CN116836324A - PVDF copolymer, preparation method thereof and application thereof in lithium ion battery - Google Patents
PVDF copolymer, preparation method thereof and application thereof in lithium ion battery Download PDFInfo
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- CN116836324A CN116836324A CN202310703678.5A CN202310703678A CN116836324A CN 116836324 A CN116836324 A CN 116836324A CN 202310703678 A CN202310703678 A CN 202310703678A CN 116836324 A CN116836324 A CN 116836324A
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- pvdf copolymer
- pvdf
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- 239000002033 PVDF binder Substances 0.000 title claims abstract description 73
- 229920002981 polyvinylidene fluoride Polymers 0.000 title claims abstract description 72
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 23
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 23
- 238000002360 preparation method Methods 0.000 title claims abstract description 11
- 239000000178 monomer Substances 0.000 claims abstract description 127
- -1 amino vinyl Chemical group 0.000 claims abstract description 53
- 238000000034 method Methods 0.000 claims abstract description 10
- VVJKKWFAADXIJK-UHFFFAOYSA-N Allylamine Chemical compound NCC=C VVJKKWFAADXIJK-UHFFFAOYSA-N 0.000 claims description 26
- 239000011230 binding agent Substances 0.000 claims description 18
- 239000002002 slurry Substances 0.000 claims description 14
- 239000000839 emulsion Substances 0.000 claims description 11
- UGIJCMNGQCUTPI-UHFFFAOYSA-N 2-aminoethyl prop-2-enoate Chemical compound NCCOC(=O)C=C UGIJCMNGQCUTPI-UHFFFAOYSA-N 0.000 claims description 5
- 239000012986 chain transfer agent Substances 0.000 claims description 5
- HCDGVLDPFQMKDK-UHFFFAOYSA-N hexafluoropropylene Chemical group FC(F)=C(F)C(F)(F)F HCDGVLDPFQMKDK-UHFFFAOYSA-N 0.000 claims description 5
- 239000001257 hydrogen Substances 0.000 claims description 5
- 229910052739 hydrogen Inorganic materials 0.000 claims description 5
- 239000002904 solvent Substances 0.000 claims description 5
- 125000000217 alkyl group Chemical group 0.000 claims description 4
- HXJGFDIZSMWOGY-UHFFFAOYSA-N n-(2-azaniumylethyl)prop-2-enimidate Chemical compound NCCNC(=O)C=C HXJGFDIZSMWOGY-UHFFFAOYSA-N 0.000 claims description 4
- 239000004215 Carbon black (E152) Substances 0.000 claims description 3
- FTWHFXMUJQRNBK-UHFFFAOYSA-N alpha-Methylen-gamma-aminobuttersaeure Natural products NCCC(=C)C(O)=O FTWHFXMUJQRNBK-UHFFFAOYSA-N 0.000 claims description 3
- 238000007720 emulsion polymerization reaction Methods 0.000 claims description 3
- 229930195733 hydrocarbon Natural products 0.000 claims description 3
- 150000002431 hydrogen Chemical class 0.000 claims description 3
- 239000002245 particle Substances 0.000 claims description 3
- 229920002554 vinyl polymer Polymers 0.000 claims description 3
- NDMMKOCNFSTXRU-UHFFFAOYSA-N 1,1,2,3,3-pentafluoroprop-1-ene Chemical compound FC(F)C(F)=C(F)F NDMMKOCNFSTXRU-UHFFFAOYSA-N 0.000 claims description 2
- BLTXWCKMNMYXEA-UHFFFAOYSA-N 1,1,2-trifluoro-2-(trifluoromethoxy)ethene Chemical compound FC(F)=C(F)OC(F)(F)F BLTXWCKMNMYXEA-UHFFFAOYSA-N 0.000 claims description 2
- BZPCMSSQHRAJCC-UHFFFAOYSA-N 1,2,3,3,4,4,5,5,5-nonafluoro-1-(1,2,3,3,4,4,5,5,5-nonafluoropent-1-enoxy)pent-1-ene Chemical compound FC(F)(F)C(F)(F)C(F)(F)C(F)=C(F)OC(F)=C(F)C(F)(F)C(F)(F)C(F)(F)F BZPCMSSQHRAJCC-UHFFFAOYSA-N 0.000 claims description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 2
- 125000005907 alkyl ester group Chemical group 0.000 claims description 2
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 claims description 2
- XUCNUKMRBVNAPB-UHFFFAOYSA-N fluoroethene Chemical compound FC=C XUCNUKMRBVNAPB-UHFFFAOYSA-N 0.000 claims description 2
- 125000001475 halogen functional group Chemical group 0.000 claims description 2
- 150000002430 hydrocarbons Chemical class 0.000 claims description 2
- 238000010557 suspension polymerization reaction Methods 0.000 claims description 2
- BFKJFAAPBSQJPD-UHFFFAOYSA-N tetrafluoroethene Chemical group FC(F)=C(F)F BFKJFAAPBSQJPD-UHFFFAOYSA-N 0.000 claims description 2
- 239000011149 active material Substances 0.000 claims 1
- 239000000853 adhesive Substances 0.000 abstract description 20
- 230000001070 adhesive effect Effects 0.000 abstract description 20
- 238000006116 polymerization reaction Methods 0.000 abstract description 16
- 230000000694 effects Effects 0.000 abstract description 11
- 238000007667 floating Methods 0.000 abstract description 8
- 238000009827 uniform distribution Methods 0.000 abstract description 2
- 238000006243 chemical reaction Methods 0.000 description 129
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 56
- BQCIDUSAKPWEOX-UHFFFAOYSA-N 1,1-Difluoroethene Chemical compound FC(F)=C BQCIDUSAKPWEOX-UHFFFAOYSA-N 0.000 description 49
- 229910001870 ammonium persulfate Inorganic materials 0.000 description 28
- LTMRRSWNXVJMBA-UHFFFAOYSA-L 2,2-diethylpropanedioate Chemical compound CCC(CC)(C([O-])=O)C([O-])=O LTMRRSWNXVJMBA-UHFFFAOYSA-L 0.000 description 19
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 18
