Ultrathin high-adhesion diaphragm coating slurry as well as preparation method, coating mode and application thereof

Abstract

The invention relates to the technical field of lithium ion batteries, and provides ultrathin high-adhesion diaphragm coating slurry as well as a preparation method, a coating mode and application thereof. The ultrathin high-adhesion diaphragm coating slurry is prepared from the following components in parts by weight: 10 to 20 parts of nano polyvinylidene fluoride particles, 2 to 3 parts of nano polymethyl methacrylate particles, 0.1 to 0.3 part of flatting agent, 0.1 to 0.3 part of pore forming agent, 0.1 to 0.3 part of lithium salt, 2.5 to 3 parts of thickening dispersant and 100 parts of water. According to the technical scheme, the problems that a lithium ion battery diaphragm coating is thick and the adhesive property of diaphragm coating slurry is poor in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to an ultra-thin high-adhesion diaphragm coating slurry, a preparation method, a coating method and an application thereof. Background Art

[0002] As an efficient and environmentally friendly energy storage device, lithium-ion batteries are widely used in mobile electronic devices, electric vehicles, energy storage systems, etc. However, existing lithium-ion battery separators have certain limitations in thickness and adhesion performance, which affects the overall performance of lithium-ion batteries.

[0003] Generally, lithium-ion battery separators are prepared by coating separator coating slurry. The performance of separator coating slurry is directly related to the performance of lithium-ion battery separators. Therefore, in order to make lithium-ion battery separators have the advantages of ultra-thinness and high adhesion, it is of great significance to develop a separator coating slurry. Summary of the invention

[0004] The present invention provides an ultra-thin high-adhesion diaphragm coating slurry and a preparation method, coating method and application thereof, which solves the problem in the related art that the diaphragm coating of lithium ion batteries is thick and the diaphragm coating slurry has poor adhesion performance.

[0005] The technical solution of the present invention is as follows: The invention provides an ultra-thin high-adhesion diaphragm coating slurry, comprising the following components in parts by weight: 10-20 parts of nano polyvinylidene fluoride particles, 2-3 parts of nano polymethyl methacrylate particles, 0.1-0.3 parts of a leveling agent, 0.1-0.3 parts of a pore-forming agent, 0.1-0.3 parts of a lithium salt, 2.5-3 parts of a thickening dispersant, and 100 parts of water.

[0006] As a further technical solution, the nano polyvinylidene fluoride particles are modified nano polyvinylidene fluoride particles, and the raw materials of the modified nano polyvinylidene fluoride particles include nano polyvinylidene fluoride particles, water-based polyurethane, formic acid and water in a weight ratio of 10:1:3 to 5:100.

[0007] In the present invention, by modifying the nano-polyvinylidene fluoride particles, the slurry can be stabilized through steric hindrance and charge repulsion, thereby improving the stability of the nano-polyvinylidene fluoride particles in the diaphragm coating slurry, thereby further improving the adhesion performance of the diaphragm coating slurry and further improving the overall performance of the lithium ion battery diaphragm.

[0008] As a further technical solution, the preparation method of the modified nano polyvinylidene fluoride particles comprises the following steps: uniformly mixing the raw materials of the modified nano polyvinylidene fluoride particles, modifying, and filtering to obtain the modified nano polyvinylidene fluoride particles.

[0009] As a further technical solution, during the modification, the temperature is 50-60°C and the time is 30-40 minutes.

[0010] As a further technical solution, the nano polymethyl methacrylate particles are modified nano polymethyl methacrylate particles, and the raw materials of the modified nano polymethyl methacrylate particles include nano polymethyl methacrylate particles, sodium hydroxide, oxalic acid and water in a weight ratio of 10:0.5:1 to 2:100.

[0011] In the present invention, by modifying the nano polymethyl methacrylate particles, the agglomeration and sedimentation of the nano polymethyl methacrylate particles can be prevented, the stability of the diaphragm coating slurry can be increased, thereby further improving the bonding performance of the diaphragm coating slurry and further improving the overall performance of the lithium ion battery diaphragm.

