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

Abstract

The application discloses a lithium-rich manganese-based positive electrode material, a positive electrode sheet, a battery cell, a battery, an electric device and a preparation method of the lithium-rich manganese-based positive electrode material, wherein the lithium-rich manganese-based positive electrode material comprises an A phase and a B phase; in an X-ray diffraction spectrum of the lithium-rich manganese-based positive electrode material, the A phase has a first specified diffraction peak distributed in a range of a Bragg angle of 19-22 degrees, and the B phase has a second specified diffraction peak distributed in a range of a Bragg angle 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 at a low voltage, the ratio of the areas of the first specified diffraction peak and the second specified diffraction peak is controlled 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 discharge capacity at a low voltage.

Description

TECHNICAL FIELD

[0001] 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 monomer, a battery, an electric equipment and a preparation method of the lithium-rich manganese-based positive electrode material. BACKGROUND

[0002] 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 the material in the low-voltage application field. Therefore, the research on the material is mainly focused on the application at high voltage.

[0003] 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 the prior art. SUMMARY

[0004] In view of the above problems, the present application provides a lithium-rich manganese-based positive electrode material, a positive electrode sheet, a battery monomer, 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 cycle charge and discharge capacity at low voltage.

[0005] The embodiments of the present application are implemented as follows:

[0006] In a first aspect, the embodiments of the present application provide a lithium-rich manganese-based positive electrode material, which comprises 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 solution of the embodiments of the present application, the first specified diffraction peak of the A phase distributed in the range of Bragg angle 19°-22° corresponds to the (020) crystal plane of Li2MnO3, which belongs to the C / 2m space group. The second specified diffraction peak of the B phase distributed in the range of Bragg angle 43°-46° corresponds to the (104) crystal plane of lithium nickel cobalt manganese oxide, which belongs to the R3m space group. The area ratio of the first specified diffraction peak to the second specified diffraction peak corresponds to specific physicochemical 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 to the second specified diffraction peak is within the specified range, the lithium-rich manganese-based positive electrode material has good cycle stability, and the lithium-rich manganese-based positive electrode material has high first cycle charge and discharge capacity at low voltage.

[0008] In some embodiments, the first specified diffraction peak has a half-peak width of 0.2°-0.8° in the X-ray diffraction spectrum. 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. In this embodiment, the half-peak width of the first specified diffraction peak is within the specified range, so that the grain size, uniformity, and defect quantity of the Li2MnO3 phase corresponding to the first specified diffraction peak are within the specified range, which is conducive to improving the cycle stability of the lithium-rich manganese-based positive electrode material.

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

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

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

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

[0014] In some embodiments, the lithium-rich manganese-based positive electrode material further comprises a coating layer, the coating layer is distributed on at least part of the surface of the host material; wherein the coating layer comprises element M, and element M comprises 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, which can inhibit the side reaction, effectively improve the electrochemical performance of the lithium-rich manganese-based positive electrode material, and effectively improve the cycle stability and the first cycle charge-discharge capacity at low voltage.

[0015] In some embodiments, the mass fraction of the coating layer based on the mass of the lithium-rich manganese-based positive electrode material is w1, 0

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

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

[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 positive electrode material is 4 μm to 9 μm; (c2) the specific surface area of the lithium-rich manganese-based positive electrode material is 0.5 m 2 / g to 1.2 m 2 / g. In this embodiment, the lithium-rich manganese-based positive electrode material has the specified volume average particle size Dv50 and / or specific surface area, which is beneficial to maintaining a higher capacity of the lithium-rich manganese-based positive electrode material.

[0019] In a second aspect, the embodiments of the present application provide a positive electrode tab, which comprises the lithium-rich manganese-based positive electrode material according to the above embodiments.

[0020] In a third aspect, the embodiments of the present application provide a battery cell, which comprises the positive electrode tab according to the above embodiments.

[0021] In some embodiments, the battery cell has a charge capacity C1 when cycled in a voltage range of 2.8 V to 4.35 V and a charge capacity C2 when cycled in a voltage range of 2.8 V to 4.8 V at a temperature of 25 °C, and C1 / C2 × 100% ≥ 40%. In this embodiment, the battery cell has a higher charge capacity at low voltage, which can be realized based on some embodiments of the lithium-rich manganese-based positive electrode material provided above, and the corresponding battery cell can have a higher discharge capacity at a low voltage of 2.8 V to 4.35 V, and can be better used in the field of low-voltage applications.

[0022] In a fourth aspect, the embodiments of the present application provide a battery, comprising the battery cell as described above.

[0023] In a fifth aspect, the embodiments of the present application provide a power consumption device, comprising the battery cell or the battery as described above.

[0024] In a sixth aspect, the embodiments of the present application provide a preparation method of the lithium-rich manganese-based positive electrode material as described above, comprising: performing at least one time of sintering on a mixture of a precursor material containing a transition metal salt and a lithium salt.

[0025] In some embodiments, the sintering temperature of the first sintering is 650-1050℃, and optionally 800-1000℃. In this embodiment, the first sintering is performed at the specified temperature, which is beneficial to control the content of residual lithium (such as Li2CO3 and / or LiOH) in the lithium-rich manganese-based positive electrode material within a suitable range, and is beneficial to improve the cycle stability and the first cycle charge-discharge capacity at low voltage of the lithium-rich manganese-based positive electrode material.

[0026] In some embodiments, the preparation method of the lithium-rich manganese-based positive electrode material further comprises: mixing the sintering product of the first sintering with a material containing element R, and performing second sintering; wherein the element R comprises one or more of Al, Zr, Ti, Nb, Te, Sb, W, Mo and Mg. In this embodiment, the R element is doped in the sintering product of the first sintering by the second sintering, and the R element is mainly distributed in the surface layer of the main body material.

[0027] In some embodiments, the preparation method of the lithium-rich manganese-based positive electrode material further comprises: mixing the sintering product of the second sintering with a material containing element M, and performing third sintering; wherein the element M comprises one or more of Nb, W, Mo, Co and Ti. In this embodiment, a protective layer containing the specified element M is generated on the surface of the sintering product of the second sintering by the third sintering, which can form a structure in which at least part of the surface of the main body material is distributed with a coating layer.

[0028] The above description is only a summary of the technical solutions of the embodiments of the present application, in order to more clearly understand the technical means of the present application, the embodiments can be implemented according to the content of the description, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those of ordinary skill in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0030] Figure 1 A structural schematic diagram of a vehicle provided for some embodiments of the present application;

[0031] Figure 2 An exploded view of a battery provided for some embodiments of the present application;

[0032] Figure 3 An exploded view of a battery cell provided for some embodiments of the present application;

[0033] Figure 4 A structural schematic diagram of a positive electrode sheet provided for some embodiments of the present application;

[0034] Figure 5 A partial structural schematic diagram of a lithium-rich manganese-based positive electrode material provided for some embodiments of the present application;

[0035] Figure 6 A process flow chart of a preparation method of a lithium-rich manganese-based positive electrode material provided for some embodiments of the present application;

[0036] Figure 7 A process flow chart of a preparation method of a lithium-rich manganese-based positive electrode material provided for some other embodiments of the present application;

[0037] Figure 8 An SEM image of a lithium-rich manganese-based positive electrode material prepared in Embodiment 1 of the present application;

[0038] Figure 9 An XRD image of a lithium-rich manganese-based positive electrode material prepared in Embodiment 1 of the present application;

[0039] Figure 10 Charge-discharge curves of a lithium-rich manganese-based positive electrode material prepared in Embodiment 1 of the present application at 0.1C under 2.8V-4.35V and 2.8V-4.8V;

[0040] Figure 11 Charge-discharge curves of a lithium-rich manganese-based positive electrode material prepared in Embodiment 5 of the present application at 0.1C under 2.8V-4.35V and 2.8V-4.8V;

[0041] Figure 12 Charge capacity retention rate curves of a lithium-rich manganese-based positive electrode material prepared in Embodiment 1 of the present application in a cycle process at 0.33C under 2.8V-4.35V and 2.8V-4.8V;

[0042] Figure 13 Charge capacity ratio curves of the lithium-rich manganese-based positive electrode material prepared for Example 1 of the present application during the cycling process at 0.33C under 2.8V-4.35V and 2.8V-4.8V;

[0043] Figure 14 The secondary sintered product 0.2Li2MnO3·0.8LiNi 0.33 Co 0.33 Mn 0.32 Zr 0.01 SEM image of the section of O2.

