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

Abstract

The invention relates to a positive electrode material and a preparation method thereof, a positive electrode plate and a secondary battery, and the preparation method of the positive electrode material comprises the following steps: carrying out first sintering treatment on a mixture to obtain a first intermediate; mixing the first intermediate with a second additive, and performing second sintering treatment to obtain a second intermediate; and mixing the second intermediate with a third additive, and carrying out third sintering treatment to obtain the positive electrode material, the positive electrode material comprises first polycrystalline particles and second polycrystalline particles, and the particle size of the first polycrystalline particles is larger than that of the second polycrystalline particles. Therefore, the preparation process can be simplified, the material loss of each process can be reduced, the probability of material pollution can be effectively reduced, meanwhile, the production cost can be reduced, the positive electrode material prepared by the preparation method has few lattice defects, and the volume energy density of the battery is relatively high.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to positive electrode materials and preparation methods thereof, positive electrode sheets and secondary batteries. Background Art

[0002] With the rapid development of the new energy industry, technological innovation in lithium-ion secondary battery cathode materials has become a key breakthrough in improving energy density. Among them, ternary cathode materials with mixed large and small particles can significantly improve the compaction density of the material by constructing a multi-level particle size distribution structure. They are currently widely used in the fields of power batteries and energy storage systems. The traditional preparation method of this material is a step-by-step synthesis method, that is, large and small particles are prepared separately and then mechanically mixed. However, this traditional preparation method has problems such as increased energy consumption due to multi-stage calcination, accumulation of lattice defects, and complex preparation procedures. Summary of the Invention

[0003] The present application provides a positive electrode material and a preparation method thereof, a positive electrode plate and a secondary battery. Compared with traditional preparation methods, the preparation method can simplify the preparation process, reduce material loss in each process, effectively reduce the probability of material contamination, and at the same time reduce production costs. In addition, the positive electrode material prepared by the preparation method has fewer lattice defects and can improve the volume energy density of the battery.

[0004] In a first aspect of the present application, a method for preparing a positive electrode material is provided, comprising the following steps:

[0005] Performing a first sintering treatment on the mixture to obtain a first intermediate; the mixture includes a first positive electrode material precursor, a second positive electrode material precursor, a lithium source and a first additive, the particle size of the first positive electrode material precursor is larger than the particle size of the second positive electrode material precursor, and the first additive contains at least one element of B, F, Mg, Al, Si, P, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sn, Nb, Mo, Sb, Sr, Y, Zr, W, Hf, In, Bi, La, Ce, Gd, Ba and Ta;

[0006] The first intermediate is mixed with a second additive, and subjected to a second sintering process to obtain a second intermediate; the second additive contains at least one element selected from Co, Mn, Al and Zr;

[0007] The second intermediate is mixed with a third additive and subjected to a third sintering treatment to obtain the positive electrode material; the third additive includes at least one of a compound containing a B element, a compound containing an Al element, and an ammonium salt; the positive electrode material includes first polycrystalline particles and second polycrystalline particles, and the particle size of the first polycrystalline particles is larger than the particle size of the second polycrystalline particles.

[0008] In some embodiments, the first polycrystalline particles have a particle size of 6 μm to 14 μm.

[0009] In some embodiments, the second polycrystalline particles have a particle size of 2 μm to 5 μm.

[0010] In some embodiments, the mass ratio of the first polycrystalline particles to the second polycrystalline particles is 5:5 to 9:1.

[0011] In some embodiments, before the step of mixing the second intermediate with the third additive, the method further comprises: washing the second intermediate with water;

[0012] Then, the second intermediate after the water washing treatment is mixed with the third additive.

[0013] In some embodiments, the method for preparing the mixture comprises the following steps:

[0014] Mixing the first cathode material precursor and the second cathode material precursor to obtain a primary mixed material;

[0015] Mixing the primary mixed material, the lithium source and the first additive to obtain the mixed material; or,

[0016] Mixing the first cathode material precursor, part of the lithium source and part of the first additive to obtain a first primary mixed material;

[0017] Mixing the second positive electrode material precursor, the remaining lithium source and the remaining first additive to obtain a second primary mixed material;

[0018] The first primary mixed material and the second primary mixed material are mixed to obtain the mixed material.

[0019] In some embodiments, the first polycrystalline particle includes a core A1, a first coating layer B1 coated on at least a portion of the surface of the core A1, and a second coating layer C1 coated on at least a portion of the surface of the first coating layer B1. The core A1 includes a chemical formula of Li a1 Ni b1 Co c1 Mn d1 X 1 e1 O2 materials, wherein 1≤a1≤1.2, 0.7≤b1<1, 0<c1<0.3, 0<d1<0.3, 0<e1≤0.01, a1+b1+c1+d1+e1=1, X 1The elements include at least one of B, F, Mg, Al, Si, P, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sn, Nb, Mo, Sb, Sr, Y, Zr, W, Hf, In, Bi, La, Ce, Gd, Ba and Ta.

[0020] In some embodiments, the second polycrystalline particle includes a core A2, a first coating layer B2 coated on at least a portion of the surface of the core A2, and a second coating layer C2 coated on at least a portion of the surface of the first coating layer B2, wherein the core A2 includes a chemical formula of Li a2 Ni b2 Co c2 Mn d2 X 2 e2 O2 material, wherein 1≤a2≤1.2, 0.7≤b2<1, 0<c2<0.3, 0<d2<0.3, 0<e2≤0.01, a2+b2+c2+d2+e2=1, X 2 The elements include at least one of B, F, Mg, Al, Si, P, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sn, Nb, Mo, Sb, Sr, Y, Zr, W, Hf, In, Bi, La, Ce, Gd, Ba and Ta.

[0021] In some embodiments, the second additive contains at least Co element, and the first coating layer B1 and the first coating layer B2 include at least LiCoO 2 .

[0022] In some embodiments, the third additive includes at least a compound containing element B, and the second coating layer C1 and the second coating layer C2 include at least Li 3 BO 3 .

[0023] In some embodiments, the particle size of the first cathode material precursor is 7 μm to 15 μm.

[0024] In some embodiments, the particle size of the second cathode material precursor is 3 μm to 6 μm.

[0025] In some embodiments, the mass ratio of the first cathode material precursor to the second cathode material precursor is 5:5 to 9:1.

[0026] In some embodiments, the first cathode material precursor includes a chemical formula of Ni x1 Co y1 Mn z1 (OH)2 material, wherein 0.7≤x1<1, 0<y1<0.3, 0<z1<0.3.

[0027] In some embodiments, the second cathode material precursor includes a chemical formula of Ni x2 Co y2 Mn z2 (OH)2 material, wherein 0.7≤x2<1, 0<y2<0.3, 0<z2<0.3.

[0028] In some embodiments, the temperature of the first sintering treatment is 650° C. to 850° C., and the time of the first sintering treatment is 10 hours to 20 hours.

