Sulfide solid electrolyte and preparation method thereof

Abstract

The invention discloses a sulfide solid electrolyte and a preparation method thereof, and belongs to the technical field of solid electrolytes.An SA / HPMC nanofiber membrane is prepared by adopting an electrostatic spinning and barium chloride solution crosslinking technology; modifying with KH-550 to obtain an amino modified SA / HPMC nanofiber membrane; lLZNO composite sulfide powder is synthesized through mechanical ball milling and a high-temperature sintering process; dissolving the sulfide solid electrolyte and PEO in anhydrous acetonitrile, dipping an amination carrier, and performing hot pressing treatment to obtain a sulfide solid electrolyte; the fiber membrane has good mechanical strength and structural stability, the optimized porous fiber structure can guide sulfide powder to be evenly attached, a framework is built for ion conduction in advance, and finally the sulfide solid electrolyte has high ion conductivity, air stability and normal-temperature cycle performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid electrolytes, and particularly relates to a sulfide solid electrolyte and a preparation method thereof. BACKGROUND

[0002] In the field of electric vehicles, lithium ion batteries as the core power source have shown key application value, but the traditional liquid electrolyte has the risk of flammability and liquid leakage under extreme conditions such as collision and high temperature, which seriously restricts the safety performance of electric vehicles, and the solid electrolyte can significantly improve the safety of the battery by replacing the liquid electrolyte, and the sulfide solid electrolyte has high ionic conductivity and becomes a research hotspot for promoting the development of electric vehicles in the direction of high safety and long endurance.

[0003] A Chinese patent with the publication number CN114933331B discloses a preparation method of a sulfide solid electrolyte, and the electrolyte material is Li6P 1-a (M) a S5X (M is one or more combinations of vanadium, niobium and tantalum elements, and X = one or more of F, Cl and Br), first, lithium source, phosphorus source, sulfur source, M source and X source are weighed according to the stoichiometric ratio, uniformly mixed and then ball milled to obtain sulfide solid electrolyte precursor powder, and then the precursor powder is sieved and pressed into a sheet-shaped solid to prepare a sulfide solid electrolyte, the present application replaces P elements with VB group elements, realizes controllable doping of vanadium, niobium and tantalum elements while ensuring that the material forms a good argyrodite crystal phase, effectively improves the compatibility and electrochemical stability of the material and lithium series negative electrode, and further significantly improves the cycle stability of the sulfide all-solid-state battery.

[0004] However, in the production, storage and application process of the all-solid-state battery for electric vehicles, the air stability of the phosphorus-containing sulfide solid electrolyte is highlighted, which is easy to react with moisture in the air, release toxic H2S gas, cause the structure of the electrolyte to degrade, and the performance to rapidly decay. SUMMARY

[0005] The purpose of the present application is to provide a sulfide solid electrolyte and a preparation method thereof, which prepares SA / HPMC nanofiber membranes by electrospinning combined with barium chloride crosslinking, modifies the nanofiber membranes with amino groups, and then composites the modified nanofiber membranes with a sulfide coating and performs heat pressing treatment, to prepare a sulfide solid electrolyte with excellent air stability, solve the problem that the phosphorus-containing sulfide solid electrolyte is easy to react with moisture in the air to release H2S gas, cause the structure to degrade and the performance to rapidly decay in the production, storage and application process, and at the same time, the synergistic optimization of the above process on the interfacial bonding force can effectively improve the ionic conductivity and cycle stability at room temperature of the electrolyte.

[0006] The purpose of the present application can be achieved by the following technical solutions: A sulfide solid-state electrolyte and a preparation method thereof, comprising the following steps: Step one: HPMC, SA and deionized water are mixed and stirred to form a spinning solution, and after vacuum degassing, electrostatic spinning is performed, and the obtained fiber membrane is placed in a barium chloride solution for crosslinking reaction to obtain a SA / HPMC nanofiber membrane; Step two: the SA / HPMC nanofiber membrane is modified with silane coupling agent KH-550 to obtain an amino-modified SA / HPMC nanofiber membrane; Step three: LiOH H2O, La2O3, ZrO2 and Nb2O5 are mechanically ball milled and combined with high-temperature sintering to obtain LLZNO powder, and then the powder is subjected to secondary mechanical ball milling and high-temperature sintering with a sulfide system to obtain LLZNO composite sulfide powder; Step four: the LLZNO composite sulfide powder and PEO binder are dissolved in anhydrous acetonitrile to form a uniform and viscous mixed slurry, the amino-modified SA / HPMC nanofiber membrane is immersed to make the sulfide uniformly adhere, and after heat pressing, a sulfide solid-state electrolyte is obtained.

