Positive electrode material, positive electrode slurry and lithium ion battery

Abstract

The invention relates to a positive electrode material, positive electrode slurry and a lithium ion battery, the chemical general formula of the positive electrode material is Li [sigma] NiaCobMncM1xM2yM3zO2 + r, 0.80 < = [sigma] < = 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 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 completely identical; the first coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is PmL / 100g, the particle size distribution width of the positive electrode material is S, S = (D90-D10) / D50, and the following relation is satisfied: E * (P-20) + S is more than or equal to 1.0 and less than or equal to 8. According to the technical scheme provided by the invention, the positive electrode material has relatively high energy density and rate capability on the basis of improving the processing performance of the positive electrode material.

Description

Technical Field

[0001] The present invention belongs to the technical field of cathode materials, and particularly relates to a cathode material, a cathode paste, and a lithium-ion battery. Background Art

[0002] A secondary battery (Rechargeable battery), also known as a rechargeable battery or a storage battery, refers to a battery that can be activated by charging after discharging. Currently, the main rechargeable batteries on the market include nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid (or lead-acid storage) batteries, lithium-ion batteries, sodium-ion batteries, polymer lithium-ion batteries, etc. In particular, the application of lithium-ion batteries is particularly extensive, and higher requirements are put forward for the application performance of lithium-ion batteries.

[0003] Currently, with the increasing requirements for the application of lithium-ion batteries in the market, lithium-ion batteries with both high energy density and fast charging performance have become the preferred products. According to research, in order to balance the energy density and fast charging performance of lithium-ion batteries, it is required that the battery materials used in lithium-ion batteries 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 cycle and impedance performance of the battery. However, in traditional battery materials, due to the presence of various chemical groups in the surface coating layer of the cathode material, the chemical groups on the surface of the ternary cathode material have different compatibilities with the electrolyte, resulting in different interfacial impedances of the materials, affecting the insertion and extraction of lithium ions during the charge and discharge process, and thus having an adverse impact on the rate performance, cycle performance, etc. of the battery.

[0004] Therefore, how to optimize the compatibility between the cathode material and the electrolyte is crucial for the performance of lithium-ion batteries. Summary of the Invention

[0005] The purpose of this application is to provide a cathode material, a cathode paste, and a lithium-ion battery, which can balance high energy density and rate performance while improving the processing performance of the cathode material.

[0006] In the first aspect, a cathode material of this application, the chemical general formula of the cathode 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;

[0007] The initial Coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is P mL / 100g, the 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.

[0008] Combined with the first aspect, in some embodiments, the initial Coulombic efficiency of the positive electrode material is E, and 0.87 ≤ E ≤ 0.93.

[0009] Combined with the first aspect, in some embodiments, the particle size distribution width S of the positive electrode material satisfies 1.0 ≤ S ≤ 1.6.

[0010] Combined with the first aspect, in some embodiments, the oil absorption value P of the positive electrode material is P mL / 100g, and 10 ≤ P ≤ 40.

[0011] Combined with the first aspect, in some embodiments, the positive electrode material satisfies the following relationship: 1.0 ≤ E*(P - 20) + S ≤ 2.0.

[0012] In a second aspect, the present application further provides a positive electrode material, and 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;

[0013] 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.

[0014] Combined with the second aspect, in some embodiments, the first Coulombic efficiency of the positive electrode material is E, and 0.87 ≤ E ≤ 0.93.

[0015] Combined with the second aspect, in some embodiments, the oil absorption value of the positive electrode material is P mL / 100g, and 10 ≤ P ≤ 40.

[0016] Combined with the second aspect, in some embodiments, the specific surface area of the positive electrode material is A m 2 / g, and 0.5 ≤ A ≤ 1.2.

[0017] Combined with the second aspect, in some embodiments, the positive electrode material satisfies the following relationship: 0.5 ≤ E*(P - 20) + A ≤ 1.0.

[0018] In the third aspect, the present application provides a positive electrode material, and 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;

[0019] 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 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.

[0020] Combined with the third aspect, in some embodiments, the first Coulombic efficiency of the positive electrode material is E, and 0.87 ≤ E ≤ 0.93.

[0021] In combination with the third aspect, in some embodiments, the oil absorption value of the positive electrode material is P mL / 100g, where 10 ≤ P ≤ 40.

[0022] In combination with the third aspect, in some embodiments, the tap density of the positive electrode material is T g / cm 3 , where 1.3 ≤ T ≤ 2.5.

[0023] In combination with the third aspect, in some embodiments, the positive electrode material satisfies the following relationship: 1.0 ≤ E*(P - 20) + T ≤ 2.0.

[0024] In some embodiments, based on the total mass of other metal elements except Li element in the positive electrode material being 100 wt%, the sum of the mass contents of M2 element and M3 element is 0.01 wt% - 50 wt%.

[0025] In some embodiments, the oil absorption value of the positive electrode material is P mL / 100g, where 15 ≤ P ≤ 25.

[0026] In some embodiments, at least one of M1, M2, and M3 is selected from B.

[0027] In some embodiments, the positive electrode material is a single crystal positive electrode material.

[0028] Fourth aspect, the present application provides a positive electrode slurry, and the positive electrode slurry includes a dispersant and the above-mentioned positive electrode material.

[0029] In combination with the fourth aspect, in some embodiments, the mass content of the dispersant in the solid components of the positive electrode slurry is M%, where 13 ≤ M ≤ 18.

[0030] In combination with the fourth aspect, in some embodiments, the positive electrode slurry satisfies the following relationship: 15 ≤ E*(P - 20) / 100 + M ≤ 18.

[0031] In combination with the fourth aspect, in some embodiments, the dispersant includes N-methylpyrrolidone.

[0032] Fifth aspect, the present application provides a battery, and the lithium ion battery includes the positive electrode material described in the first aspect, the second aspect, and the third aspect.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The positive electrode material provided by this application. The oil absorption value P of the positive electrode material can reflect the compatibility between the positive electrode material and the electrolyte. The higher the oil absorption value of the positive electrode material, the better the compatibility between the positive electrode material and the electrolyte; the lower the oil absorption value, the worse the compatibility between the positive electrode material and the electrolyte. However, an excessively large oil absorption value will consume more dispersants and binders during the preparation of the positive electrode slurry, resulting in an increase in production costs and a decrease in energy density, which affects the electrochemical performance of the positive electrode material. Therefore, by controlling the oil absorption value P, particle size distribution width S, and first Coulomb efficiency E of the positive electrode material to be within the range of 1.0 ≤ E*(P - 20) + S ≤ 8, the relationship between the first Coulomb efficiency, 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 between the positive electrode material and the electrolyte can be improved, which is beneficial to improving the intercalation and deintercalation efficiency of lithium ions during charge and discharge, 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 interfacial impedance between the positive electrode material and the electrolyte, and enabling the positive electrode material to have both high energy density and rate performance.

