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

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a method for preparing an electrolyte of a semi-solid secondary battery, a semi-solid secondary battery, an energy storage device and an electrical equipment. Background Art

[0002] Lithium-ion batteries play a vital role in stationary energy storage systems due to their high energy density and reliable power supply. With the growing demand for the next generation of higher performance batteries, efforts are needed to develop new electrode materials, electrolytes, and battery systems. An ideal electrolyte should be a good lithium ion conductor with high chemical stability and should not cause other parasitic reactions on the electrode surface except for the migration of lithium ions. Although traditional organic liquid electrolytes have high ionic conductivity, their inherent instability, such as volatility, flammability and other unsafe disadvantages, pose great safety risks to batteries. At present, the solutions to the safety problems of lithium batteries mainly include: all-solid lithium-ion battery solutions, solutions to add flame retardants to electrolytes, and semi-solid electrolyte solutions. Among them, semi-solid electrolytes are a new type of functional polymer material between all-solid polymer electrolytes and liquid electrolytes, with stable electrochemical properties, and can be used in secondary batteries in the form of diaphragm and electrolyte materials.

[0003] 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

[0004] 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.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing an electrolyte separator of a semi-solid secondary battery, the preparation method comprising 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; 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; A third solution is applied on the surface of the second intermediate layer, wherein the third solution includes a nitrile-containing monomer, a third thermal initiator and a third electrolyte, and a third curing is performed to form a gel-like functional layer on the surface of the base film to obtain an electrolyte separator; 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%~8%, and the mass ratio of the linear monomer, the multi-branched monomer and the nitrile group-containing monomer is (12~16):(3~6):1.

[0006] In some embodiments, the linear monomer includes at least one of triethylene glycol dimethacrylate, methyl methacrylate, vinyl acetate, trifluoroethyl methacrylate, and ethylene glycol diacrylate.

[0007] 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.

[0008] In some embodiments, the nitrile group-containing monomer includes at least one of acrylonitrile and methacrylonitrile.

[0009] 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%.

[0010] In some embodiments, the lithium salt includes one or more of LiPF6, LiFSI, LiBF4, LiBOB, LiDFOB, and LiTFSI.

[0011] In some embodiments, the electrolyte includes one or more of EC, PC, BC, DEC, DMC, DME, EMC, TEP, and FEC.

[0012] 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 bromine-based flame retardant.

[0013] 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.

[0014] 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.

[0015] In some embodiments, the first curing step includes: preheating the base film coated with the first solution at 40°C~45°C for 5 min~10 min, then heating to 55°C~60°C and keeping warm for 50 min~70 min, with a heating rate of ≤2°C / min, and then cooling to room temperature.

[0016] 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~65°C for 5min~10min, then heating to 75°C~80°C and keeping warm for 25min~35min, with a heating rate of ≤2°C / min, and then cooling to room temperature.

[0017] 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~55°C for 5min~10min, then heating to 65°C~75°C and keeping warm for 110min~130min, with a heating rate of ≤2°C / min, and then cooling to room temperature.

[0018] 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.

[0019] 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 disposed on at least one of the first side and the second side, and the thickness of the functional layer is 10 μm to 30 μm.

[0020] In a third aspect, an embodiment of the present application further provides an energy storage device, comprising the semi-solid secondary battery as described in the second aspect.

[0021] 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.

[0022] Compared with the prior art, this technical solution has at least the following technical effects: The technical solution of this application adopts gradient copolymerization technology to form a gel-like functional layer with a gradient structure on the surface of the base film. The electrolyte membrane obtained not only has excellent flame retardant properties, but also has excellent ionic conductivity, mechanical properties and thermal stability, so that the semi-solid secondary battery obtained 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. In the preparation process of the electrolyte membrane, a first solution containing linear monomers is first coated on the surface of the base membrane, and initially polymerized to form a flexible first intermediate layer, and then a second solution is 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 a continuous ion transmission channel, which helps 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

[0023] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0024] Figure 1 This is a process flow chart of a method for preparing an electrolyte membrane for a semi-solid secondary battery of the present application. DETAILED DESCRIPTION

[0025] The raw materials and equipment used in the present invention, unless otherwise specified, are all commonly used raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are all conventional methods in the art.