[0007] Further, the specific preparation process of the SA / HPMC nanofiber membrane is as follows: HPMC, SA and deionized water are added to a stirred tank, stirred at 200-300 rpm for 3-4 h to prepare a spinning solution, and after vacuum degassing, electrostatic spinning is performed, the voltage is set to 25-30 kV, the flow rate is controlled at 0.5-0.7 mL / h, the distance from the tip to the collector is adjusted to 12-15 cm, the spinning temperature is kept at 25°C and the humidity is 45%, a syringe with an inner diameter of 0.4 mm is used for spinning at a pushing speed of 0.005-0.008 mm / s, and the obtained fiber membrane is added to a 4wt% barium chloride solution at 25°C for crosslinking for 30-50 min, washed with deionized water for 3-4 times, and naturally dried to obtain a SA / HPMC nanofiber membrane.

[0008] Further, the amount ratio of HPMC, SA, deionized water and barium chloride solution is 8-12 g:4-8 g:150-200 g:150-300 mL.

[0009] Further, the specific preparation process of the amino-modified SA / HPMC nanofiber membrane is as follows: Under argon conditions, an ethanol solution and silane coupling agent KH-550 are added to a reaction kettle and stirred, the pH value is adjusted to 4.5-5.5 with 0.1M concentrated acetic acid, then the SA / HPMC nanofiber membrane is added to the reaction kettle and immersed in the liquid, stirred at 10-30 rpm for 2-3 h, filtered, washed and dried to obtain an amino-modified SA / HPMC nanofiber membrane.

[0010] Further, the volume ratio of the ethanol solution and KH-550 is 80-100:5-10.

[0011] Further, the specific preparation process of the LLZNO composite sulfide powder is as follows: S3: Under the condition of argon, Li2S, As2S3, Si, LiI, elemental sulfur and LLZNO powder are added into a ball mill tank, transferred to a planetary ball mill for ball milling at 600-700 rpm for 40-45 h, and then the powder is pressed into a sheet at 200-300 MPa, sealed in a quartz tube and vacuum sealed, and then the quartz tube is placed in a muffle furnace and heated at 450-550°C for 10-12 h, and then naturally cooled, ball milled at 400-500 rpm for 4 h at the same ball-to-material ratio, and sieved through a 2000 mesh screen to obtain the LLZNO composite sulfide powder.

[0012] Further, the mass ratio of Li2S, As2S3, Si, LiI, elemental sulfur, and LLZNO is 6-7:15-17:0.08-0.1:6.5-7.75:0.7-0.9:4-5.

[0013] Further, the specific preparation process of the LLZNO powder is as follows: LiOH·H2O, La2O3, ZrO2, Nb2O5 and grinding medium 2-propanol are added into a ball mill tank, then ball milled at 300-400 rpm for 7-8 h, dried, placed in an argon atmosphere, calcined at 950°C for 5-6 h to obtain cubic phase LLZNO powder, ball milled at 200-300 rpm for 6-7 h, and sieved through a 2000 mesh screen to obtain the LLZNO powder.

[0014] Further, the amount ratio of LiOH·H2O, La2O3, ZrO2, Nb2O5 and 2-propanol is 9g-13.4g:5g-7.4g:5.6-8.4g:2-3.5g:20m-40mL.

[0015] Further, the specific preparation process of the sulfide solid electrolyte is as follows: LLZNO composite sulfide powder, binder PEO and anhydrous acetonitrile are stirred and mixed to form a uniform and viscous mixed slurry, the mixed slurry is coated on both sides of the amino-modified SA / HPMC film, the coating amount on each side is 0.1-0.2g / cm 2 , then laid between two pieces of polytetrafluoroethylene plate, hot pressed at 110-130°C and 3-5 MPa for 1-3 h, vacuum dried to obtain the sulfide solid electrolyte.

