CN117954621A

CN117954621A - Positive electrode material, preparation method thereof and lithium ion battery

Info

Publication number: CN117954621A
Application number: CN202311757641.7A
Authority: CN
Inventors: 王皓逸; 宋雄; 吴小珍; 杨顺毅; 黄友元; 张金龙
Original assignee: Better Jiangsu New Material Technology Co ltd
Current assignee: Better Jiangsu New Material Technology Co ltd
Priority date: 2023-12-20
Filing date: 2023-12-20
Publication date: 2024-04-30

Abstract

The application relates to a positive electrode material and a preparation method thereof, and a lithium ion battery, wherein the chemical general formula of the positive electrode material is Li _bNi_xCo_yM1_zM2_wO₂, b is more than or equal to 0.95 and less than or equal to 1.05,0.8 and less than or equal to x is less than or equal to 1, y+z is more than or equal to 0 and less than or equal to 0.2, and x+y+z= 1,0.0001 and less than or equal to w is less than or equal to 0.003; m1 is Mn and/or Al; m2 is a metal element; the tap density of the positive electrode material is Tg/cm ³, the oil absorption value of the positive electrode material is Pml/100 g, the minimum particle size value of the positive electrode material in the particle size distribution is D _min mu m, the processing performance coefficient of the positive electrode material is B, B= |0.5-P ^‑0.5-0.00117*T-0.0541*D_min+0.0593*D_min ² +0.2696|, and B is more than or equal to 0 and less than or equal to 1. The positive electrode material has good particle dispersibility and good processing performance, can reduce particle sedimentation and agglomeration in slurry, reduce the phenomena of slurry separation, gel, layering and the like, and improve the dispersion uniformity and stability of the slurry, thereby improving the cycle performance and the multiplying power performance of the lithium ion battery.

Description

Positive electrode material, preparation method thereof and lithium ion battery

Technical Field

The invention relates to the technical field of positive electrode materials, in particular to a positive electrode material, a preparation method thereof and a lithium ion battery.

Background

The lithium ion battery has the advantages of high energy density, long cycle life, little environmental pollution, no memory effect and the like, and is widely applied to electric automobiles and consumer electronic products. The positive electrode material is a core component of the lithium ion battery, the performance of the positive electrode material directly influences the electrochemical performance and the cycle life of the lithium ion battery, and the positive electrode material is one of key materials for determining the performance of the lithium ion battery. The high-nickel positive electrode material has the advantages of low cost, high energy density, excellent multiplying power performance and the like, so that the high-nickel positive electrode material is a high-energy density lithium ion battery positive electrode material with great development potential.

The high-nickel positive electrode material has the defects of serious phase change and oxygen release phenomena, easy side reaction with electrolyte on the surface, poor storage performance and the like in the charge and discharge process, and the defects can influence the service life of the high-nickel positive electrode material, so that the wide application of the high-nickel positive electrode material is limited. In the prior art, in order to solve the service life problem of the high-nickel positive electrode material, the surface of the positive electrode material is generally subjected to coating modification, and a physical isolation layer can be constructed on the surface of the positive electrode material through coating modification, so that the side reaction of the electrolyte on the surface of the high-nickel positive electrode material can be effectively slowed down, the cycle performance and the thermal stability of the high-nickel positive electrode material are improved, and the service life of the high-nickel positive electrode material is prolonged.

The existing high-nickel positive electrode material has high charge and discharge performance and good quick charge performance after coating modification, but the processing performance of the material is poor, so that the homogenization process performance of the downstream end is seriously influenced, and the cycle performance and the multiplying power performance of the lithium ion battery are further reduced. Therefore, how to improve the processing performance of the positive electrode material, improve the homogenization process performance of the positive electrode material and improve the cycle performance and the rate capability of the lithium ion battery is a problem which still needs to be solved at present.

Disclosure of Invention

The application aims to provide a positive electrode material, a preparation method thereof and a lithium ion battery, wherein the positive electrode material has good particle dispersibility and good processing performance, can reduce particle sedimentation and agglomeration in slurry, reduce the phenomena of separation, gel, layering and the like of the slurry, and improve the dispersion uniformity and stability of the slurry, thereby improving the cycle performance and the multiplying power performance of the lithium ion battery.

In a first aspect, the application provides a positive electrode material, wherein the positive electrode material has a chemical formula of Li _bNi_xCo_yM1_zM2_wO₂, b is more than or equal to 0.95 and less than or equal to 1.05,0.8 and less than or equal to x is less than or equal to 1, y+z is more than or equal to 0 and less than or equal to 0.2, and x+y+z= 1,0.0001 and less than or equal to w is less than or equal to 0.003; m1 is Mn and/or Al; m2 is a metal element;

The tap density of the positive electrode material is T g/cm ³, the oil absorption value of the positive electrode material is Pml/100 g, the minimum particle size value of the positive electrode material in the particle size distribution is D _min mu m, the processing performance coefficient of the positive electrode material is B,

B＝|0.5-P^-0.5-0.00117*T-0.0541*D_min+0.0593*D_min ²+0.2696|，0≤B≤1。

The application also provides a positive electrode material, which has a chemical general formula of Li _bNi_xCo_yM1_zM2_wO₂, wherein b is more than or equal to 0.95 and less than or equal to 1.05,0.8 and less than or equal to x is more than or equal to 1, y+z is more than or equal to 0 and less than or equal to 0.2, and x+y+z= 1,0.0001 and less than or equal to w is more than or equal to 0.003; m1 is Mn and/or Al; m2 is a metal element;

The system average mass of the positive electrode material is A[4,3],A[4,3]＝(D₅₀ ^{^4}+D₉₀ ^{^4})/(D₅₀ ^{^3}+D₉₀ ^{^3}),11.78≤A[4,3]≤24.81.

In some embodiments, the positive electrode material comprises a base material and a coating layer on the surface of the base material, wherein the material of the coating layer comprises phosphate and/or solid electrolyte LATP.

In some embodiments, the positive electrode material includes secondary particles formed by agglomeration of a plurality of primary particles.

In some embodiments, the secondary particles are spherical or spheroid.

In some embodiments, the metal element M2 includes at least one of Al, mn, mg, sr, ca, zr, ti, la, W, nb, Y, gd.

In some embodiments, the primary particle surface has a coating layer comprising a metal M2-containing composite oxide.

In some embodiments, the metal element M2 is present in the positive electrode material in an amount of 500ppm to 2000ppm by mass based on 100% by mass of the positive electrode material.

In some embodiments, the particle size D ₅₀ of the positive electrode material is 8.25 μm to 12.75 μm.

In some embodiments, the particle size D ₉₀ of the positive electrode material is 12.6 μm to 26.2 μm.

In some embodiments, the positive electrode material has a tap density of T g/cm ³, 2.4.ltoreq.T.ltoreq.3.0.

In some embodiments, the positive electrode material has an oil absorption value of Pml/100 g, 14.5.ltoreq.O.ltoreq.18.5.

In some embodiments, the cathode material has a minimum particle size value in the particle size distribution of D _min,0.1μm≤D_min ∈0.9 μm.

In some embodiments, the specific surface area of the positive electrode material is 0.5m ²/g～2.0m²/g;

In some embodiments, the bulk density of the positive electrode material is 1.0g/m ³～3.0g/m³;

In some embodiments, the positive electrode material has a powder conductivity greater than 0.02S/cm at 4kN/cm ² under pressure.

In a second aspect, the present application provides a method for preparing a positive electrode material, comprising the steps of:

Mixing Ni _xCo_yM1_z oxide or Ni _xCo_yM1_z hydroxide with a lithium source to obtain a mixture, and sintering the mixture to obtain a sintered product, wherein x+y+z=1, and M1 is selected from Mn and/or Al;

crushing the sintering product to obtain a matrix material, wherein the matrix material comprises secondary particles formed by agglomerating a plurality of primary particles, and the average system mass of the matrix material is controlled to be A[4,3],A[4,3]＝(D₅₀ ^{^4}+D₉₀ ^{^4})/(D₅₀ ^{^3+}D₉₀ ^{^3}),11.78≤A[4,3]≤24.81;;

and coating the substrate material and a coating material containing M2 element to obtain the anode material.

