Flame-retardant polyester solid electrolyte membrane and preparation method thereof

Abstract

This invention relates to a flame-retardant polyester solid electrolyte membrane and its preparation method, belonging to the field of solid-state battery technology. The raw materials for preparing the flame-retardant polyester solid electrolyte membrane include neopentyl glycol diacrylate, 1-methyl-1-propylpiperidin-1-onium bis((trifluoromethyl)sulfonyl)imide, fluoroethylene carbonate, sulfolane, sodium bis(trifluoromethylsulfonyl)imide, triethylene glycol dimethacrylate, azobisisobutyronitrile, and a cleanroom cloth. The flame-retardant polyester solid electrolyte membrane exhibits excellent flame-retardant properties, as well as superior performance in terms of electrochemical window and ionic conductivity. The assembled solid-state battery exhibits excellent electrochemical performance and stability at room temperature and can be adapted to various cathode materials, which is beneficial to the commercial development of solid-state batteries.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery technology and relates to a flame-retardant polyester solid electrolyte membrane and its preparation method. Background Technology

[0002] Sodium-ion batteries, leveraging the natural advantages of abundant sodium resources, convenient sourcing, and low cost, possess excellent prospects for industrialization. Furthermore, the sodium metal anode has a low redox potential (2.71 V vs. standard hydrogen electrode), resulting in a considerable theoretical energy storage capacity, making it a highly promising candidate material for energy storage anodes. Currently, most sodium-ion batteries utilize traditional liquid electrolyte systems. However, liquid electrolytes are prone to inducing disordered sodium dendrite growth on the anode surface, leading to internal short circuits and severely compromising battery safety and cycle stability. Solid-state electrolytes are the optimal solution for fundamentally suppressing sodium dendrite growth and addressing various defects in liquid electrolytes. Among them, polymer solid-state electrolytes possess excellent processing and molding properties and adaptability to complex environments, making them highly versatile. However, the room-temperature ionic conductivity of traditional pure polymer solid-state electrolytes is far lower than that of liquid electrolytes and inorganic solid-state electrolytes, resulting in insufficient conductivity at room temperature, which severely hinders their practical industrial application. Introducing plasticizers into the polymer matrix can effectively reduce polymer crystallinity and promote the complete solubility and dissociation of alkali metal salts, which is an effective modification method to improve the ionic conductivity of polymer electrolytes. Polyester-based solid electrolytes not only possess excellent room-temperature ionic conductivity and stable chemical and electrochemical properties, but also can be well matched with various battery cathode materials. Furthermore, they have advantages such as simple preparation and low production cost, making them highly promising for commercial applications. Therefore, the research and development of high-performance polyester-based solid polymer electrolytes has significant practical importance and application value.

[0003] Traditional polymer solid electrolytes generally suffer from low room temperature ionic conductivity, high electrode-electrolyte interface impedance, and insufficient flame retardancy. They cannot simultaneously achieve high ion conduction, stable interface, and efficient flame retardancy, which greatly limits the industrialization and commercialization of all-solid-state sodium batteries. Summary of the Invention

[0004] The purpose of this invention is to provide a flame-retardant polyester solid electrolyte membrane and its preparation method. By constructing a dual-phase coexisting high-efficiency sodium ion transport channel, forming a stable SEI membrane in situ, and introducing a fluorine-phosphorus-nitrogen ternary synergistic flame-retardant system, the defects of traditional polymer solid electrolytes, such as low room temperature ionic conductivity, high interfacial impedance, and poor flame retardancy, are solved. At the same time, high ion conduction, stable interface and high flame retardancy are achieved, which greatly improves the electrochemical performance and safety stability of all-solid-state sodium batteries.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing a flame-retardant polyester solid electrolyte membrane includes the following steps: Step 1: Add neopentyl glycol diacrylate, microencapsulated flame retardant, 1-methyl-1-propylpiperidine-1-onium bis((trifluoromethyl)sulfonyl)imide, sulfolane, sodium bis(trifluoromethylsulfonyl)imide, triethylene glycol dimethacrylate and azobisisobutyronitrile to the reactor, heat and melt for 6-8 hours, continue stirring for 10-14 hours until clear and transparent, and then heat for another 10-14 hours to obtain a polyester solid electrolyte precursor solution.

