CN117878532A - Coating diaphragm and preparation method thereof - Google Patents
Coating diaphragm and preparation method thereof Download PDFInfo
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- CN117878532A CN117878532A CN202311874072.4A CN202311874072A CN117878532A CN 117878532 A CN117878532 A CN 117878532A CN 202311874072 A CN202311874072 A CN 202311874072A CN 117878532 A CN117878532 A CN 117878532A
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- elastomer
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- base film
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- 238000000576 coating method Methods 0.000 title claims abstract description 62
- 239000011248 coating agent Substances 0.000 title claims abstract description 59
- 238000002360 preparation method Methods 0.000 title description 19
- 239000013013 elastic material Substances 0.000 claims abstract description 37
- 239000002121 nanofiber Substances 0.000 claims abstract description 28
- 229920001971 elastomer Polymers 0.000 claims description 70
- 239000000806 elastomer Substances 0.000 claims description 70
- 239000002002 slurry Substances 0.000 claims description 32
- 239000006188 syrup Substances 0.000 claims description 27
- 235000020357 syrup Nutrition 0.000 claims description 27
- 239000007787 solid Substances 0.000 claims description 19
- 239000000835 fiber Substances 0.000 claims description 18
- 239000004743 Polypropylene Substances 0.000 claims description 17
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 claims description 9
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 9
- -1 polypropylene Polymers 0.000 claims description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 8
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 8
- 238000000034 method Methods 0.000 claims description 8
- 239000002904 solvent Substances 0.000 claims description 7
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 claims description 6
- 239000004698 Polyethylene Substances 0.000 claims description 6
- 229920002678 cellulose Polymers 0.000 claims description 5
- 239000001913 cellulose Substances 0.000 claims description 5
- 238000001035 drying Methods 0.000 claims description 5
- 229920001155 polypropylene Polymers 0.000 claims description 5
- 229920003048 styrene butadiene rubber Polymers 0.000 claims description 5
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims description 4
- 229920003235 aromatic polyamide Polymers 0.000 claims description 4
- 239000005038 ethylene vinyl acetate Substances 0.000 claims description 4
- 239000002159 nanocrystal Substances 0.000 claims description 4
- 229920001200 poly(ethylene-vinyl acetate) Polymers 0.000 claims description 4
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 3
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 3
- 239000004677 Nylon Substances 0.000 claims description 3
- 239000004433 Thermoplastic polyurethane Substances 0.000 claims description 3
- 229910001593 boehmite Inorganic materials 0.000 claims description 3
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 claims description 3
- 229920001778 nylon Polymers 0.000 claims description 3
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 3
- 229920000728 polyester Polymers 0.000 claims description 3
- 229920000573 polyethylene Polymers 0.000 claims description 3
- 229920000468 styrene butadiene styrene block copolymer Polymers 0.000 claims description 3
- 229920002803 thermoplastic polyurethane Polymers 0.000 claims description 3
- 229920002943 EPDM rubber Polymers 0.000 claims description 2
- 239000004642 Polyimide Substances 0.000 claims description 2
- 239000004760 aramid Substances 0.000 claims description 2
- 239000002134 carbon nanofiber Substances 0.000 claims description 2
- 239000000919 ceramic Substances 0.000 claims description 2
- 239000002131 composite material Substances 0.000 claims description 2
- 239000012467 final product Substances 0.000 claims description 2
- 239000003365 glass fiber Substances 0.000 claims description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical class C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 2
- 239000003208 petroleum Substances 0.000 claims description 2
- 229920001721 polyimide Polymers 0.000 claims description 2
- 229920000346 polystyrene-polyisoprene block-polystyrene Polymers 0.000 claims description 2
- 229920005604 random copolymer Polymers 0.000 claims description 2
- 229920002725 thermoplastic elastomer Polymers 0.000 claims description 2
- 238000005520 cutting process Methods 0.000 abstract description 3
- 238000011076 safety test Methods 0.000 abstract description 3
- 238000004146 energy storage Methods 0.000 abstract description 2
- 238000004804 winding Methods 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 16
- 238000003756 stirring Methods 0.000 description 14
- 239000007788 liquid Substances 0.000 description 13
- 239000000463 material Substances 0.000 description 12
- 238000010521 absorption reaction Methods 0.000 description 10
- 239000000839 emulsion Substances 0.000 description 8
- 239000012528 membrane Substances 0.000 description 8
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 6
- 238000001816 cooling Methods 0.000 description 6
- 229910001416 lithium ion Inorganic materials 0.000 description 6
- 239000012046 mixed solvent Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 230000000903 blocking effect Effects 0.000 description 4
