Preparation method of electrolyte diaphragm of semi-solid secondary battery, semi-solid secondary battery, energy storage device and electric equipment

Abstract

The invention relates to the technical field of energy storage, in particular to a preparation method of an electrolyte diaphragm of a semi-solid secondary battery, the semi-solid secondary battery, an energy storage device and electric equipment.The preparation method comprises the following steps that the surface of a base membrane is coated with a first solution, and the first solution comprises a linear monomer, a first thermal initiator and a first electrolyte; performing first curing to form a first middle layer on the surface of the base film; the surface of the first intermediate layer is coated with a second solution, the second solution comprises a multi-branched chain monomer, a second thermal initiator and a second electrolyte, secondary curing is carried out, and a second intermediate layer is formed on the surface of the base film; the surface of the second intermediate layer is coated with a third solution, the third solution comprises a nitrile group-containing monomer, a third thermal initiator and a third electrolyte, third curing is performed, and the electrolyte diaphragm is obtained. The electrolyte diaphragm has excellent flame retardant property, ionic conductivity, mechanical property and thermal stability, so that the semi-solid secondary battery has excellent safety performance and electrochemical performance.

Description

[0001] This application is a divisional application. The application number of the original application is 202510465131.5, and the original application date is April 14, 2025. The entire content of the original application is incorporated into this application by reference. Technical Field

[0002] The present invention relates to the field of energy storage technology, and in particular to a method for preparing an electrolyte membrane of a semi-solid secondary battery, a semi-solid secondary battery, an energy storage device, and electrical equipment. Background Art

[0003] Lithium-ion batteries, with their high energy density and reliable power supply, play a vital role in stationary energy storage systems. With the growing demand for next-generation, higher-performance batteries, efforts are underway to develop novel electrode materials, electrolytes, and battery systems. An ideal electrolyte should be a good lithium-ion conductor, possess high chemical stability, and, beyond the migration of lithium ions, avoid causing parasitic reactions on the electrode surface. While traditional organic liquid electrolytes offer high ionic conductivity, their inherent instability, including volatility and flammability, poses significant safety risks. Currently, solutions to lithium battery safety issues primarily include all-solid-state lithium-ion batteries, the addition of flame retardants to the electrolyte, and semi-solid electrolytes. Semi-solid electrolytes are novel functional polymer materials that lie between all-solid polymer electrolytes and liquid electrolytes. They offer stable electrochemical properties and can be used in secondary batteries as separators and electrolyte materials.

[0004] The current semi-solid electrolytes still have some shortcomings in their performance, which makes it difficult for secondary batteries to balance electrochemical performance and safety performance. Summary of the Invention

[0005] The present application proposes a method for preparing an electrolyte membrane of a semi-solid secondary battery, a semi-solid secondary battery, an energy storage device, and an electrical equipment, aiming to solve the technical problems mentioned in the above background technology.

[0006] In a first aspect, an embodiment of the present application provides a method for preparing an electrolyte separator for a semi-solid secondary battery, the preparation method comprising the following steps:

[0007] Providing a base film, coating a first solution on the surface of the base film, wherein the first solution includes a linear monomer, a first thermal initiator and a first electrolyte, and performing a first curing to form a first intermediate layer on the surface of the base film;

[0008] Applying a second solution on the surface of the first intermediate layer, wherein the second solution includes a multi-branched monomer, a second thermal initiator, and a second electrolyte, and performing a second curing to form a second intermediate layer on the surface of the base film;

[0009] Applying a third solution on the surface of the second intermediate layer, the third solution comprising a nitrile group-containing monomer, a third thermal initiator and a third electrolyte, and performing a third curing to form a gel-like functional layer on the surface of the base film to obtain an electrolyte separator;

[0010] Based on the total mass content of the first solution, the second solution and the third solution as 100%, the total mass content of the linear monomer, the multi-branched monomer and the nitrile group-containing monomer is 3% to 8%, and the mass ratio of the linear monomer, the multi-branched monomer and the nitrile group-containing monomer is (12 to 16): (3 to 6): 1.

[0011] In some embodiments, the linear monomer includes at least one of triethylene glycol dimethacrylate, methyl methacrylate, vinyl acetate, trifluoroethyl methacrylate, and ethylene glycol diacrylate.

[0012] In some embodiments, the multi-branched monomer includes at least one of trimethylolpropane trifluoroacrylate, pentaerythritol tetraacrylate, trimethylolpropane, pentaerythritol, four-arm polyethylene glycol-tetraacrylate, and hyperbranched polyester polyol.

[0013] In some embodiments, the nitrile-containing monomer includes at least one of acrylonitrile and methacrylonitrile.

[0014] In some embodiments, the first electrolyte, the second electrolyte, and the third electrolyte independently include a lithium salt, an electrolyte, and a flame retardant, and the content of the flame retardant is 2% to 15%.

[0015] In some embodiments, the lithium salt includes one or more of LiPF6, LiFSI, LiBF4, LiBOB, LiDFOB, and LiTFSI.

[0016] In some embodiments, the electrolyte includes one or more of EC, PC, BC, DEC, DMC, DME, EMC, TEP, and FEC.

[0017] In some embodiments, the flame retardant includes at least one of a phosphorus-nitrogen composite flame retardant, a phosphorus-based flame retardant, a phosphorus-fluorine composite flame retardant, a phosphazene flame retardant, and a brominated flame retardant.

[0018] In some embodiments, the first thermal initiator, the second thermal initiator, and the third thermal initiator independently include at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dicumyl peroxide, and ammonium persulfate.

[0019] In some embodiments, the temperature of the first curing is 40°C to 60°C, the temperature of the second curing is 60°C to 80°C, and the temperature of the third curing is 50°C to 70°C.

[0020] In some embodiments, the first curing step includes: preheating the base film coated with the first solution at 40°C to 45°C for 5 minutes to 10 minutes, then heating it to 55°C to 60°C and keeping it warm for 50 minutes to 70 minutes, with a heating rate of ≤2°C / min, and then cooling it to room temperature.

[0021] In some embodiments, the second curing step includes: preheating the composite structure of the base film coated with the second solution and the first intermediate layer at 60°C to 65°C for 5 minutes to 10 minutes, then heating it to 75°C to 80°C and keeping it warm for 25 minutes to 35 minutes, with a heating rate of ≤2°C / min, and then cooling it to room temperature.

