Sulfide solid electrolyte having a hydrophobic protective layer and method for preparing the same

Abstract

This invention discloses a sulfide solid electrolyte with a hydrophobic protective layer and its preparation method, belonging to the field of solid-state battery materials technology. The preparation method includes: dispersing modified hydrophobic fumed silica in a low-polarity anhydrous solvent to form a suspension; adding sulfide solid electrolyte powder to the suspension under an inert atmosphere; mixing by ball milling to uniformly coat the electrolyte particles with hydrophobic fumed silica; and finally drying to obtain the product. This invention uses specific hydrophobically modified fumed silica as the coating material. Its surface hydrophobic groups provide chemical barrier, and the accumulation of nanoparticles forms a physical barrier. The two work synergistically to isolate moisture and oxygen without hindering lithium-ion transport. This preparation method is simple, and the resulting product maintains high ionic conductivity while exhibiting high air stability, effectively solving the industry problem of balancing air stability and ionic conductivity in sulfide solid electrolytes.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery materials technology, specifically to a sulfide solid electrolyte with a hydrophobic protective layer and its preparation method. Background Technology

[0002] sulfide solid electrolytes ( Due to its high ionic conductivity (close to that of liquid electrolytes), good machinability, and compatibility with lithium metal anodes, sulfide solid electrolytes have become a core candidate material in the field of all-solid-state lithium batteries. However, sulfide solid electrolytes face three major technological bottlenecks that severely restrict their industrialization: firstly, they have extremely poor air stability and are extremely sensitive to moisture and oxygen, easily undergoing hydrolysis reactions to form sulfide solid electrolytes. First, it produces toxic byproducts that cause a sharp drop in conductivity, requiring production, processing, and use in a fully inert gas environment, which significantly increases costs. Second, it has poor interface performance, easily forming a high-resistivity interface layer when in contact with positive and negative electrode materials, and causing interface cracks due to volume changes during cycling, which exacerbates the degradation of electrochemical performance. Third, it has insufficient resistance to lithium dendrite formation, easily forming pores and defects during dry compaction, providing channels for lithium dendrite growth and causing the risk of battery short circuit.

[0003] To address the aforementioned issues, existing technologies often employ surface coating modification strategies. For example, Adv. Mater. 2025, e16613 introduces Prussian blue analogues as multifunctional additives into LPSC sulfide solid electrolytes, utilizing the abundant interstitial spaces and coordination sites within their open framework to efficiently capture... This can block moisture-induced hydrolysis-hydration reactions. Coating with a single oxide (such as alumina or lithium phosphate) can also improve moisture resistance, but poor interfacial compatibility can easily lead to a decrease in ionic conductivity. Although modifiers such as silanes and silazanes can achieve hydrophobic modification, they have problems such as high toxicity, difficult removal of byproducts, and high cost, making it difficult to meet the needs of large-scale production.

[0004] Numerous optimization studies have been conducted within the industry, including the use of hydrophobic additives, elemental doping, surface coating, and organic-inorganic composite coating systems. Among these, surface coating with hydrophobic materials, by constructing a protective layer to isolate air from electrolyte contact, has become the mainstream approach to improve air stability. Hydrophobic fumed silica, as a nanomaterial modified with organosilicon, possesses low surface energy, excellent hydrophobicity, and chemical stability. After surface treatment with modifiers such as polydimethylsiloxane (PDMS) and dimethyldichlorosilane (DDS), its surface can effectively shield hydrophilic silanol groups, forming a dense hydrophobic layer. It has demonstrated excellent moisture-proof and anti-caking properties in coatings, rubber, and other fields, providing a new technical path for the surface protection of sulfide solid electrolytes.

[0005] Current optimization schemes for the air stability of sulfide solid electrolytes all suffer from the drawback of failing to balance performance and practicality, as detailed below: For example, invention CN113745651B discloses a coated sulfide solid electrolyte, its preparation method and application. It uses an oxide solid electrolyte layer to coat the surface of sulfide solid electrolyte particles to improve air stability. However, the coating process uses highly polar alcohol solvents, which can easily damage the electrolyte structure. The stability of the coating process is difficult to control, and the coating method is cumbersome and costly.

[0006] Invention CN121172237A discloses a humid air-stable sulfide solid electrolyte and its preparation method. The method involves mixing a metal halide and a sulfide solid electrolyte in a specific ratio, ball milling, and then annealing to obtain an in-situ doped coating layer on the surface of the sulfide solid electrolyte. This method effectively improves the humid air stability of the sulfide solid electrolyte with minimal impact on its ionic conductivity. However, the coating process requires a second annealing process, making the process complex.

[0007] Invention CN121035311A reduces the risk of aggregation of sulfide solid electrolytes and reduces their electronic conductivity by coating the sulfide surface with a layer of polyvinylpyrrolidone, but does not address the issue of improving the air stability of sulfide solid electrolytes, and the use of a single polymer for surface coating will lead to the problem of blockage of lithium-ion transport channels on the material surface.

