Positive electrode active material, method for manufacturing the same, positive electrode sheet, secondary battery, battery module, battery pack, and power tool

Abstract

This application provides a positive electrode active material, which includes a matrix material and a coating layer located on the surface of the matrix material, wherein the chemical formula of the matrix material is LiNi. x Co y Mn z M a M′ b O2, M = at least one of Zr, Y, Al, Ti, W, Sr, Ta, Sb, Nb, Na, K, Ca, or Ce, M′ = at least one of N, F, S, or Cl, 0.80 ≤ x ≤ 1.0, 0 ≤ y ≤ 0.20, 0 ≤ z ≤ 0.02, 0 ≤ a ≤ 0.02, b = 1 - x - y - z - a, wherein the coating layer is a boron-containing ternary alloy or a boron-containing ternary alloy oxide. The positive electrode active material of this application has high compaction density, improved high-temperature storage performance, and safety performance. This application also provides a method for preparing the positive electrode active material, as well as a positive electrode sheet containing the positive electrode active material, a secondary battery, a battery module, a battery pack, and an electrical device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries, in particular to a positive electrode active material and a preparation method thereof, and a positive electrode tab, a secondary battery, a battery module, a battery pack and a power utilization device comprising the positive electrode active material. BACKGROUND

[0002] In recent years, with the increasingly wide application of lithium ion batteries, lithium ion batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. Since lithium ion batteries have achieved great development, higher requirements have been put forward for their energy density, cycle performance and safety performance, etc.

[0003] The positive electrode material is an important component of lithium ion batteries. Common positive electrode materials currently include layered structure materials (such as lithium cobaltate, lithium manganate, lithium nickelate, etc.), spinel structure materials, polyanion type materials and high-nickel positive electrode materials, etc. High-nickel positive electrode materials have attracted more and more attention due to their high energy density, low cost and reliable safety. Although high-nickel positive electrode materials have significantly improved energy density compared to other materials, as the nickel content increases, the thermal decomposition temperature of the material decreases, resulting in poor cycle stability and thermal stability, so the service life of the battery is short and there is a safety risk, which to some extent hinders the further development of high-nickel positive electrode materials. Therefore, certain strategies need to be taken to optimize high-nickel positive electrode materials, so as to improve the energy density of the battery while improving the high-temperature storage performance and safety performance of the battery. SUMMARY

[0004] The present application is conducted in view of the above-mentioned problems, and aims to provide a positive electrode active material having a high compaction density, improved high-temperature storage performance and safety performance, and a preparation method of the positive electrode active material, and a positive electrode tab, a secondary battery, a battery module, a battery pack and a power utilization device comprising the positive electrode active material.

[0005] To achieve the above-mentioned purpose, the first aspect of the present application provides a positive electrode active material, comprising a base material and a coating layer located on the surface of the base material, wherein,

[0006] The chemical formula of the base material is LiNi x Co y Mn z M a M′ bO2, M = at least one of Zr, Y, Al, Ti, W, Sr, Ta, Sb, Nb, Na, K, Ca or Ce, M' = at least one of N, F, S or CI, 0.80≤x≤1.0, 0≤y≤0.20, 0≤z≤0.02, 0≤a≤0.02, b = 1-x-y-z-a,

[0007] The coating layer is a boron-containing ternary alloy or a boron-containing ternary alloy oxide.

[0008] Therefore, compared with the prior art, the present application at least has the following beneficial effects: 1) the positive electrode active material of the present application has good dispersibility, high inter-particle packing degree, good material processing performance, high compaction density, and can effectively improve the energy density of the battery; 2) the positive electrode active material of the present application has improved surface structure stability, thereby improving the high-temperature storage performance and safety performance of the battery.

[0009] In any embodiment, the boron-containing ternary alloy is represented by formula I B-X1-X2(I), wherein X1 and X2 are independently selected from one of the following elements: cobalt, hafnium, niobium, titanium, zirconium, tungsten, aluminum, molybdenum, copper, and the boron-containing ternary alloy oxide is represented by formula II B-Y1-Y2-O (II), wherein Y1 and Y2 are independently selected from one of the following elements: cobalt, hafnium, niobium, titanium, zirconium, tungsten, aluminum, molybdenum, copper. When the coating layer is the boron-containing ternary alloy represented by formula I or the boron-containing ternary alloy oxide represented by formula II, the surface structure stability of the material can be improved, thereby improving the high-temperature storage performance and safety performance of the battery.

[0010] In any embodiment, the positive electrode active material satisfies 1.30≤(Dv90-Dv10) / Dv50≤2.10. When the positive electrode active material satisfies the above range, the positive electrode active material has good dispersibility, high inter-particle packing degree, good material processing performance, and high compaction density, thereby making the battery obtain high energy density.

[0011] In any embodiment, the amount of the coating layer is 500 ppm-20000 ppm, and optionally, the amount of the coating layer is 4000-15000 ppm, based on the weight of the base material. When the amount of the coating layer is within the above range, the surface structure stability of the high-nickel material can be effectively improved, thereby improving the high-temperature storage performance and safety performance of the battery.

[0012] In any embodiment, the boron-containing ternary alloy is selected from at least one of: boron-cobalt-hafnium, boron-cobalt-niobium, boron-cobalt-titanium, boron-cobalt-zirconium, boron-cobalt-tungsten, boron-cobalt-aluminum, boron-cobalt-molybdenum, boron-cobalt-copper, boron-hafnium-titanium, and optionally, the boron-containing ternary alloy is selected from at least one of: boron-cobalt-hafnium, boron-cobalt-niobium, boron-cobalt-titanium, boron-cobalt-tungsten, boron-cobalt-aluminum, boron-hafnium-titanium. When the above-described boron-containing ternary alloy is selected for surface and grain boundary coating, the surface structure stability of the material can be improved, thereby improving the high-temperature storage performance and safety performance of the battery.

[0013] In any embodiment, the boron-containing ternary alloy oxide is selected from at least one of: boron-cobalt-hafnium oxide, boron-cobalt-niobium oxide, boron-cobalt-titanium oxide, boron-cobalt-zirconium oxide, boron-cobalt-tungsten oxide, boron-cobalt-aluminum oxide, boron-cobalt-molybdenum oxide, boron-cobalt-copper oxide, boron-hafnium-titanium oxide, and optionally, the boron-containing ternary alloy oxide is selected from at least one of: boron-cobalt-hafnium oxide, boron-cobalt-niobium oxide, boron-cobalt-titanium oxide, boron-cobalt-tungsten oxide, boron-cobalt-aluminum oxide, boron-hafnium-titanium oxide. When the above-described boron-containing ternary alloy oxide is selected for surface and grain boundary coating, the surface structure stability of the material can be improved, thereby improving the high-temperature storage performance and safety performance of the battery.

[0014] In any embodiment, the molar ratio of boron, X1, and X2 in the boron-containing ternary alloy is 1:0.5:0.04-1:5:4, and optionally, 1:0.5:0.15-1:1:0.4. When the molar ratio of each element in the boron-containing ternary alloy satisfies the above-described range, the surface structure stability of the material can be improved, thereby improving the high-temperature storage performance and safety performance of the battery.

[0015] In any embodiment, the molar ratio of boron, Y1, and Y2 in the boron-containing ternary alloy oxide is 1:0.5:0.03-1:5:5, and optionally, 1:0.5:0.15-1:1:0.4. When the molar ratio of each element in the boron-containing ternary alloy oxide satisfies the above-described range, the surface structure stability of the material can be improved, thereby improving the high-temperature storage performance and safety performance of the battery.

[0016] In any embodiment, the Dv50 of the positive electrode active material is 6 μm-18 μm, and optionally, 9 μm-13 μm. When the Dv50 of the positive electrode active material is within the above-described range, the compaction density of the positive electrode active material can be optimized, thereby allowing the battery to have a high energy density.

