Method and device for improving air stability of sulfide solid electrolyte

Abstract

The invention relates to the field of solid electrolyte, in particular to a method and a device for improving air stability of sulfide solid electrolyte. The method comprises the following steps: placing a solid fluorinating agent in a first temperature zone reaction device, heating the solid fluorinating agent at a first temperature, and decomposing the solid fluorinating agent to generate HF-containing gas; and placing the sulfide solid electrolyte in a second temperature zone reaction device, vacuumizing the second temperature zone, introducing the HF-containing gas generated in the first temperature zone, and keeping the temperature for 1-3 hours at the second temperature. According to the method, a uniform and compact fluoride shell layer is generated in situ on the surface of the sulfide solid electrolyte through a gas-solid reaction, and a core-shell structure is formed. The shell layer can effectively prevent air from being in contact with a substrate, the air stability of the material is remarkably improved, the process is safe, toxic gas residues are avoided, raw materials are cheap and easy to obtain, and the shell layer is suitable for large-scale production.

Description

A method and apparatus for improving the air stability of sulfide solid electrolytes Technical Field

[0001] This invention relates to the field of solid electrolytes, and more particularly to a method and apparatus for improving the air stability of sulfide solid electrolytes. Background Technology

[0002] With the rapid development of the new energy industry, the demand for improved energy density, safety, and cycle life of lithium-ion batteries, as core energy storage devices, is becoming increasingly urgent. Traditional liquid electrolyte lithium-ion batteries, due to safety hazards such as leakage and flammability / explosion, are no longer able to meet the application requirements of high-end energy storage scenarios (such as electric vehicles and large-scale energy storage power stations). Solid-state lithium-ion batteries, which use solid electrolytes instead of liquid electrolytes, fundamentally solve the problems of electrolyte leakage and thermal runaway, and have become the core development direction of next-generation lithium-ion batteries.

[0003] Among numerous solid-state electrolyte materials, sulfide solid-state electrolytes (such as Li6PS5Cl, abbreviated as LPSC) are considered one of the most commercially promising solid-state electrolytes due to their ultra-high room-temperature ionic conductivity (reaching the level of 10⁻² S / cm, close to that of liquid electrolytes), good machinability, and compatibility with lithium metal anodes. However, sulfide solid-state electrolytes have a fatal flaw: extremely poor air stability. Their surface readily reacts with moisture (H₂O) and oxygen (O₂) in the air, generating insulating products such as LiOH and Li₂CO₃, while releasing toxic H₂S gas. This not only leads to a sharp drop in ionic conductivity but also poses safety risks and environmental hazards, seriously hindering the large-scale production, storage, transportation, and practical application of sulfide solid-state electrolytes.

[0004] Therefore, developing a modification method that can effectively improve the air stability of sulfide solid electrolytes without significantly sacrificing their intrinsic ionic conductivity has become a research hotspot and a core technological bottleneck in the field of solid-state batteries.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method and apparatus for improving the air stability of sulfide solid electrolytes, and to provide a modification method that effectively improves the air stability of sulfide solid electrolytes without significantly sacrificing their intrinsic ionic conductivity.

[0007] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for improving the air stability of a sulfide solid electrolyte, comprising the following steps: S1, placing a solid fluorinating agent in a first temperature zone reaction device and a sulfide solid electrolyte in a second temperature zone reaction device, wherein a closable connection channel is provided between the first temperature zone reaction device and the second temperature zone reaction device; the solid fluorinating agent can decompose HF-containing gas by heating; S2, closing the connection channel and evacuating the second temperature zone reaction device; S3, heating the first temperature zone reaction device to a first temperature and then holding it at that temperature until the solid fluorinating agent is completely decomposed; S4, opening the connection channel to allow the gas from the first temperature zone reaction device to flow into the second temperature zone reaction device; S5, heating the second temperature zone reaction device to a second temperature and holding it at that temperature for 1-3 hours to obtain a modified sulfide solid electrolyte with a "core-shell" structure, thus completing the method for improving the air stability of the sulfide solid electrolyte.

[0008] Optionally, in S2, before closing the connection channel, the gas inside the first and second temperature zone reaction devices is replaced with inert gas. This process typically involves repeated purging and priming three times to ensure the internal atmosphere is completely free of air, thus resulting in excellent final material properties.

