A hexagonal flaky cobalt-nickel bimetallic sulfide composite material and its preparation method and application

Abstract

The present invention provides a cobalt-nickel bimetallic sulfide composite material, comprising a hexagonal sheet of cobalt-nickel bimetallic sulfide and Li7P3S composited on the cobalt-nickel bimetallic sulfide. 11 Material. The cobalt-nickel bimetallic sulfide composite material provided by the present invention has a special micromorphology and composition, and is a hexagonal lamellar binary transition metal sulfide. The composite material can not only achieve a higher contact area with the solid electrolyte, but the lamellar structure is also conducive to interface modification. The hexagonal lamellar cobalt-nickel bimetallic sulfide positive electrode material with freely adjustable cobalt-nickel ratio prepared by the present invention has outstanding electrochemical properties, high reversible specific capacity and good cycle stability; and the preparation method has simple synthesis steps and mild conditions, which is suitable for large-scale production promotion and application. It has broad application prospects as an active substance in all-solid-state battery positive electrode materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of all-solid-state lithium-ion battery positive electrodes, and relates to a cobalt-nickel bimetallic sulfide composite material, a preparation method and applications thereof, and in particular to a hexagonal flaky cobalt-nickel bimetallic sulfide composite material, a preparation method and applications thereof. Background Art

[0002] Lithium-ion batteries typically consist of a positive electrode, a negative electrode, a separator, an electrolyte, and a casing. They offer advantages such as high operating voltage, high specific energy, long cycle life, light weight, low self-discharge, no memory effect, and a high performance-price ratio. They have become the primary choice for rechargeable power sources in high-power electric vehicles, satellites, aerospace, and other fields. However, with increasing demands for higher battery capacity and long cycle life in electronic devices, the performance of existing lithium-ion batteries is gradually failing to meet these requirements. Because traditional lithium-ion batteries pose significant safety risks when used in electric vehicles and mobile electronic devices, all-solid-state lithium batteries using inorganic solid electrolytes are considered a highly promising alternative.

[0003] Solid-state lithium batteries, as opposed to liquid lithium batteries, are energy storage devices whose structure contains no liquid, with all materials present in solid form. Specifically, they are composed of a positive electrode material, a negative electrode material, and an electrolyte, while liquid lithium batteries are composed of a positive electrode material, a negative electrode material, an electrolyte, and a separator. All-solid-state lithium-ion batteries, including the positive electrode, electrolyte, and negative electrode, are all made of solid materials. Compared to traditional liquid electrolyte lithium-ion batteries, they offer the following advantages: ① They completely eliminate the safety hazards of electrolyte corrosion and leakage, resulting in higher thermal stability; ② They do not require liquid encapsulation, supporting serial stacking and bipolar structures, improving production efficiency; ③ Due to the solid-state nature of solid electrolytes, multiple electrodes can be stacked; ④ The electrochemical stability window is wide (up to 5V or above), making them compatible with high-voltage electrode materials; ⑤ Solid electrolytes are generally single-ion conductors, with virtually no side reactions and a longer service life. Therefore, replacing traditional organic liquid electrolytes with solid electrolytes is expected to fundamentally address battery safety issues and is an ideal chemical power source for electric vehicles and large-scale energy storage.

[0004] The key to all-solid-state lithium batteries mainly includes the preparation of solid electrolytes with high room-temperature conductivity and electrochemical stability, high-energy electrode materials suitable for all-solid-state lithium-ion batteries, and improving the electrode / solid electrolyte interface compatibility. Among them, achieving high energy and high power density is the biggest challenge currently facing all-solid-state lithium batteries. Transition metal sulfides have attracted widespread attention due to their good interface compatibility with solid electrolytes, moderate operating voltage, good chemical stability and high theoretical capacity. Compared with the corresponding metal oxides, metal sulfides have better conductivity, mechanical properties and thermal stability, as well as higher electrochemical activity, and have become one of the main research directions in the industry. However, in the existing research on all-solid-state lithium batteries, the specific capacity of the positive electrode still needs to be further improved to better provide a solid foundation for subsequent applications.

[0005] Therefore, how to find a suitable material to solve the above-mentioned problems of existing all-solid-state lithium-ion batteries has become one of the focuses of widespread attention of many researchers in the industry. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a cobalt-nickel bimetallic sulfide composite material and its preparation method and application, in particular a hexagonal flake cobalt-nickel bimetallic sulfide composite material. The hexagonal flake-shaped binary transition metal sulfide provided by the present invention can not only achieve a higher contact area with the solid electrolyte, but the flake structure is also conducive to interface modification, thereby realizing an all-solid-state lithium battery with higher energy and better cycle performance.

[0007] The present invention provides a cobalt-nickel bimetallic sulfide composite material, comprising a hexagonal sheet of cobalt-nickel bimetallic sulfide and Li7P3S composited on the cobalt-nickel bimetallic sulfide. 11 Material.

[0008] Preferably, the hexagonal cobalt-nickel bimetallic sulfide has a sheet diameter of 0.1 to 20 μm;

[0009] The thickness of the square-plate cobalt-nickel bimetallic sulfide is 0.01 to 5 μm;

[0010] The molar ratio of cobalt to nickel in the cobalt-nickel bimetallic sulfide is (0.1-20):1;

[0011] The Li7P3S 11 Materials include Li7P3S 11 Solid-state electrolyte.

