High-nickel single-crystal cathode material, its preparation method, cathode electrode sheet, secondary battery and electrical device

Abstract

The present application provides a high-nickel single-crystal cathode material, a preparation method thereof, a cathode electrode sheet, a secondary battery, and an electrical device. The chemical formula of the high-nickel single-crystal cathode material is Li 1+δ Ni x M y Q 1‑x‑y O 2+ε A α R β X γ , 0.8 ≤ x < 1, 0 < y ≤ 0.2, 0 ≤ δ ≤ 0.15, 0 < ε ≤ 0.2, 0 < α ≤ 0.04, 0 < β ≤ 0.04, 0 ≤ γ ≤ 0.04. The M element and the Q element each independently include one or more of Mn, Co, Al, Ta, Ti, Nb, Ge, Y, Nb, W, Zr, Ce, Ca, Sr, Sc, V, Cr, and Mo; the A element includes one or more of Mg, Ca, Sr, Ba, Ti, Zr, V, Nb, Ta, Mo, W, La, Ce, Sc, and Cr; the R element includes one or more of B and P; the X element includes one or more of Na, K, Mn, Mg, Ca, Sr, and Al; the molar ratio of Ni 3+ on the surface of the high-nickel single-crystal cathode material is 38% - 55%, and the molar ratio of lattice oxygen on the surface is 7% - 15%. The structural defects of the material are significantly reduced, thereby improving its specific capacity and enhancing its cycling performance.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and particularly to a high-nickel single crystal cathode material, a preparation method thereof, a cathode electrode sheet, a secondary battery, and an electrical device. Background Art

[0002] New energy vehicles are becoming more and more widely used. Among them, the power source lithium-ion battery is the core part of new energy vehicles, and the cathode material in the lithium-ion battery system is a decisive factor. In the existing cathode material system, the high-nickel single crystal cathode material has the advantages of high specific capacity, high tap density, and high surface / structure stability, so it is widely used in the preparation of lithium-ion batteries. However, when preparing the high-nickel single crystal cathode material, in order to make the primary particles grow fully and separate to form a single crystal morphology, a relatively high sintering temperature is required during the preparation process; due to the poor high-temperature stability of the high-nickel single crystal cathode material, the specific capacity and cycle performance of the finally obtained material are both affected. Summary of the Invention

[0003] Based on this, the present application provides a high-nickel single crystal cathode material with relatively high specific capacity and excellent cycle performance, a preparation method thereof, a cathode electrode sheet, a secondary battery, and an electrical device.

[0004] The first aspect of the present application provides a high-nickel single crystal cathode material, and the chemical formula of the high-nickel single crystal cathode material is Li 1+δ Ni x M y Q 1-x-y O 2+ε A α R β X γ , 0.8 ≤ x < 1, 0 < y ≤ 0.2, 0 ≤ δ ≤ 0.15, 0 < ε ≤ 0.2, 0 < α ≤ 0.04, 0 < β ≤ 0.04, 0 ≤ γ ≤ 0.04, the M element and the Q element each independently include one or more of Mn, Co, Al, Ta, Ti, Nb, Ge, Y, W, Zr, Ce, Ca, Sr, Sc, V, Cr, and Mo; the A element includes one or more of Mg, Ca, Sr, Ba, Ti, Zr, V, Nb, Ta, Mo, W, La, Ce, Sc, and Cr; the R element includes one or more of B and P; the X element includes one or more of Na, K, Mn, Mg, Ca, Sr, and Al; the molar ratio of Ni 3+ on the surface of the high-nickel single crystal cathode material is 38% - 55%, and the molar ratio of lattice oxygen on the surface is 7% - 15%.

[0005] In some embodiments, the length of the primary particle of the high-nickel single crystal cathode material is denoted as L, the width is denoted as W, and W / L is 0.7 - 0.85;

[0006] Optionally, L is 1300 nm - 2000 nm;

[0007] Optionally, W is 900 nm - 1500 nm.

[0008] In some embodiments, in the XRD pattern of the high-nickel single-crystal cathode material, the diffraction peak intensities I (003) and I (104) between the following relationship is satisfied: 1.3 ≤ I (003) / I (104) ≤ 2.

[0009] The second aspect of the present application provides a method for preparing the high-nickel single-crystal cathode material of the first aspect of the present application, including the following steps:

[0010] Prepare a local oxygen-supplementing flux including a basic flux component and an oxidizing component; the oxidizing component can generate an oxidizing gas under heating conditions; the elements contained in the basic solvent component include the A element and the R element, and the elements contained in the oxidizing component include the X element;

[0011] Perform pre-sintering treatment on a powder mixture including a lithium source and a precursor to prepare a pre-sintered material; the chemical formula of the precursor is Ni c M d Q 1-c-d (OH)2, 0.8 ≤ c < 1, 0 < d ≤ 0.2, the M element and the Q element each independently include one or more of Mn, Co, Al, Ta, Ti, Nb, Ge, Y, W, Zr, Ce, Ca, Sr, Sc, V, Cr, and Mo;

[0012] Mix the local oxygen-supplementing flux and the pre-sintered material and place them in a sample container, and perform sintering treatment to prepare the high-nickel single-crystal cathode material;

[0013] Among them, the mass of the local oxygen-supplementing flux accounts for 0.1% - 4% of the mass of the pre-sintered material.

[0014] In some embodiments, the oxidizing component includes one or more of peroxides, superoxides, nitrates, nitrites, hypochlorites, chlorates, perchlorates, manganates, and permanganates of the Z element, and the Z element includes one or more of Li, Na, K, Mg, Ca, Sr, and Al; and / or

[0015] The basic flux component includes one or more of flux of type a and flux of type b; the flux of type a includes one or more of oxides, hydroxides, carbonates, sulfates, chlorides, and lithium oxides containing element A, and the element A includes one or more of Mg, Ca, Sr, Ba, Ti, Zr, V, Nb, Ta, Mo, W, La, Ce, Sc, and Cr; the flux of type b includes one or more of oxyacids and oxygen-containing salts containing boron or phosphorus elements;

[0016] Optionally, the ratio of the total molar amount of element A, boron element, and phosphorus element contained in the basic flux component to the total molar amount of element Z contained in the oxidizing component is (0.5 - 1.5):1.

