Modified positive electrode material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of batteries, and provides a modified positive electrode material and a preparation method and application thereof.The modified positive electrode material comprises a positive electrode active substance and a modified layer coating the surface of the positive electrode active substance, and the modified layer comprises oxyhalide compounds generated through reaction of acid anhydride and acid halide. Reductive electrophiles, namely acid anhydride and acid halide, are introduced, an oxyhalide compound generated by reaction of the acid anhydride and the acid halide is utilized to form a coating layer, and the coating layer plays a role of a protective layer between a positive electrode active material and a solid electrolyte; and the material can react with a sulfide solid electrolyte to generate a solid reduction electrophile interface layer with electron blocking and lithium-phobic characteristics, so that the growth of lithium dendrites can be effectively inhibited, the reduction and oxygenolysis of the solid electrolyte can be prevented, and the electrochemical performance of the all-solid-state battery can be greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and relates to a modified cathode material, a preparation method thereof, and uses thereof. Background Art

[0002] Compared with traditional lithium batteries, all-solid-state batteries are a solution that uses solid electrolytes instead of liquid electrolytes. Due to their non-flammability and potential for high energy density, the attention in the battery field has gradually shifted to all-solid-state lithium batteries.

[0003] As a key part of all-solid-state batteries, solid electrolytes can be classified into three categories according to their material composition: inorganic solid electrolytes, organic solid electrolytes, and organic-inorganic composite solid electrolytes. Among them, the research on inorganic solid electrolytes is relatively common, including oxide solid electrolytes, sulfide solid electrolytes, and polymer electrolytes. Among them, sulfide solid electrolytes have broad application prospects due to their high standard temperature, conductivity, and excellent flexibility. However, when in contact with many traditional electrodes, the narrow electrochemical stability window of solid electrolytes will cause chemical / electrochemical side reactions, thus having a negative impact on the electrochemical performance of the battery. To improve the interfacial stability between oxide cathodes and solid electrolytes, a lot of efforts have been made in the industry. It has been proven by research that coating a thin film on the surface of the cathode material can successfully prevent the degradation between the solid electrolyte and the cathode material.

[0004] CN118588903A discloses a composite cathode material, a preparation method thereof, and applications thereof. The preparation method specifically includes mixing a cathode active material with a metal lithium oxide coating agent, ball milling, and sintering to obtain a cathode active material with a first coating layer; then dissolving an organic lithium salt in an ionic liquid to obtain a composite ionic liquid; adding the cathode active material with the first coating layer and the composite ionic liquid into a solvent, stirring, and drying to obtain the composite cathode material. However, the traditional chemical coating layer of metal oxides is prone to unevenness problems, and is prone to crystallization and the generation of thick thermodynamic products, thereby reducing the protection effect and increasing the resistance.

[0005] CN115810803A discloses a fully dry preparation method for a sulfur-based all-solid-state battery with a long cycle life, comprising the following steps: placing a sulfide electrolyte and polytetrafluoroethylene in a zirconium oxide ball mill, ball milling in an argon atmosphere to obtain a bulk material, hand rolling and hot pressing the bulk material to obtain a sulfide electrolyte film; placing a sulfide electrolyte, a positive electrode material, a conductive agent and polytetrafluoroethylene in a zirconium oxide ball mill, ball milling in an argon atmosphere to obtain a bulk material, hand rolling and hot pressing the bulk material to obtain a positive electrode film; extruding a lithium film and an indium film with a certain diameter and thickness to form a lithium indium negative electrode; assembling the lithium indium negative electrode, the sulfide electrolyte film and the positive electrode film to obtain a sulfur-based all-solid-state battery with a long cycle life. This scheme forms a specific battery assembly scheme through a specific substrate and electrolyte membrane preparation method, but it can be seen that the process of this scheme is relatively cumbersome and is not conducive to large-scale application and production.

