Conductive paste, mixed paste, electrode for positive electrode of lithium ion battery and battery

Abstract

The present invention addresses the problem of providing a conductive paste that, when used in a lithium ion secondary battery, generates low internal resistance and suppresses an increase in internal resistance after repeated charge / discharge. The present invention provides a conductive paste containing a pigment dispersion resin (A), conductive carbon (B), an inorganic material (C), and a solvent (D). The pigment dispersion resin (A) has at least one polar functional group selected from the group consisting of an amide group, an imide group, an ether group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phosphate group, a silanol group, an amino group, and a pyrrolidone group. The inorganic material (C) includes at least one selected from the group consisting of glass, glass ceramics, and ceramics.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority based on Japanese Patent Application No. 2022-033011 filed on March 3, 2022, the entire contents of which are incorporated herein by reference. The present invention relates to a conductive slurry and a mixed slurry, and an electrode for a positive electrode of a lithium ion battery comprising the mixed slurry and a battery comprising the mixed slurry. Background Art

[0003] Lithium ion secondary batteries are secondary batteries in which lithium ions in the electrolyte are responsible for conducting electricity. Lithium ion secondary batteries have excellent properties, such as high energy density, excellent charging energy retention performance, and small memory effect (i.e., a significant reduction in battery capacity). Therefore, lithium ion secondary batteries are used in a wide range of fields, such as cellular phones, smart phones, personal computers, digital cameras, hybrid vehicles, electric vehicles, and medical devices.

[0004] Generally, lithium ion secondary batteries mainly include, for example, positive plates, negative plates, separators for insulating positive plates and negative plates, and electrolytes. The positive plate is obtained by forming a positive electrode composite layer on the surface of the positive electrode core. The positive electrode composite layer can be prepared by applying a positive electrode mixed slurry to the surface of the positive electrode core and then drying it. The positive electrode mixed slurry is obtained by mixing an electrode active material with a conductive slurry containing a conductive aid (such as carbon), a binder and a solvent (PTL 1 to PTL 3).

[0005] In order to improve durability and input-output characteristics, lithium ion secondary batteries are required to achieve a reduction in internal resistance. In particular, since they are used as secondary batteries, it is necessary to suppress an increase in internal resistance after repeated charge and discharge.

[0006] Reference List

[0007] Patent Literature

[0008] PTL 1: JP2013-89485A

[0009] PTL 2: JP2014-193986A

[0010] PTL 3: JPH11-250915A Summary of the invention

[0011] Technical issues

[0012] An object of the present invention is to provide a conductive paste which, when used in a lithium ion secondary battery, achieves low internal resistance and suppresses an increase in internal resistance after repeated charge and discharge.

[0013] Solution to the problem

[0014] Under such circumstances, the inventors have conducted extensive research and found that the above problems can be solved by using a conductive paste comprising a pigment dispersion resin (A), conductive carbon (B), an inorganic material (C) and a solvent (D), wherein the pigment dispersion resin (A) has at least one polar functional group selected from an amide group, an imide group, an ether group, a hydroxyl group, a carboxyl group, a sulfonate group, a phosphate group, a silanol group, an amino group and a pyrrolidone group, and wherein the inorganic material (C) includes at least one selected from glass, glass ceramics and ceramics. Therefore, the present invention provides the following items.

[0015] Item 1. A conductive paste comprising a pigment dispersion resin (A), conductive carbon (B), an inorganic material (C) and a solvent (D),

[0016] wherein the pigment dispersing resin (A) has at least one polar functional group selected from an amide group, an imide group, an ether group, a hydroxyl group, a carboxyl group, a sulfonate group, a phosphate group, a silanol group, an amino group and a pyrrolidone group, and

[0017] The inorganic material (C) comprises at least one selected from glass, glass ceramics and ceramics.

[0018] Item 2. The conductive paste according to Item 1, wherein the pigment dispersion resin (A) has a polar functional group concentration of 0.1 mmol / g to 23 mmol / g.

[0019] Item 3. The conductive paste according to Item 1 or 2, wherein the pigment dispersion resin (A) includes a polyvinyl alcohol resin (a1) having a saponification degree of 30 mol % to 100 mol %.

[0020] Item 4. The conductive paste according to any one of Items 1 to 3, wherein the pigment dispersing resin (A) includes an acrylic resin (a2).

[0021] Item 5. The conductive paste according to any one of Items 1 to 4, wherein the conductive carbon (B) comprises acetylene black (b1) and / or carbon nanotubes (b2).

[0022] Item 6. The conductive paste according to any one of Items 1 to 5, wherein the conductive carbon (B) comprises carbon nanotubes (b2).

[0023] Item 7. The conductive paste according to Item 5 or 6, wherein the carbon nanotube (b2) has a fiber length of 0.1 μm to 100 μm and an outer diameter of 1 nm to 30 nm.

[0024] Item 8. The conductive paste according to any one of Items 1 to 7, wherein the inorganic material (C) comprises, based on mass percentage:

[0025] P2O5: 15% to 60%,

[0026] SiO2: 0% to 15%,

[0027] MO2: 20% to 45%, where M represents one or more selected from Ti, Zr, Ge, Sn, Nb, and Hf,

[0028] A2O3: 0% to 25%, where A represents one or more selected from Al, Y, and Sc,

[0029] EO: 0% to 25%, where E represents one or more selected from Mg and Ca, and

[0030] Li2O: 3% to 20%.

[0031] Item 9. The conductive paste according to Item 8,

[0032] wherein the inorganic material (C) is a glass-ceramic and / or ceramic in which Li 1+x M1 y M2 2-y Si z P 1-z O 12 (0 < x < 2, 0 < y < 2, 0 ≤ z ≤ 1) crystal is precipitated, where in the formula, M1 represents one or more selected from Al, Ca, Y, Mg, and Sc, and M2 represents one or more selected from Ti, Zr, Ge, Sn, Nb, and Hf.

[0033] Item 10. The conductive paste according to any one of Items 1 to 9, wherein the solubility parameter δA of the pigment dispersion resin (A) and the solubility parameter δD of the solvent (D) satisfy the relationship |δA - δD| < 2.0.

[0034] Item 11. The conductive paste according to any one of Items 1 to 10, wherein the solvent (D) includes N-methyl-2-pyrrolidone.

[0035] Item 12. The conductive paste according to any one of Items 1 to 11, wherein the conductive paste has a water content of less than 1.0% by mass.

[0036] Item 13. A mixed paste, comprising the conductive paste according to any one of Items 1 to 12, and further comprising an electrode active material (E).

[0037] Item 14. A mixed paste, comprising a pigment dispersion resin (A), a conductive carbon (B), an inorganic material (C), a solvent (D), and an electrode active material (E),

[0038] wherein the pigment dispersing resin (A) has at least one polar functional group selected from an ester group, an amide group, an imide group, an ether group, a hydroxyl group, a carboxyl group, a sulfonate group, a phosphate group, a silanol group, an amino group and a pyrrolidone group, and

[0039] The inorganic material (C) comprises at least one selected from glass, glass ceramics and ceramics.

