Solid-state electrolyte and preparation method and application thereof

Abstract

The application provides a solid-state electrolyte and a preparation method and application thereof. The solid-state electrolyte comprises at least: electrolyte particles; a first coating layer, which coats the electrolyte particles, and the material of the first coating layer comprises fluorides; and a second coating layer, which coats the first coating layer, and the material of the second coating layer comprises non-metallic elements, and the non-metallic elements comprise at least one of sulfur elements, iodine elements, phosphorus elements and selenium elements. The solid-state electrolyte and the preparation method and application thereof can improve solid-solid contact between solid-state particles in a battery and improve the stability of the solid-state electrolyte to positive and negative electrodes.

Description

Technical Field

[0001] This invention relates to the field of power battery technology, specifically to a solid electrolyte, its preparation method, and its application. Background Technology

[0002] In all-solid-state batteries, sulfide electrolytes possess advantages such as ultra-high room-temperature ionic conductivity and good mechanical processability, making them one of the most commercially promising solid-state electrolytes and leading to their widespread application. However, in practical applications, sulfide electrolytes have a narrow electrochemical window, slow ion transport rates at the solid-solid interface, and poor stability to both positive and negative electrodes, thus limiting the further development and application of these batteries. Summary of the Invention

[0003] This invention proposes a solid electrolyte, its preparation method, and its application, which can improve the solid-solid contact between solid particles in the battery and enhance the stability of the solid electrolyte to the positive and negative electrodes.

[0004] To address the aforementioned technical problems, the present invention provides a solid electrolyte, comprising at least:

[0005] Electrolyte particles; A first coating layer covers the electrolyte particles, and the material of the first coating layer includes fluoride; and The second coating layer covers the first coating layer, and the material of the second coating layer includes a non-metallic element, which includes at least one of sulfur, iodine, phosphorus and selenium.

[0006] In one embodiment of the present invention, the particle size of the solid electrolyte satisfies D50≤0.5μm, D90≤1μm; and / or the material of the electrolyte particles includes a sulfide solid electrolyte, wherein the sulfide electrolyte includes Li7P3S. 11 β-Li3PS4, Li 10 GeP2S 12 , Li6PS5Cl, Li6PS5Br, Li7P2S8I, Li4PS4I, Li6PS5Cl x Br 1-x Li6PS5Cl y I 1-y and Li6PS5Br z I 1-z At least one of the following, wherein 0≤x≤1, 0≤y≤1, and 0≤z≤1.

[0007] In one embodiment of the present invention, the fluoride includes a fluorinated lithium salt, which includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bisfluorosulfonylimide, lithium difluorooxalateborate, lithium trifluoromethanesulfonylimide, lithium trifluorophosphorylimide, lithium hexafluorophosphate, and lithium tetrafluoroborate.

[0008] In one embodiment of the present invention, the thickness of the first coating layer is 1nm-500nm, and the thickness of the second coating layer is 1nm-500nm.

[0009] The present invention also provides a method for preparing a solid electrolyte as described above, characterized in that it includes at least the following steps: The fluoride is dissolved in a first solvent to obtain a fluoride solution; The fluoride solution and electrolyte particles are added to a second solvent to obtain an electrolyte slurry; The electrolyte slurry is refined and then dried to obtain an intermediate; and The intermediate is mixed with a non-metallic element and then sintered to obtain a solid electrolyte.

[0010] In one embodiment of the present invention, the first solvent includes at least one selected from dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethylene carbonate, dichloromethane, chloroform, n-butyl ether, anisole, cyclopentyl methyl ether, isobutyl isobutyrate, butyl formate, and ethyl hexanoate, and / or the second solvent includes at least one selected from isopentane, n-pentane, cyclohexane, isooctane, cyclopentane, n-hexane, n-heptane, tetrahydrofuran, toluene, xylene, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethylene carbonate, dichloromethane, chloroform, n-butyl ether, anisole, cyclopentyl methyl ether, isobutyl isobutyrate, butyl formate, and ethyl hexanoate.

[0011] In one embodiment of the present invention, in the electrolyte slurry, the mass ratio of the fluoride to the electrolyte particles is (0.0001-0.2):1, and / or, when refining the electrolyte slurry, at least one of the following treatment methods is used: ball milling, sand milling, high-speed homogenizer treatment, or ultrasonic treatment.

[0012] In one embodiment of the present invention, the electrolyte slurry is dried by at least one of vacuum drying, spray drying, fluidized bed drying or freeze drying, with a drying temperature of 60°C-200°C and a drying time of 0.1h-24h.

