Solid electrolyte materials, preparation methods thereof, and all-solid-state secondary batteries

Abstract

The present invention relates to the field of battery technologies, and in particular, to a solid electrolyte material, a preparation method thereof, and a all-solid-state secondary battery. The solid electrolyte material of the present invention has the following chemical formula: Li 5.4+x+3y P 1‑x‑y Sn x Ce y S 4.4 M 1.6‑2y O 2y , where M includes at least one of Cl, I, Br, and F; 0 < x + y < 1, 0 < y < 0.8, and x > 0. Under the condition of maintaining a high conductivity, the air stability and the stability towards the positive electrode of the solid electrolyte material of the present invention are both greatly improved, greatly enhancing the material chemistry and electrochemical stability thereof in the all-solid-state secondary battery, and can greatly improve the capacity utilization of the positive electrode active material and the energy density and performance of the entire battery.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular, to a solid electrolyte material, a preparation method thereof, and a all-solid-state secondary battery. Background Art

[0002] Among inorganic electrolyte materials, oxide electrolytes have a high oxidation potential and are stable to high-voltage ternary cathode materials. However, it is difficult for them to achieve high ionic conductivity, and they are rigid and have poor ductility, resulting in a large contact impedance with the cathode material. In contrast, sulfide electrolytes are a newly concerned type of solid electrolyte material, which usually have high ionic conductivity, good ductility, and can form a relatively dense physical contact with the positive and negative electrode materials. Taking the LiPSC system as an example, its ionic conductivity at room temperature (25±3°C) can reach 12 mS / cm, and its ionic conductivity can be greatly improved with the increase of temperature, comparable to that of conventional liquid electrolytes. The all-solid-state battery made from it has high initial efficiency, cycling and rate performance. However, it still has the following problems: (1) Poor stability to the cathode. When in direct contact with the cathode material, serious side reactions will occur during cycling, seriously affecting its performance. (2) Poor air stability. It is easy to react with air to form heterophases when exposed to air, and the ionic conductivity decreases significantly. At the same time, the generated heterophases will have serious side reactions with the positive and negative electrodes during the long cycling of the battery, affecting the performance of the long cycling of the battery. Moreover, the low air stability requires high requirements for the preparation environment and conditions of the electrolyte, and it needs to be carried out under an inert atmosphere or extremely low environmental humidity control, which is not conducive to the large-scale preparation of the electrolyte itself, as well as the large-scale preparation of the subsequent electrolyte membrane and the large-scale preparation of the battery, etc.

[0003] In view of this, the present invention is specifically proposed. Summary of the Invention

[0004] An object of the present invention is to provide a solid electrolyte material to solve the technical problems such as harsh environmental conditions, time-consuming, energy-consuming, and high cost faced during the large-scale preparation of solid electrolyte materials in all-solid-state secondary batteries. By doping with Sn element, Ce element and O element, the electrolyte can achieve high air stability while ensuring a high level of ionic conductivity, improve the stability of the target electrolyte to the cathode, and enhance the capacity of the cathode active material and the energy density of the entire battery.

[0005] Another object of the present invention is to provide a preparation method of the above-mentioned solid electrolyte material, which is simple and feasible and can obtain an electrolyte material with both high conductivity and high air stability.

[0006] Another object of the present invention is to provide an all-solid-state secondary battery with excellent electrochemical performance.

[0007] To achieve the above object of the present invention, the following technical solutions are specifically adopted:

[0008] A solid electrolyte material, the solid electrolyte material comprising the following chemical formula: Li 5.4+x+3y P 1-x- y Sn x Ce y S 4.4 M 1.6-2y O 2y , wherein M includes at least one of Cl, I, Br, and F; 0 < x + y < 1, 0 < y < 0.8, x > 0.

[0009] In one embodiment, M is selected from Cl, I, Br, or F, 0.1 ≤ x ≤ 0.3, 0.1 ≤ y ≤ 0.3.

[0010] In one embodiment, x is 0.1, and y is 0.1, 0.15, 0.2, 0.25, or 0.3.

[0011] In one embodiment, x is 0.15, and y is 0.1, 0.15, or 0.2.

[0012] In one embodiment, x is 0.2, and y is 0.1, 0.15, or 0.2.

[0013] In one embodiment, x is 0.25, and y is 0.1 or 0.15.

[0014] In one embodiment, x is 0.3, and y is 0.1.

[0015] In one embodiment, the solid electrolyte material is a glass-ceramic phase and / or a crystalline phase.

