A sulfide solid electrolyte, a preparation method thereof, a battery, and a power utilization device

Abstract

The application relates to a sulfide solid electrolyte and a preparation method thereof, a battery and a power utilization device, and belongs to the technical field of solid electrolytes. The preparation method comprises the following steps: mixing and grinding raw materials of a argyrodite phase sulfide solid electrolyte according to a stoichiometric ratio to obtain a precursor powder; applying a pressure of 500 MPa-1000 MPa to the precursor powder to obtain a precursor sheet; and sintering the precursor sheet at a temperature of 600 DEG C-700 DEG C to obtain the sulfide solid electrolyte. Through the grinding combined with the high-pressure pressing and high-temperature sintering process, the high-pressure pressing and high-temperature sintering process synergistically act, so that the prepared sulfide solid electrolyte has a low loss on ignition, a uniform grain size distribution and a high density, thereby making the sulfide solid electrolyte have a high ionic conductivity.

Description

Technical Field

[0001] This application relates to the field of solid electrolyte technology, and particularly to a sulfide solid electrolyte, its preparation method, battery, and electrical device. Background Technology

[0002] Sulfur-silver-germanium mineral phase sulfide solid electrolytes have high theoretical ionic conductivity (up to 20 mS / cm), good mechanical flexibility, and good processability with electrode materials. They are considered to be one of the most promising electrolyte systems for realizing high energy density all-solid-state batteries.

[0003] However, existing sulfide solid electrolytes made from silver-germanium sulfide minerals are usually prepared using a ball milling-sintering process. Due to process defects, the actual ionic conductivity of the products is usually lower than 2 mS / cm.

[0004] Therefore, there is an urgent need to develop a method for preparing a solid electrolyte of silver-germanium sulfide phase to improve the ionic conductivity of the product. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a sulfide solid electrolyte, its preparation method, battery, and power device, thereby solving the technical problem of low ionic conductivity in sulfide solid electrolytes prepared by existing technologies. In a first aspect, embodiments of this application provide a method for preparing a sulfide solid electrolyte, comprising the following steps: The raw materials of the sulfide solid electrolyte of silver-germanium sulfide phase were mixed and ground according to the stoichiometric ratio to obtain the precursor powder. Precursor powder is pressed under a pressure of 500MPa to 1000MPa to obtain precursor flakes; The precursor sheet was sintered at a temperature of 600℃~700℃ to obtain a sulfide solid electrolyte. In the aforementioned technical solution, by employing a combination of grinding, high-pressure pressing, and high-temperature sintering, the synergistic effect of these processes significantly reduces powder gaps through high-pressure pressing, providing an initial state with extremely low porosity for subsequent high-temperature sintering. This allows the high-temperature sintering process to eliminate residual small pores more efficiently. Furthermore, high-pressure pressing ensures uniform and close contact between powder particles, laying the foundation for uniform heat and material transfer. During high-temperature sintering, it inhibits raw material decomposition and promotes uniform grain nucleation and growth, resulting in fine grains with uniform size distribution and reducing defects caused by abnormal grain growth or insufficient sintering. This synergistic effect of a dense and uniform microstructure significantly reduces grain boundary resistance encountered by lithium ions during bulk transport and greatly reduces the obstruction of ion conduction paths by insulating pores, thereby effectively and reliably improving the ionic conductivity of the sulfide solid electrolyte.

[0006] In some embodiments, the pressing step includes: placing the precursor powder in a mold for cold pressing, with a holding time of 5 min to 20 min.

[0007] In the above technical solution, the cold pressing process, i.e., high-pressure pressing at room temperature, can promote the plastic deformation of precursor powder particles, fill pores, and further improve the density of the precursor sheet. Furthermore, using a longer holding time (5 min~20 min) combined with high pressure (500 MPa~1000 MPa) can further improve density, promote atomic diffusion at grain boundaries, and fully release residual stress, further improving the uniformity and consistency of the sample. Therefore, by employing the cold pressing process, combined with the synergistic control of high pressure and holding time, the ionic conductivity of the sulfide solid electrolyte can be further improved.