[0006] Therefore, it is still necessary to propose new surface modification schemes for positive electrode materials to support their good compatibility and stability with solid electrolytes in all-solid-state batteries, thereby effectively improving the performance of all-solid-state batteries and promoting the application and development of all-solid-state batteries. Summary of the invention

[0007] In view of the problems existing in the prior art, the object of the present invention is to provide a modified positive electrode material and a preparation method and use thereof, wherein the modified positive electrode material comprises a positive electrode active substance and a modified layer coated on the surface of the positive electrode active substance, wherein the modified layer comprises an oxyhalide compound generated by the reaction of an acid anhydride and an acid halide. By introducing a reducing electrophile, i.e., an acid anhydride and an acid halide, the oxyhalide compound generated by the reaction of the two is used to form a coating layer, which plays the role of a protective layer between the positive electrode active substance and the solid electrolyte, and can react with a sulfide solid electrolyte to generate a solid reducing electrophile interface layer with electron blocking and lithium-repelling properties, which can effectively inhibit the growth of lithium dendrites and prevent the reduction and oxidation decomposition of the solid electrolyte, which is conducive to significantly improving the electrochemical performance of the all-solid-state battery.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a modified positive electrode material, comprising a positive electrode active substance and a modified layer coated on the surface of the positive electrode active substance, wherein the modified layer comprises an oxyhalide compound generated by the reaction of an acid anhydride and an acid halide.

[0010] In the present invention, by introducing reducing electrophiles, namely acid anhydrides and acid halides, a coating layer is formed by using the halogen oxide compounds generated from the reaction of the two, which serves as a protective layer between the positive electrode active material and the solid electrolyte. Moreover, it can react with the sulfide solid electrolyte to generate a solid reduction electrophile interface layer with electron-blocking and lithium-phobic properties, which can effectively inhibit the growth of lithium dendrites and prevent the reduction and oxidative decomposition of the solid electrolyte, thus being beneficial to significantly improving the electrochemical performance of the all-solid-state battery.

[0011] The following are the preferred technical solutions of the present invention, but not the limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0012] As a preferred technical solution of the present invention, the positive electrode active material includes a lithium-rich manganese-based positive electrode material.

[0013] Preferably, the chemical formula of the lithium-rich manganese-based positive electrode material includes (Li 1+z (Ni x Mn y )O2), where y≥0.5. For example, y can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, or 0.8, etc., and x + y = 1, 0 < z < 1. For example, z can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc., but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0014] Preferably, the acid anhydride includes at least one of phosphoric anhydride, trifluoroacetic anhydride, acetic anhydride, benzoic anhydride, or maleic anhydride, preferably includes phosphoric anhydride, and more preferably is phosphoric anhydride.

[0015] Preferably, the acid halide includes at least one of difluorophosphoric acid, acetyl chloride, chlorous acid, or chlorobenzoic acid, preferably includes difluorophosphoric acid, and more preferably is difluorophosphoric acid.

[0016] In the present invention, when the acid anhydride includes phosphoric anhydride and the acid halide includes difluorophosphoric acid, the reaction of the phosphoric anhydride and the difluorophosphoric acid is: 4OP(OH)F2 + P4O 10 →4(PO2F)2 + 2H2O.

[0017] Preferably, the modified layer is thin and dense, and its thickness is 10 - 20 nm. For example, it can be 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, or 20 nm, etc., but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0018] Second aspect, the present invention provides a method for preparing the modified cathode material described in the first aspect, comprising:

[0019] Carry out liquid-phase mixing of the cathode active material, acid anhydride and acid halide, the acid anhydride and the acid halide react to form a halogen oxide compound, after drying to remove the solvent, carry out sintering, and the halogen oxide compound forms a modified layer on the surface of the cathode active material to obtain a modified cathode material.

[0020] It should be noted that the acid anhydride and acid halide have already started to react and coat the cathode active material during liquid-phase mixing, and the drying and sintering are to remove the liquid phase and increase the binding force between the modified layer and the cathode active material.

[0021] As a preferred technical solution of the present invention, the preparation method includes first mixing the acid anhydride, the acid halide and a solvent, the acid anhydride and the acid halide react to form the halogen oxide compound to obtain a coating solution, and then carrying out liquid-phase mixing of the coating solution and the cathode active material.

[0022] Preferably, the solvent includes absolute ethanol.