[0009] Optionally, the mass ratio of the solid fluorinating agent to the sulfide solid electrolyte is 1:2-4.

[0010] Optionally, the solid fluorinating agent is NH4F, NH4HF2, or (NH4)2SiF6.

[0011] Optionally, the sulfide solid electrolyte is Li6PS5Cl or Li7P3S. 11 Li6P 1-x Ge x S5Cl, Li 6+3x P 1- x Sn x S5Cl.

[0012] Optionally, the first temperature is 120-250℃; the second temperature is 100-150℃; and the heating rate is 3-5℃.

[0013] Optionally, in S5, after the second temperature zone reaction device is heated to the second temperature, an inert gas is introduced into the first temperature zone reaction device.

[0014] Secondly, the present invention provides an apparatus for improving the air stability of sulfide solid electrolytes, comprising: a first temperature zone reaction device, a second temperature zone reaction device, and a connecting channel, wherein the connecting channel is connected between the first temperature zone reaction device and the second temperature zone reaction device, and the connecting channel is provided with an opening and closing device; the first temperature zone reaction device includes a first reaction vessel, an air inlet and an air outlet provided on the first reaction vessel; and the second temperature zone reaction device includes a second reaction vessel, an air inlet and an air outlet provided on the second reaction vessel.

[0015] Optionally, the first temperature zone reaction device further includes a temperature control device 1 disposed at the bottom of the first reaction vessel, and the second temperature zone reaction device further includes a temperature control device 2 disposed at the bottom of the second reaction vessel.

[0016] Optionally, the second temperature zone reaction device further includes multiple multi-layered, detachable hollow platforms spaced apart along the vertical direction of the reactor.

[0017] Beneficial Effects: This invention provides a method and apparatus for improving the air stability of sulfide solid electrolytes (LPSCs). The invention employs two interconnected, independent temperature-zone reaction devices. The first temperature-zone reaction device holds a solid fluorinating agent, and the second temperature-zone reaction device holds the sulfide solid electrolyte (LPSC) to be modified. By controlling the temperature of the first temperature zone, the solid fluorinating agent evaporates into an HF-containing gas. The mixed gas enters the second temperature-zone reaction device through a connecting channel, where it undergoes a gas-solid reaction with the LPSC surface at a set temperature, generating a uniform fluoride shell layer in situ on the LPSC surface, forming a "core-shell" structure modified LPSC. This invention achieves precise control of the reaction process through precise temperature control in two temperature zones. The solid fluorinating agent raw material is inexpensive, safe, and widely available. The generated fluoride shell layer bonds tightly to the LPSC matrix interface, effectively preventing air contact with the LPSC matrix and significantly improving its air stability. Simultaneously, there is no risk of toxic gas residue. The process is simple and suitable for large-scale production. Attached Figure Description

[0018] Figure 1 is a flowchart illustrating a method for improving the air stability of a sulfide solid electrolyte according to Example 1.

[0019] Figure 2 is a schematic diagram of the device for improving the air stability of sulfide solid electrolyte in Example 1.

[0020] Figure 3 is a schematic diagram of the second temperature zone reaction device in Example 1.

[0021] Figure 4 is a schematic diagram of the hollow stage in Example 1.

[0022] Figure 5 is a scanning electron microscope image of the sulfide solid electrolyte of Example 2 after the method for improving the air stability of the sulfide solid electrolyte.

[0023] Figure 6 shows the powder diffraction pattern of the sulfide solid electrolyte of Example 2 after the method for improving the air stability of the sulfide solid electrolyte. Detailed Implementation

[0024] This invention provides a method and apparatus for improving the air stability of sulfide solid electrolytes. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] To address the air stability issue of sulfide solid electrolytes, researchers have conducted extensive studies and developed various technical solutions, but all have significant drawbacks, including: For example, solution-phase surface modification technology involves immersing sulfide solid electrolyte powder in a fluorine-, oxygen-, or nitrogen-containing modification solution (such as LiTFSI solution, fluorinated alcohol solution, silane coupling agent solution, etc.) to form a protective layer on the electrolyte surface through interfacial reactions. Its disadvantages include: ① Solvent molecules in the solution easily remain on the electrolyte surface or in the pores, making complete removal difficult. During subsequent battery assembly, these molecules can react with the electrodes, affecting battery performance; ② Electrolytes are prone to agglomeration during modification, resulting in uneven thickness of the surface protective layer, with some areas lacking effective protection; ③ Solution processing can easily damage electrolyte particles, disrupting their internal ion conduction channels and leading to a decrease in ionic conductivity; ④ The need for large amounts of organic solvents raises environmental and cost concerns, hindering large-scale application.