[0008] In some embodiments, during the sintering step, the heating rate is 1℃ / min to 10℃ / min, and the holding time is 3h to 12h. In the above technical solution, the heating rate and holding time are within a suitable range, which is conducive to balancing the densification process and particle decomposition reaction, reducing the burn-off rate, increasing the density, and promoting the uniform distribution of grain size, thereby further improving the ionic conductivity of the sulfide solid electrolyte. In some embodiments, the thickness of the precursor sheet is 1.5 mm to 3.5 mm.

[0009] In the above technical solution, the thickness of the precursor sheet is within a suitable range, which can further improve the density. In the subsequent high-temperature sintering process, it is beneficial to further improve the degree of densification and sintering uniformity, and to promote the uniform distribution of grain size, thereby further improving the ionic conductivity of the sulfide solid electrolyte.

[0010] In some embodiments, the precursor powder has a mass of 200mg to 400mg, and the mold is cylindrical with an inner diameter of 8mm to 12mm. In the above technical solution, under the condition that the mold size and high pressure are constant, the thickness of the precursor sheet can be controlled by controlling the quality of the precursor powder, thereby improving the density.

[0011] In some embodiments, the pressure applied in the pressing step is 800 MPa to 1000 MPa; the temperature in the sintering step is 600°C to 650°C. In the above technical solution, further optimization of pressure and sintering temperature is beneficial to further balance the densification and decomposition processes, thereby further improving the ionic conductivity of the sulfide solid electrolyte.

[0012] In some embodiments, the raw materials include Li2S, LiY and P2S5, and the molar ratio of Li2S, LiY and P2S5 is (5-2x):(2+2x):1, wherein -0.1≤x≤0.5, and Y is selected from at least one of F, Cl, Br or I.

[0013] In the above technical solution, Li₂S, LiY, and P₂S₅ react in a molar ratio of (5-2x):(2+2x):1 to obtain Li₂ with good stability and high ionic conductivity. 6-x PS 5-x Y 1+x .

[0014] In some implementations, the grinding method is ball milling.

[0015] In the above technical solution, ball milling is beneficial to achieve atomic-level uniform mixing between raw material particles, reduce dislocation and vacancy defects, and further improve density and control grain size in subsequent high-pressure pressing and high-temperature sintering processes, thereby further improving the ionic conductivity of sulfide solid electrolyte.

[0016] In some embodiments, the mixing and grinding step includes: placing the raw material in a planetary ball mill for mixing and grinding, with a ball-to-material ratio of (10~20):1, a rotation speed of 400rpm~700rpm, and a grinding time of 16h~30h.

[0017] In the above technical solution, by synergistically controlling the ball-to-material ratio, rotation speed and ball milling time during the ball milling process, it is beneficial to further promote atomic-level uniform mixing between powder particles and control the powder particle size to be moderate and uniformly distributed.

[0018] Secondly, embodiments of this application provide a sulfide solid electrolyte with the chemical formula Li 6-x PS 5-x Y 1+x -0.1≤x≤0.5, Y is selected from at least one of F, Cl, Br or I; the crystallite size of the sulfide solid electrolyte is 10μm~30μm, and the density is 1.6g / cm³. 3 ~1.8g / cm 3 .

[0019] In the above technical solution, the sulfide solid electrolyte has a relatively small grain size, a relatively uniform distribution, and a high density, which gives it a high ionic conductivity, up to 3.63 mS / cm, thus making it effective for the preparation of high energy density all-solid-state batteries.

[0020] Thirdly, embodiments of this application provide a battery comprising a sulfide solid electrolyte prepared by the preparation method of the first aspect, or comprising a sulfide solid electrolyte of the second aspect.

[0021] Fourthly, embodiments of this application provide an electrical device, including the battery of the third aspect. Attached Figure Description To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A process flow diagram of a method for preparing a sulfide solid electrolyte provided in this application.

[0023] Figure 2 This is a SEM image of the sulfide solid electrolyte prepared in Example 1 of this application. Detailed Implementation

[0024] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the sulfide solid electrolyte, a method for preparing the sulfide solid electrolyte, a battery, and an electrical device thereof, but some unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0025] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0026] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0027] Existing sulfide solid electrolytes of silver-germanium mineral phase are usually prepared by ball milling-sintering process. The ball milling process generates a large number of dislocations and vacancies. Furthermore, due to the poor thermal stability of sulfide solid electrolytes, the sintering temperature is usually below 550℃ to avoid high-temperature decomposition and abnormal grain growth (>50μm). This also results in the actual ionic conductivity of the product usually being below 2mS / cm.