- 239000008367 deionised water Substances 0.000 description 17
- 229910021641 deionized water Inorganic materials 0.000 description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 17
- 238000001035 drying Methods 0.000 description 13
- 238000003756 stirring Methods 0.000 description 11
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 10
- 239000000706 filtrate Substances 0.000 description 10
- 238000010438 heat treatment Methods 0.000 description 10
- 239000001301 oxygen Substances 0.000 description 10
- 229910052760 oxygen Inorganic materials 0.000 description 10
- 238000005406 washing Methods 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 9
- 239000000203 mixture Substances 0.000 description 9
- 229910052757 nitrogen Inorganic materials 0.000 description 9
- 238000005086 pumping Methods 0.000 description 9
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 5
- 239000006258 conductive agent Substances 0.000 description 5
- 239000011888 foil Substances 0.000 description 5
- 239000000523 sample Substances 0.000 description 5
- 239000013543 active substance Substances 0.000 description 4
- 238000004132 cross linking Methods 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- 238000007334 copolymerization reaction Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 239000011267 electrode slurry Substances 0.000 description 2
- 238000010556 emulsion polymerization method Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000003999 initiator Substances 0.000 description 2
- 230000000977 initiatory effect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- JRKICGRDRMAZLK-UHFFFAOYSA-L peroxydisulfate Chemical compound [O-]S(=O)(=O)OOS([O-])(=O)=O JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000001502 supplementing effect Effects 0.000 description 2
- 238000010558 suspension polymerization method Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- AQKYLAIZOGOPAW-UHFFFAOYSA-N 2-methylbutan-2-yl 2,2-dimethylpropaneperoxoate Chemical compound CCC(C)(C)OOC(=O)C(C)(C)C AQKYLAIZOGOPAW-UHFFFAOYSA-N 0.000 description 1
- RPBWMJBZQXCSFW-UHFFFAOYSA-N 2-methylpropanoyl 2-methylpropaneperoxoate Chemical compound CC(C)C(=O)OOC(=O)C(C)C RPBWMJBZQXCSFW-UHFFFAOYSA-N 0.000 description 1
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- DWAQJAXMDSEUJJ-UHFFFAOYSA-M Sodium bisulfite Chemical compound [Na+].OS([O-])=O DWAQJAXMDSEUJJ-UHFFFAOYSA-M 0.000 description 1
- 238000007718 adhesive strength test Methods 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 229920006030 multiblock copolymer Polymers 0.000 description 1
- 239000012934 organic peroxide initiator Substances 0.000 description 1
- 238000007719 peel strength test Methods 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000003505 polymerization initiator Substances 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- BWJUFXUULUEGMA-UHFFFAOYSA-N propan-2-yl propan-2-yloxycarbonyloxy carbonate Chemical compound CC(C)OC(=O)OOC(=O)OC(C)C BWJUFXUULUEGMA-UHFFFAOYSA-N 0.000 description 1
- YPVDWEHVCUBACK-UHFFFAOYSA-N propoxycarbonyloxy propyl carbonate Chemical compound CCCOC(=O)OOC(=O)OCCC YPVDWEHVCUBACK-UHFFFAOYSA-N 0.000 description 1
- 235000010267 sodium hydrogen sulphite Nutrition 0.000 description 1
- 238000011895 specific detection Methods 0.000 description 1
- OPQYOFWUFGEMRZ-UHFFFAOYSA-N tert-butyl 2,2-dimethylpropaneperoxoate Chemical compound CC(C)(C)OOC(=O)C(C)(C)C OPQYOFWUFGEMRZ-UHFFFAOYSA-N 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 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
- C08F214/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
- C08F214/18—Monomers containing fluorine
- C08F214/22—Vinylidene fluoride
- C08F214/225—Vinylidene fluoride with non-fluorinated comonomers
-
- 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
- H01M4/623—Binders being polymers fluorinated polymers
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
The invention discloses a PVDF copolymer, a preparation method thereof and application thereof in lithium ion batteries, and relates to the technical field of lithium ion batteries. The PVDF copolymer is formed by copolymerizing 1, 1-vinylidene fluoride monomer and amino vinyl monomer, wherein the dosage of the amino vinyl monomer is 0.05-10% of the mass of the 1, 1-vinylidene fluoride monomer. According to the PVDF copolymer disclosed by the invention, through the positive charge repulsive effect of the amino vinyl monomer side chain, the block polymerization of the monomer in the PVDF chain segment can be reduced, the uniform distribution of the monomer on the PVDF chain segment is realized, when the PVDF copolymer is used as a pole piece adhesive, a network structure can be formed in the high-temperature baking process, the floating phenomenon of the adhesive is prevented, the stripping strength of a pole piece is improved, meanwhile, the surface resistance of the pole piece is reduced, and the battery performance is improved.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a PVDF copolymer, a preparation method thereof and application thereof in lithium ion batteries.
