WO2023184871A1 - 复合正极材料及其制备方法和应用 - Google Patents

复合正极材料及其制备方法和应用 Download PDF

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WO2023184871A1
WO2023184871A1 PCT/CN2022/117376 CN2022117376W WO2023184871A1 WO 2023184871 A1 WO2023184871 A1 WO 2023184871A1 CN 2022117376 W CN2022117376 W CN 2022117376W WO 2023184871 A1 WO2023184871 A1 WO 2023184871A1
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conductive
cathode material
coating layer
composite
particles
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PCT/CN2022/117376
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English (en)
French (fr)
Inventor
徐荣益
杨艺
孔令涌
李意能
刘其峰
Original Assignee
深圳市德方纳米科技股份有限公司
佛山市德方纳米科技有限公司
曲靖市德方纳米科技有限公司
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Priority claimed from CN202210314912.0A external-priority patent/CN114899368B/zh
Application filed by 深圳市德方纳米科技股份有限公司, 佛山市德方纳米科技有限公司, 曲靖市德方纳米科技有限公司 filed Critical 深圳市德方纳米科技股份有限公司
Publication of WO2023184871A1 publication Critical patent/WO2023184871A1/zh

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    • 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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of 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
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • This application belongs to the field of secondary batteries, and specifically relates to a composite cathode material and its preparation method and application.
  • Lithium-ion batteries are considered to have the most application prospects due to their high operating voltage and energy density, relatively small self-discharge level, no memory effect, no pollution from heavy metal elements such as lead and cadmium, and ultra-long cycle life. one of the energy sources. Lithium-ion batteries are widely used in electric vehicles, power tools, mobile consumer electronics, and energy storage.
  • cathode materials For lithium-ion batteries, cathode materials, anode materials and electrolytes are key factors that determine their electrochemical performance.
  • the cathode material acts as the lithium source in lithium-ion batteries and is one of the important components of lithium-ion batteries. It is the key factor that restricts the electrochemical performance such as specific energy and specific power of lithium-ion batteries.
  • Currently commonly used cathode materials for lithium-ion batteries mainly include: layered structure cathode materials, including lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ), lithium manganate (LiMnO 2 ), and binary/ternary composite Layered cathode materials ( LiNi _ _ xFe1 -xPO4 ) etc.
  • lithium-ion battery materials have many advantages, they also face many problems that need to be solved during their application, such as poor conductivity of materials, low compaction density, serious capacity attenuation under large currents, and poor rate performance. And other issues. Moreover, its preparation method also has the problem of expensive raw materials and high cost, making it difficult to achieve industrial production.
  • the purpose of this application is to overcome the above-mentioned shortcomings of the prior art and provide a composite cathode material and a preparation method thereof to solve the technical problems of poor conductivity and low compaction density of the existing cathode material.
  • Another object of the present application is to provide a positive electrode sheet and a secondary battery containing the positive electrode sheet to solve the technical problems of severe capacity attenuation and poor rate performance of secondary batteries caused by existing positive electrode materials and unsatisfactory electrochemical performance.
  • the first aspect of this application provides a composite cathode material.
  • the composite cathode material of the present application includes a conductive core and a cathode material coating layer covering the conductive core. It also includes a conductive skeleton, and one end of the conductive skeleton is in contact with the conductive core, and the other end at least extends to the cathode material coating layer. middle.
  • the second aspect of this application provides a method for preparing the composite cathode material of this application.
  • the preparation method of the composite cathode material of the present application includes the following steps:
  • a cathode material coating layer covering the composite particles is formed on the surface of the composite particles, wherein the free extending end of the conductive skeleton extends at least into the cathode material coating layer to form a composite cathode material.
  • a third aspect of this application provides a positive electrode sheet.
  • the positive electrode sheet of the present application includes a current collector and a positive active layer bonded to the surface of the current collector.
  • the positive active layer contains the composite positive electrode material of the present application or the composite positive electrode material prepared by the preparation method of the composite positive electrode material of the present application.
  • a fourth aspect of the present application provides a secondary battery.
  • This application includes a positive electrode sheet and a negative electrode sheet; the positive electrode sheet is the positive electrode sheet of this application.
  • the composite cathode material of the present application adds a conductive skeleton between the conductive core and the cathode material coating layer, and extends the conductive skeleton to the cathode material coating layer.
  • the conductive skeleton enhances the conductive performance of the cathode material coating layer, and its Connected to the conductive core, and together with the conductive core, build a good conductive network structure in the composite cathode material, giving the composite cathode material excellent conductive properties.
  • the conductive skeleton can form a channel for electrolyte penetration, so that the electrolyte can penetrate into the interior of the composite cathode material through the conductive skeleton, effectively shortening the internal conduction distance of the composite cathode material, and significantly improving the compaction density and electrochemical performance of the composite cathode material. This allows the electrical properties of the composite cathode material to be fully utilized.
  • one end of the conductive skeleton is connected to the conductive core body and the other end extends into the cathode material coating layer, which effectively enhances the mechanical strength of the cathode material coating layer covering the conductive core body and enhances the structural stability of the composite cathode material, thus giving The composite cathode material has excellent electrochemical stability.
  • the preparation method of the composite cathode material of the present application can prepare the composite cathode material of the present application with the above core-shell structure, and impart the prepared composite cathode material with excellent conductive properties, electrochemical properties and structural stability as described above.
  • the preparation method of the composite cathode material can ensure that the structure and electrochemical properties of the prepared composite cathode material are stable, high-efficiency, and save production costs.
  • the positive electrode sheet of the present application contains the composite positive electrode material of the present application, the positive electrode sheet of the present application has high capacity and good rate and cycle performance.
  • the secondary battery of the present application contains the positive electrode sheet of the present application
  • the secondary battery of the present application has high capacity, rate performance and cycle performance, long life and stable electrochemical performance.
  • Figure 1 is a schematic structural diagram of a composite cathode material according to an embodiment of the present application.
  • Figure 2 is another structural schematic diagram of the composite cathode material according to the embodiment of the present application.
  • Figure 3 is a schematic flow chart of the preparation method of the composite cathode material according to the embodiment of the present application.
  • embodiments of the present application provide a composite cathode material.
  • the structure of the composite cathode material in the embodiment of the present application is shown in Figure 1, which includes a conductive core 1, a cathode material coating layer 3 covering the conductive core 1, and a conductive skeleton 2.
  • One end of the conductive skeleton 2 is in contact with the conductive core 1 , and the other end at least extends into the cathode material coating layer 3 .
  • the conductive core 1 and the conductive skeleton 2 together constitute the conductive network system of the composite cathode material of the embodiment of the present application, which gives the composite cathode material of the embodiment of the present application excellent conductivity and high rate performance. .
  • the particle size of the conductive core 1 is also one of the factors affecting the particle size of the composite cathode material of the present application. Therefore, in the embodiment of the present application, the particle size of the conductive core 1 can be controlled to 80nm, such as ⁇ 80nm. .
  • the material of the conductive core includes at least one of carbon and cathode material.
  • the carbon may include sintered carbon.
  • the cathode material may be a cathode material that has at least one of low conductivity, high specific surface area, and low compacted density, such as at least one of LFP, lithium manganate, lithium manganese phosphate, etc.
  • the above-mentioned functions of the conductive core 1 can be improved, thereby improving the conductivity, rate performance and capacity of the composite cathode material in the embodiment of the present application.
  • the particle size of the composite cathode material can be controlled and adjusted, such as increasing the particle size of the composite cathode material, thereby improving the performance of the composite cathode material.
  • the compacted density of the composite cathode material in the application example is a compacted density of the composite cathode material in the application example.
  • the conductive skeleton 2 not only forms a conductive network system with the above-mentioned conductive core 1 in the composite cathode material of the embodiment of the present application, but also can form a channel for electrolyte penetration, so that the electrolyte can penetrate into the interior of the composite cathode material through the conductive skeleton 2, effectively shortening the
  • the internal ion conduction distance of the composite cathode material is increased, and the compaction density and electrochemical performance of the composite cathode material are significantly improved, allowing the electrical properties of the composite cathode material to be fully utilized.
  • one end of the conductive skeleton 3 is connected to the conductive core 1 and the other end extends into the cathode material coating layer 3, it effectively enhances the mechanical strength of the cathode material coating layer 3 covering the conductive core 1 and enhances the composite cathode material. Structural stability, thus giving the composite cathode material excellent electrochemical stability.
  • the mass ratio of the conductive skeleton 2 to the conductive core 1 can be controlled to (1-3):1.
  • a rich conductive network structure is constructed in the composite cathode material on the basis of ensuring the capacity of the composite cathode material, that is, in the composite cathode material Rich conductive channels are formed, thereby significantly improving the conductive performance of the composite cathode material, enhancing the compaction density and electrochemical performance of the composite cathode material, and improving its structural stability.
  • the length of the conductive skeleton 2 may be 6-8 ⁇ m.
  • the length may be 6-8 ⁇ m.
  • the inner diameter of the hollow tube may be 2-20 nm.
  • it is graphite sheets, conductive graphite, or graphene its length or width or particle size can be 6-8 ⁇ m.
  • graphite sheet or graphene its thickness can be 2-40nm.
  • Dimensions such as length of the conductive skeleton 2 can at least extend into the cathode material coating layer 3 , that is, the free end of the conductive skeleton 2 extending outward from the conductive core 1 should at least extend to the cathode material coating layer 3 middle.
  • the free end extending outward of the conductive core 1 may extend into the cathode material coating layer 3 , or may extend into the cathode material coating layer 3 and then be bent or further form a network structure with other conductive skeletons 2 Or winding contact, etc., or it can also pass through the cathode material coating layer 3 and extend to the outer surface of the cathode material coating layer 3 .
