A solid-state battery and its composite electrolyte, preparation and application

Abstract

The present invention belongs to the field of solid-state batteries, and specifically relates to a solid-state battery and its composite electrolyte, preparation, and application. The composite electrolyte preparation steps are as follows: dissolving a base membrane polymer in solvent A to obtain a base membrane solution, forming the base membrane solution into a wet film; preforming the wet film in an environment with a humidity of 50-80% RH; then immersing the wet film in solvent B to form the base membrane; then compounding the base membrane with a precursor solution for forming an electrolyte and performing in-situ polymerization to obtain the composite electrolyte; wherein the base membrane polymer comprises at least one of polyethersulfone, sulfonated polyethersulfone, and polyetherimide; the solvent B is a mixed solvent of water and a C1-C4 alcohol, wherein the volume ratio of water to the C1-C4 alcohol is 1:0.1-10; and the precursor solution is a solution containing a monomer, a plasticizer, and an electrolytic salt. The method of the present invention can prepare a solid electrolyte with a special structure and excellent performance, such as fast charging stability.

Description

Technical Field

[0001] The present invention belongs to the field of battery materials, and in particular to the field of solid electrolyte technology. Background Art

[0002] With the rapid development of electronic products, electric vehicles, and intelligent energy storage systems, higher requirements are being placed on energy storage devices with high energy density, high safety, and long life. Traditional liquid lithium-ion batteries, due to their flammable and leaky electrolytes, have certain risks of thermal runaway and explosion, which limits their application in high-safety scenarios. To address this problem, solid-state batteries, as a new generation of energy storage technology, have gradually become a research hotspot. Solid-state batteries use solid electrolytes instead of liquid electrolytes, which not only significantly improves the thermal stability and safety of the battery, but also has a wider operating voltage window, which is conducive to matching high-capacity electrode materials, thereby increasing the overall energy density of the battery. Among the many solid-state electrolyte systems, polymer electrolytes are considered to be an ideal choice for the practical application of solid-state batteries due to their good flexibility, easy processing, and excellent interface contact. However, pure polymer electrolyte systems still face challenges such as low ionic conductivity, insufficient mechanical strength, and poor interface stability, which limit their practical application in high-performance solid-state batteries.

[0003] Adding a base film to a polymer system is a common method for improving the overall performance of polymer electrolytes. For example, patent publication number CN119725984A discloses a high-ionic conductivity solid electrolyte membrane, its preparation method, and application. Specifically, it describes a method for electrospinning and curing a polyimide precursor to obtain a polyimide base film; this is then polymerized to obtain the solid electrolyte membrane.

[0004] Patent document with publication number CN119560628A discloses an asymmetric solid electrolyte membrane that conducts ions / conducts ions and electrons, its preparation method, and a solid-state lithium metal battery. The asymmetric solid electrolyte membrane described therein includes an ion-conducting electrolyte facing the positive electrode side and an electrolyte that conducts ions and electrons while adding an electronically conductive material facing the negative electrode side.

[0005] Patent document with publication number CN118486884A discloses a solid electrolyte membrane, a preparation method thereof, and a secondary battery; wherein the solid electrolyte membrane includes a base membrane, a ceramic electrolyte layer located on one side of the base membrane, and a polymer electrolyte layer located on the other side of the base membrane.

[0006] Patent document CN118398874A discloses a composite solid electrolyte membrane, a preparation method and a secondary battery. The composite solid electrolyte membrane includes a halide electrolyte base membrane and a first electrolyte formed by an in-situ reaction on the halide electrolyte base membrane.

[0007] In summary, the existing technology discloses some base membrane-based composite solid electrolyte materials, but the ion and electron conductivity and cycle interface stability of the existing methods need to be further improved. Summary of the Invention

[0008] In response to the problems existing in existing polymer solid electrolytes, the first purpose of the present invention is to provide a method for preparing a composite electrolyte, aiming to prepare a composite electrolyte with a special physicochemical structure and excellent ion and electron conductivity and interface stability.

[0009] The second object of the present invention is to provide a composite electrolyte prepared by the preparation method and its application in the preparation of solid-state batteries.

[0010] A third object of the present invention is to provide a solid-state battery comprising the composite electrolyte.