[0012] As a further technical solution, the preparation method of the modified nano polymethyl methacrylate particles comprises the following steps: uniformly mixing nano polymethyl methacrylate particles, sodium hydroxide and water, reacting once, adding oxalic acid, reacting twice, and filtering to obtain the modified nano polymethyl methacrylate particles.

[0013] As a further technical solution, during the primary reaction, the temperature is 50-60°C and the time is 30-40 minutes; As a further technical solution, during the secondary reaction, the temperature is 50-60°C and the time is 30-40 minutes.

[0014] As a further technical solution, the leveling agent includes one or more of polyethylene oxide, acrylate leveling agents, and silicone leveling agents, preferably polyethylene oxide.

[0015] As a further technical solution, the pore-forming agent includes one or both of ammonium bicarbonate and sodium bicarbonate, preferably ammonium bicarbonate.

[0016] As a further technical solution, the lithium salt includes one or more of lithium difluorooxalatoborate, lithium perchlorate, and lithium dimalonateborate, preferably lithium difluorooxalatoborate.

[0017] As a further technical solution, the thickening dispersant includes one or more of sodium carboxymethyl cellulose, polyvinyl alcohol, and lithium carboxymethyl cellulose in polyethylene glycol, preferably sodium carboxymethyl cellulose.

[0018] The present invention also provides a method for preparing the ultra-thin high-adhesion diaphragm coating slurry, comprising the following steps: S1, emulsifying water and a leveling agent to obtain a first mixed solution; S2, adding nano-polyvinylidene fluoride particles to the mixed solution and dispersing them evenly to obtain a second mixed solution; S3, adding a thickening dispersant, a pore-forming agent and a lithium salt to the second mixed solution in sequence, dispersing them evenly, to obtain a third mixed solution; S4. Add nano-PMMA particles into the third mixed solution and disperse them evenly to obtain a diaphragm coating slurry.

[0019] As a further technical solution, in step S1, during the emulsification treatment, the speed is 1500~2500r / min, the vacuum degree is -0.05~-0.1MPa, and the time is 10~20min.

[0020] As a further technical solution, in steps S2 to S4, when the dispersion is uniform, the stirring speed is independently 50 to 55 r / min, the vacuum degree is -0.05 to -0.1 MPa, and the time is 20 to 40 min.

[0021] The present invention also proposes a coating method of the ultra-thin high-adhesion diaphragm coating slurry, which adopts matrix-type dot coating.

[0022] As a further technical solution, coating is applied to at least one side of the base film.

[0023] The present invention also proposes the use of the ultra-thin high-adhesion diaphragm coating slurry or the diaphragm coating slurry prepared by the preparation method in lithium-ion batteries.

[0024] The working principle and beneficial effects of the present invention are: In the present invention, the diaphragm coating slurry can not only reduce the thickness of the lithium-ion battery diaphragm coating to less than 1 μm, thereby reducing the barrier to energy transfer during application, but also improve the adhesion, ensure the stability of the internal structure of the lithium-ion battery, and effectively prevent electrolyte leakage and short circuit. (1) Nano-PVDF particles and nano-PMMA particles have a large specific surface area. Their addition can significantly improve the bonding properties of the separator coating slurry, thereby improving the overall performance of the lithium-ion battery separator; (2) The addition of leveling agent can make the nanomaterial spread evenly to form an ultra-thin coating; (3) The addition of pore-forming agents can produce holes of different sizes in the coating, making the separator have good air permeability, which is conducive to the efficient transmission of lithium ions in the battery and enhances the performance of lithium-ion batteries; (4) The addition of lithium salt can make the separator have good ionic conductivity and make the migration of lithium ions in the separator smoother, thereby improving the overall electrochemical performance of lithium-ion batteries; (5) The addition of thickening and dispersing agent can improve the uniformity of the diaphragm coating slurry, which is beneficial to the coating of the diaphragm coating slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0026] Figure 1 This is a SEM image of the diaphragm coating slurry prepared in Example 1; Figure 2 This is the SEM image of the diaphragm coating slurry prepared in Example 7. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in 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. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the following embodiments and comparative examples, unless otherwise specified, the D50 particle size of the nano-polyvinylidene fluoride particles is 160 nm, and the number average molecular weight is 580,000; the D50 particle size of the nano-polymethyl methacrylate particles is 158 nm, and the number average molecular weight is 160,000; the number average molecular weight of polyethylene oxide is 23010; the viscosity of sodium carboxymethyl cellulose dissolved in water at 25°C and 2wt% is 600 cP; the water-based polyurethane is a polyether nitrile type cationic water-based polyurethane with a number average molecular weight of 10,000; the number average molecular weight of ordinary polyvinylidene fluoride particles is 580,000.

