CN113161692A - Ceramic coating, ceramic coating diaphragm and preparation method and application thereof - Google Patents
Ceramic coating, ceramic coating diaphragm and preparation method and application thereof Download PDFInfo
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- 238000005524 ceramic coating Methods 0.000 title claims abstract description 116
- 238000002360 preparation method Methods 0.000 title abstract description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 74
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- 239000002270 dispersing agent Substances 0.000 claims abstract description 40
- 239000011256 inorganic filler Substances 0.000 claims abstract description 39
- 229910003475 inorganic filler Inorganic materials 0.000 claims abstract description 39
- 239000004094 surface-active agent Substances 0.000 claims abstract description 37
- 239000002562 thickening agent Substances 0.000 claims abstract description 37
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 28
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 28
- 238000004519 manufacturing process Methods 0.000 claims abstract description 22
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- APSBXTVYXVQYAB-UHFFFAOYSA-M sodium docusate Chemical compound [Na+].CCCCC(CC)COC(=O)CC(S([O-])(=O)=O)C(=O)OCC(CC)CCCC APSBXTVYXVQYAB-UHFFFAOYSA-M 0.000 claims description 5
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- 229910001593 boehmite Inorganic materials 0.000 claims description 4
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- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 claims description 4
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- WURBFLDFSFBTLW-UHFFFAOYSA-N benzil Chemical class C=1C=CC=CC=1C(=O)C(=O)C1=CC=CC=C1 WURBFLDFSFBTLW-UHFFFAOYSA-N 0.000 claims description 3
- ISAOCJYIOMOJEB-UHFFFAOYSA-N benzoin Chemical class C=1C=CC=CC=1C(O)C(=O)C1=CC=CC=C1 ISAOCJYIOMOJEB-UHFFFAOYSA-N 0.000 claims description 3
- NBVXSUQYWXRMNV-UHFFFAOYSA-N fluoromethane Chemical compound FC NBVXSUQYWXRMNV-UHFFFAOYSA-N 0.000 claims description 3
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- 229920002635 polyurethane Polymers 0.000 claims description 3
- 239000004814 polyurethane Substances 0.000 claims description 3
- YRHRIQCWCFGUEQ-UHFFFAOYSA-N thioxanthen-9-one Chemical class C1=CC=C2C(=O)C3=CC=CC=C3SC2=C1 YRHRIQCWCFGUEQ-UHFFFAOYSA-N 0.000 claims description 3
- 150000008366 benzophenones Chemical class 0.000 claims description 2
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- 230000001070 adhesive effect Effects 0.000 abstract description 49
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- 238000000576 coating method Methods 0.000 abstract description 22
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- 239000008367 deionised water Substances 0.000 description 8
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 7
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- 230000002349 favourable effect Effects 0.000 description 4
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- 229920000098 polyolefin Polymers 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- CHIHQLCVLOXUJW-UHFFFAOYSA-N benzoic anhydride Chemical compound C=1C=CC=CC=1C(=O)OC(=O)C1=CC=CC=C1 CHIHQLCVLOXUJW-UHFFFAOYSA-N 0.000 description 3
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- 238000005054 agglomeration Methods 0.000 description 2
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
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- 239000006087 Silane Coupling Agent Substances 0.000 description 1
- 238000003848 UV Light-Curing Methods 0.000 description 1
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- 230000004075 alteration Effects 0.000 description 1
- RWCCWEUUXYIKHB-UHFFFAOYSA-N benzophenone Chemical compound C=1C=CC=CC=1C(=O)C1=CC=CC=C1 RWCCWEUUXYIKHB-UHFFFAOYSA-N 0.000 description 1
- 239000012965 benzophenone Substances 0.000 description 1
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- KPUWHANPEXNPJT-UHFFFAOYSA-N disiloxane Chemical class [SiH3]O[SiH3] KPUWHANPEXNPJT-UHFFFAOYSA-N 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
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Images
Classifications
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Cell Separators (AREA)
Abstract
The invention discloses a ceramic coating, a ceramic coating diaphragm, a preparation method and application thereof, wherein the ceramic coating comprises the following components: the adhesive comprises an inorganic filler, a first adhesive, a second adhesive, a photoinitiator, a thickening agent, a dispersing agent and a surfactant, wherein the first adhesive is a water-soluble acrylic copolymer; the second binder includes at least one of an aqueous acrylate copolymer emulsion, polyvinyl alcohol, and polyvinyl pyrrolidone. This ceramic coating is high temperature resistant better, and the water content is low, and its surface forms fine hydrophobic structure, and is better with the affinity of base film for the diaphragm that the coating has this ceramic coating has excellent thermal stability, wholeness and low water content, has reduced the water absorption risk of ceramic coating diaphragm in production, transportation and lithium cell manufacturing procedure, thereby has guaranteed the electrical property and the security performance of lithium cell.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a ceramic coating, a ceramic coating diaphragm, and preparation methods and applications thereof.
Background
With the gradual expansion of the application of lithium ion batteries in the field of passenger cars and the continuous improvement of energy density and battery voltage, the traditional polyolefin diaphragm can not meet the high safety requirements of users on the lithium ion batteries at present, and the inorganic coating polyolefin diaphragm after ceramic treatment has greatly improved oxidation resistance, high temperature resistance and safety, and becomes the mainstream of the lithium ion battery technology at present. However, the size stability of the current commercial ceramic-coated polyolefin separator is still poor at high temperature (30% -80% of 1h thermal shrinkage at 150 ℃), and the water content of the ceramic-coated separator is generally high, which in turn can lead to the increase of the baking or drying time and cost of the battery core for subsequent battery users.