[0029] In some embodiments, the temperature of the second sintering process is 600° C. to 700° C., and the time of the second sintering process is 4 hours to 10 hours.

[0030] In some embodiments, the temperature of the third sintering process is 250° C. to 350° C., and the time of the third sintering process is 6 hours to 10 hours.

[0031] In some embodiments, the first sintering process, the second sintering process, and the third sintering process are each independently performed in an oxygen-containing atmosphere.

[0032] In some embodiments, the molar ratio of the lithium element in the lithium source to the total amount of the metal elements in the first cathode material precursor and the second cathode material precursor is 1.01:1 to 1.1:1.

[0033] In some embodiments, the mass of the first additive is 0.3% to 1.2% of the total mass of the first cathode material precursor and the second cathode material precursor.

[0034] In some embodiments, the mass of the second additive is 0.5% to 2.5% of the mass of the first intermediate.

[0035] In some embodiments, the mass of the third additive is 0.02% to 0.2% of the mass of the second intermediate.

[0036] In some embodiments, the lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium oxalate.

[0037] In a second aspect of the present application, a positive electrode material is provided, wherein the positive electrode material is prepared by the preparation method described in the first aspect of the present application.

[0038] In some embodiments, the cathode material has a powder compaction density of 3.5 g / cm at 200 MPa. 3 ~3.8g / cm 3 .

[0039] In some embodiments, the particle size number distribution of the positive electrode material has a diameter interval of 2 to 2.8.

[0040] In a third aspect of the present application, a positive electrode plate is provided, comprising the positive electrode material prepared by the preparation method described in the first aspect of the present application and at least one of the positive electrode materials described in the second aspect of the present application.

[0041] The fourth aspect of the present application provides a secondary battery, comprising at least one of the positive electrode material prepared by the preparation method described in the first aspect of the present application, the positive electrode material described in the second aspect of the present application, and the positive electrode sheet described in the third aspect of the present application.

[0042] Compared with traditional technologies, the above-mentioned method for preparing positive electrode materials has at least the following advantages:

[0043] In the above preparation method, the first positive electrode material precursor and the second positive electrode material precursor are pre-mixed and then co-sintered, which can reduce the material loss in the preparation process and each process, effectively reduce the probability of material contamination, and at the same time reduce production costs; the above elements in the first additive can stabilize the lattice structure of the positive electrode material, the coating layer formed by the above elements in the second additive can reduce the residual alkali of the positive electrode material, and the coating layer formed by the above elements in the third additive can increase the specific capacity of the positive electrode material, and the first polycrystalline particles and the second polycrystalline particles of different particle sizes can be matched with each other, so that the positive electrode material has fewer lattice defects, and the powder compaction density and discharge specific capacity are higher, thereby improving the volume energy density of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a SEM (scanning electron microscope) image of the positive electrode material prepared in Example 1. DETAILED DESCRIPTION

[0045] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0046] In this application, terms such as "first aspect," "second aspect," and "third aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor as implicitly indicating the importance or quantity of the technical features indicated. Furthermore, terms such as "first," "second," and "third," etc., are intended only to provide a non-exhaustive enumeration and description and should not constitute a closed-ended limitation on quantity.

[0047] In this application, the terms "optionally," "optional," and "optional" mean optional or dispensable, i.e., they refer to either option being selected from two parallel options: "with" or "without." If a technical solution contains multiple "optional" clauses, each "optional" clause is independent unless otherwise specified and there are no contradictions or constraints.

[0048] In this application, when referring to numerical ranges, unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges subsumed therein.

[0049] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0050] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the art to which this application belongs. The terms used in this application and in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this application includes any and all combinations of one or more related listed items. The term "multiple" in this application means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0051] One embodiment of the present application provides a method for preparing a positive electrode material, comprising the following steps:

[0052] The mixed material is subjected to a first sintering treatment to obtain a first intermediate; the mixed material includes a first positive electrode material precursor, a second positive electrode material precursor, a lithium source and a first additive, the particle size of the first positive electrode material precursor is larger than the particle size of the second positive electrode material precursor, and the first additive contains at least one element of B, F, Mg, Al, Si, P, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sn, Nb, Mo, Sb, Sr, Y, Zr, W, Hf, In, Bi, La, Ce, Gd, Ba and Ta;

[0053] The first intermediate is mixed with a second additive, and subjected to a second sintering process to obtain a second intermediate; the second additive contains at least one element selected from the group consisting of Co, Mn, Al, and Zr;

[0054] The second intermediate is mixed with a third additive and subjected to a third sintering treatment to obtain a positive electrode material; the third additive includes at least one of a compound containing a B element, a compound containing an Al element, and an ammonium salt; the positive electrode material includes first polycrystalline particles and second polycrystalline particles, and the particle size of the first polycrystalline particles is larger than the particle size of the second polycrystalline particles.

[0055] Compared with the traditional step-by-step synthesis method for preparing positive electrode materials, the above-mentioned preparation method pre-mixes the first positive electrode material precursor and the second positive electrode material precursor and then co-sinters them, which can reduce the material loss in the preparation process and each process, effectively reduce the probability of material contamination, and at the same time reduce production costs; the above-mentioned elements in the first additive can stabilize the lattice structure of the positive electrode material, the coating layer formed by the above-mentioned elements in the second additive can reduce the residual alkali of the positive electrode material, and the coating layer formed by the above-mentioned elements in the third additive can increase the specific capacity of the positive electrode material, and the first polycrystalline particles and the second polycrystalline particles of different particle sizes can be matched with each other, so that the positive electrode material has fewer lattice defects, and the powder compaction density and discharge specific capacity are higher, thereby improving the volume energy density of the battery.

[0056] The traditional step-by-step synthesis method also has the problems of difficulty in coordinated regulation of particle size gradient control and surface coating, and easy occurrence of component segregation and secondary agglomeration during the mixing process. The above preparation method can simultaneously complete particle size control, element doping and material coating on a single production line, which is easier to operate. Since the mixing process of large and small particles has been completed in the precursor stage of the positive electrode material, the distribution of the first polycrystalline particles and the second polycrystalline particles in the obtained positive electrode material is more uniform and not easy to agglomerate.

[0057] In this application, particle size refers to the average particle size of a material. Specifically, the material can be photographed using an SEM, and the particle sizes of all intact materials within the field of view are randomly measured and averaged to obtain the particle size of the material. For example, when measuring the particle size of a first polycrystalline particle, the particle sizes of all large particles within the field of view are randomly measured and averaged to obtain the particle size of the first polycrystalline particle; when measuring the particle size of a second polycrystalline particle, the particle sizes of all small particles within the field of view are randomly measured and averaged to obtain the particle size of the second polycrystalline particle.

[0058] In some embodiments, the first additive contains at least two elements of B, F, Mg, Al, Si, P, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sn, Nb, Mo, Sb, Sr, Y, Zr, W, Hf, In, Bi, La, Ce, Gd, Ba and Ta.

