A cathode material and its preparation method, and a lithium-ion battery.

Abstract

This application relates to a cathode material and its preparation method, and a lithium-ion battery, belonging to the field of lithium-ion battery technology. The cathode material includes a core material and a composite coating material. The core material includes a lithium-rich manganese-based material. The composite coating material coats the outer surface of the core material. The composite coating material includes a first material and a second material. The first material includes carbon elements and forms a three-dimensional network structure with cavities. The second material includes a portion located on the outer surface of the three-dimensional network structure and a portion located within the cavities of the three-dimensional network structure. The second material is used to at least achieve lithium storage functionality. Therefore, the technical problem of poor interfacial stability between the cathode and electrolyte in related technologies can be at least solved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a cathode material and its preparation method, and a lithium-ion battery. Background Technology

[0002] With the booming development of electric vehicles, energy storage technology, and portable electronic products, the demand for high-energy-density electrode materials is constantly increasing, greatly promoting the development of electrode materials. Among many cathode materials, lithium-rich manganese-based materials are considered the most promising cathode materials for next-generation lithium-ion batteries due to their ultra-high specific capacity, high energy density, high voltage characteristics, and significant cost advantages.

[0003] However, the interfacial reaction between lithium-rich manganese-based materials and the electrolyte during charging and discharging will cause problems such as unstable crystal structure, irreversible oxygen loss and transition metal migration in lithium-rich manganese-based materials, resulting in problems such as voltage and capacity decay during material cycling, low initial coulombic efficiency and poor cycling stability, which seriously restricts its commercial application. Summary of the Invention

[0004] This application provides a cathode material and its preparation method, as well as a lithium-ion battery, to at least solve the technical problem of poor interfacial stability between the cathode and electrolyte in related technologies. To achieve the above objective, the technical solution adopted in this application is as follows:

[0005] According to a first aspect of this application, a cathode material is provided; the cathode material includes: a core material and a composite coating material. The core material includes a lithium-rich manganese-based material. The composite coating material coats the outer surface of the core material. The composite coating material includes a first material and a second material, the first material including carbon elements, and the first material forming a three-dimensional network structure with cavities; the second material includes a portion located on the outer surface of the three-dimensional network structure, and also includes a portion located within the cavities of the three-dimensional network structure; the second material is used to at least realize lithium storage function.

[0006] According to the above-mentioned technical means, the composite coating material can form a coating layer on the outer surface of the core material. This coating layer can physically block the cathode material and electrolyte, preventing the reaction of high-valence metal cations and active oxygen species on the surface of the core material with the electrolyte, and also inhibiting the corrosion of HF in the electrolyte. Furthermore, the composite coating material can confine the active oxygen species generated during charging within the core material, preventing oxygen escape. Moreover, in the aforementioned composite coating material, the first material can interweave to form a three-dimensional network structure, allowing the second material to be disposed on the outer surface of the three-dimensional network structure and inside the cavities of the three-dimensional network structure. This results in a larger spacing within the second material, providing an effective channel for lithium-ion insertion / extraction, reducing the charge transfer impedance between lithium-ion particles in the cathode material, and facilitating the lithium-ion intercalation / extraction process. +The efficient shuttle operation improves the cell's initial coulombic efficiency, cycle stability, rate capability, and other electrochemical performance. Furthermore, the inclusion of carbon in the primary material contributes to the cathode material's superior electrochemical performance.

[0007] In one possible implementation, the first material includes at least one of carbon nanotubes, graphene, and porous carbon.

[0008] Based on the above technical means, the first material will not collapse after multiple charge-discharge cycles, which can improve the structural stability of the composite coating material.

[0009] In one possible implementation, the first material comprises multi-walled carbon nanotubes.

[0010] Based on the aforementioned techniques, multi-walled carbon nanotubes possess advantages such as high strength, high toughness, good conductivity, and durability. This can improve the electrochemical performance of the cathode material and enhance the structural stability of the composite coating material. Furthermore, the large specific surface area of ​​multi-walled carbon nanotubes facilitates the adsorption of the secondary material onto the three-dimensional network structure.

[0011] In one possible implementation, the second material includes lithium vanadate (LiV3O8).

[0012] Based on the aforementioned technical means, lithium vanadate (LiV3O8) exhibits a layered structure, which can create more spaces for storing lithium ions and reduce the irreversible insertion / extraction of lithium ions. Furthermore, when lithium vanadate (LiV3O8) includes portions located on the outer surface of the three-dimensional network structure and portions located within the cavities of the three-dimensional network structure, the second material can have a larger interlayer spacing, providing effective channels for lithium ion insertion / extraction, which is beneficial for Li... + The efficient shuttle operation improves the cell's initial coulombic efficiency, cycle stability, rate capability, and other electrochemical performance.

[0013] In one possible implementation, the thickness of the composite coating material ranges from 15 nm to 30 nm.

[0014] Based on the above technical means, the composite coating material has a larger thickness, which can improve the physical barrier effect of the composite coating material, prevent oxygen escape, and inhibit the corrosion of HF in the electrolyte. It can solve the problems of low initial coulombic efficiency, poor rate performance and cycle stability of cathode materials.

[0015] In one possible implementation, the mass ratio of the first material to the second material in the composite coating material ranges from (0.02 to 0.03):1.

[0016] Based on the above technical means, the three-dimensional network structure formed by the first material can provide sufficient space for the second material, thereby improving the structural stability of the composite coating material.

[0017] In one possible implementation, the core material includes: a core material and a doped material, wherein the doped material coats the core material; the doped material includes: a lithium-rich manganese-based material containing tungsten ions.

[0018] Based on the above technical means, the doped material can form a core material that is rich in tungsten ions (W). 6+ The doping layer of tungsten can improve the overall structural and thermal stability of the cathode material, increase cycle life, and improve the cell's cycle stability, rate capability, and other electrochemical performance.

[0019] In one possible implementation, the atomic percentage of tungsten ions in the core material ranges from 2% to 3%.

[0020] Based on the above technical means, it is possible to enhance the tungsten ion (W) 6+ To improve the stability of the crystal structure of lithium-rich manganese-based materials (LRM), reduce side reactions, and accelerate the Li + The diffusion rate effect further improves the cell's cycle stability, rate capability, and other electrochemical performance.

[0021] In one possible implementation, the core material further includes nickel and cobalt; the atomic percentage of nickel in the core material is less than the atomic percentage of manganese in the core material and greater than the atomic percentage of cobalt in the core material.

[0022] Based on the above-mentioned technical means, the core material includes lithium manganese nickel cobalt compounds, which enable the core material to have high energy density, long life, high safety, low cost and good cycle performance.

[0023] According to a second aspect provided in this application, a method for preparing a positive electrode material is provided. The preparation method includes:

[0024] The core material is formed, including lithium-rich manganese-based materials.

