Electrode mixture, active material mixture, binder solution, method for producing electrode mixture, method for producing electrode, electrode, and secondary battery

Abstract

An electrode mixture containing: an oxime; a vinylidene fluoride polymer having a content of structural units derived from vinylidene fluoride of 50% by mole or more; an electrode active material; and carbon black having an average primary particle diameter of 30 nm or less.

Description

Technical Field

[0001] This invention relates to electrode mixtures, active substance mixtures for electrode mixtures, binder solutions, methods for manufacturing electrode mixtures, methods for manufacturing electrodes, electrodes, and secondary batteries. Background Technology

[0002] The electrodes of secondary batteries, including lithium-ion secondary batteries, have a current collector and an electrode paste layer formed on the current collector. The electrode paste layer is formed by coating a slurry-like electrode paste containing a binder and electrode active materials onto the current collector and then drying the coated electrode paste. To improve the electrical characteristics of the battery, conductive additives such as carbon black are sometimes added to the electrode paste.

[0003] Electrode binders suffer from a problem where viscosity increases over time after fabrication. When viscosity increases excessively, such as during gelation, the coatability of the electrode binder deteriorates drastically. To address this, Patent Document 1 describes a method that incorporates an oxime into the electrode binder to suppress excessive viscosity increase.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2022 / 044538 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] As described in Patent Document 1, if excessive thickening of the electrode adhesive can be suppressed, the coating properties of the electrode adhesive can be improved. On the other hand, when it is desired to suppress the thickening of the electrode adhesive, the adhesion of the electrode adhesive layer to the current collector may sometimes decrease.

[0009] The present invention was made in view of the above-mentioned problems, and its object is to provide an electrode compound that does not easily become excessively viscous even over time and whose adhesive force on the current collector is not easily reduced; an active substance mixture and an adhesive solution for making the electrode compound; a method for manufacturing the electrode compound; a method for manufacturing an electrode using the electrode compound; an electrode made from the electrode compound; and a secondary battery having the electrode.

[0010] Solution for solving the problem

[0011] One embodiment of the present invention for solving the above problems relates to the electrode mixture described below [1] to

[10] .

[0012] [1] An electrode mixture comprising:

[0013] Oxime;

[0014] Polymers of vinylidene fluoride with a structural unit derived from vinylidene fluoride of 50 mol% or more;

[0015] Electrode active materials; and

[0016] Carbon black with an average primary particle size of less than 30 nm.

[0017] [2] According to the electrode mixture described in [1], wherein,

[0018] The oxime is either the oxime shown in formula (1) or the oxime shown in formula (2).

[0019] [Chemical Formula 1]

[0020]

[0021] (In formula (1), R1 and R2 independently represent functional groups selected from the group consisting of hydrogen, aldehyde, nitrile, alkyl with 1 or more but less than 10 carbon atoms, alkenyl with 2 or more but less than 10 carbon atoms, alkynyl with 2 or more but less than 10 carbon atoms, cycloalkyl with 3 or more but less than 10 carbon atoms, cycloalkenyl with 3 or more but less than 10 carbon atoms, aryl with 6 or more but less than 18 carbon atoms, aralkyl with 7 or more but less than 14 carbon atoms, and heterocyclic with 3 or more but less than 13 carbon atoms. In R1 and R2, some or all of the hydrogen atoms of these groups are optionally substituted with substituents selected from the group consisting of alkyl with 1 or more but less than 10 carbon atoms, aryl with 6 or more but less than 18 carbon atoms, hydroxyl, and amino. When the functional group or the substituent has the alkyl group, the alkyl group is optionally linear, optionally branched, and optionally has an ester bond. R1 and R2 are optionally bonded to each other to form a ring.)

[0022] [Chemical Formula 2]

[0023]

[0024] In formula (2), R3 and R4 independently represent functional groups selected from the group consisting of hydrogen atoms, aldehydes, nitriles, alkyl groups with 1 or more and 10 or less carbon atoms, alkenyl groups with 2 or more and 10 or less carbon atoms, alkynyl groups with 2 or more and 10 or less carbon atoms, cycloalkyl groups with 3 or more and 10 or less carbon atoms, cycloalkenyl groups with 3 or more and 10 or less carbon atoms, aryl groups with 6 or more and 18 or less carbon atoms, aralkyl groups with 7 or more and 14 or less carbon atoms, and heterocyclic groups with 3 or more and 13 or less carbon atoms. In R3 and R4, these... Optionally, some or all of the hydrogen atoms in the functional group are substituted with substituents selected from the group consisting of alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 18 carbon atoms, hydroxyl groups, and amino groups. When the functional group or the substituent has the alkyl group, the alkyl group is optionally linear, optionally branched, and optionally has an ester bond. R3 and R4 are optionally bonded to each other to form a ring. X represents a single bond or an alkylene group having 1 to 5 carbon atoms. The alkylene group is optionally linear and optionally branched. [3]

[0026] According to the electrode compound described in [2], wherein the oxime represented by formula (1) is an oxime in which R1 and R2 independently represent an alkyl group having 1 or more hydrogen atoms and 5 or fewer carbon atoms, the alkyl group optionally being linear, optionally having branches, and R1 and R2 optionally being bonded to each other to form a ring.

[0027] The oxime represented by formula (2) is as follows: R3 and R4 independently represent alkyl groups having 1 or more but less than 5 carbon atoms, the alkyl group being optionally linear and optionally branched, R3 and R4 being optionally bonded to each other to form a ring, and X representing a single bond or an alkylene group having 1 or more but less than 5 carbon atoms, the alkylene group being optionally linear and optionally branched.

[0028] [4] The electrode mixture according to [2] or [3], wherein the oxime is the oxime shown in formula (2).

[0029] [5] The electrode mixture according to any one of [1] to [4], wherein the content of the oxime is such that the amount of hydroxyimino in the oxime is 0.02 mmol / g or more and 0.80 mmol / g or less relative to 1g of the vinylidene fluoride polymer.

[0030] [6] The electrode mixture according to any one of [1] to [5], wherein the vinylidene fluoride polymer is a homopolymer of vinylidene fluoride.

[0031] [7] The electrode mixture according to any one of [1] to [6], wherein the vinylidene fluoride polymer is a copolymer of a monomer capable of copolymerizing with vinylidene fluoride and vinylidene fluoride.

[0032] [8] The electrode mixture according to any one of [1] to [7], wherein the vinylidene fluoride polymer is a vinylidene fluoride polymer containing structural units derived from the compound shown in formula (3) below.

[0033] [Chemical Formula 3]

[0034]

[0035] (In formula (3), R5 represents a hydrogen atom, an alkyl group having 1 or more but 5 or fewer carbon atoms, or a carboxyl group substituted with an alkyl group having 1 or more but 5 or fewer carbon atoms. R6 and R7 independently represent a hydrogen atom or an alkyl group having 1 or more but 5 or fewer carbon atoms. When R5, R6, or R7 represents the alkyl group, the alkyl group is optionally linear and optionally branched. Y represents a single bond or a group of atoms having a main chain having 1 or more but 20 or fewer atoms and a molecular weight of 500 or less.)

[0036] [9] The electrode compound according to any one of [1] to [8], wherein the vinylidene fluoride polymer is a vinylidene fluoride polymer containing structural units derived from (meth)acrylate monomers that do not have COOH groups at the ends.

[0037]

[10] The electrode mixture according to any one of [1] to [9], wherein the electrode active substance is a lithium metal oxide as shown in the following formula (4) and is a compound whose pH of the extraction water is 10.5 or higher when extracted with water at 25°C by the extraction method specified in JIS K 5101-16-2 (2004).

[0038] LiNi x Co y M z O2……(4)

[0039] (In equation (4), M is Mn or Al, 0) <x<1、0<y<1、0<z<1、x+y+z=1。)

[0040] Other embodiments of the present invention for solving the above problems involve a mixture of active substances as described below

[11] .

[0041]

[11] A mixture of active substances, the mixture comprising:

[0042] Oxime;

[0043] Electrode active materials; and

[0044] Carbon black with an average primary particle size of less than 30 nm.

[0045] Other embodiments of the present invention for solving the above problems involve adhesive solutions as described below

[12] .

[0046]

[12] A binder solution, the binder solution being a binder solution for electrode mixtures containing an electrode active material and carbon black with an average primary particle size of less than 30 nm, the binder solution comprising:

[0047] Oxime; and

[0048] Polymers of vinylidene fluoride with a structural unit derived from vinylidene fluoride of 50 mol% or more.

[0049] Other embodiments of the present invention for solving the above problems relate to a method for manufacturing an electrode mixture as described below

[13] .

