Positive electrode material, positive electrode slurry, and lithium-ion battery

Abstract

A positive electrode material, a positive electrode slurry and a lithium-ion battery. The general chemical formula of the positive electrode material is LiσNiaCobMncM1xM2yM3zO2+r, wherein 0.80≤σ≤1.20, a+b+c+x+y+z=1, 0.6≤a≤1.0, 0.0≤b≤0.10, 0.0≤c≤0.3, 0<x<0.3, 0<y<0.3, 0<z<0.3, -0.2<r<0.3, M1, M2 and M3 each independently comprise at least one of Al, Co, Zr, B, Ti, Ca, Ce, Zn, Cr, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si and Sb, and M1, M2, and M3 are not exactly the same as one another. The initial coulombic efficiency of the positive electrode material is E; the oil absorption value of the positive electrode material is P mL / 100 g; the volume-based particle size distribution width of the positive electrode material is S, and S=(D90-D10) / D50; and the positive electrode material satisfies the following relational expression: 1.0≤E×(P-20)+S≤8. The positive electrode material has both a relatively high energy density and high rate performance.

Description

Cathode materials and slurries, lithium-ion batteries

[0001] This application claims the benefit of Chinese patent application No. 2023116951398, filed on December 11, 2023. This application incorporates the entirety of the aforementioned Chinese patent application. Technical Field

[0002] The present application belongs to the technical field of positive electrode materials, and in particular relates to a positive electrode material, positive electrode slurry, and a lithium-ion battery. Background Art

[0003] A rechargeable battery, also known as a rechargeable battery or storage battery, is a battery that can be recharged after discharge to activate its active materials and continue to be used. Currently, the main rechargeable batteries on the market include nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid (or lead-acid) batteries, lithium-ion batteries, sodium-ion batteries, and polymer lithium-ion batteries. Lithium-ion batteries are particularly widely used, and their application performance has placed higher demands on them.

[0004] At present, with the increasing market requirements for lithium-ion battery applications, lithium-ion batteries with both energy density and fast charging performance have become the preferred products. According to research, in order to take into account the energy density and fast charging performance of lithium-ion batteries, the battery materials used in lithium-ion batteries are required to have more ideal compatibility with the electrolyte. At the same time, the surface properties of the battery materials also have a greater impact on the battery's cycle and impedance performance. However, in traditional battery materials, due to the presence of multiple chemical groups in the surface coating layer of the positive electrode material, the chemical groups on the surface of the ternary positive electrode material have different compatibilities with the electrolyte, resulting in different interfacial impedances of the material, affecting the insertion and extraction of lithium ions during its charge and discharge process, and thus adversely affecting the battery's rate and cycle performance.

[0005] Therefore, how to optimize the compatibility between cathode materials and electrolytes is crucial to the performance of lithium-ion batteries.

[0006] Summary of the Invention

[0007] The purpose of this application is to provide a positive electrode material, positive electrode slurry, and lithium-ion battery, which can improve the processing performance of the positive electrode material while allowing the positive electrode material to have both higher energy density and rate performance.

[0008] The present application provides a positive electrode material, the chemical formula of which is Li σ Ni a Co b Mn c M1 x M2 y M3 z O2+r , wherein, 0.80≤σ≤1.20, a+b+c+x+y+z=1, 0.6≤a≤1.0, 0.0≤b≤0.10, 0.0≤c≤0.3, 0<x<0.3, 0<y<0.3, 0<z<0.3, -0.2<0.3, M1, M2, and M3 each independently include at least one of Al, Co, Zr, B, Ti, Ca, Ce, Zn, Cr, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si, and Sb, and M1, M2, and M3 are not completely the same;

[0009] The first coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is P mL / 100 g, the volume particle size distribution width of the positive electrode material is S, S=(D90-D10) / D50, and the specific surface area of ​​the positive electrode material is Am 2 / g, the tap density of the positive electrode material is T g / cm 3 , and the positive electrode material satisfies at least one of the following formulas:

[0010] 1.0≤E*(P-20)+S≤8;

[0011] 0.5≤E*(P-20)+A≤6.0;

[0012] 1.0≤E*(P-20)+T≤8.0.

[0013] In the first aspect, the present application provides a positive electrode material, the chemical formula of which is Li σ Ni a Co b Mn c M1 x M2 y M3 z O 2+r , wherein, 0.80≤σ≤1.20, a+b+c+x+y+z=1, 0.6≤a≤1.0, 0.0≤b≤0.10, 0.0≤c≤0.3, 0<x<0.3, 0<y<0.3, 0<z<0.3, -0.2<0.3, M1, M2, and M3 each independently include at least one of Al, Co, Zr, B, Ti, Ca, Ce, Zn, Cr, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si, and Sb, and M1, M2, and M3 are not completely the same;

[0014] The first coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is P mL / 100 g, the volume particle size distribution width of the positive electrode material is S, S=(D90-D10) / D50, and satisfies the following relationship: 1.0≤E*(P-20)+S≤8.

[0015] In the second aspect, the present application also provides a positive electrode material, the chemical formula of the positive electrode material is Li σ Ni a Co b Mn c M1 x M2 y M3 z O 2+r , wherein, 0.80≤σ≤1.20, a+b+c+x+y+z=1, 0.6≤a≤1.0, 0.0≤b≤0.10, 0.0≤c≤0.3, 0<x<0.3, 0<y<0.3, 0<z<0.3, -0.2<0.3, M1, M2, and M3 each independently include at least one of Al, Co, Zr, B, Ti, Ca, Ce, Zn, Cr, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si, and Sb, and M1, M2, and M3 are not completely the same;

[0016] The first coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is P mL / 100 g, and the specific surface area of ​​the positive electrode material is A m 2 / g, and the following relationship is satisfied: 0.5≤E*(P-20)+A≤6.0.

[0017] In a third aspect, the present application provides a positive electrode material, the chemical formula of which is Li σ Ni a Co b Mn c M1 x M2 y M3 z O 2+r , wherein, 0.80≤σ≤1.20, a+b+c+x+y+z=1, 0.6≤a≤1.0, 0.0≤b≤0.10, 0.0≤c≤0.3, 0<x<0.3, 0<y<0.3, 0<z<0.3, -0.2<0.3, M1, M2, and M3 each independently include at least one of Al, Co, Zr, B, Ti, Ca, Ce, Zn, Cr, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si, and Sb, and M1, M2, and M3 are not completely the same;

[0018] The first coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is P mL / 100 g, and the tap density of the positive electrode material is T g / cm 3 , and the following relationship is satisfied: 1.0≤E*(P-20)+T≤8.0.

[0019] In combination with the third aspect, in some embodiments, the first coulombic efficiency of the positive electrode material is E, 0.87≤E≤0.93.

[0020] In a fourth aspect, the present application provides a positive electrode slurry, which includes a dispersant and the above-mentioned positive electrode material.

[0021] In a fifth aspect, the present application provides a battery, wherein the lithium-ion battery comprises the positive electrode material described in the first aspect, the second aspect, and the third aspect.

[0022] Compared with the prior art, this application has the following beneficial effects:

[0023] The positive electrode material provided in the present application has an oil absorption value P of the positive electrode material that can reflect the compatibility of the positive electrode material with the electrolyte. The higher the oil absorption value of the positive electrode material, the better the compatibility of the positive electrode material with the electrolyte, and the lower the oil absorption value, the worse the compatibility of the positive electrode material with the electrolyte. However, an excessively large oil absorption value will consume more dispersant and binder in the process of preparing the positive electrode slurry from the positive electrode material, thereby increasing the production cost and reducing the energy density, thereby affecting the electrochemical performance of the positive electrode material. Therefore, the present application controls the oil absorption value P, volume particle size distribution width S and first coulomb efficiency E of the positive electrode material to be maintained within the range of 1.0≤E*(P-20)+S≤8, thereby balancing the relationship between the first coulomb efficiency, volume particle size distribution width S and oil absorption value P of the positive electrode material. On the basis of not affecting the processing performance and processing cost of the positive electrode material, the compatibility of the positive electrode material and the electrolyte can be improved, which is beneficial to improving the lithium ion insertion and extraction efficiency of the positive electrode material during the charging and discharging process, promoting the diffusion of lithium ions at the solid-liquid interface on the surface of the positive electrode material and inside the positive electrode material, reducing the interface impedance between the positive electrode material and the electrolyte, and making the positive electrode material take into account both higher energy density and rate performance.

[0024] The positive electrode material provided in this application has an oil absorption value P that can reflect the compatibility of the positive electrode material with the electrolyte. The higher the oil absorption value of the positive electrode material, the better the compatibility of the positive electrode material with the electrolyte, and the lower the oil absorption value, the worse the compatibility of the positive electrode material with the electrolyte. However, an excessively large oil absorption value will consume more dispersants and binders during the preparation of the positive electrode slurry from the positive electrode material, thereby increasing production costs and reducing energy density, affecting the electrochemical performance of the positive electrode material. An excessively large specific surface area A of the positive electrode material will lead to an increase in side reactions, consume too many active lithium ions, and reduce the first coulombic efficiency of the positive electrode material. An excessively small specific surface area of ​​the positive electrode material will affect the capacity of the positive electrode material. Therefore, the present application controls the oil absorption value P, specific surface area A and first coulomb efficiency E of the positive electrode material to be kept within the range of 0.5≤E*(P-20)+A≤6.0, thereby balancing the relationship between the first coulomb efficiency, specific surface area A and oil absorption value P of the positive electrode material. On the basis of not affecting the processing performance and processing cost of the positive electrode material, the compatibility of the positive electrode material and the electrolyte can be improved, which is beneficial to improving the lithium ion insertion and extraction efficiency of the positive electrode material during the charging and discharging process, promoting the diffusion of lithium ions at the solid-liquid interface on the surface of the positive electrode material and inside the positive electrode material, reducing the interface impedance between the positive electrode material and the electrolyte, and making the positive electrode material take into account both higher energy density and rate performance.

