Lithium-rich manganese-based positive electrode material, positive electrode plate, battery monomer, battery, electric equipment and preparation method of lithium-rich manganese-based positive electrode material

Abstract

The invention discloses a lithium-rich manganese-based positive electrode material, a positive electrode plate, a battery monomer, a battery, electric equipment and a preparation method of the lithium-rich manganese-based positive electrode material.The lithium-rich manganese-based positive electrode material comprises a phase A and a phase B. In an X-ray diffraction pattern of the lithium-rich manganese-based positive electrode material, the phase A has a first specified diffraction peak distributed within the Bragg angle range of 19-22 degrees, and the phase B has a second specified diffraction peak distributed within the Bragg angle range of 19-22 degrees. The B phase has a second specified diffraction peak distributed within a Bragg angle range of 43-46 degrees, and a ratio of an area of the first specified diffraction peak to an area of the second specified diffraction peak is (0.05-0.3): 1. The lithium-rich manganese-based positive electrode material is researched around the application under low voltage, the area ratio of a first specified diffraction peak to a second specified diffraction peak is regulated and controlled to be within a specified range, and the lithium-rich manganese-based positive electrode material has relatively good cycling stability and relatively high first-circle discharge capacity under the low voltage.

Description

[0001] This application is a divisional application of the invention patent application No. 2023101326040 filed on February 17, 2023, with the title of "Lithium-Rich Manganese-Based Positive Electrode Material, Positive Electrode Sheet, Battery Cell, Battery, Electric Equipment and Preparation Method of Lithium-Rich Manganese-Based Positive Electrode Material". TECHNICAL FIELD

[0002] The present application relates to the technical field of batteries, in particular to a lithium-rich manganese-based positive electrode material, a positive electrode sheet, a battery cell, a battery, an electric equipment and a preparation method of the lithium-rich manganese-based positive electrode material. BACKGROUND

[0003] Generally, the capacity of the lithium-rich manganese-based positive electrode material at low voltage is low, and most of the capacity of the material cannot be utilized, resulting in low capacity utilization rate, which leads to low application value of such materials in low-voltage application fields. Therefore, the research on such materials is mainly focused on high-voltage applications.

[0004] It should be noted that the above statements are only used to provide background technical information related to the present application, and do not necessarily constitute prior art. SUMMARY

[0005] In view of the above problems, the present application provides a lithium-rich manganese-based positive electrode material, a positive electrode sheet, a battery cell, a battery, an electric equipment and a preparation method of the lithium-rich manganese-based positive electrode material, which studies the application of the lithium-rich manganese-based positive electrode material at low voltage. The lithium-rich manganese-based positive electrode material has good cycle stability, and the lithium-rich manganese-based positive electrode material has high first charge and discharge capacity at low voltage.

[0006] The embodiments of the present application are implemented as follows: In a first aspect, the embodiments of the present application provide a lithium-rich manganese-based positive electrode material, which includes an A phase and a B phase. In the X-ray diffraction pattern of the lithium-rich manganese-based positive electrode material, the A phase has a first specified diffraction peak distributed in the range of Bragg angle 19°-22°, and the B phase has a second specified diffraction peak distributed in the range of Bragg angle 43°-46°. The ratio of the area of the first specified diffraction peak to the area of the second specified diffraction peak is (0.05-0.3):1.

[0007] In the technical scheme of the embodiment of the present application, the first specified diffraction peak of the A phase distributed in the range of 19°-22° of the Bragg angle corresponds to the (020) crystal face of Li2MnO3, belonging to the C / 2m space group; the second specified diffraction peak of the B phase distributed in the range of 43°-46° of the Bragg angle corresponds to the (104) crystal face of lithium nickel cobalt manganese oxide, belonging to the R3m space group. The area ratio of the first specified diffraction peak and the second specified diffraction peak corresponds to specific physical and chemical properties, for example, including the molar content ratio of the Li2MnO3 phase and the lithium nickel cobalt manganese oxide phase in the lithium-rich manganese-based positive electrode material; when the area ratio of the first specified diffraction peak and the second specified diffraction peak is in a specified range, the lithium-rich manganese-based positive electrode material has good cycle stability, and the lithium-rich manganese-based positive electrode material has a high first cycle charge and discharge capacity at a low voltage.

[0008] In some embodiments, in the X-ray diffraction spectrum, the half-peak width of the first specified diffraction peak is 0.2°-0.8°. Generally speaking, the narrower the half-peak width of the diffraction peak corresponding to the sample, the larger, more uniform, and fewer defects the sample grain size is. In the embodiment, the half-peak width of the first specified diffraction peak is in a specified range, so that the grain size, uniformity, and defect quantity of the Li2MnO3 phase corresponding to the first specified diffraction peak are in a specified range, which is beneficial to improving the cycle stability of the lithium-rich manganese-based positive electrode material.

[0009] In some embodiments, in the lithium-rich manganese-based positive electrode material, the molar content ratio of the A phase and the B phase is a:(1-a), 0

[0010] In some embodiments, 0.1≤a≤0.3. In the embodiment, the Li2MnO3 has a suitable molar content in the lithium-rich manganese-based positive electrode material, which is beneficial to the lithium-rich manganese-based positive electrode material having good cycle stability and a high first cycle charge and discharge capacity at a low voltage.

[0011] In some embodiments, the molecular formula of the lithium-rich manganese-based positive electrode material is a[Li2MnO3]·(1-a)[LiNi x Co y Mn 1-x-y-z R z O2] or Li (1+a) Ni (1-a)x Co (1-a)y Mn ((1-x-y-z)(1-a)+a) R(1-a)z O (2+a) ; wherein 0 < a < 0.5, 0.2 < x < 0.6, 0 < y < 0.7, 0 < z < 0.03, and the element R includes one or more of Al, Zr, Ti, Nb, Te, Sb, W, Mo, and Mg. In this embodiment, the lithium-rich manganese-based positive electrode material corresponding to the molecular formula can better meet the requirements of the ratio of the area of the first specified diffraction peak to the area of the second specified diffraction peak, the half-peak width of the first specified diffraction peak, and the ratio of the molar contents of the A phase and the B phase; meanwhile, the doping of the element R is conducive to improving the crystal distortion problem of the lithium-rich manganese-based positive electrode material during the charging and discharging process from the perspective of the crystal lattice, and is conducive to improving the cycle stability of the lithium-rich manganese-based positive electrode material.

[0012] In some embodiments, the host material of the lithium-rich manganese-based positive electrode material includes a surface layer part and a central part, the surface layer part includes a part within a first specified distance from the surface of the host material, the first specified distance is 20% of the volume average particle size Dv50 of the host material, the central part includes a part above a second specified distance from the surface of the host material, the second specified distance is 70% of the volume average particle size Dv50 of the host material, the content of the element R at the surface layer part is greater than the content of the element R at the central part, and the element R includes one or more of Al, Zr, Ti, Nb, Te, Sb, W, Mo, and Mg. In this embodiment, the element R is more distributed in the surface layer part of the host material, which is conducive to better improving the cycle stability of the lithium-rich manganese-based positive electrode material; moreover, the doping of the element R in the bulk phase of the host material is reduced, which can reduce the influence of the element R on the electrochemical performance of the lithium-rich manganese-based positive electrode material, so that the lithium-rich manganese-based positive electrode material maintains a relatively high gram capacity.

[0013] In some embodiments, the ratio of the content of the element R at the surface layer part to the content of the element R at the central part is (3-9):1. In this embodiment, the element R is mainly distributed in the surface layer part of the host material, which is conducive to better improving the cycle stability of the lithium-rich manganese-based positive electrode material; the element R does not enter the bulk phase of the host material, which has a smaller influence on the electrochemical performance of the lithium-rich manganese-based positive electrode material, and is more conducive to the lithium-rich manganese-based positive electrode material maintaining a relatively high gram capacity.

[0014] In some embodiments, the lithium-rich manganese-based positive electrode material further includes a coating layer, the coating layer is distributed on at least part of the surface of the host material; wherein the coating layer includes an element M, and the element M includes one or more of Nb, W, Mo, Co, and Ti. In this embodiment, the coating layer containing the specified element M is coated on the surface of the host material, the part where the coating layer is located effectively avoids the direct contact of the host material with the electrolyte, can inhibit the side reaction, and can effectively improve the electrochemical performance of the lithium-rich manganese-based positive electrode material, so that the cycle stability and the first cycle charging and discharging capacity at low voltage of the lithium-rich manganese-based positive electrode material are effectively improved.

