CN114512771A - Green oily PVDF (polyvinylidene fluoride) membrane as well as preparation method and application thereof - Google Patents
Green oily PVDF (polyvinylidene fluoride) membrane as well as preparation method and application thereof Download PDFInfo
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- CN114512771A CN114512771A CN202210213283.2A CN202210213283A CN114512771A CN 114512771 A CN114512771 A CN 114512771A CN 202210213283 A CN202210213283 A CN 202210213283A CN 114512771 A CN114512771 A CN 114512771A
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- Prior art keywords
- polyvinylidene fluoride
- pvdf
- green
- coating
- mnmp
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- 239000002033 PVDF binder Substances 0.000 title claims abstract description 181
- 239000012528 membrane Substances 0.000 title claims abstract description 31
- 238000002360 preparation method Methods 0.000 title claims abstract description 23
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims abstract description 178
- 238000000576 coating method Methods 0.000 claims abstract description 60
- 239000011248 coating agent Substances 0.000 claims abstract description 56
- 229920000642 polymer Polymers 0.000 claims abstract description 56
- 239000011247 coating layer Substances 0.000 claims abstract description 23
- 238000000034 method Methods 0.000 claims abstract description 23
- FILVIKOEJGORQS-UHFFFAOYSA-N 1,5-dimethylpyrrolidin-2-one Chemical compound CC1CCC(=O)N1C FILVIKOEJGORQS-UHFFFAOYSA-N 0.000 claims abstract description 7
- 238000001035 drying Methods 0.000 claims description 31
- 239000011230 binding agent Substances 0.000 claims description 28
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 27
- 239000002994 raw material Substances 0.000 claims description 25
- 229920002134 Carboxymethyl cellulose Polymers 0.000 claims description 21
- 239000001768 carboxy methyl cellulose Substances 0.000 claims description 21
- 235000010948 carboxy methyl cellulose Nutrition 0.000 claims description 21
- 239000008112 carboxymethyl-cellulose Substances 0.000 claims description 21
- 229920005569 poly(vinylidene fluoride-co-hexafluoropropylene) Polymers 0.000 claims description 18
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 claims description 14
- 239000002245 particle Substances 0.000 claims description 13
- 238000007493 shaping process Methods 0.000 claims description 13
- 239000002270 dispersing agent Substances 0.000 claims description 12
- 239000000919 ceramic Substances 0.000 claims description 11
- 239000002562 thickening agent Substances 0.000 claims description 11
- KNSXNCFKSZZHEA-UHFFFAOYSA-N [3-prop-2-enoyloxy-2,2-bis(prop-2-enoyloxymethyl)propyl] prop-2-enoate Chemical class C=CC(=O)OCC(COC(=O)C=C)(COC(=O)C=C)COC(=O)C=C KNSXNCFKSZZHEA-UHFFFAOYSA-N 0.000 claims description 10
- CQEYYJKEWSMYFG-UHFFFAOYSA-N butyl acrylate Chemical compound CCCCOC(=O)C=C CQEYYJKEWSMYFG-UHFFFAOYSA-N 0.000 claims description 8
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 claims description 7
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims description 7
- 229910001870 ammonium persulfate Inorganic materials 0.000 claims description 7
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 7
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 7
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 7
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 claims description 4
- 239000013078 crystal Substances 0.000 claims description 4
- 238000004804 winding Methods 0.000 claims description 2
- 239000002904 solvent Substances 0.000 abstract description 48
- 239000002002 slurry Substances 0.000 abstract description 33
- 230000008569 process Effects 0.000 abstract description 14
- 230000001965 increasing effect Effects 0.000 abstract description 8
- 239000000853 adhesive Substances 0.000 abstract description 6
- 230000001070 adhesive effect Effects 0.000 abstract description 6
- 239000007787 solid Substances 0.000 abstract description 6
- 238000011161 development Methods 0.000 abstract description 4
- 230000036541 health Effects 0.000 abstract description 4
- 231100000419 toxicity Toxicity 0.000 abstract description 4
- 230000001988 toxicity Effects 0.000 abstract description 4
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 230000001737 promoting effect Effects 0.000 abstract description 3
- 239000002028 Biomass Substances 0.000 abstract description 2
- 238000003756 stirring Methods 0.000 description 34
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 24
- 238000000605 extraction Methods 0.000 description 21
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 18
- 238000006243 chemical reaction Methods 0.000 description 17
- 239000000463 material Substances 0.000 description 14
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 9
- 239000003795 chemical substances by application Substances 0.000 description 9
- 238000010438 heat treatment Methods 0.000 description 8
- 238000007761 roller coating Methods 0.000 description 8
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 6
- 238000010521 absorption reaction Methods 0.000 description 5
- 239000007864 aqueous solution Substances 0.000 description 5
- YLGYACDQVQQZSW-UHFFFAOYSA-N n,n-dimethylprop-2-enamide Chemical compound CN(C)C(=O)C=C YLGYACDQVQQZSW-UHFFFAOYSA-N 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- UAGJVSRUFNSIHR-UHFFFAOYSA-N Methyl levulinate Chemical compound COC(=O)CCC(C)=O UAGJVSRUFNSIHR-UHFFFAOYSA-N 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 238000004090 dissolution Methods 0.000 description 4
- 229920000098 polyolefin Polymers 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 231100000086 high toxicity Toxicity 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 230000003472 neutralizing effect Effects 0.000 description 3
- 239000012299 nitrogen atmosphere Substances 0.000 description 3
- 230000035484 reaction time Effects 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- BAVYZALUXZFZLV-UHFFFAOYSA-N Methylamine Chemical compound NC BAVYZALUXZFZLV-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 239000012295 chemical reaction liquid Substances 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 238000007334 copolymerization reaction Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 229920006316 polyvinylpyrrolidine Polymers 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- HNJBEVLQSNELDL-UHFFFAOYSA-N pyrrolidin-2-one Chemical compound O=C1CCCN1 HNJBEVLQSNELDL-UHFFFAOYSA-N 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- BQCIDUSAKPWEOX-UHFFFAOYSA-N 1,1-Difluoroethene Chemical compound FC(F)=C BQCIDUSAKPWEOX-UHFFFAOYSA-N 0.000 description 1
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- 239000011203 carbon fibre reinforced carbon Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000013043 chemical agent Substances 0.000 description 1
- 125000003636 chemical group Chemical group 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 235000019253 formic acid Nutrition 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 125000004029 hydroxymethyl group Chemical group [H]OC([H])([H])* 0.000 description 1