[0026] For example, physical vapor deposition (PVD) coating technology deposits an inorganic insulating layer (such as Al2O3 or SiO2) or a conductive polymer layer on the surface of a sulfide solid electrolyte using methods such as sputtering and evaporation. Its disadvantages include: 1. The deposition process requires a high vacuum environment, resulting in high equipment costs and low production efficiency, making it unsuitable for large-scale industrial production; 2. The deposited protective layer is physically bonded to the electrolyte substrate, resulting in weak interfacial adhesion, which can easily lead to peeling and cracking during subsequent electrode pressing or battery cycling, thus losing its protective effect; 3. The thickness of the protective layer is difficult to control precisely; excessive thickness significantly increases ion conduction resistance, leading to a substantial decrease in the overall conductivity of the electrolyte; 4. For irregularly shaped electrolyte particles, uniform coating is difficult to achieve, resulting in coating blind zones.

[0027] For example, bulk doping modification technology introduces heterogeneous elements such as fluorine and oxygen (e.g., Li) during the preparation of sulfide solid electrolytes. 6+3y P 1-y Sn y S5Cl 1-2y F 2yBulk doping alters the bulk structure of the electrolyte, improving its chemical stability. However, its drawbacks include: 1. It disrupts the original ordered crystal structure of the sulfide solid electrolyte, obstructing ion conduction channels and significantly reducing its intrinsic ionic conductivity; 2. The amount of dopant introduced is difficult to control precisely; excessive doping easily forms a second-phase impurity, further deteriorating electrochemical performance; 3. The modification effect is limited; bulk doping has a weak inhibitory effect on surface reactions and still cannot effectively resist air erosion; 4. The preparation process is complex, requiring strict control of sintering temperature, atmosphere, and other parameters, resulting in high production costs.

[0028] For example, single-zone gas-phase treatment technology attempts to perform surface fluorination treatment on sulfide solid electrolytes using fluorinating agents (such as XeF2, F2) gas in a single-zone reaction device. Its disadvantages include: 1. Fluorinating agents (such as XeF2) are expensive and highly toxic, resulting in high operational risks and costs, making them unsuitable for industrial applications; 2. The single-zone design cannot separately control the evaporation rate of the fluorinating agent and the reaction temperature, making precise control of the reaction process difficult and easily leading to over-fluorination or insufficient fluorination; 3. Highly corrosive gases such as fluorine can easily corrode the reaction device, shortening its service life; 4. Reaction products are difficult to control and easily form bulk fluorides, affecting the ion conductivity of the electrolyte.

[0029] Based on this, this embodiment provides a method for improving the air stability of sulfide solid electrolytes, as shown in Figure 1, including the following steps: S1, placing a solid fluorinating agent in a first temperature zone reaction device and a sulfide solid electrolyte in a second temperature zone reaction device, wherein a closable connection channel is provided between the first and second temperature zone reaction devices; the solid fluorinating agent can decompose HF-containing gas by heating; S2, closing the connection channel and evacuating the second temperature zone reaction device; S3, heating the first temperature zone reaction device to a first temperature and then holding it at that temperature until the solid fluorinating agent is completely decomposed; S4, opening the connection channel to allow the gas from the first temperature zone reaction device to flow into the second temperature zone reaction device; S5, heating the second temperature zone reaction device to a second temperature and holding it at that temperature for 1-3 hours to obtain a modified sulfide solid electrolyte with a "core-shell" structure, thus completing the method for improving the air stability of sulfide solid electrolytes.