[0006] Step 2: Add the polyester solid electrolyte precursor solution and fluoroethylene carbonate to the reactor, mix and stir, impregnate with a diaphragm, and allow to stand and solidify to obtain a flame-retardant polyester solid electrolyte membrane.

[0007] Furthermore, the mass ratio of neopentyl glycol diacrylate, microencapsulated flame retardant, 1-methyl-1-propylpiperidine-1-onthium bis((trifluoromethyl)sulfonyl)imide, sulfolane, sodium bis(trifluoromethylsulfonyl)imide, triethylene glycol dimethacrylate, and azobisisobutyronitrile is 0.15-0.3:0-0.35:0.35-1.4:0.25-0.75:0.1-0.2:0.025-0.075:0.05-0.2.

[0008] Furthermore, the heating and melting temperature is 65-70℃, and the stirring speed is 300-500 r / min.

[0009] Furthermore, the mass ratio of the polyester solid electrolyte precursor solution to fluoroethylene carbonate is 0.925-3.275:0.1-0.3.

[0010] Furthermore, the diaphragm can be any one of polyethylene diaphragm, polypropylene diaphragm, glass fiber diaphragm, and cleanroom cloth.

[0011] Furthermore, the diameter of the diaphragm is 9-20 mm and the thickness is 0.2-1 mm.

[0012] Furthermore, the curing time is 1-24 hours.

[0013] Furthermore, the specific preparation process of the microencapsulated flame retardant is as follows: Ammonium polyphosphate, melamine, and anhydrous ethanol were added to a reaction vessel and stirred for 15-20 minutes at 45-50℃ and 300-500 r / min. Glycidyl methacrylate was added and stirred for 15-20 minutes. Benzoyl peroxide and butanone were mixed evenly and added to the reaction vessel. The temperature was raised to 65-70℃ and copolymerized for 6-7 hours. The mixture was then filtered, washed, and dried to obtain the microencapsulated flame retardant.

[0014] Furthermore, the ratio of ammonium polyphosphate, melamine, anhydrous ethanol, glycidyl methacrylate, benzoyl peroxide, and methyl ethyl ketone is 80-100g: 15-20g: 150-200mL: 20-30mL: 0.1-0.15g: 15-20mL.

[0015] A flame-retardant polyester solid electrolyte membrane, comprising neopentyl glycol diacrylate, a microencapsulated flame retardant, 1-methyl-1-propylpiperidin-1-onthium bis((trifluoromethyl)sulfonyl)imide, sulfolane, sodium bis(trifluoromethyl)sulfonyl)imide, triethylene glycol dimethacrylate, azobisisobutyronitrile, fluoroethylene carbonate, and a separator.

[0016] The beneficial effects of this invention are: 1. The flame-retardant polyester solid electrolyte membrane prepared by the present invention achieves an integrated improvement in three core properties: ion transport, electrochemical tolerance, and fire safety through precise compounding and modification of three core components: polyester polymer matrix, ion-conducting functional phase, and flame-retardant modified component. Relying on the multiple synergistic effects of structural adaptation, performance complementarity, and interface compatibility among the components, it achieves an integrated improvement in three core properties: ion transport, electrochemical tolerance, and fire safety.