[0029] Example 1 The method for preparing an ultra-thin high-adhesion diaphragm coating slurry comprises the following steps: S1. Add 100 parts of water by weight into a centrifugal vacuum emulsification tank, add 0.1 parts of polyethylene oxide, and emulsify for 15 minutes at 2000 r / min and a vacuum degree of -0.08 MPa to obtain a first mixed solution; S2, adding 10 parts of nano-polyvinylidene fluoride particles to the first mixed solution, stirring at 52 r / min and a vacuum degree of -0.09 MPa for 30 min to obtain a second mixed solution; S3, adding 2.5 parts of sodium carboxymethyl cellulose, 0.1 parts of ammonium bicarbonate, and 0.1 parts of lithium difluorooxalate borate to the second mixed solution in sequence, stirring at 52 r / min and a vacuum degree of -0.09 MPa for 30 min to obtain a third mixed solution; S4. Add 2 parts of nano-PMMA particles to the third mixed solution, stir at 52 r / min and vacuum degree of -0.09 MPa for 30 min to obtain a diaphragm coating slurry. The SEM image is as follows: Figure 1 shown.

[0030] Example 2 The method for preparing an ultra-thin high-adhesion diaphragm coating slurry comprises the following steps: S1. Add 100 parts of water by weight into a centrifugal vacuum emulsification tank, add 0.3 parts of polyethylene oxide, and emulsify for 15 minutes at 2000 r / min and a vacuum degree of -0.08 MPa to obtain a first mixed solution; S2, adding 20 parts of nano-polyvinylidene fluoride particles to the first mixed solution, stirring at 52 r / min and a vacuum degree of -0.09 MPa for 30 min to obtain a second mixed solution; S3, add 3 parts of sodium carboxymethyl cellulose, 0.3 parts of ammonium bicarbonate, and 0.3 parts of lithium difluorooxalate borate to the second mixed solution in sequence, and stir at 52 r / min and a vacuum degree of -0.09 MPa for 30 min to obtain a third mixed solution; S4. Add 3 parts of nano-PMMA particles into the third mixed solution, stir at 52 r / min and a vacuum degree of -0.09 MPa for 30 min to obtain a diaphragm coating slurry.

[0031] Example 3 The difference between this embodiment and embodiment 2 is that, in this embodiment, the nano polyvinylidene fluoride particles are modified nano polyvinylidene fluoride particles, and the preparation method of the modified nano polyvinylidene fluoride particles comprises the following steps: adding nano polyvinylidene fluoride particles, waterborne polyurethane, formic acid and water into a synthesis reactor, stirring and modifying at 50° C. and 30 r / min for 40 min, vacuum filtering, washing and drying to obtain modified nano polyvinylidene fluoride particles; The weight ratio of nano polyvinylidene fluoride particles, water-based polyurethane, formic acid and water is 10:1:3:100.

[0032] Example 4 The difference between this embodiment and embodiment 3 is that in this embodiment, the preparation method of modified nano polyvinylidene fluoride particles comprises the following steps: adding nano polyvinylidene fluoride particles, waterborne polyurethane, formic acid and water into a synthesis reactor, stirring and modifying at 60° C. and 30 r / min for 30 min, vacuum filtering, washing and drying to obtain modified nano polyvinylidene fluoride particles; The weight ratio of nano polyvinylidene fluoride particles, water-based polyurethane, formic acid and water is 10:1:5:100.