  • the outer surface of the positive electrode material coating layer 3 refers to the surface facing away from the conductive core body 1 .
  • the conductive skeleton 2 may be a hollow tube structure. In this way, the conductive liquid can efficiently enter the interior of the composite cathode material through the pipeline of the hollow tube.
  • the material of the conductive skeleton 2 may include at least one of carbon nanotubes, graphite sheets, conductive graphite, carbon fiber, and graphene.
  • the carbon nanotubes serve as the conductive skeleton and are distributed in the cathode material coating layer 3, giving the composite cathode material
  • the cathode material coating layer 3 contained in it has abundant pores, which can allow the electrolyte (conductive liquid) to directly penetrate into the composite cathode material through the pores, thereby effectively overcoming the conduction within the cathode material such as lithium iron manganese phosphate particles.
  • the distance is too long, resulting in the disadvantage of poor electrical performance.
  • the distance between the composite cathode material particles and the conductive liquid is shortened, the particle conduction distance is shortened, and the electrical performance is fully released.
  • the positive electrode material coating layer 3 functions as a positive electrode material in the composite positive electrode material. Moreover, the conductive core 1 and the conductive skeleton 2 and the above three play a synergistic role, giving the composite cathode material high conductivity, structural stability and compaction density, giving the composite cathode material excellent cycle performance, and High chemical properties.
  • the mass ratio of the cathode material coating layer 3 to the conductive core 1 can be controlled to (100-300):1.
  • the content of the cathode material coating layer such as controlling its mass ratio to the conductive core body 1, on the basis of increasing the capacity of the composite cathode material, the synergistic effect with the above conductive core body 1 and conductive skeleton 2 is improved. , improve the high conductivity, compaction density, electrochemical performance and structural stability of the composite cathode material.
  • the thickness of the cathode material coating layer 3 may be 3-6 ⁇ m.
  • the cathode material contained in the cathode material coating layer 3 includes at least one of a phosphate cathode material and lithium manganate.
  • the phosphate cathode material may include at least one of lithium iron manganese phosphate, lithium iron phosphate, and lithium manganese phosphate.
  • the mass ratio of the above three conductive core 1, conductive skeleton 2 and the cathode material coating layer 3 can be 1: (1-3): (100-300).
  • the composite cathode material in the embodiment of the present application has the core-shell structure described above and also contains the conductive skeleton 2, it can achieve the synergistic effect of the three and improve the high conductivity and structural stability of the composite cathode material to improve
  • the mass ratio of the conductive core 1 and the cathode material coating layer 3 can also be adjusted to make the particle size of the composite cathode material appropriately larger and further improve the performance of the composite cathode material. Compact density and reduce its preparation cost.
  • the D50 of the composite cathode material can be controlled at 3-6 ⁇ m.
  • the conductive core 1 contained in the composite cathode material is sintered carbon
  • the conductive skeleton 2 is carbon nanotube
  • the cathode material is lithium iron manganese phosphate.
  • the composite cathode material is a lithium manganese iron phosphate cathode material with a core-shell structure
  • the lithium manganese iron phosphate cathode material also has a rich pore structure.
  • the lithium manganese iron phosphate cathode material with this structure not only has excellent conductive properties and structure Stable performance, and can also allow the conductive liquid to penetrate into the interior of the lithium iron manganese phosphate cathode material particles through the carbon nanotubes, overcoming the shortcomings of poor electrical performance due to the long conduction distance inside the existing lithium iron manganese phosphate particles. Due to the shortening of the contact distance between the lithium iron manganese phosphate cathode material particles and the conductive liquid, the particle conduction distance is shortened, and the electrical performance is perfectly and fully released. The electrochemical performance of the lithium manganese iron phosphate cathode material has been greatly improved.
  • the particle size of the lithium iron manganese phosphate cathode material particles can also be appropriately enlarged to produce certain small agglomerations, which can not only improve material processing and cycle performance, but also effectively increase the compaction density of the lithium iron manganese phosphate cathode material.
  • the composite cathode material in the embodiment of the present application further includes a conductive coating layer 4, as shown in Figure 2.
  • the conductive coating layer 4 covers the outer surface of the cathode material coating layer 3, which can further enhance the conductive performance of the composite cathode material. Furthermore, it can also realize the connection between the conductive core 1 and the conductive coating layer 4 through the conductive skeleton 2. Conductive connection, thereby significantly improving the rate performance of the composite cathode material.
  • the extended end of the conductive skeleton 2 extends into the conductive coating layer 4 or further extends to the outer surface of the conductive coating layer 4 and exposes the end, such as
  • the extended end of the conductive skeleton 2 shown in FIG. 2 is at least partially extended to the outer surface of the conductive coating layer 4 to improve the inward penetration efficiency of the electrolyte.
  • the thickness of the conductive coating layer 4 assisting the particle size of the conductive core 1 and the thickness of the cathode material coating layer 3, a composite cathode material with a large particle size can be further obtained, thereby improving the compaction of the composite cathode material. and density.
  • the thickness of the conductive coating layer 4 is 2-20 nm; in specific embodiments, the conductive material contained in the conductive coating layer 4 includes carbon materials, such as graphite, carbon black, and acetylene black. of at least one.
  • the conductive role of the conductive coating layer 4 can be further exerted, and the conductive performance, rate performance and compaction density of the composite cathode material can be improved.
  • the embodiments of the present application also provide the preparation method of the above composite cathode material.
  • the preparation method of the composite cathode material in the embodiment of the present application includes the following steps:
  • S01 Prepare composite particles of conductive skeleton and conductive particles; wherein one end of the conductive skeleton is bonded to the conductive particles, and the other end is away from the conductive particles to form a free extending end;
  • S02 Form a positive electrode material coating layer covering the composite particles on the surface of the composite particles, wherein the free extending end of the conductive skeleton extends at least into the positive electrode material coating layer to form a composite positive electrode material.
  • the conductive particles in step S01 are the conductive cores 1 contained in the above composite cathode material, and the conductive skeleton is the conductive skeleton 2 contained in the above composite cathode material.
  • the cathode material coating layer in step S02 is the cathode material coating layer 3 contained in the composite cathode material above. Therefore, in order to save space, the conductive particles and conductive skeleton in step S01 and the conductive skeleton in step S02 are no longer described here.
  • the material dimensions of the positive electrode material coating layer will be described in detail below.
  • the method for preparing composite particles of conductive framework and conductive particles in step S01 may include the following steps:
  • S011 Provide conductive particles, and modify the conductive particles with the first functional group to obtain modified conductive particles;
  • S012 Provide a conductive skeleton, and modify one end of the conductive skeleton with a second functional group to obtain a modified conductive skeleton; where the second functional group is a function that can chemically react with the first functional group to form a chemical bond. group;
  • the first functional group modification treatment on the conductive particles in step S011 is to graft functional groups on the conductive particles, so that the relationship between the modified conductive particles and the modified conductive skeleton in step S012 can be carried out in step S013
  • the chemical reaction enables the modified end of the conductive skeleton to be bonded to the conductive particles.
  • the first functional group may include at least one of a hydroxyl group, an aldehyde group, a carboxyl group, an amino group, an ester group, and an acid anhydride. Then, the method of modifying the first functional group on the conductive particles can also be flexibly selected and controlled according to the type of the first functional group.
  • the conductive particles when they are carbon materials such as sintered carbon, they can be made of at least one of sucrose, glucose, oxalic acid, salicylic acid, citric acid, tartaric acid, malic acid, glycine, ethylenediaminetetraacetic acid, and succinic acid. Formed by carbonization treatment.
  • the second functional group modification treatment on the conductive skeleton in step S012 is also to graft the corresponding functional group on one end of the conductive skeleton, so that The modified conductive skeleton and the modified conductive particles in step S011 can react in step S013, so that the modified ends of the modified conductive skeleton can be combined with the conductive particles.
  • the second functional group may be the same as or different from the above-mentioned first functional group, but it can ensure that the first functional group and the second functional group can carry out a chemical reaction.
  • the second functional group may include at least one of a hydroxyl group, an aldehyde group, a carboxyl group, an amino group, an ester group, and an acid anhydride.
  • the combination of the first functional group and the second functional group may be a combination of a hydroxyl group and an aldehyde group, a carboxyl group and an amino group, an aldehyde group and an aldehyde group, an ester group and an ester group, an aldehyde group and an acid anhydride, etc.
  • the method of modifying the second functional group of the conductive skeleton can also be flexibly selected and controlled according to the type of the second functional group.
  • the chemical reaction conditions between the modified conductive particles and the modified conductive skeleton in step S013 can be controlled according to the reaction conditions of the types of functional groups contained in the two, so that the first functional group and the second functional group react.
  • a chemical bond is generated so that the modified end of the conductive skeleton can be bonded to the conductive particles, and the other end forms a free extending end.
  • the modified conductive particles and the modified conductive skeleton may be first mixed at a mass ratio of the conductive particles to the conductive skeleton of 1:(1-3), so that the generated conductive particles and the conductive skeleton are The mass ratio satisfies the mass ratio of the conductive particles 1 and the conductive skeleton 2 contained in the composite cathode material mentioned above.
  • the method of forming a cathode material coating layer coating the composite particles on the surface of the composite particles in step S01 includes the following steps:
  • S014 Perform a second mixing process between the cathode material or cathode material precursor and the composite particles, coat them on the surface of the composite particles, and then perform a sintering process.
