High-nickel positive electrode material, and preparation method therefor and use thereof

Abstract

The present application provides a high-nickel positive electrode material, and a preparation method therefor and a use thereof. The high-nickel positive electrode material of the present application can effectively control the overall Co content of secondary particles, so as to prevent a decrease in the capacity per gram of a lithium-ion battery caused by an excessively high overall Co content of the secondary particles, thereby affecting the energy density; and the material can also effectively suppress the permeation and diffusion of an electrolyte, resist the erosion of the electrolyte to the interior of the high-nickel positive electrode material, and prevent the electrolyte from reacting with an active substance inside the high-nickel positive electrode material, thereby improving the structural stability of the high-nickel positive electrode material, and finally improving the cycle performance of the lithium-ion battery.

Description

High-nickel positive electrode material and preparation method and application thereof

[0001] The present application claims priority to the Chinese patent application No. 202411390258.7, filed on September 30, 2024, and entitled "High-nickel positive electrode material and preparation method and application thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application belongs to the technical field of lithium ion batteries, and specifically relates to a high-nickel positive electrode material and a preparation method and application thereof. BACKGROUND

[0003] The rapid development of the electric vehicle market has led to an increasing demand for batteries, among which high-nickel positive electrode materials are widely used in lithium ion batteries due to their high energy density and low cost advantages. However, the high-nickel positive electrode material is structurally unstable during the charging and discharging process due to the oxidation and reduction reaction of nickel elements, which affects the cycle stability of the battery. In addition, a large amount of residual alkali is often produced during the preparation of high-nickel positive electrode materials, and the reaction of these residual alkalis with electrolyte will cause capacity decay and safety problems of the battery.

[0004] To solve the above problems, water washing process is usually used to remove residual alkali in high-nickel positive electrode materials, and doping and coating methods are used to improve the structural stability of high-nickel positive electrode materials and reduce their side reactions with electrolyte. For example, Zr, Ti, Al, Y, Sr and other dopants are added to improve the structural stability of high-nickel positive electrode materials, and Al, B, Ce, P, F, Cl, Br and other coating agents are added to reduce the side reactions of high-nickel positive electrode materials with electrolyte. Although this solves the problem of cycle stability of high-nickel positive electrode materials to some extent, there are still some other problems. First, water washing process can effectively remove residual alkali, but it will cause a loss of part of the active material, resulting in a decrease in the energy density of the battery. Second, although doping and coating can improve the stability of high-nickel positive electrode materials to some extent, in actual use, due to the high surface reactivity of high-nickel materials, the penetration and diffusion of electrolyte easily lead to a large number of side reactions on the surface of high-nickel positive electrode materials, which causes the active material inside the positive electrode material to be not fully utilized, thereby affecting the cycle performance of the battery.

[0005] SUMMARY

[0006] The present application provides a high-nickel positive electrode material, which can improve the specific capacity of lithium ion batteries, thereby improving the energy density, and also can improve the structural stability of high-nickel positive electrode materials, ultimately improving the cycle performance of lithium ion batteries.

[0007] The application provides a preparation method of the high-nickel positive electrode material, which is simple in operation, free of water washing process, and capable of effectively removing residual alkali in the high-nickel positive electrode material, so as to avoid loss of part of active substances and decrease of energy density of the battery, and further improve the cycle performance of the high-nickel positive electrode material by improving sintering and coating conditions, so as to improve the utilization rate of active substances in the secondary particles while ensuring the structural stability of the high-nickel positive electrode material, thereby improving the cycle performance of the battery.

[0008] The application also provides a lithium ion battery comprising the high-nickel positive electrode material or the high-nickel positive electrode material prepared by the preparation method, which has excellent specific capacity and cycle performance.

[0009] The application provides a high-nickel positive electrode material, wherein the high-nickel positive electrode material is a secondary particle formed by agglomeration of primary particles, the ratio of the surface Co content to the central Co content of the primary particles located on the surface of the secondary particle is M1, the ratio of the surface Co content to the central Co content of the primary particles located from the surface of the secondary particle to 1 / 2 of the spherical core of the secondary particle is M2, the ratio of the surface Co content to the central Co content of the primary particles located at the spherical core of the secondary particle is M3, M1>M2>M3, M1 is greater than or equal to 2, M2 is greater than or equal to 1.5, and M3 is greater than or equal to 1.1.

[0010] The high-nickel positive electrode material as described above, wherein the chemical formula of the high-nickel positive electrode material is Li y Ni a Co b Mn c O2,

[0011] 0.98≤y≤1.10, 0.6≤a≤0.98, 0≤b≤0.4, and 0≤c≤0.4.

[0012] The high-nickel positive electrode material as described above, wherein the chemical formula of the high-nickel positive electrode material is Li y Ni a Co b Mn c A1 d B1 e O2,

[0013] 0.98≤y≤1.10, 0.6≤a≤0.98, 0≤b≤0.4, 0≤c≤0.4, 1.001≤d≤0.1, and 0.001≤e≤0.1.

[0014] A1 is at least one of Zr, Ti, Al, Y, and Sr;

[0015] B1 is at least one of Al, B, Ce, P, F, Cl, and Br.

[0016] The high-nickel positive electrode material as described above, wherein the central Co content of the primary particles located on the surface of the secondary particles > the central Co content of the primary particles located from the surface of the secondary particles to 1 / 2 of the center of the secondary particle > the central Co content of the primary particles located at the center of the secondary particle.

[0017] The high-nickel positive electrode material as described above, wherein the average grain size of the primary particles is 150-350 nm.

[0018] And / or, the particle size D50 of the secondary particles is 7.5-12.5 μm.

[0019] And / or, the average particle pressure resistance of the secondary particles is 50-200 MPa.

[0020] The high-nickel positive electrode material as described above, wherein the high-nickel positive electrode material is detected by X-ray photoelectron spectroscopy XPS and inductively coupled plasma emission spectroscopy ICP-OES to obtain Co XPS , Ni XPS , Co ICP and Ni ICP ; Co XPS , Ni XPS , Co ICP and Ni ICP satisfy the relationship formula of formula 1:

[0021] Wherein, Co XPS is the surface Co content of the secondary particles; Ni XPS is the surface Ni content of the secondary particles; Co ICP is the total Co content of the secondary particles; Ni ICP is the total Ni content of the secondary particles.

[0022] And / or, the high-nickel positive electrode material is obtained by X-ray diffraction XRD to obtain the diffraction peak intensity I003 of the (003) plane and the diffraction peak intensity I104 of the (104) plane, and I003 / I104 is 1.8-3.0.