[0025] The positive electrode material provided in this application has an oil absorption value P that can reflect the compatibility of the positive electrode material with the electrolyte. The higher the oil absorption value of the positive electrode material, the better the compatibility of the positive electrode material with the electrolyte, and the lower the oil absorption value, the worse the compatibility of the positive electrode material with the electrolyte. However, an excessively large oil absorption value will consume more dispersants and binders during the preparation of the positive electrode slurry from the positive electrode material, resulting in increased production costs and a decrease in energy density, which will affect the electrochemical performance of the positive electrode material. If the tap density T of the positive electrode material is too large, it will not be conducive to creating more lithium ion diffusion channels, and the electrochemical performance of the positive electrode material will be affected. If the tap density T of the positive electrode material is too small, it will affect the energy density of the positive electrode material. Therefore, the present application controls the oil absorption value P, tap density T and first coulomb efficiency E of the positive electrode material to be kept within the range of 1.0≤E*(P-20)+T≤8.0, thereby balancing the relationship between the first coulomb efficiency, tap density T and oil absorption value P of the positive electrode material. On the basis of not affecting the processing performance and processing cost of the positive electrode material, the compatibility of the positive electrode material and the electrolyte can be improved, which is beneficial to improving the lithium ion insertion and extraction efficiency of the positive electrode material during the charging and discharging process, promoting the diffusion of lithium ions at the solid-liquid interface on the surface of the positive electrode material and inside the positive electrode material, and reducing the interface impedance between the positive electrode material and the electrolyte. The appropriate tap density can increase the energy density of the positive electrode material, thereby allowing the positive electrode material to take into account both higher energy density and rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0027] FIG1 is a schematic flow chart of a method for preparing a positive electrode material provided in an embodiment of the present application.

[0028] FIG2 is a SEM electron microscope image of the positive electrode material provided in Example 1 of the present application. DETAILED DESCRIPTION

[0029] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0030] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity of the technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features.

[0032] In order to facilitate understanding of the present application, specific terms are appropriately defined in the present application. Unless otherwise defined herein, the scientific terms and technical terms used in the present application have the meanings commonly understood by those skilled in the art to which the present application belongs.

[0033] As used herein, the term "matrix" refers to a lithium composite oxide synthesized by mixing a precursor with a lithium salt through a high-temperature solid-phase reaction, and includes lithium and metal elements.

[0034] Due to the chemical activity of the coating layer on the surface of the ternary positive electrode material, the chemical groups on the surface of the ternary positive electrode material have different compatibilities with the electrolyte, resulting in different interfacial impedances of the material, affecting the insertion and extraction of lithium ions during its charge and discharge process, and thus adversely affecting the rate and cycle of the battery. To this end, the inventors improved the product process by using different coating agents and controlling the heat treatment temperature at different stages to increase the compatibility between the positive electrode material and the electrolyte. After research, the inventors found that the performance changes of the positive electrode material can be reflected in three aspects: the relationship between the first coulomb efficiency E and the oil absorption value P and the particle size distribution width value S, the relationship between the first coulomb efficiency E and the oil absorption value P and the specific surface area A, and the relationship between the first coulomb efficiency E and the oil absorption value P and the tap density T. Specifically, on the one hand, by controlling the oil absorption value P, volume particle size distribution width S and first coulomb efficiency E of the positive electrode material to be maintained within the range of 1.0≤E*(P-20)+S≤8, the relationship between the first coulomb efficiency, volume particle size distribution width S and oil absorption value P of the positive electrode material can be balanced. Without affecting the processing performance and processing cost of the positive electrode material, the compatibility of the positive electrode material and the electrolyte can be improved, which is beneficial to improving the lithium ion insertion and extraction efficiency of the positive electrode material during the charging and discharging process, promoting the diffusion of lithium ions at the solid-liquid interface on the surface of the positive electrode material and inside the positive electrode material, reducing the interface impedance between the positive electrode material and the electrolyte, so that the positive electrode material can take into account both higher energy density and rate performance. On the other hand, by controlling the oil absorption value P, specific surface area A and first coulomb efficiency E of the positive electrode material to be within the range of 0.5≤E*(P-20)+A≤6.0, the relationship between the first coulomb efficiency, specific surface area A and oil absorption value P of the positive electrode material can be balanced. Without affecting the processing performance and processing cost of the positive electrode material, the compatibility of the positive electrode material and the electrolyte can be improved, which is beneficial to improving the lithium ion insertion and extraction efficiency of the positive electrode material during the charging and discharging process, promoting the diffusion of lithium ions at the solid-liquid interface on the surface of the positive electrode material and inside the positive electrode material, reducing the interface impedance between the positive electrode material and the electrolyte, and making the positive electrode material have both higher energy density and rate performance. On the other hand, by controlling the oil absorption value P, tap density T and first coulomb efficiency E of the positive electrode material to be within the range of 1.0≤E*(P-20)+T≤8.0, the relationship between the first coulomb efficiency, tap density T and oil absorption value P of the positive electrode material can be balanced. Without affecting the processing performance and processing cost of the positive electrode material, the compatibility of the positive electrode material and the electrolyte can be improved, which is beneficial to improving the lithium ion insertion and extraction efficiency of the positive electrode material during the charging and discharging process, promoting the diffusion of lithium ions at the solid-liquid interface on the surface of the positive electrode material and inside the positive electrode material, and reducing the interface impedance between the positive electrode material and the electrolyte. The appropriate tap density can increase the energy density of the positive electrode material, so that the positive electrode material can take into account both higher energy density and rate performance.

[0035] The present application provides a positive electrode material, the chemical formula of which is Li σ Ni a Co b Mn c M1 x M2 y M3 z O 2+r , wherein, 0.80≤σ≤1.20, a+b+c+x+y+z=1, 0.6≤a≤1.0, 0.0≤b≤0.10, 0.0≤c≤0.3, 0<x<0.3, 0<y<0.3, 0<z<0.3, -0.2<0.3, M1, M2, and M3 each independently include at least one of Al, Co, Zr, B, Ti, Ca, Ce, Zn, Cr, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si, and Sb, and M1, M2, and M3 are not completely the same;

[0036] The first coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is P mL / 100 g, the volume particle size distribution width of the positive electrode material is S, S = (D90-D10) / D50, and the specific surface area of ​​the positive electrode material is A m 2 / g, the tap density of the positive electrode material is T g / cm 3 , and the positive electrode material satisfies at least one of the following formulas:

[0037] 1.0≤E*(P-20)+S≤8;

[0038] 0.5≤E*(P-20)+A≤6.0;

[0039] 1.0≤E*(P-20)+T≤8.0.

[0040] The present application controls the oil absorption value P, volume particle size distribution width S and first coulomb efficiency E of the positive electrode material to be maintained in the range of 1.0≤E*(P-20)+S≤8, or the oil absorption value P, specific surface area A and first coulomb efficiency E are maintained in the range of 0.5≤E*(P-20)+A≤6.0, or the oil absorption value P, tap density T and first coulomb efficiency E are maintained in the range of 1.0≤E*(P-20)+T≤8.0, thereby reducing the interfacial impedance between the positive electrode material and the electrolyte, so that the positive electrode material can take into account both higher energy density and rate performance.

[0041] The present application provides a positive electrode material, the chemical formula of which is Li σ Ni a Co b Mn c M1 x M2 y M3z O 2+r , wherein, 0.80≤σ≤1.20, a+b+c+x+y+z=1, 0.6≤a≤1.0, 0.0≤b≤0.10, 0.0≤c≤0.3, 0<x<0.3, 0<y<0.3, 0<z<0.3, -0.2<0.3, M1, M2, and M3 each independently include at least one of Al, Co, Zr, B, Ti, Ca, Ce, Zn, Cr, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si, and Sb, and M1, M2, and M3 are not completely the same;

[0042] The first coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is P mL / 100 g, the volume particle size distribution width of the positive electrode material is S, S=(D90-D10) / D50, and the following relationship is satisfied: 1.0≤E*(P-20)+S≤8.

[0043] In the above scheme, the oil absorption value P of the positive electrode material can reflect the compatibility of the positive electrode material with the electrolyte. The higher the oil absorption value of the positive electrode material, the better the compatibility of the positive electrode material with the electrolyte, and the lower the oil absorption value, the worse the compatibility of the positive electrode material with the electrolyte; however, an excessively large oil absorption value will consume more dispersant and binder in the process of preparing the positive electrode slurry from the positive electrode material, thereby increasing the production cost and reducing the energy density, thereby affecting the electrochemical performance of the positive electrode material. Therefore, the present application controls the oil absorption value P, volume particle size distribution width S and first coulomb efficiency E of the positive electrode material to be maintained within the range of 1.0≤E*(P-20)+S≤8, thereby balancing the relationship between the first coulomb efficiency, volume particle size distribution width S and oil absorption value P of the positive electrode material. On the basis of not affecting the processing performance and processing cost of the positive electrode material, the compatibility of the positive electrode material and the electrolyte can be improved, which is beneficial to improving the lithium ion insertion and extraction efficiency of the positive electrode material during the charging and discharging process, promoting the diffusion of lithium ions at the solid-liquid interface on the surface of the positive electrode material and inside the positive electrode material, reducing the interface impedance between the positive electrode material and the electrolyte, and making the positive electrode material take into account both higher energy density and rate performance.

[0044] Specifically, the value of σ can be 0.8, 0.82, 0.85, 0.88, 0.90, 0.95, 0.98, 1.0, 1.02, 1.05, 1.08, 1.1, 1.12, 1.14, 1.16, 1.18 or 1.2, etc., and of course it can also be other values ​​within the above range. The value of a can be 0.6, 0.65, 0.68, 0.7, 0.75, 0.78, 0.8, 0.85, 0.9, 0.95, 0.98 or 1.0, the value of b can be 0, 0.01, 0.02, 0.05, 0.07, 0.08, 0.085, 0.09, 0.095 or 0.10, the value of c can be 0, 0.01, 0.02, 0.05, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25 or 0.3, and the values ​​of x, y and z independently can be 0.01, 0.06, 0.1, 0.12, 0.15, 0.18, 0.2, 0.25, 0.28, 0.29 or 0.295, etc. The value of r can be -0.19, -0.15, -0.12, -0.1, -0.095, -0.08, -0.07, -0.05, 0, 0.1, 0.15, 0.2, 0.25 or 0.29, etc.

