Positive electrode material and preparation method therefor, positive electrode sheet and secondary battery

Abstract

A positive electrode material and a preparation method therefor, a positive electrode sheet, and a secondary battery. The positive electrode material comprises an inner core and a coating layer covering at least part of the surface of the inner core. The inner core comprises a material of which the chemical formula is LiNiaCobMncQdO2, wherein the Q element comprises at least one of Zr and Al, 0.89≤a≤0.98, 0≤b≤0.06, 0≤c<0.11, d>0, and a+b+c+d=1. The coating layer comprises a material of which the chemical formula is LimConX(1-n)O2, wherein the X element comprises at least one of Al, W, Ti, B and La, 0<m≤1, and 0<n≤1. The inner core and the coating layer in the positive electrode material cooperate with each other to effectively improve the rate capability and the cycle performance of the positive electrode material.

Description

Positive electrode material and preparation method thereof, positive electrode sheet and secondary battery

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application number 202410353403.8 filed with the State Intellectual Property Office of China on March 26, 2024, entitled “Positive electrode material and preparation method thereof, positive electrode sheet and secondary battery”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to a positive electrode material and a preparation method thereof, a positive electrode sheet and a secondary battery. Background Art

[0004] The rapid development and application of lithium-ion batteries has led to a clearer market demand for automobiles. Low-end models prioritize competitive cost advantages, while high-end models prioritize range. To achieve this, high-end models typically choose cathode materials with high energy density. Increasing the nickel content in cathode materials maximizes the material's specific capacity, but this reduces the Co content, leading to poor rate performance and high-temperature cycling performance.

[0005] Summary of the Invention

[0006] The present application provides a positive electrode material and a preparation method thereof, a positive electrode plate and a secondary battery, aiming to improve the rate performance and high-temperature cycle performance of the positive electrode material.

[0007] In a first aspect of the present application, a positive electrode material is provided, comprising a core and a coating layer covering at least a portion of the surface of the core, wherein the core comprises a chemical formula of LiNi a Co b Mn c Q d O2 material, wherein the Q element includes at least one of Zr and Al, 0.89≤a≤0.98, 0≤b≤0.06, 0≤c<0.11, d>0, a+b+c+d=1, and the coating layer includes a chemical formula of Li m Co n X (1-n) O2 material, wherein the X element includes at least one of Al, W, Ti, B and La, 0<m≤1, 0<n≤1.

[0008] In some embodiments, the Q element further includes at least one of Sr, Ti, Sb, W, Nb, Y, Mo, Ta, La, B, P, and S.

[0009] In some embodiments, (1-n) / n<0.2.

[0010] In some embodiments, the coating layer further comprises a chemical formula of Li m’ X'O2 material, wherein the X' element includes at least one of Al, W, Ti, B and La, and 0<m'≤1.

[0011] In some embodiments, the positive electrode material comprises a single crystal particle, the core of which comprises a LiNi a1 Co b1 Mn c1 Q1 d1 Q2 d2 O2 material, wherein the Q1 element includes Zr, the Q2 element includes at least one of Al, Sr, W, Nb, La and Sb, 0.89≤a1≤0.98, 0≤b1≤0.06, 0≤c1<0.11, d1>0, d2≥0, a1+b1+c1+d1+d2=1;

[0012] The coating layer of the single crystal particle includes a chemical formula of Li m1 Co n1 X1 (1-n1) O2 material, wherein the X1 element includes at least one of Al, W, Ti and B, 0<m1≤1, 0<n1≤1.

[0013] In some embodiments, the volume average particle size Dv50 of the single crystal particles is 2 μm to 6 μm.

[0014] In some embodiments, the core of the single crystal particle contains Q2 element, and the molar ratio of Q1 element to Q2 element in the core of the single crystal particle is (1-6):1, and can be optionally (1-5):1.

[0015] In some embodiments, the total mass content of the Q1 element and the Q2 element in the core of the single crystal particle is 3000 ppm to 6000 ppm.

[0016] In some embodiments, (1-n1) / n1<0.2.

[0017] In some embodiments, the mass content of the Co element in the single crystal particles is ≤8%, and can be optionally ≤6%.

[0018] In some embodiments, the coating layer of the single crystal particle further comprises a material having a chemical formula of LiX2O2, wherein the X2 element comprises at least one of Al, W, Ti and B.

[0019] In some embodiments, the total mass content of the Co element and the X2 element in the coating layer of the single crystal particle is 0.5% to 3%.

[0020] In some embodiments, the positive electrode material further comprises polycrystalline particles.

[0021] In some embodiments, the ratio of the volume average particle size Dv50 of the polycrystalline particles to the volume average particle size Dv50 of the single crystal particles is (3-5.5):1.

[0022] In some embodiments, the mass proportion of the single crystal particles in the positive electrode material is 20% to 80%.

[0023] In some embodiments, the volume average particle size Dv50 of the polycrystalline particles is 9 μm to 15 μm.

[0024] In some embodiments, the core of the polycrystalline particle comprises a LiNi a2 Co b2 Mn c2 Q3 d3 Q4 d4 O2 material, wherein Q3 element includes Al, Q4 element includes at least one of Zr, Sr, Sb, W, Y, Ta, Nb, B, P and S, 0.89≤a2≤0.98, 0≤b2≤0.06, 0≤c2<0.11, d3>0, d4≥0, a2+b2+c2+d3+d4=1;

[0025] The coating layer of the polycrystalline particles includes a chemical formula of Li m2 X3 n2 X4 (1-n2) O2 material, wherein the X3 element includes B, the X4 element includes at least one of Al, W, Ti and La, 0<m2≤1, 0<n2<1.

[0026] In some embodiments, based on the mass of the polycrystalline particles, the coating layer of the polycrystalline particles has a mass content of 0.1% to 0.5%.

[0027] In some embodiments, the core of the polycrystalline particle contains Q4 element, and the molar ratio of Q3 element to Q4 element in the core of the polycrystalline particle is (0.22-5):1, and can be optionally (0.22-4):1.

[0028] In some embodiments, the total mass content of the Q3 element and the Q4 element in the core of the polycrystalline particles is 3500 ppm to 12000 ppm.

[0029] In some embodiments, the mass ratio of the X3 element to the X4 element in the coating layer of the polycrystalline particles is (0.25-3):1, and can be optionally (0.25-2):1.

[0030] In a second aspect of the present application, a method for preparing a positive electrode material is provided, comprising the following steps:

[0031] Mixing a positive electrode material precursor, a lithium source and a compound containing a Q element, and performing a first calcination to obtain a core; the Q element includes at least one of Zr and Al;

[0032] The core is mixed with a compound containing an X element, and subjected to a second calcination to form a coating layer on at least a portion of the surface of the core, thereby obtaining the positive electrode material; the X element comprises at least one of Al, W, Ti, B and La;

[0033] The positive electrode material includes the core and the coating layer, and the core includes a chemical formula of LiNi a Co b Mn c Q d O2 material, wherein 0.89≤a≤0.98, 0≤b≤0.06, 0≤c<0.11, d>0, a+b+c+d=1, the coating layer includes a chemical formula of Li m Co n X (1-n) O2 material, wherein 0<m≤1, 0<n≤1.

[0034] In a third aspect of the present application, a positive electrode plate is provided, comprising at least one of the positive electrode material described in the first aspect of the present application and the positive electrode material prepared by the preparation method described in the second aspect of the present application.

[0035] In a fourth aspect of the present application, a secondary battery is provided, comprising the positive electrode sheet described in the third aspect of the present application.

[0036] Compared with conventional technologies, the above-mentioned positive electrode materials, preparation methods thereof, positive electrode sheets and secondary batteries have at least the following advantages:

[0037] The Q element in the core of the above-mentioned positive electrode material can improve the oxygen fixation ability of the transition metal layer of the positive electrode material, thereby improving the structural stability of the positive electrode material; the chemical formula of the coating layer is Li m Co n X (1-n) O2 materials can form Li on the surface of the core +The rapid transmission area and the interface stabilization area enhance the interface stability of the positive electrode material and reduce the corrosion damage of HF and other substances in the electrolyte to the positive electrode material in the early stage of battery charging and discharging. Therefore, the core and coating layer in the positive electrode material can cooperate with each other to effectively improve the rate performance and high-temperature cycle performance of the positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG1 is a scanning electron microscope (SEM) image of the positive electrode material prepared in Example 1-1 of the present application.

