A lithium battery separator
By adjusting the mass ratio of the first binder, the second binder and the ceramic particles and the particle size of the ceramic particles, the problems of excessive thickness of the PP/PE/PP three-layer coextruded base film and insufficient viscosity of the ceramic particles are solved, and the problems of excessive thickness of the PP/PE/PP three-layer coextruded base film are improved, The porosity and winding efficiency of lithium-ion batteries have been improved.
Patent Information
- Application Number
- CN202410580631.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-11
- Publication Date
- 2024-12-10
- Estimated Expiration
- 2044-05-11
AI Technical Summary
The thickness of the existing PP/PE/PP three-layer coextruded base film is too thick, resulting in a decrease in the energy density of lithium-ion batteries, and insufficient viscosity of ceramic particles at corners leads to a decrease in the winding advantage, resulting in a dislocation of the extreme ears, affecting battery performance.
The mass ratio of the first binder, the second binder and the ceramic particles is 25-28:5-7:65-70, the ceramic particles are 2μm-3μm, and the first binder is in the test electrolyte. After soaking, the viscosity is less than or equal to 9000mPa·s. Combined with the appropriate ceramic particle size, the porosity and winding efficiency of the membrane are improved, and the battery performance is enhanced.
It improves the porosity and winding advantage of lithium-ion batteries, enhances the lithium-ion transmission efficiency and battery performance, avoids the extreme ear dislocation caused by insufficient viscosity at corners, and improves the overall performance of the battery.
Abstract
Description
Technical Field
[0001] The present application belongs to the technical field of diaphragms, and specifically relates to a lithium battery diaphragm. Background Art
[0002] Lithium-ion batteries have the advantages of high energy storage density, high open circuit voltage, low self-discharge rate, long cycle life and good safety. They are now widely used as power sources in electronic products such as cameras, mobile phones, drones, laptops and smart watches. The composition of lithium-ion batteries includes positive electrode, negative electrode, diaphragm and electrolyte. As one of the four major materials of lithium-ion batteries, the diaphragm does not participate in the electrochemical reaction in the battery, but it is a key internal component in the lithium battery. The key performance of the battery, such as capacity, cycle performance and charge and discharge current density, is directly related to the diaphragm. The safety of the diaphragm is an important factor affecting the safety of lithium-ion batteries.
[0003] As the use of lithium-ion batteries continues to expand, the market has put forward higher requirements for lithium-ion batteries. As one of the important components of lithium-ion batteries, the separator will directly affect the performance of lithium-ion batteries.
[0004] The common base films for current diaphragms include dry-process PP, wet-process PE, dry-process PP / PP / PP three-layer film, PP / PE / PP three-layer co-extruded base film, etc. Because compared with wet-process PE, the PP / PE / PP three-layer co-extruded base film can provide support at high temperatures, such as greater than 120°C, when the PE layer is closed. Therefore, it is very safe and is often used in the field of consumer electronics. Summary of the invention
[0005] At present, for the three-layer co-extruded base film of PP / PE / PP containing PP, the thickness is too thick compared with the PE base film, which reduces the battery energy density within the same volume. In addition, after the three-layer co-extruded base film of PP / PE / PP is coated with a ceramic coating, due to the presence of ceramic particles, at the corners on the left and right sides of the wound battery cell, the diaphragm is bent and subjected to different forces, which can easily cause the diaphragm to be less sticky at the corners, resulting in ear dislocation of the positive electrode / diaphragm / negative electrode after winding, thereby reducing the winding quality rate.
[0006] The invention comprises a base film and a coating, wherein the coating comprises a first binder, a second binder and ceramic particles; the second binder is styrene-butadiene rubber, and the mass ratio of the first binder, the second binder and the ceramic particles is 25-28:5-7:65-70.