- 239000011244 liquid electrolyte Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000010907 mechanical stirring Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 231100000956 nontoxicity Toxicity 0.000 description 1
- 230000037361 pathway Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229920002492 poly(sulfone) Polymers 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
- 229920000915 polyvinyl chloride Polymers 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 150000003254 radicals Chemical class 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000002390 rotary evaporation Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000007581 slurry coating method Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
-
- 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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
- H01M50/497—Ionic conductivity
-
- 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)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Cell Separators (AREA)
Abstract
The invention provides a green oily PVDF (polyvinylidene fluoride) coated diaphragm, which comprises a base film and a PVDF coating layer; PVDF uses biomass-derived 1, 5-dimethyl-2-pyrrolidone (MNMP) as a green solvent. The invention uses the biological base green solvent MNMP, reduces pollution and toxicity, and successfully replaces the NMP solvent while protecting the health of personnel; and the thickness of the coating is thinner by adjusting the solid content and the process parameters of the slurry, thereby being beneficial to improving the energy density of the battery and promoting the development of the ultrathin battery. The polyvinylidene fluoride polymer with beta crystalline phase is obtained by modifying defluorinated polyvinylidene fluoride, so that the ionic conductivity of the diaphragm and the energy density of the battery are improved. The invention uses the adhesive copolymerized by a plurality of polymers, thereby effectively improving the adhesion performance and increasing the ionic conductivity. The invention also provides a preparation method and application of the green oily PVDF membrane.
Description
Technical Field
The invention belongs to the technical field of battery diaphragms, and particularly relates to a green oily PVDF diaphragm and a preparation method and application thereof.
Background
The diaphragm is used as an important component of the battery, can isolate the positive electrode and the negative electrode, prevents the positive electrode and the negative electrode from contacting to cause short circuit, can bear electrolyte, and is Li+Migration provides a pathway within the cell. At present, polyolefin microporous membranes are used for their combination of propertiesCost advantages have been widely used in most commercial lithium ion batteries. However, polyolefin microporous membranes also have some disadvantages: such as poor compatibility with a liquid electrolyte, thereby reducing battery performance, having low thermal stability, resulting in safety problems such as battery explosion. In order to solve these problems, the prior art generally improves the safety and electrochemical performance of a battery by coating a base film with a material such as polyvinylidene fluoride (PVDF). However, conventional oily solvents such as N-methylpyrrolidone (NMP) and acetone for dissolving PVDF have high toxicity, not only cause environmental pollution, but also are extremely harmful to human body, so that the application of the polyvinylidene fluoride coating film is limited by many chemical regulations in industrial application, and the european union has started to limit the use of high-toxicity solvents such as NMP at present. Therefore, it is important to find greener, safer alternatives.
Disclosure of Invention
In view of the above, the invention aims to provide a green oily PVDF membrane, and a preparation method and an application thereof.
The invention provides a green oily PVDF membrane, comprising:
a base film;
a PVDF coating layer disposed on a surface of the base film;
the PVDF coating layer is prepared from a raw material containing 1, 5-dimethyl-2-pyrrolidone.
Preferably, the preparation raw materials of the PVDF coating layer comprise, by weight:
2-5 parts of a polyvinylidene fluoride polymer having a beta crystalline phase;
0.5-4 parts of polyvinylidene fluoride-hexafluoropropylene copolymer;
20-60 parts of MNMP;
0.06-0.14 parts of binder.
Preferably, the polyvinylidene fluoride polymer with beta crystalline phase is prepared from the following raw materials:
polyvinylidene fluoride polymer, defluorinated polyvinylidene fluoride, and MNMP.
Preferably, the defluorinated polyvinylidene fluoride is prepared from the following raw materials:
polyvinylpyrrolidone, potassium hydroxide, and polyvinylidene fluoride polymer.
Preferably, the binder is prepared from the following raw materials:
carboxymethyl cellulose, butyl acrylate, ethoxylated pentaerythritol tetraacrylate, N-methyl (meth) acrylamide, acrylic acid, and ammonium persulfate.
Preferably, the raw materials for preparing the PVDF coating layer further include:
one or more of a dispersant, a thickener and ceramic particles.
The invention provides a preparation method of a green oily PVDF membrane, which comprises the following steps:
and coating the PVDF coating layer preparation raw material on the surface of the base film, and then extracting, drying and shaping to obtain the green oily PVDF membrane.
Preferably, the coating method is roller coating;
the coating tension in the coating process is 20-30N; the unwinding tension is 5-8N; the retraction tension is 17-25N; the winding tension is 5-7N.
The present invention provides a battery separator comprising:
the green oily PVDF membrane is prepared by the technical scheme.
The present invention provides a battery comprising:
the battery diaphragm of the technical scheme.
The invention uses the biological-based green solvent MNMP, reduces pollution and toxicity, protects the health of personnel and successfully replaces the NMP solvent; and the thickness of the coating prepared by adjusting the solid content and the technological parameters of the slurry is thinner, thereby being beneficial to improving the energy density of the battery and promoting the development of the ultrathin battery. The invention utilizes the defluorinated polyvinylidene fluoride to prepare the polyvinylidene fluoride polymer with beta crystalline phase, thereby improving the ionic conductivity of the diaphragm and the energy density of the battery. The invention uses the adhesive copolymerized by a plurality of polymers, thereby effectively improving the adhesion performance and increasing the ionic conductivity.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a green oily PVDF membrane, comprising:
a base film;
a PVDF coating layer disposed on a surface of the base film;
the PVDF coating layer is prepared from a raw material containing 1, 5-dimethyl-2-pyrrolidone.
