CN117186289A - Polyvinylidene fluoride material and preparation method and application thereof - Google Patents
Polyvinylidene fluoride material and preparation method and application thereof Download PDFInfo
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- 239000002033 PVDF binder Substances 0.000 title claims abstract description 44
- 229920002981 polyvinylidene fluoride Polymers 0.000 title claims abstract description 44
- 239000000463 material Substances 0.000 title claims abstract description 34
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- 238000006243 chemical reaction Methods 0.000 claims abstract description 37
- 239000000839 emulsion Substances 0.000 claims abstract description 33
- 229920000642 polymer Polymers 0.000 claims abstract description 33
- 238000010438 heat treatment Methods 0.000 claims abstract description 27
- BQCIDUSAKPWEOX-UHFFFAOYSA-N 1,1-Difluoroethene Chemical compound FC(F)=C BQCIDUSAKPWEOX-UHFFFAOYSA-N 0.000 claims abstract description 21
- 239000003999 initiator Substances 0.000 claims abstract description 20
- 239000012986 chain transfer agent Substances 0.000 claims abstract description 19
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 18
- 239000008367 deionised water Substances 0.000 claims abstract description 18
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 18
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 18
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 18
- 239000004094 surface-active agent Substances 0.000 claims abstract description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 18
- 238000000034 method Methods 0.000 claims abstract description 15
- 238000001035 drying Methods 0.000 claims abstract description 13
- BFKJFAAPBSQJPD-UHFFFAOYSA-N tetrafluoroethene Chemical group FC(F)=C(F)F BFKJFAAPBSQJPD-UHFFFAOYSA-N 0.000 claims abstract description 13
- 238000003756 stirring Methods 0.000 claims abstract description 12
- 238000005406 washing Methods 0.000 claims abstract description 11
- DKGAVHZHDRPRBM-UHFFFAOYSA-N Tert-Butanol Chemical compound CC(C)(C)O DKGAVHZHDRPRBM-UHFFFAOYSA-N 0.000 claims description 16
- YOALFLHFSFEMLP-UHFFFAOYSA-N azane;2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctanoic acid Chemical compound [NH4+].[O-]C(=O)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)F YOALFLHFSFEMLP-UHFFFAOYSA-N 0.000 claims description 12
- XRXANEMIFVRKLN-UHFFFAOYSA-N 2-hydroperoxy-2-methylbutane Chemical group CCC(C)(C)OO XRXANEMIFVRKLN-UHFFFAOYSA-N 0.000 claims description 10
- FRQQKWGDKVGLFI-UHFFFAOYSA-N 2-methylundecane-2-thiol Chemical compound CCCCCCCCCC(C)(C)S FRQQKWGDKVGLFI-UHFFFAOYSA-N 0.000 claims description 10
- DNJIEGIFACGWOD-UHFFFAOYSA-N ethyl mercaptane Natural products CCS DNJIEGIFACGWOD-UHFFFAOYSA-N 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 10
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 claims description 10
- 239000000843 powder Substances 0.000 claims description 10
- DGVVWUTYPXICAM-UHFFFAOYSA-N β‐Mercaptoethanol Chemical group OCCS DGVVWUTYPXICAM-UHFFFAOYSA-N 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 7
- -1 poly (perfluoroethylene propylene) Polymers 0.000 claims description 6
- 239000011230 binding agent Substances 0.000 claims description 4
- SNGREZUHAYWORS-UHFFFAOYSA-N perfluorooctanoic acid Chemical compound OC(=O)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)F SNGREZUHAYWORS-UHFFFAOYSA-N 0.000 claims description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 10
- 229910052760 oxygen Inorganic materials 0.000 description 10
- 239000001301 oxygen Substances 0.000 description 10
- XIUFWXXRTPHHDQ-UHFFFAOYSA-N prop-1-ene;1,1,2,2-tetrafluoroethene Chemical group CC=C.FC(F)=C(F)F XIUFWXXRTPHHDQ-UHFFFAOYSA-N 0.000 description 8
- 230000001070 adhesive effect Effects 0.000 description 7
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 229910001416 lithium ion Inorganic materials 0.000 description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- 239000000853 adhesive Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 239000011267 electrode slurry Substances 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 229910052802 copper Inorganic materials 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 239000012528 membrane Substances 0.000 description 3
- 229920005989 resin Polymers 0.000 description 3
- 239000011347 resin Substances 0.000 description 3
- 238000007789 sealing Methods 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 239000002270 dispersing agent Substances 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000002390 adhesive tape Substances 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
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- 230000008025 crystallization Effects 0.000 description 1
- 238000005520 cutting process Methods 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
- 230000000694 effects Effects 0.000 description 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 1
- 229920002313 fluoropolymer Polymers 0.000 description 1
- 239000004811 fluoropolymer Substances 0.000 description 1
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- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 238000007719 peel strength test Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000002798 polar solvent Substances 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
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- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
The invention provides a preparation method of a polyvinylidene fluoride material, which comprises the steps of adding deionized water, a chain transfer agent, a surfactant and an initiator into a reaction container, uniformly stirring, vacuumizing, deoxidizing, heating to 65-110 ℃, adding vinylidene fluoride to the reaction container, wherein the pressure is 1.5-3.5 MPa, starting a polymerization reaction, continuously adding tetrafluoroethylene to the pressure of 4.8-5.5 MPa, heating to 125-142 ℃, and finishing the reaction to obtain a polymer emulsion; and (3) condensing, washing, drying and granulating the obtained polymer emulsion to obtain the polymer emulsion. The polyvinylidene fluoride material obtained by the method has excellent bonding performance for the battery, can ensure the electrical performance of the lithium battery, and has good application prospect.
