A heat-resistant diaphragm adhesive, its preparation method and application

Abstract

The application provides a heat-resistant diaphragm adhesive as well as a preparation method and application thereof, the heat-resistant diaphragm adhesive is a polymer particle with a core-shell structure, the polymer particle comprises a core polymer and a shell polymer, the glass transition temperature of the core polymer is greater than or equal to 80 DEG C; and the glass transition temperature of the shell polymer is less than or equal to 0 DEG C. By adopting the core polymer with a specific glass transition temperature, the heat resistance of the heat-resistant diaphragm adhesive is improved; and by matching the shell polymer with a specific glass transition temperature, the room temperature cold-pressing bonding force of the heat-resistant diaphragm adhesive is improved, so that the application of the heat-resistant diaphragm adhesive in a lithium ion battery can be fully met.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a heat-resistant separator adhesive, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are a type of rechargeable battery with broad application prospects. They are favored by various industries due to their high energy density, long lifespan, small size, maintenance-free operation, and environmental friendliness. They have expanded from mobile phones and laptops to electric bicycles, electric vehicles, energy storage, and various portable devices, making them an ideal mobile power source.

[0003] Lithium-ion batteries typically consist of a positive electrode, a negative electrode, a separator, an electrolyte, and a battery casing. The separator is a crucial inner component, its function being to separate the positive and negative electrodes, preventing short circuits caused by contact between them. Currently, lithium-ion batteries generally use polyolefin porous membranes. Because these polyolefin porous membranes have a low melting point, when the battery temperature rises due to internal or external factors, the membrane may shrink or melt, causing direct contact between the positive and negative electrodes, leading to a short circuit and potentially resulting in battery combustion or explosion. To address these issues, composite separators are typically created by coating inorganic particles onto the separator substrate surface using polymer binders. For example, ceramic particles can be coated onto the separator substrate surface to create a ceramic / polymer composite separator, leveraging the heat resistance of the ceramic particles to reduce thermal shrinkage of the separator. Simultaneously, a polymer binder is coated onto the ceramic coating surface to bond the separator to the positive and negative electrode plates, thus fixing the battery structure. However, the current process for coating ceramic and polymer binder layers is relatively complex. For example, for a double-sided coated separator, a total of four coatings are required: two ceramic layers and two polymer binder layers. Furthermore, the polymer binder coated on the ceramic layer surface is typically a polymer with small particle size, which easily forms a film during subsequent battery molding, leading to reduced separator permeability and affecting battery performance.

[0004] CN112940650A discloses a membrane adhesive that can be mixed and coated with ceramic particles, greatly simplifying the membrane preparation process, reducing costs, not affecting the membrane's permeability, and exhibiting good adhesion to the electrode sheets. However, although the glass transition temperature of the described membrane adhesive is distributed between 35-90℃, the membrane adhesive prepared by the method only has one glass transition temperature, which will bring a series of problems during application. If the glass transition temperature of the adhesive is low, the heat resistance of the membrane will be poor after it is used in the membrane, resulting in large thermal shrinkage. If the glass transition temperature of the adhesive is high, the adhesion strength will easily decrease.

[0005] CN112635914A discloses a lithium-ion battery separator with heat resistance and high mechanical strength, comprising a polyolefin porous substrate and a porous heat-resistant layer coated on one or both surfaces of the aforementioned substrate. The porosity of the polyolefin porous substrate is 20%-60%, the needle penetration strength is ≥200gf, and the peel strength of the porous heat-resistant layer is ≥10N / m. The porous heat-resistant layer includes inorganic fillers, binders, thickeners, dispersants, and wetting agents. By coating at least one surface of the polyolefin porous substrate with a porous heat-resistant layer, the heat resistance of the separator is improved, effectively enhancing the safety of the lithium-ion battery and preventing phenomena such as fire and explosion caused by thermal shock. This solves the problems of high thermal shrinkage and significant decrease in strength after heating. However, the problem of poor adhesion still exists.

[0006] CN106953058A discloses a lithium-ion battery separator, comprising a non-woven fabric layer and a polyolefin porous membrane. The upper and lower parts of the non-woven fabric layer are respectively provided with grooves. The polyolefin porous membrane is pressed onto the upper and lower sides of the non-woven fabric layer. The surface of the non-woven fabric layer is uniformly distributed with micropores, and the porosity is 80%. The thickness of the non-woven fabric layer is 3-6μm, which improves the safety performance of the lithium battery. At the same time, the 3μm thickness of the non-woven fabric layer can significantly improve the thermal stability and mechanical properties of the separator, but the adhesion performance is not good.

[0007] Existing heat-resistant separators suffer from a trade-off between high thermal shrinkage and weak adhesion. Therefore, developing a heat-resistant separator with low thermal shrinkage and strong adhesion to meet the requirements of lithium-ion battery applications is a pressing issue in this field. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a heat-resistant membrane adhesive, its preparation method, and its application. The heat-resistant membrane adhesive is a polymer particle with a core-shell structure, comprising a core polymer and a shell polymer. The glass transition temperature of the core polymer is ≥80℃, and the glass transition temperature of the shell polymer is ≤0℃. This imparts excellent adhesion performance and low thermal shrinkage to the heat-resistant membrane, fully meeting the requirements for its application in lithium-ion batteries.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a heat-resistant membrane adhesive, wherein the heat-resistant membrane adhesive is a polymer particle having a core-shell structure, the polymer particle comprising a core polymer and a shell polymer, and the glass transition temperature of the core polymer is ≥80℃, for example, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0011] The glass transition temperature of the core polymer is ≥80℃, which can endow the heat-resistant membrane adhesive with excellent heat resistance.

[0012] The glass transition temperature of the shell polymer is ≤0℃, for example, it can be -50℃, -45℃, -40℃, -35℃, -30℃, -25℃, -20℃, -15℃, -10℃, -5℃, 0℃, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0013] The glass transition temperature of the shell polymer is ≤0℃, which can impart excellent adhesion to the heat-resistant membrane adhesive.

[0014] As a preferred embodiment of the present invention, the term "heat resistant" in the heat-resistant membrane adhesive refers to a low thermal shrinkage rate under high temperature conditions. For example, the thermal shrinkage rate of the membrane containing the heat-resistant membrane adhesive after being placed at 130°C for 1 hour is <5%, more preferably <4%, and even more preferably ≤3.5%, indicating that the heat-resistant membrane adhesive and the membrane containing it have excellent heat resistance.

