Halide solid electrolyte stable in air, preparation method and application thereof

Abstract

The invention relates to the field of solid electrolyte, in particular to halide solid electrolyte stable in air and a preparation method and application thereof. The preparation method comprises the following steps: adding halide solid electrolyte powder into carboxylated carbon nanotube dispersion liquid, then carrying out ball milling treatment, then carrying out spray drying, and then carrying out heat treatment in an inert gas atmosphere to obtain the halide solid electrolyte stable in the air. The halide solid electrolyte stable in air not only can be stable in air, but also has high ionic conductivity, and meets the basic requirements of the halide solid electrolyte. Therefore, the bottleneck that high conductivity and high air stability cannot be considered in the traditional doping or coating method is broken through, and an effective technical path is provided for improving the air stability of the halide solid electrolyte and commercialization of all-solid-state batteries.

Description

Technical Field

[0001] This invention relates to the field of solid electrolytes, and more particularly to an air-stable halide solid electrolyte, its preparation method, and its applications. Background Technology

[0002] With the rapid development of portable electronic devices and electric vehicles, the demand for high-performance, long-life energy storage devices is increasing. All-solid-state lithium metal batteries (ASSLMBs) have attracted much attention due to their high safety and high energy density. Among them, halide solid electrolytes (such as Li3InCl6 and Li3YCl6) have become a research hotspot due to their excellent ionic conductivity and chemical stability. However, the stability of halide electrolytes in air still presents many problems, such as easy absorption of water and hydrolysis to generate byproducts, leading to a decrease in ionic conductivity and limiting their practical applications. Currently, although some studies have improved the performance of electrolytes through methods such as surface coatings, there is still a lack of effective solutions for protecting the air stability of halide solid electrolytes.

[0003] While there have been some reports on improving the stability of solid electrolytes in the prior art, there is still no ideal method for addressing the air stability problem of halide solid electrolytes.

[0004] Therefore, existing technologies need to be improved. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide an air-stable halide solid electrolyte, its preparation method and its application, aiming to solve the problem of performance trade-offs (such as the inability to simultaneously achieve conductivity and stability) that are common in improving the air stability of halide solid electrolytes.

[0006] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing an air-stable halide solid electrolyte, comprising the following steps: Halogenated solid electrolyte powder was added to a carboxylated carbon nanotube dispersion, and then ball-milled to obtain a mixture. The mixture is spray-dried to obtain coated halide solid electrolyte powder; The encapsulated halide solid electrolyte powder is heat-treated in an inert gas atmosphere to obtain the air-stable halide solid electrolyte.

[0007] Optionally, the halide solid electrolyte powder is Li3MCl6, where M = In or Y.

[0008] Optionally, the amount of carboxylated carbon nanotubes used is 0.5-10 wt% of the halide solid electrolyte powder. Preferably, it is 1-5 wt%.

[0009] Optionally, the solid-liquid mass ratio in the mixture is 1 to 5:10. Preferably, the solid-liquid mass ratio in the mixture is 2.5:10.

[0010] Optionally, the diameter of the carboxylated carbon nanotubes (CNTs-COOH) in the carboxylated carbon nanotube dispersion is 10~100nm, and the aspect ratio is greater than 100; preferably, the aspect ratio is 10~50nm.

[0011] Optionally, the carboxylated carbon nanotubes (CNTs-COOH) in the carboxylated carbon nanotube dispersion include carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) or carboxylated single-walled carbon nanotubes (SWCNTs-COOH).

[0012] Optionally, the concentration of carboxylated carbon nanotubes (CNTs-COOH) in the carboxylated carbon nanotube dispersion is 0.5-5 mol / L; preferably, the concentration of carboxylated carbon nanotubes (CNTs-COOH) is 1 mol / L. Too high a concentration reduces ionic conductivity, while too low a concentration results in incomplete coating.

[0013] Optionally, the carboxylated carbon nanotube dispersion is prepared by adding carboxylated carbon nanotubes to a solvent and then ultrasonically treating it to obtain the carboxylated carbon nanotube dispersion.

[0014] Optionally, the ultrasonic power is 10-1000W and the ultrasonic time is 1-10h; preferably, the ultrasonic power is 600-1000W and the ultrasonic time is 5h.

[0015] Optionally, the solvent in the carboxylated carbon nanotube dispersion is selected from one or any combination of two or more of toluene, xylene, n-heptane, n-decane, n-hexane, petroleum ether, anisole, n-butyl ether, ethyl acetate, butyl acetate, and butyl butyrate.

[0016] Optionally, the ball milling process is carried out at a speed of 200-400 rpm for 1-10 hours, with a ball-to-material ratio of 10-40:1. Preferably, the ball milling process is carried out at a speed of 300 rpm for 5 hours, with a ball-to-material ratio of 25:1.

[0017] Optionally, the spray drying temperature is 80-160°C, preferably 130°C.

