Positive electrode active material, secondary battery, and electrical device

Abstract

A positive electrode active material, a secondary battery, and an electrical device. The positive electrode active material comprises: elemental nickel, the molar ratio of the elemental nickel in the total amount of nickel, cobalt, and manganese metal elements being 55% or higher; elemental cobalt, the molar ratio of the elemental cobalt in the total amount of the nickel, cobalt, and manganese metal elements being 20% or lower; a first modifying element Zr; a second modifying element Al; a third modifying element B; and a fourth modifying element, which is at least one of Nb, Mo, and W. The positive electrode active material has excellent performance, and batteries prepared therefrom exhibit both good energy density and cycling performance.

Description

Positive electrode active material, secondary battery and electric device

[0001] Cross-references

[0002] This application refers to Chinese Patent Application No. 202410246712.5, filed on March 5, 2024, entitled “Positive Electrode Active Material, Secondary Battery and Electrical Device,” which is incorporated herein by reference in its entirety. Technical Field

[0003] The present application relates to the technical field of secondary batteries, and in particular to a positive electrode active material, a secondary battery, and an electrical device. Background Art

[0004] With the escalating energy crisis and environmental issues, the development of green, low-carbon, and environmentally friendly new energy sources is urgent. Lithium-ion batteries, as electrochemical energy storage devices, offer advantages such as large capacity, no memory effect, and a wide application window, and have been widely used in various fields. In the transportation sector, new energy vehicles powered by lithium-ion batteries are gradually replacing traditional fuel vehicles and becoming the preferred mode of transportation for people worldwide. Currently, commonly used cathode active materials in the industry, such as lithium iron phosphate and medium- and low-nickel ternary materials, cannot meet the performance requirements of end users due to inherent material limitations.

[0005] Summary of the Invention

[0006] This application is made in view of the above-mentioned issues, and its purpose is to stabilize the crystal structure of the material by modifying the positive electrode active material using multiple elements, so that the material has the advantages of high energy density and structural stability, and the battery prepared therefrom can have both good energy density and cycle performance.

[0007] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a positive electrode active material containing transition metal elements, the positive electrode active material including: nickel element, the molar proportion of nickel element in the total amount of nickel, cobalt and manganese elements is more than 55%; cobalt element, the molar proportion of cobalt element in the total amount of nickel, cobalt and manganese elements is less than 20%; a first modifying element Zr; a second modifying element Al; a third modifying element B; and a fourth modifying element: which is at least one of Nb, Mo and W; wherein, based on the total mass of the positive electrode active material, the mass proportion of the first modifying element is 0.01% to 0.5%, the mass proportion of the second modifying element is 0.01% to 1%, the mass proportion of the third modifying element is 0.01% to 0.4%, and the mass proportion of the fourth modifying element is 0.01% to 2.2%.

[0008] In the ternary material, as the proportion of nickel content in the transition metal increases, the energy density of the material becomes higher and higher, but the higher energy density causes the electrochemical stability of the material to decrease. In the technical solution of the present application, by adding modifying elements to the ternary material and coupling a variety of different modifying elements with the ternary material, the capacity and cycle performance of the ternary material can be greatly improved. Among them, the first modifying element and the second modifying element can react with the bulk of the ternary material, which helps to improve the structural stability of the material and optimize the transmission of lithium ions, and also helps to reduce the side reactions between the ternary material and the electrolyte, thereby significantly improving the cycle stability and power performance of the material. At the same time, the third modifying element and the fourth modifying element can increase the capacity of the material, so that the ternary material can achieve high capacity. When the mass ratio of these four modifying elements is matched with each other within the above range, the positive electrode active material can take into account good capacity and stability, and the battery prepared therefrom can take into account good energy density and cycle performance.

[0009] In any embodiment, in the positive electrode active material, the mass ratio of (first modifying element+second modifying element):(third modifying element+fourth modifying element) is 1:(0.1-10).

[0010] In any embodiment, in the positive electrode active material, the mass ratio of (first modifying element+second modifying element):(third modifying element+fourth modifying element) is 1:(0.1-0.5).

[0011] In any embodiment, in the positive electrode active material, the mass ratio of (element Zr+element Al):(element B+element W) is 1:(0.1-0.5).

[0012] In any embodiment, in the positive electrode active material, the mass ratio of the first modifying element to the second modifying element is 1:(0.1-30).

[0013] In any embodiment, in the positive electrode active material, the mass ratio of the first modifying element to the second modifying element is 1:(0.1 to 1).

[0014] In any embodiment, in the positive electrode active material, the mass ratio of the element Zr to the element Al is 1:(0.1-1).

[0015] In any embodiment, in the positive electrode active material, the mass ratio of the third modifying element to the fourth modifying element is 1:(0.05-30).

[0016] In any embodiment, in the positive electrode active material, the mass ratio of the third modifying element:the fourth modifying element is 1:(0.1-1).

[0017] In any embodiment, in the positive electrode active material, the mass ratio of element B:element W is 1:(0.1-1).

[0018] By further precisely controlling the mass ratios of the first modifying element, the second modifying element, the third modifying element, and the fourth modifying element, the electrochemical properties and stability of the positive electrode active material can be further optimized, achieving the optimal solution for the comprehensive performance of the material.

[0019] In any embodiment, based on the total mass of the positive electrode active material, the mass of the first modifying element accounts for 0.05% to 0.5%.

[0020] In any embodiment, the mass proportion of the second modifying element is 0.05% to 0.3% based on the total mass of the positive electrode active material.

[0021] In any embodiment, based on the total mass of the positive electrode active material, the mass of the third modifying element accounts for 0.01% to 0.2%.

[0022] In any embodiment, the mass of the fourth modifying element accounts for 0.01% to 0.3% based on the total mass of the positive electrode active material.

[0023] When the mass ratios of the first modifying element, the second modifying element, the third modifying element, and the fourth modifying element are within the above ranges, the energy density and cycle performance of the material can be further improved.

[0024] In any embodiment, the molar proportion of nickel in the total amount of nickel, cobalt and manganese is 60% to 95%; and / or the molar proportion of cobalt in the total amount of nickel, cobalt and manganese is 3% to 10%.

[0025] In any embodiment, the molar ratio of nickel element in the total amount of nickel, cobalt and manganese metal elements is 80% to 95%.

[0026] When the ratio of nickel and cobalt to transition metal in the positive electrode active material is within the above range, the material has a better gram capacity, and the battery prepared therefrom can better balance energy density and cycle performance.

[0027] In any embodiment, the positive active material includes single crystal particles and polycrystalline particles.

[0028] When the positive electrode active material includes both single crystal particles and polycrystalline particles, compared with a system of single particle type, the single crystal mixed polycrystalline system is beneficial to further improve the compaction density of the material and improve its volume energy density and cycle stability.