[0015] In some embodiments, the mass percentage of the coating layer is w1, where 0 < w1 ≤ 5%, based on the mass of the lithium-rich manganese-based cathode material. In this embodiment, the specified elements in the coating layer have an appropriate mass percentage in the lithium-rich manganese-based cathode material, which effectively improves the cycle stability of the lithium-rich manganese-based cathode material while avoiding excessive element M from affecting the first-cycle discharge capacity of the lithium-rich manganese-based cathode material at low voltage.

[0016] In some embodiments, the lithium-rich manganese-based cathode material includes Li₂CO₃ and / or LiOH, satisfying at least one of the following conditions (a1) and (a2): (a1) the mass content of Li₂CO₃ is 200 ppm to 3500 ppm based on the mass of the lithium-rich manganese-based cathode material; (a2) the mass content of LiOH is ≤2000 ppm based on the mass of the lithium-rich manganese-based cathode material. In this embodiment, the residual mass content of Li₂CO₃ and / or LiOH in the lithium-rich manganese-based cathode material meets the specified range, which is beneficial to improving the cycle stability and first-cycle charge-discharge capacity of the lithium-rich manganese-based cathode material at low voltage.

[0017] In some embodiments, at least one of the following conditions (b1) and (b2) is met: (b1) the mass content of Li2CO3 is 500ppm to 2000ppm based on the mass of the lithium-rich manganese-based cathode material; (b2) the mass content of LiOH is ≤1500ppm based on the mass of the lithium-rich manganese-based cathode material. In this embodiment, the mass content of residual Li2CO3 and / or LiOH in the lithium-rich manganese-based cathode material is within a more suitable range, which is more conducive to improving the cycle stability and first-cycle charge-discharge capacity of the lithium-rich manganese-based cathode material at low voltage.

[0018] In some embodiments, at least one of the following conditions (c1) and (c2) is met: (c1) the volume average particle size Dv50 of the lithium-rich manganese-based cathode material is 4µm to 9µm; (c2) the specific surface area of ​​the lithium-rich manganese-based cathode material is 0.5m². 2 / g~1.2m 2 / g. In this embodiment, the lithium-rich manganese-based cathode material has a specified product average particle size Dv50 and / or specific surface area, which is beneficial for the lithium-rich manganese-based cathode material to maintain a high capacity.

[0019] Secondly, embodiments of this application provide a positive electrode sheet, including the lithium-rich manganese-based positive electrode material as described in the above embodiments.

[0020] Thirdly, embodiments of this application provide a battery cell including a positive electrode as described in the above embodiments.

[0021] In some embodiments, at a temperature of 25°C, the charge capacity of a single battery cell cycling within a voltage range of 2.8V to 4.35V is C1, and the charge capacity of a single battery cell cycling within a voltage range of 2.8V to 4.8V is C2, where C1 / C2×100%≥40%. In this embodiment, the battery cell exhibits a high charge capacity at low voltage, which can be achieved based on some embodiments of the lithium-rich manganese-based cathode material provided above. The corresponding battery cell can exhibit a high discharge capacity at a low voltage of 2.8V to 4.35V, enabling better use in low-voltage applications.

[0022] Fourthly, embodiments of this application provide a battery, including a battery cell as described in the above embodiments.

[0023] Fifthly, embodiments of this application provide an electrical device, including a battery cell or battery as described in the above embodiments.

[0024] Sixthly, embodiments of this application provide a method for preparing a lithium-rich manganese-based cathode material as described in the above embodiments, comprising: sintering a mixture of a precursor material containing a transition metal salt and a lithium salt at least once.

[0025] In some embodiments, the sintering temperature for a single sintering is 650°C to 1050°C, optionally 800°C to 1000°C. In this embodiment, performing a single sintering at a specified temperature is beneficial for controlling the content of residual lithium (e.g., Li2CO3 and / or LiOH) in the lithium-rich manganese-based cathode material within a suitable range, which is beneficial for improving the cycle stability and first-cycle charge-discharge capacity of the lithium-rich manganese-based cathode material at low voltage.

[0026] In some embodiments, the preparation method of lithium-rich manganese-based cathode material further includes: mixing the sintered product from a primary sintering process with a material containing element R, and then performing a secondary sintering; wherein element R includes one or more of Al, Zr, Ti, Nb, Te, Sb, W, Mo, and Mg. In this embodiment, element R is doped into the sintered product from the subsequent sintering process through secondary sintering, and element R is mainly distributed in the surface layer of the host material.

[0027] In some embodiments, the preparation method of lithium-rich manganese-based cathode material further includes: mixing the sintered product from the secondary sintering with a material containing element M, and performing a third sintering; wherein element M includes one or more of Nb, W, Mo, Co, and Ti. In this embodiment, by performing a third sintering, a protective layer containing the specified element M is generated on the surface of the sintered product from the secondary sintering, thereby forming a structure in which at least a portion of the surface of the host material is covered with a coating layer.

[0028] The above description is merely an overview of the technical solutions of the embodiments 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, specific embodiments of this application are described below. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments; Figure 2 Exploded views of batteries provided for some embodiments of this application; Figure 3 Exploded views of a single battery cell provided in some embodiments of this application; Figure 4 This is a schematic diagram of the structure of the positive electrode sheet provided in some embodiments of this application; Figure 5 This is a partial structural schematic diagram of the lithium-rich manganese-based cathode material provided in some embodiments of this application; Figure 6 A process flow diagram of the preparation method of lithium-rich manganese-based cathode material provided in some embodiments of this application; Figure 7 A process flow diagram for preparing lithium-rich manganese-based cathode materials provided in other embodiments of this application; Figure 8 This is a SEM image of the lithium-rich manganese-based cathode material prepared in Example 1 of this application; Figure 9 The image shows the XRD pattern of the lithium-rich manganese-based cathode material prepared in Example 1 of this application. Figure 10 The charge-discharge curves of the lithium-rich manganese-based cathode material prepared in Example 1 of this application at 2.8V~4.35V and 2.8V~4.8V at 0.1C; Figure 11 The charge-discharge curves of the lithium-rich manganese-based cathode material prepared in Example 5 of this application at 2.8V~4.35V and 2.8V~4.8V at 0.1C; Figure 12 The charging capacity retention curves of the lithium-rich manganese-based cathode material prepared in Example 1 of this application during cycling at 0.33C at 2.8V~4.35V and 2.8V~4.8V; Figure 13 The charging capacity ratio curves of the lithium-rich manganese-based cathode material prepared in Example 1 of this application during cycling at 2.8V~4.35V and 2.8V~4.8V at 0.33C; Figure 14 The product obtained by secondary sintering in Example 1 of this application is 0.2Li2MnO3·0.8LiNi. 0.33 Co 0.33 Mn 0.32 Zr 0.01 SEM image of O2 slices.

[0031] icon: 1000 - Vehicles; 100 - Battery; 200 - Controller; 300 - Motor; 10-Box body; 11-First part; 12-Second part; 13-Accommodation space; 20-Battery cell; 21-Casing; 22-Electrode assembly; 23-Electrode terminal; 24-Pressure relief structure; 211-Shell; 212-Cover; 221-Positive electrode sheet; 2211-Positive current collector; 2212-Positive active material layer; 2212a-Surface layer; 2212b-Central layer; D1 - First specified distance; D2 - Second specified distance. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0033] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0035] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0036] In the description of the embodiments of this application, the technical term "and / or", such as "feature 1 and / or feature 2", refers to three cases: feature 1 alone, feature 2 alone, and feature 1 plus feature 2.

[0037] In the description of the embodiments of this application, unless otherwise stated, "multiple" in "one or more" means two or more.

[0038] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0039] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the height, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall height, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0040] With the continuous development of the new energy industry, the market has put forward more diversified demands for cathode active materials. Among them, lithium-rich manganese-based cathode materials have attracted much attention due to their advantages such as high voltage, high specific capacity, good safety, abundant resources, and low pollution, and are considered to be a highly promising next-generation cathode active material. Lithium-rich manganese-based cathode materials exhibit two voltage plateaus during charging: below 4.5V and above 4.5V, corresponding to the activation processes of lithium nickel cobalt manganese oxide and Li2MnO3, respectively. Generally, the capacity of lithium-rich manganese-based cathode materials is low at low voltages, typically less than 30% of the charging capacity in the 2.8V~4.8V voltage range. This means that most of the material's capacity cannot be utilized, resulting in low capacity utilization and thus low value for such materials in low-voltage applications. Therefore, research on these materials mainly focuses on applications at high voltages. However, at high voltages, lithium-rich manganese-based cathode materials often suffer from structural, discharge capacity, and cycle life instability, making it difficult for these materials to achieve practical applications above 4.5V.

