Preparation method of ultrathin self-supporting composite solid-state electrolyte membrane and solid-state battery

Abstract

The invention discloses a preparation method of an ultrathin self-supporting composite solid-state electrolyte membrane and a solid-state battery, and relates to the technical field of solid-state electrolyte. The binary composite cross membrane with the ion-conducting characteristic and the high-strength heat-resistant characteristic is prepared through synchronous electrostatic spinning, and the binary composite cross membrane is composed of ion-conducting polymer fibers and a high-strength heat-resistant fiber matrix; and then repeatedly carrying out vacuum impregnation-drying on the sulfide electrolyte slurry in the composite membrane, and finally rolling to obtain the ultrathin high-ion-conductivity high-temperature-resistant self-supporting electrolyte membrane. The mechanical strength and the thermal stability of the electrolyte membrane can be considered, meanwhile, an effective transmission path of ions in the middle layer is increased, and the tortuosity of the ion transmission process is reduced, so that the ion transmission characteristic of the electrolyte membrane is improved.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte technology, and more specifically, to a method for preparing an ultrathin self-supporting composite solid electrolyte membrane and a solid battery. Background Technology

[0002] Solid-state batteries, with their inherent safety and high energy density, are considered a promising next-generation electrochemical energy storage technology. Among them, sulfide solid electrolytes exhibit outstanding practical potential due to their ultra-high ionic conductivity. However, the inherent brittleness of these electrolytes and the difficulty in large-scale processing into films severely limit their further application in solid-state batteries.

[0003] The thin-film and flexible development of solid-state electrolytes is a key direction for driving breakthroughs in solid-state battery technology and achieving industrial applications. Currently, there are two main technical approaches for preparing self-supporting sulfide electrolyte membranes: First, a mixture of a binder with shear-fiber properties (such as PTFE) or a low-melting-point thermoplastic binder (such as polyamide) with the sulfide electrolyte is rolled into a film. While this achieves self-support, the resulting film generally has low mechanical strength, poor interfacial reliability, and is difficult to achieve ultra-thinness, thus sacrificing the battery's energy density. Second, a mechanically supported framework (such as cellulose membranes, p-phenylenediamine terephthalate nonwoven fabrics, PET nonwoven fabrics, etc.) is used as a carrier. The sulfide electrolyte is filled into the pores of the framework, or it is directly pressed with a dry electrolyte membrane to improve the membrane's mechanical strength. However, in this approach, the ion-inert framework layer often hinders ion transport, and the sulfide filling is not always sufficient, leading to a decrease in overall ionic conductivity, which is detrimental to the battery's rate performance.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a method for preparing an ultrathin self-supporting composite solid electrolyte membrane and a solid-state battery. First, a binary composite cross-linked membrane, combining ion-conducting properties with high strength and heat resistance, is prepared by simultaneous electrospinning. This membrane consists of ion-conducting polymer fibers and a high-strength, heat-resistant fiber matrix. Subsequently, a sulfide electrolyte slurry is repeatedly vacuum-impregnated and dried within the composite membrane, and finally rolled to obtain an ultrathin, highly ion-conducting, and high-temperature-resistant self-supporting electrolyte membrane. This method balances the mechanical strength and thermal stability of the electrolyte membrane while increasing the effective ion transport pathway in the intermediate layer and reducing the tortuosity of the ion transport process, thereby improving the ion transport characteristics of the electrolyte membrane.

[0006] This invention is implemented as follows: In a first aspect, the present invention provides a method for preparing an ultrathin self-supporting composite solid electrolyte membrane, comprising the following steps: The polymer matrix and lithium salt are added to the first solvent and stirred until transparent. Then, a fast ion conductor is added and stirred until a uniform dispersion is formed to form an ion-conducting polymer fiber precursor solution. The high-temperature resistant high-strength fiber and the first solvent are stirred and mixed to form a heat-resistant high-strength fiber precursor solution. The ion-conducting polymer fiber precursor solution and the heat-resistant high-strength fiber precursor solution are simultaneously spun onto a collector by electrospinning to obtain a binary composite cross-linked membrane. The adhesive particles and the second solvent are mixed and dissolved by stirring to form an adhesive solution. Then, the adhesive solution, sulfide solid electrolyte powder, and the second solvent are stirred and dispersed to form a uniform sulfide electrolyte slurry. The sulfide electrolyte slurry is uniformly permeated and filled into the binary composite cross-fiber membrane through multiple vacuum impregnation-drying processes, and finally an ultra-thin self-supporting sulfide electrolyte membrane is obtained through a roll pressing process.

