Preparation method and application of air-stable sulfide composite electrolyte

Abstract

The invention provides a preparation method and application of an air-stable sulfide composite electrolyte, and the method comprises the following steps: S1, weighing an M source (M = Cd, Mn and Zn), P2S5 and S powder according to a ratio of 1: 1: 3, adding iodine for catalysis, carrying out heat preservation at 700-720 DEG C for 6-7 days, and carrying out K + insertion, Li + exchange and ultrasonic centrifugation to prepare a LiMyPS3 nanosheet dispersion liquid; s2, dissolving PEO and LiTFSI in acetonitrile to form a film, drying to obtain a pure PEO film, immersing the pure PEO film into a dopamine Tris buffer solution with the concentration of 2 mg / ml and the pH value of 8.5, oscillating for 12-24 hours in an oxygen environment, and washing and drying to obtain a PDA-coated PEO film; and S3, carrying out suction filtration on the LiMyPS3 dispersion liquid to obtain a self-supporting membrane, stacking according to the sequence of "PDA-coated PEO membrane-sulfide membrane-PDA-coated PEO membrane", carrying out isostatic pressing at 10-20 MPa, and then carrying out vertical cutting at 0 DEG C to obtain the 20-30 [mu] m composite membrane. The film has the advantages of good air stability, almost no loss of conductivity after 30 days, room temperature conductivity of 9.2-10.2 ms / cm, excellent interface bonding force and mechanical strength, and stable window of 4.3-4.5 V, is adaptive to a high-voltage positive electrode, and can be used for a high-energy-density solid-state lithium battery.

Description

Technical Field

[0001] This invention specifically relates to a method for preparing an air-stabilized sulfide composite electrolyte and its application. Background Technology

[0002] Currently, mainstream lithium battery systems are dominated by traditional liquid lithium-ion batteries. However, their energy density is approaching its theoretical limit (≤300 Wh / kg), making it difficult to meet the ever-increasing demands for range (≥500Wh / kg) of long-endurance devices (such as electric vehicles and energy storage power stations). Furthermore, the organic electrolytes used in liquid lithium-ion batteries are flammable and have poor thermal stability, easily leading to safety accidents such as leakage, fire, and even explosions during charging and discharging, failing to meet the stringent safety requirements of power batteries.

[0003] Solid-state electrolytes, with their excellent thermal stability and mechanical strength, effectively address the safety hazards of liquid electrolytes and provide a key pathway to achieving high energy density in power batteries, thus becoming a core direction for future power battery development. Among numerous solid-state electrolyte materials, sulfide electrolytes have attracted widespread attention in both academia and industry due to their high room-temperature ionic conductivity (comparable to liquid electrolytes) and thermal decomposition temperature more than three times that of liquid electrolyte systems.

[0004] Among them, sulfide LixMyPS3 (M = Cd, Mn, Zn) based on a novel lithium intercalation two-dimensional conduction mechanism exhibits superionic conductor properties, with a room-temperature ionic conductivity of up to 120 mS cm⁻¹, which is tens of times higher than that of traditional sulfide electrolytes. It also shows some stability in air and can be used without applying a high external pressure of hundreds of MPa. However, the lithium-ion conduction of this type of sulfide electrolyte is mainly limited to the lateral direction (parallel to the film surface). This specific conduction path greatly restricts its further application in solid-state batteries, preventing it from fully utilizing its high ionic conductivity advantage.

[0005] To address the aforementioned lateral conduction limitation, existing technologies attempt to stack polymer films and sulfide electrolyte films, followed by cutting and recombining to transform lithium-ion transport channels into vertical (perpendicular to the film surface), thereby preparing high-performance sulfide composite electrolyte films. In this composite system, polyethylene oxide (PEO) polymer electrolyte is often used as a binder to achieve bonding between sulfide particles and the polymer matrix. However, PEO has significant drawbacks: firstly, its interfacial bonding with the electrode and sulfide particles is insufficient, leading to increased interfacial impedance during battery cycling; secondly, PEO is prone to oxidative decomposition at high voltages (typically >4.0 V), making it unsuitable for high-voltage cathode materials and limiting the improvement of battery energy density.