[0017] In some embodiments, the pre-sintering treatment includes at least one of the following conditions (1)-(6):

[0018] (1) The lithium source includes one or more of lithium hydroxide monohydrate, anhydrous lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium oxalate, lithium fluoride, lithium chloride, lithium acetate, lithium sulfate, and lithium phosphate;

[0019] (2) The molar ratio of the lithium element contained in the lithium source to the total metal elements contained in the precursor is (0.95 - 1.20):1, and optionally (1.01 - 1.11):1;

[0020] (3) The temperature of the pre-sintering treatment is 500°C - 700°C, and optionally 600°C - 700°C;

[0021] (4) The time of the pre-sintering treatment is 2h - 7h, and optionally 4h - 6h;

[0022] (5) The heating rate of the pre-sintering treatment is 2°C / min - 20°C / min, and optionally 3°C / min - 10°C / min;

[0023] (6) The atmosphere of the pre-sintering treatment includes one or more of air and oxygen, and optionally air.

[0024] In some embodiments, the sintering treatment includes at least one of the following conditions (1)-(6):

[0025] (1) The stacking depth of the pre-sintered material in the sample loading container is 1cm - 30cm, and optionally 8cm - 20cm;

[0026] (2) The mass of the local oxygen-supplemented flux accounts for 0.3% - 1.8% of the mass of the pre-sintered material;

[0027] (3) The temperature of the sintering treatment is 700°C - 1000°C, and can be optionally 750°C - 850°C;

[0028] (4) The time of the sintering treatment is 6h - 20h, and can be optionally 10h - 14h;

[0029] (5) The heating rate of the pre-sintering treatment is 2°C / min - 15°C / min, and can be optionally 3°C / min - 10°C / min;

[0030] (6) The atmosphere of the sintering treatment includes one or more of air and oxygen, and can be optionally air.

[0031] The third aspect of the present application provides a positive electrode sheet, including the high-nickel single-crystal positive electrode material of the first aspect of the present application or the high-nickel single-crystal positive electrode material prepared by using the preparation method of the second aspect of the present application.

[0032] The fourth aspect of the present application provides a secondary battery, including the positive electrode sheet of the third aspect of the present application.

[0033] The fifth aspect of the present application provides an electrical device, including the secondary battery of the fourth aspect of the present application.

[0034] For the high-nickel single-crystal positive electrode material provided above, the surface Ni 3+ has a molar ratio as high as 38% - 55%, and the molar ratio of surface lattice oxygen is 7% - 15%. During the preparation process, nickel reduction and lattice oxygen precipitation are significantly inhibited, and the structural defects of the material are significantly reduced, thereby improving its specific capacity and enhancing its cycling performance.

[0035] In the preparation method of the high-nickel single-crystal positive electrode material provided by the present application, in addition to the basic functions of promoting particle growth, adjusting crystal planes and morphology, and reducing the sintering temperature possessed by conventional fluxes, the locally oxygen-supplemented flux also contains components with oxidizing properties that can decompose at high temperatures. During the sintering process, the locally high-oxidizing environment generated by its decomposition can be used to further inhibit nickel reduction and lattice oxygen precipitation, making the prepared high-nickel single-crystal positive electrode material have the advantages of reduced defects, optimized particle morphology and crystal structure, and improved electrochemical performance. At the same time, due to the reduction of the sintering temperature by this locally oxygen-supplemented flux and the problem of insufficient oxygen supply at the bottom of the loading container being alleviated by its locally oxygen-supplemented characteristics, the loading amount of the material for single sintering can be further increased, achieving the effects of improving production efficiency and reducing costs.

[0036] In addition, the dosage of the locally oxygen-supplemented flux is limited within a range equivalent to that of the doping and coating agents, and no additional washing process is required; it does not contain precious metal elements and other high-cost transition metal elements, making the additive cost of this method controllable. Description of the Drawings

[0037] To more clearly illustrate the technical solutions in the embodiments of the present application and more comprehensively understand the present application and its beneficial effects, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those skilled in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0038] Figure 1 SEM diagram of the high-nickel single-crystal cathode material in Example 1;

[0039] Figure 2 XRD diagram of the high-nickel single-crystal cathode material in Example 1;

[0040] Figure 3 Fine spectra of Ni 2p and O 1s in Example 1 and Comparative Example 1;

[0041] Figure 4 Charge-discharge curve of Example 1;

[0042] Figure 5 Cycling performance results of Example 1 and Comparative Example 1. Detailed implementation manners

[0043] To facilitate the understanding of the present invention, the following will describe the present application more comprehensively with reference to relevant embodiments. The following gives the preferred embodiments of the present application. However, the present application can be implemented 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 content of the present application more thorough and comprehensive.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used in the description of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0045] The selection scope of the terms "and / or", "or / and", and "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of the related listed items. The said any and all combinations include any two related listed items, any more related listed items, or the combination of all related listed items. It should be noted that when connecting at least three items with at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that in the present application, this technical solution undoubtedly includes the technical solution connected by "logical AND", and also undoubtedly includes the technical solution connected by "logical OR".

[0046] In this application, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, as well as an open technical solution containing the listed features.

[0047] In this application, regarding numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous, and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0048] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly recorded; and any lower limit can be combined with other lower limits to form a range not explicitly recorded. Similarly, any upper limit can be combined with any other upper limit to form a range not explicitly recorded. In addition, each individually disclosed point or single numerical value itself can be used as a lower limit or upper limit and combined with any other point or single numerical value or combined with other lower limits or upper limits to form a range not explicitly recorded.

[0049] The temperature parameter in this application, unless otherwise specifically limited, allows both constant temperature treatment and treatment within a certain temperature range. The said constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuation within a range such as ±5°C, ±4°C, ±3°C, ±2°C, ±1°C is allowed.

[0050] In this application, unless otherwise specifically limited, when referring to dimensions, particle sizes, diameters, it generally refers to the average value. In this application, "particle size" and "particle diameter" have the same definition, both representing the average particle diameter of spheres or sphere-like objects.

[0051] In this document, the "suitable combination method", "suitable method", "any suitable method", etc., the "suitable" mentioned therein is subject to being able to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0052] In this application, "further", "even further", "especially", etc. are used for descriptive purposes, indicating differences in content, but should not be understood as limiting the protection scope of this application.

[0053] In this application, "optionally", "optional", "option", mean having or not having, that is, it refers to any one of the two alternative schemes of "having" or "not having". If "optional" appears multiple times in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction relationship, each "optional" is independent of each other.

[0054] In the description of the application, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0055] If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0056] If there is no special explanation, all the steps of the present application can be performed sequentially or randomly, preferably sequentially.

[0057] When preparing high-nickel single crystal positive electrode materials, in order to make the primary particles fully grow and separate to form a single crystal form, a higher sintering temperature is required during the preparation process. As a result, the unstable LiNiO2 structure in the high-nickel layered material undergoes lattice oxygen precipitation accompanied by nickel reduction during the sintering process, leading to structural defects such as cation mixing and inactive phase transition in the crystal structure, which has an adverse effect on the specific capacity and cycle life of the material.

