CN111825804B - Copolymer latex for lithium ion secondary battery cathode, preparation method and application - Google Patents
Copolymer latex for lithium ion secondary battery cathode, preparation method and application Download PDFInfo
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- CN111825804B CN111825804B CN202010727513.8A CN202010727513A CN111825804B CN 111825804 B CN111825804 B CN 111825804B CN 202010727513 A CN202010727513 A CN 202010727513A CN 111825804 B CN111825804 B CN 111825804B
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- lithium ion
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- negative electrode
- copolymer latex
- emulsion
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- 239000004816 latex Substances 0.000 title claims abstract description 59
- 229920000126 latex Polymers 0.000 title claims abstract description 59
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 38
- 229920001577 copolymer Polymers 0.000 title claims abstract description 37
- 238000002360 preparation method Methods 0.000 title claims description 15
- 239000000178 monomer Substances 0.000 claims abstract description 112
- KAKZBPTYRLMSJV-UHFFFAOYSA-N Butadiene Chemical compound C=CC=C KAKZBPTYRLMSJV-UHFFFAOYSA-N 0.000 claims abstract description 72
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 claims abstract description 72
- 229920000642 polymer Polymers 0.000 claims abstract description 48
- 239000002245 particle Substances 0.000 claims abstract description 33
- 241000238367 Mya arenaria Species 0.000 claims abstract description 26
- 150000001732 carboxylic acid derivatives Chemical class 0.000 claims abstract description 22
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 claims abstract description 22
- 229920002554 vinyl polymer Polymers 0.000 claims abstract description 22
- 239000011230 binding agent Substances 0.000 claims abstract description 18
- 239000003999 initiator Substances 0.000 claims description 62
- 239000000839 emulsion Substances 0.000 claims description 52
- 239000010410 layer Substances 0.000 claims description 43
- 238000003756 stirring Methods 0.000 claims description 34
- 238000002156 mixing Methods 0.000 claims description 31
- 239000003995 emulsifying agent Substances 0.000 claims description 27
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 27
- 239000002041 carbon nanotube Substances 0.000 claims description 23
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 23
- 239000008367 deionised water Substances 0.000 claims description 23
- 229910021641 deionized water Inorganic materials 0.000 claims description 23
- 239000012792 core layer Substances 0.000 claims description 22
- 238000010438 heat treatment Methods 0.000 claims description 18
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 claims description 16
- VZCYOOQTPOCHFL-OWOJBTEDSA-N Fumaric acid Chemical compound OC(=O)\C=C\C(O)=O VZCYOOQTPOCHFL-OWOJBTEDSA-N 0.000 claims description 12
- 239000004530 micro-emulsion Substances 0.000 claims description 12
- -1 tetrafluoroborate modified nitrogen sulfur fluorine carbon Chemical class 0.000 claims description 12
- JAHNSTQSQJOJLO-UHFFFAOYSA-N 2-(3-fluorophenyl)-1h-imidazole Chemical compound FC1=CC=CC(C=2NC=CN=2)=C1 JAHNSTQSQJOJLO-UHFFFAOYSA-N 0.000 claims description 10
- OFOBLEOULBTSOW-UHFFFAOYSA-N Propanedioic acid Natural products OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 claims description 10
- 238000001816 cooling Methods 0.000 claims description 10
- VZCYOOQTPOCHFL-UPHRSURJSA-N maleic acid Chemical compound OC(=O)\C=C/C(O)=O VZCYOOQTPOCHFL-UPHRSURJSA-N 0.000 claims description 10
- 239000011976 maleic acid Substances 0.000 claims description 10
- LVHBHZANLOWSRM-UHFFFAOYSA-N methylenebutanedioic acid Natural products OC(=O)CC(=C)C(O)=O LVHBHZANLOWSRM-UHFFFAOYSA-N 0.000 claims description 10
- 239000011267 electrode slurry Substances 0.000 claims description 9
- 238000000034 method Methods 0.000 claims description 8
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 claims description 7
- 239000006258 conductive agent Substances 0.000 claims description 7
- BAPJBEWLBFYGME-UHFFFAOYSA-N Methyl acrylate Chemical compound COC(=O)C=C BAPJBEWLBFYGME-UHFFFAOYSA-N 0.000 claims description 6
- 239000002270 dispersing agent Substances 0.000 claims description 6
- 239000001530 fumaric acid Substances 0.000 claims description 6
- 229940065472 octyl acrylate Drugs 0.000 claims description 6
- ANISOHQJBAQUQP-UHFFFAOYSA-N octyl prop-2-enoate Chemical compound CCCCCCCCOC(=O)C=C ANISOHQJBAQUQP-UHFFFAOYSA-N 0.000 claims description 6
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 claims description 5
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims description 5
- 230000009477 glass transition Effects 0.000 claims description 5
- 239000007773 negative electrode material Substances 0.000 claims description 5
- SCYGNSGTXSSENH-UHFFFAOYSA-N 1-butyl-3-prop-2-enyl-2H-imidazole Chemical compound CCCCN1CN(CC=C)C=C1 SCYGNSGTXSSENH-UHFFFAOYSA-N 0.000 claims description 4
- QZPSOSOOLFHYRR-UHFFFAOYSA-N 3-hydroxypropyl prop-2-enoate Chemical compound OCCCOC(=O)C=C QZPSOSOOLFHYRR-UHFFFAOYSA-N 0.000 claims description 4
- 239000006257 cathode slurry Substances 0.000 claims description 4
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical compound C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 claims description 3
- VVQNEPGJFQJSBK-UHFFFAOYSA-N Methyl methacrylate Chemical compound COC(=O)C(C)=C VVQNEPGJFQJSBK-UHFFFAOYSA-N 0.000 claims description 3
- 239000002002 slurry Substances 0.000 claims description 3
- OMIGHNLMNHATMP-UHFFFAOYSA-N 2-hydroxyethyl prop-2-enoate Chemical compound OCCOC(=O)C=C OMIGHNLMNHATMP-UHFFFAOYSA-N 0.000 claims description 2
- JIGUQPWFLRLWPJ-UHFFFAOYSA-N Ethyl acrylate Chemical compound CCOC(=O)C=C JIGUQPWFLRLWPJ-UHFFFAOYSA-N 0.000 claims description 2
- CQEYYJKEWSMYFG-UHFFFAOYSA-N butyl acrylate Chemical compound CCCCOC(=O)C=C CQEYYJKEWSMYFG-UHFFFAOYSA-N 0.000 claims description 2
- 239000010406 cathode material Substances 0.000 claims description 2
- PNJWIWWMYCMZRO-UHFFFAOYSA-N pent‐4‐en‐2‐one Natural products CC(=O)CC=C PNJWIWWMYCMZRO-UHFFFAOYSA-N 0.000 claims description 2
- 238000004321 preservation Methods 0.000 claims description 2
- 239000002904 solvent Substances 0.000 claims description 2
- 239000000758 substrate Substances 0.000 claims 2
- 230000001070 adhesive effect Effects 0.000 abstract description 9
- 239000000853 adhesive Substances 0.000 abstract description 8
- 239000003792 electrolyte Substances 0.000 abstract description 4
- 230000008961 swelling Effects 0.000 abstract description 3
- 238000007334 copolymerization reaction Methods 0.000 abstract description 2
