Lithium argyrodite sulfide solid electrolyte, preparation method thereof and all-solid-state battery

Abstract

The invention discloses a lithium argyrodite sulfide solid electrolyte, a preparation method thereof and an all-solid-state battery, the chemical general formula of the electrolyte is Li7-xPS6-xMx, and the electrolyte is prepared from Li2S, LiM and excessively added P4Sy, wherein M represents halogen, 0 < = x < = 2, and y < = 10. The preparation method comprises the following steps: mixing Li2S, LiM and partially excessive P4Sy according to the stoichiometric ratio of the chemical general formula to obtain a precursor; and then preheating a container added with the residual excessive P4Sy, placing the precursor in the container, and sintering under a sealed condition to obtain the composite material. According to the method, excessive phosphorus sulfide is taken as a preparation raw material, the sealed crucible filled with the phosphorus sulfide is preheated, the ultra-high-purity lithium argyrodite sulfide solid electrolyte can be efficiently and stably synthesized, the conductivity of the electrolyte can reach 2.92 mS cm <-1 >, and the electrolyte is applied to an all-solid-state battery system.

Description

Technical Field

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

[0002] With the rapid development of emerging technologies such as new energy vehicles and drones, consumer demand for power batteries has continued to grow year after year. Currently, lithium-ion batteries account for over 99% of China's installed power battery capacity and are expected to maintain a substantial share of the domestic power battery market for a long time. The increasing demand for energy storage requires lithium-ion batteries with improved safety and higher energy density. Using non-flammable solid electrolytes instead of liquid electrolytes to assemble all-solid-state lithium-ion batteries can significantly improve battery safety and energy density, making them the most promising solution for power battery innovation.

[0003] Based on the type of material, solid electrolytes can be mainly divided into polymer electrolytes, oxide electrolytes, halide electrolytes, and sulfide electrolytes. Among them, lithium argyrodite sulfide solid electrolytes have high ionic conductivity comparable to liquid electrolytes and high ductility that is easy to process, making them the most promising solid electrolyte candidate. Currently, lithium argyrodite sulfide solid electrolytes are mainly synthesized using a high-temperature solid-phase method. The prepared electrolytes have considerable ionic conductivity, but most of the electrolytes prepared so far have technical problems such as low purity and poor stability.

[0004] Therefore, how to stably burn out high-purity, high-ionic conductivity lithium-silver-germanium sulfide solid electrolytes has always been a pain point in the industry, and existing technologies urgently need to be improved. Summary of the Invention

[0005] The present invention aims to address the low purity, poor consistency, and unstable ionic conductivity of lithium argyrodite sulfide solid electrolytes prepared by a high-temperature solid-phase process. To this end, the present invention provides a lithium argyrodite sulfide solid electrolyte, a preparation method, and an all-solid-state battery.

[0006] In order to solve the above technical problems, the first aspect of the present invention provides a lithium argyrodite sulfide solid electrolyte, the chemical formula of which is Li 7-x PS 6-x M x The raw materials for preparing the lithium argyrodite sulfide solid electrolyte include Li2S, LiM and excessively added P4S y ; Wherein: M represents halogen, 0≤x≤2, y≤10.

[0007] Specifically, since phosphorus sulfide has a melting point of 288°C and a boiling point of 514°C, it is easily volatilized by heat during the sintering stage, while Li2S and LiM raw materials remain stable at the sintering temperature (see Figure 1 ). Therefore, excessive P4S is added during the preparation process. y It can effectively replenish the phosphorus sulfide raw materials that volatilize due to heat, help inhibit the formation of lithium sulfide and lithium halide raw material phases and other impurity phases in the lithium argyrotechnical sulfide solid electrolyte product, and thus obtain a lithium argyrotechnical sulfide solid electrolyte with a purer phase.

[0008] In some embodiments of the present invention, M is selected from at least one of Cl, Br, and I. For different target lithium argyrodite sulfide solid electrolytes, M can be selected from one or more of Cl, Br, and I, and the raw material LiM is the corresponding lithium halide.

[0009] In some embodiments of the present invention, the P4S y The excess addition amount is 0.2-15wt% of the total mass of the raw materials.

