A thermo-optical dual crosslinking composite diaphragm, a preparation method thereof and a battery

Abstract

The application relates to the technical field of batteries, and discloses a heat-light double-crosslinking composite diaphragm, a preparation method thereof and a battery. The heat-light double-crosslinking composite diaphragm comprises a base film and a coating layer arranged on at least one side of the base film, and the raw materials of the coating layer comprise ceramics, a light initiator, a heat initiator, a crosslinking agent and a bonding agent. Through the above technical scheme, the problems of high-temperature shrinkage and insufficient safety performance of the polyolefin diaphragm in the related art are solved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a thermal-optical dual crosslinked composite separator, its preparation method, and a battery. Background Technology

[0002] Lithium-ion battery separators are core components ensuring battery safety and performance. With the rapid development of new energy vehicles and high-power batteries, battery systems are constantly upgrading towards higher voltage, higher nickel ternary, and higher energy density. Under extreme conditions such as fast charging, overcharging, and external short circuits, the internal temperature rise of batteries is more significant, placing far more stringent requirements on the high-temperature dimensional stability, mechanical strength, and interfacial adhesion of separators than on traditional consumer batteries. Currently, the most widely used commercially available separators are still polyolefin single / multilayer separators based on polyethylene (PE) and polypropylene (PP). However, traditional PE and PP substrate separators have poor heat resistance and are prone to thermal shrinkage at high temperatures, leading to battery short circuits and failing to meet the safety requirements of high-energy-density batteries. Aqueous ceramic coatings, due to their environmental friendliness and low cost, have become the mainstream industrial technology for improving the heat resistance and insulation of separators, and are widely used in the fields of power and energy storage batteries.

[0003] Current aqueous ceramic coating processes rely solely on drying to form a film, with the coating adhering to the base film through physical bonding. During battery winding, electrolyte injection, and long-term cycling, the coating is prone to peeling, flaking, and powdering, clogging electrode pores, increasing internal resistance, and even causing micro-short circuits. Furthermore, simple physical coating cannot suppress the thermal shrinkage of the polyolefin base film itself; at temperatures above 150°C, the separator still exhibits significant dimensional deformation, failing to meet the requirements of high-safety-level batteries. Therefore, there is an urgent need to develop a novel coated separator. Summary of the Invention

[0004] This invention proposes a thermal-optical dual crosslinked composite separator, its preparation method, and a battery, which solves the problems of high-temperature shrinkage and insufficient safety performance of polyolefin separators in related technologies.

[0005] The technical solution of the present invention is as follows: This invention proposes a thermo-optical dual crosslinked composite membrane, comprising a base membrane and a coating disposed on at least one side of the base membrane, wherein the raw materials of the coating include ceramics, photoinitiators, thermal initiators, crosslinking agents, and adhesives.

[0006] Preferably, the mass ratio of the photoinitiator to the thermal initiator is 0.1~3:1~3.

[0007] Preferably, the mass ratio of the ceramic to the photoinitiator, thermal initiator, crosslinking agent, and adhesive is 30~50:0.1~3:1~3:20~30:4~5.

[0008] Preferably, the mass ratio of the photoinitiator, thermal initiator and crosslinking agent is 1:1:30.

[0009] Preferably, the raw materials for the coating further include at least one of a thickener, a dispersant, and a wetting agent.

[0010] Preferably, the coating slurry comprises a first solution and a second solution; The first solution comprises a photoinitiator, a thermal initiator, a crosslinking agent, and a first solvent; The second solution comprises ceramics, dispersants, thickeners, binders, wetting agents, and a second solvent.

[0011] Preferably, the mass ratio of photoinitiator, thermal initiator, crosslinking agent and first solvent in the first solution is 0.1~3:1~3:20~30:70~80; The mass ratio of ceramic, dispersant, thickener, binder, wetting agent and second solvent in the second solution is 30~50:0.5~1:0.1~0.3:4~5:0.05~0.5:45~65.

[0012] The present invention also proposes a method for preparing the thermo-optical dual crosslinked composite membrane, comprising coating a slurry onto at least one side of the base membrane and curing it to obtain the thermo-optical dual crosslinked composite membrane, wherein the curing includes photocuring and thermal curing.

[0013] Preferably, the curing sequence is heat curing followed by light curing.

[0014] The present invention also proposes a battery comprising the aforementioned thermo-optical dual crosslinked composite separator or the thermo-optical dual crosslinked composite separator prepared by the aforementioned preparation method.

[0015] The beneficial effects of this invention are as follows: In this invention, photoinitiators and thermal initiators are introduced into the ceramic coating. Through thermal initiation crosslinking combined with ultraviolet light crosslinking, an integrated crosslinking network is formed, which effectively inhibits high-temperature deformation of the diaphragm, improves the diaphragm's heat resistance and interfacial adhesion, and enhances the diaphragm's high-temperature mechanical properties. The resulting diaphragm possesses the following properties: (1) High-temperature dimensional stability and heat resistance safety: The integrated cross-linked network anchors the molecular chains of the base film through covalent bonds, effectively suppressing the thermal motion and chain segment relaxation of the base film molecular chains under high temperature conditions, fundamentally solving the defect of high-temperature melt shrinkage of traditional polyolefin separators. According to the test, the cross-linked separator of the present invention has a lateral thermal shrinkage rate and a longitudinal thermal shrinkage rate of ≤4.5% after standing at 150℃ for 1 hour, which is far superior to the national standard requirements for the thermal stability of power lithium battery separators. It can effectively avoid the risk of internal short circuit and thermal runaway caused by direct contact between the positive and negative electrodes under high temperature conditions, and greatly improve the intrinsic safety of power batteries; (2) Strong mechanical properties: Rigid inorganic ceramic particles are uniformly dispersed in the organic cross-linked network through covalent bonds, forming a composite reinforcement system of rigid particle reinforcement and cross-linked network toughening, which increases the needle penetration strength of the separator at 200℃ to more than 0.8N, effectively resisting mechanical damage during the winding / stacking process of the power battery, as well as the puncture of lithium dendrites during the cycle, further reducing the safety risk of short circuit in the battery; (3) Excellent interfacial adhesion performance and controllable pore structure: The integrated cross-linking network forms a stable covalent bond and anchoring effect at the base film-coating interface, which significantly improves the interfacial adhesion between the substrate and the coating. It can effectively suppress the peeling and void generation at the substrate-coating interface during battery cycling, reduce interfacial impedance, and improve the cycle life of the battery. At the same time, the cross-linking network can precisely control the pore structure during the curing process, ensuring that the ionic conductivity of the separator is ≥1mS / cm, without affecting the rapid transport of lithium ions, and adapting to the application requirements of high-rate power batteries. Detailed Implementation