[0007] In some specific embodiments, the preparation method of the first binder is: weigh 70-75g of ethyl acrylate, 20-25g of acrylonitrile, 10-15g of methacrylonitrile and 3-4g of acrylamide, mix them, add 2-2.5g of sodium dodecyl sulfate, 1-1.5g of ammonium persulfate, and 110-120g of deionized water, stir at a speed of 1800rpm for 40min, then heat to 75°C in an N2 atmosphere for reaction for 3h, adjust the pH to 7.0-7.5, and cool to 38°C to obtain the first binder.
[0008] In some specific embodiments, the ceramic particles are aluminum oxide and / or boehmite, the base film is PP / PE / PP, and the thickness of the base film is 16 μm-18 μm.
[0009] In some specific embodiments, the pore size of the membrane is 130 nm-150 nm.
[0010] In some specific embodiments, the Dv50 of the ceramic particles is 2 μm-3 μm.
[0011] In some specific embodiments, at 85°C, after the first binder is immersed in a test electrolyte for 3 hours, the viscosity of the test electrolyte is less than or equal to 9000 mPa·s, the test electrolyte is composed of an organic solvent and lithium hexafluorophosphate, the organic solvent is a mixture of ethylene carbonate, propylene carbonate and dimethyl carbonate in a mass ratio of 5:2:3, and the concentration of the lithium hexafluorophosphate is 1 mol / L based on the volume of the organic solvent.
[0012] In some specific embodiments, the porosity of the membrane is 39%-40%.
[0013] In some specific embodiments, the coating has a thickness of 0.2 μm-0.3 μm.
[0014] In some specific embodiments, the preparation method of the diaphragm is as follows: the first binder, the second binder, and the ceramic particles are placed in deionized water and stirred to obtain a slurry, and then the slurry is coated on the base film, and dried at 60°C-65°C to remove water. The coating density of the slurry on the base film is 0.6 g / m 2 , and obtain the diaphragm.
[0015] The lithium battery separator provided by the present application, by using the separator of the present application, a first additive is added, so that the porosity and winding rate have a good range, the porosity is high, the lithium ion transmission can be accelerated, and the winding rate also improves the production efficiency. And, further, by, the mass ratio of the first binder, the second binder and the ceramic particles is 25-28:5-7:65-70 in a suitable range, the first binder is soaked in the test electrolyte for 3h, the viscosity of the test electrolyte is less than or equal to 9000mPa·s, the viscosity of the first additive is in a suitable range, and they work synergistically with each other to match the appropriate ceramic particle size, so that the corners can also have good contact, avoiding contact or The decrease in the winding rate caused by the mismatch of the separator has further improved its porosity and winding rate, and further improved the battery performance.
[0016] The lithium battery separator provided by the present application has a first binder with good viscosity when the particle size of the ceramic particles is in the range of 2μm-3μm Dv50, and the viscosity is less than or equal to 9000mPa·s. This is because larger particles may not work well with the first binder at high temperatures within a limited coating thickness range, thereby affecting the 75°C storage performance. The lower Dv50 cannot improve its high temperature resistance due to the surface characteristics of the three-layer co-extruded base film of PP / PE / PP. Therefore, on the three-layer co-extruded base film of PP / PE / PP, it is necessary to combine the first binder with a comprehensive Dv50 in the range of 2μm-3μm to achieve better battery performance. DETAILED DESCRIPTION
[0017] The following will be combined with the specific embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0018] Diaphragm porosity test:
[0019] The porosity of the diaphragm was tested by gas replacement method, porosity = (V-V0) / V×100%, pore volume is V-V0, where V0 is the real volume of the diaphragm and V is the total volume of the diaphragm. The test equipment is a fully automatic true density tester (AccuPycⅡ1340), and the test gas is helium.