The base membrane is not particularly limited in the present invention, and may be one known to those skilled in the art, and is preferably selected from polyolefin membrane, polysulfone membrane or polyvinylidene fluoride membrane.
In the present invention, the thickness of the base film is preferably 0.01 to 0.5mm, more preferably 0.05 to 0.4mm, more preferably 0.1 to 0.3mm, and most preferably 0.2 mm.
In the present invention, it is preferable that 1, 5-dimethyl-2-pyrrolidone (MNMP) derived from biomass be used as a green solvent for the preparation of the PVDF coating layer.
The source of the MNMP is not particularly limited, and the MNMP can be prepared by a preparation method of MNMP which is well known to those skilled in the art.
In the present invention, the raw materials for preparing the PVDF coating layer preferably include, in parts by weight:
2-5 parts of a polyvinylidene fluoride polymer having a beta crystalline phase;
0.5-4 parts of polyvinylidene fluoride-hexafluoropropylene copolymer;
20-60 parts of MNMP;
0.06-0.14 parts of binder.
In the invention, the weight part of the polyvinylidene fluoride polymer with beta crystalline phase is preferably 3-4 parts.
In the present invention, the polyvinylidene fluoride polymer having a β crystal phase is preferably prepared from raw materials comprising:
polyvinylidene fluoride polymer, defluorinated polyvinylidene fluoride, and MNMP.
In the invention, the polyvinylidene fluoride polymer comprises polyvinylidene fluoride as a component.
In the present invention, the method for preparing the polyvinylidene fluoride polymer having a β crystal phase preferably comprises:
and dispersing the polyvinylidene fluoride polymer and the defluorinated polyvinylidene fluoride in a green solvent MNMP for homogenization, drying and then carrying out heat treatment to obtain the polyvinylidene fluoride polymer with a beta crystalline phase.
In the present invention, the mass of the defluorinated polyvinylidene fluoride is preferably 2 to 5%, more preferably 3 to 4% of the mass of the polyvinylidene fluoride polymer.
In the invention, the carbon-carbon double bond is formed in the internal structure of the defluorinated polyvinylidene fluoride along with the increase of the reaction time, so that the conductivity is increased, but the content of a coating layer prepared by mixing the defluorinated polyvinylidene fluoride with a polyvinylidene fluoride polymer is not too high, and the breakdown strength is easy to reduce because the conductivity between the defluorinated polyvinylidene fluoride and the polyvinylidene fluoride polymer is different. Therefore, the addition amount of the defluorinated polyvinylidene fluoride is preferably 2-5% of the mass of the polyvinylidene fluoride polymer.
In the present invention, the MNMP is preferably used in an amount such that the total solubility of the polyvinylidene fluoride polymer and the defluorinated polyvinylidene fluoride is 5 to 10%, more preferably 6 to 9%, and most preferably 7 to 8%.
In the invention, the temperature of the heat treatment is preferably 100-140 ℃, more preferably 110-130 ℃, and most preferably 120 ℃; the time of the heat treatment is preferably 2 to 3 hours, and more preferably 2.5 hours.
According to the invention, polyvinylidene fluoride polymer and defluorinated polyvinylidene fluoride are mixed for pretreatment, then the pretreated polyvinylidene fluoride polymer is prepared into PVDF slurry, the defluorinated polyvinylidene fluoride and the polyvinylidene fluoride polymer are subjected to heat treatment at 120 ℃, and the defluorinated polyvinylidene fluoride can induce the polyvinylidene fluoride polymer to form beta crystal form, so that the dielectric constant and polarity of the polyvinylidene fluoride polymer are enhanced, and the ionic conductivity and the battery energy density of the oily PVDF coating diaphragm are enhanced.
In the present invention, the defluorinated polyvinylidene fluoride is preferably prepared from the following raw materials:
polyvinylpyrrolidone, potassium hydroxide, and polyvinylidene fluoride polymer.
In the present invention, the potassium hydroxide is preferably a potassium hydroxide solution, more preferably an aqueous potassium hydroxide solution; the concentration of the potassium hydroxide solution is preferably 1-10 mol/L, more preferably 2-8 mol/L, more preferably 3-6 mol/L, and most preferably 4-5 mol/L.
In the present invention, the preparation method of the defluorinated polyvinylidene fluoride preferably comprises:
and adding polyvinylpyrrolidone into the potassium hydroxide aqueous solution for dissolving, and then adding polyvinylidene fluoride polymer for reacting to obtain the defluorinated polyvinylidene fluoride.
In the invention, the mass ratio of the polyvinylpyrrolidone, the potassium hydroxide aqueous solution and the polyvinylidene fluoride polymer is preferably (1-20): 100: (1-20), more preferably (5-15): 100: (5-15), more preferably (8-12): 100: (8-12), most preferably 10: 100: 10.
in the invention, the reaction temperature is preferably 70-90 ℃, more preferably 75-85 ℃, and most preferably 80 ℃; the reaction time is preferably 12 to 24 hours, more preferably 15 to 20 hours, and most preferably 16 to 18 hours.
In the invention, the weight part of the polyvinylidene fluoride-hexafluoropropylene copolymer is preferably 1-3 parts, and more preferably 2 parts.
In the invention, the weight part of the MNMP is preferably 30-50 parts, and more preferably 40 parts.
In the invention, the binder is preferably 0.08-0.12 part by weight, and more preferably 0.1 part by weight.
In the present invention, the binder is preferably prepared from raw materials comprising:
carboxymethyl cellulose, butyl acrylate, ethoxylated pentaerythritol tetraacrylate, N-methyl (meth) acrylamide, acrylic acid, and ammonium persulfate.
