Positive electrode active material and preparation method thereof, battery and electric device

Abstract

The invention discloses a positive electrode active material and a preparation method thereof, a battery and an electric device. The positive electrode active material includes: an inner core including lithium manganese oxide; the carbon coating layer at least covers part of the surface of the inner core, the carbon coating layer comprises a first metal element M, and the dissociation energy of an M-O bond is greater than the dissociation energy of an Mn-O bond. Therefore, the electronic conductivity of the positive electrode active material can be improved through the arrangement of the carbon coating layer, and the ionic conductivity of the positive electrode active material can be improved through the first metal element M in the carbon coating layer.

Description

[0001] This application is a divisional application of the application for patent with application number 202310641003.2, application date of May 31, 2023, and title of "Positive Electrode Active Material and Preparation Method Thereof, Battery, and Electric Device". TECHNICAL FIELD

[0002] The present application relates to the field of batteries, in particular, to a positive electrode active material and a preparation method thereof, a battery, and an electric device. BACKGROUND

[0003] With the development of lithium ion battery technology, lithium ion batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind, and solar power stations due to their high energy density, long cycle life, and green environmental protection. They are also widely used in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. With the advantages of low cost, safety and reliability, high working voltage, and fast lithium ion transmission channel, lithium manganese oxide is considered to be a very promising positive electrode active material for power lithium ion batteries. However, the poor cycle performance of lithium manganese oxide makes it still have many problems to be solved in the application level.

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

[0005] In a first aspect of the present application, a positive electrode active material is provided, comprising: an inner core, the inner core comprising lithium manganese oxide; a carbon coating layer, the carbon coating layer covering at least part of the surface of the inner core, the carbon coating layer comprising a first metal element M, the dissociation energy of the M-O bond being greater than the dissociation energy of the Mn-O bond. Thus, by providing a carbon coating layer, the electronic conductivity of the positive electrode active material can be improved, and by using the first metal element M in the carbon coating layer, the ionic conductivity of the positive electrode active material can be improved.

[0006] According to an embodiment of the present application, the inner core further comprises the first metal element M, and the first metal element M is located on the side surface of the inner core close to the carbon coating layer. Thus, the crystal structure stability of the inner core can be further improved.

[0007] According to an embodiment of the present application, the first metal element M comprises at least one of Ti, Mg, Al, Cr, Ni, and Co; preferably, the first metal element M comprises Al. Thus, the crystal structure stability of the inner core can be improved.

[0008] According to an embodiment of the present application, the carbon coating layer comprises an oxide of the first metal element M. Thus, it is helpful to form a solid solution that can improve the crystal structure stability of the inner core.

[0009] According to the embodiment of the present application, the lithium manganese oxide includes at least one of a lithium-rich manganese-based solid solution, a nickel-cobalt-manganese ternary material, a lithium manganese phosphate, and a lithium manganate. Thus, the manufacturing cost of the positive electrode active material can be reduced.

[0010] According to the embodiment of the present application, the lithium manganese oxide satisfies at least one of the following conditions: the lithium-rich manganese-based solid solution satisfies the general formula: xLi a [Li 1 / 3 Mn 2 / 3 ]O b ·(1-x)Li c M1O d , wherein 0 e Ni f Co g Mn h M2 i O j , wherein 0.9 k Mn 1-m M3 m PO n , wherein 0.9 p Mn 2-q M4 q O s , wherein 0.9 Thus, the manufacturing cost of the positive electrode active material can be further reduced, and the gram capacity of the positive electrode active material can be improved.

[0011] According to the embodiment of the present application, the particle size of the core is 7 μm-15 μm, and optionally, the particle size of the core is 9 μm-12 μm. Thus, the dispersibility of the positive electrode active material in the positive electrode slurry can be improved.

[0012] According to the embodiment of the present application, the thickness of the carbon coating layer is d1, the particle size of the core is d2, and d1:d2 is 0.01-0.1. In this way, the positive electrode active material can have both high electronic conductivity and high gram capacity.

[0013] According to the embodiment of the present application, the mass fraction of the carbon coating layer in the positive electrode active material is 1%-3%. In this way, the electronic conductivity and gram capacity of the positive electrode active material can be improved.

[0014] According to the embodiment of the present application, the number of moles of the first metal element M in the carbon coating layer is m1, and the number of moles of manganese in the core is m2, and m1:m2 is 0.01%-0.5%. In this way, the crystal structure stability of the core can be improved.

[0015] In the second aspect of the present application, a method for preparing the positive electrode active material is provided, which comprises: mixing the core with the metal organic framework material to obtain a precursor, and heating the precursor to obtain the positive electrode active material. In this way, the positive electrode active material can be prepared by a relatively simple method, and the method has all the features and advantages of the positive electrode active material, which will not be repeated here.

[0016] According to the embodiment of the present application, the mass fraction of the metal organic framework material in the precursor is 1%-5%. In this way, the content of the carbon coating layer in the positive electrode active material can be controlled.

[0017] According to the embodiment of the present application, the metal organic framework material satisfies at least one of the following conditions: the metal center of the metal organic framework material comprises at least one of Ti, Mg, Al, Cr, Ni, and Co; and the organic ligand of the metal organic framework material comprises at least one of terephthalic acid, 1,2-cyclohexane dicarboxylic acid, 1,2,4-benzene tricarboxylic acid, 1,2-di(4-pyridyl)ethylene, 1,3,5-tris(4-carboxyphenyl)benzene, 2,2'-bipyridine, 2,5-dihydroxyterephthalic acid, and 2,5-dihydroxyterephthalic acid ethyl ester. In this way, the carbon coating layer with one or more first metal elements can be obtained.

[0018] According to an embodiment of the present application, the heating treatment comprises a temperature rising process, a temperature maintaining process and a temperature falling process, and the heating treatment satisfies at least one of the following conditions: a temperature rising rate of the temperature rising process is 2-8 ℃ / min, and a highest temperature of the temperature rising process is 450-900 ℃; a temperature maintaining time of the temperature maintaining process is 10-15 h, and a temperature of the temperature maintaining process is the highest temperature of the temperature rising process; a temperature falling rate of the temperature falling process is 4-10 ℃ / min, and a lowest temperature of the temperature falling process is less than or equal to 200 ℃. Thus, the positive electrode active material with a better crystal plane orientation can be obtained.