[0018] Optionally, the heat treatment involves sintering at 80-150°C for 1-5 hours. Preferably, the heat treatment involves sintering at 120°C for 35 hours. It should be noted that this embodiment strengthens the interfacial bonding through a low-temperature heat treatment process, avoiding damage to the crystal structure.

[0019] Secondly, the present invention provides an air-stable halide solid electrolyte, prepared by the aforementioned preparation method, or comprising a halide solid electrolyte layer and a carboxylated carbon nanotube layer encapsulated on the outer layer of the halide solid electrolyte layer.

[0020] Optionally, the mass of the carboxylated carbon nanotube layer is 0.5-10 wt% of the mass of the halide solid electrolyte layer, preferably 1-5 wt%.

[0021] Thirdly, the present invention provides an application of an air-stable halide solid electrolyte in an all-solid-state lithium metal battery.

[0022] Beneficial Effects: This invention provides an air-stable halide solid electrolyte, its preparation method, and its applications. The invention involves ball milling halide solid electrolyte powder and a carboxylated carbon nanotube dispersion, causing the carboxylated carbon nanotube dispersion to coat the halide solid electrolyte powder surface, forming a dense hydrophobic network layer. Uniform coating is then achieved through spray drying, and finally, heat treatment strengthens interfacial bonding, preventing crystal damage, ultimately yielding an air-stable halide solid electrolyte. The air-stable halide solid electrolyte of this invention not only exhibits stability in air but also high ionic conductivity, meeting the basic requirements of halide solid electrolytes. Therefore, this invention overcomes the bottleneck of traditional doping or coating methods that cannot simultaneously achieve high conductivity and high air stability, providing an effective technical path for improving the air stability of halide solid electrolytes and the commercialization of all-solid-state batteries. Detailed Implementation

[0023] This invention provides an air-stable halide solid electrolyte, its preparation method, and its applications. 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.

[0024] CN119627189A discloses a coating using dihexadecyl phosphate (DHP), which improves air stability and is actually a hydrophobic coating strategy. However, the organic layer has poor thermal stability (decomposition temperature <200℃), and the introduction of organic components reduces ionic conductivity (by 30–50%). In addition, there is a defect that the coating layer is prone to cracking when dried at high temperatures (>80℃).

[0025] CN119447435A discloses a method using a LiF / Al2O3 composite coating layer, which is actually an oxide / fluoride composite coating strategy. While it improves air stability, the ceramic material has low ionic conductivity (Al2O3: 10). -10 S / cm), excessive coating will reduce the overall ion mobility (conductivity decreases by 30% when coating amount >0.5wt%).

[0026] Others have adopted an element doping strategy, mainly using elements such as F, O, and N to modify and dope the initial material. Although this improves air stability, the introduction of these highly electronegative elements often leads to a significant reduction in ionic conductivity (a 28% reduction in ionic conductivity), and the effect of improving air stability is limited (the retention rate is only 62% after 5 hours in a -20±3℃ dew point drying chamber).

[0027] In summary, existing technologies for improving the air stability of halide solid electrolytes generally present several technical challenges involving necessary performance trade-offs (such as the inability to simultaneously achieve conductivity and stability).

[0028] Based on this, this embodiment provides a method for preparing an air-stable halide solid electrolyte, comprising the following steps: Halogenated solid electrolyte powder was added to a carboxylated carbon nanotube dispersion, and then ball milled to obtain a mixture. The mixture is spray-dried to obtain coated halide solid electrolyte powder; The encapsulated halide solid electrolyte powder is heat-treated in an inert gas atmosphere to obtain the air-stable halide solid electrolyte.

[0029] It should be noted that in this embodiment, the halide solid electrolyte powder and the carboxylated carbon nanotube dispersion are ball-milled to allow the carboxylated carbon nanotube dispersion to coat the surface of the halide solid electrolyte powder, forming a dense hydrophobic network layer. Uniform coating is then achieved through spray drying, and finally, heat treatment is used to strengthen the interfacial bonding, preventing crystal damage and ultimately improving its air stability. Specifically, the carbon nanotubes in the carboxylated carbon nanotubes can form a network that blocks water molecules from contacting the surface of the halide solid electrolyte; moreover, the hydrophobic groups of the carboxylated carbon nanotubes reduce surface energy and inhibit water adsorption; spray drying also allows for control of the coating layer thickness to ensure low electronic conductivity (<10). -8 (S / cm) suppresses interfacial side reactions. Therefore, the coating layer obtained in this invention is a coating layer with a triple mechanism of physical barrier, hydrophobic effect and electron channel blocking that synergistically enhances stability.

[0030] Experiments show that the coated halide electrolyte exhibits a significant improvement in ionic conductivity retention after 24 hours of exposure to air, while also meeting the requirements of large-scale production. This invention overcomes the bottleneck of traditional doping or coating methods, which cannot simultaneously achieve high conductivity and high air stability, providing an effective technical path for improving the air stability of halide solid electrolytes and the commercialization of all-solid-state batteries.

