A two-phase intermingled sulfide solid electrolyte and its preparation method

Abstract

The present invention discloses a two-phase intermingled sulfide solid electrolyte and a preparation method thereof. The electrolyte is composed of an iodine-rich antimony-based thiogermanate phase with good lithium stability and an air-stable tin-based lithium thiophosphate superionic conductor phase. Both original phases have low ionic conductivities. During the heat treatment process, antimony and tin elements diffuse and intermix into each other's phases. The antimony-doped tin-based lithium thiophosphate superionic conductor has a high ionic conductivity but poor lithium stability, and this shortcoming is compensated by the iodine-rich thiogermanate phase. At the same time, tin doping enhances the air stability of the antimony-based thiogermanate phase and improves the ionic conductivity. The present invention ingeniously combines the advantages of the two phases to prepare a highly ion-conductive, non-toxic, and highly air-stable sulfide solid electrolyte without using expensive germanium, toxic arsenic, and phosphorus that is disadvantageous to air stability.

Description

Technical Field

[0001] The present invention relates to the field of sulfide solid electrolytes for all-solid-state lithium batteries, and particularly to a sulfide solid electrolyte with two-phase intermixing and a preparation method thereof. Background Art

[0002] As one of the key technologies to cope with the increasingly severe energy storage situation, lithium-ion battery technology has currently been widely applied to various electronic devices and the grid energy storage market. However, traditional commercial liquid lithium-ion batteries use volatile and flammable organic electrolytes, which have certain safety hazards, and the energy density is limited to 300 Wh / kg. In contrast, all-solid-state lithium-ion batteries using non-flammable solid electrolytes have higher reliability and energy density, and have received attention from the global commercial and academic communities in recent years.

[0003] As an important component of all-solid-state lithium-ion batteries, the performance of solid electrolytes directly affects the large-scale application of all-solid-state batteries. Currently, the main research focuses on three types: polymer-based, oxide-based, and sulfide-based. Among them, sulfide-based solid electrolytes have been widely studied by researchers due to their high ionic conductivity and good formability. However, most current sulfide solid electrolytes have poor air stability. For example, phosphorus-containing Li 10 GeP2S 12 , Li2S-P2S5, Li6PS5Cl, etc. are prone to react with moisture in the air to release toxic hydrogen sulfide gas, and the compounds of germanium element are expensive.

[0004] The tin-based lithium thio-superionic conductor Li4SnS4 is stable in air. However, the ionic conductivity is only on the order of 10 -5 S / cm, which is not sufficient for practical applications. By doping with hetero-valent elements As and Sb, a relatively high ionic conductivity of 10 -4 ~10 -3 S / cm can be achieved. However, the stability of this type of electrolyte to lithium is also poor. High-valent metal elements are easily reduced by lithium, and an ion-electron conductor interface layer will be formed at the interface when contacting with a lithium-containing negative electrode, thus unable to inhibit the continuous occurrence of interface side reactions, showing poor electrochemical cycle stability, and the doped As element has strong toxicity.

[0005] The antimony-based argyrodite Li6SbS5I is rich in iodine element. When contacting with lithium metal, a passivation layer rich in iodine can be formed, effectively inhibiting interface side reactions. However, the ionic conductivity is only on the order of 10 -6 S / cm. By doping with Si and Ge, the lithium ion disorder can be increased, and thus the ionic conductivity can be improved. However, the raw materials of Si- and Ge-containing sulfides used are expensive. In addition, the air stability of this type of electrolyte is poor. Summary of the Invention

[0006] The object of the present invention is to provide a two-phase inter-doped sulfide solid electrolyte, a preparation method thereof, and an all-solid-state lithium battery, so as to solve the problems in the prior art such as poor air stability, high synthesis cost, toxicity of raw materials, and incompatibility with lithium-containing anodes of sulfide solid electrolytes. By cleverly precipitating an air-stable tin-based lithium thiosulfide superionic conductor phase in the iodine-rich antimony-based argyrodite phase with good lithium stability, on the one hand, doping tin elements into the iodine-rich antimony-based argyrodite phase increases lithium-site disorder and unit cell volume, improving ionic conductivity and air stability; on the other hand, precipitating an antimony-doped tin-based lithium thiosulfide superionic conductor phase with high ionic conductivity and high air stability at high antimony concentrations helps to further improve ionic conductivity and air stability. Based on the hard and soft acid-base theory, using non-toxic and low-cost soft acid elements and adopting a solid-phase sintering technology that is easy to scale up production, the problems of high cost, poor air stability, and poor lithium stability of current sulfide-based solid electrolytes are solved, which is easy to achieve batch industrial production and promote the industrialization and practical application of all-solid-state batteries.

