Positive electrode material, preparation method thereof, and lithium ion battery

Abstract

This application relates to a cathode material, a method for preparing the same, and a lithium-ion battery. The cathode material includes: a matrix material, which is a lithium transition metal composite oxide; a coating layer located on the surface of the matrix material, and the coating layer includes tungsten oxide WO doped with metal ions 3‑a ; where 0 < a < 0.5; in the coating layer, the doping concentration of the metal ions gradually decreases from the surface of the matrix material to the surface of the cathode material. The cathode material of this application has a coating layer on its surface, which can improve the electronic conductivity and ionic conductivity of the coating layer and enhance the rate performance of the cathode material.

Description

Technical Field

[0001] The present invention relates to the technical field of cathode materials, and particularly to cathode materials, their preparation methods, and lithium-ion batteries. Background Art

[0002] High-nickel cathode materials have the advantages of low cost, high energy density, and excellent rate performance, so they are cathode materials for high-energy-density lithium-ion batteries with great development potential. It has been found that increasing the Ni content can improve the energy density of high-nickel cathode materials. However, when the Ni content is too high, the structural stability of the cathode materials will be damaged; and due to the continuous side reactions between the electrolyte and the surface of the cathode materials during charge and discharge, the cycle stability of the materials will also deteriorate.

[0003] Currently, in the industry, the surface modification of materials is mainly carried out through a dry coating process to improve the electrochemical performance and stability of cathode materials. The conventional coating layers of current cathode materials have poor electronic conductivity and ionic conductivity, which will hinder the diffusion of lithium during the insertion and extraction process and reduce the rate performance of lithium batteries. Summary of the Invention

[0004] The purpose of this application is to provide a cathode material, its preparation method, and a lithium-ion battery. The surface of the cathode material has a coating layer, which can improve the electronic conductivity and ionic conductivity of the coating layer, and enhance the rate performance and safety performance of the cathode material.

[0005] In the first aspect, a cathode material of this application, the cathode material includes:

[0006] A matrix material, the matrix material is a lithium transition metal composite oxide;

[0007] A coating layer located on the surface of the matrix material, the coating layer includes tungsten oxide WO doped with metal ions 3-a ; where 0 < a < 0.5;

[0008] In the coating layer, the doping concentration of the metal ions gradually decreases from the surface of the matrix material to the surface of the cathode material.

[0009] In some embodiments, the metal ions include at least one of Mg, Ca, Ti, Cr, Mn, Fe, Zn, and V metal ions.

[0010] In some embodiments, the metal ions include two of Mg, Ca, Ti, Cr, Mn, Fe, Zn, and V metal ions.

[0011] In some embodiments, along the direction from the inside to the surface of the cathode material, the doping concentration difference of the metal ions between the outermost region and the innermost region of the coating layer is 10% - 15%.

[0012] In some embodiments, in the direction from the inside to the surface of the positive electrode material, the outermost region of the coating layer is W 18 O 49 .

[0013] In some embodiments, in the direction from the inside to the surface of the positive electrode material, the doping concentration of metal ions in the innermost region of the coating layer is 15% ± 3%.

[0014] In some embodiments, the tungsten oxide includes W 32 O 84 , W3O8, W 18 O 49 , W 17 O 47 , W5O 14 , W 20 O 58 and W 25 O 73 and at least one of them.

[0015] In some embodiments, the tungsten oxide is W 18 O 49 .

[0016] In some embodiments, the chemical general formula of the matrix material is LiNi x Co y M z O2, where 0.8 ≤ x < 1, 0 < y ≤ 0.12, 0 < z ≤ 0.08, x + y + z = 1, and the M element includes at least one of Al, Mn, Ba, Ca, Mg, Sr, Zr, Ti, La, W, Nb, Y, Gd, and Ta.

[0017] In some embodiments, the median particle size of the matrix material is 3 μm to 15 μm.

[0018] In some embodiments, the thickness of the coating layer is 5 nm to 300 nm.

[0019] In some embodiments, based on the mass of the matrix material being 100%, the mass content of the coating layer is 0.01% to 0.5%.

[0020] In some embodiments, the median particle size D 50 of the positive electrode material is 2 μm to 20 μm.

[0021] In some embodiments, the specific surface area of the positive electrode material is 0.3 m 2 / g to 3 m 2 / g.

[0022] In some embodiments, the conductivity of the positive electrode material is 10 -1 S / cm - 10 2 S / cm.

[0023] The present application also provides a method for preparing a positive electrode material, comprising the following preparation steps:

[0024] Performing magnetron sputtering treatment on a substrate material using a target doped with metal ions to obtain a positive electrode material; wherein, the target comprises tungsten oxide WO doped with metal ions 3-a ; wherein, 0 < a < 0.5, and the doping concentration of the metal ions gradually decreases from the surface to the inside of the target.

[0025] In some embodiments, the chemical general formula of the substrate material is LiNi x Co y M z O2, wherein, 0.8 ≤ x < 1, 0 < y ≤ 0.12, 0 < z ≤ 0.08, x + y + z = 1, and the M element comprises at least one of Al, Mn, Ba, Ca, Mg, Sr, Zr, Ti, La, W, Nb, Y, Gd, and Ta.

[0026] In some embodiments, the median particle size of the substrate material is 3 μm to 15 μm.

[0027] In some embodiments, the metal ions comprise at least one of Mg, Ca, Ti, Cr, Mn, Fe, Zn, and V metal ions.

[0028] In some embodiments, the metal ions comprise two of Mg, Ca, Ti, Cr, Mn, Fe, Zn, and V metal ions.

[0029] In some embodiments, the tungsten oxide comprises W 32 O 84 , W3O8, W 18 O 49 , W 17 O 47 , W5O 14 , W 20 O 58 and W 25 O 73 at least one of.

[0030] In some embodiments, the tungsten oxide is W 18 O 49 .

[0031] In some embodiments, along the direction from the inside to the surface of the target, the doping concentration difference of metal ions between the outermost layer and the innermost layer of the target is 10% to 15%.

[0032] In some embodiments, along the direction from the inside to the surface of the target, the doping concentration of metal ions in the outermost layer of the target is 15% ± 5%.

[0033] In some embodiments, along the direction from the inside to the surface of the target, the innermost layer of the target is tungsten oxide WO 3-a ; where 0 < a < 0.5.

[0034] In some embodiments, as the depth of the target increases by every 5 nm to 75 nm, the doping concentration of metal ions increases by 2.5% ± 0.5%.

[0035] In some embodiments, the target has a multi-layer structure from the inside to the outside, and the doping concentration of metal ions between any two adjacent layers increases by 2.5% ± 0.5%.

[0036] In some embodiments, the target includes four layers from the inside to the outside. The doping concentration of metal ions in the first layer is 0%, the doping concentration of metal ions in the second layer is 2.5% ± 0.5%, the doping concentration of metal ions in the third layer is 7.5% ± 0.5%, and the doping concentration of metal ions in the fourth layer is 10% ± 0.5%.

[0037] In some embodiments, the environmental vacuum degree during the magnetron sputtering process < 3.0×10 -4 Pa.