[0031] In some embodiments, the halide solid electrolyte powder is Li3MCl6 powder, wherein M = In or Y.

[0032] It should be noted that this embodiment is only an example and is not limited to the above-mentioned halide solid electrolyte powder. The preparation method of Li3MCl6 can be as follows: Under an inert (argon) atmosphere, raw materials LiCl and InCl3 or YCl are mixed at a molar ratio of 1:3, and ball-milled at 600 rpm for 10 hours. After ball milling, the material is subjected to a low-temperature sintering and recrystallization process at 260℃ for 5 hours. The sintered powder is then crushed and refined using a pulverizer or crusher to obtain halide solid electrolyte powder with the general chemical formula Li3MCl6 (M=In, Y). Experiments have shown that its particle size is D50 = 1~10 μm and its ionic conductivity is 1.8 mS / cm.

[0033] In some embodiments, the amount of carboxylated carbon nanotubes is 0.5-10 wt% of the halide solid electrolyte powder. Preferably, it is 1-5 wt%, specifically 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any value within the range.

[0034] It should be noted that a low content of carboxylated carbon nanotubes as a coating layer may result in incomplete coverage of the halide solid electrolyte powder, affecting coating uniformity; conversely, an excessive coating layer content may reduce the ionic conductivity of the halide solid electrolyte powder. The coating layer content of this invention is 0.5-10 wt%, preferably 1-5 wt%. This ensures uniform and stable coverage of the halide solid electrolyte powder surface without affecting its ionic conductivity, thus maximizing the balance between the electrolyte's ionic conductivity and chemical stability.

[0035] In some embodiments, the solid-liquid mass ratio in the mixture is 1 to 5:10. Preferably, the solid-liquid mass ratio in the mixture is 2.5:10. Specifically, it can be 1:10, 2:10, 3:10, 4:10, 5:10, or any value within the range.

[0036] Within this ratio range, the solids (halogenated electrolyte and CNTs-COOH) in the liquid can form a low-viscosity, high-flow-rate slurry, ensuring uniform atomization during spray drying and preventing nozzle clogging or deposition. Additionally, the liquid volume is sufficient to fully disperse the CNTs-COOH and wet the electrolyte surface, forming a continuous coating layer. If the ratio is too high, it will lead to excess solvent, prolonging drying time and potentially causing CNT agglomeration or coating layer cracking.

[0037] In some embodiments, the carboxylated carbon nanotube dispersion is prepared by adding carboxylated carbon nanotubes to a solvent and then sonicating them to obtain the carboxylated carbon nanotube dispersion.

[0038] In some embodiments, the ultrasonic power is 10-1000W, and the ultrasonic time is 1-10 hours; preferably, the ultrasonic power is 600-1000W, and the ultrasonic time is 5 hours. Specifically, it can be 600W power, 700W power, 800W power, 900W power, or 1000W power, with an ultrasonic time of 5 hours.

[0039] By using ultrasound with a certain power and time, a uniform suspension can be obtained, which ultimately results in uniform encapsulation.

[0040] In some embodiments, the carboxylated carbon nanotubes (CNTs-COOH) in the carboxylated carbon nanotube dispersion have a diameter of 10-100 nm and an aspect ratio greater than 100; preferably, the diameter is 10-50 nm.

[0041] It should be noted that, in this embodiment, firstly, CNTs with a diameter of 10-50 nm are paired with electrolyte particles (D50 = 1-10 μm) to form a nanoscale coating layer. CNTs can entangle or bridge the particle surface, constructing a dense three-dimensional network that blocks water molecules, thereby achieving a stabilizing effect. Secondly, CNTs with an aspect ratio >100 provide high flexibility and interpenetration capability, forming a sufficient and continuous barrier network even at low addition levels (1-5 wt%). Finally, CNTs in this size range are less prone to sedimentation after ultrasonic dispersion and can stably suspend in the solvent, ensuring uniform deposition on the electrolyte surface during spray drying and avoiding coating defects caused by agglomeration.

[0042] In some embodiments, the carboxylated carbon nanotubes (CNTs-COOH) in the carboxylated carbon nanotube dispersion include carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) or carboxylated single-walled carbon nanotubes (SWCNTs-COOH).

[0043] In some embodiments, the concentration of carboxylated carbon nanotubes (CNTs-COOH) in the carboxylated carbon nanotube dispersion is 0.5-5 mol / L; preferably, the concentration of carboxylated carbon nanotubes (CNTs-COOH) is 1 mol / L. Specifically, it can be 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, or 5 mol / L.

[0044] It should be noted that the concentration of carboxylated carbon nanotubes affects ionic conductivity. Too high a concentration will reduce ionic conductivity, while too low a concentration will result in incomplete coating, ultimately affecting air stability.

[0045] In some embodiments, the solvent in the carboxylated carbon nanotube dispersion is selected from one or any combination of two or more of toluene, xylene, n-heptane, n-decane, n-hexane, petroleum ether, anisole, n-butyl ether, ethyl acetate, butyl acetate, and butyl butyrate.

