High-heat-resistance pressure-sensitive organic lithium ion battery diaphragm coating slurry as well as preparation method and application thereof

Abstract

The invention relates to the technical field of battery diaphragms, and provides high-heat-resistance pressure-sensitive organic lithium ion battery diaphragm coating slurry as well as a preparation method and application thereof, and the high-heat-resistance pressure-sensitive organic lithium ion battery diaphragm coating slurry comprises the following components: a pressure-sensitive adhesive and polymer aerogel; the polymer aerogel is prepared from polybenzoxazole-polyamide copolymer aerogel. According to the technical scheme, the problems of insufficient heat resistance and adhesion of the battery diaphragm in the prior art are solved.

Description

Technical Field

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

[0002] In the construction system of lithium-ion batteries, the separator, as a core component, bears a crucial dual function. First, it precisely achieves physical isolation between the positive and negative electrodes, constructing a solid safety barrier, effectively avoiding the risk of short circuits, and providing fundamental protection for the safe operation of the battery. Second, its ingenious microstructure design can efficiently guide the free migration of lithium ions within it, thereby ensuring the smooth progress of the battery's charge and discharge cycles and laying a solid foundation for the battery's high performance.

[0003] Currently, the commonly used method in the industry to improve the heat resistance of battery separators is to coat the separator surface with conventional ceramic materials. However, this conventional ceramic coating process has significant limitations—to achieve the ideal thermal shrinkage effect, it is often necessary to significantly increase the thickness of the ceramic coating, which directly leads to a significant increase in the weight of the resulting lithium-ion battery separator. Therefore, there is an urgent need to conduct targeted research to develop a novel lithium-ion battery separator that combines excellent properties such as lightweight, high heat resistance, and strong adhesion to meet the industry's pressing need for high-performance battery materials. Summary of the Invention

[0004] This invention proposes a high-heat-resistant, pressure-sensitive organic lithium-ion battery separator coating slurry, its preparation method, and its application, which solves the problems of insufficient heat resistance and adhesion of battery separators in related technologies.

[0005] The technical solution of the present invention is as follows: This invention proposes a high heat-resistant pressure-sensitive organic lithium-ion battery separator coating slurry, the components of which include a pressure-sensitive binder and a polymer aerogel.

[0006] As a further technical solution, the mass ratio of the pressure-sensitive adhesive to the polymer aerogel is 0.5~0.8:2~3.

[0007] As a further technical solution, the polymer aerogel includes polybenzoxazole-polyamide copolymer aerogel.

[0008] As a further technical solution, the number-average molecular weight of the polymer aerogel is 173,623 to 206,356, and the degree of polymerization is 122 to 145.

[0009] As a further technical solution, the components of the pressure-sensitive adhesive include one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, carboxymethyl cellulose, styrene-butyl methacrylate copolymer, and polyacrylonitrile; Preferably, the components of the pressure-sensitive adhesive include polyvinylidene fluoride-hexafluoropropylene copolymer, carboxymethyl cellulose, styrene-butyl methacrylate copolymer, and polyacrylonitrile.

[0010] As a further technical solution, the mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer, carboxymethyl cellulose, styrene-butyl methacrylate copolymer and polyacrylonitrile is 1:0.005:0.4~0.6:1.2.

[0011] As a further technical solution, the carboxymethyl cellulose includes sodium carboxymethyl cellulose and / or lithium carboxymethyl cellulose.

[0012] As a further technical solution, the monomers for synthesizing the polymer aerogel include monomer A and monomer B; The monomer A comprises 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and / or 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether; The B monomer includes 2,6-pyridinedicarboxylate chloride and / or terephthaloyl chloride; Preferably, monomer A comprises 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether; monomer B comprises 2,6-pyridinedicarboxylate chloride and terephthaloyl chloride.

[0013] As a further technical solution, the mass ratio of monomer A to monomer B is 1.2~2:1.25~2.05.