[0029] In any embodiment, the specific surface area of ​​the single crystal particles is 0.9 to 1.5 m 2 / g, the specific surface area of ​​polycrystalline particles is 0.3~1.0m 2 / g.

[0030] When the specific surface area of ​​the positive electrode active material is within the above range, it is beneficial to increase the contact area between the positive electrode material and the electrolyte, so that the electrochemical activity of the material is further enhanced.

[0031] In any embodiment, in the positive electrode active material, a mass ratio of single crystal particles to polycrystalline particles is 1:9 to 5:5.

[0032] In any embodiment, the volume average particle size Dv50 of the single crystal particles is 3 to 5 μm, and the volume average particle size Dv50 of the polycrystalline particles is 4 to 13 μm.

[0033] When the single crystal particles and the polycrystalline particles in the positive electrode active material are matched in the above-mentioned mass ratio and particle size, the energy density and cycle performance of the battery can be further improved.

[0034] In any embodiment, the positive electrode active material has the molecular formula Li a (Ni b Co c Mn 1-b-c ) 1- x-y-z-q Zr x Al y B z Q q O e , wherein Q includes at least one of Nb, Mo, and W, 0.9≤a≤1.2, 0.55≤b≤0.95, 0≤c≤0.20, 1.8≤e≤2.2, 0 <x≤0.04,0<y≤0.02,0<z≤0.09,0<q≤0.03。

[0035] In any embodiment, the positive electrode active material further includes strontium (Sr), and the mass proportion of the strontium element is 0.05% to 0.2% based on the total mass of the positive electrode active material.

[0036] In any embodiment, the positive electrode active material further includes yttrium (Y), and the mass proportion of the yttrium (Y) is 0.05% to 0.2% based on the total mass of the positive electrode active material.

[0037] Further adding modifying elements strontium and / or yttrium to the ternary material can further improve the capacity and cycle performance of the ternary material.

[0038] In any embodiment, the positive electrode active material has a powder resistivity of 100 to 8000 Ω·cm at 12 MPa.

[0039] When the resistivity of the material powder is within the above range, the power performance of the material can be further improved.

[0040] In any embodiment, the tap density of the positive electrode active material is 1.9 to 2.6 g / cm 3 .

[0041] The second aspect of the present application provides a lithium secondary battery, comprising the positive electrode active material described in the first aspect of the present application.

[0042] In any embodiment, the lithium secondary battery has a gram capacity of the positive electrode active material of 193 to 210 mAh / g at 25° C. and a 1 / 3C discharge rate.

[0043] In any embodiment, the lithium secondary battery has a gram capacity of the positive electrode active material of 202 to 210 mAh / g at 25° C. and a 1 / 3C discharge rate.

[0044] A third aspect of the present application provides an electrical device comprising the lithium secondary battery described in the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] 1A and 1B are single crystal morphologies of the positive electrode active material prepared in Example 1.

[0046] FIG2 is a polycrystalline morphology of the positive electrode active material prepared in Example 1.

[0047] FIG3 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0048] FIG. 4 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 3 .

[0049] FIG5 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0050] Explanation of reference numerals: 5 secondary battery; 51 housing; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0051] Below, embodiments of the positive electrode active material, secondary battery, electrical device, and method for manufacturing the same of the present application are described in detail. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0052] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0054] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0055] Unless otherwise specified, all steps of the present application may be performed sequentially, randomly, or optionally sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0056] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0057] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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).

[0058] At present, improving the energy density of materials has become the main research direction for the development of positive electrode active materials, and increasing nickel and capacity is one of the commonly used methods. However, as the nickel content in the ternary material increases, the phase change of the material intensifies and the lattice shrinkage and expansion rate increases, which causes the cycle life of the material to deteriorate. The present application provides a positive electrode active material with good structural stability and gram capacity, so that the prepared battery can take into account good energy density and cycle performance.

[0059] [Positive electrode active material]

[0060] In order to achieve the above-mentioned purpose, the present application provides a positive electrode active material containing transition metal elements, the positive electrode active material including: nickel element, the molar proportion of nickel element in the total amount of nickel, cobalt and manganese metal elements is more than 55%; cobalt element, the molar proportion of cobalt element in the total amount of nickel, cobalt and manganese metal elements is less than 20%; a first modifying element Zr; a second modifying element Al; a third modifying element B; and a fourth modifying element: which is at least one of Nb, Mo and W; wherein, based on the total mass of the positive electrode active material, the mass proportion of the first modifying element is 0.01% to 0.5%, the mass proportion of the second modifying element is 0.01% to 1%, the mass proportion of the third modifying element is 0.01% to 0.4%, and the mass proportion of the fourth modifying element is 0.01% to 2.2%.

[0061] In the ternary material, as the proportion of nickel content in the transition metal increases, the energy density of the material becomes higher and higher, but the higher energy density causes the electrochemical stability of the material to decrease. In the technical solution of the present application, by adding modifying elements to the ternary material and coupling a variety of different modifying elements with the ternary material, the capacity and cycle performance of the ternary material can be greatly improved. Among them, the first modifying element and the second modifying element can react with the bulk of the ternary material, which helps to improve the structural stability of the material and optimize the transmission of lithium ions, and also helps to reduce the side reactions between the ternary material and the electrolyte, thereby significantly improving the cycle stability and power performance of the material. At the same time, the third modifying element and the fourth modifying element can increase the capacity of the material, so that the ternary material can achieve high capacity. When the mass ratio of these four modifying elements is matched within the above range, the positive electrode active material can take into account good capacity and stability, and the battery prepared therefrom can take into account good energy density and cycle performance.

[0062] In some embodiments, the positive electrode active material includes nickel, and the molar proportion of nickel in the total amount of nickel, cobalt, and manganese is greater than 55%, such as 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or other values ​​not listed above. In some embodiments, the molar proportion of nickel in the total amount of nickel, cobalt, and manganese is 60%, 80%, or 95%.

[0063] In some embodiments, the positive electrode active material further comprises cobalt, wherein the molar ratio of cobalt to the total amount of nickel, cobalt, and manganese is less than 20%, such as 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, or other values ​​not listed below 20%. In some embodiments, the molar ratio of cobalt to the total amount of nickel, cobalt, and manganese is 3% or 10%.

[0064] In some embodiments, the positive electrode active material further includes: a first modifying element Zr; a second modifying element Al; a third modifying element B; and a fourth modifying element: which is at least one of Nb, Mo, and W.

[0065] In some embodiments, based on the total mass of the positive electrode active material, the mass percentage of the first modifying element is 0.01% to 0.5%, such as 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or other values ​​not listed in the range of 0.01% to 0.5%. In some embodiments, the mass percentage of the first modifying element is 0.01% or 0.5%.