[0045] It should be noted that the content of each element in the positive electrode material can be measured by a well-known instrument for qualitative analysis and / or quantitative analysis of each element, such as ICP and ICP-MS.

[0046] In some embodiments, the positive electrode material is a single crystal positive electrode material, that is, a material with complete grains and no grain boundary defects. The single crystal positive electrode material has a more stable structure, a more uniform distribution of bulk components, and better particle strength than the polycrystalline positive electrode material. It can provide better cycle stability and safety for lithium-ion batteries, and can also greatly reduce the cracking of particles during the pole piece pressing process, thereby improving the pole piece compaction density and volume energy density. It should be noted that the difference between single crystal positive electrode materials and polycrystalline positive electrode materials (i.e., polycrystalline secondary particles) is that the smallest particles of polycrystalline secondary particles are secondary particles formed by the agglomeration of nanometer-scale primary particles. For single crystal positive electrode materials, the smallest particles are usually micron-scale monomer primary particles. Generally speaking, in addition to EBSD testing methods, characterization methods such as scanning electron microscopy (SEM) can also be used to determine whether the obtained positive electrode product is a single crystal material. For example, for single crystal positive electrode materials, the morphology of single crystal particles can be characterized by SEM, and it can be seen that the shape of single crystal particles generally appears as regular or irregular spherical, and there is no significant particle agglomeration. The orientation of the single crystal positive electrode material can also be characterized by EBSD. Through EBSD, it can be observed that the color within at least one grain is the same, so as to judge that the orientation within at least one grain is the same, and the grains with the same orientation are single crystals. It should be specially noted that the "single crystal positive electrode material" known to those skilled in the art is not a "single crystal" in the strict crystallographic sense. In crystallography, an ideal single crystal refers to a crystal with completely the same arrangement and orientation. However, due to impurities, strain and crystal defects, ideal single crystals are very rare and difficult to produce in the laboratory. Therefore, the single crystal positive electrode materials known in the art are actually more of a "single crystal morphology-like" positive electrode material, which only shows a large particle size similar to a single crystal in size, which is different from a polycrystal composed of many small primary particles.

[0047] In some embodiments, M1, M2, and M3 each independently include at least one of Al, Co, Zr, B, Ti, Ca, Ce, Zn, Cr, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si, and Sb, and M1, M2, and M3 are not identical. These doping elements M1, M2, and M3 can stabilize the lattice constant of the positive electrode material, improve the surface structure of the material, enhance the stability of the material cycle, and inhibit structural collapse, thereby improving the performance of the positive electrode material. However, when the doping elements M1, M2, and M3 are the same chemical element, no significant improvement effect is achieved. It should be noted that M1, M2, and M3 are not identical, that is, there is at least one different element between the elements M1, M2, and M3. For example, when M1, M2, and M3 each include only one element, M1, M2, and M3 are all different. When M1, M2, and M3 each include multiple elements, there is at least one different element between M1, M2, and M3.

[0048] In some embodiments, based on the total weight of the metal elements other than Li in the positive electrode material being 100 wt%, the sum of the weight contents of any two of M1, M2, and M3 is 0.01 wt% to 50 wt%. Specifically, it can be 0.01 wt%, 1 wt%, 2 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 35 wt%, 40 wt%, 45 wt%, or 50 wt%. In some embodiments, the doping elements M2 and M3 are located in the surface layer of the positive electrode material, which can improve the compatibility between the surface of the material and the electrolyte and improve the efficiency of lithium ion insertion and extraction. In some embodiments, based on the total mass of other metal elements in the positive electrode material except Li element as 100wt%, the sum of the mass contents of M2 element and M3 element is 0.01wt% to 50wt%; specifically, it can be 0.01wt%, 0.03wt%, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 35wt% or 50wt%, etc., and of course, it can also be other values ​​within the above range, which is not limited here. The mass content of M2 element and M3 element in the positive electrode material within this range can improve the crystal structure stability of the positive electrode material, improve the conductivity, and have the beneficial effects of significantly improving thermal stability and cycle stability. Too high a mass content of M2 element and M3 element will lead to a decrease in the first discharge specific capacity of the material, and too low a mass content will fail to achieve the effect of improving the material's cycle and thermal stability. Preferably, based on the total mass of the metal elements other than Li in the positive electrode material being 100 wt %, the sum of the mass contents of the M2 element and the M3 element is 0.01 wt % to 10 wt %.

[0049] In some embodiments, M1, M2, and M3 each independently include at least one of Al, Co, Zr, B, Ti, Ca, Ce, Zn, Cr, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si, and Sb, and M1, M2, and M3 are not completely the same, and at least one of M1, M2, and M3 contains B.

[0050] In some embodiments, the crystal structure of the positive electrode material is a hexagonal crystal structure or a monoclinic crystal structure.

[0051] In some embodiments, the first coulombic efficiency of the positive electrode material is E, 0.87 ≤ E ≤ 0.93. The first coulombic efficiency of the positive electrode material can specifically be 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.925, or 0.93, etc., and can also be other values ​​within the above range, which is not limited here. Preferably, the first coulombic efficiency of the positive electrode material is E, 0.90 ≤ E ≤ 0.93.

[0052] In some embodiments, the volume particle size distribution width S of the positive electrode material, 1.0≤S≤1.6; the volume particle size distribution width S of the positive electrode material can specifically be 1.0, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55 or 1.6, etc., of course, it can also be other values ​​within the above range, which is not limited here. It should be noted that in this application, the volume particle size distribution width S of the positive electrode material = (D90-D10) / D50. Specifically, the volume particle size distribution width of the positive electrode material here is the volume basis cumulative particle size distribution of all particles, and the particle size distribution is measured by laser diffraction method. D10 represents the particle size corresponding to the cumulative particle size distribution percentage of the powder reaching 10%, D50 represents the particle size corresponding to the cumulative particle size distribution percentage reaching 50%, and D90 represents the particle size corresponding to the cumulative particle size distribution percentage reaching 90%.

[0053] By controlling the particle size distribution width of the positive electrode material within the above range, it indicates that the positive electrode material has a more suitable volume particle size distribution, which is beneficial to improving the gram capacity of the positive electrode material; and the volume particle size distribution of the positive electrode material is relatively concentrated, indicating that the degree of adhesion between the particles of the positive electrode material is increased. The adhesion between the particles shortens the lithium ion transmission path, which is beneficial to the release and embedding of lithium ions, and is beneficial to improving the first coulombic efficiency and fast charging performance of the positive electrode material.

[0054] In some embodiments, the oil absorption value of the positive electrode material is P mL / 100g, where 10≤P≤40; the oil absorption value P of the positive electrode material can specifically be 10mL / 100g, 12mL / 100g, 15mL / 100g, 20mL / 100g, 25mL / 100g, 30mL / 100g, 35mL / 100g, 38mL / 100g, or 40mL / 100g, and of course, it can also be other values ​​within the above range, which is not limited here. In the process of preparing the positive electrode slurry, if the oil absorption value of the positive electrode material is too high, it will lead to an increase in the consumption of dispersant and binder required for preparing the slurry, that is, the mass proportion of the positive electrode material in the positive electrode slurry will decrease, reducing the battery energy density and increasing the processing cost; if the oil absorption value of the positive electrode material is too low, the dispersibility of the positive electrode material in the positive electrode slurry will decrease. In this application, without affecting the processing performance and processing costs of the positive electrode material, the oil absorption value of the positive electrode material is controlled within the above range, which is beneficial for improving the compatibility of the positive electrode material with the electrolyte, improving the positive electrode material's adsorption and wettability to the electrolyte, and effectively reducing the interfacial resistance between the positive electrode material and the electrolyte, which is beneficial for improving the transmission of lithium ions and electrons, and thus improving the electrochemical performance of the positive electrode material. Preferably, the oil absorption value of the positive electrode material is P mL / 100g, and 15≤P≤25.

[0055] In some embodiments, the positive electrode material satisfies the following relationship: 1.0≤E*(P-20)+S≤8.0, which can be 1.0, 1.2, 1.5, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, or 8.0, etc., and of course other values ​​within the above range are also possible, and are not limited here. In order for the positive electrode material to have both high energy density and rate performance, preferably, the positive electrode material satisfies the following relationship: 1.0≤E*(P-20)+S≤2.0.

[0056] In some embodiments, the specific surface area of ​​the positive electrode material is 0.5 m 2 / g~1.2m 2 / g, specifically 0.5m 2 / g, 0.55m 2 / g, 0.6m 2 / g, 0.65m 2 / g, 0.70m 2 / g, 0.75m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.1m 2 / g or 1.2m 2 / g, etc. The specific surface area of ​​the positive electrode material will affect the rate characteristics of the battery. The larger the specific surface area, the more complete the contact between the positive electrode material and the electrolyte, the more sites for lithium ion extraction and embedding, the discharge capacity of the positive electrode material, the rate capacity, and the fast charging performance, but the oil absorption value of the positive electrode material will also increase. However, an excessively large specific surface area makes the positive electrode material easy to react with the electrolyte, and the side reactions increase, resulting in poor cycle performance. When the specific surface area of ​​the positive electrode material is controlled within the above range, it is beneficial to improve the cycle performance of the lithium battery made of the positive electrode material. Preferably, the specific surface area of ​​the positive electrode material is 0.6m 2 / g~0.8m 2 / g.

[0057] In some embodiments, the specific surface area of ​​the positive electrode material is low, and the oil absorption value is also reduced. Moreover, if the specific surface area is too large, more dispersant and binder will be consumed, and the side reactions will also increase. Therefore, in this application, the first coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is P mL / 100g, and the specific surface area of ​​the positive electrode material is Am 2 / g, and the following relationship is satisfied: 0.5≤E*(P-20)+A≤6.0.