[0014] As a further technical solution, the mass ratio of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether is 1:0.2~1.

[0015] As a further technical solution, the mass ratio of 2,6-pyridinedicarboxylic acid chloride to terephthaloyl chloride is 0.25~1.05:1.

[0016] As a further technical solution, the preparation method of the polymer aerogel includes the following steps: Under an argon atmosphere, monomer A and monomer B are added sequentially to a solvent. After stirring and reacting, the mixture undergoes gelation and cyclization to obtain a polymer aerogel.

[0017] As a further technical solution, the solvent includes N-methylpyrrolidone.

[0018] As a further technical solution, the temperature of the stirring reaction is -10~5℃, the rotation speed is 30~50r / min, and the time is 8~10h; The gelation temperature is 40~45℃, the humidity is 85%~90%, and the time is 8~10h; The cyclization temperature is 300~320℃, the vacuum degree is -0.095~-0.090MPa, and the time is 4~6h.

[0019] As a further technical solution, the B monomer is added in three separate additions, with the same amount added each time.

[0020] As a further technical solution, the slurry composition also includes porous ceramics.

[0021] As a further technical solution, the mass ratio of the polymer aerogel to the porous ceramic is 0.5~0.8:1.

[0022] As a further technical solution, the pressure-sensitive adhesive also includes water and a dispersant.

[0023] As a further technical solution, the mass ratio of the water, dispersant and polyvinylidene fluoride-hexafluoropropylene copolymer is 7:0.01:1.

[0024] As a further technical solution, the preparation method of the pressure-sensitive adhesive includes the following steps: mixing the components of the pressure-sensitive adhesive to obtain the pressure-sensitive adhesive.

[0025] The present invention also proposes a method for preparing a high heat-resistant pressure-sensitive organic lithium-ion battery separator coating slurry, which is used to prepare the high heat-resistant pressure-sensitive organic lithium-ion battery separator coating slurry, comprising the following steps: mixing the components of the slurry to obtain the high heat-resistant pressure-sensitive organic lithium-ion battery separator coating slurry.

[0026] The present invention also proposes the application of the high heat resistance pressure sensitive organic lithium-ion battery separator coating slurry or the high heat resistance pressure sensitive organic lithium-ion battery separator coating slurry prepared by the preparation method described above in lithium-ion batteries, wherein the high heat resistance pressure sensitive organic lithium-ion battery separator coating slurry is coated on at least one side of the base film.

[0027] As a further technical solution, the coating method includes dot coating or roller coating.

[0028] The high-performance aerogel matrix of this invention employs a quaternary monomer copolymerization system to precisely control the molecular chain rigidity of the polymer aerogel (polybenzoxazole-polyamide copolymer aerogel), exhibiting a superior thermal decomposition temperature compared to traditional polyimide (PI). Furthermore, it fully preserves the gradient pore structure formed by nanoscale interweaving through supercritical CO2 fluid, balancing mechanical strength and porosity. This establishes a lightweight and high-strength basic framework, replacing the traditional ceramic particle stacking structure and reducing membrane density. Simultaneously, trifluoromethyl (-CF3) groups / amide groups / oxazole rings are directionally grafted into the main molecular chain of the polymer aerogel (polybenzoxazole-polyamide copolymer aerogel) and synergistically interact with N-heterocyclic rings to form a dense hydrophobic barrier layer. This achieves a dual effect: significantly inhibiting material hygroscopicity while enhancing surface electrophobic polarization. Data shows that water absorption is reduced compared to the unmodified system, and high-temperature dimensional stability is improved. Submicron-sized porous ceramic particles are then uniformly anchored in the gaps between the aerogel framework to construct a three-dimensional "point-line-surface" conduction channel; the surface hydroxyl groups of the ceramic particles form hydrogen bonds with the carbonyl groups of the polymer aerogel (polybenzoxazole-polyamide copolymer aerogel), strengthening the interfacial bonding force; performance gains: the electrolyte wetting time is shortened and the room temperature ionic conductivity is improved.