[0026] 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.

[0027] As used herein, "includes," "comprising," "including," "containing," "having," or other variations 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 includes 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.

[0028] 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 the application is expected to include all subranges within the range.

[0029] It should be understood that the term "and / or" used in the present invention is only a description of the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0030] 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 will make it difficult for secondary batteries to balance safety performance with electrochemical properties such as rate performance and cycle performance.

[0031] Based on this, in a first aspect, an embodiment of the present application proposes a method for preparing an electrolyte membrane of a semi-solid secondary battery.

[0032] See also Figure 1 In the embodiment of the present application, the preparation method comprises the following steps: S100. Providing a base film, coating a first solution on the surface of the base film, the first solution comprising 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; S200. Applying a second solution on the surface of the first intermediate layer, the second solution comprising a multi-branched monomer, a second thermal initiator and a second electrolyte, performing a second curing, and forming a second intermediate layer on the surface of the base film; S300. Coating a third solution on the surface of the second intermediate layer, the third solution comprising a nitrile-containing monomer, a third thermal initiator and a third electrolyte, performing a third curing, forming a gel-like functional layer on the surface of the base film, and obtaining an electrolyte separator; 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%~8%, and the mass ratio of the linear monomer, the multi-branched monomer and the nitrile group-containing monomer is (12~16):(3~6):1.

[0033] 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.

[0034] The technical solution of this application adopts gradient copolymerization technology to form a gel-like functional layer with a gradient structure on the surface of the base film. The electrolyte membrane obtained not only has excellent flame retardant properties, but also has excellent ionic conductivity, mechanical properties and stability, so that the semi-solid secondary battery obtained 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. In the preparation process of the electrolyte membrane, a first solution containing linear monomers is first coated on the surface of the base membrane, and initially polymerized to form a flexible first intermediate layer, and then a second solution is 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 a continuous ion transmission channel, which helps 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.

[0035] The preparation method of the electrolyte membrane of the present application is described in more detail below.

[0036] 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 to 16): (3 to 6): 1, wherein the mass ratio of the linear monomer to the nitrile-containing monomer is 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 is specifically 3:1, 4:1, 5:1, 6:1 or any value therebetween.

[0037] By controlling the mass content of linear monomers, multi-branched monomers and nitrile-containing monomers within the above range, it is beneficial to adjust the final polymerized morphology of the functional layer to a jelly-like gel structure, in which the electrochemical properties and flame retardant properties of the electrolyte separator are relatively excellent. When the mass content of linear monomers, multi-branched monomers and nitrile-containing monomers is not within the above range, it will either cause the functional layer to become hard and brittle, thereby causing a significant decrease in the cycle performance of the semi-solid secondary battery; or it will cause the first solution, the second solution and the third solution to be unable to solidify from a liquid state to a gel state, or cause the first solution, the second solution and the third solution to have a long solidification time, affecting the preparation efficiency of the electrolyte separator.

[0038] In the embodiment of the present application, the material of the base film can be polyethylene, polypropylene, etc., and of course, it can also be other base film materials commonly used in semi-solid electrolyte membranes, and the embodiment of the present application does not specifically limit this.

[0039] 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 may also select other linear monomers according to actual conditions.

[0040] In the embodiment 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 is not only conducive to further improving the ionic conductivity of the electrolyte membrane, but also conducive to improving the flame retardant performance of the electrolyte membrane.

[0041] In some embodiments, the fluorine-containing monomer includes one or more of trimethylolpropane trifluoroacrylate and trifluoroethyl methacrylate.

[0042] 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.

[0043] 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.

[0044] In some embodiments, the first thermal initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dicumyl peroxide, and ammonium persulfate.

[0045] In some embodiments, the second thermal initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dicumyl peroxide, and ammonium persulfate.

[0046] In some embodiments, the third thermal initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dicumyl peroxide, and ammonium persulfate.

[0047] 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.

[0048] In some embodiments, the first electrolyte, the second electrolyte and the third electrolyte independently include lithium salt, electrolyte and flame retardant; the content of flame retardant in the first electrolyte, the second electrolyte or the third electrolyte is 2% to 15%, specifically 2%, 4%, 6%, 8%, 10%, 12%, 15% or any value therebetween. By adding an appropriate amount of flame retardant to the first electrolyte, the second electrolyte and the third electrolyte, the flame retardant performance of the electrolyte membrane can be effectively improved.