[0058] In the above scheme, the oil absorption value P of the positive electrode material can reflect the compatibility of the positive electrode material with the electrolyte. The higher the oil absorption value of the positive electrode material, the better the compatibility of the positive electrode material with the electrolyte, and the lower the oil absorption value, the worse the compatibility of the positive electrode material with the electrolyte. However, an excessively large oil absorption value will consume more dispersants and binders during the preparation of the positive electrode slurry from the positive electrode material, resulting in increased production costs and a decrease in energy density, affecting the electrochemical performance of the positive electrode material. An excessively large specific surface area A of the positive electrode material will lead to an increase in side reactions, consume too many active lithium ions, and reduce the first coulombic efficiency of the positive electrode material. An excessively small specific surface area of ​​the positive electrode material will affect the capacity of the positive electrode material. Therefore, the present application controls the oil absorption value P, specific surface area A and first coulomb efficiency E of the positive electrode material to be kept within the range of 0.5≤E*(P-20)+A≤6.0, thereby balancing the relationship between the first coulomb efficiency, specific surface area A and oil absorption value P of the positive electrode material. On the basis of not affecting the processing performance and processing cost of the positive electrode material, the compatibility of the positive electrode material and the electrolyte can be improved, which is beneficial to improving the lithium ion insertion and extraction efficiency of the positive electrode material during the charging and discharging process, promoting the diffusion of lithium ions at the solid-liquid interface on the surface of the positive electrode material and inside the positive electrode material, reducing the interface impedance between the positive electrode material and the electrolyte, and making the positive electrode material take into account both higher energy density and rate performance.

[0059] In some embodiments, E*(P-20)+A can be specifically 0.5, 0.6, 0.8, 1.0, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5 or 6.0, etc., and of course it can also be other values ​​within the above range, which are not limited here. On the basis of not affecting the processing performance and processing cost of the positive electrode material, in order for the positive electrode material to have a high energy density, fast charging performance and cycle performance, preferably, the positive electrode material satisfies the following relationship: 0.5≤E*(P-20)+A≤1.0.

[0060] In some embodiments, the tap density of the positive electrode material is T g / cm 3 , 1.3≤T≤2.5, specifically 1.3g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 , 2.0g / cm 3 , 2.1g / cm 3 , 2.2g / cm 3 , 2.3g / cm 3 or 2.5g / cm 3The tap density of the positive electrode material is one of the indicators of the material's energy density. The tap density and the volume particle size distribution width of the positive electrode material influence each other. A large tap density of the positive electrode material indicates a larger volume particle size distribution width of the positive electrode material and better particle dispersion, which is beneficial to improving the dispersibility of the positive electrode slurry. However, an increase in the volume particle size distribution width will also lead to an increase in the lithium ion transmission path, which is not conducive to the release and embedding of lithium ions in the positive electrode material. In addition, if the tap density of the positive electrode material is too large, the positive electrode sheet will be too dense, which is not conducive to the electrolyte infiltration of the positive electrode sheet. Lithium ions are not easily embedded, which reduces the fast charging performance of the battery. If the tap density of the positive electrode material is too low, the energy density of the material will decrease.

[0061] Therefore, in order to make the positive electrode material have both high energy density and fast charging performance, preferably, the tap density of the positive electrode material is 1.5g / cm 3 Up to 2.0g / cm 3 .

[0062] In some embodiments, the first coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is PmL / 100g, and the tap density of the positive electrode material is T g / cm 3, and satisfies the following relationship: 1.0≤E*(P-20)+T≤8.0, which can be 1.0, 1.2, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 7.5 or 8.0, etc., and of course it can be other values ​​within the above range, which is not limited here. In the above scheme, the oil absorption value P of the positive electrode material can reflect the compatibility of the positive electrode material with the electrolyte. The higher the oil absorption value of the positive electrode material, the better the compatibility of the positive electrode material with the electrolyte, and the lower the oil absorption value, the worse the compatibility of the positive electrode material with the electrolyte; however, an excessively large oil absorption value will consume more dispersant and binder in the process of preparing the positive electrode slurry from the positive electrode material, which will increase the production cost and reduce the energy density, thereby affecting the electrochemical performance of the positive electrode material. If the tap density T of the positive electrode material is too large, it will not be conducive to creating more lithium ion diffusion channels, and the electrochemical performance of the positive electrode material will be affected; if the tap density T of the positive electrode material is too small, it will affect the energy density of the positive electrode material. Therefore, the present application controls the oil absorption value P, tap density T and first coulomb efficiency E of the positive electrode material to be kept within the range of 1.0≤E*(P-20)+T≤8.0, so as to balance the relationship between the first coulomb efficiency, tap density T and oil absorption value P of the positive electrode material. On the basis of not affecting the processing performance and processing cost of the positive electrode material, the compatibility of the positive electrode material and the electrolyte can be improved, which is beneficial to improving the lithium ion insertion and extraction efficiency of the positive electrode material during the charge and discharge process, promoting the diffusion of lithium ions at the solid-liquid interface on the surface of the positive electrode material and inside the positive electrode material, reducing the interface impedance between the positive electrode material and the electrolyte, and the appropriate tap density can improve the energy density of the positive electrode material, so that the positive electrode material can take into account both high energy density and rate performance.

[0063] In order for the positive electrode material to have both high energy density and rate performance, preferably, the positive electrode material satisfies the following relationship: 1.0≤E*(P-20)+T≤2.0.

[0064] In a second aspect, an embodiment of the present application provides a method for preparing a positive electrode material, as shown in FIG1 , comprising the following steps:

[0065] Step S10, drying the mixed solution containing the metal composite hydroxide precursor, the dopant containing the M1 element, and the lithium-containing compound, and subjecting the dried product to a primary heat treatment to obtain a matrix material;

[0066] Step S20: Mix the base material with the first coating agent containing the M2 element and perform a secondary heat treatment to obtain a primary coating product, wherein the temperature of the secondary heat treatment is T°C, wherein T=750-(n Ni -0.8)*500,n Ni Indicates the molar content of Ni element in the matrix material;

[0067] Step S30, mixing the obtained product of the first coating with a second coating agent containing the M3 element and then performing three heat treatments to obtain a positive electrode material; wherein M1, M2, and M3 are each independently selected from at least one of Al, Co, Zr, Ti, Ca, Ce, Zn, Cr, Mg, Y, La, Sr, Ba, W, Mo, Nb, and Si, and M1, M2, and M3 are not exactly the same.

[0068] In the above technical solution, the precursor, dopant and lithium-containing compound are mixed in a mixed solution, dried and subjected to a primary heat treatment to obtain a base material, which is then mixed with a first coating agent and subjected to a secondary heat treatment. During the secondary heat treatment, by controlling the secondary heat treatment temperature, the bonding strength between the coating layer and the base material can be effectively improved, thereby improving the stability of the positive electrode material structure. The primary coating product is then mixed with a second coating agent and subjected to a third heat treatment, so that the coating layer of the positive electrode material is tightly bonded to the base material, thereby reducing residual lithium on the surface of the material. Through multiple heat treatments, the formation of Li2Ni8O on the surface of the material can be suppressed. 10 The generation of heterogeneous phase can better improve the surface structure of the positive electrode material, improve the dispersibility of the positive electrode material, increase the tap density of the positive electrode material, and improve the oil absorption value and specific surface area of ​​the positive electrode material.

[0069] The preparation method of the present application is described in detail below with reference to the examples:

[0070] Before step S10, the method further includes:

[0071] The metal salt solution, the complexing agent and the pH regulator are mixed and treated to obtain a metal composite hydroxide precursor.

[0072] In some embodiments, the mass ratio of the metal salt solution, the complexing agent and the pH adjuster is 1:(0.01-0.10):(0.1-0.8), and the mass ratio of the metal salt solution, the complexing agent and the pH adjuster can specifically be 1:0.01:0.1, 1:0.05:0.3, 1:0.1:1.5 and 1:0.08:0.8, etc.

[0073] In some embodiments, the metal salt solution includes a nickel salt solution, a cobalt salt solution, or a manganese salt solution.

[0074] Specifically, the nickel salt solution includes at least one of nickel sulfate, nickel chloride, nickel sulfamate, nickel bromide, nickelous hydroxide, and nickel carbonyl.

[0075] The cobalt salt solution includes at least one of cobalt sulfate, cobalt chloride, and cobalt nitrate.

[0076] The manganese salt solution includes at least one of manganese sulfate, manganese nitrate and manganese chloride.

[0077] In some embodiments, the complexing agent is selected to be able to form a complex with nickel, cobalt, and manganese ions in an aqueous solution. Specifically, the complexing agent includes at least one of an ammonium ion donor, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracildiacetic acid, and glycine, and the ammonium ion donor includes ammonia water, ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium fluoride.

[0078] In some embodiments, the mixing temperature is between 10°C and 80°C. Specifically, the mixing temperature is 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, and 80°C. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the mixing temperature is between 20°C and 70°C. Controlling the coprecipitation reaction temperature within the above range is beneficial to grain growth.

[0079] The pH adjuster includes an alkali metal hydroxide, and the alkali metal oxide includes at least one of sodium hydroxide and potassium hydroxide.

[0080] In some embodiments, the pH of the mixing process is 9 to 13, specifically, the pH of the mixing process is 9, 10, 11, 12, and 13, etc., and of course, other values ​​within the above range can also be used, which is not limited here. Preferably, the pH of the coprecipitation reaction is 11 to 13.

[0081] In some embodiments, the mixing time is 10 to 200 hours. Specifically, the mixing time is 10, 15, 20, 30, 60, 80, 100, 130, 150, 180, and 200 hours, etc. Of course, other values ​​within the above range can also be used, and are not limited here.

[0082] In some embodiments, the mixing process is carried out under stirring at a stirring rate of 800 to 1200 rpm. Specifically, the stirring rate is 800, 880, 900, 960, 1000, 1060, 11130, and 1200 rpm, etc. Of course, other values ​​within the above range can also be used and are not limited here.

[0083] In some embodiments, the mixing treatment is performed in a reaction tank, and the reaction tank is at least one of a continuous method in which the formed metal composite hydroxide is separated and overflowed, and a batch method in which the metal composite hydroxide is not discharged outside the system until the reaction is completed.

[0084] In some embodiments, the metal composite hydroxide precursor prepared by the mixing treatment is a slurry suspension, which is obtained through solid-liquid separation, washing, and drying.