[0011] A method for preparing a composite electrolyte comprises dissolving a base membrane polymer in solvent A to obtain a base membrane solution, forming the base membrane solution into a wet membrane; preforming the wet membrane at a humidity of 50-80% RH; then immersing the wet membrane in solvent B to form the base membrane; and then compounding the base membrane with a precursor solution for forming an electrolyte and performing in-situ polymerization to form an electrolyte on the base membrane, thereby preparing the composite electrolyte.

[0012] Wherein, the base film polymer includes at least one of polyethersulfone, sulfonated polyethersulfone, and polyetherimide; the solvent A includes at least one of dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, γ-butyrolactone, dimethylformamide, and tetrahydrofuran;

[0013] The solvent B is a mixed solvent of water and C1~C4 alcohol, wherein the volume ratio of water to C1~C4 alcohol is 1:0.1~10;

[0014] The precursor solution is a solution containing monomers, plasticizers and electrolytic salts.

[0015] The present invention pre-forms the wet film by dry method and then performs wet forming. On this basis, the base film polymer component, the pre-forming humidity and the special control of solvent B during the forming process are further coordinated to construct a base film with a dense surface or sponge structure and asymmetric vertical pores in the bulk phase. The electrolyte is further compounded on the base film, which can achieve synergy, enhance the conductivity of ions and electrons, improve interface stability, and improve the mechanical and thermal stability of the material. In this way, the electrochemical performance of the solid-state battery can be effectively improved, especially excellent fast charging stability can be exhibited under a thin electrolyte membrane.

[0016] In the present invention, the control of the type of base membrane polymer is combined with the joint control of the preforming-molding conditions to achieve synergy, which is conducive to constructing a base membrane with special asymmetric pores in the bulk phase and a dense surface, thereby improving the fast charging stability of the composite electrolyte obtained subsequently. Preferably, the base membrane polymer is polyethersulfone. Studies have shown that the preferred base membrane polymer and the process of the present invention have better adaptability, which helps to further construct the base membrane structure and help to further enhance the fast charging stability of the prepared solid electrolyte.

[0017] In the present invention, there is no particular requirement for the concentration of the basement membrane polymer in the basement membrane solution, and it may be, for example, 0.05 to 0.5 g / mL. Considering the preparation efficiency, it may be further 0.1 to 0.2 g / mL.

[0018] In the present invention, a conditioning agent is further added to the basement membrane solution. The conditioning agent includes at least one of polyethylene glycol, polyvinyl alcohol, lithium chloride, calcium chloride, polyvinyl pyrrolidone, and glycerol. Research in the present invention has shown that the combination of the preforming and molding processes and parameters, combined with the use of a conditioning agent, can further optimize the physicochemical structure of the basement membrane, further enhance the ionic and electronic conductivity of the prepared composite electrolyte, and further strengthen interfacial stability.

[0019] In the present invention, in the base film solution, the regulator accounts for 1 to 20% by weight of the base film polymer, and can further account for 5 to 15%.

[0020] In the present invention, the film forming method includes coating, spraying, blade coating or printing.

[0021] For example, the base film solution can be formed on a substrate (such as glass) to form the wet film.

[0022] In the present invention, the wet film may be exposed to an atmosphere such as air in advance and preformed under the humidity.

[0023] In the present invention, pre-forming is innovatively performed under high humidity conditions, which is conducive to constructing a sponge or dense surface, and is conducive to combining with subsequent forming, thereby further improving the fast charging stability of the prepared solid electrolyte.

[0024] Preferably, the humidity during the preforming process is 55-65% RH; further preferably 58-62% RH.

[0025] In the present invention, the preforming temperature in the preforming process is 20-35°C, and can further be 20-25°C.

[0026] In the present invention, the preforming time is 15 to 30 s; further 15 to 25 s.

[0027] In the present invention, under the preferred preforming conditions, it is helpful to further combine with the process and help to further improve the performance of the prepared solid electrolyte.

[0028] In the present invention, under the high-humidity preforming treatment, the subsequent alcohol-water solvent phase distribution forming treatment is further coordinated, which is conducive to synergistic construction of a base membrane with special asymmetric vertical pores, which is beneficial to the fast charging stability of the prepared solid electrolyte.

[0029] In the solvent B, the C1-C4 alcohol includes at least one of methanol and ethanol.