CN108336277A with specific surface area less than 8m2The alumina coating layer is formed by preparing/g alumina powder and a binder with a cross-linked structure, so that the moisture content of the separator is below 500 ppm. However, the time for drying and crosslinking the adhesive at high temperature (50 ℃) is longer, and the production efficiency is lower.
CN104893541A obviously improves the wettability of the diaphragm by adding hydrophilic polymer, realizes the multi-functionalization of the coating property by compounding nano particles and UV curing resin, improves the thermal stability, the mechanical property and the ionic conductivity of the diaphragm, and has important significance for improving the safety and the service life of the power battery. However, the invention adopts an organic solvent system, which is not an environment-friendly aqueous system, and the preparation process of the applied silane coupling agent modified nanoparticles (with the particle size of 10-100nm) is complex and the cost is extremely expensive.
CN110581247A solves the problems that the thermal dimensional stability and the safety performance of the ceramic coating diaphragm are not ideal enough and the water content is high in the prior art by using the water-based acrylic emulsion modified by organic silicon grafting as the main adhesive to prepare the ceramic composite diaphragm. However, the adhesive in the invention adopts the water-based polyacrylate emulsion, the film forming property and the integrity of the ceramic coating are inevitably poor, and the composite diaphragm with poor integrity cannot support the shrinkage of PE when the ceramic coating is thinner and the PE is melted at higher temperature.
Therefore, the existing ceramic coated separator is to be improved.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, an object of the present invention is to provide a ceramic coating, a ceramic coated diaphragm, and a preparation method and an application thereof, wherein the ceramic coating has good high temperature resistance and low water content, a good hydrophobic structure is formed on the surface of the ceramic coating, and the affinity with a base film is good, such that the diaphragm coated with the ceramic coating has excellent thermal stability, integrity and low water content, and the risk of water absorption of the ceramic coated diaphragm in production, transportation and lithium battery manufacturing processes is reduced, thereby ensuring the electrical performance and safety performance of the lithium battery.
In one aspect of the invention, a ceramic coating is provided. According to an embodiment of the invention, the ceramic coating comprises: the adhesive comprises an inorganic filler, a first adhesive, a second adhesive, a photoinitiator, a thickening agent, a dispersing agent and a surfactant, wherein the first adhesive is a water-soluble acrylic copolymer; the second binder includes at least one of an aqueous acrylate copolymer emulsion, polyvinyl alcohol, and polyvinyl pyrrolidone.
According to the ceramic coating provided by the embodiment of the invention, the inorganic filler can improve the heat shrinkage of the diaphragm, the water-soluble acrylic copolymer is used as the first adhesive, the photoinitiator is added, and after the photoinitiator is irradiated by light, the photoinitiator absorbs the energy of the light to generate a plurality of active free radicals, and the active free radicals can initiate the cross-linking and curing of the water-soluble acrylic copolymer to form an interpenetrating network structure, so that the high temperature resistance of the ceramic coating can be improved, and polar water-absorbing groups in the ceramic coating can be consumed in the cross-linking and curing process, so that the water content of the ceramic coating is reduced, and a good hydrophobic structure is formed on the surface of the ceramic coating. Secondly, because the base film is nonpolar and has low surface energy, the affinity of the ceramic coating and the base film can be improved by adding at least one of water-based acrylate copolymer emulsion, polyvinyl alcohol and polyvinylpyrrolidone as a second adhesive, the problem of insufficient peeling strength between the ceramic coating and the base material by using the first adhesive alone is also solved, and the problem of insufficient thermal stability of the ceramic coating by using the second adhesive alone is also solved by adding the first adhesive, and the two are mutually complemented. In addition, the dispersant can prevent the particles of the inorganic filler from agglomerating, the thickener can improve the viscosity of the ceramic slurry to keep the ceramic slurry in a uniform and stable suspension state, and the surfactant can increase the interfacial tension of the ceramic particles and is more favorable for the uniformity of the thickness of the coating. To sum up, the ceramic coating of this application is high temperature resistant better, and the water content is low, and its surface forms fine hydrophobic structure, and better with the affinity of base film for the diaphragm that the coating has this ceramic coating has excellent thermal stability, wholeness and low water content, has reduced the water absorption risk of ceramic coating diaphragm in production, transportation and lithium cell manufacturing process, thereby has guaranteed the electrical property and the security performance of lithium cell.
In addition, the ceramic coating according to the above embodiment of the present invention may also have the following additional technical features:
in some embodiments of the invention, the ceramic coating comprises: 40 to 50 parts by weight of the inorganic filler, 1 to 4 parts by weight of the first binder, 0.2 to 1.5 parts by weight of the second binder, 0.005 to 0.2 parts by weight of the photoinitiator, 0.05 to 2 parts by weight of the thickener, 0.05 to 0.5 parts by weight of the dispersant, and 0.01 to 0.1 parts by weight of the surfactant. From this, can guarantee that the diaphragm that coats this ceramic coating has excellent thermal stability, wholeness and low water content, reduce the ceramic coating diaphragm in production, transportation and lithium cell manufacturing procedure absorb water the risk to the electrical property and the security performance of lithium cell have been guaranteed.
In some embodiments of the present invention, the first binder comprises at least one of a photo-curable aqueous fluorine-containing polyacrylic resin, a photo-curable silicone-modified polyacrylic resin, a photo-curable aqueous epoxy polyacrylic resin, and a photo-curable urethane acrylic resin. Therefore, the high temperature resistance of the ceramic coating can be improved, and the water content of the ceramic coating can be reduced.