[0059] In some embodiments, the ammonium salt includes at least one of ammonium acetate, ammonium chloride, ammonium metavanadate, and ammonium dihydrogen phosphate.

[0060] In some embodiments, the first polycrystalline particles have a particle size of 6 μm to 14 μm. It is understood that the particle size of the first polycrystalline particles includes, but is not limited to, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or any range therebetween.

[0061] In some embodiments, the second polycrystalline particles have a particle size of 2 μm to 5 μm. The above preparation method can produce second polycrystalline particles with a larger particle size, further facilitating an increase in the powder compaction density of the positive electrode material. It is understood that the particle size of the second polycrystalline particles includes, but is not limited to, 2 μm, 3 μm, 4 μm, 5 μm, or a range between any two of the foregoing.

[0062] In some embodiments, the mass ratio of the first polycrystalline grains to the second polycrystalline grains is 5:5 to 9:1. It is understood that the mass ratio of the first polycrystalline grains to the second polycrystalline grains includes, but is not limited to, 5:5, 6:4, 7:3, 8:2, 9:1, or any range therebetween.

[0063] Regulating the particle size of the first polycrystalline particles, the particle size of the second polycrystalline particles and the mass ratio of the two is beneficial to improving the compaction density of the positive electrode sheet, and further helps to improve the charge and discharge capacity and volume energy density of the battery.

[0064] In some embodiments, before the step of mixing the second intermediate with the third additive, the method further comprises: washing the second intermediate with water;

[0065] Then, the second intermediate after the water washing treatment is mixed with the third additive.

[0066] In this way, the residual alkali in the prepared positive electrode material can be reduced, which is beneficial to reducing battery gas production and improving battery cycle performance.

[0067] In some embodiments, the step of washing the second intermediate with water comprises: mixing the second intermediate with water in a mass ratio of 5:5 to 8:2, stirring and drying to obtain the washed second intermediate.

[0068] In some embodiments, the method for preparing the mixture comprises the following steps:

[0069] Mixing a first cathode material precursor and a second cathode material precursor to obtain a primary mixed material;

[0070] The primary mixed material, the lithium source and the first additive are mixed to obtain a mixed material.

[0071] In other embodiments, a first cathode material precursor, a portion of a lithium source, and a portion of a first additive are mixed to obtain a first primary mixed material;

[0072] mixing the second positive electrode material precursor, the remaining lithium source and the remaining first additive to obtain a second primary mixed material;

[0073] The first primary mixed material and the second primary mixed material are mixed to obtain a mixed material.

[0074] In some embodiments, the first polycrystalline particle includes a core A1, a first coating layer B1 coated on at least a portion of the surface of the core A1, and a second coating layer C1 coated on at least a portion of the surface of the first coating layer B1. The core A1 includes a chemical formula of Li a1 Ni b1 Co c1 Mn d1 X 1 e1 O2 materials, wherein 1≤a1≤1.2, 0.7≤b1<1, 0<c1<0.3, 0<d1<0.3, 0≤e1≤0.01, a1+b1+c1+d1+e1=1, X 1 The elements include at least one of B, F, Mg, Al, Si, P, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sn, Nb, Mo, Sb, Sr, Y, Zr, W, Hf, In, Bi, La, Ce, Gd, Ba and Ta. It is understood that a1 includes but is not limited to: 1, 1.05, 1.1, 1.15, 1.2 or a range between any two of the foregoing, b1 includes but is not limited to: 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 or a range between any two of the foregoing, c1 includes but is not limited to: 0.1, 0.15, 0.2, 0.25, 0.28 or a range between any two of the foregoing, d1 includes but is not limited to: 0.1, 0.15, 0.2, 0.25, 0.28 or a range between any two of the foregoing, e1 includes but is not limited to: 0.001, 0.003, 0.005, 0.008, 0.01 or a range between any two of the foregoing.

[0075] In some embodiments, the second polycrystalline particle includes a core A2, a first coating layer B2 coated on at least a portion of the surface of the core A2, and a second coating layer C2 coated on at least a portion of the surface of the first coating layer B2, wherein the core A2 includes a chemical formula of Li a2 Ni b2 Co c2 Mn d2 X 2 e2 O2 material, wherein 1≤a2≤1.2, 0.7≤b2<1, 0<c2<0.3, 0<d2<0.3, 0≤e2≤0.01, a2+b2+c2+d2+e2=1, X 2The elements include at least one of B, F, Mg, Al, Si, P, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sn, Nb, Mo, Sb, Sr, Y, Zr, W, Hf, In, Bi, La, Ce, Gd, Ba and Ta. It is understandable that a2 includes but is not limited to: 1, 1.05, 1.1, 1.15, 1.2 or a range between any two of the foregoing, b2 includes but is not limited to: 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 or a range between any two of the foregoing, c2 includes but is not limited to: 0.1, 0.15, 0.2, 0.25, 0.28 or a range between any two of the foregoing, d2 includes but is not limited to: 0.1, 0.15, 0.2, 0.25, 0.28 or a range between any two of the foregoing, e2 includes but is not limited to: 0.001, 0.003, 0.005, 0.008, 0.01 or a range between any two of the foregoing.

[0076] In some embodiments, the second additive contains at least Co, and the first coating layer B1 and the first coating layer B2 contain at least LiCoO2. This is beneficial for reducing the residual alkali in the positive electrode material and further improving the cycle performance and first coulombic efficiency of the battery.

[0077] In some embodiments, the second additive includes at least a cobalt source, and the cobalt source includes one or more of cobalt oxyhydroxide, cobalt hydroxide, cobalt oxide, and cobalt fluoride.

[0078] In some embodiments, the third additive includes at least a compound containing element B, and the second coating layer C1 and the second coating layer C2 include at least Li3BO3. This further helps to improve the charge-discharge specific capacity of the battery's cycle performance.

[0079] In some embodiments, the third additive includes at least a boron source, and the boron source includes one or more of boron oxide, boric acid, and borate.

[0080] In some embodiments, the particle size of the first cathode material precursor is 7 μm to 15 μm. It is understood that the particle size of the first cathode material precursor includes, but is not limited to, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or a range between any two of the foregoing.

[0081] In some embodiments, the particle size of the second cathode material precursor is 3 μm to 6 μm. It is understood that the particle size of the second cathode material precursor includes but is not limited to: 3 μm, 4 μm, 5 μm, 6 μm, or a range between any two of the foregoing.

[0082] In some embodiments, the mass ratio of the first cathode material precursor to the second cathode material precursor is 5:5 to 9:1. It is understood that the mass ratio of the first cathode material precursor to the second cathode material precursor includes, but is not limited to, 5:5, 6:4, 7:3, 8:2, 9:1, or a range between any two of the foregoing.

