Lithium battery coating diaphragm based on polymer ion conductor coating and preparation method of lithium battery coating diaphragm

Abstract

The invention relates to the field of lithium battery diaphragms, in particular to a lithium battery coating diaphragm based on a polymer ion conductor coating and a preparation method of the lithium battery coating diaphragm, and aims to solve the problems that hot-pressing compounding of an existing diaphragm polymer coating material and an electrode needs to be heated and pressurized, and hot-pressing compounding can generate negative effects on battery performance; and during normal-temperature compounding, the coating can block pores of the diaphragm, so that the performance of the battery is seriously influenced. The polymer ion conductor coating takes a hard monomer and a soft monomer as main raw materials, the bonding performance of the polymer ion conductor coating can be effectively improved after a bonding functional monomer is added into the polymer ion conductor coating, so that the lithium battery coating diaphragm can realize battery cell pressurized compounding at room temperature, and the stability of the battery diaphragm can be improved by adding a cross-linking monomer into the polymer ion conductor coating; lithium ion transmission can be accelerated by adding the imidazolium ionic liquid monomer and the ion-conducting functional monomer, the rate and the cycle performance of the diaphragm are greatly improved, and the comprehensive performance of the lithium battery is improved.

Description

Technical Field

[0001] The present invention relates to the field of lithium battery separators, in particular to a lithium battery coated separator based on a polymer ion conductor coating and a preparation method thereof. Background Art

[0002] In today's era, with the widespread adoption of portable electronics and the rapidly growing demand for new energy sources, lithium-ion batteries, with their outstanding advantages such as high energy density, long lifespan, and low self-discharge, have become a core force in the energy storage field. From everyday electronic devices like mobile phones and laptops to large-scale applications such as electric vehicles and energy storage power stations, lithium-ion batteries are ubiquitous, and their performance is directly related to the operating efficiency and reliability of these devices and systems.

[0003] In the structure of lithium-ion batteries, the separator is a key internal component, and its performance plays a decisive role in the overall performance of the battery. The separator performs two crucial tasks: first, it separates the positive and negative electrodes of the battery, effectively preventing contact and short circuits, which is essential for safe and stable battery operation; second, it allows electrolyte ions to pass through, creating a pathway for ion transport and ensuring the smooth progress of electrochemical reactions within the battery. Currently, commercially available separator materials are primarily polyolefins such as polyethylene and polypropylene. However, these polyolefin-based separators have several significant drawbacks. For example, their suboptimal porosity limits ion transport efficiency; their poor thermal stability makes them susceptible to shrinkage and deformation at high temperatures, even leading to internal short circuits and potential safety hazards; and their poor wettability with polar liquid electrolytes increases the resistance and reduces the energy density of lithium-ion batteries. These shortcomings not only hinder further improvements in lithium-ion battery performance but also hinder their ability to meet the increasingly stringent demands of emerging applications such as electric vehicles and large-scale energy storage. In order to break through the performance bottleneck of polyolefin-based membranes, polymer-coated membrane technology has emerged through continuous exploration and innovation, showing great potential in improving the performance and safety of lithium batteries.

[0004] Current diaphragm polymer coating materials mainly include PVDF-HFP and modified PMMA functional coating materials. These materials usually require heating and pressurization for hot pressing with electrodes, which will have a negative impact on battery performance. Attempting to use room temperature composite technology will cause the coating to block the diaphragm pores, increase the battery DCR, and the interface adhesion between the diaphragm and the electrode will fail after the battery cycle, resulting in a decrease in battery performance.

[0005] Therefore, the development of a lithium battery coated diaphragm based on a polymer ion conductor coating and a preparation method thereof has important practical significance. Summary of the Invention

[0006] In order to overcome the above-mentioned technical problems, the purpose of the present invention is to provide a lithium battery coated diaphragm based on a polymer ion conductor coating and a preparation method thereof, which solves the problem that the existing diaphragm polymer coating material and the electrode hot pressing composite need to be heated and pressurized, and the hot pressing composite will have a negative impact on the battery performance, while the room temperature composite will cause the coating to block the pores of the diaphragm, seriously affecting the battery performance.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] Lithium battery coated diaphragms based on polymer ion conductor coatings, base membranes and polymer ion conductor coatings on the surface of base membranes;

[0009] Wherein, the polymer ion conductor coating comprises the following components in parts by weight:

[0010] 60-140 parts of hard monomer, 30-60 parts of soft monomer, 10-20 parts of adhesive functional monomer, 10-20 parts of ion-conducting functional monomer, 1-10 parts of cross-linking monomer, 10-30 parts of imidazole ionic liquid monomer, 500 parts of solvent, 0.6-2 parts of initiator, 0.2-1 parts of tert-butyl hydroperoxide and 0.2-1 parts of FF6M formaldehyde-free reducing agent.