[0049] 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 may also select other lithium salts commonly used in the art according to actual conditions.

[0050] 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 may also select other electrolytes commonly used in the art according to actual conditions.

[0051] 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 bromine-based flame retardant, or other common organic flame retardants.

[0052] 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.

[0053] In some embodiments, the phosphorus-nitrogen composite flame retardant includes one or more of ammonium polyphosphate (APP), tris(nitroamine) polyphosphate (MPP), pentaerythritol phosphate-tris(nitroamine) 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 bromine-based flame retardant includes one or more of decabromodiphenyl ether (Deca-BDE), tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD), brominated polystyrene (BPS), brominated epoxy resin (BER), etc.

[0054] In some embodiments, the temperature of the first curing, the second curing and the third curing is 40°C to 80°C. Specifically, the temperature of the first curing, the second curing and the third curing can be independently 40°C, 50°C, 60°C, 70°C, 80°C or any value therebetween. By controlling the temperature of the first curing, the second curing and the third curing within the above range, it is beneficial to control the final curing 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.

[0055] 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; 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 linear monomers, multi-branched monomers and nitrile-containing monomers, so that the prepared electrolyte membrane obtains relatively good mechanical properties, electrochemical properties and flame retardant properties, and is also beneficial for improving the preparation efficiency of the electrolyte membrane.

[0056] In the above preferred embodiment, the first curing time is 55 min~70 min, specifically 55 min, 60 min, 65 min, 70 min or any value therebetween; the second curing time is 33 min~42 min, specifically 33 min, 35 min, 37 min, 39 min, 42 min or any value therebetween; the third curing time is 105 min~130 min, specifically 105 min, 110 min, 115 min, 120 min, 125 min, 130 min or any value therebetween.

[0057] In the above preferred embodiment, the first curing, the second curing and the third curing all include a preheating stage, a heating stage and a heat preservation stage which are carried out successively. The step-by-step operation of preheating first, heating second and heat preservation third not only improves the safety of the reaction, but also significantly enhances the quality controllability of the product.

[0058] In some embodiments, the temperature of the insulation stage of the first curing is T1, the temperature of the insulation stage of the second curing is T2, and the temperature of the insulation stage of the third curing is T3, T2>T1, and T2<T3. By making T2>T1, it is beneficial to allow the linear monomer to retain sufficient active groups after the first preliminary polymerization to further polymerize with the multi-branched monomer in the second curing stage to form a gel-like three-dimensional network structure; by making T2<T3, it is beneficial to prevent the aforementioned gel-like three-dimensional network structure from further polymerizing to form a fully solid structure.

[0059] 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 min to 10 min, then heating to 55°C to 65°C and keeping warm for 50 min to 70 min, and then cooling to room temperature. In the preheating stage, the first thermal initiator is activated, and the linear monomers are pre-crosslinked to form a flexible network. In the insulation stage, the linear monomers are further polymerized into a jelly-like gel state.

[0060] 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 min to 10 min, then heating to 75°C to 85°C for 25 min to 35 min, and then cooling to room temperature.

[0061] 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~55°C for 5 min~10 min, then heating to 65°C~75°C and keeping warm for 110 min~130 min, and then cooling to room temperature.

[0062] In some embodiments, in 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.

[0063] In some embodiments, during the first curing, the second curing or the third curing step, the cooling rate is ≥1°C / min. After the heat preservation, the rapid cooling process is beneficial to avoid the accumulation of thermal stress on the polymer product.

[0064] 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.

[0065] 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.

[0066] In the embodiments 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 transfer efficiency, mechanical strength, energy density and safety of the electrolyte membrane.

[0067] 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.

[0068] In the embodiment of the present application, the positive electrode sheet, the electrolyte membrane and the negative electrode sheet can be assembled into a stacked structure or a wound structure. The specific assembly method can be adjusted according to the specific type of the semi-cured secondary battery.

[0069] In the embodiments of the present application, illustratively, the method for preparing a semi-cured secondary battery includes: Prepare positive electrode sheet, negative electrode sheet and electrolyte separator; Assembling or winding the positive electrode sheet, the electrolyte separator and the negative electrode sheet to obtain a pre-assembled part; The pre-assembled component is assembled with the shell to obtain a semi-cured secondary battery.