In the invention, the mass ratio of the carboxymethyl cellulose, the butyl acrylate, the ethoxylated pentaerythritol tetraacrylate, the N-methyl (meth) acrylamide, the acrylic acid and the ammonium persulfate is preferably (40-50): (15-20): (22-28): (8-10): (5-10): (1-5), more preferably (43-47): (16-19): (24-26): (8.5-9.5): (6-9): (2-4), most preferably 45: (17-18): 25: 9: (7-8): 3.
in the present invention, the preparation method of the binder preferably includes:
dissolving carboxymethyl cellulose, sequentially adding butyl acrylate, ethoxylated pentaerythritol tetraacrylate and N-methyl (methyl) acrylamide, adding acrylic acid and ammonium persulfate, and reacting to obtain the binder.
In the present invention, the dissolution is preferably dissolution with stirring.
In the present invention, the reaction is preferably carried out under a nitrogen atmosphere; the reaction is preferably carried out in a reaction kettle; preferably, the water in the reaction kettle is deoxidized; the reaction temperature is preferably 60-80 ℃, more preferably 65-75 ℃ and most preferably 70 ℃; the reaction time is preferably 4 to 5 hours, and more preferably 4.5 hours.
In the present invention, the reaction preferably further comprises, after completion of the reaction:
and neutralizing, washing, filtering and drying the obtained reaction product to obtain the binder.
In the invention, butyl acrylate, ethoxylated pentaerythritol tetraacrylate and N-methyl (methyl) acrylamide are copolymerized to the skeleton of carboxymethyl cellulose by free radical copolymerization, so that the interface bonding force is improved; the branched chains of the ethoxylated pentaerythritol tetraacrylate and the like in the molecular chain of the adhesive obtained by copolymerization have more polar functional groups, so that the absorption of electrolyte is increased, and the ionic conductivity of the diaphragm is enhanced; meanwhile, hydroxyl in the carboxymethyl cellulose and hydroxymethyl in the N-methyl (methyl) acrylamide are condensed to form a larger and steady cross-linked network, so that the rapid transportation of the electrolyte can be ensured, and the circulation stability is increased.
In the present invention, the raw material for preparing the PVDF coating layer preferably further includes:
one or more of a dispersant, a thickener and ceramic particles.
In the present invention, the dispersant is preferably selected from polyvinylpyrrolidone K30 (which may be national chemical group ltd). In the invention, the weight part of the dispersant is preferably 5-10 parts, more preferably 6-9 parts, and most preferably 7-8 parts.
In the present invention, the thickener is preferably selected from carboxymethylcellulose (available from Aladdin reagents, Inc.). In the invention, the weight part of the thickener is preferably 1 to 5 parts, more preferably 2 to 4 parts, and most preferably 3 parts.
In the present invention, the ceramic particles are preferably alumina. In the invention, the weight part of the ceramic particles is preferably 5 to 20 parts, more preferably 10 to 15 parts, and most preferably 12 to 13 parts.
In the invention, the thickness of the PVDF coating layer is preferably 0.01-0.5 mm, more preferably 0.05-0.4 mm, more preferably 0.1-0.3 mm, and most preferably 0.2 mm.
The invention provides a preparation method of a green oily PVDF membrane, which comprises the following steps:
and coating the PVDF coating layer preparation raw material on the surface of the base film, and then extracting, drying and shaping to obtain the green oily PVDF membrane.
In the present invention, the preparation method of the PVDF coating layer preparation raw material preferably includes:
mixing polyvinylidene fluoride polymer, polyvinylidene fluoride-hexafluoropropylene copolymer, MNMP and binder to obtain PVDF slurry.
In the present invention, the preparation method of the PVDF slurry more preferably includes:
and adding the polyvinylidene fluoride polymer and the polyvinylidene fluoride-hexafluoropropylene copolymer into a green solvent MNMP for dissolving, adding the binder, and uniformly stirring to obtain the PVDF slurry.
In the present invention, the preparation method of the PVDF slurry most preferably includes:
and adding the polyvinylidene fluoride polymer and the polyvinylidene fluoride-hexafluoropropylene copolymer into a green solvent MNMP for dissolving, adding the binder, the dispersing agent, the thickening agent and the ceramic particles, and uniformly stirring to obtain the PVDF slurry.
In the invention, ceramic particles can be added into the PVDF slurry for roll coating, the ceramic particles have better dispersibility and stability in MNMP solvent, and the oily PVDF coating membrane formed by coating has better air permeability, puncture strength and shrinkage resistance.
In the invention, when the PVDF slurry contains ceramic particles, the adhesive with a cross-linking structure enhances the interface strength and the dispersibility between the ceramic particles and the base film, has stronger adhesive force, is not easy to drop the ceramic particles in the cyclic charge-discharge process, simultaneously plays a role in buffering, reduces the expansion stress in the charge-discharge process, ensures that the prepared diaphragm has better stability and ionic conductivity, and prolongs the service life of the battery.
In the present invention, the dissolution is preferably carried out by heating in a water bath; the dissolving temperature is preferably 70-100 ℃, more preferably 80-90 ℃, and most preferably 85 ℃; the dissolution is preferably carried out under stirring; the stirring speed is preferably 100 to 500rpm/min, more preferably 200 to 400rpm/min, and most preferably 300 rpm/min.
According to the preparation method, the MNMP green solvent is used as a solvent, a dispersing agent, a vinylidene fluoride Polymer (PVDF) and other raw materials, the PVDF slurry is prepared, and a PVDF coating layer is formed on the surface of a base film, so that an oily PVDF coating diaphragm with higher porosity, electrolyte wettability and ionic conductivity is formed, and the safety and electrochemical performance of the battery are enhanced. Compared with the method using water as a solvent, the oily PVDF coating membrane has better adhesion with the pole piece; and the problems that the product is easy to have light transmission points and dark points and the coating is too thick can not be caused. According to the invention, MNMP is used as a green solvent, and the thickness of the coating is thinner by adjusting the solid content and the process parameters of the slurry, so that the improvement of the energy density of the battery is facilitated, and the development of the ultrathin battery is promoted. Compared with common oily solvents such as N-methyl pyrrolidone, acetone and the like which have high toxicity, the MNMP solvent used in the invention is a novel bio-based green solvent, has similar polarity with N-methyl pyrrolidone (NMP), is non-toxic and environment-friendly, and successfully replaces NMP while protecting the body health of workers to obtain the oily PVDF membrane with the performance equivalent to that of the tambourine.