[0016] A method for preparing the solid electrolyte material, comprising the following steps:

[0017] Crushing a raw material mixture according to the chemical formula of the solid electrolyte material to obtain an electrolyte precursor; performing heat treatment on the electrolyte precursor.

[0018] In one embodiment, the raw material mixture includes Li2S, P2S5, LiM, SnS2, and CeO2, wherein M is selected from at least one of Cl, I, Br, and F.

[0019] In one embodiment, the crushing treatment includes ball milling.

[0020] The ball-to-material ratio of the ball milling is (10-30):1, the speed of the ball milling is 250-750 rpm, and the time of the ball milling is 10-40 h.

[0021] In one embodiment, the temperature of the heat treatment is 400-550 °C, and the heat preservation time of the heat treatment is 8-12 h.

[0022] In one embodiment, the heating rate of the heat treatment is 1-5 °C / min.

[0023] In one embodiment, the heat treatment is carried out in an inert atmosphere.

[0024] In one embodiment, the material obtained after the heat treatment is ground and sieved.

[0025] The all-solid-state secondary battery includes a positive electrode layer, an electrolyte layer, and a negative electrode layer;

[0026] At least one of the positive electrode layer, the electrolyte layer, and the negative electrode layer contains the solid electrolyte material described above.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) In the present invention, tin, cerium, and oxygen are doped into the sulfide electrolyte of the LiPSM (M includes at least one of Cl, I, Br, and F) system. The prepared target electrolyte has a significantly improved air stability and stability to the positive electrode while maintaining a high conductivity, greatly improving its material chemistry and electrochemical stability in the all-solid-state secondary battery, and significantly enhancing the capacity utilization of the positive electrode active material, as well as the energy density and performance of the entire battery.

[0029] (2) The preparation method of the solid electrolyte material is simple and easy to implement. By pulverizing the raw material mixture and then performing heat treatment, an electrolyte material with both high conductivity and high air stability is obtained.

[0030] (3) The present invention applies the solid electrolyte material to the all-solid-state secondary battery, making it have excellent electrochemical performance. Description of the Drawings

[0031] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1XRD patterns of the solid electrolyte materials of Example 1 and Comparative Example 1 of the present invention. Detailed implementation mode

[0033] The following will describe the implementation schemes of the present invention in detail in conjunction with the examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the examples, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0034] According to one aspect of the present invention, the present invention relates to a solid electrolyte material, and the solid electrolyte material includes the following chemical formula: Li 5.4+x+3y P 1-x-y Sn x Ce y S 4.4 M 1.6-2y O 2y , wherein, M includes at least one of Cl, I, Br and F; 0 < x + y < 1, 0 < y < 0.8, x > 0.

[0035] The present invention modifies the sulfide electrolyte of the LiPSM (M includes at least one of Cl, I, Br and F) system by simultaneously doping Sn, Ce and O, so that tin, cerium and oxygen elements are evenly distributed in the lattice of the electrolyte material. The modified electrolyte can maintain a high ionic conductivity level (≥8 mS / cm), high stability to the positive electrode and high air stability, and is expected to solve problems such as chemical and electrochemical instability of the solid electrolyte material in all-solid-state secondary batteries, and improve the capacity utilization of the positive electrode active material and the energy density and rate performance of the entire battery.

[0036] The principle that doping cerium in the electrolyte precursor can improve its stability to the positive electrode includes: the introduction of cerium elements can form a relatively stable interface layer between the electrolyte and the positive electrode material, effectively reducing the interface resistance between the electrolyte and the positive electrode material and reducing or avoiding the occurrence of side reactions. The principle that doping tin and oxygen in the precursor can improve the air stability and ionic conductivity of the electrolyte includes: the introduction of tin atoms and oxygen atoms can effectively improve the lattice stability, inhibit the reaction between the electrolyte and air to generate hydrogen sulfide gas, and at the same time, the P-O bond has a stronger binding force than the P-S bond, resulting in a relatively weak force of the P-O bond structural unit on lithium ions, which is beneficial to the rapid migration of lithium ions.

[0037] In one embodiment, the value of x + y includes but is not limited to 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9. The value of y includes but is not limited to 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9.

[0038] In one embodiment, M is selected from Cl, I, Br, or F, 0.1 ≤ x ≤ 0.3, and 0.1 ≤ y ≤ 0.3.