  • the cathode material or cathode material precursor is sintered to form a cathode material coating layer. Therefore, the positive electrode material is the positive electrode material of the positive electrode material coating layer 3 contained in the above composite positive electrode material.
  • the positive electrode material precursor is the precursor of the positive electrode material that forms the positive electrode material coating layer 3 included in the above composite positive electrode material. body.
  • the conditions for the sintering process are at least conditions that enable the cathode material or cathode material precursor to be sintered to form the cathode material coating layer.
  • the sintering process temperature can be 600-700°C and the time can be 5-8 hours. The details can be flexibly controlled according to the specific sintering characteristics of the cathode material or cathode material precursor.
  • the free extending end of the conductive skeleton contained in the composite particles faces away from the conductive particles to form a free extending end, then in the second mixing process, the free extending end of the conductive skeleton will extend into the coating layer formed by the cathode material or cathode material precursor. , then after the sintering process, the free extending end of the conductive skeleton at least extends into the cathode material coating layer to form the composite cathode material shown in Figure 1 above.
  • the second mixing process may be a ball milling process, or may be a slurry of the cathode material or cathode material precursor and the composite particles, and a mixing process such as stirring, so that the cathode material or cathode material precursor is in the composite.
  • a coating layer forms on the surface of the particles.
  • the cathode material or the cathode material precursor and the composite particles may be subjected to the second mixing process at a mass ratio of the conductive skeleton to the cathode material of 1-3: (100-300), so that the sintering
  • the mass ratio between the cathode material coating layer and the composite particles generated after the treatment satisfies the above mass ratio of the conductive particles 1 contained in the composite cathode material and the cathode material coating layer 3.
  • step S03 is also included:
  • a conductive coating layer covering the positive electrode material coating layer is formed on the surface of the positive electrode material coating layer.
  • the conductive coating layer formed in step S03 is the conductive coating layer 4 contained in the above composite cathode material, that is, the composite cathode material as shown in Figure 2 is formed. Then the material and thickness of the conductive coating layer formed in step S03 are the same as the conductive coating layer 4 included in the composite cathode material above.
  • the conductive coating layer can be formed by coating with a solution of a conductive material or a precursor of a conductive material and then sintering, or other methods of forming a coating layer can be used to form a conductive coating layer to cover the positive electrode. on the outer surface of the material coating layer 3.
  • the preparation method of the composite cathode material in the embodiment of the application can prepare the composite cathode material with the core-shell structure as above, and impart the excellent conductivity to the prepared composite cathode material as mentioned above. performance and electrochemical performance as well as structural stability.
  • the preparation method of the composite cathode material can ensure that the structure and electrochemical properties of the prepared composite cathode material are stable.
  • the preparation method of the composite cathode material in the embodiment of the present application can reduce the control and requirements for the composite cathode material, thereby making the composite cathode material in the embodiment of the present application more efficient.
  • the preparation method has high efficiency and saves production costs.
  • step S02 or step S03 a step of pulverizing or granulating the material is also included to control the particle size and uniformity of the final material.
  • embodiments of the present application also provide a positive electrode sheet.
  • the positive electrode sheet in the embodiment of the present application includes a positive current collector and a positive active layer bonded to the surface of the positive current collector.
  • the positive active layer contains the composite positive electrode material of the electrode in the embodiment of the present application. Since the positive electrode sheet of the embodiment of the present application contains the composite positive electrode material of the electrode of the embodiment of the present application, the positive electrode sheet has low internal resistance, high capacity, and good rate and cycle performance.
  • the positive electrode active layer includes, in addition to the composite positive electrode material, a binder and a conductive agent.
  • the binder can be a commonly used electrode binder, such as polyvinylidene chloride, soluble polytetrafluoroethylene, butyl styrene. One or more of rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethylcellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan and chitosan derivatives .
  • the conductive agent may be a commonly used conductive agent, including one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60 and carbon nanotubes.
  • the positive active layer may also contain a lithium supplement additive to improve the first efficiency of the battery.
  • the preparation process of the positive electrode sheet can be as follows: mixing the composite positive electrode material, the conductive agent and the binder to obtain an electrode slurry, coating the electrode slurry on the electrode current collector, and drying, rolling, die-cutting and other steps. An electrode sheet was prepared.
  • embodiments of the present application also provide a secondary battery.
  • the secondary battery in the embodiment of the present application includes necessary components such as a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, and of course other necessary or auxiliary components.
  • the positive electrode sheet is the positive electrode sheet of the above-mentioned embodiment of the present application.
  • the secondary battery of the embodiment of the present application contains the positive electrode sheet of the embodiment of the present application
  • the positive electrode sheet of the embodiment of the present application contains the composite cathode material of the embodiment of the present application, based on the characteristics of the composite cathode material of the embodiment of the present application
  • the secondary battery of the embodiment of the present application has high capacity, rate performance and cycle performance, long life, and stable electrochemical performance.
  • This embodiment provides a composite cathode material and a preparation method.
  • This embodiment provides a composite cathode material that is a lithium manganese iron phosphate cathode material with a single core-pore structure, specifically including carbon black particles and carbon nanotubes and a lithium manganese iron phosphate coating layer coating the carbon black particles.
  • the outer surface of the cladding also includes a carbon cladding. That is, the lithium iron manganese phosphate coating layer serves as the intermediate layer, and the carbon coating layer serves as the outer coating layer.
  • One end of the carbon nanotube is bonded to the surface of the carbon black particle, and the other end is away from the carbon black particle to form a free extending end, and the free extending end at least extends into the lithium iron manganese phosphate coating layer, and after detection, the free extending end
  • the free extending end is partially distributed in the lithium iron manganese phosphate coating layer and partially distributed in the carbon coating layer or/and on the surface.
  • the mass ratio of carbon black particles, carbon nanotubes, and lithium iron manganese phosphate coating layer is 1:1:100.
  • modified carbon black particles use 1g carbon black to modify with 0.01g amino group;
  • step S3 Prepare the lithium iron manganese phosphate in step S2 into a slurry using a sand grinding process, and then use spray drying to form a lithium iron manganese phosphate coating layer on the surface of the composite particles;
  • step S4 Place the composite material in step S3 in a tube furnace, pass nitrogen gas, add 20g glucose and bake at 750°C for 5 hours to form a carbon coating layer on the outer surface of the lithium iron manganese phosphate coating layer to obtain a composite cathode material;
  • step S5 After the composite cathode material generated in step S4 is cooled, it is pulverized and sieved to obtain a composite cathode material with uniform particle size.
  • This embodiment provides a composite cathode material and a preparation method.
  • the structure of the composite cathode material is the same as that of the composite cathode material in Example 1, except that the mass ratio of the carbon black particles, carbon nanotubes, lithium iron manganese phosphate coating layer and carbon coating layer is different. Among them, the mass ratio of carbon black particles, carbon nanotubes, and lithium iron manganese phosphate coating layer is 1:2:200.
  • modified carbon black particles use 1g carbon black to modify with 0.02g aldehyde group;
  • step S3 Prepare the lithium iron manganese phosphate in step S2 into a slurry using a sand grinding process, and then use spray drying to form a lithium iron manganese phosphate coating layer on the surface of the composite particles;
  • step S4 Place the composite material in step S3 in a tube furnace, circulate nitrogen, add 40g of glucose and roast at 750°C for 5 hours to form a carbon coating layer on the outer surface of the lithium iron manganese phosphate coating layer to obtain a composite cathode material;
  • step S5 After the composite cathode material generated in step S4 is cooled, it is pulverized and sieved to obtain a composite cathode material with uniform particle size.
  • This embodiment provides a composite cathode material and a preparation method.
  • the structure of the composite cathode material is the same as that of the composite cathode material in Example 1, except that the mass ratio of the carbon black particles, carbon nanotubes, lithium iron manganese phosphate coating layer and carbon coating layer is different. Among them, the mass ratio of carbon black particles, carbon nanotubes, and lithium iron manganese phosphate coating layer is 1:3:300.
  • step S3 Prepare the lithium iron manganese phosphate in step S2 into a slurry using a sand grinding process, and then use spray drying to form a lithium iron manganese phosphate coating layer on the surface of the composite particles;
  • step S4 Place the composite material in step S3 in a tube furnace, pass nitrogen gas, add 60g glucose and roast at 750°C for 5 hours to form a carbon coating layer on the outer surface of the lithium iron manganese phosphate coating layer to obtain a composite cathode material;
  • step S5 After the composite cathode material generated in step S4 is cooled, it is pulverized and sieved to obtain a composite cathode material with uniform particle size.
  • This embodiment provides a composite cathode material and a preparation method.
  • the structure of the composite cathode material is the same as that of the composite cathode material in Example 1, except that the carbon black particles are replaced with LFP particles, and the lithium iron manganese phosphate coating layer is replaced with an LFP coating layer; wherein, the carbon black particles,
  • the mass ratio of carbon nanotubes and lithium iron manganese phosphate coating layer is 1:1:200, and after testing, the free extending ends of carbon nanotubes are partially distributed in the LFP coating layer, and part of them are distributed in the carbon coating layer or /and surface.
  • step S2 After the LFP generated in step S1 is cooled, crush and sieve to obtain LFP material particles with uniform particle size;
  • step S5 Prepare the lithium iron manganese phosphate in step S2 into a slurry using a sand grinding process, and then use spray drying to form a lithium iron manganese phosphate coating layer on the surface of the composite particles;
  • step S5 Place the composite material in step S3 in a tube furnace, pass nitrogen gas, add 20g of glucose and roast at 750°C for 5 hours to form a carbon coating layer on the outer surface of the lithium iron manganese phosphate coating layer to obtain a composite cathode material;
  • step S6 After the composite cathode material generated in step S4 is cooled, it is pulverized and sieved to obtain a composite cathode material with uniform particle size.