[0030] It should be noted that this invention uses two reaction devices to completely separate the evaporation and decomposition process of the solid fluorinating agent from the surface reaction process of the sulfide solid electrolyte. The first temperature zone reaction device, acting as evaporation, is tasked with the controllable generation of reaction gases. By precisely controlling the temperature (e.g., 120-250°C), the solid fluorinating agent is stably and quantitatively converted into a gaseous HF / NH3 mixture. The design goal of this temperature zone is to ensure a stable output from the gas generation source. The second temperature zone reaction device, acting as the reaction zone, is responsible for conducting the surface modification reaction under optimal conditions. By precisely controlling a lower temperature (100-150°C), the HF gas from the first temperature zone reacts only with the particle surface of the sulfide solid electrolyte to generate a LiF protective layer. The design goal of this temperature zone is to optimize the surface reaction.

[0031] Based on the aforementioned physical separation, the dual-temperature zone design addresses several key challenges of existing technologies (especially the single-temperature zone gas-phase method): 1. Achieving "decoupling" and "precise control" of the reaction process: In a single-temperature zone, the evaporation rate of the fluorinating agent and the reaction rate with the sulfide solid electrolyte are controlled by the same temperature, resulting in mutual constraints. It is difficult to find a temperature that can efficiently evaporate the fluorinating agent while allowing the reaction to proceed gently and directionally on the surface (rather than causing bulk destruction).

[0032] This invention achieves independent setting and optimization of the "evaporation temperature" and "reaction temperature" through a dual-temperature zone. The first temperature zone uses a higher temperature (200℃) to ensure rapid and complete evaporation of NH4F. The second temperature zone uses a lower and milder temperature (150℃), which ensures sufficient reactivity between HF and surface Li and P while minimizing the risk of high-temperature damage to the crystal structure of the sulfide solid electrolyte phase, thus protecting its high ionic conductivity. This achieves a perfect balance between "shell formation" and "core protection," which is key to obtaining a synergistic improvement in "high stability and high conductivity."

[0033] 2. Ensure the directionality of the "surface reaction" and prevent "bulk phase erosion": If the reaction temperature is too high (e.g., close to the evaporation temperature), the highly reactive HF gas may not only react with the surface, but also penetrate and erode the interior of the solid particles, destroying their ion conduction framework.

[0034] This invention sets the temperature of the reaction zone (second temperature zone) significantly lower than that of the evaporation zone and precisely controls the reaction time, making the reaction kinetics more inclined to proceed on the surface with the highest activity, and making it difficult to diffuse into the bulk phase. This ensures that the final product has an ideal "core-shell" structure: the core is a sulfide solid electrolyte that maintains the original high conductivity structure; the shell is a dense and stable LiF protective layer.

[0035] 3. Improve process safety and controllability. If highly corrosive and toxic fluorinating agents (such as F) are used... 2, The single-temperature reaction of XeF2 exposes all equipment to extreme conditions, posing a high risk and making the equipment susceptible to corrosion.

[0036] This invention confines the evaporation and initial decomposition processes to a first temperature zone. The gas is then directionally and controllably transported to a second temperature zone via pipeline. Even in the event of an accident, the risk is limited to a specific area. This dual-temperature zone design allows for targeted reinforcement of the areas requiring the most severe corrosive environments (the first temperature zone and connecting pipelines), while the reaction conditions in the second temperature zone are relatively mild.

[0037] 4. Optimizing Reaction Uniformity and Efficiency: By first evacuating the second temperature zone and then using pressure difference and inert gas to propel the reaction gas from the first temperature zone, it can diffuse evenly and smoothly throughout the entire reaction space of the second temperature zone, ensuring full contact with all sulfide solid electrolyte particles. Since the reaction temperature is independent and constant, all particles are guaranteed to react under the same optimized conditions. This helps to form a uniform and complete fluoride protective layer on the surface of a large number of powder particles, avoiding any coating "blind spots."

[0038] In one embodiment, in step S2, before closing the connection channel, the gases inside the first and second temperature zone reaction devices are replaced with inert gases. This process typically involves repeated purging and priming three times to ensure the internal atmosphere is completely air-free, thereby resulting in excellent final material properties.

[0039] In one embodiment, the mass ratio of the solid fluorinating agent to the sulfide solid electrolyte is 1:2-4.

