An ultrathin polyester solid electrolyte membrane, a preparation method and application thereof

Abstract

The present application relates to a kind of ultra-thin polyester solid electrolyte membrane and its preparation method and application, belong to power battery technical field, the ultra-thin polyester solid electrolyte membrane of the present application uses ultra-thin non-woven membrane diaphragm as in-situ polymerization carrier, using neopentyl glycol diacrylate, 1-methyl-1-propyl piperidine bis (trifluoromethyl acyl) imine and NaTFSI custom electrolyte compound formation plastic crystal, then collate triethylene glycol dimethyl acrylate crosslinking agent, azobis isobutyronitrile initiator in-situ polymerization, the room temperature ionic conductivity of polyester solid electrolyte obtained can reach 1.243 mS / cm;After adding perfluorobutyl sulfonyl fluoride, conductivity is further improved to 1.657 mS / cm, electrochemical window can reach 5.73V;After NaTFSI is replaced by LiTFSI with equal mole, still can maintain 1.38 mS / cm high conductivity and 5.2V wide electrochemical window, the electrolyte is adapted to assemble with prussian white positive electrode, metal sodium negative electrode, and the discharge specific capacity of all-solid-state sodium ion battery can reach 165 mAh・g ‑1 , long cycle stability is excellent, has outstanding commercialization application potential.

Description

Technical Field

[0001] This invention belongs to the field of power battery technology, and relates to an ultra-thin polyester solid electrolyte membrane, its preparation method and application. Background Technology

[0002] Lithium-ion batteries (LIBs) have been widely used in energy storage systems and electric vehicles due to their advantages such as high energy density, long lifespan, low self-discharge, and fast charging. However, the scarcity of lithium resources, poor low-temperature performance, and safety concerns prevent them from meeting the continuously growing energy market demand and limit their application in large-scale energy storage systems. Therefore, developing high-performance and low-cost solid-state batteries is crucial. Sodium-ion batteries offer the advantages of abundant resources and low cost, while also possessing a low redox potential (2.71V vs. standard hydrogen electrode) and a high theoretical capacity (1166 mAhg). −1 Sodium dendrites (SLEs) are ideal anode materials for small and medium-sized enterprises (SMEs). Currently, the use of traditional liquid electrolytes (LEs) leads to uncontrolled growth of sodium dendrites on the anode side, causing short circuits in the battery. Solid electrolytes (SEs) are the ultimate solution to the above problems, and solid polymer electrolytes (SMBs) exhibit impressive processability and adaptability in harsh external environments.

[0003] However, the ionic conductivity of conventional solid polymer electrolytes is significantly lower than that of liquid electrolytes and inorganic solid electrolytes, which hinders their direct application in solid-state batteries at room temperature. Introducing plasticizers to reduce polymer crystallinity and promote salt solvation is considered an effective way to solve this problem. Therefore, the development of high-performance solid polymer electrolytes is essential. Polyester solid electrolytes possess advantages such as high room-temperature ionic conductivity, good chemical stability, compatibility with various cathode materials, and low cost, making them highly promising for commercial applications. Summary of the Invention

[0004] The purpose of this invention is to provide an ultrathin polyester solid electrolyte membrane, its preparation method, and its application. Using a 38μm ultrathin nonwoven membrane as an in-situ polymerization carrier, a specific ratio of plastic crystal components, crosslinking agent, and polymerization initiator is employed for in-situ thermal polymerization and curing. The plastic crystal is then integrated into the positive electrode to optimize the solid-solid interface contact. This significantly improves the room temperature ionic conductivity and electrochemical stability window of the solid electrolyte, reduces the electrode-electrolyte interface impedance, inhibits sodium dendrite growth, and enhances battery safety and energy density. Simultaneously, it broadens the compatibility range of positive electrode materials, simplifies the preparation process, reduces costs, and promotes the commercialization of all-solid-state sodium-ion batteries.

[0005] The objective of this invention can be achieved through the following technical solutions: An ultrathin polyester solid electrolyte membrane is obtained by in-situ polymerization and curing of neopentyl glycol diacrylate and triethylene glycol dimethacrylate in liquid plastic crystals using an ultrathin nonwoven membrane as an in-situ polymerization carrier and azobisisobutyronitrile as an initiator.

