CN114725612B - High-toughness lithium ion battery blending diaphragm and preparation method thereof - Google Patents
High-toughness lithium ion battery blending diaphragm and preparation method thereof Download PDFInfo
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- CN114725612B CN114725612B CN202210426404.1A CN202210426404A CN114725612B CN 114725612 B CN114725612 B CN 114725612B CN 202210426404 A CN202210426404 A CN 202210426404A CN 114725612 B CN114725612 B CN 114725612B
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- polyethylene
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 47
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 47
- 238000002156 mixing Methods 0.000 title claims abstract description 34
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- 239000000463 material Substances 0.000 claims abstract description 52
- -1 polyethylene form Polymers 0.000 claims abstract description 45
- 229920000642 polymer Polymers 0.000 claims abstract description 41
- 238000000034 method Methods 0.000 claims abstract description 28
- 239000004014 plasticizer Substances 0.000 claims abstract description 25
- 238000009998 heat setting Methods 0.000 claims abstract description 19
- 230000008569 process Effects 0.000 claims abstract description 19
- 239000011343 solid material Substances 0.000 claims abstract description 14
- 238000001125 extrusion Methods 0.000 claims abstract description 5
- 238000000605 extraction Methods 0.000 claims abstract description 3
- 239000004698 Polyethylene Substances 0.000 claims description 44
- 229920000573 polyethylene Polymers 0.000 claims description 44
- 239000003921 oil Substances 0.000 claims description 39
- 235000019198 oils Nutrition 0.000 claims description 39
- 239000005038 ethylene vinyl acetate Substances 0.000 claims description 35
- 229920001200 poly(ethylene-vinyl acetate) Polymers 0.000 claims description 35
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 claims description 27
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 25
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 claims description 22
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 21
- 229920001577 copolymer Polymers 0.000 claims description 17
- 238000005266 casting Methods 0.000 claims description 16
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 claims description 15
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 claims description 14
- QGJOPFRUJISHPQ-UHFFFAOYSA-N Carbon disulfide Chemical compound S=C=S QGJOPFRUJISHPQ-UHFFFAOYSA-N 0.000 claims description 12
- 239000002480 mineral oil Substances 0.000 claims description 12
- 235000010446 mineral oil Nutrition 0.000 claims description 12
- 230000001360 synchronised effect Effects 0.000 claims description 12
- 238000009423 ventilation Methods 0.000 claims description 12
- 238000004804 winding Methods 0.000 claims description 12
- 229920001911 maleic anhydride grafted polypropylene Polymers 0.000 claims description 10
- 238000003756 stirring Methods 0.000 claims description 10
- 239000003549 soybean oil Substances 0.000 claims description 9
- 235000012424 soybean oil Nutrition 0.000 claims description 8
- 229920001912 maleic anhydride grafted polyethylene Polymers 0.000 claims description 7
- 229920000468 styrene butadiene styrene block copolymer Polymers 0.000 claims description 7
- 239000003795 chemical substances by application Substances 0.000 claims description 3
- 239000008240 homogeneous mixture Substances 0.000 claims description 3
- 239000008096 xylene Substances 0.000 claims description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 8
- 229910052744 lithium Inorganic materials 0.000 abstract description 8
- 210000001787 dendrite Anatomy 0.000 abstract description 6
- 238000005096 rolling process Methods 0.000 abstract 1
- 239000000203 mixture Substances 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 8
- 238000005303 weighing Methods 0.000 description 7
- 230000009471 action Effects 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- DQXBYHZEEUGOBF-UHFFFAOYSA-N but-3-enoic acid;ethene Chemical compound C=C.OC(=O)CC=C DQXBYHZEEUGOBF-UHFFFAOYSA-N 0.000 description 1
- QGJOPFRUJISHPQ-NJFSPNSNSA-N carbon disulfide-14c Chemical compound S=[14C]=S QGJOPFRUJISHPQ-NJFSPNSNSA-N 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000005469 granulation Methods 0.000 description 1
- 230000003179 granulation Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
Classifications
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- 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
-
- 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
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/417—Polyolefins
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention provides a high-toughness lithium ion battery blending diaphragm and a preparation method thereof, wherein the diaphragm is composed of a solid material with micropores, and the preparation method at least comprises the following steps: pretreatment of toughening polymer; mixing of solid materials in a high speed mixer; the mixed material and the plasticizer are processed by an extrusion process, and then the high-toughness lithium ion battery blending diaphragm is obtained by a stretching process, an extraction process, a heat setting process and a rolling process. The toughening polymer is introduced into the diaphragm system by a blending method, and the toughening polymer and the polyethylene form a homogeneous system by pretreatment, a compatibilizer, strong mechanical force and promotion of a plasticizer. The diaphragm obtained by the invention has high puncture resistance, and the possibility of being punctured by lithium dendrites in the lithium ion battery is small, so that the safety of the lithium ion battery is greatly improved.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a high-toughness lithium ion battery blending diaphragm and a preparation method thereof.
