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

Abstract

The present application discloses a positive electrode material and a preparation method thereof, a positive electrode plate, a battery, and an electrical device. The positive electrode material includes a positive electrode active material and a coating layer coated on the surface of the positive electrode active material, the coating layer includes a metal-organic framework material carbide, and the metal-organic framework material carbide is doped with a sulfide element, and the sulfide element has reducing properties. The present application scheme is to coat the surface of the positive electrode active material with a metal-organic framework material carbide, and the metal-organic framework material carbide is doped with a sulfide element with reducing properties. The sulfide element with reducing properties contacts the positive electrode active material. The sulfide element with reducing properties is easily oxidized to a sulfide element with a higher valence state. The sulfide element with a higher valence state will react with the residual lithium compound to reduce the content of the residual lithium compound, thereby improving the electrochemical performance of the battery.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a positive electrode material and a preparation method thereof, a positive electrode sheet, a battery, and an electrical device. Background Art

[0002] Lithium-ion batteries, as secondary batteries, reversibly convert chemical energy into electrical energy, making them an ideal carrier for human energy utilization and storage. Since their introduction, they have been widely used due to their long lifespan, high energy density, and low maintenance costs. Currently, lithium-ion batteries are used in a variety of fields, including portable electronic devices, new energy vehicles, and energy storage systems.

[0003] The positive electrode active material is a key factor influencing the performance of lithium-ion batteries, often determining their cycle life, energy density, and power density. Due to the preparation process or the characteristics of the positive electrode active material itself, residual lithium compounds (RLCs), such as lithium hydroxide and lithium carbonate, are easily formed on the surface of the positive electrode active material. Residual lithium compounds generally have poor conductivity, which increases the cathode / electrolyte interface impedance, exacerbates battery polarization, degrades discharge capacity and cycle stability, and negatively impacts battery performance. Summary of the Invention

[0004] In view of the above problems, the embodiments of the present application provide a positive electrode material and a preparation method thereof, a positive electrode plate, a battery and an electrical device, aiming to alleviate the negative impact of residual lithium compounds in the positive electrode active material on battery performance.

[0005] In a first aspect, an embodiment of the present application provides a positive electrode material, comprising a positive electrode active substance and a coating layer coated on the surface of the positive electrode active substance, wherein the coating layer comprises a metal-organic framework material carbide, and the metal-organic framework material carbide is doped with a sulfide element, and the sulfide element has reducing properties.

[0006] The positive electrode material provided in the embodiment of the present application includes a positive electrode active material, a metal-organic framework material carbide coated on the surface of the positive electrode active material, and the metal-organic framework material carbide is doped with a reducing sulfide element, the reducing sulfide element contacts the positive electrode active material, and in combination with the subsequent charge and discharge process (for example, during the formation process), the reducing sulfide element is easily oxidized to a sulfide element with a higher valence state and reacts with the residual lithium compound on the surface of the positive electrode active material, in situ generating a sulfide-containing inorganic compound with better conductivity than the residual lithium compound, thereby improving the conductivity and electrochemical properties of the positive electrode material. In addition, during the charge and discharge process, the sulfide-containing inorganic compound further grows on the positive electrode active material to form a positive electrode-electrolyte interface (CEI) film, thereby alleviating the negative impact of the residual lithium compound on the battery performance; during the charge and discharge process, the sulfide element will also release lithium ions during the reaction with the residual lithium compound. The additional released lithium ions can also be used to compensate for the lithium ion loss caused by the formation of a solid electrolyte interface (SEI) film at the negative electrode during the charge and discharge process of the battery, thereby ensuring the capacity of the battery.

[0007] In the embodiment of the present application, since the reducing sulfide element is introduced into the surface of the positive electrode active material by doping in the metal-organic framework material carbide, the amount of the introduced sulfide element can be effectively limited, and the excessive sulfide content can be avoided, which in turn makes the conductivity of the positive electrode active material worse. The metal-organic framework material carbide with a rich and stable three-dimensional porous structure is coated on the surface of the positive electrode active material as a carbon skeleton, which can promote the ion transport in the electrochemical process, and the metal-organic framework material carbide forms a coating layer that can prevent the positive electrode active material from directly contacting the electrolyte, reducing the probability of side reactions. At the same time, the coating layer can prevent the dissolution and migration of cations in the positive electrode active material, thereby improving the cycle stability of the battery.

[0008] In some embodiments, the content of the chalcogen element in the positive electrode material is greater than 0 and less than or equal to 10 wt %; optionally, the content of the chalcogen element is less than or equal to 5 wt %.

[0009] Excessive chalcogen content in the positive electrode material can affect its conductivity. By setting the chalcogen content to less than or equal to 10wt%, the battery's cycling, storage, and rate performance are improved within this range. The battery's storage, rate, and cycling stability are optimal when the chalcogen content is 5wt%.

[0010] In some embodiments, the coating layer has a thickness of 1 nm to 20 nm.

[0011] By setting the thickness of the coating layer to 1nm to 20nm, the surface of the positive electrode active material is completely coated with the metal-organic framework material carbide, thereby effectively removing the residual lithium compounds on the surface of the positive electrode active material and reducing the internal resistance of the positive electrode material. In some embodiments, the specific surface area of ​​the positive electrode material is 1m 2 / g~10m 2 / g.

[0012] By setting the specific surface area of ​​the positive electrode material to 1 m 2 / g~10m 2 / g, which can make the positive electrode material have better wetting effect and better processing performance.

[0013] In some embodiments, the chalcogen element is evenly distributed in the coating layer, or the concentration of the chalcogen element gradually increases in the coating layer away from the positive electrode active material.

[0014] Whether by setting the sulfide elements in the coating layer to be uniformly distributed or gradually increasing the concentration in the direction away from the positive electrode active material, the sulfide content in the coating layer can be effectively reduced, avoiding the sulfide content being too high, which causes excessive sulfide elements to react with lithium compounds to generate excessive sulfide-containing inorganic compounds, and instead increase the resistance value of the contact interface between the coating layer and the positive electrode active material, thereby increasing the internal resistance of the battery.

[0015] In some embodiments, the metal-organic framework carbide has a porous structure.

[0016] By setting the metal-organic framework material carbide to a porous structure, the metal-organic framework material carbide can have a larger specific surface area. On the one hand, it can improve the effect of removing residual lithium compounds of sulfide elements. On the other hand, the porous structure can promote ion transport in the electrochemical process and improve the battery's rate performance.

[0017] In some embodiments, the metal-organic framework carbide comprises a metal element, the chalcogen element, and a carbon element covalently bonded.

[0018] Since the metal elements, chalcogens and carbon elements in the metal-organic framework material carbide are combined together in the form of covalent bonds, the chalcogens can maintain a low valence state and thus have reducing properties. In addition, the chalcogens can be stably bound to the metal-organic framework material carbide to prevent the displacement of the chalcogens.

[0019] In some embodiments, the covalent bond comprises at least one of a metal-chalcogen bond and a carbon-chalcogen bond.

[0020] By setting the covalent bonds to include metal-chalcogen bonds and carbon-chalcogen bonds, the chalcogen can maintain a low valence state and thus have stronger reducing properties, which is conducive to the oxidation of the chalcogen and its combination with residual lithium compounds to form a CEI film, thereby reducing the content of residual lithium compounds; and the chalcogen can be stably combined in the carbide of the metal-organic framework material.

[0021] In some embodiments, the metal-organic framework material carbide further comprises nitrogen, and the covalent bond further comprises a nitrogen-chalcogen bond.

[0022] By setting the covalent bond to also include a nitrogen-chalcogen bond, the chalcogen can also maintain a low valence state and thus have a stronger reducing property, which is conducive to the oxidation of the chalcogen and combining with the residual lithium compound to form a CEI film, thereby reducing the content of residual lithium compounds; and the chalcogen can be stably combined in the metal-organic framework material carbide.

[0023] In some embodiments, the coating layer further comprises metal nanoparticles, and the metal nanoparticles are distributed in the metal-organic framework carbide.

[0024] Metal nanoparticles have good electrical conductivity. The metal nanoparticles are dispersed on the metal-organic framework material carbide, thereby enhancing the conductivity of the coating layer containing the metal-organic framework material carbide and effectively promoting the transmission of ions in the electrochemical process.

[0025] In some embodiments, the chalcogen includes elemental sulfur.

[0026] In the embodiment of the present application, by coating the surface of the positive electrode active material with a metal-organic framework material carbide and doping sulfur into the metal-organic framework material carbide, sulfur residue can be reduced to meet the requirements of stable sulfur doping, low residual sulfur content and good surface conductivity.

[0027] In some embodiments, the positive electrode active material includes a chemical formula of Li a Ni m Co n M 1-m-n O2-rich nickel active material, wherein M includes at least one of Mn and Al, wherein m≥0.6, n≤0.2, 0.9≤a≤1.2; optionally, m≥0.9.

[0028] In the embodiment of the present application, a metal-organic framework material carbide is coated on the surface of the nickel-rich active material, and the metal-organic framework material carbide is doped with a reducing sulfide element. The reducing sulfide element contacts the positive electrode active material. During the charge and discharge process (for example, during the formation process), the sulfide element is easily oxidized to a sulfide element with a higher valence state, and the sulfide element with a higher valence state will react with the residual lithium compound on the surface of the positive electrode active material to in situ generate a sulfide-containing inorganic compound with better conductivity than the residual lithium compound, thereby improving the conductivity and electrochemical properties of the positive electrode material. In addition, during the charge and discharge process, the sulfide-containing inorganic compound will further grow on the positive electrode active material to form a positive electrode-electrolyte interface (CEI) film, thereby reducing the content of residual lithium compounds. At the same time, the metal-organic framework material carbide forms a coating layer coated on the surface of the nickel-rich active material, which can further inhibit the generation of residual lithium compounds. In addition, the metal-organic framework material carbide is coated on the surface of the nickel-rich active material, which can prevent the positive electrode material from directly contacting the electrolyte to produce side reactions, and can capture nickel ions, preventing nickel ions from dissolving and migrating to the electrode surface, thereby improving cycle stability.

[0029] In a second aspect, an embodiment of the present application provides a method for preparing a positive electrode material, comprising:

[0030] Providing positive electrode active material;

[0031] forming an intermediate phase layer comprising a metal-organic framework material and a chalcogen element on the surface of the positive electrode active material;

[0032] The intermediate phase layer is carbonized to obtain a coating layer, wherein the coating layer comprises a metal-organic framework material carbide, the metal-organic framework material carbide is doped with the chalcogen element, and the chalcogen element has reducing properties.

[0033] The preparation method of the positive electrode material provided in the embodiment of the present application is to coat the metal-organic framework material carbide on the surface of the positive electrode active material, and at the same time dope a reducing sulfide element into the metal-organic framework material carbide, so that the reducing sulfide element contacts the positive electrode active material. In combination with the subsequent charging and discharging process (for example, during the formation process), the reducing sulfide element is easily oxidized into a sulfide element with a higher valence, and the sulfide element with a higher valence reacts with the residual lithium compound on the surface of the positive electrode active material to generate in situ a sulfide-containing inorganic compound (for example, Li2S2O3, Li2Se2O3, Li2Te2O3, Li2SO3, Li2SO4, Li2SeO3, Li2SeO4, Li2TeO3, Li2TeO4, etc.) with better conductivity than the residual lithium compound, thereby improving the conductivity and electrochemical properties of the positive electrode material. Moreover, during the charge and discharge process, the inorganic compounds containing sulfur elements will further grow on the positive electrode active material to form a positive electrode-electrolyte interface (CEI) film, thereby alleviating the negative impact of residual lithium compounds on battery performance; during the charge and discharge process, the sulfur elements will release lithium ions in the process of reacting with the residual lithium compounds. The additional released lithium ions can also be used to compensate for the lithium ion loss caused by the formation of a solid electrolyte interface (SEI) film at the negative electrode during the charge and discharge process of the battery, thereby ensuring the capacity of the battery.

[0034] In an embodiment of the present application, a coating layer comprising a metal-organic framework material carbide doped with a reducing sulfide element is obtained by carbonizing an intermediate phase layer comprising a metal-organic framework material and a sulfide element. The metal-organic framework material carbide basically inherits the rich and stable porous structure of the metal-organic framework material (MOFs), and the reducing sulfide element can be dispersed at the atomic level in the metal-organic framework material carbide, which is beneficial for the reducing sulfide element to play its role and achieve the effect of removing lithium (including residual lithium compounds, etc.) of the sulfide element. The metal-organic framework material carbide formed after the carbonization treatment will also be dispersed with metal nanoparticles, which can enhance the conductivity of the coating layer. In addition, since the reducing sulfide element is introduced into the metal-organic framework material, and then the metal-organic framework material is carbonized, the sulfide element is doped into the metal-organic framework material carbide to achieve the introduction on the surface of the positive active material, which can effectively limit the amount of the introduced sulfide element, and avoid the sulfide element content being too high and making the conductivity of the positive active material worse. The metal-organic framework material carbide with a rich and stable three-dimensional porous structure is coated on the surface of the positive electrode active material as a carbon skeleton, which can promote ion transport in the electrochemical process. The metal-organic framework material carbide forms a coating layer to prevent the positive electrode active material from directly contacting the electrolyte, reducing the probability of side reactions. At the same time, the coating layer can prevent the dissolution and migration of cations in the positive electrode active material, thereby improving the cycle stability of the battery.