[0007] To solve the above technical problems, in the first aspect of the present invention, a two-phase inter-doped sulfide solid electrolyte is provided. In the two phases, the first phase has a crystal structure of argyrodite type, belonging to the cubic crystal system, space group F43_m, and the second phase has a crystal structure of lithium thiosulfide superionic conductor, belonging to the orthorhombic crystal system, space group pnma. The chemical formula of the sulfide solid electrolyte is: xLi6SbS5I 1-y X y ·zLi4SnS4, where 1 > x > 0, 0.5 ≥ y ≥ 0, 1 > z > 0, X is one or more of F, Cl, Br, O, Se, and the two-phase inter-doping is achieved by the mutual diffusion of the two-phase elements during the heat treatment process and finally doping into the two phases.

[0008] Furthermore, for the two-phase inter-doped sulfide solid electrolyte, the mass ratio of the argyrodite phase contained to the mass of the lithium thiosulfide superionic conductor phase is 0.2 - 19:1, that is, the mass percentage content of the argyrodite phase in the sulfide solid electrolyte is 16.7% - 95%.

[0009] In the second aspect of the present invention, a preparation method of the two-phase inter-doped sulfide solid electrolyte is provided. The two-phase inter-doped sulfide solid electrolyte can be obtained by using a one-step method or a multi-step method. The two-phase inter-doped sulfide solid electrolyte prepared by using the one-step method contains a small amount of other impurity phases, and the two-phase inter-doped sulfide solid electrolyte prepared by using the multi-step method does not contain other impurity phases.

[0010] Using the one-step method to prepare the two-phase inter-doped sulfide solid electrolyte includes the following steps:

[0011] (1-1) Mix lithium sulfide, antimony sulfide, tin sulfide, sulfur powder, lithium iodide, LiX according to xLi6SbS5I1-y X y Mix uniformly in a molar ratio of ·zLi4SnS4 to obtain a uniform mixture, where 1 > x > 0, 0.5 ≥ y ≥ 0, 1 > z > 0, and X is one or more of F, Cl, Br, O, and Se;

[0012] (1 - 2) Heat and keep the uniform mixture obtained in step (1 - 1) under vacuum or an inert atmosphere for a period of time, and this product is the two - mutually - doped sulfide solid electrolyte.

[0013] Use a multi - step method to prepare a two - mutually - doped sulfide solid electrolyte, including the following steps:

[0014] (2 - 1) Mix lithium sulfide, antimony sulfide, sulfur powder, lithium iodide, and LiX in a molar ratio of Li6SbS5I 1-y X y uniformly to obtain a uniform mixed raw material, where 0.5 ≥ y ≥ 0, and X is one or more of F, Cl, Br, O, and Se;

[0015] (2 - 2) Heat and keep the uniform mixed raw material obtained in step (2 - 1) under vacuum or an inert atmosphere for a period of time, and this product is the iodine - rich antimony - based argyrodite phase Li6SbS5I 1-y X y , where 0.5 ≥ y ≥ 0, and X is one or more of F, Cl, Br, O, and Se;

[0016] (2 - 3) Mix lithium sulfide, tin sulfide, and sulfur powder in a molar ratio of Li4SnS4 uniformly to obtain a uniform mixed raw material;

[0017] (2 - 4) Heat and keep the uniform mixed raw material obtained in step (2 - 3) under vacuum or an inert atmosphere for a period of time, and this product is the tin - based lithium thio - superionic conductor phase Li4SnS4;

[0018] (2 - 5) Mix the iodine - rich antimony - based argyrodite phase Li6SbS5I 1-y X y obtained in step (2 - 2) and the tin - based lithium thio - superionic conductor phase Li4SnS4 obtained in step (2 - 4) in a molar ratio of xLi6SbS5I 1-y X y ·zLi4SnS4 uniformly to obtain a uniform mixture, where 1 > x > 0, 0.5 ≥ y ≥ 0, 1 > z > 0, and X is one or more of F, Cl, Br, O, and Se;

[0019] (2 - 6) Heat and keep the uniform mixture obtained in step (2 - 5) under vacuum or an inert atmosphere for a period of time, and this product is the two - mutually - doped sulfide solid electrolyte.

[0020] Further, in the steps (1-1) and (2-1), the uniform mixing method can be grinding, ball milling, or solvent mixing. The solvent can be polar or non-polar. The mixing time is 0.1 to 80 h. The mixing process can occur in a vacuum, under an inert atmosphere, or in their mixed atmosphere.

[0021] Further, in the steps (1-2) and (2-2), the heating temperature is 270 to 600 °C, the heat preservation time is 1 to 72 h, and the heating rate is 1 to 20 °C / min.

[0022] Further, in the steps (1-3) and (2-3), the uniform mixing method can be grinding, ball milling, or solvent mixing. The solvent can be polar or non-polar. The mixing time is 0.1 to 49 h. The mixing process can occur in a vacuum or under an inert atmosphere.

[0023] Further, in the step (2-4), the heating temperature is 150 to 700 °C, the heat preservation time is 1 to 30 h, and the heating rate is 1 to 20 °C / min.