[0041] In some studies, to improve the stability of lithium-rich manganese-based cathode materials during charge-discharge processes above 4.5V, the Li2MnO3 component is activated through multiple charge-discharge cycles at different ambient temperatures, or through single or multiple charge-discharge cycles at gradually changing ambient temperatures. This method is rather cumbersome and complex. In other studies, a delithiation agent is used to remove some Li2O from the Li2MnO3 in lithium-rich manganese-based compounds, resulting in lithium-rich manganese-based cathode materials with lithium and oxygen vacancies. In this approach, the initial coulombic efficiency of the lithium-rich manganese-based cathode material is improved due to the reduction of irreversible product Li2O, and the rate performance and cycle performance are improved due to the presence of lithium and oxygen vacancies. However, in the above studies, the capacity contributed by Li2MnO3 in the lithium-rich manganese-based cathode material still continuously decays and decreases. The problem of instability of lithium-rich manganese-based cathode materials at high voltages remains unsolved, making it difficult to achieve practical applications in high-voltage fields above 4.5V.

[0042] Based on this, this application studies the application of lithium-rich manganese-based cathode materials under low voltage, and proposes a lithium-rich manganese-based cathode material. By adjusting the ratio of the diffraction peak areas of the Li2MnO3 phase and the lithium nickel cobalt manganese oxide phase in the X-ray diffraction pattern, the lithium-rich manganese-based cathode material has good cycle stability and high first-cycle discharge capacity under low voltage.

[0043] From a market perspective, the application of power batteries is becoming increasingly widespread. Power batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of the application areas of power batteries, the market demand is also constantly increasing.

[0044] For ease of explanation, the following embodiments use a vehicle as an example of an electrical device according to an embodiment of this application.

[0045] See Figure 1 , Figure 1This is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery 100 is disposed inside the vehicle 1000, and the battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor, for example, to meet the power needs of the vehicle 1000 during startup, navigation, and driving.

[0046] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0047] In this application, battery 100 refers to a single physical module comprising multiple battery cells 20 to provide higher voltage and capacity, which may be in the form of a battery pack, battery module, etc. Battery 100 may include a housing 10 for encapsulating the multiple battery cells 20, the housing 10 preventing liquids or other foreign objects from affecting the charging or discharging of the battery cells 20.

[0048] See Figure 2 , Figure 2 This is an exploded view of a battery 100 provided in some embodiments of this application. The battery 100 includes a housing 10 and a plurality of battery cells 20, which are housed within the housing 10. The housing 10 is used to house the battery cells 20 and can have various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other, defining a receiving space 13 for accommodating the battery cells 20. The second portion 12 may be a hollow structure with one open end, and the first portion 11 may be a plate-like structure, overlapping the open side of the second portion 12 to form a housing 10 with the receiving space 13; alternatively, the first portion 11 and the second portion 12 may both be hollow structures with one open side, overlapping the open side of the second portion 12 to form a housing 10 with the receiving space 13. Of course, the first portion 11 and the second portion 12 can have various shapes, such as cylinders, cuboids, etc.

[0049] In battery 100, multiple battery cells 20 can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells 20 are connected in both series and parallel configurations. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed configuration, and then the entire assembly of the multiple battery cells 20 is housed within the housing 10. Alternatively, multiple battery cells 20 can first be connected in series, parallel, or in a mixed configuration to form modules, and then these modules can be connected in series, parallel, or in a mixed configuration to form a whole, which is also housed within the housing 10. Battery 100 may also include other structures; for example, multiple battery cells 20 can be electrically connected through a busbar component to achieve parallel, series, or mixed configurations of the multiple battery cells 20.

[0050] Battery cell 20 refers to the smallest unit that makes up the battery pack of 100. Battery cell 20 can be a secondary battery 100 or a primary battery 100; it can also be a lithium-sulfur battery 100, a sodium-ion battery 100 or a magnesium-ion battery 100, but is not limited to these.

[0051] See Figure 3 The battery cell 20 may include a housing 21, an electrode assembly 22, and an electrolyte, with the electrode assembly 22 and the electrolyte both housed within the housing 21.

[0052] The outer casing 21 may include a housing 211 and a cover 212. The housing 211 is an assembly that fits with the cover 212 to form an internal sealed space for the battery cell 20, wherein the formed sealed space can accommodate the electrode assembly 22, electrolyte, and other components. The cover 212 is a component that covers the opening of the housing 211 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover 212 may be adapted to the shape of the housing 211 to fit the housing 211, and the cover 212 may also be provided with functional components such as electrode terminals 23 and pressure relief structures 24. A sealing ring may be provided between the opening of the housing 211 and the cover 212 to achieve a seal between the housing 211 and the cover 212.

[0053] The housing 211 and cover 212 can be of various shapes and sizes, such as cuboids, cylinders, and hexagonal prisms. Specifically, the shapes of the housing 211 and cover 212 can be determined according to the specific shape and size of the electrode assembly 22. The materials of the housing 211 and cover 212 can be various, such as, but not limited to, metals like copper, iron, aluminum, stainless steel, and aluminum alloys. The materials of the sealing ring can be various, such as, but not limited to, materials resistant to electrolyte corrosion, high toughness, and fatigue resistance, such as PP (polypropylene), PC (polycarbonate), and PET (polyethylene terephthalate). A plating layer can be formed on the outer surface of the housing 211, and the plating layer material can be various, such as, but not limited to, corrosion-resistant materials like Ni and Cr.

[0054] The electrode assembly 22 may consist of a positive electrode 221, a negative electrode 221, and a separator. The battery cell 20 primarily functions by the movement of metal ions between the positive and negative electrode 221. (See also...) Figure 4 The positive electrode 221 includes a positive current collector 2211 and a positive active material layer 2212 disposed on the surface of the positive current collector 2211. The material of the positive current collector 2211 can be aluminum, and the positive active material material in the positive active material layer 2212 can include the lithium-rich manganese-based positive electrode material provided in the embodiments of this application, and can also include positive active material materials such as lithium cobalt oxide, lithium iron phosphate, ternary lithium, lithium manganese oxide, and lithium sulfur. The negative electrode includes a negative current collector and a negative active material layer disposed on the surface of the negative current collector. The material of the negative current collector can be copper, and the negative active material material in the negative active material layer can be negative active material materials such as carbon and silicon. In addition, the electrode assembly 22 can be a wound structure or a stacked structure, and the embodiments of this application are not limited to this.

[0055] The lithium-rich manganese-based cathode material and its preparation method proposed in the embodiments of this application will be described in detail below.

[0056] In a first aspect, embodiments of this application provide a lithium-rich manganese-based cathode material, which includes an A phase and a B phase. In the X-ray diffraction pattern of the lithium-rich manganese-based cathode material, the A phase has a first designated diffraction peak distributed in the range of 19° to 22° Bragg angle, and the B phase has a second designated diffraction peak distributed in the range of 43° to 46° Bragg angle. The ratio of the area of ​​the first designated diffraction peak to the area of ​​the second designated diffraction peak is (0.05 to 0.3):1.

[0057] Lithium-rich manganese-based cathode materials may include mixtures and / or solid solutions consisting of a Li2MnO3 phase and a lithium nickel cobalt manganese oxide layered structure.

[0058] The first and second designated diffraction peaks refer to diffraction peaks distributed within different designated Bragg angle ranges. The descriptions of "first designated" and "second designated" are only used to distinguish two different peaks and have no other special limitations. It should be noted that phase A and phase B are not limited to having only the first and second designated diffraction peaks, respectively; they may also each include other diffraction peaks.

[0059] A diffraction peak is a sharp, peak-like distribution curve in an X-ray diffraction pattern that records the gradual increase and decrease in diffraction intensity.

[0060] The area of ​​a diffraction peak refers to the integral of the peak height and retention time in an X-ray diffraction pattern.

[0061] In the embodiments of this application, the ratio of the area of ​​the first specified diffraction peak to the area of ​​the second specified diffraction peak is, for example, but not limited to, any one of 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, and 0.3:1, or a range between any two. As an example, the range of the ratio of the area of ​​the first specified diffraction peak to the area of ​​the second specified diffraction peak is, for example, further 0.05 to 0.25:1, and optionally 0.1 to 0.2:1.

