WO2024234591A1 - 正极材料及其制备方法、正极极片、电池及用电装置 - Google Patents

正极材料及其制备方法、正极极片、电池及用电装置 Download PDF

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Publication number
WO2024234591A1
WO2024234591A1 PCT/CN2023/131304 CN2023131304W WO2024234591A1 WO 2024234591 A1 WO2024234591 A1 WO 2024234591A1 CN 2023131304 W CN2023131304 W CN 2023131304W WO 2024234591 A1 WO2024234591 A1 WO 2024234591A1
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Prior art keywords
positive electrode
additive
coating layer
electrode material
active material
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Ceased
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PCT/CN2023/131304
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English (en)
French (fr)
Inventor
靳超
严观福生
叶永煌
代志鹏
吴子睿
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • 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 plate, a battery and an electrical device.
  • lithium-ion batteries can reversibly convert chemical energy into electrical energy and are an ideal carrier for human use and storage of energy. Since the advent of lithium-ion batteries, they have been widely used due to their advantages such as long life, high energy density and low maintenance cost. Currently, lithium-ion batteries have been used in many fields such as portable electronic devices, new energy vehicles, and energy storage systems.
  • positive electrode active materials As a key factor affecting the performance of lithium-ion batteries, positive electrode active materials often determine the cycle life, energy density and power density of lithium-ion batteries. Affected by the preparation process of positive electrode active materials or the characteristics of positive electrode active materials themselves, residual lithium compounds (RLCs) such as lithium hydroxide, lithium carbonate, lithium oxide, etc. are easily formed on the surface of positive electrode active materials. Usually, residual lithium compounds have poor conductivity, which will increase the impedance of the positive electrode/electrolyte interface, aggravate battery polarization, deteriorate discharge capacity and cycle stability, and have a negative impact on battery performance.
  • RLCs residual lithium compounds
  • the purpose of the embodiments of the present application is to provide a positive electrode material and a preparation method thereof, a positive electrode plate, a battery and an electrical device, in order to alleviate the negative impact of residual lithium compounds in the positive electrode active material on battery performance.
  • a positive electrode material comprising: a positive electrode active material and a one-dimensional conductive material and an additive distributed on the surface of the positive electrode active material, at least a portion of the one-dimensional conductive material is wrapped by the additive, and the additive contains a reducing sulfide element.
  • the sintered material is stirred with the positive electrode active material to obtain the positive electrode material.
  • an electrical device comprising the battery provided in the fourth aspect of the embodiment of the present application.
  • the positive electrode material provided by the embodiment of the present application has the beneficial effect that: by introducing an additive on the surface of the positive electrode active material, the additive contains a chalcogen with reducing property (usually a chalcogen with low valence), the chalcogen with reducing property in the additive is easily oxidized and reacts with residual lithium compounds (such as LiOH , Li2O , Li2CO3 , etc. ) on the surface of the positive electrode active material, thereby in situ generating an intermediate product containing a chalcogen with intermediate valence state (such as Li2S2O3 , Li2Se2O3 , Li2Te2O3 , etc.
  • a chalcogen with reducing property usually a chalcogen with low valence
  • residual lithium compounds such as LiOH , Li2O , Li2CO3 , etc.
  • the final product further forms a positive electrode-electrolyte interface (CEI) film on the surface of the positive electrode active material, thereby removing the residual lithium compounds on the surface of the positive electrode active material and improving the conductivity and electrochemical performance of the positive electrode active material.
  • a one-dimensional conductive material is introduced on the surface of the positive electrode active material. Since the one-dimensional conductive material is located on the surface of the positive electrode active material and can overlap with each other to construct a conductive system, the overall conductivity of the material is improved; at the same time, at least part of the one-dimensional conductive material is wrapped by the additive, which can increase the area of physical bonding between the additive and the one-dimensional conductive material.
  • the one-dimensional conductive material itself has a high specific surface area, the bonding area between the additive and the one-dimensional carbon material is further increased, and the bonding force between the additive and the one-dimensional conductive material is increased, thereby improving the stability of the bonding between the two and achieving the anchoring of the additive. Since the additive is wrapped on the surface of the one-dimensional conductive material, when the one-dimensional conductive material is overlapped together, the additive will also wrap the nodes of the one-dimensional conductive material overlap, so as not to affect the conductive system constructed by the one-dimensional conductive material.
  • FIG1 is a schematic structural diagram of a vehicle according to some embodiments of the present application.
  • FIG2 is a schematic diagram of an exploded structure of a battery according to some embodiments of the present application.
  • FIG3 is a schematic diagram of an exploded structure of a battery cell according to some embodiments of the present application.
  • FIG4 is a schematic diagram of the structure of an electrode assembly in some embodiments of the present application.
  • FIG. 5 is a schematic diagram of the structure of the positive electrode material provided in some embodiments of the present application.
  • At least one means one or more, and “plurality” means two or more. "At least one of the following” or similar expressions refers to any combination of these items, including any combination of single or plural items.
  • at least one of a, b, or c or “at least one of a, b, and c” can all mean: a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple, respectively.
  • the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.
  • the weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application.
  • the mass in the embodiment description of the present application can be ⁇ g, mg, g, kg and other mass units known in the chemical industry.
  • the present invention introduces additives on the surface of the positive electrode active material, and the additives include a reducing sulfide element (usually The chalcogen with reducing property in the additive is easily oxidized and reacts with the residual lithium compound (such as LiOH, Li 2 O, Li 2 CO 3, etc.) on the surface of the positive electrode active material to generate in situ an intermediate product containing the chalcogen with intermediate valence (such as Li 2 S 2 O 3 , Li 2 Se 2 O 3 , Li 2 Te 2 O 3 , etc.) on the surface of the positive electrode active material, and in the subsequent formation process, the intermediate product continues to react, and the chalcogen with reducing property will continue to be oxidized and react with the residual lithium compound, and finally generate a final product containing the chalcogen with high valence (such as Li 2 SO 3 , Li 2 SO 4 , Li 2 SeO 3, Li 2 SeO 4 , Li 2 TeO 3 , Li 2 TeO 3 , etc.).
  • the final product further forms a positive electrode-electrolyte interface (CEI) film on the surface of the positive electrode active material, thereby removing the residual lithium compounds on the surface of the positive electrode active material and improving the conductivity and electrochemical properties of the positive electrode active material.
  • a one-dimensional conductive material is introduced on the surface of the positive electrode active material. Since the one-dimensional conductive material is located on the surface of the positive electrode active material and can overlap with each other to construct a conductive system, the overall conductivity of the material is improved; at the same time, at least part of the one-dimensional conductive material is wrapped by the additive, which can increase the area of physical bonding between the additive and the one-dimensional conductive material.
  • the one-dimensional conductive material itself has a high specific surface area, the bonding area between the additive and the one-dimensional conductive material is further increased, and the bonding force between the additive and the one-dimensional conductive material is increased, thereby improving the stability of the bonding between the two and achieving the anchoring of the additive. Since the additive is wrapped on the surface of the one-dimensional conductive material, when the one-dimensional conductive material is overlapped together, the additive will also wrap the nodes of the one-dimensional conductive material overlap, so as not to affect the conductive system constructed by the one-dimensional conductive material.
  • the batteries disclosed in some embodiments of the present application may be used, but not limited to, in electrical devices such as vehicles, ships, or aircraft.
  • a power supply system having the batteries disclosed in the present application and the like may be used to form the electrical device.
  • Some embodiments of the present application provide an electric device using a battery as a power source, and the electric device 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.
  • the vehicle may be, but is not limited to, a fuel vehicle, a gas vehicle, or a new energy vehicle, and the new energy vehicle may be, but is not limited to, a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, etc.
  • the spacecraft includes an airplane, a rocket, a space shuttle, and a spacecraft, etc.
  • the electric toy includes a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy, etc.
  • the electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly electric tool, and a railway electric tool, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact drill, a concrete vibrator, and an electric planer, etc.
  • FIG. 1 is a schematic diagram of the structure of a vehicle provided in some embodiments of the present application.
  • a battery 40 is provided inside the vehicle, and the battery 40 can be provided at the bottom, head, or tail of the vehicle.
  • the battery 40 can be used to power the vehicle, for example, the battery 40 can be used as an operating power source for the vehicle.
  • the vehicle may also include a controller 501 and a motor 502, and the controller 501 is used to control the battery 40 to power the motor 502, for example, for the starting, navigation, and working power requirements of the vehicle during driving.
  • the battery 40 can be used not only as the operating power source of the vehicle, but also as the driving force of the vehicle.
  • the battery 40 is a secondary battery, which has many different forms, including but not limited to battery cells, battery modules, and battery packs, etc.
  • a secondary battery here refers to a battery that can be used continuously by activating the active material by charging after the battery is discharged.
  • FIG 2 is an exploded view of a battery 40 provided in some embodiments of the present application.
  • the battery 40 includes a box 401 and a battery cell 30, and the battery cell 30 is accommodated in the box 401.
  • the box 401 is a component used to provide a space for accommodating the battery cell 30, and the box 401 can adopt a variety of structures.
  • the box body 401 may include a box body 4011 and a box cover 4012, which cover each other and define a storage space for accommodating the battery cell 30.
  • the box body 4011 may be a hollow structure with one end open, and the box cover 4012 may be a plate-like structure, and the box cover 4012 covers the open side of the box body 4011.
  • 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 multiple battery cells 30 are both connected in series and in parallel.
  • 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 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 multiple battery cells 30.
  • the battery cell 30 may be cylindrical, flat, rectangular, or in other shapes.
  • FIG. 3 is an exploded view of a battery cell 30 in some embodiments of the present application.
  • the battery cell 30 refers to a basic unit for realizing the mutual conversion of chemical energy and electrical energy, and is also the smallest unit of a battery.
  • the battery cell 30 includes a housing 301, an end cap 302, an electrode assembly 20, and other functional components.
  • 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 shape, 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 not limited to copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., which is not limited here.
  • 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.
  • the shape of the end cap 302 can be adapted to the shape of the shell 301 to match the shell 301.
  • the end cap 302 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that 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 the safety performance can also be improved.
  • 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. Certainly.
  • the battery cell 30 further includes functional components such as a negative electrode adapter 303 and a positive electrode adapter 304, wherein 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, so as to output or input the electric energy of the battery cell 30.
  • the negative electrode adapter 303 is made of a conductive material, and the material of the negative electrode adapter 303 can be but 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 not limited to copper, iron, aluminum, etc.
  • the battery cell 30 further includes an insulating member 305, which is located inside the housing 301 to isolate the housing 301 from the electrode assembly 20 and reduce the risk of short circuit.
  • the insulating member 305 may be plastic, rubber, or the like.
  • One or more electrode assemblies 20 may be contained in the housing 301 .
  • FIG. 4 is a schematic diagram of the structure of the electrode assembly 20 in some embodiments of the present application.
  • the electrode assembly 20 is a component in the battery cell 30 where an electrochemical reaction occurs.
  • the electrode assembly 20 is mainly formed by winding or stacking a negative electrode sheet 101 and a positive electrode sheet 102 as an integrated electrode sheet structure, and a separator 203 is usually provided between adjacent negative electrode sheets 101 and positive electrode sheets 102.
  • the negative electrode sheet 101 includes a negative electrode current collector and a negative electrode material layer, and the negative electrode material layer is coated on the surface of the negative electrode current collector.
  • the material of the negative electrode current collector may include copper
  • the negative electrode material layer includes a negative electrode material
  • the negative electrode material may include a silicon-based material.
  • the positive electrode sheet 102 includes a positive current collector and a positive electrode material layer, and the positive electrode material layer is coated on the surface of the positive current collector.
  • the material of the positive current collector may include aluminum
  • the positive electrode material layer includes a positive electrode material
  • the positive electrode material may include lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganese oxide.
  • 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.
  • the negative electrode collector and the positive electrode collector are not coated with the active material layer, and these parts without the active material layer are provided with connecting tabs.
  • the negative electrode collector is connected to the negative electrode tab 201
  • the positive electrode collector is connected to the positive electrode tab 202.
  • the positive electrode material layer and the negative electrode material layer react with the electrolyte
  • the negative electrode tab 201 is connected to the negative electrode adapter 303
  • the positive electrode tab 202 is connected to the positive electrode adapter 304 to form a current loop.
  • the parts of the negative electrode collector and the positive electrode collector that are not coated with the active material layer each constitute a tab.
  • Some embodiments of the present application provide a positive electrode material, a positive electrode active material, and a one-dimensional conductive material and an additive distributed on the surface of the positive electrode active material, at least part of the one-dimensional conductive material is wrapped by the additive, and the additive contains a reducing sulfide element.
  • the positive electrode material includes a positive electrode active material, which refers to a compound with a three-dimensional lithium ion channel. Used on the positive electrode for reversible insertion and removal of lithium ions.
  • the positive electrode active material includes but is not limited to at least one of lithium nickel cobalt oxide, lithium nickel manganese oxide and lithium nickel cobalt manganese oxide.
  • Lithium nickel cobalt oxide (LiNi 1-x Co x O 2 , referred to as NC binary material) is a layered structure with good electrochemical performance and thermal stability.
  • Lithium nickel manganese oxide LiNi x Mn 2-x O 4 , referred to as NM binary material
  • NM binary material is a material with the same spinel structure prepared by improving the original spinel lithium manganese oxide.
  • 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 LiNiO 2 , LiCoO 2 and LiMnO 2 , and in the electrochemical performance and thermal stability tests, these three transition metals can show their own characteristics in this material, and it has a high development potential.
  • the positive electrode active material may be doped and modified.
  • the doping element includes but is 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.
  • One-dimensional conductive materials refer to fibrous or tubular materials in which electrons can move freely in only one non-nanoscale direction.
  • One-dimensional conductive materials include, but are not limited to, metal nanowires and one-dimensional conductive carbon materials.
  • Metal nanowires include, but are not limited to, silver nanowires, copper nanowires, etc.
  • One-dimensional conductive carbon materials can be one-dimensional nanocarbon materials or one-dimensional micron carbon materials.
  • the one-dimensional conductive carbon material includes at least one of carbon fibers, nanocarbon fibers, and carbon nanotubes.
  • the additive includes a chalcogen with reducing properties, where the chalcogen refers to sulfur and elements with similar chemical properties to sulfur.
  • the chalcogen includes elements other than oxygen in the oxygen group.
  • the chalcogen includes at least one of sulfur (S), selenium (Se) and tellurium (Te).
  • the additive includes a chalcogen, where the additive can be a compound, with the chalcogen as one of the constituent elements of the compound, and the additive can also be a single substance, such as a chalcogen itself used as an additive.
  • Chalcogen has reducing properties, that is, the chalcogen can increase the valence state through oxidation-reduction reactions.
  • the valence of the chalcogen is less than or equal to zero, that is, a low-valent chalcogen, and the chalcogen is easily oxidized to a high-valent chalcogen.
  • the chalcogen includes sulfur, the valence of low-valent sulfur is -2 or zero, and the valence of high-valent sulfur is +6 or +4.
  • the one-dimensional conductive material and additives are distributed on the surface of the positive electrode active material.
  • the one-dimensional conductive material and additives may be loosely distributed on the surface of the positive electrode active material, or the one-dimensional conductive material and additives may form a coating layer wrapped around the surface of the positive electrode active material.
  • At least part of the one-dimensional conductive material is wrapped by the additive means that at least part of the surface of the one-dimensional conductive material is covered with the additive.
  • the additive may be attached to the surface of the one-dimensional conductive material in the form of a film layer, so that the additive and the one-dimensional conductive material form a skin-core structure, wherein the one-dimensional conductive material is the core layer and the additive is the skin layer; or the additive may be formed into a substrate layer, and the one-dimensional conductive material is at least partially embedded in the substrate layer to form a conductive network structure.
  • the additive may be melted and then solidified on the surface of the one-dimensional conductive material, thereby achieving the effect of the additive wrapping and covering the surface of the one-dimensional conductive material.
  • the additive may be sublimated into a gaseous state and then solidified on the surface of the one-dimensional conductive material, thereby achieving the effect of the additive wrapping and covering the surface of the one-dimensional conductive material. Wrapped on the surface of a one-dimensional conductive material.
  • the additive is wrapped on the surface of the one-dimensional conductive material.
  • the surface of the one-dimensional conductive material may be completely wrapped by the additive, or part of the surface of the one-dimensional conductive material may be wrapped by the additive.
  • the additive content is low, most of the surface of the one-dimensional conductive material may be wrapped by the additive, and a small part of the surface of the one-dimensional conductive material may be exposed.
  • At least part of the one-dimensional conductive material is wrapped by the additive means that for all the one-dimensional conductive materials, part of the one-dimensional conductive material may be wrapped by the additive, or all of the one-dimensional conductive materials (i.e., each one-dimensional conductive material) may be wrapped by the additive.
  • the positive electrode material provided in the embodiment of the present application includes a positive electrode active substance, a one-dimensional conductive material and an additive, at least a portion of the one-dimensional conductive material is wrapped by the additive, the one-dimensional conductive material and the additive are distributed on the surface of the positive electrode active substance, and the additive contains a reducing sulfide element.
  • An additive is introduced onto the surface of the positive electrode active material, wherein the additive comprises a chalcogen with reducing properties (usually a chalcogen with a low valence).
  • the chalcogen with reducing properties in the additive is easily oxidized and reacts with residual lithium compounds (such as LiOH, Li 2 O, Li 2 CO 3, etc.) on the surface of the positive electrode active material, thereby in situ generating an intermediate product containing a chalcogen with an intermediate valence state (such as Li 2 S 2 O 3 , Li 2 Se 2 O 3 , Li 2 Te 2 O 3 , etc.) on the surface of the positive electrode active material.
  • residual lithium compounds such as LiOH, Li 2 O, Li 2 CO 3, etc.
  • the intermediate product continues to react, and the chalcogen with reducing properties continues to be oxidized and reacts with the residual lithium compounds, and finally generates a final product containing a chalcogen with a high valence state (such as Li 2 SO 3 , Li 2 SO 4 , Li 2 SeO 3 , Li 2 SeO 4 , Li 2 TeO 3 , Li 2 TeO 3 , etc. ). 4 , etc.), and during the formation process, the final product further forms a positive electrode-electrolyte interface (CEI) film on the surface of the positive electrode active material, thereby removing the residual lithium compounds on the surface of the positive electrode active material and improving the conductivity and electrochemical performance of the positive electrode active material.