[0039] FIG2 is an X-ray diffraction (XRD) diagram of the positive electrode material prepared in Example 1-1 of the present application.

[0040] FIG3 is a comparison chart of the high-temperature cycle performance of the batteries of Example 1-1, Comparative Example 1-1, Comparative Example 2-1, and Comparative Example 3-1 of the present application. DETAILED DESCRIPTION

[0041] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0042] In this application, terms such as "first aspect," "second aspect," and "third aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor as implicitly indicating the importance or quantity of the technical features indicated. Furthermore, terms such as "first," "second," and "third," etc., are intended only to provide a non-exhaustive enumeration and description and should not constitute a closed-ended limitation on quantity.

[0043] In this application, the terms "optionally," "optional," and "optional" mean optional or dispensable, i.e., they refer to either option being selected from two parallel options: "with" or "without." If a technical solution contains multiple "optional" clauses, each "optional" clause is independent unless otherwise specified and there are no contradictions or constraints.

[0044] In this application, when referring to numerical ranges, unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges subsumed therein.

[0045] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0046] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in this application and in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this application includes any and all combinations of one or more related listed items. The term "multiple" in this application means at least two, such as two, three, etc., unless otherwise clearly and specifically limited.

[0047] One embodiment of the present application provides a positive electrode material, comprising a core and a coating layer covering at least a portion of the surface of the core, wherein the core comprises a LiNi a Co b Mn c Q d O2 material, wherein the Q element includes at least one of Zr and Al, 0.89≤a≤0.98, 0≤b≤0.06, 0≤c<0.11, d>0, a+b+c+d=1, and the coating layer includes a chemical formula of Li m Co n X (1-n) O2 material, wherein the X element includes at least one of Al, W, Ti, B and La, 0<m≤1, 0<n≤1.

[0048] When d is 0, Li + The chemical formula is LiNi a Co b Mn c The transmission rate of O2 in the material is very low, and the structural stability of the material under high temperature conditions is poor, which greatly limits the rate performance and high temperature cycle performance of the material. In the above embodiment, the Q element in the core can improve the oxygen fixation capacity of the transition metal layer of the positive electrode material, thereby improving the structural stability of the positive electrode material; the chemical formula of the coating layer is Li m Co n X (1-n) O2 materials can form Li on the surface of the core + The rapid transmission area and the interface stabilization area enhance the interface stability of the positive electrode material and reduce the corrosion damage of HF and other substances in the electrolyte to the positive electrode material in the early stage of battery charging and discharging. Therefore, the core and coating layer in the positive electrode material can cooperate with each other to effectively improve the rate performance and high-temperature cycle performance of the positive electrode material.

[0049] It is understood that a includes but is not limited to: 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, b includes but is not limited to: 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, c includes but is not limited to: 0, 0.01, 0.03, 0.05, 0.07, 0.09, 0.1, d includes but is not limited to: Not limited to: 0.001, 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.04, 0.05, m includes but is not limited to: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, n includes but is not limited to: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.

[0050] In some embodiments, the Q element further includes at least one of Sr, Ti, Sb, W, Nb, Y, Mo, Ta, La, B, P, and S. This is beneficial to further improve the structural stability of the positive electrode material, thereby further improving the rate performance and high-temperature cycle performance of the positive electrode material.

[0051] In some embodiments, (1-n) / n<0.2. Controlling the Co element and the X element to meet the above conditions is beneficial to further improve the rate performance of the positive electrode material.

[0052] In some embodiments, the coating layer further comprises a chemical formula of Li m’ X'O2 materials, where the X' element includes at least one of Al, W, Ti, B, and La, and 0 < m' ≤ 1. This further improves the rate capability and high-temperature cycling performance of the positive electrode material. It is understood that m' includes, but is not limited to, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.

[0053] In some embodiments, the positive electrode material comprises a single crystal particle, the core of which comprises a LiNi a1 Co b1 Mn c1 Q1 d1 Q2 d2 O2 material, wherein the Q1 element includes Zr, the Q2 element includes at least one of Al, Sr, W, Nb, La and Sb, 0.89≤a1≤0.98, 0≤b1≤0.06, 0≤c1<0.11, d1>0, d2≥0, a1+b1+c1+d1+d2=1;

[0054] The coating layer of the single crystal particle includes a chemical formula of Li m1 Co n1 X1(1-n1) O2 material, wherein the X1 element includes at least one of Al, W, Ti and B, 0<m1≤1, 0<n1≤1.

[0055] In the above embodiment, the Q1 element is beneficial to improving the mechanical stability of the lattice network of the layered structure of the single crystal particles. The Q1 element and the Q2 element cooperate with each other to improve the structural stability and thermal stability of the single crystal particles. Co and at least one of Al, W, Ti and B can improve the rate performance and high-temperature cycle performance of the single crystal particles, thereby further improving the rate performance and high-temperature cycle performance of the positive electrode material.

[0056] It can be understood that a1 includes but is not limited to: 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, b1 includes but is not limited to: 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, c1 includes but is not limited to: 0, 0.01, 0.03, 0.05, 0.07, 0.09, 0.1, d 1 includes but is not limited to: 0.001, 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.04, 0.05, d2 includes but is not limited to: 0.001, 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.04, 0.05, m1 includes but is not limited to: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, n1 includes but is not limited to: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.

[0057] In some embodiments, the volume average particle size Dv50 of the single crystal particles is 2 μm to 6 μm. It is understood that the volume average particle size Dv50 of the single crystal particles includes but is not limited to: 2 μm, 3 μm, 4 μm, 5 μm, and 6 μm.

[0058] In some embodiments, the core of the single crystal particle contains the Q2 element, and the molar ratio of the Q1 element to the Q2 element in the core of the single crystal particle is (1 to 6): 1. As a result, the structural stability and thermal stability of the single crystal particle can be improved, thereby further improving the high-temperature cycle performance of the positive electrode material. It can be understood that the above molar ratio includes but is not limited to: 1: 1, 2: 1, 3: 1, 4: 1, 5: 1, 6: 1. Furthermore, the core of the single crystal particle contains the Q2 element, and the molar ratio of the Q1 element to the Q2 element in the core of the single crystal particle is (1 to 5): 1.

[0059] In some embodiments, the sum of the mass contents of the Q1 and Q2 elements in the core of the single crystal particles is between 3000 ppm and 6000 ppm. This can further improve the high-temperature cycling performance of the single crystal particles, thereby further improving the high-temperature cycling performance of the positive electrode material. It is understood that the sum of the mass contents of the Q1 and Q2 elements in the core of the single crystal particles includes, but is not limited to, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, 5500 ppm, and 6000 ppm.

[0060] In some embodiments, (1-n1) / n1<0.2. Thus, the rate performance of the single crystal particles can be further improved, thereby further improving the rate performance of the positive electrode material.

[0061] In some embodiments, the mass content of the Co element in the single crystal particles is ≤8%. This can further improve the high-temperature cycling performance of the positive electrode material. It is understood that the mass content of the Co element in the single crystal particles includes, but is not limited to, 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, and 8%. Furthermore, the mass content of the Co element in the single crystal particles is ≤6%.

[0062] In some embodiments, the coating layer of the single crystal particles further comprises a material having a chemical formula of LiX2O2, wherein the X2 element comprises at least one of Al, W, Ti, and B. This is conducive to further improving the rate performance and high-temperature cycle performance of the single crystal particles, thereby further improving the rate performance and high-temperature cycle performance of the positive electrode material.

[0063] In some embodiments, the sum of the mass contents of the Co element and the X2 element in the coating layer of the single crystal particle is 0.5% to 3%. If the sum of the mass contents of the Co element and the X2 element in the coating layer of the single crystal particle meets the above conditions, the high-temperature cycle performance of the single crystal particle can be further improved, thereby further improving the high-temperature cycle performance of the positive electrode material. It is understood that the sum of the mass contents of the Co element and the X2 element in the coating layer of the single crystal particle includes, but is not limited to, 0.5%, 1%, 1.5%, 2%, 2.5%, and 3%.

[0064] In some embodiments, the positive electrode material further comprises polycrystalline particles.