Background
With the rapid development of new energy industries, the demand of people for high-performance energy storage equipment is increasingly rising. The lithium ion battery has the advantages of small volume, high energy density, long cycle life, no memory effect, high average output voltage, small self-discharge and the like, and becomes the most widely applied secondary battery at present.
The main components of the lithium ion battery comprise a positive electrode, a negative electrode, electrolyte and a diaphragm, wherein the diaphragm plays the roles of separating the positive electrode from the negative electrode so as to prevent the battery from being short-circuited, providing a lithium ion transmission channel and storing the electrolyte. However, in the use process of the lithium ion battery, lithium dendrites are inevitably generated due to uneven current, uneven electrode surfaces and the like, and if the generated lithium dendrites pierce a diaphragm, the battery is short-circuited, the temperature of the battery is rapidly increased, and safety accidents such as fire and explosion are easily caused. Therefore, developing a high-toughness lithium ion battery separator, improving the puncture resistance of the separator is important for improving the battery safety.
In view of the above, there is a need for improvements in lithium battery separators in the prior art to address the above-described problems.
Disclosure of Invention
The invention aims to provide a high-toughness lithium ion battery blending diaphragm, solve the problem of low puncture strength of the diaphragm, and avoid the problem of battery short circuit caused by puncture of lithium dendrites.
In order to achieve the above object, the present invention provides a high-toughness lithium ion battery blend membrane, which is composed of a solid material with micropores, wherein the solid material is a homogeneous mixture of polyethylene, toughening polymer and compatibilizer.
In some embodiments, the solid material comprises the following components in proportion: polyethylene: 74% -95% of toughening polymer: 4% -25%, compatibilizer: 0.4 to 2.5 percent.
In some embodiments, the polyethylene has a number average molecular weight between 80 and 190 thousand g/mol.
In some embodiments, the toughening polymer is one or both of an ethylene-vinyl acetate copolymer having a VA content of between 8wt% and 28wt% and an ethylene-octene copolymer.
In some embodiments, the compatibilizer is one or more of maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene, styrene-butadiene-styrene triblock copolymer.
The invention further discloses a preparation method of the high-toughness lithium ion battery blending diaphragm, and the lithium ion battery blending diaphragm with excellent performance is prepared through biaxial stretching.
In order to achieve the above purpose, the invention provides a preparation method of a high-toughness lithium ion battery blending diaphragm, which comprises the following steps:
step one: extruding the toughening polymer and the plasticizer through an extruder, and granulating to obtain a toughening polymer pretreatment material;
step two: placing polyethylene, a toughening polymer pretreatment material and a compatibilizer into a high-speed mixer to be uniformly mixed to obtain a mixed material;
step three: adding the mixed material prepared in the second step into an extruder, injecting white oil into the extruder, extruding and casting to a chill roll through a T-shaped die to obtain a cast sheet;
step four: biaxially stretching the cast sheet obtained in the step three by a synchronous biaxially stretching machine to obtain an oil-containing film;
step five: extracting the oil-containing film prepared in the step four by using an extracting agent to prepare a wet film;
step six: and (3) standing the wet film prepared in the step (V) at a ventilation position at room temperature, fixing the wet film by using a clamping die, performing heat setting, and finally performing a winding process to prepare the high-toughness lithium ion battery blending diaphragm.
In some embodiments, in step one, the extrusion temperature is between 100 ℃ and 140 ℃ and the screw speed of the extruder is between 130rpm and 150 rpm;
in the second step, the rotating speed of the fly cutter of the high-speed mixer is between 550r/min and 830r/min, the rotating speed of the charging barrel of the high-speed mixer is between 9r/min and 12r/min, and the stirring time of the high-speed mixer is between 30min and 45 min;
in the third step, the temperature of the chilling roller is between 10 ℃ and 25 ℃;
in the fourth step, the biaxial stretching temperature is between 115 ℃ and 125 ℃, and the biaxial stretching multiplying power is between 6 and 8 times;
in the fifth step, the extraction time is between 2min and 4 min;
in the sixth step, the heat setting temperature is between 90 ℃ and 130 ℃, and the heat setting time is between 0.5min and 2 min.