[0023] The application provides a preparation method of the above high-nickel positive electrode material, comprising the following steps:

[0024] The precursor Ni a Co b Mn c (OH)2 and a lithium source are mixed to perform first sintering to obtain first sintered material, and the first sintered material is crushed to obtain first crushed material with a particle size D50 of 7.5-12.5 μm.

[0025] The first crushed material and a Co source are mixed to perform second sintering to obtain the high-nickel positive electrode material.

[0026] 0.6≤a≤0.98, 0≤b≤0.4, 0≤c≤0.4;

[0027] The second sintering temperature is 540-640℃, and the second sintering time satisfies the relationship of formula 2:

[0028] Wherein, t is the second sintering time, h; D is the average grain size of the primary particles of the first crushed material, nm; D50 is the particle size D50 of the secondary particles of the first crushed material, μm; T is the second sintering temperature, ℃.

[0029] The preparation method as described above, wherein the first sintering temperature is 750-900℃, and the first sintering time is 8-15h.

[0030] The preparation method as described above, wherein before the first sintering, further comprising mixing the precursor Ni a Co b Mn c (OH)2, a lithium source and an A1 dopant;

[0031] The second sintering further comprises obtaining a second sintered material after the second sintering; mixing the second sintered material and a B1 coating agent to perform a third sintering, to obtain the high-nickel positive electrode material;

[0032] The A1 dopant comprises at least one of a Zr source, a Ti source, an Al source, a Y source and a Sr source;

[0033] The B1 coating agent comprises at least one of an Al source, a B source, a Ce source, a P source, a F source, a Cl source and a Br source;

[0034] The third sintering temperature is 240-340℃, and the third sintering time is 4-15h.

[0035] The application further provides a lithium ion battery comprising the high-nickel positive electrode material or the high-nickel positive electrode material prepared by the preparation method.

[0036] The application provides a high-nickel positive electrode material, when the position of a primary particle is closer to the center of a secondary particle, the ratio of the Co content on the surface of the primary particle to the Co content at the center of the primary particle is smaller, the high-nickel positive electrode material can effectively control the Co content of the whole secondary particle, to avoid the decrease of the gram capacity of the lithium ion battery caused by the too high Co content of the whole secondary particle, and further affect the energy density, can also effectively inhibit the penetration and diffusion of the electrolyte, avoid the active substance in the high-nickel positive electrode material from being not fully utilized, and further improve the structural stability of the high-nickel positive electrode material, and finally improve the cycle performance of the lithium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0037] FIG. 1 is a whole TEM image of the high-nickel positive electrode material in Example 1;

[0038] Figure 2 is a partial TEM image of the surface of a secondary particle in the high-nickel positive electrode material in Example 1;

[0039] Figure 3 is an EDS surface distribution map of Zr element located on the surface of a secondary particle in the high-nickel positive electrode material in Example 1;

[0040] Figure 4 is an EDS surface distribution map of Al element located on the surface of a secondary particle in the high-nickel positive electrode material in Example 1;

[0041] Figure 5 is an EDS surface distribution map of Co element located on the surface of a secondary particle in the high-nickel positive electrode material in Example 1;

[0042] Figure 6 is a partial TEM image of the core of a secondary particle in the high-nickel positive electrode material in Example 1;

[0043] Figure 7 is an EDS surface distribution map of Zr element located on the core of a secondary particle in the high-nickel positive electrode material in Example 1;

[0044] Figure 8 is an EDS surface distribution map of Al element located on the core of a secondary particle in the high-nickel positive electrode material in Example 1;

[0045] Figure 9 is an EDS surface distribution map of Co element located on the core of a secondary particle in the high-nickel positive electrode material in Example 1. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0047] The first aspect of the present application provides a high-nickel positive electrode material, which is a secondary particle formed by agglomeration of primary particles. The ratio of the surface Co content to the central Co content of the primary particles located on the surface of the secondary particle is M1; the ratio of the surface Co content to the central Co content of the primary particles located from the surface of the secondary particle to 1 / 2 of the core of the secondary particle is M2; the ratio of the surface Co content to the central Co content of the primary particles located on the core of the secondary particle is M3; M1>M2>M3; M1≥2, M2≥1.5, and M3≥1.1.

[0048] The high-nickel positive electrode material of the present application is a secondary particle formed by agglomeration of primary particles. The primary particle refers to a single fine grain. Such a grain generally has a large surface energy and is therefore prone to agglomeration due to weak interaction forces, thereby forming a secondary particle.

[0049] High-nickel cathode materials have the advantages of high energy density and high capacity in lithium ion batteries, but also have problems such as poor cycle stability and low safety. In order to improve the above problems, the high-nickel cathode material is generally subjected to surface coating treatment, and coating cobalt (Co) is a common method.

[0050] In the present application, M1, M2, and M3 of the high-nickel cathode material satisfy the above relationship, that is, the closer the position of the primary particle to the center of the secondary particle, the smaller the ratio of the surface Co content of the primary particle to the central Co content of the primary particle, and the ratio satisfies M1≥2, M2≥1.5, and M3≥1.1, which indicates that Co in the high-nickel cathode material of the present application is more accumulated on the surface of the primary particle and the surface of the secondary particle, and less distributed in the bulk phase. Therefore, compared with the cathode material in the prior art in which the Co concentration gradient from high to low is present from the surface to the center of the secondary particle, the present application can more effectively control the Co content of the whole secondary particle to avoid the decrease of the gram capacity of the lithium ion battery caused by the excessive Co content of the whole secondary particle, thereby affecting the energy density. At the same time, by the above relationship limitation, the penetration and diffusion of the electrolyte can also be effectively inhibited, the corrosion of the electrolyte to the internal active material of the high-nickel cathode material can be resisted, the reaction between the electrolyte and the internal active material of the high-nickel cathode material can be avoided, thereby improving the stability of the high-nickel cathode material, increasing the utilization rate of the internal active material of the high-nickel cathode material, and finally improving the gram capacity and cycle performance of the lithium ion battery.

[0051] It can be understood that M1, M2, and M3 satisfy M1≥2, M2≥1.5, and M3≥1.1, which means that the surface Co content of the primary particle located on the surface of the secondary particle is 2 times or more than the central Co content; the surface Co content of the primary particle located from the surface of the secondary particle to 1 / 2 of the center of the secondary particle is 1.5 times or more than the central Co content; and the surface Co content of the primary particle located at the center of the secondary particle is 1.1 times or more than the central Co content.

[0052] In one embodiment, the surface Co content of the primary particle located on the surface of the secondary particle is 8.1wt%, the central Co content is 3.4wt%, and M1 is 2.4; the surface Co content of the primary particle located from the surface of the secondary particle to 1 / 2 of the center of the secondary particle is 5.9wt%, the central Co content is 3.1wt%, and M2 is 1.9; and the surface Co content of the primary particle located at the center of the secondary particle is 3.7wt%, the central Co content is 3.0wt%, and M3 is 1.2.

