Composite cathode material, preparation method thereof, cathode sheet, secondary battery and electric device

Abstract

The application discloses a composite positive electrode material and a preparation method thereof, a positive electrode sheet, a secondary battery and an electric device. x Ni a Co b Mn c M d ]O2, x+a+b+c+d=1, 0<a、b、c<1, 0≤d≤0.05, 0≤x, the element M includes one or more of Al, B, Zr, Sr, Y, Sb, Ta, Na, K, W, Ti, Mg, Nb, Hf, Mo, Ce, the span of the composite positive electrode material is 1.2-2.0, the composite positive electrode material includes a first lithium-rich manganese-based positive electrode material and a second lithium-rich manganese-based positive electrode material, the primary particles of the first lithium-rich manganese-based positive electrode material are rod-shaped particles, the length of the rod-shaped particles is 0.1-1.5 μm, and the Dv50 of the secondary particles is 3-8 μm; the primary particles of the second lithium-rich manganese-based positive electrode material are spherical-like particles, the diameter of the spherical-like particles is 0.1-400 nm, and the Dv50 of the secondary particles is 8-20 μm. Through the control of the Dv50 of the secondary particles, the span of the composite positive electrode material and the morphology and size of the primary particles, the composite positive electrode material has a high tap density, and the secondary battery has good cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to a composite positive electrode material and a preparation method, a positive electrode sheet, a secondary battery and an electric device. BACKGROUND

[0002] Lithium ion batteries are green and environmentally friendly secondary batteries, which meet the development needs of energy and environmental protection in today's countries. In recent years, lithium-rich manganese-based positive electrode materials have been widely concerned as the most promising next-generation lithium ion power battery positive electrode materials due to their high specific capacity, high discharge platform, low cost and environmental friendliness. However, the lithium-rich manganese-based positive electrode material still has the problems of low tap density and poor cycle performance of the secondary battery. SUMMARY

[0003] In view of the above problems, the present application provides a composite positive electrode material and a preparation method, a positive electrode sheet, a secondary battery and an electric device, which can solve the problems of low tap density and poor cycle performance of the secondary battery of the lithium-rich manganese-based positive electrode material.

[0004] In a first aspect, the present application provides a composite positive electrode material, the span of the composite positive electrode material is 1.2-2.0, wherein the span SPAN=(Dv90-Dv10) / Dv50, Dv90, Dv10 and Dv50 are the volume distribution particle size Dv90, the volume distribution particle size Dv10 and the volume average particle size Dv50 of the composite positive electrode material, the composite positive electrode material comprises a first lithium-rich manganese-based positive electrode material and a second lithium-rich manganese-based positive electrode material, the primary particles of the first lithium-rich manganese-based positive electrode material are rod-shaped particles, the length of the rod-shaped particles is 0.1-1.5 μm, the volume average particle size Dv50 of the secondary particles of the first lithium-rich manganese-based positive electrode material is 3-8 μm, the primary particles of the second lithium-rich manganese-based positive electrode material are spherical-like particles, the diameter of the spherical-like particles is 0.1-400 nm, and the volume average particle size Dv50 of the secondary particles of the second lithium-rich manganese-based positive electrode material is 8-20 μm.

[0005] In the technical scheme of the embodiment of the application, the volume average particle size Dv50 of the secondary particles of the first lithium-rich manganese-based positive electrode material is 3-8 μm, the volume average particle size Dv50 of the secondary particles of the second lithium-rich manganese-based positive electrode material is 8-20 μm, and the size particles are mixed. Meanwhile, through the design of the span, if the span is less than 1.2, it indicates that the overall particle size of the positive electrode material is relatively uniform, the gap between the materials is large, and the compaction density is low. If the span is greater than 2.0, the size particle distribution between the materials is large, which may produce fine powder or material with an excessively large particle size, and the kinetic performance is poor. Therefore, when the span is 1.2-2.0, it is beneficial to the size particle filling and the improvement of the compaction density. Further, the morphology and size of the primary particles of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material are limited. The primary particles of the first lithium-rich manganese-based positive electrode material are rod-shaped particles, the length of the rod-shaped particles is 0.1-1.5 μm, the specific surface area is small, and it is beneficial to the improvement of the cycle life. The primary particles of the second lithium-rich manganese-based positive electrode material are spherical particles, the diameter of the spherical particles is 0.1-400 nm, the specific surface area is large, the kinetic performance is good, and it is beneficial to the capacity. The mixing of the two forms a composite positive electrode material, and the cycle performance of the secondary battery is improved. Therefore, through the control of the volume average particle size Dv50 of the secondary particles of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material, the control of the span of the composite positive electrode material, and the control of the morphology and size of the primary particles of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material, the composite positive electrode material has a high compaction density, and the secondary battery has good cycle performance.

[0006] In some embodiments, the volume average particle size Dv50 of the composite positive electrode material is 6-15 μm, and the BET of the composite positive electrode material is 1.5-8.5 m 2 / g.

[0007] In the technical scheme of the embodiment of the application, the volume average particle size Dv50 of the composite positive electrode material is controlled in the range of 6-15 μm, which is beneficial to the size particle filling and the improvement of the compaction density. Through the control of the BET of the composite positive electrode material in a proper range, the side reaction rate and the kinetic performance of the composite positive electrode material and the electrolyte are at a reasonable level, and the secondary battery has good cycle performance.

[0008] In some embodiments, the volume average particle size Dv50 of the composite positive electrode material is 7-10 μm, and the BET of the composite positive electrode material is 2-7 m 2 / g.

[0009] In the battery cell of the embodiment of the application, through the further limitation of the volume average particle size Dv50 and the BET range of the composite positive electrode material, the cycle performance of the secondary battery is further optimized while the compaction density of the composite positive electrode material is improved.

[0010] In some embodiments, the span of the composite positive electrode material is 1.4-1.8. By further limiting the span of the composite positive electrode material, the tap density of the composite positive electrode material is further optimized.

[0011] In some embodiments, the length of the rod-shaped particles is 0.3-1.3 pm, and the diameter of the spheroid particles is 50-350 nm. By further limiting the length range of the rod-shaped particles of the first lithium-rich manganese-based positive electrode material and the diameter range of the spheroid particles of the second lithium-rich manganese-based positive electrode material, the cycle performance of the secondary battery is improved.

[0012] In some embodiments, the mass ratio of the first lithium-rich manganese-based positive electrode material to the second lithium-rich manganese-based positive electrode material is 5:5-1:9. By limiting the mass ratio of the first lithium-rich manganese-based positive electrode material to the second lithium-rich manganese-based positive electrode material, the size particles are filled appropriately, which is beneficial to improve the tap density and optimize the cycle performance of the secondary battery.

[0013] In some embodiments, the span of the secondary particles of the first lithium-rich manganese-based positive electrode material is 0.4SPAN2.2, and the span of the secondary particles of the second lithium-rich manganese-based positive electrode material is 0.4SPAN2.2. If the span is less than 0.4, it indicates that the overall particle size is relatively uniform, the gap between materials and materials is large, and the tap density is low. If the span is greater than 2.2, the size particle size distribution is large, which may produce fine powder or oversized particle material, resulting in poor kinetics. Therefore, the span is 0.4-2.2, and the small particles are filled between the large particles, which is beneficial to improve the tap density and the kinetics.

[0014] In some embodiments, the span of the secondary particles of the first lithium-rich manganese-based positive electrode material is 0.4SPAN1.5, and the span of the secondary particles of the second lithium-rich manganese-based positive electrode material is 0.5SPAN1.5. By further optimizing the span of the secondary particles of the first lithium-rich manganese-based positive electrode material and the span of the secondary particles of the second lithium-rich manganese-based positive electrode material, the tap density is improved.

[0015] In some embodiments, the BET of the first lithium-rich manganese-based positive electrode material is 0.4-2.5 m 2 / g, and the BET of the second lithium-rich manganese-based positive electrode material is 2.5-10 m 2 / g. The specific surface area of the first lithium-rich manganese-based positive electrode material is small, which is beneficial to improve the cycle life. The specific surface area of the second lithium-rich manganese-based positive electrode material is large, and the rate of side reactions with the electrolyte and the kinetics of the positive electrode of the battery are good, which is beneficial to capacity development. Therefore, the composite positive electrode material formed by mixing the two improves the cycle performance of the secondary battery.

[0016] In some embodiments, the BET of the first lithium-rich manganese-based positive electrode material is 1.0-2.0 m 2 / g, and the BET of the second lithium-rich manganese-based positive electrode material is 3.0-7.0 m 2 / g, so that the specific surface area can be further optimized to further improve the cycle performance of the secondary battery.

[0017] In a second aspect, the application provides a preparation method of a positive electrode material, comprising: providing a first lithium-rich manganese-based positive electrode material, the primary particles of the first lithium-rich manganese-based positive electrode material being rod-like particles, the length of the rod-like particles being 0.1-1.5 μm, and the volume average particle size Dv50 of the secondary particles of the first lithium-rich manganese-based positive electrode material being 3-8 μm; providing a second lithium-rich manganese-based positive electrode material, the primary particles of the second lithium-rich manganese-based positive electrode material being spherical-like particles, the diameter of the spherical-like particles being 0.1-400 nm, and the volume average particle size Dv50 of the secondary particles of the second lithium-rich manganese-based positive electrode material being 8-20 μm. The first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material are mixed to obtain the composite positive electrode material of any one of the above embodiments, wherein the mass ratio of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material is 5:5-1:9, and the element M is selected from one or more of Al, B, Zr, Sr, Y, Sb, Ta, Na, K, W, Ti, Mg, Nb, Hf, Mo, Ce.