Background
The lithium ion battery slurry mainly comprises active substances, conductive agent particles, a solvent, a binder and the like, and after the lithium ion battery slurry is coated on a current collector aluminum foil, a tiny temperature gradient can be formed on the surface and the internal temperature of an electrode in a drying process, and the surface temperature can be higher than the internal temperature. In the drying process, the surface is firstly dried, the substance concentration is higher than the internal concentration, under the driving force, the binder in the pole piece gradually concentrates and migrates to the surface along with the volatilization of the solvent, and the binder is separated out from the surfaces of the active substances and the conductive agents, so that the surface resistance of the pole piece is larger, the battery performance is seriously affected, the binder is unevenly distributed in the pole piece, the binder on the surface contacted with the aluminum foil is less, and the stripping strength of the pole piece is obviously reduced. In the actual production process, in order to reduce the floating of the adhesive, the floating of the adhesive is reduced by reducing the drying temperature of the oven and the coating speed, but the floating problem of the adhesive cannot be completely solved by reducing the temperature and the coating speed, and the production efficiency of the product is reduced and the production cost is increased. Therefore, there is a need to solve the above-mentioned problems in terms of improvement of the performance of the adhesive itself.
In order to solve the problem of uneven distribution of the binder in the pole piece in the prior art, the polyurethane of the multiblock copolymer consisting of alternating soft segments and hard segments is provided as a novel binder for the pole piece, but the problem of larger pole piece surface resistance and reduced piece peeling strength caused by uneven precipitation distribution of the PVDF binder is not solved in the technology.
Disclosure of Invention
The invention aims to overcome the defects of larger sheet surface resistance and reduced sheet peeling strength caused by uneven precipitation distribution of the existing PVDF adhesive, and provides a PVDF copolymer, wherein the space structure of the PVDF adhesive is changed through amino vinyl monomers, so that the floating phenomenon of the adhesive is prevented, the sheet peeling strength is improved, the sheet surface resistance is reduced, and the battery performance is improved.
It is another object of the present invention to provide a method for preparing a PVDF copolymer.
It is a further object of the present invention to provide the use of a PVDF copolymer F in the preparation of lithium ion battery slurries.
It is still another object of the present invention to protect a lithium ion battery slurry.
It is still another object of the present invention to protect a lithium ion battery.
The above object of the present invention is achieved by the following technical scheme:
a PVDF copolymer is prepared by copolymerizing 1, 1-vinylidene fluoride monomer (VDF monomer) and amino vinyl monomer,
the amino vinyl monomer has the following structural formula:
wherein R is 1 、R 2 、R 3 Independently selected from hydrogen, C 1 -C 6 Alkyl or halo C 1 -C 6 An alkyl group; r is R 4 Independently selected from C 1 -C 6 Alkyl, carbonyl, C 1 -C 6 Alkylamides or C 1 -C 6 An alkyl ester of an alkyl group of a hydrocarbon,
the dosage of the amino vinyl monomer is 0.05-10% of the mass of the 1, 1-vinylidene fluoride monomer.
The following description is needed:
according to the invention, the amino vinyl monomer is selected, the side chain of the monomer has a certain positive charge repulsive effect, the block polymerization of the monomer in the PVDF chain segment can be reduced, the monomer is uniformly distributed on the PVDF chain segment, and when the monomer is used as a pole piece adhesive, amino groups can react with hydrocarbon bonds in the PVDF molecular chain in the high-temperature baking process, so that the molecular chain is rapidly crosslinked, the adhesive forms a network structure, the floating phenomenon of the adhesive is prevented, the pole piece peeling strength is improved, the surface resistance of the pole piece is reduced, and the battery performance is improved.
