Positive electrode active material and preparation method thereof, positive electrode sheet, secondary battery and electrical device

Abstract

The present application provides a positive electrode active material and a preparation method thereof, a positive electrode plate, a secondary battery and an electric device. The positive electrode active material includes an active substance, the active substance includes lithium nickel manganese oxide, the lithium nickel manganese oxide includes a spinel phase and a rock salt phase, and the X-ray diffraction analysis spectrum of the lithium nickel manganese oxide has a first diffraction peak at a diffraction angle 2θ of 18° to 19°, a second diffraction peak at a diffraction angle 2θ of 44° to 45°, and a third diffraction peak at a diffraction angle 2θ of 43° to 44°. The first diffraction peak corresponds to a crystal plane (111), and the second diffraction peak corresponds to a crystal plane (400); the peak intensity of the first diffraction peak is 1 (111) , the peak intensity of the second diffraction peak is I (400) , I (111) with I (400) Between: 2.5≤I (111) / I (400) ≤4.0; the lithium nickel manganese oxide satisfies the chemical formula Li x M y Ni z Mn 2‑y‑z O 4‑k , wherein 0.8≤x≤1.05, 0≤y≤0.2, 0.3≤z≤0.7, -0.1≤k≤0.5, and M includes one or more of B, Si, P, S, Nb, Mo, Ru, Te, Ce, Ta, and W. The positive electrode active material provided in this application can improve the storage performance of a secondary battery.

Description

[0001] Related applications

[0002] This application is a divisional application of the Chinese patent application filed on October 16, 2023, with application number CN2023113319584, and entitled "Positive electrode active material and preparation method thereof, positive electrode sheet, secondary battery and electrical device", the full text of which is hereby incorporated by reference. Technical Field

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

[0004] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0005] In recent years, the application of secondary batteries, represented by lithium-ion batteries, has become increasingly widespread. They are widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As secondary batteries have achieved significant development, higher requirements have been placed on their cycle performance and storage performance. Summary of the Invention

[0006] The present application provides a positive electrode active material and a preparation method thereof, a positive electrode plate, a secondary battery and an electrical device, which can improve the storage performance of the secondary battery.

[0007] In order to achieve the above-mentioned object, the first aspect of the present application provides a positive electrode active material, including an active substance, wherein the active substance includes lithium nickel manganese oxide, and the lithium nickel manganese oxide contains a spinel phase. The X-ray diffraction analysis spectrum of the lithium nickel manganese oxide has a first diffraction peak at a diffraction angle 2θ of 18°~19°, and a second diffraction peak at a diffraction angle 2θ of 44°~45°, wherein the first diffraction peak corresponds to a crystal plane (111), and the second diffraction peak corresponds to a crystal plane (400); the peak intensity of the first diffraction peak is I (111) , the peak intensity of the second diffraction peak is 1 (400) , I (111) with I (400) Between: 2.5≤I (111) / I (400) ≤4.

[0008] The positive electrode active material provided by the present application includes lithium nickel manganese oxide containing a spinel phase, (111) / I (400)Keeping the ratio within the above range can improve the preference for the (111) facet, thereby improving the stacking quality of the (111) facet and thus enhancing the stability of the spinel phase. The more stable the spinel phase, the slower the dissolution of transition metal ions (such as manganese ions) from the lithium nickel manganese oxide, and the slower the capacity loss rate of the negative electrode and battery, which is beneficial for improving the storage performance of the battery.

[0009] In some embodiments of the present application, the lithium nickel manganese oxide satisfies: 2.8≤I (111) / I (400) ≤3.8.

[0010] In some embodiments of the present application, the lithium nickel manganese oxide satisfies: 3.1≤I (111) / I (400) ≤3.6.

[0011] I (111) / I (400) Being within the above range is beneficial to further improve the stability of the spinel structure, thereby further reducing the dissolution of transition metal ions (such as manganese ions) in lithium nickel manganese oxide, thereby further improving the storage performance of the battery.

[0012] In some embodiments of the present application, the lithium nickel manganese oxide satisfies the chemical formula Li x M y Ni z Mn 2-y-z O 4-k , wherein 0.8≤x≤1.05, 0≤y≤0.2, 0.3≤z≤0.7, -0.1≤k≤0.5, and M includes one or more of B, Si, P, S, Nb, Mo, Ru, Te, Ce, Ta and W.

[0013] Lithium nickel manganese oxide satisfies the above chemical formula, and the lithium element content x is within the above range, which can not only enhance the preference for the (111) plane in the spinel structure and improve the stability of the spinel structure; but also ensure the proportion of active lithium ions in the lithium nickel manganese oxide and the diffusion channel of active lithium ions, so that the positive electrode active material has sufficient cycle activity.

[0014] In some embodiments of the present application, the lithium nickel manganese oxide satisfies at least one of the following conditions:

[0015] (1) 0.85≤x≤1.02;

[0016] (2) 0.01≤y≤0.2.

[0017] In some embodiments of the present application, the lithium nickel manganese oxide satisfies at least one of the following conditions:

[0018] (1) 0.9≤x≤0.99;

[0019] (2) 0.02≤y≤0.1.

[0020] In the above chemical formula, the content of M element is within the above range. On the one hand, while ensuring a relatively high lithium content, it can also make I (111) / I (400) At a relatively high level, the preference for the (111) face in the spinel structure is increased, thereby improving the stability of the spinel structure. On the other hand, since the M element itself cannot change valence and will occupy and reduce the proportion of active lithium ions in the lithium nickel manganese oxide, the M element content is within the above range, which can ensure that the positive electrode active material has sufficient cycle activity.

[0021] In some embodiments of the present application, the lithium nickel manganese oxide comprises a rock salt phase, and the X-ray diffraction analysis spectrum of the lithium nickel manganese oxide has a third diffraction peak at a diffraction angle 2θ of 43° to 44°, and the peak intensity of the third diffraction peak is 1 RS , the I RS With the I (400) Satisfy between: 0.01≤I RS / I (400) ≤0.2.

[0022] Lithium nickel manganese oxide contains a rock salt phase, and the nickel in the rock salt phase is stable low-valent nickel. RS / I (400) Controlling the content within the above range, that is, controlling the rock salt phase content within the above range, can effectively reduce the oxidative decomposition of the electrolyte by the high-valent nickel formed by separating from the spinel phase, thereby reducing the oxidation of the electrolyte.

[0023] In some embodiments of the present application, the I RS With the I (400) Satisfy between: 0.02≤I RS / I (400) ≤0.1.

[0024] In some embodiments of the present application, the I RS With the I (400) Satisfy between: 0.05≤I RS / I (400) ≤0.1.

[0025] I RS / I (400) Being within the above range is beneficial to further reduce the oxidative decomposition of the electrolyte and further reduce the dissolution of transition metal ions in the spinel phase, thereby further improving the storage performance of the battery.

[0026] In some embodiments of the present application, the lithium nickel manganese oxide satisfies the following conditions: 3.5≤(I (111) +10×I RS ) / I (400) ≤4.4.

[0027] In some embodiments of the present application, the lithium nickel manganese oxide satisfies the following conditions: 3.6≤(I (111) +10×I RS ) / I (400) ≤4.1.

[0028] In lithium nickel manganese oxide, (I (111) +10×I RS ) / I (400) Controlling within the above range is beneficial to reducing the adverse effects of the spinel phase and rock salt phase on the material capacity and kinetics, and improving the capacity and kinetic performance of the material and battery.

[0029] In some embodiments of the present application, the lithium nickel manganese oxide comprises grains of the spinel phase and grains of the rock salt phase, and the grains of the rock salt phase cover at least a portion of the surface of the grains of the spinel phase in the form of a rock salt phase layer.

[0030] Lithium nickel manganese oxide contains spinel phase grains and rock salt phase grains. Among them, the spinel phase grains provide a bulk structure for lithium nickel oxide. This bulk structure has relatively high stability, which can make the dissolution of transition metal ions in lithium nickel manganese oxide relatively slow; while the rock salt phase grains can reduce the oxidative decomposition of the electrolyte by the high-valent nickel formed by separating from the spinel phase, thereby reducing the oxidation of the electrolyte.

[0031] In some embodiments of the present application, the thickness of the rock salt phase layer is 20 nm to 200 nm.

[0032] The thickness of the rock salt phase layer is within the above range, which can improve the battery storage performance while also taking into account long life and capacity.

[0033] In some embodiments of the present application, the active material further includes phosphate, and the mass percentage of the phosphate in the active material is m, 0.2%≤m≤20%.

[0034] Among the active materials, the phosphate ions in the phosphate can not only preferentially capture HF formed by the oxidative decomposition of the electrolyte, reducing the corrosion of the electrolyte on the positive electrode active material; at the same time, they can also capture transition metal ions and inhibit the dissolution of transition metal ions in lithium nickel manganese oxide, thereby improving the storage performance of the battery.

[0035] In some embodiments of the present application, the positive electrode active material satisfies at least one of the following conditions:

[0036] (1) The m mentioned above satisfies: 0.5%≤m≤10%;

[0037] (2) the phosphate is coated on at least a portion of the surface of the lithium nickel manganese oxide;

[0038] (3) The phosphate includes at least one of orthophosphate, hydrogen phosphate, dihydrogen phosphate, metaphosphate, pyrophosphate, polyphosphate, hypophosphite, phosphite, monofluorophosphate, difluorophosphate and trifluorophosphate containing at least one element of Li, Na, K, Mg, Al, Ti, Zr, La, Ta, Nb, Te, Mo, W, Sb, Ni, Mn, Fe, Co and N.

[0039] Phosphate is coated on at least a portion of the surface of lithium nickel manganese oxide, which can effectively play the role of the phosphate in the active material without affecting the phase structure (spinel phase and rock salt phase) of lithium nickel manganese oxide.

[0040] In some embodiments of the present application, the active material includes particles of the active material, the particles of the active material include at least one of single crystal grains and quasi-single crystal grains, and the single crystal grains include at least one of truncated octahedral grains and spherical grains.