[0022] In some embodiments, the third curing step includes: preheating the composite structure of the base film coated with the third solution and the second intermediate layer at 50°C to 55°C for 5 minutes to 10 minutes, then heating it to 65°C to 75°C and keeping it warm for 110 minutes to 130 minutes, with a heating rate of ≤2°C / min, and then cooling it to room temperature.

[0023] In a second aspect, an embodiment of the present application further provides a semi-solid secondary battery, comprising a positive electrode sheet, an electrolyte membrane and a negative electrode sheet, wherein the electrolyte membrane is prepared by the preparation method described in the first aspect.

[0024] In some embodiments, in the electrolyte membrane, the base membrane has a first side facing the positive electrode sheet and a second side facing the negative electrode sheet, the functional layer is arranged on at least one of the first side and the second side, and the thickness of the functional layer is 10μm to 30μm.

[0025] In a third aspect, an embodiment of the present application further proposes an energy storage device, comprising the semi-solid secondary battery as described in the second aspect.

[0026] In a fourth aspect, an embodiment of the present application further provides an electrical device comprising the semi-solid secondary battery described in the third aspect.

[0027] Compared with the existing technology, this technical solution has at least the following technical effects:

[0028] The technical solution of this application uses gradient copolymerization technology to form a gel-like functional layer with a gradient structure on the surface of the base film. The electrolyte membrane produced in this way not only has excellent flame retardancy, but also has excellent ionic conductivity, mechanical properties, and thermal stability, thereby enabling the semi-solid secondary battery to have excellent rate performance, cycle performance, and safety performance. Compared with conventional copolymerization methods, the gradient copolymerization method of this application helps to avoid stress concentration in the functional layer and helps to improve the electrochemical stability of the electrolyte membrane. During the preparation of the electrolyte membrane, a first solution containing linear monomers is first coated on the surface of the base membrane, and preliminarily polymerized to form a flexible first intermediate layer. A second solution is then coated on the surface of the first intermediate layer, and the multi-branched monomers in the second solution are further polymerized with the first polymer layer to form a second intermediate layer. The second intermediate layer is a three-dimensional network skeleton structure, which can provide continuous ion transmission channels, thereby helping to improve the ion mobility (conductivity) of the electrolyte membrane. In addition, the three-dimensional network skeleton structure can also provide good physical support, taking into account flexibility and material stability. These characteristics enable the final electrolyte membrane to obtain relatively good rate performance and cycle performance; by coating the third solution on the surface of the second intermediate layer and further polymerizing the third solution, the polarity of the outermost surface of the final electrolyte membrane is enhanced, thereby improving the interface compatibility between the electrolyte membrane and the electrolyte, reducing the interface resistance, and further improving the rate performance and cycle performance of the semi-solid secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described below with reference to the accompanying drawings and examples.

[0030] Figure 1 This is a process flow chart of the method for preparing the electrolyte membrane of the semi-solid secondary battery of the present application. DETAILED DESCRIPTION

[0031] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0032] Unless otherwise specified, the meanings of the terms in this specification are the same as those generally understood by those skilled in the art. However, if there is any conflict, the definitions in this specification shall prevail.

[0033] As used herein, "comprises," "includes," "contains," "has," "having," or other variations thereof are intended to encompass non-exclusive inclusions, and no distinction is made between these terms. The term "comprising" means that other steps and ingredients that do not affect the end result may be added. The term "comprising" also encompasses the terms "consisting of" and "consisting essentially of." The compositions and methods / processes of the present invention comprise, consist of, and consist essentially of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein.

[0034] All numerical values ​​or expressions used in the specification and claims relating to component amounts, process conditions, etc. should be understood to be modified by "about" in all cases. All ranges relating to the same component or property include endpoints, which can be independently combined. Since these ranges are continuous, they include every numerical value between the minimum and maximum values. It should also be understood that any numerical range cited in this application is intended to include all subranges within that range.

[0035] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0036] Semi-solid electrolyte is a new type of functional polymer material between all-solid polymer electrolyte and liquid electrolyte. The current semi-solid electrolyte still has some shortcomings in performance, such as: ionic conductivity, thermal stability and poor interfacial compatibility with the electrolyte, etc. These shortcomings make it difficult for secondary batteries to balance safety performance with electrochemical properties such as rate performance and cycle performance.

[0037] Based on this, in a first aspect, embodiments of the present application provide a method for preparing an electrolyte membrane of a semi-solid secondary battery.

[0038] See also Figure 1 In the embodiment of the present application, the preparation method comprises the following steps:

[0039] S100 provides a base film, coating the surface of the base film with a first solution, the first solution comprising a linear monomer, a first thermal initiator and a first electrolyte, performing a first curing to form a first intermediate layer on the surface of the base film;

[0040] S200. A second solution is applied to the surface of the first intermediate layer, the second solution comprising a multi-branched monomer, a second thermal initiator, and a second electrolyte, and a second curing is performed to form a second intermediate layer on the surface of the base film;

[0041] S300. A third solution is applied to the surface of the second intermediate layer. The third solution comprises a nitrile-containing monomer, a third thermal initiator, and a third electrolyte. The third curing step forms a gel-like functional layer on the surface of the base film to obtain an electrolyte separator.

[0042] Taking the total mass content of the first solution, the second solution and the third solution as 100%, the total mass content of the linear monomer, the multi-branched monomer and the nitrile group-containing monomer is 3% to 8%, and the mass ratio of the linear monomer, the multi-branched monomer and the nitrile group-containing monomer is (12 to 16): (3 to 6): 1.

[0043] It should be noted that in the embodiment of the present application, the first intermediate layer is a gel polymer layer formed by the first solution after the first solidification, the second intermediate layer is a gel polymer layer formed by the second solution and the first intermediate layer after the second solidification, and the functional layer is a gel polymer layer formed by the third solution and the second intermediate layer after the third solidification.