The amino vinyl monomer must be strictly controlled, the crosslinking effect cannot be achieved due to the fact that the dosage of the amino vinyl monomer is too low, the dosage of the amino vinyl monomer is too high, the crosslinking degree of the system is too high, and the prepared positive electrode slurry is easy to gel and cannot be used.
In a specific embodiment, preferably, the R 1 、R 2 、R 3 Are all hydrogen. When R is 1 、R 2 、R 3 When the two monomers are hydrogen, the two monomers have better polymerization effect with the amino vinyl monomer vinylidene fluoride monomer, and are more beneficial to forming a network structure.
In a specific embodiment, preferably, the amino vinyl monomer is one or more of allylamine, 2-aminoethyl acrylate, and N-2 (aminoethyl) acrylamide.
Preferably, the amount of the amino vinyl monomer is 0.5 to 2% by mass of the 1, 1-vinylidene fluoride monomer. For example, the amount of the amino vinyl monomer may be 0.1% by mass of the 1, 1-vinylidene fluoride monomer; or the dosage of the amino vinyl monomer is 1% of the mass of the 1, 1-vinylidene fluoride monomer; or the amount of the amino vinyl monomer is 2% of the mass of the 1, 1-vinylidene fluoride monomer.
In particular embodiments, the co-monomers further include other fluoromonomers such as one or more of vinyl fluoride, vinyl trifluoride, vinyl trifluorochloride, tetrafluoroethylene, pentafluoropropene, hexafluoropropylene, perfluoromethyl vinyl ether, perfluoropropyl vinyl ether. The addition of the fluorine-containing monomer can reduce the crystallinity of PVDF and improve the flexibility of the pole piece.
On the other hand, the invention also specifically protects a preparation method of the PVDF copolymer, and the PVDF copolymer can be prepared by adopting an emulsion polymerization method or a suspension polymerization method.
The PVDF copolymer of the invention is prepared by emulsion polymerization or suspension polymerization, and the specific operations can be referred to as follows:
under the reaction condition that the oxygen content is less than 10ppm, part of VDF monomer is added under the condition of closed stirring and heating, then initiator and chain transfer agent are added, comonomer is added at the same time, polymerization reaction is started, and the reaction pressure is kept unchanged by continuously supplementing the VDF monomer. After a period of reaction, a quantity of initiator and chain transfer agent is added. When the VDF monomer amount is reacted to 3kg, stopping the reaction, collecting emulsion, demulsifying, and repeatedly washing until the conductivity of the filtrate is reduced to below 0.1. Finally, drying for 24 hours to obtain the PVDF copolymer.
The polymerization initiator in the emulsion polymerization or suspension polymerization method of the present invention may be one selected from the group consisting of organic peroxide initiators such as diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, diisobutyryl peroxide, t-butyl peroxypivalate, t-amyl peroxypivalate, etc. The emulsion polymerization system may also employ persulfate or persulfate/sodium bisulfite initiation systems, preferably ammonium persulfate initiation systems.
Chain transfer agents may be added to the polymerization system to adjust the molecular weight of the polymer, and the chemicals that may be used for chain transfer are: ethyl acetate, diethyl malonate, diethyl carbonate, dimethyl carbonate, acetone, ethanol, n-propanol, and the like.
Preferably, the chain transfer agent comprises 0.01 to 1% by mass of the polymerized monomer. The amount of chain transfer agent used is related to the molecular weight of the polymerization product, and is too large, small and large.
In another aspect, the invention also specifically protects the use of PVDF copolymers in the preparation of lithium ion battery slurries.
The invention also specifically protects lithium ion battery slurry, which comprises an active substance, conductive agent particles, a solvent and a binder, wherein the binder is the PVDF copolymer.
The invention also specifically protects a lithium ion battery, wherein the slurry of the lithium ion battery is the lithium ion battery slurry.
The lithium ion battery slurry contains the specific binder PVDF copolymer, a network structure can be formed in the baking high-temperature process after the binder is coated on the aluminum foil of the current collector, the binder in the pole piece cannot gradually gather and migrate to the surface along with the volatilization of the solvent, the binder cannot be separated out on the surfaces of active substances and conductive agents, the pole piece surface resistance is small, the battery performance is excellent, the distribution of the binder in the pole piece is uniform, the stripping strength of the pole piece is good, and the binder can be widely applied to the preparation of lithium ion batteries.
Compared with the prior art, the invention has the beneficial effects that:
according to the PVDF copolymer disclosed by the invention, through the positive charge repulsive effect of the amino vinyl monomer side chain, the block polymerization of the monomer in the PVDF chain segment can be reduced, the uniform distribution of the monomer on the PVDF chain segment is realized, when the PVDF copolymer is used as a pole piece adhesive, a network structure can be formed in the high-temperature baking process, the floating phenomenon of the adhesive is prevented, the stripping strength of a pole piece is improved, meanwhile, the surface resistance of the pole piece is reduced, and the battery performance is improved.