[0041] In the particles of the active material, the rock salt phase is mainly distributed on the surface of the particles. Therefore, when the particles of the active material include single crystal grains and / or single-crystal-like grains, more rock salt phases will be distributed on each surface of the single crystal grains or single-crystal-like grains, which is more conducive to improving the long-term stability of the positive electrode active material and the battery.

[0042] In some embodiments of the present application, the positive electrode active material satisfies at least one of the following conditions:

[0043] (1) The compaction density P of the positive electrode active material under a pressure of 6 tons satisfies: P ≥ 3 g / cm 3 ;

[0044] (2) The volume average particle size Dv50 of the positive electrode active material satisfies: 2 μm ≤ Dv50 ≤ 20 μm;

[0045] (3) The volume average particle sizes Dv50, Dv90 and Dv10 of the positive electrode active material satisfy the following conditions: 0.8≤(Dv90-Dv10) / Dv50≤2;

[0046] (4) The specific surface area S of the positive electrode active material satisfies: 0 <S≤1m 2 / g;

[0047] (5) The pH value of the positive electrode active material satisfies: 9≤pH≤12.

[0048] In some embodiments of the present application, the positive electrode active material satisfies at least one of the following conditions:

[0049] (1) The compaction density P of the positive electrode active material under 6 tons of pressure satisfies: 3g / cm 3 ≤P≤3.5g / cm 3 ;

[0050] (2) The volume average particle size Dv50 of the positive electrode active material satisfies: 3 μm ≤ Dv50 ≤ 15 μm;

[0051] (3) The volume average particle sizes Dv50, Dv90 and Dv10 of the positive electrode active material satisfy the following conditions: 1.0≤(Dv90-Dv10) / Dv50≤1.8;

[0052] (4) The specific surface area S of the positive electrode active material satisfies: 0 <S≤0.7m 2 / g;

[0053] (5) The pH value of the positive electrode active material satisfies: 10≤pH≤12.

[0054] The compaction density of the positive electrode active material of the present application is within the relatively high range mentioned above, which can make the material particles have a morphology that is more conducive to dense stacking, so the pressure required to achieve the same compaction is smaller, and the particles are less likely to break, thereby reducing the risk of particle cracking and reducing the side reactions and transition metal ion dissolution caused by particle cracking.

[0055] A second aspect of the present application further provides a method for preparing a positive electrode active material, comprising:

[0056] The mixture containing lithium source, nickel source and manganese source is sintered to obtain positive electrode active material.

[0057] The positive electrode active material includes an active substance, the active substance includes lithium nickel manganese oxide, the lithium nickel manganese oxide contains a spinel phase, the X-ray diffraction analysis spectrum of the lithium nickel manganese oxide has a first diffraction peak at a diffraction angle 2θ of 18° to 19°, and a second diffraction peak at a diffraction angle 2θ of 44° to 45°, the first diffraction peak corresponds to the crystal plane (111), and the second diffraction peak corresponds to the crystal plane (400); the peak intensity of the first diffraction peak is 1 (111) , the peak intensity of the second diffraction peak is 1 (400) , and I (111) with I (400) Between: 2.5≤I (111) / I (400) ≤4.

[0058] In the above steps, by sintering the mixture containing the lithium source, the nickel source, and the manganese source, a lithium nickel manganese oxide meeting the above conditions can be obtained, and a spinel phase is formed in the lithium nickel manganese oxide.

[0059] In some embodiments of the present application, the lithium nickel manganese oxide satisfies the chemical formula Li x M y Ni z Mn 2-y-z O 4-k , wherein 0.8≤x≤1.05, 0≤y≤0.2, 0.3≤z≤0.7, -0.1≤k≤0.5, and M includes one or more of B, Si, P, S, Nb, Mo, Ru, Te, Ce, Ta and W.

[0060] In some embodiments of the present application, the sintering process includes:

[0061] The mixture is heated to a first sintering temperature T1, maintained at the first sintering temperature T1 for a first preset time t1, and then cooled to room temperature at a first cooling rate v1 to obtain a sintered product.

[0062] By performing the sintering treatment under the conditions of step S110, the spinel phase and the rock salt phase can be formed simultaneously, and by regulating the first sintering temperature T1 and the first cooling rate v1, the formation and content of the spinel phase and the rock salt phase in the lithium nickel manganese oxide can be regulated, thereby achieving the goal of I (111) / I (400) and I RS / I (400) The values ​​are regulated so that they each meet the range provided in the first aspect of this application.

[0063] In some embodiments of the present application, the method satisfies at least one of the following conditions:

[0064] (1) The first sintering temperature T1 satisfies: 900°C ≤ T1 ≤ 1500°C, and T1 ≥ x × 1000°C;

[0065] (2) The first preset time t1 satisfies: 1h≤t1≤20h;

[0066] (3) The first cooling rate v1 satisfies: v1 ≥ 10°C / min.

[0067] In some embodiments of the present application, the method satisfies at least one of the following conditions:

[0068] (1) The first sintering temperature T1 satisfies: 1000°C ≤ T1 ≤ 1300°C;

[0069] (2) The first preset time t1 satisfies: 2h≤t1≤15h;

[0070] (3) The first cooling rate v1 satisfies: 10°C / min≤v1≤50°C / min.

[0071] During the sintering process, the stable phases at high temperature are spinel phase (Mn-rich part) and rock salt phase (Ni-rich part). Therefore, when T1 is in the relatively high temperature range mentioned above, it is conducive to the formation of spinel phase and rock salt phase, which is also conducive to I (111) / I (400) and I RS / I (400) It can also reduce the abnormal growth of grains, thereby taking into account the cycle storage life and dynamic performance and processing performance.

[0072] In some embodiments of the present application, the method satisfies at least one of the following conditions:

[0073] (1) The mixture further comprises an M source;

[0074] The M source includes one or more of an oxide, a nitric acid compound, a carbonate compound, a hydroxide compound, and an acetic acid compound containing an M element, and the M element includes one or more of B, Si, P, S, Nb, Mo, Ru, Te, Ce, Ta, and W;

[0075] (2) The lithium source includes one or more of lithium oxide, lithium phosphate, lithium dihydrogen phosphate, lithium acetate, lithium hydroxide, lithium carbonate and lithium nitrate;

[0076] (3) The nickel source includes one or more of nickel oxide, nickel phosphate, nickel acetate, nickel hydroxide, nickel carbonate and nickel nitrate;

[0077] (4) The manganese source includes one or more of manganese oxide, manganese phosphate, manganese acetate, manganese hydroxide, manganese carbonate and manganese nitrate.

[0078] The M element has the function of inducing the preferred orientation of the crystal and forming a strong bond with oxygen or transition metal in lithium nickel manganese oxide. Adding M source to the mixture can promote the formation of I 111 / I 400 and I RS / I 400 Reaching the appropriate range mentioned above in this application can better balance capacity and long-term performance.

[0079] In some embodiments of the present application, the sintering process further comprises:

[0080] The material containing the sintered product is heated to a second sintering temperature T2, maintained at the second sintering temperature T2 for a second preset time t2, and then cooled to room temperature at a second cooling rate v2.

[0081] By performing the sintering treatment under the conditions of step S120, the phosphate and the lithium nickel manganese oxide can be melted and mixed, and by regulating the second sintering temperature T2 and the second cooling rate v2, it is beneficial to achieve phosphate coating on the surface of the lithium nickel manganese oxide, so that the phosphate is coated on at least a portion of the surface of the lithium nickel manganese oxide.

[0082] In some embodiments of the present application, the method satisfies at least one of the following conditions:

[0083] (1) The second sintering temperature T2 satisfies: T1-200°C ≤ T2 ≤ T1, T2 ≥ 900°C;

[0084] (2) The second preset time t2 satisfies: 0.5h≤t2≤5h;

[0085] (3) The second cooling rate v2 satisfies: v2 ≥ 10°C / min;

[0086] (4) The material further comprises phosphate, wherein the phosphate comprises at least one of orthophosphate, hydrogen phosphate, dihydrogen phosphate, metaphosphate, pyrophosphate, polyphosphate, hypophosphite, phosphite, monofluorophosphate, difluorophosphate and trifluorophosphate containing at least one element selected from the group consisting of Li, Na, K, Mg, Al, Ti, Zr, La, Ta, Nb, Te, Mo, W, Sb, Ni, Mn, Fe, Co and N.

[0087] In some embodiments of the present application, the method satisfies at least one of the following conditions:

[0088] (1) The second sintering temperature T2 satisfies: T1-100°C ≤ T2 ≤ T1, T2 ≥ 950°C;

[0089] (2) The second cooling rate v2 satisfies: 10°C / min≤v2≤50°C / min.

[0090] The second sintering temperature T2 being within the above range is beneficial to improving the roundness of the lithium nickel manganese oxide grain growth, thereby increasing its compaction density and reducing the specific surface area.

[0091] The third aspect of the present application provides a positive electrode plate, comprising a positive electrode active material layer, wherein the positive electrode active material layer comprises the positive electrode active material of the first aspect of the present application or the positive electrode active material prepared by the method of the second aspect of the present application.

[0092] In some embodiments of the present application, the compaction density P' of the positive electrode active material layer satisfies: P'≥2.9 g / cm 3 .

[0093] In some embodiments of the present application, the compaction density P' of the positive electrode active material layer satisfies: 3 g / cm 3 ≤P'≤3.6g / cm 3 .

[0094] The compaction density of the positive electrode active material layer is within the above range, which is beneficial to improving the volume energy density of the battery cell and reducing side reactions and dissolution of transition metal ions. It also allows sufficient gaps in the positive electrode active material layer to allow the electrolyte to fully infiltrate and maintain normal dynamic performance of the battery.

[0095] The fourth aspect of the present application provides a secondary battery, comprising the positive electrode sheet of the third aspect of the present application.

[0096] A fifth aspect of the present application provides an electrical device comprising the secondary battery according to the fourth aspect of the present application.

[0097] The electric device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.

[0098] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0099] In order to better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes currently understood for these applications. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the accompanying drawings:

[0100] Figure 1 These are the X-ray diffraction patterns of the positive electrode active materials of Example 1, Example 2 and Comparative Example 1 of the present application.

[0101] Figure 2 This is a scanning electron microscope image of the positive electrode active material according to one embodiment of the present application.