  • the lithium iron manganese phosphate cathode material in Example 1 is provided, that is, it does not contain carbon black particles and carbon nanotubes, and is simply a lithium iron manganese phosphate cathode material.
  • This comparative example provides a single-core multi-shell structure lithium iron manganese phosphate and a preparation method thereof.
  • the lithium iron manganese phosphate in this comparative example includes a LiMn 0.7 Fe 0.29 V 0.01 PO 4 core body and a coating of LiMn 0.7 Fe 0.29 V 0.01 PO 4 A carbon intermediate cladding layer of the core body, a LiMn 0.5 Fe 0.5 PO 4 intermediate cladding layer covering the carbon intermediate cladding layer, and an amorphous carbon outer cladding layer covering the LiMn 0.5 Fe 0.5 PO 4 intermediate cladding layer.
  • the preparation method of lithium iron manganese phosphate in this comparative example includes the following steps:
  • S2 Place the first solid mixture in an alumina porcelain boat, compact it, and perform pre-firing in a tube furnace under an argon-hydrogen atmosphere. Pre-firing starts from room temperature and is heated to 300°C at a rate of 3°C/min. °C temperature, and the pre-sintered product containing the carbon coating layer is obtained after the sintering time is 5 hours;
  • a composite cathode material including a carbon core body and an LFMP coating layer covering the carbon core body.
  • the preparation method of the composite cathode material of this comparative example includes the following steps:
  • the obtained lithium iron manganese phosphate is prepared into a slurry with dispersed and uniform particles by sand grinding process, and then the lithium iron manganese phosphate slurry is sprayed on the surface of 2g solid carbon source using spray drying equipment;
  • step 4 After the sample obtained in step 3 is cooled, crush and sieve to obtain nanometer lithium iron manganese phosphate with uniform particle size.
  • a composite cathode material including an LFP core body and an LFMP coating layer coating the carbon core body.
  • the preparation method of the composite cathode material of this comparative example includes the following steps:
  • step 2 After the sample obtained in step 1 is cooled, crush and sieve to obtain nanometer lithium iron phosphate with uniform particle size;
  • the obtained lithium iron manganese phosphate is prepared into a slurry with dispersed and uniform particles using a sand grinding process, and then the lithium iron manganese phosphate slurry is sprayed on the surface of 2g solid lithium iron phosphate using spray drying equipment;
  • step 6 After the sample obtained in step 5 is cooled, crush and sieve to obtain nanometer lithium iron manganese phosphate with uniform particle size.
  • Lithium-ion battery examples are provided:
  • the composite cathode materials of the above-mentioned Examples 1 to 4 and the cathode materials provided in the comparative examples were assembled into cathode electrodes and lithium-ion batteries according to the following methods:
  • Positive electrode Under the same conditions, mix according to the ratio of positive electrode material: Super P-Li: PVDF mass ratio of 90:5:5.
  • the solvent is NMP.
  • the mixing method is ball mill mixing or degassing mixer. If If a ball mill is used, the ball milling time is 30 min; the rotational speed frequency is set to 20 HZ. If a homogenizer is used for mixing, use 600rpm for 30 seconds, and then 2000rpm for 15min. After homogenization-coating-drying-cutting operations, a positive electrode sheet is prepared. The positive electrode sheet is baked in a 100°C vacuum oven to remove traces of water.
  • the positive electrode materials are the positive electrode materials provided in the above-mentioned Examples 1 to 4 and Comparative Examples 1 to 3 respectively;
  • Negative electrode graphite
  • Electrolyte lithium hexafluorophosphate (Tianci conductive liquid);
  • Diaphragm PE diaphragm
  • Lithium-ion battery assembly Assemble the lithium-ion battery in a glove box filled with argon and with water and oxygen content below 10ppm.
  • the relevant electrochemical properties of each lithium-ion battery assembled in the above lithium-ion battery embodiment were tested.