[0035] In some embodiments, the preparation process of the intermediate phase layer includes:

[0036] With metal ions as nodes and organic ligands as connecting bridges, a metal-organic framework material is coated on the surface of the positive electrode active material, and the organic ligands contain the chalcogen element.

[0037] By coating the surface of the positive electrode active material with a metal-organic framework (MOF) using metal ions as junctions and chalcogen-containing organic ligands as bridges, the MOF exhibits advantages such as regular morphology, large specific surface area, and highly tunable pore size. The MOF carbide inherits the structural characteristics of the MOF, which facilitates the effective function of the chalcogen doped in the MOF carbide. Furthermore, since the organic ligands contain chalcogen, the MOF-containing MOF can be directly prepared by selecting a chalcogen-containing organic ligand, resulting in a simple method that improves material production efficiency. The MOF-containing MOF is then carbonized to obtain the chalcogen-doped MOF carbide. Because the chalcogen is directly introduced into the MOF via the organic ligands, it can be uniformly dispersed in the MOF carbide at the atomic level, effectively controlling the chalcogen content in the MOF carbide.

[0038] In some embodiments, the organic ligand includes at least one of 4-methylthiopyridine-2,6-dicarboxylic acid, 4,4-bipyridyl disulfide, and 2,5-di(pyridin-4-yl)thiophene.

[0039] The above organic compound contains sulfur and can be used as an organic ligand to combine with various metal ions to obtain metal-organic framework materials, thereby realizing the preparation of metal-organic framework material carbides doped with chalcogen elements.

[0040] In some embodiments, the preparation process of the intermediate phase layer includes:

[0041] Using metal ions as nodes and organic ligands as connecting bridges, a metal-organic framework material is coated on the surface of the positive electrode active material;

[0042] A chalcogen element is loaded on the metal-organic framework material.

[0043] In the embodiment of the present application, a metal-organic framework material is first prepared, and then a chalcogen element is loaded into the metal-organic framework material to obtain a metal-organic framework material loaded with a chalcogen element; the metal-organic framework material loaded with a chalcogen element is then subjected to a carbonization treatment, and during the thermal decomposition of the metal-organic framework material, the chalcogen element is covalently bonded with the metal elements, carbon elements, etc. in the metal-organic framework material, thereby achieving the doping of the chalcogen element into the metal-organic framework material carbide. Since the chalcogen element is introduced into the metal-organic framework material after the metal-organic framework material is coated on the surface of the positive electrode active material, the chalcogen element gradually penetrates into the metal-organic framework material through the pores of the metal-organic framework material. The closer to the positive electrode active material, the lower the content of the chalcogen element, so that the chalcogen element in the finally obtained metal-organic framework material carbide is also gradiently distributed, that is, the closer to the positive electrode active material, the lower the content of the chalcogen element, thereby alleviating the problem of poor conductivity of the positive electrode material due to excessive chalcogen content on the surface of the positive electrode active material.

[0044] In some embodiments, carbonization is performed while the chalcogen element is supported on the metal-organic framework material.

[0045] By combining the process of introducing elemental sulfur into the metal-organic framework material and the carbonization process into one step, the preparation process is simplified and the production cost of the material is reduced.

[0046] In some embodiments, the mass ratio of the chalcogen element to the positive electrode active material having the surface coated with the metal-organic framework material is 1:(1.5-5).

[0047] Since the chalcogen element is introduced into the metal-organic framework material after the metal-organic framework material is coated on the surface of the positive electrode active material, the amount of the chalcogen element affects the chalcogen content in the final metal-organic framework material carbide. If the amount of the chalcogen element is too low, the chalcogen content in the metal-organic framework material carbide is too low, resulting in poor removal of residual lithium compounds from the positive electrode material. If the amount of the chalcogen element is too high, the chalcogen element is likely to remain, thus affecting the conductivity of the positive electrode material. By controlling the mass ratio of the chalcogen element to the positive electrode active material coated with the metal-organic framework material to 1: (1.5-5), the prepared positive electrode active material with the metal-organic framework material carbide coated with the chalcogen element has better removal of residual lithium compounds and good conductivity.

[0048] In some embodiments, the metal ions are used as nodes and the organic ligands are used as connecting bridges, and the metal-organic framework material is coated on the surface of the positive electrode active material, including:

[0049] providing a metal ion solution comprising metal ions;

[0050] mixing the positive electrode active material with the metal ion solution to obtain a mixed solution;

[0051] An organic ligand is added to the mixed solution to obtain a metal-organic framework material coated on the surface of the positive electrode active material.

[0052] The preparation method is simple and easy to operate.

[0053] In some embodiments, the molar ratio of the metal ions to the positive electrode active material is 1:(0.02-0.1).

[0054] The amount of metal ions will affect the formation effect of the metal-organic framework material, and the molar ratio of metal ions to the positive electrode active material will affect the coating effect of the metal-organic framework material on the surface of the positive electrode active material. If the molar ratio is too small or too large, the coating on the surface of the positive electrode active material is likely to be uneven.

[0055] In some embodiments, the metal ion comprises at least one of a transition metal and a lanthanide metal.

[0056] The above-mentioned metal ions as nodes can easily form metal-organic framework materials through self-assembly with organic ligands as connecting bridges, and the formed metal-organic framework materials have the advantages of high porosity, low density, large specific surface area, regular pores, adjustable pore size, and topological structure diversity and tailorability.

[0057] In some embodiments, the transition metal includes at least one of Cu, Fe, Al, Co, Zn, Cd, and Mn.

[0058] By combining the above transition metals as central metal ions with organic ligands, metal-organic framework materials with stable structures can be obtained, and the raw materials are economical.

[0059] In some embodiments, the organic ligand comprises at least one of a carboxylic acid organic compound and a nitrogen-based organic compound.

[0060] By combining the above organic compounds as organic ligands with metal ions, a metal-organic framework material with a stable structure can be obtained.

[0061] In some embodiments, the carboxylic acid organic compound includes at least one of terephthalic acid and trimesic acid; and / or the nitrogen-containing organic compound includes 2-methylimidazole.

[0062] The above organic compounds can be combined with various metal ions as organic ligands to obtain metal-organic framework materials.

[0063] In some embodiments, the temperature of the carbonization treatment is 300°C to 600°C.

[0064] The temperature of the carbonization treatment directly affects the effectiveness and efficiency of the metal-organic framework (MOF) conversion to MOF carbide. Excessively high temperatures can cause deformation and even collapse of the MOF carbide structure, while excessively low temperatures can lead to inefficient formation of MOF carbides or even prevent the conversion of the MOF to MOF carbide. Furthermore, when a chalcogen is loaded onto the MOF, a low carbonization temperature can also affect the chalcogen doping efficiency.

[0065] In some embodiments, the carbonization treatment time is 2 hours to 5 hours.

[0066] The carbonization duration directly affects the effectiveness and efficiency of the metal-organic framework (MOF) conversion to MOF carbide. Excessive carbonization can cause deformation and even collapse of the MOF carbide structure. Too short a carbonization duration can lead to inefficient formation of the MOF carbide or even prevent the conversion of the MOF carbide from occurring. Furthermore, when a chalcogen is incorporated into the MOF, a short carbonization duration can also affect the chalcogen doping efficiency.

[0067] In some embodiments, the chalcogen includes elemental sulfur.

[0068] In the embodiment of the present application, a metal-organic framework material carbide is coated on the surface of the positive electrode active material, and a reducing sulfur element is doped into the metal-organic framework material carbide, thereby utilizing the sulfur element to effectively remove residual lithium compounds on the positive electrode active material.

[0069] In some embodiments, the positive electrode active material includes a chemical formula of Li a Ni m Co n M 1-m-n A nickel-rich active material containing O2, wherein M comprises at least one of Mn and Al, wherein m≥0.6, n≤0.2, 0.9≤a≤1.2; optionally, m≥0.9.

[0070] In the embodiment of the present application, a metal-organic framework material carbide is coated on the surface of a nickel-rich active material, and the metal-organic framework material carbide is doped with a reducing sulfide element. The reducing sulfide element contacts the positive electrode active material. During the charge and discharge process, the sulfide element is easily oxidized to a sulfide element with a higher valence state, and the sulfide element with a higher valence state reacts with the residual lithium compound on the surface of the positive electrode active material to in situ generate a sulfide-containing inorganic compound with better conductivity than the residual lithium compound, thereby improving the conductivity and electrochemical properties of the positive electrode material. Moreover, during the charge and discharge process, the sulfide-containing inorganic compound further grows on the positive electrode active material to form a positive electrode-electrolyte interface (CEI) film, thereby reducing the content of residual lithium compounds. At the same time, the metal-organic framework material carbide forms a coating layer coated on the surface of the nickel-rich active material, which can further inhibit the generation of residual lithium compounds. In addition, the metal-organic framework material carbide is coated on the surface of the nickel-rich active material, which can prevent the positive electrode material from directly contacting the electrolyte to produce side reactions, and can capture nickel ions, preventing nickel ions from dissolving and migrating to the electrode surface, thereby improving cycle stability.

[0071] In a third aspect, an embodiment of the present application provides a positive electrode plate, comprising a positive electrode current collector and a positive electrode material layer bonded to the positive electrode current collector, wherein the positive electrode material layer comprises the positive electrode material provided in the first aspect of the embodiment of the present application or a positive electrode material prepared according to the preparation method of the positive electrode material provided in the first aspect of the embodiment of the present application.

[0072] The positive electrode plate provided in the embodiment of the present application includes a positive electrode current collector and a positive electrode material layer, the positive electrode material layer includes the above-mentioned positive electrode material, and the above-mentioned positive electrode material includes a positive electrode active substance and a metal-organic framework material carbide coated on the surface of the positive electrode active substance, the metal-organic framework material carbide is doped with a reducing sulfide element, and the sulfide element can react with the residual lithium compound in the positive electrode active substance during the charging and discharging process, thereby reducing the content of residual lithium compounds in the positive electrode material, and the metal-organic framework material carbide coated on the surface of the positive electrode active substance can form a protective layer to effectively isolate the positive electrode active substance, prevent the positive electrode active substance from direct contact with the electrolyte, improve the surface stability of the positive electrode active substance, and ultimately improve the cycle performance and storage performance of the battery.

[0073] In a fourth aspect, an embodiment of the present application provides a battery, comprising a positive electrode sheet provided according to the third aspect of the embodiment of the present application.

[0074] The battery provided in the embodiment of the present application includes the above-mentioned positive electrode plate, and the battery has stable cycle performance, long high-temperature storage life, and good rate performance.

[0075] In a fifth aspect, an embodiment of the present application provides an electrical device, comprising a battery provided according to the fourth aspect of the embodiment of the present application.

[0076] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the optional embodiments below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0078] Figure 1 A schematic structural diagram of a vehicle according to some embodiments of the present application;

[0079] Figure 2 Schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

[0080] Figure 3 A schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application;

[0081] Figure 4 This is a schematic structural diagram of an electrode assembly according to some embodiments of the present application;

[0082] Figure 5 A schematic flow chart of a method for preparing a cathode material is provided for some embodiments of the present application;

[0083] Figure 6 A schematic flow chart of a method for preparing a positive electrode material is provided for other embodiments of the present application;

[0084] Figure 7 The XPS spectrum of the sample provided in Example 1 of the present application;

[0085] Figure 8 This is the XPS spectrum of the sample provided in Example 3 of the present application;

[0086] Figure 9 Figure (a) is a SEM image of the sample provided in Example 1 of the present application; Figure 9 Figure (b) is a TEM image of the sample provided in Example 1 of the present application;

[0087] Figure 10 Figure (a) is a SEM image of the sample provided in Example 3 of the present application; Figure 10 Figure (b) is a TEM image of the sample provided in Example 3 of the present application.

[0088] The accompanying drawings in the specific implementation manner are as follows:

[0089] 10. Pole piece;

[0090] 20. Electrode assembly; 101. Negative electrode sheet; 102. Positive electrode sheet; 201. Negative electrode tab; 202. Positive electrode tab; 203. Separator;

[0091] 30. Battery cell; 301. Housing; 302. End cap; 303. Negative electrode adapter; 304. Positive electrode adapter; 305. Insulator;

[0092] 40. Battery; 401. Box body; 4011. Box body; 4012. Box cover;

[0093] 50. Electrical device; 501. Controller; 502. Motor. DETAILED DESCRIPTION

[0094] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0095] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0096] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0097] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of 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.