- 125000000524 functional group Chemical group 0.000 abstract description 2
- 239000003013 cathode binding agent Substances 0.000 abstract 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 28
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 18
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 12
- 229910052731 fluorine Inorganic materials 0.000 description 12
- 239000011737 fluorine Substances 0.000 description 12
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 11
- 229910052717 sulfur Inorganic materials 0.000 description 11
- 239000011593 sulfur Substances 0.000 description 11
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 10
- 238000001035 drying Methods 0.000 description 9
- 229910052757 nitrogen Inorganic materials 0.000 description 9
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 8
- 239000007864 aqueous solution Substances 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- BSKHPKMHTQYZBB-UHFFFAOYSA-N 2-methylpyridine Chemical compound CC1=CC=CC=N1 BSKHPKMHTQYZBB-UHFFFAOYSA-N 0.000 description 6
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 description 6
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 6
- IGFHQQFPSIBGKE-UHFFFAOYSA-N Nonylphenol Natural products CCCCCCCCCC1=CC=C(O)C=C1 IGFHQQFPSIBGKE-UHFFFAOYSA-N 0.000 description 6
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 6
- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical group [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 description 6
- SNQQPOLDUKLAAF-UHFFFAOYSA-N nonylphenol Chemical compound CCCCCCCCCC1=CC=CC=C1O SNQQPOLDUKLAAF-UHFFFAOYSA-N 0.000 description 6
- 229940051841 polyoxyethylene ether Drugs 0.000 description 6
- 229920000056 polyoxyethylene ether Polymers 0.000 description 6
- 239000000725 suspension Substances 0.000 description 6
- 238000005406 washing Methods 0.000 description 6
- 229910001870 ammonium persulfate Inorganic materials 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 239000013543 active substance Substances 0.000 description 4
- 239000002482 conductive additive Substances 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 4
- 235000017557 sodium bicarbonate Nutrition 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000011889 copper foil Substances 0.000 description 3
- 239000011258 core-shell material Substances 0.000 description 3
- BNIILDVGGAEEIG-UHFFFAOYSA-L disodium hydrogen phosphate Chemical compound [Na+].[Na+].OP([O-])([O-])=O BNIILDVGGAEEIG-UHFFFAOYSA-L 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 238000001027 hydrothermal synthesis Methods 0.000 description 3
- 229910021382 natural graphite Inorganic materials 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical group [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 229910000029 sodium carbonate Inorganic materials 0.000 description 3
- 229920002125 Sokalan® Polymers 0.000 description 2
- 239000002174 Styrene-butadiene Substances 0.000 description 2
- ZBKGSTPKYXTFCV-UHFFFAOYSA-N [N].[F].[S] Chemical compound [N].[F].[S] ZBKGSTPKYXTFCV-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- MTAZNLWOLGHBHU-UHFFFAOYSA-N butadiene-styrene rubber Chemical compound C=CC=C.C=CC1=CC=CC=C1 MTAZNLWOLGHBHU-UHFFFAOYSA-N 0.000 description 2
- 239000001768 carboxy methyl cellulose Substances 0.000 description 2
- 239000002612 dispersion medium Substances 0.000 description 2
- 239000007772 electrode material Substances 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 239000000693 micelle Substances 0.000 description 2
- 239000004584 polyacrylic acid Substances 0.000 description 2
- 238000006116 polymerization reaction Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000011115 styrene butadiene Substances 0.000 description 2
- 229920003048 styrene butadiene rubber Polymers 0.000 description 2
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 239000006256 anode slurry Substances 0.000 description 1
- 239000008346 aqueous phase Substances 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 239000004917 carbon fiber Substances 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 1
- 239000006182 cathode active material Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000010556 emulsion polymerization method Methods 0.000 description 1
- 238000007720 emulsion polymerization reaction Methods 0.000 description 1
- 125000003700 epoxy group Chemical group 0.000 description 1
- 239000013022 formulation composition Substances 0.000 description 1
- 229910021389 graphene Inorganic materials 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 239000003273 ketjen black Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000002609 medium Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000002153 silicon-carbon composite material Substances 0.000 description 1
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 1
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F257/00—Macromolecular compounds obtained by polymerising monomers on to polymers of aromatic monomers as defined in group C08F12/00
- C08F257/02—Macromolecular compounds obtained by polymerising monomers on to polymers of aromatic monomers as defined in group C08F12/00 on to polymers of styrene or alkyl-substituted styrenes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
- H01M4/622—Binders being polymers
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Engineering & Computer Science (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Graft Or Block Polymers (AREA)
Abstract
The invention discloses a copolymer latex for a lithium ion secondary battery cathode, which is prepared by copolymerizing styrene, butadiene and unsaturated carboxylic acid monomers to prepare a hard core, and copolymerizing butadiene, styrene and vinyl unsaturated monomers to prepare a soft shell, thereby preparing a latex product with a hard core and soft shell structure, and is particularly suitable for a lithium ion secondary battery cathode binder. It has been found that the copolymer latex having polymer particles with hard core and soft shell structure can improve the adhesion, thereby reducing the amount of binder and the influence of the binder on the internal resistance of the battery. The polarity and dielectric property of the polymer can be changed by the functional group introduced by copolymerization, so that the electrolyte swelling resistance of the adhesive and the influence on the internal resistance of the battery are improved.
Description
Technical Field
The present invention relates to a copolymer latex for a negative electrode of a lithium ion secondary battery. Belongs to the technical field of lithium ion secondary batteries.
