A sulfide solid-state electrolyte and a preparation method and application thereof

Abstract

This invention discloses a sulfide solid electrolyte, its preparation method, and its applications, belonging to the field of solid electrolyte technology. The general chemical formula of this sulfide solid electrolyte is Li. 7‑a‑2b PS 6‑a‑ b X a Where X is one or more of Cl, Br, and I, 1≤a≤2, 0<b≤1; its room temperature ionic conductivity is greater than 10. ‑2 S / cm. The preparation method of this sulfide solid electrolyte includes: weighing Li₂S, LiX, and P₂S₅ in a molar ratio, manually grinding and mixing, ball milling, sintering under inert gas protection or vacuum, and naturally cooling to obtain the electrolyte. This invention reduces the content of Li and S proportionally and increases the content of Li. + Empty space, weaken S 2‑ For Li + The binding effect significantly improves ionic conductivity while reducing raw material costs; the preparation process is simple, highly controllable, and suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolyte technology, specifically relating to a sulfide solid electrolyte, its preparation method, and its application. Background Technology

[0002] Solid-state batteries have become an important development direction for the next generation of energy storage batteries due to their advantages such as high safety, high energy density, and wide operating temperature range. As the core component of solid-state batteries, the ionic conductivity of solid electrolytes directly determines key indicators such as rate performance and cycle performance of solid-state batteries.

[0003] Sulfide solid electrolytes have become a research hotspot in solid electrolytes due to their high ionic conductivity and good interfacial compatibility. However, traditional sulfide solid electrolytes suffer from high synthesis costs and limited potential for improving ionic conductivity. Furthermore, the preparation processes for some high-conductivity sulfide electrolytes are complex, making large-scale production difficult. Additionally, the sulfur content in traditional sulfide electrolytes... 2- For Li + The binding effect is relatively strong, Li + Limited migration rates result in ionic conductivity that fails to meet the practical application requirements of solid-state batteries. Therefore, developing a sulfide solid-state electrolyte that combines high ionic conductivity, low cost, and simple fabrication process is of great significance. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a sulfide solid electrolyte, its preparation method and application. This electrolyte has high room temperature ionic conductivity and low synthesis cost, and can effectively improve the rate performance of solid batteries.

[0005] The specific technical solution of the present invention is as follows: In a first aspect, the present invention provides a sulfide solid electrolyte, wherein the chemical formula of the sulfide solid electrolyte is Li. 7-a-2b PS 6-a-b X a , where X is one or more of Cl, Br, and I, the value of a is 1≤a≤2, and the value of b is 0<b≤1.

[0006] Furthermore, the room temperature ionic conductivity of the sulfide solid electrolyte is greater than 10. -2 S / cm.

[0007] Furthermore, the range of values ​​for a is 1 ≤ a ≤ 1.5.

[0008] Furthermore, the range of values ​​for b is 0.05 ≤ b ≤ 0.2.

[0009] This invention introduces a parameter b (0 < b ≤ 1) into the chemical formula to simultaneously reduce the content of Li and S, thereby introducing an appropriate amount of Li into the sulfide solid electrolyte. + Vacancy, weaken S² - For Li + The binding effect of Li2S significantly improves ionic conductivity; at the same time, the amount of Li2S used is reduced, thus lowering the cost of raw materials.

[0010] Secondly, the present invention provides a method for preparing the above-mentioned sulfide solid electrolyte, comprising the following steps: S1: Weigh the raw materials Li2S, LiX and P2S5 according to the molar ratio, grind and mix them to obtain a preliminary mixture; wherein, LiX is one or more of LiCl, LiBr and LiI; S2: The initial mixture is ball-milled to obtain milled material; S3: The ball milling material is sintered under inert gas protection or vacuum conditions, and then naturally cooled to obtain the sulfide solid electrolyte.

[0011] The sulfide solid electrolyte prepared using the above technical solution has ultra-high ionic conductivity, and the synthesis method is simple, the cost is reduced, and it has the potential for large-scale production.

[0012] Furthermore, in step S1, the grinding and mixing method is low-speed dispersion mixing, which is selected from manual grinding, low-speed stirring or low-speed ball milling, and the grinding and mixing time is 5 to 15 minutes.

[0013] Furthermore, in step S1, the grinding and mixing method is manual grinding in an agate mortar.

[0014] Furthermore, in step S2, the ball milling is carried out in a ball milling jar protected by inert gas, the ball milling speed is 300-600 rpm, the ball milling time is 6-24 hours, and the ball-to-material ratio is (10-20):1.