[0044] The technical solution of this application uses gradient copolymerization technology to form a gel-like functional layer with a gradient structure on the surface of the base film. The electrolyte membrane produced in this way not only has excellent flame retardancy, but also has excellent ionic conductivity, mechanical properties and stability, so that the semi-solid secondary battery produced can have excellent rate performance, cycle performance and safety performance. Compared with conventional copolymerization methods, the gradient copolymerization method of this application helps to avoid stress concentration in the functional layer and helps to improve the electrochemical stability of the electrolyte membrane. During the preparation of the electrolyte membrane, a first solution containing linear monomers is first coated on the surface of the base membrane, and preliminarily polymerized to form a flexible first intermediate layer. A second solution is then coated on the surface of the first intermediate layer, and the multi-branched monomers in the second solution are further polymerized with the first polymer layer to form a second intermediate layer. The second intermediate layer is a three-dimensional network skeleton structure, which can provide continuous ion transmission channels, thereby helping to improve the ion mobility (conductivity) of the electrolyte membrane. In addition, the three-dimensional network skeleton structure can also provide good physical support, taking into account flexibility and material stability. These characteristics enable the final electrolyte membrane to obtain relatively good rate performance and cycle performance; by coating the third solution on the surface of the second intermediate layer and further polymerizing the third solution, the polarity of the outermost surface of the final electrolyte membrane is enhanced, thereby improving the interface compatibility between the electrolyte membrane and the electrolyte, reducing the interface resistance, and further improving the rate performance and cycle performance of the semi-solid secondary battery.

[0045] The preparation method of the electrolyte membrane of the present application is described in more detail below.

[0046] In the embodiment of the present application, based on the total mass content of the first solution, the second solution, and the third solution as 100%, the total mass content of the linear monomer, the multi-branched monomer, and the nitrile-containing monomer is 3% to 8%, specifically 3%, 4%, 5%, 6%, 7%, 8%, or any value therebetween. The mass ratio of the linear monomer, the multi-branched monomer, and the nitrile-containing monomer is (12-16): (3-6): 1, wherein the mass ratio of the linear monomer to the nitrile-containing monomer can be specifically 12:1, 13:1, 14:1, 15:1, 16:1, or any value therebetween, and the mass ratio of the multi-branched monomer to the nitrile-containing monomer can be specifically 3:1, 4:1, 5:1, 6:1, or any ratio therebetween.

[0047] By controlling the mass content of linear monomers, multi-branched monomers, and nitrile-containing monomers within the aforementioned ranges, the final polymerized morphology of the functional layer is advantageously controlled to a jelly-like gel structure. In this morphology, the electrolyte membrane exhibits excellent electrochemical and flame retardant properties. When the mass content of linear monomers, multi-branched monomers, and nitrile-containing monomers is outside the aforementioned ranges, the functional layer may become hard and brittle, significantly reducing the cycling performance of the semi-solid-state secondary battery; or the first, second, and third solutions may fail to solidify from a liquid state to a gel state, or the solidification time of the first, second, and third solutions may be excessively long, affecting the preparation efficiency of the electrolyte membrane.

[0048] In the embodiment of the present application, the material of the base film can be polyethylene, polypropylene, etc. Of course, it can also be other base film materials commonly used in semi-solid electrolyte membranes. The embodiment of the present application does not specifically limit this.

[0049] In some embodiments, the linear monomer includes one or more of triethylene glycol dimethacrylate, methyl methacrylate, vinyl acetate, trifluoroethyl methacrylate, and ethylene glycol diacrylate. Of course, those skilled in the art can also select other linear monomers according to actual conditions.

[0050] In the embodiments of the present application, the multi-branched monomer can be a fluorine-containing monomer or a fluorine-free monomer. Preferably, the multi-branched monomer is a fluorine-containing monomer. The three-dimensional network structure formed by the polymerization of the fluorine-containing monomer not only helps to further improve the ionic conductivity of the electrolyte membrane, but also helps to improve the flame retardancy of the electrolyte membrane.

[0051] In some embodiments, the fluorine-containing monomer includes one or more of trimethylolpropane trifluoroacrylate and trifluoroethyl methacrylate.

[0052] In some embodiments, the non-fluorine-containing monomer includes one or more of pentaerythritol tetraacrylate, trimethylolpropane, pentaerythritol, four-arm polyethylene glycol-tetraacrylate, and hyperbranched polyester polyol.

[0053] In some embodiments, the nitrile-containing monomer includes at least one of acrylonitrile and methacrylonitrile. Of course, those skilled in the art may also select other nitrile-containing monomers according to actual conditions.

[0054] In some embodiments, the first thermal initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dicumyl peroxide, and ammonium persulfate.

[0055] In some embodiments, the second thermal initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dicumyl peroxide, and ammonium persulfate.

[0056] In some embodiments, the third thermal initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dicumyl peroxide, and ammonium persulfate.

[0057] In some embodiments, the mass content of the first thermal initiator in the first solution is 0.1%-0.3%, specifically 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3% or any value therebetween; the mass content of the second thermal initiator in the second solution is 0.1%-0.3%, specifically 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3% or any value therebetween; the mass content of the third thermal initiator in the third solution is 0.1%-0.3%, specifically 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3% or any value therebetween. By controlling the contents of the first thermal initiator, the second thermal initiator and the third thermal initiator respectively within the above ranges, it is beneficial to control the first curing, the second curing and the third curing rates, and avoid the occurrence of implosion or excessively long polymerization time.

[0058] In some embodiments, the first, second, and third electrolytes independently include a lithium salt, an electrolyte, and a flame retardant. The flame retardant content in the first, second, or third electrolytes is 2% to 15%, specifically 2%, 4%, 6%, 8%, 10%, 12%, 15%, or any value therebetween. Adding an appropriate amount of flame retardant to the first, second, and third electrolytes can effectively improve the flame retardancy of the electrolyte membrane.

[0059] In more detail, in some embodiments, the lithium salt includes one or more of LiPF6, LiFSI (lithium bis(trifluoromethanesulfonyl imide), LiBF4, LiBOB (lithium dioxalatoborate), LiDFOB (lithium difluorooxalatoborate), and LiTFSI (lithium bis(trifluoromethanesulfonyl imide). Of course, those skilled in the art can also select other lithium salts commonly used in the art according to actual conditions.

[0060] In some embodiments, the electrolyte includes one or more of EC (ethylene carbonate), PC (propylene carbonate), BC (succinonitrile), DEC (diethyl carbonate), DMC (dimethyl carbonate), DME (dimethoxyethane), EMC (ethyl methyl carbonate), TEP (triethyl phosphate), and FEC (fluoroethylene carbonate). Of course, those skilled in the art can also select other electrolytes commonly used in the art according to actual conditions.

[0061] In some embodiments, the flame retardant includes at least one of a phosphorus-nitrogen composite flame retardant, a phosphorus-based flame retardant, a phosphorus-fluorine composite flame retardant, a phosphazene flame retardant, a brominated flame retardant, or other common organic flame retardants.