[0016] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0017] In existing aqueous ceramic membranes, the polymer base membrane, organic binder, and inorganic ceramic particles are bound together only by adsorption and van der Waals forces, resulting in weak interfacial bonding, easy phase separation, and potential failure after electrolyte swelling. Based on this, this invention introduces photoinitiators, thermal initiators, and crosslinking agents into the coating, constructing a multi-active-site synergistic free radical copolymerization system covering the base membrane surface, organic binder, and inorganic ceramic particles. Highly active free radicals generated through photothermal initiation trigger a multi-active-site copolymerization reaction, forming covalent crosslinks at the base membrane-coating interface, an organic crosslinking network, and covalent crosslinks at the inorganic-organic phase interface. Specific analysis is as follows: Covalent crosslinking of the base film-coating interface: Under the action of photoinitiators and thermal initiators, the polymerizable carbon-carbon unsaturated double bonds pre-grafted onto the surface of the polyolefin base film undergo homolytic cleavage, generating a large number of macromolecular active free radicals on the base film surface. This breaks the low surface energy and non-polar inert interface state of the polyolefin base film, allowing it to participate in the free radical copolymerization reaction within the system. Ultimately, the coating crosslinking network is combined with the polyolefin base film molecular chain through carbon-carbon covalent bonds, completely replacing the traditional physical adsorption interface bonding mode. This fundamentally solves the problems of coating delamination and powder shedding, and the peel force between the coating and the base film reaches over 150 N / m.

[0018] Organic crosslinking network: Under the action of photoinitiators and thermal initiators, the polymerizable unsaturated double bonds introduced into the organic polymer molecular chains such as crosslinking agents, binders, thickeners, and dispersants in the coating undergo homolytic cleavage, generating corresponding active free radicals. Through free radical copolymerization, a continuous and dense organic crosslinking network is formed, anchoring all organic polymer molecular chains in the three-dimensional crosslinking network. This effectively avoids coating structure failure caused by the swelling and dissolution of binders by the electrolyte during battery cycling, significantly improving the electrolyte resistance and long-term cycling stability of the separator.

[0019] Inorganic-organic phase interface covalent crosslinking: The photoinitiator abstracts hydrogen atoms from the hydroxyl groups on the surface of ceramic particles through a hydrogen abstraction reaction, generating highly active ceramic-based alkoxy radicals. These radicals collide with other radicals within the system and undergo coupling reactions, ultimately binding the inorganic ceramic particles to the organic crosslinking network through carbon-oxygen covalent bonds. This solves the defects of traditional processes where ceramic particles are only physically wrapped by the binder and are prone to interfacial phase separation. It ensures that the high thermal conductivity and high rigidity of the ceramic particles are fully utilized, and achieves uniform dispersion and stable bonding of the ceramic particles in the crosslinking network, significantly improving the structural stability and heat resistance of the coating.

[0020] In this invention, the raw materials for the coating, such as ceramics, crosslinking agents, photoinitiators, thermal initiators, and adhesives, are general-purpose chemical raw materials that can be mass-produced in industrial applications. The raw materials are widely available and the costs are controllable. The preparation process of the diaphragm is fully compatible with the existing mainstream water-based ceramic diaphragm high-speed coating production line. Only a conventional UV curing unit needs to be added to achieve large-scale production without large-scale equipment modification. The production process is fully matched with the existing production line, and it has a strong industrialization capability and market competitiveness.

[0021] A specific embodiment of the first aspect of the present invention provides a thermo-optical dual crosslinked composite membrane, comprising a base membrane and a coating disposed on at least one side of the base membrane, wherein the raw materials of the coating include ceramics, photoinitiators, thermal initiators, crosslinking agents and adhesives.

[0022] In the thermo-optical dual-crosslinked composite separator of the present invention, the base film provides skeletal support. The base film can be any base film known in the art that can be used for separators, such as a polymer base film, including one of polyamide base film, polyimide base film, polyolefin base film, polyacrylonitrile base film, cellulose base film, polyester base film, and aramid base film; the polyolefin base film includes one of polyethylene base film, polypropylene base film, polyvinylidene fluoride film, and polytetrafluoroethylene film. The thickness of the base film is 2~30μm, for example, any point value or range between any two points from 2μm, 3μm, 5μm, 7μm, 9μm, 10μm, 12μm, 15μm, 20μm, 25μm, and 30μm.

[0023] In this invention, the ceramic can be an oxide ceramic or a non-oxide ceramic. Oxide ceramics may include, for example, one or more of alumina, silicon dioxide, zirconium dioxide, and titanium dioxide; non-oxide ceramics include boehmite, nitride ceramics, and carbide ceramics, for example, one or two of boron nitride and silicon carbide. The particle size D of the ceramic... 50 The wavelength range can be 50~1000nm, for example, any value from 50nm, 100nm, 150nm, 200nm, 220nm, 250nm, 300nm, 350nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, and 1000nm, or the range between any two values, preferably 300~800nm. The addition of ceramics can improve the heat resistance of the diaphragm.

[0024] In this invention, the photoinitiator can be a free radical polymerization photoinitiator or a cationic polymerization photoinitiator. For example, a free radical polymerization photoinitiator can be 2,2-dimethoxy-2-phenylacetophenone, α,α-dimethoxy-2-phenylacetophenone, etc. Diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphine acid, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, methyl benzoylcarbamate, aromatic phosphine oxide The photoinitiator is selected from one or more of the following: benzoylphenylphosphine oxide, 2-ethylthioxanthone, 2-phenylthioxanthone, benzophenone, 4-methylbenzophenone, thiopropoxythioxanthone, isopropylthioxanthone, 4-chlorobenzophenone, 2,4-dihydroxybenzophenone, and 4,4'-bis(dimethylamino)benzophenone; cationic polymerization photoinitiator is selected from one or more of the following: diarylioiodonium salt, triarylioiodonium salt, alkyliodonium salt, and cumeneferrocene hexafluorophosphate. Thermal initiator may be selected from one or more of the following: azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, ammonium persulfate, potassium persulfate, dicumyl peroxide, tert-butyl hydroperoxide, and cumene hydroperoxide.

