Positive electrode material and preparation method therefor, positive electrode sheet and secondary battery

Abstract

A positive electrode material and a preparation method therefor, a positive electrode sheet and a secondary battery. The positive electrode material comprises a first lithium nickel oxide material, the first lithium nickel oxide material comprises polycrystalline particles, the porosity in each polycrystalline particle is denoted as d, and 2%≤d≤15%; in any CP profile of the polycrystalline particle, the distance between two adjacent pore edges in the polycrystalline particle is 10-100 nm. Therefore, the cracking proportion of the positive electrode material during electrode sheet processing can be reduced, the initial stress and the stress accumulation on newly formed surfaces caused by cracking during cycling are significantly reduced, and the particle toughness and the particle strength are improved; moreover, enough support can be provided for a rigid structure of the material, and collapse and breakage of material particles are reduced, so that the stability of both the bulk phase and the surface is improved from the material level, and the long-term cycle performance and the safety performance of the material are improved.

Description

Cathode material, preparation method thereof, cathode sheet and secondary battery

[0001] The present application claims priority to the Chinese patent application No. 202410451889.9, filed on April 15, 2024, and entitled "Cathode material, preparation method thereof, cathode sheet and secondary battery", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of lithium ion batteries, in particular to a cathode material, a preparation method thereof, a cathode sheet and a secondary battery. BACKGROUND

[0003] At present, the lithium ion battery technology develops rapidly, and the electric vehicles using lithium ion batteries gradually popularize, which brings a new solution to the problems of environmental pollution and climate warming. In recent years, the market demand for the endurance mileage of electric vehicles has greatly increased, and high-energy-density high-nickel materials have gradually become a research hotspot.

[0004] Among the high-nickel materials, lithium nickel cobalt manganese oxide is more commonly used. Although this material has high energy density, its long-term cycle performance and safety performance are poor and need to be improved.

[0005] SUMMARY

[0006] Therefore, the present application provides a cathode material, a preparation method thereof, a cathode sheet and a secondary battery to simultaneously improve the long-term cycle performance and safety performance of the cathode material.

[0007] The first aspect of the present application provides a cathode material, comprising a first lithium nickel oxide material, wherein the first lithium nickel oxide material comprises polycrystalline particles, the porosity inside the polycrystalline particles is denoted as d, and 1%≤d≤15%; in any CP cross section of the polycrystalline particles, the distance between the edges of two adjacent pores inside the polycrystalline particles is 5nm-100nm.

[0008] In some embodiments, the cathode material comprises a first lithium nickel oxide material, wherein the first lithium nickel oxide material comprises polycrystalline particles, the porosity inside the polycrystalline particles is denoted as d, and 2%≤d≤15%; in any CP cross section of the polycrystalline particles, the distance between the edges of two adjacent pores inside the polycrystalline particles is 10nm-100nm.

[0009] In some embodiments, the polycrystalline particles comprise at least one of the following features (1)-(3):

[0010] (1) the polycrystalline particles comprise a plurality of primary particles;

[0011] Optionally, in any CP profile of the polycrystal particle, the angle between the direction of the long diameter of each primary particle and the direction of the diameter of the polycrystal particle is 0°-90°, optionally 0°-30°.

[0012] Optionally, the particle size of each primary particle is 200 nm-800 nm.

[0013] (2) The single particle strength of the polycrystal particle is >90 MPa.

[0014] (3) The deformation amount of the polycrystal particle before breaking is <21%.

[0015] In some embodiments, the first lithium-nickel-oxide-based material comprises at least one of the following features (1)-(3):

[0016] (1) The chemical formula of the first lithium-nickel-oxide-based material is Li a1 Ni x1 Co y1 Mn z1 Q1 u1 O2, wherein 0.98≤a1≤1.60, 0.80≤x1≤1.00, 0.00≤y1≤0.12, 0.00≤z1≤0.10, 0≤u1≤0.007, and Q1 is a doping element.

[0017] Optionally, Q1 comprises two or more of boron, fluorine, magnesium, aluminum, silicon, phosphorus, calcium, scandium, titanium, vanadium, chromium, iron, copper, zinc, gallium, germanium, tin, niobium, molybdenum, strontium, yttrium, zirconium, tungsten, hafnium, indium, bismuth, lanthanum, cerium, gadolinium, barium, and tantalum.

[0018] Optionally, 0.98≤a1≤1.05, 0.82≤x1≤1.00, 0.00≤y1≤0.08, 0.00≤z1≤0.06, and 0.0001≤u1≤0.005.

[0019] (2) The median particle size of the first lithium-nickel-oxide-based material is 9 μm-17 μm.

[0020] (3) The specific surface area of the first lithium-nickel-oxide-based material is A1, and after being fractured under a pressure of 4.5T, the specific surface area of the first lithium-nickel-oxide-based material is A2, and (A2-A1) / A1×100%≤40%.

[0021] In some embodiments, a second lithium-nickel-oxide-based material is further included, and the second lithium-nickel-oxide-based material comprises single crystal particles or single crystal-like particles.

[0022] Optionally, a mass ratio of the first lithium nickel oxide-based material and the second lithium nickel oxide-based material in the positive electrode material is 1-10.

[0023] In some embodiments, the second lithium nickel oxide-based material comprises at least one of the following features (1)-(2):

[0024] (1) a chemical formula of the second lithium nickel oxide-based material is Li a2 Ni x2 Co y2 Mn z2 Q2 u2 O2, wherein 0.98≤a2≤1.60, 0.80≤x2≤1.00, 0.00≤y2≤0.12, 0.00≤z2≤0.10, 0≤u2≤0.007, and Q2 is a doping element;

[0025] Optionally, Q2 comprises two or more of boron, fluorine, magnesium, aluminum, silicon, phosphorus, calcium, scandium, titanium, vanadium, chromium, iron, copper, zinc, gallium, germanium, tin, niobium, molybdenum, strontium, yttrium, zirconium, tungsten, hafnium, indium, bismuth, lanthanum, cerium, gadolinium, barium, and tantalum.

[0026] Optionally, 0.98≤a2≤1.05, 0.82≤x2≤1.00, 0.00≤y2≤0.08, 0.00≤z2≤0.06, and 0.0001≤u2≤0.005.

[0027] (2) a median particle size of the second lithium nickel oxide-based material is 0.5-6 μm.

[0028] A second aspect of the present application provides a preparation method of the positive electrode material of the first aspect of the present application, comprising the following steps:

[0029] sintering a first mixture comprising a first lithium source, a first nickel-containing precursor, a first molten salt, and optionally a Q1 source to prepare the first lithium nickel oxide-based material;

[0030] wherein a ratio of a total molar amount of metals contained in the first molten salt to a total molar amount of metals contained in the first nickel-containing precursor is 0.005-0.08.

[0031] In some embodiments, the preparation method comprises at least one of the following conditions:

[0032] (1) a melting point of the first molten salt is 400-1400°C, optionally 400-1000°C; cations of the first molten salt comprise one or more of alkali metals and alkaline earth metals, and anions comprise acid radicals;

[0033] Optionally, the first molten salt comprises one or more of lithium sulfate, lithium antimonate, lithium silicate, lithium selenate, lithium phosphate;

[0034] (2) the first lithium source comprises one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxalate, and lithium acetate;

[0035] (3) the first nickel-containing precursor has a chemical formula of [Ni x3 Co y3 Mn z3 ](OH)2, wherein 0.80≤x3≤1.00, 0.00≤y3≤0.12, and 0.00≤z3≤0.10;

[0036] (4) the first nickel-containing precursor has a median particle size of 9 μm-17 μm;

[0037] (5) the ratio of the total moles of metals contained in the first molten salt and the first lithium source to the total moles of metals contained in the first nickel-containing precursor is 1.02-1.08;

[0038] (6) the Q1 source comprises one or more of oxides, hydroxides, carbonates, phosphates, and nitrates containing a Q1 element; the Q1 element comprises two or more of boron, fluorine, magnesium, aluminum, silicon, phosphorus, calcium, scandium, titanium, vanadium, chromium, iron, copper, zinc, gallium, germanium, tin, niobium, molybdenum, strontium, yttrium, zirconium, tungsten, hafnium, indium, bismuth, lanthanum, cerium, gadolinium, barium, and tantalum;

[0039] (7) the first sintering process comprises a first sintering stage and a second sintering stage, wherein the positive temperature difference between the sintering temperature of the second sintering stage and the sintering temperature of the first sintering stage is ≥200℃, and the positive time difference between the sintering time of the second sintering stage and the sintering time of the first sintering stage is ≥1h;

[0040] Optionally, the sintering temperature of the first sintering stage is 550℃-750℃, and the sintering time is 3h-5h;

[0041] Optionally, the sintering temperature of the second sintering stage is 750℃-900℃, and the sintering time is 6h-15h;

[0042] (8) when the first mixture does not contain the Q1 source or contains only part of the Q1 source, the preparation method further comprises: after mixing the intermediate product obtained from the first sintering process with the Q1 source, continuing the sintering process at 200℃-350℃ for 3h-5h.