[0083] In some embodiments, the first cathode material precursor comprises a chemical formula of Ni x1 Co y1 Mn z1 (OH)2 material, wherein 0.7≤x1<1, 0<y1<0.3, and 0<z1<0.3. It is understood that x1 includes but is not limited to 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or a range between any two of the foregoing, y1 includes but is not limited to 0.1, 0.15, 0.2, 0.25, 0.28, or a range between any two of the foregoing, and z1 includes but is not limited to 0.1, 0.15, 0.2, 0.25, 0.28, or a range between any two of the foregoing.

[0084] In some embodiments, the second cathode material precursor comprises a chemical formula of Ni x2 Co y2 Mn z2 (OH)2 material, wherein 0.7≤x2<1, 0<y2<0.3, and 0<z2<0.3. It is understood that x2 includes but is not limited to 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or a range between any two of the foregoing, y2 includes but is not limited to 0.1, 0.15, 0.2, 0.25, 0.28, or a range between any two of the foregoing, and z2 includes but is not limited to 0.1, 0.15, 0.2, 0.25, 0.28, or a range between any two of the foregoing.

[0085] In some embodiments, the temperature of the first sintering process is 650° C. to 850° C., and the time of the first sintering process is 10 hours to 20 hours. It is understood that the temperature of the first sintering process includes, but is not limited to, 650° C., 700° C., 750° C., 800° C., 850° C., or a range therebetween, and the time of the first sintering process includes, but is not limited to, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, or a range therebetween.

[0086] In some embodiments, the temperature of the second sintering process is lower than the temperature of the first sintering process.

[0087] In some embodiments, the second sintering process is performed at a temperature of 600° C. to 700° C., and for a duration of 4 to 10 hours. It is understood that the second sintering process temperature includes, but is not limited to, 600° C., 620° C., 640° C., 660° C., 680° C., 700° C., or a range therebetween, and the second sintering process duration includes, but is not limited to, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or a range therebetween.

[0088] In some embodiments, the temperature of the third sintering process is 250° C. to 350° C., and the duration of the third sintering process is 6 hours to 10 hours. It is understood that the temperature of the third sintering process includes, but is not limited to, 250° C., 275° C., 300° C., 325° C., 350° C., or a range therebetween, and the duration of the third sintering process includes, but is not limited to, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or a range therebetween.

[0089] In some embodiments, the first sintering process, the second sintering process, and the third sintering process are each independently performed in an oxygen-containing atmosphere. Further, the oxygen-containing atmosphere is free of carbon dioxide. For example, the oxygen-containing atmosphere can be a carbon-free air atmosphere.

[0090] In some embodiments, the molar ratio of the lithium element in the lithium source to the total amount of the metal elements in the first cathode material precursor and the second cathode material precursor is 1.01:1 to 1.1:1. It is understood that the above molar ratio includes, but is not limited to, 1.01:1, 1.03:1, 1.05:1, 1.07:1, 1.1:1, or a range between any two of the foregoing.

[0091] In some embodiments, the mass of the first additive is 0.3% to 1.2% of the total mass of the first cathode material precursor and the second cathode material precursor. It is understood that the mass of the first additive may be 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2% of the total mass of the first cathode material precursor and the second cathode material precursor, or a range therebetween.

[0092] In some embodiments, the mass of the second additive is 0.5% to 2.5% of the mass of the first intermediate. It is understood that the mass of the second additive can be 0.5%, 0.7%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5% of the mass of the first intermediate, or any range therebetween.

[0093] In some embodiments, the mass of the third additive is 0.02% to 0.2% of the mass of the second intermediate. It is understood that the mass of the third additive can be 0.02%, 0.05%, 0.08%, 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, or any range therebetween of the mass of the second intermediate. When the second intermediate is washed and then the washed second intermediate is mixed with the third additive, the mass of the third additive is 0.02% to 0.2% of the mass of the washed second intermediate.

[0094] In some embodiments, the lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium oxalate.

[0095] Another embodiment of the present application provides a positive electrode material, which is prepared by the above preparation method.

[0096] In some embodiments, the cathode material has a powder compaction density of 3.5 g / cm at 200 MPa. 3 ~3.8g / cm 3 .

[0097] In some embodiments, the particle size distribution of the positive electrode material has a diameter interval of 2 to 2.8. As a result, the particle size span of the positive electrode material is relatively large, and its packing density is relatively high, that is, the positive electrode material is packed more densely. Therefore, the rolling performance of the positive electrode sheet containing the positive electrode material is significantly improved, thereby further increasing the volume energy density of the battery.

[0098] In this application, the particle size number distribution distance is (Dn(50)-Dn(10)) / Dn(10). Dn(10) and Dn(50) represent the particle size values ​​corresponding to the 10% and 50% cumulative distribution on the cumulative particle size distribution curve, respectively.

[0099] Yet another embodiment of the present application provides a positive electrode plate, comprising the positive electrode material prepared by the above preparation method and at least one of the above positive electrode materials.

[0100] The above-mentioned positive electrode sheet includes a positive electrode current collector and a positive electrode active layer located on at least one side of the positive electrode current collector. The positive electrode active layer includes a positive electrode active material, a conductive agent and a binder. The positive electrode active material includes at least one of the above-mentioned positive electrode materials of this application or the positive electrode materials prepared by the above-mentioned preparation method of this application. The conductive agent and the binder can adopt the conductive agents and binders commonly used in this technical field.

[0101] The present application also provides a secondary battery comprising the positive electrode material prepared by the above-mentioned preparation method, at least one of the above-mentioned positive electrode material and the above-mentioned positive electrode sheet. It should be noted that the above-mentioned secondary battery includes but is not limited to a lithium-ion secondary battery.

[0102] The above-mentioned secondary battery may, for example, include the above-mentioned positive electrode sheet, negative electrode sheet, electrolyte and diaphragm in this application. The diaphragm is arranged between the positive electrode sheet and the negative electrode sheet, and mainly plays the role of preventing the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The electrolyte plays the role of conducting active ions between the positive electrode sheet and the negative electrode sheet. During the battery charging and discharging process, the active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. This application has no special restrictions on the negative electrode sheet, electrolyte and diaphragm. The negative electrode sheet, electrolyte and diaphragm prepared by the preparation method commonly used in this technical field, or the negative electrode sheet, electrolyte and diaphragm commonly used in this field can be used.

[0103] Furthermore, the present application also provides an electrical device comprising the above-mentioned secondary battery.

[0104] The above-mentioned electrical devices may include any equipment or devices that use secondary batteries as a driving source, such as mobile phones, laptops, electric vehicles, ships, satellites, energy storage devices, smart home appliances, etc., but are not limited thereto.

[0105] To further illustrate the present application, the technical solutions of the present application are described in detail below with reference to specific examples. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the art or in accordance with the product instructions were used. Reagents or instruments used, for which the manufacturer is not specified, are all commercially available conventional products.

