High-heat-resistance and high-adhesion lithium ion battery diaphragm and preparation method thereof

Abstract

The invention relates to the technical field of battery diaphragms, and provides a high-heat-resistance and high-adhesion lithium ion battery diaphragm and a preparation method thereof.The high-heat-resistance and high-adhesion lithium ion battery diaphragm comprises a base material and a coating coated on the surface of the base material, and solid components of the coating comprise, by weight, 50%-85% of inorganic particles, 1%-5% of a binder, 1%-5% of a lubricant and 1%-5% of a lubricant. The balance is an adhesive polymer; the inorganic particles are composed of porous ceramic particles and porous linear bacterial cellulose, the particle size of the porous ceramic particles is 0.3-1 [mu] m, the aperture of the porous ceramic particles is 30-50 nm, the length of the porous linear bacterial cellulose is 0.5-2 [mu] m, and the aperture of the porous linear bacterial cellulose is 50-100 nm. According to the technical scheme, the problem of insufficient temperature resistance of the lithium ion battery diaphragm in the prior art is solved.

Description

Technical Field

[0001] This invention relates to the field of battery separator technology, specifically to a high heat-resistant and high-adhesion lithium-ion battery separator and its preparation method. Background Technology

[0002] In energy storage fields such as lithium-ion batteries, the separator is a key component, and its performance directly affects the battery's safety, electrochemical performance, and cycle life. Polyolefin membranes are widely used in battery separators due to their good chemical stability, mechanical properties, and low cost.

[0003] However, polyolefin-based membranes have some inherent performance deficiencies, such as poor high-temperature resistance. If the membrane's heat resistance is insufficient, it is prone to deformation, thermal shrinkage, or even melting under high-temperature conditions. Once these problems occur, the positive and negative electrodes lose their effective isolation barrier and are very likely to come into direct contact, leading to a serious short circuit and safety issues.

[0004] In addition, in the existing technology, different functional materials need to be coated multiple times during the preparation of the separator, and drying is required after each coating. This not only increases production time and cost, but also easily leads to poor adhesion between coatings, affecting the overall performance of the battery separator.

[0005] Therefore, it is essential to develop a high-adhesion lithium-ion battery separator with simple processing steps and high heat resistance. Summary of the Invention

[0006] This invention proposes a high heat-resistant and high-adhesion lithium-ion battery separator and its preparation method, which solves the problem of insufficient temperature resistance of lithium-ion battery separators in related technologies.

[0007] The technical solution of the present invention is as follows: The present invention proposes a high heat-resistant and high-adhesion lithium-ion battery separator, comprising a substrate and a coating applied to the surface of the substrate. The solid component of the coating consists of the following raw materials by weight percentage: 50%~85% inorganic particles, with the balance being an adhesive polymer; the inorganic particles are composed of porous ceramic particles and porous linear bacterial cellulose, wherein the porous ceramic particles have a particle size of 0.3~1μm and a pore size of 30~50nm, and the porous linear bacterial cellulose has a length of 0.5~2μm and a pore size of 50~100nm.

[0008] As a further technical solution, the porous ceramic particles include one or more of aluminum oxide, boehmite, silicon dioxide, titanium dioxide, magnesium oxide, and aluminum nitride, preferably aluminum oxide.

[0009] As a further technical solution, the substrate is a polyolefin porous substrate, preferably a polyethylene microporous membrane.

[0010] As a further technical solution, the inorganic particles are composed of porous ceramic particles and porous linear bacterial cellulose with a mass ratio of 3 to 4:1.

[0011] As a further technical solution, the adhesive polymer is composed of polyvinylidene fluoride-hexafluoropropylene copolymer and polymethyl methacrylate in a mass ratio of 3:1~3.

[0012] As a further technical solution, the polyvinylidene fluoride-hexafluoropropylene copolymer is composed of a first polyvinylidene fluoride-hexafluoropropylene copolymer and a second polyvinylidene fluoride-hexafluoropropylene copolymer, wherein the first polyvinylidene fluoride-hexafluoropropylene copolymer and the second polyvinylidene fluoride-hexafluoropropylene copolymer have different molecular weights.