[0008] Invention CN118763271A describes coating a siloxane onto a sulfide solid electrolyte precursor and sintering the electrolyte precursor containing the siloxane to obtain a doped and coated sulfide electrolyte. However, carbon residue is easily left after sintering of the siloxane, which can easily lead to electrolyte decomposition, increase electronic conductivity, and reduce electrolyte stability.

[0009] Therefore, most existing surface modification materials lack targeted design and cannot simultaneously meet the dual requirements of efficient hydrophobic barrier and ion conduction compatibility, making it difficult to meet the relaxed requirements for electrolyte storage, transportation and processing environment in the large-scale production of all-solid-state batteries. Summary of the Invention

[0010] Based on the above analysis, the present invention aims to provide a sulfide solid electrolyte with a hydrophobic protective layer and its preparation method, so as to solve the technical problem that the prior art is unable to effectively maintain the high ionic conductivity of sulfide solid electrolyte while improving its air stability.

[0011] The objective of this invention is mainly achieved through the following technical solutions: This invention provides a sulfide solid electrolyte with a hydrophobic protective layer and its preparation method, comprising the following steps: S1. Disperse hydrophobic fumed silica in a low-polarity anhydrous solvent to form a suspension; S2. Under an inert atmosphere, the sulfide solid electrolyte powder is added to the suspension and ball-milled to mix it, so that the hydrophobic fumed silica coats the surface of the sulfide solid electrolyte particles. S3. Dry the ball-milled mixture to remove the solvent and obtain the sulfide solid electrolyte with a hydrophobic protective layer.

[0012] Preferably, in step S1, the hydrophobic fumed silica is fumed silica modified with polydimethylsiloxane or dimethyldichlorosilane, with a specific surface area of ​​110-170 m² / g, a carbon content of 0.6-1.6%, a water contact angle ≥120°, and a hydrophilic silanol substitution rate ≥90%; the hydrophobic fumed silica has a particle size of 7-40 nm and a surface modification degree of 1.0-1.5 mmol / g.

[0013] Preferably, in step S1, the low-polarity anhydrous solvent is selected from one or more of toluene, xylene, n-heptane, n-hexane, octane, n-dodecane, or petroleum ether.

[0014] Preferably, in step S1, ultrasonic dispersion is used, with an ultrasonic power of 200-400 W, a dispersion temperature of 25-35℃, and a dispersion time of 30-60 min.

[0015] Preferably, in step S2, the amount of hydrophobic fumed silica added is 0.5%-3% of the mass of the sulfide solid electrolyte powder; the inert atmosphere is argon or nitrogen atmosphere, and the water and oxygen content is ≤0.1 ppm.

[0016] Preferably, in step S2, the solid content of the slurry during ball milling is 40-50%, the ball milling speed is 300-500 r / min, and the ball milling time is 2-4 h.

[0017] Preferably, in step S3, the drying is carried out under vacuum conditions, the drying temperature is 60-80℃, and the drying time is 8-12 h.

[0018] Preferably, in step S2, the sulfide solid electrolyte is... System electrolytes, One or more of the following, wherein X is Cl, Br or I. Electrolytes in the system The molar ratio is 3-5:1; the particle size of the sulfide solid electrolyte powder is 0.5-3 μm.

[0019] The present invention also provides a sulfide solid electrolyte with a hydrophobic protective layer prepared by the above preparation method.

[0020] Preferably, the hydrophobic fumed silica forms a coating layer on the surface of the sulfide solid electrolyte particles, and the thickness of the coating layer is 10-50 nm.

[0021] Compared with the prior art, the present invention can achieve the following beneficial effects: (1) The water contact angle of the hydrophobic fumed silica material is ≥120°, and its hydrophobicity is much better than that of the unmodified material. and traditional nano The coating system, with a 10-50 nm thick layer of hydrophobic fumed silica, effectively prevents contact between moisture and oxygen in the air and the sulfide electrolyte through physical barrier and the synergistic effect of surface hydrophobic groups, significantly inhibiting the reaction between the sulfide electrolyte and air components. Tests showed that after 24 hours of exposure to dehumidified air at 25°C and a dew point controlled at -50°C, the ionic conductivity retention rate of the product of this invention was ≥90%, while the conductivity retention rate of the uncoated sample was less than 50%. Simultaneously, the gas release rate in an environment with 15% relative humidity was <40 ppm, far lower than that of the uncoated sample, meeting the safety and environmental protection requirements for large-scale production.

[0022] (2) By controlling the coating thickness to an ultrathin range of 10-50 nm, the hydrophobic fumed silica layer provides effective physical barrier while causing minimal additional resistance to lithium-ion transport, and the room temperature ionic conductivity of the finished electrolyte remains at 4-6 mS / cm. -1 It has a conductivity comparable to that of the original uncoated sulfide electrolyte, ensuring that the ion transport channels are not affected.