[0010] In some embodiments of the present invention, when an excess of P4S is added 10 (ie P2S5), the excess amount of P2S5 added is 1-7wt% of the total mass of the raw materials.

[0011] A second aspect of the present invention provides a method for preparing the above-mentioned lithium argyrodite sulfide solid electrolyte, comprising the following steps:

[0012] (1) According to the chemical formula Li 7-x PS 6-x M x The stoichiometric ratio of Li2S, LiM and a part of excess P4S y Mixing to obtain a precursor;

[0013] (2) Adding excess P4S y After the container is preheated, the precursor is added and sintered under sealed conditions to obtain the lithium argyrodite sulfide solid electrolyte.

[0014] In some embodiments of the present invention, in step (1), the amount of Li2S and LiM is the same as the chemical formula Li 7-x PS 6-x M x The stoichiometric ratio is the same as that of P4S y The amount of P4S is added in excess according to the total mass of the raw materials prepared based on the stoichiometric ratio. y The excess amount of P4S added is equal to the amount of P4S in the container in step (2). yThe total amount of excess addition is 0.2-15wt% of the total mass of the raw materials.

[0015] In some embodiments of the present invention, in step (1), the mixing method is high-speed cutting at a rotation speed of 20,000-30,000 rpm for 2.5-15 min.

[0016] In some embodiments of the present invention, the high-speed cutting is performed in a high-speed cutting machine, and the volume of the raw materials fed into the high-speed cutting machine during mixing occupies one third to one half of the cutting machine cavity.

[0017] Specifically, the high-speed cutting is performed in a high-speed cutting machine. Excessive raw material powder mass cut in one go can cause the high-speed cutting machine to overheat. Excessively high operating temperatures during cutting can easily damage the raw material powder, leading to the formation of more impurity phases in the sintered lithium argyrodite sulfide solid electrolyte, thereby reducing its room-temperature ionic conductivity. Furthermore, because excessively long single cutting times can cause the high-speed cutting machine to overheat, a "short-time, multiple-pass" mixing process is preferred to help achieve uniform mixing of the raw materials. Furthermore, a considerable amount of raw material can adhere to the blades and inner walls of the high-speed cutting machine, hindering uniform mixing. For large-scale batch preparation, the uniformity of the precursor does not significantly affect the physical properties of the product. However, for small-scale preparation and trace doping experiments, the product may deviate significantly from the target electrolyte. Preferably, during small-scale preparation and trace doping experiments, the raw material on the blades and inner walls of the machine chamber should be scraped off at regular intervals before cutting. This operation should be repeated multiple times to ensure a uniformly mixed precursor powder.

[0018] In some embodiments of the present invention, in step (2), the container is selected from any one of a quartz tube, a quartz crucible, an alumina crucible, a graphite crucible, a boron nitride crucible, and a platinum crucible.

[0019] Specifically, because phosphorus sulfide raw materials are easily volatile when heated, the present invention places the precursor powder in a well-sealed container for sintering to prevent the phosphorus sulfide from volatilizing and escaping. If a poorly sealed container is used during sintering, a considerable portion of the phosphorus sulfide will volatilize and escape due to heat, resulting in a lithium argyrodite sulfide solid electrolyte of poor purity and the presence of a large number of impurities.

[0020] In some embodiments of the present invention, the container is selected from an alumina crucible with a threaded lid. The alumina crucible with a threaded lid has good sealing performance and can effectively prevent gaseous phosphorus sulfide from escaping from the crucible. As the gaseous phosphorus sulfide inside the crucible gradually becomes saturated, the phosphorus sulfide stops volatilizing, which will avoid composition deviation caused by the loss of a single raw material.

[0021] In some embodiments of the present invention, in step (2), the preheat treatment system is as follows: heating to 200-300°C at a rate of 1-10°C / min, holding for 2-3 hours, and cooling. For example, the temperature can be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, etc., including but not limited to the values ​​listed above. At the same time, other values ​​not listed within the numerical range are also applicable; after the holding period is completed, the furnace is opened for rapid cooling.

[0022] In some embodiments of the present invention, in step (2), the remaining excess P4S added to the container y The amount is 0.5-5wt% of the total mass of the raw materials.