Description
Technical Field
The invention relates to the field of organic material synthesis, in particular to a polyvinylidene fluoride material, a preparation method and application thereof.
Background
Polyvinylidene fluoride (PVDF) is a highly non-reactive thermoplastic fluoropolymer that is soluble in strongly polar solvents such as dimethylacetamide and can be synthesized by polymerization of 1, 1-difluoroethylene. Polyvinylidene fluoride has excellent performances of ageing resistance, chemical resistance, weather resistance, ultraviolet radiation resistance and the like, and is widely applied to the fields of coatings, lithium batteries, filtering films, wires and cables and the like, wherein the coatings, the filtering films and the lithium batteries are the most important three products, and more than 50% of the global yield of the polyvinylidene fluoride is concentrated on the products. In recent years, new energy automobile industry is rapidly developed, and further synchronous flight of lithium battery industry is driven, polyvinylidene fluoride is a hot material of binder, dispersing agent and electrolyte in lithium batteries, so that various large-scale production enterprises are accelerated to enter the layout of new production capacity and optimize and upgrade the performance of products, and main upgrading and optimizing directions comprise yield improvement of production process, molecular weight distribution control of products, stability improvement and the like.
Patent CN106632770B discloses a preparation method of polyvinylidene fluoride, adding vinylidene fluoride, deionized water, an initial chain transfer agent, a dispersing agent, evacuating, deoxidizing, heating to 20-150 ℃, adding an initial initiator by adding vinylidene fluoride monomer until the pressure in the kettle is 1.0-6.0 MPa; the polymerization is started, chain transfer agent is supplemented and initiator is supplemented. The patent uses 2 chain transfer agents for the first time in the polymerization process, and the obtained product has uniform molecular weight, narrow distribution and high production efficiency, but does not improve the adhesive property when used as an adhesive. The adhesion of polyvinylidene fluoride is also an important factor affecting the performance of the battery. If the adhesive property is not suitable, the electrode mixture layer may be partially or entirely peeled off from the current collector due to internal stress of the electrode with the lapse of the service time, resulting in deterioration of load characteristics and capacity deterioration.
In addition, polyvinylidene fluoride is an important binder in the lithium battery industry, but there is still a problem that a large amount of crystallization may occur in a temperature range in which lithium batteries are generally used, thereby impeding the molecular flow of an electrolytic liquid and causing an increase in charge and discharge load, resulting in poor performance of the lithium batteries.
Therefore, how to produce polyvinylidene fluoride materials suitable for lithium batteries is a very promising important research topic.
Disclosure of Invention
In order to solve the technical problems, the invention provides a preparation method of a polyvinylidene fluoride material, and the polyvinylidene fluoride material obtained by the method has excellent adhesive property for a lithium battery and can ensure the electrical property of the lithium battery.
The embodiment of the invention provides a preparation method of a polyvinylidene fluoride material, which comprises the following steps:
adding deionized water, a chain transfer agent, a surfactant and an initiator into a reaction container, uniformly stirring, vacuumizing, deoxidizing, heating to 65-110 ℃, adding vinylidene fluoride to the pressure of 1.5-3.5 MPa in the reaction container, starting a polymerization reaction, continuously adding tetrafluoroethylene to the pressure of 4.8-5.5 MPa, heating to 125-142 ℃, and finishing the reaction to obtain a polymer emulsion;
and (3) condensing, washing, drying and granulating the obtained polymer emulsion to obtain the polymer emulsion.
