Positive electrode active material, method for manufacturing the same, positive electrode sheet, battery, and electric device

Abstract

This application relates to a positive electrode active material and its preparation method, a positive electrode sheet, a battery, and an electrical device. The chemical formula of the positive electrode active material is: Li a Ni b Mn c M d O2, where 1≤a≤1.05, 0.22≤b≤0.5, 0.47≤c≤0.75, 0.01≤d≤0.03, and M includes at least one of Mg, Nb, Cr, Ce, Fe, La, Ta, Al, V, Ti, Zr, Sn, Mo, or Co; the XRD pattern of this material includes a first main diffraction peak and a second main diffraction peak; the diffraction angle of the first main diffraction peak is 16°~19°; and the diffraction angle of the second main diffraction peak is 42°~45°. This material combines the advantages of layered structure cathode active materials and spinel structure cathode active materials, which is beneficial for improving the rate performance of cathode active materials.

Description

Technical Field

[0001] This application relates to a positive electrode active material and its preparation method, a positive electrode sheet, a battery, and an electrical device. Background Technology

[0002] In recent years, with the development of lithium-ion rechargeable battery technology, lithium-ion rechargeable batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. Due to the significant advancements in lithium-ion rechargeable batteries, higher requirements have been placed on their rate performance. Summary of the Invention

[0003] The purpose of this application is to provide a positive electrode active material and its preparation method, a positive electrode sheet, a battery, and an electrical device.

[0004] The embodiments of this application are implemented as follows:

[0005] In a first aspect, embodiments of this application provide a positive electrode active material, the chemical formula of which is: Li a Ni b Mn c M d O2, where 1≤a≤1.05, 0.22≤b≤0.5, 0.47≤c≤0.75, 0.01≤d≤0.03, and M includes at least one of Mg, Nb, Cr, Ce, Fe, La, Ta, Al, V, Ti, Zr, Sn, Mo, or Co; the XRD pattern of the positive electrode active material includes a first main diffraction peak and a second main diffraction peak; the diffraction angle of the first main diffraction peak is 16°~19°; and the diffraction angle of the second main diffraction peak is 42°~45°.

[0006] Research has found that, compared to layered cathode active materials, spinel-structured cathode active materials have lower specific capacity, and it is difficult to meet the requirements of high-capacity batteries using a single spinel-structured cathode active material; while layered cathode active materials have lower conductivity and generally lower rate performance compared to spinel-structured cathode active materials, and therefore it is also difficult to meet the requirements of batteries with high rate performance.

[0007] The above-described technical solution of this application includes a positive electrode active material comprising the aforementioned first and second main diffraction peaks, and its microstructure includes both a layered structure and a spinel phase. This positive electrode active material, by introducing a spinel phase into its layered structure, enhances the stability of the layered structure, and the three-dimensional lithium-ion diffusion channels of the spinel phase improve the conductivity of the layered material. Simultaneously, by introducing a layered structure into the spinel phase, it compensates to some extent for the insufficient capacity of spinel materials. This positive electrode active material of this application combines the advantages of both layered and spinel-structured positive electrode active materials, which is beneficial for improving the material's conductivity and thus enhancing its rate performance.

[0008] In some alternative embodiments, the ratio of the intensity of the first main diffraction peak to the intensity of the second main diffraction peak is 0.8 to 2.0. Optionally, the ratio of the intensity of the first main diffraction peak to the intensity of the second main diffraction peak is 0.8 to 1.0.

[0009] In the above technical solution, the ratio of the intensity of the first main diffraction peak to the intensity of the second main diffraction peak is 0.8 to 2.0, which is beneficial to improving the conductivity of the positive electrode active material and further beneficial to improving the rate performance of the positive electrode active material.

[0010] In some alternative implementations, the specific surface area of ​​the positive electrode active material after water washing is less than 8 m². 2 / g; Optionally, the specific surface area of ​​the positive electrode active material after water washing is greater than 2m². 2 / g and less than 8m 2 / g.

[0011] In the above technical solution, the specific surface area of ​​the positive electrode active material after water washing is within the above range, which is beneficial to the reaction of the electrolyte on the surface of the positive electrode active material, thereby improving the electrochemical performance of the battery; at the same time, the specific surface area of ​​the positive electrode active material after water washing is within the above range, which is beneficial to the reversible insertion and extraction kinetics of lithium ions in the positive electrode active material.

[0012] In some alternative implementations, the dislocation density of the positive electrode active material is 1.0 × 10⁻⁶. 13 ~2.5*10 13 Optionally, the dislocation density of the positive electrode active material is 1.0*10⁻⁶. 13 ~2.0*10 13 .

[0013] In the above technical solution, the dislocation density of the positive electrode active material is within the above range, which is beneficial to reduce the stacking faults of the positive electrode active material. The dislocation density reflects the number of line defects in the material. An inappropriate amount of stacking faults will cause changes in the local Coulomb repulsion between Li-Li and Li-TM cations, which will lead to voltage decay of the material. A reasonable dislocation density can reduce voltage decay and improve cycle life.

[0014] In some alternative embodiments, the microstress of the positive electrode active material is less than or equal to 1.2%, and optionally, the microstress of the positive electrode active material is 0.1% to 0.5%.

[0015] In the above technical solution, the micro-stress of the positive electrode active material is within the above range, which helps to reduce the stress accumulation of the positive electrode active material particles during the charge and discharge cycle, improve the secondary sphere rupture phenomenon caused by excessive stress, and thus help to improve the stability of the material.

[0016] In some alternative implementations, the material pitch of the positive electrode active material is greater than 1.2; alternatively, the material pitch of the positive electrode active material is greater than 1.2 and less than 1.5.

[0017] In the above technical solution, the material span of the positive electrode active material is within the above range, which is beneficial to improve the space utilization of the positive electrode active material and improve the compaction density and specific capacity.

[0018] Secondly, embodiments of this application provide a method for preparing the positive electrode active material provided in the first aspect, including:

[0019] The mixture of hydroxide precursor and lithium salt is sintered; the total metal in the hydroxide precursor is Me, which includes nickel, manganese and M.