In some embodiments, the lithium source is added in an amount of: so that the molar content ratio of the sum of the molar contents of Ni, co and M1 to Li is 1: (0.95-1.05).

In some embodiments, the lithium source comprises at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate, and lithium oxalate.

In some embodiments, the lithium source has an average particle size of 1 μm to 50 μm.

In some embodiments, the sintering process temperature is 710 ℃ to 730 ℃.

In some embodiments, the sintering process is for a period of time ranging from 5 hours to 15 hours.

In some embodiments, the method further comprises washing and solid-liquid separation of the matrix material prior to coating the matrix material with the M2 element-containing coating material.

In some embodiments, the mass ratio of the washing solvent to the matrix material is (30-100): 100.

In some embodiments, the temperature of the wash is from 10 ℃ to 25 ℃ and the time of the wash is from 5 minutes to 30 minutes.

In some embodiments, the washing is performed in a stirred state, and the stirring speed is controlled to be 200rpm to 2000rpm.

In some embodiments, the solid-liquid separation comprises pressure filtration, the pressure filtration being for a time period of from 10 minutes to 120 minutes.

In some embodiments, the matrix material has a moisture content of 0% to 10%.

In some embodiments, the coating treatment comprises a liquid phase coating treatment and/or a solid phase coating treatment.

In some embodiments, the step of liquid phase cladding treatment specifically comprises: and coating the coating solution containing the M2 element and the matrix material by adopting a spraying mode.

In some embodiments, the step of liquid phase cladding treatment specifically comprises: coating the coating solution containing the M2 element and the matrix material in a spraying mode, wherein the solid content of the coating solution containing the M2 element is 1% -50%;

In some embodiments, the specific steps of the solid phase coating process include: and coating the coating material containing the M2 element and the matrix material by adopting a spraying mode.

In some embodiments, the M2 element-containing cladding material comprises a phosphate and/or a solid state electrolyte LATP.

In some embodiments, the M2 element-containing cladding material comprises an oxide of a metal M2, the metal M2 comprising at least one of Al, mn, mg, sr, ca, zr, ti, la, W, nb, Y, gd.

In some embodiments, the mass ratio of the matrix material to the M2 element-containing cladding material is (500-1500): (1-10).

In some embodiments, the coating treatment is performed in a stirred state, and the stirring speed is controlled to be 100rpm to 500rpm.

In some embodiments, the coating process is at a temperature of 150 ℃ to 300 ℃.

In some embodiments, the coating treatment is for a period of time ranging from 5 minutes to 60 minutes.

In a third aspect, the present application provides a lithium ion battery, where the lithium ion battery includes the positive electrode material according to the first aspect or the positive electrode material prepared by the method for preparing the positive electrode material according to the second aspect.

Compared with the prior art, the technical scheme of the application has at least the following beneficial effects:

The tap density of the positive electrode material is T g/cm ³, the oil absorption value of the positive electrode material is Pml/100 g, the minimum particle size value of the positive electrode material in particle size distribution is D _min mu m, the machining performance coefficient of the positive electrode material is B, B= |0.5-P ^-0.5-0.00117*T-0.0541*D_min+0.0593*D_min ² +0.2696|, and B is more than or equal to 0 and less than or equal to 1. The processability of the cathode material is closely related to the tap density T, the oil absorption value P, and the minimum particle size value D _min in the particle size distribution of the cathode material. In the application, the processing performance coefficient B of the positive electrode material is controlled between 0 and 1 by controlling the balance among the tap density, the oil absorption value and the minimum particle size value in the particle size distribution of the positive electrode material, so that the positive electrode material has good processing performance, the phenomena of sedimentation and agglomeration of particles in the positive electrode slurry, flocculation separation, gelation, layering hardening and the like of the positive electrode slurry can be reduced, the dispersion uniformity and stability of the positive electrode slurry can be improved, and the cycle performance and the multiplying power performance of a battery made of the positive electrode material are further improved.

The positive electrode material provided by the application has the system average mass of A[4,3],A[4,3]＝(D₅₀ ^{^4}+D₉₀ ^{^4})/(D₅₀ ^{^3}+D₉₀ ^{^3)},11.78≤A[4,3]≤24.81. and the particle size distribution which can be used for representing the particle dispersibility of the material. The better the dispersibility of the particles, the closer the particle size distribution of the particles to monodisperse particles; in contrast, the worse the particle dispersibility, the particle size distribution tends to move from monodisperse particles to coarser particles, in the present application, by controlling the particle size distribution of the positive electrode material, the system average mass A4, 3 of the positive electrode material is controlled within the above-mentioned range, so that the positive electrode material particles can be compactly arranged and uniformly dispersed, the positive electrode material particles have uniform gaps, clear grain boundaries, good dispersibility of the positive electrode material particles and better energy density; the particle size distribution of the positive electrode material is uniform, the particles are free from agglomeration, the dispersion uniformity and stability of the slurry can be improved, and the cycle performance and the multiplying power performance of the positive electrode material are improved.

The preparation method of the positive electrode material comprises the steps of firstly sintering Ni _xCo_yM1_z oxide or Ni _xCo_yM1_z hydroxide and a lithium source, and then crushing a sintered product to obtain a matrix material; the particle size distribution of the matrix material can be regulated and controlled by crushing the sintered product, the system average mass A4, 3 of the matrix material can be controlled between 11.78 and 24.81, and the dispersion uniformity of particles in the positive electrode material is further improved, so that the gaps of the particles in the positive electrode material are uniform and the grain boundary is clear, thereby being beneficial to improving the energy density of the positive electrode material; finally, coating primary particles positioned on the surface layer of the matrix material and part of primary particles positioned in the matrix material by using a coating material containing M2 element, so that a coating layer is formed on the surfaces of the primary particles; meanwhile, a protective layer can be formed on the surface of the positive electrode material, so that the surface of the positive electrode material particles and primary particles in the positive electrode material are coated, double protection is realized, and the circulation stability is improved. The positive electrode material prepared by the preparation method has uniform particle size distribution, no agglomeration of positive electrode material particles and good material processing performance, and can improve the dispersion uniformity and stability of slurry, thereby improving the cycle performance and the multiplying power performance of the positive electrode material.

Drawings

The invention will be further described with reference to the drawings and examples.

FIG. 1 is an SEM image of a positive electrode material prepared in example 1 of the present application;

fig. 2 is an SEM image of the positive electrode material prepared in comparative example 2 of the present application.

Detailed Description

For a better understanding of the technical solution of the present invention, the following detailed description of the embodiments of the present invention refers to the accompanying drawings.

It should be understood that the described embodiments are merely some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be understood that the term "and/or" as used herein is merely one relationship describing the association of the associated objects, meaning that there may be three relationships, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.

In a first aspect, the application provides a positive electrode material, wherein the chemical formula of the positive electrode material is Li _bNi_xCo_yM1_zM2_wO₂, b is more than or equal to 0.95 and less than or equal to 1.05,0.8 and less than or equal to x is less than or equal to 1, y+z is more than or equal to 0.2, and x+y+z= 1,0.0001 and less than or equal to w is more than or equal to 0.003; m1 is Mn and/or Al; m2 is a metal element;

The tap density of the positive electrode material is T g/cm ³, the oil absorption value of the positive electrode material is Pml/100 g, the minimum particle size value of the positive electrode material in the particle size distribution is D _min mu m, the processing coefficient of the positive electrode material is B,

B＝|0.5-P^-0.5-0.00117*T-0.0541*D_min+0.0593*D_min ²+0.2696|，0≤B≤1。

In the present application, the chemical formula of the positive electrode material is Li _bNi_xCo_yM1_zM2_wO₂, wherein b is more than or equal to 0.95 and less than or equal to 1.05,0.8 and less than or equal to x is less than 1, y+z is more than 0 and less than or equal to 0.2, x+y+z= 1,0.0001 and less than or equal to w and less than or equal to 0.003, b can be specifically 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, 1.01, 1.02, 1.03, 1.04 or 1.05, etc., x can be 0.8, 0.82, 0.83, 0.85, 0.90, 0.92, 0.95 or 0.98, etc., y+z can be 0.01, 0.05, 0.06, 0.08, 0.1, 0.12, 0.5, 0.18 or 0.2, etc., w can be 0.0001, 0.0005, 0.001, 0.0015, 0.002, 0.0025, or 0.0025, etc., and the like, but the values of course, are not limited thereto.