[0016] Further, the amount ratio of LLZNO composite sulfide powder, PEO and anhydrous acetonitrile is 5-9g:0.3-0.7g:8-15mL.

[0017] The beneficial effects of this invention are: 1. In this invention, HPMC and SA form a uniform spinning solution due to their good compatibility, and after electrospinning, they undergo barium chloride crosslinking treatment: Ba 2+ The coordination bonds formed with the SA carboxyl groups enhance the mechanical strength and structural stability of the fiber membrane. This optimized porous fiber structure can guide the uniform adhesion of sulfide powder and pre-build a framework for ion conduction.

[0018] 2. In this invention, when the silane coupling agent KH-550 is used to modify the SA / HPMC nanofiber membrane with amino groups, the ethoxy groups in its molecules hydrolyze under acidic conditions to generate silanol groups. These silanol groups undergo a condensation reaction with the hydroxyl groups on the surface of the SA / HPMC fiber membrane to form stable Si-OC covalent bonds, firmly grafting the amino functional groups onto the surface of the fiber membrane. The grafted amino groups also interact with the metal ions or hydroxyl active sites on the surface of the LLZNO composite sulfide powder through coordination bonds or hydrogen bonds, forming a chemical bridge at the organic-inorganic interface. This dual-action mechanism not only significantly enhances the interfacial bonding force, promotes the uniform and continuous distribution of sulfides on the surface of the fiber membrane, and reduces the interfacial obstruction of ion conduction, but also effectively blocks the intrusion of small molecules such as water molecules and oxygen in the air, reducing the risk of degradation of the sulfide electrolyte due to contact with water vapor, thereby improving the ion conduction efficiency and air stability of the material.

[0019] 3. This invention uses the pressure generated by hot pressing to force sulfide powder to overcome surface energy and achieve close packing. The resulting dense structure builds a continuous and unobstructed ion transport channel, directly improving the overall ionic conductivity. During charge-discharge cycles, the electrode material will undergo volume changes due to the insertion and extraction of lithium ions. After hot pressing, the bonding force between sulfide powders and at the interface with the electrode is significantly enhanced, which can effectively resist the peeling effect caused by cyclic stress, thereby ensuring that the material maintains good capacity retention in 100-cycle testing. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: This example provides a sulfide solid electrolyte and its preparation method, including the following steps: S1: 10g HPMC (hydroxypropyl methylcellulose), 6g SA (sodium alginate) and 184g deionized water were added to a stirred tank and stirred at 200rpm for 4h to form a homogeneous and transparent spinning solution. After vacuum degassing, electrospinning was performed with a voltage of 25kV, a flow rate of 0.6mL / h, a tip-to-collector distance of 12cm, and a spinning temperature of 25℃ and humidity of 45%. A syringe with an inner diameter of 0.4mm was used for spinning at a feed rate of 0.006mm / s. The spun fiber membrane was added to 200mL of 4wt% barium chloride solution at 25℃ for crosslinking for 30min. After washing three times with deionized water and air drying, an SA / HPMC nanofiber membrane was obtained with an average fiber diameter of 150-160nm and a membrane thickness of 55-65μm. HPMC and SA were cross-linked with barium chloride via electrospinning to form nanofiber membranes, in which Ba... 2+ SA / HPMC nanofiber membranes are obtained by coordinating with the carboxyl groups of SA to form stable ionic bonds to enhance mechanical properties.

[0022] S2: Under argon atmosphere, 95 mL of ethanol solution and 5 mL of silane coupling agent KH-550 were added to the reaction vessel and stirred. The pH was adjusted to 5.0 with 0.1 M glacial acetic acid. Then, the SA / HPMC nanofiber membrane was added to the reaction vessel and immersed in the liquid. The reaction was stirred at 10-20 rpm for 2 h. The membrane was washed three times with anhydrous ethanol and dried under vacuum at 40 °C for 6 h to obtain the amino-modified SA / HPMC nanofiber membrane.

