CN110993859A - Polymer coating diaphragm with improved structure and preparation method thereof - Google Patents
Polymer coating diaphragm with improved structure and preparation method thereof Download PDFInfo
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- CN110993859A CN110993859A CN201911360365.4A CN201911360365A CN110993859A CN 110993859 A CN110993859 A CN 110993859A CN 201911360365 A CN201911360365 A CN 201911360365A CN 110993859 A CN110993859 A CN 110993859A
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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
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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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
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y02E60/10—Energy storage using batteries
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Abstract
The application discloses a polymer coating diaphragm with an improved structure and a preparation method thereof. The polymer coating diaphragm comprises a base film and polymer coatings coated on one or two surfaces of the base film, wherein the polymer coatings are distributed on the base film in a linear shape along the longitudinal direction, the line width is 0.5-10 mu m, and the line interval is 0.5-1 mu m; the polymer coating layer is formed by coating the surface of the base film grafted with carboxyl on coating slurry prepared by gel polymer particles grafted with amino on the surface. According to the polymer coating diaphragm, the surfaces of the gel polymer particles and the base film are respectively subjected to grafting modification, and the gel polymer particles are fixed by using chemical bonds of chemical reaction of carboxyl and amino, so that the cohesiveness and stability of the polymer coating diaphragm are improved; the problems of battery core bulge and battery deformation are solved through the designed stripe-shaped coating structure; the polymer coating diaphragm improves the safety of the lithium ion battery and prolongs the service life of the lithium ion battery.
Description
Technical Field
The application relates to the field of battery separators, in particular to a polymer coating separator with an improved structure and a preparation method thereof.
Background
With the increasing energy density of lithium ion power batteries, the safety problem becomes the first problem to be solved in battery design. Particularly, when the energy density of the single battery reaches 300Wh/kg, the traditional polyolefin diaphragm and the ceramic diaphragm are difficult to meet the requirements of battery application. Due to the contribution of the polymer coating diaphragm to the structural design of the battery core, the safety performance of the battery is improved to a great extent, the service life of the battery is prolonged, and the polymer coating diaphragm becomes the first choice for the application of the power battery.
At present, a power battery cell comprises a square battery, a soft package battery and a cylinder, wherein the square battery adopting a winding process is more adopted by a cell manufacturer due to high manufacturing efficiency. However, the energy density of the battery cell is higher and higher, and the expansion and shrinkage rate of the electrode generated in the charging and discharging process is relatively large, and particularly, in the case of a battery cell in a winding process, the battery cell is easy to bulge under a certain winding tension of an electrode plate, and finally, the battery is deformed, so that the battery cell is scrapped.
Disclosure of Invention
It is an object of the present application to provide a polymer coated separator having an improved structure and a method for preparing the same.
In order to achieve the purpose, the following technical scheme is adopted in the application:
one aspect of the application discloses a polymer coating diaphragm with an improved structure, which comprises a base film and a polymer coating coated on at least one surface of the base film, wherein the polymer coating is distributed on the base film in a linear shape along the longitudinal direction, the line width is 0.5-10 mu m, and the line interval is 0.5-1 m; the polymer coating layer is formed by coating a coating slurry made of gel polymer particles with amino groups grafted on the surface thereof on the surface of a base film with carboxyl groups grafted on the surface thereof, and the gel polymer particles are fixed on the surface of the base film through the reaction of the carboxyl groups and the amino groups.
The polymer coating diaphragm has better air permeability through the design of the stripe-shaped coating, and solves the problems of battery core bulge and battery deformation; on the other hand, by the surface grafting technology, the gel polymer particles are fixed on the surface of the base film by utilizing the reaction of carboxyl and amino, so that the adhesion of the coating is enhanced; the gel polymer coating diaphragm has better adhesion with the positive electrode and the negative electrode. The polymer coating diaphragm improves the safety performance of the lithium ion battery and prolongs the service life of the lithium ion battery.
Preferably, the polymer coating has a thickness of 0.5 μm to 4 μm and line spacing of 0.5 μm to 10 μm.
In the stripe coating of the present application, the interval of each line is usually 0.5 μm to 10 μm; however, for some special use requirements, the spacing of the lines may be increased to 1m or even more.
