CN107623099B - Composite multilayer polyolefin lithium battery diaphragm and preparation method thereof - Google Patents
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Abstract
The invention discloses a composite multilayer polyolefin lithium battery diaphragm, which takes a porous polyolefin diaphragm as a base material, wherein a coating is formed by electrospinning a composite solution of polyethylene terephthalate and vinylidene fluoride-hexafluoropropylene copolymer on one side or two sides of the polyolefin diaphragm. Aiming at the problems of low high-temperature integrity of the existing polypropylene or polyethylene porous diaphragm and unreasonable pore structure of the existing lithium battery composite diaphragm with a coating, the composite type multilayer polyolefin lithium battery diaphragm provided by the invention is formed by coating a PET and PVDF-HFP composite coating on the surface of the polyolefin porous diaphragm, wherein the melting point of PET is about 250 ℃, the melting point of PVDF-HFP is about 170 ℃, PET mainly plays a role in high-temperature integrity in the coating, and PVDF-HFP plays a role in improving the wettability of the diaphragm on the swelling characteristic of electrolyte, so that the composite type multilayer polyolefin lithium battery diaphragm has high temperature resistance and high electrolyte wettability.
Description
Technical Field
The invention belongs to the field of new energy materials, and particularly relates to a composite multilayer polyolefin lithium battery diaphragm and a preparation method thereof.
Background
The diaphragm is the most critical material for determining the safety of the lithium battery, and is generally prepared from polypropylene or polyethylene by a dry-method single-drawing process, a dry-method double-drawing process or a wet-method process. However, the polypropylene or polyethylene porous membrane has internal stress in the process of stretching and pore-forming, and the membrane can generate obvious thermal shrinkage effect when the stress is released in a high-temperature environment, so that the anode and cathode materials in the battery are in direct contact to cause internal short circuit. In addition, the porous polyolefin diaphragm and the organic electrolyte have different polarities, so that the electrolyte has low wettability to the diaphragm and forms high resistance.
The coating is an effective method for improving the thermal stability and wettability of the diaphragm, and is generally prepared from materials with better thermal stability such as electrodeless oxides and high-melting-point polymers, so that the thermal stability of the diaphragm is improved by using the coating, the internal short circuit caused by diaphragm shrinkage can be avoided, and the safety of the battery is obviously improved. For example, patent CN201110048688 discloses a method for preparing an inorganic coating by dispersing polymer binder such as polyvinylidene fluoride and inorganic particles such as alumina in an aqueous solution with the aid of aqueous dispersing agent such as polyethylene glycol; patent CN201310017708 discloses a method for preparing a diaphragm ceramic coating by mixing a binder such as vinylidene fluoride-hexafluoropropylene copolymer with zeolite under the assistance of a thickener such as carboxymethyl cellulose; patent CN201510706160.2 discloses a lithium battery separator containing lithium ion conductive porous inorganic oxide and a preparation method thereof, which comprises the steps of forming a lithium ion conductive polymer and an inorganic oxide precursor under the action of a surfactant, compounding, crystallizing under a hydrothermal condition to form a porous inorganic oxide capable of conducting lithium ions, mixing with a binder, a stabilizer and an alkyl chain ultraviolet crosslinking agent to prepare a slurry, coating the slurry on the surface of the lithium battery separator, irradiating with ultraviolet rays, and drying to obtain a separator with a coating. However, the thermal stability temperature of the high molecular binder in the coating also has great influence on the thermal stability of the coating, and the binder loses binding power and falls off after being softened; in addition, the coating cannot exist independently after the diaphragm body is softened, and the pulverization of the coating can be caused by the melting of the diaphragm body with a larger area, so that the function of blocking the positive electrode and the negative electrode under extreme conditions is difficult to play.
