Solid electrolyte membrane and preparation method thereof, secondary battery and electric equipment

Abstract

The invention provides a solid electrolyte membrane and a preparation method thereof, a secondary battery and electric equipment. The solid electrolyte membrane comprises the following components: polyvinylidene fluoride or a copolymer thereof, polyimide or a copolymer thereof, electrolyte salt and amino polycarboxylic acid salt. The solid electrolyte membrane is prepared by taking polyvinylidene fluoride or a copolymer thereof as a matrix, and polyimide and amino polycarboxylate are added to improve the crystallization property of polyvinylidene fluoride, so that the compact flame-retardant composite polymer electrolyte membrane with high Young's modulus is obtained. The Young modulus of the prepared solid electrolyte membrane is larger than or equal to 9.5 GPa under the thickness of 10 microns, the ionic conductivity is larger than 4 * 10 <-4 > S / cm at the temperature of 25 DEG C, and the capacity retention ratio is 85% or above after 600 cycles at the temperature of 1 DEG C.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, in particular to a solid electrolyte membrane, a preparation method thereof, a secondary battery, and an electrical device. Background Art

[0002] Currently, polymer electrolytes exhibit greater processing versatility and better electrode compatibility than inorganic ceramic electrolytes. Unfortunately, due to the insufficient mechanical strength of polymer electrolytes, the inhibitory effect on lithium dendrites is relatively poor, and a greater thickness is still required to ensure the long-term operation of lithium metal batteries, thereby reducing the energy density of the batteries. In addition, the low ionic conductivity and unsatisfactory thermal stability of polymer electrolytes also hinder their practical applications in high-energy and high-safety lithium metal batteries.

[0003] In view of this, the present application is proposed. Summary of the Invention

[0004] The purpose of the present application is to overcome the above problems in the prior art and provide a polymer solid electrolyte membrane with high ionic conductivity, easy cutting and processing, high mechanical strength, good electrochemical and thermal stability, etc., so as to realize the preparation and application of an ultra-thin lithium metal electrolyte with high energy density, long cycle life, and good safety.

[0005] To achieve the above purpose, in the first aspect of the present application, a solid electrolyte membrane is provided, which comprises the following components:

[0006] A polymer matrix, an electrolyte salt, an aminopolycarboxylate; the polymer matrix comprises polyvinylidene fluoride or its copolymer, polyimide or its copolymer.

[0007] As an embodiment of the present application, the solid electrolyte membrane comprises the following components in parts by weight:

[0008] 100 parts of polymer matrix, 15-20 parts of electrolyte salt, 0.1-5 parts of film-forming agent, 1-5 parts of aminopolycarboxylate.

[0009] As an embodiment of the present application, the polymer matrix satisfies: 30% ≤ M2 / (M1 + M2) ≤ 45%, where M1 represents the parts by weight of polyvinylidene fluoride or its copolymer; M2 represents the parts by weight of polyimide or its copolymer.

[0010] As an embodiment of the present application, the polyvinylidene fluoride or its copolymer includes at least one of polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (P(VDF-HFP)) copolymer, and vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene terpolymer (P(VDF-TrFE-CTFE)).

[0011] As an embodiment of the present application, the polyimide or its copolymer includes at least one of polyimide (PI), polyimide-siloxane block copolymer, and polylactic acid-polyimide block copolymer (PLA-PI-PLA).

[0012] As an embodiment of the present application, the melt viscosity of the polyvinylidene fluoride or its copolymer is denoted as η A , and the melt viscosity of the polyimide or its copolymer is denoted as η B , satisfying: η B -η A ≥500 cps.

[0013] As an embodiment of the present application, it satisfies: 1.0 ≤ η B / η A ≤1.5.

[0014] As an embodiment of the present application, η A = 3000 - 4000 cps.

[0015] As an embodiment of the present application, η B = 3500 - 5000 cps.

[0016] As an embodiment of the present application, the electrolyte salt includes at least one of sodium bis(trifluoromethylsulfonyl)imide (NaTFSI) and sodium hexafluorophosphate (NaPF 6 ).