The bonding strength of the positive electrode prepared by the PVDF copolymer can reach 18.5-25.0N/m, the surface resistance can be reduced to 1.2-1.8/omega, and the PVDF copolymer has higher bonding force and lower surface resistance.
Detailed Description
The invention will be further described with reference to the following specific embodiments, but the examples are not intended to limit the invention in any way. Raw materials reagents used in the examples of the present invention are conventionally purchased raw materials reagents unless otherwise specified.
Example 1
A PVDF copolymer is formed by copolymerizing a VDF monomer and an amino vinyl monomer, wherein the amino vinyl monomer is allylamine, and the dosage of the amino vinyl monomer is 0.5% of the weight of the VDF monomer.
The PVDF copolymer of example 1 was prepared as follows:
into a 20L vertical polymerizer, 11.5kg deionized water was added. And closing the reaction kettle, vacuumizing, and replacing the reaction kettle with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm. Heating the reaction kettle to 85 ℃, and starting the reaction kettle to stir at the rotating speed of 400r/min. And (3) pumping a certain amount of VDF monomer into the reaction kettle until the pressure of the reaction kettle is 4.1MPa. 30g of comonomer allylamine was dissolved in 500g of deionized water and added to the reaction vessel by means of an auxiliary pump at a rate of 150 g/hr. Simultaneously, 0.64g of ammonium persulfate and 3.48g of diethyl malonate were added, and the polymerization was started, and the reaction pressure was kept constant by continuously adding the VDF monomer. After 1h of reaction, 0.28g of ammonium persulfate was added, and after 2h of reaction, 0.28g of ammonium persulfate and 0.93g of diethyl malonate were added. When the VDF monomer reaction amount was 3kg, the reaction was stopped for 4.7 hours. The reaction kettle is depressurized, emulsion is collected, demulsification is carried out, and washing is repeated until the conductivity of filtrate is reduced to below 0.1. Finally, drying the mixture in an oven at 95 ℃ for 24 hours to obtain the PVDF copolymer.
Example 2
A PVDF copolymer is formed by copolymerizing a VDF monomer and an amino vinyl monomer, wherein the amino vinyl monomer is allylamine, and the dosage of the amino vinyl monomer is 1.0% of the mass of the VDF monomer.
The PVDF copolymer of example 2 was prepared as follows:
into a 20L vertical polymerizer, 11.5kg deionized water was added. And closing the reaction kettle, vacuumizing, and replacing the reaction kettle with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm. Heating the reaction kettle to 85 ℃, and starting the reaction kettle to stir at the rotating speed of 400r/min. And (3) pumping a certain amount of VDF monomer into the reaction kettle until the pressure of the reaction kettle is 4.1MPa. 60g of comonomer allylamine was dissolved in 500g of deionized water and added to the reaction vessel by means of an auxiliary pump at a rate of 150 g/hr. Simultaneously, 0.64g of ammonium persulfate and 3.48g of diethyl malonate were added, and the polymerization was started, and the reaction pressure was kept constant by continuously adding the VDF monomer. After 1h of reaction, 0.28g of ammonium persulfate was added, and after 2h of reaction, 0.28g of ammonium persulfate and 0.93g of diethyl malonate were added. When the VDF monomer reaction amount was 3kg, the reaction was stopped for 4.7 hours. The reaction kettle is depressurized, emulsion is collected, demulsification is carried out, and washing is repeated until the conductivity of filtrate is reduced to below 0.1. Finally, drying the mixture in an oven at 95 ℃ for 24 hours to obtain the PVDF copolymer.
Example 3
A PVDF copolymer is formed by copolymerizing a VDF monomer and an amino vinyl monomer, wherein the amino vinyl monomer is allylamine, and the dosage of the amino vinyl monomer is 2.0% of the mass of the VDF monomer.
The PVDF copolymer of example 3 was prepared as follows:
into a 20L vertical polymerizer, 11.5kg deionized water was added. And closing the reaction kettle, vacuumizing, and replacing the reaction kettle with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm. Heating the reaction kettle to 85 ℃, and starting the reaction kettle to stir at the rotating speed of 400r/min. And (3) pumping a certain amount of VDF monomer into the reaction kettle until the pressure of the reaction kettle is 4.1MPa. 120g of comonomer allylamine was dissolved in 500g of deionized water and added to the reaction vessel by means of an auxiliary pump at a rate of 150 g/hr. Simultaneously, 0.64g of ammonium persulfate and 3.48g of diethyl malonate were added, and the polymerization was started, and the reaction pressure was kept constant by continuously adding the VDF monomer. After 1h of reaction, 0.28g of ammonium persulfate was added, and after 2h of reaction, 0.28g of ammonium persulfate and 0.93g of diethyl malonate were added. When the VDF monomer reaction amount was 3kg, the reaction was stopped for 4.7 hours. The reaction kettle is depressurized, emulsion is collected, demulsification is carried out, and washing is repeated until the conductivity of filtrate is reduced to below 0.1. Finally, drying the mixture in an oven at 95 ℃ for 24 hours to obtain the PVDF copolymer.