[0013] As a further technical solution, the molecular weight of the first polyvinylidene fluoride-hexafluoropropylene copolymer is 290,000 to 310,000, and the model number is 21510; the molecular weight of the second polyvinylidene fluoride-hexafluoropropylene copolymer is 570,000 to 600,000, and the model number is 21216.

[0014] As a further technical solution, the mass ratio of the first polyvinylidene fluoride-hexafluoropropylene copolymer to the second polyvinylidene fluoride-hexafluoropropylene copolymer is 3~5:5.

[0015] In the coating of the high heat-resistant and high-adhesion lithium-ion battery separator of this invention, the polyvinylidene fluoride-hexafluoropropylene copolymer is composed of a first polyvinylidene fluoride-hexafluoropropylene copolymer and a second polyvinylidene fluoride-hexafluoropropylene copolymer with different molecular weights. The low molecular weight polyvinylidene fluoride-hexafluoropropylene copolymer has excellent flowability and wettability, which can fully fill the gaps between inorganic particles and adhere tightly to the substrate surface, improving the interfacial bonding state. The high molecular weight polyvinylidene fluoride-hexafluoropropylene copolymer can provide stronger intermolecular forces and entanglement effects, laying a high-strength foundation for the bonding system. The two work together to resist peeling force with the strong cohesive force of the high molecular weight component and enhance interfacial adhesion through the good spreadability of the low molecular weight component, effectively improving the bonding strength of the lithium-ion battery separator.

[0016] This invention also proposes a method for preparing a high heat-resistant and high-adhesion lithium-ion battery separator, which includes the following steps: S1. Disperse the inorganic particles in N-methylpyrrolidone to form dispersion A; S2. Disperse the adhesive polymer in N-methylpyrrolidone to form dispersion B; S3. Mix the dispersion A and the dispersion B, and stir until homogeneous to obtain a slurry; S4. The slurry is coated onto the substrate, and after water bath extraction and drying, the high heat resistance and high adhesion lithium-ion battery separator is obtained.

[0017] As a further technical solution, the single-layer coating amount of the slurry is 2~8 g / m². 2 .

[0018] As a further technical solution, the thickness of the lithium-ion battery separator is 6~16μm, and the porosity of the lithium-ion battery separator is 30%~70%.

[0019] As a further technical solution, in step S1, the mass ratio of the inorganic particles to the N-methylpyrrolidone is 45:55.

[0020] As a further technical solution, in step S1, the dispersion rotation speed is 2500~3000 r / min, and the dispersion time is 1 h.

[0021] As a further technical solution, in step S2, the dispersion temperature is 20°C.

[0022] As a further technical solution, in step S2, the mass ratio of the adhesive polymer to the N-methylpyrrolidone is 3:100.

[0023] As a further technical solution, in step S3, the stirring time is 1 hour.

[0024] As a further technical solution, in step S4, the drying temperature is 60°C and the drying time is 3 minutes.

[0025] As a further technical solution, in step S4, the coating method includes one of blade coating, roller coating, and spray coating.

[0026] The working principle and beneficial effects of this invention are as follows: In this invention, a high-heat-resistant and high-adhesion lithium-ion battery separator incorporates porous ceramic particles and porous linear bacterial cellulose in its coating. The porous ceramic particles themselves possess excellent thermal stability; their 0.3–1 μm particle size and 30–50 nm pore size form a dense and regular heat-resistant skeleton, maintaining structural integrity under high-temperature environments and effectively preventing pore closure caused by thermal shrinkage in the substrate. The porous linear bacterial cellulose, with a length of 0.5–2 μm and a pore size of 50–100 nm, forms an interwoven network, not only filling the tiny gaps between ceramic particles but also further enhancing the overall heat resistance of the coating due to its excellent thermal stability, delaying melting and collapse at high temperatures. Through the synergistic effect of these two components, the separator maintains its porous structure and dimensional stability even in extreme temperature scenarios, further improving the temperature resistance of the lithium-ion battery separator. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] In the following examples and comparative examples: Aluminum oxide: average particle size is 1μm, pore size is 30~50nm; Porous linear bacterial cellulose: average length 0.5 μm, pore size 50~100 nm; First polyvinylidene fluoride-hexafluoropropylene copolymer: molecular weight 290,000 to 310,000, model number Solvay 21510; Second polyvinylidene fluoride-hexafluoropropylene copolymer: molecular weight 570,000 to 600,000, model number Solvay 21216; Polymethyl methacrylate: Purchased from Shandong Yousuo Chemical Technology Co., Ltd.

