A sulfide solid electrolyte and its preparation method and application

Abstract

The present invention provides a sulfide solid electrolyte and its preparation method and application. The sulfide solid electrolyte is Li 5.4+3.5x+y P 1‑x‑y Bi x Sn y S 4.4 O 1.5x M 1.6‑1.5x , wherein M is selected from Cl ‑ , I ‑ 、F ‑ or Br ‑ Any one or a combination of at least two, 0.01

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion batteries, and in particular to a sulfide solid electrolyte and a preparation method and application thereof. Background Art

[0002] Since Sony introduced lithium-ion batteries in 1991, they have found widespread application in a wide range of portable electronic products (such as laptops, mobile phones, and digital cameras) and electric vehicles. However, recent safety incidents involving new energy vehicles have been frequent, primarily due to the fact that traditional lithium-ion batteries require flammable organic solvents as their electrolyte, posing significant safety risks that cannot be fully addressed using conventional improvement methods. In contrast, solid-state lithium-ion batteries, which use solid-state electrolytes, offer significant safety advantages. Using solid-state electrolytes not only fundamentally addresses the safety concerns of lithium-ion batteries but also promises to significantly simplify the manufacturing and packaging process, improving battery energy density, reliability, and design freedom. Among various new battery systems, solid-state batteries are the next-generation technology closest to industrialization, a consensus among both industry and scientific communities. To match the ionic conductivity of conventional liquid electrolytes while simultaneously meeting the requirements for higher energy density, enhanced safety, and improved battery performance, strong demands are placed on solid-state electrolytes with high ionic conductivity, high oxidation potential, and high lithium stability.

[0003] Among inorganic electrolyte materials, oxide electrolytes have high oxidation potentials and are stable for high-voltage ternary cathode materials, but they are difficult to achieve high ionic conductivity, and they have high rigidity and poor ductility, resulting in large contact impedance with the cathode material. In comparison, sulfide electrolytes are a type of solid electrolyte material that has recently received attention. They usually have high ionic conductivity, good ductility, and can form 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℃) can reach 12ms / cm, and its ionic conductivity can be greatly improved with increasing temperature, which is comparable to the ionic conductivity level of conventional liquid electrolytes. The solid-state batteries made from them have high first efficiency and rate performance, but they still have some problems.

[0004] 1) Poor air stability. Even when exposed to an environment with very little moisture, it will undergo spontaneous hydrolysis to generate highly toxic H2S gas, resulting in a significant decrease in ionic conductivity. At the same time, the generated impurities will have serious side reactions with the positive and negative electrodes during the long cycle of the battery, affecting the long-cycle performance of the battery. Moreover, the low air stability places high demands on the electrolyte preparation environment and conditions. It must be carried out under an inert atmosphere or under extremely low ambient humidity control, which is not conducive to the mass production of the electrolyte itself, as well as the subsequent mass production of electrolyte membranes and batteries. CN111129572A discloses a sulfide electrolyte and its preparation method. By referring to the two elements Ge and M in the sulfide electrolyte, after dual doping, the internal crystal structure is changed, so that some S atoms are wrapped and blocked, the activity of S is relatively reduced, the contact reaction between moisture and S elements is avoided, and the air stability of the product is improved. However, the improvement in interface impedance is not obvious.

[0005] 2) Poor compatibility with the lithium metal interface, the side reaction produced will not only greatly increase the interface impedance, but also induce the uneven deposition of lithium ions, resulting in the generation of lithium dendrites, which is unfavorable for the development and application of higher energy density (≥400wh / kg) lithium metal negative battery. CN112242555A discloses a sulfide solid electrolyte sheet and its preparation method, which introduces boron into the sulfide solid electrolyte to effectively reduce the binding effect of anions on lithium ions, improve the exposition ability of lithium ions, and the uniform distribution of boron in the sulfide solid electrolyte. The doping uniformity and electrical conductivity of the solid electrolyte are improved, and the roughness of the solid electrolyte surface is improved, thereby facilitating the diffusion process of lithium ions at the interface of the sulfide solid electrolyte sheet and the lithium metal anode, reducing the interface impedance. However, only doping boron into the sulfide solid electrolyte reduces the impedance of the battery, but it does not help the improvement of other electrochemical properties such as battery energy density.

[0006] Therefore, improving the air stability of sulfide electrolytes and their compatibility with lithium is of great significance for accelerating the large-scale manufacturing and commercialization of high-energy-density all-solid-state lithium metal batteries. Summary of the Invention

[0007] The object of the present invention is to provide a sulfide solid electrolyte capable of improving the air stability of the sulfide electrolyte, and a preparation method and application thereof.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] One of the purposes of the present invention is to provide a sulfide solid electrolyte, wherein the sulfide solid electrolyte is Li 5.4+3.5x+y P 1-x-y Bi x Sn y S4.4 O 1.5x M 1.6-1.5x , wherein, M is selected from Cl - 、I - 、F - or Br - or any combination of at least two of them. Typical but non-limiting examples of the combination are: the combination of Cl - and I - , the combination of I - and F - , or the combination of F - and Br - etc. 0.01 < x + y < 0.8, x ≥ 0.01, y ≥ 0.01. The value of x can be 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75 or 0.79 etc. The value of y can be 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75 or 0.79 etc., but not limited to the listed values. Other unlisted values within the above numerical ranges are equally applicable.