[0058] At present, the measures commonly taken by the industry to alleviate the defect problem of high-nickel single crystal materials are: (1) lowering the sintering temperature: using appropriate flux to lower the sintering temperature, thereby inhibiting the lattice oxygen precipitation of high-nickel single crystal materials and the structural defects induced by it; (2) ensuring sufficient oxygen supply: using a pure oxygen atmosphere and limiting the charging depth during the sintering process to ensure that oxygen can diffuse to the bottom of the sagger, increase the local oxygen concentration, allow the material to fully contact with oxygen, promote the movement of chemical equilibrium, and thus inhibit the lattice oxygen precipitation. However, measure (2) will limit the amount of material charged in a single sintering, which is not conducive to increasing production capacity and reducing costs.

[0059] The use of common flux in measure (1) cannot solve the problem of insufficient oxygen supply to the material at the bottom of the sagger and limited loading depth. On the contrary, the formation of a eutectic by the material at the top may further hinder the diffusion of oxygen to the bottom of the sagger.

[0060] Based on the above problems, this application studies the process parameters such as flux composition, addition amount and material loading amount, and prepares a high-nickel single crystal positive electrode material with reduced structural defects, improved particle morphology and crystal structure, and enhanced electrical performance.

[0061] The first aspect of the present application provides a high-nickel single crystal positive electrode material, the chemical formula of the high-nickel single crystal positive electrode material is Li 1+δ Ni x M y Q 1-x-y O 2+ε A α R β X γ, 0.8 ≤ x < 1, 0 < y ≤ 0.2, 0 ≤ δ ≤ 0.15, 0 < ε ≤ 0.2, 0 < α ≤ 0.04, 0 < β ≤ 0.04, 0 ≤ γ ≤ 0.04, element M and element Q each independently include one or more of Mn, Co, Al, Ta, Ti, Nb, Ge, Y, W, Zr, Ce, Ca, Sr, Sc, V, Cr, and Mo; element A includes one or more of Mg, Ca, Sr, Ba, Ti, Zr, V, Nb, Ta, Mo, W, La, Ce, Sc, and Cr; element R includes one or more of B and P; element X includes one or more of Na, K, Mn, Mg, Ca, Sr, and Al; the surface Ni 3+ has a molar ratio of 38% - 55%, and the molar ratio of surface lattice oxygen is 7% - 15%.

[0062] As an example, the surface Ni 3+ molar ratio of the high-nickel single-crystal cathode material can be, but is not limited to, 38%, 38.5%, 39%, 39.5%, 40%, 40.5%, 41%, 41.5%, 42%, 42.5%, 43%, 43.5%, 44%, 44.5%, 45%, 45.5%, 46%, 46.5%, 47%, 47.5%, 48%, 48.5%, 49%, 49.5%, 50%, 50.5%, 51%, 51.5%, 52%, 52.5%, 53%, 53.5%, 54%, 54.5%, 55% or the range between any two of the above values, etc.

[0063] The molar ratio of surface lattice oxygen of the high-nickel single-crystal cathode material can be, but is not limited to, 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 the range between any two of the above values, etc.

[0064] It can be understood that the molar ratio of surface Ni3+ of the high-nickel single-crystal cathode material is as high as 38% - 55%, and the molar ratio of surface lattice oxygen is 7% - 15%. During the preparation process, nickel reduction and lattice oxygen precipitation are significantly inhibited, and the structural defects of the material are significantly reduced, thereby improving its specific capacity and enhancing its cycling performance.

[0065] It should be noted that the surface Ni 3+The molar ratio and the molar ratio of surface lattice oxygen can be measured by X-ray photoelectron spectroscopy (XPS). The measurement process can be as follows: Using Al-Kα as the ray source (energy hν = 1486.6 eV), and using the binding energy of the C1s peak at 284.80 eV as the charge correction standard; further analyzing the two fine spectra of Ni 2p and O 1s, and performing deconvolution processing according to the unified characteristic peak positions to obtain the relative proportions of the following chemical states, based on Ni 3+ / (Ni 3+ + Ni 2+ ), O 吸附 / (O 吸附 + O 晶格 ) to calculate the molar ratio of surface Ni 3+ and the molar ratio of surface lattice oxygen; and through the ratio of Ni 3+ / (Ni 3+ + Ni 2+ ), the ratio of O 吸附 / (O 吸附 + O 晶格 ) reflects the degree of nickel reduction and lattice oxygen precipitation.

[0066] In some embodiments, the length of the primary particles of the high-nickel single-crystal cathode material is denoted as L, the width is denoted as W, and W / L is 0.7 - 0.85; for example, it can be but not limited to 0.7, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.8, 0.81, 0.82, 0.83, 0.84, 0.85 or the range between any two of the above values, etc. When the ratio of the length L to the width W is within the above range, it indicates that the particle morphology of the high-nickel single-crystal cathode material is optimized, which is beneficial to improving the reversible capacity and cycle stability of the material.

[0067] It should be noted that the primary particles of the high-nickel single-crystal cathode material are converted into a rectangle with equal area and the closest shape. The long side of the rectangle is the length L, and the short side is the width W.

[0068] In some alternative embodiments, the length L of the primary particles of the high-nickel single-crystal cathode material is 1300 nm - 2000 nm; for example, it can be, but is not limited to, 1300 nm, 1350 nm, 1400 nm, 1450 nm, 1500 nm, 1550 nm, 1600 nm, 1650 nm, 1700 nm, 1750 nm, 1800 nm, 1850 nm, 1900 nm, 1950 nm, 2000 nm, or the range between any two of the above lengths, etc. When the length L is within the above range, the contact area between the high-nickel single-crystal cathode material particles and the electrolyte is appropriate, which is sufficient for lithium ions to undergo insertion / extraction reactions and can avoid excessive surface side reactions, thereby improving the cycle performance of the battery.

[0069] As a possible embodiment, the length L of the primary particles of the high-nickel single-crystal cathode material is 900 nm - 1500 nm; for example, it can be, but is not limited to, 900 nm, 950 nm, 1000 nm, 1050 nm, 1100 nm, 1150 nm, 1200 nm, 1250 nm, 1300 nm, 1350 nm, 1400 nm, 1450 nm, 1500 nm, or the range between any two of the above lengths, etc. When the width W is within the above range, the contact area between the high-nickel single-crystal cathode material particles and the electrolyte is appropriate, which is sufficient for lithium ions to undergo insertion / extraction reactions and can avoid excessive surface side reactions, thereby improving the cycle performance of the battery.