In some embodiments of the present invention, the inorganic filler has an average particle size of 200 to 1500nm, preferably 400 to 1000 nm. This can improve the heat shrinkability of the separator.
In some embodiments of the present invention, the inorganic filler comprises at least one of aluminum oxide, boehmite, barium sulfate, and magnesium hydroxide. This can improve the heat shrinkability of the separator.
In some embodiments of the present invention, the photoinitiator comprises at least one of a benzoin derivative, an acetophenone derivative, a thioxanthone derivative, a benzophenone-based derivative, and a benzil derivative. Therefore, the high temperature resistance of the ceramic coating can be improved, and the water content of the ceramic coating can be reduced.
In some embodiments of the invention, the thickener comprises at least one of a carboxymethyl cellulose-based thickener and polyvinyl alcohol. This can increase the viscosity of the ceramic slurry and maintain a uniform and stable suspension state.
In some embodiments of the present invention, the dispersant comprises at least one of a polyacrylate-based dispersant, a carboxymethyl cellulose-based dispersant, and polyvinyl alcohol. Thereby, agglomeration of the particles of the inorganic filler can be prevented.
In some embodiments of the invention, the surfactant comprises at least one of polyethylene glycol, docusate sodium, polyether modified organosiloxane, and fluorocarbon type surfactant. Therefore, the interfacial tension of the ceramic particles can be increased, and the uniformity of the coating thickness is more facilitated.
In a second aspect of the invention, a ceramic coated separator is provided. According to an embodiment of the present invention, the ceramic coated separator includes a base film and the ceramic coating layer described above, which is formed on at least one side surface of the base film. Therefore, the ceramic coating diaphragm has excellent thermal stability, integrity and low water content, and the water absorption risk of the ceramic coating diaphragm in production, transportation and lithium battery manufacturing procedures is lower, so that the electrical property and the safety performance of the lithium battery are ensured.
In some embodiments of the present invention, the base film comprises at least one of a polyethylene separator, a polypropylene separator, and a polypropylene/polyethylene/polypropylene three-layer co-extruded separator.
In some embodiments of the present invention, the ceramic coating has a thickness of 1 to 5 microns. Therefore, the electrical property and the safety performance of the lithium battery are ensured.
In a third aspect of the present invention, the present invention provides a method of preparing the above ceramic-coated separator. According to an embodiment of the invention, the method comprises:
(1) mixing an inorganic filler, a first binder, a second binder, a photoinitiator, a thickener, a dispersant, a surfactant, and water with stirring to obtain a ceramic slurry;
(2) the ceramic slurry is applied on at least one side surface of a base film and dried, photocured, to obtain a ceramic-coated separator.
According to the method of preparing the above ceramic-coated separator of the embodiment of the present invention, the inorganic filler, the first binder, the second binder, the photoinitiator, the thickener, the dispersant, the surfactant, and water are mixed with stirring to obtain a ceramic slurry, wherein the inorganic filler can improve the contractibility of the thermal diaphragm, the second adhesive comprising at least one of the water-based acrylate copolymer emulsion, the polyvinyl alcohol and the polyvinylpyrrolidone can be added to improve the affinity of the ceramic coating and the base film, the method has the advantages that the integrity of the ceramic coating diaphragm is improved, the dispersing agent is added to prevent the particles of the inorganic filler from agglomerating, the thickening agent is added to improve the viscosity of the ceramic slurry to keep the ceramic slurry in a uniform and stable suspension state, the surfactant is added to increase the interfacial tension of the ceramic particles, the uniformity of the thickness of the coating is facilitated, and the added water as a solvent is more environment-friendly compared with an organic solvent system. And then the ceramic slurry is applied to at least one side surface of the base film, and is dried and photocured, after the photoinitiator is irradiated by light, the photoinitiator absorbs the energy of the light to generate a plurality of active free radicals, and the active free radicals can initiate the crosslinking and curing of the water-soluble acrylic copolymer serving as the first adhesive to form an interpenetrating network structure, so that the high temperature resistance of the ceramic coating can be improved, polar water-absorbing groups in the ceramic coating can be consumed in the crosslinking and curing process, the water content of the ceramic coating is reduced, a good hydrophobic structure is formed on the surface, and the ceramic coating diaphragm can be obtained after photocuring. In summary, the ceramic coating diaphragm prepared by the method has excellent thermal stability, integrity and low water content, and the risk of water absorption in production, transportation and lithium battery manufacturing procedures is low, so that the electrical performance and safety performance of the lithium battery are ensured.
In some embodiments of the present invention, in step (1), the water, the dispersant, the thickener, and the inorganic filler are mixed and then sanded with stirring, and then the first binder, the second binder, the photoinitiator, and the surfactant are added, mixed uniformly, and then filtered to obtain the ceramic slurry. From this, the sanding can make inorganic filler dispersion more even, keeps even stable suspended state more easily, filters and can shorten subsequent drying time.
In some embodiments of the present invention, the water has a resistivity of not less than 8 M.OMEGA.cm and is added in an amount of 50 to 80 parts by weight.