[0010] In this invention, by simultaneously doping Bi, O and Sn elements into the sulfide electrolyte of the LiPSM system to make them uniformly distributed in the lattice of the electrolyte material, the modified electrolyte can maintain a high conductivity level (≥8 mS / cm), high air stability and high lithium 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, as well as the energy density and rate performance of the entire battery.

[0011] The introduction of the precursor Bi element can in-situ form a Li-Bi alloy on the lithium metal surface, which can effectively reduce the diffusion barrier of lithium ions at the interface, thereby regulating the plating / stripping behavior of lithium ions on the negative electrode interface, and thus obtaining a strong lithium dendrite inhibition ability, and further improving the lithium stability of the electrolyte; the introduction of the precursor oxygen element can form P-O bonds with stronger binding than P-S bonds, resulting in relatively weaker forces of the structural units of P-O bonds on lithium ions, which is beneficial to the rapid migration of lithium ions, and thus ensuring a high ionic conductivity of the electrolyte; moreover, the introduction of Bi element and oxygen element can form a more stable crystal structure, which can effectively inhibit the hydrolysis reaction of the electrolyte, and at the same time introduce Sn-S bonds that can stably exist in the air, which can effectively improve the air stability of the electrolyte.

[0012] As a preferred technical solution of this invention, the M is Cl -When the sulfide solid electrolyte is Li 5.4+3.5m+n P 1-m- n Bi m Sn n S 4.4 O 1.5m Cl 1.6-1.5m , wherein, 0.2≤m+n≤0.5, 0.1≤m≤0.4, 0.1≤n≤0.4, wherein the value of m can be 0.1, 0.15, 0.20, 0.25, 0.30, 0.35 or 0.4, etc., and the value of n can be 0.1, 0.15, 0.20, 0.25, 0.30, 0.35 or 0.4, etc., but are not limited to the listed values, and other values not listed within the above numerical ranges are also applicable.

[0013] A second object of the present invention is to provide a method for preparing the sulfide solid electrolyte as described in the first object, the preparation method comprising the following steps:

[0014] (1) Under an inert atmosphere, the raw materials are sequentially dispersed at a low speed and a high speed to obtain a solid electrolyte precursor;

[0015] (2) subjecting the solid electrolyte precursor of step (1) to high-temperature heat treatment to obtain the sulfide solid electrolyte.

[0016] Compared with the traditional ball milling preparation method with a maximum kilogram level, the preparation method of the present invention adopts high-speed dispersion mixing and reaction, which is more conducive to the scale-up of the preparation equipment and the preparation of electrolytes at the level of 100 kilograms and above, thereby promoting cost control and rapid development of the entire industrial chain.

[0017] As a preferred technical solution of the present invention, the inert atmosphere in step (1) includes an argon atmosphere.

[0018] Preferably, the raw materials in step (1) are Li2S, P2S5, LiCl, Bi2O3 and SnS2.

[0019] Preferably, the molar mass ratio of Li2S, P2S5, LiCl, Bi2O3 and SnS2 is (2.2-2.95): (0.25-0.4): (1-1.45): (0.05-0.2): (0.1-0.4), wherein the molar mass ratio can be 2.2:0.25:1:0.05:0.1, 2.5:0.25:1:0.05:0.1, 2.95:0.25:1:0.05:0.1, 2.5:0.3:1:0.05:0.1, 2.5:0.4:1:0.05:0 .1, 2.5:0.4:1:0.05:0.1, 2.5:0.3:1.2:0.05:0.1, 2.5:0.3:1.45:0.05:0.1, 2.5:0.3:1.2:0.1:0.1, 2.5:0.3:1.2:0.2:0.1, 2.5:0.3:1.2:0.1:0.2, 2.5:0.3:1.2:0.1:0.3 or 2.5:0.3:1.2:0.1:0.4, etc., but are not limited to the listed values, other values not listed within the numerical range are also applicable.

[0020] As a preferred technical solution of the present invention, the low-speed dispersion and high-speed dispersion in step (1) are carried out in a dispersion tank.

[0021] Preferably, the height of the raw materials added into the dispersion tank in step (1) is higher than the height of the dispersion slurry in the dispersion tank.

[0022] Preferably, the volume of the raw materials added to the dispersion tank in step (1) is less than 2 / 3 of the volume of the dispersion tank.

[0023] Preferably, the dispersion speed of the low-speed dispersion in step (1) is 200 to 800 rpm, wherein the dispersion speed can be 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm or 800 rpm, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0024] Preferably, the dispersion time of the low-speed dispersion in step (1) is 1 to 4 hours, wherein the dispersion time can be 1 hour, 2 hours, 3 hours or 4 hours, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0025] As a preferred technical solution of the present invention, the dispersion speed of the high-speed dispersion in step (1) is 1000-3000 rpm, wherein the dispersion speed can be 1000 rpm, 1200 rpm, 1400 rpm, 1600 rpm, 1800 rpm, 2000 rpm, 2200 rpm, 2400 rpm, 2600 rpm, 2800 rpm or 3000 rpm, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0026] Preferably, the dispersion time of the high-speed dispersion in step (1) is 6 to 15 hours, wherein the dispersion time can be 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0027] Preferably, ultrasonic vibration and static elimination treatment are performed during the high-speed dispersion in step (1).