[0013] In one embodiment of the present invention, in the solid electrolyte, the mass ratio of the non-metallic element to the electrolyte particles is (0.0001-0.2):1, and / or the sintering temperature is 200°C-400°C, and the sintering time is 0.5h-5h.

[0014] The present invention also provides an all-solid-state battery, characterized in that it comprises at least: Positive electrode sheet; Negative electrode sheet; and A solid electrolyte membrane is disposed between the positive electrode and the negative electrode, and the solid electrolyte membrane contains the solid electrolyte described above, or the solid electrolyte is obtained according to the preparation method described above.

[0015] In summary, this invention proposes a solid electrolyte, its preparation method, and its application, which can improve the stability of the solid electrolyte to both the positive and negative electrodes, thereby enabling stable cycling of the all-solid-state battery without short-circuit phenomena. Furthermore, the solid electrolyte, its preparation method, and its application proposed in this invention can reduce the particle size of the solid electrolyte, effectively improving the solid-solid contact between solid particles in the battery, thereby increasing the ion transport rate at the solid-solid interface. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the solid electrolyte in this invention.

[0018] Figure 2 This is a scanning electron microscope characterization image of the solid electrolyte in Example 1.

[0019] Figure 3 The graph shows the charge-discharge cycle test results of the all-solid-state battery in Example 1 at different current densities.

[0020] Label Explanation: 10. Electrolyte particles; 11. First coating layer; 12. Second coating layer. Detailed Implementation

[0021] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0022] It should be understood that the invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0023] The technical solution of the present invention will be further described in detail below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a solid electrolyte, comprising at least electrolyte particles 10, a first coating layer 11, and a second coating layer 12. The first coating layer 11 coats the electrolyte particles 10, and the material of the first coating layer 11 includes a fluoride. The second coating layer 12 coats the first coating layer 11, and the material of the second coating layer 12 includes a non-metallic element, including at least one of sulfur, iodine, phosphorus, and selenium. In the solid electrolyte provided by this invention, on the positive electrode side, the first coating layer 11 can decompose in situ into a lithium fluoride interface layer, thereby effectively mitigating the interfacial side reactions between the solid electrolyte and the positive electrode active material under high voltage and improving the stability of the solid electrolyte to the positive electrode. On the negative electrode side, the second coating layer 12 can reduce the electronic conductivity of the electrolyte particles 10, inhibit lithium dendrite growth, and avoid side reactions between the electrolyte particles 10 and the negative electrode, thereby improving the stability of the solid electrolyte to the negative electrode. By using a double-layer coating to synergistically enhance the stability of the solid electrolyte to both the positive and negative electrodes, all-solid-state batteries can cycle stably without short circuits.

[0025] In one embodiment of the present invention, the particle size of the solid electrolyte satisfies D50 ≤ 0.5 μm and D90 ≤ 1 μm, where D50 is the particle size value corresponding to a cumulative volume distribution percentage of 50% in the volume distribution curve, and D90 is the particle size value corresponding to a cumulative volume distribution percentage of 90% in the volume distribution curve. By reducing the particle size of the solid electrolyte, the solid-solid contact between solid particles in the battery is effectively improved, thereby increasing the ion transport rate at the solid-solid interface.

[0026] In one embodiment of the present invention, the material of the electrolyte particles 10 in the solid electrolyte includes a sulfide solid electrolyte, wherein the sulfide electrolyte includes Li7P3S. 11 β-Li3PS4, Li 10 GeP2S 12 , Li6PS5Cl, Li6PS5Br, Li7P2S8I, Li4PS4I, Li6PS5Cl x Br 1-x Li6PS5Cl y I 1-y and Li6PS5Br z I 1-z At least one of the following, wherein 0≤x≤1, 0≤y≤1, and 0≤z≤1.

[0027] In one embodiment of the present invention, in the solid electrolyte, a first coating layer 11 coats the surface of the electrolyte particles 10. The thickness of the first coating layer 11 is, for example, 1 nm to 500 nm. The material of the first coating layer 11 includes fluorides, such as lithium fluoride salts. The lithium fluoride salts include at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bisfluorosulfonylimide, lithium difluorooxalateborate, lithium trifluoromethanesulfonylimide (LiFSI), lithium ternary fluorophosphorylimide, lithium hexafluorophosphate, and lithium tetrafluoroborate (LiBF4). By providing the first coating layer 11, a lithium fluoride interface layer can be formed in situ on the positive electrode side, thereby effectively mitigating the interfacial side reactions between the solid electrolyte and the positive electrode material under high voltage and improving the stability of the solid electrolyte to the positive electrode.