[0025] A composite coating material is formed and coated on the outer surface of the core material; the composite coating material includes a first material and a second material, the first material includes carbon elements and forms a three-dimensional network structure with cavities; the second material includes a portion located on the outer surface of the three-dimensional network structure and a portion located inside the cavity of the three-dimensional network structure; the second material is used to at least realize the lithium storage function.

[0026] It should be noted that the technical effects brought about by the second aspect can be referred to the technical effects brought about by the corresponding implementation method in the first aspect, and will not be repeated here.

[0027] In one possible implementation, forming the core material includes: mixing a first lithium source, a manganese source, and a tungsten source to obtain a mixed powder; and calcining the mixed powder to obtain the core material.

[0028] In one possible implementation, the manganese source is selected from any of the following general formulas shown in the structure: Ni b Co c Mn 1-b-c (OH)₂; where 0 ≤ c ≤ 0.05, 0 <b≤0.4。

[0029] Based on the aforementioned technical methods, a core material was synthesized using a high-temperature solid-state method. On one hand, this allows the core material to include lithium manganese nickel cobalt compounds or lithium manganese nickel compounds, resulting in high energy density, long lifespan, high safety, low cost, and good cycle performance. On the other hand, it enables the formation of a core material rich in tungsten ions (W). 6+ The introduction of W element into the doped layer can improve the overall structural stability and thermal stability of the cathode material.

[0030] In one possible implementation, the first lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate; and / or, the tungsten source includes at least one of tungsten trioxide, tungsten sulfide, and tungsten carbide.

[0031] In one possible implementation, the calcination temperature of the mixed powder is in the range of 600°C to 800°C; and / or, the calcination time of the mixed powder is in the range of 6h to 8h.

[0032] In one possible implementation, the second material comprises lithium vanadate, and the reaction that forms the second material is a solvothermal reaction.

[0033] Based on the aforementioned technical means, on the one hand, the layered structure of lithium vanadate (LiV3O8) can be utilized to increase the space for storing lithium ions and reduce the irreversible insertion / extraction of lithium ions. Furthermore, it allows the second material to have a larger interlayer spacing, providing an effective channel for lithium ion insertion / extraction. On the other hand, it allows for a more uniform distribution of the formed second material, and enables the second material to be more evenly distributed on the outer surface of the three-dimensional network structure formed by the first material, as well as within the cavities of the three-dimensional network structure. This reduces the charge transfer impedance between lithium ions and the cathode material particles, which is beneficial for LiV3O8. + The efficient shuttle operation improves the cell's initial coulombic efficiency, cycle stability, rate capability, and other electrochemical performance.

[0034] In one possible implementation, the reaction temperature range for the solvothermal reaction that forms the second material is 60°C to 80°C.

[0035] In one possible implementation, forming a composite coating material and coating the outer surface of the core material with the composite coating material includes: a first stage of solvothermal reaction of a vanadium source and a second lithium source to obtain a first solution; wherein the ratio of vanadium in the vanadium source to lithium in the second lithium source is 3:1, and the first solution includes lithium vanadate; adding a carbon source to the first solution and performing a second stage of solvothermal reaction to obtain a second solution; adding the core material to the second solution and performing a third stage of solvothermal reaction to obtain a first precipitate; and calcining the first precipitate to obtain the cathode material.

[0036] According to the above-mentioned technical means, lithium vanadate (LiV3O8) formed in the first stage of the solvothermal reaction can enter the cavity of the three-dimensional network structure formed by the first material. In the second stage of the solvothermal reaction, lithium vanadate (LiV3O8) can be formed in situ within the cavity and on the outer surface of the three-dimensional network structure formed by the first material, and the composite coating material is densely coated on the surface of the core material. In this way, firstly, the electronic conductivity and ionic conductivity of the cathode material can be improved, and secondly, the lithium-ion storage space can be enhanced, reducing the Li-ion concentration. + The irreversible insertion / extraction of lithium ions enhances overall electrochemical performance; thirdly, it provides an effective channel for lithium ion insertion / extraction, which is beneficial for Li... + The efficient shuttle process improves the cell's initial coulombic efficiency, cycle stability, rate capability, and other electrochemical performance. Furthermore, the third stage of the solvothermal reaction allows for the in-situ formation of lithium vanadate (LiV3O8) on the outer surface of the core material, further enhancing the cell's initial coulombic efficiency, cycle stability, rate capability, and other electrochemical performance.

[0037] In one possible implementation, the reaction time of the first stage of the solvothermal reaction is greater than or equal to the reaction time of the second stage of the solvothermal reaction; and / or, the reaction time of the third stage of the solvothermal reaction is greater than or equal to the reaction time of the second stage of the solvothermal reaction.

[0038] In one possible implementation, the reaction time of the first stage of the solvothermal reaction ranges from 1 h to 2 h; and / or, the reaction time of the second stage of the solvothermal reaction ranges from 0.2 h to 1 h; and / or, the reaction time of the third stage of the solvothermal reaction ranges from 1 h to 2 h.

[0039] Based on the above technical means, firstly, it can increase the amount of lithium vanadate (LiV3O8) formed in the first stage of the solvothermal reaction, which is beneficial for lithium vanadate (LiV3O8) to enter the cavity of the three-dimensional network structure formed by the first material. Secondly, it can improve the sufficiency of the reaction when lithium vanadate (LiV3O8) is formed in situ in the cavity and on the outer surface of the three-dimensional network structure in the second stage of the solvothermal reaction. Thirdly, it can improve the sufficiency of the reaction when lithium vanadate (LiV3O8) is formed in situ on the outer surface of the core material in the third stage of the solvothermal reaction.

[0040] In one possible implementation, the carbon source includes at least one of carbon nanotubes, graphene, and porous carbon.

[0041] In one possible implementation, the carbon source comprises acid-treated multi-walled carbon nanotubes.

[0042] According to the above-mentioned technical means, multiple active sites can be formed on the surface of multi-walled carbon nanotubes. These active sites can be used to connect the second material, which can increase the connection reliability between the first material and the second material, and can increase the adsorption amount of the second material on the three-dimensional network structure formed by the first material, thereby forming more space for storing lithium ions and reducing the irreversible insertion and extraction of lithium ions.

[0043] In one possible implementation, the carbon source is multi-walled carbon nanotubes treated with concentrated sulfuric acid and / or concentrated nitric acid; the acid treatment process is ultrasonic treatment; and the acid treatment time ranges from 2 h to 4 h.

[0044] The above-mentioned technical methods can improve the acid treatment degree of multi-walled carbon nanotubes, and can form more active sites on multi-walled carbon nanotubes.