[0040] Item 15. An electrode for a positive electrode of a non-aqueous electrolyte lithium-ion battery, obtained by using the mixed slurry described in Item 13 or 14.

[0041] Item 16. An electrode for a positive electrode of a solid electrolyte lithium-ion battery, obtained by using the mixed slurry described in Item 13 or 14.

[0042] Item 17. An all-solid-state battery obtained by using the electrode for a positive electrode as described in Item 16.

[0043] Beneficial effects of the present invention

[0044] The present invention can provide a conductive paste that achieves low internal resistance and suppresses an increase in internal resistance after repeated charge and discharge when used in a lithium ion secondary battery. DETAILED DESCRIPTION

[0045] In the present specification, singular forms (for example, a, an, and the) shall include both singular and plural forms unless otherwise indicated herein or clearly contradicted by context.

[0046] Conductive paste

[0047] The present invention provides a conductive paste comprising a pigment-dispersed resin (A), conductive carbon (B), an inorganic material (C) and a solvent (D), wherein the pigment-dispersed resin (A) has at least one polar functional group selected from an amide group, an imide group, an ether group, a hydroxyl group, a carboxyl group, a sulfonate group, a phosphate group, a silanol group, an amino group and a pyrrolidone group, and wherein the inorganic material (C) includes at least one selected from glass, glass ceramics and ceramics.

[0048] Pigment dispersion resin (A)

[0049] The pigment dispersion resin (A) has at least one polar functional group selected from an amide group, an imide group, an ether group, a hydroxyl group, a carboxyl group, a sulfonate group, a phosphate group, a silanol group, an amino group and a pyrrolidone group. The concentration of the polar functional group in the pigment dispersion resin (A) is not particularly limited, and is generally 0.1 mmol / g to 23 mmol / g, preferably 5 mmol / g to 22.5 mmol / g, and more preferably 11 mmol / g to 22 mmol / g from the viewpoint of dispersibility, storage stability and compatibility with a solvent.

[0050] Specific examples of the resin type used for the pigment dispersion resin (A) include acrylic resins, polyester resins, epoxy resins, polyether resins, alkyd resins, polyurethane resins, polyvinyl alcohol, polyvinyl acetal, polyvinyl pyrrolidone, polyvinyl acetate, silicone resins, polycarbonate resins, silicate resins, chlorine-based resins, fluorine-based resins and composite resins thereof. These resins can be used alone or in combination of two or more.

[0051] In particular, the pigment dispersion resin (A) preferably comprises a vinyl (co)polymer (A') obtained by polymerizing or copolymerizing one or more monomers including a polymerizable unsaturated group-containing monomer of the following formula (1).

[0052] The term "(co)polymer" in the present invention includes both a polymer obtained by polymerizing a single type of monomer and a copolymer obtained by copolymerizing two or more types of monomers.

[0053] C(-R) 2 =C(-R) 2 Formula (1)

[0054] In the formula, R may be the same or different, and each represents a hydrogen atom or an organic group.

[0055] The vinyl (co)polymer (A') preferably contains a structural unit represented by "-CH2-CH(-X)-" in its structure, wherein X represents an organic group having a polar functional group. The polar functional group X in the structural unit is at least one polar functional group selected from an amide group, an imide group, an ether group, a hydroxyl group, a carboxyl group, a sulfonate group, a phosphate group, a silanol group, an amino group and a pyrrolidone group. In the present invention, a "pyrrolidone group" refers to a monovalent group obtained by removing a hydrogen atom from the -NH- part of pyrrolidone.

[0056] Examples of vinyl (co)polymers (A') include hydroxyl-containing vinyl (co)polymers, carboxyl-containing vinyl (co)polymers, pyrrolidone-containing vinyl (co)polymers, amide-containing vinyl (co)polymers, sulfonate-containing vinyl (co)polymers, phosphate-containing vinyl (co)polymers, and amino-containing vinyl (co)polymers. These (co)polymers can be used alone or in combination of two or more.

[0057] Examples of hydroxyl-containing vinyl (co)polymers include polyhydroxyethyl (meth)acrylate, polyvinyl alcohol, vinyl alcohol-fatty acid vinyl copolymers, vinyl alcohol-ethylene copolymers, vinyl alcohol-(N-vinyl formamide) copolymers, and copolymers of hydroxyethyl (meth)acrylate and other monomers containing polymerizable unsaturated groups. The vinyl alcohol unit in the (co)polymer can be obtained by hydrolysis after (co)polymerization with the fatty acid vinyl unit.

[0058] Examples of the carboxyl group-containing vinyl (co)polymer include polymers of (meth)acrylic acid and copolymers of poly(meth)acrylic acid and other polymerizable unsaturated group-containing monomers.

[0059] Examples of the pyrrolidone group-containing vinyl (co)polymer include polyvinyl pyrrolidone, N-vinyl-2-pyrrolidone-ethylene copolymer and N-vinyl-2-pyrrolidone-vinyl acetate copolymer.

[0060] Examples of the amide group-containing vinyl (co)polymer include polymers of (meth)acrylamide and copolymers of (meth)acrylamide and other polymerizable unsaturated group-containing monomers.

[0061] Examples of the sulfonate group-containing vinyl (co)polymer include polymers of propylene sulfonic acid, styrene sulfonic acid and the like, and copolymers of propylene sulfonic acid and / or styrene sulfonic acid with other polymerizable unsaturated group-containing monomers.

[0062] Examples of the vinyl (co)polymer containing a phosphate group include polymers of (meth)acryloyloxyalkyl acid phosphate esters, and copolymers of (meth)acryloyloxyalkyl acid phosphate esters and other polymerizable unsaturated group-containing monomers.

[0063] Examples of the amino group-containing vinyl (co)polymer include polyvinylamine, polyallylamine, polymers of dimethylaminoethyl (meth)acrylate, and copolymers of dimethylaminoethyl (meth)acrylate and other polymerizable unsaturated group-containing monomers.

[0064] In the above description, from the viewpoint of improving the dispersibility and storage property of the conductive paste and reducing the resistance of the conductive paste, the vinyl (co)polymer (A') is preferably a hydroxyl-containing polyvinyl (co)polymer, a carboxyl-containing polyvinyl (co)polymer, a pyrrolidone-containing polyvinyl (co)polymer, etc., and more preferably a hydroxyl-containing polyvinyl (co)polymer, etc. The type of resin is even more preferably a polyvinyl alcohol resin (a1) and / or an acrylic resin (a2), and still more preferably a polyvinyl alcohol resin (a1).

