Ceramic coated lithium ion battery diaphragm and preparation method thereof

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a ceramic coated lithium ion battery diaphragm and a preparation method thereof.The preparation method of the ceramic coated lithium ion battery diaphragm comprises the steps that a dispersing agent and ceramic particles are sequentially added into deionized water to be stirred and mixed, and ceramic dispersion liquid is prepared; adding a thickening agent into the ceramic dispersion liquid, stirring and dissolving, then adding a binder and a wetting aid, stirring until a uniform dispersion liquid is formed, and then adding a wetting agent, stirring and mixing to prepare ceramic slurry; coating one surface or two surfaces of a polyolefin base membrane with the ceramic slurry, and drying to obtain the ceramic coated lithium ion battery diaphragm; according to the invention, the amphiphilic polymer wetting aid is used as an auxiliary wetting agent and a binder, and the affinity of the ceramic slurry and the polyolefin-based membrane is improved through an alkane structure similar to the polyolefin-based membrane in a molecular chain segment of the amphiphilic polymer wetting aid and hydroxyl capable of forming hydrogen bonds with water molecules.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a ceramic-coated lithium ion battery separator and a preparation method thereof. Background Art

[0002] The diaphragm is one of the important components of lithium-ion batteries. It has the function of blocking the positive and negative electrodes and conducting the electrolyte. The main diaphragm products currently used in the market are ceramic-coated polyolefin diaphragms. This type of diaphragm material has the advantages of high temperature resistance, ultra-thinness, good air permeability, and high strength.

[0003] However, ceramic-coated polyolefin separators may cause micro-leaks due to the poor affinity between the coating slurry and the polyolefin base film, which will lead to weakened barrier properties and ion conductivity of the separator, thereby affecting the safety and performance of lithium-ion batteries and increasing battery manufacturing costs. Therefore, there is an urgent need to develop a dense, leak-free ceramic-coated lithium-ion battery separator. Summary of the invention

[0004] The object of the present invention is to provide a ceramic coated lithium ion battery separator and a preparation method thereof, utilizing the reinforcing effect of a wetting agent to improve the affinity between the ceramic slurry and the polyolefin separator and eliminate micro-leaking defects.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a ceramic-coated lithium-ion battery separator, comprising:

[0006] Adding dispersant and ceramic particles into deionized water in sequence and stirring to mix, thereby preparing a ceramic dispersion;

[0007] Adding a thickener to the ceramic dispersion and stirring to dissolve, then adding a binder and a wetting agent and stirring to form a uniform dispersion, then adding a wetting agent and stirring to mix, to obtain a ceramic slurry;

[0008] The ceramic slurry is coated on one side or both sides of a polyolefin base film and then dried to obtain a ceramic coated lithium ion battery separator.

[0009] The ceramic particles are one of alumina, boehmite, lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide, and lithium lanthanum titanate. The D50 particle size of the ceramic particles is 0.1 μm to 0.8 μm, and the D90 particle size of the ceramic particles is less than or equal to 2.0 μm.

[0010] Wherein, the dispersant is one of fluoroalkyl ethoxy alcohol ether, fatty alcohol polyoxyethylene ether, sodium butylbenzene naphthalene sulfonate, sodium hydroxyethyl sulfate, and sodium dodecyl sulfate.

[0011] Wherein, the thickener is one of carboxymethyl cellulose and sodium carboxymethyl cellulose.

[0012] Wherein, the binder is one of polyethyl acrylate, polypropyl acrylate, polybutyl acrylate, polyisobutyl acrylate, polypentyl acrylate, polyhexyl acrylate, poly2-ethylhexyl acrylate, polyhydroxyethyl acrylate, polyhydroxypropyl acrylate, polydimethylaminoethyl methacrylate, polymethacrylic acid, polymethacrylamide and polyacrylamide.

[0013] Wherein, the wetting agent is one of polyvinyl alcohol, polyethylene glycol and polypropylene glycol.

[0014] Wherein, the wetting agent is one of fluoroalkyl methoxy ether alcohol, acetylene glycol vinyl ether, fatty acid polyoxyethylene ether, siloxane, and fatty acid salt.

[0015] The ceramic slurry comprises, by mass percentage, 0.05-0.5wt% of dispersant, 30-40wt% of ceramic particles, 0.05-0.5wt% of thickener, 3-5wt% of binder, 0.06-0.12wt% of wetting agent, 0.05-0.12wt% of wetting agent, and the rest is ultrapure water.