[0085] In some embodiments, the solid-liquid separation method includes any one of centrifugation and filtration. The purpose of the solid-liquid separation is to separate the metal composite hydroxide from the solvent.

[0086] In some embodiments, the washing is performed with deionized water multiple times to remove impurities.

[0087] In some embodiments, the drying temperature is 100°C to 130°C, and the drying temperature can specifically be 100°C, 110°C, 120°C and 130°C, etc. The drying time is 12h to 24h, and the drying time can specifically be 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h and 24h, etc.

[0088] In some embodiments, the metal composite hydroxide precursor is in powder form with an average particle size of 3 μm to 10 μm. The median particle size of the metal composite hydroxide precursor can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc.

[0089] In step S10 , a metal composite hydroxide precursor, a dopant containing an M1 element, and a lithium-containing compound are subjected to a heat treatment to obtain a base material.

[0090] In some embodiments, the mass ratio of the metal composite hydroxide precursor, the lithium-containing compound, and the dopant containing the M1 element is 1:0.46:0.001 to 1:0.48:0.003.

[0091] In some embodiments, the molar ratio of metal Me in the metal composite hydroxide precursor to Li in the lithium-containing compound is 1.0 < Li / Me < 1.2. Specifically, Li / Me can be 1.01, 1.02, 1.03, 1.05, 1.06, 1.08, 1.09, 1.1, 1.12, 1.15, or 1.19, where Me represents the molar content of all metals in the metal composite hydroxide precursor. Controlling the molar ratio of metal Me in the metal composite hydroxide precursor to Li in the lithium-containing compound within the above range is beneficial to the formation of matrix material grains and the improvement of the electrochemical properties of the material. Preferably, 1.0 < Li / Me < 1.1.

[0092] In some embodiments, the metal composite hydroxide precursor has the general chemical formula Ni a Co b Mn c (OH)2, where 0.6≤a≤1.0, 0.0≤b≤0.10, and 0.0≤c≤0.3.

[0093] In some embodiments, the M1 element includes at least one of Al, Co, Zr, B, Ti, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si, and Sb.

[0094] In some embodiments, the added amount of the M1 element accounts for 0 to 0.3 of the total molar amount of the matrix material.

[0095] In some embodiments, the dopant containing the M1 element includes at least one of lithium zirconate, lithium titanate, niobium oxide, lithium tungstate, barium oxide, and magnesium hydroxide.

[0096] In some embodiments, the average particle size of the dopant containing the M1 element is 10 nm to 50 nm. The average particle size of the dopant can specifically be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0097] In some embodiments, the lithium-containing compound includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate. Preferably, the lithium-containing compound includes lithium hydroxide, specifically, the lithium hydroxide includes at least one of anhydrous lithium hydroxide and monohydrate lithium hydroxide.

[0098] In some embodiments, the temperature of the primary heat treatment is 680°C to 900°C. Specifically, the temperature of the primary heat treatment is 680°C, 700°C, 720°C, 750°C, 780°C, 800°C, 820°C, 850°C and 900°C, etc. Of course, it can also be other values ​​within the above range, which is not limited here. Preferably, the temperature of the primary heat treatment is 780°C to 870°C. The temperature of the heat treatment sintering is limited to the above range, which is conducive to the grain growth of the nickel-cobalt-manganese ternary single crystal positive electrode material and obtains a suitable volume particle size distribution width S.

[0099] In some embodiments, the time for a single heat treatment is 5 hours to 20 hours. Specifically, the time for a single heat treatment is 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, and 20 hours. Of course, other values ​​within the above ranges are also possible and are not limited here. Preferably, the time for a single heat treatment is 8 hours to 15 hours.

[0100] In some embodiments, the heating rate of the primary heat treatment is 50°C / h to 550°C / h. Specifically, the heating rate of the primary heat treatment is 50°C / h, 100°C / h, 140°C / h, 200°C / h, 250°C / h, 300°C / h, 380°C / h, 400°C / h, 450°C / h, 500°C / h, and 550°C / h. Of course, other values ​​within the above ranges are also possible and are not limited here. Preferably, the heating rate of the primary heat treatment is 100°C / h to 400°C / h. More preferably, the heating rate of the primary heat treatment is 140°C / h to 380°C / h.

[0101] In some embodiments, the primary heat treatment is performed in an oxygen-containing atmosphere, and the oxygen content of the oxygen-containing gas is greater than or equal to 85%. Specifically, the oxygen content of the oxygen-containing gas can be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or 100%, etc., and of course other values ​​within the above ranges are also possible, and are not limited herein. Preferably, the oxygen content of the oxygen-containing gas is greater than or equal to 95%.

[0102] In some embodiments, the equipment for the primary heat treatment includes a stationary box furnace, a roller hearth continuous furnace, and the like.

[0103] Step S20: mixing the base material with the first coating agent containing the M2 element and performing a secondary heat treatment to obtain a primary coating product, wherein the temperature of the secondary heat treatment is T0°C, wherein T0=750-(n Ni -0.8)*500,n Ni Indicates the molar content of Ni element in the matrix material.

[0104] In some embodiments, the first capping agent includes at least one of an oxide of M2 and a hydroxide of M2.

[0105] In some embodiments, the mass ratio of the base material to the first coating agent is 1000:(0.5-3). Specifically, the mass ratio of the base material to the first coating agent can be 1000:0.5, 1000:1, 1000:1.5, 1000:2, 1000:2.5, and 1000:3. By controlling the mass ratio of the base material to the first coating agent, not only can the proportions of M1, M2, and M3 in the positive electrode material be optimized to meet the requirements of the general chemical formula, but it can also help adjust the specific surface area of ​​the positive electrode material.

[0106] In some embodiments, the first coating agent may be at least one of lithium aluminate, lithium titanate, lithium lanthanum titanate, yttrium oxide, aluminum oxide, and titanium oxide. In some embodiments, the temperature of the secondary heat treatment is T0°C, where T0=750-(n Ni -0.8)*500,n NiRepresents the molar content of the Ni element in the matrix material. That is, the higher the doping amount of the Ni element in the matrix material, the lower the temperature of the secondary heat treatment. It can be understood that the higher the temperature of the secondary heat treatment, the more obvious the particle adhesion effect, and the oil absorption value of the positive electrode material will also increase accordingly, which will result in the need to add more dispersant during the preparation of the positive electrode material slurry. Therefore, adjusting the temperature of the secondary heat treatment by the nickel content can effectively suppress the degree of particle adhesion, so that the oil absorption value of the positive electrode material can be controlled within an appropriate range, balancing the relationship between the first coulomb efficiency, tap density T and oil absorption value P of the positive electrode material, and improving the compatibility of the positive electrode material with the electrolyte without affecting the processing performance and processing cost of the positive electrode material. In addition, the temperature of the secondary heat treatment will also affect the values ​​of the specific surface area A and the volume particle size distribution width S. The above-mentioned secondary treatment temperature is conducive to obtaining a suitable specific surface area A and volume particle size distribution width S.

[0107] In some embodiments, the temperature of the secondary heat treatment is 600°C to 800°C. Specifically, the temperature of the secondary heat treatment is 600°C, 650°C, 680°C, 700°C, 720°C, 750°C, 780°C, and 800°C. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the temperature of the secondary heat treatment is 650°C to 750°C.

[0108] In some embodiments, the secondary heat treatment time is 1 hour to 20 hours. Specifically, the secondary heat treatment time is 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, and 20 hours. Of course, other values ​​within the above ranges are also possible and are not limited here. Preferably, the secondary heat treatment time is 3 hours to 10 hours.

[0109] In some embodiments, the heating rate of the secondary heat treatment is 50°C / h to 550°C / h. Specifically, the heating rate of the secondary heat treatment is 50°C / h, 100°C / h, 140°C / h, 200°C / h, 250°C / h, 300°C / h, 380°C / h, 400°C / h, 450°C / h, 500°C / h, and 550°C / h. Of course, other values ​​within the above ranges are also possible and are not limited here. Preferably, the heating rate of the secondary heat treatment is 100°C / h to 400°C / h. More preferably, the heating rate of the secondary heat treatment is 140°C / h to 380°C / h.

[0110] In some embodiments, the secondary heat treatment is performed in an oxygen-containing atmosphere, and the oxygen content of the oxygen-containing gas is greater than or equal to 85%. Specifically, the oxygen content of the oxygen-containing gas can be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or 100%, etc., and of course other values ​​within the above ranges are also possible, and are not limited herein. Preferably, the oxygen content of the oxygen-containing gas is greater than or equal to 95%.

[0111] In some embodiments, the equipment for the secondary heat treatment includes a stationary box furnace, a roller hearth continuous furnace, and the like.

[0112] In some embodiments, the secondary heat-treated product is fed into an ultrafine stone mill for crushing, and the grinding disc gap of the ultrafine stone mill is 5 μm to 50 μm. The grinding disc gap can specifically be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 45 μm, or 50 μm, etc. Of course, it can also be other values ​​within the above range, which is not limited here. Preferably, the grinding disc gap of the ultrafine stone mill is 5 μm to 30 μm.

[0113] Step S30: mixing the primary coating product with a second coating agent containing the M3 element and then performing three heat treatments to obtain a positive electrode material.

[0114] In some embodiments, the M3 element includes at least one of Al, Co, Zr, B, Ti, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si, and Sb. Preferably, the M3 element is selected from B.

[0115] In some embodiments, the second coating agent includes a boron-containing compound, and the boron-containing compound includes B2O3, H3BO3, Li2O-B2O3, Li3BO3, Li2B4O7, Li2B2O7, Li2B8O 13 At least one of the above, by adding a boron-containing compound to the primary coating result, the above boron-containing compound can not only chemically react with the alkaline impurities on the surface of the material but also cover the surface of the material to form a stable coating layer, which not only reduces the alkaline impurities on the surface of the material but also protects the surface of the material, reduces the decomposition and gas production of Li2CO3 in the alkaline impurities and the side reaction with the electrolyte to produce gas.

[0116] In some embodiments, the mass ratio of the primary coating product to the second coating agent is 1:1 to 1:5.