[0044] Figure:

[0045] 1000 - vehicle;

[0046] 100 - battery; 200 - controller; 300 - motor;

[0047] 10 - box body; 11 - first part; 12 - second part; 13 - containing space;

[0048] 20 - battery cell; 21 - shell; 22 - electrode assembly; 23 - electrode terminal; 24 - pressure relief structure;

[0049] 211 - shell; 212 - cover;

[0050] 221 - positive electrode sheet; 2211 - positive electrode current collector; 2212 - positive electrode active material layer; 2212a - surface site; 2212b - central site;

[0051] D1 - first specified distance; D2 - second specified distance. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0053] The embodiments of the technical solutions of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to make the technical solutions of the present application clearer, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0054] 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 terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the description and claims of this application as well as the above discussion of the background of the application, provide examples of the technical features of the application. The terms "comprises," "comprising," "includes," "including" and "has," "having" as used herein, are intended to be interpreted as specifying the presence of the stated features but not precluding the presence of one or more other features.

[0055] 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.

[0056] In the description of the embodiments of the present application, the technical term "and / or", such as "feature 1 and / or feature 2", means that it can be "feature 1" alone, "feature 2" alone, or "feature 1" plus "feature 2".

[0057] In the description of the embodiments of the present application, unless otherwise specified, the meaning of "multiple" in "one or more" is two and more than two.

[0058] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. It is expressly understood that the embodiments described herein are merely examples from a multitude of embodiments that are in substantial compliance with the principles of the application.

[0059] In the embodiments of the present application, the same reference signs represent the same components, and for the sake of brevity, detailed description of the same components is omitted in different embodiments. It should be understood that the height, length, width, etc. of various components in the embodiments of the present application shown in the drawings, and the overall height, length, width, etc. of the integrated device are only exemplary and should not constitute any limitation on the present application.

[0060] With the continuous development of new energy industry, the market puts forward more diversified demands for positive active material. Among them, lithium-rich manganese-based positive electrode material is concerned due to its high voltage, high specific capacity, good safety, rich resources and less pollution, and is considered as the next generation of positive active material. Lithium-rich manganese-based positive electrode material has two voltage platforms in the charging process, which are below 4.5V and above 4.5V, respectively corresponding to the activation process of lithium nickel cobalt manganese oxide and Li2MnO3. Generally, the capacity of lithium-rich manganese-based positive electrode material at low voltage is low, usually less than 30% of the charging capacity in the voltage range of 2.8V-4.8V, so that the majority of the capacity of the material cannot be utilized, the capacity utilization rate is low, and the application value of such material in the low voltage field is low. Therefore, the research of such material mainly focuses on the application at high voltage. However, at high voltage, lithium-rich manganese-based positive electrode material usually has defects such as unstable structure, discharge capacity and cycle life, which makes it difficult to be applied in the field above 4.5V.

[0061] In some studies, in order to improve the stability of lithium-rich manganese-based positive electrode material in the charging and discharging process above 4.5V, Li2MnO3 component is activated by charging and discharging in different gradient environment temperatures for multiple cycles, or by charging and discharging in gradually changing environment temperatures for single cycle or multiple cycles. This method is more complicated. In other studies, lithium-rich manganese-based compounds are removed by lithium extraction agent to remove part of Li2O in Li2MnO3, and lithium-rich manganese-based positive electrode material with lithium vacancy and oxygen vacancy is obtained. In this technical solution, the first coulombic efficiency is improved due to the reduction of irreversible product Li2O, and the rate performance and cycle performance are improved due to the existence of lithium vacancy and oxygen vacancy. However, in the above studies, the capacity contributed by Li2MnO3 in lithium-rich manganese-based positive electrode material will continue to decay and decrease, and the problem of instability of lithium-rich manganese-based positive electrode material at high voltage has not been solved, and it is still difficult to realize its practical application in the field above 4.5V high voltage.

[0062] Therefore, the application examples of the present application study the application of lithium-rich manganese-based positive electrode material at low voltage, and propose a lithium-rich manganese-based positive electrode material, which controls the ratio of diffraction peak area of Li2MnO3 phase and lithium nickel cobalt manganese oxide phase in X-ray diffraction pattern. The lithium-rich manganese-based positive electrode material has good cycle stability, and the lithium-rich manganese-based positive electrode material has high first discharge capacity at low voltage.

[0063] From the development of market situation, the application of power battery is more and more extensive. The power battery is not only applied to the energy storage power supply system of water power, fire power, wind power and solar power station, but also widely applied to 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 demand of its market is also increasing.

[0064] The following embodiments are described by taking a vehicle as an example for convenience of description.

[0065] Referring to Figure 1 , Figure 1 A structural schematic diagram of a vehicle 1000 is provided for some embodiments of the application. The vehicle 1000 can be a fuel automobile, a gas automobile or a new energy automobile, and the new energy automobile can be a pure electric vehicle, a hybrid electric vehicle or a range extended vehicle. The vehicle 1000 is internally provided with a battery 100, which can be arranged at the bottom, head or tail of the vehicle 1000. The battery 100 can be used for power supply of the vehicle 1000, for example, the battery 100 can be used as the operating power supply of the vehicle 1000. The vehicle 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, for example, to meet the power demand of the vehicle 1000 during starting, navigation and driving.

[0066] In some embodiments of the application, the battery 100 can not only be used as the operating power supply of the vehicle 1000, but also be used as the driving power supply of the vehicle 1000, instead of or partially instead of fuel or natural gas to provide driving power for the vehicle 1000.

[0067] In the present application, the battery 100 refers to a single physical module including a plurality of battery monomers 20 to provide higher voltage and capacity, which can be in the form of a battery pack, a battery module, etc. The battery 100 can include a box 10 for packaging a plurality of battery monomers 20, and the box 10 can avoid the influence of liquid or other foreign matters on the charging or discharging of the battery monomers 20.

[0068] Referring to Figure 2 , Figure 2An exploded view of a battery 100 is provided for some embodiments of the present application. The battery 100 includes a box 10 and a plurality of battery cells 20, which are accommodated in the box 10. The box 10 is used to accommodate the battery cells 20, and the box 10 can be of various structures. In some embodiments, the box 10 can include a first part 11 and a second part 12, the first part 11 and the second part 12 are mutually covered, and the first part 11 and the second part 12 jointly define an accommodation space 13 for accommodating the battery cells 20. The second part 12 can be a hollow structure with one end open, and the first part 11 is a plate-like structure, which is covered on the open side of the second part 12 to form the box 10 with the accommodation space 13; the first part 11 and the second part 12 can also be hollow structures with one side open, and the open side of the first part 11 is covered on the open side of the second part 12 to form the box 10 with the accommodation space 13. Of course, the first part 11 and the second part 12 can be of various shapes, such as a cylinder, a cuboid, etc.

[0069] In the battery 100, the plurality of battery cells 20 can be connected in series, in parallel, or in a mixed manner, and the mixed manner means that the plurality of battery cells 20 are connected in series and in parallel. The plurality of battery cells 20 can be directly connected in series, in parallel, or in a mixed manner, and then the plurality of battery cells 20 are accommodated in the box 10 as a whole. Alternatively, the plurality of battery cells 20 can be connected in series, in parallel, or in a mixed manner to form a module, and then a plurality of modules are connected in series, in parallel, or in a mixed manner to form a whole, which is accommodated in the box 10. The battery 100 can also include other structures, for example, the plurality of battery cells 20 can be electrically connected through a busbar to realize the parallel, series, or mixed connection of the plurality of battery cells 20.