Patent CN201610511146.1 discloses a high temperature resistant composite lithium battery diaphragm and a preparation method thereof, the diaphragm includes a base film and a high temperature resistant resin layer coated on at least one surface of the base film, the high temperature resistant resin layer contains high temperature resistant resin and inorganic materials such as alumina and titanium oxide as heat stable phase, the prepared diaphragm has higher strength, the heat resistance is also greatly improved, and the use safety of the diaphragm is improved. Patent CN201610600027.3 discloses a lithium ion battery separator coating, its preparation method and application. The battery diaphragm coating is a silicon oxide material with the surface coated with a high molecular copolymer, and is sprayed on the surface of the lithium battery diaphragm by adopting a spin-coating method to form the coating. However, the high-temperature resistant resin and the inorganic material such as alumina and titanium oxide do not swell in the electrolyte, and the conduction of lithium ions is greatly inhibited. Patent CN201410160804.8 provides a preparation process of a low-ionic-impedance high-temperature-resistant lithium battery coating membrane, in which a lithium compound and an organic acid binder are directly added in a mixing process to synthesize a lithium-containing high molecular compound, thereby improving the lithium ion conductivity of the coating membrane. However, many organic acids have a small voltage window that affects the performance stability of the battery, and in addition, the conductivity of the coating returns to an initial state without a lithium salt after Li ion migration.
Disclosure of Invention
The invention aims to solve the technical problem of providing a composite multilayer polyolefin lithium battery diaphragm and a preparation method thereof aiming at the defects of the prior art, wherein the diaphragm has high temperature resistance and high electrolyte wettability, can bear the temperature of 294-253 ℃, and can greatly improve the thermal safety of a battery.
The technical scheme adopted by the invention for solving the problems is as follows:
the composite multilayer polyolefin lithium battery diaphragm takes a porous polyolefin diaphragm as a base material, and one side or two sides of the polyolefin diaphragm are coated with a coating formed by compounding polyethylene terephthalate (PET) and vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP).
According to the scheme, the thickness of the porous polyolefin diaphragm is 6-50 mu m, and the porosity is 35-50 vol%.
According to the scheme, the thickness of the coating is 2-10 mu m.
According to the scheme, the porous polyolefin diaphragm base material is mainly selected from any one of dry-process single-drawing polypropylene, dry-process double-drawing polypropylene or wet-process polyethylene lithium battery diaphragm and the like.
According to the scheme, the weight ratio of polyethylene terephthalate (PET) to vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) in the coating is 1: 0.1 to 0.3.
According to the scheme, the molecular weight of polyethylene terephthalate (PET) in the coating is 5-20 ten thousand; the molecular weight of the vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) is 25-50 ten thousand, wherein the content of HFP is 2-10 wt%.
The invention also provides a preparation method of the composite multilayer polyolefin lithium battery diaphragm, which mainly comprises the following steps:
firstly, PET and PVDF-HFP granules are mixed according to the weight ratio of 1: 0.1-0.3, dissolving the sealed swelling cake in the dispersed mixed solvent, and taking out to obtain a PET and PVDF-HFP mixed solution;
and secondly, coating the PET and PVDF-HFP mixed solution obtained in the first step on the porous polyolefin diaphragm substrate in a single-sided or double-sided manner by adopting blade coating, roller coating, spraying and the like, and drying after coating to obtain the PET and PVDF-HFP coating composite porous polyolefin diaphragm, namely the composite multi-layer polyolefin lithium battery diaphragm.
According to the scheme, in the first step, the mixed solvent consists of a fluorine-containing organic solvent and alkyl halide, and the volume ratio of the fluorine-containing organic solvent to the alkyl halide is 1:0.2 to 0.3. Wherein the fluorine-containing organic solvent is selected from one of trifluoroacetic acid, hexafluoroisopropanol and the like, and the alkyl halide is selected from one of trichloromethane, dichloromethane and the like.
According to the scheme, in the first step, the ratio of the total weight of PET and PVDF-HFP granules to the total weight of the mixed solvent is 1: 10 to 20.
According to the scheme, in the first step, the sealing swelling time is 10-24 hours.
According to the scheme, in the first step, the dissolving conditions are as follows: dissolving for 4-8 h at 100-140 ℃ under the condition of 2-4 MPa of nitrogen pressure.
According to the scheme, in the second step, the coating conditions are as follows: controlling the temperature to be 10-30 ℃ and the humidity to be 50-70 RH%; the thickness of the coating layer is controlled to be 2 to 10 μm.
According to the scheme, in the second step, the drying conditions are as follows: drying at 70-80 ℃ for 0.5-3 hours.