In some embodiments, the positive electrode material has a tap density of T g/cm ³, 2.4.ltoreq.T.ltoreq.3.0. The value of T may be specifically 2.4, 2.45, 2.5, 2.6, 2.65, 2.7, 2.8, 2.85, 2.9, 2.95, or 3.0, etc., and is not limited herein. When the T value is too small, the combination of the positive electrode material particles and the slurry is poor, and the slurry is easy to generate layering hardening phenomenon. When the T value is too large, the positive electrode material particles and the slurry are unevenly mixed, and the slurry is easy to harden and settle.

In some embodiments, the positive electrode material has an oil absorption value of Pml/100 g, 14.5.ltoreq.P.ltoreq.18.5. The value of P may be, specifically, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.2, 18.3, or 18.5, etc., and is not limited herein. When the P value is too large, the contact area between the positive electrode material and N-methyl pyrrolidone (NMP) and polyvinylidene fluoride (PVDF) in the slurry is large, the solvent in the slurry is consumed, and the slurry is easy to gel.

In some embodiments, the minimum particle size value D _min,0.1μm≤D_min≤0.9μm.D_min of the positive electrode material in the particle size distribution may be specifically 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, or 0.9 μm, etc., without limitation herein. When D _min is too small, the cathode material has more micro powder, the specific surface area of the cathode material is increased, and side reactions are increased; meanwhile, the micro powder is easy to generate violent collision, so that slurry is flocculated and even separated.

In the present application, the value of B may be specifically 0, 0.1, 0.2, 0.25, 0.30, 0.36, 0.45, 0.57, 0.69, 0.75, 0.8, 0.86, 0.9, 0.95, 1, or the like, and is not limited herein. When the value of B is larger than 1, the dispersion degree of secondary particles of the positive electrode material is poor, the slurry solid content is improved in the processing process of the battery slurry, the initial viscosity of the slurry is large, and the viscosity of the slurry is increased rapidly along with the delay of the standing time of the slurry, so that the processing performance of the positive electrode material is seriously influenced. Preferably, the positive electrode material has a processability coefficient B value of 0.498 to 0.534.

The application also provides a positive electrode material, wherein the chemical general formula of the positive electrode material is Li _bNi_xCo_yM1_zM2_wO₂, b is more than or equal to 0.95 and less than or equal to 1.05,0.8 and less than or equal to x is less than 1, y+z is more than 0 and less than or equal to 0.2, and x+y+z= 1,0.0001 and less than or equal to w is less than or equal to 0.003; m1 is Mn and/or Al; m2 is a metal element;

The system average mass a 4,3 of the positive electrode material may be specifically 11.78, 11.85, 12.56, 13.62, 14.57, 15.64, 16.43, 18.95, 19.89, 20.51, 22.32, 23.50, 24.0, 24.56, 24.81, or the like, but may be other values within the above range, and is not limited thereto.

The application limits the average mass of the whole positive electrode material system, when the average mass of the system is overlarge in the limited system volume, the particles of the positive electrode material are agglomerated, and the cohesiveness of the positive electrode material is larger; when the average mass of the system is too small, the structure of the positive electrode material is loose and dispersed in a limited system volume, the number of secondary particles is small, and the energy density of the material is reduced. Under the conventional condition, a technician only pays attention to the value range of a single particle diameter parameter to further control the specific surface area of the positive electrode material and improve the mass production stability of the positive electrode material; the application ignores the whole momentum balance and relative grain size distribution of the positive electrode material system, and solves the problem of the dispersibility of the positive electrode material by correlating the grain size with the whole momentum of the positive electrode material system. By controlling the system average mass A4, 3 of the positive electrode material within the above range, the positive electrode material is made to have a good dispersibility and a good energy density.

In some embodiments, the particle diameter D ₅₀ of the positive electrode material is 8.25 μm to 12.75 μm, specifically, 8.25 μm, 8.56 μm, 8.87 μm, 9.0 μm, 9.54 μm, 9.87 μm, 10.0 μm, 10.67 μm, 11.0 μm, 11.54 μm, 11.98 μm, 12.0 μm, or 12.75 μm, etc., but other values within the above range are also possible, and the present invention is not limited thereto. Preferably, the particle diameter D ₅₀ of the positive electrode material is 10.25 μm to 12.75 μm.

In some embodiments, the particle diameter D ₉₀ of the positive electrode material may be specifically 12.6 μm to 26.2 μm, specifically 12.6 μm, 13.0 μm, 13.58 μm, 14.87 μm, 15.0 μm, 16.5 μm, 17.8 μm, 18.9 μm, 20.0 μm, 21.4 μm, 24.5 μm, 25.9 μm, 26.2 μm, or the like, but other values within the above range are also possible, and the present invention is not limited thereto. Preferably, the particle diameter D ₉₀ of the positive electrode material is 15.0 μm to 20.0 μm.

The volume-based cumulative particle size distribution measured by measuring the particle size distribution by the laser diffraction method, D ₅₀ represents the particle size corresponding to the case where the cumulative particle size distribution percentage reaches 50%, and D ₉₀ represents the particle size corresponding to the case where the cumulative particle size distribution percentage reaches 90%.

In some embodiments, the positive electrode material includes a base material and a coating layer on a surface of the base material, the material of the coating layer including phosphate and/or a solid electrolyte LATP. Phosphate and/or solid electrolyte LATP react with residual Li on the surface of the material to generate a coating layer containing Li, so that side reactions are prevented, and the cycle performance of the material can be effectively improved.

In some embodiments, the positive electrode material includes secondary particles formed by agglomeration of a plurality of primary particles, the secondary particles being spherical or spheroid.

In some embodiments, the metallic element N comprises at least one of Al, mn, mg, sr, ca, zr, ti, la, W, nb, Y, gd.

In some embodiments, the primary particle surface has a coating layer comprising a metal M2-containing composite oxide. It can be understood that the coating layer on the surface of the primary particles can prevent the electrolyte from directly contacting with the matrix material, reduce the occurrence of side reactions, and further improve the cycle stability of the cathode material.

In some embodiments, the metal element M2 in the positive electrode material is 500ppm to 2000ppm by mass based on 100% by mass of the positive electrode material, specifically 500ppm, 600ppm, 700ppm, 800ppm, 1000ppm, 1200ppm, 1500ppm, 1800ppm, 2000ppm, or the like, but other values within the above range are also possible, and the present invention is not limited thereto.

In some embodiments, the specific surface area of the positive electrode material is 0.5m ²/g～2.0m²/g, specifically 0.5m²/g、0.6m²/g、0.8m²/g、1.0m²/g、1.2m²/g、1.5m²/g、1.6m²/g、1.8m²/g or 2.0m ²/g, or the like, but may be other values within the above range, and is not limited thereto. The specific surface area of the positive electrode material is controlled in the range, and the positive electrode material and the electrolyte have a good contact area, so that the lithium ion transmission and diffusion are facilitated, and the cycle performance and the multiplying power performance of a lithium battery made of the positive electrode material are improved.