[0023] S3: 13.4g LiOH・H2O, 7.4g La2O3, 8.4g ZrO2, 3g Nb2O5 and 30mL of grinding medium 2-propanol were added to a ball mill jar, and zirconia balls were added at a material-to-ball mass ratio of 1:15. The mixture was then transferred to a planetary ball mill and ball-milled at 300rpm for 8h. After drying, the mixture was calcined at 950℃ for 6h under an argon atmosphere to obtain cubic phase LLZNO powder. This powder was ball-milled at 200rpm for 6h at the same material-to-ball ratio, passed through a 2000-mesh sieve, and dried to obtain LLZNO powder. Under argon atmosphere, 7g Li2S, 17g As2S3, 0.1g Si, 7.75g LiI, 0.9g elemental sulfur, and 5g LLZNO powder were added to a ball mill jar. Zirconia balls were added at a material-to-ball mass ratio of 1:20. The mixture was then transferred to a planetary ball mill and ball-milled at 600 rpm for 45 hours. After ball milling, the powder was pressed into sheets at 250 MPa, sealed in a quartz tube, and vacuum-sealed. The quartz tube was then placed in a muffle furnace and heated at 550℃ for 12 hours. After natural cooling, the powder was ball-milled at 400 rpm for 4 hours at the same material-to-ball ratio and passed through a 2000-mesh sieve to obtain LLZNO composite sulfide powder.

[0024] S4: Mix 8g of LLZNO composite sulfide powder, 0.5g of binder PEO, and 10mL of anhydrous acetonitrile to form a uniform and viscous slurry. Coat the slurry onto both sides of the amino-modified SA / HPMC membrane, with a coating amount of 0.15g / cm² on each side. 2 Then, it is laid flat between two polytetrafluoroethylene plates, hot-pressed at 120℃ and 5MPa for 2 hours, and then vacuum dried at 80℃ for 12 hours to obtain sulfide solid electrolyte.

[0025] Example 2: This example provides a sulfide solid electrolyte and its preparation method, including the following steps: S1: Add 8g HPMC, 4g SA and 150g deionized water to a stirred tank and stir for 3h at 200rpm to form a uniform and transparent spinning solution. After vacuum degassing, electrospinning is performed with a voltage of 28kV, a flow rate of 0.5mL / h, a tip-to-collector distance of 14cm, and a spinning temperature of 25℃ and humidity of 45%. Use a syringe with an inner diameter of 0.4mm and a feed rate of 0.005mm / s to spin the fiber membrane. At 25℃, add the spun fiber membrane to 150mL of 4wt% barium chloride solution for crosslinking for 45min. Wash with deionized water 3 times and air dry to obtain SA / HPMC nanofiber membrane with an average fiber diameter of 150-160nm and a membrane thickness of 55-65μm. S2: Under argon atmosphere, 95 mL of ethanol solution and 5 mL of silane coupling agent KH-550 were added to the reaction vessel and stirred. The pH was adjusted to 5.0 with 0.1 M glacial acetic acid. Then, the SA / HPMC nanofiber membrane was added to the reaction vessel and immersed in the liquid. The reaction was stirred at 20-30 rpm for 2 h. The membrane was washed three times with anhydrous ethanol and dried under vacuum at 40 °C for 5 h to obtain the amino-modified SA / HPMC nanofiber membrane.

[0026] S3: Add 9g LiOH・H2O, 5g La2O3, 5.6g ZrO2, 2g Nb2O5 and 20mL of grinding medium 2-propanol to a ball mill jar, add zirconia balls at a material-to-ball mass ratio of 1:15, then transfer to a planetary ball mill and ball mill at 350rpm for 7h. After drying, place under an argon atmosphere and calcine at 950℃ for 5h to obtain cubic phase LLZNO powder. This powder is ball milled at 250rpm for 6h at the same material-to-ball ratio, passed through a 2000-mesh sieve, and dried to obtain LLZNO powder. Under argon atmosphere, 6g Li2S, 15g As2S3, 0.08g Si, 6.5g LiI, 0.7g elemental sulfur, and 4g LLZNO powder were added to a ball mill jar. Zirconia balls were added at a material-to-ball mass ratio of 1:20. The mixture was then transferred to a planetary ball mill and milled at 650 rpm for 45 hours. After milling, the powder was pressed into sheets at 250 MPa, sealed in a quartz tube, and vacuum-sealed. The quartz tube was then placed in a muffle furnace and heated at 550℃ for 10 hours. After natural cooling, the powder was milled at 450 rpm for 4 hours at the same material-to-ball ratio and passed through a 2000-mesh sieve to obtain LLZNO composite sulfide powder.