[0038] In some embodiments, the environmental temperature during the magnetron sputtering process is 300°C to 400°C.

[0039] In some embodiments, the sputtering power during the magnetron sputtering process is 80 W to 120 W.

[0040] In some embodiments, the sputtering power density of the target during the magnetron sputtering process is 2.0 to 5.0 W / cm 2 .

[0041] In some embodiments, the sputtering pressure during the magnetron sputtering process is 0.2 to 1.0 Pa.

[0042] In some embodiments, the sputtering time of the magnetron sputtering process is 15 to 80 min.

[0043] In some embodiments, the magnetron sputtering process is carried out in a protective atmosphere.

[0044] In some embodiments, the magnetron sputtering treatment is carried out in a protective atmosphere, and the protective atmosphere includes at least one of nitrogen, helium, neon, and argon.

[0045] In some embodiments, before the magnetron sputtering treatment of the substrate material with the target doped with metal ions, the method further includes: subjecting a mixed solution of WCl6, an inorganic salt of a metal ion, and a solvent to a hydrothermal reaction, filtering, washing the obtained product, and drying to obtain tungsten oxide WO doped with metal ions 3-a ; wherein, 0 < a < 0.5.

[0046] In some embodiments, the temperature of the hydrothermal reaction is 140°C to 200°C.

[0047] In some embodiments, the time of the hydrothermal reaction is 10 h to 20 h.

[0048] In some embodiments, the steps of washing the product include ultrasonic washing with water for 10 min to 15 min, ultrasonic washing with ethanol for 10 min to 15 min, and ultrasonic washing with acetone for 10 min to 15 min.

[0049] In some embodiments, the drying temperature is 60°C to 100°C.

[0050] In some embodiments, the drying time is 20 min to 100 min.

[0051] In some embodiments, the mass ratio of WCl6 to the inorganic salt of the metal ion is 1:(0.001 - 0.1).

[0052] In a third aspect, the present application provides a lithium-ion battery, and the lithium-ion battery includes the positive electrode material described in the first aspect or the positive electrode material prepared by the method described in the second aspect.

[0053] Compared with the prior art, the present invention has at least the following beneficial effects:

[0054] The positive electrode material proposed in the present application includes a substrate material and a coating layer on the surface of the substrate material, and the coating layer includes tungsten oxide WO doped with metal ions 3-a ; wherein, 0 < a < 0.5; sub-stoichiometric WO 3-a has a higher carrier density than conventional tungsten oxide WO3, and its electronic conductivity also increases accordingly. WO 3-aIt has a wider Li+ ion channel and higher conductivity. Coated on the surface of the matrix material, it can effectively improve the rate performance of the battery. And in the coating layer, the doping concentration of metal ions gradually decreases from the surface of the matrix material to the surface of the positive electrode material. That is, the region of the coating layer close to the matrix material has metal ions with a high doping concentration, which can greatly increase the electronic conductivity and ionic conductivity of the coating layer; the region of the coating layer far from the matrix material has metal ions with a low doping concentration or even no doped metal ions, which can improve the interfacial stability of the coating layer in contact with the electrolyte; a small amount of reactive oxygen generated during the charge and discharge cycle of the positive electrode material will preferentially react with the sub-stoichiometric WO in the coating layer 3-a to improve the safety performance of the battery; the surface of the positive electrode material of this application has a coating layer with a decreasing doping ion concentration gradient, which can improve the electronic conductivity and ionic conductivity of the coating layer, and enhance the rate performance and safety performance of the positive electrode material.

[0055] The preparation method of the positive electrode material provided by this application uses a target doped with metal ions to perform magnetron sputtering treatment on the matrix material. The doping metal ion concentration in the target increases in a gradient. After the sputtering treatment, a coating layer with a decreasing doping metal ion concentration gradient can be formed on the surface of the matrix material. The preparation method is simple and controllable. The prepared coating layer can improve the electronic conductivity and ionic conductivity of the coating layer, and enhance the rate performance and safety performance of the positive electrode material. And this preparation method is simple and controllable, which can reduce the production cost. Brief Description of the Drawings

[0056] The present invention will be further described below with reference to the drawings and embodiments.

[0057] Figure 1 It is a schematic flow chart of the preparation method of the positive electrode material provided by the embodiment of this application.

[0058] Figure 2 It is the XRD pattern of W in the coating layer on the surface of the positive electrode material prepared in Example 1 of this application 18 O 49 in the coating layer.

[0059] Figure 3 It is the SEM image of the cross-section of the positive electrode material obtained in Example 1.

[0060] Figure 4 It is the EDS image of the cross-section of the positive electrode material obtained in Example 1.

[0061] Figure 5 It is the charge and discharge curves of the positive electrode materials obtained in Examples 1 and 2 and Comparative Examples 1 and 2. Detailed Embodiments

[0062] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0063] It should be clear that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0065] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0066] After research, it was found that there are many active sites on the surface of the positive electrode material. During the charge and discharge cycle, not only will Li+ be deintercalated, but the organic components in the electrolyte will also undergo dehydrogenation reactions and decompose to produce oligomers. The oligomers form a passivation layer on the surface of the high-nickel material, thereby reducing Li + Migration speed; in addition, the electrolyte will continue to consume the active lithium ions in the positive electrode material, seriously damaging the battery's specific capacity and cycle life.

[0067] The common solution is to coat the surface of high-nickel materials with an "inert" coating layer to isolate the active ingredients from direct contact with the electrolyte, inhibit electrolyte oxidation, and improve the stability of the structure during the charge and discharge process; however, most "inert" coating materials are non-electrochemically active materials, with poor electronic and ionic conductivity, and poor lithium ion conductivity, which to some extent damages the rate performance of the positive electrode material and reduces the energy density of the material. At present, some solutions are to use carbon materials with higher conductivity to improve the conductivity of the coating layer, or to reduce the thickness of the coating layer, but this easily destroys the inertness of the coating layer.

[0068] Based on this, the present application provides a positive electrode material, the positive electrode material comprising:

[0069] A matrix material, wherein the matrix material is a lithium transition metal composite oxide;

[0070] The coating layer is located on the surface of the base material, and the coating layer includes tungsten oxide WO doped with metal ions. 3-a ; Among them, 0<a<0.5;

[0071] In the coating layer, the doping concentration of the metal ions gradually decreases from the surface of the matrix material to the surface of the positive electrode material.