[0012] Preferably, the Li7P3S composited on the cobalt-nickel bimetallic sulfide 11 The material includes Li7P3S composited on cobalt-nickel bimetallic sulfide 11 Material layer;

[0013] The Li7P3S 11 The specific material is Li7P3S 11 granular materials;

[0014] The Li7P3S 11 The granular material has a spherical morphology;

[0015] The Li7P3S 11 The particle size of the granular material is 0.001 to 5 μm.

[0016] Preferably, the cobalt-nickel bimetallic sulfide and the Li7P3S 11 The mass ratio of the materials is (0.1-10):1;

[0017] The Li7P3S 11 The material is coated on the surface of the hexagonal sheet-shaped cobalt-nickel bimetallic sulfide to form a coating structure;

[0018] The cobalt-nickel bimetallic sulfide composite material comprises a hexagonal sheet-shaped cobalt-nickel bimetallic sulfide composite material;

[0019] The cobalt-nickel bimetallic sulfide composite material is specifically a cobalt-nickel bimetallic sulfide composite positive electrode material;

[0020] The positive electrode material includes a positive electrode material of an all-solid-state lithium-ion battery.

[0021] The present invention provides a method for preparing a cobalt-nickel bimetallic sulfide composite material, comprising the following steps:

[0022] 1) reacting a cobalt salt, a nickel salt, an alkali and water to obtain a Co-Ni layered double hydroxide;

[0023] 2) mixing the Co-Ni layered double hydroxide obtained in the above step, liquid bromine and acetonitrile to react to obtain an intermediate product;

[0024] 3) mixing the intermediate product obtained in the above step, a sulfur source, and water, and performing a hydrothermal reaction to obtain a hexagonal sheet-shaped cobalt-nickel bimetallic sulfide;

[0025] 4) The hexagonal flaky cobalt-nickel bimetallic sulfide, lithium sulfide, phosphorus pentasulfide and organic solvent obtained in the above steps are mixed again, and then annealed to obtain a cobalt-nickel bimetallic sulfide composite material.

[0026] Preferably, the cobalt salt includes one or more of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt sulfate heptahydrate, cobalt carbonate, cobalt bromide and cobalt iodide;

[0027] The nickel salt includes one or more of nickel nitrate hexahydrate, cobalt sulfate hexahydrate, nickel chloride hexahydrate, nickel carbonate, nickel bromide and nickel iodide;

[0028] The base includes one or more of hexamethylenetetramine, ammonia water and sodium hydroxide;

[0029] The molar ratio of the cobalt salt to the nickel salt is (0.1-20):1;

[0030] The usage ratio of water to hexamethylenetetramine is (0.5-15) mL:1 mM;

[0031] The molar ratio of the nickel salt to hexamethylenetetramine is (0.01-3):1.

[0032] Preferably, the reaction temperature is 80-150°C;

[0033] The reaction time is 2 to 40 hours;

[0034] The reaction further includes a drying step;

[0035] The drying temperature is 40-80°C;

[0036] The ratio of the liquid bromine to the Co-Ni layered double hydroxide is (0.1-10) mL: 1 g;

[0037] The mixed reaction is carried out under light-proof conditions;

[0038] The mixing reaction time is 1 to 50 hours.

[0039] Preferably, the sulfur source includes one or more of cysteine, sulfur powder, sodium sulfide, thioacetamide, thiourea and sodium thiosulfate;

[0040] The mass ratio of the sulfur source to the Co-Ni layered double hydroxide is (0.1-20):1;

[0041] The temperature of the hydrothermal reaction is 100-200°C;

[0042] The hydrothermal reaction time is 20 to 48 hours;

[0043] After the hydrothermal reaction, the step further includes one or more steps of water washing, alcohol washing, separation and drying;

[0044] The organic solvent includes one or more of acetonitrile, chlorobenzene, n-heptane, n-hexane, deionized water, glycerol, ethanol and methanol.

[0045] Preferably, the mass ratio of the hexagonal sheet-shaped cobalt-nickel bimetallic sulfide to phosphorus pentasulfide is (0.1-40):1;

[0046] The mass ratio of lithium sulfide to phosphorus pentasulfide is (0.1-10):1;

[0047] The ratio of the organic solvent to the hexagonal sheet-shaped cobalt-nickel bimetallic sulfide is (5-100) mL: 1 g;

[0048] The temperature of the remixing is 20 to 70° C.

[0049] The time for remixing is 20 to 48 hours;

[0050] The annealing temperature is 200-300°C;

[0051] The annealing treatment time is 0.1 to 8 hours.

[0052] The present invention also provides the use of the cobalt-nickel bimetallic sulfide composite material described in any one of the above technical solutions or the cobalt-nickel bimetallic sulfide composite material prepared by the preparation method described in any one of the above technical solutions in the field of all-solid-state lithium-ion battery positive electrode materials.

[0053] The present invention provides a cobalt-nickel bimetallic sulfide composite material, comprising a hexagonal sheet of cobalt-nickel bimetallic sulfide and Li7P3S composited on the cobalt-nickel bimetallic sulfide. 11 Materials. Compared with the prior art, the present invention is aimed at the demand that the specific capacity of the positive electrode of the existing all-solid-state lithium-ion battery positive electrode materials still needs to be further improved. Based on the research, the present invention believes that compared with single metal sulfides, multi-metal sulfides have higher electronic conductivity and richer redox reactions, and can show great advantages when applied to electrode materials of lithium-ion batteries. However, in all-solid-state batteries, the electrodes and electrolytes are in solid-solid contact, and the element diffusion, space charge layer and possible interface stress from the interface will cause huge interface impedance. Therefore, it is very necessary to synthesize electrode materials that can achieve better contact with solid electrolytes.