In a fourth aspect of the present invention, a lithium battery is provided. According to an embodiment of the present invention, the lithium battery has the ceramic-coated separator described above or the ceramic-coated separator prepared by the method described above. Thus, the lithium battery having the ceramic-coated separator, which is excellent in thermal stability and integrity, and low in water content and risk of water absorption, has excellent electrical properties and safety.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a schematic structural view of a ceramic coated membrane according to one embodiment of the invention;
FIG. 2 is a schematic structural view of a ceramic coated membrane according to yet another embodiment of the present invention;
FIG. 3 is a schematic flow diagram of a method of making a ceramic coated membrane according to one embodiment of the invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In a first aspect of the invention, a ceramic coating is presented. According to an embodiment of the present invention, the ceramic coating layer includes an inorganic filler, a first binder, a second binder, a photoinitiator, a thickener, a dispersant, and a surfactant, wherein the first binder is a water-soluble acrylic copolymer, and the second binder includes at least one of an aqueous acrylate copolymer emulsion, polyvinyl alcohol, and polyvinyl pyrrolidone.
The inventor finds that the inorganic filler can improve the heat shrinkage of the diaphragm, the water-soluble acrylic copolymer is used as the first adhesive, the photoinitiator is added, after the photoinitiator is irradiated by light, the photoinitiator absorbs the energy of the light to generate a plurality of active free radicals, the active free radicals can initiate the cross-linking and curing of the water-soluble acrylic copolymer to form an interpenetrating network structure, so that the high temperature resistance of the ceramic coating can be improved, and the polar water-absorbing groups in the ceramic coating can be consumed in the cross-linking and curing process, so that the water content of the ceramic coating is reduced, and a good hydrophobic structure is formed on the surface of the ceramic coating. Secondly, because the base film is nonpolar and has low surface energy, the affinity of the ceramic coating and the base film can be improved by adding at least one of water-based acrylate copolymer emulsion, polyvinyl alcohol and polyvinylpyrrolidone as a second adhesive, the problem of insufficient peeling strength of the ceramic coating and the base material which are singly used by the first adhesive is also solved by adding the second adhesive, and the problem of insufficient thermal stability of the ceramic coating which is singly used by the second adhesive is also solved by adding the first adhesive, and the first adhesive and the second adhesive are mutually complemented. In addition, the dispersant can prevent the particles of the inorganic filler from agglomerating, the thickener can improve the viscosity of the ceramic slurry to keep the ceramic slurry in a uniform and stable suspension state, and the surfactant can increase the interfacial tension of the ceramic particles and is more favorable for the uniformity of the thickness of the coating. To sum up, the ceramic coating of this application is high temperature resistant better, and the water content is low, and its surface forms fine hydrophobic structure, and better with the affinity of base film for the diaphragm that the coating has this ceramic coating has excellent thermal stability, wholeness and low water content, has reduced the water absorption risk of ceramic coating diaphragm in production, transportation and lithium cell manufacturing process, thereby has guaranteed the electrical property and the security performance of lithium cell.
Further, the ceramic coating includes: 40-50 parts by weight of inorganic filler, 1-4 parts by weight of first adhesive, 0.2-1.5 parts by weight of second adhesive, 0.005-0.2 parts by weight of photoinitiator, 0.05-2 parts by weight of thickening agent, 0.05-0.5 parts by weight of dispersant and 0.01-0.1 parts by weight of surfactant. The inventors have found that when the proportion of the inorganic filler is too low, the proportion of the organic material such as a binder becomes too high, and the air permeability of the separator increases, whereby the air permeability becomes poor and the lithium ion transport resistance becomes large; on the other hand, if the ratio of the inorganic filler is too high, the ratio of the organic material such as the binder is too low, the peel strength of the ceramic coating is reduced, and the inorganic filler cannot be firmly attached to the base film. Meanwhile, if the proportion of the first adhesive is too high, the air permeability value of the ceramic coating is increased; if the proportion is too low, the crosslinking curing degree of the coating is insufficient, and the high-temperature resistance of the diaphragm cannot be effectively improved. In addition, if the proportion of the second adhesive is too high, the air permeability of the ceramic coating is increased, the air permeability is poor, and the lithium ion transmission resistance is increased; if the ratio of the second binder is too low, the peel strength of the ceramic coating is reduced. If the addition amount of the photoinitiator is too small, the crosslinking curing degree of the coating is insufficient, and the high-temperature resistance of the diaphragm cannot be effectively improved; on the other hand, if the amount of the photoinitiator added is too large, the crosslinking and curing degree of the coating is too high, and the gas permeability is deteriorated, and the lithium ion transport resistance becomes large. If the dosage of the dispersant is too low, the inorganic filler is not easy to disperse; and if the amount of the dispersant is too high, the cost is increased. If the amount of the thickener is too low, the storage stability of the ceramic slurry is poor; if the amount of the thickener is too high, the viscosity increases to be unfavorable for coating production, and the water content increases. If the dosage of the surfactant is too high, the air permeability value of the ceramic coating is increased, and the air permeability is deteriorated; if the amount of the surfactant is too low, the ceramic slurry cannot be spread rapidly on the base film during coating, thereby reducing the production efficiency. Thus, with the ceramic coating composition of the present application, the resulting ceramic coated diaphragm can be guaranteed to have excellent gas permeability, integrity and thermal stability, as well as low water content.