- 239000011148 porous material Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 238000007790 scraping Methods 0.000 description 3
- 238000009423 ventilation Methods 0.000 description 3
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 2
- KAKZBPTYRLMSJV-UHFFFAOYSA-N Butadiene Chemical compound C=CC=C KAKZBPTYRLMSJV-UHFFFAOYSA-N 0.000 description 2
- RRHGJUQNOFWUDK-UHFFFAOYSA-N Isoprene Chemical compound CC(=C)C=C RRHGJUQNOFWUDK-UHFFFAOYSA-N 0.000 description 2
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 description 2
- 239000013536 elastomeric material Substances 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000003014 reinforcing effect Effects 0.000 description 2
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical compound C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 239000004721 Polyphenylene oxide Substances 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000000280 densification Methods 0.000 description 1
- 150000001993 dienes Chemical class 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 239000007888 film coating Substances 0.000 description 1
- 238000009501 film coating Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000007756 gravure coating Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000012948 isocyanate Substances 0.000 description 1
- 150000002513 isocyanates Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920000570 polyether Polymers 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 150000005846 sugar alcohols Polymers 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- 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
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
- H01M50/494—Tensile strength
-
- 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)
- Engineering & Computer Science (AREA)
- General Chemical & Material Sciences (AREA)
- Electrochemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Nanotechnology (AREA)
- Composite Materials (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- General Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Cell Separators (AREA)
Abstract
The invention discloses a coating diaphragm which comprises a base film layer, wherein an elastic material layer is coated on the base film layer, and nanofibers are mixed in the elastic material layer. The coating diaphragm has higher strength and toughness, and can prevent the diaphragm from being transversely torn, thereby solving the problems that the diaphragm has higher short circuit rate, winding, cutting and tearing, heavy impact and other safety tests are difficult to pass in battery application, and the like, and the power-assisted thinned diaphragm is applied to power and energy storage batteries in a large scale.
Description
Technical Field
The invention belongs to the technical field of battery diaphragms, and particularly relates to a coating diaphragm and a preparation method thereof.
Background
The lithium ion battery has high energy density, long cycle life, small self-discharge, good safety performance and fast charge and discharge rate, so the lithium ion battery is accepted by the application market and develops rapidly. The wet PE diaphragm and the dry PP diaphragm are diaphragm products for lithium ion batteries with highest maturity and cost performance at present, wherein the wet diaphragm mainly uses PE as a raw material, the dry diaphragm mainly uses PP as a raw material, but with the increasing performance requirements of the market on the capacity of the lithium ion batteries, such as energy density, cycle life, rapid charge and discharge and the like, the PE or PP diaphragm simply prepared has a certain performance short plate, and cannot meet the application requirements.
At present, in the preparation of a dry-method diaphragm, the transverse strength and toughness of the diaphragm are mainly improved through fine adjustment of a process heat treatment and a stretching process, but the overall effect is not obvious, so that the problems that the short circuit rate is high, safety tests such as cutting tearing, heavy impact and the like are difficult to pass when the dry-method thinned diaphragm is applied to a battery are caused.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the invention provides the coating diaphragm and the preparation method thereof, the coating diaphragm has higher strength and toughness, and can prevent the diaphragm from being transversely torn, thereby solving the problems that the diaphragm has higher short circuit rate, winding, cutting and tearing, heavy impact and other safety tests are difficult to pass in battery application, and the like, and the power-assisted thinned diaphragm is applied to power and energy storage batteries in a large scale.
The technical aim of the invention is realized by the following technical scheme:
a coated membrane comprising a base membrane layer having a layer of elastomeric material coated thereon, the elastomeric material layer having nanofibers intermixed therein.
Preferably, the elastic material layer is a network porous structure with inner sparse and outer dense.
Preferably, the nanofiber comprises at least one of cellulose nanocrystals, polypropylene fibers, polyethylene fibers, polyacrylonitrile fibers, polyester fibers, carbon nanofibers, meta-aramid nanofibers, para-aramid nanofibers, polyimide fibers, boehmite fibers, ceramic fibers, and glass fibers.