[0040] In one embodiment, the solid fluorinating agent is NH4F, NH4HF2, or (NH4)2SiF6.

[0041] It should be noted that NH4F, as a fluorinating agent, has inexpensive, safe, and widely available raw materials; the generated fluoride shell is tightly bonded to the LPSC matrix interface, effectively blocking air from contacting the LPSC matrix and significantly improving its air stability, while having no risk of toxic gas residue. The process is simple and suitable for large-scale production. NH4HF2 (ammonium fluoride) has a lower evaporation temperature (120-150℃), which can reduce energy consumption in the first temperature zone; after decomposition, (NH4)2SiF6 (ammonium fluorosilide) generates SiO2 in addition to HF, which can be introduced into the LiF shell to further improve the shell density.

[0042] In one embodiment, the sulfide solid electrolyte is Li6PS5Cl or Li7P3S. 11 Li6P 1-x Ge xS5Cl, Li 6+3x P 1-x Sn x S5Cl.

[0043] In one embodiment, the first temperature is 120-250°C; the second temperature is 100-150°C; and the heating rate is 3-5°C. It should be noted that the decomposition temperature of NH4F is 200°C, so when using NH4F, the first temperature is 180-220°C. When using NH4HF2, the first temperature is 120-150°C. When using (NH4)2SiF6, the first temperature is 200-250°C.

[0044] In one embodiment, in step S5, after the second temperature zone reaction device is heated to the second temperature, an inert gas is introduced into the first temperature zone reaction device. The purpose is to force all the gas decomposed from the first temperature zone reaction device into the second temperature zone reaction device, so that the sulfide solid electrolyte in the second temperature zone reaction device reacts completely.

[0045] This embodiment also provides a device for improving the air stability of sulfide solid electrolytes, as shown in Figure 2, including: a first temperature zone reaction device 1, a second temperature zone reaction device 2, and a connecting channel 3. The connecting channel 3 is connected between the first temperature zone reaction device 1 and the second temperature zone reaction device 2. The connecting channel 3 is provided with an opening and closing device 4. The first temperature zone reaction device 1 includes a reaction vessel 1-1, an air inlet 1-2 and an air outlet 1-3 provided on the reaction vessel 1-1. The second temperature zone reaction device 2 includes a reaction vessel 2-1, an air inlet 2-2 and an air outlet 2-3 provided on the reaction vessel 2-1.

[0046] Optionally, the first temperature zone reaction device 1 further includes a temperature control device 1-4 disposed at the bottom of the reaction vessel 1-1, and the second temperature zone reaction device 2 further includes a temperature control device 2-4 disposed at the bottom of the reaction vessel 2-1.

[0047] It should be noted that the device for improving the air stability of sulfide solid electrolyte in this embodiment is also equipped with a temperature control device and an inert gas supply system. The temperature control device can be directly installed at the bottom of the first temperature zone reaction device 1 and the second temperature zone reaction device 2 respectively to control the temperature. It is connected to the external inert gas through the air inlet and the air outlet can be connected to a pump for evacuation and exhaust. The opening and closing device can be a ball valve. The reactor of the first temperature zone reaction device 1 can be made of polytetrafluoroethylene (PTFE), which is resistant to HF corrosion. Its volume can be 500-1000mL, and 500mL is selected in this embodiment. It is equipped with a raw material feeding port and a pressure monitoring port at the top, and a temperature control device, including a heating element and a temperature sensor, is installed at the bottom. The connecting channel can be a PTFE pipe with a diameter of 10-20mm. The reactor of the second temperature zone reaction device 2 can also be made of PTFE, and its volume can be 1000-2000mL, preferably 1000mL in this embodiment. A temperature control device, including a heating element and a temperature sensor, is installed at the bottom. The outer walls of the first temperature zone reaction device 1, the second temperature zone reaction device 2, and the connecting channel are also equipped with a heat insulation layer, which can be made of aluminum silicate cotton with a heat insulation coefficient ≥0.9.