[0043] In some embodiments, the preparation method further comprises:

[0044] subjecting a second mixture material comprising a second lithium source, a second nickel-containing precursor, a second molten salt, and optionally a Q2 source to a second sintering treatment to prepare the second lithium-nickel-oxide-based material; the second nickel-containing precursor has a median particle size smaller than the median particle size of the first nickel-containing precursor;

[0045] wherein a ratio of a total molar amount of metals contained in the second molten salt to a total molar amount of metals contained in the second nickel-containing precursor is 0.005-0.08;

[0046] Optionally, the second molten salt has a melting point of 400-1400℃, optionally 400-1000℃; the cations of the second molten salt comprise one or more of alkali metals and alkaline earth metals, and the anions of the second molten salt comprise acid radicals;

[0047] Optionally, the second molten salt comprises one or more of lithium sulfate, lithium antimonate, lithium silicate, lithium selenate, and lithium phosphate;

[0048] Optionally, the second lithium source comprises one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxalate, and lithium acetate;

[0049] Optionally, the second nickel-containing precursor has a chemical formula of [Ni x4 Co y4 Mn z4 ](OH)2, wherein 0.80≤x4≤1.00, 0.00≤y4≤0.12, and 0.00≤z4≤0.10;

[0050] Optionally, the second nickel-containing precursor has a median particle size of 0.5-6μm;

[0051] Optionally, a ratio of a total molar amount of metals contained in the second molten salt and the second lithium source to a total molar amount of metals contained in the second nickel-containing precursor is 1.02-1.08;

[0052] Optionally, the Q2 source comprises one or more of oxides, hydroxides, carbonates, phosphates, and nitrates of a Q2 element; the Q2 element comprises two or more of boron, fluorine, magnesium, aluminum, silicon, phosphorus, calcium, scandium, titanium, vanadium, chromium, iron, copper, zinc, gallium, germanium, tin, niobium, molybdenum, strontium, yttrium, zirconium, tungsten, hafnium, indium, bismuth, lanthanum, cerium, gadolinium, barium, and tantalum;

[0053] Optionally, when the second mixture material does not contain the Q2 source or contains only part of the Q2 source, the preparation method further comprises: after mixing the intermediate product obtained from the second sintering treatment with the Q2 source, continuing the sintering treatment at 200-350℃ for 3-5h;

[0054] Optionally, the second sintering process comprises a third sintering stage and a fourth sintering stage, a positive temperature difference between a sintering temperature of the fourth sintering stage and a sintering temperature of the third sintering stage is greater than or equal to 200℃, and a positive time difference between a sintering time of the fourth sintering stage and a sintering time of the third sintering stage is greater than or equal to 1h.

[0055] Optionally, the sintering temperature of the third sintering stage is 550℃-750℃, and the sintering time is 3h-5h.

[0056] Optionally, the sintering temperature of the fourth sintering stage is 800℃-950℃, and the sintering time is 6h-15h.

[0057] The third aspect of the present application provides a positive electrode tab comprising the positive electrode material of the first aspect of the present application or the positive electrode material prepared by the method of the second aspect of the present application.

[0058] The fourth aspect of the present application provides a secondary battery comprising the positive electrode tab of the third aspect of the present application.

[0059] The fifth aspect of the present application provides an electric device comprising the secondary battery of the fourth aspect of the present application.

[0060] The positive electrode material provided above comprises a first lithium-nickel oxide material, the first lithium-nickel oxide material comprises polycrystalline particles, the porosity inside the polycrystalline particles is greater than or equal to 2% and less than or equal to 15%, and in any CP cross-sectional view of the polycrystalline particles, the distance between the edges of two adjacent pores inside the polycrystalline particles is 10nm-100nm. Thus, the cracking ratio of the positive electrode material during the tab processing process can be reduced, and the initial stress and the stress accumulation of the new surface due to cracking during the cycle process are significantly reduced, the grain toughness and grain strength are improved; at the same time, sufficient support can be provided for the rigid structure of the material, and the collapse and fragmentation of the material particles are reduced; therefore, the stability of the bulk phase and the surface is improved from the material level, and the long-term cycle performance and safety performance of the material are improved.

[0061] In addition, the present application uses a molten salt method to regulate the heat field distribution and melting mode during the sintering process of the material, and the added molten salt is difficult to volatilize during the sintering process, but flows along the grain boundary as lava, etches the grain boundary, and forms relatively uniform pores; thus, the microstructure of the single-crystal particles of the lithium-nickel oxide material is changed, the internal stress of the material is reduced, and the toughness and resistance performance of the material are improved. BRIEF DESCRIPTION OF DRAWINGS

[0062] In order to more clearly illustrate the technical solutions in the embodiments of the present application, more completely understand the present application and its beneficial effects, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained from these drawings without creative labor.

[0063] Figure 1 is an electron scanning electron microscope image of the positive electrode material in Example 1.

[0064] Figure 2 is a CP profile of the positive electrode material in Example 1. DETAILED DESCRIPTION

[0065] In order to facilitate the understanding of the present application, the following will be described with reference to the relevant embodiments. The following gives the preferred embodiments of the present application. However, the present application can be realized in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the present application.

[0067] The selection range of the terms "and / or", "or / and", "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, including any two related listed items, any more related listed items, or all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or", "or / and", "and / or", it should be understood that in the present application, the technical solution undoubtedly includes the technical solution connected by "logical and", and also undoubtedly includes the technical solution connected by "logical or".

[0068] In the present application, the technical features described in an open manner include both the closed technical solution consisting of the listed features and the open technical solution containing the listed features.

[0069] In the present application, when referring to a numerical interval, unless otherwise specified, the numerical interval is considered to be continuous and includes the minimum and maximum values of the range and every value between the minimum and maximum values. Further, when the range refers to integers, 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 indicated, all ranges disclosed herein are to be understood to include any and all sub-ranges subsumed therein.

[0070] Only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, as can any upper limit be combined with any other upper limit to form a range not explicitly recited. In addition, each individual disclosed point or single numerical value can itself be combined as a lower limit or an upper limit with any other point or single numerical value or with other lower limits or upper limits to form a range not explicitly recited.

[0071] In the present application, unless otherwise specified, the temperature parameter allows for constant temperature treatment as well as treatment within a certain temperature interval. The constant temperature treatment allows for fluctuations within the accuracy range of the instrument control. Fluctuations within a range of, for example, ±5°C, ±4°C, ±3°C, ±2°C, ±1°C are allowed.

[0072] In the present application, unless otherwise specified, the term “size”, “particle size”, “diameter” generally refers to the average value. In the present application, “particle size” and “particle diameter” have the same definition, both representing the average particle diameter of a spherical or spherical-like object.

[0073] In the present application, unless otherwise specified, the term “suitable combination”, “suitable manner”, “any suitable manner” and the like refer to the ability to implement the technical solutions of the present application, solve the technical problems of the present application, and achieve the intended technical effects of the present application.

[0074] In the present application, “further”, “even further”, “in particular” and the like are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of the present application.

[0075] In the present application, “optionally”, “optional” and “optional” mean that it can or can not be present, i.e., it can be selected from either of the two parallel schemes “yes” or “no”. If there are multiple “optionally” in a technical solution, unless otherwise specified, and there is no contradictory or mutually restrictive relationship, each “optionally” is independent.

[0076] In the description of the application, “multiple” means at least two, for example, two, three, etc., unless otherwise specifically limited.

[0077] If there is no special indication, all the embodiments and optional embodiments of the present application can be combined to form new technical solutions. If there is no special indication, all the technical features and optional technical features of the present application can be combined to form new technical solutions.

[0078] If there is no special indication, all the steps of the present application can be performed in sequence or randomly, and preferably in sequence.

[0079] In the present application, the terms "first lithium nickel oxide material", "second lithium nickel oxide material", "first lithium source", "first nickel-containing precursor", "first molten salt", "first mixed material", "first sintering treatment", "second lithium source", "second nickel-containing precursor", "second molten salt", "second mixed material", "second sintering treatment", "first sintering platform", "second sintering platform", "third sintering platform", "fourth sintering platform", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implying the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and should be understood as not constituting a closed limitation on the quantity.

[0080] High-nickel materials are widely used in lithium nickel manganese oxide. Although the energy density of this material is high, the bulk and surface structure stability of the material is poor. During the preparation of the pole piece, many broken particles are produced, which further reacts with the electrolyte to produce many irreversible phase changes, causing the material performance to deteriorate, and ultimately leading to poor long-term cycle performance and safety performance.

[0081] Currently, the method for improving particle strength mainly focuses on the precursor level. By designing a loose and porous precursor, the positive electrode material obtained by sintering can partially inherit this feature of the precursor. This method belongs to front-end design, and the characteristics of the precursor are affected by the process formula during the complex process. The final positive electrode material has a large uncertainty in inheriting these advantages. The improvement direction and inheritance weight cannot be completely positively correlated.

[0082] How to improve the bulk and surface stability from the material level by developing new processes and new formulas, reduce the cracking rate of material particles under high pole piece rolling intensity, and reduce the particle cracking differentiation degree of material during the cycle process has become a technical problem in the field of lithium ion battery positive electrode materials.

[0083] Based on the above problems, the present applicant found that the cracking problem of the positive electrode material in the process of crushing the pole piece is mainly due to the fact that the material cannot relieve the local stress conduction by micro-deformation inside the particles when subjected to pressure, resulting in particle cracking caused by excessive pressure. According to the cause, the toughness of the particles is increased, and micro-deformation can occur after being pressed, and the mortise and tenon effect between the primary particles is increased, which can effectively improve the pressure resistance of the particles. Therefore, the present application continuously adjusts the internal grain size, porosity and orientation of the material by the molten salt method, reduces the cracking rate of the material in the process of processing the pole piece, significantly reduces the initial stress of the material and the stress accumulation of the new surface generated due to cracking in the cycle process, and improves the toughness of the particles.