It should be noted that, the skilled person can select specific types of the first binder, the inorganic filler, the photoinitiator, the thickener, the dispersant and the surfactant according to actual needs, for example, the first binder includes at least one of a photo-curable aqueous fluorine-containing polyacrylic resin, a photo-curable silicone modified polyacrylic resin, a photo-curable aqueous epoxy polyacrylic resin and a photo-curable polyurethane acrylic resin, the addition of the second binder also improves the problem of insufficient peel strength between the ceramic coating and the substrate when the first binder is used alone, and the addition of the first binder also improves the problem of insufficient thermal stability of the ceramic coating when the second binder is used alone, which are complementary to each other; the inorganic filler includes at least one of aluminum oxide, boehmite, barium sulfate, and magnesium hydroxide; the photoinitiator comprises at least one of benzoin derivatives, acetophenone derivatives, thioxanthone derivatives, benzophenone derivatives and benzil derivatives; the thickener comprises at least one of carboxymethyl cellulose thickener and polyvinyl alcohol; the dispersant comprises at least one of polyacrylate dispersant, carboxymethyl cellulose dispersant and polyvinyl alcohol; the surfactant comprises at least one of polyethylene glycol, docusate sodium, polyether modified organic siloxane and fluorocarbon surfactant.
Further, the inorganic filler has an average particle diameter of 200 to 1500nm, preferably 400 to 1000 nm. The inventors found that if the average particle size of the inorganic filler is too large, the appearance and consistency of the ceramic coating are deteriorated; if the average particle size of the inorganic filler is too small, the surface density of the ceramic coating layer is increased, which is not favorable for increasing the energy density of the lithium battery. Therefore, the average particle size is beneficial to improving the appearance consistency of the ceramic coating and improving the energy density of the lithium battery.
In a second aspect of the invention, a ceramic coated separator is provided. According to an embodiment of the present invention, referring to fig. 1 to 2, the ceramic coated separator includes a base film 100 and the ceramic coating layer 200 described above, the ceramic coating layer 200 being formed on at least one side surface of the base film 100, and in particular, the ceramic coating layer 200 may be formed on at least a portion of one or both side surfaces of the base film 100, and preferably, the ceramic coating layer 200 is formed on the entire one or both side surfaces of the base film 100. Therefore, the ceramic coating diaphragm has excellent thermal stability, integrity and low water content, and the water absorption risk of the ceramic coating diaphragm in production, transportation and lithium battery manufacturing procedures is lower, so that the electrical property and the safety performance of the lithium battery are ensured. It should be noted that the features and advantages described above for the ceramic coating are equally applicable to the ceramic coated membrane and will not be described in further detail here.
It should be noted that, the specific type of the base film can be selected by those skilled in the art according to actual needs, for example, the base film includes at least one of a polyethylene film, a polypropylene film, and a polypropylene/polyethylene/polypropylene three-layer co-extruded film. In addition, the thickness of the base film is 5-20 microns.
Further, the thickness of the ceramic coating is 1-5 microns. The inventor finds that if the thickness of the ceramic coating is too large, the energy density of the battery is not improved; however, if the thickness of the ceramic coating is too small, the thermal stability of the polyolefin-based film cannot be effectively improved. Therefore, the thickness of the ceramic coating is beneficial to improving the electrical property and the safety performance of the lithium battery.
It should be noted that, unless otherwise specified, "ceramic coating thickness" in the present application refers to the thickness of a coating formed on one side of a base film.
In a third aspect of the present invention, the present invention provides a method of preparing the above ceramic-coated separator. According to an embodiment of the invention, referring to fig. 3, the method comprises:
s100: mixing the inorganic filler, the first binder, the second binder, the photoinitiator, the thickener, the dispersant, the surfactant and water with stirring
In this step, the inorganic filler, the first binder, the second binder, the photoinitiator, the thickener, the dispersant, the surfactant, and water are mixed in a certain ratio with stirring (the stirring manner is not limited) to obtain a ceramic slurry. The inventors have found that affinity of a ceramic coating layer to a base film can be improved by adding the above-mentioned second binder including at least one of an aqueous acrylate copolymer emulsion, polyvinyl alcohol, and polyvinylpyrrolidone, thereby improving the integrity of a ceramic-coated separator, agglomeration of particles of an inorganic filler can be prevented by adding a dispersant, viscosity of a ceramic slurry can be improved by adding a thickener so as to maintain a uniform and stable suspension state, interfacial tension of ceramic particles can be increased by adding a surfactant, uniformity of coating thickness is more facilitated, and the addition of water as a solvent is more environmentally friendly than an organic solvent system.
Preferably, in the step, water, a dispersing agent, a thickening agent and an inorganic filler are stirred at a high speed for 25-35 min, preferably 30min, and then sanding is performed, and then a first adhesive, a second adhesive, a photoinitiator and a surfactant are added, and the ceramic slurry can be obtained after fully stirring uniformly and filtering. The inventor finds that the sanding can disperse the inorganic filler more uniformly, the uniform and stable suspension state can be maintained more easily, and the subsequent drying time can be shortened by filtering. It should be noted that the specific types and mixing ratios of the inorganic filler, the first binder, the second binder, the photoinitiator, the thickener, the dispersant, the surfactant, and the water are the same as those described above, and are not described herein again.
Further, the resistivity of the water is not less than 8 M.OMEGA.cm. The inventors found that if the specific resistance of water is too low, it means that the impurity ions in water are large, and the battery performance is not favorable. The amount of water added is 50 to 80 parts by weight. The inventor finds that if the adding amount of water is too small, the components are not favorably mixed uniformly, and the viscosity of the ceramic slurry is higher, so that the coating production is not favorably realized; if the amount of water added is too large, the burden of subsequent drying increases.