[0053] In an alternative embodiment, the chemical formula of the high-nickel cathode material is Li y Ni a Co bMn c O2, wherein 0.98≤y≤1.10, 0.6≤a≤0.98, 0≤b≤0.4, 0≤c≤0.4.

[0054] By limiting the composition and proportion of the high-nickel positive electrode material, the specific capacity and energy density can be further improved, and the structural stability can be improved to improve the cycle performance.

[0055] In another alternative embodiment, the chemical formula of the high-nickel positive electrode material is Li y Ni a Co b Mn c A1 d B1 e O2, wherein 0.98≤y≤1.10, 0.6≤a≤0.98, 0≤b≤0.4, 0≤c≤0.4, 0.001≤d≤0.1, 0.001≤e≤0.1.

[0056] A1 is at least one of Zr, Ti, Al, Y, and Sr;

[0057] B1 is at least one of Al, B, Ce, P, F, Cl, and Br.

[0058] In the present application, in order to further improve the structural stability and cycle performance, the high-nickel positive electrode material can further include A1 doping elements and B1 coating layers. The use of A1 doping elements and the limitation of A1 doping elements selected from the above range can dope A1 doping elements into the positive electrode material body phase, thereby improving the particle pressure strength of the secondary particles, reducing the transition metal mixing, stabilizing the crystal structure, relieving the lattice contraction and expansion of the positive electrode material during the charging and discharging process, and improving the structural stability; the use of B1 coating layers and the limitation of B1 coating layers selected from the above range can play a protective role on the surface of the positive electrode material, slow down the side reaction of the electrolyte with the surface of the positive electrode material, and further improve the cycle performance of the lithium ion battery.

[0059] Therefore, by limiting the composition and proportion of the high-nickel positive electrode material to meet the above range, A1 doping elements and B1 coating layers can be introduced to further improve the structural stability and improve the cycle performance.

[0060] In a specific embodiment, the central Co content of the primary particles located on the surface of the secondary particles > the central Co content of the primary particles located from the surface of the secondary particles to 1 / 2 of the spherical center of the secondary particles > the central Co content of the primary particles located at the spherical center of the secondary particles.

[0061] The positive electrode material obtained by the above limitation of the present application, the closer the position of the primary particle to the center of the secondary particle, the smaller the Co content at the center of the primary particle. This not only can further control the overall Co content of the secondary particle to avoid the decrease of the gram capacity of the lithium ion battery caused by the too high overall Co content of the secondary particle, thereby affecting the energy density, but also can further inhibit the penetration and diffusion of the electrolyte, resist the corrosion of the electrolyte to the internal active material of the high-nickel positive electrode material, avoid the reaction between the electrolyte and the internal active material of the high-nickel positive electrode material, thereby improving the structural stability of the high-nickel positive electrode material, improving the utilization rate of the internal active material of the high-nickel positive electrode material, and ultimately improving the gram capacity and cycle performance of the lithium ion battery.

[0062] In the scheme of the present application, the average grain size of the primary particle is 150-350 nm;

[0063] And / or, the particle size D50 of the secondary particle is 7.5-12.5 μm;

[0064] And / or, the average particle pressure strength of the secondary particle is 50-200 MPa.

[0065] In the high-nickel positive electrode material, if the average grain size of the primary particle is too large, the lithium ion transmission speed will be too slow, affecting the cycle performance; if the average grain size of the primary particle is too small, the material sintering will be insufficient, the gram capacity will be low, and the particle pressure strength of the material will be low, the BET specific surface area will be large, affecting the cycle performance, therefore, the present application limits the average grain size of the primary particle to meet the above range, which can effectively balance the energy density and cycle performance of the high-nickel positive electrode material.

[0066] In the high-nickel positive electrode material, if the particle size D50 of the secondary particle is too large, the lithium ion in the material will not be fully removed, affecting the gram capacity; if the particle size of the secondary particle is too small, the BET specific surface area will be too large, affecting the cycle performance, therefore, the present application limits the particle size D50 of the secondary particle to meet the above range, which can balance the energy density and cycle performance of the high-nickel positive electrode material.

[0067] In addition, limiting the average particle pressure strength of the secondary particle to meet the above range is helpful to further improve the structural stability of the high-nickel positive electrode material, thereby improving the cycle performance.

[0068] In the scheme of the present application, the high-nickel positive electrode material is detected by X-ray photoelectron spectroscopy XPS and inductively coupled plasma emission spectroscopy ICP-OES to obtain Co XPS , Ni XPS , Co ICP and Ni ICP ; Co XPS , Ni XPS , Co ICP and Ni ICPsatisfy the relationship of formula 1:

[0069] wherein Co XPS is the surface Co content of the secondary particles; Ni XPS is the surface Ni content of the secondary particles; Co ICP is the total Co content of the secondary particles; Ni ICP is the total Ni content of the secondary particles;

[0070] and / or, the diffraction peak intensity I003 of the (003) plane and the diffraction peak intensity I104 of the (104) plane of the high-nickel positive electrode material obtained by X-ray diffraction (XRD) satisfy I003 / I104 of 1.8-3.0.

[0071] X-ray photoelectron spectroscopy (XPS) is a technology for measuring the energy distribution of photoelectrons and Auger electrons emitted from the surface of a sample when irradiated by X-rays using an electron spectrometer, and can be used for qualitative analysis and semi-quantitative analysis, and can obtain information such as the elemental composition, chemical state, and molecular structure of the sample surface from the peak position and peak shape of the XPS spectrum, and can obtain the elemental content or concentration of the sample surface from the peak intensity. Therefore, the high-nickel positive electrode material of the present application can obtain Co XPS representing the surface Co content of the secondary particles, in wt%; similarly, XPS detection can also obtain Ni XPS representing the surface Ni content of the secondary particles, in wt%.

[0072] Inductively coupled plasma optical emission spectrometry (ICP-OES) is a technology for atomic emission spectroscopy analysis using a light source generated by high-frequency inductively coupled plasma discharge, and is a flame technology with a flame temperature range of 6000 to 10000 K, and the emission intensity represents the concentration of elements in the sample. Therefore, the high-nickel positive electrode material of the present application can obtain Co ICP representing the total Co content of the secondary particles, in wt%; similarly, ICP-OES detection can also obtain Ni ICP representing the total Ni content of the secondary particles, in wt%.

[0073] When the Co XPS , Ni XPS , Co ICP and Ni ICPWhen the relationship of formula 1 is met, it indicates that the contents of Co and Ni in the high-nickel positive electrode material have a good matching effect, and the coating effect of Co on the surface of the secondary particles is good, so that the penetration and diffusion of the electrolyte can be effectively inhibited, thereby improving the interface stability of the high-nickel positive electrode material and improving the cycle performance of the lithium ion battery.