[0046] In some embodiments, the ball milling process is carried out at a speed of 200-400 rpm for 1-10 hours, with a ball-to-material ratio of 10-40:1. Preferably, the ball milling process is carried out at a speed of 300 rpm for 5 hours, with a ball-to-material ratio of 25:1. Alternatively, the process can be ball milling at 200 rpm for 10 hours or at 400 rpm for 1 hour.

[0047] It should be noted that under these ball milling conditions, the solid electrolyte material powder can be thoroughly and uniformly mixed with the coating material, achieving a sufficient coating effect. Excessive rotation speed will result in insufficient coating, while insufficient rotation speed will lead to prolonged processing time.

[0048] In some embodiments, the spray drying temperature is 80-160°C, preferably 130°C. It can also be 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C or any value within the range.

[0049] It should be noted that the spray drying temperature and time can both avoid agglomeration caused by excessive temperature and effectively and quickly remove the solvent from the slurry.

[0050] In some embodiments, the heat treatment involves sintering at 80-150°C for 1-5 hours. Preferably, the heat treatment involves sintering at 120°C for 35 hours. It should be noted that this embodiment strengthens the interfacial bonding through a low-temperature heat treatment process, avoiding damage to the crystal structure.

[0051] This embodiment also provides an air-stable halide solid electrolyte, prepared by the aforementioned preparation method, or comprising a halide solid electrolyte layer and a carboxylated carbon nanotube layer encapsulating the outer layer of the halide solid electrolyte layer.

[0052] It should be noted that the air-stable halide solid electrolyte prepared in this embodiment mainly consists of a halide solid electrolyte layer and a carboxylated carbon nanotube layer wrapped around the halide solid electrolyte layer. The carbon nanotubes in the carboxylated carbon nanotubes in the wrapping layer can form a network to block water molecules from contacting the surface of the halide solid electrolyte. Moreover, the hydrophobic groups of the carboxylated carbon nanotubes reduce the surface energy and inhibit water adsorption. The resulting halide solid electrolyte with a certain thickness of wrapping layer not only has air stability but also maintains the conductivity of the halide solid electrolyte.

[0053] In some embodiments, the mass of the carboxylated carbon nanotube layer is 0.5-10 wt% of the mass of the halide solid electrolyte layer, preferably 1-5 wt%. Specifically, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt%.

[0054] This embodiment also provides the application of an air-stable halide solid electrolyte in an all-solid-state lithium metal battery.

[0055] Applying the air-stable halide solid electrolyte of this embodiment to all-solid-state lithium metal batteries not only achieves high air temperature but also high ionic conductivity, breaking through the bottleneck of traditional doping or coating methods that cannot simultaneously achieve high conductivity and high air stability. This provides an effective technical path for improving the air stability of halide solid electrolytes and the commercialization of all-solid-state batteries.

[0056] The present invention will be further described below through specific embodiments.

[0057] Example 1 1. Preparation of halide solid electrolyte powder: Under an argon atmosphere, raw materials LiCl and InCl3 were mixed at a molar ratio of 1:3 and added to a high-energy ball mill jar for ball milling at 600 rpm for 10 hours. After ball milling, the material was subjected to low-temperature sintering and recrystallization under an argon atmosphere at 260℃ for 5 hours. The sintered powder was then crushed and refined using a pulverizer to obtain halide solid electrolyte powder (Li3InCl6 solid electrolyte powder with a particle size of D50 = 5 μm). 2. Preparation of carboxylated carbon nanotube dispersion: Carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) were added to toluene solvent at a concentration of 1 mol / L. The resulting dispersion was then sonicated at 800 W for 5 h to form a homogeneous dispersion of carboxylated carbon nanotubes. 3. Preparation of air-stable halide solid electrolytes: Halogenated solid electrolyte powder (Li3InCl6 solid electrolyte powder with a particle size of D50=5μm) was added to a carboxylated carbon nanotube dispersion to obtain a mixed solution with a solid-liquid mass ratio of 2.5:10. Then, ball milling was performed to uniformly coat the Li3InCl6 solid electrolyte powder surface with MWCNTs-COOH. The ball milling speed was 300 rpm, the milling time was 5 h, and the ball-to-powder ratio was 25:1. The mixture was first sieved and then spray-dried at a temperature of 130°C to obtain coated Li3InCl6 solid electrolyte powder.

[0058] The coated Li3InCl6 solid electrolyte powder was subjected to low-temperature heat treatment at 120℃ for 3 hours under an argon atmosphere to enhance interfacial bonding.

[0059] In this embodiment, the content of carboxylated carbon nanotubes in the coating layer is 2.5 wt% of the Li3InCl6 solid electrolyte. Example 2 The difference between this embodiment and Embodiment 1 is that in this embodiment, carboxylated single-walled carbon nanotubes (SWCNTs-COOH) are used instead of carboxylated multi-walled carbon nanotubes.