[0106] Example 1

[0107] The preparation method of the positive electrode material comprises the following steps:

[0108] (1) The first cathode material precursor (Ni 0.96 Co 0.02 Mn 0.02 (OH)2, particle size of 13 μm) and the second cathode material precursor (Ni 0.96 Co 0.02 Mn 0.02 (OH)2, particle size of 3 μm), were mixed at a mass ratio of 8:2 and then mixed at a low speed (speed of 300 rpm, mixing time of 10 min) to obtain a primary mixture A;

[0109] (2) The primary mixture A, the lithium source and the first additive are dry-mixed in a mixer (rotation speed of 1000 rpm, mixing time of 30 min) to obtain a mixture B; the mixture B is moved into an atmosphere furnace and sintered in a decarbonized air atmosphere at a sintering temperature of 780° C. and a sintering time of 13 h. The mixture is cooled in the furnace, and the obtained materials are crushed and sieved in sequence to obtain a first intermediate; the molar ratio of the lithium element in the lithium source to the total amount of the metal elements in the primary mixture A is 1.06:1, the lithium source is lithium hydroxide, and the first additive is aluminum oxide, niobium oxide, antimony oxide, strontium carbonate and zirconium oxide; based on the mass of the primary mixture A, the mass content of aluminum oxide is 1000 ppm, the mass content of niobium oxide is 2500 ppm, the mass content of antimony oxide is 2500 ppm, the mass content of strontium carbonate is 1500 ppm, and the mass content of zirconium oxide is 3000 ppm;

[0110] (3) After the first intermediate and the cobalt source (the mass of the cobalt source is 1.75% of the mass of the first intermediate, and the cobalt source is cobalt hydroxide) are fully mixed, the mixture is moved to an atmosphere furnace, and sintered in a decarbonized air atmosphere at a temperature of 650°C for 7 hours. The mixture is cooled in the furnace and the material is sieved to obtain a second intermediate;

[0111] (4) The second intermediate was mixed with pure water in a mass ratio of 7:3, stirred for 5 minutes, filtered to remove the water, and then transferred to a vibration dryer and dried at 170°C for 70 minutes. After drying, the mixture was taken out and sieved to obtain a washed second intermediate;

[0112] (5) The washed second intermediate is dry-mixed with a boron source (the mass of the boron source is 0.08 wt % of the mass of the washed second intermediate, and boric acid is selected as the boron source) so that the boron source is evenly attached to the surface of the washed second intermediate. After mixing, the mixture is moved to an atmosphere furnace and sintered in a decarbonized air atmosphere at a temperature of 280°C for 8 hours. The mixture is cooled in the furnace and sieved and demagnetized to obtain the positive electrode material.

[0113] The prepared positive electrode material includes first polycrystalline particles with a particle size of about 12 μm and second polycrystalline particles with a particle size of about 2 μm, and the mass ratio of the first polycrystalline particles to the second polycrystalline particles is about 8:2; the first polycrystalline particles include a core A1, a first coating layer B1 coated on a portion of the surface of the core A1, and a second coating layer C1 coated on a portion of the surface of the first coating layer B1, and the core A1 includes a chemical formula of Li 1.06 Ni 0.932 Co 0.0375 Mn 0.02 Nb 0.0025 Al 0.001 Sb 0.0025 Sr0.0015 Zr 0.003 O2 material, the first coating layer B1 includes LiCoO2, the second coating layer C1 includes Li3BO3; the second polycrystalline particle includes a core A2, a first coating layer B2 coated on a portion of the surface of the core A2, and a second coating layer C2 coated on a portion of the surface of the first coating layer B2, the core A2 includes a chemical formula of Li 1.06 Ni 0.932 Co 0.0375 Mn 0.02 Nb 0.0025 Al 0.001 Sb 0.0025 Sr 0.0015 Zr 0.003 O2, the first coating layer B2 includes LiCoO2, and the second coating layer C2 includes Li3BO3.

[0114] Example 2

[0115] The preparation method of the positive electrode material is basically the same as that of Example 1, except that: in step (1), the mass ratio of the first positive electrode material precursor to the second positive electrode material precursor is 7:3;

[0116] The mass ratio of the first polycrystalline particles to the second polycrystalline particles in the prepared positive electrode material is approximately 7:3.

[0117] Example 3

[0118] The preparation method of the positive electrode material is basically the same as that of Example 1, except that: in step (1), the mass ratio of the first positive electrode material precursor to the second positive electrode material precursor is 6:4;

[0119] The mass ratio of the first polycrystalline particles to the second polycrystalline particles in the prepared positive electrode material is approximately 6:4.

[0120] Example 4

[0121] The preparation method of the positive electrode material is basically the same as that of Example 1, except that: in step (1), the mass ratio of the first positive electrode material precursor to the second positive electrode material precursor is 5:5;

[0122] The mass ratio of the first polycrystalline particles to the second polycrystalline particles in the prepared positive electrode material is approximately 5:5.

[0123] Example 5

[0124] The preparation method of the positive electrode material is basically the same as that of Example 1, except that: in step (1), the mass ratio of the first positive electrode material precursor to the second positive electrode material precursor is 9:1;

[0125] The mass ratio of the first polycrystalline particles to the second polycrystalline particles in the prepared positive electrode material is approximately 9:1.

[0126] Example 6

[0127] The preparation method of the positive electrode material is basically the same as that of Example 1, except that: in step (1), the particle size of the first positive electrode material precursor is 9 μm;

[0128] The particle size of the first polycrystalline particles in the prepared positive electrode material is 8 μm.

[0129] Comparative Example 1

[0130] The preparation method of the positive electrode material comprises the following steps:

[0131] (1) The first cathode material precursor (Ni 0.96 Co 0.02 Mn 0.02 (OH)2, with a particle size of 13 μm), a lithium source and a first additive are dry-mixed in a mixer (rotation speed of 900 rpm, time for 30 min) to obtain a mixture B; the mixture B is moved into an atmosphere furnace and sintered in a decarbonized air atmosphere at a sintering temperature of 750°C and a sintering time of 15 h. The mixture is cooled with the furnace, and the obtained materials are crushed and sieved in turn to obtain a first intermediate; the molar ratio of the lithium element in the lithium source to the total amount of the metal elements in the first positive electrode material precursor is 1.06:1, the lithium source is lithium hydroxide, and the first additive is aluminum oxide, niobium oxide, antimony oxide, strontium carbonate and zirconium oxide; based on the mass of the first positive electrode material precursor, the mass content of aluminum oxide is 1000 ppm, the mass content of niobium oxide is 2500 ppm, the mass content of antimony oxide is 2500 ppm, the mass content of strontium carbonate is 1500 ppm, and the mass content of zirconium oxide is 3000 ppm;