As one embodiment, the initiator is a composition of tertiary amyl hydroperoxide, tertiary dodecyl mercaptan and potassium persulfate, and the mass ratio of the initiator to the composition is (3-7) to (2-5) to (0.01-0.6).
In one embodiment, the initiator is added in an amount of 0.08 to 1.8 parts by mass per 100 parts by mass of deionized water.
In one embodiment, the chain transfer agent is a composition of mercaptoethanol and t-butanol in a mass ratio of (1 to 2) to (3 to 7).
In one embodiment, the chain transfer agent is added in an amount of 0.2 to 4.0 parts by mass per 100 parts by mass of deionized water.
As one embodiment, the surfactant is a composition of poly (perfluoroethylene propylene) micropowder and perfluoro octanoic acid or ammonium perfluoro octanoate; preferably, the surfactant is a composition of the poly (perfluoroethylene propylene) micro powder and ammonium perfluorooctanoate according to the mass ratio of (4-7) to 1.
As one embodiment, the surfactant is added in an amount of 0.2 to 1.5 parts by mass per 100 parts by mass of deionized water.
As one implementation mode, vacuumizing, deoxidizing, heating to 98-110 ℃, adding vinylidene fluoride to the pressure of 2.1-3.3 MPa in a reaction vessel, starting the polymerization reaction, and continuously adding tetrafluoroethylene to the pressure of 5.1-5.5 MPa and heating to 130-140 ℃.
The invention also provides the vinylidene fluoride material prepared by any one of the methods.
The invention further provides application of the polyvinylidene fluoride material, and the polyvinylidene fluoride material is used as a binder of a lithium battery.
Compared with the prior art, the invention has the following advantages:
1. the PVDF material prepared by the method has proper cohesiveness, is particularly suitable for lithium batteries, and forms an electrode mixture layer which is not easy to be partially or completely peeled off from a current collector.
2. When the PVDF material prepared by the method is used for a lithium battery, good load characteristics and capacity can be ensured to be kept, and the battery performance is more reliable.
3. Compared with other improved formulas disclosed in the prior art, the preparation raw materials adopted by the method are simpler, the cost can be reduced, and the industrial applicability is higher.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention are clearly and completely described below. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by a person skilled in the art without creative efforts, based on the described embodiments of the present invention fall within the protection scope of the present invention.
Without being specifically stated, the materials or equipment used in the following cases are all general materials obtained from the market by commercial purchasing means, and different manufacturers or batches do not affect the achievement of the excellent effects of the present invention.
In the case, the mass ratio of the initiator, the chain transfer agent and the surfactant is the mass ratio.
Example 1
Adding 100 parts of deionized water, 0.2 part of chain transfer agent (mercaptoethanol: tertiary butanol=1:7), 0.2 part of surfactant (poly perfluoroethylene propylene micro powder: ammonium perfluorooctanoate=4:1) and 0.08 part of initiator (tertiary amyl hydroperoxide: tertiary dodecyl mercaptan: potassium persulfate=3:2:0.6) into a reaction vessel, uniformly stirring, vacuumizing, deoxidizing until the oxygen content is reduced to below 30ppm, heating to 65 ℃, then adding vinylidene fluoride until the pressure in the reaction vessel is 3.5MPa, starting polymerization, continuously adding tetrafluoroethylene until the pressure is 4.8MPa, heating to 142 ℃, and obtaining polymer emulsion after the reaction is finished; and (3) condensing, washing, drying and granulating the obtained polymer emulsion to obtain the polymer emulsion.
Example 2
Adding 100 parts of deionized water, 0.4 part of chain transfer agent (mercaptoethanol: tertiary butanol=2:3), 0.4 part of surfactant (poly perfluoroethylene propylene micro powder: ammonium perfluorooctanoate=5:1) and 0.1 part of initiator (tertiary amyl hydroperoxide: tertiary dodecyl mercaptan: potassium persulfate=7:5:0.01) into a reaction vessel, uniformly stirring, vacuumizing, deoxidizing until the oxygen content is reduced to below 30ppm, heating to 80 ℃, then adding vinylidene fluoride until the pressure in the reaction vessel is 1.5MPa, starting polymerization, continuously adding tetrafluoroethylene until the pressure is 5.0MPa, heating to 142 ℃, and ending the reaction to obtain polymer emulsion; and (3) condensing, washing, drying and granulating the obtained polymer emulsion to obtain the polymer emulsion.