[0017] As an embodiment of the present application, the number of carboxyl groups in the aminopolycarboxylate is 5 - 6.

[0018] In the second aspect of the present invention, there is provided a method for preparing the solid electrolyte membrane described in the first aspect of the present application, including the following steps:

[0019] According to the parts by weight, dissolve the polyvinylidene fluoride or its copolymer, the polyimide or its copolymer, and the electrolyte salt in an organic solvent, mix them evenly, then add the aminopolycarboxylate, dissolve to obtain a mixed solution, and use the casting method to obtain a precursor film, and dry it to obtain the solid electrolyte membrane.

[0020] As an embodiment of the present application, the organic solvent includes at least one of trimethyl phosphate (TMP), triethyl phosphate (TEP), triphenyl phosphate (TPP), and N,N-dimethylformamide (DMF).

[0021] As an embodiment of the present application, the dissolution temperature is 60 - 160 °C.

[0022] As an embodiment of the present application, the drying temperature is 80 - 100 °C.

[0023] In a third aspect of the present application, a secondary battery is provided, which includes a positive electrode sheet, the solid electrolyte membrane described in the first aspect of the present application, and a negative electrode sheet.

[0024] In a fourth aspect of the present application, an electrical device is provided, which includes the secondary battery described in the third aspect of the present application.

[0025] Compared with the prior art, the beneficial effects of the present application are as follows:

[0026] In the present application, a solid electrolyte membrane is prepared using polyvinylidene fluoride or its copolymer, polyimide or its copolymer as the polymer matrix, and aminopolycarboxylate is added to improve the crystallization performance of the polymer matrix, resulting in a dense, high Young's modulus flame-retardant composite polymer electrolyte membrane. Among them, the solid electrolyte membrane prepared in the present application has a Young's modulus ≥ 9.5 GPa at a thickness of 10 μm, an ionic conductivity > 4×10 -4 S / cm at 25 °C, and a capacity retention rate of more than 85% after 600 cycles at 1C. Detailed Embodiments

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0028] In the present application, among the technically described features in an open-ended manner, a closed technical solution composed of the listed features is included, and an open technical solution including the listed features is also included.

[0029] In the present application, regarding numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, each integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0030] Reagents or instruments used in the present application that are not indicated by the manufacturer can all be obtained as conventional products through commercial purchase.

[0031] In a first aspect of the present application, a solid electrolyte membrane is provided, which includes the following components:

[0032] Polymer matrix, electrolyte salt, aminopolycarboxylate; the polymer matrix includes polyvinylidene fluoride (PVDF) or its copolymer, polyimide (PI) or its copolymer.

[0033] In this application, polyvinylidene fluoride or its copolymer, polyimide or its copolymer are used as the polymer matrix to prepare a solid electrolyte membrane, and aminopolycarboxylate is added to improve the crystallization performance of the polymer matrix, obtaining a dense, high Young's modulus flame-retardant composite polymer electrolyte membrane.

[0034] Among them, the active conjugated carbonyl groups in the PI polymer backbone are beneficial to ion conduction because the negatively charged N and O atoms accelerate the dissociation of sodium salts through electrostatic interaction, significantly improving the ionic conductivity and ion transfer number of the electrolyte. In addition, the polyimide with high flame retardancy has a certain affinity for polyvinylidene fluoride, thus enhancing the mechanical strength of the electrolyte membrane and reducing the thermal shrinkage rate; the conventional PVDF structure is of the TGTG' type, and its fluorine atoms are arranged on both sides of the carbon chain. The large steric hindrance and long transmission path seriously affect its lithium ion transmission efficiency. However, the strong electron-donating property of the amino group in aminopolycarboxylate induces the conformation of PVDF to change from TGTG' to TTTT'. The PVDF with the TTTT' structure can ensure that all fluorine atoms are arranged on the same side, shortening the ion transmission path, promoting the dissociation of the ions in the electrolyte, and fixing the anions of the electrolyte salt, thereby increasing the ionic conductivity of the electrolyte. In addition, the strong electron-donating effect of aminopolycarboxylate will also increase the electron density around the polymer molecules, resulting in more nucleation sites in the polymer, reducing the diameter of the polymer spheres, and increasing the continuity of the polymer membrane.