[0065] The polyvinyl alcohol resin (a1) may be a modified or unmodified polyvinyl alcohol resin. The saponification degree of the polyvinyl alcohol resin (a1) is not particularly limited, and is generally 30 mol% to 100 mol%, preferably 65 mol% to 99.9 mol%, more preferably 85 mol% to 99.9 mol%.

[0066] The vinyl (co)polymer (A') can be produced by known polymerization methods. For example, solution polymerization is preferably used. However, the method is not limited thereto, and may be bulk polymerization, emulsion polymerization, suspension polymerization, etc. In solution polymerization, continuous polymerization or intermittent polymerization may be performed, the monomers may be added all at once or in portions, and the addition may be performed continuously or intermittently.

[0067] The polymerization initiator used for solution polymerization is not particularly limited. Specific examples include the following known free radical polymerization initiators: azo compounds, such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile and azobis(4-methoxy-2,4-dimethylvaleronitrile); peroxides, such as acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide and 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate; percarbonate compounds, such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate and diethoxyethyl peroxydicarbonate; perester compounds, such as tert-butyl peroxyneodecanoate, α-cumyl peroxyneodecanoate and tert-butyl peroxyneodecanoate; azobisdimethylvaleronitrile; azobismethoxyvaleronitrile; etc.

[0068] The polymerization reaction temperature is not particularly limited and can be generally set to about 30°C to 200°C.

[0069] The vinyl (co)polymer (A′) thus obtained preferably has a degree of polymerization of 100 to 4,000, more preferably 100 to 3,000, even more preferably 150 to 700.

[0070] The weight average molecular weight of the pigment dispersion resin (A) is not limited, and is preferably 1000 to 200000, more preferably 2000 to 100000, even more preferably 7000 to 30000. In the present invention, the weight average molecular weight can be measured with GPC equipped with an RI probe.

[0071] Specifically, under the conditions where the mobile phase is tetrahydrofuran, the measuring temperature is 40°C, the flow rate is 1 mL / min, and the detector is RI, measurement is performed by using a gel permeation chromatography (GPC) apparatus HLC8120GPC (trade name, produced by Tosoh Corporation) and using four columns (i.e., TSKgel G-4000HXL, TSKgel G-3000HXL, TSKgel G-2500HXL, and TSKgel G-2000HXL (trade names, all produced by Tosoh Corporation)).

[0072] After completion of the synthesis, the vinyl (co)polymer (A') may be subjected to solvent removal and / or solvent replacement to obtain a solid or a resin solution in which the solvent has been replaced with a desired solvent.

[0073] Solvent removal can be performed by heating under normal pressure. Solvent removal can also be performed under reduced pressure. Solvent replacement can be performed by introducing a solvent for replacement at any step before, during or after solvent removal.

[0074] The solid content of the pigment dispersion resin (A) is, for example, 0.1% by mass or more, preferably 0.5% by mass or more, and more preferably 1% by mass or more, and is, for example, 10% by mass or less, preferably 7.5% by mass or less, and more preferably 5% by mass or less, based on the total solid content of the conductive paste.

[0075] Based on the content of conductive carbon (B), the solid content of the pigment dispersion resin (A) is, for example, 0.1 mass % or more, preferably 0.5 mass % or more, and more preferably 1 mass % or more, and is, for example, 20 mass % or less, preferably 15 mass % or less, and more preferably 10 mass % or less.

[0076] Conductive pigment (B)

[0077] The conductive pigment (B) used may be any conductive pigment that can be used in the technical field of conductive pastes to which the present invention belongs, and preferably comprises carbon nanotubes (B-1) and / or conductive carbon (B-2) having an average particle size of 10 nm to 80 nm. The conductive pigment (B) may further comprise an additional conductive pigment (B-3) that is different from the carbon nanotubes (B-1) and different from the conductive carbon (B-2) having an average particle size of 10 nm to 80 nm.

[0078] Carbon nanotubes (B-1)

[0079] The carbon nanotube (B-1) used may be a single-walled carbon nanotube or a multi-walled carbon nanotube, which may be used alone or in combination. In particular, multi-walled carbon nanotubes are preferably used in view of viscosity, conductivity and cost.

[0080] The average outer diameter of the carbon nanotubes (B-1) is not particularly limited, and is, for example, 1 nm or more, preferably 3 nm or more, more preferably 5 nm or more, and is, for example, 30 nm or less, preferably 25 nm or less, more preferably 20 nm or less. The average outer diameter of the carbon nanotubes (B-1) can be determined by observing the morphology of, for example, 100 carbon nanotubes under a transmission electron microscope, measuring the length of their minor axes, and calculating the number average.

[0081] The average length of the carbon nanotubes (B-1) is not particularly limited, and is, for example, 0.1 μm or more, preferably 1 μm or more, and more preferably 5 μm or more. The upper limit of the average length of the carbon nanotubes (B-1) is not particularly limited, and is, for example, 100 μm or less, preferably 80 μm or less, and more preferably 60 μm or less. The average length of the carbon nanotubes (B-1) can be determined by observing the morphology of, for example, 100 carbon nanotubes under SEM, measuring the fiber length, and calculating the number average.

[0082] The specific surface area of ​​the carbon nanotube (B-1) is not particularly limited, and is, for example, 1 m 2 / g or more, preferably 10m 2 / g or more, and is, for example, 1000m 2 / g or less, more preferably 500m 2 / g or less, which is related to viscosity and conductivity. The specific surface area of ​​carbon nanotube (B-1) can be measured using a fully automatic specific surface area measuring device.

[0083] Conductive carbon (B-2) having an average particle size of 10 nm to 80 nm

[0084] Conductive carbon (B-2) with an average particle size of 10nm to 80nm refers to conductive carbon with an average primary particle size of 10nm to 80nm. Examples of conductive carbon (B-2) with an average primary particle size of 10nm to 80nm include at least one conductive carbon selected from acetylene black, Ketjen black, furnace black, thermal black, graphene and graphite. Conductive carbon (B-2) is preferably one or more selected from acetylene black, Ketjen black, furnace black and thermal black, more preferably one or more selected from acetylene black and Ketjen black, and even more preferably one or more types of acetylene black. One or more types of acetylene black refers to one or more types of acetylene black having one or more different physical properties (e.g., average primary particle size, BET specific surface area, pH and DBP oil absorption).

[0085] The average primary particle size of the conductive carbon (B-2) used here refers to the average primary particle size obtained by observing the conductive carbon (B-2) under an electron microscope, calculating the projected areas of 100 individual particles, determining the diameter of an imaginary circle equal to these areas, and then simply averaging the diameters of the 100 particles. If the pigment is in an aggregated state, the calculation is performed using the primary particles constituting the aggregated particles.