In the present invention, the method of coating is preferably roll coating; the tension in the coating process is preferably 20-30N, and more preferably 25N; the unwinding tension is preferably 5-8N, and more preferably 6-7N; the retraction tension is preferably 17-25N, more preferably 20-22N; the rolling tension is preferably 5-7N, and more preferably 6N; the feeding speed is preferably 300-400 rpm/min, more preferably 330-370 rpm/min, and most preferably 350 rpm/min; the gravure speed ratio is preferably 0.8-1.2, more preferably 0.9-1.1, and most preferably 1.0; the coating speed is preferably 10 to 30m/min, more preferably 15 to 25m/min, and most preferably 20 m/min.
In the invention, the extracting agent in the extraction process is preferably water, the extraction stage number is preferably 7-9 stages, more preferably 8 stages, and the MNMP green solvent is extracted cleanly.
In the invention, the drying temperature is preferably 60-70 ℃, and more preferably 65 ℃; the drying is preferably carried out in an oven.
The present invention provides a battery separator comprising:
the green oily PVDF membrane is prepared by the technical scheme.
The present invention provides a battery comprising:
the battery diaphragm of the technical scheme.
In the invention, the 1, 5-dimethyl-2-pyrrolidone (MNMP) has basic physical properties similar to NMP, simultaneously has greatly reduced toxicity, and is a high-efficiency selective solvent which has the advantages of no toxicity, high boiling point (217 ℃), low melting point (-70 ℃), strong polarity, low viscosity, low corrosivity, high solubility, low volatility, good stability and easy recovery. The MNMP replaces NMP, so that the process efficiency of battery electrode preparation can be effectively improved, the viscosity of the MNMP is lower than that of the NMP, the solid content is favorably improved, the solvent volatilization efficiency is improved, the production rate of an electrode plate is improved, the dispersion uniformity of slurry coating can be improved, the boiling point of the MNMP is higher, and the distillation separation and the reutilization of a mixed solvent are more favorably realized; more importantly, the MNMP is used for replacing NMP, the carbon emission reduction of 1.95 tons per ton can be realized, the low-carbon environment-friendly significance is outstanding, the target industrial characteristics of double carbon are completely met, and the preparation of the green oily PVDF coating membrane by using the MNMP as a green solvent capable of replacing NMP and acetone is of great significance.
The raw materials used in the following examples of the present invention are commercially available products, polyvinylidene fluoride PVDF from eastern guan kadaler plastics materials ltd, polyvinylidene fluoride-hexafluoropropylene copolymer from eastern guan kadaler plastics materials ltd, and carboxymethyl cellulose from alatin reagents ltd; the dispersant polyvinylpyrrolidone K30, the thickener carboxymethyl cellulose and the alumina are purchased from national drug group chemical agents, Inc., and the basal membrane is purchased from Shenzhen condenser electronics, Inc.;
the specific preparation method of the MNMP comprises the following steps: using a 10L high-temperature high-pressure mechanical stirring reaction kettle, firstly putting 2.172kg of methyl levulinate into the reaction kettle for stirring, then adding 1.771kg of 28 wt% methylamine solution into the reaction kettle for continuous stirring, and finally quickly adding 1.502kg of 49 wt% formic acid aqueous solution into the reaction kettle for continuous stirring; closing the reaction kettle, heating to 160 ℃, and carrying out heat preservation reaction for 5 hours; cooling after the reaction is finished, and collecting reaction liquid; performing rotary evaporation on the reaction liquid at 60 ℃ to remove water, and concentrating to obtain mixed concentrated solution of ML (methyl levulinate) and pyrrolidone; distilling at 100 ℃ under reduced pressure to remove the incompletely reacted methyl levulinate raw material to obtain a crude pyrrolidone concentrated solution; and distilling at 120-130 ℃ under reduced pressure to obtain the pure 1, 5-dimethyl-2-pyrrolidone.
Example 1
2kg of polyvinylidene fluoride polymer and 0.5kg of polyvinylidene fluoride-hexafluoropropylene copolymer were added to 20kg of MNMP green solvent under the following conditions: stirring at 70 ℃ and 100 rmp; adding 0.06kg of binder carboxymethyl cellulose, and stirring for 1 hour to obtain PVDF slurry;
circulating the prepared PVDF slurry into a material box, and performing roller coating on a base film, wherein the process parameters are as follows: the coating tension is 20N, the unreeling tension is 5N, the reeling tension is 17N, the reeling tension is 5N, the feeding speed is 300rpm/min, the gravure speed ratio is 0.9, and the coating speed is 30 m/min; the coated diaphragm enters an extraction workshop; extracting the MNMP green solvent cleanly by eight-stage extraction with water as an extracting agent; and setting the temperature of a drying oven to 65 ℃ for drying and shaping to obtain the green and ultrathin oily PVDF coating diaphragm.
Example 2
Adding 3kg of polyvinylidene fluoride polymer and 1kg of polyvinylidene fluoride-hexafluoropropylene copolymer into 50kg of MNMP green solvent, and setting the conditions as follows: stirring at the water bath temperature of 90 ℃ and the stirring speed of 200 rmp; adding 0.06kg of binder carboxymethyl cellulose, and stirring for 1 hour to obtain PVDF slurry;
circulating the prepared PVDF slurry into a material box, and performing roller coating on a base film, wherein the process parameters are as follows: the coating tension is 20N, the unreeling tension is 5N, the reeling tension is 17N, the reeling tension is 5N, the feeding speed is 300rpm/min, the gravure speed ratio is 0.9, and the coating speed is 20 m/min; the coated diaphragm enters an extraction workshop; extracting the MNMP green solvent cleanly by eight-stage extraction with water as an extracting agent; and setting the temperature of a drying oven to 65 ℃ for drying and shaping to obtain the green and ultrathin oily PVDF coating diaphragm.