[0045] In one possible implementation, the vanadium source comprises ammonium vanadate; and / or, the second lithium source comprises lithium hydroxide monohydrate.

[0046] In one possible implementation, the calcination temperature of the first precipitate is in the range of 350°C to 400°C; and / or, the calcination time of the first precipitate is in the range of 10h to 12h.

[0047] According to a third aspect provided in this application, a lithium-ion battery is provided, comprising a positive electrode material of any of the above possible embodiments, or a positive electrode material prepared by any of the above possible embodiments.

[0048] It should be noted that the technical effects brought about by the third aspect can be referred to the technical effects brought about by the corresponding implementation method in the first aspect, and will not be repeated here.

[0049] The beneficial effects of this application are:

[0050] (1) The cathode material in this application includes a composite coating material. The composite coating material can form a coating layer on the outer surface of the core material. The coating layer can physically block the cathode material and the electrolyte, preventing high-valence metal cations and active oxygen species on the surface of the core material from reacting with the electrolyte, and can also inhibit the corrosion of HF in the electrolyte. In addition, the composite coating material can also confine the active oxygen species generated during charging inside the core material, preventing oxygen escape. Moreover, in the above-mentioned composite coating material, the first material can be interwoven to form a three-dimensional network structure, so that the second material can be disposed on the outer surface of the three-dimensional network structure and in the cavity of the three-dimensional network structure, so that the second material has a large spacing inside, which can provide an effective channel for lithium ion insertion / extraction, reduce the charge transfer impedance of lithium ions between cathode material particles, and is beneficial to Li + The efficient shuttle operation enhances the initial coulombic efficiency, high voltage, high rate, and high cycle performance of the cathode material, thereby improving the cell's initial coulombic efficiency, cycle stability, rate capability, and other electrochemical properties. Furthermore, the inclusion of carbon in the primary material contributes to the cathode material's superior electrochemical performance.

[0051] (2) When the core material includes a core material and a doped material, the doped material can form a coating on the core material and is rich in tungsten ions (W). 6+ The doping layer of tungsten can improve the overall structural and thermal stability of the cathode material, increase cycle life, and improve the cell's cycle stability, rate capability, and other electrochemical performance.

[0052] (3) In the method for preparing the cathode material in this application, the reaction for forming the second material can be a solvothermal reaction, and the solvothermal reaction can be carried out in at least three stages. In the first stage of the solvothermal reaction, lithium vanadate (LiV3O8) formed can enter the cavity of the three-dimensional network structure formed by the first material. In the second stage of the solvothermal reaction, lithium vanadate (LiV3O8) can be formed in situ within the cavity and on the outer surface of the three-dimensional network structure formed by the first material, and the composite coating material can be densely coated on the surface of the core material. This improves the electronic conductivity and ionic conductivity of the cathode material, enhances the lithium-ion storage space, and reduces the lithium content of lithium-ion batteries. + The irreversible insertion / extraction of lithium ions enhances overall electrochemical performance; it also provides an effective channel for lithium-ion insertion / extraction, which is beneficial for Li... + The efficient shuttle operation improves the cell's initial coulombic efficiency, cycle stability, rate capability, and other electrochemical performance.

[0053] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0054] Figure 1This is a schematic diagram of the structure of a positive electrode material according to an exemplary embodiment;

[0055] Figure 2 yes Figure 1 A magnified view of a section at point A in the middle;

[0056] Figure 3 This is a graph showing the rate cycling test results of a lithium-ion battery according to an exemplary embodiment;

[0057] Figure 4 This is a diagram illustrating the first charge-discharge test results of a lithium-ion battery according to an exemplary embodiment.

[0058] Among them, 100-cathode material; 10-core material; 11-core material; 12-doped material; 20-composite coating material; 21-first material; 22-second material. Detailed Implementation

[0059] The embodiments of this application will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be understood that the preferred embodiments are only for illustrating this application and are not intended to limit the scope of protection of this application.

[0060] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. Therefore, the drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0061] Some embodiments of this application provide a lithium-ion battery. This lithium-ion battery includes, for example, a positive electrode, a negative electrode, an electrolyte, and a separator. The separator is disposed between the positive and negative electrode. The electrolyte comprises lithium ions.

[0062] Based on the above structure, during battery charging and discharging, lithium ions can be inserted and extracted back and forth between the positive and negative electrodes. The electrolyte acts as a conductor for lithium ions. The separator allows lithium ions to pass through and prevents short circuits between the positive and negative electrodes.

[0063] For example, the positive electrode includes a first current collector and a positive electrode film layer disposed on at least one surface of the first current collector, the positive electrode film layer including a positive electrode material.

[0064] For example, the first current collector can be a metal foil, such as aluminum foil or copper foil; or, the first current collector can be a composite current collector, which may include, for example, a base layer and a metal layer stacked together, and the base layer may be, for example, a polymer material base layer.

[0065] For example, the cathode material may include at least one of lithium phosphate and lithium transition metal oxide. The lithium transition metal oxide includes, for example, at least one of lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium manganese nickel oxide, and lithium manganese nickel cobalt oxide.

[0066] For example, the negative electrode sheet includes a second current collector and a negative electrode film layer disposed on at least one surface of the second current collector, the negative electrode film layer including a negative electrode material.

[0067] For an exemplary description of the second current collector, please refer to the above description of the first current collector, which will not be repeated here. Moreover, the first current collector and the second current collector may be the same or different, and there is no limitation here.

[0068] For example, the negative electrode material may include at least one of soft carbon, hard carbon, graphite, silicon, silicon oxide, silicon alloy, tin, tin oxide, and tin alloy.

[0069] For example, the electrolyte includes an electrolyte salt and a solvent. The electrolyte salt includes, for example, at least one of lithium difluorophosphate, lithium hexafluorophosphate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, and lithium tetrafluorooxalate phosphate. Of course, the electrolyte salt can also be other types of lithium electrolyte salts.

[0070] Among the aforementioned cathode materials, lithium-rich manganese-based materials (LRM) are considered the most promising cathode material for next-generation lithium-ion batteries. With technological advancements and a more complete industrial chain, various modification strategies have been proposed to improve the electrochemical performance of lithium-rich manganese-based cathodes.

[0071] In some embodiments, lithium-rich manganese-based materials are modified using methods such as surface modification, bulk doping, and morphology / structure alteration. This modification effectively mitigates problems such as lattice oxygen loss and metal ion migration during cycling, thereby improving the material's cycling performance and first-time coulombic efficiency.

[0072] In some implementations, a Na-doped cobalt-free lithium-rich manganese-based cathode material was prepared. This Na-doped high-capacity cobalt-free lithium-rich manganese-based cathode material was prepared via the sol-gel method. Na doping into the material lattice expands the Li interlayer spacing and promotes Li... + The diffusion of the material acts as a "pillar" in the crystal lattice, preventing the collapse of the crystal structure and effectively improving the material's capacity utilization and cycle stability.