[0028] In addition, although some existing technologies disclose pressing the precursor powder into tablets before sintering, the applied pressure is usually below 500 MPa, possibly due to equipment limitations or concerns that excessive pressure may introduce harmful defects. This does not effectively improve the density of the tablets, and it cannot effectively suppress the decomposition of raw materials or promote uniform grain size distribution during subsequent sintering. In other words, temperatures above 550°C cannot be used during high-temperature sintering, and therefore the improvement in ionic conductivity is also very limited.

[0029] Therefore, there is an urgent need to develop a method for preparing a solid electrolyte of silver-germanium sulfide phase to improve the ionic conductivity of the product.

[0030] Based on this, the first aspect of this application provides a method for preparing a sulfide solid electrolyte, which combines grinding with high-pressure pressing (500MPa~1000MPa) and high-temperature sintering (600℃~700℃), with the high-pressure pressing and high-temperature sintering processes working synergistically: (1) In terms of microstructure, high pressure pressing greatly reduces the gap between powder particles, providing an initial state with extremely low porosity for subsequent high-temperature sintering, which enables the high-temperature sintering process to eliminate residual small pores with higher efficiency.

[0031] (2) At the crystallographic level, high pressure pressing makes the powder particles come into uniform and close contact, laying the foundation for uniform heat and material transfer. During the high-temperature sintering process, it promotes uniform nucleation and growth of grains, thereby obtaining fine grains with uniform size distribution and reducing defects caused by abnormal grain growth or insufficient sintering.

[0032] (3) In terms of electrochemical performance, the synergistic effect of this dense and uniform microstructure significantly reduces the grain boundary resistance encountered by lithium ions in bulk transport and greatly reduces the blockage of ion conduction paths by insulating pores, thereby effectively and reliably improving the ionic conductivity of sulfide solid electrolytes.

[0033] (4) In terms of process optimization, the preparation method does not require the use of organic solvents throughout the process, eliminating the risk of solvent residue and ensuring high long-term stability of the electrolyte. Furthermore, the precursor sheets obtained by high-pressure pressing are intermediates with relatively standardized shape, size, and density, which can effectively reduce the variables in the subsequent high-temperature sintering process, improve batch-to-batch consistency and reproducibility, and provide a simple and feasible path for the stable production of high-performance electrolyte sheets in industrialization.

[0034] The following description, in conjunction with the accompanying drawings, details the sulfide solid electrolyte, its preparation method, battery, and power-consuming device according to embodiments of this application.

[0035] Figure 1 For a process flow diagram of a method for preparing a sulfide solid electrolyte provided in this application embodiment, please refer to [link / reference]. Figure 1 The preparation method includes the following steps: S10: The raw materials of the sulfur-silver-germanium mineral phase sulfide solid electrolyte are mixed and ground according to the stoichiometric ratio to obtain the precursor powder.

[0036] In some embodiments, the raw materials include Li₂S, LiY, and P₂S₅, with a molar ratio of (5-2x):(2+2x):1, wherein -0.1 ≤ x ≤ 0.5, and Y is selected from at least one of F, Cl, Br, or I. As an example, the raw materials include Li₂S, LiCl, and P₂S₅, and the molar ratio of Li₂S, LiCl, and P₂S₅ can be 5:2:1, 4.6:2.4:1, etc.

[0037] The grinding method can be manual grinding in a mortar and pestle, mechanical grinding, mechanical ball milling, planetary ball milling, etc., and this application does not make specific limitations on it.

[0038] In some embodiments, the grinding method is ball milling.

[0039] Furthermore, the mixing and grinding step includes: placing the raw material in a planetary ball mill for mixing and ball milling, with a ball-to-material ratio of (10~20):1, a rotation speed of 400rpm~700rpm, and a milling time of 16h~30h. Even further, it also includes: placing the raw material in a polytetrafluoroethylene ball milling jar inside an argon glove box, loading it with zirconia pellets, and then placing it in the planetary ball mill.

