Cathode materials and their preparation methods, lithium-ion batteries

Abstract

This application relates to a cathode material and its preparation method, and a lithium-ion battery. The cathode material includes a substrate and a coating layer covering at least a portion of the surface of the substrate. The general chemical formula of the substrate is shown in formula (I): Li a Ni x Co y M 1‑x‑y In formula (I) of O2(I), M includes at least one of Mn and Al, 0.95≤a<1.05, 0.8≤x<0.95, 0.05≤y≤0.2; the coating material includes oxides, and the metal element in the oxide includes at least one of W, Al, Co, Zr, Y and Ti; in the XRD pattern of the cathode material, the intensity ratio of the diffraction peaks between the (001) plane and the (101) plane is I 001 / Ⅰ 101 ≤1.10; diffraction peak intensity ratio between (003) plane and (104) plane I 003 / Ⅰ 104 ≥1.70.

Description

Technical Field

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

[0002] In recent years, with the increasing demand for new energy vehicles and the booming development of the domestic and international new energy power battery market, consumers' requirements for the driving range of electric vehicles have been continuously increasing. Layered LiNi, with its characteristics of high discharge capacity, good cycle life, and low cost, has become increasingly popular. 1-x-y Co x MyO2 ternary cathode materials have emerged. Cathode materials (Ni≥80%), such as LiNi 0.8 Co 0.1 Mn 0.1 O2 and LiNi 0.8 Co 0.15 Al 0.05 O2 is suitable as a cathode material for high-energy-density power batteries due to its high reversible specific capacity (>200mAh / g) and good cycle stability.

[0003] Although ternary cathode materials have a significant advantage in energy density compared to other cathode materials, their poor cycle performance and rate capability hinder their large-scale application in the power battery field. Current research suggests that the instability of the surface crystal structure is a major cause of rapid capacity decay, and crystal defects are a significant contributing factor to this instability. On one hand, ternary materials are currently mostly prepared using a co-precipitation method. The intense stirring during the precursor synthesis process leads to disordered particle distribution, leaving numerous crystal defects (especially on the particle surface) during subsequent sintering, including grain boundaries and micropores. On the other hand, the Ni element inside the ternary cathode material particles mainly exists in the +3 form, while on the surface it exists as Ni. 2+ Mainly. A relatively high amount of Ni. 2+ This can cause numerous crystal defects in the surface structure of the material, including severe cation mixing, inactive NiO impurities, and spinel phases. Crystal defects not only hinder the rapid insertion and extraction of lithium ions but also increase battery polarization and reduce electrochemical activity.

[0004] Therefore, in order to promote the widespread use of ternary materials in power batteries, there is an urgent need for a cathode material that can improve cycle performance and rate performance. Summary of the Invention

[0005] The purpose of this invention is to provide a cathode material and its preparation method, as well as a lithium-ion battery. The cathode material has a stable surface crystal structure, which gives it excellent capacity, cycle performance, and rate performance.

[0006] In a first aspect, embodiments of this application provide a positive electrode material, the positive electrode material comprising a substrate and a coating layer covering at least a portion of the surface of the substrate, wherein the general chemical formula of the substrate is shown in formula (Ⅰ):

[0007] Li a Ni x Co y M 1-x-y O2 (Ⅰ)

[0008] In formula (Ⅰ), M includes at least one of Mn and Al, 0.95≤a<1.05, 0.8≤x<0.95, and 0.05≤y≤0.2;

[0009] The coating layer is made of an oxide, and the metal element in the oxide includes at least one of W, Al, Co, Zr, Y and Ti;

[0010] In the XRD pattern of the cathode material, the intensity ratio of the diffraction peaks between the (001) plane and the (101) plane is I. 001 / Ⅰ 101 ≤1.10; diffraction peak intensity ratio between (003) plane and (104) plane I 003 / Ⅰ 104 ≥1.70;

[0011] The nucleation rate k of the cathode material is ≥90%, wherein:

[0012]

[0013] In equation (II), H β(300) H represents the characteristic diffraction peak intensity of the β-crystal (300) crystal plane of the cathode material in the XRD pattern. α(110) , H α(040) and H α(130) The intensity of the characteristic diffraction peaks corresponding to the α crystal planes (110), (040) and (130) of the cathode material in the XRD pattern are respectively.

[0014] In some embodiments, the material includes at least one of the following characteristics (1) to (3):

[0015] (1) The oxide includes at least one of WO3, WO2, Al2O3, CoO, Co2O4, B2O3, ZrO2, Y2O3 and TiO2;

[0016] (2) The thickness of the coating layer is 4 nm to 11 nm;

[0017] (3) Ni in the surface layer of the positive electrode material 3+ The mass and the Ni in the cathode material2+ and Ni 3+ The ratio of the total mass is greater than or equal to 0.9, wherein the surface layer of the positive electrode material refers to the portion of the positive electrode material extending from the surface of the positive electrode material into the interior of the positive electrode material with a thickness of 0 nm to 20 nm.

[0018] In some embodiments, the positive electrode material includes at least one of the following features (1) to (5):

[0019] (1) The median particle size of the cathode material is 3.5 μm to 4.5 μm;

[0020] (2) The specific surface area of ​​the positive electrode material is 0.4 m². 2 / g~0.8m 2 / g;

[0021] (3) The moisture content of the positive electrode material is less than or equal to 300 ppm;

[0022] (4) The mass content of Li2CO3 in the cathode material is less than or equal to 0.3%;

[0023] (5) The mass content of LiOH in the cathode material is less than or equal to 0.4%.

[0024] Secondly, embodiments of this application provide a method for preparing a positive electrode material, comprising the following steps:

[0025] A cathode material is obtained by heat-treating a mixture containing a lithium source, a nickel source, a cobalt source, a metal source, a polyoxometalate, and a β-nucleating agent. The metal source includes at least one of a manganese source and an aluminum source, and the polyoxometalate includes Na₅CoW₂. 12 O 40 Na5BW 12 O 40 Na5AlW 12 O 40 Na5TiW 12 O 40 Na5YW 12 O 40 and Na5ZrW 12 O 40 At least one of them.