[0020] In the above technical solution, the mixture of hydroxide precursor and lithium salt is sintered, and a layered structure is introduced into the spinel phase, which to some extent compensates for the insufficient capacity of spinel materials. This is beneficial to improving the conductivity of the positive electrode active material and improving its rate performance.

[0021] In some alternative embodiments, sintering includes sintering the mixture at 400°C to 480°C for 25 to 75 hours.

[0022] In the above technical solution, a positive electrode active material containing both spinel phase and layered structure was prepared by long-term sintering at a low temperature of 400℃~480℃ for 25h~75h. The introduction of spinel phase improves the stability of layered structure, and the three-dimensional lithium ion diffusion channel improves the conductivity of layered material; while the layered structure compensates for the lack of capacity of spinel material to a certain extent.

[0023] In some alternative embodiments, the molar ratio of Li in the lithium salt to Me in the hydroxide precursor is 1.0 to 1.05.

[0024] In the above technical solution, the molar ratio of Li element in lithium salt to Me element in hydroxide precursor is 1.0 to 1.05. Within this range, it is beneficial to improve the conductivity of positive electrode active material and further beneficial to improve the rate performance of positive electrode active material.

[0025] In some alternative embodiments, the mixture is sintered at 400°C to 480°C for 25 to 75 hours, including:

[0026] The temperature was increased from room temperature to 400℃ to 480℃ at a heating rate of 1℃ / min to 3℃ / min, and sintered for 25h to 75h.

[0027] In the above technical solution, the heating rate described above is beneficial for obtaining a positive electrode active material that simultaneously contains a spinel phase and a layered structure.

[0028] In some alternative implementations, the sintering atmosphere is air.

[0029] In the above technical solution, the use of air atmosphere sintering is beneficial for obtaining positive electrode active materials that simultaneously contain spinel phase and layered structure.

[0030] In some alternative implementations, the method further includes:

[0031] The sintered material is washed with water.

[0032] The mass ratio of water to calcined material is (15-30):1; optionally, the washing time is 15-30 minutes.

[0033] In the above technical solution, washing the sintered material with water can remove residual lithium, which is beneficial to obtaining a positive electrode active material with fewer impurities.

[0034] Thirdly, embodiments of this application provide a positive electrode sheet comprising the positive active material provided in the first aspect; or the positive electrode sheet comprises a positive active material prepared by the preparation method of the positive active material provided in the second aspect.

[0035] In the above technical solution, the electrode sheet can improve rate performance by using a positive active material prepared by the method provided in the first aspect or the second aspect.

[0036] Fourthly, embodiments of this application provide a battery that includes the positive electrode provided in the second aspect.

[0037] In the above technical solution, the battery improves rate performance by setting a positive electrode provided by a third party.

[0038] Fifthly, embodiments of this application provide an electrical device that includes the battery provided in the fourth aspect. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0041] Figure 2 Exploded views of batteries provided for some embodiments of this application;

[0042] Figure 3 for Figure 2 The exploded view of the battery cell shown;

[0043] Figure 4 A partial structural schematic diagram of an electrode assembly provided in some embodiments of this application;

[0044] Figure 5 A partial structural schematic diagram of the positive electrode sheet provided in some embodiments of this application;

[0045] Figure 6 Charge-discharge curves are provided for comparative examples and some embodiments of this application.

[0046] icon:

[0047] 1000 vehicles;

[0048] Battery 100; Controller 200; Motor 300;

[0049] Box body 10; First part 11; Second part 12; Storage space 13;

[0050] Battery cell 20; casing 21; electrode assembly 22; electrode terminals 23; pressure relief structure 24;

[0051] 211 housing; 212 cover; 221 positive electrode plate; 222 negative electrode plate; 223 separator;

[0052] Positive electrode current collector 2211; Positive electrode active material layer 2212;

[0053] Negative electrode current collector 2221; negative electrode active material layer 2222. Detailed Implementation

[0054] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0056] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0057] In the description of the embodiments of this application, the technical terms "inner" and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0058] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0059] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0060] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the height, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall height, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0061] Research has found that, compared to layered cathode active materials, spinel-structured cathode active materials have lower specific capacity, and it is difficult to meet the requirements of high-capacity batteries using a single spinel-structured cathode active material; while layered cathode active materials have lower conductivity and generally lower rate performance compared to spinel-structured cathode active materials, and therefore it is also difficult to meet the requirements of batteries with high rate performance.

[0062] This application provides a positive electrode active material, the chemical formula of which is: Li a Ni b Mn c M d O2, where 1≤a≤1.05, 0.22≤b≤0.5, 0.47≤c≤0.75, 0.01≤d≤0.03, and M includes at least one of Mg, Nb, Cr, Ce, Fe, La, Ta, Al, V, Ti, Zr, Sn, Mo, or Co; the XRD pattern of the positive electrode active material includes a first main diffraction peak and a second main diffraction peak; the diffraction angle of the first main diffraction peak is 16°~19°; and the diffraction angle of the second main diffraction peak is 42°~45°.

[0063] The aforementioned technical solution uses a cathode active material that includes the first and second main diffraction peaks, and its microstructure includes both a layered structure and a spinel phase. This cathode active material incorporates a spinel phase into its layered structure, enhancing its stability. The three-dimensional lithium-ion diffusion channels of the spinel phase improve the conductivity of the layered material. Simultaneously, the layered structure introduced into the spinel phase compensates for the insufficient capacity of spinel materials to some extent. This cathode active material combines the advantages of both layered and spinel structures, which is beneficial for improving the conductivity and rate performance of the cathode active material.

[0064] The positive electrode sheet provided in this application includes the aforementioned positive electrode active material.

[0065] By incorporating the aforementioned positive electrode active material, the rate performance of this electrode can be improved.

[0066] The battery provided in this application includes the aforementioned positive electrode plate.

[0067] By incorporating a positive electrode provided by a third party, the battery's rate performance can be improved.