[0098] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0099] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0100] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0101] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0102] Lithium-ion batteries, as secondary batteries, reversibly convert chemical energy into electrical energy, making them an ideal carrier for human energy utilization and storage. Since their advent, they have been widely used due to their long lifespan, high energy density, and low maintenance costs. Currently, lithium-ion batteries are used in a variety of fields, including portable electronic devices, new energy vehicles, and energy storage systems.

[0103] The positive electrode active material is a key factor influencing the performance of lithium-ion batteries, often determining their cycle life, energy density, and power density. Due to the preparation process or the characteristics of the positive electrode active material itself, residual lithium compounds (RLCs), such as lithium hydroxide and lithium carbonate, are easily formed on the surface of the positive electrode active material. Residual lithium compounds generally have poor conductivity, which increases the cathode / electrolyte interface impedance, exacerbates battery polarization, degrades discharge capacity and cycle stability, and negatively impacts battery performance.

[0104] Based on this, the present application proposes a technical solution to alleviate the negative impact of residual lithium compounds in the positive active material on battery performance. Specifically, by introducing a reducing low-valent sulfide element, such as low-valent sulfur, on the surface of the positive active material, during the charge and discharge process of the battery, the reducing low-valent sulfide element contacts the positive active material, and the low-valent sulfide element is easily oxidized to a high-valent sulfide element, such as low-valent sulfur converted to high-valent sulfur, including sulfate, thiosulfate, etc. The high-valent sulfide element will react with the residual lithium compound to generate a sulfide-containing inorganic compound and a positive electrode-electrolyte interface (CEI) film with better conductivity than the residual lithium compound, thereby alleviating the negative impact of the residual lithium compound on battery performance.

[0105] However, the amount of the reducing low-valent sulfide element introduced on the surface of the positive active material is not the higher the better. If the content of the low-valent sulfide element is too high, it will reduce the conductivity of the positive active material and cause the internal resistance (DCR) of the lithium-ion battery to increase. Therefore, the present application proposes to coat the surface of the positive active material with a metal-organic framework material carbide having a pore structure, and the metal-organic framework material carbide is doped with a low-valent sulfide element, thereby achieving the introduction of a low-valent sulfide element on the surface of the positive active material. Since the low-valent sulfide element is doped in the metal-organic framework material carbide, the amount of the introduced low-valent sulfide element can be limited, and thanks to the three-dimensional porous structure of the metal-organic framework material carbide, the ion transport in the electrochemical process can be promoted, thereby ensuring the conductivity of the positive active material.

[0106] The batteries disclosed in some embodiments of the present application may be used, but are not limited to, in electrical devices such as vehicles, ships, or aircraft. A power supply system comprising the batteries disclosed in the present application may be used to form the electrical device.

[0107] Some embodiments of the present application provide an electrical device using a battery as a power source, which may be, but is not limited to, a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, etc. Vehicles may be, but are not limited to, fuel-powered vehicles, gas-powered vehicles, or new energy vehicles; new energy vehicles may be, but are not limited to, pure electric vehicles, hybrid vehicles, or extended-range vehicles; spacecraft include, but are not limited to, airplanes, rockets, space shuttles, and spacecraft; electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys; and electric tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers.

[0108] For the convenience of description, the following embodiments are described by taking a vehicle 50 as an example of an electrical device according to an embodiment of the present application.

[0109] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle 50 provided in some embodiments of the present application. A battery 40 is provided within the vehicle 50, and the battery 40 can be located at the bottom, front, or rear of the vehicle 50. The battery 40 can be used to power the vehicle 50, for example, as an operating power source for the vehicle 50. The vehicle 50 may also include a controller 501 and a motor 502. The controller 501 is used to control the battery 40 to power the motor 502, for example, to meet the power requirements of the vehicle 50 during startup, navigation, and driving.

[0110] In some embodiments of the present application, the battery 40 can serve not only as an operating power source for the vehicle 50 , but also as a driving power source for the vehicle 50 , replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 50 .

[0111] In some embodiments of the present application, the battery 40 is a secondary battery, which has various forms, including but not limited to battery cells, battery modules, and battery packs. A secondary battery here refers to a battery that can be recharged to activate the active material after discharge and continue to be used.

[0112] Please refer to Figure 2 , Figure 2 This is an exploded view of a battery 40 provided in some embodiments of the present application. The battery 40 includes a housing 401 and a battery cell 30, with the battery cell 30 housed within the housing 401. The housing 401 is used to provide a space for the battery cell 30 and can have various structures.

[0113] In some embodiments, the box body 401 may include a box body 4011 and a box cover 4012, which cover each other and together define a storage space for accommodating the battery cells 30. Alternatively, the box body 4011 may be a hollow structure with one end open, and the box cover 4012 may be a plate-like structure that covers the open side of the box body 4011.

[0114] In the battery 40, there can be multiple battery cells 30, and the multiple battery cells 30 can be connected in series, in parallel, or in a mixed connection. Mixed connection means that the multiple battery cells 30 are both connected in series and in parallel. The multiple battery cells 30 can be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 30 is accommodated in the box 401; of course, the battery 40 can also be a battery module formed by first connecting multiple battery cells 30 in series, in parallel, or in a mixed connection, and then the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the box 401. The battery 40 may also include other structures, such as a confluence component (not shown), which is used to achieve electrical connection between the multiple battery cells 30. Among them, the battery cells 30 may be cylindrical, flat, rectangular, or other shapes.

[0115] Please refer to Figure 3 , Figure 3 The exploded view of the battery cell 30 in some embodiments of the present application. The battery cell 30 is the basic unit that realizes the mutual conversion of chemical energy and electrical energy, and is also the smallest unit of the battery. Figure 3 The battery cell 30 includes a shell 301, an end cover 302, an electrode assembly 20 and other functional components.

[0116] The shell 301 is a hollow structure with one end open. The shell 301 is used to cooperate with the end cap 302 to form an internal environment for accommodating the electrode assembly 20, the electrolyte and other functional components. The shell 301 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the shell 301 can be determined according to the specific shape and size of the electrode assembly 20. The material of the shell 301 can be, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and is not limited here.

[0117] The end cap 302 refers to a component that covers the opening of the shell 301 to isolate the internal environment of the battery cell 30 from the external environment. Optionally, the shape of the end cap 302 can be adapted to the shape of the shell 301 to match the shell 301. Optionally, the end cap 302 can be made of a material with a certain hardness and strength (such as aluminum alloy). In this way, the end cap 302 is not easily deformed when squeezed or collided, so that the battery cell 30 can have a higher structural strength and improved safety performance. The material of the end cap 302 can be, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and is not limited here.

[0118] In some embodiments, the battery cell 30 further includes functional components such as a negative electrode adapter 303 and a positive electrode adapter 304. The negative electrode adapter 303 is used to electrically connect to the negative electrode tab on the electrode assembly 20, and the positive electrode adapter 304 is used to electrically connect to the positive electrode tab on the electrode assembly 20 to output or input electrical energy to the battery cell 30. It is understood that the negative electrode adapter 303 is made of a conductive material, and the material of the negative electrode adapter 303 can be, but is not limited to, copper, iron, aluminum, etc. The positive electrode adapter 304 is made of a conductive material, and the material of the positive electrode adapter 304 can be, but is not limited to, copper, iron, aluminum, etc.

[0119] In some embodiments, the battery cell 30 further includes an insulating member 305 located inside the housing 301 to isolate the housing 301 from the electrode assembly 20 and reduce the risk of short circuits. For example, the insulating member 305 may be made of plastic, rubber, or the like.

[0120] One or more electrode assemblies 20 may be contained within the housing 301 .

[0121] Please refer to Figure 4 , Figure 4 This is a schematic diagram of the structure of the electrode assembly 20 in some embodiments of the present application. The electrode assembly 20 is the component in the battery cell 30 where the electrochemical reaction occurs. The electrode assembly 20 is primarily formed by winding or stacking a negative electrode sheet 101 and a positive electrode sheet 102 into an integrated structure, and a separator 203 is typically provided between adjacent negative electrode sheets 101 and positive electrode sheets 102.

[0122] The negative electrode sheet 101 includes a negative electrode current collector and a negative electrode material layer, which is coated on the surface of the negative electrode current collector. Taking a lithium-ion battery as an example, the negative electrode current collector may be made of copper, and the negative electrode material layer may include a negative electrode material, which may include a silicon-based material.

[0123] The positive electrode sheet 102 includes a positive electrode current collector and a positive electrode material layer, which is coated on the surface of the positive electrode current collector. Taking a lithium-ion battery as an example, the positive electrode current collector may be made of aluminum, and the positive electrode material layer may include a positive electrode material, such as lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide.

[0124] The isolation membrane 203 is a porous plastic film that allows lithium ions in the electrolyte to pass freely, but isolates the negative electrode plate 101 and the positive electrode plate 102, so that electrons inside the battery cannot pass freely.

[0125] The negative electrode current collector and the positive electrode current collector also have portions that are not coated with the active material layer. These portions without the active material layer are provided with connecting tabs. Specifically, the negative electrode current collector is connected to the negative electrode tab 201, and the positive electrode current collector is connected to the positive electrode tab 202. During the charge and discharge process of the battery, the positive electrode material layer and the negative electrode material layer react with the electrolyte, the tab 201 is connected to the negative electrode adapter 303, and the positive electrode tab 202 is connected to the positive electrode adapter 304 to form a current loop. Of course, in some embodiments, the portions of the negative electrode current collector and the positive electrode current collector that are not coated with the active material layer each constitute a tab.

[0126] Some embodiments of the present application provide a positive electrode material, comprising a positive electrode active substance and a coating layer coated on the surface of the positive electrode active substance, wherein the coating layer comprises a metal-organic framework material carbide, wherein the metal-organic framework material carbide is doped with a chalcogen element, and the chalcogen element has reducing properties.

[0127] The positive electrode material includes a positive electrode active material, which refers to a compound with a three-dimensional lithium ion channel, which is used on the positive electrode for the reversible insertion and removal of lithium ions. Optionally, the positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium iron manganese phosphate, lithium nickel cobalt oxide, lithium nickel manganese oxide and lithium nickel cobalt manganese oxide. Lithium cobalt oxide (LiCoO2) is relatively easy to prepare because it contains relatively few elements, and the layered structure of lithium cobalt oxide has the advantages of high energy density, high discharge voltage, good filling and long cycle life. Lithium manganese oxide (Li2Mn2O4) has the advantages of low price, high potential, environmental friendliness and high safety performance as an electrode material. Among them, the spinel type lithium manganese oxide has a stable structure and is easier to achieve industrial production. Lithium iron phosphate (LiFePO4, abbreviated as LFP) has an olivine structure, good lattice stability, and the insertion and removal of lithium ions have little effect on the lattice, so it has good reversibility. Lithium manganese iron phosphate (LMFP) is equivalent to an improved material of lithium iron phosphate. It has many advantages of LFP. Both are olivine structures, with high safety and stability. At the same time, because LMFP contains manganese elements, it has a higher capacity. 1-x Co x O2, referred to as NC binary material) also has a layered structure and has good electrochemical performance and thermal stability. x Mn 2-xO4, referred to as NM binary material) is a material with a spinel structure prepared by improving the original spinel lithium manganese oxide. Compared with lithium manganese oxide, it has higher cycle stability and voltage platform. Lithium nickel cobalt manganese oxide (referred to as NCM ternary material) contains three transition metal elements: Ni, Co and Mn. It effectively overcomes the shortcomings of the three materials LiNiO2, LiCoO2 and LiMnO2, and in the electrochemical performance and thermal stability tests, these three transition metals can show their respective characteristics in this material, and it has high development potential. Optionally, the positive electrode active material can also be doped and modified. Optionally, the doping elements include but are not limited to at least one of Zr, Zn, Cu, V, Ti, Sr, Sb, Y, W, Nb, B, Ba, Ce, Si, Ga, Sn, Mo, P, Al, Fe, Mg, Cr, F, N, S, and Cl.

[0128] The positive electrode material also includes a coating layer, which coats the surface of the positive electrode active material. The coating layer refers to a layer of material that wraps around the surface of the positive electrode active material. Optionally, the positive electrode active material is in a granular form, and the coating layer wraps around the outer surface of the positive electrode active material particles.

[0129] The coating layer includes a metal-organic framework material carbide, which refers to a carbon material that is converted from a metal-organic framework material (Metal-Organic Frameworks, referred to as MOFs) after carbonization treatment and has a three-dimensional porous structure similar to or the same as that of the metal-organic framework material. Metal-organic framework materials refer to organic-inorganic hybrid materials with intramolecular pores formed by self-assembly of organic ligands and metal ions or clusters through coordination bonds. Carbonization treatment refers to the reaction process of heating and decomposing metal-organic framework materials under oxygen-deficient or oxygen-deficient conditions. Optionally, the carbonization treatment includes a calcination treatment.