[0070] As an example, the length L, width W, and the ratio of width to length W / L of the primary particles of the above-mentioned high-nickel single-crystal cathode material can be measured by a field emission scanning electron microscope.

[0071] In some embodiments, in the XRD pattern of the high-nickel single-crystal cathode material, the diffraction peak intensities I (003) and I (104) between the crystal planes (003) and (104) satisfy the following relationship: 1.3 ≤ I (003) / I (104) ≤ 2. As an example, I (003) / I (104) can be, but is not limited to, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or the range between any two of the above values, etc. When I (003) / I (104) is within the above range, it indicates that the crystal structure of the high-nickel single-crystal cathode material is effectively optimized, which is beneficial to improving the reversible capacity and cycle stability of the material.

[0072] It should be noted that the above-mentioned I (003) and I (104)It can be measured by powder X-ray diffraction. The specific measurement process can be as follows: Use Cu-Kα ray as the radiation source, with a wavelength of 0.154 nm (the test data does not remove Kα2), the accelerating voltage and current are 40 kV and 100 mA respectively, scan in the range of 10° - 80° at a rate of 5 ° / min, and calculate the area ratio I (003) / I (104) .

[0073] The second aspect of the present application provides a preparation method of the high-nickel single-crystal cathode material of the first aspect of the present application, including the following steps:

[0074] Prepare a local oxygen-supplementing flux including a basic flux component and an oxidizing component; the oxidizing component can generate an oxidizing gas under heating conditions; the elements contained in the basic flux component include element A and element R, and the elements contained in the oxidizing component include element X;

[0075] Perform pre-sintering treatment on the powder mixture including a lithium source and a precursor to prepare a pre-sintered material; the chemical formula of the precursor is Ni c M d Q 1-c-d (OH)2, 0.8 ≤ c < 1, 0 < d ≤ 0.2, element M and element Q each independently include one or more of Mn, Co, Al, Ta, Ti, Nb, Ge, Y, W, Zr, Ce, Ca, Sr, Sc, V, Cr, and Mo;

[0076] Mix the local oxygen-supplementing flux and the pre-sintered material and place them in a sample container, and perform sintering treatment to prepare a high-nickel single-crystal cathode material; wherein, the mass of the local oxygen-supplementing flux accounts for 0.1% - 4% of the mass of the pre-sintered material.

[0077] It should be noted that the basic flux component is a substance with functions such as promoting particle growth, regulating particle shape, and reducing the sintering temperature. Adding the basic flux during the preparation process can promote particle growth, regulate particle shape, reduce the sintering temperature, etc.

[0078] Understandably, in addition to the basic functions of promoting particle growth, regulating crystal planes and morphology, and reducing the sintering temperature that conventional fluxes possess, the locally oxygen-supplemented flux used in the application also contains components with oxidizing properties that can decompose at high temperatures. During the sintering process, the locally high-oxidizing environment generated by their decomposition can be used to further inhibit nickel reduction and lattice oxygen precipitation, enabling the prepared high-nickel single-crystal cathode material to have the advantages of reduced defects, optimized particle morphology and crystal structure, and improved electrochemical performance. At the same time, since this locally oxygen-supplemented flux reduces the sintering temperature and its locally oxygen-supplementing characteristic alleviates the problem of insufficient oxygen supply to the material at the bottom of the loading container, the loading amount of the material for a single sintering can be further increased, achieving the effects of improving production efficiency and reducing costs.

[0079] In addition, the dosage of the locally oxygen-supplemented flux is limited to a range equivalent to that of the doping and coating agents, and no additional washing process is required; it does not contain precious metal elements and other high-cost transition metal elements, making the additive cost of this method controllable.

[0080] As an example, the percentage of the mass of the locally oxygen-supplemented flux in the mass of the pre-sintered material can be, but is not limited to, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or the range between any two of the above values, etc. When the dosage of the locally oxygen-supplemented flux is within the above range, oxidizing gases can be decomposed during the sintering process to solve the problem that oxygen is difficult to diffuse to the surface of the material (especially the material at the bottom of the container), provide sufficient oxygen concentration for it, effectively inhibit nickel reduction and lattice oxygen precipitation, reduce defects, optimize particle morphology and crystal structure, and improve electrochemical performance; on the other hand, it can also avoid the problem of reduced electrochemical performance caused by excessive electrochemically inert residues.

[0081] As an example, when performing the sintering treatment, the percentage of the mass of the locally oxygen-supplemented flux in the mass of the pre-sintered material can be, but is not limited to, 0.4% - 1.8%, 0.8% - 1.8%, 1.2% - 1.8%, 0.4% - 1.2%, 0.8% - 1.2%, or 0.4% - 0.8%, etc.

[0082] As a possible implementation manner, the basic flux components include one or more of type-a fluxes and type-b fluxes; type-a fluxes include one or more of oxides, hydroxides, carbonates, sulfates, chlorides, and lithium oxides containing element A, and element A includes one or more of Mg, Ca, Sr, Ba, Ti, Zr, V, Nb, Ta, Mo, W, La, Ce, Sc, and Cr; type-b fluxes include one or more of oxyacids and oxysalts containing boron or phosphorus elements.

[0083] In some of these embodiments, the ratio of the total molar amount of element A, boron element, and phosphorus element contained in the basic flux component to the total molar amount of element Z contained in the oxidizing component is (0.5 - 1.5):1; for example, it can be but is not limited to 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, or the range between any two of the above ratios, etc. Thus, the basic flux component and the oxidizing component in the local oxygen-supplementing flux both contain appropriate ratios and play the above-mentioned roles respectively, thereby obtaining the beneficial effects of reducing the sintering temperature and improving the electrochemical performance.

[0084] In some alternative embodiments, the oxidizing component includes one or more of peroxides, superoxides, nitrates, nitrites, hypochlorites, chlorates, perchlorates, manganates, and permanganates of element Z, and the element Z includes one or more of Li, Na, K, Mg, Ca, Sr, and Al.

[0085] In some embodiments, when performing the pre-sintering treatment, the lithium source includes one or more of lithium hydroxide monohydrate, anhydrous lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium oxalate, lithium fluoride, lithium chloride, lithium acetate, lithium sulfate, and lithium phosphate.

[0086] In some exemplary embodiments, when performing the pre-sintering treatment, the molar ratio of the lithium element contained in the lithium source to the total metal elements contained in the precursor is (0.95 - 1.20):1; for example, it can be but is not limited to 0.95:1, 0.97:1, 1:1, 1.03:1, 1.05:1, 1.08:1, 1.1:1, 1.13:1, 1.15:1, 1.18:1, 1.2:1, or the range between any two of the above ratios, etc. Optionally, the molar ratio of the lithium element contained in the lithium source to the total metal elements contained in the precursor is (1.01 - 1.11):1.