[0060] Specifically, it includes: 1. Preparation of halide solid electrolyte powder: Under an argon atmosphere, raw materials LiCl and InCl3 were mixed at a molar ratio of 1:3 and added to a high-energy ball mill jar for ball milling at 600 rpm for 10 hours. After ball milling, the material was subjected to low-temperature sintering and recrystallization under an argon atmosphere at 260℃ for 5 hours. The sintered powder was then crushed and refined using a pulverizer to obtain halide solid electrolyte powder (Li3InCl6 solid electrolyte powder with a particle size of D50 = 5 μm). 2. Preparation of carboxylated carbon nanotube dispersion: Single-walled carbon nanotubes (SWCNTs-COOH) were added to toluene solvent, with a carboxylated carbon nanotube concentration of 1 mol / L. The resulting dispersion was then sonicated at 800 W for 5 h to form a homogeneous carboxylated carbon nanotube dispersion. 3. Preparation of air-stable halide solid electrolytes: Halogenated solid electrolyte powder (Li3InCl6 solid electrolyte powder with a particle size of D50=5μm) was added to a carboxylated carbon nanotube dispersion to obtain a mixed solution with a solid-liquid ratio of 2.5:10. Then, ball milling was performed to uniformly coat the Li3InCl6 solid electrolyte powder surface with SWCNTs-COOH. The ball milling speed was 300 rpm, the milling time was 5 h, and the ball-to-powder ratio was 25:1. The mixture was first sieved and then spray-dried at a temperature of 130°C to obtain coated Li3InCl6 solid electrolyte powder.

[0061] The coated Li3InCl6 solid electrolyte powder was subjected to low-temperature heat treatment at 120℃ for 3 hours under an argon atmosphere to enhance interfacial bonding.

[0062] In this embodiment, the content of carboxylated carbon nanotubes in the coating layer is 2.5 wt% of the Li3InCl6 solid electrolyte. Example 3 The difference between this embodiment and Embodiment 1 is that the content of carboxylated carbon nanotubes in the coating layer of this embodiment is 1.0 wt% of the Li3InCl6 solid electrolyte. Specifically, it includes: 1. Preparation of halide solid electrolyte powder: Under an argon atmosphere, raw materials LiCl and InCl3 were mixed at a molar ratio of 1:3 and added to a high-energy ball mill jar for ball milling at 600 rpm for 10 hours. After ball milling, the material was subjected to low-temperature sintering and recrystallization under an argon atmosphere at 260℃ for 5 hours. The sintered powder was then crushed and refined using a pulverizer to obtain halide solid electrolyte powder (Li3InCl6 solid electrolyte powder with a particle size of D50 = 5 μm). 2. Preparation of carboxylated carbon nanotube dispersion: Single-walled carbon nanotubes (SWCNTs-COOH) were added to toluene solvent, with a carboxylated carbon nanotube concentration of 1 mol / L. The resulting dispersion was then sonicated at 800 W for 5 h to form a homogeneous carboxylated carbon nanotube dispersion. 3. Preparation of air-stable halide solid electrolytes: Halogenated solid electrolyte powder (Li3InCl6 solid electrolyte powder with a particle size of D50=5μm) was added to a carboxylated carbon nanotube dispersion to obtain a mixed solution with a solid-liquid ratio of 2.5:10. Then, ball milling was performed to uniformly coat the Li3InCl6 solid electrolyte powder surface with MWCNTs-COOH. The ball milling speed was 300 rpm, the milling time was 5 h, and the ball-to-powder ratio was 25:1. The mixture was first sieved and then spray-dried at a temperature of 130°C to obtain coated Li3InCl6 solid electrolyte powder.

[0063] The coated Li3InCl6 solid electrolyte powder was subjected to low-temperature heat treatment at 120℃ for 3 hours under an argon atmosphere to enhance interfacial bonding.

[0064] In this embodiment, the content of carboxylated carbon nanotubes in the coating layer is 1.0 wt% of the Li3InCl6 solid electrolyte. Example 4 The difference between this embodiment and Embodiment 1 is that the content of carboxylated carbon nanotubes in the coating layer of this embodiment is 5.0 wt% of the Li3InCl6 solid electrolyte. Specifically, it includes: 1. Preparation of halide solid electrolyte powder: Under an argon atmosphere, raw materials LiCl and InCl3 were mixed at a molar ratio of 1:3 and added to a high-energy ball mill jar for ball milling at 600 rpm for 10 hours. After ball milling, the material was subjected to low-temperature sintering and recrystallization under an argon atmosphere at 260℃ for 5 hours. The sintered powder was then crushed and refined using a pulverizer to obtain halide solid electrolyte powder (Li3InCl6 solid electrolyte powder with a particle size of D50 = 5 μm). 2. Preparation of carboxylated carbon nanotube dispersion: Single-walled carbon nanotubes (SWCNTs-COOH) were added to toluene solvent, with a carboxylated carbon nanotube concentration of 1 mol / L. The resulting dispersion was then sonicated at 800 W for 5 h to form a homogeneous carboxylated carbon nanotube dispersion. 3. Preparation of air-stable halide solid electrolytes: Halogenated solid electrolyte powder (Li3InCl6 solid electrolyte powder with a particle size of D50=5μm) was added to a carboxylated carbon nanotube dispersion to obtain a mixed solution with a solid-liquid ratio of 2.5:10. Then, ball milling was performed to uniformly coat the Li3InCl6 solid electrolyte powder surface with MWCNTs-COOH. The ball milling speed was 300 rpm, the milling time was 5 h, and the ball-to-powder ratio was 25:1.