[0065] In some embodiments, the ratio of the volume average particle size Dv50 of the polycrystalline particles to the volume average particle size Dv50 of the single crystal particles is (3-5.5):1. The polycrystalline particles and the single crystal particles are matched in this way so that the single crystal particles can fill the gaps between the polycrystalline particles, thereby improving the space utilization of the positive electrode material, thereby improving the rolling density of the positive electrode sheet and the energy density of the battery. It can be understood that the ratio of the volume average particle size Dv50 of the polycrystalline particles to the volume average particle size Dv50 of the single crystal particles includes but is not limited to: 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1.

[0066] In some embodiments, the molar percentage of Ni in the single crystal particles in the non-Li metal elements is ≥ the molar percentage of Ni in the polycrystalline particles in the non-Li metal elements minus 1%. This design can make the discharge capacity of the single crystal particles and the polycrystalline particles basically at the same level, reducing the Li after multiple charge and discharge. + In the case of uneven deintercalation / intercalation of the positive electrode material, the long-term stability of the positive electrode material is improved.

[0067] In some embodiments, the mass proportion of single crystal particles in the positive electrode material is 20% to 80%. The above design allows the single crystal particles to be evenly dispersed around the polycrystalline particles, increasing the contact area between the positive electrode materials and alleviating the problem of poor rate performance of the positive electrode materials; single crystal particles can fill the gaps between the polycrystalline particles, improve the rolling density and pole piece ductility of the positive electrode material, thereby improving the energy density and processability of the battery; polycrystalline particles mixed with single crystal particles can increase the adhesion between material particles, effectively preventing polycrystalline particles or single crystal particles from falling off from the positive electrode sheets or positive electrode materials; single crystal particles can alleviate the problem of poor thermal stability and cycle performance of polycrystalline materials, thereby further improving the long-term cycle life of the positive electrode material. It can be understood that the mass proportion of single crystal particles in the positive electrode material includes but is not limited to: 20%, 30%, 40%, 50%, 60%, 70%, 80%.

[0068] In some embodiments, the volume average particle size Dv50 of the polycrystalline particles is 9 μm to 15 μm. It is understood that the volume average particle size Dv50 of the polycrystalline particles includes but is not limited to: 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, and 15 μm.

[0069] In some embodiments, the core of the polycrystalline particle comprises a LiNi a2 Co b2 Mn c2 Q3 d3 Q4 d4O2 material, wherein Q3 element includes Al, Q4 element includes at least one of Zr, Sr, Sb, W, Y, Ta, Nb, B, P and S, 0.89≤a2≤0.98, 0≤b2≤0.06, 0≤c2<0.11, d3>0, d4≥0, a2+b2+c2+d3+d4=1;

[0070] The coating layer of the polycrystalline particles includes a chemical formula of Li m2 X3 n2 X4 (1-n2) O2 material, wherein the X3 element includes B, the X4 element includes at least one of Al, W, Ti and La, 0<m2≤1, 0<n2<1.

[0071] In the above embodiment, the Q3 element and the Q4 element in the core of the polycrystalline particles can stabilize the transition metal layer structure of the polycrystalline particles and refine the primary particles, thereby improving the rate performance and compressive resistance of the secondary particles and improving the Li + The X3 and X4 elements in the coating layer of polycrystalline particles can increase the capacity of Li + The transmission rate is increased, and at the same time, the interface stability of the material is enhanced, and the corrosion damage of the electrolyte to the positive electrode material is reduced, so that the rate performance and high-temperature cycle performance of the polycrystalline particles are improved, thereby further improving the rate performance and high-temperature cycle performance of the positive electrode material.

[0072] It can be understood that a2 includes but is not limited to: 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, b2 includes but is not limited to: 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, c2 includes but is not limited to: 0, 0.01, 0.03, 0.05, 0.07, 0.09, 0.1, d3 includes but is not limited to: 0.001, 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.04, 0.05, d4 includes but is not limited to: 0.001, 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.04, 0.05, m2 includes but is not limited to: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, n2 includes but is not limited to: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9.

[0073] In some embodiments, the coating layer of the polycrystalline particles has a mass content of 0.1% to 0.5% based on the mass of the polycrystalline particles. This helps further improve the rate capability and high-temperature cycling performance of the positive electrode material. It is understood that the above mass content includes, but is not limited to, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%.

[0074] In some embodiments, the core of the polycrystalline particles contains Q4 elements, and the molar ratio of the Q3 elements to the Q4 elements in the core of the polycrystalline particles is (0.22 to 4):1. As a result, the rate performance and cycle performance of the polycrystalline particles can be further improved. It can be understood that the above molar ratios include but are not limited to: 0.22:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1. Optionally, the sum of the mass contents of the Q3 elements and the Q4 elements in the core of the polycrystalline particles is 3500ppm to 12000ppm.

[0075] In some embodiments, the mass ratio of the X3 element to the X4 element in the coating layer of the polycrystalline particles is (0.25-2):1. This can further improve the rate capability and cycling performance of the polycrystalline particles. It is understood that the above mass ratio includes but is not limited to: 0.25:1, 0.5:1, 0.75:1, 1:1, 1.5:1, and 2:1.

[0076] Another embodiment of the present application provides a method for preparing a positive electrode material, comprising the following steps:

[0077] The positive electrode material precursor, the lithium source and the compound containing the Q element are mixed and subjected to a first calcination to obtain a core; the Q element includes at least one of Zr and Al;

[0078] The core is mixed with a compound containing an X element, and subjected to a second calcination to form a coating layer on at least a portion of the surface of the core to obtain a positive electrode material; the X element includes at least one of Al, W, Ti, B and La;

[0079] The positive electrode material includes a core and a coating layer, and the core includes a chemical formula of LiNi a Co b Mn c Q d O2 material, wherein 0.89≤a≤0.98, 0≤b≤0.06, 0≤c<0.11, d>0, a+b+c+d=1, and the coating layer includes a chemical formula of Li m Co n X (1-n) O2 material, wherein 0<m≤1, 0<n≤1.

[0080] The above preparation method is simple and convenient, and is convenient for mass production of positive electrode materials. In the above embodiment, the Q element in the core can improve the oxygen fixation capacity of the transition metal layer of the positive electrode material, thereby improving the structural stability of the positive electrode material; the chemical formula of the coating layer is Li m Co n X (1-n) O2 materials can form Li on the surface of the core + The rapid transmission area and the interface stabilization area enhance the interface stability of the positive electrode material and reduce the corrosion damage of HF and other substances in the electrolyte to the positive electrode material in the early stage of battery charging and discharging. Therefore, the core and coating layer in the positive electrode material can cooperate with each other to effectively improve the rate performance and high-temperature cycle performance of the positive electrode material.

[0081] In some embodiments, after the first calcination step, the method further comprises: washing and drying the material obtained by the first calcination in sequence to obtain a core.

[0082] In some embodiments, the cathode material precursor comprises a LiNi a0 Co b0 Mn c0 (OH)2 material, 0.89≤a0≤0.98, 0≤b0≤0.06, 0≤c0<0.11, a0+b0+c0=1.

[0083] In some embodiments, the first calcination and the second calcination are each independently performed in an oxygen-containing atmosphere.

[0084] In some embodiments, the process conditions of the first calcination include: a calcination temperature of 730° C. to 820° C., and a calcination time of 11 to 16 hours. It is understood that the calcination temperature includes, but is not limited to, 730° C., 750° C., 770° C., 790° C., 800° C., and 820° C., and the calcination time includes, but is not limited to, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, and 16 hours.

[0085] In some embodiments, the process conditions of the second calcination include: a calcination temperature of 260° C. to 660° C., and a calcination time of 5 to 10 hours. It is understood that the calcination temperature includes, but is not limited to, 260° C., 300° C., 400° C., 500° C., 600° C., and 660° C., and the calcination time includes, but is not limited to, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, and 10 hours.

[0086] In some embodiments, the compound containing element Q includes at least one of an oxide containing element Q, a chloride containing element Q, a fluoride containing element Q, and a hydroxide containing element Q. Alternatively, the hydroxide containing element Q includes aluminum hydroxide.

[0087] In some embodiments, the compound containing element X includes at least one of an oxide containing element X, a carbonate containing element X, and a hydroxide containing element X.