Preferably, the gel polymer particles are made of one or a copolymer or a mixture of at least two of polyvinylidene fluoride, polyurethane, polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyacrylamide, polymethyl acrylate, polymethyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone and polytetraethylene glycol diacrylate.
Preferably, the coating slurry includes 30 to 50 parts by weight of the gel polymer particles having the surface grafted with the amino group, 0.3 to 1.5 parts by weight of the condensing agent, 5 to 25 parts by weight of the binder, and 30 to 50 parts by weight of deionized water.
Preferably, the condensing agent is 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and/or N-hydroxysuccinimide.
Preferably, the binder is at least one of polyethylene oxide, polymethyl methacrylate, acrylic and acrylic esters.
Preferably, the base membrane is one or a composite membrane formed by laminating at least two of a polyolefin membrane, a ceramic coating membrane, a non-woven fabric membrane and a polyimide membrane; the ceramic coating diaphragm is formed by coating a polyolefin diaphragm with a ceramic coating.
Preferably, the polyolefin separator is a microporous membrane made of at least one of polyethylene, polypropylene, poly-1-butene and polypentene.
The other side of the application discloses a preparation method of the polymer coating diaphragm, which specifically comprises the following steps,
(1) preparation of gel polymer particles with amino groups grafted on surface
Dispersing gel polymer particles into water to prepare an aqueous dispersion, adding an aminosilane coupling agent accounting for 5-20% of the weight of the gel polymer particles, adjusting the pH value of the system to 7-8, stirring for 0.5-2 hours, centrifuging to remove supernatant, washing at least once with water, centrifuging to obtain precipitate, and drying to obtain the gel polymer particles with the surface grafted with the aminosilane coupling agent, namely the gel polymer particles with the surface grafted with amino; the pH value of the system is adjusted, and oxalic acid and ammonia water are specifically adopted for adjustment in an implementation mode of the application, and a pH meter is used for measurement and monitoring;
(2) preparation of base film with surface grafted with carboxyl
Dissolving 1.0-10 wt% of photosensitizer in a solvent to prepare photosensitizer solution; the photosensitizer can be a conventional photosensitizer, and in an implementation manner of the application, benzophenone is specifically adopted; as the solvent of the photosensitizer, there can be also referred to existing photosensitizers and solvents thereof, such as ethanol, diethyl ether, chloroform, tetrahydrofuran, dimethyl sulfoxide and the like;
dissolving acrylic acid and/or methacrylic acid in water to prepare a monomer solution with the concentration of 10-30 wt%;
immersing a base film into a photosensitizer solution, taking out and drying the base film, irradiating the base film by ultraviolet light, immersing the base film into a monomer solution, taking out the base film from the monomer solution, and irradiating the surface by the ultraviolet light to obtain the base film with surface grafted carboxyl; the purpose of immersing in a photosensitizer solution, ultraviolet irradiation, monomer solution and the like is to graft carboxyl on the surface of a base film, and it can be understood that the time for immersing in the solution and ultraviolet irradiation is not strictly limited, in principle, the base film can be immersed completely or can be immersed for several minutes or tens of minutes, and the ultraviolet irradiation generally only needs to irradiate for several minutes; for example, in one implementation of the present application, the base film is soaked in a photosensitizer solution for 2-10min, taken out and dried, then irradiated with ultraviolet light for 5-10min, then soaked in a monomer solution for 2-10min, and then taken out and irradiated with ultraviolet light for 5-10 min;
(3) preparation of coating slurries
Adding 30-50 parts by weight of gel polymer particles with amino grafted on the surface, 0.3-1.5 parts by weight of condensing agent and 5-25 parts by weight of binder into 30-50 parts by weight of deionized water, and uniformly mixing to obtain the coating slurry;
(4) coating of
And (3) coating the coating slurry prepared in the step (3) on the surface of the base film with the surface grafted with carboxyl by adopting at least one of roll coating, dip coating, blade coating, spray coating, brush coating and extrusion coating, and drying to obtain the polymer coating diaphragm.