[0132] (2) After the first intermediate and the cobalt source (the mass of the cobalt source is 1.5wt% of the mass of the first intermediate, and the cobalt source is cobalt hydroxide) are fully mixed, the mixture is moved to an atmosphere furnace, and sintered in a decarbonized air atmosphere at a temperature of 650°C for 7 hours. The mixture is cooled in the furnace and the material is sieved to obtain a second intermediate;

[0133] (3) The second intermediate was mixed with pure water in a mass ratio of 7:3, stirred for 5 minutes, filtered to remove the water, and then transferred to a vibration dryer and dried at 150°C for 70 minutes. After drying, the mixture was taken out and sieved to obtain a washed second intermediate;

[0134] (4) The washed second intermediate is dry-mixed with a boron source (the mass of the boron source is 0.08 wt % of the mass of the washed second intermediate, and boric acid is selected as the boron source) so that the boron source is evenly attached to the surface of the washed second intermediate. After mixing, the mixture is moved to an atmosphere furnace and sintered in a decarbonized air atmosphere at a temperature of 280°C for 8 hours. The mixture is cooled in the furnace and sieved and demagnetized to obtain the positive electrode material.

[0135] The prepared positive electrode material includes a first polycrystalline particle with a particle size of about 12 μm, the first polycrystalline particle includes a core A1, a first coating layer B1 coated on a portion of the surface of the core A1, and a second coating layer C1 coated on a portion of the surface of the first coating layer B1, the core A1 includes a chemical formula of Li 1.06 Ni 0.9345 Co 0.035 Mn 0.02 Nb 0.0025 Al 0.001 Sb 0.0025 Sr 0.0015 Zr 0.003 O2, the first coating layer B1 includes LiCoO2, and the second coating layer C1 includes Li3BO3.

[0136] Comparative Example 2

[0137] The preparation method of the positive electrode material comprises the following steps:

[0138] (1) The second cathode material precursor (Ni 0.96 Co 0.02 Mn 0.02 (OH)2, with a particle size of 3 μm), a lithium source and a first additive are fully mixed by a dry method in a mixer (rotation speed of 300 rpm, mixing time of 10 min) to obtain a mixture B; the molar ratio of the lithium element in the lithium source to the total amount of the metal elements in the second positive electrode material precursor is 1.06:1, the lithium source is lithium hydroxide, and the first additive is aluminum oxide, niobium oxide, antimony oxide, strontium carbonate and zirconium oxide; based on the mass of the second positive electrode material precursor, the mass content of aluminum oxide is 1000 ppm, the mass content of niobium oxide is 2500 ppm, the mass content of antimony oxide is 2500 ppm, the mass content of strontium carbonate is 1500 ppm, and the mass content of zirconium oxide is 3000 ppm;

[0139] (2) Mixture B is transferred to an atmosphere furnace and sintered in a decarbonized air atmosphere at a temperature of 800° C. for 12 h. The mixture is cooled in the furnace and the obtained material is crushed and sieved in sequence to obtain a first intermediate;

[0140] (3) After the first intermediate and the cobalt source (the mass of the cobalt source is 2 wt % of the mass of the first intermediate, and the cobalt source is cobalt hydroxide) are fully mixed, the mixture is moved to an atmosphere furnace, and sintered in a decarbonized air atmosphere at a temperature of 650° C. for 7 h. The mixture is cooled in the furnace and the material is sieved to obtain a second intermediate;

[0141] (4) The second intermediate was mixed with pure water in a mass ratio of 7:3, stirred for 5 minutes, filtered to remove the water, and then transferred to a vibration dryer and dried at 150°C for 100 minutes. After drying, the mixture was taken out and sieved to obtain a washed second intermediate;

[0142] (5) The washed second intermediate is dry-mixed with a boron source (the mass of the boron source is 0.1 wt % of the mass of the washed second intermediate, and boric acid is selected as the boron source) so that the boron source is evenly attached to the surface of the washed second intermediate. After mixing, the mixture is moved to an atmosphere furnace and sintered in a decarbonized air atmosphere at a temperature of 300 ° C and a sintering time of 6 h. The mixture is cooled in the furnace and the positive electrode material is obtained after screening and demagnetization.

[0143] The prepared positive electrode material includes a second polycrystalline particle with a particle size of about 2 μm, the second polycrystalline particle includes a core A2, a first coating layer B2 coated on a portion of the surface of the core A2, and a second coating layer C2 coated on a portion of the surface of the first coating layer B2, the core A2 includes a chemical formula of Li 1.06 Ni 0.9295 Co 0.04 Mn 0.02 Nb 0.0025 Al 0.001 Sb 0.0025 Sr 0.0015 Zr 0.003 O2, the first coating layer B2 includes LiCoO2, and the second coating layer C2 includes Li3BO3.

[0144] Comparative Example 3

[0145] The preparation method of the positive electrode material comprises the following steps:

[0146] The first polycrystalline particles prepared in Comparative Example 1 and the second polycrystalline particles prepared in Comparative Example 2 were mixed at a mass ratio of 8:2 to prepare a positive electrode material.

[0147] Comparative Example 4

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

[0149] (1) Preparation of polycrystalline particles

[0150] (1.1) The first cathode material precursor (Ni 0.96 Co0.02 Mn 0.02 (OH)2, particle size of 13 μm), a lithium source and a first additive are dry-mixed in a mixer (rotation speed of 1000 rpm, mixing time of 30 min) to obtain a mixture B; the mixture B is moved into an atmosphere furnace and sintered in a decarbonized air atmosphere at a sintering temperature of 780°C and a sintering time of 13 h. The mixture is cooled with the furnace, and the obtained materials are crushed and sieved in turn to obtain a first intermediate; the molar ratio of the lithium element in the lithium source to the total amount of the metal elements in the first positive electrode material precursor is 1.06:1, the lithium source is lithium hydroxide, and the first additive is aluminum oxide, niobium oxide, antimony oxide, strontium carbonate and zirconium oxide; based on the mass of the first positive electrode material precursor, the mass content of aluminum oxide is 1000 ppm, the mass content of niobium oxide is 2500 ppm, the mass content of antimony oxide is 2500 ppm, the mass content of strontium carbonate is 1500 ppm, and the mass content of zirconium oxide is 3000 ppm;

[0151] (1.2) The first intermediate is thoroughly mixed with a cobalt source (the mass of the cobalt source is 1.75% of the mass of the first intermediate, and the cobalt source is cobalt hydroxide), and then transferred to an atmosphere furnace for sintering in a decarbonized air atmosphere at a temperature of 650°C for 7 hours. The mixture is cooled in the furnace and sieved to obtain a second intermediate.