[0027] S4: Mix 5g of LLZNO composite sulfide powder, 0.3g of PEO, and 8mL of anhydrous acetonitrile to form a uniform and viscous slurry. Coat the slurry onto both sides of the amino-modified SA / HPMC membrane, with a coating amount of 0.1g / cm² on each side. 2 Then, it is laid flat between two polytetrafluoroethylene plates, hot-pressed at 120℃ and 5MPa for 2 hours, and then vacuum dried at 80℃ for 12 hours to obtain sulfide solid electrolyte.

[0028] Example 3: This example provides a sulfide solid electrolyte and its preparation method, including the following steps: S1: 12g HPMC, 8g SA and 200g deionized water were added to a stirred tank and stirred at 200rpm for 3h to form a homogeneous and transparent spinning solution. After vacuum degassing, electrospinning was performed with a voltage of 30kV, a flow rate of 0.7mL / h, a tip-to-collector distance of 15cm, and a spinning temperature of 25℃ and humidity of 45%. A syringe with an inner diameter of 0.4mm was used for spinning at a feed rate of 0.008mm / s. The spun fiber membrane was added to 300mL of 4wt% barium chloride solution at 25℃ for crosslinking for 50min. After washing three times with deionized water and air drying, an SA / HPMC nanofiber membrane was obtained with an average fiber diameter of 150-160nm and a membrane thickness of 55-65μm. S2: Under argon atmosphere, 100 mL of ethanol solution and 10 mL of silane coupling agent KH-550 were added to the reaction vessel and stirred. The pH was adjusted to 5.0 with 0.1 M glacial acetic acid. Then, the SA / HPMC nanofiber membrane was added to the reaction vessel and immersed in the liquid. The reaction was stirred at 30-40 rpm for 2 h. The membrane was washed three times with anhydrous ethanol and dried under vacuum at 40 °C for 5 h to obtain the amino-modified SA / HPMC nanofiber membrane.

[0029] S3: 12g LiOH・H2O, 6.5g La2O3, 7g ZrO2, 3.5g Nb2O5 and 40mL of grinding media 2-propanol were added to a ball mill jar. Zirconia balls were added at a material-to-ball mass ratio of 1:15. The mixture was then transferred to a planetary ball mill and ball-milled at 400rpm for 8h. After drying, the mixture was calcined at 950℃ for 6h under an argon atmosphere to obtain cubic phase LLZNO powder. This powder was ball-milled at 300rpm for 6h at the same material-to-ball ratio, passed through a 2000-mesh sieve, and dried to obtain LLZNO powder. Under argon atmosphere, 6g Li2S, 15g As2S3, 0.08g Si, 6.5g LiI, 0.7g elemental sulfur, and 4g LLZNO powder were added to a ball mill jar. Zirconia balls were added at a material-to-ball mass ratio of 1:20. The mixture was then transferred to a planetary ball mill and milled at 700 rpm for 45 hours. After milling, the powder was pressed into sheets at 250 MPa, sealed in a quartz tube, and vacuum-sealed. The quartz tube was then placed in a muffle furnace and heated at 550℃ for 10 hours. After natural cooling, the powder was milled at 500 rpm for 4 hours at the same material-to-ball ratio and passed through a 2000-mesh sieve to obtain LLZNO composite sulfide powder.

[0030] S4: Mix 9g of LLZNO composite sulfide powder, 0.7g of PEO, and 15mL of anhydrous acetonitrile to form a uniform and viscous slurry. Coat the slurry onto both sides of the amino-modified SA / HPMC membrane, with a coating amount of 0.15g / cm² on each side. 2 The mixture was laid flat between two polytetrafluoroethylene plates, hot-pressed at 120℃ and 5MPa for 2 hours, and then vacuum-dried at 80℃ for 12 hours to obtain a sulfide solid electrolyte.