[0074] In addition, the Miller index is an index used to determine the direction of a crystal, also known as a crystal plane index. The present application can obtain the diffraction peak intensity I003 of the (003) plane and the diffraction peak intensity I104 of the (104) plane of the high-nickel positive electrode material in the Miller index through X-ray diffraction (XRD), and I003 / I104 can reflect the degree of mixing of Li + / Ni 2+ The degree of mixing of the cations, which is limited to the value meeting the above range, helps to further reduce the transition metal mixing and improve the cycle performance.

[0075] The second aspect of the present application provides a preparation method of the above high-nickel positive electrode material, comprising the following steps:

[0076] mixing the precursor Ni a Co b Mn c (OH)2 and a lithium source to obtain a first sintered material, crushing the first sintered material to obtain a first crushed material with a particle size D50 of 7.5-12.5 μm;

[0077] mixing the first crushed material and a Co source to perform a second sintering to obtain the high-nickel positive electrode material;

[0078] 0.6≤a≤0.98, 0≤b≤0.4, 0≤c≤0.4;

[0079] The second sintering temperature is 540-640℃, and the second sintering time meets the relationship of formula 2:

[0080] wherein t is the second sintering time, h; D is the average grain size of the primary particles of the first crushed material, nm; D50 is the particle size D50 of the secondary particles of the first crushed material, μm; and T is the second sintering temperature, ℃.

[0081] The preparation method described in this application is simple to operate and does not involve water washing. The introduction of a Co source effectively removes residual alkali from the high-nickel cathode material, preventing the loss of some active material and thus reducing the battery's energy density. Furthermore, by improving sintering conditions, a high-nickel cathode material with a specific Co concentration gradient is obtained, further improving the cycle performance of the high-nickel cathode material. While ensuring the structural stability of the high-nickel cathode material, the utilization rate of active material within the secondary particles is increased, thereby enhancing the battery's cycle performance. Firstly, the precursor Ni... a Co b Mn c The first sintered material is obtained by mixing (OH)2 with a lithium source and performing a first sintering. The first sintered material is then crushed and the D50 range is controlled to obtain a first crushed material. Subsequently, the first crushed material is mixed with a Co source and subjected to a second sintering to obtain a high-nickel cathode material. The above steps help to control the overall Co content of the secondary particles to improve the specific capacity and energy density of the lithium-ion battery, and suppress the penetration and diffusion of the electrolyte to improve the structural stability of the high-nickel cathode material and thus improve the cycle performance of the lithium-ion battery.

[0082] In this application, the lithium source may be at least one of lithium hydroxide, lithium nitrate, lithium carbonate, lithium oxalate, lithium acetate, lithium oxide, and lithium citrate.

[0083] To more precisely control high-nickel cathode materials and improve their energy density and cycle performance, the precursor Ni can be... a Co b Mn c (OH)₂ and a lithium source are mixed at a molar ratio of 1:(1.010-1.090). Simultaneously, to ensure more thorough mixing, the precursor Ni can be added. a Co b Mn c (OH)2 and lithium source are added to a high-speed mixer for mixing. The mixing speed can be 500 rpm and the mixing time can be 60 min.

[0084] After the precursor and lithium source are thoroughly mixed, the first sintering is carried out. The precursor will undergo a solid-state lithium intercalation reaction during the first sintering to obtain the first sintered material. The first sintering has a key impact on the crystal structure of the high-nickel cathode material.

[0085] The atmosphere for the first sintering can be oxygen or air. To further improve sintering efficiency, a mixture of oxygen concentration ≥80% and the remaining gas is air can be selected.

[0086] After the first sintering is completed, the first sintered material is obtained. In order to facilitate subsequent operations and strengthen the control of the parameters of high-nickel cathode material, the first sintered material needs to be crushed and the D50 needs to be controlled within 7.5-12.5μm to obtain the first crushed material. The first crushed material is then used for subsequent experiments.

[0087] Then, to further precisely regulate the high-nickel positive electrode material to improve its energy density and cycle performance, the first crushed material and the Co source can be mixed in a molar ratio of 1:(0.001-0.100), wherein the Co source can be at least one of tricobalt tetroxide, cobalt carbonate, cobalt hydroxide, cobalt oxyhydroxide, cobalt acetate, cobalt oxalate, cobalt nitrate, cobalt sulfate, and cobalt chloride. Meanwhile, to make the mixing more sufficient, the first crushed material and the Co source can be added to a high-speed mixer for mixing, and the mixing speed can be 500 rpm, and the mixing time can be 60 min.

[0088] After the first crushed material and the Co source are mixed sufficiently, second sintering needs to be performed within a defined temperature and time range, at this time, the Co source will react with the first crushed material and penetrate into the material, thereby obtaining the high-nickel positive electrode material with the specific Co concentration gradient provided by the present application.

[0089] The applicant found in the long-term research process that the temperature and time of the second sintering have a key influence on whether the high-nickel positive electrode material provided by the first aspect of the present application can be obtained. The present application first limits the second sintering temperature to 540-640℃, if the second sintering temperature is too low, Co will mainly coat the surface of the secondary particles, if the second sintering temperature is too high, Co will tend to be uniformly distributed in the bulk phase of the high-nickel positive electrode material, only when the second sintering temperature meets the above limitation, a good foundation can be laid for the specific gradient distribution of Co. After the second sintering temperature is limited, the present application limits the second sintering time to satisfy the relationship of formula 2, i.e. the second sintering time is adjusted according to the second sintering temperature, the average grain size of the primary particles of the first crushed material, and the particle size D50 of the secondary particles of the first crushed material, which can promote the second sintering time to have a good matching effect with the second sintering temperature, the average grain size of the primary particles of the first crushed material, and the particle size D50 of the secondary particles of the first crushed material, and finally obtain the high-nickel positive electrode material provided by the first aspect of the present application, and in the high-nickel positive electrode material, the closer the position of the primary particle to the center of the secondary particle, the smaller the ratio of the Co content on the surface of the primary particle to the Co content at the center of the primary particle.

[0090] It can be understood that the high-nickel positive electrode material obtained after the first crushed material and the Co source of the present application are mixed for second sintering has an average grain size of the primary particles and a particle size D50 of the secondary particles that are basically equivalent to the average grain size and the particle size D50 of the first crushed material.

[0091] In addition, the atmosphere of the second sintering can be oxygen or air, to further improve the sintering efficiency, a mixed gas with an oxygen concentration ≥80% and the rest being air can be selected.