[0102] Figure 3 This is a transmission electron microscope image of a cross section of the positive electrode active material according to one embodiment of the present application.

[0103] Figure 4 This is a schematic diagram of a battery cell according to one embodiment of the present application.

[0104] Figure 5 for Figure 5 FIG. 1 is an exploded view of a battery cell according to an embodiment of the present application.

[0105] Figure 6 This is a schematic diagram of a battery module according to one embodiment of the present application.

[0106] Figure 7 Schematic diagram of a battery pack according to one embodiment of the present application.

[0107] Figure 8 for Figure 7 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0108] Figure 9 FIG. 1 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.

[0109] Description of reference numerals:

[0110] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery module; 5. Battery cell; 5. Casing; 5. Electrode assembly; 5. Cover; 6. Electrical device. DETAILED DESCRIPTION

[0111] Below, some embodiments of the positive electrode active material and its preparation method, positive electrode sheet, secondary battery and electric device of the present application are described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0112] " scope " disclosed in the present application can be limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and any end value can be included or not included independently, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 listed, and if the maximum range value 3,4 and 5 are also listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is merely an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to listing the parameter as, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and so on. For example, when a parameter is expressed as an integer selected from "2-10", this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0113] In this application, "a plurality of" or "a plurality of" refers to a number greater than or equal to 2 unless otherwise specified. For example, "one or more" means one or more than or equal to two.

[0114] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0115] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0116] It will be appreciated by those skilled in the art that, in the methods of various embodiments or examples, the order in which the steps are written does not imply a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible inherent logic. Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0117] In this application, open technical features or technical solutions described with words such as "contain," "include," and "include" do not exclude additional members beyond the listed members, unless otherwise specified. This can be considered as providing both closed features or solutions consisting of the listed members and open features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may or may not include other members unless otherwise specified. This can be considered as providing both the feature or solution that "A consists of a1, a2, and a3," and the feature or solution that "A includes not only a1, a2, and a3, but also other members." In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0118] In this application, the terms "optionally," "optional," and "optional" are optional and refer to either option being present or absent. If a technical solution contains multiple "options," each option is considered independent unless otherwise specified and there are no conflicts or constraints.

[0119] At present, spinel lithium nickel manganese oxide LiNi 0.5 Mn 1.5 When used in full batteries, O4 cathode materials, due to their extremely high lithium insertion / deintercalation potential (4.7V vs Li / Li+) and oxidation of high-valent Ni, cause severe side reactions between the cathode material and the electrolyte. This consumes the electrolyte and produces large amounts of gas, increasing the risk of cell swelling and accelerating capacity decay. Furthermore, the spinel nickel manganese oxide cathode material, due to its unstable structure, experiences dissolution of transition metal ions (such as manganese ions). These dissolved transition metal ions deposit on the anode surface, damaging the SEI film and accelerating capacity decay of the anode and battery, ultimately leading to a decrease in battery storage performance.

[0120] To address the aforementioned technical issues, this application proposes a positive electrode active material. By regulating the crystal structure of the positive electrode active material, this material can not only reduce the positive electrode's oxidative consumption of the electrolyte, but also stabilize the material's structure, significantly reducing the dissolution of transition metal ions from the material, thereby improving the battery's storage performance. This positive electrode active material is described in more detail below.

[0121] In a first aspect, the present application provides a positive electrode active material, which includes an active substance, wherein the active substance includes lithium nickel manganese oxide, the lithium nickel manganese oxide contains a spinel phase, and the X-ray diffraction analysis spectrum of the lithium nickel manganese oxide has a first diffraction peak at a diffraction angle 2θ of 18°~19°, and a second diffraction peak at a diffraction angle 2θ of 44°~45°, the first diffraction peak corresponds to a crystal plane (111), and the second diffraction peak corresponds to a crystal plane (400); the peak intensity of the first diffraction peak is I (111) , the peak intensity of the second diffraction peak is 1 (400) , I (111) with I (400) Between: 2.5≤I (111) / I (400) ≤4.0.

[0122] It can be understood that in the X-ray diffraction analysis spectrum of the above lithium nickel manganese oxide, the first diffraction peak and the second diffraction peak both correspond to the spinel phase of the lithium nickel manganese oxide, that is, the first diffraction peak and the second diffraction peak are both peaks of the spinel phase.

[0123] It can be understood that the above-mentioned “active material” refers to a material that can provide activity to the positive electrode active material and realize battery energy conversion.

[0124] In some embodiments, I (111) / I (400) It can be 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0 or a range consisting of any of the above values.

[0125] The positive electrode active material provided by the present application includes a lithium nickel manganese oxide containing a spinel phase. The first preferred growth crystal plane of the lithium nickel manganese oxide (LNMO) is the (111) plane, that is, the atoms spread and grow layer by layer along the (111) plane, so the stacking quality of the (111) plane determines the stability of the crystal structure. A spinel LNMO grain can have multiple (111) planes (eight sides in the octahedral grain shape) growing synchronously at the same time, forming (a00) sides after contacting each other, so that the (111) plane can serve as the "basal plane" of the spinel phase, and the (a00) plane can serve as the "end face" of the spinel phase. Therefore, in the XRD spectrum of lithium nickel manganese oxide, the ratio of the peak intensity of the "basal plane" (111) to the peak intensity of the end face (a00) is 1 (111) / I (a00) It can indicate the preference of crystal plane (111). In the XRD spectrum of conventional spinel structure lithium nickel manganese oxide, (111) and (400) peaks are two of the three strongest peaks, so this application selects I (111) / I (400) As an indicator of the degree of preference of (111) facets. (111) / I (400) Keeping the ratio within the above range can improve the preference for the (111) facet, thereby improving the stacking quality of the (111) facet and thus enhancing the stability of the spinel phase. The more stable the spinel phase, the slower the dissolution of transition metal ions (such as manganese ions) from the lithium nickel manganese oxide, and the slower the capacity loss rate of the negative electrode and battery, which is beneficial for improving the storage performance of the battery.

[0126] In some embodiments, the lithium nickel manganese oxide satisfies: 2.8≤I (111) / I (400) ≤3.8.

[0127] In some embodiments, the lithium nickel manganese oxide satisfies: 3.1≤I (111) / I (400) ≤3.6.

[0128] In the XRD pattern of spinel lithium nickel manganese oxide, I (111) / I (400) Being within the above range is beneficial to further improve the stability of the spinel structure, thereby further reducing the dissolution of transition metal ions (such as manganese ions) in lithium nickel manganese oxide, thereby further improving the storage performance of the battery.

[0129] X-ray diffraction analysis patterns are well known in the art and can be measured using methods known in the art. For example, the X-ray diffraction analysis patterns of the positive electrode active material can be measured using CuKα1 radiation with reference to JIS K 0131-1996, General Rules for X-ray Diffraction Analysis Methods.

[0130] In some embodiments, the lithium nickel manganese oxide satisfies the chemical formula Li x M y Ni z Mn 2-y-z O 4-k , wherein 0.8≤x≤1.05, 0≤y≤0.2, 0.3≤z≤0.7, -0.1≤k≤0.5, and M includes one or more of B, Si, P, S, Nb, Mo, Ru, Te, Ce, Ta and W.

[0131] In some embodiments, the lithium content x in the lithium nickel manganese oxide may be 0.8, 0.85, 0.9, 0.95, 1.0, 1.05 or any range thereof.

[0132] In the positive electrode active material provided in the present application, the lithium nickel manganese oxide satisfies the above chemical formula, and the content x of the lithium element is within the above range, which can not only enhance the preference for the (111) face in the spinel structure and improve the stability of the spinel structure; but also ensure the proportion of active lithium ions in the lithium nickel manganese oxide and the diffusion channel of active lithium ions, so that the positive electrode active material has sufficient cycle activity.

[0133] In addition, in lithium nickel manganese oxide, the close-packed plane of oxygen or transition metal ions (such as manganese ions) is the (111) plane; and when lithium nickel manganese oxide satisfies the above chemical formula, the M element in the chemical formula can form a strong bond with oxygen or transition metal ions and increase the preference for the (111) plane.

[0134] In some embodiments, 0.85≤x≤1.02. For example, x can be 0.85, 0.88, 0.91, 0.93, 0.95, 0.97, 0.99, 1.01, 1.02, or any range thereof.

[0135] In some embodiments, 0.9≤x≤0.99. For example, x can be 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, or any range thereof.

[0136] In the lithium nickel manganese oxide, the content x of the lithium element is within the above range, which can further improve the stability of the spinel structure while allowing the positive electrode active material to have sufficient cycle activity.

[0137] In some embodiments, the content y of the M element in the lithium nickel manganese oxide may be 0, 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2 or any range thereof.

[0138] In the above chemical formula, the content of M element is within the above range. On the one hand, while ensuring a relatively high lithium content, it can also make I (111) / I (400) At a relatively high level, the preference for the (111) face in the spinel structure is increased, thereby improving the stability of the spinel structure. On the other hand, since the M element itself cannot change valence and will occupy and reduce the proportion of active lithium ions in the lithium nickel manganese oxide, the M element content is within the above range, which can ensure that the positive electrode active material has sufficient cycle activity.

[0139] In some embodiments, 0.01≤y≤0.2. For example, y can be 0.01, 0.03, 0.05, 0.07, 0.09, 0.11, 0.13, 0.15, 0.17, 0.19, 0.2, or any range thereof.

[0140] In some embodiments, 0.02≤y≤0.1. For example, y can be 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any range thereof.

[0141] In lithium nickel manganese oxide, the content y of the M element is within the above range, which can further improve the stability of the spinel structure while enabling the positive electrode active material to have sufficient cycle activity, thereby better balancing the capacity and long-term performance of the positive electrode active material.

[0142] In some embodiments, the lithium nickel manganese oxide comprises a rock salt phase, and the X-ray diffraction analysis spectrum of the lithium nickel manganese oxide has a third diffraction peak at a diffraction angle 2θ of 43° to 44°, and the peak intensity of the third diffraction peak is 1 RS , the I RS With the I (400) Satisfy between: 0.01≤I RS / I (400) ≤0.2.