[0035] The positive electrode material provided by this application. The oil absorption value P of the positive electrode material can reflect the compatibility between the positive electrode material and the electrolyte. The higher the oil absorption value of the positive electrode material, the better the compatibility between the positive electrode material and the electrolyte; the lower the oil absorption value, the worse the compatibility between the positive electrode material and the electrolyte. However, an excessively large oil absorption value will consume more dispersants and binders during the preparation of the positive electrode slurry, resulting in an increase in production costs and a decrease in energy density, which affects 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 and consume too many active lithium ions, resulting in the first Coulomb efficiency of the positive electrode material; if the specific surface area of the positive electrode material is too small, it will affect the capacity performance of the positive electrode material. Therefore, 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 between the positive electrode material and the electrolyte can be improved, which is beneficial to improving the intercalation and deintercalation efficiency of lithium ions during charge and discharge, 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 interfacial impedance between the positive electrode material and the electrolyte, and enabling the positive electrode material to have both high energy density and rate performance.

[0036] The positive electrode material provided by the present application. The oil absorption value P of the positive electrode material can reflect the compatibility between the positive electrode material and the electrolyte. The higher the oil absorption value of the positive electrode material, the better the compatibility between the positive electrode material and the electrolyte; the lower the oil absorption value, the worse the compatibility between the positive electrode material and 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 an increase in production cost and a decrease in energy density, which affects the electrochemical performance of the positive electrode material. An excessively large tapped density T of the positive electrode material is not conducive to creating more lithium ion diffusion channels, and the electrochemical performance of the positive electrode material is affected; if the tapped density T of the positive electrode material is too small, it will affect the energy density of the positive electrode material. Therefore, by controlling the oil absorption value P, tapped 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 present application can balance the relationship between the first Coulomb efficiency, tapped density T, and oil absorption value P of the positive electrode material. Without affecting the processing performance and processing cost of the positive electrode material, it is possible to improve the compatibility between the positive electrode material and the electrolyte, which is beneficial to improving the intercalation and deintercalation efficiency of lithium ions during charge and discharge of the positive electrode material, 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 interfacial impedance between the positive electrode material and the electrolyte, and an appropriate tapped density can improve the energy density of the positive electrode material, so that the positive electrode material has both a high energy density and rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0038] Figure 1 It is a schematic flow chart of the preparation method of the positive electrode material provided by the embodiment of the present application.

[0039] Figure 2 It is a SEM electron micrograph of the positive electrode material provided by Embodiment 1 of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] In order to better understand the technical solutions of the present application, the following will describe the embodiments of the present application in detail with reference to the drawings.

[0041] It should be clear that the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0042] In addition, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0043] For ease of understanding the present invention, specific terms are appropriately defined in this application. Unless otherwise defined herein, scientific and technical terms used in the present invention have the meanings commonly understood by those skilled in the art to which the present invention pertains.

[0044] As used herein, the term "matrix" refers to a lithium-based composite oxide synthesized by a high-temperature solid-phase reaction after mixing a precursor with a lithium salt, and includes lithium and metal elements.

[0045] In traditional battery materials, due to the presence of amorphous carbon coated on the surfaces of the positive electrode material and the negative electrode graphite, 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 materials, affecting the insertion and extraction of lithium ions during the charge and discharge process, and further having an adverse impact on the rate performance, cycle performance, etc. of the battery.

[0046] Therefore, how to optimize the compatibility between the positive electrode material and the electrolyte is crucial for the performance of lithium-ion batteries.

[0047] This application provides a positive electrode material, and 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 the same;

[0048] The initial Coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is P mL / 100g, the 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.

[0049] In the above solution, the oil absorption value P of the positive electrode material can reflect the compatibility between the positive electrode material and the electrolyte. The higher the oil absorption value of the positive electrode material, the better the compatibility between the positive electrode material and the electrolyte; the lower the oil absorption value, the worse the compatibility between the positive electrode material and the electrolyte. However, an excessive oil absorption value will consume more dispersants and binders during the preparation of the positive electrode slurry from the positive electrode material, resulting in an increase in production costs and a decrease in energy density, which affects the electrochemical performance of the positive electrode material. Therefore, in this application, by controlling the oil absorption value P, particle size distribution width S, and first Coulomb efficiency E of the positive electrode material to be within the range of 1.0 ≤ E*(P - 20) + S ≤ 8, the relationship between the first Coulomb efficiency, 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 between the positive electrode material and the electrolyte can be improved, which is beneficial to improving the intercalation and deintercalation efficiency of lithium ions during charge and discharge of the positive electrode material, 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 interfacial impedance between the positive electrode material and the electrolyte, and enabling the positive electrode material to have both high energy density and rate performance.

[0050] Specifically, the value range 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. Of course, it can also be other values within the above range. The value range 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, etc. The value range of b can be 0, 0.01, 0.02, 0.05, 0.07, 0.08, 0.085, 0.09, 0.095, or 0.1, etc. The value range 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, etc. The value ranges 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 range 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.

[0051] It should be noted that the content of each element in the positive electrode material can be determined by well-known instruments for qualitative analysis and / or quantitative analysis of each element such as ICP and ICP-MS.

[0052] In some embodiments, the positive electrode material is a single-crystal positive electrode material. The single-crystal positive electrode material has a more stable structure, a more uniform bulk composition distribution, 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 significantly reduce particle cracking during the electrode pressing process, improving the electrode compaction density and volume energy density.

[0053] 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. These doping elements M1, M2, and M3 can change the lattice constant of the positive electrode material or the valence state of the elements in the material body, reduce cation mixing, improve the conductivity and particle conductivity of the material, enhance the stability of the material structure, and inhibit structural collapse, thereby improving the performance of the positive electrode material.

[0054] In some embodiments, based on the total mass of other metal elements in the positive electrode material except for the Li element being 100 wt%, the sum of the mass contents of the M2 element and the M3 element is 0.01 wt% to 50 wt%; specifically, it can be 0.01 wt%, 0.03 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 35 wt%, or 50 wt%, etc. Of course, it can also be other values within the above range, which are not limited herein. When the mass contents of the M2 element and the M3 element in the positive electrode material are within this range, it can improve the crystal structure stability of the positive electrode material, improve conductivity, and significantly enhance thermal stability and cycle stability. If the mass contents of the M2 element and the M3 element are too high, the initial discharge specific capacity of the material will decrease, and if they are too low, the effect of improving the cycle and thermal stability of the material will not be achieved. Preferably, based on the total mass of other metal elements in the positive electrode material except for the Li element being 100 wt%, the sum of the mass contents of the M2 element and the M3 element is 0.01 wt% to 10 wt%.