[0007] In some preferred embodiments, the polymer matrix in the ion-conducting polymer fiber precursor solution accounts for 1%-8% by mass, the fast ion conductor accounts for 5%-30% by mass, and the mass ratio of the polymer matrix to the lithium salt is 2:(0.1-1).

[0008] In some preferred embodiments, the first solvent is at least one of dimethylformamide, dimethylacetamide, N-methylpyrrolidone, acetone, tetrahydrofuran, dimethyl sulfoxide, and imidazole ionic liquids; the polymer matrix includes at least one of polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, and polyvinyl alcohol; the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(difluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(oxalateborate), and lithium difluorooxalateborate; the fast ion conductor includes at least one of garnet-type lithium lanthanum zirconium oxide, perovskite-type lithium lanthanum titanium oxide, and lithium aluminum titanium phosphate.

[0009] In some preferred embodiments, the heat-resistant high-strength fiber in the heat-resistant high-strength fiber precursor solution is 1%-10% by mass; the heat-resistant high-strength fiber includes at least one of polyvinyl alcohol, polyethersulfone, polyaramid, polyetherimide and polyimide.

[0010] In some preferred embodiments, during the preparation of the ion-conducting polymer fiber precursor solution and the heat-resistant high-strength fiber precursor solution, the stirring speed is 300-800 rpm, the stirring time is 12-24 h, and the stirring temperature is 25-80℃; during the electrospinning process, the spinning voltage is 5-20 kV, the distance between the spinning needle and the collector is 5-20 cm, and the liquid supply rate of the spinning syringe is 1-5 ml / h.

[0011] In some preferred embodiments, the mass fraction of adhesive particles in the adhesive solution is 3%-10%; in the sulfide electrolyte slurry, the mass ratio of sulfide electrolyte to adhesive is (99:1)-(95:5), and the solid content is 30%-70%.

[0012] In some preferred embodiments, the sulfide solid electrolyte is one of a glass phase electrolyte or a crystalline phase electrolyte; the particles include at least one of styrene-butadiene rubber, nitrile rubber, hydrogenated styrene-butadiene rubber, and carboxylated styrene-butadiene rubber; the second solvent is a non-polar or low-polar solvent, including at least one of benzene solvents, ester solvents, or alkane solvents.

[0013] In some preferred embodiments, the stirring speed during the preparation of the adhesive solution is 200-1000 rpm, the stirring time is 12-24 h, and the heating temperature is 40-60℃; the stirring speed during the preparation of the sulfide electrolyte slurry is 1000-2000 rpm, and the stirring time is 1-5 h.

[0014] In some preferred embodiments, the vacuum degree of the vacuum impregnation-drying process is 0.1-50 kPa, the drying temperature is 40-80℃, and the drying time is 1-5 h; the roller gap of the roller pressing process is 0.01-0.2 mm, the roller pressure is 0.5T-5T, and the roller speed is 1-5 cm / min.

[0015] Secondly, the present invention provides a solid-state battery, which includes a positive electrode, a negative electrode and a solid electrolyte membrane disposed between the positive electrode and the negative electrode, wherein the solid electrolyte membrane is an ultrathin self-supporting composite solid electrolyte membrane obtained by the above preparation method, the positive electrode is a high nickel positive electrode and the negative electrode is a lithium indium alloy.