[0054] This invention creatively provides a cobalt-nickel bimetallic sulfide composite material with a unique micromorphology and composition. It is a hexagonal, flaky binary transition metal sulfide. This composite material not only achieves a higher contact area with solid electrolytes, but its flaky structure also facilitates interfacial modification, such as in-situ solid electrolyte coating of the electrode surface. Furthermore, this composite material is a hexagonal, flaky cobalt-nickel bimetallic sulfide cathode material with a freely adjustable metal ratio. By freely adjusting the ratio of the bimetallic cobalt and nickel, the optimal performance component can be identified, enabling the realization of all-solid-state lithium batteries with higher energy and improved cycle performance.

[0055] The hexagonal bimetallic sulfide sheets with freely adjustable cobalt-nickel ratios prepared by the present invention have outstanding electrochemical properties, high reversible specific capacity and good cycle stability. Moreover, the preparation method has simple synthesis steps and mild conditions, making it suitable for large-scale production promotion and application. As an active substance, it has broad application prospects in all-solid-state battery positive electrode materials.

[0056] Experimental results show that the cobalt-nickel bimetallic sulfide with a nickel-to-cobalt ratio of 1:9 prepared by the present invention is used as a battery positive electrode material in all-solid-state batteries. After 60 cycles at a current density of 1 A / g, it can still maintain a discharge specific capacity of 660.8 mAh / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 X-ray images of bimetallic sulfides with a certain cobalt-nickel ratio prepared in an embodiment of the present invention;

[0058] Figure 2 This is a SEM image of a bimetallic sulfide with a certain cobalt-nickel ratio prepared in an embodiment of the present invention;

[0059] Figure 3 This is a SEM image of the bimetallic sulfide composite material prepared in Example 1 of the present invention;

[0060] Figure 4 This is a charge-discharge cycle diagram of 60 cycles of the bimetallic sulfide composite material prepared in Example 1 of the present invention as an electrode material assembled in an all-solid state at a current density of 1 A / g. DETAILED DESCRIPTION

[0061] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than for limiting the claims of the invention.

[0062] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0063] The raw materials used in the present invention are not particularly limited in purity. The present invention preferably uses analytically pure materials or conventional purities in the field of manufacturing positive electrode materials for all-solid-state lithium-ion batteries.

[0064] All raw materials of the present invention, their brands and abbreviations are conventional brands and abbreviations in the field. Each brand and abbreviation is clear and unambiguous in the field of its relevant use. Those skilled in the art can purchase them from the market or prepare them by conventional methods based on the brand, abbreviation and corresponding use.

[0065] The abbreviations of all processes of the present invention are conventional abbreviations in the field. Each abbreviation is clear and unambiguous in the field of its relevant use. Those skilled in the art can understand its conventional process steps based on the abbreviations.

[0066] The present invention provides a cobalt-nickel bimetallic sulfide composite material, comprising a hexagonal sheet of cobalt-nickel bimetallic sulfide and Li7P3S composited on the cobalt-nickel bimetallic sulfide. 11 Material.

[0067] The cobalt-nickel bimetallic sulfide composite material of the present invention comprises hexagonal sheet-shaped cobalt-nickel bimetallic sulfide.

[0068] In the present invention, the hexagonal sheet-shaped cobalt-nickel bimetallic sulfide preferably has a sheet diameter of 0.1 to 20 μm, more preferably 0.5 to 18 μm, more preferably 1 to 15 μm, and more preferably 5 to 10 μm.

[0069] In the present invention, the thickness of the square-plate-shaped cobalt-nickel bimetallic sulfide is preferably 0.01 to 5 μm, more preferably 0.05 to 4.5 μm, more preferably 0.1 to 4 μm, more preferably 0.5 to 3.5 μm, and more preferably 1 to 3 μm.

[0070] In the present invention, the molar ratio of cobalt to nickel in the cobalt-nickel bimetallic sulfide is preferably (0.1-20):1, more preferably (0.5-18):1, more preferably (1-15):1, and more preferably (5-10):1.

[0071] The cobalt-nickel bimetallic sulfide composite material of the present invention further comprises Li7P3S composited on the cobalt-nickel bimetallic sulfide. 11 Material.

[0072] In the present invention, the Li7P3S 11 The material preferably includes Li7P3S 11 Solid-state electrolyte.

[0073] In the present invention, the Li7P3S composited on the cobalt-nickel bimetallic sulfide 11 The material preferably includes Li7P3S composited on cobalt-nickel bimetallic sulfide 11 Specifically, the surface of the cobalt-nickel bimetallic sulfide is preferably coated with Li7P3S 11 More specifically, the Li7P3S 11 The material is coated on the surface of the hexagonal sheet-shaped cobalt-nickel bimetallic sulfide to form a coating structure.

[0074] In particular, in the present invention, the hexagonal sheet-like cobalt-nickel bimetallic sulfide is composited with Li7P3S 11After the material is processed, the original hexagonal sheet structure is still maintained. That is, the cobalt-nickel bimetallic sulfide composite material is preferably a hexagonal sheet cobalt-nickel bimetallic sulfide composite material. The cobalt-nickel bimetallic sulfide composite material of the present invention preferably has a hexagonal sheet microstructure.