[0062] In the technical solution of this application embodiment, the first designated diffraction peak of phase A, distributed in the range of Bragg angle of 19°~22°, corresponds to the (020) crystal plane of Li2MnO3 (JCPDS card number No. 27-1252), which belongs to the C / 2m space group; the second designated diffraction peak of phase B, distributed in the range of Bragg angle of 43°~46°, corresponds to the (104) crystal plane of lithium nickel cobalt manganese oxide (JCPDS card number No. 52-0457), which belongs to the R3m space group.

[0063] Studies have found that the Li2MnO3 phase exhibits high stability in the low voltage range of 4.2V to 4.5V and can also serve as a support layer for the lithium nickel cobalt manganese oxide phase, which is beneficial to improving the cycle stability of lithium-rich manganese-based cathode materials. However, the Li2MnO3 phase provides almost no capacity at the low voltage range of 4.2V to 4.5V. In order to obtain lithium-rich manganese-based cathode materials with high specific capacity, it is necessary to control the molar content of the Li2MnO3 phase within an appropriate range so that the Li2MnO3 phase can play a role in stabilizing the structure without excessively affecting the specific capacity of the lithium-rich manganese-based cathode material.

[0064] The ratio of the area of ​​the first specified diffraction peak to the area of ​​the second specified diffraction peak corresponds to specific physicochemical properties, such as the molar ratio of the Li2MnO3 phase and the lithium nickel cobalt manganese oxide phase in the lithium-rich manganese-based cathode material. When the ratio of the area of ​​the first specified diffraction peak to the area of ​​the second specified diffraction peak is within a specified range, the Li2MnO3 phase has a suitable molar content in the lithium-rich manganese-based cathode material, the lithium-rich manganese-based cathode material has good cycle stability, and the lithium-rich manganese-based cathode material has a high first-cycle charge-discharge capacity at low voltage.

[0065] In some embodiments, the full width at half maximum (FWHM) of the first specified diffraction peak in the X-ray diffraction pattern is 0.2° to 0.8°.

[0066] The half-width at half-maximum (WHM) of the first specified diffraction peak refers to the peak width of the diffraction peak at half its peak height in the X-ray diffraction pattern.

[0067] In this embodiment of the application, the full width at half maximum (FWHM) of the first specified diffraction peak is, for example, but not limited to, any one of 0.2°, 0.3°, 0.4°, 0.5°, 0.6°, 0.7°, and 0.8°, or a range between any two. As an example, the FWHM of the first specified diffraction peak is further 0.3° to 0.7°, and optionally 0.3° to 0.5°.

[0068] Generally speaking, the narrower the half-width at half-maximum (WHM) of the diffraction peak corresponding to the sample, the larger and more uniform the sample grain size and the fewer defects. In this embodiment, the WHM of the first specified diffraction peak is within a specified range, so that the grain size, uniformity and number of defects of the Li2MnO3 phase corresponding to the first specified diffraction peak are within a specified range, which is beneficial to improving the cycle stability of lithium-rich manganese-based cathode materials.

[0069] In some embodiments, in lithium-rich manganese-based cathode materials, the molar ratio of phase A to phase B is a:(1-a), where 0 < a < 0.5.

[0070] In this embodiment of the application, the value of 'a' is, for example, but not limited to, any one of the points 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4 and 0.45 or a range between any two.

[0071] In this embodiment, Li2MnO3 has a suitable molar content in the lithium-rich manganese-based cathode material, which can play a good role in stabilizing the phase structure of lithium nickel cobalt manganese oxide. At the same time, it avoids the specific capacity of the lithium-rich manganese-based cathode material being affected by excessively high Li2MnO3 content. It is also beneficial to control the full width at half maximum (FWHM) of the first specified diffraction peak within the specified range. Therefore, it is beneficial for the lithium-rich manganese-based cathode material to have both good cycle stability and high first-cycle charge-discharge capacity at low voltage.

[0072] In some embodiments, 0.1 ≤ a ≤ 0.3.

[0073] In this embodiment, Li2MnO3 has a suitable molar content in the lithium-rich manganese-based cathode material, which is beneficial for the lithium-rich manganese-based cathode material to have both good cycle stability and high first-cycle charge-discharge capacity at low voltage.

[0074] In some embodiments, the molecular formula of the lithium-rich manganese-based cathode material is a[Li₂MnO₃]·(1-a)[LiNi x Co y Mn 1-x-y-z R z O2] or Li (1+a) Ni (1-a)x Co (1-a)y Mn ((1-x-y-z)(1-a)+a) R (1-a)z O (2+a)Wherein, 0 < a < 0.5, 0.2 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.7, 0 ≤ z ≤ 0.03, and element R includes one or more of Al, Zr, Ti, Nb, Te, Sb, W, Mo and Mg.

[0075] Regarding the molecular formula a[Li2MnO3]·(1-a)[LiNi x Co y Mn 1-x-y-z R z O2], where phase A and phase B are represented by separate terms, a[Li2MnO3] represents phase A, (1-a)[LiNi x Co y Mn 1-x-y-z R z O2] represents phase B.

[0076] Regarding the molecular formula Li (1+a) Ni (1-a)x Co (1-a)y Mn ((1-x-y-z)(1-a)+a) R (1-a)z O (2+a) In this embodiment, phase A and phase B are represented as a combined term. The molecular formula of the above combined term for the lithium-rich manganese-based cathode material can be determined using conventional methods; for example, ICP emission spectroscopy can be used.

[0077] Regarding the molecular formula of lithium-rich manganese-based cathode materials, the most basic requirement for the value of a is that the ratio of the area of ​​the first specified diffraction peak to the area of ​​the second specified diffraction peak must be met. As an example, the value of a is determined with reference to the description in the above embodiments, and will not be repeated here.

[0078] In the embodiments of this application, element R is a doping element in the lithium-rich manganese-based cathode material; regarding other coefficients in the lithium-rich manganese-based cathode material, the value of coefficient x is, for example, but not limited to, 0.2, 0.3, 0.4, 0.5, 0.6, etc., the value of coefficient y is, for example, but not limited to, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, etc., and the value of coefficient z is, for example, but not limited to, 0, 0.1, 0.2, 0.3, etc.

[0079] In this embodiment, the lithium-rich manganese-based cathode material corresponding to the molecular formula can better meet the requirements of the ratio of the area of ​​the first specified diffraction peak to the area of ​​the second specified diffraction peak, the half-width of the first specified diffraction peak, and the ratio of the molar content of the A phase and the B phase. At the same time, the doping of the R element is beneficial to improve the crystal distortion problem of the lithium-rich manganese-based cathode material during the charge and discharge process from the perspective of crystal lattice, and is beneficial to improve the cycle stability of the lithium-rich manganese-based cathode material.

[0080] See Figure 5In some embodiments, the main material of the lithium-rich manganese-based cathode material includes a surface portion and a central portion 2212b. The surface portion includes a portion within a first specified distance D1 from the surface of the main material, where the first specified distance D1 is 20% of the volume average particle size Dv50 of the main material. The central portion 2212b includes a portion above a second specified distance D2 from the surface of the main material, where the second specified distance D2 is 70% of the volume average particle size Dv50 of the main material. The content of element R at the surface portion is greater than the content of element R at the central portion 2212b.

[0081] The main material refers to the main component of the lithium-rich manganese-based cathode material. In other words, the lithium-rich manganese-based cathode material may consist only of this main material or may include other functional materials. Based on the mass of the lithium-rich manganese-based cathode material, the mass proportion of the main material is >50%, for example ≥60%, or further ≥70%, or further ≥80%, or further ≥90%, or further ≥95%, or further ≥99%.

[0082] The main components of the material are mainly composed of phase A and phase B, and may also include small amounts of other components (e.g., mass percentage ≤20%, 10%, 5% or 1%), such as small amounts of doping elements, or residual lithium such as Li2CO3 and LiOH that are unavoidable in the preparation process.

[0083] In the embodiments of this application, the volume average particle size Dv50 refers to the particle size corresponding to 50% of the volume distribution. It can be determined using conventional methods. As an example, referring to GB / T 19077-2016 / ISO 13320:2009 Particle size distribution laser diffraction method, the measurement is performed using a Malvern 3000 device.