[0025] In this invention, photoinitiators and thermal initiators work synergistically to initiate cross-linking polymerization, promoting the formation of a three-dimensional network structure in the diaphragm and significantly improving the diaphragm's resistance to electrolytes and long-term cycling stability.

[0026] In this invention, the crosslinking agent is a multifunctional acrylate crosslinking agent, such as one or more selected from polyurethane acrylate, dipentaerythritol hexaacrylate, trimethylolpropane triacrylate, bismaleic acid diacrylate, triallyl isocyanate, hexanediol diacrylate, and polyethylene glycol diacrylate. The addition of the crosslinking agent promotes the polymerization of the adhesive to form a crosslinked network structure, which helps to prevent coating structure failure caused by the swelling and dissolution of the adhesive by the electrolyte during battery cycling, significantly improving the electrolyte resistance and long-term cycle stability of the separator.

[0027] In this invention, the adhesive includes one or more of polyvinylidene fluoride (PVDF) and its derivatives, polyacrylates and their derivatives, polyvinyl alcohol and its derivatives, polyvinyl acetate, and polyvinylpyrrolidone. Polyacrylates may, for example, be one or more of hydroxyethyl acrylate, polybutyl acrylate, polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polyoctyl methacrylate, and 2-ethylhexyl acrylate. PVDF and its derivatives may, for example, be one or more of PVDF homopolymer, PVDF-hexafluoropropylene copolymer, PVDF-trifluoroethylene copolymer, PVDF-chlorotrifluoroethylene copolymer, PVDF-tetrafluoroethylene copolymer, and PVDF-tetrafluoroethylene-hexafluoropropylene copolymer.

[0028] In one embodiment of the present invention, the mass ratio of photoinitiator to thermal initiator is 0.1~3:1~3.

[0029] In one embodiment of the present invention, the mass ratio of ceramic to photoinitiator, thermal initiator, crosslinking agent and adhesive is 30~50:0.1~3:1~3:20~30:4~5.

[0030] In one embodiment of the present invention, the mass ratio of photoinitiator, thermal initiator and crosslinking agent is 1:1:30.

[0031] When the mass ratio of photoinitiator, thermal initiator and crosslinking agent is 1:1:30, the curing effect is better, which further improves the heat resistance, puncture resistance and peel strength of the diaphragm.

[0032] In one embodiment of the present invention, the raw materials for the coating further include at least one of a thickener, a dispersant, and a wetting agent.

[0033] In this invention, the thickener includes one or more of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, methyl hydroxyethyl cellulose, sodium alginate, carbomer resin, and polyvinyl alcohol.

[0034] Wetting agents include one or more of the following: acetylenic diol nonionic wetting agents, polyacrylate wetting agents, styrene-modified polyacrylate wetting agents, styrene-acrylate copolymer wetting agents, styrene-maleic acid copolymer wetting agents, styrene-maleic anhydride ester copolymer wetting agents, and styrene-maleic anhydride copolymer wetting agents.

[0035] The dispersant includes at least one of polyvinylpyrrolidone, sodium polyacrylate, ammonium polyacrylate, polyethylene glycol, and polyoxyethylene ether.

[0036] In one embodiment of the present invention, the coating slurry comprises a first solution and a second solution; The first solution includes a photoinitiator, a thermal initiator, a crosslinking agent, and a first solvent; The second solution includes ceramics, dispersants, thickeners, binders, wetting agents, and a second solvent.

[0037] In this invention, the first solvent is a non-aqueous solvent that is miscible with water in any ratio, such as one or more of methanol, ethanol, acetone, isopropanol, n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol, and propylene glycol; the second solvent is water.

[0038] In this invention, water and non-aqueous solvents that are miscible with water in any ratio are used as dispersion media, thus avoiding the environmental risks of oil-based coating processes while retaining the environmental and low-cost advantages of water-based coating processes.

[0039] In one embodiment of the present invention, the mass ratio of photoinitiator, thermal initiator, crosslinking agent and first solvent in the first solution is 0.1~3:1~3:20~30:70~80; The mass ratio of ceramic, dispersant, thickener, binder, wetting agent and second solvent in the second solution is 30~50:0.5~1:0.1~0.3:4~5:0.05~0.5:45~65.

[0040] A specific embodiment of the second aspect of the present invention provides a method for preparing a thermo-optical dual-crosslinked composite membrane, used to prepare the thermo-optical dual-crosslinked composite membrane provided in the specific embodiment of the first aspect of the present invention, comprising coating a coating slurry onto at least one side of a base membrane, curing, and obtaining a thermo-optical dual-crosslinked composite membrane, wherein curing includes photocuring and thermal curing.

[0041] In this invention, curing can be performed by first photocuring and then thermal curing. For example, photocuring can be completed by irradiating with ultraviolet light for 1-3 minutes and then thermally initiating deep cross-linking curing at 60-80°C for 10-30 minutes to obtain a thermal-photocurable dual cross-linked composite membrane. Alternatively, thermal curing can be performed by first photocuring and then photocuring. For example, thermally initiating pre-cross-linking curing can be completed by irradiating with ultraviolet light for 1-3 minutes and then photo-initiating deep curing to obtain a thermal-photocurable dual cross-linked composite membrane.

[0042] In this invention, a photothermal dual-initiation synergistic process is adopted to break through the technical bottleneck of traditional single curing system and achieve a two-way adaptation between crosslinking uniformity and production efficiency.

[0043] In one embodiment of the present invention, the curing method is preferably thermal curing followed by photocuring, and a drying step is also included before curing, wherein the drying temperature may be, for example, 60~80°C.

