WO2023041063A1 - 复合电极材料及其制备方法、锂电池及电子设备 - Google Patents

复合电极材料及其制备方法、锂电池及电子设备 Download PDF

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WO2023041063A1
WO2023041063A1 PCT/CN2022/119412 CN2022119412W WO2023041063A1 WO 2023041063 A1 WO2023041063 A1 WO 2023041063A1 CN 2022119412 W CN2022119412 W CN 2022119412W WO 2023041063 A1 WO2023041063 A1 WO 2023041063A1
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electrode material
composite
particles
organic fiber
composite electrode
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PCT/CN2022/119412
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English (en)
French (fr)
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沙玉静
夏圣安
谢封超
李阳兴
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华为技术有限公司
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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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • H01M4/04—Processes of manufacture in general
    • 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
    • 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

Definitions

  • the present application relates to the technical field of electrode materials, in particular to a composite electrode material and a preparation method thereof, a lithium battery and electronic equipment.
  • Secondary batteries and alkali metal batteries, especially lithium-ion batteries in secondary batteries, are widely used in consumer electronics, electric vehicles, electric ships, electric tools and sharing due to their high energy utilization efficiency, environmental friendliness and high energy density. It has gradually become the mainstream battery technology in the battery replacement market. Battery swelling is a common safe failure mode. For lithium-ion batteries, the main factor causing battery swelling is the gradual expansion of the thickness of the battery pole pieces during cycling. The reasons for the thickness expansion of the battery pole piece include crystal expansion caused by the lithium-deintercalation process of positive and negative electrode materials, surface SEI instability and repeated film formation caused by crystal expansion. Therefore, some electrode materials with high capacity characteristics cannot be widely used due to their high expansion rate.
  • the theoretical capacity of silicon is as high as 4200mAh/g, and it is a next-generation negative electrode material that is given high expectations in this field.
  • the expansion of silicon-based anode materials is as high as 300%. Therefore, the degradation of battery cycle performance and battery swelling caused by thickness expansion has become the biggest challenge in promoting the application of silicon batteries.
  • the application provides a composite electrode material and a preparation method thereof, a lithium battery and an electronic device, so as to solve the problem of electrode volume expansion.
  • the core surface of the material forms a solid cladding layer with a skeleton structure.
  • the high-strength properties and small tensile strain of the organic fiber coating can limit the volume expansion of the electrode material, while ensuring that the coating itself is not easily plastically deformed.
  • the organic fiber further has -COOH and/or -NH2. Based on -COOH and/or -NH2, the organic fibers can form abundant hydrogen bonds with the -OH on the surface of the inner core of the electrode material, so that the organic fibers can be firmly recombined on the inner core surface, thereby exerting a stable effect of reducing the volume expansion of the pole piece. effect.
  • the mass proportion of the organic fiber in the composite electrode material is 0.05%-1%.
  • This composite ratio can make the organic fibers form a coherent and uniform skeleton structure on the surface of the electrode material, ensuring the coating effect.
  • the composite ratio will not cause changes in the crystal structure and phase properties of the crystal particles of the electrode material, thereby ensuring stable electrochemical performance of the electrode material while limiting the volume expansion of the electrode material. That is to say, the composite ratio can take into account the effect of the organic fiber skeleton on the expansion limitation of the electrode material and the surface charge conductivity of the material.
  • the benzene ring structure is located in the macromolecular chain of the organic fiber, thereby forming a strong intermolecular conjugation, and such an organic fiber has higher stability.
  • the breaking strength of the organic fiber is greater than 3cN dtex-1, and the initial modulus of the above-mentioned organic fiber is greater than 50cN dtex-1, thereby ensuring the structural strength of the organic fiber and its binding to the electrode material effect.
  • the thickness of the organic fiber covering layer is 10 nm-200 nm.
  • the diameter of the organic fiber is 5nm-60nm, and the length is 1 ⁇ m-20 ⁇ m. This aspect ratio can form the best winding and wrapping effect with a small amount of compounding.
  • the organic fiber is aramid fiber, polyarylene oxadiazole fiber or aramid sulfone fiber.
  • the content of the aramid chain link in the aramid fiber is greater than 85%, the diameter of the aramid fiber is 5nm-40nm, and the length is 2 ⁇ m-20 ⁇ m. amount to form the best winding and wrapping effect.
  • the composite electrode material includes composite particles and/or polymer particles, the composite particles include an electrode material core and an organic fiber coating compounded on the surface of the electrode material core through bonding, and the polymer particles Formed by aggregation of composite particles.
  • the composite particles include primary composite particles and secondary composite particles, wherein the inner core of the primary composite particles is the inner core of the electrode material, and the inner core of the secondary composite particles is aggregated particles formed by polymerization of the primary composite particles.
  • the particles constituting the composite electrode material may be one or more of primary composite particles, secondary composite particles, and aggregated particles of primary composite particles and/or secondary composite particles. Since the particle structure and particle size of primary composite particles, secondary composite particles and their aggregated particles are different, when the composite electrode material contains multiple particles, the various particles can complement each other in performance, and can also be adjusted by adjusting the particle size of each particle. The content adjusts the particle size distribution of the composite electrode material, thereby adjusting the compaction density of the composite electrode material.
  • the composite electrode material further includes a conductive agent and/or an ion conductor.
  • the addition of the conductive agent and/or the ion conductor can compensate for the weakening of the conductivity of the composite electrode material caused by the non-conductivity of the organic fiber, thereby ensuring the surface charge conductivity of the composite electrode material.
  • the conductive agent and/or the ion conductor is coated on the surface of the composite particles and/or polymer particles, or mixed between the composite particles and/or polymer particles.
  • the conductive agent includes one or a combination of amorphous carbon, soft carbon, hard carbon, graphite, carbon nanotubes, graphene, and metal particles.
  • the electrode material includes a ternary positive electrode material, silicon-based, tin-based, sulfur-based, and metallic lithium negative electrode materials.
  • the composite electrode material includes an electrode material inner core and an organic fiber coating layer with a skeleton structure, and the organic fiber coating layer is compounded on the surface of the electrode material inner core through bonding.
  • the core surface of the material forms a solid cladding layer with a skeleton structure.
  • the high-strength properties and small tensile strain of the organic fiber coating can limit the volume expansion of the electrode material, while ensuring that the coating itself is not easily plastically deformed.
  • the present application also provides a composite electrode material, which is prepared by the preparation method described in the second aspect.
  • the present application also provides an application of a composite electrode material in the field of preparing lithium batteries.
  • the present application also provides a lithium battery, including a positive electrode material, an electrolyte, a separator, and a negative electrode material.
  • the positive electrode material or the negative electrode material adopts the composite electrode material described in any one of the implementations in the first aspect.
  • the present application also provides an electronic device, including a charge-discharge circuit and power consumption components, and also includes the lithium battery described in the fifth aspect, the lithium battery is connected to the charge-discharge circuit, and is charged through the charge-discharge circuit or used Electric components supply power.
  • the composite electrode material includes an electrode material inner core and an organic fiber coating layer with a skeleton structure, and the organic fiber coating layer is compounded on the surface of the electrode material inner core through bonding.
  • the core surface of the material forms a solid cladding layer with a skeleton structure.
  • the high-strength properties and small tensile strain of the organic fiber coating can limit the volume expansion of the electrode material, while ensuring that the coating itself is not easily plastically deformed. Furthermore, the cycle stability of the battery can be improved, the proportion of the battery in the internal cavity of the electronic device can be reduced, the available cavity space of key components such as chips and circuit boards in the electronic device can be increased, and the battery bulge and afterlife after a long cycle can be avoided. Cover tilt and other problems, improve the life and safety of electronic products.
  • Fig. 1 is the structural representation of the lithium-ion battery shown exemplary in the present application
  • Fig. 2 is the structural representation of the lithium ion battery composite electrode material that the embodiment of the present application provides;
  • Fig. 3 is the structural representation of the composite electrode material of lithium ion battery that the embodiment of the present application provides;
  • Fig. 4 is the structural representation of the lithium ion battery composite electrode material that the embodiment of the present application provides;
  • FIG. 5 is a schematic structural view of a lithium-ion battery composite electrode material provided in an embodiment of the present application.
