A molybdenum-based cathode material, its preparation method, and cathode sheet

Abstract

This invention relates to a molybdenum-based cathode material, its preparation method, and the cathode sheet. The preparation method includes the following steps: (1) mixing a lithium source, a molybdenum source, additives, and a solvent to obtain a mixed solution A; (2) drying the mixed solution A obtained in step (1), grinding, and calcining to obtain a molybdenum-based precursor; (3) mixing a borate, a lithium source, a solvent, and the molybdenum-based precursor obtained in step (2) to obtain a mixed solution B; (4) drying the mixed solution B obtained in step (2) and calcining to obtain the molybdenum-based cathode material. The preparation method provided by this invention yields a molybdenum-based cathode material with a sheet-like structure, which has a high energy density. During the lithium-ion insertion / extraction process in the battery, it can effectively shorten the diffusion path of lithium ions and accelerate the migration rate of lithium ions, thereby achieving excellent electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material manufacturing technology, and relates to a method for preparing a molybdenum-based cathode material, and more particularly to a molybdenum-based cathode material, its preparation method and cathode sheet. Background Technology

[0002] As the most crucial component of lithium-ion batteries, the cathode material accounts for approximately 40% of the total battery cost. Furthermore, since the actual capacity of the cathode material is far smaller than that of the current anode material, its performance has a vital impact on the electrochemical performance of lithium-ion batteries. Lithium-rich materials are considered one of the most promising cathode materials due to their advantages such as high reversible specific capacity, low cost, and environmental friendliness. However, to achieve their industrial application, several key technical challenges must be addressed: first, reducing initial irreversible capacity loss; second, improving rate performance and cycle life; and third, suppressing voltage decay during cycling. These problems are mainly caused by internal defects affecting the structure, necessitating the search for alternative materials with higher specific capacity to overcome these inherent defects. Therefore, it is essential to start with the microstructure of the materials.

[0003] Replacing Li₂MnO₃ with a Li₂MO₃ phase composed of non-manganese transition metals to construct novel non-manganese-based lithium-rich materials leverages the lithium storage advantages of the Li₂MO₃ phase while suppressing structural instability at high potentials. Among these, the novel cathode material Li₂MnO₃ possesses a high theoretical specific capacity due to its ability to allow for multi-electron transfer, while the transition metal Mo exhibits multi-electron redox reactions and can form hexavalent forms in various oxidation states. These unique advantages make Li₂MnO₃ a promising candidate for next-generation novel cathode materials.

[0004] CN 106206046A provides a method for preparing graphene composite Li2MoO3 cathode material. The method includes the following steps: Step (1) mixing Li2CO3 and MoO3, mixing them evenly, and then reacting them in a muffle furnace. After the reaction, Li2MoO4 material is obtained; Step (2) the obtained Li2MoO4 is reacted in a muffle furnace under a hydrogen-nitrogen mixed atmosphere. After the reaction, Li2MoO3 material is obtained; Step (3) high specific surface area graphene material and Li2MoO3 material are mixed and ball-milled to obtain graphene composite Li2MoO3 material. This invention has the following beneficial effects: (1) As the cathode of a lithium-ion supercapacitor, graphene composite Li2MoO3 material eliminates the need for lithium sheets or complex pre-lithiation processes in the anode, simplifying the preparation process and reducing costs; (2) Graphene composite Li2MoO3 material has high conductivity and high specific surface area, effectively replacing conventional activated carbon cathode materials to achieve high energy density.

[0005] CN 105895893A relates to a method for preparing a positive electrode material for lithium-ion batteries using lithium molybdenum vanadium oxide (LMV) batteries, comprising the following steps: 1) Weighing lithium source, molybdenum source, and vanadium source, dissolving them in deionized water, and mixing with a citric acid aqueous solution; 2) After thorough mixing of the solution in step 1), adjusting the pH of the mixed solution with ammonia water, stirring thoroughly in a water bath to obtain a sol, drying, foaming, and then performing combustion treatment in air, cooling, and grinding into powder; 3) Calcining the powder obtained after grinding in step 2) in air for 24 hours to obtain a precursor; then calcining the obtained precursor at 600-700℃ for 12-24 hours in a reducing atmosphere, grinding it, and then calcining it at 700-800℃ for 36-48 hours to obtain the final product. The advantages of this invention are: the design method is simple, easy to implement, and can obtain materials with excellent electrochemical performance. It has a significant effect on improving the cycle stability and rate performance of Li2MoO3-based lithium-ion battery positive electrode materials.