  • CEI positive electrode-electrolyte interface
  • a one-dimensional conductive material is introduced on the surface of the positive electrode active material. Since the one-dimensional conductive material is located on the surface of the positive electrode active material and can overlap with each other to construct a conductive system, the overall conductivity of the material is improved; at the same time, at least part of the one-dimensional conductive material is wrapped in the additive, which can increase the area of physical bonding between the additive and the one-dimensional conductive material. At the same time, since the one-dimensional conductive material itself has a high specific surface area, the bonding area between the additive and the one-dimensional conductive material is further increased, and the bonding force between the additive and the one-dimensional conductive material is increased, thereby improving the stability of the bonding between the two and achieving the anchoring of the additive.
  • the additive Since the additive is wrapped on the surface of the one-dimensional conductive material, when the one-dimensional conductive material is overlapped together, the additive will also wrap the nodes of the one-dimensional conductive material overlap, so as not to affect the conductive system constructed by the one-dimensional conductive material.
  • the one-dimensional conductive material not only acts as a carrier to anchor the additive, but the one-dimensional conductive material is also distributed on the surface of the positive electrode active material.
  • the conductive network constructed by the one-dimensional conductive material With the help of the conductive network constructed by the one-dimensional conductive material, the overall conductivity of the positive electrode material is better; in addition, the one-dimensional conductive material has a large specific surface area, which not only promotes the anchoring of the additive, but also increases the contact area between the one-dimensional conductive material and the positive electrode active material, thereby accelerating the electron/ion transfer rate on the positive electrode material and the kinetic reaction rate of the sulfide element.
  • the chalcogen element includes at least one of sulfur, selenium, and tellurium.
  • the chalcogen element includes sulfur, that is, the additive includes sulfur with reducing properties.
  • the additive is sulfur element
  • the positive electrode material is obtained by introducing sulfur element S and a one-dimensional conductive material into the surface of a positive electrode active material (e.g., a nickel-rich active material). Part of the sulfur element S in the positive electrode material undergoes an oxidation-reduction reaction with the metal cations in the positive electrode active material, and residual lithium compounds (e.g., LiOH, Li 2 O, Li 2 CO 3 , etc.) on the surface of the positive electrode active material also participate in the reaction. In this process, the sulfur element S is oxidized and combines with the residual lithium compound to form Li 2 S 2 O 3 .
  • the positive electrode material is further prepared into a positive electrode sheet and applied to a battery.
  • Li 2 S 2 O 3 is further oxidized and converted into Li 2 SO 3 and/or Li 2 SO 4 .
  • the sulfur element S in the positive electrode material continues to react with the residual lithium compound to generate Li 2 SO 3 and/or Li 2 SO 4 .
  • the battery is charged and discharged, and a CEI film is formed on the positive electrode of the battery.
  • Li2SO3 and/or Li2SO4 can participate in the growth of the CEI film, thereby converting residual lithium compounds that have a negative impact on battery performance into a CEI film, thereby improving the electrochemical performance of the battery.
  • lithium ions can be used to compensate for the lithium ion loss caused by the formation of the SEI film, thereby ensuring the capacity of the battery.
  • the chalcogen element includes tellurium, that is, the additive contains tellurium with reducing properties.
  • the additive is tellurium element
  • the positive electrode material is obtained by introducing tellurium element Te and a one-dimensional conductive material onto the surface of a positive electrode active material (e.g., a nickel-rich active material).
  • part of tellurium element Te in the positive electrode material first combines with residual lithium compounds to form Li 2 Te 2 O 3 , and in the subsequent battery formation process, Li 2 Te 2 O 3 and tellurium element Te are further converted into Li 2 TeO 3 and/or Li 2 TeO 4 and participate in the growth of CEI film, thereby improving the electrochemical performance of the battery; in this process, additional lithium ions are simultaneously released to compensate for the lithium ion loss caused by the formation of SEI film, thereby ensuring the capacity of the battery.
  • the chalcogen element includes selenium, that is, the additive includes selenium with reducing properties.
  • the additive is selenium element
  • the positive electrode material is obtained by introducing selenium element Se and a one-dimensional conductive material into the surface of the positive electrode active material (e.g., nickel-rich active material).
  • part of the selenium element Se in the positive electrode material first combines with the residual lithium compound to form Li 2 Se 2 O 3 , and in the subsequent battery formation process, Li 2 Se 2 O 3 and selenium element Se are further converted into Li 2 SeO 3 and/or Li 2 SeO 4 and participate in the growth of CEI film, thereby improving the electrochemical performance of the battery; in this process, additional lithium ions are simultaneously released to compensate for the lithium ion loss caused by the formation of SEI film, thereby ensuring the capacity of the battery.
  • the chalcogen element includes selenium and sulfur.
  • the chalcogen element includes sulfur and tellurium.
  • the chalcogen element includes selenium and tellurium.
  • the chalcogen element includes sulfur, selenium and tellurium.
  • the additive is set to contain a reducing sulfide element, the sulfide element includes at least one of sulfur, selenium and tellurium, and the above sulfide element can react with the residual lithium compound, consume the residual lithium compound and promote the growth of the CEI film on the positive electrode, thereby improving the electrochemical performance of the battery; in this process, additional lithium ions are simultaneously released to compensate for the lithium ion loss caused by the formation of the SEI film in the battery, thereby ensuring the capacity of the battery.
  • the chalcogen element includes sulfur
  • the additive includes sulfur, metal sulfide, polysulfide, At least one of a sulfur-containing organic polymer or copolymer and polymerized sulfur.
  • Chalcogens include sulfur, that is, the additive contains sulfur, and the additive can be a sulfur element or a sulfur-containing compound.
  • the sulfur-containing compound includes a metal sulfide.
  • the metal sulfide includes a transition metal sulfide, and the basic chemical formula of the transition metal sulfide (TMDs) is MS 2 , where M represents a transition metal element, including Ti, V, Ta, Mo, W, Re, etc.
  • TMDs transition metal sulfide
  • the sulfur-containing compound includes a polysulfide, and the polysulfide is a compound containing polysulfide ions.
  • the polysulfide is a polysulfide of an alkali metal or an alkaline earth metal.
  • the sulfur-containing compound includes a sulfur-containing organic polymer or copolymer.
  • the sulfur-containing compound includes polysulfur, and polysulfur is a product obtained by a polymerization reaction of a sulfur element and an organic matter at a high temperature.
  • the above-mentioned additives all contain sulfur element, and the sulfur element has a low valence.
  • the sulfur element has reducing properties, which is beneficial to eliminate residual lithium compounds on the surface of the positive electrode active material.
  • the additive includes a chalcogen.
  • the additive includes a chalcogen element, and optionally, the chalcogen element includes at least one of sulfur, selenium and tellurium. Then the additive includes at least one of sulfur, selenium and tellurium.
  • sulfide elements The valence of sulfide elements is zero, and sulfide elements themselves have strong reducing properties, which makes it easy for sulfide elements to eliminate residual lithium compounds.
  • the composition of sulfide elements is single. Introducing sulfide elements into the surface of the positive electrode active material can reduce the introduction of other elements, thereby reducing the risk of side reactions.
  • the one-dimensional conductive material includes a one-dimensional conductive carbon material.
  • One-dimensional conductive carbon materials refer to fibrous or tubular carbon materials in which electrons can move freely in only one non-nanoscale direction.
  • the one-dimensional conductive carbon material also has a strong adsorption capacity, which enables the one-dimensional conductive carbon material to effectively adsorb additives attached to the surface of the one-dimensional conductive carbon material, enhance the binding ability between the one-dimensional conductive carbon material and the additive, and enhance the anchoring effect of the one-dimensional conductive carbon material on the additive.
  • the one-dimensional conductive carbon material includes at least one of short carbon fiber filaments, nanocarbon fibers, and carbon nanotubes.
  • Nanocarbon fiber is also called carbon nanofiber (CNF). Its diameter is generally between 50nm and 500nm, and its length is between 50 ⁇ m and 100 ⁇ m. It is a one-dimensional conductive carbon material between carbon nanotubes and ordinary carbon fibers.
  • the one-dimensional conductive carbon material has good conductivity, which is conducive to building a more developed conductive network. It also has a large specific surface area, which is conducive to increasing the contact area between the one-dimensional conductive carbon material and the additive and enhancing the anchoring effect on the additive.
  • the short carbon fiber filaments include at least one of PAN-based carbon fiber, phenolic-based carbon fiber, viscose-based carbon fiber, pitch-based carbon fiber, biomass-based carbon fiber, and activated carbon fiber.
  • PAN-based carbon fiber is made of polyurethane (PA) and nylon (N) through high-temperature thermosolid-liquid phase polymerization.
  • Viscose-based carbon fiber refers to carbon fiber prepared by pre-oxidation and carbonization of viscose fiber.
  • Pitch-based carbon fiber refers to a type of carbon fiber that is made from materials rich in polycyclic aromatic hydrocarbons such as asphalt through polymerization, spinning, infusibility, and carbonization.
  • Bio-based carbon fibers are made from cellulose and lignin, which come from trees.
  • Activated carbon fiber is an activated carbon fiber.
  • a certain carbon fiber such as phenolic-based fiber, PAN-based fiber, viscose-based fiber, asphalt-based fiber, etc.
  • high temperature different activation methods have different activation temperatures
  • the above-mentioned short carbon fiber filaments not only have good conductivity and large specific surface area, but also the raw materials are easily available and have high cost performance.
  • the diameter of the short carbon fiber filaments is 100 nm to 500 nm.
  • the diameter of short carbon fiber filaments will affect the specific surface area of the short carbon fiber filaments.
  • the diameter of the short carbon fiber filaments is too small, it will cause the short carbon fiber filaments to aggregate, which is not conducive to the dispersion of the short carbon fiber filaments. Instead, it will affect the construction of the conductive system, and thus affect the conductivity of the positive electrode material.
  • the diameter of the short carbon fiber filaments is any value among 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm and 500 nm, or a range value between any two values.
  • the diameter of the short carbon fiber filaments By setting the diameter of the short carbon fiber filaments to 100nm-500nm, it is beneficial to ensure that the short carbon fiber filaments have a larger specific surface area, thereby improving the anchoring effect on additives. At the same time, the short carbon fiber filaments have good dispersibility, which is beneficial to improving the conductivity of the positive electrode material.
  • the short carbon fiber filaments have a length of 1 ⁇ m to 5 ⁇ m.
  • the positive electrode active material is usually granular, and the short carbon fiber filaments are distributed on the surface of the positive electrode active material. If the short carbon fiber filaments are too long, it will be unfavorable for the short carbon fiber filaments to contact with the positive electrode active material, affecting the transmission of current between different materials; if the short carbon fiber filaments are too short, it will affect the overlapping effect between the short carbon fiber filaments, especially after the short carbon fiber filaments are wrapped with additives, the short carbon fiber filaments are easily completely wrapped by the additives to produce conductive dead corners, thereby reducing the conductive effect of the positive electrode material.
  • the length of the short carbon fiber filaments is 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 2.5 ⁇ m, 3 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, 4.5 ⁇ m. Any point value between 5 ⁇ m and 10 ⁇ m, or the range value between any two points.
  • the short carbon fiber filaments By setting the length of the short carbon fiber filaments to 1 ⁇ m-5 ⁇ m, it is beneficial to ensure the contact effect between the short carbon fiber filaments and the surface of the positive electrode active material. At the same time, the short carbon fiber filaments can be well overlapped together to build a conductive network, thereby improving the conductivity of the positive electrode material.
  • the mass percentage of the chalcogen element is 0.02 wt % to 5 wt %.
  • the content of sulfide in the positive electrode material will affect the removal effect of residual lithium compounds.
  • the content of sulfide in the positive electrode material is too low, especially when the mass percentage of sulfide in the positive electrode material is less than 0.02wt%, the residual lithium compounds on the surface of the positive electrode active material are difficult to be eliminated, and the presence of residual lithium compounds will affect the conductivity of the positive electrode material, and will also cause side reactions, thereby causing the battery's cycle stability to deteriorate.
  • the greater the amount of sulfide loaded in the positive electrode material the more conducive it is for the sulfide to be dispersed on the surface of the positive electrode active material and to react with the residual lithium compounds to eliminate the residual lithium compounds.
  • the mass percentage of sulfide in the positive electrode material is greater than 5wt%, it is easy to cause additive residues, reduce the conductivity of the positive electrode material, increase battery polarization, increase the battery internal resistance (DRC), and continue to consume the active lithium inside the battery during battery storage, and the battery performance will deteriorate.
  • the mass percentage of the sulfide element is any point value among 0.02wt%, 0.05wt%, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% and 5wt%, or a range value between any two points.
  • the mass percentage of the chalcogen element in the positive electrode material is 0.02wt% to 5wt%, the residual lithium compounds on the surface of the positive electrode active material can be effectively removed, while preventing the excessive chalcogen element from causing an increase in battery polarization.
  • the mass percentage of the one-dimensional conductive material is greater than 0 and less than or equal to 1 wt %.
  • One-dimensional conductive materials are mainly used to improve the conductivity of positive electrode materials.
  • the one-dimensional conductive material itself is easy to agglomerate. If the content of one-dimensional conductive materials in the positive electrode material is too high, especially when the content of one-dimensional conductive materials in the positive electrode material is greater than 1wt%, it will easily lead to an increase in the surface energy of the positive electrode material particles, physical gelation will easily occur, and the processing performance of the positive electrode material will deteriorate.
  • the mass percentage of the one-dimensional conductive material is any point value among 0.001wt%, 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt% and 1wt%, or the range value between any two points.
  • the positive electrode material By setting the mass percentage of the one-dimensional conductive material in the positive electrode material to be greater than 0 and less than or equal to 1wt%, the positive electrode material has both better conductivity and processing performance.
  • the surface of the positive electrode active material is coated with a coating layer.
  • the coating layer includes a first sub-coating layer 71 .
  • the first sub-coating layer 71 includes a one-dimensional conductive material and an additive wrapped on the one-dimensional conductive material.
  • the positive electrode active material includes positive electrode active material particles 6, and the one-dimensional conductive material and the additive are distributed on the surface of the positive electrode active material.
  • the one-dimensional conductive material and the additive are wrapped on the surface of the positive electrode active material particles 6 and form a coating layer.
  • the coating layer including the one-dimensional conductive material and the additive wrapped on the one-dimensional conductive material is defined as the first sub-coating layer 71.
  • the coating layer includes the first sub-coating layer 71.
  • the coating layer may only include the first sub-coating layer 71. In other embodiments, the coating layer may also include other sub-coating layers.
  • the additive is helpful to eliminate the residual lithium compounds on the surface of the positive electrode active material, thereby improving the performance of the positive electrode active material.
  • the coating layer includes at least two sub-coating layers, namely, a first sub-coating layer 71 and a second sub-coating layer 72, wherein the first sub-coating layer 71 is directly coated on the surface of the positive electrode active material particles 6, and the second sub-coating layer 72 is arranged on the outside of the first sub-coating layer 71, that is, the first sub-coating layer 71 is arranged between the positive electrode active material particles 6 and the second sub-coating layer 72.
  • the first sub-coating layer 71 and the second sub-coating layer 72 can be in direct contact or can be arranged at intervals.
  • the second sub-coating layer 72 contains a conductive agent, a binder and an additive.
  • the conductive agent in the second sub-coating layer 72 includes but is not limited to at least one of conductive carbon black, carbon nanotubes, conductive graphite, graphene, acetylene black and nano-carbon fibers. That is to say, the conductive agent in the second sub-coating layer 72 can be selected from the above-mentioned one-dimensional conductive material, or other conductive materials can be used, which increases the material selection range of the second sub-coating layer 72, which is conducive to controlling the cost of the positive electrode material.
  • the binder in the second sub-coating layer 72 is used to bond the conductive agent and the additive together and further bond with the first sub-coating layer 71.
  • the second sub-coating layer 72 may contain additives (i.e., the content of chalcogen is greater than 0) or may not contain additives (i.e., the content of chalcogen is equal to 0).
  • the content of chalcogen in the second sub-coating layer 72 is less than the content of chalcogen in the first sub-coating layer 71.
  • the first sub-coating layer 71 and the second sub-coating layer 72 are sequentially coated on the surface of the positive electrode active material, and the content of the chalcogen in the first sub-coating layer 71 is greater than the content of the chalcogen in the second sub-coating layer 71.
  • the first sub-coating layer 71 is used as an inner layer, and a one-dimensional conductive material with a high specific surface area is used as a conductive material in the first sub-coating layer 71, which is conducive to fixing the additive and inhibiting the chalcogen from diffusing outward.
  • the coating layer also includes a third sub-coating layer 73.
  • the third sub-coating layer 73 is coated on the surface of the second sub-coating layer 72.
  • the third sub-coating layer 73 contains a conductive agent and a binder.
  • the coating layer includes at least three sub-coating layers, namely, a first sub-coating layer 71, a second sub-coating layer and a third sub-coating layer 73, wherein the second sub-coating layer 72 contains additives, while the third sub-coating layer 73 does not contain additives.
  • the third sub-coating layer 73 contains a conductive agent and a binder.
  • the surface of the positive electrode active material is coated with a first sub-coating layer 71, a second sub-coating layer and a third sub-coating layer 73 in sequence, and the content of chalcogen in each sub-coating layer decreases from the inside to the outside.
  • the outermost third sub-coating layer 73 does not contain chalcogen, which can provide a diffusion space for chalcogen, enhance the barrier effect on chalcogen, and confine as much chalcogen as possible inside the positive electrode material.
  • the coating layer has a thickness of 100 nm to 1000 nm.
  • the thickness of the coating layer refers to the total thickness of the coating layer.
  • the thickness of the coating layer is the sum of the thicknesses of the respective coating layers.
  • the thickness of the coating layer is the thickness of the first sub-coating layer 71.