[0024] Further, in the step (2-5), the uniform mixing method can be grinding, ball milling, or solvent mixing. The solvent can be polar or non-polar. The mixing time is 0.1 to 31 h. The mixing process can occur in a vacuum, under an inert atmosphere, or in their mixed atmosphere.

[0025] Further, in the step (2-6), the heating temperature is 270 to 600 °C. To ensure sufficient diffusion of the two phases and no decomposition of the sulfide, the preferred heating temperature is 400 to 500 °C, the heat preservation time is 0.5 to 30 h, and the heating rate is 1 to 20 °C / min.

[0026] The third aspect of the present invention provides the application of the described solid electrolyte in a all-solid-state lithium-ion battery.

[0027] The fourth aspect of the present invention provides a all-solid-state lithium-ion battery that uses the solid electrolyte provided by the present invention.

[0028] Compared with the prior art, the advantages of the present invention are as follows:

[0029] First, for the two mutually doped sulfide solid electrolytes prepared by the present invention, both of the original two phases have low conductivity. Based on the principle of element interdiffusion during heat treatment, a tin-based lithium thiosulfide superionic conductor phase is formed at a high antimony concentration to obtain antimony-doped Li4SnS4, which has high ionic conductivity and air stability and is a favorable phase for improving the ionic conductivity of sulfide electrolytes. At the same time, the tetravalent element Sn with a larger ionic radius 4+ replaces the pentavalent Sb with a smaller ionic radius in the antimony-based thiogermanate Li6SbS5I 5+ , which can increase the unit cell volume and lithium-site disorder of the antimony-based thiogermanate phase, thereby improving the ionic conductivity. The conductivity can be increased from the order of 10 -6 S / cm to the order of 10 -4 S / cm. Higher ionic conductivity helps to exhibit better electrochemical cycling performance during practical applications.

[0030] Second, based on the hard and soft acid-base theory, by doping the soft acid atom Sn into the antimony-based thiogermanate Li6SbS5I, the present invention can improve the air stability of the electrolyte. The second phase is an air-stable tin-based lithium thiosulfide superionic conductor phase, which is a favorable phase for improving air stability. The improvement of air stability not only helps with low-cost large-scale production but also benefits the performance stability and safety during use.

[0031] Third, when antimony-doped Li4SnS4 contacts lithium alone, it is unstable, and the high-valence elements are easily reduced, forming an electron-ion mixed conductor interface at the contact surface, which cannot effectively inhibit the continuous occurrence of side reactions. However, when antimony-doped Li4SnS4 is formed in iodine-rich antimony-based thiogermanate Li6SbS5I, an effective passivation layer with low electronic conductivity rich in iodine elements can be formed when contacting lithium metal, preventing the occurrence of interface side reactions.

[0032] Finally, the raw materials used contain only non-toxic elements and have a low cost, which has great advantages compared to sulfide solid electrolytes using toxic or expensive elements such as Ge, As, and V. The electrolyte of the present invention can effectively solve a series of technical problems that hinder the practical application of sulfide solid electrolytes, such as low ionic conductivity, poor air stability, incompatibility with lithium, and high cost.

[0033] The present invention can obtain two mutually doped sulfide solid electrolytes by a one-step method or a multi-step method. Among them, the two mutually doped sulfide solid electrolytes prepared by the one-step method contain a small amount of other impurity phases, such as residues of lithium sulfide and lithium iodide raw materials. The two mutually doped sulfide solid electrolytes prepared by the multi-step method do not contain other impurity phases because two pure phases are synthesized separately first, and the third heating allows the elements of the two phases to diffuse to obtain a mutually doped electrolyte containing only the two phases. Description of the Drawings

[0034] Figure 1 X-ray diffraction patterns of the samples prepared in Example 3, Example 6 and Comparative Example 1. Detailed implementation manners

[0035] In order to make the invention object, technical solution and beneficial technical effects of the present invention clearer, the present invention will be described in detail below in conjunction with specific embodiments. It should be understood that the embodiments described in this specification are only for explaining the present invention and not for limiting the present invention.

[0036] For those not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents used or those not indicating the manufacturer can be obtained as conventional products through commercial purchase.

[0037] Example 1

[0038] Lithium sulfide, antimony sulfide, sulfur powder, and lithium iodide were weighed in a glove box under argon protection according to the molar ratio of Li6SbS5I, and preliminarily mixed by grinding in an agate mortar for five minutes. The preliminarily mixed raw materials were transferred into a ball milling jar filled with zirconia balls and sealed, and the ball milling was carried out at a rotation speed of 350 r / min for 16 hours to obtain a well-mixed powder.

[0039] The obtained well-mixed powder was sealed in a glass tube. The glass tube was placed in a tube furnace and heated to 505 °C at a heating rate of 3 °C / min and kept warm for 6 hours. After waiting for the product to cool naturally to room temperature, the glass tube was taken out to obtain the Li6SbS5I sample.