[0015] The particle size of the polymer particles is 2-7 μm, for example, it can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0016] Preferably, the particle size of the nucleus in the core-shell structure is 1-5 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0017] Preferably, the polymer monomers of the core polymer include a combination of reactive monomer a1 and crosslinking agent a2.

[0018] Preferably, the reactive monomer a1 comprises any one or a combination of at least two of styrene, methylstyrene, ethylstyrene, acrylonitrile, methacrylonitrile, methyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, isobornyl acrylate, dicyclopentenyl acrylate, maleic acid monoester, maleic acid diester, maleamide, and maleimide.

[0019] Preferably, the crosslinking agent a2 comprises any one or a combination of at least two of the following: divinylbenzene, diallyl phthalate, diethanol diacrylate, ethylene glycol dimethacrylate, allyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol diacrylate, or pentaerythritol triacrylate.

[0020] Preferably, the mass of the polymer monomer of the core polymer is 100%, and the mass of the crosslinking agent a2 is 1-20%, for example, it can be 1%, 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 20%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0021] Preferably, the polymer monomers of the shell polymer include a combination of reactive monomer b1, crosslinking agent b2, acidic monomer b3, and long-chain alkyl monomer b4.

[0022] Preferably, the reactive monomer b1 comprises any one or a combination of at least two of ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isooctyl acrylate, hexyl methacrylate, or tetrahydrofuran acrylate.

[0023] Preferably, the crosslinking agent b2 comprises any one or a combination of at least two of the following: divinylbenzene, diallyl phthalate, diethanol diacrylate, ethylene glycol dimethacrylate, allyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol diacrylate, or pentaerythritol triacrylate.

[0024] Preferably, the acidic monomer b3 comprises any one or a combination of at least two of acrylic acid, methacrylic acid, itaconic acid, β-carboxyethyl acrylate, fumaric acid, crotonic acid, or maleic acid.

[0025] Preferably, the long-chain alkyl monomer b4 is an alkyl acrylate and / or alkyl methacrylate having 12 or more carbons (e.g., 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 carbons), and more preferably an alkyl acrylate and / or alkyl methacrylate having 12-26 carbons.

[0026] Preferably, the long-chain alkyl monomer b4 comprises any one or a combination of at least two of the following: dodecyl acrylate, tetradecyl acrylate, hexadecyl acrylate, octadecyl acrylate, eicosyl acrylate, dodecyl methacrylate, tetradecyl methacrylate, hexadecyl methacrylate, octadecyl methacrylate, eicosyl methacrylate, or docosyl methacrylate.

[0027] Preferably, the mass of the polymer monomers of the shell polymer is 100%, and the mass of the crosslinking agent b2 is 0.05-2%, for example, it can be 0.05%, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0028] Preferably, the mass of the polymeric monomers of the shell polymer is 100%, and the mass of the acidic monomer b3 is 1-5%, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0029] Preferably, the mass of the polymeric monomers of the shell polymer is 100%, and the mass of the long-chain alkyl monomer b4 is 5-10%, for example, it can be 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0030] Preferably, the mass percentage of the core polymer in the polymer particles is 15-80%, for example, it can be 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0031] Preferably, the mass percentage of the shell polymer in the polymer particles is 20-85%, for example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0032] In a second aspect, the present invention provides a method for preparing the heat-resistant membrane adhesive as described in the first aspect, the method comprising the following steps:

[0033] (1) The reactive monomer a1 reacts with the crosslinking agent a2 to obtain the core polymer;

[0034] (2) Using the nuclear polymer obtained in step (1) as a seed, a seed polymerization reaction is carried out with the reactive monomer b1, crosslinking agent b2, acidic monomer b3 and long-chain alkyl monomer b4 to obtain the durable diaphragm adhesive.

[0035] Preferably, the reaction in step (1) is a suspension polymerization reaction, which is carried out in the presence of dispersant a3 and initiator a4.

[0036] Preferably, the dispersant a3 comprises polyvinyl alcohol.

[0037] Preferably, the degree of hydrolysis of the polyvinyl alcohol is 70-90%, for example, it can be 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0038] Preferably, the dispersant a3 is an aqueous solution of polyvinyl alcohol.

[0039] Preferably, the aqueous solution of polyvinyl alcohol has a polyvinyl alcohol mass fraction of 0.1-3 wt%, for example, it can be 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0040] Preferably, the initiator a4 is an oil-soluble initiator.

[0041] Preferably, the initiator a4 comprises any one or a combination of at least two of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovalerate, benzoyl peroxide, or dilauryl peroxide.

[0042] Preferably, the amount of initiator a4 is 0.1-3 wt% of the total mass of reactant monomer a1 and crosslinking agent a2, for example, it can be 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0043] Preferably, before the reaction in step (1), the reactant a1, crosslinking agent a2, and initiator a4 are stirred and mixed, and then added to the aqueous solution of dispersant a3. The mixture is homogenized into an aqueous dispersion using a high-speed homogenizer before the reaction is carried out.

[0044] Preferably, the particle size of the aqueous dispersion is 1-5 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0045] Preferably, the nucleopolymer obtained from the reaction in step (1) is an aqueous dispersion of the nucleopolymer.

[0046] Preferably, the mass ratio of the total mass of the reactant a1 and the crosslinking agent a2 to the mass of water is 1:(2.5-10), for example, it can be 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, 1:10, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0047] Preferably, the reaction in step (1) is carried out in a nitrogen atmosphere.

[0048] Preferably, the reaction temperature in step (1) is 50-90℃, for example, it can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0049] Preferably, the reaction time in step (1) is 3-12 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0050] Preferably, the seed polymerization reaction in step (2) is carried out in the presence of initiator b5 and emulsifier b6.

[0051] Preferably, the initiator b5 is a water-soluble initiator.

[0052] Preferably, the initiator b5 comprises any one or a combination of at least two of potassium sulfate, sodium persulfate, or ammonium persulfate.

[0053] Preferably, the emulsifier b6 is any one or a combination of at least two of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, or sodium fatty alcohol polyoxyethylene ether sulfate.

[0054] Preferably, the emulsifier b6 in step (2) is an aqueous solution of emulsifier b6.

[0055] Preferably, the mass of the emulsifier b6 is 0.1-2 wt% of the total mass of the reactive monomer b1, crosslinking agent b2, acidic monomer b3, and long-chain alkyl monomer b4. For example, it can be 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.7 wt%, 0.9 wt%, 1 wt%, 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt%, 2 wt%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0056] Preferably, before the seed polymerization reaction in step (2), deionized water is added to the aqueous dispersion of the nucleopolymer in step (1) to prepare a reaction substrate.

