A cathode material for a solid-state battery, its preparation method and application

Abstract

The present invention provides a cathode material for a solid-state battery, a preparation method thereof, and an application thereof. The preparation method includes the following steps: (1) dry-mixing a lithium salt, an iron source, and a doped non-metal source, and obtaining an anti-perovskite material through sintering treatment; (2) subjecting a plurality of lithium salts to one-step grinding and then one-step heat treatment, subjecting them to two-step grinding and then pressing treatment, and obtaining an anti-perovskite solid electrolyte after two-step heat treatment; (3) mixing the anti-perovskite material obtained in step (1) and the anti-perovskite solid electrolyte obtained in step (2), subjecting them to three-step grinding treatment, and then calcining to obtain the cathode material for the solid-state battery. The present invention develops an anti-perovskite material for an anti-perovskite solid electrolyte, and combines the two to prepare a cathode material for a solid-state battery. The cathode material for the solid-state battery has a high capacity, good stability, and low preparation cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and relates to a cathode material for solid-state batteries, a preparation method thereof, and an application thereof. Background Art

[0002] Currently, the cathode materials used in solid-state batteries are still the cathode materials used in liquid lithium batteries. The physical and chemical instabilities between the cathode materials and the solid electrolytes are the main reasons for the relatively large interfacial resistance. The instabilities usually result in by-products, which are not conducive to the transport of lithium ions.

[0003] The cathode materials of lithium batteries include olivine-type Li 1-x FePO4, Li with delafossite structure 1-x TMO2 (TM = Co, Mn), and spinel-type Li 1+x Mn2O4. In order to facilitate the insertion and extraction of Li + ions, the host lattice must allow cation migration: Li 1-x FePO4 has a one-dimensional tunnel filled with Li+, Li 1-x CoO2 has a two-dimensional layered crystal structure, and Li + ions are between two adjacent CoO2 layers. Li 1+x Mn2O4 is a three-dimensional structure, and Li + enters the interstitial positions. These three materials all have relatively high theoretical specific capacities, but they are different in other aspects; Li 1-x FePO4 is both cheap and harmless, but the migration of Li + is hindered by Li-Fe disorder, thereby reducing the battery life and charge-discharge rate. Li 1-x CoO2 can be charged and discharged at a high rate, but due to the limited resources of environmentally unfriendly cobalt, it is very expensive and not conducive to large-scale use. Li 1+x Mn2O4 is cheap and can work at a high charging rate, but the working voltage causes irreversible deterioration of battery components, resulting in significantly lower charge density or charge rate of other oxide candidate materials. Therefore, it is not suitable for application. Non-oxide lithium-sulfur battery materials are under development, but due to the irreversible dual migration of sulfur and lithium, the battery life is short. In the inverse perovskite cathode material Li2FeChO (Ch = S, Se or Te), Li and Fe are randomly arranged but share the same position in the atomic lattice. Li, Fe, and Ch together form a closely packed cube, and O 2- occupies the octahedral hole position. During the charge-discharge process, Li+ migrates along a three-dimensional path.

[0004] CN113394383A discloses a coating method for a cathode material of a sulfide solid-state battery. The method includes: (1) placing the cathode material in the reaction chamber of an ALD device; (2) waiting for the temperature of the reaction chamber to reach the first set value, loading each precursor source into the reaction chamber through an inert gas, and depositing a fast ion conductor on the surface of the cathode material; (3) replacing the precursor source, waiting for the temperature of the reaction chamber to reach the second set value, and continuing to load the sulfide electrolyte precursor source into the reaction chamber through the inert gas to deposit a layer of sulfide solid electrolyte on the surface of the fast ion conductor layer; (4) annealing the coated cathode material directly in the ALD reaction chamber, and after natural cooling, the double-layer coated cathode material is obtained.

[0005] CN112164776A discloses a composite-coated cathode material for all-solid-state batteries, its preparation method and all-solid-state batteries. The composite-coated cathode material for all-solid-state batteries includes a cathode material and a composite coating layer coated on the surface of the cathode material; the composite coating layer is a composite coating of a lithium-containing metal oxide and a conductive material.