[0023] (3) The low-temperature ball milling and vacuum drying process is adopted, which does not require high-temperature treatment, has low energy consumption, short process, and readily available raw materials. It can be directly adapted to existing large-scale production equipment for sulfide electrolytes, making it easy to promote industrialization. Attached Figure Description

[0024] Figure 1 This is a schematic diagram showing the hydrogen sulfide release of different sulfide solid electrolytes of the present invention; Figure 2 This is a process flow diagram of the present invention. Detailed Implementation

[0025] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0026] The present invention provides a sulfide solid electrolyte with a hydrophobic protective layer, which is a coated sulfide solid electrolyte in which hydrophobic fumed silica is coated on the surface of sulfide solid electrolyte particles; by designing the composition and preparation process of the coating layer, the air stability and ionic conductivity are synergistically improved.

[0027] Hydrophobic fumed silica modified with polydimethylsiloxane (PDMS) or dimethyldichlorosilane (DDS) is specifically selected. Its surface hydrophobic groups can form a dense and strong coating layer. At the same time, by utilizing its nanoscale size and high specific surface area, it can achieve full coating of the surface of sulfide electrolyte particles with low addition amount, avoiding the loss of ionic conductivity caused by interfacial incompatibility or excessive thickness of traditional inorganic coating layers.

[0028] The coating layer simultaneously serves as a physical barrier and a hydrophobic protection layer. On the one hand, the 10-50 nm thick fumed silica-shaped spatial barrier layer blocks the penetration of air components. On the other hand, its surface hydrophobic groups greatly reduce the water adsorption capacity of the material surface, forming a hydrophobic interface similar to the "lotus leaf effect". The two work together to inhibit the hydrolysis and oxidation reactions of sulfide electrolytes, achieving a balance between "coating integrity" and "intrinsic electrolyte properties". This solves the problem of limited effectiveness of traditional single protection methods and achieves a synergistic improvement in air stability and ion conduction performance.

[0029] By controlling the amount of hydrophobic fumed silica added to 0.5-3%, and optimizing the degree of surface modification and coating uniformity, the best protective effect is achieved at the lowest addition amount, avoiding the obstruction of ion conduction and the increase in cost caused by excessive addition, thus balancing performance and economy.

[0030] The specific plan is as follows: (1) Raw material selection Core electrolyte: Sulfide solid electrolyte powder is selected, including but not limited to LPSX (X = one or more of Cl, Br, and I). (Molar ratio 3:1-5:1) One or more mixtures of these particles, with a particle size controlled between 0.5 and 3 μm, ensure efficient ion conduction.

[0031] Coating material: In a preferred embodiment of the present invention, hydrophobic fumed silica modified with PDMS or DDS is selected, and the silanol groups (-OH) on the surface of silica are partially or completely replaced with non-polar organic groups (such as methyl, alkyl, etc.) through reactions such as silanization, so that it exhibits significant hydrophobicity and organic affinity.

[0032] In a preferred embodiment of the present invention, the specific surface area of ​​the hydrophobic fumed silica is 110-170 m². 2 / g, particle size: 7-40nm, carbon content 0.6-1.6%, surface modification degree 1.0-1.5 mmol / g, water contact angle ≥120°, hydrophilic silanol substitution rate ≥90%, excellent dispersibility in organic solvent systems, forming a dense hydrophobic layer through surface organic groups (such as methyl), and good compatibility with sulfide electrolytes.

[0033] Dispersion medium: In a preferred embodiment of the present invention, a low-polarity anhydrous solvent such as toluene, xylene, n-heptane, n-hexane, octane, n-dodecane, or petroleum ether is selected to avoid introducing a high-polarity solvent that could attack the structure of the sulfide solid electrolyte and trigger side reactions.

[0034] (2) Preparation process: 1. Dispersion treatment: Add hydrophobic fumed silica to the dispersion medium and disperse it by ultrasonication (power 200-400W, time 30-60 min) to form a uniform suspension. The dispersion temperature is controlled at 25-35℃ to prevent the solvent from evaporating too quickly.

[0035] 2. Coating reaction: The sulfide solid electrolyte powder is slowly added to the above suspension, and the solid content is controlled to be 40-50%. Under the protection of inert gas (argon or nitrogen, water and oxygen content ≤0.1 ppm), the mixture is mixed by high-energy ball milling (300-500 r / min, 2-4 h) to make the hydrophobic fumed silica uniformly adsorbed and coated on the surface of the electrolyte particles.

[0036] 3. Drying and curing: The ball-milled mixture is placed in a vacuum drying oven and dried at 60-80℃ for 8-12 h to remove the dispersion medium, resulting in a hydrophobic fumed silica-coated sulfide solid electrolyte product. The coating thickness is controlled at 10-50 nm. The hydrophobic fumed silica and the sulfide electrolyte surface are mainly bonded by van der Waals forces. This weak interaction is conducive to forming a uniform coating layer that does not introduce a high impedance interface. The coating layer will exhibit multilayer adsorption depending on the coating amount.