[0029] Example 1 A method for preparing a high heat-resistant and high-adhesion lithium-ion battery separator includes the following steps: S1. Disperse inorganic particles in N-methylpyrrolidone at 3000 r / min for 1 h to form dispersion A. The mass ratio of inorganic particles to N-methylpyrrolidone is 45:55. S2. The adhesive polymer is dispersed in N-methylpyrrolidone and dispersed evenly at 20°C to form dispersion B. The mass ratio of the adhesive polymer to the N-methylpyrrolidone is 3:100. S3. Mix dispersion A and dispersion B and stir for 1 hour to obtain a slurry; S4. The slurry is coated onto one side of the polyethylene microporous membrane using a doctor blade. After water bath extraction and drying at 60°C for 3 min, the coating thickness is 3 μm, resulting in a high heat-resistant and high-adhesion lithium-ion battery separator. Among them, the inorganic particles are composed of porous ceramic particles and porous linear bacterial cellulose with a mass ratio of 3:1; The adhesive polymer is composed of polyvinylidene fluoride-hexafluoropropylene copolymer and polymethyl methacrylate in a mass ratio of 3:1, wherein the polyvinylidene fluoride-hexafluoropropylene copolymer is the first polyvinylidene fluoride-hexafluoropropylene copolymer; The solid composition of the coating consists of the following raw materials by weight percentage: 50% inorganic particles and 50% adhesive polymer.

[0030] Example 2 A method for preparing a high heat-resistant and high-adhesion lithium-ion battery separator includes the following steps: S1. Disperse inorganic particles in N-methylpyrrolidone at 3000 r / min for 1 h to form dispersion A. The mass ratio of inorganic particles to N-methylpyrrolidone is 45:55. S2. The adhesive polymer is dispersed in N-methylpyrrolidone and dispersed evenly at 20°C to form dispersion B. The mass ratio of the adhesive polymer to the N-methylpyrrolidone is 3:100. S3. Mix dispersion A and dispersion B and stir for 1 hour to obtain a slurry; S4. The slurry is coated onto one side of the polyethylene microporous membrane using a doctor blade. After water bath extraction and drying at 60°C for 3 min, the coating thickness is 3 μm, resulting in a high heat-resistant and high-adhesion lithium-ion battery separator. Among them, the inorganic particles are composed of porous ceramic particles and porous linear bacterial cellulose with a mass ratio of 3:1; The adhesive polymer is composed of polyvinylidene fluoride-hexafluoropropylene copolymer and polymethyl methacrylate in a mass ratio of 3:2, wherein the polyvinylidene fluoride-hexafluoropropylene copolymer is the first polyvinylidene fluoride-hexafluoropropylene copolymer; The solid composition of the coating consists of the following raw materials by weight percentage: 75% inorganic particles and 25% adhesive polymer.