[0040] As an example, the ball-to-material ratio is any one value or any two values ​​within the range of 10:1, 12:1, 15:1, 18:1, and 20:1; the rotational speed is any one value or any two values ​​within the range of 400 rpm, 500 rpm, 600 rpm, and 700 rpm; and the ball milling time is any one value or any two values ​​within the range of 16h, 20h, 24h, 28h, and 30h.

[0041] S20: Apply a pressure of 500MPa~1000MPa to the precursor powder to press it and obtain precursor flakes.

[0042] As an example, the pressure applied in the pressing step is any value or a range between any two values ​​from 500 MPa, 550 MPa, 630 MPa, 700 MPa, 800 MPa, 900 MPa, and 1000 MPa. Further, the pressure applied in the pressing step is between 800 MPa and 1000 MPa.

[0043] In some embodiments, the pressing step includes: placing the precursor powder in a mold for cold pressing, with a holding time of 5 min to 20 min.

[0044] As an example, the holding time is any value among 5 min, 8 min, 10 min, 15 min, and 20 min, or a value between any two values.

[0045] Understandably, cold pressing is carried out at room temperature and in an inert atmosphere.

[0046] In some embodiments, the thickness of the precursor sheet is 1.5 mm to 3.5 mm. As an example, the thickness of the precursor sheet is any one value or a value between any two values ​​from 1.5 mm, 2 mm, 2.5 mm, 3 mm, to 3.5 mm.

[0047] In some embodiments, the mass of the precursor powder is 200 mg to 400 mg, and the mold is cylindrical with an inner diameter of 8 mm to 12 mm. As an example, the mass of the precursor powder is any one value or a range between any two values ​​from 200 mg, 250 mg, 300 mg, 350 mg, and 400 mg; the mold is cylindrical with an inner diameter from any one value or a range between any two values ​​from 8 mm, 9 mm, 10 mm, 11 mm, and 12 mm.

[0048] S30: The precursor sheet is sintered at a temperature of 600℃~700℃ to obtain a sulfide solid electrolyte. As an example, the temperature used in the sintering step is any value or a range between any two values ​​from 600℃, 620℃, 650℃, 680℃, and 700℃. Further, the temperature used in the sintering step is 650℃ to 700℃.

[0049] In some embodiments, during the sintering step, the heating rate is 1℃ / min to 10℃ / min, and the holding time is 3h to 12h.

[0050] As an example, the heating rate is any one value or a range between any two values ​​from 1℃ / min, 3℃ / min, 5℃ / min, 8℃ / min, and 10℃ / min; the holding time is any one value or a range between any two values ​​from 3h, 5h, 8h, 10h, and 12h.

[0051] In some embodiments, the sintering step can be carried out in a tube furnace by placing the precursor sheet in a quartz tube under controlled inert atmosphere.

[0052] Secondly, this application also provides a sulfide solid electrolyte with the chemical formula Li 6-x PS 5-x Y 1+x -0.1≤x≤0.5, Y is selected from at least one of F, Cl, Br or I; the crystallite size of the sulfide solid electrolyte is 10μm~30μm, and the density is 1.6g / cm³. 3 ~1.8g / cm 3 .

[0053] Understandably, this sulfide solid electrolyte can be prepared using the preparation method described in the first aspect above. The sulfide solid electrolyte has relatively small grain size, a relatively uniform distribution, and a high density, resulting in high ionic conductivity, >2.8 mS / cm (up to 3.63 mS / cm), thus making it effectively applicable to the preparation of high-energy-density all-solid-state batteries.

[0054] Thirdly, this application also provides a battery using the above-mentioned sulfide solid electrolyte.

[0055] In some embodiments, the battery can be a solid-state battery. A solid-state battery typically includes a positive electrode, a negative electrode, and a solid electrolyte membrane disposed between the positive and negative electrodes.

[0056] Furthermore, the sulfide solid electrolyte provided in the first and second aspects of this application can be used as a raw material for solid electrolyte membranes. It is understood that the raw material may consist solely of the sulfide solid electrolyte, or it may be compounded with other solid electrolytes such as halide solid electrolytes, polymer solid electrolytes, oxide solid electrolytes, etc.

[0057] Furthermore, solid electrolyte membranes can be prepared from solid electrolytes using either dry or wet membrane fabrication methods.

