CN111234278A - Porous polyimide film and preparation method thereof - Google Patents
Porous polyimide film and preparation method thereof Download PDFInfo
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- CN111234278A CN111234278A CN202010169911.2A CN202010169911A CN111234278A CN 111234278 A CN111234278 A CN 111234278A CN 202010169911 A CN202010169911 A CN 202010169911A CN 111234278 A CN111234278 A CN 111234278A
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- polyimide film
- porous polyimide
- imidization
- polyamic acid
- dianhydride
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- 229920001721 polyimide Polymers 0.000 title claims abstract description 49
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 229920005575 poly(amic acid) Polymers 0.000 claims abstract description 41
- WFDIJRYMOXRFFG-UHFFFAOYSA-N Acetic anhydride Chemical compound CC(=O)OC(C)=O WFDIJRYMOXRFFG-UHFFFAOYSA-N 0.000 claims abstract description 39
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 27
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical compound C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 claims abstract description 26
- 239000012528 membrane Substances 0.000 claims abstract description 26
- 238000006243 chemical reaction Methods 0.000 claims abstract description 23
- GTDPSWPPOUPBNX-UHFFFAOYSA-N ac1mqpva Chemical compound CC12C(=O)OC(=O)C1(C)C1(C)C2(C)C(=O)OC1=O GTDPSWPPOUPBNX-UHFFFAOYSA-N 0.000 claims abstract description 22
- 238000005266 casting Methods 0.000 claims abstract description 22
- 150000004985 diamines Chemical class 0.000 claims abstract description 20
- 238000000034 method Methods 0.000 claims abstract description 19
- 230000001112 coagulating effect Effects 0.000 claims abstract description 18
- 239000002798 polar solvent Substances 0.000 claims abstract description 17
- 239000003153 chemical reaction reagent Substances 0.000 claims abstract description 15
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000000758 substrate Substances 0.000 claims abstract description 12
- 238000001035 drying Methods 0.000 claims abstract description 11
- 239000011248 coating agent Substances 0.000 claims abstract description 10
- 238000000576 coating method Methods 0.000 claims abstract description 10
- 238000006068 polycondensation reaction Methods 0.000 claims abstract description 10
- 239000004952 Polyamide Substances 0.000 claims abstract description 9
- 239000002253 acid Substances 0.000 claims abstract description 9
- 229920002647 polyamide Polymers 0.000 claims abstract description 9
- 239000000203 mixture Substances 0.000 claims abstract description 5
- 238000002156 mixing Methods 0.000 claims abstract description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 9
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 8
- WECDUOXQLAIPQW-UHFFFAOYSA-N 4,4'-Methylene bis(2-methylaniline) Chemical group C1=C(N)C(C)=CC(CC=2C=C(C)C(N)=CC=2)=C1 WECDUOXQLAIPQW-UHFFFAOYSA-N 0.000 claims description 6
- VQVIHDPBMFABCQ-UHFFFAOYSA-N 5-(1,3-dioxo-2-benzofuran-5-carbonyl)-2-benzofuran-1,3-dione Chemical group C1=C2C(=O)OC(=O)C2=CC(C(C=2C=C3C(=O)OC(=O)C3=CC=2)=O)=C1 VQVIHDPBMFABCQ-UHFFFAOYSA-N 0.000 claims description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 6
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 claims description 6
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 4
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 4
- 239000002202 Polyethylene glycol Substances 0.000 claims description 4
- 229920001223 polyethylene glycol Polymers 0.000 claims description 4
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 4
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 4
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 4
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 238000007654 immersion Methods 0.000 claims description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 7
- 229910052744 lithium Inorganic materials 0.000 abstract description 7
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 6
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 6
- 239000000243 solution Substances 0.000 description 20
- 239000004642 Polyimide Substances 0.000 description 14
- 239000011521 glass Substances 0.000 description 6
- 239000007788 liquid Substances 0.000 description 5
- 238000000614 phase inversion technique Methods 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- -1 Polyethylene Polymers 0.000 description 3
- 230000003197 catalytic effect Effects 0.000 description 3
- 229920000098 polyolefin Polymers 0.000 description 3