[0018] In the technical solution of the embodiments of the application, the volume average particle size Dv50 of the secondary particles of the first lithium-rich manganese-based positive electrode material is controlled to be 3-8 μm, and the volume average particle size Dv50 of the secondary particles of the second lithium-rich manganese-based positive electrode material is controlled to be 8-20 μm, so that the large and small particles are mixed, and the diameter distance of the composite positive electrode material can be optimized by controlling the mass ratio of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material, so as to optimize the compaction density and the cycle performance of the secondary battery. The morphology and size of the primary particles of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material are limited, the primary particles of the first lithium-rich manganese-based positive electrode material are rod-like particles, the length of the rod-like particles is 0.1-1.5 μm, and the specific surface area is small, which is beneficial to improving the cycle life. The primary particles of the second lithium-rich manganese-based positive electrode material are spherical-like particles, the diameter of the spherical-like particles is 0.1-400 nm, the specific surface area is large, the rate of the side reaction with the electrolyte and the kinetic performance of the positive electrode of the battery are good, which is beneficial to capacity development, and the cycle performance of the secondary battery is improved.

[0019] In some embodiments, in the step of providing the first lithium-rich manganese-based cathode material, it includes: mixing a first lithium source and a first precursor evenly at a molar ratio of 1.1 - 1.9, adding a first additive, and sintering to obtain the first lithium-rich manganese-based cathode material. Among them, the first lithium source is one or more of lithium carbonate, lithium hydroxide, lithium phosphate, lithium nitrate, and lithium acetate, and the chemical formula of the first precursor is Ni a1 Co b1 Mn c1 (OH)2, 0 < a1, b1, c1 < 1. The addition amount of the first additive is 0 - 20000 ppm calculated based on the total mass of the first lithium source and the first precursor, and the first additive is a compound containing element M.

[0020] By defining the material type and preparation process of the first precursor, a first lithium-rich manganese-based cathode material with primary particles being rod-shaped particles with a length of 0.1 - 1.5 μm and a volume average particle size Dv50 of secondary particles being 3 - 8 μm is prepared.

[0021] In some embodiments, in the step of providing the second lithium-rich manganese-based cathode material, it includes: mixing a second lithium source and a second precursor evenly at a molar ratio of 1.1 - 1.9, adding a second additive, and sintering to obtain the second lithium-rich manganese-based cathode material. Among them, the second lithium source is one or more of lithium carbonate, lithium hydroxide, lithium phosphate, lithium nitrate, and lithium acetate, and the chemical formula of the second precursor is Ni a2 Co b2 Mn c2 CO3, 0 < a2, b2, c2 < 1. The addition amount of the second additive is 0 - 20000 ppm calculated based on the total mass of the second lithium source and the second precursor, and the second additive is a compound containing element M.

[0022] By defining the material type and preparation process of the second precursor, a second lithium-rich manganese-based cathode material with primary particles being spherical-like particles with a diameter of 0.1 - 400 nm and a volume average particle size Dv50 of secondary particles being 8 - 20 μm is prepared.

[0023] In the third aspect, the present application provides a positive electrode sheet, which includes a positive electrode film layer and a substrate. The positive electrode film layer includes the composite positive electrode material provided in the first aspect above or the composite positive electrode material prepared by the preparation method of the composite positive electrode material provided in the second aspect.

[0024] In some embodiments, the positive electrode film layer further contains a conductive agent and a binder. Among them, based on the total weight of the positive electrode film layer, the positive electrode film layer contains 95% - 99.5% of the composite positive electrode material. By adjusting the proportion of the composite positive electrode material in the positive electrode film layer, the performance of the positive electrode sheet is improved.

[0025] Fourthly, this application provides a secondary battery, including the positive electrode provided in the third aspect above.

[0026] Fifthly, this application provides an electrical device including the secondary battery provided in the fourth aspect above.

[0027] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0028] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0029] Figure 1 This is a schematic diagram of the structure of an electrical device according to some embodiments of this application;

[0030] Figure 2 This is an exploded structural diagram of a battery according to some embodiments of this application;

[0031] Figure 3 This is an exploded structural diagram of a battery cell according to some embodiments of this application;

[0032] Figure 4 SEM images of the first lithium-rich manganese-based cathode material according to some embodiments of this application;

[0033] Figure 5 SEM images of a second lithium-rich manganese-based cathode material according to some embodiments of this application.

[0034] Figure 6 SEM images of composite cathode materials from some embodiments of this application.

[0035] The reference numerals in the detailed embodiments are as follows:

[0036] 1000 electrical appliances;

[0037] Battery 100, controller 200, motor 300;

[0038] Box 10, Part 11, Part 2 12;

[0039] Battery cell 20, end cap 21, electrode terminal 21a, housing 22, cell assembly 23, tab 23a. Detailed Implementation

[0040] The embodiments of the technical solutions of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0041] 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 belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion.

[0042] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0043] In this paper, the reference to "embodiments" means that the specific features, structures or properties described in conjunction with the embodiments can be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor is it an independent or alternative embodiment to other embodiments. The skilled person in the art explicitly and implicitly understands that the embodiments described herein can be combined with other embodiments.

[0044] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship between the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0045] In the description of the embodiments of the present application, the term "a plurality of" refers to two or more (including two), and similarly, "a plurality of groups" refers to two or more groups (including two groups), and "a plurality of pieces" refers to two or more pieces (including two pieces).

[0046] In the description of the embodiments of the present application, the orientations or positional relationships indicated by the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the embodiments of the present application.

[0047] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "mounting", "connection", "connection", "fixing" and the like should be understood broadly, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection; can be direct connection, can also be indirect connection through an intermediate medium, can be internal communication of two elements or interaction relationship between two elements. For those skilled in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0048] At present, from the development of market situation, the application of power battery is more and more extensive. The power battery is not only applied to energy storage power supply systems such as hydroelectric, thermal, wind and solar power stations, but also widely used in electric bicycles, electric motorcycles, electric vehicles and other electric vehicles, military equipment, aerospace and other fields. With the continuous expansion of the application field of power battery, the market demand is also increasing.

[0049] The present inventors have noticed that in recent years, the new energy industry has developed rapidly, and the increasing range of new energy vehicles has also increased the demand for energy density of power batteries. Commercial lithium-ion batteries are limited by the embedded energy storage mechanism of their own materials, and the actual energy density is slow to increase, gradually approaching the limit of 300 Wh / kg; therefore, in order to meet the consumer demand of the electric vehicle market, the development of secondary batteries with higher energy density has become a social consensus. In recent years, lithium-rich manganese-based positive electrode materials have attracted attention due to their high energy density and high discharge platform. However, the lithium-rich manganese-based positive electrode materials reported so far still have the problems of low tap density and poor cycle performance.

[0050] In order to alleviate the problems of low tap density and poor cycle performance of lithium-rich manganese-based positive electrode materials, the applicant has found that research can be carried out on the composition of the positive electrode material and the ratio between the components.

[0051] The application provides a high-compaction-density lithium-rich manganese-based positive electrode material and a preparation method.

[0052] Based on the above consideration, in order to solve the problems of low compaction density and poor cycle performance of the lithium-rich manganese-based positive electrode material, the inventors have designed a composite positive electrode material through in-depth research, the span of the composite positive electrode material is 1.2-2.0, wherein the span is (Dv90-Dv10) / Dv50, Dv90, Dv10 and Dv50 are the volume distribution particle size Dv90, the volume distribution particle size Dv10 and the volume average particle size Dv50 of the composite positive electrode material, the composite positive electrode material comprises a first lithium-rich manganese-based positive electrode material and a second lithium-rich manganese-based positive electrode material, the primary particles of the first lithium-rich manganese-based positive electrode material are rod-shaped particles, the length of the rod-shaped particles is 0.1-1.5 microns, the volume average particle size Dv50 of the secondary particles of the first lithium-rich manganese-based positive electrode material is 3-8 microns, the primary particles of the second lithium-rich manganese-based positive electrode material are spherical-like particles, the diameter of the spherical-like particles is 0.1-400 nanometers, and the volume average particle size Dv50 of the secondary particles of the second lithium-rich manganese-based positive electrode material is 8-20 microns.

[0053] In the technical scheme of the embodiment of the present application, the volume average particle size Dv50 of the secondary particles of the first lithium-rich manganese-based positive electrode material is 3-8 μm, and the volume average particle size Dv50 of the secondary particles of the second lithium-rich manganese-based positive electrode material is 8-20 μm, so that the large and small particles are mixed. Meanwhile, through the design of the span, if the span is less than 1.2, it indicates that the overall particle size of the positive electrode material is relatively uniform, the gap between the materials is large, and the compaction density is low. If the span is greater than 2.0, the size distribution of the materials is greatly different, which may produce fine powder or oversized particle materials, and the kinetic performance is poor. Therefore, when the span is 1.2-2.0, it is beneficial to fill the gap between the large and small particles and improve the compaction density. Further, the morphology and size of the primary particles of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material are limited. The primary particles of the first lithium-rich manganese-based positive electrode material are rod-shaped particles, the length of the rod-shaped particles is 0.1-1.5 μm, and the specific surface area is small, which is beneficial to improve the cycle life. The primary particles of the second lithium-rich manganese-based positive electrode material are spherical particles, the diameter of the spherical particles is 0.1-400 nm, and the specific surface area is large, which has good kinetic performance and is beneficial to capacity development. The mixture of the two forms a composite positive electrode material, so that the cycle performance of the secondary battery is improved. Therefore, through the control of the volume average particle size Dv50 of the secondary particles of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material, the control of the span of the composite positive electrode material, and the control of the morphology and size of the primary particles of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material, the composite positive electrode material has high compaction density, and the secondary battery has good cycle performance.

