A functional combination coating separator and secondary battery

Abstract

The utility model provides a function combination coating diaphragm and secondary battery, including diaphragm base film, first function coating and second function coating, first function coating and second function coating respectively coating setting in diaphragm base film's both sides, the thickness range of first function coating is 1 5 microns, the thickness range of second function coating is 0.5 2 microns, the ceramic particle is non -spherical particle, in practical application, both can reduce the electric core self -discharge, can improve the electric core porosity to improve diaphragm liquid -retention effect, make the battery electric performance and safety performance can be promoted.

Description

[Technical Field]

[0001] This utility model relates to the field of novel battery technology, and in particular to a functional combination coating and coating separator with outstanding application effect and preparation method. [Background Technology]

[0002] With the development of lithium-ion battery technology, higher requirements have been placed on the function of lithium battery separators. As an important component of lithium-ion batteries, the separator is crucial to the energy density and safety performance of lithium-ion batteries. Its main function is to separate the positive and negative electrodes to prevent internal short circuits. Therefore, it needs to have good insulation performance and heat insulation and high temperature resistance characteristics. At the same time, it must provide high porosity to store sufficient electrolyte and have good lithium-ion transport channels.

[0003] To improve the performance of separators and meet the technical requirements of next-generation lithium batteries, such as safety and energy density, coated separators have emerged. Coated separators can improve the thermal stability, insulation, and liquid retention of separators, thereby enhancing the safety and cycle life of lithium-ion batteries. However, currently commercially available coated separators typically use ceramic materials with limited insulation properties, such as alumina, silicon oxide, and barium sulfate, leading to significant self-discharge issues between the positive and negative electrodes. Therefore, it is necessary to provide a double-sided coated separator with high insulation performance and its preparation method.

[0004] Patent No. CN 105047845 provides a nanocomposite coating separator with high dielectric constant and high ionic conductivity and excellent battery performance, and its preparation method. The inorganic-organic polymer composite particles are composed of 50-90 parts by weight of gel polymer and 10-50 parts by weight of nano-inorganic ceramic particles. The high dielectric constant of the prepared nanocomposite coating is much higher than that of the prior art, and the safety performance is better.

[0005] The main components of existing commercially available coated separators are materials such as aluminum oxide, boehmite, magnesium hydroxide, and silicon dioxide. These types of coatings improve the thermal shrinkage and liquid absorption capacity of the separator to some extent. However, these types of coated separators have poor insulation performance and cannot meet the demands for improved battery safety. Other patents propose using high dielectric constant materials to ensure the insulation performance of the separator, but high dielectric constant materials also have certain issues with high temperature resistance and oxidation resistance.

[0006] To address the problems existing in existing coated separators, this invention proposes a double-sided composite coating for the separator, which not only ensures the separator's heat insulation and high-temperature resistance but also its insulation performance, effectively improving battery safety and cycle life. [Utility Model Content]

[0007] The problem with the prior art that this application addresses is:

[0008] The main components of existing commercially available coated separators are materials such as aluminum oxide, boehmite, magnesium hydroxide, and silicon dioxide. These types of coatings improve the thermal shrinkage and liquid absorption capacity of the separator to some extent. However, these types of coated separators have poor insulation performance and cannot meet the demands for improved battery safety. Other patents propose using high dielectric constant materials to ensure the insulation performance of the separator, but high dielectric constant materials also have certain issues with high temperature resistance and oxidation resistance.

[0009] The solution to the technical problem of this utility model is:

[0010] A functional combination coating and a coated diaphragm are provided, comprising a diaphragm base membrane, a first functional coating, and a second functional coating; the first functional coating and the second functional coating are respectively coated on both sides of the diaphragm base membrane; the thickness of the first functional coating is in the range of 1-5 micrometers; the thickness of the second functional coating is in the range of 0.5-2 micrometers; and the ceramic particles are non-spherical particles.

[0011] Preferably, the diaphragm base membrane comprises at least one of polyethylene, polypropylene, and a composite material of polyethylene and polypropylene.