[0016] In a second aspect, the present invention further provides a ceramic-coated lithium-ion battery separator, which is prepared using the ceramic-coated lithium-ion battery separator preparation method.

[0017] The present invention discloses a ceramic-coated lithium-ion battery separator and a preparation method thereof. The amphiphilic polymer wetting agent is used as an auxiliary wetting agent and a binder. The affinity between the ceramic slurry and the polyolefin base membrane is improved through the alkane structure similar to the polyolefin base membrane in the molecular chain segment and the hydroxyl group that can form hydrogen bonds with water molecules. The amphiphilic polymer will not promote or stabilize the generation of small bubbles when in contact with air or the base membrane, which fundamentally solves the problem of micro-leaking of ceramic coating and improves the barrier property and ionic conductivity of the ceramic coated separator. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0019] Figure 1 The present invention is a flow chart of a method for preparing a ceramic-coated lithium-ion battery separator.

[0020] Figure 2 It is a performance diagram of the diaphragms prepared in various embodiments and comparative examples of the method for preparing a ceramic-coated lithium-ion battery diaphragm of the present invention.

[0021] Figure 3 This is a picture of online defect detection in Example 1 of a method for preparing a ceramic-coated lithium-ion battery separator of the present invention.

[0022] Figure 4 This is a method for preparing a ceramic-coated lithium-ion battery separator according to the present invention. Example 2 Online defect detection image

[0023] Figure 5 This is an online defect detection picture of comparative example 1 of a ceramic-coated lithium-ion battery separator preparation method of the present invention. DETAILED DESCRIPTION

[0024] Embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0025] See also Figure 1 to Figure 5 In a first aspect, the present invention provides a method for preparing a ceramic-coated lithium-ion battery separator, comprising:

[0026] S1: adding a dispersant and ceramic particles into deionized water in sequence and stirring to obtain a ceramic dispersion;

[0027] In an embodiment of the present invention, the dispersant and ceramic particles are added to deionized water in sequence and stirred at high speed to obtain a ceramic dispersion liquid. The stirring rate of the high-speed stirring is 600-900 rpm, the stirring time is 30-60 min, and the stirring temperature is 20-30°C. The dispersant is one of fluoroalkyl ethoxy alcohol ether, fatty alcohol polyoxyethylene ether, sodium butylbenzene naphthalene sulfonate, sodium hydroxyethyl sulfate, and sodium dodecyl sulfate. The ceramic particles are one of alumina, boehmite, lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide, and lithium lanthanum titanate. The D50 particle size of the ceramic particles is 0.1 μm to 0.8 μm, and the D90 particle size of the ceramic particles is less than or equal to 2.0 μm.

[0028] S2: adding a thickener to the ceramic dispersion and stirring to dissolve, then adding a binder and a wetting agent and stirring to form a uniform dispersion, then adding a wetting agent and stirring to mix, to obtain a ceramic slurry;

[0029] In an embodiment of the present invention, the thickener is added to the ceramic dispersion, stirred at medium speed to dissolve evenly, and then the binder and the wetting agent are added, stirred at low speed to form a uniform dispersion, and finally the wetting agent is added, stirred at low speed to form a uniform ceramic slurry. The stirring rate of the medium-speed stirring is 300-500rpm, the stirring time is 30-60min, the low-speed stirring stirring rate is 50-200rpm, the stirring time is 30-60min, and the stirring temperature is 20-30°C. The thickener is one of carboxymethyl cellulose and sodium carboxymethyl cellulose, and the binder is The binder is one of polyethyl acrylate, polyn-propyl acrylate, polyn-butyl acrylate, polyisobutyl acrylate, polyn-pentyl acrylate, polyn-hexyl acrylate, poly-2-ethylhexyl acrylate, polyhydroxyethyl acrylate, polyhydroxypropyl acrylate, polydimethylaminoethyl methacrylate, polymethacrylic acid, polymethacrylamide, and polyacrylamide; the lubricant is one of polyvinyl alcohol, polyethylene glycol, and polypropylene glycol; the wetting agent is one of fluoroalkyl methoxy ether alcohol, acetylene glycol vinyl ether, fatty acid polyoxyethylene ether, siloxane, and fatty acid salt. The ceramic slurry comprises, by mass percentage, 0.05-0.5wt% of dispersant, 30-40wt% of ceramic particles, 0.05-0.5wt% of thickener, 3-5wt% of binder, 0.06-0.12wt% of lubricant, 0.05-0.12wt% of wetting agent, and the rest is ultrapure water.