[0048] As shown in Figure 3, the second temperature zone reaction device 2 also includes a plurality of multi-layered detachable hollow platforms 2-5 spaced apart along the vertical direction of the second reactor 2-1. As shown in Figure 4, the hollow platform 2-5 in this embodiment includes a carrying body 2-5-1. The carrying body 2-5-1 has one or more through holes 2-5-2 penetrating the upper and lower surfaces. It also has one or more side grooves 2-5-3 on the side to facilitate the passage of the support on the inner wall of the second reactor 2-1. When placing, align the side groove with the support on the inner wall of the second reactor 2-1, and then rotate it to place it on the support on the inner wall of the second reactor 2-1.

[0049] It should be noted that the hollow stage 2-5 in this embodiment is used to place LPSC to increase the gas-solid contact area. The hollow stage 2-5 can be disc-shaped to match the shape of the reactor, and its material can be alumina, which is easy to mold and can withstand high temperatures.

[0050] The present invention will be further described below with reference to specific embodiments.

[0051] Example 1: A method for improving the air stability of a sulfide solid electrolyte, comprising the following steps: placing 300g of solid fluorinating agent (NH4F) in a first temperature zone reaction device, and placing 1200g of sulfide solid electrolyte (Li6PS5Cl) in a second temperature zone reaction device; a closable connection channel is provided between the first and second temperature zone reaction devices; the solid fluorinating agent can decompose HF-containing gas upon heating; the gas inside the first and second temperature zone reaction devices is first replaced with inert gas, and the process is repeated three times to ensure that the internal atmosphere is completely free of air, thereby... The final material exhibits excellent properties. The connection channel is closed, and the second temperature zone reaction device is evacuated. The first temperature zone reaction device is heated to 200°C at a rate of 5°C / min, and then held at that temperature until the solid fluorinating agent is completely decomposed. The connection channel is opened, allowing the gas from the first temperature zone reaction device to flow into the second temperature zone reaction device. The second temperature zone reaction device is heated to 150°C at a rate of 3°C / min and held at that temperature for 2 hours. Simultaneously, inert gas is introduced into the first temperature zone reaction device, and the device is cooled, resulting in a modified sulfide solid electrolyte with a "core-shell" structure. This completes the method for improving the air stability of the sulfide solid electrolyte.

[0052] Example 2: The solid fluorinating agent (NH4F) in Example 1 is 300g, and the sulfide solid electrolyte (Li6PS5Cl) is 900g. The difference between this example and Example 1 is that the solid fluorinating agent (NH4F) in this example is 300g, and the sulfide solid electrolyte (Li6PS5Cl) is 900g.

[0053] Example 3 differs from Example 1 in that the solid fluorinating agent (NH4F) in this example is 300g, and the sulfide solid electrolyte (Li6PS5Cl) is 600g.

[0054] Performance testing: 1. Examples 1, 2, 3 and the original sulfide solid electrolyte (LPSC) were cold-pressed into sheets at a pressure of 360–500 MPa, with a thickness of approximately 0.1–1 mm and a diameter of approximately 10–14 mm. The thickness needs to be measured using a micrometer.

[0055] The sample is held in place using a blocking electrode (such as stainless steel or sputtered metal film), and an AC voltage (amplitude 10mV, frequency range 1MHz to 0.1Hz) is applied. The bulk resistance Rbulk is obtained by fitting the semicircular intercept in the high-frequency region using EIS, while the low-frequency region reflects the interfacial resistance and the double-layer effect.

[0056] According to the formula The ionic conductivity of the corresponding material was calculated, where thickness (L) was measured directly using a micrometer, and area (A) was calculated based on the effective contact area according to the electrode diameter. The results are shown in Table 1. As can be seen from Table 1, different ratios of sulfide solid electrolyte (Li6PS5Cl) and solid fluorinating agent (NH4F) reacted in a dual-temperature zone gas-solid reaction apparatus significantly improved the material's air stability. While the change was minimal beyond a 3:1 ratio, there was still a significant improvement compared to the initial sample. It should be noted that the powder in this table was tested after exposing the powder to a fixed dew point of -35℃ for a certain period of time, and then measuring the ionic conductivity of the powder.

[0057] Table 1

[0058] 2. The sulfide solid electrolyte of Example 2 after the method of improving the air stability of the sulfide solid electrolyte was subjected to scanning electron microscopy. The results are shown in Figure 5. It can be seen that after the gas-solid reaction, the F element is indeed attached to the particle surface and plays a role.