[0015] Furthermore, in step S3, the sintering temperature is 450–600°C, the sintering heating rate is 1.5–10°C / min, and the sintering time is 8–14 hours.

[0016] Furthermore, in step S3, sintering is carried out under vacuum or inert gas atmosphere protection.

[0017] Thirdly, the present invention provides an all-solid-state battery, wherein the all-solid-state battery comprises a sulfide solid electrolyte as described in any one of the preceding claims or a sulfide solid electrolyte prepared by any one of the preceding claims.

[0018] Compared with the prior art, the beneficial technical effects of this invention are reflected in: 1. The sulfide solid electrolyte provided by this invention, by controlling the b parameter (0 < b ≤ 1) in the general chemical formula, simultaneously reduces the content of Li and S, and introduces an appropriate amount of Li. + Empty space, weaken S 2- For Li + The binding effect of the ion-binding structure significantly improves the ionic conductivity, achieving a room temperature ionic conductivity of up to 10. -2 S / cm or higher.

[0019] 2. This invention reduces the amount of Li2S used, thereby lowering the cost of raw materials and achieving both high performance and low cost.

[0020] 3. The preparation method of the present invention is simple and highly controllable, requiring only three steps: grinding and mixing, ball milling, and sintering, making it suitable for large-scale production.

[0021] 4. The all-solid-state battery containing the sulfide solid electrolyte of the present invention has high ionic conductivity, which can effectively improve the rate performance of the battery. Attached Figure Description

[0022] Figure 1 The AC impedance spectra of the materials obtained in Examples 1-4; Figure 2 The AC impedance spectra of the materials obtained in Comparative Examples 1 and 2 are shown. Detailed Implementation

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0024] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0025] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0026] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0027] Example 1 A sulfide solid electrolyte with high ionic conductivity, having the chemical formula Li5.1PS4.3Cl1.5.

[0028] The method for synthesizing the above electrolyte includes the following steps: S1: Weigh the raw materials Li2S, LiCl and P2S5 according to the molar ratio of the general chemical formula Li5.1PS4.3Cl1.5, place the raw materials in an agate mortar and grind them manually for 10 min to obtain the initial mixture. S2: The initial mixture is transferred to a ball mill jar protected by inert gas and ball milled at 400 rpm for 12 hours with a ball-to-material ratio of 15:1 to obtain the ball milled material; S3: The ball milling material is placed in a sintering furnace and heated to 500°C at a heating rate of 5°C / min under argon protection. It is sintered for 10 hours and then naturally cooled to room temperature to obtain the sulfide solid electrolyte Li5.1PS4.3Cl1.5.

[0029] Example 2 A high ionic conductivity sulfide solid electrolyte with the general chemical formula Li 5.2 PS 4.35 Cl 1.5 The electrolyte has a room temperature ionic conductivity of 1.5 × 10⁻⁶. -2 S / cm.

[0030] The method for synthesizing the above electrolyte includes the following steps: S1: According to the general chemical formula Li5.2PS4. 35 Weigh the raw materials Li2S, LiCl and P2S5 in the molar ratio of Cl1.5, place the raw materials in an agate mortar and grind them manually for 10 min to obtain the initial mixture. S2: The initial mixture is transferred to a ball mill jar protected by inert gas and ball milled at 400 rpm for 12 hours with a ball-to-material ratio of 15:1 to obtain the ball milled material; S3: The ball milling material is placed in a sintering furnace and heated to 500°C at a heating rate of 5°C / min under argon protection. It is then sintered for 10 hours and naturally cooled to room temperature to obtain the sulfide solid electrolyte Li5.2PS4. 35 Cl1.5.

[0031] Example 3 A sulfide solid electrolyte with high ionic conductivity, having the general chemical formula Li5.3PS4.4Cl1.5.

[0032] The method for synthesizing the above electrolyte includes the following steps: S1: Weigh the raw materials Li2S, LiCl and P2S5 according to the molar ratio of the general chemical formula Li5.3PS4.4Cl1.5, place the raw materials in an agate mortar and grind them manually for 10 min to obtain the initial mixture. S2: The initial mixture is transferred to a ball mill jar protected by inert gas and ball milled at 400 rpm for 12 hours with a ball-to-material ratio of 15:1 to obtain the ball milled material; S3: The ball milling material is placed in a sintering furnace and heated to 500°C at a heating rate of 5°C / min under argon protection. It is then sintered for 10 hours and naturally cooled to room temperature to obtain the sulfide solid electrolyte Li5.3PS4.4Cl1.5.