[0087] In some of these embodiments, when performing the pre-sintering treatment, the temperature of the pre-sintering treatment is 500°C - 700°C; for example, it can be but is not limited to 500°C, 530°C, 550°C, 570°C, 600°C, 630°C, 650°C, 680°C, 700°C, or the range between any two of the above temperatures, etc. Optionally, the temperature of the pre-sintering treatment is 600°C - 700°C. When the temperature of the pre-sintering treatment is within the above range, the moisture in the material can be removed sufficiently in advance, its density can be increased, thereby increasing the material loading amount and yield of the subsequent sintering process and improving the production capacity. Optionally, the temperature of the pre-sintering treatment is 600°C - 700°C.

[0088] As a possible implementation, when performing pre-sintering treatment, the time of the pre-sintering treatment is 2h - 7h; for example, it can be, but is not limited to, 2h, 3h, 4h, 5h, 6h, 7h, or the range between any two of the above times, etc. Optionally, the time of the pre-sintering treatment is 4h - 6h.

[0089] In some alternative implementations, when performing pre-sintering treatment, the heating rate of the pre-sintering treatment is 2°C / min - 20°C / min; for example, it can be, but is not limited to, 2°C / min, 5°C / min, 7°C / min, 10°C / min, 13°C / min, 15°C / min, 18°C / min, 20°C / min, or the range between any two of the above heating rates, etc. Optionally, the heating rate of the pre-sintering treatment is 3°C / min - 10°C / min.

[0090] In some implementations, the atmosphere of the pre-sintering treatment includes one or more of air and oxygen. Optionally, the atmosphere of the pre-sintering treatment is air.

[0091] As an example, the air is dry air.

[0092] It should be noted that the temperature, time, heating rate, and atmosphere of the pre-sintering treatment can be combined in any suitable manner, and the four can be selected respectively from any of the temperatures, times, heating rates, and atmospheres of the pre-sintering treatment described herein.

[0093] In some implementations, when performing sintering treatment, the stacking depth of the pre-sintered material in the sample loading container is 1cm - 30cm; the sample loading amount is increased, achieving the effects of improving production efficiency and reducing costs. As an example, the stacking depth can be, but is not limited to, 1cm, 2cm, 3cm, 4cm, 5cm, 6cm, 7cm, 8cm, 9cm, 10cm, 11cm, 12cm, 13cm, 14cm, 15cm, 16cm, 17cm, 18cm, 19cm, 20cm, 21cm, 22cm, 23cm, 24cm, 25cm, 26cm, 27cm, 28cm, 29cm, 30cm, or the range between any two of the above depths, etc.

[0094] As an example, the stacking depth of the pre-sintered material in the sample loading container can be, but is not limited to, 9cm - 18cm, 12cm - 18cm, 6cm - 18cm, 6cm - 12cm, 6cm - 9cm, or 9cm - 12cm, etc.

[0095] Optionally, the stacking depth of the pre-sintered material in the sample loading container is 8cm - 20cm. Further optionally, the stacking depth of the pre-sintered material in the sample loading container is 9cm - 18cm. More optionally, the stacking depth of the pre-sintered material in the sample loading container is 12cm - 18cm.

[0096] During the sintering process, compared with the case of not adding an oxidizing component, by adding a local oxygen supplement flux, the lattice oxygen precipitation can be inhibited to reduce defects. On the premise that the sintered product has the same degree of defects (surface nickel valence ratio, lattice oxygen ratio, (003) / (104) peak intensity ratio), the stacking depth of the raw material can be increased by 5 cm - 12 cm, improving production efficiency. When the stacking depth ≥ 8 cm and other conditions are the same, compared with the case of not adding an oxidizing component, the surface Ni 3+ molar ratio increases by 5% - 20 percentage points, and the molar ratio of surface lattice oxygen increases by 2% - 10%.

[0097] As a possible implementation, the sample loading container is a sagger.

[0098] In some alternative implementations, when performing the sintering treatment, the mass of the local oxygen supplement flux accounts for 0.3% - 1.8% of the mass of the pre-sintered material.

[0099] As a possible implementation, when performing the sintering treatment, the temperature of the sintering treatment is 700°C - 1000°C; for example, it can be but not limited to 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C or the range between any two of the above temperatures, etc. When the temperature of the sintering treatment is within the above range, the primary particles can grow fully and separate to form a single crystal morphology, the particle size is within the above range, and the nickel reduction and lattice oxygen precipitation caused by too high sintering temperature can be avoided. Optionally, the temperature of the sintering treatment is 750°C - 850°C.

[0100] As an example, when performing the sintering treatment, the temperature of the sintering treatment can be 800°C - 840°C, 800°C - 820°C or 820°C - 840°C, etc., and there is no specific limitation.

[0101] It should be noted that compared with not adding the local oxygen supplement flux, when other conditions are the same, adding the local oxygen supplement flux can reduce the temperature of the sintering treatment by 50°C - 100°C through its effects of promoting growth and regulating the growth direction, optimize the particle morphology and crystal structure of the high-nickel single crystal material, improve its reversible capacity and cycle stability, and reduce the processing cost.

[0102] In some alternative embodiments, during the sintering process, the sintering time is 6h - 20h; for example, it can be, but is not limited to, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, or the range between any two of the above times, etc. When the sintering time is within the above range, the primary particles can grow and separate sufficiently to form a single crystal morphology, and the particle size is within the above range. Optionally, the sintering time is 10h - 14h.

[0103] In some exemplary embodiments, during the sintering process, the heating rate of the sintering process is 2℃ / min - 15℃ / min; for example, it can be, but is not limited to, 2℃ / min, 5℃ / min, 7℃ / min, 10℃ / min, 13℃ / min, 15℃ / min, or the range between any two of the above heating rates, etc. Optionally, the heating rate of the sintering process is 3℃ / min - 10℃ / min.

[0104] In some embodiments, the atmosphere for the sintering process includes one or more of air and oxygen. Optionally, the atmosphere for the sintering process is air. Further optionally, the atmosphere for the sintering process is dry air.

[0105] It should be noted that the temperature, time, heating rate, and atmosphere of the sintering process can be combined in any suitable manner, and the four can be selected respectively from any of the temperatures, times, heating rates, and atmospheres of the sintering processes described herein.

[0106] The third aspect of the present application provides a positive electrode sheet, including the high-nickel single-crystal cathode material of the first aspect or the high-nickel single-crystal cathode material prepared by using the preparation method of the second aspect.