[0012] Preferably, the first functional coating comprises an inorganic ceramic layer and an organic polymer layer; the inorganic ceramic layer comprises a ceramic material and a binder; wherein the ceramic material has a porous structure with a pore size ranging from 600 to 1500 nm; the ceramic material is one or a mixture of several of alumina, boehmite, magnesium hydroxide, and silicon dioxide; the binder is at least one of styrene-butadiene rubber, hydroxypropyl methylcellulose, sodium carboxymethyl cellulose, polyacrylic acid, and hydroxyethyl cellulose; the organic polymer layer comprises at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, and polyacrylonitrile.

[0013] Preferably, the first functional coating comprises an inorganic ceramic layer and an organic polymer layer; the inorganic ceramic layer comprises a ceramic material and a binder; wherein the ceramic material has a dense structure with a pore size ranging from 100-500 nm; the ceramic material is BaTiO3, BaSnO3, BaZrO3, or Pb(Mg) 1 / 3 Nb 2 / 3 O3, PbTiO3, Ba(Zn) 1 / 3 Nb 2 / 3 The adhesive is one or more of the following: styrene-butadiene rubber, hydroxypropyl methylcellulose, sodium carboxymethyl cellulose, polyacrylic acid, and hydroxyethyl cellulose; the organic polymer layer contains at least one of the following polymer materials: polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, and polyacrylonitrile.

[0014] Preferably, the first functional coating and / or the second functional coating contains an organic polymer layer.

[0015] A method for preparing a coated diaphragm includes the following steps:

[0016] S1: Prepare ceramic slurry and organic polymer slurry for coating the diaphragm, and prepare the diaphragm base membrane;

[0017] S2: Mix the ceramic slurry, organic polymer material, wetting agent, deionized water and ethylene glycol into a mixed solvent evenly to form a slurry;

[0018] S3: The above slurry is applied to both sides of the base film by spraying or roller coating.

[0019] S4: Dry, slit, to obtain a functional composite coating diaphragm.

[0020] Preferably, the ceramic slurry contains 85%-95% ceramic material, 3%-5% binder material, and 0.5%-1% wetting agent by weight; the organic polymer slurry contains 70%-90% organic polymer material and 10%-30% wetting agent by weight.

[0021] A secondary battery includes the aforementioned combined coating separator; the first functional coating faces the positive electrode, the second functional coating faces the negative electrode, and the separator is wound or stacked with the positive and negative electrode sheets to form a core, thereby obtaining the secondary battery.

[0022] The technical effects achieved by this application in solving the technical problem are as follows:

[0023] Compared with the prior art, the present invention provides a functional composite coating, a coated diaphragm, and a preparation method by simultaneously setting a diaphragm base film, a first functional coating, and a second functional coating; the first functional coating and the second functional coating are respectively coated on both sides of the diaphragm base film; the thickness of the first functional coating ranges from 1 to 5 micrometers; the thickness of the second functional coating ranges from 0.5 to 2 micrometers; the ceramic particles are non-spherical particles. In practical applications, the double-sided composite coated diaphragm provided by the present invention has one side containing a high dielectric constant ceramic diaphragm, which can ensure the insulation performance of the diaphragm; the other side adopts a porous ceramic design to increase the liquid retention performance of the diaphragm and improve the cell cycle. [Image Description]

[0024] Figure 1 This is a schematic diagram of the layered structure of a functional combination coating diaphragm according to the present invention. [Detailed Implementation]

[0025] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments.

[0026] It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0027] Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0028] It should be noted that when a component is said to be "fixed" to another component, it can be directly on the other component or it can be in a middle component. When a component is said to be "connected" to another component, it can be directly connected to the other component or it may be in a middle component.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0030] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] The following detailed description, in conjunction with the accompanying drawings, outlines some embodiments of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0032] Please see Figure 1 The present invention discloses a functional combination coating, a coated diaphragm, and a preparation method thereof, comprising a diaphragm base membrane, a first functional coating, and a second functional coating; the first functional coating and the second functional coating are respectively coated on both sides of the diaphragm base membrane; the thickness of the first functional coating is 1-5 micrometers; the thickness of the second functional coating is 0.5-2 micrometers; and the ceramic particles are non-spherical particles.

[0033] This application simultaneously sets a separator base membrane, a first functional coating, and a second functional coating; the first functional coating and the second functional coating are respectively coated on both sides of the separator base membrane; the thickness of the first functional coating ranges from 1 to 5 micrometers; the thickness of the second functional coating ranges from 0.5 to 2 micrometers; the ceramic particles are non-spherical particles. In practical applications, the double-sided composite coated separator provided by this utility model has a high dielectric constant ceramic separator on one side, which can ensure the insulation performance of the separator; the other side adopts a porous ceramic design to increase the liquid retention performance of the separator and improve the cell cycle.

