A method for improving stability of halide electrolytes

Abstract

The application discloses a method for improving stability of halide electrolyte, which comprises the following steps: exposing the halide electrolyte to wet air, and then performing sintering treatment under an oxygen-free condition to obtain stable halide electrolyte. By exposing the halide electrolyte to wet air and then performing sintering treatment, water and oxygen in the wet air are used to react with the halide material to form an oxygen-rich shell layer on the surface of the electrolyte, so that the electrolyte material is prevented from being oxidized and decomposed by the positive electrode material when being in contact with the positive electrode, the positive electrode interface stability of the halide electrolyte material and the compatibility between the halide electrolyte material and the sulfide electrolyte are significantly improved, the interface resistance is reduced, and the electrochemical stability of the full solid-state battery is improved.

Description

Technical Field

[0001] This invention belongs to the field of electrolyte materials technology, and particularly relates to a method for improving the stability of halide electrolytes. Background Technology

[0002] Solid-state electrolyte materials play a crucial role in solid-state batteries, especially halide electrolytes, which have become key materials in solid-state battery development due to their excellent ionic conductivity. However, halide electrolytes face the problem of insufficient stability during solid-state battery fabrication.

[0003] Current solutions mainly include the following: First, introducing functional groups (such as carboxylic acid groups, sulfide groups, etc.) onto the surface of halide electrolyte materials to enhance the interfacial compatibility of the materials; second, element doping (i.e., introducing other elements) to improve the stability of halide solid electrolytes; and third, improving the surface structure through low-temperature annealing, chemical treatment, etc., to enhance the stability of halide electrolyte materials. However, whether it is element doping, surface modification, or optimized treatment methods, all of these will increase the complexity of the halide electrolyte preparation process and cannot effectively improve the stability of halide electrolytes.

[0004] Given the above shortcomings, there is an urgent need to propose a novel method to improve the stability of halide electrolytes. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the purpose of this invention is to provide a method for improving the stability of halide electrolytes, thereby solving the technical problem that existing methods cannot effectively improve the stability of halide electrolytes.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The present invention provides a method for improving the stability of halide electrolytes, comprising the following steps: exposing the halide electrolyte to humid air, and then sintering it under anaerobic conditions to obtain a stable halide electrolyte; wherein the humidity of the humid air is 10%-35%.

[0008] Furthermore, the halide electrolyte includes at least one of LiTaOCl4 and LiNbOCl4.

[0009] Furthermore, the humidity of humid air is 20%-25%.

[0010] Furthermore, the temperature of humid air is 15-30℃.

[0011] Furthermore, the temperature of humid air is 20-25℃.

[0012] Furthermore, the halide electrolyte is exposed to humid air for 10-180 minutes.

[0013] Furthermore, the halide electrolyte is exposed to humid air for 30-120 minutes.

[0014] Furthermore, the sintering conditions include: a sintering temperature of 90-110℃ and a sintering time of 1-3h.

[0015] Furthermore, the sintering conditions include: a sintering temperature of 100℃ and a sintering time of 2 hours.

[0016] The beneficial effects of this invention are:

[0017] This invention involves sintering a halide electrolyte after exposing it to humid air. The moisture and oxygen in the humid air react with the halide material to form an oxygen-rich shell on the surface of the electrolyte particles. This prevents the electrolyte material from being oxidized and decomposed by the positive electrode material when in contact with the positive electrode. This significantly enhances the positive electrode interface stability of the halide electrolyte material and its compatibility with sulfide electrolytes, reduces the interface resistance, and thus improves the electrochemical stability of the all-solid-state battery. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below.

[0019] Figure 1 The impedance of the halide electrolyte prepared in Example 1 of this invention before and after cycling in an all-solid-state battery.

[0020] Figure 2 The impedance of the halide electrolyte prepared in Example 2 of this invention before and after cycling in an all-solid-state battery.

[0021] Figure 3 The impedance of the halide electrolyte prepared in Example 3 of this invention before and after cycling in an all-solid-state battery.

[0022] Figure 4 The impedance of the halide electrolyte prepared in Example 4 of this invention before and after cycling in an all-solid-state battery.

[0023] Figure 5 The impedance of the halide electrolyte prepared in Example 5 of this invention before and after cycling in an all-solid-state battery.

[0024] Figure 6 The impedance of the halide electrolyte prepared in Comparative Example 1 of this invention before and after cycling in an all-solid-state battery is shown.

[0025] Figure 7The impedance of the halide electrolyte prepared in Comparative Example 2 of this invention before and after cycling in an all-solid-state battery is shown. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] The method for improving the stability of halide electrolytes provided in this invention includes the following steps: exposing the halide electrolyte to humid air with a humidity of 10%-35% and a temperature of 15-30℃ for 10-180 min, and then sintering it at 90-110℃ for 1-3 h under anaerobic conditions to obtain a stable halide electrolyte.