[0070] In the above preparation method, when the semi-cured secondary battery is a soft-pack battery, the shell is a membrane structure of aluminum-plastic composite film, and the stacking assembly of the positive electrode sheet, electrolyte membrane and negative electrode sheet can be carried out on the membrane structure. When the semi-cured secondary battery is a hard shell battery such as a square shell battery, the positive electrode sheet, electrolyte membrane and negative electrode sheet are usually assembled first, and then the assembled structure is placed in the shell.

[0071] In a third aspect, an embodiment of the present application further provides an energy storage device, the 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 connection and series connection.

[0072] 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.

[0073] 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.

[0074] In the embodiments of the present application, electrical equipment may include but is not limited to: containers, household energy storage systems, battery vehicles, electric vehicles, ships, spacecraft, electric toys and electric tools, etc., wherein spacecrafts include airplanes, rockets, space shuttles and spacecrafts, etc., electric toys include fixed or mobile electric toys, such as electric car toys, electric ship toys and electric airplane toys, etc., and electric tools include metal cutting power tools, grinding power tools, assembly power tools and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers.

[0075] The present application is further described below through specific embodiments and comparative examples, but the present application is not limited to these specific examples.

[0076] Example 1 1. Preparation of Electrolyte Separator (1) Raw materials: 3.29wt% triethylene glycol dimethacrylate + 1.175wt% trimethylolpropane trifluoroacrylate + 0.235wt% acrylonitrile + 0.1wt% ammonium persulfate + 0.1wt% azobisisobutyronitrile + 0.1wt% benzoyl peroxide + 95wt% liquid electrolyte (90wt% (1M LiPF6EC:EMC:DMC=3:4:3 vol%) + 5wt% hexaphenoxycyclotriphosphazene).

[0077] 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.

[0078] The triethylene glycol dimethacrylate, ammonium persulfate and the first electrolyte in the raw materials are mixed to prepare a first solution; The trimethylolpropane trifluoroacrylate, azobisisobutyronitrile and the second electrolyte in the raw materials are mixed to prepare a second solution; The acrylonitrile, benzoyl peroxide and the third electrolyte in the raw materials are prepared into a third solution.

[0079] (2) Preparation steps: S100. Provide a base film (polypropylene film), evenly coat the first solution on the surface of the base film, put it into 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.

[0080] 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 60°C for 5 minutes, and then heated to 80°C at a rate of ≤2°C / min. The solution is then kept warm for 30 minutes, and then quickly cooled to room temperature to form a second intermediate layer on the surface of the base film.

[0081] S300. The third solution is evenly coated on the surface of the second intermediate layer, and the layer is placed in a segmented oven, preheated at 50°C for 10 minutes, then heated to 70°C at a rate of ≤2°C / min, and then kept warm for 120 minutes, and then rapidly cooled to room temperature to obtain an electrolyte membrane.

[0082] 2. Assembly of half-cell 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 at 105°C under vacuum for 10 hours to obtain a positive electrode sheet. The counter electrode was a lithium sheet.

[0083] The positive electrode sheet and the lithium sheet were cut into small discs with a diameter of 13 mm using a cutting machine, and the positive electrode shell, spring sheet, gasket, positive electrode sheet, the above-prepared electrolyte membrane, lithium sheet, and negative electrode shell were assembled into a button battery in a glove box filled with argon (Ar).

[0084] 3. Performance Testing (1) Conductivity test before and after polymerization At 25°C, the conductivity of the functional layer material of the electrolyte separator was tested using a conductivity meter.

[0085] (2) Self-extinguishing time test Take a small amount of electrolyte and put it on the negative electrode shell of the buckle battery. After igniting it with an igniter for 5 seconds, count and observe the self-extinguishing time.

[0086] (3) Electrochemical performance test In this paper, the LAND test system was used to test the cycle performance and rate performance of the button cell assembled above in a constant temperature test cabinet at 25°C. The current density of the cycle performance test was 0.3 C for 5 cycles of activation followed by a current density of 1 C, with a voltage range of 2-3.75 V. The specified current density for the rate performance test was 10 mA˙g -1 、30mA˙g -1 , 50mA˙g -1 , 70mA˙g -1 , 100mA˙g -1 , 10mA˙g -1 , and 5 cycles were performed at each current density.