[0040] Lithium sulfide and tin sulfide were weighed in a glove box under argon protection according to the molar ratio of Li4SnS4, and preliminarily mixed by grinding in an agate mortar for ten minutes. The preliminarily mixed raw materials were transferred into a ball milling jar filled with zirconia balls and sealed, and the ball milling was carried out at a rotation speed of 450 r / min for 18 hours to obtain a well-mixed powder.

[0041] The obtained well-mixed powder was sealed in a glass tube. The glass tube was placed in a tube furnace and heated to 500 °C at a heating rate of 4 °C / min and kept warm for 12 hours. After waiting for the product to cool to room temperature, the Li4SnS4 sample was obtained.

[0042] Li6SbS5I and Li4SnS4 were weighed in a glove box under argon protection according to the molar ratio of 0.9Li6SbS5I·0.1Li4SnS4, and preliminarily mixed by grinding in an agate mortar for ten minutes. The preliminarily mixed raw materials were transferred into a ball milling jar filled with zirconia balls and sealed, and the ball milling was carried out at a rotation speed of 400 r / min for 18 hours to obtain a well-mixed powder.

[0043] Seal the obtained well - mixed powder in a glass tube. Place the glass tube in a tube furnace and heat it at a heating rate of 4 °C / minute to 490 °C, hold for 7 hours, and wait for the product to cool naturally to room temperature to obtain a 0.9Li6SbS5I·0.1Li4SnS4 sample.

[0044] Example 2

[0045] Weigh lithium sulfide, antimony sulfide, sulfur powder, and lithium iodide according to the molar ratio of Li6SbS5I in a glove box under argon protection, and grind them in an agate mortar for ten minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball - milling jar filled with zirconia balls, seal it, and run it at a rotation speed of 350 r / minute for 12 hours to obtain a well - mixed powder.

[0046] Seal the obtained well - mixed powder in a glass tube. Place the glass tube in a tube furnace and heat it at a heating rate of 3 °C / minute to 510 °C, hold for 5 hours, and wait for the product to cool naturally to room temperature, then take out the glass tube to obtain a Li6SbS5I sample.

[0047] Weigh lithium sulfide, tin sulfide, and sulfur powder according to the molar ratio of Li4SnS4 in a glove box under argon protection, and grind them in an agate mortar for ten minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball - milling jar filled with zirconia balls, seal it, and run it at a rotation speed of 400 r / minute for 18 hours to obtain a well - mixed powder.

[0048] Seal the obtained well - mixed powder in a glass tube. Place the glass tube in a tube furnace and heat it at a heating rate of 4 °C / minute to 490 °C, hold for 7 hours, and wait for the product to cool naturally to room temperature to obtain a Li4SnS4 sample.

[0049] Weigh Li6SbS5I and Li4SnS4 according to the molar ratio of 0.8Li6SbS5I·0.2Li4SnS4 in a glove box under argon protection, and grind them in an agate mortar for ten minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball - milling jar filled with zirconia balls, seal it, and run it at a rotation speed of 420 r / minute for 19 hours to obtain a well - mixed powder.

[0050] Seal the obtained well - mixed powder in a glass tube. Place the glass tube in a tube furnace and heat it at a heating rate of 5 °C / minute to 495 °C, hold for 7 hours, and wait for the product to cool naturally to room temperature to obtain a 0.8Li6SbS5I·0.2Li4SnS4 sample.

[0051] Example 3

[0052] Weigh lithium sulfide, antimony sulfide, sulfur powder, and lithium iodide in a glove box under argon protection according to the molar ratio of Li6SbS5I, and grind them in an agate mortar for five minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball milling jar filled with zirconia balls, seal it, and run it at a speed of 380 r / min for 9 hours to obtain the well-mixed powder.

[0053] Seal the obtained well-mixed powder in a glass tube. Place the glass tube in a tube furnace, heat it to 490 °C at a heating rate of 5 °C / min, hold it for 8 hours, and wait for the product to cool naturally to room temperature. Then take out the glass tube to obtain the Li6SbS5I sample.

[0054] Weigh lithium sulfide and tin sulfide in a glove box under argon protection according to the molar ratio of Li4SnS4, and grind them in an agate mortar for ten minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball milling jar filled with zirconia balls, seal it, and run it at a speed of 500 r / min for 15 hours to obtain the well-mixed powder.

[0055] Seal the obtained well-mixed powder in a glass tube. Place the glass tube in a tube furnace, heat it to 490 °C at a heating rate of 5 °C / min, hold it for 8 hours, and wait for the product to cool to room temperature to obtain the Li4SnS4 sample.