Compared with the prior art, the invention has the beneficial effects that:
firstly, aiming at the problems of low high-temperature integrity of the existing polypropylene or polyethylene porous diaphragm and unreasonable pore structure of the existing lithium battery composite diaphragm with a coating, the composite type multilayer polyolefin lithium battery diaphragm provided by the invention is coated on the surface of the polyolefin porous diaphragm to form a PET and PVDF-HFP composite coating, wherein the melting point of PET is about 250 ℃, the melting point of PVDF-HFP is about 170 ℃, PET mainly plays a role in high-temperature integrity in the coating, and PVDF-HFP plays a role in improving the wettability of the diaphragm on account of the swelling characteristic in electrolyte, so that the composite type multilayer polyolefin lithium battery diaphragm has high temperature resistance and high electrolyte wettability.
Secondly, under the limit condition of battery abuse, the polyolefin diaphragm at 120-160 ℃ can be closed due to material melting, and the PET/PVDF-HFP fiber in the coating forms a stable single-layer structure, so that the composite type multilayer polyolefin lithium battery diaphragm can bear the temperature of 249-253 ℃ and can greatly improve the thermal safety of the battery. In addition, PVDF-HFP in the coating has good swelling property in ester electrolyte commonly used for lithium batteries, and the composite type multilayer polyolefin lithium battery diaphragm provided by the invention also has good liquid absorption rate and lithium ion conduction performance.
And thirdly, PET and PVDF-HFP are both materials with good physical stability and are difficult to dissolve in a plurality of solvents, and the composite multi-layer polyolefin lithium battery diaphragm is prepared by compounding a mixed solvent of a fluorine-containing organic solvent and alkyl halide, dissolving the PET and the PVDF-HFP at high temperature and high pressure after an initial swelling process to form a uniformly dispersed solution, thereby providing necessary conditions for successfully preparing the composite multi-layer polyolefin lithium battery diaphragm by in-situ coating on a porous polyolefin diaphragm substrate.
Detailed Description
In order to better understand the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples.
Example 1
A composite multilayer polyolefin lithium battery diaphragm takes a dry-method single-drawing polypropylene porous diaphragm (20 mu m, the porosity is 42 vol%) as a base material, both sides of the polypropylene porous diaphragm are electrospun with a coating formed by compounding polyethylene terephthalate (PET) and vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and the thickness of the coating is 3 mu m; wherein the weight ratio of polyethylene terephthalate (PET) to vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) is 1: 0.1.
the preparation method of the composite multilayer polyolefin lithium battery diaphragm comprises the following specific steps:
1) PET (molecular weight, Mw-10 ten thousand) and PVDF-HFP granules (HFP content is 2wt percent, and PVDF-HFP molecular weight Mw-25 ten thousand are mixed; PET: PVDF-HFP weight ratio 1: 0.01) based on the total weight of the solid particles: the total weight of the mixed solvent is 1: dispersing the mixed solvent (the mixed solvent consists of trifluoroacetic acid and trichloromethane according to the volume ratio of 1: 0.2) according to the proportion of 10, sealing and swelling for 10 hours, transferring into a high-pressure kettle, dissolving for 4 hours at the temperature of 100 ℃ under the condition of nitrogen pressure supplement of 2MPa, cooling and taking out to obtain a PET and PVDF-HFP mixed solution;
2) carrying out blade coating on the PET and PVDF-HFP mixed solution prepared in the step 1) on a dry-method single-drawing polypropylene (20 mu m, porosity of 42 vol%) porous diaphragm base material by a scraper coater, wherein the coating environment temperature is controlled to be 10 ℃ and the humidity is controlled to be 50 RH%; the thickness of the coating layer is controlled to be 3 mu m, and after the coating is finished, the film is placed in a 70 ℃ drying oven to be dried for 0.5 hour, so that the PET and PVDF-HFP coating composite polyolefin lithium battery diaphragm, namely the composite multilayer polyolefin lithium battery diaphragm, is obtained.
In example 1 and other examples described below, a universal material stretcher was used to measure the coating peel force, breaking strength, and puncture strength of the composite multilayer polyolefin lithium battery separator; measuring the porosity by using a Gurley permeameter; assembling a button cell by using powdered lithium iron phosphate as a positive electrode material and artificial graphite as a negative electrode, heating at the speed of 0.1 ℃/min in an environment test box, and measuring the temperature when a short circuit occurs by using an electrochemical workstation; using 1mol/L LiPF6DMC DEC (v/v/v, EC, DMC, DEC are ethylene carbonate, diethyl carbonate, dimethyl carbonate, respectively, which are classical electrolyte components) is soaked for 1 hour to test the liquid absorption rate of the diaphragm, and all performance results are shown in Table 1. Meanwhile, various performance indexes of the base material itself used in each example are also shown in table 1.