[0058] The dry film-forming method is as follows: A sulfide solid electrolyte is placed in a mold and pressed into a film. The pressing method can be cold pressing or hot pressing. The pressing can be a one-step pressing or a multi-step pressing.

[0059] The wet membrane preparation method is as follows: the sulfide solid electrolyte and binder are mixed in an organic solvent and dispersed into a slurry; the slurry is coated on a glass substrate, dried, and then pressed to obtain a sulfide electrolyte membrane.

[0060] In other embodiments, the sulfide solid electrolyte can also be used as an ion-conducting additive in the positive electrode and / or negative electrode; it can also be used to prepare the interface layer between the positive electrode and the solid electrolyte membrane, and between the negative electrode and the solid electrolyte membrane.

[0061] In some embodiments, the method for preparing a solid-state battery may include the following steps: stacking and pressing a positive electrode, a solid electrolyte membrane, and a negative electrode, encapsulating and forming the solid-state battery.

[0062] Fourthly, this application also provides an electrical device using the aforementioned battery.

[0063] In some embodiments, the electrical device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. As another example, the electrical device may be a mobile phone, tablet computer, laptop computer, etc.

[0064] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0065] Example 1 This embodiment provides a sulfide solid electrolyte, the preparation method of which includes the following steps: Ball milling: In an argon-filled glove box, raw materials Li₂S, LiCl, and P₂S₅ were mixed in a molar ratio of 5:2:1 and loaded into a polytetrafluoroethylene (PTFE) ball milling jar. Zirconia pellets were then added, with a pellet-to-material ratio of 20:1. The PTFE ball milling jar was placed in a planetary ball mill for ball milling at 700 rpm / min for 16 hours to obtain precursor powder.

[0066] Pressing: In an argon glove box, 400 mg of precursor powder was placed in a cylindrical mold with an inner diameter of 10 mm. Then, a press was used to cold press the powder at room temperature with a pressure of 1000 MPa and a holding time of 10 min to obtain a precursor sheet with a diameter of 10 mm and a thickness of 3.6 mm.

[0067] Sintering: The precursor sheet was placed in a quartz tube, and after the argon atmosphere was replaced, it was placed in a tube furnace and heated to 630°C at a heating rate of 5°C / min. After holding at that temperature for 9 hours, it was cooled to room temperature with the furnace to obtain Li6PS5Cl sulfide solid electrolyte.

[0068] Example 2 This embodiment provides a sulfide solid electrolyte, the preparation method of which includes the following steps: Ball milling: In an argon-filled glove box, raw materials Li₂S, LiCl, and P₂S₅ were mixed in a molar ratio of 5:2:1 and loaded into a polytetrafluoroethylene (PTFE) ball milling jar. Zirconia pellets were then added, with a pellet-to-material ratio of 20:1. The PTFE ball milling jar was placed in a planetary ball mill for ball milling at 700 rpm / min for 16 hours to obtain precursor powder.

[0069] Pressing: In an argon glove box, 400 mg of precursor powder was placed in a cylindrical mold with an inner diameter of 10 mm. Then, a press was used to cold press the powder at room temperature with a pressure of 500 MPa and a holding time of 10 min to obtain a precursor sheet with a diameter of 10 mm and a thickness of 3.8 mm.

[0070] Sintering: The precursor sheet was placed in a quartz tube, and after the argon atmosphere was replaced, it was placed in a tube furnace and heated to 630°C at a heating rate of 5°C / min. After holding at that temperature for 9 hours, it was cooled to room temperature with the furnace to obtain Li6PS5Cl sulfide solid electrolyte.

[0071] Example 3 This embodiment provides a sulfide solid electrolyte, the preparation method of which includes the following steps: Ball milling: In an argon-filled glove box, raw materials Li₂S, LiCl, and P₂S₅ were mixed in a molar ratio of 4.6:2.4:1 and loaded into a polytetrafluoroethylene (PTFE) ball milling jar. Zirconia pellets were then added, with a pellet-to-material ratio of 20:1. The PTFE ball milling jar was placed in a planetary ball mill for ball milling at 700 rpm / min for 16 hours to obtain precursor powder.