[0028] In one embodiment of the present invention, in the solid electrolyte, a second coating layer 12 covers the surface of the first coating layer 11. The thickness of the second coating layer 12 is, for example, 1 nm to 500 nm, and the material of the second coating layer 12 includes non-metallic elements, such as sulfur, iodine, phosphorus, and selenium. By providing the second coating layer 12, the electronic conductivity of the electrolyte particles 10 can be reduced on the negative electrode side, suppressing lithium dendrite growth and avoiding side reactions between the electrolyte particles 10 and the negative electrode, thereby improving the stability of the solid electrolyte to the negative electrode.

[0029] Based on the above-mentioned solid electrolyte, the present invention also provides a method for preparing a solid electrolyte, including steps S11-S14.

[0030] Step S11: Dissolve the fluoride in the first solvent to obtain a fluoride solution.

[0031] Step S12: Add the fluoride solution and electrolyte particles to the second solvent to obtain an electrolyte slurry.

[0032] Step S13: After refining the electrolyte slurry, dry it to obtain an intermediate.

[0033] Step S14: After mixing the intermediate with the non-metallic element, perform low-temperature sealing sintering treatment to obtain a solid electrolyte.

[0034] In one embodiment of the present invention, in step S11, the fluoride is added to a first solvent and then heated and stirred to dissolve the fluoride in the first solvent, thereby obtaining a fluoride solution. The first solvent may include, for example, at least one selected from dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethylene carbonate, dichloromethane, chloroform, n-butyl ether, anisole, cyclopentyl methyl ether, isobutyl isobutyrate, butyl formate, and ethyl hexanoate. The heating temperature is, for example, 50°C-90°C, and the stirring time is, for example, 0.2h-2h.

[0035] In one embodiment of the present invention, after obtaining the fluoride solution, in step S12, the fluoride solution is mixed evenly with the electrolyte particles 10 and then added to a second solvent to obtain an electrolyte slurry. The second solvent includes, for example, at least one of isopentane, n-pentane, cyclohexane, isooctane, cyclopentane, n-hexane, n-heptane, tetrahydrofuran, toluene, xylene, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethylene carbonate, dichloromethane, chloroform, n-butyl ether, anisole, cyclopentyl methyl ether, isobutyl isobutyrate, butyl formate, and ethyl hexanoate. The mass ratio of fluoride to electrolyte particles 10 is, for example, (0.0001-0.2):1.

[0036] In one embodiment of the present invention, after obtaining the electrolyte slurry, the electrolyte slurry is refined in step S13. The refining process is performed by at least one of the following methods: ball milling, sand milling, high-speed homogenization, or ultrasonic treatment. In this embodiment, the electrolyte slurry is refined by ball milling, for example, at a rotation speed of 600 rpm-1000 rpm and a milling time of 12 h-36 h. This refining process enables the micro-nanoization of the solid electrolyte, reducing its particle size and effectively improving the solid-solid contact between solid particles in the battery, thereby increasing the ion transport rate at the solid-solid interface.

[0037] In one embodiment of the present invention, after refining the electrolyte slurry, in step S13, the electrolyte slurry is dried by at least one of the following methods: vacuum drying, spray drying, fluidized bed drying, or freeze drying, to remove the first and second solvents from the electrolyte slurry, while fluoride is coated on the surface of the electrolyte particles 10, thereby obtaining an intermediate. The drying temperature is, for example, 60°C-200°C, and the drying time is, for example, 0.1h-24h. In this embodiment, the electrolyte slurry is dried by vacuum drying, for example, with a vacuum degree of, for example, 0.5mbar-2mbar.

[0038] In one embodiment of the present invention, after obtaining the intermediate, in step S14, the intermediate is mixed with a non-metallic element and then sintered, so that the non-metallic element coats the surface of the intermediate, thereby obtaining a solid electrolyte. The mass ratio of the non-metallic element to the electrolyte particles 10 is, for example, (0.0001-0.2):1, the sintering temperature is, for example, 200°C-400°C, and the sintering time is, for example, 0.5h-5h.