S200: applying ceramic slurry on at least one side surface of the base film, drying and photocuring
In the step, the ceramic slurry obtained in the step S100 is applied to at least one side surface of the base film, and is dried (the drying manner is not limited), and photocured, after the photoinitiator is irradiated by light, the photoinitiator absorbs the energy of the light to generate a plurality of active free radicals, and the active free radicals can initiate the crosslinking and curing of the water-soluble acrylic copolymer serving as the first adhesive to form an interpenetrating network structure, so that the high temperature resistance of the ceramic coating can be improved, and the polar water-absorbing groups in the ceramic slurry can be consumed in the crosslinking and curing process, so that the water content of the ceramic coating is reduced, a good hydrophobic structure is formed on the surface, and the ceramic coating diaphragm can be obtained after photocuring. It should be noted that the application mode of the ceramic coating is not particularly limited, and those skilled in the art can select the application mode according to actual needs, for example, micro gravure, wire rod, knife coating, etc. In addition, the specific type of the base film is the same as that described above, and is not described herein again.
It should be noted that the features and advantages described above for the ceramic coated membrane are also applicable to the method for preparing the ceramic coated membrane, and are not described in detail here.
In a fourth aspect of the present invention, a lithium battery is provided. According to an embodiment of the present invention, the lithium battery cell has the ceramic-coated separator described above or the ceramic-coated separator prepared by the method described above. Thus, the lithium battery having the ceramic-coated separator, which is excellent in thermal stability and integrity, and low in water content and risk of water absorption, has excellent electrical properties and safety. It should be noted that the features and advantages described above for the ceramic coating, the ceramic coated separator and the method for preparing the same are also applicable to the lithium battery, and are not described herein again.
The following embodiments of the present invention are described in detail, and it should be noted that the following embodiments are exemplary only, and are not to be construed as limiting the present invention. In addition, all reagents used in the following examples are commercially available or can be synthesized according to methods herein or known, and are readily available to those skilled in the art for reaction conditions not listed, if not explicitly stated.
Example 1
Step 1: weighing 40 parts by weight of deionized water (with the resistivity of 18M omega cm), adding 0.2 part by weight of dispersant ammonium polyacrylate while stirring, adding 0.3 part by weight of thickener (CMC1140), and then adding 40 parts by weight of D50 400nm boehmite; stirring at a high speed for 30 minutes, sanding once, adding 1.5 parts by weight of a first adhesive (photocuring aqueous fluorine-containing polyacrylic resin), 0.8 part by weight of a second adhesive (aqueous acrylate copolymer emulsion), 0.1 part by weight of a surfactant (polyethylene glycol) and 0.1 part by weight of a photoinitiator (dibenzoyl oxide), fully stirring, and filtering to obtain ceramic slurry;
step 2: the ceramic slurry was coated on one side of a polyethylene microporous membrane having a thickness of 12 μm by a wire rod, dried and photo-cured to form a ceramic-coated separator having a ceramic coating thickness of 2 μm.
Example 2
Step 1: weighing 100 parts by weight of deionized water (with the resistivity of 18 MOmega cm), adding 0.6 part by weight of dispersant sodium polyacrylate while stirring, adding 1.2 parts by weight of thickener (CMC1220), and then adding 100 parts by weight of 600nm aluminum oxide D50; stirring at a high speed for 30 minutes, sanding once, adding 4.5 parts by weight of a first adhesive (photocuring waterborne epoxy polyacrylic resin) and 2.0 parts by weight of a second adhesive (waterborne acrylic copolymer emulsion), 0.1 part by weight of a surfactant (polyether modified organosiloxane) and 0.15 part by weight of a photoinitiator (2-hydroxy-2-methyl-1-phenyl acetone), fully stirring, and filtering to obtain ceramic slurry;
step 2: and coating the ceramic slurry on one side of a polyethylene microporous membrane with the thickness of 12 mu m through a wire rod, and drying and photocuring to form a ceramic coating diaphragm with the ceramic coating thickness of 2 mu m.
Example 3
The ceramic slurry prepared in example 2 was coated on one side of a polyethylene microporous membrane having a thickness of 9 μm by a wire rod, and dried and photo-cured to form a ceramic-coated separator having a ceramic coating thickness of 3 μm.
Example 4
Step 1: weighing 50 parts by weight of deionized water (with the resistivity of 18 MOmega cm), adding 0.15 part by weight of dispersant ammonium polyacrylate while stirring, adding 0.5 part by weight of thickener (CMC1220), and adding 50 parts by weight of D50 (500 nm aluminum oxide); stirring at a high speed for 30 minutes, sanding once, adding 3 parts by weight of a first adhesive (photocuring polyurethane acrylic resin) and 1.0 part by weight of a second adhesive (aqueous acrylic copolymer emulsion), 0.02 part by weight of a surfactant (perfluoroalkyl polyoxyethylene ether) and 0.1 part by weight of a photoinitiator (acylphosphine oxide), and filtering after fully stirring to obtain ceramic slurry;
step 2: and coating the ceramic slurry on one side of a polyethylene microporous membrane with the thickness of 9 mu m through a wire rod, and drying and photocuring to form a ceramic coating diaphragm with the ceramic coating thickness of 3 mu m.