[0072] Pressing: In an argon glove box, 400 mg of precursor powder was placed in a cylindrical mold with an inner diameter of 10 mm. Then, a press was used to cold press the powder at room temperature with a pressure of 1000 MPa and a holding time of 10 min to obtain a precursor sheet with a diameter of 10 mm and a thickness of 3.6 mm.

[0073] Sintering: The precursor sheet was placed in a quartz tube, purged with argon atmosphere, and then placed in a tube furnace. It was heated to 630℃ at a heating rate of 5℃ / min, held at that temperature for 9 hours, and then cooled to room temperature in the furnace to obtain Li. 5.8 PS 4.8 Cl 1.2 Sulfide solid electrolyte.

[0074] Example 4 This embodiment provides a sulfide solid electrolyte, the preparation method of which includes the following steps: Ball milling: In an argon-filled glove box, raw materials Li₂S, LiCl, and P₂S₅ were mixed in a molar ratio of 4.6:2.4:1 and loaded into a polytetrafluoroethylene (PTFE) ball milling jar. Zirconia pellets were then added, with a pellet-to-material ratio of 20:1. The PTFE ball milling jar was placed in a planetary ball mill for ball milling at 700 rpm / min for 16 hours to obtain precursor powder.

[0075] Pressing: In an argon glove box, 400 mg of precursor powder was placed in a cylindrical mold with an inner diameter of 10 mm. Then, a press was used to cold press the powder at room temperature with a pressure of 1000 MPa and a holding time of 10 min to obtain a precursor sheet with a diameter of 10 mm and a thickness of 3.6 mm.

[0076] Sintering: The precursor sheet was placed in a quartz tube, purged with argon atmosphere, and then placed in a tube furnace. It was heated to 650℃ at a heating rate of 5℃ / min, held at that temperature for 9 hours, and then cooled to room temperature in the furnace to obtain Li. 5.8 PS 4.8 Cl 1.2 Sulfide solid electrolyte.

[0077] Comparative Example 1 This comparative example provides a sulfide solid electrolyte, the preparation method of which includes the following steps: Ball milling: In an argon-filled glove box, raw materials Li₂S, LiCl, and P₂S₅ were mixed in a molar ratio of 5:2:1 and loaded into a polytetrafluoroethylene (PTFE) ball milling jar. Zirconia pellets were then added, with a pellet-to-material ratio of 20:1. The PTFE ball milling jar was placed in a planetary ball mill for ball milling at 700 rpm / min for 16 hours to obtain precursor powder.

[0078] Sintering: The precursor powder was placed in a quartz tube, and after the argon atmosphere was replaced, it was placed in a tube furnace and heated to 630°C at a heating rate of 5°C / min. After holding at this temperature for 9 hours, it was cooled to room temperature with the furnace to obtain Li6PS5Cl sulfide solid electrolyte.

[0079] Comparative Example 2 This comparative example provides a sulfide solid electrolyte, the preparation method of which includes the following steps: Ball milling: In an argon-filled glove box, raw materials Li₂S, LiCl, and P₂S₅ were mixed in a molar ratio of 5:2:1 and loaded into a polytetrafluoroethylene (PTFE) ball milling jar. Zirconia pellets were then added, with a pellet-to-material ratio of 20:1. The PTFE ball milling jar was placed in a planetary ball mill for ball milling at 700 rpm / min for 16 hours to obtain precursor powder.

[0080] Pressing: In an argon glove box, 400 mg of precursor powder was placed in a cylindrical mold with an inner diameter of 10 mm. Then, a press was used to cold press the powder at room temperature with a pressure of 100 MPa and a holding time of 10 min to obtain a precursor sheet with a diameter of 10 mm and a thickness of 5.0 mm.

[0081] Sintering: The precursor sheet was placed in a quartz tube, and after the argon atmosphere was replaced, it was placed in a tube furnace and heated to 630°C at a heating rate of 5°C / min. After holding at that temperature for 9 hours, it was cooled to room temperature with the furnace to obtain Li6PS5Cl sulfide solid electrolyte.