[0055] In some embodiments, the positive electrode material includes secondary particles and / or primary particles. It can be understood that the secondary particles are aggregates of multiple primary particles. The positive electrode material of the present application can include only primary particles, or only secondary particles, or a mixture of primary particles and secondary particles.

[0056] 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.

[0057] In some embodiments, the crystal structure of the positive electrode material belongs to a hexagonal crystal structure or a monoclinic crystal structure.

[0058] In some embodiments, the initial Coulombic efficiency of the positive electrode material is E, where 0.87 ≤ E ≤ 0.93; the initial 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. Of course, it can also be other values within the above range, which are not limited herein. Preferably, for the initial Coulombic efficiency E of the positive electrode material, 0.90 ≤ E ≤ 0.93.

[0059] In some embodiments, the particle size distribution width S of the positive electrode material satisfies 1.0 ≤ S ≤ 1.6; the 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 are not limited herein. It should be noted that in this application, the particle size distribution width S of the positive electrode material = (D90 - D10) / D50. Specifically, the particle size distribution width of the positive electrode material here is based on all particles, and the volume-based cumulative particle size distribution measured by laser diffraction method is used. D10 represents the particle size corresponding to when the cumulative particle size distribution percentage of the powder reaches 10%, D50 represents the particle size corresponding to when the cumulative particle size distribution percentage reaches 50%, and D90 represents the particle size corresponding to when the cumulative particle size distribution percentage reaches 90%.

[0060] By controlling the particle size distribution width of the positive electrode material within the above range, it shows that the positive electrode material has a relatively appropriate particle size distribution, which is beneficial to improving the specific capacity of the positive electrode material; and the particle size distribution of the positive electrode material is relatively concentrated, indicating that the degree of agglomeration between the particles of the positive electrode material increases. The agglomeration between the particles shortens the lithium ion transmission path, which is beneficial to the deintercalation and intercalation of lithium ions, and is beneficial to improving the initial Coulombic efficiency and fast charging performance of the positive electrode material.

[0061] In some embodiments, the oil absorption value of the positive electrode material is P mL / 100g, where 10 ≤ P ≤ 40; specifically, the oil absorption value P of the positive electrode material can be 10 mL / 100g, 12 mL / 100g, 15 mL / 100g, 20 mL / 100g, 25 mL / 100g, 30 mL / 100g, 35 mL / 100g, 38 mL / 100g, 40 mL / 100g, etc. Of course, it can also be other values within the above range, which are not limited herein. During the preparation of 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 dispersant and binder consumed in formulating the slurry, that is, the mass ratio of the positive electrode material in the positive electrode slurry decreases, reducing the battery energy density and increasing the processing cost; when the oil absorption value of the positive electrode material is too low, the dispersibility of the positive electrode material in the positive electrode slurry decreases. In this application, on the basis of not affecting the processing performance and processing cost of the positive electrode material, the oil absorption value of the positive electrode material is controlled within the above range, which is beneficial to improving the compatibility between the positive electrode material and the electrolyte, and the adsorption and wetting properties of the positive electrode material to the electrolyte are better, which can effectively reduce the interfacial resistance between the positive electrode material and the electrolyte, and is beneficial to improving the transport of lithium ions and electrons, making the electrochemical performance of the positive electrode material better. Preferably, the oil absorption value of the positive electrode material is P mL / 100g, where 15 ≤ P ≤ 25.

[0062] In some embodiments, the positive electrode material satisfies the following relationship: 1.0 ≤ E*(P - 20) + S ≤ 8, specifically it can be 1.0, 1.2, 1.5, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, etc. Of course, it can also be other values within the above range, which are not limited herein. 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.

[0063] In some embodiments, the specific surface area of the positive electrode material is 0.5 m 2 / g to 1.2 m 2 / g, specifically it can be 0.5 m 2 / g, 0.55 m 2 / g, 0.6 m 2 / g, 0.65 m 2 / g, 0.70 m 2 / g, 0.75 m 2 / g, 0.8 m 2 / g, 0.9 m 2 / g, 1.0 m 2 / g, 1.1 m 2 / g or 1.2 m 2 / g, etc. The specific surface area of the positive electrode material affects the rate performance of the battery. The larger the specific surface area, the more sufficient the contact between the positive electrode material and the electrolyte, the increase in the sites where lithium ions are extracted and inserted, the increase in the discharge capacity of the positive electrode material, the increase in the rate capacity, and the improvement of the fast charging performance. However, the oil absorption value of the positive electrode material also increases. But an overly large specific surface area makes the positive electrode material prone to react with the electrolyte, increasing side reactions and resulting in poor cycling performance. When the specific surface area of the positive electrode material is controlled within the above range, it is beneficial to improve the cycling performance of the lithium battery made from this positive electrode material. Preferably, the specific surface area of the positive electrode material is 0.6 m 2 / g to 0.8 m 2 / g.

[0064] In some embodiments, when the specific surface area of the positive electrode material is low, the oil absorption value also decreases, and an overly large specific surface area will consume more dispersant and binder, and at the same time, side reactions will also increase. Therefore, in this application, the initial 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.

[0065] In the above scheme, the oil absorption value P of the positive electrode material can reflect the compatibility between the positive electrode material and the electrolyte. The higher the oil absorption value of the positive electrode material, the better the compatibility between the positive electrode material and the electrolyte, and the lower the oil absorption value, the worse the compatibility between the positive electrode material and the electrolyte; however, an overly large oil absorption value will consume more dispersant and binder during the preparation of the positive electrode slurry of the positive electrode material, resulting in an increase in production cost and a decrease in energy density, affecting the electrochemical performance of the positive electrode material. An overly large specific surface area A of the positive electrode material will lead to an increase in side reactions and consume too many active lithium ions, resulting in the initial Coulombic efficiency of the positive electrode material; if the specific surface area of the positive electrode material is too small, it will affect the capacity performance of the positive electrode material. Therefore, in this application, by controlling the oil absorption value P, the specific surface area A, and the initial Coulombic 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 initial Coulombic efficiency, the specific surface area A, and the 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 between the positive electrode material and the electrolyte can be improved, which is beneficial to improving the intercalation and deintercalation efficiency of lithium ions during charge and discharge of the positive electrode material, 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 interfacial impedance between the positive electrode material and the electrolyte, and enabling the positive electrode material to have both a high energy density and rate performance.