[0030] The present invention studies show that the molding process includes a first molding process under solvent B1 and a second molding process under solvent B2;

[0031] Among them, solvent B1 is solvent B with a volume ratio of water to alcohol of 1-5:6-10; solvent B2 is solvent B with a volume ratio of water to alcohol of 5-10:1-3. Research in the present invention shows that based on the special two-stage molding process, combined with the special control of the solvent composition of the two-stage molding, it is possible to further enhance the special control of the base membrane, help further construct the asymmetric vertical pore structure required for fast charging, and help further improve the fast charging stability of the prepared solid electrolyte.

[0032] Furthermore, the volume ratio of water to alcohol in solvent B1 is 3-4:6-7. The volume ratio of water to alcohol in solvent B2 is 8-10:1-2.

[0033] In the present invention, the preforming process, combined with humidity and temperature control, is further combined with subsequent segmented wet-forming processes and parameters to create asymmetric vertical pores in the base film bulk phase based on gradient phase differences. Asymmetric vertical pores refer to smaller pores on the surface and larger pores closer to the base.

[0034] In the present invention, the temperature during the molding process may be 5-35°C, and further may be 20-30°C.

[0035] In the present invention, the molding process lasts for 1 to 25 minutes. For example, when a two-stage molding process is used, the first stage molding process may last for 0.1 to 1 minute, or even 15 to 30 seconds; the second stage molding process may last for 1 to 20 minutes, or even 15 to 20 minutes.

[0036] In the present invention, the process for compounding the electrolyte on the base film can be conventional. For example, the precursor solution and the base film can be compounded by coating, spraying, doctor blade coating, or printing. The precursor solution can then be polymerized based on conventional principles and methods.

[0037] For example, in the precursor solution, the monomers include one or more of methoxypolyethylene glycol acrylate, polyethylene glycol diacrylate, polymethyl methacrylate, polyethylene oxide, polyethylene glycol, poly(vinylidene fluoride-co-hexafluoropropylene), polyvinylidene fluoride, polyacrylonitrile, and triethylene glycol dimethacrylate.

[0038] The plasticizer includes one or more of fluoroethylene carbonate, 1,3-dioxolane, ethylene glycol dimethyl ether, ethylene carbonate, diethyl carbonate, dimethyl carbonate, propylene carbonate, ethyl methyl carbonate, trifluoroacetate, dimethoxyethane, triethylene glycol dimethyl ether, and dimethyl sulfoxide.

[0039] The electrolyte salt is selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bisoxalatoborate, lithium difluorobisoxalatophosphate, lithium difluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium difluorobisoxalatophosphate, sodium difluorophosphate, potassium bis(fluorosulfonyl)imide, potassium fluoroborate, potassium hexafluorophosphate, and potassium perchlorate.

[0040] The precursor solution has a monomer content of 0.1 to 50 wt%, and a plasticizer content of 1 to 60 wt%. Furthermore, the precursor solution has a monomer content of 20 to 30 wt%, and a plasticizer content of 40 to 50 wt%. The electrolyte salt concentration is 0.1 to 5 mol / L, and further can be 0.5 to 1.5 mol / L.

[0041] In the present invention, the precursor solution further comprises at least one of a multi-arm cross-linking agent and an initiator;

[0042] Wherein, the multi-arm crosslinking agent is selected from one or more of ethoxylated glycerol triacrylate, ethoxylated bisphenol A diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, ethoxylated pentaerythritol tetraacrylate, pentaerythritol tetraacrylate, pentaerythritol glycidyl ether, trimethylolpropane triglycidyl ether, glycerol diglycidyl ether, 1,4-butanediol diglycidyl ether, and polyethylene glycol diacrylate;

[0043] The initiator can be divided into at least one of a photoinitiator and a thermal initiator according to the initiation conditions, for example, one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, azobisisobutyronitrile, 2,2-dimethoxy-2-phenylethanone, 1-hydroxycyclohexylphenyl ketone, and benzoyl peroxide;

[0044] In the precursor solution, the content of the multi-arm crosslinking agent in the precursor solution is less than 10 wt.%, and the content of the initiator is less than 5 wt.%. Furthermore, the content of the multi-arm crosslinking agent in the precursor solution is 1-5 wt.%, and the content of the initiator is 0.1-0.5 wt.%.

[0045] In the present invention, the precursor solution can be compounded on the base film based on conventional coating, printing and other processes.

[0046] In the present invention, the precursor solution can be cured and cross-linked based on a conventional ultraviolet curing process to form a solid electrolyte.

[0047] In the present invention, the wavelength of ultraviolet light irradiation is 254-365 nm, and the ultraviolet light irradiation time is 0.1-100 min.