[0017] In any embodiment, the compaction density of the positive electrode active material under a pressure of 5 tons (i.e., 5T) is 3.65-3.75 g / cm3 The positive electrode active material has high compaction density and high inter-particle filling degree, which is beneficial to improving the processing performance of the positive electrode active material and effectively improving the energy density of the battery.

[0018] The second aspect of the present application provides a preparation method of the positive electrode active material of the first aspect of the present application, comprising

[0019] S1) preparing a base material;

[0020] S2) mixing the base material, a boron-containing compound and a metal element according to a mass ratio of 1:0.004-0.02:0.0001-0.2, or mixing the base material, a boron-containing compound and a metal oxide according to a mass ratio of 1:0.004-0.02:0.0002-0.018, and then sintering to obtain an intermediate material, wherein the sintering atmosphere is inert gas or oxygen atmosphere;

[0021] S3) washing the intermediate material with water, centrifuging, filtering, and then vibration drying to obtain a positive electrode active material,

[0022] wherein the base material has a chemical formula of LiNi x Co y Mn z M a M′ b O2, M is at least one of Zr, Y, Al, Ti, W, Sr, Ta, Sb, Nb, Na, K, Ca or Ce, M′ is at least one of N, F, S or Cl, 0.80≤x≤1.0, 0≤y≤0.20, 0≤z≤0.02, 0≤a≤0.02, and b=1-x-y-z-a.

[0023] Therefore, the positive electrode active material prepared by the above method has good dispersibility, high inter-particle filling degree, good material processing performance, high compaction density and improved surface structure stability, and the secondary battery prepared thereby has improved high-temperature storage performance and safety performance.

[0024] In any embodiment, the boron-containing compound is selected from one or more of cobalt boride, hafnium boride, niobium boride, titanium boride, zirconium boride, tungsten boride, aluminum boride, molybdenum boride and copper boride, and / or the metal element is selected from one or more of cobalt, hafnium, niobium, titanium, zirconium, tungsten, aluminum, molybdenum and copper, and / or the metal oxide is selected from one or more of cobalt oxide, hafnium oxide, niobium oxide, titanium oxide, zirconium oxide, tungsten oxide, aluminum oxide, molybdenum oxide and copper oxide. When the boron-containing compound, the metal element compound and the metal oxide are selected from the above-mentioned materials respectively, the surface structure stability of the material can be improved, thereby improving the high-temperature storage performance and safety performance of the battery.

[0025] In any embodiment, the base material prepared in step S1) has a (Dv90-Dv10) / Dv50≥1.2, or alternatively, (Dv90-Dv10) / Dv50≥1.25. When the distribution of the base material satisfies the above range, a positive electrode active material with good dispersibility, high inter-particle packing degree, and good material processing performance can be obtained.

[0026] In any embodiment, in step S2), the base material, the boron-containing compound, and the metal element are mixed and sintered in an inert atmosphere, the sintering temperature is 300-700°C, or alternatively, 300-550°C, and the sintering time is 3-10h, or alternatively, 5-10h. In this way, a positive electrode active material coated with a boron-containing ternary alloy can be obtained, thereby improving the surface structure stability of the material and improving the high-temperature storage performance and safety performance of the battery.

[0027] In any embodiment, in step S2), the base material, the boron-containing compound, and the metal oxide are sintered in an oxygen atmosphere, the sintering temperature is 300-700°C, or alternatively, 550-650°C, and the sintering time is 3-10h, or alternatively, 3-8h. In this way, a positive electrode active material coated with a boron-containing ternary alloy oxide can be obtained, thereby improving the surface structure stability of the material and improving the high-temperature storage performance and safety performance of the battery.

[0028] In any embodiment, in step S3), the mass ratio of the intermediate material to water is 1:1-1:5, the water washing time is 1-10min, the vibration frequency of the vibration drying is 10-50Hz, and the drying time is 2-8h. In this way, a positive electrode active material with good dispersibility, high inter-particle packing degree, and good material processing performance can be obtained.

[0029] The third aspect of the present application provides a positive electrode tab, which comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, the positive electrode film layer comprising a first positive electrode active material, the first positive electrode active material being the positive electrode active material of the first aspect of the present application or the positive electrode active material prepared by the method of the second aspect of the present application, and the content of the first positive electrode active material in the positive electrode film layer being 10wt% or more, based on the total weight of the positive electrode film layer. In this way, the processing performance of the tab can be improved.

[0030] In any embodiment, the positive electrode film layer further comprises a second positive electrode active material, and the quantity ratio of the first positive electrode active material to the second positive electrode active material is 6:4-8:2, or alternatively, 6.5:3.5-7.5:2.5, and the chemical formula of the second positive electrode active material is LiNi x Co yMn z M a M′ b O2, M = at least one of Zr, Y, Al, Ti, W, Sr, Ta, Sb, Nb, Na, K, Ca, or Ce, M′ = at least one of N, F, S, or Cl, 0.80 ≤ x ≤ 1.0, 0 ≤ y ≤ 0.20, 0 ≤ z ≤ 0.02, 0 ≤ a ≤ 0.02, b = 1 - xyza, and the Dv50 of the second positive electrode active material is 2 μm-5 μm, optionally 2.5 μm-3.5 μm. This further improves the processing performance of the electrode.

[0031] In any embodiment, the tap density of the second positive electrode active material is ≤1.8 g / cm³. 3 The optional concentration is 1.2-1.5 g / cm³. 3 This allows for further improvement in the processing performance of the electrode sheets.

[0032] A fourth aspect of this application provides a secondary battery that includes the positive electrode sheet of the third aspect of this application.

[0033] A fifth aspect of this application provides a battery module that includes the secondary battery of the fourth aspect of this application.

[0034] A sixth aspect of this application provides a battery pack that includes the battery module of the fifth aspect of this application.

[0035] A seventh aspect of this application provides an electrical device comprising at least one selected from the fourth aspect of this application, the fifth aspect of this application, or the sixth aspect of this application.

[0036] The battery module, battery pack, and power device of this application include the secondary battery provided in this application, and therefore have at least the same advantages as the secondary battery. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0038] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0039] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0040] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0041] Figure 5 yesFigure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0042] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0043] Explanation of reference numerals in the attached figures:

[0044] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Casing; 52 Electrode assembly; 53 Top cover assembly Detailed Implementation

[0045] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode active material, its preparation method, positive electrode sheet, secondary battery, battery module, battery pack, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0046] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0047] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0048] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0049] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0050] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0051] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0052] Despite significant progress in research on high-nickel cathode materials in recent years, many problems still need to be solved: 1) High-nickel cathode materials may experience excessive Ni during cycling. 2+ and Li + Mixed arrangement, Ni 2+ Occupy Li + The position makes Li + 1) The material cannot embed lithium layers during discharge, resulting in a loss of capacity and a reduction in rate performance; 2) Due to Ni 4+ It has reducing properties and readily forms Ni. 3+ To maintain charge balance, oxygen is released from the material, leading to structural damage, reduced thermal stability, and poor high-temperature storage performance; 3) Due to Li +Diffusion is influenced by kinetic factors, leading to increased Li extraction and reduction of transition metal ions. To maintain electroneutrality, the material readily forms new phases and pores on its surface, resulting in structural instability in high-nickel cathode materials. Overcharge conditions accelerate this instability, as it is accompanied by partial structural transformations to spinel-type and NiO-type rock salt phases, and the generation of oxygen, posing certain safety risks to the battery. Currently, surface coating and ion doping are commonly used to improve the electrochemical performance of high-nickel cathode materials. Oxygen evolution during cycling of high-nickel cathode materials not only oxidizes organic electrolytes and forms gases but also leads to cation reduction and / or densification, potentially initiating other degradation processes in a chain reaction. While thin coatings with high stability and catalytic inertness are beneficial for addressing the surface oxygen stability issue of high-nickel cathode materials, achieving 100% coverage is often difficult in synthesis due to solid-to-solid wetting issues and the need to maintain conformity during electrochemical cycling.