  • the thickness of the coating layer is the sum of the thicknesses of the above three.
  • the coating layer mainly contains conductive materials and additives, which have almost no contribution to the battery capacity. If the thickness of the coating layer is too large, the theoretical specific capacity of the positive electrode material will be reduced. If the thickness of the coating layer is too small, the coating will be uneven, thereby affecting the removal effect of the residual lithium compound.
  • the thickness of the coating layer is 100nm to 1000nm. Specifically, the thickness of the coating layer can be any point value among 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm and 1000nm, or a range value between any two points.
  • the thickness of the coating layer is 100 nm to 1000 nm, the theoretical specific capacity of the positive electrode material can be ensured while the residual lithium compound is effectively removed.
  • the mass percentage of the coating layer is 0.01 wt % to 6 wt %.
  • the coating layer has almost no contribution to the battery capacity. If the mass percentage of the coating layer in the positive electrode material is too large, the theoretical specific capacity of the positive electrode material will be reduced, and if it is too small, the removal effect of residual lithium compounds will be affected.
  • the mass percentage of the coating layer in the positive electrode material is 0.01wt% to 6wt%, specifically, the mass percentage of the coating layer is 0.01wt%, 0.05wt%, Any value among 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt% and 6wt% or the range between any two points.
  • the mass percentage of the coating layer is 0.1 wt % to 1 wt %. Within this range, the removal effect of the residual lithium compound in the positive electrode material and the theoretical specific capacity of the positive electrode material reach an optimal balance.
  • the mass percentage of the coating layer in the positive electrode material By setting the mass percentage of the coating layer in the positive electrode material to 0.01wt% to 6wt%, the theoretical specific capacity of the positive electrode material can be ensured while the residual lithium compound is effectively removed.
  • the positive electrode active material includes a nickel-rich active material with a chemical formula of LiaNimCoNM1 -mnO2 , wherein M includes at least one of Mn and Al , wherein m ⁇ 0.6 , n ⁇ 0.2, and 0.9 ⁇ a ⁇ 1.2.
  • the chemical formula of the nickel-rich active material is Li a Ni m Co n M 1-mn O 2 , wherein M includes at least one of Mn and Al.
  • M includes Mn
  • the chemical formula of the nickel-rich active material is Li a Ni m Co n M 1-mn O 2 .
  • M includes Al
  • the chemical formula of the nickel-rich active material is Li a Ni m Co n Al 1-mn O 2 .
  • 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.
  • m is any one of 0.6, 0.7, 0.8, 0.9, 0.95 and 0.99, or a range value between any two of them.
  • m ⁇ 0.9, and the reversible lithium insertion capacity of the positive electrode material is large within this range.
  • n ⁇ 0.2 the nickel-rich active material is usually a layered structure, 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.
  • n is any one of 0.05, 0.1, 0.15 and 0.2, or a range value between any two of them.
  • the lithium content in the nickel-rich active material can be greater than 1, or equal to 1, or less than 1.
  • the nickel-rich active material is a lithium-rich positive electrode material.
  • the Li content can be greater than 1.
  • a is any one of 0.9, 0.95, 1, 1.05, 1.1, 1.15 and 1.2, or a range value between any two of them.
  • the nickel element in the nickel-rich active material is alkaline. As the nickel content increases, the nickel-rich active material is easily exposed to the air to absorb moisture and carbon dioxide, and residual lithium compounds (RLCs) are generated on its surface, such as lithium hydroxide (LiOH) and lithium carbonate (Li2CO3), which further increase the pH of the nickel-rich active material and seriously affect the electrochemical properties and storage performance of the nickel-rich active material.
  • RLCs lithium hydroxide
  • Li2CO3 lithium carbonate
  • the present application introduces an additive on the surface of a nickel-rich active material, wherein the additive includes a reducing sulfide element.
  • Ni, Co, and Mn in the nickel-rich active material exist in the form of Ni 3+ /Ni 2+ , Co 3+ and Mn 4+ ions.
  • the reducing sulfide element in the additive is easily oxidized by the nickel-rich active material and reacts with the residual lithium compound on the surface of the nickel-rich active material to generate an intermediate product containing an intermediate-valent sulfide element in situ on the surface of the nickel-rich active material.
  • the intermediate product continues to react, and the reducing sulfide element will continue to be oxidized and react with the residual lithium compound, and finally generate a final product containing a high-valent sulfide element (for example, Li 2 SO 3 , Li 2 SO 4, Li 2 SeO 3 , Li 2 SeO 4 , Li 2 TeO 3 , Li 2 TeO 4 , etc. ).
  • a high-valent sulfide element for example, Li 2 SO 3 , Li 2 SO 4, Li 2 SeO 3 , Li 2 SeO 4 , Li 2 TeO 3 , Li 2 TeO 4 , etc.
  • the positive electrode-electrolyte interface (CEI) film is formed, thereby removing the residual lithium compounds on the surface of the nickel-rich active material and improving the conductivity and electrochemical properties of the nickel-rich active material; in this process, additional lithium ions are released synchronously to compensate for the lithium ion loss caused by the formation of the SEI film, thereby ensuring the capacity of the battery.
  • CEI positive electrode-electrolyte interface
  • the DV50 particle size of the positive electrode active material is 5 ⁇ m to 15 ⁇ m.
  • the average particle size is generally expressed as DV50, which means that the powder particles larger and smaller than this particle size each account for 50%.
  • the positive electrode active material is granular, and the particle size of the positive electrode active material will affect the processing performance and electrochemical performance of the positive electrode material.
  • the larger the particle size of the positive electrode active material the longer the migration path of lithium ions in the positive electrode active material, which affects the rate performance of the battery.
  • the smaller the particle size of the positive electrode active material the more unstable the viscosity of the slurry will be during the slurrying process of the positive electrode material, which will affect the subsequent slurry coating effect.
  • the DV50 particle size of the positive electrode active material is any one of 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m and 15 ⁇ m, or a range value between any two of them.
  • the DV50 particle size of the positive electrode active material By setting the DV50 particle size of the positive electrode active material to 5 ⁇ m to 15 ⁇ m, it can be ensured that the positive electrode material has better processing performance and electrochemical performance.
  • Some embodiments of the present application also provide a method for preparing a positive electrode material, comprising:
  • the one-dimensional conductive material and an additive are mixed to obtain a mixture, wherein the additive comprises a reducing chalcogen element;
  • the sintered material is stirred with the positive electrode active material to obtain the positive electrode material.
  • one-dimensional conductive materials refer to fibrous or tubular materials in which electrons can move freely in only one non-nanoscale direction.
  • One-dimensional conductive materials include, but are not limited to, metal nanowires and one-dimensional conductive carbon materials.
  • Metal nanowires include, but are not limited to, silver nanowires, copper nanowires, etc.
  • One-dimensional conductive carbon materials can be one-dimensional nanocarbon materials or one-dimensional micron carbon materials.
  • the one-dimensional conductive carbon material includes at least one of carbon fibers, nanocarbon fibers, and carbon nanotubes.
  • the additive includes a chalcogen with reducing properties, where the chalcogen refers to sulfur and elements with similar chemical properties to sulfur.
  • the chalcogen includes elements other than oxygen in the oxygen group.
  • the chalcogen includes at least one of sulfur (S), selenium (Se) and tellurium (Te).
  • the additive includes a chalcogen, where the additive can be a compound, with the chalcogen as one of the constituent elements of the compound, and the additive can also be a single substance, such as a chalcogen itself used as an additive.
  • Chalcogen has reducing properties, that is, the chalcogen can increase the valence state through oxidation-reduction reactions.
  • the valence of the chalcogen is less than or equal to zero, that is, a low-valent chalcogen, and the chalcogen is easily oxidized to a high-valent chalcogen.
  • the chalcogen includes sulfur, the valence of low-valent sulfur is -2 or zero, and the valence of high-valent sulfur is +6 or +4.
  • the mixing process of the one-dimensional conductive material and the additive refers to mixing the additive and the one-dimensional conductive material together so that the additive is pre-attached to the one-dimensional conductive material.
  • Sintering treatment refers to heat treating the mixture at a suitable temperature so that the additive melts, but the additive only changes in physical form without chemical reaction.
  • the additive melts into a more fluid liquid during the sintering process.
  • the liquid additive spreads and disperses on the surface of the one-dimensional conductive material.
  • the liquid additive solidifies into a solid additive and maintains a spread state, and the additive wraps the one-dimensional conductive material in the form of a film and/or a block.
  • the one-dimensional conductive material and the additive are physically combined, but because the contact area is relatively large, the bonding stability of the additive is enhanced.
  • the mixture is sintered under a protective atmosphere, and the protective atmosphere is used to isolate oxygen to prevent the mixture from high-temperature oxidation.
  • the protective atmosphere here can be an inert gas or nitrogen. It can be understood that there are many types of chalcogens, so there will be more types of additives, and different additives have different melting temperatures, so the temperature of the sintering treatment will also be different, as long as the sintering temperature is controlled to melt the additive.
  • the preparation method of the positive electrode material provided in the embodiment of the present application is to mix the one-dimensional conductive material and the additive and then sinter the mixture so that the additive is melted, and at least part of the one-dimensional conductive material is wrapped by the additive, thereby increasing the physical contact area between the additive and the one-dimensional conductive material, and combining the large specific surface area of the one-dimensional conductive material itself, so that the binding ability of the additive and the one-dimensional conductive material is enhanced, and the additive containing the sulfide element is effectively fixed.
  • the sintered material obtained after the sintering treatment is further stirred and mixed with the positive electrode active material, so that the one-dimensional conductive material with the additive wrapped on the surface is distributed on the surface of the positive electrode active material, thereby forming a positive electrode material. Since the one-dimensional conductive material itself has good conductivity, a conductive network is overlapped by the one-dimensional conductive material. Even after the additive is wrapped, the conductive network can be well connected, thereby ensuring the overall conductive effect of the positive electrode material. In addition, the additive wrapped on the surface of the one-dimensional conductive material will contact the positive electrode active material.
  • the reducing chalcogen in the additive will undergo redox reaction with the metal cations in the positive electrode active material and consume the residual lithium compound on the surface of the positive electrode active material to generate in situ on the surface of the positive electrode active material an intermediate product containing chalcogen with intermediate valence (such as Li 2 S 2 O 3 , Li 2 Se 2 O 3 , Li 2 Te 2 O 3 , etc.).
  • intermediate valence such as Li 2 S 2 O 3 , Li 2 Se 2 O 3 , Li 2 Te 2 O 3 , etc.
  • the intermediate product continues to react, and the reducing chalcogen will continue to be oxidized and react with the residual lithium compound, and finally generate a final product containing chalcogen with high valence (such as Li 2 SO 3 , Li 2 SO 4 , Li 2 SeO 3 , Li 2 SeO 4 , Li 2 TeO 3 , Li 2 TeO 3 , etc. ). 4 , etc.), and at the same time, during the formation process, the final product further forms a positive electrode-electrolyte interface (CEI) film on the surface of the positive electrode active material, thereby removing the residual lithium compounds on the surface of the positive electrode active material and improving the conductivity and electrochemical properties of the positive electrode active material.
  • CEI positive electrode-electrolyte interface
  • the preparation method of the positive electrode material provided in the embodiment of the present application is simple, easy to operate, and conducive to industrialization.
  • the chalcogen element includes at least one of sulfur, selenium, and tellurium.
  • the additive by setting the additive to contain a chalcogen element having reducing properties, the chalcogen element includes sulfur, At least one of selenium and tellurium, the above-mentioned sulfide elements can react with residual lithium compounds, consume the residual lithium compounds and promote the growth of CEI film on the positive electrode, thereby improving the electrochemical performance of the battery; in this process, additional lithium ions are simultaneously released to compensate for the lithium ion loss caused by the formation of SEI film in the battery, thereby ensuring the capacity of the battery.
  • the additive includes a chalcogen.
  • the additive includes a chalcogen element, and optionally, the chalcogen element includes at least one of sulfur, selenium and tellurium. Then the additive includes at least one of sulfur, selenium and tellurium.
  • sulfide elements The valence of sulfide elements is zero, and sulfide elements themselves have strong reducing properties, which makes it easy for sulfide elements to eliminate residual lithium compounds.
  • the composition of sulfide elements is single. Introducing sulfide elements into the surface of the positive electrode active material can reduce the introduction of other elements, thereby reducing the risk of side reactions.
  • the one-dimensional conductive material includes a one-dimensional conductive carbon material.
  • One-dimensional conductive carbon materials refer to fibrous or tubular carbon materials in which electrons can move freely in only one non-nanoscale direction.
  • the one-dimensional conductive carbon material also has a strong adsorption capacity, which enables the one-dimensional conductive carbon material to effectively adsorb additives attached to the surface of the one-dimensional conductive carbon material, enhance the binding ability between the one-dimensional conductive carbon material and the additive, and enhance the anchoring effect of the one-dimensional conductive carbon material on the additive.
  • the additive includes elemental sulfur, the sintering temperature is 180° C. to 220° C., and/or the sintering time is 5 h to 7 h.
  • the temperature of sintering treatment will affect the melting effect of sulfur. If the temperature is too low, sulfur cannot melt, and if the temperature is too high, sulfur will undergo a chemical reaction.
  • the temperature of the sintering process is any one of 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C and 220°C, or a range value between any two of them.
  • the sintering time will affect the amount of sulfur coated on the surface of the one-dimensional conductive material. If the sintering time is too short, the sulfur content in the positive electrode material will be too low, and the effect of removing residual lithium compounds will be poor. If the sintering time is too long, the sulfur content in the positive electrode material will be too high, resulting in sulfur residue, which will eventually affect the internal resistance of the battery and increase the battery polarization.
  • the sintering time is any one of 5 h, 5.5 h, 6 h, 6.5 h and 7 h, or a range value between any two of them.
  • sulfur As an additive, compared with other additives, the chemical properties of sulfur are more active, and the effect of removing residual lithium compounds is better. In addition, the raw materials of sulfur are easy to obtain and the cost is low. Using sulfur as an additive is cost-effective. Furthermore, by setting the sintering temperature to 180°C to 220°C, sulfur can exist stably in the form of molten liquid within this temperature range, and then be coated on the surface of the one-dimensional conductive material. In addition, by setting the sintering time to The time is 5h to 7h, which can effectively control the content of sulfur in the positive electrode material, so that the sulfur will not increase the polarization of the battery while effectively removing the residual lithium compounds.
  • the additive has a DV50 particle size greater than 0 and less than or equal to 1 ⁇ m.
  • the additive is pre-loaded on the one-dimensional conductive material.
  • the binding force between the additive and the one-dimensional conductive material is very weak. If the particle size of the additive is too large, it is not conducive to the pre-loading of the additive. However, if the particle size of the additive is too small, the additive may agglomerate and cannot be well dispersed on the one-dimensional conductive material, which will also affect the pre-loading effect.
  • the DV50 particle size of the additive is any one of 10 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm and 1 ⁇ m, or a range value between any two of them.
  • the DV50 particle size of the additive is 100 nm to 500 nm. Within this particle size range, the dispersibility of the additive and its bonding with the one-dimensional conductive material achieve an optimal balance.
  • the DV50 particle size of the additive By setting the DV50 particle size of the additive to be greater than 0 and less than or equal to 1 ⁇ m, within this range, the dispersion effect of the additive is good, and the combination of the additive and the one-dimensional conductive material is good when the additive is pre-loaded.
  • the mixing process includes a ball milling process.
  • the additives In order to prevent the additives from agglomerating, the additives usually have a larger particle size. However, the larger particle size of the additives will make the binding between the additives and the one-dimensional conductive material during pre-loading poor. Based on this, ball milling is designed in the mixing process to make the additive particles larger and better dispersed during the initial mixing of the additives and the one-dimensional conductive material. Then, the particle size of the additive is reduced through ball milling to improve the binding stability between the additives and the one-dimensional conductive material.
  • the restriction on the particle size of the additive before the mixing process can be reduced, and on the other hand, the particle size of the additive can be reduced through the ball milling process, thereby improving the bonding stability between the additive and the one-dimensional conductive material.
  • the stirring process has a rotation speed of 400 r/s to 1000 r/s.
  • the rotation speed of the stirring process is any one of 400 r/s, 500 r/s, 600 r/s, 700 r/s, 800 r/s, 900 r/s and 1000 r/s, or a range value between any two of them.
  • the sintering material and the positive electrode active material can be effectively mixed together.
  • the positive electrode active material includes a nickel-rich active material with a chemical formula of LiaNimCoNM1 -mnO2 , wherein M includes at least one of Mn and Al , wherein m ⁇ 0.6 , n ⁇ 0.2, and 0.9 ⁇ a ⁇ 1.2.
  • the chemical formula of the nickel-rich active material is Li a Ni m Co n M 1-mn O 2 , wherein M includes at least one of Mn and Al.
  • M includes Mn
  • the chemical formula of the nickel-rich active material is Li a Ni m Co n Mn 1-mn O 2 .
  • M includes Al
  • the chemical formula of the nickel-rich active material is Li a Ni m Co n Al 1-mn O 2 .
  • m ⁇ 0.6 and the nickel-rich active material is increased by increasing the value of m. Increase the content of nickel in the nickel-rich active material, thereby increasing the reversible lithium insertion capacity of the positive electrode material.
  • m is any one of 0.6, 0.7, 0.8, 0.9, 0.95 and 0.99 or a range value between any two of them.
  • m is any one of 0.6, 0.7, 0.8, 0.9, 0.95 and 0.99 or a range value between any two of them.
  • m is any one of 0.6, 0.7, 0.8, 0.9, 0.95 and 0.99 or a range value between any two of them.
  • m is any one of 0.6, 0.7, 0.8, 0.9, 0.95 and 0.99 or a range value between any two of them.
  • m is any one of 0.6, 0.7, 0.8, 0.9, 0.95 and 0.99 or a range value between any two of them.
  • m is any one of 0.6, 0.7, 0.8, 0.9, 0.95 and 0.99 or a range value between any two of them.
  • m is any one of 0.6, 0.7, 0.8, 0.9, 0.95 and 0.99 or a range value between any two of them.