[0030] S3: coating the ceramic slurry on one side or both sides of the polyolefin base film and drying the film to obtain a ceramic-coated lithium-ion battery separator;

[0031] In an embodiment of the present invention, conventional membrane coating methods such as micro-concave rollers and wire rods are used to coat the ceramic slurry on one or both sides of the polyolefin base film, and the coating thickness is controlled to be 0.2-3um. Drying is performed to obtain a dense and leak-free ceramic-coated lithium-ion battery membrane. The drying temperature is 70-90°C and the drying time is 1-2min.

[0032] In order to better understand the present invention, several specific manufacturing processes are used for illustration below.

[0033] Example 1: 36wt% of aluminum oxide (D50 is 0.3um, D90 is 0.5um), 0.5wt% of fluoroalkyl ethoxy alcohol ether, are added to ultrapure water, and stirred at 25°C, 900rpm for 0.5h, then 0.25wt% of carboxymethyl cellulose is added, and at 25°C, 400rpm is stirred for 0.5h, then 4wt% of polymethyl acrylamide is added, and at 25°C, 100rpm is stirred for 0.5h, then 0.1wt% of polyvinyl alcohol is added, and at 25°C, 100rpm is stirred for 0.5h, then 0.08wt% of fluoroalkyl methoxy ether alcohol is added, and then stirred at 25°C, 100rpm for 0.5h to form a uniform ceramic slurry, and the uniform ceramic slurry is coated on one side of a 5um commercial polyethylene diaphragm through a micro-concave roller, the coating thickness is 0.5um, and it is dried at 70°C for 2min to obtain the ceramic coated lithium ion battery diaphragm.

[0034] Example 2: 36wt% of boehmite (D50 is 0.8um, D90 is 2.0um), 0.12wt% of fluoroalkyl ethoxy alcohol ether, are added to ultrapure water, and stirred at 25°C, 900rpm for 0.5h, then 0.4wt% of carboxymethyl cellulose is added, and stirred at 25°C, 400rpm for 0.5h, then 3wt% of polyethyl acrylate is added, and stirred at 25°C, 100rpm for 0.5h, then 0.09wt% of polyvinyl alcohol is added, and stirred at 25°C, 100rpm for 0.5h, then 0.1wt% of acetylene glycol vinyl ether is added, and then stirred at 25°C, 100rpm for 0.5h to form a uniform ceramic slurry, and the uniform ceramic slurry is coated on one side of a 9um commercial polyethylene diaphragm through a micro-concave roller, the coating thickness is 3um, and the film is dried at 90°C for 1min to obtain the ceramic coated lithium ion battery diaphragm.

[0035] Example 3: 36wt% of aluminum oxide (D50 is 0.7um, D90 is 1.8um), 0.5wt% of fluoroalkyl ethoxy alcohol ether, are added to ultrapure water, and stirred at 25°C, 900rpm for 0.5h, then 0.4wt% of carboxymethyl cellulose is added, and then 5wt% of polymethyl methacrylamide is added, and then 0.06wt% of polyvinyl alcohol is added, and then 0.05wt% of fluoroalkyl methoxy ether alcohol is added, and then stirred at 25°C, 100rpm for 0.5h to form a uniform ceramic slurry, and the uniform ceramic slurry is applied to one side of a 7um commercial polyethylene diaphragm through a micro-concave roller, the coating thickness is 2.0um, and the film is dried at 80°C for 2min to obtain the ceramic coated lithium ion battery diaphragm.

[0036] Comparative Example 1: This comparative example is different from Example 1 in that 0.1 wt % of polyvinyl alcohol is not added.

[0037] Comparative Example 2: This comparative example is different from Example 2 in that 0.09 wt % of polyvinyl alcohol is not added.

[0038] The invention discloses a method for preparing a ceramic-coated lithium-ion battery separator, which uses an amphiphilic polymer wetting agent as an auxiliary wetting agent and a binder, and improves the affinity between the ceramic slurry and the polyolefin-based membrane through the alkane structure in its molecular chain segment that is similar to that of the polyolefin-based membrane and the hydroxyl group that can form hydrogen bonds with water molecules.