[0084] The first aspect of the present application provides a positive electrode material, comprising a first lithium nickel oxide material, the first lithium nickel oxide material comprising polycrystalline particles, the porosity inside the polycrystalline particles being denoted as d, 1%≤d≤15%; in any CP section of the polycrystalline particles, the distance between the edges of two adjacent pores inside the polycrystalline particles is 5nm-100nm.

[0085] Specifically, the positive electrode material comprises a first lithium nickel oxide material, the first lithium nickel oxide material comprising polycrystalline particles, the porosity inside the polycrystalline particles being denoted as d, 2%≤d≤15%; in any CP section of the polycrystalline particles, the distance between the edges of two adjacent pores inside the polycrystalline particles is 10nm-100nm.

[0086] It should be noted that the "lithium nickel oxide material" mentioned herein refers to a material containing lithium, nickel and oxygen elements, but is not limited to a material containing only these three elements, and can also include other metal elements, which are not specifically limited.

[0087] The distance between the edges of two adjacent pores refers to the shortest distance between the edges of two adjacent pores.

[0088] The CP section refers to the section prepared when the positive electrode material is subjected to CP testing.

[0089] As an example, the porosity inside the polycrystalline particles can be, but is not limited to, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15% or a range between any two of the above values.

[0090] When the porosity of the polycrystalline particle is in the above range, the initial stress of the particle after sintering is reduced, the mechanical impact resistance is improved, and the particle toughness is enhanced. The stress accumulation during the charging and discharging process is slowed down, and the risk of particle micro-crack generation and grain transverse breakage and pulverization is reduced. When the material is compact and has no or few pores (d < 1%), the stress generated by the phase change during the charging and discharging process cannot be released and will continue to accumulate, finally leading to grain transverse breakage and even pulverization; when the internal porosity is greater than 15%, the material structure is too loose, the electrolyte penetrates through the gap between the particles, leading to an increase in the side reaction, irreversible phase change of the material structure, and deterioration of the performance.

[0091] The porosity of the polycrystalline particle mentioned above can be measured by the minimum unit counting method, as follows: first, a grid composed of 1 nm square grids is made, the grid transparency is adjusted, and the grid is calibrated with the CP picture ruler, then the grid is overlaid on the CP surface, and the number of grids in the range of the pore is determined, which is the cross-sectional area occupied by the pore.

[0092] For example, the distance between the edges of two adjacent pores in the polycrystalline particle can be, but is not limited to, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, or a range between any two of the above distances. When the distance between the edges of two adjacent pores in the polycrystalline particle is in the above range, it indicates that the pores in the polycrystalline particle are uniformly distributed.

[0093] When the distance between the edges of two adjacent pores in the polycrystalline particle is in the above range, there is enough support between the pores, which improves the stability of the crystal structure and the mechanical impact resistance.

[0094] The distance between the edges of two adjacent pores in the polycrystalline particle mentioned above can be measured by the following method: in the CP picture, two adjacent pores refer to two pores that are completely independent and have no intersection in the plane, the distance between the two pores is the thinnest part of the pore wall edge, the measurement scale is perpendicular to the pore wall, and the thickness of the pore wall obtained by measurement is the distance between the pores.

[0095] Understandably, the first lithium-nickel oxide-based material comprises polycrystalline particles, the porosity inside the polycrystalline particles is greater than or equal to 2% and less than or equal to 15%, and in any CP profile of the polycrystalline particles, the distance between the edges of two adjacent pores inside the polycrystalline particles is 10 nm-100 nm. Thus, the cracking rate of the positive electrode material during the processing of the electrode sheet can be reduced, and the initial stress and the stress accumulation of the new surface due to cracking during the cycle process are significantly reduced, the particle toughness and particle strength are improved; at the same time, it can also provide sufficient support for the rigid structure of the material, reduce the collapse and breakage of the material particles; therefore, the stability of the bulk phase and the surface is improved from the material level, and the long-term cycle performance and safety performance of the material are improved.

[0096] In some optional embodiments, the porosity d inside the polycrystalline particles satisfies: 2%≤d≤15%;

[0097] In some optional embodiments, the porosity d inside the polycrystalline particles satisfies: 2.3%≤d≤14.8%;

[0098] In some optional embodiments, the distance between the edges of two adjacent pores inside the polycrystalline particles is 10 nm-100 nm.

[0099] In some optional embodiments, the distance between the edges of two adjacent pores inside the polycrystalline particles is 12 nm-98 nm.

[0100] In some embodiments, the polycrystalline particles comprise a plurality of primary particles, and in any CP profile of the polycrystalline particles, the angle between the direction of the long diameter of each primary particle and the direction of the diameter of the polycrystalline particle is 0°-90°; for example, it can be but is not limited to 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, 90° or a range between any two of the above angles. When the angle is between 0° and 90°, it indicates that the orientation consistency of each primary particle contained in the polycrystalline particles is better, and the stress generated during the phase change of the material when the orientation is consistent is smaller.

[0101] In some optional embodiments, the polycrystalline particles comprise a plurality of primary particles, and in any CP profile of the polycrystalline particles, the angle between the direction of the long diameter of each primary particle and the direction of the diameter of the polycrystalline particle is 0°-30°.

[0102] As an example, the angle between the direction of the long diameter of each primary particle and the direction of the diameter of the polycrystal particle in the CP profile mentioned above can be determined by the following method: select the CP profile passing through the center of the sphere, determine the long diameter of the primary particle by the cross method, connect and extend the center of the sphere and the end point of the long diameter close to the center of the sphere, and measure the angle between the two line segments ≤90°. The angle is the angle between the direction of the long diameter of the primary particle and the direction of the diameter of the polycrystal particle.

[0103] In some embodiments, the polycrystal particle comprises a plurality of primary particles, and the particle size of each primary particle is 200 nm-800 nm. For example, it can be, but is not limited to, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, or a range between any two of the above particle sizes. When the particle size of each primary particle is in the above range, the particle size of the primary particle is more concentrated, and it is easier to form a forward arrangement with a smaller angle in the particle, which helps to release the stress between the particles, improve the stability of the material, and improve the performance.

[0104] In some embodiments, the single particle strength of the polycrystal particle is >90 MPa, and the deformation amount of the polycrystal particle before breaking is <21%. This indicates that the compressive strength of the polycrystal particle is effectively improved.

[0105] As a possible embodiment, the chemical formula of the first lithium-nickel oxide-based material is Li a1 Ni x1 Co y1 Mn z1 Q1 u1 O2, wherein 0.98≤a1≤1.60, 0.80≤x1≤1.00, 0.00≤y1≤0.12, 0.00≤z1≤0.10, 0≤u1≤0.007, and Q1 is a doping element.

[0106] In some example embodiments, Q1 includes two or more of boron, fluorine, magnesium, aluminum, silicon, phosphorus, calcium, scandium, titanium, vanadium, chromium, iron, copper, zinc, gallium, germanium, tin, niobium, molybdenum, strontium, yttrium, zirconium, tungsten, hafnium, indium, bismuth, lanthanum, cerium, gadolinium, barium, and tantalum.

[0107] In some example embodiments, 0.98≤a1≤1.05, 0.82≤x1≤1.00, 0.00≤y1≤0.08, 0.00≤z1≤0.06, and 0.0001≤u1≤0.005.

[0108] As a possible implementation, the median particle size of the first lithium-nickel-oxide-based material is 9-17 μm; for example, it can be, but is not limited to, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, or a range between any two of the above particle sizes. When the median particle size of the first lithium-nickel-oxide-based material is within the above range, it is beneficial to both improve the compaction density and achieve a higher capacity. The particles within the above particle size range have certain advantages in terms of compressive strength, which can ensure the stability of the particle structure and reduce the risk of side reactions due to the generation of fresh interfaces caused by the crushing of the particles in the subsequent battery.

[0109] In some optional embodiments, the specific surface area of the first lithium-nickel-oxide-based material is denoted as A1, and the specific surface area of the first lithium-nickel-oxide-based material after being fractured under a pressure of 4.5T is denoted as A2, (A2-A1) / A1*100%≤40%. This indicates that the degree of cracking or crushing of the particles after being pressed is relatively small, and the stability of the particle structure is relatively high.

[0110] Optionally, 3.8≤(A2-A1) / A1*100%≤35.2%.

[0111] In some embodiments, the positive electrode material further comprises a second lithium-nickel-oxide-based material, and the second lithium-nickel-oxide-based material comprises single-crystal particles or single-crystal-like particles. In this way, the advantages of high capacity of single-crystal-like particles and long life of single crystals can be achieved, and by adjusting the proportions of the first lithium-nickel-oxide-based material and the second lithium-nickel-oxide-based material, the performance of the material can be more balanced.

[0112] It should be noted that the single-crystal-like particles refer to microcrystalline particles similar to single crystals.

[0113] In some embodiments, the chemical formula of the second lithium-nickel-oxide-based material is Li a2 Ni x2 Co y2 Mn z2 Q2 u2 O2, wherein 0.98≤a2≤1.60, 0.80≤x2≤1.00, 0.00≤y2≤0.12, 0.00≤z2≤0.10, 0≤u2≤0.007, and Q2 is a doping element.

[0114] In some optional embodiments, Q2 includes one or more of boron, fluorine, magnesium, aluminum, silicon, phosphorus, calcium, scandium, titanium, vanadium, chromium, iron, copper, zinc, gallium, germanium, tin, niobium, molybdenum, strontium, yttrium, zirconium, tungsten, hafnium, indium, bismuth, lanthanum, cerium, gadolinium, barium, and tantalum.

[0115] In some optional embodiments, 0.98≤a2≤1.05, 0.82≤x2≤1.00, 0.00≤y2≤0.08, 0.00≤z2≤0.06, 0.0001≤u2≤0.005.