  • m
  • the lithium content in the nickel-rich active material can be greater than 1, equal to 1, or less than 1.
  • the nickel-rich active material is a lithium-rich positive electrode material.
  • the Li content can be greater than 1.
  • a is any one of 0.9, 0.95, 1, 1.05, 1.1, 1.15 and 1.2, or a range between any two of them.
  • the nickel element in the nickel-rich active material is alkaline. As the nickel content increases, the nickel-rich active material is easily exposed to the air and absorbs moisture and carbon dioxide, and generates residual lithium compounds (RLCs) on its surface, such as lithium hydroxide (LiOH) and lithium carbonate (Li 2 CO 3 ), which further increase the pH of the nickel-rich active material and seriously affect the electrochemical properties and storage performance of the nickel-rich active material.
  • RLCs lithium compounds
  • the present application introduces an additive on the surface of a nickel-rich active material, wherein the additive includes a chalcogen with reducing properties, and the Ni, Co, and Mn in the nickel-rich active material exist in the form of Ni 3+ /Ni 2+ , Co 3+ and Mn 4+ ions.
  • the chalcogen with reducing properties in the additive is easily oxidized by the nickel-rich active material and reacts with the residual lithium compound on the surface of the nickel-rich active material, thereby in situ generating an intermediate product containing a chalcogen with an intermediate valence state on the surface of the nickel-rich active material, and in the subsequent formation process, the intermediate product continues to react, and the chalcogen with reducing properties will also continue to be oxidized and react with the residual lithium compound, and finally generate a final product containing a chalcogen with a high valence state (for example, Li 2 SO 3 , Li 2 SO 4 , Li 2 SeO 3 , Li 2 SeO 4 , Li 2 TeO 3 , Li 2 TeO 4 ).
  • the final product further forms a positive electrode-electrolyte interface (CEI) film on the surface of the nickel-rich active material, thereby removing the residual lithium compounds on the surface of the nickel-rich active material and improving the conductivity and electrochemical properties of the nickel-rich active material; in this process, additional lithium ions will be released synchronously to compensate for the lithium ion loss caused by the formation of the SEI film, thereby ensuring the capacity of the battery.
  • CEI positive electrode-electrolyte interface
  • the current collector is a structure or part used to collect current in a battery.
  • the current collector is usually a metal foil.
  • the positive electrode current collector refers to the structure or part used to collect current in the positive electrode of a battery.
  • the positive electrode current collector includes but is not limited to aluminum foil.
  • the positive electrode material layer refers to a film layer disposed on the positive electrode current collector and containing positive electrode active materials.
  • the positive electrode material layer may be disposed on one side of the positive electrode current collector, or may be disposed on both sides of the positive electrode current collector.
  • the positive electrode material layer includes a conductive agent and a binder.
  • some embodiments of the present application further provide a battery 40 , and the battery 40 includes the above-mentioned positive electrode plate 102 .
  • the battery 40 is a secondary battery, which has many different forms, including but not limited to battery cells, battery modules, and battery packs.
  • the battery 40 provided in the embodiment of the present application includes the above-mentioned positive electrode plate 102, and the battery 40 has stable cycle performance and good rate performance.
  • some embodiments of the present application further provide an electrical device 50 , which includes the battery 40 described above.
  • the electric device 50 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, and the like.
  • Preparation of positive electrode materials sulfur element and polypropylene-based carbon fiber are ball-milled and mixed evenly, and then sintered in an inert atmosphere, wherein the sintering temperature is 200°C and the sintering time is 6 hours. Finally, the sintered material is mixed with positive electrode active material NCM (LiNi 0.9 Co 0.05 Mn 0.05 ), and stirred and mixed at a rotation speed of 600 r/s to obtain a modified positive electrode material.
  • sulfur element polypropylene-based carbon fiber: positive electrode active material NCM in the positive electrode material is 0.02:0.5:99.48.
  • negative electrode sheets The negative electrode active material graphite, silicon, conductive agent acetylene black, styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are dissolved in deionized water as a solvent in a weight ratio of 90:5:2:2:1, and mixed evenly to prepare negative electrode slurry. The slurry is coated on copper foil, dried, and then cold-pressed and cut to obtain negative electrode sheets.
  • deionized water as a solvent
  • CMC thickener sodium carboxymethyl cellulose
  • Preparation of secondary battery stack the positive electrode sheet, separator, and negative electrode sheet in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to isolate them, then wind them to obtain a bare cell, weld the tabs to the bare cell, and put the bare cell into an aluminum shell, bake it at 80°C to remove water, then inject electrolyte and seal it to obtain an uncharged battery.
  • the uncharged battery then goes through the processes of static, hot and cold pressing, formation, shaping, capacity testing, etc. to obtain a secondary battery product.
  • the above-mentioned isolation membrane is a PE membrane, and its surface is coated with PVDF and alumina coating to improve adhesion and heat resistance.
  • the preparation process of the above-mentioned electrolyte is to mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1, and then evenly dissolve LiPF 6 :LiFSI (2:8) in the above solution to obtain an electrolyte, in which the concentration of lithium salt is 1 mol/L.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • Example 2 The same as Example 1, except that S1: the sulfur element and polypropylene-based carbon fiber are ball-milled and mixed evenly, and then sintered in an inert atmosphere, wherein the sintering temperature is 200°C and the sintering time is 6 hours. Finally, the sintered material is mixed with the positive electrode active material NCM, and stirred and mixed at a rotation speed of 600 r/s to obtain a modified positive electrode material.
  • the sulfur element: polypropylene-based carbon fiber: positive electrode active material NCM in the positive electrode material is 1:0.5:98.5.
  • Example 2 The same as Example 1, except that S1: the sulfur element and polypropylene-based carbon fiber are ball-milled and mixed evenly, and then sintered in an inert atmosphere, wherein the sintering temperature is 200°C and the sintering time is 6 hours. Finally, the sintered material is mixed with the positive electrode active material NCM, and stirred and mixed at a rotation speed of 600 r/s to obtain a modified positive electrode material.
  • the sulfur element: polypropylene-based carbon fiber: positive electrode active material NCM in the positive electrode material is 3:0.5:96.5.
  • Example 2 The same as Example 1, except that S1: the sulfur element and polypropylene-based carbon fiber are ball-milled and mixed evenly, and then sintered in an inert atmosphere, wherein the sintering temperature is 200°C and the sintering time is 6 hours. Finally, the sintered material is mixed with the positive electrode active material NCM, and stirred and mixed at a rotation speed of 600 r/s to obtain a modified positive electrode material.
  • the sulfur element: polypropylene-based carbon fiber: positive electrode active material NCM in the positive electrode material is 5:0.5:94.5.
  • Example 2 The same as Example 1, except that S1: the sulfur element and polypropylene-based carbon fiber are ball-milled and mixed evenly, and then sintered in an inert atmosphere, wherein the sintering temperature is 200°C and the sintering time is 6 hours. Finally, the sintered material is mixed with the positive electrode active material NCM, and stirred and mixed at a rotation speed of 600 r/s to obtain a modified positive electrode material.
  • the sulfur element: polypropylene-based carbon fiber: positive electrode active material NCM in the positive electrode material is 6:0.5:93.5.
  • Example 2 The same as Example 1, except that S1: the sulfur element and polypropylene-based carbon fiber are ball-milled and mixed evenly, and then sintered in an inert atmosphere, wherein the sintering temperature is 200°C and the sintering time is 6 hours. Finally, the sintered material is mixed with the positive electrode active material NCM, and stirred and mixed at a rotation speed of 600 r/s to obtain a modified positive electrode material.
  • the sulfur element: polypropylene-based carbon fiber: positive electrode active material NCM in the positive electrode material is 6:1.5:92.5.
  • Example 2 Same as Example 1, except that S1: the sulfur element and the polypropylene-based carbon fiber are ball-milled and mixed uniformly, and then in an inert The material was sintered in a carbon atmosphere, wherein the sintering temperature was 200°C and the sintering time was 6 hours. Finally, the sintered material was mixed with the positive electrode active material NCM, and stirred and mixed at a rotation speed of 600 r/s to obtain a modified positive electrode material. The mass ratio of sulfur element: polypropylene-based carbon fiber: positive electrode active material NCM in the positive electrode material was 3:0.02:96.98.
  • Example 2 The same as Example 1, except that S1: the sulfur element and polypropylene-based carbon fiber are ball-milled and mixed evenly, and then sintered in an inert atmosphere, wherein the sintering temperature is 200°C and the sintering time is 6 hours. Finally, the sintered material is mixed with the positive electrode active material NCM, and stirred and mixed at a rotation speed of 600 r/s to obtain a modified positive electrode material.
  • the sulfur element: polypropylene-based carbon fiber: positive electrode active material NCM in the positive electrode material is 3:1:96.
  • Example 2 The same as Example 1, except that S1: the sulfur element and polypropylene-based carbon fiber are ball-milled and mixed evenly, and then sintered in an inert atmosphere, wherein the sintering temperature is 200°C and the sintering time is 6 hours. Finally, the sintered material is mixed with the positive electrode active material NCM, and stirred and mixed at a rotation speed of 600 r/s to obtain a modified positive electrode material.
  • the sulfur element: polypropylene-based carbon fiber: positive electrode active material NCM in the positive electrode material is 3:1.5:95.5.
  • Example 3 The same as Example 3, except that S1: the sulfur element and the polypropylene-based carbon fiber are ball-milled and mixed evenly, and then sintered in an inert atmosphere, wherein the sintering temperature is 200°C and the sintering time is 6 hours. Finally, the sintered material is mixed with the positive electrode active material NCM, and stirred and mixed at a rotation speed of 600 r/s to obtain a positive electrode material having a first coating layer on the surface.
  • S1 the sulfur element and the polypropylene-based carbon fiber are ball-milled and mixed evenly, and then sintered in an inert atmosphere, wherein the sintering temperature is 200°C and the sintering time is 6 hours.
  • the sintered material is mixed with the positive electrode active material NCM, and stirred and mixed at a rotation speed of 600 r/s to obtain a positive electrode material having a first coating layer on the surface.
  • the mass ratio of sulfur element: polypropylene-based carbon fiber: positive electrode active material NCM in the positive electrode material is 2.5:0.5:96.5; the obtained positive electrode material is then mixed with sulfur element, conductive carbon black, and PVDF in a mass ratio of 100:2:2:1 to obtain a positive electrode material having a double-layer coating on the surface; and then mixed with conductive carbon black and PVDF in a mass ratio of 95:3:2 to obtain a three-layer coated positive electrode material.
  • Example 1 Same as Example 1, except that S1: no sulfur and polypropylene-based carbon fiber filaments are added.
  • Example 2 The same as Example 1, except that S1: sulfur element and positive electrode active material NCM are mixed, and stirred and mixed at a rotation speed of 600 r/s to obtain a modified positive electrode material, in which the mass ratio of sulfur element in the positive electrode material to positive electrode active material NCM is 0.02:99.98.
  • Example 2 The same as Example 1, except that S1: polypropylene-based carbon fiber filaments are mixed with positive electrode active material NCM, and stirred and mixed at a rotation speed of 600 r/s to obtain a modified positive electrode material, in which the mass ratio of polypropylene-based carbon fiber filaments to positive electrode active material NCM in the positive electrode material is 0.5:99.5.
  • Each secondary battery was placed at 25°C for 30 minutes, charged to 4.25V at a rate of 1/3C, and ended at a constant voltage of 0.05C. After being placed at rest for 10 minutes, the battery was discharged at a rate of 1/3C until the battery cell's capacity was 50% of the full charge, which was called 50% SOC; after being placed at rest for 60 minutes, the battery was discharged at a rate of 4C for 10 seconds, and the DCR value of the battery cell was recorded.
  • Example 1 and Comparative Example 1 in Table 1 From the comparison of Example 1 and Comparative Example 1 in Table 1, it can be seen that compared with not adding sulfur and carbon fiber, sulfur and carbon fiber are added simultaneously to the positive electrode active material NCM, and the capacity retention rate of the battery after storage and the capacity retention rate after cycling are improved. This is because sulfur and carbon fiber filaments are introduced simultaneously on the surface of the positive electrode active material NCM.
  • the carbon fiber filaments can construct a conductive network on the surface of the positive electrode active material NCM to improve the conductivity of the positive electrode material and reduce the polarization loss of the battery.
  • the carbon fiber filaments anchor the sulfur element, thereby introducing sulfur element on the surface of the positive electrode active material NCM, promoting the sulfur element to fully react with the residual lithium compound on the surface of the positive electrode active material NCM and generating an artificial CEI film on the surface of the positive electrode active material NCM, effectively reducing the amount of residual lithium compounds, thereby reducing the occurrence of side reactions in the battery, improving the stability of the positive electrode material structure and the interface stability on the positive electrode, and maintaining the capacity of the battery.
  • additional lithium ions will be released synchronously to compensate for the lithium ion loss caused by the formation of SEI film in the battery, thereby ensuring the stock of active lithium and further ensuring the capacity of the battery.
  • Example 1 and Comparative Example 2 in Table 1 From the comparison of Example 1 and Comparative Example 2 in Table 1, it can be seen that compared with adding only sulfur, adding sulfur and carbon fiber simultaneously to the positive electrode active material NCM, the capacity retention rate of the battery after storage and the capacity retention rate after cycling are improved. This is because the conductivity of sulfur itself is poor. Adding only sulfur will make the conductivity of the positive electrode material poor, increase the polarization of the battery, and at the same time, the sulfur is not sufficiently anchored in the positive electrode active material NCM, and it is easy to detach from the positive electrode active material NCM, so that the sulfur reacts insufficiently with the residual lithium compound, and the capacity of the battery cannot be effectively maintained.
  • Example 1 From the comparison between Example 1 and Comparative Example 3 in Table 1, it can be seen that, compared with adding only carbon fiber, adding sulfur and carbon fiber simultaneously to the positive electrode active material NCM, the capacity retention rate of the battery after storage and the capacity retention rate after cycling are improved. This is because the conductivity of the positive electrode material is improved by adding only carbon fiber, but the residual lithium compounds on the surface of the positive electrode active material NCM cannot be eliminated. The presence of residual lithium compounds will affect the conductivity of the positive electrode active material NCM on the one hand, and will also promote the occurrence of side reactions, thereby affecting the capacity of the battery.
  • Example 7 Example 3, Example 8 and Example 9 in Table 1 that when the sulfur content is fixed and the carbon fiber content is increased, the battery DCR decreases, and the battery capacity retention rate after storage and the capacity retention rate after cycle are relatively high.
  • Example 6 and Example 9 in Table 1 that although increasing the content of carbon fiber can reduce the battery DCR, when the content of carbon fiber is greater than 1wt%, for example 1.4wt% or 1.5wt%, physical gelation of the positive electrode material is prone to occur during slurrying, and the processing performance of the positive electrode material deteriorates.
  • Example 3 In addition, from the comparison of Example 3 and Example 10 in Table 1, it can be seen that a plurality of coating layers are arranged on the surface of the positive electrode active material NCM, and from the inside to the outside, the content of elemental sulfur in each coating layer decreases successively, and the capacity retention rate of the battery after storage is significantly improved.
  • the outer coating layer with a low content of elemental sulfur can block the inner coating layer with a high content of elemental sulfur, and limit the elemental sulfur as much as possible inside the positive electrode material, inhibiting the flow of elemental sulfur to the negative electrode to react with the active lithium and cause lithium consumption, thereby improving the battery capacity retention rate.