[0028] Preferably, the frequency of the ultrasonic vibration is 1 time / 1h to 1 time / 2h, wherein the frequency can be 1 time / 1h, 1 time / 1.2h, 1 time / 1.4h, 1 time / 1.6h, 1 time / 1.8h or 1 time / 2h, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0029] Preferably, the ultrasonic power of the ultrasonic vibration is 500-1000W, wherein the ultrasonic power can be 500W, 600W, 700W, 800W, 900W or 1000W, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0030] Preferably, the ultrasonic vibration time is 1 to 5 minutes per time, wherein the time can be 1 minute per time, 2 minutes per time, 3 minutes per time, 4 minutes per time or 5 minutes per time, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0031] As a preferred technical solution of the present invention, the atmosphere of the high-temperature heat treatment in step (2) includes an argon atmosphere.

[0032] Preferably, the temperature of the high-temperature heat treatment in step (2) is 400-550°C, wherein the temperature can be 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C or 550°C, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0033] Preferably, the temperature rise rate of the high temperature heat treatment in step (2) is 1 to 5°C / min, wherein the temperature rise rate can be 1°C / min, 2°C / min, 3°C / min, 4°C / min or 5°C / min, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0034] Preferably, the holding time of the high-temperature heat treatment in step (2) is 8 to 20 hours, wherein the holding time can be 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours or 20 hours, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0035] As a preferred technical solution of the present invention, the high-temperature heat treatment in step (2) is followed by cooling to obtain a crude electrolyte product, and the crude electrolyte product is ground and sieved to obtain the sulfide solid electrolyte;

[0036] Preferably, the cooling process includes natural cooling.

[0037] Preferably, the grinding time is 5 to 30 min, wherein the time can be 5 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min or 30 min, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0038] Preferably, the grinding rate is 10 to 80 r / min, wherein the rate can be 10 r / min, 15 r / min, 20 r / min, 25 r / min, 30 r / min, 35 r / min, 40 r / min, 45 r / min, 50 r / min, 55 r / min, 60 r / min, 65 r / min, 70 r / min, 75 r / min or 80 r / min, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0039] Preferably, the mesh number of the sieving is ≥250 mesh, wherein the mesh number can be 250 mesh, 260 mesh, 270 mesh, 280 mesh, 290 mesh or 300 mesh, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0040] Preferably, the D50 particle size of the sulfide solid electrolyte is ≤60 μm, wherein the D50 particle size may be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm or 60 μm, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0041] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0042] (1) Under an inert atmosphere, the raw materials are placed in a dispersion tank, and after sealing the dispersion tank, low-speed dispersion at a dispersion speed of 200 to 800 rpm for 1 to 4 hours and high-speed dispersion at a dispersion speed of 1000 to 3000 rpm for 6 to 15 hours are performed to obtain a solid electrolyte precursor;

[0043] (2) subjecting the solid electrolyte precursor of step (1) to a high-temperature heat treatment at a temperature of 400-550° C. at a temperature rise rate of 1-5° C. / min and a holding time of 8-20 h, followed by natural cooling to obtain a crude electrolyte product, and grinding and sieving the crude electrolyte product to obtain the sulfide solid electrolyte.

[0044] A third object of the present invention is to provide an application of the sulfide solid electrolyte as described in the first object, wherein the sulfide solid electrolyte is applied in the field of lithium-ion batteries.

[0045] The sulfide solid electrolyte material prepared by the present invention is applied to at least one or more of the positive electrode layer, electrolyte layer and negative electrode layer in lithium secondary batteries including liquid phase lithium secondary batteries, semi-solid lithium secondary batteries and all-solid lithium secondary batteries.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] (1) The high air stability and high-speed dispersion preparation method of the electrolyte material of the present invention solve the two major bottleneck problems that restrict the large-scale preparation and mass production of sulfide electrolytes, greatly saving manufacturing costs.

[0048] (2) The electrolyte material of the present invention has high stability to lithium, which can greatly enhance the application and promotion of lithium metal negative electrodes and significantly improve the electrochemical performance of solid-state batteries. The electrolyte prepared by the present invention can achieve a 200-cycle discharge capacity retention rate of lithium solid-state batteries of over 99%, and can even reach over 96% after exposure.

[0049] (3) The preparation method of the electrolyte of the present invention is expected to solve the problems of chemical and electrochemical instability of solid electrolyte materials in all-solid-state secondary batteries, improve the capacity of positive electrode active materials and the energy density and rate performance of the entire battery, and accelerate the development of the entire solid-state battery industry chain. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 1 is the XRD pattern of the sulfide solid electrolyte prepared in Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0052] Example 1

[0053] This embodiment provides a sulfide solid electrolyte and a preparation method thereof:

[0054] Sulfide solid electrolyte is Li 5.85 P 0.8 Bi 0.1 Sn 0.1 S 4.4 O 0.15 Cl 1.45 .

