative particle size (D50) of the carbon material contained in the carbon material resin composite in the solvent is in the range of 0.01 to 5 μm, as this facilitates uniform dispersion of the carbon material in electrodes made from this dispersion. It is more preferable that it is in the range of 0.02 to 3 μm, and even more preferable that it is in the range of 0.1 to 1 μm.

[0050] [solvent] The solvent contained in the dispersion for non-aqueous electrolyte secondary batteries may be one of the solvents described in the description of the manufacturing of carbon material resin composites.

[0051] <Method for manufacturing dispersions for non-aqueous electrolyte secondary batteries> To obtain a dispersion for non-aqueous electrolyte secondary batteries, it is preferable to disperse the carbon material resin composite in a solvent. The dispersion apparatus used for such processing is not particularly limited, and for example, the dispersion apparatus described in the section on the dispersion of the carbon material resin composite can be used. In the present invention, the carbon material resin composite is easily broken down without applying strong impact force, shear force, or cavitation, so among dispersion apparatuses, mixers such as dispersers and planetary mixers used for making composite slurry, and rotational / revolutional mixers such as the "Awatori Rentaro" manufactured by Thinky Co., Ltd. are preferred.

[0052] The content of the carbon material resin composite in the above dispersion is preferably 0.1 to 60% by mass, and more preferably 1 to 40% by mass, based on the total mass of the dispersion.

[0053] <Asphalt slurry> The carbon material resin composite of the present invention can be incorporated into an asphalt slurry. The asphalt slurry contains the carbon material resin composite, an active material, a solvent, and a binder.

[0054] [Active material] The active material in the present invention refers to the material that serves as the basis for the battery reaction. The active material can be divided into a positive electrode active material and a negative electrode active material based on the electromotive force.

[0055] (Positive electrode active material) The positive electrode active material is not particularly limited. For example, metal compounds such as metal oxides and metal sulfides capable of doping or intercalating lithium ions; conductive polymers can be used. Examples of the above metal compounds include inorganic compounds such as oxides of transition metals such as Fe, Co, Ni, Mn, composite oxides with lithium, and transition metal sulfides. Specifically, transition metal oxide powders such as MnO, V2O5, V6O 13 , TiO2, etc., composite oxide powders of lithium and transition metals such as lithium nickelate, lithium cobaltate, lithium manganate with a layered structure, lithium iron phosphate-based materials which are olivine structure phosphate compounds, transition metal sulfide powders such as TiS2, FeS, etc. can be used. Examples of the above conductive polymers include polyaniline, polyacetylene, polypyrrole, and polythiophene. Also, the above metal compound and the conductive polymer may be mixed and used.

[0056] (Negative electrode active material) The negative electrode active material is not particularly limited as long as it can dope or intercalate lithium ions. For example, alloy systems such as metallic Li, lead alloys such as tin alloys and silicon alloys which are alloys with metallic Li, metal oxide systems such as LixFe2O3, LixFe3O4, LixWO2 (x is a number between 0 < x < 1), lithium titanate, lithium vanadate, lithium silicate, conductive polymer systems such as polyacetylene and poly-p-phenylene, artificial graphite such as soft carbon, hard carbon, highly graphitized carbon materials, or carbonaceous powders such as natural graphite, carbon black, mesophase carbon black, resin-fired carbon materials, gas-phase grown carbon fibers, carbon fibers, etc. carbon-based materials can be mentioned. These negative electrode active materials can also be used alone or in combination of two or more.

[0057] In the present invention, it is preferable to use a combination of a silicon-based negative electrode active material and a carbonaceous powder such as artificial graphite or natural graphite as the negative electrode active material.

[0058] The blending ratio of the silicon-based anode active material is preferably 3 to 50% by mass, and more preferably 5 to 25% by mass, based on the mass of carbonaceous powder such as artificial graphite or natural graphite.

[0059] [solvent] The solvent included in the composite slurry can be one of the solvents described in the description of the manufacturing of the carbon material resin composite.

[0060] [binder] The binder included in the composite slurry can be the binder resin described in the description of the carbon material resin composite.

[0061] <Method for manufacturing asphalt slurry> The composite slurry of this embodiment can be prepared by various conventionally known methods. For example, it can be prepared by adding a binder and an active material to a dispersion of carbon material resin composites, by dispersing the carbon material resin composite and binder in a solvent and then adding an active material, or by simultaneously dispersing the carbon material resin composite, binder, active material, and solvent.