[0143] It can be understood that in the X-ray diffraction analysis spectrum of the above lithium nickel manganese oxide, the third diffraction peak corresponds to the rock salt phase of the lithium nickel manganese oxide, that is, the third diffraction peak is a peak of the rock salt phase.

[0144] In some embodiments, I RS / I (400) It can be 0.01, 0.03, 0.05, 0.07, 0.09, 0.11, 0.13, 0.15, 0.17, 0.19, 0.2 or within a range consisting of any of the above values.

[0145] Lithium nickel manganese oxide contains a rock salt phase, wherein the nickel in the rock salt phase is stable low-valent nickel. RS / I (400) Controlling the content of the rock salt phase within the above range, that is, controlling the content of the rock salt phase within the above range, can effectively reduce the oxidative decomposition of the electrolyte by the high-valent nickel separated from the spinel phase, thereby reducing the oxidation of the electrolyte; at the same time, the reduction in the oxidative decomposition of the electrolyte can also reduce the dissolution of transition metal ions in the spinel phase, thereby reducing the attenuation of the negative electrode and battery capacity, and improving the storage performance of the battery.

[0146] Furthermore, in lithium nickel manganese oxide, by (111) / I (400) and I RS / I (400) By controlling each within the corresponding range, the stability of the spinel phase is improved, its oxidation at high voltage (such as 4.7V) and the dissolution of transition metal ions are reduced, while the oxidative decomposition of the electrolyte is reduced, and the dissolution of transition metal ions is further reduced, thereby effectively improving the storage performance of the battery.

[0147] In some embodiments, the I RS With the I (400) Satisfy between: 0.02≤I RS / I (400) ≤0.1. For example, I RS / I (400) It can be 0.02, 0.04, 0.06, 0.08, 0.1 or any range consisting of the above values.

[0148] In some embodiments, the I RS With the I (400) Satisfy between: 0.05≤I RS / I (400) ≤0.1. For example, I RS / I (400) It can be 0.05, 0.06, 0.07, 0.08, 0.09, 0.1 or within a range consisting of any of the above values.

[0149] I RS / I (400) Being within the above range is beneficial to further reduce the oxidative decomposition of the electrolyte and further reduce the dissolution of transition metal ions in the spinel phase, thereby further improving the storage performance of the battery.

[0150] In some embodiments, the lithium nickel manganese oxide satisfies the following conditions: 3.5≤(I (111) +10×I RS ) / I (400) ≤4.4. For example, (I (111)+10×I RS ) / I (400) It can be 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4 or within a range consisting of any of the above values.

[0151] In lithium nickel manganese oxide, (I (111) +10×I RS ) / I (400) Controlling within the above range is beneficial to reducing the adverse effects of the spinel phase and rock salt phase on the material capacity and kinetics, and improving the capacity and kinetic performance of the material and battery.

[0152] In some embodiments, the lithium nickel manganese oxide satisfies the following conditions: 3.6≤(I (111) +10×I RS ) / I (400) ≤4.1. For example, (I (111) +10×I RS ) / I (400) It can be 3.6, 3.65, 3.7, 3.75, 3.8, 3.85, 3.9, 3.95, 4, 4.05, 4.1 or within a range consisting of any of the above values.

[0153] (I (111) +10×I RS ) / I (400) Being within the above range is beneficial to further reduce the adverse effects of the spinel phase and rock salt phase on the material capacity and kinetics, and further improve the capacity and kinetic performance of the material and battery.

[0154] In some embodiments, the lithium nickel manganese oxide comprises crystals of the spinel phase and crystals of the rock salt phase, wherein the crystals of the rock salt phase cover at least a portion of the surface of the crystals of the spinel phase in the form of a rock salt phase layer (see Figure 3 ).

[0155] Lithium nickel manganese oxide contains spinel phase grains and rock salt phase grains. Among them, the spinel phase grains provide a bulk structure for lithium nickel oxide. This bulk structure has relatively high stability, which can make the dissolution of transition metal ions in lithium nickel manganese oxide relatively slow; while the rock salt phase grains can reduce the oxidative decomposition of the electrolyte by the high-valent nickel formed by separating from the spinel phase, thereby reducing the oxidation of the electrolyte.

[0156] At the same time, the rock salt phase grains are covered on at least part of the surface of the spinel phase grains in the form of a rock salt phase layer. That is, when the rock salt phase is on the surface of the lithium nickel manganese oxide, the lithium nickel manganese oxide can keep the surface nickel in a relatively low valence state after charging, which can further reduce the oxidation of the electrolyte and thereby improve the storage performance of the battery.

[0157] In some embodiments, the thickness of the rock salt phase layer is 20 nm to 200 nm. For example, the thickness of the rock salt phase layer can be 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, or any range thereof. Alternatively, the thickness of the rock salt phase layer is 50 nm to 100 nm.

[0158] The thickness of the rock salt phase layer is within the above range, which can improve the battery storage performance while also taking into account long life and capacity.

[0159] The thickness of the rock salt phase layer is well known in the art and can be measured using methods known in the art, for example, using a transmission electron microscope (TEM, model: Hitachi, JEM-2100F).

[0160] In some embodiments, the active material further comprises phosphate.

[0161] Among the active materials, the phosphate ions in the phosphate can not only preferentially capture HF formed by the oxidative decomposition of the electrolyte, reducing the corrosion of the electrolyte on the positive electrode active material; at the same time, they can also capture transition metal ions and inhibit the dissolution of transition metal ions in lithium nickel manganese oxide, thereby improving the storage performance of the battery.

[0162] In some embodiments, the mass percentage of the phosphate in the active material is m, and 0.2%≤m≤20%. For example, m can be 0.2%, 0.5%, 0.8%, 1%, 3%, 5%, 7%, 9%, 10%, 12%, 14%, 16%, 18%, 20%, or any range thereof.

[0163] The mass percentage of phosphate in the active material is well known in the art and can be measured using methods known in the art. For example, it can be measured using an inductively coupled plasma (ICP, such as an Optima 5300 DV) in accordance with EPA 6010D-2014 Inductively Coupled Plasma Atomic Emission Spectrometry.

[0164] In some embodiments, m satisfies the following: 0.5% ≤ m ≤ 10%. For example, m can be 0.5%, 0.7%, 0.9%, 1%, 2%, 4%, 6%, 8%, 10%, or a range consisting of any of the above values. Alternatively, m satisfies the following: 1% ≤ m ≤ 5%.

[0165] The mass percentage of phosphate in the active material is within the above range, which is beneficial to further reduce the corrosion of the electrolyte on the positive electrode active material; at the same time, it further inhibits the dissolution of transition metal ions in lithium nickel manganese oxide, thereby further improving the storage performance of the battery.

[0166] In some embodiments, the phosphate is coated on at least a portion of the surface of the lithium nickel manganese oxide.

[0167] Phosphate is coated on at least a portion of the surface of lithium nickel manganese oxide, which can effectively play the role of the phosphate in the active material without affecting the phase structure (spinel phase and rock salt phase) of lithium nickel manganese oxide.

[0168] In some embodiments, the phosphate includes but is not limited to at least one of orthophosphate, hydrogen phosphate, dihydrogen phosphate, metaphosphate, pyrophosphate, polyphosphate, hypophosphite, phosphite, monofluorophosphate, difluorophosphate and trifluorophosphate containing at least one element of Li, Na, K, Mg, Al, Ti, Zr, La, Ta, Nb, Te, Mo, W, Sb, Ni, Mn, Fe, Co and N (nitrogen).

[0169] In some embodiments, the active material includes particles of the active material, and the particles of the active material include at least one of single crystal grains and quasi-single crystal grains.

[0170] In the particles of the active material, the rock salt phase is mainly distributed on the surface of the particles. Therefore, when the particles of the active material include single crystal grains and / or single-crystal-like grains, more rock salt phases will be distributed on each surface of the single crystal grains or single-crystal-like grains, which is more conducive to improving the long-term stability of the positive electrode active material and the battery.

[0171] In some embodiments, the single crystal grains include at least one of truncated octahedral grains and spherical grains (see Figure 2 The truncated octahedral and spherical grains are more resistant to pressure, which is beneficial for obtaining a higher compaction density of the positive electrode active material and reducing its cracking.

[0172] In some embodiments, the compaction density P of the positive electrode active material under 6 tons of pressure satisfies: P ≥ 3 g / cm 3 .

[0173] In some embodiments, the compaction density P of the positive electrode active material under 6 tons of pressure satisfies: 3 g / cm 3 ≤P≤3.5g / cm 3 For example, P can be 3g / cm 3 , 3.1g / cm 3 , 3.2g / cm 3 , 3.3g / cm3 , 3.4g / cm 3 , 3.5g / cm 3 Or within the range of any of the above values. Optionally, P satisfies: 3.1 g / cm 3 ≤P≤3.4g / cm 3 .

[0174] In the positive electrode active material, particle cracking will expose unstable fresh interfaces, accelerating side reactions and transition metal ion dissolution. The compaction density of the positive electrode active material of the present application is within the relatively high range mentioned above, which can make the material particles have a morphology that is more conducive to dense stacking, so the pressure required to achieve the same compaction is smaller, and the particles are less likely to break, thereby reducing the risk of particle cracking and the occurrence of side reactions and transition metal ion dissolution caused by particle cracking. In addition, the relatively high compaction density is conducive to improving the volume energy density of battery cells and batteries.

[0175] The compaction density of the positive electrode active material under 6 tons of pressure is well known in the art and can be tested using methods known in the art. For example, it can be tested using an electronic pressure tester, such as the UTM7305 electronic pressure tester, in accordance with GB / T24533-2009. Accurately weigh about 1g of the sample and add a sample with a bottom area of ​​1.327cm 2 In a mold, a pressurizing device applies 6 tons of pressure to the sample, maintains this pressure for 30 seconds, and then releases the pressure. The sample's height is then measured, and the material's compacted density can be calculated using the formula P = m / (1.327 × h). Here, P represents the material's compacted density, m represents the sample's mass, and h represents the sample's height after the 6 tons of pressure is applied, maintained for 30 seconds, and then released.