[0088] In some embodiments, the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium oxalate, and lithium peroxide.

[0089] By adjusting the parameters of the above-mentioned preparation method, the positive electrode material provided in one embodiment of the present application can be obtained.

[0090] Another embodiment of the present application provides a positive electrode plate, comprising at least one of the above-mentioned positive electrode material of the present application and the positive electrode material prepared by the above-mentioned preparation method of the present application.

[0091] The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector. The positive electrode active material layer comprises a positive electrode active material, a conductive agent, and a binder. The positive electrode active material comprises at least one of the above-mentioned positive electrode materials or the positive electrode materials prepared by the above-mentioned preparation method. The conductive agent and binder can be those commonly used in the art.

[0092] Another embodiment of the present application further provides a secondary battery, comprising the above-mentioned positive electrode sheet of the present application.

[0093] The above-mentioned secondary battery may, for example, include the above-mentioned positive electrode sheet, negative electrode sheet, electrolyte and diaphragm in this application. The diaphragm is arranged between the positive electrode sheet and the negative electrode sheet, and mainly plays the role of preventing the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The electrolyte plays the role of conducting active ions between the positive electrode sheet and the negative electrode sheet. During the charging and discharging process of the secondary battery, the active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. This application has no special restrictions on the negative electrode sheet, electrolyte and diaphragm. The negative electrode sheet, electrolyte and diaphragm prepared by the preparation method commonly used in this technical field, or the negative electrode sheet, electrolyte and diaphragm commonly used in this field can be used. Optionally, the above-mentioned secondary battery includes a lithium-ion battery.

[0094] Furthermore, another embodiment of the present application also provides an electrical device, including the above-mentioned battery of the present application.

[0095] The above-mentioned electrical devices may include any equipment or devices that use secondary batteries as a driving source, such as mobile phones, laptops, electric vehicles, ships, satellites, energy storage devices, smart home appliances, etc., but are not limited thereto.

[0096] To further illustrate the present application, the technical solutions of the present application are described in detail below with reference to specific examples. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the art or in accordance with the product instructions were used. Reagents or instruments used, for which the manufacturer is not specified, are all commercially available conventional products.

[0097] Example 1-1

[0098] The preparation method of the positive electrode material comprises the following steps:

[0099] S1: ① The polycrystalline particle precursor (chemical formula is LiNi 0.94 Mn 0.06 (OH)2) was prepared with lithium hydroxide, Al2O3, and ZrO2 in a molar ratio of 1:0.40:0.002:0.003 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 780°C for 15h under the condition of oxygen concentration >70%, and then crushed and sieved to obtain intermediate A, whose chemical formula is LiNi 0.935 Mn 0.06 Al 0.002 Zr 0.003 O2;

[0100] ② The intermediate A was thoroughly mixed with clean water at a mass ratio of 6:4, washed for 3 minutes, and then dried at 150°C for 120 minutes to obtain the core of the polycrystalline particles;

[0101] ③ The core of the polycrystalline particles was fully mixed with H3BO3 and Al2O3 in a mass ratio of 1:0.001:0.001 (H3BO3 and Al2O3 were calculated according to the mass of B element and Al element, respectively), and then calcined at 300 ° C for 8 hours to obtain polycrystalline particles (polycrystalline positive electrode materials) with a volume average particle size Dv50 of 13 μm. The polycrystalline particles contained a uniform coating layer of Li3BO3 and an island coating layer of Al2O3+LiAlO2, as well as a core LiNi 0.935 Mn 0.06 Al 0.002 Zr 0.003 O2; the molar ratio of Al element and Zr element in the inner core of the polycrystalline particles is 0.67:1, and the total mass content of Al element and Zr element in the inner core of the polycrystalline particles is 5000 ppm; the mass ratio of B element and Al element in the coating layer of the polycrystalline particles is 1:1; based on the mass of the polycrystalline particles, the mass content of the coating layer of the polycrystalline particles is 0.2%.

[0102] S2: ① Single crystal particle precursor (chemical formula is LiNi 0.94 Mn 0.06(OH)2) was prepared with lithium hydroxide, ZrO2, and Al2O3 in a molar ratio of 1:0.460:0.003:0.001 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 830 ° C for 14 h under the condition of oxygen concentration >70% and then crushed and sieved to obtain the core of the single crystal particle, whose chemical formula is LiNi 0.936 Mn 0.06 Al 0.001 Zr 0.003 O2;

[0103] ② After the core of the single crystal particle is fully mixed with Co(OH)2 and Al2O3 in a mass ratio of 1:0.01:0.0005 (Co(OH)2 and Al2O3 are calculated according to the mass of Co element and Al element respectively), the single crystal particle (single crystal positive electrode material) is obtained after calcination at 680℃ for 7h. The volume average particle size Dv50 is 3μm. The single crystal particle contains LiCoO2, Al2O3, LiAlO2 coating layer and core LiNi 0.936 Mn 0.06 Al 0.001 Zr 0.003 The molar ratio of the Zr element to the Al element in the core of the single crystal particle is 3:1, and the total mass content of the Zr element and the Al element in the core of the single crystal particle is 4000 ppm; the mass content of the Co element in the single crystal particle is 1%.

[0104] S3: The polycrystalline particles in step S1 and the single crystal particles in step S2 are mixed uniformly in a mass ratio of 7:3 to obtain a bimodal positive electrode material, whose SEM image is shown in FIG1 and XRD pattern is shown in FIG2.

[0105] Example 1-2

[0106] The preparation method of the positive electrode material comprises the following steps:

[0107] ① The single crystal particle precursor (chemical formula is LiNi 0.94 Mn 0.06 (OH)2) was prepared with lithium hydroxide, ZrO2, and Al2O3 in a molar ratio of 1:0.460:0.003:0.001 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 830 ° C for 14 h under the condition of oxygen concentration >70% and then crushed and sieved to obtain the core of the single crystal particle, whose chemical formula is LiNi 0.936 Mn 0.06 Al 0.001 Zr 0.003 O2;

[0108] ② After the core of the single crystal particle is fully mixed with Co(OH)2 and Al2O3 in a mass ratio of 1:0.01:0.0005 (Co(OH)2 and Al2O3 are calculated according to the mass of Co element and Al element respectively), the single crystal particle (single crystal positive electrode material) is obtained after calcination at 680℃ for 7h. The volume average particle size Dv50 is 3μm. The single crystal particle contains LiCoO2, Al2O3, LiAlO2 coating layer and core LiNi 0.936 Mn 0.06 Al 0.001 Zr 0.003 The molar ratio of the Zr element to the Al element in the core of the single crystal particle is 3:1, and the total mass content of the Zr element and the Al element in the core of the single crystal particle is 4000 ppm; the mass content of the Co element in the single crystal particle is 1%.

[0109] Example 2-1

[0110] Basically the same as Example 1-1, except that: the preparation method of the polycrystalline particles in step S1 is changed;

[0111] The method for preparing polycrystalline particles in this embodiment includes the following steps:

[0112] S1: ① The polycrystalline particle precursor (chemical formula is LiNi 0.94 Mn 0.06 (OH)2) was prepared with lithium hydroxide, Al2O3, and ZrO2 in a molar ratio of 1:0.480:0.005:0.001 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 780°C for 15h under the condition of oxygen concentration >70%, and then crushed and sieved to obtain intermediate A, whose chemical formula is LiNi 0.934 Mn 0.06 Al 0.005 Zr 0.001 O2;

[0113] ② The intermediate A was thoroughly mixed with clean water at a mass ratio of 6:4, washed for 3 minutes, and then dried at 150°C for 120 minutes to obtain the core of the polycrystalline particles;

[0114] ③ The core of the polycrystalline particles was fully mixed with H3BO3 and Al2O3 in a mass ratio of 1:0.001:0.001 (H3BO3 and Al2O3 were calculated according to the mass of B element and Al element, respectively), and then calcined at 300 ° C for 8 hours to obtain polycrystalline particles (polycrystalline positive electrode materials) with a volume average particle size Dv50 of 13 μm. The polycrystalline particles contained a uniform coating layer of Li3BO3 and an island coating layer of Al2O3+LiAlO2, as well as a core LiNi 0.934 Mn0.06 Al 0.005 Zr 0.001 O2; the molar ratio of Al element and Zr element in the core of the polycrystalline particles is 5:1, and the total mass content of Al element and Zr element in the core of the polycrystalline particles is 6000 ppm; the mass ratio of B element and Al element in the coating layer of the polycrystalline particles is 1:1; based on the mass of the polycrystalline particles, the mass content of the coating layer of the polycrystalline particles is 0.2%.