Preferably, in the step (1), the aminosilane coupling agent is at least one of 3-aminopropyltrimethoxysilane, 3-aminopropyldimethylsilane, 3-aminopropyltriethoxysilane, 3-aminopropylethoxydimethylsilane, N-methyl-3-aminopropyltriethoxysilane, and N-methyl-3-aminopropyltrimethoxysilane.
Preferably, in the step (4), the drying temperature is 40-80 ℃.
Preferably, the particle size of the gel polymer particles is 0.01 μm. ltoreq. D50. ltoreq.5 μm.
More preferably, the gel polymer particles have a particle size of 0.1 μm. ltoreq. D50. ltoreq.3 μm.
More preferably, the gel polymer particles have a particle size of 0.1 μm. ltoreq. D50. ltoreq.1 μm.
Due to the adoption of the technical scheme, the beneficial effects of the application are as follows:
according to the polymer coating diaphragm, the surfaces of the gel polymer particles and the base film are respectively subjected to grafting modification, and the gel polymer particles are fixed on the surface of the base film by using chemical bonds formed by chemical reaction of carboxyl and amino, so that the cohesiveness and stability of the polymer coating diaphragm are improved; the problems of battery core bulge and battery deformation are solved through a specially designed coating structure distributed in a stripe shape; the polymer coating diaphragm improves the safety performance of the lithium ion battery and prolongs the service life of the lithium ion battery.
Drawings
FIG. 1 is a schematic representation of the structure of a polymer-coated membrane of a striped coating in an embodiment of the present application.
Detailed Description
At present, no good solution is provided for the problems of battery deformation, battery core scrapping and the like caused by expansion and contraction of the battery in the charging and discharging process and battery core bulging.
The structure of the coated separator is improved in an inventive manner, namely, a striped coating layer which is distributed in a line shape along the longitudinal direction (MD) and has the line width of 0.5-10 mu m and the line interval of 0.5-1 m is formed on the base film, namely, as shown in figure 1, a striped coating layer 02 is formed on the surface of the base film 01 along the MD direction. The coating diaphragm of the application enables the polymer coating diaphragm to have better air permeability, and solves the problems of expansion and contraction, battery core bulge and battery deformation; and the stripe coating has higher ionic conductivity and can obviously improve the liquid absorption and liquid retention of the porous base membrane. Meanwhile, the gel polymer particles are further subjected to amino grafting modification, the surface of the base membrane is subjected to carboxyl grafting modification, and the gel polymer particles are fixed on the surface of the base membrane through the reaction of carboxyl and amino; the chemical bond generated by the reaction of the amino and the carboxyl is utilized to enhance the bonding property of the coating, so that the bonding property of the gel polymer coating diaphragm and the positive and negative electrodes is better, the safety performance of the lithium ion battery is further improved, and the service life of the lithium ion battery is prolonged.
The present application is described in further detail below with reference to specific embodiments and the attached drawings. The following examples are intended to be illustrative of the present application only and should not be construed as limiting the present application.
Example 1
In this example, a 16 μm polypropylene microporous membrane from Shenzhen Zhongxing New Material technology corporation was used as a base membrane, and a striped coating was applied to the surface of the base membrane in the longitudinal direction using a polyvinylidene fluoride-hexafluoropropylene gel polymer coating slurry. Wherein, the surface of the polyvinylidene fluoride-hexafluoropropylene particles is modified with amino, and the surface of the base membrane is modified with carboxyl. The preparation method comprises the following steps:
(1) aminosilane coupling agent modified gel polymer particle surface
Stirring and heating 6.0g of polyvinylidene fluoride-hexafluoropropylene aqueous dispersion with the average particle size of 200nm to 50 ℃, adjusting the pH value to 7.5, slowly adding 1.2g of 3-aminopropyltriethoxysilane, reacting for 1 hour to obtain polyvinylidene fluoride-hexafluoropropylene with the surface grafted with the 3-aminopropyltriethoxysilane, and drying in vacuum at room temperature for later use. In the polyvinylidene fluoride-hexafluoropropylene surface-grafted with 3-aminopropyltriethoxysilane of this example, the grafted 3-aminopropyltriethoxysilane contains an amino group.