[0054] In some embodiments, the chemical formula of the composite positive electrode material is Li[Li x Ni a Co b Mn c M d ]O2, wherein x+a+b+c+d=1, 0

[0055] The composite positive electrode material disclosed in the embodiment of the present application can be applied to a secondary battery, and the secondary battery can be used in an electric device using a battery as a power source or a variety of energy storage systems using a battery as an energy storage element. The electric device can be, but is not limited to, a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric vehicle, an electric automobile, a ship, a spacecraft, etc. The electric toy can include a fixed or mobile electric toy, such as a game console, an electric automobile toy, an electric ship toy, an electric aircraft toy, etc. The spacecraft can include an airplane, a rocket, a space shuttle, a spacecraft, etc.

[0056] The following embodiments are described by taking a vehicle as an example for convenience of illustration.

[0057] Please refer to Figure 1 , Figure 1 The structural schematic diagram of the power utilization device provided by some embodiments of the present application is shown in FIG. 1. The power utilization device 1000 can be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid vehicle or a range extended vehicle, etc. The power utilization device 1000 is internally provided with a battery 100, which can be arranged at the bottom, the head or the tail of the power utilization device 1000. The battery 100 can be used to supply power to the power utilization device 1000, for example, the battery 100 can be used as the operating power supply of the power utilization device 1000. The power utilization device 1000 can further include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the working power demand of the vehicle 1000 during starting, navigation and driving.

[0058] In some embodiments of the present application, the battery 100 can not only be used as the operating power supply of the power utilization device 1000, but also be used as the driving power supply of the power utilization device 1000, to replace or partially replace the fuel or natural gas to provide driving power for the power utilization device 1000.

[0059] Please refer to Figure 2 , Figure 2 The exploded view of the battery 100 provided by some embodiments of the present application is shown in FIG. 2. The battery 100 includes a box body 10 and a battery cell 20, and the battery cell 20 is accommodated in the box body 10. The box body 10 is used to provide an accommodation space for the battery cell 20, and the box body 10 can adopt various structures. In some embodiments, the box body 10 can include a first part 11 and a second part 12, and the first part 11 and the second part 12 are overlapped with each other, and the first part 11 and the second part 12 jointly define an accommodation space for accommodating the battery cell 20. The second part 12 can be a hollow structure with one end open, and the first part 11 can be a plate-shaped structure, which is overlapped with the open side of the second part 12 to jointly define the accommodation space with the second part 12; or the first part 11 and the second part 12 can both be hollow structures with one side open, and the open side of the first part 11 is overlapped with the open side of the second part 12. Of course, the box body 10 formed by the first part 11 and the second part 12 can have various shapes, such as a cylinder, a cuboid, etc.

[0060] In the battery 100, the battery cells 20 can be multiple, and the multiple battery cells 20 can be connected in series, in parallel, or in a mixed manner. The mixed manner means that the multiple battery cells 20 are connected in series and in parallel. The multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed manner, and the whole of the multiple battery cells 20 is accommodated in the case 10. Of course, the battery 100 can also be in a form that the multiple battery cells 20 are connected in series, in parallel, or in a mixed manner to form a battery module, and the multiple battery modules are connected in series, in parallel, or in a mixed manner to form a whole, and the whole is accommodated in the case 10. The battery 100 can also include other structures. For example, the battery 100 can also include a current collecting component for realizing the electrical connection between the multiple battery cells 20.

[0061] Each battery cell 20 can be a secondary battery or a primary battery, and can also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 20 can be in a shape of a cylinder, a flat body, a cuboid, or other shapes.

[0062] Please refer to Figure 3 , Figure 3 The battery cell 20 is the smallest unit of the battery. As shown in FIG. 1, the battery cell 20 includes an end cover 21, a shell 22, a cell assembly 23, and other functional components. Figure 3

[0063] The end cover 21 is a component that covers the opening of the shell 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cover 21 can be adapted to the shape of the shell 22 to fit the shell 22. The end cover 21 can be made of a material with certain hardness and strength (such as aluminum alloy), so that the end cover 21 is not easy to deform when subjected to extrusion and collision, so that the battery cell 20 can have higher structural strength, and the safety performance can also be improved. The end cover 21 can be provided with functional components such as an electrode terminal 21a. The electrode terminal 21a can be used to electrically connect with the cell assembly 23 for outputting or inputting the electrical energy of the battery cell 20. In some embodiments, the end cover 21 can also be provided with a pressure relief mechanism for relieving the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold value. The material of the end cover 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not make special limitations thereon. In some embodiments, an insulating piece can also be provided on the inner side of the end cover 21, which can be used to isolate the electrical connection components in the shell 22 from the end cover 21 to reduce the risk of short circuit. Exemplarily, the insulating piece can be plastic, rubber, etc.

[0064] ​The shell 22 is a component for cooperating with the end cover 21 to form an internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the electrode assembly 23, electrolyte and other components. The shell 22 and the end cover 21 can be independent components, and an opening can be provided on the shell 22, and the end cover 21 is made to cover the opening to form the internal environment of the battery cell 20. Without limitation, the end cover 21 and the shell 22 can also be integrated, specifically, the end cover 21 and the shell 22 can form a common connecting surface before other components enter the shell, and when it is necessary to seal the internal environment of the shell 22, the end cover 21 is made to cover the shell 22. The shell 22 can be various shapes and various sizes, such as a cuboid, a cylinder, a hexagonal prism, etc. Specifically, the shape of the shell 22 can be determined according to the specific shape and size of the electrode assembly 23. The material of the shell 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not make special limitations thereto.

[0065] The electrode assembly 23 is a component in which electrochemical reactions occur in the battery cell 20. One or more electrode assemblies 23 can be contained in the shell 22. The electrode assembly 23 is mainly formed by winding or stacking the positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets. The positive and negative electrode sheets have a portion of active material constituting the main body of the electrode assembly, and each of the portions of the positive and negative electrode sheets without active material constitutes a tab 23a. The positive and negative tabs can be located together at one end of the main body or at two ends of the main body, respectively. In the charging and discharging process of the battery, the positive and negative active materials react with the electrolyte, and the tabs 23a connect the electrode terminals to form a current loop.

[0066] According to some embodiments of the present application, the present application provides a composite positive electrode material, the span of the composite positive electrode material is 1.2-2.0, wherein the span is (Dv90-Dv10) / Dv50, Dv90, Dv10 and Dv50 are the volume distribution particle size Dv90, the volume distribution particle size Dv10 and the volume average particle size Dv50 of the composite positive electrode material, the composite positive electrode material comprises a first lithium-rich manganese-based positive electrode material and a second lithium-rich manganese-based positive electrode material, the primary particles of the first lithium-rich manganese-based positive electrode material are rod-like particles, the length of the rod-like particles is 0.1-1.5 μm, the volume average particle size Dv50 of the secondary particles of the first lithium-rich manganese-based positive electrode material is 3-8 μm, the primary particles of the second lithium-rich manganese-based positive electrode material are spherical-like particles, the diameter of the spherical-like particles is 0.1-400 nm, and the volume average particle size Dv50 of the secondary particles of the second lithium-rich manganese-based positive electrode material is 8-20 μm.

[0067] In some embodiments, the composite cathode material can also have a diameter distance of 1.2, 1.3, 1.35, 1.38, 1.4, 1.5, 1.55, 1.57, 1.6, 1.62, 1.65, 1.7, 1.75, 1.8, 1.85, 1.86, 1.9, 1.95, 2.0, etc.

[0068] In some embodiments, the composite cathode material can also have a diameter distance of 1.2-1.5, 1.3-1.6, 1.35-1.65, 1.38-1.7, 1.4-1.85, 1.5-1.9, 1.55-1.95, 1.57-2, 1.6-2, 1.7-2.0, etc.

[0069] In some embodiments, the rod-like particle can also have a length of 0.1 μm, 0.2 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.42 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.83 μm, 0.85 μm, 0.9 μm, 1.0 μm, 1.05 μm, 1.07 μm, 1.1 μm, 1.2 μm, 1.25 μm, 1.3 μm, 1.35 μm, 1.4 μm, 1.45 μm, 1.48 μm, 1.5 μm, etc.

[0070] In some embodiments, the rod-like particle can also have a length of 0.1-0.2 μm, 0.3-1 μm, 0.35-0.9 μm, 0.4-0.82 μm, 0.3-1.48 μm, 0.35-1.5 μm, 0.4-1.45 μm, 0.5-1.31 μm, 0.55-1.4 μm, 0.6-1.35 μm, 0.7-1.3 μm, 0.83-1.5 μm, etc.

[0071] In some embodiments, the spheroid-like particle can have a diameter of 0.1 nm, 0.5 nm, 0.85 nm, 1 nm, 2 nm, 5 nm, 7.5 nm, 10 nm, 12 nm, 22 nm, 25 nm, 28 nm, 30 nm, 44 nm, 52 nm, 60 nm, 70 nm, 82 nm, 90 nm, 95 nm, 100 nm, 120 nm, 132 nm, 140 nm, 160 nm, 180 nm, 200 nm, 220 nm, 232 nm, 240 nm, 245 nm, 260 nm, 270 nm, 285 nm, 290 nm, 292 nm, 300 nm, 320 nm, 325 nm, 350 nm, 365 nm, 372 nm, 385 nm, 390 nm, 400 nm, etc.

[0072] In some embodiments, the diameter of the spheroid-like particle can be 0.1-200 nm, 0.1-390 nm, 0.5-350 nm, 0.85-385 nm, 1-100 nm, 2-120 nm, 10-100 nm, 12-300 nm, 30-150 nm, 60-300 nm, 70-200 nm, 90.15-300 nm, 95-250 nm, 140-320 nm, 160-400 nm, 180-300 nm, 200-400 nm, etc.