[0017] The polyester polymer matrix forms a stable and flexible three-dimensional framework network, which provides a molding substrate and mechanical support for the electrolyte, while also reserving continuous and interconnected ion migration gaps. The ion-conducting active components are uniformly dispersed and anchored in the polyester segments, which can efficiently dissociate the sodium ion source and reduce the ion migration barrier. The two form a structure-mass transfer synergy, opening up a continuous sodium ion transport channel throughout the entire domain, which greatly improves the carrier migration efficiency, and ultimately enables the room temperature ionic conductivity of the electrolyte membrane to reach 2.5 mS / cm.

[0018] Meanwhile, the conductive modification component forms strong intermolecular forces with the polyester matrix, effectively binding the disordered movement of polymer chain segments and inhibiting the redox decomposition of the electrolyte under high voltage. Together with the interface regulation component, it optimizes the energy level structure of the system, forming a synergistic effect of electrochemical stability. This widens the electrochemical window of the electrolyte to 5.4V, effectively avoiding problems such as electrolyte cracking and the generation of interfacial side reactions under high voltage, thus consolidating the foundation for electrochemical stability.

[0019] When this composite solid electrolyte membrane is matched with Prussian white cathode and metallic sodium anode to assemble an all-solid sodium-ion battery, the multi-functional components inside the electrolyte can achieve excellent solid-solid interface wetting and interface adaptation synergy with the cathode and anode materials, closely adhering to the electrode active sites. This ensures that sodium ions can be rapidly and smoothly inserted and extracted at the electrode-electrolyte interface, and effectively inhibits dendrite growth in the metallic sodium anode and alleviates structural collapse of the cathode active material.

[0020] In addition, the uniformly doped flame-retardant functional components form a flame-retardant-matrix synergistic protection system with the polyester matrix. The two do not interfere with each other's ion conduction pathways. When exposed to high-temperature open flames, they can quickly trigger a synergistic flame-retardant mechanism. Through multiple functions such as heat absorption and cooling, oxygen isolation, and the formation of a dense flame-retardant carbon layer, the combustion chain reaction is quickly blocked, giving the electrolyte membrane excellent self-extinguishing flame-retardant ability. It can quickly suppress and extinguish flames, and comprehensively improve the safety of energy storage batteries from the core level of the electrolyte.

[0021] In summary, this flame-retardant polyester solid electrolyte, relying on the combined advantages of multi-component mass transfer synergy, electrochemical stability synergy, electrode interface adaptation synergy, and safety flame retardancy synergy, perfectly balances high conductivity, wide voltage adaptability, long cycle stability, and intrinsic fire safety, and has extremely high potential for commercialization and large-scale application in the field of all-solid-state sodium-ion batteries.

[0022] 2. The flame-retardant polyester solid electrolyte of this invention constructs a highly efficient sodium ion transport pathway with "dual-phase coexistence" within it. Sodium ions can migrate rapidly within the system by relying on the solvated sheath layer. Fluoroethylene carbonate has a synergistic effect with the polyester matrix and ionic liquid components. Its fluoride ions can preferentially combine with sodium ions to form a uniform and dense stable solid electrolyte interface (SEI) film, which inhibits the disordered growth of sodium dendrites from the source. At the same time, it synergistically broadens the electrochemical stability window. The phosphorus-nitrogen flame-retardant system of the microencapsulated flame retardant forms a fluorine-phosphorus-nitrogen ternary synergistic flame-retardant mechanism with excellent compatibility. Without damaging the ion conduction performance, it further significantly improves the battery safety performance. The Na||polyester solid electrolyte||Na symmetric battery assembled with this electrolyte can stably cycle for more than 1500 hours at low current density and more than 700 hours at high current density. The interface stability and long-term cycle reliability are extremely outstanding.