Example 3
Adding 4kg of polyvinylidene fluoride polymer and 1.5kg of polyvinylidene fluoride-hexafluoropropylene copolymer into 60kg of MNMP green solvent, and setting the conditions as follows: the water bath temperature is 90 ℃, the stirring speed is 200rmp/min, and stirring is carried out; adding 0.12kg of binder carboxymethyl cellulose, and stirring for 1 hour to obtain PVDF slurry;
the prepared PVDF slurry is circulated into a material box, and the base film is roll-coated, wherein the technological parameters are as follows: the coating tension is 20N, the unreeling tension is 5N, the reeling tension is 17N, the reeling tension is 5N, the feeding speed is 300rpm/min, the gravure speed ratio is 0.9, and the coating speed is 20 m/min; the coated diaphragm enters an extraction workshop; extracting the MNMP green solvent cleanly by eight-stage extraction with water as an extracting agent; and setting the temperature of a drying oven to be 60 ℃, drying and shaping to obtain the green and ultrathin oily PVDF coating diaphragm.
Example 4
Adding 5kg of polyvinylidene fluoride polymer and 2kg of polyvinylidene fluoride-hexafluoropropylene copolymer into 50kg of MNMP green solvent, and setting the conditions as follows: the water bath temperature is 100 ℃, the stirring speed is 400rmp/min, and stirring is carried out; adding 0.14kg of binder carboxymethyl cellulose, and stirring for 1 hour to obtain PVDF slurry;
circulating the prepared PVDF slurry into a material box, and performing roller coating on a base film, wherein the process parameters are as follows: the coating tension is 20N, the unreeling tension is 5N, the reeling tension is 17N, the reeling tension is 5N, the feeding speed is 300rpm/min, the gravure speed ratio is 1, and the coating speed is 30 m/min; the coated diaphragm enters an extraction workshop; extracting the MNMP green solvent cleanly by eight-stage extraction with water as an extracting agent; and setting the temperature of a drying oven to 65 ℃ for drying and shaping to obtain the green and ultrathin oily PVDF coating diaphragm.
Comparative example 1 Using NMP as solvent
Adding 2kg of polyvinylidene fluoride polymer and 3kg of polyvinylidene fluoride-hexafluoropropylene copolymer into 50kg of N-methyl pyrrolidone, and setting the conditions as follows: the temperature of the water bath is 60 ℃, the stirring speed is 400rmp/min, and stirring is carried out; adding 0.08kg of binder carboxymethyl cellulose, and stirring for 1 hour to obtain PVDF slurry;
the prepared PVDF slurry is circulated into a material box, and the base film is roll-coated, wherein the process parameters are as follows: the coating tension is 20N, the unreeling tension is 5N, the reeling tension is 17N, the reeling tension is 5N, the feeding speed is 300rpm/min, the gravure speed ratio is 1, and the coating speed is 30 m/min; the coated diaphragm enters an extraction workshop; extracting N-methyl pyrrolidone completely by eight-stage extraction with water as an extractant; and setting the temperature of a drying oven to 70 ℃ for drying and shaping to obtain the green and ultrathin oily PVDF coating diaphragm.
Comparative example 2 Using Water as solvent
Adding 2kg of polyvinylidene fluoride polymer and 3kg of polyvinylidene fluoride-hexafluoropropylene copolymer into 50kg of deionized water, and stirring for 30 minutes at a stirring speed of 400 rmp/min; 0.08kg of binder carboxymethyl cellulose and 0.5kg of surfactant polyethylene glycol (purchased from national pharmaceutical group chemical agents Co., Ltd.) were added thereto and stirred for 1 hour to obtain PVDF slurry;
circulating the prepared PVDF slurry into a material box, and performing roller coating on a base film, wherein the process parameters are as follows: the coating tension is 20N, the unreeling tension is 5N, the reeling tension is 17N, the reeling tension is 5N, the feeding speed is 300rpm/min, the gravure speed ratio is 1, and the coating speed is 30 m/min; the coated diaphragm enters an extraction workshop; and setting the temperature of a drying oven to 70 ℃ for drying and shaping to obtain the green and ultrathin oily PVDF coating diaphragm.
Example 5 addition of alumina
Adding 2kg of polyvinylidene fluoride polymer and 4kg of polyvinylidene fluoride-hexafluoropropylene copolymer into 25kg of MNMP green solvent, and setting the conditions as follows: the water bath temperature is 100 ℃, the stirring speed is 400rmp/min, and stirring is carried out; adding 0.05kg of binder carboxymethyl cellulose, 0.05kg of dispersant, 0.5kg of thickener and 3kg of alumina, and stirring for 1 hour to obtain PVDF slurry;
the prepared PVDF slurry is circulated into a material box, and the base film is roll-coated, wherein the technological parameters are as follows: the coating tension is 20N, the unreeling tension is 5N, the reeling tension is 17N, the reeling tension is 5N, the feeding speed is 300rpm/min, the gravure speed ratio is 1, and the coating speed is 30 m/min; the coated diaphragm enters an extraction workshop; extracting the MNMP green solvent cleanly by eight-stage extraction with water as an extracting agent; and setting the temperature of a drying oven to 70 ℃ for drying and shaping to obtain the green and ultrathin oily PVDF coating diaphragm.