[0066] In some embodiments, E*(P - 20)+A may specifically be 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. Of course, it may also be other values within the above range, which are not limited herein. On the basis of not affecting the processing performance and processing cost of the cathode material, in order for the cathode material to have both high energy density, fast charging performance, and cycling performance, preferably, the cathode material satisfies the following relationship: 0.5 ≤ E*(P - 20)+A ≤ 1.0.

[0067] In some embodiments, the tap density of the cathode material is T g / cm 3 , 1.3 ≤ T ≤ 2.5, and specifically may be 1.3 g / cm 3 , 1.4 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 , 1.7 g / cm 3 , 1.8 g / cm 3 , 1.9 g / cm 3 , 2.0 g / cm 3 , 2.1 g / cm 3 , 2.2 g / cm 3 , 2.3 g / cm 3 , or 2.5 g / cm 3 etc. The tap density of the cathode material is one of the indicators of the material energy density. The tap density and the particle size distribution width of the cathode material affect each other. A larger tap density of the cathode material indicates a larger particle size distribution width of the cathode material and better particle dispersion, which is beneficial to improving the dispersion of the cathode slurry. However, an increase in the particle size distribution width will also lead to an increase in the lithium ion transmission path, which is not conducive to the extraction and insertion of lithium ions in the cathode material. And if the tap density of the cathode material is too large, the cathode electrode sheet is too dense, which is not conducive to the infiltration of the electrolyte into the cathode electrode sheet, and it is not easy for lithium ions to be inserted, resulting in a decrease in the fast charging performance of the battery. If the tap density of the cathode material is too low, it will lead to a decrease in the energy density of the material.

[0068] Therefore, in order for the cathode material to have both high energy density and meet the fast charging performance, preferably, the tap density of the cathode material is 1.5 g / cm 3 to 2.0 g / cm 3 .

[0069] In some embodiments, the initial Coulombic efficiency of the cathode material is E, the oil absorption value of the cathode material is P mL / 100g, and the tap density of the cathode material is T g / cm 3, and satisfy the following relationship: 1.0 ≤ E*(P - 20) + T ≤ 8.0, specifically, it 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. Of course, it can also be other values within the above range, which are not limited here. In the above solution, the oil absorption value P of the cathode material can reflect the compatibility between the cathode material and the electrolyte. The higher the oil absorption value of the cathode material, the better the compatibility between the cathode material and the electrolyte. The lower the oil absorption value, the worse the compatibility between the cathode material and the electrolyte. However, an excessive oil absorption value will consume more dispersants and binders during the preparation of the cathode slurry, resulting in an increase in production costs and a decrease in energy density, affecting the electrochemical performance of the cathode material. If the tap density T of the cathode material is too large, it is not conducive to creating more lithium-ion diffusion channels, and the electrochemical performance of the cathode material is affected. If the tap density T of the cathode material is too small, it will affect the energy density of the cathode material. Therefore, by controlling the oil absorption value P, tap density T, and first Coulomb efficiency E of the cathode 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 cathode material can be balanced. Without affecting the processing performance and processing cost of the cathode material, the compatibility between the cathode material and the electrolyte can be improved, which is beneficial to improving the intercalation and deintercalation efficiency of lithium ions during charge and discharge, promoting the diffusion of lithium ions at the solid-liquid interface on the surface of the cathode material and inside the cathode material, reducing the interfacial impedance between the cathode material and the electrolyte, and an appropriate tap density can improve the energy density of the cathode material, so that the cathode material can have both high energy density and rate performance.

[0070] Preferably, in order for the cathode material to have both high energy density and rate performance, the cathode material satisfies the following relationship: 1.0 ≤ E*(P - 20) + T ≤ 2.0.

[0071] In the second aspect, an embodiment of the present application provides a method for preparing a cathode material, as Figure 1 shown, including the following steps:

[0072] Step S10: Dry the mixed solution containing the metal composite hydroxide precursor, the dopant containing the M1 element, and the lithium-containing compound, and subject the dried product to a first heat treatment to obtain a matrix material;

[0073] Step S20: Mix the matrix material with the first coating agent containing the M2 element and then perform a second heat treatment to obtain the first coating product. Among them, the temperature of the second heat treatment is T °C, where T = 750 - (n Ni - 0.8)*500, and n Ni represents the molar content of Ni element in the matrix material;

[0074] Step S30: Mix the product obtained from the first coating with a second coating agent containing element M3, and then perform three heat treatments to obtain a cathode material; where 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 completely the same as each other.

[0075] In the above technical solution, the precursor, the dopant, and the lithium-containing compound are mixed in a mixed solution. Through drying and the first heat treatment, a matrix material is obtained. Then, it is mixed with the first coating agent and subjected to a second heat treatment. During the second heat treatment, by controlling the second heat treatment temperature, the bonding strength between the coating layer and the matrix material can be effectively improved, and the stability of the cathode material structure can be enhanced. Then, the product obtained from the first coating is mixed with the second coating agent and subjected to a third heat treatment, so that the coating layer of the cathode material is tightly bonded to the matrix material, reducing the residual lithium on the material surface. Through multiple heat treatments, the generation of Li 2 Ni 8 O 10 heterophase can be inhibited, which can better improve the surface structure of the cathode material, improve the dispersibility of the cathode material, and increase the tap density of the cathode material.

[0076] The preparation method of the present application is specifically introduced below in combination with examples:

[0077] Before step S10, the method further includes:

[0078] Mix and process a metal salt solution, a complexing agent, and a pH regulator to obtain a metal composite hydroxide precursor.

[0079] In some embodiments, the mass ratio of the metal salt solution, the complexing agent, and the pH regulator is 1:(0.01 - 0.10):(0.1 - 0.8). Specifically, the mass ratio of the metal salt solution, the complexing agent, and the pH regulator can be 1:0.01:0.1, 1:0.05:0.3, 1:0.1:1.5, 1:0.08:0.8, etc.

[0080] In some embodiments, the metal salt solution includes a nickel salt solution, a cobalt salt solution, and a manganese salt solution.

[0081] Specifically, the nickel salt solution includes at least one of nickel sulfate, nickel chloride, nickel sulfamate, nickel bromide, nickel hydroxide, and nickel carbonyl.

[0082] The cobalt salt solution includes at least one of cobalt sulfate, cobalt chloride, and cobalt nitrate.

[0083] The manganese salt solution includes at least one of manganese sulfate, manganese nitrate, and manganese chloride.

[0084] In some embodiments, the complexing agent can be selected as long as it can form complexes with nickel, cobalt, and manganese ions in an aqueous solution. Specifically, the complexing agent includes at least one of ammonium ion donors, hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracil diacetic acid, and glycine. The ammonium ion donors include ammonia water, ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium fluoride.