[0006] The above technical solutions have improved the cathode material, but Li2MoO3 material still has certain drawbacks, such as the material itself having insulating properties, resulting in poor electrochemical performance in practical applications; and the material has poor structural stability, making it prone to phase transitions during charge and discharge, which affects electrochemical performance; thus greatly restricting its research and development.

[0007] Therefore, it is necessary to provide a Li2MoO3 material that is simple to process and improves the high current density cycling performance of lithium-ion batteries. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a molybdenum-based cathode material, its preparation method, and the cathode sheet. This yields a molybdenum-based cathode material with a sheet-like structure, exhibiting high energy density. During lithium-ion insertion / extraction in the battery, it effectively shortens the lithium-ion diffusion path and accelerates the lithium-ion migration rate, thereby achieving excellent electrochemical performance. The molybdenum-based cathode material can be processed with Mo... 4+ to Mo 6+ The electron transfer process avoids the problem of oxygen release, thus ensuring the safety performance of lithium-ion batteries.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a molybdenum-based cathode material, the method comprising the following steps:

[0011] (1) Mix lithium source, molybdenum source, additives and solvent to obtain mixed solution A;

[0012] (2) Dry the mixed solution A obtained in step (1), grind and calcine to obtain the molybdenum-based precursor;

[0013] (3) Mix borate, lithium source, solvent and molybdenum-based precursor obtained in step (2) to obtain mixed solution B;

[0014] (4) The mixed solution B obtained in step (2) is dried and calcined to obtain the molybdenum-based cathode material.

[0015] The preparation method provided by this invention yields a molybdenum-based cathode material with a sheet-like structure, exhibiting high energy density. During lithium-ion insertion / extraction in the battery, it effectively shortens the lithium-ion diffusion path and accelerates the lithium-ion migration rate, thus achieving excellent electrochemical performance. The molybdenum-based cathode material can be prepared by Mo... 4+ to Mo 6+ The electron transfer process avoids the problem of oxygen release, thus ensuring the safety performance of lithium-ion batteries.

[0016] By uniformly coating the surface of the cathode material with borate fast ion conductors, the problem of electrolyte erosion of the cathode material and rapid performance degradation during high current density cycling is solved. Borate possesses excellent lithium-ion conductivity, effectively improving the lithium-ion diffusion rate and providing a new approach to improving the high current density cycling performance of lithium-ion batteries.

[0017] The additives are used because the low-melting-point salt acts as the reaction medium, and a liquid phase appears during the synthesis process. The reactants have a certain solubility in this liquid phase, which greatly accelerates the diffusion rate of ions, enabling atomic-scale mixing of the reactants in the liquid phase. This transforms the reaction from a solid-solid reaction to a solid-liquid reaction. Compared to conventional solid-phase methods, this invention has advantages such as simple process, low synthesis temperature, short holding time, uniform chemical composition of the synthesized powder, good crystal morphology, and high phase purity. Furthermore, the additives used in this invention are easy to separate and can be reused.

[0018] In this invention, there is no specific limit to the amount of additives added; the amount added is greater than 0.

[0019] Preferably, the additive in step (1) includes an alkali metal salt.

[0020] Preferably, the alkali metal salt includes potassium salt and / or sodium salt.

[0021] Preferably, the solvent in step (1) includes deionized water.

[0022] Preferably, the drying in step (2) includes a first drying and a second drying.

[0023] The two-step drying process in this invention makes the synthesis reaction more complete and the coating layer more uniform.

[0024] Preferably, the temperature of the first drying is 75 to 90°C, for example, it can be 75°C, 80°C, 82°C, 88°C or 90°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the first drying time is 3 to 8 hours, for example, it can be 3 hours, 4 hours, 5 hours, 7 hours or 8 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the temperature of the second drying is 5 to 10°C lower than the temperature of the first drying, for example, it can be 5°C, 6°C, 7°C, 8°C, 9°C or 10°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the second drying time is 1 to 5 hours, for example, it can be 1 hour, 2 hours, 3 hours, 4 hours or 5 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Preferably, the particle size after grinding in step (2) is 80 to 200 nm, for example, it can be 80 nm, 100 nm, 120 nm, 150 nm or 200 nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the calcination temperature in step (2) is 500 to 700°C, for example, 500°C, 550°C, 600°C, 650°C, or 700°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the calcination time in step (2) is 5 to 10 hours, for example, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] The molybdenum-based precursor obtained in step (2) of this invention is Li2MoO3 material.