In some embodiments, in the first step, the mass ratio of the components of the toughening polymer pretreatment material is 50-65wt% of the toughening polymer, 35-50wt% of the plasticizer, and the plasticizer is one or more of white oil, mineral oil, soybean oil, toluene and xylene.
In some embodiments, in the third step, the cast sheet comprises 18wt% to 30wt% of solid material, 70wt% to 82wt% of plasticizer, and the thickness of the cast sheet is between 700 μm and 1000 μm.
In some embodiments, in the fifth step, the extractant is one or more of dichloromethane, chloroform, benzene, carbon disulfide, and ethanol.
Compared with the prior art, the invention has the beneficial effects that: according to the invention, the toughening polymer is introduced into the diaphragm system, a homogeneous system is difficult to form between the polar toughening polymer and the nonpolar polyethylene, and the toughening polymer is pretreated through an extrusion and granulation process, so that the toughening polymer is dispersed in the plasticizer in advance, and a necessary basis is provided for the uniform dispersion of the subsequent toughening polymer in the diaphragm system. The action force between the nonpolar chain segment of the compatibilizer and the polyethylene is strong, the action force between the polar chain segment of the compatibilizer and the toughening polymer is strong, and the interaction between the toughening polymer and the polyethylene is promoted. In addition, under the action of the plasticizer, the mechanical force action of the high-speed stirrer and the double-screw extruder provides favorable conditions for realizing good compatibility between the toughening polymer and the polyethylene, so that entanglement is formed between molecular chains of the toughening polymer and the polyethylene, and the toughness of the modified diaphragm is improved, thereby obtaining higher puncture resistance and improving the elongation at break. The puncture resistance strength of the diaphragm prepared by the invention is more than or equal to 500g, the elongation at break is more than or equal to 95%, and the diaphragm is not easy to be pierced by lithium dendrites generated in the use process of the lithium ion battery, so that the safety of the lithium ion battery is improved.
Drawings
Fig. 1 is a process flow diagram of a method for preparing a high-toughness lithium ion battery blend membrane of the invention.
Detailed Description
The present invention will be described in detail below with reference to the embodiments shown in the drawings, but it should be understood that the embodiments are not limited to the present invention, and functional, method, or structural equivalents and alternatives according to the embodiments are within the scope of protection of the present invention by those skilled in the art.
Example 1
The high-toughness lithium ion battery blending diaphragm is composed of a solid material with micropores, wherein the solid material is a homogeneous mixture of polyethylene, a toughening polymer and a compatibilizer. The solid material comprises the following components in percentage by weight: polyethylene: 74% -95% of toughening polymer: 4% -25%, compatibilizer: 0.4 to 2.5 percent.
Wherein the number average molecular weight of the polyethylene is between 80 and 190 ten thousand g/mol. The toughening polymer is one or two of ethylene-vinyl acetate copolymer and ethylene-octene copolymer, and the VA content of the ethylene-vinyl acetate copolymer is between 8wt% and 28 wt%. The compatibilizer is one or more of maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene and styrene-butadiene-styrene triblock copolymer.
The preparation method of the high-toughness lithium ion battery blending diaphragm comprises the following steps:
step one: extruding the toughening polymer and the plasticizer through an extruder, and granulating to obtain a toughening polymer pretreatment material, wherein the extrusion temperature is between 100 and 140 ℃, and the screw speed of the extruder is between 130 and 150 rpm;
step two: uniformly mixing polyethylene, a toughening polymer pretreatment material and a compatibilizer in a high-speed mixer to obtain a mixed material, wherein the fly cutter rotating speed of the high-speed mixer is between 550r/min and 830r/min, the charging barrel rotating speed of the high-speed mixer is between 9r/min and 12r/min, and the stirring time of the high-speed mixer is between 30min and 45 min;
step three: adding the mixed material prepared in the second step into an extruder, injecting white oil into the extruder, extruding and casting to a chilling roller through a T-shaped die head to obtain a casting sheet, wherein the temperature of the chilling roller is between 10 and 25 ℃;
step four: biaxially stretching the cast sheet obtained in the step three by a synchronous biaxially stretching machine to obtain an oil-containing film, wherein the biaxially stretching temperature is 115-125 ℃, and the biaxially stretching multiplying power is 6-8 times;
step five: extracting the oil-containing film prepared in the step four by using an extracting agent to prepare a wet film, wherein the extracting time is between 2 and 4 minutes;
step six: and (3) standing the wet film prepared in the step (V) at a ventilation position at room temperature, fixing the wet film by using a clamping die, performing heat setting, wherein the heat setting temperature is between 90 and 130 ℃, the heat setting time is between 0.5 and 2 minutes, and finally, performing a winding process to prepare the high-toughness lithium ion battery blending diaphragm.