  • Fig. 6 is the stress-strain curve of the aramid fiber, arylsulfone fiber, polyarylene oxadiazole, styrene-butadiene rubber and polyacrylic acid provided by the embodiment of the present application;
  • Fig. 7 is a flow chart of the preparation method of the composite electrode material provided by the embodiment of the present application.
  • Fig. 8 is the SEM image of the aramid nanofiber composite silicon oxide prepared in Example 2.
  • FIG. 9 is an electron microscope image of secondary composite particles of sulfonamide nanofibers and silicon oxide prepared in Example 5.
  • FIG. 1 is a schematic structural diagram of a lithium-ion battery exemplarily shown in the present application.
  • the lithium-ion battery includes a positive electrode, a negative electrode, an electrolyte, a diaphragm, and a corresponding circuit.
  • the positive/negative electrode material can deintercalate lithium ions to realize energy storage and release.
  • the electrolyte is the carrier for lithium ions to be transported between the positive/negative electrodes.
  • the non-conductive separator can permeate lithium ions but separates the positive/negative electrodes to prevent short circuits.
  • the positive/negative electrode material is the main part of the energy storage function, and it is the most direct embodiment of the energy density, cycle performance and safety performance of the battery cell.
  • the positive electrode in the lithium ion battery, can include an aluminum electrode plate and a positive electrode material, and the positive electrode material includes LiNixCoyMnzO, a ternary positive electrode material, nickel-cobalt-manganese oxide LiNixCoyMnzO2, wherein the ratio of nickel-cobalt-manganese (x: y:z) can be adjusted according to actual needs.
  • the positive electrode material includes LiNixCoyMnzO, a ternary positive electrode material, nickel-cobalt-manganese oxide LiNixCoyMnzO2, wherein the ratio of nickel-cobalt-manganese (x: y:z) can be adjusted according to actual needs.
  • the negative electrode may include copper electrode plates and negative electrode materials, and the negative electrode materials include carbon materials, silicon-based, tin-based, sulfur-based, metal lithium and other negative electrode materials.
  • lithium ions are extracted from the lattice of the positive electrode material, and inserted into the negative electrode material after passing through the electrolyte, so that the negative electrode is rich in lithium and the positive electrode is poor in lithium;
  • the material is detached from the material, and embedded in the lattice of the positive electrode material after passing through the electrolyte, making the positive electrode rich in lithium and the negative electrode poor in lithium.
  • the difference in the potential of the positive and negative electrode materials relative to the metal lithium when inserting and extracting lithium ions is the working voltage of the battery.
  • the positive electrode material and the negative electrode material are collectively referred to as electrode materials. That is to say, unless otherwise specified, the electrode material in the following embodiments refers to the positive electrode material and/or the negative electrode material, and the composite electrode material refers to the composite positive electrode material and/or the composite negative electrode material.
  • the embodiments of the present application provide a composite electrode material and a preparation method thereof.
  • the composite electrode material here is the active material of the lithium ion battery, which is used to make the electrode.
  • the composite electrode material uses the electrode material as the core material, and can effectively limit the volume expansion of the core material through the organic fiber skeleton structure coated on the outer layer of the core material.
  • FIG. 2 to FIG. 5 are structural schematic diagrams of the composite electrode materials for lithium-ion batteries provided in the embodiments of the present application.
  • the composite electrode material includes: an electrode material inner core 201 and an organic fiber coating layer 202 with a skeleton structure
  • the organic fiber coating layer 202 is made of organic fibers, which are formed by bonding Composite on the surface of the inner core 201 of the electrode material.
  • the organic fibers are bonded and entangled with each other, and at the same time cover the surface of the inner core 201 of the electrode material, forming an organic fiber skeleton on the surface of the inner core 201 of the electrode material.
  • the high-strength properties and small tensile strain of the organic fiber skeleton can limit the volume expansion of the electrode material, while ensuring that the organic fiber skeleton itself is not easily plastically deformed.
  • the so-called bonding between the organic fiber and the inner core of the electrode material in this application is not limited to chemical bonds such as metal bonds, ionic bonds, and covalent bonds, but also refers to hydrogen bonding.
  • the benzene ring structure is located in the macromolecular chain of the organic fiber, thereby forming a strong intermolecular conjugation, which provides force for the mutual adhesion and entanglement of the organic fibers, thereby ensuring the structure of the skeleton structure strength and stability.
  • the organic fiber may also contain -COOH and/or -NH2. Based on -COOH and/or -NH2, organic fibers can form abundant hydrogen bonds with -OH on the surface of the core material, so that the organic fibers can be firmly recombined on the surface of the core material, thereby exerting a stable reduction in the volume of the core material The role of expansion.
  • the organic fiber coating layer is not limited to being composited on the inner surface of the electrode material through hydrogen bonding.
  • groups that can form stable chemical bonds with the electrode material can be grafted on the chain structure of the organic fiber through a specific chemical treatment method, so that the organic fiber can be compounded in the inner core of the electrode material through chemical bonding. surface.
  • the mass proportion of organic fibers in the composite electrode material is a key factor affecting the strength and coating effect of the skeleton structure, and is also a key factor affecting the limiting effect on the volume expansion of the core material.
  • the composite ratio is too low, the skeleton structure formed by the organic fibers is not coherent enough, the gaps are too large, and a coherent coating effect cannot be formed on the surface of the core material, and the ability to limit the expansion of the core material is insufficient; the composite ratio is too high.
  • the poor conductivity of the organic fiber will lead to a decrease in the surface charge conductivity of the core material and affect the rate performance.
  • the mass proportion of the organic fiber in the composite electrode material is 0.05%-1%.
  • This composite ratio can make the organic fiber form a coherent and uniform skeleton structure on the surface of the core material, ensuring the coating effect.
  • the composite ratio will not cause changes in the crystal structure and phase properties of the crystal particles of the core material, thereby ensuring stable electrochemical performance of the electrode material while limiting the volume expansion of the electrode material. That is to say, the composite ratio can take into account the effect of the organic fiber skeleton on the expansion limitation of the core material and the surface charge conductivity of the material.
  • the breaking strength of the organic fiber is greater than 3 cN ⁇ dtex-1, and the initial modulus of the organic fiber is greater than 50 cN ⁇ dtex-1, so as to ensure the structural strength of the organic fiber and its binding effect on the electrode material.
  • the diameter of the organic fiber is 5 nm-60 nm, and the length is 1 ⁇ m-20 ⁇ m.
  • the aspect ratio of the organic fiber is greater than 30. Appropriate aspect ratio can form the best winding and wrapping effect with less compounding amount.
  • the thickness of the organic fiber coating is 10 nm-200 nm.
  • the above-mentioned organic fiber skeleton is composed of aramid fibers.
  • Aramid fiber is a kind of aromatic polyamide fiber, mainly including poly-p-phenylene diamine terephthalamide fiber (PPTA), hereinafter referred to as para-aramid fiber, and polyisophthalamide fiber.
  • PPTA poly-p-phenylene diamine terephthalamide fiber
  • MPIA Poly-metaphenylene isophthalamides
  • meta-aramid fiber The molecular structural formula of the meta-aramid fiber is as follows (1), and the molecular structural formula of the para-aramid fiber is as follows (2):
  • the diameter of the aramid fiber is 5nm-40nm, and the length is 2 ⁇ m-20 ⁇ m. Using the aramid fiber with an appropriate aspect ratio can form the best winding and wrapping effect with a small amount of compounding.
  • the above-mentioned organic fiber skeleton is composed of polyareneoxadiazole fibers.
  • Polyoxadiazole fiber aromaticpolyoxadiazole fiber, referred to as POD.
  • the main chain contains benzene rings and oxadiazole rings, the chain segments contain aromatic groups, and the macromolecular chains have a rigid rod-like structure.
  • Its molecular structural formula is as follows formula (3):
  • the above-mentioned organic fiber skeleton is composed of sulfonamide fibers.
  • Aramid sulfonamide fiber (Polysulfonamide fiber, referred to as PSA), is a kind of aromatic polyamide fiber containing sulfone group (-SO2-) in the polymer main chain, and its chemical name is terephthaloyl- 3,3-4,4-Diaminodiphenylsulfone fiber.