Preferably, the length-diameter ratio L/D of the nanofiber is more than 10, the diameter D is less than 100nm, and the length L is more than 100nm.
Preferably, the base film layer is a PP diaphragm, the thickness of the base film layer is 9-25 mu m, and the porosity of the base film layer is 40% -60%.
Preferably, the thickness of the elastic material layer is 0.5-3 μm.
A method of making a coated separator as described above, comprising the steps of: first on the base filmCoating a layer with solid content TS 1 Elastomer syrup A of (2) 1 Then in the elastomer slurry A 1 Coating a layer with solid content TS 2 Elastomer syrup A of (2) 2 Drying to obtain the final product, wherein TS is less than 1% 1 ≤10％，10％＜TS 2 Less than or equal to 50 percent of the elastomer slurry A 1 And the elastomer slurry A 2 Obtained by dissolving an elastomer in a solvent, said elastomer syrup A 1 And the elastomer slurry A 2 The middle part is uniformly distributed with nano fibers. Wherein the elastomer syrup A 1 The solid content is limited to be 1% < TS 1 Less than or equal to 10 percent, if the elastomer slurry A 1 The solid content of (2) is less than 1%, the slurry is too thin, the coating amount is too small, and a continuous network coating structure cannot be formed; and if the concentration of the slurry is high, the filling amount of the material in the inner hole of the diaphragm is high, and the hole is blocked. Elastomer syrup A 2 The solid content is limited to 10% < TS 2 Less than or equal to 50% of the elastomer syrup A 2 The solid content of (2) is less than 10%, so that the slurry is thinner, the coating amount on the surface of the diaphragm is smaller, and a network coating structure with inner thinning and outer densification cannot be formed; and if the concentration of the slurry is high, the filling amount of the material in the holes on the surface of the diaphragm is high, and the holes are blocked. The addition proportion of the nanofibers is the same, if the addition amount is small, the coating cannot be supported by a certain strength, and if the addition amount of the cellulose is too large, the pores are blocked.
Preferably, the elastomer includes at least one of thermoplastic polyurethane, ethylene-vinyl acetate copolymer, ethylene propylene diene monomer, styrene-butadiene-styrene block copolymer, styrene-butadiene copolymer, styrene-isoprene-styrene block copolymer, ethylene-1-octene random copolymer, polypropylene thermoplastic elastomer, and nylon elastomer. Wherein the elastomer is composed of a soft segment (soft segment) and a rigid segment (hard segment), the soft segment shows flexibility and toughness, and the material is endowed with high elasticity; the hard segments impart stiffness and rigidity to the material, and the hard segments act as physical cross-links after crystallization. The combination of soft segments and hardness imparts high strength and high elasticity to the material. The soft segment can be selected from one or a combination of alcohols or polyalcohols, lower esters (the C atom number is less than or equal to 8), non-conjugated dienes, butadiene, isoprene, polyether or polyester; the hard segment selection can be one or a combination of several of isocyanate, ethylene, propylene, octene, styrene, acrylonitrile and polyamide.
Preferably, the elastomer has an elongation at break of > 100%.
Preferably TS 2 With TS 1 The difference of (2) is more than or equal to 5 percent.
Preferably, the solvent comprises at least one of water, acetone, methanol, ethanol, butanol, petroleum ether, N-methylpyrrolidone, N-dimethylacetamide and ethyl acetate.
Preferably, the solvent further comprises water.
Preferably, the elastomer syrup A is configured 1 The weight ratio of elastomer to nanofiber used was 1: (0.01-0.2).
Preferably, the elastomer syrup A is configured 2 The weight ratio of elastomer to nanofiber used was 1: (0.1-1).