[0176] In some embodiments, the volume average particle size Dv50 of the positive electrode active material satisfies: 2 μm ≤ Dv50 ≤ 20 μm. For example, Dv50 may be 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, or within a range consisting of any of the above values.

[0177] In some embodiments, the volume average particle size Dv50 of the positive electrode active material satisfies the following: 3 μm ≤ Dv50 ≤ 15 μm. For example, Dv50 may be 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, or within a range consisting of any of the foregoing values. Alternatively, Dv50 satisfies the following: 5 μm ≤ Dv50 ≤ 10 μm.

[0178] The volume average particle size Dv50 of the positive electrode active material is within the above range, which can better regulate parameters such as the crystal structure, oxygen defects and specific surface area of ​​the positive electrode active material, thereby improving its cycle performance.

[0179] The volume average particle size Dv50 of the positive electrode active material is well known in the art and can be measured using methods known in the art. For example, it can be measured using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK, in accordance with GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method.

[0180] In some embodiments, the volume average particle sizes Dv50, Dv90, and Dv10 of the positive electrode active material satisfy the following relationship: 0.8 ≤ (Dv90 - Dv10) / Dv50 ≤ 2. For example, (Dv90 - Dv10) / Dv50 may be 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, or any range thereof.

[0181] In some embodiments, the volume average particle size Dv50, Dv90, and Dv10 of the positive electrode active material satisfy the following relationship: 1 ≤ (Dv90 - Dv10) / Dv50 ≤ 1.8. For example, (Dv90 - Dv10) / Dv50 may be 1, 1.1, 1.3, 1.5, 1.7, 1.8, or any range thereof. Alternatively, Dv50, Dv90, and Dv10 satisfy the following relationship: 1.2 ≤ (Dv90 - Dv10) / Dv50 ≤ 1.5.

[0182] A larger (Dv90-Dv10) / Dv50 ratio indicates a wider particle size distribution in the cathode material, meaning greater variation in particle size. A (Dv90-Dv10) / Dv50 ratio within this range is beneficial for achieving a higher compaction density while better balancing a relatively small specific surface area, thereby improving the material's volumetric energy density.

[0183] The volume average particle size Dv90 of the positive electrode active material refers to the value at which 90% of the particles in the volume-based particle size distribution of the positive electrode active material have a particle size smaller than this value; Dv10 refers to the value at which 10% of the particles in the volume-based particle size distribution of the positive electrode active material have a particle size smaller than this value. Both Dv90 and Dv10 can be measured using methods known in the art, for example, referring to the particle size distribution laser diffraction method according to GB / T 19077-2016, using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd. in the UK.

[0184] In some embodiments, the specific surface area S of the positive electrode active material satisfies: <S≤1m2 / g. For example, S can be 0.1m 2 / g,0.2m 2 / g,0.4m 2 / g,0.6m 2 / g,0.8m 2 / g,1m 2 / g or within a range consisting of any of the above values.

[0185] In some embodiments, the specific surface area S of the positive electrode active material satisfies: <S≤0.7m 2 / g. For example, S can be 0.1m 2 / g,0.2m 2 / g,0.3m 2 / g,0.4m 2 / g,0.5m 2 / g,0.6m 2 / g,0.7m 2 / g or within the range of any of the above values. Optionally, S satisfies: 0.1m 2 / g≤S≤0.5m 2 / g.

[0186] The specific surface area of ​​the positive electrode active material is within the above range, which is beneficial to slowing down the occurrence of side reactions on its surface, thereby improving its long-term performance.

[0187] The specific surface area of ​​a positive electrode active material is well known in the art and can be measured using methods known in the art. For example, according to the BET gas adsorption method (GB / T 19587-2004), after heating and degassing the sample, the amount of gas adsorbed on the solid surface at different adsorption pressures is measured at a constant low temperature. Based on the BET multilayer adsorption theory and its formula, the monolayer adsorption amount of the sample is calculated, thereby calculating the specific surface area per unit mass of the solid sample.

[0188] In some embodiments, the pH value of the positive electrode active material satisfies: 9≤pH≤12. The pH value may be 9, 10, 11, 12, or within a range consisting of any of the above values.

[0189] In some embodiments, the pH value of the positive electrode active material satisfies: 10≤pH≤12. For example, the pH value can be 10, 10.5, 11, 11.5, 12, or within a range consisting of any of the above values. Alternatively, the pH value satisfies: 10.5≤pH≤11.5.

[0190] The pH of the positive electrode active material is within the above range, indicating that the material contains an appropriate amount of alkaline groups, which can neutralize the strong acid (such as hydrofluoric acid) generated under high voltage (such as 4.7V) to reduce the damage to the surface of the positive electrode active material; without affecting the processing performance of the material, and will not cause the material to deteriorate battery performance due to the impact on processing performance (such as easy moisture absorption, reaction with binder, etc.).

[0191] The pH value of a positive electrode active material is well known in the art and can be measured using methods known in the art. For example, referring to GB / T 9724-2007, General Guide for the Determination of pH Value of Chemical Reagents, a solution of the sample and DI water in a fixed ratio of 1:9 is sealed and stirred on a magnetic stirrer for 30 minutes. After stirring, the conical flask is placed in a 25°C water bath and allowed to stand for 1.5 hours. The pH of the mixture is then measured using a pH meter.

[0192] In a second aspect, the present application provides a method for preparing a positive electrode active material, which is used to prepare the positive electrode active material of the first aspect of the present application, and may include the following steps:

[0193] S10. Sintering a mixture containing a lithium source, a nickel source, and a manganese source to obtain a positive electrode active material, wherein the positive electrode active material includes an active substance, the active substance includes lithium nickel manganese oxide, the lithium nickel manganese oxide includes a spinel phase, and the X-ray diffraction analysis spectrum of the lithium nickel manganese oxide has a first diffraction peak at a diffraction angle 2θ of 18° to 19°, and a second diffraction peak at a diffraction angle 2θ of 44° to 45°, the first diffraction peak corresponds to the crystal plane (111), and the second diffraction peak corresponds to the crystal plane (400); the peak intensity of the first diffraction peak is 1 (111) , the peak intensity of the second diffraction peak is 1 (400) , and I (111) with I (400) Between: 2.5≤I (111) / I (400) ≤4.

[0194] In the above steps, by sintering the mixture containing the lithium source, the nickel source, and the manganese source, a lithium nickel manganese oxide meeting the above conditions can be obtained, and a spinel phase is formed in the lithium nickel manganese oxide.

[0195] In some embodiments, the lithium nickel manganese oxide satisfies the chemical formula Li x M y Ni z Mn 2-y-z O 4-k, wherein 0.8≤x≤1.05, 0≤y≤0.2, 0.3≤z≤0.7, -0.1≤k≤0.5, and M includes one or more of B, Si, P, S, Nb, Mo, Ru, Te, Ce, Ta and W.

[0196] It should be noted that the chemical formula satisfied by the lithium nickel manganese oxide can be pre-designed according to the target components actually required before the step of preparing the positive electrode active material, and then the positive electrode active material can be prepared in reverse according to the pre-designed target components.

[0197] In some embodiments, the sintering process in step S10 may further include the following steps:

[0198] S110 , heating the mixture to a first sintering temperature T1 , maintaining the mixture at the first sintering temperature T1 for a first preset time t1 , and then cooling the mixture to room temperature at a first cooling rate v1 to obtain a sintered product.

[0199] By performing the sintering treatment under the conditions of step S110, the spinel phase and the rock salt phase can be formed simultaneously, and by regulating the first sintering temperature T1 and the first cooling rate v1, the formation and content of the spinel phase and the rock salt phase in the lithium nickel manganese oxide can be regulated, thereby achieving the goal of I (111) / I (400) and I RS / I (400) The values ​​are regulated so that they each meet the range provided in the first aspect of this application.

[0200] In some embodiments, the first sintering temperature T1 satisfies: 900° C. ≤ T1 ≤ 1500° C., and T1 ≥ x×1000° C. For example, T1 may be 900° C., 1000° C., 1100° C., 1200° C., 1300° C., 1400° C., 1500° C., or any range thereof.

[0201] During the sintering process, the stable phases at high temperature are spinel phase (Mn-rich part) and rock salt phase (Ni-rich part). Therefore, when T1 is in the relatively high temperature range mentioned above, it is conducive to the formation of spinel phase and rock salt phase, which is also conducive to I (111) / I (400) and I RS / I (400)The increase in the cyclic storage life and the abnormal growth of the grains can be reduced, thereby balancing the cycle storage life with the dynamic performance and processing performance. At the same time, the lithium content x in the lithium nickel manganese oxide, that is, the content of the lithium source in the mixture in step S10, will affect the formation of the spinel phase and the rock salt phase. By setting T1 ≥ x × 1000°C, the minimum temperature of the first sintering treatment can still be kept at a relatively high level, thereby promoting the formation of the spinel phase and the rock salt phase.

[0202] In some embodiments, the first sintering temperature T1 satisfies: 1000° C. ≤ T1 ≤ 1300° C. For example, T1 can be 1000° C., 1050° C., 1150° C., 1250° C., 1300° C., or any range thereof. Alternatively, 1000° C. ≤ T1 ≤ 1200° C.

[0203] In some embodiments, the first preset time t1 satisfies: 1 hour ≤ t1 ≤ 20 hours. For example, t1 can be 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, or any of the above ranges.

[0204] In some embodiments, the first preset time t1 satisfies: 2 hours ≤ t1 ≤ 15 hours. For example, t1 can be 2 hours, 3 hours, 5 hours, 7 hours, 9 hours, 11 hours, 13 hours, 15 hours, or any range thereof.

[0205] In some embodiments, the first cooling rate v1 satisfies: v1 ≥ 10°C / min.

[0206] In some embodiments, the first cooling rate v1 satisfies the following: 10°C / min≤v1≤50°C / min. For example, v1 can be 10°C / min, 20°C / min, 30°C / min, 40°C / min, 50°C / min, or any range thereof.

[0207] The first cooling rate v1 is within the above range, which is beneficial to suppress the reduction of rock salt phase caused by annealing, thereby promoting I RS / I (400) improvement.