[0026] In some embodiments, the method includes at least one of the following features (1) to (12):

[0027] (1) The lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium sulfate, lithium chloride and lithium nitrate;

[0028] (2) The median particle size of the lithium source is 3μm to 5μm;

[0029] (3) The nickel source includes at least one of nickel acid, nickel acetate, nickel oxalate, nickel nitrate, nickel chloride, and nickel nitrate;

[0030] (4) The median particle size of the nickel source is 3μm to 5μm;

[0031] (5) The cobalt source includes at least one of cobalt carbonate, cobalt acetate, cobalt oxalate, cobalt sulfate, cobalt chloride, and cobalt nitrate;

[0032] (6) The median particle size of the cobalt source is 3 μm to 5 μm;

[0033] (7) The manganese source includes at least one of manganese carbonate, manganese acetate, manganese oxalate, manganese sulfate, manganese chloride, and manganese nitrate;

[0034] (8) The median particle size of the manganese source is 3 μm to 5 μm;

[0035] (9) The aluminum source includes at least one of aluminum carbonate, aluminum acetate, aluminum oxalate, aluminum sulfate, aluminum chloride, and aluminum nitrate;

[0036] (10) The median particle size of the aluminum source is 3μm to 5μm;

[0037] (11) The lithium source, nickel source, cobalt source, and metal source are added in stoichiometric ratios as shown by the following general chemical formula: Li a Ni x Co y M 1-x-y O2, where M is the metal source, 0.95≤a<1.05, 0.8≤x<0.95, 0.05≤y≤0.2;

[0038] (12) The mass percentage of the polyoxometalate in the mixture is 1% to 5%;

[0039] In some embodiments, the method includes at least one of the following features (1) to (6):

[0040] (1) The mixture containing lithium source, nickel source, cobalt source, metal source and polyoxometalate also includes a dispersant;

[0041] (2) The mixture containing lithium source, nickel source, cobalt source, metal source and polyoxometalate further includes a dispersant, wherein the dispersant includes at least one of polyethylene glycol-2000 and imidazole ionic liquid;

[0042] (3) The mixture containing lithium source, nickel source, cobalt source, metal source and polyoxometalate further includes a dispersant, wherein the mass percentage of the dispersant in the mixture is 0.1% to 0.3%;

[0043] (4) The mixture containing lithium source, nickel source, cobalt source, metal source and polyoxometalate also includes solvent;

[0044] (5) The mixture containing lithium source, nickel source, cobalt source, metal source and polyoxometalate further includes a solvent, wherein the solvent includes at least one of water and ethanol;

[0045] (6) The mixture containing lithium source, nickel source, cobalt source, metal source and polyoxometalate also includes a solvent, and the solid content of the mixture is 20% to 70%.

[0046] In some embodiments, the β-nucleating agent includes at least one of p-cyclohexylamide carboxylic acid benzene, zinc adipic acid, supported calcium pimecrolate, zinc phthalate, and liquid crystal polyester.

[0047] In some embodiments, the β-nucleating agent accounts for 0.05% to 0.5% of the mass of the mixture.

[0048] In some embodiments, the method includes at least one of the following features (1) to (3):

[0049] (1) The heat treatment is carried out in an air or oxygen atmosphere;

[0050] (2) The temperature of the heat treatment is 500℃~800℃;

[0051] (3) The feed rate of the mixture containing lithium source, nickel source, cobalt source, metal source and polyoxometalate is 20 mL / min to 80 mL / min.

[0052] Thirdly, embodiments of this application provide a lithium-ion battery, the lithium-ion battery comprising 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 the following advantages:

[0054] The cathode material of this application satisfies the following relationship as determined by XRD: Ⅰ 001 / Ⅰ 101 ≤1.10, Ⅰ 003 / Ⅰ 104 ≥1.70, of which, Ⅰ 001 / Ⅰ 101 ≤1.10 indicates that the substrate surface of the cathode material in this application has a relatively complete crystal structure, which is beneficial to improving the cycle performance and capacity of the cathode material. Simultaneously, the relatively complete crystal structure is beneficial to lithium-ion insertion / extraction, which is beneficial to improving the rate performance of the cathode material; Ⅰ 003 / Ⅰ 104≥1.70 indicates that the cathode material of this application has a good layered structure and a small NiO rock salt phase, which can reduce lithium-nickel mixing and thus reduce the impedance of the material. This is beneficial to reducing the occurrence of interfacial side reactions, thereby improving the capacity and rate performance of the material. The cathode material of this application also includes a metal oxide coating layer on the surface of the substrate. The presence of the metal oxide coating layer can reduce the generation of grain boundary cracks, improve the particle strength of the material, and enhance the electrochemical performance of the cathode material. The nucleation rate of this application can reach 90%. The matrix crystals are matched with low lattice spacing mismatch rate, thereby reducing the lithium-nickel mixing degree of the material and improving the rate performance of the cathode material.

[0055] In the preparation method of this application, a precursor is generated during heat treatment using a lithium source, a nickel source, a cobalt source, and a metal source. A polyoxometalate acts as an oxidant, and a portion of the polyoxometalate can remove Ni oxides from the surface of the precursor during heat treatment. 2+ Oxidation generates NiOOH (Ni in NiOOH has a +3 valence), which reacts with lithium to form lithium nickelate. This eliminates crystal defects on the material surface, improving the capacity, rate performance, and cycle performance of the cathode material. Another portion of the polyoxometalate is reduced to its corresponding oxide during heat treatment, forming a coating layer on the substrate surface. This coating layer reduces grain boundary cracks, increases particle strength, and enhances electrochemical performance. As a β-nucleating agent in the mixture, it achieves lattice matching with the substrate crystals with a lattice mismatch rate of less than 15%, increasing the nucleation rate and thus reducing lithium-nickel mixing, thereby improving the rate performance of the cathode material. This application utilizes in-situ reaction and heat treatment to simultaneously modify the material as both a dopant and a coating material, thereby enhancing its electrochemical performance. Attached Figure Description

[0056] To more clearly illustrate the technical solutions of the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 This is a flowchart illustrating the preparation process of the cathode material in this application;

[0058] Figure 2 A comparison of discharge capacity curves for the materials prepared in the Examples and Comparative Example 1;

[0059] Figure 3 SEM comparison images of the materials prepared in Example 1 and Comparative Example 1;

[0060] Figure 4 The image shows a comparison of the DSC curves of the materials prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0061] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0062] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0063] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0064] For ease of understanding of this invention, specific terms have been appropriately defined in this application. Unless otherwise defined herein, the scientific and technical terms used in this invention have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains.

[0065] As described in the background section, existing ternary cathode materials suffer from poor cycle performance and rate capability, hindering their large-scale application in the power battery field. To address these issues, current research focuses on ion doping and coating to improve structural stability and stabilize the surface crystal structure of ternary materials during charge and discharge. However, this does not fundamentally eliminate crystal defects in ternary materials, and common coating materials generally hinder lithium-ion insertion / extraction to varying degrees, while also reducing the material's specific capacity. Furthermore, some researchers have used spray pyrolysis to synthesize ternary cathode materials, which significantly reduces the incorporation of impurities. The small droplets formed after the metal solution is atomized result in a more uniform composition of metal ions. However, materials prepared using these methods suffer from defects such as poor crystallinity.