[0087] Example 2 The difference from Example 1 is that the trimethylolpropane trifluoroacrylate in the raw material is replaced by pentaerythritol tetraacrylate.

[0088] Example 3 The difference from Example 1 is that: (1) Raw materials: 2.4wt% triethylene glycol dimethacrylate + 0.6wt% trimethylolpropane trifluoroacrylate + 0.2wt% acrylonitrile + 0.1wt% ammonium persulfate + 0.1wt% azobisisobutyronitrile + 0.1wt% benzoyl peroxide + 96.5wt% liquid electrolyte (91.7wt% (1M LiPF6EC:EMC:DMC=3:4:3 vol%) + 5wt% hexaphenoxy cyclotriphosphazene).

[0089] 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.

[0090] Example 4 The difference from Example 1 is that: (1) Raw materials: 5.44wt% triethylene glycol dimethacrylate + 2.04wt% trimethylolpropane trifluoroacrylate + 0.34wt% acrylonitrile + 0.1wt% ammonium persulfate + 0.1wt% azobisisobutyronitrile + 0.1wt% benzoyl peroxide + 91.7wt% liquid electrolyte (86.7wt% (1M LiPF6EC:EMC:DMC=3:4:3 vol%) + 5wt% hexaphenoxycyclotriphosphazene).

[0091] 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.

[0092] Example 5 The difference from Example 1 is that: (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.

[0093] (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.

[0094] S300. The third solution is evenly coated on the surface of the second intermediate layer, and the layer is placed in a segmented oven, 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, and then rapidly cooled to room temperature to obtain an electrolyte membrane.

[0095] Example 6 The difference from Example 1 is that: (1) The triethylene glycol dimethacrylate, azobisisobutyronitrile and the first electrolyte in the raw materials are mixed to prepare a first solution; the trimethylolpropane trifluoroacrylate, benzoyl peroxide and the second electrolyte in the raw materials are mixed to prepare a second solution; and the acrylonitrile, ammonium persulfate and the third electrolyte in the raw materials are mixed to prepare a third solution.

[0096] (2) S100. Provide a base film (polypropylene film), evenly coat the first solution on the surface of the base film, put it into 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.

[0097] S200. The second solution is evenly coated on the surface of the first intermediate layer, and the solution is placed in a segmented oven, preheated at 50°C for 10 minutes, then heated to 70°C at a rate of ≤2°C / min, and then kept warm for 120 minutes, and then quickly cooled to room temperature to form a second intermediate layer on the surface of the base film.

[0098] S300. The third solution is evenly coated on the surface of the second intermediate layer, and the solution is placed in a segmented oven, preheated at 40°C for 10 minutes, then heated to 60°C at a rate of ≤2°C / min, and then kept warm for 60 minutes, and then rapidly cooled to room temperature to obtain an electrolyte membrane.

[0099] Comparative Example 1 Liquid electrolyte (1M LiPF6EC:EMC:DMC=3:4:3 vol%).

[0100] Comparative Example 2 The difference from Example 1 is that: 1. Preparation of Electrolyte Separator (1) Raw materials: 4.7wt% triethylene glycol dimethacrylate + 0.3wt% ammonium persulfate + 95wt% liquid electrolyte (90wt% (1M LiPF6 EC:EMC:DMC=3:4:3 vol%) + 5wt% hexaphenoxycyclotriphosphazene).

[0101] The triethylene glycol dimethacrylate, ammonium persulfate and electrolyte in the raw materials are mixed to prepare a first solution.

[0102] (2) Preparation steps: S100. Provide a base film (polypropylene film), evenly coat the first solution on the surface of the base film, put it into 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.

[0103] Comparative Example 3 The difference from Example 1 is that: 1. Preparation of Electrolyte Separator (1) Raw materials: 3.54wt% triethylene glycol dimethacrylate + 1.26wt% trimethylolpropane trifluoroacrylate + 0.1wt% ammonium persulfate + 0.1wt% azobisisobutyronitrile + 95wt% liquid electrolyte (85wt% (1M LiPF6 EC:EMC:DMC=3:4:3 vol%) + 5wt% hexaphenoxycyclotriphosphazene).