[0037] In a preferred embodiment of the present invention, the amount of hydrophobic fumed silica added is 0.5-3% of the mass of the sulfide solid electrolyte. If the amount added is too low, a complete coating layer cannot be formed, and if the amount added is too high, the ionic conductivity will be reduced.

[0038] In a preferred embodiment of the present invention, in the above process, the solid content of the ball milling slurry needs to be controlled at 40-45%, and the ball milling speed and time need to be precisely matched to ensure that the coating layer is uniform and dense and does not damage the electrolyte crystal structure.

[0039] Test methods and equipment: The hydrophobic properties of this invention originate from the properties of the coating material itself: the hydrophilic silanol groups (-OH) on the surface of the hydrophobic fumed silica are coated with nonpolar organic groups (such as... The coating layer is replaced by a stable low-surface-energy hydrophobic interface. It should be noted that, due to the ultra-thin coating layer and the strong hygroscopicity of the sulfide electrolyte matrix, traditional bulk material contact angle testing methods are not suitable for directly quantifying the macroscopic hydrophobicity of this product. Therefore, this invention compares performance degradation in simulated humid environments (such as conductivity retention rate, etc.). The release amount was used to indirectly verify its hydrophobic protective effect.

[0040] Ion conductivity test The electrolyte test mold was subjected to AC impedance spectroscopy to determine its ionic conductivity. Electrochemical impedance spectroscopy (EIS) was performed in a constant temperature and humidity chamber at 25°C and below 20% humidity, with a frequency range of 10 Hz. -1 Hz-10 6 Hz, the test results are shown in Table 1.

[0041] Air stability test The ionic conductivity at room temperature before and after air exposure was tested after 24 h of exposure to dry air at 25℃ and dew point of -50℃. The results are shown in Table 1.

[0042] Release test 150 mg of the obtained sulfide solid electrolyte was weighed and exposed to air at 15% relative humidity for 20 minutes. The amount of hydrogen sulfide released during the air exposure was recorded. The results are as follows: Figure 1 As shown.

[0043] The present invention also provides the application of the above-mentioned sulfide solid electrolyte with hydrophobic protective layer or the sulfide solid electrolyte with hydrophobic protective layer prepared by the above preparation method in solid-state batteries.

[0044] The present invention also provides a solid-state battery, comprising a positive electrode, a solid electrolyte, and a negative electrode, wherein at least one of the positive electrode, the solid electrolyte, and the negative electrode comprises the above-mentioned sulfide solid electrolyte with a hydrophobic protective layer or the sulfide solid electrolyte with a hydrophobic protective layer prepared by the above-mentioned preparation method.

[0045] The present invention will now be described in more detail with reference to embodiments and comparative examples, but the technical scope of the present invention is not limited thereto. Example. Example

[0046] This embodiment provides a method for preparing a sulfide solid electrolyte with a hydrophobic protective layer, comprising the following steps: 1. Dispersion treatment: 0.1g of hydrophobic fumed silica was added to 15.15g of xylene and dispersed by ultrasonication (400 W power, 30 min time) to form a uniform suspension. The dispersion temperature was controlled at 35℃ to prevent the solvent from evaporating too quickly.

[0047] 2. Coating reaction: Add 10g of... The sulfide solid electrolyte powder was slowly added to the above suspension, with the solid content controlled at 40%. Under the protection of an inert gas (argon or nitrogen, water and oxygen content ≤0.1 ppm), it was mixed by high-energy ball milling (300 r / min, 2 h) to allow the hydrophobic fumed silica to be uniformly adsorbed and coated on the surface of the electrolyte particles.

[0048] 3. Drying and curing: The ball-milled mixture is placed in a vacuum drying oven and dried at 80°C for 8 hours to remove the dispersion medium. The electrolyte powder is collected to obtain the hydrophobic fumed silica-coated sulfide solid electrolyte product.

[0049] The sulfide solid electrolyte product obtained in Example 1 was subjected to ionic conductivity testing, air stability testing, and... The release rate test results are shown in Table 1. The sulfide solid electrolyte obtained in this embodiment has an ionic conductivity of 5.5 mS / cm, and the ionic conductivity retention rate is 93% after exposure to dehumidified air at -50℃ dew point for 24 h. Figure 1 As shown, after exposure to air at 15% relative humidity for 20 minutes, The release amount is 32 ppm. Example

[0050] This embodiment provides a method for preparing a sulfide solid electrolyte with a hydrophobic protective layer. The only difference from Example 1 is that the amount of hydrophobic fumed silica added is 0.5 wt%. The specific steps are as follows: 1. Dispersion treatment: 0.05g of hydrophobic fumed silica was added to 15.075g of xylene and dispersed by ultrasonication (400 W power, 30 min time) to form a uniform suspension. The dispersion temperature was controlled at 35℃ to prevent the solvent from evaporating too quickly.