[0044] Addressing three common problems in the industry: ① Traditional aqueous ceramic membranes rely solely on solvent evaporation for physical film formation, lacking a stable chemical cross-linking structure, resulting in extremely poor coating stability and interfacial adhesion; ② Single thermosetting systems suffer from long curing cycles and high energy consumption, and are prone to adhesive migration, coating pore blockage, and uneven pore structure during drying; ③ Single UV-curing systems suffer from incomplete curing in shadowed areas of thick coatings due to ceramic particle shading, insufficient cross-linking depth, and weak interfacial adhesion. This invention innovatively designs a stepwise synergistic cross-linking process involving thermally initiated pre-cross-linking and UV-initiated deep cross-linking. The thermally initiated pre-cross-linking and drying processes are seamlessly integrated, locking the spatial distribution of organic components within the coating, preventing surface enrichment and pore blockage, stabilizing ceramic particle arrangement, preventing agglomeration and sedimentation, improving wet coating strength, and eliminating sagging and deformation during subsequent UV curing, making it fully adaptable to high-speed continuous production. The UV-initiated deep cross-linking stage overcomes the problems of insufficient depth in single thermosetting and curing in shadowed areas caused by ceramic particle shading, achieving uniform cross-linking across the entire coating thickness without dead zones. Specific analysis follows: In the thermally initiated pre-crosslinking stage, the decomposition temperature of the thermal initiator is precisely matched with the drying temperature of the diaphragm coating process. During the simultaneous solvent evaporation and drying, the thermal initiator decomposes to generate primary free radicals, initiating a preliminary pre-crosslinking reaction of the crosslinking agent within the system. On the one hand, this can quickly fix the spatial distribution of organic components within the coating during the drying process, effectively inhibiting the migration of binders and crosslinking agents to the coating surface as the solvent evaporates, avoiding pore blockage caused by enrichment on the coating surface, and ensuring the uniformity and connectivity of the diaphragm's pore structure. On the other hand, the initially formed crosslinking network can anchor the spatial arrangement of inorganic ceramic particles, preventing agglomeration and sedimentation of inorganic ceramic particles during the drying process, while also improving the wet structural stability of the coating, avoiding problems such as coating sagging, deformation, and uneven thickness in the subsequent UV curing process, perfectly adapting to the process steps of high-speed continuous coating production.

[0045] Photo-crosslinking stage: After drying and pre-crosslinking, the diaphragm is irradiated with ultraviolet light from a low-pressure mercury lamp / UV-LED light source. The photoinitiator in the system efficiently captures ultraviolet photon energy, rapidly generating highly active primary free radicals through intramolecular homolytic cleavage reaction, initiating free radical polymerization reaction throughout the entire thickness of the coating. This process overcomes the crosslinking depth limitation of single thermosetting, and simultaneously solves the industry problem of incomplete curing in shadow areas caused by light shading from inorganic ceramic particles through the chain transfer and diffusion effects of free radicals. It achieves uniform crosslinking throughout the entire thickness of the coating, without dead corners, from the base film-coating interface to the coating surface, constructing a complete and dense three-dimensional crosslinked network.

[0046] This process does not require large-scale equipment modifications to existing water-based diaphragm coating production lines. It can be industrialized simply by adding a UV curing unit after the drying section. The crosslinking reaction conditions are mild, energy consumption is low, and there are no harmful byproducts. The curing efficiency is fully matched with the existing industrial high-speed coating line speed, and it has extremely high industrialization and promotion value.

[0047] A specific embodiment of the third aspect of the present invention provides a battery comprising a thermo-optical dual-crosslinked composite separator provided in the specific embodiment of the first aspect of the present invention or a thermo-optical dual-crosslinked composite separator prepared by the preparation method provided in the specific embodiment of the second aspect of the present invention.

[0048] A specific embodiment of the fourth aspect of the present invention provides a thermo-optical dual crosslinked composite membrane, comprising a base membrane and a coating disposed on at least one side of the base membrane, wherein the raw materials of the coating include ceramics, photoinitiators, thermal initiators, crosslinking agents and adhesives.

[0049] The coating includes a first coating and a second coating, wherein the first coating is disposed on at least one side of the base film, and the second coating is disposed on the first coating; In the raw materials for the first coating, the mass of the photoinitiator is less than the mass of the thermal initiator; In the raw materials for the second coating, the mass of the photoinitiator is greater than the mass of the thermal initiator.

[0050] In this invention, the coating is configured as a first coating and a second coating with an increasing gradient of photoinitiator dosage and a decreasing gradient of thermal initiator concentration, which further enhances the synergistic effect of photoinitiator and thermal initiator, thereby further improving the heat resistance, puncture resistance and peel strength of the diaphragm.

[0051] In one embodiment of the present invention, in the raw materials of the first coating, the mass of the photoinitiator is less than 1 / 2 of the mass of the thermal initiator; in the raw materials of the second coating, the mass of the photoinitiator is more than twice the mass of the thermal initiator.

[0052] In this invention, the inventors discovered that when the mass of the photoinitiator in the raw material of the first coating is less than 1 / 2 of the mass of the thermal initiator, and the mass of the photoinitiator in the raw material of the second coating is more than twice the mass of the thermal initiator, the heat resistance, puncture resistance and peel strength of the diaphragm are further improved.

[0053] In one embodiment of the present invention, the mass ratio of ceramic to photoinitiator, thermal initiator, crosslinking agent and adhesive is 30~50:0.1~3:1~3:20~30:4~5.

[0054] In one embodiment of the present invention, the mass ratio of photoinitiator, thermal initiator and crosslinking agent is 1:1:30.

[0055] In one embodiment of the present invention, the raw materials for the coating further include at least one of a thickener, a dispersant, and a wetting agent.

[0056] Thickeners include one or more of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, methyl hydroxyethyl cellulose, sodium alginate, carbomer resin, and polyvinyl alcohol.

[0057] The wetting agent is selected from one or more of the following: acetylenic diol nonionic wetting agents, polyacrylate wetting agents, styrene-modified polyacrylate wetting agents, styrene-acrylate copolymer wetting agents, styrene-maleic acid copolymer wetting agents, styrene-maleic anhydride ester copolymer wetting agents, and styrene-maleic anhydride copolymer wetting agents.

[0058] The dispersant includes one or more of polyvinylpyrrolidone, sodium polyacrylate, ammonium polyacrylate, polyethylene glycol, and polyoxyethylene ether.

[0059] In one embodiment of the present invention, the coating slurry includes a first coating slurry and a second coating slurry; The first coating slurry includes a first solution and a second solution; The first solution comprises a photoinitiator, a thermal initiator, a crosslinking agent, and a first solvent in a mass ratio of 0.1~1:1.1~3:20~30:70~80; The second solution comprises ceramics, dispersants, thickeners, binders, wetting agents, and a second solvent in a mass ratio of 30~50:0.5~1:0.1~0.3:4~5:0.05~0.5:45~65. The second coating slurry comprises a third solution and a fourth solution. The third solution comprises a photoinitiator, a thermal initiator, a crosslinking agent, and a first solvent in a mass ratio of 1.1~3:1:20~30:70~80; The fourth solution comprises ceramics, dispersants, thickeners, binders, wetting agents, and a second solvent in a mass ratio of 30~50:0.5~1:0.1~0.3:4~5:0.05~0.5:45~65.