[0068] This application provides an electrical device, including the aforementioned battery.

[0069] See Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery 100 is disposed inside the vehicle 1000, and the battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during startup, navigation, and driving.

[0070] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0071] In this application, battery 100 refers to a single physical module comprising one or more battery cells 20 to provide voltage and capacity. Battery 100 generally includes a housing 10 for encapsulating one or more battery cells 20. The housing 10 prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells 20.

[0072] See Figure 2 , Figure 2The exploded view of a battery 100 provided in some embodiments of this application shows that the battery 100 may include a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 is used to house the battery cell 20 and may have various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other, defining a housing space 13 for accommodating the battery cell 20. The second portion 12 may be a hollow structure with one open end, and the first portion 11 may be a plate-like structure, overlapping the open side of the second portion 12 to form a housing 10 with the housing space 13. Alternatively, both the first portion 11 and the second portion 12 may be hollow structures with one open side, overlapping the open side of the second portion 12 to form a housing 10 with the housing space 13. Of course, the first portion 11 and the second portion 12 may have various shapes, such as cylinders, cuboids, etc.

[0073] In battery 100, there can be one or more battery cells 20. If there are multiple battery cells 20, they can be connected in series, in parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells 20 are connected in both series and parallel. Multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed configuration, and then the whole assembly of multiple battery cells 20 is housed in housing 10. Alternatively, multiple battery cells 20 can first be connected in series, in parallel, or in a mixed configuration to form modules, and then multiple modules can be connected in series, in parallel, or in a mixed configuration to form a whole, which is then housed in housing 10. Battery 100 may also include other structures. For example, multiple battery cells 20 can be electrically connected through a busbar component to achieve parallel, series, or mixed configuration of multiple battery cells 20.

[0074] See Figure 3 , Figure 3 for Figure 2 The diagram shows an exploded view of a single battery cell 20. A single battery cell 20 refers to the smallest unit that makes up the battery 100. A single battery cell 20 may include a housing 21, an electrode assembly 22, and an electrolyte, with the electrode assembly 22 and electrolyte both housed within the housing 21.

[0075] The outer casing 21 may include a housing 211 and a cover 212. The housing 211 is an assembly that fits with the cover 212 to form an internal sealed space for the battery cell 20, wherein the formed sealed space can accommodate the electrode assembly 22, electrolyte, and other components. The cover 212 is a component that covers the opening of the housing 211 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover 212 may be adapted to the shape of the housing 211 to fit the housing 211, and the cover 212 may also be provided with functional components such as electrode terminals 23 and pressure relief structures 24. A sealing ring may be provided between the opening of the housing 211 and the cover 212 to achieve a seal between the housing 211 and the cover 212.

[0076] The housing 211 and cover 212 can be of various shapes and sizes, such as cuboids, cylinders, and hexagonal prisms. Specifically, the shapes of the housing 211 and cover 212 can be determined according to the specific shape and size of the electrode assembly 22. The materials of the housing 211 and cover 212 can be various, such as, but not limited to, metals like copper, iron, aluminum, stainless steel, and aluminum alloys. The materials of the sealing ring can be various, such as, but not limited to, materials resistant to electrolyte corrosion, high toughness, and fatigue resistance, such as PP (polypropylene), PC (polycarbonate), and PET (polyethylene terephthalate). A plating layer can be formed on the outer surface of the housing 211, and the plating layer material can be various, such as, but not limited to, corrosion-resistant materials like Ni and Cr.

[0077] See Figure 4 The electrode assembly 22 may consist of a positive electrode 221, a negative electrode 222, and a separator 223. The separator 223 is located between the positive electrode 221 and the negative electrode 222 and serves as an separator. The electrode assembly 22 may be a wound structure or a stacked structure, and the embodiments of this application are not limited thereto.

[0078] See Figure 5 The negative electrode 222 includes a negative current collector 2221 and a negative active material layer 2222. The negative current collector 2221 can be made of copper, and the negative active material layer 2222 includes a negative active material. The negative active material includes at least one of graphite, silicon, silicon alloy, or tin alloy.

[0079] Please continue reading Figure 5 The positive electrode 221 includes a positive current collector 2211 and a positive active material layer 2212. Taking a lithium-ion battery cell 20 as an example, the material of the positive current collector 2211 can be aluminum. The positive active material layer 2212 includes a positive active material.

[0080] In some embodiments of this application, the chemical formula of the above-mentioned positive electrode active material is: Li a Nib Mn c M d O2, where 1≤a≤1.05, 0.22≤b≤0.5, 0.47≤c≤0.75, 0.01≤d≤0.03, and M includes at least one of Mg, Nb, Cr, Ce, Fe, La, Ta, Al, V, Ti, Zr, Sn, Mo, or Co; the XRD pattern of the positive electrode active material includes a first main diffraction peak and a second main diffraction peak; the diffraction angle of the first main diffraction peak is 16°~19°; and the diffraction angle of the second main diffraction peak is 42°~45°.

[0081] Diffraction peaks refer to the diffraction peaks produced by the reflection of X-rays by the crystal planes of a sample's crystal structure at different angles during X-ray diffraction testing. The diffraction angle is the angle between the X-ray and the crystal plane.

[0082] The aforementioned technical solution uses a cathode active material that includes the first and second main diffraction peaks, and its microstructure includes both a layered structure and a spinel phase. This cathode active material incorporates a spinel phase into its layered structure, enhancing its stability. The three-dimensional lithium-ion diffusion channels of the spinel phase improve the conductivity of the layered material. Simultaneously, the layered structure introduced into the spinel phase compensates for the insufficient capacity of spinel materials to some extent. This cathode active material combines the advantages of both layered and spinel structures, which is beneficial for improving the conductivity and rate performance of the cathode active material.

[0083] It should be noted that the microstructure of the above-mentioned positive electrode active material can be observed by transmission electron microscopy (TEM). Under TEM, it can be seen that the above-mentioned positive electrode active material includes both a layered structure and a spinel phase.