[0115] Example 3-1

[0116] Basically the same as Example 1-1, except that: the preparation method of the polycrystalline particles in step S1 is changed;

[0117] The method for preparing polycrystalline particles in this embodiment includes the following steps:

[0118] S1: ① The polycrystalline particle precursor (chemical formula is LiNi 0.94 Mn 0.06 (OH)2) was prepared with lithium hydroxide, Al2O3, and ZrO2 in a molar ratio of 1:0.40:0.002:0.003 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 780°C for 15h under the condition of oxygen concentration >70%, and then crushed and sieved to obtain intermediate A, whose chemical formula is LiNi 0.935 Mn 0.06 Al 0.002 Zr 0.003 O2;

[0119] ② The intermediate A was thoroughly mixed with clean water at a mass ratio of 6:4, washed for 3 minutes, and then dried at 150°C for 120 minutes to obtain the core of the polycrystalline particles;

[0120] ③ The core of the polycrystalline particles was fully mixed with H3BO3 and Al2O3 in a mass ratio of 1:0.0015:0.0005 (H3BO3 and Al2O3 were calculated according to the mass of B element and Al element, respectively), and then calcined at 320 ° C for 8 h to obtain polycrystalline particles (polycrystalline positive electrode materials) with a volume average particle size Dv50 of 13 μm. The polycrystalline particles contained a uniform coating layer of Li3BO3 and an island coating layer of Al2O3+LiAlO2, as well as a core LiNi 0.935 Mn 0.06 Al 0.002 Zr 0.003O2; the molar ratio of Al element and Zr element in the inner core of the polycrystalline particles is 0.67:1, and the total mass content of Al element and Zr element in the inner core of the polycrystalline particles is 5000 ppm; the mass ratio of B element and Al element in the coating layer of the polycrystalline particles is 3:1; based on the mass of the polycrystalline particles, the mass content of the coating layer of the polycrystalline particles is 0.2%.

[0121] Example 4-1

[0122] Basically the same as Example 1-1, except that: the preparation method of the single crystal particles in step S2 is changed;

[0123] The method for preparing single crystal particles in this embodiment includes the following steps:

[0124] ① The single crystal particle precursor (chemical formula is LiNi 0.94 Mn 0.06 (OH)2) was prepared with lithium hydroxide, ZrO2, and Al2O3 in a molar ratio of 1:0.460:0.006:0.001 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 830 ° C for 14 h under the condition of oxygen concentration >70% and then crushed and sieved to obtain the core of the single crystal particle, whose chemical formula is LiNi 0.933 Mn 0.06 Al 0.001 Zr 0.006 O2;

[0125] ② After the core of the single crystal particle is fully mixed with Co(OH)2 and Al2O3 in a mass ratio of 1:0.01:0.0005 (Co(OH)2 and Al2O3 are calculated according to the mass of Co element and Al element respectively), the single crystal particle (single crystal positive electrode material) is obtained after calcination at 680℃ for 7h. The volume average particle size Dv50 is 3μm. The single crystal particle contains LiCoO2, Al2O3, LiAlO2 coating layer and core LiNi 0.933 Mn 0.06 Al 0.001 Zr 0.006 The molar ratio of the Zr element to the Al element in the core of the single crystal particle is 6:1, and the total mass content of the Zr element and the Al element in the core of the single crystal particle is 7000 ppm; the mass content of the Co element in the single crystal particle is 1%.

[0126] Example 4-2

[0127] The preparation method of the positive electrode material comprises the following steps:

[0128] ① The single crystal particle precursor (chemical formula is LiNi 0.94 Mn0.06 (OH)2) was prepared with lithium hydroxide, ZrO2, and Al2O3 in a molar ratio of 1:0.460:0.006:0.001 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 830 ° C for 14 h under the condition of oxygen concentration >70% and then crushed and sieved to obtain the core of the single crystal particle, whose chemical formula is LiNi 0.933 Mn 0.06 Al 0.001 Zr 0.006 O2;

[0129] ② After the core of the single crystal particle is fully mixed with Co(OH)2 and Al2O3 in a mass ratio of 1:0.01:0.0005 (Co(OH)2 and Al2O3 are calculated according to the mass of Co element and Al element respectively), the single crystal particle (single crystal positive electrode material) is obtained after calcination at 680℃ for 7h. The volume average particle size Dv50 is 3μm. The single crystal particle contains LiCoO2, Al2O3, LiAlO2 coating layer and core LiNi 0.933 Mn 0.06 Al 0.001 Zr 0.006 The molar ratio of the Zr element to the Al element in the core of the single crystal particle is 6:1, and the total mass content of the Zr element and the Al element in the core of the single crystal particle is 7000 ppm; the mass content of the Co element in the single crystal particle is 1%.

[0130] Example 5-1

[0131] Basically the same as Example 1-1, except that: the preparation method of the single crystal particles in step S2 is changed;

[0132] The method for preparing single crystal particles in this embodiment includes the following steps:

[0133] ① The single crystal particle precursor (chemical formula is LiNi 0.94 Mn 0.06 (OH)2) was prepared with lithium hydroxide, ZrO2, and Al2O3 in a molar ratio of 1:0.460:0.003:0.001 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 830 ° C for 14 h under the condition of oxygen concentration >70% and then crushed and sieved to obtain the core of the single crystal particle, whose chemical formula is LiNi 0.936 Mn 0.06 Al 0.001 Zr 0.003 O2;

[0134] ② After the core of the single crystal particle is fully mixed with Co(OH)2 and Al2O3 in a mass ratio of 1:0.08:0.001 (Co(OH)2 and Al2O3 are calculated according to the mass of Co element and W element respectively), the single crystal particle (single crystal positive electrode material) is obtained after calcination at 680℃ for 7h. The volume average particle size Dv50 is 3μm. The single crystal particle contains LiCoO2, Al2O3, LiAlO2 coating layer and core LiNi 0.936 Mn 0.06 Al 0.001 Zr 0.003 The molar ratio of the Zr element to the Al element in the core of the single crystal particle is 3:1, and the total mass content of the Zr element and the Al element in the core of the single crystal particle is 6000 ppm; the mass content of the Co element in the single crystal particle is 8%.

[0135] Example 5-2

[0136] The preparation method of the positive electrode material comprises the following steps:

[0137] ① The single crystal particle precursor (chemical formula is LiNi 0.94 Mn 0.06 (OH)2) was prepared with lithium hydroxide, ZrO2, and Al2O3 in a molar ratio of 1:0.460:0.003:0.001 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 830 ° C for 14 h under the condition of oxygen concentration >70% and then crushed and sieved to obtain the core of the single crystal particle, whose chemical formula is LiNi 0.936 Mn 0.06 Al 0.001 Zr 0.003 O2;

[0138] ② After the core of the single crystal particle is fully mixed with Co(OH)2 and Al2O3 in a mass ratio of 1:0.08:0.001 (Co(OH)2 and Al2O3 are calculated according to the mass of Co element and W element respectively), the single crystal particle (single crystal positive electrode material) is obtained after calcination at 680℃ for 7h. The volume average particle size Dv50 is 3μm. The single crystal particle contains LiCoO2, Al2O3, LiAlO2 coating layer and core LiNi 0.936 Mn 0.06 Al 0.001 Zr 0.003 The mass ratio of the Zr element to the Al element in the core of the single crystal particle is 3:1, and the total mass content of the Zr element and the Al element in the core of the single crystal particle is 6000 ppm; the mass content of the Co element in the single crystal particle is 8%.