[0019] In a third aspect of the present application, a battery is provided, which comprises a positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer at least on one side of the positive electrode current collector, wherein the positive electrode active material layer comprises the aforementioned positive electrode active material, and / or the positive electrode active material prepared by the aforementioned method. Thus, the battery has all the features and advantages of the aforementioned positive electrode active material, which will not be repeated here.

[0020] In a fourth aspect of the present application, an electric device is provided, which comprises the aforementioned battery. Thus, the electric device has all the features and advantages of the aforementioned battery, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0021] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the appended drawings, wherein: Figure 1 A structural schematic diagram of a positive electrode active material according to an embodiment of the present application is shown; Figure 2 A structural schematic diagram of a positive electrode active material according to another embodiment of the present application is shown; Figure 3 A schematic diagram of a battery according to an embodiment of the present application is shown; Figure 4 is Figure 3 An exploded view of a battery according to an embodiment of the present application is shown; Figure 5 A schematic diagram of a battery module according to an embodiment of the present application is shown; Figure 6 A schematic diagram of a battery pack according to an embodiment of the present application is shown; Figure 7 is Figure 6 An exploded view of a battery pack according to an embodiment of the present application is shown; Figure 8 A schematic diagram of an electric device using the battery as a power source according to an embodiment of the present application is shown.

[0022] Reference Signs List: 1: battery pack, 2: upper case, 3: lower case, 4: battery module, 5: battery, 10: core, 20: carbon coating layer, 21: first metal element M, 22: oxide of the first metal element M, 51: shell, 52: electrode assembly, 53: top cover assembly. DETAILED DESCRIPTION

[0023] Embodiments of the present application are described below in detail with reference to examples illustrated in the accompanying drawings, in which like or similar elements or elements having the same or similar functions are denoted by the same or similar reference numerals throughout the drawings. The embodiments described below by reference to the drawings are exemplary and are for the purpose of explaining the present application only, and are not to be understood as limiting the present application.

[0024] In the description of the present application, it is to be understood that the orientation or positional relationship indicated by the terms "thickness" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0025] In the description of the present application, "A and / or B" can include any one of the case of A alone, the case of B alone, and the case of A and B, where A and B are used only for example, and can be any technical feature connected by "and / or" in the present application.

[0026] In the description of the present application, the meaning of "a plurality of" is two or more.

[0027] Unless otherwise specified, all technical terms used in the present application have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. All patents and publications referred to in the present application are incorporated by reference in their entirety. The terms "comprising" or "including" are open-ended expressions, i.e., include the contents indicated in the present application, but do not exclude other aspects.

[0028] In the description of the present application, all numbers disclosed herein are approximate. The numerical parameters set forth in the specification and attached claims are approximations that can vary depending on the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. At the very least, each numerical limitation or numerical value set forth in the detailed description and claims is intended to indicate at least one

[0029] The poor cycle performance of lithium manganese oxide is attributed to manganese dissolution and irreversible phase transition occurring in the lithium manganese oxide during charging and discharging. Taking lithium manganate as an example, in the spinel structure of lithium manganate, the average valence of manganese is +3.5, a part of Mn exists in the form of +3 valence, and Mn 3+very unstable and easy to disproportionation to form Mn 4+ (solid) and Mn 2+ (solution), the generated Mn 2+ dissolved in the liquid electrolyte, and then deposited on the negative electrode plate after being reduced on the surface of the negative electrode plate, resulting in an increase in the impedance of the electrode plate, and also causing the structure of the skeleton Mn2O4 to be destroyed, with poor structural stability during the charging and discharging process, resulting in a decrease in the cycle performance.

[0030] At the same time, when the electrolyte contains moisture, the water reacts with the lithium salt to generate HF, which reacts with lithium manganate to cause the Mn 2+ dissolved in the electrolyte and the generation of water, which further aggravates the side reaction, thus causing a vicious cycle. In addition, during the charging and discharging process, the spinel structure LiMn2O4 will undergo irreversible phase transition to generate substances such as λ-MnO2, LiMn3O4, and rock salt structure MnO with a defective spinel structure. The continuous accumulation of irreversible phase transition will cause cracks in the lithium manganate particles, and the newly exposed surface caused by the particle cracks will interact with the electrolyte, thus promoting the dissolution of manganese from the lithium manganate. The manganese dissolution phenomenon is more obvious under high temperature conditions, and manganese dissolution is one of the main reasons for the poor cycle performance and poor high-temperature cycle performance of lithium manganate.

[0031] Based on the above considerations, in the present application, by coating a carbon coating layer containing a first metal element M on the surface of the lithium manganate, the crystal structure of the lithium manganate can be stabilized, the occurrence of manganese dissolution during the charging and discharging cycle process can be reduced, and the ionic conductivity and electronic conductivity of the lithium manganate can be improved. Specifically, by coating a metal-organic framework material on the surface of the core, the metal center of the metal-organic framework can be the first metal element M, and after heat treatment, the metal-organic framework material is carbonized to generate a carbon coating layer containing the first metal element M. The carbon coating layer containing the first metal element M has high electronic conductivity and fast lithium ion transport capacity, which can effectively hinder the direct contact between the liquid electrolyte and the positive active material particles, thereby inhibiting the dissolution of manganese; at the same time, the first metal element M can also stabilize the crystal structure of the positive active material, further inhibit the dissolution of manganese, and thus improve the cycle stability and rate performance of the positive active material.