[0048] The invention also provides a composite electrolyte prepared by the preparation method.

[0049] The preparation method described in the present invention can impart unique physicochemical characteristics to the prepared material, and based on these unique physicochemical characteristics, can exhibit excellent solid-state battery performance. For example, the composite electrolyte described in the present invention includes a base membrane with asymmetric vertical pores and an electrolyte composited on the base membrane. The thickness of the composite electrolyte can be 10-150 μm, wherein the thickness of the base membrane can be 3-100 μm.

[0050] The present invention also provides an application of the composite electrolyte prepared by the preparation method, which is used to prepare solid-state batteries.

[0051] The present invention can prepare the composite electrolyte of the present invention into a desired solid-state battery based on known principles and methods. The solid-state battery can be a solid-state lithium battery, a solid-state sodium battery, etc.

[0052] The present invention also provides a solid-state battery, comprising a positive electrode, a solid electrolyte and a negative electrode that are composited in sequence, wherein the solid electrolyte is a composite electrolyte prepared by the preparation method.

[0053] The solid-state battery of the present invention, in addition to comprising the composite electrolyte of the present invention, may have other components and structural relationships that are well known.

[0054] The solid-state battery is a fully solid-state battery or a semi-solid-state battery.

[0055] Beneficial effects

[0056] The present invention pre-forms the wet film by dry method, and then performs wet forming. On this basis, the base film polymer type, pre-forming humidity and special control of the solvent in the forming process are further coordinated, so that a base film with a dense surface or sponge structure and asymmetric vertical pores in the bulk phase can be constructed. Its asymmetric structure is manifested as a top dense layer + a bottom vertical channel layer. The bottom vertical channel layer can guide lithium ions to migrate preferentially along a specific direction, which can reduce the energy barrier of ion migration across the membrane and provide a fast transmission channel. At the same time, it has a certain flexibility compared to the dense layer, can buffer the interface stress, and adapt to expansion and contraction; the top dense layer has higher strength, can resist the growth of lithium dendrites, prevent short circuit, and thus improve the interface stability. Based on the porous base film and the adapted polymer system, the effective thickness of the polymer system electrolyte membrane can be significantly reduced, the energy density of the battery can be improved, and the conductivity and ion mobility of the composite solid electrolyte can be synergistically improved.

[0057] In the present invention, the two-stage molding process is adopted, combined with the joint control of the two-stage solvents, so that further synergy can be achieved, which helps to further enhance the fast charging stability of the prepared solid electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is an optical photograph of the base film prepared in step 1 of Example 1.

[0059] Figure 2 This is the SEM of the base film prepared in step 1 of Example 1.

[0060] Figure 3 This is the impedance diagram of the composite electrolyte membrane prepared in step 2 of Example 1.

[0061] Figure 4 This is the linear sweep voltammogram of the composite electrolyte membrane prepared in step 2 of Example 1.

[0062] Figure 5 The lithium ion transference number of the composite electrolyte membrane prepared in step 2 of Example 1 is the constant potential current time curve and the impedance change before and after.

[0063] Figure 6 Schematic diagram of the long cycle of the Li||LiCoO2 full battery with the composite electrolyte membrane prepared in step 2 of Example 1 at room temperature and 2 C rate. DETAILED DESCRIPTION

[0064] The following examples are intended to further illustrate the present invention in detail, but are not intended to limit the scope of protection of the claims of the present invention.

[0065] The present invention provides an application of the composite electrolyte as a barrier layer for preparing a solid-state or semi-solid-state secondary battery;

[0066] Furthermore, it is arranged between the positive electrode and the negative electrode;

[0067] Further, it is compounded on the positive electrode to form a composite positive electrode, and / or, it is compounded on the negative electrode to form a composite negative electrode;

[0068] Furthermore, the solid-state or semi-solid-state secondary battery is a lithium-ion battery and / or a sodium-ion battery.

[0069] The present invention also provides a solid-state or semi-solid-state secondary battery, comprising the composite electrolyte, or prepared by using the composite electrolyte.

[0070] The solid-state or semi-solid-state secondary battery of the present invention may contain, in addition to the composite solid-state electrolyte of the present invention, other components and structures thereof may be known.

[0071] In the present invention, the application of the asymmetric vertical pore base membrane composite solid electrolyte prepared by any one of the preparation methods described above in lithium metal, sodium metal or potassium metal batteries.