[0057] Preferably, before the reaction in step (2), an aqueous solution of the reactant monomer b1, crosslinking agent b2, acidic monomer b3, long-chain alkyl monomer b4 and emulsifier b6 is mixed and emulsified to obtain a pre-emulsion.

[0058] Preferably, the emulsification time is 5-20 minutes, for example, 5 minutes, 10 minutes, 15 minutes, 20 minutes, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0059] Preferably, in step (2), the pre-emulsion is added dropwise to the reaction substrate while the initiator b5 is added to the seed polymerization reaction.

[0060] Preferably, the dripping time is 2-6 hours, for example, it can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0061] Preferably, the seed polymerization reaction in step (2) is carried out in a nitrogen atmosphere.

[0062] Preferably, the temperature of the seed polymerization reaction in step (2) is 65-90℃, for example, it can be 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0063] Preferably, the seed polymerization reaction time in step (2) is 3-6 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0064] Thirdly, the present invention provides a heat-resistant membrane, the heat-resistant membrane comprising a porous polyolefin substrate and a coating disposed on the porous polyolefin substrate, wherein the material of the coating comprises the heat-resistant membrane adhesive described in the first aspect.

[0065] Preferably, the coating material comprises, by weight, 5-10 parts of heat-resistant membrane adhesive, 80-100 parts of ceramic particles, 3-5 parts of ceramic adhesive, and 1-3 parts of rheology modifier.

[0066] Preferably, the heat-resistant membrane adhesive is 5-10 parts, for example, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, and specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0067] As a preferred embodiment of the present invention, the heat-resistant diaphragm adhesive mainly serves to ensure the adhesion between the diaphragm and the electrode.

[0068] Preferably, the ceramic particles comprise any one or a combination of at least two of boehmite, zirconium oxide, alumina, or silicon oxide.

[0069] Preferably, the ceramic particles are in the range of 80-100 parts, for example, 80 parts, 81 parts, 82 parts, 83 parts, 84 parts, 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts, 91 parts, 92 parts, 93 parts, 94 parts, 95 parts, 96 parts, 97 parts, 98 parts, 99 parts, 100 parts, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0070] Preferably, the ceramic binder comprises any one or a combination of at least two of polyacrylates, styrene-butadiene latex, or polyvinylidene fluoride.

[0071] Preferably, the glass transition temperature of the ceramic binder is -70 to 10°C, for example, it can be -70°C, -65°C, -60°C, -55°C, -50°C, -45°C, -40°C, -35°C, -30°C, -25°C, -20°C, -15°C, -10°C, -5°C, 0°C, 5°C, 10°C, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0072] Preferably, the particle size of the ceramic binder is 50-1000nm, for example, it can be 1000nm, 900nm, 800nm, 700nm, 600nm, 500nm, 400nm, 300nm, 200nm, 100nm, 50nm, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but preferably it is 100-700nm.

[0073] Preferably, the ceramic adhesive is 3-5 parts, for example, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, and specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0074] As a preferred embodiment of the present invention, the main function of the ceramic binder is to ensure the bonding between ceramic particles and the bonding between the ceramic layer and the membrane substrate.

[0075] Preferably, the rheology modifier comprises any one or a combination of at least two of carboxymethyl cellulose, sodium polyacrylate, or lithium polyacrylate.

[0076] Preferably, the rheology modifier is 1-3 parts, for example, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, and specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0077] As a preferred embodiment of the present invention, the rheology modifier is used to adjust the viscosity of the ceramic slurry to facilitate coating.

[0078] Preferably, the porous polyolefin membrane substrate is a porous polypropylene film and / or a porous polyethylene film.

[0079] Preferably, the thickness of the porous polyolefin membrane substrate is 7-11 μm, for example, it can be 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0080] Preferably, the method for preparing the heat-resistant membrane includes: mixing the heat-resistant membrane adhesive, ceramic particles, ceramic adhesive and rheology modifier to obtain a water-dispersible ceramic slurry, coating it on the surface of a porous polyolefin substrate, and drying it to obtain the heat-resistant membrane.

[0081] Preferably, the solid content of the water-dispersible ceramic slurry is 30-50 wt%, for example, it can be 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0082] Preferably, the drying temperature is 40-80℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0083] Preferably, the drying time is 10-300s, for example, it can be 10s, 20s, 30s, 60s, 120s, 180s, 240s, 300s and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0084] Preferably, the thickness of the single-sided coating of the dried heat-resistant diaphragm is 1-5 μm, for example, it can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but 1-3 μm is preferred.

[0085] Fourthly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising at least one of the heat-resistant separator adhesive described in the first aspect and the heat-resistant separator described in the third aspect.

[0086] Compared with the prior art, the present invention has the following beneficial effects:

[0087] This invention provides a heat-resistant separator adhesive, which is a polymer particle with a core-shell structure. The polymer particle includes a core polymer and a shell polymer. The glass transition temperature of the core polymer is ≥80℃, and the glass transition temperature of the shell polymer is ≤0℃. The core layer of this separator adhesive has a high glass transition temperature, which can effectively reduce the thermal shrinkage of the separator; the shell layer has a low glass transition temperature, which significantly improves the room temperature cold pressing bonding performance. The heat-resistant separator for lithium-ion batteries prepared using this separator adhesive has a low thermal shrinkage rate, ≤5% at 130℃, and strong adhesion between the separator and the negative electrode sheet, with an adhesion strength ≥1.4 N / m. Detailed Implementation

[0088] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0089] The experimental materials used in the embodiments, comparative examples, application examples, and comparative application examples of this invention are as follows:

[0090] (1) Dispersant a3: Polyvinyl alcohol with a degree of alcoholysis between 70-90%, polyvinyl alcohol 1788.

[0091] (2) Porous polyolefin membrane substrate: from Sinoma Lithium Membrane Co., Ltd.;

[0092] (3) Ceramic adhesive: Brand SWA610, from Shenzhen Haodian Technology Co., Ltd.;

[0093] (4) Rheology modifier: carboxymethyl cellulose.