In the preparation process, the mass ratio of the components of the toughening polymer pretreatment material in the first step is 50-65wt% of the toughening polymer, 35-50wt% of the plasticizer, and the plasticizer is one or more of white oil, mineral oil, soybean oil, toluene and xylene; in the third step, the mass ratio of the components of the cast sheet is 18-30wt% of solid materials, 70-82wt% of plasticizers, and the thickness of the cast sheet is 700-1000 mu m; in the fifth step, the extractant is one or more of dichloromethane, chloroform, benzene, carbon disulfide and ethanol.
In the embodiment, polyethylene with the number average molecular weight of 150 ten thousand g/mol is selected, ethylene-vinyl acetate copolymer with the VA content of 9wt% is selected, maleic anhydride grafted polyethylene is selected as a compatibilizer, white oil is selected as a plasticizer, and methylene dichloride is selected as an extractant;
respectively weighing 50% of ethylene-vinyl acetate copolymer and 50% of white oil according to the mass percentage, extruding the ethylene-vinyl acetate copolymer and the white oil sample by a granulator after the extruder temperature is 105 ℃ and the screw speed is 150rpm, and granulating to obtain an ethylene-vinyl acetate copolymer pretreatment material;
respectively taking 20.90% of polyethylene, 2.18% of ethylene-vinyl acetate copolymer pretreatment material, 0.02% of maleic anhydride grafted polyethylene and 76.90% of white oil according to mass percentage, uniformly mixing the polyethylene, the ethylene-vinyl acetate copolymer pretreatment material and a compatibilizer in a high-speed mixer, wherein the fly cutter rotating speed of the high-speed mixer is 750r/min, the charging barrel rotating speed is 9r/min, stirring time is 35min, extruding the obtained mixed material and the white oil through a double-screw extruder, extruding and casting the mixed material and the white oil to a chilling roller through a T-shaped die, wherein the chilling roller temperature is 18 ℃, and obtaining a casting sheet with the casting sheet thickness of 750 mu m;
biaxially stretching the cast sheet by a synchronous biaxially stretching machine at 125 ℃ and stretching multiplying power of 6 times to obtain an oil-containing film; extracting the oil-containing film by using methylene dichloride for 2min to obtain a wet film; and standing the wet film at a ventilation position at room temperature, fixing the wet film by using a clamping die, performing heat setting at 130 ℃ for 1min, and obtaining the high-toughness lithium ion battery blend diaphragm through a winding process.
Example 2
In the embodiment, polyethylene with the number average molecular weight of 170 ten thousand g/mol is selected, ethylene-octene copolymer is selected as a toughening polymer, maleic anhydride grafted polypropylene is selected as a compatibilizer, mineral oil is selected as a plasticizer, and chloroform is selected as an extractant;
respectively weighing 60% of ethylene-octene copolymer and 40% of mineral oil according to mass percentage, extruding the ethylene-octene copolymer and mineral oil sample bars at the extruder temperature of 130 ℃ and the screw speed of 130rpm, and granulating by a granulator to obtain an ethylene-octene copolymer pretreatment material;
respectively taking 18.24% of polyethylene, 2.02% of ethylene-octene copolymer pretreatment material, 0.01% of maleic anhydride grafted polypropylene and 79.73% of mineral oil according to mass percentage, uniformly mixing the polyethylene, the ethylene-octene copolymer pretreatment material and a compatibilizer in a high-speed mixer, wherein the fly cutter rotating speed of the high-speed mixer is 800r/min, the charging barrel rotating speed is 10r/min, stirring time is 30min, extruding the obtained mixed material and the mineral oil through a double-screw extruder, extruding and casting the mixed material and the mineral oil to a chilling roller through a T-shaped die head, wherein the chilling roller temperature is 20 ℃, and obtaining a cast sheet with the thickness of 800 mu m;
biaxially stretching the cast sheet by a synchronous biaxially stretching machine at a stretching temperature of 122 ℃ and a stretching multiplying power of 7 times to obtain an oil-containing film; extracting the oily film by chloroform for 3min to obtain a wet film; and standing the wet film at a ventilation position at room temperature, fixing the wet film by using a clamping die, performing heat setting at 120 ℃ for 1min, and obtaining the high-toughness lithium ion battery blend diaphragm through a winding process.