[0039] Based on the aforementioned solid electrolyte and its preparation method, this invention also provides an all-solid-state battery. The all-solid-state battery can be, for example, a primary battery or a secondary battery. A secondary battery can be, for example, a pouch battery, a hard-case battery, or a cylindrical battery. This invention does not specifically limit the type or category of all-solid-state batteries. The all-solid-state battery includes, for example, a positive electrode, a negative electrode, and a solid electrolyte membrane. The solid electrolyte membrane is disposed between the positive and negative electrode, and is, for example, obtained by cold pressing the aforementioned solid electrolyte under a pressure of 300 MPa-400 MPa. The thickness of the solid electrolyte membrane is, for example, 100 μm-500 μm.

[0040] In one embodiment of the present invention, the positive electrode sheet includes, for example, a positive electrode active layer, which includes, for example, a positive electrode active material, a positive electrode electrolyte, a conductive agent, and a binder. The present invention does not limit the mass ratio of the positive electrode active material, positive electrode electrolyte, conductive agent, and binder, and these ratios can be selected according to actual needs. In other embodiments of the present invention, in addition to the positive electrode active layer, the positive electrode sheet may also include a positive electrode current collector, with the positive electrode active layer coated on at least one side of the current collector. The positive electrode current collector may be, for example, a foil formed by surface treatment of nickel, titanium, aluminum, silver, stainless steel, or carbon. Besides foil, the positive electrode current collector may also be used in any one or more combinations of various forms such as film, mesh, porous, foam, or non-woven fabric.

[0041] In one embodiment of the present invention, the positive electrode active material in the positive electrode active layer is selected from at least one of lithium nickel cobalt manganese oxide (NCM), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium cobalt oxide (LCO), or lithium nickel cobalt aluminum oxide (NCA). The positive electrode electrolyte is, for example, the solid electrolyte provided by the present invention or a halide solid electrolyte. Using the solid electrolyte provided by the present invention can improve the high-voltage stability of the positive electrode electrolyte, which is beneficial to its performance in the positive electrode sheet. The halide solid electrolyte is, for example, selected from Li 10 GeP2S 12 Li6PS5Cl or Li7P3S 11At least one of the following, the conductive agent is selected from at least one of graphite, graphene, conductive carbon black (Super P), vapor-grown carbon fiber (VGCF), or carbon nanotubes, and the binder is selected from at least one of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), polymerized styrene-butadiene rubber (SBR), polyvinyl pyrrolidone (PVP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyurethane, polyvinyl alcohol (PVA), sodium alginate, etc. alginate (Alg), ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, β-cyclodextrin polymer (β-CDp), polypropylene emulsion (LA132), polyvinylidene fluoride (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), fluorinated ethylene-propylene copolymer (FEP), polyfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride-hexafluoropropylene copolymer, or polyvinylidene fluoride-trifluorochloroethylene copolymer, etc.

[0042] In one embodiment of the present invention, the positive electrode active material is, for example, LiNi. 0.8 Co 0.1 Mn 0.1 O2, positive electrode electrolyte such as Li6PS5Cl, conductive agent such as Super P and VGCF, with a mass ratio of Super P to VGCF of 1:1, and binder such as PTFE. After uniformly mixing the positive electrode active material, positive electrode electrolyte, conductive agent and binder in a mass ratio of 69:29:1:1, the positive electrode sheet is directly obtained by dry pressing.

[0043] In another embodiment of the present invention, the positive electrode current collector is, for example, aluminum foil, and the positive electrode active material is, for example, LiNi. 0.8 Co 0.1 Mn 0.1 O2, positive electrode electrolyte such as Li 2.35 Zr 0.65 Fe 0.35 Cl5Br 0.5 I 0.5 The conductive agent includes, for example, SuperP and VGCF, and the mass ratio of SuperP to VGCF is, for example, 1:1. The binder is, for example, PTFE. After the positive electrode active material, positive electrode electrolyte, conductive agent and binder are mixed evenly in a mass ratio of, for example, 69:29:1:1, the mixture is rolled and covered onto the surface of aluminum foil to obtain a positive electrode sheet.

[0044] In one embodiment of the present invention, the negative electrode sheet is selected from at least one of lithium metal sheets, indium metal sheets, or lithium-indium alloy sheets. Specifically, in this embodiment, the negative electrode sheet is, for example, a lithium metal sheet.

[0045] In one embodiment of the present invention, the above-mentioned positive electrode, solid electrolyte membrane, and negative electrode are sequentially stacked, packaged, hot-pressed, and cold-pressed to assemble an all-solid-state battery. The assembly process of the all-solid-state battery is completed in a glove box with an inert atmosphere.