[0117] In some embodiments, the temperature of the three heat treatments is 200°C to 400°C. Specifically, the temperatures of the three heat treatments are 200°C, 250°C, 280°C, 300°C, 320°C, 360°C, 380°C, and 400°C. Of course, other values ​​within the above ranges are also possible and are not limited here. Preferably, the temperature of the three heat treatments is 250°C to 360°C.

[0118] In some embodiments, the three heat treatments are performed for 1 to 20 hours; the three heat treatments are performed for 5 to 20 hours. Specifically, the three heat treatments are performed for 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, and 20 hours. Of course, other values ​​within the above ranges are also possible and are not limited here. Preferably, the three heat treatments are performed for 5 to 10 hours.

[0119] In some embodiments, the heating rate of the three heat treatments is 50°C / h to 550°C / h. Specifically, the heating rate of the three heat treatments is 50°C / h, 100°C / h, 140°C / h, 200°C / h, 250°C / h, 300°C / h, 380°C / h, 400°C / h, 450°C / h, 500°C / h, and 550°C / h, etc. Of course, other values ​​within the above ranges are also possible and are not limited here. Preferably, the heating rate of the three heat treatments is 100°C / h to 400°C / h, and more preferably, the heating rate of the three heat treatments is 140°C / h to 380°C / h.

[0120] In some embodiments, the three heat treatments are performed in an oxygen-containing atmosphere, and the oxygen content of the oxygen-containing gas is greater than or equal to 85%. Specifically, the oxygen content of the oxygen-containing gas can be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or 100%, etc., and of course other values ​​within the above ranges are also possible, and are not limited herein. Preferably, the oxygen content of the oxygen-containing gas is greater than or equal to 95%.

[0121] In some embodiments, the equipment for the tertiary heat treatment includes a stationary box furnace, a roller hearth continuous furnace, and the like.

[0122] In some embodiments, the tertiary heat treatment further includes the steps of screening and demagnetization.

[0123] In some embodiments, the sieving purpose is 200-400 mesh.

[0124] In a third aspect, the present application also provides a positive electrode slurry, which includes a dispersant and the above-mentioned positive electrode material.

[0125] Since the oil absorption value of the positive electrode material in this application maintains a certain balance with the specific surface area, tap density or volume particle size distribution width, the amount of binder used can be reduced in the process of preparing the cathode slurry, and the mass proportion of the positive electrode material in the positive electrode slurry can be increased, thereby improving the energy density of the positive electrode sheet. In addition, in order to improve the problem of uneven dispersion caused by insufficient binder, adding an appropriate amount of dispersant to the positive electrode slurry can effectively improve the dispersion uniformity of the positive electrode slurry, reduce the formation of filter residue, and improve the filtration performance of the positive electrode slurry during filtration, so that the positive electrode sheet formed by coating the positive electrode slurry can achieve high energy density, rate performance and better cycle performance.

[0126] In some embodiments, based on 100% by mass of the positive electrode material in the positive electrode slurry, the mass content of the dispersant is M%, and 13≤M≤18. Specifically, the mass content of the dispersant is 13%, 14%, 15%, 15.5%, 16%, 16.5%, 17%, or 18%, etc., without limitation herein. Preferably, the mass content of the dispersant is 15% to 17%.

[0127] In this application, by using a suitable dispersant and a positive electrode material with suitable physical and chemical properties, the dispersion uniformity of the positive electrode material in the positive electrode slurry can be improved, the adhesion of the positive electrode material in the positive electrode slurry can be reduced, the filtration efficiency of the positive electrode slurry can be improved, and filtration loss can be reduced. At the same time, large particles of filter residue can be reduced from being coated on the positive electrode sheet, which can reduce the cycle performance during the charge and discharge process.

[0128] In some embodiments, the positive electrode slurry satisfies the following relationship: 15≤E*(P-20) / 100+M≤18, where E represents the first coulombic efficiency of the positive electrode material, and P represents the oil absorption value of the positive electrode material.

[0129] In the preparation process of positive electrode slurry, the amount of dispersant used is related to the oil absorption value of the positive electrode material. The lower the oil absorption value of the positive electrode material, the more dispersant is needed to improve the dispersibility of the positive electrode material particles and reduce the amount of filter residue. In theory, the more dispersant, the better the dispersibility of the positive electrode material particles. However, too much dispersant will reduce the energy density and increase the cost. For comprehensive consideration of various performance aspects, E, M and P satisfy the relationship: 15≤E*(P-20) / 100+M≤18.

[0130] The present application also provides a positive electrode plate, which includes a current collector and a positive electrode slurry arranged on the current collector.

[0131] In the preparation process of lithium-ion batteries, the quality of the slurry directly affects the performance of the lithium-ion battery. By coating the above-mentioned positive electrode slurry with good dispersibility on the current collector, the performance of the battery can be improved.

[0132] The present application also provides a battery, comprising: a negative electrode plate, a positive electrode plate, a separator and an electrolyte, wherein the positive electrode plate is a positive electrode plate.

[0133] The performance of the battery can be improved by coating the cathode slurry with good dispersion on the current collector to prepare the positive electrode sheet.

[0134] The present application also provides an electrical device, which includes the above-mentioned battery.

[0135] As battery performance is improved, the performance of electrical equipment using the battery will also be improved.

[0136] The following further illustrates the embodiments of the present application in multiple embodiments. The embodiments of the present application are not limited to the following specific embodiments. Within the scope of the unchanged main rights, appropriate changes can be made to the implementation.

[0137] Example 1

[0138] A method for preparing a positive electrode material comprises the following steps:

[0139] (1) Preparation of Ni by coprecipitation method 0.885 Co 0.09 Mn 0.025 (OH)2 precursor, D50 of the precursor = 3.5 μm;

[0140] (2) Ni 0.885 Co 0.09 Mn 0.025 The (OH)2 precursor, LiOH*H2O and dopant nano-TiO2, ZrO2, and MgO were mixed uniformly, and then subjected to a single heat treatment at 840°C to prepare a matrix material. The single heat treatment was conducted by introducing oxygen with an oxygen content greater than 95%. Among them, Li / Me=1.05, Me=(Ni, Co, and Mn), and D50=3.0 μm of the single crystal matrix material;

[0141] (3) the base material prepared in step (2), nano-Al2O3 and nano-Co3O4 were mixed uniformly, and then subjected to a secondary heat treatment at 707.5°C, and then subjected to an ultrafine stone grinding process with a gap of 10 μm to obtain a primary coating product;

[0142] (4) The coated product was mixed with H3BO3 and heat treated at 300℃ for three times. After screening and demagnetization, the positive electrode material was obtained. The chemical formula is LiNi 0.877 Co 0.098 Mn 0.024 Al 0.002 Ti 0.002 Zr 0.002 Mg 0.001 B0.005 O2, SEM electron microscope image is shown in Figure 2.

[0143] The positive electrode material was prepared into positive electrode slurry according to the following method:

[0144] Step 1: Add the positive electrode material, carbon black, and carbon nanotubes into a double planetary mixing device and mix them; wherein the mass ratio of the positive electrode material, carbon black, and carbon nanotubes is 97.3:1.0:0.5.

[0145] Step 2: Stirring the positive electrode binder PVDF and NMP to prepare a PVDF glue solution, wherein the mass ratio of PVDF to NMP is 6:94;

[0146] Step 3: Add the prepared PVDF glue to the mixture obtained in step 1 three times to obtain a slurry, wherein the time interval between each addition is 2 hours; the slurry is put into a high-speed shear disperser for dispersion to obtain a dispersed slurry;

[0147] Step 4: Add NMP solvent to the dispersed slurry, adjust the viscosity of the solution to 4500 mPa.s, and filter through a 100-mesh sieve for 80 seconds to obtain a positive electrode slurry.

[0148] Example 2-10

[0149] Examples 2-10 were prepared using the same method as Example 1, with the exception of the type of precursor, particle size, coating amount of B, or temperature of the secondary heat treatment, as shown in Tables 1 and 2 below. The positive electrode slurries of the above examples were prepared in the same manner as Example 1, and the dispersant content and filtration time were adjusted to control the viscosity, as shown in Table 2 below.

[0150] Example 11

[0151] The difference from Example 1 is that in step (2), the dopant nano-SrO is used to replace the dopant nano-MgO; in step (3), the nano-Y2O3 is used to replace the nano-Al2O3; the chemical formula of the positive electrode material obtained in step (4) is LiNi 0.877 Co 0.098 Mn 0.024 Ti 0.002 Zr 0.002 Sr 0.001 Y 0.002 B 0.005 O2. Please refer to Table 1 and Table 2 below for details.

[0152] Example 12

[0153] The difference from Example 1 is that in step (4), H3BO3 is replaced by B2O3, and the obtained positive electrode material has the chemical formula LiNi 0.877 Co 0.098 Mn 0.024 Al 0.002 Ti 0.002 Zr 0.002 Mg 0.001 B 0.005 O2. Please refer to Table 1 and Table 2 below for details.

[0154] Example 13

[0155] The difference from Example 1 is that in step (2), no dopant nano-TiO2, ZrO2 and MgO are added; in step (3), the base material prepared in step (2) and nano-Al2O3 are mixed evenly. The obtained positive electrode material has the chemical formula of LiNi 0.881 Co 0.09 Mn 0.024 Al 0.002 B 0.005 O2. Please refer to Table 1 and Table 2 below for details.

[0156] Example 14

[0157] The difference from Example 1 is that step (1) adopts coprecipitation method to prepare Ni 0.70 Co 0.10 Mn 0.20 (OH)2 precursor. The precursor in step (2) is Ni 0.70 Co 0.10 Mn 0.20 (OH)2; the heat treatment temperature in step (3) is 800°C. The chemical formula of the positive electrode material is LiNi 0.692 Co 0.108 Mn 0.024 Al 0.002 Ti 0.002 Zr 0.002 Mg 0.001 B 0.005 O2. Please refer to Table 1 and Table 2 below for details.