[0066] Therefore, this application provides a positive electrode material, which includes a substrate and a coating layer covering at least a portion of the surface of the substrate. The chemical formula of the substrate is shown in formula (Ⅰ):

[0067] Li a Ni x Co y M 1-x-y O2 (Ⅰ)

[0068] In formula (Ⅰ), M includes at least one of Mn and Al, 0.95≤a<1.05, 0.8≤x<0.95, and 0.05≤y≤0.2;

[0069] The coating material includes oxides, and the metal element in the oxide includes at least one of W, Al, Co, Zr, Y and Ti;

[0070] In the XRD pattern of the cathode material, the intensity ratio of the diffraction peaks between the (001) plane and the (101) plane is I. 001 / Ⅰ 101 ≤1.10; diffraction peak intensity ratio between (003) plane and (104) plane I 003 / Ⅰ 104 ≥1.70.

[0071] The nucleation rate k of the cathode material is greater than or equal to 90%, where:

[0072]

[0073] In equation (II), H β(300) H represents the characteristic diffraction peak intensity of the β-crystal (300) plane of the cathode material in the XRD pattern. α(110) , H α(040) and H α(130) The values ​​correspond to the characteristic diffraction peak intensities of the α crystal planes (110), (040), and (130) of the cathode material in the XRD pattern, respectively.

[0074] In the above scheme, the cathode material of this application satisfies the following relationship as determined by XRD: Ⅰ 001 / Ⅰ 101 ≤1.10, Ⅰ 003 / Ⅰ 104 ≥1.70, of which, Ⅰ 001 / Ⅰ 101 ≤1.10 indicates that the substrate surface of the cathode material in this application has a relatively complete crystal structure, which is beneficial to improving the cycle performance and capacity of the cathode material. Simultaneously, the relatively complete crystal structure is beneficial to lithium-ion insertion / extraction, which is beneficial to improving the rate performance of the cathode material; Ⅰ 003 / Ⅰ 104≥1.70 indicates that the cathode material of this application has a good layered structure and a small NiO rock salt phase, which can reduce lithium-nickel mixing and thus reduce the impedance of the material. This is beneficial to reducing the occurrence of interfacial side reactions, thereby improving the capacity and rate performance of the material. The cathode material of this application also includes an oxide coating layer on the surface of the substrate. The presence of the oxide coating layer can reduce the generation of grain boundary cracks, improve the particle strength of the material, and enhance the electrochemical performance of the cathode material. The nucleation rate of this application can reach 90%, and the matrix crystals are matched with low lattice spacing mismatch rate, thereby reducing the lithium-nickel mixing degree of the material and improving the rate performance of the cathode material.

[0075] In this application, I 001 / Ⅰ 101 ≤1.10, exemplary, Ⅰ 001 / Ⅰ 101 It can be 1.00, 1.01, 1.03, 1.05, 1.07, 1.08, and 1.10, etc., or of course, other values ​​within the above range. This application does not impose any restrictions here. If I 001 / Ⅰ 101 A value greater than 1.10 will result in more crystal defects on the matrix surface, which is not conducive to the formation of a complete crystal structure. 003 / Ⅰ 104 ≥1.70, exemplary, I 003 / Ⅰ 104 It can be 1.70, 1.73, 1.75, 1.78, and 1.80, etc., or of course, other values ​​within the above range. This application does not impose any restrictions here. If I 003 / Ⅰ 104 If the value is less than 1.70, it will lead to severe lithium-nickel mixing on the surface of the cathode material, which is not conducive to the formation of layered structure materials.

[0076] Specifically, the nucleation rate k of the cathode material can be, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, and 98%, or other values ​​within the above range, which are not limited here. Within the above range, it indicates that the nucleation rate of the cathode material of this application is high, indicating that the lattice spacing mismatch rate of the crystals in the material of this application is small, which is beneficial to improving the crystallization rate of the cathode material, thereby shortening the material preparation cycle.

[0077] In some embodiments, the oxide includes at least one of WO3, WO2, Al2O3, CoO, Co2O4, B2O3, ZrO2, Y2O3, and TiO2. For example, the presence of WO3, WO2, CoO, Co2O4, and B2O3 oxide coatings can improve the capacity of the cathode material; the presence of Al2O3 and ZrO2 oxide coatings can improve the cycle performance of the material; the presence of Y2O3 oxide coatings can reduce gas generation; and the presence of TiO2 oxide coatings can resolve the side reactions caused by free lithium on the surface of the cathode material.

[0078] In some embodiments, the thickness of the coating layer is 4nm to 11nm. Specifically, the thickness of the coating layer is 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm and 11nm, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0079] In some implementations, Ni in the surface layer of the cathode material 3+ The quality and Ni in the cathode material 2+ and Ni 3+ The ratio of the total mass to the total mass is greater than or equal to 0.9, where the surface layer of the cathode material refers to the portion extending from the surface of the cathode material into its interior with a thickness of 0 nm to 20 nm. For example, the Ni in the surface layer of the cathode material... 3+ The quality and Ni in the cathode material 2+ and Ni 3+ The ratio of the total mass can be 0.9, 0.92, 0.95, 0.96, 0.98, and 0.99, or other values ​​within the above range, and is not limited here. Within the above-mentioned range, it indicates that the Ni on the surface of the cathode material of this application... 3+ More, Ni 3+ The presence of [a substance] can improve the crystal structure on the surface of the cathode material, thereby reducing the lithium-nickel mixing degree, enhancing the conductivity of the material, and improving the cycle performance of the material.

[0080] In some embodiments, the median particle size of the cathode material is 3.5 μm to 4.5 μm. Specifically, the median particle size of the cathode material is 3.5 μm, 3.7 μm, 3.9 μm, 40 μm, 4.3 μm and 4.5 μm, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0081] In some implementations, the specific surface area of ​​the cathode material is 0.4 m². 2 / g~0.8m 2 / g, specifically, the specific surface area of ​​the cathode material can be 0.4m². 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g and 0.8m 2 / g, etc., can also be other values ​​within the above range, and are not limited here.