Example 5
Step 1: weighing 100 parts by weight of deionized water (with the resistivity of 18 MOmega cm), adding 0.3 part by weight of dispersant ammonium polyacrylate while stirring, adding 1.2 parts by weight of thickener (CMC1220), and then adding 100 parts by weight of 600nm aluminum oxide D50; stirring at a high speed for 30 minutes, sanding once, adding 5.5 parts by weight of a first adhesive (photocuring waterborne epoxy polyacrylic resin) and 2 parts by weight of a second adhesive (polyvinyl alcohol), 0.1 part by weight of a surfactant (polyether modified organosiloxane) and 0.1 part by weight of a photoinitiator (2-hydroxy-2-methyl-1-phenyl acetone), and filtering after fully stirring to obtain ceramic slurry;
step 2: and coating the ceramic slurry on one side of a polyethylene microporous membrane with the thickness of 9 mu m through a wire rod, and drying and photocuring to form a ceramic coating diaphragm with the ceramic coating thickness of 3 mu m.
Example 6
Step 1: weighing 100 parts by weight of deionized water (with the resistivity of 18 MOmega cm), adding 0.8 part by weight of dispersant sodium polyacrylate while stirring, adding 0.6 part by weight of thickener (CMC1140), and then adding 100 parts by weight of D50 (500 nm) aluminum oxide; stirring at a high speed for 30 minutes, sanding once, adding 4.5 parts by weight of a first adhesive (photocuring waterborne epoxy polyacrylic resin) and 1.5 parts by weight of a second adhesive (waterborne fluorine-containing acrylic copolymer emulsion), 0.1 part by weight of a surfactant (perfluoroalkyl polyoxyethylene ether) and 0.2 part by weight of a photoinitiator (2-hydroxy-2-methyl-1-phenyl acetone), fully stirring, and filtering to obtain ceramic slurry;
step 2: and coating the ceramic slurry on one side of a polyethylene microporous membrane with the thickness of 12 mu m through a wire rod, and drying and photocuring to form a ceramic coating diaphragm with the ceramic coating thickness of 2 mu m.
Example 7
Step 1: weighing 65 parts by weight of deionized water (with the resistivity of 18 MOmega cm), adding 0.25 part by weight of dispersant ammonium polyacrylate while stirring, adding 0.12 part by weight of thickener (polyvinyl alcohol), and adding 45 parts by weight of barium sulfate D50 with the particle size of 700 nm; stirring at a high speed for 30 minutes, sanding once, adding 2.5 parts by weight of a first adhesive (photocuring organic silicon modified polyacrylic resin), 0.8 part by weight of a second adhesive (polyvinyl alcohol), 0.05 part by weight of a surfactant (docusate sodium) and 0.12 part by weight of a photoinitiator (dibenzoyl oxide), fully stirring, and filtering to obtain ceramic slurry;
step 2: the ceramic slurry was coated on one side of a polyethylene microporous membrane having a thickness of 9 μm by a wire rod, dried and photo-cured to form a ceramic-coated separator having a ceramic coating thickness of 3 μm.
Example 8
Step 1: weighing 65 parts by weight of deionized water (with the resistivity of 18 MOmega cm), adding 0.25 part by weight of dispersant sodium polyacrylate while stirring, adding 0.12 part by weight of thickener (polyvinyl alcohol), and adding 45 parts by weight of magnesium hydroxide with the particle size of 600nm of D50; stirring at a high speed for 30 minutes, sanding once, adding 2.5 parts by weight of a first adhesive (photocuring organic silicon modified polyacrylic resin), 0.8 part by weight of a second adhesive (polyvinylpyrrolidone), 0.05 part by weight of a surfactant (docusate sodium) and 0.12 part by weight of a photoinitiator (dibenzoyl oxide), fully stirring, and filtering to obtain ceramic slurry;
step 2: the ceramic slurry was coated on one side of a polyethylene microporous membrane having a thickness of 9 μm by a wire rod, dried and photo-cured to form a ceramic-coated separator having a ceramic coating thickness of 3 μm.
Comparative example 1
Step 1: weighing 100 parts by weight of deionized water (with the resistivity of 18 MOmega cm), adding 1.0 part by weight of dispersant ammonium polyacrylate while stirring, adding 1.5 parts by weight of thickener (CMC1220), and adding 100 parts by weight of 600nm aluminum oxide D50; stirring at a high speed for 30 minutes, sanding once, adding 6 parts by weight of adhesive (emulsion type acrylate copolymer) and 0.1 part by weight of surfactant (polyethylene glycol), stirring fully, and filtering to obtain ceramic slurry;
step 2: and coating the ceramic slurry on one side of a polyethylene microporous membrane with the thickness of 12 mu m through a wire rod, and drying and photocuring to form a ceramic coating diaphragm with the ceramic coating thickness of 2 mu m.
Comparative example 2
The ceramic slurry prepared in comparative example 1 was coated on one side of a polyethylene microporous membrane having a thickness of 9 μm by a wire rod, and dried and photo-cured to form a ceramic-coated separator having a ceramic coating thickness of 3 μm.
Comparative example 3
Step 1 was carried out without adding a second binder, as in example 3.
The data in examples 1 to 8 and comparative examples 1 to 3 were tested as follows:
1. and (3) thickness testing: the prepared ceramic coated membrane product was directly subjected to thickness measurement at multiple points using a malter thickness gauge, and the results are shown in table 1, taking the average.
2. And (3) testing the peel strength: the test was carried out according to method 3 in GB/T2792-.
3. Thermal shrinkage test: the ceramic coated membrane was cut into 12cm by 12cm coupons.
Drawing two lines perpendicular to each other and having a length of about 10cm in the middle of the sample, marking the longitudinal direction and the transverse direction, and measuring the length L of the two lines by using an Abbe's comparator0And recording, placing the sample on weighing paper. Placing in an oven (150 deg.C + -1 deg.C) for 1h, taking out the sample, standing for 30min to cool the sample to room temperature, and measuring the length L of two lines1And recorded, and the heat shrinkage ratio was calculated from the change in length of the two lines before and after baking (shrinkage ratio ═ L)0-L1)/L0) And taking an average value in three parallel determinations as an experimental result of the direction, wherein two decimal places are reserved in the experimental result.