[0023] Preferably, the dosage of the acid anhydride is 0.1 - 0.5 mol / L, such as 0.1 mol / L, 0.13 mol / L, 0.15 mol / L, 0.18 mol / L, 0.2 mol / L, 0.23 mol / L, 0.25 mol / L, 0.28 mol / L, 0.3 mol / L, 0.32 mol / L, 0.35 mol / L, 0.38 mol / L, 0.4 mol / L, 0.43 mol / L, 0.45 mol / L, 0.48 mol / L or 0.5 mol / L, etc., but not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0024] Preferably, the dosage of the acid halide is 0.5 - 1.5 mol / L, such as 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, 0.85 mol / L, 0.9 mol / L, 0.95 mol / L, 1 mol / L, 1.05 mol / L, 1.1 mol / L, 1.15 mol / L, 1.2 mol / L, 1.25 mol / L, 1.3 mol / L, 1.35 mol / L, 1.4 mol / L, 1.45 mol / L or 1.5 mol / L, etc., but not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0025] It should be noted that the dosages of the acid anhydride and the acid halide are adjusted according to the stoichiometric ratio of the actual reaction.

[0026] Preferably, the positive electrode active material and the coating solution are subjected to the liquid-phase mixing according to a solid-liquid mass ratio of 1:(2 - 6), such as 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, or 1:6, etc., but not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0027] It should be noted that the thickness of the modified layer is related to the solid-liquid mass ratio of the positive electrode active material and the coating solution, and should be reasonably adjusted according to needs.

[0028] As a preferred technical solution of the present invention, the temperature of the liquid-phase mixing is 60 - 100 °C, such as 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, or 100 °C, etc., the rotation speed is 300 - 600 rpm, such as 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, or 600 rpm, etc., and the time is 2 - 5 h, such as 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, or 5 h, etc., but not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0029] As a preferred technical solution of the present invention, the sintering is carried out in an oxygen-containing atmosphere.

[0030] Preferably, the heating rate of the sintering is 2 - 10 °C / min, such as 2 °C / min, 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, or 10 °C / min, etc., the holding temperature is 400 - 650 °C, such as 400 °C, 430 °C, 450 °C, 480 °C, 500 °C, 520 °C, 550 °C, 580 °C, 600 °C, 620 °C, or 650 °C, etc., and the holding time is 4 - 7 h, such as 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, or 7 h, etc., but not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0031] As a preferred technical solution of the present invention, when the positive electrode active material includes a lithium-rich manganese-based positive electrode material, the synthesis method of the lithium-rich manganese-based positive electrode material includes: mixing a nickel-manganese hydroxide precursor and a lithium source, and performing calcination to obtain the lithium-rich manganese-based positive electrode material.

[0032] Preferably, the lithium source includes lithium carbonate and / or lithium hydroxide.

[0033] Preferably, the molar ratio of the nickel-manganese hydroxide precursor to the lithium source is 1:(1.1 to 1.5), such as 1:1.1, 1:1.15, 1:1.2, 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45 or 1:5.1, etc., but not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0034] Preferably, the calcination temperature is 700 to 900 °C, such as 700 °C, 730 °C, 750 °C, 780 °C, 800 °C, 820 °C, 850 °C, 880 °C or 900 °C, etc., and the time is 8 to 15 h, such as 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h or 15 h, etc., but not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0035] As a preferred technical solution of the present invention, the method for preparing the nickel-manganese hydroxide precursor includes: formulating a nickel-manganese salt solution from a nickel source and a manganese source, adding a precipitant and a complexing agent, carrying out a precipitation reaction, and after solid-liquid separation, drying and grinding, obtaining the nickel-manganese hydroxide precursor.

[0036] Preferably, the nickel source and the manganese source are each independently selected from at least one of sulfates, nitrates, acetates or oxalates.

[0037] Preferably, the concentration of the nickel-manganese salt solution is 50 to 200 g / L, such as 50 g / L, 80 g / L, 100 g / L, 120 g / L, 150 g / L, 180 g / L or 200 g / L, etc., but not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0038] Preferably, the precipitant includes a sodium hydroxide solution with a concentration of 10 to 100 g / L, such as 10 g / L, 30 g / L, 50 g / L, 80 g / L or 100 g / L, etc., but not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0039] Preferably, the complexing agent includes at least one of citric acid, ammonia water, carbonate or bicarbonate, with a concentration of 0.05 to 5 g / L, such as 0.05 g / L, 0.1 g / L, 0.5 g / L, 0.8 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L or 5 g / L, etc., but not limited to the listed values. Other unlisted values within the above numerical range are equally applicable.