[0031] Example 3 A method for preparing a high heat-resistant and high-adhesion lithium-ion battery separator includes the following steps: S1. Disperse inorganic particles in N-methylpyrrolidone at 2500 r / min for 1 h to form dispersion A. The mass ratio of inorganic particles to N-methylpyrrolidone is 45:55. S2. The adhesive polymer is dispersed in N-methylpyrrolidone and dispersed evenly at 20°C to form dispersion B. The mass ratio of the adhesive polymer to the N-methylpyrrolidone is 3:100. S3. Mix dispersion A and dispersion B and stir for 1 hour to obtain a slurry; S4. The slurry is coated onto one side of the polyethylene microporous membrane using a doctor blade. After water bath extraction and drying at 60°C for 3 min, the coating thickness is 3 μm, resulting in a high heat-resistant and high-adhesion lithium-ion battery separator. Among them, the inorganic particles are composed of porous ceramic particles and porous linear bacterial cellulose with a mass ratio of 4:1; The adhesive polymer is composed of polyvinylidene fluoride-hexafluoropropylene copolymer and polymethyl methacrylate in a mass ratio of 1:1, wherein the polyvinylidene fluoride-hexafluoropropylene copolymer is the first polyvinylidene fluoride-hexafluoropropylene copolymer; The solid composition of the coating consists of the following raw materials by weight percentage: 85% inorganic particles and 15% adhesive polymer.

[0032] Example 4 Compared with Example 2, Example 4 differs in that aluminum oxide (average particle size of 1 μm and pore size of 30~50 nm) is replaced with an equal amount of aluminum oxide with an average particle size of 2 μm and a pore size of 50~100 nm.

[0033] Example 5 Compared with Example 2, Example 5 differs in that aluminum oxide (average particle size of 1 μm and pore size of 30~50 nm) is replaced with an equal amount of aluminum oxide with an average particle size of 3 μm and a pore size of 120~150 nm.

[0034] Example 6 The difference between Example 6 and Example 2 is that the polyvinylidene fluoride-hexafluoropropylene copolymer is a second polyvinylidene fluoride-hexafluoropropylene copolymer.

[0035] Example 7 The difference between Example 7 and Example 2 is that the polyvinylidene fluoride-hexafluoropropylene copolymer is composed of a first polyvinylidene fluoride-hexafluoropropylene copolymer and a second polyvinylidene fluoride-hexafluoropropylene copolymer in a mass ratio of 3:5.

[0036] Example 8 The difference between Example 7 and Example 2 is that the polyvinylidene fluoride-hexafluoropropylene copolymer is composed of a first polyvinylidene fluoride-hexafluoropropylene copolymer and a second polyvinylidene fluoride-hexafluoropropylene copolymer in a mass ratio of 1:1.

[0037] Comparative Example 1 The difference between Comparative Example 1 and Example 2 is that the inorganic particles are only aluminum oxide.

[0038] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that the inorganic particles are only porous linear bacterial cellulose.

[0039] Comparative Example 3 The difference between Comparative Example 3 and Example 2 is that no coating was applied.

[0040] Experimental Example 1 For the high heat-resistant and high-adhesion lithium-ion battery separators prepared in Examples 1-5 and Comparative Examples 1-3, separator test pieces (6cm × 4cm) were prepared and placed in an oven at 130°C for 60 minutes of heat treatment. After heat treatment, they were removed and left at room temperature for 30 minutes before measuring their dimensions. The heat shrinkage rate (%) was calculated using the following formula: Heat shrinkage rate (%) = (Length of test piece before heat treatment - Length of test piece after heat treatment) / (Length of test piece before heat treatment) × 100%.

[0041] The test results are shown in Table 1: Table 1 Performance test results of Examples 1-5 and Comparative Examples 1-3

[0042] As shown in Table 1, when the inorganic particles are composed of porous ceramic particles and porous linear bacterial cellulose, the temperature resistance of the lithium-ion battery separator can be improved.

[0043] Experiment Example 2 For the lithium-ion battery separators prepared in Examples 2 and 6-8, 10cm × 3cm samples were cut, and the coated side of the separator was aligned with the positive electrode side. The samples were placed under a hot press and subjected to 80°C and 5MPa pressure for 10 seconds. After hot pressing, an electronic tensile testing machine was used to measure the adhesion strength between the separator coating and the electrode. The positive electrode material was lithium nickel cobalt aluminum oxide (NCA), with the chemical formula LiNi. 0.8 Co 0.15 Al 0.05 O2.