[0039] In one embodiment, x is 0.1 and y is 0.1, 0.15, 0.2, 0.25, or 0.3. In one embodiment, when M is Cl, x is 0.1 and y is 0.1, and the chemical formula of the solid electrolyte material is Li 5.8 P 0.8 Sn 0.1 Ce 0.1 S 4.4 Cl 1. 4O 0.2 ; when x is 0.1 and y is 0.15, the chemical formula of the solid electrolyte material is Li 5.95 P 0.75 Sn 0.1 Ce 0.15 S 4.4 Cl 1.3 O 0.3 ; when x is 0.1 and y is 0.2, the chemical formula of the solid electrolyte material is Li 6.1 P 0.7 Sn 0.1 Ce 0.2 S 4.4 Cl 1.2 O 0.4 ; when x is 0.1 and y is 0.25, the chemical formula of the solid electrolyte material is Li 6.25 P 0.65 Sn 0.1 Ce 0.25 S 4.4 Cl 1.1 O 0.5 . When x is 0.1 and y is 0.3, the chemical formula of the solid electrolyte material is Li 6.4 P 0.6 Sn 0.1 Ce 0.3 S 4.4 ClO 0.6 .

[0040] In one embodiment, x is 0.15 and y is 0.1, 0.15 or 0.2. In one embodiment, when M is Cl, x is 0.15 and y is 0.1, and the chemical formula of the solid electrolyte material is Li 5.85 P 0.75 Sn 0.15 Ce 0.1 S 4.4 Cl 1.4 O 0.2 ; when x is 0.15 and y is 0.15, the chemical formula of the solid electrolyte material is Li6P 0.7 Sn 0.15 Ce 0.15 S 4.4 Cl 1.3 O 0.3 . When x is 0.15 and y is 0.2, the chemical formula of the solid electrolyte material is Li 6.15 P 0.65 Sn 0.15 Ce 0.2 S 4. 4Cl 1.2 O 0.4 .

[0041] In one embodiment, x is 0.2 and y is 0.1, 0.15 or 0.2. In one embodiment, when M is Cl, x is 0.2 and y is 0.1, and the chemical formula of the solid electrolyte material is Li 6.3 P 0.6 Sn 0.15 Ce 0.25 S 4.4 Cl 1. 1O 0.5 ; when x is 0.2 and y is 0.15, the chemical formula of the solid electrolyte material is Li 5.9 P 0.7 Sn 0.2 Ce 0.1 S 4.4 Cl 1. 4O 0.2 . When x is 0.2 and y is 0.2, the chemical formula of the solid electrolyte material is Li 6.1 P 0.6 Sn 0.25 Ce 0.15 S 4.4 Cl 1. 3O 0.3 .

[0042] In one embodiment, x is 0.25 and y is 0.1 or 0.15. In one embodiment, when M is Cl, x is 0.25 and y is 0.1, and the chemical formula of the solid electrolyte material is Li 5.95 P 0.65 Sn 0.25 Ce 0.1 S 4.4 Cl 1. 4O 0.2 ; x is 0.25 and y is 0.12, and the chemical formula of the solid electrolyte material is Li 6.1 P 0.6 Sn 0.25 Ce 0.15 S 4.4 Cl 1.3 O 0.3 .

[0043] In one embodiment, x is 0.3 and y is 0.1. In one embodiment, when M is Cl, the chemical formula of the solid electrolyte material is Li6P 0.6 Sn 0.3 Ce 0.1 S 4.4 Cl 1.4 O 0.2 .

[0044] The chemical formulas listed above are some specific chemical formulas of the solid electrolyte material. In addition, it also includes Li 5.85 P 0.75 Sn 0.15 Ce 0.1 S 4.4 I 1.4 O 0.2 , Li 5.95 P 0.65 Sn 0.25 Ce 0.1 S 4.4 Br 1.4 O0.2, Li 5.95 P 0.75 Sn 0.1 Ce 0.1 5S 4.4 F 1.3 O 0.3 etc.

[0045] In one embodiment, the solid electrolyte material is a glass-ceramic phase and / or a crystalline phase;

[0046] In one embodiment, the particle size of the solid electrolyte material is ≤ 75 μm.

[0047] According to another aspect of the present invention, the present invention also relates to a method for preparing the solid electrolyte material, comprising the following steps:

[0048] Crush the raw material mixture according to the chemical formula of the solid electrolyte material to obtain an electrolyte precursor; perform heat treatment on the electrolyte precursor.

[0049] The method for preparing the solid electrolyte material of the present invention is simple and easy to implement. According to the chemical formula of the solid electrolyte material, the mixture of raw materials corresponding to each element is first crushed to obtain an electrolyte precursor, and then the electrolyte precursor is further subjected to high-temperature heat treatment.