The beneficial effects of the invention are as follows:
(1) The air permeability value of the coating diaphragm is not higher than 250s/100ml, the liquid absorption rate can reach more than 82 percent, and the transverse tensile strength can reach 192kgf/cm 2 The puncture strength can reach 250gf, the puncture strength test perforation is round, the internal resistance of the battery prepared by the coating diaphragm is not higher than 0.33mΩ, the short-circuit rate is not higher than 0.5%, and the multiplying power 3C/0.5C can reach 86%;
(2) The coating diaphragm is composed of the high-elasticity high polymer material and the nano fiber, the nano fiber is taken as a framework to improve the strength of the coating, the high-elasticity material provides flexibility and elasticity, the composite material composed of the high-elasticity material and the nano fiber is like a net filled in the diaphragm pores and covered on the outer surface of the diaphragm, so that the high-elasticity material, the nano fiber and the base material form an integral structure, the anisotropic problem of the diaphragm material can be effectively improved, the integral strength and toughness of the diaphragm are improved, and the transverse tearing problem of the diaphragm is prevented;
(3) According to the preparation method of the coating diaphragm, the elastic material layer with the network porous structure with the inner sparse and the outer dense can be formed on the base film layer by coating the elastic material layer with the low solid content on the base film layer, then coating the elastic material layer with the high solid content, and then drying, so that the obtained coating diaphragm has excellent strength and toughness, and the electrochemical performance of a battery can be effectively improved after the battery is prepared.
Drawings
FIG. 1 is a cross-sectional SEM of a coated separator of example 1 of the invention;
fig. 2 is an SEM image of the elastic material layer of the coated separator of example 2 of the present invention.
Reference numerals:
100. a base film layer; 200. and an elastic material layer.
Detailed Description
The invention will be further illustrated with reference to specific examples.
Example 1:
as shown in fig. 1, the coated membrane comprises a base membrane layer 100, an elastic material layer 200 is coated on the base membrane layer 100, nano fibers are mixed in the elastic material layer 200, and as can be seen from fig. 1 and 2, the elastic material layer 200 is of a network porous structure with inner and outer layers, wherein the base membrane layer 100 is a dry unidirectional stretching PP membrane with a thickness of 12 μm and a porosity of 45%, and the thickness of the elastic material layer 200 is 1 μm.
A method of making a coated separator as described above, comprising the steps of:
s1, preparing elastomer slurry:
(1) preparation of elastomer syrup A 1 : adding 10 parts of ethylene-vinyl acetate copolymer emulsion with 50% of solid content into a mixed solvent composed of 11 parts of ethanol and 89 parts of water, fully dissolving and uniformly stirring at 500rpm for 0.5h; then adding 0.55 part of cellulose nanocrystals with the length-diameter ratio L/D of approximately 70, the diameter D of 6-8nm and the length L of 300-400nm, uniformly dispersing by using ultrasonic, and carrying out ultrasonic power of 800W for 1h; cooling and standing to obtain elastomer slurry A with solid content of about 4.55% 1 ；
(2) Preparation of elastomer syrup A 2 : 10 parts of an ethylene-vinyl acetate copolymer emulsion having a solid content of 50% was added to a mixed solvent composed of 5 parts of methanol and 15 parts of water, and the mixture was sufficiently stirredDissolving and stirring uniformly, wherein the stirring speed is 800rpm, and the stirring time is 1.0h; then adding 3.33 parts of cellulose nanocrystals with the length-diameter ratio L/D of approximately 70, the diameter D of 6-8nm and the length L of 300-400nm, uniformly dispersing by using ultrasonic waves, and carrying out ultrasonic power of 1200W for 1.5 hours; cooling and standing to obtain elastomer slurry A with solid content of about 16.67% 2 ；
S2, coating: the above elastomer slurry was coated in two passes, (1) first coating: the elastomer slurry A is applied by a dip coater 1 Coating the surface of the base film layer 100 at the coating speed of 60m/min, and scraping off redundant liquid on the surface of the base film layer by using a double metering roller; (2) and (3) coating for the second time: the elastomer slurry A is coated by micro gravure coating 2 Coating on elastomer syrup A 1 The surface was coated at a coating speed of 60m/min, and then dried by hot air in an oven at a drying temperature of 70℃for 20s to thereby obtain a coated separator comprising the inner and outer dense elastic material layers 200.
Example 2:
the coating diaphragm comprises a base film layer, wherein an elastic material layer is coated on the base film layer, nano fibers are mixed in the elastic material layer, the elastic material layer is of a network porous structure with inner and outer layers being dense, the base film layer is a dry unidirectional stretching PP diaphragm with the thickness of 12 mu m and the porosity of 45%, and the thickness of the elastic material layer is 0.5 mu m.