[0073] In some embodiments, the chemical formula of the composite cathode material is Li[Li x Ni a Co b Mn c M d ]O2, wherein x+a+b+c+d=1, 0

[0074] In some embodiments, 0.1≤x≤0.9, 0.1≤a≤0.5, 0≤b≤0.2, 0.5≤c<1, 0≤d≤0.05, x+a+b+c+d=1, so that the composite cathode material has a higher compaction density, and the secondary battery has better cycle performance.

[0075] x can also be 0.1, 0.2, 0.25, 0.3, 0.4, 0.5, 0.55, 0.6, 0.7, 0.78, 0.8, 0.9, etc., or a range formed by any two of the above values, for example, 0.1-0.2, 0.25-0.4, 0.5-0.78, 0.8-0.9, etc.

[0076] a can also be 0.1, 0.15, 0.2, 0.25, 0.3, 0.38, 0.4, 0.42, 0.5, etc., or a range formed by any two of the above values, for example, 0.1-0.15, 0.2-0.3, 0.38-0.4, 0.42-0.5, etc.

[0077] b can also be 0, 0.02, 0.03, 0.05, 0.08, 0.1, 0.11, 0.125, 0.13, 0.14, 0.15, 0.16, 0.17, 0.185, 0.19, 0.2, etc., or a range formed by any two of the above values, for example, 0-0.03, 0.05-0.1, 0.11-0.125, 0.13-0.15, 0.16-0.185, 0.19-0.2, etc.

[0078] c can also be 0.5, 0.6, 0.65, 0.7, 0.8, 0.85, 0.88, 0.9, 0.95, 0.99, 0.9999, etc., or a range between any two of the above values, for example, 0.5-0.6, 0.65-0.7, 0.8-0.88, 0.9-0.95, 0.99-0.9999, etc.

[0079] d can also be 0, 0.001, 0.005, 0.008, 0.01, 0.015, 0.02, 0.028, 0.03, 0.04, 0.045, 0.048, 0.05, etc., or a range between any two of the above values, for example, 0-0.001, 0.005-0.01, 0.015-0.028, 0.03-0.04, 0.045-0.05, etc.

[0080] According to embodiments of the present application, the span SPAN = (Dv90-Dv10) / Dv50, "Dv90" refers to the particle size in the volume-based particle size distribution of the composite cathode material reaching 90% of the volume accumulation from the small particle size, that is, the volume of the composite cathode material smaller than this particle size accounts for 90% of the total volume of the composite cathode material. "Dv10" refers to the particle size in the volume-based particle size distribution of the composite cathode material reaching 10% of the volume accumulation from the small particle size, that is, the volume of the composite cathode material smaller than this particle size accounts for 10% of the total volume of the composite cathode material. "Dv50" refers to the particle size in the volume-based particle size distribution of the composite cathode material reaching 50% of the volume accumulation from the small particle size, that is, the volume of the composite cathode material smaller than this particle size accounts for 50% of the total volume of the composite cathode material. The particle size of the composite cathode material can be tested by a particle size tester.

[0081] Primary particles, also known as primary particles and primary particles. The first particle obtained by various chemical reaction methods is also called a crystal grain. Fine primary particles are easily combined together due to weak interaction forces, leading to agglomeration between primary particles, that is, many fine primary particles are in a group, and the larger particle formed at this time is called a secondary particle. The particle before aggregation is a primary particle, and the particle after aggregation is a secondary particle.

[0082] The secondary particles are obtained by agglomeration of primary particles. Fine primary particles are easily combined together due to weak interaction forces, leading to agglomeration of primary particles, that is, a large number of fine primary particles are in a cluster, and the larger cluster formed at this time is called a secondary particle. The particle before aggregation is a primary particle, and the particle after aggregation is a secondary particle. The volume average particle size Dv50 of the secondary particles of the first lithium-rich manganese-based positive electrode material is 3-8 μm, that is, the particle size of the secondary particles of the first lithium-rich manganese-based positive electrode material in the particle size distribution on the volume basis reaches 3-8 μm at a volume accumulation of 50% from a small particle size, that is, the volume of the secondary particles of the first lithium-rich manganese-based positive electrode material smaller than this particle size accounts for 50% of the total volume of the secondary particles of the first lithium-rich manganese-based positive electrode material. The volume average particle size Dv50 of the secondary particles of the second lithium-rich manganese-based positive electrode material is 8-20 μm, that is, the particle size of the secondary particles of the second lithium-rich manganese-based positive electrode material in the particle size distribution on the volume basis reaches 8-20 μm at a volume accumulation of 50% from a small particle size, that is, the volume of the secondary particles of the second lithium-rich manganese-based positive electrode material smaller than this particle size accounts for 50% of the total volume of the secondary particles of the second lithium-rich manganese-based positive electrode material.

[0083] The volume average particle size Dv50 of the secondary particles of the first lithium-rich manganese-based positive electrode material is 3-8 μm, and the volume average particle size Dv50 of the secondary particles of the second lithium-rich manganese-based positive electrode material is 8-20 μm, achieving a mixture of large and small particles. At the same time, by designing the span, if the span is less than 1.2, it indicates that the overall particle size of the positive electrode material is relatively uniform, the gap between the materials is large, and the compaction density is low. If the span is greater than 2.0, the size distribution of the materials is large, which will produce fine powder or super-large particle materials, and the kinetic performance is poor. Therefore, when the span is 1.2-2.0, it is beneficial to fill the gap between large and small particles and improve the compaction density. Further, the morphology and size of the primary particles of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material are limited. The primary particles of the first lithium-rich manganese-based positive electrode material are rod-shaped particles, and the length of the rod-shaped particles is 0.1-1.5 μm, and the specific surface area is small, which is beneficial to improve the cycle life. The primary particles of the second lithium-rich manganese-based positive electrode material are spherical particles, and the diameter of the spherical particles is 0.1-400 nm, and the specific surface area is large, and the kinetic performance is good, which is beneficial to capacity development. The mixture of the two forms a composite positive electrode material, which improves the cycle performance of the secondary battery. Therefore, by controlling the volume average particle size Dv50 of the secondary particles of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material, controlling the span of the composite positive electrode material, and controlling the morphology and size of the primary particles of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material, the composite positive electrode material has high compaction density, and the secondary battery has good cycle performance.

[0084] According to some embodiments of the present application, the volume average particle size Dv50 of the composite cathode material is 6-15 μm, and the BET of the composite cathode material is 1.5-8.5 m 2 / g.

[0085] In some embodiments, the volume average particle size Dv50 of the composite cathode material can be 6 μm, 6.5 μm, 7 μm, 7.2 μm, 7.5 μm, 8 μm, 9 μm, 10 μm, 10.5 μm, 11 μm, 12 μm, 13 μm, 13.5 μm, 14 μm, 15 μm, etc.

[0086] In some embodiments, the volume average particle size Dv50 of the composite cathode material can be 6-10 μm, 6-11 μm, 6-12 μm, 6-13 μm, 6.5-14 μm, 7-12 μm, 7.2-12 μm, 7.5-10 μm, 8-14 μm, 9-14 μm, 10-13 μm, etc.

[0087] In some embodiments, the BET of the composite cathode material can be 1.5 m 2 / g, 2 m 2 / g, 2.5 m 2 / g, 2.85 m 2 / g, 3 m 2 / g, 3.5 m 2 / g, 4 m 2 / g, 4.35 m 2 / g, 4.5 m 2 / g, 5 m 2 / g, 6.5 m 2 / g, 7 m 2 / g, 7.64 m 2 / g, 8 m 2 / g, 8.38 m 2 / g, 8.5 m 2 / g, etc.

[0088] In some embodiments, the BET of the composite cathode material can be 1.5-8.38 m 2 / g, 2-8 m 2 / g, 2.5-7.64 m 2 / g, 2.85-7 m 2 / g, 3-6.5 m 2 / g, 3.5-5 m 2 / g, 4-8.5 m 2 / g, 4.35-7.85 m 2 / g, 4.5-7 m 2 / g, 5-8 m 2 / g, etc.

[0089] The volume average particle size Dv50 of the composite cathode material is 6-15 μm, that is, the particle size of the composite cathode material reaching 50% of the volume accumulation in the particle size distribution on the volume basis is 6-15 μm, that is, the volume of the composite cathode material less than this particle size accounts for 50% of the total volume of the composite cathode material. The BET of the composite cathode material is 12.5-8.5 m 2 / g, the BET refers to the specific surface area, which is the specific surface area of the material per unit mass

[0090] By limiting the volume average particle size Dv50 and the BET of the composite cathode material in the appropriate range, the size particles are filled in the gaps, the compaction density is improved, after the formation of the secondary battery, the particles can be in close contact while forming a pore structure convenient for the electrolyte to infiltrate, the side reaction rate of the composite cathode material and the electrolyte and the kinetic performance of the battery cathode are at a reasonable level, so that the secondary battery has good cycle performance.

[0091] According to some embodiments of the present application, the volume average particle size Dv50 of the composite cathode material is 7-10 μm, and the BET of the composite cathode material is 2-7 m 2 / g.

[0092] The volume average particle size Dv50 of the composite cathode material is 7-10 μm, that is, the particle size of the composite cathode material reaching 50% of the volume accumulation in the particle size distribution on the volume basis is 7-10 μm, that is, the volume of the composite cathode material less than this particle size accounts for 50% of the total volume of the composite cathode material.

[0093] By further limiting the volume average particle size Dv50 and the BET range of the composite cathode material, the cycle performance of the secondary battery is further optimized while improving the compaction density of the composite cathode material.

[0094] According to some embodiments of the present application, the span SPAN of the composite cathode material is 1.4-1.8.

[0095] The span SPAN of the composite cathode material is 1.4-1.8, that is, the span SPAN=(Dv90-Dv10) / Dv50 is 1.4-1.8.