[0130] The metal-organic framework material carbide is doped with chalcogens, which refer to sulfur and elements with similar chemical properties to sulfur. Optionally, the chalcogens include elements in the oxygen group except oxygen. Optionally, the chalcogens include at least one of sulfur (S), selenium (Se) and tellurium (Te). When chalcogens are doped in the metal-organic framework material carbide, it can be understood that the chalcogens are combined with other elements in the metal-organic framework material carbide through chemical bonds, which can improve the stability of the chalcogens in the metal-organic framework material carbide and reduce the probability of the chalcogens migrating out of the electrode into the electrolyte. Optionally, the chalcogens are combined with other elements in the metal-organic framework material carbide through covalent bonds.

[0131] Chalcogens are reducing, meaning they can increase in valence through redox reactions. Alternatively, chalcogens with a valence less than zero, also known as low-valent chalcogens, are easily oxidized to high-valent chalcogens, i.e., chalcogens with a valence greater than zero. For example, chalcogens include sulfur, where low-valent sulfur has a valence of -2 and high-valent sulfur has a valence of +6 or +4.

[0132] The positive electrode material provided in the embodiment of the present application includes a positive electrode active substance, a metal-organic framework material carbide is coated on the surface of the positive electrode active substance, and the metal-organic framework material carbide is doped with a reducing sulfide element, and the reducing sulfide element is in contact with the positive electrode active substance (direct contact or indirect contact). In combination with the subsequent charging and discharging process (for example, during the formation process), the reducing sulfide element is easily oxidized into a sulfide element with a higher valence state and reacts with the residual lithium compound (for example, LiOH, Li2O, Li2CO3, etc.) on the surface of the positive electrode active substance, and generates in situ a sulfide-containing inorganic compound (for example, Li2S2O3, Li2Se2O3, Li2Te2O3, Li2SO3, Li2SO4, Li2SeO3, Li2SeO4, Li2TeO3, Li2TeO4, etc.) with better conductivity than the residual lithium compound, thereby improving the conductivity and electrochemical properties of the positive electrode material. Moreover, during the charge and discharge process, the inorganic compounds containing sulfur elements will further grow on the positive electrode active material to form a positive electrode-electrolyte interface (CEI) film, thereby alleviating the negative impact of residual lithium compounds on battery performance; during the charge and discharge process, lithium ions will be released during the reaction between sulfur elements and residual lithium compounds. The additional released lithium ions can also be used to compensate for the lithium ion loss caused by the formation of a solid electrolyte interface (SEI) film at the negative electrode during the charge and discharge process of the battery, thereby ensuring the capacity of the battery.

[0133] In the embodiment of the present application, since the reducing sulfide element is introduced into the surface of the positive electrode active material by doping in the metal-organic framework material carbide, the amount of the introduced sulfide element can be effectively limited, and the excessive sulfide content can be avoided, which in turn makes the conductivity of the positive electrode active material worse. The metal-organic framework material carbide with a rich and stable three-dimensional porous structure is coated on the surface of the positive electrode active material as a carbon skeleton, which can promote the ion transport in the electrochemical process, and the metal-organic framework material carbide forms a coating layer that can prevent the positive electrode active material from directly contacting the electrolyte, reducing the probability of side reactions. At the same time, the coating layer can prevent the dissolution and migration of cations in the positive electrode active material, thereby improving the cycle stability of the battery.

[0134] In some embodiments, the positive electrode active material includes a chemical formula of Li a Ni m Co nM 1-m-n A nickel-rich active material containing O2, wherein M comprises at least one of Mn and Al, wherein m≥0.6, n≤0.2, and 0.9≤a≤1.2.

[0135] The chemical formula of nickel-rich active material is Li a Ni m Co n M 1-m-n O2, wherein M includes at least one of Mn and Al. As an example, M includes Mn, and the chemical formula of the nickel-rich active material is Li a Ni m Co n Mn 1-m-n O2. As an example, M includes Al, and the chemical formula of the nickel-rich active material is Li a Ni m Co n Al 1-m-n O2. Specifically, m≥0.6, and the content of nickel in the nickel-rich active material is increased by increasing the value of m, thereby increasing the reversible lithium insertion capacity of the positive electrode material. Optionally, m is any one of 0.6, 0.7, 0.8, 0.9 and 0.99, or a range value between any two of them. Specifically, n≤0.2, the nickel-rich active material is usually a layered structure, and Co can stabilize the layered structure, but the high price of Co will increase the cost of the nickel-rich active material. The cost of the nickel-rich active material can be controlled by controlling n≤0.2. Optionally, n is any one of 0.05, 0.1, 0.15 and 0.2, or a range value between any two of them. 0.9≤a≤1.2, that is, the lithium content in the nickel-rich active material can be greater than 1, equal to 1, or less than 1. When a is greater than 1, the nickel-rich active material is a lithium-rich positive electrode material. As an example, for the nickel-rich active material, which is a material obtained by pre-lithiation, the Li content can be greater than 1. Optionally, a is any one of 1, 1.05, 1.1, 1.15 and 1.2, or a range value between any two of them.

[0136] However, the nickel element in nickel-rich active materials is alkaline. As the nickel content increases, the nickel-rich active materials are easily exposed to air and absorb moisture and carbon dioxide, and residual lithium compounds (RLCs) are generated on their surface, such as lithium hydroxide (LiOH) and lithium carbonate (Li2CO3), further increasing the pH of the nickel-rich active materials and seriously affecting the electrochemical and storage properties of the nickel-rich active materials.

[0137] Based on this, the embodiment of the present application coats the surface of the nickel-rich active material with a metal-organic framework material carbide, and the metal-organic framework material carbide is doped with a reducing sulfide element. The reducing sulfide element contacts the positive electrode active material, and the sulfide element is easily oxidized into a sulfide element with a higher valence state. The sulfide element with a higher valence state will react with the residual lithium compound on the surface of the positive electrode active material to in situ generate a sulfide-containing inorganic compound (such as Li2SO4, Li2SeO4, Li2TeO4, etc.) with better conductivity than the residual lithium compound, thereby improving the conductivity and electrochemical properties of the positive electrode material. In addition, during the charge and discharge process, the sulfide-containing inorganic compound will further grow on the positive electrode active material to form a positive electrode-electrolyte interface (CEI) film, thereby reducing the content of residual lithium compounds. At the same time, the metal-organic framework material carbide forms a coating layer coated on the surface of the nickel-rich active material, which can further inhibit the generation of residual lithium compounds. In addition, the metal-organic framework material carbide is coated on the surface of the nickel-rich active material, which can prevent the positive electrode material from directly contacting the electrolyte to produce side reactions, and can capture nickel ions, preventing nickel ions from dissolving and migrating to the electrode surface, thereby improving cycle stability.

[0138] In some embodiments, m ≥ 0.9.

[0139] Optionally, m is any one of 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98 and 0.99, or a range value between any two of them.

[0140] As an example, m is 0.9, M includes Mn, and the chemical formula of the nickel-rich active material is LiNi 0.9 Mn 0.1 O2.

[0141] As an example, m is 0.95, M includes Mn, and the chemical formula of the nickel-rich active material is LiNi 0.95 Co 0.025 Mn 0.025 O2.

[0142] By setting the nickel content in the nickel-rich active material to be greater than 90%, the reversible lithium insertion capacity of the positive electrode material can be increased.

[0143] In some embodiments, the content of chalcogen in the positive electrode material is greater than 0 and less than or equal to 10 wt %.

[0144] The content of chalcogen in the positive electrode material refers to the percentage of chalcogen in the positive electrode material, specifically the percentage by mass.

[0145] Optionally, the content of sulfide in the positive electrode material is any one of 0.1wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt% and 10wt%, or a range value between any two of them.

[0146] Too high a chalcogen content in the positive electrode material will affect the conductivity of the positive electrode material. By setting the chalcogen content in the positive electrode material to be greater than 0 and less than or equal to 10wt%, the battery's cycle, storage, and rate performance are all improved within this range.

[0147] In some embodiments, the content of chalcogen is less than or equal to 5 wt %.

[0148] When the sulfide content is less than or equal to 5wt%, as the sulfide content increases, the effect of removing impurity lithium from the positive electrode material becomes better. The best effect is achieved when the sulfide content in the positive electrode material is 5wt%, and the battery storage, rate and cycle stability are the best. Continuing to increase the sulfide content will lead to an increase in the battery internal resistance (DCR).

[0149] In some embodiments, the coating layer has a thickness of 1 nm to 20 nm.

[0150] The thickness of the coating layer will affect the coating effect on the surface of the positive electrode active material. If the coating layer is too thin, the surface of the positive electrode active material cannot be completely coated with the metal-organic framework material carbide. However, if the coating layer is too thick, the internal resistance of the positive electrode material will increase. At the same time, it will also make the migration path of lithium ions in the positive electrode material longer, affecting the rate performance of the battery.

[0151] Optionally, the thickness of the coating layer is any value among 1 nm, 2 nm, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm and 20 nm, or a range value between any two values.

[0152] By setting the thickness of the coating layer to 1nm to 20nm, the surface of the positive electrode active material is ensured to be completely coated with the metal-organic framework material carbide, thereby effectively removing the residual lithium compounds on the surface of the positive electrode active material and reducing the internal resistance of the positive electrode material.

[0153] In some embodiments, the specific surface area of ​​the positive electrode material is 1 m 2 / g~10m 2 / g. Due to the porous structure of metal-organic framework carbides, coating the surface of the cathode active material with metal-organic framework carbides increases the specific surface area of ​​the resulting cathode material. This increased specific surface area can effectively improve the infiltration efficiency of the cathode material. However, an excessively large specific surface area can easily lead to gelation during the slurry preparation process, affecting the processability of the cathode material.

[0154] Optionally, the specific surface area of ​​the positive electrode material is 1m 2 / g, 2m 2 / g、4m 2 / g、6m 2 / g、8m 2 / g and 10m 2 Any point value in / g or the range between any two points.

[0155] By setting the specific surface area of ​​the positive electrode material to 1 m 2 / g~10m 2 / g, which can make the positive electrode material have better wetting effect and better processing performance.

[0156] In some embodiments, the chalcogen element is evenly distributed in the coating layer, or the concentration of the chalcogen element gradually increases in the coating layer away from the positive electrode active material.

[0157] The chalcogen is uniformly distributed in the coating layer. It is understood that the concentration of the chalcogen remains the same, or substantially the same, across the thickness of the coating layer. Alternatively, the chalcogen is distributed within the metal-organic framework carbide as a constituent element of the metal-organic framework carbide.

[0158] The chalcogen content in the coating gradually increases as it moves away from the positive electrode active material. It is understood that the element content in the coating varies along its thickness. Specifically, the concentration of chalcogen in the region of the coating away from the positive electrode active material is higher than the concentration of chalcogen in the region of the coating near the positive electrode active material. Alternatively, chalcogen is distributed in the metal-organic framework carbide as a constituent element of the metal-organic framework carbide.

[0159] Whether by setting the sulfide elements in the coating layer to be uniformly distributed or gradually increasing the concentration in the direction away from the positive electrode active material, the sulfide content in the coating layer can be effectively reduced, avoiding the sulfide content being too high, which causes excessive sulfide elements to react with lithium compounds to generate excessive sulfide-containing inorganic compounds, and instead increase the resistance value of the contact interface between the coating layer and the positive electrode active material, thereby increasing the internal resistance of the battery.

[0160] In some embodiments, the metal-organic framework carbide has a porous structure.

[0161] A porous structure refers to a structure consisting of a network of interconnected or closed pores.

[0162] By setting the metal-organic framework material carbide to a porous structure, the metal-organic framework material carbide can have a larger specific surface area. On the one hand, it can improve the effect of removing residual lithium compounds of sulfide elements. On the other hand, the porous structure can promote ion transport in the electrochemical process and improve the battery's rate performance.

[0163] In some embodiments, the metal-organic framework carbide comprises a metal element, a chalcogen element, and a carbon element covalently bonded together.

[0164] Specifically, the metal-organic framework material carbide itself contains metal elements and carbon elements. The metal-organic framework material carbide is also doped with chalcogen elements. The chalcogen elements are combined with the metal elements in the form of covalent bonds, and the chalcogen elements are combined with the carbon elements in the form of covalent bonds.

[0165] Since the metal elements, chalcogens and carbon elements in the metal-organic framework material carbide are combined together in the form of covalent bonds, the chalcogens can maintain a low valence state and thus have reducing properties. In addition, the chalcogens can be stably bound to the metal-organic framework material carbide to prevent the displacement of the chalcogens.

[0166] In some embodiments, the covalent bond includes at least one of a metal-chalcogen bond and a carbon-chalcogen bond.

[0167] As an example, chalcogens include elemental sulfur, and covalent bonds include metal-sulfur bonds and carbon-sulfur bonds.