(2) Grafting carboxyl on the surface of a base film
Dissolving 2 wt% of benzophenone in tetrahydrofuran to prepare a benzophenone solution, placing a diaphragm in the benzophenone solution to soak for 2min, taking out and drying, and performing ultraviolet illumination for 5 min; and then soaking the diaphragm into a deionized water solution with the acrylic acid concentration of 20% for 2min, taking out, irradiating by ultraviolet light for 5min, and drying to obtain the base film with the surface grafted with carboxyl.
(3) Coating of base film surface
Adding 30 parts by weight of the surface modified amino polyvinylidene fluoride-hexafluoropropylene particles prepared in the step (1), 1 part by weight of EDC and 15 parts by weight of polyethylene oxide into 45 parts by weight of deionized water, and stirring for 1 hour by a sand mill to obtain coating slurry.
Coating the coating slurry prepared in the embodiment on the base film with the surface grafted with carboxyl prepared in the step (2) in a roll coating mode, coating on two sides, drying at 50 ℃, and obtaining a gel polymer coating diaphragm with the thickness of 18 mu m, wherein the coating thickness of each side is 1 mu m; the coating was controlled to form stripe-like coatings with a line width of 2 μm and a line interval of 100 μm on both sides.
Example 2
In this example, a 12 μm polyethylene microporous film from Shenzhen Zhongxing New Material technology corporation was used as a base film, and a striped coating was applied to the surface of the base film in the longitudinal direction using a gel polymer coating slurry of polymethyl methacrylate. Wherein, the surface of the polymethyl methacrylate is modified with amino, and the surface of the basement membrane is modified with carboxyl. The preparation method comprises the following steps:
(1) aminosilane coupling agent modified gel polymer particle surface
8.0g of an aqueous dispersion of polymethyl methacrylate having an average particle diameter of 150nm was stirred and heated to 50 ℃ to adjust the pH to 7.5, 1g of 3-aminopropyltriethoxysilane was slowly added to the mixture to react for 1 hour to obtain polymethyl methacrylate having 3-aminopropyltriethoxysilane grafted on the surface, and the mixture was vacuum-dried at room temperature.
(2) Grafting carboxyl on the surface of a base film
Dissolving 2 wt% of benzophenone in tetrahydrofuran to prepare a benzophenone solution, placing a diaphragm in the benzophenone solution to soak for 2min, taking out and drying, and performing ultraviolet illumination for 5 min; and then soaking the diaphragm into a deionized water solution with acrylic acid concentration of 15% for 2min, taking out, irradiating by ultraviolet light for 5min, and drying to obtain the base film with the surface grafted with carboxyl.
(3) Coating of base film surface
Adding 49 parts of the surface-modified amino polymethyl methacrylate particles prepared in the step (1), 1.5 parts of EDC and 20 parts of acrylic acid hydrosol into 30 parts of deionized water, and stirring for 1 hour by a sand mill to obtain coating slurry.
Coating the coating slurry prepared in the embodiment on the base film with the surface grafted with carboxyl prepared in the step (2) in a roller coating mode, coating on two sides, drying in a 45 ℃ oven, and obtaining a gel polymer coating diaphragm with the thickness of 15.8 mu m, wherein the coating thickness of each side is 1.9 mu m; the coating was controlled to form stripe-like coatings with a line width of 2 μm and a line interval of 100 μm on both sides.
Comparative experiment 1
Comparative analysis was carried out using the 16 μm polypropylene microporous membrane of example 1 as comparative test 1.
Comparative experiment 2
Comparative analysis was performed using the 12 μm polyethylene microporous membrane of example 2 as comparative test 2.
Comparative experiment 3
A polymer coating diaphragm with the thickness of 18 mu m, which is a product model ZP18 of Shenzhen Zhongxing New Material technology GmbH, is adopted as a comparison test 3 for comparison analysis, wherein the polymer coating diaphragm with the thickness of 18 mu m takes a polypropylene microporous membrane with the thickness of 16 mu m as a base membrane, and a polyvinylidene fluoride-hexafluoropropylene coating with the thickness of 1 mu m is coated on both sides of the polymer coating diaphragm normally in a full covering manner. Compared with the example 1, the test is different in the covering mode of the coating, the example 1 adopts a stripe-shaped coating, and the test is normal film-type covering, namely the coating is a film and covers two surfaces of the base film in a normal mode; in addition, the surface of the polymer particles of this test was not subjected to amino grafting, nor was the surface of the base film subjected to carboxyl grafting.