Background
The negative electrode of the lithium ion secondary battery is composed of an active material graphite, a conductive additive, a binder and a current collector. The preparation method of the negative electrode generally comprises the steps of mixing and dispersing an active substance, a conductive additive and a binder into uniform slurry by taking water as a medium, coating the uniform slurry on a copper foil on a current collector, and drying and pressing the copper foil to prepare the negative electrode.
The performance of the binder is one of important indexes that determine the capacity and life of the lithium ion secondary battery. The binder is used as a non-conductive substance in an amount that affects the capacity and internal resistance of the lithium ion secondary battery, and thus the amount of the binder should be minimized while securing the adhesion. The adhesive has poor bonding performance, and the situations of powder falling and the falling of active substances and conductive additives from a current collector can occur in the manufacturing process of the negative electrode; the powder falling condition can also occur in the process of manufacturing the ultrasonic welding pole lug of the battery. In the process of charging and discharging the battery, the electrolyte swelling resistance of the adhesive is poor, and the situation that the active substance and the conductive additive fall off from the current collector can also occur, so that the service life of the battery is influenced.
Binders for negative electrodes of lithium ion secondary batteries are mainly classified into two types, one being an oily binder using an organic solvent as a dispersion medium, and the other being an aqueous binder using water as a dispersion medium. The oil-based binder is mainly a polyvinylidene fluoride-based polymer, and since the binding power to the electrode active material and the current collector is low, a larger amount of the binder is required to achieve a required binding strength, which affects the capacity of the battery. In addition, organic solvents in the oily adhesive volatilize during the manufacturing process, pollute the environment and are harmful to health, and the organic solvents are gradually replaced by aqueous adhesives at present.
The water-based adhesive mainly comprises styrene-butadiene latex, polyacrylic acid and the like. Patent application CN107868160A reports an epoxy group-containing styrene-butadiene latex, the adhesive has good cohesiveness, and does not fall off powder and fall off in the manufacturing process of a battery pole piece; is stable in electrolyte, does not swell and has high retention rate of the battery cycle capacity. Patent application CN105576284A reports a polyacrylic acid binder, which has the characteristics of small usage amount and excellent dispersibility for electrode materials such as graphite, and is excellent in battery capacity exertion and cycle performance.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides copolymer latex for a negative electrode of a lithium ion secondary battery, a preparation method and application thereof, and the copolymer latex has excellent battery cycle performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
1. a copolymer latex for a lithium ion secondary battery cathode contains latex particles with a hard core and soft shell structure, wherein the hard core is a polymer formed by copolymerizing 80-100 parts by weight of styrene, 0-15 parts by weight of butadiene and 0-5 parts by weight of unsaturated carboxylic acid monomers, the glass transition temperature of the hard core is above 60 ℃, the soft shell is a polymer formed by copolymerizing 30-80 parts by weight of butadiene, 20-70 parts by weight of styrene and 0-30 parts by weight of vinyl unsaturated monomers, and the hard core and the soft shell respectively account for 5-20% and 80-95% of the weight of the latex particles.
Preferably, the unsaturated carboxylic acid is selected from one or more of acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid.
Preferably, the ethylenically unsaturated monomer is selected from one or more of methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, methyl methacrylate, acrylonitrile, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, hydroxyethyl acrylate, hydroxypropyl acrylate.
Preferably, the hard core is a polymer copolymerized by 80-100 parts by weight of styrene, 10-15 parts by weight of butadiene and 3-5 parts by weight of unsaturated carboxylic acid monomer, and the soft shell is a polymer copolymerized by 30-80 parts by weight of butadiene, 20-70 parts by weight of styrene and 20-30 parts by weight of vinyl unsaturated monomer.
Preferably, the soft shell is a polymer prepared by copolymerizing 30-80 parts of butadiene, 20-70 parts of styrene, 20-30 parts of vinyl unsaturated monomer and 0.5-0.8 part of 1-allyl-3-butylimidazolium tetrafluoroborate modified nitrogen, sulfur and fluorine co-doped carbon nanotube.
More preferably, the specific method for modifying the 1-allyl-3-butylimidazolium tetrafluoroborate by weight parts is as follows: mixing and stirring 1 part of 1-allyl-3-butylimidazole tetrafluoroborate and 5-7 parts of isopropanol uniformly, adding 3-4 parts of nitrogen, sulfur and fluorine co-doped carbon nanotubes, stirring and reacting at 70-80 ℃ for 2-3 hours under the atmosphere of nitrogen, naturally cooling to room temperature (25 ℃), centrifuging to obtain precipitate, washing, and drying.
Still preferably, the preparation method of the nitrogen, sulfur and fluorine co-doped carbon nanotube comprises the following steps: adding 1 part of carbon nano tube into 30-40 parts of dimethyl sulfoxide, uniformly dispersing by ultrasonic waves, adding 0.008-0.01 part of 2-methylpyridine and 1.8-2 parts of N-butyl-N-methylpiperidine bis (trifluoromethanesulfonyl) imide salt, and uniformly dispersing by ultrasonic waves to obtain a suspension; and then transferring the suspension into a hydrothermal reaction kettle, reacting for 6-8 hours at the temperature of 60-70 ℃, filtering, washing and drying to obtain the catalyst.
2. The preparation method of the copolymer latex for the negative electrode of the lithium ion secondary battery comprises the following specific steps:
(1) fully stirring and mixing styrene, butadiene and unsaturated carboxylic acid monomers, an emulsifier and deionized water according to the formula ratio to obtain a core layer monomer pre-emulsion;
(2) fully stirring and mixing butadiene, styrene and vinyl unsaturated monomers with a formula ratio, an emulsifier and deionized water to obtain a shell layer monomer pre-emulsion;
(3) mixing 30-50% of the total mass of the nuclear layer monomer pre-emulsion obtained in the step (1) with a first part of pH regulator and a first part of initiator, stirring and heating to 70-75 ℃, and stirring for 4-6 hours under heat preservation to obtain nuclear seed microemulsion;
(4) heating the nuclear seed microemulsion prepared in the step (3) to 75-80 ℃, then respectively and uniformly dripping the rest nuclear layer monomer pre-emulsion and the second part of initiator into the nuclear layer monomer pre-emulsion and the second part of initiator simultaneously, and continuing to keep the temperature at 75-80 ℃ for 30-40 minutes after dripping to prepare nuclear polymer emulsion;
(5) heating the nuclear polymer emulsion prepared in the step (4) to 80-85 ℃, adding a second part of pH regulator, then respectively and uniformly dropwise adding the shell layer monomer pre-emulsion obtained in the step (2) and a third part of initiator into the nuclear polymer emulsion, preserving heat for 30-40 minutes at 80-85 ℃ after dropwise adding, and then cooling to room temperature to obtain the polymer emulsion.