- 239000000376 reactant Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- CBCKQZAAMUWICA-UHFFFAOYSA-N 1,4-phenylenediamine Chemical compound NC1=CC=C(N)C=C1 CBCKQZAAMUWICA-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 150000001412 amines Chemical class 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- IISBACLAFKSPIT-UHFFFAOYSA-N bisphenol A Chemical compound C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 IISBACLAFKSPIT-UHFFFAOYSA-N 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000010907 mechanical stirring Methods 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 230000036632 reaction speed Effects 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- WZCQRUWWHSTZEM-UHFFFAOYSA-N 1,3-phenylenediamine Chemical compound NC1=CC=CC(N)=C1 WZCQRUWWHSTZEM-UHFFFAOYSA-N 0.000 description 1
- VLDPXPPHXDGHEW-UHFFFAOYSA-N 1-chloro-2-dichlorophosphoryloxybenzene Chemical compound ClC1=CC=CC=C1OP(Cl)(Cl)=O VLDPXPPHXDGHEW-UHFFFAOYSA-N 0.000 description 1
- ZBMISJGHVWNWTE-UHFFFAOYSA-N 3-(4-aminophenoxy)aniline Chemical compound C1=CC(N)=CC=C1OC1=CC=CC(N)=C1 ZBMISJGHVWNWTE-UHFFFAOYSA-N 0.000 description 1
- UNIBAJHMJGXVHL-UHFFFAOYSA-N 3-phenylbenzene-1,2,4,5-tetracarboxylic acid Chemical compound OC(=O)C1=CC(C(O)=O)=C(C(O)=O)C(C=2C=CC=CC=2)=C1C(O)=O UNIBAJHMJGXVHL-UHFFFAOYSA-N 0.000 description 1
- 229920000604 Polyethylene Glycol 200 Polymers 0.000 description 1
- 150000008065 acid anhydrides Chemical class 0.000 description 1
- 150000008064 anhydrides Chemical class 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- WKDNYTOXBCRNPV-UHFFFAOYSA-N bpda Chemical compound C1=C2C(=O)OC(=O)C2=CC(C=2C=C3C(=O)OC(C3=CC=2)=O)=C1 WKDNYTOXBCRNPV-UHFFFAOYSA-N 0.000 description 1
- 230000015271 coagulation Effects 0.000 description 1
- 238000005345 coagulation Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000010041 electrostatic spinning Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 239000011256 inorganic filler Substances 0.000 description 1
- 229910003475 inorganic filler Inorganic materials 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 230000037427 ion transport Effects 0.000 description 1
- 229940018564 m-phenylenediamine Drugs 0.000 description 1
- 238000003760 magnetic stirring Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000012876 topography Methods 0.000 description 1
- 238000009423 ventilation Methods 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/26—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a solid phase from a macromolecular composition or article, e.g. leaching out
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2201/00—Foams characterised by the foaming process
- C08J2201/04—Foams characterised by the foaming process characterised by the elimination of a liquid or solid component, e.g. precipitation, leaching out, evaporation
- C08J2201/042—Elimination of an organic solid phase
- C08J2201/0422—Elimination of an organic solid phase containing oxygen atoms, e.g. saccharose
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2205/00—Foams characterised by their properties
- C08J2205/04—Foams characterised by their properties characterised by the foam pores
- C08J2205/044—Micropores, i.e. average diameter being between 0,1 micrometer and 0,1 millimeter
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2379/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen, or carbon only, not provided for in groups C08J2361/00 - C08J2377/00
- C08J2379/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
- C08J2379/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
-
- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- General Chemical & Material Sciences (AREA)
- Electrochemistry (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Macromolecular Compounds Obtained By Forming Nitrogen-Containing Linkages In General (AREA)
Abstract
The invention relates to a porous polyimide film, a preparation method thereof and a lithium ion battery. The preparation method of the porous polyimide film comprises the following steps: performing polycondensation reaction on dianhydride and diamine in a polar solvent, adding a pore-forming agent after the reaction is finished, and uniformly mixing to obtain a polyamide acid membrane casting solution; coating the polyamic acid casting solution on a substrate with a smooth surface, and then immersing the substrate in a coagulating bath for phase conversion reaction to obtain a polyamic acid coagulating film; drying the polyamic acid solidified membrane, and then putting the polyamic acid solidified membrane into steam of an imidization reagent for imidization treatment to obtain a porous polyimide film; wherein the imidization reagent is a mixture of acetic anhydride and pyridine, the steam temperature of the imidization treatment is 70-80 ℃, and the time of the imidization treatment is 4-6 h. The porous polyimide film prepared by the method has smooth and flat surface, no crack, good mechanical property and high porosity, and can improve the safety performance of a lithium battery.