[0060] In this invention, the first solvent is a non-aqueous solvent that is miscible with water in any ratio, such as one or more of methanol, ethanol, acetone, isopropanol, n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol, and propylene glycol; the second solvent is water.

[0061] A specific embodiment of the fifth aspect of the present invention provides a method for preparing a thermo-optical dual crosslinked composite membrane, used to prepare the thermo-optical dual crosslinked composite membrane provided in the specific embodiment of the fourth aspect of the present invention, comprising coating a slurry of a first coating onto at least one layer of a base membrane, drying to obtain a first coating, coating a slurry of a second coating onto the first coating, and curing to obtain a thermo-optical dual crosslinked composite membrane, wherein curing includes photocuring and thermal curing.

[0062] In one embodiment of the present invention, the curing sequence is first thermal curing followed by photocuring.

[0063] A specific embodiment of the sixth aspect of the present invention provides a battery comprising a thermo-optical dual-crosslinked composite separator provided in the specific embodiment of the fourth aspect of the present invention or a thermo-optical dual-crosslinked composite separator prepared by the preparation method provided in the specific embodiment of the fifth aspect of the present invention.

[0064] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will be described through embodiments.

[0065] In the following embodiments and comparative examples, PE base film: 7μm thickness, air permeability 143s / 100mL; Aqueous polyacrylate: weight average molecular weight of 80,000 g / mol, synthesized from methyl methacrylate; Polyacrylamide: weight average molecular weight 1,000,000 g / mol.

[0066] Example 1 A thermo-optical dual crosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 20 parts of trimethylolpropane triacrylate in 80 parts of isopropanol, stir for 5 min, then add 0.5 parts of benzophenone and 1 part of azobisisobutyronitrile sequentially, and stir for 10 min to obtain the first solution; add 1 part of polyacrylamide to 65 parts of water, stir for 10 min, then add 30 parts of nano-alumina (particle size D) 50Disperse the solution at 400 nm for 30 min, then add 0.2 parts sodium alginate, 5 parts aqueous polyacrylate and 0.05 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol in sequence, and stir for 15 min to obtain the second solution; A homogeneous slurry was prepared by mixing the two solutions and coated on both sides of a PE base film by roller coating. After drying at 70°C for 20 min, it was heated at 70°C for 10 min and then irradiated with 365nm LED ultraviolet light for 1 min to obtain a thermal-optical double crosslinked composite membrane with a coating thickness of 4μm.

[0067] Example 2 A thermo-optical dual crosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 20 parts of trimethylolpropane triacrylate in 80 parts of isopropanol, stir for 5 min, then add 1 part of benzophenone and 1 part of azobisisobutyronitrile sequentially, stir for 10 min to obtain the first solution; add 1 part of polyacrylamide to 65 parts of water, stir for 10 min, then add 30 parts of nano-alumina (particle size D) 50 Disperse the solution at 400 nm for 30 min, then add 0.2 parts sodium alginate, 5 parts aqueous polyacrylate and 0.05 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol in sequence, and stir for 15 min to obtain the second solution; A homogeneous slurry was prepared by mixing the two solutions and coated on both sides of a PE base film by roller coating. After drying at 70°C for 20 min, it was heated at 70°C for 10 min and then irradiated with 365nm LED ultraviolet light for 1 min to obtain a thermal-optical double crosslinked composite membrane with a coating thickness of 4μm.

[0068] Example 3 A thermo-optical dual crosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 20 parts of trimethylolpropane triacrylate in 80 parts of isopropanol, stir for 5 min, then add 0.5 parts of benzophenone and 2 parts of azobisisobutyronitrile sequentially, and stir for 10 min to obtain the first solution; add 1 part of polyacrylamide to 65 parts of water and stir for 10 min, then add 30 parts of nano-alumina (particle size D) 50 Disperse the solution at 400 nm for 30 min, then add 0.2 parts sodium alginate, 5 parts aqueous polyacrylate and 0.05 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol in sequence, and stir for 15 min to obtain the second solution; A homogeneous slurry was prepared by mixing the two solutions and coated on both sides of a PE base film by roller coating. After drying at 70°C for 20 min, it was heated at 70°C for 10 min and then irradiated with 365nm LED ultraviolet light for 1 min to obtain a thermal-optical double crosslinked composite membrane with a coating thickness of 4μm.

[0069] Example 4 A thermo-optical dual crosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 30 parts of trimethylolpropane triacrylate in 80 parts of isopropanol, stir for 5 min, then add 0.5 parts of benzophenone and 1 part of azobisisobutyronitrile sequentially, and stir for 10 min to obtain the first solution; add 1 part of polyacrylamide to 65 parts of water and stir for 10 min, then add 30 parts of nano-alumina (particle size D) 50 Disperse the solution at 400 nm for 30 min, then add 0.2 parts sodium alginate, 5 parts aqueous polyacrylate and 0.05 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol in sequence, and stir for 15 min to obtain the second solution; A homogeneous slurry was prepared by mixing the two solutions and coated on both sides of a PE base film by roller coating. After drying at 70°C for 20 min, it was heated at 70°C for 10 min and then irradiated with 365nm LED ultraviolet light for 1 min to obtain a thermal-optical double crosslinked composite membrane with a coating thickness of 4μm.

[0070] Example 5 A thermo-optical dual crosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 30 parts of trimethylolpropane triacrylate in 80 parts of isopropanol, stir for 5 min, then add 1 part of benzophenone and 1 part of azobisisobutyronitrile sequentially, and stir for 10 min to obtain the first solution; add 1 part of polyacrylamide to 65 parts of water and stir for 10 min, then add 30 parts of nano-alumina (particle size D) 50 Disperse the solution at 400 nm for 30 min, then add 0.2 parts sodium alginate, 5 parts aqueous polyacrylate and 0.05 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol in sequence, and stir for 15 min to obtain the second solution; A homogeneous slurry was prepared by mixing the two solutions and coated on both sides of a PE base film by roller coating. After drying at 70°C for 20 min, it was heated at 70°C for 10 min and then irradiated with 365nm LED ultraviolet light for 1 min to obtain a thermal-optical double crosslinked composite membrane with a coating thickness of 4μm.