[0062] To obtain the composite slurry of this embodiment, it is preferable to add the active material to a dispersion of carbon material resin composites and then perform a dispersion process. The dispersion apparatus used for this process is not particularly limited, and for example, the dispersion apparatus described in the description of the manufacturing of the carbon material resin composites can be used. In particular, in order to suppress the crushing and peeling of the active material, it is preferable to use mixers such as dispersers and planetary mixers, or rotational / revolutional mixers such as the "Awatori Rentaro" manufactured by Thinky Co., Ltd.

[0063] In this embodiment, the amount of active material in the asphalt slurry is preferably 20 to 85 parts by mass, more preferably 30 to 75 parts by mass, and even more preferably 40 to 70 parts by mass, per 100 parts by mass of the asphalt slurry.

[0064] The amount of carbon material contained in the composite slurry of this embodiment is preferably 0.01 to 10 parts by mass, more preferably 0.02 to 5 parts by mass, and even more preferably 0.03 to 1 part by mass, per 100 parts by mass of active material.

[0065] In this embodiment, the amount of binder in the asphalt slurry is preferably 0.5 to 30% by mass, more preferably 1 to 25% by mass, and even more preferably 2 to 20% by mass, based on 100 parts by mass of active material.

[0066] The amount of solids in the asphalt slurry of this embodiment is preferably 30 to 90% by mass, more preferably 30 to 80% by mass, and even more preferably 40 to 75% by mass, based on 100% by mass of the asphalt slurry.

[0067] <Non-aqueous electrolyte secondary battery electrode> Electrodes for non-aqueous electrolyte secondary batteries are formed using the above-mentioned asphalt slurry, and can be formed, for example, by coating a current collector with the asphalt slurry. In this specification, the layer formed from the asphalt slurry may be abbreviated as electrode film, coating film, or asphalt layer.

[0068] [Current collector] The material and shape of the current collector are not particularly limited, and one suitable for various secondary batteries can be appropriately selected. Examples of current collector materials include metals and alloys such as aluminum, copper, nickel, titanium, and stainless steel. In terms of shape, a flat foil is generally used, but foils with roughened surfaces, perforated foils, or mesh-like foils may also be used.

[0069] The method for applying the asphalt slurry to the current collector is not particularly limited, and known methods can be used. Examples of such methods include die coating, dip coating, roll coating, doctor coating, knife coating, spray coating, gravure coating, screen printing, and electrostatic coating.

[0070] A method for manufacturing electrodes for non-aqueous electrolyte secondary batteries may include a drying step after coating a current collector with an asphalt slurry. When a drying step is included, the drying method can include, but is not limited to, standing drying, forced-air drying, hot-air drying, infrared heating, far-infrared heating.

[0071] Furthermore, as a method for manufacturing electrodes for non-aqueous electrolyte secondary batteries, the composite slurry may be coated onto a current collector, followed by a drying process as needed, and then rolled using a flatbed press or calender roll. The thickness of the electrode composite layer is generally 1 μm or more and 500 μm or less, preferably 10 μm or more and 300 μm or less.

[0072] <Nonaqueous electrolyte secondary battery> A non-aqueous electrolyte secondary battery is equipped with the above-mentioned electrodes for non-aqueous electrolyte secondary batteries. The configuration of the non-aqueous electrolyte secondary battery is not particularly limited and can be in various shapes depending on the purpose of use, such as paper type, cylindrical type, button type, or laminated type. A non-aqueous electrolyte secondary battery usually comprises a positive electrode and a negative electrode, an electrolyte, a separator, etc., and at least one of the positive electrode or the negative electrode may be an electrode for non-aqueous electrolyte secondary battery containing the carbon material resin composite of the present invention.

[0073] As the positive electrode, an electrode can be prepared by coating a slurry containing the positive electrode active material onto a current collector and drying it.

[0074] As the negative electrode, an electrode can be prepared by coating and drying a slurry containing the negative electrode active material onto the current collector.

[0075] [Electrolyte] The electrolyte is not particularly limited, and various conventionally known electrolytes can be used. For example, those containing lithium salts such as LiBF4, LiClO4, LiPF6, LiAsF6, LiSbF6, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, Li(CF3SO2)3C, LiI, LiBr, LiCl, LiAlCl, LiHF2, LiSCN, or LiBPh4 (where Ph is a phenyl group) can be used, but are not limited to these, and those containing sodium salts or calcium salts can also be used.