[0050]

[13] A method for manufacturing an electrode mixture, wherein the method comprises mixing an oxime, a vinylidene fluoride polymer having a structural unit derived from vinylidene fluoride in an amount of 50 mol% or more, an electrode active material, and carbon black having an average primary particle size of 30 nm or less, and then slurrying the mixture.

[0051] Other embodiments of the present invention for solving the above problems relate to a method of manufacturing an electrode as described below

[14] .

[0052] A method for manufacturing an electrode, the method comprising the following steps:

[0053] The process of applying the electrode mixture according to any one of [1] to

[10] to the current collector; and

[0054] The process of drying the coated electrode mixture.

[0055] Other embodiments of the present invention used to solve the above problems involve electrodes described below

[15] to

[17] .

[0056]

[15] An electrode manufactured by the manufacturing method described in

[14] .

[0057]

[16] According to the electrode described in

[15] , wherein,

[0058] Regarding the electrode compound layer manufactured from the aforementioned electrode compound, the peel strength of the self-collector, as determined by the 90° peel test, is 80% or more of the peel strength of the self-collector of the electrode compound layer of an electrode manufactured under the same manufacturing conditions with the same electrode compound composition except that it does not contain oxime.

[0059]

[17] An electrode having a current collector and an electrode binder layer.

[0060] The electrode mixture layer contains:

[0061] Oxime;

[0062] Polymers of vinylidene fluoride with a structural unit derived from vinylidene fluoride of 50 mol% or more;

[0063] Electrode active materials; and

[0064] Carbon black with an average primary particle size of less than 30 nm.

[0065] Other embodiments of the present invention for solving the above problems relate to a secondary battery as described below

[18] .

[0066]

[18] A secondary battery having electrodes according to

[17] .

[0067] Invention Effects

[0068] According to the present invention, an electrode mixture is provided that does not easily become excessively viscous even over time and the adhesion of the electrode mixture layer to the current collector is not easily reduced; an active substance mixture and an adhesive solution for making the electrode mixture are provided; a method for manufacturing the electrode mixture is provided; a method for manufacturing an electrode using the electrode mixture is provided; an electrode made from the electrode mixture is provided; and a secondary battery having the electrode is provided. Detailed Implementation

[0069] [Electrode mixture]

[0070] One embodiment of the present invention relates to an electrode mixture for coating a current collector to manufacture an electrode.

[0071] The above electrode mixture contains: oxime; a vinylidene fluoride polymer with a structural unit derived from vinylidene fluoride in an amount of 50 mol% or more; an electrode active material; and carbon black with an average primary particle size of less than 30 nm.

[0072] (oxime)

[0073] Oxime reduces the initial viscosity of the electrode mixture and also inhibits the increase in viscosity over time.

[0074] Oximes are compounds formed by replacing the oxygen atom of the carbonyl group of an aldehyde or ketone with a hydroxyimino group (=NOH). Oximes can be derived from aldehydes (RCH=NOH) or ketones (R'RC=NOH).

[0075] There are no specific limitations on the types of oximes. Examples of oximes include: acetoxime, 2-butanone oxime (methyl ethyl ketone oxime), methyl isopropyl ketone oxime, methyl tert-butyl ketone oxime, di-tert-butyl ketone oxime, 2-pentanone oxime, 3-pentanone oxime, 1-cyclohexyl-1-propanone oxime, formaldehyde oxime, and acetaldehyde oxime. oxime), butyraldoxime, benzaldoxime, acetophenone oxime, benzophenone oxime, 4-hydroxyacetophenone oxime, cyclopropanone oxime, cyclobutanone oxime, cyclopentanone oxime, cyclohexanone oxime, cycloheptanone oxime, cyclooctanone oxime, cyclononanone oxime, cyclodecanone oxime, cyclododecanone oxime, benzoquinone dioxime, benzoquinone monooxime, 2,3-butanedione monooxime, Acetamide oxime, 3-hydroxy-3-methyl-2-butanone oxime, α-benzoin oxime, 1,3-dihydroxyacetone oxime, 2-isonitrosophenylacetone, dimethylglyoxime, methylethylglyoxime, diethylglyoxime, diphenylglyoxime, benzophenone dioxime, piperidone oxime, 2,4-pentanedione dioxime, 2-diethyl ether oxime, ethyl acetylhydroxamic acid, ethyl cyanoglyoxylate oxime, etc.

[0076] In addition, the oxime can be a polymer containing hydroxyimino (hereinafter also referred to as "oxime polymer") or an oligomer containing hydroxyimino (hereinafter also referred to as "oxime oligomer").

[0077] Oxime polymers and oxime oligomers can be synthesized by polymerizing monomers or oligomers containing hydroxyimino groups, or by reacting hydroxylamines with polymers or oligomers having ketone groups in their backbone. Examples of polymers having ketone groups in their backbone include: poly(methyl vinyl ketone), polyketone (PK), polyether ketone (PEK), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polyether ether ketone ketone (PEEKK), and polyether ketone ether ketone ketone (PEKEKK), etc. Specific examples of oxime polymers and oxime oligomers include poly(methyl vinyl oxime), etc.

[0078] These oximes can be used in single or multiple ways.

[0079] These oximes can be represented by the oxime shown in equation (1) or the oxime shown in equation (2).

[0080] [Chemical Formula 4]

[0081]

[0082] In formula (1), R1 and R2 independently represent functional groups such as hydrogen atom, aldehyde group, nitrile group, alkyl group with 1 or more but less than 10 carbon atoms, alkenyl group with 2 or more but less than 10 carbon atoms, alkynyl group with 2 or more but less than 10 carbon atoms, cycloalkyl group with 3 or more but less than 10 carbon atoms, cycloalkenyl group with 3 or more but less than 10 carbon atoms, aryl group with 6 or more but less than 18 carbon atoms, aralkyl group with 7 or more but less than 14 carbon atoms, or heterocyclic group with 3 or more but less than 13 carbon atoms. It should be noted that each of the above alkyl groups is optionally linear, optionally branched, and optionally has ester bonds. R1 and R2 are optionally bonded to each other to form a ring.

[0083] The alkyl group preferably has 1 or more and 10 or less carbon atoms, more preferably 1 or more and 5 or less, and even more preferably 1 or more and 2 or less. The alkenyl group preferably has 2 or more and 10 or less carbon atoms, more preferably 2 or more and 6 or less, and even more preferably 2 or more and 4 or less. The alkynyl group preferably has 2 or more and 10 or less carbon atoms, more preferably 2 or more and 6 or less, and even more preferably 2 or more and 4 or less. The cycloalkyl group preferably has 3 or more and 10 or less carbon atoms, more preferably 3 or more and 7 or less, and even more preferably 5 or more and 7 or less. The aryl group preferably has 6 or more and 18 or less carbon atoms, more preferably 6 or more and 10 or less, and even more preferably 6 or more and 8 or less. The aralkyl group preferably has 7 or more and 14 or less carbon atoms, more preferably 7 or more and 11 or less, and even more preferably 7 or more and 9 or less. The heterocyclic group preferably has 3 or more and 13 or less carbon atoms, more preferably 3 or more and 10 or less, and even more preferably 3 or more and 8 or less.

[0084] [Chemical Formula 5]

[0085]

[0086] In formula (2), R3 and R4 independently represent functional groups of hydrogen atom, aldehyde group, nitrile group, alkyl group with 1 or more but less than 10 carbon atoms, alkenyl group with 2 or more but less than 10 carbon atoms, alkynyl group with 2 or more but less than 10 carbon atoms, cycloalkyl group with 3 or more but less than 10 carbon atoms, cycloalkenyl group with 3 or more but less than 10 carbon atoms, aryl group with 6 or more but less than 18 carbon atoms, aralkyl group with 7 or more but less than 14 carbon atoms, or heterocyclic group with 3 or more but less than 13 carbon atoms. It should be noted that each of the above alkyl groups is optionally linear, optionally branched, and optionally has ester bonds. R3 and R4 are optionally bonded to each other to form a ring.