[0066] In some embodiments, based on the total mass of the positive electrode active material, the mass percentage of the second modifying element is 0.01% to 1%, such as 0.01%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or other values ​​not listed in the range of 0.01% to 1%. In some embodiments, the mass percentage of the second modifying element is 0.0.1%, 0.05%, 0.3%, or 1%.

[0067] In some embodiments, based on the total mass of the positive electrode active material, the mass percentage of the third modifying element is 0.01% to 0.4%, such as 0.01%, 0.1%, 0.2%, 0.3%, 0.4%, or other values ​​not listed in the range of 0.01% to 0.4%. In some embodiments, the mass percentage of the third modifying element is 0.01%, 0.1%, 0.2%, or 0.4%.

[0068] In some embodiments, based on the total mass of the positive electrode active material, the mass percentage of the fourth modifying element is 0.01% to 2.2%, such as 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, or other values ​​not listed in the range of 0.01% to 2.2%. In some embodiments, the mass percentage of the fourth modifying element is 0.01%, 0.3%, 2.0%, or 2.2%.

[0069] In some embodiments, in the positive electrode active material, the mass ratio of (first modifying element + second modifying element): (third modifying element + fourth modifying element) is 1:(0.1-10), such as 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or other values ​​not listed in the range of 1:(0.1-10). In some embodiments, in the positive electrode active material, the mass ratio of (first modifying element + second modifying element): (third modifying element + fourth modifying element) is 1:0.625, 1:0.5, 1:3, 1:0.91, 1:0.33, 1:2.75, 1:0.3875, 1:0.875, 1:1.61, 1:0.15, 1:0.98, 1:0.2, 1:1.625, or 1:0.26.

[0070] In some embodiments, in the positive electrode active material, the mass ratio of (first modifying element+second modifying element):(third modifying element+fourth modifying element) is 1:(0.33-3).

[0071] In some embodiments, in the positive electrode active material, the mass ratio of (first modifying element+second modifying element):(third modifying element+fourth modifying element) is 1:(0.1-0.5).

[0072] In some embodiments, the mass ratio of the first modifying element to the second modifying element in the positive electrode active material is 1:(0.1-30), such as 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:15, 1:20, 1:25, 1:30, or other values ​​not listed in the range of 1:(0.1-30). In some embodiments, the mass ratio of the first modifying element to the second modifying element in the positive electrode active material is 1:0.6, 1:0.1, 1:2, 1:30, 1:0.1, 1:0.02, or 1:4.

[0073] In some embodiments, in the positive electrode active material, the mass ratio of the first modifying element to the second modifying element is 1:(0.1-2).

[0074] In some embodiments, in the positive electrode active material, the mass ratio of the first modifying element to the second modifying element is 1:(0.1-1).

[0075] In some embodiments, the mass ratio of the third modifying element to the fourth modifying element in the positive electrode active material is 1:(0.05-30), such as 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:15, 1:20, 1:25, 1:30, or other values ​​not listed in the range of 1:(0.05-30). In some embodiments, the mass ratio of the third modifying element to the fourth modifying element in the positive electrode active material is 1:1.5, 1:3, 1:11, 1:1, 1:10, 1:30, 1:0.75, 1:0.3, or 1:0.05.

[0076] In some embodiments, in the positive electrode active material, the mass ratio of the third modifying element to the fourth modifying element is 1:(1-10).

[0077] In some embodiments, in the positive electrode active material, the mass ratio of the third modifying element:the fourth modifying element is 1:(0.1-1).

[0078] In some embodiments, the fourth modifying element is W. In some embodiments, in the positive electrode active material, the mass ratio of (element Zr + element Al): (element B + element W) is 1:(0.1-0.5), for example, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, or other unlisted values ​​within the range of 1:(0.1-0.5).

[0079] In some embodiments, in the positive electrode active material, the mass ratio of element Zr:element Al is 1:(0.1-1), for example, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, or other unlisted values ​​within the range of 1:(0.1-1).

[0080] In some embodiments, the fourth modifying element is W. In some embodiments, in the positive electrode active material, the mass ratio of the third modifying element B: the fourth modifying element W is 1:(0.1-1), for example, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, or other unlisted values ​​within the range of 1:(0.1-1).

[0081] By further precisely controlling the mass ratios of the first modifying element, the second modifying element, the third modifying element, and the fourth modifying element, the electrochemical properties and stability of the positive electrode active material can be further optimized to achieve the optimal solution for material performance.

[0082] In some embodiments, based on the total mass of the positive electrode active material, the mass of the first modifying element accounts for 0.05% to 0.5%.

[0083] In some embodiments, based on the total mass of the positive electrode active material, the mass of the second modifying element accounts for 0.05% to 0.3%.

[0084] In some embodiments, based on the total mass of the positive electrode active material, the mass of the third modifying element accounts for 0.01% to 0.2%.

[0085] In some embodiments, based on the total mass of the positive electrode active material, the mass of the fourth modifying element accounts for 0.01% to 0.3%.

[0086] When the mass ratios of the first modifying element, the second modifying element, the third modifying element, and the fourth modifying element are within the above ranges, the energy density and cycle performance of the material can be further improved.

[0087] In some embodiments, the molar ratio of nickel to the total amount of nickel, cobalt, and manganese elements is 60% to 95%.

[0088] In some embodiments, the molar ratio of nickel element to the total amount of nickel, cobalt, and manganese metal elements is 80% to 95%.

[0089] In some embodiments, the molar ratio of cobalt element to the total amount of nickel, cobalt and manganese elements is 3% to 10%.

[0090] When the ratio of nickel and cobalt to transition metal in the positive electrode active material is within the above range, the material has a better gram capacity, and the battery prepared therefrom can better balance energy density and cycle performance.

[0091] In some embodiments, the positive active material includes single crystal particles and polycrystalline particles.

[0092] As used herein, "single crystal" refers to a complete particle, or an agglomerate of 2 to 9 primary particles, or an agglomerate of 10 to 49 primary particles, or a mixture of the above types of particles and / or agglomerates, see Figures 1A and 1B.

[0093] As used herein, "polycrystalline" refers to secondary particles formed by the agglomeration of multiple primary particles. "Multiple" here usually refers to more than 10, also usually refers to more than 50, also usually refers to more than 100, or a mixture of the above types of agglomerates, see Figure 2.

[0094] When used in this article, when "single crystal" and "polycrystalline" appear at the same time, "single crystal" refers to particles with a polygonal or irregular outer contour, see Figures 1A and 1B; "polycrystalline" refers to particles with a circular or nearly circular outer contour, see Figure 2.