[0034] In some other embodiments, the diaphragm base membrane comprises at least one of polyethylene, polypropylene, and polyethylene and polypropylene composite materials.

[0035] The first functional coating comprises an inorganic ceramic layer and an organic polymer layer; the inorganic ceramic layer comprises a ceramic material and a binder; wherein the ceramic material has a porous structure with a pore size ranging from 600 to 1500 nm; the ceramic material is one or a mixture of several of alumina, boehmite, magnesium hydroxide, and silicon dioxide; the binder is at least one of styrene-butadiene rubber, hydroxypropyl methylcellulose, sodium carboxymethyl cellulose, polyacrylic acid, and hydroxyethyl cellulose; the organic polymer layer comprises at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, and polyacrylonitrile.

[0036] The first functional coating comprises an inorganic ceramic layer and an organic polymer layer; the inorganic ceramic layer comprises ceramic materials and a binder; wherein the ceramic material has a dense structure with a pore size ranging from 100-500 nm; the ceramic material is BaTiO3, BaSnO3, BaZrO3, or Pb(Mg) 1 / 3 Nb 2 / 3 O3, PbTiO3, Ba(Zn) 1 / 3 Nb 2 / 3 The adhesive is one or more of the following: styrene-butadiene rubber, hydroxypropyl methylcellulose, sodium carboxymethyl cellulose, polyacrylic acid, and hydroxyethyl cellulose; the organic polymer layer contains at least one of the following polymer materials: polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, and polyacrylonitrile.

[0037] The first functional coating and / or the second functional coating contain an organic polymer layer.

[0038] A method for preparing a coated diaphragm includes the following steps:

[0039] S1: Prepare ceramic slurry and organic polymer slurry for coating the diaphragm, and prepare the diaphragm base membrane;

[0040] S2: Mix the ceramic slurry, organic polymer material, wetting agent, deionized water and ethylene glycol into a mixed solvent evenly to form a slurry;

[0041] S3: The above slurry is applied to both sides of the base film by spraying or roller coating.

[0042] S4: Dry, slit, to obtain a functional composite coating diaphragm.

[0043] Preferably, the ceramic slurry contains 85%-95% ceramic material, 3%-5% binder material, and 0.5%-1% wetting agent by weight; the organic polymer slurry contains 70%-90% organic polymer material and 10%-30% wetting agent by weight.

[0044] A secondary battery includes the aforementioned combined coating separator; the first functional coating faces the positive electrode, the second functional coating faces the negative electrode, and the separator is wound or stacked with the positive and negative electrode sheets to form a core, thereby obtaining the secondary battery.

[0045] In the following examples and comparative examples, the base film used is a PE material base film with a thickness of 9 μm, a porosity of 45%, a tortuosity of 1.0, an air permeability of 130s / 100cc, and an average pore size of 35nm.

[0046] Example 1:

[0047] The coating membrane preparation method is as follows: ① Disperse 80 parts of polyvinylidene fluoride (PVDF) and 20 parts of sodium carboxymethyl cellulose (CMC) evenly to obtain an organic polymer slurry; ② Take 90 parts of BaTiO3 ceramic material and 4 parts of styrene-butadiene rubber (SBR) and stir until evenly dispersed to obtain a first ceramic slurry; ③ Take 90 parts of alumina ceramic material and 4 parts of styrene-butadiene rubber (SBR) and stir until evenly dispersed to obtain a second ceramic slurry; ④ Coat the first and second ceramic slurries evenly on the two surfaces of a PE base membrane, with a single-sided ceramic layer thickness of 1 μm. After drying, the resulting membrane is then evenly sprayed with organic polymer slurry on both sides, with a single-sided thickness of 1.5 μm. (Double-sided adhesive)

[0048] Example 2:

[0049] The coating membrane preparation method is as follows: ① Disperse 80 parts of polyvinylidene fluoride (PVDF) and 20 parts of sodium carboxymethyl cellulose (CMC) evenly to obtain an organic polymer slurry; ② Take 90 parts of BaTiO3 ceramic material and 4 parts of styrene-butadiene rubber (SBR) and stir until evenly dispersed to obtain a first ceramic slurry; ③ Take 90 parts of alumina ceramic material and 4 parts of styrene-butadiene rubber (SBR) and stir until evenly dispersed to obtain a second ceramic slurry; ④ Coat the first and second ceramic slurries evenly on the two surfaces of a PE base membrane, with a single-sided ceramic layer thickness of 1 μm. After drying, the resulting membrane is then evenly coated on one side with an organic polymer slurry, with a thickness of 1.5 μm. (Single-sided adhesive)

[0050] Example 3:

[0051] The coating membrane preparation method is as follows: ① Take 90 parts of BaTiO3 ceramic material and 4 parts of styrene-butadiene rubber (SBR) and stir until uniformly dispersed to obtain the first ceramic slurry; ② Take 90 parts of alumina ceramic material and 4 parts of styrene-butadiene rubber (SBR) and stir until uniformly dispersed to obtain the second ceramic slurry; ③ Coat the first and second ceramic slurries uniformly onto the two surfaces of the PE base film, respectively, with a single-sided ceramic layer thickness of 1 μm. (No adhesive)

[0052] Comparative Example 1:

[0053] The coating membrane preparation method is as follows: ① Disperse 80 parts of polyvinylidene fluoride (PVDF) and 20 parts of sodium carboxymethyl cellulose (CMC) evenly to obtain an organic polymer slurry; ② Take 90 parts of BaTiO3 ceramic material and 4 parts of styrene-butadiene rubber (SBR) and stir until evenly dispersed to obtain a ceramic slurry; ③ Coat the obtained ceramic slurry evenly on both surfaces of the PE base membrane, with a single-sided ceramic layer thickness of 1 μm. After drying, the obtained membrane ceramic surface is then evenly sprayed with an organic polymer slurry with a thickness of 1.5 μm.

[0054] Comparative Example 2:

[0055] The coating membrane preparation method is as follows: ① Disperse 80 parts of polyvinylidene fluoride (PVDF) and 20 parts of sodium carboxymethyl cellulose (CMC) evenly to obtain an organic polymer slurry; ② Take 90 parts of alumina ceramic material and 4 parts of styrene-butadiene rubber (SBR) and stir until evenly dispersed to obtain a ceramic slurry; ④ Coat the obtained ceramic slurry evenly on both surfaces of the PE base membrane, with a single-sided ceramic layer thickness of 1 μm. After drying, the obtained membrane ceramic surface is then evenly sprayed with an organic polymer slurry with a thickness of 1.5 μm.

[0056] The above-mentioned separator was tested for porosity, air permeability, puncture strength, liquid absorption rate, ionic conductivity and heat shrinkage performance, and then used in lithium-ion batteries to conduct cycle tests on the cells. The test results are summarized in Table 1.

[0057] [Testing Method]

[0058] 1. Membrane permeability: Record the time required for 100ml of gas to pass through a membrane of fixed area;

[0059] 2. Thermal shrinkage properties of ceramic diaphragms: The diaphragm was baked in an oven at 130℃ for 1 hour, and the change in length in the TD / MD direction was measured to calculate the shrinkage rate. Shrinkage rate (%) = (original length - length after baking) / original length × 100;

[0060] 3. Puncture strength: A universal testing machine was used, with a needle curvature radius of 0.5 mm.

[0061] 4. Porosity: Cut the diaphragm into circular pieces with a diameter of 47 mm, calculate the volume based on the surface area and thickness, and weigh the mass using an analytical balance. Porosity (%) = (Volume - Mass / Diaphragm raw material density) / Volume × 100;

[0062] 5. Liquid retention capacity of ceramic diaphragm: The diaphragm is immersed in electrolyte for 24 hours. The weight of the diaphragm before and after the test is calculated. Liquid retention rate per unit coating = (diaphragm immersion mass - mass before immersion) / (mass before immersion * coating thickness).

[0063] 6. Capacity retention rate of ceramic separator at the battery end: The battery is cycled 200 times at 0.33C charge and discharge, and the capacity before and after the cycle is tested. Capacity retention rate = capacity after cycle / capacity before cycle.