[0016] The present invention has the following beneficial effects: (1) The present invention uses electrospinning to prepare a binary composite cross-mechanical skeleton fiber membrane. The fiber diameter, fiber membrane thickness and pore size are controllable and adjustable, thereby obtaining an ultra-thin electrolyte membrane. At the same time, the amount of sulfide electrolyte filling is increased, which effectively improves the ion transport capacity of the electrolyte membrane.

[0017] (2) The binary composite cross membrane proposed in this invention has a polymer fiber matrix with good ion transport characteristics, which avoids the hindrance effect of conventional non-ion-conducting fiber membranes on ion transport. Ions are transported directly along the ion-conducting fibers, providing multiple transport pathways for ions, reducing the tortuosity of ion transport, and greatly improving the ion transport capability of the electrolyte membrane. In addition, the high-strength heat-resistant fiber matrix can greatly improve the mechanical strength and high-temperature thermal stability of the electrolyte membrane, which helps to further improve the thermal safety of solid-state batteries.

[0018] (3) In this invention, the sulfide electrolyte slurry is repeatedly vacuum impregnated and dried with the composite cross-linked membrane. The slurry can penetrate evenly into the fiber membrane, increasing the amount of sulfide filling in the fiber membrane. At the same time, the sulfide particles and fibers can form a strong interfacial bond, reducing the interfacial contact resistance. Roll pressing can further reduce the gap between the filling fibers, improve the density of the sulfide electrolyte membrane, and significantly improve the ionic conductivity of the electrolyte membrane. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the ultrathin self-supporting solid electrolyte membrane prepared according to an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0022] The following provides a detailed description of the preparation method of an ultrathin self-supporting composite solid electrolyte membrane and the solid electrolyte proposed in this invention.

[0023] In a first aspect, the present invention provides a method for preparing an ultrathin self-supporting composite solid electrolyte membrane, comprising the following steps: S1. The polymer matrix and lithium salt are added to the first solvent and stirred until transparent. Then, a fast ion conductor is added and stirred until a uniform dispersion is formed to form an ion-conducting polymer fiber precursor solution.

[0024] In some preferred embodiments, in the ion-conducting polymer fiber precursor solution, the polymer matrix accounts for 1%-8% by mass, the fast ion conductor accounts for 5%-30% by mass, and the mass ratio of polymer matrix to lithium salt is 2:(0.1-1), preferably 2:1.

[0025] Furthermore, the first solvent is at least one of dimethylformamide (DMF), dimethylacetamide (DMA), N-methylpyrrolidone (NMP), acetone (AC), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), and imidazole ionic liquids, including but not limited to 1-butyl-3-methylimidazolium chloride. The polymer matrix includes at least one of polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinylidene fluoride, polymethyl methacrylate (PMMA), and polyvinyl alcohol (PVA), wherein polyvinylidene fluoride includes, but is not limited to, polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP). The lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(difluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bis(oxalateborate)borate (LiBOB), and lithium difluorooxalateborate (LiDFOB). The fast ion conductor includes, but is not limited to, oxide-based solid electrolytes, which include at least one of garnet-type lithium lanthanum zirconium oxide, perovskite-type lithium lanthanum titanium oxide, and NASICON-type lithium aluminum titanium phosphate.

[0026] S2, high-temperature resistant high-strength fiber and the first solvent are stirred and mixed to form a heat-resistant high-strength fiber precursor solution.

[0027] In some preferred embodiments, the heat-resistant high-strength fiber precursor solution contains 1%-10% by mass of heat-resistant high-strength fiber; the heat-resistant high-strength fiber includes at least one of polyvinyl alcohol (PVA), polyethersulfone (PES), polyaramid (PMIA), polyetherimide (PEI), and polyimide (PI).

[0028] It should be noted that steps S1 and S2 are not sequential and can be performed simultaneously. During the preparation of steps S1 and S2, the stirring speed is 300-800 rpm, the stirring time is 12-24 h, and the stirring temperature is 25-80℃.

[0029] S3. The ion-conducting polymer fiber precursor solution and the heat-resistant high-strength fiber precursor solution are simultaneously spun onto the collector by electrospinning to obtain a binary composite cross-linked membrane.