[0168] By setting the covalent bonds to include metal-chalcogen bonds and carbon-chalcogen bonds, the chalcogen can maintain a low valence state and thus have stronger reducing properties, which is conducive to the oxidation of the chalcogen and its combination with residual lithium compounds to form a CEI film, thereby reducing the content of residual lithium compounds; and the chalcogen can be stably combined in the carbide of the metal-organic framework material.

[0169] In some embodiments, the metal-organic framework carbide contains nitrogen, and the covalent bonds further include nitrogen-chalcogen bonds.

[0170] As an example, the chalcogen includes the element sulfur, and the covalent bond includes a nitrogen-sulfur bond.

[0171] By setting the covalent bond to also include a nitrogen-chalcogen bond, the chalcogen can also maintain a low valence state and thus have a stronger reducing property, which is conducive to the oxidation of the chalcogen and combining with the residual lithium compound to form a CEI film, thereby reducing the content of residual lithium compounds; and the chalcogen can be stably combined in the metal-organic framework material carbide.

[0172] In some embodiments, the coating layer further comprises metal nanoparticles, and the metal nanoparticles are distributed in the metal-organic framework material carbide.

[0173] Metal nanoparticles refer to metals or alloys that form nanocrystals.

[0174] Metal nanoparticles have good electrical conductivity. The metal nanoparticles are dispersed on the metal-organic framework material carbide, thereby enhancing the conductivity of the coating layer containing the metal-organic framework material carbide and effectively promoting the transmission of ions in the electrochemical process.

[0175] In some embodiments, the chalcogen includes at least one of sulfur and selenium.

[0176] As an example, the chalcogen element includes sulfur, and the resulting metal-organic framework carbide includes a sulfur-containing metal-organic framework carbide.

[0177] Low-valent sulfur elements (also known as reducing sulfur elements) and their compounds have strong reducing properties. The positive electrode active material, with the chemical formula Li a Ni m Co n M 1-m-n The Ni, Co, and Mn in the layered nickel-rich active material are Ni 3+ / Ni 2+ 、Co 3+ and Mn 4+ It exists in the form of ions. When the layered nickel-rich active material comes into contact with sulfur, during the charge and discharge process, for example, during the formation process, the layered nickel-rich active material can easily oxidize the low-valent sulfur and react with the residual lithium compound to form lithium thiosulfate (Li2S2O3) and lithium sulfate (Li2SO4). These substances form an electrochemically stable artificial CEI layer on the surface of the nickel-rich active material particles or exist alone, and the additional Li released by the sulfurization reaction + It can also be used to compensate for the Li + loss.

[0178] In the conventional preparation process, sulfur can be reacted with the positive electrode active material to undergo a gas-solid phase reaction to achieve the loading of sulfur element on the positive electrode active material. However, this preparation method is prone to produce sulfur residue, and the residual lithium compounds on the surface of the positive electrode active material react with the residual sulfur to form the sulfur inorganic substance Li2SO4. However, Li2SO4 has the problem of insufficient conductivity, which will affect the rate performance of the positive electrode material. Therefore, it is critical to reduce the residual sulfur content while ensuring sulfur doping.

[0179] In the embodiment of the present application, by coating the surface of the positive electrode active material with a metal-organic framework material carbide and doping sulfur into the metal-organic framework material carbide, sulfur residue can be reduced to meet the requirements of stable sulfur doping, low residual sulfur content and good surface conductivity.

[0180] As an example, the chalcogen element includes selenium, and the obtained metal-organic framework material carbide includes a selenium-containing metal-organic framework material carbide.

[0181] In the embodiment of the present application, by coating the surface of the positive electrode active material with a metal-organic framework material carbide and doping selenium into the metal-organic framework material carbide, selenium residue can be reduced to meet the requirements of stable selenium doping, low residual selenium content and good surface conductivity of the interface coating.

[0182] Some embodiments of the present application also provide a method for preparing a positive electrode material, comprising:

[0183] A positive electrode active material is provided; an intermediate phase layer containing a metal-organic framework material and a chalcogen is formed on the surface of the positive electrode active material; and the intermediate phase layer is carbonized to obtain a coating layer, wherein the coating layer contains a metal-organic framework material carbide, the metal-organic framework material carbide is doped with a chalcogen, and the chalcogen has reducing properties.

[0184] As mentioned above, the positive electrode active material refers to a compound having a three-dimensional lithium ion channel, which is used on the positive electrode for reversible insertion and removal of lithium ions. Optionally, providing the positive electrode active material also includes preparing the positive electrode active material. Optionally, the positive electrode active material includes at least one of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium iron manganese phosphate, lithium nickel cobaltate, lithium nickel manganese oxide and lithium nickel cobalt manganese oxide. The preparation methods of different positive electrode active materials may be the same or different. Of course, in some embodiments, the positive electrode active material may also be directly purchased. The positive electrode active material here may be, but is not limited to, granular, blocky, etc.

[0185] An intermediate phase layer is formed on the surface of the positive electrode active material, and the intermediate phase layer refers to a material layer containing a metal-organic framework material and a chalcogen. Metal-organic framework materials (MOFs) refer to organic-inorganic hybrid materials with intramolecular pores formed by self-assembly of organic ligands and metal ions or clusters through coordination bonds. Chalcogen refers to sulfur and elements with similar chemical properties to sulfur. Optionally, the chalcogen includes elements other than oxygen in the oxygen group. Optionally, the chalcogen includes at least one of sulfur (S), selenium (Se), and tellurium (Te). The intermediate phase layer includes a metal-organic framework material and a chalcogen. The chalcogen can be doped into the metal-organic framework material as a constituent element of the metal-organic framework material, or the chalcogen can be loaded on the metal-organic framework material as an independent substance, for example, the chalcogen is a single chalcogen, and the single chalcogen is loaded on the metal-organic framework material.

[0186] The mesophase layer is subjected to a carbonization treatment, which refers to the reaction process of thermal decomposition of the mesophase layer under oxygen-deficient or oxygen-deficient conditions. During the carbonization process, the porous structure of the metal-organic framework material in the mesophase layer remains unchanged or substantially unchanged, and only the metal-organic framework material undergoes thermal decomposition and is converted into a metal-organic framework material carbide containing chalcogens, carbon elements, and metal elements covalently bonded. Optionally, the covalent bonds include but are not limited to metal-chalcogen bonds, carbon-chalcogen bonds, etc. Optionally, the chalcogen includes sulfur, and the covalent bonds include metal-sulfur bonds and carbon-sulfur bonds. Optionally, the metal-organic framework material carbide also contains nitrogen, and the covalent bonds also include nitrogen-chalcogen bonds. By covalently bonding with other elements, the chalcogen can maintain a low valence state, thereby having strong reducing properties, which is conducive to the oxidation of the chalcogen and its combination with residual lithium compounds to form a CEI film, thereby reducing the content of residual lithium compounds. Optionally, the metal-organic framework material carbide further comprises metal nanoparticles, which can improve the conductivity of the coating layer.

[0187] The intermediate phase layer is converted into a coating layer through carbonization treatment, and the coating layer includes metal-organic framework material carbide. The metal-organic framework material carbide is formed by carbonization treatment of the metal-organic framework material. The metal-organic framework material carbide has a three-dimensional porous structure similar to or the same as the metal-organic framework material, but compared with the metal-organic framework material, the metal-organic framework material carbide has a carbon skeleton, its conductivity is better than the metal-organic framework material, and it is not easily dissolved in the organic electrolyte.

[0188] The metal-organic framework carbide is doped with a chalcogen. This can be done by doping the metal-organic framework with a chalcogen before carbonization, converting the chalcogen-doped metal-organic framework into a chalcogen-doped metal-organic framework carbide after carbonization. Alternatively, the metal-organic framework does not contain a chalcogen before carbonization, introducing a single chalcogen into the metal-organic framework, and doping the metal-organic framework carbide after carbonization. Chalcogens are reducing, meaning they can increase in valence through redox reactions. Alternatively, chalcogens with a valence less than zero, i.e., low-valent chalcogens, can be easily oxidized to high-valent chalcogens, i.e., chalcogens with a valence greater than zero. For example, chalcogens include sulfur, where low-valent sulfur has a valence of -2 and high-valent sulfur has a valence of +6.

[0189] Metal-organic frameworks (MOFs) typically have poor electrical conductivity and pose a risk of dissolution in organic electrolytes. Carbonizing MOFs to form MOF carbides, which have a carbon skeleton, can improve the overall conductivity of the cathode material. Furthermore, MOF carbides are less soluble in organic electrolytes, ensuring the stability of the cathode material's performance. Furthermore, the MOF carbides obtained after carbonization essentially inherit the rich and stable porous structure of MOFs (MOFs). Reducible sulfides can be dispersed in the MOF carbides at the atomic level, facilitating their removal of lithium (including residual lithium compounds). Furthermore, the MOF carbides formed after carbonization also contain metal nanoparticles, which enhance the conductivity of the coating layer.

[0190] The preparation method of the positive electrode material provided in the embodiment of the present application is by coating the surface of the positive electrode active material with a metal-organic framework material carbide, and at the same time, a reducing sulfide element is doped into the metal-organic framework material carbide, and the reducing sulfide element contacts the positive electrode active material, and in the subsequent charge and discharge process (for example, during the formation process), the reducing sulfide element is easily oxidized to a sulfide element with a higher valence state, and the sulfide element with a higher valence state reacts with the residual lithium compound on the surface of the positive electrode active material to generate a compound with better conductivity than the residual lithium compound in situ, thereby improving the conductivity and electrochemical properties of the positive electrode material. And in the charge and discharge process (for example, during the formation process), the product generated by the action of the reducing sulfide element and the residual lithium compound will further grow on the positive electrode active material to form a positive electrode-electrolyte interface (CEI) film, thereby alleviating the negative impact of the residual lithium compound on the battery performance; in the charge and discharge process, the sulfide element will release lithium ions during the action of the residual lithium compound, and the additional released lithium ions can also be used to compensate for the lithium ion loss caused by the formation of a solid electrolyte interface (SEI) film at the negative electrode during the charge and discharge process of the battery, thereby ensuring the capacity of the battery.

[0191] At the same time, the coating layer comprising a metal-organic framework material carbide doped with a reducing chalcogen is obtained by carbonizing an intermediate phase layer comprising the metal-organic framework material and the chalcogen. The metal-organic framework material carbide essentially inherits the rich and stable porous structure of the metal-organic framework material (MOFs), and the reducing chalcogen can be dispersed at the atomic level in the metal-organic framework material carbide, which facilitates the reducing chalcogen to exert its function and achieve the effect of the chalcogen removing lithium (including residual lithium compounds, etc.). Moreover, the metal-organic framework material carbide formed after the carbonization treatment of the metal-organic framework material also contains metal nanoparticles, which can enhance the conductivity of the coating layer. In addition, because the reducing chalcogen is introduced into the metal-organic framework material, followed by the carbonization treatment of the metal-organic framework material, and the chalcogen is doped into the metal-organic framework material carbide to achieve its introduction on the surface of the positive electrode active material, the amount of introduced chalcogen can be effectively limited, avoiding excessive chalcogen content that would otherwise deteriorate the conductivity of the positive electrode active material. The metal-organic framework material carbide with a rich and stable three-dimensional porous structure is coated on the surface of the positive electrode active material as a carbon skeleton, which can promote ion transport in the electrochemical process. The metal-organic framework material carbide forms a coating layer to prevent the positive electrode active material from directly contacting the electrolyte, reducing the probability of side reactions. At the same time, the coating layer can prevent the dissolution and migration of cations in the positive electrode active material, thereby improving the cycle stability of the battery.

[0192] See Figure 5In some embodiments, the preparation process of the intermediate layer includes:

[0193] With metal ions as nodes and organic ligands as connecting bridges, the surface of the positive electrode active material is coated with a metal-organic framework material, and the organic ligands include sulfide elements.

[0194] Organic ligands refer to organic compounds that can self-assemble with metal ions through coordination bonds to form porous coordination polymers (PCPs) with intramolecular pores.

[0195] The organic ligand includes a chalcogen element. Optionally, the organic ligand may include but is not limited to at least one of a thiophene organic compound, a selenophene organic compound, and a sulfide organic compound.

[0196] In the embodiment of the present application, a metal-organic framework material is coated on the surface of the positive electrode active material using metal ions as nodes and organic ligands containing sulfide elements as connecting bridges. The metal-organic framework material has the advantages of regular morphology, large specific surface area, and strong pore size adjustability, and the metal-organic framework material carbide inherits the structural characteristics of the metal-organic framework material, which is conducive to the sulfide element doped in the metal-organic framework material carbide to play its role. In addition, the organic ligand contains sulfide elements. By selecting organic ligands containing sulfide elements, the metal-organic framework material containing sulfide elements is directly prepared. The method is simple and conducive to improving the production efficiency of the material. The metal-organic framework material containing sulfide elements is then carbonized to obtain the metal-organic framework material carbide doped with sulfide elements. Since the sulfide elements are directly introduced into the metal-organic framework material through organic ligands, the sulfide elements can be evenly dispersed in the metal-organic framework material carbide at the atomic level, thereby effectively controlling the content of sulfide elements in the metal-organic framework material carbide.