[0035] In some embodiments of this application, the solid electrolyte membrane comprises the following components in parts by weight:

[0036] 100 parts of polymer matrix, 15 - 20 parts of electrolyte salt, 0.1 - 5 parts of film-forming agent, 1 - 5 parts of aminopolycarboxylate.

[0037] In some embodiments of this application, the polymer matrix satisfies: 30% ≤ M2 / (M1 + M2) ≤ 45%, where M1 represents the parts by weight of polyvinylidene fluoride or its copolymer; M2 represents the parts by weight of polyimide or its copolymer.

[0038] When a relatively high content of PI is introduced into the polyvinylidene fluoride-based polymer, although the mechanical strength and non-flammability of the composite electrolyte are greatly improved, a large amount of PI tends to form a porous structure during film formation, thus deteriorating the interface between the electrode and the electrolyte and reducing the ion transport path; after adding an appropriate amount of amino polycarboxylate with electron-donating properties, the electron density around the PI and PVDF polymer molecules increases, resulting in more nucleation sites in the polymer, reducing the diameter of the polymer microspheres, inhibiting the formation of the porous structure and enabling the preparation of a thinner and denser composite electrolyte film.

[0039] In some embodiments of the present application, the polyvinylidene fluoride or its copolymer includes at least one of polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (P(VDF-HFP)) copolymer, and vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene terpolymer (P(VDF-TrFE-CTFE)).

[0040] In some embodiments of the present application, the polyimide or its copolymer includes at least one of polyimide (PI), polyimide-siloxane block copolymer, and polylactic acid-polyimide block copolymer (PLA-PI-PLA).

[0041] In some embodiments of the present application, the melt viscosity of the polyvinylidene fluoride or its copolymer is denoted as η A and the melt viscosity of the polyimide or its copolymer is denoted as η B satisfying: η B - η A ≥500 cps. During the film formation process, a polyimide-based polymer with a higher viscosity (i.e., polyimide or its copolymer) and a polyvinylidene fluoride-based polymer with a lower viscosity (including polyvinylidene fluoride and vinylidene fluoride copolymer) are likely to form a sea-island structure. The polyimide-based polymer with a higher viscosity can act together with the amino polycarboxylate to function as a certain nucleating agent, improving the crystallization performance of the polyvinylidene fluoride-based polymer and contributing to the improvement of the Young's modulus of the solid electrolyte membrane. The value of η B - η A can be selected from 500 cps, 1000 cps, 2000 cps, or the range composed of any two of these values.

[0042] In some embodiments of the present application, it further satisfies: 1.0 ≤ η B / η A ≤ 1.5. When the viscosity ratio of polyimide to polyvinylidene fluoride is within the above preferred range, the particle size of the "island" phase formed by polyimide in the polyvinylidene fluoride-based matrix is smaller, which is more conducive to exerting its nucleating agent function and is beneficial to improving the Young's modulus of the solid electrolyte membrane; at the same time, it is more uniformly dispersed in the polyvinylidene fluoride-based matrix, improving the ion transport channels and being beneficial to increasing the conductivity of the electrolyte membrane.B / η A The value of can be selected from 1.0, 1.125, 1.17, 1.14, 1.33 or the range composed of any two of these values.

[0043] In some embodiments of the present application, the melt viscosity η of the polyvinylidene fluoride or its copolymer A = 3000 - 4000 cps. Within this viscosity range, the electrolyte membrane has good casting film-forming properties. The value of η A can be selected from 3000 cps, 3500 cps, 4000 cps, or the range composed of any two of these values.