[0055] The preparation method comprises the following steps:

[0056] (1) Under an argon atmosphere, 2.2 mol Li2S, 0.4 mol P2S5, 1.45 mol LiCl, 0.1 mol SnS2 and 0.05 mol Bi2O3 were placed in a dispersion tank. After the dispersion tank was sealed, low-speed dispersion at a dispersion speed of 600 rpm for 2 h and high-speed dispersion at a dispersion speed of 2000 rpm for 8 h were performed to obtain a solid electrolyte precursor. During the period, the ultrasonic treatment frequency was 1 time / 2 h, the ultrasonic power was 800 W, and the ultrasonic time was 5 min / time;

[0057] (2) The solid electrolyte precursor of step (1) is subjected to a high-temperature heat treatment in an argon atmosphere at a temperature rise rate of 2°C / min, a temperature of 520°C, and a holding time of 15 hours, and then naturally cooled to obtain a crude electrolyte product, and the crude electrolyte product is ground and sieved to obtain the sulfide solid electrolyte.

[0058] Example 2

[0059] This embodiment provides a sulfide solid electrolyte and a preparation method thereof:

[0060] Sulfide solid electrolyte is Li5.445 P 0.98 Bi 0.01 Sn 0.01 S 4.4 O 0.015 Br 1.485 .

[0061] The preparation method comprises the following steps:

[0062] (1) Under an argon atmosphere, 2.2 mol Li2S, 0.49 mol P2S5, 1.585 mol LiBr, 0.01 mol SnS2 and 0.005 mol Bi2O3 were placed in a dispersion tank. After the dispersion tank was sealed, low-speed dispersion at a dispersion speed of 800 rpm for 1 hour and high-speed dispersion at a dispersion speed of 3000 rpm for 6 hours were carried out to obtain a solid electrolyte precursor. During the period, the ultrasonic treatment frequency was 1 time / 1 hour, the ultrasonic power was 1000 W, and the ultrasonic time was 1 min / time;

[0063] (2) The solid electrolyte precursor of step (1) is subjected to a high-temperature heat treatment in an argon atmosphere at a temperature rise rate of 5°C / min, a temperature of 550°C, and a holding time of 8 hours, and then naturally cooled to obtain a crude electrolyte product, and the crude electrolyte product is ground and sieved to obtain the sulfide solid electrolyte.

[0064] Example 3

[0065] This embodiment provides Li 5.95 P 0.7 Bi 0.1 Sn 0.2 S 4.4 O 0.15 Cl 1.45 .

[0066] The preparation method comprises:

[0067] (1) Under an argon atmosphere, 2.25 mol Li2S, 0.35 mol P2S5, 1.45 mol LiCl, 0.2 mol SnS2 and 0.05 mol Bi2O3 were placed in a dispersion tank. After the dispersion tank was sealed, low-speed dispersion at a dispersion speed of 600 rpm for 2 h and high-speed dispersion at a dispersion speed of 2000 rpm for 8 h were performed to obtain a solid electrolyte precursor. During the period, the ultrasonic treatment frequency was 1 time / 2 h, the ultrasonic power was 800 W, and the ultrasonic time was 5 min / time;

[0068] (2) The solid electrolyte precursor of step (1) is subjected to a high-temperature heat treatment in an argon atmosphere at a temperature rise rate of 2°C / min, a temperature of 520°C, and a holding time of 15 hours, and then naturally cooled to obtain a crude electrolyte product, and the crude electrolyte product is ground and sieved to obtain the sulfide solid electrolyte.

[0069] Example 4

[0070] This embodiment provides Li 6.05 P 0.6 Bi 0.1 Sn 0.3 S 4.4 O 0.15 I 1.45 .

[0071] The preparation method comprises the following steps:

[0072] (1) Under an argon atmosphere, 2.3 mol Li2S, 0.3 mol P2S5, 1.45 mol LiI, 0.3 mol SnS2 and 0.05 mol Bi2O3 were placed in a dispersion tank. After the dispersion tank was sealed, low-speed dispersion at a dispersion speed of 200 rpm for 4 h and high-speed dispersion at a dispersion speed of 1000 rpm for 15 h were performed to obtain a solid electrolyte precursor. During the period, the ultrasonic treatment frequency was 1 time / 1.5 h, the ultrasonic power was 500 W, and the ultrasonic time was 3 min / time;

[0073] (2) The solid electrolyte precursor of step (1) is subjected to a high-temperature heat treatment in an argon atmosphere at a temperature rise rate of 1°C / min, a temperature of 400°C, and a holding time of 20 hours, and then naturally cooled to obtain a crude electrolyte product, and the crude electrolyte product is ground and sieved to obtain the sulfide solid electrolyte.

[0074] Example 5

[0075] This embodiment provides Li 6.15 P 0.5 Bi 0.1 Sn 0.4 S 4.4 O 0.15 F 1.45 Except that the raw materials 2.2 mol Li2S, 0.4 mol P2S5, 1.45 mol LiF, 0.1 mol SnS2 and 0.05 mol Bi2O3 were replaced by 2.35 mol Li2S, 0.25 mol P2S5, 1.45 mol LiCl, 0.4 mol SnS2 and 0.05 mol Bi2O3, other conditions were the same as those in Example 1.

[0076] Example 6

[0077] This embodiment provides Li 6.2 P 0.7 Bi 0.2 Sn 0.1 S 4.4 O 0.3 Cl 1.3 Except that the raw materials 2.2 mol Li2S, 0.4 mol P2S5, 1.45 mol LiCl, 0.1 mol SnS2 and 0.05 mol Bi2O3 are replaced by 2.45 mol Li2S, 0.35 mol P2S5, 1.3 mol LiCl, 0.1 mol SnS2 and 0.1 mol Bi2O3, other conditions are the same as those in Example 1.