[0084] The main material includes a description of a surface portion 2212a and a central portion 2212b, dividing the main material into a core-shell structure; wherein, the central portion 2212b corresponds to the core part of the core-shell structure, which is, for example, close to the shape of a sphere; the surface portion 2212a corresponds to the shell portion 211 of the core-shell structure, which is, for example, close to the shape of a hollow sphere.

[0085] The surface portion 2212a is within a first specified distance D1 from the surface of the main material. In other words, in the main material, the area where the distance from the surface of the main material is ≤ the first specified distance D1 is the surface portion 2212a.

[0086] The central portion 2212b is at least 2 specified distances D2 away from the surface of the main material. In other words, the central portion 2212b is the area in the main material that is at least 2 specified distances D2 away from the surface of the main material.

[0087] In this embodiment, element R is more distributed in the surface layer 2212a of the main material, which is beneficial to improve the cycle stability of the lithium-rich manganese-based cathode material. Moreover, the doping of element R into the bulk phase of the main material is reduced, which can reduce the influence of element R on the electrochemical performance of the lithium-rich manganese-based cathode material, so that the lithium-rich manganese-based cathode material can maintain a high specific capacity.

[0088] In some embodiments, the ratio of the content of element R at the surface portion 2212a to the content of element R at the central portion 2212b is (3~9):1.

[0089] The content of element R in different parts can be determined using conventional methods. For example, the positive electrode active material layer 2212 can be cut, and the content of element R in different parts can be observed and determined by scanning electron microscopy on the cut surface.

[0090] The ratio of element R content at the surface region 2212a to that at the central region 2212b is (3~9):1, which can be achieved by surface doping with element R. Based on the surface doping method, element R is mainly distributed in the surface region 2212a, with a small amount of element R penetrating into the central region 2212b.

[0091] In the embodiments of this application, the ratio of the content of element R at the surface portion 2212a to the content of element R at the central portion 2212b is, for example, but not limited to, any one of 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1 and 9:1, or any range between the two.

[0092] In this embodiment, element R is mainly distributed in the surface layer 2212a of the main material, which is beneficial to improve the cycle stability of the lithium-rich manganese-based cathode material. Element R does not enter the bulk phase of the main material, so it has less impact on the electrochemical performance of the lithium-rich manganese-based cathode material and is more conducive to maintaining a high specific capacity.

[0093] In some embodiments, the lithium-rich manganese-based cathode material further includes a coating layer distributed on at least a portion of the surface of the host material; wherein the coating layer includes element M, and element M includes one or more of Nb, W, Mo, Co and Ti.

[0094] In the embodiments of this application, the coating layer is a structure that covers at least part of the surface of the host material. It can be observed that some of the coating material is distributed in the form of small particles on the surface of the host material. The interface between the two can be determined by conventional methods, such as observing the material directly using a scanning electron microscope.

[0095] The coating layer is distributed on at least part of the surface of the main material; that is, the coating layer can partially cover the surface of the main material or completely cover the surface of the main material.

[0096] In this embodiment, a coating layer containing a specified element M is coated on the surface of the main material. The coating layer effectively avoids direct contact between the main material and the electrolyte, suppresses side reactions, and effectively improves the electrochemical performance of the lithium-rich manganese-based cathode material, thereby effectively enhancing its cycle stability and first-cycle charge-discharge capacity at low voltage.

[0097] In some embodiments, the mass percentage of the coating layer is w1, where 0 < w1 ≤ 5%, based on the mass of the lithium-rich manganese-based cathode material.

[0098] In this embodiment of the application, the value of w1 is, for example, but not limited to, any one of 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% and 5%, or a range between any two.

[0099] In this embodiment, the specified elements in the coating layer have an appropriate mass ratio in the lithium-rich manganese-based cathode material. This effectively improves the cycle stability of the lithium-rich manganese-based cathode material while avoiding excessive element M from affecting the first-cycle discharge capacity of the lithium-rich manganese-based cathode material at low voltage.

[0100] In some embodiments, the lithium-rich manganese-based cathode material includes Li2CO3 and / or LiOH, satisfying at least one of the following conditions (a1) and (a2): (a1) the mass content of Li2CO3 is 200ppm to 3500ppm based on the mass of the lithium-rich manganese-based cathode material; (a2) the mass content of LiOH is ≤2000ppm based on the mass of the lithium-rich manganese-based cathode material.

[0101] Based on the quality of the lithium-rich manganese-based cathode material, the mass content of Li2CO3 is, for example, but not limited to, 200 ppm to 3500 ppm, for example, but not limited to, any one of 200 ppm, 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm and 3500 ppm or a range between any two.

[0102] Based on the mass of the lithium-rich manganese-based cathode material, the mass content of LiOH is, for example, but not limited to, any one of 100 ppm, 500 ppm, 1000 ppm, 1500 ppm and 2000 ppm or a range between any two.

[0103] Where 1ppm = 0.0001%.

[0104] Li2CO3 and LiOH are both possible residual lithium forms in lithium-rich manganese-based cathode materials. These Li2CO3 and LiOH are mainly distributed on the surface of lithium-rich manganese-based cathode materials, and may also partially remain inside the lithium-rich manganese-based cathode materials.

[0105] When measuring the content of Li2CO3 and LiOH, the total content of each in the lithium-rich manganese-based cathode material can be measured. The test method can refer to the conventional method. For example, the general method for determining chemical reagents, acidity and alkalinity can be used for the determination.

[0106] In this embodiment, the residual Li2CO3 and / or LiOH content in the lithium-rich manganese-based cathode material meets the specified range, which is beneficial to improving the cycle stability and first-cycle charge-discharge capacity of the lithium-rich manganese-based cathode material at low voltage.

[0107] In some embodiments, at least one of the following conditions (b1) and (b2) is met: (b1) the mass content of Li2CO3 is 500ppm to 2000ppm based on the mass of the lithium-rich manganese-based cathode material; (b2) the mass content of LiOH is ≤1500ppm based on the mass of the lithium-rich manganese-based cathode material.

[0108] In this embodiment, the mass content of residual Li2CO3 and / or LiOH in the lithium-rich manganese-based cathode material is within a more suitable range, which is more conducive to improving the cycle stability and first charge-discharge capacity of the lithium-rich manganese-based cathode material at low voltage.

[0109] In some embodiments, at least one of the following conditions (c1) and (c2) is met: (c1) the volume average particle size Dv50 of the lithium-rich manganese-based cathode material is 4µm to 9µm; (c2) the specific surface area of ​​the lithium-rich manganese-based cathode material is 0.5m². 2 / g~1.2m 2 / g.

[0110] Specific surface area refers to the total area per unit mass of material, and the unit is m². 2 / g.

[0111] The volume average particle size Dv50 of lithium-rich manganese-based cathode materials is, for example, but not limited to, 4µm, 5µm, 6µm, 7µm, 8µm, 9µm, etc.

[0112] The specific surface area of ​​lithium-rich manganese-based cathode materials is, for example, but not limited to, 0.5 m². 2 / g, 0.6 m 2 / g, 0.7 m 2 / g, 0.8m 2 / g, 0.9 m 2 / g、1 m2 / g、1.1 m 2 / g, 1.2 m 2 / g, 1.3 m 2 / g, 1.4 m 2 / g, 1.5 m 2 / g etc.

[0113] In this embodiment, the lithium-rich manganese-based cathode material has a specified product average particle size Dv50 and / or specific surface area, which is beneficial for the lithium-rich manganese-based cathode material to maintain a high capacity.

[0114] Secondly, embodiments of this application provide a positive electrode 221, comprising the lithium-rich manganese-based positive electrode material as described in the above embodiments.

[0115] Thirdly, embodiments of this application provide a battery cell 20, including a positive electrode 221 as described in the above embodiments.

[0116] In some embodiments, at a temperature of 25°C, the charge capacity of battery cell 20 cycling within a voltage range of 2.8V to 4.35V is C1, the charge capacity of battery cell 20 cycling within a voltage range of 2.8V to 4.8V is C2, and C1 / C2×100%≥40%.

[0117] The battery cell 20 is not limited in system, and the electrode assembly 22 is, for example, but not limited to, a stacked form, and its packaging form is, for example, but not limited to, a button cell, a pouch cell, etc.

[0118] In this embodiment, the battery cell 20 has a high charging capacity at low voltage, which can be achieved based on some embodiments of the lithium-rich manganese-based cathode material provided above. The corresponding battery cell 20 can exhibit a high discharge capacity at a low voltage of 2.8V to 4.35V, and can be better used in low voltage application fields.