[0064] Table 1

[0065]

[0066]

[0067] As shown in Table 1, compared with Examples 1-3 and Comparative Examples 1-2, the diaphragm prepared in this application has good performance in terms of heat shrinkage rate, puncture strength, liquid retention rate and cycle capacity retention rate.

[0068] This demonstrates that the double-sided composite coating diaphragm prepared in this application has excellent cycle performance and safety performance.

[0069] This utility model discloses a separator that combines a high dielectric constant ceramic particle coating and a porous ceramic coating, which can reduce cell self-discharge and increase cell porosity, thereby improving the separator's liquid retention effect and enhancing the battery's electrical and safety performance.

[0070] The double-sided composite coating diaphragm provided by this utility model has a high dielectric constant ceramic diaphragm on one side, which can ensure the insulation performance of the diaphragm; the other side adopts a porous ceramic design to increase the liquid retention performance of the diaphragm and improve the cell cycle.

[0071] The technical effects achieved by this application in solving the technical problem are as follows:

[0072] Compared with the prior art, the present invention provides a functional combination coating, a coated diaphragm, and a preparation method 1, by simultaneously setting a diaphragm base film, a first functional coating, and a second functional coating; the first functional coating and the second functional coating are respectively coated on both sides of the diaphragm base film; the thickness of the first functional coating ranges from 1 to 5 micrometers; the thickness of the second functional coating ranges from 0.5 to 2 micrometers; the ceramic particles are non-spherical particles. In practical applications, the double-sided combined coating diaphragm provided by the present invention has one side containing a high dielectric constant ceramic diaphragm, which can ensure the insulation performance of the diaphragm; the other side adopts a porous ceramic design to increase the liquid retention performance of the diaphragm and improve the cell cycle.

[0073] The embodiments of this utility model described above do not constitute a limitation on the scope of protection of this utility model. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the scope of protection of the claims of this utility model.

Claims

1. A functional combination coating membrane, characterized in that: It includes a diaphragm base membrane, a first functional coating, and a second functional coating; the first functional coating and the second functional coating are respectively coated on both sides of the diaphragm base membrane; The thickness of the first functional coating ranges from 1 to 5 micrometers; the thickness of the second functional coating ranges from 0.5 to 2 micrometers.

2. The functional combination coating membrane as described in claim 1, characterized in that: The diaphragm base membrane includes at least one of polyethylene, polypropylene, and polyethylene and polypropylene composite materials.

3. The functional combination coating membrane as described in claim 1, characterized in that: The first functional coating comprises an inorganic ceramic layer and an organic polymer layer; the inorganic ceramic layer comprises a ceramic material and a binder; wherein the ceramic material has a porous structure with a pore size ranging from 600 to 1500 nm; the ceramic material is one or a mixture of several of alumina, boehmite, magnesium hydroxide, and silicon dioxide; the binder is at least one of styrene-butadiene rubber, hydroxypropyl methylcellulose, sodium carboxymethyl cellulose, polyacrylic acid, and hydroxyethyl cellulose; the organic polymer layer comprises at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, and polyacrylonitrile.

4. The functional combination coating membrane as described in claim 1, characterized in that: The first functional coating comprises an inorganic ceramic layer and an organic polymer layer; the inorganic ceramic layer comprises ceramic materials and a binder; wherein the ceramic material has a dense structure with a pore size ranging from 100-500 nm; the ceramic material is BaTiO3, BaSnO3, BaZrO3, or Pb(Mg) 1 / 3 Nb 2 / 3 O3, PbTiO3, Ba(Zn) 1 / 3 Nb 2 / 3 The adhesive is one or more of the following: styrene-butadiene rubber, hydroxypropyl methylcellulose, sodium carboxymethyl cellulose, polyacrylic acid, and hydroxyethyl cellulose; the organic polymer layer contains at least one of the following polymer materials: polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, and polyacrylonitrile.

5. A functional combination coating membrane as described in any one of claims 1 to 4, characterized in that: The first functional coating and / or the second functional coating contain an organic polymer layer.

6. A secondary battery, characterized in that: The membrane includes the combined coating membrane according to any one of claims 1-4; the first functional coating faces the positive electrode, the second functional coating faces the negative electrode, and the membrane is wound or stacked with the positive electrode sheet and the negative electrode sheet to form a core, thereby obtaining a secondary battery.

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