[0029] Through a three-pronged innovation encompassing materials, structure, and process, this invention successfully resolves the inherent contradictions of "thickness / weight / brittleness" in traditional ceramic-coated separators, providing a novel separator solution for high-energy-density lithium batteries that combines safety protection with efficient ion transport. This invention achieves greater integration between the ceramic and separator through polymer aerogel (polybenzoxazole-polyamide copolymer aerogel), porous ceramics, and a compounded pressure-sensitive coating slurry. The coated separator exhibits high thermal stability, excellent wettability, and cold-pressing properties.

[0030] The working principle and beneficial effects of this invention are as follows: This invention, for the first time, incorporates polymer aerogel (polybenzoxazole-polyamide copolymer aerogel) into the battery separator coating slurry, significantly improving the heat resistance and adhesion of the battery separator. The polybenzoxazole-polyamide copolymer is a lyotropic liquid crystal heterocyclic semi-trapezoidal polymer. The high strength, high modulus, chemical corrosion resistance, and high temperature resistance of the polybenzoxazole-polyamide copolymer are due to the high aromaticity of its molecular chains. The polybenzoxazole-polyamide copolymer has a low density, a tensile strength approximately twice that of Kevlar, a tensile modulus six times that of steel, significantly higher heat resistance than other high-performance polymers, and low water absorption. Attached Figure Description

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0032] Figure 1 This is a synthesis route diagram of the polybenzoxazole-polyamide copolymer aerogel of Example 1 of the present invention. Detailed Implementation

[0033] 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.

[0034] The dispersant is a polyacrylate polymer with a density of 1.38 kg / m³. 3 ; PVDF is a copolymer of polyvinylidene fluoride and hexafluoropropylene, with a melting point of 140~147℃; CMC is lithium carboxymethyl cellulose, a white powder with a viscosity of 600~1000 cP (3% solubility in water at 25℃). The styrene-butyl methacrylate copolymer is a white emulsion with a viscosity of 10~30 Pa·s (tested at 25℃) and a solid content of 40%~50%. PMMA has a viscosity of 10~30 Pa·s (tested at 25℃) and a solid content of 40%~50%. PAN has a viscosity of 30,000~40,000 mPa·s (tested at 40℃) and a solid content of 10%~20%. 2,2-Di(trifluoromethyl)diaminobiphenyl is a white powder with a melting point of 183℃ and a density of 1.4±0.1 g / cm³. 3 ; 2,2'-Bis(trifluoromethyl)-4,4'-diaminophenyl ether is a white powder, 336.23 g / mol, with a density of 1.5 ± 0.1 g / cm³. 3 ; 2,6-Pyridinedicarboxylic acid chloride is a light brown crystal with a concentration of 204.01 g / mol and a density of 1.45 ± 0.05 g / cm³. 3 ; 2,5-Pyridinedicarboxylic acid chloride is a brown crystal with a concentration of 204.01 g / mol and a density of 1.45 ± 0.05 g / cm³. 3 ; Terephthaloyl chloride is a white, flaky crystal with a concentration of 203.02 g / mol and a density of 1.32 ± 0.05 g / cm³. 3 ; Isophthaloyl chloride is a white needle-like crystal with a concentration of 203.02 g / mol and a density of 1.32 ± 0.05 g / cm³. 3 ; Porous ceramic: white powder, D10 is 0.205 μm, D50 is 0.385 μm, D90 is 1.001 μm, specific surface area is 19.4 m².2 / g, average pore size 10.05nm.