[0032] Preferably, the solvent in step (3) includes deionized water.

[0033] Preferably, in step (3), the mass ratio of borate, lithium source and molybdenum-based precursor is (3-5):(1-3):(0.5-2), for example, it can be 4:2:1, 3:1:0.5, 5:3:2, 3:3:0.5 or 5:1:2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the drying temperature in step (4) is 60 to 90°C, for example, 60°C, 70°C, 80°C, 85°C, or 90°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the calcination temperature in step (4) is 300 to 500°C, for example, 300°C, 350°C, 400°C, 450°C, or 500°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the calcination time in step (4) is 3 to 5 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours, or 5 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] As a preferred embodiment of the preparation method described in the first aspect of the present invention, the preparation method includes the following steps:

[0038] (1) Mix lithium source, molybdenum source, additives and deionized water to obtain mixed solution A;

[0039] (2) After drying the mixed solution A obtained in step (1) at a temperature of 75-90℃ for 3-8 hours, it is dried for 1-5 hours at a temperature of 5-10℃ lower than the first drying temperature. Then it is ground until the particle size is 80-200nm. Finally, it is calcined at a temperature of 500-700℃ for 5-10 hours to obtain the molybdenum-based precursor.

[0040] (3) Borate, lithium source and molybdenum-based precursor obtained in step (2) are mixed with deionized water in a mass ratio of (3-5):(1-3):(0.5-2) to obtain mixed solution B;

[0041] (4) The mixed solution B obtained in step (2) is dried at a temperature of 60-90℃ and calcined at 300-500℃ for 3-5 hours to obtain the molybdenum-based cathode material.

[0042] In a second aspect, the present invention provides a molybdenum-based cathode material, which is obtained by the preparation method described in the first aspect.

[0043] Thirdly, the present invention provides a positive electrode sheet, the positive electrode sheet comprising a current collector and a positive electrode active layer, the positive electrode active layer comprising the molybdenum-based positive electrode material as described in the second aspect.

[0044] Preferably, the positive electrode active layer comprises a molybdenum-based positive electrode material, a conductive agent, and a binder.

[0045] Preferably, in the positive electrode active layer, the mass percentage of the molybdenum-based positive electrode material is 70-98 wt%, for example, it can be 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, or 98 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0046] Preferably, in the positive electrode active layer, the mass percentage of the conductive agent is 0.5 to 15 wt%, for example, it can be 0.5 wt%, 1 wt%, 5 wt%, 7 wt%, 10 wt%, or 15 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] Preferably, in the positive electrode active layer, the mass percentage of the binder is 0.5 to 15 wt%, for example, it can be 0.5 wt%, 1 wt%, 5 wt%, 7 wt%, 10 wt%, or 15 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] Preferably, the conductive agent comprises any one or a combination of at least two of carbon black, conductive graphite, carbon fiber, graphene, or carbon nanotubes. Typical but non-limiting combinations include combinations of carbon black and conductive graphite, combinations of conductive graphite and carbon fiber, combinations of carbon fiber and graphene, combinations of graphene and carbon nanotubes, combinations of carbon black, conductive graphite, and carbon fiber, combinations of conductive graphite, carbon fiber, and graphene, and combinations of carbon fiber, graphene, and carbon nanotubes.

[0049] Preferably, the adhesive comprises any one or a combination of at least two of sodium carboxymethyl cellulose, styrene-butadiene rubber, or polyacrylic acid, a combination of sodium carboxymethyl cellulose and styrene-butadiene rubber, a combination of styrene-butadiene rubber and polyacrylic acid, a combination of sodium carboxymethyl cellulose and polyacrylic acid, or a combination of sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid.