[0095] When the positive electrode active material includes both single crystal particles and polycrystalline particles, compared with a system of single particle type, the single crystal mixed polycrystalline system is beneficial to further improve the volume energy density and cycle stability of the material.

[0096] In some embodiments, the specific surface area of ​​the single crystal particles is 0.9 to 1.5 m 2 / g, for example 0.9m 2 / g, 1.0m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g, or 0.9~1.5m 2 In some embodiments, the specific surface area of ​​the single crystal particles is 0.9 to 1.2 m 2 In some embodiments, the specific surface area of ​​the single crystal particles is 0.9 m 2 / g.

[0097] In some embodiments, the specific surface area of ​​the polycrystalline particles is 0.3 to 1.0 m 2 / g, for example 0.3m 2 / g, 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, or 0.3~1.0m 2 In some embodiments, the specific surface area of ​​the polycrystalline particles is 0.3 m 2 / g, 0.5m 2 / g, 1.0m 2 / g.

[0098] As used herein, "specific surface area" refers to the total surface area per unit mass of a material. This specific surface area can be determined according to GB / T 19587-2017 using nitrogen adsorption specific surface area analysis and calculation using the Brunauer-Emmett-Teller (BET) method. Nitrogen adsorption specific surface area analysis can be performed using a Micromeritics Tri-Star 3020 specific surface area pore size analyzer.

[0099] When the specific surface area of ​​the positive electrode active material is within the above range, it is beneficial to increase the contact area between the positive electrode material and the electrolyte, so that the electrochemical activity of the material is further enhanced.

[0100] In some embodiments, in the positive electrode active material, the mass ratio of the single crystal particles to the polycrystalline particles is 1:9 to 5:5, for example, 1:9, 2:8, 3:7, 4:6, 5:5, or other unlisted values ​​within the range of 1:9 to 5:5.

[0101] In some embodiments, in the positive electrode active material, a mass ratio of the single crystal particles to the polycrystalline particles is 1:9 to 3:7.

[0102] In some embodiments, the volume average particle size Dv50 of the single crystal particles is 3 to 5 μm, such as 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, 5.0 μm, or other values ​​not listed in the range of 3 to 5 μm. In some embodiments, the volume average particle size Dv50 of the single crystal particles is 4 μm.

[0103] In some embodiments, the volume average particle size Dv50 of the polycrystalline grains is 4 to 13 μm, such as 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, or other values ​​not listed in the range of 4 to 13 μm. In some embodiments, the volume average particle size Dv50 of the polycrystalline grains is 4 μm, 10 μm, or 13 μm.

[0104] As used herein, "volume average particle size Dv50" refers to the particle size at which the cumulative volume distribution percentage, starting from the smallest particle size, reaches 50%. This value can be determined using a Malvern MasterSizer 2000 laser particle size analyzer, in accordance with GB / T19077-2016 / ISO 13320:2009.

[0105] When the single crystal particles and the polycrystalline particles in the positive electrode active material are matched in the above-mentioned mass ratio and particle size, the energy density and cycle performance of the battery can be further improved.

[0106] In some embodiments, the positive electrode active material has the molecular formula Li a (Ni b Co c Mn 1-b-c ) 1- x-y-z-q Zr x Al y B z Q q O e , wherein Q includes at least one of Nb, Mo, and W, 0.9≤a≤1.2, 0.55≤b≤0.95, 0≤c≤0.20, 1.8≤e≤2.2, 0≤x≤0.04, 0≤y≤0.02, 0≤z≤0.09, and 0≤q≤0.03.

[0107] When used in this article, "having a molecular formula" is not limited to the substance represented by the molecular formula, but also includes other substances formed after further appropriate modification on the basis of the molecular formula, which is not limited here. The use of "having a molecular formula" is only for the convenience of description and is not intended to limit this application. It can be understood that new materials or new substances obtained by appropriate modification on the basis of the listed positive active materials are also within the scope of positive active materials. The aforementioned appropriate modification refers to an acceptable modification method for the positive active material, and a non-limiting example is coating modification.

[0108] In the enumeration of positive electrode active materials in this application, unless otherwise specified, the Li content refers to the initial state of the material. When the positive electrode active material is applied to the positive electrode sheet in the battery system, the Li content in the positive electrode active material contained in the positive electrode sheet will usually change after charge and discharge cycles. The Li content can be measured by atomic molar content, but is not limited to this. Regarding "the Li content refers to the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry.

[0109] In the list of positive electrode active materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause the atomic molar content of oxygen to change, and the actual O content will fluctuate. The O content can be measured by atomic molar content, but is not limited to this.

[0110] In some embodiments, the positive electrode active material further includes strontium (Sr), and the mass proportion of the strontium element is 0.05% to 0.2%, based on the total mass of the positive electrode active material, for example, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, or other unlisted values ​​within the range of 0.05% to 0.2%.

[0111] In some embodiments, the positive electrode active material further includes yttrium element (Y), and the mass proportion of yttrium element is 0.05% to 0.2% based on the total mass of the positive electrode active material, for example, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, or other unlisted values ​​within the range of 0.05% to 0.2%.

[0112] Further adding modifying elements strontium and / or yttrium to the ternary material can further improve the capacity and cycle performance of the ternary material.

[0113] In some embodiments, the powder resistivity of the positive electrode active material at 12 MPa is 100 to 8000 Ω·cm, such as 100 Ω·cm, 500 Ω·cm, 1000 Ω·cm, 1500 Ω·cm, 2000 Ω·cm, 2500 Ω·cm, 3000 Ω·cm, 3500 Ω·cm, 4000 Ω·cm, 4500 Ω·cm, 5000 Ω·cm, 6000 Ω·cm, 7000 Ω·cm, 8000 Ω·cm, or other values ​​not listed in the range of 100 to 8000 Ω·cm. In some embodiments, the powder resistivity of the positive electrode active material at 12 MPa is 2000 Ω·cm, 1500 Ω·cm, 2200 Ω·cm, 1900 Ω·cm, 8000 Ω·cm, 1600 Ω·cm, 100 Ω·cm, or 5000 Ω·cm.

[0114] As used herein, "powder resistivity" describes the electrical conductivity of a powder material, typically referring to the resistance per unit length or area, expressed in ohm-centimeter (Ω·cm). It is measured using a powder resistivity tester (ST2722) according to standard GB / T 30835-2014.

[0115] When the resistivity of the material powder is within the above range, the power performance of the material can be further improved.

[0116] In some embodiments, the tap density of the positive electrode active material is 1.9 to 2.6 g / cm 3 , for example 1.9 g / cm 3 , 2.0g / cm 3 , 2.1g / cm 3 , 2.2g / cm 3 , 2.3g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3, 2.6g / cm 3 , or 1.9~2.6g / cm 3 In some embodiments, the tap density of the positive electrode active material is 2.52 g / cm 3 , 2.55g / cm 3 , 2.50g / cm 3 , 2.60g / cm 3 .