[0020] Preparation of positive electrode: The positive electrode active material LiCoO2, conductive carbon black, and polyvinylidene fluoride are mixed in a mass ratio of 96:2:2, N-methylpyrrolidone (NMP) is added, and the mixture is stirred evenly under the action of a vacuum mixer to obtain a positive electrode slurry, wherein the solid content of the positive electrode slurry is 70wt%. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 12μm, and the aluminum foil is dried at 120°C for 1h to obtain a positive electrode coated with a positive electrode material layer on one side. Repeat the above steps on the other surface of the aluminum foil to obtain a positive electrode coated with a positive electrode material layer on both sides. Then, after cold pressing, cutting, and slitting, it is dried under vacuum conditions at 120°C for 1h to obtain a positive electrode.
[0021] Preparation of negative electrode: negative electrode active material graphite, binder styrene butadiene rubber, and sodium carboxymethyl cellulose are mixed in a mass ratio of 97.4:1.4:1.2, deionized water is added, and the mixture is stirred evenly under the action of a vacuum mixer to obtain a negative electrode slurry, wherein the solid content of the negative electrode slurry is 75wt%. The negative electrode slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 8μm, and the copper foil is dried at 120°C to obtain a negative electrode with a coating thickness of 130μm and a single-sided negative electrode material layer. Repeat the above steps on the other surface of the aluminum foil to obtain a negative electrode with a double-sided negative electrode material layer. Then, after cold pressing, cutting, and slitting, it is dried under vacuum conditions at 120°C for 1h to obtain a negative electrode.
[0022] Preparation of electrolyte: In an argon atmosphere glove box with a water content of <10 ppm, EC, PC and DMC were mixed in a mass ratio of 3:2.5:4.5 to obtain an organic solvent, and then lithium hexafluorophosphate was added to the organic solvent to obtain an electrolyte, wherein the concentration of the lithium salt was 1 mol / L.
[0023] Preparation of diaphragm: put the first binder, styrene-butadiene rubber and ceramic particles into deionized water and stir to mix evenly to obtain slurry, then coat the slurry on the base film, dry at 60℃-65℃ to remove water, and the coating density of the slurry on the base material is 0.6g / m 2 , and obtain the diaphragm.
[0024] The preparation method of the first adhesive is as follows: weigh 70-75g of ethyl acrylate, 20-25g of acrylonitrile, 10-15g of isobutylene nitrile and 3-4g of acrylamide, mix them, add 2-2.5g of sodium dodecyl sulfate, 1-1.5g of ammonium persulfate and 110-120g of deionized water, stir for 40min at a speed of 1800rpm, then heat to 75°C in an N2 atmosphere, react for 3h, adjust the pH to 7.0-7.5, cool to 38°C, and obtain the first adhesive.
[0025] Preparation of lithium-ion battery: After the prepared positive electrode / diaphragm / negative electrode / diaphragm are placed in order, they are wound in one direction so that the diaphragm is between the positive electrode and the negative electrode to play a role of isolation, and the electrode assembly is wound. The electrode assembly is placed in an aluminum-plastic film, and after drying, the electrolyte is injected, and the lithium-ion battery is obtained through vacuum packaging, standing, formation, degassing, trimming and other processes. In different embodiments, only the preparation of the diaphragm is different, and the others are the same.
[0026] Winding quality test:
[0027] Use a winding device to continuously produce 2,000 lithium-ion batteries, and count the number of lithium-ion batteries that are scrapped due to tab misalignment; winding quality rate = (1-number of scrapped tab misalignment / 2,000) × 100%. Among them, when the tab misalignment is serious and cannot be welded, it is determined to be tab misalignment.
[0028] At present, for the three-layer co-extruded base film of PP / PE / PP containing PP, the thickness is too thick compared with the PE base film, which reduces the battery energy density within the same volume. In addition, after the three-layer co-extruded base film of PP / PE / PP is coated with a ceramic coating, due to the presence of ceramic particles, at the corners on the left and right sides of the wound battery cell, the diaphragm is bent and subjected to different forces, which can easily cause the diaphragm to be less sticky at the corners, resulting in ear dislocation of the positive electrode / diaphragm / negative electrode after winding, thereby reducing the winding quality rate.