[0006] Polydopamine (PDA), a common biomimetic adhesive material for mussels, possesses unique molecular structure and performance advantages. The catechol / quinone groups in the PDA molecule can be linked through covalent bonds and coordination bonds (such as with Co...). 3+ / Ni 2+ Through bonding, hydrogen bonding, and π-π stacking, PDA achieves universal and ultra-strong adhesion, with a peel strength of 50-100 N / m, far exceeding the 10-20 N / m of PEO, making it particularly suitable for bonding highly active electrode surfaces such as silicon anodes and lithium metal. Furthermore, the quinone / hydroquinone structure of PDA exhibits redox reversibility, enabling dynamic repair of interfacial microcracks caused by volume changes during battery charging and discharging. Its nitrogen-containing groups (-NH-) promote uniform diffusion of Li+ at the interface, reducing ion transport impedance. Simultaneously, PDA is rich in reducing groups such as phenolic hydroxyl and amino groups, effectively scavenging free radicals in the electrolyte system and enhancing the electrolyte's chemical stability and antioxidant capacity. In terms of processing, PDA can be in-situ deposited using room-temperature aqueous solutions, offering extremely low cost and simple processing, and enabling three-dimensional permeation and coating of materials with pore sizes >50 nm. PDA, as a single-component material, achieves a three-in-one function of "bonding-conduction-protection," providing an ideal solution to the interface problems of high-energy-density solid-state batteries. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for preparing and applying an air-stabilized sulfide composite electrolyte.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing an air-stabilized sulfide composite electrolyte, the preparation method comprising the following steps: S1: Preparation of LiMyPS3 nanosheet dispersion: S11: Accurately weigh the metal source (M source, such as Mn powder, Cd powder or Zn powder, purity ≥99%), phosphorus source (such as P2S5, purity ≥98%) and sulfur source (such as S powder, purity ≥99%) according to the stoichiometric ratio of 1:1:3, and add a small amount of iodine as a catalyst; S12: After thoroughly mixing the above-weighed raw materials, vacuum seal them in a quartz tube, place the quartz tube in the middle of a tube furnace, and carry out a high-temperature reaction at 700-720℃ for 6-7 days. After the reaction is completed, wait for the quartz tube to cool to room temperature, collect the reaction product at the cold end of the quartz tube, and wash the product repeatedly with ethanol to remove residual iodine to obtain MPS3 crystals (such as MnPS3, CdPS3 or ZnPS3). S13: MPS3 crystals were immersed in a mixed solution (0.5M KCl + 1M K₂CO₃ + 1M EDTA) and stirred at 50°C for 2 hours; during this process, the hydrated K₂... + Insertion into the MPS3 interlayer promotes the equivalent M 2+ The crystal structure is broken down, forming M vacancies; after the reaction is complete, the product is washed multiple times with deionized water to remove excess K. + ; S14: The product obtained in S13 was mixed with 2M LiCl solution and stirred at room temperature for 4 hours to allow K to be converted through ion exchange. + By Li + The LiMPS3 nanosheets were obtained by substitution (e.g., LiMnPS3, LiCdPS3, or LiZnPS3). The LiMPS3 was redispersed in deionized water and sonicated for 15 minutes to promote crystal exfoliation. Then, the nanosheets were centrifuged at 10,000 rpm for 5 minutes to remove the unexfoliated blocky crystals, thus obtaining the LiMyPS3 nanosheet dispersion.