[0117] In some embodiments, the tap density of the positive electrode active material is 2.5 to 2.6 g / cm 3 .

[0118] As used herein, "tap density" refers to the density obtained by dividing the mass of a powder by the tapped volume after vibrating and rotating a container until the powder volume no longer decreases. The tap density can be determined according to GB / T5162-2006 using a powder tap density tester (such as the Dandong Better BT-301) with the following parameters: vibration frequency of 250 ± 15 times / minute, amplitude of 3 ± 0.2 mm, vibration frequency of 5000 times, and a graduated cylinder volume of 25 mL.

[0119] In some embodiments, the lithium secondary battery has a gram capacity of the positive electrode active material of 193 to 210 mAh / g, such as 193 mAh / g, 194 mAh / g, 195 mAh / g, 196 mAh / g, 197 mAh / g, 198 mAh / g, 199 mAh / g, 200 mAh / g, 201 mAh / g, 202 mAh / g, 203 mAh / g, 204 mAh / g, 205 mAh / g, 206 mAh / g, 207 mAh / g, 208 mAh / g, 209 mAh / g, 210 mAh / g, or other unlisted values ​​within the range of 193 to 210 mAh / g.

[0120] In some embodiments, the lithium secondary battery has a gram capacity of the positive electrode active material of 202 to 210 mAh / g at 25° C. and a 1 / 3C discharge rate.

[0121] [Positive electrode]

[0122] The present application also provides a positive electrode plate, characterized in that it includes a positive electrode current collector and a positive electrode active material arranged on at least one surface of the positive electrode current collector, wherein the positive electrode active material is the positive electrode active material of the present application.

[0123] In some embodiments, the positive electrode 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 material base and a metal layer formed on at least one surface of the polymer material base. 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 material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0124] In some embodiments, the positive electrode plate further includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0125] In some embodiments, the positive electrode sheet further includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0126] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0127] [Negative electrode]

[0128] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0129] As an example, the negative electrode current collector has two surfaces opposite to each other in its 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.

[0130] 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 base layer and a metal layer formed on at least one surface of the polymer base material. 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 base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0131] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. 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. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional 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.

[0132] In some embodiments, the negative electrode film layer further includes a binder. The binder can 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).

[0133] In some embodiments, the negative electrode film layer further includes a conductive agent, which can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0134] In some embodiments, the negative electrode film layer further includes other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0135] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0136] [Electrolytes]

[0137] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. This application has no specific restrictions on the type of electrolyte, and it can be selected according to needs.

[0138] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0139] 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 difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0140] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0141] In some embodiments, the electrolyte further includes additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0142] [Isolation film]

[0143] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0144] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven 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.

[0145] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0146] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0147] 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. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0148] [Lithium secondary battery]

[0149] The present application also provides a lithium secondary battery, characterized in that it includes the positive electrode sheet of the present application.

[0150] The present application has no particular limitation on the shape of the lithium secondary battery, which can be cylindrical, square, or any other shape. For example, FIG3 shows a secondary battery 5 with a square structure as an example.

[0151] In some embodiments, referring to Figure 4, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0152] [Electrical devices]

[0153] In addition, the present application also provides an electrical device, which includes the lithium secondary battery provided by the present application. The lithium secondary battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can include, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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.

[0154] As an electrical device, a lithium secondary battery can be selected according to its usage requirements.

[0155] Figure 5 shows an example of an electric device. This device can 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 lithium secondary batteries, a battery pack or battery module can be used.

[0156] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a lithium secondary battery as a power source.

[0157] Example

[0158] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0159] 1. Preparation method

[0160] Example 1

[0161] 1.1. Preparation of positive electrode active materials

[0162] (1) Polycrystalline preparation method:

[0163] The ternary polycrystalline precursor (Ni 0.80 Co 0.10 Mn 0.10 )OH2 (volume average particle size Dv50 = 10 μm), LiOH·H2O, ZrO2, Al2O3, and MoO3 are mixed in a mixer at the molar ratio of the corresponding elements in the molecular formula, and then sintered at 800°C in an oxygen atmosphere (oxygen volume concentration>99.9%) for 20 h to obtain material 1. After mechanical crushing, the crushed material 1 is washed in deionized water (material-liquid mass ratio 0.5:1 to ensure that the material does not sink to the bottom during stirring) for 1 min.

[0164] Then, the washed material 1 was mixed with H3BO3 in the molar ratio of the corresponding elements in the molecular formula, and sintered at 400℃ for 10h in an oxygen atmosphere (oxygen volume concentration>99.9%) to obtain a polycrystalline positive electrode active material. The molecular formula of the obtained polycrystalline positive electrode active material is Li(Ni 0.8 Co 0.1 Mn 0.1 ) 0.963 Zr 0.005 Al 0.011 B 0.018 Mo 0.003 O2, with a specific surface area of ​​0.5m 2 / g, and the volume average particle size Dv50 is 10 μm.

[0165] (2) Single crystal preparation method:

[0166] The ternary single crystal precursor (Ni 0.80 Co 0.10 Mn0.10 )OH2 (volume average particle size Dv50 = 3 μm), LiOH·H2O, ZrO2, Al2O3, and MoO3 are mixed in a mixer at a molar ratio of the corresponding elements in the molecular formula, and then sintered at 850°C for 25 hours in an oxygen atmosphere (oxygen volume concentration > 99.9%), and crushed by air flow to obtain material 2.

[0167] Then, material 2 was mixed with H3BO3 in the molar ratio of the corresponding elements in the molecular formula, and sintered at 400℃ for 10h in an oxygen atmosphere (oxygen volume concentration>99.9%) to obtain a single crystal positive electrode active material. The molecular formula of the obtained single crystal positive electrode active material is Li(Ni 0.8 Co 0.1 Mn 0.1 ) 0.963 Zr 0.005 Al 0.011 B 0.018 Mo 0.003 O2, with a specific surface area of ​​0.9m 2 / g, and the volume average particle size Dv50 is 4 μm.

[0168] (3) Preparation method of polycrystalline mixed single crystal:

[0169] The polycrystalline positive electrode active material and the single crystal positive electrode active material were physically mixed in a mass ratio of 5:5 to obtain a polycrystalline mixed single crystal positive electrode active material. The obtained polycrystalline mixed single crystal positive electrode active material had a powder resistivity of 2000 Ω·cm at 12 MPa.