[0085] In some embodiments, the temperature of the mixing treatment is 10°C to 80°C. Specifically, the temperature of the mixing treatment is 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, and 80°C, etc. Of course, it can also be other values within the above range, which are not limited herein. Preferably, the temperature of the mixing treatment is 20°C to 70°C. Controlling the temperature of the coprecipitation reaction within the above range is beneficial to crystal grain growth.

[0086] The pH regulator includes alkali metal hydroxides, and the alkali metal oxides include at least one of sodium hydroxide and potassium hydroxide.

[0087] In some embodiments, the pH of the mixing treatment is 9 to 13. Specifically, the pH of the mixing treatment is 9, 10, 11, 12, and 13, etc. Of course, it can also be other values within the above range, which are not limited herein. Preferably, the pH of the coprecipitation reaction is 11 to 13.

[0088] In some embodiments, the time of the mixing treatment is 10 to 200 h.

[0089] In some embodiments, the mixing treatment is carried out under a stirring state, and the stirring rate is 800 to 1200 rpm.

[0090] In some embodiments, the mixing treatment is carried out in a reaction tank, and the reaction tank is at least one of a continuous type that overflows to separate the formed metal composite hydroxide and an intermittent type that does not discharge to the outside of the system until the reaction ends.

[0091] In some embodiments, the metal composite hydroxide precursor prepared by the mixing treatment is a slurry-like suspension, and the metal composite hydroxide precursor is obtained through solid-liquid separation, washing, and drying.

[0092] In some embodiments, the method of solid-liquid separation includes any one of centrifugation and filtration. The purpose of solid-liquid separation is to separate the metal composite hydroxide from the solvent.

[0093] In some embodiments, washing is carried out with deionized water multiple times to remove impurities.

[0094] In some embodiments, the drying temperature is 100°C to 130°C. Specifically, the drying temperature can be 100°C, 110°C, 120°C, 130°C, etc. The drying time is 12h to 24h. Specifically, the drying time can be 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, etc.

[0095] In some embodiments, the metal composite hydroxide precursor is in powder form, and its average particle size is 3μm to 10μm. The median particle size of the metal composite hydroxide precursor can be 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc.

[0096] Step S10: Perform a primary heat treatment on the metal composite hydroxide precursor, the dopant containing M1 element, and the lithium-containing compound to obtain a matrix material.

[0097] In some embodiments, the mass ratio of the metal composite hydroxide precursor, the lithium-containing compound, and the dopant containing M1 element is 1:0.46:0.001 to 1:0.48:0.003.

[0098] 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, etc. 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 performance of the material. Preferably, 1.0 < Li / Me < 1.1.

[0099] In some embodiments, the chemical general formula of the metal composite hydroxide precursor is Ni a Co b Mn c (OH) 2 , where 0.6 ≤ a ≤ 1.0, 0.0 ≤ b ≤ 0.10, 0.0 ≤ c ≤ 0.3.

[0100] 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.

[0101] In some embodiments, the addition amount of the M1 element accounts for 0 to 0.3 of the total molar amount of the matrix material.

[0102] 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.

[0103] In some embodiments, the average particle size of the dopant containing the M1 element is 10 nm to 50 nm. Specifically, the average particle size of the dopant can 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 are not limited herein.

[0104] 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, lithium hydroxide includes at least one of anhydrous lithium hydroxide and lithium hydroxide monohydrate.

[0105] In some embodiments, the temperature of the first heat treatment is 680 °C to 900 °C. Specifically, the temperature of the first heat treatment is 680 °C, 700 °C, 720 °C, 750 °C, 780 °C, 800 °C, 820 °C, 850 °C, 900 °C, etc. Of course, it can also be other values within the above range, which are not limited herein. Preferably, the temperature of the first heat treatment is 780 °C to 870 °C. Limiting the temperature of the heat treatment sintering to the above range is beneficial to the grain growth of the nickel-cobalt-manganese ternary single-crystal cathode material.

[0106] In some embodiments, the time of the first heat treatment is 5 h to 20 h. Specifically, the time of the first heat treatment is 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, etc. Of course, it can also be other values within the above range, which are not limited herein. Preferably, the time of the first heat treatment is 8 h to 15 h.

[0107] In some embodiments, the heating rate of the first heat treatment is 50 °C / h to 550 °C / h. Specifically, the heating rate of the first 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, 550 °C / h, etc. Of course, it can also be other values within the above range, which are not limited herein. Preferably, the heating rate of the first heat treatment is 100 °C / h to 400 °C / h. Further preferably, the heating rate of the first heat treatment is 140 °C / h to 380 °C / h.

[0108] In some embodiments, the first heat treatment is carried out 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. Of course, it can also be other values within the above range, which are not limited herein. Preferably, the oxygen content of the oxygen-containing gas is greater than or equal to 95%.

[0109] In some embodiments, the equipment for the first heat treatment includes a stationary box furnace, a roller hearth kiln continuous furnace, etc.

[0110] Step S20: Mix the matrix material with the first coating agent containing element M2 and then perform a second heat treatment to obtain the product obtained by the first coating. The temperature of the second heat treatment is T °C, where T = 750 - (n Ni - 0.8) * 500, n Ni represents the molar content of Ni element in the matrix material.

[0111] In some embodiments, the first coating agent includes at least one of the oxide of M2 and the hydroxide of M2.

[0112] In some embodiments, the mass ratio of the matrix material to the first coating agent is 1000:(0.5 - 3). Specifically, the mass of the matrix material to the first coating agent can be 1000:0.5, 1000:1, 1000:1.5, 1000:2, 1000:2.5, and 1000:3, etc.

[0113] In some embodiments, the first coating agent can 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 second heat treatment is T °C, where T = 750 - (n Ni - 0.8) * 500, n Ni represents the molar content of Ni element in the matrix material. That is, the higher the doping amount of Ni element in the matrix material, the lower the temperature of the second heat treatment. It can be understood that the higher the temperature of the second heat treatment, the more obvious the particle agglomeration effect, and the oil absorption value of the cathode material will also increase accordingly. This will lead to the need to add more dispersants during the preparation of the cathode material slurry. Therefore, by adjusting the temperature of the second heat treatment through the nickel content, the degree of particle agglomeration can be effectively inhibited, so that the oil absorption value of the cathode material can be controlled within a suitable range, balancing the relationship between the first Coulomb efficiency, the tap density T, and the oil absorption value P of the cathode material. On the basis of not affecting the processing performance and processing cost of the cathode material, the compatibility between the cathode material and the electrolyte can be improved.

[0114] 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, 800°C, etc. Of course, it can also be other values within the above range, which is not limited herein. Preferably, the temperature of the secondary heat treatment is 650°C to 750°C.