  • the fiber-forming polymer polysulfone amide is composed of terephthaloyl chloride and 4,4'-diaminodiphenylsulfone (4,4'-DDS) and 3,3'-diaminodiphenylsulfone (3,3' -DDS) is polycondensed, and is a linear macromolecule composed of amide groups and sulfone groups connected to p-phenyl and m-phenyl groups. Its molecular structure is shown in the following formula (4).
  • the organic fiber polymer used to prepare the composite electrode material has a film-forming tensile stress greater than 5 MPa and a tensile strain of less than 50%, so as to ensure that the organic fiber skeleton formed on the surface of the core material has high strength characteristics And low tensile strain characteristics, so that it can effectively limit the volume expansion of the electrode material, while ensuring that it is not easy to plastic deformation.
  • organic polymers that can be used to prepare composite electrode materials can be selected by testing the film-forming tensile stress and tensile strain of various organic polymers. For example, film-forming performance tests are performed on aramid, sulfonamide and polyarylene oxadiazole, styrene-butadiene rubber and polyacrylic acid.
  • aramid fiber slurry first prepare aramid fiber slurry, polysulfone fiber slurry, polyarylene oxadiazole slurry, styrene-butadiene rubber slurry and polyacrylic acid slurry respectively;
  • polytetrafluoroethylene mold frame air-dry at room temperature to form a film; cut the film into a 30mm ⁇ 3mm sample strip, and use the DMA-800 instrument of TA Company to test the tensile properties of the sample.
  • test conditions include, test mode: control Force mode (DMA Controlled force), test target: stress-strain (Stress-Strain), fixture: tensile film (Tensile Film), preload force: 0.1N, constant temperature: 25°C, standing time: 1min, lift rate : 1N/min; After testing, the stress-strain curve shown in Figure 6 was obtained.
  • A is the stress-strain curve of styrene-butadiene rubber film formation
  • B is the stress-strain curve of polyacrylic acid film formation
  • C is the stress-strain curve of aramid fiber film formation
  • D is the stress-strain curve of aramid fiber film formation
  • E is the stress-strain curve of polyarylene oxadiazole film formation.
  • the film-forming tensile stress of aramid fiber, polyaryl sulfone fiber and polyarylene oxadiazole is greater than 5MPa, and the tensile strain is less than 50%.
  • the film-forming tensile stress of styrene-butadiene rubber is less than 5MPa, and the tensile strain is greater than 500%.
  • the film-forming tensile stress of polyacrylic acid is greater than 5MPa, and the tensile strain is greater than 300%.
  • the organic fiber skeleton compounded on the surface of the core material is formed by intertwining high-strength nanofibers. Based on the high-strength properties of the organic fiber skeleton, the volume expansion of electrode materials can be effectively limited. It is worth noting that some strategies for coating with organic polymers to limit expansion take advantage of the elasticity and toughness of the polymer coating without considering the strength of the polymer coating. Unlike the rigid confinement of the organic fiber backbone described in this application, such polymer coatings act like "gummy candy". In addition, since the structure of the polymer coating layer is different from the structure of the organic fiber skeleton in this application, the principle and effect of limiting the expansion of the core material are also different.
  • the host particles of the composite electrode material comprise composite particles and/or polymeric particles.
  • Composite particles are based on a core body which has an organic fiber coating on its surface. It should be understood that the composite particles based on different nuclei have different particle structures, see Fig. 2 to Fig. 5 for details.
  • Aggregated particles refer to composite particle clusters formed by agglomeration of one or more types of composite particles.
  • FIG. 2 schematically shows an example of composite particles.
  • the composite particle 200 may include an electrode material inner core 201 and an organic fiber skeleton 202 compounded on the surface of the electrode material inner core 201 .
  • the composite particles shown in Fig. 2 with electrode material crystal particles as the core and coated with the organic fiber skeleton can be called primary composite particles.
  • the composite particle 300 may include a core group 301 formed by agglomerating multiple electrode material cores 201 and an organic fiber skeleton 302 compounded on the outer surface of the core group 301 .
  • the composite particle may also include a composite particle group formed by agglomerating a plurality of primary composite particles and an organic fiber skeleton compounded on the outer surface of the composite particle group.
  • a composite particle group formed by agglomerating a plurality of primary composite particles and an organic fiber skeleton compounded on the outer surface of the composite particle group.
  • the above-mentioned composite particles with the core group and/or composite particle group as the inner core and coated with the organic fiber skeleton can be called secondary composite particles.
  • Fig. 4 schematically shows an example of aggregated particles.
  • the aggregated particles 400 are formed by agglomerating primary composite particles 200 .
  • Fig. 5 schematically shows an example of aggregated particles.
  • the aggregated particles 500 are formed by agglomerating secondary composite particles 300 .
  • the structures of the polymeric particles provided in the present application include but are not limited to the structures shown in FIG. 4 and FIG. 5 above.
  • aggregated particles may also be aggregated from primary composite particles and secondary composite particles.
  • the host particles constituting the composite electrode material may be one or more of primary composite particles, secondary composite particles, and aggregated particles of primary composite particles and/or secondary composite particles. Since the particle structure and particle size of primary composite particles, secondary composite particles and their aggregated particles are different, when the composite electrode material contains multiple particles, the various particles can complement each other in performance, and can also be adjusted by adjusting the particle size of each particle. The content adjusts the particle size distribution of the composite electrode material, thereby adjusting the compaction density of the composite electrode material.
  • secondary composite particles and aggregated particles can be obtained by granulation.
  • the nucleosome group mentioned above can be obtained after a plurality of nucleosomes are bonded together.
  • nuclei clusters can be formed by the aggregation of multiple nuclei
  • particle clusters can be obtained after bonding particles with an organic fiber skeleton.
  • the way to obtain secondary composite particles and aggregated particles can be, for example, by controlling the temperature at which the core material particles or composite particles are located, so that the core material particles and composite particles form a core through the cohesiveness of their own materials. Agglomerates or particle groups; or, by adding a binder, the core material particles and composite particles have cohesive properties, thereby forming core groups or particle groups.
  • the method of obtaining secondary particles through granulation is not limited thereto, and the present application is not limited thereto.
  • the composite electrode material also includes a conductive agent.
  • the addition of the conductive agent can compensate for the weakening of the conductivity of the composite electrode material caused by the non-conductivity of the organic fiber, thereby ensuring the surface charge conductivity of the composite electrode material.
  • the conductive agent includes, but is not limited to, one or more combinations of amorphous carbon, soft carbon, hard carbon, graphite, carbon nanotubes, graphene, and metal particles.
  • the composite electrode material also includes an ionic conductor.
  • the addition of the ion conductor can improve the lithium ion diffusion ability of the composite electrode material.
  • Ionic conductors include, but are not limited to, solid electrolytes such as oxides and sulfides, and materials with multidimensional lithium ion channels.
  • the conductive agent and/or ion conductor is coated on the surface of the composite particles and/or polymeric particles, or mixed between the composite particles and/or polymeric particles.
  • the electrode material used to prepare the above-mentioned composite electrode material can be a positive electrode material or a negative electrode material.
  • the positive electrode material may be a ternary material.
  • the negative electrode material can be silicon-based, tin-based, sulfur-based, metal lithium and other materials, such as silicon, nano-silicon, micro-silicon, silicon oxide, silicon oxide (SiOx, 0 ⁇ x ⁇ 2), silicon carbon (Si/C) , porous silicon, thin film silicon, tin, tin dioxide, silicon-tin alloy, lithium-silicon alloy, lithium-phosphorus alloy, lithium titanate, etc.
  • negative electrode materials and positive electrode materials of the lithium ion battery listed above are only exemplary, and may also include other various materials, which are not limited in the embodiments of the present application.
  • Fig. 7 shows a flow chart of the preparation method of the composite electrode material provided by the embodiment of the present application. As shown in Figure 7, the following steps may be included:
  • a nanoscale organic fiber solution is prepared through S701, which is hereinafter referred to as a nanofiber solution for convenience of description.
  • the organic nanofiber solution can be prepared by using the precursor of the organic fiber molecule as the initial raw material.