[0031] Comparative Example 1: The difference from Example 1 is that the barium chloride crosslinking step of spinning the fiber membrane is omitted in S1. After spinning, the uncrosslinked SA / HPMC nanofiber membrane is directly washed with water and dried to obtain an uncrosslinked SA / HPMC nanofiber membrane. This membrane is used to replace the amino-modified SA / HPMC membrane in S4. The other steps remain unchanged to obtain a sulfide solid electrolyte.

[0032] Comparative Example 2: The difference from Example 1 is that step S2, which involves modification with silane coupling agent KH-550, is omitted. The original SA / HPMC nanofiber membrane prepared in S1 is directly coated with the coating in step S4. The remaining steps remain unchanged, resulting in a sulfide solid electrolyte.

[0033] Comparative Example 3: The difference from Example 1 is that the hot pressing process in step S4 is omitted, and the film with attached powder is directly placed in a vacuum dryer at 80°C for 12 hours. The remaining steps remain unchanged, and a sulfide solid electrolyte is obtained.

[0034] Comparative Example 4: The difference from Example 1 is that HPMC in step S1 is replaced with HEC (hydroxyethyl cellulose) to prepare an HEC / SA nanofiber membrane, which is then used to replace the amino-modified SA / HPMC membrane in step S4. The remaining steps remain unchanged to obtain a sulfide solid electrolyte.

[0035] Performance testing experiments: Performance tests were conducted on Examples 1-3 and Comparative Examples 1-4.

[0036] (1) Ionic conductivity test: A circular membrane with a diameter of 10 mm was cut from the synthesized sulfide solid electrolyte and placed in an insulating sleeve with an inner diameter of 10 mm. Stainless steel sheets were placed on both sides and a pressure of 10 MPa was applied to ensure that the electrodes and the membrane were in close contact. The impedance value R was obtained by AC impedance spectroscopy. At the same time, the actual thickness d and area S of the membrane were measured. The ionic conductivity was calculated according to the formula σ=d / (R×S).

[0037] (2) Cyclic stability test of all-solid-state lithium metal battery: During assembly, high-nickel ternary NCM811, sulfide solid electrolyte of Examples 1-3 and Comparative Examples 1-4, conductive agent vapor-grown carbon fiber, and binder styrene-butadiene-styrene block copolymer were added to isobutyl isobutyrate in a certain mass ratio. After slurrying, the positive electrode sheet was coated with a scraper and punched into a positive electrode sheet with a diameter of 10 mm. A 10 mm diameter film was cut from the sulfide solid electrolyte film and placed directly into a 10 mm diameter polyether ether ketone mold. The positive electrode sheet was placed on one side and pressed at 500 MPa for 10 min to ensure tight bonding at the interface. The lithium metal negative electrode was placed on the other side and pressed at 20 MPa for 1 min to make an all-solid-state lithium metal battery. Its cycle stability was tested by constant current charge and discharge cycle (expressed as capacity retention rate after 100 cycles / %).

[0038] (3) Air stability test: Take each sulfide solid electrolyte membrane (cut into a uniform membrane with a diameter of 10 mm), place it in an environment with a temperature of 25±3℃ and a dew point of ≤-55℃ and let it stand for 6 hours. After standing, test the ionic conductivity and cycle performance according to the above method, calculate the ionic conductivity reduction rate ((conductivity before exposure - conductivity after exposure) / conductivity before exposure × 100%), and evaluate the air stability by combining the reduction rate and the cycle performance after exposure.

[0039] Table 1. Ionic conductivity and cycling performance of various sulfide solid electrolytes Table 2. Ionic conductivity and cycling performance of various sulfide solid electrolytes after air exposure. As shown in Table 1, the ionic conductivity of Examples 1-3 is between 11.9 and 12.8 mS / cm, and the 100-cycle discharge capacity retention is between 93% and 96%. The overall performance is better than that of Comparative Examples 1-4. The specific differences and reasons are as follows: Comparative Example 1 did not form Ba because barium chloride crosslinking was omitted. 2+ The coordination bond with the carboxyl group of SA results in insufficient stability of the fiber membrane, making it difficult to support continuous coating and leading to performance degradation. Comparative Example 2 omits silane coupling agent modification, lacking the effect of amino groups in enhancing the interfacial bonding between the fiber membrane and sulfide. The loose interface hinders ion conduction and makes the coating easy to fall off, exacerbating performance degradation. Comparative Example 3 omits hot pressing, failing to promote coating densification to reduce porosity and enhance bonding strength. The loose coating leads to broken ion transport paths and extremely poor cycle stability. Comparative Example 4 uses HEC instead of HPMC to prepare fiber membranes. The compatibility between HEC and SA is not as good as that of HPMC. The nanofiber membrane structure formed after spinning and crosslinking has poor adaptability to coating adhesion and is difficult to provide a favorable ion conduction environment. Therefore, although its performance is better than other comparative examples, it is still lower than that of the examples.