[0023] In some embodiments of the present invention, in step (2), the sintering temperature regime is: heating to 460-550°C at a rate of 1-5°C / min, holding for 4-16 hours, and cooling. For example, the temperature may be 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, etc., and the holding time may be 4 hours, 6 hours, 8 hours, 10 hours, 16 hours, etc., including but not limited to the listed values. At the same time, other values ​​not listed within the numerical range are also applicable. The heating rate does not significantly affect the physical phase and ionic conductivity of the lithium argyrodite sulfide solid electrolyte, and is generally suitable within the heating rate range of 1-5°C / min.

[0024] In some embodiments of the present invention, both step (1) and step (2) are performed under the condition that the water oxygen content is less than 3 ppm.

[0025] Specifically, due to Li2S, P4S y Both the raw materials and the lithium argyrodite sulfide solid electrolyte will react with water and deteriorate to generate toxic H2S gas. Therefore, all preparation processes of the present invention are carried out under an environment with strictly controlled water and oxygen content.

[0026] A third aspect of the present invention provides an all-solid-state battery, comprising the above-mentioned lithium argyrodite sulfide solid electrolyte, or comprising the lithium argyrodite sulfide solid electrolyte prepared by the above-mentioned preparation method.

[0027] Compared with the prior art, the above technical solution of the present invention has at least the following technical effects or advantages:

[0028] (1) The lithium argyrotechnical sulfide solid electrolyte of the present invention uses excess phosphorus sulfide as a preparation raw material, which effectively replenishes the phosphorus sulfide raw material that volatilizes and decomposes during the temperature-raising sintering process, thereby suppressing the generation of impurities during the temperature-raising sintering process, improving the purity and consistency of the lithium argyrotechnical sulfide solid electrolyte, and further improving the ionic conductivity, which can meet the product quality requirements in large-scale production applications.

[0029] (2) During the preparation of the lithium argyrodite sulfide solid electrolyte of the present invention, by preheating the container to which phosphorus sulfide is added, supersaturated phosphorus sulfide vapor can be provided in the inner cavity of the container during the sintering stage, thereby effectively suppressing the escape of the phosphorus sulfide raw material at high temperature and avoiding the deviation of the electrolyte composition caused by the loss of a single raw material.

[0030] (3) The lithium argyrodite sulfide solid electrolyte of the present invention has high purity and high ionic conductivity (up to 2.92mS cm -1 ) characteristics, and applied it to all-solid-state batteries, with excellent cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a comparison chart of high temperature stability tests of raw materials Li2S, LiCl and P2S5;

[0032] Figure 2 XRD patterns of the lithium argyrodite sulfide solid electrolytes prepared in Examples 1-4 and Comparative Examples 1-3;

[0033] Figure 3 The electrochemical impedance and ionic conductivity of the lithium argyrodite sulfide solid electrolyte prepared in Examples 1-4 and Comparative Examples 1-3;

[0034] Figure 4 This is a microstructure diagram of the lithium argyrodite sulfide solid electrolyte prepared in Example 2;

[0035] Figure 5 This is a performance test diagram of an all-solid-state battery assembled with the lithium argyrodite sulfide solid electrolyte prepared in Example 2. DETAILED DESCRIPTION

[0036] The present invention is described in detail below with reference to the examples to facilitate understanding of the present invention by those skilled in the art. It is necessary to point out that the examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above-mentioned invention should still fall within the scope of protection of the present invention. At the same time, the raw materials mentioned below that are not described in detail are all commercially available products; the process steps or preparation methods that are not mentioned in detail are all process steps or preparation methods known to those skilled in the art.

[0037] Example 1

[0038] A method for preparing a lithium argyrodite sulfide solid electrolyte comprises the following steps:

[0039] (1) According to the stoichiometric ratio of the general chemical formula Li6PS5Cl, 1.40 g of Li2S2, 7.90 g of LiCl, and 20.95 g of P2S5 (including 20.70 g according to the stoichiometric ratio and 0.25 g of excess 0.5 wt%) were weighed and placed in a high-speed cutting machine. The high-speed cutting process was performed at a speed of 20,000 rpm for 2.5 minutes to obtain a uniformly mixed precursor powder.