[0170] 1.2. Preparation of positive electrode sheet

[0171] The positive electrode active material of the polycrystalline mixed single crystal prepared in 1.1, polyvinylidene fluoride and conductive carbon black are mixed in a mass ratio of 90:5:5, and then N-methylpyrrolidone (NMP) is added and stirred for 2 hours. Then, it is stirred in a homogenizer at 1200r / min until the mixture is uniformly mixed, and then evenly coated on the double-sided surface of a 13-micron thick aluminum foil current collector. After the coating is completed, it is dried in a drying oven at 120°C, cold pressed, and cut to obtain the positive electrode sheet.

[0172] Preparation of electrolyte

[0173] A mixed solvent was prepared by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:2. Then, in an argon atmosphere glove box, thoroughly dried lithium hexafluorophosphate was dissolved in the mixed solvent and mixed thoroughly to obtain an electrolyte solution. The lithium salt concentration in the electrolyte was 1 mol / L.

[0174] 1.4. Preparation of negative electrode sheet

[0175] The negative electrode active material graphite, sodium carboxymethyl cellulose, styrene-butadiene rubber and acetylene black were mixed in a mass ratio of 96:1:1:2, deionized water was added, and the mixture was stirred evenly in a blender. The slurry was then coated on both sides of an 8-micron-thick copper foil, dried in an oven at 120°C, cold pressed, and cut to obtain negative electrode sheets.

[0176] 1.5. Preparation of battery cells

[0177] The positive electrode sheet, isolation film, and negative electrode sheet are stacked from top to bottom to ensure that the positive and negative electrode sheets cannot touch each other. Then they are wound into bare cells using a winding needle, placed in a square aluminum shell, and the electrolyte is injected. The cells are prepared by steps such as standing, forming, and capacity.

[0178] Examples 2 to 20 and 22

[0179] The secondary batteries of Examples 2-20 and 22 were prepared similarly to Example 1, except that the types and contents of the elements in the positive electrode active material, the BET and powder resistivity of the positive electrode active material, the mass ratio of single crystal particles, DV50 (single crystal particles and polycrystalline particles), and the tap density of the positive electrode active material were adjusted. The different preparation parameters are detailed in Tables 1-5. The chemical formulas of the positive electrode active materials prepared in Examples 2-20 and 22 can be calculated based on the types and mass ratios of the different elements in Tables 1-5.

[0180] Example 21

[0181] The secondary battery of Example 21 is prepared in a similar manner to that of Example 1, but the types of raw materials are adjusted to change the types of elements in the positive electrode active material. The difference between the preparation method of Example 21 and that of Example 1 is as follows:

[0182] (1) Polycrystalline preparation method:

[0183] The ternary polycrystalline precursor (Ni 0.80 Co 0.10 Mn 0.10 )OH2 (volume average particle size Dv50 = 10 μm), LiOH·H2O, ZrO2, Al2O3, MoO3, SrO, and Y2O3 are mixed in a mixer at a molar ratio of the corresponding elements in the molecular formula, and then the same preparation steps as in Example 1 are carried out.

[0184] (2) Single crystal preparation method:

[0185] The ternary single crystal precursor (Ni 0.80 Co 0.10 Mn 0.10)OH2 (volume average particle size Dv50 = 3 μm), LiOH·H2O, ZrO2, Al2O3, MoO3, SrO, and Y2O3 are mixed in a mixer at a molar ratio of the corresponding elements in the molecular formula, and then the same preparation steps as in Example 1 are carried out.

[0186] Other different preparation parameters are detailed in Tables 1 to 5. According to the types and mass proportions of different elements in Tables 1 to 5, the chemical formula of the positive electrode active material prepared in Example 21 can be converted.

[0187] Comparative Examples 1 to 6

[0188] The secondary batteries of Comparative Examples 1 to 6 were prepared in a similar manner to Example 1, except that the type and content of the modifying element in the positive electrode active material were adjusted. The different preparation parameters are detailed in Tables 1 to 5.

[0189] 2. Performance Testing

[0190] 1. Test methods for parameters related to positive electrode active materials

[0191] (1) Material composition testing method

[0192] Inductively coupled plasma optical emission spectrometry was used, using a Thermo Scientific iCAP 7400 inductively coupled plasma optical emission spectrometer.

[0193] (2) BET specific surface area test method

[0194] The nitrogen adsorption specific surface area analysis test method is used for testing and is calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis test can be performed using a Tri Star II surface area and pore analyzer from Micromeritics, USA. The test steps can refer to GB / T 19587-2004.

[0195] The detailed steps are as follows: dry the sample to be tested in a vacuum drying oven at 200°C for 2 hours; weigh 1g of the sample to be tested and place it in a test tube, fill the liquid nitrogen cup with liquid nitrogen, insert it into the test tube, use nitrogen as the adsorption gas, and use the specific surface and pore analyzer to map the adsorption and desorption curve with a relative pressure P / P0 of 0 to 0.99, where P is the equilibrium adsorption pressure and P0 is the saturated vapor pressure. The BET specific surface area of ​​the positive electrode active material is calculated by the BET method.

[0196] (3) Powder resistivity test method

[0197] On a four-probe powder resistivity meter, 2.4g of positive electrode active material was placed in a feeding cup, a pressure of 12Mpa was applied, and the powder resistivity of the material was recorded.

[0198] (4) Scanning electron microscope test method

[0199] The positive electrode material is tested by SEM to obtain the microscopic morphology of the material.

[0200] (5) Volume average particle size Dv50 test method

[0201] Equipment model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer, reference standard process: GB / T19077-2016 / ISO 13320:2009.

[0202] Detailed test process: Take an appropriate amount of washed sample (sample concentration ensures 8% to 12% shading), add 20mL of anhydrous ethanol, and ultrasonicate for 5 minutes (53KHz / 120W) to ensure that the sample is completely dispersed. Then, measure the sample according to GB / T19077-2016 / ISO 13320:2009 standard.

[0203] (6) Tap density test method

[0204] Using Dandong BT-300, a 25ml graduated cylinder was used to fill the material to 20ml, and then the tap density of the material was measured using a vibration number of 5000 and a vibration frequency of 250 times / min.

[0205] (7) Pole compaction density test method

[0206] 1) Cut the above-mentioned positive electrode sheet into a film sheet with a length of 1000 mm;

[0207] 2) The positive electrode film is rolled with a certain pressure. Due to the ductility of the aluminum foil, the film length is 1006mm;

[0208] 3) Punching area is 1540.25mm 2 The weight and thickness of the small disc are measured, and the compacted density can be calculated as (small disc weight - substrate weight) / 1540.25 / (coating thickness - substrate thickness).

[0209] 2. Battery performance test method

[0210] (1) Gram capacity test method

[0211] At 25°C, first discharge at a 1 / 3C rate to a voltage of 2.80V and hold for 30 minutes. Then charge at a constant current rate of 1 / 3C to a voltage of 4.25V. Then discharge at a 1 / 3C rate to a voltage of 2.80V. The discharge capacity of the first cycle of the battery is recorded as C0. Finally, divide C0 by the mass of the positive electrode active material to obtain the gram capacity.