[0115] In some embodiments, the time of the secondary heat treatment is 1 h to 20 h. Specifically, the time of the secondary heat treatment is 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, etc. Of course, it can also be other values within the above range, which is not limited herein. Preferably, the time of the secondary heat treatment is 3 h to 10 h.

[0116] 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, 550°C / h, etc. Of course, it can also be other values within the above range, which is not limited herein. Preferably, the heating rate of the secondary heat treatment is 100°C / h to 400°C / h. Further preferably, the heating rate of the secondary heat treatment is 140°C / h to 380°C / h.

[0117] In some embodiments, the secondary heat treatment is carried out 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. Of course, it can also be other values within the above range, which is not limited herein. Preferably, the oxygen content of the oxygen-containing gas is greater than or equal to 95%.

[0118] In some embodiments, the equipment for the secondary heat treatment includes a stationary box furnace, a roller hearth kiln continuous furnace, etc.

[0119] In some embodiments, the secondary heat treatment product is put into an ultrafine stone disk mill for crushing. The disk gap of the ultrafine stone disk mill is 5 μm to 50 μm. Specifically, the disk gap can be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 45 μm, 50 μm, etc. Of course, it can also be other values within the above range, which is not limited herein. Preferably, the disk gap of the ultrafine stone disk mill is 5 μm to 30 μm.

[0120] Step S30: The product obtained from the first coating is mixed with a second coating agent containing element M3 and then undergoes three heat treatments to obtain the cathode material.

[0121] In some embodiments, element M3 includes at least one of Al, Co, Zr, B, Ti, Mg, Y, La, Sr, Ba, W, Mo, Nb, Si, and Sb. Preferably, element M3 is selected from B.

[0122] In some embodiments, the second coating agent includes a boron-containing compound, and the boron-containing compound includes B 2 O 3 、H 3 BO 3 、Li 2 O-B 2 O 3 、Li 3 BO 3 、Li 2 B 4 O 7 、Li 2 B 2 O 7 、Li 2 B 8 O 13 at least one of them. By adding the boron-containing compound to the product obtained from the first coating, the above boron-containing compound can not only chemically react with the alkaline impurities on the material surface but also cover the material surface to form a stable coating layer, thus not only reducing the alkaline impurities on the material surface but also protecting the material surface and reducing the gas generation caused by the decomposition of Li 2 CO 3 and the side reaction with the electrolyte to generate gas.

[0123] In some embodiments, the mass ratio of the product obtained from the first coating to the second coating agent is 1:1 to 1:5.

[0124] 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, etc. Of course, it can also be other values within the above range, which are not limited here. Preferably, the temperature of the three heat treatments is 250°C to 360°C.

[0125] In some embodiments, the time of the three heat treatments is 1 h to 20 h; the time of the three heat treatments is 5 h to 20 h. Specifically, the time of the three heat treatments is 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, and 20 h, etc. Of course, it can also be other values within the above range, which are not limited herein. Preferably, the time of the three heat treatments is 5 h to 10 h.

[0126] 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, it can also be other values within the above range, which are not limited herein. Preferably, the heating rate of the three heat treatments is 100 °C / h to 400 °C / h. Further preferably, the heating rate of the three heat treatments is 140 °C / h to 380 °C / h.

[0127] In some embodiments, the three heat treatments are carried out 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. Of course, it can also be other values within the above range, which are not limited herein. Preferably, the oxygen content of the oxygen-containing gas is greater than or equal to 95%.

[0128] In some embodiments, the equipment for the three heat treatments includes a stationary box furnace, a roller hearth kiln continuous furnace, etc.

[0129] In some embodiments, the three heat treatments further include steps of screening and demagnetization.

[0130] In some embodiments, the purpose of screening is 200 to 400 mesh.

[0131] In a third aspect, the present application further provides a positive electrode paste, and the positive electrode paste includes a dispersant and the above positive electrode material.

[0132] Since there is a certain balance relationship between the oil absorption value of the positive electrode material in this application and the specific surface area, tap density or particle size distribution width, during the preparation of the cathode slurry, the amount of binder can be reduced, and the mass ratio of the positive electrode material in the positive electrode slurry can be increased, thereby improving the energy density of the positive electrode sheet. And in order to improve the problem of uneven dispersion caused by insufficient binder, an appropriate amount of dispersant is added to the positive electrode slurry, which can effectively improve the dispersion uniformity of the positive electrode slurry, reduce the formation of filter residue, improve the filtration performance of the positive electrode slurry during filtration, and enable the positive electrode sheet formed by coating the corrected positive electrode slurry to have both high energy density, rate performance and excellent cycle performance.

[0133] In some embodiments, based on the mass of the positive electrode material in the positive electrode slurry being 100%, 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., which are not limited herein. Preferably, the mass content of the dispersant is 15% - 17%.

[0134] In this application, by using a suitable dispersant and combining it with a positive electrode material having suitable physical and chemical properties, the dispersion uniformity of the positive electrode material in the positive electrode slurry can be improved, the agglomeration 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 the filtration loss can be reduced. At the same time, the coating of large - particle filter residue on the positive electrode sheet is reduced, which reduces the cycle performance during charge and discharge.

[0135] In some embodiments, the positive electrode slurry satisfies the following relationship: 15 ≤ E*(P - 20) / 100 + M ≤ 18. Wherein, E represents the first Coulomb efficiency of the positive electrode material, and P is the oil absorption value of the positive electrode material.

[0136] During the preparation of the positive electrode slurry, the amount of the dispersant 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 required to improve the dispersion of the positive electrode material particles and reduce the number of filter residues. In theory, the more dispersant, the better the dispersion of the positive electrode material particles, but too much dispersant will reduce the energy density and increase the cost. Considering various performance aspects comprehensively, E, M and P satisfy the relational expression: 15 ≤ E*(P - 20) / 100 + M ≤ 18.

[0137] This application also provides a positive electrode sheet, which includes a current collector and a positive electrode slurry disposed on the current collector.

[0138] During the preparation of the lithium - ion battery, the quality of the slurry directly affects the performance of the lithium - ion battery. By coating the above - mentioned well - dispersed positive electrode slurry on the current collector, the performance of the battery is improved.

[0139] The present application also provides a battery, including: a negative electrode plate, a positive electrode plate, a separator, and an electrolyte, wherein the positive electrode plate is a positive electrode plate.

[0140] Coating a cathode slurry with good dispersibility on a current collector to prepare a positive electrode plate can improve the performance of the battery.

[0141] The present application also provides an electrical device, and the electrical device includes the battery.

[0142] The performance of the battery is improved, and the performance of the electrical device applying this battery will also be enhanced.