[0094] Example 1

[0095] This embodiment provides a heat-resistant membrane adhesive and its preparation method. The heat-resistant membrane adhesive is a polymer particle with a core-shell structure. The polymer particle includes a core polymer and a shell polymer. The glass transition temperature of the core polymer is 90°C, and its polymer monomers include 40 parts of styrene and 10 parts of divinylbenzene. The glass transition temperature of the shell polymer is -50°C, and its polymer monomers include a combination of 29.88 parts of butyl acrylate, 0.72 parts of diallyl phthalate, 1.8 parts of acrylic acid, and 3.6 parts of lauryl acrylate.

[0096] The preparation method specifically includes the following steps:

[0097] (1) Add 40 parts of styrene, 10 parts of divinylbenzene, and 1.5 parts of azobisisobutyronitrile to a beaker, mix and stir to dissolve evenly to obtain a mixed monomer; in another beaker, dissolve 15 parts of polyvinyl alcohol 1788 in deionized water to prepare a dispersant aqueous solution with a concentration of 3 wt%; pour the mixed monomer into the dispersant aqueous solution and homogenize it for 10 minutes at 8000 rpm using a high-speed homogenizer to obtain a mixed monomer aqueous dispersion with a particle size of 5 μm; transfer the mixed monomer aqueous dispersion to a reactor equipped with a stirrer, thermometer, and nitrogen inlet, purge with nitrogen for 30 minutes, and then heat to 70 degrees Celsius for constant temperature polymerization for 12 hours. After polymerization, a core polymer aqueous dispersion with a solid content of 11.5 wt% and a particle size of about 4.9 μm is obtained.

[0098] (2) The above-mentioned core polymer dispersion was added to a reactor equipped with a stirrer, thermometer, and nitrogen inlet to form a reaction substrate. 29.88 parts of butyl acrylate, 0.72 parts of diallyl phthalate, 1.8 parts of acrylic acid, and 3.6 parts of lauryl acrylate were added to 84g of deionized water containing 0.72 parts of sodium dodecylbenzenesulfonate. The mixture was stirred and emulsified for 10 minutes to form a pre-emulsion. Nitrogen gas was passed through the reaction substrate for 30 minutes, and the temperature was raised to 80°C. 0.72 parts of ammonium persulfate were added, and the pre-emulsion was simultaneously added dropwise over 4 hours. After the addition was complete, the reaction was continued at this temperature for 3 hours. After cooling, the heat-resistant membrane adhesive with a core-shell structure was obtained, with a solid content of 15.1% and a particle size of 6.2μm.

[0099] Example 2

[0100] This embodiment provides a heat-resistant membrane adhesive and its preparation method. The heat-resistant membrane adhesive is a polymer particle with a core-shell structure. The polymer particle includes a core polymer and a shell polymer. The glass transition temperature of the core polymer is about 105°C, and its polymer monomers include 198 parts of cyclohexyl methacrylate and 2 parts of allyl methacrylate. The glass transition temperature of the shell polymer is about -5°C, and its polymer monomers include a combination of 164.4 parts of hexyl methacrylate, 164.4 parts of isobutyl acrylate, 0.175 parts of trimethylolpropane triacrylate, 3.5 parts of itaconic acid, and 17.5 parts of docosyl acrylate.

[0101] The preparation method specifically includes the following steps:

[0102] (1) Add 198 parts of cyclohexyl methacrylate, 2 parts of allyl methacrylate, and 0.2 parts of dilauryl peroxide to a beaker, mix and stir to dissolve evenly to obtain a mixed monomer; in another beaker, dissolve 0.5 parts of polyvinyl alcohol 1788 in 499.5 parts of deionized water to prepare a dispersant aqueous solution, at which time the dispersant concentration is 0.1 wt%; pour the mixed monomer into the dispersant aqueous solution, and homogenize it for 10 minutes at 7000 rpm using a high-speed homogenizer to obtain a mixed monomer aqueous dispersion with a particle size of about 5.5 μm; transfer the mixed monomer aqueous dispersion to a reactor equipped with a stirrer, thermometer, and nitrogen inlet, purge with nitrogen for 30 minutes, and then heat to 90 degrees Celsius for constant temperature polymerization for 3 hours. After polymerization, a core polymer aqueous dispersion with a solid content of 28.5 wt% and a particle size of about 5.5 μm is obtained.

[0103] (2) All of the above-mentioned core polymer dispersion was added to a reactor equipped with a stirrer, thermometer, and nitrogen inlet to form a reaction substrate; 164.4 parts of hexyl methacrylate, 164.4 parts of isobutyl acrylate, 0.175 parts of trimethylolpropane triacrylate, 3.5 parts of itaconic acid and 17.5 parts of dodecyl acrylate were added to 400g of deionized water containing 0.35 parts of sodium dodecyl sulfate, and stirred and emulsified for 10 minutes to form a pre-emulsion; after purging the reaction substrate with nitrogen for 30 minutes, the temperature was raised to 70°C, 0.35 parts of potassium persulfate were added, and the pre-emulsion was added dropwise at the same time for 6 hours. After the dropwise addition was completed, the reaction was kept at the temperature for another 6 hours. After cooling, the heat-resistant membrane adhesive with the core-shell structure was obtained, with a solid content of 38.0% and a particle size of 7.0μm.

[0104] Example 3

[0105] This embodiment provides a heat-resistant membrane adhesive and its preparation method. The heat-resistant membrane adhesive is a polymer particle with a core-shell structure. The polymer particle includes a core polymer and a shell polymer. The glass transition temperature of the core polymer is 170°C, and its polymer monomers include 45 parts of isobornyl methacrylate and 5 parts of trimethylolpropane triacrylate. The glass transition temperature of the shell polymer is -70°C, and its polymer monomers include a combination of 311.5 parts of isooctyl acrylate, 3.5 parts of ethylene glycol diacrylate, 10.5 parts of methacrylic acid, and 24.5 parts of octadecyl acrylate.

[0106] The preparation method specifically includes the following steps:

[0107] (1) Add 45 parts of cyclohexyl methacrylate, 5 parts of trimethylolpropane triacrylate, and 0.5 parts of azobisisobutyronitrile to a beaker, mix and stir to dissolve evenly to obtain a mixed monomer; in another beaker, dissolve 2.5 parts of polyvinyl alcohol 1788 in 497.5 parts of deionized water to prepare a dispersant aqueous solution, at which time the dispersant concentration is 0.5wt%; pour the mixed monomer into the dispersant aqueous solution, and homogenize it for 10 minutes at 25000 rpm using a high-speed homogenizer to obtain a mixed monomer aqueous dispersion with a particle size of about 1μm; transfer the mixed monomer aqueous dispersion to a reactor equipped with a stirrer, thermometer, and nitrogen inlet, purge with nitrogen for 30 minutes, and then heat to 50 degrees Celsius for constant temperature polymerization for 5 hours. After polymerization, a core polymer aqueous dispersion with a solid content of 9.5wt% and a particle size of about 5.5μm is obtained.