[0197] In some embodiments, the chalcogen-containing organic ligand includes at least one of 4-methylthiopyridine-2,6-dicarboxylic acid, 4,4-bipyridyl disulfide, and 2,5-bis(pyridin-4-yl)thiophene.

[0198] The structural formula of 4-methylthiopyridine-2,6-dicarboxylic acid is shown below:

[0199]

[0200] The structural formula of 4,4-bipyridyl disulfide is shown below:

[0201]

[0202] The structural formula of 2,5-di(pyridin-4-yl)thiophene is shown below:

[0203]

[0204] The above organic compound contains sulfur and can be used as an organic ligand to combine with various metal ions to obtain metal-organic framework materials, thereby realizing the preparation of metal-organic framework material carbides doped with chalcogen elements.

[0205] See Figure 6 In some embodiments, forming an intermediate layer comprising a metal-organic framework material and a chalcogen element on the surface of the positive electrode active material further comprises:

[0206] Using metal ions as nodes and organic ligands as connecting bridges, a metal-organic framework material is coated on the surface of the positive electrode active material;

[0207] Sulfur elements are loaded on metal-organic framework materials.

[0208] In the above steps, the metal-organic framework material may contain a chalcogen or may not contain a chalcogen, depending on whether the organic ligand contains an organic ligand. If the organic ligand contains a chalcogen, the prepared metal-organic framework material is a chalcogen-containing metal-organic framework material. If the organic ligand does not contain a chalcogen, the prepared metal-organic framework material is a chalcogen-free metal-organic framework material.

[0209] Chalcogen element simple substance refers to simple substance of chalcogen element. As an example, chalcogen element includes sulfur element, and chalcogen element simple substance includes sulfur simple substance.

[0210] Optionally, loading the chalcogen element onto the metal-organic framework material includes: heating the chalcogen element so that the solid chalcogen element sublimates into a gaseous chalcogen element, and the gaseous chalcogen element diffuses into the pores in the metal-organic framework material. Usually, the carbonization treatment also requires heating. It should be noted that the chalcogen element can be loaded into the metal-organic framework material at the same time as the carbonization treatment, or the chalcogen element can be first loaded into the metal-organic framework material and then subjected to the carbonization treatment. Here, the metal-organic framework material can be prepared with metal ions as nodes and organic ligands that do not contain chalcogen elements as connecting bridges, or it can be prepared with metal ions as nodes and organic ligands that contain chalcogen elements as connecting bridges.

[0211] In the embodiment of the present application, a chalcogen element is loaded into a metal-organic framework material to obtain a metal-organic framework material loaded with a chalcogen element; the metal-organic framework material loaded with a chalcogen element is then subjected to a carbonization treatment, and during the thermal decomposition of the metal-organic framework material, the chalcogen element is covalently bonded with the metal elements, carbon elements, etc. in the metal-organic framework material, thereby achieving the doping of the chalcogen element into the metal-organic framework material carbide. Since the chalcogen element is introduced into the metal-organic framework material after the metal-organic framework material is coated on the surface of the positive electrode active material, the chalcogen element gradually penetrates into the metal-organic framework material through the pores of the metal-organic framework material. The closer to the positive electrode active material, the lower the content of the chalcogen element, so that the chalcogen element in the finally obtained metal-organic framework material carbide is also gradiently distributed, that is, the closer to the positive electrode active material, the lower the content of the chalcogen element, thereby alleviating the problem of poor conductivity of the positive electrode material due to excessive chalcogen content on the surface of the positive electrode active material.

[0212] In some embodiments, the carbonization process is performed while the chalcogen element is supported on the metal-organic framework material.

[0213] Since carbonization treatment is a process of thermal decomposition of metal-organic framework materials, heating is also required during the carbonization process. By controlling the temperature of the carbonization treatment, optionally, the temperature of the carbonization treatment is 300°C to 600°C, so as to realize the conversion of the sulfide element into a gaseous state and enter the metal-organic framework material. At the same time, the metal-organic framework material is thermally decomposed. During the thermal decomposition process, the sulfide element entering the metal-organic framework material is covalently bonded with the metal elements, carbon elements, etc. in the metal-organic framework material to obtain a metal-organic framework material carbide doped with sulfide elements.

[0214] As an example, chalcogens include sulfur, and the simultaneous carbonization treatment of introducing a single chalcogen into a metal-organic framework material includes: placing sulfur powder (i.e., single sulfur) in a first quartz boat, placing a positive electrode active material having a surface coated with a metal-organic framework material in a second quartz boat, placing the first quartz boat and the second quartz boat together in a heating tube, introducing an inert gas, heating the heating tube, and then cooling, filtering, washing, and drying to obtain a positive electrode active material coated with a carbide of a metal-organic framework material doped with a chalcogen.

[0215] By combining the process of introducing elemental sulfur into the metal-organic framework material and the carbonization process into one step, the preparation process is simplified and the production cost of the material is reduced.

[0216] In some embodiments, the mass ratio of the chalcogen element to the positive electrode active material coated with the metal-organic framework material is 1:(1.5-5).

[0217] Optionally, the mass ratio of the chalcogen element to the positive electrode active material of the surface-coated metal-organic framework material is 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5.

[0218] Since the chalcogen element is introduced into the metal-organic framework material after the metal-organic framework material is coated on the surface of the positive electrode active material, the amount of the chalcogen element affects the chalcogen content in the final metal-organic framework material carbide. If the amount of the chalcogen element is too low, the chalcogen content in the metal-organic framework material carbide is too low, resulting in poor removal of residual lithium compounds from the positive electrode material. If the amount of the chalcogen element is too high, the chalcogen element is likely to remain, thus affecting the conductivity of the positive electrode material. By controlling the mass ratio of the chalcogen element to the positive electrode active material coated with the metal-organic framework material to 1: (1.5-5), the prepared positive electrode active material with the metal-organic framework material carbide coated with the chalcogen element has better removal of residual lithium compounds and good conductivity.

[0219] In some embodiments, the metal-organic framework material is coated on the surface of the positive electrode active material with metal ions as nodes and organic ligands as connecting bridges, including:

[0220] providing a metal ion solution comprising metal ions;

[0221] Mixing the positive electrode active material with the metal ion solution to obtain a mixed solution;

[0222] An organic ligand is added to the mixed solution to obtain a metal-organic framework material coated on the surface of the positive electrode active material.

[0223] The metal ion solution refers to a solution containing metal ions. Optionally, the method further comprises preparing the metal ion solution before providing the metal ion solution. Specifically, a metal salt containing the metal ions is weighed, the metal salt including but not limited to nitrates, tetrafluoroborates, acetates, etc., and the metal salt is dissolved in a solvent to obtain the metal ion solution. Optionally, the metal ion solution comprises at least one of tetraacetonitrile copper tetrafluoroborate, cobalt tetrafluoroborate, copper nitrate, zinc nitrate, cobalt nitrate, cadmium nitrate, manganese nitrate, and cobalt acetate.

[0224] Optionally, mixing the positive electrode active material with the metal ion solution to obtain the mixed solution includes: adding the positive electrode active material to the metal ion solution, stirring the metal ion solution to disperse the positive electrode active material, thereby obtaining the mixed solution. Optionally, the positive electrode active material includes a nickel-rich active material. The mixed solution may be a suspension.

[0225] Optionally, adding an organic ligand to the mixed solution includes: while the mixed solution is in a stirring state, injecting an organic ligand solution containing an organic ligand into the mixed solution, maintaining stirring for 1 hour to 3 hours, for example, 2 hours, filtering the mixed solution to obtain a positive electrode active material with a surface coated with a metal-organic framework material, and drying and grinding the positive electrode active material.

[0226] The preparation method is simple and easy to operate.

[0227] In some embodiments, the molar ratio of metal ions to positive electrode active material is 1:(0.02-0.1).

[0228] Optionally, the molar ratio of the metal ion to the positive electrode active material is 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09 or 1:0.1.

[0229] The amount of metal ions will affect the formation effect of the metal-organic framework material, and the molar ratio of metal ions to the positive electrode active material will affect the coating effect of the metal-organic framework material on the surface of the positive electrode active material. If the molar ratio is too small or too large, the coating on the surface of the positive electrode active material is likely to be uneven.

[0230] In some embodiments, the metal ion comprises at least one of a transition metal and a lanthanide metal.

[0231] Transition metals refer to a series of metallic elements in the d-block of the periodic table. Metal-organic frameworks (MOFs), also known as porous coordination polymers (PCPs), are complexes formed by assembling organic ligands as nodes or clusters due to their unfilled valence-shell d-orbitals.

[0232] Lanthanide metals are a collective term for 15 elements in the periodic table, from lanthanum (element 57) to lutetium (element 71). They have similar chemical properties and form a separate series.

[0233] The above-mentioned metal ions act as connectors and are easy to self-assemble with organic ligands as linkers to form metal-organic framework materials. The formed metal-organic framework materials have the advantages of high porosity, low density, large specific surface area, regular pores, adjustable pore size, and topological structure diversity and tailorability.

[0234] In some embodiments, the transition metal includes at least one of Cu, Fe, Al, Co, Zn, Cd, and Mn.

[0235] As an example, the copper-based metal-organic framework material HKUST-1 is a transition metal-organic framework material with 3,5-pyrazoledicarboxylic acid as an organic ligand and Cu as a central metal ion.

[0236] As an example, the iron-based metal-organic framework material MIL-100(Fe) is a transition metal-organic framework material with trimesic acid as an organic ligand and Fe as a central metal ion.

[0237] As an example, the cobalt-based metal-organic framework material ZIF-67 is a transition metal-organic framework material with dimethylimidazole as an organic ligand and Co as a central metal ion.

[0238] As an example, the zinc-based metal-organic framework material MOF-5 is a transition metal-organic framework material with terephthalic acid as an organic ligand and Zn as a central metal ion.

[0239] As an example, the aluminum-based metal-organic framework material MIL-68(Al) is a transition metal-organic framework material with terephthalic acid as an organic ligand and Al as a central metal ion.

[0240] By combining the above transition metals as central metal ions with organic ligands, metal-organic framework materials with stable structures can be obtained, and the raw materials are economical.

[0241] In some embodiments, the organic ligand includes at least one of a carboxylic acid organic compound and a nitrogen organic compound.

[0242] Carboxylic acid organic compounds refer to organic compounds having a carboxyl (-COOH) functional group in the molecule. The number of carboxyl functional groups in the carboxylic acid organic compounds includes, but is not limited to, 1, 2, or 3.

[0243] The nitrogen-containing organic compound refers to an organic compound containing nitrogen (N) in its molecule. The nitrogen-containing organic compound may include, but is not limited to, at least one of an imidazole organic compound, a pyridine organic compound, and a pyrrole organic compound.

[0244] By combining the above organic compounds as organic ligands with metal ions, a metal-organic framework material with a stable structure can be obtained.

[0245] In some embodiments, the carboxylic acid organic compound includes at least one of terephthalic acid and trimesic acid; and / or the nitrogen-containing organic compound includes 2-methylimidazole.

[0246] Terephthalic acid (C8H6O4) is a white needle-shaped crystal or powder that is easily soluble in ethanol, acetone, and glacial acetic acid, slightly soluble in boiling water, and difficult to dissolve in cold water. The structural formula of terephthalic acid is shown below:

[0247]

[0248] Trimellitic acid (C9H6O6) is a white crystalline powder that is soluble in water, easily soluble in ethanol, and soluble in ether. The structural formula of trimesic acid is shown below:

[0249]

[0250] 2-Methylimidazole (C4H6N2) is soluble in water and ethanol, and its structural formula is shown below:

[0251]

[0252] The above organic compounds can be combined with various metal ions as organic ligands to obtain metal-organic framework materials.

[0253] In some embodiments, the temperature of the carbonization treatment is 300°C to 600°C.

[0254] Optionally, the temperature of the carbonization treatment may be, but is not limited to, any value among 300°C, 350°C, 400°C, 450°C, 500°C, 550°C and 600°C, or a range between any two values.

[0255] The temperature of the carbonization treatment directly affects the effectiveness and efficiency of the metal-organic framework (MOF) conversion to MOF carbide. Excessively high temperatures can cause deformation and even collapse of the MOF carbide structure, while excessively low temperatures can lead to inefficient formation of MOF carbides or even prevent the conversion of the MOF to MOF carbide. Furthermore, when a chalcogen is loaded onto the MOF, a low carbonization temperature can also affect the chalcogen doping efficiency.

[0256] In some embodiments, the carbonization treatment time is 2 hours to 5 hours.