[0053] To address the aforementioned problems, this application provides a positive electrode active material, which includes a matrix material and a coating layer located on the surface of the matrix material, wherein...

[0054] The chemical formula of the matrix material is LiNi. x Co y Mn z M a M′ b O2, M = at least one of Zr, Y, Al, Ti, W, Sr, Ta, Sb, Nb, Na, K, Ca, or Ce, M′ = at least one of N, F, S, or CI, 0.80 ≤ x ≤ 1.0, 0 ≤ y ≤ 0.20, 0 ≤ z ≤ 0.02, 0 ≤ a ≤ 0.02, b = 1 - xyza.

[0055] The coating layer is a boron-containing ternary alloy or a boron-containing ternary alloy oxide.

[0056] Although the mechanism is not yet clear, the applicant has unexpectedly discovered that the positive electrode active material provided in this application, on the one hand, achieves a double coating effect on the surface and grain boundaries of the matrix material through boron-containing ternary alloys or boron-containing ternary alloy oxides, which greatly improves the stability of the material surface structure and thus enhances the storage stability and safety of the material; on the other hand, the positive electrode active material of this application has good dispersibility, high interparticle filling degree, good material processing performance, and high compaction density, which can effectively improve the energy density of the battery. In this application, the matrix material is a secondary particle composed of primary particles. The boron-containing ternary alloy or boron-containing ternary alloy oxide forms a tight bond and comprehensive coverage with the matrix material through high-quality wetting. It not only coats the surface of the secondary particles but also is located at the grain boundary of the primary particles. This achieves all-round coating of the surface and grain boundary of the polycrystalline matrix material, which can alleviate intergranular stress corrosion cracking, microstructure degradation and side reactions on the positive electrode side, as well as the cross-effect of transition metals on the negative electrode. It greatly reduces the gas generation of the material, making the structure of the positive electrode active material more stable, and significantly improving its thermal stability and safety. This, in turn, improves the high-temperature storage performance and safety performance of the material.

[0057] In this application, unless otherwise stated, for the chemical formula of the matrix material, when M consists of two or more elements, the aforementioned limitation on the range of values ​​for 'a' applies not only to the stoichiometric coefficient of each element as M, but also to the sum of the stoichiometric coefficients of all elements as M. That is, when M consists of two or more elements M1, M2...Mn, the stoichiometric coefficients a1, a2...an of each of M1, M2...Mn must each fall within the range of values ​​for 'a' defined in this application, and the sum of a1, a2...an must also fall within this range. For the case where M′ consists of two or more elements, the limitation on the range of values ​​for the stoichiometric coefficients of M′ in this application also has the above meaning.

[0058] In this application, Dv10 is the particle size corresponding to a cumulative volume percentage of 10% of the sample, Dv50 is the particle size corresponding to a cumulative volume percentage of 50% of the sample, and Dv90 is the particle size corresponding to a cumulative volume percentage of 90% of the sample. The dispersibility of the material can be calculated by (Dv90-Dv10) / Dv50.

[0059] In some embodiments, the boron-containing ternary alloy is as shown in Formula I, B-X1-X2(I), wherein X1 and X2 are independently selected from one of the following elements: cobalt, hafnium, niobium, titanium, zirconium, tungsten, aluminum, molybdenum, and copper; and the boron-containing ternary alloy oxide is as shown in Formula II, B-Y1-Y2-O(II), wherein Y1 and Y2 are independently selected from one of the following elements: cobalt, hafnium, niobium, titanium, zirconium, tungsten, aluminum, molybdenum, and copper. When the coating layer is the boron-containing ternary alloy shown in Formula I or the boron-containing ternary alloy oxide shown in Formula II, the surface structure stability of the material can be improved, thereby improving the high-temperature storage performance and safety performance of the battery.

[0060] In some embodiments, the positive electrode active material satisfies the following condition: 1.30 ≤ (Dv90 - Dv10) / Dv50 ≤ 2.10. When the positive electrode active material meets the above range, it exhibits good dispersibility, high interparticle filling degree, good material processing performance, and high compaction density, thereby enabling the battery to achieve high energy density.

[0061] In some embodiments, the amount of the coating layer is 500ppm-20000ppm, optionally 4000-15000ppm, based on the weight of the matrix material. For example, the amount of the coating layer can be 500ppm, 2000ppm, 4000ppm, 10000ppm, 15000ppm, 17000ppm, or 20000ppm. When the amount of the coating layer is within the above range, it can uniformly wet the material surface and grain boundaries, improve the surface structural stability of the material, and thus improve the high-temperature storage performance and safety performance of the battery. If the amount of the coating layer is too small, it cannot form a good coating on the material and cannot effectively improve the surface structural stability of the material; if the amount of the coating layer is too large, it will form island-like accumulation, resulting in a decrease in the specific capacity of the material and an increase in the cell's DCR.

[0062] In some embodiments, the boron-containing ternary alloy is selected from at least one of the following: boron-cobalt-hafnium, boron-cobalt-niobium, boron-cobalt-titanium, boron-cobalt-zirconium, boron-cobalt-tungsten, boron-cobalt-aluminum, boron-cobalt-molybdenum, boron-cobalt-copper, and boron-hafnium-titanium. Optionally, the boron-containing ternary alloy is selected from at least one of the following: boron-cobalt-hafnium, boron-cobalt-niobium, boron-cobalt-titanium, boron-cobalt-tungsten, boron-cobalt-aluminum, and boron-hafnium-titanium. When the above-mentioned boron-containing ternary alloys are selected for surface and grain boundary coating, the surface structure stability of the material can be improved, thereby improving the high-temperature storage performance and safety performance of the battery.

[0063] In some embodiments, the boron-containing ternary alloy oxide is selected from at least one of the following: boron-cobalt-hafnium oxide, boron-cobalt-niobium oxide, boron-cobalt-titanium oxide, boron-cobalt-zirconium oxide, boron-cobalt-tungsten oxide, boron-cobalt-aluminum oxide, boron-cobalt-molybdenum oxide, boron-cobalt-copper oxide, and boron-hafnium-titanium oxide. Optionally, the boron-containing ternary alloy oxide is selected from at least one of the following: boron-cobalt-hafnium oxide, boron-cobalt-niobium oxide, boron-cobalt-titanium oxide, boron-cobalt-tungsten oxide, boron-cobalt-aluminum oxide, and boron-hafnium-titanium oxide. When the above-mentioned boron-containing ternary alloy oxides are selected for surface and grain boundary coating, the surface structure stability of the material can be improved, thereby improving the high-temperature storage performance and safety performance of the battery.

[0064] In some embodiments, the molar ratio of boron, X1, and X2 in the boron-containing ternary alloy is 1:0.5:0.04 to 1:5:4, and optionally 1:0.5:0.15 to 1:1:0.4. When the molar ratio of each element in the boron-containing ternary alloy meets the above range, the surface structure stability of the material can be improved, thereby improving the high-temperature storage performance and safety performance of the battery.

[0065] In some embodiments, the molar ratio of boron, Y1, and Y2 in the boron-containing ternary alloy oxide is 1:0.5:0.03-1:5:5, optionally 1:0.5:0.15-1:1:0.4. When the molar ratio of each element in the boron-containing ternary alloy oxide meets the above range, the surface structure stability of the material can be improved, thereby improving the high-temperature storage performance and safety performance of the battery.

[0066] In some embodiments, the Dv50 of the positive electrode active material is 6μm-18μm, optionally 9μm-13μm. When the Dv50 of the positive electrode active material is within the above range, the compaction density of the positive electrode active material can be optimized, thereby enabling the battery to obtain a high energy density.