Example 3
In the embodiment, polyethylene with the number average molecular weight of 120 ten thousand g/mol is selected, ethylene-vinyl acetate copolymer with the VA content of 18wt% is selected, styrene-butadiene-styrene triblock copolymer is selected as a compatibilizer, dimethylbenzene is selected as a plasticizer, and ethanol is selected as an extractant;
respectively weighing 55% of ethylene-vinyl acetate copolymer and 45% of dimethylbenzene according to the mass percentage, extruding the ethylene-vinyl acetate copolymer and dimethylbenzene sample strips at the temperature of 115 ℃ of an extruder and the screw speed of 140rpm, and granulating by a granulator to obtain an ethylene-vinyl acetate copolymer pretreatment material;
respectively taking 20.35% of polyethylene, 6.52% of ethylene-vinyl acetate copolymer pretreatment material, 0.03% of styrene-butadiene-styrene triblock copolymer and 73.10% of dimethylbenzene according to mass percentage, uniformly mixing the polyethylene, the ethylene-vinyl acetate copolymer pretreatment material and a compatibilizer in a high-speed mixer, wherein the fly cutter speed of the high-speed mixer is 650r/min, the rotating speed of a charging barrel is 10r/min, the stirring time is 40min, extruding the obtained mixed material and dimethylbenzene through a double-screw extruder, extruding and casting the mixed material and dimethylbenzene to a chilled roller through a T-shaped die, and obtaining a cast sheet with the thickness of 800 mu m at the temperature of the chilled roller of 15 ℃;
biaxially stretching the cast sheet by a synchronous biaxially stretching machine at 120 ℃ with a stretching multiplying power of 8 times to obtain an oil-containing film; extracting the oily film by ethanol for 3.5min to obtain a wet film; and standing the wet film at a ventilation position at room temperature, fixing the wet film by using a clamping die, performing heat setting at 110 ℃ for 1.5min, and obtaining the high-toughness lithium ion battery blend diaphragm through a winding process.
Example 4
In the embodiment, polyethylene with the number average molecular weight of 100 ten thousand g/mol is selected, ethylene-octene copolymer is selected as a toughening polymer, styrene-butadiene-styrene triblock copolymer is selected as a compatibilizer, toluene is selected as a plasticizer, and carbon disulfide is selected as an extractant;
respectively weighing 65% of ethylene-octene copolymer and 35% of toluene according to mass percentage, extruding the ethylene-octene copolymer-toluene spline at the temperature of an extruder of 135 ℃ and the screw speed of 130rpm, and granulating by a granulator to obtain an ethylene-octene copolymer pretreatment material;
respectively taking 20.80% of polyethylene, 7.96% of ethylene-octene copolymer pretreatment material, 0.04% of styrene-butadiene-styrene triblock copolymer and 71.20% of toluene according to mass percentage, uniformly mixing the polyethylene, the ethylene-octene copolymer pretreatment material and a compatibilizer in a high-speed mixer, wherein the fly cutter rotating speed of the high-speed mixer is 600r/min, the charging barrel rotating speed is 12r/min, stirring time is 40min, extruding the obtained mixed material and toluene through a double-screw extruder, extruding and casting the mixed material and toluene to a chilling roller through a T-shaped die, wherein the chilling roller temperature is 13 ℃, and obtaining cast sheets with the thickness of 900 mu m;
biaxially stretching the cast sheet by a synchronous biaxially stretching machine at a stretching temperature of 118 ℃ and a stretching multiplying power of 8 times to obtain an oil-containing film; extracting the oily film by carbon disulfide for 4min to obtain a wet film; and standing the wet film at a ventilation position at room temperature, fixing the wet film by using a clamping die, performing heat setting at 90 ℃ for 2min, and obtaining the high-toughness lithium ion battery blend diaphragm through a winding process.