In some embodiments, the bulk density of the positive electrode material is 1.0g/m ³～3.0g/m³, which may be 1.0g/m³、1.1g/m³、1.5g/m³、1.8g/m³、2.0g/m³、2.2g/m³、2.5g/m³、2.8g/m³ or 3.0g/m ³, or the like, although other values within the above range are also possible, and the present invention is not limited thereto. The bulk density of the positive electrode material is controlled within the above range, so that the bonding tightness between the active substance and the electrolyte can be improved, and the cycle performance and the rate performance of the lithium ion battery made of the positive electrode material can be improved.

In some embodiments, the powder conductivity of the positive electrode material under 4kN/cm ² of pressure is greater than 0.02S/cm, specifically, may be 0.25S/cm, 0.5S/cm, 0.8S/cm, 1.0S/cm, 1.1S/cm, 1.2S/cm, 1.5S/cm, 2.0S/c or 2.1S/cm, etc., but other values within the above range are also possible, and the present invention is not limited thereto. The powder conductivity of the positive electrode material is controlled in the range, and the positive electrode material has better conductivity and small battery impedance.

Step S100, mixing Ni _xCo_yM1_z oxide or Ni _xCo_yM1_z hydroxide with a lithium source to obtain a mixture, and sintering the mixture to obtain a sintered product, wherein x+y+z=1, and M1 is selected from Mn and/or Al;

Step S200, crushing the sintered product to obtain a matrix material, wherein the matrix material comprises secondary particles formed by agglomerating a plurality of primary particles by controlling the mass momentum average value of the matrix material to be D[4,3],D[4,3]＝(D₅₀ ^{^4}+D₉₀ ^{^4})/(D₅₀ ^{^3+}D₉₀ ^{^3}),11.78≤D[4,3]≤24.81;;

And step S300, coating the substrate material and the coating material containing the M2 element to obtain the positive electrode material.

The preparation method of the application is specifically described below with reference to examples:

Step S100, mixing Ni _xCo_yM1_z oxide or Ni _xCo_yM1_z hydroxide with a lithium source to obtain a mixture, and sintering the mixture to obtain a sintered product, wherein x+y+z=1, and M1 is selected from Mn and/or Al.

In some embodiments, the mixing manner of mixing the Ni _xCo_yM1_z oxide or Ni _xCo_yM1_z hydroxide, lithium source may be dry milling, ball milling, etc., without limitation, as long as the components are uniformly mixed.

In some embodiments, the mixing device may be at least one of a ball mill, a three-dimensional blendor, a high-speed blendor, and a VC blendor.

In some embodiments, the speed of the mixing device is 100rpm to 1500rpm, specifically, 100rpm, 200rpm, 500rpm, 800rpm, 1000rpm, 1200rpm, 1500rpm, etc., but other values within the above range are also possible, and the present invention is not limited thereto.

In some embodiments, the lithium source is added in an amount of: so that the molar content ratio of the sum of the molar contents of Ni, co and M1 to Li is 1: (0.95-1.2). Specifically, the values may be 1:0.95, 1:0.98, 1:1.0, 1:1.05, 1:1.1, 1:1.15, or 1:1.2, etc., but other values within the above range are also possible, and the present invention is not limited thereto.

In some embodiments, the median particle diameter D ₅₀ of the lithium source is 1 μm to 50. Mu.m, specifically 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm, etc., but other values within the above range are also possible, and the present invention is not limited thereto. It will be appreciated that controlling the particle size of the lithium source within the above range is advantageous in improving the uniformity of mixing of the precursor with the lithium source, which can be sufficiently contacted with the precursor during the reaction.

In some embodiments, the sintering temperature may be 710 ℃ to 730 ℃, specifically 710 ℃, 715 ℃, 718 ℃, 720 ℃, 725 ℃, 726 ℃, 730 ℃, or the like, but may be any other value within the above range, and the sintering temperature is not limited thereto.

In some embodiments, the sintering treatment time is 5h to 15h, specifically 5h, 6h, 8h, 10h, 12h, 13h, 15h, etc., but the present invention is not limited to the recited values, and other non-recited values within the range are equally applicable.

And step S200, crushing the sintered product to obtain a matrix material, wherein the matrix material comprises secondary particles formed by agglomerating a plurality of primary particles, and the system average mass of the matrix material is controlled to be A[4,3],A[4,3]＝(D₅₀ ^{^4}+D₉₀ ^{^4})/(D₅₀ ^{^3+}D₉₀ ^{^3}),11.78≤A[4,3]≤24.81;.

The values of D4, 3 may specifically be 11.78, 11.85, 12.56, 13.62, 14.57, 15.64, 16.43, 18.95, 19.89, 20.51, 22.32, 23.50, 24.0, 24.56, 24.81, etc., but may also be other values within the above ranges, and are not limited thereto. It can be understood that controlling the system average mass A4, 3 of the matrix material within the above range is beneficial to improving the dispersion uniformity of the particles in the positive electrode material, so that the positive electrode material has uniform particle size distribution, the positive electrode particles are free from agglomeration, the dispersion uniformity and stability of the slurry are beneficial to improving the cycle performance and rate performance of the positive electrode material. In addition, the average system quality A4, 3 of the matrix material is controlled within the above range, which is favorable for controlling the minimum granularity value D _min of the positive electrode material in granularity distribution, reducing the micro powder in the positive electrode material and improving the processing performance of the positive electrode material.

In some embodiments, the crushing mode comprises mechanical grinding, and the granularity of the sintered product is regulated and controlled by controlling the feeding frequency of the sintered product to be 5-30 HZ, the crushing frequency to be 10-30 HZ and the classifying wheel frequency to be 5-30 HZ.

Specifically, the sintering product feed frequency may be 5HZ, 8HZ, 10HZ, 15HZ, 18HZ, 20HZ, 25HZ, 30HZ, or the like; the pulverization frequency may be specifically 10HZ, 15HZ, 18HZ, 20HZ, 25HZ, 30HZ, etc.; the classification wheel frequency may specifically be 10HZ, 15HZ, 18HZ, 20HZ, 25HZ, 30HZ, or the like, and is not limited herein. It is understood that the present application can control the particle size distribution of the base material and thus the mass momentum average value D4, 3 of the base material to 11.78-24.81 by controlling the feeding frequency, the pulverizing frequency and the classifying frequency of the sintered product within the above ranges.

Before step S300, the above preparation method further includes washing the substrate and performing solid-liquid separation.

In some embodiments, the mass ratio of wash solvent to sintered product is (30-100): 100, the substrate may be 30: 100. 40: 100. 50: 100. 60: 100. 70: 100. 80: 100. 90:100 or 100:100, etc., but may be any other value within the above range, and is not limited thereto. It can be understood that the mass ratio of the washing solvent to the sintered product is controlled within the above range, so that impurities attached to the surface of the substrate can be removed, the residual alkali content on the surface of the positive electrode material can be reduced, and the processing performance of the positive electrode material can be improved; the oil absorption value of the positive electrode material can be reduced, and the processing performance of the positive electrode material is further improved.

In some embodiments, the temperature of the wash is from 10 ℃ to 25 ℃ and the time of the wash is from 5 minutes to 30 minutes. The washing temperature may be specifically 10 ℃,15 ℃,18 ℃,20 ℃,25 ℃, or the like, and is not limited herein. The washing time may be specifically 5min, 10min, 15min, 20min, 25min or 30min, etc., and is not limited herein. It can be understood that the washing temperature and time are controlled within the above ranges, which is beneficial to reducing the residual alkali content on the surface of the positive electrode material, reducing the precipitation of lattice lithium on the surface of the positive electrode material, improving the structural stability of the positive electrode material and improving the electrochemical performance of the positive electrode material.