[0092] In the scheme of the present application, the first sintering temperature is 750-900°C, and the first sintering time is 8-15h. As mentioned above, the first sintering has a key influence on the crystal structure of the high-nickel positive electrode material, and thus regulating the first sintering temperature and the first sintering time within the above ranges can obtain a suitable crystal structure, which in turn helps to improve the cycle performance of the battery to some extent and greatly improve the gram capacity.

[0093] In a specific embodiment, before the first sintering, the precursor Ni a Co b Mn c (OH)2, a lithium source, and an A1 dopant are mixed;

[0094] The second sintering further comprises obtaining a second sintering material after the second sintering; mixing the second sintering material and a B1 coating agent to perform a third sintering, thereby obtaining the high-nickel positive electrode material;

[0095] The A1 dopant comprises at least one of a Zr source, a Ti source, an Al source, a Y source, and a Sr source;

[0096] The B1 coating agent comprises at least one of an Al source, a B source, a Ce source, a P source, an F source, a Cl source, and a Br source;

[0097] The third sintering temperature is 240-340°C, and the third sintering time is 4-15h.

[0098] In the present application, the precursor Ni a Co b Mn c (OH)2, a lithium source, and an A1 dopant can be mixed before the first sintering, and the second sintering material and a B1 coating agent can be mixed after the second sintering to perform a third sintering, thereby finally obtaining the high-nickel positive electrode material. By limiting the types of the A1 dopant and the B1 coating agent, as well as the temperature and time of the third sintering, the structural stability of the high-nickel positive electrode material and the cycle performance of the lithium ion battery can be effectively improved.

[0099] First, the precursor Ni a Co b Mn c (OH)2, a lithium source, and an A1 dopant are mixed and then sintered, at which time the A1 dopant is doped into the bulk phase of the positive electrode material, thereby improving the particle pressure strength of the secondary particles, reducing the transition metal mixing, stabilizing the crystal structure, and relieving the lattice shrinkage and expansion of the positive electrode material during the charging and discharging process. In the A1 dopant, the Zr source, the Ti source, the Al source, the Y source, and the Sr source can be at least one of an oxide, a hydroxide, a hydroxyl oxide, an acetate, an oxalate, a nitrate, a sulfate, and a chloride. In addition, the precursor Ni a Co b Mnc The (OH)2, the lithium source and the Al dopant can be mixed in a molar ratio of 1:(0.980-1.100):(0.001-0.100), which helps to better control the performance of the high-nickel positive electrode material.

[0100] Secondly, after obtaining the second sintered material through the second sintering, the second sintered material and the B1 coating agent are mixed for the third sintering. By limiting the type of the B1 coating agent and the temperature and time of the third sintering, the B1 coating agent can play a protective role on the surface of the positive electrode material, slow down the side reaction between the electrolyte and the surface of the positive electrode material, and further improve the cycle performance of the lithium ion battery. In the B1 coating agent, the Al source, the B source, the Ce source, the P source, the F source, the Cl source and the Br source can be at least one of oxides, hydroxides, hydroxyl oxides, acetates, oxalates, nitrates, sulfates and chlorides. In addition, the second sintered material and the B1 coating agent are mixed in a molar ratio of 1:(0.001-0.100), which helps to better control the performance of the high-nickel positive electrode material.

[0101] The third aspect of the present application provides a lithium ion battery comprising the high-nickel positive electrode material or the high-nickel positive electrode material prepared by the preparation method.

[0102] The lithium ion battery of the present application comprises a positive electrode sheet, which can be prepared by conventional technical means in the art. Specifically, the positive electrode material, the conductive agent and the binder can be uniformly dispersed in a solvent to obtain a positive electrode active layer slurry. Then, the positive electrode active layer slurry is coated on at least one functional surface of the positive electrode current collector, and after drying, a positive electrode sheet can be obtained.

[0103] The lithium ion battery of the present application comprises a positive electrode sheet, a separator and a negative electrode sheet, and an electrolyte. The composition of the negative electrode sheet can refer to conventional negative electrode sheets in the art, and the separator can also be a conventional separator used in the art. The lithium ion battery of the present application can be prepared by conventional methods in the art. Specifically, the positive electrode sheet, the separator and the negative electrode sheet are sequentially stacked, and then a cell is obtained by stacking or winding process. After that, the above lithium ion battery can be obtained through processes such as baking, liquid injection, formation and packaging.

[0104] The present application will be further described below through specific examples and comparative examples. Unless otherwise specified, the reagents, materials and instruments used in the following description are conventional reagents, conventional materials and conventional instruments, which can be commercially available. The reagents and materials involved can also be synthesized by conventional synthesis methods.

[0105] Example 1:

[0106] The present embodiment provides a preparation method of a high-nickel positive electrode material, comprising the following steps:

[0107] (1) The precursor Ni 0.85 Co 0.05 Mn 0.10 (OH)2, a lithium source LiOH H2O, an Al dopant ZrO2, and Al2O3 are mixed in a molar ratio of 1:1.050:0.020:0.010, and are added to a high-speed mixer for mixing, at a mixing speed of 500 rpm and for a mixing time of 60 min. The mixed material is loaded into a sagger, and first sintering is performed in a kiln, at a first sintering temperature of 820°C, for a first sintering time of 12 h, and in an oxygen atmosphere (oxygen concentration ≥ 80%, with the remainder being air), to obtain a first sintered material. The first sintered material is crushed to control the D50 to be in a range of 9.5-10.5 pm, to obtain a first crushed material.

[0108] (2) The first crushed material and a Co coating agent Co(OH)2 are mixed in a molar ratio of 1:0.015, and are added to a high-speed mixer for mixing, at a mixing speed of 500 rpm and for a mixing time of 60 min. The mixed material is loaded into a sagger, and second sintering is performed in a kiln, at a second sintering temperature of 590°C, for a second sintering time of t, and in an oxygen atmosphere (oxygen concentration ≥ 80%, with the remainder being air), to obtain a second sintered material;

[0109] The value of t is shown in formula 1:

[0110] wherein t is the second sintering time, h; D is the average grain size of the primary particles of the first crushed material, nm; D50 is the particle size D50 of the secondary particles of the first crushed material, pm; and T is the second sintering temperature, °C.

[0111] (3) The second sintered material, a B1 coating agent A1F3, and H3BO3 are mixed in a molar ratio of 1:0.010:0.010, and are added to a high-speed mixer for mixing, at a mixing speed of 500 rpm and for a mixing time of 60 min. The mixed material is loaded into a sagger, and third sintering is performed in a kiln, at a third sintering temperature of 290°C, for a third sintering time of 6 h, and in an oxygen atmosphere (oxygen concentration ≥ 80%, with the remainder being air), to obtain a third sintered material, which is then sieved, de-ironed, and packaged to obtain a high-nickel positive electrode material.