[0033] Example 4 A sulfide solid electrolyte with high ionic conductivity, having the general chemical formula Li4.9PS4.2Cl1.5.

[0034] The method for synthesizing the above electrolyte includes the following steps: S1: Weigh the raw materials Li2S, LiCl and P2S5 according to the molar ratio of the general chemical formula Li4.9PS4.2Cl1.5, place the raw materials in an agate mortar and grind them manually for 10 min to obtain the initial mixture. S2: The initial mixture is transferred to a ball mill jar protected by inert gas and ball milled at 400 rpm for 12 hours with a ball-to-material ratio of 15:1 to obtain the ball milled material; S3: The ball milling material is placed in a sintering furnace and heated to 500°C at a heating rate of 5°C / min under argon protection. It is sintered for 10 hours and then naturally cooled to room temperature to obtain the sulfide solid electrolyte Li4.9PS4.2Cl1.5.

[0035] Comparative Example 1 A sulfide solid electrolyte with the general chemical formula Li5.5PS4.5Cl1.5.

[0036] The method for synthesizing the above electrolyte includes the following steps: S1: Weigh the raw materials Li2S, LiCl and P2S5 according to the molar ratio of the chemical formula Li5.5PS4.5Cl1.5, place the raw materials in an agate mortar and grind them manually for 10 min to obtain the initial mixture. S2: The initial mixture is transferred to a ball mill jar protected by inert gas and ball milled at 400 rpm for 12 hours with a ball-to-material ratio of 15:1 to obtain the ball milled material; S3: The ball milling material is placed in a sintering furnace and heated to 500°C at a heating rate of 5°C / min under argon protection. It is sintered for 10 hours and then naturally cooled to room temperature to obtain the sulfide solid electrolyte Li5.5PS4.5Cl1.5.

[0037] Comparative Example 2 A sulfide solid electrolyte with the general chemical formula Li3.3PS3.4Cl1.5.

[0038] The method for synthesizing the above electrolyte includes the following steps: S1: Weigh the raw materials Li2S, LiCl and P2S5 according to the molar ratio of the chemical formula Li3.3PS3.4Cl1.5, place the raw materials in an agate mortar and grind them manually for 10 min to obtain the initial mixture. S2: The initial mixture is transferred to a ball mill jar protected by inert gas and ball milled at 400 rpm for 12 hours with a ball-to-material ratio of 15:1 to obtain the ball milled material; S3: The ball milling material is placed in a sintering furnace and heated to 500°C at a heating rate of 5°C / min under argon protection. It is sintered for 10 hours and then naturally cooled to room temperature to obtain the sulfide solid electrolyte Li3.3PS3.4Cl1.5.

[0039] Performance testing The sulfide solid electrolytes prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to room temperature ionic conductivity tests, and the results are shown in Table 1. The test method was as follows: a) Assemble the sleeve and the lower mold core; b) Weigh 150mg of sulfide solid electrolyte and place it in the mold battery sleeve, then use vibration to distribute it evenly. c) Press the upper mold core into the sleeve, place the assembled mold battery in the fixture, and slowly apply 2T pressure to it using a pressurizing device and hold it. d) Let stand at 25°C for no less than 1 hour.

[0040] e) Enter the electrochemical workstation AC impedance spectrum test mode, set the parameters to amplitude 30mV and frequency to 1Hz~10MHz, start testing the EIS impedance spectrum from high frequency, and record the test temperature and impedance; f) Calculate the room temperature ionic conductivity of the sample according to the formula: σ =

[0041] In the formula, σ — Ionic conductivity of the sample being tested, in Siemens units per centimeter (S / cm); l —The thickness of the sample being measured is in centimeters (cm); S —Cross-sectional area of ​​the sample being tested, in square centimeters (cm²) 2 ); R —The impedance value of the sample being measured, in ohms (Ω).

[0042] Impedance test results are as follows Figures 1-2 As shown in Table 1, the ionic conductivity calculated from this is shown in Table 1.