[0040] As shown in Table 2, the ionic conductivity (11.2-12.3 mS / cm), first-cycle discharge capacity (204-209 mAh / g), and 100-cycle capacity retention (90-93%) of Examples 1-3 are all superior to those of Comparative Examples 1-4, and the ionic conductivity reduction rate (3.9-5.9%) is also lower, indicating that their air stability and overall performance are better. The specific differences and reasons are as follows: Comparative Example 1 did not form Ba because barium chloride crosslinking was omitted. 2+The coordination bond with the SA carboxyl group results in insufficient stability of the fiber membrane, failing to provide a stable substrate for the sulfide coating to ensure continuous ion conduction pathways. The loose membrane structure leads to easy coating detachment, and the loose structure is more prone to adsorbing moisture, exacerbating sulfide degradation. Therefore, the performance is significantly lower than that of the examples. Comparative Example 2 omits the silane coupling agent modification, lacking the effect of amino groups on enhancing the interfacial bonding between the fiber membrane and the sulfide, failing to reduce interfacial defects to enhance ion conduction and prevent air intrusion. The loose interface is susceptible to air erosion, affecting conductivity and initial cycle capacity. Interfacial peeling intensifies during cycling, and the 100-cycle discharge capacity retention rate remains low, resulting in performance inferior to Comparative Example 1. Comparative Example 3 omits the hot-pressing process, which cannot densify the coating to reduce porosity and enhance bonding strength. The loose coating leads to obstructed ion conduction, and the pores become channels for air intrusion. The structure is easily damaged during cycling, and the first-cycle capacity and 100-cycle discharge capacity retention are not ideal. Comparative Example 4 replaces HPMC with HEC. The compatibility between HEC and SA is not as good as that of HPMC. The resulting fiber membrane has slightly inferior compatibility and support effect on the coating, and it is difficult to provide a favorable ion conduction environment and air stability. Therefore, although its performance is better than other comparative examples, it is still inferior to the example. The conductivity, first-cycle capacity and 100-cycle discharge capacity retention are slightly reduced.

[0041] 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 process, method, article, or apparatus.

[0042] 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 sulfide solid electrolyte, characterized in that, The preparation includes the following steps: Step 1: HPMC, SA and deionized water are mixed and stirred to form a spinning solution. After vacuum degassing, electrospinning is performed. The resulting fiber membrane is placed in barium chloride solution for cross-linking reaction to obtain SA / HPMC nanofiber membrane. Step 2: Modify the SA / HPMC nanofiber membrane with silane coupling agent KH-550 to obtain an amino-modified SA / HPMC nanofiber membrane; Step 3: LiOH・H2O, La2O3, ZrO2, and Nb2O5 are mechanically ball-milled and then sintered at high temperature to obtain LLZNO powder. The powder is then combined with the sulfide system through a second mechanical ball milling and high-temperature sintering to obtain LLZNO composite sulfide powder. Step 4: Dissolve LLZNO composite sulfide powder and PEO binder in anhydrous acetonitrile to form a uniform and viscous slurry. Impregnate the slurry with an amino-modified SA / HPMC nanofiber membrane to ensure uniform adhesion of the sulfide powder. After hot pressing, a sulfide solid electrolyte is obtained.