  • the precursor here is based on the premise that the organic fiber molecule is the target product.
  • the precursor of organic fiber molecules is the existing form before obtaining organic fiber molecules.
  • aramid fiber as an example, in the embodiment of preparing aramid fiber by using p-phenylenediamine and terephthaloyl chloride, p-phenylenediamine and terephthaloyl chloride are precursors.
  • the nanofiber solution can also be prepared from the fiber-forming high polymer as the initial raw material.
  • the fiber-forming polymer namely fibril fibers, refers to large-sized fibers relative to nanofibers.
  • aramid nanofibers can be prepared using large-sized aramid fibers.
  • the methods for preparing the nanofiber solution include but are not limited to: polymerization-induced self-assembly method, electrospinning method, mechanical disintegration method and deprotonation method. in:
  • Polymerization-induced self-assembly refers to the method of directly preparing polymer nanofibers by polymerization of monomers.
  • aramid fiber as an example, in the traditional polymerization process, PPTA molecular chains are aggregated as the chain grows to form high molecular weight aramid fiber.
  • an inducer such as methoxypolyethylene glycol or polyethylene glycol dimethyl ether, needs to be added during the synthesis process.
  • the role of the inducer is to adjust the chain direction by forming hydrogen bonds with aramid nanofiber monomers, inhibit the irregular aggregation of aramid nanofiber monomer molecular chains caused by free assembly hydrogen bonds, and promote stable aramid fibers Nanofiber solution formation.
  • the self-assembly method is difficult to control the degree of polymerization, and often needs to introduce some inert groups to control the reaction speed and degree, so it is difficult to control the size of the final nanofibers.
  • the mechanical disintegration method is based on the strong atomic bonds along the axial direction and weak molecular bonds along the radial direction of the fiber molecular chain, so that the fiber has obvious strength anisotropy, so that the skin layer of the fiber is easily peeled off along the fiber axis under the action of mechanical fibrillation.
  • the fiber molecules can be hydrolyzed and pretreated by acid/alkali solution to assist mechanical disintegration, combined with alkane hydrolysis to change the ionic charge on the fiber surface, and finally prepare a nanoscale fiber solution.
  • the principle of the deprotonation method is to place the fiber in a strong alkali DMSO solution, and the negative charges gradually accumulate on the fiber molecular chain, generating electrostatic repulsion, and splitting the top fiber into PPTA microfibers with an average size of 1-2 ⁇ m.
  • the electrostatic repulsion between polymer chains becomes stronger and stronger, which provides the energy needed to break the hydrogen bonds between polymer chains, and finally obtains nanofibers with high aspect ratio.
  • the nanofibers Under the electrostatic repulsion, van der Waals force and ⁇ - ⁇ stack balance, the nanofibers can be stably dispersed.
  • the core material is the electrode material without surface treatment, which can be positive electrode material or negative electrode material.
  • the cathode material includes but not limited to ternary materials, such as NCM811.
  • Negative electrode materials include, but are not limited to, silicon-based, tin-based, sulfur-based, metallic lithium, and the like. It can be understood that the core material used is generally an electrode material with severe volume expansion.
  • freeze-drying, spray-drying, and hot-air drying can be used to dry the mixture of nuclei materials and organic fibers, and the drying parameters can be adjusted according to requirements.
  • the preparation method of the composite electrode material is introduced below through specific examples, and a lithium-ion battery is prepared with the sample of the composite electrode material prepared in the example, and the performance of the lithium-ion battery and the expansion of the pole pieces are tested.
  • Aramid nanofiber (ANFs) composite ternary cathode material (NCM811) was prepared with a composite ratio of 0.05%, hereinafter referred to as "ANFs-NCM811-0.05", and the specific implementation steps were as follows.
  • S110 preparing an aramid nanofiber solution. Specifically include:
  • the stirring speed can be controlled at 400 rpm.
  • the concentrations of terephthaloyl chloride and p-phenylenediamine are 0.21 and 0.20 mol/L respectively, and methyl ether accounts for 3 wt% of the total weight of terephthaloyl chloride and p-phenylenediamine.
  • Aramid nanofiber (ANFs) composite silicon oxide is prepared, the composite ratio is 0.1%, hereinafter referred to as "ANFs-SiO-0.1", the specific implementation steps are as follows.
  • S210 preparing an aramid fiber nanofiber solution. Specifically include:
  • S240 adding the lyophilized product into ethanol containing a small amount of water.
  • the ANF is reprotonated at a slower speed, and the connection between some nanofibers is repaired, so as to ensure the strength of the aramid nanofiber and its adhesion effect on the silicon oxide particles.
  • FIG. 8 is an electron microscope image of the aramid nanofiber composite silicon oxide prepared in Example 2.
  • aramid nanofiber (ANFs) composite silicon oxide the composite ratio is 0.5%, hereinafter referred to as "ANFs-SiO-0.5", the specific implementation steps are as follows.
  • S310 preparing an aramid fiber nanofiber solution. Specifically include:
  • Aramid nanofiber (ANFs) composite silicon oxide is prepared, the composite ratio is 1%, hereinafter referred to as "ANFs-SiO-1", the specific implementation steps are as follows.
  • S410 preparing an aramid nanofiber solution. Specifically include:
  • PSA-SiO-agg-0.5 sulfonamide nanofiber
  • S510 preparing a sulfonamide nanofiber solution. Specifically include:
  • S521 adding silicon oxide powder with a D50 of 5 ⁇ m into an ethanol solution to obtain a silicon oxide slurry; using zirconia sand ball milling beads with a diameter of 3 mm to perform sand grinding on the silicon oxide slurry.
  • the ball-to-material ratio is 10:1
  • the rotating speed is 3000rpm
  • the sanding time is 30min.
  • Sanding the silicon oxide powder by S521 can reduce the D50 of silicon oxide to less than 1 ⁇ m, and make the particle size distribution of silicon oxide more uniform.
  • the compounding ratio uniformly mixing the sand-milled silicon dioxide slurry and the polysulfone fiber nanofiber solution according to the compounding ratio, the compounding ratio is 0.5%.
  • FIG. 9 is an electron microscope image of secondary composite particles of sulfonamide nanofibers and silicon oxide prepared in Example 5.
  • S610 preparing a polyarylene oxadiazole nanofiber solution. Specifically include:
  • Si/C silicon carbon
  • Si/C silicon carbon
  • POD polyarylene oxadiazole nanofibers
  • SiO blank A silicon oxide material without surface treatment was used as the negative electrode material in Comparative Example 1, hereinafter referred to as "SiO blank".
  • a polyurethane (PUR) composite silicon oxide negative electrode material was prepared, with a composite ratio of 0.1%, hereinafter referred to as "PUR-SiO-0.1".
  • the specific preparation steps include: weighing 1g of polyurethane and dissolving it in water, stirring until the polyurethane is completely dissolved; weighing 1000g of SiO and adding it to the polyurethane solution, and stirring to obtain a mixed slurry; transferring the mixed slurry to a spray dryer, feeding N2, at 130 The spray drying is carried out at °C to obtain polyurethane (PUR) composite silicon oxide powder.
  • PUR polyurethane
  • a polyaniline (PANI) composite silicon oxide negative electrode material was prepared, with a compounding ratio of 0.5%, hereinafter referred to as "PANI-SiO-0.5".
  • the specific preparation steps include: weighing 1g of polyaniline and dissolving it in NMP, and stirring until the polyaniline is completely dissolved; weighing 200g of SiO and adding it to the polyaniline solution, and stirring to obtain a mixed slurry; transferring the mixed slurry to a spray dryer, and feeding N2, spray drying at 200°C to obtain solid powder.
  • Si/C blank The Si/C material without surface treatment was used as the negative electrode material in Comparative Example 4, hereinafter referred to as "Si/C blank".
  • SiO-agg blanks Aggregated silicon oxide particles were prepared, hereinafter referred to as "SiO-agg blanks".
  • the composite positive electrode material "ANFs-NCM811-0.05" prepared in Example 1 and the positive electrode material “NCM811 blank” prepared in Comparative Example 1 were respectively matched with graphite negative electrodes to assemble two sets of soft pack batteries with a capacity of 4Ah.