[0039] In a second aspect, the present invention further provides a ceramic-coated lithium-ion battery separator, which is prepared using the ceramic-coated lithium-ion battery separator preparation method.

[0040] The present invention discloses a ceramic-coated lithium-ion battery separator, in which an amphiphilic polymer wetting aid is used as an auxiliary wetting agent and a binder. The amphiphilic polymer wetting aid has an alkane structure similar to that of a polyolefin-based membrane in its molecular chain segment, and a hydroxyl group that can form hydrogen bonds with water molecules, thereby improving the affinity between the ceramic slurry and the polyolefin-based membrane. Furthermore, the amphiphilic polymer will not promote or stabilize the generation of small bubbles when in contact with air or the base membrane, thereby fundamentally solving the problem of micro-leaking in ceramic coating and improving the barrier properties and ionic conductivity of the ceramic-coated separator.

[0041] What is disclosed above is only one or more preferred embodiments of the present application, and cannot be used to limit the scope of rights of the present application. Ordinary technicians in this field can understand that all or part of the processes of implementing the above embodiments and equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. A method for preparing a ceramic-coated lithium-ion battery separator, characterized in that: Adding dispersant and ceramic particles into deionized water in sequence and stirring to mix, thereby preparing a ceramic dispersion; Adding a thickener to the ceramic dispersion and stirring to dissolve, then adding a binder and a wetting agent and stirring to form a uniform dispersion, then adding a wetting agent and stirring to mix, to obtain a ceramic slurry; The ceramic slurry is coated on one side or both sides of a polyolefin base film and then dried to obtain a ceramic coated lithium ion battery separator.

2. The method for preparing a ceramic-coated lithium-ion battery separator according to claim 1, characterized in that: The ceramic particles are one of alumina, boehmite, lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide, and lithium lanthanum titanate. The D50 particle size of the ceramic particles is 0.1 μm to 0.8 μm, and the D90 particle size of the ceramic particles is less than or equal to 2.0 μm.

3. The method for preparing a ceramic-coated lithium-ion battery separator according to claim 1, characterized in that: The dispersant is one of fluoroalkyl ethoxy alcohol ether, fatty alcohol polyoxyethylene ether, sodium butylbenzene naphthalene sulfonate, sodium hydroxyethyl sulfate, and sodium dodecyl sulfate.

4. The method for preparing a ceramic-coated lithium-ion battery separator according to claim 1, characterized in that: The thickener is one of carboxymethyl cellulose and sodium carboxymethyl cellulose.

5. The method for preparing a ceramic-coated lithium-ion battery separator according to claim 1, characterized in that: The binder is one of polyethyl acrylate, polypropyl acrylate, polybutyl acrylate, polyisobutyl acrylate, polypentyl acrylate, polyhexyl acrylate, poly-2-ethylhexyl acrylate, polyhydroxyethyl acrylate, polyhydroxypropyl acrylate, polydimethylaminoethyl methacrylate, polymethacrylic acid, polymethacrylamide and polyacrylamide.

6. The method for preparing a ceramic-coated lithium-ion battery separator according to claim 1, characterized in that: The wetting agent is one of polyvinyl alcohol, polyethylene glycol and polypropylene glycol.

7. The method for preparing a ceramic-coated lithium-ion battery separator according to claim 1, characterized in that: The wetting agent is one of fluoroalkyl methoxy ether alcohol, acetylene glycol vinyl ether, fatty acid polyoxyethylene ether, siloxane, and fatty acid salt.

8. The method for preparing a ceramic-coated lithium-ion battery separator according to claim 1, characterized in that: The ceramic slurry comprises, by weight percentage, 0.05-0.5wt% of dispersant, 30-40wt% of ceramic particles, 0.05-0.5wt% of thickener, 3-5wt% of binder, 0.06-0.12wt% of wetting agent, 0.05-0.12wt% of wetting agent, and the rest is ultrapure water.

9. A ceramic coated lithium ion battery separator, characterized in that: The ceramic-coated lithium-ion battery separator is prepared by the method for preparing the ceramic-coated lithium-ion battery separator according to any one of claims 1 to 8.

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