In some embodiments, the washing is performed in a stirring state, and the stirring speed is controlled to be 200rpm to 2000rpm, specifically 200rpm, 300rpm, 500rpm, 800rpm, 1000rpm, 1200rpm, 1500rpm, 1800rpm, 2000rpm, or the like, but other values within the above range are also possible, and the present invention is not limited thereto. It can be understood that the stirring speed in the washing process is controlled within the range, so that the substrate material can be sufficiently washed, the residual alkali content on the surface of the positive electrode material is reduced, and the processing performance of the positive electrode material is improved; meanwhile, when the stirring speed is controlled within the range, the structure of the matrix material is hardly damaged in the washing process, so that the structural stability of the positive electrode material is improved, and the circulation stability of the positive electrode material is improved.

In some embodiments, the solid-liquid separation includes pressure filtration, where the time of the pressure filtration is 10min to 120min, specifically, 10min, 20min, 50min, 60min, 80min, 100min or 120min, and the like, but the present application is not limited to the recited values, and other non-recited values within the range of the values are equally applicable. In the application, the solid-liquid separation is carried out by the filter press, the side blowing treatment can be carried out on the substrate at the same time of the filter press, and the water content of the substrate can be further controlled by controlling the time of the filter press and the side blowing.

In some embodiments, the water content of the base material is 0% to 10%, specifically, 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or the like, but may be other values within the above range, and the present invention is not limited thereto. It can be understood that the water content of the matrix material is controlled within the above range, which is beneficial to reducing the hardening phenomenon of slurry, improving the processing performance of the positive electrode material and improving the electrochemical performance of the positive electrode material.

In some embodiments, the step of liquid phase cladding treatment specifically comprises: and coating the coating solution containing the M2 element and the matrix material by adopting a spraying mode. It can be appreciated that the coating uniformity of the coating material on the base material can be improved by spraying the coating manner.

In some embodiments, prior to performing the liquid phase coating, further comprising dissolving the M2 element-containing coating material in water to obtain an M2 element-containing coating solution.

In some embodiments, the solid content of the coating solution containing M2 element is 1% to 50%, specifically 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 48% or 50%, etc., and is not limited herein.

In some embodiments, the M2 element-containing cladding material comprises phosphate and/or a solid state electrolyte LATP.

In some embodiments, the mass ratio of the matrix material to the M2 element-containing cladding material is (500-1500): (1-10), specifically, it may be 500:1, 500:2, 500:5, 500:10 or 600:1, 600:10, 1000:1, 1000:5, 1000:10, 1500:1 or 1500:10, etc., but it may also be other values within the above range, and the present invention is not limited thereto.

In some embodiments, the coating treatment is performed in a stirring state, and the stirring speed is controlled to be 100rpm to 500rpm, specifically, 100rpm, 150rpm, 200rpm, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, or the like, but other values within the above range are also possible, and the present invention is not limited thereto.

In some embodiments, the temperature of the coating treatment is 150 to 300 ℃, specifically 150 ℃, 180 ℃, 200 ℃, 220 ℃, 240 ℃, 260 ℃, 280 ℃, 300 ℃ or the like, but may be any other value within the above range, and the coating treatment is not limited thereto.

In some embodiments, the coating treatment time is 5min to 60min, specifically, may be 5min, 10min, 15min, 20min, 30min, 40min, 50min or 60min, or may be other values within the above range, which is not limited herein.

The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.

Example 1

(1) 3Kg of Ni _0.905Co_0.042Al_0.053(OH)₂ and 1.725kg of lithium hydroxide (D ₅₀: 18 μm) were uniformly mixed in a high-speed mixer at a speed of 800rpm to obtain a mixture in which n (Li) [ n (Ni) +n (Co) +n (Al) ] is 1.015; the mixture was placed in a box furnace and sintered at 720 ℃ for 9 hours to obtain a sintered product.

(2) Mechanically grinding and crushing the sintered product, controlling the feeding frequency of the sintered product to 25HZ, the crushing frequency to 20HZ, the grading wheel frequency to 20HZ, and the granularity regulation and sieving to obtain the base material with average system quality A4, 3 of 12.86.

(3) Weighing 3kg of the matrix material, placing the matrix material in a reaction kettle, adding 2.4kg of pure water into the reaction kettle for washing, wherein the washing temperature is 20 ℃, the washing time is 30min, and the stirring speed of the reaction kettle is controlled to be 800rpm; and (3) introducing the washed slurry into a filter press for filter pressing for 30min, wherein the moisture of the matrix material is 5%.

(4) And 5g of tungsten oxide powder and 30mL of pure water are weighed and subjected to ultrasonic dispersion to obtain a tungsten oxide coating solution with 17% of solid content, the substrate material is placed in a reaction kettle, the temperature of the reaction kettle is set to be 200 ℃, the stirring speed is controlled to be 100rpm, the tungsten oxide coating solution is sprayed into the reaction kettle, and after the tungsten oxide coating solution is completely sprayed into the reaction kettle, the stirring is continued for 24 hours at the stirring speed of 100rpm, so that the anode material is obtained.

The general formula of the positive electrode material prepared in the embodiment is Li _0.98Ni_0.905Co_0.042Al_0.053W_0.001O₂.

The positive electrode material prepared in this example had a specific surface area of 1.02m ²/g, a bulk density of 2.00g/m ³,4kN/cm² and a powder conductivity of 0.03S/cm under pressure.

Fig. 1 is an SEM image of the positive electrode material prepared in example 1 of the present application, and as shown in fig. 1, the particles in the positive electrode material are uniformly dispersed, and no obvious agglomeration phenomenon exists, which indicates that the dispersibility of the particles in the positive electrode material is good.

Example 2

The difference from example 1 is that: ni _0.905Co_0.042Mn_0.053O₂ was used in step (1), and the other conditions were exactly the same as in example 1.

The general formula of the positive electrode material prepared in the embodiment is Li _1.00Ni_0.905Co_0.042Mn_0.053W_0.001O₂.

The positive electrode material prepared in this example had a specific surface area of 1.03m ²/g, a bulk density of 1.90g/m ³,4kN/cm² and a powder conductivity of 0.025S/cm under pressure.

Example 3

The difference from example 1 is that: the lithium source used in step (1) was lithium carbonate, and the other conditions were exactly the same as in example 1.

The general formula of the positive electrode material prepared in the embodiment is Li _0.99Ni_0.905Co_0.042Al_0.053W_0.001O₂.

The specific surface area of the positive electrode material prepared in this example was 1.02m ²/g, the apparent density was 1.85g/m ³,4kN/cm², and the powder conductivity under pressure was 0.022S/cm.

Example 4

The difference from example 1 is that: the lithium source used in step (1) was lithium acetate, and the other conditions were exactly the same as in example 1.

The general formula of the positive electrode material prepared in the embodiment is Li _0.97Ni_0.905Co_0.042Al_0.053W_0.001O₂.

The positive electrode material prepared in this example had a specific surface area of 1.03m ²/g, a bulk density of 1.91g/m ³,4kN/cm² and a powder conductivity of 0.023S/cm under pressure.

Example 5

The difference from example 1 is that: the lithium source used in step (1) was lithium nitrate, and the other conditions were exactly the same as in example 1.

The specific surface area of the positive electrode material prepared in the embodiment is 1.02m ²/g, the apparent density is 1.98g/m ³,4kN/cm², and the powder conductivity under pressure is 0.024S/cm.

Example 6

The difference from example 1 is that: the lithium source used in step (1) was lithium oxalate, and the other conditions were exactly the same as in example 1.

The general formula of the positive electrode material prepared in the embodiment is Li _0.99Ni_0.905Co_0.042A_0.053W_0.001O₂.

The specific surface area of the positive electrode material prepared in the embodiment is 1.03m ²/g, the apparent density is 1.95g/m ³,4kN/cm², and the powder conductivity under pressure is 0.03S/cm.

Example 7

The difference from example 1 is that: the sintering temperature in step (1) was 710℃and the other conditions were exactly the same as in example 1.

The positive electrode material prepared in this example had a specific surface area of 1.03m ²/g, a bulk density of 2.00g/m ³,4kN/cm² and a powder conductivity of 0.025S/cm under pressure.