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Abstract

一种正极材料及其制备方法、正极极片、电池及用电装置，正极材料包括正极活性物质及分布在正极活性物质的表面的一维导电材料和添加剂，至少部分一维导电材料被添加剂包裹，添加剂包含具有还原性的硫属元素。通过在正极活性物质表面引入包含具有还原性的硫属元素的添加剂，利用添加剂可以有效去除正极活性物质表面的残留锂化合物，同时在正极活性物质表面还引入一维导电材料，至少部分一维导电材料被该添加剂包裹，利用一维导电材料作为载体来锚定添加剂，同时一维导电材料还可以构筑三维导电体系从而提升正极材料的导电性。

Description

正极材料及其制备方法、正极极片、电池及用电装置
本申请要求于2023年05月15日在中国专利局提交的、申请号为2023105432655、发明名称为“正极材料及其制备方法、正极极片、电池及用电装置”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及电池技术领域，具体涉及一种正极材料及其制备方法，一种正极极片、电池及用电装置。
背景技术
锂离子电池作为二次电池能将化学能和电能可逆地转化，是人类利用和储存能源的理想载体。自锂离子电池问世以来，由于其具有长寿命、高能量密度和低维护成本等优势而被广泛的应用。目前锂离子电池已经用于便携式电子设备、新能源汽车、储能系统等多种领域。
正极活性物质作为影响锂离子电池性能的关键因素，往往决定了锂离子电池的循环寿命、能量密度和功率密度等。受正极活性物质制备工艺或正极活性物质自身特性的影响，正极活性物质表面容易形成残留锂化合物(RLCs)，例如氢氧化锂、碳酸锂、氧化锂等。通常残留锂化合物导电性较差，会增加正极/电解质界面阻抗，加剧电池极化，恶化放电容量和循环稳定性能，对电池性能造成负面影响。
申请内容
本申请实施例的目的在于：提供一种正极材料及其制备方法、正极极片、电池及用电装置，旨在缓解正极活性物质中残留锂化合物对电池性能的负面影响。
本申请实施例采用的技术方案是：
第一方面，提供了一种正极材料，包括：正极活性物质及分布在所述正极活性物质的表面的一维导电材料和添加剂，至少部分所述一维导电材料被所述添加剂包裹，所述添加剂包含具有还原性的硫属元素。
第二方面，提供了一种正极材料的制备方法，包括：
将一维导电材料和添加剂进行混合处理得到混合料，所述添加剂包含具有还原性的硫属元素；
将所述混合料进行烧结处理以使得所述添加剂融化，至少部分所述一维导电材料被所述添加剂包裹，从而得到烧结料；
将所述烧结料与正极活性物质搅拌处理，得到正极材料。
第三方面，提供了一种正极极片，包括正极集流体和结合在所述正极集流体上的正极材料层，所述正极材料层包括本申请实施例第一方面提供的正极材料或本申请实施例第二方面提供的正极材料的制备方法制备得到的正极材料。
第四方面，提供了一种电池，包括本申请实施例第三方面提供的正极极片。
第五方面，提供了一种用电装置，包括本申请实施例第四方面提供的电池。
本申请实施例提供的正极材料的有益效果在于：通过在正极活性物质表面引入添加剂，添加剂包含具有还原性的硫属元素(通常为低价态的硫属元素)，添加剂中具有还原性的硫属元素容易被氧化并与正极活性物质表面的残留锂化合物(例如LiOH、Li2O、Li2CO3等)作用进而在正极活性物质表面原位生成含中间价态的硫属元素的中间产物(例如Li2S2O3、Li2Se2O3、Li2Te2O3等)，并且在后续的化成过程中，中间产物继续反应，且具有还原性的硫属元素也会继续被氧化并与残留锂化合物作用，并且最终都生成含高价态的硫属元素的终产物(例如Li2SO3、Li2SO4、Li2SeO3、Li2SeO4、Li2TeO3、Li2TeO4等)，同时在化成过程中终产物进一步在正极活性物质表面形成正极-电解质界面(CEI)膜，从而实现除去正极活性物质表面的残留锂化合物，并改善正极活性物质的导电性及电化学性能。进一步，在正极活性物质表面引入一维导电材料，由于一维导电材料位于正极活性物质表面并可以相互搭接在一起从而构筑导电体系，提升材料整体的导电性；同时，至少部分一维导电材料被添加剂包裹，可以增大添加剂与一维导电材料之间物理结合的面积，又由于一维导电材料本身具备较高的比表面，进一步使得添加剂与一维碳材料之间结合面积增大，添加剂与一维导电材料之间的结合力增加，从而提升二者结合的稳定性，实现对添加剂的锚定。由于添加剂是包裹在一维导电材料的表面，在一维导电材料搭接在一起时，添加剂也会将一维导电材料搭接的结点包裹在内，从而不会影响一维导电材料构筑的导电体系。
附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例或示范性技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其它的附图。
图1为本申请一些实施例的车辆的结构示意图；
图2为本申请一些实施例的电池的爆炸结构示意图；
图3为本申请一些实施例的电池单体的爆炸结构示意图；
图4为本申请一些实施例的电极组件的结构示意图；
图5为本申请一些实施例提供的正极材料的结构示意图。
具体实施方式中的附图标号如下：
10、极片；
20、电极组件；101、负极极片；102、正极极片；201、负极极耳；202、正极极耳；203、隔离膜；
30、电池单体；301、壳体；302、端盖；303、负极转接片；304、正极转接片；305、绝缘件；
40、电池；401、箱体；4011、箱本体；4012、箱盖体；
50、用电装置；501、控制器；502、马达；
6、正极活性物质颗粒；
71、第一子包覆层；72、第二子包覆层；73、第三子包覆层。
具体实施方式
为了使本申请的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本申请进行进一步详细说明。应当理解，此处所描述的具体实施例仅用以解释本发明，并不用于限定本申请。
需说明的是，“至少一个”是指一个或者多个，“多个”是指两个或两个以上。“以下至少一项(个)”或其类似表达，是指的这些项中的任意组合，包括单项(个)或复数项(个)的任意组合。例如，“a,b,或c中的至少一项(个)”，或，“a,b,和c中的至少一项(个)”，均可以表示：a,b,c,a-b(即a和b),a-c,b-c,或a-b-c，其中a,b,c分别可以是单个，也可以是多个。
应理解，在本申请的各种实施例中，上述各过程的序号的大小并不意味着执行顺序的先后，部分或全部步骤可以并行执行或先后执行，各过程的执行顺序应以其功能和内在逻辑确定，而不应对本申请实施例的实施过程构成任何限定。
本申请实施例说明书中所提到的相关成分的重量不仅仅可以指代各组分的具体含量，也可以表示各组分间重量的比例关系，因此，只要是按照本申请实施例说明书相关组分的含量按比例放大或缩小均在本申请实施例说明书公开的范围之内。具体地，本申请实施例说明书中的质量可以是μg、mg、g、kg等化工领域公知的质量单位。
为了说明本申请所提供的技术方案，以下结合具体附图及实施例进行详细说明。
本申请通过在正极活性物质表面引入添加剂，添加剂包含具有还原性的硫属元素(通常 为低价态的硫属元素)，添加剂中具有还原性的硫属元素容易被氧化并与正极活性物质表面的残留锂化合物(例如LiOH、Li2O、Li2CO3等)作用进而在正极活性物质表面原位生成含中间价态的硫属元素的中间产物(例如Li2S2O3、Li2Se2O3、Li2Te2O3等)，并且在后续的化成过程中，中间产物继续反应，且具有还原性的硫属元素也会继续被氧化并与残留锂化合物作用，并且最终都生成含高价态的硫属元素的终产物(例如Li2SO3、Li2SO4、Li2SeO3、Li2SeO4、Li2TeO3、Li2TeO4等)，同时在化成过程中终产物进一步在正极活性物质表面形成正极-电解质界面(CEI)膜，从而实现除去正极活性物质表面的残留锂化合物，并改善正极活性物质的导电性及电化学性能。进一步，在正极活性物质表面引入一维导电材料，由于一维导电材料位于正极活性物质表面并可以相互搭接在一起从而构筑导电体系，提升材料整体的导电性；同时，至少部分一维导电材料被添加剂包裹，可以增大添加剂与一维导电材料之间物理结合的面积，同时由于一维导电材料本身具备较高的比表面，进一步使得添加剂与一维导电材料之间结合面积增大，添加剂与一维导电材料之间的结合力增加，从而提升二者结合的稳定性，实现对添加剂的锚定。由于添加剂是包裹在一维导电材料的表面，在一维导电材料搭接在一起时，添加剂也会将一维导电材料搭接的结点包裹在内，从而不会影响一维导电材料构筑的导电体系。
本申请的一些实施例公开的电池可以但不限用于车辆、船舶或飞行器等用电装置中。可以使用具备本申请公开的电池等组成该用电装置的电源系统。
本申请的一些实施例提供一种使用电池作为电源的用电装置，用电装置可以是但不限于车辆、手机、便携式设备、笔记本电脑、轮船、航天器、电动玩具和电动工具等等。车辆可以是但不限于燃油汽车、燃气汽车或新能源汽车，新能源汽车可以是但不限于纯电动汽车、混合动力汽车或增程式汽车等；航天器包括飞机、火箭、航天飞机和宇宙飞船等等；电动玩具包括固定式或移动式的电动玩具，例如，游戏机、电动汽车玩具、电动轮船玩具和电动飞机玩具等等；电动工具包括金属切削电动工具、研磨电动工具、装配电动工具和铁道用电动工具，例如，电钻、电动砂轮机、电动扳手、电动螺丝刀、电锤、冲击电钻、混凝土振动器和电刨等等。
以下实施例为了方便说明，以本申请一实施例的一种用电装置为车辆为例进行说明。
请参照图1，图1为本申请一些实施例提供的车辆的结构示意图。车辆的内部设置有电池40，电池40可以设置在车辆的底部或头部或尾部。电池40可以用于车辆的供电，例如，电池40可以作为车辆的操作电源。车辆还可以包括控制器501和马达502，控制器501用来控制电池40为马达502供电，例如，用于车辆的启动、导航和行驶时的工作用电需求。
在本申请一些实施例中，电池40不仅可以作为车辆的操作电源，还可以作为车辆的驱 动电源，代替或部分地代替燃油或天然气为车辆提供驱动动力。
在本申请一些实施例中，电池40为二次电池，二次电池有多种不同形式，包括但不限于电池单体、电池模组和电池包等。这里二次电池指的是在电池放电后可通过充电的方式使活性物质激活而继续使用的电池。
请参照图2，图2为本申请一些实施例提供的电池40的爆炸图。电池40包括箱体401和电池单体30，电池单体30容纳于箱体401内。其中，箱体401用于为电池单体30提供容纳空间的部件，箱体401可以采用多种结构。
在一些实施例中，箱体401可以包括箱本体4011和箱盖体4012，箱本体4011和箱盖体4012相互盖合并共同限定出用于容纳电池单体30的容纳空间。可选地，箱本体4011可以为一端开口的空心结构，箱盖体4012可以为板状结构，箱盖体4012盖合于箱本体4011的开口侧。
在电池40中，电池单体30可以是多个，多个电池单体30之间可串联或并联或混联。混联是指多个电池单体30中既有串联又有并联。多个电池单体30之间可直接串联或并联或混联在一起，再将多个电池单体30构成的整体容纳于箱体401内；当然，电池40也可以是多个电池单体30先串联或并联或混联组成电池模块形式，多个电池模块再串联或并联或混联形成一个整体，并容纳于箱体401内。电池40还可以包括其他结构，例如汇流部件(图未示)，用于实现多个电池单体30之间的电连接。其中，电池单体30可呈圆柱体、扁平体、长方体或其它形状等。
请参照图3，图3为本申请一些实施例中电池单体30的爆炸图。电池单体30是指实现化学能和电能相互转化的基本单元，也是组成电池的最小单元。如图3，电池单体30包括有壳体301、端盖302、电极组件20以及其他的功能性部件。
壳体301是具有一端开口的中空结构，壳体301用于配合端盖302以形成容纳电极组件20、电解液以及其他的功能性部件的内部环境。壳体301可以是多种形状和多种尺寸的，例如长方体形、圆柱体形、六棱柱形等。具体地，壳体301的形状可以根据电极组件20的具体形状和尺寸大小来确定。壳体301的材质可以是但不限于铜、铁、铝、不锈钢、铝合金、塑胶等，在此不作限定。
端盖302是指盖合于壳体301的开口处以将电池单体30的内部环境隔绝于外部环境的部件。可选地，端盖302的形状可以与壳体301的形状相适应以配合壳体301。可选地，端盖302可以由具有一定硬度和强度的材质(如铝合金)制成，这样，端盖302在受挤压碰撞时就不易发生形变，使电池单体30能够具备更高的结构强度，安全性能也可以有所提高。端盖302的材质可以是但不限于铜、铁、铝、不锈钢、铝合金、塑胶等，在此不作限 定。
在一些实施例中，电池单体30还包括负极转接片303和正极转接片304等功能性部件，其中负极转接片303用于与电极组件20上的负极极耳电连接，正极转接片304用于与电极组件20上的正极极耳电连接，以用于输出或输入电池单体30的电能。可以理解地，负极转接片303采用导电材料制成，负极转接片303的材质可以是但不限于铜、铁、铝等。正极转接片304采用导电材料制成，正极转接片304的材质可以是但不限于铜、铁、铝等。
在一些实施例中，电池单体30还包括绝缘件305，绝缘件305位于壳体301的内侧，以用于隔离壳体301与电极组件20，降低短路的风险。示例性的，绝缘件305可以是塑料、橡胶等。
壳体301内可以包含一个或多个电极组件20。
请参照图4，图4为本申请一些实施例中电极组件20的结构示意图。电极组件20是电池单体30中发生电化学反应的部件。电极组件20主要由负极极片101和正极极片102集成为一体的极片结构卷绕或层叠放置形成，并且通常在相邻的负极极片101和正极极片102之间设有隔离膜203。
负极极片101包括负极集流体和负极材料层，负极材料层涂覆于负极集流体的表面。以锂离子电池为例，负极集流体的材料可以包括铜，负极材料层包括负极材料，负极材料可以包括硅基材料等。
正极极片102包括正极集流体和正极材料层，正极材料层涂覆于正极集流体的表面。以锂离子电池为例，正极集流体的材料可以包括铝，正极材料层包括正极材料，正极材料可以包括钴酸锂、磷酸铁锂、三元锂或锰酸锂等。
隔离膜203是一种多孔塑料薄膜，能够让电解液中的锂离子自由通过，但隔离负极极片101和正极极片102，使电池内部的电子不能自由穿过。
负极集流体和正极集流体还存在未涂覆活性材料层的部分，这些不具有活性材料层的部分设有连接极耳。具体地，负极集流体连接有负极极耳201，正极集流体连接有正极极耳202。在电池的充放电过程中，正极材料层和负极材料层与电解液发生反应，负极极耳201连接负极转接片303且正极极耳202连接正极转接片304以形成电流回路。当然，在一些实施例中，负极集流体和正极集流体中未涂覆活性材料层的部分各自构成极耳。
本申请的一些实施例提供一种正极材料，正极活性物质及分布在正极活性物质的表面的一维导电材料和添加剂，至少部分一维导电材料被添加剂包裹，添加剂包含具有还原性的硫属元素。
正极材料包括正极活性物质，正极活性物质指的是具有三维锂离子通道的化合物，其 用于正极上以供锂离子可逆地插入及脱出。可选地，正极活性物质包括但不限于镍钴酸锂、镍锰酸锂和镍钴锰酸锂中的至少一种。镍钴酸锂(LiNi1-xCoxO2，简称NC二元材料)为层状结构，具有较好的电化学性能和热稳定性。镍锰酸锂(LiNixMn2-xO4，简称NM二元材料)是基于对原有尖晶石型锰酸锂进行改进而制备出的同样具备尖晶石型结构的材料，与锰酸锂相比，其具有更高的循环稳定性和电压平台。镍钴锰酸锂(简称NCM三元材料)包含Ni，Co和Mn三种过渡金属元素，它有效的克服了LiNiO2，LiCoO2和LiMnO2这三种材料各自的缺点，并且在电化学性能和热稳定性测试中，这三种过渡金属在这种材料中都能表现出各自特点，具有很高的发展潜力。可选地，还可以对正极活性物质进行掺杂改性。可选地，掺杂元素包括但不限于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、Cl中的至少一种。
一维导电材料指的是电子仅在一个非纳米尺度方向上自由移动的纤维状或管状材料。一维导电材料包括但不限于金属纳米线、一维导电碳材料。金属纳米线包括但不限于银纳米线、铜纳米线等。一维导电碳材料可以为一维纳米碳材料或一维微米碳材料。可选地，一维导电碳材料包括碳纤维、纳米碳纤维和碳纳米管中的至少一种。
添加剂包含具有还原性的硫属元素，这里硫属元素指的是硫元素及具有与硫元素相似化学性质的元素。可选地，硫属元素包括氧族元素中除氧之外的元素。可选地，硫属元素包括硫(S)元素、硒(Se)元素和碲(Te)元素中的至少一种。添加剂包含硫属元素，这里添加剂可以是化合物，硫属元素作为该化合物的组成元素之一，添加剂还可以是单质，例如硫属元素单质本身作为添加剂使用。硫属元素具有还原性，即硫属元素可以通过氧化还原反应提升价态。可选地，硫属元素的化合价小于或者等于零价，也即低价硫属元素，此时硫属元素易于被氧化为高价硫属元素。作为示例，硫属元素包括硫，低价硫的化合价为-2价或者零价，高价硫的化合价为+6价或+4价。
一维导电材料和添加剂分布在正极活性物质的表面，可以是一维导电材料和添加剂松散的分布在正极活性物质的表面，也可以是一维导电材料和添加剂形成包覆层包裹在正极活性物质的表面。