[0119] Fourthly, embodiments of this application provide a battery 100, including a battery cell 20 as described in the above embodiments.

[0120] Fifthly, embodiments of this application provide an electrical device, including a battery cell 20 or a battery 100 as described in the above embodiments.

[0121] Sixth aspect, see Figure 6 This application provides a method for preparing a lithium-rich manganese-based cathode material as described in the above embodiments, comprising: sintering a mixture of a precursor material containing a transition metal salt and a lithium salt at least once.

[0122] A sintering pass is a designation for a single sintering pass. The term "pass" is used to distinguish it from other sintering passes and does not imply that only one sintering pass is performed in the entire process.

[0123] One-time sintering can be used to sinter the main material of lithium-rich manganese-based cathode materials.

[0124] In the embodiments of this application, the precursor material containing transition metal salts can be based on the main material composition of the lithium-rich manganese-based cathode material, for example, by adjusting the molar ratio of nickel, cobalt, and manganese to a certain range. This adjustment can be achieved by controlling the molar ratio of the corresponding raw materials; it should be noted that the molar percentage of cobalt can be zero. Furthermore, when the precursor material containing transition metal salts is mixed with lithium salts, the molar ratio between the two can also be adjusted based on the main material composition of the lithium-rich manganese-based cathode material.

[0125] As an example, precursor materials containing transition metal salts can be prepared by referring to the following method: According to the specified ratio of nickel, cobalt and manganese molar ratio, the corresponding transition metal salts are weighed to prepare the base solution. A certain concentration of sodium hydroxide solution is used as the precipitant and a certain concentration of ammonia water is used as the complexing agent. Under heating and protective gas conditions, the reaction conditions such as pH and stirring speed can be controlled to obtain the precursor material containing the transition metal salt.

[0126] The specified molar ratio of nickel, cobalt, and manganese can be optionally 0.8~1.2: 0~1.2:1~4.5, for example 1:1:1.75.

[0127] The heating temperature is, for example, 25℃~80℃, the pH adjustment range is, for example, 10.5~11.5, the stirring speed is, for example, 300rpm~800rpm, and the reaction time is, for example, 15h~25h.

[0128] As an example, when a precursor material containing a transition metal salt is mixed with a lithium salt, the lithium salt can be selected as lithium carbonate; wherein, the molar ratio of the total molar amount of nickel, cobalt, and manganese in the precursor material containing the transition metal salt to the molar amount of lithium in the lithium salt can be selected as 1:0.9 to 1.7, further selected as 1:1.1 to 1.5, and even further selected as 1:1.1 to 1.3, for example 1:1.2.

[0129] In some embodiments, the sintering temperature for a single sintering is 650°C to 1050°C, and optionally 800°C to 1000°C.

[0130] In the embodiments of this application, the sintering temperature for a single sintering is, for example, but not limited to, any one of 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C and 1000°C or a range between any two.

[0131] Optionally, the sintering time for a single sintering is 9 h to 16 h, for example, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, etc.

[0132] In this embodiment, sintering at a specified temperature helps to control the content of residual lithium (e.g., Li2CO3 and / or LiOH) in the lithium-rich manganese-based cathode material within a suitable range, which is beneficial to improving the cycle stability and first-cycle charge-discharge capacity of the lithium-rich manganese-based cathode material at low voltage.

[0133] See Figure 7 In some embodiments, the preparation method of lithium-rich manganese-based cathode material further includes: mixing the sintered product of primary sintering with a material containing element R, and performing secondary sintering; wherein element R includes one or more of Al, Zr, Ti, Nb, Te, Sb, W, Mo and Mg.

[0134] Optionally, the sintering temperature for the secondary sintering is 500℃~800℃, for example, 500℃, 600℃, 700℃, 800℃, etc.

[0135] Optionally, the sintering time for the secondary sintering is 2 h to 6 h, for example, 2 h, 3 h, 4 h, 5 h, 6 h, etc.

[0136] In this embodiment, R element is doped into the sintered products of sequential sintering through secondary sintering, and R element is mainly distributed in the surface layer 2212a of the main material.

[0137] In the embodiments of this application, during the secondary sintering, element R is doped into the main material by a material containing element R. This process is carried out in steps similar to the primary sintering, so that element R is mainly distributed in the part of the main material near the surface. This satisfies the requirement that the content of element R at the surface part 2212a is greater than the content of element R at the central part 2212b. Furthermore, this can be used to achieve a ratio of element R content at the surface part 2212a to element R content at the central part 2212b of (3~9):1.

[0138] See Figure 7 In some embodiments, the preparation method of lithium-rich manganese-based cathode material further includes: mixing the sintered product of secondary sintering with a material containing element M, and performing a third sintering; wherein element M includes one or more of Nb, W, Mo, Co and Ti.

[0139] Optionally, the sintering temperature for the three sintering processes is 350℃~500℃, for example, 300℃, 350℃, 400℃, 450℃, 500℃, etc.

[0140] Optionally, the sintering time for the three sintering processes is 4 h to 8 h, for example, 4 h, 5 h, 6 h, 7 h, 8 h, etc.

[0141] In this embodiment, a protective layer containing a specified element M is generated on the surface of the sintered product after secondary sintering through tertiary sintering, thereby forming a structure in which at least a portion of the surface of the main material is covered with a coating layer.

[0142] In the embodiments of this application, the terms "first sintering," "second sintering," and "third sintering" do not represent the nth sintering pass or the total number of sintering passes, but rather serve to distinguish between different sintering passes. For example, in a process that does not include a second sintering pass, the third sintering pass may be the second sintering pass based on a time sequence.

[0143] The following specific embodiments are provided to better illustrate this application.

[0144] I. Preparation of battery cells (1) Preparation of lithium-rich manganese-based cathode materials Example 1 1) Prepare a base solution by weighing the corresponding transition metal salts according to the nickel-cobalt-manganese molar ratio of 1:1:1.75, with a total metal concentration of 2 mol / L. Prepare a 4 mol / L sodium hydroxide solution as a precipitant and a 20% ammonia solution as a complexing agent. Under a nitrogen atmosphere at 50℃, add the three solutions to a reactor containing a certain amount of deionized water. Control the stirring speed appropriately, adjust the pH to stabilize at 11.2, and continuously stir for 18 hours. After aging, wash, filter, and dry to obtain the precursor material (Ni). 0.242 Co 0.242 Mn 0.424 )(OH)2.

[0145] 2) Weigh the obtained precursor material and lithium carbonate at a molar ratio of 1:1.2, mix and stir evenly, then sinter at 900℃ for 12 hours in air or oxygen atmosphere, and finally cool naturally to room temperature to obtain the product 0.2Li2MnO3·0.8LiNi after one sintering. 0.33 Co 0.33 Mn 0.33 O2.

[0146] 3) Weigh the obtained primary sintered material and ZrO according to a molar ratio of nickel, cobalt, and manganese to zirconium of 1:0.01, mix them evenly, and sinter at 700℃ for 3 hours. After natural cooling, obtain the secondary sintered product 0.2Li2MnO3·0.8LiNi. 0.33 Co 0.33 Mn 0.32 Zr0.01 O2.

[0147] 4) The obtained sintered material after secondary sintering and WO3 were mixed evenly at a mass ratio of 1:0.01, and sintered at 450℃ for 6 hours to obtain the lithium-rich manganese-based cathode material 0.2Li2MnO3·0.8LiNi. 0.33 Co 0.33 Mn 0.32 Zr 0.01 O2@WO3.

[0148] In the molecular formula of the lithium-rich manganese-based cathode material prepared in this embodiment, @ is used to separate the host material and the coating layer, 0.2Li2MnO3·0.8LiNi 0.33 Co 0.33 Mn 0.32 Zr 0.01 O2 represents the main material, WO3 represents the coating layer, and residual lithium such as Li2CO3 and LiOH are not shown.

[0149] It should be noted that in other embodiments and comparative examples of this application, the explanation of the molecular formula of the prepared lithium-rich manganese-based cathode material is similar to that of this embodiment, and can be referred to this embodiment. For the sake of brevity, it will not be repeated here.

[0150] Example 2 The difference from Example 1 is that the nickel-cobalt-manganese ratio in step 1) is 1:1:2.286, and the molar ratio of the precursor to lithium carbonate in step 2) is changed to 1:1.3, ultimately yielding 0.3Li₂MnO₃·0.7LiNi 0.33 Co 0.33 Mn 0.32 Zr 0.01 O2@WO3.