[0112] Example 2:

[0113] This example provides a method for preparing a high-nickel positive electrode material, and the specific steps can refer to Example 1, with the only difference being that in step (1) of this example, the Al dopant is TiO2 and Y2O3.

[0114] Example 3:

[0115] The embodiment provides a preparation method of a high-nickel positive electrode material, and specific steps can refer to embodiment 1, and the only difference is that in step (1) of the embodiment, the precursor Ni 0.85 Co 0.05 Mn 0.10 The precursor Ni (OH) 2 and the lithium source LiOH H2O are mixed in a molar ratio of 1:1.050, that is, no A1 dopant is added.

[0116] Embodiment 4:

[0117] The embodiment provides a preparation method of a high-nickel positive electrode material, and specific steps can refer to embodiment 1, and the only difference is that in step (1) of the embodiment, the first sintering material is crushed and the D50 is controlled to be 7.5-8.5 μm.

[0118] Embodiment 5:

[0119] The embodiment provides a preparation method of a high-nickel positive electrode material, and specific steps can refer to embodiment 1, and the only difference is that in step (1) of the embodiment, the first sintering material is crushed and the D50 is controlled to be 11.5-12.5 μm.

[0120] Embodiment 6:

[0121] The embodiment provides a preparation method of a high-nickel positive electrode material, and specific steps can refer to embodiment 1, and the only difference is that in step (2) of the embodiment, the second sintering temperature is 540 DEG C, and the second sintering atmosphere is air.

[0122] Embodiment 7:

[0123] The embodiment provides a preparation method of a high-nickel positive electrode material, and specific steps can refer to embodiment 1, and the only difference is that in step (2) of the embodiment, the second sintering temperature is 640 DEG C, and the second sintering atmosphere is oxygen (oxygen concentration is greater than or equal to 90%, and the rest is air).

[0124] Embodiment 8:

[0125] The embodiment provides a preparation method of a high-nickel positive electrode material, and specific steps can refer to embodiment 1, and the only difference is that in step (2) of the embodiment, the second sintering temperature is 590 DEG C, and the second sintering atmosphere is air.

[0126] Embodiment 9:

[0127] The embodiment provides a preparation method of a high-nickel positive electrode material, and specific steps can refer to embodiment 1, and the only difference is that in step (3) of the embodiment, the B1 coating agent is CeF3 and NH4H2PO4.

[0128] Embodiment 10:

[0129] The embodiment provides a preparation method of a high-nickel positive electrode material, and specific steps can refer to those in the embodiment 1, and the only difference is that steps (2) and (3) are different. In the step (2) of the embodiment, the first crushed material and the Co coating agent Co(OH)2 are mixed according to a molar ratio of 1:0.020; in the step (3) of the embodiment, the second sintered material is directly screened, iron is removed, and the high-nickel positive electrode material is obtained after packaging, that is, no B1 coating agent is added.

[0130] Embodiment 11

[0131] The embodiment provides a preparation method of a high-nickel positive electrode material, and specific steps can refer to those in the embodiment 1, and the only difference is that, in the step (3) of the embodiment, the third sintering time is 20 h.

[0132] Embodiment 12

[0133] The embodiment provides a preparation method of a high-nickel positive electrode material, and specific steps can refer to those in the embodiment 1, and the only difference is that, in the step (1) of the embodiment, the first sintering temperature is 740 DEG C.

[0134] Embodiment 13

[0135] The embodiment provides a preparation method of a high-nickel positive electrode material, and specific steps can refer to those in the embodiment 1, and the only difference is that, in the step (1) of the embodiment, no A1 dopant is added, in the step (2), the first crushed material and the Co coating agent Co(OH)2 are mixed according to a molar ratio of 1:0.020, and in the step (3), the second sintered material is directly screened, iron is removed, and the high-nickel positive electrode material is obtained after packaging, that is, no B1 coating agent is added.

[0136] Comparative Example 1

[0137] The comparative example provides a preparation method of a high-nickel positive electrode material, and specific steps can refer to those in the embodiment 1, and the only difference is that, in the comparative example, the step (2) is not performed, and the first crushed material is directly mixed with the B1 coating agent A1F3 and H3BO3 according to a molar ratio of 1:0.015:0.015.

[0138] Comparative Example 2

[0139] The comparative example provides a preparation method of a high-nickel positive electrode material, and specific steps can refer to those in the embodiment 1, and the only difference is that, in the step (2) of the comparative example, the second sintering temperature is 520 DEG C, and the second sintering atmosphere is oxygen (oxygen concentration is greater than or equal to 90%, and the rest is air).

[0140] Comparative Example 3

[0141] The present comparative example provides a preparation method of a high-nickel positive electrode material, and the specific steps can refer to Example 1, and the only difference is that in step (2) of the present comparative example, the second sintering temperature is 660°C, and the second sintering atmosphere is air.

[0142] Comparative Example 4:

[0143] The present comparative example provides a preparation method of a high-nickel positive electrode material, and the specific steps can refer to Example 1, and the only difference is that in step (2) of the present comparative example, the second sintering time is t+1h, that is, the second sintering time is always 1 hour longer than the sintering time of step (2) of Example 1.

[0144] Test Example:

[0145] (1) The average grain size of the first crushed material primary particles in the above examples and the above comparative examples was detected by X-ray diffraction (XRD) test of Bruker Company, specifically, powder X-ray diffraction test was carried out using Cu Kα ray; the particle size D50 of the first crushed material secondary particles in the above examples and the above comparative examples was detected by a laser particle size analyzer of Malvern Company; the average particle pressure resistance strength of the high-nickel positive electrode material secondary particles in the above examples and the above comparative examples was detected by a micro compression testing machine of Shimadzu Company, at least 10 particles with particle size D50 were tested for each sample, and the average value was taken as the result; the weight percentage of Co on the surface of the high-nickel positive electrode material in the above examples and the above comparative examples was detected by X-ray photoelectron spectroscopy (XPS) of Shimadzu Company to obtain Co XPS , and the weight percentage of Ni on the surface of the high-nickel positive electrode material was obtained as Ni XPS , wherein the quantitative calculation used the Wagner experimental sensitivity factor; the total Co content of the high-nickel positive electrode material in the above examples and the above comparative examples was detected by inductively coupled plasma emission spectrometer (ICP-OES) to obtain Co ICP , and the total Ni content was obtained as Ni ICP ; the diffraction peak intensity I003 on the (003) plane and the diffraction peak intensity I104 on the (104) plane of the high-nickel positive electrode material in the above examples and the above comparative examples were detected by XRD test of Bruker Company, specifically, powder X-ray diffraction test was carried out using Cu Kα ray. The specific results can be seen in Table 1, wherein, according to Co XPS , Ni XPS , Co ICP and Ni ICP , the M value can be obtained, and the M value is calculated by the following relationship:

[0146] (2) The particle size D50 of the secondary particles of the first crushed material in the above examples and the above comparative examples meets the range of 7.5-12.5 μm. The focused ion beam (FIB) is used to slice and sample, and a slice with a thickness of 50-100 nm is obtained. Then, the slice is subjected to point scanning of transmission electron microscope energy dispersive X-ray spectroscopy (TEM-EDS) to obtain the content of each element on the surface and in the center of the primary particles. The specific results are shown in Table 2 and Figures 1-9.