[0050] In one embodiment, the raw material mixture includes Li2S, P2S5, LiM, SnS2 and CeO2, wherein M is selected from at least one of Cl, I, Br or F.

[0051] In one embodiment, the crushing treatment described below includes ball milling.

[0052] In one embodiment, the ball-to-material ratio of the ball milling is (10-30):1. In one embodiment, the ball-to-material ratio of the ball milling includes but is not limited to 12:1, 15:1, 17:1, 20:1, 22:1, 25:1, 27:1 or 30:1. By adopting a suitable ball-to-material ratio, the present invention can better grind the mixed raw materials to obtain an electrolyte precursor with a suitable particle size.

[0053] In one embodiment, the speed of the ball milling is 250-750 rpm. In one embodiment, the speed of the ball milling includes but is not limited to 250 rpm, 270 rpm, 300 rpm, 320 rpm, 350 rpm, 400 rpm, 450 rpm, 470 rpm, 500 rpm, 550 rpm, 570 rpm, 600 rpm, 620 rpm, 650 rpm, 670 rpm, 700 rpm, 720 rpm or 750 rpm. In one embodiment, the time of the ball milling is 10-40 h. In one embodiment, the time of the ball milling includes but is not limited to 12 h, 15 h, 17 h, 20 h, 22 h, 25 h, 27 h, 30 h, 32 h, 35 h, 37 h or 40 h. By adopting a suitable ball milling speed and ball milling time, the present invention can obtain an electrolyte precursor.

[0054] In one embodiment, the temperature of the heat treatment is 400 - 550 °C, and the heat preservation time of the heat treatment is 8 - 12 h. In one embodiment, the temperature of the heat treatment includes but is not limited to 420 °C, 450 °C, 470 °C, 500 °C, 520 °C or 550 °C. The heat preservation time of the heat treatment includes but is not limited to 8 h, 8.5 h, 9 h, 9.5 h, 10 h or 11 h.

[0055] In one embodiment, the heating rate of the heat treatment is 1 - 5 °C / min. In one embodiment, the heating rate of the heat treatment includes but is not limited to 1.5 °C / min, 2 °C / min, 2.5 °C / min, 3 °C / min, 2.5 °C / min or 4 °C / min.

[0056] In one embodiment, the heat treatment is carried out in an inert atmosphere. The inert atmosphere includes argon, etc.

[0057] In one embodiment, the material obtained after the heat treatment is ground and sieved. Through further grinding and sieving, an electrolyte material is obtained.

[0058] According to another aspect of the present invention, the present invention also relates to a all-solid-state secondary battery, comprising a positive electrode layer, an electrolyte layer and a negative electrode layer;

[0059] At least one layer of the positive electrode layer, the electrolyte layer and the negative electrode layer contains the solid electrolyte material described above.

[0060] The all-solid-state secondary battery of the present invention has excellent cycle performance.

[0061] The following is further explained and illustrated in conjunction with specific examples, comparative examples and drawings.

[0062] Example 1

[0063] A preparation method of a solid electrolyte material, comprising the following steps:

[0064] Weigh 2.2 mol of Li2S, 0.4 mol of P2S5, 1.4 mol of LiCl, 0.1 mol of SnS2 and 0.1 mol of CeO2 according to the molar ratio, place them in a ball milling tank, seal it and then carry out ball milling treatment. The ball-to-material ratio is 30:1, the ball milling speed is 660 rpm, and the ball milling time is 30 h. After ball milling, an electrolyte precursor is obtained; under an argon atmosphere, use a muffle furnace to carry out high-temperature heat treatment on the precursor. The temperature of the heat treatment is 500 °C, the temperature rise rate is 2 °C / min, and the heat preservation time is 10 h. After natural cooling, a crude electrolyte product is obtained, and the crude product is ground and sieved to obtain Li 5.8 P 0.8 Sn 0.1 Ce 0.1 S4.4 Cl 1.4 O 0.2 。

[0065] Example 2

[0066] A method for preparing a solid electrolyte material, except that the raw materials are 2.325 mol of Li2S, 0.375 mol of P2S5, 1.3 mol of LiCl, 0.1 mol of SnS2 and 0.15 mol of CeO2, and other conditions are the same as in Example 1, to obtain Li 5.95 P 0.75 Sn 0.1 Ce 0.15 S 4.4 Cl 1.3 O 0.3 。