[0108] (2) All of the above-mentioned core polymer dispersion was added to a reactor equipped with a stirrer, thermometer, and nitrogen inlet to form a reaction substrate; 311.5 parts of isooctyl acrylate, 3.5 parts of ethylene glycol diacrylate, 10.5 parts of methacrylic acid and 24.5 parts of octadecyl acrylate were added to 150g of deionized water containing 3.5 parts of sodium dodecyl sulfate, and stirred and emulsified for 10 minutes to form a pre-emulsion; after passing nitrogen through the reaction substrate for 30 minutes, the temperature was raised to 90°C, 3.5 parts of potassium persulfate were added, and the pre-emulsion was added dropwise at the same time for 2 hours. After the dropwise addition was completed, the reaction was kept at the temperature for 4 hours. After cooling, the heat-resistant membrane adhesive with core-shell structure was obtained with a solid content of 39.0% and a particle size of 2.2μm.

[0109] Example 4

[0110] This embodiment provides a heat-resistant membrane adhesive and its preparation method. The heat-resistant membrane adhesive is a polymer particle with a core-shell structure. The polymer particle includes a core polymer and a shell polymer. The glass transition temperature of the core polymer is 90°C, and its polymer monomers include 45 parts of styrene and 5 parts of divinylbenzene. The glass transition temperature of the shell polymer is -50°C, and its polymer monomers include a combination of 84 parts of butyl acrylate, 1 part of diallyl phthalate, 5 parts of acrylic acid, and 10 parts of lauryl acrylate.

[0111] The preparation method specifically includes the following steps:

[0112] (1) Add 45 parts of styrene, 5 parts of divinylbenzene, and 1 part of azobisisobutyronitrile to a beaker, mix and stir until dissolved to obtain a mixed monomer; in another beaker, dissolve 2.5 parts of polyvinyl alcohol 1788 in 497.5 parts of deionized water to prepare a dispersant aqueous solution with a concentration of 0.5 wt%; pour the mixed monomer into the dispersant aqueous solution and homogenize it for 10 minutes at 9500 rpm using a high-speed homogenizer to obtain a mixed monomer aqueous dispersion with a particle size of 4 μm; transfer the mixed monomer aqueous dispersion to a reactor equipped with a stirrer, thermometer, and nitrogen inlet, purge with nitrogen for 30 minutes, and then heat to 70 degrees Celsius for 12 hours of constant temperature polymerization. After polymerization, a core polymer aqueous dispersion with a solid content of 17.0 wt% and a particle size of about 4.1 μm is obtained.

[0113] (2) All of the above-mentioned core polymer dispersion was added to a reactor equipped with a stirrer, thermometer, and nitrogen inlet to form a reaction substrate; 84 parts of butyl acrylate, 1 part of diallyl phthalate, 5 parts of acrylic acid and 10 parts of lauryl acrylate were added to 66.7 g of deionized water containing 0.5 parts of sodium dodecylbenzenesulfonate, and stirred and emulsified for 10 minutes to form a pre-emulsion; after passing nitrogen through the reaction substrate for 30 minutes, the temperature was raised to 80°C, 0.5 parts of ammonium persulfate were added, and the pre-emulsion was added dropwise at the same time for 4 hours. After the dropwise addition was completed, the reaction was kept at the temperature for 3 hours. After cooling, the heat-resistant membrane adhesive with core-shell structure was obtained with a solid content of 26.5% and a particle size of 5.3 μm.

[0114] Comparative Example 1

[0115] A heat-resistant membrane adhesive, differing from Example 1 in that the heat-resistant membrane adhesive uses non-core-shell polymer particles, obtained by blending a polymer with a glass transition temperature of 90°C and a polymer with a glass transition temperature of -50°C (the amount of the core-shell polymer remains the same as in Example 1). The preparation method is as follows:

[0116] (1) Add 40 parts of styrene, 10 parts of divinylbenzene, and 1.5 parts of azobisisobutyronitrile to a beaker, mix and stir until dissolved to obtain a mixed monomer; in another beaker, dissolve 15 parts of polyvinyl alcohol 1788 in 485 parts of deionized water to prepare a dispersant aqueous solution with a concentration of 3 wt%; pour the mixed monomer into the dispersant aqueous solution and homogenize it for 10 minutes at 8000 rpm using a high-speed homogenizer to obtain a mixed monomer aqueous dispersion with a particle size of 5 μm; transfer the mixed monomer aqueous dispersion to a reactor equipped with a stirrer, thermometer, and nitrogen inlet, purge with nitrogen for 30 minutes, and then heat to 70 degrees Celsius for constant temperature polymerization for 12 hours. After polymerization, a high glass transition temperature polymer aqueous dispersion with a solid content of 11.5 wt% and a particle size of about 4.9 μm is obtained.

[0117] (2) In a reactor equipped with a stirrer, thermometer, and nitrogen inlet, 29.88 parts of butyl acrylate, 0.72 parts of diallyl phthalate, 1.8 parts of acrylic acid, and 3.6 parts of lauryl acrylate were added to a mixture containing 0.72 parts of sodium dodecylbenzenesulfonate and 84 g of deionized water. The mixture was stirred and emulsified for 10 minutes to form a pre-emulsion. After purging the reaction mixture with nitrogen for 30 minutes, the temperature was raised to 80°C, and 0.72 parts of ammonium persulfate were added. The mixture was kept at this temperature for 3 hours, and after cooling, the polymer with a low glass transition temperature was obtained.

[0118] After mixing all the polymers obtained from (1) and (2), a non-core-shell structured blend polymer is obtained.

[0119] Comparative Example 2

[0120] A heat-resistant membrane adhesive differs from Example 1 only in that the glass transition temperature of the core polymer is 53°C; the types, amounts, and preparation methods of other components are the same as in Example 1.