Comparative experiment 4
A polymer coating membrane with the thickness of 14 microns and produced by Shenzhen Zhongxing New Material technology corporation product model ZW14 is adopted as a comparative test 4 for comparative analysis, wherein the polymer coating membrane with the thickness of 14 microns takes a polyethylene microporous membrane with the thickness of 12 microns as a base membrane, and a polymethyl methacrylate coating with the thickness of 1 micron is normally coated on the two sides of the polymer coating membrane with the thickness of 14 microns. Compared with the example 2, the difference of the test is that the coating is covered in a different way, the example 2 adopts a stripe-shaped coating, and the test is a normal island-shaped coating, namely, the coating is distributed in an island shape and is covered on two surfaces of the base film in a normal way; in addition, the surface of the polymer particles of this test was not subjected to amino grafting, nor was the surface of the base film subjected to carboxyl grafting.
The polymer-coated separator or base film of the above examples 1, 2, comparative experiments 1 to 4 was subjected to thickness (μm), air permeability value (s/100mL), peel strength (N/m), positive electrode dry adhesive strength (N/m), negative electrode dry adhesive strength (N/m), and positive electrode wet adhesive strength (N/m) tests. The specific test method is as follows:
the thickness testing method is carried out by referring to GB/T6672-2001, a Mark thickness gauge with a flat contact head is adopted for measurement, the gauge is calibrated and cleared before measurement, the contact surface is kept clean, one point is taken along the TD direction of the film every 5cm for measurement, and the average value of 5 points is measured to be the thickness of the film.
And (3) testing the peel strength: 5 pieces of a sample with the length of 80mm multiplied by the width of 10mm are cut out from the diaphragm, the coated surface is fixed on a smooth and clean stainless steel sheet by a double-sided adhesive tape, one end of the stainless steel sheet is fixed on a universal tensile machine, peeling is carried out at 180 degrees at a constant speed of 10mm/min, and the experiment is repeated for 5 times to obtain an average value.
And (3) testing the air permeability value: reference is made to GB/T458-.
Dry adhesive strength (N/m) test of positive and negative electrodes: cutting a sample with the width of 20mm multiplied by the length of 80mm from the diaphragm and the pole piece, pressing the sample on a hot press, fixing one end of the diaphragm and one end of the pole piece on a universal tensile machine, peeling the sample at 180 degrees at a constant speed of 10mm/min, and repeating the experiment for 5 times to obtain an average value.
The wet adhesion strength (N/m), namely the adhesive force after winding the anode, the cathode and the diaphragm and soaking the electrolyte, is tested by the following specific test method: cutting a sample with the width of 63.5mm from the diaphragm, manually winding the sample into a battery, standing for 0.5h after liquid injection, disassembling the battery after hot pressing by a hot press, a, observing the adhesion tightness of the diaphragm and the pole piece, and observing the amount of the active substances adhered to the negative pole piece; b. a sample of 20mm multiplied by 80mm is cut out, one end of the diaphragm and one end of the pole piece are fixed on a universal tensile machine, peeling is carried out at 180 degrees at a constant speed of 10mm/min, the experiment is repeated for 5 times, and the average value is obtained, so that the wet adhesion strength (N/m) of the pole piece is obtained.
The results of the tests are shown in Table 1.
Table 1 separator performance test results
The results in table 1 show that the polymer separators of examples 1 and 2 have good air permeability and peel strength, and the adhesion of the polymer separators to the positive and negative electrodes is equivalent to that of the same type of separators commercially available. In particular, in terms of peel strength, example 1 is significantly better than comparative test 3 of the same type, and example 2 is significantly better than comparative test 4 of the same type; the polymeric membranes of examples 1 and 2 also outperformed the same type of commercial product in terms of gas permeability values. Therefore, the polymer coating separators of embodiments 1 and 2 have better air permeability and peel strength, can solve the problems of cell bulging and battery deformation, improve the safety performance of the lithium ion battery, and prolong the service life of the lithium ion battery.