[0073] As mentioned in the background, improving the interfacial stability between the cathode and the electrolyte is a major challenge for lithium-rich manganese-based cathode materials.

[0074] Based on this, some embodiments of this application provide a positive electrode material 100, such as... Figure 1 and Figure 2 As shown, the cathode material 100 includes a core material 10 and a composite coating material 20. The core material 10 includes a lithium-rich manganese-based material. The composite coating material 20 coats the outer surface of the core material 10. The composite coating material 20 includes a first material 21 and a second material 22. The first material 21 includes carbon elements and forms a three-dimensional network structure with cavities. The second material 22 includes a portion located on the outer surface of the three-dimensional network structure and a portion located within the cavities of the three-dimensional network structure. The second material 22 is used to at least realize the lithium storage function.

[0075] Through the above-described configuration, surface coating of the core material 10 can be achieved. Surface coating is an effective means of suppressing oxygen loss and surface side reactions. The aforementioned composite coating material 20 can form a coating layer on the outer surface of the core material 10. This coating layer can physically block the cathode material 100 and the electrolyte, preventing high-valence metal cations and active oxygen species on the surface of the core material 10 from reacting with the electrolyte, and also suppressing the corrosion of HF in the electrolyte. In addition, the composite coating material 20 can also confine the active oxygen species generated during charging inside the core material 10, preventing oxygen escape, thereby alleviating problems such as low initial coulombic efficiency, poor rate performance, and poor cycle stability of the cathode material 100.

[0076] Furthermore, the aforementioned composite coating material 20 includes a first material 21 and a second material 22. The first material 21 can be interwoven to form a three-dimensional mesh structure with cavities, allowing the second material 22 to be disposed on the outer surface and inside the three-dimensional mesh structure. This enables the composite of the first material 21 and the second material 22 (e.g., in particulate form), and provides a larger spacing within the second material 22, offering an effective channel for lithium-ion insertion / extraction. This reduces the charge transfer impedance of lithium ions between the cathode material 100 particles, which is beneficial for Li... + The efficient shuttle operation improves the cell's initial coulombic efficiency, cycle stability, rate capability, and other electrochemical performance. Furthermore, the first material 21 includes carbon, giving it good electronic conductivity and thus the cathode material 100 good electrochemical performance.

[0077] In one possible implementation, the first material 21 includes at least one of carbon nanotubes, graphene, and porous carbon.

[0078] In some examples, the first material 21 includes carbon nanotubes, graphene, or porous carbon; in still other examples, the first material 21 includes any combination of carbon nanotubes, graphene, and porous carbon.

[0079] When the first material 21 includes at least one of carbon nanotubes, graphene, and porous carbon, the first material 21 will not collapse after multiple charge-discharge cycles. For example, when the first material 21 includes carbon nanotubes, the cylindrical structure formed by the first material 21 will not collapse. In this way, the structural stability of the composite coating material 20 can be improved.

[0080] In one possible implementation, the first material 21 comprises multi-walled carbon nanotubes (MWCNTs).

[0081] Multi-walled carbon nanotubes possess advantages such as high strength, high toughness, good conductivity, and durability, which can improve the electrochemical performance of the cathode material 100 and enhance the structural stability of the composite coating material 20. Furthermore, the large specific surface area of ​​multi-walled carbon nanotubes facilitates the adsorption of the second material 22 onto the three-dimensional network structure.

[0082] In one possible implementation, the second material 22 comprises lithium vanadate (LiV3O8).

[0083] Lithium vanadate (LiV3O8) has a layered structure with lithium intercalation, which can create more space for storing lithium ions and reduce irreversible lithium ion intercalation / deintercalation. Furthermore, when the second material 22 includes lithium vanadate (LiV3O8), and the second material 22 includes portions located on the outer surface of the three-dimensional network structure and portions located within the cavities of the three-dimensional network structure, the second material 22 can have a larger interlayer spacing, providing an effective channel for lithium ion intercalation / deintercalation. This reduces the charge transfer resistance of lithium ions between the cathode material 100 particles, which is beneficial for Li... + The efficient shuttle operation improves the cell's initial coulombic efficiency, cycle stability, rate capability, and other electrochemical performance.

[0084] In one possible implementation, the thickness of the composite coating material 20 ranges from 15 nm to 30 nm.

[0085] For example, the thickness of the composite coating material 20 is 15nm, 18nm, 21nm, 24nm, 27nm or 30nm, etc., and there is no limitation here.

[0086] When the thickness of the composite coating material 20 is in the range of 15nm to 30nm, the thickness of the composite coating material 20 is relatively large, which can improve the physical barrier, prevent oxygen escape, and inhibit the corrosion of HF in the electrolyte. It can solve the problems of low initial coulombic efficiency, poor rate performance and cycle stability of the cathode material 100.

[0087] In one possible implementation, the mass ratio of the first material 21 to the second material 22 in the composite coating material 20 is in the range of (0.02 to 0.03):1.

[0088] For example, in the composite coating material 20, the mass ratio of the first material 21 to the second material 22 can be 0.02:1, 0.023:1, 0.025:1, 0.028:1 or 0.03:1, etc., and there is no limitation here.

[0089] By setting it as described above, the mass ratio of the first material 21 to the second material 22 in the composite coating material 20 can be kept within a suitable range, so that the three-dimensional mesh structure formed by the first material 21 can provide sufficient space for the second material 22. In this way, the structural stability of the composite coating material 20 can be improved.

[0090] In one possible implementation, such as Figure 1 and Figure 2 As shown, the core material 10 includes: a core material 11 and a doped material 12, wherein the doped material 12 covers the core material 11; the doped material 12 includes: a material containing tungsten ions (W... 6+ Lithium-rich manganese-based materials.

[0091] Understandably, it contains tungsten ions (W 6+ The doped material 12 can form a coating core material 11 and is rich in tungsten ions (W). 6+ The doping layer of tungsten (W) can improve the overall structural and thermal stability of the cathode material 100, increase cycle life, and improve the cell's cycle stability, rate capability, and other electrochemical performance. Specifically, firstly, tungsten ions (W... 6+ Tungsten ions can enter the crystal lattice of lithium-rich manganese-based materials (LRM) and have a strong bonding force with oxygen, which can improve the stability of the LRM crystal structure. Secondly, tungsten ions (W...) 6+ ) is a high-valence W element ion. In the case where the core material 10 includes nickel, tungsten ions (W) 6+ It can induce low-valence Ni 2+The formation of W induces the formation of a surface rock salt or spinel structure, inhibiting the release of lattice oxygen on the material surface and preventing the transformation of the structure from layered to rock salt phase during cycling. This effectively reduces the occurrence of side reactions and improves the structural stability and cycle life of layered lithium-rich manganese-based materials (LRM). Thirdly, W doping can expand the lattice parameters, forming a highly ionicly conductive layer that effectively reduces lithium diffusion resistance and electron migration resistance, improves lithium diffusion kinetics, and accelerates Li-Li diffusion. + The diffusion rate is improved, thereby enhancing the cell's cycle stability, rate capability, and other electrochemical performance.