[0030] The thickness of the binary composite cross-linked membrane can be adjusted by controlling the amount of spinning precursor solution or the spinning time, and the fiber diameter can be controlled by adjusting the spinning voltage, the orifice diameter of the spinning needle, and the distance to the collector. Therefore, in some preferred embodiments, during the electrospinning process, the spinning voltage is 5-20kV, the distance between the spinning needle and the collector is 5-20cm, and the liquid supply rate of the spinning syringe is 1-5ml / h.

[0031] The binary composite cross-linked mechanical framework fiber membrane prepared by this invention has polymer fibers with good lithium conductivity that can act as fast ion transport channels, reduce ion transport tortuosity, and avoid the hindrance effect of traditional non-lithium-conducting fiber frameworks on ion transport. At the same time, the heat-resistant high-strength fibers in the fiber framework can significantly improve the mechanical strength and high-temperature thermal stability of the electrolyte membrane.

[0032] S4. The adhesive particles and the second solvent are mixed and dissolved by stirring to form an adhesive solution. Then, the adhesive solution, sulfide solid electrolyte powder and the second solvent are stirred and dispersed to form a uniform sulfide electrolyte slurry.

[0033] In some preferred embodiments, the mass fraction of adhesive particles in the adhesive solution is 3%-10%; in the sulfide electrolyte slurry, the mass ratio of sulfide electrolyte to adhesive is (99:1)-(95:5), and the solid content is 30%-70%.

[0034] The sulfide solid electrolyte is either a glassy phase electrolyte or a crystalline phase electrolyte. The glassy phase electrolyte includes, but is not limited to, a binary or multi-component system composed of Li₂S and other sulfides such as P₂S₅, SiS₂, B₂S₃, and GeS₃. The crystalline phase electrolyte includes, but is not limited to, LiGeP₂S. 12 One of the following: (LGPS), lithium-sulfur silver-germanium ore (LiPS5X, X = Cl, Br or I); The rubber particles include at least one of styrene-butadiene rubber (SBR), nitrile rubber (NBR), hydrogenated styrene-butadiene rubber (SEBS), and carboxylated styrene-butadiene rubber (XSBR); The second solvent is a nonpolar or low-polar solvent, including at least one of benzene solvents, ester solvents or alkane solvents. Benzene solvents include, but are not limited to, toluene and xylene. Ester solvents include, but are not limited to, ethyl acetate and isobutyl isobutyrate. Alkane solvents include, but are not limited to, cyclohexane and isododecane.

[0035] In some preferred embodiments, the stirring speed during the preparation of the adhesive solution is 200-1000 rpm, the stirring time is 12-24 h, and the heating temperature is 40-60℃; the stirring speed during the preparation of the sulfide electrolyte slurry is 1000-2000 rpm, and the stirring time is 1-5 h.

[0036] It should be noted that steps S4 and S1, 2 and 3 are not in any particular order and can be performed simultaneously.

[0037] S5. The sulfide electrolyte slurry is uniformly permeated and filled into the binary composite cross-fiber membrane through multiple vacuum impregnation-drying processes, and finally an ultra-thin self-supporting sulfide electrolyte membrane is obtained through a roll pressing process.

[0038] In some preferred embodiments, the vacuum degree of the vacuum impregnation-drying process is 0.1-50 kPa, the drying temperature is 40-80℃, and the drying time is 1-5 h; the roller gap of the roller pressing process is 0.01-0.2 mm, the roller pressure is 0.5T-5T, and the roller speed is 1-5 cm / min.

[0039] In this invention, the sulfide electrolyte slurry is repeatedly vacuum-impregnated to uniformly penetrate the fiber skeleton. This increases the sulfide electrolyte loading and, moreover, the binder in the slurry enhances the interfacial bonding between the sulfide electrolyte particles and the fiber skeleton. Furthermore, roller pressing further reduces the porosity of the fiber layer, increasing the density of the electrolyte membrane and significantly improving the electrolyte's ionic conductivity. In contrast, traditional methods often involve directly pressing a solid electrolyte membrane onto a fiber skeleton to form a self-supporting membrane. This results in uneven distribution and filling of the sulfide electrolyte within the fiber skeleton, along with low bonding strength, leading to increased interfacial impedance and a significant decrease in ionic conductivity.