[0257] Optionally, the carbonization treatment time is 2 h, 3 h, 4 h or 5 h.

[0258] The carbonization duration directly affects the effectiveness and efficiency of the metal-organic framework (MOF) conversion to MOF carbide. Excessive carbonization can cause deformation and even collapse of the MOF carbide structure. Too short a carbonization duration can lead to inefficient formation of the MOF carbide or even prevent the conversion of the MOF carbide from occurring. Furthermore, when a chalcogen is incorporated into the MOF, a short carbonization duration can also affect the chalcogen doping efficiency.

[0259] In some embodiments, the chalcogen includes at least one of sulfur and selenium.

[0260] As an example, the chalcogen element includes sulfur, and the resulting metal-organic framework carbide includes a sulfur-containing metal-organic framework carbide.

[0261] As an example, the chalcogen element includes selenium, and the obtained metal-organic framework material carbide includes a selenium-containing metal-organic framework material carbide.

[0262] In the embodiment of the present application, a metal-organic framework material carbide is coated on the surface of the positive electrode active material, and a reducing selenium element or sulfur element is doped into the metal-organic framework material carbide, so that the selenium element or sulfur element is used to effectively remove the residual lithium compounds on the positive electrode active material.

[0263] In some embodiments, the positive electrode active material includes a chemical formula of Li a Ni m Co n M 1-m-n A nickel-rich active material of O2, wherein M comprises at least one of Mn and Al, wherein m≥0.6, n≤0.2, 0.9≤a≤1.2, optionally, m≥0.9.

[0264] The chemical formula of nickel-rich active material is Li a Ni m Co n M 1-m-n O2, wherein M includes at least one of Mn and Al. As an example, M includes Mn, and the chemical formula of the nickel-rich active material is Li 1-a Ni m Co n Mn 1-m-n O2. As an example, M includes Al, and the chemical formula of the nickel-rich active material is Li 1-a Ni m Co n Al 1-m-nO2. Specifically, m≥0.6, and the content of nickel in the nickel-rich active material is increased by increasing the value of m, thereby increasing the reversible lithium insertion capacity of the positive electrode material. Optionally, m is any one of 0.6, 0.7, 0.8, 0.9 and 0.99, or a range value between any two of them. Specifically, n≤0.2, the nickel-rich active material is usually a layered structure, and Co can stabilize the layered structure, but the high price of Co will increase the cost of the nickel-rich active material. The cost of the nickel-rich active material can be controlled by controlling n≤0.2. Optionally, n is any one of 0.05, 0.1, 0.15 and 0.2, or a range value between any two of them. 0.9≤a≤1.2, that is, the lithium content in the nickel-rich active material can be greater than 1, equal to 1, or less than 1. When a is greater than 1, the nickel-rich active material is a lithium-rich positive electrode material. As an example, for the nickel-rich active material, which is a material obtained by pre-lithiation, the Li content can be greater than 1. Optionally, a may be any one of 1, 1.05, 1.1, 1.15 and 1.2, or a value in a range between any two of them.

[0265] In the embodiment of the present application, a metal-organic framework material carbide is coated on the surface of the nickel-rich active material, and the metal-organic framework material carbide is doped with a reducing sulfide element. The reducing sulfide element contacts the positive electrode active material. During the charge and discharge process (for example, during the formation process), the sulfide element is easily oxidized to a sulfide element with a higher valence state, and the sulfide element with a higher valence state will react with the residual lithium compound on the surface of the positive electrode active material to in situ generate a sulfide-containing inorganic compound with better conductivity than the residual lithium compound, thereby improving the conductivity and electrochemical properties of the positive electrode material. In addition, during the charge and discharge process, the sulfide-containing inorganic compound will further grow on the positive electrode active material to form a positive electrode-electrolyte interface (CEI) film, thereby reducing the content of residual lithium compounds. At the same time, the metal-organic framework material carbide forms a coating layer coated on the surface of the nickel-rich active material, which can further inhibit the generation of residual lithium compounds. In addition, the metal-organic framework material carbide is coated on the surface of the nickel-rich active material, which can prevent the positive electrode material from directly contacting the electrolyte to produce side reactions, and can capture nickel ions, preventing nickel ions from dissolving and migrating to the electrode surface, thereby improving cycle stability.

[0266] See Figure 4 Some embodiments of the present application further provide a positive electrode plate 102, which includes a positive electrode current collector and a positive electrode material layer combined on the positive electrode current collector, and the positive electrode material layer includes the above-mentioned positive electrode material.

[0267] A current collector is a structure or component in a battery that collects current. It's typically made of metal foil. The positive electrode current collector is the structure or component in a battery's positive electrode that collects current. Positive electrode current collectors include, but are not limited to, aluminum foil.

[0268] The positive electrode material layer refers to a film layer disposed on the positive electrode current collector and containing the positive electrode active material. The positive electrode material layer can be disposed on one surface of the positive electrode current collector or on both surfaces. Optionally, the positive electrode material layer includes a conductive agent and a binder.

[0269] The positive electrode plate 102 provided in the embodiment of the present application includes a positive electrode current collector and a positive electrode material layer, the positive electrode material layer includes the above-mentioned positive electrode material, and the above-mentioned positive electrode material includes a positive electrode active substance and a metal-organic framework material carbide coated on the surface of the positive electrode active substance, the metal-organic framework material carbide is doped with a reducing sulfide element, and the sulfide element can react with the residual lithium compound in the positive electrode active substance during the charging and discharging process, thereby reducing the content of residual lithium compounds in the positive electrode material, and the metal-organic framework material carbide coated on the surface of the positive electrode active substance can form a protective layer to effectively isolate the positive electrode active substance, prevent the positive electrode active substance from direct contact with the electrolyte, improve the surface stability of the positive electrode active substance, and ultimately improve the cycle performance and storage performance of the battery.

[0270] See Figure 2 Some embodiments of the present application further provide a battery 40 , which includes the above-mentioned positive electrode plate 102 .

[0271] Optionally, the battery 40 is a secondary battery, which has many different forms, including but not limited to battery cells, battery modules, and battery packs.

[0272] The battery 40 provided in the embodiment of the present application includes the above-mentioned positive electrode plate 102. The battery 40 has stable cycle performance, long high-temperature storage life, and good rate performance.

[0273] See Figure 1 Some embodiments of the present application further provide an electrical device, which includes the above-mentioned battery 40.

[0274] The following describes the details in conjunction with specific embodiments.

[0275] Example 1

[0276] See Figure 5 The method for preparing the positive electrode material provided in this embodiment includes the following steps:

[0277] S1: adding a nickel-rich layered oxide (NCM811) positive electrode active material to a metal ion solution and stirring and dispersing the mixture uniformly to obtain a mixed solution, wherein the metal ion solution is a tetrafluoroborate tetraacetonitrile copper solution, and the molar ratio of the metal ion to the nickel-rich layered oxide is 1:0.06;

[0278] S2: keeping the mixed solution provided in S1 in a stirring state, and rapidly injecting the organic ligand solution into the mixed solution, wherein the organic ligand contained in the organic ligand solution is a sulfur-containing organic ligand 4-methylthiopyridine-2,6-dicarboxylic acid, and the molar ratio of the metal ion to the sulfur-containing organic ligand is 3:1;

[0279] S3: After stirring the solution obtained in S2 for 2 h, the obtained solution was filtered to obtain a nickel-rich layered oxide cathode material containing sulfur MOFs@NCM coated with sulfur MOFs, which was then dried and ground.

[0280] S4: The sulfur-containing MOFs@NCM powder was placed in a quartz boat, which was placed in the same heating tube. Inert gas was introduced into the heating tube and heated (heating temperature was 300°C for 3 hours). The mixture was cooled, filtered, washed, and dried to obtain a sulfur-containing MOFs carbide-coated nickel-rich layered oxide positive electrode material.

[0281] Example 2

[0282] Same as Example 1, except that the molar ratio of metal ions to nickel-rich layered oxide is 1:0.03.

[0283] Example 3

[0284] See Figure 6 The method for preparing the positive electrode material provided in this embodiment includes the following steps:

[0285] S1: adding the nickel-rich layered oxide (NCM811) positive electrode active material to the metal ion solution (copper ion solution) and stirring and dispersing the mixture uniformly to obtain a mixed solution, wherein the molar ratio of the metal ion to the nickel-rich layered oxide is 1:0.1;

[0286] S2: Keep the mixed solution provided by S1 in a stirring state, and quickly inject the organic ligand (trimesic acid) solution into the mixed solution;

[0287] S3: After continuing to stir the solution obtained in S2 for 2 hours, filtering to obtain a nickel-rich layered oxide positive electrode material MOFs@NCM coated with MOFs on the surface, drying and grinding, wherein the MOFs is HKUST-1;

[0288] S4: Sulfur powder was placed in a quartz boat and MOFs@NCM powder was placed in another quartz boat, where the mass ratio of S powder to MOFs@NCM was 1:4. Both quartz boats were placed in the same heating tube, and inert gas was introduced into the heating tube. The tube was heated (heating temperature was 500°C for 3 hours), cooled, filtered, washed, and dried to obtain a sulfur-containing MOFs carbide-coated nickel-rich layered oxide positive electrode material.

[0289] Example 4

[0290] The same as Example 3, except that the amount of sulfur powder used in step S4 is different, wherein the mass ratio of sulfur powder to MOFs@NCM is 1:2.

[0291] Comparative Example 1

[0292] Same as Example 3, except that sulfur is not doped in step S4.

[0293] Comparative Example 2

[0294] The preparation method of the positive electrode material provided in this comparative example includes: mixing a nickel-rich layered oxide (NCM811) positive electrode active material and a sulfur element in a mass ratio of 4:1 and performing ball milling to obtain the positive electrode material.

[0295] Comparative Example 3

[0296] The same as Comparative Example 2, except that the amount of sulfur used was different, the mass ratio of the nickel-rich layered oxide to the sulfur was 2:1.

[0297] In order to verify the progress of the examples of the present application, the samples prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were tested as follows:

[0298] 1. X-ray photoelectron spectroscopy (XPS) test:

[0299] X-ray photoelectron spectroscopy was used to quantitatively analyze the sulfur content in the samples prepared in Examples 1 to 4 and Comparative Examples 1 to 3. The results are shown in Table 1. As can be seen from the table, in Examples 1 to 4, the sulfur content in the positive electrode materials was 5%, 10%, 5%, and 10%, respectively, and in Comparative Examples 1 to 3, the sulfur content in the positive electrode materials was 0%, 5%, and 10%, respectively.

[0300] Furthermore, X-ray photoelectron spectroscopy was used to analyze the chemical bonding of the samples prepared in Example 1 and Example 3. The results are as follows: Figure 7 and Figure 8 shown. Figure 7 The XPS spectrum of the sample prepared in Example 1 is shown. It can be seen from the figure that sulfur is distributed in the sample, and the sulfur is covalently bonded with copper, carbon, oxygen, etc. Figure 8 The XPS spectrum of the sample prepared in Example 3 is shown. It can be seen from the figure that sulfur is distributed in the sample, and the sulfur is combined with copper, carbon, etc. by covalent bonds.

[0301] 2. Scanning electron microscope (SEM) and transmission electron microscope (TEM) test: The morphology of the samples prepared in Example 1 and Example 3 was characterized by scanning electron microscope and transmission electron microscope. The results are as follows: Figure 9and Figure 10 shown. Figure 9 Figure (a) shows the SEM image of the sample prepared in Example 1. Figure 10 Figure (a) shows the SEM image of the sample prepared in Example 3. It can be seen from the figure that the samples prepared in Example 1 and Example 3 are granular. Figure 9 Figure (b) shows the TEM image of the sample prepared in Example 1. Figure 10 Figure (b) shows the TEM image of the sample prepared in Example 3. It can be seen from the figure that the samples prepared in Example 1 and Example 3 are core-shell structures, specifically, the surface of NCM811 as the core structure is wrapped with a coating layer.

[0302] 3. Battery performance test:

[0303] S1. Sample preparation:

[0304] The lithium-ion battery is prepared by the following method:

[0305]

Preparation of positive electrode sheet

[0306] The coated NCM811 ternary material, conductive agent carbon black, binder polyvinylidene fluoride (PVDF), and carbon nanotubes (CNT) were dry-mixed and stirred at a weight ratio of 90.3:5.7:2.7:1.3, stirred and mixed at a speed of 400-1000 r / s, and then wetted, kneaded, and dispersed to obtain a positive electrode slurry. The obtained slurry was then coated on aluminum foil and dried, cold pressed, and slit to obtain a positive electrode sheet.

[0307]

Preparation of negative electrode sheet

[0308] The precursor (graphite) of the first active material layer is evenly coated on the current collector, and the first active material layer is obtained by drying at a temperature of 60°C and drying for 35 minutes; the precursor (graphite) of the second active material layer is evenly coated on the first active material layer, and the second active material layer is obtained by drying at a temperature of 60°C and drying for 35 minutes, and the negative electrode sheet is obtained after cold pressing and slitting.