[0032] In some embodiments, the lithium manganate coated with a carbon coating layer containing a first metal element on the surface has better ionic conductivity than the lithium manganate coated with a metal oxide on the surface, so that the lithium ion diffusion migration energy barrier is smaller, to a certain extent, reducing the internal polarization of the battery; it has better electronic conductivity, thereby reducing the difficulty of internal electron transport and improving the rate performance of the positive active material; during the charging and discharging process, i.e. Li +In the process of embedding and de-embedding of the active ions, the carbon coating layer has good binding capacity for the core, and the volume change of the carbon coating layer is also small, so that the positive active material is not prone to pulverization and agglomeration in the long cycle process, and the decrease of the rate performance and the cycle performance caused by the generation of the new solid-state electrolyte film and the consumption of the electrolyte is not prone to occur in the later cycle stage; while hindering the contact of the liquid electrolyte with the positive active material, the electronic conductivity and the ionic conductivity of the positive active material can be improved.

[0033] Generally, the battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. In the process of charging and discharging of the battery, the active ions are embedded and de-embedded between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly plays a role in preventing the short circuit of the positive and negative electrodes, and can also make the ions pass through.

[0034] In some embodiments, the lithium manganese oxide can include lithium manganate, nickel-cobalt-manganese ternary material, lithium-rich manganese-based solid solution; the lithium manganese oxide can also include other positive active materials containing lithium manganese oxygen elements, for example, lithium manganese phosphate.

[0035] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive active material layer located at least on one side of the positive electrode current collector, and the positive active material layer includes the positive active material.

[0036] The battery disclosed in the embodiments of the present application can be used in a power consumption device using the battery as a power source, or a power source system of the power consumption device composed of the battery disclosed in the present application, or various energy storage systems using the battery as an energy storage element. The power consumption device can include a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric vehicle, an electric car, a ship, a spacecraft, etc. Among them, the electric toy can include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy and an electric aircraft toy, etc., and the spacecraft can include an airplane, a rocket, a space shuttle and a spacecraft, etc.

[0037] It should be understood that the technical solutions described in the embodiments of the present application are not only limited to the above-described batteries and power consumption devices, but can also be applied to all other batteries and power consumption devices using the batteries, but for the sake of brevity of description, the following embodiments are described by taking the electric vehicle as an example.

[0038] In the first aspect of the present application, the present application provides a positive active material, referring to Figure 1 , comprising: a core 10, the core 10 comprising a lithium manganese oxide; a carbon coating layer 20, the carbon coating layer 20 covering at least part of the surface of the core 10, the carbon coating layer 20 comprising a first metal element M (i.e. Figure 1The dissociation energy of the M-O bond is greater than the dissociation energy of the Mn-O bond. When the dissociation energy of the M-O bond is greater than the dissociation energy of the Mn-O bond, the structural stability of the M-O bond is higher. When the first metal element enters the crystal lattice of the core, the crystal structure of the core is partially distorted, thereby expanding the lithium ion deintercalation channel of the core, which is beneficial to the diffusion of lithium ions in the crystal structure of the core, thereby improving the ionic conductivity and the structural stability of the positive electrode active material. Meanwhile, the carbon coating layer can effectively improve the transmission efficiency of electrons and reduce the polarization phenomenon in the charging and discharging process of the battery, thereby further improving the cycle performance of the battery.

[0039] The dissociation energy of a bond is the energy required to homolytically cleave a chemical bond. Specifically, the process in which atoms form covalent bonds through the sharing of valence electrons and combine into stable molecules is a process in which the energy of a system decreases, i.e., an exothermic process, and the energy released in this process is the bond energy of the chemical bond formed. When a chemical bond is broken, energy needs to be provided, and the energy required to homolytically cleave a chemical bond is the dissociation energy.

[0040] In some embodiments, the dissociation energy of a bond is a common sense in the art, has a meaning known in the art, and can be measured by a test method and instrument known in the art.

[0041] In some embodiments, with reference to Figure 2 The core 10 can further include a first metal element M located on the surface of the core 10 close to the carbon coating layer 20.

[0042] When the metal organic framework material is carbonized to form the carbon coating layer through a high-temperature heating process, the first metal element M in the carbon coating layer 20 in contact with the core 10 will exchange elements with the manganese element in the core 10 at high temperature, and then enter the crystal structure of the core 10, thereby achieving the effect of stabilizing the core crystal structure.

[0043] For example, the first metal element in the core 10 exists in a small amount in the surface layer of the core 10, for example, when the number of moles of the first metal element in the core 10 is m3 and the number of moles of the manganese element in the core 10 is m4, m3:m4 can be 0.001%-0.004%.

[0044] In some embodiments, the number of moles of any element in a compound is a common sense in the art, has a meaning known in the art, and can be measured by a test method and instrument known in the art.

[0045] In some embodiments, the first metal element M can include at least one of Ti, Mg, Al, Cr, Ni, and Co; further, the first metal element M can include Al.

[0046] As an example, when the ionic radius of the first metal element is close to that of the manganese element, the first metal element M can be more easily doped into the surface structure of the inner core 10 and replace Mn 3+ during high-temperature heating of the metal organic framework material. The first metal element can increase the average valence of the manganese element in the inner core while reducing the content of Mn 3+ , stabilizing the crystal structure of the inner core and inhibiting the occurrence of the Jahn-Teller effect. At the same time, the dissociation energy of M-O is greater than that of the Mn-O bond, thereby improving the ionic conductivity of the inner core, reducing polarization, and improving the kinetic performance of the positive electrode active material.

[0047] In some embodiments, the valence and average valence of the element are well known in the art and have the meanings known in the art, and can be measured by test methods and instruments known in the art.

[0048] As an example, the Jahn-Teller effect refers to the distortion of a high-energy orbital in an electron shell in a symmetric nonlinear molecule to reduce orbital energy and eliminate degeneracy. For example, when the average valence of Mn in spinel-structured lithium manganate is less than +3.5 during the charging and discharging process, the Jahn-Teller distortion occurs, causing the unit cell to expand and contract asymmetrically, causing the spinel structure to change from cubic symmetry to tetragonal symmetry, causing the positive electrode active material to undergo irreversible phase transition, and thus causing the cycle performance to decrease significantly.