[0006] The cathode materials for solid-state batteries described in the above solutions have problems such as low energy density, poor stability or low specific capacity. Therefore, it is very necessary to develop a cathode material for solid-state batteries with high energy density, good stability and high specific capacity. Summary of the Invention

[0007] The purpose of the present invention is to provide a cathode material for solid-state batteries, its preparation method and application. The present invention develops an anti-perovskite material for an anti-perovskite solid electrolyte, and combines the two to prepare a cathode material for solid-state batteries. The cathode material for solid-state batteries has a high capacity, good stability and low preparation cost.

[0008] To achieve the purpose of this invention, the following technical solutions are adopted:

[0009] In the first aspect, the present invention provides a preparation method for a cathode material for solid-state batteries. The preparation method includes the following steps:

[0010] (1) Dry-mix a lithium source, an iron source and a doped non-metal source, and obtain an anti-perovskite material through sintering treatment;

[0011] (2) Mix a first lithium salt and a second lithium salt, perform one-step heat treatment after one-step grinding, perform pressing treatment after two-step grinding, and obtain an anti-perovskite solid electrolyte after two-step heat treatment;

[0012] (3) Mix the anti-perovskite material obtained in step (1) and the anti-perovskite solid electrolyte obtained in step (2), perform three-step grinding treatment, and then perform calcination to obtain the cathode material for solid-state batteries.

[0013] The present invention does not limit the operation sequence of steps (1) and (2). Step (1) can be carried out first or step (2) can be carried out first.

[0014] The present invention has developed an inverse perovskite cathode material for inverse perovskite solid electrolytes. By compounding the two, a cathode material for solid-state batteries is prepared. The two have a higher degree of matching, can effectively reduce the interfacial resistance, improve the lithium-ion transport efficiency, and better solve the problem of the solid-solid interface in solid-state batteries.

[0015] The theoretical specific capacity of the inverse perovskite material described in the present invention is high, iron has rich reserves and low cost, the inverse perovskite solid electrolyte has high conductivity and low electronic conductivity; it has a small density and is light in weight, which is beneficial to improving the energy density of the battery; it is stable with lithium metal and has a high electrochemical window. The combination of the two can significantly improve the efficiency of solid-state batteries.

[0016] Preferably, the lithium source in step (1) includes lithium hydroxide and / or lithium carbonate.

[0017] Preferably, the iron source includes elemental iron.

[0018] Preferably, the doped non-metal source includes any one or a combination of at least two of elemental sulfur, selenium oxide or tellurium oxide.

[0019] Preferably, the dry mixing method includes ball milling.

[0020] Preferably, the speed of the dry mixing is 200 - 600 rpm, for example: 200 rpm, 300 rpm, 400 rpm, 500 rpm or 600 rpm, etc.

[0021] Preferably, the time of the dry mixing is 2 - 12 h, for example: 2 h, 5 h, 8 h, 10 h or 12 h, etc.

[0022] Preferably, the dew point of the dry mixing is -20 - -40 °C, for example: -20 °C, -25 °C, -30 °C, -35 °C or -40 °C, etc.

[0023] Preferably, the temperature of the sintering treatment in step (1) is 800 - 1000 °C, for example: 800 °C, 850 °C, 900 °C, 950 °C or 1000 °C, etc.

[0024] Preferably, the sintering atmosphere includes a nitrogen atmosphere.

[0025] Preferably, the heating rate of the sintering is 2 - 5 °C / min, for example: 2 °C / min, 3 °C / min, 4 °C / min or 5 °C / min, etc.

[0026] Preferably, the sintering time is 1 to 8 h, such as: 1 h, 2 h, 4 h, 6 h, or 8 h, etc.

[0027] Preferably, after sintering, ice-water quenching treatment is carried out, and it is transferred to be stored in an inert gas.

[0028] Preferably, the first lithium salt in step (2) includes lithium hydroxide and / or lithium carbonate.

[0029] Preferably, the second lithium salt includes any one or a combination of at least two of lithium chloride, lithium bromide, lithium iodide, or lithium fluoride.

[0030] Preferably, the molar ratio of the first lithium salt to the second lithium salt is (1 to 2):1, such as: 1:1, 1.2:1, 1.5:1, 1.8:1, or 2:1, etc.

[0031] Preferably, the grinding medium for the one-step grinding includes isopropyl alcohol.

[0032] Preferably, the temperature for the one-step grinding is 60 to 80 °C, such as: 60 °C, 65 °C, 70 °C, 75 °C, or 80 °C, etc.

[0033] Preferably, the time for the one-step grinding is 2 to 6 h, such as: 2 h, 3 h, 4 h, 5 h, or 6 h, etc.