[0082] In some embodiments, the moisture content of the cathode material is less than or equal to 300 ppm. Specifically, the moisture content of the cathode material can be 50 ppm, 100 ppm, 150 ppm, 200 ppm, 250 ppm, and 300 ppm, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0083] In some embodiments, the surface alkaline impurities of the cathode material mainly refer to Li2CO3 and LiOH. The mass content of Li2CO3 in the cathode material is less than or equal to 0.3%. Specifically, the mass content of Li2CO3 in the cathode material can be 0.05%, 0.1%, 0.2%, and 0.3%, etc., or other values ​​within the above range, which are not limited here.

[0084] In some embodiments, the mass content of LiOH in the cathode material is less than or equal to 0.4%. Specifically, the mass content of LiOH in the cathode material can be 0.05%, 0.1%, 0.2%, 0.3%, and 0.4%, etc., or other values ​​within the above range, which are not limited here.

[0085] Controlling the mass content of Li2CO3 and LiOH in the cathode material within the above-mentioned range is beneficial to improving the processing performance of the cathode material and reducing gas production in the battery prepared from the cathode material.

[0086] This application provides a method for preparing a positive electrode material, such as... Figure 1 As shown, it includes the following steps:

[0087] A cathode material is obtained by heat-treating a mixture containing a lithium source, a nickel source, a cobalt source, a metal source, a polyoxometalate, and a β-nucleating agent. The metal source includes at least one of a manganese source and an aluminum source, and the polyoxometalate includes Na₅CoW₂. 12 O 40 Na5BW 12 O 40 Na5AlW 12 O 40 Na5TiW 12 O 40 Na5YW 12 O 40 and Na5ZrW 12 O 40 At least one of them.

[0088] In the above scheme, lithium, nickel, cobalt, and metal sources generate precursors during heat treatment. Polyoxometalates act as oxidants, and a portion of the polyoxometalates can remove Ni from the surface of the precursors during heat treatment. 2+ Oxidation generates NiOOH (Ni in NiOOH has a +3 valence), which reacts with lithium to form lithium nickelate. This eliminates crystal defects on the material surface, improving the capacity, rate performance, and cycle performance of the cathode material. Another portion of the polyoxometalate is reduced to its corresponding oxide during heat treatment, forming a coating layer on the substrate surface. This coating layer reduces grain boundary cracks, increases particle strength, and enhances the electrochemical performance of the material. This application utilizes in-situ reaction and heat treatment to simultaneously modify the material as both a dopant and a coating material, thereby improving its electrochemical performance. The heat treatment in this application is carried out using a spray pyrolysis device, in which a mixed solution containing lithium source, nickel source, cobalt source, metal source, polyoxometalate, dispersant, solvent and β nucleating agent is sprayed into a high-temperature atmosphere in the form of a mist, causing the materials in the mixed solution to undergo thermal decomposition, and then precipitate solid phase due to supersaturation. During the spray pyrolysis process, due to the short stroke of the spray pyrolysis device and the low temperature control precision, the lattice matching degree of the material is low during the heat treatment process, resulting in low crystallinity of the prepared cathode material. This application improves the nucleation rate of the material by using a β nucleating agent in the mixture, which can reduce the lattice mismatch rate between the agent and the matrix crystal, thereby reducing the lithium-nickel mixing degree of the material, improving the rate performance of the cathode material and shortening the processing cycle.

[0089] The preparation method of this application is described in detail below with reference to the embodiments:

[0090] A cathode material is obtained by heat-treating a mixture containing a lithium source, a nickel source, a cobalt source, a metal source, a polyoxometalate, and a β-nucleating agent. The metal source includes at least one of a manganese source and an aluminum source, and the polyoxometalate includes Na₂CoW₃. 12 O 40 Na5BW 12 O 40 Na5AlW 12 O 40 Na5TiW 12 O 40 Na5YW 12 O 40 and Na5ZrW 12 O 40 At least one of them.

[0091] In some embodiments, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium sulfate, lithium chloride, and lithium nitrate.

[0092] In some embodiments, the median particle size of the lithium source is 3μm to 5μm. Specifically, the median particle size of the lithium source can be 3μm, 4μm, and 5μm, or other values ​​within the above range, which are not limited here.

[0093] In some embodiments, the nickel source includes at least one of nickel acid, nickel acetate, nickel oxalate, nickel nitrate, nickel chloride, and nickel nitrate.

[0094] In some embodiments, the median particle size of the nickel source is 3 μm to 5 μm. Specifically, the median particle size of the nickel source can be 3 μm, 4 μm, and 5 μm, or other values ​​within the above range, which are not limited here.

[0095] In some embodiments, the cobalt source includes at least one of cobalt carbonate, cobalt acetate, cobalt oxalate, cobalt sulfate, cobalt chloride, and cobalt nitrate.

[0096] In some embodiments, the median particle size of the cobalt source is 3 μm to 5 μm. Specifically, the median particle size of the cobalt source can be 3 μm, 4 μm, and 5 μm, or other values ​​within the above range, which are not limited here.

[0097] In some embodiments, the manganese source includes at least one of manganese carbonate, manganese acetate, manganese oxalate, manganese sulfate, manganese chloride, and manganese nitrate.

[0098] In some embodiments, the median particle size of the manganese source is 3 μm to 5 μm. Specifically, the median particle size of the manganese source can be 3 μm, 4 μm, and 5 μm, or other values ​​within the above range, which are not limited here.

[0099] In some embodiments, the aluminum source includes at least one of aluminum carbonate, aluminum acetate, aluminum oxalate, aluminum sulfate, aluminum chloride, and aluminum nitrate.

[0100] In some embodiments, the median particle size of the aluminum source is 3μm to 5μm. Specifically, the median particle size of the aluminum source can be 3μm, 4μm, and 5μm, or other values ​​within the above range, which are not limited here.

[0101] In some embodiments, the lithium source, nickel source, cobalt source, and metal source are added in stoichiometric ratios as shown by the following general chemical formula: Li a Ni x Co y M 1-x-y O2, where M is the metal source, 0.95≤a<1.05, 0.8≤x<0.95, 0.05≤y≤0.2.

[0102] In some embodiments, the mass percentage of polyoxometalates in the mixture is 1% to 5%. Specifically, the mass percentage of polyoxometalates in the mixture can be 1%, 2%, 3%, 4%, and 5%, etc., and of course, other values ​​within the above range are also possible and are not limited here. If the mass percentage of polyoxometalates is greater than 5%, it will result in excessive oxide coating on the surface of the mixture, which will negatively affect the electrochemical performance of the cathode material. If the mass percentage of polyoxometalates is less than 1%, the Ni on the surface of the precursor will be less than 1%. 2+ Cannot be completely oxidized to Ni 3+ The improvement of surface crystal structure defects is not significant.