[0023] 3. The flame-retardant polyester solid electrolyte membrane of this invention effectively solves the core problem of excessively high interfacial impedance between the cathode and solid electrolyte in all-solid-state sodium batteries, significantly reduces the cathode-side interfacial resistance, and significantly optimizes the electrochemical performance at room temperature. This electrolyte is compatible with a variety of mainstream cathode materials such as Prussian white, sodium vanadium phosphate, and sodium vanadium fluoride phosphate. The assembled all-solid-state sodium batteries all exhibit stable long-cycle performance and excellent rate performance. Among them, the sodium vanadium phosphate-based full battery has a capacity retention rate of 88.4% after 1200 cycles at room temperature, and the sodium vanadium fluoride phosphate-based full battery has a capacity retention rate of 85.5% after 200 cycles at 1C rate. Moreover, the preparation process is simple and the raw material cost is low. It has both high safety and high cycle stability, providing reliable support for the large-scale commercial development of all-solid-state sodium batteries. Attached Figure Description

[0024] Figure 1Digital photographs of the polyester solid electrolyte precursor solution (left) and the cured polyester solid electrolyte (right) prepared in Example 1 of the present invention; Figure 2 Digital photographs of the flame-retardant polyester solid electrolyte membrane (left) prepared in Example 1 and the flame-retardant polyester solid electrolyte membrane (right) prepared in Example 3 of the present invention; Figure 3 The flame retardant properties of the flame-retardant polyester solid electrolyte membrane prepared in Example 1 of this invention are shown in the figure. Figure 4 The impedance spectrum of the flame-retardant polyester solid electrolyte membrane prepared in Example 1 of this invention; Figure 5 Linear scan voltammetry curve of the flame-retardant polyester solid electrolyte membrane prepared in Example 1 of this invention; Figure 6 This is a low current density cycling performance diagram of the Na||polyester solid electrolyte||Na symmetric battery prepared in Example 7 of the present invention; Figure 7 This is a high current density cycling performance diagram of the Na||polyester solid electrolyte||Na symmetric battery prepared in Example 7 of the present invention; Figure 8 The charge-discharge curve of the Prussian white || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 4 of this invention; Figure 9 The cycling performance curve of the Prussian white || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 4 of this invention is shown in the figure. Figure 10 The charge-discharge curve of the sodium vanadium fluoride phosphate || polyester solid electrolyte || Na all-solid sodium battery prepared in Example 6 of the present invention is shown. Figure 11 The charge-discharge curve of the sodium vanadium phosphate || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 5 of the present invention is shown. Figure 12 The cycling performance diagram of the sodium vanadium phosphate || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 5 of the present invention is shown. Figure 13 The circuit performance diagram shows the sodium vanadium fluoride phosphate || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 6 of this invention. Detailed Implementation

[0025] 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.

[0026] Example 1: This example provides a flame-retardant polyester solid electrolyte membrane, which is prepared through the following steps: S1: Add 100g ammonium polyphosphate, 20g melamine and 200mL anhydrous ethanol to a reaction vessel and stir for 20min at 50℃ and 500r / min. Add 30mL glycidyl methacrylate and stir for 20min at 50℃. Add 0.15g benzoyl peroxide and 20mL butanone evenly to the reaction vessel and heat to 70℃. Copolymerize and precipitate for 7h. Filter the product using a nylon filter membrane and wash the product three times with cyclohexane. Place it in an oven and dry at 70℃ for 12h to obtain the microencapsulated flame retardant.

[0027] The carbon-carbon double bonds in the glycidyl methacrylate molecule undergo free radical in-situ copolymerization under the action of benzoyl peroxide free radical initiator, which promotes the continuous polymerization and deposition of monomers on the particle surface of ammonium polyphosphate and melamine, gradually forming a dense polymer coating shell. The copolymerization precipitation completes the encapsulation of the core material, resulting in a microencapsulated flame retardant.