[0076] Non-aqueous solvents are not particularly limited, but examples include carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; lactones such as γ-butyrolactone, γ-valerolactone, and γ-octanoic lactone; glycines such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1,2-dibutoxyethane; esters such as methyl formate, methyl acetate, and methyl propionate; sulfoxides such as dimethyl sulfoxide and sulfolane; and nitriles such as acetonitrile. These solvents may be used individually or in mixtures of two or more.

[0077] The non-aqueous electrolyte secondary battery of this embodiment preferably includes a separator. Examples of separators include, but are not limited to, polyethylene nonwoven fabric, polypropylene nonwoven fabric, polyamide nonwoven fabric, and those treated to be hydrophilic. [Examples]

[0078] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples unless it exceeds the gist of the invention. Unless otherwise specified, "parts" refers to "parts by mass" and "%" refers to "percentage by mass".

[0079] The compounds used in the examples and comparative examples are shown below. <Carbon materials> • CNT: JENOTUBE10B (manufactured by JEIO) <Resin-type dispersant> • PVPK-15: Polyvinylpyrrolidone K-15 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (Mw10,000) • PVPK-30: Polyvinylpyrrolidone K-30 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (Mw40,000) • CMC APP-84: Carboxymethylcellulose (manufactured by Nippon Paper Industries Co., Ltd.) (Mw20,000) • PVB BL-10: Polyvinyl butylaldehyde (manufactured by Sekisui Chemical Co., Ltd.) (Mw15,000) • PAN: Polyacrylonitrile (Synthesis Example 1) (Mw 45,000) <Binder resin> • CMC #1190: Carboxymethylcellulose (manufactured by Daicel Mirise) (Mw>100,000) • PVDF #5130: Polyvinylidene fluoride (Solvey Corporation) (Mw > 1,000,000~1,200,000) <Solvent> • NMP: N-methylpyrrolidone (manufactured by Kishida Chemical Co., Ltd.) <Negative electrode active material> • SiO: Silicon monoxide (manufactured by Osaka Titanium Technology Co., Ltd., SILICONMONOOXIDE) <Cathode active material> • NCM: Nickel-based cathode material (manufactured by BASF Toda Battery Materials LLC, HED(registered trademark) NCM-111 1100)

[0080] [Weight average molecular weight (Mw)] The weight-average molecular weight was measured using gel permeation chromatography (GPC) equipped with an RI detector and expressed as a polystyrene equivalent. The apparatus used was an HLC-8320GPC (Tosoh Corporation), with three separation columns connected in series. The packing materials used were, in order, Tosoh Corporation's "TSK-GELSUPERAW-4000," "AW-3000," and "AW-2500." The oven temperature was 40°C, and the eluent was a 30 mM triethylamine and 10 mM LiBr N,N-dimethylformamide solution. Measurements were taken at a flow rate of 0.6 ml / min. Samples were prepared at a concentration of 1% by mass in the solvent consisting of the above eluents, and 20 μL was injected.

[0081] <Synthesis of dispersants> (Synthesis Example 1) Synthesis of Polyacrylonitrile 100 parts of acetonitrile were charged into a reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer, and the vessel was purged with nitrogen gas. The reaction vessel was heated to 70°C, and a mixture of 90.0 parts acrylonitrile, 10.0 parts acrylic acid, and 5.0 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) (manufactured by NOF Corporation; V-65) was added dropwise over 3 hours to carry out the polymerization reaction. After the dropwise addition was complete, the reaction was continued at 70°C for another hour, then 0.5 parts of V-65 were added, and the reaction was continued at 70°C for another hour. Subsequently, the conversion rate was confirmed to be over 98% by non-volatile content measurement, and the mixture was concentrated under reduced pressure to remove acetonitrile and obtain polyacrylonitrile (PAN), a nonionic resin-type dispersant. The weight-average molecular weight of the obtained resin was 45,000.

[0082] <Preparation of carbon material resin composites for non-aqueous electrolyte secondary batteries> [Example 1] In a glass bottle, 98 parts water and 0.25 parts dispersion resin (PVPK-30) were placed and thoroughly mixed and dissolved. Then, 1 part carbon material (CNT) was added. Next, 200 parts of 1.25 mmφ zirconia beads were added as media. After sealing the bottle, the mixture was dispersed in a paint shaker for 2 hours to obtain a dispersion. 1 part binder resin (CMC #1190) was added to the obtained dispersion and thoroughly dissolved and mixed using a PRIMIX homodisperser. Finally, the mixture was spray-dried at 125°C using a Nippon Buch spray dryer (B290) to obtain a carbon material resin composite (1).