Example 4
A PVDF copolymer is formed by copolymerizing a VDF monomer and an amino vinyl monomer, wherein the amino vinyl monomer is acrylic acid-2-aminoethyl ester, and the dosage of the amino vinyl monomer is 2.0% of the mass of the VDF/hexafluoropropylene monomer.
The PVDF copolymer of example 4 was prepared as follows:
into a 20L vertical polymerizer, 11.5kg deionized water was added. And closing the reaction kettle, vacuumizing, and replacing the reaction kettle with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm. Heating the reaction kettle to 85 ℃, and starting the reaction kettle to stir at the rotating speed of 400r/min. And (3) pumping a certain amount of VDF/hexafluoropropylene mixed monomer into the reaction kettle until the pressure is 4.1MPa. 120g of comonomer allylamine was dissolved in 500g of deionized water and added to the reaction vessel by means of an auxiliary pump at a rate of 150 g/hr. Simultaneously, 0.64g of ammonium persulfate and 3.48g of diethyl malonate were added, and the polymerization was started, and the reaction pressure was kept constant by continuously supplementing the VDF/hexafluoropropylene monomer. After 1h of reaction, 0.28g of ammonium persulfate was added, and after 2h of reaction, 0.28g of ammonium persulfate and 0.93g of diethyl malonate were added. When the VDF monomer reaction amount was 3kg, the reaction was stopped for 4.7 hours. The reaction kettle is depressurized, emulsion is collected, demulsification is carried out, and washing is repeated until the conductivity of filtrate is reduced to below 0.1. Finally, drying the mixture in an oven at 95 ℃ for 24 hours to obtain the PVDF copolymer.
Example 5
A PVDF copolymer is formed by copolymerizing a VDF monomer and an amino vinyl monomer, wherein the amino vinyl monomer is acrylic acid-2-amino ethyl ester, and the dosage of the amino vinyl monomer is 5.0% of the mass of the VDF monomer.
The PVDF copolymer of example 5 was prepared as follows:
into a 20L vertical polymerizer, 11.5kg deionized water was added. And closing the reaction kettle, vacuumizing, and replacing the reaction kettle with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm. Heating the reaction kettle to 85 ℃, and starting the reaction kettle to stir at the rotating speed of 400r/min. And (3) pumping a certain amount of VDF monomer into the reaction kettle until the pressure of the reaction kettle is 4.1MPa. 300g of the comonomer 2-aminoethyl acrylate was dissolved in 500g of deionized water and added to the reaction vessel by means of an auxiliary pump at a rate of 150 g/hr. Simultaneously, 0.64g of ammonium persulfate and 3.48g of diethyl malonate were added, and the polymerization was started, and the reaction pressure was kept constant by continuously adding the VDF monomer. After 1h of reaction, 0.28g of ammonium persulfate was added, and after 2h of reaction, 0.28g of ammonium persulfate and 0.93g of diethyl malonate were added. When the VDF monomer reaction amount was 3kg, the reaction was stopped for 4.7 hours. The reaction kettle is depressurized, emulsion is collected, demulsification is carried out, and washing is repeated until the conductivity of filtrate is reduced to below 0.1. Finally, drying the mixture in an oven at 95 ℃ for 24 hours to obtain the PVDF copolymer.
Example 6
A PVDF copolymer is formed by copolymerizing a VDF monomer and an amino vinyl monomer, wherein the amino vinyl monomer is N-2 (amino ethyl) acrylamide, and the dosage of the amino vinyl monomer is 2.0% of the mass of the VDF monomer.
The PVDF copolymer of example 6 was prepared as follows:
into a 20L vertical polymerizer, 11.5kg deionized water was added. And closing the reaction kettle, vacuumizing, and replacing the reaction kettle with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm. Heating the reaction kettle to 85 ℃, and starting the reaction kettle to stir at the rotating speed of 400r/min. And (3) pumping a certain amount of VDF monomer into the reaction kettle until the pressure of the reaction kettle is 4.1MPa. 120g of comonomer N-2 (aminoethyl) acrylamide was dissolved in 500g of deionized water and added to the reaction vessel by means of an auxiliary pump at a rate of 150 g/hr. Simultaneously, 0.64g of ammonium persulfate and 3.48g of diethyl malonate were added, and the polymerization was started, and the reaction pressure was kept constant by continuously adding the VDF monomer. After 1h of reaction, 0.28g of ammonium persulfate was added, and after 2h of reaction, 0.28g of ammonium persulfate and 0.93g of diethyl malonate were added. When the VDF monomer reaction amount was 3kg, the reaction was stopped for 4.7 hours. The reaction kettle is depressurized, emulsion is collected, demulsification is carried out, and washing is repeated until the conductivity of filtrate is reduced to below 0.1. Finally, drying the mixture in an oven at 95 ℃ for 24 hours to obtain the PVDF copolymer.