[0051] 2. Coating reaction: Add 10g of... The sulfide solid electrolyte powder was slowly added to the above suspension, with the solid content controlled at 40%. Under the protection of an inert gas (argon or nitrogen, water and oxygen content ≤0.1 ppm), it was mixed by high-energy ball milling (300 r / min, 2 h) to allow the hydrophobic fumed silica to be uniformly adsorbed and coated on the surface of the electrolyte particles.

[0052] 3. Drying and curing: The ball-milled mixture is placed in a vacuum drying oven and dried at 80°C for 8 hours to remove the dispersion medium. The electrolyte powder is collected to obtain the hydrophobic fumed silica-coated sulfide solid electrolyte product.

[0053] The sulfide solid electrolyte product obtained in Example 2 was subjected to ionic conductivity tests, air stability tests, and H2S release tests. The results are shown in Table 1. The ionic conductivity of the sulfide solid electrolyte obtained in this example was 5.8 mS / cm, and the ionic conductivity retention rate was 89% after exposure to dehumidified air at a dew point of -50°C for 24 hours. Figure 1 As shown, after exposure to air at 15% relative humidity for 20 minutes, the H2S release was 41 ppm. Example

[0054] This embodiment provides a method for preparing a sulfide solid electrolyte with a hydrophobic protective layer. The only difference from Example 1 is that the amount of hydrophobic fumed silica added is 2wt%. The specific steps are as follows: 1. Dispersion treatment: 0.2g of hydrophobic fumed silica was added to 15.3g of xylene and dispersed by ultrasonication (400W power, 30 min) to form a uniform suspension. The dispersion temperature was controlled at 35℃ to prevent the solvent from evaporating too quickly.

[0055] 2. Coating reaction: Add 10g of... The sulfide solid electrolyte powder was slowly added to the above suspension, with the solid content controlled at 40%. Under the protection of an inert gas (argon or nitrogen, water and oxygen content ≤0.1 ppm), it was mixed by high-energy ball milling (300 r / min, 2 h) to allow the hydrophobic fumed silica to be uniformly adsorbed and coated on the surface of the electrolyte particles.

[0056] 3. Drying and curing: The ball-milled mixture is placed in a vacuum drying oven and dried at 80°C for 8 hours to remove the dispersion medium. The electrolyte powder is collected to obtain the hydrophobic fumed silica-coated sulfide solid electrolyte product.

[0057] The sulfide solid electrolyte product obtained in Example 3 was subjected to ionic conductivity testing, air stability testing, and H2S release testing. The results are shown in Table 1. The ionic conductivity of the sulfide solid electrolyte obtained in this example was 4.5 mS / cm, and the ionic conductivity retention rate was 94% after exposure to dehumidified air at a dew point of -50°C for 24 h. Figure 1 As shown, after exposure to air at 15% relative humidity for 20 minutes, The release amount is 28 ppm.

[0058] Example 4 This embodiment provides a method for preparing a sulfide solid electrolyte with a hydrophobic protective layer. The only difference from Example 1 is that the amount of hydrophobic fumed silica added is 3 wt%. The specific steps are as follows: 1. Dispersion treatment: 0.3g of hydrophobic fumed silica was added to 15.45g of xylene and dispersed by ultrasonication (400 W power, 30 min time) to form a uniform suspension. The dispersion temperature was controlled at 35℃ to prevent the solvent from evaporating too quickly.

[0059] 2. Coating reaction: Add 10g of... The sulfide solid electrolyte powder was slowly added to the above suspension, with the solid content controlled at 40%. Under the protection of an inert gas (argon or nitrogen, water and oxygen content ≤0.1 ppm), it was mixed by high-energy ball milling (300 r / min, 2 h) to allow the hydrophobic fumed silica to be uniformly adsorbed and coated on the surface of the electrolyte particles.

[0060] 3. Drying and curing: The ball-milled mixture is placed in a vacuum drying oven and dried at 80°C for 8 hours to remove the dispersion medium. The electrolyte powder is collected to obtain the hydrophobic fumed silica-coated sulfide solid electrolyte product.

[0061] The sulfide solid electrolyte product obtained in Example 4 was subjected to ionic conductivity testing, air stability testing, and... The release rate test results are shown in Table 1. The sulfide solid electrolyte obtained in this embodiment has an ionic conductivity of 3.7 mS / cm, and the ionic conductivity retention rate is 95% after exposure to dehumidified air at a dew point of -50℃ for 24 h. Figure 1 As shown, after exposure to air at 15% relative humidity for 20 minutes, The release amount is 21 ppm.