[0011] As a preferred embodiment of the present invention, the hard monomer is styrene, methyl methacrylate, or a mixture of the two in any proportion.

[0012] As a preferred embodiment of the present invention, the soft monomer is one or a mixture of two or more of isooctyl acrylate, isooctyl methacrylate, butyl acrylate, butyl methacrylate and ethyl acrylate in any proportion.

[0013] As a preferred embodiment of the present invention, the adhesive functional monomer is one or a mixture of two or more of vinyl acetate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, 4-hydroxybutyl acrylate, ethyl methacrylate, glycidyl methacrylate and acrylonitrile in any proportion.

[0014] As a preferred embodiment of the present invention, the ion-conducting functional monomer is one of acrylic acid, methacrylic acid and β-carboxyethyl acrylate, or a mixture of two or more of them in any proportion.

[0015] As a preferred embodiment of the present invention, the cross-linking monomer is one or a mixture of two or more of N-hydroxyethyl acrylamide, N-(hydroxymethyl) acrylamide, diacetone acrylamide, 1,4-butanediol diacrylate, divinylbenzene, ethylene glycol diacrylate and 1,6-hexanediol diacrylate in any proportion.

[0016] As a preferred embodiment of the present invention, the imidazole ionic liquid monomer is one of 1-vinyl-3-ethylimidazolium lithium tetrafluoroborate and 1-allyl-3-ethylimidazolium lithium tetrafluoroborate, or a mixture of the two in any proportion.

[0017] As a preferred embodiment of the present invention, the solvent is a methanol solution or an ethanol solution with a volume fraction of 30-70%.

[0018] As a preferred embodiment of the present invention, the initiator is one or a mixture of two or more of ammonium persulfate, potassium persulfate, azobisisobutyronitrile and benzoyl peroxide in any proportion.

[0019] As a preferred embodiment of the present invention, a method for preparing a lithium battery coated separator based on a polymer ion conductor coating comprises the following steps:

[0020] Step 1: Add hard monomer, soft monomer, adhesive functional monomer, ion-conducting functional monomer, and cross-linking monomer to the solvent, stir and react for 10-20 minutes at a temperature of 25-30°C and a stirring rate of 300-400r / min, then adjust the pH value to 5-7 with lithium hydroxide, then add the initiator and continue stirring and reacting at 70-85°C for 2-4 hours, then add the imidazole ionic liquid monomer and continue stirring and reacting at 85-95°C for 3-5 hours, then add tert-butyl hydroperoxide and FF6M formaldehyde-free reducing agent under the condition of cooling to 50-70°C and continue stirring and reacting for 30-40 minutes, and after the reaction is completed, cool the reaction product to room temperature to obtain a pressure-sensitive ion-conducting polymer functional coating glue;

[0021] Step 2: spray drying the pressure-sensitive ion-conducting polymer functional coating solution at a drying temperature of 100-200° C. to form granules, introducing the powder formed after atomization drying into a cooling tower, and cooling it at a cooling temperature of 30-45° C. to obtain a pressure-sensitive polymer ion-conducting coating powder;

[0022] Step 3: Add the pressure-sensitive polymer ion-conductive coating powder to deionized water, stir and disperse at a temperature of 25-30° C. and a stirring rate of 2000-3000 r / min to obtain a dispersed and stable slurry with a solid content of 5-20%;

[0023] Step 4: coating the dispersed stable slurry on one surface or both surfaces of the base film to form a polymer ion conductor coating, thereby obtaining a lithium battery coated diaphragm based on the polymer ion conductor coating.

[0024] As a preferred embodiment of the present invention, the particle size D50 of the pressure-sensitive polymer ion-conducting coating powder is 2-6 μm, and the particle size D90 is less than 15 μm.

[0025] As a preferred embodiment of the present invention, the base membrane has a thickness of 5-16 μm and a porosity of 30-60%; and the base membrane is a polyolefin single-sided ceramic diaphragm.