[0087] The alkyl group preferably has 1 or more and 10 or less carbon atoms, more preferably 1 or more and 5 or less, and even more preferably 1 or more and 2 or less. The alkenyl group preferably has 2 or more and 10 or less carbon atoms, more preferably 2 or more and 6 or less, and even more preferably 2 or more and 4 or less. The alkynyl group preferably has 2 or more and 10 or less carbon atoms, more preferably 2 or more and 6 or less, and even more preferably 2 or more and 4 or less. The cycloalkyl group preferably has 3 or more and 10 or less carbon atoms, more preferably 3 or more and 7 or less, and even more preferably 5 or more and 7 or less. The aryl group preferably has 6 or more and 18 or less carbon atoms, more preferably 6 or more and 10 or less, and even more preferably 6 or more and 8 or less. The aralkyl group preferably has 7 or more and 14 or less carbon atoms, more preferably 7 or more and 11 or less, and even more preferably 7 or more and 9 or less. The heterocyclic group preferably has 3 or more and 13 or less carbon atoms, more preferably 3 or more and 10 or less, and even more preferably 3 or more and 8 or less.

[0088] X represents a single bond or an alkylene group having 1 or more but less than 5 carbon atoms. The aforementioned alkylene groups are optionally linear in shape and optionally branched.

[0089] From the viewpoint of more effectively suppressing the reduction of the adhesion of the electrode adhesive layer to the current collector, the oxime shown in formula (1) is preferably an oxime in which R1 and R2 independently represent alkyl groups having 1 or more hydrogen atoms and 5 or fewer carbon atoms. The alkyl group is optionally linear and optionally branched. R1 and R2 are optionally bonded to each other to form a ring. When the alkyl group constituting R1 or R2 is linear or branched, the number of carbon atoms in one or both of the alkyl groups is preferably 1 or more and 3 or fewer, more preferably 1 or more and 2 or fewer, and even more preferably 1.

[0090] Furthermore, from the viewpoint of more effectively suppressing the decrease in the adhesion of the electrode adhesive layer to the current collector or further improving the adhesion, the total number of carbon atoms in R1 and R2 is preferably 1 or more and 3 or less, more preferably 1 or more and 2 or less, and even more preferably 1.

[0091] Furthermore, from the viewpoint of more effectively suppressing the decrease in adhesion of the electrode adhesive layer to the current collector or further improving the adhesion, R1 and R2 are preferably bonded together to form a ring. The number of carbon atoms constituting the ring is preferably 3 or more and 12 or less, more preferably 4 or more and 8 or less.

[0092] Examples of oximes represented by formula (1) where R1 or R2 represents an alkyl group with 1 or more hydrogen atoms and less than 5 carbon atoms include: acetone oxime, 2-butanone oxime, methyl isopropyl ketone oxime, methyl tert-butyl ketone oxime, di-tert-butyl ketone oxime, 2-pentanone oxime, formaldehyde oxime, acetaldehyde oxime, butyraldehyde oxime, cycloacetone oxime, cyclobutanone oxime, cyclopentanone oxime, cyclohexanone oxime, cycloheptanone oxime, cyclooctanone oxime, cyclononanone oxime, and cyclodecanone oxime, etc.

[0093] Furthermore, from the viewpoint of more effectively suppressing the reduction of the adhesion of the electrode adhesive layer to the current collector, the oxime shown in formula (2) is preferably an oxime in which R3 and R4 independently represent alkyl groups having 1 or more hydrogen atoms and 5 or fewer carbon atoms. The alkyl group is optionally linear and optionally branched. R3 and R4 are optionally bonded to each other to form a ring. When the alkyl group constituting R3 or R4 is linear or branched, the number of carbon atoms in one or both of the alkyl groups is preferably 1 or more and 3 or fewer, more preferably 1 or more and 2 or fewer, and even more preferably 1.

[0094] Furthermore, from the viewpoint of more effectively suppressing the decrease in the adhesion of the electrode adhesive layer to the current collector or further improving the adhesion, X is preferably an alkylene group having 1 or more and 5 or less carbon atoms, more preferably an alkylene group having 1 or more and 3 or less carbon atoms, and even more preferably an alkylene group having 1 carbon atom.

[0095] Examples of oximes represented by formula (2) where R3 and R4 represent alkyl groups with 1 or more hydrogen atoms and 5 or fewer carbon atoms include dimethylglyoxime, methylethylglyoxime, diethylglyoxime, 2,4-pentanedione dioxime, etc.

[0096] From the viewpoint of more effectively suppressing the decrease in adhesion of the electrode adhesive layer to the current collector or further improving the adhesion, the oxime is preferably represented by formula (1) where R1 and R2 independently represent alkyl groups having 1 or more hydrogen atoms and 5 or fewer carbon atoms, or represented by formula (2) where R3 and R4 independently represent alkyl groups having 1 or more hydrogen atoms and 5 or fewer carbon atoms. Among these, the oxime represented by formula (2) where R3 and R4 independently represent alkyl groups having 1 or more hydrogen atoms and 5 or fewer carbon atoms is more preferred.

[0097] It should be noted that some or all of the hydrogen atoms of the alkyl group in the oxime shown in formula (1) and the oxime shown in formula (2) may be replaced by an alkyl group with 1 or more carbon atoms and less than 10, an aryl group with 6 or more carbon atoms and less than 18, a hydroxyl group or an amino group.

[0098] In the oxime content of the electrode mixture, the amount of hydroxyimino groups in the oxime is preferably 0.005 mmol or more and 5.00 mmol or less relative to 1 g of vinylidene fluoride polymer, more preferably 0.01 mmol or more and 3.00 mmol or less, even more preferably 0.02 mmol or more and 0.80 mmol or less, and particularly preferably 0.20 mmol or more and 0.80 mmol or less. Increasing the amount of hydroxyimino groups further reduces the initial viscosity of the electrode mixture and more effectively suppresses the increase in viscosity over time. On the other hand, setting the amount of hydroxyimino groups to 3.00 mmol or less or 0.80 mmol or less relative to 1 g of vinylidene fluoride polymer, or setting it to 0.20 mmol or more relative to 1 g of vinylidene fluoride polymer, further improves the adhesion of the electrode mixture layer to the current collector.

[0099] Furthermore, regarding the oxime content in the electrode mixture, the amount of hydroxyimino groups present in the oxime relative to 100g of the active material is preferably 0.0075 mmol or more and 7.50 mmol or less, more preferably 0.015 mmol or more and 4.50 mmol or less, even more preferably 0.03 mmol or more and 1.20 mmol or less, and particularly preferably 0.30 mmol or more and 1.20 mmol or less. Increasing the amount of hydroxyimino groups further reduces the initial viscosity of the electrode mixture and more effectively suppresses the increase in viscosity over time. On the other hand, setting the amount of hydroxyimino groups relative to 100g of the active material to 4.50 mmol or less or 1.20 mmol or less, or setting the amount of hydroxyimino groups relative to 100g of the active material to 0.30 mmol or more, further improves the adhesion of the electrode mixture layer to the current collector.

[0100] The presence and amount of oxime in the electrode mixture can be determined by mass spectrometry (P&T-GCMS, solvent extraction-GCMS, etc.) and nuclear magnetic resonance (NMR). 1 H-NMR, 13 The analysis was performed using C-NMR and other methods.

[0101] (Polyvinylidene fluoride polymer)

[0102] Polyvinylidene fluoride polymers function as adhesives for bonding electrode active materials to current collectors.

[0103] Vinylidene fluoride polymers are polymers that contain structural units derived from vinylidene fluoride as their main components. Specifically, the vinylidene fluoride polymer contains at least 50 mol% of structural units derived from vinylidene fluoride, preferably at least 80 mol%, and more preferably at least 90 mol%. There is no particular upper limit to the amount of structural units derived from vinylidene fluoride, and it can be set to 100 mol%.

[0104] Polymers of vinylidene fluoride can be homopolymers of vinylidene fluoride or copolymers of vinylidene fluoride with monomers that can be copolymerized with vinylidene fluoride.

[0105] When the vinylidene fluoride polymer is a copolymer, it can also be a copolymer with any known monomer that can copolymerize with vinylidene fluoride.

[0106] When the vinylidene fluoride polymer is a copolymer, it preferably contains structural units derived from the compound shown in formula (3) below.

[0107] [Chemical Formula 6]

[0108]

[0109] In formula (3), R5 represents a hydrogen atom, an alkyl group having 1 or more but 5 or fewer carbon atoms, or a carboxyl group substituted with an alkyl group having 1 or more but 5 or fewer carbon atoms. R6 and R7 independently represent a hydrogen atom or an alkyl group having 1 or more but 5 or fewer carbon atoms. When R5, R6, or R7 represents the aforementioned alkyl group, the alkyl group is optionally linear and optionally branched. From the viewpoint of facilitating the polymerization reaction, R5 and R6 are preferably substituents with low steric hindrance. Specifically, R5 and R6 are independently preferably hydrogen or an alkyl group having 1 or more but 3 or fewer carbon atoms, more preferably hydrogen or methyl.