Example 6
10g of polyvinylpyrrolidone is added into 500mL of 5mol/L potassium hydroxide aqueous solution to be dissolved; adding 200g of polyvinylidene fluoride polymer, setting the temperature to 80 ℃ and reacting for 24 hours to obtain defluorinated polyvinylidene fluoride for later use;
deoxidizing water in the reaction kettle in a nitrogen atmosphere, adding 40 parts by weight of carboxymethyl cellulose, and stirring for dissolving; adding 15 parts of butyl acrylate, 22 parts of ethoxylated pentaerythritol tetraacrylate and 8 parts of N-methyl (methyl) acrylamide in sequence; adding 8 parts of acrylic acid and 3 parts of ammonium persulfate, reacting for 5 hours at the set temperature of 80 ℃, neutralizing, washing, filtering and drying to obtain a binder for later use;
dispersing 2kg of polyvinylidene fluoride polymer and 0.1kg of defluorinated polyvinylidene fluoride in 20kg of MNMP green solvent, homogenizing, drying, and placing at 120 ℃ for heat treatment for 3 hours to obtain the polyvinylidene fluoride polymer with beta crystalline phase;
adding the prepared polyvinylidene fluoride polymer with beta crystalline phase and 4kg of polyvinylidene fluoride-hexafluoropropylene copolymer into 30kg of MNMP green solvent for dissolving; adding 0.08kg of the prepared binder, 0.05kg of dispersant, 0.5kg of thickener and 3kg of alumina, and stirring for 1 hour to obtain PVDF slurry;
circulating the prepared PVDF slurry into a material box, and performing roller coating on a base film, wherein the process parameters are as follows: the coating tension is 30N, the unreeling tension is 8N, the reeling tension is 25N, the reeling tension is 7N, the feeding speed is 400rpm/min, the gravure speed ratio is 1.2, and the coating speed is 10 m/min; the coated diaphragm enters an extraction workshop; extracting the MNMP green solvent cleanly by eight-stage extraction with water as an extracting agent; and setting the temperature of a drying oven to 70 ℃ for drying and shaping to obtain the green and ultrathin oily PVDF coating diaphragm.
Example 7 defluorinated PVDF was not added
Deoxidizing water in the reaction kettle in a nitrogen atmosphere, adding 50 parts by weight of carboxymethyl cellulose, and stirring for dissolving; sequentially adding 20 parts of butyl acrylate, 28 parts of ethoxylated pentaerythritol tetraacrylate and 10 parts of N-methyl (methyl) acrylamide; adding 8 parts of acrylic acid and 3 parts of ammonium persulfate, reacting for 4 hours at the set temperature of 80 ℃, neutralizing, washing, filtering and drying to obtain a binder for later use;
adding 2kg of polyvinylidene fluoride polymer and 4kg of polyvinylidene fluoride-hexafluoropropylene copolymer into 30kg of MNMP green solvent, and setting the conditions as follows: the water bath temperature is 100 ℃, the stirring speed is 500rmp/min, and stirring is carried out; adding 0.08kg of the prepared binder, 0.05kg of dispersant, 0.5kg of thickener and 3kg of alumina, and stirring for 1 hour to obtain PVDF slurry;
circulating the prepared PVDF slurry into a material box, and performing roller coating on a base film, wherein the process parameters are as follows: the coating tension is 30N, the unreeling tension is 8N, the reeling tension is 25N, the reeling tension is 7N, the feeding speed is 400rpm/min, the gravure speed ratio is 1.2, and the coating speed is 10 m/min; the coated diaphragm enters an extraction workshop; extracting the MNMP green solvent cleanly by eight-stage extraction with water as an extracting agent; and setting the temperature of a drying oven to 70 ℃ for drying and shaping to obtain the green and ultrathin oily PVDF coating diaphragm.
Example 8 Binder is carboxymethyl cellulose
10g of polyvinylpyrrolidone is added into 500mL of 5mol/L potassium hydroxide aqueous solution to be dissolved; adding 200g of polyvinylidene fluoride polymer, setting the temperature to 80 ℃ and reacting for 12 hours to obtain defluorinated polyvinylidene fluoride for later use;
dispersing 2kg of polyvinylidene fluoride polymer and 0.1kg of defluorinated polyvinylidene fluoride in 20kg of MNMP green solvent, homogenizing, drying, and performing heat treatment at 120 ℃ for 2 hours to obtain the polyvinylidene fluoride polymer with a beta crystalline phase;
adding the prepared polyvinylidene fluoride polymer with beta crystalline phase and 4kg of polyvinylidene fluoride-hexafluoropropylene copolymer into 30kg of MNMP green solvent for dissolving; adding 0.08kg of binder carboxymethyl cellulose, 0.05kg of dispersing agent, 0.5kg of thickening agent and 3kg of alumina, and stirring for 1 hour to obtain PVDF slurry;
circulating the prepared PVDF slurry into a material box, and performing roller coating on the base film, wherein the process parameters are as follows: the coating tension is 30N, the unreeling tension is 8N, the reeling tension is 25N, the reeling tension is 7N, the feeding speed is 400rpm/min, the gravure speed ratio is 1.2, and the coating speed is 10 m/min; the coated diaphragm enters an extraction workshop; extracting the MNMP green solvent cleanly by eight-stage extraction with water as an extracting agent; and setting the temperature of a drying oven to 70 ℃ for drying and shaping to obtain the green and ultrathin oily PVDF coated membrane.
Performance detection
The separators prepared in the examples of the present invention and comparative examples were subjected to basic performance tests including: solid content, coating layer thickness, hot press strength, air permeability, peel strength, MD tensile strength, TD tensile strength, MD shrinkage% and TD shrinkage%; and the oily PVDF-coated membranes prepared in examples 5 to 8 were subjected to a liquid absorption test; the test is carried out according to the standard GB/T36363-2018 polyolefin diaphragm for the lithium ion battery.