[0040] (2) An alumina crucible with a screw lid and 0.25 g of P2S5 with a remaining excess of 0.5 wt% was preheated (heated to 300° C. at a rate of 5° C. / min, kept warm for 2 hours, and then cooled rapidly in the furnace). Then, the precursor powder obtained in step (1) was placed in the preheated alumina crucible and sintered (heated to 490° C. at a rate of 5° C. / min, kept warm for 16 hours, and then cooled in the furnace). The powder was ground and passed through a 200-mesh sieve to obtain the lithium argyrodite sulfide solid electrolyte of this embodiment, which was recorded as LPSC-1-A.

[0041] Both step (1) and step (2) are carried out in a glove box with a water and oxygen content of less than 3 ppm.

[0042] Example 2

[0043] A method for preparing a lithium argyrodite sulfide solid electrolyte comprises the following steps:

[0044] (1) According to the stoichiometric ratio of the general chemical formula Li6PS5Cl, 1.40 g of Li2S2, 7.90 g of LiCl, and 21.45 g of P2S5 (including 20.70 g according to the stoichiometric ratio and 0.75 g of an excess of 1.5 wt%) were weighed and placed in a high-speed cutting machine. The high-speed cutting process was performed at a speed of 20,000 rpm for 2.5 minutes to obtain a uniformly mixed precursor powder.

[0045] (2) An alumina crucible with a screw lid and 0.25 g of P2S5 with a remaining excess of 0.5 wt% was preheated (heated to 300° C. at a rate of 5° C. / min, kept warm for 2 hours, and then cooled rapidly in the furnace). Then, the precursor powder obtained in step (1) was placed in the preheated alumina crucible and sintered (heated to 490° C. at a rate of 5° C. / min, kept warm for 16 hours, and then cooled in the furnace). The powder was ground and passed through a 200-mesh sieve to obtain the lithium argyrodite sulfide solid electrolyte of this embodiment, which was recorded as LPSC-2-A.

[0046] Both step (1) and step (2) are carried out in a glove box with a water and oxygen content of less than 3 ppm.

[0047] Example 3

[0048] A method for preparing a lithium argyrodite sulfide solid electrolyte comprises the following steps:

[0049] (1) According to the stoichiometric ratio of the general chemical formula Li6PS5Cl, 1.40 g of Li2S2, 7.90 g of LiCl, and 22.95 g of P2S5 (including 20.70 g according to the stoichiometric ratio and 2.25 g of excess 4.5 wt%) were weighed and placed in a high-speed cutting machine. The high-speed cutting process was performed at a speed of 20,000 rpm for 2.5 minutes to obtain a uniformly mixed precursor powder.

[0050] (2) An alumina crucible with a screw lid and 0.25 g of P2S5 with a remaining excess of 0.5 wt% was preheated (heated to 300° C. at a rate of 5° C. / min, kept warm for 2 hours, and then cooled rapidly in the furnace). Then, the precursor powder obtained in step (1) was placed in the preheated alumina crucible and sintered (heated to 490° C. at a rate of 5° C. / min, kept warm for 16 hours, and then cooled in the furnace). The powder was ground and passed through a 200-mesh sieve to obtain the lithium argyrodite sulfide solid electrolyte of this embodiment, which was recorded as LPSC-5-A.

[0051] Both step (1) and step (2) are carried out in a glove box with a water and oxygen content of less than 3 ppm.

[0052] Example 4

[0053] A method for preparing a lithium argyrodite sulfide solid electrolyte comprises the following steps:

[0054] (1) According to the stoichiometric ratio of the general chemical formula Li6PS5Cl, 1.40 g of Li2S2, 7.90 g of LiCl, and 23.95 g of P2S5 (including 20.70 g according to the stoichiometric ratio and 3.25 g of excess 6.5 wt%) were weighed and placed in a high-speed cutting machine. The high-speed cutting process was performed at a speed of 20,000 rpm for 2.5 minutes to obtain a uniformly mixed precursor powder.