[0062] In some embodiments, the flame retardant includes an organic flame retardant and an inorganic flame retardant. The organic flame retardant and the inorganic flame retardant can synergistically improve the flame retardant properties of the electrolyte separator.

[0063] In some embodiments, the phosphorus-nitrogen composite flame retardant includes one or more of ammonium polyphosphate (APP), trimethylolamine polyphosphate (MPP), pentaerythritol phosphate-trimethylolamine complex, etc.; the phosphorus-based flame retardant includes one or more of triphenyl phosphate (TPP), tricresyl phosphate (TCP), bisphenol A bis(diphenyl phosphate) (BDP), 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), etc.; the phosphorus-fluorine composite flame retardant includes one or more of tris(2,2,2-trifluoroethyl) phosphate, hexafluorocyclotriphosphazene, etc.; the phosphazene flame retardant includes one or more of hexaphenoxycyclotriphosphazene (HPCTP), hexa(4-aminophenoxy)cyclotriphosphazene, hexachlorocyclotriphosphazene, etc.; the brominated flame retardant includes one or more of decabromodiphenyl ether (Deca-BDE), tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD), brominated polystyrene (BPS), brominated epoxy resin (BER), etc.

[0064] In some embodiments, the temperatures for the first, second, and third curings are between 40° C. and 80° C. Specifically, the temperatures for the first, second, and third curings can independently be 40° C., 50° C., 60° C., 70° C., 80° C., or any value therebetween. By controlling the temperatures for the first, second, and third curings within the above ranges, it is beneficial to control the final cured state of the functional layer formed on the surface of the base film to a gel state, and it is also beneficial to improve the preparation efficiency of the electrolyte separator.

[0065] In a preferred embodiment, the temperature of the first curing is 40°C to 60°C, specifically 40°C, 45°C, 50°C, 55°C, 60°C, or any value therebetween; the temperature of the second curing is 60°C to 80°C, specifically 60°C, 65°C, 70°C, 75°C, 80°C, or any value therebetween; and the temperature of the third curing is 50°C to 70°C, specifically 50°C, 55°C, 60°C, 65°C, 70°C, or any value therebetween. This arrangement is beneficial for controlling the degree of polymerization of the linear monomer, the multi-branched monomer, and the nitrile-containing monomer, thereby enabling the prepared electrolyte membrane to obtain relatively excellent mechanical properties, electrochemical properties, and flame retardant properties, while also being beneficial for improving the preparation efficiency of the electrolyte membrane.

[0066] In the above preferred embodiment, the first curing time is 55min~70min, specifically 55min, 60min, 65min, 70min or any value therebetween; the second curing time is 33min~42min, specifically 33min, 35min, 37min, 39min, 42min or any value therebetween; the third curing time is 105min~130min, specifically 105min, 110min, 115min, 120min, 125min, 130min or any value therebetween.

[0067] In the preferred embodiment described above, the first, second, and third curing steps each include a preheating phase, a temperature increase phase, and a temperature holding phase. This step-by-step process of preheating, temperature increase, and temperature holding not only improves reaction safety but also significantly enhances product quality controllability.

[0068] In some embodiments, the temperature during the first curing holding stage is T1, the temperature during the second curing holding stage is T2, and the temperature during the third curing holding stage is T3, wherein T2>T1 and T2<T3. By ensuring that T2>T1, the linear monomers, after the first initial polymerization, are able to retain sufficient reactive groups to further polymerize with the multi-branched monomers during the second curing stage to form a gel-like three-dimensional network structure. By ensuring that T2<T3, the gel-like three-dimensional network structure is prevented from further polymerization to form a fully solid structure.

[0069] In some embodiments, the first curing step includes preheating the base film coated with the first solution at 40°C to 45°C for 5 to 10 minutes, then heating it to 55°C to 65°C and holding it there for 50 to 70 minutes, and then cooling it to room temperature. During the preheating stage, the first thermal initiator is activated, and the linear monomers are pre-crosslinked to form a flexible network. During the holding stage, the linear monomers further polymerize into a jelly-like gel state.

[0070] In some embodiments, the second curing step includes: preheating the composite structure of the base film coated with the second solution and the first intermediate layer at 60°C to 65°C for 5 minutes to 10 minutes, then heating it to 75°C to 85°C and keeping it warm for 25 minutes to 35 minutes, and then cooling it to room temperature.

[0071] In some embodiments, the third curing step includes: preheating the composite structure of the base film coated with the third solution and the second intermediate layer at 50°C to 55°C for 5 minutes to 10 minutes, then heating it to 65°C to 75°C and keeping it warm for 110 minutes to 130 minutes, and then cooling it to room temperature.

[0072] In some embodiments, during the first curing, the second curing, or the third curing step, the heating rate is ≤2° C. / min. By controlling the heating rate within this range, the quality controllability of the product is enhanced.

[0073] In some embodiments, during the first, second, or third curing step, the cooling rate is ≥1° C. / min. After the heat preservation step, rapid cooling is performed to avoid the accumulation of thermal stress on the polymer product.

[0074] In a second aspect, an embodiment of the present application further provides a semi-solid secondary battery, comprising a positive electrode sheet, an electrolyte membrane and a negative electrode sheet, wherein the electrolyte membrane is prepared by the preparation method described in the first aspect.

[0075] The semi-cured secondary battery of the present application uses the electrolyte separator prepared by the preparation method as described in the first aspect, which makes the semi-cured secondary battery have not only excellent safety performance but also excellent electrochemical performance.

[0076] In the embodiment of the present application, in the electrolyte membrane, the thickness of the functional layer on the surface of the base membrane is 10 to 30 μm. By controlling the thickness of the functional layer within this range, it is beneficial to balance the ion transmission efficiency, mechanical strength, energy density and safety of the electrolyte membrane.

[0077] In the embodiment of the present application, in the electrolyte membrane, the base membrane has a first side facing the positive electrode sheet and a second side facing the negative electrode sheet, and the functional layer is disposed on at least one of the first side and the second side.

[0078] In the embodiment of the present application, the positive electrode sheet, the electrolyte membrane and the negative electrode sheet can be assembled into a laminated structure or a wound structure. The specific assembly method can be adjusted according to the specific type of the semi-cured secondary battery.

[0079] In the embodiments of the present application, illustratively, the method for preparing a semi-cured secondary battery includes:

[0080] Prepare positive electrode sheets, negative electrode sheets and electrolyte separators;

[0081] Assembling or winding the positive electrode sheet, the electrolyte separator and the negative electrode sheet to obtain a pre-assembled component;

[0082] The pre-assembled component is assembled with the shell to obtain a semi-cured secondary battery.