[0072] The positive electrode material proposed in this application includes a matrix material and a coating layer located on the surface of the matrix material. The coating layer includes tungsten oxide WO doped with metal ions 3-a , sub-stoichiometric WO 3-a has a higher carrier density than conventional tungsten oxide WO3, and its electronic conductivity also increases accordingly. WO 3-a has a wider Li + ion channel and higher conductivity. Coated on the surface of the matrix material, it can effectively improve the rate performance of the battery. And in the coating layer, the doping concentration of the metal ions gradually decreases from the surface of the matrix material to the surface of the positive electrode material. That is, the region of the coating layer close to the matrix material has a high doping concentration of metal ions, which can greatly increase the electronic conductivity and ionic conductivity of the coating layer; the region of the coating layer far from the matrix material has a low doping concentration of metal ions or even no doped metal ions, which can improve the interface stability between the coating layer and the electrolyte; a small amount of active oxygen electrolytically generated during the charge and discharge cycle of the positive electrode material will preferentially react with the sub-stoichiometric WO 3-a in the coating layer, improving the safety performance of the battery; the positive electrode material of the present application has a coating layer with a decreasing doping ion concentration gradient on its surface, which can improve the electronic conductivity and ionic conductivity of the coating layer, and enhance the rate performance and safety performance of the positive electrode material. In some embodiments, the chemical general formula of the matrix material is LiNi x Co y M z O2, where 0.8 ≤ x < 1, 0 < y ≤ 0.12, 0 < z ≤ 0.08, x + y + z = 1, and the M element includes at least one of Al, Mn, Ba, Ca, Mg, Sr, Zr, Ti, La, W, Nb, Y, Gd, and Ta.

[0073] In some embodiments, the value of x can be 0.8, 0.85, 0.9, 0.95, 0.96, 0.97, 0.98, or 0.99, etc., the value of y can be 0.01, 0.05, 0.07, 0.09, 0.1, 0.15, 0.17, 0.19, or 0.2, etc., and the value of z can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, or 0.08, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0074] In some embodiments, the median particle size of the matrix material is 3 μm to 15 μm, specifically it can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm. Of course, it can also be other values within the above range, which are not limited herein.

[0075] In some embodiments, the matrix material is a lithium transition metal composite oxide, specifically it can be a high-nickel ternary material, a lithium-rich material, etc.

[0076] In some embodiments, the crystal structure of the matrix material belongs to the hexagonal crystal system.

[0077] In some embodiments, the thickness of the coating layer is 5 nm to 300 nm, specifically it can be 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 50 nm, 80 nm, 100 nm or 300 nm, etc. Of course, it can also be other values within the above range, which are not limited herein. Preferably, the thickness of the coating layer is 5 nm to 100 nm. It can be understood that too large a thickness will cause an increase in the Li+ transport resistance and affect the rate performance of the cathode material; too thin a thickness is likely to result in incomplete coating in some areas of the cathode material, causing instability at the interface between the cathode material and the electrolyte.

[0078] In some embodiments, the coating layer includes tungsten oxide WO 3-a ; where 0 < a < 0.5. Specifically, the value of a can be 0.1, 0.2, 0.24, 0.28, 0.34, 0.375, 0.4, etc. Of course, it can also be other values within the above range, which are not limited herein. WO 3-a is a typical ReO3-type peroxide structure, and its polycrystals have a narrow bandgap of about 2.5 - 2.8 eV, with a higher carrier density. The structural diversity and crystal phase transition of WO 3-a are beneficial to the transport of small ions and charges, and have high chemical stability. Since WO 3-a has less oxygen content compared to traditional WO3, its lattice network changes from an octahedral structure to an open structure composed of triangular, quadrilateral, pentagonal and hexagonal tunnels. The formation of this open structure can effectively increase the Li + transport speed. Tungsten oxide doped with metal ions can further improve the electrical conductivity.

[0079] In some embodiments, the tungsten oxide includes W 32 O 84 、W3O8、W 18 O 49 、W 17 O 47 、W5O14 , W 20 O 58 and W 25 O 73 or at least one of them. Preferably, the tungsten oxide is WO 18 O 49 , W 18 O 49 with a carrier density as high as 1.87×10 22 cm -3 , which can have higher conductivity compared to other subtypes of tungsten oxide.

[0080] In some embodiments, the metal ions include at least one of Mg, Ca, Ti, Cr, Mn, Fe, Zn, and V metal ions; preferably, the metal ions include two of Mg, Ca, Ti, Cr, Mn, Fe, Zn, and V metal ions. Exemplarily, the metal ions are Zn and V, or the metal ions are Mg and V, and there is no limitation here. It can be understood that the presence of metal ions can further improve the conductivity of the coating layer.

[0081] In some embodiments, as the distance from the region in the coating layer to the surface of the substrate material increases, the doping concentration of metal ions decreases linearly. Exemplarily, for every 5 nm to 75 nm increase in the distance between the two, the doping concentration of metal ions decreases by 2.5% ± 0.5%.

[0082] In some embodiments, as the distance from the region in the coating layer to the surface of the substrate material increases, the doping concentration of metal ions decreases stepwise. Exemplarily, the coating layer includes the innermost region, the second region, the third region, and the outermost region. Among them, the metal ion doping concentration in the innermost region is 10%, the metal ion doping concentration in the second region is 5%, the metal ion doping concentration in the third region is 2.5%, and the metal ion doping concentration in the outermost region is 0%.

[0083] In some embodiments, along the direction from the inside to the surface of the positive electrode material, the difference in the doping concentration of metal ions between the outermost region and the innermost region of the coating layer is 10% - 15%.

[0084] It should be noted that the outermost region of the coating layer refers to the region of the coating layer far from the surface of the substrate material. Exemplarily, when the thickness of the coating layer is 50 nm, the doping concentration of metal ions in the region from the surface of the coating layer to a depth of 10 nm (i.e., the outermost region) is β1, and the doping concentration of metal ions in the region from the surface of the substrate material to a depth of 10 nm (i.e., the innermost region) of the coating layer is β2, and β2 - β1 = 10% - 15%.

[0085] In some embodiments, along the direction from the inside to the surface of the positive electrode material, the outermost region of the coating layer is W 18 O 49 , that is, without doping metal ions, the chemical inertness of the coating layer is stronger, and the outermost region can improve the interfacial stability of the coating layer in contact with the electrolyte.

[0086] In some embodiments, along the direction from the inside to the surface of the positive electrode material, the doping concentration of metal ions in the innermost region of the coating layer is 15% ± 3%, specifically, it can be 12%, 14%, 15%, 16%, 18%, etc., which are not limited herein. The innermost region of the coating layer has the highest doping concentration of metal ions. On the basis of tungsten oxide WO 3-a having high conductivity, the metal ions with high doping concentration can further improve the conductivity of the coating layer, so that the inner region of the coating layer has a wider Li + channel and higher conductivity. That is, along the direction from the inside to the surface of the positive electrode material, as the thickness of the coating layer increases, the conductivity of the coating layer decreases slightly, but the inertness increases, so that the coating layer has both high conductivity and low chemical inertness to the electrolyte.