[0043] Table 1

[0044] As shown in Table 1, the room temperature ionic conductivity of the sulfide solid electrolytes prepared in Examples 1-4 is all greater than 10 mS / cm (i.e., 10 mS / cm). - The ionic conductivity of Example 3 was the highest, reaching 17.0 mS / cm. Comparative Example 1 (stoichiometric ratio Li5.5PS4.5Cl1.5, i.e., b=0) had an ionic conductivity of only 8.7 mS / cm, while Comparative Example 2 (excessively reduced Li / S, b=1.1) showed a further decrease to 2.4 mS / cm. This indicates that controlling the chemical composition within the Li2S / cm range... 7-a-2b PS 6-a-b X a Furthermore, within the range of 0 < b ≤ 1, it can significantly improve the ionic conductivity of sulfide solid electrolytes.

[0045] like Figure 1 and Figure 2 As shown in the AC impedance spectra, the sulfide solid electrolytes prepared in Examples 1-4 have lower impedance, resulting in higher calculated ionic conductivity. In contrast, Comparative Examples 1-2 have higher impedance, leading to lower calculated ionic conductivity.

[0046] In summary, this application introduces an appropriate amount of Li into the sulfide solid electrolyte by simultaneously reducing the content of Li and S (i.e., controlling the value of b within the range of 0 < b ≤ 1) while ensuring that a satisfies 1 ≤ a ≤ 2. + Vacancy, weaken S² - For Li + The binding effect of Li2S significantly improves the ionic conductivity; while Comparative Example 1 (b=0) did not introduce vacancies, and Comparative Example 2 (b>1, i.e., excessive reduction of Li and S) had too many vacancies, leading to structural distortion, and neither could achieve the ideal ionic conductivity. The technical solution of this application effectively solves the problem of low ionic conductivity in traditional sulfide solid electrolytes, and at the same time, it reduces raw material costs by reducing the amount of Li2S used.

[0047] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

[0048] It should be particularly noted that the various embodiments listed in this specification and accompanying drawings are intended to illustrate the technical solutions and advantages of the present invention, and not to limit the scope of protection of the present invention. Without departing from the core ideas and technical effects of the present invention, those skilled in the art can make any form of improvement, substitution, combination, or modification to the structural arrangement, process parameters, material selection, control logic, etc., of the described embodiments; any obvious changes based on the same concept should be considered equivalent solutions of the present invention and should be included within the scope of protection defined by the claims of the present invention. The actual scope of protection of the present invention is determined by the appended claims and should be correctly understood in conjunction with the specification and accompanying drawings.

Claims

1. A sulfide solid electrolyte, characterized in that, The chemical formula of the sulfide solid electrolyte is Li 7-a- 2b PS 6-a-b X a , where X is one or more of Cl, Br, and I, the value of a is 1≤a≤2, and the value of b is 0<b≤1.

2. The sulfide solid electrolyte according to claim 1, characterized in that, The room temperature ionic conductivity of the sulfide solid electrolyte is greater than 10. -2 S / cm.

3. The sulfide solid electrolyte according to claim 1, characterized in that, The range of values ​​for a is 1 ≤ a ≤ 1.

5.

4. The sulfide solid electrolyte according to claim 1, characterized in that, The value of b is in the range of 0.05 ≤ b ≤ 0.

2.

5. A method for preparing a sulfide solid electrolyte as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Weigh the raw materials Li2S, LiX and P2S5 according to the molar ratio, grind and mix them to obtain a preliminary mixture; wherein, LiX is one or more of LiCl, LiBr and LiI; S2: The initial mixture is ball-milled to obtain milled material; S3: The ball milling material is sintered under inert gas protection or vacuum conditions, and then naturally cooled to obtain the sulfide solid electrolyte.

6. The preparation method according to claim 5, characterized in that, In step S1, the grinding and mixing method is low-speed dispersion mixing, which is selected from manual grinding, low-speed stirring or low-speed ball milling, and the grinding and mixing time is 5 to 15 minutes.

7. The preparation method according to claim 5, characterized in that, In step S2, ball milling is carried out in a ball milling jar protected by inert gas, the ball milling speed is 300-600 rpm, the ball milling time is 6-24 hours, and the ball-to-material ratio is (10-20):

1.

8. The preparation method according to claim 5, characterized in that, In step S3, the sintering temperature is 450–600°C, the sintering heating rate is 1.5–10°C / min, and the sintering time is 8–14 hours.

9. The preparation method according to claim 5, characterized in that, In step S3, sintering is carried out under vacuum or inert gas atmosphere protection.

10. An all-solid-state battery, characterized in that, The all-solid-state battery comprises a sulfide solid electrolyte as described in any one of claims 1 to 4 or a sulfide solid electrolyte prepared by any one of claims 5 to 9.

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