[0072] In the following embodiments, the selected negative electrode is lithium metal, and the specific performance testing method includes the following steps:

[0073] (1) Impedance test: In a glove box, the prepared composite solid electrolyte membrane was sandwiched between two steel sheets to form a CR2025 button cell. The cell was tested using the electrochemical impedance spectroscopy (EIS) technique in a Gamry electrochemical workstation.

[0074] (2) Electrochemical stability window test: The prepared composite solid electrolyte membrane was sandwiched between a steel sheet and a commercial lithium sheet to form a CR2025 button cell in a glove box. The cell was tested using linear sweep voltammetry (LSV) on a Gamry electrochemical workstation.

[0075] (3) Ion migration number test: In a glove box, the prepared composite solid electrolyte membrane was sandwiched between two commercial lithium sheets to form a CR2025 button cell. The cell was tested using electrochemical impedance spectroscopy (EIS) and potentiostatic polarization on a Gamry electrochemical workstation to measure the constant potential current change and the impedance change before and after the cell.

[0076] (4) LiCoO2 battery (Li||LiCoO2 full battery):

[0077] In a glove box, the prepared composite solid-state electrolyte membrane was sandwiched between a lithium sheet (d = 15.4 mm) and a LiCoO2 positive electrode to form a CR2025 button cell. The battery's charge and discharge performance was tested using a LAND battery testing system. The LiCoO2 battery was tested at a 2C charge and discharge rate (five cycles at initial activation temperatures of 0.2, 0.5, and 1C). The voltage range of the LiCoO2 battery was 3-4.3 V. The battery was then cycled for 400 cycles at 2C and 25°C.

[0078] In the present invention, the ion transference number refers to the lithium ion transference number in a lithium ion battery.

[0079] In the present invention, the film-forming substrate may be an existing commercial polymer with a molecular weight of 20,000 to 80,000. As an alternative, polyethersulfone has an Mn of ≈60,000, sulfonated polyethersulfone has an Mn of ≈50,000, and polyetherimide has an Mn of ≈28,000.

[0080] Example 1

[0081] A composite electrolyte based on an asymmetric vertical pore base membrane, wherein the membrane-forming substrate is polyethersulfone, the solvent is dimethylacetamide, the regulator is polyvinylpyrrolidone, the polymer monomer is methoxypolyethylene glycol acrylate, the lithium salt is lithium bis(trifluoromethanesulfonyl imide), the plasticizer is fluoroethylene carbonate, the crosslinker is trimethylolpropane triacrylate, and the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0082] Step 1: Basement membrane preparation:

[0083] (1.1) Dissolve 0.5 g of polyethersulfone and 0.05 g of polyvinylpyrrolidone in 3 ml of dimethylacetamide and stir at 60°C for 6 h.

[0084] (1.2) Preforming:

[0085] The film-forming solution was coated onto a glass plate using a 50 μm doctor blade and then preformed in an air atmosphere at 60% RH and 25 °C (preforming time was 20 s).

[0086] (1.3) Molding:

[0087] Then, it is immersed in solvent B1 (solvent B1 is a mixture of water and ethanol with a volume ratio of 3:7) for 15 seconds to perform the first step of molding; then immersed in solvent B2 (a mixture of water and ethanol with a volume ratio of 10:1) for 20 minutes to perform the second step of molding;

[0088] (1.4) Dry at 50 °C for 24 h to obtain a base membrane (also called an asymmetric vertical pore base membrane with a thickness of 20 μm).

[0089] Step 2: The preparation method of the composite solid electrolyte includes the following steps:

[0090] (2.1) Precursor solution: A solution containing a polymer monomer (methoxy polyethylene glycol acrylate, in this case, the amount used can be 0.5 g), a lithium salt (lithium bistrifluoromethanesulfonyl imide), a plasticizer (fluoroethylene carbonate), a cross-linker (trimethylolpropane triacrylate), and a photoinitiator (2-hydroxy-2-methyl-1-phenyl-1-propanone). In the precursor solution, the polymer monomer content is 27.1 wt.%, the plasticizer content is 43.4 wt.%, the cross-linker content is 2.7 wt.%, and the photoinitiator content is 0.3 wt.%; the balance is lithium salt.

[0091] (2.2) The precursor solution was scraped onto one side of the asymmetric vertical pore base membrane and transferred to a 365 nm UV lamp for UV polymerization for 3 min to obtain the composite electrolyte membrane (total thickness of 26 μm).