[0083] In the above preparation method, when the semi-cured secondary battery is a soft-pack battery, the housing is a membrane structure such as an aluminum-plastic composite film, and the positive electrode sheet, electrolyte separator, and negative electrode sheet can be stacked and assembled on the membrane structure. When the semi-cured secondary battery is a hard-shell battery such as a prismatic battery, the positive electrode sheet, electrolyte separator, and negative electrode sheet are typically assembled first, and then this assembly is placed into the housing.

[0084] In a third aspect, embodiments of the present application further provide an energy storage device comprising at least one semi-solid secondary battery as described in aspect 2. When the energy storage device comprises multiple batteries, the multiple batteries may be connected in at least one of parallel and series connection.

[0085] In a fourth aspect, an embodiment of the present application further provides an electrical device comprising the energy storage device described in the third aspect.

[0086] It can be understood that the electrical equipment also includes an electrical equipment body, and the energy storage device is used to supply power to the electrical equipment body.

[0087] In the embodiments of the present application, electrical equipment may include but is not limited to: containers, household energy storage systems, electric vehicles, electric vehicles, ships, spacecraft, electric toys and electric tools, etc., wherein spacecraft include airplanes, rockets, space shuttles and spacecraft, etc., electric toys include fixed or mobile electric toys, specifically electric car toys, electric ship toys and electric airplane toys, etc., electric tools include metal cutting power tools, grinding power tools, assembly power tools and railway power tools, specifically electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers.

[0088] The present application is further described below through specific examples and comparative examples, but the present application is not limited to these specific examples.

[0089] Example 1

[0090] 1. Preparation of Electrolyte Separator

[0091] (1) Raw materials: 3.29 wt% triethylene glycol dimethacrylate + 1.175 wt% trimethylolpropane trifluoroacrylate + 0.235 wt% acrylonitrile + 0.1 wt% ammonium persulfate + 0.1 wt% azobisisobutyronitrile + 0.1 wt% benzoyl peroxide + 95 wt% liquid electrolyte (90 wt% (1 M LiPF6EC:EMC:DMC=3:4:3 vol%) + 5 wt% hexaphenoxycyclotriphosphazene).

[0092] The liquid electrolyte is divided into three parts, namely a first electrolyte, a second electrolyte and a third electrolyte, and the mass ratio of the first electrolyte, the second electrolyte and the third electrolyte is 3.29:1.175:0.235.

[0093] Mixing triethylene glycol dimethacrylate, ammonium persulfate and the first electrolyte in the raw materials to prepare a first solution;

[0094] Mixing trimethylolpropane trifluoroacrylate, azobisisobutyronitrile and the second electrolyte in the raw materials to prepare a second solution;

[0095] The acrylonitrile, benzoyl peroxide and the third electrolyte in the raw materials are prepared into a third solution.

[0096] (2) Preparation steps:

[0097] S100. Provide a base film (polypropylene film), evenly coat the first solution on the surface of the base film, place it in a segmented oven, preheat it at 40°C for 10 minutes, then heat it to 60°C at a rate of ≤2°C / min, then keep it warm for 60 minutes, and then quickly cool it to room temperature to form a first intermediate layer on the surface of the base film.

[0098] S200. Evenly apply the second solution on the surface of the first intermediate layer, place it in a segmented oven, preheat it at 60°C for 5 minutes, then heat it to 80°C at a rate of ≤2°C / min, then keep it warm for 30 minutes, and then quickly cool it to room temperature to form a second intermediate layer on the surface of the base film.

[0099] S300. Evenly coat the third solution on the surface of the second intermediate layer, place it in a segmented oven, preheat it at 50°C for 10 minutes, then heat it to 70°C at a rate of ≤2°C / min, then keep it warm for 120 minutes, and then quickly cool it to room temperature to obtain an electrolyte membrane.

[0100] 2. Assembly of Half-Cells

[0101] The positive electrode material (lithium iron phosphate), conductive agent Super and polyvinylidene fluoride (PVDF) were mixed in N-methyl-2-pyrrolidone (NMP) in a ratio of 90:5:5. The resulting slurry was coated on aluminum foil and dried under vacuum at 105°C for 10 hours to obtain a positive electrode sheet. The counter electrode was a lithium sheet.

[0102] The positive electrode sheet and lithium sheet were cut into small discs with a diameter of 13 mm using a cutting machine. The positive electrode shell, spring, gasket, positive electrode sheet, the above-prepared electrolyte separator, lithium sheet, and negative electrode shell were assembled into a button battery in a glove box filled with argon (Ar).

[0103] 3. Performance Testing

[0104] (1) Conductivity test before and after polymerization

[0105] The conductivity of the functional layer material of the electrolyte separator was tested using a conductivity meter at 25°C.

[0106] (2) Self-extinguishing time test

[0107] Take a small amount of electrolyte and place it on the negative electrode shell of the buckle battery. After igniting it with an igniter for 5 seconds, time and observe the self-extinguishing time.

[0108] (3) Electrochemical performance test

[0109] This article uses the LAND test system to test the cycle performance and rate performance of the assembled button cell in a constant temperature test cabinet at 25°C. The cycle performance test uses a current density of 0.3C for 5 activation cycles followed by a current density of 1C, with a voltage range of 2-3.75V. The rate performance test specifies a current density of 10mA˙g -1 、30mA˙g -1 , 50mA˙g -1 , 70mA˙g -1 , 100mA˙g -1 , 10mA˙g -1 , 5 cycles were performed at each current density.

[0110] Example 2

[0111] The difference from Example 1 is that trimethylolpropane trifluoroacrylate in the raw material is replaced by pentaerythritol tetraacrylate.

[0112] Example 3

[0113] The difference from Example 1 is that:

[0114] (1) Raw materials: 2.4 wt% triethylene glycol dimethacrylate + 0.6 wt% trimethylolpropane trifluoroacrylate + 0.2 wt% acrylonitrile + 0.1 wt% ammonium persulfate + 0.1 wt% azobisisobutyronitrile + 0.1 wt% benzoyl peroxide + 96.5 wt% liquid electrolyte (91.7 wt% (1 M LiPF6 EC:EMC:DMC=3:4:3 vol%) + 5 wt% hexaphenoxycyclotriphosphazene).