[0158] Example 15

[0159] The difference from Example 14 is that in step (4), the coating is not mixed evenly with H3BO3, and the heat treatment is not performed three times at 300°C. The chemical formula of the positive electrode material obtained is LiNi 0.693 Co 0.109 Mn 0.025 Al 0.002 Ti 0.002 Zr 0.002 Mg0.001 O2. Refer to Table 1 and Table 2 below.

[0160] Example 16

[0161] The difference from Example 1 is that step (1) adopts coprecipitation method to prepare Ni 0.70 Co 0.10 Mn 0.20 (OH)2 precursor. The precursor in step (2) is Ni 0.50 Co 0.20 Mn 0.29 (OH)2; the heat treatment temperature in step (3) is 800°C. The chemical formula of the positive electrode material is LiNi 0.492 Co 0.208 Mn 0.324 Al 0.002 Ti 0.002 Zr 0.002 Mg 0.001 B 0.005 O2. Please refer to Table 1 and Table 2 below for details.

[0162] Example 17

[0163] The difference from Example 1 is that step (1) adopts coprecipitation method to prepare Ni 0.70 Co 0.10 Mn 0.20 (OH)2 precursor. The precursor in step (2) is Ni 0.60 Co 0.20 Mn 0.20 (OH)2; the heat treatment temperature in step (3) is 800°C. The chemical formula of the positive electrode material is LiNi 0.592 Co 0.208 Mn 0.19 Al 0.002 Ti 0.002 Zr 0.002 Mg 0.001 B 0.005 O2. Please refer to Table 1 and Table 2 below for details.

[0164] Example 18

[0165] The difference from Example 1 is that step (1) adopts coprecipitation method to prepare Ni 0.90 Co 0.05 Mn 0.05 (OH)2 precursor. The precursor in step (2) is Ni 0.90 Co 0.05 Mn 0.05 (OH)2; the heat treatment temperature in step (3) is 800°C. The chemical formula of the positive electrode material is LiNi 0.892Co 0.058 Mn 0.049 Al 0.002 Ti 0.002 Zr 0.002 Mg 0.001 B 0.005 O2. Please refer to Table 1 and Table 2 below for details.

[0166] Comparative Examples 1-3 prepared positive electrode materials in the same manner as Example 1, with the differences being the particle size of the precursor, the coating amount of the secondary heat treatment B, or the temperature of the secondary heat treatment, as shown in Tables 1 and 2 below. The positive electrode slurries of the above comparative examples were prepared in the same manner as Example 1, and the dispersant content and filtration time were adjusted to control the viscosity, as shown in Table 2.

[0167] Comparative Example 4

[0168] The difference from Example 1 is that in step (2), no dopant nano-TiO2, ZrO2 and MgO are added; and step (3) is not performed; in step (4), the base material prepared in step (1) and H3BO3 are mixed evenly. The chemical formula of the obtained positive electrode material is LiNi 0.883 Co 0.09 Mn 0.024 B 0.005 O2. Details are as follows Table 1 and Table 2.

[0169] Comparative Example 5

[0170] The difference from Example 14 is that the sintering temperature of step (3) is changed to 700°C, and the other steps are the same as those of Example 14. The chemical formula of the positive electrode material obtained is LiNi 0.692 Co 0.108 Mn 0.024 Al 0.002 Ti 0.002 Zr 0.002 Mg 0.001 B 0.005 O2. See Table 1 and Table 2 for details.

[0171] Table 1

[0172] Table 2. Cathode material and cathode slurry preparation process parameters

[0173] Preparation of positive electrode

[0174] The positive electrode slurry prepared in the above embodiment or comparative example is evenly coated on the positive electrode current collector with a primer, and then dried, cold pressed, and cut to obtain a positive electrode sheet.

[0175] Negative electrode preparation

[0176] The active material graphite, silicon, conductive agent acetylene black, high molecular polymer, and carboxymethyl cellulose (CMC) are dissolved in the solvent deionized water in a weight ratio of 90:5:2:1.9:1.1, and are evenly mixed to prepare a negative electrode slurry. The slurry is coated on copper foil, dried, and then cold-pressed and cut to obtain a negative electrode sheet.

[0177] diaphragm

[0178] The diaphragm is a PE diaphragm with PVDF and alumina coating on the surface to improve adhesion and heat resistance.

[0179] electrolyte

[0180] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and LiPF6:LiFSI (2:8) was uniformly dissolved in the above solution to obtain an electrolyte solution. The concentration of lithium salt in the electrolyte solution was 1 mol / L.

[0181] Battery preparation

[0182] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative sheets to provide insulation. The cells are then wound to form bare cells, with tabs welded to the cells. The cells are then placed in aluminum shells and baked at 80°C to remove moisture. Electrolyte is then injected and sealed to create an uncharged battery. The uncharged battery then undergoes a series of processes, including resting, hot and cold pressing, formation, shaping, and capacity testing, to produce a lithium-ion battery product.

[0183] Table 3 Dispersant addition parameters in positive electrode slurry and battery performance parameters

[0184] Performance Testing

[0185] 1. Test method for tap density of positive electrode materials

[0186] GB / T5162-1985 Metal powder - Determination of tap density was used.

[0187] 2. Determination of the specific surface area of ​​the positive electrode material

[0188] The specific surface area of ​​the cathode material was determined using the gas adsorption BET method according to GB / T19587-2004.

[0189] 3. Determination of oil absorption value of positive electrode material

[0190] The oil absorption value O is the amount of linseed oil added when the torque generated by the change in viscosity reaches 70% of the maximum torque, and the unit is mL / 100g.

[0191] 4. Test method for volume particle size distribution width of positive electrode materials

[0192] The particle size test method refers to GB / T 19077-2016. It can be conveniently measured using a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0193] The volume particle size distribution width function Span of the two peaks is expressed as:

[0194] 5.Battery capacity test:

[0195] ① Let it stand for 30 minutes; ② Charge to 4.25V at 1 / 3C, and then charge at 4.25V at a constant voltage of 0.05C; ③ Let it stand for 30 minutes; ④ Discharge to 2.8V at 1 / 3C to obtain the capacity C0; the energy obtained is the battery energy, and the weight energy density = energy / battery weight.

[0196] The first coulombic efficiency test method

[0197] ① Let it stand for 120 minutes; ② Charge at 0.1C to 4.25V, and then charge at a constant voltage of 4.25V to 0.05C to obtain capacity C1; ③ Let it stand for 30 minutes; ④ Discharge at 0.1C to 2.8V to obtain capacity C2; First coulombic efficiency = C1 / C2.

[0198] 6. Battery lithium deposition test:

[0199] ① Let stand for 5 minutes; ② Discharge 1 / 3C0 to 2.8V; ③ Let stand for 5 minutes; ④ Charge 1.2C0 to 50% SOC; ⑤ Charge 0.87C0 to 80% SOC; ⑥ Charge 1 / 3C0 to 4.25V, constant voltage charge at 4.25V to 0.05C; ⑦ Let stand for 10 minutes; ⑧ Discharge 1 / 3C0 to 2.8V; ⑨ Let stand for 5 minutes; ⑩ Repeat steps 4-9 5 times; Charge 1 / 3C to 4.25V, constant voltage charge at 4.25V to 0.05C; Let stand for 5 minutes.

[0200] 7.Battery cycle test:

[0201] Adjust the temperature to 45°C and keep warm for 2 hours.

[0202] ①Rest for 5 minutes; ②1 / 3C charge to 4.25V, constant voltage charge at 4.25V to 0.05C end; ③Stand for 5 minutes, discharge at 0.5C0 to 2.8V; ⑤Stand for 5 minutes; ⑥Repeat steps 7-9 until capacity fading ≤ 80%.

[0203] As shown in Table 3, the test data of Examples 1 to 18 show that in different positive electrode material systems, the positive electrode material satisfies any of the three relationship equations of 1.0≤E*(P-20)+S≤8, 0.5≤E*(P-20)+A≤6.0 or 1.0≤E*(P-20)+T≤8.0. The relationship between the first coulombic efficiency, oil absorption value P and volume particle size distribution width S, tap density T or specific surface area S of the positive electrode material can be balanced. On the basis of not affecting the processing performance and processing cost of the positive electrode material, the compatibility of the positive electrode material and the electrolyte can be improved, which is beneficial to improving the lithium ion insertion and extraction efficiency of the positive electrode material during the charge and discharge process, promoting the diffusion of lithium ions at the solid-liquid interface on the surface of the positive electrode material and inside the positive electrode material, reducing the interface impedance between the positive electrode material and the electrolyte, so that the positive electrode material takes into account both higher energy density and rate performance. According to the test data of Examples 1 to 4, as the amount of boron-containing compound added gradually increases during the three heat treatments, the B element content in the positive electrode material increases, and the oil absorption value of the positive electrode material shows an upward trend. This is because the higher the molar content of B in the positive electrode material, the higher the degree of agglomeration of the positive electrode material particles, the lower the tap density, and the gradual decrease in filtration performance.

[0204] In order to improve the dispersion uniformity of the positive electrode slurry, more dispersants and binders may need to be consumed. If insufficient dispersants are added, the prepared positive electrode slurry will form filter residue, thus resulting in poor filtration.

[0205] According to the relevant data of Example 1, Example 5, Example 6, Example 7, and Comparative Example 2, the higher the residual lithium on the surface of the positive electrode material, the more inactive the residual lithium on the surface is, which will cause the viscosity of the binder to increase, and more dispersant needs to be added to disperse the particles. In order to reduce the formation of filter residue in the positive electrode slurry, the filtration time will also increase accordingly.

[0206] According to the relevant data of Example 1 and Example 8, the increase in nickel content in the positive electrode material of Example 8 requires adjustment of the temperature of the secondary heat treatment, so that the degree of adhesion between the particles of the positive electrode material increases, the oil absorption value of the positive electrode material increases, and more dispersant needs to be added to disperse the particles. However, due to the increase in nickel content, the energy density increases, but the cycle performance decreases.

[0207] The data from Examples 4 and 9 show that the median particle size of the cathode material precursor increases in Example 9, while the volume particle size distribution width and tap density of the cathode material decrease. This increases the lithium ion transport path and hinders the extraction and insertion of lithium ions from the cathode material. Although the oil absorption value does not change much, the fast-charging performance of the cathode material is reduced compared to Example 1, and the high-temperature cycling performance is also reduced.