In addition, the coating of comparative test 4 is distributed in island shape on the surface of the base film, so the air permeability value is less increased on the basis of the base film. The increase in permeability is related to the coating amount/coating thickness in addition to the morphology of the coating, and is generally synchronized with the coating amount increase rate, the total thickness of the coating of example 2 is 3.8 μm, the total thickness of the coating of comparative test 4 is 2 μm, and according to the increase in permeability of the comparative test, the permeability of example 2 should be around 275, and actually the permeability of example 2 is 260, so the increase in permeability of example 2 is relatively small.
Example 3
In this example, based on the above tests and comparison, stripe design of the coating layer was further tested, that is, stripe coating layers with different line widths and different line intervals were formed by the same coating method as in example 1 based on the base film and the coating slurry in example 1, and the coating thickness was the same as in example 1, and the specific tests were as follows:
test 1: the width of the lines is 0.5 μm, and the interval between the lines is 0.5 μm;
test 2: the width of the lines is 2 μm, and the line interval is 2 μm;
test 3: the width of the lines is 4 μm, and the line interval is 4 μm;
test 4: the width of the lines is 6 μm, and the line interval is 8 μm;
test 5: the width of the lines is 8 μm, and the line interval is 10 μm;
test 6: the line width is 10 μm, and the line interval is 10 μm;
test 7: the line width is 12 μm, and the line interval is 10 μm;
test 8: the line width was 14 μm and the line spacing was 12 μm.
In this example eight coated membranes of different line widths and spacings were prepared and tested for peel strength and air permeability, respectively, according to the eight tests described above. The results show that the eight polymer-coated membranes of this example all have better peel strengths, comparable to example 1; the breathability is inversely related to the area covered by the coating, i.e. the wider the lines of the coating, the smaller the spacing, the poorer the breathability. Therefore, analysis has shown that a preferred embodiment is a coating with line widths of 0.5 μm to 10 μm and line spacings of 0.5 μm to 10 μm. Line widths too small, e.g., less than 0.5 μm, can affect the performance of the coating; if the line width is too wide, for example, greater than 10 μm, the gas permeability is not improved, and the problems of cell bulge and battery deformation are not solved. As for the line interval, similarly, the interval is too small, which is not favorable for improving the air permeability; too large a spacing will affect the properties of the coating itself.
However, in the actual production process, the line spacing can be large according to special use requirements, for example, the applicant designs a stripe-shaped coating diaphragm with the line spacing of 1m according to customer requirements, but the performance of the corresponding coating is affected.
The foregoing is a more detailed description of the present application in connection with specific embodiments thereof, and it is not intended that the present application be limited to the specific embodiments thereof. It will be apparent to those skilled in the art from this disclosure that many more simple derivations or substitutions can be made without departing from the spirit of the disclosure.
Claims (10)
1. A polymer-coated separator having an improved structure, comprising a base film and a polymer coating layer coated on at least one surface of the base film, wherein: the polymer coating is distributed on the base film in a linear shape along the longitudinal direction, the width of the linear is 0.5-10 mu m, and the interval of the linear is 0.5-1 m;
and the polymer coating layer is formed by coating the coating slurry prepared by the gel polymer particles with the amino groups grafted on the surface of the base film with the carboxyl groups grafted on the surface, and the gel polymer particles are fixed on the surface of the base film through the reaction of the carboxyl groups and the amino groups.
2. The polymer-coated separator of claim 1, wherein: the polymer coating has a thickness of 0.5-4 μm and the line spacing is 0.5-10 μm.
3. The polymer-coated separator of claim 1, wherein: the gel polymer particles are made of one or a copolymer or a mixture of at least two of polyvinylidene fluoride, polyurethane, polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyacrylamide, polymethyl acrylate, polymethyl methacrylate, polyvinyl acetate, polyvinyl pyrrolidone and polytetraethylene glycol diacrylate.
4. A polymer coated separator as claimed in any one of claims 1 to 3, wherein: the coating slurry comprises 30-50 parts by weight of gel polymer particles with amino groups grafted on the surface, 0.3-1.5 parts by weight of condensing agent, 5-25 parts by weight of binder and 30-50 parts by weight of deionized water.
5. The polymer-coated membrane of claim 4, wherein: the condensing agent is 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and/or N-hydroxysuccinimide.