[0103] In some embodiments, the mixture containing lithium source, nickel source, cobalt source, metal source and polyoxometalate also includes a dispersant.

[0104] In some embodiments, the dispersant includes at least one of polyethylene glycol-2000 and imidazole ionic liquids. Of course, the dispersant can also be other conventional dispersants in the art, and this application does not limit it.

[0105] In some embodiments, the mass percentage of the dispersant in the mixture is 0.1% to 0.3%. Specifically, the mass percentage of the dispersant in the mixture can be, for example, 0.1%, 0.15%, 0.2%, 0.25%, and 0.3%, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0106] In some embodiments, the mixture containing lithium source, nickel source, cobalt source, metal source and polyoxometalate also includes a solvent. That is, the cathode material of this application is prepared by a wet process. Specifically, the cathode material of this application is prepared by the following steps:

[0107] The cathode material is obtained by heat treatment after mixing a lithium source, nickel source, cobalt source, metal source, polyoxometalate, dispersant and solvent.

[0108] In some embodiments, the solvent includes at least one of water and ethanol.

[0109] In some embodiments, the solid content of the mixture is 20% to 70%. Specifically, the solid content of the mixture can be, for example, 20%, 30%, 40%, 50%, 60%, and 70%, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0110] In some embodiments, mixing is carried out under ultrasonic stirring conditions.

[0111] In some embodiments, the β-nucleating agent includes at least one of p-cyclohexylamide carboxylic acid benzene, zinc adipate, supported calcium pimecronate, zinc phthalate, and liquid crystal polyester, wherein the liquid crystal polyester is the main chain liquid crystal polyester.

[0112] In some embodiments, the mass percentage of the β-nucleating agent in the mixture is 0.05% to 0.5%. Specifically, the mass percentage of the β-nucleating agent in the mixture can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%, etc., and of course, other values ​​within the above range are also possible and are not limited here. If the mass percentage of the β-nucleating agent in the mixture is less than 0.05%, the amount added is too small and cannot effectively improve the nucleation rate of the material; if the mass percentage of the β-nucleating agent in the mixture is greater than 0.5%, the improvement in the nucleation efficiency of the material is not significant, and the cost increases.

[0113] In some embodiments, the injection rate of the spray pyrolysis device is 20 mL / min to 80 mL / min. Specifically, the injection rate of the spray pyrolysis device can be, for example, 20 mL / min, 30 mL / min, 40 mL / min, 50 mL / min, 60 mL / min, 70 mL / min, and 80 mL / min, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0114] In some implementations, the heat treatment is carried out in an air or oxygen atmosphere.

[0115] In some embodiments, the heat treatment temperature is 500°C to 800°C. Specifically, the heat treatment temperature can be, for example, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, and 800°C, etc., and of course, other values ​​within the above range are also possible and are not limited herein. Within the above temperature range, the polyoxometalate oxidizes the precursor, causing the Ni on the precursor surface to... 2+ Oxidized to Ni 3+ This allows the precursor surface to undergo structural reorganization, eliminating crystallization defects on the material surface.

[0116] In some embodiments, the heating rate of the heat treatment is 1℃ / min to 5℃ / min. Specifically, the heating rate of the heat treatment can be, for example, 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min and 5℃ / min, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0117] This application also provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, a non-aqueous electrolyte, and a casing. The positive electrode includes a current collector and a positive electrode material prepared by the above-described positive electrode material or by the above-described positive electrode material preparation method coated on the current collector.

[0118] In some embodiments, a positive electrode slurry containing a material (the positive electrode material of the present invention), a conductive agent, a binder, and NMP is prepared, and the positive electrode slurry is loaded onto a positive electrode current collector, thereby enabling the manufacture of a positive electrode sheet for a secondary battery.

[0119] The embodiments of the present invention are described, but the present invention is not limited to these examples as long as it does not depart from its spirit.

[0120] Example 1

[0121] (1) According to the stoichiometric ratio LiNi 0.8 Co 0.1 Mn 0.1 Weigh out 21.20g lithium chloride, 129.60g nickel chloride, 129.84g cobalt chloride, 125.84g manganese chloride, and 2.60g Na₂CoW. 12 O 40 A mixture was prepared by adding 0.20g of p-cyclohexylamide carboxylic acid benzene and 0.41g of polyethylene glycol-2000.

[0122] (2) The above mixture is put into the reactor, 1000 mL of deionized water is added, and after ultrasonic stirring for 3 hours, it is pumped by peristaltic pump to the spray pyrolysis equipment to react and obtain ternary cathode material. The pyrolysis temperature is 700℃ and the feed rate is 20 mL / min.

[0123] The cathode material prepared in this application includes LiNi. 0.8 Co 0.1 Mn 0.1 O2 matrix and coating on LiNi 0.8 Co 0.1 Mn 0.1 The coating layer on the surface of the O2 substrate, the coating layer material includes CoO, WO2 and WO3.

[0124] Example 2

[0125] (1) According to the stoichiometric ratio of LiNi 0.8 Co 0.1 Mn 0.1 Weigh out 21.20g lithium chloride, 129.60g nickel chloride, 129.84g cobalt chloride, 125.84g manganese chloride, and 2.60g Na₂CoW. 12 O 40 0.41g zinc adipate and 0.41g polyethylene glycol-2000 were added to obtain a mixture.

[0126] (2) The above mixture is put into the reactor, 1000 mL of deionized water is added, and after ultrasonic stirring for 3 hours, it is pumped by peristaltic pump to the spray pyrolysis equipment to react and obtain ternary cathode material. The pyrolysis temperature is 700℃ and the feed rate is 20 mL / min.

[0127] The cathode material prepared in this application includes LiNi. 0.8 Co 0.1 Mn 0.1 O2 matrix and coating on LiNi 0.8 Co 0.1 Mn 0.1 The coating layer on the surface of the O2 substrate, the coating layer material includes CoO, WO2 and WO3.

[0128] Example 3

[0129] (1) According to the stoichiometric ratio Li 1.05 Ni 0.85 Co 0.05 Mn 0.1 Weigh out 21.20g lithium chloride, 129.60g nickel chloride, 129.84g cobalt chloride, 125.84g manganese chloride, and 2.60g Na₂CoW. 12 O 40 A mixture was prepared by adding 0.82g of zinc phthalate and 0.41g of polyethylene glycol-2000.

[0130] (2) The above mixture is put into the reactor, 1000 mL of deionized water is added, and after ultrasonic stirring for 3 hours, it is pumped by peristaltic pump to the spray pyrolysis equipment to react and obtain ternary cathode material. The pyrolysis temperature is 700℃ and the feed rate is 20 mL / min.