[0116] As a possible embodiment, the median particle size of the second lithium-nickel-oxide-like material is 0.5-6 μm; for example, it can be but is not limited to 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, or a range between any two of the above particle sizes. When the median particle size of the second lithium-nickel-oxide-like material is in the above range, the morphology profile of the single-crystal material is clearly controllable, and it can be well mixed with the large particles to fill the interstitial space between the large particles, thereby improving the compaction density of the mixed product.

[0117] As a possible embodiment, the mass ratio of the first lithium-nickel-oxide-like material to the second lithium-nickel-oxide-like material in the positive electrode material is 1-10; for example, it can be but is not limited to 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or a range between any two of the above numbers. When the mass ratio of the first lithium-nickel-oxide-like material to the second lithium-nickel-oxide-like material in the positive electrode material is in the above range, the high capacity advantage of the polycrystalline large particles can be exerted, and the long cycle performance of the single-crystal particles can be exerted, and after mixing, the filling degree between the particles is greatly improved, the compaction density is improved, and the final energy density is improved. The performance of the mixed sample is superior to the performance of the large and small particles alone.

[0118] The second aspect of the present application provides a preparation method of the positive electrode material of the first aspect of the present application, comprising the following steps:

[0119] The first mixture material comprising a first lithium source, a first nickel-containing precursor, a first molten salt, and an optional Q1 source is subjected to a first sintering treatment to prepare a first lithium-nickel-oxide-like material; wherein the ratio of the total molar amount of metals contained in the first molten salt to the total molar amount of metals contained in the first nickel-containing precursor is 0.005-0.08.

[0120] The ratio of the total molar amount of metals contained in the first molten salt to the total molar amount of metals contained in the first nickel-containing precursor can be but is not limited to 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.45, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, or a range between any two of the above numbers.

[0121] When the ratio of the total moles of metal contained in the first molten salt to the total moles of metal contained in the first nickel-containing precursor is within the above range, the impurities introduced by the molten salt itself will not affect the material, and meanwhile, the molten salt can play a role in regulating the structure of the material.

[0122] Understandably, the present application uses the molten salt method to regulate the thermal field distribution and melting mode in the sintering process of the material. The added molten salt is difficult to volatilize in the sintering process, but flows along the grain boundary as lava, etches the grain boundary, and forms relatively uniform pores. Thus, the microstructure of the single crystal particles of the lithium-nickel oxide material is changed, the internal stress of the material is reduced, and thus the toughness and resistance performance of the material are improved.

[0123] It should be noted that the molten salt added in the preparation method provided by the present application is generally a high-melting-point salt, which is not easy to volatilize and has certain chemical reaction inertness. The added molten salt only plays a role in etching the grain boundary and expanding the pores, and has no obvious effect on the surface morphology of the material.

[0124] It should be pointed out that during the preparation of the positive electrode material, if only oxide additives are added during sintering, according to the difference in sintering temperature, most of the additives will be coated on the surface of the material, and a small part will enter the grain boundary or crystal lattice of the material, which is not conducive to the formation of pores.

[0125] In some embodiments, the first molten salt has a melting point of 400-1400℃; for example, it can be but is not limited to 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, or a range between any two of the above melting points. Alternatively, the first molten salt has a melting point of 400-1000℃.

[0126] In some embodiments, the cations of the first molten salt include one or more of alkali metals and alkaline earth metals, and the anions include acid radicals.

[0127] In some embodiments, the first molten salt includes a salt composed of acid radicals of elements of the III, IV, V, and VI main groups.

[0128] As a possible embodiment, the first molten salt includes one or more of lithium sulfate, lithium antimonate, lithium silicate, lithium selenate, and lithium phosphate.

[0129] In some embodiments, the first lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxalate, and lithium acetate.

[0130] In some embodiments, the chemical formula of the first nickel-containing precursor is [Ni x3 Co y3 Mn z3](OH)2, wherein 0.80≤x3≤1.00, 0.00≤y3≤0.12, 0.00≤z3≤0.10.

[0131] As one possible implementation, the first nickel-containing precursor has a median particle size of 9 μm-17 μm.

[0132] In some embodiments, the ratio of the total moles of metals contained in the first molten salt and the first lithium source to the total moles of metals contained in the first nickel-containing precursor is 1.02-1.08. As an example, the ratio of the total moles of metals contained in the first molten salt and the first lithium source to the total moles of metals contained in the first nickel-containing precursor can be, but is not limited to, 1.02, 1.025, 1.03, 1.035, 1.04, 1.045, 1.05, 1.055, 1.06, 1.065, 1.07, 1.075, 1.08, or a range between any two of the aforementioned values. In this way, the residual alkali of the material can be controlled within a controllable range, which does not affect the homogenate of the material, and the fluxing agent effect can be better played to adjust the internal structure of the material.

[0133] In some alternative embodiments, the Q1 source includes one or more of oxides, hydroxides, carbonates, phosphates, nitrates containing Q1 elements; the Q1 elements include two or more of boron, fluorine, magnesium, aluminum, silicon, phosphorus, calcium, scandium, titanium, vanadium, chromium, iron, copper, zinc, gallium, germanium, tin, niobium, molybdenum, strontium, yttrium, zirconium, tungsten, hafnium, indium, bismuth, lanthanum, cerium, gadolinium, barium, and tantalum.

[0134] In some embodiments, the first sintering process includes a first sintering platform and a second sintering platform, and the positive temperature difference between the sintering temperature of the second sintering platform and the sintering temperature of the first sintering platform is ≥200°C, and the positive time difference between the sintering time of the second sintering platform and the sintering time of the first sintering platform is ≥1h. In this way, the material can be removed at a low temperature platform to remove the generated impurities and waste gas to achieve the purpose of purifying the initial reactants, and the reactants can be activated at a low temperature segment to achieve a high reaction activity and a reaction efficiency intermediate for the next step of the main reaction. The second sintering platform provides sufficient heat energy and gas for the reaction of the reactants, so that the reactants can stably react, crystallize, and obtain the product.

[0135] In some alternative embodiments, the sintering temperature of the first sintering platform is 550-750°C; for example, but not limited to, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, or a range between any two of the aforementioned temperatures. The sintering time is 3-5h; for example, but not limited to, 3h, 3.1h, 3.2h, 3.3h, 3.4h, 3.5h, 3.6h, 3.7h, 3.8h, 3.9h, 4h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, 4.6h, 4.7h, 4.8h, 4.9h, 5h, or a range between any two of the aforementioned times. When the sintering temperature and sintering time of the first sintering platform are within the aforementioned ranges, respectively, the material can be removed from the generated impurities and waste gas at a low temperature platform, and the purpose of purifying the initial reactants can be achieved. In addition, the reactants can be activated at a low temperature stage, and the intermediate with high reaction activity and reaction efficiency can be obtained, which can prepare for the next main reaction.

[0136] It should be noted that the sintering temperature and sintering time of the first sintering platform can be combined in any suitable manner, and both can be selected from any of the sintering temperature and sintering time of the first sintering platform described herein.

[0137] In some alternative embodiments, the sintering temperature of the second sintering platform is 750-900°C; for example, but not limited to, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, or a range between any two of the aforementioned temperatures. The sintering time is 6-15h; for example, but not limited to, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h, 15h, or a range between any two of the aforementioned times. When the sintering temperature and sintering time of the second sintering platform are within the aforementioned ranges, respectively, the material can be crystallized at a high temperature platform, the consistency of the crystal orientation is improved, and sufficient heat energy and gas are provided for the reaction of the reactants, so that the reactants can stably react, and the product can be obtained by melting and crystallization.

[0138] It should be noted that the sintering temperature and sintering time of the second sintering platform can be combined in any suitable manner, and both can be selected from any of the sintering temperature and sintering time of the second sintering platform described herein.

[0139] As a possible implementation, when the first mixture does not contain the Q1 source or only contains part of the Q1 source, the preparation method further comprises: after mixing the intermediate product obtained by the first sintering treatment with the Q1 source, continuing the sintering treatment at 200-350°C for 3-5h.

[0140] It should be noted that the "part of the Q1 source" mentioned above refers to that the first mixture does not contain the required total mass of the Q1 source.

[0141] In some optional implementations, before mixing the intermediate product obtained by the first sintering treatment with the Q1 source, the method further comprises a step of water washing the intermediate product obtained by the first sintering treatment; so as to remove the free lithium on the surface of the intermediate product.

[0142] As an example, the first lithium-nickel oxide material prepared after the first sintering treatment can be dispersed and depolymerized by mechanical milling or jet milling.

[0143] In some implementations, the preparation method further comprises: preparing a second lithium-nickel oxide material by subjecting a second mixture comprising a second lithium source, a second nickel-containing precursor, a second molten salt and an optional Q2 source to a second sintering treatment; the median particle size of the second nickel-containing precursor is smaller than that of the first nickel-containing precursor; and the ratio of the total molar amount of metals contained in the second molten salt to the total molar amount of metals contained in the second nickel-containing precursor is 0.005-0.08.

[0144] The ratio of the total molar amount of metals contained in the second molten salt to the total molar amount of metals contained in the second nickel-containing precursor can be, but is not limited to, 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.45, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08 or a range between any two of the above values.

[0145] When the ratio of the total molar amount of metals contained in the second molten salt to the total molar amount of metals contained in the second nickel-containing precursor is within the above range, respectively, the initial stress of the second lithium-nickel-manganese-cobalt oxide positive electrode material is smaller, the polarization degree in the electrochemical reaction is lower, the stress accumulation is weaker, and the material can be inhibited from pulverization and grain transverse breakage during long-term cycling.