[0143] The embodiments of the present invention will be further described below in multiple embodiments. Among them, the embodiments of the present invention are not limited to the following specific embodiments. Within the scope of the main rights unchanged, appropriate modifications can be made for implementation.

[0144] Embodiment 1

[0145] A preparation method of a positive electrode material includes the following steps:

[0146] (1) Prepare a Ni 0.885 Co 0.09 Mn 0.025 (OH) 2 precursor, and the D50 of the precursor is 3.5 μm;

[0147] (2) Mix the Ni 0.885 Co 0.09 Mn 0.025 (OH) 2 precursor, LiOH*H 2 O, and dopants nano-TiO 2 , ZrO 2 , MgO evenly, and then conduct a first heat treatment at 840 °C to obtain a matrix material. The first heat treatment is carried out by introducing oxygen with an oxygen content greater than 95%. Among them, Li / Me = 1.05, M = (Ni, Co, and Mn), and the D50 of the single-crystal matrix material is 3.0 μm. The single-crystal matrix material is shown in Figure 1 ;

[0148] (3) Mix the matrix material prepared in step (1), nano-Al 2 O 3 and nano-Co 3 O 4 evenly, and then conduct a second heat treatment at 708 °C, and then carry out an ultrafine stone disk grinding and crushing treatment. The gap of the ultrafine stone disk is 10 μm to obtain the product of the first coating.

[0149] (4) Mix the product of the first coating and H 3 BO 3Mix evenly, conduct three heat treatments at 300 °C, then perform screening and demagnetization to obtain the cathode material with the chemical formula LiNi 0.877 Co 0.098 Mn 0.024 Ti 0.002 Zr 0.002 Mg 0.001 B 0.005 O 2 . Prepare Examples 2 to 10 according to the steps of Example 1. The differences in the preparation processes are shown in Table 1:

[0150] Table 1. Parameters in the preparation process of the cathode material

[0151]

[0152] Preparation of the positive electrode sheet

[0153] Dissolve the cathode material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) prepared in the example or comparative example in the solvent N-methylpyrrolidone (NMP) at a weight ratio of 96.5:1.5:2, and stir well to obtain a uniform cathode slurry; then evenly coat the cathode slurry on the cathode current collector with a primer, and then dry, cold press, and slit to obtain the positive electrode sheet.

[0154] Preparation of the negative electrode sheet

[0155] Dissolve the active substances graphite, silicon, conductive agent acetylene black, polymer, and carboxymethyl cellulose (CMC) in deionized water at a weight ratio of 90:5:2:1.9:1.1, and uniformly mix to prepare a negative electrode slurry. Coat the slurry on the copper foil, dry it, and then cold press and slit to obtain the negative electrode sheet.

[0156] Separator

[0157] The separator is a PE separator with a PVDF and alumina coating on the surface to improve the adhesion and heat resistance.

[0158] Electrolyte

[0159] Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) at a volume ratio of 1:1:1, and then uniformly dissolve LiPF 6 :LiFSI (2:8) in the above solution to obtain the electrolyte. In this electrolyte, the concentration of the lithium salt is 1 mol / L.

[0160] Preparation of the battery

[0161] Stack the positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive and negative electrode sheets to play an insulating role. Then wind them to obtain a bare battery cell, weld the tabs to the bare battery cell, place the bare battery cell into an aluminum case, and bake it at 80 °C to remove water. Immediately inject the electrolyte and seal it to obtain a non-charged battery. The non-charged battery then undergoes processes such as standing, hot and cold pressing, formation, shaping, and capacity testing in sequence to obtain a lithium-ion battery product.

[0162] Table 2 Parameters for the addition of dispersant in the positive electrode paste and battery performance parameters

[0163]

[0164] Performance testing

[0165] 1. Test method for the tapped density of the positive electrode material

[0166] Determination of the tapped density of metallic powders - Method using a tapped density tester, GB / T 5162 - 1985 is adopted.

[0167] 2. Determination method for the specific surface area of the positive electrode material

[0168] Determination of the specific surface area of the positive electrode material by the gas adsorption BET method, GB / T 19587 - 2004 is adopted.

[0169] 3. Determination method for the oil absorption value of the positive electrode material

[0170] Test using an oil absorption value tester ASAHI S - 500 from ASAHI SOUKEN of Japan. The oil absorption value O is the amount of linseed oil added when the torque generated by the viscosity characteristic change reaches 70% of the maximum torque, with the unit of mL / 100g.

[0171] 4. Test method for the particle size distribution width of the positive electrode material

[0172] The test method for particle size refers to GB / T 19077 - 2016. It can be conveniently determined using a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Limited of the UK.

[0173] The particle size distribution width function Span of two peaks is expressed as:

[0174]

[0175] 5. Battery capacity test:

[0176] ① Stand still for 30 min; ② Charge at 1 / 3C to 4.25 V, and continue constant voltage charging at 4.25 V until it ends at 0.05C; ③ Stand still for 30 min; ④ Discharge at 1 / 3C to 2.8 V to obtain the capacity C0; the obtained energy is the battery energy, and the weight energy density = energy / battery weight.

[0177] Test method for the initial Coulombic efficiency

[0178] ① Stand still for 120 min; ② Charge at 0.1C to 4.25 V, and continue constant voltage charging at 4.25 V until it ends at 0.05C to obtain the capacity C1; ③ Stand still for 30 min; ④ Discharge at 0.1C to 2.8 V to obtain the capacity C2; the initial Coulombic efficiency = C1 / C2.

[0179] 6. Battery lithium plating test:

[0180] ① Stand still for 5 min; ② Discharge at 1 / 3C0 to 2.8 V; ③ Stand still for 5 min; ④ Charge at 1.2C0 to 50% SOC; ⑤ Charge at 0.87C0 to 80% SOC; ⑥ Charge at 1 / 3C0 to 4.25 V, and continue constant voltage charging at 4.25 V until it ends at 0.05C; ⑦ Stand still for 10 min; ⑧ Discharge at 1 / 3C0 to 2.8 V; ⑨ Stand still for 5 min; ⑩ Repeat steps 4 - 9 five times; Charge at 1 / 3C to 4.25 V, and continue constant voltage charging at 4.25 V until it ends at 0.05C; Stand still for 5 min.

[0181] 7. Battery cycle test:

[0182] Adjust the temperature to 45 °C and keep it warm for 2 h.

[0183] ① Rest for 5 min; ② Charge at 1 / 3C to 4.25 V, and continue constant voltage charging at 4.25 V until it ends at 0.05C; ③ Stand still for 5 min, discharge at 0.5C0 to 2.8 V; ⑤ Stand still for 5 min; ⑥ Repeat steps 7 - 9 until the capacity fading ≤ 80%.