[0009] S2: Preparation of PDA-modified PEO electrolyte membrane: S21: Preparation of PEO polymer electrolyte membrane: PEO powder (preferably with a molecular weight of 100,000 g / mol) and lithium salt (such as lithium bis(trifluoromethanesulfonyl)imide, LiTFSI) were dissolved in acetonitrile solvent, and the solid content of the system was controlled to be 10 wt%. Furthermore, the EO units in PEO and Li... + The molar ratio was 15:1; the mixed solution was uniformly coated onto a polytetrafluoroethylene (PTFE) plate to form a film, and then the film was transferred to an oven and vacuum dried at 40-60℃ for 12 hours to obtain a pure PEO electrolyte membrane. S22: Preparation of dopamine derivative solution: Dopamine powder was dissolved in a Tris buffer solution at pH 8.5, and the concentration was controlled at 2 mg / ml to obtain a dopamine derivative solution. S23: PDA modification treatment: The pure PEO electrolyte membrane prepared in step S21 is immersed in the dopamine derivative solution obtained in step S2 and shaken in an oxygen environment for 12-24 hours to allow dopamine to polymerize in situ on the PEO membrane surface to form a PDA coating with a thickness of 50-100 nm. After the treatment is completed, the membrane surface is rinsed with deionized water to remove unreacted dopamine monomers and loosely adhered PDA particles. Then, it is vacuum dried at 40-60℃ for 12 hours to obtain the PDA-modified PEO electrolyte membrane, i.e., PDA@PEO membrane.

[0010] S3: Assembly and cutting of air-stabilized sulfide composite electrolyte membranes: S31: The LiMyPS3 nanosheet dispersion prepared in step S1 is filtered by vacuum filtration. After the solvent evaporates naturally, the self-supporting LiMyPS3 sulfide membrane is peeled off from the filter membrane.

[0011] S32: Stacking operation: Stack the membranes repeatedly in the order of “PDA@PEO membrane → self-supporting LiMyPS3 sulfide membrane → PDA@PEO membrane” until the target size is reached. The outermost layer is the PDA@PEO membrane, ensuring that the self-supporting LiMyPS3 sulfide membrane is completely wrapped by the PDA@PEO membrane.

[0012] S33: Pressure bonding: The stacked membrane layers are placed in an isostatic press and subjected to appropriate pressure (preferably 10-20 MPa) to ensure tight bonding of the membrane layers and reduce interfacial voids.

[0013] S34: Low-temperature cutting: Under low-temperature conditions of 0℃, the pressurized composite membrane is cut along a direction perpendicular to the membrane surface to finally obtain a solid sulfide composite electrolyte membrane with a longitudinal lithium-ion transport path. The membrane thickness is controlled to be 20-30 μm.

[0014] Compared with existing technologies, the beneficial effects of this invention are as follows: The LiMyPS3 / PDA@PEO composite electrolyte membrane prepared by this invention exhibits excellent stability in humid air due to the antioxidant protection of the PDA coating and the layered stable structure of LiMyPS3 itself. Experimental data shows that after being placed in air for 30 days, the ionic conductivity of the composite electrolyte membrane is almost unaffected (e.g., the LiMnPS3 / PDA@PEO membrane decreases from 9.2 mS / cm to 8.9 mS / cm, and the LiCdPS3 / PDA@PEO membrane decreases from 10.2 mS / cm to 9.8 mS / cm), which is far superior to traditional sulfide electrolytes (which typically experience a conductivity decrease of more than 50% after one week of placement).

[0015] Secondly, by using the "stack-low temperature cutting" process, the lithium-ion conduction path of LiMyPS3 is changed from horizontal to vertical, effectively solving the conduction direction limitation of the original sulfide; the room temperature ionic conductivity of the composite electrolyte membrane can reach 9.2-10.2 mS / cm, which is close to the level of liquid electrolyte, and can meet the high-rate charge and discharge requirements of solid-state batteries.

[0016] Furthermore, the PDA's superior adhesion (peel strength 50-100 N / m) significantly enhances the interfacial bonding between PEO and the electrode and sulfide film, reducing interfacial impedance. Meanwhile, the composite electrolyte membrane possesses excellent mechanical strength, with tensile strength reaching 2.4-2.7 MPa in the machine direction (MD) and 3.0-3.3 MPa in the transverse direction (TD), enabling it to withstand volume changes during battery assembly and cycling, and reducing the generation of microcracks.