[0131] The cathode material prepared in this application includes LiNi. 0.8 Co 0.1 Mn 0.1 O2 matrix and coating on LiNi 0.8 Co 0.1 Mn 0.1 The coating layer on the surface of the O2 substrate, the coating layer material includes CoO, WO2 and WO3.

[0132] Example 4

[0133] Unlike Example 1, the amount of cyclohexylamide carboxylic acid benzene added in step (1) is 2.05g.

[0134] The cathode material prepared in this application includes LiNi. 0.8 Co 0.1 Mn 0.1 O2 matrix and coating on LiNi 0.8 Co 0.1Mn 0.1 The coating layer on the surface of the O2 substrate, the coating layer material includes CoO, WO2 and WO3.

[0135] Example 5

[0136] Unlike Example 1, the Na5CoW in step (1) is... 12 O 40 Replace with: Na5BW 12 O 40 .

[0137] The cathode material prepared in this application includes LiNi. 0.8 Co 0.1 Mn 0.1 O2 matrix and coating on LiNi 0.8 Co 0.1 Mn 0.1 The coating layer on the surface of the O2 substrate, the coating layer material includes B2O3, WO2 and WO3.

[0138] Example 6

[0139] Unlike Example 1, the Na5CoW in step (1) is... 12 O 40 Replace with: Na5AlW 12 O 40 .

[0140] The cathode material prepared in this application includes LiNi. 0.8 Co 0.1 Mn 0.1 O2 matrix and coating on LiNi 0.8 Co 0.1 Mn 0.1 The coating layer on the surface of the O2 substrate, the materials of which include Al2O3, WO2 and WO3.

[0141] Example 7

[0142] (1) According to the stoichiometric ratio LiNi 0.8 Co 0.1 Mn 0.1 Weigh out 21.20g lithium chloride, 129.60g nickel chloride, 129.84g cobalt chloride, 125.84g manganese chloride, and 2.60g Na₂CoW. 12 O 40 Add 0.41g of polyethylene glycol-2000 to obtain a mixture.

[0143] (2) The above mixture is put into the reactor, 1000 mL of deionized water is added, and after ultrasonic stirring for 3 hours, it is pumped by peristaltic pump to the spray pyrolysis equipment to react and obtain ternary cathode material. The pyrolysis temperature is 700℃ and the feed rate is 20 mL / min.

[0144] The cathode material prepared in this application includes LiNi. 0.8 Co 0.1 Mn 0.1 O2 matrix and coating on LiNi 0.8 Co 0.1 Mn 0.1 The coating layer on the surface of the O2 substrate, the coating layer material includes CoO, WO2 and WO3.

[0145] Comparative Example 1

[0146] (1) According to the stoichiometric ratio of LiNi 0.8 Co 0.1 Mn 0.05 Mg 0.05 O2 was prepared by weighing 21.20g lithium chloride, 129.60g nickel chloride, 129.84g cobalt chloride, 125.84g manganese chloride, 0.15g cobalt oxide, 0.20g tungsten oxide, and 0.41g polyethylene glycol-2000 to obtain a mixture.

[0147] (2) The above mixture is put into the reactor, 1000 mL of deionized water is added, and after ultrasonic stirring for 3 hours, it is pumped by peristaltic pump to the spray pyrolysis equipment to react and obtain ternary cathode material. The pyrolysis temperature is 700℃ and the feed rate is 20 mL / min.

[0148] Comparative Example 2

[0149] (1) According to the stoichiometric ratio of LiNi 0.8 Co 0.1 Mn 0.1 O2 was prepared by weighing 21.20g of lithium chloride, 129.60g of nickel chloride, 129.84g of cobalt chloride, 125.84g of manganese chloride, 0.20g of p-cyclohexylamide carboxylic acid benzene, and 0.41g of polyethylene glycol-2000.

[0150] (2) The above materials were put into the reaction vessel, 1000 mL of deionized water was added, and the mixture was ultrasonically stirred for 3 hours. Then, it was pumped by a peristaltic pump to the spray pyrolysis equipment to react and obtain ternary cathode material. The pyrolysis temperature was 700℃ and the feed rate was 20 mL / min.

[0151] Comparative Example 3

[0152] (1) According to the stoichiometric ratio of LiNi 0.8 Co 0.1 Mn 0.1O2 was prepared by weighing 21.20g of lithium chloride, 129.60g of nickel chloride, 129.84g of cobalt chloride, 125.84g of manganese chloride, 2.94g of potassium dichromate, and 0.41g of polyethylene glycol-2000.

[0153] (2) The above mixture is put into the reactor, 1000 mL of deionized water is added, and after ultrasonic stirring for 3 hours, it is pumped by peristaltic pump to the spray pyrolysis equipment to react and obtain ternary cathode material. The pyrolysis temperature is 700℃ and the feed rate is 20 mL / min.

[0154] Comparative Example 4

[0155] (1) According to the stoichiometric ratio of LiNi 0.8 Co 0.1 Mn 0.1 O2 was prepared by weighing 21.20g of lithium chloride, 129.60g of nickel chloride, 129.84g of cobalt chloride, 125.84g of manganese chloride, 18.70g of nano titanium dioxide and 0.41g of polyethylene glycol-2000.

[0156] (2) The above mixture is put into the reactor, 1000 mL of deionized water is added, and after ultrasonic stirring for 3 hours, it is pumped by peristaltic pump to the spray pyrolysis equipment to react and obtain ternary cathode material. The pyrolysis temperature is 700℃ and the feed rate is 20 mL / min.

[0157] Performance testing:

[0158] (1) DSC test method for materials: The sample is first kept at 50℃ for 2 min, then heated to 300℃ at a rate of 10℃ / min, kept at 300℃ for 5 min to eliminate thermal history, and then cooled to 50℃ at a rate of 10℃ / min to obtain the crystallization curve of the sample. Finally, it is kept at 50℃ for 2 min, then heated to 300℃ at a rate of 10℃ / min to record the melting curve of the sample.

[0159] (2) Nucleation rate test of the material: The material was characterized by X-ray powder diffraction at a scanning speed of 10° / min and a 2θ angle test range of 10-70°. The nucleation rate k of the material was calculated according to the Turner-Jones formula.

[0160]

[0161] Among them, H β(300) H represents the characteristic diffraction peak intensity of the β-crystal (300) crystal plane. α(110) , H α(040) and H α(130) The intensity of the characteristic diffraction peaks corresponding to the (110), (040) and (130) crystal planes of α crystal, respectively.