[0044] In some embodiments of the present application, the melt viscosity η of the polyimide or its copolymer B = 3500 - 5000 cps. Within this viscosity range, the electrolyte membrane has good casting film-forming properties. The value of η B can be selected from 3500 cps, 4000 cps, 4000 cps, 5000 cps, or the range composed of any two of these values.

[0045] In some embodiments of the present application, the number of carboxyl groups in the aminopolycarboxylate is 5 - 6. Specifically, diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetraacetic acid (EDTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), ethylene glycol diethylether diamine tetraacetic acid (EGTA), nitrilotriacetic acid (NTA) can be preferably used. The carboxyl group is an electron-withdrawing group. With the increase of the carboxyl group content, the ionic conductivity of the solid electrolyte membrane can be improved, but the adsorption ability of the lithium salt also becomes stronger, and it is easy to agglomerate, resulting in a loose and porous interface, and the polarization becomes too large. The loose and porous caused by too low PI cannot be alleviated, and then the ionic conductivity of the solid electrolyte membrane is reduced. Therefore, when the carboxyl group content is within the above suitable range, it has a suitable ionic conductivity and can ensure that it does not agglomerate with the lithium salt. In some embodiments of the present application, the electrolyte salt includes at least one of sodium bis(trifluoromethylsulfonyl)imide (NaTFSI), sodium hexafluorophosphate (NaPF 6 )

[0046] In some embodiments of the present application, a film-forming agent can also be added as needed. The film-forming agent includes but is not limited to at least one of perfluorobenzene, 3-iodooxetane, and difluoroethylene carbonate.

[0047] The second aspect of the present invention provides a method for preparing the solid electrolyte membrane described in the first aspect of the present application, including the following steps:

[0048] According to the parts by weight, polyvinylidene fluoride or its copolymer, polyimide or its copolymer, and electrolyte salt are dissolved in an organic solvent and mixed evenly, then aminopolycarboxylate and a film-forming agent (if added) are added and dissolved to obtain a mixed solution. The precursor film is obtained by the casting method and dried to obtain the solid electrolyte membrane.

[0049] In some embodiments of the present application, the temperature of the dissolution is 60-160 °C, which can be specifically selected according to the types of raw materials and solvents, as long as each component can be dissolved.

[0050] In some embodiments of the present application, the temperature of the drying is 80-100 °C.

[0051] The good solvents of the above-mentioned raw materials of the electrolyte membrane well-known in the art can all be used in the present application. In some embodiments of the present application, by way of example, the organic solvent includes but is not limited to at least one of trimethyl phosphate (TMP), triethyl phosphate (TEP), triphenyl phosphate (TPP), and N,N-dimethylformamide (DMF).

[0052] In some embodiments of the present application, in the mixed solution, the weight of the film-forming agent is denoted as N2, and the weight of the organic solvent is denoted as N1, satisfying: 5% ≤ N2 / (N1 + N2) ≤ 20%. Within this concentration range, the mixed solution for film formation has good homogeneity and fluidity, and can be coated to obtain a precursor film with a uniform thickness.

[0053] In some embodiments of the present application, the specific operation of the casting method is: depositing the obtained mixed solution on a glass plate and using a doctor blade with adjustable height to scrape and coat to obtain a precursor film with a uniform thickness.

[0054] In the third aspect of the present application, a secondary battery is provided, and the secondary battery includes a positive electrode plate, the solid electrolyte membrane described in the first aspect of the present application, and a negative electrode plate.

[0055] The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and the positive electrode active material layer contains a positive electrode active material.

[0056] The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode active material layer contains a negative electrode active material.

[0057] The types of the negative electrode current collector and the positive electrode current collector are not specifically limited and can be selected according to actual needs.

[0058] The negative electrode current collector is preferably a copper foil or a carbon-coated copper foil, etc.

[0059] The positive current collector may include, but is not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, tantalum, etc.; carbon materials such as carbon cloth and carbon paper; composite materials formed by polymers and metal layers. In some embodiments, aluminum foil is preferably used as the positive current collector.