[0084] Furthermore, exemplarily, in some embodiments of this application, the chemical formula of the above-mentioned positive electrode active material is: LiNi 0.5 Mn 0.5 O2, LiNi 0.25 Mn 0.5 O2, LiNi 0.5 Mn 0.75 O2, LiNi 0.5 Mn 0.5 Mg 0.01 O2, LiNi 0.5 Mn 0.5 Nb 0.01 O2, Li 1.05 Ni 0.25 Mn 0.75 Cr 0.03 O2, Li 1.02 Ni0.3 Mn 0.6 Ce 0.03 O2, Li 1.03 Ni 0.35 Mn 0.65 Fe 0.02 O2, Li 1.04 Ni 0.45 Mn 0.55 Ta 0.01 O2, Li 1.01 Ni 0.26 Mn 0.56 Al 0.03 O2, Li 1.01 Ni 0.26 Mn 0.56 V 0.03 O2, Li 1.05 Ni 0.25 Mn 0.75 Ti 0.03 O2, LiNi 0.5 Mn 0.5 Zr 0.01 Sn 0.02 O2 or Li 1.05 Ni 0.25 Mn 0.75 Mo 0.03 Co 0.01 O2.

[0085] It should be noted that when M is selected from two or more elements, the content of each element satisfies 0.01≤d≤0.03.

[0086] For example, in some embodiments of this application, the chemical formula of the above-mentioned positive electrode active material is: LiNi 0.5 Mn 0.5 Zr 0.01 Sn 0.02 O2, Li 1.05 Ni 0.25 Mn 0.75 Mo 0.03 Co 0.01 O2 or LiNi 0.5 Mn 0.5 Nb 0.01 Ti 0.01 Zr 0.01 O2.

[0087] It should be further noted that during the charging and discharging process, Li undergoes insertion / extraction and consumption, resulting in different molar contents of Li at different discharge states. In the examples of positive electrode active materials in this application, the molar contents of Li refer to the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar contents of Li will change after charge-discharge cycles.

[0088] In the examples of positive electrode active materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0089] Further, alternatively, in some embodiments of this application, the diffraction angle of the first main diffraction peak is 17° to 18°.

[0090] For example, in some embodiments of this application, the diffraction angle of the first main diffraction peak is 16°, 17°, 18°, 19° or any two of the aforementioned values.

[0091] Furthermore, in some embodiments of this application, the diffraction angle of the second main diffraction peak is 43° to 44°.

[0092] For example, in some embodiments of this application, the diffraction angle of the second main diffraction peak is 42°, 43°, 44°, 45° or a range between any two of the aforementioned values.

[0093] Furthermore, in some embodiments of this application, the ratio of the intensity of the first main diffraction peak to the intensity of the second main diffraction peak is 0.8 to 2.0.

[0094] The intensity of a diffraction peak indicates the degree of crystallinity. The greater the intensity of the diffraction peak, the better the degree of crystallinity.

[0095] In some embodiments of this application, the intensity of the diffraction peaks can be tested with reference to the test method: JSK 0131-1996.

[0096] In the above technical solution, the ratio of the intensity of the first main diffraction peak to the intensity of the second main diffraction peak is 0.8 to 2.0, which is beneficial to improving the conductivity of the positive electrode active material and further beneficial to improving the rate performance of the positive electrode active material.

[0097] For example, in some embodiments of this application, the ratio of the intensity of the first main diffraction peak to the intensity of the second main diffraction peak is 0.81, 0.83, 0.85, 0.88, 1.90, 1.92, 1.95, 2.0 or any two of the aforementioned values.

[0098] Further optionally, in some embodiments of this application, the ratio of the intensity of the first main diffraction peak to the intensity of the second main diffraction peak is 0.81 to 1.99.

[0099] Furthermore, in some embodiments of this application, the specific surface area of ​​the positive electrode active material after water washing is less than 8m². 2 / g.

[0100] Further, optionally, in some embodiments of this application, the specific surface area of ​​the positive electrode active material after water washing is greater than 2m². 2 / g and less than 8m 2 / g.

[0101] In the above technical solution, the specific surface area of ​​the positive electrode active material after water washing is within the above range, which is beneficial to the reaction of the electrolyte on the surface of the positive electrode active material, thereby improving the electrochemical performance of the battery; at the same time, the specific surface area of ​​the positive electrode active material after water washing is within the above range, which is beneficial to the reversible insertion and extraction kinetics of lithium ions in the positive electrode active material.

[0102] For example, in some embodiments of this application, the specific surface area of ​​the positive electrode active material after water washing is 7.5 m². 2 / g、6m 2 / g、5m 2 / g、4m 2 / g、3m 2 / g、2m 2 / g, 1m 2 / g or the range between any two of the aforementioned values.

[0103] Furthermore, in some embodiments of this application, the dislocation density (β) of the positive electrode active material is 1.0*10^6 13 ~2.5*10 13 .

[0104] In the above technical solution, the dislocation density of the positive electrode active material is within the above range, which is beneficial to reduce stacking faults and improve voltage decay during cycling.

[0105] Further, optionally, in some embodiments of this application, the dislocation density of the positive electrode active material is 1.1*10^6. 13 ~2.4*10 13 .

[0106] For example, in some embodiments of this application, the dislocation density of the positive electrode active material is 1.1*10^6. 13 1.5*10 13 1.8*10 13 2.0*10 13 2.2*10 13 2.3*1013 2.4*10 13 2.5*10 13 Or the range between any two of the aforementioned values.

[0107] Furthermore, in some embodiments of this application, the dislocation density testing method is as follows:

[0108] The dislocation density of the positive electrode active material was measured using XRD diffraction patterns.

[0109] Dislocation density β=(1 / D) 2 ×10 16 Where D = K λ / Bcosθ, K=0.9, λ=1.5406, B is the full width at half maximum (FWHM) of the positive electrode active material (hkl) crystal plane in the XRD diffraction pattern, and θ is the diffraction angle.

[0110] Furthermore, in some embodiments of this application, the micro-stress of the positive electrode active material is less than or equal to 1.2%.