[0059] The scanning electron microscope imaging includes the following steps: Module 1: Sample preparation (core step of inert gas protection) Pretreatment environment: The entire process is carried out in an Ar gas glove box (O2 / H2O content ≤0.1ppm) to avoid exposing the sample to air.

[0060] Sample type adaptation: Bulk / Sintered wafer: Powder sample: Fix the silicon wafer to the sample stage with conductive adhesive, and spray the powder sample onto the surface of the conductive adhesive.

[0061] Module 2: Instrument Preparation and Vacuum Optimization: Instrument Selection: SEM: Field Emission Scanning Electron Microscope (FE-SEM), resolution ≥1nm; EDS Detector: Silicon Drift Detector (SDD), energy resolution ≤129eV.

[0062] Instrument warm-up and calibration: Turn on the SEM main unit, EDS system, and vacuum system, and warm up for 30 minutes; EDS energy calibration: Calibrate using standard samples to ensure accurate positions of the characteristic peaks S (2.31 keV) and P (2.01 keV); Vacuum requirement: Sample chamber vacuum ≥ 1 × 10⁻⁶ -4 Pa.

[0063] Sample transfer and installation: Use a sealed sample transfer box (fill the sample into the glove box and seal it) to reduce exposure time (≤30 seconds); quickly place the sample stage into the SEM sample chamber, ensuring that the sample center is aligned with the electron beam scanning area; close the sample chamber door and start vacuuming (wait 15 minutes until the vacuum indicator light turns green).

[0064] Module 3: SEM Parameter Optimization (Adapting to LPSC Insulation + Easily Hydrolyzed Characteristics) Morphological Observation and Region Localization: Magnification: First, observe the overall morphology at low magnification (100×) to confirm the absence of hydrolysis (no white flocculent deposits) and fragmentation; then adjust to medium-high magnification (2000×) and select a region with a smooth surface and no pores / cracks as the ROI; Accelerating Voltage: 12kV (key parameter, balancing signal strength and sample stability); Working Distance: 10mm (balancing signal strength and spatial resolution); Beam Current: 3nA (ensuring signal strength while avoiding sample damage); Manually optimize focusing and astigmatism correction to ensure clear images of the ROI region (no blurring, no ghosting).

[0065] Charge accumulation suppression measures: If charge accumulation still occurs, reduce the accelerating voltage to 9kV, increase the beam current to 4nA, or turn on the "low vacuum mode" (vacuum degree 15Pa) of the SEM.

[0066] Module 4: EDSMapping Parameter Settings (for LPSC element characteristics) Element Channel Selection: Required Element: Li (K α ,0.05keV), P(K α ,2.01keV), S(K α , 2.31keV), Ge (Lα, 9.89keV, if present); optional element: O (K α 0.52 keV, used to determine whether the sample has been hydrolyzed.

[0067] Key acquisition parameter settings: Pixel dwell time: 15ms / pixel (Li element signal is weak, so sufficient time is required); Scan resolution: 1024×1024 pixels (to ensure detailed element distribution); Count rate control: target 3000cps (counts per second); Acquisition mode: "NetMap" (net count mode), automatically subtracting background noise.

[0068] Pre-scan before acquisition: Perform two rapid pre-scans of the ROI region (dwell time 5ms) and observe the count rate of each element; if the Li element count rate is <50cps, adjust the parameters (extend the dwell time to 18ms or increase the beam current to 4nA); confirm that there is no obvious peak overlap, and adjust the element channel energy window if necessary.

[0069] Module 5: Mapping Data Acquisition and Monitoring Start Acquisition: Acquisition Time: Approximately 20 minutes (1024×1024 pixels, 15ms / pixel); Real-time Monitoring: Count Rate Curve: Maintain stability between 2000~4000cps; SEM Image: If increased charge accumulation or whitening of the sample surface (signs of hydrolysis) occurs, immediately terminate the test.

[0070] Data acquisition complete: Save the raw data (.azt / .emd format), export the elemental distribution image; close the EDS acquisition interface, but keep the SEM image interface to observe the sample status.