[0082] Comparative Example 3 This comparative example provides a sulfide solid electrolyte, the preparation method of which includes the following steps: Ball milling: In an argon-filled glove box, raw materials Li₂S, LiCl, and P₂S₅ were mixed in a molar ratio of 5:2:1 and loaded into a polytetrafluoroethylene (PTFE) ball milling jar. Zirconia pellets were then added, with a pellet-to-material ratio of 20:1. The PTFE ball milling jar was placed in a planetary ball mill for ball milling at 700 rpm / min for 16 hours to obtain precursor powder.

[0083] Pressing: In an argon glove box, 400 mg of precursor powder was placed in a cylindrical mold with an inner diameter of 10 mm. Then, a press was used to cold press the powder at room temperature with a pressure of 1000 MPa and a holding time of 10 min to obtain a precursor sheet with a diameter of 10 mm and a thickness of 3.6 mm.

[0084] Sintering: The precursor sheet was placed in a quartz tube, and after the argon atmosphere was replaced, it was placed in a tube furnace and heated to 550°C at a heating rate of 5°C / min. After holding at that temperature for 9 hours, it was cooled to room temperature with the furnace to obtain Li6PS5Cl sulfide solid electrolyte.

[0085] Comparative Example 4 This comparative example provides a sulfide solid electrolyte, the preparation method of which includes the following steps: Ball milling: In an argon-filled glove box, raw materials Li₂S, LiCl, and P₂S₅ were mixed in a molar ratio of 4.6:2.4:1 and loaded into a polytetrafluoroethylene (PTFE) ball milling jar. Zirconia pellets were then added, with a pellet-to-material ratio of 20:1. The PTFE ball milling jar was placed in a planetary ball mill for ball milling at 700 rpm / min for 16 hours to obtain precursor powder.

[0086] Sintering: The precursor powder was placed in a quartz tube, purged with argon atmosphere, and then placed in a tube furnace. The furnace was heated to 650°C at a heating rate of 5°C / min, held at that temperature for 9 hours, and then cooled to room temperature with the furnace to obtain Li. 5.8 PS 4.8 Cl 1.2 Sulfide solid electrolyte.

[0087] Some of the process parameters used in the preparation methods of the above embodiments and comparative examples are shown in Table 1.

[0088] Table 1. Partial preparation process parameters of sulfide solid electrolytes

[0089] Performance testing and results analysis The performance of the sulfide solid electrolytes prepared in Examples 1-4 and Comparative Examples 1-4 was tested, and the test results are shown in Table 2 and 3. Figure 2 The specific testing method is as follows: (1) Grain size distribution The electrolyte sheet prepared in Example 1 was tested by scanning electron microscopy (SEM) to obtain SEM images. The size of at least 200 grains was statistically analyzed using image processing software to obtain the grain size distribution.

[0090] (2) Density Grind and polish the sintered electrolyte sheet to ensure it is parallel from top to bottom. Measure the diameter D (cm) and thickness h (cm) using a micrometer / micrometer gauge. Weigh the mass m (g) using a precision balance. Calculate the density using the following formula: Volume: V = π × (D / 2) 2 ×h; Density: ρ = m / V.

[0091] (3) Loss on ignition After the high-pressure pressing step, the mass of the precursor sheet is weighed in the glove box and recorded as m0; after the high-temperature sintering step, the mass of the product sulfide solid electrolyte is weighed in the glove box and recorded as m1. The burn-off rate is calculated according to the following formula: Loss on ignition (%) = (m0 - m1) / m0 × 100%.

[0092] (4) Ionic conductivity The obtained electrolyte sheet was ground into powder, loaded into a mold battery, pressed into a powder cake, and the electrochemical impedance spectroscopy was tested using an electrochemical workstation with a scanning frequency of 10~100kHz and an amplitude of 10mV to obtain the electrochemical impedance spectrum. The bulk resistance R of the electrolyte can then be obtained. The ionic conductivity σ is calculated using the formula σ = L / (R×S), where L is the thickness of the solid electrolyte powder cake, R is the bulk resistance of the solid electrolyte, and S is the area of ​​the solid electrolyte powder cake.

[0093] Table 2 Performance test results of sulfide solid electrolyte

[0094] Figure 2 This is a SEM image of the sulfide solid electrolyte prepared in Example 1 of this application. Figure 1 As can be seen, the grain size is relatively uniform, with the size basically distributed between 10μm and 30μm.