Preferably, in the steps (1) and (2), the dosages of the emulsifier and the deionized water are respectively 0.02-0.04 times and 1.5-2 times of the total weight of the core layer monomer or the shell layer monomer; the emulsifier is sodium dodecyl sulfate and nonylphenol polyoxyethylene ether according to a mass ratio of 1: 0.2 to 0.3, respectively.
Preferably, the pH regulator is selected from any one of sodium carbonate, sodium bicarbonate or disodium hydrogen phosphate; the initiator is selected from potassium persulfate or ammonium persulfate; the initiator is prepared into an aqueous solution with the mass concentration of 20-30% and is added dropwise; the dosage of the first part of pH regulator is 0.2-0.4% of the total weight of the core layer monomer, the total amount of the first part of initiator and the second part of initiator is 0.4-0.7% of the total weight of the core layer monomer, and the weight ratio of the first part of initiator to the second part of initiator is 1: 1.1 to 1.3; the dosage of the pH regulator in the second part is 0.2-0.4% of the total weight of the shell monomer, and the dosage of the initiator in the third part is 0.4-0.7% of the total weight of the shell monomer.
Preferably, 1-allyl-3-butylimidazolium tetrafluoroborate modified nitrogen, sulfur and fluorine co-doped carbon nanotubes are further added in the step (2).
3. The copolymer latex for the negative electrode of the lithium ion secondary battery is used as a binder of negative electrode slurry of the lithium ion secondary battery.
4. The negative electrode slurry of the lithium ion battery prepared by the copolymer latex is prepared by mixing a negative electrode active substance, a conductive agent, a dispersing agent, deionized water and the copolymer latex.
Preferably, the mass ratio of the negative electrode active material, the conductive agent, the dispersant, and the copolymer latex is 100: 1: 1: 0.5 to 2; the solid content (mass content) of the negative electrode slurry is 40-60%.
Preferably, the negative active material is selected from any one or more of a silicon-carbon composite material, natural graphite or artificial graphite; the conductive agent is selected from any one of Ketjen black, acetylene black, superconducting carbon black, carbon nanotubes, carbon fibers or graphene; the dispersing agent is carboxymethyl cellulose or salt thereof.
5. The preparation method of the lithium ion battery cathode slurry comprises the steps of mixing and stirring the cathode active material, the conductive agent, the dispersing agent and the deionized water to obtain a premix, adding the copolymer latex into the premix, and uniformly stirring to obtain the lithium ion battery cathode slurry.
6. The lithium ion battery cathode material is prepared by uniformly coating the cathode slurry on the surface of a conductive matrix, and drying to remove a solvent.
The invention has the beneficial effects that:
the invention uses styrene, butadiene and unsaturated carboxylic acid monomer to copolymerize and make into hard core, uses butadiene, styrene, vinyl unsaturated monomer to copolymerize and make into soft shell, and then prepare and get a latex product with hard core soft shell structure, especially suitable for the lithium ion secondary battery negative pole binder. It has been found that the copolymer latex having polymer particles with hard core and soft shell structure can improve the adhesion, thereby reducing the amount of binder and the influence of the binder on the internal resistance of the battery. The polarity and dielectric property of the polymer can be changed by the functional group introduced by copolymerization, so that the electrolyte swelling resistance of the adhesive and the influence on the internal resistance of the battery are improved.
The copolymer latex of the core-shell polymer particles of the present invention is produced using a seeded emulsion polymerization process. Firstly, a seed latex of a copolymer forming core is produced by a known emulsion polymerization method, and the average particle diameter of the seed latex forming core is 50-90 nm.
The shell polymer is formed by polymerization in the presence of a seed latex constituting the core. The particle size of the obtained copolymer latex is between 100 and 200 nm. In order to be able to form core-shell polymer particles, the aqueous phase cannot contain emulsifier micelles, otherwise the monomers used to form the shell polymer would enter the emulsifier micelles to form new particles.
The invention also introduces 1-allyl-3-butylimidazolium tetrafluoroborate modified nitrogen, sulfur and fluorine co-doped carbon nanotubes into the soft shell monomer, the carbon nanotubes have excellent electrical properties, the applicant firstly utilizes N-butyl-N-methylpiperidine bis (trifluoromethanesulfonyl) imide salt to dope nitrogen, sulfur and fluorine into the carbon nanotubes and then utilizes 1-allyl-3-butylimidazolium tetrafluoroborate to modify, on one hand, the compatibility and dispersibility of the carbon nanotubes in a system are thoroughly solved through double bond reaction, on the other hand, active sites are increased through doping, fluorine is introduced, and hydrogen bond action is formed with water, so that the stability of latex is improved, and the adhesive property of the latex and the cycle performance of the obtained battery are greatly improved through the two actions.
Detailed Description
The present invention will be further illustrated by the following examples, which are intended to be merely illustrative and not limitative.
Examples 1 to 7
The specific formula of the copolymer latex for the negative electrode of the lithium ion secondary battery is shown in Table 1.
The preparation method is characterized by comprising the following steps:
(1) fully stirring and mixing styrene, butadiene and unsaturated carboxylic acid monomers, an emulsifier and deionized water according to the formula ratio to obtain a core layer monomer pre-emulsion;
(2) fully stirring and mixing butadiene, styrene and vinyl unsaturated monomers with a formula ratio, an emulsifier and deionized water to obtain a shell layer monomer pre-emulsion;
(3) mixing 40% of the total mass of the nuclear layer monomer pre-emulsion obtained in the step (1) with a first part of pH regulator and a first part of initiator, stirring and heating to 72 ℃, and keeping the temperature and stirring for 5 hours to obtain nuclear seed microemulsion;
(4) heating the nuclear seed microemulsion prepared in the step (3) to 78 ℃, then respectively and uniformly dripping the rest nuclear layer monomer pre-emulsion and the second part of initiator into the nuclear layer monomer pre-emulsion and the second part of initiator simultaneously, and continuing to keep the temperature at 78 ℃ for 35 minutes after dripping to prepare nuclear polymer emulsion;
(5) heating the nuclear polymer emulsion prepared in the step (4) to 82 ℃, adding a second part of pH regulator, then respectively and uniformly dropwise adding the shell layer monomer pre-emulsion obtained in the step (2) and a third part of initiator simultaneously, preserving heat for 35 minutes at 82 ℃ after dropwise adding, and then cooling to room temperature to obtain the polymer.