TABLE 1
| Composite multilayer polyolefin lithium battery diaphragm | Base material | |
| Porosity% | 40 | 42 |
| Air permeability s/100mL | 483 | 328 |
| Puncture strength, gf | 712 | 653 |
| Longitudinal tensile strength, MPa | 165 | 162 |
| Coating peeling force Nm-1 | 54.7 | / |
| Short circuit temperature deg.C | 251 | 166 |
| Liquid absorption rate | 204％ | 110％ |
Example 2
A composite multilayer polyolefin lithium battery diaphragm takes dry-process double-drawn polypropylene (50 mu m, the porosity is 39 vol%) as a base material, a coating formed by compounding polyethylene terephthalate (PET) and vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) is electrospun on both sides of the polypropylene porous diaphragm, and the thickness of the coating is 10 mu m; wherein the weight ratio of polyethylene terephthalate (PET) to vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) is 1: 0.3.
the preparation method of the composite multilayer polyolefin lithium battery diaphragm comprises the following specific steps:
1) PET (molecular weight, Mw-5 ten thousand), PVDF-HFP granules (HFP content is 10 wt%, PVDF-HFP molecular weight Mw-50 ten thousand; PET: PVDF-HFP weight ratio 1: 0.3) pellets of PET, PVDF-HFP (PET: PVDF-HFP weight ratio 1: 0.3) based on the total weight of the solid particles: the total weight of the mixed solvent is 1: 20 in proportion, dispersing in a mixed solvent (the mixed solvent consists of hexafluoroisopropanol and dichloromethane in a volume ratio of 1: 0.3), sealing and swelling for 24 hours, transferring into a high-pressure kettle, dissolving for 8 hours at 140 ℃ under the condition of nitrogen pressure supplement of 4MPa, cooling and taking out to obtain a PET and PVDF-HFP mixed solution;
2) carrying out single-side coating on the PET and PVDF-HFP mixed solution prepared in the step 1) on a dry-method double-drawn polypropylene (50 mu m, porosity of 39 vol%) base film by a roller coater, wherein the coating environment temperature is controlled to be 30 ℃, the humidity is controlled to be 70 RH%, and the thickness of a coating layer is controlled to be 10 mu m; and after the coating is finished, drying the film in an oven at 80 ℃ for 3 hours to obtain the PET and PVDF-HFP coating composite polyolefin lithium battery diaphragm.
The performance indexes of the composite multilayer polyolefin lithium battery separator obtained in example 2 in all respects are shown in table 2, and the performance indexes of the base material adopted in the present example in all respects are also attached to table 2.
TABLE 2
| Composite multilayer polyolefin lithium battery diaphragm | Base material | |
| Porosity% | 35 | 39 |
| Air permeability s/100mL | 645 | 517 |
| Puncture strength, gf | 918 | 792 |
| Longitudinal tensile strength, MPa | 162 | 153 |
| Coating peeling force Nm-1 | 68.7 | / |
| Short circuit temperature deg.C | 253 | 173 |
| Liquid absorption rate | 216％ | 102％ |
Example 3
A composite multilayer polyolefin lithium battery diaphragm takes a wet-process polyethylene lithium battery diaphragm (12 mu m, the porosity is 46 vol%) as a base material, both sides of the polypropylene porous diaphragm are electrospun with a coating formed by compounding polyethylene terephthalate (PET) and vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and the thickness of the coating is 6 mu m; wherein the weight ratio of polyethylene terephthalate (PET) to vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) is 1: 0.2.