Example 8

The difference from example 1 is that: the sintering temperature in step (1) was 730℃and the other conditions were exactly the same as in example 1.

The general formula of the positive electrode material prepared in the embodiment is Li _0.97Ni_0.905Co_0.042A_0.053W_0.0015O₂.

The specific surface area of the positive electrode material prepared in this example was 1.02m ²/g, the apparent density was 1.90g/m ³,4kN/cm², and the powder conductivity under pressure was 0.03S/cm.

Example 9

The difference from example 1 is that: the amount of pure water used in the step (3) was 0.9kg, and the other conditions were exactly the same as in example 1.

Example 10

The difference from example 1 is that: the amount of pure water used in the step (3) was 1.8kg, and the other conditions were exactly the same as in example 1.

The specific surface area of the positive electrode material prepared in this example was 1.02m ²/g, the apparent density was 2.00g/m ³,4kN/cm², and the powder conductivity under pressure was 0.024S/cm.

Example 11

The difference from example 1 is that: the amount of pure water used in the step (3) was 3kg, and the other conditions were exactly the same as in example 1.

The general formula of the positive electrode material prepared in the embodiment is Li _0.99Ni_0.905C_0.042Al_0.053W_0.001O₂.

The specific surface area of the positive electrode material prepared in this example was 1.03m ²/g, the apparent density was 2.01g/m ³,4kN/cm², and the powder conductivity under pressure was 0.03S/cm.

Example 12

The difference from example 1 is that: the washing temperature in step (3) was 10℃and the other conditions were exactly the same as in example 1.

The general formula of the positive electrode material prepared in the embodiment is Li _0.99N_0.905Co_0.042Al_0.053W_0.001O₂.

The positive electrode material prepared in this example had a specific surface area of 1.02m ²/g, a bulk density of 1.90g/m ³,4kN/cm² and a powder conductivity of 0.023S/cm under pressure.

Example 13

The difference from example 1 is that: the temperature of the washing in the step (3) was 15℃and the other conditions were exactly the same as in example 1.

The specific surface area of the positive electrode material prepared in this example was 1.02m ²/g, the apparent density was 1.95g/m ³,4kN/cm², and the powder conductivity under pressure was 0.027S/cm.

Example 14

The difference from example 1 is that: the washing temperature in step (3) was 25℃and the other conditions were exactly the same as in example 1.

The specific surface area of the positive electrode material prepared in this example was 1.03m ²/g, the apparent density was 2.00g/m ³,4kN/cm², and the powder conductivity under pressure was 0.03S/cm.

Example 15

The difference from example 1 is that: in the step (3), the stirring speed of the reaction vessel was controlled to 200rpm during the washing, and the other conditions were exactly the same as in example 1.

The specific surface area of the positive electrode material prepared in the embodiment is 1.02m ²/g, the apparent density is 1.98g/m ³,4kN/cm², and the powder conductivity under pressure is 0.03S/cm.

Example 16

The difference from example 1 is that: in the step (3), the stirring speed of the reaction vessel was controlled to 1000rpm during the washing, and the other conditions were exactly the same as in example 1.

The specific surface area of the positive electrode material prepared in this example was 1.04m ²/g, the apparent density was 2.00g/m ³,4kN/cm², and the powder conductivity under pressure was 0.03S/cm.

Example 17

The difference from example 1 is that: in the step (3), the stirring speed of the reaction vessel was controlled to 2000rpm during the washing, and the other conditions were exactly the same as in example 1.

The positive electrode material prepared in this example had a specific surface area of 1.04m ²/g, a bulk density of 2.00g/m ³,4kN/cm² and a powder conductivity of 0.025S/cm under pressure.

Example 18

The difference from example 1 is that: the pressure filtration time in the step (3) was 120min, the moisture content of the base material was 0%, and the other conditions were exactly the same as in example 1.

The positive electrode material prepared in this example had a specific surface area of 1.01m ²/g, a bulk density of 2.00g/m ³,4kN/cm² and a powder conductivity of 0.026S/cm under pressure.

Example 19

The difference from example 1 is that: the pressure filtration time in the step (3) was 10min, the moisture content of the base material was 10%, and the other conditions were exactly the same as in example 1.

The general formula of the positive electrode material prepared in the embodiment is Li _.099Ni_0.905Co_0.042Al_0.053W_0.001O₂.

The specific surface area of the positive electrode material prepared in this example was 1.04m ²/g, the apparent density was 1.96g/m ³,4kN/cm², and the powder conductivity under pressure was 0.03S/cm.

Example 20

The difference from example 1 is that: the solid content of the coating solution in the step (4) was 1%, and the other conditions were exactly the same as in example 1.

The specific surface area of the positive electrode material prepared in the embodiment is 1.03m ²/g, the apparent density is 1.94g/m ³,4kN/cm², and the powder conductivity under pressure is 0.028S/cm.

Example 21

The difference from example 1 is that: (4) Placing a substrate material into a reaction kettle, weighing 5g of tungsten oxide powder, adding the tungsten oxide powder into the reaction kettle, setting the temperature of the reaction kettle to be 200 ℃, controlling the stirring speed to be 100rpm, spraying the tungsten oxide powder into the reaction kettle, and continuously stirring the tungsten oxide powder for 24 hours at the stirring speed of 100rpm after the tungsten oxide powder is completely sprayed into the reaction kettle to obtain the positive electrode material.

The specific surface area of the positive electrode material prepared in this example was 1.05m ²/g, the apparent density was 2.00g/m ³,4kN/cm², and the powder conductivity under pressure was 0.024S/cm.

Example 22

The difference from example 1 is that: in the step (4), the tungsten oxide was replaced with monoammonium phosphate, and the other conditions were exactly the same as in example 1.

The general formula of the positive electrode material prepared in the embodiment is Li _0.99Ni_0.905Co_0.042Al_0.053P_0.001O₂.

The positive electrode material prepared in this example had a specific surface area of 1.03m ²/g, a bulk density of 1.95g/m ³,4kN/cm² and a powder conductivity of 0.025S/cm under pressure.

Example 23

The difference from example 1 is that: in the step (4), the tungsten oxide was replaced with the solid electrolyte LATP, and the other conditions were exactly the same as in example 1.

The general formula of the positive electrode material prepared in the embodiment is Li _0.98Ni_0.905Co_0.042Al_0.053Ti_0.001O₂.

The positive electrode material prepared in this example had a specific surface area of 1.05m ²/g, a bulk density of 2.00g/m ³,4kN/cm² and a powder conductivity of 0.03S/cm under pressure.

Example 24

The difference from example 1 is that: in the step (2), the classification wheel frequency of 20HZ was changed to 30HZ, and the system average mass A4, 3 of the base material was 12.75, and the other conditions were exactly the same as in example 1.

Comparative example 1

The difference from example 1 is that:

(2) Mechanically grinding and crushing the sintered product, controlling the feeding frequency of the sintered product to 5HZ, the crushing frequency to 40HZ, the grading wheel frequency to 40HZ, and the granularity regulation and sieving to obtain the base material with average system quality A4, 3 of 11.00.

The positive electrode material prepared in this comparative example had a specific surface area of 1.05m ²/g, a bulk density of 1.81g/m ³,4kN/cm² and a powder conductivity of 0.01S/cm under pressure.

Comparative example 2

The difference from example 1 is that:

(2) Mechanically grinding and crushing the sintered product, controlling the feeding frequency of the sintered product to 40HZ, the crushing frequency to 3HZ, the grading wheel frequency to 3HZ, and the granularity regulation and sieving to obtain the base material with average system quality A4, 3 of 26.38.

The positive electrode material prepared in this comparative example had a specific surface area of 1.00m ²/g, a bulk density of 1.87g/m ³,4kN/cm² and a powder conductivity of 0.01S/cm under pressure.