[0026] As a preferred embodiment of the present invention, the coating process is one of spray coating, gravure roller coating and spot coating, and the coating amount is 0.5-1g / m2 per side. 2 .

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The polymer ion conductor coating is mainly made of hard monomers and soft monomers. After adding adhesive functional monomers, its bonding performance can be effectively improved. In the hot pressing composite process of the battery cell manufacturing, the lithium battery coated separator based on the polymer ion conductor coating can achieve battery cell pressurization composite at room temperature, avoiding negative impact on battery performance and significantly reducing production energy consumption. It can be widely used and promoted. Adding cross-linking monomers can effectively improve the cross-linking degree of the polymer ion conductor coating, improve the stability of the battery separator, and thus improve the cycle stability of the lithium battery. Adding imidazole ionic liquid monomers can provide imidazole cations, provide a positive electric field at the electrode / diaphragm interface, limit the movement of anions through electrostatic attraction, and improve the lithium ion diffusion kinetics through electrostatic repulsion, accelerate lithium ion transmission, and utilize the imidazole ionic liquid monomers and ion-conducting functional monomers (using the lithium ions provided by the carboxyl complex lithium hydroxide on them) to provide a large amount of lithium ions, thereby optimizing the lithium ion conduction path, thereby significantly improving the surface resistance of the separator, thereby greatly improving the rate and cycle performance of the separator, and improving the overall performance of the lithium battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] To facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0030] Figure 1 This is a 5000x electron microscope image of the pressure-sensitive polymer ion-conductive coating powder in Example 1 of the present invention.

[0031] Figure 2 This is a 1000x electron microscope image of the pressure-sensitive polymer ion-conductive coating powder in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] Example 1:

[0034] This embodiment is a method for preparing a lithium battery coated separator based on a polymer ion conductor coating, comprising the following steps:

[0035] Step 1: Weigh 100 parts of hard monomer, 40 parts of soft monomer, 14 parts of adhesive functional monomer, 20 parts of ion-conducting functional monomer, 6 parts of cross-linking monomer, 20 parts of imidazole ionic liquid monomer, 500 parts of solvent, 1.1 parts of initiator, 0.2 parts of tert-butyl hydroperoxide and 0.2 parts of FF6M formaldehyde-free reducing agent according to weight parts and set aside;

[0036] The hard monomer is styrene;

[0037] The soft monomer is isooctyl acrylate;

[0038] The adhesive functional monomer is a mixture of vinyl acetate and glycidyl methacrylate in a mass ratio of 5:2;

[0039] The ion-conducting functional monomer is acrylic acid;

[0040] The cross-linking monomer is a mixture of N-hydroxyethyl acrylamide and 1,4-butanediol diacrylate in a mass ratio of 1:2;

[0041] The imidazole ionic liquid monomer is 1-vinyl-3-ethylimidazolium lithium tetrafluoroborate;

[0042] The solvent is a methanol solution with a volume fraction of 40%;

[0043] The initiator is a mixture of ammonium persulfate and azobisisobutyronitrile in a mass ratio of 7:4;

[0044] Step 2: Add the hard monomer, soft monomer, adhesive functional monomer, ion-conducting functional monomer, and cross-linking monomer to the solvent, stir and react for 10 minutes at a temperature of 25°C and a stirring rate of 300r / min, then adjust the pH value to 7 with lithium hydroxide, then add the initiator and continue stirring and reacting at 70°C for 2 hours, then add the imidazole ionic liquid monomer and continue stirring and reacting at 85°C for 3 hours, then add tert-butyl hydroperoxide and FF6M formaldehyde-free reducing agent under the condition of cooling to 50°C and continue stirring and reacting for 30 minutes, and after the reaction is completed, cool the reaction product to room temperature to obtain a pressure-sensitive ion-conducting polymer functional coating glue;

[0045] Step 3: spray-dry the pressure-sensitive ion-conducting polymer functional coating solution at a drying temperature of 150°C to form granules, introduce the powder formed after atomization and drying into a cooling tower, and cool it down at a cooling temperature of 40°C to obtain a pressure-sensitive polymer ion-conducting coating powder; the pressure-sensitive polymer ion-conducting coating powder in Example 1 is subjected to electron microscopy, see Figure 1 (5000 times)- Figure 2 (1000 times), it can be known that the particle size D50 of the pressure-sensitive polymer ion-conducting coating powder is 2-6 μm, and the particle size D90 is less than 15 μm;