[0049] In some embodiments, the introduction of the first metal element improves the crystal structure stability of the lithium manganate, which helps to inhibit the occurrence of irreversible phase transition of the lithium manganate at a low discharge voltage platform (e.g., less than 3V), effectively improves the discharge capacity of the lithium manganate at a low state of charge, and thus improves the power performance of the lithium manganate.

[0050] In some embodiments, the carbon coating layer can include an oxide of the first metal element M.

[0051] As an example, when the carbon coating layer contains an oxide of the first metal element M, the oxide of the first metal element M near the side of the inner core 10 will react with the surface structure of the inner core to form a solid solution, thereby improving the stability of the crystal structure of the inner core and improving the high-temperature cycle performance and storage performance of the positive electrode active material. For example, when the inner core is lithium manganate and the first metal element is Ti, the oxide of the titanium element (titanium dioxide) near the side of the inner core 10 will react with the surface structure of the inner core to form a solid solution of LiMn 2-q TiO2, where 0≤q≤0.2.

[0052] In some embodiments, the lithium manganese oxide can include at least one of a lithium-rich manganese-based solid solution, a nickel cobalt manganese ternary material, a lithium manganese phosphate, lithium manganate.

[0053] As an example, the lithium manganese oxide has a lower production manufacturing cost and a higher discharge specific capacity.

[0054] In some embodiments, the lithium-rich manganese-based solid solution can satisfy a general formula: xLi a [Li 1 / 3 Mn 2 / 3 ]O b ·(1-x)Li c M1O d wherein 0

[0055] As an example, x can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9; a+c can be 0.9, 1.0, 1.1, or 1.2; b+d can be 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, or 2.5.

[0056] In some embodiments, the nickel cobalt manganese ternary material can satisfy a general formula: Li e Ni f Co g Mn h M2 i O j wherein 0.9

[0057] As an example, f can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9; g can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9; h can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9; i can be 0, 0.1, 0.15, or 0.2; j can be 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, or 2.5.

[0058] In some embodiments, the lithium manganese phosphate can satisfy the general formula: Li k Mn 1-m M3 m PO n wherein 0.9≤k≤1.2, 0≤m≤0.8, 3.0≤n≤4.5, and M3 includes one of Al, Fe, Ti, Mg, V, Mn, Cr, Zr, Nb, and W.

[0059] As an example, k can be 0.9, 1.0, 1.1, or 1.2; m can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8; and n can be 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, or 4.5.

[0060] In some embodiments, the lithium manganese phosphate can satisfy the general formula: Li p Mn 2-q M4 q O s wherein 0.9≤p≤1.2, 0≤q≤0.2, 3.0≤s≤4.5, and M4 includes at least one of Li, Cr, Co, Ni, Mg, Ca, Sr, Ba, Na, K, Al, Be, B, Ti, Zr, Cu, Zn, Ga, Sn, and V.

[0061] It can be understood that the doping elements M1, M2, M3, and M4 can be doping elements contained in the core itself or doping elements introduced by the first metal element in the carbon coating layer.

[0062] As an example, p can be 0.9, 1.0, 1.1, or 1.2; q can be 0, 0.1, 0.15, or 0.2; and s can be 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, or 4.5.

[0063] In some embodiments, the chemical formula of the compound is known in the art and has a meaning known in the art, and can be measured by a test method and instrument known in the art.

[0064] In some embodiments, the particle size of the core can be 7 μm-15 μm, and optionally, the particle size of the core can be 9 μm-12 μm.

[0065] For example, the particle size of the inner core can be 7 pm, 7.2 pm, 7.5 pm, 7.8 pm, 8 pm, 8.2 pm, 8.5 pm, 8.8 pm, 9 pm, 9.2 pm, 9.5 pm, 9.8 pm, 10 pm, 10.2 pm, 10.5 pm, 10.8 pm, 11 pm, 11.2 pm, 11.5 pm, 11.8 pm, 12 pm, 12.2 pm, 12.5 pm, 12.8 pm, 13 pm, 13.2 pm, 13.5 pm, 13.8 pm, 14 pm, 14.2 pm, 14.5 pm, 14.8 pm, or 15 pm.

[0066] In some embodiments, the particle size of the inner core is well known in the art and has the meaning commonly known in the art, and can be measured by commonly known testing methods and instruments.

[0067] For example, the particle size of the inner core can be measured by the following method: the testing instrument is a JEM-2100 high-resolution transmission electron microscope, the testing acceleration voltage is 300 kV, and the resolution is 0.1 nm-0.2 nm. 10 mg of the positive electrode active material to be tested is uniformly dispersed in anhydrous ethanol, and then the suspension is added to the surface of a microgrid copper mesh. After drying, transmission electron microscope testing is performed, and the copper mesh is observed under a transmission electron microscope to obtain the particle size of the inner core.

[0068] For example, when the particle size of the inner core is 7 pm-15 pm, the particle size of the inner core particle is moderate, the stability of the positive electrode slurry is high, and adverse phenomena such as sedimentation and poor consistency of the slurry are less likely to occur. In the coating process of the positive electrode slurry, adverse phenomena such as material blockage, particle scratches, and pitting after drying of the pole piece are less likely to occur, thereby causing pole piece quality problems. At the same time, the specific surface area of the inner core is moderate, the surface defects are less, and the inner core powder is less likely to agglomerate and induce battery polarization.

[0069] In some embodiments, referring to Figure 2 , the thickness of the carbon coating layer is d1, the particle size of the inner core is d2, and d1:d1 can be 0.01-0.1.

[0070] For example, d1:d1 can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1.

[0071] When d1:d1 is 0.01-0.1, the thickness of the carbon coating layer is moderate, which can effectively reduce the direct contact between the electrolyte and the positive electrode active material, thereby reducing the occurrence of side reactions and manganese dissolution, and also does not hinder the diffusion and migration of lithium ions between the inner core 10 and the electrolyte interface.

[0072] In some embodiments, the thickness of the carbon coating layer is a common knowledge in the art, has a meaning known in the art, and can be measured by a test method and instrument known in the art.