[0070] The battery cell 20 refers to the smallest unit that constitutes the battery 100. The 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 thereto.

[0071] Referring to Figure 3 , the battery cell 20 can include a shell 21, an electrode assembly 22, and an electrolyte, and the electrode assembly 22 and the electrolyte are accommodated in the shell 21.

[0072] The shell 21 can include a shell body 211 and a cover body 212. The shell body 211 is a component for cooperating with the cover body 212 to form an internal sealed space of the battery monomer 20, wherein the formed sealed space can be used to accommodate the electrode assembly 22, the electrolyte and other components. The cover body 212 refers to a component that is covered on the opening of the shell body 211 to isolate the internal environment of the battery monomer 20 from the external environment. The shape of the cover body 212 can be adapted to the shape of the shell body 211 to cooperate with the shell body 211. The cover body 212 can also be provided with functional components such as the electrode terminal 23, the pressure relief structure 24 and the like. A sealing ring can be arranged between the opening of the shell body 211 and the cover body 212 to realize the sealing between the shell body 211 and the cover body 212.

[0073] The shell body 211 and the cover body 212 can be in various shapes and sizes, such as a cuboid, a cylinder, a hexagonal prism and the like. Specifically, the shape of the shell body 211 and the cover body 212 can be determined according to the specific shape and size of the electrode assembly 22. The material of the shell body 211 and the cover body 212 can be various, such as but not limited to copper, iron, aluminum, stainless steel, aluminum alloy and the like. The material of the sealing ring can be various, such as but not limited to PP (polypropylene), PC (polycarbonate), PET (polyethylene terephthalate) and the like, which are electrolyte corrosion resistant, high toughness and fatigue resistant. The outer surface of the shell body 211 can form a plating layer, and the material of the plating layer can be various, such as but not limited to Ni, Cr and the like, which are corrosion resistant materials.

[0074] The electrode assembly 22 can be composed of a positive electrode sheet 221, a negative electrode sheet and a separator. The battery monomer 20 mainly relies on the movement of metal ions between the positive electrode sheet 221 and the negative electrode sheet to work. Referring to Figure 4 The positive electrode sheet 221 includes a positive electrode current collector 2211 and a positive electrode active material layer 2212 provided on the surface of the positive electrode current collector 2211. The material of the positive electrode current collector 2211 can be aluminum, and the positive electrode active material in the positive electrode active material layer 2212 can include the lithium-rich manganese-based positive electrode material provided by the embodiments of the present application, and can also include lithium cobaltate, lithium iron phosphate, ternary lithium, lithium manganate, lithium-sulfur and the like. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on the surface of the negative electrode current collector. The material of the negative electrode current collector can be copper, and the negative electrode active material in the negative electrode active material layer can be carbon, silicon and the like. In addition, the electrode assembly 22 can be a winding type structure or a laminated type structure, and the embodiments of the present application are not limited thereto.

[0075] Next, the lithium-rich manganese-based positive electrode material and the preparation method thereof provided by the embodiments of the present application are described in detail.

[0076] 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 an X-ray diffraction pattern of the lithium-rich manganese-based positive electrode material, the A phase has a first specified diffraction peak distributed in a range of Bragg angles of 19°-22°, and the B phase has a second specified diffraction peak distributed in a range of Bragg angles of 43°-46°, 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.

[0077] The lithium-rich manganese-based positive electrode material can include a mixture and / or a solid solution composed of a Li2MnO3 phase and a lithium nickel cobalt manganese oxide layered structure.

[0078] The first specified diffraction peak and the second specified diffraction peak refer to diffraction peaks distributed in different specified ranges of Bragg angles, respectively, and the first specified and the second specified are only used to distinguish the two different peaks and have no other particular limitations. It should be noted that the A phase and the B phase are not limited to only having the first specified diffraction peak and the second specified diffraction peak, respectively, and each of the two can also include other diffraction peaks.

[0079] The diffraction peak refers to a sharp peak-shaped distribution curve in which the diffraction intensity gradually increases and decreases in the X-ray diffraction pattern.

[0080] The area of the diffraction peak refers to an integral value of the peak height and the retention time of the diffraction peak in the X-ray diffraction pattern.

[0081] In the embodiments of the present 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 value between any two of them. 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 0.05-0.25:1, and optionally 0.1-0.2:1.

[0082] In the technical solutions of the embodiments of the present application, the first specified diffraction peak of the A phase distributed in the range of Bragg angles of 19°-22° corresponds to a (020) crystal face of Li2MnO3 (JCPDS card No. 27-1252) and belongs to a C / 2m space group; and the second specified diffraction peak of the B phase distributed in the range of Bragg angles of 43°-46° corresponds to a (104) crystal face of lithium nickel cobalt manganese oxide (JCPDS card No. 52-0457) and belongs to an R3m space group.

[0083] The research finds that the Li2MnO3 phase shows high stability in a low voltage range of 4.2 V-4.5 V, and can serve as a support layer of the lithium nickel cobalt manganese oxide phase, which is conducive to improving the cycle stability of the lithium-rich manganese-based positive electrode material; however, the Li2MnO3 phase hardly provides capacity at a low voltage of 4.2 V-4.5 V, and in order to obtain the lithium-rich manganese-based positive electrode material with high gram capacity, the molar content of the Li2MnO3 phase needs to be regulated in a proper range, so that the Li2MnO3 phase can play a role in stabilizing the structure and will not excessively affect the gram capacity of the lithium-rich manganese-based positive electrode material.

[0084] The ratio of the areas of the first specified diffraction peak and the second specified diffraction peak corresponds to specific physicochemical properties, for example, including the ratio of the molar contents of the Li2MnO3 phase and the lithium nickel cobalt manganese oxide phase in the lithium-rich manganese-based positive electrode material; the ratio of the areas of the first specified diffraction peak and the second specified diffraction peak is in a specified range, so that the Li2MnO3 phase has a proper molar content in the lithium-rich manganese-based positive electrode material, the lithium-rich manganese-based positive electrode material has good cycle stability, and the lithium-rich manganese-based positive electrode material has high first-cycle charge and discharge capacity at a low voltage.

[0085] In some embodiments, the half-peak width of the first specified diffraction peak is 0.2°-0.8° in the X-ray diffraction spectrum.

[0086] The half-peak width of the first specified diffraction peak refers to the peak width at half the peak height in the X-ray diffraction spectrum.

[0087] In the embodiments of the present application, the half-peak width 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 value between any two thereof. As an example, the half-peak width of the first specified diffraction peak is further 0.3°-0.7°, and optionally 0.3°-0.5°.

[0088] Generally speaking, the narrower the half-peak width of the diffraction peak corresponding to the sample, the larger, more uniform and fewer defects the grain size of the sample. In the embodiments, 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 conducive to improving the cycle stability of the lithium-rich manganese-based positive electrode material.

[0089] In some embodiments, in the lithium-rich manganese-based positive electrode material, the ratio of the molar contents of the A phase and the B phase is a:(1-a), 0

[0090] In the embodiments of the present application, the value of a is, for example but not limited to, any one of 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4 and 0.45 or a range value between any two of them.

[0091] In the embodiments, Li2MnO3 has a suitable molar content in the lithium-rich manganese-based positive electrode material, can better play a stabilizing role on the phase structure of lithium nickel manganese oxide, while avoiding excessive Li2MnO3 content from excessively affecting the gram capacity of the lithium-rich manganese-based positive electrode material, and is also conducive to regulating the half-peak width of the first designated diffraction peak within a designated range, and thus, the lithium-rich manganese-based positive electrode material has better cycle stability and higher first cycle charge and discharge capacity at low voltage.

[0092] In some embodiments, 0.1≤a≤0.3.

[0093] In the embodiments, Li2MnO3 has a suitable molar content in the lithium-rich manganese-based positive electrode material, is conducive to the lithium-rich manganese-based positive electrode material having better cycle stability and higher first cycle charge and discharge capacity at low voltage.