[0152] (1.3) The second intermediate was mixed with pure water in a mass ratio of 7:3, stirred for 5 minutes, drained, and then transferred to a vibration dryer and dried at 170°C for 70 minutes. After drying, the mixture was removed and sieved to obtain a washed second intermediate;

[0153] (1.4) The washed second intermediate is dry-mixed with a boron source (the mass of the boron source is 0.08 wt% of the mass of the washed second intermediate, and boric acid is selected as the boron source) so that the boron source is evenly attached to the surface of the washed second intermediate. After mixing, the mixture is moved to an atmosphere furnace and sintered in a decarbonized air atmosphere at a temperature of 280°C for 8 hours. The mixture is cooled in the furnace and sieved and demagnetized to obtain polycrystalline particles with a particle size of about 12 μm.

[0154] The polycrystalline particle includes a core A1, a first coating layer B1 coated on a portion of the surface of the core A1, and a second coating layer C1 coated on a portion of the surface of the first coating layer B1. The core A1 includes a chemical formula of Li 1.06 Ni 0.932 Co 0.0375 Mn 0.02 Nb 0.0025 Al 0.001 Sb 0.0025 Sr 0.0015 Zr0.003 O2, the first coating layer B1 includes LiCoO2, and the second coating layer C1 includes Li3BO3.

[0155] (2) Preparation of single crystal particles

[0156] (2.1) The second cathode material precursor (Ni 0.96 Co 0.02 Mn 0.02 (OH)2, particle size of 3μm), a lithium source and a first additive are dry-mixed in a mixer (rotation speed of 1000rpm, mixing time of 30min) to obtain a premix A; the premix A is moved to an atmosphere furnace and sintered in a decarbonized air atmosphere at a sintering temperature of 950°C and a sintering time of 13h. The premix is ​​cooled with the furnace, and the obtained materials are crushed and sieved in turn to obtain a first intermediate; the molar ratio of the lithium element in the lithium source to the total amount of the metal elements in the first positive electrode material precursor is 1.06:1, the lithium source is lithium hydroxide, and the first additive is aluminum oxide, niobium oxide, antimony oxide, strontium carbonate and zirconium oxide; based on the mass of the second positive electrode material precursor, the mass content of aluminum oxide is 1000 ppm, the mass content of niobium oxide is 2500 ppm, the mass content of antimony oxide is 2500ppm, the mass content of strontium carbonate is 1500 ppm, and the mass content of zirconium oxide is 3000 ppm;

[0157] (2.2) The first intermediate is thoroughly mixed with a cobalt source (the mass of the cobalt source is 1.75% of the mass of the first intermediate, and the cobalt source is cobalt hydroxide), and then transferred to an atmosphere furnace for sintering in a decarbonized air atmosphere at a temperature of 650°C for 7 hours. The mixture is cooled in the furnace and sieved to obtain a second intermediate.

[0158] (2.3) The second intermediate was mixed with pure water in a mass ratio of 7:3, stirred for 5 minutes, drained, and then transferred to a vibration dryer and dried at 170°C for 70 minutes. After drying, the mixture was removed and sieved to obtain a washed second intermediate.

[0159] (2.4) The washed second intermediate is dry-mixed with a boron source (the mass of the boron source is 0.08 wt% of the mass of the washed second intermediate, and boric acid is selected as the boron source) so that the boron source is evenly attached to the surface of the washed second intermediate. After mixing, the mixture is moved to an atmosphere furnace and sintered in a decarbonized air atmosphere at a temperature of 280°C for 8 hours. The mixture is cooled in the furnace and sieved and demagnetized to obtain single crystal particles with a particle size of about 1 μm.

[0160] The single crystal particle includes a core A2, a first coating layer B2 coated on a portion of the surface of the core A2, and a second coating layer C2 coated on a portion of the surface of the first coating layer B2. The core A2 includes a chemical formula of Li 1.06 Ni 0.932 Co 0.0375 Mn 0.02 Nb 0.0025 Al 0.001 Sb 0.0025 Sr 0.0015 Zr 0.003 O2, the first coating layer B2 includes LiCoO2, and the second coating layer C2 includes Li3BO3.

[0161] (3) Mixing

[0162] The polycrystalline particles and the single crystal particles were mixed in a mass ratio of 8:2 to prepare the positive electrode material.

[0163] Test Case

[0164] (1) SEM test and particle size test

[0165] The morphology of the positive electrode materials prepared in each embodiment and each comparative example was observed using SEM;

[0166] The cathode material is photographed by SEM, and the particle sizes of all intact large particles within the field of view are randomly measured, and the average value is taken to obtain the particle size of the large particles. The particle sizes of all intact small particles within the field of view are randomly measured, and the average value is taken to obtain the particle size of the small particles.

[0167] The cathode material precursor is photographed by SEM, and the particle sizes of all complete cathode material precursors within the field of view are randomly measured, and the average value is taken to obtain the particle size of the cathode material precursor.

[0168] (2) Powder compaction density test

[0169] The powder compaction density of the positive electrode materials prepared in each embodiment and each comparative example was tested in sequence using a powder compaction density tester under the conditions of 20 MPa, 50 MPa, 80 MPa, 110 MPa, 140 MPa, 170 MPa, and 200 MPa.

[0170] (3) Particle size distribution distance test

[0171] The Dn(10) and Dn(50) of the positive electrode materials prepared in each embodiment and each comparative example were tested by laser diffraction particle size analysis, and the particle size number distribution diameter distance was calculated, and the particle size number distribution diameter distance = Dn((50)-Dn(10)) / Dn(10).

[0172] (4) Battery specific capacity test

[0173] The positive electrode materials of each embodiment and comparative example were assembled into batteries for specific capacity testing. Specifically, the positive electrode material, acetylene black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 90:5:5, and N-methylpyrrolidone (NMP) was added and ground into a slurry. The slurry was then evenly coated on aluminum foil and vacuum-dried at 120°C for 12 hours to obtain a positive electrode sheet. The positive electrode sheet was then rolled and cut into circular pieces. Then, a half-cell was assembled in an argon atmosphere glove box using metallic lithium as the negative electrode and a 1M LiPF6 solution as the electrolyte.

[0174] The assembled battery was charged at a constant current density of 0.1C to 4.3V, and then discharged at a constant current density of 0.1C to 2.8V to obtain the first discharge specific capacity of the battery.

[0175] The test results are as follows Figure 1 and as shown in Table 1.

[0176] Table 1

[0177]

[0178] Depend on Figure 1 It can be seen that the positive electrode material prepared in Example 1 includes first polycrystalline particles and second polycrystalline particles, and the particle size of the first polycrystalline particles is larger than that of the second polycrystalline particles.