[0110] In formula (3), Y is an atomic group with a molecular weight of 500 or less, having a single bond or main chain with 1 or more but less than 20 atoms. More preferably, the molecular weight of the aforementioned atomic group is 200 or less. There is no particular limitation on the lower limit of the molecular weight of the aforementioned atomic group; it is usually 15. The smaller the molecular weight of the aforementioned atomic group, the less likely the electrode mixture is to gel. In this specification, "number of atoms in the main chain" refers to the minimum number of atoms required to combine the carboxyl group on the right side of Y in formula (3) with the group (R5R6C=CR) on the left side of Y. 7- The number of atoms in the backbone of the chain formed by connecting the atoms. It should be noted that Y can be a straight chain or a branched chain containing functional groups as side chains. When it has side chains, Y can have only one side chain or multiple side chains. It should be noted that when Y is a single bond, the compound shown in formula (3) has a structure in which the carboxyl group is directly bonded to the carbon atom bonded to R7.

[0111] Examples of compounds shown in formula (3) include acrylic acid (AA), methacrylic acid, 2-carboxyethyl acrylate (CEA), 2-carboxyethyl methacrylate, monomethyl maleate, acryloyloxyethyl succinic acid (AES), acryloyloxypropyl succinic acid (APS), methacryloyloxyethyl succinic acid, methacryloyloxypropyl succinic acid, etc. Only one of these compounds may be used, or multiple compounds may be used in combination.

[0112] When the vinylidene fluoride polymer is a copolymer, it may have structural units derived from compounds other than those shown in formula (3). Examples of the other compounds mentioned above include: perfluoroalkyl vinyl ethers such as vinyl fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene (HFP), and perfluoromethyl vinyl ether; (meth)acrylate monomers such as glycidyl acrylate and methyl methacrylate that do not have a COOH group at the end; and unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and citrate; and unsaturated dicarboxylic acid esters such as monomethyl maleate, monoethyl maleate, monomethyl citrate, and monoethyl citrate. Only one of these compounds may be used, or multiple compounds may be used in combination. It should be noted that when the vinylidene fluoride polymer is a copolymer, it may be a copolymer with only the compound shown in formula (3), or a copolymer with only the other compounds mentioned above, or a copolymer with both the compound shown in formula (3) and the other compounds mentioned above.

[0113] When the vinylidene fluoride polymer is a copolymer of the compound shown in formula (3), the amount of modification (the ratio of the number of moles of structural units derived from the compound shown in formula (3) to the total number of moles of all structural units contained in the vinylidene fluoride polymer) is preferably 0.01 mol% or more and 10 mol% or less, more preferably 0.1 mol% or more and 5 mol% or less, and even more preferably 0.2 mol% or more and 1 mol% or less. Furthermore, the amount of structural units derived from vinylidene fluoride in the vinylidene fluoride polymer (the ratio of the number of moles of structural units derived from vinylidene fluoride to the total number of moles of all structural units contained in the vinylidene fluoride polymer) is preferably 90 mol% or more and 99.99 mol% or less, more preferably 95 mol% or more and 99.90 mol% or less, even more preferably 99.00 mol% or more and 99.80 mol% or less, and particularly preferably 99.50 mol% or more and 99.80 mol% or less. When the amount of modification is within the above range, the change in viscosity of the electrode mixture after storage relative to the viscosity of the freshly prepared electrode mixture can be reduced, making the viscosity of the electrode mixture more stable.

[0114] The amount of modification to the vinylidene fluoride polymer and the amount of structural units derived from vinylidene fluoride can be determined by the copolymer. 1 HNMR spectrum or 19The result can be determined by F NMR spectroscopy or neutralization titration.

[0115] Commercially available vinylidene fluoride polymers can be used. Examples of commercially available vinylidene fluoride polymers include KF#7300, KF#9100, KF#9700, KF#7500, and KF#9400 manufactured by KUREHA Corporation.

[0116] The specific logarithmic viscosity (ηi) of the vinylidene fluoride polymer is not particularly limited, but is preferably 0.5 dl / g or more and 5.0 dl / g or less, more preferably 1.0 dl / g or more and 4.5 dl / g or less, and even more preferably 1.5 dl / g or more and 4.0 dl / g or less. When the specific logarithmic viscosity is within the above range, uneven coating thickness is less likely to occur, making electrode fabrication easier.

[0117] The specific logarithmic viscosity (ηi) is calculated using the following method. A polymer solution is prepared by dissolving 80 mg of vinylidene fluoride polymer in 20 mL of N,N-dimethylformamide. The viscosity η of the prepared polymer solution is measured using an Ubbelohde viscometer in a constant temperature bath at 30°C. The specific logarithmic viscosity (ηi) is then calculated according to the following formula. i ).

[0118] η i =(1 / C)・ln(η / η0)

[0119] In the above formula, η0 is the viscosity of N,N-dimethylformamide as a solvent, and C is the concentration of vinylidene fluoride polymer in the prepared polymer solution (0.4 g / dL).

[0120] There are no particular limitations on the polymerization method for vinylidene fluoride polymers; conventionally known polymerization methods can be used. Examples of polymerization methods include suspension polymerization, emulsion polymerization, and solution polymerization. Among these, aqueous suspension polymerization or emulsion polymerization is preferred from the perspective of ease of post-processing, and aqueous suspension polymerization is more preferred.

[0121] The content of vinylidene fluoride polymer in the electrode mixture relative to the total amount of solid components in the electrode mixture can be set to 0.2% by mass or more and 20% by mass or less, preferably 0.2% by mass or more and 10% by mass or less, and more preferably 0.2% by mass or more and 4% by mass or less.

[0122] (Electrode active material)

[0123] The electrode active material inserts or deinserts lithium ions, etc. This allows the electrode active material to perform charging and discharging in a secondary battery.

[0124] Electrode active materials can be either positive or negative electrode active materials.

[0125] There are no particular limitations on the positive electrode active material, but lithium metal oxide is preferred.

[0126] Examples of lithium metal oxides include LiMnO2, LiMn2O4, LiCoO2, LiNiO2, and LiNi. x Co 1-x O2 (0) <x<1)、LiNi x Co y Mn 1-x-y O2 (0) <x<1、0<y<1)、LiNi x Co y Al 1-x-y O2 (0) <x<1、0<y<1)、LiM a PO4 (where M a (elements selected from one or more of Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, Zr, etc.)

[0127] From the viewpoint of increasing capacity density to achieve high capacity in secondary batteries, the positive electrode active material is preferably a lithium metal compound containing Ni. Furthermore, from the viewpoint of suppressing crystal structure changes during charge and discharge processes to stabilize cycle characteristics, the positive electrode active material is more preferably a lithium metal compound containing Ni and Co.

[0128] From the viewpoint of increasing the charging potential of the secondary battery and thus improving the cycle characteristics, the cathode compound is preferably a lithium metal oxide (ternary lithium metal oxide) as shown in the following formula (4).

[0129] LiNi x Co y M z O2……(4)

[0130] In equation (4), M is Mn or Al, 0 <x<1、0<y<1、0<z<1、x+y+z=1。

[0131] Examples of ternary lithium metal oxides include Li 1.00 Ni 0.5 Co 0.2 Mn 0.3 O2 (NCM523), Li 1.00 Ni 0.6 Co 0.2 Mn 0.2 O2 (NCM622), Li 1.00 Ni 0.8 Co 0.1 Mn 0.1 O2 (NCM811) and Li 1.00 Ni 0.8 Co0.15 Al 0.05 O2 (NCA811), etc. It should be noted that these ternary lithium metal oxides are preferably compounds whose extraction water has a pH of 10.5 or higher when extracted with water at room temperature (25°C) using the extraction method specified in JISK 5101-16-2 (2004). Such ternary lithium metal oxides readily defluorinate the vinylidene fluoride polymer, easily causing viscosity increase in the electrode mixture. However, the electrode mixture of this embodiment can suppress the increase in viscosity through oxime.

[0132] Specifically, the pH of the extracted water was obtained as follows: the electrode active material was placed in 50 times its weight of ultrapure water, stirred at 600 rpm for 10 minutes using a magnetic stirrer, and the pH of the extracted water was measured using a pH meter MODEL: F-21 manufactured by Horiba Corporation.

[0133] Electrode mixtures containing positive electrode active materials with a pH of 10.5 or higher, including the aforementioned extraction water, are prone to deterioration of vinylidene fluoride due to their high alkali content, leading to increased viscosity. Therefore, typically, to suppress viscosity increase and resulting gelation in the electrode mixture slurry, it is necessary to remove the alkali by washing the positive electrode active material with water. In contrast, the electrode mixture of this embodiment does not easily exhibit viscosity increase and gelation even when using a positive electrode active material containing a large amount of such alkali. Therefore, the electrode mixture of this embodiment can be manufactured without washing the positive electrode active material with water.