Fig. 2 is a view showing that the positive electrode material prepared in comparative example 2 of the present application has significant particle agglomeration and poor particle dispersibility as shown in fig. 2.

Test method

(1) The method for testing the tap density of the positive electrode material comprises the following steps:

And (3) testing by using BT-303 equipment, placing a powder sample with certain mass into a sample tube, and generating certain pressure by up-and-down vibration. And after vibrating the sample tube for a period of time, the ratio of the mass of the sample to the volume after compaction is the tap density.

(2) The method for testing the particle size of the positive electrode material comprises the following steps:

The particle size distribution range of the negative electrode material was measured by a malvern laser particle size analyzer (Mastersizer 3000), the volume-based cumulative particle size distribution measured by the particle size distribution measured by a laser diffraction method was D ₅₀, D ₉₀, and D _min, respectively, to the particle size corresponding to the cumulative particle size distribution percentage reaching 50%, to the cumulative particle size distribution percentage reaching 90%, and to the minimum particle size value in the sample particle size distribution.

And (3) testing by adopting a Markov 3000 laser particle sizer to obtain the particle size distribution of the positive electrode material, and carrying out (D ₅₀ ^{^4}+D₉₀ ^{^4})/(D₅₀ ^{^3}+D₉₀ ^{^3}) to calculate the system average mass A4, 3 of the positive electrode material.

(3) The method for testing the specific surface area of the positive electrode material comprises the following steps:

the dynamic specific surface area rapid tester JW-DX of Beijing micro-advanced high-Bo scientific technology Co., ltd is adopted for testing, and the unit is m2/g.

(4) The method for testing the powder conductivity of the positive electrode material comprises the following steps:

the powder conductivity of the positive electrode material is tested by adopting a FT-8100 series four-probe method powder conductivity tester, and the unit is S/cm

(5) The method for testing the apparent density of the positive electrode material comprises the following steps:

The bulk density of the powder is tested by adopting a BT-100 general powder bulk density testing instrument, and the unit is g/m ³

(6) Scanning electron microscope test:

the material was tested using an S4800 scanning electron microscope to observe microscopic particle states.

(7) The method for testing the oil absorption value of the positive electrode material comprises the following steps:

Using an ASAHI S-500 oil absorption tester apparatus, a powder sample of a certain mass was placed into a mixing chamber, and flaxseed oil was dropped onto the sample at a certain constant rate to form semi-plastic agglomerates, which were simultaneously stirred with two motor-driven rotating wings. The viscosity of the mixture gradually increases and peaks. The measurement end point is the amount of linseed oil added dropwise when the torque generated by the viscosity characteristic change reaches a set value or reaches a constant percentage of the maximum torque obtained from the torque curve, to calculate the oil absorption value (mL/100 g) of the sample against linseed oil.

(8) The testing method for the mass content of the metal element M2 in the positive electrode material comprises the following steps:

And dissolving the positive electrode material into an acidic solution by utilizing ICP-OES (IRIS Intrepid II) equipment, and obtaining the content of the M2 element through qualitative, semi-quantitative and quantitative analysis of one or more elements in the test sample.

(9) Electrochemical performance test:

The electrochemical performance of the prepared positive electrode material is evaluated by adopting a button half cell, and the specific method is as follows: the positive electrode active material, SP and polyvinylidene fluoride (PVDF) are weighed according to the mass ratio of 8:1:1, N-methyl pyrrolidone is added, the mixture is prepared into thick slurry by a high-speed dispersing machine, the thick slurry is uniformly coated on aluminum foil by a scraper, and the aluminum foil is dried by baking in an oven at 80 ℃, rolled and cut into positive plates with the diameter of 14 mm. Lithium sheets with the diameter of 16mm are used as a negative electrode sheet, celgard polyethylene PP film is used as a diaphragm, a solution of carbonic ester (DEC/EC volume ratio of 1:1) of LiPF6 with the concentration of 1mol/L is used as electrolyte, and the assembly is carried out in a glove box filled with argon.

And a LAND battery test system is adopted to test the discharge capacity and the first-cycle charge-discharge efficiency performance at 25 ℃ and 2.5-4.3V, wherein the reference capacity is set to 200mA/g, and the corresponding current density of 1C is set to 200mA/g.

First time efficiency test: the test cell was mounted on a blue instrument and placed in a (25.+ -. 1) C test environment. The following procedure was set up: standing for 10min; constant-current charging is carried out to 4.3V by 0.1C current, then constant-voltage charging is carried out until the current is reduced to 0.05C, and the charging is stopped; standing for 5min; then discharging to 2.5V at constant current of 0.1C to obtain first efficiency. The test results are shown in table 2 below.

And (3) testing the cycle performance: the test cell was mounted on a blue instrument and placed in a (25.+ -. 1) C test environment. The following procedure was set up: standing for 10min; constant-current charging is carried out to 4.3V by 1.0C current, then constant-voltage charging is carried out until the current is reduced to 0.05C, and the charging is stopped; standing for 5min; then discharging to 2.5V at a constant current of 1.0C; according to the procedure, the charge and discharge are carried out 55 times, and the capacity retention rate after 55 times is obtained, namely the cycle performance. The test results are shown in table 2 below.

(10) The method for testing the solid content of the slurry comprises the following steps:

And (3) testing the material processing performance index by using a JFGHL-120A battery slurry solid content tester, spreading about 5g of battery slurry on glass fiber paper in a sample tray, covering a heating bin cover, starting heating by pressing a Start key, evaporating water, drying the sample, and automatically ending the test by the instrument after the constant weight of the sample is achieved, so as to finish the measurement. At this time the screen directly displays the slurry solids content.

(11) The viscosity test method of the slurry comprises the following steps:

And (3) testing the material processing performance index by adopting a TVB-shaped viscometer, connecting a host computer by using software, performing program editing and data acquisition, and drawing a viscosity change curve. A certain amount of the prepared lithium ion battery slurry is taken in a sample cup of the SSA, and a rotor is slowly immersed into the sample, so that the viscosity reading or the viscosity change number is continuously carried out.

The results of the above tests are shown in Table 1 and Table 2.

Table 1 relevant performance test parameters of the positive electrode materials prepared in examples and comparative examples

Table 2 results of electrochemical performance tests of the positive electrode materials prepared in examples and comparative examples

From the test data in tables 1 and 2, it can be seen that controlling the balance between the tap density, oil absorption value and minimum particle size in the particle size distribution of the positive electrode material can control the processing coefficient B of the positive electrode material between 0 and 1, so that the positive electrode material has good processing performance, thereby reducing the phenomena of sedimentation and agglomeration of particles in the slurry, flocculation separation, gelation, layering hardening and the like of the slurry, improving the dispersion uniformity and stability of the slurry, improving the coating performance of the slurry, and further improving the cycle performance and multiplying power performance of the positive electrode material.

The positive electrode materials prepared in examples 1 to 14, 16 and 18 to 25 have average system masses A4 and 3 of 11.78 to 24.81, and have processing performance analysis coefficients B of 0 to 1, which indicates that the positive electrode materials have good dispersibility and processing performance, and the slurry prepared from the positive electrode materials has low solid content and viscosity, so that the slurry has good dispersibility and stability, the coating performance of the slurry can be improved, and the positive electrode materials have good cycle performance and rate performance.

Compared with example 1, the substrate material of example 15 has too small stirring speed during the washing process, insufficient washing of the substrate material, high residual alkali on the surface of the positive electrode material, and thus the stability of the surface structure of the positive electrode material is reduced, which results in a rise in the oil absorption value of the positive electrode material, a fall in the tap density of the positive electrode material, an increase in the minimum particle size value in the particle size distribution of the positive electrode material, and an imbalance in the relationship between the tap density, the oil absorption value and the minimum particle size value in the particle size distribution of the positive electrode material, which results in a coefficient of processability of the positive electrode material of more than 1, a fall in the processability of the positive electrode material, a hardening phenomenon of the slurry made of the positive electrode material easily occurs, a rise in the solid content and viscosity of the slurry, and a fall in the cycle performance of the lithium ion battery made of the positive electrode material.