Description
Technical Field
The invention relates to the technical field of lithium ion battery diaphragms, in particular to a porous polyimide film and a preparation method thereof.
Background
In recent years, because of the problems of energy shortage and environmental pollution, lithium batteries have become the research focus of researchers as a safe, efficient and clean energy source. Separators are an important component of lithium batteries, and function to prevent physical contact between the positive and negative electrodes of the battery and to allow free ion transport in the battery. The separator also has an important influence on the safety of the battery. When the battery is not used properly, the inside or the outside of the battery may be overheated, and the battery of the conventional polyolefin separator may be fused when the temperature exceeds 160 ℃, so that the positive and negative electrodes are in contact with each other to cause short circuit, thereby causing ignition or explosion of the battery and posing great threat to the life safety of users. In addition, the separator can affect rate performance, energy density, cycle life, etc. of the battery, and thus the separator is required to have good insulating properties and mechanical strength, as well as excellent chemical stability, thermal stability, porosity, electrolyte absorption rate and retention rate, etc. At present, Polyolefin (PO) microporous membranes such as Polyethylene (PE) and polypropylene (PP) microporous membranes are widely applied to commercial lithium battery membranes, but the membranes have poor thermal stability, low porosity and low absorption rate of electrolyte, have great potential safety hazards and cannot meet the further development requirements of lithium batteries.
Polyimide (PI) is a novel insulating material with good comprehensive performance, has excellent thermal stability and mechanical properties, can be used for a long time at the temperature of more than 300 ℃, and is an ideal battery diaphragm material. The battery diaphragm prepared by using PI can reduce the risk of safety accidents caused by internal overheating of the battery, and has high application value. The existing method for preparing the polyimide battery diaphragm mainly comprises an electrostatic spinning method, a phase inversion method and an inorganic filler removal method. The preparation of the polyimide battery diaphragm by the phase inversion method is mainly divided into two routes, wherein the first route is to synthesize a polyimide solution by using amine and anhydride, and then prepare the polyimide diaphragm by phase inversion; the second method is that polyamide acid is prepared by amine and acid anhydride, then phase inversion is carried out to prepare polyamide acid diaphragm, and then imidization treatment is carried out on the polyamide acid diaphragm to obtain the polyimide diaphragm. Currently, a second phase inversion method is mainly used to prepare polyimide membranes.
However, in the second phase inversion method, the polyamic acid membrane is converted into the polyimide membrane by a heating method, and the polyamic acid is dehydrated and closed-loop-formed into polyimide during the heating process, but the imidization reaction temperature of the method is high, generally above 200 ℃, and the problems of membrane curling deformation, surface cracks and the like are easily caused.
Disclosure of Invention
Therefore, it is necessary to provide a method for preparing a porous polyimide film, which can prepare the porous polyimide film with a smooth and crack-free surface, aiming at the problems of dry cracking and curling deformation in the process of imidizing a polyamic acid film into the polyimide film under a high temperature condition.