[0092] In one possible implementation, tungsten ions (W 6+ The atomic percentage of the core material 10 ranges from 2% to 3%.

[0093] For example, tungsten ions (W 6+ The atomic percentage in the core material 10 is 2%, 2.3%, 2.5%, 2.7%, or 3%, etc., and no limit is set here.

[0094] Based on the above settings, tungsten ions (W 6+ The atomic percentage of tungsten ions (W) in the core material 10 is relatively large, which can increase the yield of tungsten ions (W). 6+ To improve the stability of the crystal structure of lithium-rich manganese-based materials (LRM), reduce side reactions, and accelerate the Li + The diffusion rate effect further improves the cell's cycle stability, rate capability, and other electrochemical performance.

[0095] In one possible implementation, the core material 10 further includes nickel (Ni) and cobalt (Co); the atomic percentage of nickel (Ni) in the core material 10 is less than the atomic percentage of manganese (Mn) in the core material 10 and greater than the atomic percentage of cobalt (Co) in the core material 10.

[0096] With this configuration, the core material 10 includes lithium manganese nickel cobalt compounds, giving it high energy density, long lifespan, high safety, low cost, and good cycle performance.

[0097] Secondly, some embodiments of this disclosure also provide a method for preparing a positive electrode material 100. This preparation method includes steps S1 to S2.

[0098] S1: Forming core material 10, which includes lithium-rich manganese-based material.

[0099] S2: Form a composite coating material 20 and coat the composite coating material 20 on the outer surface of the core material 10. The composite coating material 20 includes a first material 21 and a second material 22. The first material 21 includes carbon elements and forms a three-dimensional network structure with cavities; the second material 22 includes a part located on the outer surface of the three-dimensional network structure and also includes a part located in the cavities of the three-dimensional network structure; the second material 22 is at least used to achieve the function of lithium storage.

[0100] It should be noted that for the technical effects brought by the second aspect, reference can be made to the technical effects brought by the corresponding implementation manners in the first aspect, which will not be elaborated here.

[0101] In a possible implementation manner, forming the core material 10 includes S1.1 to S1.2.

[0102] S1.1: Mix a first lithium source, a manganese source, and a tungsten source to obtain a mixed powder.

[0103] In some embodiments, the manganese source is selected from any one of the following general formula shown structures: Ni b Co c Mn 1-b-c (OH)2; where 0 ≤ c ≤ 0.05, 0 < b ≤ 0.4. For example, when c = 0.04 and b = 0.3, the manganese source is Ni 0.3 Co 0.04 Mn 0.66 (OH)2. The above manganese source can also be called a manganese-based ternary hydroxide precursor.

[0104] Exemplarily, in the general formula Ni b Co c Mn 1-b-c (OH)2, the value of c can be 0, 0.01, 0.02, 0.03, 0.04, or 0.05, etc., and there is no limitation here.

[0105] Exemplarily, in the general formula Ni b Co c Mn 1-b-c (OH)2, the value of b can be 0.05, 0.1, 0.3, 0.3, or 0.4, etc., and there is no limitation here.

[0106] In some embodiments, the first lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate.

[0107] In some embodiments, the tungsten source includes at least one of tungsten trioxide, tungsten sulfide, and tungsten carbide.

[0108] In some embodiments, the process of mixing the first lithium source, the manganese source, and the tungsten source is a ball milling process.

[0109] For example, the rotational speed range of the ball milling process can be 300 r / min to 500 r / min, such as 300 r / min, 350 r / min, 400 r / min, 450 r / min or 500 r / min, etc., and there is no limitation here.

[0110] For example, the ball milling time for mixing the first lithium source, manganese source and tungsten source can be 1h to 2h, such as 1h, 1.2h, 1.4h, 1.6h, 1.8h or 2h, etc., and there is no limitation here.

[0111] S1.2: The mixed powder is calcined to obtain core material 10.

[0112] In some embodiments, the calcination temperature of the mixed powder ranges from 600°C to 800°C.

[0113] For example, the calcination temperature of the mixed powder can be 600°C, 650°C, 700°C, 750°C or 800°C, etc., and there is no limitation here.

[0114] In some embodiments, the calcination time of the mixed powder ranges from 6 h to 8 h.

[0115] For example, the calcination time of the mixed powder can be 6h, 6.5h, 7h, 7.5h or 8h, etc., and there is no limitation here.

[0116] Understandably, through the above setup, the core material 10 was synthesized using a high-temperature solid-state method. On the one hand, this allows the core material 10 to include lithium manganese nickel cobalt compounds or lithium manganese nickel compounds, giving it high energy density, long lifespan, high safety, low cost, and good cycle performance. On the other hand, it enables the formation of a core material 11 that is rich in tungsten ions (W). 6+ The doping layer of W can improve the overall structural and thermal stability of the cathode material 100, as mentioned above.

[0117] In one possible implementation, the second material 20 comprises lithium vanadate (LiV3O8), and the reaction that forms the second material 20 is a solvothermal reaction.

[0118] Through the above configuration, on the one hand, the layered structure of lithium vanadate (LiV3O8) can be utilized to increase the space for storing lithium ions and reduce the irreversible insertion / extraction of lithium ions. Furthermore, the second material 22 can have a larger interlayer spacing, providing an effective channel for lithium ion insertion / extraction. On the other hand, when the second material 20 is formed using a solvothermal reaction, compared to forming the second material 20 through a solid-state reaction, the distribution of the formed second material 20 can be more uniform. The second material 20 can be more evenly distributed on the outer surface of the three-dimensional network structure formed by the first material 21 and within the cavities of the three-dimensional network structure. Thus, the second material 22 can have a larger interlayer spacing, providing an effective channel for lithium ion insertion / extraction. This reduces the charge transfer resistance between lithium ions in the cathode material 100 particles, which is beneficial for Li... + The efficient shuttle operation improves the cell's initial coulombic efficiency, cycle stability, rate capability, and other electrochemical performance.

[0119] In one possible implementation, the reaction temperature range for the solvothermal reaction that forms the second material 20 is 60°C to 80°C.

[0120] For example, the reaction temperature of the solvothermal reaction that forms the second material 20 can be 60°C, 65°C, 70°C, 75°C or 80°C, etc., and there is no limitation here.