[0046] The present invention will be explained in more detail below by referring to embodiments, which should not be construed as limiting. Appropriate modifications can be made within the scope of the present invention, and all such modifications fall within the technical scope of the present invention.

[0047] Example 1 Preparation of solid electrolyte: 0.5 g LiTFSI was added to 5 mL of isobutyl isobutyrate and heated at 80 °C for 1 h to dissolve, yielding a fluoride solution. 10 g of coarse Li6PS5Cl powder was mixed with the fluoride solution, controlling the mass ratio of LiTFSI to Li6PS5Cl to be 0.05:1. 10 mL of xylene solvent was added to the mixture to obtain an electrolyte slurry. The electrolyte slurry was refined by wet ball milling at 800 rpm for 8 h. The ball-milled electrolyte slurry was then placed in a vacuum oven to obtain an intermediate. The vacuum drying process was carried out at 120 °C for 24 h at a vacuum degree of 1.5 mbar. The intermediate was mixed with elemental sulfur and sintered at 300 °C for 2 h to obtain the solid electrolyte. The mass ratio of Li6PS5Cl to elemental sulfur is 1:0.05, the thickness of the LiTFSI layer on the surface of the intermediate is 50 nm, the thickness of the elemental sulfur layer on the surface of the solid electrolyte is 50 nm, the D50 of the solid electrolyte is 0.5 μm, and the D90 is 1 μm.

[0048] Preparation of solid electrolyte membrane: The solid electrolyte obtained above was cold-pressed at 350 MPa to obtain a solid electrolyte membrane with a thickness of 300 μm.

[0049] Preparation of positive electrode: LiNi 0.8 Co 0.1 Mn 0.1 The positive electrode active material (O2), positive electrode electrolyte (Li6PS5Cl), conductive agent, and binder (PTFE) are mixed uniformly in a mass ratio of 69:29:1:1, and then the positive electrode sheet is directly obtained by dry pressing. The conductive agents include Super P and VGCF, with a mass ratio of Super P to VGCF of 1:1.

[0050] Selection of negative electrode: Lithium metal is selected as the negative electrode.

[0051] Preparation of all-solid-state batteries: The positive electrode, solid electrolyte membrane and negative electrode are stacked, packaged, hot-pressed and cold-pressed in sequence to assemble an all-solid-state battery.

[0052] Example 2 The difference between this embodiment and Embodiment 1 is that LiFSI is used instead of LiTFSI.

[0053] Example 3 The difference between this embodiment and Embodiment 1 is that LiBF4 is used instead of LiTFSI.

[0054] Example 4 The difference between this embodiment and Embodiment 1 is that elemental iodine is used instead of elemental sulfur.

[0055] Example 5 The difference between this embodiment and Embodiment 1 is that elemental phosphorus is used instead of elemental sulfur.

[0056] Example 6 The difference between this embodiment and Embodiment 1 is that elemental selenium is used instead of elemental sulfur.

[0057] Example 7 The difference between this embodiment and Embodiment 1 is that the mass ratio of LiTFSI to Li6PS5Cl is 0.2:1.

[0058] Example 8 The difference between this embodiment and Embodiment 1 is that the mass ratio of LiTFSI to Li6PS5Cl is 0.0001:1.

[0059] Example 9 The difference between this embodiment and Embodiment 1 is that the mass ratio of Li6PS5Cl to elemental sulfur is 1:0.0001.

[0060] Example 10 The difference between this embodiment and Embodiment 1 is that the mass ratio of Li6PS5Cl to elemental sulfur is 1:0.2.

[0061] Example 11 The difference between this embodiment and Example 1 lies in the preparation of the solid electrolyte. Specifically, 5g of LiTFSI was added to 50mL of isobutyl isobutyrate and heated at 80°C for 1 hour to obtain a fluoride solution. 100g of coarse Li6PS5Cl powder was mixed with the fluoride solution, controlling the mass ratio of LiTFSI to Li6PS5Cl to be 0.05:1. 100mL of xylene solvent was added to the mixed material to obtain an electrolyte slurry. The electrolyte slurry was refined by wet ball milling at 800rpm for 8 hours. The ball-milled electrolyte slurry was then placed in a vacuum oven to obtain an intermediate. The vacuum drying process was carried out at 120°C for 24 hours under a vacuum of 1.5mbar. The intermediate was mixed with elemental sulfur and sintered at 300°C for 2 hours to obtain a solid electrolyte. The mass ratio of Li6PS5Cl to elemental sulfur was 1:0.05.