[0078] Example 7

[0079] This embodiment provides Li 6.3 P 0.6 Bi 0.2 Sn 0.2 S 4.4 O 0.3 Cl 1.3 Except that the raw materials 2.2 mol Li2S, 0.4 mol P2S5, 1.45 mol LiCl, 0.1 mol SnS2 and 0.05 mol Bi2O3 are replaced by 2.5 mol Li2S, 0.3 mol P2S5, 1.3 mol LiCl, 0.2 mol SnS2 and 0.1 mol Bi2O3, other conditions are the same as those in Example 1.

[0080] Example 8

[0081] This embodiment provides Li 6.4 P 0.5 Bi 0.2 Sn 0.3 S 4.4 O 0.3 Cl 1.3 Except that the raw materials 2.2 mol Li2S, 0.4 mol P2S5, 1.45 mol LiCl, 0.1 mol SnS2 and 0.05 mol Bi2O3 are replaced by 2.55 mol Li2S, 0.25 mol P2S5, 1.3 mol LiCl, 0.3 mol SnS2 and 0.1 mol Bi2O3, other conditions are the same as those in Example 1.

[0082] Example 9

[0083] This embodiment provides Li 6.55 P 0.6 Bi 0.3 Sn0.1 S 4.4 O 0.45 Cl 1.15 Except that the raw materials 2.2 mol Li2S, 0.4 mol P2S5, 1.45 mol LiCl, 0.1 mol SnS2 and 0.05 mol Bi2O3 are replaced by 2.7 mol Li2S, 0.3 mol P2S5, 1.15 mol LiCl, 0.1 mol SnS2 and 0.15 mol Bi2O3, other conditions are the same as those in Example 1.

[0084] Example 10

[0085] This embodiment provides Li 6.65 P 0.5 Bi 0.3 Sn 0.2 S 4.4 O 0.45 Cl 1.15 Except that the raw materials 2.2 mol Li2S, 0.4 mol P2S5, 1.45 mol LiCl, 0.1 mol SnS2 and 0.05 mol Bi2O3 are replaced by 2.75 mol Li2S, 0.25 mol P2S5, 1.15 mol LiCl, 0.2 mol SnS2 and 0.15 mol Bi2O3, other conditions are the same as those in Example 1.

[0086] Example 11

[0087] This embodiment provides Li 6.9 P 0.5 Bi 0.4 Sn 0.1 S 4.4 O 0.6 Cl, wherein the raw materials 2.2 mol Li2S, 0.4 mol P2S5, 1.45 mol LiCl, 0.1 mol SnS2 and 0.05 mol Bi2O3 are replaced by 2.95 mol Li2S, 0.25 mol P2S5, 1 mol LiCl, 0.1 mol SnS2 and 0.2 mol Bi2O3, and other conditions are the same as those in Example 1.

[0088] Example 12

[0089] This embodiment provides Li 7.25 P 0.4 Bi 0.5 Sn 0.1 S 4.4 O 0.75 Cl 0.85Except that the raw materials 2.2 mol Li2S, 0.4 mol P2S5, 1.45 mol LiCl, 0.1 mol SnS2 and 0.05 mol Bi2O3 are replaced by 3.2 mol Li2S, 0.2 mol P2S5, 0.85 mol LiCl, 0.1 mol SnS2 and 0.25 mol Bi2O3, other conditions are the same as those in Example 1.

[0090] Example 13

[0091] This embodiment provides Li 6.7 P 0.2 Bi 0.2 Sn 0.6 S 4.4 O 0.3 Cl 1.3 Except that the raw materials 2.2 mol Li2S, 0.4 mol P2S5, 1.45 mol LiCl, 0.1 mol SnS2 and 0.05 mol Bi2O3 are replaced by 2.7 mol Li2S, 0.1 mol P2S5, 1.3 mol LiCl, 0.6 mol SnS2 and 0.1 mol Bi2O3, other conditions are the same as those in Example 1.

[0092] Comparative Example 1

[0093] This comparative example provides Li 5.4 PS 4.4 Cl 1.6 Except that the raw materials 2.2 mol Li2S, 0.4 mol P2S5, 1.45 mol LiCl, 0.1 mol SnS2 and 0.05 mol Bi2O3 are replaced by 1.9 mol Li2S, 0.5 mol P2S5 and 1.6 mol LiCl, other conditions are the same as those in Example 1.

[0094] The XRD patterns of the sulfide solid electrolytes prepared in this comparative example and Example 1 are as follows: Figure 1 As shown. From the perspective of doping, compared with the electrolyte of comparative example 1, the modified electrolyte of embodiment 1 only partially replaces the P element with Bi and Sn elements, and partially replaces the Cl element with O elements, without changing the overall structure of the electrolyte. Therefore, the XRD test pattern of the modified electrolyte should be consistent with the physical phase of the comparative electrolyte. Figure 1It can be seen that the characteristic peaks of Bi2O3 and SnS2 crystal phases do not appear in the XRD spectrum of the doped and modified sulfide electrolyte material prepared in Example 1. Compared with the XRD spectrum of the undoped and modified sulfide electrolyte material prepared in Comparative Example 1, there is only a certain angle offset and a slight difference in peak intensity, indicating that the product finally prepared in Example 1 does not contain Bi2O3 and SnS2 crystal phases, and the reaction is complete.