A preparation method of a porous polyimide film comprises the following steps:
performing polycondensation reaction on dianhydride and diamine in a polar solvent, adding a pore-forming agent after the reaction is finished, and uniformly mixing to obtain a polyamide acid membrane casting solution;
coating the polyamic acid casting solution on a substrate with a smooth surface, and then immersing the substrate in a coagulating bath for phase conversion reaction to obtain a porous polyamic acid coagulating film;
drying the porous polyamic acid solidified membrane, and then putting the porous polyamic acid solidified membrane into steam of an imidization reagent for imidization treatment to obtain a porous polyimide film;
wherein the imidization reagent is a mixture of acetic anhydride and pyridine, the steam temperature of imidization treatment is 65-85 ℃, and the time of imidization treatment is 4-8 h.
The method comprises the steps of taking dianhydride and diamine as raw materials, carrying out low-temperature polycondensation reaction in a polar solvent, adding a pore-forming agent, uniformly dispersing the pore-forming agent in a mixed system after the polycondensation reaction, defoaming, coating on a substrate, carrying out phase conversion reaction in a coagulating bath, removing the pore-forming agent to obtain a porous polyamic acid solidified film, integrating the advantages of thermal imidization and chemical imidization, and carrying out imidization treatment on the dried polyamic acid solidified film to obtain the porous polyimide film. Under the catalytic action of acetic anhydride and pyridine steam, the imidization reaction temperature is greatly reduced, so that the imidization reaction of polyamic acid can be rapidly carried out under the condition of being far lower than the reaction temperature of the traditional thermal imidization, and the porous polyimide film prepared by the imidization reaction temperature is low and the imidization reaction speed is high, has smooth and flat surface, no crack, good mechanical property and high porosity. In one embodiment, the volume ratio of the acetic anhydride to the pyridine is 1 (0.8-1.2).
In one embodiment, the sum of the mass of the diamine and the dianhydride is 15-28% of the total mass, the mass of the polar solvent is 70-80% of the total mass, and the mass of the pore-forming agent is 2-5% of the total mass based on the total mass of the diamine, the dianhydride, the polar solvent and the pore-forming agent;
wherein the molar ratio of the diamine to the dianhydride is 1 (1.005-1.01); .
Further, the diamine is 3,3 '-dimethyl-4, 4' -diaminodiphenylmethane (DMMDA) and the dianhydride is 3,3 ', 4, 4' -Benzophenone Tetracarboxylic Dianhydride (BTDA).
In one embodiment, the polar solvent is selected from at least one of N-methylpyrrolidone (NMP), N-Dimethylformamide (DMF), and Tetrahydrofuran (THF).
In one embodiment, the pore-forming agent is at least one selected from polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) with molecular weight of 200-400.
In one embodiment, the polyamic acid casting solution is coated to a thickness of 50 μm to 300 μm;
the coagulating bath is selected from at least one of methanol, ethanol, n-butanol and water; the temperature of the coagulating bath is 25-45 ℃, and the immersion time is 30-180 min.
In one embodiment, the temperature of the drying treatment is 25 ℃ +/-3 ℃, and the time of the drying treatment is 50-70 min.
The invention also aims to provide the porous polyimide film prepared by the preparation method.
The porous polyimide film has the advantages of smooth and flat surface, no crack, good mechanical property, high porosity and good ventilation value, can improve the safety performance of the lithium battery, and reduces the transmission resistance of the lithium battery in the diaphragm.
Drawings
FIG. 1 is a photograph of the surface topography of a porous polyimide film of comparative example 1;
Detailed Description
In order that the invention may be more fully understood, a more particular description of the invention will now be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
One embodiment of the present invention provides a method for preparing a porous polyimide film, including the following steps S1 to S4.
S1, preparing polyamic acid casting solution
And (3) carrying out polycondensation reaction on dianhydride and diamine in a polar solvent, adding a pore-forming agent after the reaction is finished, and uniformly mixing to obtain the polyamic acid casting solution.
In one embodiment, the total mass of the diamine, the dianhydride, the polar solvent and the pore-forming agent is used as a reference for preparing the polyamic acid casting solution, the sum of the mass of the diamine and the dianhydride is 15-28% of the total mass, the mass of the polar solvent is 70-80% of the total mass, and the mass of the pore-forming agent is 2-5% of the total mass; wherein the molar ratio of the diamine to the dianhydride is 1 (1.005-1.01).