[0050] Preferably, the coating thickness of the positive electrode active layer is 50-80 μm, for example, it can be 50 μm, 55 μm, 60 μm, 70 μm, or 80 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0051] Fourthly, the present invention provides a lithium-ion battery containing a molybdenum-based cathode material as described in the second aspect.

[0052] Compared with the prior art, the present invention has at least the following beneficial effects:

[0053] (1) The preparation method provided by the present invention yields a molybdenum-based cathode material with a sheet-like structure, which has a high energy density. During the lithium-ion insertion and extraction process in the battery, it can effectively shorten the diffusion path of lithium ions and accelerate the migration rate of lithium ions, thereby obtaining excellent electrochemical performance.

[0054] (2) The molybdenum-based cathode material can be processed with Mo 4+ to Mo 6+ The electron transfer process avoids the problem of oxygen release, thus ensuring the safety performance of lithium-ion batteries.

[0055] (2) By uniformly coating the surface of the positive electrode material with borate fast ion conductors, the problem of electrolyte erosion of the positive electrode material and rapid degradation of material performance during high current density cycling is solved. In addition, borate has excellent lithium-ion conductivity, which effectively improves the diffusion rate of lithium ions and provides a new idea for improving the high current density cycling performance of lithium-ion batteries. Detailed Implementation

[0056] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0057] Example 1

[0058] This embodiment provides a method for preparing a molybdenum-based cathode material, the method comprising the following steps:

[0059] (1) Mix lithium sulfate, molybdenum sulfate, sodium sulfate, potassium sulfate and deionized water to obtain mixed solution A;

[0060] (2) After drying the mixed solution A obtained in step (1) at a temperature of 80℃ for 5 hours, it is dried for 3 hours at a temperature 10℃ lower than the temperature of the first drying. Then it is ground until the particle size is 100nm. Finally, it is calcined at a temperature of 650℃ for 7 hours to obtain the molybdenum-based precursor.

[0061] (3) Sodium borate, lithium sulfate and the molybdenum-based precursor obtained in step (2) are mixed with deionized water in a mass ratio of 4:2:1 to obtain mixed solution B;

[0062] (4) The mixed solution B obtained in step (2) is dried at 90°C and calcined at 400°C for 4 hours to obtain the molybdenum-based cathode material.

[0063] Example 2

[0064] This embodiment provides a method for preparing a molybdenum-based cathode material, the method comprising the following steps:

[0065] (1) Mix lithium chloride, molybdenum chloride, sodium chloride, potassium chloride and deionized water to obtain mixed solution A;

[0066] (2) After drying the mixed solution A obtained in step (1) at a temperature of 75℃ for 3 hours, it is dried for 5 hours at a temperature 10℃ lower than the first drying temperature. Then it is ground until the particle size is 80nm. Finally, it is calcined at a temperature of 500℃ for 10 hours to obtain the molybdenum-based precursor.

[0067] (3) Sodium borate, lithium chloride and the molybdenum-based precursor obtained in step (2) are mixed with deionized water in a mass ratio of 3:1:0.5 to obtain mixed solution B;

[0068] (4) The mixed solution B obtained in step (2) is dried at 60°C and calcined at 300°C for 5 hours to obtain the molybdenum-based cathode material.

[0069] Example 3

[0070] This embodiment provides a method for preparing a molybdenum-based cathode material, the method comprising the following steps:

[0071] (1) Mix lithium chloride, molybdenum chloride, sodium chloride, potassium chloride and deionized water to obtain mixed solution A;

[0072] (2) After drying the mixed solution A obtained in step (1) at a temperature of 90℃ for 8 hours, it is dried for 1 hour at a temperature 10℃ lower than the temperature of the first drying. Then it is ground until the particle size is 200nm. Finally, it is calcined at a temperature of 700℃ for 5 hours to obtain the molybdenum-based precursor.

[0073] (3) Potassium borate, lithium chloride and the molybdenum-based precursor obtained in step (2) are mixed with deionized water in a mass ratio of 5:3:2 to obtain mixed solution B;

[0074] (4) The mixed solution B obtained in step (2) is dried at 90°C and calcined at 500°C for 3 hours to obtain the molybdenum-based cathode material.

[0075] Example 4

[0076] This embodiment provides a method for preparing a molybdenum-based cathode material, which differs from Embodiment 1 only in that the first drying step (2) is not performed.