In the steps (1) and (2), the dosages of the emulsifier and the deionized water are respectively 0.03 time and 1.8 time of the total weight of the core layer monomer or the shell layer monomer; the emulsifier is sodium dodecyl sulfate and nonylphenol polyoxyethylene ether according to a mass ratio of 1: 0.25 and mixing.
The pH regulator is sodium carbonate, sodium bicarbonate or disodium hydrogen phosphate; the initiator is potassium persulfate or ammonium persulfate; the initiator is prepared into an aqueous solution with the mass concentration of 25 percent, and the aqueous solution is dropwise added with the feed; the dosage of the first part of pH regulator is 0.3 percent of the total weight of the core layer monomer, the total amount of the first part of initiator and the second part of initiator is 0.5 percent of the total weight of the core layer monomer, and the weight ratio of the first part of initiator to the second part of initiator is 1: 1.2; the dosage of the pH regulator of the second part is 0.3 percent of the total weight of the shell layer monomers, and the dosage of the initiator of the third part is 0.6 percent of the total weight of the shell layer monomers.
The average particle size of the latex particles was determined according to the test requirements of a malvern (Nano-ZS90) laser particle sizer.
TABLE 1 formulation compositions of examples 1-7
Example 8
The copolymer latex for the negative electrode of the lithium ion secondary battery contains latex particles with a hard core and soft shell structure, wherein the average particle size is 100nm, the hard core is a polymer formed by copolymerizing 80 parts of styrene, 15 parts of butadiene and 1 part of unsaturated carboxylic acid monomer, the glass transition temperature of the hard core is above 60 ℃, the soft shell is a polymer formed by copolymerizing 80 parts of butadiene, 20 parts of styrene, 30 parts of vinyl unsaturated monomer and 0.5 part of nitrogen-sulfur-fluorine co-doped carbon nano tube, and the hard core and the soft shell respectively account for 20% and 80% of the weight of the latex particles.
The unsaturated carboxylic acid is acrylic acid.
The vinyl unsaturated monomer is methyl acrylate.
The hard core is a polymer formed by copolymerizing 100 parts of styrene, 10 parts of butadiene and 5 parts of unsaturated carboxylic acid monomers, and the soft shell is a polymer formed by copolymerizing 30 parts of butadiene, 70 parts of styrene and 20 parts of vinyl unsaturated monomers.
The preparation method of the nitrogen, sulfur and fluorine co-doped carbon nano tube comprises the following steps of: adding 1 part of carbon nano tube into 40 parts of dimethyl sulfoxide, uniformly dispersing by ultrasonic waves, adding 0.008 part of 2-methylpyridine and 2 parts of N-butyl-N-methylpiperidine bis (trifluoromethanesulfonyl) imide salt, and uniformly dispersing by ultrasonic waves to obtain a suspension; and then transferring the suspension into a hydrothermal reaction kettle, reacting for 8 hours at 60 ℃, filtering, washing and drying to obtain the catalyst.
The preparation method of the copolymer latex for the negative electrode of the lithium ion secondary battery comprises the following specific steps:
(1) fully stirring and mixing styrene, butadiene and unsaturated carboxylic acid monomers, an emulsifier and deionized water according to the formula ratio to obtain a core layer monomer pre-emulsion;
(2) fully stirring and mixing butadiene, styrene, vinyl unsaturated monomer, nitrogen-sulfur-fluorine co-doped carbon nano tube, emulsifier and deionized water according to the formula ratio to obtain a shell monomer pre-emulsion;
(3) mixing 30% of the total mass of the nuclear layer monomer pre-emulsion obtained in the step (1) with a first part of pH regulator and a first part of initiator, stirring and heating to 75 ℃, and keeping the temperature and stirring for 4 hours to obtain nuclear seed microemulsion;
(4) heating the nuclear seed microemulsion prepared in the step (3) to 80 ℃, then respectively and uniformly dripping the rest nuclear layer monomer pre-emulsion and the second part of initiator into the nuclear layer monomer pre-emulsion and the second part of initiator simultaneously, and continuing to keep the temperature at 75 ℃ for 40 minutes after dripping to prepare nuclear polymer emulsion;
(5) heating the nuclear polymer emulsion prepared in the step (4) to 80 ℃, adding a second part of pH regulator, then respectively and uniformly dropwise adding the shell layer monomer pre-emulsion obtained in the step (2) and a third part of initiator simultaneously, preserving heat for 30 minutes at 85 ℃ after dropwise adding, and then cooling to room temperature to obtain the polymer.
In the steps (1) and (2), the dosages of the emulsifier and the deionized water are respectively 0.04 time and 1.5 times of the total weight of the core layer monomer or the shell layer monomer; the emulsifier is sodium dodecyl sulfate and nonylphenol polyoxyethylene ether according to a mass ratio of 1: 0.3 and mixing.
The pH regulator is sodium carbonate; the initiator is ammonium persulfate; the initiator is prepared into an aqueous solution with the mass concentration of 20 percent, and is added dropwise; the dosage of the first part of pH regulator is 0.4 percent of the total weight of the core layer monomer, the total amount of the first part of initiator and the second part of initiator is 0.4 percent of the total weight of the core layer monomer, and the weight ratio of the first part of initiator to the second part of initiator is 1: 1.3; the dosage of the pH regulator of the second part is 0.2 percent of the total weight of the shell layer monomers, and the dosage of the initiator of the third part is 0.7 percent of the total weight of the shell layer monomers.
The average particle size of the latex particles was determined according to the test requirements of a malvern (Nano-ZS90) laser particle sizer.
Example 9
A copolymer latex for a negative electrode of a lithium ion secondary battery, which comprises latex particles having a hard core-soft shell structure, wherein the average particle diameter of the latex particles is 100nm, the hard core is a polymer obtained by copolymerizing 100 parts of styrene, 5 parts of butadiene and 5 parts of unsaturated carboxylic acid monomers, the glass transition temperature of the hard core is 60 ℃ or higher, the soft shell is a polymer obtained by copolymerizing 30 parts of butadiene, 70 parts of styrene, 20 parts of vinyl unsaturated monomers and 0.8 part of 1-allyl-3-butylimidazolium tetrafluoroborate-modified carbon nanotubes, and the hard core and the soft shell respectively account for 5% and 95% of the weight of the latex particles.