[0162] (3) Ni on the surface of the positive electrode material 3+ Ni content and the amount of Ni in the cathode material 2+ and Ni 3+ The content was tested using XPS.

[0163] (4) Median particle size of the material: Take an appropriate amount of sample and add it to a 100ml beaker. Add three drops of 3% sodium hexametaphosphate reagent, and then add 20ml of water. Place the beaker in an ultrasonic instrument and ultrasonically stir for 30s. Add the prepared sample to the dispersion cup of the instrument, keeping the added sample so that the instrument's light-blocking degree is between 8% and 12%. Click "Start Measurement," wait for the test to finish, and record the data.

[0164] (5) Specific surface area test of materials: After weighing the sample, place it in a clean and dried sample tube, degas it, and then assemble the sample tube. After placing the assembled sample tube on the corresponding analysis station, add liquid nitrogen to the Dewar flask, then place the Dewar flask on the lifting platform, close the door, and open the test software for analysis.

[0165] (6) Moisture content test of materials: Accurately add 1g of sample (accurate to 0.0001g) to a clean and dry sample bottle. Record the sample mass data after the value stabilizes. Cover the weighed sample with a rubber cap. Prepare two empty bottles and place them sequentially on the Stromboli Karl Fischer furnace sample converter turntable at the drift bottle and blank bottle positions; place the sample bottle after the blank bottle in order. Click "Start Measurement," wait for the test to finish, and record the data.

[0166] (7) Electrochemical testing method for materials: Weigh 0.8g of material, 0.1g of conductive carbon black, and 0.1g of polyvinylidene fluoride and place them in a ball mill jar. Add 15mL of N-methylpyrrolidone and ball mill to form a uniform slurry. Then, uniformly coat the slurry onto aluminum foil and vacuum dry at 80℃ for 12h to obtain the positive electrode sheet. Press the electrode sheet into 12mm round pieces using a tablet press. Assemble a 2016 battery in a glove box (H2O, O2 < 0.1ppm), using the positive electrode sheet as the positive electrode, lithium metal sheet as the counter electrode, PP separator as the separator, and 1M LiPF6 / EC:DEC (1:1) electrolyte. After the assembled battery has been left to stand for 12h, test its electrochemical performance on a blue electric system (voltage range 3-4.3V, temperature 25℃).

[0167] The test results are shown in Tables 1 and 2.

[0168] Table 1. Performance parameters of the cathode materials prepared in each embodiment and comparative example

[0169]

[0170] Table 2. Electrochemical performance tests of cathode materials prepared in each example and comparative example

[0171]

[0172]

[0173] According to the data in Tables 1 and 2, the cathode materials prepared in Examples 1 to 7 of this application satisfy the following relationship as determined by XRD: Ⅰ 001 / Ⅰ 101 ≤1.10, Ⅰ 003 / Ⅰ 104 ≥1.70 indicates that the prepared precursor surface has a relatively complete crystal structure, which is conducive to lithium ion insertion / extraction and improves the rate performance of the material; and the cathode material has a layered structure, which is conducive to reducing the lithium-nickel mixing of cations on the material surface and reducing the occurrence of interfacial side reactions, thereby improving the capacity of the material; the cathode material of this application also includes an oxide coating layer deposited on the substrate surface, which can reduce the generation of grain boundary cracks, improve the particle strength of the material, and improve the electrochemical performance of the material.

[0174] Compared with Comparative Example 1, Example 1 is a cathode material prepared without the polyoxometalate and nucleating agent of this application. According to the data in Table 2, the electrochemical performance of Example 1 is significantly better than that of Comparative Example 1. This indicates that the electrochemical performance of the material is significantly improved after pre-oxidation of the precursors generated from the lithium, nickel, cobalt, and metal sources using polyoxometalates, as described in this application. The modified capacity and cycle efficiency are also significantly enhanced. The rate performance test graphs of the materials prepared in Example 1 and Comparative Example 1 are shown below. Figure 2 As shown, Figure 2 It can be seen that the rate performance of the cathode material in Example 1 of this application is significantly better than that of the cathode material prepared in Comparative Example 1.

[0175] The XRD data of Example 1 and Comparative Example 1 are shown in Table 1. It can be seen that, compared to the XRD data of Comparative Example 1, the polyoxometalate of Example 1, after heat treatment and oxidation, exhibits higher XRD performance (Ig). 001 / Ⅰ 101 A decrease in peak intensity ratio indicates that heat treatment generates β-NiOOH on the material surface; Ⅰ 003 / Ⅰ 104 The increased ratio indicates a decrease in the degree of cation mixing in the surface crystal structure of the material. In addition, the nucleation rate of the material in Comparative Example 1 was 70.3%, while that of the material in Example 1 was 90.8%, indicating that the p-cyclohexylamide carboxylic acid benzene nucleating agent in Example 1 can significantly improve the efficiency of heterogeneous nucleation of the material. Therefore, the lithium-nickel mixing degree of the modified material in Example 1 of this application is significantly reduced, and the nucleation rate is significantly improved, which is beneficial to the improvement of electrochemical performance.

[0176] Figure 3SEM images of the materials prepared in Example 1 and Comparative Example 1. Figure 3 (a) is a SEM image of the material from Example 1. Figure 3 (b) is the SEM image of the material in Comparative Example 1, from... Figure 3 (a) and Figure 3 (b) It can be seen that, compared with the cathode material prepared in Comparative Example 1, the material prepared in Example 1 has a more uniform surface coating.

[0177] The DSC melting curves of the cathode materials prepared in Example 1 and Comparative Example 1 are as follows: Figure 4 As shown, by Figure 4 It can be seen that the characteristic melting peak of the β crystal form appeared near 150°C in Example 1, which indicates that p-cyclohexylamide carboxylic acid benzene is an effective β nucleating agent that can induce the formation of β crystals.

[0178] Comparative Example 2 added a nucleating agent but did not add a polyoxometalate, which could not improve the crystal structure on the surface of the material, resulting in low capacity, first-pass efficiency and rate performance of the prepared cathode material.

[0179] In Comparative Example 3, no nucleating agent was added, but potassium dichromate oxidant was added to prepare the cathode material. The cathode material could not form a relatively complete surface lattice structure, and the crystallinity of the material was low, resulting in low capacity, first-pass efficiency, and rate performance of the prepared cathode material.

[0180] In Comparative Example 4, no polyoxometalates were added. Instead, nano-titanium dioxide nucleating agents were added to prepare the cathode material. However, the cathode material could not form a relatively complete surface lattice structure, and the crystallinity of the material was low. As a result, the capacity, first-pass efficiency, and rate performance of the prepared cathode material were all low.