[0077] Example 5

[0078] This embodiment provides a method for preparing a molybdenum-based cathode material, which differs from Embodiment 1 only in that a second drying step is not performed in step (2).

[0079] Example 6

[0080] This embodiment provides a method for preparing a molybdenum-based cathode material, which differs from Embodiment 1 only in that the additive in step (1) is aluminum chloride.

[0081] Example 7

[0082] This embodiment provides a method for preparing a molybdenum-based cathode material, which differs from Embodiment 1 only in that the calcination temperature in step (2) is 450°C.

[0083] Example 8

[0084] This embodiment provides a method for preparing a molybdenum-based cathode material, which differs from Embodiment 1 only in that the calcination temperature in step (2) is 750°C.

[0085] Example 9

[0086] This embodiment provides a method for preparing a molybdenum-based cathode material, which differs from Embodiment 1 only in that the calcination temperature in step (4) is 250°C.

[0087] Example 10

[0088] This embodiment provides a method for preparing a molybdenum-based cathode material, which differs from Embodiment 1 only in that the calcination temperature in step (4) is 550°C.

[0089] Comparative Example 1

[0090] This comparative example provides a method for preparing a molybdenum-based cathode material, which differs from Example 1 only in that steps (3) and (4) are omitted.

[0091] Comparative Example 2

[0092] This comparative example provides a method for preparing a molybdenum-based cathode material, which differs from Example 1 only in that sodium borate is not added in step (3).

[0093] Comparative Example 3

[0094] This comparative example provides a method for preparing a molybdenum-based cathode material, which differs from Example 1 only in that lithium sulfate is not added in step (3).

[0095] Comparative Example 4

[0096] This comparative example provides a method for preparing a molybdenum-based cathode material, which differs from Example 1 only in that no additives are used in step (1).

[0097] Application Example 1

[0098] This application example provides a positive electrode sheet, which includes an aluminum foil and a positive electrode active layer coated on the surface of the aluminum foil. The positive electrode active layer includes a molybdenum-based positive electrode material, carbon black, and sodium carboxymethyl cellulose in a mass ratio of 95:2:3. The molybdenum-based positive electrode material is obtained by the preparation method described in Example 1.

[0099] The coating thickness of the positive electrode active layer is 65 μm.

[0100] Application Example 2

[0101] This application example provides a positive electrode sheet, which includes an aluminum foil and a positive electrode active layer coated on the surface of the aluminum foil. The positive electrode active layer includes a molybdenum-based positive electrode material in a mass ratio of 70:15:15, conductive graphite, and styrene-butadiene rubber. The molybdenum-based positive electrode material is obtained by the preparation method described in Example 2.

[0102] The coating thickness of the positive electrode active layer is 50 μm.

[0103] Application Example 3

[0104] This application example provides a positive electrode sheet, which includes an aluminum foil and a positive electrode active layer coated on the surface of the aluminum foil. The positive electrode active layer includes a molybdenum-based positive electrode material, carbon black, and sodium carboxymethyl cellulose in a mass ratio of 98:1:1. The molybdenum-based positive electrode material is obtained by the preparation method described in Example 3.

[0105] The coating thickness of the positive electrode active layer is 80 μm.

[0106] Application Example 4

[0107] This application example provides a positive electrode sheet, which differs from Application Example 1 only in that the molybdenum-based positive electrode material is obtained by the preparation method described in Example 4.

[0108] Application Example 5

[0109] This application example provides a positive electrode sheet, which differs from Application Example 1 only in that the molybdenum-based positive electrode material is obtained by the preparation method described in Example 5.

[0110] Application Example 6

[0111] This application example provides a positive electrode sheet, which differs from Application Example 1 only in that the molybdenum-based positive electrode material is obtained by the preparation method described in Example 6.

[0112] Application Example 7

[0113] This application example provides a positive electrode sheet, which differs from Application Example 1 only in that the molybdenum-based positive electrode material is obtained by the preparation method described in Example 7.

[0114] Application Example 8

[0115] This application example provides a positive electrode sheet, which differs from Application Example 1 only in that the molybdenum-based positive electrode material is obtained by the preparation method described in Example 8.