[0104] 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.

[0105] The triethylene glycol dimethacrylate, ammonium persulfate and the first electrolyte in the raw materials are mixed to prepare a first solution; The trimethylolpropane trifluoroacrylate, azobisisobutyronitrile and the second electrolyte in the raw materials are mixed to prepare a second solution.

[0106] (2) Preparation steps: S100. Provide a base film (polypropylene film), evenly coat the first solution on the surface of the base film, put it into 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.

[0107] S200. The second solution is evenly coated on the surface of the first intermediate layer, and the layer is placed in a segmented oven, preheated at 60°C for 5 minutes, and then heated to 80°C at a rate of ≤2°C / min, and then kept warm for 30 minutes, and then quickly cooled to room temperature to obtain an electrolyte membrane.

[0108] Comparative Example 4 The difference from Example 1 is that: (1) Raw materials: 1.19wt% triethylene glycol dimethacrylate + 0.425wt% trimethylolpropane trifluoroacrylate + 0.085wt% acrylonitrile + 0.1wt% ammonium persulfate + 0.1wt% azobisisobutyronitrile + 0.1wt% benzoyl peroxide + 98wt% liquid electrolyte (93wt% (1M LiPF6EC:EMC:DMC=3:4:3 vol%) + 5wt% hexaphenoxycyclotriphosphazene).

[0109] 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.

[0110] Comparative Example 5 The difference from Example 1 is that: (1) Raw materials: 6.09wt% triethylene glycol dimethacrylate + 2.175wt% trimethylolpropane trifluoroacrylate + 0.435wt% acrylonitrile + 0.1wt% ammonium persulfate + 0.1wt% azobisisobutyronitrile + 0.1wt% benzoyl peroxide + 91wt% liquid electrolyte (86wt% (1M LiPF6EC:EMC:DMC=3:4:3 vol%) + 5wt% hexaphenoxycyclotriphosphazene).

[0111] Comparative Example 6 The difference from Example 1 is that: (1) Raw materials: 2.35wt% triethylene glycol dimethacrylate + 1.645wt% trimethylolpropane trifluoroacrylate + 0.705wt% acrylonitrile + 0.1wt% ammonium persulfate + 0.1wt% azobisisobutyronitrile + 0.1wt% benzoyl peroxide + 95wt% liquid electrolyte (90wt% (1M LiPF6EC:EMC:DMC=3:4:3 vol%) + 5wt% hexaphenoxycyclotriphosphazene).

[0112] 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.

[0113] Comparative Example 7 The difference from Example 1 is that: (1) Raw materials: 3.995wt% triethylene glycol dimethacrylate + 0.611wt% trimethylolpropane trifluoroacrylate + 0.094wt% acrylonitrile + 0.1wt% ammonium persulfate + 0.1wt% azobisisobutyronitrile + 0.1wt% benzoyl peroxide + 95wt% liquid electrolyte (90wt% (1M LiPF6EC:EMC:DMC=3:4:3 vol%) + 5wt% hexaphenoxy cyclotriphosphazene).

[0114] 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.

[0115] Comparative Example 8 The difference from Example 1 is that: Preparation steps: (2) S100. Provide a base film (polypropylene film), evenly mix the first solution and the second solution, and then evenly coat the mixture on the surface of the base film. Place the base film in a segmented oven, preheat at 60°C for 10 minutes, then heat to 80°C at a rate of ≤2°C / min, and then keep the temperature for 60 minutes. Then, quickly cool the film to room temperature to form an intermediate layer on the surface of the base film.

[0116] S200. The third solution is evenly coated on the surface of the first intermediate layer, and the layer is placed in a segmented oven, preheated at 50°C for 10 minutes, then heated to 70°C at a rate of ≤2°C / min, and then kept warm for 120 minutes, and then rapidly cooled to room temperature to obtain an electrolyte membrane.

[0117] Comparative Example 9 The difference from Example 1 is that: Preparation steps: S100. Provide a base film (polypropylene film), evenly coat the first solution on the surface of the base film, put it into 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.