[0096] By further limiting the span SPAN range of the composite cathode material, the compaction density of the composite cathode material is further optimized.

[0097] According to some embodiments of the present application, the length of the rod-shaped particles is 0.3-1.3 μm, and the diameter of the spheroid particles is 50-350 nm.

[0098] The primary particles of the first lithium-rich manganese-based positive electrode material are rod-like particles, the length of the rod-like particles is 0.3-1.3 μm, the specific surface area is small, although the capacity play is limited, but it is beneficial to have a longer cycle life; the primary particles of the second lithium-rich manganese-based positive electrode material are spherical-like particles, the diameter of the spherical-like particles is 50-350 nm, the specific surface area is large, although the cycle life is reduced when applied in the battery due to too much contact with the electrolyte, but it is beneficial to the capacity play, so that the kinetic performance is at a reasonable level, and the cycle performance of the secondary battery is improved.

[0099] According to some embodiments of the present application, the mass ratio of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material is 5:5-1:9.

[0100] By limiting the mass ratio of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material, the size of the particles is filled appropriately, which is beneficial to improve the compaction density, and the cycle performance of the secondary battery is optimized.

[0101] According to some embodiments of the present application, the diameter distance SPAN of the secondary particles of the first lithium-rich manganese-based positive electrode material is 0.4≤SPAN≤2.2, and the diameter distance SPAN of the secondary particles of the second lithium-rich manganese-based positive electrode material is 0.4≤SPAN≤2.2.

[0102] In some embodiments, the diameter distance SPAN of the secondary particles of the first lithium-rich manganese-based positive electrode material can be 0.4, 0.5, 0.55, 0.58, 0.6, 0.65, 0.7, 0.8, 0.84, 0.88, 0.9, 0.95, 1.0, 1.15, 1.2, 1.35, 1.4, 1.5, 1.7, 1.8, 1.9, 1.95, 2.0, 2.05, 2.1, 2.2, etc.

[0103] In some embodiments, the diameter distance SPAN of the secondary particles of the first lithium-rich manganese-based positive electrode material can be 0.3-1.3.5, 0.4-2.1, 0.5-2.05, 0.55-2.0, 0.6-1.95, 0.65-1.9, 0.7-1.8, 0.84-1.7, 0.88-1.5, 0.9-1.4, 0.95-1.35, 1.0-2.2, 1.15-2.2, 1.2-2.2, etc.

[0104] In some embodiments, the diameter distance SPAN of the secondary particles of the second lithium-rich manganese-based positive electrode material can be 0.4, 0.45, 0.5, 0.58, 0.6, 0.68, 0.75, 0.8, 0.85, 0.88, 0.9, 0.95, 1.0, 1.15, 1.2, 1.25, 1.45, 1.5, 1.7, 1.8, 1.9, 1.98, 2.0, 2.15, 2.2, etc. In some embodiments, the diameter distance SPAN of the secondary particles of the second lithium-rich manganese-based positive electrode material can be 0.3-1.3.5, 0.4-2.1, 0.5-2.05, 0.55-2.0, 0.6-1.95, 0.65-1.9, 0.7-1.8, 0.84-1.7, 0.88-1.5, 0.9-1.4, 0.95-1.35, 1.0-2.2, 1.15-2.2, 1.2-2.2, etc.

[0105] In some embodiments, the second lithium-rich manganese-based positive electrode material has a span of the secondary particles of 0.4-2.15, 0.45-2.1, 0.5-1.5, 0.5-2.0, 0.58-1.98, 0.6-1.9, 0.75-1.8, 0.85-1.7, 0.9-1.5, 1.0-1.8, 1.15-1.9, 1.2-2.05, 1.25-2.1, 1.45-2.2, 1.5-2.2, etc.

[0106] If the span is less than 0.4, the overall particle size is relatively uniform, the gap between materials and materials is large, and the compaction density is low. If the span is greater than 2.2, the size particle size distribution is uneven, which can produce fine powder or oversized material, resulting in poor kinetic performance. Therefore, the span is 0.4-2.2, and the small particles are better at filling the gaps between large particles, which improves the compaction density and is beneficial to good kinetic performance.

[0107] According to some embodiments of the present application, the first lithium-rich manganese-based positive electrode material has a span of the secondary particles of 0.4≤SPAN≤1.5, and the second lithium-rich manganese-based positive electrode material has a span of the secondary particles of 0.5≤SPAN≤1.5.

[0108] The span of the secondary particles of the first lithium-rich manganese-based positive electrode material and the span of the secondary particles of the second lithium-rich manganese-based positive electrode material are further optimized to improve the compaction density.

[0109] According to some embodiments of the present application, the first lithium-rich manganese-based positive electrode material has a BET of 0.4-2.5m 2 / g, and the second lithium-rich manganese-based positive electrode material has a BET of 2.5-10m 2 / g.

[0110] In some embodiments, the first lithium-rich manganese-based positive electrode material has a BET of 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.65m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.14m 2 / g, 1.15m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g, 1.54m 2 / g, 1.6m2 / g, 1.7 m 2 / g, 1.8 m 2 / g, 1.9 m 2 / g, 2.0 m 2 / g, 2.1 m 2 / g, 2.15 m 2 / g, 2.2 m 2 / g, 2.35 m 2 / g, 2.4 m 2 / g, 2.5 m 2 / g, etc.

[0111] In some embodiments, the BET of the first lithium-rich manganese-based cathode material can be 0.4-2.4 m 2 / g, 0.5-2.35 m 2 / g, 0.6-2.2 m 2 / g, 0.65-2.15 m 2 / g, 0.7-2.1 m 2 / g, 0.8-2.0 m 2 / g, 0.9-1.9 m 2 / g, 1.0-1.8 m 2 / g, 1.0-2 m 2 / g, 1.14-2.5 m 2 / g, 1.15-2.41 m 2 / g, 1.2-2.35 m 2 / g, 1.3-2.3 m 2 / g, 1.4-2.5 m 2 / g, 1.5-2.5 m 2 / g, 1.54-2.5 m 2 / g, 1.6-2.5 m 2 / g, 1.7-2.5 m 2 / g, etc.

[0112] In some embodiments, the BET of the second lithium-rich manganese-based cathode material can be 2.5 m 2 / g, 2.6 m 2 / g, 2.65 m 2 / g, 2.9 m 2 / g, 3.0 m 2 / g, 3.4 m 2 / g, 4.0 m 2 / g, 4.2 m 2 / g, 4.8 m 2 / g, 5.9 m 2 / g, 5.0 m 2 / g, 6.0 m 2 / g, 7.0 m 2 / g, 7.2 m 2 / g, 8.0 m 2 / g, 8.45 m 2 / g, 9.0 m 2 / g, 9.5 m 2 / g, 9.85 m 2 / g, 10 m 2 / g, etc.

[0113] In some embodiments, the BET of the second lithium-rich manganese-based positive electrode material can be 2.5-9.85 m 2 / g, 2.6-9.5 m 2 / g, 2.65-9.0 m 2 / g, 2.9-8.45 m 2 / g, 3.0-7.0 m 2 / g, 3.0-8.0 m 2 / g, 3.4-8 m 2 / g, 4.0-8 m 2 / g, 4.2-8.05 m 2 / g, 4.8-7.2 m 2 / g, 5.9-9 m 2 / g, 5.0-9.3 m 2 / g, 6.0-9.65 m 2 / g, 7.0-10 m 2 / g, etc.

[0114] The specific surface area of the first lithium-rich manganese-based positive electrode material is small, which is beneficial to improving the cycle life; the specific surface area of the second lithium-rich manganese-based positive electrode material is large, the rate of side reactions with electrolyte and the kinetic performance of the positive electrode of the battery are good, which is beneficial to capacity development, therefore, the composite positive electrode material formed by mixing the two improves the cycle performance of the secondary battery.

[0115] According to some embodiments of the present application, the BET of the first lithium-rich manganese-based positive electrode material is 1.0-2.0 m 2 / g, and the BET of the second lithium-rich manganese-based positive electrode material is 3.0-7.0 m 2 / g.

[0116] By further optimizing the specific surface area, the cycle performance of the secondary battery is further improved.

[0117] According to some embodiments of the present application, the present application provides a preparation method of a positive electrode material, comprising: providing a first lithium-rich manganese-based positive electrode material, primary particles of the first lithium-rich manganese-based positive electrode material are rod-like particles, the length of the rod-like particles is 0.1-1.5 μm, and the volume average particle size Dv50 of secondary particles of the first lithium-rich manganese-based positive electrode material is 3-8 μm. A second lithium-rich manganese-based positive electrode material is provided, primary particles of the second lithium-rich manganese-based positive electrode material are spheroid-like particles, the diameter of the spheroid-like particles is 0.1-400 nm, and the volume average particle size Dv50 of secondary particles of the second lithium-rich manganese-based positive electrode material is 8-20 μm. The first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material are mixed to obtain the composite positive electrode material of any one of the above embodiments, wherein the mass ratio of the mixing of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material is 5:5-1:9, and the element M is selected from one or more of Al, B, Zr, Sr, Y, Sb, Ta, Na, K, W, Ti, Mg, Nb, Hf, Mo, Ce.

[0118] In some embodiments, the length of the rod-like particles can also be 0.3 μm, 0.35 μm, 0.4 μm, 0.42 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.83 μm, 0.85 μm, 0.9 μm, 1.0 μm, 1.05 μm, 1.07 μm, 1.1 μm, 1.2 μm, 1.25 μm, 1.3 μm, 1.35 μm, 1.4 μm, 1.45 μm, 1.48 μm, 1.5 μm, etc.