[0184] As shown in Table 1 and Table 2, from the test data of Examples 1 to 10, it can be seen that when the positive electrode material satisfies any one of the three relational expressions 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 initial Coulomb efficiency of the positive electrode material, the oil absorption value P and the particle size distribution width S, the tap density T or the specific surface area S can be balanced. Without affecting the processing performance and processing cost of the positive electrode material, the compatibility between the positive electrode material and the electrolyte can be improved, which is beneficial to improving the intercalation and deintercalation efficiency of lithium ions during charge and discharge, 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 interfacial impedance between the positive electrode material and the electrolyte, and enabling the positive electrode material to have both high energy density and rate performance. According to the test data of Examples 1 to 4, it can be seen that as the addition amount of the boron-containing compound gradually increases during the three heat treatment processes, the content of B element 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 particle aggregation of the positive electrode material, the lower the tap density, resulting in a gradual decrease in the filtration performance.

[0185] In order to improve the dispersion uniformity of the positive electrode slurry, more dispersant and binder may need to be consumed. In the case of insufficient dispersant added, filter residue will be formed in the prepared positive electrode slurry, thus resulting in worse filtration.

[0186] According to the relevant data of Examples 1, 5, 6, 7, and Comparative Example 2, the higher the residual lithium on the surface of the positive electrode material, the surface residual lithium is inactive lithium, which will cause an increase in the viscosity of the binder, 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.

[0187] According to the relevant data of Example 1 and Example 8, with the increase in the nickel content in the positive electrode material of Example 8, the temperature of the secondary heat treatment needs to be adjusted, which increases the degree of particle aggregation between the positive electrode materials, increases the oil absorption value of the positive electrode material, 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.

[0188] According to the relevant data of Example 4 and Example 9, the median particle size of the positive electrode material precursor in Example 9 increases, the particle size distribution width of the positive electrode material decreases, and the tap density decreases, which will lead to an increase in the lithium ion transmission path and is not conducive to the deintercalation and intercalation of lithium ions in the positive electrode material. Although the oil absorption value changes little, the fast charging performance of the positive electrode material is lower than that of Example 1, and the high temperature cycle performance decreases.

[0189] According to the relevant data of Example 3 and Example 10, it can be seen that in the preparation process of the positive electrode material of Example 10, no boron-containing compound was added, the residual lithium on the surface of the positive electrode material was relatively high, the stability of the properties of the coating layer formed on the surface of the positive electrode material decreased, the specific surface area of the positive electrode material increased, side reactions increased, and the cycle performance of the positive electrode material decreased.

[0190] As can be seen from the data in Table 1 and Table 2 above, as shown in Example 3, the median particle size D50 of the precursor is 3.5 μm, the median particle size D50 of the matrix material is 3.0 μm, the residual lithium on the surface is <1000 ppm, and the B coating amount is 300 ppm, and the comprehensive performance of the battery is better.

[0191] As can be seen from the data in Table 1 and Table 2 above, as shown in Comparative Examples 1 to 3 and the data of Example 1, the higher the temperature of the secondary heat treatment, the greater the degree of agglomeration between particles, the smaller the tap density T, and the corresponding increase in the oil absorption value, resulting in an increase in the dispersant and binder to be consumed. In the case of insufficient dispersant added, filter residue will be formed in the prepared positive electrode slurry. Thus, the filtration becomes worse and the filtration time is long; however, if the tap density is too large, the oil absorption value will decrease correspondingly, the specific surface area will be smaller, and the energy density will decrease.

[0192] As can be seen from the data in Table 2 above, the shorter the filtration time, the more uniformly the positive electrode material particles are dispersed and no filter residue is formed; while the longer the filtration time and the appearance of filter residue on the surface prove that the local dispersion of the positive electrode slurry is poor and there may be a problem of local lithium deposition.

[0193] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A cathode 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 initial Coulombic efficiency of the cathode material is E, the oil absorption value of the cathode material is P mL / 100g, the particle size distribution width of the cathode material is S, S=(D90-D10) / D50, and the following relationship is satisfied: 1.0≤E*(P-20)+S≤8.

2. The cathode material according to claim 1, characterized in that, it satisfies at least one of the following characteristics: (1) The initial Coulombic efficiency of the cathode material is E, 0.87≤E≤0.93; (2) The particle size distribution width of the cathode material is S, 1.0≤S≤1.6; (3) The oil absorption value of the cathode material is P mL / 100g, 10≤P≤40; (4) The cathode material satisfies the following relationship: 1.0≤E*(P-20)+S≤2.

0.

3. A cathode 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 initial 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.

4. The cathode material according to claim 3, characterized in that, it satisfies at least one of the following characteristics: (1) The initial Coulombic efficiency of the cathode material is E, 0.87≤E≤0.93; (2) The oil absorption value of the cathode material is P mL / 100g, 10≤P≤40; (3) The specific surface area of the positive electrode material is Am 2 / g, where 0.5 ≤ A ≤ 1.2; (4) The cathode material satisfies the following relationship: 0.5≤E*(P-20)+A≤1.

0.

5. A cathode 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 completely the same; The initial Coulombic efficiency of the positive electrode material is E, the oil absorption value of the positive electrode material is P mL / 100g, and the tapped 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.

6. The cathode material according to claim 5, characterized in that, it satisfies at least one of the following characteristics: (1) The initial Coulombic efficiency of the cathode material is E, 0.87≤E≤0.93; (2) The oil absorption value of the cathode material is P mL / 100g, 10≤P≤40; (3) The tap density of the positive electrode material is T g / cm 3 , 1.3 ≤ T ≤ 2.5; (4) The cathode material satisfies the following relationship: 1.0≤E*(P-20)+T≤2.

0.

7. The cathode material according to any one of claims 1 to 6, characterized in that, it satisfies at least one of the following characteristics: (1) Based on the total mass of other metal elements except Li element in the cathode material being 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 cathode material is P mL / 100g, 15≤P≤25; (3) The cathode material is a single crystal cathode material; (4) At least one of M1, M2, and M3 contains B.

8. A cathode paste, characterized in that, the cathode paste includes a dispersant and the cathode material according to any one of claims 1 to 7.

9. The cathode paste according to claim 8, characterized in that, based on the mass of the cathode material in the cathode paste being 100%, the mass content of the dispersant is M%, and the cathode paste satisfies at least one of the following characteristics: (1) In the cathode paste, 13≤M≤18; (2) The cathode paste satisfies the following relationship: 15≤E*(P-20) / 100+M≤18; (3) The dispersant includes N-methylpyrrolidone.

10. A battery, characterized in that, the battery includes the cathode material according to any one of claims 1 to 7.

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