4. And (3) testing air permeability: the test was carried out according to the Gerlay method of GB/T458 + 2008 "determination of air Permeability of paper and cardboard", and the time required for 100mL of air to pass through was recorded.
5. Testing the water content: taking a sample with a diaphragm of about 0.1g, and accurately weighing the sample by mass m0(g) And placing the mixture into a dry and clean jaw bottle, and sealing the sample by using a sealing machine.
The Karl Fei autumn moisture meter is set at 150 ℃ and 4 r/s in rotation speed, and the absolute water content mu of the empty bottle is respectively testedAir conditionerAnd absolute water content mu of sample bottleAbsolute. The formula for calculating the water content X of the sample is shown in formula (1).
X＝(μAbsolute-μAir conditioner)/m0…………………………(1)
In the formula:
x is the water content of the sample in ppm;
m0-mass of the membrane sample in grams (g);
μair conditionerAbsolute water content of the empty bottle in milligrams (. mu.g);
μabsoluteAbsolute water content of the sample vial in milligrams (. mu.g).
The results of the performance test of the ceramic-coated separators prepared in examples 1 to 8 and comparative examples 1 to 3 are shown in table 1:
TABLE 1 Performance test results for examples 1-8 and comparative examples 1-3
As shown in Table 1, as can be seen from the comparison of the data of the examples 1-8 and the comparative examples 1-2, the thermal stability of the ceramic coated diaphragm prepared by using the emulsion type acrylate copolymer as the adhesive is poorer than that of the examples 1-8 and the water content is higher than that of the examples 1-8 in the comparative examples 1-2; as can be seen from the comparison of the data of example 3 with comparative example 3, the peel strength of the ceramic coated separator prepared in comparative example 3 without the addition of the second binder was lower than that of example 3.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (10)
1. A ceramic coating, comprising: inorganic filler, a first binder, a second binder, a photoinitiator, a thickener, a dispersant and a surfactant,
wherein the first binder is a water-soluble acrylic copolymer;
the second binder includes at least one of an aqueous acrylate copolymer emulsion, polyvinyl alcohol, and polyvinyl pyrrolidone.
2. The ceramic coating of claim 1, wherein the ceramic coating comprises: 40 to 50 parts by weight of the inorganic filler, 1 to 4 parts by weight of the first binder, 0.2 to 1.5 parts by weight of the second binder, 0.005 to 0.2 parts by weight of the photoinitiator, 0.05 to 2 parts by weight of the thickener, 0.05 to 0.5 parts by weight of the dispersant, and 0.01 to 0.1 parts by weight of the surfactant.
3. The ceramic coating of claim 1 or 2, wherein the first binder comprises at least one of a photo-curable aqueous fluorine-containing polyacrylic resin, a photo-curable silicone-modified polyacrylic resin, a photo-curable aqueous epoxy polyacrylic resin, and a photo-curable polyurethane acrylic resin.
4. Ceramic coating according to claim 1 or 2, characterized in that the inorganic filler has an average particle size of 200 to 1500nm, preferably 400 to 1000 nm;
optionally, the inorganic filler comprises at least one of aluminum oxide, boehmite, barium sulfate, and magnesium hydroxide;
optionally, the photoinitiator comprises at least one of benzoin derivatives, acetophenone derivatives, thioxanthone derivatives, benzophenone derivatives and benzil derivatives;
optionally, the thickener comprises at least one of a carboxymethyl cellulose-based thickener and polyvinyl alcohol;
optionally, the dispersant comprises at least one of a polyacrylate dispersant, a carboxymethyl cellulose dispersant, and polyvinyl alcohol;
optionally, the surfactant comprises at least one of polyethylene glycol, docusate sodium, polyether modified organosiloxane, and fluorocarbon surfactant.
5. A ceramic-coated separator comprising a base film and the ceramic coating layer according to any one of claims 1 to 4, the ceramic coating layer being formed on at least one side surface of the base film.
6. The ceramic coated membrane of claim 5, wherein the base membrane comprises at least one of a polyethylene membrane, a polypropylene/polyethylene/polypropylene tri-layer co-extruded membrane.
7. The ceramic coated membrane of claim 5, wherein the ceramic coating has a thickness of 1 to 5 microns.
8. A method of making the ceramic coated separator of any of claims 5 to 7, comprising:
(1) mixing an inorganic filler, a first binder, a second binder, a photoinitiator, a thickener, a dispersant, a surfactant, and water with stirring to obtain a ceramic slurry;
(2) the ceramic slurry is applied on at least one side surface of a base film and dried, photocured, to obtain a ceramic-coated separator.
9. The method according to claim 8, wherein in the step (1), the water, the dispersant, the thickener and the inorganic filler are mixed with stirring and then subjected to sand grinding, and then the first binder, the second binder, the photoinitiator and the surfactant are added and mixed uniformly and then filtered to obtain the ceramic slurry;
optionally, the resistivity of the water is not less than 8M omega cm, and the adding amount is 50-80 parts by weight.
10. A lithium battery having a ceramic-coated separator as claimed in any one of claims 5 to 7 or a ceramic-coated separator prepared by the method as claimed in claim 8 or 9.
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