[0073] For example, the thickness of the carbon coating layer can be measured by a test method for measuring the core particle size, for example, the positive electrode active material to be measured can be dispersed in anhydrous ethanol, then added dropwise to the surface of a copper mesh, and then observed under a transmission electron microscope after drying to obtain the thickness of the carbon coating layer.

[0074] In some embodiments, the mass fraction of the carbon coating layer in the positive electrode active material can be 1%-3%.

[0075] For example, the mass fraction of the carbon coating layer in the positive electrode active material can be 1%, 1.5%, 2%, 2.5% or 3%. When the mass fraction of the carbon coating layer in the positive electrode active material is 1%-3%, the proportion of the coating layer in the positive electrode active material is appropriate, which can inhibit the side reaction between lithium manganese oxide and electrolyte, and has little effect on the capacity and energy density of the positive electrode active material.

[0076] In some embodiments, the mass fraction of the carbon coating layer in the positive electrode active material is a common knowledge in the art, has a meaning known in the art, and can be measured by a test method and instrument known in the art.

[0077] For example, the mass fraction of the carbon coating layer in the positive electrode active material can be obtained by the reaction between an acid solution and the positive electrode active material. Specifically, a certain amount of the positive electrode active material to be measured can be dissolved in hydrochloric acid, then filtered, washed with deionized water, dried and weighed to obtain the mass of the carbon coating layer. The mass fraction of the carbon coating layer in the positive electrode active material can be obtained by dividing the mass of the carbon coating layer by the total mass of the positive electrode active material.

[0078] In some embodiments, the number of moles of the first metal element M in the carbon coating layer is m1, the number of moles of manganese in the core is m2, and m1:m2 can be 0.01%-0.5%.

[0079] In some embodiments, the number of moles of any element in the carbon coating layer is a common knowledge in the art, has a meaning known in the art, and can be measured by a test method and instrument known in the art.

[0080] For example, the number of moles of the first metal element in the carbon coating layer can be measured by the following method: using a scanning electron microscope to analyze the elements of the carbon coating layer of the positive electrode active material, measuring the weight percentage of the first metal element in the carbon coating layer, and then converting the weight percentage to the number of moles according to the molar mass of the corresponding element.

[0081] In some embodiments, the number of moles of any element in the core is a matter of common general knowledge in the art, has a meaning known in the art, and can be measured by a test method and instrument known in the art.

[0082] As an example, the number of moles of manganese in the core can be measured by the following method: a quantitative amount of the positive electrode active material is nitrated using a strong acid, so that the manganese element is leached from the core, and then the number of moles of the manganese element is measured using an inductively coupled plasma spectrometer (ICP).

[0083] As an example, m1:m2 can be 0.01%, 0.03%, 0.08%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%. By introducing a small amount of the first metal element, the stability of the crystal structure of the core can be effectively improved while retaining the original core structure.

[0084] In a second aspect of the present application, a method for preparing the positive electrode active material described above is provided, comprising: S100: mixing the core with a metal organic framework material In some embodiments, the core is mixed with the metal organic framework material in this step to obtain a precursor, and specifically, the mass fraction of the metal organic framework material in the precursor can be 1%-5%.

[0085] As an example, the mass fraction of the metal organic framework material in the precursor can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%.

[0086] A metal organic framework (MOF) is a material formed by a metal center and an organic ligand through a coordination bond into a one-dimensional structure, a two-dimensional structure, or a three-dimensional structure.

[0087] In some embodiments, the metal center of the metal organic framework material can include at least one of Ti, Mg, Al, Cr, Ni, and Co. By adjusting the metal center, the type of the first metal element in the carbon coating layer formed by the metal organic framework can be adjusted.

[0088] In some embodiments, the organic ligand of the metal organic framework material can include at least one of terephthalic acid, 1,2-cyclohexane dicarboxylic acid, 1,2,4-benzene tricarboxylic acid, 1,2-di(4-pyridyl)ethylene, 1,3,5-tris(4-carboxyphenyl)benzene, 2,2'-bipyridine, 2,5-dihydroxyterephthalic acid, and 2,5-dihydroxyterephthalic acid ethyl ester.

[0089] As an example, the metal organic framework can include at least one of MOF-74 (Mg), MIL-53 (Cr), Ni-MOF-74, Co-ZIF-9, MIL-125 (Ti), MIL-53 (Al), and the like. By virtue of the adjustable characteristics of the metal center and the organic ligand of the MOF, an MOF material with an adjustable pore structure can be obtained, which facilitates adjustment of the structural parameters of the first metal element of the finally formed carbon-coated layer, the compactness of the coating layer, the porosity of the coating layer, and the like, while achieving high conductivity and high crystal structure stability, and also has less impact on the embedding and de-embedding of lithium ions.

[0090] S200: heating treatment on the precursor In some embodiments, the heating treatment is performed on the precursor to obtain the positive electrode active material. Through the heating treatment on the precursor, the lithium manganese oxide coated with the carbon-coated layer containing the first metal element can be generated in one step.

[0091] In some embodiments, the heating treatment includes a temperature rising process, a temperature holding process, and a temperature falling process, and the heating treatment satisfies at least one of the following conditions: the temperature rising rate of the temperature rising process is 2-8 ℃ / min, and the highest temperature of the temperature rising process is 450-900 ℃; the temperature holding time of the temperature holding process is 10-15 h, and the temperature of the temperature holding process is the highest temperature of the temperature rising process; the temperature falling rate of the temperature falling process is 4-10 ℃ / min, and the lowest temperature of the temperature falling process is less than or equal to 200 ℃.

[0092] As an example, the temperature rising rate of the temperature rising process can be 2 ℃ / min, 3 ℃ / min, 4 ℃ / min, 5 ℃ / min, 6 ℃ / min, 7 ℃ / min, or 8 ℃ / min; and the highest temperature of the temperature rising process can be 450 ℃, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, or 900 ℃. By adjusting the temperature rising rate and the highest temperature of the temperature rising process, the energy consumption can be reduced, and the preparation time can be shortened, thereby improving the production efficiency.