[0111] In the above technical solution, the micro-stress of the positive electrode active material is within the above range, which helps to reduce the stress accumulation of the positive electrode active material particles during the charge and discharge cycle, improve the secondary sphere rupture phenomenon caused by excessive stress, and thus help to improve the stability of the material.

[0112] Further optionally, in some embodiments of this application, the micro-stress of the positive electrode active material is 0.1% to 0.5%.

[0113] For example, in some embodiments of this application, the micro-stress of the positive electrode active material is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or a range between any two of the aforementioned values.

[0114] Furthermore, in some embodiments of this application, the micro-stress detection method is as follows:

[0115] The micro-stress of the positive electrode active material was tested using XRD diffraction patterns.

[0116] Micro-stress = (βhkl × Cosθhkl) / (4sinθhkl), where θhkl is the diffraction angle of the cathode material (hkl) crystal plane in the XRD diffraction pattern, and βhkl is the full width at half maximum (FWHM) of the cathode material (hkl) crystal plane in the XRD diffraction pattern.

[0117] Furthermore, in some embodiments of this application, the material diameter of the positive electrode active material is greater than 1.2.

[0118] In the above technical solution, the material span of the positive electrode active material is within the above range, which is beneficial to improve the space utilization of the positive electrode active material and improve the compaction density and specific capacity.

[0119] Further optionally, in some embodiments of this application, the material diameter of the positive electrode active material is greater than 1.2 and less than 1.5.

[0120] For example, in some embodiments of this application, the material span of the positive electrode active material is 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 or a range between any two of the aforementioned values.

[0121] Furthermore, in some embodiments of this application, the method for detecting the material span is as follows: referring to GB / T19077-2016 / ISO 13320:2009 Particle size distribution laser diffraction method, the measurement is performed using a Malvern 3000 instrument, where Span = (D v90 -D v10 ) / D v50 .

[0122] The above D V50 This refers to the following: When positive electrode active material particles are added in ascending order of size, and when they accumulate to 50% of the total volume, the particle size of all positive electrode active material particles at this point is less than a certain value, then that value is D. v50 The value of .

[0123] The above D v10 This refers to the following: When positive electrode active material particles are added in ascending order of size, and the accumulated particles reach 10% of the total volume, the particle size of all the positive electrode active material particles at this point is less than a certain value. This value is then called D. v10 The value of .

[0124] The above D v90 This refers to the following: When positive electrode active material particles are added in ascending order of size, and when they accumulate to 90% of the total volume, the particle size of all the positive electrode active material particles is less than a certain value, then that value is D. v90 The value of .

[0125] The above D v10 D v50 Or D v90 Particle size distribution was determined using laser diffraction method according to GB / T 19077-2016 / ISO 13320:2009, and the equipment was Malvern 3000.

[0126] Some embodiments of this application provide a method for preparing a positive electrode active material, including: sintering a mixture of a hydroxide precursor and a lithium salt; the total metal in the hydroxide precursor is Me, and Me includes nickel, manganese and M.

[0127] In the above technical solution, the mixture of hydroxide precursor and lithium salt is sintered, and a layered structure is introduced into the spinel phase, which to some extent compensates for the insufficient capacity of spinel materials. This is beneficial to improving the conductivity of the positive electrode active material and improving its rate performance.

[0128] Furthermore, in some embodiments of this application, sintering includes sintering the mixture at 400°C to 480°C for 25 to 75 hours.

[0129] In the above technical solution, a positive electrode active material containing both layered structure and spinel phase was prepared by long-term sintering at a low temperature of 400℃~480℃ for 25h~75h. The introduction of spinel phase improves the stability of layered structure, and the three-dimensional lithium-ion diffusion channel improves the conductivity of layered material; while the layered structure compensates for the lack of capacity of spinel material to a certain extent.

[0130] Further alternatively, in some embodiments of this application, the hydroxide precursor is mixed with a lithium salt; then the mixture is sintered at 401°C to 479°C for 25.5 h to 74.5 h.

[0131] For example, in some embodiments of this application, a hydroxide precursor is mixed with a lithium salt; then the mixture is sintered at 401°C, 405°C, 410°C, 415°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C or any two of the aforementioned values ​​for 26h, 28h, 30h, 32h, 35h, 38h, 40h, 45h, 50h, 55h, 60h, 65h, 70h or any two of the aforementioned values.

[0132] Furthermore, in some embodiments of this application, the molar ratio of Li element in the lithium salt to Me element in the hydroxide precursor is 1.0 to 1.05.

[0133] In the above technical solution, the molar ratio of Li element in lithium salt to Me element in hydroxide precursor is 1.0 to 1.05. Within this range, it is beneficial to improve the conductivity of positive electrode active material and further beneficial to improve the rate performance of positive electrode active material.

[0134] Further optionally, in some embodiments of this application, the molar ratio of Li element in the lithium salt to Me element in the hydroxide precursor is 1.01 to 1.05.

[0135] For example, in some embodiments of this application, the molar ratio of Li element in the lithium salt to Me element in the hydroxide precursor is 1.01, 1.02, 1.03, 1.04, 1.05 or any two of the aforementioned values.

[0136] Furthermore, in some embodiments of this application, sintering the mixture at 400°C to 480°C for 25 to 75 hours includes:

[0137] The temperature was increased from room temperature to 400℃ to 480℃ at a heating rate of 1℃ / min to 3℃ / min, and sintered for 25h to 75h.

[0138] In the above technical solution, the heating rate described above is beneficial for obtaining a positive electrode active material that simultaneously contains a spinel phase and a layered structure.

[0139] Further, optionally, in some embodiments of this application, the mixture is sintered at 400°C to 480°C for 25 to 75 hours, including:

[0140] The temperature was increased from room temperature to 400℃ to 480℃ at a heating rate of 1.1℃ / min to 2.9℃ / min, and sintered for 25h to 75h.