Compared with example 1, the matrix material of example 17 was excessively stirred during washing, the matrix material was excessively washed, precipitation of lattice lithium during washing led to damage to the surface structure of the positive electrode material, and at the same time, the excessive stirring speed may lead to partial breakage of the matrix material, so that the oil absorption value of the positive electrode material was increased, and at the same time, the tap density of the positive electrode material was decreased, the minimum particle size value in the particle size distribution of the positive electrode material was also increased, the relationship between the tap density, the oil absorption value and the minimum particle size value in the particle size distribution of the positive electrode material was unbalanced, so that the coefficient of processability of the positive electrode material was greater than 1, the processability of the positive electrode material was decreased, the solid content and viscosity of the slurry made of the positive electrode material were increased, and further the cycle performance of the lithium ion battery made of the positive electrode material was decreased.

Compared with example 1, the matrix material of comparative example 1 has too small system average mass A4, 3, the prepared positive electrode material has too small system average mass A4, 3, the positive electrode material has loose and dispersed structure, the particle structure in the positive electrode material is too dispersed, the bonding tightness degree among the particles of the positive electrode material is reduced, the structural stability of the material is reduced, and the tap density of the positive electrode material is reduced; meanwhile, pores in the positive electrode material are increased, the pores are increased, the oil absorption value of the positive electrode material is increased, the relationship among the tap density, the oil absorption value and the minimum particle size value in the particle size distribution of the positive electrode material is unbalanced, the processing performance coefficient of the positive electrode material is reduced, the processing performance of the positive electrode material is poor, the viscosity and the solid content of slurry prepared from the positive electrode material are increased, and the electrochemical performance of a lithium ion battery prepared from the positive electrode material is reduced.

Compared with example 1, the matrix material of comparative example 2 has too large system average mass A4, 3, the prepared positive electrode material has too large system average mass A4, 3, the positive electrode material has poor particle dispersibility, the positive electrode material has obvious particle agglomeration, the particles in the slurry prepared from the positive electrode material are easy to generate local agglomeration and adhesion, the slurry has poor dispersibility, the viscosity and solid content of the slurry are increased, and the processability of the positive electrode material is poor, so that the electrochemical performance of the lithium ion battery prepared from the positive electrode material is reduced.

Claims

1. The positive electrode material is characterized by having a chemical formula of Li _bNi_xCo_yM1_zM2_wO₂, wherein b is more than or equal to 0.95 and less than or equal to 1.05,0.8 and less than or equal to x is more than or equal to 1, y+z is more than or equal to 0 and less than or equal to 0.2, and x+y+z= 1,0.0001 and less than or equal to w is more than or equal to 0.003; m1 is Mn and/or Al; m2 is a metal element;

B＝|0.5-P^-0.5-0.00117*T-0.0541*D_min+0.0593*D_min ²+0.2696|，0≤B≤1。

2. The positive electrode material is characterized by having a chemical formula of Li _bNi_xCo_yM1_zM2_wO₂, wherein b is more than or equal to 0.95 and less than or equal to 1.05,0.8 and less than or equal to x is more than or equal to 1, y+z is more than or equal to 0 and less than or equal to 0.2, and x+y+z= 1,0.0001 and less than or equal to w is more than or equal to 0.003; m1 is Mn and/or Al; m2 is a metal element;

3. The cathode material according to claim 1 or 2, characterized in that the cathode material comprises a matrix material and a coating layer on the surface of the matrix material, the material of the coating layer comprising phosphate and/or solid electrolyte LATP.

4. The positive electrode material according to claim 1 or 2, characterized in that the positive electrode material comprises secondary particles formed by agglomeration of a plurality of primary particles, the positive electrode material comprising at least one of the following features (1) to (12):

(1) The secondary particles are spherical or spheroid;

(2) The metal element M2 includes at least one of Al, mn, mg, sr, ca, zr, ti, la, W, nb, Y, gd;

(3) The surface of the primary particles is provided with a coating layer, and the coating layer comprises an oxide containing a metal element M2 and/or a lithium composite oxide containing a metal element N;

(4) The mass content of the metal element M2 in the positive electrode material is 500 ppm-2000 ppm based on 100% of the mass of the positive electrode material;

(5) The particle diameter D ₅₀ of the positive electrode material is 8.25-12.75 mu m;

(6) The particle diameter D ₉₀ of the positive electrode material is 12.6-26.2 mu m;

(7) The tap density of the positive electrode material is T g/cm ³, and T is more than or equal to 2.4 and less than or equal to 3.0;

(8) The oil absorption value of the positive electrode material is Pml/100 g, and P is more than or equal to 14.5 and less than or equal to 18.5;

(9) The minimum particle size value of the positive electrode material in the particle size distribution is D _min,0.1μm≤D_min less than or equal to 0.9 mu m;

(10) The specific surface area of the positive electrode material is 0.5m ²/g～2.0m²/g;

(11) The bulk density of the positive electrode material is 1.0g/m ³～3.0g/m³;

(12) The powder conductivity of the positive electrode material under the pressure of 4kN/cm ² is more than 0.02S/cm.

5. The preparation method of the positive electrode material is characterized by comprising the following steps:

6. The production method according to claim 5, characterized in that the production method comprises at least one of the following features (1) to (5):

(1) The addition amount of the lithium source is as follows: so that the molar content ratio of the sum of the molar contents of Ni, co and M1 to Li is 1: (0.95-1.05);

(2) The lithium source comprises at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate and lithium oxalate;

(3) The median particle diameter D ₅₀ of the lithium source is 1-50 mu m;

(4) The sintering treatment temperature is 710-730 ℃;

(5) The sintering treatment time is 5-15 h.

7. The method according to claim 5, wherein before the coating treatment of the base material with the coating material containing M2 element, the method further comprises washing and solid-liquid separation of the base material, which satisfies at least one of the following characteristics (1) to (5):

(1) The mass ratio of the washing solvent to the matrix material is (30-100): 100;

(2) The washing temperature is 10-25 ℃, and the washing time is 5-30 min;

(3) The washing is carried out in a stirring state, and the stirring speed is controlled to be 200 rpm-2000 rpm;

(4) The solid-liquid separation comprises filter pressing, wherein the time of the filter pressing is 10-120 min;

(5) The water content of the matrix material is 0-10%.

8. The method according to claim 5, wherein the coating treatment comprises a liquid phase coating treatment and/or a solid phase coating treatment.

9. The production method according to claim 8, characterized in that the production method comprises at least one of the following features (1) to (9):

(1) The liquid phase cladding treatment comprises the following steps: coating the coating solution containing M2 element and the matrix material by adopting a spraying mode;

(2) The specific steps of the liquid phase cladding treatment comprise: coating the coating solution containing the M2 element and the matrix material in a spraying mode, wherein the solid content of the coating solution containing the M2 element is 1% -50%;

(3) The specific steps of the solid phase coating treatment comprise: coating the coating material containing M2 element and the matrix material by adopting a spraying mode;

(4) The coating material containing the M2 element comprises phosphate and/or solid electrolyte LATP;

(5) The coating material containing the M2 element comprises an oxide of a metal M2, and the metal M2 comprises at least one of Al, mn, mg, sr, ca, zr, ti, la, W, nb, Y, gd;

(6) The mass ratio of the matrix material to the coating material containing M2 element is (500-1500): (1-10);

(7) The coating treatment is carried out in a stirring state, and the stirring speed is controlled to be 100 rpm-500 rpm;

(8) The temperature of the coating treatment is 150-300 ℃;

(9) The coating treatment time is 5-60 min.

10. A lithium ion battery, characterized in that the lithium ion battery comprises the positive electrode material according to any one of claims 1 to 4 or the positive electrode material prepared by the method for preparing a positive electrode material according to any one of claims 5 to 9.