  • the battery packs are of the same design. Specifically, the surface density of the negative electrode is 12.8mg/cm2, the compacted density is 1.7g/cm3, the surface density of the positive electrode is 20.7mg/cm2, the compacted density is 3.5g/cm3, and the N/P ratio is 1.1.
  • NCM811 blank As shown in Table 1, compared with "NCM811 blank", the 1000-cycle capacity retention rate of "ANFs-NCM811-0.05” increased by 6%, and at the same time, the expansion rate of the positive electrode sheet improved by 2%. From the above results, the use of aramid nanofibers (ANFs) composite ternary cathode material (NCM811) can limit the expansion of the positive electrode sheet and improve the electrical performance of the battery. This is because, when charged to 4.3V, the polycrystalline high-nickel material releases nearly 80% of the lithium, the grain shrinks, and the micro-stress changes drastically.
  • the gram capacity, first-time efficiency, and rate performance of the composite electrode material remained basically unchanged.
  • the organic fiber coating on the surface of the negative core material will not affect the basic electrochemical performance of the core material. It is worth noting that, compared with the negative electrode material without surface treatment, the expansion rate of the composite negative electrode sheet was significantly improved after the battery was cycled for 50 cyls. It can be seen that the composite negative electrode material provided by the embodiment of the present application with an organic fiber coating layer on the surface has a significant effect of reducing the expansion of the pole piece.
  • composite electrode materials provided in the embodiments of the present application are not limited to the ones listed above. Based on the core idea of coating the surface of the core material with an organic fiber coating layer with a skeleton structure, the selection of the core material and organic fibers also depends on Other types may be included, which is not limited in this application.
  • the core surface of the material forms a solid cladding layer with a skeleton structure.
  • the high-strength properties and small tensile strain of the organic fiber coating can limit the volume expansion of the electrode material, while ensuring that the coating itself is not easily plastically deformed.
  • an embodiment of the present application also provides a lithium battery, including a positive electrode material, an electrolyte, a separator, and a negative electrode material, wherein the positive electrode material or the negative electrode material is the composite electrode material described above.
  • the embodiment of the present application also provides an electronic device, which includes a charging and discharging circuit and power consumption components, and also includes the above-mentioned lithium battery, the lithium battery is connected to the charging and discharging circuit, and is charged through the charging and discharging circuit or supplies power to the power consumption components.
  • the composite electrode material includes an electrode material inner core and an organic fiber coating layer with a skeleton structure, and the organic fiber coating layer is compounded on the surface of the electrode material inner core through bonding.
  • the core surface of the material forms a solid cladding layer with a skeleton structure.