In one embodiment, the diamine is selected from at least one of 3,3 ' -dimethyl-4, 4 ' -diaminodiphenylmethane, p-phenylenediamine, m-phenylenediamine, 4 ' -diaminodiphenyl ether, 4 ' -diaminobiphenyl, and 3,4 ' -diaminodiphenyl ether p-phenylenediamine; the dianhydride is at least one selected from 3,3 ', 4, 4' -benzophenone tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3 ', 4, 4' -biphenyl tetracarboxylic dianhydride, 2 ', 3, 3' -biphenyl tetracarboxylic dianhydride and bisphenol A type diether dianhydride.
Further, the diamine is 3,3 '-dimethyl-4, 4' -diaminodiphenylmethane, and the dianhydride is 3,3 ', 4, 4' -benzophenone tetracarboxylic dianhydride.
In one embodiment, the polar solvent is selected from at least one of N-methylpyrrolidone, N-dimethylformamide, and tetrahydrofuran.
In one embodiment, the pore-forming agent is at least one selected from polyvinylpyrrolidone and polyethylene glycol with molecular weight of 200-400.
In one embodiment, the polycondensation reaction is a low temperature polycondensation reaction.
Further, the polycondensation reaction is carried out at the temperature of 0-5 ℃ under the protection of inert atmosphere, and the reaction time is 10-12 h.
Specifically, dry 3,3 '-dimethyl-4, 4' -diaminodiphenylmethane (DMMDA) is added into a three-neck flask filled with 70-80 wt% of polar solvent at the temperature of 0-5 ℃ under the atmosphere of nitrogen, mechanical stirring is carried out until the DMMDA is dissolved, then 3,3 ', 4, 4' -Benzophenone Tetracarboxylic Dianhydride (BTDA) is added, mechanical stirring reaction is carried out for 10-12 h, wherein the molar ratio of the DMMDA to the BTDA is 1 (1.005-1.01), the sum of the mass fractions of the DMMDA and the BTDA is 15-28%, 2-5 wt% of pore-forming agent is added into the reactant, stirring is carried out for 3-4 h, the pore-forming agent is uniformly dispersed in the reactant system, and the mixed solution obtained by the reaction is subjected to vacuum standing to obtain the polyamic acid casting solution.
And S2, coating the polyamic acid casting solution on a substrate with a smooth surface, and then immersing the substrate in a coagulating bath for phase inversion reaction to obtain the porous polyamic acid coagulating film.
In this way, the polyamic acid casting solution coated on the substrate with a smooth surface is immersed in the coagulating bath to perform phase conversion film formation, and the pore-forming agent is removed by dissolving the pore-forming agent to form a microporous structure, thereby obtaining a polyamic acid coagulated film having a porous structure.
In one embodiment, the substrate with a smooth surface is a glass plate.
In one embodiment, the polyamic acid film-casting solution is coated to a thickness of 50 μm to 300 μm.
Further, the thickness of the polyamic acid casting solution is 50 μm to 110 μm.
In one embodiment, the polyamic acid film casting solution is applied by blade coating.
Specifically, the polyamic acid casting solution is coated on a glass plate with a doctor blade, and the thickness of the coating is adjusted by controlling the coating gap between the doctor blade and the glass plate, so that the thickness of the obtained film can be adjusted to be within an appropriate range.
Further, the gap between the scraper and the glass plate is 50 to 300 μm, and more preferably 50 to 110 μm.
In one embodiment, the coagulation bath is selected from at least one of methanol, ethanol, n-butanol, and water; the temperature of the coagulating bath is 25-45 ℃, and the time of immersing in the coagulating bath is 30-180 min.
S3, drying the porous polyamic acid solidified membrane, and putting the porous polyamic acid solidified membrane into steam of an imidization reagent for imidization to obtain a polyimide film; wherein the imidization reagent is a mixture of acetic anhydride and pyridine, the steam temperature of imidization treatment is 65-85 ℃, and the time of imidization treatment is 4-8 h.