[0006] Furthermore, the liquid plastic crystal is composed of neopentyl glycol diacrylate, 1-methyl-1-propylpiperidine bis(trifluoromethyl amide)imide, a customized electrolyte, and perfluorobutyl sulfonyl fluoride in a volume ratio of 20-30:260-280:1300-1500:0-12.

[0007] Furthermore, the custom electrolyte can be either NaTFSI custom electrolyte or LiTFSI custom electrolyte.

[0008] Furthermore, the ratio of liquid plastic crystal, triethylene glycol dimethacrylate, and azobisisobutyronitrile is 0.5-1.5 mL: 10-30 μL: 3-7 mg.

[0009] Furthermore, the NaTFSI custom electrolyte is prepared by dissolving 1 mol of sodium bis(trifluoromethanesulfonyl)imide in a 1:1 volume ratio mixed solvent of dimethoxyethane (DME) and dioxolane (DOL), with a concentration of 1 mol / L.

[0010] Furthermore, the LiTFSI custom electrolyte is prepared by dissolving 1 mol of bis(trifluoromethanesulfonyl)imide lithium in a 1:1 volume ratio mixed solvent of dimethoxyethane (DME) and dioxolane (DOL), with a concentration of 1 mol / L.

[0011] This invention also provides a method for preparing an ultrathin polyester solid electrolyte membrane, comprising the following steps: Step 1: Add neopentyl glycol diacrylate to a glass bottle, heat to melt, then add 1-methyl-1-propylpiperidine bis(trifluoromethyl amide)imide and NaTFSI custom electrolyte, keep warm and stir to obtain liquid plastic crystals.

[0012] Step 2: Add liquid plastic crystal to a glass bottle, then add triethylene glycol dimethacrylate and azobisisobutyronitrile, heat and stir, use the diaphragm as a carrier for impregnation, cool to room temperature, and let it stand to solidify to obtain an ultra-thin polyester solid electrolyte membrane.

[0013] Furthermore, the temperature for heating and melting is 70-75℃.

[0014] Furthermore, the temperature for heat preservation and stirring is 70-75℃, and the time is 1-2 hours.

[0015] Furthermore, the curing time is 6-18 hours.

[0016] Furthermore, the ultra-thin nonwoven membrane can be either a polyethylene nonwoven membrane or a polypropylene nonwoven membrane.

[0017] Furthermore, the ultra-thin nonwoven membrane has a side length of 6-20mm and a thickness of 30-60μm.

[0018] The present invention also provides an application of an ultrathin polyester solid electrolyte membrane in an all-solid-state sodium-ion battery. The all-solid-state sodium-ion battery is assembled from a positive electrode shell, a positive electrode, the ultrathin polyester solid electrolyte membrane prepared above, a metallic sodium disc negative electrode, and a negative electrode shell.

[0019] Furthermore, the positive electrode is prepared through the following steps: The positive electrode material, conductive agent, binder and liquid plastic crystal are mixed, and N-methylpyrrolidone is used as solvent. After being ground evenly, the mixture is coated on the current collector and dried to obtain the positive electrode.

[0020] Furthermore, the cathode material is any one of Prussian white, sodium vanadium fluorophosphate, and layered oxides.

[0021] Furthermore, the mass ratio of the positive electrode material, conductive agent, binder, and liquid plastic crystal is 6.0-7.5:0.5-1:0.5-1:1-3.

[0022] Furthermore, the current collector can be any one of copper foil, aluminum foil, Al@C foil, titanium foil, and stainless steel.

[0023] Furthermore, the conductive agent is any one or a mixture of two or more of acetylene black, Ketjen black, conductive carbon black, activated carbon, and carbon nanotubes in any proportion.

[0024] Furthermore, the binder is a mixture of any one or more of polyvinyl alcohol, polyvinylidene fluoride, polytetrafluoroethylene, and sodium carboxymethyl cellulose in any proportion.