[0067] In some embodiments, the compaction density of the positive electrode active material under a pressure of 5T is 3.65-3.75 g / cm³. 3 Higher compaction density results in a greater weight of active material per unit volume; therefore, increasing compaction density is beneficial for improving the volumetric energy density of the battery cell. The positive electrode active material exhibits high compaction density and high interparticle filling density, which not only improves the processing performance of the positive electrode active material but also further enhances the energy density of the battery. Compaction density can be measured according to GB / T 24533-2009.

[0068] The second aspect of this application provides a method for preparing the positive electrode active material of the first aspect of this application, including...

[0069] S1) Preparation of matrix material;

[0070] S2) The matrix material, boron-containing compound, and metal element are mixed in a mass ratio of 1:0.004-0.02:0.0001-0.2, or the matrix material, boron-containing compound, and metal oxide are mixed in a mass ratio of 1:0.004-0.02:0.0002-0.018, and then sintered in an inert or oxygen atmosphere to obtain an intermediate material.

[0071] S3) The intermediate material is washed with water, centrifuged, filtered, and then dried by vibration to obtain the positive electrode active material.

[0072] The chemical formula of the matrix material is LiNi. x Co y Mn z M a M′ b O2, M = at least one of Zr, Y, Al, Ti, W, Sr, Ta, Sb, Nb, Na, K, Ca or Ce, M′ = at least one of N, F, S or Cl, 0.80≤x≤1.0, 0≤y≤0.20, 0≤z≤0.02, 0≤a≤0.02, b = 1-xyza.

[0073] In this application, the matrix material is a secondary particle composed of primary particles. Thus, through the above preparation method, a boron-containing ternary alloy is formed by reacting a boron-containing compound with a metallic element during calcination, or a boron-containing compound with a metal oxide is formed by reacting a boron-containing ternary alloy oxide during calcination. Utilizing the reactive wettability between the boron-containing ternary alloy or boron-containing ternary alloy oxide and the matrix material, driven by a strong interfacial chemical reaction, the boron-containing ternary alloy or boron-containing ternary alloy oxide not only completely coats the surface of the secondary particles but also injects itself into the grain boundary positions of the primary particles. That is, a dual coating effect of surface and grain boundary is simultaneously achieved, greatly improving the stability of the material's surface structure, thereby enhancing the material's storage stability and safety.

[0074] In some embodiments, the boron-containing compound is selected from one or more of cobalt boride, hafnium boride, niobium boride, titanium boride, zirconium boride, tungsten boride, aluminum boride, molybdenum boride, and copper boride, and / or the elemental metal is selected from one or more of cobalt, hafnium, niobium, titanium, zirconium, tungsten, aluminum, molybdenum, and copper, and / or the metal oxide is selected from one or more of cobalt oxide, hafnium oxide, niobium oxide, titanium oxide, zirconium oxide, tungsten oxide, aluminum oxide, molybdenum oxide, and copper oxide. Selecting the aforementioned boron-containing compounds, elemental metals, and metal oxides can improve the surface structural stability of the material, thereby improving the high-temperature storage performance and safety performance of the battery.

[0075] In this application, the matrix material of this application can be prepared using methods known in the art for preparing high-nickel cathode materials, such as PCT / CN2021 / 141873. That is, the lithium source, high-nickel hydroxide precursor, and dopant are mixed and then sintered at 650-850°C in an oxygen atmosphere to obtain the matrix material of this application.

[0076] In some embodiments, the ratio of (Dv90-Dv10) / Dv50 of the matrix material obtained in step S1) is ≥1.2, and optionally, (Dv90-Dv10) / Dv50 is ≥1.25. When the distribution of the matrix material meets the above range, a positive electrode active material with good dispersibility, high interparticle filling degree, and good material processing performance can be obtained.

[0077] In some embodiments, in step S2), the matrix material, boron-containing compound, and elemental metal are mixed under an inert atmosphere and sintered under an inert atmosphere at a temperature of 300-700°C, optionally 300-550°C, for a sintering time of 3-10 hours, optionally 5-10 hours. This yields a positive electrode active material coated with a boron-containing ternary alloy, thereby improving the surface structure stability of the material and enhancing the high-temperature storage performance and safety performance of the battery.

[0078] In some embodiments, in step S2), the matrix material, boron-containing compound, and metal oxide are sintered in an oxygen atmosphere at a temperature of 300-700°C, optionally 550-650°C, for a sintering time of 3-10 hours, optionally 3-8 hours. This yields a positive electrode active material coated with a boron-containing ternary alloy oxide, thereby improving the surface structure stability of the material and enhancing the high-temperature storage performance and safety performance of the battery.

[0079] In this application, in step S3), the mass ratio of the intermediate material to water is 1:1 to 1:5, the water washing time is 1-10 minutes, the vibration frequency of the vibration drying is 10-50 Hz, and the drying time is 2-8 hours. The vibration drying can be carried out on, for example, a WZG series horizontal vibration dryer, with a vibration frequency of, for example, above 10 Hz, above 15 Hz, above 20 Hz, above 30 Hz, or above 50 Hz, and a drying time of, for example, above 2 hours, above 3 hours, above 4 hours, above 5 hours, above 6 hours, above 7 hours, or above 8 hours. Through the vibration drying in step S3), large truncated sections on the secondary particles can be peeled off, broadening the particle size distribution of the material, resulting in good dispersion of the positive electrode active material, high interparticle filling degree, good material processing performance, high compaction density, and effectively improving the energy density of the battery.

[0080] A third aspect of this application provides a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer comprising a first positive electrode active material, the first positive electrode active material being the positive electrode active material of the first aspect of this application or a positive electrode active material prepared by the method of the second aspect of this application, and the content of the first positive electrode active material in the positive electrode film layer being 10% by weight or more, based on the total weight of the positive electrode film layer. The positive electrode active material obtained by using the method of the first aspect of this application or the method of the second aspect of this application has good dispersibility and high interparticle filling degree, thereby improving the processing performance of the electrode sheet.

[0081] In some embodiments, the positive electrode film layer further includes a second positive electrode active material, and the ratio of the first positive electrode active material to the second positive electrode active material is 6:4-8:2, optionally 6.5:3.5-7.5:2.5, wherein the chemical formula of the second positive electrode active material is LiNi. x Co y Mn z M a M′ b O2, M = at least one of Zr, Y, Al, Ti, W, Sr, Ta, Sb, Nb, Na, K, Ca, or Ce, M′ = at least one of N, F, S, or Cl, 0.80 ≤ x ≤ 1.0, 0 ≤ y ≤ 0.20, 0 ≤ z ≤ 0.02, 0 ≤ a ≤ 0.02, b = 1 - xyza, and the Dv50 of the second positive electrode active material is 2 μm-5 μm, optionally 2.5 μm-3.5 μm. When two positive electrode active materials with different particle sizes are used, namely the positive electrode active material obtained by the first aspect of this application or by the preparation method of the second aspect of this application, and the second positive electrode active material, to form a positive electrode sheet, the smaller particles of the second positive electrode active material can effectively fill the pores of the larger particles of the first positive electrode active material, thereby further improving the processing performance of the electrode sheet.

[0082] In some embodiments, the tap density of the second positive electrode active material is ≤1.8 g / cm³. 3 The optional concentration is 1.2-1.5 g / cm³. 3 When the tap density of the second positive electrode active material is within the above-mentioned range, the processing performance of the electrode can be further improved.

[0083] In this application, when the positive electrode film layer of the positive electrode sheet includes a first positive electrode material and a second positive electrode material, the powder compaction density of the first positive electrode material and the second positive electrode material at 5T is 3.71-3.83 g / cm³. 3 .

[0084] In addition, the secondary battery, battery module, battery pack and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0085] In one embodiment of this application, a secondary battery is provided.

[0086] Typically, a secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through. In this application, the battery pack margin is 90-95%.

[0087] [Positive electrode plate]

[0088] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0089] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0090] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0091] In some embodiments, the positive electrode active material is the positive electrode active material of the first aspect of this application or the positive electrode active material obtained by the method of the second aspect of this application. The weight ratio of the positive electrode active material in the positive electrode film layer is 80-100% by weight, based on the total weight of the positive electrode film layer.