[0044] The test results are shown in Table 2: Table 2 Performance test results of Examples 2 and 6-8

[0045] As shown in Table 2, when the polyvinylidene fluoride-hexafluoropropylene copolymer is composed of a first polyvinylidene fluoride-hexafluoropropylene copolymer and a second polyvinylidene fluoride-hexafluoropropylene copolymer with different molecular weights, the bonding strength of the lithium-ion battery separator can be improved.

[0046] The above are merely 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 within the protection scope of the present invention.

Claims

1. A high heat-resistant and high-adhesion lithium-ion battery separator, characterized in that, The coating comprises a substrate and a coating applied to the surface of the substrate. The solid component of the coating consists of the following raw materials by weight percentage: 50% to 85% inorganic particles, with the balance being a binding polymer. The inorganic particles consist of porous ceramic particles and porous linear bacterial cellulose. The porous ceramic particles have a particle size of 0.3 to 1 μm and a pore size of 30 to 50 nm. The porous linear bacterial cellulose has a length of 0.5 to 2 μm and a pore size of 50 to 100 nm.

2. The high heat resistance and high adhesion lithium-ion battery separator according to claim 1, characterized in that, The porous ceramic particles include one or more of aluminum oxide, boehmite, silicon dioxide, titanium dioxide, magnesium oxide, and aluminum nitride.

3. The high heat resistance and high adhesion lithium-ion battery separator according to claim 1, characterized in that, The substrate is a polyolefin porous substrate.

4. The high heat resistance and high adhesion lithium-ion battery separator according to claim 1, characterized in that, The inorganic particles consist of porous ceramic particles and porous linear bacterial cellulose in a mass ratio of 3 to 4:

1.

5. The high heat resistance and high adhesion lithium-ion battery separator according to claim 1, characterized in that, The adhesive polymer is composed of polyvinylidene fluoride-hexafluoropropylene copolymer and polymethyl methacrylate in a mass ratio of 3:1 to 3.

6. The high heat resistance and high adhesion lithium-ion battery separator according to claim 5, characterized in that, The polyvinylidene fluoride-hexafluoropropylene copolymer is composed of a first polyvinylidene fluoride-hexafluoropropylene copolymer and a second polyvinylidene fluoride-hexafluoropropylene copolymer, wherein the first polyvinylidene fluoride-hexafluoropropylene copolymer and the second polyvinylidene fluoride-hexafluoropropylene copolymer have different molecular weights.

7. The high heat resistance and high adhesion lithium-ion battery separator according to claim 6, characterized in that, The first polyvinylidene fluoride-hexafluoropropylene copolymer has a molecular weight of 290,000 to 310,000 and a model number of 21510. The second polyvinylidene fluoride-hexafluoropropylene copolymer has a molecular weight of 570,000 to 600,000 and a model number of 21216.

8. The high heat resistance and high adhesion lithium-ion battery separator according to claim 6, characterized in that, The mass ratio of the first polyvinylidene fluoride-hexafluoropropylene copolymer to the second polyvinylidene fluoride-hexafluoropropylene copolymer is 3~5:

5.

9. A method for preparing a high heat-resistant and high-adhesion lithium-ion battery separator, used to prepare the high heat-resistant and high-adhesion lithium-ion battery separator according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Disperse the inorganic particles in N-methylpyrrolidone to form dispersion A; S2. Disperse the adhesive polymer in N-methylpyrrolidone to form dispersion B; S3. Mix the dispersion A and the dispersion B, and stir until homogeneous to obtain a slurry; S4. The slurry is coated onto the substrate, and after water bath extraction and drying, the high heat resistance and high adhesion lithium-ion battery separator is obtained.

10. The method for preparing a high heat-resistant and high-adhesion lithium-ion battery separator according to claim 9, characterized in that, The coating weight of the slurry in a single layer is 2~8 g / m. 2 .

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