[0046] Step 4: Add the pressure-sensitive polymer ion-conductive coating powder to deionized water, stir and disperse at a temperature of 25° C. and a stirring rate of 2000 r / min to obtain a dispersed and stable slurry with a solid content of 10%;

[0047] Step 5: Use the spray coating process to apply the dispersed stable slurry on both sides of the polyolefin single-sided ceramic diaphragm with a thickness of 12μm and a porosity of 40%, and control the coating amount to 0.5g / m 2 , forming a polymer ion conductor coating to obtain a lithium battery coated diaphragm based on the polymer ion conductor coating; wherein, the thickness of the polyolefin layer in the polyolefin single-sided ceramic diaphragm is 9μm and the ceramic layer is 3μm; the thickness of the polymer ion conductor coating is 0.5μm; the structural specifications of the lithium battery coated diaphragm based on the polymer ion conductor coating are 0.5μm+3μm+9μm+0.5μm.

[0048] Example 2:

[0049] The difference between this embodiment and embodiment 1 is that the coating process adopts gravure roller coating.

[0050] Example 3:

[0051] This embodiment is a method for preparing a lithium battery coated separator based on a polymer ion conductor coating, comprising the following steps:

[0052] Step 1: Weigh 80 parts of hard monomer, 40 parts of soft monomer, 20 parts of adhesive functional monomer, 20 parts of ion-conducting functional monomer, 6 parts of cross-linking monomer, 30 parts of imidazole ionic liquid monomer, 500 parts of solvent, 1.1 parts of initiator, 0.2 parts of tert-butyl hydroperoxide and 0.2 parts of FF6M formaldehyde-free reducing agent according to weight parts and set aside;

[0053] The hard monomer is a mixture of styrene and methyl methacrylate in a mass ratio of 3:1;

[0054] The soft monomer is isooctyl methacrylate;

[0055] The adhesive functional monomer is a mixture of vinyl acetate, glycidyl methacrylate and acrylonitrile in a mass ratio of 3:1:1;

[0056] The ion-conducting functional monomer is methacrylic acid;

[0057] The cross-linking monomer is a mixture of N-(hydroxymethyl)acrylamide and divinylbenzene in a mass ratio of 1:2;

[0058] The imidazole ionic liquid monomer is 1-vinyl-3-ethylimidazolium lithium tetrafluoroborate;

[0059] The solvent is a methanol solution with a volume fraction of 50%;

[0060] The initiator is a mixture of ammonium persulfate and azobisisobutyronitrile in a mass ratio of 7:4;

[0061] Step 2: Add the hard monomer, soft monomer, adhesive functional monomer, ion-conducting functional monomer, and cross-linking monomer to the solvent, stir and react for 15 minutes at a temperature of 28°C and a stirring rate of 350r / min, then adjust the pH value to 6 with lithium hydroxide, then add the initiator and continue stirring and reacting for 3 hours under the condition of raising the temperature to 80°C, then add the imidazole ionic liquid monomer and continue stirring and reacting for 4 hours under the condition of raising the temperature to 90°C, then add tert-butyl hydroperoxide and FF6M formaldehyde-free reducing agent under the condition of cooling to 60°C and continue stirring and reacting for 35 minutes, and after the reaction is completed, cool the reaction product to room temperature to obtain a pressure-sensitive ion-conducting polymer functional coating glue;

[0062] Step 3: spray drying the pressure-sensitive ion-conducting polymer functional coating solution at a drying temperature of 160° C. to form granules, and introducing the powder formed after atomization drying into a cooling tower, and cooling it at a cooling temperature of 45° C. to obtain a pressure-sensitive polymer ion-conducting coating powder;

[0063] Step 4: Add the pressure-sensitive polymer ion-conductive coating powder to deionized water, stir and disperse at a temperature of 28° C. and a stirring rate of 2500 r / min to obtain a dispersed and stable slurry with a solid content of 10%;

[0064] Step 5: Use the spray coating process to apply the dispersed stable slurry on both sides of the polyolefin single-sided ceramic diaphragm with a thickness of 10μm and a porosity of 42%, and control the coating amount to 0.5g / m 2 , forming a polymer ion conductor coating to obtain a lithium battery coated diaphragm based on the polymer ion conductor coating; wherein, the thickness of the polyolefin layer in the polyolefin single-sided ceramic diaphragm is 7μm and the ceramic layer is 3μm; the thickness of the polymer ion conductor coating is 0.5μm; the structural specifications of the lithium battery coated diaphragm based on the polymer ion conductor coating are 0.5μm+3μm+7μm+0.5μm.