[0134] There are no particular limitations on the negative electrode active material; known materials such as carbon materials, metal / alloy materials, and metal oxides can be used. Among these, carbon materials are preferred from the viewpoint of further improving the energy density of the secondary battery. Examples of the aforementioned carbon materials include artificial graphite, natural graphite, difficult-to-graphitize carbon, and easily-graphitize carbon.

[0135] These electrode active materials can be used in single or multiple ways.

[0136] Regarding the content of vinylidene fluoride and electrode active material in the electrode mixture, the amount of vinylidene fluoride is preferably 0.2 parts by mass or more and 15 parts by mass or less per 100 parts by mass of electrode active material, more preferably 0.5 parts by mass or more and 10 parts by mass or less.

[0137] Furthermore, the content of electrode active material in the electrode mixture is preferably 40% by mass or more and 99.9% by mass or less relative to the total amount of solid components in the electrode mixture. When the amount of electrode active material is within this range, sufficient charge and discharge capacity can be obtained, and battery performance tends to be good.

[0138] (Carbon black)

[0139] Carbon black can be used as a so-called conductive additive to improve the conductivity of electrodes through its conductive properties.

[0140] Carbon black is not particularly limited and can be any of the following: furnace black, Ketjen black, channel black, acetylene black, and thermal cracking black. Among these, acetylene black is preferred because it is easier to reduce the metallic content as an impurity.

[0141] In addition, carbon black can undergo oxidation and graphitization treatments. Oxidized carbon black can have oxygen-containing polar functional groups such as phenolic, quinone, carboxyl, and carbonyl groups on its surface.

[0142] Carbon black consists of particles with an average primary particle size of 30 nm or less. By combining such small-particle-size carbon black with oxime, the reduction in adhesion between the electrode binder layer and the current collector can be more effectively suppressed, and even the adhesion can be further improved. From the above perspective, the average primary particle size of the carbon black is preferably 26 nm or less, more preferably 24 nm or less. The lower limit of the average primary particle size of the carbon black is not particularly limited, and can be set to 5 nm or more.

[0143] The average primary particle size of carbon black is a value obtained by averaging the particle sizes measured using photographs taken with a transmission electron microscope (TEM). Specifically, five 100,000x images are taken using a JEM-2000FX TEM (manufactured by Nippon Electron Corporation). The particle size is determined by analyzing the images of more than 200 randomly selected primary particles, and the average of these values ​​is calculated. It should be noted that the primary particle size refers to the equivalent circular diameter of the primary particle.

[0144] Carbon black can be secondary particles obtained by linking primary particles into chains or flocs. The preferred specific surface area of ​​the secondary particles based on the BET method is 20 m². 2 / g or more and 1500m 2 / g or less, preferably 40m 2 / g or more and 1500m 2 / g or less, more preferably 100m 2 / g or more and 1000m 2 / g or less, especially preferably 100m 2 / g or more and 500m 2 Below / g. The larger the specific surface area of ​​carbon black, the more effectively it can suppress the reduction of the adhesion of the electrode binder layer to the current collector or further improve the adhesion.

[0145] The carbon black content in the electrode mixture is preferably 0.1% by mass and 15% by mass or less relative to the total amount of solid components in the electrode mixture, more preferably 0.1% by mass or more and 7% by mass or less, and even more preferably 0.1% by mass or more and 5% by mass or less.

[0146] (Non-aqueous solvent)

[0147] The electrode mixture is preferably a slurry containing a non-aqueous solvent.

[0148] Examples of non-aqueous solvents include N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate, trimethyl phosphate, acetone, ethyl acetate, n-butyl acetate, n-butanol, dipropylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, and cyclohexanone. Among these, N-methylpyrrolidone is preferred. Only one of these non-aqueous solvents may be used, or multiple solvents may be used in combination.

[0149] There is no particular limitation on the content of non-aqueous solvent in the electrode mixture, but it is preferably 20 parts by mass or more and 150 parts by mass or less relative to 100 parts by mass of the electrode active material.

[0150] (Other substances)

[0151] Electrode binders may include binders other than vinylidene fluoride polymers, conductive additives other than carbon black, pigment dispersants, dispersion stabilizers, adhesive aids, tackifiers, and various coupling agents.

[0152] Examples of conductive additives other than carbon black include carbonaceous materials such as carbon nanotubes, graphite powder and graphite fibers, as well as metal powders and fibers such as nickel and aluminum.

[0153] Examples of pigment dispersants include polyvinylpyrrolidone (PVP).

[0154] The content of these other substances in the electrode mixture is preferably less than 15% by mass relative to the total amount of solid components in the electrode mixture.

[0155] [Electrode mixture]

[0156] Electrode mixtures can be manufactured by mixing the above-mentioned components and then slurrying them.

[0157] There are no particular limitations on the method of adding the components during mixing. The vinylidene fluoride polymer, electrode active material, carbon black, oxime, and non-aqueous solvent can be added to the mixing container separately, or multiple components can be premixed and the resulting premix added to the mixing container.

[0158] For example, vinylidene fluoride polymers can be pre-prepared as liquid premixes (solutions or dispersions) containing vinylidene fluoride polymers and non-aqueous solvents. Alternatively, vinylidene fluoride polymers can be pre-prepared as powder premixes obtained by mixing electrode active materials or carbon black, or as liquid premixes (dispersions) obtained by further adding non-aqueous solvents. Oximes can also be further pre-added and mixed into these liquid components.

[0159] Furthermore, the electrode active material can be pre-prepared as a liquid premixture, i.e., an active material mixture (dispersion), containing the electrode active material and a non-aqueous solvent. Alternatively, the electrode active material can be pre-mixed with carbon black to form an active material mixture as a premixture. The electrode active material and carbon black can be prepared as a powder premixture, i.e., an active material mixture, obtained by powder mixing, or as a liquid premixture, i.e., an active material mixture (dispersion), obtained by further adding a non-aqueous solvent. Oxime can also be further pre-added and mixed into these liquid premixtures, i.e., active material mixtures.

[0160] Furthermore, carbon black can be pre-prepared as a liquid premix (dispersion) containing carbon black and non-aqueous solvents. Oxime can also be further pre-added and mixed into this liquid premix.

[0161] There is no particular order in which these ingredients are added to the mixing container.

[0162] There are no particular limitations on the preparation method of the slurry; any known method can be used.

[0163] The obtained electrode mixture comprises a vinylidene fluoride polymer, an electrode active material, carbon black with an average primary particle size of 30 nm or less, oxime, and a non-aqueous solvent. The viscosity of the electrode mixture immediately after preparation is preferably 1000 mPa·s or more and 30000 mPa·s or less, more preferably 1000 mPa·s or more and 20000 mPa·s or less. Furthermore, the viscosity of the electrode mixture after storage at 40°C under a nitrogen atmosphere for 7 days from preparation is preferably 1000 mPa·s or more and 50000 mPa·s or less, more preferably 1000 mPa·s or more and 20000 mPa·s or less. The viscosity immediately after preparation and the viscosity after storage can be adjusted by the amount of oxime added, etc.

[0164] [electrode]

[0165] Electrode binders can be used to create electrode binder layers contained in electrodes by coating them onto current collectors and allowing them to dry.

[0166] The current collector is the substrate of the electrode and also serves as the terminal for extracting electricity. The current collector can be made of metals such as iron, stainless steel, steel, copper, aluminum, nickel, and titanium. The shape of the current collector can be foil-like or mesh-like. For example, when manufacturing the positive electrode, aluminum foil is preferred as the current collector. The thickness of the current collector is preferably 5 μm or more and 100 μm or less, more preferably 5 μm or more and 20 μm or less.

[0167] The electrode mixture can be applied to the current collector using known methods such as a doctor blade coater, a die coater, and a comma coater. Drying can be performed, for example, at a temperature above 50°C and below 170°C, preferably at a temperature above 50°C and below 170°C. The coating of the current collector and the formation of the electrode mixture layer based on drying can be performed on both sides of the current collector, or only on one side of the current collector. After coating and drying, the formed electrode mixture layer can also be pressed to increase its density.

[0168] The thickness of the electrode mixture layer can be set to, for example, 20 μm or more and 600 μm or less, preferably 20 μm or more and 350 μm or less. The weight per unit area of ​​the electrode mixture layer can be set to, for example, 20 g / m². 2 Above and 700g / m 2 The following can also be set to 20g / m 2 Above and 500g / m 2 the following.