[0092] In some embodiments, the positive electrode active material is the positive electrode active material of the first aspect of this application as the first positive electrode material, and at the same time, a second positive electrode active material is used as the second positive electrode active material: the chemical formula of the second positive electrode active material is LiNi. x Co y Mn z M a M′ bO2, M = at least one of Zr, Y, Al, Ti, W, Sr, Ta, Sb, Nb, Na, K, Ca, or Ce, M′ = at least one of N, F, S, or Cl, 0.80 ≤ x ≤ 1.0, 0 ≤ y ≤ 0.20, 0 ≤ z ≤ 0.02, 0 ≤ a ≤ 0.02, b = 1 - xyza, and the Dv50 of the second positive electrode active material is 2 μm-5 μm, optionally 2.5 μm-3.5 μm. When the positive electrode active material is a first positive electrode active material and a second positive electrode active material, the mass ratio of the first positive electrode active material to the second positive electrode active material is 8.5:1.5-5:5. The weight percentage of the positive electrode active material in the positive electrode film layer is 80-100% by weight, based on the total weight of the positive electrode film layer.

[0093] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of PVDF-tetrafluoroethylene-propylene, a terpolymer of PVDF-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorinated acrylate resin. The binder constitutes 0-20% by weight of the positive electrode film layer, based on the total weight of the positive electrode film layer.

[0094] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive agent accounts for 0-20% by weight of the positive electrode film, based on the total weight of the positive electrode film.

[0095] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; wherein the solid content of the positive electrode slurry is 40-80% by weight, and the viscosity at room temperature is adjusted to 5000-25000 mPa·s; the positive electrode slurry is coated onto a positive electrode current collector, and after drying, cold pressing, and other processes, the positive electrode sheet is obtained, and the areal density of the positive electrode powder coating is 150-350 mg / m². 2 The compaction density of the positive electrode sheet is 3.0-3.6 g / cm³. 3 The concentration can be selected as 3.3-3.5 g / cm³. 3 The formula for calculating the compaction density is:

[0096] Compacted density = Coated surface density / (Extreme electrode thickness after extrusion - Current collector thickness).

[0097] [Negative electrode plate]

[0098] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0099] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0100] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0101] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more. The negative electrode active material may have an average particle size (D0) of 1 μm-15 μm, preferably 4 μm-9 μm. 10 ), with an average particle size (D) of 12μm-22μm, preferably 14μm-17μm. 50 It has an average particle size of 26 μm to 40 μm, preferably 30 μm to 37 μm (D). 90 D 10 D represents the particle size at which the cumulative volume distribution percentage of the sample reaches 10%. 50 D represents the particle size at which the cumulative volume distribution percentage of the sample reaches 50%. 90 The particle size corresponding to a cumulative volume distribution percentage of 90% for the sample. The weight ratio of the negative electrode active material in the negative electrode film is 70-100% by weight, based on the total weight of the negative electrode film.

[0102] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). The binder accounts for 0-30% by weight of the negative electrode film layer, based on the total weight of the negative electrode film layer.

[0103] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive agent accounts for 0-20% by weight of the negative electrode film, based on the total weight of the negative electrode film.

[0104] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)). The other additives constitute 0-15% by weight of the negative electrode film, based on the total weight of the negative electrode film.

[0105] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70% by weight, and the viscosity at room temperature is adjusted to 2000-10000 mPa·s; the negative electrode slurry is coated onto a negative electrode current collector, and after drying, cold pressing, and other processes, the negative electrode sheet is obtained. The areal density of the negative electrode powder coating is 75-220 mg / m³. 2 The compacted density of the negative electrode sheet is 1.2-2.0 g / m³. 3 .

[0106] [Electrolytes]

[0107] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0108] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0109] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. The concentration of the electrolyte salt is typically 0.5-5 mol / L.

[0110] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0111] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0112] [Isolation membrane]

[0113] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0114] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0115] In some embodiments, the thickness of the isolation membrane is 6-40 μm, optionally 12-20 μm.

[0116] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0117] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0118] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0119] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0120] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0121] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0122] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0123] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0124] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0125] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0126] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0127] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0128] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0129] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0130] Example

[0131] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0132] Preparation of primary and secondary batteries

[0133] Example 1

[0134] 1. Preparation of positive electrode active materials

[0135] S1) Matrix material LiNi 0.92 Co 0.07 Mn 0.0086 Y 0.0014Preparation of O2: Weigh lithium hydroxide and dried high-nickel ternary precursor Ni according to the stoichiometric ratio of the chemical formula. 0.92 Co 0.07 Mn 0.01 The mixture consists of (OH)2 ((Dv90-Dv10) / Dv50 is 1.45) and yttrium oxide, wherein the molar ratio of Li / Me (Me is the sum of all metal elements except lithium) is 1.03, and the doping amount of yttrium is 1500ppm. After the mixture is evenly mixed in a high-speed mixer, it is sintered in a kiln at a temperature of 760℃ for 20h in an oxygen atmosphere. After cooling, the matrix material is obtained.

[0136] S2) The above matrix material, cobalt boride (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS: 12006-77-8), and titanium were mixed in a high-speed mixer under a nitrogen atmosphere at a mass ratio of 1:0.015:0.0041. The mixture was then placed in a kiln for sintering at a temperature of 350°C for 5 hours under a nitrogen atmosphere to obtain an intermediate material.

[0137] S3) The intermediate material is washed with water at a mass ratio of 1:5 for 30 minutes, centrifuged, filtered, and then subjected to vibration drying at a vibration frequency of 30 Hz for 5 hours to obtain the positive electrode active material.

[0138] 2. Preparation of secondary batteries

[0139] [Positive Electrode Sheet] The above-mentioned positive electrode active material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) at a weight ratio of 96:2:2 to form a uniform positive electrode slurry with a solid content of 70% by weight. This positive electrode slurry is coated onto the surface of an aluminum foil with a thickness of 12 μm. After drying and cold pressing, a positive electrode sheet is obtained. The positive electrode active material loading of this electrode sheet is 21.5 mg / cm³. 2 .

[0140] [Negative Electrode Sheet] The negative electrode active material (artificial graphite), hard carbon, conductive agent (acetylene black), binder (styrene-butadiene rubber (SBR), tackifier (lithium-based montmorillonite), and thickener (sodium carboxymethyl cellulose (CMC-Na)) are mixed evenly in deionized water at a weight ratio of 90:5:2:2:1. This mixture is then coated onto copper foil, dried, and cold-pressed to obtain the negative electrode sheet. The coating amount is 0.015 g / cm³. 2 The compacted density is 1.65 g / cm³. 3 .

[0141] [Electrolyte] Ethyl carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1. Then, LiPF6 is uniformly dissolved in the above solution to obtain the electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0142]

Separation Membrane

[0143] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The cells are then wound to obtain a bare cell. A 4.3Ah bare cell is placed in an outer packaging foil. 8.6g of the prepared electrolyte is injected into the dried battery. After vacuum sealing, settling, formation, and shaping, the secondary battery of Example 1 is obtained. The outer packaging is a hard-shell casing with dimensions of 148mm × 28.5mm × 97.5mm (length × width × height), made of aluminum, with a thickness of 0.8mm. The battery's group margin is 94%.

[0144] Example 2

[0145] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the matrix material, cobalt boride, and hafnium are mixed in a mass ratio of 1:0.015:0.0154 in step S2).

[0146] Example 3

[0147] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the matrix material, cobalt boride, and niobium are mixed in a mass ratio of 1:0.015:0.0080 in step S2).

[0148] Example 4

[0149] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the matrix material, cobalt boride, and tungsten are mixed in a mass ratio of 1:0.015:0.0158 in step S2).