[0025] The beneficial effects of this invention are: 1. This invention relates to an ultrathin polyester solid electrolyte membrane, its preparation method, and its application. The membrane is prepared by compounding neopentyl glycol diacrylate, 1-methyl-1-propylpiperidine bis(trifluoromethyl amide)imide, and a customized NaTFSI electrolyte to form a plastic crystal. This crystal is then polymerized in situ on a 38-micron ultrathin nonwoven fabric membrane using triethylene glycol dimethacrylate crosslinking agent and azobisisobutyronitrile initiator. The resulting polyester solid electrolyte exhibits a room-temperature ionic conductivity of 1.657 mS / cm. Adding perfluorobutyl sulfonyl fluoride further enhances the conductivity to 1.243 mS / cm, and the electrochemical window is further improved to 5.73 V. Replacing NaTFSI with an equimolar amount of LiTFSI maintains a high conductivity of 1.38 mS / cm and a wide electrochemical window of 5.2 V. When this electrolyte is assembled with a Prussian white cathode and a metallic sodium anode, the discharge specific capacity of the all-solid-state sodium-ion battery can reach 165 mAh·g. -1 It exhibits excellent long-term cycle stability and has outstanding commercial application potential.

[0026] 2. This invention constructs a "dual-phase coexistence" sodium ion transport mechanism within the polyester solid electrolyte. Sodium ions can migrate efficiently in the neopentyl glycol diacrylate phase by relying on the solvated sheath layer. At the same time, the fluorine component in the system can preferentially combine with sodium ions to form a stable SEI film, which can not only block the disordered growth of sodium dendrites and avoid battery short circuits, but also further improve the electrochemical stability window of the electrolyte, ensuring the safety and reliability of the battery in long-term operation.

[0027] 3. This invention directly integrates the plastic crystal component into the Prussian white cathode, effectively solving the industry problem of excessively high solid-solid interface impedance between the cathode and electrolyte in solid-state sodium batteries. This significantly improves interface contact and ion transport efficiency, resulting in an all-solid-state sodium-ion battery with excellent cycle stability and rate performance. Furthermore, relying on the support of a 38μm ultra-thin non-woven membrane, the in-situ polymerized flame-retardant polyester solid electrolyte enables the battery to achieve intrinsic safety while maintaining high energy density. Moreover, this electrolyte is compatible with various cathode materials, and the preparation process is simple and low-cost, greatly promoting the commercialization of all-solid-state sodium-ion batteries. Attached Figure Description

[0028] Figure 1 The images show the upright (left) and inverted (right) views of the polyester solid electrolyte prepared in Example 1 of this invention. Figure 2 The images show the electrochemical impedance spectroscopy of the ultrathin polyester solid electrolyte membrane of the present invention; the left image shows the impedance spectra of Examples 1 and 2 of the present invention; the right image shows the impedance spectra of Example 3. Figure 3The figures show linear scanning voltammetry curves of the ultrathin polyester solid electrolyte membrane of the present invention; the left figure shows the linear scanning voltammetry curves of Examples 1 and 2 of the present invention; the right figure shows the linear scanning voltammetry curve of Example 3. Figure 4 This is a charge-discharge curve of the all-solid-state sodium-ion battery of Example 5 of the present invention; Figure 5 The graphs show the cycle performance of the all-solid-state sodium-ion battery of Example 4 of the present invention; the left graph shows the full-cell performance at 0.5C rate; and the right graph shows the full-cell performance at 1C rate. Figure 6 The rate performance diagram of the all-solid-state sodium-ion battery of Example 4 of the present invention is shown. Figure 7 Flame retardant performance test of the ultrathin polyester solid electrolyte membrane prepared in Example 1 of the present invention: before ignition (left), ignition test (middle), and after ignition (right). Figure 8 The images show the actual nonwoven membrane (left 1), the performance parameter table (left 2), the ultrathin membrane of this invention (right 2), and the thickness diagram of the ultrathin membrane under an electron microscope (right 1). Detailed Implementation

[0029] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0030] Example 1: This example provides an ultrathin polyester solid electrolyte membrane, which is prepared through the following steps: S1: Weigh 21 μL of neopentyl glycol diacrylate and add it to a 10 mL glass bottle. Heat and melt it at 70 °C. Then add 260 μL of anhydrous 1-methyl-1-propylpiperidine bis(trifluoromethyl)imide and 1300 μL of NaTFSI custom electrolyte (dissolve 1 mol of sodium bis(trifluoromethanesulfonyl)imide in a 1:1 volume ratio mixed solvent of dimethoxyethane (DME) and dioxolane (DOL) to prepare a sodium ion electrolyte with a concentration of 1 mol / L). Heat and stir at 70 °C for 1 h to obtain liquid plastic crystals.