[0040] The preparation method proposed in this invention can produce an ultrathin self-supporting composite solid electrolyte membrane with a thickness of less than 30 micrometers. The ultrathin electrolyte membrane thickness reduces the obstacle to ion transport in the electrolyte membrane, improving the rate performance of the battery. On the other hand, it is beneficial to significantly improve the volumetric and mass energy density of the battery.

[0041] Secondly, the present invention provides a solid-state battery, which includes a positive electrode, a negative electrode and a solid electrolyte membrane disposed between the positive electrode and the negative electrode, wherein the solid electrolyte membrane is an ultrathin self-supporting composite solid electrolyte membrane obtained by the above preparation method, the positive electrode is a high nickel positive electrode and the negative electrode is a lithium indium alloy.

[0042] Its preparation method includes the following steps: S1. Use a cutting machine to cut the film into ultra-thin support electrolyte membrane discs with a diameter of 10 mm, and place them in a glove box for later use; S2. Solid-state mold batteries are assembled in a glove box under an argon atmosphere, according to the structure of high-nickel cathode - ultra-thin self-supporting electrolyte membrane - lithium indium alloy.

[0043] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0044] Example 1 This embodiment provides a method for preparing an ultrathin self-supporting composite solid electrolyte membrane, the steps of which include: S1. Preparation of binary composite cross-supported membrane: 2g of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP, Sigma-Aldrich, 427187) and 2g of lithium salt LiTFSI were dispersed in 98g of N-methylpyrrolidone (NMP) solvent and stirred at 80 °C to form a 2% (w / w) PVDF-HFP solution. Then, 10% (w / w) of fast ion conductor LLZO was added to the above PVDF-HFP solution and stirred thoroughly to form a precursor solution for ion-conducting fiber spinning. 5g of poly(isophthalamide) (PMIA) was dispersed in 95g of DMA solvent and mechanically stirred to form a 5% (w / w) heat-resistant high-strength fiber spinning precursor solution. Subsequently, a binary composite cross-supported membrane was prepared by synchronous electrospinning, with the spinning voltage set to 15kV and the collector distance from the spinning needle 15cm.

[0045] S2, Preparation of sulfide electrolyte slurry: First, add 5g of SBR granules to 95g of xylene solvent and mechanically stir to dissolve for 12 hours to form an SBR solution with a mass fraction of 5%.

[0046] S3. Preparation of ultrathin self-supporting electrolyte membrane: 20g of sulfide electrolyte LPSC was added to a certain amount of SBR adhesive and xylene mixture and mechanically stirred at 1200rpm for 5h to form an LPSC sulfide electrolyte slurry with a sulfide electrolyte to SBR mass ratio of 99:1 and a solid content of 60%. The prepared sulfide slurry was vacuum impregnated into a binary composite cross-supported mechanical membrane and dried at 50℃ for 1h to evaporate the solvent. This process was repeated three times to obtain a sulfide-filled binary composite membrane. Finally, an ultrathin self-supporting sulfide electrolyte membrane was obtained through mechanical rolling. Figure 1 As shown.

[0047] Example 2 This embodiment provides a method for preparing an ultrathin self-supporting composite solid electrolyte membrane, which is the same as that in Example 1, except that the concentration of the polymer PVDF-HFP is adjusted to 5%.

[0048] Example 3 This embodiment provides a method for preparing an ultrathin self-supporting composite solid electrolyte membrane, which is the same as that in Example 1, except that the solid content of the sulfide material slurry is adjusted to 35%.

[0049] Example 4 This embodiment provides a method for preparing an ultrathin self-supporting composite solid electrolyte membrane, which is the same as that in Example 1, except that the polymer PVDF-HFP is changed to PAN.