[0040] Preferably, the chemical formula of the obtained nickel-manganese hydroxide precursor includes Ni x Mn y(OH)2, where y ≥ 0.5. For example, y can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, etc., and x + y = 1, but it is not limited to the listed values. Other unlisted values within the above numerical range are also applicable.

[0041] In a third aspect, the present invention provides a positive electrode sheet, and the positive electrode sheet contains the modified positive electrode material described in the second aspect.

[0042] In a fourth aspect, the present invention provides a all-solid-state battery, and the all-solid-state battery contains the positive electrode sheet described in the third aspect, and the electrolyte of the all-solid-state battery includes a sulfide solid electrolyte.

[0043] It can be understood that in the all-solid-state battery, the modified positive electrode material in the positive electrode sheet should be able to directly contact the sulfide solid electrolyte, so that the modified layer can react with the sulfide solid electrolyte to generate a solid reduction electrophile interface layer.

[0044] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0045] By introducing reduction electrophiles, namely acid anhydrides and acid halides, the present invention uses the halogen oxide compounds formed by the reaction of the two to form a coating layer, which acts as a protective layer between the positive electrode active material and the solid electrolyte, and it can react with the sulfide solid electrolyte to generate a solid reduction electrophile interface layer with electron blocking and lithium-phobic characteristics, which can effectively inhibit the growth of lithium dendrites and prevent the reduction and oxidative decomposition of the solid electrolyte, and is beneficial to greatly improving the electrochemical performance of the all-solid-state battery. Specific Embodiments

[0046] The technical solutions of the present invention will be further described below through specific embodiments.

[0047] Those skilled in the art should understand that the embodiments are only helpful for understanding the present invention and should not be regarded as specific limitations on the present invention.

[0048] Example 1

[0049] This example provides a modified positive electrode material. The modified positive electrode material includes a positive electrode active material, and the positive electrode active material is a lithium-rich manganese-based positive electrode material. It also includes a modified layer coated on the surface of the positive electrode active material. The modified layer includes difluorophosphorus fluoride formed by the reaction of phosphoric anhydride and difluorophosphoric acid; the thickness of the modified layer is 15 nm.

[0050] This example also provides a preparation method of the modified positive electrode material, including:

[0051] According to the lithium-rich manganese-based positive electrode material Li 1.2 (Ni0.25 Mn 0.75 ) The stoichiometric ratio of Ni:Mn required for O2 is 25:75. Weigh the nickel source nickel sulfate and the manganese source manganese sulfate, dissolve them in water to obtain a uniformly mixed nickel-manganese salt solution with a concentration of 50 g / L. Then, co-drip it with the precipitant solution, that is, a sodium hydroxide solution with a concentration of 20 g / L, into the reaction kettle for reaction. At the same time, add a complexing agent, that is, ammonia water with a concentration of 2 g / L, to inhibit the precipitation rate of metal salts. Stir well at 50 °C to carry out the precipitation reaction. After the particle size D of the reactants 50 grows to 3.0 - 4.5 μm, filter, dry, grind and screen to obtain a lithium-rich manganese-based precursor powder, that is, a nickel-manganese hydroxide precursor Ni 0.25 Mn 0.75 (OH)2; Then mix it with the lithium source lithium carbonate in a molar ratio of 1:1.2 and carry out high-temperature calcination. The calcination temperature is 700 °C and the time is 10 h to obtain a lithium-rich manganese-based cathode material Li 1.2 (Ni 0.25 Mn 0.75 )O2;

[0052] Using absolute ethanol as a solvent, prepare a 0.25 mol / L phosphoric anhydride and a 1 mol / L difluorophosphoric acid solution. The phosphoric anhydride reacts with the difluorophosphoric acid to form the difluorophosphate fluoride. The reaction formula is 4OP(OH)F2 + P4O 10 → 4(PO2F)2 + 2H2O to obtain a coating solution. Then, mix the lithium-rich manganese-based cathode material and the coating solution in a solid-liquid mass ratio of 1:4 for liquid-phase mixing. Stir at 70 °C and 500 rpm for 5 h to remove absolute ethanol. Then, sinter at 600 °C for 6 h in an oxygen atmosphere at a heating rate of 5 °C / min to form a modified layer of the difluorophosphate fluoride on the surface of the lithium-rich manganese-based cathode material, obtaining a surface-modified lithium-rich manganese-based cathode material, that is, a modified cathode material.