  • the high-strength properties and small tensile strain of the organic fiber coating can limit the volume expansion of the electrode material, while ensuring that the coating itself is not easily plastically deformed. Furthermore, the cycle stability of the battery can be improved, the proportion of the battery in the internal cavity of the electronic device can be reduced, the available cavity space of key components such as chips and circuit boards in the electronic device can be increased, and the battery bulge and afterlife after a long cycle can be avoided. Cover tilt and other problems, improve the life and safety of electronic products.

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Abstract

本申请公开了复合电极材料及其制备方法、锂电池及电子设备。该复合电极材料包括电极材料内核和包覆的有机纤维骨架。其中，有机纤维所含有的-CO-NH-或者-C＝N-可以与电极材料内核表面的-OH形成丰富的氢键，使得有机纤维相互缠绕地复合在电极材料内核表面上，从而在电极材料内核表面形成牢固的有机纤维骨架。该有机纤维骨架的高强度特性和较小的拉伸应变可以限制电极材料的体积膨胀，同时保证本身不易发生塑性变形。进而，可以提高电池循环稳定性，减小电池在电子设备内部腔体中的占比，提高电子设备中芯片、电路板等关键器件的可用腔体空间，避免长循环后出现的电池鼓包、后盖翘起等问题，提高电子产品的寿命和安全性。

Description

复合电极材料及其制备方法、锂电池及电子设备
本申请要求在2021年9月17日提交中国专利局、申请号为202111117941.X、发明名称为“复合电极材料及其制备方法、锂电池及电子设备”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
本申请涉及电极材料技术领域，尤其涉及一种复合电极材料及其制备方法、锂电池及电子设备。
背景技术
二次电池及碱金属电池，尤其是二次电池中的锂离子电池，由于其能量利用效率高，环境友好，能量密度高等优点，在消费类电子产品、电动车、电动船舶、电动工具和共享换电市场中逐渐成为主流电池技术。电池鼓胀是一种常见的安全失效模式，对于锂离子电池而言，导致电池鼓胀的主要因素是循环过程中逐渐造成的电池极片厚度膨胀。而造成电池极片厚度膨胀的原因包括由于正负极材料的脱嵌锂过程引起的晶体膨胀、因晶体膨胀引起的表面SEI失稳和反复成膜等。因此，一些具有高容量特性的电极材料，却因具有较高的膨胀率而无法得到广泛应用。例如，硅的理论容量高达4200mAh/g，是本领域内被给予厚望的下一代负极材料。但硅基负极材料的膨胀高达300％。因此，因厚度膨胀带来的电池循环性能衰减和电池鼓胀成为推广硅电池应用的最大挑战。
针对电极材料晶体膨胀的问题，很多本领域技术人员通过在电极材料晶体颗粒表面包覆碳质材料或者陶瓷材料，来限制电极材料的晶体膨胀。但是，对于碳质材料来说，如果包覆量过多会影响可逆脱嵌锂效率，并且由于其结构强度不足，因此对电极材料晶体膨胀的改善效果较小。对于陶瓷材料来说，虽然其结构强度对于晶体膨胀的改善效果较好，但是由于其本身极易发生塑性变形，因此在晶体膨胀力或者膨胀程度较大时，晶体表面的陶瓷材料层将会破碎而失去效果。
发明内容
本申请提供一种复合电极材料及其制备方法和一种锂电池及电子设备，以解决电极体积膨胀的问题。
第一方面，本申请提供一种复合电极材料，包括电极材料内核和具有骨架结构的有机纤维包覆层，该有机纤维包覆层通过键合作用复合在电极材料内核表面；该有机纤维含有-CO-NH-和-C＝N-中的至少一种，以及苯环结构。其中，有机纤维所含有的-CO-NH-或者-C＝N-可以与电极材料内核表面的-OH形成丰富的氢键，使得有机纤维相互缠绕地复合在电极材料内核表面上，从而在电极材料内核表面形成牢固的且具有骨架结构的包覆层。该有机纤维包覆层的高强度特性和较小的拉伸应变可以限制电极材料的体积膨胀，同时保证包覆层本身不易发生塑性变形。
在第一方面可选择的实现方式中，该有机纤维还具有-COOH和/或-NH2。基于-COOH和/或-NH2，该有机纤维可与电极材料内核表面的-OH形成丰富的氢键，使得有机纤维足够牢固地的复合在内核表面，从而发挥出稳定的降低极片体积膨胀的作用。
在第一方面可选择的实现方式中，有机纤维在复合电极材料中的质量占比为0.05％-1％。该复合比例，可以使有机纤维在电极材料表面形成连贯、均匀的骨架结构，保证包覆效果。并且，该复合比例不会引起电极材料晶体颗粒的晶体结构及物相特性的改变，从而在限制电极材料体积膨胀的同时，保证电极材料的电化学性能稳定。也就是说，该复合比例可以兼顾有机纤维骨架对电极材料膨胀限制效果和材料表面电荷传导能力。
在第一方面可选择的实现方式中，苯环结构位于有机纤维的大分子链中，从而形成较强的分子间共轭作用，这样的有机纤维具有更高的稳定性。
在第一方面可选择的实现方式中，有机纤维的断裂强度大于3cN·dtex-1，上述有机纤维的初始模量大于50cN·dtex-1，从而保证有机纤维的结构强度及其对电极材料束缚作用。
在第一方面可选择的实现方式中，有机纤维包覆层的厚度为10nm-200nm。
在第一方面可选择的实现方式中，有机纤维的直径为5nm-60nm，长度为1μm-20μm，该长径比可以在较少的复合量形成最佳的缠绕及包覆效果。
在第一方面可选择的实现方式中，有机纤维为芳纶纤维、聚芳噁二唑纤维或芳砜纶纤维。
在第一方面可选择的实现方式中，芳纶纤维中芳酰胺链节含量大于85％，芳纶纤维的直径为5nm-40nm，长度为2μm-20μm，该长径比可以在较少的复合量形成最佳的缠绕及包覆效果。
在第一方面可选择的实现方式中，复合电极材料包括复合颗粒和/或聚合颗粒，复合颗粒包括电极材料内核和通过键合作用复合在电极材料内核表面上的有机纤维包覆层，聚合颗粒由复合颗粒聚合形成。
可选择的，复合颗粒包括一次复合颗粒和二次复合颗粒，其中，一次复合颗粒的内核为电极材料内核，二次复合颗粒的内核为一次复合颗粒聚合形成的聚合颗粒。也就是说，组成该复合电极材料的颗粒可以是一次复合颗粒、二次复合颗粒以及一次复合颗粒和/或二次复合颗粒的聚合颗粒中的一种或者多种。由于一次复合颗粒、二次复合颗粒及其聚合颗粒的颗粒结构、粒度均不同，因此当该复合电极材料包含多种颗粒时，多种颗粒在性能上相互弥补，还可以通过调整每种颗粒的含量调整复合电极材料的粒度分布，从而调整复合电极材料的压实密度。
在第一方面可选择的实现方式中，该复合电极材料还包括导电剂和/或离子导体。导电剂和/或离子导体的加入，可以补偿由于有机纤维不导电而造成的复合电极材料导电能力减弱的问题，从而保证复合电极材料表面电荷传导能力。
在第一方面可选择的实现方式中，导电剂和/或离子导体包覆在复合颗粒和/或聚合颗粒的表面，或者混合在复合颗粒和/或聚合颗粒之间。
在第一方面可选择的实现方式中，导电剂包括无定形碳、软碳、硬碳、石墨、碳纳米管、石墨烯、金属颗粒中的一种或多种的组合。
在第一方面可选择的实现方式中，电极材料包括三元正极材料，硅基、锡基、硫基、金属锂负极材料。
第二方面，本申请还提供一种复合电极材料的制备方法，该方法包括：制备有机纤维溶液，有机纤维含有-CO-NH-和-C＝N-中的至少一种，以及苯环结构；按照预定复合比例，将电极材料添加到所述有机纤维溶液中，搅拌至分散均匀；对电极材料与有机纤维的混合液进行干燥处理，得到复合电极材料。该复合电极材料包括电极材料内核和具有骨架结构的有机纤维包覆层，该有机纤维包覆层通过键合作用复合在电极材料内核表面。其中，有机纤维所含有的-CO-NH-或者-C＝N-可以与电极材料内核表面的-OH形成丰富的氢键，使得有机纤维相互缠绕地复合在电极材料内核表面上，从而在电极材料内核表面形成牢固的且具有骨架结构的包覆层。该有机纤维包覆层的高强度特性和较小的拉伸应变可以限制电极材料的体积膨胀，同时保证包覆层本身不易发生塑性变形。
第三方面，本申请还提供一种复合电极材料，该复合电极材料采用第二方面所述的制备方法制备得到。
第四方面，本申请还提供一种复合电极材料在制备锂电池的领域中的应用。
第五方面，本申请还提供一种锂电池，包括正极材料、电解液、隔膜和负极材料，正极材料或者负极材料采用第一方面中任一种实现方式所述的复合电极材料。
第六方面，本申请还提供一种电子设备，包括充放电电路以及用电元件，还包括第五方面所述的锂电池，锂电池与充放电电路连接，通过充放电电路进行充电或者为用电元件供电。