[0075] In the present invention, the Li7P3S 11 The material can be specifically Li7P3S 11 Granular material.

[0076] In the present invention, the Li7P3S 11 The particulate material preferably has a spherical morphology;.

[0077] In the present invention, the Li7P3S 11 The particle size of the granular material is preferably 0.001 to 5 μm, more preferably 0.01 to 4.5 μm, more preferably 0.1 to 4 μm, and even more preferably 1 to 3 μm.

[0078] In the present invention, the cobalt-nickel bimetallic sulfide and the Li7P3S 11 The mass ratio of the materials is preferably (0.1 to 10):1, more preferably (0.5 to 8):1, more preferably (1 to 6):1, and even more preferably (2 to 5):1.

[0079] In the present invention, the cobalt-nickel bimetallic sulfide composite material is specifically a cobalt-nickel bimetallic sulfide composite positive electrode material.

[0080] In the present invention, the positive electrode material preferably includes a positive electrode material of an all-solid-state lithium-ion battery.

[0081] The present invention provides a method for preparing a cobalt-nickel bimetallic sulfide composite material, comprising the following steps:

[0082] 1) reacting a cobalt salt, a nickel salt, an alkali and water to obtain a Co-Ni layered double hydroxide;

[0083] 2) mixing the Co-Ni layered double hydroxide obtained in the above step, liquid bromine and acetonitrile to react to obtain an intermediate product;

[0084] 3) mixing the intermediate product obtained in the above step, a sulfur source, and water, and performing a hydrothermal reaction to obtain a hexagonal sheet-shaped cobalt-nickel bimetallic sulfide;

[0085] 4) The hexagonal flaky cobalt-nickel bimetallic sulfide, lithium sulfide, phosphorus pentasulfide and organic solvent obtained in the above steps are mixed again, and then annealed to obtain a cobalt-nickel bimetallic sulfide composite material.

[0086] The invention firstly reacts cobalt salt, nickel salt, alkali and water to obtain Co-Ni layered double metal hydroxide.

[0087] In the present invention, the cobalt salt preferably includes one or more of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt sulfate heptahydrate, cobalt carbonate, cobalt bromide and cobalt iodide, more preferably cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt sulfate heptahydrate, cobalt carbonate, cobalt bromide or cobalt iodide.

[0088] In the present invention, the nickel salt preferably includes one or more of nickel nitrate hexahydrate, cobalt sulfate hexahydrate, nickel chloride hexahydrate, nickel carbonate, nickel bromide and nickel iodide, more preferably nickel nitrate hexahydrate, cobalt sulfate hexahydrate, nickel chloride hexahydrate, nickel carbonate, nickel bromide or nickel iodide.

[0089] In the present invention, the base preferably includes one or more of hexamethylenetetramine, ammonia water and sodium hydroxide, more preferably hexamethylenetetramine, ammonia water or sodium hydroxide.

[0090] In the present invention, the molar ratio of the cobalt salt to the nickel salt is preferably (0.1-20):1, more preferably (0.5-15):1, more preferably (1-10):1, and more preferably (3-8):1.

[0091] In the present invention, the usage ratio of water to hexamethylenetetramine is preferably (0.5-15) mL:1 mM, more preferably (2.5-13) mL:1 mM, more preferably (4.5-11) mL:1 mM, and more preferably (6.5-9) mL:1 mM.

[0092] In the present invention, the molar ratio of the nickel salt to hexamethylenetetramine is preferably (0.01-3):1, more preferably (0.1-2.5):1, more preferably (0.5-2):1, and more preferably (1-1.5):1.

[0093] In the present invention, the reaction temperature is preferably 80-150°C, more preferably 90-140°C, more preferably 100-130°C, and more preferably 110-120°C.

[0094] In the present invention, the reaction time is preferably 2 to 40 hours, more preferably 7 to 35 hours, more preferably 12 to 30 hours, and more preferably 17 to 25 hours.

[0095] In the present invention, the reaction is followed by a drying step, preferably at a temperature of 40 to 80°C, more preferably 50 to 70°C.

[0096] The present invention then mixes the Co-Ni layered double metal hydroxide obtained in the above steps, liquid bromine and acetonitrile to react, thereby obtaining an intermediate product.

[0097] In the present invention, the usage ratio of the liquid bromine to the Co-Ni layered double hydroxide is preferably (0.1-10) mL:1 g, more preferably (0.5-8) mL:1 g, more preferably (1-6) mL:1 g, and more preferably (2-5) mL:1 g.

[0098] In the present invention, the mixing reaction is preferably carried out under light-proof conditions.

[0099] In the present invention, the mixing reaction time is preferably 1 to 50 hours, more preferably 10 to 40 hours, and even more preferably 20 to 30 hours.

[0100] The present invention mixes the intermediate product obtained in the above steps, a sulfur source and water, and performs a hydrothermal reaction to obtain hexagonal sheet-shaped cobalt-nickel bimetallic sulfide.

[0101] In the present invention, the sulfur source preferably includes one or more of cysteine, sulfur powder, sodium sulfide, thioacetamide, thiourea and sodium thiosulfate, more preferably cysteine, sulfur powder, sodium sulfide, thioacetamide, thiourea or sodium thiosulfate.

[0102] In the present invention, the mass ratio of the sulfur source to the Co-Ni layered double hydroxide is preferably (0.1-20):1, more preferably (1-18):1, more preferably (5-15):1, and more preferably (8-12):1.