[0056] Weigh Li6SbS5I and Li4SnS4 in a glove box under argon protection according to the molar ratio of 0.6Li6SbS5I·0.4Li4SnS4, and grind them in an agate mortar for ten minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball milling jar filled with zirconia balls, seal it, and run it at a speed of 550 r / min for 18 hours to obtain the well-mixed powder.

[0057] Seal the obtained well-mixed powder in a glass tube. Place the glass tube in a tube furnace, heat it to 490 °C at a heating rate of 5 °C / min, hold it for 8 hours, and wait for the product to cool naturally to room temperature to obtain the 0.6Li6SbS5I·0.4Li4SnS4 sample.

[0058] Example 4

[0059] Weigh lithium sulfide, antimony sulfide, sulfur powder, and lithium iodide in a glove box under argon protection according to the molar ratio of Li6SbS5I, and grind them in an agate mortar for five minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball milling jar filled with zirconia balls, seal it, and run it at a speed of 450 r / min for 6 hours to obtain the well-mixed powder.

[0060] Seal the obtained well-mixed powder in a glass tube. Place the glass tube in a tube furnace, heat it to 475 °C at a heating rate of 3 °C / min, hold it for 13 hours, and wait for the product to cool naturally to room temperature. Then take out the glass tube to obtain the Li6SbS5I sample.

[0061] Weigh lithium sulfide and tin sulfide in a glove box under argon protection according to the molar ratio of Li4SnS4, and grind them in an agate mortar for ten minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball milling jar filled with zirconia balls, seal it, and run it at a speed of 450 r / min for 15 hours to obtain the well-mixed powder.

[0062] Seal the obtained well-mixed powder in a glass tube. Place the glass tube in a tube furnace, heat it to 490 °C at a heating rate of 3 °C / min, hold for 10 hours, and wait for the product to cool naturally to room temperature to obtain the Li4SnS4 sample.

[0063] Weigh Li6SbS5I and Li4SnS4 in a glove box under argon protection according to the molar ratio of 0.4Li6SbS5I·0.6Li4SnS4, and grind them in an agate mortar for ten minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball milling jar filled with zirconia balls, seal it, and run it at a speed of 350 r / min for 8 hours to obtain the well-mixed powder.

[0064] Seal the obtained well-mixed powder in a glass tube. Place the glass tube in a tube furnace, heat it to 500 °C at a heating rate of 3 °C / min, hold for 12 hours, and wait for the product to cool naturally to room temperature to obtain the 0.4Li6SbS5I·0.6Li4SnS4 sample.

[0065] Example 5

[0066] Weigh lithium sulfide, antimony sulfide, sulfur powder, lithium iodide, and lithium fluoride in a glove box under argon protection according to the molar ratio of Li6SbS5I 0.95 F 0.05 and grind them in an agate mortar for seven minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball milling jar filled with zirconia balls, seal it, and run it at a speed of 420 r / min for 11 hours to obtain the well-mixed powder.

[0067] Seal the obtained well-mixed powder in a glass tube. Place the glass tube in a tube furnace, heat it to 510 °C at a heating rate of 8 °C / min, hold for 6 hours, and wait for the product to cool naturally to room temperature, then take out the glass tube to obtain the Li6SbS5I 0.95 F 0.05 sample.

[0068] Weigh lithium sulfide and tin sulfide in a glove box under argon protection according to the molar ratio of Li4SnS4, and grind them in an agate mortar for ten minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball milling jar filled with zirconia balls, seal it, and run it at a speed of 450 r / min for 15 hours to obtain the well-mixed powder.

[0069] Seal the obtained well - mixed powder in a glass tube. Place the glass tube in a tube furnace and heat it at a heating rate of 3 °C per minute to 490 °C, then hold for 9 hours. Wait for the product to cool naturally to room temperature to obtain the Li4SnS4 sample.

[0070] Take Li6SbS5I 0.95 F 0.05 , Li4SnS4 and weigh them in a glove box under argon protection according to the molar ratio of 0.3Li6SbS5I 0.95 F 0.05 ·0.7Li4SnS4. Grind them in an agate mortar for ten minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball - milling jar filled with zirconia balls, seal it, and run it at a rotation speed of 400 r / min for 21 hours to obtain the well - mixed powder.

[0071] Seal the obtained well - mixed powder in a glass tube. Place the glass tube in a tube furnace and heat it at a heating rate of 9 °C per minute to 490 °C, then hold for 12 hours. Wait for the product to cool naturally to room temperature to obtain the 0.3Li6SbS5I 0.95 F 0.05 ·0.7Li4SnS4 sample.

[0072] Example 6

[0073] Weigh lithium sulfide, antimony sulfide, tin sulfide, lithium iodide, and sulfur powder in a glove box under argon protection according to the molar ratio of 0.6Li6SbS5I·0.4Li4SnS4. Grind them in an agate mortar for thirty minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball - milling jar filled with zirconia balls, seal it, and run it at a rotation speed of 550 r / min for 30 hours to obtain the well - mixed powder.