[0034] Preferably, the temperature for the one-step heat treatment is 200 to 800 °C, such as: 200 °C, 300 °C, 500 °C, 600 °C, or 800 °C, etc.

[0035] Preferably, the atmosphere for the one-step heat treatment is an inert atmosphere.

[0036] Preferably, the time for the one-step heat treatment is 2 to 12 h, such as: 2 h, 5 h, 8 h, 10 h, or 12 h, etc.

[0037] Preferably, the pressure for the pressing treatment in step (2) is 5 to 30 t, such as: 5 t, 10 t, 15 t, 20 t, or 30 t, etc.

[0038] Preferably, the temperature for the two-step grinding is 60 to 80 °C, such as: 60 °C, 65 °C, 70 °C, 75 °C, or 80 °C, etc.

[0039] Preferably, the time for the two-step grinding is 2 to 6 h, such as: 2 h, 3 h, 4 h, 5 h, or 6 h, etc.

[0040] Preferably, the temperature for the two-step heat treatment is 100 to 400 °C, such as: 100 °C, 150 °C, 200 °C, 300 °C, or 400 °C, etc.

[0041] Preferably, the atmosphere for the two-step heat treatment is an inert atmosphere.

[0042] Preferably, the time for the two-step heat treatment is 0.5 - 6 h, such as 0.5 h, 1 h, 3 h, 5 h, or 6 h, etc.

[0043] Preferably, the chemical formula of the inverse perovskite material in step (3) is Li2FeChO, where Ch is any one of S, Se, or Te.

[0044] Preferably, the chemical formula of the inverse perovskite solid electrolyte is Li 3-x H x OA 1-y B y , where A and B are different kinds of halogen elements, and the halogen includes any one of Cl, Br, F, or I, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1.

[0045] Preferably, the mass ratio of the inverse perovskite solid electrolyte to the inverse perovskite material is 1:(7 - 10), such as 1:7, 1:8, 1:8.5, 1:9.8, or 1:10, etc.

[0046] Preferably, a lithium source of 2 - 5% (such as 2%, 2.5%, 3%, 4%, or 5%, etc.) of the mass of the positive electrode material is added during the mixing.

[0047] Preferably, the speed of the three-step grinding treatment in step (3) is 300 - 500 rpm, such as 300 rpm, 350 rpm, 400 rpm, 450 rpm, or 500 rpm, etc.

[0048] Preferably, the time for the three-step grinding treatment is 10 - 15 h, such as 10 h, 11 h, 12 h, 13 h, 14 h, or 15 h, etc.

[0049] Preferably, the temperature of the calcination is 500 - 800 °C, such as 500 °C, 550 °C, 600 °C, 700 °C, or 800 °C, etc.

[0050] Preferably, the heating rate of the calcination is 2 - 5 °C / min, such as 2 °C / min, 3 °C / min, 4 °C / min, or 5 °C / min, etc.

[0051] Preferably, the time for the calcination is 1 - 8 h, such as 1 h, 2 h, 4 h, 6 h, or 8 h, etc.

[0052] Preferably, after the calcination and cooling to room temperature, it is continuously ball-milled for 2 - 6 h (such as 2 h, 3 h, 4 h, 5 h, or 6 h, etc.) and then passed through a 300-mesh sieve.

[0053] Second aspect, the present invention provides a cathode material for a solid-state battery, and the cathode material for the solid-state battery is prepared by the method described in the first aspect.

[0054] The cathode material for the solid-state battery of the present invention has good thermal stability and no phase change occurs even when the temperature is raised to 1000°C. The perovskite inverse cathode material has many advantages such as easy structural regulation, good stability with the lithium metal anode, and excellent interfacial fusion.

[0055] Third aspect, the present invention provides a positive electrode plate, and the positive electrode plate comprises the cathode material for the solid-state battery described in the second aspect.

[0056] Fourth aspect, the present invention provides a solid-state battery, and the solid-state battery comprises the positive electrode plate described in the third aspect.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] (1) The present invention develops a perovskite inverse material for the perovskite inverse solid electrolyte and combines the two to prepare a cathode material for a solid-state battery. The cathode material for the solid-state battery has high capacity, good stability and low preparation cost.