[0060] The types of negative active materials are also not limited. Common negative active materials in the art, such as carbon, silicon, silicon-carbon composite negative electrode materials, etc., can all be used in this application and can be selected according to actual needs.

[0061] In addition, in the negative active material layer and the positive active material layer, at least one of a conductive agent, a binder, and a thickener is included.

[0062] Common conductive agents, binders, and thickeners for batteries in the art can all be used in this application.

[0063] In some embodiments, the conductive agent includes, but is not limited to, at least one of graphite, carbon black, acetylene black, Ketjen black, carbon nanotubes, and graphene.

[0064] In some embodiments, the binder includes, but is not limited to, at least one of styrene-butadiene rubber, polyacrylic acid, polyacrylonitrile, polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene copolymer, and vinylidene fluoride-hexafluoropropylene copolymer.

[0065] In some embodiments, the thickener includes, but is not limited to, at least one of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose.

[0066] In some embodiments, the types of solvents used to form the positive electrode slurry and / or the negative electrode slurry are not limited, as long as they can dissolve or disperse the positive active material, negative active material, conductive agent, binder, and dispersant.

[0067] In some embodiments, the preparation of the secondary battery includes: stacking the positive electrode sheet, the solid electrolyte membrane, and the negative electrode sheet in sequence, with the solid electrolyte membrane placed between the positive and negative electrode sheets to play a role of isolation, and assembling them into a secondary battery.

[0068] In the fourth aspect of the present application, an electrical device is provided, including the secondary battery described in the third aspect of the present application.

[0069] The following are specific embodiments of the present application, and the technical solutions of the present application are further described in combination with the embodiments, but the present application is not limited to these embodiments. The reagents, methods, and equipment used in the present application are all conventional reagents, methods, and equipment in the technical field, unless otherwise specified.

[0070] Examples 1 to 13, Comparative Examples 1 to 5

[0071] A solid electrolyte membrane is provided and is prepared by a method comprising the following steps:

[0072] According to the formulations shown in Table 1 and Table 2 (the numbers represent parts by weight), polyvinylidene fluoride or its copolymer, polyimide or its copolymer, and an electrolyte salt are dissolved in an organic solvent and mixed evenly. Then, aminopolycarboxylate (in Comparative Examples 4 and 5, it is replaced with the corresponding 4-aminobenzoic acid and hydroxybenzotriazole) and a film-forming agent are added. After stirring and dissolving at 60-160 °C, a mixed solution is obtained (in the mixed solution, N2 / (N1 + N2) = 5%, where the weight of the film-forming agent is denoted as N2 and the weight of the organic solvent is denoted as N1). A precursor film is obtained by the casting method and vacuum-dried at 80-100 °C until a constant weight is achieved, obtaining a solid electrolyte membrane with a thickness of 10 ± 2 μm.

[0073] Table 1

[0074]

[0075] In Table 1, η A represents the melt viscosity of the polyvinylidene fluoride or its copolymer; η B represents the melt viscosity of the polyimide or its copolymer, and the melt viscosity is obtained by testing with a rotational viscometer.

[0076] Table 2

[0077] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 P(VDF-HFP) 100 65 50 65 65 65 PI / 35 50 35 35 35 EDTA 1 / / / / 1 4-Aminobenzoic acid / / / 1 / / Hydroxybenzotriazole / / / / 1 / NaTFSI 19 19 19 19 19 19 Perfluorobenzene 1 1 1 1 1 /

[0078] In Table 2, unless otherwise specified, the selection of the molecular weight types of P(VDF-HFP) and PI is the same as that in Example 5.

[0079] Example 15

[0080] A solid electrolyte membrane is provided and is prepared by referring to the method of Example 1. The difference from Example 1 is that in the mixed solution formed by the reaction raw materials, N2 / (N1 + N2) = 10%, where the weight of the film-forming agent is denoted as N2 and the weight of the organic solvent is denoted as N1.