[0115] The liquid electrolyte is divided into three parts, namely a first electrolyte, a second electrolyte and a third electrolyte, and the mass ratio of the first electrolyte, the second electrolyte and the third electrolyte is 2.4:0.6:0.2.

[0116] Example 4

[0117] The difference from Example 1 is that:

[0118] (1) Raw materials: 5.44 wt% triethylene glycol dimethacrylate + 2.04 wt% trimethylolpropane trifluoroacrylate + 0.34 wt% acrylonitrile + 0.1 wt% ammonium persulfate + 0.1 wt% azobisisobutyronitrile + 0.1 wt% benzoyl peroxide + 91.7 wt% liquid electrolyte (86.7 wt% (1 M LiPF6 EC:EMC:DMC=3:4:3 vol%) + 5 wt% hexaphenoxycyclotriphosphazene).

[0119] The liquid electrolyte is divided into three parts, namely a first electrolyte, a second electrolyte and a third electrolyte, and the mass ratio of the first electrolyte, the second electrolyte and the third electrolyte is 5.6:2.04:0.34.

[0120] Example 5

[0121] The difference from Example 1 is that:

[0122] (1) The trimethylolpropane trifluoroacrylate, benzoyl peroxide and the second electrolyte in the raw materials are mixed to prepare a second solution; and the acrylonitrile, azobisisobutyronitrile and the third electrolyte in the raw materials are mixed to prepare a third solution.

[0123] (2) S200. The second solution is evenly coated on the surface of the first intermediate layer, and the solution is placed in a segmented oven. The solution is preheated at 50°C for 10 minutes, and then heated to 70°C at a rate of ≤2°C / min. The solution is then kept warm for 120 minutes, and then rapidly cooled to room temperature to form a second intermediate layer on the surface of the base film.

[0124] S300. Evenly coat the third solution on the surface of the second intermediate layer, place it in a segmented oven, preheat it at 60°C for 5 minutes, then heat it to 80°C at a rate of ≤2°C / min, then keep it warm for 30 minutes, and then quickly cool it to room temperature to obtain an electrolyte membrane.

[0125] Example 6

[0126] The difference from Example 1 is that:

[0127] (1) triethylene glycol dimethacrylate, azobisisobutyronitrile and the first electrolyte in the raw materials are mixed to prepare a first solution; trimethylolpropane trifluoroacrylate, benzoyl peroxide and the second electrolyte in the raw materials are mixed to prepare a second solution; acrylonitrile, ammonium persulfate and the third electrolyte in the raw materials are mixed to prepare a third solution.

[0128] (2) S100. Provide a base film (polypropylene film), evenly coat the first solution on the surface of the base film, place it in a segmented oven, preheat it at 60°C for 5 minutes, then heat it to 80°C at a rate of ≤2°C / min, keep it warm for 30 minutes, and then quickly cool it to room temperature to form a first intermediate layer on the surface of the base film.

[0129] S200. Evenly apply the second solution on the surface of the first intermediate layer, place it in a segmented oven, preheat it at 50°C for 10 minutes, then heat it to 70°C at a rate of ≤2°C / min, then keep it warm for 120 minutes, and then quickly cool it to room temperature to form a second intermediate layer on the surface of the base film.

[0130] S300. Evenly coat the third solution on the surface of the second intermediate layer, place it in a segmented oven, preheat it at 40°C for 10 minutes, then heat it to 60°C at a rate of ≤2°C / min, then keep it warm for 60 minutes, and then quickly cool it to room temperature to obtain an electrolyte membrane.

[0131] Comparative Example 1

[0132] Liquid electrolyte (1M LiPF6 EC:EMC:DMC=3:4:3 vol%).

[0133] Comparative Example 2

[0134] The difference from Example 1 is that:

[0135] 1. Preparation of Electrolyte Separator

[0136] (1) Raw materials: 4.7 wt% triethylene glycol dimethacrylate + 0.3 wt% ammonium persulfate + 95 wt% liquid electrolyte (90 wt% (1 M LiPF6 EC:EMC:DMC=3:4:3 vol%) + 5 wt% hexaphenoxycyclotriphosphazene).

[0137] The triethylene glycol dimethacrylate, ammonium persulfate and electrolyte in the raw materials are mixed to prepare a first solution.

[0138] (2) Preparation steps:

[0139] S100. Provide a base film (polypropylene film), evenly coat the first solution on the surface of the base film, place it in a segmented oven, preheat it at 40°C for 10 minutes, then heat it to 60°C at a rate of ≤2°C / min, then keep it warm for 60 minutes, and then quickly cool it to room temperature to obtain an electrolyte membrane.

[0140] Comparative Example 3

[0141] The difference from Example 1 is that:

[0142] 1. Preparation of Electrolyte Separator

[0143] (1) Raw materials: 3.54 wt% triethylene glycol dimethacrylate + 1.26 wt% trimethylolpropane trifluoroacrylate + 0.1 wt% ammonium persulfate + 0.1 wt% azobisisobutyronitrile + 95 wt% liquid electrolyte (85 wt% (1M LiPF6 EC:EMC:DMC=3:4:3 vol%) + 5 wt% hexaphenoxycyclotriphosphazene).

[0144] The liquid electrolyte is divided into two parts, namely a first electrolyte and a second electrolyte, and the mass ratio of the first electrolyte to the second electrolyte is 3.54:1.26.

[0145] Mixing triethylene glycol dimethacrylate, ammonium persulfate and the first electrolyte in the raw materials to prepare a first solution;

[0146] The trimethylolpropane trifluoroacrylate, azobisisobutyronitrile and the second electrolyte in the raw materials are mixed to prepare a second solution.

[0147] (2) Preparation steps:

[0148] S100. Provide a base film (polypropylene film), evenly coat the first solution on the surface of the base film, place it in a segmented oven, preheat it at 40°C for 10 minutes, then heat it to 60°C at a rate of ≤2°C / min, then keep it warm for 60 minutes, and then quickly cool it to room temperature to form a first intermediate layer on the surface of the base film.

[0149] S200. The second solution is evenly coated on the surface of the first intermediate layer, and the solution is placed in a segmented oven. The solution is first preheated at 60°C for 5 minutes, then heated to 80°C at a rate of ≤2°C / min, and then kept warm for 30 minutes. The solution is then rapidly cooled to room temperature to obtain an electrolyte membrane.