至少部分一维导电材料被添加剂包裹指的是至少部分一维导电材料的表面覆盖有添加剂。可以是添加剂以膜层的形式附着在一维导电材料的表面，使得添加剂与一维导电材料构成皮芯结构，其中一维导电材料为芯层，添加剂为皮层；也可以是添加剂形成为基材层，一维导电材料至少部分嵌入在基材层内部并形成导电网络结构。作为示例，可以是将添加剂熔化后在一维导电材料的表面凝固，从而实现添加剂包裹覆盖在一维导电材料的表面。作为示例，可以是将添加剂升华为气态后在一维导电材料的表面凝固，从而实现添加剂包 裹在一维导电材料的表面。这里添加剂包裹在一维导电材料的表面，针对单根一维导电材料，可以一维导电材料的表面全部被添加剂包裹，也可以是一维导电材料的部分表面被添加剂包裹，例如在添加剂含量较少时可能一维导电材料的大部分表面被添加剂包裹，一维导电材料的小部分表面裸露，或者添加剂含量较高但受工艺的影响，存在一维导电材料的小部分表面没有包裹上添加剂而裸露。至少部分一维导电材料被添加剂包裹指的是针对所有的一维导电材料，可以是其中一部分一维导电材料被添加剂包裹，也可以是所有的一维导电材料(即每一根一维导电材料)都被添加剂包裹。
本申请实施例提供的正极材料包括正极活性物质、一维导电材料和添加剂，至少部分一维导电材料被添加剂包裹，一维导电材料和添加剂分布在正极活性物质的表面，添加剂包含具有还原性的硫属元素。通过在正极活性物质表面引入添加剂，添加剂包含具有还原性的硫属元素(通常为低价态的硫属元素)，添加剂中具有还原性的硫属元素容易被氧化并与正极活性物质表面的残留锂化合物(例如LiOH、Li2O、Li2CO3等)作用进而在正极活性物质表面原位生成含中间价态的硫属元素的中间产物(例如Li2S2O3、Li2Se2O3、Li2Te2O3等)，并且在后续的化成过程中，中间产物继续反应，且具有还原性的硫属元素也会继续被氧化并与残留锂化合物作用，并且最终都生成含高价态的硫属元素的终产物(例如Li2SO3、Li2SO4、Li2SeO3、Li2SeO4、Li2TeO3、Li2TeO4等)，同时在化成过程中终产物进一步在正极活性物质表面形成正极-电解质界面(CEI)膜，从而实现除去正极活性物质表面的残留锂化合物，并改善正极活性物质的导电性及电化学性能。进一步，在正极活性物质表面引入一维导电材料，由于一维导电材料位于正极活性物质表面并可以相互搭接在一起从而构筑导电体系，提升材料整体的导电性；同时，至少部分一维导电材料被添加剂包裹在内，可以增大添加剂与一维导电材料之间物理结合的面积，同时又由于一维导电材料本身具备较高的比表面，进一步使得添加剂与一维导电材料之间结合面积增大，添加剂与一维导电材料之间的结合力增加，从而提升二者结合的稳定性，实现对添加剂的锚定。由于添加剂是包裹在一维导电材料的表面，在一维导电材料搭接在一起时，添加剂也会将一维导电材料搭接的结点包裹在内，从而不会影响一维导电材料构筑的导电体系。
综上所述，在本申请实施例中，一维导电材料不仅作为承载体对添加剂进行锚定，同时一维导电材料分布在正极活性物质的表面，借助一维导电材料构筑的导电网络，使得正极材料整体的导电性较佳；另外，一维导电材料具有较大的比表面，在促进其对添加剂进行锚定的同时也提高了一维导电材料与正极活性物质的接触面积，加快正极材料上电子/离子传输速率和硫属元素的动力学反应速度。
在一些实施例中，硫属元素包括硫元素、硒元素以及碲元素中的至少一种。
可选地，硫属元素包括硫元素，即添加剂包含具有还原性的硫元素。作为示例，添加剂为硫单质，通过将硫单质S和一维导电材料引入正极活性物质(例如富镍活性物质)的表面得到正极材料，正极材料中部分硫单质S会与正极活性物质中的金属阳离子发生氧化还原反应，同时参与反应的还有正极活性物质表面的残留锂化合物(例如LiOH、Li2O、Li2CO3等)，在该过程中硫单质S被氧化并与残留锂化合物结合形成Li2S2O3，进一步将正极材料制备成正极极片并应用在电池上，在电池进行化成的过程中，Li2S2O3会被进一步氧化并转化为Li2SO3和/或Li2SO4，同时，正极材料中的硫单质S还会继续与残留锂化合物发生反应并生成Li2SO3和/或Li2SO4。在化成过程中，电池进行充放电，会在电池的正极上形成CEI膜，而Li2SO3和/或Li2SO4可以参与CEI膜的生长，从而实现将对电池性能造成负面影响的残留锂化合物转化为CEI膜，改善电池的电化学性能；此外，在硫单质S与残留锂化合物反应并生成Li2SO3和/或Li2SO4时通常还会释放额外的锂离子，锂离子可以可用于补偿电池由于形成SEI膜而造成的锂离子损失，从而保证电池的容量。
可选地，硫属元素包括碲元素，即添加剂包含具有还原性的碲元素。作为示例，添加剂为碲单质，通过将碲单质Te和一维导电材料引入正极活性物质(例如富镍活性物质)的表面得到正极材料，与硫单质S类似，正极材料中部分碲单质Te先与残留锂化合物结合形成Li2Te2O3，并在后续电池进行化成的过程中，Li2Te2O3和碲单质Te被进一步转化为Li2TeO3和/或Li2TeO4并参与CEI膜的生长，改善电池的电化学性能；在此过程中同步释放额外的锂离子用于补偿电池由于形成SEI膜而造成的锂离子损失，从而保证电池的容量。
可选地，硫属元素包括硒元素，即添加剂包含具有还原性的硒元素。作为示例，添加剂为硒单质，通过将硒单质Se和一维导电材料引入正极活性物质(例如富镍活性物质)的表面得到正极材料，与硫单质S类似，正极材料中部分硒单质Se先与残留锂化合物结合形成Li2Se2O3，并在后续电池进行化成的过程中，Li2Se2O3和硒单质Se被进一步转化为Li2SeO3和/或Li2SeO4并参与CEI膜的生长，改善电池的电化学性能；在此过程中同步释放额外的锂离子用于补偿电池由于形成SEI膜而造成的锂离子损失，从而保证电池的容量。
可选地，硫属元素包括硒元素和硫元素。可选地，硫属元素包括硫元素和碲元素。可选地，硫属元素包括硒元素和碲元素。可选地，硫属元素包括硫元素、硒元素和碲元素。
通过将添加剂设置为包含具有还原性的硫属元素，硫属元素包括硫元素、硒元素以及碲元素中的至少一种，利用上述硫属元素可以与残留锂化合物发生作用，消耗残留锂化合物的同时促进正极上CEI膜的生长，改善电池的电化学性能；在此过程中同步释放额外的锂离子用于补偿电池由于形成SEI膜而造成的锂离子损失，从而保证电池的容量。
在一些实施例中，硫属元素包括硫元素，添加剂包括硫单质、金属硫化物、多硫化物、 含硫有机聚合物或共聚物和聚合硫中的至少一种。
硫属元素包括硫元素，即添加剂包含硫元素，添加剂可以是硫单质也可以是含硫化合物。可选地，含硫化合物包括金属硫化物。可选地，金属硫化物包括过渡金属硫化物，过渡金属硫化物(Transition Metal Dichalcogenides，TMDs)基本化学式为MS2，其中M代表过渡金属元素，包括Ti、V、Ta、Mo、W、Re等。可选地，含硫化合物包括多硫化物，多硫化物是含多硫离子的化合物。可选地，多硫化物为碱金属或碱土金属的多硫化物。可选地，多硫化物包括多硫化锂(Li2Sn，其中n＝2～8)。可选地，含硫化合物包括含硫有机聚合物或共聚物。可选地，含硫化合物包括聚合硫，聚合硫是硫单质与有机物在高温下发生聚合反应后得到的产物。
上述添加剂中均包含硫元素，且硫元素的化合价较低，硫元素具有还原性，利于消除正极活性物质表面的残留锂化合物。
在一些实施例中，添加剂包括硫属元素单质。
添加剂包括硫属元素单质，可选地，硫属元素包括硫元素、硒元素以及碲元素中的至少一种，则添加剂包括硫单质、硒单质以及碲单质中的至少一种。
硫属元素单质的化合价为零价，硫属元素单质本身具有较强的还原性，这样易于硫属元素单质消除残留锂化合物，同时硫属元素单质的组成单一，将硫属元素单质引入正极活性物质的表面，可以减少其他元素的引入，从而减小副反应发生的风险。
在一些实施例中，一维导电材料包括一维导电碳材料。
一维导电碳材料指的是电子仅在一个非纳米尺度方向上自由移动的纤维状或管状碳材料。
一维导电碳材料除了具有较大的比表面积外还具有较强的吸附能力，使得一维导电碳材料能对附着在一维导电碳材料表面的添加剂进行有效的吸附，增强一维导电碳材料与添加剂之前的结合能力，提升一维导电碳材料对添加剂的锚定作用。
在一些实施例中，一维导电碳材料包括短碳纤维丝、纳米碳纤维和碳纳米管中的至少一种。
短碳纤维丝指的是长度较短、直径较小的碳纤维丝。可选地，地短碳纤维丝的长度小于10微米。可选地，短碳纤维丝的直径小于1微米。
纳米碳纤维也称碳纳米纤维(Carbon Nanofiber，简称CNF)，其直径一般在50nm～500nm，长度分布在50μm～100μm，是介于碳纳米管和普通碳纤维之间的一维导电碳材料。
纳米碳管(carbon nanotubes，简称CNT)为管状的纳米级石墨晶体，是单层或多层石墨片围绕中心轴按一定的螺旋角卷曲而成的无缝纳米级管。纳米炭管直径通常在50nm以下。
上述一维导电碳材料导电性好，利于构筑更发达的导电网络，同时还具有较大的比表面积，利于提高一维导电碳材料与添加剂的接触面积，提升对添加剂的锚定作用。
在一些实施例中，短碳纤维丝包括PAN基碳纤维、酚醛基碳纤维、黏胶基碳纤维、沥青基碳纤维、生物质基碳纤维以及活性碳纤维中的至少一种。
PAN基碳纤维是由氨基甲酸酯(PA)和尼龙(N)经高温热固液相聚合而成。
酚醛基碳纤维是由酚醛原丝制成的非晶质碳纤维。
粘胶基碳纤维是指以粘胶纤维经过预氧化、碳化所制备的碳纤维。
沥青基碳纤维是指以沥青等富含稠环芳烃的物质为原料，通过聚合、纺丝、不熔化、碳化处理制备的一类碳纤维。
生物基碳纤维是以来自树木的纤维素和木质素为原料制成。
活性碳纤维是经过活化的含碳纤维。具体地，将某种含碳纤维(如酚醛基纤维、PAN基纤维、黏胶基纤维、沥青基纤维等)经过高温活化(不同的活化方法活化温度不一样)，使其表面产生纳米级的孔径，增加比表面积。
上述短碳纤维丝不仅导电性好、比表面积大，且原料易得，性价比高。
在一些实施例中，短碳纤维丝的直径为100nm-500nm。
通常短碳纤维丝的直径会影响短碳纤维丝的比表面，短碳纤维丝的直径越小，短碳纤维丝的比表面积越大，然而短碳纤维丝的直径过小会导致短碳纤维丝聚合，不利于短碳纤维丝分散，反而会影响导电体系的搭建，进而影响正极材料的导电性。
可选地，短碳纤维丝的直径为100nm、150nm、200nm、250nm、300nm、350nm、400nm、450nm和500nm中的任一点值或者任意两点值之间的范围值。
通过将短碳纤维丝的直径设置为100nm-500nm，利于保证短碳纤维丝具有较大的比表面积，提升对添加剂的锚定效果，同时短碳纤维丝具有较好的分散性，利于提升正极材料的导电性。
在一些实施例中，短碳纤维丝的长度为1μm-5μm。
短碳纤维丝的长度越长，短碳纤维丝更容易缠绕并搭接在一起，从而构筑起三维导电网络，但是通常正极活性物质为颗粒状，短碳纤维丝分布在正极活性物质的表面，短碳纤维丝的长度过长将不利于短碳纤维丝与正极活性物质接触，影响电流在不同材料之间的传输；短碳纤维丝的长度过短会影响短碳纤维丝之间搭接的效果，尤其是在短碳纤维丝包裹上添加剂后，短碳纤维丝容易被添加剂完全包裹起来而产生导电死角，进而降低正极材料的导电效果。
可选地，短碳纤维丝的长度为1μm、1.5μm、2μm、2.5μm、3μm、3.5μm、4μm、4.5μm 和5μm中的任一点值或者任意两点值之间的范围值。
通过将短碳纤维丝的长度设置为1μm-5μm，利于保证短碳纤维丝与正极活性物质的表面的接触效果，同时短碳纤维丝之间能很好地搭接在一起并构筑出导电网络，提升正极材料的导电性。
在一些实施例中，基于正极材料的总质量，硫属元素的质量百分数为0.02wt％～5wt％。
正极材料中硫属元素的含量会影响残锂化合物的去除效果，正极材料中硫属元素的含量过低，尤其是在正极材料中硫属元素的质量百分数低于0.02wt％时，正极活性物质表面的残锂化合物难以被消除，而残锂化合物的存在会影响正极材料的导电性，同时也会导致副反应的发生，进而导致电池的循环稳定性变差。通常正极材料中负载的硫属元素的量越大，越利于硫属元素分散在正极活性物质表面并与残锂化合物作用以消除残锂化合物，然而，在正极材料中硫属元素的质量百分数大于5wt％时，容易导致添加剂残留，降低正极材料的导电性，增大电池极化，电池内阻(DRC)增加，且在电池存储时会持续消耗电池内部的活性锂，电池性能会发生恶化。
可选地，基于正极材料的总质量，硫属元素的质量百分数为0.02wt％、0.05wt％、0.1wt％、0.5wt％、1wt％、1.5wt％、2wt％、2.5wt％、3wt％、3.5wt％、4wt％、4.5wt％和5wt％中的任一点值或者任意两点值之间的范围值。
通过将正极材料中硫属元素的质量百分数设置为0.02wt％～5wt％，可以有效除去正极活性物质表面的残锂化合物，同时防止硫属元素过量而导致电池极化增大。
在一些实施例中，基于正极材料的总质量，一维导电材料的质量百分数大于0且小于或者等于1wt％。
一维导电材料主要用于提升正极材料的导电性，正极材料中一维导电材料的含量越高，正极材料的导电性越好，然而一维导电材料本身容易团聚，正极材料中一维导电材料的含量过高会，尤其是在正极材料中一维导电材料的含量大于1wt％时容易导致正极材料颗粒表面能增加，容易发生物理凝胶，正极材料的加工性能变差。
可选地，基于正极材料的总质量，一维导电材料的质量百分数为0.001wt％、0.05wt％、0.1wt％、0.2wt％、0.3wt％、0.4wt％、0.5wt％、0.6wt％、0.7wt％、0.8wt％、0.9wt％和1wt％中的任一点值或者任意两点值之间的范围值。
通过将正极材料中一维导电材料的质量百分数设为大于0且小于或者等于1wt％，使得正极材料兼具较佳的导电性及加工性能。
请参见图5，在一些实施例中，正极活性物质的表面包覆有包覆层，包覆层包括第一子包覆层71，第一子包覆层71包含一维导电材料和包裹在一维导电材料上的添加剂。
具体地，正极活性物质包括正极活性物质颗粒6，一维导电材料和添加剂分布在正极活性物质的表面为一维导电材料和添加剂包裹在正极活性物质颗粒6的表面并构成包覆层。为了便于区分，将包含一维导电材料和包裹在一维导电材料上的添加剂的包覆层定义为第一子包覆层71。包覆层包括第一子包覆层71，在一些实施方式中，包覆层可以仅包括第一子包覆层71，在另外一些实施例中，包覆层可能还包括其他子包覆层。
通过将包裹有添加剂的一维导电材料包裹在正极活性物质的表面并形成第一子包覆层71，利于添加剂将正极活性物质表面的残留锂化合物消除，改善正极活性物质的性能。
请参见图5，在一些实施例中，包覆层还包括第二子包覆层72，第二子包覆层72设置在第一子包覆层71远离正极活性物质的一侧，第二子包覆层72包含导电剂、粘结剂和添加剂，第二子包覆层72中硫属元素的含量大于或者等于0且小于第一子包覆层71中硫属元素的含量。
具体地，包覆层包括至少两层子包覆层，分别为第一子包覆层71和第二子包覆层72，其中第一子包覆层71直接包覆在正极活性物质颗粒6的表面，第二子包覆层72设置在第一子包覆层71的外侧，即第一子包覆层71设置在正极活性物质颗粒6与第二子包覆层72之间。这里第一子包覆层71和第二子包覆层72可以是直接接触，也可以是间隔设置。进一步，第二子包覆层72包含导电剂、粘结剂和添加剂。第二子包覆层72中的导电剂包括但不限于导电炭黑、碳纳米管、导电石墨、石墨烯、乙炔黑和纳米碳纤维中的至少一种。也就是说第二子包覆层72中的导电剂可以选用上述的一维导电材料，也可以使用其他导电材料，这样就增大了第二子包覆层72的选材范围，利于控制正极材料的成本。第二子包覆层72中的粘结剂用于将导电剂和添加剂粘接在一起并进一步与第一子包覆层71粘接，该粘结剂包括但不限于聚偏二氟乙烯、偏氟乙烯-氟化烯烃的共聚物、聚乙烯吡咯烷酮、聚丙烯腈、聚丙烯酸甲酯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚胺酯、氟化橡胶和聚乙烯醇中的至少一种。第二子包覆层72中硫属元素的含量大于或者等于0且小于第一子包覆层71中硫属元素的含量，可以理解，第二子包覆层72中可以包含添加剂(即硫属元素的含量大于0)，也可以不包含添加剂(即硫属元素的含量等于0)，在第二子包覆层72中包含添加剂时，第二子包覆层72中硫属元素的含量小于第一子包覆层71中硫属元素的含量。
通过在正极活性物质的表面依次包覆第一子包覆层71和第二子包覆层72，且第一子包覆层71中硫属元素的含量大于第一子包覆层71中硫属元素的含量，第一子包覆层71作为内层，第一子包覆层71中采用高比表面的一维导电材料作为导电物质，利于对添加剂进行固定，抑制硫属元素向外扩散，第二子包覆层72作为外层其可以采用一维导电材料作为导电剂也可以采用其他碳材作为导电剂，从而扩大了选材范围，利于控制成本，且第二子 包覆层72中硫属元素的含量小于第一子包覆层71中硫属元素的含量，一方面第二子包覆层72中硫属元素含量减小，可以减少硫属元素向外扩散，同时外层的第二子包覆层72可以对内层的第一子包覆层71形成阻挡，缓解第一子包覆层71中硫属元素向外扩散，因为硫属元素向外扩散后容易流向负极，在负极硫属元素再与活性锂反应而造成耗锂，降低电池容量。
请参见图5，在一些实施例中，第二子包覆层72中硫属元素的含量大于0，包覆层还包括第三子包覆层73，第三子包覆层73包覆在第二子包覆层72的表面，第三子包覆层73包含导电剂和粘结剂。
具体地，包覆层包括至少三层子包覆层，分别为第一子包覆层71、第二子包覆和第三子包覆层73，其中第二子包覆层72中包含添加剂，而第三子包覆层73中不包含添加剂。第三子包覆层73包含导电剂和粘结剂。