[0081] Example 16

[0082] A solid electrolyte membrane is provided and is prepared by referring to the method of Example 1. The difference from Example 1 is that in the mixed solution formed by the reaction raw materials, N2 / (N1 + N2) = 15%, where the weight of the film-forming agent is denoted as N2 and the weight of the organic solvent is denoted as N1.

[0083] Example 17

[0084] A solid electrolyte membrane is provided and prepared according to the method of Example 1. The difference from Example 1 is that in the mixed solution formed by each reaction raw material, N2 / (N1 + N2) = 20%, where the weight of the film-forming agent is denoted as N2 and the weight of the organic solvent is denoted as N1.

[0085] Example 18

[0086] A solid electrolyte membrane is provided and prepared according to the method of Example 1. The difference from Example 1 is that in the mixed solution formed by each reaction raw material, N2 / (N1 + N2) = 25%, where the weight of the film-forming agent is denoted as N2 and the weight of the organic solvent is denoted as N1.

[0087] Performance Test

[0088] The performance of the electrolyte membranes prepared in the above examples and comparative examples was tested. The relevant test indicators and test methods are as follows, and the test results are shown in Table 3:

[0089] (1) Young's modulus (unit: GPa): According to the standard "ASTM D638-2014", the tensile performance of the electrolyte was tested. The specific test temperature was 25 ± 1 °C, and the tensile rate was 50 mm / min.

[0090] (2) Room temperature (25 ± 1 °C) ionic conductivity: The electrolyte membrane was punched into circular pieces with a diameter of 16 mm and its thickness L and area S were measured. Subsequently, a steel-to-steel (SS / SPE / SS) symmetric cell was assembled, and the ohmic resistance R1 of the electrolyte membrane was tested by EIS (0.1 Hz - 100 kHz), and the ionic conductivity was calculated by the formula ;

[0091] (3) Cycling performance of the battery

[0092] A secondary battery was prepared, and then the kinetic performance of the secondary battery was tested. Among them, the preparation of the secondary battery included the following steps:

[0093] Prepare the positive electrode sheet

[0094] The positive electrode active material, conductive agent acetylene black, dispersant PVP, and binder polyvinylidene fluoride were dispersed in NMP according to a mass ratio of 97:0.8:0.4:1.8 to prepare a slurry, which was then coated on a 12-μm aluminum foil. After baking, rolling, and cutting, a positive electrode plate (surface density 0.22 g / 1540.25 mm 2 ) was obtained;

[0095] Prepare the negative electrode sheet

[0096] When the electrolyte salt added in the solid electrolyte membrane is NaTFSI, a sodium metal negative electrode sheet is correspondingly selected as the negative electrode;

[0097] Assemble the coin-type half cell

[0098] Stack the positive electrode sheet, the solid electrolyte membrane prepared in the above examples or comparative examples, and the negative electrode sheet in sequence and assemble a button-type half cell.

[0099] Charge the assembled button-type half cell on a blue electrochemical workstation first at a rate of 1C to 4.1V, then at a rate of 1C to 2.5V, and cycle 600 times. Calculate the cycle capacity retention rate = discharge capacity after 600 cycles / initial discharge capacity * 100%. The test results are shown in Table 3.

[0100] Table 3

[0101]

[0102]

[0103] It can be seen from the above results that:

[0104] A solid electrolyte membrane is prepared with polyvinylidene fluoride or its copolymer as the matrix, and polyimide and ethylenediaminetetraacetic acid are added to improve the crystallization performance of polyvinylidene fluoride, obtaining a dense, high Young's modulus flame-retardant composite polymer electrolyte membrane. Among them, the solid electrolyte membrane prepared in this application has a Young's modulus ≥ 9.5 GPa at a thickness of 10 μm, an ionic conductivity > 4×10 -4 S / cm at 25°C, and the capacity retention rate after 600 cycles at 1C is above 85%.

[0105] It should be noted that in this application, the amount of the polymer matrix is fixed, and different types and amounts of additives are studied to be added to the polymer matrix to improve the performance of the solid electrolyte membrane. The addition amount of the additives (such as electrolyte salts, aminopolycarboxylates) is based on 100 parts by weight of the polymer matrix.