[0059] (2) The impedance of the battery made of the cathode material for the solid-state battery of the present invention can reach below 352.5 Ω, and the discharge specific capacity can reach above 110.5 mAh / g. Compared with the conventional cathode, after the cathode material for the solid-state battery of the present invention is made into a solid-state battery, the impedance of the battery is reduced by more than 1-2 orders of magnitude. Description of the Drawings

[0060] Figure 1 is a schematic diagram of the lattice structure of the perovskite inverse material Li2FeTeO described in Example 1.

[0061] Figure 2 is a schematic diagram of the lattice structure of the perovskite inverse material Li2FeSeO described in Example 2.

[0062] Figure 3 is the XRD pattern of the perovskite inverse material Li2FeTeO described in Example 1.

[0063] Figure 4 is the XRD pattern of the perovskite inverse material Li2FeSeO described in Example 2.

[0064] Figure 5 is the EIS diagram of the all-solid-state battery made of the cathode material for the solid-state battery described in Example 1.

[0065] Figure 6 is the EIS diagram of the all-solid-state battery made of the electrode material described in Comparative Example 2. Detailed Embodiments

[0066] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0067] Embodiment 1

[0068] This embodiment provides a cathode material for a solid-state battery. The preparation method of the cathode material for the solid-state battery is as follows:

[0069] (1) Lithium carbonate, elemental iron, and TeO2 are placed in a ball mill for mixing, with the rotation speed controlled at 400 rpm and ball milling for 6 h. The environment is strictly controlled for moisture, and the dew point is controlled at -30 °C. Under a nitrogen atmosphere, it is heated to 900 °C at a rate of 3 °C / min and held for 6 h to obtain the perovskite-like material Li2FeTeO. After taking it out, it is quenched in ice water and then immediately transferred to an inert gas for drying and storage. The lattice structure schematic diagram of the perovskite-like material Li2FeTeO is as Figure 1 shown, and the XRD pattern of the perovskite-like material Li2FeTeO is as Figure 3 shown;

[0070] (2) LiOH·H2O, LiCl, and LiBr are weighed in a molar ratio of 1:0.5:0.5 and ball milled for 10 h under vacuum conditions in isopropanol. Then it is dried at 70 °C for 4 h, and then held at 600 °C for 8 h under a nitrogen atmosphere. Then, under vacuum conditions, isopropanol is added for ball milling for 5 h and dried at 70 °C. The powder is pressed into a blank under a pressure of 15 t and held at 200 °C for 100 min under a nitrogen atmosphere to obtain the perovskite-like solid electrolyte Li2OHCl 0.5 Br 0.5 ;

[0071] (3) The perovskite-like material obtained in step (1) and the perovskite-like solid electrolyte obtained in step (2) are mixed in a mass ratio of 9:1, and 3 wt% of a lithium salt is added. It is ball milled at a speed of 400 rpm for 12 h. Then, under a nitrogen atmosphere, it is heated to about 600 °C at a rate of 3 °C / min and held for 6 h. After cooling to room temperature, it is ball milled for another 4 h, and the cathode material for the solid-state battery is obtained after passing through a 300-mesh sieve.

[0072] The EIS diagram of the all-solid-state battery made of the cathode material for the solid-state battery is as Figure 5 shown.

[0073] Embodiment 2

[0074] This embodiment provides a cathode material for a solid-state battery. The preparation method of the cathode material for the solid-state battery is as follows:

[0075] (1) Mix lithium carbonate, elemental iron, and SeO2 in a ball mill with a rotation speed controlled at 450 rpm and ball mill for 6 h. Strictly control the moisture in the environment and control the dew point at -35°C. Heat up to 850°C at a rate of 3°C / min under a nitrogen atmosphere and hold for 6 h to obtain the perovskite-like material Li2FeSeO. After taking it out, quench it in ice water, and then immediately transfer it to an inert gas for drying and preservation. The lattice structure diagram of the perovskite-like material Li2FeSeO is as shown in Figure 2 shown, and the XRD pattern of the perovskite-like material Li2FeSeO is as shown in Figure 4 shown;

[0076] (2) Mix LiOH·H2O and LiCl in a molar ratio of 2:1 and ball mill for 10 h under vacuum conditions in isopropyl alcohol. Then dry it at 72°C for 4 h, and then hold it at 650°C for 8 h under a nitrogen atmosphere. Then add isopropyl alcohol under vacuum conditions and ball mill for 5 h, dry it at 70°C, press the powder into a blank under a pressure of 15 t, and hold it at 220°C for 100 min under a nitrogen atmosphere to obtain the perovskite-like solid electrolyte Li3OCl;