[0065] The mixture was first sieved and then spray-dried at a temperature of 130°C to obtain coated Li3InCl6 solid electrolyte powder.

[0066] The coated Li3InCl6 solid electrolyte powder was subjected to low-temperature heat treatment at 120℃ for 3 hours under an argon atmosphere to enhance interfacial bonding.

[0067] In this embodiment, the content of carboxylated carbon nanotubes in the coating layer is 5.0 wt% of the Li3InCl6 solid electrolyte.

[0068] Example 5 The difference between this embodiment and embodiment 1 is that the ultrasonic power in this embodiment is 400W and the ultrasonic time is 1 hour.

[0069] Specifically, it includes: 1. Preparation of halide solid electrolyte powder: Under an argon atmosphere, raw materials LiCl and InCl3 were mixed at a molar ratio of 1:3 and added to a high-energy ball mill jar for ball milling at 600 rpm for 10 hours. After ball milling, the material was subjected to low-temperature sintering and recrystallization under an argon atmosphere at 260℃ for 5 hours. The sintered powder was then crushed and refined using a pulverizer to obtain halide solid electrolyte powder (Li3InCl6 solid electrolyte powder with a particle size of D50 = 5 μm).

[0070] 2. Preparation of carboxylated carbon nanotube dispersion: Single-walled carbon nanotubes (SWCNTs-COOH) were added to toluene solvent, with a carboxylated carbon nanotube concentration of 1 mol / L. The resulting dispersion was then sonicated at 400 W for 1 h to form a homogeneous carboxylated carbon nanotube dispersion.

[0071] 3. Preparation of air-stable halide solid electrolytes: Halogenated solid electrolyte powder (Li3InCl6 solid electrolyte powder with a particle size of D50=5μm) was added to a carboxylated carbon nanotube dispersion to obtain a mixed solution with a solid-liquid ratio of 2.5:10. Then, ball milling was performed to uniformly coat the Li3InCl6 solid electrolyte powder surface with MWCNTs-COOH. The ball milling speed was 300 rpm, the milling time was 5 h, and the ball-to-powder ratio was 25:1.

[0072] The mixture was first sieved and then spray-dried at a temperature of 130°C to obtain coated Li3InCl6 solid electrolyte powder.

[0073] The coated Li3InCl6 solid electrolyte powder was subjected to low-temperature heat treatment at 120℃ for 3 hours under an argon atmosphere to enhance interfacial bonding.

[0074] In this embodiment, the content of carboxylated carbon nanotubes in the coating layer is 2.5 wt% of the Li3InCl6 solid electrolyte.

[0075] Example 6 The difference between this embodiment and Embodiment 1 is that the ultrasonic power in this embodiment is 1000W and the ultrasonic time is 10h.

[0076] Specifically, it includes: 1. Preparation of halide solid electrolyte powder: Under an argon atmosphere, raw materials LiCl and InCl3 were mixed at a molar ratio of 1:3 and added to a high-energy ball mill jar for ball milling at 600 rpm for 10 hours. After ball milling, the material was subjected to low-temperature sintering and recrystallization under an argon atmosphere at 260℃ for 5 hours. The sintered powder was then crushed and refined using a pulverizer to obtain halide solid electrolyte powder (Li3InCl6 solid electrolyte powder with a particle size of D50 = 5 μm).

[0077] 2. Preparation of carboxylated carbon nanotube dispersion: Single-walled carbon nanotubes (SWCNTs-COOH) were added to toluene solvent, with a carboxylated carbon nanotube concentration of 1 mol / L. The resulting dispersion was then sonicated at 1000 W for 10 h to form a homogeneous carboxylated carbon nanotube dispersion.

[0078] 3. Preparation of air-stable halide solid electrolytes: Halogenated solid electrolyte powder (Li3InCl6 solid electrolyte powder with a particle size of D50=5μm) was added to a carboxylated carbon nanotube dispersion to obtain a mixed solution with a solid-liquid ratio of 2.5:10. Then, ball milling was performed to uniformly coat the Li3InCl6 solid electrolyte powder surface with MWCNTs-COOH. The ball milling speed was 300 rpm, the milling time was 5 h, and the ball-to-powder ratio was 25:1.