the preparation method of the composite multilayer polyolefin lithium battery diaphragm comprises the following specific steps:
1) PET (molecular weight, Mw-20 ten thousand), PVDF-HFP granules (HFP content is 5 wt%, PVDF-HFP molecular weight Mw-30 ten thousand; PET: PVDF-HFP weight ratio 1: 0.2) based on the total weight of the solid particles: the total weight of the mixed solvent is 1: 14 in proportion, dispersing in a mixed solvent (the mixed solvent consists of trifluoroacetic acid and dichloromethane in a volume ratio of 1: 0.25), sealing and swelling for 15h, transferring into a high-pressure kettle, dissolving for 5h at 130 ℃ under the condition of nitrogen pressure supplement of 4MPa, cooling and taking out to obtain a PET and PVDF-HFP mixed solution;
2) carrying out single-side spraying on the PET and PVDF-HFP mixed solution prepared in the step 1) on a wet polyethylene lithium battery diaphragm (12 mu m, 46 vol%) base film by a spraying machine, wherein the spraying environment temperature is controlled to be 25 ℃, the humidity is controlled to be 60 RH%, and the coating thickness is controlled to be 6 mu m; and after the coating is finished, drying the film in a 75 ℃ oven for 1 hour to obtain the PET and PVDF-HFP coating composite polyolefin lithium battery diaphragm.
The performance indexes of the composite multilayer polyolefin lithium battery separator obtained in example 3 are shown in table 3, and the performance indexes of the base material used in this example are also shown in table 3.
TABLE 3
| Composite multilayer polyolefin lithium battery diaphragm | Base material | |
| Porosity% | 41 | 46 |
| Air permeability s/100mL | 214 | 167 |
| Puncture strength, gf | 345 | 326 |
| Longitudinal tensile strength, MPa | 166 | 153 |
| Coating peeling force Nm-1 | 58.3 | / |
| Short circuit temperature deg.C | 252 | 135 |
| Liquid absorption rate | 205％ | 118％ |
Example 4
A composite multilayer polyolefin lithium battery diaphragm takes dry-process single-drawn polypropylene (with the thickness of 18 mu m and the porosity of 40 vol%) as a base material, a coating formed by compounding polyethylene terephthalate (PET) and vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) is electrospun on both sides of the polypropylene porous diaphragm, and the thickness of the coating is 2 mu m; wherein the weight ratio of polyethylene terephthalate (PET) to vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) is 1: 0.25.
the preparation method of the composite multilayer polyolefin lithium battery diaphragm comprises the following specific steps:
1) PET (molecular weight, Mw-15 ten thousand), PVDF-HFP granules (HFP content 4 wt%, PVDF-HFP molecular weight Mw-36 ten thousand; PET: PVDF-HFP weight ratio 1: 0.25) pellets of PET, PVDF-HFP (PET: PVDF-HFP weight ratio 1: 0.25) based on the total weight of the solid particles: the total weight of the mixed solvent is 1: 18 (in the mixed solvent, the volume ratio of hexafluoroisopropanol to trichloromethane is 1:0.22), sealing and swelling for 18h, transferring into an autoclave, dissolving for 7h at 130 ℃ under the condition of nitrogen pressure supplement of 3.3MPa, cooling and taking out to obtain a PET and PVDF-HFP mixed solution;
2) coating the PET and PVDF-HFP mixed solution prepared in the step 1) on a dry-method single-drawing polypropylene (18 mu m, 40 vol%) base film on two sides by a scraper coater, wherein the coating environment temperature is controlled to be 22 ℃ and the humidity is controlled to be 56 RH%; the thickness of the coating layer is controlled to be 2 mu m, and after the coating is finished, the film is placed in a 74 ℃ oven to be dried for 2 hours, so that the PET and PVDF-HFP coating layer composite polyolefin lithium battery diaphragm is obtained.
The performance indexes of the composite multilayer polyolefin lithium battery separator obtained in example 4 are shown in table 4, and the performance indexes of the base material used in this example are also shown in table 4.
TABLE 4
| Composite multilayer polyolefin lithium battery diaphragm | Base material | |
| Porosity% | 39 | 40 |
| Air permeability s/100mL | 243 | 215 |
| Puncture strength, gf | 372 | 363 |
| Longitudinal tensile strength, MPa | 157 | 152 |
| Coating peeling force Nm-1 | 47.3 | / |
| Short circuit temperature deg.C | 249 | 166 |
| Liquid absorption rate | 203％ | 112％ |
As shown in tables 1-4, the composite multilayer polyolefin lithium battery diaphragm prepared by the invention has the advantages of high porosity, good air permeability, proper puncture strength, longitudinal tensile strength and shrinkage rate, short circuit temperature of 249-253 ℃, good high-temperature integrity and high temperature resistance, liquid absorption rate of 203-216%, good liquid absorption rate and high electrolyte wettability, and can greatly improve the thermal safety and lithium ion conductivity of a battery. Compared with respective matrixes, the composite multilayer polyolefin lithium battery diaphragm has the advantages that the porosity, the air permeability and the like of the composite multilayer polyolefin lithium battery diaphragm are not obviously influenced, and the composite multilayer polyolefin lithium battery diaphragm is slightly improved.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, many modifications and changes can be made without departing from the inventive concept of the present invention, and these modifications and changes are within the protection scope of the present invention.