[0093] In some embodiments, different heating temperatures affect the generation of crystal faces of the lithium manganese oxide. When the highest temperature of the heating treatment is 500 ℃, it is easier to generate a crystal structure with more (111) crystal faces. The (111) crystal face helps to improve the structural stability of the crystal, thereby improving the cycle stability of the positive electrode active material.

[0094] In some embodiments, when the maximum temperature of the temperature increasing process is greater than 900°C, i.e., the temperature of the temperature holding process is greater than 900°C, for example, 1000°C, 1200°C or 1500°C, although a crystal structure with a better crystal face orientation can also be generated, a large amount of energy consumption will be caused, and the requirements for the production equipment will also be greatly increased.

[0095] As an example, the temperature holding process is performed at the maximum temperature reached by the temperature increasing process, and the temperature holding process time can be 10 h, 10.5 h, 11 h, 11.5 h, 12 h, 12.5 h, 13 h, 13.5 h, 14 h, 14.5 h or 15 h.

[0096] As an example, the cooling rate of the temperature decreasing process can be 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min or 10°C / min. A faster cooling rate can improve the stability of the crystal structure of the positive electrode active material and reduce the crystal phase transition of the crystal structure of the positive electrode active material during the cooling process. The minimum temperature of the temperature decreasing process can be less than or equal to 200°C. When the temperature decreases to below 200°C, the crystal structure of the positive electrode active material is relatively stable and is not prone to re-preparation. Subsequently, room temperature cooling can be used for subsequent cooling.

[0097] It should be noted that the related parameters in the above method for preparing the positive electrode active material can refer to part or all of the technical features in the foregoing embodiments. The parts not described in the related embodiments of the method for preparing the positive electrode active material can also refer to the foregoing embodiments and the related drawings, which will not be described here.

[0098] The above description of each embodiment tends to emphasize the differences between each embodiment, and the same or similar parts can be referred to each other. For the sake of brevity, they will not be described here.

[0099] In a third aspect of the present application, a battery is provided, which includes a positive electrode sheet, the positive electrode sheet including a positive electrode current collector and a positive electrode active material layer located at least on one side of the positive electrode current collector, the positive electrode active material layer including the aforementioned positive electrode active material and / or the positive electrode active material prepared by the aforementioned method.

[0100] In the embodiments of the present application, the battery 5 can be a metal battery, for example, the battery 5 can be a lithium metal battery, etc.

[0101] In some embodiments, the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator film located between the positive electrode sheet and the negative electrode sheet.

[0102] In some embodiments, the electrode assembly is a winding structure. The positive electrode sheet and the negative electrode sheet are wound to form the winding structure.

[0103] In some embodiments, the electrode assembly is a stack structure.

[0104] As an example, a plurality of positive electrode tabs and a plurality of negative electrode tabs are alternately stacked.

[0105] As an example, a plurality of positive electrode tabs are provided, and the negative electrode tab is folded to form a plurality of folded segments which are stacked.

[0106] As an example, both the positive electrode tab and the negative electrode tab are folded to form a plurality of folded segments which are stacked.

[0107] As an example, a plurality of isolation films are provided, and each of the isolation films is provided between any adjacent positive electrode tab or negative electrode tab.

[0108] As an example, the isolation film is continuously provided, and is provided between any adjacent positive electrode tab or negative electrode tab by folding or winding.

[0109] In some embodiments, the electrode assembly can have a cylindrical shape, a flat shape, or a multi-prism shape, etc.

[0110] In some embodiments, the electrode assembly is provided with a tab, and the tab can guide current out of the electrode assembly. The tab includes a positive tab and a negative tab.

[0111] As an example, the positive current collector has two opposite surfaces in the thickness direction thereof, and the positive active material layer is provided on any one or both of the two opposite surfaces of the positive current collector.

[0112] As an example, the positive current collector can be a metal foil, a foam metal, or a composite current collector. For example, as the metal foil, silver surface treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon, carbon, nickel, or titanium, etc. can be used. The composite current collector can include a polymer material base layer and a metal layer. The foam metal can be foam nickel, foam copper, foam aluminum, foam alloy, or foam carbon, etc. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0113] In some embodiments, the negative electrode tab can include a negative electrode current collector, which can be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, silver surface-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, a carbon electrode, or the like can be used. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, or the like. The composite current collector can include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, or the like) on a polymer material base material (such as a base material of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, or the like).

[0114] In some embodiments, the negative electrode tab can be a metal foil calendered or a surface-coated inert layer metal powder coated on the current collector.

[0115] In some embodiments, the negative electrode current collector can be a composite current collector, for example, the composite current collector can include at least one of a carbon cloth, a carbon film, a carbonaceous material, a porous current collector, an alloy-modified current collector, a lithiumophilic-modified current collector, and a sodiumophilic-modified current collector.

[0116] In some embodiments, the negative electrode tab can include a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, and the negative electrode active material layer can include a negative electrode active material, which can be a high-capacity material, for example, the negative electrode active material can include at least one of natural graphite, artificial graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, and lithium titanate.

[0117] For example, the silicon-based material can include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material, and the tin-based material can include at least one of elemental tin, tin oxide, and tin alloy material.

[0118] In some embodiments, the separator film is a separator film. The type of the separator film is not particularly limited in the present application, and any porous structure separator film having good chemical stability and mechanical stability can be selected.

[0119] For example, the main material of the separator film can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, ceramic, and polyvinylidene fluoride. The separator film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited. The separator film can be a separate component located between the positive electrode tab and the negative electrode tab, or can be attached to the surface of the positive electrode and the negative electrode.

[0120] As an example, the shape of the battery is not particularly limited, and can be cylindrical, square, or any other shape. For example, Figure 3 is a battery 5 of a square structure as an example. Specifically, referring to Figure 4 , the outer package of the battery 5 can include a case 51 and a top cover assembly 53. Among them, the case 51 can 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 case 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity.

[0121] As an example, the positive electrode sheet, the negative electrode sheet, and the separator film can form the electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity, and the gel polymer electrolyte fills the internal space of the electrode assembly 52. The number of electrode assemblies 52 contained in the battery 5 can be one or more, and a person skilled in the art can select according to the specific actual needs.