[0121] In one possible implementation, a composite coating material 20 is formed and the composite coating material 20 is coated on the outer surface of the core material 10, including S2.1 to S2.4.

[0122] S2.1: The first stage of the solvothermal reaction of the vanadium source and the second lithium source is carried out to obtain the first solution; wherein the ratio of vanadium in the vanadium source to lithium in the second lithium source is 3:1, and the first solution includes lithium vanadate (LiV3O8).

[0123] For example, the solvent of the first solution is deionized water.

[0124] For example, the vanadium source includes ammonium vanadate (NH4VO3).

[0125] For example, the second lithium source includes lithium hydroxide monohydrate (LiOH·H2O).

[0126] S2.2: Add the carbon source to the first solution to carry out the second stage of the solvothermal reaction and obtain the second solution.

[0127] For example, the carbon source includes at least one of carbon nanotubes, graphene, and porous carbon.

[0128] For example, the ratio of the carbon source added in S2.2 to the second material 22 is (0.02 to 0.03):1, such as 0.02:1, 0.023:1, 0.025:1, 0.028:1 or 0.03:1, etc., and there is no limitation here.

[0129] S2.3: The core material is added to the second solution to carry out the third stage of the solvothermal reaction, resulting in the first precipitate.

[0130] For example, in S2.1, S2.2 and S2.3, the solvothermal reaction is carried out in a water bath under magnetic stirring. The stirring speed can be in the range of 250 r / min to 300 r / min, such as 250 r / min, 260 r / min, 270 r / min, 280 r / min, 290 r / min or 300 r / min, etc., and there is no limitation here.

[0131] S2.4: Calcining the first precipitate to obtain the cathode material.

[0132] In some embodiments, the calcination temperature of the first precipitate is in the range of 350°C to 400°C.

[0133] For example, the calcination temperature of the first precipitate can be 350°C, 360°C, 370°C, 380°C, 390°C or 400°C, etc., and there is no limitation here.

[0134] This setup avoids the impact of the calcination process on the primary material.

[0135] In some embodiments, the calcination time of the first precipitate ranges from 10 h to 12 h.

[0136] For example, the calcination time of the first precipitate can be 10h, 10.5h, 11h, 11.5h or 12h, etc., and there is no limitation here.

[0137] Based on the above steps, the lithium vanadate (LiV3O8) formed in S2.1 can enter the cavity of the three-dimensional network structure formed by the first material 21. In S2.2, lithium vanadate (LiV3O8) can be formed in situ within the cavity and on the outer surface of the three-dimensional network structure formed by the first material 21. For example, the co-precipitation reaction of NH4VO3 and LiOH·H2O generates LiV3O8 in situ within the cavity and on the outer surface of the three-dimensional network structure. This makes the second material 22 include the portion located on the outer surface of the three-dimensional network structure and the portion located within the cavity of the three-dimensional network structure. The composite coating material 20 is densely coated on the surface of the core material 10. In this way, firstly, the electronic conductivity and ionic conductivity of the cathode material 100 can be improved, and secondly, the lithium-ion storage space can be enhanced, reducing the Li-ion concentration. +The irreversible insertion / extraction of lithium ions enhances overall electrochemical performance; thirdly, it provides an effective channel for lithium ion insertion / extraction, reducing the charge transfer impedance between lithium ions in the cathode material particles, which is beneficial for Li... + The efficient shuttle operation improves the cell's initial coulombic efficiency, cycle stability, rate capability, and other electrochemical performance. Furthermore, lithium vanadate (LiV3O8) can be formed in situ on the outer surface of the core material 10 in S2.3, which further improves the cell's initial coulombic efficiency, cycle stability, rate capability, and other electrochemical performance.

[0138] In some embodiments, S2.3A is included after S2.3 and before S2.4.

[0139] S2.3A: Filtration, washing, drying.

[0140] For example, the solvent used for washing is deionized water, and the washing is performed 3 times.

[0141] For example, drying is performed in a vacuum oven. The drying time can be 8 hours to 12 hours, for example, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours, etc., and there is no limitation here.

[0142] For example, the temperature of the vacuum oven can be 100℃ to 120℃, such as 100℃, 105℃, 110℃, 115℃ or 120℃, etc., and there is no limitation here.

[0143] Based on the above settings, the temperature of the vacuum oven is within a suitable range, which can prevent the structure of the composite coating material 20 from being adversely affected during the drying process.

[0144] In one possible implementation, the reaction time of the first stage of the solvothermal reaction is greater than or equal to the reaction time of the second stage of the solvothermal reaction.

[0145] In one possible implementation, the reaction time of the third stage of the solvothermal reaction is greater than or equal to the reaction time of the second stage of the solvothermal reaction.

[0146] In one possible implementation, the reaction time of the first stage of the solvothermal reaction ranges from 1 h to 2 h.

[0147] For example, the reaction time of the first stage of the solvothermal reaction can be 1h, 1.2h, 1.4h, 1.6h, 1.8h or 2h, etc., and there is no limitation here.

[0148] Understandably, by setting it up as described above, the reaction time of the first stage of the solvothermal reaction is within a suitable range, which can increase the amount of lithium vanadate (LiV3O8) formed in S2.1, and facilitate the entry of lithium vanadate (LiV3O8) into the cavity of the three-dimensional network structure formed by the first material 21.

[0149] In one possible implementation, the reaction time of the second stage of the solvothermal reaction ranges from 0.2 h to 1 h.

[0150] For example, the reaction time of the second stage of the solvothermal reaction can be 0.2h, 0.4h, 0.6h, 0.8h or 1h, etc., and there is no limitation here.

[0151] With the above settings, the reaction time of the second stage of the solvothermal reaction is within a suitable range, which can improve the sufficiency of the reaction when lithium vanadate (LiV3O8) is formed in situ in the cavity and on the outer surface of the three-dimensional network structure in S2.2.

[0152] In one possible implementation, the reaction time of the third stage of the solvothermal reaction ranges from 1 h to 2 h.

[0153] For example, the reaction time of the first stage of the solvothermal reaction can be 1h, 1.2h, 1.5h, 1.6h, 1.8h or 2h, etc., and there is no limitation here.

[0154] With the above settings, the reaction time of the third stage of the solvothermal reaction is within a suitable range, which can improve the sufficiency of the reaction when lithium vanadate (LiV3O8) is formed in situ on the outer surface of the core material 10 in S2.3.

[0155] In one possible implementation, the carbon source comprises acid-treated multi-walled carbon nanotubes.

[0156] When the carbon source includes acid-treated multi-walled carbon nanotubes, multiple active sites can be formed on the surface of the multi-walled carbon nanotubes. These active sites can be used to connect the second material 22. In this way, firstly, the connection reliability between the first material 21 and the second material 22 can be increased, and secondly, the adsorption amount of the second material 22 on the three-dimensional network structure formed by the first material 21 can be increased, which can form more space for storing lithium ions and reduce the irreversible insertion and extraction of lithium ions.