[0146] Understandably, the internal structure of the particles of the second lithium-nickel oxide material is optimized, the phase reversibility is better, and the particle toughness is significantly improved.

[0147] In some embodiments, the second molten salt has a melting point of 400-1400 °C; for example, it can be, but is not limited to, 400 °C, 500 °C, 600 °C, 700 °C, 800 °C, 900 °C, 1000 °C, 1100 °C, 1200 °C, 1300 °C, 1400 °C, or a range between any two of the above-mentioned melting points. Alternatively, the second molten salt has a melting point of 400-1000 °C.

[0148] In some embodiments, the cations of the second molten salt comprise one or more of alkali metals and alkaline earth metals, and the anions comprise acid radicals.

[0149] In some embodiments, the second molten salt comprises a salt of acid radicals of elements of the III, IV, V, VI main groups.

[0150] As a possible embodiment, the second molten salt comprises one or more of lithium sulfate, lithium antimonate, lithium silicate, lithium selenate, lithium phosphate.

[0151] In some embodiments, the second lithium source comprises one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxalate, and lithium acetate.

[0152] In some embodiments, the second nickel-containing precursor has a chemical formula of [Ni x4 Co y4 Mn z4 ](OH)2, wherein 0.80≤x4≤1.00, 0.00≤y4≤0.12, 0.00≤z4≤0.10.

[0153] As a possible embodiment, the second nickel-containing precursor has a median particle size of 0.5-6 μm.

[0154] In some embodiments, the ratio of the total moles of metals contained in the second molten salt and the second lithium source to the total moles of metals contained in the second nickel-containing precursor is 1.02-1.08. As an example, the ratio of the total moles of metals contained in the second molten salt and the second lithium source to the total moles of metals contained in the second nickel-containing precursor can be, but is not limited to, 1.02, 1.025, 1.03, 1.035, 1.04, 1.045, 1.05, 1.055, 1.06, 1.065, 1.07, 1.075, 1.08, or a range between any two of the above-mentioned values. In this way, the material can be ensured to have sufficient lithium doping, so that the material can react to form a positive electrode material with good performance.

[0155] In some embodiments, the Q2 source comprises one or more of an oxide, a hydroxide, a carbonate, a phosphate, a nitrate containing a Q2 element; the Q2 element comprises two or more of boron, fluorine, magnesium, aluminum, silicon, phosphorus, calcium, scandium, titanium, vanadium, chromium, iron, copper, zinc, gallium, germanium, tin, niobium, molybdenum, strontium, yttrium, zirconium, tungsten, hafnium, indium, bismuth, lanthanum, cerium, gadolinium, barium, and tantalum.

[0156] In some embodiments, the second sintering process comprises a third sintering stage and a fourth sintering stage, the positive temperature difference between the sintering temperature of the fourth sintering stage and the sintering temperature of the third sintering stage is ≥ 200℃, and the positive time difference between the sintering time of the fourth sintering stage and the sintering time of the third sintering stage is ≥ 1h. In this way, the crystallization process is designed in stages, avoiding waste of energy, and ensuring that the obtained grain size is uniform, and better performance is achieved.

[0157] As a possible embodiment, the sintering temperature of the third sintering stage is 550℃-750℃; for example, it can be but is not limited to 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, or a range between any two of the above temperatures. The sintering time is 3h-5h; for example, it can be but is not limited to 3h, 3.1h, 3.2h, 3.3h, 3.4h, 3.5h, 3.6h, 3.7h, 3.8h, 3.9h, 4h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, 4.6h, 4.7h, 4.8h, 4.9h, 5h, or a range between any two of the above times. When the sintering temperature and the sintering time of the third sintering stage are within the above ranges respectively, the grains can nucleate and grow under more suitable conditions, and the lithium salt has sufficient time and suitable temperature to diffuse into the material, making the lithium atmosphere inside the material uniform.

[0158] It should be noted that the sintering temperature and the sintering time of the third sintering stage can be combined in any suitable manner, and both can be selected from any of the sintering temperatures and sintering times of the third sintering stage described herein.

[0159] In some exemplary embodiments, the sintering temperature of the fourth sintering platform is 800-950°C; for example, it can be, but is not limited to, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, or a range between any two of the above temperatures. The sintering time is 6-15h; for example, it can be, but is not limited to, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h, 15h, or a range between any two of the above times. When the sintering temperature and the sintering time of the fourth sintering platform are within the above ranges respectively, the grains can nucleate and grow under more suitable conditions, and there is enough time and energy to grow to the target size and morphology.

[0160] It should be noted that the sintering temperature and the sintering time of the fourth sintering platform can be combined in any suitable manner, and both can be selected from any of the sintering temperatures and sintering times of the fourth sintering platform described herein.

[0161] In some embodiments, when the second mixture does not contain Q2 source or contains only part of the Q2 source, the preparation method further comprises: mixing the intermediate product obtained after the second sintering treatment with a Q2 source, and continuing the sintering treatment at 200-350°C for 3-5h.

[0162] It should be noted that the "part of the Q2 source" mentioned above refers to that the second mixture does not contain the required total mass of Q2 source.

[0163] In some optional embodiments, before mixing the intermediate product obtained after the second sintering treatment with the Q2 source, the method further comprises a step of washing the intermediate product with water; to remove the free lithium on the surface of the intermediate product.

[0164] As an example, the second lithium-nickel oxide material prepared after the second sintering treatment can be dispersed and depolymerized by using an airflow mill.

[0165] The third aspect of the present application provides a positive electrode tab, which comprises the positive electrode material of the first aspect or the positive electrode material prepared by the preparation method of the second aspect.

[0166] The fourth aspect of the present application provides a secondary battery, which comprises the positive electrode tab of the third aspect.

[0167] The secondary battery of the present application contains the above-mentioned positive electrode material, and has excellent long-term cycle performance and safety performance.

[0168] The fifth aspect of the present application provides a power consuming device comprising the secondary battery of the fourth aspect. The power consuming device can be an electric vehicle, an electric bicycle, an electric motorcycle, an electric vehicle power system, an energy storage system, a mobile storage device, etc., and is not particularly limited.

[0169] The technical solutions of the present application are described in detail below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application. If the experimental methods are not specified in the following examples, the guidelines given in the present application are preferred, and the experimental methods can also be performed according to the experimental manuals or conventional conditions in the art, or according to the conditions suggested by the manufacturers, or according to the known experimental methods in the art.

[0170] In the following specific examples, the measurement parameters of the raw material components may, without specific instructions, have slight deviations within the weighing accuracy range. With respect to temperature and time parameters, acceptable deviations caused by instrument testing accuracy or operation accuracy are allowed.

[0171] I. Preparation of the positive electrode material

[0172] Example 1

[0173] 1) Weigh 463 g of lithium hydroxide monohydrate (as the first lithium source), 1000 g of [Ni 0.9 Co 0.06 Mn 0.04 ](OH)2precursor (as the first nickel-containing precursor) with a particle size of 13.5 μm, 4.9 g of zirconium oxide (ZrO2, as a Q1 source), and 5.9 g of lithium sulfate (Li2SO4, as a first molten salt), and uniformly stir them at high speed, and then perform a first sintering treatment under an oxygen atmosphere; the first sintering treatment is specifically as follows: the obtained mixture is subjected to a first sintering platform at a temperature of 550 ℃ for 4.5 h; then it is heated to a second sintering platform at a temperature of 785 ℃ for 13 h, and an intermediate product A is obtained by mechanical crushing;

[0174] 2) The intermediate product A obtained in step 1) is washed with water at a solid content of 60% for 5 min, then centrifuged, and then dried at a temperature of 150 ℃ for 1 h to obtain an intermediate product A*;

[0175] 3) The intermediate product A* obtained in step 2) is mixed with H3BO3 (as a Q1 source) at a weight ratio of 1:0.001 at high speed, and then sintered at a temperature of 300 ℃ for 4 h under an oxygen atmosphere to obtain a first lithium nickel cobalt manganese oxide material with a median particle size of 12.6 μm and a chemical formula of LiNi 0.9 Co 0.06 Mn 0.04 Zr 0.004 B 0.003 O2.

[0176] 4) Refer to the above steps 1) - step 3), change [Ni 0.9 Co 0.06 Mn 0.04 ](OH)2precursor with a particle size of 3 pm, to prepare a second lithium nickel cobalt manganese oxide material with a median particle size of 2.8 pm and a chemical formula of LiNi 0.9 Co 0.06 Mn 0.04 Zr 0.004 B 0.003 O2.

[0177] 5) Mix the first lithium nickel cobalt manganese oxide material and the second lithium nickel cobalt manganese oxide material prepared above in a mass ratio of 8:2 to obtain a positive electrode material.

[0178] Example 2

[0179] Example 2 and the preparation method of Example 1 are similar, the main difference is that the amount of lithium sulfate added is different; specific as follows:

[0180] 1) Take 463 g of lithium hydroxide monohydrate (as a first lithium source), 1000 g of [Ni 0.9 Co 0.06 Mn 0.04 ](OH)2precursor (as a first nickel-containing precursor) with a particle size of 13.5 pm, 4.9 g of zirconium oxide (ZrO2, as a Q1 source), and 8.85 g of lithium sulfate (Li2SO4, as a first molten salt), and uniformly stir them at high speed, then perform a first sintering treatment under an oxygen atmosphere; the first sintering treatment is as follows: the obtained mixture is subjected to a first sintering platform at a temperature of 550°C for 4.5 h; then it is heated again to pass through a second sintering platform at a temperature of 785°C for 13 h, and after mechanical crushing, an intermediate product A is obtained;

[0181] 2) Wash the intermediate product A obtained in step 1) with water at a solid content of 60% for 5 min, then centrifuge, and then dry at a temperature of 150°C for 1 h to obtain an intermediate product A*;

[0182] 3) High-speed mix the intermediate product A* obtained in step 2) with H3BO3 (as a Q1 source) at a weight ratio of 1:0.001, then sinter at a temperature of 300°C for 4 h under an oxygen atmosphere to obtain a first lithium nickel cobalt manganese oxide material with a median particle size of 12.6 pm and a chemical formula of LiNi 0.9 Co 0.06 Mn 0.04 Zr 0.004 B 0.003 O2.