[0031] S2: Add 1 mL of liquid plastic crystal to a 5 mL glass bottle, then add 20 μL of triethylene glycol dimethacrylate and 3 mg of azobisisobutyronitrile. Heat and stir at 70 °C for 10 min, then impregnate with an ultra-thin nonwoven fabric with a diameter of 16 mm and a thickness of 50 μm. Allow to stand and thermally polymerize in situ for 12 h to obtain an ultra-thin polyester solid electrolyte membrane.

[0032] Using azobisisobutyronitrile (AIBN) as an initiator, triethylene glycol dimethacrylate and neopentyl glycol diacrylate in liquid plastic crystals as crosslinking monomers, and an ultra-thin rectangular nonwoven membrane as an in-situ polymerization carrier, the system undergoes a free radical in-situ copolymerization reaction triggered by heating at 70°C to form a three-dimensional network crosslinked polyester polymer matrix. At the same time, the ionic liquid and NaTFSI customized electrolyte in the system are uniformly anchored in the crosslinked polyester matrix, constructing a continuous sodium ion transport channel, so that the electrolyte membrane has both excellent mechanical strength and high ionic conductivity.

[0033] like Figure 1 As shown, Figure 1 A digital photograph of the prepared ultrathin polyester solid electrolyte membrane. Figure 1 Left is the upright position. Figure 1 The one on the right is inverted.

[0034] Example 2: This example provides an ultrathin polyester solid electrolyte membrane. The difference from Example 1 is that 6 μL of perfluorobutyl sulfonyl fluoride is added in step S1.

[0035] Example 3: This example provides an ultrathin polyester solid electrolyte membrane. The difference from Example 1 is that 6 μL of perfluorobutyl sulfonyl fluoride is added in step S1, and the NaTFSI custom electrolyte is replaced with LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) custom electrolyte. The preparation process of the LiTFSI custom electrolyte is the same as that of the NaTFSI custom electrolyte.

[0036] Example 4: This example provides an all-solid-state sodium-ion battery, which is prepared through the following steps: Step 1: Dissolve 8 mmol Na4Fe(CN)6·10H2O (sodium ferrocyanide decahydrate) in 400 mL of deionized water to form solution A. Slowly add 12 mmol FeSO4 solution (2 mol / L), mix and stir for 6 h, age at room temperature for 24 h, centrifuge the precipitate, wash 3-5 times with deionized water and anhydrous ethanol to remove excess impurities, and dry at 80℃ for 24 h to obtain Prussian white material Na2Fe[Fe(CN)6].

[0037] Step 2: Mix the positive electrode material Prussian white material Na2Fe[Fe(CN)6], conductive carbon black powder, binder polyvinylidene fluoride (PVDF), and plastic crystal (prepared in Example 1) in a mass ratio of 6.5:0.5:0.5:2.5. Use N-methyl-2-pyrrolidone (NMP) as solvent (30% of the total mass of other materials, which can be converted to volume according to density). Grind the mixture in an agate mortar to form a positive electrode slurry. Coat the slurry evenly on Al@C foil and dry it at 50°C for 12 hours to obtain the Prussian white positive electrode sheet.

[0038] Step 3: Remove the oxides on the sodium surface, roll it into a thin sheet, and then punch holes in it to obtain a metallic sodium disc negative electrode with a diameter of 12mm and a thickness of 1mm.