[0169] The resulting electrode mixture has a current collector and an electrode mixture layer formed on the current collector. The electrode mixture layer comprises a vinylidene fluoride polymer, an electrode active material, and carbon black with an average primary particle size of less than 30 nm. The oxime can be completely volatilized during drying, or it may remain on the electrode. The residual amount of oxime is not particularly limited and can be set to be greater than 0 μg / m³. 2 (Or above the detection limit) and 500 μg / m 2 the following.

[0170] The formed electrode can be set as the positive electrode when the electrode active material is the positive electrode active material, and as the negative electrode when the electrode active material is the negative electrode active material.

[0171] [Other Implementation Methods]

[0172] It should be noted that the above-described embodiments are exemplary embodiments of the present invention, and the present invention can of course include embodiments other than those described above within the scope of its core technical concept.

[0173] Example

[0174] The present invention will be described in detail based on the embodiments, but the present invention is not limited to these embodiments.

[0175] 1. Preparation of vinylidene fluoride polymer

[0176] 1-1. (Preparation of VDF / APS copolymer)

[0177] A 2-liter autoclave was filled with 1096 g of ion-exchanged water, 0.2 g of Metrolose 90SH-100 (manufactured by Shin-Etsu Chemical Co., Ltd.), 2.2 g of a 50 wt% diisopropyl peroxide-CFC 225cb solution, 426 g of vinylidene fluoride, and an initial addition of 0.2 g of acryloyloxypropyl succinic acid (APS). The temperature was raised to 26°C over one hour and maintained at 26°C. A 6 wt% APS aqueous solution was slowly added at a rate of 0.5 g / min. The resulting polymer slurry was dehydrated and dried to obtain a vinylidene fluoride copolymer containing polar groups (VDF / APS copolymer). The total amount of APS added, including the initial addition, was 4.0 g.

[0178] 1-2. (Preparation of VDF / AA copolymer)

[0179] A 2-liter autoclave was filled with 524 g of deionized water, 0.4 g of Metrolose 90SH-100 (manufactured by Shin-Etsu Chemical Co., Ltd.), 4 g of a 50 wt% tert-butyl peroxypentanoate-CFC 225cb solution, 396 g of vinylidene fluoride, and an initial addition of 0.2 g of acrylic acid (AA), and heated to 50°C. Under constant pressure during polymerization, a 1 wt% aqueous solution of AA was continuously supplied to the reaction vessel. The resulting polymer slurry was dehydrated and dried to obtain a vinylidene fluoride copolymer (VDF / AA). The total amount of AA added, including the initial addition, was 3.96 g.

[0180] 2. Preparation of electrode mixture

[0181] 2-1. Preparation of Electrode Mixture 1

[0182] NCA811 was used as the electrode active material. Carbon black (manufactured by Denka Co., Ltd., DENKABLACK Li-435, average primary particle size: 23 nm) was added to NCA811 and the powder was mixed.

[0183] The VDF / APS copolymer obtained in Preparation Example 1 and pentylene dioxime were dissolved in N-methyl-2-pyrrolidone (NMP) to prepare an adhesive solution. The amount of pentylene dioxime added was adjusted to include 6 wt% of vinylidene fluoride polymer and 0.22 mmol of pentylene dioxime per 1 g of vinylidene fluoride polymer. Furthermore, the amount of hydroxyimino groups in the pentylene dioxime was 0.44 mmol per 1 g of vinylidene fluoride polymer.

[0184] Electrode compound 1 was prepared by mixing NCA811, carbon black, and a binder solution. Specifically, the binder solution was added at a solids concentration of 11.3 wt% relative to carbon black, and the mixture was kneaded for one minute at 2000 rpm. Next, NCA811 was added, and the mixture was kneaded for two minutes at 2000 rpm. Then, the binder solution and NMP were added at a solids concentration of 71.0 wt%, and the mixture was kneaded for three minutes at 2000 rpm to obtain electrode compound 1. The weight ratio of the electrode active material, carbon black, and VDF / APS copolymer in electrode compound 1 (electrode active material: carbon black: VDF / APS copolymer) was 100:1.5:1.5.

[0185] 2-2. Preparation of Electrode Mixture 2

[0186] The dipentylene dioxime was replaced with dimethylglyoxime, and the amount of dimethylglyoxime in the adhesive solution was set to 0.22 mmol relative to 1 g of vinylidene fluoride polymer. Electrode mixture 2 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in the dimethylglyoxime in electrode mixture 2 was 0.44 mmol relative to 1 g of vinylidene fluoride polymer.

[0187] 2-3. Preparation of Electrode Mixture 3

[0188] The dipentylene dioxime was replaced with dimethylglyoxime, and the amount of dimethylglyoxime in the adhesive solution was set to 0.055 mmol relative to 1 g of vinylidene fluoride polymer. Electrode mixture 3 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in the dimethylglyoxime in electrode mixture 3 was 0.11 mmol relative to 1 g of vinylidene fluoride polymer.

[0189] 2-4. Preparation of Electrode Mixture 4

[0190] The dipentylene dioxime was replaced with 2-butanone oxime, and the amount of 2-butanone oxime in the adhesive solution was set to 0.44 mmol relative to 1 g of vinylidene fluoride polymer. Electrode mixture 4 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in the 2-butanone oxime in electrode mixture 4 was 0.44 mmol relative to 1 g of vinylidene fluoride polymer.

[0191] 2-5. Preparation of Electrode Mixture 5

[0192] The dipentylene dioxime was replaced with 2-butanone oxime, and the amount of 2-butanone oxime in the adhesive solution was set to 0.11 mmol relative to 1 g of vinylidene fluoride polymer. Electrode mixture 5 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in the 2-butanone oxime in electrode mixture 5 was 0.11 mmol relative to 1 g of vinylidene fluoride polymer.

[0193] 2-6. Preparation of Electrode Mixture 6

[0194] The dipentylene dioxime was replaced with 2-butanone oxime, and the amount of 2-butanone oxime in the adhesive solution was set to 0.02 mmol relative to 1 g of vinylidene fluoride polymer. Electrode mixture 6 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in the 2-butanone oxime in electrode mixture 6 was 0.02 mmol relative to 1 g of vinylidene fluoride polymer.

[0195] 2-7. Preparation of Electrode Mixture 7

[0196] The dipentylene dioxime was replaced with acetaldehyde oxime, and the amount of acetaldehyde oxime in the adhesive solution was set to 0.44 mmol relative to 1 g of vinylidene fluoride polymer. Electrode mixture 7 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in the acetaldehyde oxime in electrode mixture 7 was 0.44 mmol relative to 1 g of vinylidene fluoride polymer.

[0197] 2-8. Preparation of Electrode Mixture 8

[0198] The dipentanedione oxime was replaced with cyclohexanone oxime, and the amount of cyclohexanone oxime in the adhesive solution was set to 0.44 mmol relative to 1 g of vinylidene fluoride polymer. Electrode mixture 8 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in the cyclohexanone oxime in electrode mixture 8 was 0.44 mmol relative to 1 g of vinylidene fluoride polymer.

[0199] 2-9. Preparation of Electrode Mixture 9

[0200] The VDF / APS copolymer was replaced with a VDF / AA copolymer, and the pentanedione dioxime was replaced with dimethylglyoxime. The amount of dimethylglyoxime in the adhesive solution was set to 0.22 mmol relative to 1 g of vinylidene fluoride polymer. Electrode mixture 9 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in the dimethylglyoxime in electrode mixture 9 was 0.44 mmol relative to 1 g of vinylidene fluoride polymer.

[0201] 2-10. Preparation of Electrode Mixture 10

[0202] Electrode mixture 10 was prepared in the same manner as electrode mixture 1, except that no pentanedione dioxime was added to the binder solution.

[0203] 2-11. Preparation of Electrode Mixture 11

[0204] Carbon black was replaced with DENKA BLACK Li-400 (average primary particle size: 48 nm) manufactured by Denka Co., Ltd., and pentanedione dioxime was replaced with 2-butanone oxime. The amount of 2-butanone oxime in the binder solution was set to 0.44 mmol relative to 1 g of vinylidene fluoride polymer, and the solid component concentration of the electrode mixture was set to 75%. Otherwise, electrode mixture 11 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in 2-butanone oxime in electrode mixture 11 was 0.44 mmol relative to 1 g of vinylidene fluoride polymer.