[0055] (2) An alumina crucible with a screw lid and 0.25 g of P2S5 with a remaining excess of 0.5 wt% was preheated (heated to 300° C. at a rate of 5° C. / min, kept warm for 2 hours, and then cooled rapidly in the furnace). Then, the precursor powder obtained in step (1) was placed in the preheated alumina crucible and sintered (heated to 490° C. at a rate of 5° C. / min, kept warm for 16 hours, and then cooled in the furnace). The powder was ground and passed through a 200-mesh sieve to obtain the lithium argyrodite sulfide solid electrolyte of this embodiment, which was recorded as LPSC-7-A.

[0056] Both step (1) and step (2) are carried out in a glove box with a water and oxygen content of less than 3 ppm.

[0057] Comparative Example 1

[0058] A method for preparing a lithium argyrodite sulfide solid electrolyte comprises the following steps:

[0059] (1) Li2S2 1.40 g, LiCl 7.90 g, and P2S5 20.70 g were weighed in a stoichiometric ratio according to the general chemical formula Li6PS5Cl. The raw materials were placed in a high-speed cutting machine and subjected to high-speed cutting at a speed of 20,000 rpm for 2.5 minutes to obtain a uniformly mixed precursor powder.

[0060] (2) The alumina crucible with a screw lid was preheated (heated to 300°C at a rate of 5°C / min, kept warm for 2 hours, and then cooled rapidly in the furnace). The precursor powder obtained in step (1) was then placed in the preheated alumina crucible and sintered (heated to 490°C at a rate of 5°C / min, kept warm for 16 hours, and then cooled in the furnace). The powder was ground and passed through a 200-mesh sieve to obtain the lithium argyrodite sulfide solid electrolyte of this comparative example, which was recorded as LPSC-0-A.

[0061] Both step (1) and step (2) are carried out in a glove box with a water and oxygen content of less than 3 ppm.

[0062] Comparative Example 2

[0063] A method for preparing a lithium argyrodite sulfide solid electrolyte comprises the following steps:

[0064] (1) According to the stoichiometric ratio of the general chemical formula Li6PS5Cl, 1.40 g of Li2S2, 7.90 g of LiCl, and 21.45 g of LiCl (including 20.70 g according to the stoichiometric ratio and 0.75 g of excess 1.5 wt%) were weighed. The above raw materials were placed in a high-speed cutting machine and subjected to high-speed cutting treatment at a speed of 20,000 rpm for 2.5 minutes to obtain a uniformly mixed precursor powder.

[0065] (2) A quartz crucible without a screw cap to which 0.25 g of P2S5 with a remaining excess of 0.5 wt% was added was preheated (heated to 300°C at a heating rate of 5°C / min, kept warm for 2 hours, and then cooled in the furnace). Then, the precursor powder prepared in step (1) was placed in the preheated quartz crucible and sintered (heated to 490°C at a heating rate of 5°C / min, kept warm for 16 hours, and then cooled in the furnace). The powder was ground and passed through a 200-mesh sieve to obtain the lithium argyrodite sulfide solid electrolyte of this comparative example, which was recorded as LPSC-2-Q.

[0066] Both step (1) and step (2) are carried out in a glove box with a water and oxygen content of less than 3 ppm.

[0067] Comparative Example 3

[0068] A method for preparing a lithium argyrodite sulfide solid electrolyte comprises the following steps:

[0069] (1) Li2S2 1.40 g, LiCl 7.90 g, and P2S5 21.70 g (including 20.70 g according to the stoichiometric ratio and 1.00 g of excess 2 wt%) were weighed according to the stoichiometric ratio of the general chemical formula Li6PS5Cl. The above raw materials were placed in a high-speed cutting machine and subjected to high-speed cutting treatment at a speed of 20,000 rpm for 2.5 minutes to obtain a uniformly mixed precursor powder.

[0070] (2) The precursor powder prepared in step (1) was placed in an alumina crucible with a screw cap and sintered (heated to 490° C. at a heating rate of 5° C. / min, kept warm for 16 hours, and then cooled in the furnace), ground, and passed through a 200-mesh sieve to obtain the lithium argyrodite sulfide solid electrolyte of this comparative example, which was recorded as LPSC-2-A′.