[0017] Finally, the reducing groups of PDA can effectively inhibit the oxidative decomposition of PEO under high voltage. The linear sweep voltammetry (LSV) test of the composite electrolyte membrane shows that its electrochemical stability window can reach 4.3-4.5 V, which can be adapted to high voltage cathode materials such as LiNi0.8Co0.1Mn0.1O2, providing a possibility for improving battery energy density. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of two-dimensional electrolyte conduction obstruction; Figure 2 This is a schematic diagram of the LiCdPS3 / PEO composite electrolyte membrane after cutting. Figure 3 This is a schematic diagram of the process flow for the polymerization of dopamine on the surface of an electrolyte membrane. Figure 4 This is a schematic diagram of the cycle performance of an all-solid-state battery. Detailed Implementation

[0019] To provide a further understanding of the purpose, structure, features, and functions of the present invention, detailed descriptions are provided below with reference to specific embodiments.

[0020] Please refer to the reference. Figures 1 to 4 This invention provides a method for preparing an air-stabilized sulfide composite electrolyte and its application.

[0021] Figure 1 The results show that lithium ions can only be conducted within the LiMyPS3 layered structure in a direction parallel to the film surface, while conduction in the vertical direction is blocked, which cannot meet the battery's requirements for ion transport.

[0022] Figure 2 The results show that after low-temperature cutting, the conduction direction of the LiCdPS3 layered structure changes to be perpendicular to the film surface, and lithium ions can be efficiently transported through the longitudinal channel formed by the LiCdPS3 layer and the PEO layer.

[0023] Figure 3 The process of immersing the PEO membrane in a Tris buffer solution at pH 8.5, the in-situ polymerization of dopamine under the action of oxygen to form a PDA coating, and finally obtaining the PDA@PEO membrane are shown in sequence.

[0024] Figure 4 The horizontal axis represents the number of cycles, and the vertical axis represents the discharge specific capacity (mAh / g). The curves correspond to the cycle performance of the batteries assembled in Example 1 (LiMnPS3 / PDA@PEO), Example 2 (LiCdPS3 / PDA@PEO), and Example 3 (LiZnPS3 / PDA@PEO) at a 0.5 C rate, respectively, showing that all three batteries have good cycle stability.

[0025] Example 1: Preparation of LiMnPS3 / PDA@PEO composite electrolyte membrane.

[0026] S11: Accurately weigh 0.55 g of Mn powder (99.5% purity), 2.22 g of P2S5 (98.5% purity), and 0.96 g of S powder (99.9% purity) according to a stoichiometric ratio of 1:1:3, and add 0.05 g of iodine as a catalyst; S12: After thoroughly mixing the above raw materials in a glove box, vacuum seal them in a quartz tube (10 mm inner diameter, 20 cm length). Place the quartz tube in the middle of a tube furnace and program the temperature to 710°C, holding for 6.5 days. After the tube furnace cools to room temperature, open the quartz tube and collect the black MnPS3 crystals at the cold end. Wash them three times with anhydrous ethanol, soaking for 10 minutes each time to remove residual iodine. Vacuum dry them for later use.

[0027] S13: Immerse 1.0 g of MnPS3 crystals in 50 mL of a mixed solution (0.5 M KCl + 1 M K2CO3 + 1 M EDTA) and stir for 2 hours in a constant temperature water bath at 50 °C. After the reaction is complete, wash the solution three times by centrifugation (5000 rpm, 5 minutes) with deionized water to remove excess K. + .

[0028] S14: Mix the washed product with 50 mL of 2M LiCl solution and stir magnetically at room temperature for 4 hours; then redisperse the product in 30 mL of deionized water, sonicate for 15 minutes (300 W power), and then centrifuge at 10000 rpm for 5 minutes. The supernatant is the LiMnPS3 nanosheet dispersion.

[0029] S21: Weigh 1.9 g of PEO powder (molecular weight 100,000 g / mol) and 0.53 g of LiTFSI (where EO:Li + Add 20 mL of acetonitrile solvent (ratio 15:1) and stir magnetically for 6 hours until completely dissolved to form a 10 wt% mixed solution.