[0151] Example 3 The difference from Example 1 is that the nickel-cobalt-manganese ratio in step 1) is 1:1:1.529, and the molar ratio of the precursor to lithium carbonate in step 2) is changed to 1:1.15, ultimately yielding 0.15Li₂MnO₃·0.85LiNi 0.33 Co 0.33 Mn 0.32 Zr 0.0 1O2@WO3.

[0152] Example 4 The difference from Example 1 is that the nickel-cobalt-manganese ratio in step 1) is 1:1:1.133, and the molar ratio of the precursor to lithium carbonate in step 2) is changed to 1:1.1, ultimately yielding 0.1Li₂MnO₃·0.9LiNi 0.33 Co 0.33 Mn0.32 Zr 0.01 O2@WO3.

[0153] Example 5 The difference from Example 1 is that the nickel-cobalt-manganese ratio in step 1) is 1:1:4, and the molar ratio of the precursor to lithium carbonate in step 2) is changed to 1:1.5, ultimately yielding 0.5Li2MnO3·0.5LiNi 0.33 Co 0.33 Mn 0.32 Zr 0.01 O2@WO3.

[0154] Examples 6-7 The difference from Example 1 is that the compound containing dopant element R added in step 3) is changed from ZrO to Nb2O5 and MoO respectively.

[0155] Example 8 The difference from Example 1 is that in step 3), the compound ZrO containing doped element R was not added, and the secondary sintering was performed directly.

[0156] Example 9 The difference from Example 1 is that: in step 1), the corresponding transition metal salts are weighed according to the molar ratio of nickel, cobalt, manganese and zirconium elements of 1:1:1.75:0.06 to prepare the base solution, and in step 3), the compound ZrO containing doped element R is no longer added, and the secondary sintering is directly carried out. In the final lithium-rich manganese-based cathode material, Zr is directly doped in the bulk phase of the host material.

[0157] Examples 10-11 The difference from Example 1 is that the compound containing element M added in step 4) is changed from WO3 to TiO2 and CoO respectively.

[0158] Examples 12-15 The difference from Example 1 is that the mass ratio of the sintered material and WO3 after the second sintering in step 4) is changed to 1:0.005, 1:0.02, 1:0.05 and 1:0.1 respectively.

[0159] Example 16 The difference from Example 1 is that: in step 4), the compound WO3 containing doped element M was not added, and the material was directly sintered three times to obtain a lithium-rich manganese-based cathode material without a coating layer.

[0160] Examples 17-18 The difference from Example 1 is that the sintering temperature in step 2) is changed to 800℃ and 1000℃ respectively.

[0161] Comparative Example 1 The difference from Example 1 is that the nickel-cobalt-manganese ratio in step 1) is 1:1:8, and the molar ratio of the precursor to lithium carbonate in step 2) is changed to 1:1.7, ultimately yielding 0.7Li₂MnO₃·0.3LiNi 0.33 Co 0.33 Mn 0.32 Zr 0.01 O2@WO3.

[0162] The descriptions of the various embodiments and comparative examples above tend to emphasize the differences between the various embodiments and comparative examples. Their similarities or similarities can be referred to each other. For the sake of brevity, these will not be repeated here.

[0163] (2) Preparation of positive electrode sheet The lithium-rich manganese-based cathode material, conductive agent (super-P), carbon nanotubes (CNT), and polyvinylidene fluoride (PVDF) prepared above were combined in a mass ratio of 94:1.5:0.5:3 to prepare a cathode slurry. The slurry was coated on a 13 μm Al foil and then vacuum dried at 120 °C, cold-pressed, and cut into strips to obtain the cathode sheet.

[0164] (3) Preparation of negative electrode sheet A negative electrode slurry was prepared by mixing graphite negative electrode material, conductive agent (Super P), binder (SBR), and thickener (CMC-Na) in a mass ratio of 96.2:0.8:1.8:1.2. The slurry was coated onto an 8μm copper foil and then vacuum dried at 120℃, cold pressed, and cut into strips to obtain the negative electrode sheet.

[0165] (4) Assemble the battery The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the anode and cathode to provide isolation. After being wound up, they are placed in an outer package, injected with the prepared electrolyte, and then encapsulated, filled with electrolyte, formed, and vented to obtain a lithium-ion battery.

[0166] Those skilled in the art will understand that in the methods described above in the specific embodiments and comparative examples, the order in which the steps are written does not imply a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of each step should be determined by its function and possible internal logic.

[0167] II. Testing Methods (1) X-ray diffraction test X-ray diffraction measurement conditions: Cu target, tube voltage 40V, tube current 40mA, scanning speed 2° / min, 2θ scanning range 15°~70°, step size 0.02°, emission slit (DS) 1mm, anti-scattering slit (SS) 8mm, graphite monochromator.

[0168] in, The method / standard for confirming the diffraction peak area is: JIS K 0131-1996.

[0169] The method / standard for confirming the full width at half maximum (FWHM) of a diffraction peak is JIS K 0131-1996.

[0170] (2) Gram capacity test Using the positive electrode sheet from section "I. Preparation of Battery Cells" as the positive electrode and a lithium sheet as the negative electrode, a coin cell was assembled. The charge / discharge capacity at 0.1C rate was tested at 2.8~4.35V and 2.8~4.8V under temperature conditions of 25℃±2℃. Simultaneously, the coulombic efficiency was calculated based on the charge / discharge capacity: First-cycle coulombic efficiency = First-cycle discharge capacity / First-cycle charge capacity × 100%.

[0171] (3) Cyclic performance test At 25℃, the lithium-ion batteries in the "I. Preparation of Battery Cells" section were subjected to charge-discharge cycle tests at a rate of 0.33C. The charge-discharge capacity retention rate of the lithium-ion batteries after a specified number of cycles was obtained under specified voltage conditions. The charge capacity retention rate = first cycle charge capacity / charge capacity at the specified number of cycles × 100%, and the discharge capacity retention rate at the specified number of cycles = first cycle discharge capacity / discharge capacity at the specified number of cycles × 100%.

[0172] (4) Chemical composition test 1) Confirmation of molecular formula: The content of each element in the substance can be tested using inductively coupled plasma atomic emission spectrometry according to standard EPA6010D-2014.

[0173] 2) Detection of the mass content of Li2CO3 and LiOH: The mass content can be determined by the general method for determining the acidity and alkalinity of chemical reagents (GB / T 9724-2007).

[0174] III. Experimental Conditions and Test Results The main experimental conditions and test results for each experimental group are shown in Tables 1-4. Figure 8~Figure 13 As shown, for experimental conditions not described, please refer to the above descriptions of the specific embodiments and comparative examples, and they will not be repeated here.

[0175] Table 1

[0176] Table 2

[0177] Table 3

[0178] Table 4

[0179] Figure 8 This is a SEM image of the lithium-rich manganese-based cathode material prepared in Example 1 of this application; according to Figure 8 It can be seen that the lithium-rich manganese-based cathode material prepared in Example 1 exhibits a polycrystalline particle morphology composed of multiple primary small particles, and has good sphericity and roundness.

[0180] Figure 9 The image shows the XRD pattern of the lithium-rich manganese-based cathode material prepared in Example 1 of this application; according to Figure 9 It can be seen that the lithium-rich manganese-based cathode material has obvious diffraction peaks in the range of 19°~22° and 43°~46°, which correspond to the (020) crystal plane of the Li2MnO3 phase and the (104) crystal plane of lithium nickel cobalt manganese oxide, respectively.

[0181] Figure 10 The charge-discharge curves of the lithium-rich manganese-based cathode material prepared in Example 1 of this application at 2.8V~4.35V and 2.8V~4.8V at 0.1C are shown. Figure 11 The charge-discharge curves of the lithium-rich manganese-based cathode material prepared in Example 5 of this application at 2.8V~4.35V and 2.8V~4.8V at 0.1C are shown; according to Figure 10 and Figure 11 It can be seen that the lithium-rich manganese-based cathode material provided in Example 1 has a significantly higher capacity below 4.35V than that in Example 5, and has greater value for low-voltage applications.