[0208] According to the relevant data of Example 3 and Example 10, it can be seen that no boron-containing compound was added during the preparation of the positive electrode material of Example 10, the residual lithium on the surface of the positive electrode material was relatively high, the stability of the coating layer formed on the surface of the positive electrode material decreased, the specific surface area of ​​the positive electrode material increased, the side reactions increased, and the cycle performance of the positive electrode material decreased.

[0209] According to the relevant data of Example 1 and Example 11, by replacing Mg in the positive electrode material of Example 1 with Sr and Al with Y, the corresponding P, S, A, T and E values ​​of the obtained positive electrode material meet the requirements of 1.0≤E*(P-20)+S≤8, 0.5≤E*(P-20)+A≤6.0, and 1.0≤E*(P-20)+T≤8.0. The battery prepared using it as the positive electrode material has high energy density and cycle life, especially the energy density.

[0210] According to the relevant data of Example 1 and Example 13, only two elements are doped in the positive electrode material of Example 13, and the corresponding P, S, A, T and E values ​​of the obtained positive electrode material meet 1.0≤E*(P-20)+S≤8, 0.5≤E*(P-20)+A≤6.0, and 1.0≤E*(P-20)+T≤8.0. The battery prepared with it as the positive electrode material has a high discharge capacity and a decreased cycle performance. According to the relevant data of Example 1 and Comparative Example 4, only one element is doped in Comparative Example 4, and the energy density and cycle performance of the battery prepared with it as the positive electrode material are significantly decreased.

[0211] From the data in Tables 2 and 3 above, it can be seen that, as shown in Example 3, the median particle size of the precursor is D50 = 3.5 μm, the median particle size of the matrix material is D50 = 3.0 μm, the residual lithium on the surface is <1000 ppm, the B coating amount is 300 ppm, and the overall performance of the battery is good.

[0212] It can be seen from the data in Tables 2 and 3 above that, as shown in the data of Comparative Examples 1 to 3 and Example 1, the higher the temperature of the secondary heat treatment, the greater the degree of adhesion between the particles, the smaller the tap density T, and the correspondingly larger the oil absorption value, resulting in an increase in the dispersant and binder required for consumption. When insufficient dispersant is added, the prepared positive electrode slurry will form filter residue, resulting in worse filtration and longer filtration time. However, if the tap density is too high, the oil absorption value becomes correspondingly smaller, the specific surface area becomes smaller, and the energy density decreases.

[0213] From the data in Table 3 above, it can be seen that the shorter the filtration time, the more evenly dispersed the positive electrode material particles are and no filter residue is formed; while the longer the filtration time, the more filter residue appears on the surface, which proves that the positive electrode slurry is poorly dispersed locally and there may be a local lithium precipitation problem.

[0214] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A positive electrode material, characterized in that: The chemical general formula of the positive electrode material is Li σ Ni a Co b Mn c M1 x M2 y M3 z O 2+r , where 0.80 ≤ σ ≤ 1.20, a + b + c + x + y + z = 1, 0.6 ≤ a ≤ 1.0, 0.0 ≤ b ≤ 0.10, 0.0 ≤ c ≤ 0.3, 0 < x < 0.3, 0 < y < 0.3, 0 < z < 0.3, -0.2 < r < 0.3, M1, M2, and M3 each independently include at least one of Al, Co, Zr, B, Ti, Ca, Ce, Zn, Cr, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si, and Sb, and M1, M2, and M3 are not all exactly the same; The first coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is P mL / 100 g, the volume particle size distribution width of the positive electrode material is S, S=(D90-D10) / D50, and the specific surface area of ​​the positive electrode material is A m 2 / g, the tap density of the positive electrode material is T g / cm 3 , and the positive electrode material satisfies at least one of the following formulas: 1.0≤E*(P-20)+S≤8.0; 0.5≤E*(P-20)+A≤6.0; 1.0≤E*(P-20)+T≤8.

0.

2. The positive electrode material according to claim 1, characterized in that The chemical general formula of the positive electrode material is Li σ Ni a Co b Mn c M1 x M2 y M3 z O 2+r , where 0.80 ≤ σ ≤ 1.20, a + b + c + x + y + z = 1, 0.6 ≤ a ≤ 1.0, 0.0 ≤ b ≤ 0.10, 0.0 ≤ c ≤ 0.3, 0 < x < 0.3, 0 < y < 0.3, 0 < z < 0.3, -0.2 < r < 0.3, M1, M2, and M3 each independently include at least one of Al, Co, Zr, B, Ti, Ca, Ce, Zn, Cr, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si, and Sb, and M1, M2, and M3 are not all exactly the same; The first coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is P mL / 100g, the volume particle size distribution width of the positive electrode material is S, S=(D90-D10) / D50, and the following relationship is satisfied: 1.0≤E*(P-20)+S≤8.

0.

3. The positive electrode material according to claim 2, characterized in that It meets at least one of the following characteristics: (1) The first coulombic efficiency of the positive electrode material is E, 0.87≤E≤0.93; (2) The volume particle size distribution width of the positive electrode material is S, 1.0≤S≤1.

6.

4. The positive electrode material according to claim 2, characterized in that It meets at least one of the following characteristics: (1) The oil absorption value of the positive electrode material is P mL / 100g, 10≤P≤40; (2) The positive electrode material satisfies the following relationship: 1.0≤E*(P-20)+S≤2.

0.

5. The positive electrode material according to claim 1, characterized in that The chemical general formula of the positive electrode material is Li σ Ni a Co b Mn c M1 x M2 y M3 z O 2+r , where 0.80 ≤ σ ≤ 1.20, a + b + c + x + y + z = 1, 0.6 ≤ a ≤ 1.0, 0.0 ≤ b ≤ 0.10, 0.0 ≤ c ≤ 0.3, 0 < x < 0.3, 0 < y < 0.3, 0 < z < 0.3, -0.2 < r < 0.3, M1, M2, and M3 each independently include at least one of Al, Co, Zr, B, Ti, Ca, Ce, Zn, Cr, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si, and Sb, and M1, M2, and M3 are not completely the same; The first coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is P mL / 100g, and the specific surface area of ​​the positive electrode material is A m 2 / g, and the following relationship is satisfied: 0.5≤E*(P-20)+A≤6.

0.

6. The positive electrode material according to claim 5, characterized in that It meets at least one of the following characteristics: (1) The first coulombic efficiency of the positive electrode material is E, 0.87≤E≤0.93; (2) The oil absorption value of the positive electrode material is P mL / 100 g, 10≤P≤40.

7. The positive electrode material according to claim 5, characterized in that It meets at least one of the following characteristics: (1) The specific surface area of ​​the positive electrode material is A m 2 / g, 0.5≤A≤1.2; (2) The positive electrode material satisfies the following relationship: 0.5≤E*(P-20)+A≤1.

0.

8. The positive electrode material according to claim 1, characterized in that The chemical general formula of the positive electrode material is Li σ Ni a Co b Mn c M1 x M2 y M3 z O 2+r , where 0.80 ≤ σ ≤ 1.20, a + b + c + x + y + z = 1, 0.6 ≤ a ≤ 1.0, 0.0 ≤ b ≤ 0.10, 0.0 ≤ c ≤ 0.3, 0 < x < 0.3, 0 < y < 0.3, 0 < z < 0.3, -0.2 < r < 0.3, M1, M2, and M3 each independently include at least one of Al, Co, Zr, B, Ti, Ca, Ce, Zn, Cr, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si, and Sb, and M1, M2, and M3 are not all identical; The first coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is P mL / 100 g, and the tap density of the positive electrode material is T g / cm 3 , and the following relationship is satisfied: 1.0≤E*(P-20)+T≤8.

0.

9. The positive electrode material according to claim 8, characterized in that It meets at least one of the following characteristics: (1) The first coulombic efficiency of the positive electrode material is E, 0.87≤E≤0.93; (2) The oil absorption value of the positive electrode material is P mL / 100 g, 10≤P≤40.

10. The positive electrode material according to claim 8, characterized in that It meets at least one of the following characteristics: (1) The tap density of the positive electrode material is T g / cm 3 , 1.3≤T≤2.5; (2) The positive electrode material satisfies the following relationship: 1.0≤E*(P-20)+T≤2.

0.

11. The positive electrode material according to any one of claims 1 to 10, characterized in that It meets at least one of the following characteristics: (1) Based on the total mass of other metal elements in the positive electrode material except Li element as 100wt%, the sum of the mass contents of M2 element and M3 element is 0.01wt% to 50wt%; (2) The oil absorption value of the positive electrode material is P mL / 100 g, 15≤P≤25; (3) The positive electrode material is a single crystal positive electrode material.

12. The positive electrode material according to any one of claims 1 to 10, characterized in that: It meets at least one of the following characteristics: (1) At least one of M1, M2, and M3 contains B; (2) M1 and M3 each independently include at least one of Al, Co, Zr, B, Ti, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si and Sb; (3) M1 is selected from Ti, Zr and Mg, M2 is selected from Al and Co, M3 is selected from B, x is 0.005, y is 0.01, and z is 0.005; (4) The M1 is selected from Ti, Zr and Sr, the M2 is selected from Y and Co, the M3 is selected from B, x is 0.005, y is 0.01, and z is 0.

005.

13. A positive electrode slurry, characterized in that: The positive electrode slurry comprises a dispersant and the positive electrode material according to any one of claims 1 to 12.

14. The positive electrode slurry according to claim 13, characterized in that: Taking the mass of the positive electrode material in the positive electrode slurry as 100%, the mass content of the dispersant is M%, and the positive electrode slurry satisfies at least one of the following characteristics: (1) In the positive electrode slurry, 13≤M≤18; (2) The positive electrode slurry satisfies the following relationship: 15≤E*(P-20) / 100+M≤18; (3) The dispersant includes N-methylpyrrolidone.

15. A battery, characterized in that: The battery comprises the positive electrode material according to any one of claims 1 to 12.

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