[0150] Comparative Example 4

[0151] The difference from Example 1 is that:

[0152] (1) Raw materials: 1.19 wt% triethylene glycol dimethacrylate + 0.425 wt% trimethylolpropane trifluoroacrylate + 0.085 wt% acrylonitrile + 0.1 wt% ammonium persulfate + 0.1 wt% azobisisobutyronitrile + 0.1 wt% benzoyl peroxide + 98 wt% liquid electrolyte (93 wt% (1 M LiPF6EC:EMC:DMC=3:4:3 vol%) + 5 wt% hexaphenoxycyclotriphosphazene).

[0153] The liquid electrolyte is divided into three parts, namely a first electrolyte, a second electrolyte and a third electrolyte, and the mass ratio of the first electrolyte, the second electrolyte and the third electrolyte is 1.19:0.425:0.085.

[0154] Comparative Example 5

[0155] The difference from Example 1 is that:

[0156] (1) Raw materials: 6.09 wt% triethylene glycol dimethacrylate + 2.175 wt% trimethylolpropane trifluoroacrylate + 0.435 wt% acrylonitrile + 0.1 wt% ammonium persulfate + 0.1 wt% azobisisobutyronitrile + 0.1 wt% benzoyl peroxide + 91 wt% liquid electrolyte (86 wt% (1 M LiPF6EC:EMC:DMC=3:4:3 vol%) + 5 wt% hexaphenoxycyclotriphosphazene).

[0157] Comparative Example 6

[0158] The difference from Example 1 is that:

[0159] (1) Raw materials: 2.35 wt% triethylene glycol dimethacrylate + 1.645 wt% trimethylolpropane trifluoroacrylate + 0.705 wt% acrylonitrile + 0.1 wt% ammonium persulfate + 0.1 wt% azobisisobutyronitrile + 0.1 wt% benzoyl peroxide + 95 wt% liquid electrolyte (90 wt% (1 M LiPF6EC:EMC:DMC=3:4:3 vol%) + 5 wt% hexaphenoxycyclotriphosphazene).

[0160] The liquid electrolyte is divided into three parts, namely a first electrolyte, a second electrolyte and a third electrolyte, and the mass ratio of the first electrolyte, the second electrolyte and the third electrolyte is 2.35:1.645:0.705.

[0161] Comparative Example 7

[0162] The difference from Example 1 is that:

[0163] (1) Raw materials: 3.995 wt% triethylene glycol dimethacrylate + 0.611 wt% trimethylolpropane trifluoroacrylate + 0.094 wt% acrylonitrile + 0.1 wt% ammonium persulfate + 0.1 wt% azobisisobutyronitrile + 0.1 wt% benzoyl peroxide + 95 wt% liquid electrolyte (90 wt% (1 M LiPF6EC:EMC:DMC=3:4:3 vol%) + 5 wt% hexaphenoxycyclotriphosphazene).

[0164] The liquid electrolyte is divided into three parts, namely a first electrolyte, a second electrolyte and a third electrolyte, and the mass ratio of the first electrolyte, the second electrolyte and the third electrolyte is 3.995:0.611:0.094.

[0165] Comparative Example 8

[0166] The difference from Example 1 is that:

[0167] Preparation steps:

[0168] (2) S100. Provide a base film (polypropylene film), uniformly mix the first solution and the second solution, and then evenly coat them on the surface of the base film. Place it in a segmented oven, preheat it at 60°C for 10 minutes, then heat it to 80°C at a rate of ≤2°C / min, and then keep it warm for 60 minutes. After that, quickly cool it to room temperature to form an intermediate layer on the surface of the base film.

[0169] S200. Evenly coat the third solution on the surface of the first intermediate layer, place it in a segmented oven, preheat it at 50°C for 10 minutes, then heat it to 70°C at a rate of ≤2°C / min, then keep it warm for 120 minutes, and then quickly cool it to room temperature to obtain an electrolyte membrane.

[0170] Comparative Example 9

[0171] The difference from Example 1 is that:

[0172] Preparation steps:

[0173] S100. Provide a base film (polypropylene film), evenly coat the first solution on the surface of the base film, place it in a segmented oven, preheat it at 40°C for 10 minutes, then heat it to 60°C at a rate of ≤2°C / min, then keep it warm for 60 minutes, and then quickly cool it to room temperature to form an intermediate layer on the surface of the base film.

[0174] S200. The second solution and the third solution are uniformly mixed and then evenly coated on the first intermediate layer, placed in a segmented oven, preheated at 60°C for 5 minutes, then heated to 80°C at a rate of ≤2°C / min, then kept warm for 30 minutes, and then quickly cooled to room temperature to obtain an electrolyte membrane.

[0175] Test results:

[0176] Table 1. Test results of electrical conductivity and flame retardancy of various embodiments and comparative examples

[0177] sample Conductivity (mS / cm) Self-extinguishing time (s) Example 1 8.985 Unburned Example 2 8.752 2s Example 3 8.623 5s Example 4 8.568 Unburned Example 5 8.765 Unburned Example 6 8.802 Unburned Comparative Example 1 - 20s Comparative Example 2 8.224 Unburned Comparative Example 3 8.478 Unburned Comparative Example 4 Unformed 15s Comparative Example 5 6.523 Unburned Comparative Example 6 8.213 Unburned Comparative Example 7 8.462 Unburned Comparative Example 8 8.224 Unburned Comparative Example 9 8.475 Unburned

[0178] Table 2. Cyclic performance test results of various embodiments and comparative examples

[0179]

[0180]

[0181] Table 3. Rate performance test results of various embodiments and comparative examples

[0182]

[0183] The test results of Examples 1-6 and Comparative Examples 1-9 demonstrate that the electrolyte membrane produced by the gradient copolymerization technology described in this application not only has excellent flame retardancy, but also has excellent ionic conductivity and material stability. The semi-solid secondary battery produced thereby has significantly improved safety performance, while its electrochemical properties such as rate capability and cycle performance are similar to those of liquid electrolytes.

[0184] By comparing Examples 1-6 with Comparative Example 1, it can be demonstrated that, compared with the existing common liquid electrolytes, the semi-solid electrolyte (diaphragm) of the present application has better flame retardant properties.

[0185] By comparing Example 1 with Comparative Examples 2 and 3, it can be proved that by adding multi-branched monomers to form a three-dimensional network structure, the conductivity of the electrolyte membrane can be improved, the stability of the electrode material is ensured, and the cycle performance of the semi-solid secondary battery is improved.