[0074] Seal the obtained well - mixed powder in a glass tube. Place the glass tube in a tube furnace and heat it at a heating rate of 3 °C per minute to 490 °C, then hold for 15 hours. Wait for the product to cool naturally to room temperature to obtain the 0.6Li6SbS5I·0.4Li4SnS4 sample.

[0075] Comparative Example 1

[0076] Weigh lithium sulfide, antimony sulfide, sulfur powder, and lithium iodide in a glove box under argon protection according to the molar ratio of Li6SbS5I. Grind them in an agate mortar for five minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball - milling jar filled with zirconia balls, seal it, and run it at a rotation speed of 350 r / min for 16 hours to obtain the well - mixed powder.

[0077] Seal the obtained well - mixed powder in a glass tube. Place the glass tube in a tube furnace and heat it at a heating rate of 3 °C per minute to 505 °C, hold for 6 hours, wait for the product to cool naturally to room temperature, and then take out the glass tube to obtain the Li6SbS5I sample.

[0078] Comparative Example 2

[0079] Weigh lithium sulfide, tin powder, and sulfur powder according to the molar ratio of Li4SnS4 in a glove box under argon protection, and grind them in an agate mortar for ten minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball - milling jar filled with zirconia balls, seal it, and run it at a rotation speed of 400 r / min for 16 hours to obtain the well - mixed powder.

[0080] Seal the obtained well - mixed powder in a glass tube. Place the glass tube in a tube furnace and heat it at a heating rate of 3 °C per minute to 500 °C, hold for 8 hours, wait for the product to cool naturally to room temperature to obtain the Li4SnS4 sample.

[0081] Comparative Example 3

[0082] Weigh lithium sulfide, antimony sulfide, sulfur powder, and lithium iodide according to the molar ratio of Li6SbS5I in a glove box under argon protection, and grind them in an agate mortar for five minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball - milling jar filled with zirconia balls, seal it, and run it at a rotation speed of 380 r / min for 9 hours to obtain the well - mixed powder.

[0083] Seal the obtained well - mixed powder in a glass tube. Place the glass tube in a tube furnace and heat it at a heating rate of 5 °C per minute to 490 °C, hold for 8 hours, wait for the product to cool naturally to room temperature, and then take out the glass tube to obtain the Li6SbS5I sample.

[0084] Weigh lithium sulfide and tin sulfide according to the molar ratio of Li4SnS4 in a glove box under argon protection, and grind them in an agate mortar for ten minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball - milling jar filled with zirconia balls, seal it, and run it at a rotation speed of 500 r / min for 17 hours to obtain the well - mixed powder.

[0085] Seal the obtained well - mixed powder in a glass tube. Place the glass tube in a tube furnace and heat it at a heating rate of 5 °C per minute to 490 °C, hold for 8 hours, wait for the product to cool naturally to room temperature to obtain the Li4SnS4 sample.

[0086] Weigh Li6SbS5I and Li4SnS4 in a glove box under argon protection according to the molar ratio of 0.6Li6SbS5I·0.4Li4SnS4, and grind them in an agate mortar for ten minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball milling jar filled with zirconia balls, seal it, and run it at a speed of 550 r / min for 18 hours to obtain the well-mixed 0.6Li6SbS5I + 0.4Li4SnS4 powder.

[0087] Comparative Example 4

[0088] Weigh lithium sulfide, antimony sulfide, sulfur powder, and lithium iodide in a glove box under argon protection according to the molar ratio of Li6SbS5I, and grind them in an agate mortar for five minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball milling jar filled with zirconia balls, seal it, and run it at a speed of 380 r / min for 9 hours to obtain the well-mixed powder.

[0089] Seal the obtained well-mixed powder in a glass tube. Place the glass tube in a tube furnace, heat it at a heating rate of 5 °C / min to 475 °C, hold it for 10 hours, wait for the product to cool naturally to room temperature, and take out the glass tube to obtain the Li6SbS5I sample.

[0090] Weigh lithium sulfide and tin sulfide in a glove box under argon protection according to the molar ratio of Li4SnS4, and grind them in an agate mortar for ten minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball milling jar filled with zirconia balls, seal it, and run it at a speed of 500 r / min for 15 hours to obtain the well-mixed powder.

[0091] Seal the obtained well-mixed powder in a glass tube. Place the glass tube in a tube furnace, heat it at a heating rate of 5 °C / min to 490 °C, hold it for 10 hours, and wait for the product to cool naturally to room temperature to obtain the Li4SnS4 sample.

[0092] Weigh Li6SbS5I and Li4SnS4 in a glove box under argon protection according to the molar ratio of 0.6Li6SbS5I·0.4Li4SnS4, and grind them in an agate mortar for ten minutes for preliminary mixing. Transfer the preliminarily mixed raw materials into a ball milling jar filled with zirconia balls, seal it, and run it at a speed of 550 r / min for 18 hours to obtain the well-mixed powder.