[0039] Step 4: Assembly is carried out in the glove box. The Prussian white positive electrode sheet, the ultra-thin polyester solid electrolyte membrane prepared in Example 1, and the metallic sodium disc negative electrode are assembled into an all-solid-state sodium-ion battery (CR2032 button cell) in the order of negative electrode shell-negative electrode-polyester solid electrolyte-positive electrode-positive electrode shell.

[0040] Example 5: This example provides an all-solid-state sodium-ion battery, which is prepared through the following steps: Step 1: The positive electrode material sodium vanadium fluoride phosphate, conductive carbon black powder, binder polyvinylidene fluoride (PVDF), and liquid plastic crystal (prepared in Example 1) are mixed in a mass ratio of 6.5:0.5:0.5:2.5. N-methylpyrrolidone (NMP) is used as a solvent and the mixture is ground in an agate mortar to form a positive electrode slurry. The slurry is then uniformly coated onto an Al@C foil and dried at 50°C for 12 hours to obtain a sodium vanadium fluoride phosphate positive electrode sheet.

[0041] Step 2: Remove the oxides on the sodium surface, roll it into a thin sheet, and then punch holes in it to obtain a metallic sodium disc negative electrode with a diameter of 12mm and a thickness of 1mm.

[0042] Step 3: Assembly is carried out in the glove box. Following the order of negative electrode shell - negative electrode - polyester solid electrolyte - positive electrode - positive electrode shell, the sodium vanadium fluoride phosphate positive electrode sheet, the ultra-thin polyester solid electrolyte membrane prepared in Example 1 and the metallic sodium disc negative electrode are assembled into an all-solid-state sodium-ion battery (CR2032 button cell).

[0043] Example 6: This example provides an all-solid-state sodium-ion battery, which is prepared through the following steps: Step 1: The positive electrode material, conductive carbon black powder, polyvinylidene fluoride (PVDF) binder, and liquid plastic crystal (prepared in Example 1) are mixed in a mass ratio of 6.5:0.5:0.5:2.5. N-methylpyrrolidone (NMP) is used as a solvent and the mixture is ground in an agate mortar to form a positive electrode slurry. The slurry is then uniformly coated onto an Al@C foil and dried at 50°C for 12 hours to obtain a layered oxide positive electrode sheet.

[0044] Step 2: Remove the oxides on the sodium surface, roll it into a thin sheet, and then punch holes in it to obtain a metallic sodium disc negative electrode with a diameter of 12mm and a thickness of 1mm.

[0045] Step 3: Assembly is carried out in a glove box. Following the sequence of negative electrode shell - negative electrode - polyester solid electrolyte - positive electrode - positive electrode shell, the layered oxide positive electrode sheet, the ultrathin polyester solid electrolyte membrane prepared in Example 1, and the metallic sodium disc negative electrode are assembled into an all-solid-state sodium-ion battery (CR2032 coin cell). (Compared to conventionally thick separators, the battery assembled using the ultrathin separator of this invention has a lighter battery density, and consequently, a higher specific energy density).

[0046] The NaTFSI and LiTFSI custom electrolytes used in the examples are both custom electrolytes.

[0047] In the examples, the Prussian white material Na2Fe[Fe(CN)6], sodium vanadium fluorophosphate, and sodium nickel iron manganate are all positive electrode materials.

[0048] The materials obtained in the above embodiments were subjected to the following performance tests: 1. Ionic conductivity test After the polyester solid electrolyte impregnated with the separator prepared in Example 1 was allowed to stand and cure, coin cells were assembled using steel sheets as blocking electrodes on both sides, and the ionic conductivity of the solid electrolyte was tested using the AC impedance method. Figure 2 The image shown is the impedance spectrum of a polyester solid electrolyte. Figure 2 As can be seen from the data, the room temperature ionic conductivity of the polyester solid electrolyte reached 1.243 mS / cm, and the total impedance of the polyester solid electrolyte was 16 Ω. After adding perfluorobutyl sulfonyl fluoride, the conductivity increased to 1.657 mS / cm, and the total impedance of the polyester solid electrolyte was 12 Ω. (Based on the addition of perfluorobutyl sulfonyl fluoride, replacing NaTFSI with LiTFSI in an equimolar ratio resulted in an ionic conductivity of 1.38 mS / cm and a total impedance of 18 Ω for the polyester solid electrolyte.)