[0035] Example 1 Synthesis of polybenzoxazole-polyamide copolymer aerogel (synthetic route as follows) Figure 1 (As shown), including the following steps: Argon gas was first introduced into the polymerization reactor to replace the system. N-methylpyrrolidone was added as solvent, followed by 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether. The mixture was stirred at 30 rpm for 10 min, then cooled to -10°C. 2,6-pyridinedicarboxylic acid chloride and terephthaloyl chloride were added in three equal portions, with stirring at 30 rpm for 8 hours. The reaction solution was then introduced into a constant temperature chamber at a gel conversion temperature of 40°C and a humidity of 85% for 8 hours. During the reaction, argon gas was pumped in using a peristaltic pump. The argon gas pipe was made of polytetrafluoroethylene and was introduced below the surface of the reaction solution at a rate of 10 L / min. The treated reaction solution was placed in a supercritical fluid analyzer at 40°C and 8 MPa, and treated with carbon dioxide for 2 hours to obtain a precursor aerogel. The precursor aerogel was then transferred to a vacuum furnace, purged with argon gas, heated to 300°C, and subjected to a vacuum of -0.095 MPa for cyclization for 4 hours to obtain a polybenzoxazole-polyamide copolymer aerogel (number average molecular weight of 206356, degree of polymerization of 145). The mass ratio of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether, 2,6-pyridinedicarboxyl chloride, terephthaloyl chloride, and solvent was 1:1:1.05:1:10. The preparation of pressure-sensitive adhesives includes the following steps; Deionized water and dispersant were added to the polymerization reactor and dispersed at 1200 rpm, stirred at 45 rpm for 10 min; PVDF was added and dispersed at 2200 rpm, stirred at 55 rpm for 60 min; CMC was added and dispersed at 1000 rpm, stirred at 45 rpm for 30 min; styrene / butyl methacrylate copolymer was added and stirred at 45 rpm for 10 min; PAN was added and stirred at 45 rpm for 30 min. The mixture was emulsified until homogeneous, yielding a compound pressure-sensitive adhesive. The mass ratio of deionized water, dispersant, PVDF, CMC, styrene / butyl methacrylate copolymer, and PAN was 7:0.010:1:0.005:0.6:1.2. A method for preparing a high-heat-resistant, pressure-sensitive organic lithium-ion battery separator coating slurry includes the following steps; The polybenzoxazole-polyamide copolymer aerogel was added to a polymerization reactor (containing a compound pressure-sensitive adhesive), dispersed at 2200 rpm, stirred at 45 rpm for 60 min, and then porous ceramics were added and dispersed at 2200 rpm, stirred at 45 rpm for 30 min until the emulsification was uniform, thus obtaining a high heat-resistant pressure-sensitive coating slurry. The mass ratio of the compound pressure-sensitive adhesive, polybenzoxazole-polyamide copolymer aerogel, and porous ceramics was 0.8:3:1.