[0087] In some embodiments, based on the mass of the matrix material being 100%, the mass content of the coating layer is 0.01% - 0.5%, specifically, it can be 0.01%, 0.05%, 0.08%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.4% or 0.5%, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0088] In some embodiments, the median particle size D50 of the positive electrode material is 2 μm - 20 μm, specifically, it can be 2 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 18 μm or 20 μm, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0089] In some embodiments, the specific surface area of the positive electrode material is 0.3 m 2 / g - 3 m 2 / g, specifically, it can be 0.3 m 2 / g, 0.5 m 2 / g, 0.7 m 2 / g, 0.9 m 2 / g, 1 m 2 / g, 1.5 m 2 / g, 1.7 m 2 / g, 1.9 m 2 / g, 2 m2 / g, 2.5 m 2 / g, 2.7 m 2 / g, 2.9 m 2 / g or 3 m 2 / g, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0090] In some embodiments, the conductivity of the positive electrode material is 10 -1 S / cm to 10 2 S / cm, specifically it can be 10 - 1 S / cm, 1 S / cm, 5 S / cm, 10 S / cm, 20 S / cm, 50 S / cm or 10 2 S / cm, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0091] In a second aspect, the present application provides a method for preparing a positive electrode material, as Figure 1 shown, the method for preparing the positive electrode material includes the following steps:

[0092] S100: Magnetron sputtering treatment is carried out on the substrate material by using a target doped with metal ions to obtain the positive electrode material; wherein, the target includes tungsten oxide WO doped with metal ions 3-a ; wherein, 0 < a < 0.5, and the doping concentration of the metal ions gradually decreases from the surface to the inside of the target.

[0093] The method for preparing the positive electrode material provided by the present application uses a target doped with metal ions to carry out magnetron sputtering treatment on the substrate material. The doping metal ion concentration in the target increases in gradient. After the sputtering treatment, a coating layer with a decreasing doping metal ion concentration can be formed on the surface of the substrate material. The preparation method is simple and controllable. The obtained coating layer can improve the electronic conductivity and ionic conductivity of the coating layer, and enhance the rate performance and safety performance of the positive electrode material. And this preparation method is simple and controllable, which can reduce the production cost.

[0094] The following specifically introduces the preparation method of the present application in combination with examples:

[0095] Before S100, the method further includes:

[0096] A hydrothermal reaction and filtration are carried out on a mixed solution containing WCl6, an inorganic salt of a metal ion and a solvent, and the obtained product is washed and dried to obtain tungsten oxide WO doped with metal ions 3-a ; wherein, 0 < a < 0.5.

[0097] In some embodiments, the metal ions include at least one of Mg, Ca, Ti, Cr, Mn, Fe, Zn, and V metal ions; preferably two of them.

[0098] In some embodiments, the inorganic salt can be at least one of sulfates, hydrochlorides, nitrates, and phosphates.

[0099] In some embodiments, the solvent includes at least one of ethanol, propanol, acetone, and methanol.

[0100] In some embodiments, the mass ratio of WCl6 to the inorganic salt of the metal ions is 1:(0.001 - 0.1), specifically it can be 1:0.001, 1:0.005, 1:0.01, 1:0.03, 1:0.05, 1:0.08, 1:0.09, or 1:0.1, etc., which is not limited herein.

[0101] In some embodiments, the metal ions include Zn and V, the mass ratio of WCl6 to VCl3 is 1:(0.003 - 0.04), and the mass ratio of WCl6 to ZnCl2 is 1:(0.003 - 0.07).

[0102] In some embodiments, the mass concentration of WCl6 in the mixed solution is 1 mg / ml - 50 mg / ml, specifically it can be 1 mg / ml, 5 mg / ml, 8 mg / ml, 10 mg / ml, 20 mg / ml, 30 mg / ml, 40 mg / ml, or 50 mg / ml, etc., which is not limited herein.

[0103] In some embodiments, the hydrothermal reaction of the mixed solution is carried out under stirring, and the stirring rate is controlled to be 30 r / min - 200 r / min, specifically it can be 30 r / min, 50 r / min, 60 r / min, 80 r / min, 100 r / min, 120 r / min, 150 r / min, or 200 r / min, etc., which is not limited herein.

[0104] In some embodiments, the temperature of the hydrothermal reaction is 140°C - 200°C, specifically it can be 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, or 200°C. Of course, it can also be other values within the above range, which is not limited herein. It can be understood that the hydrothermal reaction can achieve hydrothermal crystallization. At high temperatures, the solubility of salts in the mixed solution is high, and then by cooling, the solubility decreases, and recrystallization can be achieved.

[0105] In some embodiments, the hydrothermal reaction time is 10 h to 20 h, specifically it can be 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h or 20 h, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0106] In some embodiments, the filtration method includes at least one of centrifugal filtration, vacuum filtration, and negative pressure suction filtration.

[0107] In some embodiments, the steps of washing the product include ultrasonic washing with water for 10 min to 15 min, ultrasonic washing with ethanol for 10 min to 15 min, and ultrasonic washing with acetone for 10 min to 15 min. The reaction product can be purified by washing.

[0108] In some embodiments, the drying temperature is 60 °C to 100 °C, specifically it can be 60 °C, 70 °C, 80 °C, 90 °C or 100 °C. Of course, it can also be other values within the above range, which are not limited herein.

[0109] In some embodiments, the drying time is 20 min to 100 min; specifically it can be 20 min, 40 min, 50 min, 60 min, 80 min or 100 min, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0110] It can be understood that tungsten oxide doped with metal ions WO 3-a is obtained after drying; wherein, 0 < a < 0.5, and the doping concentration of metal ions can be adjusted by adjusting the mass ratio of WCl6 to the inorganic salt of the metal ion according to requirements.

[0111] In some embodiments, the value of a can be 0.1, 0.2, 0.24, 0.28, 0.34, 0.375, 0.4, etc. Of course, it can also be other values within the above range, which are not limited herein. WO 3-a is a typical ReO3-type peroxide structure, and its polycrystal has a narrow band gap of about 2.5 - 2.8 eV and has a higher carrier density. WO 3-a 's structural diversity and its crystal phase transition are beneficial to the transport of small ions and charges, and it has high chemical stability. Since WO 3-a has less oxygen content compared to traditional WO3, its lattice network changes from an octahedral structure to an open structure composed of triangular, quadrilateral, pentagonal, and hexagonal tunnels. The formation of this open structure can effectively increase the Li + transport speed.

[0112] In some embodiments, the tungsten oxide includes W 32 O84 , W3O8, W 18 O 49 , W 17 O 47 , W5O 14 , W 20 O 58 and W 25 O 73 and at least one of WO 18 O 49 , W 18 O 49 has a carrier density as high as 1.87×10 22 cm -3 and has higher conductivity compared to other subtypes of tungsten oxide.

[0113] In some embodiments, the target has a multi-layer structure from the inside to the outside, and the doping concentration of metal ions between any two adjacent layers increases by 2.5% ± 0.5%. That is, from the inside to the outside of the target, the doping concentration gradient of metal ions increases. During the preparation process, tungsten oxide WO 3-a with different doping concentrations can be prepared in batches, and then these metal powders are gradually laminated and molded to form a metal ingot (i.e., the target).

[0114] In some embodiments, tungsten oxide WO 3-a with different doping concentrations can also be magnetron sputtered in batches until the desired coating layer is obtained.

[0115] In some embodiments, as the depth of the target increases by 5 nm to 75 nm, the doping concentration of metal ions increases by 2.5% ± 0.5%.

[0116] In some embodiments, along the direction from the inside to the surface of the target, the doping concentration difference of metal ions between the outermost layer and the innermost layer of the target is 10% to 15%; it should be noted that the outermost layer of the target is a target with a high doping concentration, which is first sputtered onto the surface of the substrate material, while the innermost layer of the target is a target with a low doping concentration or an undoped target, which is finally sputtered onto the surface of the substrate material and is in the outermost region of the coating layer.