[0050] Example 5 This embodiment provides a method for preparing an ultrathin self-supporting composite solid electrolyte membrane. The preparation method is the same as that in Example 1, except that the mass ratio of the fast ion conductor LLZO is adjusted to 20%.

[0051] Example 6 This embodiment provides a method for preparing an ultrathin self-supporting composite solid electrolyte membrane. The preparation method is the same as that in Example 1, except that the mass ratio of sulfide to SBR in the sulfide slurry is adjusted to 95:5.

[0052] Comparative Example 1 This comparative example provides a method for preparing an ultrathin self-supporting composite solid electrolyte membrane, which is the same as that in Example 1, except that the electrospun fiber skeleton membrane does not contain heat-resistant high-strength PMIA fiber components.

[0053] Comparative Example 2 This comparative example provides a method for preparing an ultrathin self-supporting composite solid electrolyte membrane, which is the same as that in Example 1, except that the electrospun fiber skeleton membrane does not contain ion-conducting polymer fiber components.

[0054] Comparative Example 3 This comparative example provides a method for preparing an ultrathin self-supporting composite solid electrolyte membrane, which is prepared by a dry rolling method. The specific preparation process involves shearing and mixing 0.02g of PTFE binder with 1.98g of sulfide electrolyte LPSC, followed by mechanical rolling to obtain the self-supporting electrolyte membrane.

[0055] Comparative Example 4 This comparative example provides a method for preparing an ultrathin self-supporting composite solid electrolyte membrane. The preparation method is the same as that in Example 1, except that instead of using vacuum impregnation to penetrate the sulfide slurry into the binary composite cross membrane, the sulfide slurry is first coated on aluminum foil and dried to form a film. Then, the ultrathin self-supporting electrolyte membrane is obtained by mechanical pressing according to the structure of sulfide electrolyte membrane-binary composite cross membrane-sulfide electrolyte membrane.

[0056] Comparative Example 5 This comparative example provides a method for preparing an ultrathin self-supporting composite solid electrolyte membrane, which is the same as that in Example 1, except that a glass fiber skeleton membrane is used instead of a binary composite cross membrane.

[0057] Comparative Example 6 This comparative example provides a method for preparing an ultrathin self-supporting composite solid electrolyte membrane, which is the same as that in Example 1, except that it does not undergo a rolling process.

[0058] Test case The ultrathin self-supporting composite solid electrolyte membranes prepared in Examples 1-6 and Comparative Examples 1-6 were tested for their reverse performance. Tensile strength test: The self-supporting electrolyte was cut into rectangular strips, 20 mm wide and 100 mm long. The thickness of the test sample was recorded. Tensile tests were performed using an electronic universal testing machine at a tensile speed of 10 mm / min, and the tensile strength values ​​were recorded. The test results are shown in Table 1.

[0059] Thermal stability test: Thermomechanical analysis was used to test the dimensional stability of the electrolyte membrane during heating. The specific test steps are as follows: the electrolyte membrane was cut into 10 mm diameter discs, a small constant force (0.1 N) was applied, and the temperature was increased from room temperature to 500 °C at a rate of 5 °C / min under an Ar atmosphere. The changes in sample size and temperature were recorded in real time, and the temperature corresponding to the change in sample size was finally recorded. The test results are shown in Table 1.

[0060] Ion conductivity test: By assembling a stainless steel SS | self-supporting sulfide electrolyte membrane | SS solid-state mold battery, electrochemical impedance spectroscopy was performed at an ambient temperature of 30℃ to obtain the ionic conductivity of the self-supporting electrolyte membrane. The test results are shown in Table 1.

[0061] Constant current charge and discharge test Galvanostatic charge-discharge (GCD) testing involves charging and discharging a battery with a constant current to study its charge-discharge performance. This includes information such as charge-discharge voltage plateau, specific capacity, charge-discharge efficiency, and cycle stability. All-solid-state batteries are assembled from a composite positive electrode, a lithium-indium alloy negative electrode, and a sulfide electrolyte. Their charge-discharge cutoff voltage range is 1.9–3.7 V (vs Li). + / Li-In), tested at 30℃, constant current charge / discharge rate of 1C (1C=220mA / g), and capacity retention was recorded after 200 cycles. The above data are shown in Table 2.