[0065] Example 4:

[0066] The difference between this embodiment and embodiment 3 is that the coating process adopts gravure roller coating.

[0067] Example 5:

[0068] This embodiment is a method for preparing a lithium battery coated separator based on a polymer ion conductor coating, comprising the following steps:

[0069] Step 1: Weigh 60 parts of hard monomer, 60 parts of soft monomer, 20 parts of adhesive functional monomer, 14 parts of ion-conducting functional monomer, 6 parts of cross-linking monomer, 20 parts of imidazole ionic liquid monomer, 500 parts of solvent, 1.1 parts of initiator, 0.2 parts of tert-butyl hydroperoxide and 0.2 parts of FF6M formaldehyde-free reducing agent according to weight parts and set aside;

[0070] The hard monomer is methyl methacrylate;

[0071] The soft monomer is a mixture of isooctyl methacrylate and butyl acrylate in a mass ratio of 2:1;

[0072] The adhesive functional monomer is a mixture of hydroxyethyl acrylate and glycidyl methacrylate in a mass ratio of 1:1;

[0073] The ion-conducting functional monomer is β-carboxyethyl acrylate;

[0074] The cross-linking monomer is a mixture of N-(hydroxymethyl)acrylamide, diacetone acrylamide, and 1,6-hexanediol diacrylate in a mass ratio of 1:2;

[0075] The imidazole ionic liquid monomer is 1-allyl-3-ethylimidazolium lithium tetrafluoroborate;

[0076] The solvent is an ethanol solution with a volume fraction of 50%;

[0077] The initiator is a mixture of ammonium persulfate and azobisisobutyronitrile in a mass ratio of 7:4;

[0078] Step 2: Add the hard monomer, soft monomer, adhesive functional monomer, ion-conducting functional monomer, and cross-linking monomer to the solvent, stir and react for 20 minutes at a temperature of 30°C and a stirring rate of 400r / min, then adjust the pH value to 5 with lithium hydroxide, then add the initiator and continue stirring and reacting at 80°C for 4 hours, then add the imidazole ionic liquid monomer and continue stirring and reacting at 90°C for 5 hours, then add tert-butyl hydroperoxide and FF6M formaldehyde-free reducing agent under the condition of cooling to 60°C and continue stirring and reacting for 40 minutes, and after the reaction is completed, cool the reaction product to room temperature to obtain a pressure-sensitive ion-conducting polymer functional coating glue;

[0079] Step 3: spray drying the pressure-sensitive ion-conducting polymer functional coating solution at a drying temperature of 140° C. to form granules, and introducing the powder formed after atomization drying into a cooling tower, and cooling it at a cooling temperature of 45° C. to obtain a pressure-sensitive polymer ion-conducting coating powder;

[0080] Step 4: Add the pressure-sensitive polymer ion-conductive coating powder to deionized water, stir and disperse at a temperature of 30° C. and a stirring rate of 3000 r / min to obtain a dispersed and stable slurry with a solid content of 10%;

[0081] Step 5: Use the spray coating process to apply the dispersed stable slurry to one or both sides of the polyolefin single-sided ceramic diaphragm with a thickness of 7μm and a porosity of 38%, and control the coating amount to 1g / m 2 , forming a polymer ion conductor coating to obtain a lithium battery coated diaphragm based on the polymer ion conductor coating; wherein, the thickness of the polyolefin layer in the polyolefin single-sided ceramic diaphragm is 5μm and the ceramic layer is 2μm; the thickness of the polymer ion conductor coating is 1μm; the structural specifications of the lithium battery coated diaphragm based on the polymer ion conductor coating are 1μm+2μm+5μm+1μm.

[0082] Example 6:

[0083] The difference between this embodiment and embodiment 5 is that the coating process adopts gravure roller coating.

[0084] Comparative Example 1:

[0085] The difference between this comparative example and Example 1 is that the pressure-sensitive coating material prepared according to the method disclosed in Example 1 of patent CN115717011A is used to replace the pressure-sensitive polymer ion-conductive coating powder.

[0086] Comparative Example 2:

[0087] The difference between this comparative example and Example 2 is that the pressure-sensitive coating material prepared according to the method disclosed in Example 1 of patent CN115717011A is used to replace the pressure-sensitive polymer ion-conductive coating powder.