[0107] The fourth aspect of the present application provides a secondary battery, including the positive electrode sheet of the third aspect.

[0108] The secondary battery of the present application contains the above-mentioned high-nickel single-crystal cathode material, and has a relatively high specific capacity and excellent cycling performance.

[0109] The fifth aspect of the present application provides an electrical device, including the secondary battery of the fourth aspect. The electrical device can be an electric vehicle, an electric bicycle, an electric two-wheeler, an electric vehicle power system, an energy storage system, a mobile storage device, etc., and is not specifically limited.

[0110] The electrical device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.

[0111] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. For the experimental methods without specific conditions indicated in the following embodiments, the guidelines given in the present invention shall be preferentially referred to, and it is also possible to follow the experimental manuals or conventional conditions in the art, or the conditions recommended by the manufacturer, or refer to the experimental methods known in the art.

[0112] In the following specific embodiments, for the measurement parameters of the raw material components, if not otherwise specified, there may be slight deviations within the weighing accuracy range. For the temperature and time parameters, acceptable deviations caused by instrument test accuracy or operation accuracy are allowed.

[0113] I. Preparation of high-nickel single-crystal cathode material

[0114] Example 1

[0115] Step S1. Weigh the basic flux components Sr(OH)2, H3BO3, (NH4)2HPO4 and the oxidizing components Li2O2, LiClO4, and the amounts are calculated according to the molar ratio of Sr, B, P, Li, and Li atoms of 1:1:1:2:2 respectively, and mix them evenly to obtain a local oxygen-supplemented flux.

[0116] Step S2. Weigh 913.31 g of the lithium source LiOH·H2O and 1933.58 g of the precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 according to the molar ratio of lithium element in the lithium source to the total metal elements in the precursor of 1.06, stir and mix in a mixing device at 3000 rpm for 4 min to obtain a uniformly mixed material, load it into a crucible, put it into a sintering furnace for pre-sintering treatment, and crush the product of the pre-sintering treatment to obtain a pre-sintered material. The temperature of the pre-sintering treatment is 625 °C, the time is 6 h, the heating rate is 3 °C / min, the pre-sintering atmosphere is dry compressed air, and the gas flow rate is 3 L / min.

[0117] Step S3. Add a local oxygen-supplemented flux with a mass of 0.8% of the pre-sintered material, stir and mix in a mixing device at 2000 rpm for 4 min, and divide it into crucibles of appropriate size so that the depth of the material is 12 cm. Put the crucible into a sintering furnace for sintering treatment to obtain a high-nickel single-crystal cathode material. The parameters of the sintering treatment are: the temperature of the sintering treatment is 820 °C, the time is 10 h, the heating rate is 5 °C / min, the atmosphere is pure oxygen (oxygen content ≥ 97%), and the gas flow rate is 4 L / min. The sintered product is crushed and screened to obtain the product. Physical and chemical characterization and electrochemical performance tests are carried out.

[0118] Example 2

[0119] The difference between Example 2 and Example 1 is that: in step S3, the sintering temperature is 800 °C, and the others are the same.

[0120] Example 3

[0121] The difference between Example 3 and Example 1 is that: in step S3, the sintering temperature is 840 °C, and the others are the same.

[0122] Example 4

[0123] The difference between Example 4 and Example 3 is that: in step S3, the mass of the locally added oxygen-supplementing flux is 1.2% of the pre-sintered material, and the others are the same.

[0124] Example 5

[0125] The difference between Example 5 and Example 3 is that: in step S3, the mass of the locally added oxygen-supplementing flux is 0.4% of the pre-sintered material, and the others are the same.

[0126] Example 6

[0127] The difference between Example 6 and Example 1 is that: in step S3, the depth of the material in the sagger is 9 cm, and the others are the same.

[0128] Example 7

[0129] The difference between Example 7 and Example 1 is that: in step S3, the depth of the material in the sagger is 6 cm, and the others are the same.

[0130] Example 8

[0131] The difference between Example 8 and Example 1 is that: in step S1. Weigh the basic flux components BaCO3, TiO2, LiBO2 and the oxidizing components LiNO3, NaNO3, and the dosages are calculated according to the molar ratio of Ba, Ti, B, Li, and Na atoms of 1:1:1:2:2 respectively, and mix them evenly to obtain the locally added oxygen-supplementing flux. The others are the same.

[0132] Example 9

[0133] The difference between Example 9 and Example 1 is that: in step S1. Weigh the basic flux components Mg(OH)2, ZrO2, Li3PO4 and the oxidizing components KMnO4, NaClO4, and the dosages are calculated according to the molar ratio of Mg, Zr, P, K, and Na atoms of 1:1:1:2:2 respectively, and mix them evenly to obtain the locally added oxygen-supplementing flux. The others are the same.

[0134] Example 10

[0135] Example 10 is different from Example 1 in that: In step S1, the basic flux components Sr(OH)2, H3BO3, (NH4)2HPO4 and the oxidizing components Li2O2, Na2O2 are weighed, and the amounts are calculated according to the molar ratios of Sr, B, P, Li, and Na atoms of 1:1:1:2:2 respectively, and then mixed evenly to obtain a local oxygen-supplementing flux. Others are the same.

[0136] Example 11

[0137] Example 11 is different from Example 1 in that: In step S1, the basic flux components Sr(OH)2, H3BO3, (NH4)2HPO4 and the oxidizing components Li2O2, LiNO3 are weighed, and the amounts are calculated according to the molar ratios of Sr, B, P, Li, and Li atoms of 1:1:1:2:2 respectively, and then mixed evenly to obtain a local oxygen-supplementing flux. Others are the same.

[0138] Example 12

[0139] Example 12 is different from Example 1 in that: In step S3, the mass of the local oxygen-supplementing flux added is 1.8% of the pre-sintered material. Others are the same.

[0140] Example 13

[0141] Example 13 is different from Example 1 in that: In step S3, the depth of the material in the sagger is 18 cm. Others are the same.

[0142] Comparative Example 1

[0143] The difference between Comparative Example 1 and Example 1 is that: In step S3, no flux is added, and the sintering temperature is 880 °C. Others are the same.

[0144] Comparative Example 2

[0145] The difference between Comparative Example 2 and Example 1 is that: In step S1, no oxidizing component is added when preparing the flux, in step S3, the sintering temperature is 840 °C, and the depth of the material in the sagger is 12 cm. Others are the same.

[0146] Comparative Example 3

[0147] The difference between Comparative Example 3 and Example 1 is that: In step S1, no oxidizing component is added when preparing the flux, in step S3, the sintering temperature is 840 °C, and the depth of the material in the sagger is 6 cm. Others are the same.