[0103] In the present invention, the temperature of the hydrothermal reaction is preferably 100-200°C, more preferably 120-180°C, and even more preferably 140-160°C.

[0104] In the present invention, the hydrothermal reaction time is preferably 20 to 48 hours, more preferably 26 to 42 hours, and even more preferably 32 to 26 hours.

[0105] In the present invention, the hydrothermal reaction preferably further comprises one or more steps of water washing, alcohol washing, separation and drying, more preferably water washing, alcohol washing, separation and drying.

[0106] Finally, the present invention mixes the hexagonal sheet-shaped cobalt-nickel bimetallic sulfide, lithium sulfide, phosphorus pentasulfide and organic solvent obtained in the above steps again, and then performs annealing treatment to obtain a cobalt-nickel bimetallic sulfide composite material.

[0107] In the present invention, the organic solvent preferably includes one or more of acetonitrile, chlorobenzene, n-heptane, n-hexane, deionized water, glycerol, ethanol and methanol, more preferably acetonitrile, chlorobenzene, n-heptane, n-hexane, deionized water, glycerol, ethanol or methanol.

[0108] In the present invention, the mass ratio of the hexagonal sheet-shaped cobalt-nickel bimetallic sulfide to phosphorus pentasulfide is preferably (0.1-40):1, more preferably (1-35):1, more preferably (10-30):1, and more preferably (15-25):1.

[0109] In the present invention, the mass ratio of lithium sulfide to phosphorus pentasulfide is preferably (0.1-10):1, more preferably (0.5-8):1, more preferably (1-6):1, and more preferably (2-5):1.

[0110] In the present invention, the usage ratio of the organic solvent to the hexagonal sheet-shaped cobalt-nickel bimetallic sulfide is preferably (5-100) mL:1 g, more preferably (25-80) mL:1 g, and even more preferably (45-60) mL:1 g.

[0111] In the present invention, the temperature of the remixing is preferably 20 to 70°C, more preferably 30 to 60°C, and even more preferably 40 to 50°C.

[0112] In the present invention, the remixing time is preferably 20 to 48 hours, more preferably 26 to 42 hours, and even more preferably 32 to 26 hours.

[0113] In the present invention, the temperature of the annealing treatment is preferably 200-300°C, more preferably 220-280°C, and even more preferably 240-260°C.

[0114] In the present invention, the annealing treatment time is 0.1 to 8 hours, more preferably 0.5 to 6 hours, more preferably 1 to 5 hours, and more preferably 2 to 4 hours.

[0115] The present invention is to complete and refine the overall preparation scheme, better ensure the structure, morphology and parameters of the cobalt-nickel bimetallic sulfide composite material, and improve the performance as a positive electrode material for all-solid-state lithium-ion batteries. The above preparation method can specifically include the following steps:

[0116] (a) Weigh a certain amount of cobalt salt, nickel salt, and alkaline source and add them to a certain amount of deionized water. Stir in an oil bath at a constant temperature.

[0117] (b) The reaction solution is filtered using a Buchner funnel and dried under certain temperature conditions to obtain a Co-Ni layered double hydroxide (LDH).

[0118] (c) A certain amount of LDH solid was dissolved in acetonitrile, and a certain amount of liquid bromine was added and stirred under light-proof conditions. The solution turned dark yellow.

[0119] (d) Wash the product with deionized water and ethanol, respectively, and dry it in air.

[0120] (e) Add a certain amount of the collected solid and sulfur source to the solvent water and stir until the mixture is uniform. The above mixture is transferred to a hydrothermal reactor and subjected to hydrothermal reaction to obtain a black precipitate.

[0121] (f) The hexagonal cobalt-nickel bimetallic sulfide was obtained by centrifugation and washing with water and ethanol several times, and freeze-drying.

[0122] (g) adding a certain amount of bimetallic sulfide, lithium sulfide, and phosphorus pentasulfide to an organic solvent, heating and stirring, and then removing the organic solvent by suction filtration and drying.

[0123] (h) The solid was annealed at 260 °C to obtain surface-coated Li7P3S 11 Hexagonal sheets of cobalt-nickel bimetallic sulfide.

[0124] The present invention uses cobalt salt, nickel salt and sulfur source as main raw materials, adjusts the ratio of cobalt and nickel, and uses alkaline source to make them uniformly hydrolyzed and precipitated. After collecting the product and oxidizing it with bromine, it is added together with sulfur source at a certain temperature and pressure. After centrifugal washing and freeze drying, hexagonal sheet-shaped cobalt-nickel bimetallic sulfide with different cobalt-nickel ratios is obtained, and finally a layer of Li7P3S is in situ coated. 11 The solid electrolyte optimizes interfacial contact, resulting in a cobalt-nickel bimetallic sulfide with a hexagonal sheet structure and a freely adjustable metal ratio. The hexagonal bimetallic sulfide sheet with a freely adjustable cobalt-nickel ratio prepared by the present invention exhibits outstanding electrochemical performance, high reversible specific capacity, and good cycling stability.

[0125] The present invention also provides the use of the cobalt-nickel bimetallic sulfide composite material described in any one of the above technical solutions or the cobalt-nickel bimetallic sulfide composite material prepared by the preparation method described in any one of the above technical solutions in the field of all-solid-state lithium-ion battery positive electrode materials.