[0119] In some embodiments, the length of the rod-like particles can also be 0.3-1 μm, 0.35-0.9 μm, 0.4-0.82 μm, 0.3-1.48 μm, 0.35-1.5 μm, 0.4-1.45 μm, 0.5-1.31 μm, 0.55-1.4 μm, 0.6-1.35 μm, 0.7-1.3 μm, 0.83-1.5 μm, etc.

[0120] In some embodiments, the diameter of the spheroid-like particle can be 0.1 nm, 0.5 nm, 0.85 nm, 1 nm, 2 nm, 5 nm, 7.5 nm, 10 nm, 12 nm, 22 nm, 25 nm, 28 nm, 30 nm, 44 nm, 52 nm, 60 nm, 70 nm, 82 nm, 90 nm, 95 nm, 100 nm, 120 nm, 132 nm, 140 nm, 160 nm, 180 nm, 200 nm, 220 nm, 232 nm, 240 nm, 245 nm, 260 nm, 270 nm, 285 nm, 290 nm, 292 nm, 300 nm, 320 nm, 325 nm, 350 nm, 365 nm, 372 nm, 385 nm, 390 nm, 400 nm, etc.

[0121] In some embodiments, the diameter of the spheroid-like particle can be 0.1-200 nm, 0.1-390 nm, 0.5-350 nm, 0.85-385 nm, 1-100 nm, 2-120 nm, 10-100 nm, 12-300 nm, 30-150 nm, 60-300 nm, 70-200 nm, 90.15-300 nm, 95-250 nm, 140-320 nm, 160-400 nm, 180-300 nm, 200-400 nm, etc.

[0122] In some embodiments, the mass ratio of the mixture of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material can be 5:5, 5:6, 4:7, 5:9, 3:11, 4:13, 1:3, 1:5, 2:9, 1:6, 1:7, 1:8, 1:9, etc.

[0123] In some embodiments, the mass ratio of the mixture of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material can be 5:5-1:8, 5:6-1:7, 4:7-1:6, 5:9-1:5, 3:11-1:4, 4:13-1:9, 1:3-1:8, 1:5-1:7, 2:9-1:6, 1:7-1:9, etc.

[0124] In some embodiments, the chemical formula of the first lithium-rich manganese-based positive electrode material can be Li[Li x1’ Ni a1’ Co b1’ Mn c1’ M d1’ ]O2, x1’+a1’+b1’+c1’+d1’=1, 0

[0125] In some embodiments, 0.1≤x1’≤0.9, 0.1≤a1’≤0.5, 0≤b1’≤0.2, 0.5≤c1’<1, 0≤d1’≤0.05, x1’+a1’+b1’+c1’+d1’=1, so that the composite cathode material has a higher compaction density, and the secondary battery has better cycle performance.

[0126] x1’ can also be 0.1, 0.22, 0.25, 0.3, 0.44, 0.5, 0.55, 0.65, 0.7, 0.78, 0.8, 0.9, etc., or a range between any two of the above values, such as 0.1-0.22, 0.25-0.44, 0.55-0.78, 0.8-0.9, etc.

[0127] a1’ can also be 0.1, 0.15, 0.2, 0.25, 0.35, 0.38, 0.4, 0.45, 0.5, etc., or a range between any two of the above values, such as 0.1-0.15, 0.2-0.35, 0.38-0.4, 0.45-0.5, etc.

[0128] b1’ can also be 0, 0.02, 0.05, 0.08, 0.1, 0.11, 0.125, 0.14, 0.15, 0.17, 0.185, 0.19, 0.2, etc., or a range between any two of the above values, such as 0-0.02, 0.05-0.1, 0.11-0.125, 0.14-0.15, 0.17-0.185, 0.19-0.2, etc.

[0129] c1’ can also be 0.5, 0.6, 0.65, 0.77, 0.8, 0.85, 0.88, 0.92, 0.95, 0.99, 0.9999, etc., or a range between any two of the above values, such as 0.5-0.6, 0.65-0.77, 0.8-0.88, 0.92-0.95, 0.99-0.9999, etc.

[0130] d1’ can also be 0, 0.001, 0.003, 0.005, 0.01, 0.015, 0.023, 0.028, 0.03, 0.04, 0.045, 0.048, 0.05, etc., or a range between any two of the above values, such as 0-0.001, 0.003-0.01, 0.015-0.023, 0.03-0.04, 0.045-0.05, etc.

[0131] In some embodiments, the chemical formula of the second lithium-rich manganese-based cathode material is Li[Li x2’ Ni a2’ Co b2’ Mnc2’ M d2’ ]O2, x2’ + a2’ + b2’ + c2’ + d2’ = 1, 0 < a2’, b2’, c2’ < 1, 0 ≤ d2’ ≤ 0.05, 0 ≤ x2’.

[0132] In some embodiments, 0.1 ≤ x2’ ≤ 0.9, 0.1 ≤ a2’ ≤ 0.5, 0 ≤ b2’ ≤ 0.2, 0.5 ≤ c2’ < 1, 0 ≤ d2’ ≤ 0.05, x2’ + a2’ + b2’ + c2’ + d2’ = 1, so that the composite cathode material has a higher compaction density and the secondary battery has better cycle performance.

[0133] x2’ can also be 0.1, 0.2, 0.25, 0.3, 0.44, 0.5, 0.55, 0.65, 0.75, 0.78, 0.8, 0.9, etc., or a range formed by any two of the above values, for example, 0.1-0.2, 0.25-0.44, 0.55-0.75, 0.78-0.9, etc.

[0134] a2’ can also be 0.1, 0.18, 0.2, 0.25, 0.32, 0.35, 0.4, 0.47, 0.5, etc., or a range formed by any two of the above values, for example, 0.1-0.18, 0.2-0.35, 0.35-0.4, 0.47-0.5, etc.

[0135] b2’ can also be 0, 0.03, 0.05, 0.08, 0.1, 0.118, 0.125, 0.145, 0.15, 0.17, 0.185, 0.195, 0.2, etc., or a range formed by any two of the above values, for example, 0-0.03, 0.05-0.1, 0.118-0.125, 0.145-0.15, 0.17-0.185, 0.195-0.2, etc.

[0136] c2’ can also be 0.5, 0.6, 0.65, 0.7, 0.8, 0.85, 0.88, 0.9, 0.95, 0.99, 0.999, etc., or a range formed by any two of the above values, for example, 0.5-0.6, 0.65-0.7, 0.85-0.88, 0.9-0.95, 0.99-0.999, etc.

[0137] d2' can also be 0, 0.001, 0.004, 0.005, 0.01, 0.015, 0.024, 0.028, 0.03, 0.042, 0.045, 0.048, 0.05, etc., or a range formed by any two of the above values, for example, 0-0.001, 0.004-0.01, 0.015-0.028, 0.03-0.042, 0.045-0.05, etc.

[0138] By controlling the volume average particle size Dv50 of the secondary particles of the first lithium-rich manganese-based positive electrode material to be 3-8 μm and the volume average particle size Dv50 of the secondary particles of the second lithium-rich manganese-based positive electrode material to be 8-20 μm, the size particle mixing is achieved, and by controlling the mass ratio of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material, the optimization of the diameter distance of the composite positive electrode material can be achieved, so as to optimize the compaction density and the cycle performance of the secondary battery; the morphology and size of the primary particles of the first lithium-rich manganese-based positive electrode material and the second lithium-rich manganese-based positive electrode material are limited, the primary particles of the first lithium-rich manganese-based positive electrode material are rod-shaped particles, the length of the rod-shaped particles is 0.1-1.5 μm, and the specific surface area is small, which is beneficial to improving the cycle life; the primary particles of the second lithium-rich manganese-based positive electrode material are spherical particles, the diameter of the spherical particles is 0.1-400 nm, and the specific surface area is large, the rate of the side reaction with the electrolyte and the kinetic performance of the positive electrode of the battery are good, which is beneficial to capacity development, so as to improve the cycle performance of the secondary battery.

[0139] According to some embodiments of the present application, in the step of providing the first lithium-rich manganese-based positive electrode material, the first lithium source and the first precursor are uniformly mixed in a molar ratio of 1.1-1.9, a first additive is added, and sintering is performed to obtain the first lithium-rich manganese-based positive electrode material, wherein the first lithium source is one or more of lithium carbonate, lithium hydroxide, lithium phosphate, lithium nitrate, and lithium acetate, the chemical formula of the first precursor is Ni a1 Co b1 Mn c1 (OH)2, 0

[0140] In some embodiments, the molar ratio of the first lithium source and the first precursor can be 1.1, 1.15, 1.2, 1.3, 1.4, 1.45, 1.5, 1.6, 1.7, 1.78, 1.8, 1.85, 1.9, etc.

[0141] In some embodiments, the molar ratio of the first lithium source and the first precursor mixed can be 1.1-1.85, 1.15-1.78, 1.2-1.7, 1.3-1.6, 1.4-1.8, 1.45-1.9, 1.5-1.9, etc.

[0142] In some embodiments, the amount of the first additive added can be 300 ppm, 400 ppm, 450 ppm, 500 ppm, 800 ppm, 1000 ppm, 2000 ppm, 8000 ppm, 10000 ppm, 12000 ppm, 15000 ppm, 20000 ppm, etc., calculated on the basis of the total mass of the first lithium source and the first precursor.

[0143] In some embodiments, the amount of the first additive added can be 300 ppm-18000 ppm, 400 ppm-17000 ppm, 450 ppm-16500 ppm, 500 ppm-16000 ppm, 800 ppm-15000 ppm, 1000 ppm-15000 ppm, 2000 ppm-14000 ppm, 8000 ppm-18000 ppm, 10000 ppm-15000 ppm, 12000 ppm-16000 ppm, 13000 ppm-18000 ppm, 15000 ppm-20000 ppm, etc., calculated on the basis of the total mass of the first lithium source and the first precursor.