[0094] 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

[0095] Regarding the molecular formula a[Li2MnO3]·(1-a)[LiNi x Co y Mn 1-x-y-z R z O2], A phase and B phase are represented in a separate manner, a[Li2MnO3] represents the A phase, and (1-a)[LiNi x Co y Mn 1-x-y-z R z O2] represents the B phase.

[0096] 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) wherein, the A phase and the B phase are expressed in a combined manner. In the embodiments of the present application, regarding the above-mentioned combined molecular formula of the lithium-rich manganese-based positive electrode material, the value of a can be determined by using a conventional method, as an example, the ICP emission spectrometry can be used for determination.

[0097] Regarding the molecular formula of the lithium-rich manganese-based positive electrode material, the value of a most basically needs to meet the requirement of the ratio of the area of the first specified diffraction peak to the area of the second specified diffraction peak; as an example, the value of a is described with reference to the above-mentioned embodiments, which will not be repeated herein.

[0098] In the embodiments of the present application, the element R is a doping element in the lithium-rich manganese-based positive electrode material; regarding other coefficients in the lithium-rich manganese-based positive electrode material, the value of the coefficient x is for example but not limited to 0.2, 0.3, 0.4, 0.5, 0.6, etc., the value of the 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 the coefficient z is for example but not limited to 0, 0.1, 0.2, 0.3, etc.

[0099] In this embodiment, the lithium-rich manganese-based positive electrode material corresponding to the molecular formula can better meet the above-mentioned 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 content of the A phase to the B phase; at the same time, the doping of the R element is beneficial to improving the crystal distortion problem of the lithium-rich manganese-based positive electrode material in the charging and discharging process from the crystal lattice angle, and is beneficial to improving the cycle stability of the lithium-rich manganese-based positive electrode material.

[0100] Referring to Figure 5 In some embodiments, the main body material of the lithium-rich manganese-based positive electrode material includes a surface layer part and a central part 2212b, the surface layer part includes a part within a first specified distance D1 from the surface of the main body material, the first specified distance D1 is 20% of the volume average particle size Dv50 of the main body material, the central part 2212b includes a part above a second specified distance D2 from the surface of the main body material, the second specified distance D2 is 70% of the volume average particle size Dv50 of the main body material, and the content of the element R at the surface layer part is greater than the content of the element R at the central part 2212b.

[0101] The main body material refers to the main component of the lithium-rich manganese-based positive electrode material, that is, the lithium-rich manganese-based positive electrode material can be composed of only the main body material, or can include other functional materials; based on the mass of the lithium-rich manganese-based positive electrode material, the mass proportion of the main body material is >50%, for example, ≥60%, or further ≥70%, or further ≥80%, or further ≥90%, or further ≥95%, or further ≥99%.

[0102] The composition of the host material mainly consists of the A phase and the B phase, and can further include a small amount (for example, ≤20%, 10%, 5%, or 1% by mass) of other components, such as a small amount of a doping element, or residual lithium such as Li2CO3, LiOH, and the like that cannot be avoided in the preparation process.

[0103] In the embodiments of the present application, the volume average particle size Dv50 refers to the particle size corresponding to 50% in the volume distribution, which can be measured by a conventional method. For example, refer to GB / T 19077-2016 / ISO13320:2009 Particle Size Distribution Laser Diffraction Method, and use the equipment Malvern 3000 to measure.

[0104] The host material includes a description of the surface layer part 2212a and the center part 2212b, and divides the host material into a core-shell structure; wherein the center part 2212b corresponds to the inner core part of the core-shell structure, which is, for example, close to the shape of a sphere; the surface layer part 2212a corresponds to the shell 211 part of the core-shell structure, which is, for example, close to the shape of a hollow sphere.

[0105] The surface layer part 2212a is within a first specified distance D1 from the surface of the host material, that is, in the host material, the region with a distance ≤ the first specified distance D1 from the surface of the host material is the surface layer part 2212a.

[0106] The center part 2212b is at a distance ≥ the second specified distance D2 from the surface of the host material, that is, in the host material, the region with a distance ≥ the second specified distance D2 from the surface of the host material is the center part 2212b.

[0107] In this embodiment, the element R is more distributed in the surface layer part 2212a of the host material, which is beneficial to better improve the cycle stability of the lithium-rich manganese-based positive electrode material; and moreover, reduces the doping of the element R inside the bulk phase of the host material, 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 specific capacity.

[0108] In some embodiments, the ratio of the content of the element R at the surface layer part 2212a to the content of the element R at the center part 2212b is (3-9):1.

[0109] The content of the element R at different parts can be measured by a conventional method. For example, the positive electrode active material layer 2212 can be cut, and then the content of the element R at different parts can be observed and measured by a scanning electron microscope on the cut surface.

[0110] The ratio of the content of element R at the surface layer site 2212a to the content of element R at the center site 2212b is (3-9): 1, which can be achieved by surface doping element R. Based on the mode of surface doping element R, element R is mainly distributed in the surface layer site 2212a, and a small amount of element R penetrates into the center site 2212b.

[0111] In the embodiments of the present application, the ratio of the content of element R at the surface layer site 2212a to the content of element R at the center site 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 a range value between any two of them.

[0112] In this embodiment, element R is mainly distributed in the surface layer site 2212a of the host material, which is beneficial to better improve the cycle stability of the lithium-rich manganese-based positive electrode material; element R does not basically enter the bulk phase inside the host material, which has less influence on the electrochemical performance of the lithium-rich manganese-based positive electrode material, and is more beneficial to the lithium-rich manganese-based positive electrode material to maintain a higher specific capacity.

[0113] In some embodiments, the lithium-rich manganese-based positive electrode material further comprises a coating layer, the coating layer being distributed on at least part of the surface of the host material; wherein the coating layer comprises element M, and the element M comprises one or more of Nb, W, Mo, Co and Ti.

[0114] In the embodiments of the present application, the coating layer is a structure coated on at least part of the surface of the host material, and part of the coating substance between the coating layer and the host material is observed to be distributed in the form of small particles on the surface of the host material. The interface between the two can be determined by a conventional method, for example, by directly observing the material with a scanning electron microscope.

[0115] The coating layer is distributed on at least part of the surface of the host material, that is, the coating layer can partially coat the surface of the host material, or can completely coat the surface of the host material.

[0116] In this embodiment, the coating layer containing the specified element M is coated on the surface of the host material, the site 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 charge-discharge capacity at low voltage are effectively improved.

[0117] In some embodiments, based on the mass of the lithium-rich manganese-based positive electrode material, the mass ratio of the coating layer is w1, and 0

[0118] In the embodiments of the present 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 value between any two of them.

[0119] In the embodiments, the specified elements in the coating layer have a suitable mass fraction in the lithium-rich manganese-based positive electrode material, which effectively improves the cycle stability of the lithium-rich manganese-based positive electrode material while avoiding excessive element M from affecting the first-cycle discharge capacity of the lithium-rich manganese-based positive electrode material at low voltage.

[0120] In some embodiments, the lithium-rich manganese-based positive electrode material includes Li2CO3 and / or LiOH, and at least one of the following conditions (a1) and (a2) is met: (a1) the mass content of Li2CO3 is 200 ppm to 3500 ppm based on the mass of the lithium-rich manganese-based positive electrode material; and (a2) the mass content of LiOH is ≤2000 ppm based on the mass of the lithium-rich manganese-based positive electrode material.

[0121] The mass content of Li2CO3 is, for example but not limited to, 200 ppm to 3500 ppm based on the mass of the lithium-rich manganese-based positive electrode material, such as, 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 value between any two of them.

[0122] 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 value between any two of them, based on the mass of the lithium-rich manganese-based positive electrode material.

[0123] Wherein, 1 ppm = 0.0001%.