[0028] S2: 0.30g neopentyl glycol diacrylate, 0.35g microencapsulated flame retardant, 1.4g 1-methyl-1-propylpiperidin-1-onthium bis((trifluoromethyl)sulfonyl)imide, 0.75g sulfolane, 0.2g sodium bis(trifluoromethyl)sulfonyl)imide, 0.075g triethylene glycol dimethacrylate, and 0.2g azobisisobutyronitrile were added to a reaction vessel. The mixture was heated and stirred at 70℃ and 500r / min for 8 hours to melt, and then stirred for another 14 hours until clear and transparent. Finally, the mixture was heated at 80℃ for 12 hours to obtain a polyester solid electrolyte precursor solution. See attached image for details. Figure 1 As shown on the left, the cured state is as follows. Figure 1 As shown on the right.

[0029] S3: 3.275g of polyester solid electrolyte precursor solution and 0.3g of fluoroethylene carbonate were added to a reactor and stirred at 80℃ for 10min. Then, a 9mm diameter, 1mm thick glass fiber diaphragm was impregnated, cooled to room temperature, and allowed to cure for 12h to obtain a flame-retardant polyester solid electrolyte membrane. See attached image for details. Figure 2 As shown on the left.

[0030] Example 2: This example provides a flame-retardant polyester solid electrolyte membrane, which is prepared through the following steps: S1: Add 80g ammonium polyphosphate, 15g melamine and 150mL anhydrous ethanol to a reaction vessel and stir for 15min at 45℃ and 300r / min. Add 20mL glycidyl methacrylate and stir for 15min at 45℃. Add 0.1g benzoyl peroxide and 15mL butanone evenly to the reaction vessel and heat to 65℃. Copolymerize and precipitate for 6h. Filter the product using a nylon filter membrane and wash the product twice with cyclohexane. Place it in an oven and dry at 70℃ for 12h to obtain the microencapsulated flame retardant.

[0031] The carbon-carbon double bonds in the glycidyl methacrylate molecule undergo free radical in-situ copolymerization under the action of benzoyl peroxide free radical initiator, which promotes the continuous polymerization and deposition of monomers on the particle surface of ammonium polyphosphate and melamine, gradually forming a dense polymer coating shell. The copolymerization precipitation completes the encapsulation of the core material, resulting in a microencapsulated flame retardant.

[0032] S2: 0.15g neopentyl glycol diacrylate, 0.11g microencapsulated flame retardant, 0.35g 1-methyl-1-propylpiperidin-1-onthium bis((trifluoromethyl)sulfonyl)imide, 0.25g sulfolane, 0.1g sodium bis(trifluoromethyl)sulfonyl)imide, 0.025g triethylene glycol dimethacrylate and 0.05g azobisisobutyronitrile were added to a reaction vessel and heated and stirred at 65℃ and 300r / min for 7h to melt. Stirring was continued for 12h until a clear and transparent state was reached. The mixture was then heated at 75℃ for 10h to obtain a polyester solid electrolyte precursor solution.

[0033] S3: Add 0.925g of polyester solid electrolyte precursor solution and 0.1g of fluoroethylene carbonate to the reactor, stir at 75℃ for 8min, then impregnate with a glass fiber membrane with a diameter of 9mm and a thickness of 1mm, cool to room temperature, and let stand to cure for 10h to obtain a flame-retardant polyester solid electrolyte membrane.

[0034] Example 3: This example provides a flame-retardant polyester solid electrolyte membrane. The difference from Example 1 is that a cleanroom cloth is used instead of a glass fiber membrane in step S3. See attached image for a physical example. Figure 2 As shown on the right.

[0035] Example 4: This example provides an all-solid-state sodium 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, stir the reaction at 300-500 r / min for 6 h, age at 25 °C for 24 h, centrifuge the precipitate, wash it 5 times with deionized water and anhydrous ethanol to remove excess impurities, and vacuum dry it at 80 °C for 24 h to obtain Prussian white material Na2Fe[Fe(CN)6].

[0036] Step 2: Mix Prussian white material Na2Fe[Fe(CN)6], conductive carbon black powder as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder in a mass ratio of 6.5:0.5:0.5. Use N-methyl-2-pyrrolidone (NMP) as a solvent and 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.