[0126] The above steps of the present invention provide a hexagonal flaky cobalt-nickel bimetallic sulfide composite material, its preparation method, and its application. The cobalt-nickel bimetallic sulfide composite material provided by the present invention has a unique microscopic morphology and composition. It is a hexagonal flaky binary transition metal sulfide. This composite material not only achieves a higher contact area with the solid electrolyte, but its flaky structure also facilitates interfacial modification, such as in-situ solid electrolyte coating of the electrode surface.

[0127] The present invention also discloses a method for preparing a hexagonal sheet-shaped cobalt-nickel bimetallic sulfide with an adjustable cobalt-nickel ratio. The method uses cobalt nitrate hexahydrate, nickel nitrate hexahydrate, hexamethylenetetramine, bromine, and sodium sulfide as main raw materials. First, a uniform hydrolysis process is carried out. Then, the product is collected by filtration and drying and added to an acetonitrile solvent together with bromine and stirred. After the solid is collected, it is dissolved in water together with sodium sulfide, heated at a certain temperature and pressure, washed, and freeze-dried to obtain the cobalt-nickel bimetallic sulfide. The product, lithium sulfide, and phosphorus pentasulfide are added to acetonitrile and stirred, the solvent is removed, and annealing is performed to finally obtain Li7P3S 11 Uniformly coated cobalt-nickel bimetallic sulfide, as an active substance, has broad application prospects in all-solid-state battery positive electrode materials.

[0128] The hexagonal bimetallic sulfide sheets with a freely adjustable cobalt-nickel ratio, prepared by the present invention, exhibit outstanding electrochemical properties, high reversible specific capacity, and excellent cycling stability. By freely adjusting the ratio of bimetallic cobalt and nickel, the optimal component can be found, enabling the realization of all-solid-state lithium batteries with higher energy and improved cycling performance. Furthermore, the preparation method features simple synthesis steps and mild conditions, making it suitable for large-scale production and application. Using this active material as a cathode material for all-solid-state lithium-ion batteries holds broad application prospects.

[0129] Experimental results show that the cobalt-nickel bimetallic sulfide with a nickel-to-cobalt ratio of 1:9 prepared by the present invention is used as a battery positive electrode material in all-solid-state batteries. After 60 cycles at a current density of 1 A / g, it can still maintain a discharge specific capacity of 660.8 mAh / g.

[0130] To further illustrate the present invention, a cobalt-nickel bimetallic sulfide composite material provided by the present invention, its preparation method, and application are described in detail below in conjunction with examples. However, it should be understood that these examples are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operating procedures are provided only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention. The scope of protection of the present invention is not limited to the following examples.

[0131] Example 1

[0132] 1) Add 0.2 g of nickel nitrate hexahydrate and 1.8 g of cobalt nitrate hexahydrate to 1000 mL of deionized water, add 100 mM hexamethylenetetramine hydrolyzing agent, and stir in a 90°C oil bath for 5 h to obtain Co-NiLDH with a certain cobalt-nickel ratio (Ni:Co = 0.1:0.9);

[0133] 2) Weigh 0.5 g of the product and 3 mL of bromine into 500 mL of acetonitrile and stir at room temperature in the dark for 48 h. Filter and wash with deionized water and ethanol, then dry at 50°C.

[0134] 3) Weigh 0.1 g of the collected solid and 0.6 g of sodium sulfide, add them to 70 mL of water and stir evenly. Transfer the solution to the liner of a reactor, heat at 180° C. for 24 h, cool, centrifuge, wash with deionized water, and freeze-dry to obtain a certain proportion of cobalt-nickel bimetallic sulfide;

[0135] The cobalt-nickel bimetallic sulfide prepared in Example 1 of the present invention was characterized.

[0136] See also Figure 1 , Figure 1 X-ray images of bimetallic sulfides with a certain cobalt-nickel ratio prepared in an embodiment of the present invention.

[0137] See also Figure 2 , Figure 2 This is a SEM image of a bimetallic sulfide with a certain cobalt-nickel ratio prepared in an embodiment of the present invention.

[0138] 4) 0.85 g of bimetallic sulfide, 0.11 g of lithium sulfide, and 0.05 g of phosphorus pentasulfide were added to 20 mL of acetonitrile and stirred at 50° C. for 24 h under an argon atmosphere. The acetonitrile solvent was then removed by filtration and drying at 60° C., and finally annealed at 260° C. to obtain the final product.

[0139] The cobalt-nickel bimetallic sulfide composite material prepared in Example 1 of the present invention was characterized.

[0140] See also Figure 3 , Figure 3 This is a SEM scanning electron microscope image of the bimetallic sulfide composite material prepared in Example 1 of the present invention.

[0141] See also Figure 4 , Figure 4 This is a charge-discharge cycle diagram of 60 cycles of the bimetallic sulfide composite material prepared in Example 1 of the present invention as an electrode material assembled in an all-solid state at a current density of 1 A / g.

[0142] Example 2

[0143] 1) Add 0.4 g nickel nitrate hexahydrate and 1.6 g cobalt nitrate hexahydrate to 1000 mL deionized water, add 90 mM hexamethylenetetramine hydrolyzing agent, and stir in a 90°C oil bath for 5 h to obtain Co-NiLDH with a certain cobalt-nickel ratio (Ni:Co = 0.2:0.8);

[0144] 2) Weigh 0.5 g of the product and 3 mL of bromine into 500 mL of acetonitrile and stir at room temperature in the dark for 48 h. Filter and wash with deionized water and ethanol, then dry at 50°C.