[0124] Both Li2CO3 and LiOH are possible residual lithium forms in the lithium-rich manganese-based positive electrode material, and the Li2CO3 and LiOH are mainly distributed on the surface of the lithium-rich manganese-based positive electrode material, and can also be partially residual inside the lithium-rich manganese-based positive electrode material.

[0125] When measuring the content of Li2CO3 and LiOH, the total content of each in the lithium-rich manganese-based positive electrode material can be measured, and the test method can refer to the conventional method. For example, the chemical reagent, the general method for determining acidity and alkalinity can be used for determination.

[0126] In the embodiments, the mass content of residual Li2CO3 and / or LiOH in the lithium-rich manganese-based positive electrode material meets the specified range, which is beneficial to improve the cycle stability and the first-cycle charge-discharge capacity at low voltage of the lithium-rich manganese-based positive electrode material.

[0127] In some embodiments, at least one of the following conditions (b1) and (b2) is satisfied: (b1) the mass content of Li2CO3 is 500 ppm to 2000 ppm based on the mass of the lithium-rich manganese-based positive electrode material; (b2) the mass content of LiOH is ≤ 1500 ppm based on the mass of the lithium-rich manganese-based positive electrode material.

[0128] In this embodiment, the mass content of residual Li2CO3 and / or LiOH in the lithium-rich manganese-based positive electrode material satisfies a more suitable range, which is more conducive to improving the cycle stability and the first cycle charge-discharge capacity at low voltage of the lithium-rich manganese-based positive electrode material.

[0129] In some embodiments, at least one of the following conditions (c1) and (c2) is satisfied: (c1) the volume average particle size Dv50 of the lithium-rich manganese-based positive electrode material is 4 μm to 9 μm; (c2) the specific surface area of the lithium-rich manganese-based positive electrode material is 0.5 m 2 / g to 1.2 m 2 / g.

[0130] The specific surface area refers to the total area possessed by unit mass of material, and the unit is m 2 / g.

[0131] The volume average particle size Dv50 of the lithium-rich manganese-based positive electrode material is, for example but not limited to, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, etc.

[0132] The specific surface area of the lithium-rich manganese-based positive electrode material is, for example but not limited to, 0.5 m 2 / g, 0.6 m 2 / g, 0.7 m 2 / g, 0.8 m 2 / g, 0.9 m 2 / g, 1 m 2 / 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.

[0133] In this embodiment, the lithium-rich manganese-based positive electrode material has a specified volume average particle size Dv50 and / or specific surface area, which is conducive to maintaining a high capacity of the lithium-rich manganese-based positive electrode material.

[0134] In a second aspect, the embodiments of the present application provide a positive electrode sheet 221, which comprises the lithium-rich manganese-based positive electrode material according to the above embodiments.

[0135] In a third aspect, the embodiments of the present application provide a battery monomer 20 comprising the positive electrode sheet 221 of the above embodiments.

[0136] In some embodiments, the battery monomer 20 has a charge capacity of C1 when cycled in a voltage range of 2.8V-4.35V and a charge capacity of C2 when cycled in a voltage range of 2.8V-4.8V at a temperature condition of 25°C, and C1 / C2 x 100% ≥ 40%.

[0137] The system of the battery monomer 20 is not limited, and the electrode assembly 22 is, for example but not limited to, a stacked form, and the battery is, for example but not limited to, a button cell, a soft pack battery, etc.

[0138] In this embodiment, the battery monomer 20 has a higher charge capacity at a low voltage, which can be achieved based on some embodiments of the above-provided lithium-rich manganese-based positive electrode material, and the corresponding battery monomer 20 can have a higher discharge capacity at a low voltage of 2.8V-4.35V, and can be better used in low-voltage application fields.

[0139] In a fourth aspect, the embodiments of the present application provide a battery 100 comprising the battery monomer 20 of the above embodiments.

[0140] In a fifth aspect, the embodiments of the present application provide an electric device comprising the battery monomer 20 or the battery 100 of the above embodiments.

[0141] In a sixth aspect, referring to Figure 6 The embodiments of the present application provide a preparation method of the lithium-rich manganese-based positive electrode material of the above embodiments, comprising: sintering a mixture of a precursor material containing a transition metal salt and a lithium salt at least once.

[0142] The first sintering is a designation for one sintering pass, and the description of the first is used to distinguish from other sintering passes, and does not mean that only one sintering pass is performed in the whole process.

[0143] The first sintering can be used to sinter the main material of the lithium-rich manganese-based positive electrode material.

[0144] In the embodiments of the present application, the precursor material containing a transition metal salt can be based on the main material composition of the lithium-rich manganese-based positive electrode material, for example, the molar ratio of nickel, cobalt and manganese is adjusted to a certain range, and the adjustment method can be to adjust the molar ratio of the corresponding raw materials of nickel, cobalt and manganese; it should be noted that the molar ratio of cobalt can be zero. In addition, when the precursor material containing a transition metal salt is mixed with a lithium salt, the molar ratio of the two can also be adjusted based on the main material composition of the lithium-rich manganese-based positive electrode material.

[0145] As an example, the precursor material containing a transition metal salt can be prepared by the following method:

[0146] According to the specified molar ratio of nickel, cobalt, and manganese, the corresponding transition metal salt is weighed to prepare a base solution, a certain concentration of sodium hydroxide solution is used as a precipitant, a certain concentration of ammonia is used as a complexing agent, and under the conditions of heating and protective gas, the reaction conditions such as pH and stirring speed are controlled to obtain a precursor material containing a transition metal salt.

[0147] Among them, the specified molar ratio of nickel, cobalt, and manganese can be selected as 0.8-1.2:0-1.2:1-4.5, for example, 1:1:1.75.

[0148] The heating temperature is, for example, 25-80℃, the pH control range is, for example, 10.5-11.5, the stirring speed is, for example, 300-800rpm, and the reaction time is, for example, 15-25h.

[0149] As an example, when the precursor material containing a transition metal salt is mixed with a lithium salt, the lithium salt can be selected as lithium carbonate; wherein, regarding the total molar amount of nickel, cobalt, and manganese in the precursor material containing a transition metal salt and the molar amount of lithium in the lithium salt, the molar ratio of the two can be selected as 1:0.9-1.7, further selected as 1:1.1-1.5, and more further selected as 1:1.1-1.3, for example, 1:1.2.

[0150] In some embodiments, the sintering temperature of the first sintering is 650-1050℃, which can be selected as 800-1000℃.

[0151] In the embodiments of the present application, the sintering temperature of the first sintering is, for example, but not limited to, any one of 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, and 1000℃, or a range value between any two of them.

[0152] Optionally, the sintering time of the first sintering is 9-16h, for example, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, etc.

[0153] In this embodiment, the first sintering is carried out at a specified temperature, which is beneficial to control the content of residual lithium (such as Li2CO3 and / or LiOH) in the lithium-rich manganese-based positive electrode material within a suitable range, and is beneficial to improve the cycle stability and the first cycle charge-discharge capacity at low voltage of the lithium-rich manganese-based positive electrode material.

[0154] Referring to Figure 7 In some embodiments, the preparation method of the lithium-rich manganese-based positive electrode material further comprises: mixing the sintering product of the first sintering with a material containing element R, and performing second sintering; wherein, the element R includes one or more of Al, Zr, Ti, Nb, Te, Sb, W, Mo, and Mg. In some embodiments, the preparation method of the lithium-rich manganese-based positive electrode material further comprises: mixing the sintering product of the first sintering with a material containing element R, and performing second sintering; wherein, the element R includes one or more of Al, Zr, Ti, Nb, Te, Sb, W, Mo, and Mg.

[0155] Optionally, the sintering temperature of the secondary sintering is 500-800℃, for example, 500℃, 600℃, 700℃, 800℃, etc.

[0156] Optionally, the sintering time of the secondary sintering is 2-6h, for example, 2h, 3h, 4h, 5h, 6h, etc.

[0157] In this embodiment, the R element is doped in the sequentially sintered sintered product by secondary sintering, and the R element is mainly distributed in the surface layer part 2212a of the host material.