[0028] Specifically, the humidity of the humid air can be 10%, 15%, 20%, 25%, 30%, 35%, or any value within the above range; the temperature of the humid air can be 15℃, 20℃, 25℃, 30℃, or any value within the above range; the exposure time in the humid air can be 10min, 40min, 60min, 80min, 100min, 120min, 140min, 160min, 180min, or any value within the above range; the sintering temperature can be 90℃, 100℃, 110℃, or any value within the above range; and the sintering time can be 1h, 2h, 3h, or any value within the above range.

[0029] Preferably, the humidity of the humid air is 20%-25%, and the temperature of the humid air is 20-25℃. The halide electrolyte is exposed to the humid air for 30-120 minutes. The sintering temperature is 100℃, and the sintering time is 2 hours.

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below.

[0031] Example 1

[0032] LiNbOCl4 electrolyte powder was placed in humid air with a humidity of 20% and a temperature of 25°C and exposed to this environment for 120 min. Then, it was sintered at 100°C for 2 h under argon atmosphere to obtain a halide electrolyte material with an oxygen shell.

[0033] Example 2

[0034] The LiNbOCl4 electrolyte powder was placed in humid air with a humidity of 20% and a temperature of 25°C and exposed to this environment for 30 minutes. Then, it was sintered at 100°C for 2 hours under argon atmosphere to obtain a halide electrolyte material with an oxygen shell.

[0035] Example 3

[0036] LiNbOCl4 electrolyte powder was placed in humid air with a humidity of 20% and a temperature of 25°C and exposed to this environment for 180 min. Then, it was sintered at 100°C for 2 h under argon atmosphere to obtain a halide electrolyte material with an oxygen shell.

[0037] Example 4

[0038] LiNbOCl4 electrolyte powder was placed in humid air with a humidity of 25% and a temperature of 25°C and exposed to this environment for 120 min. Then, it was sintered at 100°C for 2 h under argon atmosphere to obtain a halide electrolyte material with an oxygen shell.

[0039] Example 5

[0040] The LiTaOCl4 electrolyte powder was placed in humid air with a humidity of 20% and a temperature of 25°C and exposed to this environment for 120 min. Then, it was sintered at 100°C for 2 h under argon conditions to obtain a halide electrolyte material with an oxygen shell.

[0041] Comparative Example 1

[0042] A LiNbOCl4 electrolyte material, without any treatment.

[0043] Comparative Example 2

[0044] A LiTaOCl4 electrolyte material, without any treatment.

[0045] The processing conditions for the above embodiments and comparative examples are shown in Table 1.

[0046] Table 1

[0047]

[0048] As shown in Table 1, a comparison of Examples 1-5 and Comparative Examples 1 and 2 reveals that the exposure time and humidity in humid air significantly affect ionic conductivity. An oxygen-rich shell forms on the material surface, and the thickness of this shell is highly correlated with ion transport capacity and oxidation stability. As the exposure time increases from 30 min to 180 min, and the humidity increases from 20% to 25%, the ion transport capacity decreases, primarily due to the influence of the oxygen-rich shell. For example, in Example 2 (30 min, 20% humidity), the shell thickness is 8 nm, and the ionic conductivity is 8.7 mS / cm. -1 This is higher than that of Example 1 (120 min, 20% humidity, ionic conductivity 4.2 mS cm⁻¹). -1 With prolonged exposure time (e.g., Example 3, 180 min, 20% humidity), the ionic conductivity decreased significantly (3.5 mS / cm). -1 The shell thickness increased significantly (100 nm). Of course, increasing humidity also significantly increased the shell thickness (95 nm) and decreased the ionic conductivity (e.g., in Example 4, 120 min, 25% humidity, ionic conductivity was 3.9 mS / cm). -1 Compared with the two comparative examples, although the comparative examples have higher ionic conductivity, they do not form an oxygen-rich shell, and the electrochemical stability of the prepared all-solid-state batteries is poor. However, the halide electrolyte of this application, which is treated with humid air exposure and sintering, can improve the electrochemical stability of the solid-state batteries prepared by it while ensuring that the room temperature ionic conductivity meets the requirements of solid-state batteries.

[0049] Performance testing

[0050] 1. Assemble solid-state batteries

[0051] The positive electrode active material (LiNi) was weighed out according to a mass ratio of 60:35:5. 0.9 Co 0.05 Mn 0.05 O2), halide solid electrolyte materials and conductive additives (VGCF) prepared in the examples and comparative examples were placed in a planetary high-energy ball mill and ball-milled at a low speed of 100-250 rpm for 2 hours to obtain a positive electrode mixture.