[0062] Comparative Example 1 The difference between this comparative example and Example 1 is that the mass ratio of LiTFSI to Li6PS5Cl is 0.3:1.

[0063] Comparative Example 2 The difference between this comparative example and Example 1 is that the mass ratio of LiTFSI to Li6PS5Cl is 0.00005:1.

[0064] Comparative Example 3 The difference between this comparative example and Example 1 is that the mass ratio of Li6PS5Cl to elemental sulfur is 1:0.3.

[0065] Comparative Example 4 The difference between this comparative example and Example 1 is that the mass ratio of Li6PS5Cl to elemental sulfur is 1:0.00005.

[0066] Comparative Example 5 The difference between this embodiment and Example 1 lies in the preparation of the solid electrolyte. Specifically, 10g of coarse Li6PS5Cl powder was added to 10mL of xylene solvent to obtain an electrolyte slurry. The electrolyte slurry was then refined using wet ball milling at 800rpm for 8 hours. The milled electrolyte slurry was then placed in a vacuum oven to obtain a solid electrolyte. The vacuum drying process was carried out at 120℃ for 24 hours at a vacuum level of 1.5mbar.

[0067] Comparative Example 6 The difference between this comparative example and Example 1 is that after obtaining the intermediate, the intermediate was sealed and sintered at 300°C for 2 hours to obtain a solid electrolyte.

[0068] Comparative Example 7 The difference between this comparative example and Example 1 lies in the preparation of the solid electrolyte. Specifically, 10g of coarse Li6PS5Cl powder was added to 10mL of xylene solvent to obtain an electrolyte slurry. The electrolyte slurry was then refined using wet ball milling at 800rpm for 8 hours. The ball-milled electrolyte slurry was then placed in a vacuum oven to obtain an intermediate. Vacuum drying was performed at 120℃ for 24 hours at a vacuum level of 1.5mbar. The intermediate was mixed with elemental sulfur and then sintered at 300℃ for 2 hours to obtain the solid electrolyte. The mass ratio of Li6PS5Cl to elemental sulfur was 1:0.05.

[0069] In this invention, the solid electrolyte membranes and all-solid-state batteries in Examples 1-11 and Comparative Examples 1-7 were subjected to performance tests.

[0070] Please see Figure 2 As shown, in one embodiment of the invention, the solid electrolyte in Example 1 is characterized, for example, by scanning electron microscopy. Figure 2 It can be seen that the electrolyte particles in solid electrolytes are relatively uniform in size.

[0071] Please see Figure 3 As shown, in one embodiment of the present invention, a charge-discharge cycle test is performed on the all-solid-state battery of Example 1. Specifically, the charge-discharge cycle test is performed sequentially at 0.11 mA cm⁻¹. -2 0.28mA cm -2 0.48mA cm -2 0.96mA cm -2 and 1.27mAcm -2 Charge-discharge cycles were performed at different current densities, and voltage-capacity data were collected at each current density. Finally, discharge voltage-specific capacity curves were plotted. Figure 3 It can be seen that the curves at different current densities are smooth and without obvious abrupt changes, indicating that the battery does not have serious side reactions, interface peeling, short circuits, etc. Therefore, the battery can cycle stably.

[0072] Please refer to Table 1. In one embodiment of the present invention, the ionic conductivity of the solid electrolyte membrane is determined, for example, by alternating current impedance spectroscopy. Specifically, after coating both sides of the solid electrolyte membrane with silver paste and drying it, it is placed in the test fixture of an electrochemical workstation to form an "electrode-electrolyte-electrode" sandwich structure. Then, impedance data is collected by scanning with a sinusoidal AC signal from 5 MHz to 0.1 Hz to plot the Nyquist plot. The bulk resistance R of the electrolyte is obtained by equivalent circuit fitting. b Then, combining the thickness L of the solid electrolyte membrane and the electrode area A, the ionic conductivity can be calculated using the formula: Ionic conductivity = L / (R b ×A). Among them, the model of the electrochemical workstation is, for example, Gamry Reference 620.

[0073] Please refer to Table 1. In one embodiment of the present invention, for example, the first charge-discharge capacity test is performed on an all-solid-state battery. Specifically, at 25°C, the battery is charged and discharged for the first time at a 1C rate within the range of 2.4V-4.6V. The integral value of "current × time" during the charging and discharging process is recorded by the device, and then divided by the mass of the positive electrode active material in the positive electrode sheet to obtain the first charge-discharge specific capacity. Then, the first-cycle coulombic efficiency is calculated based on the ratio of the first discharge specific capacity to the first charge specific capacity.