[0062] Table 1. Tensile strength, thermal stability, and ionic conductivity of self-supporting electrolyte membranes

[0063] Table 2. First-efficiency, initial discharge capacity and cycle capacity retention of all-solid-state batteries

[0064] Based on the above experimental results, it can be seen that, in terms of mechanical properties, the ultrathin self-supporting composite solid electrolyte membrane prepared in Example 1 exhibits excellent tensile strength (50 MPa) and thermal stability (>200℃), with a thickness of only 29 μm. In contrast, Comparative Example 1, due to the lack of use of heat-resistant high-strength PMIA fibers, showed a significant decrease in tensile strength (<5 MPa) and a substantial reduction in thermal stability (90℃), indicating that PMIA fibers play a crucial role in improving the mechanical strength and heat resistance of the membrane. The electrolyte membrane prepared by the dry rolling method in Comparative Example 3 reached a thickness of 120 μm and had low tensile strength, further verifying the advantages of electrospun composite structures in achieving ultrathin and high-strength characteristics.

[0065] Regarding ionic conductivity, Example 1 achieved an ionic conductivity of 5.2 × 10⁻⁶. -3 The S / cm concentration was significantly higher than that of Comparative Example 2 (which did not contain the ion-conducting polymer PVDF-HFP) and Comparative Example 4 (which used a non-impregnated laminated structure), indicating that the ion-conducting fiber network composed of PVDF-HFP and LLZO, along with the vacuum impregnation process, helps to form a continuous and efficient ion conduction pathway. Comparative Example 5, which used glass fiber instead of the composite fiber skeleton, also had a lower ion conductivity, demonstrating that both the material's inherent ion-conducting ability and structural design affect the overall electrochemical performance.

[0066] Regarding the electrochemical performance of all-solid-state batteries, all example groups exhibited high initial efficiency (92–95%), good discharge capacity (>200 mAh / g at 0.1C; >170 mAh / g at 1C), and excellent cycle stability (capacity retention >88% after 200 cycles). Comparative Examples 1–6 generally performed poorly in these indicators, especially Comparative Examples 1, 3, and 5, whose capacity retention was all below 70%, indicating significant defects in structural stability or interfacial compatibility during cycling. Comparative Example 6, which did not undergo the rolling process, also showed lower 1C discharge capacity and cycle retention, suggesting that rolling helps improve electrode / electrolyte interface contact and ion transport efficiency.

[0067] In summary, by constructing a binary composite cross-membrane framework using electrospinning, combined with vacuum impregnation of sulfide electrolyte and roll pressing, a self-supporting electrolyte membrane with high mechanical strength, excellent thermal stability, and high ionic conductivity can be prepared, thereby achieving high initial efficiency, high capacity, and long cycle life of all-solid-state batteries.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of preparing an ultrathin self-supporting composite solid-state electrolyte film, characterized by, The method comprises the following steps: adding the polymer matrix and the lithium salt into the first solvent to stir until transparent, then adding the fast ion conductor to stir until uniformly dispersed to form an ion-conductive polymer fiber precursor solution; mixing the high-temperature-resistant and high-strength fiber and the first solvent to form a high-temperature-resistant and high-strength fiber precursor solution; synchronously spinning the ion-conductive polymer fiber precursor solution and the high-temperature-resistant and high-strength fiber precursor solution on a collector by electrospinning to obtain a binary composite cross-membrane; mixing and dissolving the colloidal particles and the second solvent by stirring to form a glue solution, then stirring and dispersing the glue solution, the sulfide solid electrolyte powder and the second solvent to form a uniform sulfide electrolyte slurry; filling the sulfide electrolyte slurry into the binary composite cross-fiber membrane by a multiple vacuum impregnation-drying process, and finally obtaining an ultra-thin self-supporting sulfide electrolyte membrane by a rolling process.