[0122] As an example, the battery can be assembled into a battery module, and the number of batteries contained in the battery module can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery module. Figure 5 is a battery module 4 as an example. Referring to Figure 5 In the battery module 4, a plurality of batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, it can also be arranged in any other way. Further, the plurality of batteries 5 can be fixed by fasteners. The battery module 4 can also include a housing having a receiving space, and the plurality of batteries 5 are received in the receiving space.

[0123] As an example, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery pack. Figure 6 and Figure 7 is a battery pack 1 as an example. Referring to Figure 6 and Figure 7 The battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and form a closed space for receiving the battery module 4. The plurality of battery modules 4 can be arranged in the battery box in any way.

[0124] In a fourth aspect of the present application, a power consuming device is provided, which includes the above-mentioned battery 5. Therefore, the power consuming device has all the features and advantages of the above-mentioned battery 5, which will not be repeated here.

[0125] A battery, a battery module, or a battery pack can be used as a power source of an electric device, and can also be used as an energy storage unit of the electric device. The electric device can include a mobile device (e.g., a cell phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto. The electric device can select a battery, a battery module, or a battery pack according to its use requirements.

[0126] As an example, Figure 8 is an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of high power and high energy density of the electric device for the battery, a battery pack or a battery module can be used.

[0127] As an example, the electric device can also be a cell phone, a tablet computer, a laptop, etc. The device usually requires thinning, and a battery can be used as a power source.

[0128] The scheme of the present application is described below through specific examples. It should be noted that the following examples are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. If the specific technology or condition is not specified in the examples, it is performed according to the technology or condition described in the literature in the art or according to the product instruction. If the reagent or instrument used is not specified by the manufacturer, it is a conventional product that can be obtained from the market.

[0129] Example 1 1. Preparation of positive active material MIL-125 (Ti) powder is mixed with lithium manganese oxide positive electrode material to obtain a precursor, wherein the mass fraction of metal organic framework (MOF) material in the precursor is 3wt%. The precursor is ground by high-energy ball milling at a speed of 300r / min for 5h, and then heated to 500℃ at a heating rate of 5℃ / min in an air atmosphere (oxygen-containing atmosphere) and kept for 12h, and then cooled to 200℃ at a cooling rate of 5℃ / min, and then naturally cooled to room temperature, to obtain a positive active material.

[0130] 2. Preparation of positive electrode sheet The obtained positive active material, conductive agent (carbon black), binder (polyvinylidene fluoride (PVDF)), and solvent (N-methyl pyrrolidone (NMP)) are stirred and mixed uniformly at a weight ratio of 95.48:1.47:1.55:1.14 to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on a positive electrode current collector (aluminum foil) with a coating density of 0.35g / 1540mm 2 After cold pressing, a positive electrode sheet is obtained.

[0131] 3. Preparation of negative electrode sheet The negative active material (graphite), conductive agent (carbon black), binder (styrene-butadiene rubber (SBR)), thickening agent (sodium hydroxymethyl cellulose (CMC)) were dissolved in the solvent deionized water according to the weight ratio of 97.2:0.8:0.8:1.2, and the negative electrode slurry was obtained after mixing uniformly. The negative electrode slurry was coated on the negative current collector (copper foil) with a coating density of 0.175 g / 1540 mm 2 , and the negative electrode sheet was obtained after cold pressing.

[0132] 4. Preparation of electrolyte In an argon atmosphere glove box, the organic solvents ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed uniformly according to the volume ratio of 36:29:35 to obtain a mixed solvent, and 1M LiPF6 lithium salt was dissolved in the mixed solvent to obtain the electrolyte.

[0133] 5. Preparation of battery The positive electrode sheet, the separator, and the negative electrode sheet were stacked in order with the separator between the positive and negative electrode sheets to play a role of isolation, and then the bare cell was obtained by winding. The bare cell was welded with tabs, and was placed in an aluminum shell and baked at 100°C to remove water. Then, the electrolyte was injected and sealed to obtain the uncharged battery. The uncharged battery was subjected to static, hot and cold pressing, formation, and shaping treatment in sequence to obtain the battery.

[0134] The preparation of the positive electrode sheet, the preparation of the negative electrode sheet, the preparation of the electrolyte, and the preparation of the battery in Example 1 and Examples 2-16, and Comparative Examples 1-2 were the same, except for the preparation of the positive active material. See Table 1 for details. In Comparative Example 1, the inner core was not modified by carbon coating, and in Comparative Example 2, only the inner core was mixed with MOF without heating treatment.

[0135] Table 1

[0136] The positive active materials in Examples 1-16 and Comparative Examples 1-2 were subjected to the following tests, and the test results are shown in Table 2. 1. Thickness of carbon coating layer: The positive active material to be tested was dispersed in anhydrous ethanol, then added dropwise to the surface of a copper mesh, and then dried. The copper mesh was observed under a transmission electron microscope to obtain the thickness of the carbon coating layer.

[0137] 2. The number of moles of the first metal element in the carbon coating layer: The weight percentage of the first metal element in the carbon coating layer of the positive electrode active material is measured by scanning electron microscopy, and the number of moles is obtained by conversion according to the molar mass of the corresponding element.

[0138] 3. The number of moles of manganese element in the core: The quantitative positive electrode active material is nitrated with strong acid, and the manganese element is leached out of the core. The number of moles of manganese element is measured by inductively coupled plasma spectrometer (ICP).

[0139] 4. The mass fraction of the carbon coating layer in the positive electrode active material: The positive electrode active material to be tested is dissolved in hydrochloric acid, filtered, washed with deionized water, dried and weighed to obtain the mass of the carbon coating layer. The mass fraction of the carbon coating layer in the positive electrode active material is obtained by dividing the mass of the carbon coating layer by the total mass of the positive electrode active material.