[0049] 2. Electrochemical window test After the polyester solid electrolyte prepared in Example 1 was impregnated with a separator and allowed to stand for curing, a titanium sheet was used as a blocking electrode on the positive electrode side and metallic sodium was used on the negative electrode side. The electrochemical window of the solid electrolyte was tested by linear sweep voltammetry. Figure 3 This is a linear sweep voltammetry curve of a polyester solid electrolyte.

[0050] Depend on Figure 3 It can be seen that the electrochemical window of the prepared polyester solid electrolyte is 5.61V (the oxidation window increases to 5.73V after the addition of perfluorobutylsulfonyl fluoride (i.e., Example 2)) and the electrochemical window of the electrolyte obtained by replacing NaTFSI with LiTFSI in an equal molar ratio based on the addition of perfluorobutylsulfonyl fluoride (i.e., Example 3) is 5.2V (right figure).

[0051] 3. Full battery performance test The all-solid-state sodium-ion battery (positive electrode Prussian white) prepared in Example 4 and the all-solid-state sodium-ion battery (positive electrode sodium vanadium fluoride phosphate) prepared in Example 6 were charged and discharged at room temperature at a current density of 150 mA / g. Figure 4 The left side shows the charge-discharge curves of the all-solid-state sodium-ion battery (positive electrode: sodium vanadium fluoride phosphate) prepared in Example 5. The results show that the all-solid-state sodium-ion battery prepared in Example 5 (sodium vanadium fluoride phosphate || polyester solid electrolyte || Na) has a first-cycle discharge specific capacity of 80 mAh g at room temperature. -1 (After adding additives, the charge / discharge capacity is increased to 95mAh g) -1 ).

[0052] Figure 5 The graph shows the cycling performance of the sodium vanadium fluoride phosphate || polyester solid electrolyte || Na all-solid-state sodium ion battery. The results show that the sodium vanadium fluoride phosphate || polyester solid electrolyte || Na all-solid-state sodium ion battery prepared in Example 5 retains a capacity of nearly 95% and a coulombic efficiency of nearly 100% after cycling at 0.5C for 50 cycles (left figure) and at 1C for 100 cycles (right figure) at room temperature.

[0053] Figure 6 The graph shows the rate performance of the sodium vanadium fluoride phosphate || polyester solid electrolyte || Na all-solid-state sodium-ion battery. The results show that the sodium vanadium fluoride phosphate || polyester solid electrolyte || Na all-solid-state sodium-ion battery prepared in Example 5 can cycle stably at current densities up to 2C, and still has excellent capacity when it eventually returns to a current density of 0.1C.

[0054] Figure 7 For the flame retardancy test of polyester solid electrolyte, polyester solid electrolyte cannot be ignited at all, showing a clear advantage compared to flammable electrolyte, and even extinguishing itself after burning for a few seconds.

[0055] Figure 8 The images show a physical picture of the nonwoven membrane (left 1), a performance parameter table (left 2), a picture of the ultrathin membrane of this invention (right 2), and a thickness diagram of the ultrathin membrane under an electron microscope (right 1). As shown in the figures, the areal density of the nonwoven membrane is 14.6 g / m³. 2 It has a thickness of 38 μm and a bulk density of 0.4 g / m³. 3 The porosity is 71.4%, and the size is 210×297×0.038mm. The second one on the right is an ultra-thin diaphragm, model P-PP13-F50, with a size of 210x297x0.05mm.

[0056] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0057] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. An ultra-thin polyester solid electrolyte membrane, characterized by, This ultrathin polyester solid electrolyte membrane is obtained by in-situ polymerization and solidification of neopentyl glycol diacrylate and triethylene glycol dimethacrylate in liquid plastic crystals using an ultrathin nonwoven membrane as the in-situ polymerization carrier and azobisisobutyronitrile as the initiator. The liquid plastic crystal is composed of neopentyl glycol diacrylate, 1-methyl-1-propylpiperidine bis(trifluoromethyl amide)imide, a customized electrolyte, and perfluorobutyl sulfonyl fluoride in a volume ratio of 20-30: 260-280: 1300-1500: 0-12. The customized electrolyte is either NaTFSI customized electrolyte or LiTFSI customized electrolyte; The ratio of the liquid plastic crystal, triethylene glycol dimethacrylate, and azobisisobutyronitrile is 0.5-1.5 mL: 10-30 μL: 3-7 mg.