[0145] 3) Weigh 0.1 g of the collected solid and 0.7 g of sodium sulfide, add them to 70 mL of water and stir evenly. Transfer the solution to the liner of a reactor, heat at 180° C. for 24 h, cool, centrifuge, wash with deionized water, and freeze-dry to obtain a certain proportion of cobalt-nickel bimetallic sulfide;

[0146] The cobalt-nickel bimetallic sulfide prepared in Example 2 of the present invention was characterized.

[0147] See also Figure 1 , Figure 1 X-ray images of bimetallic sulfides with a certain cobalt-nickel ratio prepared in an embodiment of the present invention.

[0148] See also Figure 2 , Figure 2 This is a SEM image of a bimetallic sulfide with a certain cobalt-nickel ratio prepared in an embodiment of the present invention.

[0149] 4) 0.5 g of bimetallic sulfide, 0.07 g of lithium sulfide, and 0.03 g of phosphorus pentasulfide were added to 20 mL of acetonitrile, stirred at 50° C. for 24 h under an argon atmosphere, then filtered and dried at 60° C. to remove the acetonitrile solvent, and finally annealed at 260° C. to obtain the final product.

[0150] Example 3

[0151] 1) Add 0.67 g nickel nitrate hexahydrate and 1.33 g cobalt nitrate hexahydrate to 1000 mL deionized water, add 80 mM hexamethylenetetramine hydrolyzing agent, and stir in a 90°C oil bath for 5 h to obtain Co-NiLDH with a certain cobalt-nickel ratio (Ni:Co = 1 / 3:2 / 3);

[0152] 2) Weigh 0.5 g of the product and 2 mL of bromine into 500 mL of acetonitrile and stir at room temperature in the dark for 48 h. Filter and wash with deionized water and ethanol, then dry at 50°C.

[0153] 3) Weigh 0.1 g of the collected solid and 0.8 g of sodium sulfide, add them to 70 mL of water and stir evenly. Transfer the solution to the liner of a reactor, heat at 180°C for 24 h, cool, centrifuge, wash with deionized water, and freeze-dry to obtain a certain proportion of cobalt-nickel bimetallic sulfide;

[0154] The cobalt-nickel bimetallic sulfide prepared in Example 3 of the present invention was characterized.

[0155] See also Figure 1 , Figure 1 X-ray images of bimetallic sulfides with a certain cobalt-nickel ratio prepared in an embodiment of the present invention.

[0156] See also Figure 2 , Figure 2This is a SEM image of a bimetallic sulfide with a certain cobalt-nickel ratio prepared in an embodiment of the present invention.

[0157] 4) 1 g of bimetallic sulfide, 0.14 g of lithium sulfide, and 0.06 g of phosphorus pentasulfide were added to 20 mL of acetonitrile and stirred at 50°C for 24 h under an argon atmosphere. The acetonitrile solvent was then removed by filtration and drying at 60°C. Finally, the final product was annealed at 260°C.

[0158] The cobalt-nickel bimetallic sulfide composite material prepared in Example 3 of the present invention was characterized.

[0159] See also Figure 1 , Figure 1 X-ray images of bimetallic sulfides with a certain cobalt-nickel ratio prepared in an embodiment of the present invention.

[0160] See also Figure 2 , Figure 2 This is a SEM image of a bimetallic sulfide with a certain cobalt-nickel ratio prepared in an embodiment of the present invention.

[0161] Example 4

[0162] 1) Add 1 g of nickel nitrate hexahydrate and 1 g of cobalt nitrate hexahydrate to 1000 mL of deionized water, add 110 mM hexamethylenetetramine hydrolyzing agent, and stir in a 90°C oil bath for 5 h to obtain Co-NiLDH with a certain cobalt-nickel ratio (Ni:Co = 0.5:0.5);

[0163] 2) Weigh 0.5 g of the product and 2 mL of bromine into 500 mL of acetonitrile and stir at room temperature in the dark for 48 h. Filter and wash with deionized water and ethanol, then dry at 50°C.

[0164] 3) Weigh 0.1 g of the collected solid and 0.5 g of sodium sulfide, add them to 70 mL of water and stir evenly. Transfer the solution to the liner of a reactor, heat at 180° C. for 24 h, cool, centrifuge, wash with deionized water, and freeze-dry to obtain a certain proportion of cobalt-nickel bimetallic sulfide;

[0165] The cobalt-nickel bimetallic sulfide prepared in Example 4 of the present invention was characterized.

[0166] See also Figure 1 , Figure 1 X-ray images of bimetallic sulfides with a certain cobalt-nickel ratio prepared in an embodiment of the present invention.

[0167] See also Figure 2 , Figure 2 This is a SEM image of a bimetallic sulfide with a certain cobalt-nickel ratio prepared in an embodiment of the present invention.

[0168] 4) 1.5 g of bimetallic sulfide, 0.19 g of lithium sulfide, and 0.08 g of phosphorus pentasulfide were added to 30 mL of acetonitrile and stirred at 50°C under an argon atmosphere for 24 h. The acetonitrile solvent was then removed by filtration and drying at 60°C. Finally, the final product was annealed at 260°C.

[0169] The above describes in detail the hexagonal sheet-shaped cobalt-nickel bimetallic sulfide composite material provided by the present invention, its preparation method, and its application. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above examples is intended only to facilitate understanding of the methods and core concepts of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including the manufacture and use of any device or system, and the implementation of any combined method. It should be noted that, without departing from the principles of the present invention, a person skilled in the art may make several improvements and modifications to the present invention, and such improvements and modifications fall within the scope of protection of the claims of the present invention. The scope of patent protection for the present invention is defined by the claims and may include other embodiments that may be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims, then these other embodiments are also intended to be included within the scope of the claims.