[0205] 2-12. Preparation of Electrode Mixture 12

[0206] Carbon black was replaced with DENKA BLACK Li-400 (average primary particle size: 48 nm) manufactured by Denka Co., Ltd., and pentanedione dioxime was replaced with 2-butanone oxime. The amount of 2-butanone oxime in the binder solution was set to 0.11 mmol relative to 1 g of vinylidene fluoride polymer, and the solid component concentration of the electrode mixture was set to 75%. Otherwise, electrode mixture 12 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in 2-butanone oxime in electrode mixture 12 was 0.11 mmol relative to 1 g of vinylidene fluoride polymer.

[0207] 2-13. Preparation of Electrode Mixture 13

[0208] Carbon black was replaced with DENKA BLACK Li-400 (average primary particle size: 48 nm) manufactured by Denka Co., Ltd., and pentanedione dioxime was replaced with 2-butanone oxime. The amount of 2-butanone oxime in the binder solution was set to 0.02 mmol relative to 1 g of vinylidene fluoride polymer, and the solid component concentration of the electrode mixture was set to 75%. Otherwise, electrode mixture 13 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in 2-butanone oxime in electrode mixture 13 was 0.02 mmol relative to 1 g of vinylidene fluoride polymer.

[0209] 2-14. Preparation of Electrode Mixture 14

[0210] Carbon black was replaced with DENKA BLACK Li-400 (average primary particle size: 48 nm) manufactured by Denka Co., Ltd., and dipentylene dioxime was replaced with dimethylglyoxime. The amount of dimethylglyoxime in the binder solution was set to 0.22 mmol relative to 1 g of vinylidene fluoride polymer, and the solid component concentration of the electrode mixture was set to 75%. Otherwise, electrode mixture 14 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in dimethylglyoxime in electrode mixture 14 was 0.44 mmol relative to 1 g of vinylidene fluoride polymer.

[0211] 2-15. Preparation of Electrode Mixture 15

[0212] Carbon black was replaced with DENKA BLACK Li-400 (average primary particle size: 48 nm) manufactured by Denka Co., Ltd., and dipentylene dioxime was replaced with dimethylglyoxime. The amount of dimethylglyoxime in the binder solution was set to 0.055 mmol relative to 1 g of vinylidene fluoride polymer, and the solid component concentration of the electrode mixture was set to 75%. Otherwise, electrode mixture 15 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in dimethylglyoxime in electrode mixture 15 was 0.11 mmol relative to 1 g of vinylidene fluoride polymer.

[0213] 2-16. Preparation of Electrode Mixture 16

[0214] Carbon black was replaced with DENKA BLACK Li-400 (average primary particle size: 48 nm) manufactured by Denka Co., Ltd., and dipentylene dioxime was replaced with dimethylglyoxime. The amount of dimethylglyoxime in the binder solution was set to 0.01 mmol relative to 1 g of vinylidene fluoride polymer, and the solid component concentration of the electrode mixture was set to 75%. Otherwise, electrode mixture 16 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in dimethylglyoxime in electrode mixture 16 was 0.02 mmol relative to 1 g of vinylidene fluoride polymer.

[0215] 2-17. Preparation of Electrode Mixture 17

[0216] Carbon black was replaced with DENKA BLACK Li-400 (average primary particle size: 48 nm) manufactured by Denka Co., Ltd., and dipentylene dioxime was replaced with diacetyl monooxime. The amount of diacetyl monooxime in the binder solution was set to 0.44 mmol relative to 1 g of vinylidene fluoride polymer, and the solid component concentration of the electrode mixture was set to 75%. Otherwise, electrode mixture 17 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in the diacetyl monooxime in electrode mixture 17 was 0.44 mmol relative to 1 g of vinylidene fluoride polymer.

[0217] 2-18. Preparation of Electrode Mixture 18

[0218] Carbon black was replaced with DENKA BLACK Li-400 (average primary particle size: 48 nm) manufactured by Denka Co., Ltd., and dipentanedione dioxime was replaced with diacetyl monooxime. The amount of diacetyl monooxime in the binder solution was set to 0.11 mmol relative to 1 g of vinylidene fluoride polymer, and the solid component concentration of the electrode mixture was set to 75%. Otherwise, electrode mixture 18 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in the diacetyl monooxime in electrode mixture 18 was 0.11 mmol relative to 1 g of vinylidene fluoride polymer.

[0219] 2-19. Preparation of Electrode Mixture 19

[0220] Carbon black was replaced with DENKA BLACK Li-400 (average primary particle size: 48 nm) manufactured by Denka Co., Ltd., and dipentylene dioxime was replaced with diacetyl monooxime. The amount of diacetyl monooxime in the binder solution was set to 0.02 mmol relative to 1 g of vinylidene fluoride polymer, and the solid component concentration of the electrode mixture was set to 75%. Otherwise, electrode mixture 19 was prepared in the same manner as electrode mixture 1. The amount of hydroxyimino group in the diacetyl monooxime in electrode mixture 19 was 0.02 mmol relative to 1 g of vinylidene fluoride polymer.

[0221] 2-20. Preparation of Electrode Mixture 20

[0222] The carbon black was changed to DENKA BLACK Li-400 manufactured by Denka Co., Ltd. (average primary particle size: 48 nm). Pentylene dioxime was not added to the binder solution. The solid component concentration of the electrode mixture was set to 75%. Otherwise, electrode mixture 20 was prepared in the same manner as electrode mixture 1.

[0223] 3. Measurement

[0224] 3-1. pH of electrode active material

[0225] The pH of the electrode active material (NCA811) was set to the pH of the water used for water extraction of the electrode active material at room temperature (25°C). The electrode active material was extracted into water using the extraction method specified in JIS K 5101-16-2 (2004). Specifically, the electrode active material was placed in 50 times its weight of ultrapure water, and stirred for 10 minutes using a magnetic stirrer at 600 rpm. The pH of the solution was measured using a pH meter MODEL: F-21 manufactured by Horiba Corporation. The pH after extraction of NCA811 using water was 11.5.

[0226] 3-2. Specific Concentration Logarithmic Viscosity (ηi) of Vinylidene Fluoride Polymer

[0227] 80 mg of vinylidene fluoride polymer was dissolved in 20 mL of N,N-dimethylformamide to prepare a polymer solution. The viscosity η of the prepared polymer solution was measured using an Ubbelohde viscometer in a constant temperature bath at 30 °C. Then, the specific logarithmic viscosity (ηi) was calculated according to the following formula.

[0228] ηi=(1 / C)・ln(η / η0)

[0229] In the above formula, η0 is the viscosity of N,N-dimethylformamide as a solvent, and C is the concentration of vinylidene fluoride polymer in the prepared polymer solution (0.4 g / dL).

[0230] The specific logarithmic viscosity of the VDF / APS copolymer is 2.5 dL / g, and the specific logarithmic viscosity of the VDF / AA copolymer is 2.5 dL / g.

[0231] 4. Evaluation

[0232] 4-1. Viscosity

[0233] Using an E-type viscometer, at 25°C and a shear rate of 2s... -1 Viscosity was measured. Specifically, the slurry (electrode mixture) was loaded into the measuring device and left idle for 60 seconds, then the rotor was rotated to measure the viscosity. The value 300 seconds after the rotor began rotating was taken as the slurry viscosity. For each prepared electrode mixture, the viscosity was measured immediately after preparation and after storage at 40°C under a nitrogen atmosphere for 7 days (168 hours).

[0234] 4-2. Peel strength

[0235] The prepared electrode mixtures were applied to 15 μm thick aluminum foil (used as current collectors) using a doctor blade coater. The foil was then dried once at 110°C for 30 minutes in a constant temperature bath under a nitrogen atmosphere. A second drying process was then performed at 130°C for 2 hours under a nitrogen atmosphere, yielding a yield with a unit area weight of approximately 250 g / m². 2 The electrode (electrode stripping measurement sample).

[0236] The fabricated electrodes were cut into 100mm long and 20mm wide pieces. Then, according to JIS F6854-1, a tensile testing machine (ORIENTEC CHSIA-1150 universal testing machine) was used to perform a 90° peel test on the electrode adhesive layer at a head speed of 10mm / min to determine the peel strength.

[0237] For the electrode compound layer in an electrode made from various oxime-containing electrode compounds, the rate of change (%) of the peel strength relative to the peel strength of the electrode compound layer in an electrode made from an electrode compound containing the same vinylidene fluoride polymer, the same electrode active material, and the same carbon black but without added oxime (when using a VDF / APS copolymer as the vinylidene fluoride polymer, the electrode compound is electrode compound 10 or electrode compound 20; when using a VDF / AA copolymer as the vinylidene fluoride polymer, the electrode compound is an electrode compound separately prepared using a VDF / AA copolymer). Based on the obtained rate of change, the peel strength is evaluated according to the following criteria.