[0071] Module 6: Data Analysis and Precautions Key points of data analysis: Qualitative analysis: Confirm whether the distribution of Li, P, S, and Ge is uniform, and observe the distribution of O element to determine whether hydrolysis has occurred; Semi-quantitative analysis: Compare the signal intensity of P, S, and Ge in different regions to assess the uniformity of distribution (Li is only used for qualitative judgment); Data processing: Background subtraction, adjust image contrast to highlight differences in element distribution, and P and S element images can be superimposed to observe co-distribution.

[0072] 3. Phase characterization test diagram: The sulfide solid electrolyte of Example 2 after the method of improving the air stability of sulfide solid electrolyte was subjected to powder diffraction analysis. The results are shown in Figure 6. The gas-solid reaction in the dual temperature zone did not cause significant damage to the phase of the original LPSC material.

[0073] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for improving the air stability of sulfide solid electrolytes, characterized in that, The method includes the following steps: S1, placing a solid fluorinating agent in a first-temperature zone reaction device and a sulfide solid electrolyte in a second-temperature zone reaction device, wherein a closable connection channel is provided between the first-temperature zone reaction device and the second-temperature zone reaction device; the solid fluorinating agent decomposes into a gas containing HF upon heating; S2, closing the connection channel and evacuating the second-temperature zone reaction device; S3, heating the first-temperature zone reaction device to a first temperature and then holding it at that temperature until the solid fluorinating agent is completely decomposed; S4, opening the connection channel to allow the gas from the first-temperature zone reaction device to flow into the second-temperature zone reaction device; S5, heating the second-temperature zone reaction device to a second temperature and holding it at that temperature for 1-3 hours to obtain a modified sulfide solid electrolyte with a "core-shell" structure, thus completing the method for improving the air stability of the sulfide solid electrolyte.

2. The method for improving the air stability of sulfide solid electrolytes according to claim 1, characterized in that, In S2, before closing the connection channel, the gas inside the first temperature zone reaction device and the second temperature zone reaction device is replaced with inert gas.

3. The method for improving the air stability of sulfide solid electrolytes according to claim 1, characterized in that, The mass ratio of solid fluorinating agent to sulfide solid electrolyte is 1:2-4.

4. The method for improving the air stability of sulfide solid electrolytes according to claim 1, characterized in that, The solid fluorinating agent is NH4F, NH4HF2 or (NH4)2SiF6.

5. The method for improving the air stability of sulfide solid electrolytes according to claim 1, characterized in that, The sulfide solid electrolyte is Li6PS5Cl or Li7P3S 11 Li6P 1-x Ge x S5Cl, Li 6+3x P 1-x Sn x At least one of S5Cl.

6. The method for improving the air stability of sulfide solid electrolytes according to claim 1, characterized in that, The first temperature is 120-250℃; the second temperature is 100-150℃; the heating rate is 3-5℃.

7. The method for improving the air stability of sulfide solid electrolytes according to claim 1, characterized in that, In S5, after the second temperature zone reaction device is heated to the second temperature, inert gas is introduced into the first temperature zone reaction device.

8. A device for improving the air stability of sulfide solid electrolytes, characterized in that, include: A first temperature zone reaction device (1), a second temperature zone reaction device (2), and a connecting channel (3) are provided. The connecting channel (3) is connected between the first temperature zone reaction device (1) and the second temperature zone reaction device (2). The connecting channel (3) is provided with an opening and closing device (4). The first temperature zone reaction device (1) includes a first reaction vessel (1-1), an inlet (1-2) and an outlet (1-3) provided on the first reaction vessel (1-1). The second temperature zone reaction device (2) includes a second reaction vessel (2-1), an inlet (2-2) and an outlet (2-3) provided on the second reaction vessel (2-1).

9. The apparatus for improving the air stability of sulfide solid electrolytes according to claim 8, characterized in that, The first temperature zone reaction device (1) further includes a temperature control device (1-4) located at the bottom of the first reaction vessel (1-1), and the second temperature zone reaction device (2) further includes a temperature control device (2-4) located at the bottom of the second reaction vessel (2-1).

10. The apparatus for improving the air stability of sulfide solid electrolytes according to claim 8, characterized in that, The second temperature zone reaction device (2) also includes multiple multi-layer detachable hollow platforms (2-5) spaced apart along the vertical direction of the second reactor (2-1).

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