Comparative example 1
A PVDF copolymer polymerized from VDF monomers.
The PVDF copolymer of example 1 was prepared as follows:
into a 20L vertical polymerizer, 11.5kg deionized water was added. And closing the reaction kettle, vacuumizing, and replacing the reaction kettle with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm. Heating the reaction kettle to 85 ℃, and starting the reaction kettle to stir at the rotating speed of 400r/min. And (3) pumping a certain amount of VDF monomer into the reaction kettle until the pressure of the reaction kettle is 4.1MPa. The polymerization was started by adding 0.64g of ammonium persulfate and 3.48g of diethyl malonate, and the reaction pressure was kept constant by continuously replenishing the VDF monomer. After 1h of reaction, 0.28g of ammonium persulfate was added, and after 2h of reaction, 0.28g of ammonium persulfate and 0.93g of diethyl malonate were added. When the VDF monomer reaction amount was 3kg, the reaction was stopped for 4.7 hours. The reaction kettle is depressurized, emulsion is collected, demulsification is carried out, and washing is repeated until the conductivity of filtrate is reduced to below 0.1. Finally, drying the mixture in an oven at 95 ℃ for 24 hours to obtain the PVDF copolymer.
Comparative example 2
A PVDF copolymer is formed by copolymerizing a VDF monomer and an amino vinyl monomer, wherein the amino vinyl monomer is allylamine, and the dosage of the amino vinyl monomer is 0.03% of the weight of the VDF monomer.
The PVDF copolymer of comparative example 2 was prepared as follows:
into a 20L vertical polymerizer, 11.5kg deionized water was added. And closing the reaction kettle, vacuumizing, and replacing the reaction kettle with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm. Heating the reaction kettle to 85 ℃, and starting the reaction kettle to stir at the rotating speed of 400r/min. And (3) pumping a certain amount of VDF monomer into the reaction kettle until the pressure of the reaction kettle is 4.1MPa. 10g of comonomer allylamine was dissolved in 500g of deionized water and added to the reaction vessel by means of an auxiliary pump at a rate of 150 g/hr. Simultaneously, 0.64g of ammonium persulfate and 3.48g of diethyl malonate were added, and the polymerization was started, and the reaction pressure was kept constant by continuously adding the VDF monomer. After 1h of reaction, 0.28g of ammonium persulfate was added, and after 2h of reaction, 0.28g of ammonium persulfate and 0.93g of diethyl malonate were added. When the VDF monomer reaction amount was 3kg, the reaction was stopped for 4.7 hours. The reaction kettle is depressurized, emulsion is collected, demulsification is carried out, and washing is repeated until the conductivity of filtrate is reduced to below 0.1. Finally, drying the mixture in an oven at 95 ℃ for 24 hours to obtain the PVDF copolymer.
Comparative example 3
A PVDF copolymer is formed by copolymerizing a VDF monomer and an amino vinyl monomer, wherein the amino vinyl monomer is allylamine, and the dosage of the amino vinyl monomer is 12% of the mass of the VDF monomer.
The PVDF copolymer of comparative example 2 was prepared as follows:
into a 20L vertical polymerizer, 11.5kg deionized water was added. And closing the reaction kettle, vacuumizing, and replacing the reaction kettle with nitrogen for several times until the oxygen content in the reaction kettle is less than 10ppm. Heating the reaction kettle to 85 ℃, and starting the reaction kettle to stir at the rotating speed of 400r/min. And (3) pumping a certain amount of VDF monomer into the reaction kettle until the pressure of the reaction kettle is 4.1MPa. 720g of comonomer allylamine was dissolved in 500g of deionized water and added to the reaction vessel by means of an auxiliary pump at a rate of 150 g/hr. Simultaneously, 0.64g of ammonium persulfate and 3.48g of diethyl malonate were added, and the polymerization was started, and the reaction pressure was kept constant by continuously adding the VDF monomer. After 1h of reaction, 0.28g of ammonium persulfate was added, and after 2h of reaction, 0.28g of ammonium persulfate and 0.93g of diethyl malonate were added. When the VDF monomer reaction amount was 3kg, the reaction was stopped for 4.7 hours. The reaction kettle is depressurized, emulsion is collected, demulsification is carried out, and washing is repeated until the conductivity of filtrate is reduced to below 0.1. Finally, drying the mixture in an oven at 95 ℃ for 24 hours to obtain the PVDF copolymer.