[0121] The preparation method specifically includes the following steps:

[0122] (1) Add 40 parts of isobutyl methacrylate, 10 parts of divinylbenzene, and 1.5 parts of azobisisobutyronitrile to a beaker, mix and stir until dissolved to obtain a mixed monomer; in another beaker, dissolve 15 parts of polyvinyl alcohol 1788 in 485 parts of deionized water to prepare a dispersant aqueous solution with a concentration of 3 wt%; pour the mixed monomer into the dispersant aqueous solution and homogenize it for 10 minutes at 8000 rpm using a high-speed homogenizer to obtain a mixed monomer aqueous dispersion with a particle size of 5 μm; transfer the mixed monomer aqueous dispersion to a reactor equipped with a stirrer, thermometer, and nitrogen inlet, purge with nitrogen for 30 minutes, and then heat to 70 degrees Celsius for constant temperature polymerization for 12 hours. After polymerization, a core polymer aqueous dispersion with a solid content of 11.0 wt% and a particle size of about 4.7 μm is obtained.

[0123] (2) All of the above-mentioned core polymer dispersion was added to a reactor equipped with a stirrer, thermometer, and nitrogen inlet to form a reaction substrate; 29.88 parts of butyl acrylate, 0.72 parts of diallyl phthalate, 1.8 parts of acrylic acid and 3.6 parts of lauryl acrylate were added to 84g of deionized water containing 0.72 parts of sodium dodecylbenzenesulfonate, and stirred and emulsified for 10 minutes to form a pre-emulsion; after passing nitrogen through the reaction substrate for 30 minutes, the temperature was raised to 80°C, and 0.72 parts of ammonium persulfate were added. At the same time, the pre-emulsion was started to be added dropwise for 4 hours. After the addition was completed, the reaction was kept at the temperature for 3 hours. After cooling, the heat-resistant membrane adhesive with core-shell structure was obtained with a solid content of 15.3% and a particle size of 6.0μm.

[0124] Comparative Example 3

[0125] A heat-resistant membrane adhesive differs from Example 1 only in that the glass transition temperature of the shell polymer is 7°C; the types, amounts, and preparation methods of other components are the same as in Example 1.

[0126] The preparation method specifically includes the following steps:

[0127] (1) Add 40 parts of styrene, 10 parts of divinylbenzene, and 1.5 parts of azobisisobutyronitrile to a beaker, mix and stir until dissolved to obtain a mixed monomer; in another beaker, dissolve 15 parts of polyvinyl alcohol 1788 in 485 parts of deionized water to prepare a dispersant aqueous solution with a concentration of 3 wt%; pour the mixed monomer into the dispersant aqueous solution and homogenize it for 10 minutes at 8000 rpm using a high-speed homogenizer to obtain a mixed monomer aqueous dispersion with a particle size of 5 μm; transfer the mixed monomer aqueous dispersion to a reactor equipped with a stirrer, thermometer, and nitrogen inlet, purge with nitrogen for 30 minutes, and then heat to 70 degrees Celsius for constant temperature polymerization for 12 hours. After polymerization, a core polymer aqueous dispersion with a solid content of 11.5 wt% and a particle size of about 4.9 μm is obtained.

[0128] (2) All of the above-mentioned core polymer dispersion was added to a reactor equipped with a stirrer, thermometer, and nitrogen inlet to form a reaction substrate; 29.88 parts of methyl acrylate, 0.72 parts of diallyl phthalate, 1.8 parts of acrylic acid and 3.6 parts of lauryl acrylate were added to 84g of deionized water containing 0.72 parts of sodium dodecylbenzenesulfonate, and stirred and emulsified for 10 minutes to form a pre-emulsion; after passing nitrogen through the reaction substrate for 30 minutes, the temperature was raised to 80°C, 0.72 parts of ammonium persulfate were added, and the pre-emulsion was added dropwise at the same time for 4 hours. After the dropwise addition was completed, the reaction was kept at the temperature for 3 hours. After cooling, the heat-resistant membrane adhesive with core-shell structure was obtained with a solid content of 15.1% and a particle size of 6.2μm.

[0129] Comparative Example 4

[0130] A heat-resistant membrane adhesive differs from Example 1 only in that the shell polymer monomer does not contain lauryl acrylate, the amount of butyl acrylate is 33.48 parts (the sum of the original butyl acrylate and lauryl acrylate parts), the glass transition temperature of the core polymer is 90°C, and the glass transition temperature of the shell polymer is -43°C; the types, amounts, and preparation methods of other components are the same as in Example 1.

[0131] Comparative Example 5

[0132] A heat-resistant membrane adhesive differs from Example 1 only in that the shell polymer monomers in the heat-resistant membrane adhesive do not contain acrylic acid, the amount of butyl acrylate is 31.68 parts (the sum of the original butyl acrylate and acrylic acid parts), the glass transition temperature of the core polymer is 90°C, and the glass transition temperature of the shell polymer is -51°C; the types, amounts, and preparation methods of other components are the same as in Example 1.

[0133] Comparative Example 6

[0134] A heat-resistant membrane adhesive differs from Example 1 only in that the shell polymer monomers in the heat-resistant membrane adhesive do not contain acrylic acid and lauryl acrylate, the amount of butyl acrylate is 35.28 parts (the sum of the original butyl acrylate, acrylic acid and lauryl acrylate parts), the glass transition temperature of the core polymer is 90°C, and the glass transition temperature of the shell polymer is -47°C; the types, amounts and preparation methods of other components are the same as in Example 1.

[0135] The glass transition temperature of the heat-resistant diaphragm adhesives provided in Examples 1-4 and Comparative Examples 1-6 was tested using the following methods:

[0136] The glass transition temperatures of the core polymer and the shell polymer were measured using a differential scanning calorimeter (Shanghai Qunhong Instrument Equipment Co., Ltd., model: DSC-100).

[0137] Application Example 1

[0138] This application example provides a heat-resistant membrane and its preparation method. The heat-resistant membrane includes a porous polyethylene film and a coating disposed on the porous polyethylene film. The material of the coating, by mass parts, includes: 10 parts of heat-resistant membrane adhesive (Example 1), 82 parts of hydrated alumina, 5 parts of SWA610 ceramic adhesive, and 1 part of carboxymethyl cellulose.

[0139] The preparation method specifically includes the following steps:

[0140] (1) Preparation of ceramic slurry: 82 parts of hydrated alumina (average particle size of 0.825 μm), 10 parts of the heat-resistant diaphragm binder of Example 1, 5 parts of SWA610 ceramic binder, 1 part of carboxymethyl cellulose, and an appropriate amount of deionized water were added to a stirring container. The stirring speed was controlled at 1000 rpm and stirred at room temperature for 4 hours to obtain a ceramic slurry with a solid content of 30%. The heat-resistant diaphragm binder and the ceramic binder are dry weights.