[0150] Example 5

[0151] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the matrix material, cobalt boride, and aluminum are mixed in a mass ratio of 1:0.015:0.0023 in step S2).

[0152] Example 6

[0153] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, in step S2), the matrix material, hafnium boride (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS: 12007-23-7), and titanium are mixed in a mass ratio of 1:0.015:0.0014.

[0154] Example 7

[0155] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, in step S2), the matrix material, cobalt boride and titanium dioxide are mixed in an air atmosphere at a mass ratio of 1:0.015:0.007, the sintering temperature is 650°C, and the sintering atmosphere is oxygen.

[0156] Example 8

[0157] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, in step S2), the matrix material, cobalt boride, and hafnium dioxide are mixed in an air atmosphere at a mass ratio of 1:0.015:0.018, the sintering temperature is 650°C, and the sintering atmosphere is oxygen.

[0158] Example 9

[0159] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, in step S2), the matrix material, cobalt boride, and niobium pentoxide are mixed in an air atmosphere at a mass ratio of 1:0.015:0.023, the sintering temperature is 650°C, and the sintering atmosphere is oxygen.

[0160] Example 10

[0161] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, in step S2), the matrix material, cobalt boride, and tungsten trioxide are mixed in an air atmosphere at a mass ratio of 1:0.015:0.020, the sintering temperature is 650°C, and the sintering atmosphere is oxygen.

[0162] Example 11

[0163] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, in step S2), the matrix material, cobalt boride, and aluminum oxide are mixed in an air atmosphere at a mass ratio of 1:0.015:0.009, the sintering temperature is 650°C, and the sintering atmosphere is oxygen.

[0164] Example 12

[0165] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, in step S2), the matrix material, hafnium boride, and titanium dioxide are mixed in an air atmosphere at a mass ratio of 1:0.015:0.002, the sintering temperature is 650°C, and the sintering atmosphere is oxygen.

[0166] Example 13

[0167] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, in step S2), the matrix material, cobalt boride, and titanium are mixed in a mass ratio of 1:0.0005:0.0001.

[0168] Example 14

[0169] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the matrix material, cobalt boride, and titanium are mixed in a mass ratio of 1:0.002:0.0005 in step S2).

[0170] Example 15

[0171] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the matrix material, cobalt boride, and titanium are mixed in a mass ratio of 1:0.004:0.0011 in step S2).

[0172] Example 16

[0173] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the matrix material, cobalt boride, and titanium are mixed in a mass ratio of 1:0.01:0.0027 in step S2).

[0174] Example 17

[0175] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the matrix material, cobalt boride, and titanium are mixed in a mass ratio of 1:0.017:0.0047 in step S2).

[0176] Example 18

[0177] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the matrix material, cobalt boride, and titanium are mixed in a mass ratio of 1:0.02:0.0055 in step S2).

[0178] Example 19

[0179] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the matrix material, cobalt boride, and hafnium are mixed in a mass ratio of 1:0.02:0.0036 in step S2).

[0180] Example 20

[0181] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the matrix material, cobalt boride, and hafnium are mixed in a mass ratio of 1:0.02:0.0136 in step S2).

[0182] Example 21

[0183] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the matrix material, cobalt boride, and hafnium are mixed in a mass ratio of 1:0.015:0.0384 in step S2).

[0184] Example 22

[0185] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the matrix material, cobalt boride, and hafnium are mixed in a mass ratio of 1:0.015:0.1152 in step S2).

[0186] Example 23

[0187] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the matrix material, cobalt boride, and hafnium are mixed in a mass ratio of 1:0.015:0.0351 in step S2).

[0188] Example 24

[0189] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, in step S2), the matrix material, hafnium boride, and titanium dioxide are mixed in an air atmosphere at a mass ratio of 1:0.015:0.0004, the sintering temperature is 650°C, and the sintering atmosphere is oxygen.

[0190] Example 25

[0191] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, in step S2), the matrix material, hafnium boride, and titanium dioxide are mixed in an air atmosphere at a mass ratio of 1:0.015:0.0018, the sintering temperature is 650°C, and the sintering atmosphere is oxygen.

[0192] Example 26

[0193] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, in step S2), the matrix material, hafnium boride, and titanium dioxide are mixed in an air atmosphere at a mass ratio of 1:0.015:0.0120, the sintering temperature is 650°C, and the sintering atmosphere is oxygen.

[0194] Example 27

[0195] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, in step S2), the matrix material, hafnium boride, and titanium dioxide are mixed in an air atmosphere at a mass ratio of 1:0.015:0.0359, the sintering temperature is 650°C, and the sintering atmosphere is oxygen.

[0196] Example 28

[0197] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the intermediate material is washed with water in step S3) at a mass ratio of 1:1.

[0198] Example 29

[0199] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the intermediate material is washed with water in step S3) at a mass ratio of 1:3.

[0200] Example 30

[0201] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the vibration frequency of the vibration drying in step S3) is 10 Hz.

[0202] Example 31

[0203] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the vibration frequency for vibration drying in step S3) is 15 Hz.

[0204] Example 32

[0205] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the vibration frequency for vibration drying in step S3) is 20Hz.

[0206] Example 33

[0207] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the vibration frequency of the vibration drying in step S3) is 50Hz.

[0208] Example 34

[0209] The preparation of the secondary battery is the same as in Example 1, except that the matrix material in the preparation of the positive electrode active material is LiNi. 0.92 Co 0.07 Mn 0.0087 Sr 0.0013 O2, wherein the molar ratio of Li / Me (Me is the sum of all metal elements except lithium) is 1.03 and the doping amount of strontium is 1500 ppm, and its preparation method is similar to that of Example 1.

[0210] Example 35

[0211] The preparation of the secondary battery is the same as in Example 1, except that the matrix material in the preparation of the positive electrode active material is LiNi. 0.83 Co 0.06 Mn 0.1086 Y 0.0014 O2, wherein the molar ratio of Li / Me (Me is the sum of all metal elements except lithium) is 1.03 and the doping amount of yttrium is 1500 ppm, and its preparation method is similar to that of Example 1.

[0212] Example 36

[0213] First positive electrode active material: The positive electrode active material prepared in Example 1 is used as the first positive electrode material.

[0214] Second positive electrode active material LiNi 0.92 Co 0.07 Mn 0.009 Sr 0.001 Preparation of O2: Weigh lithium hydroxide and dried high-nickel ternary precursor Ni according to the stoichiometric ratio of the chemical formula. 0.92 Co 0.07 Mn 0.01 (OH)2 and yttrium oxide, wherein the molar ratio of Li / Me (Me is the sum of all metal elements except lithium) is 1.03, and the strontium doping amount is 1500ppm, are mixed evenly in a high-speed mixer and then sintered in a kiln at a temperature of 760℃ for 20h in an oxygen atmosphere. After cooling, the mixture is crushed by an air jet mill, separated into micro powder by cyclone separation, and sieved to obtain a second positive electrode active material with a Dv50 of 3.0μm.

[0215] The first positive electrode active material and the second positive electrode active material are mixed evenly at a mass ratio of 1:1, and the resulting mixture is used as the positive electrode active material for preparing the positive electrode sheet.

[0216] The preparation process of the secondary battery is the same as in Example 1.

[0217] Example 37

[0218] The preparation of the secondary battery is the same as in Example 37, except that the first positive electrode active material and the second positive electrode active material are mixed at a mass ratio of 2:1.

[0219] Example 38

[0220] The preparation of the secondary battery is the same as in Example 37, except that the first positive electrode active material and the second positive electrode active material are mixed at a mass ratio of 3:1.

[0221] Example 39

[0222] The preparation of the secondary battery is the same as in Example 37, except that the first positive electrode active material and the second positive electrode active material are mixed at a mass ratio of 4:1.

[0223] Example 40

[0224] The preparation of the secondary battery is the same as in Example 37, except that the first positive electrode active material and the second positive electrode active material are mixed at a mass ratio of 8.5:1.5.