[0158] In the embodiments of the present application, the R element is doped in the host material by the material containing the element R during the secondary sintering, and the way of performing the first sintering in steps makes the element R mainly distributed in the part close to the surface of the host material, so that the content of the element R at the surface layer part 2212a is greater than the content of the element R at the center part 2212b, and further can be used to realize that the ratio of the content of the element R at the surface layer part 2212a to the content of the element R at the center part 2212b is (3-9):1.

[0159] Reference is made to Figure 7 In some embodiments, the preparation method of the lithium-rich manganese-based positive electrode material further comprises: mixing the sintered product of the secondary sintering with a material containing an element M, and performing tertiary sintering; wherein the element M comprises one or more of Nb, W, Mo, Co and Ti.

[0160] Optionally, the sintering temperature of the tertiary sintering is 350-500℃, for example, 300℃, 350℃, 400℃, 450℃, 500℃, etc.

[0161] Optionally, the sintering time of the tertiary sintering is 4-8h, for example, 4h, 5h, 6h, 7h, 8h, etc.

[0162] In this embodiment, a protective layer containing a specified element M is generated on the surface of the sintered product of the secondary sintering by tertiary sintering, which can form a structure in which at least part of the surface of the host material is distributed with a coating layer.

[0163] In the embodiments of the present application, the first, second and third of the first sintering, the secondary sintering and the tertiary sintering do not represent the number of sintering passes or the total number of sintering passes, but are used to distinguish different sintering passes. For example, in a process that does not include a secondary sintering pass, the tertiary sintering can be the second sintering pass based on the time sequence.

[0164] Some specific embodiments are listed below to better illustrate the present application.

[0165] I. Preparation of battery monomer

[0166] (1) Preparation of lithium-rich manganese-based positive electrode material

[0167] Example 1

[0168] 1) The corresponding transition metal salts were weighed according to the molar ratio of nickel, cobalt and manganese elements of 1:1:1.75 to prepare a base solution, and the total metal concentration of the base solution was 2 mol / L; a 4 mol / L sodium hydroxide solution was prepared as a precipitant, and a 20% ammonia solution was prepared as a complexing agent. Under the protection of nitrogen atmosphere at 50°C, the three solutions were added to a reaction kettle containing deionized water, the stirring speed was controlled, the reaction pH was adjusted to be stable at 11.2, and the reaction was continuously stirred for 18h. After aging, the precursor material (Ni 0.242 Co 0.242 Mn 0.424 )(OH)2 was obtained after washing, filtering and drying.

[0169] 2) The obtained precursor material and lithium carbonate were weighed according to the molar ratio of 1:1.2, mixed and stirred uniformly, and then sintered at 900°C in air or oxygen atmosphere, with a holding time of 12h, and finally naturally cooled to room temperature to obtain the primary sintered product 0.2Li2MnO3·0.8LiNi 0.33 Co 0.33 Mn 0.33 O2.

[0170] 3) The primary sintered material and ZrO were weighed according to the molar ratio of 1:0.01 of the total amount of nickel, cobalt and manganese elements in the material to zirconium element, mixed uniformly, and sintered at 700°C for 3h to obtain the secondary sintered product 0.2Li2MnO3·0.8LiNi 0.33 Co 0.33 Mn 0.32 Zr 0.01 O2.

[0171] 4) The secondary sintered sintered material and WO3 were mixed uniformly according to the mass ratio of 1:0.01, and sintered at 450°C for 6h to obtain the lithium-rich manganese-based positive electrode material 0.2Li2MnO3·0.8LiNi 0.33 Co 0.33 Mn 0.32 Zr 0.01 O2@WO3.

[0172] In the molecular formula of the lithium-rich manganese-based positive electrode material prepared in this example, @ is used to separate the main material and the coating layer, 0.2Li2MnO3·0.8LiNi 0.33 Co 0.33 Mn 0.32 Zr 0.01O2 represents the host material, WO3 represents the coating layer, and residual lithium such as Li2CO3 and LiOH is not shown.

[0173] It should be noted that in other embodiments and comparative examples of the present application, the interpretation of the molecular formula of the prepared lithium-rich manganese-based positive electrode material is similar to that of the present embodiment, and can be referred to the present embodiment. For the sake of brevity, the present text will not be repeated.

[0174] Example 2

[0175] The difference from Example 1 is that the element ratio of nickel, cobalt and manganese in step 1) is 1:1:2.286, and the molar ratio of the precursor and lithium carbonate in step 2) is changed to 1:1.3, and finally 0.3Li2MnO3·0.7LiNi 0.33 Co 0.33 Mn 0.32 Zr 0.01 O2@WO3.

[0176] Example 3

[0177] The difference from Example 1 is that the element ratio of nickel, cobalt and manganese in step 1) is 1:1:1.529, and the molar ratio of the precursor and lithium carbonate in step 2) is changed to 1:1.15, and finally 0.15Li2MnO3·0.85LiNi 0.33 Co 0.33 Mn 0.32 Zr 0.0 1O2@WO3.

[0178] Example 4

[0179] The difference from Example 1 is that the element ratio of nickel, cobalt and manganese in step 1) is 1:1:1.133, and the molar ratio of the precursor and lithium carbonate in step 2) is changed to 1:1.1, and finally 0.1Li2MnO3·0.9LiNi 0.33 Co 0.33 Mn 0.32 Zr 0.01 O2@WO3.

[0180] Example 5

[0181] The difference from Example 1 is that the element ratio of nickel, cobalt and manganese in step 1) is 1:1:4, and the molar ratio of the precursor and lithium carbonate in step 2) is changed to 1:1.5, and finally 0.5Li2MnO3·0.5LiNi 0.33 Co 0.33 Mn 0.32 Zr 0.01 O2@WO3.

[0182] Example 6-Example 7

[0183] The difference from Example 1 is that the compound containing doping element R added in step 3) is changed from ZrO to Nb2O5 and MoO, respectively.

[0184] Example 8

[0185] The difference from Example 1 is that the compound containing doping element R ZrO is not added in step 3), and the secondary sintering is directly performed.

[0186] Example 9

[0187] The difference from Example 1 is that the corresponding transition metal salt is weighed according to the molar ratio of nickel-cobalt-manganese-zirconium elements of 1:1:1.75:0.06 in step 1) to prepare the bottom solution, and the compound containing doping element R ZrO is not added in step 3), and the secondary sintering is directly performed. In the finally prepared lithium-rich manganese-based positive electrode material, Zr is directly doped in the bulk phase of the main material.

[0188] Examples 10-11

[0189] 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.

[0190] Examples 12-15

[0191] The difference from Example 1 is that the mass ratio of the sintered material after secondary sintering and WO3 in step 4) is changed to 1:0.005, 1:0.02, 1:0.05 and 1:0.1, respectively.

[0192] Example 16

[0193] The difference from Example 1 is that the compound containing doping element M WO3 is not added in step 4), and the third sintering is directly performed to obtain a lithium-rich manganese-based positive electrode material without a coating layer.

[0194] Examples 17-18

[0195] The difference from Example 1 is that the temperature of the primary sintering in step 2) is changed to 800°C and 1000°C, respectively.

[0196] Comparative Example 1

[0197] The difference from Example 1 is that the molar ratio of nickel-cobalt-manganese elements in step 1) is 1:1:8, and the molar ratio of the precursor and lithium carbonate in step 2) is changed to 1:1.7. The finally prepared 0.7Li2MnO3·0.3LiNi 0.33 Co 0.33 Mn 0.32 Zr 0.01 O2@WO3.

[0198] The above description of various embodiments and comparative examples tends to emphasize the differences between the various embodiments and comparative examples, and the same or similar parts can be referred to each other, and for the sake of brevity, will not be repeated here.