[0079] The mixture was first sieved and then spray-dried at a temperature of 130°C to obtain coated Li3InCl6 solid electrolyte powder.

[0080] The coated Li3InCl6 solid electrolyte powder was subjected to low-temperature heat treatment at 120℃ for 3 hours under an argon atmosphere to enhance interfacial bonding.

[0081] In this embodiment, the content of carboxylated carbon nanotubes in the coating layer is 2.5 wt% of the Li3InCl6 solid electrolyte.

[0082] Example 7 The main difference from Example 1 is that this example uses Li3YCl6 as the halide solid electrolyte powder.

[0083] Specifically, it includes: 1. Preparation of halide solid electrolyte powder: Under an argon atmosphere, raw materials LiCl and YCl were mixed at a molar ratio of 1:3 and added to a high-energy ball mill jar for ball milling at a speed of 600 rpm for 10 hours. After ball milling, the material was subjected to low-temperature sintering and recrystallization under an argon atmosphere at a temperature of 260℃ for 5 hours. The sintered powder was then crushed and refined using a pulverizer to obtain halide solid electrolyte powder (Li3YCl6 solid electrolyte powder with a particle size of D50=8μm). 2. Preparation of carboxylated carbon nanotube dispersion: Single-walled carbon nanotubes (SWCNTs-COOH) were added to toluene solvent, with a carboxylated carbon nanotube concentration of 1 mol / L. The resulting dispersion was then sonicated at 1000 W for 10 h to form a homogeneous carboxylated carbon nanotube dispersion. 3. Preparation of air-stable halide solid electrolytes: Halogenated solid electrolyte powder (Li3YCl6 solid electrolyte powder with a particle size of D50=8μm) was added to a carboxylated carbon nanotube dispersion to obtain a mixed solution with a solid-liquid ratio of 2.5:10. Then, ball milling was performed to uniformly coat the Li3InCl6 solid electrolyte powder surface with SWCNTs-COOH. The ball milling speed was 400 rpm, the milling time was 2 h, and the ball-to-powder ratio was 25:1. The mixture was first sieved and then spray-dried at a temperature of 100℃ to obtain coated Li3YCl6 solid electrolyte powder.

[0084] The coated Li3InCl6 solid electrolyte powder was subjected to low-temperature heat treatment at 120℃ for 3 hours under an argon atmosphere to enhance interfacial bonding.

[0085] In this embodiment, the content of carboxylated carbon nanotubes in the coating layer is 3.0 wt% of the Li3YCl6 solid electrolyte.

[0086] Example 8 The difference between this embodiment and Embodiment 1 is that the concentration of carboxylated carbon nanotubes in the solvent is 5 mol / L, and the content of carboxylated carbon nanotubes in the coating layer is adjusted to 10 wt% of the Li3InCl6 solid electrolyte.

[0087] Comparative Example 1 The difference between this comparative example and Example 1 is that this comparative example only includes the step of preparing halide solid electrolyte powder, that is, the solid electrolyte obtained is not coated. Specifically, it includes: Under an argon atmosphere, raw materials LiCl and InCl3 were mixed at a molar ratio of 1:3 and added to a high-energy ball mill jar for ball milling at 600 rpm for 10 hours. After ball milling, the material was subjected to low-temperature sintering and recrystallization under an argon atmosphere at 260℃ for 5 hours. The sintered powder was then crushed and refined using a pulverizer to obtain halide solid electrolyte powder (Li3InCl6 solid electrolyte powder with a particle size of D50 = 5 μm). Comparative Example 2 The difference between this comparative example and Example 1 is that Li3InCl6 solid electrolyte powder was added to toluene solvent containing pure single-walled carbon nanotubes; all other operations were the same as in Example 1. In other words, this comparative example uses pure single-walled carbon nanotubes, rather than carboxylated single-walled carbon nanotubes (SWCNTs-COOH).

[0088] Performance testing: The halide solid electrolytes obtained in the above examples and comparative examples were subjected to tests of ionic conductivity and air stability. The ionic conductivity of the halide solid electrolytes was tested by pressing 200 mg of sulfide electrolyte into a 10 mm diameter disc at 380 MPa, using carbon-coated aluminum foil as the blocking electrode, and measuring the electrochemical impedance spectroscopy under conditions of 1 MHz to 100 Hz. The air stability of the halide solid electrolytes was tested by exposing 1 g of halide solid electrolyte to a -30°C dew-point dry environment for 8 hours, followed by testing the ionic conductivity. The results are shown in Table 1.

[0089] Table 1. Comparison of some preparation conditions and performance of halide solid electrolytes in Examples 1-7 and Comparative Examples 1-3

[0090] Comparing the results of Comparative Examples 1 and 2 with those of Example 1, it was found that the electrolyte material coated with carboxylated CNTs had good air stability. In contrast, the electrolyte material without coating (such as Comparative Example 1) or only coated with carbon nanotubes (such as Comparative Example 2) had poor air stability and reached a general level.