[0225] Comparative Example 1

[0226] The preparation of the secondary battery was the same as in Example 1, except that the matrix material LiNi from Example 1 was used directly. 0.92 Co 0.07 Mn 0.0086 Y 0.0014 O2 is used as the positive electrode active material in secondary batteries.

[0227] Comparative Example 2

[0228] The preparation of the secondary battery is the same as in Example 1, except that step S3 is not performed in the preparation of the positive electrode active material, that is, water washing and vibration drying are not performed.

[0229] II. Testing of relevant parameters

[0230] (1) Compacted density test

[0231] A certain amount of powder is placed in a compaction mold, and then the mold is placed on a compaction density instrument. A pressure of 5T is applied, and the thickness of the powder under pressure (the thickness after depressurization) is read on the instrument. The compaction density is calculated using ρ = m / v.

[0232] The results are shown in Table 1.

[0233] (2) Particle size test

[0234] The particle size of the positive electrode active material was determined according to GB / T 19077.1-2016 / ISO 13320:2009 (Laser diffraction method for particle size distribution). A clean beaker was used, containing an appropriate amount of the above-mentioned positive electrode active material and a suitable amount of pure water. The mixture was sonicated at 120W / 5min to ensure complete dispersion of the material powder in the water. The solution was then poured into the sample column of a laser particle size analyzer (Malvin, model: Mastersizer3000) and circulated to the test optical path system. Under laser beam irradiation, the particle size distribution characteristics (opause level: 8-12%) were obtained by receiving and measuring the energy distribution of the scattered light. The corresponding values ​​of Dv10, Dv50, and Dv90 were read, and (Dv90-Dv10) / Dv50 was calculated.

[0235] See Yuan 1 and Yuan 2 for the results.

[0236] (3) Compacted density of the positive electrode sheet

[0237] The compaction density PD of the positive electrode sheet is calculated using the formula PD = M / (d × A). In the formula, M is the mass of a small circular piece with a diameter of 40 mm cut from the positive electrode sheet, which is the average value obtained by weighing 10 times; d is the thickness of the positive electrode sheet, which is the average value obtained by measuring the thickness 10 times; and A is the area of ​​the small circular piece with a diameter of 40 mm.

[0238] The test results are shown in Tables 1 and 2.

[0239] (4) Elongation of the positive electrode sheet

[0240] The elongation in the longitudinal direction of the positive electrode sheet after cold pressing is calculated using the formula ΔEL% = (L2 - L1) / L1 × 100%. In this formula, L1 is the distance between the marks before cold pressing, which is 1000 mm, and L2 is the distance between the marks after cold pressing. The marks are formed as follows: In the central region of the electrode sheet, three line segments extending 1000 mm in length are taken at different positions along the width direction of the electrode sheet, and the two endpoints of each line segment are marked. L2 is recorded as the average of the measured distances between the two endpoints of each line segment after cold pressing.

[0241] The test results are shown in Yuan 1 and Yuan 2.

[0242] (5) Particle size and quantity of positive electrode active material in positive electrode sheet

[0243] Ten regions were randomly selected on the cross-section of the positive electrode sheet. Using a ZEISS Sigma 300 scanning electron microscope (SEM) and referring to JY / T010-1996, SEM images of each region were obtained. The particle size was measured in the SEM images. The particle size was used to determine whether the particles in the SEM images belonged to the first or second positive electrode active material. The number of particles of the first and second positive electrode active materials in each test region was counted from the SEM images, and the average number of particles of both materials was calculated.

[0244] III. Testing of Secondary Battery Performance

[0245] Storage capacity retention at 60℃:

[0246] Under constant temperature of 25℃, the battery was left to stand for 5 minutes, then discharged at 1 / 3C to 2.8V, left to stand for 5 minutes, then charged at 1 / 3C to 4.25V, and then charged at 4.25V with constant voltage until the current ≤0.05mA, left to stand for 5 minutes. This charged capacity is recorded as C0. The battery was then discharged at 1 / 3C to 2.8V, and this discharged capacity is the initial specific capacity, recorded as D0. The battery was then charged at a constant current of 0.33C to 4.25V and then charged with constant voltage until the current ≤0.05mA, left to stand for 5 minutes, and then placed in a high-low temperature chamber at 60℃ for 1 hour until the battery temperature reached the target temperature before storage. After 15 days, the battery was removed and the above process was repeated under constant temperature of 25℃, with the capacity Dn (n=0, 1, 2...) recorded every 15 days. The capacity retention rate after 60 days of storage was calculated as: (D4-D0) / D0*100%.

[0247]

[0248]

[0249] As can be seen from the above, 1) compared with the uncoated high-nickel cathode material of Comparative Example 1 (i.e., the high-nickel cathode material in the prior art), the cathode active material of this application achieves a double coating effect on the surface and grain boundaries of the substrate material through boron-containing ternary alloys or boron-containing ternary alloy oxides, which greatly improves the stability of the material surface structure and significantly improves the high-temperature storage performance of the secondary battery; 2) compared with the high-nickel cathode material of Comparative Example 2 that has not undergone water washing and vibration drying process (i.e., only the coating process was carried out, but no subsequent water washing and vibration drying was carried out), the cathode active material of this application has better dispersibility, higher interparticle filling degree, and while having high electrode compaction density, lower electrode elongation, which greatly improves the processing performance of the cathode electrode. Furthermore, the results of Examples 36-40 show that when the positive electrode active material of the first aspect of this application is used as the first positive electrode active material in combination with a second positive electrode active material with a smaller particle size (Dv50 is 3 μm), the second positive electrode active material with a smaller particle size can effectively fill the pores of the first positive electrode active material with a larger particle size, thereby further improving the processing performance of the electrode sheet.

[0250] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A positive electrode active material, characterized in that, The positive electrode active material includes a matrix material and a coating layer located on the surface of the matrix material, wherein, The chemical formula of the matrix material is LiNi. x Co y Mn z M a M' b O2, M = at least one of Zr, Y, Al, Ti, W, Sr, Ta, Sb, Nb, Na, K, Ca, or Ce, M′ = at least one of N, F, S, or Cl, 0.80 ≤ x ≤ 1.0, 0 ≤ y ≤ 0.20, 0 ≤ z ≤ 0.02, 0 ≤ a ≤ 0.02, b = 1 - xyza. The coating layer is a boron-containing ternary alloy or a boron-containing ternary alloy oxide, and the coating layer is also located on the surface of the grain boundary of the matrix material.

2. The positive electrode active material according to claim 1, characterized in that, The boron-containing ternary alloy is shown in Formula I, B-X1-X2(I). X1 and X2 are independently selected from one of the following elements: cobalt, hafnium, niobium, titanium, zirconium, tungsten, aluminum, molybdenum, and copper. The boron-containing ternary alloy oxide is shown in Formula II as B-Y1-Y2-O(II). Y1 and Y2 are independently selected from one of the following elements: cobalt, hafnium, niobium, titanium, zirconium, tungsten, aluminum, molybdenum, and copper.

3. The positive electrode active material according to claim 1, characterized in that, The positive electrode active material satisfies: 1.30≤(Dv90-Dv10) / Dv50≤2.

10.

4. The positive electrode active material according to claim 1 or 2, characterized in that, The amount of the coating layer is 500ppm-20000ppm, based on the weight of the matrix material.

5. The positive electrode active material according to claim 1 or 2, characterized in that, The amount of the coating layer is 4000-15000 ppm, based on the weight of the matrix material.

6. The positive electrode active material according to claim 1 or 2, characterized in that, The boron-containing ternary alloy is selected from at least one of the following: boron-cobalt-hafnium, boron-cobalt-niobium, boron-cobalt-titanium, boron-cobalt-zirconium, boron-cobalt-tungsten, boron-cobalt-aluminum, boron-cobalt-molybdenum, boron-cobalt-copper, and boron-hafnium-titanium.