[0062] Example 5 The experimental method in Example 5 was the same as in Example 1, except that the sulfide solid electrolyte material was used. Replace with The specific experimental steps are as follows: 1. Dispersion treatment: 0.1g of hydrophobic fumed silica was added to 15.15g of xylene and dispersed by ultrasonication (400 W power, 30 min time) to form a uniform suspension. The dispersion temperature was controlled at 35℃ to prevent the solvent from evaporating too quickly.

[0063] 2. Coating reaction: Add 10g of... The sulfide solid electrolyte powder was slowly added to the above suspension, with the solid content controlled at 40%. Under the protection of an inert gas (argon or nitrogen, water and oxygen content ≤0.1 ppm), it was mixed by high-energy ball milling (300 r / min, 2 h) to allow the hydrophobic fumed silica to be uniformly adsorbed and coated on the surface of the electrolyte particles.

[0064] 3. Drying and curing: The ball-milled mixture is placed in a vacuum drying oven and dried at 80°C for 8 hours to remove the dispersion medium. The electrolyte powder is collected to obtain the hydrophobic fumed silica-coated sulfide solid electrolyte product.

[0065] The sulfide solid electrolyte product obtained in Example 5 was subjected to ionic conductivity testing, air stability testing, and... The release test results are shown in Table 1. The ionic conductivity of the sulfide solid electrolyte obtained in this embodiment is 4.8 mS / cm, and the ionic conductivity retention rate is 90% after exposure to dehumidified air at -50℃ dew point for 24 h.

[0066] Example 6 The experimental method in Example 6 was the same as in Example 1, except that the sulfide solid electrolyte material was used. Replace with The specific experimental steps are as follows: 1. Dispersion treatment: Add 0.1g of hydrophobic fumed silica to 15.15g of xylene and disperse it by ultrasonic dispersion (power 400 W, time 30 min) to form a uniform suspension. The dispersion temperature is controlled at 35℃ to prevent the solvent from evaporating too quickly.

[0067] 2. Coating reaction: Add 10g of... The sulfide solid electrolyte powder was slowly added to the above suspension, with the solid content controlled at 40%. Under the protection of an inert gas (argon or nitrogen, water and oxygen content ≤0.1 ppm), it was mixed by high-energy ball milling (300 r / min, 2 h) to allow the hydrophobic fumed silica to be uniformly adsorbed and coated on the surface of the electrolyte particles.

[0068] 3. Drying and curing: The ball-milled mixture is placed in a vacuum drying oven and dried at 80°C for 8 hours to remove the dispersion medium. The electrolyte powder is collected to obtain the hydrophobic fumed silica-coated sulfide solid electrolyte product.

[0069] The sulfide solid electrolyte product obtained in Example 6 was subjected to ionic conductivity testing, air stability testing, and... The release test results are shown in Table 1. The ionic conductivity of the sulfide solid electrolyte obtained in this embodiment is 0.7 mS / cm, and the ionic conductivity retention rate is 94% after exposure to dehumidified air at -50℃ dew point for 24 h.

[0070] Comparative Example 1 Will The electrolyte was directly placed in a vacuum oven and dried under vacuum at 80°C for 8 hours to obtain an untreated sulfide solid electrolyte.

[0071] The sulfide solid electrolyte product obtained in Comparative Example 1 was subjected to ionic conductivity testing, air stability testing, and... The release rate test results are shown in Table 1. The sulfide solid electrolyte obtained in this embodiment has an ionic conductivity of 6.0 mS / cm. After exposure to dehumidified air at a dew point of -50°C for 24 hours, the ionic conductivity retention rate is approximately 41%. Figure 1 As shown, after exposure to air at 15% relative humidity for 20 minutes, The release amount was 91 ppm, indicating that the uncoated sulfide solid electrolyte has very poor air stability.

[0072] Comparative Example 2 The experimental method for Comparative Example 2 was the same as that for Example 1, except that the coating material, hydrophobic fumed silica, was replaced with a material with a specific surface area of ​​100 m². 2 / g; Particle size: 10-30nm nano-alumina, the specific experimental steps are as follows: 1. Dispersion treatment: 0.1g of nano alumina is added to 15.15g of xylene and dispersed by ultrasonication (400 W power, 30 min time) to form a uniform suspension. The dispersion temperature is controlled at 35℃ to prevent the solvent from evaporating too quickly.

[0073] 2. Coating reaction: Add 10g of... The sulfide solid electrolyte powder was slowly added to the above suspension, with the solid content controlled at 40%. Under the protection of an inert gas (argon or nitrogen, water and oxygen content ≤0.1 ppm), it was mixed by high-energy ball milling (300 r / min, 2 h) to allow the hydrophobic fumed silica to be uniformly adsorbed and coated on the surface of the electrolyte particles.

[0074] 3. Drying and curing: The ball-milled mixture is placed in a vacuum drying oven and dried at 80°C for 8 hours to remove the dispersion medium. The electrolyte powder is collected to obtain the finished product of nano-alumina-coated sulfide solid electrolyte.