[0238] ◎ Improved peel strength (change rate over 100%).

[0239] ○ The peel strength is approximately the same (the rate of change is greater than 80% and less than 100%).

[0240] × Peel strength decreased (rate of change less than 80%).

[0241] The types of electrode active materials used in the preparation of electrode mixtures 1 to 20, the average primary particle size of carbon black, the amount (by weight) of comonomers of vinylidene fluoride polymer (PVDF), the types and amounts of oximes added, and the evaluation results are shown in Tables 1 and 2. It should be noted that the amount of oxime added represents the amount of hydroxyimino relative to 1 g of PVDF.

[0242]

[0243]

[0244] Tables 1 and 2 clearly show that electrode mixtures containing oxime, vinylidene fluoride polymers with a content of 50 mol% or more of structural units derived from vinylidene fluoride, electrode active materials, and carbon black with an average primary particle size of less than 30 nm are not prone to increasing adhesion, and the adhesion of the electrode mixture layer to the current collector is not easily reduced.

[0245] This application claims priority to Japanese Patent Application No. 2023-182455, filed on October 24, 2023. The matters set forth in the original description and claims of that application are incorporated herein by reference.

[0246] Industrial availability

[0247] The electrode adhesive of the present invention can produce an electrode adhesive layer that is not prone to adhesion and more effectively suppresses the reduction of the adhesion of the electrode adhesive layer to the current collector or further improves the adhesion.

Claims

1. An electrode mixture, said electrode mixture comprising: Oxime; Polymers of vinylidene fluoride with a structural unit derived from vinylidene fluoride of 50 mol% or more. Electrode active materials; and Carbon black with an average primary particle size of less than 30 nm.

2. The electrode mixture according to claim 1, wherein, The oxime is either the oxime shown in formula (1) or the oxime shown in formula (2). [Chemical Formula 1] In formula (1), R1 and R2 independently represent functional groups selected from the group consisting of hydrogen atoms, aldehydes, nitriles, alkyl groups with 1 or more but less than 10 carbon atoms, alkenyl groups with 2 or more but less than 10 carbon atoms, alkynyl groups with 2 or more but less than 10 carbon atoms, cycloalkyl groups with 3 or more but less than 10 carbon atoms, cycloalkenyl groups with 3 or more but less than 10 carbon atoms, aryl groups with 6 or more but less than 18 carbon atoms, aralkyl groups with 7 or more but less than 14 carbon atoms, and heterocyclic groups with 3 or more but less than 13 carbon atoms. In R1 and R2, some or all of the hydrogen atoms in these groups are optionally substituted with substituents selected from the group consisting of alkyl groups with 1 or more but less than 10 carbon atoms, aryl groups with 6 or more but less than 18 carbon atoms, hydroxyl groups, and amino groups. When the functional group or the substituent has the alkyl group, the alkyl group is optionally linear, optionally branched, and optionally has an ester bond. R1 and R2 are optionally bonded to each other to form a ring. [Chemical Formula 2] In formula (2), R3 and R4 independently represent functional groups selected from the group consisting of hydrogen atoms, aldehyde groups, nitrile groups, alkyl groups with 1 or more and 10 or less carbon atoms, alkenyl groups with 2 or more and 10 or less carbon atoms, alkynyl groups with 2 or more and 10 or less carbon atoms, cycloalkyl groups with 3 or more and 10 or less carbon atoms, cycloalkenyl groups with 3 or more and 10 or less carbon atoms, aryl groups with 6 or more and 18 or less carbon atoms, aralkyl groups with 7 or more and 14 or less carbon atoms, and heterocyclic groups with 3 or more and 13 or less carbon atoms. Optionally, some or all of the hydrogen atoms in the functional group are substituted with substituents selected from the group consisting of alkyl groups having 1 or more but less than 10 carbon atoms, aryl groups having 6 or more but less than 18 carbon atoms, hydroxyl groups, and amino groups. When the functional group or the substituent has the alkyl group, the alkyl group is optionally linear, optionally branched, optionally has an ester bond, and R3 and R4 are optionally bonded to each other to form a ring. X represents a single bond or an alkylene group having 1 or more but less than 5 carbon atoms, the alkylene group being optionally linear and optionally branched.

3. The electrode mixture according to claim 2, wherein, The oxime represented by formula (1) is an oxime in which R1 and R2 independently represent an alkyl group having 1 or more hydrogen atoms and 5 or fewer carbon atoms, the alkyl group being optionally linear, optionally branched, and R1 and R2 optionally bonded together to form a ring. The oxime represented by formula (2) is as follows: R3 and R4 independently represent alkyl groups having 1 or more but less than 5 carbon atoms, the alkyl group being optionally linear and optionally branched, R3 and R4 being optionally bonded to each other to form a ring, and X representing a single bond or an alkylene group having 1 or more but less than 5 carbon atoms, the alkylene group being optionally linear and optionally branched.

4. The electrode mixture according to claim 2, wherein, The oxime is the oxime shown in equation (2).

5. The electrode mixture according to claim 1, wherein, The oxime content is as follows: the amount of hydroxyimino in the oxime relative to 1g of the vinylidene fluoride polymer is more than 0.02 mmol / g and less than 0.80 mmol / g.

6. The electrode mixture according to claim 1, wherein, The vinylidene fluoride polymer is a homopolymer of vinylidene fluoride.

7. The electrode mixture according to claim 1, wherein, The vinylidene fluoride polymer is a copolymer of a monomer that can copolymerize with vinylidene fluoride and vinylidene fluoride.

8. The electrode mixture according to claim 1, wherein, The vinylidene fluoride polymer is a vinylidene fluoride polymer containing structural units derived from the compound shown in formula (3) below. [Chemical Formula 3] In formula (3), R5 represents a hydrogen atom, an alkyl group having 1 or more but less than 5 carbon atoms, or a carboxyl group substituted by an alkyl group having 1 or more but less than 5 carbon atoms, R6 and R7 independently represent a hydrogen atom or an alkyl group having 1 or more but less than 5 carbon atoms, and when R5, R6 or R7 represents the alkyl group, the alkyl group is optionally straight-chain, optionally branched, and Y represents a single bond or a group of atoms with a main chain having 1 or more but less than 20 atoms and a molecular weight of 500 or less.

9. The electrode mixture according to claim 1, wherein, The vinylidene fluoride polymer is a vinylidene fluoride polymer containing structural units derived from (meth)acrylate monomers that do not have COOH groups at the ends.

10. The electrode mixture according to claim 1, wherein, The electrode active material is a lithium metal oxide as shown in formula (4), and is a compound in which the pH of the extraction water is 10.5 or higher when extracted with water at 25°C using the extraction method specified in JIS K 5101-16-2 of 2004. LiNi x Co y M z O2……(4) In equation (4), M is Mn or Al, 0 <x<1、0<y<1、0<z<1、x+y+z=1。 11. A mixture of active substances, said mixture comprising: Oxime; Electrode active materials; and Carbon black with an average primary particle size of less than 30 nm.

12. A binder solution, said binder solution being a binder solution for electrode mixtures comprising an electrode active material and carbon black with an average primary particle size of 30 nm or less, said binder solution containing: Oxime; and Polymers of vinylidene fluoride with a structural unit derived from vinylidene fluoride accounting for more than 50 mol%.

13. A method for manufacturing an electrode mixture, wherein the method comprises mixing an oxime, a vinylidene fluoride polymer having a structural unit derived from vinylidene fluoride in an amount of 50 mol% or more, an electrode active material, and carbon black having an average primary particle size of 30 nm or less, and then slurrying the mixture.

14. A method for manufacturing an electrode, the method comprising the following steps: The process of applying the electrode mixture according to any one of claims 1 to 10 to the current collector; and The process of drying the coated electrode mixture.

15. An electrode manufactured by the manufacturing method according to claim 14.

16. The electrode according to claim 15, wherein, Regarding the electrode compound layer manufactured from the aforementioned electrode compound, the peel strength of the self-collector, as determined by the 90° peel test, is 80% or more of the peel strength of the self-collector of the electrode compound layer of an electrode manufactured under the same manufacturing conditions with the same electrode compound composition except that it does not contain oxime.

17. An electrode having a current collector and an electrode binder layer, The electrode mixture layer contains: Oxime; Polymers of vinylidene fluoride with a structural unit derived from vinylidene fluoride of 50 mol% or more. Electrode active materials; and Carbon black with an average primary particle size of less than 30 nm.

18. A secondary battery having the electrodes according to claim 17.

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