[0036] Example 2 The synthesis of polybenzoxazole-polyamide copolymer aerogel includes the following steps: Argon gas was first introduced into the polymerization reactor to replace the system. N-methylpyrrolidone was added as solvent, followed by 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether. The mixture was stirred at 30 rpm for 10 min, then cooled to -10°C. 2,6-pyridinedicarboxylic acid chloride and terephthaloyl chloride were added in three equal portions, with stirring at 30 rpm for 8 hours. The reaction solution was then introduced into a constant temperature chamber at a gel conversion temperature of 40°C and a humidity of 85% for 8 hours. During the reaction, argon gas was pumped in using a peristaltic pump. The argon gas pipe was made of polytetrafluoroethylene and was introduced below the surface of the reaction solution at a rate of 10 L / min. The treated reaction solution was placed in a supercritical fluid analyzer at 40°C and 8 MPa, and treated with carbon dioxide for 2 hours to obtain a precursor aerogel. The precursor aerogel was then transferred to a vacuum atmosphere furnace, purged with argon gas, heated to 300°C, and subjected to a vacuum of -0.095 MPa for cyclization for 4 hours to obtain a polybenzoxazole-polyamide copolymer aerogel (number average molecular weight 173623, degree of polymerization 122). The mass ratio of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether, 2,6-pyridinedicarboxyl chloride, terephthaloyl chloride, and solvent was 1:0.2:0.25:1:10. The preparation of pressure-sensitive adhesives includes the following steps; Deionized water and dispersant were added to the polymerization reactor and dispersed at 1200 rpm, stirred at 45 rpm for 10 min; PVDF was added and dispersed at 2200 rpm, stirred at 55 rpm for 60 min; CMC was added and dispersed at 1000 rpm, stirred at 45 rpm for 30 min; styrene / butyl methacrylate copolymer was added and stirred at 45 rpm for 10 min; PAN was added and stirred at 45 rpm for 30 min. The mixture was emulsified until homogeneous to obtain a compound pressure-sensitive adhesive. The mass ratio of deionized water, dispersant, PVDF, CMC, styrene / butyl methacrylate copolymer, and PAN was 7:0.010:1:0.005:0.4:1.2. A method for preparing a high-heat-resistant, pressure-sensitive organic lithium-ion battery separator coating slurry includes the following steps; The polybenzoxazole-polyamide copolymer aerogel was added to a polymerization reactor (containing a compound pressure-sensitive adhesive), dispersed at 2200 rpm, stirred at 45 rpm for 60 min, and then porous ceramic was added and dispersed at 2200 rpm, stirred at 45 rpm for 30 min until the emulsification was uniform, thus obtaining a high heat-resistant pressure-sensitive coating slurry. The mass ratio of the compound pressure-sensitive adhesive, polybenzoxazole-polyamide copolymer aerogel, and porous ceramic was 0.5:2:1.

[0037] Example 3 The synthesis of polybenzoxazole-polyamide copolymer aerogel includes the following steps: Argon gas was first introduced into the polymerization reactor to replace the system. N-methylpyrrolidone was added as solvent, followed by 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether. The mixture was stirred at 30 rpm for 10 min, then cooled to -10°C. 2,6-pyridinedicarboxylic acid chloride and terephthaloyl chloride were added in three equal portions, with stirring at 30 rpm for 8 hours. The reaction solution was then introduced into a constant temperature chamber at a gel conversion temperature of 40°C and a humidity of 85% for 8 hours. During the reaction, argon gas was pumped in using a peristaltic pump. The argon gas pipe was made of polytetrafluoroethylene and was introduced below the surface of the reaction solution at a rate of 10 L / min. The treated reaction solution was placed in a supercritical fluid analyzer at 40°C and 8 MPa, and treated with carbon dioxide for 2 hours to obtain a precursor aerogel. The precursor aerogel was then transferred to a vacuum furnace, where argon was introduced to replace the gas, the temperature was raised to 300°C, the vacuum degree was -0.095 MPa, and the mixture was heated and cyclized for 4 hours to obtain a polybenzoxazole-polyamide copolymer aerogel (number average molecular weight 192124, degree of polymerization 135). The mass ratio of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether, 2,6-pyridinedicarboxyl chloride, terephthaloyl chloride, and solvent was 1:0.5:0.85:1:10. The preparation of pressure-sensitive adhesives includes the following steps; Deionized water and dispersant were added to the polymerization reactor and dispersed at 1200 rpm, stirred at 45 rpm for 10 min; PVDF was added and dispersed at 2200 rpm, stirred at 55 rpm for 60 min; CMC was added and dispersed at 1000 rpm, stirred at 45 rpm for 30 min; styrene / butyl methacrylate copolymer was added and stirred at 45 rpm for 10 min; PAN was added and stirred at 45 rpm for 30 min. The mixture was emulsified until homogeneous to obtain a compound pressure-sensitive adhesive. The mass ratio of deionized water, dispersant, PVDF, CMC, styrene / butyl methacrylate copolymer, and PAN was 7:0.010:1:0.005:0.5:1.2. A method for preparing a high-heat-resistant, pressure-sensitive organic lithium-ion battery separator coating slurry includes the following steps; The polybenzoxazole-polyamide copolymer aerogel was added to a polymerization reactor (containing a compound pressure-sensitive adhesive), dispersed at 2200 rpm, stirred at 45 rpm for 60 min, and then porous ceramics were added and dispersed at 2200 rpm, stirred at 45 rpm for 30 min until the emulsification was uniform, thus obtaining a high heat-resistant pressure-sensitive coating slurry. The mass ratio of the compound pressure-sensitive adhesive, polybenzoxazole-polyamide copolymer aerogel, and porous ceramics was 0.7:3:1.