[0309] Preparation of electrolyte

[0310] In an argon atmosphere glove box (H2O<0.01ppm, O2<0.01ppm), organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed uniformly in a volume ratio of 4 / 6, 12.5% ​​LiPF6 lithium salt was added and dissolved in the organic solvent, and stirred uniformly to obtain an electrolyte.

[0311]

Isolation film

[0312] Polyethylene film is used as the isolation film.

[0313] Preparation of lithium-ion batteries

[0314] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in order with the separator placed between the positive and negative electrode sheets, and then wound to obtain a bare battery cell; the bare battery cell is placed in the battery outer packaging, and then the electrolyte is injected, packaged, allowed to stand, formed, shaped, and capacity tested to complete the preparation of the lithium-ion battery, wherein the lithium-ion battery has a thickness of 4.2 mm, a width of 32 mm, and a length of 82 mm.

[0315] S2. Performance test:

[0316] a. Storage test:

[0317] Capacity test before storage: charge at 0.33C constant current to 4.25V, charge at constant voltage to a cut-off current of 0.05C; discharge at 0.33C to 2.8V, and record the discharge capacity.

[0318] Capacity test after storage: After 60 days of storage, perform the same capacity test as before storage.

[0319] Capacity test after recovery: After 60 days of storage, charge the battery to 4.25V at 0.04C constant current and charge it to a cutoff current of 0.05C at constant voltage. Discharge the battery to 2.8V at 0.33C, and record the discharge capacity.

[0320] b. Rate performance test:

[0321] Rate test before cycling:

[0322] Charge at 0.33C to 4.25V, discharge at 0.33C to 2.8V, and record the 0.33C discharge capacity;

[0323] Charge at 0.33C to 4.25V, discharge at 0.5C to 2.8V, and record the 0.5C discharge capacity;

[0324] Charge at 0.33C to 4.25V, discharge at 1C to 2.8V, and record the 1C discharge capacity.

[0325] Cycle test: measure capacity before cycle; charge at 0.5C constant current to 97% SOC, charge at constant voltage to 0.05C; discharge at 0.5C to 5% SOC; repeat 100 cycles, measure capacity after cycle;

[0326] Post-cycle rate test: same as pre-cycle rate test.

[0327] Table 1

[0328]

[0329]

[0330] Table 1 shows the storage test results of the samples prepared in Examples 1-4 and Comparative Examples 1-3. Specifically, when the storage test results of the samples prepared in Examples 1-4 are compared with those of the samples provided in Comparative Examples 1-3, at the same sulfur content, the former have higher post-storage capacity retention, recovered capacity, and recovery rate than the latter, and the former have lower DCR and pressure drop than the latter.

[0331] Table 2

[0332]

[0333] Table 2 shows the rate performance test results of the samples prepared in Examples 1 to 4 and Comparative Examples 1 to 3. Specifically, when the rate performance test results of the samples prepared in Examples 1 to 4 are compared with the rate performance test results of the samples provided in Comparative Examples 1 to 3, at the same sulfur content, the capacity retention rate of the former is higher than that of the latter, whether at 0.33C, 0.5C, or 1C.

[0334] Compared with Comparative Example 1, Examples 1 to 4 have better performance in all the above aspects. This is because the former is coated with MOFs carbide on the surface of the nickel-rich layered oxide (NCM811), and the MOFs carbide is doped with low-valent sulfur. The low-valent sulfur has reducing properties and reacts with the residual lithium compounds on the surface of the nickel-rich layered oxide to form compounds with better conductivity than the residual lithium compounds, such as Li2S2O3, Li2SO4, etc., thereby improving the conductivity and electrochemical performance of the nickel-rich layered oxide. Furthermore, when the battery is charged and discharged, the low-valent sulfur in the MOFs carbide will continue to react with the residual lithium compounds and form an electrochemically stable artificial CEI layer on the surface of the nickel-rich layered oxide, further reducing the content of the residual lithium compounds while optimizing the performance of the battery. However, in Examples 1 to 4, under the same preparation process, the performance of the battery provided by Example 1 is better than that of the battery provided by Example 2, and the performance of the battery provided by Example 3 is better than that of the battery provided by Example 4. This is because the content of low-valent sulfur in the positive electrode material in Examples 2 and 4 is 10 wt%, which is higher than 5 wt% in Examples 1 and 3. If the content of low-valent sulfur in the positive electrode material is too high, the amount of Li2SO4 and the like generated will be too large. Although the conductivity of Li2SO4 is better than that of residual lithium compounds, Li2SO4 still has the problem of insufficient conductivity. If the amount of Li2SO4 and the like is too large, it will increase battery polarization and deteriorate battery performance.

[0335] Comparing Examples 1 to 4 with Comparative Examples 2 to 3 (specifically, comparing Examples 1 and 3 with Comparative Example 2, and comparing Examples 2 and 4 with Comparative Example 3), the former also has better performance in the above-mentioned aspects. This is because the former coats MOFs carbide on the surface of nickel-rich layered oxide (NCM811), and low-valent sulfur is doped in MOFs carbide, which can effectively limit the amount of sulfide introduced, avoiding excessive sulfide content that makes the conductivity of the positive active material worse. At the same time, thanks to the three-dimensional porous structure of MOFs carbide, the dispersion of low-valent sulfur is better, which is more conducive to the reaction of low-valent sulfur with residual lithium compounds. At the same time, the porous structure can also promote ion transport in the electrochemical process and improve rate performance. In addition, the formation of a coating layer by MOFs carbide can prevent the nickel-rich layered oxide from directly contacting the electrolyte, reducing the probability of side reactions. The coating layer can also prevent the dissolution and migration of nickel ions in the positive active material, thereby improving the cycle stability of the battery.

[0336] Comprehensive analysis of the data in Tables 1 and 2 shows that as long as at least one of a chalcogen element and a sulfur-containing MOFs carbide is added during the preparation of the nickel-rich positive electrode slurry to prepare the nickel-rich positive electrode material and the positive electrode sheet, the battery's cycle, storage, and rate performance can be improved. Furthermore, when the sulfur content in the positive electrode modification material is 5wt%, the battery storage, rate, and cycle stability are optimal. Furthermore, sulfur-doped MOFs carbide coating exhibits superior electrical properties compared to the positive electrode material obtained by directly grinding and doping sulfur-doped nickel-rich positive electrode materials. This is mainly attributed to the dispersion of S and the improvement of the material's DCR. The two different MOFs carbide coatings also have different effects on the modification of the positive electrode material. The second coating (Examples 3 and 4) achieves gradient doping of S, which can better realize its reductive modification of the nickel-rich positive electrode material, exhibiting the best battery cycle, storage, and rate performance at 5wt% sulfur doping.

[0337] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A positive electrode material, characterized in that The invention comprises a positive electrode active material and a coating layer coated on the surface of the positive electrode active material, wherein the coating layer comprises a metal-organic framework material carbide, the metal-organic framework material carbide is doped with a chalcogen element, and the chalcogen element has reducing properties; the content of the chalcogen element in the positive electrode material is greater than 0 and less than or equal to 10wt%.

2. The positive electrode material according to claim 1, characterized in that The content of the chalcogen element is less than or equal to 5 wt %.

3. The positive electrode material according to any one of claims 1 to 2, characterized in that The thickness of the coating layer is 1 nm to 20 nm; and / or the specific surface area of ​​the positive electrode material is 1 m 2 / g~10 m 2 / g; and / or, the metal-organic framework material carbide has a porous structure.

4. The positive electrode material according to claim 3, characterized in that The chalcogen element is evenly distributed in the coating layer, or the concentration of the chalcogen element gradually increases in the coating layer as it moves away from the positive electrode active material.

5. The positive electrode material according to claim 1, characterized in that The metal-organic framework material carbide comprises a metal element, a chalcogen element and a carbon element bonded by covalent bonds.

6. The positive electrode material according to claim 5, characterized in that The covalent bond includes at least one of a metal-chalcogen bond and a carbon-chalcogen bond.

7. The positive electrode material according to claim 5, characterized in that The metal-organic framework material carbide further contains nitrogen, and the covalent bond further contains a nitrogen-chalcogen bond.

8. The positive electrode material according to claim 4, characterized in that The coating layer further comprises metal nanoparticles, and the metal nanoparticles are distributed in the metal-organic framework material carbide.

9. The positive electrode material according to claim 1, characterized in that The chalcogen element includes sulfur.

10. The positive electrode material according to claim 1, characterized in that The positive electrode active material includes a chemical formula of Li a Ni m Co n M 1-m-n A nickel-rich active material containing O2, wherein M comprises at least one of Mn and Al, wherein m≥0.6, n≤0.2, and 0.9≤a≤1.

2.

11. The positive electrode material according to claim 10, characterized in that The m≥0.

9.

12. A method for preparing the positive electrode material according to any one of claims 1 to 11, characterized in that: include: Providing positive electrode active material; forming an intermediate phase layer containing a metal-organic framework material and a chalcogen element on the surface of the positive electrode active material; The intermediate phase layer is carbonized to obtain a coating layer, wherein the coating layer comprises a metal-organic framework material carbide, the metal-organic framework material carbide is doped with the chalcogen element, and the chalcogen element has reducing properties.

13. The method for preparing the positive electrode material according to claim 12, wherein: The preparation process of the intermediate phase layer comprises: With metal ions as nodes and organic ligands as connecting bridges, a metal-organic framework material is coated on the surface of the positive electrode active material, and the organic ligands contain the chalcogen element.

14. The method for preparing the positive electrode material according to claim 13, wherein: The organic ligand includes at least one of 4-methylthiopyridine-2,6-dicarboxylic acid, 4,4-bipyridyl disulfide, and 2,5-di(pyridin-4-yl)thiophene.

15. The method for preparing the positive electrode material according to claim 12, wherein: The preparation process of the intermediate phase layer comprises: Using metal ions as nodes and organic ligands as connecting bridges, a metal-organic framework material is coated on the surface of the positive electrode active material; A chalcogen element is loaded on the metal-organic framework material.

16. The method for preparing the positive electrode material according to claim 15, wherein: The carbonization treatment is performed while the chalcogen element is loaded on the metal-organic framework material.

17. The method for preparing a positive electrode material according to any one of claims 15 to 16, characterized in that: The mass ratio of the chalcogen element to the positive electrode active material coated with the metal-organic framework material is 1: (1.5-5).

18. The method for preparing a positive electrode material according to any one of claims 13 to 16, characterized in that: The metal-organic framework material coated on the surface of the positive electrode active material with metal ions as nodes and organic ligands as connecting bridges includes: providing a metal ion solution comprising metal ions; mixing the positive electrode active material with the metal ion solution to obtain a mixed solution; An organic ligand is added to the mixed solution to obtain a metal-organic framework material coated on the surface of the positive electrode active material.

19. The method for preparing a positive electrode material according to claim 18, wherein: The molar ratio of the metal ion to the positive electrode active material is 1:(0.02-0.1).

20. The method for preparing a positive electrode material according to claim 19, wherein: The metal ions include at least one of a transition metal and a lanthanide metal.

21. The method for preparing a positive electrode material according to claim 20, wherein: The transition metal includes at least one of Cu, Fe, Al, Co, Zn, Cd, and Mn.

22. The method for preparing the positive electrode material according to claim 15, wherein: The organic ligand includes at least one of a carboxylic acid organic compound and a nitrogen-containing organic compound.

23. The method for preparing a positive electrode material according to claim 22, wherein: The carboxylic acid organic compound includes at least one of terephthalic acid and trimesic acid, and / or the nitrogen-containing organic compound includes 2-methylimidazole.

24. The method for preparing a cathode material according to claim 12, wherein: The temperature of the carbonization treatment is 300° C. to 600° C.; and / or the time of the carbonization treatment is 2 h to 5 h.

25. The method for preparing a cathode material according to claim 12, wherein: The chalcogen element includes sulfur.

26. The method for preparing a positive electrode material according to claim 12, wherein: The positive electrode active material includes a chemical formula of Li a Ni m Co n M 1-m-n A nickel-rich active material containing O2, wherein M comprises at least one of Mn and Al, wherein m≥0.6, n≤0.2, and 0.9≤a≤1.

2.

27. The method for preparing a cathode material according to claim 26, wherein: m≥0.9。 28. A positive electrode plate, characterized in that: The invention comprises a positive electrode current collector and a positive electrode material layer bonded to the positive electrode current collector, wherein the positive electrode material layer comprises the positive electrode material according to any one of claims 1 to 11 or the positive electrode material prepared by the method for preparing the positive electrode material according to any one of claims 12 to 27.

29. A battery, characterized in that: Comprising the positive electrode sheet according to claim 28.

30. An electrical device, characterized in that: Comprising a battery according to claim 29.

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