[0033] Example 5 The difference between this embodiment and embodiment 2 is that in this embodiment, the nano polymethyl methacrylate particles are modified nano polymethyl methacrylate particles, and the preparation method of the modified nano polymethyl methacrylate particles comprises the following steps: adding nano polymethyl methacrylate particles, water and sodium hydroxide into a synthesis reactor, stirring and reacting at 60° C. and 30 r / min for 30 min, then adding oxalic acid, stirring and reacting at 60° C. and 30 r / min for 30 min, vacuum filtering, washing and drying to obtain modified nano polymethyl methacrylate particles; The weight ratio of nano-PMMA particles, sodium hydroxide, oxalic acid and water is 10:0.5:1:100.

[0034] Example 6 The difference between this embodiment and embodiment 5 is that in this embodiment, the preparation method of modified nano polymethyl methacrylate particles comprises the following steps: adding nano polymethyl methacrylate particles, water and sodium hydroxide into a synthesis reactor, stirring and reacting at 50° C. and 30 r / min for 40 min, then adding oxalic acid, stirring and reacting at 50° C. and 30 r / min for 40 min, vacuum filtering, washing and drying to obtain modified nano polymethyl methacrylate particles; The weight ratio of nano-PMMA particles, sodium hydroxide, oxalic acid and water is 10:0.5:2:100.

[0035] Example 7 The difference between this embodiment and embodiment 2 is that, in this embodiment, the nano-polyvinylidene fluoride particles are modified nano-polyvinylidene fluoride particles, and the nano-polymethyl methacrylate particles are modified nano-polymethyl methacrylate particles; The preparation method of modified nano polyvinylidene fluoride particles comprises the following steps: adding nano polyvinylidene fluoride particles, waterborne polyurethane, formic acid and water into a synthesis reactor, stirring and modifying at 50°C and 30 r / min for 40 minutes, vacuum filtering, washing and drying to obtain modified nano polyvinylidene fluoride particles; The weight ratio of nano polyvinylidene fluoride particles, waterborne polyurethane, formic acid and water is 10:1:3:100; The preparation method of modified nano polymethyl methacrylate particles comprises the following steps: adding nano polymethyl methacrylate particles, water and sodium hydroxide into a synthesis reactor, stirring and reacting at 60°C and 30 r / min for 30 minutes, adding oxalic acid, stirring and reacting at 60°C and 30 r / min for 30 minutes, vacuum filtering, washing and drying to obtain modified nano polymethyl methacrylate particles; The weight ratio of nano-PMMA particles, sodium hydroxide, oxalic acid and water is 10:0.5:1:100; The SEM image of the diaphragm coating slurry is shown in Figure 2 shown.

[0036] Example 8 The method for preparing an ultra-thin high-adhesion diaphragm coating slurry comprises the following steps: S1. Add 100 parts of water by weight into a centrifugal vacuum emulsification tank, add 0.3 parts of polyethylene oxide, and emulsify for 15 minutes at 2000 r / min and a vacuum degree of -0.08 MPa to obtain a first mixed solution; S2, adding 3 parts of modified nano-polymethyl methacrylate particles to the first mixed solution, stirring at 52 r / min and a vacuum degree of -0.09 MPa for 30 min to obtain a second mixed solution; S3, add 3 parts of sodium carboxymethyl cellulose, 0.3 parts of ammonium bicarbonate, and 0.3 parts of lithium difluorooxalate borate to the second mixed solution in sequence, and stir at 52 r / min and a vacuum degree of -0.09 MPa for 30 min to obtain a third mixed solution; S4, adding 20 parts of modified nano-polyvinylidene fluoride particles to the third mixed solution, stirring at 52 r / min and a vacuum degree of -0.09 MPa for 30 min to obtain a diaphragm coating slurry; The preparation method of modified nano polyvinylidene fluoride particles comprises the following steps: adding nano polyvinylidene fluoride particles, waterborne polyurethane, formic acid and water into a synthesis reactor, stirring and modifying at 50°C and 30 r / min for 40 minutes, vacuum filtering, washing and drying to obtain modified nano polyvinylidene fluoride particles; The weight ratio of nano polyvinylidene fluoride particles, waterborne polyurethane, formic acid and water is 10:1:3:100; The preparation method of modified nano polymethyl methacrylate particles comprises the following steps: adding nano polymethyl methacrylate particles, water and sodium hydroxide into a synthesis reactor, stirring and reacting at 60°C and 30 r / min for 30 minutes, adding oxalic acid, stirring and reacting at 60°C and 30 r / min for 30 minutes, vacuum filtering, washing and drying to obtain modified nano polymethyl methacrylate particles; The weight ratio of nano-PMMA particles, sodium hydroxide, oxalic acid and water is 10:0.5:1:100.