[0086] The BET specific surface area of ​​the conductive carbon (B-2) is not particularly limited. The BET specific surface area is, for example, 1 m 2 / g or more, preferably 10m 2 / g or more, more preferably 20m 2 / g or more, and for example 500m 2 / g or less, preferably 250m 2 / g or less, more preferably 200m 2 / g or less, which is related to viscosity and conductivity.

[0087] The dibutyl phthalate (DBP) oil absorption of the conductive carbon (B-2) is not particularly limited. The dibutyl phthalate (DBP) oil absorption is, for example, 60 ml / 100 g or more, preferably 150 ml / 100 g or more, and is, for example, 1000 ml / 100 g or less, preferably 800 ml / 100 g or less, which is related to pigment dispersibility and conductivity.

[0088] From the viewpoint of electrical conductivity, the conductive carbon (B-2) is preferably in a state where the primary particles form a chain structure. The structural index is not limited and is, for example, 1.5 or greater, preferably 1.7 or greater. From the viewpoint of developing the structure and obtaining sufficient electrical conductivity, the lower limit of the structural index is preferably within the above range. The upper limit of the structural index is also not limited and is 4.0 or less, preferably 3.2 or less. From the viewpoint of preventing the particle size from becoming too large relative to the DBP oil absorption (thereby suppressing the reduction of the conductive path) to thereby obtain sufficient electrical conductivity and further preventing the viscosity of the slurry from increasing, the upper limit of the structural index is preferably within the above range.

[0089] The structure itself can be observed relatively easily using images taken with an electron microscope. The structural index is a numerical value that quantifies the degree of structure. The structural index can generally be defined as the DBP oil absorption (ml / 100g) divided by the specific surface area (m 2 / g) to obtain the value.

[0090] Additional conductive pigment (B-3)

[0091] The conductive pigment (B) may contain an additional conductive pigment (B-3). The additional conductive pigment (B-3) is a conductive pigment other than the carbon nanotube (B-1) and other than the conductive carbon (B-2) having an average particle size of 10 nm to 80 nm.

[0092] Examples of additional conductive pigments (B-3) include one or more selected from metal powders, metal fibers, metal compounds, and conductive ceramics. The metal in the metal powders, metal fibers, metal compounds, etc. may be, for example, one or more metal elements selected from copper, silver, gold, nickel, aluminum, titanium, etc.

[0093] Specific examples include one or more selected from the following:

[0094] Metal powders of copper, silver, gold, nickel, aluminum, titanium, etc.;

[0095] Metal compounds doped with various elements, such as antimony-doped tin oxide and phosphorus-doped tin oxide;

[0096] Coated pigments such as needle-like titanium oxide, antimony oxide, zinc antimonate, and indium tin oxide, each having a surface coated with tin oxide and / or antimony, pigments wherein whiskers on the surface of carbon or graphite are coated with tin oxide and the like, and pigments wherein the surface of platelet-like mica is coated with at least one conductive metal oxide selected from tin oxide, antimony-doped tin oxide, tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), phosphorus-doped tin oxide, and nickel oxide; and

[0097] Conductive pigments comprising tin oxide and phosphorus on the surface of titanium dioxide particles.

[0098] Inorganic materials (C)

[0099] The conductive paste of the present invention is characterized in that the inorganic material (C) includes at least one selected from glass, glass ceramics and ceramics. Among these inorganic materials (C), in the present invention, glass ceramics are preferred. In addition, in the present invention, the inorganic material (C) is preferably an electrolyte that provides a conductive paste with ionic conductivity (for example, lithium ion conductivity). In the present invention, the inorganic material (C) preferably includes, based on mass percentage,

[0100] P2O5: 15% to 60%,

[0101] SiO2: 0% to 15%,

[0102] MO2: 20% to 45%, wherein M represents one or more selected from Ti, Zr, Ge, Sn, Nb and Hf,

[0103] A2O3: 0% to 25%, wherein A represents one or more selected from Al, Y and Sc,

[0104] EO: 0% to 25%, wherein E represents one or more selected from Mg and Ca, and

[0105] Li2O: 3% to 20%,

[0106] More preferably,

[0107] P2O5: 25% to 47%,

[0108] SiO2: 0% to 12%,

[0109] MO2: 25% to 45%, wherein M represents one or more selected from Ti, Zr and Ge,

[0110] A2O3: 0% to 18%, wherein A represents one or more selected from Al and Y,

[0111] EO: 0% to 15%, wherein E represents one or more selected from Mg and Ca, and

[0112] Li2O: 5% to 20%, and

[0113] Most preferably,

[0114] P2O5: 30% to 42%,

[0115] SiO2: 0% to 9%,

[0116] TiO2: 30% to 45%,

[0117] A2O3: 0% to 12%, and

[0118] Li2O: 9% to 20%.

[0119] When glass is used as the inorganic material (C), the glass may be, for example, a glass electrolyte. Examples of the glass electrolyte include glass electrolytes represented by Li2O-G (G = one or more of Al2O3, Nb2O5, Y2O3, SiO2, B2O5, P2O5, V2O5, TeO2, CeO2, GeO2, Bi2O3, etc.). The glass electrolyte is not particularly limited as long as the lithium concentration is 15% by mass or more in terms of oxide, the form is amorphous, and the lithium ion conductivity at room temperature is 1×10 -11It suffices that it is S / cm or greater. The glass electrolyte having particularly excellent properties has a basic composition represented by Li2O-Al2O3-P2O5. Unless otherwise specified, the content of each component in the glass electrolyte of the present invention is expressed in mass% based on oxides. The "composition based on oxides" used herein refers to the composition of the components contained in the glass electrolyte, where it is assumed that oxides, double salts, metal fluorides, etc. (used as starting materials for the glass electrolyte) are all decomposed and converted into oxides upon melting, and the total mass of the formed oxides is 100 mass%.

[0120] The ceramic and / or glass ceramic used as the inorganic material (C) is preferably a ceramic electrolyte and / or a glass ceramic electrolyte.

[0121] In the ceramic and / or glass ceramic used as the inorganic material (C), it is preferable to precipitate a crystal represented by Li 1+x M1 y M2 2-y Si z P 1-z O 12 (0 < x < 2, 0 < y < 2, 0 ≤ z ≤ 1), where in the formula, M1 represents one or more selected from Al, Ca, Y, Mg, and Sc, and M2 represents one or more selected from Ti, Zr, Ge, Sn, Nb, and Hf.

[0122] The ceramic electrolyte or glass ceramic electrolyte is not particularly limited, and is preferably a lithium-containing phosphate compound having a rhombohedral crystal system. Materials with different compositions can be mixed or combined. The surface can be coated with a glass electrolyte or the like. Alternatively, it is also possible to use a glass ceramic in which a crystalline phase of a lithium-containing phosphate compound having a NASICON-type structure is precipitated by heat treatment. In addition to those having a NASICON structure, a solid electrolyte containing Li, La, Mg, Ca, Fe, Co, Cr, Mn, Ti, Zr, Sn, Y, Sc, P, Si, O, In, Nb, and / or F, which has a LISICON-type, perovskite-type, β-Fe2(SO4)3-type, and / or Li3In2(PO4)3-type crystal structure and has a Li ion conductivity of 1 × 10 -5 S / cm or greater at room temperature can also be used. These electrolytes can be used by mixing.