[0106] The results of Comparative Example 6 and Examples 1, 15-18 show that when the composite electrolyte membrane does not contain perfluorobenzene, during the cycling of the battery, and under high voltage conditions, the remaining phosphate groups in the electrolyte will continuously undergo severe side reactions with the positive and negative electrode plates, and the rapid consumption of active sodium ions causes the capacity of the battery to decay rapidly. In Examples 1, 15-18, with the increase in the content of perfluorobenzene, the cycling stability of the battery is also significantly improved. This is mainly because perfluorobenzene forms a proper amount of uniform and firm solid electrolyte interface layer (SEI / CEI) on the surfaces of the positive and negative electrodes, which greatly inhibits the damage of phosphate esters to the positive and negative electrodes. However, when the content of perfluorobenzene exceeds 20%, the cycling stability of the battery will also show a certain degree of decay, which is mainly attributed to the excessive formation of the SEI film, the increase in thickness and interface impedance, and the resulting hindrance to ion transport at the interface.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application rather than to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A solid electrolyte membrane, characterized in that: The components include: A polymer matrix, an electrolyte salt, and an aminopolycarboxylate; the polymer matrix comprises polyvinylidene fluoride or a copolymer thereof, polyimide or a copolymer thereof.

2. The solid electrolyte membrane according to claim 1, characterized in that The solid electrolyte membrane comprises the following components in parts by weight: 100 parts of polymer matrix, 15-20 parts of electrolyte salt, 0.1-5 parts of film former, 1-5 parts of aminopolycarboxylate; The polymer matrix satisfies: 30%≤M2 / (M1+M2)≤45%, M1 represents the weight part of polyvinylidene fluoride or its copolymer; M2 represents the weight part of polyimide or its copolymer.

3. The solid electrolyte membrane according to claim 1, characterized in that The polyvinylidene fluoride or its copolymer includes at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, and vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene terpolymer; the polyimide or its copolymer includes at least one of polyimide, polyimide-siloxane block copolymer, and polylactic acid-polyimide block copolymer.

4. The solid electrolyte membrane according to claim 1, characterized in that The melt viscosity of the polyvinylidene fluoride or its copolymer is denoted as η A The melt viscosity of the polyimide or its copolymer is denoted as η B , satisfying: η B -η A ≥500cps.

5. The solid electrolyte membrane according to claim 4, characterized in that Satisfy at least one of the following characteristics: (1)the A =3000~4000cps; (2)the B =3500~5000cps; (3)1.0≤η B / or A ≤1.5。 6. The solid electrolyte membrane according to claim 1, characterized in that The electrolyte salt includes at least one of sodium bis(trifluoromethylsulfonyl)imide and sodium hexafluorophosphate; and / or the number of carboxyl groups in the aminopolycarboxylate is 5-6.

7. The method for preparing a solid electrolyte membrane according to any one of claims 1 to 6, characterized in that: The steps include: Polyvinylidene fluoride or its copolymer, polyimide or its copolymer, and electrolyte salt are dissolved in an organic solvent and mixed evenly, and then aminopolycarboxylate is added and dissolved to obtain a mixed solution, and a precursor film is obtained by a casting method, and dried to obtain the solid electrolyte membrane.

8. The method for preparing a solid electrolyte membrane according to claim 7, characterized in that: At least one of the following conditions is met: (1) The organic solvent comprises at least one of trimethyl phosphate, triethyl phosphate, triphenyl phosphate, and N,N-dimethylformamide; (2) The dissolving temperature is 60 to 160° C.; (3) The drying temperature is 80-100°C.

9. A secondary battery, characterized in that: It comprises a positive electrode sheet, a solid electrolyte membrane as described in any one of claims 1 to 6, and a negative electrode sheet.

10. An electrical device, characterized in that: A secondary battery comprising the secondary battery according to claim 9.

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