[0067] Example 3

[0068] A method for preparing a solid electrolyte material, except that the raw materials are 2.45 mol of Li2S, 0.35 mol of P2S5, 1.2 mol of LiCl, 0.1 mol of SnS2 and 0.2 mol of CeO2, and other conditions are the same as in Example 1, to obtain Li 6.1 P 0.7 Sn 0.1 Ce 0.2 S 4.4 Cl 1. 2O 0.4 。

[0069] Example 4

[0070] A method for preparing a solid electrolyte material, except that the raw materials are 2.575 mol of Li2S, 0.325 mol of P2S5, 1.1 mol of LiCl, 0.1 mol of SnS2 and mol 0.25 CeO2, and other conditions are the same as in Example 1, to obtain Li 6.25 P 0.65 Sn 0.1 Ce 0.25 S 4.4 Cl 1.1 O 0.5 。

[0071] Example 5

[0072] A method for preparing a solid electrolyte material, except that the raw materials are 2.7 mol of Li2S, 0.3 mol of P2S5, 1 mol of LiCl, 0.1 mol of SnS2 and mol 0.3 CeO2, and other conditions are the same as in Example 1, to obtain Li 6.4 P 0.6 Sn 0.1 Ce0.3 S 4.4 ClO 0.6 。

[0073] Example 6

[0074] Preparation method of solid electrolyte material. Except that the raw materials are 2.225 mol of Li2S, 0.375 mol of P2S5, 1.4 mol of LiCl, 0.15 mol of SnS2 and 0.1 mol of CeO2, other conditions are the same as those in Example 1, and Li 5.85 P 0.75 Sn 0.15 Ce 0.1 S 4.4 Cl 1.4 O 0.2 。

[0075] Example 7

[0076] Preparation method of solid electrolyte material. Except that the raw materials are 2.35 mol of Li2S, 0.35 mol of P2S5, 1.3 mol of LiCl, 0.15 mol of SnS2 and 0.15 mol of CeO2, other conditions are the same as those in Example 1, and Li6P 0.7 Sn 0.15 Ce 0.15 S 4.4 Cl 1.3 O 0.3 。

[0077] Example 8

[0078] Preparation method of solid electrolyte material. Except that the raw materials are 2.475 mol of Li2S, 0.325 mol of P2S5, 1.2 mol of LiCl, 0.15 mol of SnS2 and mol 0.2 CeO2, other conditions are the same as those in Example 1, and Li 6.15 P 0.65 Sn 0.15 Ce 0.2 S 4.4 Cl 1.2 O 0.4 。

[0079] Example 9

[0080] Preparation method of solid electrolyte material. Except that the raw materials are 2.6 mol of Li2S, 0.3 mol of P2S5, 1.1 mol of LiCl, 0.15 mol of SnS2 and 0.25 mol of CeO2, other conditions are the same as those in Example 1, and Li 6.3 P 0.6 Sn 0.15 Ce 0.25 S4.4 Cl 1. 1O 0.5 。

[0081] Example 10

[0082] A method for preparing a solid electrolyte material, except that the raw materials are 2.25 mol of Li2S, 0.35 mol of P2S5, 1.4 mol of LiCl, 0.2 mol of SnS2 and 0.1 mol of CeO2, and other conditions are the same as in Example 1, to prepare Li 5.9 P 0.7 Sn 0.2 Ce 0.1 S 4.4 Cl 1. 4O 0.2 。

[0083] Example 11

[0084] A method for preparing a solid electrolyte material, except that the raw materials are 2.375 mol of Li2S, 0.325 mol of P2S5, 1.3 mol of LiCl, 0.2 mol of SnS2 and 0.15 mol of CeO2, and other conditions are the same as in Example 1, to prepare Li 6.05 P 0.65 Sn 0.2 Ce 0.15 S 4.4 Cl 1.3 O 0.3 。

[0085] Example 12

[0086] A method for preparing a solid electrolyte material, except that the raw materials are 2.5 mol of Li2S, 0.3 mol of P2S5, 1.2 mol of LiCl, 0.2 mol of SnS2 and 0.2 mol of CeO2, and other conditions are the same as in Example 1, to prepare Li 6.2 P 0.6 Sn 0.2 Ce 0.2 S 4.4 Cl 1.2 O 0.4 。