[0088] Comparative Example 3:

[0089] The difference between this comparative example and Example 3 is that the pressure-sensitive coating material prepared according to the method disclosed in Example 1 of patent CN115717011A is used to replace the pressure-sensitive polymer ion-conductive coating powder.

[0090] Comparative Example 4:

[0091] The difference between this comparative example and Example 4 is that the pressure-sensitive coating material prepared according to the method disclosed in Example 1 of patent CN115717011A is used to replace the pressure-sensitive polymer ion-conductive coating powder.

[0092] Comparative Example 5:

[0093] The difference between this comparative example and Example 5 is that the pressure-sensitive coating material prepared according to the method disclosed in Example 1 of patent CN115717011A is used to replace the pressure-sensitive polymer ion-conductive coating powder.

[0094] Comparative Example 6:

[0095] The difference between this comparative example and Example 6 is that the pressure-sensitive coating material prepared according to the method disclosed in Example 1 of patent CN115717011A is used to replace the pressure-sensitive polymer ion-conductive coating powder.

[0096] The lithium battery coated separators based on polymer ion conductor coatings of Examples 1-6 and Comparative Examples 1-6 were assembled into 3Ah ternary 622 / graphite soft pack batteries, and their rate and cycle performance were tested. The test results are shown in the following table:

[0097]

[0098] Referring to the data in the above table, according to the comparison between Examples 1-6 and Comparative Examples 1-6, it can be seen that the lithium battery coated diaphragm based on the polymer ion conductor coating of the present application has excellent bonding properties and electrochemical properties. In summary, the present invention uses alcohol / water as a mixed solvent and free radical polymerization to prepare a pressure-sensitive ion-conducting polymer functional coating glue, and introduces lithium acrylate and ionic liquid monomer structures into the molecular structure to improve the ionic conductivity of the pressure-sensitive polymer composite coating material. It can be seen from the above table that the introduction of lithium carboxylate structure and imidazole ionic liquid monomer can still maintain good room temperature pressure sensitivity, and the bonding force with the positive and negative electrodes can meet the requirements of battery application, and the surface resistance of the diaphragm is significantly improved, thereby greatly improving the rate and cycle performance of the diaphragm.

[0099] Among them, the adhesion test method is as follows: the lithium battery coated diaphragm is compounded with the positive electrode sheet ternary 622 and the negative electrode graphite sheet respectively. The pressurized compounding conditions are temperature 25°C, pressure 6MPa, and time 60s. The diaphragm compounded with the positive and negative electrode sheets is then subjected to a 180° peeling test.

[0100] Among them, the diaphragm surface resistance test method is as follows:

[0101] 1) Assemble a simulated battery: Place the diaphragm between two flat electrodes made of stainless steel and inject electrolyte to simulate the internal environment of the battery.

[0102] 2) Testing and calculation: Use the linear sweep voltammetry method in the electrochemical workstation to test the linear voltammetry curve of the simulated battery, calculate the polarization resistance of the simulated battery based on the curve, and then prepare simulated batteries with different numbers of diaphragm layers, calculate their polarization resistance, and obtain the diaphragm surface resistance by drawing a curve of the ionic resistance and number of layers of simulated batteries with different numbers of diaphragm layers.

[0103] Among them, the rate and cycle performance test methods are as follows:

[0104] The lithium battery coated separator was assembled into a 3Ah ternary 622 / graphite soft-pack battery, and its rate and cycle performance were tested. The rate performance was 0.5C charge / 0.5C, 1C, 2C, and 5C discharge, and the cycle performance was 1C / 1C charge and discharge.

[0105] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0106] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined in this application, they should all fall within the scope of protection of the present invention.

Claims

1. A lithium battery coated separator based on a polymer ion conductor coating, characterized in that: Base membrane and polymer ion conductor coating on the surface of the base membrane; Wherein, the base membrane is a polyolefin single-sided ceramic diaphragm; Wherein, the polymer ion conductor coating comprises the following components in parts by weight: 60-140 parts of hard monomer, 30-60 parts of soft monomer, 10-20 parts of adhesive functional monomer, 10-20 parts of ion-conducting functional monomer, 1-10 parts of cross-linking monomer, 10-30 parts of imidazole ionic liquid monomer, 500 parts of solvent, 0.6-2 parts of initiator, 0.2-1 parts of tert-butyl hydroperoxide and 0.2-1 parts of FF6M formaldehyde-free reducing agent; Wherein, the ion-conducting functional monomer is one or a mixture of two or more of acrylic acid, methacrylic acid and β-carboxyethyl acrylate in any proportion; The imidazole ionic liquid monomer is one of 1-vinyl-3-ethylimidazolium lithium tetrafluoroborate and 1-allyl-3-ethylimidazolium lithium tetrafluoroborate, or a mixture of the two in any proportion.