[0157] In one possible implementation, the carbon source is multi-walled carbon nanotubes treated with concentrated sulfuric acid and / or concentrated nitric acid; the acid treatment process is ultrasonic treatment; and the acid treatment time ranges from 2 h to 4 h.

[0158] For example, the acid treatment time can be 2h, 2.5h, 3h, 3.5h, or 4h, etc., and there is no limitation here.

[0159] For example, the temperature of the acid treatment can be 25°C to 30°C, such as 25°C, 26°C, 27°C, 28°C, 29°C or 30°C, etc., and there is no limitation here.

[0160] The above settings can improve the acid treatment of multi-walled carbon nanotubes, forming more active sites on them. This increases the connection reliability between the first material 21 and the second material 22, creates more space for storing lithium ions, and reduces the irreversible insertion and extraction of lithium ions.

[0161] The following are embodiments of the cathode material and lithium-ion battery provided in this application, as well as comparative examples provided in accordance with related technologies.

[0162] Example 1

[0163] In this embodiment, cathode material A was prepared by means of R1 to R6.

[0164] R1: Lithium carbonate, tungsten trioxide, and manganese-based ternary hydroxide Ni 0.4 Co 0.05 Mn 0.55 (OH)2 was prepared according to the following molar ratio: Li / (Ni+Co+Mn)=1.2:1, W / (Ni+Co+Mn+W)=0.05:1; and the mixture was ball-milled at 400 r / min for 2 h to obtain a mixed powder.

[0165] R2: The mixed powder obtained from R1 is calcined in air at 650°C for 7 hours, naturally cooled, and then crushed and sieved to obtain a core material with W element doped on the surface.

[0166] R3: Prepare NH4VO3 and LiOH·H2O according to the following molar ratio: V / Li=3 / 1.0; and dissolve NH4VO3 and LiOH·H2O in deionized water under magnetic stirring (the ratio of the sum of the masses of NH4VO3 and LiOH·H2O to the mass of deionized water is 1:40), and react in a water bath at 65℃ for 2 hours to obtain the first solution.

[0167] R4: Prepare acid-pretreated multi-walled carbon nanotubes (MWCNTs) at a ratio of 2% to the mass m(MWCNTs) of lithium vanadate (LiV3O8). Add the acid-pretreated MWCNTs to the first solution and continue the reaction in a water bath for 0.5 h to obtain the second solution.

[0168] R5: Add the surface-doped W core material prepared by R2 to the second solution, continue stirring for 1 hour, filter, wash 3 times with deionized water, and dry in a vacuum oven at 100°C for 8 hours to obtain the first precipitate.

[0169] R6: The first precipitate was calcined in air at 350°C for 10 hours to obtain cathode material A, which is a lithium-rich manganese-based cathode material modified by W element doping and synergistic LiV3O8-MWCNTs composite material coating.

[0170] Example 2

[0171] A lithium-ion coin cell A was prepared based on the cathode material A prepared in Example 1.

[0172] Example 3

[0173] In this embodiment, cathode material B was prepared. The preparation method is similar to that in Example 1, except that R1 is replaced with R1' as described below.

[0174] R1': Lithium carbonate reacted with manganese-based ternary hydroxide Ni 0.4 Co 0.05 Mn 0.55 (OH)2 was prepared according to the following molar ratio: Li / (Ni+Co+Mn)=1.2:1; and the mixture was ball-milled at 400r / min for 2h to obtain a mixed powder.

[0175] Example 4

[0176] Based on the cathode material B prepared in Example 3, a lithium-ion coin cell B was prepared.

[0177] Comparative Example 1

[0178] In this comparative example, a comparative cathode material C was prepared using methods P1 to P2.

[0179] P1: Lithium carbonate is reacted with manganese-based ternary hydroxide Ni 0.4 Co 0.05 Mn 0.55 (OH)2 was prepared according to the following molar ratio: Li / (Ni+Co+Mn)=1.2:1; and the mixture was ball-milled at 400r / min for 2h to obtain mixed powder C.

[0180] P2: The mixed powder C obtained in P1 was calcined in air at 650°C for 7 hours, then naturally cooled, and then crushed and sieved to obtain the comparative cathode material C with W element doped on the surface.

[0181] Comparative Example 2

[0182] Based on the comparative cathode material C prepared in Comparative Example 1, a lithium-ion coin cell C was prepared.

[0183] Comparative Example 3

[0184] In this comparative example, a comparative cathode material D was prepared using methods Q1 to Q2.

[0185] Q1: Lithium carbonate, tungsten trioxide, and manganese-based ternary hydroxide Ni 0.4 Co 0.05 Mn 0.55 (OH)2 was prepared according to the following molar ratio: Li / (Ni+Co+Mn)=1.2:1, W / (Ni+Co+Mn+W)=0.05:1; and the mixture was ball-milled at 400 r / min for 2 h to obtain mixed powder D.

[0186] Q2: The mixed powder D obtained in Q1 is calcined in air at 650°C for 7 hours, naturally cooled, and then crushed and sieved to obtain the comparative cathode material D with W element doped on the surface.

[0187] Comparative Example 4

[0188] Based on the comparative cathode material D prepared in Comparative Example 3, a lithium-ion coin cell D was prepared.

[0189] The lithium-ion coin cells prepared in Examples 2, 4, Comparative Examples 2, and 4 were subjected to initial charge-discharge and rate cycle tests. The test conditions were as follows: initial charge-discharge tests were conducted at 25°C with a rate of 0.1C / 0.1C, followed by 5 cycles at discharge rates of 0.1C, 0.33C, 0.5C, 1C, 2C, and 0.1C, respectively, with a voltage range of 2.0–4.6V. The test results are as follows. Figure 3 and Figure 4 As shown.

[0190] Depend on Figure 3 and Figure 4 As can be seen, compared with Comparative Examples 2 and 4, the lithium-ion coin cell half-cells in Examples 2 and 4 showed significantly improved initial charge-discharge specific capacity, initial coulombic efficiency, and rate cycle test results under high voltage conditions. The main reason for this is that the composite coating material (LiV3O8-MWCNTs) gives the lithium-rich manganese-based cathode material better electrochemical performance. Because the layered structure of LiV3O8 has a lithium intercalation structure, it can provide more space for storing lithium ions and reduce the Li-ion degradation rate. +The irreversible insertion and extraction of lithium ions is a problem, while MWCNTs have excellent electronic conductivity. Their large interlayer spacing provides an effective channel for lithium ion insertion / extraction, and the cylindrical structure does not collapse after multiple charge-discharge cycles. The combination of LiV3O8 and MWCNTs can reduce the charge transfer resistance between material particles, which is conducive to the efficient shuttle of Li+, thereby improving the electrochemical performance of the cell, such as the first coulombic efficiency, cycle stability, and rate capability.