[0141] Exemplarily, in some embodiments of this application, sintering the mixture at 400°C to 480°C for 25 to 75 hours includes:

[0142] The temperature was increased from room temperature to 400℃~480℃ at a heating rate of 1.2℃ / min, 1.5℃ / min, 1.8℃ / min, 2.0℃ / min, 2.2℃ / min, 2.5℃ / min or 2.8℃ / min and sintered for 25h~75h.

[0143] Furthermore, in some embodiments of this application, the sintering atmosphere is air.

[0144] In the above technical solution, the use of air atmosphere sintering is beneficial for obtaining positive electrode active materials that simultaneously contain spinel phase and layered structure.

[0145] Furthermore, in some embodiments of this application, the sintered material is washed with water;

[0146] The mass ratio of water to calcined material is (15-30):1.

[0147] In the above technical solution, washing the sintered material with water can remove residual lithium, which is beneficial to obtaining a positive electrode active material with fewer impurities.

[0148] Further optionally, the mass ratio of water to fuel is 15:1, 18:1, 20:1, 25:1, 28:1, 30:1 or any two of the aforementioned values.

[0149] Furthermore, the above washing time is 15 min to 30 min.

[0150] Within the aforementioned water washing time range, residual lithium can be effectively removed, which is beneficial for obtaining positive electrode active materials with fewer impurities.

[0151] Alternatively, the washing time can be 16 min to 29 min.

[0152] For example, in some embodiments of this application, the water washing time is 16 min, 17 min, 18 min, 20 min, 22 min, 25 min, 28 min or any two of the aforementioned values.

[0153] Furthermore, in some embodiments of this application, the lithium salt includes one or more of lithium hydroxide, lithium carbonate, lithium acetate, lithium nitrate, lithium oxalate, or lithium sulfate.

[0154] Further, optionally and exemplary, in some embodiments of this application, the method for preparing the positive electrode active material is carried out according to the following steps:

[0155] Step S1: The hydroxide precursor, lithium salt, and milled zirconium beads are mixed in a drum-type ball mill mixer at a ball-to-material mass ratio of 25-80. The Li / Me molar ratio is 1.0-1.05, where Me represents the total metal in the hydroxide precursor. The mixture is then sintered in a muffle furnace at a temperature of 400℃-480℃, a heating rate of 1℃ / min-3℃ / min, and a sintering time of 25-75 hours. The sintering atmosphere is air. After sintering, the sintered material is mechanically ground and sieved to obtain the final product.

[0156] Step S2: The calcined material obtained in step S1 is washed with water at a water-to-material mass ratio of (15-30):1 for 15-30 minutes. After washing, the calcined material is filtered and transferred to a forced-air drying oven for drying at 100°C for 10 hours. After drying, the calcined material is mechanically ground and sieved.

[0157] The following specific embodiments are provided to better illustrate this application.

[0158] Preparation of positive electrode active materials

[0159] The hydroxide precursor, lithium salt, and ball-milled zirconium beads were mixed in a drum-type ball mill mixer at a ball-to-material mass ratio of 50. The Li / Me molar ratio was controlled, where Me is the total metal in the hydroxide precursor. The mixture was then placed in a muffle furnace for sintering, with the sintering temperature and time controlled. The heating rate was 1℃ / min, and the sintering atmosphere was air. After sintering, the material was mechanically ground and sieved to obtain the sintered material.

[0160] The prepared calcined material was washed with water, controlling the water-to-material ratio (mass ratio) and washing time. After washing, the calcined material was filtered and transferred to a forced-air drying oven for drying at 100℃ for 10 hours. The dried calcined material was then mechanically ground and sieved to obtain the positive electrode active material.

[0161] The aforementioned hydroxide precursors can be obtained by purchasing commercially available precursors.

[0162] Example

[0163] A positive electrode active material is provided, which is prepared according to the aforementioned preparation steps. The preparation process parameters of each embodiment are shown in Table 1. The performance parameters of the obtained positive electrode active material are tested, and the results are shown in Tables 1 and 2.

[0164] Comparative Example 1

[0165] A positive electrode active material is provided, which is an undoped positive electrode active material, and its chemical formula is: LiNi 0.5 Mn 0.5 O2.

[0166] This positive electrode active material can be purchased commercially.

[0167] Comparative Example 2

[0168] A positive electrode active material is provided, which is a pure layered structure positive electrode active material. Chemical formula: LiNi 0.4 Mn 0.4 La 0.2 O2.

[0169] Comparative Example 3

[0170] Provides a positive electrode active material, which is a pure spinel positive electrode material, with the chemical formula: LiNi 0.5 Mn 1.5 O4.

[0171] Comparative Example 4

[0172] A positive electrode active material is provided, and its preparation process is as follows:

[0173] 1) Preparation of Ni-Co-Manganese Precursor Ni by Hydroxide Coprecipitation 0.5 Co0.2 Mn 0.3 (OH)2;

[0174] 2) The nickel-cobalt-manganese precursor Ni 0.5 Co 0.2 Mn 0.3 (OH)₂, Li₂CO₃, and additive ZrO₂ are mixed evenly to achieve a Li / Me molar ratio of 0.95, where Me represents the total transition metal content in the nickel-cobalt-manganese precursor. The ZrO₂ content is 4000 ppm, and the material is introduced into the air at a rate of 8 m³ / min. 3 The lithium-deficient cathode material Li was obtained by first sintering at 1000℃ in a box furnace for 10 hours, followed by cooling to 250℃ and holding for 4 hours. δ Ni 0.5 Co 0.2 Mn 0.3 O2 (0.5≤δ<1);

[0175] 3) Using lithium-deficient cathode material Li δ Ni 0.5 Co 0.2 Mn 0.3 O2 is crushed and then mixed with TiO2 and Li2CO3 to achieve a Li / Me molar ratio of 1.07, where Me represents the total transition metal content in the lithium-deficient cathode material. The TiO2 addition is 500 ppm, and the material is introduced into the air at a rate of 6 m³ / min. 3 The material is sintered for 7 hours in a box furnace at a temperature of 600℃ for a second time. After crushing and sieving, the layered-spinel phase composite cathode material is obtained.