[0087] Example 13

[0088] A method for preparing a solid electrolyte material, except that the raw materials are 2.275 mol of Li2S, 0.325 mol of P2S5, 1.4 mol of LiCl, 0.25 mol of SnS2 and 0.1 mol of CeO2, and other conditions are the same as in Example 1, to prepare Li 5.95 P 0.65 Sn 0.25 Ce0.1 S 4.4 Cl 1.4 O 0.2 。

[0089] Example 14

[0090] Preparation method of solid electrolyte material. Except that the raw materials are 2.4 mol of Li2S, 0.3 mol of P2S5, 1.3 mol of LiCl, 0.25 mol of SnS2 and 0.15 mol of CeO2, other conditions are the same as those in Example 1, and Li 6.1 P 0.6 Sn 0.25 Ce 0.15 S 4.4 Cl 1. 3O 0.3 。

[0091] Example 15

[0092] Preparation method of solid electrolyte material. Except that the raw materials are 2.3 mol of Li2S, 0.3 mol of P2S5, 1.4 mol of LiCl, 0.3 mol of SnS2 and 0.1 mol of CeO2, other conditions are the same as those in Example 1, and Li6P 0.6 Sn 0.3 Ce 0.1 S 4.4 Cl 1.4 O 0.2 。

[0093] Comparative Example 1

[0094] Under the protection of argon atmosphere, weigh 1.9 mol of Li2S, 0.5 mol of P2S5, and 1.6 mol of LiCl according to the molar ratio, place them in a ball milling tank, seal it and then carry out ball milling treatment. The ball-to-material ratio is 30:1, the ball milling speed is 660 rpm, and the ball milling time is 30 h. After ball milling, an electrolyte precursor is obtained. Under the argon atmosphere, use a muffle furnace to perform high-temperature heat treatment on the precursor. The heat treatment temperature is 500 °C, the temperature rise rate is 2 °C / min, and the holding time is 10 h. After natural cooling, an electrolyte crude product is obtained. After grinding and sieving the crude product, an electrolyte product Li 5.4 PS 4.4 Cl 1.6 。

[0095] Experimental Example

[0096] I. XRD Test

[0097] The sulfide solid electrolytes prepared in Examples 1 to 15 and Comparative Example 1 were subjected to XRD tests. Among them, the sample preparation method for XRD tests included: preparing a glass slide with a square groove (length 10 mm, depth 0.2 - 0.5 mm) on the surface, taking an appropriate amount of electrolyte powder and placing it in the groove, flattening it with a powder pressing glass slide, scraping off the excess powder, and it was most appropriate to keep the powder plane flush with the large surface of the glass slide. Then, it was encapsulated with a polyimide tape with a thickness of 20 μm or 30 μm. During the encapsulation process, it was ensured that the tape on the powder surface was flat and free of wrinkles, and the influence of the encapsulation tape on the test results was reduced as much as possible. The prepared samples were subjected to XRD tests, and the test parameters were: the test angle was (10 - 80)°, and the scanning speed was 1° / min. For the examples and comparative examples, the intensities of the third, fourth, and fifth characteristic peaks (i.e., at 2Theta = 25.5 ± 0.5°, 30.0 ± 0.5°, 31.5 ± 0.5°) of the XRD test electrolyte were set as I1, I2, and I3 respectively, and it was known that (I1 + I3) / I2 = 1.5 ± 0.1, as shown in Table 1 below.

[0098] The XRD test results of Example 1 and Comparative Example 1 are as Figure 1 shown. The characteristic peak 2Theta values of the solid electrolyte material obtained in Example 1 were 15.71°, 18.15°, 25.76°, 30.29°, 31.67°, 37.08°, 40.14°, 41.45°, 45.35°, 48.28°, 52.88°, 55.50°, 56.53°, 59.70°, 62.88°, 62.93°, 68.59°, 69.07°, 72.14°, 74.34°, 78.03° in sequence, and (I1 + I3) / I2 = 1.46; the characteristic peak 2Theta values of the solid electrolyte material obtained in Comparative Example 1 were 15.54°, 17.98°, 25.60°, 30.12°, 31.50°, 36.45°, 39.85°, 40.94°, 45.05°, 47.94°, 52.51°, 55.11°, 55.27°, 59.27°, 61.71°, 62.49°, 68.66°, 68.85°, 72.64°, 73.85°, 77.69° in sequence, and (I1 + I3) / I2 = 1.58.