Example 5
In the embodiment, polyethylene with the number average molecular weight of 80 ten thousand g/mol is selected, ethylene-vinyl acetate copolymer with the VA content of 24wt% is selected, maleic anhydride grafted polypropylene is selected as a compatibilizer, soybean oil is selected as a plasticizer, and methylene dichloride is selected as an extractant;
respectively weighing 50% of ethylene-vinyl acetate copolymer and 50% of soybean oil according to mass percentage, extruding the ethylene-vinyl acetate copolymer-soybean oil sample bars at the extruder temperature of 110 ℃ and the screw speed of 140rpm, and granulating by a granulator to obtain an ethylene-vinyl acetate copolymer pretreatment material;
respectively taking, by mass, 21.56% of polyethylene, 12.83% of ethylene-vinyl acetate copolymer pretreatment material, 0.05% of maleic anhydride grafted polypropylene and 65.56% of soybean oil, uniformly mixing the polyethylene, the ethylene-vinyl acetate copolymer pretreatment material and a compatibilizer in a high-speed mixer, wherein the fly cutter speed of the high-speed mixer is 780r/min, the charging barrel speed is 12r/min, the stirring time is 35min, extruding the obtained mixed material and the soybean oil through a double-screw extruder, extruding and casting the extruded mixed material and the soybean oil to a chill roll through a T-shaped die, wherein the chill roll temperature is 18 ℃, and obtaining a cast sheet with the thickness of 850 mu m;
biaxially stretching the cast sheet by a synchronous biaxially stretching machine at a stretching temperature of 118 ℃ and a stretching multiplying power of 7 times to obtain an oil-containing film; extracting the oily film by using methylene dichloride for 3min to obtain a wet film; and standing the wet film at a ventilation position at room temperature, fixing the wet film by using a clamping die, performing heat setting at 90 ℃ for 1.5min, and obtaining the high-toughness lithium ion battery blend diaphragm through a winding process.
Example 6
In the embodiment, polyethylene with the number average molecular weight of 180 ten thousand g/mol is selected, ethylene-vinyl acetate copolymer with the VA content of 28wt% is selected, maleic anhydride grafted polyethylene is selected as a compatibilizer, white oil is selected as a plasticizer, and benzene is selected as an extractant;
respectively weighing 55% of ethylene-vinyl acetate copolymer and 45% of white oil according to the mass percentage, extruding the ethylene-vinyl acetate copolymer and the white oil sample by a granulator after the extruder temperature is 115 ℃ and the screw speed is 150rpm, and granulating to obtain an ethylene-vinyl acetate copolymer pretreatment material;
respectively taking 22.50% of polyethylene, 13.57% of ethylene-vinyl acetate copolymer pretreatment material, 0.07% of maleic anhydride grafted polyethylene and 63.86% of white oil according to mass percentage, uniformly mixing the polyethylene, the ethylene-vinyl acetate copolymer pretreatment material and a compatibilizer in a high-speed mixer, wherein the fly cutter speed of the high-speed mixer is 820r/min, the charging barrel speed is 12r/min, stirring time is 30min, extruding the obtained mixed material and the white oil through a double-screw extruder, extruding and casting the mixed material and the white oil to a chilling roller through a T-shaped die, wherein the chilling roller temperature is 20 ℃, and obtaining a casting piece with the thickness of 950 mu m;
biaxially stretching the cast sheet by a synchronous biaxially stretching machine at 120 ℃ with a stretching ratio of 7 times to obtain an oil-containing film; extracting the oil-containing film by benzene for 3.5min to obtain a wet film; and standing the wet film at a ventilation position at room temperature, fixing the wet film by using a clamping die, performing heat setting at 100 ℃ for 1min, and obtaining the high-toughness lithium ion battery blend diaphragm through a winding process.
Comparative example 1
Polyethylene with the number average molecular weight of 150 ten thousand g/mol is selected, white oil is selected as a plasticizer, and dichloromethane is selected as an extractant; extruding polyethylene and white oil through a double-screw extruder, wherein the polyethylene accounts for 23% of the total mass, the white oil accounts for 77% of the total mass, extruding and casting to a chill roll through a T-shaped die, wherein the chill roll temperature is 18 ℃, and obtaining cast sheets with the thickness of 750 mu m; biaxially stretching the cast sheet by a synchronous biaxially stretching machine at 125 ℃ and stretching multiplying power of 6 times to obtain an oil-containing film; extracting the oil-containing film by using methylene dichloride for 2min to obtain a wet film; and standing the wet film at a ventilation position at room temperature, fixing the wet film by using a clamping die, performing heat setting at 130 ℃ for 1min, and obtaining the lithium ion battery diaphragm through a winding process.