[0147] (3) The high-nickel positive electrode material in the above examples and the above comparative examples is mixed with conductive agent conductive carbon black (Super-P) and binder polyvinylidene fluoride (PVDF) according to a mass ratio of 94.5:3:2.5, and an appropriate amount of N-methyl pyrrolidone (NMP) solution is added to form a slurry. Then, the slurry is coated on a positive electrode sheet with an aluminum foil material, and after drying, the sheet is baked in a vacuum oven at 120°C for 12 h. After the end, the positive electrode sheet is assembled with an artificial graphite negative electrode sheet, a PP / PE / PP composite separator, and 1.0M LiPF6 / ethylene carbonate (EC)+dimethyl carbonate (DMC)+ethyl methyl carbonate (EMC) electrolyte to obtain a soft package battery with a capacity of 800 mAh, wherein the volume ratio of EC:DMC:EMC is 1:1:1. The gram capacity and 300 cycle retention rate of the above soft package battery are detected, wherein the 300 cycle test conditions are 25°C, 2.8-4.25V, 1C. The specific results are shown in Table 2.

[0148] Table 1

[0149] Table 2

[0150] As shown in Table 1 and Table 2, compared with Example 1, Example 2 uses TiO2 and Y2O3 to replace the A1 dopant, and it can be found that it has no great influence on the battery gram capacity and cycle performance; compared with Example 1, Example 3 does not add A1 dopant, and it can be found that the average particle pressure strength of the secondary particles and I003 / I104 are extremely low, and the 300-cycle retention rate is poorer than Example 1 and Example 2, indicating that the A1 dopant can improve the cycle performance; the first broken material D50 in Example 1 is 9.5-10.5 μm, the first broken material D50 in Example 4 is 7.5-8.5 μm, and the first broken material D50 in Example 5 is 11.5-12.5 μm, and it can be found that when the first broken material D50 is 7.5-12.5 μm, the battery gram capacity and cycle performance obtained are better; the first sintering temperature of Example 1 is 590℃, and the second sintering atmosphere is mainly oxygen, the second sintering temperature of Example 6 is 540℃, and the second sintering atmosphere is air, the second sintering temperature of Example 7 is 640℃, and the second sintering atmosphere is mainly oxygen, and the second sintering temperature of Example 8 is 590℃, and the second sintering atmosphere is air, and it can be found that when the second sintering temperature is in the range of 540-640℃, the battery gram capacity and cycle performance obtained are better; compared with Example 1, Example 9 uses CeF3 and NH4H2PO4 to replace the B1 coating agent, and it can be found that it has no great influence on the battery gram capacity and cycle performance; Example 10 does not add B1 coating agent, and it can be found that the average particle pressure strength of the secondary particles is low, the M value is high, the gram capacity is decreased, and the 300-cycle retention rate is obviously worse than Example 1 and Example 9, indicating that the B1 coating agent can obviously improve the cycle performance and also has a certain promoting effect on the gram capacity; the third sintering time of Example 11 is 20h, and the 300-cycle retention rate is obviously worse than Example 1 and Example 9, indicating that when the third sintering time exceeds 15h, the cycle performance of the obtained battery will be reduced; the first sintering temperature of Example 12 is 740℃, and the average particle pressure strength of the secondary particles and I003 / I104 are extremely low, the gram capacity is obviously decreased, and the 300-cycle retention rate is also decreased to a certain extent, indicating that the first sintering temperature is too high, which is easy to cause the significant decrease of the battery gram capacity; compared with Example 1, Example 13 does not add A1 dopant and B1 coating agent, and it can be found that the average particle pressure strength of the secondary particles and I003 / I104 are extremely low, the M value is high, the gram capacity is decreased, and the 300-cycle retention rate is poorer than Example 1, Example 3 and Example 10, indicating that the A1 dopant and B1 coating agent can improve the cycle performance, and the B1 coating agent also has a certain promoting effect on the gram capacity.

[0151] The comparative example 1 does not perform the step (2), and the obtained high-nickel positive electrode material has a lower surface Co content of the primary particles on the surface of the secondary particles and a substantially consistent Co content at the remaining positions, a significantly reduced M value, and a significantly decreased retention rate at 300 cycles, indicating that the step (2) or the second sintering has an extremely important role in obtaining the high-nickel positive electrode material with the specific Co concentration gradient and the balanced capacity and cycle performance. The second sintering temperature of the comparative example 2 is 520°C, and the second sintering atmosphere is mainly oxygen. It can be found that M2 of the comparative example 2 is about 1.3, and M3 is about 1.0, indicating that more Co is gathered on the surface of the secondary particles, which is not conducive to the formation of the Co concentration gradient and cannot effectively improve the cycle performance. The second sintering temperature of the comparative example 3 is 660°C, and the second sintering atmosphere is air. It can be found that the M value of the comparative example 3 is significantly reduced, and the Co is more uniformly distributed in the secondary particle body, which is not conducive to the formation of the Co concentration gradient and cannot effectively improve the cycle performance. The second sintering time of the comparative example 4 is 1 hour more than that of the example 1, that is, the value relationship of the formula 1 is not met. It can be found that M1 of the comparative example 4 is about 1.8, and M2 is about 1.4, indicating that the distribution of Co tends to be uniform, which is not conducive to the formation of the special structure of the Co-rich primary particle surface, and the 300-cycle retention rate is significantly reduced, which indicates that the control of the second sintering time has an important role in improving the cycle performance.

[0152] FIG. 1 is a whole TEM image of the high-nickel positive electrode material in the example 1, and it can be found that the high-nickel positive electrode material of the present application is a secondary particle formed by agglomeration of primary particles.