[0030] The mixed solution was uniformly coated on a PTFE plate (wet film thickness of about 200 μm), transferred to a vacuum oven, and vacuum dried at 50°C for 12 hours to obtain a pure PEO electrolyte membrane.

[0031] S22: Prepare 50 mL of Tris buffer solution with pH=8.5, add 0.1 g of dopamine powder, stir until completely dissolved, to obtain a 2 mg / mL dopamine derivative solution.

[0032] S23: Immerse the pure PEO electrolyte membrane in the above dopamine derivative solution, introduce oxygen (flow rate 10 mL / min), and shake at room temperature for 20 hours; after removing the membrane, rinse the surface twice with deionized water, and vacuum dry at 50℃ for 12 hours to obtain the PDA@PEO membrane.

[0033] S31: The LiMnPS3 nanosheet dispersion was filtered in a vacuum filtration device (filter membrane pore size 0.22 μm). After the solvent evaporated, a self-supporting LiMnPS3 sulfide membrane (thickness about 5 μm) was obtained by peeling it off from the filter membrane.

[0034] S32: Stack 3 groups in the order of “PDA@PEO film (thickness 10μm) → self-supporting LiMnPS3 sulfide film → PDA@PEO film” to form a stacked structure with a total thickness of about 45μm.

[0035] S33: Place the laminated structure into an isostatic press and maintain it at a pressure of 15 MPa for 30 minutes to ensure that the film layers are tightly bonded.

[0036] S34: Place the pressurized laminated membrane in a low-temperature environment of about 0-10℃ to facilitate cutting. Use a blade to cut along the direction perpendicular to the membrane surface to obtain a LiMnPS3 / PDA@PEO composite electrolyte membrane with a thickness of 20μm.

[0037] Example 2: Preparation of LiCdPS3 / PDA@PEO composite electrolyte membrane.

[0038] Accurately weigh 1.12 g of Cd powder (99.5% purity), 2.22 g of P2S5 (98.5% purity), and 0.96 g of S powder (99.9% purity) in a stoichiometric ratio of 1:1:3. Add 0.05 g of iodine as a catalyst. The subsequent high-temperature reaction, washing, ion exchange, and exfoliation operations are the same as in Example 1 to obtain a LiCdPS3 nanosheet dispersion.

[0039] Weigh out 2.0 g of PEO powder (molecular weight 100,000 g / mol) and 0.56 g of LiTFSI (where EO:Li +=15:1), add 20 mL of acetonitrile solvent, stir to dissolve, coat into a film, and vacuum dry at 50℃ for 12 hours to obtain a pure PEO film.

[0040] The pure PEO membrane was immersed in a 2 mg / ml dopamine Tris buffer solution (pH=8.5) and shaken for 12 hours under oxygen. The subsequent rinsing and drying operations were the same as in Example 1 to obtain the PDA@PEO membrane.

[0041] The LiCdPS3 nanosheet dispersion was filtered to obtain a self-supporting LiCdPS3 membrane (approximately 5 μm thick). Three sets were stacked in the order of "PDA@PEO membrane → self-supporting LiCdPS3 membrane → PDA@PEO membrane". After being subjected to isostatic pressing at 15 MPa, the LiCdPS3 / PDA@PEO composite electrolyte membrane with a thickness of 20 μm was obtained by cutting at 0℃.

[0042] Example 3: Preparation of LiZnPS3 / PDA@PEO composite electrolyte membrane.

[0043] Accurately weigh 0.65 g of Zn powder (99.5% purity), 2.22 g of P2S5 (98.5% purity), and 0.96 g of S powder (99.9% purity) according to a stoichiometric ratio of 1:1:3. Add 0.05 g of iodine as a catalyst. The subsequent high-temperature reaction, washing, ion exchange, and exfoliation operations are the same as in Example 1 to obtain a LiZnPS3 nanosheet dispersion.