[0208] In some embodiments, the mixture further comprises an M source; the M source comprises one or more of oxides, nitric acid compounds, carbonate compounds, hydroxide compounds and acetic acid compounds containing the M element, and the M element comprises one or more of B, Si, P, S, Nb, Mo, Ru, Te, Ce, Ta and W.

[0209] The M element has the function of inducing the preferred orientation of the crystal and forming a strong bond with oxygen or transition metal in lithium nickel manganese oxide. Adding M source to the mixture can promote the formation of I 111 / I 400 and I RS / I 400 Reaching the appropriate range mentioned above in this application can better balance capacity and long-term performance.

[0210] In some embodiments, the lithium source includes, but is not limited to, one or more of lithium oxide, lithium phosphate, lithium dihydrogen phosphate, lithium acetate, lithium hydroxide, lithium carbonate, and lithium nitrate.

[0211] In some embodiments, the nickel source includes, but is not limited to, one or more of nickel oxide, nickel phosphate, nickel acetate, nickel hydroxide, nickel carbonate, and nickel nitrate.

[0212] In some embodiments, the manganese source includes, but is not limited to, one or more of manganese oxide, manganese phosphate, manganese acetate, manganese hydroxide, manganese carbonate, and manganese nitrate.

[0213] In some embodiments, after step S110, the sintering process in step S10 may further include the following steps:

[0214] S120 , heating the material including the sintered product to a second sintering temperature T2 , maintaining the temperature at the second sintering temperature T2 for a second preset time t2 , and then cooling the material to room temperature at a second cooling rate v2 .

[0215] It can be understood that the "room temperature" in steps S110 and S120 refers to 20°C to 30°C, and further, can be 25°C.

[0216] In some embodiments, the material in step S120 may further include phosphate.

[0217] In some embodiments, the phosphate includes but is not limited to at least one of orthophosphate, hydrogen phosphate, dihydrogen phosphate, metaphosphate, pyrophosphate, polyphosphate, hypophosphite, phosphite, monofluorophosphate, difluorophosphate and trifluorophosphate containing at least one element of Li, Na, K, Mg, Al, Ti, Zr, La, Ta, Nb, Te, Mo, W, Sb, Ni, Mn, Fe, Co and N (nitrogen).

[0218] By performing the sintering treatment under the conditions of step S120, the phosphate and the lithium nickel manganese oxide can be melted and mixed, and by regulating the second sintering temperature T2 and the second cooling rate v2, it is beneficial to achieve phosphate coating on the surface of the lithium nickel manganese oxide, so that the phosphate is coated on at least a portion of the surface of the lithium nickel manganese oxide.

[0219] The spinel phase and the rock salt phase can be formed at the same time, and by regulating the first sintering temperature T1 and the first cooling rate v1, the formation and content of the spinel phase and the rock salt phase in the lithium nickel manganese oxide can be regulated, so that the I (111) / I (400) and I RS / I (400) The values ​​are regulated so that they each meet the range provided in the first aspect of this application.

[0220] In some embodiments, the second sintering temperature T2 satisfies: T1-200°C≤T2≤T1, T2≥900°C.

[0221] In some embodiments, the second sintering temperature T2 satisfies: T1-100°C≤T2≤T1, T2≥950°C.

[0222] The second sintering temperature T2 being within the above range is beneficial to improving the roundness of the lithium nickel manganese oxide grain growth, thereby increasing its compaction density and reducing the specific surface area.

[0223] In some embodiments, the second preset time t2 satisfies: 0.5h≤t2≤5h. For example, t2 can be 0.5h, 1h, 2h, 3h, 4h, 5h, or any range thereof.

[0224] In some embodiments, the second cooling rate v2 satisfies: v2 ≥ 10°C / min.

[0225] In some embodiments, the second cooling rate v2 satisfies the following: 10°C / min≤v2≤50°C / min. For example, v2 can be 10°C / min, 20°C / min, 30°C / min, 40°C / min, 50°C / min, or any range thereof.

[0226] In some embodiments, the material in step S120 may further include a nickel-containing compound. Adding the nickel-containing compound in step 120 is beneficial to further promote the formation of the rock salt phase layer.

[0227] In some embodiments, the nickel-containing compound includes but is not limited to one or more of nickel oxide, nickel phosphate, nickel acetate, nickel hydroxide, nickel carbonate, and nickel nitrate.

[0228] In addition, the secondary battery and the electric device of the present application will be described below with reference to the drawings as appropriate.

[0229] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0230] Positive electrode

[0231] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, and the positive electrode active material layer includes the positive electrode active material of the first aspect of the present application or the positive electrode active material prepared by the method of the second aspect of the present application.

[0232] In some embodiments, the compaction density P' of the positive electrode active material layer satisfies: P'≥2.9 g / cm 3 .

[0233] In some embodiments, the compaction density P' of the positive electrode active material layer satisfies: 3 g / cm 3 ≤P'≤3.6g / cm 3 For example, P' can be 3g / cm 3 , 3.1g / cm 3 , 3.2g / cm 3 , 3.3g / cm 3 , 3.4g / cm 3 , 3.5g / cm 3 , 3.6g / cm 3 Or within the range of any of the above values. Optionally, P' satisfies: 3.1 g / cm 3 ≤P'≤3.5g / cm 3 .

[0234] The compaction density of the positive electrode active material layer is within the above range, which is beneficial to improving the volume energy density of the battery cell and reducing side reactions and dissolution of transition metal ions. It also allows sufficient gaps in the positive electrode active material layer to allow the electrolyte to fully infiltrate and maintain normal dynamic performance of the battery.

[0235] As a non-limiting example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0236] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0237] In some embodiments, the positive electrode active material may also utilize other positive electrode active materials for batteries known in the art. As non-limiting examples, other positive electrode active materials may include one or more of the following: olivine-structured lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials; other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxide (such as LiCoO2), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Non-limiting examples of olivine-structured lithium-containing phosphates include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.85 Co 0.15 Al 0.05 O2.

[0238] Given that the Li content in the cathode material changes, how should the subscript of Li be defined in the general formula?

[0239] For ternary materials:

[0240] Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y , x is 0.2-1.2;

[0241] Li x A a (Ni a Co b Mn c ) 1-d M d O 2-y A y , x+a is 0.2-1.2.

[0242] For lithium manganese iron phosphate materials:

[0243] Li a Mn 1-y B y P 1-z C z O 4-n D n , a is 0-1.1;

[0244] Li a A x Mn 1-y B y P 1-z C z O 4-n D n , a+x is 0-1.1.

[0245] The above limitation on x includes the molar content of Li in different charge and discharge states of the battery (usually the battery voltage is between 2-5V).

[0246] It is understandable that the battery will be accompanied by lithium (Li) deintercalation and consumption during the charge and discharge process, and the content of Li in the positive electrode plate is different when the battery is discharged to different states. In the list of positive electrode materials in this application, unless otherwise specified, the Li content is the initial state of the material. The positive electrode material is applied to the positive electrode plate in the battery system, and after the charge and discharge cycle, the Li content in the positive electrode material contained in the plate will usually change. Among them, the Li content can be measured by molar content, but is not limited to this. Regarding "the Li content is the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry. It is understandable that new materials obtained by appropriate modification on the basis of the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode materials, and non-limiting examples include coating modification.

[0247] In the examples of positive electrode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual O content will fluctuate. The O content can be measured by molar content, but is not limited to this.

[0248] In some embodiments, the positive electrode active material may also include at least one of the following materials: one or more of a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound. However, the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries may also be used.

[0249] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Non-limiting examples of sodium transition metal oxides may be Na x MO2, wherein M may include one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0250] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be one or more of P, S, and Si; n represents (YO4) n- valence.

[0251] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n-A class of compounds containing anion units and halogen anions. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be one or more of P, S, and Si, and n represents (YO4) n- valence state; the halogen can be one or more of F, Cl and Br.

[0252] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y can be one or more of P, S and Si, and n represents (YO4) n- valence state; Z represents a transition metal, which may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents (ZO y ) m+ valence state; the halogen can be one or more of F, Cl and Br.

[0253] Polyanionic compounds can include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, referred to as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F and Na3(VO y )2(PO4)2F 3-2y (0≤y≤1) wherein M′ in NaM′PO4F may include one or more of V, Fe, Mn and Ni.

[0254] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ). The transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Non-limiting examples of Prussian blue compounds may include Na a Me b Me' c (CN)6, wherein Me and Me' can each independently be one or more of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0255] In some embodiments, the positive electrode active material layer may further optionally include a binder. As non-limiting examples, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0256] In some embodiments, the positive electrode active material layer may further include a conductive agent. As non-limiting examples, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0257] In some embodiments, the positive electrode sheet can be prepared by dispersing the components for preparing the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one side of the positive electrode current collector, and performing drying, cold pressing, and other processes to obtain the positive electrode sheet. The type of solvent can be selected from, but not limited to, any of the aforementioned embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40 wt% to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000-25000 mPa·s. When applying the positive electrode slurry, the coating unit area density based on dry weight (excluding solvent) can be 15-35 mg / cm 2 The compaction density of the positive electrode can be 3.0~3.6 g / cm 3 , optional range is 3.3~3.5 g / cm 3 .

[0258] Negative electrode

[0259] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0260] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0261] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be obtained by forming a metal material on a polymer substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymer substrate in the negative electrode current collector may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0262] In some of these embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As a non-limiting example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0263] In some embodiments, the negative electrode active material layer may further include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0264] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0265] In some embodiments, the negative electrode active material layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0266] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt%~60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000-10000mPa·s. When coating the negative electrode slurry, the coating unit surface density based on dry weight (excluding solvent) can be 75-220 g / m 2 The compaction density of the negative electrode sheet can be 1.0 g / cm 3 ~ 1.8 g / cm 3 .

[0267] electrolytes

[0268] The electrolyte conducts ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0269] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0270] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorobis(oxalatophosphate) (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0271] In some embodiments, the solvent may include ethylene carbonate (EC, ), propylene carbonate (PC, ), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate ( ), one or more of fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0272] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0273] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), and the like.

[0274] Isolation film

[0275] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0276] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0277] In some embodiments, the isolation film has a thickness of 6-40 μm, and optionally 12-20 μm.