[0183] 4) Refer to the above steps 1) - step 3), change [Ni 0.9 Co 0.06 Mn 0.04 ](OH)2precursor with a particle size of 3 μm, to obtain a second lithium nickel cobalt manganese oxide material with a median particle size of 2.8 μm and a chemical formula of LiNi 0.9 Co 0.06 Mn 0.04 Zr 0.004 B 0.003 O2.

[0184] 5) Mix the first lithium nickel cobalt manganese oxide material and the second lithium nickel cobalt manganese oxide material prepared above according to a mass ratio of 8:2 to obtain a positive electrode material.

[0185] Example 3

[0186] Example 3 and the preparation method of Example 1 are similar, the main difference is that the amount of lithium sulfate added is different; specific as follows:

[0187] 1) Take lithium hydroxide monohydrate (as a first lithium source) 463 g, [Ni 0.9 Co 0.06 Mn 0.04 ](OH)2precursor (as a first nickel-containing precursor) with a particle size of 13.5 μm 1000 g, zirconium oxide (ZrO2, as a Q1 source) 4.9 g and lithium sulfate (Li2SO4, as a first molten salt) 11.8 g, uniformly stirred at high speed, and then subjected to a first sintering treatment under an oxygen atmosphere; the first sintering treatment is specifically that the obtained mixture is subjected to a first sintering platform at a temperature of 550 ℃ for 4.5 h; and then is subjected to a second sintering platform at a temperature of 785 ℃ for 13 h, and is subjected to mechanical crushing to obtain an intermediate product A;

[0188] 2) Wash the intermediate product A obtained in step 1) with water according to a solid content of 60% for 5 min, then centrifuge, and then dry at a temperature of 150 ℃ for 1 h to obtain an intermediate product A*;

[0189] 3) High-speed mix the intermediate product A* obtained in step 2) with H3BO3 (as a Q1 source) according to a weight ratio of 1:0.001, and then sinter at a temperature of 300 ℃ for 4 h under an oxygen atmosphere to obtain a first lithium nickel cobalt manganese oxide material with a median particle size of 12.6 μm and a chemical formula of LiNi 0.9 Co 0.06 Mn 0.04 Zr 0.004 B 0.003 O2.

[0190] 4) Refer to the above steps 1) - step 3), change [Ni 0.9 Co0.06 Mn 0.04 ](OH)2precursor with a particle size of 3 pm, to obtain a first lithium nickel cobalt manganese oxide material with a median particle size of 2.8 pm and a chemical formula of LiNi 0.9 Co 0.06 Mn 0.04 Zr 0.004 B 0.003 O2, and a second lithium nickel cobalt manganese oxide material with a chemical formula of LiNi

[0191] 5) The first lithium nickel cobalt manganese oxide material and the second lithium nickel cobalt manganese oxide material prepared above are mixed in a mass ratio of 8:2 to obtain the positive electrode material.

[0192] Example 4

[0193] Example 4 and Example 1 are similar in preparation method, the main difference being that the amount of lithium sulfate added is different; the specific process is as follows:

[0194] 1) 463 g of lithium hydroxide monohydrate (as a first lithium source), 1000 g of [Ni 0.9 Co 0.06 Mn 0.04 ](OH)2precursor (as a first nickel-containing precursor), 4.9 g of zirconium oxide (ZrO2, as a Q1 source), and 21.65 g of lithium sulfate (Li2SO4, as a first molten salt) are uniformly stirred at high speed, and then subjected to a first sintering treatment under an oxygen atmosphere; the first sintering treatment is as follows: the obtained mixture is subjected to a first sintering platform at a temperature of 550°C for 4.5 h; then it is heated to a second sintering platform at a temperature of 785°C for 13 h, and is subjected to mechanical crushing to obtain intermediate product A;

[0195] 2) The intermediate product A obtained in step 1) is washed with water at a solid content of 60% for 5 min, then centrifuged, and then dried at a temperature of 150°C for 1 h to obtain intermediate product A*;

[0196] 3) The intermediate product A* obtained in step 2) is mixed with H3BO3 (as a Q1 source) at a weight ratio of 1:0.001 at high speed, and then sintered at a temperature of 300°C for 4 h under an oxygen atmosphere to obtain a first lithium nickel cobalt manganese oxide material with a median particle size of 12.6 pm and a chemical formula of LiNi 0.9 Co 0.06 Mn 0.04 Zr 0.004 B 0.003 O2, and a second lithium nickel cobalt manganese oxide material with a chemical formula of LiNi

[0197] 4) Refer to steps 1) to 3) above, and change the [Ni 0.9 Co 0.06 Mn 0.04particle size of 3 μm, to prepare a first lithium nickel cobalt manganese oxide material with a median particle size of 2.8 μm and a chemical formula of LiNi 0.9 Co 0.06 Mn 0.04 Zr 0.004 B 0.003 O2, and a second lithium nickel cobalt manganese oxide material with a median particle size of 12.6 μm and a chemical formula of LiNi

[0198] 5) mixing the first lithium nickel cobalt manganese oxide material and the second lithium nickel cobalt manganese oxide material prepared above according to a mass ratio of 8:2 to obtain the positive electrode material.

[0199] Example 5

[0200] Example 5 and Example 1 are different in that the preparation of the second lithium nickel cobalt manganese oxide material is not performed, and the positive electrode material prepared only includes the first lithium nickel cobalt manganese oxide material; the details are as follows:

[0201] 1) taking 463 g of lithium hydroxide monohydrate (as a first lithium source), 1000 g of [Ni 0.9 Co 0.06 Mn 0.04 ](OH)2precursor (as a first nickel-containing precursor), 4.9 g of zirconium oxide (ZrO2, as a Q1 source), and 33 g of lithium sulfate (Li2SO4, as a first molten salt), uniformly stirring them at high speed, and then performing a first sintering treatment under an oxygen atmosphere; the first sintering treatment is specifically as follows: making the obtained mixture pass through a first sintering platform at a temperature of 550 ℃ for a sintering time of 4.5 h; and then increasing the temperature to pass through a second sintering platform at a temperature of 785 ℃ for a sintering time of 13 h, and obtaining an intermediate product A through mechanical crushing;

[0202] 2) washing the intermediate product A obtained in step 1) with water according to a solid content of 60% for 5 min, and then performing centrifugation, and then drying at a temperature of 150 ℃ for 1 h to obtain an intermediate product A*;

[0203] 3) high-speed mixing the intermediate product A* obtained in step 2) with H3BO3(as a Q1 source) according to a weight ratio of 1:0.001, and then sintering at a temperature of 300 ℃ for 4 h under an oxygen atmosphere to obtain a first lithium nickel cobalt manganese oxide material with a median particle size of 12.6 μm and a chemical formula of LiNi 0.9 Co 0.06 Mn 0.04 Zr 0.004 B 0.003 O2, and a second lithium nickel cobalt manganese oxide material with a median particle size of 12.6 μm and a chemical formula of LiNi

[0204] Comparative Example 1

[0205] Comparative Example 1 and Example 1 are similar in the preparation method of the positive electrode material, and are different in that lithium sulfate is not added; the details are as follows:

[0206] 1) 463 g of lithium hydroxide monohydrate (as a first lithium source), 1000 g of [Ni 0.9 Co 0.06 Mn 0.04 ](OH)2precursor (as a first nickel-containing precursor), and 4.9 g of zirconium oxide (ZrO2, as a Q1 source) were uniformly stirred at high speed, and then subjected to a first sintering treatment under an oxygen atmosphere; the first sintering treatment was as follows: the obtained mixture was subjected to a first sintering platform at a temperature of 550°C for 4.5 h, and then subjected to a second sintering platform at a temperature of 785°C for 10 h, and then mechanically crushed to obtain intermediate product A;

[0207] 2) The intermediate product A obtained in step 1) was washed with water at a solid content of 60% for 5 min, and then centrifuged, and then dried at a temperature of 150°C for 1 h to obtain intermediate product A*;

[0208] 3) The intermediate product A* obtained in step 2) was mixed with H3BO3 (as a Q1 source) at a weight ratio of 1:0.001 at high speed, and then sintered at a temperature of 300°C for 4 h under an oxygen atmosphere to obtain a first lithium nickel cobalt manganese oxide material having a median particle size of 12.6 μm and a chemical formula of LiNi 0.9 Co 0.06 Mn 0.04 Zr 0.004 B 0.003 O2.

[0209] 4) Referring to steps 1) to 3) above, the particle size of the [Ni 0.9 Co 0.06 Mn 0.04 ](OH)2precursor was changed to 3 μm, and a second lithium nickel cobalt manganese oxide material having a median particle size of 2.8 μm and a chemical formula of LiNi 0.9 Co 0.06 Mn 0.04 Zr 0.004 B 0.003 O2was prepared.