6. The polymer-coated membrane of claim 4, wherein: the binder is at least one of polyethylene oxide, polymethyl methacrylate, acrylic acid and acrylate.
7. The polymer-coated separator of claim 1, wherein: the base membrane is one or a composite membrane formed by laminating at least two of a polyolefin membrane, a ceramic coating membrane, a non-woven fabric membrane and a polyimide membrane; the ceramic coating diaphragm is formed by coating a polyolefin diaphragm with a ceramic coating;
preferably, the polyolefin separator is a microporous membrane prepared from at least one of polyethylene, polypropylene, poly-1-butene and polypentene.
8. The method for producing a polymer-coated separator according to any one of claims 1 to 7, wherein: comprises the following steps of (a) carrying out,
(1) preparation of gel polymer particles with amino groups grafted on surface
Dispersing gel polymer particles into water to prepare an aqueous dispersion, adding an aminosilane coupling agent accounting for 5-20% of the weight of the gel polymer particles, adjusting the pH value of the system to 7-8, stirring for 0.5-2 hours, centrifuging to remove supernatant, washing at least once with water, centrifuging to obtain precipitate, and drying to obtain the gel polymer particles with the surface grafted with the aminosilane coupling agent, namely the gel polymer particles with the surface grafted with amino;
(2) preparation of base film with surface grafted with carboxyl
Dissolving 1.0-10 wt% of photosensitizer in a solvent to prepare photosensitizer solution;
dissolving acrylic acid and/or methacrylic acid in water to prepare a monomer solution with the concentration of 10-30 wt%;
immersing a base film into a photosensitizer solution, taking out and drying the base film, irradiating the base film by ultraviolet light, immersing the base film into a monomer solution, taking out the base film from the monomer solution, and irradiating the surface by the ultraviolet light to obtain the base film with surface grafted carboxyl;
(3) preparation of coating slurries
Adding 30-50 parts by weight of gel polymer particles with amino grafted on the surface, 0.3-1.5 parts by weight of condensing agent and 5-25 parts by weight of binder into 30-50 parts by weight of deionized water, and uniformly mixing to obtain the coating slurry;
(4) coating of
And (3) coating the coating slurry prepared in the step (3) on the surface of the base film with the surface grafted with carboxyl by adopting at least one of roll coating, dip coating, blade coating, spray coating, brush coating and extrusion coating, and drying to obtain the polymer coating diaphragm.
9. The method of claim 8, wherein: in the step (1), the aminosilane coupling agent is at least one of 3-aminopropyltrimethoxysilane, 3-aminopropyldimethylsilane, 3-aminopropyltriethoxysilane, 3-aminopropylethoxydimethylsilane, N-methyl-3-aminopropyltriethoxysilane and N-methyl-3-aminopropyltrimethoxysilane;
preferably, in the step (4), the drying temperature is 40-80 ℃.
10. The production method according to claim 8 or 9, characterized in that: the particle size of the gel polymer particles is not less than 0.01 mu m and not more than D50 and not more than 5 mu m; preferably 0.1 mu m < D50 < 3 mu m; more preferably 0.1. mu.m.ltoreq.D 50.ltoreq.1. mu.m.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
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| CN113555645A (en) * | 2021-06-01 | 2021-10-26 | 惠州锂威新能源科技有限公司 | Modified diaphragm, lithium ion battery and power consumption device |
| CN115411459A (en) * | 2022-09-27 | 2022-11-29 | 惠州锂威新能源科技有限公司 | Diaphragm, battery and preparation method of diaphragm |
| CN116826308A (en) * | 2023-08-31 | 2023-09-29 | 天津市捷威动力工业有限公司 | Composite diaphragm, preparation method thereof and secondary battery |
| WO2024000580A1 (en) * | 2022-07-01 | 2024-01-04 | 宁德时代新能源科技股份有限公司 | Separator, secondary battery, battery module, battery pack and electric device |
| WO2024059996A1 (en) * | 2022-09-20 | 2024-03-28 | 宁德时代新能源科技股份有限公司 | Composite film and preparation method therefor, battery module, battery pack, and electric device |
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Application publication date: 20200410 |