通过本申请实施例提供的复合电极材料及其制备方法，可以获得包括该复合电极材料锂电池，以及包括该锂电池的电子设备。该复合电极材料包括电极材料内核和具有骨架结构的有机纤维包覆层，该有机纤维包覆层通过键合作用复合在电极材料内核表面。其中，有机纤维所含有的-CO-NH-或者-C＝N-可以与电极材料内核表面的-OH形成丰富的氢键，使得有机纤维相互缠绕地复合在电极材料内核表面上，从而在电极材料内核表面形成牢固的且具有骨架结构的包覆层。该有机纤维包覆层的高强度特性和较小的拉伸应变可以限制电极材料的体积膨胀，同时保证包覆层本身不易发生塑性变形。进而，可以提高电池循环稳定性，减小电池在电子设备内部腔体中的占比，提高电子设备中芯片、电路板等关键器件的可用腔体空间，避免长循环后出现的电池鼓包、后盖翘起等问题，提高电子产品的寿命和安全性。
附图说明
图1为本申请示例性示出的锂离子电池结构示意图；
图2为本申请实施例提供的锂离子电池复合电极材料的结构示意图；
图3为本申请实施例提供的锂离子电池复合电极材料的结构示意图；
图4为本申请实施例提供的锂离子电池复合电极材料的结构示意图；
图5为本申请实施例提供的锂离子电池复合电极材料的结构示意图；
图6为本申请实施例提供的芳纶、芳砜纶及聚芳噁二唑、丁苯橡胶和聚丙烯酸的应力-应变曲线；
图7为本申请实施例提供的复合电极材料制备方法流程图；
图8为实施例2制得的芳纶纳米纤维复合氧化亚硅电镜图；
图9为实施例5制得的芳砜纶纳米纤维与氧化亚硅的二次复合颗粒的电镜图。
具体实施方式
为了使本技术领域的人员更好地理解本申请中的技术方案，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都应当属于本申请保护的范围。
图1为本申请示例性示出的锂离子电池结构示意图。其中，该锂离子电池包括正极、负极、电解液、隔膜以及相应的回路等。正/负极材料可以脱嵌锂离子实现能量的存储和释放，电解液是锂离子在正/负极之间传输的载体，不导电的隔膜可透过锂离子但将正/负极隔开防止短路。其中，正/负极材料是发挥储能功用的主体部分，是电芯的能量密度、循环性能及安全性能最直接的体现者。
在一种实现方式中，在该锂离子电池中，正极可以包括铝质电极板和正极材料，正极材料包括如三元正极材料镍钴锰酸锂LiNixCoyMnzO2，其中，镍钴锰的比例(x：y：z)可以根据实际需要调整。
在一种实现方式中，在该锂离子电池中，负极可以包括铜质电极板和负极材料，负极材料包括碳素材料、硅基、锡基、硫基、金属锂等负极材料。
示例性的，锂离子电池充电时，锂离子从正极材料的晶格中脱出，经过电解质后嵌入到负极材料中，使得负极富锂，正极贫锂；锂离子电池放电时，锂离子从负极材料中脱出，经过电解质后嵌入到正极材料的晶格中，使得正极富锂，负极贫锂。这样正负极材料在嵌入及脱出锂离子时相对于金属锂的电位的差值，就是电池的工作电压。
为便于说明，以下实施例中，将正极材料及负极材料统称为电极材料。也就是说，在没有特别说明的情况下，以下实施例中的电极材料指代正极材料和/或负极材料，复合电极材料指代复合正极材料和/或复合负极材料。
随电子产品对电池能量密度和快速充电能力的要求逐渐提高，锂离子电池的安全事故频发，引起市场和用户的广泛担忧。软包锂离子电池鼓胀是某些电子产品的常见安全失效模式。因电极材料晶体颗粒在循环充放电过程中的体积膨胀而导致的电极极片厚度增加，是引发电池鼓胀的常见原因。
基于此，一些具有高容量特性的电极材料，却因具有较高的膨胀率而无法得到广泛应用。以硅基负极材料为例，硅的理论容量高达4200mAh/g，是本领域内被给予厚望的下一代负极材料。然而，晶体硅在充电过程中会发生Si-Si键断裂，生成锂硅合金，该过程伴随巨大的体积膨胀。对材料本体来说，体积膨胀所产生大量的切应力，使硅颗粒破裂，内阻增大，影响电子在电极上的直接传输；对整个电极而言，体积膨胀导致的应力会引起电极结构的破坏，包括活性物质脱落、与粘结剂和导电网络剥离等，从而导致容量衰减。同时，体积膨胀会引起硅表面SEI失稳，继而反复破裂并与电解液不断产生新的SEI膜，消耗大量锂离子，并导致SEI逐渐增厚，阻碍电子转移和锂离子扩散，且阻抗和极化增加。此外，体积膨胀会导致原来分散的硅颗粒在嵌锂后出现融合，使局部硅颗粒尺寸变大，对后期循环和应力释放不利。可见，由于硅基 负极材料的体积膨胀，而带来的电池循环性能衰减和电池鼓胀成为硅基广泛应用的最大挑战。
针对电极材料体积膨胀的问题，本申请实施例提供一种复合电极材料及其制备方法。这里的复合电极材料为锂离子电池的活性材料，用于制作电极。该复合电极材料以电极材料作为核体材料，通过包覆在核体材料外层的有机纤维骨架结构，可以有效限制核体材料的体积膨胀。
图2至图5为本申请实施例提供的锂离子电池复合电极材料的结构示意图。
参阅图2，在某些实施例中，该复合电极材料包括：电极材料内核201和具有骨架结构的有机纤维包覆层202，该有机纤维包覆层202由有机纤维构成，其通过键合作用复合在电极材料内核201的表面。换句话说，有机纤维之间相互粘合、缠绕，同时包覆在电极材料内核201表面，在电极材料内核201表面形成有机纤维骨架。该有机纤维骨架的高强度特性和较小的拉伸应变可以限制电极材料的体积膨胀，同时保证有机纤维骨架本身不易发生塑性变形。
需要说明的是，本申请中有机纤维与电极材料内核之间的所谓键合作用，不仅限于指代金属键、离子键以及共价键等化学键，还指代氢键作用。其中，有机纤维的分子结构中含有-CO-NH-和-C＝N-中的至少一种，以及苯环结构。其中，该苯环结构位于有机纤维的大分子链中，从而形成较强的分子间共轭作用，该共轭作用为有机纤维之间相互粘合及缠绕提供作用力，进而保证骨架结构的结构强度和稳定性。-CO-NH-或者-C＝N-可以与电极材料内核表面的-OH形成丰富的氢键，氢键为有机纤维和电极材料内核之间提供结合力，使有机纤维牢固地复合在电极材料内核表面上。
在某些实施例中，该有机纤维还可以含有-COOH和/或-NH2。基于-COOH和/或-NH2，有机纤维可与核体材料表面的-OH形成丰富的氢键，使得有机纤维足够牢固地的复合在核体材料表面，从而发挥出稳定的降低核体材料体积膨胀的作用。
需要说明的是，有机纤维包覆层不限于通过氢键作用复合在电极材料内容表面。例如，在某些实施例中，可以通过特定的化学处理方法在有机纤维的链状结构上接枝可与电极材料形成稳定化学键的基团，从而使有机纤维可以通过化学键作用复合在电极材料内核表面。
值得注意的是，有机纤维在复合电极材料中的质量占比，是影响骨架结构的强度、包覆效果的关键因素，进而也是影响对核体材料体积膨胀的限制效果的关键因素。具体来说，复合比例过低时，有机纤维形成的骨架结构不够连贯、空隙过大且也无法在核体材料表面形成连贯的包覆效果，对核体材料膨胀的限制能力不足；复合比例过高时，因有机纤维导电性不佳，会导致核体材料表面电荷传导能力下降，影响倍率性能。
某些实施例中，有机纤维在复合电极材料中的质量占比为0.05％-1％。该复合比例，可以使有机纤维在核体材料表面形成连贯、均匀的骨架结构，保证包覆效果。并且，该复合比例不会引起核体材料晶体颗粒的晶体结构及物相特性的改变，从而在限制电极材料体积膨胀的同时，保证电极材料的电化学性能稳定。也就是说，该复合比例可以兼顾有机纤维骨架对核体材料膨胀限制效果和材料表面电荷传导能力。
某些实施例中，有机纤维的断裂强度大于3cN·dtex-1，上述有机纤维的初始模量大于50cN·dtex-1，从而保证有机纤维的结构强度及其对电极材料束缚作用。
某些实施例中，有机纤维的直径为5nm-60nm，长度为1μm-20μm。或者说，有机纤维的长径比大于30。适当的长径比可以在较少的复合量形成最佳的缠绕及包覆效果。
某些实施例中，有机纤维包覆层的厚度为10nm-200nm。
作为一个示例，上述有机纤维骨架由芳纶纤维构成。芳纶纤维是一种芳香族聚酰胺纤维，主要包括聚对苯二甲酰对苯二胺纤维(Poly-p-phenylene diamine terephthalamide fiber，PPTA)，以下简称对位芳纶纤维，和聚间苯二甲酰间苯二胺纤维(poly-metaphenylene isophthalamides,MPIA)，以下简称间位芳纶纤维。间位芳纶纤维的分子结构式如下式(1)，对位芳纶纤维的分子结构式如下式(2)：
(1)
Figure PCTCN2022119412-appb-000001
(2)
Figure PCTCN2022119412-appb-000002
在一些实现方式中，芳纶纤维的直径为5nm-40nm，长度为2μm-20μm，采用具有适当长径比的芳纶纤维，可以在较少的复合量形成最佳的缠绕及包覆效果。
作为一个示例，上述有机纤维骨架由聚芳噁二唑纤维构成。聚芳噁二唑纤维(aromaticpolyoxadiazole fiber，简称POD)。分子结构上，主链含有苯环和二唑环，链段含有芳香族基团，大分子链呈刚性棒状结构。其分子结构式如下式(3)：
(3)
Figure PCTCN2022119412-appb-000003