[0075] The sulfide solid electrolyte product obtained in Comparative Example 2 was subjected to ionic conductivity tests, air stability tests, and H2S release tests. The results are shown in Table 1. The ionic conductivity of the sulfide solid electrolyte obtained in this example was 4.1 mS / cm, and the ionic conductivity retention rate was 82% after exposure to dehumidified air at a dew point of -50°C for 24 h. Figure 1 As shown, after exposure to air at 15% relative humidity for 20 minutes, The release amount is 45 ppm.

[0076] Comparative Example 3 The experimental method for Comparative Example 3 was the same as that for Example 1, except that the coating material, hydrophobic fumed silica, was replaced with nano zinc oxide with a specific surface area of ​​100 m² / g and a particle size of 10-30 nm. The specific experimental steps are as follows: 1. Dispersion treatment: 0.1g of nano zinc oxide is added to 15.15g of xylene and dispersed by ultrasonication (400 W power, 30 min time) to form a uniform suspension. The dispersion temperature is controlled at 35℃ to prevent the solvent from evaporating too quickly.

[0077] 2. Coating reaction: Add 10g of... The sulfide solid electrolyte powder was slowly added to the above suspension, with the solid content controlled at 40%. Under the protection of an inert gas (argon or nitrogen, water and oxygen content ≤0.1 ppm), it was mixed by high-energy ball milling (300 r / min, 2 h) to allow the hydrophobic fumed silica to be uniformly adsorbed and coated on the surface of the electrolyte particles.

[0078] 3. Drying and curing: The ball-milled mixture is placed in a vacuum drying oven and dried at 80°C for 8 hours to remove the dispersion medium. The electrolyte powder is collected to obtain the finished product of nano zinc oxide coated sulfide solid electrolyte.

[0079] The sulfide solid electrolyte product obtained in Comparative Example 3 was subjected to ionic conductivity tests, air stability tests, and H2S release tests. The results are shown in Table 1. The ionic conductivity of the sulfide solid electrolyte obtained in this example was 3.8 mS / cm, and the ionic conductivity retention rate was 84% ​​after exposure to dehumidified air at a dew point of -50℃ for 24 h. Figure 1 As shown, after exposure to air at 15% relative humidity for 20 minutes, The release rate is 50 ppm.

[0080] Comparative Example 4 The experimental method for Comparative Example 4 was the same as that for Example 1, except that the coating material, hydrophobic fumed silica, was replaced with unmodified nano-silica with a specific surface area of ​​150 m² / g and a particle size of 10-40 nm. In its unmodified state, it is hydrophilic with a water contact angle of only 20-40°. The specific experimental steps are as follows: 1. Dispersion treatment: 0.1g of nano silica was added to 15.15g of xylene and dispersed by ultrasonication (400 W power, 30 min time) to form a uniform suspension. The dispersion temperature was controlled at 35℃ to prevent the solvent from evaporating too quickly.

[0081] 2. Coating reaction: Add 10g of... The sulfide solid electrolyte powder was slowly added to the above suspension, with the solid content controlled at 40%. Under the protection of an inert gas (argon or nitrogen, water and oxygen content ≤0.1 ppm), it was mixed by high-energy ball milling (300 r / min, 2 h) to allow the hydrophobic fumed silica to be uniformly adsorbed and coated on the surface of the electrolyte particles.

[0082] 3. Drying and curing: The ball-milled mixture is placed in a vacuum drying oven and dried at 80°C for 8 hours to remove the dispersion medium. The electrolyte powder is collected to obtain the finished nano-silica-coated sulfide solid electrolyte product.

[0083] The sulfide solid electrolyte product obtained in Comparative Example 4 was subjected to ionic conductivity testing, air stability testing, and... The release rate test results are shown in Table 1. The sulfide solid electrolyte obtained in this embodiment has an ionic conductivity of 5.2 mS / cm, and the ionic conductivity retention rate is 84% ​​after exposure to dehumidified air at -50℃ dew point for 24 h. Figure 1 As shown, after exposure to air at 15% relative humidity for 20 minutes, The release amount was 77 ppm.

[0084] Based on the test results of Examples 1-6 and Comparative Examples 1-4, the following table 1 was compiled.

[0085]

[0086] Table 1: Test results of ionic conductivity and air stability of different sulfide solid electrolytes Based on Table 1 above, as well as the various embodiments and comparative examples, the following conclusions can be drawn: Examples 1-4 demonstrate that the thickness of the ultrathin hydrophobic fumed silica coating is controllable, and an addition amount of 0.5-1% does not hinder lithium-ion transport, while the room temperature ionic conductivity of the finished electrolyte remains at 4-6 mS / cm. -1 .