The detection result is as follows:
from the comparison of the test data of examples 1 to 4 with comparative examples 1 to 2, it can be seen that: the oily PVDF-coated separator prepared in the example has a thinner coating layer and a larger hot-press peeling, indicating that the use of MNMP green solvent not only reduces pollution, but also reduces coating thickness, has a higher energy density, and has potential for developing ultra-thin batteries; meanwhile, the performance of the diaphragm prepared in the embodiment is equivalent to that of the diaphragm prepared in the embodiment when an NMP solvent is used, and the diaphragm has stronger peel strength. From the test data of example 5, it can be seen that: the PVDF coating added with the alumina particles has better hot-pressing stripping and other properties, which shows that the MNMP solvent has good dispersibility and stability to the alumina particles. From the test data of examples 6 to 7, it can be seen that: the peel strength is increased, the liquid absorption rate is enhanced and can reach 262 percent, the reasons are as follows: the defluorinated polyvinyl chloride can promote the change of the crystalline phase of the polyvinylidene fluoride, enhance the polarity of the polyvinylidene fluoride polymer and promote the absorption of electrolyte liquid, thereby enhancing the ionic conductivity and the energy density of the battery of the oily PVDF coating diaphragm; in addition, the copolymerized binder improves the binding strength, and the molecular chain of the binder has more polar functional groups in branches of ethoxylated pentaerythritol tetraacrylate and the like, so that the absorption of electrolyte is increased, and the ionic conductivity of the diaphragm is enhanced.
The invention uses the biological-based green solvent MNMP, reduces pollution and toxicity, protects the health of personnel and successfully replaces the NMP solvent; and the thickness of the coating prepared by adjusting the solid content and the technological parameters of the slurry is thinner, thereby being beneficial to improving the energy density of the battery and promoting the development of the ultrathin battery. The invention utilizes the defluorinated polyvinylidene fluoride to prepare the polyvinylidene fluoride polymer with beta crystalline phase, thereby improving the ionic conductivity of the diaphragm and the energy density of the battery. The invention uses the adhesive copolymerized by a plurality of polymers, thereby effectively improving the adhesion performance and increasing the ionic conductivity.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
While the invention has been described and illustrated with reference to specific embodiments thereof, such description and illustration are not intended to limit the invention. It will be clearly understood by those skilled in the art that various changes in form and details may be made therein without departing from the true spirit and scope of the invention as defined by the appended claims, to adapt a particular situation, material, composition of matter, substance, method or process to the objective, spirit and scope of this application. All such modifications are intended to be within the scope of the claims appended hereto. Although the methods disclosed herein have been described with reference to particular operations performed in a particular order, it should be understood that these operations may be combined, sub-divided, or reordered to form equivalent methods without departing from the teachings of the present disclosure. Accordingly, unless specifically indicated herein, the order and grouping of the operations is not a limitation of the present application.
Claims (10)
1. A green-type oily PVDF separator, comprising:
a base film;
a PVDF coating layer disposed on a surface of the base film;
the PVDF coating layer is prepared from a raw material containing 1, 5-dimethyl-2-pyrrolidone.
2. The green oily PVDF membrane as claimed in claim 1, wherein the PVDF coating layer is prepared from raw materials in parts by weight:
2-5 parts of a polyvinylidene fluoride polymer having a beta crystalline phase;
0.5-4 parts of polyvinylidene fluoride-hexafluoropropylene copolymer;
20-60 parts of MNMP;
0.06-0.14 part of binder.
3. The green oily PVDF separator film according to claim 2, wherein the polyvinylidene fluoride polymer having a β crystal phase is prepared from raw materials comprising:
polyvinylidene fluoride polymer, defluorinated polyvinylidene fluoride, and MNMP.
4. The green oily PVDF membrane as claimed in claim 3, wherein the defluorinated PVDF is prepared from the following raw materials:
polyvinylpyrrolidone, potassium hydroxide, and polyvinylidene fluoride polymer.
5. The green oily PVDF membrane as claimed in claim 2, wherein the binder is prepared from raw materials comprising:
carboxymethyl cellulose, butyl acrylate, ethoxylated pentaerythritol tetraacrylate, N-methyl (meth) acrylamide, acrylic acid, and ammonium persulfate.
6. The green oily PVDF membrane as claimed in claim 2, wherein the raw material for preparing the PVDF coating layer further comprises:
one or more of a dispersant, a thickener and ceramic particles.
7. A method for preparing the green type oily PVDF separator as claimed in claim 1, comprising:
and coating the PVDF coating layer preparation raw material on the surface of the base film, and then extracting, drying and shaping to obtain the green oily PVDF membrane.
8. The method of claim 7, wherein the method of coating is roll coating;
the coating tension in the coating process is 20-30N; the unwinding tension is 5-8N; the retraction tension is 17-25N; the winding tension is 5-7N.
9. A battery separator, comprising: the green type oily PVDF membrane as claimed in claim 1.
10. A battery, comprising: the battery separator of claim 9.
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| CN109103397A (en) * | 2018-09-28 | 2018-12-28 | 河南福森新能源科技有限公司 | A kind of preparation method of lithium ion battery ceramic coating membrane |
| KR20210052010A (en) * | 2019-10-31 | 2021-05-10 | 주식회사 엘지화학 | A separator for an electrochemical device and an electrochemical device comprising the same |
| CN113540692A (en) * | 2021-07-12 | 2021-10-22 | 江苏厚生新能源科技有限公司 | Environment-friendly oily PVDF (polyvinylidene fluoride) coated diaphragm and preparation method thereof |
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| CN109103397A (en) * | 2018-09-28 | 2018-12-28 | 河南福森新能源科技有限公司 | A kind of preparation method of lithium ion battery ceramic coating membrane |
| KR20210052010A (en) * | 2019-10-31 | 2021-05-10 | 주식회사 엘지화학 | A separator for an electrochemical device and an electrochemical device comprising the same |
| CN113540692A (en) * | 2021-07-12 | 2021-10-22 | 江苏厚生新能源科技有限公司 | Environment-friendly oily PVDF (polyvinylidene fluoride) coated diaphragm and preparation method thereof |
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Application publication date: 20220517 |