Result detection
The PVDF copolymers of the above examples and comparative examples were prepared as positive electrodes according to the following electrode preparation method.
The preparation process of the electrode comprises the following steps: 2g PVDF was dissolved in 100g NMP solution and stirred to dissolve well. Then, 2.8g of carbon black as a conductive agent and 56.2g of lithium iron phosphate were added in a stirred state, and further ultrasonic stirring was performed for 2 hours to prepare a uniform slurry. The slurry was coated on a 12 μm rear electrode aluminum foil by a coater. The aluminum foil was then dried in a vacuum oven at 100℃for 12h. And obtaining the positive electrode.
Adhesive strength test was carried out according to the test method in the national Standard GB/T2790-1995 "180-degree peel Strength test method of adhesive Flexible Material vs. rigid Material".
The surface resistance measurement method comprises the following steps:
test instrument: pole piece resistance instrument, model BER2500 (IEST element energy technology), electrode diameter 14mm, pressure 5-60 MPa
Four-probe method: four probes are arranged on the surface of a sample during testing, direct current signals are input, voltage signals among the probes are collected, and the resistivity of the sample is obtained through conversion relation.
The specific detection results are shown in the following table 1:
TABLE 1
The lower the melting point, the higher the proportion of amino vinyl monomer copolymerized. As can be seen from the data in the table 1, the PVDF copolymer provided by the invention has a good copolymerization effect, and when the PVDF copolymer is used as a pole piece adhesive, a network structure can be formed in a high-temperature baking process, the floating phenomenon of the adhesive is prevented, the stripping strength of the pole piece is improved, the bonding strength can reach more than 18.5N/m and can reach 25.0N/m at most, meanwhile, the surface resistance of the pole piece can be effectively reduced, the surface resistance is 1.8Ω or lower, the minimum surface resistance can be reduced to 1.2Ω, and the battery performance is effectively improved.
Wherein, the comparative example 1 is that no amino vinyl monomer is added, the copolymerization effect is poor, the melting point is high, the bonding strength as a binder is low, the resistivity is high, and the technical effect of the invention cannot be achieved.
The amino vinyl monomer used in comparative example 2 was too low to have a good crosslinking effect, the copolymerization effect was poor, the melting point was high, and the adhesive strength as an adhesive was low, and the specific resistance was also high, failing to achieve the technical effect of the present invention.
In comparative example 3, the amount of the amino vinyl monomer used was too high, the degree of crosslinking of the system was too high, and the prepared positive electrode slurry was easily gelled, and the adhesive strength was remarkably lowered.
It is to be understood that the above examples of the present invention are provided by way of illustration only and not by way of limitation of the embodiments of the present invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the invention are desired to be protected by the following claims.
Claims (10)
1. A PVDF copolymer is characterized in that the PVDF copolymer is formed by copolymerizing 1, 1-vinylidene fluoride monomer and amino vinyl monomer,
the amino vinyl monomer has the following structural formula:
wherein R is 1 、R 2 、R 3 Independently selected from hydrogen, C 1 -C 6 Alkyl or halo C 1 -C 6 An alkyl group; r is R 4 Independently selected from C 1 -C 6 Alkyl, carbonyl, C 1 -C 6 Alkylamides or C 1 -C 6 An alkyl ester of an alkyl group of a hydrocarbon,
the dosage of the amino vinyl monomer is 0.05-10% of the mass of the 1, 1-vinylidene fluoride monomer.
2. The PVDF copolymer of claim 1, wherein R 1 、R 2 、R 3 Are all hydrogen.
3. The PVDF copolymer of claim 1, wherein the amino vinyl monomer is one or more of allylamine, 2-aminoethyl acrylate, and N-2 (aminoethyl) acrylamide.
4. The PVDF copolymer as claimed in claim 1, wherein the amino vinyl monomer is used in an amount of 0.5 to 2% by mass of the 1, 1-vinylidene fluoride monomer.
5. The PVDF copolymer of claim 1, wherein the co-monomers further comprise one or more of vinyl fluoride, vinyl trifluoride, tetrafluoroethylene, pentafluoropropene, hexafluoropropylene, perfluoromethyl vinyl ether, perfluoropropyl vinyl ether.
6. A method for preparing a PVDF copolymer according to any of claims 1 to 5, characterized in that it is prepared by emulsion or suspension polymerization.
7. The process according to claim 6, wherein a chain transfer agent is added to the specific monomer in an amount of 0.01 to 1% by mass based on the mass of the polymerized monomer.
8. Use of a PVDF copolymer according to any of claims 1 to 5 for the preparation of lithium ion battery pastes.
9. A lithium ion battery slurry comprising an active material, conductive particles, a solvent and a binder, wherein the binder is the PVDF copolymer of any of claims 1-5.
10. A lithium ion battery, characterized in that the slurry of the lithium ion battery is the lithium ion battery slurry of claim 9.
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