The unsaturated carboxylic acid is methacrylic acid and maleic acid, and the mass ratio of the methacrylic acid to the maleic acid is 1: 1.
the vinyl unsaturated monomer is octyl acrylate and itaconic acid, and the mass ratio of the octyl acrylate to the itaconic acid is 1: 1.
the hard core is a polymer formed by copolymerizing 80 parts of styrene, 15 parts of butadiene and 3 parts of unsaturated carboxylic acid monomers, and the soft shell is a polymer formed by copolymerizing 80 parts of butadiene, 20 parts of styrene and 30 parts of vinyl unsaturated monomers.
The specific method for modifying the 1-allyl-3-butylimidazolium tetrafluoroborate comprises the following steps in parts by weight: mixing 1 part of 1-allyl-3-butylimidazole tetrafluoroborate and 5 parts of isopropanol, uniformly stirring, adding 4 parts of carbon nanotubes, stirring and reacting at 70 ℃ for 3 hours under the nitrogen atmosphere, naturally cooling to room temperature (25 ℃), centrifuging to obtain a precipitate, washing, and drying.
The preparation method of the copolymer latex for the negative electrode of the lithium ion secondary battery comprises the following specific steps:
(1) fully stirring and mixing styrene, butadiene and unsaturated carboxylic acid monomers, an emulsifier and deionized water according to the formula ratio to obtain a core layer monomer pre-emulsion;
(2) fully stirring and mixing butadiene, styrene, vinyl unsaturated monomers, 1-allyl-3-butylimidazolium tetrafluoroborate-modified carbon nanotubes, an emulsifier and deionized water according to the formula ratio to obtain a shell monomer pre-emulsion;
(3) mixing 50% of the total mass of the nuclear layer monomer pre-emulsion obtained in the step (1) with a first part of pH regulator and a first part of initiator, stirring and heating to 70 ℃, and keeping the temperature and stirring for 6 hours to obtain nuclear seed microemulsion;
(4) heating the nuclear seed microemulsion prepared in the step (3) to 75 ℃, then respectively and uniformly dripping the rest nuclear layer monomer pre-emulsion and the second part of initiator into the nuclear layer monomer pre-emulsion and the second part of initiator simultaneously, and continuing to keep the temperature at 80 ℃ for 30 minutes after dripping to prepare nuclear polymer emulsion;
(5) heating the nuclear polymer emulsion prepared in the step (4) to 85 ℃, adding a second part of pH regulator, then respectively and uniformly dropwise adding the shell layer monomer pre-emulsion obtained in the step (2) and a third part of initiator simultaneously, preserving heat for 40 minutes at 80 ℃ after dropwise adding, and then cooling to room temperature to obtain the polymer.
In the steps (1) and (2), the dosages of the emulsifier and the deionized water are respectively 0.02 time and 2 times of the total weight of the core layer monomer or the shell layer monomer; the emulsifier is sodium dodecyl sulfate and nonylphenol polyoxyethylene ether according to a mass ratio of 1: 0.2 and mixing.
The pH regulator is sodium bicarbonate; the initiator is potassium persulfate; the initiator is prepared into an aqueous solution with the mass concentration of 30 percent, and is added dropwise; the dosage of the first part of pH regulator is 0.2 percent of the total weight of the core layer monomer, the total amount of the first part of initiator and the second part of initiator is 0.7 percent of the total weight of the core layer monomer, and the weight ratio of the first part of initiator to the second part of initiator is 1: 1.1; the dosage of the pH regulator of the second part is 0.4 percent of the total weight of the shell layer monomers, and the dosage of the initiator of the third part is 0.4 percent of the total weight of the shell layer monomers.
The average particle size of the latex particles was determined according to the test requirements of a malvern (Nano-ZS90) laser particle sizer.
Example 10
The copolymer latex for the negative electrode of the lithium ion secondary battery contains latex particles with a hard core and soft shell structure, wherein the average particle size is 100nm, the hard core is a polymer formed by copolymerizing 90 parts of styrene, 10 parts of butadiene and 3 parts of unsaturated carboxylic acid monomers in parts by weight, the glass transition temperature of the hard core is more than 60 ℃, the soft shell is a polymer formed by copolymerizing 50 parts of butadiene, 45 parts of styrene, 25 parts of vinyl unsaturated monomers and 0.6 part of 1-allyl-3-butylimidazolium tetrafluoroborate modified nitrogen, sulfur and fluorine co-doped carbon nano tubes, and the hard core and the soft shell respectively account for 10% and 90% of the weight of the latex particles.
The unsaturated carboxylic acid is maleic acid, fumaric acid and itaconic acid, and the mass ratio of the maleic acid to the fumaric acid to the itaconic acid is 1: 1: 1.
the vinyl unsaturated monomer is octyl acrylate, maleic acid and hydroxypropyl acrylate, and the mass ratio of the octyl acrylate, the maleic acid and the hydroxypropyl acrylate is 1: 1: 1.
the hard core is a polymer formed by copolymerizing 90 parts of styrene, 12 parts of butadiene and 4 parts of unsaturated carboxylic acid monomers, and the soft shell is a polymer formed by copolymerizing 55 parts of butadiene, 48 parts of styrene and 25 parts of vinyl unsaturated monomers.
The specific method for modifying the 1-allyl-3-butylimidazolium tetrafluoroborate comprises the following steps in parts by weight: mixing 1 part of 1-allyl-3-butylimidazole tetrafluoroborate and 6 parts of isopropanol, uniformly stirring, adding 3.5 parts of nitrogen, sulfur and fluorine co-doped carbon nanotube, stirring and reacting at 75 ℃ for 2.5 hours under the atmosphere of nitrogen, naturally cooling to room temperature (25 ℃), centrifuging to obtain precipitate, washing and drying.
The preparation method of the nitrogen, sulfur and fluorine co-doped carbon nano tube comprises the following steps of: adding 1 part of carbon nano tube into 35 parts of dimethyl sulfoxide, uniformly dispersing by ultrasonic waves, adding 0.009 part of 2-methylpyridine and 1.9 parts of N-butyl-N-methylpiperidine bis (trifluoromethanesulfonyl) imide salt, and uniformly dispersing by ultrasonic waves to obtain a suspension; and then transferring the suspension into a hydrothermal reaction kettle, reacting for 7 hours at 65 ℃, filtering, washing and drying to obtain the catalyst.