[0176] Preparation of the positive electrode sheet

[0177] Positive electrode sheets were prepared using the positive active materials obtained from the aforementioned embodiments or comparative examples.

[0178] The positive electrode active material was premixed in a 5L mixing tank for 30 minutes. Then, conductive agent acetylene black (SP) and binder polyvinylidene fluoride (PVDF) were added and mixed again for 30 minutes. Finally, solvent N-methylpyrrolidone (NMP) was added and the mixture was rapidly stirred under vacuum to form a slurry. The mass ratio of positive electrode active material:acetylene black:PVDF was 96:2:2, and the solid content of the slurry was 70 wt.%. The slurry was uniformly coated on both sides of a 12 μm thick aluminum foil. The coated electrode was then dried in an oven at 100-130℃ for half an hour. The positive electrode active material loading of the electrode was 21.5 mg / cm³. 2 .

[0179] Preparation of the negative electrode sheet

[0180] The negative electrode active materials, artificial graphite and hard carbon, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are thoroughly mixed in a deionized water solvent system at a weight ratio of 90:5:2:2:1. The mixture is then coated onto copper foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0181] [Battery Manufacturing]

[0182] A porous polyethylene polymer film was used as the separator. The aforementioned positive electrode, separator, and negative electrode were stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The resulting cells were then wound to obtain a bare cell. The bare cell was placed in an outer packaging, and a prepared base electrolyte, namely 1 mol / L LiPF6 / (EC+EMC+DMC) (volume ratio 1:1:1), was injected and sealed to obtain a full cell.

[0183] The battery performance was tested, and the test results are shown in Table 2.

[0184] [Performance Testing Methods]

[0185] (1) XRD:

[0186] XRD diffraction patterns were analyzed for the positive electrode active materials of each embodiment or comparative example.

[0187] The diffraction angles (2θ1) of the first main diffraction peak, the diffraction angles (2θ2) of the second main diffraction peak, and the ratio of the intensity of the first main diffraction peak to the intensity of the second main diffraction peak (I1 / I2) are determined based on the XRD diffraction pattern.

[0188] (2) Dislocation density:

[0189] The dislocation density of the positive electrode active material was characterized by the XRD diffraction pattern described in (1) above.

[0190] Dislocation density β=(1 / D) 2 ×10 16 Where D = K λ / Bcosθ, K=0.9, λ=1.5406, B is the full width at half maximum (FWHM) of the positive electrode active material (hkl) crystal plane in the XRD diffraction pattern, and θ is the diffraction angle.

[0191] (3) Micro-stress:

[0192] The micro-stress of the positive electrode active material was characterized by the XRD diffraction pattern described in (1) above.

[0193] Micro-stress = (βhkl × Cosθhkl) / (4sinθhkl), where θhkl is the diffraction angle of the cathode material (hkl) crystal plane in the XRD diffraction pattern, and βhkl is the full width at half maximum (FWHM) of the cathode material (hkl) crystal plane in the XRD diffraction pattern.

[0194] (4) Material Spacing:

[0195] Particle size distribution was determined using laser diffraction, referring to GB / T 19077-2016 / ISO 13320:2009, and the measurement was performed using a Malvern 3000 instrument. Span = (D v90 -D v10 ) / D v50 .

[0196] (5) BET:

[0197] Specific surface area (BET) refers to the total surface area per unit mass of material. The specific surface area of ​​positive electrode active materials can be obtained through conventional testing methods. For example, refer to the national standard GB / T 19587-2004 for testing.

[0198] The BET test method is the same before and after water washing in Table 1. Unit: (m) 2 / g)

[0199] (6) Battery cell cycle retention rate (%)

[0200] Using a single full-cell battery as the test object, under a constant temperature environment of 25℃, the battery was charged to 4.55V at a 1C rate at a voltage of 2.5V to 4.55V, and then charged at a constant voltage of 4.45V until the current was ≤0.05mA. After resting for 5 minutes, the battery was discharged to 2.5V at a 1C rate, and the discharge energy was recorded. The previous process was repeated to obtain the capacity retention rate after a specified number of cycles. The capacity retention rate = discharge energy in the first cycle / discharge energy at the specified number of cycles × 100%. The number of cycles in this test was 100.

[0201] (7) Testing methods for determining the storage performance of individual battery cells:

[0202] Under constant temperature of 25℃, the battery was left to stand for 5 minutes, then discharged at 1 / 3C to 2.5V, left to stand for 5 minutes, then charged at 1 / 3C to 4.46V, and then charged at 4.46V with constant voltage until the current ≤0.05mA, left to stand for 5 minutes. The charging capacity at this point is recorded as C0. Next, the battery was discharged at 1 / 3C to 2.5V, and the discharge capacity at this point is the initial specific capacity, recorded as D0. Then, the battery was charged from 0.33C with constant current to 4.5V and then charged with constant voltage until the current ≤0.05mA, left to stand for 5 minutes, and finally placed in a high and 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 D recorded every 15 days. n (n=0,1,2……), calculate the capacity retention rate after 60 days of storage: (D4-D0) / D0*100%.

[0203] (8) Battery capacity test:

[0204] Under constant temperature of 25℃, after standing for 30 minutes, discharge at 0.1C to 2.5V, stand for 5 minutes, charge at 0.1C to 4.65V, then charge at 4.65V at constant voltage until the current is ≤0.05mA, stand for 5 minutes, and then discharge at 0.1C to 2.5V. The discharge capacity at this time is the initial specific capacity.

[0205] (9) Battery rate performance test: Under constant temperature environment of 25℃, let stand for 30 minutes, discharge at 0.1C to 2.5V, let stand for 5 minutes, charge at 0.1C to 4.65V, then charge at 4.65V at constant voltage until the current is ≤0.05mA, let stand for 5 minutes, then discharge at 0.1C to 2.5V. The discharge capacity at this time is recorded as C0. Let stand for 30 minutes, charge at 0.5C to 4.65V, then charge at 4.65V at constant voltage until the current is ≤0.05mA, let stand for 5 minutes, then discharge at 0.5C to 2.5V. The discharge capacity at this time is recorded as C1. Rate performance = C0 / C1*100%.