[0139] Example 6-1

[0140] The preparation method of the positive electrode material comprises the following steps:

[0141] S1: ① The polycrystalline particle precursor (chemical formula is LiNi 0.92 Co 0.05 Mn 0.03 (OH)2) was prepared with lithium hydroxide, Al2O3, and ZrO2 in a molar ratio of 1:0.40:0.001:0.003 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 760°C for 15h under the condition of oxygen concentration >70%, and then crushed and sieved to obtain intermediate A, whose chemical formula is LiNi 0.916 Co 0.050 Mn 0.030 Al 0.001 Zr 0.003 O2;

[0142] ② The intermediate A was thoroughly mixed with clean water at a mass ratio of 6:4, washed for 3 minutes, and then dried at 150°C for 120 minutes to obtain the core of the polycrystalline particles;

[0143] ③ The core of the polycrystalline particles was fully mixed with H3BO3 and Al2O3 in a mass ratio of 1:0.001:0.001 (H3BO3 and Al2O3 were calculated according to the mass of B element and Al element, respectively), and then calcined at 300 ° C for 8 hours to obtain polycrystalline particles (polycrystalline positive electrode materials) with a volume average particle size Dv50 of 10 μm. The polycrystalline particles contained a uniform coating layer of Li3BO3 and an island coating layer of Al2O3+LiAlO2, as well as a core LiNi 0.916 Co 0.050 Mn 0.030 Al 0.001 Zr 0.003 O2; the molar ratio of Al element and Zr element in the core of the polycrystalline particles is 0.33:1, and the total mass content of Al element and Zr element in the core of the polycrystalline particles is 4000ppm; the mass ratio of B element and Al element in the coating layer of the polycrystalline particles is 1:1; based on the mass of the polycrystalline particles, the mass content of the coating layer of the polycrystalline particles is 0.2%.

[0144] S2: ① Single crystal particle precursor (chemical formula is LiNi 0.93 Co 0.05 Mn 0.02(OH)2) was prepared with lithium hydroxide, ZrO2, and Al2O3 in a molar ratio of 1:0.460:0.003:0.001 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 830 ° C for 14 h under the condition of oxygen concentration >70% and then crushed and sieved to obtain the core of the single crystal particle, whose chemical formula is LiNi 0.926 Co 0.050 Mn 0.020 Al 0.001 Zr 0.003 O2;

[0145] ② After the core of the single crystal particle is fully mixed with Co(OH)2 and Al2O3 in a mass ratio of 1:0.01:0.0005 (Co(OH)2 and Al2O3 are calculated according to the mass of Co element and Al element respectively), the single crystal particle (single crystal positive electrode material) is obtained after calcination at 680℃ for 7h. The volume average particle size Dv50 is 3μm. The single crystal particle contains LiCoO2, Al2O3, LiAlO2 coating layer and core LiNi 0.926 Co 0.050 Mn 0.020 Al 0.001 Zr 0.003 The molar ratio of the Zr element to the Al element in the core of the single crystal particle is 3:1, and the total mass content of the Zr element and the Al element in the core of the single crystal particle is 4000 ppm; the mass content of the Co element in the single crystal particle is 1%.

[0146] S3: The polycrystalline particles in step S1 and the single crystal particles in step S2 are mixed uniformly in a mass ratio of 7:3 to obtain a bimodal positive electrode material.

[0147] Example 7-1

[0148] The preparation method of the positive electrode material comprises the following steps:

[0149] S1: ① The polycrystalline particle precursor (chemical formula is LiNi 0.90 Co 0.05 Mn 0.05 (OH)2) was prepared with lithium hydroxide, Al2O3, and ZrO2 in a molar ratio of 1:0.40:0.001:0.003 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 760°C for 15h under the condition of oxygen concentration >70%, and then crushed and sieved to obtain intermediate A, whose chemical formula is LiNi 0.896 Co 0.050 Mn 0.050 Al 0.001 Zr0.003 O2;

[0150] ② The intermediate A was thoroughly mixed with clean water at a mass ratio of 6:4, washed for 3 minutes, and then dried at 150°C for 120 minutes to obtain the core of the polycrystalline particles;

[0151] ③ The core of the polycrystalline particles was fully mixed with H3BO3 and Al2O3 in a mass ratio of 1:0.001:0.001 (H3BO3 and Al2O3 were calculated according to the mass of B element and Al element, respectively), and then calcined at 300 ° C for 8 hours to obtain polycrystalline particles (polycrystalline positive electrode materials) with a volume average particle size Dv50 of 10 μm. The polycrystalline particles contained a uniform coating layer of Li3BO3 and an island coating layer of Al2O3+LiAlO2, as well as a core LiNi 0.896 Co 0.050 Mn 0.050 Al 0.001 Zr 0.003 O2; the molar ratio of Al element and Zr element in the core of the polycrystalline particles is 0.33:1, and the total mass content of Al element and Zr element in the core of the polycrystalline particles is 4000ppm; the mass ratio of B element and Al element in the coating layer of the polycrystalline particles is 1:1; based on the mass of the polycrystalline particles, the mass content of the coating layer of the polycrystalline particles is 0.2%.

[0152] S2: ① Single crystal particle precursor (chemical formula is LiNi 0.93 Co 0.05 Mn 0.02 (OH)2) was prepared with lithium hydroxide, ZrO2, and Al2O3 in a molar ratio of 1:0.460:0.003:0.001 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 830 ° C for 14 h under the condition of oxygen concentration >70% and then crushed and sieved to obtain the core of the single crystal particle, whose chemical formula is LiNi 0.926 Co 0.050 Mn 0.020 Al 0.001 Zr 0.003 O2;

[0153] ② After the core of the single crystal particle is fully mixed with Co(OH)2 and Al2O3 in a mass ratio of 1:0.01:0.0005 (Co(OH)2 and Al2O3 are calculated according to the mass of Co element and Al element respectively), the single crystal particle (single crystal positive electrode material) is obtained after calcination at 680℃ for 7h. The volume average particle size Dv50 is 3μm. The single crystal particle contains LiCoO2, Al2O3, LiAlO2 coating layer and core LiNi 0.926 Co 0.050Mn 0.020 Al 0.001 Zr 0.003 The molar ratio of the Zr element to the Al element in the core of the single crystal particle is 3:1, and the total mass content of the Zr element and the Al element in the core of the single crystal particle is 4000 ppm; the mass content of the Co element in the single crystal particle is 1%.

[0154] S3: The polycrystalline particles in step S1 and the single crystal particles in step S2 are mixed uniformly in a mass ratio of 7:3 to obtain a bimodal positive electrode material.

[0155] Comparative Example 1-1

[0156] The preparation method of the positive electrode material comprises the following steps:

[0157] S1: ① The polycrystalline particle precursor (chemical formula is LiNi 0.94 Mn 0.06 (OH)2) and lithium hydroxide were prepared in a molar ratio of 1:0.480 and mixed evenly. The mixture was calcined at 780°C for 15h under an oxygen concentration of >70% and then crushed and sieved to obtain intermediate A, whose chemical formula is LiNi 0.94 Mn 0.06 O2;

[0158] ② The intermediate A was thoroughly mixed with clean water at a mass ratio of 6:4, washed for 3 minutes, and then dried at 150°C for 120 minutes to obtain the core of the polycrystalline particles;

[0159] ③ The core of the polycrystalline particles was fully mixed with H3BO3 and Al2O3 in a mass ratio of 1:0.001:0.001 (H3BO3 and Al2O3 were calculated according to the mass of B element and Al element, respectively), and then calcined at 300 ° C for 8 hours to obtain polycrystalline particles (polycrystalline positive electrode materials) with a volume average particle size Dv50 of 13 μm. The polycrystalline particles contained a uniform coating layer of Li3BO3 and an island coating layer of Al2O3+LiAlO2, as well as a core LiNi 0.94 Mn 0.06 O2; the mass ratio of the B element and the Al element in the coating layer of the polycrystalline particles is 1:1; based on the mass of the polycrystalline particles, the mass content of the coating layer of the polycrystalline particles is 0.2%.

[0160] S2: ① The single crystal particle precursor (chemical formula is LiNi 0.94 Mn 0.06 (OH)2) and lithium hydroxide were prepared in a molar ratio of 1:0.460 and mixed evenly. The mixture was calcined at 830 ° C for 14 h under an oxygen concentration of >70% and then crushed and sieved to obtain the core of the single crystal particles, whose chemical formula is LiNi 0.94 Mn0.06 O2;

[0161] ② After the core of the single crystal particle is fully mixed with Co(OH)2 and Al2O3 in a mass ratio of 1:0.01:0.0005 (Co(OH)2 and Al2O3 are calculated according to the mass of Co element and Al element respectively), the single crystal particle (single crystal positive electrode material) is obtained after calcination at 680℃ for 7h. The volume average particle size Dv50 is 3μm. The single crystal particle contains LiCoO2, Al2O3, LiAlO2 coating layer and core LiNi 0.94 Mn 0.06 O2. The mass content of Co element in the single crystal particles is 1%.