[0092] The room temperature ionic conductivity of the composite solid electrolyte (M-CPE) prepared in Example 1 is 2.8×10 -4 Scm -1 The electrochemical window is 4.86 V, the migration number is 0.24, and the assembled LiCoO2 battery can be stably cycled for 400 cycles at a high rate of 2 C with a capacity retention rate of 90%.

[0093] Example 2

[0094] Compared with Example 1, the only difference is that the composition of the film-forming substrate is changed. Other operations and parameters are the same as Example 1. The experimental results are as follows:

[0095] Group A: The membrane substrate is sulfonated polyethersulfone. Other operations and parameters are the same as in Example 1. The results are: the ionic conductivity is 2.5×10 -4 S cm -1 , the electrochemical window is 4.76 V, the migration number is 0.19, and the assembled LiCoO2 battery is cycled 400 times at 2 C with a capacity retention rate of 74%.

[0096] Group B: The film-forming substrate is polyetherimide. Other operations and parameters are the same as in Example 1. The results are: ionic conductivity is 2.3×10 -4 S cm -1 , the electrochemical window is 4.80 V, the migration number is 0.20, and the assembled LiCoO2 battery is cycled 400 times at 2 C with a capacity retention rate of 72%.

[0097] It can be seen from Examples 1 and 2 that the use of sulfonated polyethersulfone, polyetherimide, and polyethersulfone as base membrane polymers, especially polyethersulfone as the base membrane polymer, can adapt to the process of the present invention and obtain better fast charging stability.

[0098] Example 3

[0099] Compared with Example 1, the only difference is that the preforming conditions in step 1.2 are changed. The experimental groups are:

[0100] Group A: preformed at 65% RH;

[0101] Group B: preformed at 55% RH;

[0102] Group C: preforming temperature was 30 °C and preforming time was 10 s;

[0103] Other operations, parameters and tests are the same as in Example 1, and the results are as follows:

[0104] Group A: ionic conductivity is 2.5×10 -4 S cm -1 , the electrochemical window is 4.87 V, the migration number is 0.23, and the assembled LiCoO2 battery is cycled 400 times at 2 C with a capacity retention rate of 91%;

[0105] Group B: ionic conductivity is 3.0×10 -4 S cm -1 , the electrochemical window is 4.78 V, the migration number is 0.20, and the assembled LiCoO2 battery is cycled 400 times at 2 C with a capacity retention rate of 86%;

[0106] Group C: ionic conductivity is 2.1×10 -4 S cm -1 , the electrochemical window is 4.75 V, the migration number is 0.21, and the assembled LiCoO2 battery is cycled 400 times at 2 C with a capacity retention rate of 88%.

[0107] Example 4

[0108] Compared with Example 1, the only difference is that the molding conditions in step 1.3 are changed. The experimental groups are:

[0109] Group A: The preformed membrane was formed in solvent B1 for the first stage only, and the time for the first stage was 20 min + 15 s; other operations and parameters were the same as those in Example 1;

[0110] Group B: The preformed film was directly subjected to the second stage of molding in solvent B2 without undergoing the first stage of molding, and the second stage of molding time was 20 min + 15 s; other operations and parameters were the same as in Example 1;

[0111] Group C: Two-stage molding process, wherein solvent B1 is a mixture of water and ethanol in a volume ratio of 4:6, and the first stage molding time is 30 s; solvent B2 is a mixture of water and ethanol in a volume ratio of 8:2, and the second stage molding time is 15 min; other operations and parameters are the same as Example 1.

[0112] The results are:

[0113] Group A: ionic conductivity is 2.1×10 -4 S cm -1 , the electrochemical window is 4.67 V, the migration number is 0.21, and the assembled LiCoO2 battery is cycled 400 times at 2 C with a capacity retention rate of 81%;

[0114] Group B: ionic conductivity is 2.3×10 -4 S cm -1 , the electrochemical window is 4.58 V, the migration number is 0.21, and the assembled LiCoO2 battery is cycled 400 times at 2 C with a capacity retention rate of 76%;

[0115] Group C: ionic conductivity is 2.6×10 -4 S cm -1 The electrochemical window is 4.79 V, the migration number is 0.23, and the assembled LiCoO2 battery is cycled 400 times at 2 C with a capacity retention rate of 89%.