[0044] Weigh 1.9 g of PEO powder (molecular weight 100,000 g / mol), 0.53 g of LiTFSI, and 0.1 g of PDA nanoparticles (PDA addition amount is 5 wt% of PEO weight), add 20 mL of acetonitrile solvent, stir for 6 hours until completely dispersed, coat into a film, and vacuum dry at 50℃ for 12 hours to obtain a PEO film containing PDA particles.

[0045] The PEO membrane containing PDA particles was immersed in a 2 mg / ml dopamine Tris buffer solution (pH=8.5) and shaken for 18 hours under oxygen conditions. The subsequent rinsing and drying operations were the same as in Example 1 to obtain a PDA@PEO membrane with dual PDA modification.

[0046] The LiZnPS3 nanosheet dispersion was filtered to obtain a self-supporting LiZnPS3 membrane (approximately 5 μm thick). Three sets were stacked in the order of "PDA@PEO membrane → self-supporting LiZnPS3 membrane → PDA@PEO membrane". After being subjected to isostatic pressing at 15 MPa, the LiZnPS3 / PDA@PEO composite electrolyte membrane with a thickness of 20 μm was obtained by cutting at 0℃.

[0047] Example 4: Composite electrolyte membrane performance testing and battery assembly.

[0048] Ionic conductivity testing: Electrochemical impedance spectroscopy (EIS) was used. The composite electrolyte membrane was sandwiched between two stainless steel electrodes to assemble an SS / electrolyte / SS symmetrical cell. Testing was conducted at 25°C, with a frequency range of 10 Hz. 6 -10⁻¹ Hz, ionic conductivity calculated from impedance spectrum.

[0049] Electrochemical stability testing: Linear sweep voltammetry (LSV) was used to assemble a Li / electrolyte / SS battery by sandwiching the composite electrolyte membrane between a lithium sheet (working electrode) and a stainless steel sheet (counter electrode). The scan rate was 1 mV / s and the scan range was 0-5 V to determine the electrochemical stability window.

[0050] Mechanical property testing: Using a universal testing machine, the composite electrolyte membrane was cut into strips of 10 mm × 50 mm, and the tensile strength was tested at a stretching rate of 10 mm / min.

[0051] Air stability test: The composite electrolyte membrane was placed in air with 50% humidity and 25°C for 30 days, and its ionic conductivity was tested to evaluate its stability.

[0052] The test results are shown in Table 1 below: Table 1 Test performance of composite electrolyte membranes Electrochemical stability (LSV) Tensile strength (MPa) Ionic conductivity (mS / cm) Ionization rate (mS / cm) after 30 days of storage <![CDATA[LiMnPS3 / PDA@PEO]]> 4.3–4.4 V MD: 2.4TD: 3 9.2 8.9 <![CDATA[LiCdPS3 / PDA@PEO]]> 4.4 V MD: 2.6 TD: 3.2 10.2 9.8 <![CDATA[LiZnPS3 / PDA@PEO]]> 4.4–4.5 V MD: 2.7 TD: 3.3 9.4 9.1 .

[0053] The present invention has been described in the above-described embodiments; however, these embodiments are merely examples for implementing the present invention. It must be noted that the disclosed embodiments do not limit the scope of the present invention. Conversely, any modifications and refinements made without departing from the spirit and scope of the present invention are within the scope of patent protection of the present invention.