[0095] Comparative Example 2

[0096] This comparative example provides a sulfide solid electrolyte and a preparation method thereof:

[0097] Sulfide solid electrolyte is Li 6.451 P 0.01 Bi x Sn 0.98 S 4.4 O 0.015 Cl 1.585 Except that the raw materials 2.2 mol Li2S, 0.4 mol P2S5, 1.45 mol LiCl, 0.1 mol SnS2 and 0.05 mol Bi2O3 were replaced by 2.415 mol Li2S, 0.005 mol P2S5, 1.585 mol Li Cl, 0.98 mol SnS2 and 0.005 mol Bi2O3, other conditions were the same as those in Example 1.

[0098] Comparative Example 3

[0099] This embodiment provides a sulfide solid electrolyte and a preparation method thereof:

[0100] Sulfide solid electrolyte is Li 7.2 P 0.2 Bi 0.4 Sn 0.4 S 4.4 O 0.6 Cl.

[0101] Except that the raw materials 2.2 mol Li2S, 0.4 mol P2S5, 1.45 mol LiCl, 0.1 mol SnS2 and 0.05 mol Bi2O3 are replaced by 2.2 mol Li2S, 0.1 mol P2S5, 1 mol Li Cl, 0.4 mol SnS2 and 0.2 mol Bi2O3, other conditions are the same as those in Example 1.

[0102] Comparative Example 4

[0103] In this comparative example, the conditions are the same as those in Example 1, except that the low-speed dispersion at a dispersion speed of 600 rpm for 2 h and the high-speed dispersion at a dispersion speed of 2000 rpm for 8 h are replaced by dispersion at a dispersion speed of 2000 rpm for 10 h.

[0104] Comparative Example 5

[0105] In this comparative example, the conditions are the same as those in Example 1, except that the low-speed dispersion at a dispersion speed of 600 rpm for 2 h and the high-speed dispersion at a dispersion speed of 2000 rpm for 8 h are replaced by dispersion at a dispersion speed of 600 rpm for 10 h.

[0106] The sulfide solid electrolytes prepared in Examples 1-13 and Comparative Examples 1-5 were tested for ionic conductivity, and the solid-state batteries prepared using the sulfide solid electrolytes in Examples 1-13 and Comparative Examples 1-5 were tested for cycling performance. The test results are shown in Table 1.

[0107] The sulfide solid electrolytes prepared in Examples 1-13 and Comparative Examples 1-5 of the present invention were subjected to XRD testing. The sample preparation method for the XRD test was as follows: a glass slide with a square groove (length 10 mm, depth 0.2-0.5 mm) was prepared on the surface, an appropriate amount of electrolyte powder was placed in the groove, flattened with a powdered glass slide, excess powder was scraped off, and the powder plane was kept flush with the large surface of the glass slide. The powder was then packaged with a polyimide tape having a thickness of 20 μm or 30 μm. During the packaging process, the tape on the powder surface was ensured to be flat and wrinkle-free to minimize the impact of the packaging tape on the test results. The prepared samples were subjected to XRD testing with the following test parameters: a test angle of (10-80)° and a scanning speed of 1° / min. The intensities of the third, fourth and fifth characteristic peaks of the XRD test electrolyte (i.e., 2Theta = 25.5±0.5°, 30.0±0.5°, 31.5±0.5°) are set to I1, I2, and I3, respectively. It can be seen that Example 1 (I1+I3) / I2=1.60, Comparative Example 1 (I1+I3) / I2=1.58, and the overall (I1+I3) / I2=1.6±0.1.

[0108] The ionic conductivity test of the sulfide solid electrolyte is as follows: 100mg of electrolyte powder is weighed, placed in an insulating sleeve with an inner diameter of 10mm, and pressed at a pressure of 300MPa. The AC impedance spectrum test can measure the impedance value of the electrolyte material. The thickness of the pressurized sheet electrolyte is then tested. Based on the sheet impedance value, thickness value and area, the ionic conductivity of the electrolyte material is calculated using the formula σ=d / (R*S), where σ is the ionic conductivity in s / cm; d is the sheet thickness in cm; R is the impedance value in Ω; and S is the sheet area in cm. 2 The test results are shown in Table 1.

[0109] Battery test: The sulfide solid electrolytes prepared in Examples 1-13 and Comparative Examples 1-5 were assembled into batteries. The battery preparation method was as follows: the sulfide solid electrolytes in Examples 1-13 and Comparative Examples 1-5 were mixed with the positive electrode active material Li (Ni 0.8 Co 0.1 Mn 0.1 )O2 were weighed at a weight ratio of 20:80. They were ground evenly using an agate mortar to produce a composite positive electrode material. In an insulating outer cylinder with a diameter of 10 mm, 14 mg of the above-mentioned composite positive electrode material and 70 mg of the sulfide solid electrolyte in Examples 1-13 and Comparative Examples 1-5 were stacked and press-formed at a pressure of 360 MPa to obtain a positive electrode and a solid electrolyte layer. Next, a piece of aluminum foil was stacked on the positive electrode side to form a current collector on the positive electrode side. Then, an indium sheet with a thickness and a diameter of 200 μm and 10 mm, respectively, was placed on the opposite side of the solid electrolyte layer in contact with the positive electrode as a negative electrode material. It was press-formed at a pressure of 80 MPa to produce a stack consisting of a positive electrode, a solid electrolyte layer and a negative electrode. Next, stainless steel current collectors were arranged above and below the stack, and current collector leads were attached to the current collector to obtain a solid-state battery. The cycle performance test of the assembled solid-state battery was carried out under the following test conditions: current density 0.3C, voltage range 2.7-4.3V (Li + / Li). The test results are shown in Table 1.