Example 3
Adding 100 parts of deionized water, 0.8 part of chain transfer agent (mercaptoethanol: tertiary butanol=1:4), 0.6 part of surfactant (poly perfluoroethylene propylene micro powder: ammonium perfluorooctanoate=5:1) and 0.3 part of initiator (tertiary amyl hydroperoxide: tertiary dodecyl mercaptan: potassium persulfate=3:3:0.3) into a reaction vessel, uniformly stirring, vacuumizing, deoxidizing until the oxygen content is reduced to below 30ppm, heating to 75 ℃, then adding vinylidene fluoride until the pressure in the reaction vessel is 2.0MPa, starting polymerization, continuously adding tetrafluoroethylene until the pressure is 5.4MPa, heating to 128 ℃, and ending the reaction to obtain polymer emulsion; and (3) condensing, washing, drying and granulating the obtained polymer emulsion to obtain the polymer emulsion.
Example 4
Adding 100 parts of deionized water, 1.5 parts of chain transfer agent (mercaptoethanol: tertiary butanol=2:5), 0.8 part of surfactant (poly perfluoroethylene propylene micro powder: ammonium perfluorooctanoate=7:1) and 0.7 part of initiator (tertiary amyl hydroperoxide: tertiary dodecyl mercaptan: potassium persulfate=4:5:0.5) into a reaction vessel, uniformly stirring, vacuumizing, deoxidizing until the oxygen content is reduced to below 30ppm, heating to 105 ℃, then adding vinylidene fluoride until the pressure in the reaction vessel is 3.5MPa, starting polymerization, continuously adding tetrafluoroethylene until the pressure is 5.2MPa, heating to 135 ℃, and obtaining polymer emulsion after the reaction is finished; and (3) condensing, washing, drying and granulating the obtained polymer emulsion to obtain the polymer emulsion.
Example 5
Adding 100 parts of deionized water, 2.0 parts of chain transfer agent (mercaptoethanol: tertiary butanol=1:6), 1.0 part of surfactant (poly perfluoroethylene propylene micro powder: ammonium perfluorooctanoate=7:1) and 1.1 parts of initiator (tertiary amyl hydroperoxide: tertiary dodecyl mercaptan: potassium persulfate=7:4:0.2) into a reaction vessel, uniformly stirring, vacuumizing, deoxidizing until the oxygen content is reduced to below 30ppm, heating to 98 ℃, then adding vinylidene fluoride until the pressure in the reaction vessel is 3.3MPa, starting polymerization, continuously adding tetrafluoroethylene until the pressure is 5.3MPa, heating to 130 ℃, and ending the reaction to obtain polymer emulsion; and (3) condensing, washing, drying and granulating the obtained polymer emulsion to obtain the polymer emulsion.
Example 6
Adding 100 parts of deionized water, 2.8 parts of chain transfer agent (mercaptoethanol: tertiary butanol=1:3), 1.2 parts of surfactant (poly perfluoroethylene propylene micro powder: ammonium perfluorooctanoate=5:1) and 1.3 parts of initiator (tertiary amyl hydroperoxide: tertiary dodecyl mercaptan: potassium persulfate=6:4:0.1) into a reaction vessel, uniformly stirring, vacuumizing, deoxidizing until the oxygen content is reduced to below 30ppm, heating to 106 ℃, then adding vinylidene fluoride until the pressure in the reaction vessel is 2.8MPa, starting polymerization, continuously adding tetrafluoroethylene until the pressure is 5.4MPa and heating to 139 ℃, and obtaining polymer emulsion after the reaction is finished; and (3) condensing, washing, drying and granulating the obtained polymer emulsion to obtain the polymer emulsion.
Example 7
Adding 100 parts of deionized water, 3.6 parts of chain transfer agent (mercaptoethanol: tertiary butanol=1:5), 1.4 parts of surfactant (poly perfluoroethylene propylene micro powder: ammonium perfluorooctanoate=6:1) and 1.5 parts of initiator (tertiary amyl hydroperoxide: tertiary dodecyl mercaptan: potassium persulfate=5:5:0.5) into a reaction vessel, uniformly stirring, vacuumizing, deoxidizing until the oxygen content is reduced to below 30ppm, heating to 110 ℃, then adding vinylidene fluoride until the pressure in the reaction vessel is 3.3MPa, starting polymerization, continuously adding tetrafluoroethylene until the pressure is 5.1MPa and heating to 133 ℃, and obtaining polymer emulsion after the reaction is finished; and (3) condensing, washing, drying and granulating the obtained polymer emulsion to obtain the polymer emulsion.