[0053] Example 2

[0054] This example provides a modified cathode material. In the modified cathode material, the thickness of the modified layer is adjusted from 15 nm to 7 nm. Except for the above, other conditions are exactly the same as those in Example 1.

[0055] Example 3

[0056] This example provides a modified cathode material. In the modified cathode material, the thickness of the modified layer is adjusted from 15 nm to 10 nm. Except for the above, other conditions are exactly the same as those in Example 1.

[0057] Example 4

[0058] This embodiment provides a modified cathode material. In the modified cathode material, the thickness of the modified layer is adjusted from 15 nm to 20 nm. Except for the above, other conditions are exactly the same as those in Embodiment 1.

[0059] Example 5

[0060] This embodiment provides a modified cathode material. In the modified cathode material, the thickness of the modified layer is adjusted from 15 nm to 23 nm. Except for the above, other conditions are exactly the same as those in Embodiment 1.

[0061] Example 6

[0062] This embodiment provides a modified cathode material. In the preparation method of the modified cathode material, phosphoric anhydride is replaced by trifluoroacetic anhydride, and difluorophosphoric acid is replaced by acetyl chloride. Except for the above, other conditions are exactly the same as those in Embodiment 1.

[0063] Example 7

[0064] This embodiment provides a modified cathode material. In the preparation method of the modified cathode material, phosphoric anhydride is replaced by benzoic anhydride, and difluorophosphoric acid is replaced by benzoyl chloride. Except for the above, other conditions are exactly the same as those in Embodiment 1.

[0065] Example 8

[0066] This embodiment provides a modified cathode material. In the preparation method of the modified cathode material, phosphoric anhydride is replaced by maleic anhydride, and difluorophosphoric acid is replaced by chlorous acid. Except for the above, other conditions are exactly the same as those in Embodiment 1.

[0067] Comparative Example 1

[0068] This comparative example provides a cathode material. In the preparation method of the cathode material, phosphoric anhydride is not used. Except for the above, other conditions are exactly the same as those in Embodiment 1.

[0069] Comparative Example 2

[0070] This comparative example provides a cathode material. In the preparation method of the cathode material, difluorophosphoric acid is not used. Except for the above, other conditions are exactly the same as those in Embodiment 1.

[0071] Comparative Example 3

[0072] This comparative example provides a cathode material, and the subsequent tests are carried out with the lithium-rich manganese-based cathode material obtained in Example 1 as the cathode material.

[0073] The cathode materials obtained in the examples and comparative examples are tested:

[0074] The positive electrode materials obtained in the above embodiments and comparative examples were prepared into positive electrode sheets, which were then prepared into all-solid-state batteries with Ag-alloy negative electrodes and Li6PS5C1 electrolyte sheets. The all-solid-state batteries were tested for electrochemical performance and cycle performance at a voltage of 2.0 to 4.8 V and a charge and discharge rate of 0.1 C.

[0075] The above results are shown in Table 1.

[0076] Table 1

[0077]

[0078] It can be seen from Table 1 that:

[0079] Compared to Comparative Examples 1-3, in the embodiments, by introducing a reducing electrophile, i.e., anhydride and acid halide, a halide oxide compound generated by the reaction of the two is used to form a coating layer, which plays the role of a protective layer between the positive electrode active material and the solid electrolyte, and it can react with the sulfide solid electrolyte to generate a solid reducing electrophile interface layer with electron blocking and lithium-repelling properties, which can effectively inhibit the growth of lithium dendrites and prevent the reduction and oxidative decomposition of the solid electrolyte, which is conducive to greatly improving the electrochemical performance of the all-solid-state battery. From the comparison of Examples 1-5, it can be seen that the thickness of the coated modified layer has an optimal range, and the optimization effect is significantly improved at the most suitable thickness. Comparative Examples 1 and 2 use only one of anhydride or acid halide, which has an adverse effect on the electrochemical performance.