[0083] [Examples 2, 3, 10] Carbon material resin composites (2), (3), and (10) were obtained in the same manner as in Example 1, except that the compound composition and drying temperature shown in Table 1 were changed.

[0084] [Example 4] In a glass bottle, 98 parts water and 0.5 parts dispersant (CMC APP-84) were added and thoroughly mixed and dissolved. Then, 1 part carbon material (CNT) was added. Next, 200 parts of 1.25 mmφ zirconia beads were added as media. After sealing the bottle, the mixture was dispersed in a paint shaker for 2 hours to obtain a dispersion. The obtained dispersion was spray-dried at 125°C using a spray dryer (B290) manufactured by Nippon Buch Co., Ltd. to obtain a carbon material resin composite (4).

[0085] [Examples 5-9, Comparative Examples 1-4] Carbon material resin composites (5) to (9) and (11) to (14) were obtained in the same manner as in Example 5, except that the compound composition and drying temperature shown in Table 1 were changed.

[0086] <Preparation of dispersions of carbon material resin composites for non-aqueous electrolyte secondary batteries> [Example 11] 99 parts water and 1 part carbon material resin composite (1) were placed in a glass bottle, and the mixture was simply dispersed at 3000 rpm for 1 hour using a PRIMIX homodisperser to obtain a dispersion (1) of carbon material resin composite for non-aqueous electrolyte secondary batteries.

[0087] [Examples 12-20, Comparative Examples 5-8] Dispersions of carbon material resin composites (2) to (14) were obtained in the same manner as in Example 11, except that the compound composition was changed as shown in Table 1. The same solvent used in preparing the carbon material resin composites was used in this process.

[0088] <Evaluation of dispersed particle size of carbon materials in carbon material resin composites> The particle size of the dispersed carbon material in the carbon material resin composite was evaluated by analyzing the particle size distribution of the carbon material resin composite dispersion. The results are shown in Table 1.

[0089] [Particle size distribution evaluation] After allowing the dispersion of the present invention to stand in a 25°C constant temperature bath for at least one hour, the dispersion was thoroughly stirred and diluted, and then the cumulative particle size D50 of the dispersion was measured using a particle size analyzer (Microtrac-Bell Co., Ltd., NanotracWave). The carbon particles were non-spherical, and the dispersion concentration was diluted during measurement so that the loading index value was in the range of 0.8 to 1.2. The obtained cumulative particle size D50 values ​​were evaluated according to the following criteria. ◎: D50 is between 0.01 μm and 0.4 μm. 〇〇:D50 is greater than 0.4 μm and less than or equal to 1 μm ○: D50 is greater than 1 μm and less than or equal to 5 μm ×: D50 is greater than 5 μm

[0090] [Table 1]

[0091] <Preparation of a slurry for non-aqueous electrolyte secondary batteries containing negative electrode active material> [Manufacturing Example 1] 0.75 parts of carbon material resin composite (1) and 99 parts of water were weighed into a plastic container and stirred at 3000 rpm for 30 minutes using a PRIMIX homodisperser. Then, 2.25 parts of binder resin (CMC #1190) were added and completely dissolved. Subsequently, 96 parts of silicon monoxide (Osaka Titanium Technology Co., Ltd., SILICONMONOOXIDE, SiO₂ 1.3C 5μm), which is the negative electrode active material, were added and stirred at 2000 rpm for 3 minutes using a Shinky rotation / revolution mixer. Then, 2.0 parts of emulsion-type acrylic resin dispersion solution (Toyochem Co., Ltd.: W-168) (50% solid content) were added and stirred at 2000 rpm for 30 seconds using the same rotation / revolution mixer to obtain composite slurry (1).

[0092] [Manufacturing Examples 2-6, Comparative Manufacturing Examples 1, 2] Except for changing the carbon material resin composite to carbon material resin composites (2) to (6), (11), and (12), and adjusting the amount of binder resin (CMC #1190) added so that the total amount of dispersed resin and binder resin in the asphalt slurry was 2.5 parts, asphalt slurries (2) to (6), (11), and (12) were obtained in the same manner as in Production Example 1.