[0212] (2) Cyclic performance test method

[0213] At 25°C, the battery is charged at a constant current rate of 1 / 3C to a voltage of 4.25V, then charged at a constant voltage of 4.25V to a rate of 0.05C, and discharged at a rate of 1 / 3C to a voltage of 2.80V. This is the first cycle, and the discharge capacity of the first cycle is recorded as C0. The cycle is repeated as above, and the discharge capacity of the nth cycle is recorded as Cn. The capacity retention rate of each cycle is Cn / C0*100%, and the capacity retention rate after 100 cycles is calculated.

[0214] 3. Analysis of test results of various embodiments and comparative examples

[0215] Batteries of various examples and comparative examples were prepared according to the above method, and various performance parameters were measured. The results are shown in Table 5 below.

[0216] Table 1 Preparation parameters

[0217] Table 2 Preparation parameters

[0218] Table 3 Preparation parameters

[0219] Table 4 Preparation parameters

[0220] Table 5 Preparation parameters and performance parameters

[0221] The positive electrode active materials in Examples 1 to 22 are all added with a first modifying element Zr, a second modifying element Al, a third modifying element B, and a fourth modifying element (at least one of Nb, Mo, and W). The batteries prepared therefrom have excellent gram capacity and cycle performance.

[0222] No modifying element is added to the positive electrode active material of Comparative Example 1. A comparison of Comparative Example 1 with Examples 1 to 22 shows that the addition of the first modifying element Zr, the second modifying element Al, the third modifying element B, and the fourth modifying element (at least one of Nb, Mo, and W) to the positive electrode active material can effectively increase the specific capacity of the positive electrode active material and improve the cycle performance of the lithium secondary battery.

[0223] Comparative Example 2 contains only the first modifying element Zr and the second modifying element Al in the positive electrode active material, Comparative Example 3 contains only the third modifying element B and the fourth modifying element Mo in the positive electrode active material, and Comparative Example 6 contains only the first modifying element Zr, the second modifying element Al, and the fourth modifying element Mo in the positive electrode active material. Comparison of Comparative Examples 2-3 and 6 with Examples 1-22 shows that the simultaneous addition of four modifying elements to the positive electrode active material effectively increases the specific capacity of the positive electrode active material and improves the cycling performance of the lithium secondary battery. However, the addition of only two or three of the four modifying elements to the positive electrode active material results in limited improvement in the overall battery performance.

[0224] It can be seen from Examples 1 to 6 that when the mass ratio of (first modifying element + second modifying element): (third modifying element + fourth modifying element) in the positive electrode active material is controlled to be 1:(0.1 to 10), or when the mass ratio of the first modifying element: the second modifying element is controlled to be 1:(0.1 to 30), or when the mass ratio of the third modifying element: the fourth modifying element is controlled to be 1:(0.05 to 30), the positive electrode active material can have a higher gram capacity and the lithium secondary battery can have excellent cycle performance.

[0225] It can be seen from Examples 1 to 22 that, based on the total mass of the positive electrode active material, when the mass proportion of the first modifying element is controlled to be 0.01% to 0.5%, or when the mass proportion of the second modifying element is controlled to be 0.01% to 1%, or when the mass proportion of the third modifying element is controlled to be 0.01% to 0.4%, or when the mass proportion of the fourth modifying element is controlled to be 0.01% to 2.2%, the positive electrode active material can have a higher gram capacity and the lithium secondary battery can have excellent cycle performance.

[0226] In the positive electrode active material of Comparative Example 4, the mass proportion of the first modifying element exceeds the range of 0.01% to 0.5%, and the mass proportion of the second modifying element exceeds the range of 0.01% to 1%. In the positive electrode active material of Comparative Example 5, the mass proportion of the third modifying element exceeds the range of 0.01% to 0.4%, and the mass proportion of the fourth modifying element exceeds the range of 0.01% to 2.2%. From the comparison of Comparative Examples 4 to 5 with Examples 1 to 22, it can be seen that only when the mass proportion of the modifying elements in the positive electrode active material is controlled within a certain range can the gram capacity of the positive electrode active material be effectively increased and the cycle performance of the lithium secondary battery be improved; when the mass proportion of the modifying elements exceeds the above range, the improvement in battery performance is small.

[0227] It can be seen from Examples 1 and 7 to 8 that when various types of fourth modifying elements (such as Nb, Mo, and W) are added to the positive electrode active material, the batteries prepared therefrom all have excellent gram capacity and cycle performance.

[0228] As can be seen from Examples 1 and 9 to 11, when the molar ratio of nickel in the total amount of transition metal elements in the positive electrode active material is greater than 55% (preferably within the range of 60% to 95%), the batteries prepared therefrom all have excellent gram capacity and cycle performance. At the same time, when the molar ratio of cobalt in the total amount of transition metal elements in the positive electrode active material is less than 20% (preferably within the range of 3% to 10%), the batteries prepared therefrom all have excellent gram capacity and cycle performance.

[0229] It can be seen from Examples 1 and 21 that, on the basis of adding four modifying elements simultaneously to the positive electrode active material, further adding Sr and Y can further improve the cycle performance of the battery.

[0230] [Corrected 13.01.2025 according to Rule 91] As can be seen from Examples 1 to 21, the batteries prepared using a single crystal mixed polycrystalline system for the positive electrode active material have good specific capacity and cycle performance. Figures 1A, 1B, and 2 show the morphology of single crystal particles and polycrystalline particles of the positive electrode active material, respectively. At the same time, when the mass ratio of single crystal particles to polycrystalline particles in the positive electrode active material is controlled to be 1:9 to 5:5 (preferably within the range of 1:9 to 3:7), the batteries prepared therefrom all have excellent specific capacity and cycle performance.

[0231] The positive electrode active material of Example 22 utilizes only a single crystal system, without any polycrystals. A comparison of Example 22 with Examples 1-21 shows that the single crystal system has a lower compaction density than the single crystal mixed polycrystal system. The use of a single crystal mixed polycrystal system in the positive electrode active material of this application can further improve the compaction density of the active material, thereby comprehensively improving its performance.

[0232] It can be seen from Examples 1 to 22 that the specific surface area of ​​the single crystal particles in the positive electrode active material is controlled to be 0.9 to 1.5 m 2 / g, or control the specific surface area of ​​polycrystalline particles to 0.3~1.0m 2 / g, the batteries prepared therefrom have excellent gram capacity and cycle performance; when the powder resistivity of the positive electrode active material is controlled in the range of 100 to 5000Ω·cm at 12MPa, the batteries prepared therefrom have excellent gram capacity and cycle performance.