The preparation method of the copolymer latex for the negative electrode of the lithium ion secondary battery comprises the following specific steps:
(1) fully stirring and mixing styrene, butadiene and unsaturated carboxylic acid monomers, an emulsifier and deionized water according to the formula ratio to obtain a core layer monomer pre-emulsion;
(2) fully stirring and mixing butadiene, styrene and vinyl unsaturated monomers with a formula ratio, an emulsifier and deionized water to obtain a shell layer monomer pre-emulsion;
(3) mixing 40% of the total mass of the nuclear layer monomer pre-emulsion obtained in the step (1) with a first part of pH regulator and a first part of initiator, stirring and heating to 72 ℃, and keeping the temperature and stirring for 5 hours to obtain nuclear seed microemulsion;
(4) heating the nuclear seed microemulsion prepared in the step (3) to 78 ℃, then respectively and uniformly dripping the rest nuclear layer monomer pre-emulsion and the second part of initiator into the nuclear layer monomer pre-emulsion and the second part of initiator simultaneously, and continuing to keep the temperature at 78 ℃ for 35 minutes after dripping to prepare nuclear polymer emulsion;
(5) heating the nuclear polymer emulsion prepared in the step (4) to 83 ℃, adding a second part of pH regulator, then respectively and uniformly dropwise adding the shell layer monomer pre-emulsion obtained in the step (2) and a third part of initiator simultaneously, preserving heat for 35 minutes at 82 ℃ after dropwise adding, and then cooling to room temperature to obtain the polymer.
In the steps (1) and (2), the dosages of the emulsifier and the deionized water are respectively 0.03 time and 1.8 time of the total weight of the core layer monomer or the shell layer monomer; the emulsifier is sodium dodecyl sulfate and nonylphenol polyoxyethylene ether according to a mass ratio of 1: 0.25 and mixing.
The pH regulator is disodium hydrogen phosphate; the initiator is ammonium persulfate; the initiator is prepared into an aqueous solution with the mass concentration of 25 percent, and the aqueous solution is dropwise added with the feed; the dosage of the first part of pH regulator is 0.3 percent of the total weight of the core layer monomer, the total amount of the first part of initiator and the second part of initiator is 0.6 percent of the total weight of the core layer monomer, and the weight ratio of the first part of initiator to the second part of initiator is 1: 1.2; the dosage of the pH regulator of the second part is 0.3 percent of the total weight of the shell layer monomers, and the dosage of the initiator of the third part is 0.6 percent of the total weight of the shell layer monomers.
The average particle size of the latex particles was determined according to the test requirements of a malvern (Nano-ZS90) laser particle sizer.
Comparative example
A copolymer latex is copolymerized by 130 parts of styrene, 40 parts of butadiene, 20 parts of itaconic acid and 10 parts of vinyl unsaturated monomers (5 parts of methyl methacrylate, 2 parts of acrylonitrile, 1 part of methacrylic acid and 2 parts of itaconic acid) in parts by weight, and the specific preparation method is as follows: fully stirring and mixing the monomers with the emulsifier and the deionized water according to the formula ratio, adding the pH regulator and the initiator, stirring and reacting for 6 hours at 75 ℃, and naturally cooling to room temperature to obtain the product. Wherein the dosage of the emulsifier and the deionized water is respectively 0.03 time and 1.8 time of the total weight of the core layer monomer or the shell layer monomer; the emulsifier is sodium dodecyl sulfate and nonylphenol polyoxyethylene ether according to a mass ratio of 1: 0.25, mixing; the pH regulator is sodium bicarbonate; the initiator is ammonium persulfate; the initiator is prepared into an aqueous solution with the mass concentration of 20-30% and is added dropwise.
Test examples
The copolymer latexes of examples 1-10 and comparative examples of the invention were used to prepare negative electrode slurries with natural graphite as the negative electrode active material. The negative electrode slurry comprises the following components in percentage by weight: natural graphite/conductive agent/sodium carboxymethylcellulose/copolymer latex 100/1/1/1 (weight ratio). The solid content of the anode slurry was 51%.
And coating the prepared negative electrode slurry on a current collector copper foil, and drying and rolling to obtain a negative electrode plate. In the process of manufacturing the negative pole piece, the phenomena of powder falling and peeling-off do not occur. The peel strength of the negative electrode sheet was measured in accordance with the JISK6854-2 standard. And testing the peel strength of the negative pole piece.
The negative pole piece is matched with the lithium cobaltate positive pole to assemble a square lithium ion battery for application test. The charge/discharge end voltage of the test cell was 4.0V. The viscosity, peel strength and cycle performance of the battery were measured, and the results are shown in table 2.
TABLE 2 comparison of Properties
As can be seen from Table 2, the latexes obtained in examples 1 to 10 have high viscosity, high peel strength and good cycle performance, and the capacity retention rate of the battery is more than 96% (standard is more than or equal to 94%) after 50 cycles at 0.5C, the capacity retention rate of the battery is more than 94.5% (standard is more than or equal to 90%) after 100 cycles, and the capacity retention rate of the battery is more than 90.0% (standard is more than or equal to 80%) after 300 cycles, which meet the standards. In embodiments 8 to 10, carbon nanotubes are introduced into the shell layer, and thus, indexes of the battery are significantly better, in embodiment 8, the nitrogen, sulfur and fluorine co-doped carbon nanotubes are not modified, in embodiment 9, the carbon nanotubes are not doped, and indexes are slightly inferior to those of embodiment 10.
The comparative example adopts direct polymerization, does not form a core-shell structure, and has obviously poor performances.
Although the present invention has been described with reference to the specific embodiments, it is not intended to limit the scope of the present invention, and various modifications and variations can be made by those skilled in the art without inventive changes based on the technical solution of the present invention.
Claims (8)
1. The copolymer latex for the negative electrode of the lithium ion secondary battery is characterized in that latex particles contained in the copolymer latex have a hard core and soft shell structure, the hard core is a polymer formed by copolymerizing 80-100 parts by weight of styrene, 0-15 parts by weight of butadiene and 0-5 parts by weight of unsaturated carboxylic acid monomers, the glass transition temperature of the hard core is above 60 ℃, the soft shell is a polymer formed by copolymerizing 30-80 parts by weight of butadiene, 20-70 parts by weight of styrene, 20-30 parts by weight of vinyl unsaturated monomers and 0.5-0.8 part by weight of 1-allyl-3-butylimidazole co-doped tetrafluoroborate modified nitrogen sulfur fluorine carbon nano tubes, and the hard core and the soft shell respectively account for 5-20% and 80-95% of the weight of the latex particles.