[0099] From the perspective of the doping method, compared with the electrolyte of Comparative Example 1, the solid electrolyte material of the present invention only partially replaces P element with Sn element and Ce element, and S element with O element, without changing the overall structure of the electrolyte. Therefore, the XRD test pattern of the modified electrolyte should be consistent with the overall phase of the electrolyte of the comparative example. From the analysis of the actual measurement results: From Figure 1It can be seen that in the XRD pattern of the doped and modified sulfide electrolyte material prepared in Example 1, the characteristic peaks of the SnS2 and CeO2 crystal phases do not appear. Compared with the XRD pattern of the undoped and unmodified sulfide electrolyte material prepared in Comparative Example 1, there are only certain angular offsets or changes in the intensity of the characteristic peaks, indicating that it does not contain the SnS2 and CeO2 crystal phases and the reaction is relatively complete.

[0100] II. For Li in Example 1 5.8 P 0.8 Sn 0.1 Ce 0.1 S 4.4 Cl 1.4 O 0.2 perform voltage window test, ionic conductivity test, air stability characterization, and battery cycle performance test, specifically including:

[0101] 1. Li in Example 1 5.8 P 0.8 Sn 0.1 Ce 0.1 S 4.4 Cl 1.4 O 0.2 Voltage window test

[0102] Under the protection of an argon atmosphere, weigh Li 5.8 P 0.8 Sn 0.1 Ce 0.1 S 4.4 Cl 1.4 O 0.2 and conductive carbon powder in a weight ratio of 70:30, and grind them evenly using an agate mortar. In an insulating outer cylinder with a diameter of 10 mm, take 20 mg of the above Li 5. 8P 0.8 Sn 0.1 Ce 0.1 S 4.4 Cl 1.4 O 0.2 -conductive carbon powder mixture, 60 mg of Li 5.8 P 0.8 Sn 0.1 Ce 0.1 S 4.4 Cl 1.4 O 0.2 、20 mg of Li 5.4 PS4.4Cl 1.6 and stack them. Press them into a mold under a pressure of 360 MPa. Then, in Li 5.4 PS4.4Cl 1.6A lithium foil was stacked side by side and pressed at a pressure of 100 MPa. Then, stainless steel collectors were placed on the upper and lower sides of the stack, and collector leads were attached to the collectors. Linear sweep voltammetry was performed with a scan range of 2-5 V and a scan rate of 0.1 mV / S. A tangent line was drawn to the oxidation peak of the test curve, and the intersection with the horizontal axis was the oxidation potential of the material. The results are shown in Table 1.

[0103] 2. Li in Example 1 5.8 P 0.8 Sn 0.1 Ce 0.1 S 4.4 Cl 1.4 O 0.2 Ionic conductivity test

[0104] Weigh 100 mg of electrolyte powder, put it in an insulating sleeve with an inner diameter of 10 mm, press it at a pressure of 300 MPa, and perform AC impedance spectrum test to measure the impedance value of the electrolyte material. Then, the thickness of the pressurized sheet electrolyte is tested, and the ionic conductivity of the electrolyte material is calculated based on the impedance value and the Arrhenius formula. The test results are shown in Table 1.

[0105] 3. Li 5.8 P 0.8 Sn 0.1 Ce 0.1 S 4.4 Cl 1.4 O 0.2 Air stability characterization

[0106] After the ion conductivity test of the same batch of electrolytes was completed as above, 100 mg of electrolyte powder was sampled and placed in an environment with a temperature of 25±3°C and a dew point of ≤-55°C for 6 hours. After the standing period, the electrolyte ion conductivity was retested and the reduction ratio of the ion conductivity was calculated to judge the air stability of the electrolyte. The test results are shown in Table 1.

[0107] 4. Battery test: In an argon glove box, 5.8 P 0.8 Sn 0.1 Ce 0.1 S 4.4 Cl 1.4 O 0.2 、Positive electrode active material Li(Ni 0.8 Co 0.1 Mn 0.1)O2(NCM811) was weighed at a weight ratio of 20:80. They were ground evenly using an agate mortar to produce the composite cathode material. In an insulating outer cylinder with a diameter of 10 mm, 14 mg of the above composite cathode material and 70 mg of the solid electrolyte material Li 5.8 P 0.8 Sn 0.1 Ce 0.1 S 4.4 Cl 1.4 O 0.2 were stacked. It was pressure-molded at a pressure of 360 MPa to obtain the cathode and the solid electrolyte layer. Then, a piece of aluminum foil was stacked on the cathode side to form a current collector on the cathode side. Then, on the side of the solid electrolyte layer opposite to the side in contact with the cathode, an indium sheet with a thickness and diameter of 200 μm and 10 mm respectively was placed as the anode material. It was pressure-molded at a pressure of 80 MPa to produce a laminate composed of a cathode, a solid electrolyte layer, and an anode. Then, stainless steel current collectors were arranged above and below the laminate, and current collector leads were attached to the current collectors. The assembled solid-state battery was subjected to a cycle performance test under the test conditions of: current density of 0.3C and voltage range of 2.7 - 4.3V (Li + / Li). The test results are shown in Table 1.