[0052] The battery is assembled using a double electrolyte layer method, as shown in the following battery configuration: LiIn|Li 5.5 PS 4.5 Cl 1.5 |Halide electrolyte|Positive electrode material. A certain amount of Li was weighed in a glove box. 5.5 PS 4.5 Cl 1.5Electrolyte powder is cold-pressed in a mold at a pressure controlled at 50 MPa to form the first electrolyte layer. Then, a certain amount of halide electrolyte powder is weighed onto the surface of the first electrolyte layer and cold-pressed in the mold at a pressure controlled at 50 MPa to form the second electrolyte layer. At this point, a double electrolyte layer (Li) is formed. 5.5 PS 4.5 Cl 1.5 Electrolyte layer (halide electrolyte layer). The positive electrode mixture is weighed and added to the surface of the cold-pressed second electrolyte layer, which is then cold-pressed in a mold at a pressure controlled at 300 MPa. Subsequently, a Li-In alloy sheet is attached to the other side of the first electrolyte layer and cold-pressed at 100 MPa.

[0053] 2. Battery EIS testing

[0054] The all-solid-state batteries assembled in the glove box were subjected to AC impedance spectroscopy using an impedance analyzer (Admiral electrochemical workstation, USA), with a test frequency range of 0.1 Hz–2 MHz. The test results are shown in Table 3 and… Figures 1-7 As shown.

[0055] 3. Discharge capacity test

[0056] The charge and discharge tests were conducted in the range of 2.4-3.7V, with a charge and discharge current density of 2C.

[0057] Table 2

[0058]

[0059] Comparative analysis of the battery performance data from the examples and comparative examples reveals that Examples 1 and 5 exhibit the best overall performance. This is primarily due to the oxygen-rich layer obtained through post-exposure heating, which ensures the interfacial stability of the cathode / electrolyte interface. Specifically, although the initial discharge capacities of Comparative Examples 1 and 2 are 208 mAh / g and 206 mAh / g, respectively, slightly higher than those of Examples 1 (196 mAh / g) and 5 (197 mAh / g), their capacity retention rates are only 90.9% and 90.8%, indicating poor cycle stability. In contrast, Example 1 has a capacity retention rate of 92.9%, and Example 5 has a capacity retention rate of 92.4%, exhibiting the highest capacity retention rates among all data points. This is attributed to the appropriately thick oxygen-rich shell, indicating high stability and reliability during long-term use. Therefore, Examples 1 and 5 demonstrate the best battery performance and possess significant research value and application potential.

[0060] Table 3

[0061]

[0062] As shown in Table 3, the solid-state batteries prepared with halide electrolytes after humid air exposure and sintering treatment in the embodiments of the present invention exhibited a significant decrease in the rate of change of the positive electrode interface impedance after 200 cycles. Among them, the solid-state batteries prepared with halide electrolytes from Examples 1 and 5 showed the smallest rate of change in the positive electrode interface impedance. This is because the oxygen-rich layer formed in Examples 1 and 5 was of moderate thickness, while the oxygen-rich layer in Example 2 was too thin, and the oxygen-rich layers in Examples 3 and 4 were too thick, all of which affected the rate of change of the positive electrode impedance. The positive electrode showed the largest rate of change in Comparative Examples 1 and 2, mainly because the LNOC and LTOC materials in the comparative examples did not form an oxygen-rich layer with the positive electrode to suppress the interfacial reaction.

[0063] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0064] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. 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 all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for improving the stability of halide electrolytes, characterized in that, Includes the following steps: A stable halide electrolyte is obtained by exposing the halide electrolyte to humid air and then sintering it under anaerobic conditions; wherein the humidity of the humid air is 10%-35%. The halide electrolyte includes at least one of LiTaOCl4 and LiNbOCl4; The time for exposing the halide electrolyte to humid air is 10-180 min; The sintering temperature for the sintering treatment is 90-110℃; The sintering time for the sintering treatment is 1-3 hours.

2. The method for improving the stability of halide electrolytes according to claim 1, characterized in that, The humidity of the humid air is 20%-25%.

3. The method for improving the stability of halide electrolytes according to claim 1, characterized in that, The temperature of the humid air is 15-30℃.

4. The method for improving the stability of halide electrolytes according to claim 3, characterized in that, The temperature of the humid air is 20-25℃.

5. The method for improving the stability of halide electrolytes according to claim 1, characterized in that, The time for which the halide electrolyte is exposed to humid air is 30-120 minutes.

6. The method for improving the stability of halide electrolytes according to claim 1, characterized in that, The conditions for the sintering process include: a sintering temperature of 100°C and a sintering time of 2 hours.

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