[0095] As can be seen from Tables 1 and 2, compared with Comparative Examples 1 to 4, the sulfide solid electrolytes prepared in Examples 1 to 4 of this application have both higher density and lower burn-off rate, and higher ionic conductivity, with a density of 1.6 g / cm³. 3 ~1.8g / cm 3 Loss on ignition ≤3%, ionic conductivity >2.8mS / cm.

[0096] As can be seen from the comparison between Examples 1 and Examples 2 to 4, by adjusting the raw material ratio, high pressure pressing and high temperature sintering process parameters, the density can be further improved, the burn-off rate can be reduced, and the ionic conductivity can be improved.

[0097] As can be seen from Examples 1 and 1, and Examples 4 and 4, when high-temperature sintering is carried out directly without pressing, the density is significantly reduced because the gaps between the precursor powder particles are large and there are many residual pores during the sintering process, which prevents the uniform nucleation and growth of the grains. Furthermore, the high-temperature sintering causes a large amount of raw material decomposition, resulting in a significant increase in the burn-off rate. The ionic conductivity of the final product is also significantly reduced.

[0098] A comparison of Example 1 with Comparative Examples 2 and 3 shows that in Comparative Example 2, low-pressure pressing combined with high-temperature sintering resulted in significant decomposition of the raw materials and abnormal nucleation and growth of grains during high-temperature sintering, leading to a marked decrease in product density, a significant increase in burn-off rate, and a significant decrease in ionic conductivity. In Comparative Example 3, high-pressure pressing combined with low-temperature sintering resulted in high density, which only achieved physical densification of particles and could not achieve chemical and metallurgical bonding. During low-temperature sintering, effective chemical bonding between particles was impossible, resulting in numerous gaps at grain boundaries and high grain boundary resistance. Furthermore, defects introduced during ball milling and high-pressure pressing could not be effectively eliminated, leading to a decrease in product density and a significant decrease in ionic conductivity.

[0099] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for preparing a sulfide solid electrolyte, characterized in that, Includes the following steps: The raw materials of the sulfide solid electrolyte of silver-germanium sulfide phase were mixed and ground according to the stoichiometric ratio to obtain the precursor powder. The precursor powder is pressed under a pressure of 500 MPa to 1000 MPa to obtain precursor flakes; The precursor sheet is sintered at a temperature of 600℃~700℃ to obtain a sulfide solid electrolyte.

2. The preparation method according to claim 1, characterized in that, The pressing step includes: placing the precursor powder in a mold for cold pressing, with a holding time of 5 min to 20 min.

3. The preparation method according to claim 1, characterized in that, In the sintering step, the heating rate is 1℃ / min to 10℃ / min, and the holding time is 3h to 12h.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The thickness of the precursor sheet is 1.5mm to 3.5mm; The precursor powder has a mass of 200mg to 400mg, and the mold is cylindrical with an inner diameter of 8mm to 12mm.

5. The preparation method according to claim 1, characterized in that, The pressure applied in the pressing step is 800MPa~1000MPa; And / or, the temperature of the sintering step is 600℃~650℃.

6. The preparation method according to claim 1, characterized in that, The raw materials include Li2S, LiY and P2S5, and the molar ratio of Li2S, LiY and P2S5 is (5-2x):(2+2x):1, wherein -0.1≤x≤0.5, and Y is selected from at least one of F, Cl, Br or I.

7. The preparation method according to claim 1, characterized in that, The mixing and grinding step includes: placing the raw material in a planetary ball mill for mixing and grinding, with a ball-to-material ratio of (10~20):1, a rotation speed of 400rpm~700rpm, and a grinding time of 16h~30h.

8. A sulfide solid electrolyte, characterized in that, The chemical formula of the sulfide solid electrolyte is Li 6-x PS 5- x Y 1+x -0.1≤x≤0.5, Y is selected from at least one of F, Cl, Br or I; The sulfide solid electrolyte has a grain size of 10 μm to 30 μm and a density of 1.6 g / cm³. 3 ~1.8g / cm 3 .

9. A battery, characterized in that, It includes the sulfide solid electrolyte prepared by the preparation method according to any one of claims 1 to 7, or includes the sulfide solid electrolyte according to claim 8.

10. An electrical device, characterized in that, Includes the battery as described in claim 9.

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