[0210] 5) The first lithium nickel cobalt manganese oxide material and the second lithium nickel cobalt manganese oxide material prepared above were mixed at a mass ratio of 8:2 to obtain a positive electrode material.

[0211] Comparative Example 2

[0212] The positive electrode material of Comparative Example 2 and Example 1 was prepared in a similar manner, except that lithium sulfate was not added, and lithium hydroxide monohydrate was added instead of lithium sulfate; the preparation was as follows:

[0213] 1) 463 g of lithium hydroxide monohydrate (as a first lithium source), 1000 g of [Ni 0.9 Co 0.06 Mn 0.04 ](OH)2precursor (as a first nickel-containing precursor), 4.9 g of zirconium oxide (ZrO2, as a Q1 source), and 8.15 g of lithium hydroxide monohydrate were uniformly stirred at high speed, and then subjected to a first sintering treatment under an oxygen atmosphere; the first sintering treatment was as follows: the resulting mixture was subjected to a first sintering plateau at a temperature of 550°C for 4.5 h, and then subjected to a second sintering plateau at a temperature of 785°C for 10 h, and then mechanically crushed to obtain intermediate product A;

[0214] 2) The intermediate product A obtained in step 1) was washed with water at a solid content of 60% for 5 min, and then centrifuged, and then dried at a temperature of 150°C for 1 h to obtain intermediate product A*;

[0215] 3) The intermediate product A* obtained in step 2) was mixed with H3BO3(as a Q1 source) at a weight ratio of 1:0.001 at high speed, and then sintered at a temperature of 300°C for 4 h under an oxygen atmosphere to obtain a first lithium nickel cobalt manganese oxide material having a median particle size of 12.6 μm and a chemical formula of LiNi 0.9 Co 0.06 Mn 0.04 Zr 0.004 B 0.003 O2;

[0216] 4) Referring to steps 1) to 3) above, the particle size of the [Ni 0.9 Co 0.06 Mn 0.04 ](OH)2precursor was changed to 3 μm, and a second lithium nickel cobalt manganese oxide material having a median particle size of 2.8 μm and a chemical formula of LiNi 0.9 Co 0.06 Mn 0.04 Zr 0.004 B 0.003 O2was prepared;

[0217] 5) The first lithium nickel cobalt manganese oxide material and the second lithium nickel cobalt manganese oxide material prepared above were mixed at a mass ratio of 8:2 to obtain a positive electrode material.

[0218] The first lithium nickel cobalt manganese oxide material prepared in each of the above examples and comparative examples was subjected to tests including the following: the porosity d of the polycrystalline particle, the distance L between the edges of two adjacent pores in the polycrystalline particle, and the angle θ between the direction of the diameter of each primary particle in an arbitrary CP cross section of the polycrystalline particle and the direction of the diameter of the polycrystalline particle, and the results are shown in Table 1 below.

[0219] Table 1

[0220] II. Performance test

[0221] 1. Morphology test

[0222] The positive electrode material prepared in Example 1 was scanned by an electron scanning electron microscope, and the result is shown in Figure 1. As shown in Figure 1, the prepared positive electrode material is a mixture of large and small particles, the large particles are polycrystalline particles, and the small particles are single-crystal particles.

[0223] The CP test was performed on the positive electrode material prepared in Example 1, and the CP profile is shown in Figure 2. As shown in Figure 2, the large particles in the positive electrode material have a good internal radial structure, and there is a relatively uniform pore distribution inside.

[0224] 2. Deformation amount test

[0225] In the micromechanics test, the single particle strength of the polycrystalline particles is > 90 MPa.

[0226] The deformation amount test method of the polycrystalline particles before breaking is as follows:

[0227] MCT-210 micro compression tester was used for measurement. First, open the MCT-210 test software, clamp the sample stage in the middle position of the tablet without sliding, and ensure that the sample stage height is at least 3 cm below the objective lens; turn on the LED light switch of the main machine, shake the hand wheel at the lower right position of the main machine, and adjust the sample stage height to the clear sample particle image in the CCD image display window; click start testing, measure the particle diameter, save the image before compression; rotate the hand wheel to move the particle vertex to the lens focus, push the sample stage to the bottom of the compression disc, and start the compression test; after compression, push the sample stage to the objective lens, rotate the hand wheel to the clear image after compression, and save the image.

[0228] The deformation amount test results of the above examples and comparative examples are shown in Table 2.

[0229] 3. Particle strength test

[0230] The MCT-210 micro compression tester is used for measurement. First, open the MCT-210 test software, clamp the sample stage in the middle position of the tablet without sliding, and ensure that the sample stage height is at least 3 cm below the objective lens; turn on the LED light switch of the main machine, shake the hand wheel at the lower right position of the main machine, and adjust the sample stage height to the clear sample particle image in the CCD image display window; click start testing, measure the particle diameter, and save the image before compression; rotate the hand wheel to move the particle vertex to the lens focal point, push the sample stage to the bottom of the compression disc to the right, and start the compression test; after the compression is completed, push the sample stage to the objective lens to the left, rotate the hand wheel to the clear image after compression, and save the image.

[0231] The particle strength test results of the above examples and comparative examples are shown in Table 2.

[0232] 4. BET change amount test before and after rolling

[0233] The BET change amount of the positive electrode material is defined as β, the specific surface area of the positive electrode material before compression is A1, and the specific surface area of the positive electrode material after the cold compression process is A2; wherein β = (A2-A1) / A1x100%. The sample weight (4-8) g is taken by dynamic adsorption method, the sample is placed in a 1 / 2 foot, 12 mm sample U-shaped tube, and the sample is degassed at 105°C for 2 hours, and the adsorption gas is 99.99% N2 or He gas. The sample U-shaped tube is placed in liquid N2 at-196°C, and the sample with a specific surface area of 0.22 m 2 / g is selected as a standard sample for testing.

[0234] The BET change amount test results of the above examples and comparative examples after rolling are shown in Table 2.

[0235] 5. Capacity test

[0236] The positive electrode material, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) prepared in each example and comparative example are mixed in a mass ratio of 96.5:1.5:2, a solvent N-methyl pyrrolidone (NMP) is added, and the mixture is stirred uniformly in a glove box by using a high-speed stirrer to obtain a positive electrode material slurry; the positive electrode slurry is uniformly coated on a positive electrode current collector aluminum foil, and then subjected to a drying, cold pressing and other processes to prepare a positive electrode sheet, and the compaction density of the positive electrode sheet is 3.6±0.5 g / cm 3 .

[0237] A commercially available electrolyte is used as a battery electrolyte (1M LiPF6(EC / DMC, volume ratio 1:1) solution), and a lithium sheet is used as a negative electrode sheet, and a standard button cell is assembled with the prepared positive electrode sheet.

[0238] The button cell was charged at 0.1C constant current to 4.25V under 2.5V-4.25V voltage, then charged at 4.25V constant voltage to current≤0.05mA, and rested for 2min, at which time the charge capacity was recorded as C 0 ; then discharged at 0.1C constant current to 2.8V, at which time the discharge capacity was recorded as D 0 . The discharge capacity D 0 was divided by the mass of the positive electrode active material to obtain the gram capacity of the positive electrode active material. The first coulombic efficiency of the positive electrode active material (%) = D 0 / C 0 x 100%.

[0239] The capacity test results of the above examples and comparative examples are shown in Table 2.

[0240] 6. Cycle performance test

[0241] The button cell prepared above was subjected to cycle test, and the high-temperature cycle performance test was carried out at 45°C constant temperature environment, the battery was charged at 1 / 3C constant current to 4.25V, then charged at 4.25V constant voltage to current≤0.05mA, rested for 5min, then discharged at 1 / 3C constant current to 2.8V, which was one charge / discharge cycle process, and the discharge capacity at this time was the discharge capacity of the first cycle. Then the battery was subjected to 50 cycle charge / discharge tests according to the above method, and the discharge capacity of the 50th cycle was detected.

[0242] The cycle performance test results of the above examples and comparative examples are shown in Table 2.

[0243] Table 2

[0244] From the results of Examples 1-5 in the table, it can be seen that as the amount of molten salt added increases, the deformation of the material after being pressed becomes smaller, the particle strength is improved to some extent, and the structural stability of the particles is improved. Due to the unique regulation of the molten salt method on the primary particles inside the polycrystalline particles, the primary particles inside the large particles are arranged more orderly, accompanied by an increase in internal porosity, an increase in active surface exposure, and an increase in capacity of the material. However, the corresponding cycle performance first increases and then decreases, which is due to the excessive internal porosity of the polycrystalline particles, resulting in a decrease in the mechanical stability of the contact between the particles. This decrease in mechanical properties will lead to particle pulverization and cracking during the cycle of the material, resulting in a decrease in cycle capacity retention rate.

[0245] From the results of Example 1 and Comparative Example 1, it can be seen that when no molten salt is added during the preparation of the positive electrode material, the structure of the material is not optimized, and the capacity of the material is slightly lower, and the cycle retention rate is general.

[0246] From the comparison of the results of Example 1 and Comparative Example 2, it can be seen that when a low-boiling-point cosolvent is added in the preparation of the positive electrode material, both the capacity and the cycle retention rate of the material are improved, but the deformation of the particles is large, the toughness between the polycrystalline primary particles is poor, the particle strength is not high, and the degree of pulverization is high.

[0247] The technical features of the above-described embodiments can be combined arbitrarily, and for the sake of brevity, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not contradict each other, they should be considered as falling within the scope of the present disclosure.