[0074] Table 1 shows the test results of solid electrolyte membranes and all-solid-state batteries in Examples 1-11 and Comparative Examples 1-7.

[0075] Please refer to Table 1. Comparing Example 1 and Comparative Examples 5-7, it can be seen that when the surface of the electrolyte particles is only coated with the first coating layer or the second coating layer, the ionic conductivity of the solid electrolyte membrane decreases, the specific capacity of the first charge cycle and the specific capacity of the first discharge cycle do not change significantly, and the coulombic efficiency of the first cycle increases slightly. However, when the surface of the electrolyte particles is coated with both the first coating layer and the second coating layer, the ionic conductivity of the solid electrolyte membrane decreases, the specific capacity of the first charge cycle and the specific capacity of the first discharge cycle do not change significantly, and the coulombic efficiency of the first cycle increases significantly. This shows that by coating the surface of the electrolyte particles with the first coating layer and the second coating layer, the stability of the solid electrolyte to the positive and negative electrodes can be improved, and the all-solid-state battery can be cycled stably.

[0076] Please refer to Table 1. Comparing Examples 1-3, it can be seen that, compared with the three fluorides LiTFSI, LiFSI and LiBF4, the solid electrolyte membrane prepared with LiTFSI as the first coating layer material has the highest ionic conductivity, first-cycle charge specific capacity, first-cycle discharge specific capacity and first-cycle coulombic efficiency. This shows that by changing the material of the fluoride in the first coating layer, the performance of the solid electrolyte membrane and the battery can be changed.

[0077] Please refer to Table 1. Comparing Examples 1 and 4-6, it can be seen that when four different non-metallic elements—sulfur, iodine, phosphorus, and selenium—are used as the second coating layer materials, the ionic conductivity, first-cycle charge specific capacity, first-cycle discharge specific capacity, and first-cycle coulombic efficiency of the prepared solid electrolyte membrane are all different. This shows that by changing the material of the non-metallic element in the second coating layer, the performance of the solid electrolyte membrane and the battery can be changed.

[0078] Please refer to Table 1. Comparing Examples 1, 7-8, and 1-2, it can be seen that when the mass ratio of LiTFSI to Li6PS5Cl is greater than 0.2:1, the ionic conductivity of the solid electrolyte membrane, the specific capacity of the battery during the first charge cycle, the specific capacity of the battery during the first discharge cycle, and the coulombic efficiency during the first cycle all decrease. When the mass ratio of LiTFSI to Li6PS5Cl is less than 0.0001:1, the ionic conductivity of the solid electrolyte membrane increases, while the specific capacity of the battery during the first charge cycle, the specific capacity of the battery during the first discharge cycle, and the coulombic efficiency during the first cycle all decrease. This indicates that by controlling the mass ratio of fluoride to electrolyte particles 10 to (0.0001-0.2):1, the cycle performance of the battery can be improved.

[0079] Please refer to Table 1. Comparing Examples 1, 9-10, and 3-4, it can be seen that when the mass ratio of Li6PS5Cl to elemental sulfur is less than 1:0.2, the ionic conductivity of the solid electrolyte membrane, the specific capacity of the battery during the first charge cycle, the specific capacity of the battery during the first discharge cycle, and the coulombic efficiency of the first cycle all decrease. When the mass ratio of Li6PS5Cl to elemental sulfur is greater than 1:0.0001, the specific capacity of the battery during the first discharge cycle and the coulombic efficiency of the first cycle all decrease. This shows that by controlling the mass ratio of electrolyte particles to non-metallic elements to be 1:(0.0001-0.2), the cycle performance of the battery can be improved.

[0080] Please refer to Table 1. Comparing Example 1 and Example 11, it can be seen that when the amounts of fluoride, electrolyte particles, non-metallic elements, first solvent, and second solvent in the solid electrolyte preparation process are increased, the ionic conductivity of the solid electrolyte membrane, the specific capacity of the battery during the first charge cycle, the specific capacity of the battery during the first discharge cycle, and the coulombic efficiency during the first cycle all change significantly. This indicates that the solid electrolyte and its preparation method provided by the present invention can be scaled up and promoted in industry, thereby enabling large-scale commercial application.