Under the catalytic action of acetic anhydride and pyridine vapor, the imidization reaction can be promoted, and the imidization reaction temperature can be reduced. Therefore, the imidization reaction can be rapidly carried out at the temperature of 65-85 ℃ to obtain the polyimide film with a porous structure, and the defects of film curling deformation and surface cracks caused by high temperature of the traditional thermal imidization reaction are avoided.
It should be noted that, when the polyamic acid cured film is put into the steam of the imidizing agent for imidization, the polyamic acid cured film is not in contact with the liquid of the imidizing agent, but is completely treated in the steam of the imidizing agent, so that the problem of uneven pore distribution of the film caused by too fast imidization reaction speed in contact with the liquid imidizing agent can be avoided.
Specifically, the polyamic acid cured film may be placed in an imidization reactor to perform imidization. The imidization reactor consists of a heat collection type magnetic stirring oil bath kettle, an opening reactor, a condenser pipe, a thermometer and a liquid seal pipe; the thermometer indicates the temperature of the imidizing agent vapor in the upper portion of the reactor. The lower part of the imidization reactor is filled with liquid imidization reagents of acetic anhydride and pyridine, the imidization reagents are heated to form steam, and an imidization membrane (a polyamide acid solidified membrane) is placed in the steam at the upper part of the imidization reactor without contacting with the liquid imidization reagents at the lower part.
In one embodiment, the drying treatment is carried out at 25 ℃ + -3 ℃ for 50min to 70 min.
In one embodiment, the volume ratio of acetic anhydride to pyridine is 1 (0.8-1.2).
Further, the volume ratio of acetic anhydride to pyridine was 1: 1.
Another embodiment of the present invention provides a porous polyimide film prepared by the above preparation method.
According to the preparation method, diamine and dianhydride are subjected to low-temperature polycondensation reaction in a polar solvent to generate polyamide acid precursor solution, then a pore-forming agent is added, the mixture is uniformly stirred and defoamed to form polyamide acid membrane casting solution, the membrane casting solution is coated on a substrate in a scraping mode and is immersed in a coagulating bath for phase conversion to form a membrane, and after drying, imidization treatment is carried out in steam of an imidization reagent to obtain a porous polyimide membrane; on one hand, the structural diversity and controllability of the polyamic acid film can be realized by adjusting the types and the proportion of diamine, dianhydride, a polar solvent and a pore-forming agent and the temperature and the time of a coagulating bath, on the other hand, the polyamic acid film is placed in the steam of an imidization reagent for imidization treatment, the advantages of thermal imidization and chemical imidization are combined, the imidization treatment temperature is reduced under the catalytic action of acetic anhydride and pyridine, and the imidization can be rapidly carried out under the condition of being far lower than the reaction temperature of the traditional thermal imidization, so that the porous polyimide film with high imidization degree, good consistency, smooth and flat surface, high porosity and good mechanical property is prepared.
In one embodiment, the porous polyimide film has a thickness of 20 to 30 μm, a permeability of 250 to 400s/in 2, and a porosity of 40 to 60%.
In another embodiment of the present invention, a lithium ion battery is provided, which includes a positive plate, a negative plate, and a separator disposed between the positive plate and the negative plate, wherein the separator is the above porous polyimide film.
The porous polyimide film prepared by the method has smooth and flat surface, no crack, high porosity and good air permeability, is particularly suitable for being used as a diaphragm of a lithium ion battery, can improve the safety performance of the lithium ion battery, and reduces the transmission resistance of lithium ions in the diaphragm.