[0077] (3) Mix the perovskite-like material obtained in step (1) and the perovskite-like solid electrolyte obtained in step (2) in a mass ratio of 7:1 and supplement 2.2 wt% of the lithium salt. Ball mill at a speed of 400 rpm for 12 h. Then heat up to about 650°C at a rate of 3°C / min in a nitrogen atmosphere and hold for 6 h. After cooling to room temperature, continue to ball mill for 4 h, and obtain the positive electrode material for solid-state batteries after passing through a 300-mesh sieve.

[0078] Example 3

[0079] The difference between this example and Example 1 is only that the sintering temperature in step (1) is 600°C, and other conditions and parameters are exactly the same as those in Example 1.

[0080] Example 4

[0081] The difference between this example and Example 1 is only that the sintering temperature in step (1) is 1200°C, and other conditions and parameters are exactly the same as those in Example 1.

[0082] Example 5

[0083] The difference between this example and Example 1 is only that the mass ratio of the perovskite-like solid electrolyte to the perovskite-like material in step (3) is 1:6, and other conditions and parameters are exactly the same as those in Example 1.

[0084] Example 6

[0085] The difference between this embodiment and Embodiment 1 is only that the mass ratio of the inverse perovskite solid electrolyte to the inverse perovskite material in step (3) is 1:12, and other conditions and parameters are exactly the same as those in Embodiment 1.

[0086] Comparative Example 1

[0087] In this comparative example, the inverse perovskite material prepared in step (1) is used as the electrode material.

[0088] Comparative Example 2

[0089] In this comparative example, LiCoO2 is used as the electrode material.

[0090] The EIS diagram of the all-solid-state battery made of the electrode material is as Figure 6 shown.

[0091] Performance test:

[0092] The positive electrode materials obtained in Examples 1-6 and Comparative Examples 1-2, conductive carbon black, and PVDF binder are made into a positive electrode sheet in a ratio of 85:5:10. The graphite or silicon-based negative electrode material, conductive carbon black, and PVDF binder are made into a negative electrode sheet. A lithium metal negative electrode can also be used. The positive electrode sheet, negative electrode sheet, and the inverse perovskite solid electrolyte prepared in step (2) of Example 1 are assembled into a solid-state battery in the order of positive electrode / solid electrolyte / negative electrode for performance testing. The test results are shown in Table 1:

[0093] Table 1

[0094] Battery impedance (Ω) Discharge specific capacity (mAh / g) Example 1 50.2 165.4 Example 2 56.8 155.8 Example 3 113.3 131.2 Example 4 352.5 110.5 Example 5 60.1 160.1 Example 6 150.5 132.4 Comparative Example 1 7750.8 98.5 Comparative Example 2 1442.2 122.6

[0095] As can be seen from Table 1, from Examples 1-6, it can be obtained that the impedance of the battery made of the positive electrode material of the solid-state battery of the present invention can reach below 352.5 Q, and the discharge specific capacity can reach above 110.5 mAh / g.

[0096] From the comparison between Example 1 and Examples 3-4, it can be obtained that during the preparation process of the inverse perovskite material of the present invention, the sintering temperature will affect its performance, and thus affect the performance of the positive electrode material for the solid-state battery. Controlling the sintering temperature at 800-1000 °C results in better performance of the obtained inverse perovskite material. If the sintering temperature is too low, the raw materials do not react completely, and the obtained material has an impure crystal phase and the presence of impurity phases. If the sintering temperature is too high, element loss occurs and the material capacity is low.

[0097] It can be seen from the comparison between Example 1 and Examples 5-6 that during the preparation process of the cathode material for the solid-state battery according to the present invention, the mass ratio of the anti-perovskite material to the anti-perovskite solid electrolyte will affect the performance of the cathode material for the solid-state battery prepared. Controlling the mass ratio of the anti-perovskite material to the anti-perovskite solid electrolyte at 7-10:1 results in better performance of the cathode material for the solid-state battery. If the doping amount of the solid electrolyte is too large, the content of the cathode active material is too low, and the energy density of the battery is not high. If the doping amount of the solid electrolyte is too small, there are fewer lithium-ion migration channels in the cathode, and the impedance is high, which affects the performance of the cathode capacity.