[0071] Example 6 A thermo-optical dual crosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 20 parts of trimethylolpropane triacrylate in 70 parts of isopropanol, stir for 5 min, then add 0.1 parts of benzophenone and 1 part of azobisisobutyronitrile sequentially, and stir for 10 min to obtain the first solution; add 1 part of polyacrylamide to 45 parts of water, stir for 10 min, then add 50 parts of nano-alumina (particle size D) 50Disperse the solution at 400 nm for 30 min, then add 0.1 parts sodium alginate, 4 parts aqueous polyacrylate and 0.5 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol in sequence, and stir for 15 min to obtain the second solution; A homogeneous slurry was prepared by mixing the two solutions and coated on both sides of a PE base film by roller coating. After drying at 70°C for 20 min, it was heated at 70°C for 10 min and then irradiated with 365nm LED ultraviolet light for 1 min to obtain a thermal-optical double crosslinked composite membrane with a coating thickness of 4μm.

[0072] Example 7 A thermo-optical dual crosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 30 parts of trimethylolpropane triacrylate in 80 parts of isopropanol, stir for 5 min, then add 3 parts of benzophenone and 3 parts of azobisisobutyronitrile sequentially, stir for 10 min to obtain the first solution; add 1 part of polyacrylamide to 65 parts of water, stir for 10 min, then add 30 parts of nano-alumina (particle size D) 50 Disperse the solution at 400 nm for 30 min, then add 0.3 parts sodium alginate, 5 parts aqueous polyacrylate and 0.05 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol in sequence, and stir for 15 min to obtain the second solution; A homogeneous slurry was prepared by mixing the two solutions and coated on both sides of a PE base film by roller coating. After drying at 70°C for 20 min, it was heated at 70°C for 10 min and then irradiated with 365nm LED ultraviolet light for 1 min to obtain a thermal-optical double crosslinked composite membrane with a coating thickness of 4μm.

[0073] Example 8 A thermo-optical dual crosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 30 parts of trimethylolpropane triacrylate in 80 parts of isopropanol, stir for 5 min, then add 1.5 parts of benzophenone and 1 part of azobisisobutyronitrile sequentially, and stir for 10 min to obtain the first solution; add 1 part of polyacrylamide to 65 parts of water, stir for 10 min, then add 30 parts of nano-alumina (particle size D) 50 Disperse the solution at 400 nm for 30 min, then add 0.2 parts sodium alginate, 5 parts aqueous polyacrylate and 0.05 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol in sequence, and stir for 15 min to obtain the second solution; A homogeneous slurry was prepared by mixing the two solutions and coated on both sides of a PE base film by roller coating. After drying at 70°C for 20 min, it was heated at 70°C for 10 min and then irradiated with 365nm LED ultraviolet light for 1 min to obtain a thermal-optical double crosslinked composite membrane with a coating thickness of 4μm.

[0074] Example 9 A thermo-optical dual crosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 15 parts of trimethylolpropane triacrylate in 40 parts of isopropanol, stir for 5 min, then add 0.4 parts of benzophenone and 0.6 parts of azobisisobutyronitrile sequentially, and stir for 10 min to obtain the first solution; add 1 part of polyacrylamide to 32.5 parts of water and stir for 10 min, then add 15 parts of nano-alumina (particle size D) 50 The solution was dispersed at 400 nm for 30 min, followed by the sequential addition of 0.1 parts sodium alginate, 2.5 parts aqueous polyacrylate and 0.025 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol, and stirred for 15 min to obtain a second solution; the two solutions were then mixed to obtain the first slurry. Dissolve 15 parts of trimethylolpropane triacrylate in 40 parts of isopropanol, stir for 5 min, then add 0.6 parts of benzophenone and 0.4 parts of azobisisobutyronitrile sequentially, and stir for 10 min to obtain the third solution; add 1 part of polyacrylamide to 32.5 parts of water and stir for 10 min, then add 15 parts of nano-alumina (particle size D) 50 The solution was dispersed at 400 nm for 30 min, followed by the sequential addition of 0.1 parts sodium alginate, 2.5 parts aqueous polyacrylate, and 0.025 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol, and stirred for 15 min to obtain the fourth solution; the two solutions were then mixed to prepare the second slurry. The first slurry was coated on both sides of the PE base film by roller coating. After drying at 70°C for 20 minutes, it was heated at 70°C for 10 minutes to obtain the first coating. The second slurry was then coated on the first coating by roller coating. After drying at 70°C for 20 minutes, it was heated at 70°C for 10 minutes, and then irradiated with 365nm LED ultraviolet light for 1 minute to obtain a thermal-optical double crosslinked composite membrane with a coating thickness of 4μm.

[0075] Example 10 A thermo-optical dual crosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 15 parts of trimethylolpropane triacrylate in 40 parts of isopropanol, stir for 5 min, then add 0.3 parts of benzophenone and 0.7 parts of azobisisobutyronitrile sequentially, and stir for 10 min to obtain the first solution; add 1 part of polyacrylamide to 32.5 parts of water and stir for 10 min, then add 15 parts of nano-alumina (particle size D) 50 The solution was dispersed at 400 nm for 30 min, followed by the sequential addition of 0.1 parts sodium alginate, 2.5 parts aqueous polyacrylate and 0.025 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol, and stirred for 15 min to obtain a second solution; the two solutions were then mixed to obtain the first slurry. Dissolve 15 parts of trimethylolpropane triacrylate in 40 parts of isopropanol, stir for 5 min, then add 0.7 parts of benzophenone and 0.3 parts of azobisisobutyronitrile sequentially, and stir for 10 min to obtain the third solution; add 1 part of polyacrylamide to 32.5 parts of water and stir for 10 min, then add 15 parts of nano-alumina (particle size D) 50 The solution was dispersed at 400 nm for 30 min, followed by the sequential addition of 0.1 parts sodium alginate, 2.5 parts aqueous polyacrylate, and 0.025 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol, and stirred for 15 min to obtain the fourth solution; the two solutions were then mixed to prepare the second slurry. The first slurry was coated on both sides of the PE base film by roller coating. After drying at 70°C for 20 minutes, it was heated at 70°C for 10 minutes to obtain the first coating. The second slurry was then coated on the first coating by roller coating. After drying at 70°C for 20 minutes, it was heated at 70°C for 10 minutes, and then irradiated with 365nm LED ultraviolet light for 1 minute to obtain a thermal-optical double crosslinked composite membrane with a coating thickness of 4μm.