[0110] Table 1

[0111]

[0112]

[0113] It can be seen from the above table that, through a series of experimental exploration examples 1-13, when x=0.1, y=0.2, the prepared electrolyte is optimal, and at this time has the highest ionic conductivity and the best battery performance; it can be seen from Examples 12 and 13 of the present invention that when x>0.4, y>0.4, x+y>0.5, the target electrolyte conductivity level and battery performance are poor. The reason is that the excess doping elements cannot be completely incorporated, and then form an impurity phase in the target electrolyte, which seriously affects its performance.

[0114] From Comparative Example 1, it can be seen that without doping B, Sn and O elements, the electrochemical performance of the battery decreases. From Comparative Examples 2-3, when the values of x and y are too large or too small, and the value of x+y is too large, the electrochemical performance of the battery decreases sharply.

[0115] In Comparative Example 4, the dispersion speed is a high-speed dispersion, and the dispersion effect is poorer than that in Example 1, resulting in the prepared target electrolyte phase being impure and the performance being worse than that in Example 1. In Comparative Example 5, due to the low dispersion speed, the materials cannot be fully mixed and reacted evenly, resulting in the target electrolyte phase being impure and the performance being poor.

[0116] The sulfide solid electrolytes prepared in Examples 1-13 and Comparative Examples 1-5 were preliminarily screened, with the screening criterion being ionic conductivity ≥ 8 ms / cm. The screened electrolytes were subjected to lithium stability tests and air stability characterizations. The test results are shown in Table 2.

[0117] The test of the stability of sulfide solid electrolyte to lithium is as follows: in an argon glove box, sulfide solid electrolyte, positive electrode active material Li (Ni 0.8 Co 0.1 Mn 0.1 )O2(NCM811) were weighed at a weight ratio of 20:80. They were ground evenly using an agate mortar to produce a composite positive electrode material. In an insulating outer cylinder with a diameter of 10 mm, 14 mg of the above-mentioned composite positive electrode material and 70 mg of sulfide solid electrolyte were stacked. It was press-formed at a pressure of 360 MPa to obtain a positive electrode and a solid electrolyte layer. Next, a piece of aluminum foil was stacked on the positive electrode side to form a current collector on the positive electrode side. Then, a lithium-copper composite tape with a thickness and a diameter of 50 μm and 10 mm, respectively, was placed on the opposite side of the solid electrolyte layer in contact with the positive electrode as a negative electrode material and a current collector. It was press-formed at a pressure of 80 MPa to produce a stack consisting of a positive electrode, a solid electrolyte layer and a negative electrode. Next, stainless steel current collectors were arranged above and below the stack, and current collector leads were attached to the current collectors. The cycle performance test of the assembled solid-state battery was carried out under the following test conditions: current density 0.3C, voltage range 2.7-4.3V (Li + The test results are shown in Table 2.

[0118] Air stability characterization: After the ionic conductivity test of the same batch of electrolyte is completed as described above, 100 mg of electrolyte powder is 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 stagnant period, the electrolyte ionic conductivity is retested and the reduction rate of ionic conductivity is calculated. If the reduction rate of electrolyte ionic conductivity is ≤5% and the battery performance is good, the battery performance test is performed on the exposed electrolyte again using the same test method as above. This is used to comprehensively evaluate the air stability of the electrolyte. The test results are shown in Table 2.

[0119] Table 2

[0120]

[0121]

[0122] It can be seen from the above table that, through a series of experimental exploration examples 1-13, when x=0.1, y=0.2, the prepared electrolyte is optimal, and at this time it has the highest ionic conductivity and the best battery performance. It can be seen from Examples 12 and 13 of the present invention that when x>0.4, y>0.4 and x+y>0.5, the target electrolyte conductivity level and battery performance are poor. The reason is that the excess doping elements cannot be completely incorporated, and then form an impurity phase in the target electrolyte, which seriously affects its performance.

[0123] From Comparative Example 1, it can be seen that without doping B, Sn and O elements, the electrochemical performance of the battery decreases. From Comparative Examples 2-3, when the values of x and y are too large or too small, and the value of x+y is too large, the electrochemical performance of the battery decreases sharply.

[0124] In Comparative Example 4, the dispersion speed is a high-speed dispersion, and the dispersion effect is poorer than that in Example 1, resulting in the prepared target electrolyte phase being impure and the performance being worse than that in Example 1. In Comparative Example 5, due to the low dispersion speed, the materials cannot be fully mixed and reacted evenly, resulting in the target electrolyte phase being impure and the performance being poor.