[0199] (2) Preparation of positive electrode sheet

[0200] The lithium-rich manganese-based positive electrode material prepared above, conductive agent (super-P), carbon nanotube (CNT), and polyvinylidene fluoride (PVDF) were prepared into a positive electrode slurry in a mass ratio of 94:1.5:0.5:3, coated on a 13 μm Al foil, vacuum dried at 120°C, cold-pressed, and cut and banded to obtain a positive electrode sheet.

[0201] (3) Preparation of negative electrode sheet

[0202] The graphite negative electrode material, conductive agent (Super P), binder (SBR), and thickening agent (CMC-Na) were prepared into a negative electrode slurry in a mass ratio of 96.2:0.8:1.8:1.2, coated on a 8 μm copper foil, vacuum dried at 120°C, cold-pressed, cut and banded to obtain a negative electrode sheet.

[0203] (4) Assembly of battery

[0204] The positive electrode sheet, separator, and negative electrode sheet were stacked in order with the separator in the middle of the anode and cathode to play a separating role, and then wound and placed in an outer package, injected with prepared electrolyte, and subjected to processes such as packaging, liquid injection, formation, and degassing to obtain a lithium ion battery.

[0205] Those skilled in the art can understand that in the above method of the specific embodiments and comparative examples, the writing order of each step does not mean a strict execution order and does not constitute any limitation on the implementation process, and the specific execution order of each step should be determined by its function and possible internal logic.

[0206] II. Test methods

[0207] (1) X-ray diffraction test

[0208] The determination conditions of X-ray diffraction are as follows: Cu target, tube voltage 40 V, tube current 40 mA, scanning speed 2° / min, 2θ scanning range 15°-70°, step length 0.02°, emission slit (DS) 1 mm, anti-scattering slit (SS) 8 mm, and graphite monochromator.

[0209] wherein,

[0210] The confirmation method or standard of the diffraction peak area is JIS K 0131-1996.

[0211] The method for confirming the half-peak width of the diffraction peak or the standard is JIS K 0131-1996.

[0212] (2) Capacity test

[0213] A coin cell was assembled with the positive electrode tab in the "Preparation of battery monomer" section as the positive electrode and lithium sheet as the negative electrode. The charge and discharge capacity at 2.8-4.35 V and 2.8-4.8 V at 0.1C rate was tested at a temperature of 25℃±2℃; at the same time, the coulombic efficiency was calculated according to the charge and discharge capacity, and the first cycle coulombic efficiency = first cycle discharge capacity / first cycle charge capacity x 100%.

[0214] (3) Cycle performance test

[0215] The lithium ion battery in the "Preparation of battery monomer" section was subjected to charge and discharge cycle test at 0.33C rate at 25℃, and the charge and discharge capacity retention rate of the lithium ion battery after cycling for a specified number of cycles was obtained under the specified voltage conditions, the charge capacity retention rate = first cycle charge capacity / charge capacity at a specified number of cycles x 100%, and the discharge capacity retention rate at a specified number of cycles = first cycle discharge capacity / discharge capacity at a specified number of cycles x 100%.

[0216] (4) Chemical composition test

[0217] 1) Confirmation of molecular formula: The inductively coupled plasma atomic emission spectrometry method can be used to test the content of each element in the substance according to the standard EPA6010D-2014.

[0218] 2) Detection of mass content of Li2CO3 and mass content of LiOH: The general method for determination of chemical reagent acidity and alkalinity can be used for determination (GB / T 9724-2007).

[0219] III. Experimental conditions and test results

[0220] The main experimental conditions and test results in each experimental group are shown in Tables 1-4 and Figures 8-13 For experimental conditions not described, refer to the above description of specific examples and comparative examples, which will not be repeated here.

[0221] Table 1

[0222]

[0223] Table 2

[0224]

[0225]

[0226] Table 3

[0227]

[0228] Table 4

[0229]

[0230] Figure 8 SEM image of the lithium-rich manganese-based positive electrode material prepared in Example 1 of the present application; according to Figure 8 It can be seen that the lithium-rich manganese-based positive electrode material prepared in Example 1 presents a polycrystalline particle morphology composed of a plurality of primary small particles, and has good sphericity and roundness.

[0231] Figure 9 XRD image of the lithium-rich manganese-based positive electrode material prepared in Example 1 of the present application; according to Figure 9 It can be seen that the lithium-rich manganese-based positive electrode material has obvious diffraction peaks in the range of 19°-22° and 43°-46°, respectively corresponding to the (020) crystal plane of the Li2MnO3 phase and the (104) crystal plane of the lithium nickel cobalt manganese oxide.

[0232] Figure 10 Charge-discharge curves of the lithium-rich manganese-based positive electrode material prepared in Example 1 of the present application at 0.1C in the range of 2.8V-4.35V and 2.8V-4.8V, Figure 11 Charge-discharge curves of the lithium-rich manganese-based positive electrode material prepared in Example 5 of the present application at 0.1C in the range of 2.8V-4.35V and 2.8V-4.8V; according to Figure 10 and Figure 11 It can be seen that the lithium-rich manganese-based positive electrode material provided in Example 1 has a capacity obviously higher than that of Example 5 below 4.35V, and has greater application value at low voltage.

[0233] Figure 12 Charging capacity retention rate curve of the lithium-rich manganese-based positive electrode material prepared in Example 1 of the present application at 0.33C in the cycle process in the range of 2.8V-4.35V and 2.8V-4.8V; Figure 13 Charging capacity ratio curve of the lithium-rich manganese-based positive electrode material prepared in Example 1 of the present application at 0.33C in the cycle process in the range of 2.8V-4.35V and 2.8V-4.8V; according to Figure 12 and Figure 13 It can be seen that the charging capacity retention rate of the lithium-rich manganese-based positive electrode material provided in Example 1 at low voltage is higher than that at high voltage, and the ratio of the charging capacity in the range of 2.8V-4.35V to the charging capacity in the range of 2.8V-4.8V is always above 40%.

[0234] Figure 14 Secondary sintered product 0.2Li2MnO3·0.8LiNi 0.33 Co0.33 Mn 0.32 Zr 0.01 The mass percentage and atomic percentage of Zr element corresponding to each site in the spectrum of the SEM image of the O2 slice are shown in Table 5.

[0235] Table 5

[0236]

[0237] The ratio of the Zr element content of each surface site to the Zr element content at site 12 is calculated in atomic percentage, and is rounded to two decimal places.

[0238] Based on the above Tables 1-4 and Figures 7-13 The brief analysis is as follows:

[0239] In Examples 1-5 and Comparative Example 1:

[0240] As the area ratio of the first specified diffraction peak to the second specified diffraction peak decreases, the Li2MnO3 molar content decreases, and the half-peak width of the first specified diffraction peak increases (meaning that the grain size is more uneven and has more defects), which means that the stability of the material will decrease at a lower Li2MnO3 content, i.e., the presence of an appropriate amount of Li2MnO3 phase can stabilize the material structure and improve the electrochemical performance of the material. The ratio of the first cycle charge capacity of the lithium-rich manganese-based positive electrode material at a voltage of 2.8V-4.35V to the first cycle charge capacity of the lithium-rich manganese-based positive electrode material at a voltage of 2.8V-4.8V gradually increases from 23.2% to 65%, and the first cycle discharge capacity of the lithium-rich manganese-based positive electrode material at a low voltage of 2.8V-4.35V increases from 57.7mAh / g to 157mAh / g.

[0241] Wherein, when the area ratio of the first specified diffraction peak to the second specified diffraction peak is too large, for example, >0.2 (Example 5) and especially >0.3 (Comparative Example 1), the ratio of the first cycle charge capacity of the lithium-rich manganese-based positive electrode material at a voltage of 2.8V-4.35V to the first cycle charge capacity of the lithium-rich manganese-based positive electrode material at a voltage of 2.8V-4.8V is relatively low, and the first cycle discharge capacity of the lithium-rich manganese-based positive electrode material at a low voltage of 2.8V-4.35V is relatively low.