A method of making a coated separator as described above, comprising the steps of:
s1, preparing elastomer slurry:
(1) preparation of elastomer syrup A 1 : adding 21.8 parts of styrene-butadiene copolymer emulsion with the solid content of 48% into a mixed solvent consisting of 150 parts of butanone and 850 parts of water, fully dissolving and uniformly stirring at a stirring speed of 400rpm for 0.3h; then adding 0.1 part of polypropylene fiber with the length-diameter ratio L/D of approximately equal to 56, the diameter D of 10-15nm and the length L of 600-800nm, uniformly dispersing by using ultrasonic, and the ultrasonic power is 600W, wherein the ultrasonic time is 0.8h; cooling and standing to obtain elastomer slurry A with solid content of about 1.02% 1 ；
(2) Preparation of elastomer syrup A 2 : will be 23Adding 50% of styrene-butadiene-styrene block copolymer emulsion into a mixed solvent composed of 20 parts of acetone and 68 parts of water, fully dissolving and uniformly stirring at 600rpm for 0.7h; then adding 1 part of polyethylene fiber with the length-diameter ratio L/D approximately equal to 100, the diameter D of 10-12nm and the length L of 1000-1200nm, uniformly dispersing by using ultrasonic, and the ultrasonic power is 1000W, wherein the ultrasonic time is 1.0h; cooling and standing to obtain elastomer slurry A with solid content of about 10.36% 2 ；
S2, coating: the above elastomer slurry was coated in two passes, (1) first coating: the elastomer slurry A is applied by a dip coater 1 Coating the surface of the base film layer at the coating speed of 50m/min, and scraping off redundant liquid on the surface of the base film layer by using a double metering roller; (2) and (3) coating for the second time: the elastomer slurry A is coated by a wire rod 2 Coating on elastomer syrup A 1 The surface was coated at a coating rate of 50m/min, and then dried by hot air in a human oven to remove the solvent at 80℃for 24 seconds, thereby producing a coated separator having an inner-sparse outer-dense elastic material layer.
Example 3:
the coating diaphragm comprises a base film layer, wherein an elastic material layer is coated on the base film layer, nano fibers are mixed in the elastic material layer, the elastic material layer is of a network porous structure with inner and outer layers being dense, the base film layer is a dry unidirectional stretching PP diaphragm with the thickness of 12 mu m and the porosity of 45%, and the thickness of the elastic material layer is 3 mu m.
A method of making a coated separator as described above, comprising the steps of:
s1, preparing elastomer slurry:
(1) preparation of elastomer syrup A 1 : adding 10 parts of thermoplastic polyurethane into a mixed solvent consisting of 80 parts of N-methylpyrrolidone, 5 parts of water and 14 parts of butanol, fully dissolving and uniformly stirring at a stirring speed of 1000rpm, and stirring at 60 ℃ for 2 hours; then adding 1 part of polyacrylonitrile fiber with the length-diameter ratio L/D=40-60, the diameter D is 8-10nm and the length L is 400-600nm, uniformly dispersing by using ultrasonic, and the ultrasonic power is 900W and the ultrasonic time is 1.0h; cooling and standing to obtain the product with solid content of 9.17% elastomer syrup A 1 ；
(2) Preparation of elastomer syrup A 2 : adding 20 parts of nylon elastomer into a mixed solvent consisting of 16 parts of N, N-dimethylacetamide, 2 parts of water and 2 parts of ethyl acetate, fully dissolving and uniformly stirring at a stirring speed of 1200rpm, wherein the stirring temperature is 80 ℃ and the stirring time is 1.5h; then adding 10 parts of boehmite fibers with the length-diameter ratio L/D approximately equal to 15, the diameter D of 40-60nm and the length L of 600-900nm, uniformly dispersing by using ultrasonic, and carrying out ultrasonic power of 1500W for 3.0h; cooling and standing to obtain elastomer slurry A with solid content of 50% 2 ；
S2, coating: the above elastomer slurry was coated in two passes, (1) first coating: the elastomer slurry A is applied by a slit coater 1 Coating the surface of the base film layer at the coating speed of 40m/min, and scraping off redundant liquid on the surface of the base film layer by a metering roller; (2) and (3) coating for the second time: the elastomer slurry A is coated by comma doctor blade 2 Coating on elastomer syrup A 1 The surface was coated at a coating rate of 40m/min, and then dried by hot air in an oven to remove the solvent at a drying temperature of 70℃for 30 seconds, thereby producing a coated separator comprising an inner-sparse outer-dense elastic material layer.
Comparative example 1:
a coated separator was different from example 1 in that: the elastic material layer does not contain nanofibers, and the rest of the components and the preparation method are the same as in example 1.