[0182] Figure 12 The charging capacity retention curves of the lithium-rich manganese-based cathode material prepared in Example 1 of this application during cycling at 0.33C at 2.8V~4.35V and 2.8V~4.8V; Figure 13 The charging capacity ratio curves of the lithium-rich manganese-based cathode material prepared in Example 1 of this application during cycling at 2.8V~4.35V and 2.8V~4.8V at 0.33C are shown; according to Figure 12 and Figure 13 It can be seen that the lithium-rich manganese-based cathode material provided in Example 1 has a higher charging capacity retention rate at low voltage than at high voltage, and the ratio of charging capacity at 2.8V~4.35V to charging capacity at 2.8V~4.8V is always above 40%.

[0183] Figure 14 The product obtained by secondary sintering in Example 1 of this application is 0.2Li2MnO3·0.8LiNi. 0.33 Co 0.33 Mn 0.32 Zr 0.01SEM images of O2 slices, with the mass percentage and atomic percentage of Zr element corresponding to each site in the spectrum shown in Table 5.

[0184] Table 5

[0185] The ratio of the Zr content at each surface site to that at site 12 is calculated as the atomic percentage of Zr and rounded to two decimal places.

[0186] Combining Tables 1 to 4 above and Figure 7~Figure 13 A brief analysis is as follows: In Examples 1 through 5 and Comparative Example 1: As the area ratio of the first and second specified diffraction peaks decreases, the molar content of Li2MnO3 decreases, while the full width at half maximum (FWHM) of the first specified diffraction peak increases (meaning more uneven grain size and more defects). This implies that the stability of the material will decrease at lower Li2MnO3 contents, meaning that the presence of an appropriate amount of Li2MnO3 phase can stabilize the material structure and improve its electrochemical performance. The ratio of the first-cycle charging capacity of the lithium-rich manganese-based cathode material at voltages of 2.8V to 4.35V to its first-cycle charging capacity at voltages of 2.8V to 4.8V gradually increases from 23.2% to 65%, corresponding to an increase in the first-cycle discharge capacity of the lithium-rich manganese-based cathode material at low voltages of 2.8V to 4.35V from 57.7 mAh / g to 157 mAh / g.

[0187] When the ratio of the area of ​​the first specified diffraction peak to the area of ​​the second specified diffraction peak is too large, for example, >0.2 (Example 5), especially >0.3 (Comparative Example 1), the ratio of the first charge capacity of the lithium-rich manganese-based cathode material at voltages of 2.8V to 4.35V to its first charge capacity at voltages of 2.8V to 4.8V is relatively low, and the first discharge capacity of the lithium-rich manganese-based cathode material at low voltages of 2.8V to 4.35V is relatively low.

[0188] As the ratio of the area of ​​the first specified diffraction peak to that of the second specified diffraction peak decreases, when the molar content of Li2MnO3 is reduced to a certain standard, for example, after being reduced to 0.2 (Example 1), as the molar content of Li2MnO3 continues to decrease, the structural stabilizing effect of Li2MnO3 on the lithium nickel cobalt manganese oxide phase gradually weakens, resulting in a gradual decrease in the cycle stability of the lithium-rich manganese-based cathode material.

[0189] In Examples 1 and 6-9: The surfaces of Examples 1, 6 and 7 were doped with Zr, Nb and Mo, respectively. The lithium-rich manganese-based cathode materials all exhibited good cycle stability and high first-cycle charge-discharge capacity at low voltage.

[0190] In Example 8, no Zr was doped. Compared with Example 1, the ratio of the first-cycle charging capacity of the lithium-rich manganese-based cathode material at 2.8V~4.35V to its first-cycle charging capacity at 2.8V~4.8V decreased, and the cycle stability of the lithium-rich manganese-based cathode material also decreased.

[0191] In Example 9, Zr was doped in bulk phase. Compared with the method of Zr doping mainly on the surface in Example 1, the cycle stability of the lithium-rich manganese-based cathode material decreased, and its first discharge capacity at low voltage also decreased.

[0192] In Examples 1 and 10-16: The main materials of Examples 1, 10 and 11 are respectively coated with coating layers containing WO3, TiO2 and CoO. The lithium-rich manganese-based cathode materials all have good cycle stability and high first charge and discharge capacity at low voltage.

[0193] In Examples 1 and 12-15, the mass ratio of the coating layer in the lithium-rich manganese-based cathode material is different. When the mass ratio of the coating layer in the lithium-rich manganese-based cathode material is low, the improvement in the cycle stability of the lithium-rich manganese-based cathode material is relatively low. When the mass ratio of the coating layer in the lithium-rich manganese-based cathode material is high, the first discharge capacity of the lithium-rich manganese-based cathode material at low voltage will decrease.

[0194] In Example 16, the surface of the main material is not covered with a coating layer. Compared with Example 1, the coating layer effectively improves the cycle stability and first charge-discharge capacity of the lithium-rich manganese-based cathode material under low voltage.

[0195] In Examples 1, 17, and 18: The sintering temperatures of Examples 1, 17, and 18 are different, resulting in different residual lithium (including Li2CO3 and LiOH) contents in the corresponding lithium-rich manganese-based cathode materials. The residual lithium content in Example 1 is higher than that in Example 18. The lithium-rich manganese-based cathode material in Example 1 has both better cycle stability and higher first-cycle charge-discharge capacity at low voltage. This is because, within a certain range, an appropriate amount of residual lithium can strengthen the structural strength of the coating layer and the main material, thereby suppressing side reactions. At the same time, it can serve as a solid electrolyte layer to provide lithium-ion transport sites, enabling the material to obtain better capacity and cycle performance.

[0196] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This 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 lithium-rich manganese-based cathode material, characterized in that, The lithium-rich manganese-based cathode material comprises phase A and phase B; In the X-ray diffraction pattern of the lithium-rich manganese-based cathode material, phase A has a first designated diffraction peak distributed in the range of Bragg angle from 19° to 22°, and phase B has a second designated diffraction peak distributed in the range of Bragg angle from 43° to 46°. The molar ratio of phase A to phase B is a:(1-a), where 0 < a < 0.

5.

2. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, 0.1≤a≤0.3。 3. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, In the X-ray diffraction pattern, the full width at half maximum (FWHM) of the first specified diffraction peak is 0.2° to 0.8°.

4. The lithium-rich manganese-based cathode material according to any one of claims 1 to 3, characterized in that, The lithium-rich manganese-based cathode material comprises Li2CO3 and / or LiOH, and satisfies at least one of the following conditions (a1) and (a2): (a1) Based on the mass of the lithium-rich manganese-based cathode material, the mass content of the Li2CO3 is 200ppm~3500ppm; (a2) Based on the mass of the lithium-rich manganese-based cathode material, the mass content of the LiOH is ≤2000ppm.

5. The lithium-rich manganese-based cathode material according to any one of claims 1 to 3, characterized in that, The molecular formula of the lithium-rich manganese-based cathode material is a[Li2MnO3]·(1-a)[LiNi x Co y Mn 1-x-y-z R z O2] or Li (1+a) Ni (1-a)x Co (1-a) y Mn ((1-x-y-z)(1-a)+a) R (1-a)z O (2+a) ; Wherein, 0 < a < 0.5, 0.2 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.7, 0 ≤ z ≤ 0.03, and element R includes one or more of Al, Zr, Ti, Nb, Te, Sb, W, Mo and Mg.

6. The lithium-rich manganese-based cathode material according to any one of claims 1 to 3, characterized in that, The main body material of the lithium-rich manganese-based cathode material includes a surface portion and a central portion. The surface portion includes a portion within a first specified distance from the surface of the main body material, where the first specified distance is 20% of the volume average particle size Dv50 of the main body material. The central portion includes a portion at or above a second specified distance from the surface of the main body material, where the second specified distance is 70% of the volume average particle size Dv50 of the main body material. The content of element R in the surface portion is greater than the content of element R in the central portion. Element R includes one or more of Al, Zr, Ti, Nb, Te, Sb, W, Mo, and Mg.

7. The lithium-rich manganese-based cathode material according to claim 6, characterized in that, The lithium-rich manganese-based cathode material further includes a coating layer, which is distributed on at least a portion of the surface of the host material; The coating layer includes element M, which includes one or more of Nb, W, Mo, Co, and Ti.

8. A single battery cell, characterized in that, It includes a positive electrode sheet, wherein the positive electrode sheet comprises the lithium-rich manganese-based positive electrode material according to any one of claims 1 to 7.

9. A battery, characterized in that, Includes the battery cell as described in claim 8.

10. An electrical appliance, characterized in that, It includes the battery cell as described in claim 8 or the battery as described in claim 9.

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