[0242] Wherein, as the area ratio of the first specified diffraction peak to the second specified diffraction peak decreases, when the Li2MnO3 molar content decreases to a certain standard, for example, after decreasing to 0.2 (Example 1), as the Li2MnO3 molar content 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 positive electrode material.

[0243] In Examples 1 and 6-9:

[0244] The surfaces of the lithium-rich manganese-based positive electrode materials in Embodiment 1, Embodiment 6 and Embodiment 7 are respectively doped with Zr, Nb and Mo, and the lithium-rich manganese-based positive electrode materials all have good cycle stability and high first cycle charge-discharge capacity at low voltage.

[0245] In Embodiment 8, Zr is not doped, and compared with Embodiment 1, the ratio of the first cycle charge capacity of the lithium-rich manganese-based positive electrode material at 2.8V-4.35V voltage to the first cycle charge capacity of the lithium-rich manganese-based positive electrode material at 2.8V-4.8V voltage decreases, and the cycle stability of the lithium-rich manganese-based positive electrode material decreases.

[0246] In Embodiment 9, Zr is doped in the bulk phase, and compared with Embodiment 1 in which Zr is doped on the surface, the cycle stability of the lithium-rich manganese-based positive electrode material decreases, and the first cycle discharge capacity of the lithium-rich manganese-based positive electrode material at low voltage also decreases.

[0247] In Embodiment 1 and Embodiments 10-16:

[0248] The surfaces of the lithium-rich manganese-based positive electrode materials in Embodiment 1, Embodiment 10 and Embodiment 11 are respectively coated with coating layers containing WO3, TiO2 and CoO, and the lithium-rich manganese-based positive electrode materials all have good cycle stability and high first cycle charge-discharge capacity at low voltage.

[0249] In Embodiments 1, Embodiments 12-15, the mass ratios of the coating layers in the lithium-rich manganese-based positive electrode materials are different, wherein, when the mass ratio of the coating layer in the lithium-rich manganese-based positive electrode material is low, the degree of improvement of the cycle stability of the lithium-rich manganese-based positive electrode material is relatively low; when the mass ratio of the coating layer in the lithium-rich manganese-based positive electrode material is high, the first cycle discharge capacity of the lithium-rich manganese-based positive electrode material at low voltage decreases.

[0250] In Embodiment 16, the surface of the host material is not coated with a coating layer, and compared with Embodiment 1, the setting of the coating layer effectively improves the cycle stability and the first cycle charge-discharge capacity at low voltage of the lithium-rich manganese-based positive electrode material.

[0251] In Embodiments 1, Embodiment 17 and Embodiment 18:

[0252] The temperatures of one-time sintering in Embodiment 1, Embodiment 17 and Embodiment 18 are different, and the residual lithium (including Li2CO3 and LiOH) contents in the corresponding lithium-rich manganese-based positive electrode materials are different, wherein, the residual lithium mass content in Embodiment 1 is higher than that in Embodiment 18, and the lithium-rich manganese-based positive electrode material in Embodiment 1 has better cycle stability and higher first cycle charge-discharge capacity at low voltage, because within a certain range, appropriate residual lithium can strengthen the structural strength of the coating layer and the host material and inhibit side reactions, and at the same time, the residual lithium can provide lithium ion transmission sites as a solid-state electrolyte layer to make the material have better capacity and cycle performance.

[0253] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the description of the present application. In particular, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any way. 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 lithium-rich manganese-based positive electrode material, characterized in that, The lithium-rich manganese-based positive electrode material comprises 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 a Bragg angle of 19°-22°, and the B phase has a second specified diffraction peak distributed in the range of a Bragg angle of 43°-46°, and 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.

2. The lithium-rich manganese-based positive electrode material according to claim 1, characterized in that, In the X-ray diffraction pattern, the half-peak width of the first specified diffraction peak is 0.2°-0.8°. 3.The lithium-rich manganese-based cathode material of claim 1 or 2, characterized in that, In the lithium-rich manganese-based positive electrode material, the molar content ratio of the A phase to the B phase is a:(1-a), 0 4. The lithium-rich manganese-based positive electrode material according to claim 3, characterized in that, 0.1≤a≤0.3。 5. The lithium-rich manganese-based positive electrode material according to any one of claims 1 to 4, characterized in that, 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) ; 0 6.The lithium-rich manganese-based cathode material of any one of claims 1-5, wherein, 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.

7. The lithium-rich manganese-based positive electrode material according to claim 6, characterized in that, The main material of the lithium-rich manganese-based positive electrode material comprises a surface layer part and a central part, the surface layer part comprises a part within a first specified distance from the surface of the main material, the first specified distance is 20% of the volume average particle size Dv50 of the main material, the central part comprises a part above a second specified distance from the surface of the main material, the second specified distance is 70% of the volume average particle size Dv50 of the main material, the content of element R at the surface layer part is greater than the content of 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.

8. The lithium-rich manganese-based positive electrode material according to claim 6 or 7, characterized in that The ratio of the content of element R at the surface layer part to the content of element R at the central part is (3-9):

1. The lithium-rich manganese-based positive electrode material further comprises a coating layer distributed on at least part of the surface of the main material.

9. The lithium-rich manganese-based positive electrode material of claim 8, characterized in that, The coating layer comprises element M, and the element M includes one or more of Nb, W, Mo, Co, and Ti.

10. The lithium-rich manganese-based positive electrode material according to any one of claims 1 to 9, characterized in that, The mass proportion of the coating layer based on the mass of the lithium-rich manganese-based positive electrode material is w1, 0 The lithium-rich manganese-based positive electrode material comprises Li2CO3 and / or LiOH, and at least one of the following conditions (a1) and (a2) is met: (a1) The mass content of Li2CO3 is 200ppm-3500ppm based on the mass of the lithium-rich manganese-based positive electrode material; 11. The lithium-rich manganese-based positive electrode material of claim 10, characterized in that, (a2) The mass content of LiOH is ≤2000ppm based on the mass of the lithium-rich manganese-based positive electrode material. At least one of the following conditions (b1) and (b2) is met: (b1) The mass content of Li2CO3 is 500ppm-2000ppm based on the mass of the lithium-rich manganese-based positive electrode material; 12. The lithium-rich manganese-based positive electrode material according to any one of claims 1 to 11, characterized in that, (b2) The mass content of LiOH is ≤1500ppm based on the mass of the lithium-rich manganese-based positive electrode material. At least one of the following conditions (c1) and (c2) is met: (c1) the lithium-rich manganese-based positive electrode material has a volume average particle size Dv50 of 4 µm to 9 µm; (c2) the lithium-rich manganese-based positive electrode material has a specific surface area of 0.5 m 2 / g ~ 1.2 m 2 / g.

13. A positive electrode sheet characterized by comprising: The lithium-rich manganese-based positive electrode material as claimed in any one of claims 1 to 12.

14. A battery cell, characterized by The positive electrode sheet as claimed in claim 13.

15. The battery cell of claim 14, wherein, The battery cell as claimed in claim 14 or 15.

16. A battery, characterized by The battery cell as claimed in claim 14 or 15.

17. An electrical device, characterized by The battery as claimed in claim 16.

18. A method of producing the lithium-rich manganese-based positive electrode material according to any one of claims 1 to 12, characterized by, Comprising: sintering the mixture of the precursor material containing the transition metal salt and the lithium salt at least once.

19. The method of claim 18, wherein, The sintering temperature of the first sintering is 650 °C to 1050 °C.

20. The method of claim 18, wherein, The sintering temperature of the first sintering is 800 °C to 1000 °C.

21. The production method according to claim 18 or 19, characterized by, Further comprising: mixing the sintering product of the first sintering with a material containing an element R and sintering a second time; wherein the element R comprises one or more of Al, Zr, Ti, Nb, Te, Sb, W, Mo and Mg.

22. The method of claim 21, wherein, Further comprising: mixing the sintering product of the second sintering with a material containing an element M and sintering a third time; wherein the element M comprises one or more of Nb, W, Mo, Co and Ti.

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