Comparative example 2:
a coated separator was different from example 1 in that: in step S1, an elastomer syrup A is prepared 1 Elastomer syrup A 2 The styrene-butadiene copolymer emulsion used was changed to a polyacrylic emulsion (non-elastomer material), and the remaining components and the preparation method were the same as those of example 1.
Comparative example 3:
a coated separator was different from example 1 in that: step S1 omits elastomer syrup A 1 The first coating step is omitted in step S2, the thickness of the elastic material layer is 1.0 μm, and the rest components, preparation method and application methodExample 1 is the same.
Comparative example 4:
a coated separator was different from example 1 in that: step S1 omits elastomer syrup A 2 The second coating step was omitted in step S2, the thickness of the elastic material layer was 0.2 μm, and the remaining components and the preparation method were the same as in example 1.
Comparative example 5:
a separator which was the dry uniaxially stretched PP separator of example 1, without any coating process, and had a thickness of 12 μ and a porosity of 45%.
Test example:
coating thickness, air permeability, liquid absorption, tensile strength and puncture strength of 8 groups of diaphragms in examples 1-3 and comparative examples 1-5 were tested respectively, and square aluminum-shell lithium ion batteries were manufactured by using 8 groups of diaphragms in examples 1-3 and comparative examples 1-5, and parameters of the square aluminum-shell lithium ion batteries were as follows: rated capacity: 280Ah; and (3) a positive electrode: liFePO 4 The method comprises the steps of carrying out a first treatment on the surface of the And (3) a negative electrode: graphite; electrolyte solution: EC/emc=3/7 (v/v), 1M LiPF 6 VC 2%; and testing the internal resistance, the short circuit rate and the multiplying power performance of the prepared battery. The test results are shown in Table 1.
Table 1: separator and battery performance test results
As is clear from Table 1, the coated separator of the present invention has a ventilation value of not more than 250s/100ml, a liquid absorption of 82% or more and a transverse tensile strength of 192kgf/cm 2 The puncture strength can reach 250gf, the puncture strength test perforation is round, the internal resistance of the battery prepared by the coating diaphragm is not higher than 0.33mΩ, the short-circuit rate is not higher than 0.5%, and the multiplying power 3C/0.5C can reach 86%.
In the preparation method of the embodiment 1, the coating diaphragm prepared by the method through the optimal formula combination and process has the optimal physicochemical comprehensive performance: the coating is thin, the ventilation value is low, the liquid absorption rate is high, the transverse tensile strength is high, the puncture strength is high, and the puncture hole is circular; the battery prepared from the coated separator prepared in example 1 had the best overall battery performance: the internal resistance of the battery is small, the short circuit rate is low, and the 3C rate performance is good.
As the thickness of the elastic material layer was reduced to 0.5 μm in example 2, the liquid absorption rate of the coated separator was lowered, and the transverse tensile strength and puncture strength were slightly lowered; the battery manufactured from the coated separator of example 2 had an increased short-circuit rate and a deteriorated rate, which was not preferable;
in example 3, as the thickness of the elastic material layer was increased to 3 μm, the transverse tensile strength and puncture strength of the coated separator were increased, and the liquid absorption rate was increased, but since the thickness of the elastic material layer was increased, the hole blocking was increased, and thus the gas permeation value of the coated separator was increased, and the short circuit rate of the battery manufactured from the coated separator of example 3 was decreased, but the rate was deteriorated, and thus, it was not preferable;
compared with the example 1, the comparative example 1 lacks nanofibers in the elastic material layer, the nanofibers serve as a framework of the coating, the transverse tensile strength and the puncture strength of the coating diaphragm obtained after the nanofibers are absent are obviously reduced, the liquid absorption rate is obviously reduced, and the puncture hole is torn; the short-circuit rate of the battery manufactured by the coated separator of comparative example 1 was significantly increased, and the rate was deteriorated;
compared with the comparative example 2, when the styrene-butadiene copolymer emulsion is changed into the polyacrylic emulsion (non-elastomer material), the pore-forming property of the coating is poor, so that the pore blocking is obvious, the ventilation value of the prepared coating diaphragm is obviously increased, the transverse tensile strength, the puncture strength and the liquid absorption rate are reduced to different degrees, and the puncture hole is torn; the short circuit rate of the battery fabricated from the coated separator of comparative example 2 was significantly increased, the fold difference;