[0153] FIG. 2 is a local TEM image of the surface of the secondary particle of the high-nickel positive electrode material in the example 1, FIG. 3 is an EDS surface distribution map of the Zr element on the surface of the secondary particle of the high-nickel positive electrode material in the example 1, FIG. 4 is an EDS surface distribution map of the Al element on the surface of the secondary particle of the high-nickel positive electrode material in the example 1, and FIG. 5 is an EDS surface distribution map of the Co element on the surface of the secondary particle of the high-nickel positive electrode material in the example 1. According to FIGS. 1-5, it can be found that on the surface of the secondary particle, the Zr element and the Al element are uniformly distributed, indicating that the Al dopant is uniformly doped; and the primary particle on the surface of the secondary particle has a significant concentration gradient between the surface Co element and the central Co element, and more Co elements are uniformly coated on the surface of the primary particle.

[0154] Figure 6 is a local TEM image of the secondary particle core in the high-nickel positive electrode material of Example 1, Figure 7 is an EDS area distribution map of Zr element located at the secondary particle core in the high-nickel positive electrode material of Example 1, Figure 8 is an EDS area distribution map of Al element located at the secondary particle core in the high-nickel positive electrode material of Example 1, and Figure 9 is an EDS area distribution map of Co element located at the secondary particle core in the high-nickel positive electrode material of Example 1. According to Figures 6-9, it can be found that, at the secondary particle core, the Zr element and the Al element are still uniformly distributed, indicating that the Al dopant is still uniformly doped at the core; and the surface Co element and the central Co element of the primary particle located at the secondary particle core have a relatively obvious concentration gradient, and more Co element is uniformly coated on the surface of the primary particle.

[0155] In addition, comparing Figure 5 and Figure 9, it can be found that the surface Co element of the primary particle located at the surface of the secondary particle is obviously higher than the surface Co element of the primary particle located at the core of the secondary particle, and the central Co element of the primary particle located at the surface of the secondary particle is obviously higher than the central Co element of the primary particle located at the core of the secondary particle.

[0156] The above describes the preferred embodiments of the present application and the experimental verification in detail. It should be understood that those skilled in the art can make many modifications and changes to the present application without creative labor according to the concept of the present application. Therefore, any technical solution that can be obtained by logical analysis, reasoning or limited experiments by those skilled in the art on the basis of the prior art according to the concept of the present application shall be within the protection scope of the present application.

Claims

1. A high nickel positive electrode material, wherein, The high-nickel positive electrode material is secondary particles formed by agglomeration of primary particles, wherein the ratio of the surface Co content to the central Co content of the primary particles located on the surface of the secondary particles is M1; the ratio of the surface Co content to the central Co content of the primary particles located from the surface of the secondary particles to 1 / 2 of the spherical core of the secondary particles is M2; the ratio of the surface Co content to the central Co content of the primary particles located at the spherical core of the secondary particles is M3; M1>M2>M3; the M1 is greater than or equal to 2, the M2 is greater than or equal to 1.5, and the M3 is greater than or equal to 1.

1.

2. The high-nickel cathode material of claim 1, wherein, The high-nickel positive electrode material has a chemical formula of Li y Ni a Co b Mn c O2, 0.98≤y≤1.10, 0.6≤a≤0.98, 0≤b≤0.4, and 0≤c≤0.

4.

3. The high-nickel cathode material of claim 1, wherein, The high-nickel positive electrode material has a chemical formula of Li y Ni a Co b Mn c A1 d B1 e O2, 0.98≤y≤1.10, 0.6≤a≤0.98, 0≤b≤0.4, 0≤c≤0.4, 0.001≤d≤0.1, and 0.001≤e≤0.

1. A1 is at least one of Zr, Ti, Al, Y, and Sr; B1 is at least one of Al, B, Ce, P, F, Cl, and Br.

4. The high-nickel cathode material of any one of claims 1-3, wherein, The central Co content of the primary particles located on the surface of the secondary particles is greater than the central Co content of the primary particles located from the surface of the secondary particles to 1 / 2 of the spherical core of the secondary particles, which is greater than the central Co content of the primary particles located at the spherical core of the secondary particles.

5. The high-nickel cathode material of any one of claims 1-4, wherein, The average grain size of the primary particles is 150-350 nm; And / or, the particle size D50 of the secondary particles is 7.5-12.5 μm; And / or, the average particle pressure resistance of the secondary particles is 50-200 MPa.

6. The high-nickel cathode material of any one of claims 1-5, wherein, The high-nickel positive electrode material is detected by X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma emission spectroscopy (ICP-OES) to obtain Co XPS , Ni XPS , Co ICP , and Ni ICP ; the Co XPS , Ni XPS , Co ICP , and Ni ICP satisfy the relationship of formula 1: wherein the Co XPS is the Co content of the surface of the secondary particles; the Ni XPS is the Ni content of the surface of the secondary particles; the Co ICP is the total Co content of the secondary particles; the Ni ICP is the total Ni content of the secondary particles The total Ni content of the high-nickel positive electrode material is 18.5-22.5 wt.%; And / or, the ratio of the diffraction peak intensity I003 of the (003) plane to the diffraction peak intensity I104 of the (104) plane obtained by X-ray diffraction XRD of the high-nickel positive electrode material is 1.8-3.

0.

7. A method of producing the high-nickel positive electrode material according to any one of claims 1 to 6, wherein The method comprises the following steps: The precursor Ni a Co b Mn c (OH)2 and a lithium source are mixed to perform a first sintering to obtain a first sintered material, and the first sintered material is crushed to obtain a first crushed material with a particle size D50 of 7.5-12.5 μm; Mixing the first crushed material and a Co source to perform second sintering to obtain the high-nickel positive electrode material; 0.6≤a≤0.98, 0≤b≤0.4, and 0≤c≤0.

4. The second sintering temperature is 540-640℃, and the second sintering time satisfies the relationship of formula 2: t is the second sintering time, h; D is the average grain size of the primary particles of the first crushed material, nm; D50 is the particle size D50 of the secondary particles of the first crushed material, μm; and T is the second sintering temperature, ℃.

8. The production method according to claim 7, wherein The first sintering temperature is 750-900 ℃, and the first sintering time is 8-15 h.

9. The production method according to claim 7 or 8, wherein The first sintering further comprises mixing a precursor Ni a Co b Mn c (OH)2, a lithium source and an Al dopant The second sintering further comprises obtaining a second sintered material after the second sintering; mixing the second sintered material and a B1 coating agent to perform third sintering to obtain the high-nickel positive electrode material; The A1 dopant comprises at least one of a Zr source, a Ti source, an Al source, a Y source, and a Sr source; The B1 coating agent comprises at least one of an Al source, a B source, a Ce source, a P source, a F source, a Cl source, and a Br source; The third sintering temperature is 240-340 ℃, and the third sintering time is 4-15 h.

10. A lithium-ion battery, wherein, The lithium ion battery comprises the high-nickel positive electrode material according to any one of claims 1-8 or the high-nickel positive electrode material prepared by the preparation method according to claim 9.

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