[0278] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0279] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0280] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft shell, such as a pouch-type soft shell. The material of the soft shell can be plastic. Further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0281] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0282] In this application, unless otherwise specified, a "battery cell" refers to a basic unit that can achieve the mutual conversion of chemical energy and electrical energy. Further, generally speaking, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the battery's charge and discharge process, active ions are embedded in and out of the positive and negative electrode plates. The electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0283] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 4 The battery cell 5 is a square structure as an example.

[0284] In some of these embodiments, reference Figure 5 The outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0285] The secondary battery may be a battery module 4 or a battery pack 1 .

[0286] A battery module includes at least one battery cell. The number of battery cells contained in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0287] Figure 6 4 is an example of a battery module. Figure 6 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. The plurality of battery cells 5 may further be fixed by fasteners.

[0288] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0289] In some embodiments, the battery modules may be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select an appropriate number based on the application and capacity of the battery pack.

[0290] Figure 7 and Figure 8The battery pack 1 is used as an example. Figure 7 and Figure 8 The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0291] In addition, the present application also provides an electrical device, which includes the secondary battery provided in the present application. The secondary battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc. Among them, mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0292] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0293] Figure 9 The power consumption device 6 is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module can be used.

[0294] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0295] Example

[0296] Below, the embodiment of the present application is described. The embodiment described below is exemplary, is only used to explain the present application, and is not to be construed as limiting the present application. Where the technology or conditions are not specified in the embodiment, the technology or conditions described in the literature in this area or the product instructions are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0297] Example 1

[0298] (1) Preparation of positive electrode active materials

[0299] By target component Li 0.95 Ni 0.5 Mn 1.5 O 4-kLi2CO3, NiO, and Mn3O4 powders corresponding to the stoichiometric ratio are weighed and then mixed uniformly to obtain a mixture powder of the raw materials.

[0300] The mixture powder was subjected to the first sintering treatment (first sintering), that is, the temperature was raised to 1100 ° C in an air atmosphere and kept at this temperature for 6 hours, and then cooled to room temperature at a rate of 20 ° C / min to obtain a sintered product, and the positive electrode active material Li 0.95 Ni 0.5 Mn 1.5 O 3.8 .

[0301] (2) Preparation of positive electrode

[0302] The positive electrode active material of step (1) was mixed with conductive carbon black (Super P) and PVDF in a weight ratio of 96:2.5:1.5, and an appropriate amount of solvent N-methylpyrrolidone (NMP) was added and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry was coated on both sides of the positive electrode current collector aluminum foil, and dried after coating to obtain a positive electrode sheet. The positive electrode active material loading on one side of the positive electrode current collector was 0.016 g / cm 2 .

[0303] (3) Preparation of negative electrode sheet

[0304] The negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose were thoroughly mixed in a suitable amount of deionized water in a mass ratio of 96:1:1:2 to form a uniform negative electrode slurry. The negative electrode slurry was evenly coated on both sides of the negative electrode current collector copper foil, dried, and cold pressed to obtain a negative electrode sheet. The negative electrode active material loading on one side of the negative electrode current collector was 0.007 g / cm 2 .

[0305] (4) Isolation film

[0306] A 12μm thick polypropylene isolation film was selected.

[0307] (5) Preparation of electrolyte

[0308] The organic solvent is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), with the volume ratio of EC, EMC, and DEC being 20:20:60. In an argon atmosphere glove box with a water content of <10 ppm, fully dried lithium salt LiPF6 is dissolved in the organic solvent and mixed thoroughly to obtain an electrolyte solution. The concentration of the lithium salt is 1 mol / L.

[0309] (6) Battery preparation

[0310] The prepared positive electrode sheet, separator, and negative electrode sheet are placed in order, with the separator positioned between the positive and negative electrodes to provide isolation. The cells are then processed and packaged in aluminum-plastic bags. Electrolyte is then injected, and the cells are packaged and then charged to form a soft-pack battery.

[0311] Examples 2 to 38

[0312] The preparation of the positive electrode active materials and batteries in Examples 2 to 38 is similar to that in Example 1, except that the relevant parameters of the positive electrode active materials are adjusted. The specific parameters are detailed in Tables 1 and 2 below.

[0313] Example 39

[0314] The preparation of the positive electrode active material and the battery in Example 39 is similar to that in Example 1, except that after obtaining the sintered product in step (1), the sintered product is mechanically mixed with lithium phosphate. Specific parameters are shown in Table 1 below.

[0315] Example 40

[0316] The preparation of the positive electrode active material and the battery in Example 40 is similar to that in Example 1, except that after obtaining the sintered product in step (1), the sintered product is mixed evenly with lithium phosphate and then subjected to a second sintering treatment (second sintering) to achieve coating of the sintered product with lithium phosphate. Specific parameters are detailed in Tables 1 and 2 below.

[0317] Examples 41 to 49

[0318] The preparation of the positive electrode active materials and batteries in Examples 41 to 49 is similar to that in Example 41, except that the type and content of phosphate are changed. Specific parameters are detailed in Tables 1 and 2 below.

[0319] Examples 50-51

[0320] The preparation of the positive electrode active material and the battery in Examples 50-51 is similar to that in Example 1, except that after obtaining the sintered product in step (1), the sintered product is mixed evenly with nickel oxide equivalent to 2% by mass of the sintered product and then subjected to a second sintering treatment (second sintering). Specific parameters are detailed in Tables 1 and 2 below.

[0321] Examples 52-53

[0322] The preparation of the positive electrode active material and the battery in Examples 52-53 is similar to that in Example 1, except that after obtaining the sintered product in step (1), the sintered product is mixed evenly with nickel oxide equivalent to 5% by mass of the sintered product and then subjected to a second sintering treatment (second sintering). Specific parameters are detailed in Tables 1 and 2 below.

[0323] Comparative Examples 1 to 4

[0324] The preparation of the positive electrode active materials and batteries in Comparative Examples 1 to 4 is similar to that in Example 1, except that the parameters of the lithium nickel manganese oxide in the positive electrode active material are adjusted. The specific parameters are detailed in Tables 1 and 2 below.

[0325] The relevant parameters of the positive electrode active materials and their preparation processes for Examples 1-53 and Comparative Examples 1-4 are shown in Tables 1 and 2 below, where " / " indicates the absence of the corresponding value. In Table 1, the amount of phosphate added is expressed as a percentage of the mass of the sintered product; for example, the 3% addition in Example 39 represents 3% of the mass of the sintered product.

[0326] Table 1

[0327]

[0328]

[0329]

[0330] Table 2

[0331]

[0332]

[0333]

[0334] In addition, the performance tests were performed on the positive electrode active materials and batteries obtained in Examples 1 to 53 and Comparative Examples 1 to 4, and the test results are shown in Table 3 below.

[0335] Test section

[0336] (1) X-ray diffraction analysis test

[0337] X-ray diffraction patterns of the positive electrode active materials were measured using CuKα1 radiation in accordance with JIS K 0131-1996, General Rules for X-ray Diffraction Analysis. A Bruker D8 Discover instrument was used. XRD analysis conditions were: Cu target, 40 kV scanning voltage, 40 mA current, and a scanning range of 10°–90°. To minimize spectral fitting errors, the instrument's measurement step size was 0.02°, and the scanning speed was 2° / min.

[0338] (2) Morphology test

[0339] The morphology of the positive electrode active materials was tested using a scanning electron microscope (ZEISS sigma 300) and a transmission electron microscope (Hitachi, JEM-2100F).

[0340] (3) High temperature full charge storage performance test

[0341] A full charge is a battery that is charged at a constant current of 0.3C to a voltage of 4.9V, then charged at a constant voltage of 4.9V to a current of 0.05C. A full discharge is a battery that is discharged at a constant current of 0.33C to a voltage of 3.0V. After a full charge and 5 minutes of rest, the full discharge capacity is the battery's discharge capacity. Dividing this capacity by the mass of the positive electrode active material in the battery gives the discharge capacity in grams of the positive electrode active material, Cn.

[0342] After fully charging the battery at 25°C, place it in a 45°C oven and let it sit. Remove it and fully discharge it every 10 days. Then, perform a full charge and discharge cycle at 25°C to extract Cn. Then, fully charge it again and continue storing it at 45°C. Storage ends when the discharge capacity Cn decays to 100mAh / g (125mAh / g is the benchmark level for the capacity of conventional spinel nickel manganese oxide (LNMO), and 80% is the generally recognized end-of-life condition in the industry). The total storage time at 45°C after full charge is the high-temperature full-charge storage time, which represents the battery's high-temperature full-charge storage performance.

[0343] Table 3

[0344]

[0345]

[0346]

[0347] Comparing Examples 1 to 53 with Comparative Examples 1 to 4, it can be seen that when the X-ray diffraction peak intensity of the positive electrode active material in Comparative Examples 1 to 4 is (111) / I (400) When it is not within the protection scope of this application, the storage life of the battery is significantly reduced, indicating that this application will (111) / I (400) Controlling within the corresponding protection range is beneficial to improving the storage performance of the battery.

[0348] The above description of the various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced to each other and will not be repeated herein for the sake of brevity.

[0349] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A positive electrode active material, characterized in that The invention comprises an active material, wherein the active material comprises lithium nickel manganese oxide, wherein the lithium nickel manganese oxide comprises a spinel phase and a rock salt phase, wherein an X-ray diffraction analysis spectrum of the lithium nickel manganese oxide has a first diffraction peak at a diffraction angle 2θ of 18° to 19°, a second diffraction peak at a diffraction angle 2θ of 44° to 45°, and a third diffraction peak at a diffraction angle 2θ of 43° to 44°, wherein the first diffraction peak corresponds to a crystal plane (111), and the second diffraction peak corresponds to a crystal plane (400); The peak intensity of the first diffraction peak is 1 (111) , the peak intensity of the second diffraction peak is 1 (400) , I (111) with I (400) Between: 2.5≤I (111) / I (400) ≤4; The lithium nickel manganese oxide satisfies the chemical formula Li x M y Ni z Mn 2-y-z O 4-k , wherein 0.8≤x≤1.05, 0≤y≤0.2, 0.3≤z≤0.7, -0.1≤k≤0.5, and M includes one or more of B, Si, P, S, Nb, Mo, Ru, Te, Ce, Ta and W.