[0029] The invention comprises a base film and a coating, wherein the coating comprises a first binder, a second binder and ceramic particles; the second binder is styrene-butadiene rubber, and the mass ratio of the first binder, the second binder and the ceramic particles is 25-28:5-7:65-70.
[0030] In some specific embodiments, the preparation method of the first binder is: weigh 70-75g of ethyl acrylate, 20-25g of acrylonitrile, 10-15g of methacrylonitrile and 3-4g of acrylamide, mix them, add 2-2.5g of sodium dodecyl sulfate, 1-1.5g of ammonium persulfate, and 110-120g of deionized water, stir at a speed of 1800rpm for 40min, then heat to 75°C in an N2 atmosphere for reaction for 3h, adjust the pH to 7.0-7.5, and cool to 38°C to obtain the first binder.
[0031] In some specific embodiments, the ceramic particles are aluminum oxide and / or boehmite, the base film is PP / PE / PP, and the thickness of the base film is 16 μm-18 μm.
[0032] In some specific embodiments, the pore size of the membrane is 130 nm-150 nm.
[0033] In some specific embodiments, the Dv50 of the ceramic particles is 2 μm-3 μm.
[0034] In some specific embodiments, at 85°C, after the first binder is immersed in a test electrolyte for 3 hours, the viscosity of the test electrolyte is less than or equal to 9000 mPa·s, the test electrolyte is composed of an organic solvent and lithium hexafluorophosphate, the organic solvent is a mixture of ethylene carbonate, propylene carbonate and dimethyl carbonate in a mass ratio of 5:2:3, and the concentration of the lithium hexafluorophosphate is 1 mol / L based on the volume of the organic solvent.
[0035] In some specific embodiments, the porosity of the membrane is 39%-40%.
[0036] In some specific embodiments, the coating has a thickness of 0.2 μm-0.3 μm.
[0037] In some specific embodiments, the preparation method of the diaphragm is as follows: the first binder, the second binder, and the ceramic particles are placed in deionized water and stirred to obtain a slurry, and then the slurry is coated on the base film, and dried at 60°C-65°C to remove water. The coating density of the slurry on the base film is 0.6 g / m 2 , and obtain the diaphragm.
[0038] Example 1: Preparation of diaphragm: The first binder, styrene-butadiene rubber (second binder), and ceramic boehmite particles were placed in deionized water and stirred to obtain a slurry. The slurry was then coated on a three-layer co-extruded base film of PP / PE / PP, and dried at 60°C to remove water. The coating density of the slurry on the substrate was 0.6 g / m 2 , and obtain the diaphragm.
[0039] The preparation method of the first adhesive is as follows: weigh 70g of ethyl acrylate, 20g of acrylonitrile, 10g of isobutylene nitrile and 3g of acrylamide, mix them, add 2g of sodium dodecyl sulfate, 1g of ammonium persulfate and 110g of deionized water, stir for 40min at a speed of 1800rpm, then heat to 75°C in an N2 atmosphere for reaction for 3h, adjust the pH to 7.0-7.5, cool to 38°C to obtain the first adhesive.
[0040] Example 2: Preparation of diaphragm: The first binder, styrene-butadiene rubber, and ceramic boehmite particles were placed in deionized water and stirred to obtain a slurry, and then the slurry was coated on a three-layer co-extruded base film of PP / PE / PP, and dried at 60°C to remove water. The coating density of the slurry on the substrate was 0.6 g / m 2 , and obtain the diaphragm.
[0041] The preparation method of the first adhesive is as follows: weigh 73g of ethyl acrylate, 20g of acrylonitrile, 10g of isobutylene nitrile and 3g of acrylamide, mix them, add 2g of sodium dodecyl sulfate, 1g of ammonium persulfate and 110g of deionized water, stir for 40min at a speed of 1800rpm, then heat to 75°C in an N2 atmosphere for reaction for 3h, adjust the pH to 7.0-7.5, cool to 38°C to obtain the first adhesive.