2. The copolymer latex for the negative electrode of the lithium ion secondary battery according to claim 1, wherein the unsaturated carboxylic acid is one or more selected from acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid.
3. The copolymer latex for negative electrodes of lithium ion secondary batteries according to claim 1, wherein the ethylenically unsaturated monomer is selected from one or more of methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, methyl methacrylate, acrylonitrile, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, hydroxyethyl acrylate, and hydroxypropyl acrylate.
4. The method for preparing the copolymer latex for the negative electrode of the lithium ion secondary battery according to any one of claims 1 to 3, which is characterized by comprising the following steps:
(1) fully stirring and mixing styrene, butadiene and unsaturated carboxylic acid monomers, an emulsifier and deionized water according to the formula ratio to obtain a core layer monomer pre-emulsion;
(2) fully stirring and mixing butadiene, styrene and vinyl unsaturated monomers with a formula ratio, an emulsifier and deionized water to obtain a shell layer monomer pre-emulsion;
(3) mixing 30-50% of the total mass of the nuclear layer monomer pre-emulsion obtained in the step (1) with a first part of pH regulator and a first part of initiator, stirring and heating to 70-75 ℃, and stirring for 4-6 hours under heat preservation to obtain nuclear seed microemulsion;
(4) heating the nuclear seed microemulsion prepared in the step (3) to 75-80 ℃, then respectively and uniformly dripping the rest nuclear layer monomer pre-emulsion and the second part of initiator into the nuclear layer monomer pre-emulsion and the second part of initiator simultaneously, and continuing to keep the temperature at 75-80 ℃ for 30-40 minutes after dripping to prepare nuclear polymer emulsion;
(5) heating the nuclear polymer emulsion prepared in the step (4) to 80-85 ℃, adding a second part of pH regulator, then respectively and uniformly dropwise adding the shell layer monomer pre-emulsion obtained in the step (2) and a third part of initiator into the nuclear polymer emulsion, preserving heat for 30-40 minutes at 80-85 ℃ after dropwise adding, and then cooling to room temperature to obtain the polymer emulsion.
5. Use of the copolymer latex for a negative electrode of a lithium ion secondary battery according to any one of claims 1 to 3 as a binder for a slurry of a negative electrode of a lithium ion secondary battery.
6. A lithium ion battery negative electrode slurry prepared by using the copolymer latex of any one of claims 1 to 3, which is prepared by mixing a negative electrode active material, a conductive agent, a dispersant, deionized water and the copolymer latex of any one of claims 1 to 3.
7. The preparation method of the lithium ion battery negative electrode slurry, according to claim 6, is characterized in that the negative electrode active material, the conductive agent, the dispersing agent and the deionized water are mixed and stirred to obtain a premix, and then the copolymer latex is added into the premix and stirred uniformly to obtain the lithium ion battery negative electrode slurry.
8. A lithium ion battery cathode material is characterized in that the cathode slurry of claim 6 is uniformly coated on the surface of a conductive substrate, and the conductive substrate is dried to remove a solvent.
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| CN112321761A (en) * | 2020-11-04 | 2021-02-05 | 深圳港池科技有限公司 | Preparation method of adhesive for lithium ion battery |
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| EP4239727A1 (en) * | 2020-12-18 | 2023-09-06 | Lg Chem, Ltd. | Binder composition for secondary battery, and electrode mixture |
| CN113880999A (en) * | 2021-10-14 | 2022-01-04 | 惠州亿纬锂能股份有限公司 | Adhesive and preparation method and application thereof |
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| CN115050963B (en) * | 2022-06-29 | 2024-05-10 | 上海道赢实业有限公司 | Adhesive for negative electrode of lithium ion battery, and preparation method and application thereof |
| EP4450580A1 (en) * | 2022-07-07 | 2024-10-23 | Contemporary Amperex Technology (Hong Kong) Limited | Binder, binder composition, preparation method, negative electrode slurry, negative electrode sheet, secondary battery, battery module, battery pack, and electric apparatus |
| CN115260403B (en) * | 2022-08-29 | 2023-12-08 | 深圳市鸿星创新材料有限公司 | Aqueous binder, modified diaphragm, battery and preparation method of aqueous binder |
| CN115842132B (en) * | 2022-12-29 | 2023-09-22 | 江苏道赢科技有限公司 | Lithium battery composite binder and preparation method thereof |
| CN116217775A (en) * | 2023-03-15 | 2023-06-06 | 山东亿科化学有限责任公司 | Adhesive for negative electrode of lithium ion secondary battery and preparation method thereof |
| CN118307729B (en) * | 2024-06-04 | 2024-09-20 | 珠海金鸡化工有限公司 | Carboxylated styrene-butadiene latex, preparation method thereof and stirring device |
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| JP2000067871A (en) * | 1998-06-09 | 2000-03-03 | Matsushita Electric Ind Co Ltd | Negative electrode for nonaqueous secondary battery, and nonaqueous secondary battery using it |
| CN107565135A (en) * | 2016-06-30 | 2018-01-09 | 江苏国泰超威新材料有限公司 | Application, lithium ion cell electrode, its preparation method and application of a kind of fluorophosphates in lithium ion cell electrode is prepared |
| CN110416547A (en) * | 2018-04-26 | 2019-11-05 | 中国石油化工股份有限公司 | Paste compound and preparation method thereof and battery cathode and lithium ion battery |
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Patent Citations (3)
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|---|---|---|---|---|
| JP2000067871A (en) * | 1998-06-09 | 2000-03-03 | Matsushita Electric Ind Co Ltd | Negative electrode for nonaqueous secondary battery, and nonaqueous secondary battery using it |
| CN107565135A (en) * | 2016-06-30 | 2018-01-09 | 江苏国泰超威新材料有限公司 | Application, lithium ion cell electrode, its preparation method and application of a kind of fluorophosphates in lithium ion cell electrode is prepared |
| CN110416547A (en) * | 2018-04-26 | 2019-11-05 | 中国石油化工股份有限公司 | Paste compound and preparation method thereof and battery cathode and lithium ion battery |
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