[0037] Example 9 The difference between this embodiment and embodiment 8 is that, in this embodiment, the method for preparing the ultra-thin high-adhesion diaphragm coating slurry comprises the following steps: S1. Add 100 parts of water by weight into a centrifugal vacuum emulsification tank, add 0.3 parts of polyethylene oxide, and emulsify for 15 minutes at 2000 r / min and a vacuum degree of -0.08 MPa to obtain a first mixed solution; S2. Add 3 parts of modified nano-polymethyl methacrylate particles, 3 parts of sodium carboxymethyl cellulose, 0.3 parts of ammonium bicarbonate, 0.3 parts of lithium difluorooxalate borate and 20 parts of modified nano-polyvinylidene fluoride particles to the first mixed liquid, stir at 52 r / min and a vacuum degree of -0.09 MPa for 90 minutes to obtain a diaphragm coating slurry.

[0038] Comparative Example 1 The only difference between this comparative example and Example 1 is that in this comparative example, the nano-polyvinylidene fluoride particles are replaced by an equal amount of common polyvinylidene fluoride particles with a D50 particle size of 7 μm.

[0039] Comparative Example 2 The only difference between this comparative example and Example 1 is that in this comparative example, sodium carboxymethyl cellulose was not added. After the diaphragm coating slurry was left to stand for 10 minutes, powder sedimentation and powder floating occurred, and a uniform and stable slurry could not be formed, and spot coating preparation could not be performed.

[0040] The membrane coating slurry prepared in Examples 1 to 9 and Comparative Example 1 was coated in a matrix dot pattern (dot spacing 680 μm, dot diameter 350 μm, coating amount 0.45 g / m 2 ) was coated on one side of a wet polyethylene film (thickness 7.1μm, air permeability 71 Sec / 100mL), and the following performance tests were performed: ① Coating thickness: Refer to GB / T 36363-2018 "Polyolefin separators for lithium-ion batteries" to test the battery separator thickness, and calculate the coating thickness according to coating thickness = battery separator thickness - base film thickness; ② Air permeability: Refer to GB / T 36363-2018 "Polyolefin separator for lithium-ion batteries" to test air permeability; ③ Ionic conductivity: Refer to GB / T 36363-2018 "Polyolefin separator for lithium-ion batteries" to test the ionic conductivity, where the temperature is 40°C and the relative humidity is 50%; ④ Adhesion strength of positive electrode: Use electronic tensile testing machine to test the adhesion strength of hot pressed positive electrode. The positive electrode is 25mm×150mm LiNi 0.8 Co 0.15 Al 0.05 O2 pole piece, hot pressing temperature is 80℃, hot pressing pressure is 1000KG, hot pressing time is 1s, stretching distance is 50mm, test speed is 300mm / min, peeling degree is 180°; ⑤ Adhesion strength of negative electrode sheet: Use an electronic tensile testing machine to test the adhesion strength of the hot-pressed negative electrode sheet. The negative electrode sheet is a 25mm×150mm carbon-based graphite sheet (carbon content 91wt%), the hot pressing temperature is 80°C, the hot pressing pressure is 1000KG, the hot pressing time is 1s, the stretching distance is 50mm, the test speed is 300mm / min, and the peeling degree is 180°.

[0041] The test results are shown in Table 1 below.

[0042] Table 1 Performance test results

[0043] Comparison between Example 1 and Comparative Example 1 shows that, compared with micron-sized polyvinylidene fluoride particles, nano-polyvinylidene fluoride particles can significantly reduce the thickness of the diaphragm coating and improve the bonding performance.

[0044] Comparison between Example 2 and Examples 3 to 7 shows that by modifying the nano polyvinylidene fluoride particles and nano polymethyl methacrylate particles, the adhesion performance of the diaphragm coating slurry can be further improved, and the overall performance of the lithium-ion battery diaphragm can be further improved. Comparison between Example 2 and Examples 8 to 9 shows that when preparing the diaphragm coating slurry, first adding nano polyvinylidene fluoride particles, then adding thickening dispersants, pore-forming agents and lithium salts and other additives, and finally adding nano polymethyl methacrylate particles can further improve the adhesion performance of the diaphragm coating slurry and further improve the overall performance of the lithium-ion battery diaphragm.