[0148] Comparative Example 4

[0149] The difference between Comparative Example 4 and Example 1 is that: In step S1, no oxidizing component is added when preparing the flux. Others are the same.

[0150] Comparative Example 5

[0151] The difference between Comparative Example 5 and Example 1 is as follows: in step S1, no oxidizing component is added when preparing the flux, and the sintering temperature in step S3 is 800 °C. Others are the same.

[0152] Comparative Example 6

[0153] The difference between Comparative Example 6 and Example 1 is as follows: the mass of the local oxygen-supplemented flux added in step S3 is 5.0% of the pre-sintered material, and others are the same.

[0154] II. Morphology, Size and Crystal Structure Characterization of the Cathode Material

[0155] The cathode material was observed using a field emission scanning electron microscope. For micrographs at an appropriate magnification, the length L and width W of each visible primary particle were measured and counted (the particle was converted into a rectangle with equal area and the closest shape, the long side of the rectangle was the length L, and the short side was the width W), and the ratio W / L of the two was calculated. The test results of Examples 1-11 and Comparative Examples 1-5 are shown in Table 1. The observation result of the scanning electron microscope of Example 1 is as Figure 1 shown. It can be Figure 1 seen that the primary particles of the high-nickel single-crystal cathode material prepared in Example 1 have fully grown to an appropriate size range and are separated.

[0156] The cathode material was tested using a powder X-ray diffractometer. Cu-Kα rays were used as the radiation source, with a wavelength of 0.154 nm (the test data was not corrected for Kα2), the accelerating voltage and current were 40 kV and 100 mA respectively, and the scan was performed at a rate of 5 ° / min in the range of 10° - 80 °. The area ratio I (003) / I (104) of the (003) peak and the (104) peak in the obtained curve was calculated. The test results of Examples 1-11 and Comparative Examples 1-5 are shown in Table 1. The XRD pattern of Example 1 is as Figure 2 shown. It can be Figure 2 seen that the high-nickel single-crystal cathode material prepared in Example 1 has a typical α-NaFeO2-type layered crystal structure, belonging to the hexagonal crystal system, the R-3m space group, and the two strongest diffraction peaks are the (003) crystal plane peak near 18.7° and the (104) crystal plane peak near 44.3° respectively.

[0157] Table 1

[0158]

[0159] III. Surface Chemical Valence State Test of the Cathode Material

[0160] The cathode material was tested using an X-ray photoelectron spectrometer (XPS). During the test, Al-Kα was used as the ray source (energy hν = 1486.6 eV), and the binding energy of the C1s peak at 284.80 eV was used as the charge correction standard. Further analysis was performed on the two fine spectra of Ni 2p and O 1s, and deconvolution was carried out according to the unified characteristic peak positions to obtain the relative proportions of the following chemical states. Among them, Ni 2+ and Ni 3+ , O 吸附 and O 晶格 The characteristic peak positions of are defined as 855.1 ± 0.1 eV, 856.5 ± 0.1 eV, 531.6 ± 0.1 eV, and 529.0 ± 0.1 eV, respectively. Through Ni 3+ / (Ni 3+ + Ni 2+ ) ratio, O 吸附 / (O 吸附 + O 晶格 ) ratio reflects the degree of nickel reduction and lattice oxygen evolution. The results are shown in Table 2. The Ni 2p and O 1s fine spectra of Example 1 and Comparative Example 1 are as shown in Figure 3 . Figure 3 In (a) is the Ni 2p fine spectrum of Example 1 and Comparative Example 1, Figure 3 In (b) is the O 1s fine spectrum of Example 1 and Comparative Example 1.

[0161] Table 2

[0162]

[0163] As can be seen from the results in Table 2, the molar proportion of surface Ni 3+ in Examples 1-13 is higher than that in Comparative Examples 1-5. At the same time, the molar proportion of surface lattice oxygen in the examples is generally higher than that in the comparative examples, indicating that the local oxygen supplement flux plays a role in inhibiting nickel reduction and oxygen evolution, especially in the case of a large material depth.

[0164] In Comparative Example 6, the molar proportion of surface Ni 3+ is the highest, while the molar proportion of surface lattice oxygen is the lowest. Analyzing the reason may be that: the local oxygen supplement flux is added in excess, resulting in too much surface attachment (manifested as adsorbed oxygen in the O 1s spectrum of XPS), which increases the relative proportion of adsorbed oxygen and decreases the relative proportion of lattice oxygen in the test results.

[0165] IV. Electrochemical performance test

[0166] The positive electrode material, PVDF binder, conductive carbon black, and N-methylpyrrolidone solvent were thoroughly stirred and mixed in a mass ratio of 100:4.3:3.8:137 to form a uniform slurry, which was evenly coated on one side of the aluminum foil. After drying, compaction, and punching processes, a button cell positive electrode sheet was made. Using the lithium sheet as the negative electrode and the positive electrode sheet as the positive electrode respectively, a button cell was assembled. Charge-discharge specific capacity and cycle performance tests were carried out at room temperature, and the voltage range was 3.0V - 4.3V. The results are shown in Table 3. The charge-discharge curve of Example 1 is as Figure 4 shown. The cycle performance results of Example 1 and Comparative Example 1 are as Figure 5 shown.

[0167] Table 3

[0168]

[0169] From the results in Tables 1 - 3, it can be seen that the high-nickel single-crystal positive electrode material provided by this application has a relatively high surface Ni 3+ molar ratio and surface lattice oxygen molar ratio, which are 38% - 55% and 7% - 15% respectively. The length L and width W of the primary particles of the material satisfy 0.7 ≤ W / L ≤ 0.85. The ratio of the diffraction peak intensities I (003) / I (104) of crystal planes (003) and (104) in the XRD pattern of the material is 1.3 - 2; that is, the structural defects of the high-nickel single-crystal positive electrode material are significantly reduced, the particle morphology and crystal structure are significantly improved, and both the reversible capacity and cycle stability are significantly enhanced.

[0170] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope described in this specification.

[0171] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A high-nickel single-crystal cathode material, characterized in that, The chemical formula of the high-nickel single-crystal cathode material is Li 1+δ Ni x M y Q 1-x-y O 2+ε A α R β X γ , 0.8 ≤ x < 1, 0 < y ≤ 0.2, 0 ≤ δ ≤ 0.15, 0 < ε ≤ 0.2, 0 < α ≤ 0.04, 0 < β ≤ 0.04, 0 ≤ γ ≤ 0.