[0186] By comparing Example 1 with Comparative Example 3, it can be proved that by finally adding the cyano group-containing monomer, the interfacial compatibility between the electrolyte membrane and the electrolyte is improved, the conductivity of the electrolyte membrane can be increased, and it is beneficial to improve the rate performance of the semi-solid secondary battery.

[0187] By comparing Example 1 with Comparative Examples 8 and 9, it can be proved that, compared with the synchronous copolymerization method, the present application successively adds linear monomers, multi-branched monomers and cyano-containing monomers for gradient polymerization to form a layered structure, and the layers interact with each other, thereby improving the rate performance and cycle performance of the semi-cured secondary battery.

[0188] By comparing Example 1 with Comparative Examples 4-7, it can be proved that when the total mass content of the linear monomer, the multi-branched monomer and the nitrile-containing monomer in the raw material does not meet 3% to 8%, or the mass ratio of the linear monomer, the multi-branched monomer and the nitrile-containing monomer does not meet (12 to 16): (3 to 6): 1, the electrolyte solidifies severely, cannot form gel, and the gel state is poor, resulting in poor rate performance and cycle performance of the semi-cured secondary battery.

[0189] Comparison of Example 1 with Example 2 demonstrates that when the multi-branched monomer is a fluorine-containing monomer, it is more conducive to improving the conductivity of the electrolyte separator, thereby being more conducive to improving the flame retardancy and rate performance of the semi-cured secondary battery.

[0190] By comparing Example 1 with Example 5 and Example 6, it can be concluded that, compared with increasing or decreasing the temperatures of the first curing, second curing and third curing (keeping temperature, the same below) in sequence, making the temperature of the second curing higher than the temperature of the first curing and lower than the temperature of the third curing is more conducive to promoting the polymerization between the electrolyte layers, thereby being more conducive to improving the rate performance and cycle performance of the semi-cured secondary battery.

[0191] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an electrolyte membrane for a semi-solid secondary battery, characterized in that: The preparation method comprises the following steps: Providing a base film, coating a first solution on the surface of the base film, wherein the first solution includes a linear monomer, a first thermal initiator, and a first electrolyte, performing a first curing, and forming a first intermediate layer on the surface of the base film, wherein the linear monomer includes at least one of triethylene glycol dimethacrylate, methyl methacrylate, vinyl acetate, trifluoroethyl methacrylate, and ethylene glycol diacrylate; A second solution is coated on the surface of the first intermediate layer, wherein the second solution includes a multi-branched monomer, a second thermal initiator, and a second electrolyte, and a second curing is performed to form a second intermediate layer on the surface of the base film to obtain an electrolyte separator; wherein, The multi-branched monomer includes at least one of trimethylolpropane trifluoroacrylate, pentaerythritol tetraacrylate and four-arm polyethylene glycol-tetraacrylate.

2. The preparation method according to claim 1, wherein After the second curing, the preparation method further includes the steps of: coating a third solution on the surface of the second intermediate layer, the third solution including a nitrile-containing monomer, a third thermal initiator and a third electrolyte, and performing a third curing to form a gel-like functional layer on the surface of the base film.

3. The preparation method according to claim 2, wherein Based on the total mass content of the first solution, the second solution and the third solution as 100%, the total mass content of the linear monomer, the multi-branched monomer and the nitrile group-containing monomer is 3% to 8%, and the mass ratio of the linear monomer, the multi-branched monomer and the nitrile group-containing monomer is (14 to 16): (5 to 6):

1.

4. The preparation method according to claim 2, wherein The nitrile group-containing monomer includes at least one of acrylonitrile and methacrylonitrile.

5. The preparation method according to claim 2, wherein The first electrolyte, the second electrolyte and the third electrolyte independently include lithium salt, electrolyte and flame retardant, and the content of the flame retardant is 2% to 15%.

6. The preparation method according to claim 5, wherein Includes at least one of the following features (1)-(3): (1) The lithium salt includes one or more of LiPF6, LiFSI, LiBF4, LiBOB, LiDFOB and LiTFSI; (2) The electrolyte includes one or more of EC, PC, BC, DEC, DMC, DME, EMC, TEP and FEC; (3) The flame retardant includes at least one of a phosphorus-nitrogen composite flame retardant, a phosphorus-based flame retardant, a phosphorus-fluorine composite flame retardant, a phosphazene flame retardant, and a brominated flame retardant.

7. The preparation method according to claim 2, wherein The first thermal initiator, the second thermal initiator, and the third thermal initiator independently include at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dicumyl peroxide, and ammonium persulfate.

8. The preparation method according to any one of claims 2 to 7, characterized in that: The temperature of the first curing is 40°C to 60°C, the temperature of the second curing is 60°C to 80°C, and the temperature of the third curing is 50°C to 70°C.

9. The preparation method according to claim 8, wherein Includes at least one of the following features (1)-(3): (1) The first curing step comprises: preheating the base film coated with the first solution at 40°C to 45°C for 5 minutes to 10 minutes, then heating it to 55°C to 60°C and keeping it at that temperature for 50 minutes to 70 minutes, with a heating rate of ≤2°C / min, and then cooling it to room temperature; (2) the second curing step comprises: preheating the composite structure of the base film coated with the second solution and the first intermediate layer at 60° C. to 65° C. for 5 to 10 minutes, then heating it to 75° C. to 80° C. and keeping it at that temperature for 25 to 35 minutes, at a heating rate of ≤2° C. / min, and then cooling it to room temperature; (3) The third curing step includes: preheating the composite structure of the base film coated with the third solution and the second intermediate layer at 50°C to 55°C for 5 minutes to 10 minutes, then heating it to 65°C to 75°C and keeping it warm for 110 minutes to 130 minutes, with a heating rate of ≤2°C / min, and then cooling it to room temperature.

10. A semi-solid secondary battery, characterized in that: The invention comprises a positive electrode sheet, an electrolyte membrane and a negative electrode sheet, wherein the electrolyte membrane is prepared by the preparation method according to any one of claims 1 to 9.

11. The semi-solid secondary battery according to claim 10, wherein: In the electrolyte separator, the base film has a first side facing the positive electrode sheet and a second side facing the negative electrode sheet, at least one of the first side and the second side is provided with a functional layer, and the thickness of the functional layer is 10 μm to 30 μm.

12. An energy storage device, characterized in that: The semi-solid secondary battery according to claim 11 is included.

13. An electrical device, characterized in that: Comprising the energy storage device as claimed in claim 12.

Images