[0117] In some embodiments, the target includes four layers from the inside to the outside. The doping concentration of metal ions in the first layer is 0%, the doping concentration of metal ions in the second layer is 2.5% ± 0.5%, the doping concentration of metal ions in the third layer is 7.5% ± 0.5%, and the doping concentration of metal ions in the fourth layer is 10% ± 0.5%. That is, the doping concentration difference of metal ions between the fourth layer and the first layer is 10% ± 0.5%.

[0118] In some embodiments, along the direction from the inside to the surface of the target, the doping concentration of metal ions in the outermost layer of the target is 15% ± 5%.

[0119] In some embodiments, along the direction from the inside to the surface of the target, the innermost layer of the target is tungsten oxide WO 3-a ; where 0 < a < 0.5.

[0120] S100: Magnetron sputtering treatment is performed on the substrate material using a target doped with metal ions to obtain a cathode material; where the target includes tungsten oxide WO doped with metal ions 3-a ; where 0 < a < 0.5, and the doping concentration of the metal ions gradually decreases from the surface to the inside of the target.

[0121] In some embodiments, the chemical general formula of the substrate material is LiNi x Co y M z O2, where 0.8 ≤ x < 1, 0 < y ≤ 0.12, 0 < z ≤ 0.08, x + y + z = 1, and the M element includes at least one of Al, Mn, Ba, Ca, Mg, Sr, Zr, Ti, La, W, Nb, Y, Gd, and Ta.

[0122] In some embodiments, the value of x can be 0.8, 0.85, 0.9, 0.95, 0.96, 0.97, 0.98, or 0.99, etc., the value of y can be 0.01, 0.05, 0.07, 0.09, 0.1, 0.15, 0.17, 0.19, or 0.2, etc., and the value of z can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, or 0.08, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0123] In some embodiments, the median particle size of the substrate material is 3 μm to 15 μm, specifically it can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm. Of course, it can also be other values within the above range, which are not limited herein.

[0124] In some embodiments, the substrate material is a lithium transition metal composite oxide, specifically it can be a high-nickel ternary material, a lithium-rich material, etc.

[0125] In some embodiments, the crystal structure of the substrate material belongs to the hexagonal crystal system.

[0126] In some embodiments, the substrate material can be prepared by sintering a lithium source, a nickel source, and a cobalt source, or a ready-made substrate material can be purchased, and no limitation is made here.

[0127] In some embodiments, the environmental vacuum degree during the magnetron sputtering treatment is < 3.0×10 -4 Pa, specifically it can be 2.9×10 -4 Pa, 2.5×10 -4 Pa, 2.0×10 -4 Pa, 1.0×10 -4 Pa, 0.5×10 -4 Pa or 1×10 -5 Pa, etc. Of course, it can also be other values within the above range, and no limitation is made here.

[0128] In some embodiments, the environmental temperature during the magnetron sputtering treatment is 300°C to 400°C; specifically it can be 300°C, 320°C, 350°C, 380°C or 400°C. Of course, it can also be other values within the above range, and no limitation is made here.

[0129] In some embodiments, the sputtering power during the magnetron sputtering treatment is 80W to 120W, specifically it can be 80W, 90W, 100W, 110W or 120W, etc. Of course, it can also be other values within the above range, and no limitation is made here.

[0130] In some embodiments, the sputtering power density of the target during the magnetron sputtering treatment is 2.0W / cm 2 ~5.0W / cm 2 Specifically it can be 2.0W / cm 2 、3.0W / cm 2 、4.0W / cm 2 、4.5W / cm 2 or 5.0W / cm 2 etc. Of course, it can also be other values within the above range, and no limitation is made here.

[0131] In some embodiments, the sputtering pressure during the magnetron sputtering treatment is 0.2Pa to 1.0Pa, specifically it can be 0.2Pa, 0.4Pa, 0.5Pa, 0.6Pa, 0.7Pa, 0.8Pa or 1.0Pa, etc. Of course, it can also be other values within the above range, and no limitation is made here.

[0132] In some embodiments, the sputtering time of the magnetron sputtering treatment is 15 to 80 minutes, specifically, it can be 15 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes or 80 minutes, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0133] In some embodiments, the magnetron sputtering treatment is carried out in a protective atmosphere, and the protective atmosphere includes at least one of nitrogen, helium, neon, and argon.

[0134] In some embodiments, the preparation method further includes sieving the product after magnetron sputtering;

[0135] In a third aspect, the present application provides a lithium-ion battery, and the lithium-ion battery includes the above positive electrode material or the positive electrode material prepared by the above preparation method.

[0136] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the scope of protection of the present invention.

[0137] Example 1

[0138] (1) Weigh 60 mg of WCl6, 1.2 mg of VCl3, and 2.1 mg of ZnCl2 and add them to 30 ml of ethanol. Stir at a speed of 100 r / min to obtain a transparent mixed solution. After transferring the mixed solution to a 50 ml Teflon reaction kettle, place it in an oven at 180 °C for 16 h. After the reaction is completed, let it cool naturally, centrifuge to obtain a blue powder, wash it three times with water, ethanol, and acetone respectively, and then place it in a vacuum oven at 60 °C to dry, to obtain vanadium- and zinc-codoped W 18 O 49 powder.

[0139] (2) According to the preparation method of step (1), adjust the dosages of the doping raw materials VCl3 and ZnCl2 to obtain four kinds of W 18 O 49 powders with different doping concentrations, namely undoped W 18 O 49 powder, vanadium (2.5%)- and zinc (2.5%)-codoped W 18 O 49 powder, vanadium (5%)- and zinc (5%)-codoped W 18 O 49 powder, vanadium (10%)- and zinc (10%)-codoped W 18 O 49 powder.

[0140] (3) For W powders with different doping concentrations 18 O49 Made into a target, the ternary cathode material lithium nickel cobalt manganese oxide (NCM811) is placed on a vibrating sample stage, and the vacuum is pumped to < 3.0×10 -4 Pa, the temperature is set at 350 °C, the power density is 4 W / cm 2 , 30 sccm of argon is introduced, and it is operated at a sputtering pressure of 0.8 Pa for 40 min to obtain the modified cathode material.

[0141] The cathode material prepared in this example includes a matrix material (NCM811) and a coating layer on the surface of the matrix material. The coating layer includes tungsten oxide WO doped with vanadium and zinc 2.7 (i.e., W 18 O 49 ); in the coating layer, the doping concentration of the metal ions gradually decreases from the surface of the matrix material to the surface of the cathode material.

[0142] Figure 2 This is the X-ray diffraction pattern of the WO 18 O 49 prepared in this example. As shown Figure 2 , the XRD of this example corresponds to the standard card PDF#71-2450, indicating that WO 18 O 49 is successfully prepared; Figure 3 This is the SEM image of the cross-section of the cathode material prepared in this example. It can be seen from the figure that there is an obvious coating layer on the surface of the cathode material, proving that the vanadium and zinc co-doped WO 18 O 49 material is coated on the surface of the matrix material; Figure 4 This is the EDS of the cross-section of the cathode material. It can be obtained from the figure that the W element in the coating layer is evenly distributed, and the content of the V element gradually decreases towards the outer layer. The doping concentration difference of the metal ions between the outermost region and the innermost region of the coating layer is 10%.