2. The positive electrode active material according to claim 1, characterized in that The lithium nickel manganese oxide satisfies: 2.8≤I (111) / I (400) ≤3.

8.

3. The positive electrode active material according to claim 1 or 2, characterized in that The lithium nickel manganese oxide satisfies: 3.1≤I (111) / I (400) ≤3.

6.

4. The positive electrode active material according to any one of claims 1 to 3, characterized in that The lithium nickel manganese oxide satisfies at least one of the following conditions: （1）0.85≤x≤1.02； （2）0.01≤y≤0.2。 5. The positive electrode active material according to any one of claims 1 to 4, characterized in that The lithium nickel manganese oxide satisfies at least one of the following conditions: （1）0.9≤x≤0.99； （2）0.02≤y≤0.1。 6. The positive electrode active material according to any one of claims 1 to 5, characterized in that The peak intensity of the third diffraction peak is 1 RS , the I RS With the I (400) Satisfy between: 0.01≤I RS / I (400) ≤0.

2.

7. The positive electrode active material according to claim 6, characterized in that I RS With the I (400) Satisfy between: 0.02≤I RS / I (400) ≤0.

1.

8. The positive electrode active material according to claim 6 or 7, characterized in that I RS With the I (400) Satisfy between: 0.05≤I RS / I (400) ≤0.

1.

9. The positive electrode active material according to any one of claims 6 to 8, characterized in that The lithium nickel manganese oxide satisfies the following conditions: 3.5≤(I (111) +10×I RS ) / I (400) ≤4.

4.

10. The positive electrode active material according to any one of claims 6 to 9, characterized in that: The lithium nickel manganese oxide satisfies the following conditions: 3.6≤(I (111) +10×I RS ) / I (400) ≤4.

1.

11. The positive electrode active material according to any one of claims 1 to 10, characterized in that: The lithium nickel manganese oxide includes crystal grains of the spinel phase and crystal grains of the rock salt phase, and the crystal grains of the rock salt phase cover at least a portion of the surface of the crystal grains of the spinel phase in the form of a rock salt phase layer.

12. The positive electrode active material according to claim 11, characterized in that The thickness of the rock salt phase layer is 20nm~200nm.

13. The positive electrode active material according to any one of claims 1 to 12, characterized in that: The active material further includes phosphate, and the mass percentage of the phosphate in the active material is m, 0.2%≤m≤20%.

14. The positive electrode active material according to claim 13, characterized in that At least one of the following conditions is met: (1) The m mentioned above satisfies: 0.5%≤m≤10%; (2) the phosphate is coated on at least a portion of the surface of the lithium nickel manganese oxide; (3) The phosphate includes at least one of orthophosphate, hydrogen phosphate, dihydrogen phosphate, metaphosphate, pyrophosphate, polyphosphate, hypophosphite, phosphite, monofluorophosphate, difluorophosphate and trifluorophosphate containing at least one element of Li, Na, K, Mg, Al, Ti, Zr, La, Ta, Nb, Te, Mo, W, Sb, Ni, Mn, Fe, Co and N.

15. The positive electrode active material according to any one of claims 1 to 14, characterized in that The active material includes particles of the active material. The particles of the active material include at least one of single crystal grains and quasi-single crystal grains. The single crystal grains include at least one of truncated octahedral grains and spherical grains.

16. The positive electrode active material according to any one of claims 1 to 15, characterized in that At least one of the following conditions is met: (1) The compaction density P of the positive electrode active material under a pressure of 6 tons satisfies: P ≥ 3 g / cm 3 ; (2) The volume average particle size Dv50 of the positive electrode active material satisfies: 2 μm ≤ Dv50 ≤ 20 μm; (3) The volume average particle sizes Dv50, Dv90 and Dv10 of the positive electrode active material satisfy the following conditions: 0.8≤(Dv90-Dv10) / Dv50≤2; (4) The specific surface area S of the positive electrode active material satisfies: 0 <S≤1m 2 / g; (5) The pH value of the positive electrode active material satisfies: 9≤pH≤12.

17. The positive electrode active material according to any one of claims 1 to 16, characterized in that: At least one of the following conditions is met: (1) The compaction density P of the positive electrode active material under 6 tons of pressure satisfies: 3g / cm 3 ≤P≤3.5g / cm 3 ; (2) The volume average particle size Dv50 of the positive electrode active material satisfies: 3 μm ≤ Dv50 ≤ 15 μm; (3) The volume average particle sizes Dv50, Dv90 and Dv10 of the positive electrode active material satisfy the following conditions: 1.0≤(Dv90-Dv10) / Dv50≤1.8; (4) The specific surface area S of the positive electrode active material satisfies: 0 <S≤0.7m 2 / g; (5) The pH value of the positive electrode active material satisfies: 10≤pH≤12.

18. A method for preparing a positive electrode active material, characterized in that: include: The mixture containing lithium source, nickel source and manganese source is sintered to obtain positive electrode active material. The positive electrode active material includes an active substance, the active substance includes lithium nickel manganese oxide, the lithium nickel manganese oxide includes a spinel phase and a rock salt phase, the X-ray diffraction analysis spectrum of the lithium nickel manganese oxide has a first diffraction peak at a diffraction angle 2θ of 18° to 19°, a second diffraction peak at a diffraction angle 2θ of 44° to 45°, and a third diffraction peak at a diffraction angle 2θ of 43° to 44°, the first diffraction peak corresponds to the crystal plane (111), and the second diffraction peak corresponds to the crystal plane (400); the peak intensity of the first diffraction peak is 1 (111) , the peak intensity of the second diffraction peak is 1 (400) , and I (111) with I (400) Between: 2.5≤I (111) / I (400) ≤4; the lithium nickel manganese oxide satisfies the chemical formula Li x M y Ni z Mn 2-y-z O 4-k , wherein 0.8≤x≤1.05, 0≤y≤0.2, 0.3≤z≤0.7, -0.1≤k≤0.5, and M includes one or more of B, Si, P, S, Nb, Mo, Ru, Te, Ce, Ta and W.

19. The method according to claim 18, characterized in that The sintering process includes: The mixture is heated to a first sintering temperature T1, maintained at the first sintering temperature T1 for a first preset time t1, and then cooled to room temperature at a first cooling rate v1 to obtain a sintered product.

20. The method according to claim 19, characterized in that At least one of the following conditions is met: (1) The first sintering temperature T1 satisfies: 900°C ≤ T1 ≤ 1500°C, and T1 ≥ x × 1000°C; (2) The first preset time t1 satisfies: 1h≤t1≤20h; (3) The first cooling rate v1 satisfies: v1 ≥ 10°C / min.

21. The method according to claim 19 or 20, characterized in that At least one of the following conditions is met: (1) The first sintering temperature T1 satisfies: 1000°C ≤ T1 ≤ 1300°C; (2) The first preset time t1 satisfies: 2h≤t1≤15h; (3) The first cooling rate v1 satisfies: 10°C / min≤v1≤50°C / min.

22. The method according to any one of claims 18 to 21, characterized in that At least one of the following conditions is met: (1) The mixture further comprises an M source; The M source includes one or more of an oxide, a nitric acid compound, a carbonate compound, a hydroxide compound, and an acetic acid compound containing an M element, and the M element includes one or more of B, Si, P, S, Nb, Mo, Ru, Te, Ce, Ta, and W; (2) The lithium source includes one or more of lithium oxide, lithium phosphate, lithium dihydrogen phosphate, lithium acetate, lithium hydroxide, lithium carbonate and lithium nitrate; (3) The nickel source includes one or more of nickel oxide, nickel phosphate, nickel acetate, nickel hydroxide, nickel carbonate and nickel nitrate; (4) The manganese source includes one or more of manganese oxide, manganese phosphate, manganese acetate, manganese hydroxide, manganese carbonate and manganese nitrate.

23. The method according to any one of claims 19 to 22, characterized in that: The sintering process further comprises: The material containing the sintered product is heated to a second sintering temperature T2, maintained at the second sintering temperature T2 for a second preset time t2, and then cooled to room temperature at a second cooling rate v2.

24. The method according to claim 23, wherein At least one of the following conditions is met: (1) The second sintering temperature T2 satisfies: T1-200°C ≤ T2 ≤ T1, T2 ≥ 900°C; (2) The second preset time t2 satisfies: 0.5h≤t2≤5h; (3) The second cooling rate v2 satisfies: v2 ≥ 10°C / min; (4) The material further comprises phosphate, wherein the phosphate comprises at least one of orthophosphate, hydrogen phosphate, dihydrogen phosphate, metaphosphate, pyrophosphate, polyphosphate, hypophosphite, phosphite, monofluorophosphate, difluorophosphate and trifluorophosphate containing at least one element selected from the group consisting of Li, Na, K, Mg, Al, Ti, Zr, La, Ta, Nb, Te, Mo, W, Sb, Ni, Mn, Fe, Co and N.

25. The method according to claim 23 or 24, characterized in that At least one of the following conditions is met: (1) The second sintering temperature T2 satisfies: T1-100°C ≤ T2 ≤ T1, T2 ≥ 950°C; (2) The second cooling rate v2 satisfies: 10°C / min≤v2≤50°C / min.

26. A positive electrode plate, characterized in that: The invention comprises a positive electrode active material layer, wherein the positive electrode active material layer comprises the positive electrode active material according to any one of claims 1 to 17 or the positive electrode active material prepared by the method according to any one of claims 18 to 25.

27. The positive electrode sheet according to claim 26, characterized in that: The compaction density P' of the positive electrode active material layer satisfies: P'≥2.9g / cm 3 .

28. The positive electrode sheet according to claim 26 or 27, characterized in that: The compaction density P' of the positive electrode active material layer satisfies: 3 g / cm 3 ≤P'≤3.6g / cm 3 .

29. A secondary battery, characterized in that: Including the positive electrode sheet according to any one of claims 26 to 28.

30. An electrical device, characterized in that: A secondary battery according to claim 29 is included.

Images