[0037] Step 3: Remove the oxides on the sodium surface, roll it into a thin sheet, and then punch it with a punch to obtain a metallic sodium disc negative electrode with a diameter of 12mm and a thickness of 1mm.

[0038] Step 4: Assembly is carried out in the glove box. The Prussian white positive electrode sheet, the flame-retardant polyester solid electrolyte membrane prepared in Example 1, and the metallic sodium disc negative electrode are assembled in the order of negative electrode shell-negative electrode-polyester solid electrolyte-positive electrode-positive electrode shell to obtain the Prussian white||polyester solid electrolyte||Na all-solid sodium battery (CR2032 button cell).

[0039] Example 5: This example provides an all-solid-state sodium battery, which is prepared through the following steps: Step 1: Mix sodium vanadium phosphate, conductive carbon black powder (conductive agent), and polyvinylidene fluoride (PVDF) (binder) in a mass ratio of 6.5:0.5:0.5. Use N-methyl-2-pyrrolidone (NMP) as solvent and grind the mixture in an agate mortar to form a positive electrode slurry. Coat the slurry evenly on an Al@C foil and dry it at 50°C for 12 hours to obtain a sodium vanadium phosphate positive electrode sheet.

[0040] Step 2: Remove the oxides on the surface of the sodium, roll it into a thin sheet, and then punch it with a punch to obtain a metallic sodium disc negative electrode with a diameter of 12mm and a thickness of 1mm.

[0041] Step 3: Assembly is carried out in the glove box. The sodium vanadium phosphate positive electrode sheet, the flame-retardant polyester solid electrolyte membrane prepared in Example 1, and the metallic sodium disc negative electrode are assembled in the order of negative electrode shell-negative electrode-polyester solid electrolyte-positive electrode-positive electrode shell to obtain sodium vanadium phosphate||polyester solid electrolyte||Na all-solid sodium battery (CR2032 button cell).

[0042] Example 6: This example provides an all-solid-state sodium battery, prepared through the following steps: Step 1: Mix sodium vanadium fluoride phosphate, conductive carbon black powder (conductive agent), and polyvinylidene fluoride (PVDF) (binder) in a mass ratio of 6.5:0.5:0.5. Using N-methyl-2-pyrrolidone (NMP) as solvent, grind the mixture in an agate mortar to form a positive electrode slurry. Coat the slurry evenly onto an Al@C foil and dry it at 50°C for 12 hours to obtain a sodium vanadium fluoride phosphate positive electrode sheet.

[0043] Step 2: Remove the oxides on the surface of the sodium, roll it into a thin sheet, and then punch it with a punch to obtain a metallic sodium disc negative electrode with a diameter of 12mm and a thickness of 1mm.

[0044] Step 3: Assembly is carried out in the glove box. The sodium vanadium fluoride phosphate positive electrode sheet, the flame-retardant polyester solid electrolyte membrane prepared in Example 1, and the metallic sodium disc negative electrode are assembled in the order of negative electrode shell-negative electrode-polyester solid electrolyte-positive electrode-positive electrode shell to obtain sodium vanadium fluoride phosphate||polyester solid electrolyte||Na all-solid sodium battery (CR2032 button cell).

[0045] Example 7: This example provides an all-solid-state sodium battery, prepared through the following steps: Assembly was carried out in a glove box. The sodium metal disc negative electrode, the flame-retardant polyester solid electrolyte membrane prepared in Example 1, and the sodium metal disc negative electrode were assembled in the order of negative electrode shell-negative electrode-polyester solid electrolyte-positive electrode-positive electrode shell to obtain a Na||polyester solid electrolyte||Na symmetric battery.

[0046] In the above embodiments, both the glass fiber diaphragm and the cleanroom cloth are diaphragms.