[0191] Moreover, compared with Example 4, the lithium-ion coin cell in Example 2 showed significantly improved initial charge-discharge specific capacity, initial coulombic efficiency, and rate cycle test results. This is mainly because the introduction of W element can enhance the overall structural and thermal stability of the lithium-rich manganese-based cathode material. Due to its strong bonding force with oxygen, W can improve the stability of the material's crystal structure, and high-valence W ions can induce low-valence Ni ions. 2+ The generation of these substances induces the formation of surface rock salt or spinel structures, which can suppress oxygen release and phase transformation, effectively reduce the occurrence of side reactions, and improve the cycle stability of the battery cell.

[0192] The above embodiments are merely preferred embodiments provided to fully illustrate this application, and the scope of protection of this application is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on this application are all within the scope of protection of this application.

Claims

1. A method for producing a positive electrode material, characterized by, The application relates to a positive electrode material, and relates to a method for preparing the positive electrode material. The method comprises the following steps: forming an inner core material, wherein the inner core material comprises a lithium-rich manganese-based material; forming a composite coating material, and coating the composite coating material on the outer surface of the inner core material; the composite coating material comprises a first material and a second material, the first material comprises carbon elements, and the first material forms a three-dimensional network structure with cavities; the second material comprises a part located on the outer surface of the three-dimensional network structure and a part located in the cavities of the three-dimensional network structure; and the second material is used at least for realizing a lithium storage function; the second material comprises lithium vanadate, and the reaction for forming the second material is a solvothermal reaction; wherein the step of forming the composite coating material and coating the composite coating material on the outer surface of the inner core material comprises the following steps: carrying out a first stage of the solvothermal reaction on a vanadium source and a second lithium source to obtain a first solution; wherein the configuration ratio of vanadium in the vanadium source to lithium in the second lithium source is 3:1, and the first solution comprises lithium vanadate; adding a carbon source into the first solution to carry out a second stage of the solvothermal reaction, and obtaining a second solution; adding the inner core material into the second solution to carry out a third stage of the solvothermal reaction, and obtaining a first precipitate; 2. The method of claim 1, wherein the method further comprises a step of mixing the lithium transition metal oxide and the lithium source. calcining the first precipitate to obtain the positive electrode material.

3. The method of claim 2, wherein the lithium transition metal oxide is prepared by the steps of: preparing a lithium transition metal oxide precursor; and calcining the lithium transition metal oxide precursor in the presence of a lithium source. The first material comprises at least one of carbon nanotubes, graphene and porous carbon.

4. The method of claim 1, wherein the method further comprises: The first material comprises multi-walled carbon nanotubes.

5. The method of claim 1, wherein the method further comprises: The thickness of the composite coating material ranges from 15nm to 30nm.

6. The method of producing a positive electrode material according to any one of claims 1 to 5, characterized by, In the composite coating material, the mass ratio of the first material to the second material ranges from (0.02-0.03):

1.

7. The method for preparing the cathode material according to claim 6, characterized in that, The inner core material comprises a core material and a doping material, and the doping material coats the core material; the doping material comprises a lithium-rich manganese-based material containing tungsten ions.

8. The method of producing a positive electrode material according to any one of claims 1 to 5, characterized by, The atomic percentage of the tungsten ions in the inner core material ranges from 2% to 3%.

9. The method of claim 1, wherein the method further comprises the step of: The inner core material further comprises nickel and cobalt; the atomic percentage of nickel in the inner core material is less than the atomic percentage of manganese in the inner core material and greater than the atomic percentage of cobalt in the inner core material. ​ The method for forming the inner core material comprises the following steps: mixing a first lithium source, a manganese source and a tungsten source to obtain a mixed powder; 10. The method of claim 9, wherein the method further comprises a step of calcining the mixture at a temperature of 700-900°C for 1-10 hours. The manganese source is selected from any one of the following general structures as shown in the structures: Ni b Co c Mn 1-b-c (OH)2; wherein 0≤c≤0.05, 0<b≤0.

4.

11. The method of claim 9, wherein the method further comprises a step of mixing the lithium transition metal oxide and the lithium source. calcining the mixed powder to obtain the inner core material. The first lithium source comprises at least one of lithium carbonate, lithium hydroxide, lithium nitrate and lithium acetate; and / or 12. The method of claim 9, wherein the method further comprises a step of mixing the lithium transition metal oxide and the lithium source. The tungsten source comprises at least one of tungsten trioxide, tungsten sulfide and tungsten carbide. The calcination temperature of the mixed powder ranges from 600 DEG C to 800 DEG C; and / or 13. The method of claim 1, wherein the method is carried out at a temperature of 500- 1000 °C. The calcination time of the mixed powder ranges from 6h to 8h.

14. The method for preparing the cathode material according to claim 1, characterized in that, The reaction temperature of the solvothermal reaction for forming the second material ranges from 60 DEG C to 80 DEG C. The reaction time of the first stage of the solvothermal reaction is greater than or equal to the reaction time of the second stage of the solvothermal reaction; and / or 15. The method for preparing the cathode material according to claim 14, characterized in that, The reaction time of the third stage of the solvothermal reaction is greater than or equal to the reaction time of the second stage of the solvothermal reaction. The reaction time of the first stage of the solvothermal reaction ranges from 1h to 2h; and / or, the reaction time length of the second stage of the solvothermal reaction ranges from 0.2 h to 1 h; and / or, the reaction time length of the third stage of the solvothermal reaction ranges from 1 h to 2 h.

16. The method of claim 1, wherein the method is carried out at a temperature of 500- 1000 °C. The carbon source includes at least one of carbon nanotubes, graphene and porous carbon.

17. The method for preparing the cathode material according to claim 1, characterized in that, The carbon source includes acid-treated multi-walled carbon nanotubes.

18. The method of claim 17, wherein the method further comprises: The carbon source is multi-walled carbon nanotubes treated with concentrated sulfuric acid and / or concentrated nitric acid; the acid treatment process is ultrasonic treatment; and the acid treatment time ranges from 2 h to 4 h.

19. The method for preparing the cathode material according to claim 1, characterized in that, The vanadium source includes ammonium vanadate; and / or, the second lithium source includes lithium hydroxide monohydrate.

20. The method of claim 1, wherein the method is carried out at a temperature of 500- 1000 °C. The first precipitation calcination temperature ranges from 350 ℃ to 400 ℃; and / or, The first precipitation calcination time ranges from 10 h to 12 h.

21. A lithium-ion battery, characterized by, The positive electrode material is prepared by the preparation method according to any one of claims 1-20.

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