[0141] (2) The ceramic slurry obtained in step (1) was coated on both sides of a 7 μm porous polyethylene film by roller coating and dried at 60°C. The thickness of the single-sided ceramic layer after drying was 3 μm.

[0142] Application Example 2

[0143] A heat-resistant membrane, which differs from Application Example 1 only in that the heat-resistant membrane adhesive is obtained in Example 2, while the types, amounts and preparation methods of other components are the same as in Application Example 1.

[0144] Application Example 3

[0145] A heat-resistant diaphragm, which differs from Application Example 1 only in that the heat-resistant diaphragm adhesive is obtained in Example 3, the thickness of the single-sided ceramic layer after drying is 1 μm, and the types, amounts and preparation methods of other components are the same as in Application Example 1.

[0146] Application Example 4

[0147] A heat-resistant membrane, which differs from Application Example 1 only in that the heat-resistant membrane adhesive is obtained in Example 4, while the types, amounts and preparation methods of other components are the same as in Application Example 1.

[0148] Application Example 5

[0149] A heat-resistant membrane, which differs from Application Example 1 only in that the heat-resistant membrane adhesive is the one obtained in Example 1, and the ceramic particles used are boehmite (average particle size of 1.5 μm), which is coated on both sides of an 11 μm polypropylene porous membrane, and the coating thickness on one side is 1 μm after drying.

[0150] Application Example 6

[0151] A heat-resistant membrane, which differs from Application Example 1 only in that the heat-resistant membrane adhesive is the one obtained in Example 1, the ceramic particles used are boehmite (average particle size of 1.5 μm), coated on one side of a 7 μm porous polyethylene membrane, and the coating thickness on one side after drying is 5 μm.

[0152] Comparative Application Example 1

[0153] A heat-resistant membrane, which differs from Application Example 1 only in that the heat-resistant membrane adhesive is obtained from Comparative Example 1; the types, amounts and preparation methods of other components are the same as in Application Example 1.

[0154] Comparative Application Example 2

[0155] A heat-resistant membrane, which differs from Application Example 1 only in that the heat-resistant membrane adhesive is obtained from Comparative Example 2; the types, amounts and preparation methods of other components are the same as in Application Example 1.

[0156] Comparative Application Example 3

[0157] A heat-resistant membrane, which differs from Application Example 1 only in that the heat-resistant membrane adhesive is obtained from Comparative Example 3; the types, amounts and preparation methods of other components are the same as in Application Example 1.

[0158] Comparative Application Example 4

[0159] A heat-resistant membrane, which differs from Application Example 1 only in that the heat-resistant membrane adhesive is obtained from Comparative Example 4; the types, amounts and preparation methods of other components are the same as in Application Example 1.

[0160] Comparative Application Example 5

[0161] A heat-resistant membrane, which differs from Application Example 1 only in that the heat-resistant membrane adhesive is obtained from Comparative Example 5; the types, amounts and preparation methods of other components are the same as in Application Example 1.

[0162] Comparative Application Example 6

[0163] A heat-resistant membrane, which differs from Application Example 1 only in that the heat-resistant membrane adhesive is obtained from Comparative Example 6; the types, amounts and preparation methods of other components are the same as in Application Example 1.

[0164] For use cases 1-6, the performance of the heat-resistant diaphragm provided in application example 1-6 is tested. The specific method is as follows:

[0165] Bonding strength test between the separator and the negative electrode sheet: The separator and the graphite negative electrode sheet prepared by the scheme described in this invention are cut into strips of 20*100mm, and cold-pressed for 20s at room temperature of 25℃ and 1MPa. The bonding strength is then tested using an electronic tensile testing machine.

[0166] Diaphragm heat resistance test: The diaphragm prepared using the method described in this invention was stacked into 3 layers, the air between the layers was expelled, and a sample cut into 300mm*100mm pieces was taken out. The length A1 of the cut sample was measured. The oven temperature was set to 130℃ and held at that temperature for 1 hour. The sample was placed in the oven and held at that temperature for 1 hour. After the holding period, the diaphragm was removed, cooled for 10 minutes, and the length A2 of the sample was measured. The diaphragm exhibited thermal shrinkage.

[0167] = (A1-A2) / A1*100%.

[0168] The test results are shown in Table 1.

[0169] Table 1

[0170] Heat shrinkage (%) Bond strength (N / m) Application Example 1 3.4 1.5 Application Example 2 2.8 1.6 Application Example 3 2.9 2.1 Application Example 4 3.0 1.9 Application Example 5 3.0 1.6 Application Example 6 3.5 1.8 Comparative Application Example 1 4.7 0.9 Comparative Application Example 2 7.5 1.6 Comparative Application Example 3 2.4 1.3 Comparative Application Example 4 3.3 1.2 Comparative Application Example 5 3.9 1.3 Comparative Application Example 6 4.2 1.0

[0171] As shown in Table 1, the heat-resistant membranes used in Application Examples 1-6, prepared with the core-shell structured heat-resistant membrane adhesives obtained in Examples 1-4, exhibit low thermal shrinkage rates, with a thermal shrinkage rate ≤5% at 130°C. Furthermore, the membranes demonstrate strong adhesion to the negative electrode, with a bond strength ≥1.4 N / m. In contrast, membranes prepared using adhesives obtained through simple blending of polymers with different glass transition temperatures show extremely low adhesion. When the glass transition temperature of the core polymer is lower than that of the core polymers in the examples, the heat resistance of the membrane decreases. When the glass transition temperature of the shell polymer is not within the preferred range, or when acidic monomers or long-chain alkyl monomers are not used, the adhesive strength of the prepared adhesive is insufficient.