[0091] The results of Examples 2 and 1 show that the type of coating material also affects the coating effect. The air-stable halide solid electrolyte obtained by coating with carboxylated single-walled carbon nanotubes (SWCNTs-COOH) has a slightly worse effect on improving air stability compared with the air-stable halide solid electrolyte obtained by using carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) in Example 1.

[0092] The results of Examples 1, 3, 4, and 8 show that the content of the coating material has a significant impact on air stability. When the coating content is too low, the electrolyte material cannot be fully coated, and its improvement in air stability is only moderate to high. When the coating content is high or excessive, although the improvement in air stability is better, it will lead to a significant decrease in the initial ionic conductivity of the coated electrolyte material.

[0093] Examples 5 and 6 show that when the ultrasonic dispersion energy is too high or too low during the processing of the precursor slurry of the coating material, the dispersion effect of the coating material slurry will be poor, thereby affecting the coating effect and the improvement effect of air stability. When the ultrasonic power and time exceed the protection range of this embodiment, it will have too great an impact on the coating effect. Examples 5 and 6 have been used as the upper and lower limits of ultrasonic power.

[0094] The results of Example 7 show that the method is still effective in improving air stability for different types of halide solid electrolyte materials, so the present invention has a wide range of applications.

[0095] In summary, this invention provides an air-stable halide solid electrolyte, its preparation method, and its applications. By ball milling halide solid electrolyte powder and a carboxylated carbon nanotube dispersion, the carboxylated carbon nanotube dispersion coats the surface of the halide solid electrolyte powder, forming a dense hydrophobic network layer. Uniform coating is then achieved through spray drying, and finally, heat treatment strengthens interfacial bonding, preventing crystal damage, ultimately yielding an air-stable halide solid electrolyte. The air-stable halide solid electrolyte of this invention not only exhibits stability in air but also high ionic conductivity, meeting the basic requirements of halide solid electrolytes. Furthermore, it has a wide range of applications, overcoming the bottleneck of traditional doping or coating methods that cannot simultaneously achieve high conductivity and high air stability. This provides an effective technical path for improving the air stability of halide solid electrolytes and the commercialization of all-solid-state batteries.

[0096] 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 producing an air-stable halide solid-state electrolyte, characterized by, Includes the following steps: Halogenated solid electrolyte powder was added to a carboxylated carbon nanotube dispersion, and then ball-milled to obtain a mixture. The mixture is spray-dried to obtain coated halide solid electrolyte powder; The encapsulated halide solid electrolyte powder is heat-treated in an inert gas atmosphere to obtain the air-stable halide solid electrolyte.

2. The method of claim 1, wherein the air-stable halide solid-state electrolyte is prepared by the method comprising: The amount of carboxylated carbon nanotubes used is 0.5-10 wt% of the halide solid electrolyte powder. ​ 3. The method of claim 1, wherein the air-stable halide solid-state electrolyte is prepared by the method comprising: The solid-liquid mass ratio in the mixture is 1~5:10; ​ The carboxylated carbon nanotubes in the dispersion have a diameter of 10-100 nm and an aspect ratio greater than 100.

4. The method for preparing an air-stable halide solid electrolyte according to claim 1, characterized in that, The concentration of carboxylated carbon nanotubes in the carboxylated carbon nanotube dispersion is 0.5-5 mol / L.

5. The method for preparing an air-stable halide solid electrolyte according to claim 1, characterized in that, The carboxylated carbon nanotube dispersion is prepared by the following method: adding carboxylated carbon nanotubes to a solvent and then ultrasonically treating it to obtain the carboxylated carbon nanotube dispersion. The power of the ultrasound is 10-1000W, and the duration of the ultrasound is 1-10 hours. The solvent in the carboxylated carbon nanotube dispersion is selected from one or any combination of two or more of the following: toluene, xylene, n-heptane, n-decane, n-hexane, petroleum ether, anisole, n-butyl ether, ethyl acetate, butyl acetate, and butyl butyrate.

6. The method for preparing an air-stable halide solid electrolyte according to claim 1, characterized in that, The ball milling process is performed at a speed of 200-400 rpm for 1-10 hours, with a ball-to-material ratio of 10-40:

1.

7. The method for preparing an air-stable halide solid electrolyte according to claim 1, characterized in that, The spray drying temperature is 80-160℃.

8. The method for preparing an air-stable halide solid electrolyte according to claim 1, characterized in that, The heat treatment is sintering at 80~150℃ for 1~5 hours.

9. An air-stable halide solid electrolyte, characterized in that, Prepared by the preparation method of any one of claims 1-8, or comprising a halide solid electrolyte layer and a carboxylated carbon nanotube layer encapsulated on the outer layer of the halide solid electrolyte layer.

10. The application of an air-stable halide solid electrolyte as described in claim 9 in an all-solid-state lithium metal battery.

Images