[0047] The following performance tests were performed on the above embodiments: 1. Flame retardant performance test Ignition experiments were conducted on the flame-retardant polyester solid electrolyte membrane prepared in Example 1, and it was found that it could effectively suppress and extinguish flames. Figure 3 This is a flame-retardant diagram of a flame-retardant polyester solid electrolyte membrane.

[0048] 2. Ionic conductivity test In Example 1, steel sheets were used as blocking electrodes on both sides of the flame-retardant polyester solid electrolyte membrane and a coin cell was assembled. The ionic conductivity of the solid electrolyte was tested by AC impedance method. Figure 4 The impedance spectrum of a flame-retardant polyester solid electrolyte membrane is shown.

[0049] from Figure 4 It can be seen that the total impedance of the flame-retardant polyester solid electrolyte membrane is 20Ω. The ionic conductivity of the flame-retardant polyester solid electrolyte membrane is calculated to be 2.5mS / cm, indicating that the flame-retardant polyester solid electrolyte membrane can improve the conductivity and cycle stability of the battery.

[0050] 3. Electrochemical window test In the flame-retardant polyester solid electrolyte membrane prepared in Example 1, 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 5 This is a linear scan voltammetry curve of a flame-retardant polyester solid electrolyte membrane.

[0051] from Figure 5 It can be seen that the electrochemical window of the flame-retardant polyester solid electrolyte membrane is 5.4V.

[0052] 4. Symmetrical battery performance test The performance of the Na||polyester solid electrolyte||Na symmetric battery prepared in Example 7 was tested. Figure 6 With a current density of 0.25 mA·cm -2 Surface capacity 0.125mAh·cm -2 Long-cycle performance at low current density Figure 7 For a current density of 0.5 mA·cm -2 Surface capacity 0.25mAh·cm -2 Cyclic performance at high current density.

[0053] Depend on Figure 6 , Figure 7 It can be seen that the flame-retardant polyester solid electrolyte membrane has excellent interfacial stability with sodium metal anode under both high and low current densities, effectively inhibiting sodium dendrite growth. It can achieve stable cycling for over 1500 hours at low current densities and over 700 hours at high current densities.

[0054] 5. Full battery performance test The Prussian white || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 4 and the sodium vanadium fluoride phosphate || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 6 were subjected to charge-discharge tests at room temperature and a current density of 150 mA / g. Figure 8The chart shows the charge-discharge curves of the Prussian white || polyester solid electrolyte || Na all-solid-state sodium battery. The results indicate that the Prussian white || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 4 has a specific capacity of 150 mAh g⁻¹ after 100 discharge cycles at 0.5C rate at room temperature. -1 .

[0055] Figure 9 The cycling curve of the Prussian white || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 4 shows that after 1000 cycles at 1C rate, the capacity retention rate is 87.6% and the coulombic efficiency is close to 100%.

[0056] Figure 10 The image shows the charge-discharge curves of the sodium vanadium fluoride phosphate || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 6. The results show that the specific discharge capacity of the sodium vanadium fluoride phosphate || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 6 at room temperature and a 0.1C rate on the 10th cycle is 118 mAh g. -1 .

[0057] Figure 11 The charge-discharge curve of the sodium vanadium phosphate || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 5 shows that at a rate of 0.5C, the discharge specific capacity after 100 cycles is close to 115 mAh g. -1 The discharge specific capacity at the 500th cycle is close to 105 mAh g. -1 .

[0058] Figure 12 The graph shows the cycling performance of the sodium vanadium phosphate || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 5. The results show that after 1200 cycles at room temperature, the capacity retention of the sodium vanadium phosphate || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 5 can reach 88.4%, and the coulombic efficiency is close to 100%.

[0059] Figure 13 The graph shows the battery cycle performance at room temperature of the sodium vanadium fluoride phosphate || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 6. The results show that the sodium vanadium fluoride phosphate || polyester solid electrolyte || Na all-solid-state sodium battery prepared in Example 6 can maintain a capacity retention of 85.5% and a coulombic efficiency close to 100% after 200 cycles at 1C.