[0144] By limiting the material type and preparation process of the first precursor, a first lithium-rich manganese-based positive electrode material is prepared, in which primary particles are rod-shaped particles with a length of 0.1-1.5 μm, and the volume average particle size Dv50 of the secondary particles is 3-8 μm.

[0145] According to some embodiments of the present application, in the step of providing the second lithium-rich manganese-based positive electrode material, the second lithium source and the second precursor are mixed uniformly in a molar ratio of 1.1-1.9, a second additive is added, and sintering is performed to obtain the second lithium-rich manganese-based positive electrode material, wherein the second lithium source is one or more of lithium carbonate, lithium hydroxide, lithium phosphate, lithium nitrate, and lithium acetate, the chemical formula of the second precursor is Ni a2 Co b2 Mn c2 CO3, 0

[0146] In some embodiments, the molar ratio of the second lithium source and the second precursor mixed can be 1.1, 1.25, 1.3, 1.35, 1.4, 1.5, 1.55, 1.6, 1.65, 1.7, 1.8, 1.85, 1.9, etc.

[0147] In some embodiments, the molar ratio of the second lithium source and the second precursor mixed can be 1.1-1.85, 1.15-1.78, 1.2-1.7, 1.3-1.6, 1.4-1.8, 1.45-1.9, 1.5-1.9, etc.

[0148] In some embodiments, the amount of the second additive added can be 300 ppm, 800 ppm, 1500 ppm, 2500 ppm, 5000 ppm, 8000 ppm, 9000 ppm, 10000 ppm, 13500 ppm, 15000 ppm, 18000 ppm, 20000 ppm, etc., based on the total mass of the second lithium source and the second precursor.

[0149] In some embodiments, the amount of the second additive added can be 300 ppm-18000 ppm, 400 ppm-17000 ppm, 450 ppm-16500 ppm, 500 ppm-16000 ppm, 800 ppm-15000 ppm, 1000 ppm-15000 ppm, 2000 ppm-14000 ppm, 8000 ppm-18000 ppm, 10000 ppm-15000 ppm, 12000 ppm-16000 ppm, 13000 ppm-18000 ppm, 15000 ppm-20000 ppm, etc., based on the total mass of the second lithium source and the second precursor.

[0150] By limiting the material type and preparation process of the second precursor, a primary particle is prepared as a spherical particle with a diameter of 0.1-400 nm, and a secondary particle is prepared as a second lithium-rich manganese-based positive electrode material with a volume average particle size Dv50 of 8-20 μm.

[0151] According to some embodiments of the present application, in the steps of preparing the first lithium-rich manganese-based positive electrode material and preparing the second lithium-rich manganese-based positive electrode material, the sintering temperature is 700-1000 ℃, the sintering time is 10-40 h, and the sintering atmosphere is air or inert atmosphere.

[0152] In some embodiments, the sintering temperature can be 700 ℃, 720 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃, 1000 ℃, etc.

[0153] In some embodiments, the sintering time can be 10 h, 12 h, 15 h, 20 h, 24 h, 30 h, 36 h, 40 h, etc.

[0154] The sintering temperature refers to a temperature at which complex physical and chemical changes occur during sintering, and the physical and chemical changes can be dehydration of raw materials, oxidative decomposition, melting of fusible substances, formation of a liquid phase, disappearance of old crystal phases, generation of new crystal phases, and continuous changes in the amount of newly generated compounds, the composition, amount, and viscosity of the liquid phase.

[0155] By limiting the material types and preparation processes of the precursors, it is beneficial to prepare the first and second lithium-rich manganese-based positive electrode materials with suitable morphology and size. Among them, the first precursor is a hydroxide matrix, which is beneficial to form the first lithium-rich manganese-based positive electrode material with rod-shaped particles with a length of 0.1-1.5 μm as primary particles and a volume average particle size Dv50 of 3-8 μm as secondary particles, and the second precursor is a carbonate matrix, which is beneficial to form the second lithium-rich manganese-based positive electrode material with spherical particles with a diameter of 0.1-400 nm as primary particles and a volume average particle size Dv50 of 8-20 μm as secondary particles. Mixing the two materials can improve the compaction density of the composite positive electrode material and improve the cycle performance of the secondary battery.

[0156] According to some embodiments of the present application, the present application provides a positive electrode sheet, which comprises a positive electrode film layer and a substrate, and the positive electrode film layer comprises the composite positive electrode material of any one of the above solutions or the composite positive electrode material prepared by the preparation method of the composite positive electrode material.

[0157] The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer comprises the composite positive electrode material of any one of the above solutions.

[0158] For example, the positive electrode current collector has two opposite surfaces in the thickness direction of the positive electrode current collector, and the positive electrode film layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collector.

[0159] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can comprise a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0160] The positive electrode film layer comprises a composite positive electrode material or a composite positive electrode material prepared by a preparation method of the composite positive electrode material, and can improve the cycle performance of the secondary battery.

[0161] According to some embodiments of the present application, the positive electrode film layer further comprises a conductive agent and a binder, wherein the composite positive electrode material accounts for 95%-99.5% in the positive electrode film layer based on the total weight of the positive electrode film layer.

[0162] In some embodiments, the mass fraction of the composite positive electrode material in the positive electrode film layer can be 95%, 95.5%, 96%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, etc. based on the total weight of the positive electrode film layer.

[0163] In some embodiments, the binder can comprise 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 acrylic ester resin.

[0164] In some embodiments, the conductive agent can comprise at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0165] By adjusting the proportion of the composite positive electrode material in the positive electrode film layer, the energy density and cycle life of the secondary battery can be further improved.

[0166] According to some embodiments of the present application, the present application provides a secondary battery comprising the positive electrode sheet of any one of the above solutions. The secondary battery can be the battery 100 or the battery monomer 20 as described above.

[0167] The secondary battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent short circuiting of the positive and negative electrodes, while allowing ions to pass through.

[0168] The secondary battery comprises a positive electrode sheet with a composite positive electrode material, so that the secondary battery has excellent cycle performance.

[0169] According to some embodiments of the present application, the present application further provides an electric device comprising the secondary battery of any one of the above solutions, and the secondary battery is used to provide electric energy for the electric device.

[0170] The electric device can be any of the electric devices or systems as described above.

[0171] According to one embodiment of the present application, a composite cathode material is provided, first, two kinds of lithium-rich manganese-based cathode material first precursor A0 and second precursor B0 are prepared by coprecipitation method. The specific steps are as follows:

[0172] S1: configure nickel sulfate, cobalt sulfate and manganese sulfate into a 2 mol / L solution according to a molar ratio of 33:4:63, place the solution in a reaction kettle, add a 10 mol / L sodium hydroxide solution and a 5 mol / L ammonia water, control the reaction temperature to be 40-60°C, the pH value to be 7.5-8.5 and the stirring speed to be 600-1000 rpm under an inert atmosphere, the reaction time is 8-12 h, after the reaction is completed, the reaction conditions are controlled unchanged, and the particle size and micro morphology are adjusted by aging for 12-48 h, to prepare the first precursor A0 (Ni 0.33 Co 0.04 Mn 0.63 (OH)2), the particle size of the first precursor A0 is 4.5 μm, and the SPAN is about 1.25. Mix lithium hydroxide and A0 uniformly according to a molar ratio of 1.35:1, then add 1000 ppm ZrO2 additives, mix all the powders in a high-speed mixer at 200 r / min for 2 h, and finally sinter at 950°C for 20 h in an air atmosphere to obtain the first lithium-rich manganese-based cathode material A, the first lithium-rich manganese-based cathode material A is Li 1.15 Ni 0.28 Co 0.03 Mn 0.54 O2, the SEM image of the first lithium-rich manganese-based cathode material A is shown in Figure 4 .

[0173] S2: configure nickel sulfate, cobalt sulfate and manganese sulfate into a 2 mol / L solution according to a molar ratio of 29:8:63, place the solution in a reaction kettle, add a 10 mol / L sodium carbonate solution and a 5 mol / L ammonia water, control the reaction temperature to be 40-60°C, the pH value to be 7.5-8.5 and the stirring speed to be 600-1000 rpm under an inert atmosphere, the reaction time is 8-12 h, after the reaction is completed, the reaction conditions are controlled unchanged, and the particle size and micro morphology are adjusted by aging for 12-48 h, to prepare the second precursor B0 (Ni 0.29 Co 0.08 Mn 0.63 CO3), the particle size of the second precursor B0 is 9 μm, and the SPAN is about 1.5. Mix lithium carbonate and B0 uniformly according to a molar ratio of 1.35:1, then add 1000 ppm Al2O3 additives, mix all the powders in a high-speed mixer at 200 r / min for 2 h, and finally sinter at 950°C for 20 h in an air atmosphere to obtain the second lithium-rich manganese-based cathode material B, the second lithium-rich manganese-based cathode material B is Li 1.15 Ni0.25 Co 0.06 Mn 0.54 O2, SEM image of the second lithium-rich manganese-based positive electrode material B is shown in Figure 5 .

[0174] S3: The first lithium-rich manganese-based positive electrode material A and the second lithium-rich manganese-based positive electrode material B are mixed uniformly at a mass ratio of 3:7 to obtain the composite positive electrode material.

[0175] SEM image of the composite positive electrode material of some embodiments of the present application is shown in Figure 6 , Figure 6 SEM image of the composite positive electrode material of some embodiments of the present application is shown in

[0176] In the process of making the positive electrode sheet, the cathode powder: PVDF: NMP = 96:2:2; the surface density of the cathode sheet is 11.5 mg / cm 2 .