[0143] Example 2

[0144] (1) Weigh 60 mg of WCl6, 0.3 mg of VCl3, and 0.5 mg of ZnCl2 and add them to 30 ml of ethanol. Stir at a rotation speed of 100 r / min to obtain a transparent mixed solution. After transferring the mixed solution to a 50 ml Teflon reaction kettle, place it in an oven at 180 °C for 16 h. After the reaction is completed, let it cool naturally, centrifuge to obtain a blue powder, wash it three times with water, ethanol, and acetone respectively, and then place it in a vacuum oven at 60 °C to dry, to obtain vanadium and zinc co-doped WO 18 O 49 powder;

[0145] (2) According to the preparation method in step (1), adjust the dosages of the doping raw materials VCl3 and ZnCl2 to obtain four different doping concentrations of W18 O 49 powders, namely undoped WO 18 O 49 powders, WO 18 O 49 powders co-doped with 5% vanadium and 5% zinc, WO 18 O 49 powders co-doped with 7.5% vanadium and 7.5% zinc, WO 18 O 49 powders.

[0146] (3) Prepare target materials from WO 18 O 49 with different doping concentrations. Place the ternary cathode material (NCM811) on a vibrating sample stage, evacuate to a pressure less than 3.0×10-4 Pa, set the temperature at 350 °C, and the power density at 4 W / cm 2 . Introduce 30 sccm of argon gas and operate at a sputtering pressure of 0.8 Pa for 40 min to obtain the modified cathode material.

[0147] The cathode material prepared in this example includes a matrix material (NCM811) and a coating layer on the surface of the matrix material. The coating layer includes tungsten oxide WO doped with vanadium and zinc 2.7 (i.e., WO 18 O 49 ); in the coating layer, the doping concentration of the metal ions gradually decreases from the surface of the matrix material to the surface of the cathode material. The difference in the doping concentration of the metal ions between the outermost region and the innermost region of the coating layer is 10%.

[0148] Example 3

[0149] The difference from Example 1 is:

[0150] (1) Weigh 60 mg of WCl6, 0.3 mg of VCl3, and 0.5 mg of MgCl2 and add them to 30 ml of ethanol. Stir at a speed of 100 r / min to obtain a transparent mixed solution. Transfer the mixed solution to a 50 ml Teflon reaction kettle and place it in an oven at 180 °C for 16 h. After the reaction is completed, let it cool naturally, centrifuge to obtain blue powders, wash them three times with water, ethanol, and acetone respectively, and then dry them in a vacuum oven at 60 °C to obtain WO 18 O 49 powders co-doped with vanadium and magnesium.

[0151] The cathode material prepared in this example includes a matrix material (NCM811) and a coating layer on the surface of the matrix material. The coating layer includes tungsten oxide WO doped with vanadium and magnesium 2.7 (i.e., WO 18 O49 ); In the coating layer, the doping concentration of the metal ions gradually decreases from the surface of the matrix material to the surface of the positive electrode material. The difference in the doping concentration of the metal ions between the outermost region and the innermost region of the coating layer is 10%.

[0152] Example 4

[0153] Differing from Example 1:

[0154] (1) Weigh 60 mg of WCl6 and 1.2 mg of VCl3 and add them to 30 ml of ethanol. Stir at a speed of 100 r / min to obtain a transparent mixed solution. After transferring the mixed solution to a 50 ml Teflon reaction kettle, place it in an oven at 180 °C and react for 16 h. After the reaction is completed, let it cool naturally, centrifuge to obtain a blue powder, wash it three times with water, ethanol, and acetone respectively, and then place it in a vacuum oven at 60 °C to dry, obtaining vanadium-doped W 18 O 49 powder.

[0155] The positive electrode material prepared in this example includes a matrix material (NCM811) and a coating layer located on the surface of the matrix material. The coating layer includes tungsten oxide doped with vanadium, WO 2.7 (i.e., W 18 O 49 ); In the coating layer, the doping concentration of the metal ions gradually decreases from the surface of the matrix material to the surface of the positive electrode material. The difference in the doping concentration of the metal ions between the outermost region and the innermost region of the coating layer is 10%.

[0156] Example 5

[0157] Differing from Example 1:

[0158] (1) Weigh 60 mg of WCl6, 1.2 mg of AlCl3, and 2.1 mg of YCl2 and add them to 30 ml of ethanol. Stir at a speed of 100 r / min to obtain a transparent mixed solution. After transferring the mixed solution to a 50 ml Teflon reaction kettle, place it in an oven at 180 °C and react for 16 h. After the reaction is completed, let it cool naturally, centrifuge to obtain a blue powder, wash it three times with water, ethanol, and acetone respectively, and then place it in a vacuum oven at 60 °C to dry, obtaining aluminum- and yttrium-codoped W 18 O 49 powder.

[0159] The positive electrode material prepared in this example includes a matrix material (NCM811) and a coating layer located on the surface of the matrix material. The coating layer includes tungsten oxide doped with aluminum and yttrium, WO 2.7 (i.e., W 18 O 49); In the coating layer, the doping concentration of the metal ions gradually decreases from the surface of the matrix material to the surface of the cathode material. The difference in the doping concentration of the metal ions between the outermost region and the innermost region of the coating layer is 10%.

[0160] Example 6

[0161] Different from Example 1:

[0162] (2) According to the preparation method in step (1), adjust the dosages of the doping raw materials VCl3 and ZnCl2 to obtain four W powders with different doping concentrations 18 O 49 powders, namely undoped W 18 O 49 powder, W 18 O 49 powder co-doped with vanadium (5%) and zinc (5%), W 18 O 49 powder co-doped with vanadium (10%) and zinc (10%), W 18 O 49 powder co-doped with vanadium (15%) and zinc (15%).

[0163] The cathode material prepared in this example includes a matrix material (NCM811) and a coating layer located on the surface of the matrix material. The coating layer includes tungsten oxide WO 2.7 (i.e., W 18 O 49 ); In the coating layer, the doping concentration of the metal ions gradually decreases from the surface of the matrix material to the surface of the cathode material. The difference in the doping concentration of the metal ions between the outermost region and the innermost region of the coating layer is 15%.

[0164] Example 7

[0165] (2) According to the preparation method in step (1), adjust the dosages of the doping raw materials VCl3 and ZnCl2 to obtain three W powders with different doping concentrations 18 O 49 powders, namely undoped W 18 O 49 powder, W 18 O 49 powder co-doped with vanadium (2.5%) and zinc (2.5%), W 18 O 49 powder co-doped with vanadium (10%) and zinc (10%).