[0172] The applicant declares that this invention illustrates a heat-resistant membrane adhesive, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials in the product, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A heat-resistant diaphragm adhesive, characterized in that, The heat-resistant membrane adhesive is a polymer particle with a core-shell structure; The polymer particles comprise a core polymer and a shell polymer; The glass transition temperature of the nuclear polymer is ≥80℃; The glass transition temperature of the shell polymer is ≤0℃; The polymer monomers of the shell polymer include a combination of reactive monomer b1, crosslinking agent b2, acidic monomer b3, and long-chain alkyl monomer b4. The reactive monomer b1 includes any one or a combination of at least two of the following: ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isooctyl acrylate, hexyl methacrylate, or tetrahydrofuran acrylate. The crosslinking agent b2 includes any one or a combination of at least two of the following: divinylbenzene, diallyl phthalate, ethylene glycol dimethacrylate, allyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol diacrylate, or pentaerythritol triacrylate. The acidic monomer b3 includes any one or a combination of at least two of the following: acrylic acid, methacrylic acid, itaconic acid, β-carboxyethyl acrylate, fumaric acid, crotonic acid, or maleic acid. The long-chain alkyl monomer b4 includes any one or a combination of at least two of the following: dodecyl acrylate, tetradecyl acrylate, hexadecyl acrylate, octadecyl acrylate, eicosyl acrylate, dodecyl methacrylate, tetradecyl methacrylate, hexadecyl methacrylate, octadecyl methacrylate, eicosyl methacrylate, or dodecyl methacrylate. The polymer monomers of the core polymer include a combination of reactive monomer a1 and crosslinking agent a2; The reactive monomer a1 includes any one or a combination of at least two of the following: styrene, methylstyrene, ethylstyrene, acrylonitrile, methacrylonitrile, methyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, isobornyl acrylate, dicyclopentenyl acrylate, maleic acid monoester, maleic acid diester, maleamide, and maleimide. The crosslinking agent a2 includes any one or a combination of at least two of the following: divinylbenzene, diallyl phthalate, ethylene glycol dimethacrylate, allyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol diacrylate, or pentaerythritol triacrylate. The mass percentage of the polymer monomers in the core polymer is 100%, and the mass percentage of the crosslinking agent a2 is 1-20%. The mass of the polymer monomers in the shell polymer is 100%, and the mass of the crosslinking agent b2 is 0.05-2%. The mass of the polymer monomers in the shell polymer is 100%, and the mass of the acidic monomer b3 is 1-5%. The mass percentage of the polymer monomers in the shell polymer is 100%, and the mass percentage of the long-chain alkyl monomer b4 is 5-10%. The mass percentage of the core polymer in the polymer particles is 15-80%.

2. The heat-resistant membrane adhesive according to claim 1, characterized in that, The polymer particles have a particle size of 2-7 μm.

3. The heat-resistant membrane adhesive according to claim 1, characterized in that, The core in the core-shell structure has a particle size of 1-5 μm.

4. The heat-resistant membrane adhesive according to claim 1, characterized in that, The polymer particles contain 20-85% by mass of the shell polymer.

5. A method for preparing a heat-resistant membrane adhesive as described in any one of claims 1-4, characterized in that, The preparation method includes the following steps: (1) The reactive monomer a1 reacts with the crosslinking agent a2 to obtain the core polymer; (2) Using the nuclear polymer obtained in step (1) as a seed, a seed polymerization reaction is carried out with the reactive monomer b1, crosslinking agent b2, acidic monomer b3 and long-chain alkyl monomer b4 to obtain the heat-resistant membrane adhesive.

6. The preparation method according to claim 5, characterized in that, The reaction in step (1) is a suspension polymerization reaction, which is carried out in the presence of dispersant a3 and initiator a4.

7. The preparation method according to claim 6, characterized in that, The dispersant a3 includes polyvinyl alcohol.

8. The preparation method according to claim 7, characterized in that, The degree of alcoholysis of the polyvinyl alcohol is 70-90%.

9. The preparation method according to claim 6, characterized in that, The initiator a4 is an oil-soluble initiator.

10. The preparation method according to claim 9, characterized in that, The initiator a4 includes any one or a combination of at least two of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovalerate, benzoyl peroxide, or dilauryl peroxide.

11. The preparation method according to claim 5, characterized in that, The reaction temperature in step (1) is 50-90℃.

12. The preparation method according to claim 5, characterized in that, The reaction time in step (1) is 3-12 h.

13. The preparation method according to claim 5, characterized in that, The seed polymerization reaction in step (2) is carried out in the presence of initiator b5 and emulsifier b6.

14. The preparation method according to claim 13, characterized in that, The initiator b5 is a water-soluble initiator.

15. The preparation method according to claim 14, characterized in that, The initiator b5 includes any one or a combination of at least two of potassium persulfate, sodium persulfate, or ammonium persulfate.

16. The preparation method according to claim 13, characterized in that, The emulsifier b6 includes any one or a combination of at least two of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, or sodium fatty alcohol polyoxyethylene ether sulfate.

17. The preparation method according to claim 5, characterized in that, The temperature of the seed polymerization reaction in step (2) is 65-90℃.

18. The preparation method according to claim 5, characterized in that, The seed polymerization reaction in step (2) takes 3-6 hours.

19. A heat-resistant diaphragm, characterized in that, The heat-resistant membrane includes a porous polyolefin substrate and a coating disposed on the porous polyolefin substrate, wherein the material of the coating includes the heat-resistant membrane adhesive as described in any one of claims 1-4.

20. The heat-resistant diaphragm according to claim 19, characterized in that, The coating material, by weight, includes: 5-10 parts of heat-resistant membrane adhesive, 80-100 parts of ceramic particles, 3-5 parts of ceramic adhesive, and 1-3 parts of rheology modifier.

21. The heat-resistant diaphragm according to claim 20, characterized in that, The ceramic particles include any one or a combination of at least two of boehmite, zirconium oxide, alumina, or silicon oxide.

22. The heat-resistant diaphragm according to claim 20, characterized in that, The ceramic binder includes any one or a combination of at least two of polyacrylates, styrene-butadiene latex, or polyvinylidene fluoride.

23. The heat-resistant diaphragm according to claim 20, characterized in that, The glass transition temperature of the ceramic binder is -70 to 10°C.

24. The heat-resistant diaphragm according to claim 20, characterized in that, The particle size of the ceramic binder is 50-1000 nm.

25. The heat-resistant diaphragm according to claim 24, characterized in that, The ceramic binder has a particle size of 100-700 nm.

26. The heat-resistant diaphragm according to claim 20, characterized in that, The rheology modifier includes any one or a combination of at least two of carboxymethyl cellulose, sodium polyacrylate, or lithium polyacrylate.

27. The heat-resistant diaphragm according to claim 19, characterized in that, The porous polyolefin substrate is a porous polypropylene film and / or a porous polyethylene film.

28. The heat-resistant diaphragm according to claim 27, characterized in that, The thickness of the porous polyolefin substrate is 7-11 μm.

29. A lithium-ion battery, characterized in that, The lithium-ion battery includes at least one of the heat-resistant separator adhesive as described in any one of claims 1-4 and the heat-resistant separator as described in any one of claims 19-28.