[0093] Seal the obtained well-mixed powder in a glass tube. Place the glass tube in a tube furnace, heat it at a heating rate of 5 °C / min to 360 °C, hold it for 8 hours, and wait for the product to cool naturally to room temperature to obtain the 0.6Li6SbS5I·0.4Li4SnS4 sample.

[0094] Test Example

[0095] Open the sealed glass tube inside the glove box, take out the prepared sample, and grind it for 2 - 30 minutes to obtain a solid electrolyte powder with a particle size of 5 - 25 microns for H2S detection, ionic conductivity testing, and all-solid-state battery assembly.

[0096] H2S detection: Place 150 mg of the obtained solid electrolyte powder in a sealed and dry air-filled desiccator with a volume of 3.5 L, and place an H2S detector inside. The relative humidity of the air is 15%, and the test temperature is 20°C. The sample exposed to air will react with the moisture in the air and release H2S gas. The more stable the sample is in air, the less likely this reaction is to occur. By detecting the hydrogen sulfide concentration in the sealed container with an H2S detector, the air stability of the prepared sample can be reflected.

[0097] Ionic conductivity testing: Load 110 mg of the solid electrolyte powder into a mold with a diameter of 10 mm, press it with stainless steel current collector rods on the top and bottom, and use a press to apply a pressure of 450 MPa at both ends to form an electrolyte sheet with a diameter of 10 mm. Perform AC impedance testing at 30°C using an electrochemical workstation. The amplitude of the applied alternating current is 15 mV, and the frequency range is 0.001 HZ - 1 MHz.

[0098] The test performance parameters of the sulfide solid electrolytes prepared in Examples 1 - 6 and Comparative Examples 1 - 4 were summarized, as shown in Table 1.

[0099] Table 1

[0100]

[0101] From the data in the table, it can be seen that compared with Comparative Example 1, as the content of Li4SnS4 increases, the H2S detection amount of the samples in Examples 1 - 5 continuously decreases, and the air stability continuously enhances. Example 5 (the two-phase inter-doped sulfide solid electrolyte) has an H2S release amount similar to that of Comparative Example 2 (the air-stable tin-based lithium thiosulfide superionic conductor). Comparative Example 3 is an untreated two-phase mechanical mixture, and its H2S release amount is much higher than that of Example 3 with the same elemental ratio. In Comparative Example 4, the heat treatment temperature is too low, and the element diffusion between the two phases is insufficient. The H2S detection amount is slightly higher than that of Example 3, and the ionic conductivity is slightly lower than that of Example 3. The enhancement of the air stability of the two-phase inter-doped sulfide solid electrolyte is attributed to the introduction of the soft acid atom Sn. In addition, the precipitated antimony-doped lithium thiosulfide superionic conductor phase is a favorable phase with better air stability.

[0102] In Examples 1 to 3, as the content of Sn continuously increases, the ionic conductivity continuously increases. The increase in ionic conductivity is due to the increase in unit cell volume and the increase in lithium site disorder. In Example 4, the ionic conductivity slightly decreases due to the formation of other unknown impurity phases. In Example 5, a small amount of F doping can effectively alleviate volume expansion and inhibit the formation of impurity phases, further enhancing the ionic conductivity. In addition, the precipitated antimony-doped lithium thiosulfide superionic conductor also has high ionic conductivity and is a favorable phase.

[0103] The samples synthesized in Example 3 and Example 6 have the same composition. In Example 3, the multi-step method is used, and the obtained sample has a more uniform composition, higher air stability and ionic conductivity. In Example 6, the conventional one-step method is used. When mixing multiple raw materials, the uniformity of the raw material mixture is slightly worse. Residuals of raw materials such as lithium sulfide and lithium iodide are present in the final obtained sample, and the uniformity of the sample composition is slightly worse. Although the air stability and ionic conductivity of Example 6 are significantly improved compared to the individual two phases, they are inferior to the sample of Example 3 prepared by the multi-step method.

[0104] Figure 1 It is the X-ray diffraction pattern of the samples prepared in Example 3, Example 6 and Comparative Example 1. It can be seen that the product of Comparative Example 1 is Li6SbS5I. The product phases of Example 3 are Li6SbS5I and Li4SnS4 phases. The product phases of Example 6 are mainly Li6SbS5I and Li4SnS4 phases, containing a small amount of residual lithium sulfide and lithium iodide.

[0105] As described above, it is only the specific implementation manners of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope determined by the claims.