comparative example 3 compared with example 1, the preparation of low-concentration elastomer slurry and the first coating process are omitted, and the blocking holes are reduced, but because the porous network structure with inner sparse and outer dense is not formed in the elastic material layer, the overall toughening and reinforcing effects are poor, and the transverse tensile strength and the puncture strength of the manufactured coating diaphragm are reduced to a certain extent; the battery manufactured by the comparative example 3 separator had a significantly increased short-circuit rate and a poor rate;
compared with the embodiment 1, the preparation of high-concentration elastomer slurry and the secondary coating process are omitted, and the blocking holes are reduced, but because the porous network structure with inner sparse and outer dense is not formed in the elastic material layer, the whole toughening and reinforcing effects are poor, the thickness of the coating is too thin, the liquid absorption rate of the prepared functional coating dry PP diaphragm is reduced, and the transverse tensile strength and the puncture strength are reduced to a certain extent; the battery manufactured by the comparative example 4 separator had a significantly increased short-circuit rate and a poor rate;
comparative example 5 directly adopts a dry unidirectional stretching PP membrane with a thickness of 12 μm and a porosity of 45%, no processing is performed, the transverse tensile strength and puncture strength of the product are the lowest, the tearing of the perforation holes is serious, and the manufactured battery has high short circuit rate, large internal resistance and poor multiple.
The coated separator of example 1 had a > 5% increase in transverse tensile strength, a > 5% increase in puncture strength, a round puncture strength test, no tearing, and a short circuit rate drop of more than 20% after the separator was applied to a battery, compared to the single PP separator of comparative example 5. The liquid absorption rate of the diaphragm is improved by more than 20 percent.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (10)
1. A coated separator, characterized by: the composite film comprises a base film layer, wherein an elastic material layer is coated on the base film layer, and nanofibers are mixed in the elastic material layer.
2. A coated separator according to claim 1, wherein: the elastic material layer is of a network porous structure with the inner part being sparse and the outer part being dense.
3. A coated separator according to claim 1, wherein: the nanofiber comprises at least one of cellulose nanocrystals, polypropylene fibers, polyethylene fibers, polyacrylonitrile fibers, polyester fibers, carbon nanofibers, meta-aramid nanofibers, para-aramid nanofibers, polyimide fibers, boehmite fibers, ceramic fibers and glass fibers.
4. A coated separator according to claim 1, wherein: the base film layer is a PP diaphragm, the thickness of the base film layer is 9-25 mu m, and the porosity of the base film layer is 40% -60%.
5. A coated separator according to claim 1, wherein: the thickness of the elastic material layer is 0.5-3 mu m.
6. A method of making the coated separator of any one of claims 1-5, wherein: the method comprises the following steps: coating a layer with a solid content TS on the base film layer 1 Elastomer syrup A of (2) 1 Then in the elastomer slurry A 1 Coating a layer with solid content TS 2 Elastomer syrup A of (2) 2 Drying to obtain the final product, wherein TS is less than 1% 1 ≤10％，10％＜TS 2 Less than or equal to 50 percent of the elastomer slurry A 1 And the elastomer slurry A 2 Obtained by dissolving an elastomer in a solvent, said elastomer syrup A 1 And the elastomer slurry A 2 The middle part is uniformly distributed with nano fibers.
7. The method of manufacturing according to claim 6, wherein: the elastomer comprises at least one of thermoplastic polyurethane, ethylene-vinyl acetate copolymer, ethylene propylene diene monomer, styrene-butadiene-styrene block copolymer, styrene-butadiene copolymer, styrene-isoprene-styrene block copolymer, ethylene-1-octene random copolymer, polypropylene thermoplastic elastomer and nylon elastomer.
8. The method of manufacturing according to claim 6, wherein: the solvent comprises at least one of water, acetone, methanol, ethanol, butanol, petroleum ether, N-methylpyrrolidone, N-dimethylacetamide and ethyl acetate.
9. The method of manufacturing according to claim 6, wherein: configuring the elastomer syrup A 1 The weight ratio of elastomer to nanofiber used was 1: (0.01-0.2).
10. The method of manufacturing according to claim 6, wherein: configuring the elastomer syrup A 2 The weight ratio of elastomer to nanofiber used was 1: (0.1-1).
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