[0081] In summary, this invention proposes a solid electrolyte, its preparation method, and its application. By modifying the surface of the electrolyte particles with a double-layer coating, the stability of the solid electrolyte to both the positive and negative electrodes can be improved, thereby enabling stable cycling of the all-solid-state battery without short-circuit phenomena. Furthermore, the solid electrolyte, its preparation method, and its application proposed in this invention, through micro-nano processing of the electrolyte particles, can reduce the particle size of the solid electrolyte, effectively improving the solid-solid contact between solid particles in the battery, thereby increasing the ion transport rate at the solid-solid interface.

[0082] The above description is merely a preferred embodiment of this application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept. For example, technical solutions formed by replacing the above-mentioned features with technical features with similar functions disclosed in this application (but not limited to) each other.

[0083] Apart from the technical features described in the specification, the other technical features are known to those skilled in the art. To highlight the innovative features of this invention, the other technical features will not be described in detail here.

Claims

1. A solid electrolyte, characterized in that, At least include: Electrolyte particles; A first coating layer covers the electrolyte particles, and the material of the first coating layer includes fluoride; and The second coating layer covers the first coating layer, and the material of the second coating layer includes a non-metallic element, which includes at least one of sulfur, iodine, phosphorus and selenium.

2. The solid electrolyte according to claim 1, characterized in that, The particle size of the solid electrolyte satisfies D50≤0.5μm, D90≤1μm; and / or the material of the electrolyte particles includes a sulfide solid electrolyte, wherein the sulfide electrolyte includes Li7P3S. 11 β-Li3PS4, Li 10 GeP2S 12 , Li6PS5Cl, Li6PS5Br, Li7P2S8I, Li4PS4I, Li6PS5Cl x Br 1-x Li6PS5Cl y I 1-y and Li6PS5Br z I 1-z At least one of the following, wherein 0≤x≤1, 0≤y≤1, and 0≤z≤1.

3. The solid electrolyte according to claim 1, characterized in that, The fluoride includes a fluorinated lithium salt, which includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bisfluorosulfonylimide, lithium difluorooxalateborate, lithium trifluoromethanesulfonylimide, lithium trifluorophosphorylimide, lithium hexafluorophosphate, and lithium tetrafluoroborate.

4. The solid electrolyte according to claim 1, characterized in that, The thickness of the first coating layer is 1nm-500nm, and the thickness of the second coating layer is 1nm-500nm.

5. A method for preparing a solid electrolyte as described in any one of claims 1-4, characterized in that, At least the following steps are included: The fluoride is dissolved in a first solvent to obtain a fluoride solution; The fluoride solution and electrolyte particles are added to a second solvent to obtain an electrolyte slurry; The electrolyte slurry is refined and then dried to obtain an intermediate. as well as The intermediate is mixed with a non-metallic element and then sintered to obtain a solid electrolyte.

6. The preparation method according to claim 5, characterized in that, The first solvent includes at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethylene carbonate, dichloromethane, chloroform, n-butyl ether, anisole, cyclopentyl methyl ether, isobutyl isobutyrate, butyl formate, and ethyl hexanoate, and / or the second solvent includes at least one of isopentane, n-pentane, cyclohexane, isooctane, cyclopentane, n-hexane, n-heptane, tetrahydrofuran, toluene, xylene, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethylene carbonate, dichloromethane, chloroform, n-butyl ether, anisole, cyclopentyl methyl ether, isobutyl isobutyrate, butyl formate, and ethyl hexanoate.

7. The preparation method according to claim 5, characterized in that, In the electrolyte slurry, the mass ratio of the fluoride to the electrolyte particles is (0.0001-0.2):1, and / or, when refining the electrolyte slurry, at least one of the following treatment methods is used: ball milling, sand milling, high-speed homogenizer treatment, or ultrasonic treatment.

8. The preparation method according to claim 5, characterized in that, The electrolyte slurry is dried by at least one of vacuum drying, spray drying, fluidized bed drying, or freeze drying, with a drying temperature of 60°C-200°C and a drying time of 0.1h-24h.

9. The preparation method according to claim 5, characterized in that, In the solid electrolyte, the mass ratio of the non-metallic element to the electrolyte particles is (0.0001-0.2):1, and / or the sintering temperature is 200°C-400°C, and the sintering time is 0.5h-5h.

10. An all-solid-state battery, characterized in that, At least including: Positive electrode sheet; Negative electrode sheet; as well as A solid electrolyte membrane is disposed between the positive electrode and the negative electrode, and the solid electrolyte membrane contains the solid electrolyte according to any one of claims 1-4, or the solid electrolyte is obtained by the preparation method according to any one of claims 5-9.

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