  • the test conditions are:
  • Example 1 >2000 circles 156.2 585.6 2.453 1.3
  • Example 2 >2000 circles 154.6 579.4 2.464 1.8
  • Example 3 >2000 circles 154.3 578.9 2.458 2.8
  • Example 4 >2000 circles 156.4 576.9 2.468 0.5
  • Comparative example 1 >2000 circles 137.6 520.2 2.458 54.3
  • Comparative example 2 >1500 circles 153.3 570.7 2.456 42.6
  • Comparative example 4 >2000 circles 144.3 536.8 2.458 48.3
  • the present invention greatly shortens the transmission distance of lithium ions and can make the particles larger without affecting the cycle performance of the product. Therefore, it has good cycle performance, high discharge efficiency, and high pressure. It has the advantages of high practical performance and good conductivity.

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Abstract

本申请公开了一种复合正极材料及其制备方法和应用。本申请复合正极材料包括导电核体和包覆导电核体的正极材料包覆层，其中，还包括导电骨架，且导电骨架一端与导电核体接触，另一端至少是延伸至正极材料包覆层中。本申请复合正极材料导电性能和结构稳定性以及压实密度高，具有高的循环性能，电化学性能。复合正极材料的制备方法能够保证制备的复合正极材料结构和电化学性能稳定，而且效率高，节约生产成本。

Description

复合正极材料及其制备方法和应用
本申请要求于2022年03月28日提交中国专利局，申请号为202210314912.0，申请名称为“复合正极材料及其制备方法和应用”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
本申请属于二次电池领域，具体涉及一种复合正极材料及其制备方法和应用。
 背景技术
20世纪60、70年代的石油能源危机问题迫使人们去寻找新的可替代的新能源，随着人们对环境保护和能源危机意识的增强。锂离子电池因其具备较高的工作电压与能量密度、相对较小的自放电水平、无记忆效应、无铅镉等重金属元素污染、超长的循环寿命等优点，被认为是最具应用前景的能源之一。锂离子电池被广泛应用于电动车、电动工具、可移动电子消费品以及储能等诸多方面。
对于锂离子电池而言，正极材料、负极材料和电解质是决定其电化学性能的关键因素，而正极材料充当锂离子电池中的锂源的角色，是锂离子电池的重要组成部分之一，更是制约锂离子电池比能量和比功率等电化学性能的关键因素。目前常用的锂离子电池正极材料主要有：层状结构的正极材料，其中包括钴酸锂(LiCoO 2)、镍酸锂(LiNiO 2)、锰酸锂(LiMnO 2) ，以及二/三元复合层状正极材料(LiNi xCo yMn zO 2)等；尖晶石结构的锰酸锂(LiMn 2O 2)；橄榄石型结构的磷酸铁锂(LiFePO 4) 以及磷酸锰铁锂（LiMn xFe 1-xPO 4）等。
虽然锂离子电池材料具有诸多优点，但是在其应用过程中，它也面临着亟需解决的诸多问题，如材料导电性能差，压实密度低，在大电流下容量的衰减严重和倍率性能差等问题。而且其制备方法也存在原料价格昂贵、成本高，难以实现工业化生产的问题。
 技术问题
本申请的目的在于克服现有技术的上述不足，提供一种复合正极材料及其制备方法，以解决现有正极材料存在导电性差、压实密度低等技术问题。
本申请的另一目的在于提供一种正极片和含有该正极片的二次电池，以解决现有正极材料导致二次电池的容量衰减严重和倍率性能差等电化学性能不理想的技术问题。
 技术解决方案
为了实现上述申请目的，本申请的第一方面，提供了一种复合正极材料。本申请复合正极材料包括导电核体和包覆导电核体的正极材料包覆层，其中，还包括导电骨架，且导电骨架一端与导电核体接触，另一端至少是延伸至正极材料包覆层中。
本申请的第二方面，提供了本申请复合正极材料的制备方法。本申请复合正极材料的制备方法包括如下步骤：
制备导电骨架与导电颗粒的复合物颗粒；其中，导电骨架的一端是结合在导电颗粒上，另一端背离导电颗粒形成自由延伸端；
在复合物颗粒表面形成包覆于复合物颗粒的正极材料包覆层，其中，导电骨架的自由延伸端至少延伸至正极材料包覆层中，形成复合正极材料。
本申请的第三方面，提供了一种正极片。本申请正极片包括集流体和结合在集流体表面的正极活性层，正极活性层中含有本申请复合正极材料或由本申请复合正极材料制备方法制备的复合正极材料。
本申请的第四方面，提供了一种二次电池。本申请包括正极片和负极片；正极片为本申请正极片。
与现有技术相比，本申请具有以下的技术效果：
本申请复合正极材料在导电核体与正极材料包覆层之间增设导电骨架，并将导电骨架延伸至正极材料包覆层，这样，导电骨架增强了正极材料包覆层的导电性能，且其与导电核体连接，与导电核体一起在复合正极材料中构建良好的导电网络结构，赋予复合正极材料优异的导电性能。而且导电骨架能够构成电解液渗透的通道，使得电解液能够通过导电骨架向复合正极材料内部渗入，有效缩短了复合正极材料内部传导距离，显著提高了复合正极材料的压实密度和电化学性能，使得复合正极材料的电性能得到充分发挥。另外，导电骨架一端连接导电核体、另一端延伸至正极材料包覆层中，其有效增强了正极材料包覆层包覆导电核体的力学强度，增强了复合正极材料结构稳定性，从而赋予复合正极材料优异的电化学稳定性。
本申请复合正极材料的制备方法能够制备如上文核壳结构的本申请复合正极材料，并赋予制备的复合正极材料如上文所述的优异导电性能和电化学性能以及结构稳定性。另外，复合正极材料的制备方法能够保证制备的复合正极材料结构和电化学性能等性能稳定，而且效率高，节约生产成本。
本申请正极片由于含有本申请复合正极材料，因此，本申请正极片容量高，倍率和循环性能好。
本申请二次电池由于含有本申请正极片，因此，本申请二次电池具有高的容量和倍率性能以及循环性能，寿命长，电化学性能稳定。
 附图说明
为了更清楚地说明本申请具体实施方式或现有技术中的技术方案，下面将对具体实施方式或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图是本申请的一些实施方式，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他的附图。
图1为本申请实施例复合正极材料的一种结构示意图；
图2为本申请实施例复合正极材料的另一种结构示意图；
图3为本申请实施例复合正极材料的制备方法流程示意图。
 本发明的实施方式
第一方面，本申请实施例提供了一种复合正极材料。本申请实施例复合正极材料的结构如图1所示，包括导电核体1和包覆导电核体1的正极材料包覆层3以及导电骨架2。其中，该导电骨架2一端与导电核体1接触，另一端至少是延伸至正极材料包覆层3中。
其中，导电核体1与导电骨架2一起构成了本申请实施例复合正极材料的导电网络体系，赋予本申请实施例复合正极材料优异的导电性，赋予本申请实施例复合正极材料高的倍率性能。
另外，该导电核体1的粒径大小还是影响本申请复合正极材料的粒径因素之一，因此，在本申请实施例中，该导电核体1的粒径可以控制到80nm，如≤80nm。在具体实施例中，导电核体的材料包括碳、正极材料中的至少一种。其中，碳可以包括烧结碳。正极材料可以是具有导电率低、比表面积高、压实密度低至少一种性能的正极材料，具体如LFP、锰酸锂、磷酸锰锂等中的至少一种。通过对导电核体1的粒径和材料种类的控制和选择，能够提高该导电核体1如上述的作用，从而提高本申请实施例复合正极材料导电性和倍率性能以及容量。而且还可以通过控制和调节导电核体1的粒径大小，结合正极材料包覆层3的厚度，可以控制和调节复合正极材料的粒径，如增大复合正极材料的粒径，从而提高本申请实施例复合正极材料的压实密度。
导电骨架2不仅与上述导电核体1在本申请实施例复合正极材料中构成导电网络体系，而且能够构成电解液渗透的通道，使得电解液能够通过导电骨架2向复合正极材料内部渗入，有效缩短了复合正极材料内部离子传导距离，显著提高了复合正极材料的压实密度和电化学性能，使得复合正极材料的电性能得到充分发挥。另外，由于导电骨架3一端连接导电核体1、另一端延伸至正极材料包覆层3中，其有效增强了正极材料包覆层3包覆导电核体1的力学强度，增强了复合正极材料结构稳定性，从而赋予复合正极材料优异的电化学稳定性。
实施例中，该导电骨架2与导电核体1的质量比可以控制为（1-3）：1。通过控制导电骨架2的含量如控制其与导电核体1的质量比，从而在保证复合正极材料容量的基础上，在复合正极材料中构建丰富的导电网络结构，也即是在复合正极材料中形成丰富的导电通道，从而显著提高复合正极材料的导电性能，增强复合正极材料的压实密度和电化学性能，同时提高其结构稳定性。