[0071] Both step (1) and step (2) are carried out in a glove box with a water and oxygen content of less than 3 ppm.

[0072] Performance Testing

[0073] 1.XRD analysis

[0074] The lithium argyrodextrin sulfide solid electrolyte samples prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to X-ray diffraction (XRD) tests. Figure 2 As shown in the figure, the horizontal axis 2Theta represents the 2θ diffraction angle, and the vertical axis Intensity represents the intensity of the diffraction peak. Figure 2 As can be seen, compared to the sample LPSC-0-A in Comparative Example 1, which did not contain excess P2S5, the phase purity of the Li6PS5Cl electrolyte was effectively improved by sintering with varying proportions of excess P2S5 in Examples 1-4. Specifically, the sample LPSC-2-A in Example 2, which contained 2 wt% excess P2S5, exhibited high purity, with no observed diffraction peaks associated with the raw material or impurity phases. Compared to the sample LPSC-2-A in Example 2, which was sintered using a pretreated sealed alumina crucible with a threaded lid, the sample LPSC-2-Q in Comparative Example 2, which was sintered using a pretreated quartz crucible without a screw lid, contained more impurities and exhibited lower purity. The sample LPSC-2-A' in Comparative Example 3, which was sintered using a threaded alumina crucible without preheat treatment, also contained significant impurity phases.

[0075] 2. Ionic conductivity

[0076] The electrochemical impedance and ionic conductivity tests of the lithium argyrodite sulfide solid electrolyte samples prepared in Examples 1-4 and Comparative Examples 1-3 were performed. Figure 3 As shown, Figure 3 a is the electrochemical impedance spectroscopy, Figure 3 b is the relationship between the excess content of P2S5 and its corresponding ionic conductivity. Figure 3 As can be seen from b, Examples 1-4 all have higher ionic conductivity due to the addition of excess P2S5, among which the ionic conductivity of sample LPSC-2-A (Example 2) is the highest, reaching 2.92 mS cm -1 , which is significantly higher than the ionic conductivity of the sample of Comparative Example 2 using a pretreated quartz crucible without a screw cap and the sample of Comparative Example 3 which is not preheated (unprocessed).

[0077] 3. Microstructure

[0078] Figure 4 The microstructure of the lithium argyrodite sulfide solid electrolyte sample LPSC-2-A prepared in Example 2 is shown in FIG. Figure 4 It can be observed that the electrolyte particles are intact, the particle size is maintained at the micron level, the average particle size is small, and the crystallinity is good.

[0079] 4. Electrochemical performance

[0080] The lithium argyrodite sulfide solid electrolyte sample Li6PS5Cl-2-A prepared in Example 2 above was used as the electrolyte, LiNbO3-coated NCM811 was used as the positive electrode, and Li-In alloy negative electrode was assembled into an all-solid-state battery for charge and discharge capacity testing.

[0081] The results are as follows Figure 5 As shown, Figure 5 The horizontal axis Specific Capacity represents the discharge capacity, and the vertical axis Voltage represents the voltage. Figure 5 It can be seen that after the all-solid-state battery was activated at a current of 0.1C for 5 weeks, it continued to undergo cycle testing at a current density of 0.5C, and the coulombic efficiency of the first cycle could reach 75.5%; after 10 and 30 weeks of cycling, the discharge specific capacity of the battery was 210mAh / g and 195mAh / g, respectively, showing good capacity reversibility.