通过在正极活性物质的表面依次包覆第一子包覆层71、第二子包覆和第三子包覆层73，且由内到外，各子包覆层中硫属元素的含量递减，同时作为最外侧的第三子包覆层73中不包含硫属元素，其可以提供硫属元素扩散空间，增强对硫属元素的阻挡作用，尽可能多的将硫属元素限制在正极材料内部。
在一些实施例中，包覆层的厚度为100nm～1000nm。
包覆层的厚度指的是包覆层的总厚度，在包覆层中包括多个子包覆层时，包覆层的厚度是各自包覆层厚度的总和。作为示例，包覆层仅包括第一子包覆层71时，包覆层的厚度就是第一子包覆层71的厚度。作为示例，在包覆层包括第一子包覆层71、第二子包覆和第三子包覆层73时，包覆层的厚度是上述三者厚度的总和。
包覆层中主要包含导电材料和添加剂，其对电池容量几乎没有贡献，包覆层的厚度过大会导致正极材料的理论比容量降低，包覆层的厚度过小会导致包覆不均，从而影响残留锂化合物的去除效果。可选地，包覆层的厚度为100nm～1000nm，具体地，包覆层的厚度可以为100nm、200nm、300nm、400nm、500nm、600nm、700nm、800nm、900nm和1000nm中的任一点值或者任意两点值之间的范围值。
通过将包覆层的厚度设置为100nm～1000nm，在有效去除残留锂化合物的同时保证正极材料的理论比容量。
在一些实施例中，基于正极材料的总质量，包覆层的质量百分数为0.01wt％～6wt％。
如上所述，包覆层对电池容量几乎没有贡献，正极材料中包覆层的质量百分数过大会降低正极材料的理论比容量，过小会影响残留锂化合物的去除效果。可选地，正极材料中包覆层的质量百分数为0.01wt％～6wt％，具体地，包覆层的质量百分数为0.01wt％、0.05wt％、 0.1wt％、0.5wt％、1wt％、1.5wt％、2wt％、2.5wt％、3wt％、3.5wt％、4wt％、4.5wt％、5wt％、5.5wt％和6wt％中的任一点值或者任意两点值之间的范围值。
可选地，包覆层的质量百分数为0.1wt％～1wt％。在该范围内正极材料中残留锂化合物的除去效果和正极材料的理论比容量达到最佳平衡。
通过将正极材料中包覆层的质量百分数设置为0.01wt％～6wt％，在有效去除残留锂化合物的同时保证正极材料的理论比容量。
在一些实施例中，正极活性物质包括化学式为LiaNimConM1-m-nO2的富镍活性物质，其中M包括Mn和Al中的至少一种，其中m≥0.6，n≤0.2，0.9≤a≤1.2。
富镍活性物质的化学式为LiaNimConM1-m-nO2，其中M包括Mn和Al中的至少一种。作为示例，M包括Mn，富镍活性物质的化学式为LiaNimConM1-m-nO2。作为示例，M包括Al，富镍活性物质的化学式为LiaNimConAl1-m-nO2。具体地，m≥0.6，通过增大m的值来提升富镍活性物质中镍元素的含量，进而提高正极材料的可逆嵌锂容量。可选地，m为0.6、0.7、0.8、0.9、0.95和0.99中的任意一者或者任意两者之间的范围值。可选地，m≥0.9，在该范围内正极材料的可逆嵌锂容量较大。具体地，n≤0.2，富镍活性物质通常为层状结构，Co可以稳定层状结构，但由于Co价格昂贵会导致富镍活性物质成本增加，通过控制n≤0.2可以控制富镍活性物质的成本。可选地，n为0.05、0.1、0.15和0.2中的任意一者或者任意两者之间的范围值。0.9≤a≤1.2，即富镍活性物质中锂的含量可以是大于1，也可以是等于1，还可以是小于1。在a大于1时，富镍活性物质为富锂正极材料。作为示例，对富镍活性物质是经过预锂化得到的材料，Li的含量可以实现大于1。可选地，a为0.9、0.95、1、1.05、1.1、1.15和1.2中的任意一者或者任意两者之间的范围值。
然而富镍活性物质中镍元素呈碱性，随着镍元素含量的增大，富镍活性物质暴露在空气中容易吸收水分和二氧化碳，并在其表面生成残留锂化合物(RLCs)，例如氢氧化锂(LiOH)、碳酸锂(Li2CO3)等，进一步增加富镍活性物质的PH，严重影响富镍活性物质的电化学性能和存储性能。
基于此，本申请通过在富镍活性物质表面引入添加剂，添加剂包含具有还原性的硫属元素，富镍活性物质中的Ni、Co、Mn以Ni3+/Ni2+、Co3+和Mn4+离子的形式存在，添加剂中具有还原性的硫属元素容易被富镍活性物质氧化并与富镍活性物质表面的残留锂化合物作用进而在富镍活性物质表面原位生成含中间价态的硫属元素的中间产物，并且在后续的化成过程中，中间产物继续反应，且具有还原性的硫属元素也会继续被氧化并与残留锂化合物作用，并且最终都生成含高价态的硫属元素的终产物(例如Li2SO3、Li2SO4、Li2SeO3、Li2SeO4、Li2TeO3、Li2TeO4等)，同时在化成过程中终产物进一步在富镍活性物质表面形成 正极-电解质界面(CEI)膜，从而实现除去富镍活性物质表面的残留锂化合物，并改善富镍活性物质的导电性及电化学性能；在此过程中还会同步释放额外的锂离子用于补偿电池由于形成SEI膜而造成的锂离子损失，从而保证电池的容量。
在一些实施例中，正极活性物质的DV50粒径为5μm～15μm。
平均粒径一般以DV50表示，是指大于和小于该粒径的粉末粒子各占50％。通常正极活性物质为颗粒状，正极活性物质的粒径大小会影响正极材料的加工性能和电化学性能产生影响。通常，正极活性物质的粒径越大，那么锂离子在正极活性物质中的迁移路径越长，影响电池的倍率性能，然而正极活性物质的粒径越小，会使得正极材料在制浆过程中浆料的粘度不稳定，影响后续的浆料涂覆效果。
可选地，正极活性物质的DV50粒径为5μm、6μm、7μm、8μm、9μm、10μm、11μm、12μm、13μm、14μm和15μm中的任意一者或者任意两者之间的范围值。
通过将正极活性物质的DV50粒径设置为5μm～15μm，可以保证正极材料具有较佳的加工性能和电化学性能。
本申请的一些实施例还提供一种正极材料的制备方法，包括：
将一维导电材料和添加剂进行混合处理得到混合料，添加剂包含具有还原性的硫属元素；
将混合料进行烧结处理以使得添加剂融化，至少部分一维导电材料被添加剂包裹，从而得到烧结料；
将烧结料与正极活性物质搅拌处理，得到正极材料。
如上所述，一维导电材料指的是电子仅在一个非纳米尺度方向上自由移动的纤维状或管状材料。一维导电材料包括但不限于金属纳米线、一维导电碳材料。金属纳米线包括但不限于银纳米线、铜纳米线等。一维导电碳材料可以为一维纳米碳材料或一维微米碳材料。可选地，一维导电碳材料包括碳纤维、纳米碳纤维和碳纳米管中的至少一种。
添加剂包含具有还原性的硫属元素，这里硫属元素指的是硫元素及具有与硫元素相似化学性质的元素。可选地，硫属元素包括氧族元素中除氧之外的元素。可选地，硫属元素包括硫(S)元素、硒(Se)元素和碲(Te)元素中的至少一种。添加剂包含硫属元素，这里添加剂可以是化合物，硫属元素作为该化合物的组成元素之一，添加剂还可以是单质，例如硫属元素单质本身作为添加剂使用。硫属元素具有还原性，即硫属元素可以通过氧化还原反应提升价态。可选地，硫属元素的化合价小于或者等于零价，也即低价硫属元素，此时硫属元素易于被氧化为高价硫属元素。作为示例，硫属元素包括硫，低价硫的化合价为-2价或者零价，高价硫的化合价为+6价或+4价。
将一维导电材料和添加剂进行混合处理指的是将添加剂和一维导电材料混合在一起，使得添加剂预先附着在一维导电材料上。
烧结处理指的是将混合料在适宜温度下进行热处理，以使得添加剂融化成，但是添加剂仅仅是物理形态发生变化，而不会发生化学反应。添加剂在烧结处理过程中融化成流动性更强的液态，液态的添加剂会铺展分散在一维导电材料表面，在温度降低后，液态的添加剂凝固为固态的添加剂，并保持铺展的状态，及添加剂以薄膜和/或块体的形式包裹住一维导电材料。这时候，一维导电材料与添加剂之间是物理结合，但是由于接触的面积比较大，从而使得添加剂的结合稳定性增强。可选地，在保护气氛下对混合料进行烧结处理，利用保护气氛隔绝氧气，防止混合料高温氧化。这里保护气氛可以是惰性气体，也可以是氮气。可以理解地，硫属元素有多种，那么添加剂会有更多种，不同的添加剂融化温度不同，那么烧结处理的温度也会不同，只要烧结的温度控制为使得添加剂融化即可。
本申请实施例提供的正极材料的制备方法通过将一维导电材料和添加剂混合后烧结处理以使得添加剂融化，且至少部分一维导电材料被添加剂包裹，增大添加剂与一维导电材料的物理接触面积，结合一维导电材料自身较大的比表面积，使得添加剂与一维导电材料的结合能力增强，实现对含硫属元素的添加剂进行有效固定。进一步将烧结处理后得到的烧结料与正极活性物质进行搅拌混合，使得表面包裹有添加剂的一维导电材料分布在正极活性物质表面，从而形成正极材料，由于一维导电材料本身具有较佳的导电性，利用一维导电材料搭接出导电网络，即使在包裹上添加剂后，导电网络也能较好地连通，从而保证正极材料整体的导电效果。另外，包裹在一维导电材料表面的添加剂会与正极活性物质接触，在这过程中添加剂中具有还原性的硫属元素会与正极活性物质中的金属阳离子发生氧化还原反应并消耗正极活性物质表面的残留锂化合物以在正极活性物质表面原位生成含中间价态的硫属元素的中间产物(例如Li2S2O3、Li2Se2O3、Li2Te2O3等)，并且在后续的化成过程中，中间产物继续反应，且具有还原性的硫属元素也会继续被氧化并与残留锂化合物作用，并且最终都生成含高价态的硫属元素的终产物(例如Li2SO3、Li2SO4、Li2SeO3、Li2SeO4、Li2TeO3、Li2TeO4等)，同时在化成过程中终产物进一步在正极活性物质表面形成正极-电解质界面(CEI)膜，从而实现除去正极活性物质表面的残留锂化合物，并改善正极活性物质的导电性及电化学性能。在具有还原性的硫属元素转化为CEI膜的过程中，还会同步释放额外的锂离子用于补偿电池由于形成SEI膜而造成的锂离子损失，从而保证电池的容量。另外，本申请实施例提供的正极材料的制备方法简单，易于操作，利于实现工业化。
在一些实施例中，硫属元素包括硫元素、硒元素以及碲元素中的至少一种。
如前所述，通过将添加剂设置为包含具有还原性的硫属元素，硫属元素包括硫元素、 硒元素以及碲元素中的至少一种，利用上述硫属元素可以与残留锂化合物发生作用，消耗残留锂化合物的同时促进正极上CEI膜的生长，改善电池的电化学性能；在此过程中同步释放额外的锂离子用于补偿电池由于形成SEI膜而造成的锂离子损失，从而保证电池的容量。
在一些实施例中，添加剂包括硫属元素单质。
添加剂包括硫属元素单质，可选地，硫属元素包括硫元素、硒元素以及碲元素中的至少一种，则添加剂包括硫单质、硒单质以及碲单质中的至少一种。
硫属元素单质的化合价为零价，硫属元素单质本身具有较强的还原性，这样易于硫属元素单质消除残留锂化合物，同时硫属元素单质的组成单一，将硫属元素单质引入正极活性物质的表面，可以减少其他元素的引入，从而减小副反应发生的风险。
在一些实施例中，一维导电材料包括一维导电碳材料。
一维导电碳材料指的是电子仅在一个非纳米尺度方向上自由移动的纤维状或管状碳材料。
一维导电碳材料除了具有较大的比表面积外还具有较强的吸附能力，使得一维导电碳材料能对附着在一维导电碳材料表面的添加剂进行有效的吸附，增强一维导电碳材料与添加剂之前的结合能力，提升一维导电碳材料对添加剂的锚定作用。
在一些实施例中，添加剂包括硫单质，烧结处理的温度为180℃～220℃，和/或，烧结时间为5h～7h。
通常烧结处理的温度会影响硫单质的融化效果，温度过低硫单质无法融化，温度过高会使得硫单质发生化学反应。
可选地，烧结处理的温度为180℃、185℃、190℃、195℃、200℃、205℃、210℃、215℃和220℃中的任意一者或者任意两者之间的范围值。
烧结时间会影响一维导电材料表面包覆的硫单质的量，烧结时间过短会使得正极材料中硫单质的含量过低，除残留锂化合物的效果不佳，烧结时间过长会使得正极材料中硫单质的含量过高，会导致硫残留，最终会影响电池的内阻，增大电池极化。
可选地，烧结时间为5h、5.5h、6h、6.5h和7h中的任意一者或者任意两者之间的范围值。
通过以硫单质作为添加剂，相比于其他添加剂，硫单质的化学性质更加活泼，除残留锂化合物的效果更好，且硫单质的原料易得，成本低，将硫单质作为添加剂使用，性价比高。进一步，通过将烧结处理的温度设置为180℃～220℃，在该温度范围内硫单质能够以熔融液态的形式稳定性存在，进而包覆在一维导电材料表面。还有，通过将烧结时间设置 为5h～7h，可以有效控制正极材料中硫单质的含量，使得硫单质在有效除去残留锂化合物的同时不会导致电池极化增大。
在一些实施例中，添加剂的DV50粒径大于0且小于或者等于1μm。
通常在制备正极材料中，需要先将添加剂和一维导电材料混合处理，使得添加剂预负载在一维导电材料上，在这个过程中，添加剂与一维导电材料的结合力很弱，如果添加剂的粒径过大，不利于添加剂预负载，但是如果添加剂的粒径过小，有会导致添加剂发生团聚而不能很好的分散在一维导电材料上，一样会影响预负载效果。
可选地，添加剂的DV50粒径为10nm、100nm、200nm、300nm、400nm、500nm、600nm、700nm、800nm、900nm和1μm中的任意一者或者任意两者之间的范围值。
可选地，添加剂的DV50粒径为100nm～500nm。在该粒径范围内，添加剂的分散性及与一维导电材料的结合性达到最佳平衡。
通过将添加剂的DV50粒径设置为大于0且小于或者等于1μm，在该范围内，添加剂的分散效果好，且添加剂与一维导电材料预负载时二者的结合性较好。
在一些实施例中，混合处理包括球磨处理。
为了防止添加剂发生团聚，通常选用的添加剂的粒径较大，但是添加剂的粒径较大又会使得添加剂与一维导电材料的预负载时的结合性较差，基于此，在混合处理过程中设计球磨处理，使得添加剂与一维导电材料在初始混合的过程中添加剂粒径较大且分散较好，然后通过球磨处理使得添加剂的粒径减小，提升添加剂与一维导电材料的结合稳定性。
通过在混合处理中设计球磨处理，一方面可以降低对混合处理前添加剂的粒径大小的限制，而且通过球磨处理还可以使得添加剂的粒径减小，提升添加剂与一维导电材料的结合稳定性。
在一些实施例中，搅拌处理的转速为400r/s～1000r/s。
可选地，搅拌处理的转速为400r/s、500r/s、600r/s、700r/s、800r/s、900r/s和1000r/s中的任意一者或者任意两者之间的范围值。
通过将搅拌处理的转速设置为400r/s～1000r/s，可以使得烧结料和正极活性物质有效混合在一起。
在一些实施例中，正极活性物质包括化学式为LiaNimConM1-m-nO2的富镍活性物质，其中M包括Mn和Al中的至少一种，其中m≥0.6，n≤0.2，0.9≤a≤1.2。
富镍活性物质的化学式为LiaNimConM1-m-nO2，其中M包括Mn和Al中的至少一种。作为示例，M包括Mn，富镍活性物质的化学式为LiaNimConMn1-m-nO2。作为示例，M包括Al，富镍活性物质的化学式为LiaNimConAl1-m-nO2。具体地，m≥0.6，通过增大m的值来提 升富镍活性物质中镍元素的含量，进而提高正极材料的可逆嵌锂容量。可选地，m为0.6、0.7、0.8、0.9、0.95和0.99中的任意一者或者任意两者之间的范围值。可选地，m≥0.9，在该范围内正极材料的可逆嵌锂容量较大。具体地，n≤0.2，富镍活性物质通常为层状结构，Co可以稳定层状结构，但由于Co价格昂贵会导致富镍活性物质成本增加，通过控制n≤0.2可以控制富镍活性物质的成本。可选地，n为0.05、0.1、0.15和0.2中的任意一者或者任意两者之间的范围值。0.9≤a≤1.2，即富镍活性物质中锂的含量可以是大于1，也可以是等于1，还可以是小于1。在a大于1时，富镍活性物质为富锂正极材料。作为示例，对富镍活性物质是经过预锂化得到的材料，Li的含量可以实现大于1。可选地，a为0.9、0.95、1、1.05、1.1、1.15和1.2中的任意一者或者任意两者之间的范围值。
然而富镍活性物质中镍元素呈碱性，随着镍元素含量的增大，富镍活性物质暴露在空气中容易吸收水分和二氧化碳，并在其表面生成残留锂化合物(RLCs)，例如氢氧化锂(LiOH)、碳酸锂(Li2CO3)等，进一步增加富镍活性物质的PH，严重影响富镍活性物质的电化学性能和存储性能。
基于此，本申请通过在富镍活性物质表面引入添加剂，添加剂包含具有还原性的硫属元素，富镍活性物质中的Ni、Co、Mn以Ni3+/Ni2+、Co3+和Mn4+离子的形式存在，添加剂中具有还原性的硫属元素容易被富镍活性物质氧化并与富镍活性物质表面的残留锂化合物作用进而在富镍活性物质表面原位生成含中间价态的硫属元素的中间产物，并且在后续的化成过程中，中间产物继续反应，且具有还原性的硫属元素也会继续被氧化并与残留锂化合物作用，并且最终都生成含高价态的硫属元素的终产物(例如Li2SO3、Li2SO4、Li2SeO3、Li2SeO4、Li2TeO3、Li2TeO4等)，同时在化成过程中终产物进一步在富镍活性物质表面形成正极-电解质界面(CEI)膜，从而实现除去富镍活性物质表面的残留锂化合物，并改善富镍活性物质的导电性及电化学性能；在此过程中还会同步释放额外的锂离子用于补偿电池由于形成SEI膜而造成的锂离子损失，从而保证电池的容量。
请参见图4，本申请的一些实施例还提供一种正极极片102，包括正极集流体和结合在正极集流体上的正极材料层，正极材料层包括上述正极材料或根据上述正极材料的制备方法制备得到的正极材料。
集流体是电池中用于汇集电流的结构或零件。集流体通常为金属箔。正极集流体指的是电池中正极用于汇集电流的结构或零件。正极集流体包括但不限于铝箔。