2. The method of claim 1, wherein the method further comprises: The mass percentage of the polymer matrix in the ion-conductive polymer fiber precursor solution is 1%-8%, the mass percentage of the fast ion conductor is 5%-30%, and the mass ratio of the polymer matrix to the lithium salt is 2: (0.1-1).

3. The method of claim 1, wherein the self-supporting composite solid-state electrolyte film has a thickness of 100 nm or less. The first solvent is at least one of dimethylformamide, dimethylacetamide, N-methylpyrrolidone, acetone, tetrahydrofuran, dimethyl sulfoxide and imidazole ionic liquid; the polymer matrix comprises at least one of polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride and polymethyl methacrylate; the lithium salt comprises at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisdifluorosulfonylimide, lithium bis-trifluoromethylsulfonylimide, lithium bis-oxalate borate and lithium difluoro-oxalate borate; and the fast ion conductor comprises at least one of garnet-type lithium lanthanum zirconium oxide, perovskite-type lithium lanthanum titanium oxide and lithium aluminum titanium phosphate.

4. The method of claim 1, wherein the self-supporting composite solid-state electrolyte film has a thickness of 100 nm or less. The mass percentage of the high-temperature-resistant and high-strength fiber in the high-temperature-resistant and high-strength fiber precursor solution is 1%-10%; and the high-temperature-resistant and high-strength fiber comprises at least one of polyvinyl alcohol, polyether sulfone, polyaramid, polyetherimide and polyimide.

5. The method of claim 1, wherein the self-supporting composite solid-state electrolyte film has a thickness of 100 nm or less. During the preparation of the ion-conductive polymer fiber precursor solution and the high-temperature-resistant and high-strength fiber precursor solution, the stirring speed is 300-800 rpm, the stirring time is 12-24 h and the stirring temperature is 25-80℃; during the electrospinning process, the spinning voltage is 5-20 kV, the distance between the spinning needle and the collector is 5-20 cm, and the liquid supply rate of the spinning injector is 1-5 ml / h.

6. The method of claim 1, wherein the self-supporting composite solid-state electrolyte film has a thickness of 100 nm or less. The mass fraction of the colloidal particles in the glue solution is 3%-10%; and in the sulfide electrolyte slurry, the mass ratio of the sulfide electrolyte to the glue is (99:1)-(95:5), and the solid content is 30%-70%.

7. The method of claim 1, wherein the self-supporting composite solid-state electrolyte film has a thickness of 100 nm or less. The sulfide solid electrolyte is one of a glass-phase electrolyte or a crystal-phase electrolyte; the colloidal particles comprise at least one of styrene-butadiene rubber, nitrile-butadiene rubber, hydrogenated styrene-butadiene rubber and carboxylated styrene-butadiene rubber; and the second solvent is a non-polar or low-polar solvent, comprising at least one of a benzene-based solvent, an ester-based solvent or an alkane-based solvent.

8. The method of claim 1, wherein the self-supporting composite solid-state electrolyte film has a thickness of 100 nm or less. The stirring speed in the preparation of the glue solution is 200-1000 rpm, the stirring time is 12-24 h, and the heating temperature is 40-60℃; the stirring speed in the preparation of the sulfide electrolyte slurry is 1000-2000 rpm, and the stirring time is 1-5 h.

9. The method of claim 1, wherein the self-supporting composite solid-state electrolyte film has a thickness of 100 nm or less. The vacuum degree of the vacuum impregnation-drying process is 0.1-50 kPa, the drying temperature is 40-80℃, and the drying time is 1-5 h; the roll gap of the rolling process is 0.01-0.2 mm, the rolling pressure is 0.5T-5T, and the roll speed is 1-5 cm / min.

10. A solid state battery, characterized by It comprises a positive electrode, a negative electrode and a solid electrolyte membrane arranged between the positive electrode and the negative electrode, wherein the solid electrolyte membrane is an ultrathin self-supporting composite solid electrolyte membrane obtained by the preparation method of any one of claims 1-9, the positive electrode is a high-nickel positive electrode, and the negative electrode is selected from lithium-indium alloy.

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