Claims (5)
1. The composite multilayer polyolefin lithium battery diaphragm is characterized in that a porous polyolefin diaphragm is used as a base material, and polyethylene terephthalate and vinylidene fluoride-hexafluoropropylene copolymer are coated on two sides of the polyolefin diaphragm to form a coating in a composite manner;
the thickness of the porous polyolefin diaphragm is 6-50 mu m, and the porosity is 35-50 vol%; the thickness of the coating is 2-10 mu m;
the weight ratio of the polyethylene terephthalate to the vinylidene fluoride-hexafluoropropylene copolymer in the coating is 1: 0.1-0.3, the molecular weight of the polyethylene glycol terephthalate is 5-20 ten thousand; the molecular weight of the vinylidene fluoride-hexafluoropropylene copolymer is 25-50 ten thousand, wherein the hexafluoropropylene content is 2-10 wt%.
2. The composite multilayer polyolefin lithium battery separator according to claim 1, wherein the porous polyolefin separator substrate is selected from any one of dry mono-drawn polypropylene, dry bi-drawn polypropylene or wet polyethylene lithium battery separator.
3. The preparation method of the composite multilayer polyolefin lithium battery separator as claimed in claim 1, is characterized by comprising the following main processes:
firstly, polyethylene terephthalate and vinylidene fluoride-hexafluoropropylene copolymer granules are mixed according to the weight ratio of 1: 0.1-0.3, sealing, swelling and dissolving in the mixed solvent, and taking out to obtain a mixed solution of polyethylene terephthalate and vinylidene fluoride-hexafluoropropylene copolymer; wherein the mixed solvent consists of a fluorine-containing organic solvent and alkyl halide, and the volume ratio of the fluorine-containing organic solvent to the alkyl halide is 1:0.2 to 0.3; the fluorine-containing organic solvent is mainly selected from any one of trifluoroacetic acid and hexafluoroisopropanol, and the alkyl halide is mainly selected from any one of trichloromethane and dichloromethane; the sealing swelling time is 10-24 h; the dissolution conditions were: dissolving for 4-8 h at 100-140 ℃ under the condition of 2-4 MPa of nitrogen pressure;
and secondly, coating the mixed solution of the polyethylene glycol terephthalate and the vinylidene fluoride-hexafluoropropylene copolymer obtained in the first step on the porous polyolefin diaphragm substrate on one side or two sides, and drying to obtain the composite porous polyolefin diaphragm with the polyethylene glycol terephthalate and the vinylidene fluoride-hexafluoropropylene copolymer coating, namely the composite multilayer polyolefin lithium battery diaphragm.
4. The preparation method of the composite multilayer polyolefin lithium battery separator as claimed in claim 3, wherein in the first step, the ratio of the total weight of the polyethylene terephthalate and vinylidene fluoride-hexafluoropropylene copolymer particles to the total weight of the mixed solvent is 1: 10 to 20.
5. The preparation method of the composite multilayer polyolefin lithium battery separator according to claim 3, wherein the coating conditions are as follows: controlling the temperature to be 10-30 ℃ and the humidity to be 50-70 RH%; the thickness of the coating layer is controlled to be 2 to 10 μm.
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| CN102779964A (en) * | 2012-08-08 | 2012-11-14 | 龙能科技（苏州）有限公司 | Method for preparing multilayer composite membrane for secondary battery by using electrostatic spinning coating method |
| CN104022246A (en) * | 2014-06-24 | 2014-09-03 | 中国第一汽车股份有限公司 | High-performance lithium battery ceramic diaphragm and preparation method thereof |
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| CN104022246A (en) * | 2014-06-24 | 2014-09-03 | 中国第一汽车股份有限公司 | High-performance lithium battery ceramic diaphragm and preparation method thereof |
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