[0177] According to one comparative example of the present application, a positive electrode material is provided, and the specific steps are as follows:

[0178] Nickel sulfate, cobalt sulfate, and manganese sulfate are configured into a 2 mol / L solution according to a molar ratio of 29:8:63. The solution is placed in a reaction kettle, and a 10 mol / L molar concentration of sodium carbonate solution and a 5 mol / L molar concentration of ammonia water are added. In an inert atmosphere, the reaction temperature is controlled to be 40-60℃, the pH value is controlled to be in the range of 7.5-8.5, and the stirring speed is controlled to be in the range of 600-1000 rpm. The reaction time is 8-12 h. After the reaction is completed, the reaction conditions are controlled unchanged, and the particle size and micro morphology are adjusted by aging for 12-48 h. The second precursor B0(Ni 0.29 Co 0.08 Mn 0.63 CO3) is prepared. The particle size of the second precursor B0 is 9 μm, and the SPAN is about 1.5. Lithium carbonate and B0 are mixed uniformly according to a molar ratio of 1.35:1, and then 1000 ppm of Al2O3 additive is added. All the powders are placed in a high-speed mixer and mixed at 200 r / min for 2 h. Finally, the second lithium-rich manganese-based positive electrode material B is obtained by sintering at 950℃ in an air atmosphere for 20 h. The second lithium-rich manganese-based positive electrode material B is Li 1.15 Ni 0.25 Co 0.06 Mn 0.54 O2, SEM image of the second lithium-rich manganese-based positive electrode material B is shown in Figure 5 .

[0179] In the process of making the lithium-rich manganese-based positive electrode sheet, the cathode powder: PVDF: NMP = 96:2:2; the surface density of the cathode sheet is 11.5 mg / cm 2 .

[0180] For comparison, the first lithium-rich manganese-based positive electrode material A, denoted as material A in the table, has the chemical formula Li 1.15 Ni 0.28 Co 0.03 Mn 0.54 O2, the second lithium-rich manganese-based positive electrode material B, denoted as material B in the table, has the chemical formula Li 1.15 Ni 0.25 Co 0.06 Mn 0.54 O2; the preparation method of the composite positive electrode material of examples 2-5 is similar to that of the composite positive electrode material in example 1, the difference is that materials A and B with different particle sizes are prepared, the mixing ratio of materials A and B is different, and the comparative example only has material A or material B. Other preparation methods are consistent with the preparation method of the lithium-rich manganese-based positive electrode material in example 1. The lithium-rich manganese-based positive electrode material prepared by the above method is subjected to compaction density and related performance test, and the specific results are shown in table 1.

[0181] 25℃ under full battery capacity retention rate determination method: at 25℃, charge to 4.55V with 1C constant current, then charge to 4.55V constant voltage until the current drops to 0.05C, then discharge to 2.5V with 1C constant current, get the first week discharge specific capacity (Cd1); so repeat the charge and discharge to 100 weeks, get the discharge specific capacity after n cycles of lithium ion battery is denoted as (Cdn). Capacity retention rate = discharge specific capacity after n cycles / first week discharge specific capacity. 1C = 250mAh / g.

[0182] Table 1: capacity retention rate of battery containing positive electrode sheet of each example and comparative example

[0183]

[0184] From the comparison of the above examples and comparative examples, it can be seen that the composite positive electrode material prepared by the present application has higher compaction density, and can improve the cycle performance of the secondary battery.

[0185] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than limit them. Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be replaced equivalently. Such modifications or replacements do not change the essence of the corresponding technical solutions, which should be covered in the scope of the claims and the specification of the present application. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A composite cathode material, characterized in that, The composite cathode material has a span of 1.2-2.0, wherein the span=(Dv90-Dv10) / Dv50, Dv90, Dv10 and Dv50 are the volume distribution particle size Dv90, the volume distribution particle size Dv10 and the volume average particle size Dv50 of the composite cathode material, the composite cathode material comprises a first lithium-rich manganese-based cathode material and a second lithium-rich manganese-based cathode material, the primary particles of the first lithium-rich manganese-based cathode material are rod-shaped particles, the length of the rod-shaped particles is 0.1-1.5 μm, the volume average particle size Dv50 of the secondary particles of the first lithium-rich manganese-based cathode material is 3-8 μm, the primary particles of the second lithium-rich manganese-based cathode material are spherical-like particles, the diameter of the spherical-like particles is 0.1-400 nm, and the volume average particle size Dv50 of the secondary particles of the second lithium-rich manganese-based cathode material is 8-20 μm.

2. The composite cathode material of claim 1, wherein, The volume average particle size Dv50 of the composite cathode material is 6-15 μm, and the BET of the composite cathode material is 1.5-8.5 m 2 / g.

3. The composite cathode material of claim 1 or 2, wherein, The volume average particle size Dv50 of the composite cathode material is 7-10 μm, and the BET of the composite cathode material is 2-7 m 2 / g.

4. The composite cathode material of any one of claims 1-3, wherein, The composite cathode material has a span of 1.4-1.

8.

5. The composite cathode material of any one of claims 1-4, wherein, The length of the rod-shaped particles is 0.3-1.3 μm, and the diameter of the spherical-like particles is 50-350 nm.

6. The composite cathode material of any one of claims 1-5, wherein, The mass ratio of the first lithium-rich manganese-based cathode material to the second lithium-rich manganese-based cathode material is 5:5-1:

9.

7. The composite cathode material of any one of claims 1-6, wherein, The span of the secondary particles of the first lithium-rich manganese-based cathode material is 0.4SPAN2.2, and the span of the secondary particles of the second lithium-rich manganese-based cathode material is 0.4SPAN2.

2.

8. The composite cathode material of any one of claims 1-7, wherein, The span of the secondary particles of the first lithium-rich manganese-based cathode material is 0.4SPAN1.5, and the span of the secondary particles of the second lithium-rich manganese-based cathode material is 0.5SPAN1.

5.

9. The composite cathode material of any one of claims 1-8, wherein, The BET of the first lithium-rich manganese-based positive electrode material is 0.4-2.5 m 2 / g, and the BET of the second lithium-rich manganese-based positive electrode material is 2.5-10 m 2 / g.

10. The composite cathode material of any one of claims 1-9, wherein, The BET of the first lithium-rich manganese-based positive electrode material is 1.0-2.0 m 2 / g, and the BET of the second lithium-rich manganese-based positive electrode material is 3.0-7.0 m 2 / g.

11. A method of preparing a composite cathode material, characterized by, Comprising: a first lithium-rich manganese-based cathode material is provided, the primary particles of the first lithium-rich manganese-based cathode material are rod-shaped particles, the length of the rod-shaped particles is 0.1-1.5 μm, and the volume average particle size Dv50 of the secondary particles of the first lithium-rich manganese-based cathode material is 3-8 μm; a second lithium-rich manganese-based cathode material is provided, the primary particles of the second lithium-rich manganese-based cathode material are spherical-like particles, the diameter of the spherical-like particles is 0.1-400 nm, and the volume average particle size Dv50 of the secondary particles of the second lithium-rich manganese-based cathode material is 8-20 μm; and the first lithium-rich manganese-based cathode material and the second lithium-rich manganese-based cathode material are mixed to obtain the composite cathode material according to any one of claims 1-10, wherein the mass ratio of the mixing of the first lithium-rich manganese-based cathode material and the second lithium-rich manganese-based cathode material is 5:5-1:9, the first lithium-rich manganese-based cathode material and / or the second lithium-rich manganese-based cathode material comprises an element M, and the element M is selected from one or more of Al, B, Zr, Sr, Y, Sb, Ta, Na, K, W, Ti, Mg, Nb, Hf, Mo, Ce.

12. The method of claim 11, wherein the composite cathode material is prepared by the steps of: mixing the lithium transition metal oxide, the carbon material, and the binder to form a mixture; and compressing the mixture to form the composite cathode material. In the step of providing the first lithium-rich manganese-based cathode material, comprising: A first lithium source and a first precursor are mixed uniformly in a proportion of 1.1-1.9 in terms of molar ratio, a first additive is added, and sintering is performed to obtain a first lithium-rich manganese-based positive electrode material, wherein the first lithium source is one or more of lithium carbonate, lithium hydroxide, lithium phosphate, lithium nitrate, and lithium acetate, the chemical formula of the first precursor is Ni a1 Co b1 Mn c1 (OH)2, 0 The first additive is added in an amount of 0-20000 ppm, calculated based on the total mass of the first lithium source and the first precursor, and the first additive is a compound containing the element M.

13. The method for preparing a composite cathode material according to claim 11 or 12, wherein the lithium transition metal oxide is prepared by a co-precipitation method. In the step of providing the first lithium-rich manganese-based cathode material, comprising: The second lithium source and the second precursor are mixed uniformly in a proportion of 1.1-1.9 in mole ratio, the second additive is added, and sintering is performed to obtain a second lithium-rich manganese-based positive electrode material, wherein the second lithium source is one or more of lithium carbonate, lithium hydroxide, lithium phosphate, lithium nitrate, and lithium acetate, the chemical formula of the second precursor is Ni a2 Co b2 Mn c2 CO3, 0 The second additive is added in an amount of 0-20000 ppm, calculated based on the total mass of the second lithium source and the second precursor, and the second additive is a compound containing the element M.

14. A positive electrode sheet characterized by comprising: The positive electrode sheet comprises a positive electrode film layer and a substrate, and the positive electrode film layer comprises the composite positive electrode material according to any one of claims 1-10 or the composite positive electrode material prepared by the method according to any one of claims 10-13.

15. The positive electrode sheet according to claim 14, wherein The positive electrode film layer further comprises a conductive agent and a binder, and the composite positive electrode material accounts for 95%-99.5% in the positive electrode film layer based on the total weight of the positive electrode film layer.

16. A secondary battery characterized by comprising: The positive electrode sheet according to claim 14 or 15.

17. An electric device comprising the secondary battery according to claim 16.

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