[0233] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included within the technical scope of the present application. In addition, without departing from the scope of the present application, any other modifications that can be imagined by those skilled in the art to the embodiments, or any other methods constructed by combining some of the constituent elements in the embodiments are also included within the scope of the present application.

Claims

1. A positive electrode active material containing a transition metal element, characterized in that: The positive electrode active material includes: Nickel element, wherein the molar proportion of the nickel element in the total amount of nickel, cobalt and manganese metal elements is greater than 55%; Cobalt element, wherein the molar proportion of the cobalt element in the total amount of nickel, cobalt and manganese metal elements is less than 20%; The first modifying element Zr; The second modifying element is Al; a third modifying element B; and The fourth modifying element is at least one of Nb, Mo, and W; Among them, based on the total mass of the positive electrode active material, the mass proportion of the first modifying element is 0.01% to 0.5%, the mass proportion of the second modifying element is 0.01% to 1%, the mass proportion of the third modifying element is 0.01% to 0.4%, and the mass proportion of the fourth modifying element is 0.01% to 2.2%.

2. The positive electrode active material according to claim 1, characterized in that In the positive electrode active material, the mass ratio of (first modifying element+second modifying element):(third modifying element+fourth modifying element) is 1:(0.1-10).

3. The positive electrode active material according to claim 1 or 2, characterized in that In the positive electrode active material, the mass ratio of (first modifying element+second modifying element):(third modifying element+fourth modifying element) is 1:(0.1-0.5).

4. The positive electrode active material according to any one of claims 1 to 3, characterized in that In the positive electrode active material, the mass ratio of (element Zr+element Al): (element B+element W) is 1:(0.1-0.5).

5. The positive electrode active material according to any one of claims 1 to 4, characterized in that In the positive electrode active material, the mass ratio of the first modifying element to the second modifying element is 1:(0.1-30).

6. The positive electrode active material according to any one of claims 1 to 5, characterized in that In the positive electrode active material, the mass ratio of the first modifying element to the second modifying element is 1:(0.1-1).

7. The positive electrode active material according to any one of claims 1 to 6, characterized in that In the positive electrode active material, the mass ratio of element Zr to element Al is 1:(0.1-1).

8. The positive electrode active material according to any one of claims 1 to 7, characterized in that In the positive electrode active material, the mass ratio of the third modifying element to the fourth modifying element is 1:(0.05-30).

9. The positive electrode active material according to any one of claims 1 to 8, characterized in that In the positive electrode active material, the mass ratio of the third modifying element to the fourth modifying element is 1:(0.1-1).

10. The positive electrode active material according to any one of claims 1 to 9, characterized in that In the positive electrode active material, the mass ratio of element B to element W is 1:(0.1-1).

11. The positive electrode active material according to any one of claims 1 to 10, characterized in that Based on the total mass of the positive electrode active material, the mass proportion of the first modifying element is 0.05% to 0.5%.

12. The positive electrode active material according to any one of claims 1 to 11, characterized in that Based on the total mass of the positive electrode active material, the mass proportion of the second modifying element is 0.05% to 0.3%.

13. The positive electrode active material according to any one of claims 1 to 12, characterized in that Based on the total mass of the positive electrode active material, the mass proportion of the third modifying element is 0.01% to 0.2%.

14. The positive electrode active material according to any one of claims 1 to 13, characterized in that Based on the total mass of the positive electrode active material, the mass proportion of the fourth modifying element is 0.01% to 0.3%.

15. The positive electrode active material according to any one of claims 1 to 14, characterized in that The molar proportion of the nickel element in the total amount of nickel, cobalt and manganese metal elements is 60% to 95%; and / or the molar proportion of the cobalt element in the total amount of nickel, cobalt and manganese metal elements is 3% to 10%.

16. The positive electrode active material according to any one of claims 1 to 15, characterized in that The molar proportion of the nickel element in the total amount of nickel, cobalt and manganese metal elements is 80% to 95%.

17. The positive electrode active material according to any one of claims 1 to 16, characterized in that The positive electrode active material includes single crystal particles and polycrystalline particles.

18. The positive electrode active material according to claim 17, characterized in that The specific surface area of ​​the single crystal particles is 0.9 to 1.5 m 2 / g, the specific surface area of ​​the polycrystalline particles is 0.3 to 1.0 m 2 / g.

19. The positive electrode active material according to claim 17 or 18, characterized in that In the positive electrode active material, the mass ratio of the single crystal particles to the polycrystalline particles is 1:9 to 5:

5.

20. The positive electrode active material according to any one of claims 17 to 19, characterized in that The volume average particle size Dv50 of the single crystal particles is 3 to 5 μm, and the volume average particle size Dv50 of the polycrystalline particles is 4 to 13 μm.

21. The positive electrode active material according to any one of claims 1 to 20, characterized in that The positive electrode active material has the molecular formula Li a (Ni b Co c Mn 1-b-c ) 1-x-y-z- q Zr x Al y B z Q q O e , wherein Q includes at least one of Nb, Mo, and W, 0.9≤a≤1.2, 0.55≤b≤0.95, 0≤c≤0.20, 1.8≤e≤2.2, 0 <x≤0.04,0<y≤0.02,0<z≤0.09,0<q≤0.03。 22. The positive electrode active material according to any one of claims 1 to 21, characterized in that The positive electrode active material further includes strontium (Sr). Based on the total mass of the positive electrode active material, the mass proportion of the strontium is 0.05% to 0.2%.

23. The positive electrode active material according to any one of claims 1 to 22, characterized in that The positive electrode active material further includes yttrium element (Y). Based on the total mass of the positive electrode active material, the mass proportion of the yttrium element is 0.05% to 0.2%.

24. The positive electrode active material according to any one of claims 1 to 23, characterized in that The powder resistivity of the positive electrode active material at 12 MPa is 100 to 8000 Ω·cm.

25. The positive electrode active material according to any one of claims 1 to 24, characterized in that The tap density of the positive electrode active material is 1.9 to 2.6 g / cm 3 .

26. A lithium secondary battery, characterized in that: The positive electrode active material comprises the positive electrode active material according to any one of claims 1 to 25.

27. The lithium secondary battery according to claim 26, characterized in that The lithium secondary battery has a gram capacity of the positive electrode active material of 193 to 210 mAh / g at 25° C. and a 1 / 3C discharge rate.

28. The lithium secondary battery according to claim 26 or 27, characterized in that The lithium secondary battery has a gram capacity of the positive electrode active material of 202 to 210 mAh / g at 25° C. and a 1 / 3C discharge rate.

29. An electrical device, characterized in that: A lithium secondary battery comprising the lithium secondary battery according to any one of claims 26 to 28.

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