2. The lithium battery coated separator based on polymer ion conductor coating according to claim 1, characterized in that The hard monomer is one of styrene and methyl methacrylate or a mixture of the two in any proportion.

3. The lithium battery coated separator based on polymer ion conductor coating according to claim 1, characterized in that The soft monomer is one of isooctyl acrylate, isooctyl methacrylate, butyl acrylate, butyl methacrylate and ethyl acrylate, or a mixture of two or more of them in any proportion.

4. The lithium battery coated separator based on polymer ion conductor coating according to claim 1, characterized in that The bonding functional monomer is one of vinyl acetate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, 4-hydroxybutyl acrylate, ethyl methacrylate, glycidyl methacrylate and acrylonitrile, or a mixture of two or more in any proportion.

5. The lithium battery coated separator based on polymer ion conductor coating according to claim 1, characterized in that The crosslinking monomer is one or a mixture of two or more of N-hydroxyethyl acrylamide, N-(hydroxymethyl) acrylamide, diacetone acrylamide, 1,4-butanediol diacrylate, divinylbenzene, ethylene glycol diacrylate and 1,6-hexanediol diacrylate in any proportion.

6. The lithium battery coated separator based on polymer ion conductor coating according to claim 1, characterized in that The solvent is a methanol solution or an ethanol solution with a volume fraction of 30-70%.

7. The lithium battery coated separator based on polymer ion conductor coating according to claim 1, characterized in that The initiator is one of ammonium persulfate, potassium persulfate, azobisisobutyronitrile and benzoyl peroxide, or a mixture of two or more of the two in any proportion.

8. A method for preparing a lithium battery coated diaphragm based on a polymer ion conductor coating, characterized in that: The following steps are involved: Step 1: Add hard monomer, soft monomer, adhesive functional monomer, ion-conducting functional monomer, and cross-linking monomer to the solvent, stir and react for 10-20 minutes at a temperature of 25-30°C and a stirring rate of 300-400r / min, then adjust the pH value to 5-7 with lithium hydroxide, then add the initiator and continue stirring and reacting at 70-85°C for 2-4 hours, then add the imidazole ionic liquid monomer and continue stirring and reacting at 85-95°C for 3-5 hours, then add tert-butyl hydroperoxide and FF6M formaldehyde-free reducing agent under the condition of cooling to 50-70°C and continue stirring and reacting for 30-40 minutes, and after the reaction is completed, cool the reaction product to room temperature to obtain a pressure-sensitive ion-conducting polymer functional coating glue; Step 2: spray drying the pressure-sensitive ion-conducting polymer functional coating solution at a drying temperature of 100-200° C. to form granules, introducing the powder formed after atomization drying into a cooling tower, and cooling it at a cooling temperature of 30-45° C. to obtain a pressure-sensitive polymer ion-conducting coating powder; Step 3: Add the pressure-sensitive polymer ion-conductive coating powder to deionized water, stir and disperse at a temperature of 25-30° C. and a stirring rate of 2000-3000 r / min to obtain a dispersed and stable slurry with a solid content of 5-20%; Step 4: coating the dispersed stable slurry on one surface or both surfaces of the base film to form a polymer ion conductor coating, thereby obtaining a lithium battery coated diaphragm based on the polymer ion conductor coating.

9. The method for preparing a lithium battery coated diaphragm based on a polymer ion conductor coating according to claim 8, characterized in that: The particle size D50 of the pressure-sensitive polymer ion-conducting coating powder is 2-6 μm, and the particle size D90 is less than 15 μm.

10. The method for preparing a lithium battery coated diaphragm based on a polymer ion conductor coating according to claim 8, characterized in that: The thickness of the base film is 5-16 μm and the porosity is 30-60%. The coating process is one of spraying, gravure roller coating and spot coating, and the coating amount is 0.5-1 g / m2 per side. 2 .

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