[0076] Example 11 A thermo-optical dual crosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 20 parts of trimethylolpropane triacrylate in 80 parts of isopropanol, stir for 5 min, then add 0.5 parts of benzophenone and 1 part of azobisisobutyronitrile sequentially, and stir for 10 min to obtain the first solution; add 1 part of polyacrylamide to 65 parts of water, stir for 10 min, then add 30 parts of nano-alumina (particle size D) 50 Disperse the solution at 300 nm for 30 min, then add 0.2 parts sodium alginate, 5 parts aqueous polyacrylate and 0.05 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol in sequence, and stir for 15 min to obtain the second solution; A homogeneous slurry was prepared by mixing the two solutions and coated on both sides of a PE base film by roller coating. After drying at 70°C for 20 min, it was heated at 70°C for 10 min and then irradiated with 365nm LED ultraviolet light for 1 min to obtain a thermal-optical double crosslinked composite membrane with a coating thickness of 4μm.

[0077] Example 12 A thermo-optical dual crosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 20 parts of trimethylolpropane triacrylate in 80 parts of isopropanol, stir for 5 min, then add 0.5 parts of benzophenone and 1 part of azobisisobutyronitrile sequentially, and stir for 10 min to obtain the first solution; add 1 part of polyacrylamide to 65 parts of water, stir for 10 min, then add 30 parts of nano-alumina (particle size D) 50Disperse the solution at 800 nm for 30 min, then add 0.2 parts sodium alginate, 5 parts aqueous polyacrylate and 0.05 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol in sequence, and stir for 15 min to obtain the second solution; A homogeneous slurry was prepared by mixing the two solutions and coated on both sides of a PE base film by roller coating. After drying at 70°C for 20 min, it was heated at 70°C for 10 min and then irradiated with 365nm LED ultraviolet light for 1 min to obtain a thermal-optical double crosslinked composite membrane with a coating thickness of 4μm.

[0078] Example 13 A thermo-optical dual crosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 20 parts of trimethylolpropane triacrylate in 80 parts of isopropanol, stir for 5 min, then add 0.5 parts of benzophenone and 1 part of azobisisobutyronitrile sequentially, and stir for 10 min to obtain the first solution; add 1 part of polyacrylamide to 65 parts of water and stir for 10 min, then add 30 parts of boehmite (particle size D) 50 Disperse the solution at 400 nm for 30 min, then add 0.2 parts sodium alginate, 5 parts aqueous polyacrylate and 0.05 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol in sequence, and stir for 15 min to obtain the second solution; A homogeneous slurry was prepared by mixing the two solutions and coated on both sides of a PE base film by roller coating. After drying at 70°C for 20 min, it was heated at 70°C for 10 min and then irradiated with 365nm LED ultraviolet light for 1 min to obtain a thermal-optical double crosslinked composite membrane with a coating thickness of 4μm.

[0079] Example 14 A thermo-optical dual crosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 20 parts of trimethylolpropane triacrylate in 80 parts of isopropanol, stir for 5 min, then add 0.5 parts of benzophenone and 1 part of azobisisobutyronitrile sequentially, and stir for 10 min to obtain the first solution; add 1 part of polyacrylamide to 65 parts of water and stir for 10 min, then add 30 parts of boehmite (particle size D) 50 Disperse the solution at 800 nm for 30 min, then add 0.2 parts sodium alginate, 5 parts aqueous polyacrylate and 0.05 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol in sequence, and stir for 15 min to obtain the second solution; A homogeneous slurry was prepared by mixing the two solutions and coated on both sides of a PE base film by roller coating. After drying at 70°C for 20 min, it was heated at 70°C for 10 min and then irradiated with 365nm LED ultraviolet light for 1 min to obtain a thermal-optical double crosslinked composite membrane with a coating thickness of 4μm.

[0080] Comparative Example 1 A composite membrane includes a base membrane and coatings disposed on both sides of the base membrane, and is prepared by the following method: Add 1 part polyacrylamide to 65 parts water and stir for 10 minutes, then add 30 parts nano alumina (particle size D). 50 Disperse the sample at 400 nm for 30 min, then add 0.2 parts sodium alginate, 5 parts aqueous polyacrylate and 0.05 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol in sequence, and stir for 15 min to obtain a slurry; The slurry was coated on both sides of the PE base film by roller coating, and after drying at 70℃ for 20 minutes, a composite diaphragm was obtained with a coating thickness of 4μm.

[0081] Comparative Example 2 A thermally crosslinked composite separator includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 20 parts of trimethylolpropane triacrylate in 80 parts of isopropanol, stir for 5 min, then add 1 part of azobisisobutyronitrile, and stir for 10 min to obtain the first solution; add 1 part of polyacrylamide to 65 parts of water, stir for 10 min, then add 30 parts of nano-alumina (particle size D) 50 Disperse the solution at 400 nm for 30 min, then add 0.2 parts sodium alginate, 5 parts aqueous polyacrylate and 0.05 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol in sequence, and stir for 15 min to obtain the second solution; A homogeneous slurry was prepared by mixing the two solutions and then coated on both sides of a PE base film by roller coating. After drying at 70°C for 20 minutes, the film was heated at 70°C for 10 minutes to obtain a thermally crosslinked composite membrane with a coating thickness of 4 μm.

[0082] Comparative Example 3 A photocrosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 20 parts of trimethylolpropane triacrylate in 80 parts of isopropanol, stir for 5 minutes, then add 0.5 parts of benzophenone sequentially, and stir for 10 minutes to obtain the first solution; add 1 part of polyacrylamide to 65 parts of water, stir for 10 minutes, then add 30 parts of nano-alumina (particle size D) 50 Disperse the solution at 400 nm for 30 min, then add 0.2 parts sodium alginate, 5 parts aqueous polyacrylate and 0.05 parts 2,4,7,9-tetramethyl-5-decyn-4,7-diol in sequence, and stir for 15 min to obtain the second solution; A homogeneous slurry was prepared by mixing the two solutions and then coated on both sides of a PE base film by roller coating. After drying at 70°C for 20 minutes, the film was then irradiated with 365nm LED ultraviolet light for 1 minute to obtain a photocrosslinked composite membrane with a coating thickness of 4μm.