7. The positive electrode active material according to claim 1 or 2, characterized in that, The boron-containing ternary alloy is selected from at least one of the following: boron-cobalt-hafnium, boron-cobalt-niobium, boron-cobalt-titanium, boron-cobalt-tungsten, boron-cobalt-aluminum, and boron-hafnium-titanium.

8. The positive electrode active material according to claim 1 or 2, characterized in that, The boron-containing ternary alloy oxide is selected from at least one of the following: boron-cobalt-hafnium oxide, boron-cobalt-niobium oxide, boron-cobalt-titanium oxide, boron-cobalt-zirconium oxide, boron-cobalt-tungsten oxide, boron-cobalt-aluminum oxide, boron-cobalt-molybdenum oxide, boron-cobalt-copper oxide, and boron-hafnium-titanium oxide.

9. The positive electrode active material according to claim 1 or 2, characterized in that, The boron-containing ternary alloy oxide is selected from at least one of the following: boron-cobalt-hafnium oxide, boron-cobalt-niobium oxide, boron-cobalt-titanium oxide, boron-cobalt-tungsten oxide, boron-cobalt-aluminum oxide, and boron-hafnium-titanium oxide.

10. The positive electrode active material according to claim 1 or 2, characterized in that, The molar ratio of boron, X1, and X2 in the boron-containing ternary alloy is 1:0.5:0.04-1:5:

4.

11. The positive electrode active material according to claim 1 or 2, characterized in that, The molar ratio of boron, X1, and X2 in the boron-containing ternary alloy is 1:0.5:0.15 to 1:1:0.

4.

12. The positive electrode active material according to claim 1 or 2, characterized in that, The molar ratio of boron, Y1 and Y2 in the boron-containing ternary alloy oxide is 1:0.5:0.03-1:5:

5.

13. The positive electrode active material according to claim 1 or 2, characterized in that, The molar ratio of boron, Y1 and Y2 in the boron-containing ternary alloy oxide is 1:0.5:0.15-1:1:0.

4.

14. The positive electrode active material according to claim 1 or 2, characterized in that, The Dv50 of the positive electrode active material is 6μm-18μm.

15. The positive electrode active material according to claim 1 or 2, characterized in that, The Dv50 of the positive electrode active material is 9μm-13μm.

16. The positive electrode active material according to claim 1 or 2, characterized in that, The compaction density of the positive electrode active material under 5T pressure is 3.65-3.75 g / cm³. 3 .

17. A method for preparing the positive electrode active material according to any one of claims 1-16, characterized in that, include S1) Preparation of matrix material; S2) The matrix material, boron-containing compound, and metal element are mixed in a mass ratio of 1:0.004-0.02:0.0001-0.2, or the matrix material, boron-containing compound, and metal oxide are mixed in a mass ratio of 1:0.004-0.02:0.0002-0.018, and then sintered in an inert atmosphere or an oxygen atmosphere to obtain an intermediate material; S3) The intermediate material is washed with water, centrifuged, filtered, and then dried by vibration to obtain the positive electrode active material. The chemical formula of the matrix material is LiNi. x Co y Mn z M a M' b O2, M = at least one of Zr, Y, Al, Ti, W, Sr, Ta, Sb, Nb, Na, K, Ca or Ce, M′ = at least one of N, F, S or Cl, 0.80≤x≤1.0, 0≤y≤0.20, 0≤z≤0.02, 0≤a≤0.02, b = 1-xyza.

18. The preparation method according to claim 17, characterized in that, The boron-containing compound is selected from one or more of cobalt boride, hafnium boride, niobium boride, titanium boride, zirconium boride, tungsten boride, aluminum boride, molybdenum boride, and copper boride, and / or The metallic element is selected from one or more of cobalt, hafnium, niobium, titanium, zirconium, tungsten, aluminum, molybdenum, and copper, and / or The metal oxide is selected from one or more of cobalt oxide, hafnium oxide, niobium oxide, titanium oxide, zirconium oxide, tungsten oxide, aluminum oxide, molybdenum oxide, and copper oxide.

19. The preparation method according to claim 17 or 18, characterized in that, The matrix material obtained in step S1) has a ratio of (Dv90-Dv10) / Dv50 ≥ 1.

2.

20. The preparation method according to claim 17 or 18, characterized in that, The matrix material obtained in step S1) has a ratio of (Dv90-Dv10) / Dv50 ≥ 1.

25.

21. The preparation method according to claim 17 or 18, characterized in that, In step S2), the matrix material, boron-containing compound and metal element are mixed in an inert atmosphere and sintered in an inert atmosphere at a temperature of 300-700℃ for 3-10 hours.

22. The preparation method according to claim 17 or 18, characterized in that, In step S2), the matrix material, boron-containing compound and metal element are mixed in an inert atmosphere and sintered in an inert atmosphere at a temperature of 300-550°C for 5-10 hours.

23. The preparation method according to claim 17 or 18, characterized in that, In step S2), the matrix material, boron-containing compound and metal oxide are sintered in an oxygen atmosphere at a temperature of 300-700°C for 3-10 hours.

24. The preparation method according to claim 17 or 18, characterized in that, In step S2), the matrix material, boron-containing compound and metal oxide are sintered in an oxygen atmosphere at a temperature of 550-650°C for 3-8 hours.

25. The preparation method according to claim 17 or 18, characterized in that, In step S3), the mass ratio of the intermediate material to water is 1:1 to 1:5, the water washing time is 1 to 10 minutes, the vibration frequency of the vibration drying is 10 to 50 Hz, and the drying time is 2 to 8 hours.

26. A positive electrode plate, characterized in that, The positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes a first positive electrode active material, which is the positive electrode active material according to any one of claims 1-16 or the positive electrode active material prepared by any one of claims 17-25. The content of the first positive electrode active material in the positive electrode film layer is 10% by weight or more, based on the total weight of the positive electrode film layer.

27. The positive electrode sheet according to claim 26, characterized in that, The positive electrode film layer further includes a second positive electrode active material, and the ratio of the first positive electrode active material to the second positive electrode active material is 6:4-8:

2. The chemical formula of the second positive electrode active material is LiNi x Co y Mn z M a M′ b O2, M = at least one of Zr, Y, Al, Ti, W, Sr, Ta, Sb, Nb, Na, K, Ca or Ce, M′ = at least one of N, F, S or Cl, 0.80≤x≤1.0, 0≤y≤0.20, 0≤z≤0.02, 0≤a≤0.02, b = 1-xyza, and the Dv50 of the second positive electrode active material is 2μm-5μm.

28. The positive electrode sheet according to claim 26, characterized in that, The positive electrode film layer further includes a second positive electrode active material, and the ratio of the first positive electrode active material to the second positive electrode active material is 6.5:3.5-7.5:2.

5. The chemical formula of the second positive electrode active material is LiNi x Co y Mn z M a M' b O2, M = at least one of Zr, Y, Al, Ti, W, Sr, Ta, Sb, Nb, Na, K, Ca or Ce, M′ = at least one of N, F, S or Cl, 0.80≤x≤1.0, 0≤y≤0.20, 0≤z≤0.02, 0≤a≤0.02, b = 1-xyza, and the Dv50 of the second positive electrode active material is 2.5μm-3.5μm.

29. The positive electrode sheet according to claim 27, characterized in that, The tap density of the second positive electrode active material is ≤1.8 g / cm³. 3 .

30. The positive electrode sheet according to claim 27, characterized in that, The tap density of the second positive electrode active material is 1.2-1.5 g / cm³. 3 .

31. A secondary battery, characterized in that, The positive electrode sheet included in any one of claims 26-30.

32. A battery module, characterized in that, Includes the secondary battery as described in claim 31.

33. A battery pack, characterized in that, Includes the battery module as described in claim 32.

34. An electrical appliance, characterized in that, It includes at least one selected from the secondary battery of claim 31, the battery module of claim 32, or the battery pack of claim 33.

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