另些实施例中，导电骨架2的长度可以是6-8μm，具体如为碳纳米管、碳纤维等时，其长度可以是6-8μm。当为中空管结构如碳纳米管时，其中空管的中空管内径可以是2-20nm。如为石墨片、导电石墨、石墨烯时，其长度或宽度或粒径为可以是6-8μm。当为石墨片或石墨烯时，其厚厚度可以为2-40nm。导电骨架2的如长度等尺寸可以至少是要延伸至正极材料包覆层3中，也即是导电骨架2由导电核体1向外延伸的自由端至少是要延伸至正极材料包覆层3中。如导电核体1向外延伸的自由端可以是延伸至正极材料包覆层3中，也可以是在延伸至正极材料包覆层3中后弯曲或进一步与其他导电骨架2之间形成网络结构或者缠绕接触等，还可以是穿过正极材料包覆层3并延伸至正极材料包覆层3的外表面。该正极材料包覆层3外表面是指背离导电核体1的表面。通过控制导电骨架2的直径和长度等控制和优化，能够充分发挥导电骨架2起到如上述的导电通道作用和提高加强筋的作用，进一步增强复合正极材料的压实密度和电化学性能以及结构稳定性。
实施例中，导电骨架2可以是中空管结构。这样，能够使得导电液通过中空管的管路高效的进入到复合正极材料的内部。在具体实施例中，导电骨架2的材料可以包括碳纳米管、石墨片、导电石墨、碳纤维、石墨烯中的至少种。通过对导电骨架2材料的选用，提高导电骨架2的导电性能和增强力学加强筋的作用，进一步提高复合正极材料的压实密度和电化学性能以及结构稳定性。其中，碳纳米管由于为中空微管结构，其自身特殊的结构，当导电骨架2的材料为碳纳米管时，碳纳米管作为导电骨架分布在正极材料包覆层3中，赋予复合正极材料具体是其所含的正极材料包覆层3呈现丰富的孔道，该孔道能够使得电解液（导电液）通过孔道直接渗入复合正极材料内部，从而有效克服正极材料如磷酸锰铁锂颗粒内部因传导距离过长，导致电性能差的缺点。同时由于复合正极材料颗粒内部接触导电液距离被缩短，颗粒传导距离变短，电性能得到充分释放。
正极材料包覆层3在复合正极材料中发挥正极材料的功能。而且在上文导电核体1和导电骨架2以及三者之间起到增效作用，赋予复合正极材料高的导电性能和结构稳定性以及压实密度，赋予复合正极材料优异的循环性能，电化学性能高。
实施例中，该正极材料包覆层3与导电核体1的质量比可以控制为（100-300）：1。通过控制正极材料包覆层的含量如控制其与导电核体1的质量比，在提高复合正极材料容量的从基础上，提高与上文导电核体1和导电骨架2之间的增效作用，提高复合正极材料高导电性能、压实密度和电化学性能以及结构稳定性。
实施例中，正极材料包覆层3的厚度可以为3-6μm。在具体实施例中，正极材料包覆层3所含的正极材料包括磷酸盐系正极材料、锰酸锂中的至少一种。其中，磷酸盐系正极材料可以包括磷酸锰铁锂、磷酸铁锂、磷酸锰锂中的至少一种。通过对导电包覆层3的厚度和材料的控制和优化，充分发挥复合正极材料中发挥正极材料的功能。
基于上文导电核体1、导电骨架2和正极材料包覆层3的质量比，实施例中，上文导电核体1、导电骨架2和正极材料包覆层3三者的质量比可以为1：（1-3）：（100-300）。通过协调三者的含量比例，在成分发挥三者各自作用的基础上，成分发挥三者之间的增效作用，从而提高复合正极材料导电性能和结构稳定性以及压实密度，赋予复合正极材料优异的循环性能，电化学性能高。
由于本申请实施例复合正极材料具有上文所述的核壳结构，而且还含有导电骨架2，因此，在能够实现三者增效作用，提高复合正极材料高的导电性能和结构稳定性以提高本申请实施例复合正极材料电化学性能的基础上，还可以通过调节导电核体1和正极材料包覆层3的质量比，使得复合正极材料的粒径适当做大，进一步提高复合正极材料的压实密度，降低其制备成本。如实施例中，复合正极材料的D50可以控制在3-6 μm。
基于上文各实施例复合正极材料所含的导电核体1、导电骨架2和正极材料包覆层3各自所选的材料，如复合正极材料所含的导电核体1为烧结碳，导电骨架2为碳纳米管，正极材料为磷酸锰铁锂。这样，该复合正极材料为核壳结构的磷酸锰铁锂正极材料，而且该磷酸锰铁锂正极材料还具有丰富的孔道结构，该结构的磷酸锰铁锂正极材料不仅具有优异的导电性能和结构稳定性能，而且还能够使得导电液通过碳纳米管渗入磷酸锰铁锂正极材料颗粒内部，克服了现有磷酸锰铁锂颗粒内部因传导距离过长而导致电性能差的缺点。由于磷酸锰铁锂正极材料颗粒内部接触导电液距离被缩短的特点，颗粒传导距离变短，电性能得到完美和充分释放，磷酸锰铁锂正极材料的电化学性能得到了大幅度提升，由此还可以将磷酸锰铁锂正极材料颗粒的粒径适当做大，产生一定的小团聚，提高材料加工、循环性能的同时，能够有效提升磷酸锰铁锂正极材料压实密度。
在进一步实施例中，在上文各实施例的基础上，本申请实施例复合正极材料还包括导电包覆层4，如图2所示。该导电包覆层4包覆在正极材料包覆层3的外表面，能够进一步增强复合正极材料的导电性能，进一步的还能够通过导电骨架2，实现导电核体1和导电包覆层4的导电连接，从而显著提高复合正极材料的倍率性能，如实施例中，该导电骨架2的延伸端延伸至导电包覆层4中或进一步延伸至导电包覆层4的外表面并裸露末端，如图2中所示的导电骨架2的延伸端至少部分是延伸至导电包覆层4的外表面，以提高电解液向内渗透效率。进一步地，通过控制导电包覆层4的厚度，协助导电核体1的粒径和正极材料包覆层3的厚度，可以进一步获得大粒径的复合正极材料，从而提高复合正极材料的压实及密度。
实施例中，该导电包覆层4的厚度为2-20 nm；在具体实施例中，该导电包覆层4所含的导电材料包括碳材料，如可以是石墨、炭黑、乙炔黑中的至少一种。通过对导电包覆层4的厚度和材料的控制和优化，进一步发挥导电包覆层4的导电作用，提高复合正极材料的导电性能和倍率性能以及压实密度。
第二方面，本申请实施例还提供了上文复合正极材料的制备方法。本申请实施例复合正极材料的制备方法包括以下步骤：
S01：制备导电骨架与导电颗粒的复合物颗粒；其中，导电骨架的一端是结合在导电颗粒上，另一端背离导电颗粒形成自由延伸端；
S02：在复合物颗粒表面形成包覆于复合物颗粒的正极材料包覆层，其中，导电骨架的自由延伸端至少延伸至正极材料包覆层中，形成复合正极材料。
其中，步骤S01中的导电颗粒为上文复合正极材料所含的导电核体1，导电骨架为上文复合正极材料所含导电骨架2。步骤S02中的正极材料包覆层为上文复合正极材料所含的正极材料包覆层3，因此，为了节约篇幅，在此不再对步骤S01中的导电颗粒、导电骨架和步骤S02中的正极材料包覆层的材料尺寸等料进行赘述。
实施例中，步骤S01中的制备导电骨架与导电颗粒的复合物颗粒的方法可以是包括如下步骤：
S011：提供导电颗粒，对导电颗粒进行第一功能基团改性处理，得到改性导电颗粒；
S012：提供导电骨架，对导电骨架的其中一端进行第二功能基团改性处理，得到改性导电骨架；其中，第二功能基团为能够与第一功能基团进行化学反应形成化学键的功能基团；
S013：将改性导电颗粒与改性导电骨架进行第一混合处理并进行化学反应处理，使得导电骨架的改性端通过化学键结合在导电颗粒上，得到该复合物颗粒。
其中，步骤S011中对导电颗粒进行第一功能基团改性处理是为了在导电颗粒上接枝功能基团，使得改性导电颗粒与步骤S012中改性导电骨架之间能够在步骤S013中进行化学反应，使得导电骨架的改性端能够结合在导电颗粒上。因此，实施例中，该第一功能基团可以是包括羟基、醛基、羧基、氨基、酯基、酸酐中的至少一种。那么对导电颗粒进行第一功能基团改性处理的方法也可以根据第一功能基团的种类进行灵活选择和控制。其中，当导电颗粒为碳材料如烧结碳时，其可以是由包括蔗糖、葡萄糖、草酸、水杨酸、柠檬酸、酒石酸、苹果酸、甘氨酸、乙二胺四乙酸、琥珀酸中至少一种碳化处理形成。
基于步骤S011中对导电颗粒进行第一功能基团改性处理，步骤S012中对导电骨架进行第二功能基团改性处理也是为了在导电骨架的一端部上接枝相应的功能基团，使得改性导电骨架与步骤S011中改性导电颗粒之间能够在步骤S013中进行反应，使得改性导电骨架的改性端能够结合在导电颗粒上。因此，实施例中，该第二功能基团可以是与上述第一功能基团相同或不相同，但是能够保证第一功能基团与第二功能基团能够进行化学反应，因此，第二功能基团可以包括羟基、醛基、羧基、氨基、酯基、酸酐中的至少一种。具体实施例中，第一功能基团与第二功能基团的组合可以是羟基与醛基、羧基与氨基、醛基和醛基、酯基与酯基、醛基与酸酐等的组合。对导电骨架的进行第二功能基团改性处理的方法也可以根据第二功能基团的种类进行灵活选择和控制。
步骤S013中改性导电颗粒与改性导电骨架之间的化学反应条件可以根据两者所含的功能基团种类的反应条件进行控制，使得第一功能基团与第二功能基团之间反应生成化学键，从而将导电骨架的改性端能够结合在导电颗粒上，另一端形成自由延伸端。
实施例中，改性导电颗粒与改性导电骨架可以是按照导电颗粒与导电骨架质量比为1:（1-3）的比例进行第一混合处理，使得生成的导电颗粒和导电骨架之间的质量比满足上文复合正极材料所含导电颗粒1和导电骨架2的质量比。
实施例中，步骤S01中的在复合物颗粒表面形成包覆于复合物颗粒的正极材料包覆层的方法包括如下步骤：
S014：将正极材料或正极材料前驱体与复合物颗粒进行第二混合处理，并包覆在复合物颗粒表面，后进行烧结处理。
在步骤S014中的经烧结处理后，正极材料或正极材料前驱体烧结形成正极材料包覆层。因此，正极材料为上文复合正极材料所含的正极材料包覆层3的正极材料，同理正极材料前驱体为形成上文复合正极材料所含的正极材料包覆层3的正极材料的前驱体。那么烧结处理的条件至少是能够使得正极材料或正极材料前驱体烧结形成正极材料包覆层的条件，如实施例中，烧结处理的温度可以为600-700℃，时间可以为5-8h。具体可以根据正极材料或正极材料前驱体的具体烧结特性而灵活控制。
由于复合物颗粒所含导电骨架的另一端背离导电颗粒形成自由延伸端，那么在第二混合处理中，该导电骨架的自由延伸端会延伸至正极材料或正极材料前驱体形成的包覆层中，那么经烧结处理后，该导电骨架的自由延伸端至少是延伸至正极材料包覆层中，形成上文图1所示的复合正极材料。实施例中，该第二混合处理可以是球磨处理，也可以是将正极材料或正极材料前驱体与复合物颗粒形成浆料进行如搅拌等混合处理，使得正极材料或正极材料前驱体在复合物颗粒表面形成包覆层。
实施例中，该正极材料或正极材料前驱体与复合物颗粒可以是按照导电骨架与正极材料的质量比为1-3：（100-300）的比例进行该第二混合处理，以使得经烧结处理后生成的正极材料包覆层和复合物颗粒之间的质量比满足上文复合正极材料所含导电颗粒1和正极材料包覆层3的质量比。