[0060] 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.

[0061] 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. A method for preparing a flame-retardant polyester solid electrolyte membrane, characterized in that, Includes the following steps: Step 1: Add neopentyl glycol diacrylate, microencapsulated flame retardant, 1-methyl-1-propylpiperidine-1-onium bis((trifluoromethyl)sulfonyl)imide, sulfolane, sodium bis(trifluoromethylsulfonyl)imide, triethylene glycol dimethacrylate and azobisisobutyronitrile to a reaction vessel, heat and melt for 6-8 hours, continue stirring for 10-14 hours until clear and transparent, and then heat for another 10-14 hours to obtain a polyester solid electrolyte precursor solution; Step 2: Add the polyester solid electrolyte precursor solution and fluoroethylene carbonate to the reactor, mix and stir, impregnate with a diaphragm, and allow to stand and solidify to obtain a flame-retardant polyester solid electrolyte membrane.

2. The method for preparing a flame-retardant polyester solid electrolyte membrane according to claim 1, characterized in that, The mass ratio of neopentyl glycol diacrylate, microencapsulated flame retardant, 1-methyl-1-propylpiperidine-1-onthium bis((trifluoromethyl)sulfonyl)imide, sulfolane, sodium bis(trifluoromethylsulfonyl)imide, triethylene glycol dimethacrylate, and azobisisobutyronitrile in step one is 0.15-0.3:0-0.35:0.35-1.4:0.25-0.75:0.1-0.2:0.025-0.075:0.05-0.

2.

3. The method for preparing a flame-retardant polyester solid electrolyte membrane according to claim 1, characterized in that, The heating and melting temperature in step one is 65-70℃, and the stirring speed is 300-500 r / min.

4. The method for preparing a flame-retardant polyester solid electrolyte membrane according to claim 1, characterized in that, In step two, the mass ratio of the polyester solid electrolyte precursor solution to fluoroethylene carbonate is 0.925-3.275:0.1-0.

3.

5. The method for preparing a flame-retardant polyester solid electrolyte membrane according to claim 1, characterized in that, The diaphragm mentioned in step two is any one of polyethylene diaphragm, polypropylene diaphragm, glass fiber diaphragm, and cleanroom cloth.

6. The method for preparing a flame-retardant polyester solid electrolyte membrane according to claim 1, characterized in that, The diaphragm mentioned in step two has a diameter of 9-20 mm and a thickness of 0.2-1 mm.

7. The method for preparing a flame-retardant polyester solid electrolyte membrane according to claim 1, characterized in that, The static curing time mentioned in step two is 1-24 hours.

8. The method for preparing a flame-retardant polyester solid electrolyte membrane according to claim 1, characterized in that, The specific preparation process of the microencapsulated flame retardant mentioned in step one is as follows: Ammonium polyphosphate, melamine, and anhydrous ethanol were added to a reaction vessel and stirred for 15-20 minutes at 45-50℃ and 300-500 r / min. Glycidyl methacrylate was added and stirred for 15-20 minutes. Benzoyl peroxide and butanone were mixed evenly and added to the reaction vessel. The temperature was raised to 65-70℃ and copolymerized for 6-7 hours. The mixture was then filtered, washed, and dried to obtain the microencapsulated flame retardant.

9. The method for preparing a flame-retardant polyester solid electrolyte membrane according to claim 8, characterized in that, The ratio of the amount of ammonium polyphosphate, melamine, anhydrous ethanol, glycidyl methacrylate, benzoyl peroxide and methyl ethyl ketone is 80-100g: 15-20g: 150-200mL: 20-30mL: 0.1-0.15g: 15-20mL.

10. A flame-retardant polyester solid electrolyte membrane, characterized in that, It is prepared by the method for preparing a flame-retardant polyester solid electrolyte membrane according to any one of claims 1-9.

Images