[0140] 5. Test of ionic conductivity and electronic conductivity: The positive electrode active material powder is placed in a battery test mold lined with stainless steel gaskets as blocking electrodes, and pressed at a pressure of 350 MPa for 3 min to form a conductivity mold battery. The ionic conductivity is tested by an electrochemical workstation impedance module; the electronic conductivity is obtained by constant voltage direct current test of the mold battery by the electrochemical workstation; The calculation formula is as follows:

[0141] Wherein, σ represents the conductivity, d represents the thickness of the electrode to be tested, R represents the electrochemical impedance (both the ionic impedance value and the electronic impedance value are measured by the electrochemical workstation), and S represents the effective area of the electrode to be tested.

[0142] Table 2

[0143] The batteries in Examples 1-16 and Comparative Examples 1-2 were subjected to the following tests, and the test results are shown in Table 3. 1. High-rate capacity retention rate test At 25°C, the battery was charged at 1 / 3C constant current to 4.4V, then charged at 4.4V constant voltage to 0.05C current, and then discharged at 1 / 3C to 2.5V after 5min standby, and the obtained capacity was recorded as the initial capacity C0; again charged at 1 / 3C constant current to 4.4V, then charged at 4.4V constant voltage to 0.05C current, and then discharged at 4C to 2.5V after 5min standby, and the obtained capacity was recorded as the initial capacity C1, and C1 / C0 was the high-rate capacity retention rate.

[0144] 2. Cycle capacity retention rate test The battery was charged at 45°C at 1 / 3C constant current to 4.4V, then charged at 4.4V constant voltage to a current of 0.05C, rested for 5min, then discharged at 1 / 3C to 2.5V, and the capacity obtained was recorded as the initial capacity C0. The above steps were repeated for the same battery, and the discharge capacity of the battery after the nth cycle was recorded as Cn. n The capacity retention rate P of the battery after each cycle was then calculated as follows: n = Cn / C0x 100% n When n was 500, P was recorded. 500 as the cycle capacity retention rate of the battery.

[0145] 3. Mn dissolution ICP test The full-charge negative electrode sheet after 500 cycles was disassembled, and the Mn content in the negative electrode sheet was tested by inductively coupled plasma (ICP) to confirm the manganese dissolution.

[0146] Table 3

[0147] In the description of the present specification, the description referring to the terms "one embodiment", "another embodiment", and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment are included in at least one embodiment of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples, without contradiction.

[0148] In the description of the present specification, the terms "first", "second" are used only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and the person skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A positive electrode active material, characterized in that, Comprising: A core, the core comprising lithium manganese oxide; A carbon coating layer, the carbon coating layer at least covering a part of the surface of the core, the carbon coating layer comprising a first metal doping element M, the first metal element M comprising at least one of Ti, Mg, Al, Cr, Ni, Co; the number of moles of the first metal element M in the carbon coating layer is m1, the number of moles of manganese element in the core is m2, and m1:m2 is 0.01% - 0.5%.

2. The positive electrode active material according to claim 1, characterized in that, The core further comprises the first metal element M, and the first metal element M is located on the surface of the core close to the carbon coating layer.

3. The positive electrode active material according to claim 1 or 2, characterized in that, The first metal element M comprises Al.

4. The positive electrode active material according to any one of claims 1-3, characterized in that, The carbon coating layer comprises an oxide of the first metal element M.

5. The positive electrode active material according to any one of claims 1-4, characterized in that, The lithium manganese oxide comprises at least one of lithium-rich manganese-based solid solution, nickel cobalt manganese ternary material, lithium manganese phosphate, and lithium manganate.

6. The positive electrode active material according to claim 5, characterized in that, The lithium manganese oxide satisfies at least one of the following conditions: The lithium-rich manganese-based solid solution satisfies the general formula: xLi a [Li 1 / 3 Mn 2 / 3 O b ·(1-x)Li c M1O d , Where 0 < x < 1, 0.9 ≤ a + c ≤ 1.2, 1.0 ≤ b + d ≤ 2.5, M1 comprises at least one of Al, Mn, Cr, Co, Ni, Fe, Ru; The nickel-cobalt-manganese ternary material satisfies the general formula: Li e Ni f Co g Mn h M2 i O j , Where 0.9 ≤ e ≤ 1.2, 0 < f < 1, 0 < g < 1, 0 < h < 1, 0 ≤ i ≤ 0.2, f + g + h + i = 1, 1.0 ≤ j ≤ 2.5, M2 comprises at least one of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb, Al; The lithium manganese phosphate satisfies the general formula: Li k Mn 1-m M3 m PO n , Where 0.9 ≤ k ≤ 1.2, 0 ≤ m ≤ 0.8, 3.0 ≤ n ≤ 4.5, M3 comprises one of Al, Fe, Ti, Mg, V, Mn, Cr, Zr, Nb, W; The lithium manganese oxide satisfies the general formula: Li p Mn 2-q M4 q O s , Where 0.9 ≤ p ≤ 1.2, 0 ≤ q ≤ 0.2, 3.0 ≤ s ≤ 4.5; M4 comprises at least one of Li, Cr, Co, Ni, Mg, Ca, Sr, Ba, Na, K, Al, Be, B, Ti, Zr, Cu, Zn, Ga, Sn, V.

7. The positive electrode active material according to any one of claims 1-6, characterized in that, The particle size of the core is 7 μm - 15 μm, and optionally, the particle size of the core is 9 μm - 12 μm.

8. The positive electrode active material according to any one of claims 1-7, characterized in that, The thickness of the carbon coating layer is d1, the particle size of the core is d2, and d1:d2 is 0.01 - 0.

1.

9. The positive electrode active material according to any one of claims 1-8, characterized in that, The mass fraction of the carbon coating layer in the positive electrode active material is 1% - 3%.

10. A battery, characterized in that, Comprising a positive electrode plate, the positive electrode plate comprising a positive electrode current collector and a positive electrode active material layer at least on one side of the positive electrode current collector, the positive electrode active material layer comprising the positive electrode active material according to any one of claims 1 - 9.

11. An electrical appliance, characterized in that, Comprising the battery according to claim 10.

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