[0042] Example 3: Preparation of diaphragm: The first binder, styrene-butadiene rubber, and ceramic boehmite particles were placed in deionized water and stirred to obtain a slurry, and then the slurry was coated on a three-layer co-extruded base film of PP / PE / PP, and dried at 60°C to remove water. The coating density of the slurry on the substrate was 0.6 g / m 2 , and obtain the diaphragm.
[0043] The preparation method of the first adhesive is as follows: weigh 75g of ethyl acrylate, 20g of acrylonitrile, 10g of isobutylene nitrile and 3g of acrylamide, mix them, add 2g of sodium dodecyl sulfate, 1g of ammonium persulfate and 110g of deionized water, stir at a speed of 1800rpm for 40min, then heat to 75°C in a N2 atmosphere for reaction for 3h, adjust the pH to 7.0-7.5, cool to 38°C to obtain the first adhesive.
[0044] Example 4: Preparation of diaphragm: The first binder, styrene-butadiene rubber, and ceramic boehmite particles were placed in deionized water and stirred to obtain a slurry, and then the slurry was coated on a three-layer co-extruded base film of PP / PE / PP, and dried at 60°C to remove water. The coating density of the slurry on the substrate was 0.6 g / m 2 , and obtain the diaphragm.
[0045] The preparation method of the first adhesive is as follows: weigh 65g of ethyl acrylate, 20g of acrylonitrile, 10g of isobutylene nitrile and 3g of acrylamide, mix them, add 2g of sodium dodecyl sulfate, 1g of ammonium persulfate and 110g of deionized water, stir for 40min at a speed of 1800rpm, then heat to 75°C in an N2 atmosphere for reaction for 3h, adjust the pH to 7.0-7.5, cool to 38°C to obtain the first adhesive.
[0046] Example 5: Preparation of diaphragm: The first binder, styrene-butadiene rubber, and ceramic boehmite particles were placed in deionized water and stirred to obtain a slurry. The slurry was then coated on a three-layer co-extruded base film of PP / PE / PP and dried at 60°C to remove water. The coating density of the slurry on the substrate was 0.6 g / m 2 , and obtain the diaphragm.
[0047] The preparation method of the first adhesive is as follows: weigh 77g of ethyl acrylate, 20g of acrylonitrile, 10g of isobutylene nitrile and 3g of acrylamide, mix them, add 2g of sodium dodecyl sulfate, 1g of ammonium persulfate and 110g of deionized water, stir for 40min at a speed of 1800rpm, then heat to 75°C in an N2 atmosphere for reaction for 3h, adjust the pH to 7.0-7.5, cool to 38°C to obtain the first adhesive.
[0048] Comparative Example 1: Preparation of diaphragm: Styrene-butadiene rubber and ceramic boehmite particles were placed in deionized water and stirred to obtain a slurry, and then the slurry was coated on a three-layer co-extruded base film of PP / PE / PP, and dried at 60°C to remove water. The coating density of the slurry on the substrate was 0.6 g / m 2 , and obtain the diaphragm.
[0049] In Examples 1 to 5 and Comparative Example 1, the thickness of the three-layer co-extruded base film of base film PP / PE / PP is 16 μm (purchased from Huiqiang New Materials), boehmite is commercially available, the particle size is selected from Dv50 of 2 μm-3 μm, the mass ratio of the first binder, the second binder and the ceramic particles is 25:5:65, and the thickness of the coating is 0.3 μm.