进一步实施例中，在复合物颗粒表面形成包覆于复合物颗粒的正极材料包覆层的步骤之后，还包括如下步骤S03：
在正极材料包覆层的表面形成包覆该正极材料包覆层的导电包覆层。
其中，该步骤S03中形成的导电包覆层为上文复合正极材料所含的导电包覆层4，也即是形成如图2中的复合正极材料。那么步骤S03中形成的导电包覆层的材料和厚度等均如上文复合正极材料所含的导电包覆层4。
实施例中，形成导电包覆层的方法可以采用导电材料或导电材料的前驱体的溶液包覆后烧结处理，也可以采用形成包覆层的其他方法形成导电包覆层，以包覆在正极材料包覆层3的外表面上。
由上文本申请实施例复合正极材料的制备方法可知，本申请实施例复合正极材料的制备方法能够制备如上文核壳结构的复合正极材料，并赋予制备的复合正极材料如上文所述的优异导电性能和电化学性能以及结构稳定性。另外，复合正极材料的制备方法能够保证制备的复合正极材料结构和电化学性能等性能稳定。由于本申请实施例复合正极材料可以是相对较大的粒径，因此，本申请实施例复合正极材料的制备方法可以降低对复合正极材料的控制和要求，从而使得本申请实施例复合正极材料的制备方法的效率高，节约生产成本。
另外，待上述步骤S02或步骤S03之后，还包括对材料进行粉碎或造粒的步骤，以控制最终材料的粒径大小和均匀性。
第三方面，本申请实施例还提供了一种正极片。本申请实施例正极片包括正极集流体和结合在正极集流体表面的正极活性层，正极活性层中含有上文本申请实施例电极复合正极材料。由于本申请实施例正极片含有上述本申请实施例电极复合正极材料，因此，正极片的内阻低，容量高，倍率和循环性能好。
正极活性层包括除了该复合正极材料之外，还包括粘结剂和导电剂，其中，粘结剂可以是常用的电极粘结剂，如包括聚偏氯乙烯、可溶性聚四氟乙烯、丁苯橡胶、羟丙基甲基纤维素、甲基纤维素、羧甲基纤维素、聚乙烯醇、丙烯腈共聚物、海藻酸钠、壳聚糖和壳聚糖衍生物中的一种或多种。本申请实施方式中，导电剂可以是常用的导电剂，如包括石墨、碳黑、乙炔黑、石墨烯、碳纤维、C60和碳纳米管中的一种或多种。或进一步地，正极活性层还可以含有补锂添加剂，以提高电池的首效。
实施例中，正极片制备过程可以为：将复合正极材料、导电剂与粘结剂混合得到电极浆料，将电极浆料涂布在电极集流体上，经干燥、辊压、模切等步骤制备得到电极片。
第四方面，本申请实施例还提供了一种二次电池。本申请实施例二次电池包括正极片、负极片、隔膜和电解质等必要的部件，当然还包括其他必要或辅助的部件。其中，正极片为上述本申请实施例正极片。
由于本申请实施例二次电池中含有上文本申请实施例正极片，而该本申请实施例正极片含有上文本申请实施例复合正极材料，基于上文本申请实施例复合正极材料所具有的特性，本申请实施例二次电池具有高的容量和倍率性能以及循环性能，寿命长，电化学性能稳定。
以下通过多个具体实施例来举例说明本申请实施例复合正极材料及其制备方法和应用等。
1. 复合正极材料及其制备方法实施例：
实施例1
本实施例提供一种复合正极材料及制备方法。本实施例提供复合正极材料为单核-孔道结构的磷酸锰铁锂正极材料，具体包括炭黑颗粒和碳纳米管以及包覆炭黑颗粒的磷酸锰铁锂包覆层，在磷酸锰铁锂包覆层的外表面还包括碳包覆层。也即是，磷酸锰铁锂包覆层作为中间层，碳包覆层作为外包覆层。其中，碳纳米管的一端结合在炭黑颗粒的表面，另一端背离该炭黑颗粒形成自由延伸端，且该自由延伸端至少是延伸至磷酸锰铁锂包覆层中，而且经检测，该自由延伸端部分分布在磷酸锰铁锂包覆层中，部分分布在碳包覆层中或/和表面。其中，炭黑颗粒、碳纳米管、磷酸锰铁锂包覆层的质量比为1：1：100。
本实施例复合正极材料的制备方法包括如下步骤：
S1.碳纳米管与炭黑颗粒的复合物颗粒的制备：
S11.改性炭黑颗粒的制备：用1g炭黑使用0.01g氨基改性；
S12.改性碳纳米管的制备：取1g碳纳米管一端使用0.01g羧基改性；
S13.将改性炭黑颗粒与改性碳纳米管进行缩合反应：将改性碳纳米管与改性炭黑进行混合并进行酰胺化反应，将碳纳米管的改性端通过酰胺键连接在炭黑的表面；
S2：将100g磷酸锰铁锂于管式炉内，通氮气，加1g葡萄糖650℃焙烧5h；
S3: 将步骤S2中磷酸锰铁锂利用砂磨工艺制备成浆料，然后利用喷雾干燥使得磷酸锰铁锂在复合物颗粒表面形成磷酸锰铁锂包覆层；
S4：将步骤S3中的复合材料于管式炉内，通氮气，加20g葡萄糖750℃焙烧5h，在磷酸锰铁锂包覆层外表面形成碳包覆层，得到复合正极材料；
S5：待步骤S4中生成的复合正极材料冷却后，进行粉碎、过筛制得粒径均一的复合正极材料。
实施例2
本实施例提供一种复合正极材料及制备方法。该复合正极材料的结构与实施例1中的复合正极材料结构相同，不同在于所含的炭黑颗粒、碳纳米管、磷酸锰铁锂包覆层和碳包覆层的质量比有区别。其中，炭黑颗粒、碳纳米管、磷酸锰铁锂包覆层的质量比为1：2：200。
本实施例复合正极材料的制备方法包括如下步骤：
S1. 导电骨架与导电颗粒的复合物颗粒的制备：
S11.改性炭黑颗粒的制备：用1g炭黑使用0.02g醛基改性；
S12.改性碳纳米管的制备：取2g碳纳米管一端使用0.02g醛基改性；
S13.将改性炭黑与改性碳纳米管进行缩合反应：将改性碳纳米管与改性炭黑颗粒进行混合并进行加成化反应，将碳纳米管的改性端通过化学键连接在导电石墨的表面；
S2：将200g磷酸锰铁锂于管式炉内，通氮气，加2g葡萄糖650℃焙烧5h；
S3: 将步骤S2中磷酸锰铁锂利用砂磨工艺制备成浆料，然后利用喷雾干燥使得磷酸锰铁锂在复合物颗粒表面形成磷酸锰铁锂包覆层；
S4：将步骤S3中的复合材料于管式炉内，通氮气，加40g葡萄糖750℃焙烧5h，在磷酸锰铁锂包覆层外表面形成碳包覆层，得到复合正极材料；
S5：待步骤S4中生成的复合正极材料冷却后，进行粉碎、过筛制得粒径均一的复合正极材料。
实施例3
本实施例提供一种复合正极材料及制备方法。该复合正极材料的结构与实施例1中的复合正极材料结构相同，不同在于所含的炭黑颗粒、碳纳米管、磷酸锰铁锂包覆层和碳包覆层的质量比有区别。其中，炭黑颗粒、碳纳米管、磷酸锰铁锂包覆层的质量比为1：3：300。
本实施例复合正极材料的制备方法包括如下步骤：
S1. 导电骨架与导电颗粒的复合物颗粒的制备：
S11.改性炭黑的制备：用1g炭黑使用0.03g醛基改性；
S12.改性碳纳米管的制备：取3g碳纳米管一端使用0.03g酸酐改性；
S13.将改性碳源与改性碳纳米管进行缩合反应：将改性碳纳米管与改性炭黑颗粒进行混合并进行缩合化反应，将碳纳米管的改性端通过化学键连接在炭黑颗粒的表面；
S2：将300g磷酸锰铁锂于管式炉内，通氮气，加3g葡萄糖650℃焙烧5h；
S3: 将步骤S2中磷酸锰铁锂利用砂磨工艺制备成浆料，然后利用喷雾干燥使得磷酸锰铁锂在复合物颗粒表面形成磷酸锰铁锂包覆层；
S4：将步骤S3中的复合材料于管式炉内，通氮气，加60g葡萄糖750℃焙烧5h，在磷酸锰铁锂包覆层外表面形成碳包覆层，得到复合正极材料；
S5：待步骤S4中生成的复合正极材料冷却后，进行粉碎、过筛制得粒径均一的复合正极材料。
实施例4
本实施例提供一种复合正极材料及制备方法。该复合正极材料的结构与实施例1中的复合正极材料结构相同，不同在于炭黑颗粒被替换成LFP颗粒，磷酸锰铁锂包覆层被替换成LFP包覆层；其中，炭黑颗粒、碳纳米管、磷酸锰铁锂包覆层的质量比为1：1：200，而且经检测，碳纳米管的自由延伸端部分分布在LFP包覆层中，部分分布在碳包覆层中或/和表面。
本实施例复合正极材料的制备方法包括如下步骤：
S1. 1g LFP通氮气，加0.1g葡萄糖650℃焙烧5h；
S2. 待步骤S1中生成的LFP冷却后，进行粉碎、过筛制得粒径均一的LFP材料颗粒；
S3. 碳纳米管与LFP颗粒的复合物颗粒的制备：
S31.用1g LFP使用0.02g氨基改性；
S32.取1g碳纳米管末端使用0.02g羧基包覆；
S33.让含有氨基的LFP与羧基的碳纳米管球磨2h，使碳纳米管的改性端定向包覆于LFP表面，将骨架固定住。
S4：将200g磷酸锰铁锂于管式炉内，通氮气，加2g葡萄糖650℃焙烧5h；
S5: 将步骤S2中磷酸锰铁锂利用砂磨工艺制备成浆料，然后利用喷雾干燥使得磷酸锰铁锂在复合物颗粒表面形成磷酸锰铁锂包覆层；
S5：将步骤S3中的复合材料于管式炉内，通氮气，加20g葡萄糖750℃焙烧5h，在磷酸锰铁锂包覆层外表面形成碳包覆层，得到复合正极材料；
S6：待步骤S4中生成的复合正极材料冷却后，进行粉碎、过筛制得粒径均一的复合正极材料。
对比例1
提供实施例1中的磷酸锰铁锂正极材料，也即是不含炭黑颗粒和碳纳米管，单纯的为磷酸锰铁锂正极材料。
对比例2
本对比例提供一种单核多壳结构的磷酸锰铁锂及其制备方法，本对比例磷酸锰铁锂包括LiMn 0.7Fe 0.29V 0.01PO 4核体、包覆LiMn 0.7Fe 0.29V 0.01PO 4核体的碳中间包覆层、包覆碳中间包覆层的LiMn 0.5Fe 0.5PO 4中间包覆层和包覆LiMn 0.5Fe 0.5PO 4中间包覆层的无定型碳外包覆层。
本对比例磷酸锰铁锂的制备方法，包括如下步骤：
S1：称取化学计量比为0.7:0.29:1:1:0.005的Mn(CH 3COO) 2·4H 2O、FeC 2O 4· 2H2O、NH 4H 2PO 4、LiOH·H 2O和V 2O 5，再加入Mn(CH 3COO) 2·4H 2O、FeC 2O 4·2H 2O、NH 4H 2PO 4、LiOH·H 2O和V 2O 5总质量的20wt%的C 12H 22O 11葡萄糖，加入1g柠檬酸作为抗氧化剂，加入适量的去离子水作为助磨剂，以400rpm的转速球磨10h，将球磨产物于烘箱内60℃下干燥后，研磨并过200目筛，得到第一固体混合物；
S2：将第一固体混合物置于氧化铝瓷舟内，压实，于管式炉内，氩氢气氛下进行预烧成，预烧成从室温开始，以3℃/min的速率升温至300℃温度，烧成时间为5h后得到含碳包覆层的预烧成产物；