[0179] It can be seen from the data in Table 1 that the number distribution diameter of the positive electrode materials of Examples 1 to 6 is in the range of 2 to 2.8. Compared with Comparative Examples 1 to 4, the powder compaction density of the positive electrode materials of Examples 1 to 6 is higher, the rolling performance of the positive electrode sheet is better, and the first discharge specific capacity of the battery is also relatively higher. Therefore, compared with the batteries of Comparative Examples 1 to 4, the volume energy density of the batteries of Examples 1 to 6 is significantly improved, which shows that the positive electrode materials prepared by the preparation methods of Examples 1 to 4 of the present application can effectively improve the volume energy density of the battery. In addition, in the preparation methods of Examples 1 to 6, the first positive electrode material precursor and the second positive electrode material precursor are pre-mixed and then co-sintered, which not only reduces the material loss in the preparation process and each process, but also effectively reduces the probability of material contamination, while significantly reducing production costs.

[0180] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0181] The above-described embodiments merely represent several implementation methods of the present application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims, and the specification may be used to interpret the content of the claims.

Claims

1. A method for preparing a positive electrode material, characterized in that: The steps include: Performing a first sintering treatment on the mixture to obtain a first intermediate; the mixture includes a first positive electrode material precursor, a second positive electrode material precursor, a lithium source and a first additive, the particle size of the first positive electrode material precursor is larger than the particle size of the second positive electrode material precursor, and the first additive contains at least one element of B, F, Mg, Al, Si, P, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sn, Nb, Mo, Sb, Sr, Y, Zr, W, Hf, In, Bi, La, Ce, Gd, Ba and Ta; The first intermediate is mixed with a second additive, and subjected to a second sintering process to obtain a second intermediate; the second additive contains at least one element selected from Co, Mn, Al and Zr; The second intermediate is mixed with a third additive and subjected to a third sintering treatment to obtain the positive electrode material; the third additive includes at least one of a compound containing a B element, a compound containing an Al element, and an ammonium salt; the positive electrode material includes first polycrystalline particles and second polycrystalline particles, and the particle size of the first polycrystalline particles is larger than the particle size of the second polycrystalline particles.

2. The preparation method according to claim 1, characterized in that The preparation method satisfies at least one of the following conditions: (1) The particle size of the first polycrystalline particles is 6 μm to 14 μm; (2) The particle size of the second polycrystalline particles is 2 μm to 5 μm; (3) The mass ratio of the first polycrystalline particles to the second polycrystalline particles is 5:5 to 9:

1.

3. The preparation method according to claim 1, characterized in that Before the step of mixing the second intermediate with the third additive, the method further includes: washing the second intermediate with water; and then mixing the washed second intermediate with the third additive.

4. The preparation method according to any one of claims 1 to 3, characterized in that The preparation method of the mixture comprises the following steps: Mixing the first cathode material precursor and the second cathode material precursor to obtain a primary mixed material; Mixing the primary mixed material, the lithium source and the first additive to obtain the mixed material; or, Mixing the first cathode material precursor, part of the lithium source and part of the first additive to obtain a first primary mixed material; Mixing the second positive electrode material precursor, the remaining lithium source and the remaining first additive to obtain a second primary mixed material; The first primary mixed material and the second primary mixed material are mixed to obtain the mixed material.

5. The preparation method according to any one of claims 1 to 3, characterized in that The preparation method satisfies at least one of the following conditions: (1) The first polycrystalline particle includes a core A1, a first coating layer B1 coated on at least a portion of the surface of the core A1, and a second coating layer C1 coated on at least a portion of the surface of the first coating layer B1. The core A1 includes a chemical formula of Li a1 Ni b1 Co c1 Mn d1 X 1 e1 O2 materials, wherein 1≤a1≤1.2, 0.7≤b1<1, 0<c1<0.3, 0<d1<0.3, 0<e1≤0.01, a1+b1+c1+d1+e1=1, X 1 The element includes at least one of B, F, Mg, Al, Si, P, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sn, Nb, Mo, Sb, Sr, Y, Zr, W, Hf, In, Bi, La, Ce, Gd, Ba and Ta; (2) The second polycrystalline particle includes a core A2, a first coating layer B2 coated on at least a portion of the surface of the core A2, and a second coating layer C2 coated on at least a portion of the surface of the first coating layer B2. The core A2 includes a chemical formula of Li a2 Ni b2 Co c2 Mn d2 X 2 e2 O2 material, wherein 1≤a2≤1.2, 0.7≤b2<1, 0<c2<0.3, 0<d2<0.3, 0<e2≤0.01, a2+b2+c2+d2+e2=1, X 2 The elements include at least one of B, F, Mg, Al, Si, P, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sn, Nb, Mo, Sb, Sr, Y, Zr, W, Hf, In, Bi, La, Ce, Gd, Ba and Ta.

6. The preparation method according to claim 5, characterized in that The preparation method satisfies at least one of the following conditions: (1) The second additive contains at least Co element, and the first coating layer B1 and the first coating layer B2 contain at least LiCoO2; (2) The third additive contains at least a compound of element B, and the second coating layer C1 and the second coating layer C2 contain at least Li3BO3.

7. The preparation method according to any one of claims 1 to 3, characterized in that The preparation method satisfies one or more of the following conditions: (1) The particle size of the first positive electrode material precursor is 7 μm to 15 μm; (2) The particle size of the second cathode material precursor is 3 μm to 6 μm; (3) The mass ratio of the first cathode material precursor to the second cathode material precursor is 5:5 to 9:1; (4) The first positive electrode material precursor includes a chemical formula of Ni x1 Co y1 Mn z1 (OH)2 materials, wherein 0.7≤x1<1, 0<y1<0.3, 0<z1<0.3; (5) The second positive electrode material precursor includes a chemical formula of Ni x2 Co y2 Mn z2 (OH)2 materials, wherein 0.7≤x2<1, 0<y2<0.3, 0<z2<0.3; (6) The temperature of the first sintering treatment is 650° C. to 850° C., and the time of the first sintering treatment is 10 h to 20 h; (7) The temperature of the second sintering treatment is 600° C. to 700° C., and the time of the second sintering treatment is 4 h to 10 h; (8) The temperature of the third sintering treatment is 250° C. to 350° C., and the time of the third sintering treatment is 6 h to 10 h; (9) The first sintering treatment, the second sintering treatment, and the third sintering treatment are each independently performed in an oxygen-containing atmosphere; (10) The molar ratio of the lithium element in the lithium source to the total amount of the metal elements in the first positive electrode material precursor and the second positive electrode material precursor is 1.01:1 to 1.1:1; (11) The mass of the first additive is 0.3% to 1.2% of the total mass of the first positive electrode material precursor and the second positive electrode material precursor; (12) The mass of the second additive is 0.5% to 2.5% of the mass of the first intermediate; (13) The mass of the third additive is 0.02% to 0.2% of the mass of the second intermediate; (14) The lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate and lithium oxalate.

8. A positive electrode material, characterized in that The positive electrode material is prepared by the preparation method according to any one of claims 1 to 7; Optionally, the powder compaction density of the positive electrode material at 200 MPa is 3.5 g / cm 3 ~3.8g / cm 3 ; Optionally, the particle size number distribution diameter of the positive electrode material is 2 to 2.

8.

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

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

Images