Comparative example 2
Polyethylene with the number average molecular weight of 170 ten thousand g/mol is selected, ethylene-octene copolymer is selected as a toughening polymer, maleic anhydride grafted polypropylene is selected as a compatibilizer, mineral oil is selected as a plasticizer, and chloroform is selected as an extractant; extruding polyethylene, ethylene-octene copolymer, maleic anhydride grafted polypropylene and mineral oil through an extruder, wherein the polyethylene accounts for 18.24% of the total mass, the ethylene-octene copolymer pretreatment material accounts for 2.02%, the maleic anhydride grafted polypropylene accounts for 0.01%, and the mineral oil accounts for 79.73% of the total mass, extruding and casting the mixture to a chilled roll through a T-shaped die, wherein the temperature of the chilled roll is 20 ℃, so as to obtain a cast sheet, and the thickness of the cast sheet is 800 mu m; biaxially stretching the cast sheet by a synchronous biaxially stretching machine at a stretching temperature of 122 ℃ and a stretching multiplying power of 7 times to obtain an oil-containing film; extracting the oily film by chloroform for 3min to obtain a wet film; and standing the wet film at a ventilation position at room temperature, fixing the wet film by using a clamping die, performing heat setting at 120 ℃ for 1min, and obtaining the high-toughness lithium ion battery blend diaphragm through a winding process.
Comparative example 3
Polyethylene with the number average molecular weight of 120 ten thousand g/mol is selected, ethylene-vinyl acetate copolymer with the VA content of 18wt% is selected, dimethylbenzene is selected as a plasticizer, and ethanol is selected as an extractant; respectively weighing 55% of ethylene-vinyl acetate copolymer and 45% of dimethylbenzene according to the mass percentage, extruding the ethylene-vinyl acetate copolymer and dimethylbenzene sample strips at the temperature of 115 ℃ of an extruder and the screw speed of 140rpm, and granulating by a granulator to obtain an ethylene-vinyl acetate copolymer pretreatment material; respectively taking 20.35% of polyethylene, 6.55% of ethylene-vinyl acetate copolymer pretreatment material and 73.10% of dimethylbenzene according to mass percentage, uniformly mixing the polyethylene and the ethylene-vinyl acetate copolymer pretreatment material in a high-speed mixer, wherein the rotating speed of a fly cutter of the high-speed mixer is 650r/min, the rotating speed of a charging barrel is 10r/min, the stirring time is 40min, extruding the obtained mixed material and dimethylbenzene through a double-screw extruder, extruding and casting the mixed material and dimethylbenzene to a chilled roller through a T-shaped die, wherein the temperature of the chilled roller is 15 ℃, and obtaining cast sheets with the thickness of 800 mu m; biaxially stretching the cast sheet by a synchronous biaxially stretching machine at 120 ℃ with a stretching multiplying power of 8 times to obtain an oil-containing film; extracting the oily film by ethanol for 3.5min to obtain a wet film; and standing the wet film at a ventilation position at room temperature, fixing the wet film by using a clamping die, performing heat setting at 110 ℃ for 1.5min, and obtaining the high-toughness lithium ion battery blend diaphragm through a winding process.
Table 1 comparative properties of separator prepared in examples
| Project | Puncture resistance strength (g) | Tensile Strength (MPa) | Elongation at break (%) |
| Example 1 | 552.49 | 210.55 | 96.13 |
| Example 2 | 662.71 | 230.38 | 99.37 |
| Example 3 | 567.44 | 216.71 | 95.74 |
| Example 4 | 688.32 | 222.57 | 98.28 |
| Example 5 | 636.24 | 223.76 | 95.27 |
| Example 6 | 711.93 | 242.57 | 100.89 |
| Comparative example 1 | 384.55 | 169.12 | 66.73 |
| Comparative example 2 | 424.15 | 197.22 | 72.91 |
| Comparative example 3 | 454.154 | 213.76 | 70.28 |
As can be seen from Table 1, the puncture resistance, tensile strength and elongation at break of the separator prepared by the invention are improved compared with those of the separator prepared by the comparative example, and the toughness of the separator can be improved by adding the toughening polymer into the separator system, pre-treating the toughening polymer and adding the compatibilizer, so that the high-toughness lithium ion battery blended separator can be obtained, and the higher puncture resistance can be obtained.