[0098] It can be seen from the comparison between Example 1 and Comparative Example 1 that the present invention combines the anti-perovskite material and the anti-perovskite solid electrolyte to form an electrode material, which can improve the conductivity of the material, the stability with lithium metal, and the energy density of the battery while improving the matching degree.

[0099] It can be seen from the comparison between Example 1 and Comparative Example 2 that the cathode material according to the present invention, compared with commercial LiCoO2, has improved performance while the cost is reduced by nearly 95%, and the manufacturing cost is very low.

[0100] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of within the technical scope disclosed by the present invention by those skilled in the art all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of a cathode material for a solid-state battery, characterized in that, The preparation method includes the following steps: (1) Dry-mix a lithium source, an iron source, and a doped non-metal source, and obtain a perovskite-like material through sintering treatment; (2) Mix a first lithium salt and a second lithium salt, perform first grinding, then perform first heat treatment, perform second grinding, and then perform pressing treatment. After second heat treatment, obtain a perovskite-like solid electrolyte; (3) Mix the perovskite-like material obtained in step (1) and the perovskite-like solid electrolyte obtained in step (2), perform third grinding treatment, and then perform calcination to obtain the positive electrode material for the solid-state battery; The temperature of the sintering treatment in step (1) is 800-1000 °C, the sintering atmosphere is a nitrogen atmosphere, the heating rate of the sintering is 2-5 °C / min, the sintering time is 1-8 h, and after sintering, perform ice-water quenching treatment and transfer to an inert gas for storage; The doped non-metal source in step (1) includes any one or a combination of at least two of a sulfur source, a selenium source, or a tellurium source; The chemical formula of the inverse perovskite material described in step (3) is Li2FeChO, where Ch is any one of S, Se or Te, and the chemical formula of the inverse perovskite solid electrolyte is Li 3-x H x OA 1-y B y , where A and B are halogen elements of different types, the halogen includes any one of Cl, Br, F or I, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, and the mass ratio of the inverse perovskite solid electrolyte to the inverse perovskite material is 1:(7-10). During the mixing, a lithium source of 2-5% of the mass of the positive electrode material is added.

2. The preparation method according to claim 1, characterized in that, The lithium source in step (1) includes lithium hydroxide and / or lithium carbonate, the iron source includes any one or a combination of at least two of elemental iron, iron oxide, or ferrous oxide. The dry-mixing method includes ball milling, the dry-mixing speed is 200-600 rpm, the dry-mixing time is 2-12 h, and the dew point of the dry-mixing is -20 to -40 °C.

3. The preparation method according to claim 1, wherein The first lithium salt in step (2) includes lithium hydroxide and / or lithium carbonate, the second lithium salt includes any one or a combination of at least two of lithium chloride, lithium bromide, lithium iodide, or lithium fluoride. The molar ratio of the first lithium salt to the second lithium salt is (1-2):

1. The grinding medium for the first grinding includes isopropyl alcohol, the temperature of the first grinding is 60-80 °C, the time of the first grinding is 2-6 h, the temperature of the first heat treatment is 200-800 °C, the atmosphere of the first heat treatment is an inert atmosphere, and the time of the first heat treatment is 2-12 h.

4. The preparation method according to claim 1, characterized in that, The pressure of the pressing treatment in step (2) is 5-30 t, the temperature of the second grinding is 60-80 °C, the time of the second grinding is 2-6 h, the temperature of the second heat treatment is 100-400 °C, the atmosphere of the second heat treatment is an inert atmosphere, and the time of the second heat treatment is 0.5-6 h.

5. The preparation method according to claim 1, characterized in that, The speed of the third grinding treatment in step (3) is 300-500 rpm, the time of the third grinding treatment is 10-15 h, the temperature of the calcination is 500-800 °C, the heating rate of the calcination is 2-5 °C / min, the time of the calcination is 1-8 h. After calcination, cool to room temperature and then continue ball milling for 2-6 h, and pass through a 300-mesh sieve.

6. A cathode material for a solid-state battery, characterized in that, The positive electrode material for the solid-state battery is prepared by the method according to any one of claims 1-5.

7. A positive electrode sheet, characterized in that, The positive electrode sheet includes the positive electrode material for the solid-state battery according to claim 6.

8. A solid-state battery, characterized in that, The solid-state battery includes the positive electrode sheet according to claim 7.

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