[0166] The cathode material prepared in this example includes a matrix material (NCM811) and a coating layer located on the surface of the matrix material. The coating layer includes tungsten oxide WO 2.7(i.e., W 18 O 49 ); In the coating layer, the doping concentration of the metal ions gradually decreases from the surface of the matrix material to the surface of the cathode material. The difference in the doping concentration of the metal ions between the outermost region and the innermost region of the coating layer is 10%.

[0167] Example 8

[0168] (2) According to the preparation method in step (1), adjust the dosages of the doping raw materials VCl3 and ZnCl2 to obtain two kinds of W 18 O 49 powders with different doping concentrations, namely undoped W 18 O 49 powder, W 18 O 49 powder co-doped with vanadium (10%) and zinc (10%), and W 18 O 49 powder co-doped with vanadium (10%) and zinc (10%).

[0169] The cathode material prepared in this example includes a matrix material (NCM811) and a coating layer located on the surface of the matrix material. The coating layer includes tungsten oxide WO doped with vanadium and zinc 2.7 (i.e., W 18 O 49 ); In the coating layer, the doping concentration of the metal ions gradually decreases from the surface of the matrix material to the surface of the cathode material. The difference in the doping concentration of the metal ions between the outermost region and the innermost region of the coating layer is 10%.

[0170] Example 9

[0171] The difference from Example 1 is that

[0172] the matrix material is lithium nickel cobalt manganese oxide NCM523.

[0173] The cathode material prepared in this example includes a matrix material (NCM523) and a coating layer located on the surface of the matrix material. The coating layer includes tungsten oxide WO doped with vanadium and zinc 2.7 (i.e., W 18 O 49 ); In the coating layer, the doping concentration of the metal ions gradually decreases from the surface of the matrix material to the surface of the cathode material. The difference in the doping concentration of the metal ions between the outermost region and the innermost region of the coating layer is 10%.

[0174] Example 10

[0175] The difference from Example 1 is that the magnetron sputtering time is increased to 60 min.

[0176] The positive electrode material prepared in this embodiment includes a matrix material (NCM523) and a coating layer located on the surface of the matrix material. The coating layer includes tungsten oxide WO doped with vanadium and zinc 2.7 (i.e., W 18 O 49 ); in the coating layer, the doping concentration of the metal ions gradually decreases from the surface of the matrix material to the surface of the positive electrode material. The thickness of the coating layer is 64 nm, and the difference in the doping concentration of the metal ions between the outermost region and the innermost region of the coating layer is 10%.

[0177] Comparative Example 1

[0178] (1) Weigh 0.3 g of Na2WO4·2H2O and 0.15 g of Na2SO4 and add them to a beaker with 21 mL of water. Stir at a speed of 100 r / min to obtain a transparent mixed solution. Continue stirring and add 3 mol / L hydrochloric acid to adjust the pH of the solution to 2.0. After transferring the mixed solution to a 50 ml Teflon reactor, place it in an oven at 180 °C and react for 16 h. After the reaction is completed, cool it naturally, centrifuge to obtain a white powder, wash it three times with water, ethanol, and acetone respectively, and then place it in a vacuum oven at 60 °C to dry, obtaining WO3 powder;

[0179] (2) Fabricate WO3 into a target. Place the ternary positive electrode material (NCM811) on a vibrating sample stage, evacuate to <3.0×10-4 Pa, set the temperature at 350 °C, the power density at 4 W / cm 2 , introduce 30 sccm of argon gas, and operate at a sputtering pressure of 0.8 Pa for 40 min to obtain the modified positive electrode material.

[0180] Comparative Example 2

[0181] (1) Weigh 60 mg of WCl6 and add it to 30 ml of ethanol. Stir at a speed of 100 r / min to obtain a transparent mixed solution. After transferring the mixed solution to a 50 ml Teflon reactor, place it in an oven at 180 °C and react for 16 h. After the reaction is completed, cool it naturally, centrifuge to obtain a blue powder, wash it three times with water, ethanol, and acetone respectively, and then place it in a vacuum oven at 60 °C to dry, obtaining W 18 O 49 powder;

[0182] (2) Fabricate (W18O49 into a target. Place the ternary positive electrode material (NCM811) on a vibrating sample stage, evacuate to <3.0×10-4 Pa, set the temperature at 350 °C, the power density at 4 W / cm 2 , introduce 30 sccm of argon gas, and operate at a sputtering pressure of 0.8 Pa for 40 min to obtain the modified positive electrode material.

[0183] Testing methods:

[0184] (1) Testing method for the particle size of the cathode material:

[0185] The particle size distribution range of the cathode material is tested by a Malvern laser particle size analyzer.

[0186] (2) Testing method for the specific surface area of the cathode material:

[0187] It is tested by the JW-DX dynamic specific surface area rapid determination instrument of Beijing Jingwei Gaobo Science and Technology Co., Ltd., and the unit is m 2 / g.

[0188] (3) Testing method for the SEM of the cathode material:

[0189] The scanning electron microscope characterization is carried out on a transmission electron microscope, the operating voltage is 200 kV, and the structure of the cathode material is observed.

[0190] (4) Testing method for the coating layer thickness:

[0191] Ten randomly sampled cathode material particles are sectioned by a FIB-TEM device, and the average thickness (D0) of the coating layer is measured from 10 samples, and the average thickness is taken as the thickness of the coating layer.

[0192] (5) Testing the mass content of the coating layer

[0193] The content of the coating elements in the cathode material is tested by ICP-OES.

[0194] (6) Testing the conductivity of the cathode material:

[0195] The conductivity of the high-nickel cathode material is tested by a conductivity meter.

[0196] (7) Electrochemical performance testing

[0197] The cathode materials obtained in Examples 1 to 10 and Comparative Examples 1 to 2 are assembled into coin cells: the cathode material, conductive carbon and polyvinylidene fluoride are added to N-methyl-2-pyrrolidone (NMP) in a mass ratio of 96:2:2, and uniformly mixed to make a cathode slurry, which is coated on the cathode current collector and vacuum dried to form a cathode electrode sheet (the compaction density of the electrode sheet is: 2.8 g / cm 3 ), using a lithium sheet as the anode, a separator as Celgard C2400, and an electrolyte as a 1.3 mol / L LiPF6 electrolyte (where the solvent is EC, PC and DEC with a volume ratio of 3:1:6), and assembled into a 2016 coin cell in a glove box.

[0198] In the discharge range of 3.0V - 4.3V, under the condition of a theoretical capacity of 250 mAh / g at 1C, the test was carried out using the CT2001A battery testing system of Wuhan Blue Electronic Co., Ltd. The test results are shown in Table 1.

[0199] Table 1 Electrochemical properties of the materials in the comparative examples and examples

[0200]

[0201]

[0202] Comparing Examples 1 - 10 in Table 1, it can be seen that the coating layer includes tungsten oxide WO doped with metal ions 3-a ; sub-stoichiometric WO 3-a has a higher carrier density, and its electronic conductivity also increases accordingly. WO 3-a has a wider Li+ ion channel and higher conductivity. Coated on the surface of the matrix material, it can effectively improve the rate performance of the battery; the surface of the positive electrode material of the present application has a coating layer with a decreasing doping ion concentration gradient, which can improve the electronic conductivity and ion conductivity of the coating layer, and enhance the rate performance and safety performance of the positive electrode material.