Example 8
Adding 100 parts of deionized water, 4.0 parts of chain transfer agent (mercaptoethanol: tertiary butanol=1:3), 1.5 parts of surfactant (poly perfluoroethylene propylene micro powder: ammonium perfluorooctanoate=4:1) and 1.8 parts of initiator (tertiary amyl hydroperoxide: tertiary dodecyl mercaptan: potassium persulfate=4:4:0.4) into a reaction vessel, uniformly stirring, vacuumizing, deoxidizing until the oxygen content is reduced to below 30ppm, heating to 98 ℃, then adding vinylidene fluoride until the pressure in the reaction vessel is 2.9MPa, starting polymerization, continuously adding tetrafluoroethylene until the pressure is 5.1MPa, heating to 135 ℃, and obtaining polymer emulsion after the reaction is finished; and (3) condensing, washing, drying and granulating the obtained polymer emulsion to obtain the polymer emulsion.
Comparative example 1
The difference from example 1 is that the reaction vessel was evacuated, deoxygenated to an oxygen content of less than 30ppm, warmed to 65℃and then charged with vinylidene fluoride to a pressure of 3.5MPa, polymerization was started, and further charged with vinylidene fluoride to 4.8MPa and warmed to 142 ℃. Others remain the same.
Comparative example 2
The difference from example 1 is that the reaction vessel was evacuated, deoxygenated to a level of less than 30ppm of oxygen, directly warmed to 142℃and then charged with vinylidene fluoride to a pressure of 3.5MPa, polymerization was initiated and then fed with vinylidene fluoride to a pressure of 4.8MPa. Others remain the same.
Test example 1 adhesion test
The PVDF material obtained in examples 1-8, the PVDF material obtained in comparative examples 1-2 and commercially available PVDF product JH-D2500 homopolymerized resin are respectively dissolved in DMAc solvent to prepare 8wt% solution, the solution is coated on a clean copper plate by using a coater, the copper plate is placed for 24 hours at 60 ℃, the film is formed, then the copper plate is adhered on the surface of a positive plate by using a transparent adhesive tape, and 200 x 40mm sample strips are cut for 180 DEG peel strength test.
TABLE 1
Test example 2 lithium ion battery Performance test
(1) Preparation of lithium ion batteries
Step 1: preparing a positive plate of the lithium ion battery: liCoO as positive electrode active material 2 Mixing PVDF adhesive and conductive carbon black in an N-methyl pyrrolidone solvent according to the mass ratio of 95:3:2, and uniformly stirring to obtain positive electrode slurry; coating the obtained positive electrode slurry on a positive electrode current collector with the thickness of 0.2mm, drying, and cold pressing to obtain a compacted density of 1.6g/cm 3 Then cutting and welding the tab to obtain a positive plate;
step two: preparation of lithium ion battery negative plate
Mixing a carbon negative electrode material, a PVDF adhesive and a conductive agent in an N-methyl pyrrolidone solvent according to a mass ratio of 95:3:2, uniformly mixing to obtain negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector copper foil, drying to form a negative electrode membrane, and carrying out cold pressing, slitting and welding of tabs to obtain a negative electrode plate;
step three: preparation of electrolyte for lithium ion battery
Ethylene carbonate: methyl ethyl carbonate: uniformly mixing dimethyl carbonate according to the mass ratio of 2:1:7, and adding 16wt% of lithium hexafluorophosphate as a solute to prepare electrolyte;
step four: a membrane, which adopts a polyethylene porous membrane with the thickness of 16 mu m;
step five: and (3) assembling the lithium battery, sequentially winding the obtained positive plate, negative plate and diaphragm into a battery core, sealing the battery core by using an aluminum film in a top sealing manner and a side sealing manner, leaving a liquid injection port to be filled with electrolyte, and then carrying out the working procedures of formation, capacity and the like to obtain the lithium ion battery.
The PVDF adhesive is prepared from PVDF materials obtained in examples 1-8, PVDF materials obtained in comparative examples 1-2 and commercially available PVDF product JH-D2500 homopolymerized resin, and the PVDF materials and the PVDF resins are respectively used for manufacturing electrode plates, assembling the electrode plates into batteries, and testing the electrical properties of the batteries.