[0123] In this specification, glass ceramics refers to a material obtained by precipitating a crystalline phase in a glass phase by heat treatment of glass, and also refers to a material containing an amorphous solid and a crystal, and includes a material in which the glass phase undergoes a phase transition to a crystalline phase, i.e., a material in which the amount of crystals (crystallinity) is 100% by mass. Even in glass ceramics of 100% crystalline material, almost no voids are observed between the crystal particles or inside the crystals. In contrast, due to their production process, typical ceramics and sintered materials have inevitable voids and / or grain boundaries between the crystal particles and inside the crystals, and can be distinguished from the glass ceramics used in the present invention. For glass ceramics, by controlling the crystallization process, the reduction in conductivity between crystals can be suppressed, making it easy to achieve a conductivity comparable to the intrinsic conductivity of the crystal particles themselves.

[0124] In the present invention, the average particle size of the glass, ceramic and / or glass ceramic contained in the inorganic material (C) is not particularly limited, and is preferably 3 μm or less, more preferably 1 μm or less, and most preferably 0.5 μm or less, in consideration of the particle size of the active material in the electrode and the electrode thickness, and in order to easily achieve excellent dispersibility in the electrode. The lower limit of the average particle size of the glass, ceramic and / or glass ceramic in the inorganic material (C) is also not limited, and is preferably 0.01 μm or more, more preferably 0.05 μm or more, and most preferably 0.10 μm or more, so as to easily achieve excellent dispersion in the electrode and excellent bonding between electrode materials.

[0125] The average particle size of the glass, ceramics and / or glass ceramics in the inorganic material (C) is the value of D50 (50% cumulative particle diameter) measured by laser diffraction. Specifically, the value measured by a particle size analyzer (Microtrac MT3300EXII, produced by Nikkiso Co., Ltd.) or a submicron particle analyzer (N5, produced by Beckman Coulter) can be used. The above average particle size is expressed on a volume basis.

[0126] The inorganic material (C) of the present invention used may be a commercially available lithium ion conductive glass ceramic having the above composition and physical properties. Examples of commercial products include LICGC produced by Ohara Co., Ltd. TM PW-01.

[0127] Solvent (D)

[0128] The solvent (D) used in the conductive paste of the present invention is not particularly limited as long as it is compatible with the pigment dispersion resin (A) and can disperse the conductive carbon (B). Specific examples include: hydrocarbon solvents such as n-butane, n-hexane, n-heptane, n-octane, cyclopentane, cyclohexane and cyclobutane; aromatic-based solvents such as toluene and xylene; ketone-based solvents such as methyl isobutyl ketone; ether-based solvents such as n-butyl ether, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether and diethylene glycol; ester-based solvents such as ethyl acetate, n-butyl acetate, isobutyl acetate, ethylene glycol monomethyl ether acetate and diethylene glycol butyl ether acetate; ketone-based solvents such as methyl ethyl ketone, methyl isobutyl ketone and diisobutyl ketone; alcohol-based solvents such as ethanol, isopropanol, n-butanol, sec-butanol and isobutyl alcohol; and amide-based solvents such as Equamide (trade name, manufactured by Idemitsu Kosan Co., Ltd. Co., Ltd.), amide-based solvents), N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformamide, N-methylacetamide, N-methylpropionamide and N-methyl-2-pyrrolidone. Among them, N-methyl-2-pyrrolidone is preferred. These solvents can be used alone or in combination of two or more.

[0129] From the viewpoint of solubility of the pigment dispersion resin (A) having an active hydrogen group and storage stability of the conductive pigment slurry, the solvent (D) usable in the conductive paste of the present invention preferably contains a solvent having a polar functional group (e.g., a hydroxyl group, a carboxyl group, an amide group, an amino group, or an ether group).

[0130] From the viewpoint of pigment dispersibility of the conductive pigment paste and avoiding mass change or hydrolysis of the resin component, it is preferred that substantially no water is contained. As used herein, the phrase "substantially no water is contained" means that the water content is generally 1% by mass or less, preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, based on the total amount of the conductive pigment paste.

[0131] In the present invention, the water content of the conductive paste can be measured by Karl Fischer coulometric titration. Specifically, the measurement can be performed using a Karl Fischer moisture analyzer (produced by Kyoto Electronics Manufacturing Co., Ltd., trade name: MKC-610) and setting a moisture evaporator (produced by Kyoto Electronics Manufacturing Co., Ltd., trade name: ADP-611) provided in the Karl Fischer moisture analyzer to a temperature of 130°C.

[0132] The solubility parameter δA of the pigment-dispersing resin (A) and the solubility parameter δD of the solvent (D) preferably satisfy the relationship of |δA-δD|<2.0.

[0133] From the viewpoint of pigment dispersibility, storage stability and compatibility with solvents, the solubility parameter δA of the pigment dispersion resin (A) is, for example, 9.3 or more, preferably 10.0 or more, and more preferably 11.0 or more, and is, for example, 13.5 or less, preferably 13.0 or less, and more preferably 12.5 or less.

[0134] The units of the above solubility parameters are all "(cal / cm 3 ) 1 / 2 ”.

[0135] The solubility parameter of the resin is numerically quantified based on a turbidity measurement method known to those skilled in the art. Specifically, the solubility parameter can be determined according to the formula proposed by KW Suh and JM Corbett (Journal of Applied Polymer Science, 12, 2359, 1968).

[0136] When two or more pigment-dispersing resins are used for the pigment-dispersing resin (A), "the solubility parameter δA of the pigment-dispersing resin (A)" is the sum of the solubility parameter values ​​of each resin multiplied by the mass fraction.

[0137] Other additives

[0138] The conductive paste of the present invention may contain components other than the above components (A), (B), (C) and (D) (sometimes referred to as "other additives"). Examples of other additives may include neutralizers, pigment dispersants, defoamers, preservatives, rust inhibitors, plasticizers and adhesives (binders).

[0139] The example of pigment dispersant and / or adhesive comprises acrylic resin, polyester resin, epoxy resin, polyether resin, alkyd resin, polyurethane resin, silicone resin, polycarbonate resin, silicate resin, resin based on chlorine, resin based on fluorine, polyvinyl pyrrolidone resin, polyvinyl alcohol resin, polyvinyl acetal resin and its composite resin, rather than the dispersed resin (A) described above.These resins can be used alone or in combination of two or more.Wherein, polyvinylidene fluoride (PVDF) is particularly preferred.