[0087] Example 4 shows that with increased coating amount and coating thickness to 63 nm, the hydrophobically modified silica forms a weak interaction (van der Waals forces rather than chemical bonding) with the sulfide electrolyte surface. The coating layer exhibits multilayer adsorption depending on the coating amount. As the coating layer thickness increases, the conductivity retention rate after 24 hours of exposure at -50°C dew point increases accordingly. However, the ion transport channels are partially blocked, which reduces the overall ion conductivity.

[0088] Examples 5 and 6 demonstrate that the coating strategy of the present invention is also applicable to, for example, and Other types of solid electrolyte materials.

[0089] Example 1 and Comparative Example 1 show that a coating amount of 1% results in a thinner coating layer with negligible lithium-ion transport resistance, avoiding the insulating layer effect. A 1% amount can significantly improve air stability while maintaining an ionic conductivity greater than 90% after coating.

[0090] Examples 1 and Comparative Examples 2 and 3 show that, due to the traditional unmodified nano-ZnO, The coating system has no hydrophobic functional groups on its surface, providing only physical barrier properties without hydrophobic functionality. Therefore, it is effective in air with a relative humidity of 15%. The release rate is greater than in Example 1; and the hydrophobic fumed silica is bonded to the sulfide electrolyte by van der Waals forces, unlike nano-sized silica. The strong chemical bonding with sulfides easily leads to a high-resistivity interface phase, so the ionic conductivity of the hydrophobic vapor phase silica coating is higher than that of the control.

[0091] Example 1 and Comparative Example 4 show that the unmodified With a water contact angle of 20-40°, it only has a physical barrier function and does not have a hydrophobic function. Moreover, the hydrophilic hydroxyl groups on the surface easily adsorb water and accelerate the hydrolysis of electrolytes. Therefore, in humid air with a humidity of 15%, the hydrogen sulfide release of Comparative Example 4 (77 ppm) is significantly higher than that of Example 1 (32 ppm). After being exposed to dehumidified air at -50°C for 24 hours, the ionic conductivity retention rate is only 73%, which is far inferior to that of Example 1 (conductivity retention rate of 93%). This indicates that the hydrophobic fumed silica of the present invention simultaneously plays a dual role of physical barrier and hydrophobic protection, thereby improving the air stability of the material.

[0092] The above-described embodiments are merely examples of several implementations of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A method for preparing a sulfide solid electrolyte with a hydrophobic protective layer, characterized in that, Includes the following steps: S1. Disperse hydrophobic fumed silica in a low-polarity anhydrous solvent to form a suspension; S2. Under an inert atmosphere, the sulfide solid electrolyte powder is added to the suspension and ball-milled to mix it, so that the hydrophobic fumed silica coats the surface of the sulfide solid electrolyte particles. S3. Dry the ball-milled mixture to remove the solvent and obtain the sulfide solid electrolyte with a hydrophobic protective layer.

2. The method according to claim 1, characterized in that, In step S1, the hydrophobic fumed silica is fumed silica modified with polydimethylsiloxane or dimethyldichlorosilane, with a specific surface area of ​​110-170 m² / g, a carbon content of 0.6-1.6%, a water contact angle ≥120°, and a hydrophilic silanol substitution rate ≥90%; the particle size of the hydrophobic fumed silica is 7-40 nm, and the surface modification degree is 1.0-1.5 mmol / g.

3. The method according to claim 1, characterized in that, In step S1, the low-polarity anhydrous solvent is selected from one or more of toluene, xylene, n-heptane, n-hexane, octane, n-dodecane, or petroleum ether.

4. The method according to claim 1, characterized in that, In step S1, ultrasonic dispersion is performed with an ultrasonic power of 200-400 W, a dispersion temperature of 25-35℃, and a dispersion time of 30-60 min.

5. The method according to claim 1, characterized in that, In step S2, the amount of hydrophobic fumed silica added is 0.5%-3% of the mass of the sulfide solid electrolyte powder; the inert atmosphere is argon or nitrogen atmosphere, and the water and oxygen content is ≤0.1 ppm.

6. The method according to claim 1, characterized in that, In step S2, the solid content of the slurry during ball milling is 40-50%, the ball milling speed is 300-500 r / min, and the ball milling time is 2-4 h.

7. The method according to claim 1, characterized in that, In step S3, drying is carried out under vacuum conditions, at a temperature of 60-80℃, for a time of 8-12 hours.

8. The method according to claim 1, characterized in that, In step S2, the sulfide solid electrolyte is System electrolytes, or One or more of the following, wherein X is Cl, Br or I. In the electrolyte of the system and The molar ratio is 3-5:1; the particle size of the sulfide solid electrolyte powder is 0.5-3 μm.

9. A sulfide solid electrolyte having a hydrophobic protective layer prepared by any one of the preparation methods of claims 1-8.

10. The sulfide solid electrolyte according to claim 9, characterized in that, The hydrophobic fumed silica forms a coating layer on the surface of the sulfide solid electrolyte particles, and the thickness of the coating layer is 10-50 nm.

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