[0162] S3: The polycrystalline particles in step S1 and the single crystal particles in step S2 are mixed in a mass ratio of 7:3 to obtain a bimodal positive electrode material, which includes a chemical formula of LiNi 0.94 Mn 0.06 O2 material.

[0163] Comparative Example 1-2

[0164] The preparation method of the positive electrode material comprises the following steps:

[0165] ① The single crystal particle precursor (chemical formula is LiNi 0.94 Mn 0.06 (OH)2) and lithium hydroxide were prepared in a molar ratio of 1:0.460 and mixed evenly. The mixture was calcined at 830 ° C for 14 h under an oxygen concentration of >70% and then crushed and sieved to obtain the core of the single crystal particles, whose chemical formula is LiNi 0.94 Mn 0.06 O2;

[0166] ② After the core of the single crystal particle is fully mixed with Co(OH)2 and Al2O3 in a mass ratio of 1:0.01:0.0005 (Co(OH)2 and Al2O3 are calculated according to the mass of Co element and Al element respectively), the single crystal particle (single crystal positive electrode material) is obtained after calcination at 680℃ for 7h. The volume average particle size Dv50 is 3μm. The single crystal particle contains LiCoO2, Al2O3, LiAlO2 coating layer and core LiNi 0.94 Mn 0.06 O2. The mass content of Co element in the single crystal particles is 1%.

[0167] Comparative Example 2-1

[0168] The preparation method of the positive electrode material comprises the following steps:

[0169] S1: ① The polycrystalline particle precursor (chemical formula is LiNi0.94 Mn 0.06 (OH)2) was prepared with lithium hydroxide, Al2O3, and ZrO2 in a molar ratio of 1:0.40:0.002:0.003 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 780°C for 15h under the condition of oxygen concentration >70%, and then crushed and sieved to obtain intermediate A, whose chemical formula is LiNi 0.935 Mn 0.06 Al 0.002 Zr 0.003 O2;

[0170] ② Intermediate A was thoroughly mixed with clean water at a mass ratio of 6:4, washed for 3 minutes, and then dried at 150°C for 120 minutes to obtain intermediate B;

[0171] ③ The intermediate B was calcined at 300℃ for 8h to obtain polycrystalline LiNi particles. 0.935 Mn 0.06 Al 0.002 Zr 0.003 The volume average particle size Dv50 of the polycrystalline particles was 13 μm. The molar ratio of Al to Zr in the core of the polycrystalline particles was 0.67:1, and the total mass content of Al and Zr in the core of the polycrystalline particles was 5000 ppm.

[0172] S2: ① The single crystal particle precursor (chemical formula is LiNi 0.94 Mn 0.06 (OH)2) was prepared with lithium hydroxide, ZrO2, and Al2O3 in a molar ratio of 1:0.460:0.003:0.001 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 830°C for 14h under the condition of oxygen concentration >70%, and then crushed and sieved to obtain intermediate A, whose chemical formula is LiNi 0.936 Mn 0.06 Al 0.001 Zr 0.003 O2; ② calcining the intermediate A at 680℃ for 7h to obtain single crystal particles of LiNi 0.936 Mn 0.06 Al 0.001 Zr 0.003 O2, with a volume average particle size Dv50 of 3 μm. The molar ratio of Zr element to Al element in the core of the single crystal particle is 3:1, and the total mass content of Zr element and Al element in the core of the single crystal particle is 4000 ppm.

[0173] S3: The polycrystalline particles in step S1 and the single crystal particles in step S2 are mixed uniformly in a mass ratio of 7:3 to obtain a bimodal positive electrode material.

[0174] Comparative Example 2-2

[0175] The preparation method of the positive electrode material comprises the following steps:

[0176] ① The single crystal particle precursor (chemical formula is LiNi 0.94 Mn 0.06 (OH)2) was prepared with lithium hydroxide, ZrO2, and Al2O3 in a molar ratio of 1:0.460:0.003:0.001 (Al2O3 and ZrO2 were calculated according to the molar amount of Al and Zr respectively) and then mixed evenly. The mixture was calcined at 830°C for 14h under the condition of oxygen concentration >70%, and then crushed and sieved to obtain intermediate A, whose chemical formula is LiNi 0.936 Mn 0.06 Al 0.001 Zr 0.003 O2; ② calcining the intermediate A at 680 ° C for 7 h to obtain single crystal particles (single crystal positive electrode material) LiNi 0.936 Mn 0.06 Al 0.001 Zr 0.003 O2, with a volume average particle size Dv50 of 3 μm. The molar ratio of Zr element to Al element in the core of the single crystal particle is 3:1, and the total mass content of Zr element and Al element in the core of the single crystal particle is 4000 ppm.

[0177] Comparative Example 3-1

[0178] The preparation method of the positive electrode material comprises the following steps:

[0179] S1: ① Polycrystalline particle precursor (chemical formula LiNi 0.94 Mn 0.06 (OH)2) and lithium hydroxide were prepared in a molar ratio of 1:0.480 and mixed evenly. The mixture was calcined at 780°C for 15h under an oxygen concentration of >70% and then crushed and sieved to obtain intermediate A, whose chemical formula is LiNi 0.94 Mn 0.06 O2; ② Intermediate A was fully mixed with clean water at a mass ratio of 6:4 and washed for 3 minutes, then dried at 150°C for 120 minutes to obtain intermediate B; ③ Intermediate B was calcined at 300°C for 8 hours to obtain polycrystalline LiNi particles 0.94 Mn 0.06 O2, whose volume average particle size Dv50 is 13 μm;

[0180] S2: ① The single crystal particle precursor (chemical formula is LiNi0.94 Mn 0.06 (OH)2) and lithium hydroxide were prepared in a molar ratio of 1:0.460 and mixed evenly. The mixture was calcined at 830°C for 14h under an oxygen concentration of >70% and then crushed and sieved to obtain intermediate A, whose chemical formula is LiNi 0.94 Mn 0.06 O2; ② calcining the intermediate A at 680℃ for 7h to obtain single crystal particles of LiNi 0.94 Mn 0.06 O2, whose volume average particle size Dv50 is 3 μm;

[0181] S3: The polycrystalline particles in step S1 and the single crystal particles in step S2 are mixed uniformly in a mass ratio of 7:3 to obtain a bimodal positive electrode material.

[0182] Comparative Example 3-2

[0183] The preparation method of the positive electrode material comprises the following steps:

[0184] ① The single crystal particle precursor (chemical formula is LiNi 0.94 Mn 0.06 (OH)2) and lithium hydroxide were prepared in a molar ratio of 1:0.460 and mixed evenly. The mixture was calcined at 830°C for 14h under an oxygen concentration of >70% and then crushed and sieved to obtain intermediate A, whose chemical formula is LiNi 0.94 Mn 0.06 O2;

[0185] ② Calcinate intermediate A at 680℃ for 7h to obtain single crystal LiNi particles 0.94 Mn 0.06 O2, whose volume average particle size Dv50 is 3 μm.

[0186] The components of the positive electrode materials prepared in each embodiment and each comparative example were measured using an ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy) tester.

[0187] The volume average particle size Dv50 of the positive electrode materials prepared in each embodiment and each comparative example was measured using a particle size tester.

[0188] Battery assembly and electrochemical performance testing

[0189] The positive electrode materials prepared in each example and comparative example were fabricated into positive electrode sheets. The materials were prepared in a mass ratio of positive electrode material: conductive agent super carbon black: PVDF (polyvinylidene fluoride) = 96.5:2:1.5. These positive electrode sheets were assembled into LR2032 button-type batteries, and the rate performance and high-temperature cycling performance were tested. The test results are shown in Tables 1 and 2 and Figure 3.

[0190] The test conditions for the rate performance of button batteries are: 25℃, 0.1C charge, 1C discharge, and an operating voltage of 2.5V to 4.25V vs.Li + / Li; 1C / 0.1C rate (%) = discharge capacity at 1C / charge capacity at 0.1C × 100%;

[0191] 25℃, 0.1C charge, 3C discharge, operating voltage is 2.5V~4.25V vs.Li + / Li; 3C / 0.1C rate (%) = discharge specific capacity at 3C / charge specific capacity at 0.1C × 100%.