[0080] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0081] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0082] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A modified cathode material, characterized in that, It includes a positive electrode active material and a modified layer coated on the surface of the positive electrode active material, and the modified layer includes a halogen oxide compound formed by the reaction of an acid anhydride and an acid halide.

2. The modified cathode material according to claim 1, wherein, The positive electrode active material includes a lithium-rich manganese-based positive electrode material; Preferably, the acid anhydride includes at least one of phosphoric anhydride, trifluoroacetic anhydride, acetic anhydride, benzoic anhydride or maleic anhydride, and preferably phosphoric anhydride; Preferably, the acid halide includes at least one of difluorophosphoric acid, acetyl chloride, chlorous acid or chlorobenzoic acid, and preferably difluorophosphoric acid; Preferably, the thickness of the modified layer is 10-20 nm.

3. A method for preparing the modified cathode material according to claim 1 or 2, characterized in that, It includes: The positive electrode active material, the acid anhydride and the acid halide are mixed in liquid phase, the acid anhydride and the acid halide react to form a halogen oxide compound, and after drying to remove the solvent, sintering is carried out, and the halogen oxide compound forms a modified layer on the surface of the positive electrode active material to obtain a modified positive electrode material.

4. The preparation method of the modified cathode material according to claim 3, characterized in that, The preparation method includes first mixing the acid anhydride, the acid halide and a solvent, the acid anhydride and the acid halide react to form the halogen oxide compound to obtain a coating solution, and then mixing the coating solution and the positive electrode active material in liquid phase; Preferably, the solvent includes absolute ethanol; Preferably, the dosage of the acid anhydride is 0.1-0.5 mol / L; Preferably, the dosage of the acid halide is 0.5-1.5 mol / L; The molar ratio of the acid anhydride to the acid halide is 1:(1-15); Preferably, the positive electrode active material and the coating solution are mixed in liquid phase according to a solid-liquid mass ratio of 1:(2-6).

5. The preparation method of the modified cathode material according to claim 3 or 4, characterized in that, The temperature of the liquid phase mixing is 60-100 °C, the rotation speed is 300-600 rpm, and the time is 2-5 h.

6. The preparation method of the modified cathode material according to any one of claims 3-5, characterized in that, The sintering is carried out in an oxygen-containing atmosphere; Preferably, the heating rate of the sintering is 2-10 °C / min, the holding temperature is 400-650 °C, and the holding time is 4-7 h.

7. The preparation method of the modified cathode material according to any one of claims 3-6, characterized in that, When the positive electrode active material includes a lithium-rich manganese-based positive electrode material, the synthesis method of the lithium-rich manganese-based positive electrode material includes: mixing a nickel-manganese hydroxide precursor and a lithium source, and carrying out calcination to obtain a lithium-rich manganese-based positive electrode material; Preferably, the lithium source includes lithium carbonate and / or lithium hydroxide; Preferably, the molar ratio of the nickel-manganese hydroxide precursor to the lithium source is 1:(1.1-1.5); Preferably, the temperature of the calcination is 700-900 °C, and the time is 8-15 h.

8. The preparation method of the modified cathode material according to claim 7, characterized in that, The method for preparing the nickel-manganese hydroxide precursor includes: formulating a nickel-manganese salt solution from a nickel source and a manganese source, adding a precipitant and a complexing agent, carrying out a precipitation reaction, and after solid-liquid separation, drying and grinding, obtaining a nickel-manganese hydroxide precursor; Preferably, the nickel source and the manganese source are each selected from at least one of sulfates, nitrates, acetates or oxalates; Preferably, the concentration of the nickel-manganese salt solution is 50-200 g / L; Preferably, the precipitant includes a sodium hydroxide solution with a concentration of 10-100 g / L; Preferably, the complexing agent includes at least one of citric acid, ammonia water, carbonate or bicarbonate, and the concentration is 0.05-5 g / L; Preferably, the chemical formula of the obtained nickel manganese hydroxide precursor includes Ni x Mn y (OH)2, where y ≥ 0.5 and x + y = 1.

9. A positive electrode sheet, characterized in that, It contains the modified positive electrode material according to claim 1 or 2.

10. A all-solid-state battery, characterized in that, Comprising the positive electrode sheet described in claim 9, and the electrolyte of the all-solid-state battery comprising a sulfide solid electrolyte.

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