Claims

1. A method for preparing an air-stabilized sulfide composite electrolyte, characterized in that: The preparation method includes the following steps: S1: Preparation of LiMyPS3 nanosheet dispersion: Manganese source, Mn powder, phosphorus source, P2S5, sulfur source, and S powder were weighed according to a stoichiometric ratio of 1:1:3, with a small amount of iodine added as a catalyst. The weighed raw materials were mixed and vacuum-sealed in a quartz tube, placed in the middle of a tube furnace, and kept at 700-720℃ for 6-7 days. After cooling to room temperature, the product was collected at the cold end and washed with ethanol to remove residual iodine, yielding MPS3 crystals. The MPS3 crystals were then immersed in the mixed solution and hydrated with K... + Insert, Li + LiMyPS3 nanosheet dispersion was obtained by exchange and ultrasonic exfoliation; S2: Preparation of PEO electrolyte membrane: PEO powder and lithium salt were dissolved in acetonitrile to prepare a solution with a solid content of 10 wt%. The solution was coated onto a PTFE plate to form a film, which was then vacuum dried at 40-60℃ for 12 hours to obtain a pure PEO membrane. Dopamine was then dissolved in a Tris buffer solution with a pH of 8.5 to obtain a dopamine derivative solution with a concentration of 2 mg / ml. The pure PEO membrane was then immersed in the dopamine derivative solution and shaken in an oxygen environment for 12-24 hours. After rinsing with deionized water, it was vacuum dried at 40-60℃ for 12 hours to obtain a PDA@PEO membrane. S3: Assembly and Cutting The LiMyPS3 nanosheet dispersion obtained in step S1 was filtered. After the solvent evaporated, a self-supporting LiMyPS3 sulfide membrane was peeled off from the filter membrane. The membrane was repeatedly stacked in the order of "PDA@PEO membrane → self-supporting LiMyPS3 sulfide membrane → PDA@PEO membrane" until the required size was reached. After isostatic pressing, the membrane was cut at 0°C along the direction perpendicular to the membrane surface to obtain a composite electrolyte membrane with a thickness of 20-30 μm, which is the final solid electrolyte membrane with a vertical transport path.

2. The method for preparing an air-stabilized sulfide composite electrolyte as described in claim 1, characterized in that: In step S1, the purity of the manganese source is ≥99%, the purity of the phosphorus source is ≥98%, and the purity of the sulfur source is ≥99%. The K⁺ insertion process used a mixed solution of 0.5M KCl + 1M K₂CO₃ + 1M EDTA, stirred at 50℃ for 2 hours; Li + The exchange process used 2M LiCl solution and was stirred at room temperature for 4 hours.

3. The method for preparing an air-stabilized sulfide composite electrolyte as described in claim 1, characterized in that: In step S2, the molecular weight of the PEO powder is 100,000 g / mol, the lithium salt is lithium bis(trifluoromethanesulfonyl)imide, and the thickness of the PDA coating in the PDA@PEO film is 50-100 nm.

4. The method for preparing an air-stabilized sulfide composite electrolyte as described in claim 1, characterized in that: In step S2, it can be replaced by mixing PEO powder with PDA nanoparticles, then adding lithium salt and acetonitrile solvent, coating and drying to obtain a PEO@PDA film containing PDA particles, followed by surface PDA coating treatment.

5. The method for preparing an air-stabilized sulfide composite electrolyte as described in claim 1, characterized in that: In step S3, the isostatic pressing pressure is 10-20 MPa, and the holding time is 30 minutes; the cutting direction is perpendicular to the membrane surface to construct a longitudinal lithium-ion transport channel.

6. The composite electrolyte membrane prepared by the preparation method according to any one of claims 1-5, characterized in that: The composite electrolyte membrane has a room temperature ionic conductivity of 9.2-10.2 mS / cm; an electrochemical stability window of 4.3-4.5 V; a tensile strength MD of 2.4-2.7 MPa and a tensile strength TD of 3.0-3.3 MPa; and an ionic conductivity retention rate of ≥96% after being placed in air for 30 days.

7. The application of the composite electrolyte membrane according to claim 6 in a solid-state lithium battery, characterized in that: The composite electrolyte membrane can be assembled into pouch cells or button cells without the application of external pressure, and is compatible with high-voltage cathode materials such as LiNi0.8, Co0.1, and Mn0.1O2.

8. A PDA-modified PEO-based solid electrolyte, characterized in that: It is composed of a PEO polymer matrix, lithium salt, and PDA as a functional additive; the PDA is introduced into the PEO polymer matrix through in-situ polymerization or physical blending to improve the peel strength between the solid electrolyte and the electrode and sulfide electrolyte, while also enhancing the oxidation resistance and high voltage stability of the solid electrolyte; the EO units in the PEO polymer matrix and Li + The molar ratio is 15:1, and the amount of PDA added is 5 wt% of the weight of the PEO polymer matrix.

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