The method for detecting the internal resistance value of the battery comprises the following steps: the internal resistance value of each battery is tested by adopting an alternating-current voltage drop internal resistance measurement method, namely, a small current with the frequency of 1kHz and the voltage of 50mA is applied to the lithium battery, then the voltage is sampled, and the internal resistance value of the lithium battery is calculated through an operational amplifier circuit after a series of treatments such as rectification, filtering and the like.
The method for detecting the cycle life of the battery comprises the following steps: the detection condition is 1C charge and discharge, the capacity after 300 times of battery circulation is tested through an electrochemical workstation, and the capacity retention rate is calculated.
The specific properties obtained are shown in Table 2.
TABLE 2
| PVDF material used | Internal resistance mΩ of battery | Capacity retention% |
| Example 1 | 43 | 80 |
| Example 2 | 41 | 83 |
| Example 3 | 39 | 81 |
| Example 4 | 40 | 82 |
| Example 5 | 35 | 86 |
| Example 6 | 37 | 85 |
| Example 7 | 34 | 89 |
| Example 8 | 36 | 87 |
| Comparative example 1 | 47 | 62 |
| Comparative example 2 | 45 | 69 |
| JH-D2500 | 38 | 32 |
Although the embodiments of the present invention are described above, the embodiments are only used for facilitating understanding of the present invention, and are not intended to limit the present invention. Any person skilled in the art can make any modification and variation in form and detail without departing from the spirit and scope of the present disclosure, but the scope of the present disclosure is to be determined by the appended claims.
Claims (10)
1. A method for preparing polyvinylidene fluoride material, comprising:
adding deionized water, a chain transfer agent, a surfactant and an initiator into a reaction container, uniformly stirring, vacuumizing, deoxidizing, heating to 65-110 ℃, adding vinylidene fluoride to the pressure of 1.5-3.5 MPa in the reaction container, starting a polymerization reaction, continuously adding tetrafluoroethylene to the pressure of 4.8-5.5 MPa, heating to 125-142 ℃, and finishing the reaction to obtain a polymer emulsion;
and (3) condensing, washing, drying and granulating the obtained polymer emulsion to obtain the polymer emulsion.
2. The preparation method of the polyvinylidene fluoride material according to claim 1, wherein the initiator is a composition of tertiary amyl hydroperoxide, tertiary dodecyl mercaptan and potassium persulfate, and the mass ratio of the initiator is (3-7): 2-5): 0.01-0.6.
3. The method for preparing a polyvinylidene fluoride material according to claim 1 or 2, wherein the initiator is added in an amount of 0.08 to 1.8 parts by mass based on 100 parts by mass of deionized water.
4. The preparation method of the polyvinylidene fluoride material according to claim 1, wherein the chain transfer agent is a composition of mercaptoethanol and tert-butyl alcohol, and the mass ratio of the chain transfer agent to the tert-butyl alcohol is (1-2) (3-7).
5. The method for producing a polyvinylidene fluoride material according to claim 1 or 4, wherein the chain transfer agent is added in an amount of 0.2 to 4.0 parts by mass based on 100 parts by mass of deionized water.
6. The method for preparing polyvinylidene fluoride material according to claim 1, wherein the surfactant is a composition of poly (perfluoroethylene propylene) micropowder and perfluoro octanoic acid or ammonium perfluoro octanoate; preferably, the surfactant is poly (perfluoroethylene propylene) micro powder and ammonium perfluorooctanoate according to the mass ratio of (4-7): 1.
7. The method for producing a polyvinylidene fluoride material according to claim 1 or 6, wherein the surfactant is added in an amount of 0.2 to 1.5 parts by mass based on 100 parts by mass of deionized water.
8. The method for preparing a polyvinylidene fluoride material according to claim 1, wherein the method is characterized in that the method comprises the steps of vacuumizing, deoxidizing, heating to 98-110 ℃, adding vinylidene fluoride to the pressure of 2.1-3.3 MPa in a reaction vessel, starting the polymerization reaction, continuously adding tetrafluoroethylene to the pressure of 5.1-5.5 MPa, and heating to 130-140 ℃.
9. A polyvinylidene fluoride material obtained by the production method according to any one of claims 1 to 8.
10. Use of the polyvinylidene fluoride material according to claim 9, wherein the polyvinylidene fluoride material is used as a binder for lithium batteries.
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