[0116] It can be seen from Examples 1 and 4 that the use of the alcohol-water combined molding process described in the present invention for molding treatment is beneficial to the fast charging stability of the solid electrolyte.

[0117] Example 5

[0118] Compared with Example 1, the only difference is that the composition of the precursor solution in step 2 is changed, specifically:

[0119] The precursor solution contains triethylene glycol dimethacrylate as the polymer monomer (25 wt.%), lithium hexafluorophosphate as the lithium salt, ethylene glycol dimethyl ether as the plasticizer (50 wt.%), trimethylolpropane triacrylate as the crosslinker (2 wt.%), and phenyl di(2,4,6-trimethylbenzoyl)phosphine oxide as the photoinitiator (0.2 wt.%). The balance is the lithium salt. The light curing time is 2 minutes.

[0120] Other operations, parameters and tests are the same as in Example 1.

[0121] The room temperature ionic conductivity of the composite solid electrolyte (M-CPE) prepared in Example 5 is 2.6×10 -4 Scm -1 The electrochemical window is 4.82 V, the migration number is 0.23, and the assembled LiCoO2 battery can be stably cycled for 400 cycles at a high rate of 2 C with a capacity retention rate of 87%.

[0122] Comparative Example 1

[0123] Compared with Example 1, the only difference is that the membrane substrate is polysulfone. Other operations and parameters are the same as in Example 1. The results are: the ionic conductivity is 1.1×10 -4 S cm -1 , the electrochemical window is 4.77 V, the migration number is 0.20, and the assembled LiCoO2 battery is cycled 400 times at 2 C with a capacity retention rate of 51%.

[0124] Comparative Example 2

[0125] Compared with Example 1, the only difference is that the preforming conditions in step 1.2 are changed. The experimental groups are:

[0126] Comparative group A: preformed humidity was 20% RH;

[0127] Comparative group B: preformed at 40% RH;

[0128] The results are:

[0129] Compared with group A: the ionic conductivity is 9.8×10 -5 S cm -1 , the electrochemical window is 4.59 V, the migration number is 0.20, and the assembled LiCoO2 battery is cycled 400 times at 2 C with a capacity retention rate of 55%;

[0130] Compared with group B: the ionic conductivity was 6.3×10 -5 S cm -1 The electrochemical window is 4.55 V, the migration number is 0.18, and the assembled LiCoO2 battery is cycled 400 times at 2 C with a capacity retention rate of 67%.

[0131] Comparative Example 3

[0132] Compared with Example 1, the only difference is that in step 1.3, solvent B1 and solvent B2 are both water, and other operations and parameters are the same as in Example 1.

[0133] The results showed that the ionic conductivity was 1.1×10 -4 S cm-1 , the electrochemical window is 4.64 V, and the migration number is 0.16; the assembled LiCoO2 battery is cycled 400 times at 2 C with a capacity retention rate of 57%.

[0134] Comparative Example 4

[0135] Compared with Example 1, the only difference is that in step 1.3, solvent B1 and solvent B2 are both ethanol, and other operations and parameters are the same as in Example 1.

[0136] The results showed that the ionic conductivity was 2.2×10 -5 S cm -1 , the electrochemical window is 4.76 V, and the migration number is 0.21; the assembled LiCoO2 battery is cycled 400 times at 2 C with a capacity retention rate of 71%.

[0137] It can be seen from Example 1 and Comparative Examples 1 to 4 that the wet membrane is preformed by a dry method and then wet-formed. On this basis, the type of base membrane polymer, the humidity of the preforming, and the special control of the solvent during the forming process are further coordinated. In this way, a base membrane with a dense surface or sponge structure and asymmetric vertical pores in the bulk phase can be constructed, which can improve the performance of the solid electrolyte, such as fast charging stability.

[0138] In addition, it can be seen from Examples 1 and 4 that the two-stage molding process described above, combined with the joint control of the two-stage solvents, can further achieve synergy and help further enhance the fast-charging stability of the prepared solid electrolyte.