S3：将预烧成产物研磨过筛后，加入一定量的Mn(CH 3COO) 2·4H 2O、FeC 2O 4·2H 2O、LiOH·H 2O和NH 4H 2PO 4使Mn:Fe:L:P＝0.5:0.5:1:1，超声分散于去离子水后移入球磨罐中，400rpm下二次球磨5h；二次球磨产物于60℃下干燥后，研磨过200目筛，得到第二固体混合物；
S4：在液态碳源存在的条件下，将第二固体混合物在700℃下高温烧成10h，自然降温至室温得到核壳结构磷酸锰铁锂复合电极材料。
对比例3
提供一种复合正极材料，包括碳核体和包覆碳核体的LFMP包覆层。
本对比例复合正极材料的制备方法包括如下步骤：
S1：200g磷酸锰铁锂利用管式炉内通氮气，加2g葡萄糖650℃焙烧5h；
S2：得到的磷酸锰铁锂利用砂磨工艺制备成颗粒分散、均匀的浆料，然后利用喷雾干燥设备将磷酸锰铁锂浆料喷雾在2g固体碳源表面；
S3：取步骤2的磷酸锰铁锂利用管式炉内通氮气，加40g葡萄糖750℃焙烧5h；
S4：待步骤3获得的样品冷却后，进行粉碎、过筛制得粒径均一的纳米磷酸锰铁锂。
对比例4
提供一种复合正极材料，包括LFP核体和包覆碳核体的LFMP包覆层。
本对比例复合正极材料的制备方法包括如下步骤：
S1：2g磷酸铁锂和利用管式炉内通氮气，加0.1g葡萄糖650℃焙烧5h；
S2：待步骤1获得的样品冷却后，进行粉碎、过筛制得粒径均一的纳米磷酸铁锂；
S3：200g磷酸锰铁锂和利用管式炉内通氮气，加2g葡萄糖650℃焙烧5h；
S4：得到的磷酸锰铁锂利用砂磨工艺制备成颗粒分散、均匀的浆料，然后利用喷雾干燥设备将磷酸锰铁锂浆料喷雾在2g固体磷酸铁锂表面；
S5：取步骤4的磷酸锰铁锂利用管式炉内通氮气，加40g葡萄糖750℃焙烧5h；
S6：待步骤5获得的样品冷却后，进行粉碎、过筛制得粒径均一的纳米磷酸锰铁锂。
2. 锂离子电池实施例：
将上述实施例1至实施例4的复合正极材料和对比例提供的正极材料分别按照如下方法组装成正极电极和锂离子电池：
正电极：在相同的条件下，按照正极材料：Super P-Li:PVDF质量比为90:5:5的比例进行混合，溶剂采用NMP，混合方式为球磨机混合或者脱泡混料机混合，如果采用球磨机，则球磨时间为30 min；转速频率设置为20 HZ，如果采用匀浆脱泡机混合，则采用600rpm转速先混合30秒，再用2000rpm转速混合15min即可。经过匀浆-涂布-烘干-裁片操作，制备成正极片，正极片在100℃真空烘箱中烘烤，除去痕量水。其中，正极材料分别为上述实施例1至实施例4和对比例1至对比例3提供的正极材料；
负电极：石墨；
电解液：六氟磷酸锂（天赐导电液）；
隔膜：PE隔膜；
锂离子电池组装：在充满氩气，且水氧含量均低于10ppm的手套箱内组装成锂离子电池。
3.锂离子电池相关性能测试：
将上述锂离子电池实施例中组装的各锂离子电池相关电化学性能进行测试，测试条件为：
1.将导电剂SuperP-Li，粘结剂PVDF，活性物质LMFP，溶剂NMP，按一定比例加入到球磨杯中球磨至材料溶解并分散均匀，环境温度控制在25±10℃；
2.将配置好的浆料进行涂布并烘干得到LMFP极片，环境温度控制在25±10℃；
3.将极片进行裁圆，组装制作成扣电，环境温度控制在25±10℃；
4.将制作好的电池装上测试架进行测试，测试环境恒温25±2℃。
测得的结果如下表1 所示。
表1 
实验组别 循环性能 0.1C容量 mAh/g 0.1C比容量 wh/kg 压实 g/cm3 电阻率 Ω .cm
实施例1 ＞2000圈 156.2 585.6 2.453 1.3
实施例2 ＞2000圈 154.6 579.4 2.464 1.8
实施例3 ＞2000圈 154.3 578.9 2.458 2.8
实施例4 ＞2000圈 156.4 576.9 2.468 0.5
对比例1 ＞2000圈 137.6 520.2 2.458 54.3
对比例2 ＞1500圈 153.3 570.7 2.456 42.6
对比例3 ＞2000圈 138.3 519.8 2.453 64.1
对比例4 ＞2000圈 144.3 536.8 2.458 48.3
通过上表1的实施例以及对比例可以看出，本发明由于大大缩短了锂离子传输距离，能够将颗粒做大，且不影响产品循环性能，因此拥于循环性能好，放电效率高，压实性能高，电导率好等优点。
以上实施例仅表达了本申请的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对本申请专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请专利的保护范围应以所附权利要求为准。

Claims (15)

  1. 一种复合正极材料，其特征在于：包括导电核体和包覆所述导电核体的正极材料包覆层，其中，还包括导电骨架，且所述导电骨架一端与所述导电核体接触，另一端至少是延伸至所述正极材料包覆层中。
  2. 根据权利要求1所述的复合正极材料，其特征在于：所述导电核体、导电骨架和正极材料包覆层的质量比为1：（1-3）：（100-300）；和/或
    还包括导电包覆层，所述导电包覆层包覆在所述正极材料包覆层的外表面；和/或
    所述导电骨架的所述另一端延伸至所述正极材料包覆层的外表面。
  3. 根据权利要求2所述的复合正极材料，其特征在于：所述导电包覆层的厚度为2-20 nm；和/或
    所述导电包覆层所含的导电材料包括石墨、炭黑、乙炔黑中的至少一种；和/或
    所述导电骨架的所述另一端至少是延伸至所述导电包覆层的外表面。
  4. 根据权利要求1-3任一项所述的复合正极材料，其特征在于：所述导电骨架在延伸至所述正极材料包覆层中后弯曲或与所述导电骨架之间形成网络结构或者缠绕接触。
  5. 根据权利要求1所述的复合正极材料，其特征在于：所述导电核体的粒径为＜80nm；和/或
    所述导电骨架的长度为6-8 μm和/或
    所述正极材料包覆层的厚度为3-6 μm；和/或
    所述复合正极材料的D50为3-6 μm。
  6. 根据权利要求1-5任一项所述的复合正极材料，其特征在于：所述导电骨架为中空管结构；和/或
    导电骨架的材料包括碳纳米管、石墨片、导电石墨、碳纤维、石墨烯导电剂中的至少一种；和/或
    所述导电核体的材料包括正极材料、碳中的至少一种；和/或
    所述正极材料包覆层所含的正极材料包括磷酸盐系正极材料、锰酸锂中的至少一种。
  7. 根据权利要求6所述的复合正极材料，其特征在于：所述空管的中空管内径为2-20nm；
    所述导电骨架的材料为石墨片、导电石墨、碳纤维、石墨烯导电剂中的至少一种时，其长度或宽度或粒径为6-8μm；
    所述导电骨架的材料为石墨片或石墨烯时，其厚厚度为2-40nm。
  8. 根据权利要求6所述的复合正极材料，其特征在于：所述导电核体的材料所含的所述碳包括烧结碳；
    所述导电核体的材料所含的所述正极材料包括LFP、锰酸锂、磷酸锰锂等中的至少一种。
  9. 根据权利要求6所述的复合正极材料，其特征在于：所述导电核体为碳，所述导电骨架为碳纳米管，所述正极材料为磷酸锰铁锂；和/或
    所述中空管结构的长度为6-8 μm，中空管内径为2-20nm。
  10. 一种复合正极材料的制备方法，其特征在于，包括如下步骤：
    制备导电骨架与导电颗粒的复合物颗粒；其中，所述导电骨架的一端是结合在所述导电颗粒上，另一端背离所述导电颗粒形成自由延伸端；
    在所述复合物颗粒表面形成包覆于所述复合物颗粒的正极材料包覆层，其中，所述导电骨架的所述自由延伸端至少延伸至所述正极材料包覆层中，形成复合正极材料。
  11. 根据权利要求10所述的制备方法，其特征在于：所述制备导电骨架与导电颗粒的复合物颗粒的方法包括如下步骤：
    提供导电颗粒，对所述导电颗粒进行第一功能基团改性处理，得到改性导电颗粒；
    提供所述导电骨架，对所述导电骨架的其中一端进行第二功能基团改性处理，得到改性导电骨架；其中，所述第二功能基团为能够与所述第一功能基团进行化学反应形成化学键的功能基团；
    将所述改性导电颗粒与所述改性导电骨架进行第一混合处理并进行化学反应处理，使得所述导电骨架的改性端结合在所述导电颗粒上，得到所述复合物颗粒；
    和/或
    在所述复合物颗粒表面形成包覆于所述复合物颗粒的正极材料包覆层的方法包括如下步骤：
    将正极材料或正极材料前驱体与所述复合物颗粒进行第二混合处理，并包覆在所述复合物颗粒表面，后进行烧结处理；
    和/或
    在所述复合物颗粒表面形成包覆于所述复合物颗粒的正极材料包覆层的步骤之后，还包括在所述正极材料包覆层的表面形成包覆所述正极材料包覆层的导电包覆层的步骤。
  12. 根据权利要求11所述的制备方法，其特征在于：所述改性导电颗粒与所述改性导电骨架是按照所述导电颗粒与导电骨架质量比为1:（1-3）的比例进行所述第一混合处理；和/或
    所述导电颗粒包括导电颗粒；和/或
    所述第一功能基团和所述第二功能基团各自独立的包括羟基、醛基、羧基、氨基、酯基、酸酐中的至少一种。
  13. 根据权利要求11所述的制备方法，其特征在于：所述正极材料或正极材料前驱体与所述复合物颗粒是按照所述导电骨架与正极材料的质量比为1-3：（100-300）的比例进行所述第二混合处理；和/或
    所述烧结处理的温度为600-700℃，时间为5-8h。
  14. 一种正极片，包括集流体和结合在集流体表面的正极活性层，其特征在于：所述正极活性层中含有权利要求1-9任一项所述的复合正极材料或由权利要求10-13任一项所述的制备方法制备的复合正极材料。
  15. 一种二次电池，包括正极片和负极片，其特征在于：所述正极片为权利要求14所述的正极片。
PCT/CN2022/117376 2022-03-28 2022-09-06 复合正极材料及其制备方法和应用 WO2023184871A1 (zh)

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