[0038] Example 4 The only difference between this embodiment and Example 3 is that 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane is replaced with 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether, and 2,6-pyridinedicarboxylic chloride is replaced with terephthaloyl chloride.

[0039] Example 5 The only difference between this embodiment and Example 3 is that 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether is replaced with 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, and terephthaloyl chloride is replaced with 2,6-pyridinedicarboxylate chloride.

[0040] Example 6 The only difference between this embodiment and Example 3 is that the mass ratio of polyvinylidene fluoride-hexafluoropropylene copolymer, carboxymethyl cellulose, styrene-butyl methacrylate copolymer and polyacrylonitrile is 1:0.005:0.2:1.2.

[0041] Example 7 The only difference between this embodiment and Example 3 is that the mass ratio of polyvinylidene fluoride-hexafluoropropylene copolymer, carboxymethyl cellulose, styrene-butyl methacrylate copolymer and polyacrylonitrile is 1:0.005:8:1.2.

[0042] Example 8 The only difference between this embodiment and Example 3 is that 2,6-pyridinedicarboxylic acid chloride and terephthaloyl chloride are added all at once, instead of in three separate additions.

[0043] Comparative Example 1 The only difference between this comparative example and Example 3 is that polybenzoxazole-polyamide copolymer aerogel and porous ceramics are not added during the preparation of the high heat resistance pressure sensitive organic lithium-ion battery separator coating slurry.

[0044] Comparative Example 2 The only difference between this comparative example and Example 3 is that the polybenzoxazole-polyamide copolymer aerogel was replaced with an equal amount of porous ceramic in the preparation of the high heat resistance pressure sensitive organic lithium-ion battery separator coating slurry.

[0045] Experimental Example The slurries prepared in Examples 1-8 and Comparative Examples 1-2 were coated onto the surface of the diaphragm for testing. Preparation of lithium battery separator: Dot coating: The slurries prepared in Examples 1-8 and Comparative Examples 1-2 are pumped into a matrix dot coating system. The slurries are coated on one side of the base film using a dot coating method (coated on any side of the base film, the base film thickness is 5.1 μm, and other thicknesses and areal densities are 3.56 g / m²). 2(Alternatively, a base film can be used.) The base film is dried at 80°C for 10 minutes to obtain a coating, thus obtaining a lithium-ion battery separator; the thickness increase is 1.0 μm, and the coating amount per micrometer is 1.1 g / m². 2 .

[0046] Roller coating: The slurry prepared in Example 3 is pumped into a grooved roller coating structure, and the slurry is coated on one side of the base film by roller coating (coated on any side of the base film, the thickness of the base film is 5.1 μm, and the other thicknesses and areal densities are 3.56 g / m²). 2 (Alternatively, a base film can be used.) The base film is dried at 80°C for 10 minutes to obtain a coating, thus obtaining a lithium-ion battery separator; the thickness increase is 1.8 μm, and the coating amount per micrometer is 1.1 g / m². 2 .

[0047] The aforementioned thickness increment and coating amount per micrometer were tested according to the following test method: Thickness increment (μm) test: The thickness of the battery separator was tested according to the method in GB / T 36363-2018 "Polyolefin separator for lithium-ion batteries". The thickness increment of the lithium battery separator was calculated according to the formula: thickness increment = battery separator thickness - base film thickness. The thickness of the wet-process polyethylene base film was 5.1 μm. Coating amount per micrometer (g / m) 2 Test: The areal density of the battery separator was tested according to the method in GB / T 36363-2018 "Polyolefin Separators for Lithium-ion Batteries". Coating amount = (Battery separator areal density - Base film areal density) / Coating thickness increment; where the areal density of wet-process polyethylene base film is 3.56 g / m³. 2 .