The diaphragm prepared by the method is applied to the lithium ion battery, so that the risk of the diaphragm being pierced by lithium dendrites can be reduced, and the safety of the lithium ion battery is improved.
The above list of detailed descriptions is only specific to practical embodiments of the present invention, and they are not intended to limit the scope of the present invention, and all equivalent embodiments or modifications that do not depart from the spirit of the present invention should be included in the scope of the present invention.
Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.
Claims (8)
1. The preparation method of the high-toughness lithium ion battery blending diaphragm is characterized in that the high-toughness lithium ion battery blending diaphragm is composed of a solid material with micropores, and the solid material is a homogeneous mixture of polyethylene, toughening polymer and compatibilizer;
the preparation method of the high-toughness lithium ion battery blending diaphragm comprises the following steps:
step one: extruding the toughening polymer and the plasticizer through an extruder, and granulating to obtain a toughening polymer pretreatment material;
step two: placing polyethylene, a toughening polymer pretreatment material and a compatibilizer into a high-speed mixer to be uniformly mixed to obtain a mixed material;
step three: adding the mixed material prepared in the second step into an extruder, injecting white oil into the extruder, extruding and casting to a chill roll through a T-shaped die to obtain a cast sheet;
step four: biaxially stretching the cast sheet obtained in the step three by a synchronous biaxially stretching machine to obtain an oil-containing film;
step five: extracting the oil-containing film prepared in the step four by using an extracting agent to prepare a wet film;
step six: standing the wet film prepared in the fifth step at a ventilation position at room temperature, fixing the wet film by a clamping die, performing heat setting, and finally performing a winding process to prepare the high-toughness lithium ion battery blending diaphragm;
in the first step, the extrusion temperature is between 100 and 140 ℃, and the screw rotation speed of the extruder is between 130 and 150 rpm;
in the second step, the rotating speed of the fly cutter of the high-speed mixer is between 550r/min and 830r/min, the rotating speed of the charging barrel of the high-speed mixer is between 9r/min and 12r/min, and the stirring time of the high-speed mixer is between 30min and 45 min;
in the third step, the temperature of the chilling roller is between 10 ℃ and 25 ℃;
in the fourth step, the biaxial stretching temperature is between 115 ℃ and 125 ℃, and the stretching multiplying power of biaxial stretching is between 6 and 8 times;
in the fifth step, the extraction time is between 2min and 4 min;
in the sixth step, the heat setting temperature is between 90 ℃ and 130 ℃, and the heat setting time is between 0.5min and 2 min.
2. The method for preparing the high-toughness lithium ion battery blending diaphragm according to claim 1, wherein the solid material comprises the following components in percentage by weight: polyethylene: 74% -95% of toughening polymer: 4% -25%, compatibilizer: 0.4 to 2.5 percent.
3. The method for preparing the high-toughness lithium ion battery blending diaphragm according to claim 1, wherein the number average molecular weight of the polyethylene is 80-190 ten thousand g/mol.
4. The method for preparing the high-toughness lithium ion battery blending diaphragm according to claim 1, wherein the toughening polymer is one or two of ethylene-vinyl acetate copolymer and ethylene-octene copolymer, and the VA content of the ethylene-vinyl acetate copolymer is between 8wt% and 28 wt%.
5. The method for preparing the high-toughness lithium ion battery blending diaphragm according to claim 1, wherein the compatibilizer is more than one of maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene and styrene-butadiene-styrene triblock copolymer.
6. The preparation method of the high-toughness lithium ion battery blending diaphragm according to claim 1, wherein in the first step, the toughening polymer pretreatment material comprises 50-65wt% of toughening polymer and 35-50wt% of plasticizer, and the plasticizer is more than one of white oil, mineral oil, soybean oil, toluene and xylene.
7. The preparation method of the high-toughness lithium ion battery blending diaphragm according to claim 1, wherein in the third step, the mass ratio of the components of the cast sheet is 18-30wt% of solid materials, 70-82wt% of plasticizers, and the thickness of the cast sheet is 700-1000 μm.
8. The method for preparing the high-toughness lithium ion battery blending diaphragm according to claim 1, wherein in the fifth step, the extractant is more than one of dichloromethane, chloroform, benzene, carbon disulfide and ethanol.
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