[0140] The conductive paste of the present invention may optionally contain an acidic compound. The acidic compound is not particularly limited, and both inorganic acids and organic acids can be used. Examples of inorganic acids include hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid. Examples of organic acids include carboxylic acid compounds and sulfonic acid compounds. Examples of carboxylic acid compounds include formic acid, acetic acid, propionic acid, butyric acid, tartaric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, (methyl) acrylic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, citraconic acid and fluoroacetic acid. Examples of sulfonic acid compounds include methanesulfonic acid, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid and dinonylnaphthalene disulfonic acid. In addition to the above, anhydrides or hydrates of these acidic compounds, or acidic compounds in which a portion is in the form of salts, can also be used. These can be used alone or in combination of two or more.

[0141] Production method of conductive paste of the present invention

[0142] The total solid content of the dispersed resin (A) in the solid of the conductive paste of the present invention is not limited and is generally 20 to 99.95 mass %, preferably 40 to 99.9 mass %, more preferably 60 to 99.7 mass % in terms of conductivity and the like.

[0143] The solid content of the inorganic material (C) in the solid of the conductive paste of the present invention is not limited and is usually 0.05 to 80 mass %, preferably 0.1 to 60 mass %, more preferably 0.3 to 40 mass % from the viewpoint of conductivity and the like.

[0144] The content of the solvent (D) in the conductive paste of the present invention is not limited, and is generally 65 to 99.9% by mass, preferably 70 to 99.5% by mass, more preferably 75 to 99% by mass, from the viewpoints of viscosity when the pigment is dispersed, pigment dispersibility, storage stability and production efficiency.

[0145] The conductive slurry of the present invention can be prepared by uniformly mixing and dispersing the above-described components using, for example, a known dispersing device (e.g., a paint shaker, a sand mill, a ball mill, a pebble mill, an LMZ mill, a DCP bead mill, a planetary ball mill, a homogenizer, a twin-screw compounder, and a film spinning system high-speed mixer).

[0146] As described later, the conductive paste of the present invention can be used to produce a mixed slurry by mixing with an electrode active material. The mixed slurry can be used to produce a positive electrode of a lithium ion battery. Therefore, in a preferred embodiment, the conductive paste of the present invention is a conductive paste for a positive electrode of a lithium ion battery.

[0147] Mixed slurry

[0148] The present invention provides a mixed slurry comprising the conductive slurry described above and further comprising an electrode active material.

[0149] Electrode active materials

[0150] Examples of electrode active materials include lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), lithium cobalt oxide (LiCoO2), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2, NCA, lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium manganese phosphate (LMP), lithium cobalt phosphate (LCP), lithium nickel phosphate (LNP), LNMO and other lithium composite oxides. These electrode active materials can be used alone or in combination of two or more. In terms of battery capacity and battery resistance, for example, the solid content of the electrode active material in the solid of the mixed slurry of the present invention is generally 70% by mass or more and less than 100% by mass, preferably 80% by mass or more and less than 100% by mass.

[0151] Production method of mixed slurry

[0152] The mixed slurry of the present invention can be obtained by first preparing the conductive slurry described above and then mixing the electrode active material with the conductive slurry. The mixed slurry of the present invention can also be prepared by mixing the components (A), (B), (C) and (D) described above with the electrode active material.

[0153] The total solid content of the dispersed resin (A) in the solid of the mixed slurry of the present invention is not particularly limited, and is generally 0.01% by mass to 50% by mass or less, preferably 0.05% by mass to 30% by mass, more preferably 0.1% by mass to 20% by mass in terms of, for example, production efficiency and conductivity.

[0154] The solid content of the inorganic material (C) in the solid of the mixed slurry of the present invention is not particularly limited, and is generally 0.01 to 10% by mass, preferably 0.02 to 5% by mass, more preferably 0.05 to 3% by mass from the viewpoint of conductivity of the mixed layer.

[0155] The content of the solvent (D) in the mixed slurry of the present invention is not limited, and is generally 25 to 55% by mass, preferably 30 to 50% by mass, more preferably 35 to 45% by mass, from the viewpoints of viscosity when the pigment is dispersed, pigment dispersibility, storage stability and productivity.

[0156] Method for producing positive electrode for lithium-ion battery

[0157] The positive electrode mixed layer of the lithium ion secondary battery can be produced by applying the mixed slurry to the positive electrode core surface and then drying. The slurry of the present invention can be used as a slurry for forming a mixed layer and can also be used as a slurry for forming a primer layer between the positive electrode core and the composite layer.

[0158] The mixed slurry can be applied by using a known method using a die coater or the like. The amount of the mixed slurry applied is not particularly limited. For example, the amount can be set so that the thickness of the positive electrode mixed layer after drying is 0.04 mm to 0.30 mm, preferably 0.06 mm to 0.24 mm. The temperature of the drying step can be appropriately set, for example, 80° C. to 200° C., preferably 100° C. to 180° C. The time of the drying step can be appropriately set, for example, 5 seconds to 120 seconds, preferably 5 seconds to 60 seconds.

[0159] Battery

[0160] The present invention provides a battery obtained by using the electrode described above. Generally, the battery of the present invention includes an electrode for the positive electrode of the lithium ion battery described above, an electrolyte layer and an electrode for the negative electrode. The battery of the present invention includes, for example, a non-aqueous electrolyte lithium ion battery using a non-aqueous electrolyte for the electrolyte layer, and an all-solid-state lithium ion battery using a solid electrolyte for the electrolyte layer.

[0161] In the present invention, the non-aqueous electrolyte lithium ion battery includes, for example, a lithium ion secondary battery including a microporous separator provided between a positive electrode and a negative electrode, an ion-conductive non-aqueous electrolyte solution, etc., and a lithium polymer secondary battery containing a polymer absorbing a non-aqueous electrolyte solution, etc. as a separator between the positive electrode and the negative electrode. In the present invention, the all-solid-state lithium ion battery includes, for example, a battery containing, as a lithium ion-conductive solid electrolyte, a material obtained by sintering at least one material selected from a glass electrolyte, a ceramic electrolyte, and a glass-ceramic electrolyte.

[0162] The non-aqueous electrolyte solution used may be any known non-aqueous electrolyte solution. For example, a solution obtained by dissolving a lithium salt in an organic solvent may be used. The organic solvent used herein may be, for example, an ester-based solvent, an ether-based solvent, a carbonate-based solvent, or a ketone-based solvent.

[0163] The lithium salt used may be, for example, LiPF6, LiBF4, LiClO4, LiN(SO2CF3)2, LiN(SO2C2F5)2 or LiC(SO2CF3)3.