[0118] S200. The second solution and the third solution are uniformly mixed and then uniformly coated on the first intermediate layer, and placed in a segmented oven, 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, and then quickly cooled to room temperature to obtain an electrolyte membrane.

[0119] Test results: Table 1. Test results of electrical conductivity and flame retardancy of various embodiments and comparative examples

[0120] Table 2. Cyclic performance test results of various embodiments and comparative examples

[0121] Table 3. Rate performance test results of various embodiments and comparative examples

[0122] The test results of Examples 1-6 and Comparative Examples 1-9 prove that the electrolyte membrane prepared by the gradient copolymerization technology described in the present application not only has excellent flame retardancy, but also has excellent ionic conductivity and material stability. The semi-solid secondary battery prepared by the invention has significantly improved safety performance, and its electrochemical properties such as rate performance and cycle performance are similar to those of liquid electrolytes. 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 (membrane) of the present application has better flame retardant properties.

[0123] 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.

[0124] By comparing Example 1 with Comparative Example 3, it can be proved that by finally adding the cyanide-containing monomer, the interfacial compatibility between the electrolyte membrane and the electrolyte is improved, the conductivity of the electrolyte membrane can be increased, which is beneficial to the improvement of the rate performance of the semi-solid secondary battery.

[0125] 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.

[0126] 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 group-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 group-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.

[0127] By comparing Example 1 with Example 2, it can be proved that when the multi-branched monomer is a fluorine-containing monomer, it is more conducive to improving the conductivity of the electrolyte membrane, thereby being more conducive to improving the flame retardant performance and rate performance of the semi-cured secondary battery.

[0128] 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, the second curing and the 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 enhancing the polymerization between the electrolyte layers, thereby being more conducive to improving the rate performance and cycle performance of the semi-cured secondary battery.

[0129] 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; 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; A third solution is applied on the surface of the second intermediate layer, wherein the third solution includes a nitrile-containing monomer, a third thermal initiator and a third electrolyte, and a third curing is performed to form a gel-like functional layer on the surface of the base film to obtain an electrolyte separator; 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%~8%, and the mass ratio of the linear monomer, the multi-branched monomer and the nitrile group-containing monomer is (12~16):(3~6):

1.

2. The preparation method according to claim 1, characterized in that: The invention comprises at least one of the following features (1) to (3): (1) The linear monomer includes at least one of triethylene glycol dimethacrylate, methyl methacrylate, vinyl acetate, trifluoroethyl methacrylate and ethylene glycol diacrylate; (2) the multi-branched monomer comprises at least one of trimethylolpropane trifluoroacrylate, pentaerythritol tetraacrylate, trimethylolpropane, pentaerythritol, four-arm polyethylene glycol-tetraacrylate and hyperbranched polyester polyol; (3) The nitrile group-containing monomer includes at least one of acrylonitrile and methacrylonitrile.

3. The preparation method according to claim 1, characterized in that: 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%.

4. The preparation method according to claim 3, characterized in that: The invention comprises at least one of the following features (1) to (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 bromine-based flame retardant.

5. The preparation method according to claim 1, characterized in that: 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.

6. The preparation method according to any one of claims 1 to 5, 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.

7. The preparation method according to claim 6, characterized in that: The invention comprises at least one of the following features (1) to (3): (1) The first curing step comprises: preheating the base film coated with the first solution at 40°C to 45°C for 5 min to 10 min, then heating it to 55°C to 60°C and keeping it at that temperature for 50 min to 70 min, 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 min to 10 min, then heating to 75°C to 80°C and keeping the temperature for 25 min to 35 min, with a heating rate of ≤2°C / min, and then cooling to room temperature; (3) The third curing step comprises: 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 min to 10 min, then heating to 65°C to 75°C and keeping the temperature for 110 min to 130 min, with a heating rate of ≤2°C / min, and then cooling to room temperature.

8. 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 7.

9. The semi-solid secondary battery according to claim 8, characterized in that: 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, the functional layer is disposed on at least one of the first side and the second side, and the thickness of the functional layer is 10 μm to 30 μm.

10. An energy storage device, characterized in that: Comprising the semi-solid secondary battery as claimed in claim 9.

11. An electrical device, characterized in that: Comprising the energy storage device as claimed in claim 10.

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