[0050] The following table summarizes the relevant properties of the above examples 1 to 5 and the comparative examples:
[0051] Porosity Winding quality Example 1 39％ 99.5％ Example 2 39％ 99.4％ Example 3 39％ 99.6％ Example 4 39％ 96.3％ Example 5 38％ 96.8％ Comparative Example 1 36％ 94.6％
[0052] Through the analysis of Examples 1 to 5 and Comparative Example 1, we use the diaphragm of the present application and add the first additive, so that the porosity and winding rate have a good range, the porosity is high, the lithium ion transmission can be accelerated, and the winding rate also improves the production efficiency. And, further, by, the mass ratio of the first binder, the second binder and the ceramic particles is 25-28:5-7:65-70 in a suitable range, the first binder is immersed in the test electrolyte for 3 hours, the viscosity of the test electrolyte is less than or equal to 9000mPa·s, the viscosity of the first additive is in a suitable range, and they work synergistically with each other to match the appropriate ceramic particle size, so that there can be good contact at the corners, avoiding contact or The decrease in the winding rate caused by the mismatch of the diaphragm, the porosity and winding rate are further improved, and the battery performance is further improved.
[0053] To further verify the performance of lithium batteries, we conducted a 75°C storage performance test: the lithium-ion battery was placed in a 25°C environment for 30 minutes, then charged to 4.2V at a constant current rate of 0.2C, then charged to 0.05C at a constant voltage of 4.2V, placed for 30 minutes, and then discharged to 2.8V at a rate of 0.5C, and the appearance dimensions of the lithium-ion battery were recorded; the fully charged battery was then placed in an oven at about 80°C for about 7 days, and the appearance dimensions of the lithium-ion battery were recorded. The storage performance of lithium-ion batteries is judged according to the following deformation standards: No deformation: The thickness change rate of the lithium-ion battery is less than or equal to 3%; Slight deformation: The thickness change rate of the lithium-ion battery is greater than 3%.
[0054] Dv50: represents the cumulative value of the particle size volume distribution, indicating that particles smaller than this particle size value in the sample account for 50% of the total volume of the total sample. Test instrument: Malvern Mastersizer 2000. Test standard can use GB / T 41949-2022.
[0055] Example 6: Preparation of diaphragm: The first binder, styrene-butadiene rubber, and ceramic boehmite particles were placed in deionized water and stirred to obtain a slurry, and then the slurry was coated on a three-layer co-extruded base film of PP / PE / PP, and dried at 60°C to remove water. The coating density of the slurry on the substrate was 0.6 g / m 2 , and obtain the diaphragm.
[0056] The preparation method of the first binder is as follows: weigh 75g of ethyl acrylate, 20g of acrylonitrile, 10g of isobutylene nitrile and 3g of acrylamide, mix them, add 2g of sodium dodecyl sulfate, 1g of ammonium persulfate and 110g of deionized water, stir at 1800rpm for 40min, then heat to 75℃ in N2 atmosphere for 3h, adjust pH to 7.0-7.5, cool to 38℃ to obtain the first binder. The thickness of the three-layer co-extruded base film of base film PP / PE / PP is 16μm (purchased from Huiqiang New Materials), boehmite is commercially available, the particle size is selected from Dv50 of 3.5μm, the mass ratio of the first binder, the second binder and the ceramic particles is 25:5:65, and the thickness of the coating is 0.3μm.
[0057] Example 7: Preparation of diaphragm: The first binder, styrene-butadiene rubber, and ceramic boehmite particles were placed in deionized water and stirred to obtain a slurry, and then the slurry was coated on a three-layer co-extruded base film of PP / PE / PP, and dried at 60°C to remove water. The coating density of the slurry on the substrate was 0.6 g / m 2 , and obtain the diaphragm.