[0192] The high temperature cycle performance test conditions of button batteries are: 45℃, battery charging at 0.5C, discharging at 0.5C, cycle 100 cycles, working voltage 2.5V~4.25V vs.Li + / Li, 100-week capacity retention rate (%) = 100th-week discharge capacity / 1st-week discharge capacity × 100%

[0193] Table 1

[0194] Table 2

[0195] Figure 1 is a SEM image of the positive electrode material prepared in Example 1-1. As can be seen from Figure 1, the positive electrode material of Example 1-1 contains both single crystal particles and polycrystalline particles, and the particle size of the single crystal particles is relatively small. Figure 2 is an XRD pattern of the positive electrode material prepared in Example 1-1. As can be seen from Figure 2, the positive electrode material of Example 1-1 does not contain any impurity phases.

[0196] As can be seen from Table 1 and Figure 3, compared with the batteries of Comparative Example 1-1, Comparative Example 2-1, and Comparative Example 3-1, the batteries of Examples 1-1 to 7-1 of the present application have better rate performance and high temperature performance; as can be seen from Table 2, compared with the batteries of Comparative Example 1-2, Comparative Example 2-2, and Comparative Example 3-2, the batteries of Examples 1-2, 4-2, and 5-2 of the present application have better rate performance and cycle performance. Since the cores of the positive electrode materials of Comparative Example 1-1 and Comparative Example 1-2 are not doped with specific elements, the stability of the layered structure of the positive electrode materials formed is poor, and the high temperature cycle retention rate is significantly reduced; at the same time, due to the absence of doping elements, no Li+ is formed between the grain boundaries. + Conductor, Li +The transmission speed decreases, and the 1C and 3C rate performances decrease; since the positive electrode materials prepared in Comparative Examples 2-1 and 2-2 are not coated with specific elements, no fast ion transmission area is formed on the surface of the positive electrode materials, and the 3C rate performance deteriorates significantly. At the same time, since there is no coating layer, the interface damage is aggravated during the high-temperature cycle, resulting in a significant deterioration in the high-temperature cycle retention rate; since the positive electrode materials prepared in Comparative Examples 3-1 and 3-2 are not doped with specific elements and no interface coating is performed, the structural stability and interface stability of the materials are greatly deteriorated, and the rate performance and high-temperature cycle performance are significantly reduced.

[0197] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0198] The above-described embodiments merely represent several implementation methods of the present application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims, and the specification may be used to interpret the content of the claims.

Claims

1. A positive electrode material, characterized in that It comprises a core and a coating layer covering at least a portion of the surface of the core, wherein the core comprises a chemical formula of LiNi a Co b Mn c Q d O2 material, wherein the Q element includes at least one of Zr and Al, 0.89≤a≤0.98, 0≤b≤0.06, 0≤c<0.11, d>0, a+b+c+d=1, and the coating layer includes a chemical formula of Li m Co n X (1-n) O2 material, wherein the X element includes at least one of Al, W, Ti, B and La, 0<m≤1, 0<n≤1.

2. The positive electrode material according to claim 1, characterized in that The positive electrode material has at least one of the following characteristics (1) to (3): (1) The Q element further includes at least one of Sr, Ti, Sb, W, Nb, Y, Mo, Ta, La, B, P and S; (2)(1-n) / n<0.2; (3) The coating layer also includes a chemical formula of Li m’ X'O2 material, wherein the X' element includes at least one of Al, W, Ti, B and La, and 0<m'≤1.

3. The positive electrode material according to claim 1, characterized in that The positive electrode material includes single crystal particles, the core of which includes a chemical formula of LiNi a1 Co b1 Mn c1 Q1 d1 Q2 d2 O2 material, wherein the Q1 element includes Zr, the Q2 element includes at least one of Al, Sr, W, Nb, La and Sb, 0.89≤a1≤0.98, 0≤b1≤0.06, 0≤c1<0.11, d1>0, d2≥0, a1+b1+c1+d1+d2=1; The coating layer of the single crystal particle includes a chemical formula of Li m1 Co n1 X1 (1-n1) O2 material, wherein the X1 element includes at least one of Al, W, Ti and B, 0<m1≤1, 0<n1≤1; Optionally, the volume average particle size Dv50 of the single crystal particles is 2 μm to 6 μm.

4. The positive electrode material according to claim 3, characterized in that The positive electrode material has at least one of the following characteristics (1) to (4): (1) The core of the single crystal particle contains Q2 element, and the molar ratio of Q1 element to Q2 element in the core of the single crystal particle is (1-6):1, and can be (1-5):1; (2) The sum of the mass contents of the Q1 element and the Q2 element in the core of the single crystal particle is 3000 ppm to 6000 ppm; (3)(1-n1) / n1<0.2; (4) The mass content of the Co element in the single crystal particles is ≤8%, and can be optionally ≤6%.

5. The positive electrode material according to claim 3, characterized in that The coating layer of the single crystal particle further comprises a material having a chemical formula of LiX2O2, wherein the X2 element comprises at least one of Al, W, Ti and B; Optionally, the total mass content of the Co element and the X2 element in the coating layer of the single crystal particle is 0.5% to 3%.

6. The positive electrode material according to any one of claims 1 to 5, characterized in that The positive electrode material also includes polycrystalline particles; Optionally, the ratio of the volume average particle size Dv50 of the polycrystalline particles to the volume average particle size Dv50 of the single crystal particles is (3-5.5):1; Optionally, the mass proportion of the single crystal particles in the positive electrode material is 20% to 80%; Optionally, the volume average particle size Dv50 of the polycrystalline particles is 9 μm to 15 μm.

7. The positive electrode material according to claim 6, characterized in that The core of the polycrystalline particle comprises a chemical formula of LiNi a2 Co b2 Mn c2 Q3 d3 Q4 d4 O2 material, wherein Q3 element includes Al, Q4 element includes at least one of Zr, Sr, Sb, W, Y, Ta, Nb, B, P and S, 0.89≤a2≤0.98, 0≤b2≤0.06, 0≤c2<0.11, d3>0, d4≥0, a2+b2+c2+d3+d4=1; The coating layer of the polycrystalline particles includes a chemical formula of Li m2 X3 n2 X4 (1-n2) O2 materials, wherein X3 elements include B, X4 elements Including at least one of Al, W, Ti and La, 0<m2≤1, 0<n2<1; Optionally, based on the mass of the polycrystalline particles, the mass content of the coating layer of the polycrystalline particles is 0.1% to 0.5%; Optionally, the core of the polycrystalline particle contains Q4 element, and the molar ratio of Q3 element to Q4 element in the core of the polycrystalline particle is (0.22-5):1, and can further be (0.22-4):1; Optionally, the total mass content of the Q3 element and the Q4 element in the core of the polycrystalline particle is 3500ppm to 12000ppm; Optionally, the mass ratio of the X3 element to the X4 element in the coating layer of the polycrystalline particles is (0.25-3):1, and can further be (0.25-2):

1.

8. A method for preparing a positive electrode material, characterized in that: The steps include: Mixing a positive electrode material precursor, a lithium source and a compound containing a Q element, and performing a first calcination to obtain a core; the Q element includes at least one of Zr and Al; The core is mixed with a compound containing an X element, and subjected to a second calcination to form a coating layer on at least a portion of the surface of the core, thereby obtaining the positive electrode material; the X element comprises at least one of Al, W, Ti, B and La; The positive electrode material includes the core and the coating layer, and the core includes a chemical formula of LiNi a Co b Mn c Q d O2 material, wherein 0.89≤a≤0.98, 0≤b≤0.06, 0≤c<0.11, d>0, a+b+c+d=1, the coating layer includes a chemical formula of Li m Co n X (1-n) O2 material, wherein 0<m≤1, 0<n≤1.

9. A positive electrode plate, characterized in that: The invention comprises at least one of the positive electrode materials according to any one of claims 1 to 7 and the positive electrode material prepared by the preparation method according to claim 8.

10. A secondary battery, characterized in that: Including the positive electrode sheet according to claim 9.

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