[0116] Application Example 9

[0117] This application example provides a positive electrode sheet, which differs from Application Example 1 only in that the molybdenum-based positive electrode material is obtained by the preparation method described in Example 9.

[0118] Application Example 10

[0119] This application example provides a positive electrode sheet, which differs from Application Example 1 only in that the molybdenum-based positive electrode material is obtained by the preparation method described in Example 10.

[0120] Application Example 11

[0121] This application example provides a positive electrode sheet, which differs from Application Example 1 only in that the coating thickness of the positive electrode active layer is 40 μm.

[0122] Application Example 12

[0123] This application example provides a positive electrode sheet, which differs from Application Example 1 only in that the coating thickness of the positive electrode active layer is 90 μm.

[0124] Comparative Application Example 1

[0125] This application example provides a positive electrode sheet, which differs from Application Example 1 only in that the molybdenum-based positive electrode material is obtained by the preparation method described in Comparative Example 1.

[0126] Comparative Application Example 2

[0127] This application example provides a positive electrode sheet, which differs from Application Example 1 only in that the molybdenum-based positive electrode material is obtained by the preparation method described in Comparative Example 2.

[0128] Comparative Application Example 3

[0129] This application example provides a positive electrode sheet, which differs from Application Example 1 only in that the molybdenum-based positive electrode material is obtained by the preparation method described in Comparative Example 3.

[0130] Comparative Application Example 4

[0131] This application example provides a positive electrode sheet, which differs from Application Example 1 only in that the molybdenum-based positive electrode material is obtained by the preparation method described in Comparative Example 4.

[0132] The above positive electrode sheets were used to assemble lithium-ion batteries according to GB31241-2014, and then tested.

[0133] Cyclic test conditions: 25℃, 1C / 1C cycle for 100 cycles.

[0134] The test results are shown in Table 1.

[0135] Table 1

[0136]

[0137]

[0138] The following conclusions can be drawn from Table 1:

[0139] (1) As can be seen from Application Examples 1-3, the preparation method provided by the present invention yields a molybdenum-based cathode material with a sheet-like structure, which has a high energy density. During the lithium-ion insertion and extraction process in the battery, it can effectively shorten the diffusion path of lithium ions and accelerate the migration rate of lithium ions, thereby obtaining excellent electrochemical cycle performance.

[0140] (2) By comparing application examples 4 and 5 with application example 1, it can be seen that when the two-step drying is not performed in step (2), the surface of the prepared molybdenum-based precursor Li2MoO3 particles is uneven and difficult to aggregate into a sheet-like structure, which affects the electrochemical cycling performance of the molybdenum-based cathode material.

[0141] (3) As can be seen from the comparison between Application Example 6 and Application Example 1, when the additive in step (1) is replaced with aluminum salt, the prepared molybdenum-based cathode material is not conducive to shortening the diffusion path of lithium ions during the lithium ion deintercalation process in the battery, and has poor electrochemical cycle performance.

[0142] (4) By comparing Application Examples 7 and 8 with Application Example 1, it can be seen that when the calcination temperature in step (2) is not within the preferred range, the prepared molybdenum-based cathode material is not conducive to shortening the diffusion path of lithium ions during the lithium ion deintercalation process in the battery, and has poor electrochemical cycle performance.

[0143] (5) As can be seen from the comparison between Application Examples 9 and 10 and Application Example 1, when the calcination temperature in step (3) is not within the preferred range, the prepared molybdenum-based cathode material is not conducive to shortening the diffusion path of lithium ions during the lithium ion deintercalation process in the battery, and has poor electrochemical cycle performance.

[0144] (6) As can be seen from the comparison between Application Examples 11 and 12 and Application Example 1, when the thickness of the positive electrode active layer is not within the preferred range of the present invention, the cycle performance of the lithium-ion battery is poor.

[0145] (7) As can be seen from the comparison between Application Examples 1-3 and Application Example 1, when borate fast ion conductors are not coated on the surface of molybdenum-based precursor Li2MoO3, the material is easily corroded by the electrolyte, thus affecting the cycle performance.

[0146] In summary, the preparation method provided by this invention yields a molybdenum-based cathode material with a sheet-like structure, exhibiting high energy density. During the lithium-ion insertion / extraction process in the battery, it can effectively shorten the lithium-ion diffusion path and accelerate the lithium-ion migration rate, thereby achieving excellent electrochemical performance.