正极材料层指的是设置在正极集流体上并包含正极活性物质的膜层。可以是在正极集流体的一侧表面设置正极材料层，也可以是在正极集流体的双侧表面设置正极材料层。可选地，正极材料层中包括导电剂和粘结剂。
本申请实施例提供的正极极片102包括正极集流体和正极材料层，正极材料层中包括上述正极材料，从而该正极极片102中残留锂化合的含量较低，正极极片102整体的导电效果提升，循环性能得到改善。
请参见图2，本申请的一些实施例还提供一种电池40，该电池40包括上述正极极片102。
可选地，电池40为二次电池，二次电池有多种不同形式，包括但不限于电池单体、电池模组和电池包等。
本申请实施例提供的电池40包括上述正极极片102，该电池40的循环性能稳定、倍率性能好。
请参见图1，本申请的一些实施例还提供一种用电装置50，该用电装置50包括上述电池40。
如上所述，用电装置50可以是但不限于车辆、手机、便携式设备、笔记本电脑、轮船、航天器、电动玩具和电动工具等等。
下面结合具体实施例进行说明。
实施例1
S1.正极材料的制备：将硫单质、聚丙烯基碳纤维丝球磨混合均匀，然后在惰性气氛中烧结处理，其中烧结的温度为200℃，烧结的时间为6h，最后将得到的烧结料与正极活性物质NCM(LiNi0.9Co0.05Mn0.05)混合，在转速为600r/s的条件下进行搅拌混合，得到改性的正极材料，按质量比，正极材料中硫单质：聚丙烯基碳纤维丝：正极活性物质NCM为0.02:0.5:99.48。
S2.正极极片的制备：将上述S1制备得到的正极材料、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比为96.5:1.5:2溶于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料；之后将正极浆料均匀涂覆于带有底涂的正极集流体上，之后经过烘干、冷压、分切，得到正极极片。
S3.负极极片的制备：将负极活性物质石墨、硅、导电剂乙炔黑、丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照重量比为90:5:2:2:1溶于溶剂去离子水中均匀混合后制备成负极浆料，将浆料涂布在铜箔上，烘干后经过冷压分切，获得负极极片。
S4.二次电池的制备：将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极极片和负极极片之间以起到隔离的作用，然后卷绕得到裸电芯，给裸电芯焊接极耳，并将裸电芯装入铝壳中，并在80℃下烘烤除水，随即注入电解液并封口，得到不带电的电池。不带电的电池再依次经过静置、热冷压、化成、整形、容量测试等工序，获得二次电池产 品。上述隔离膜为PE隔膜，其表面涂敷PVDF和氧化铝涂层，改善粘接力和耐热性。上述电解液的制备过程为将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按体积比1:1:1混合，然后将LiPF6：LiFSI(2:8)均匀溶解在上述溶液中，得到电解液，该电解液中，锂盐的浓度为1mol/L。
实施例2
同实施例1，区别在于S1：将硫单质、聚丙烯基碳纤维丝球磨混合均匀，然后在惰性气氛中烧结处理，其中烧结的温度为200℃，烧结的时间为6h，最后将得到的烧结料与正极活性物质NCM混合，在转速为600r/s的条件下进行搅拌混合，得到改性的正极材料，按质量比，正极材料中硫单质：聚丙烯基碳纤维丝：正极活性物质NCM为1:0.5:98.5。
实施例3
同实施例1，区别在于S1：将硫单质、聚丙烯基碳纤维丝球磨混合均匀，然后在惰性气氛中烧结处理，其中烧结的温度为200℃，烧结的时间为6h，最后将得到的烧结料与正极活性物质NCM混合，在转速为600r/s的条件下进行搅拌混合，得到改性的正极材料，按质量比，正极材料中硫单质：聚丙烯基碳纤维丝：正极活性物质NCM为3:0.5:96.5。
实施例4
同实施例1，区别在于S1：将硫单质、聚丙烯基碳纤维丝球磨混合均匀，然后在惰性气氛中烧结处理，其中烧结的温度为200℃，烧结的时间为6h，最后将得到的烧结料与正极活性物质NCM混合，在转速为600r/s的条件下进行搅拌混合，得到改性的正极材料，按质量比，正极材料中硫单质：聚丙烯基碳纤维丝：正极活性物质NCM为5:0.5:94.5。
实施例5
同实施例1，区别在于S1：将硫单质、聚丙烯基碳纤维丝球磨混合均匀，然后在惰性气氛中烧结处理，其中烧结的温度为200℃，烧结的时间为6h，最后将得到的烧结料与正极活性物质NCM混合，在转速为600r/s的条件下进行搅拌混合，得到改性的正极材料，按质量比，正极材料中硫单质：聚丙烯基碳纤维丝：正极活性物质NCM为6:0.5:93.5。
实施例6
同实施例1，区别在于S1：将硫单质、聚丙烯基碳纤维丝球磨混合均匀，然后在惰性气氛中烧结处理，其中烧结的温度为200℃，烧结的时间为6h，最后将得到的烧结料与正极活性物质NCM混合，在转速为600r/s的条件下进行搅拌混合，得到改性的正极材料，按质量比，正极材料中硫单质：聚丙烯基碳纤维丝：正极活性物质NCM为6:1.5:92.5。
实施例7
同实施例1，区别在于S1：将硫单质、聚丙烯基碳纤维丝球磨混合均匀，然后在惰性 气氛中烧结处理，其中烧结的温度为200℃，烧结的时间为6h，最后将得到的烧结料与正极活性物质NCM混合，在转速为600r/s的条件下进行搅拌混合，得到改性的正极材料，按质量比，正极材料中硫单质：聚丙烯基碳纤维丝：正极活性物质NCM为3:0.02:96.98。
实施例8
同实施例1，区别在于S1：将硫单质、聚丙烯基碳纤维丝球磨混合均匀，然后在惰性气氛中烧结处理，其中烧结的温度为200℃，烧结的时间为6h，最后将得到的烧结料与正极活性物质NCM混合，在转速为600r/s的条件下进行搅拌混合，得到改性的正极材料，按质量比，正极材料中硫单质：聚丙烯基碳纤维丝：正极活性物质NCM为3:1:96。
实施例9
同实施例1，区别在于S1：将硫单质、聚丙烯基碳纤维丝球磨混合均匀，然后在惰性气氛中烧结处理，其中烧结的温度为200℃，烧结的时间为6h，最后将得到的烧结料与正极活性物质NCM混合，在转速为600r/s的条件下进行搅拌混合，得到改性的正极材料，按质量比，正极材料中硫单质：聚丙烯基碳纤维丝：正极活性物质NCM为3:1.5:95.5。
实施例10
同实施例3，区别在于S1：将硫单质、聚丙烯基碳纤维球磨混合均匀，然后在惰性气氛中烧结处理，其中烧结的温度为200℃，烧结的时间为6h，最后将得到的烧结料与正极活性物质NCM混合，在转速为600r/s的条件下进行搅拌混合，得到表面含有第一包覆层的正极材料，按质量比，正极材料中硫单质：聚丙烯基碳纤维丝：正极活性物质NCM为2.5:0.5:96.5；所得正极材料再与硫单质、导电炭黑、PVDF按质量比为100：2：2：1:混合，得到表面含有双层包覆的正极材料；再与导电炭黑、PVDF按质量比95：3：2混合，得到三层包覆的正极材料。
对比例1
同实施例1，区别在于S1：不添加硫单质和聚丙烯基碳纤维丝。
对比例2
同实施例1，区别在于S1：将硫单质与正极活性物质NCM混合，在转速为600r/s的条件下进行搅拌混合，得到改性的正极材料，按质量比，正极材料中硫单质：正极活性物质NCM为0.02:99.98。
对比例3
同实施例1，区别在于S1：将聚丙烯基碳纤维丝与正极活性物质NCM混合，在转速为600r/s的条件下进行搅拌混合，得到改性的正极材料，按质量比，正极材料中聚丙烯基碳纤维丝：正极活性物质NCM为0.5:99.5。
为了验证本申请实施例的进步性，现对实施例1至10及对比例1至3制备得到的二次电池进行如下测试：
1.二次电池放电DCR测试：
将制作好的各二次电池于25℃静置30min，以1/3C的倍率充电至4.25V，恒压至0.05C结束。静置10min，以1/3C的倍率放电至电芯的电量为满充时的50％，将其称之为50％SOC；静置60min，以4C的倍率放电10s，记录电芯的DCR值。
2.存储测试：
将制作好的各二次电池于60℃、97％SOC下存储，存储前和存储过程中C0和Cn分别取电芯的初始可逆容量和实际可逆容量，间隔15天取出测试一次。测试过程如下：将各二次电池于25℃下静置30min，以1/3C的倍率充电至4.25V，恒压至0.05C结束，静置30min，以1/3C的倍率放电至2.8V，记录初始可逆容量C0。间隔15d测试一次，记录Cn(n＝1、2、3、4、5……)；Cn/C0≤80％时，记录n；EOL存储天数＝15*n。
3.循环测试：
调节温度至45℃，保温2h。静止5min，1/3C充电至4.25V，4.25V恒压充电至0.05C结束。静置5min，0.5C放电至2.8V。静置5min，重复以上流程，直至容量衰减至80％。
测试结果如表1所示。
表1
从表1中实施例1与对比例1的比对可以看出，相比于不添加硫单质和碳纤维，在正极活性物质NCM中同时添加硫单质和碳纤维，电池无论是存储后容量保持率还是循环后容量保持率均得到提升，这是因为正极活性物质NCM表面同时引入硫单质和碳纤维丝，碳纤维丝可以在正极活性物质NCM表面构筑导电网络提升正极材料的导电性，降低电池的极化损失，同时碳纤维丝对硫单质进行锚定，实现在正极活性物质NCM表面引入硫单质，促进硫单质与正极活性物质NCM表面的残留锂化合物充分作用并在正极活性物质NCM表面生成人工CEI膜，有效降低残留锂化合物的量，从而减少电池中副反应的发生，提升正极上正极材料结构的稳定性和界面稳定性，利于保持电池的容量，在硫单质与残留锂化合物作用的过程中还会同步释放额外的锂离子用于补偿电池由于形成SEI膜而造成的锂离子损失，保证活性锂的存量，进一步保证电池的容量。
从表1中实施例1与对比例2的比对可以看出,相比于仅添加硫单质，在正极活性物质NCM中同时添加硫单质和碳纤维，电池无论是存储后容量保持率还是循环后容量保持率均得到提升，这是因为硫单质本身导电性不好，仅添加硫单质会使得正极材料的导电性不佳，电池极化增大，同时硫单质在正极活性物质NCM锚定不足，容易脱离正极活性物质NCM，使得硫单质与残留锂化合物反应不充分，无法有效保持电池的容量。
从表1中实施例1与对比例3的比对可以看出,相比于仅添加碳纤维，在正极活性物质NCM中同时添加硫单质和碳纤维，电池无论是存储后容量保持率还是循环后容量保持率均得到提升，这是因为仅添加碳纤维，正极材料的导电性得到改善，但是正极活性物质NCM表面的残留锂化合物无法消除，残留锂化合物的存在一方面会影响正极活性物质NCM的导电性，同时还会促进副反应的发生，从而影响电池的容量。
从表1中实施例1至实施例5的可以看出，碳纤维含量固定，随着硫单质含量增大，电池的存储后容量保持率和循环后容量保持率均增大，但是在硫单质含量大于5wt％后，存储后容量保持率和循环后容量保持率反而降低，这是因为硫单质含量过大导致硫残留，降低正极材料的导电性，增大电池极化，且在电池存储时会持续消耗电池内部的活性锂，电池性能会发生恶化。
从表1中实施例7、实施例3、实施例8和实施例9的可以看出，硫单质含量固定，增大碳纤维的含量的增大，电池DCR降低，电池的存储后容量保持率和循环后容量保持率均比较高。
从表1中实施例6和实施例9可以看出，虽然增大碳纤维的含量可以降低电池DCR，但是碳纤维的含量大于1wt％时，例如为1.4wt％或1.5wt％，正极材料在制浆时容易发生物理凝胶，正极材料的加工性能变差。
另外，从表1中实施例3和实施例10的比对可以看出，在正极活性物质NCM表面设置多层包覆层，且由里到外，各包覆层中硫单质的含量依次减少，电池的存储后容量保持率得到显著提升，这是因为硫单质含量低的外层包覆层可以对硫单质含量高的内层包覆层进行阻挡作用，尽可能多的将硫单质限制在正极材料内部，抑制硫单质流向负极与活性锂反应而造成耗锂，从而提升电池容量保持率。
以上仅为本申请的可选实施例而已，并不用于限制本申请。对于本领域的技术人员来说，本申请可以有各种更改和变化。凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的权利要求范围之内。

Claims (26)

  1. 一种正极材料，其特征在于，包括：正极活性物质及分布在所述正极活性物质的表面的一维导电材料和添加剂，至少部分所述一维导电材料被所述添加剂包裹，所述添加剂包含具有还原性的硫属元素。
  2. 根据权利要求1所述的正极材料，其特征在于，所述硫属元素包括硫元素、硒元素以及碲元素中的至少一种。
  3. 根据权利要求1或2所述的正极材料，其特征在于，所述硫属元素包括硫元素，所述添加剂包括硫单质、金属硫化物、多硫化物、含硫有机聚合物或共聚物和聚合硫中的至少一种。
  4. 根据权利要求1至3任一项所述的正极材料，其特征在于，所述添加剂包括硫属元素单质。
  5. 根据权利要求1至4任一项所述的正极材料，其特征在于，所述一维导电材料包括一维导电碳材料。
  6. 根据权利要求5所述的正极材料，其特征在于，所述一维导电碳材料包括短碳纤维丝、纳米碳纤维和碳纳米管中的至少一种；可选地，所述短碳纤维丝包括PAN基碳纤维、酚醛基碳纤维、黏胶基碳纤维、沥青基碳纤维、生物质基碳纤维以及活性碳纤维中的至少一种。
  7. 根据权利要求6所述的正极材料，其特征在于，所述短碳纤维丝的直径为100nm-500nm；和/或，所述短碳纤维丝的长度为1μm-5μm。
  8. 根据权利要求1至7任一项所述的正极材料，其特征在于，基于所述正极材料的总质量，所述硫属元素的质量百分数为0.02wt％～5wt％。
  9. 根据权利要求1至8任一项所述的正极材料，其特征在于，基于所述正极材料的总质量，所述一维导电材料的质量百分数大于0且小于或者等于1wt％。
  10. 根据权利要求1至9任一项所述的正极材料，其特征在于，所述正极活性物质的表面包覆有包覆层，所述包覆层包括第一子包覆层，所述第一子包覆层包含所述一维导电材料和包裹在所述一维导电材料上的所述添加剂。
  11. 根据权利要求10所述的正极材料，其特征在于，所述包覆层还包括第二子包覆层，所述第二子包覆层设置在所述第一子包覆层远离所述正极活性物质的一侧，所述第二子包覆层包含导电剂和粘结剂，所述第二子包覆层中所述硫属元素的含量大于或者等于0且小 于所述第一子包覆层中所述硫属元素的含量。
  12. 根据权利要求11所述的正极材料，其特征在于，所述第二子包覆层中所述硫属元素的含量大于0，所述包覆层还包括第三子包覆层，所述第三子包覆层包覆在所述第二子包覆层的表面，所述第三子包覆层包含所述导电剂和所述粘结剂。
  13. 根据权利要求10至12任一项所述的正极材料，其特征在于，所述包覆层的厚度为100nm～1000nm。
  14. 根据权利要求10至13任一项所述的正极材料，其特征在于，基于所述正极材料的总质量，所述包覆层的质量百分数为0.01wt％～6wt％；可选地，所述包覆层的质量百分数为0.1wt％～1wt％。
  15. 根据权利要求1至14任一项所述的正极材料，其特征在于，所述正极活性物质包括化学式为LiaNimConM1-m-nO2的富镍活性物质，其中M包括Mn和Al中的至少一种，其中m≥0.6，n≤0.2，0.9≤a≤1.2；可选地，所述m≥0.9。
  16. 根据权利要求1至15任一项所述的正极材料，其特征在于，所述正极活性物质的DV50粒径为5μm～15μm。
  17. 一种正极材料的制备方法，其特征在于，包括：
    将一维导电材料和添加剂进行混合处理得到混合料，所述添加剂包含具有还原性的硫属元素；
    将所述混合料进行烧结处理以使得所述添加剂融化，且至少部分所述一维导电材料被所述添加剂包裹，从而得到烧结料；
    将所述烧结料与正极活性物质搅拌处理，得到正极材料。
  18. 根据权利要求17所述的正极材料的制备方法，其特征在于，所述硫属元素包括硫元素、硒元素以及碲元素中的至少一种。
  19. 根据权利要求17或18任一项所述的正极材料的制备方法，其特征在于，所述添加剂包括硫属元素单质；和/或，所述一维导电材料包括一维导电碳材料。
  20. 根据权利要求19所述的正极材料的制备方法，其特征在于，所述添加剂包括硫单质，所述烧结处理的温度为180℃～220℃，和/或，烧结时间为5h～7h。
  21. 根据权利要求17至20任一项所述的正极材料的制备方法，其特征在于，所述添加剂的DV50粒径大于0且小于或者等于1μm；可选地，所述添加剂的DV50粒径为100nm～500nm。
  22. 根据权利要求17至21任一项所述的正极材料的制备方法，其特征在于，所述混合处理包括球磨处理；和/或，所述搅拌处理的转速为400r/s～1000r/s。
  23. 根据权利要求17至22任一项所述的正极材料的制备方法，其特征在于，所述正极活性物质包括化学式为LiaNimConM1-m-nO2的富镍活性物质，其中M包括Mn和Al中的至少一种，其中m≥0.6，n≤0.2，0.9≤a≤1.2；可选地，所述m≥0.9。
  24. 一种正极极片，其特征在于，包括正极集流体和结合在所述正极集流体上的正极材料层，所述正极材料层包括根据权利要求1至16任一项所述的正极材料或根据权利要求17至23任一项所述的正极材料的制备方法制备得到的正极材料。
  25. 一种电池，其特征在于，包括根据权利要求24所述的正极极片。
  26. 一种用电装置，其特征在于，包括根据权利要求25所述的电池。
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