04. The M element and the Q element each independently include one or more of Mn, Co, Al, Ta, Ti, Nb, Ge, Y, W, Zr, Ce, Ca, Sr, Sc, V, Cr, and Mo; the A element includes one or more of Mg, Ca, Sr, Ba, Ti, Zr, V, Nb, Ta, Mo, W, La, Ce, Sc, and Cr; the R element includes one or more of B and P; the X element includes one or more of Na, K, Mn, Mg, Ca, Sr, and Al; the molar ratio of Ni 3+ on the surface of the high-nickel single-crystal cathode material is 38% - 55%, and the molar ratio of lattice oxygen on the surface is 7% - 15%.

2. The high-nickel single-crystal cathode material according to claim 1, characterized in that The length of the primary particles of the high-nickel single-crystal cathode material is denoted as L, the width is denoted as W, and W / L is 0.7 - 0.85; wherein, the length L and width W of the primary particles of the high-nickel single-crystal cathode material respectively refer to the long side and short side of the rectangle when the primary particles of the high-nickel single-crystal cathode material are converted into a rectangle with equal area and the closest shape.

3. The high-nickel single-crystal cathode material according to claim 2, wherein L is 1300nm - 2000nm.

4. The high-nickel single-crystal cathode material according to claim 2, wherein, W is 900nm - 1500nm.

5. The high-nickel single-crystal cathode material according to any one of claims 1 to 4, characterized in that, In the XRD pattern of the high-nickel single-crystal cathode material, the diffraction peak intensities I of crystal plane (003) and crystal plane (104) (003) and I (104) satisfy the following relational expression: 1.3 ≤ I (003) / I (104) ≤ 2.

6. A method for preparing a high-nickel single-crystal cathode material according to any one of claims 1 to 5, characterized in that, It includes the following steps: Prepare a local oxygen-supplemented flux including a basic flux component and an oxidizing component; the oxidizing component can generate oxidizing gas under heating conditions; the elements contained in the basic flux component include the A element and the R element, and the elements contained in the oxidizing component include the X element; The powder mixture including a lithium source and a precursor is subjected to a pre-sintering treatment to prepare a pre-sintered material; the chemical formula of the precursor is Ni c M d Q 1-c-d (OH)2, 0.8 ≤ c < 1, 0 < d ≤ 0.2, and the M element and the Q element each independently include one or more of Mn, Co, Al, Ta, Ti, Nb, Ge, Y, W, Zr, Ce, Ca, Sr, Sc, V, Cr, and Mo; Mix the local oxygen-supplemented flux and the pre-sintered material and place them in a sample container, and perform sintering treatment to prepare the high-nickel single-crystal cathode material; Among them, the mass of the local oxygen-supplemented flux accounts for 0.1% - 4% of the mass of the pre-sintered material.

7. The preparation method according to claim 6, characterized in that, The oxidizing component includes one or more of peroxides, superoxides, nitrates, nitrites, hypochlorites, chlorates, perchlorates, manganates, and permanganates of the Z element, and the Z element includes one or more of Li, Na, K, Mg, Ca, Sr, and Al; and / or The basic flux component includes one or more of a-type fluxes and b-type fluxes; the a-type flux includes one or more of oxides, hydroxides, carbonates, sulfates, chlorides, and lithium oxides containing the A element, and the A element includes one or more of Mg, Ca, Sr, Ba, Ti, Zr, V, Nb, Ta, Mo, W, La, Ce, Sc, and Cr; the b-type flux includes one or more of oxyacids and oxysalts containing boron or phosphorus elements.

8. The preparation method according to claim 7, wherein, The ratio of the total molar amount of the A element, boron element, and phosphorus element contained in the basic flux component to the total molar amount of the Z element contained in the oxidizing component is (0.5 - 1.5):

1.

9. The preparation method according to any one of claims 6 to 8, characterized in that, The pre-sintering treatment includes at least one of the following conditions (1) - (6): (1) The lithium source includes one or more of lithium hydroxide monohydrate, anhydrous lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium oxalate, lithium fluoride, lithium chloride, lithium acetate, lithium sulfate, and lithium phosphate; (2) The molar ratio of the lithium element contained in the lithium source to the total metal elements contained in the precursor is (0.95 - 1.20):1; (3) The temperature of the pre-sintering treatment is 500°C - 700°C; (4) The time of the pre-sintering treatment is 2h - 7h; (5) The heating rate of the pre-sintering treatment is 2°C / min - 20°C / min; (6) The atmosphere of the pre-sintering treatment includes one or more of air and oxygen.

10. The preparation method according to claim 9, characterized in that, The molar ratio of the lithium element contained in the lithium source to the total metal elements contained in the precursor is (1.01 - 1.11):

1.

11. The preparation method according to claim 9, characterized in that, The temperature of the pre-sintering treatment is 600°C - 700°C.

12. The preparation method according to claim 9, characterized in that, The time of the pre-sintering treatment is 4h - 6h.

13. The preparation method according to claim 9, characterized in that, The heating rate of the pre-sintering treatment is 3°C / min - 10°C / min.

14. The preparation method according to claim 9, characterized in that, The atmosphere of the pre-sintering treatment is air.

15. The preparation method according to any one of claims 6 to 8, characterized in that, The sintering treatment includes at least one of the following conditions (1) - (6): (1) The stacking depth of the pre-sintered material in the sample loading container is 1 cm - 30 cm; (2) The mass of the local oxygen supplementing flux accounts for 0.3% - 1.8% of the mass of the pre-sintered material; (3) The temperature of the sintering treatment is 700°C - 1000°C; (4) The time of the sintering treatment is 6h - 20h; (5) The heating rate of the sintering treatment is 2°C / min - 15°C / min; (6) The atmosphere of the sintering treatment includes one or more of air and oxygen.

16. The preparation method according to claim 15, characterized in that, The stacking depth of the pre-sintered material in the sample loading container is 8 cm - 20 cm.

17. The preparation method according to claim 15, characterized in that, The temperature of the sintering treatment is 750°C - 850°C.

18. The preparation method according to claim 15, characterized in that, The time of the sintering treatment is 10h - 14h.

19. The preparation method according to claim 15, characterized in that, The heating rate of the sintering treatment is 3°C / min - 10°C / min.

20. The preparation method according to claim 15, characterized in that, The atmosphere of the sintering treatment is air.

21. A positive electrode sheet, characterized in that, It includes the high-nickel single-crystal cathode material as described in any one of claims 1 to 5 or the high-nickel single-crystal cathode material prepared by using the preparation method as described in any one of claims 6 to 20.

22. A secondary battery, characterized in that, It includes the positive electrode sheet as described in claim 21.

23. An electrical device, characterized in that, It includes the secondary battery as described in claim 22.

Images