Claims

1. A method for preparing a cobalt-nickel bimetallic sulfide composite material, characterized in that: The following steps are involved: 1) A cobalt salt, a nickel salt, an alkali and water are hydrolyzed to obtain a Co-Ni layered double hydroxide; 2) mixing the Co-Ni layered double hydroxide obtained in the above step, liquid bromine and acetonitrile to obtain an intermediate product; The mixed reaction is carried out under light-proof conditions; The mixing reaction time is 1 to 50 hours; 3) mixing the intermediate product obtained in the above step, a sulfur source, and water, and performing a hydrothermal reaction to obtain a hexagonal sheet-like cobalt-nickel bimetallic sulfide; 4) The hexagonal sheet-like cobalt-nickel bimetallic sulfide, lithium sulfide, phosphorus pentasulfide and organic solvent obtained in the above steps are mixed again, and then annealed to obtain a cobalt-nickel bimetallic sulfide composite material.

2. The preparation method according to claim 1, characterized in that The cobalt salt includes one or more of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt sulfate heptahydrate, cobalt carbonate, cobalt bromide and cobalt iodide; The nickel salt includes one or more of nickel nitrate hexahydrate, cobalt sulfate hexahydrate, nickel chloride hexahydrate, nickel carbonate, nickel bromide and nickel iodide; The base includes one or more of hexamethylenetetramine, ammonia water and sodium hydroxide; The molar ratio of the cobalt salt to the nickel salt is (0.1-20):1; In the step 1), the ratio of water to hexamethylenetetramine is (0.5-15) mL:1 mM; The molar ratio of the nickel salt to hexamethylenetetramine is (0.01-3):

1.

3. The preparation method according to claim 1, characterized in that In the step 1), the reaction temperature is 80-150°C; In the step 1), the reaction time is 2 to 40 hours; In the step 1), a drying step is further included after the reaction; The drying temperature is 40-80°C; The usage ratio of the liquid bromine to the Co-Ni layered double hydroxide is (0.1-10) mL:1 g.

4. The preparation method according to claim 1, characterized in that The sulfur source includes one or more of cysteine, sulfur powder, sodium sulfide, thioacetamide, thiourea and sodium thiosulfate; The mass ratio of the sulfur source to the Co-Ni layered double hydroxide is (0.1-20):1; The temperature of the hydrothermal reaction is 100-200°C; The hydrothermal reaction time is 20 to 48 hours; After the hydrothermal reaction, the step further includes one or more steps of water washing, alcohol washing, separation and drying; The organic solvent includes one or more of acetonitrile, chlorobenzene, n-heptane, n-hexane, deionized water, glycerol, ethanol and methanol.

5. The preparation method according to claim 1, characterized in that The mass ratio of the hexagonal sheet-shaped cobalt-nickel bimetallic sulfide to phosphorus pentasulfide is (0.1-40): 1; The mass ratio of lithium sulfide to phosphorus pentasulfide is (0.1-10):1; The ratio of the organic solvent to the hexagonal cobalt-nickel bimetallic sulfide is (5-100) mL: 1 g; The temperature of the remixing is 20-70°C; The time for remixing is 20 to 48 hours; The annealing temperature is 200-300°C; The annealing treatment time is 0.1~8h.

6. The preparation method according to claim 1, characterized in that The cobalt-nickel bimetallic sulfide composite material comprises hexagonal sheet-shaped cobalt-nickel bimetallic sulfide and Li7P3S composited on the cobalt-nickel bimetallic sulfide. 11 Material.

7. The preparation method according to claim 6, characterized in that The hexagonal cobalt-nickel bimetallic sulfide has a sheet diameter of 0.1 to 20 μm; The thickness of the hexagonal sheet of cobalt-nickel bimetallic sulfide is 0.01-5 μm; The molar ratio of cobalt to nickel in the cobalt-nickel bimetallic sulfide is (0.1-20):1; The Li7P3S 11 Materials include Li7P3S 11 Solid-state electrolyte.

8. The preparation method according to claim 6, characterized in that The Li7P3S composite on the cobalt-nickel bimetallic sulfide 11 The material includes Li7P3S composited on cobalt-nickel bimetallic sulfide 11 Material layer; The Li7P3S 11 The specific material is Li7P3S 11 granular materials; The Li7P3S 11 The granular material has a spherical morphology; The Li7P3S 11 The particle size of the granular material is 0.001~5μm.

9. The preparation method according to claim 6, characterized in that The cobalt-nickel bimetallic sulfide and the Li7P3S 11 The mass ratio of the materials is (0.1~10):1; The Li7P3S 11 The material is coated on the surface of the hexagonal sheet-shaped cobalt-nickel bimetallic sulfide to form a coating structure; The cobalt-nickel bimetallic sulfide composite material comprises a hexagonal sheet-shaped cobalt-nickel bimetallic sulfide composite material; The cobalt-nickel bimetallic sulfide composite material is specifically a cobalt-nickel bimetallic sulfide composite positive electrode material; The positive electrode material includes a positive electrode material of an all-solid-state lithium-ion battery.

10. Use of the cobalt-nickel bimetallic sulfide composite material prepared by the preparation method according to any one of claims 1 to 9 in the field of all-solid-state lithium-ion battery positive electrode materials.

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