[0045] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An ultra-thin high-adhesion diaphragm coating slurry, characterized in that: The invention comprises the following components in parts by weight: 10-20 parts of nano polyvinylidene fluoride particles, 2-3 parts of nano polymethyl methacrylate particles, 0.1-0.3 parts of leveling agent, 0.1-0.3 parts of pore-forming agent, 0.1-0.3 parts of lithium salt, 2.5-3 parts of thickening dispersant and 100 parts of water.

2. The ultra-thin high-adhesion diaphragm coating slurry according to claim 1, characterized in that: The nano polyvinylidene fluoride particles are modified nano polyvinylidene fluoride particles, and the raw materials of the modified nano polyvinylidene fluoride particles include nano polyvinylidene fluoride particles, waterborne polyurethane, formic acid and water in a weight ratio of 10:1:3 to 5:

100.

3. The ultra-thin high-adhesion diaphragm coating slurry according to claim 2, characterized in that: The preparation method of the modified nano polyvinylidene fluoride particles comprises the following steps: uniformly mixing the raw materials of the modified nano polyvinylidene fluoride particles, modifying, and filtering to obtain the modified nano polyvinylidene fluoride particles; Preferably, during the modification, the temperature is 50-60° C. and the time is 30-40 min.

4. The ultra-thin high-adhesion diaphragm coating slurry according to claim 1, characterized in that: The nano polymethyl methacrylate particles are modified nano polymethyl methacrylate particles, and the raw materials of the modified nano polymethyl methacrylate particles include nano polymethyl methacrylate particles, sodium hydroxide, oxalic acid and water in a weight ratio of 10:0.5:1-2:

100.

5. The ultra-thin high-adhesion diaphragm coating slurry according to claim 4, characterized in that: The preparation method of the modified nano polymethyl methacrylate particles comprises the following steps: uniformly mixing nano polymethyl methacrylate particles, sodium hydroxide and water, reacting once, adding oxalic acid, reacting twice, and filtering to obtain the modified nano polymethyl methacrylate particles; Preferably, during the primary reaction, the temperature is 50-60°C and the time is 30-40 minutes; Preferably, during the secondary reaction, the temperature is 50-60° C. and the time is 30-40 min.

6. The ultra-thin high-adhesion membrane coating slurry according to claim 1, characterized in that: The leveling agent includes one or more of polyethylene oxide, acrylate leveling agent, and silicone leveling agent; and / or The pore-forming agent comprises one or both of ammonium bicarbonate and sodium bicarbonate; and / or The lithium salt includes one or more of lithium difluorooxalatoborate, lithium perchlorate, and lithium dimalonateborate; and / or The thickening dispersant includes one or more of sodium carboxymethyl cellulose, polyvinyl alcohol, polyethylene glycol, and lithium carboxymethyl cellulose.

7. The method for preparing the ultra-thin high-adhesion diaphragm coating slurry according to claim 1, characterized in that: The following steps are involved: S1, emulsifying water and a leveling agent to obtain a first mixed solution; S2, adding nano-polyvinylidene fluoride particles to the mixed solution and dispersing them evenly to obtain a second mixed solution; S3, adding a thickening dispersant, a pore-forming agent and a lithium salt to the second mixed solution in sequence, dispersing them evenly, to obtain a third mixed solution; S4. Add nano-PMMA particles into the third mixed solution and disperse them evenly to obtain a diaphragm coating slurry.

8. The coating method of the ultra-thin high-adhesion diaphragm coating slurry according to any one of claims 1 to 6, characterized in that: Matrix dot coating is used.

9. The coating method according to claim 8, characterized in that: Coated on at least one side of the base film.

10. Use of the ultra-thin high-adhesion diaphragm coating slurry according to any one of claims 1 to 6 or the diaphragm coating slurry prepared by the preparation method according to claim 7 in lithium-ion batteries.

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