2. The ultra-thin polyester solid-state electrolyte film according to claim 1, wherein, The NaTFSI customized electrolyte was prepared by dissolving 1 mol of sodium bis(trifluoromethanesulfonyl)imide in a mixed solvent of dimethoxyethane and dioxolane in a volume ratio of 1:1, with a concentration of 1 mol / L. The LiTFSI custom electrolyte is prepared by dissolving 1 mol of bis(trifluoromethanesulfonyl)imide lithium in a 1:1 volume ratio mixed solvent of dimethoxyethane and dioxolane, with a concentration of 1 mol / L.

3. The method for preparing an ultrathin polyester solid electrolyte membrane according to any one of claims 1-2, characterized in that, Includes the following steps: Step 1: Add neopentyl glycol diacrylate to a glass bottle, heat to melt, then add 1-methyl-1-propylpiperidine bis(trifluoromethyl amide)imide and NaTFSI customized electrolyte, keep warm and stir to obtain liquid plastic crystals; Step 2: Add liquid plastic crystal to a glass bottle, then add triethylene glycol dimethacrylate and azobisisobutyronitrile, heat and stir, impregnate with an ultra-thin non-woven membrane as a carrier, cool to room temperature, and let stand to solidify to obtain an ultra-thin polyester solid electrolyte membrane.

4. The method of claim 3, wherein the method is characterized by: The heating and melting temperature in step one is 70-75℃; the temperature for heat preservation and stirring is 70-75℃, and the time is 1-2 hours. The curing time in step two is 6-18 hours.

5. The method of claim 3, wherein the thickness of the solid electrolyte membrane is 100 μm or less. The ultra-thin nonwoven membrane mentioned in step two can be either a polyethylene nonwoven membrane or a polypropylene nonwoven membrane.

6. The method for preparing an ultrathin polyester solid electrolyte membrane according to claim 5, characterized in that, The ultra-thin nonwoven membrane has a side length of 6-20mm and a thickness of 30-60μm.

7. The application of an ultrathin polyester solid electrolyte membrane in an all-solid-state sodium-ion battery, characterized in that, The all-solid-state sodium-ion battery is assembled from a positive electrode shell, a positive electrode, an ultra-thin polyester solid electrolyte membrane, a metallic sodium disc negative electrode, and a negative electrode shell. The ultrathin polyester solid electrolyte membrane is an ultrathin polyester solid electrolyte membrane according to any one of claims 1-2.

8. The application of the ultrathin polyester solid electrolyte membrane according to claim 7 in an all-solid-state sodium-ion battery, characterized in that, The positive electrode is prepared by the following steps: The positive electrode material, conductive agent, binder and liquid plastic crystal are mixed, and N-methylpyrrolidone is used as solvent. After being ground evenly, the mixture is coated onto the current collector and dried to obtain the positive electrode. The cathode material is any one of Prussian white, sodium vanadium fluoride phosphate, and layered oxides.

9. The application of the ultrathin polyester solid electrolyte membrane according to claim 8 in an all-solid-state sodium-ion battery, characterized in that, The mass ratio of the positive electrode material, conductive agent, binder, and liquid plastic crystal is 6.0-7.5:0.5-1:0.5-1:1-3; The current collector is any one of copper foil, aluminum foil, Al@C foil, titanium foil, and stainless steel. The conductive agent is any one or a mixture of two or more of acetylene black, Ketjen black, conductive carbon black, activated carbon, and carbon nanotubes in any proportion.

10. The application of the ultrathin polyester solid electrolyte membrane according to claim 9 in an all-solid-state sodium-ion battery, characterized in that, The adhesive is any one or more of polyvinyl alcohol, polyvinylidene fluoride, polytetrafluoroethylene and sodium carboxymethyl cellulose in any proportion.

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