[0147] By uniformly coating the surface of the cathode material with borate fast ion conductors, the problem of electrolyte erosion of the cathode material and rapid performance degradation during high current density cycling is solved. Furthermore, borate has excellent lithium-ion conductivity, which effectively improves the lithium-ion diffusion rate, providing a new approach to improving the high current density cycling performance of lithium-ion batteries.

[0148] This invention illustrates the detailed process equipment and process flow through the above embodiments. However, this invention is not limited to the detailed process equipment and process flow described above, meaning that this invention does not necessarily depend on the detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product of this invention, addition of auxiliary components, and selection of specific methods, all fall within the protection scope and disclosure scope of this invention.

Claims

1. A method for preparing a molybdenum-based positive electrode material, characterized by, The preparation method comprises the following steps: (1) mixing a lithium source, a molybdenum source, an additive and a solvent to obtain a mixed solution A; (2) drying the mixed solution A obtained in step (1), grinding and calcining to obtain a molybdenum-based precursor; (3) mixing a borate, a lithium source, a solvent and the molybdenum-based precursor obtained in step (2) to obtain a mixed solution B; (4) drying the mixed solution B obtained in step (2) and calcining at 300-500°C for 3-5h to obtain the molybdenum-based positive electrode material. The additive in step (1) comprises a potassium salt and / or a sodium salt. The solvent in step (1) comprises deionized water. The drying in step (2) comprises first drying and second drying. The calcining in step (2) is performed at a temperature of 500-700°C for 5-10h. The solvent in step (3) comprises deionized water. The mass ratio of the borate, the lithium source and the molybdenum-based precursor obtained in step (2) in step (3) is (3-5):(1-3):(0.5-2). The calcining in step (4) is performed at a temperature of 300-500°C for 3-5h.

2. The production method according to claim 1, characterized by, The temperature of the first drying is 75-90°C.

3. The preparation method according to claim 1, characterized in that, The time of the first drying is 3-8h.

4. The method of claim 1, wherein, The temperature of the second drying is 5-10°C lower than that of the first drying.

5. The preparation method according to claim 1, characterized in that, The time of the second drying is 1-5h.

6. The method of claim 1, wherein, The particle size of the molybdenum-based precursor after grinding in step (2) is 80-200nm.

7. The preparation method according to claim 1, characterized in that, The temperature of the drying in step (4) is 60-90°C.

8. The method of claim 1, wherein, The preparation method comprises the following steps: (1) mixing a lithium source, a molybdenum source, an additive and deionized water to obtain a mixed solution A; (2) performing first drying on the mixed solution A obtained in step (1) at a temperature of 75-90°C for 3-8h, then performing second drying at a temperature 5-10°C lower than that of the first drying for 1-5h, grinding to a particle size of 80-200nm, and calcining at a temperature of 500-700°C for 5-10h to obtain a molybdenum-based precursor; (3) mixing a borate, a lithium source, the molybdenum-based precursor obtained in step (2) and deionized water in a mass ratio of (3-5):(1-3):(0.5-2) to obtain a mixed solution B; (4) drying the mixed solution B obtained in step (2) at a temperature of 60-90°C and calcining at 300-500°C for 3-5h to obtain the molybdenum-based positive electrode material.

9. A molybdenum-based positive electrode material, characterized by, The molybdenum-based positive electrode material is obtained by the preparation method in any one of claims 1-8.

10. A positive electrode sheet characterized by comprising: The positive electrode sheet comprises a current collector and a positive electrode active layer, and the positive electrode active layer comprises the molybdenum-based positive electrode material in claim 9.

11. The positive electrode sheet according to claim 10, characterized by The positive electrode active layer comprises a molybdenum-based positive electrode material, a conductive agent and a binder; The mass percentage of the molybdenum-based positive electrode material in the positive electrode active layer is 70-98wt%; The mass percentage of the conductive agent in the positive electrode active layer is 0.5-15wt%; The mass percentage of the binder in the positive electrode active layer is 0.5-15wt%; The coating thickness of the positive electrode active layer is 50-80μm.

12. A lithium-ion battery, characterized by, The lithium ion battery contains the molybdenum-based positive electrode material in claim 9.

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