[0181] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A positive electrode material, characterized in that, The positive electrode material includes a substrate and a coating layer covering at least a portion of the surface of the substrate, wherein the general chemical formula of the substrate is shown in formula (Ⅰ): Li a Ni x Co y M 1-x-y O2(Ⅰ) In formula (Ⅰ), M includes at least one of Mn and Al, 0.95≤a<1.05, 0.8≤x<0.95, and 0.05≤y≤0.2; The coating layer is made of metal oxides, and the metal oxides include at least one of WO3, WO2, Al2O3, CoO, Co2O4, B2O3, ZrO2, Y2O3 and TiO2; In the XRD pattern of the cathode material, the intensity ratio of the diffraction peaks between the (001) and (101) planes is... Ⅰ 001 / Ⅰ 101 ≤1.10; the ratio of diffraction peak intensity between the (003) plane and the (104) plane is I 003 / Ⅰ 104 ≥1.70; The nucleation rate k of the cathode material is ≥90%, wherein: In equation (II), H β(300) H represents the characteristic diffraction peak intensity of the β-crystal (300) crystal plane of the cathode material in the XRD pattern. α(110) H α(040) and H α(130) The intensity of the characteristic diffraction peaks corresponding to the α crystal planes (110), (040) and (130) of the cathode material in the XRD pattern are respectively.

2. The cathode material according to claim 1, characterized in that, The material includes at least one of the following features (1) to (2): (1) The thickness of the coating layer is 4 nm to 11 nm; (2) Ni in the surface layer of the positive electrode material 3+ The mass and the Ni in the cathode material 2+ and Ni 3+ The ratio of the total mass is greater than or equal to 0.9, wherein the surface layer of the positive electrode material refers to the portion of the positive electrode material extending from the surface of the positive electrode material into the interior of the positive electrode material with a thickness of 0 nm to 20 nm.

3. The cathode material according to claim 1, characterized in that, The positive electrode material includes at least one of the following features (1) to (5): (1) The median particle size of the cathode material is 3.5 μm to 4.5 μm; (2) The specific surface area of ​​the positive electrode material is 0.4 m². 2 / g~0.8m 2 / g; (3) The moisture content of the positive electrode material is less than or equal to 300 ppm; (4) The mass content of Li2CO3 in the cathode material is less than or equal to 0.3%; (5) The mass content of LiOH in the cathode material is less than or equal to 0.4%.

4. A method for preparing a positive electrode material, characterized in that, Includes the following steps: A mixture containing a lithium source, a nickel source, a cobalt source, a metal source, a polyoxometalate, and a β-nucleating agent is heat-treated by spray pyrolysis to obtain a cathode material. The metal source includes at least one of a manganese source and an aluminum source, and the polyoxometalate includes Na₅CoW₂. 12 O 40 Na5BW 12 O 40 Na5AlW 12 O 40 Na5TiW 12 O 40 Na5YW 12 O 40 and Na5ZrW 12 O 40 At least one of the following, the lithium source, nickel source, cobalt source, and metal source are added in stoichiometric ratios as shown by the following general chemical formula: Li a Ni x Co y M 1-x- y O2, wherein M is a metal source, 0.95≤a<1.05, 0.8≤x<0.95, 0.05≤y≤0.2, the β nucleating agent accounts for 0.05% to 0.5% of the mass of the mixture, and the polyoxometalate accounts for 1% to 5% of the mass of the mixture.

5. The preparation method according to claim 4, characterized in that, The method includes at least one of the following features (1) to (10): (1) The lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium sulfate, lithium chloride and lithium nitrate; (2) The median particle size of the lithium source is 3μm to 5μm; (3) The nickel source includes at least one of nickel acid, nickel acetate, nickel oxalate, nickel nitrate, nickel chloride, and nickel nitrate; (4) The median particle size of the nickel source is 3μm to 5μm; (5) The cobalt source includes at least one of cobalt carbonate, cobalt acetate, cobalt oxalate, cobalt sulfate, cobalt chloride, and cobalt nitrate; (6) The median particle size of the cobalt source is 3 μm to 5 μm; (7) The manganese source includes at least one of manganese carbonate, manganese acetate, manganese oxalate, manganese sulfate, manganese chloride, and manganese nitrate; (8) The median particle size of the manganese source is 3 μm to 5 μm; (9) The aluminum source includes at least one of aluminum carbonate, aluminum acetate, aluminum oxalate, aluminum sulfate, aluminum chloride, and aluminum nitrate; (10) The median particle size of the aluminum source is 3μm to 5μm.

6. The preparation method according to claim 4, characterized in that, The method includes at least one of the following features (1) to (6): (1) The mixture containing lithium source, nickel source, cobalt source, metal source and polyoxometalate also includes a dispersant; (2) The mixture containing lithium source, nickel source, cobalt source, metal source and polyoxometalate further includes a dispersant, wherein the dispersant includes at least one of polyethylene glycol-2000 and imidazole ionic liquid; (3) The mixture containing lithium source, nickel source, cobalt source, metal source and polyoxometalate further includes a dispersant, wherein the mass percentage of the dispersant in the mixture is 0.1% to 0.3%; (4) The mixture containing lithium source, nickel source, cobalt source, metal source, polyoxometalate and β nucleating agent also includes solvent; (5) The mixture containing lithium source, nickel source, cobalt source, metal source, polyoxometalate and β nucleating agent further includes a solvent, wherein the solvent includes at least one of water and ethanol; (6) The mixture containing lithium source, nickel source, cobalt source, metal source, polyoxometalate and β nucleating agent also includes a solvent, and the solid content of the mixture is 20% to 70%.

7. The preparation method according to claim 4, characterized in that, The β-nucleating agent includes at least one of p-cyclohexylamide carboxylic acid benzene, zinc adipic acid, supported calcium pimecrolate, zinc phthalate, and liquid crystal polyester.

8. The preparation method according to claim 4, characterized in that, The method includes at least one of the following features (1) to (3): (1) The heat treatment is carried out in an air or oxygen atmosphere; (2) The temperature of the heat treatment is 500℃~800℃; (3) The feed rate of the mixture containing lithium source, nickel source, cobalt source, metal source and polyoxometalate is 20 mL / min to 80 mL / min.

9. A lithium-ion battery, characterized in that, The lithium-ion battery includes the cathode material according to any one of claims 1 to 3 or the cathode material prepared by the preparation method according to any one of claims 4 to 8.

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