2. The method for preparing a sulfide solid electrolyte according to claim 1, characterized in that, The specific preparation process of the SA / HPMC nanofiber membrane is as follows: HPMC, SA, and deionized water were added to a stirred tank and stirred at 200-300 rpm for 3-4 hours to prepare a spinning solution. After vacuum degassing, electrospinning was performed with a voltage of 25-30 kV, a flow rate of 0.5-0.7 mL / h, and a distance of 12-15 cm from the tip to the collector. The spinning temperature was maintained at 25℃ and the humidity at 45%. A syringe with an inner diameter of 0.4 mm was used for spinning at a feed rate of 0.005-0.008 mm / s. The spun fiber membrane was added to a 4 wt% barium chloride solution at 25-35℃ for crosslinking for 30-50 minutes. After washing and air drying, SA / HPMC nanofiber membrane was obtained.

3. The method for preparing a sulfide solid electrolyte according to claim 2, characterized in that, The ratio of HPMC, SA, deionized water and barium chloride solution used is 8-12g: 4-8g: 150-200g: 150-300mL.

4. The method for preparing a sulfide solid electrolyte according to claim 1, characterized in that, The specific preparation process of the amino-modified SA / HPMC nanofiber membrane is as follows: Under argon atmosphere, ethanol solution and silane coupling agent KH-550 were added to a reaction vessel and stirred. The pH was adjusted to 4.5-5.5 with 0.1M glacial acetic acid. Then, the SA / HPMC nanofiber membrane was added to the reaction vessel and immersed in the liquid. The reaction was stirred at 10-30 rpm for 2-3 hours. After filtration, washing, and drying, amino-modified SA / HPMC nanofiber membrane was obtained. The volume ratio of the ethanol solution to KH-550 is 80-100:5-10.

5. The method for preparing a sulfide solid electrolyte according to claim 1, characterized in that, The specific preparation process of the LLZNO composite sulfide powder is as follows: Under argon atmosphere, Li2S, As2S3, Si, LiI, elemental sulfur, and LLZNO powders were added to a ball mill jar and then transferred to a planetary ball mill and ball-milled at 600-700 rpm for 40-45 h. After ball milling, the powder was pressed into sheets at 200-300 MPa, sealed in a quartz tube, and vacuum-sealed. The quartz tube was then placed in a muffle furnace and heated at 450-550℃ for 10-12 h. After natural cooling, the powder was ball-milled at 400-500 rpm for 4 h and passed through a 2000-mesh sieve to obtain LLZNO composite sulfide powder.

6. The method for preparing a sulfide solid electrolyte according to claim 5, characterized in that, The mass ratio of Li2S, As2S3, Si, LiI, elemental sulfur and LLZNO powder is 6-7:15-17:0.08-0.1:6.5-7.75:0.7-0.9:4-5.

7. The method for preparing a sulfide solid electrolyte according to claim 5, characterized in that, The specific preparation process of the LLZNO powder is as follows: LiOH・H2O, La2O3, ZrO2, Nb2O5 and 2-propanol grinding media were added to a ball mill jar and ball-milled at 300-400 rpm for 7-8 h. After drying, the mixture was placed in an argon atmosphere and calcined at 950℃ for 5-6 h to obtain cubic phase LLZNO powder. The powder was then ball-milled at 200-300 rpm for 6-7 h and dried to obtain LLZNO powder.

8. The method for preparing a sulfide solid electrolyte according to claim 7, characterized in that, The ratio of LiOH・H2O, La2O3, ZrO2, Nb2O5 and 2-propanol is 9g-13.4g: 5g-7.4g: 5.6-8.4g: 2-3.5g: 20m-40mL.

9. The method for preparing a sulfide solid electrolyte according to claim 1, characterized in that, The specific preparation process of the sulfide solid electrolyte is as follows: LLZNO composite sulfide powder, PEO binder, and anhydrous acetonitrile were mixed to form a uniform and viscous slurry. This slurry was then coated onto both sides of an amino-modified SA / HPMC membrane, with a coating amount of 0.1-0.2 g / cm³ on each side. 2 Then, it is laid flat between two polytetrafluoroethylene plates, hot-pressed at 110-130℃ and 3-5MPa for 1-3 hours, and vacuum dried to obtain sulfide solid electrolyte. The ratio of LLZNO composite sulfide powder, PEO, and anhydrous acetonitrile is 5-9g: 0.3-0.7g: 8-15mL.

10. A sulfide solid electrolyte, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

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