[0093] <Preparation of a slurry for non-aqueous electrolyte secondary batteries containing positive electrode active material> [Manufacturing Example 7] One part of carbon material resin composite (7) and 100 parts of NMP were weighed into a plastic container and stirred at 3000 rpm for 30 minutes using a PRIMIX homodisperser. Then, three parts of binder resin (PVDF #5130) were added and completely dissolved. Subsequently, 96 parts of positive electrode active material (BASF Toda Battery Materials LLC, HED® NCM-111 1100) were added and stirred at 2000 rpm for 3 minutes using a Thinky rotation / revolution mixer to obtain the composite slurry (7).

[0094] [Manufacturing Examples 8-10, Comparative Manufacturing Examples 3, 4] The carbon material resin composites (8) to (10), (13), and (14) were obtained in the same manner as in Production Example 7, except that the carbon material resin composites were changed to carbon material resin composites (8) to (10), (13), and (14), and the amount of binder resin (PVDF #5130) added was adjusted so that the total amount of dispersed resin and binder resin in the asphalt slurry was 3.5 parts.

[0095] <Fabrication of electrodes for aqueducts in non-aqueous electrolyte secondary batteries> [Example 21] The asphalt slurry (1) is applied using an applicator, and the basis weight per unit of the electrode is 8 mg / cm³. 2 After coating the copper foil in this manner, the coating film was dried in an electric oven at 120°C for 30 minutes to obtain electrode (1).

[0096] [Examples 22-26, Comparative Examples 9, 10] Electrodes (2)-(6), (11), and (12) were prepared in the same manner, except that the asphalt slurry (1) was changed to (2)-(6), (11), and (12).

[0097] <Fabrication of electrodes for the positive electrode of a non-aqueous electrolyte secondary battery> [Example 27] The asphalt slurry (7) is applied using an applicator, and the basis weight per unit of the electrode is 20 mg / cm³. 2 After coating the aluminum foil in this manner, the coating was dried in an electric oven at 120°C for 30 minutes to obtain the electrode (7).

[0098] [Examples 28-30, Comparative Examples 11, 12] Electrodes (8)-(10), (13), and (14) were prepared in the same manner, except that the asphalt slurry (7) was changed to (8)-(10), (13), and (14).

[0099] <Evaluation of electrode volume resistivity> The surface resistivity (Ω / □) of the electrode was measured using a Loresta GX MCP-T700 manufactured by Nitto Seiko Analytech Co., Ltd. After measurement, the volume resistivity (Ω·cm) of the electrode was obtained by multiplying the measured surface resistivity by the thickness of the composite layer formed on the PET substrate. The thickness of the electrode composite layer was determined by subtracting the thickness of the PET substrate from the average value of measurements taken at four points in the electrode film using a film thickness gauge (NIKON DIGIMICROMH-15M) to obtain the volume resistivity (Ω·cm) of the electrode.

[0100] From the obtained volume resistivity values, the ratio of the volume resistivity of the negative electrode to that of Comparative Example 9 was calculated, and the ratio of the volume resistivity of the positive electrode to that of Comparative Example 11 was calculated, and these were evaluated according to the following criteria. ◎: Volume resistivity ratio is less than 10% 〇〇: Volume resistivity ratio is 10% or more but less than 40% ○: Volume resistivity ratio is 40% or more but less than 70% △: Volume resistivity ratio is 70% or more but less than 90% ×: Volume resistivity ratio is 90% or higher

[0101] [Table 2]

[0102] Tables 1 and 2 show that the examples using the carbon material resin composite of the present invention showed better volume resistivity of the negative and positive electrodes compared to the comparative example. This is thought to be because the aggregation of carbon material in the carbon material resin composite was suppressed, and as is clear from the figures, the carbon material could be effectively disintegrated in the examples with only simple dispersion compared to the comparative example, which effectively contributed to the formation of conductive paths in the electrodes. This invention makes it possible to resolve the stability and moisture issues that are problems with dispersions.

Claims

1. A carbon material resin composite for a non-aqueous electrolyte secondary battery, comprising a carbon material and a resin material, but free of an active material and a solvent, wherein the carbon material is a carbon nanotube, the mass ratio of the resin material to the total mass of the carbon material is in the range of 0.3 to 10, and the 50% cumulative particle size (D50) of the carbon material in the resin composite is 0.01 to 5 μm.

2. The carbon material resin composite for a non-aqueous electrolyte secondary battery according to claim 1, wherein the mass ratio of the resin material to the total mass of the carbon material is in the range of 0.4 to 10.

3. A carbon material resin composite for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the weight-average molecular weight of the resin material is 20,000 to 10,000,000.

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