The following are specific examples
Example 1:
step S1: adding 7.69g of dried 3,3 '-dimethyl-4, 4' -diaminodiphenylmethane (DMMDA) into a three-neck flask filled with 78g of solvent at the temperature of 0 ℃ in a nitrogen atmosphere, mechanically stirring until the DMMDA is dissolved, then adding 12.31g of dried 3,3 ', 4, 4' -Benzophenone Tetracarboxylic Dianhydride (BTDA) to continue mechanically stirring and reacting for 12 hours, finally adding 2g of PEG (200) into the reactant to stir for 3 hours, and carrying out vacuum standing and defoaming on the solution obtained by the reaction to obtain the polyamic acid casting solution.
Step S2: and coating the casting solution on the glass plate by using a scraper, and controlling the coating gap between the scraper and the glass plate to be 80 um. The scraped polyamic acid film was immersed in water at 25 ℃ for phase conversion to a solidified film for 120 min.
Step S3: the above-mentioned solidified film was dried in a 25 ℃ drying oven for 1 hour. And then placing the dried membrane into an imidization reactor shown in figure 1 for reaction to obtain the polyimide diaphragm. Wherein the steam temperature of the imidization reaction is controlled to be 75 ℃, the imidization reagent is a mixed reagent of acetic anhydride and pyridine according to the volume ratio of 1:1, and the imidization reaction time is 6 hours. After imidization, a polyimide separator having a porosity of 51% was obtained.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (9)
1. The preparation method of the porous polyimide film is characterized by comprising the following steps:
performing polycondensation reaction on dianhydride and diamine in a polar solvent, adding a pore-forming agent after the reaction is finished, and uniformly mixing to obtain a polyamide acid membrane casting solution; coating the polyamic acid casting solution on a substrate with a smooth surface, and then immersing the substrate in a coagulating bath for phase conversion reaction to obtain a porous polyamic acid coagulating film; drying the porous polyamic acid solidified membrane, and then putting the porous polyamic acid solidified membrane into steam of an imidization reagent for imidization treatment to obtain a porous polyimide film; wherein the imidization reagent is a mixture of acetic anhydride and pyridine, the steam temperature of imidization treatment is 65-85 ℃, and the time of imidization treatment is 4-8 h.
2. The method for preparing a porous polyimide film according to claim 1, wherein the volume ratio of the acetic anhydride to the pyridine is 1 (0.8-1.2).
3. The method for preparing a porous polyimide film according to claim 1, wherein the sum of the mass of the diamine and the dianhydride is 15 to 28% of the total mass, the mass of the polar solvent is 70 to 80% of the total mass, and the mass of the pore-forming agent is 2 to 5% of the total mass, based on the total mass of the diamine, the dianhydride, the polar solvent and the pore-forming agent;
wherein the molar ratio of the diamine to the dianhydride is 1 (1.005-1.01).
4. The method for preparing a porous polyimide film according to claim 3, wherein the diamine is 3,3 '-dimethyl-4, 4' -diaminodiphenylmethane and the dianhydride is 3,3 ', 4, 4' -benzophenone tetracarboxylic dianhydride.
5. The method for preparing a porous polyimide film according to claim 1, wherein the polar solvent is at least one selected from the group consisting of N-methylpyrrolidone, N-dimethylformamide, and tetrahydrofuran.
6. The method for preparing a porous polyimide film according to claim 1, wherein the pore-forming agent is at least one selected from the group consisting of polyvinylpyrrolidone and polyethylene glycol having a molecular weight of 200 to 400.
7. The method for preparing a porous polyimide film according to any one of claims 1 to 6, wherein the polyamic acid film casting solution is coated to a thickness of 50 μm to 300 μm; the coagulating bath is selected from at least one of methanol, ethanol, n-butanol and water; the temperature of the coagulating bath is 25-45 ℃, and the immersion time is 30-180 min.
8. The method for preparing a porous polyimide film according to any one of claims 1 to 6, wherein the temperature of the drying treatment is 25 ℃ ± 3 ℃, and the time of the drying treatment is 50min to 70 min.
9. A porous polyimide film, which is prepared by the preparation method of any one of claims 1 to 8.
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| CN112321886A (en) * | 2020-10-20 | 2021-02-05 | 深圳市华星光电半导体显示技术有限公司 | Preparation method of optical film, optical film and display device |
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