[0108] For the electrolyte materials of Examples 2 to 15 and Comparative Example 1, voltage window tests, ionic conductivity tests, air stability characterizations, and battery cycle performance tests were carried out according to the test method of the electrolyte material in Example 1 above. The results are shown in Table 1.

[0109] Table 1 Performance of electrolyte materials and cycle performance of corresponding batteries

[0110]

[0111] It is known that theoretically, the higher the oxidation potential of the electrolyte, the ionic conductivity, the first-cycle discharge specific capacity of the battery, the first-cycle Coulombic efficiency, and the discharge capacity retention rate value for the same number of cycles, the better. Under the same test conditions, the lower the value of the electrolyte ionic conductivity reduction rate, the better. Among them, preferably, the electrolyte oxidation potential ≥ 4V, the ionic conductivity level ≥ 4 ms / cm, the ionic conductivity reduction rate ≤ 6%, the first-cycle discharge specific capacity of the test battery ≥ 225 mAh / g, and the first-cycle Coulombic efficiency ≥ 93%.

[0112] It can be seen from Table 1 that by simultaneously doping tin, cerium, and oxygen into the LiPSM-based sulfide electrolyte in the present invention, the prepared target electrolyte significantly improves its stability to the cathode and air stability while still maintaining a high ionic conductivity, can significantly improve the initial capacity performance and cycle stability of the battery, and can increase the possibility of the application of solid-state batteries.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A solid electrolyte material, characterized in that, The solid electrolyte material includes the following chemical formula: Li 5.4+x+3y P 1-x- y Sn x Ce y S 4.4 M 1.6-2y O 2y , where M includes at least one of Cl, I, Br, and F; 0.2 ≤ x + y ≤ 0.4, 0.1 ≤ y ≤ 0.3, 0.1 ≤ x ≤ 0.

3.

2. The solid electrolyte material according to claim 1, wherein M is selected from Cl, I, Br or F.

3. The solid electrolyte material according to claim 2, characterized in that, comprising at least one of the following features (1) to (5): (1) x is 0.1 and y is 0.1, 0.15, 0.2, 0.25 or 0.3; (2) x is 0.15 and y is 0.1, 0.15 or 0.2; (3) x is 0.2 and y is 0.1, 0.15 or 0.2; (4) x is 0.25 and y is 0.1 or 0.15; (5) x is 0.3 and y is 0.

1.

4. The solid electrolyte material according to claim 1, characterized in that, The solid electrolyte material is a glass-ceramic phase and / or a crystalline phase.

5. The preparation method of the solid electrolyte material according to any one of claims 1 to 4, characterized in that, comprising the following steps: crushing a raw material mixture according to the chemical formula of the solid electrolyte material to obtain an electrolyte precursor; performing heat treatment on the electrolyte precursor.

6. The preparation method of the solid electrolyte material according to claim 5, wherein The raw material mixture includes Li2S, P2S5, LiM, SnS2 and CeO2, wherein M is selected from at least one of Cl, I, Br or F.

7. The preparation method of the solid electrolyte material according to claim 5, characterized in that, The crushing treatment includes ball milling; The ball-to-material ratio of the ball milling is (10 to 30):1, the speed of the ball milling is 250 to 750 rpm, and the time of the ball milling is 10 to 40 h.

8. The preparation method of the solid electrolyte material according to claim 5, characterized in that, comprising at least one of the following features (1) to (3): (1) The temperature of the heat treatment is 400 to 550 °C, and the heat preservation time of the heat treatment is 8 to 12 h; (2) The heating rate of the heat treatment is 1 to 5 °C / min; (3) The heat treatment is carried out in an inert atmosphere.

9. The preparation method of the solid electrolyte material according to claim 5, characterized in that, grinding and sieving the material obtained after the heat treatment.

10. All-solid-state secondary battery, characterized in that, comprising a positive electrode layer, an electrolyte layer and a negative electrode layer; at least one of the positive electrode layer, the electrolyte layer and the negative electrode layer contains the solid electrolyte material according to any one of claims 1 to 4.

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