[0048] The following performance tests were performed on the battery separator: Liquid absorption rate and liquid retention rate: The test standard is QB / T 2303.11-2008; Ionic conductivity and thermal shrinkage: The test standard is GB / T 36363-2018, in which the temperature for testing ionic conductivity is 40℃ and the relative humidity is 45%~50%; Heat shrinkage, thickness and areal density: tested according to GB / T 36363-2018; Wettability: Characterizes the affinity between the separator and the electrolyte. The higher the wettability value, the better the wettability and the stronger the liquid absorption and retention, which can result in lower battery internal resistance. The wettability v is calculated as: v = h / t, where h is the wetting height (the height of electrolyte penetration in the vertical direction of the separator), in mm, and t is the wetting time, in min. The electrolyte used in the wettability test is a mixture of electrolyte and solvent. The electrolyte is lithium hexafluorophosphate, and the solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (the volume ratio of EC to DEC is 1:1). The concentration of the electrolyte in the electrolyte is 1 mol / L. Cold-pressed electrode adhesion test: The electrode is either a positive electrode or a negative electrode. The adhesion strength is obtained when the electrode is a positive electrode and when it is a negative electrode. Positive electrode adhesion strength: The diaphragm and positive electrode are cut to 25×150mm. The hot press temperature is set to 25℃ and the pressure to 1000Kg. The diaphragm and positive electrode are preheated for 1 second and then cold-pressed for 1 second. The adhesion strength of the cold-pressed positive electrode is tested using an electronic tensile testing machine. The diaphragm and positive electrode are peeled until the tensile distance of the electronic tensile testing machine reaches 50mm. The speed of the electronic tensile testing machine is 300mm / min, and the peel angle is 180°. Positive electrode bonding strength = peel force divided by the tensile distance of the electronic tensile testing machine; Peel force: The average value of the force collected by the electronic tensile testing machine during the peeling process of the diaphragm and the positive electrode sheet. The bonding strength test of the cold-pressed positive electrode sheet is calculated based on the data of the tensile distance between 10 and 40 mm, that is, the bonding strength of the positive electrode sheet = peel force between 10 and 40 mm divided by 30 mm. The positive electrode is a ternary lithium nickel cobalt aluminum oxide with the chemical formula LiNi. 0.8 Co 0.15 Al 0.05 The O2 electrode is a carbon-based graphite electrode (containing 91% carbon). Moisture content: Three groups were tested using a Karl Fischer moisture meter, and the average value was taken. Breakdown voltage: Tested according to GB / T 13542.2-2009, the average value of 100 sets of diaphragm test data is taken; The test results are shown in Table 1 below.

[0049] Table 1 Performance Test Results

[0050] Compared with Comparative Examples 1-2, the separator coating slurry prepared in Examples 1-8 exhibits less thermal shrinkage and higher adhesion to the electrode in lithium-ion battery separators at 150°C, indicating that the polymer aerogel (polybenzoxazole and polyamide copolymer) and pressure-sensitive adhesive of the present invention can improve the heat resistance of the battery separator and its adhesion to the electrode.

[0051] Battery capacity retention test: The lithium-ion battery separators prepared by the above-described dot-coating process using the slurries of Examples 3 and 1-2 were used for battery assembly and testing: the lithium-ion battery separators were encapsulated in CR2032 button cells, and the cell capacity retention rate was tested after the button cells were subjected to 500 charge-discharge cycles at 0.5C; the electrolyte was a 1 mol / L LiPF6 / EC (ethylene carbonate) / DEC (diethyl carbonate) solution. The results are shown in Table 2.