[0083] Comparative Example 4 A thermo-optical dual crosslinked composite membrane includes a base membrane and coatings disposed on both sides of the base membrane. The preparation method is as follows: Dissolve 20 parts of trimethylolpropane triacrylate in 80 parts of isopropanol, stir for 5 minutes, then add 0.5 parts of benzophenone and 1 part of azobisisobutyronitrile in sequence, and stir for 10 minutes to obtain a slurry; The slurry was coated on both sides of the PE base film by roller coating, dried at 70℃ for 20 min, heated at 70℃ for 10 min, and then irradiated with 365nm LED ultraviolet light for 1 min to obtain a thermal-optical double crosslinked composite membrane with a coating thickness of 4μm.

[0084] The composite membranes of Examples 1-14 and Comparative Examples 1-4 were subjected to the following performance tests: (1) Heat shrinkage: The transverse (TD) and longitudinal (MD) heat shrinkage rates were determined according to the test method specified in GB / T 36363-2018 "Polyolefin separators for lithium-ion batteries". The separator sample size was: length × width = 60mm × 40mm. The test results of transverse and longitudinal heat shrinkage rates were the average values ​​of three samples. (2) Membrane rupture temperature: The membrane rupture temperature of the diaphragm sample was tested using a thermomechanical analyzer. The dimensions of the diaphragm sample were: length × width = 8 mm × 4.5 mm. The tensile force during the test was 0.03 N, and the heating rate was 5 °C / min. (3) Peel force: Take a diaphragm with a size of 150mm×30mm as a sample, press a 100mm×25mm tape on the sample, and clamp the sample and tape at both ends of the tensile testing machine to obtain the coating peel force; (4) 200℃ needle penetration strength: The test was conducted using an electronic tensile testing machine AGS-50N. A diaphragm with a length of 100mm and a width of 96mm was cut as a sample. The temperature of the electronic tensile testing machine was set to 200℃ to obtain the needle penetration strength at this temperature. (5) Ionic conductivity: Ionic conductivity was tested according to GB / T 36363-2018 "Polyolefin separator for lithium-ion batteries".

[0085] The test results are shown in Table 1 below.

[0086] Table 1 Performance test results of the composite membranes of Examples 1-14 and Comparative Examples 1-4

[0087] As can be seen from Table 1, compared with Comparative Examples 1-4, the composite separators of Examples 1-14 exhibited reduced thermal shrinkage at 150°C, increased membrane rupture temperature, improved peel strength, and increased needle penetration strength at 200°C. This indicates that the introduction of photoinitiators and thermal initiators into the ceramic coating in this invention, combined with thermally initiated pre-crosslinking and ultraviolet light deep crosslinking, synergistically constructs an integrated three-dimensional covalent crosslinking network, which significantly improves the overall performance of the composite separator. This solves the common problems of high-temperature shrinkage and easy coating peeling in existing aqueous ceramic-coated separators. The resulting separator achieves improvements in core safety indicators such as high-temperature dimensional stability, membrane rupture temperature, peel strength, and resistance to 200°C puncture, while maintaining excellent ionic conductivity and stable lithium-ion transport capability, thus achieving synergistic optimization of battery safety and electrochemical performance. Compared with Example 5, the performance of the composite membranes in Examples 9 and 10 is further improved, indicating that the coating in this invention is set as a first coating and a second coating with a gradient increase in the amount of photoinitiator and a gradient decrease in the concentration of thermal initiator. The double-layer coating design with gradient distribution of initiator concentration can further enhance the uniform crosslinking degree of the coating and further improve the overall performance of the membrane.

[0088] 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 thermo-optical dual crosslinked composite membrane, characterized in that, It includes a base film and a coating disposed on at least one side of the base film, wherein the raw materials of the coating include ceramics, photoinitiators, thermal initiators, crosslinking agents and adhesives.

2. The thermo-optical dual crosslinked composite diaphragm according to claim 1, characterized in that, The mass ratio of the photoinitiator to the thermal initiator is 0.1~3:1~3.

3. The thermo-optical dual crosslinked composite diaphragm according to claim 1, characterized in that, The mass ratio of the ceramic to the photoinitiator, thermal initiator, crosslinking agent, and adhesive is 30~50:0.1~3:1~3:20~30:4~5.

4. The thermo-optical dual crosslinked composite diaphragm according to claim 1, characterized in that, The mass ratio of the photoinitiator, thermal initiator and crosslinking agent is 1:1:

30.

5. The thermo-optical dual crosslinked composite diaphragm according to claim 1, characterized in that, The raw materials for the coating also include at least one of thickener, dispersant and wetting agent.

6. The thermo-optical dual crosslinked composite diaphragm according to claim 1, characterized in that, The coating slurry comprises a first solution and a second solution; The first solution comprises a photoinitiator, a thermal initiator, a crosslinking agent, and a first solvent; The second solution comprises ceramics, dispersants, thickeners, binders, wetting agents, and a second solvent.

7. The thermo-optical dual crosslinked composite diaphragm according to claim 6, characterized in that, The mass ratio of photoinitiator, thermal initiator, crosslinking agent and first solvent in the first solution is 0.1~3:1~3:20~30:70~80; The mass ratio of ceramic, dispersant, thickener, binder, wetting agent and second solvent in the second solution is 30~50:0.5~1:0.1~0.3:4~5:0.05~0.5:45~65.

8. The method for preparing the thermo-optical dual crosslinked composite membrane according to any one of claims 1 to 7, characterized in that, The process includes applying a coating slurry to at least one side of the base film and curing it to obtain the thermo-photochemical dual crosslinked composite membrane, wherein the curing includes photocuring and thermocuring.

9. The method for preparing the thermo-optical dual crosslinked composite membrane according to claim 8, characterized in that, The curing sequence is first thermal curing followed by photocuring.

10. A battery, characterized in that, The thermo-optical dual-crosslinked composite membrane according to any one of claims 1 to 7 or the thermo-optical dual-crosslinked composite membrane prepared by the preparation method according to any one of claims 8 to 9 is included.

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