[0082] In summary, the present invention provides a lithium argyrodite sulfide solid electrolyte, a preparation method thereof, and an all-solid-state battery. This preparation method involves weighing lithium sulfide, lithium halide, and an excess of phosphorus sulfide according to the stoichiometric ratio of the lithium argyrodite sulfide solid electrolyte. The phosphorus sulfide raw material is added in excess, and a uniformly mixed precursor powder is obtained by high-speed cutting. The mixture is then sintered in a preheated sealed crucible as a sintering vessel at a temperature of 460-550°C for 4-16 hours to obtain the lithium argyrodite sulfide solid electrolyte. By adding an excess of phosphorus sulfide raw material during the high-speed cutting of the raw material to prepare the precursor powder, the phosphorus sulfide raw material that volatilizes and decomposes during the elevated temperature sintering process is effectively replenished, thereby suppressing the formation of impurities during the elevated temperature sintering process. By preheating the sealed crucible containing phosphorus sulfide, the supersaturated phosphorus sulfide vapor in the crucible cavity during the electrolyte sintering stage effectively suppresses the escape of the phosphorus sulfide raw material at high temperatures, thereby avoiding electrolyte composition deviations caused by the loss of a single raw material. This preparation method can efficiently and stably synthesize ultra-high-purity lithium argyrodite sulfide solid electrolytes. The prepared electrolyte has a conductivity of nearly 3mS cm at room temperature. -1 . Using the preparation method provided by the present invention, the prepared lithium argyrodite sulfide solid electrolyte, LiNbO3-coated NCM811 positive electrode, and Li-In alloy negative electrode are used to assemble an all-solid-state battery, showing good capacity reversibility, proving that the lithium argyrodite sulfide solid electrolyte prepared by the present invention can be well applied to the all-solid-state battery system.

[0083] For those skilled in the art to which the present invention belongs, a number of simple deductions or substitutions can be made without departing from the concept of the present invention, without having to resort to creative work. Therefore, based on the disclosure of the present invention, simple improvements made by those skilled in the art to the present invention should be within the scope of protection of the present invention. The above embodiments are preferred embodiments of the present invention, and all processes similar to the present invention and equivalent changes made should fall within the scope of protection of the present invention.

Claims

1. A lithium argyrodite sulfide solid electrolyte, characterized in that: Its chemical formula is Li 7-x PS 6-x M x The raw materials for preparing the lithium argyrodite sulfide solid electrolyte include Li2S, LiM and excessively added P4S y ; Wherein: M represents halogen, 0≤x≤2, y≤10.

2. The lithium argyrodite sulfide solid electrolyte according to claim 1, characterized in that The M is selected from at least one of Cl, Br, and I.

3. The lithium argyrodite sulfide solid electrolyte according to claim 1 or 2, characterized in that: The P4S y The excess addition amount is 0.2-15wt% of the total mass of the raw materials.

4. A method for preparing the lithium argyrodite sulfide solid electrolyte according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) According to the chemical formula Li 7-x PS 6-x M x The stoichiometric ratio of Li2S, LiM and a part of excess P4S y Mixing to obtain a precursor; (2) Adding excess P4S y After the container is preheated, the precursor is added and sintered under sealed conditions to obtain the lithium argyrodite sulfide solid electrolyte.

5. The method for preparing the lithium argyrodite sulfide solid electrolyte according to claim 4, characterized in that: In step (2), the container is selected from any one of a quartz tube, a quartz crucible, an alumina crucible, a graphite crucible, a boron nitride crucible, and a platinum crucible.

6. The method for preparing the lithium argyrodite sulfide solid electrolyte according to claim 4, characterized in that: In step (2), the temperature regime of the preheating treatment is: heating to 200-300°C at a rate of 1-10°C / min, keeping the temperature for 2-3 hours, and cooling; and / or, the remaining excess P4S added to the container y The amount is 0.5-5wt% of the total mass of the raw materials.

7. The method for preparing the lithium argyrodite sulfide solid electrolyte according to claim 4, characterized in that: In step (2), the sintering temperature regime is: heating to 460-550°C at a rate of 1-5°C / min, keeping the temperature for 4-16 hours, and cooling.

8. The method for preparing the lithium argyrodite sulfide solid electrolyte according to claim 4, characterized in that: In step (1), the mixing method is high-speed cutting at a rotation speed of 20,000-30,000 rpm for 2.5-15 min.

9. The method for preparing lithium argyrodite sulfide solid electrolyte according to claim 4, characterized in that: Both step (1) and step (2) are carried out under the condition that the water oxygen content is less than 3 ppm.

10. An all-solid-state battery, characterized in that: The invention comprises the lithium argyrodite sulfide solid electrolyte as described in any one of claims 1 to 3, or the lithium argyrodite sulfide solid electrolyte prepared by the preparation method as described in any one of claims 4 to 9.

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