Claims

1. A two-intermingled sulfide solid electrolyte, characterized in that, In the two phases, the first phase has a thiogermanate crystal structure, belonging to the cubic crystal system F43 _ m space group, and the second phase has a lithium thiide superionic conductor crystal structure, belonging to the orthorhombic crystal system pnma space group; The chemical formula of the sulfide solid electrolyte is: xLi6SbS5I 1-y X y ·zLi4SnS4, where 1 > x > 0, 0.5 ≥ y ≥ 0, 1 > z > 0, and X is one or more of F, Cl, Br, O, and Se.

2. The two mutually doped sulfide solid electrolytes according to claim 1, characterized in that, The mass ratio of the argyrodite phase contained to the lithium thiophosphate superionic conductor phase is 0.2 to 19:

1.

3. The preparation method of the two mutually doped sulfide solid electrolytes according to claim 1 or 2, characterized in that, A two-phase inter-doped sulfide solid electrolyte is obtained by a one-step method or a multi-step method.

4. The preparation method of the two mutually doped sulfide solid electrolytes according to claim 3, characterized in that, When using a one-step method to prepare a two-phase inter-doped sulfide solid electrolyte, it includes the following steps: (1-1) Mix lithium sulfide, antimony sulfide, tin sulfide, sulfur powder, lithium iodide, and LiX in a molar ratio of xLi6SbS5I 1-y X y ·zLi4SnS4 uniformly to obtain a uniform mixture, where 1 > x > 0, 0.5 ≥ y ≥ 0, 1 > z > 0, and X is one or more of F, Cl, Br, O, and Se; (1-2) Heat and keep the homogeneous mixture obtained in step (1-1) under vacuum or an inert atmosphere for a period of time, and this product is the two-phase inter-doped sulfide solid electrolyte; When using a multi-step method to prepare a two-phase inter-doped sulfide solid electrolyte, it includes the following steps: (2-1) Uniformly mix lithium sulfide, antimony sulfide, sulfur powder, lithium iodide, and LiX according to the molar ratio of Li6SbS5I 1-y X y to obtain a uniformly mixed raw material, where 0.5 ≥ y ≥ 0, and X is one or more of F, Cl, Br, O, and Se; (2-2) Heat and keep the uniformly mixed raw materials obtained in step (2-1) under vacuum or an inert atmosphere for a period of time, and the product is an iodine-rich stibnite-based argyrodite phase Li6SbS5I 1-y X y , where 0.5 ≥ y ≥ 0, and X is one or more of F, Cl, Br, O, and Se; (2-3) Uniformly mix lithium sulfide, tin sulfide, and sulfur powder according to the molar ratio of Li4SnS4 to obtain a uniformly mixed raw material; (2-4) Heat and keep the uniformly mixed raw material obtained in step (2-3) under vacuum or an inert atmosphere for a period of time, and this product is the tin-based lithium thiophosphate superionic conductor phase Li4SnS4; (2-5) Mix the iodine-rich stibnite-based argyrodite phase Li6SbS5I obtained in step (2-2) 1-y X y and the tin-based lithium thio superionic conductor phase Li4SnS4 obtained in step (2-4) in a molar ratio of xLi6SbS5I 1-y X y ·zLi4SnS4 to obtain a homogeneous mixture, where 1 > x > 0, 0.5 ≥ y ≥ 0, 1 > z > 0, and X is one or more of F, Cl, Br, O, and Se; (2-6) Heat and keep the homogeneous mixture obtained in step (2-5) under vacuum or an inert atmosphere for a period of time, and this product is the two-phase inter-doped sulfide solid electrolyte.

5. The preparation method of the two mutually doped sulfide solid electrolytes according to claim 3, characterized in that, In steps (1-2) and (2-2), the heating temperature is 270 to 600 °C, the heat preservation time is 1 to 72 h, and the heating rate is 1 to 20 °C / min.

6. The preparation method of the two mutually doped sulfide solid electrolytes according to claim 3, characterized in that, In step (2-4), the heating temperature is 150 to 700 °C, the heat preservation time is 1 to 30 h, and the heating rate is 1 to 20 °C / min.

7. The preparation method of the two mutually doped sulfide solid electrolytes according to claim 3, characterized in that, In steps (1-2), (2-1), (2-3), and (2-5), the method of uniform mixing is selected from any one of grinding, ball milling, and solvent mixing. The solvent is polar or non-polar, the mixing time is 0.1 to 50 h, and the mixing atmosphere is selected from vacuum or an inert atmosphere.

8. The preparation method of the two mutually doped sulfide solid electrolytes according to claim 3, characterized in that, In step (2-6), the heating temperature is 270 to 600 °C, the heat preservation time is 0.5 to 30 h, and the heating rate is 1 to 20 °C / min.

9. Application of the solid electrolyte according to claim 1 or 2 or the solid electrolyte prepared by the method according to any one of claims 3 to 8 in a all-solid-state lithium-ion battery.

10. A all-solid-state lithium-ion battery, characterized in that, Use the solid electrolyte according to claim 1 or 2 or the solid electrolyte prepared by the method according to any one of claims 3 to 8.

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