[0248] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent of the present application. It should be pointed out that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all fall within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A positive electrode material, characterized by, The first lithium-nickel-oxide-based material comprises polycrystal particles, porosity inside the polycrystal particles is denoted as d, 1%≤d≤15%; in any CP profile of the polycrystal particles, the distance between the edges of two adjacent pores inside the polycrystal particles is 5nm-100nm.

2. A positive electrode material, characterized by, The first lithium-nickel-oxide-based material comprises polycrystal particles, porosity inside the polycrystal particles is denoted as d, 2%≤d≤15%; in any CP profile of the polycrystal particles, the distance between the edges of two adjacent pores inside the polycrystal particles is 10nm-100nm.

3. The positive electrode material according to claim 1 or 2, characterized in that, The polycrystal particles comprise at least one of the following features (1)-(3): (1) the polycrystal particles comprise a plurality of primary particles; Optionally, in any CP profile of the polycrystal particles, the angle between the direction of the long diameter of each primary particle and the direction of the diameter of the polycrystal particle is 0°-90°, optionally 0°-30°; Optionally, the particle size of each primary particle is 200nm-800nm; (2) the single particle strength of the polycrystal particles is >90Mpa; (3) the deformation amount of the polycrystal particles before rupture is <21%.

4. The positive electrode material according to any one of claims 1 to 3, wherein The first lithium-nickel-oxide-based material comprises at least one of the following features (1)-(3): (1) the chemical formula of the first lithium nickel oxide-based material is Li a1 Ni x1 Co y1 Mn z1 Q1 u1 O2, wherein 0.98≤a1≤1.60, 0.80≤x1≤1.00, 0.00≤y1≤0.12, 0.00≤z1≤0.10, 0≤u1≤0.007, and Q1 is a doping element; Optionally, the Q1 element comprises two or more of boron, fluorine, magnesium, aluminum, silicon, phosphorus, calcium, scandium, titanium, vanadium, chromium, iron, copper, zinc, gallium, germanium, tin, niobium, molybdenum, strontium, yttrium, zirconium, tungsten, hafnium, indium, bismuth, lanthanum, cerium, gadolinium, barium and tantalum; Optionally, 0.98≤a1≤1.05, 0.82≤x1≤1.00, 0.00≤y1≤0.08, 0.00≤z1≤0.06, 0.0001≤u1≤0.005; (2) the median particle size of the first lithium-nickel-oxide-based material is 9μm-17μm; (3) the specific surface area of the first lithium-nickel-oxide-based material is denoted as A1, after pressure fracturing at 4.5T, the specific surface area of the first lithium-nickel-oxide-based material is denoted as A2, (A2-A1) / A1×100%≤40%.

5. The positive electrode material according to claim 1 or 2, wherein The second lithium-nickel-oxide-based material comprises single crystal particles or quasi-single crystal particles; Optionally, the mass ratio of the first lithium-nickel-oxide-based material and the second lithium-nickel-oxide-based material in the positive electrode material is 1-10.

6. The positive electrode material of claim 5, wherein, The second lithium-nickel-oxide-based material comprises at least one of the following features (1)-(2): (1) the chemical formula of the second lithium nickel oxide-based material is Li a2 Ni x2 Co y2 Mn z2 Q2 u2 O2, wherein 0.98≤a2≤1.60, 0.80≤x2≤1.00, 0.00≤y2≤0.12, 0.00≤z2≤0.10, 0≤u2≤0.007, and Q2 is a doping element; Optionally, the Q2 element comprises two or more of boron, fluorine, magnesium, aluminum, silicon, phosphorus, calcium, scandium, titanium, vanadium, chromium, iron, copper, zinc, gallium, germanium, tin, niobium, molybdenum, strontium, yttrium, zirconium, tungsten, hafnium, indium, bismuth, lanthanum, cerium, gadolinium, barium and tantalum; Optionally, 0.98≤a2≤1.05, 0.82≤x2≤1.00, 0.00≤y2≤0.08, 0.00≤z2≤0.06, 0.0001≤u2≤0.005; (2) the median particle size of the second lithium-nickel-oxide-based material is 0.5μm-6μm.

7. A method of producing the positive electrode material as claimed in any one of claims 1 to 6, characterized by, The method comprises the following steps: a first mixture material comprising a first lithium source, a first nickel-containing precursor, a first molten salt and an optional Q1 source is subjected to a first sintering treatment to prepare the first lithium-nickel oxide material; wherein the ratio of the total moles of metals contained in the first molten salt to the total moles of metals contained in the first nickel-containing precursor is 0.005-0.

08.

8. The method for preparing the positive electrode material according to claim 7, wherein: The preparation method comprises at least one of the following conditions: (1) the melting point of the first molten salt is 400-1400℃, which can be optionally 400-1000℃; the cations of the first molten salt comprise one or more of alkali metals and alkaline earth metals, and the anions comprise acid radicals; optionally, the first molten salt comprises one or more of lithium sulfate, lithium antimonate, lithium silicate, lithium selenate and lithium phosphate; (2) the first lithium source comprises one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxalate and lithium acetate; (3) the first nickel-containing precursor has a chemical formula of [Ni x3 Co y3 Mn z3 ](OH)2, wherein 0.80≤x3≤1.00, 0.00≤y3≤0.12, 0.00≤z3≤0.10; (4) the median particle size of the first nickel-containing precursor is 9-17μm; (5) the ratio of the total moles of metals contained in the first molten salt and the first lithium source to the total moles of metals contained in the first nickel-containing precursor is 1.02-1.08; (6) the Q1 source comprises one or more of oxides, hydroxides, carbonates, phosphates and nitrates containing a Q1 element; the Q1 element comprises two or more of boron, fluorine, magnesium, aluminum, silicon, phosphorus, calcium, scandium, titanium, vanadium, chromium, iron, copper, zinc, gallium, germanium, tin, niobium, molybdenum, strontium, yttrium, zirconium, tungsten, hafnium, indium, bismuth, lanthanum, cerium, gadolinium, barium and tantalum; (7) the first sintering treatment comprises a first sintering platform and a second sintering platform, the positive temperature difference between the sintering temperature of the second sintering platform and the sintering temperature of the first sintering platform is ≥200℃, and the positive time difference between the sintering time of the second sintering platform and the sintering time of the first sintering platform is ≥1h; optionally, the sintering temperature of the first sintering platform is 550-750℃, and the sintering time is 3-5h; optionally, the sintering temperature of the second sintering platform is 750-900℃, and the sintering time is 6-15h; (8) when the first mixture material does not contain the Q1 source or only contains part of the Q1 source, the preparation method further comprises: after mixing the intermediate product obtained by the first sintering treatment with the Q1 source, continuing the sintering treatment at 200-350℃ for 3-5h.

9. The method for preparing a positive electrode material according to any one of claims 7 to 8, wherein: The preparation method further comprises: a second mixture material comprising a second lithium source, a second nickel-containing precursor, a second molten salt and an optional Q2 source is subjected to a second sintering treatment to prepare the second lithium-nickel oxide material; the median particle size of the second nickel-containing precursor is smaller than that of the first nickel-containing precursor; wherein the ratio of the total moles of metals contained in the second molten salt to the total moles of metals contained in the second nickel-containing precursor is 0.005-0.

08. Optionally, the second molten salt has a melting point of 400-1400°C, optionally 400-1000°C; the cation of the second molten salt comprises one or more of alkali metals and alkaline earth metals, and the anion comprises an acid radical; Optionally, the second molten salt comprises one or more of lithium sulfate, lithium antimonate, lithium silicate, lithium selenate, and lithium phosphate; Optionally, the second lithium source comprises one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxalate, and lithium acetate; Optionally, the second nickel-containing precursor has a median particle size of 0.5-6 μm; Optionally, the second nickel-containing precursor has a chemical formula of [Ni x4 Co y4 Mn z4 ](OH)2, wherein 0.80≤x4≤1.00, 0.00≤y4≤0.12, 0.00≤z4≤0.

10. Optionally, the ratio of the total molar amount of metals contained in the second molten salt and the second lithium source to the total molar amount of metals contained in the second nickel-containing precursor is 1.02-1.08; Optionally, the Q2 source comprises one or more of oxides, hydroxides, carbonates, phosphates, and nitrates of Q2 elements; the Q2 elements comprise two or more of boron, fluorine, magnesium, aluminum, silicon, phosphorus, calcium, scandium, titanium, vanadium, chromium, iron, copper, zinc, gallium, germanium, tin, niobium, molybdenum, strontium, yttrium, zirconium, tungsten, hafnium, indium, bismuth, lanthanum, cerium, gadolinium, barium, and tantalum; Optionally, when the second mixture does not contain the Q2 source or contains only part of the Q2 source, the preparation method further comprises: mixing the intermediate product obtained after the second sintering treatment with the Q2 source, and then continuing the sintering treatment at 200-350°C for 3-5 h; Optionally, the second sintering treatment comprises a third sintering platform and a fourth sintering platform, the positive temperature difference between the sintering temperature of the fourth sintering platform and the sintering temperature of the third sintering platform is ≥200°C, and the positive time difference between the sintering time of the fourth sintering platform and the sintering time of the third sintering platform is ≥1 h; Optionally, the sintering temperature of the third sintering platform is 550-750°C, and the sintering time is 3-5 h; Optionally, the sintering temperature of the fourth sintering platform is 800-950°C, and the sintering time is 6-15 h. The positive electrode material as claimed in any one of claims 1 to 6 or prepared by the method as claimed in any one of claims 7 to 9.

10. A positive electrode sheet characterized by comprising: The positive electrode tab as claimed in claim 10.

11. A secondary battery characterized by comprising: ​

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