[0052] Table 2 Retention Rate Test Results

[0053] Compared with Comparative Examples 1 and 2, the separator coating slurry prepared in Example 3 has a higher cell capacity retention rate when used for assembling lithium-ion battery separators into batteries, indicating that the presence of polybenzoxazole and polyamide copolymers and pressure-sensitive binders in the separator slurry of the present invention improves the cycle life of the battery.

[0054] 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, pressure-sensitive organic lithium-ion battery separator coating slurry, characterized in that, The slurry components include pressure-sensitive adhesives and polymer aerogels; The polymer aerogel includes polybenzoxazole-polyamide copolymer aerogel.

2. The high heat-resistant pressure-sensitive organic lithium-ion battery separator coating slurry according to claim 1, characterized in that, The components of the pressure-sensitive adhesive include one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, carboxymethyl cellulose, styrene-butyl methacrylate copolymer, and polyacrylonitrile; Preferably, the components of the pressure-sensitive adhesive include polyvinylidene fluoride-hexafluoropropylene copolymer, carboxymethyl cellulose, styrene-butyl methacrylate copolymer, and polyacrylonitrile.

3. The high heat-resistant pressure-sensitive organic lithium-ion battery separator coating slurry according to claim 1, characterized in that, The number-average molecular weight of the polymer aerogel is 173,623 to 206,356, and the degree of polymerization is 122 to 145. The monomers used to synthesize the polymer aerogel include monomer A and monomer B; The monomer A comprises 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and / or 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether; The B monomer includes 2,6-pyridinedicarboxylate chloride and / or terephthaloyl chloride; Preferably, monomer A comprises 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether; monomer B comprises 2,6-pyridinedicarboxylate chloride and terephthaloyl chloride.

4. The high heat-resistant pressure-sensitive organic lithium-ion battery separator coating slurry according to claim 1, characterized in that, The preparation method of the polymer aerogel includes the following steps: Under an argon atmosphere, monomer A and monomer B are added sequentially to a solvent. After stirring and reacting, the mixture undergoes gelation and cyclization to obtain a polymer aerogel.

5. The high heat-resistant pressure-sensitive organic lithium-ion battery separator coating slurry according to claim 4, characterized in that, The stirring reaction is carried out at a temperature of -10 to 5°C, a rotation speed of 30 to 50 r / min, and a time of 8 to 10 h. The gelation temperature is 40~45℃, the humidity is 85%~90%, and the time is 8~10h; The cyclization temperature is 300~320℃, the vacuum degree is -0.095~-0.090MPa, and the time is 4~6h.

6. The high heat-resistant pressure-sensitive organic lithium-ion battery separator coating slurry according to claim 4, characterized in that, The B monomer was added in three separate additions, with the same amount added each time.

7. The high heat-resistant pressure-sensitive organic lithium-ion battery separator coating slurry according to claim 1, characterized in that, The slurry also includes porous ceramics.

8. The high heat resistance and pressure-sensitive organic lithium-ion battery separator coating slurry according to claim 1, characterized in that, The method for preparing the pressure-sensitive adhesive includes the following steps: mixing the components of the pressure-sensitive adhesive to obtain the pressure-sensitive adhesive.

9. A method for preparing a high-heat-resistant, pressure-sensitive organic lithium-ion battery separator coating slurry, used to prepare the high-heat-resistant, pressure-sensitive organic lithium-ion battery separator coating slurry according to any one of claims 1 to 8, characterized in that, Includes the following steps: The components of the slurry are mixed to obtain a high-heat-resistant, pressure-sensitive organic lithium-ion battery separator coating slurry.

10. The application of the high heat-resistant pressure-sensitive organic lithium-ion battery separator coating slurry according to any one of claims 1 to 8 or the high heat-resistant pressure-sensitive organic lithium-ion battery separator coating slurry prepared by the preparation method according to claim 9 in lithium-ion batteries, characterized in that, The high heat-resistant pressure-sensitive organic lithium-ion battery separator coating slurry is coated on at least one side of the base membrane.

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