[0058] The preparation method of the first binder is as follows: weigh 75g of ethyl acrylate, 20g of acrylonitrile, 10g of isobutylene nitrile and 3g of acrylamide, mix them, add 2g of sodium dodecyl sulfate, 1g of ammonium persulfate and 110g of deionized water, stir for 40min at a speed of 1800rpm, then heat to 75℃ in an N2 atmosphere for 3h, adjust the pH to 7.0-7.5, cool to 38℃, and obtain the first binder. The thickness of the three-layer co-extruded base film of the base film PP / PE / PP is 16μm (purchased from Huiqiang New Materials), boehmite is commercially available, the particle size is selected from Dv50 of 1.5μm, the mass ratio of the first binder, the second binder and the ceramic particles is 25:5:65, and the thickness of the coating is 0.3μm.
[0059] Winding quality 75℃ Storage Performance Example 3 99.6％ No deformation Example 6 99.1％ Slight deformation Example 7 99.0％ Slight deformation
[0060] By comparing Example 6-Example 7 with Example 3, we found that when the particle size of the ceramic particles is in the range of Dv50 of 2μm-3μm, the first binder has a better viscosity, less than or equal to 9000mPa·s, because larger particles may not work well with the first binder at high temperatures within a limited coating thickness range, thereby affecting the 75°C storage performance, and the lower Dv50, because the surface properties of the three-layer co-extruded base film of the base film PP / PE / PP cannot improve its high temperature resistance. Therefore, on the three-layer co-extruded base film of the base film PP / PE / PP, it is necessary to combine the first binder with a comprehensive Dv50 in the range of 2μm-3μm to make the battery performance better.
[0061] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.
[0062] The above are only preferred embodiments of the present application and do not constitute any form of limitation to the present application. Any technician familiar with the profession can make some changes or modify the technical contents disclosed above into equivalent embodiments with equivalent changes without departing from the scope of the technical solution of the present application. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application still fall within the scope of the technical solution of the present application.
Claims
1. A lithium battery separator, characterized in that: It comprises a base film and a coating, wherein the coating comprises a first binder, a second binder, and ceramic particles; the second binder is styrene-butadiene rubber, and the mass ratio of the first binder, the second binder, and the ceramic particles is 25-28:5-7:65-70; The preparation method of the first binder is as follows: weigh 70-75g of ethyl acrylate, 20-25g of acrylonitrile, 10-15g of methacrylonitrile and 3-4g of acrylamide, mix them, add 2-2.5g of sodium dodecyl sulfate, 1-1.5g of ammonium persulfate and 110-120g of deionized water, stir for 40min at a speed of 1800rpm, then heat to 75°C in an N2 atmosphere for reaction for 3h, adjust the pH to 7.0-7.5, and cool to 38°C to obtain the first binder; The base film is PP / PE / PP, the ceramic particles are boehmite, and the porosity of the diaphragm is 39% or 38%; The winding rate of lithium batteries using the lithium battery separator is 99.6%; At 85° C., after the first binder is immersed in a test electrolyte for 3 hours, the viscosity of the test electrolyte is less than or equal to 9000 mPa·s, the test electrolyte is composed of an organic solvent and lithium hexafluorophosphate, the organic solvent is a mixture of ethylene carbonate, propylene carbonate and dimethyl carbonate in a mass ratio of 5:2:3, and the concentration of the lithium hexafluorophosphate is 1 mol / L based on the volume of the organic solvent; The Dv50 of the ceramic particles is 2 μm-3 μm.
2. The lithium battery separator according to claim 1, characterized in that: The base film has a thickness of 16 μm-18 μm.
3. The lithium battery separator according to claim 1, characterized in that The pore size of the membrane is 130nm-150nm.
4. The lithium battery separator according to claim 1, characterized in that The coating has a thickness of 0.2 μm-0.3 μm.
5. The lithium battery separator according to claim 1, characterized in that: The preparation method of the diaphragm is as follows: a first binder, a second binder and ceramic particles are placed in deionized water and stirred to obtain a slurry, and then the slurry is coated on a base film, and dried at 60°C-65°C to remove water. The coating density of the slurry on the base film is 0.6g / m 2 , and obtain the diaphragm.