[0164] The non-aqueous electrolyte solution used may be a room temperature molten salt having lithium ion conductivity. The room temperature molten salt having lithium ion conductivity used may be those obtained by mixing a molten salt (e.g., EMI-TFSI (1-ethyl-3-methylimidazolium-bis(trifluoromethanesulfonyl)imide), EMI-BF4 (1-ethyl-3-methylimidazolium tetrafluoroborate), TMPA-TFSI (trimethylpropylammonium-bis(trifluoromethanesulfonyl)imide), or PP13 (N-methyl-N-propylpiperidinium)) with a lithium salt (e.g., LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiN(SO2CF3)2 (lithium bis(trifluoromethanesulfonyl)imide), LiN(SO2C2F5)2 (lithium bis(pentafluoroethanesulfonyl)imide), LiSO3CF3 (lithium trifluoromethanesulfonate), or LiPF6 (lithium hexafluorophosphate)). However, the room temperature molten salt is not limited to these, and various molten salts, lithium salts, etc. may be used. Furthermore, the above room temperature molten salt may be mixed with a nonaqueous solvent.

[0165] Example

[0166] The present invention is described in more detail below with reference to Examples and Comparative Examples. However, the present invention is not limited to these Examples.

[0167] Below, "AB" stands for acetylene black, "CNT" stands for carbon nanotube, "PVA" stands for polyvinyl alcohol, and "PVDF" stands for polyvinylidene fluoride.

[0168] Conductive paste production

[0169] Examples 1 to 9 and Comparative Examples 1 to 7

[0170] The components except the glass ceramic in Tables 1 and 2 below were added to a container and mixed with a disperser for 10 minutes. Subsequently, the mixture was dispersed in Scandex (trade name, LAU disperser, produced by O-Well Corporation), and the glass ceramic was added while stirring the dispersed solution with a disperser. After the addition, the mixture was mixed with a disperser for 10 minutes to obtain conductive pastes X-1 to X-9 and conductive pastes Y-1 to Y-7.

[0171] For X-1 to X-6 and Y-1 to Y-3, dispersion was carried out in Scandex for 3 hours, and for X-7 to X-9 and Y-4 to Y-7, dispersion was carried out in Scandex for 6 hours. The amounts of dispersing resin in the table are based on solid content.

[0172]

[0173]

[0174] Viscosity measurement

[0175] The viscosity of the conductive pastes obtained in Examples and Comparative Examples was measured at a shear rate of 1.0 sec-1 at 25° C. using a cone and plate viscometer (manufactured by ThermoFisher Scientific KK, trade name HAAKE Mars 3, diameter: 35 mm, 2° inclined cone and plate) and evaluated according to the following criteria.

[0176] S, A, and B are considered acceptable, and C and D are considered unacceptable.

[0177] The evaluation results are shown in Tables 1 and 2 above.

[0178] S: Viscosity is less than 1.0 Pa·s.

[0179] A: The viscosity is 1.0 Pa·s or more and less than 10.0 Pa·s.

[0180] B: The viscosity is 10.0 Pa·s or more and less than 25.0 Pa·s.

[0181] C: Viscosity is 25.0 Pa s or more.

[0182] D: Viscosity cannot be measured.

[0183] Production of cathode slurry

[0184] Production of cathode slurry using carbon nanotubes (CNT)

[0185] LiCoO2 (average particle size: 5 μm), conductive pastes X-1 to X-6 and conductive paste Y-1 (CNT applied thereto) obtained in the embodiment, and polyvinylidene fluoride (PVDF) diluted to 5 wt% with N-methyl-2-pyrrolidone (NMP) (as a binder) were mixed at a material weight ratio of LiCoO2:AB:PVDF=97:1.5:1.5. Then, the mixture was stirred and mixed with a disperser, while N-methyl-2-pyrrolidone (NMP) was appropriately added so that the solid content was 55% to 60%, thereby obtaining a slurry for application to the positive electrode.

[0186] Production of positive electrode slurry using acetylene black (AB)

[0187] LiCoO2 (average particle size: 8 μm), conductive paste X-7 to conductive paste X-9 and conductive paste Y-4 (AB applied thereto) obtained in the example, and polyvinylidene fluoride (PVDF) diluted to 5 wt% with N-methyl-2-pyrrolidone (NMP) (as a binder) were mixed at a material weight ratio of LiCoO2:AB:PVDF=92:4:4. Then, the mixture was stirred and mixed with a disperser, while appropriately adding N-methyl-2-pyrrolidone (NMP) so that the solid content was 60% to 65%, thereby obtaining a slurry for application to the positive electrode.

[0188] Lithium-ion battery production

[0189] Production of positive electrode sheets

[0190] Each of the slurries was applied to a 20 μm thick aluminum foil with an applicator and then dried to obtain a sheet for a positive electrode. The obtained sheet for a positive electrode was pressed to 2.9 g / cm 3 density to obtain the positive electrode sheet.

[0191] The dry film thickness of the slurry is shown in the "Fine Adjustment of Positive and Negative Electrode Capacity Ratio" section below.

[0192] Negative plate

[0193] For the negative electrode, HIS-LIB-N-Gr-002 spherulite graphite TSG-A1 (3.2 mAh / cm 2 , produced by HohsenCorp.).

[0194] Fine-tuning of the positive and negative electrode capacity ratio

[0195] The thickness of each slurry used to apply the positive electrode when applied was finely adjusted so that the ratio of the capacity of the opposite side of the positive electrode sheet to the capacity of the negative electrode sheet was 1.05 to 1.2.

[0196] Electrolyte solution

[0197] For lithium-ion batteries, the electrolyte solution used is a liquid obtained by mixing 2 wt % of vinylene carbonate (VC) with a solvent, in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 1:3, and the electrolyte LiPF6 is further dissolved in the mixture to a concentration of 1 mol / L.

[0198] Production of two-electrode batteries (lithium-ion batteries)

[0199] The positive and negative electrode sheets described above were punched to obtain holes with a diameter of 18 cm 2 and 19.74cm 2 The positive electrode sheet and the negative electrode of the coating area of ​​​​the positive electrode sheet are connected. The aluminum sheet is connected to the aluminum foil of the positive electrode sheet, and the nickel sheet is connected to the copper foil of the negative electrode sheet. A polypropylene microporous membrane (Selion P2010, produced by CS Tech Co., Ltd.) is placed between the positive electrode sheet and the negative electrode sheet so that the positive electrode sheet is assembled on the opposite side of the negative electrode sheet. The obtained product is then placed inside a bag-shaped aluminum laminate packaging material, and 0.75ml of an electrolyte solution is introduced. The opening portion is then sealed with a small vacuum packaging machine (trade name SV-150, produced by Tosei Corporation) to obtain a double-electrode battery for evaluation.

[0200] Battery performance evaluation

[0201] Cycle Test

[0202] Using a battery charge / discharge device (trade name HJ1001SD8, manufactured by Hokuto Denko Corporation), one hundred cycles of charge and discharge were performed at 45° C. for the lithium ion battery obtained by using the conductive slurry (positive electrode slurry) containing AB of the embodiment and the comparative example, and one hundred cycles of charge and discharge were performed at 60° C. for the lithium ion battery obtained by using the conductive slurry containing CNT, so that charging was performed to 4.35 V at a current of 0.5 C, and after standing for 30 minutes, discharging was performed to 3 V at a current of 1 C.