[0203] Compared with Example 1, the conductivity of the positive electrode material in Comparative Example 1 decreases, and the rate performance and capacity performance of the battery also decrease significantly. According to Figure 5 It can be seen that the charge-discharge curve of Example 1 is slightly improved compared with that of Example 2, and is significantly improved compared with the charge-discharge curves of Comparative Example 1 or Comparative Example 2.

[0204] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A cathode material, characterized in that, The positive electrode material includes: A matrix material, which is a lithium transition metal composite oxide; A coating layer located on the surface of the matrix material, the coating layer comprising tungsten oxide WO doped with metal ions 3-a ; wherein, 0 < a < 0.5, and the metal ions include at least one of Mg, Ca, Ti, Cr, Mn, Fe, Zn, and V metal ions; In the coating layer, the doping concentration of the metal ions gradually decreases from the surface of the matrix material to the surface of the positive electrode material.

2. The cathode material according to claim 1, characterized in that, The positive electrode material includes at least one of the following characteristics (1) to (5): (1) Along the direction from the inside to the surface of the positive electrode material, the doping concentration difference of the metal ions between the outermost region and the innermost region of the coating layer is 10% - 15%; (2)In the direction from the inside to the surface of the positive electrode material, the outermost region of the coating layer is W 18 O 49 ; (3) Along the direction from the inside to the surface of the positive electrode material, the doping concentration of the metal ions in the innermost region of the coating layer is 15% ± 3%; (4)The tungsten oxide includes W 32 O 84 , W3O8, W 18 O 49 , W 17 O 47 , W5O 14 , W 20 O 58 and W 25 O 73 and at least one of them; (5) The metal ions include at least two of Mg, Ca, Ti, Cr, Mn, Fe, Zn, and V metal ions.

3. The cathode material according to any one of claims 1 to 2, characterized in that, The positive electrode material includes at least one of the following characteristics (1) to (3): (1) The chemical general formula of the matrix material is LiNi x Co y M z O2, where 0.8 ≤ x < 1, 0 < y ≤ 0.12, 0 < z ≤ 0.08, x + y + z = 1, and the M element includes at least one of Al, Mn, Ba, Ca, Mg, Sr, Zr, Ti, La, W, Nb, Y, Gd, and Ta; (2) The thickness of the coating layer is 5nm - 300nm; (3) Based on the mass of the matrix material being 100%, the mass content of the coating layer is 0.01% - 0.5%.

4. The cathode material according to claim 3, characterized in that, The positive electrode material includes at least one of the following characteristics (1) to (3): (1) The median particle size D of the positive electrode material 50 is 2 μm to 20 μm; (2) The specific surface area of the positive electrode material is 0.3 m 2 / g to 3 m 2 / g; (3) The conductivity of the positive electrode material is 10 -1 S / cm to 10 2 S / cm.

5. A method for preparing a cathode material, characterized in that, It includes the following preparation steps: The matrix material is subjected to magnetron sputtering treatment using a target doped with metal ions to obtain a positive electrode material; wherein, the target includes tungsten oxide WO doped with metal ions 3-a ; wherein, 0 < a < 0.5, and the doping concentration of the metal ions gradually decreases from the surface to the interior of the target; the matrix material is a lithium transition metal composite oxide; the metal ions include at least one of Mg, Ca, Ti, Cr, Mn, Fe, Zn, and V metal ions.

6. The preparation method according to claim 5, characterized in that The method includes at least one of the following characteristics (1) to (3): (1) The chemical general formula of the matrix material is LiNi x Co y M z O2, where 0.8 ≤ x < 1, 0 < y ≤ 0.12, 0 < z ≤ 0.08, x + y + z = 1, and the M element includes at least one of Al, Mn, Ba, Ca, Mg, Sr, Zr, Ti, La, W, Nb, Y, Gd, and Ta; (2)The tungsten oxide includes W 32 O 84 , W3O8, W 18 O 49 , W 17 O 47 , W5O 14 , W 20 O 58 , and W 25 O 73 and at least one of them; (3) The metal ions include at least two of Mg, Ca, Ti, Cr, Mn, Fe, Zn, and V metal ions.

7. The preparation method according to claim 5, characterized in that, The method includes at least one of the following characteristics (1) to (13): (1) Along the direction from the inside to the surface of the target, the doping concentration difference of the metal ions between the outermost layer and the innermost layer of the target is 10% - 15%; (2) Along the direction from the inside to the surface of the target, the doping concentration of the metal ions in the outermost layer of the target is 15% ± 5%; (3) Along the direction from the inside to the surface of the target, the innermost layer of the target is tungsten oxide WO 3-a ; where 0 < a < 0.5; (4) As the depth of the target increases by 5nm - 75nm each time, the doping concentration of the metal ions increases by 2.5% ± 0.5%; (5) The target has a multi-layer structure from the inside to the outside, and the doping concentration of the metal ions increases by 2.5% ± 0.5% between any two adjacent layers; (6) The target includes four layers from the inside to the outside. The doping concentration of the metal ions in the first layer is 0%, the doping concentration of the metal ions in the second layer is 2.5% ± 0.5%, the doping concentration of the metal ions in the third layer is 7.5% ± 0.5%, and the doping concentration of the metal ions in the fourth layer is 10% ± 0.5%; (7) The environmental vacuum degree during the magnetron sputtering treatment < 3.0×10 -4 Pa; (8) The ambient temperature during the magnetron sputtering treatment is 300°C - 400°C; (9) The sputtering power during the magnetron sputtering treatment is 80 W - 120W; (10) During the magnetron sputtering treatment, the sputtering power density of the target is 2.0 to 5.0 W / cm 2 ; (11) The sputtering pressure during the magnetron sputtering treatment is 0.2 - 1.0Pa; (12) The sputtering time of the magnetron sputtering treatment is 15 - 80min; (13) The magnetron sputtering treatment is carried out in a protective atmosphere.

8. The preparation method according to claim 6, characterized in that, Before the magnetron sputtering treatment of the matrix material with the target doped with metal ions, the method further includes: A hydrothermal reaction and filtration are carried out on a mixed solution containing WCl6, an inorganic salt of a metal ion, and a solvent, and the obtained product is washed and dried to obtain tungsten oxide WO doped with metal ions 3-a ; wherein, 0 < a < 0.

5.

9. The preparation method according to claim 8, wherein The method includes at least one of the following characteristics (1) to (6): (1) The temperature of the hydrothermal reaction is 140°C - 200°C; (2) The time of the hydrothermal reaction is 10h - 20h; (3) The steps for washing the product include ultrasonic washing with water for 10 min to 15 min, ultrasonic washing with ethanol for 10 min to 15 min, and ultrasonic washing with acetone for 10 min to 15 min; (4) The temperature for drying is 60 °C to 100 °C; (5) The time for drying is 20 min to 100 min; (6) The mass ratio of WCl6 to the inorganic salt of the metal ion is 1:(0.001 to 0.1).

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode material described in claims 1 to 4 or the positive electrode material prepared by the preparation method described in claims 5 to 9.

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