Claims

1. A method for preparing a composite electrolyte, characterized in that: The base membrane polymer is dissolved in solvent A to obtain a base membrane solution, and the base membrane solution is formed into a wet membrane; the wet membrane is preformed at a humidity of 50-80% RH; the wet membrane is then immersed in solvent B to form the base membrane; the base membrane and a precursor solution for forming an electrolyte are then compounded and in-situ polymerized to form an electrolyte on the base membrane, thereby preparing the composite electrolyte; Wherein, the base film polymer includes at least one of polyethersulfone, sulfonated polyethersulfone, and polyetherimide; the solvent A includes at least one of dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, γ-butyrolactone, dimethylformamide, and tetrahydrofuran; The solvent B is a mixed solvent of water and C1~C4 alcohol; The molding process includes a first molding process under solvent B1 and a second molding process under solvent B2; Wherein, solvent B1 is solvent B with a volume ratio of water to alcohol of 1-5:6-10; solvent B2 is solvent B with a volume ratio of water to alcohol of 5-10:1-3; The precursor solution is a solution containing monomers, plasticizers and electrolyte salts.

2. The method for preparing a composite electrolyte according to claim 1, wherein The concentration of the basement membrane polymer in the basement membrane solution is 0.05 to 0.5 g / mL; A regulator is further added to the basement membrane solution, and the regulator includes at least one of polyethylene glycol, polyvinyl alcohol, lithium chloride, calcium chloride, polyvinyl pyrrolidone, and glycerol; In the base film solution, the regulator is 1-20% by weight of the base film polymer.

3. The method for preparing a composite electrolyte according to claim 1, wherein Film forming methods include spraying, doctor blade coating or printing; The preforming temperature is 20~35℃; The preforming time is 15~30 s.

4. The method for preparing a composite electrolyte according to claim 1, wherein In the solvent B, the C1-C4 alcohol includes at least one of methanol and ethanol.

5. The method for preparing a composite electrolyte according to claim 1 or 4, wherein: The volume ratio of water to alcohol in solvent B1 is 3~4:6~7; the volume ratio of water to alcohol in solvent B2 is 8~10:1~2.

6. The method for preparing a composite electrolyte according to claim 1, wherein In the precursor solution, the monomers include one or more of methoxy polyethylene glycol acrylate, polyethylene glycol diacrylate, polymethyl methacrylate, polyethylene oxide, polyethylene glycol, poly(vinylidene fluoride-co-hexafluoropropylene), polyvinylidene fluoride, polyacrylonitrile, and triethylene glycol dimethacrylate; The plasticizer includes one or more of fluoroethylene carbonate, 1,3-dioxolane, ethylene glycol dimethyl ether, ethylene carbonate, diethyl carbonate, dimethyl carbonate, propylene carbonate, ethyl methyl carbonate, trifluoroacetate, dimethoxyethane, triethylene glycol dimethyl ether, and dimethyl sulfoxide; The electrolyte salt is selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bisoxalatoborate, lithium difluorobisoxalatophosphate, lithium difluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium difluorobisoxalatophosphate, sodium difluorophosphate, potassium bis(fluorosulfonyl)imide, potassium fluoroborate, potassium hexafluorophosphate, and potassium perchlorate; In the precursor solution, the content of the monomer is 0.1~50 wt.%, the content of the plasticizer is 1~60 wt.%, and the concentration of the electrolyte salt is 0.1~5 mol / L.

7. The method for preparing a composite electrolyte according to claim 1 or 6, wherein: The precursor solution further comprises at least one of a multi-arm cross-linking agent and an initiator; Wherein, the multi-arm crosslinking agent is selected from one or more of ethoxylated glycerol triacrylate, ethoxylated bisphenol A diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, ethoxylated pentaerythritol tetraacrylate, pentaerythritol tetraacrylate, pentaerythritol glycidyl ether, trimethylolpropane triglycidyl ether, glycerol diglycidyl ether, 1,4-butanediol diglycidyl ether, and polyethylene glycol diacrylate; The initiator is selected from one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, azobisisobutyronitrile, 2,2-dimethoxy-2-phenylethanone, 1-hydroxycyclohexylphenyl ketone, and benzoyl peroxide; In the precursor solution, the content of the multi-arm cross-linking agent is less than 10 wt.%, and the content of the initiator is less than 5 wt.%.

8. A composite electrolyte prepared by the preparation method according to any one of claims 1 to 7.

9. Use of a composite electrolyte prepared by the preparation method according to any one of claims 1 to 7, characterized in that: It is used to prepare solid-state batteries.

10. A solid-state battery comprising a positive electrode, a solid electrolyte and a negative electrode which are compounded in sequence, characterized in that: The solid electrolyte is a composite electrolyte prepared by the preparation method according to any one of claims 1 to 7.

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