[0206] (10) Charge-discharge curves

[0207] Under constant temperature of 25℃, let stand for 30 minutes, discharge at 0.1C to 2.5V, let stand for 5 minutes, charge at 0.1C to 4.65V, then charge at 4.65V at constant voltage until the current is ≤0.05mA, let stand for 5 minutes, and then discharge at 0.1C to 2.5V.

[0208] Table 1

[0209]

[0210] Table 2

[0211]

[0212]

[0213] As can be seen from the data in the table above and the accompanying diagrams in the instruction manual:

[0214] Compared to Comparative Examples 1-4, the rate performance of each of the above embodiments is improved.

[0215] Furthermore, Comparative Example 2 is a cathode material with a pure layered structure. Compared with Example 1, it can be seen that the cathode active material of Example 1 effectively improves the battery capacity, cycle performance, storage performance, and rate performance compared with the pure layered cathode material of Comparative Example 2.

[0216] Furthermore, Comparative Example 3 is a pure spinel cathode material. Compared with Example 1, it can be seen that the cathode active material obtained in Example 1 has an effective improvement in battery capacity, cycle performance, storage performance, and rate performance compared with the pure spinel cathode material in Comparative Example 3.

[0217] Furthermore, the sintering temperature of Comparative Example 4 was too high. The lithium-deficient material was obtained by first sintering at high temperature and then supplementing lithium. The material obtained in Comparative Example 4 no longer has the characteristics of spinel structure and is more inclined to layered structure. Its I1 / I2 value is much larger than the I1 / I2 of the above embodiments.

[0218] Furthermore, as can be seen from Table 2, the positive electrode active material obtained in Example 1, compared with the positive electrode material in Comparative Example 4, effectively improves battery capacity, cycle performance, storage performance, and rate performance.

[0219] Furthermore, from the instruction manual appendix Figure 6 It can be seen that Examples 1-3 show charge-discharge curves of spinel and layered structure materials, respectively; while Comparative Examples 2 and 4 show charge-discharge curves of the single layered structure cathode material at the 2.5V-3.0V spinel-free discharge platform.

[0220] Furthermore, compared with Example 1, Comparative Example 1 is an undoped cathode material. It can be seen that the battery capacity, cycle performance, storage performance and rate performance of the cathode active material obtained in Example 1 are effectively improved.

[0221] Furthermore, compared with Example 1, Example 12 is an unwashed material. It can be seen that the positive electrode active material of Example 1 has better battery capacity, cycle performance, storage performance and rate performance.

[0222] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A positive electrode active material, characterized in that, The chemical formula of the positive electrode active material is: Li a Ni b Mn c M d O2, wherein 1≤a≤1.05, 0.22≤b≤0.5, 0.47≤c≤0.75, 0.01≤d≤0.03, and M includes at least one of Mg, Nb, Cr, Ce, Fe, La, Ta, Al, V, Ti, Zr, Sn, Mo, or Co; the XRD pattern of the positive electrode active material includes a first main diffraction peak and a second main diffraction peak; the diffraction angle of the first main diffraction peak is 16°~19°; and the diffraction angle of the second main diffraction peak is 42°~45°.

2. The positive electrode active material according to claim 1, characterized in that, The ratio of the intensity of the first main diffraction peak to the intensity of the second main diffraction peak is 0.8 to 2.

0.

3. The positive electrode active material according to claim 1, characterized in that, The ratio of the intensity of the first main diffraction peak to the intensity of the second main diffraction peak is 0.81 to 1.

99.

4. The positive electrode active material according to claim 1, characterized in that, The specific surface area of ​​the positive electrode active material after washing with water is less than 8m². 2 / g.

5. The positive electrode active material according to claim 1, characterized in that, The specific surface area of ​​the positive electrode active material after washing with water is greater than 2m². 2 / g and less than 8m 2 / g.

6. The positive electrode active material according to claim 1, characterized in that, The dislocation density of the positive electrode active material is 1.0*10⁻⁶. 13 ~2.5*10 13 .

7. The positive electrode active material according to claim 1, characterized in that, The dislocation density of the positive electrode active material is 1.1*10⁻⁶. 13 ~2.4*10 13 .

8. The positive electrode active material according to claim 1, characterized in that, The micro-stress of the positive electrode active material is less than or equal to 1.2%.

9. The positive electrode active material according to claim 1, characterized in that, The micro-stress of the positive electrode active material is 0.1%~0.5%.

10. The positive electrode active material according to claim 1, characterized in that, The diameter of the positive electrode active material is greater than 1.

2.

11. The positive electrode active material according to claim 1, characterized in that, The diameter of the positive electrode active material is greater than 1.2 and less than 1.

5.

12. The method for preparing the positive electrode active material according to any one of claims 1-11, characterized in that, include: A mixture of hydroxide precursor and lithium salt is sintered; the total metal in the hydroxide precursor is Me, which includes nickel, manganese and M.

13. The method for preparing the positive electrode active material according to claim 12, characterized in that, The sintering process includes sintering the mixture at 400℃~480℃ for 25 h~75 h.

14. The method for preparing the positive electrode active material according to claim 12, characterized in that, The molar ratio of Li element in the lithium salt to Me element in the hydroxide precursor is 1.0~1.

05.

15. The method for preparing the positive electrode active material according to claim 12, characterized in that, The method further includes: washing the sintered material with water; The mass ratio of water to the sintered material is (15~30):

1.

16. The method for preparing the positive electrode active material according to claim 12, characterized in that, The washing time is 15 min to 30 min.

17. A positive electrode plate, characterized in that, The positive electrode sheet comprises the positive active material according to any one of claims 1-11; or the positive electrode sheet comprises the positive active material prepared by the preparation method of the positive active material according to any one of claims 12-16.

18. A battery, characterized in that, The battery includes the positive electrode sheet as described in claim 17.

19. An electrical appliance, characterized in that, The electrical device includes the battery as described in claim 18.

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