[0203] DC resistance measurement

[0204] The DC resistance of the lithium ion battery obtained by using the conductive slurry (positive electrode slurry) of the embodiment and the comparative example was measured at the first cycle (initial) and the 100th cycle with a battery charge / discharge device (produced by Hokuto Denko Corporation, trade name HJ1001SD8). After charging to 4.35V at 25°C with a current of 1 / 3C, standing for 30 minutes, discharging for 1.5 hours with a current of 1 / 3C, and then standing for 3 hours, the DC resistance was measured at a specified temperature. The DC resistance at 25°C was calculated from the slope of the curve obtained by alternately discharging and charging for 10 seconds with a current of 1 / 5C, 1 / 2C, 1C, and 2C, and extracting the voltage and current values ​​after discharging for 10 seconds. The DC resistance at -20°C was calculated from the slope of the curve obtained by alternately discharging and charging for 10 seconds with a current of 1 / 200C, 1 / 100C, 1 / 80C, and 1 / 60C, and extracting the voltage and current values ​​after discharging for 10 seconds. A 30 minute rest period was provided between discharging and charging.

[0205] Evaluation when CNT is included

[0206] The lithium ion battery obtained by using the conductive paste containing CNTs was evaluated according to the following criteria: In this evaluation, when the results of both tests at 25° C. and −20° C. were acceptable, the battery performance was considered to be acceptable.

[0207] Acceptable: DC resistance at room temperature (25°C) is less than 3.5Ω at the 100th cycle. Acceptable: DC resistance at low temperature (-20°C) is less than 87Ω at the 100th cycle. Unacceptable: DC resistance at room temperature (25°C) is 3.5Ω or more at the 100th cycle.

[0208] Unacceptable: DC resistance at low temperature (-20°C) at the 100th cycle is 87Ω or more.

[0209] Evaluation when AB is included

[0210] The lithium ion battery obtained by using the conductive paste containing AB was evaluated according to the following criteria: In this evaluation, when the results of both tests at 25° C. and −20° C. were acceptable, the battery performance was considered to be acceptable.

[0211] Acceptable: DC resistance at room temperature (25°C) is less than 4.0Ω at the 100th cycle. Acceptable: DC resistance at low temperature (-20°C) is less than 155Ω at the 100th cycle. Unacceptable: DC resistance at room temperature (25°C) is 4.0Ω or more at the 100th cycle.

[0212] Unacceptable: DC resistance at low temperature (-20°C) at the 100th cycle is 155Ω or more.

[0213] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made based on the technical idea of ​​the present invention.

[0214] For example, the compositions and numerical values ​​stated in the above embodiments are merely examples, and compositions and numerical values ​​different from those may be used if necessary.

[0215] Although the above embodiments show examples in which glass ceramics are used as the inorganic material, glass or ceramics disclosed in this specification may also be appropriately used.

Claims

1. A conductive paste comprising a pigment dispersion resin (A), conductive carbon (B), an inorganic material (C) and a solvent (D), wherein the pigment dispersing resin (A) has at least one polar functional group selected from an amide group, an imide group, an ether group, a hydroxyl group, a carboxyl group, a sulfonate group, a phosphate group, a silanol group, an amino group and a pyrrolidone group, and The inorganic material (C) comprises at least one selected from glass, glass ceramics and ceramics. 2 . The conductive paste according to claim 1 , wherein the pigment dispersion resin (A) has a polar functional group concentration of 0.1 mmol / g to 23 mmol / g. 3 . The conductive paste according to claim 1 , wherein the pigment dispersion resin (A) comprises a polyvinyl alcohol resin (a1) having a saponification degree of 30 mol % to 100 mol %. 4 . The conductive paste according to claim 1 , wherein the pigment dispersion resin (A) comprises an acrylic resin (a2). 5 . The conductive paste according to claim 1 , wherein the conductive carbon (B) comprises acetylene black (b1) and / or carbon nanotubes (b2). 6 . The conductive paste according to claim 1 , wherein the conductive carbon (B) comprises carbon nanotubes (b2). 7 . The conductive paste according to claim 5 , wherein the carbon nanotube ( b2 ) has a fiber length of 0.1 μm to 100 μm and an outer diameter of 1 nm to 30 nm.

8. The conductive paste according to any one of claims 1 to 7, wherein the inorganic material (C) comprises, based on mass percentage: P2O5: 15% to 60%, SiO2: 0% to 15%, MO2: 20% to 45%, wherein M represents one or more selected from Ti, Zr, Ge, Sn, Nb and Hf, A2O3: 0% to 25%, wherein A represents one or more selected from Al, Y and Sc, EO: 0% to 25%, wherein E represents one or more selected from Mg and Ca, and Li2O: 3% to 20%.

9. The conductive paste according to claim 8, wherein the inorganic material (C) is a glass-ceramic and / or ceramic of a crystal of Li 1+x M1 y M2 2-y Si z P 1-z O 12 (0 < x < 2, 0 < y < 2, 0 ≤ z ≤ 1), wherein in the formula, M1 represents one or more selected from Al, Ca, Y, Mg, and Sc, and M2 represents one or more selected from Ti, Zr, Ge, Sn, Nb, and Hf. 10 . The conductive paste according to claim 1 , wherein a solubility parameter δA of the pigment dispersion resin (A) and a solubility parameter δD of the solvent (D) satisfy a relationship of |δA−δD|<2.

0. 11 . The conductive paste according to claim 1 , wherein the solvent (D) comprises N-methyl-2-pyrrolidone. 12 . The conductive paste according to claim 1 , wherein the conductive paste has a water content of less than 1.0% by mass. 13 . A mixed slurry comprising the conductive slurry according to claim 1 , and further comprising an electrode active material (E).

14. A mixed slurry comprising a pigment dispersion resin (A), conductive carbon (B), an inorganic material (C), a solvent (D) and an electrode active material (E), wherein the pigment dispersing resin (A) has at least one polar functional group selected from an ester group, an amide group, an imide group, an ether group, a hydroxyl group, a carboxyl group, a sulfonate group, a phosphate group, a silanol group, an amino group and a pyrrolidone group, and The inorganic material (C) comprises at least one selected from glass, glass ceramics and ceramics.

15. An electrode for a positive electrode of a non-aqueous electrolyte lithium ion battery obtained by using the mixed slurry according to claim 13 or 14.

16. An electrode for a positive electrode of a solid electrolyte lithium ion battery obtained by using the mixed slurry according to claim 13 or 14.

17. An all-solid-state battery obtained by using the electrode for a positive electrode according to claim 16.

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