[0125] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A sulfide solid electrolyte, characterized in that: The sulfide solid electrolyte is Li 5.4+3.5m+n P 1-m- n Bi m Sn n S 4.4 O 1.5m Cl 1.6-1.5m , where 0.2≤m+n≤0.5, 0.1≤m≤0.4, 0.1≤n≤0.4; The sulfide solid electrolyte is prepared by the following method: (1) Under an inert atmosphere, the raw materials are sequentially dispersed at low speed and high speed to obtain a solid electrolyte precursor; (2) subjecting the solid electrolyte precursor of step (1) to high-temperature heat treatment to obtain the sulfide solid electrolyte; The dispersion speed of the low-speed dispersion in step (1) is 200-800 rpm, the dispersion speed of the high-speed dispersion in step (1) is 1000-3000 rpm, and the temperature of the high-temperature heat treatment in step (2) is 400-550°C.

2. A method for preparing the sulfide solid electrolyte according to claim 1, characterized in that: The preparation method comprises the following steps: (1) Under an inert atmosphere, the raw materials are sequentially dispersed at low speed and high speed to obtain a solid electrolyte precursor; (2) subjecting the solid electrolyte precursor of step (1) to high-temperature heat treatment to obtain the sulfide solid electrolyte; The dispersion speed of the low-speed dispersion in step (1) is 200-800 rpm, the dispersion speed of the high-speed dispersion in step (1) is 1000-3000 rpm, and the temperature of the high-temperature heat treatment in step (2) is 400-550°C.

3. The preparation method according to claim 2, characterized in that The inert atmosphere in step (1) includes an argon atmosphere.

4. The preparation method according to claim 2, characterized in that The raw materials in step (1) are Li2S, P2S5, LiCl, Bi2O3 and SnS2.

5. The preparation method according to claim 4, characterized in that The molar mass ratios of Li2S, P2S5, LiCl, Bi2O3 and SnS2 are (2.2~2.95):(0.25~0.4):(1~1.45):(0.05~0.2):(0.1~0.4).

6. The preparation method according to claim 2, characterized in that The low-speed dispersion and high-speed dispersion in step (1) are carried out in a dispersion tank.

7. The preparation method according to claim 2, characterized in that The height of the raw materials added into the dispersion tank in step (1) is higher than the height of the dispersion slurry in the dispersion tank.

8. The preparation method according to claim 2, characterized in that The volume of the raw materials added to the dispersion tank in step (1) is less than 2 / 3 of the volume of the dispersion tank.

9. The preparation method according to claim 2, characterized in that The dispersion time of the low-speed dispersion in step (1) is 1 to 4 hours.

10. The preparation method according to claim 2, characterized in that The dispersion time of the high-speed dispersion in step (1) is 6 to 15 hours.

11. The preparation method according to claim 2, characterized in that Ultrasonic vibration and static elimination treatment are performed during the high-speed dispersion in step (1).

12. The preparation method according to claim 11, characterized in that The frequency of the ultrasonic vibration is 1 time / 1h to 1 time / 2h.

13. The preparation method according to claim 11, characterized in that The ultrasonic power of the ultrasonic vibration is 500-1000W.

14. The preparation method according to claim 11, characterized in that The ultrasonic vibration time is 1 to 5 minutes per time.

15. The preparation method according to claim 2, characterized in that The atmosphere of the high-temperature heat treatment in step (2) includes an argon atmosphere.

16. The preparation method according to claim 2, characterized in that The temperature rise rate of the high temperature heat treatment in step (2) is 1~5℃ / min.

17. The preparation method according to claim 2, characterized in that The holding time of the high temperature heat treatment in step (2) is 8 to 20 hours.

18. The preparation method according to claim 2, characterized in that The high-temperature heat treatment in step (2) is followed by cooling to obtain a crude electrolyte product, which is then ground and sieved to obtain the sulfide solid electrolyte.

19. The preparation method according to claim 18, characterized in that The cooling process includes natural cooling.

20. The preparation method according to claim 18, characterized in that The grinding time is 5 to 30 minutes.

21. The preparation method according to claim 18, characterized in that The grinding speed is 10-80 r / min.

22. The preparation method according to claim 18, characterized in that The mesh number of the sieving is ≥250 meshes.

23. The preparation method according to claim 18, characterized in that The D50 particle size of the sulfide solid electrolyte is ≤60µm.

24. The preparation method according to claim 2, characterized in that The preparation method comprises the following steps: (1) Under an inert atmosphere, the raw materials are placed in a dispersion tank, and after sealing the dispersion tank, low-speed dispersion at a dispersion speed of 200-800 rpm for 1-4 hours and high-speed dispersion at a dispersion speed of 1000-3000 rpm for 6-15 hours are sequentially performed to obtain a solid electrolyte precursor; (2) The solid electrolyte precursor of step (1) is subjected to a high-temperature heat treatment at a temperature of 400-550°C for a holding time of 8-20h at a temperature rise rate of 1-5°C / min, and then naturally cooled to obtain a crude electrolyte product. The crude electrolyte product is ground and sieved to obtain the sulfide solid electrolyte.

25. A use of the sulfide solid electrolyte according to claim 1, characterized in that: The sulfide solid electrolyte is applied in the field of lithium-ion batteries.

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