作为一个示例，上述有机纤维骨架由芳砜纶纤维构成。芳砜纶即聚砜酰胺纤维(Polysulfonamide fiber，简称PSA)，是一种在高分子主链上含有砜基(-SO2-)的芳香族聚酰胺纤维，其化学名称为对苯二甲酰-3，3-4，4-二胺基二苯砜纤维。成纤高聚物聚砜酰胺是由对苯二甲酰氯和4，4'-二氨基二苯矾(4，4'-DDS)及3，3'-二氨基二苯砜(3，3'-DDS)缩聚而成，是由酰胺基和砜基相互连接对位苯基和间位苯基所构成的线型大分子，其分子结构如下式(4)所示。
(4)
Figure PCTCN2022119412-appb-000004
在一些实施例中，用于制备复合电极材料的有机纤维高分子，其成膜拉伸应力大于5MPa，拉伸应变小于50％，以保证在核体材料表面形成的有机纤维骨架具有高强度特性和低拉伸应变特性，从而使其可以有效限制电极材料的体积膨胀，同时保证本身不易发生塑性变形。
示例性的，可以通过测试各种有机高分子的成膜拉伸应力及拉伸应变，选取可用于制备复合电极材料的有机高分子。例如，针对芳纶、芳砜纶及聚芳噁二唑、丁苯橡 胶和聚丙烯酸进行成膜性能测试。具体的，首先分别制备芳纶浆料、芳砜纶浆料及聚芳噁二唑浆料、丁苯橡胶浆料和聚丙烯酸浆料；然后依据预定固含量，取适量前述浆料分别注入到聚四氟乙烯模框中，室温下风干成膜；将成膜裁成30mm×3mm的样条，采用TA公司DMA-800仪器对样品进行拉伸性能测试，测试条件具体包括，测试模式：控制力模式(DMA Controlled force)，测试目标：应力-应变(Stress-Strain)，夹具：拉伸薄膜(Tensile Film)，预负载力：0.1N，恒温：25℃，静置时间：1min，升力速率：1N/min；经测试，得到如图6所示的应力-应变曲线。其中，A为丁苯橡胶成膜的应力-应变曲线，B为聚丙烯酸成膜的应力-应变曲线，C为芳砜纶成膜的应力-应变曲线，D为芳纶成膜的应力-应变曲线，E为聚芳噁二唑成膜的应力-应变曲线。
可以看出，芳纶、芳砜纶及聚芳噁二唑的成膜拉伸应力大于5MPa，拉伸应变小于50％，丁苯橡胶的成膜拉伸应力小于5MPa，拉伸应变大于500％，聚丙烯酸的成膜拉伸应力大于5MPa，拉伸应变大于300％。
需要说明的是，本申请中，复合在核体材料表面的有机纤维骨架是由高强度纳米纤维相互缠绕而成。基于该有机纤维骨架的高强度特性，可以有效限制电极材料的体积膨胀。值得注意的是，一些采用有机聚合物进行包覆以限制膨胀的方案，是利用聚合物包覆层的弹性和韧性，而未考虑聚合物包覆层的强度。不同于本申请所述有机纤维骨架的刚性限制作用，此类聚合物包覆层的作用效果类似于“橡皮糖”。另外，由于此类聚合物包覆层的结构与本申请中的有机纤维骨架的结构是不同的，因此二者限制核体材料膨胀的原理及效果也是不同的。
在某些实施例中，复合电极材料的主体颗粒包括复合颗粒和/或聚合颗粒。复合颗粒是指基于某个核体，该核体的表面具有有机纤维包覆层。应理解的是，基于不同核体的复合颗粒，其颗粒结构是不同的，具体可参见图2至图5。聚合颗粒是指由一种或者多种类型的复合颗粒团聚而成的复合颗粒团。
图2示例性示出了复合颗粒的一个示例。如图2所示，复合颗粒200可以包括电极材料内核201和复合在电极材料内核201表面上的有机纤维骨架202。为便于说明，可以将图2所示的以电极材料晶体颗粒为内核并包覆有机纤维骨架的复合颗粒称为一次复合颗粒。
图3示例性示出了复合颗粒的另一个示例。如图3所示，复合颗粒300可以包括由多个电极材料内核201团聚而成的核体团301以及复合在该核体团301外侧表面上的有机纤维骨架302。
应理解的是，复合颗粒还可以包括由多个一次复合颗粒团聚而成的复合颗粒团以及复合在该复合颗粒团外侧表面上的有机纤维骨架。为便于说明，可以将上述以核体团和/或复合颗粒团为内核并包覆有机纤维骨架的复合颗粒称为二次复合颗粒。
图4示例性示出了聚合颗粒的一个示例。如图4所示，该聚合颗粒400由一次复合颗粒200团聚而成。
图5示例性示出了聚合颗粒的一个示例。如图5所示，该聚合颗粒500由二次复合颗粒300团聚而成。
需要说明的是，本申请所提供的聚合颗粒的结构包括但不局限于上述图4及图5所示的结构。例如，聚合颗粒还可以由一次复合颗粒和二次复合颗粒聚合而成。
换句话说，组成该复合电极材料的主体颗粒可以是一次复合颗粒、二次复合颗粒以及一次复合颗粒和/或二次复合颗粒的聚合颗粒中的一种或者多种。由于一次复合颗粒、二次复合颗粒及其聚合颗粒的颗粒结构、粒度均不同，因此当该复合电极材料包含多种颗粒时，多种颗粒在性能上相互弥补，还可以通过调整每种颗粒的含量调整复合电极材料的粒度分布，从而调整复合电极材料的压实密度。
应理解的是，二次复合颗粒及聚合颗粒可以通过造粒的方式获得。其中，上文所说的核体团可以是多个核体粘结后获得的。换句话说，核体团可以是多个核体聚集形成的，颗粒团可以指具有有机纤维骨架的颗粒粘结后获得的。示例性的，获得二次复合颗粒及聚合颗粒的方式例如可以是：通过控制核体材料颗粒或者复合颗粒所处的温度，使得核体材料颗粒和复合颗粒通过自身材料的粘结性，形成核体团或者颗粒团；或者，通过添加粘结剂的方式，使得核体材料颗粒和复合颗粒具有粘结性，从而形成核体团或者颗粒团。其中，通过造粒方式获得二次颗粒的方式不限于此，本申请对此并不限定。
在某些实施例中，复合电极材料还包括导电剂。导电剂的加入，可以补偿由于有机纤维不导电而造成的复合电极材料导电能力减弱的问题，从而保证复合电极材料表面电荷传导能力。导电剂包括但不限于无定形碳、软碳、硬碳、石墨、碳纳米管、石墨烯、金属颗粒中的一种或多种的组合。
在某些实施例中，复合电极材料还包括离子导体。离子导体的加入，可以提高复合电极材料的锂离子扩散能力。离子导体包括但不限于氧化物、硫化物等固态电解质，以及具有多维锂离子通道的材料。
在可选择的实现方式中，导电剂和/或离子导体包覆在复合颗粒和/或聚合颗粒的表面，或者混合在复合颗粒和/或聚合颗粒之间。
在一些实施例中，用于制备上述复合电极材料的电极材料，即核体材料，可以是正极材料，也可以是负极材料。其中，正极材料可以是三元材料。负极材料可以是硅基、锡基、硫基、金属锂等材料，如硅、纳米硅、微米硅、氧化硅、氧化亚硅(SiOx,0<x<2)、硅碳(Si/C)、多孔硅、薄膜硅、锡、二氧化锡、硅锡合金、锂硅合金、锂磷合金、钛酸锂等。
应理解，以上列举的锂离子电池的负极材料、正极材料仅为示例性举例，其还可以包括其他多种材料，本申请实施例对此并不限定。
以下对本申请实施例提供的复合电极材料的制备方法进行介绍。图7示出了本申请实施例提供的复合电极材料制备方法流程图。如图7所示，可以包括如下步骤：
S701，制备有机纤维溶液，该有机纤维的分子结构中含有-CO-NH-和-C＝N-中的至少一种，以及苯环结构。
在一些实施例中，通过S701制备纳米级的有机纤维溶液，为便于说明，以下称为纳米纤维溶液。
其中，可以以有机纤维分子的前驱体为初始原料，制备有机纳米纤维溶液。这里的前驱体是在将有机纤维分子作为目标产物的前提下而言的。换句话说，有机纤维分子的前驱体是获得有机纤维分子前的存在形式。以芳纶纤维为例，在采用对苯二胺和对苯二甲酰氯制备芳纶纤维的实施例中，对苯二胺和对苯二甲酰氯即为前驱体。也可 以以成纤高聚物为初始原料，制备纳米纤维溶液。这里的成纤高聚物即原纤纤维，是指相对于纳米纤维而言的大尺寸纤维。例如，可以采用大尺寸芳纶纤维制备芳纶纳米纤维。
具体的，制备纳米纤维溶液的方法包括但不限于：聚合诱导自组装法、电纺丝法、机械解体法和去质子法。其中：
聚合诱导自组装是指利用单体聚合直接制备高分子纳米纤维的方法。以芳纶纤维为例，在传统的聚合工艺中，PPTA分子链随着链的生长而聚集，并形成高分子量芳纶纤维。为得到芳纶纳米纤维，而不是大尺寸芳纶纤维，在合成过程中需要加入诱导剂，如甲氧基聚乙二醇或聚乙二醇二甲醚。诱导剂的作用是通过与芳纶纳米纤维单体之间形成氢键来调整链的方向，抑制由自由组装氢键引起的芳纶纳米纤维单体分子链的不规则聚集，促进稳定的芳纶纳米纤维溶液形成。但需注意的是，自组装法难控制聚合程度，往往需要引入一些惰性基团控制反应速度和程度，因此难以控制最终得到的纳米纤维的尺寸。
静电纺丝制备纤维的工艺过程中，需先使用强酸或者强碱溶解纤维得到电纺原液，并使得到的溶液在强电场中进行喷射纺丝。在电场作用下，针头处的液滴会由球形变为圆锥形(即“泰勒锥”)，并从圆锥尖端延展得到纤维细丝。因需要用强酸或者强碱溶解纤维，使电纺原液的电导率偏高，或溶液粘度不匹配，导致出丝难度增加。
机械解体法是基于纤维分子链沿轴向强原子键和沿径向弱分子键使纤维具有明显的强度各项异性，使纤维的表皮层在机械纤颤力作用下容易沿纤维轴剥落。其中，可以通过酸/碱溶液对纤维分子进行水解预处理，以辅助机械力崩解，并结合烷烃水解处理改变纤维表面的离子电荷，最终制备得到纳米级纤维溶液。
去质子法的原理是将纤维置于强碱DMSO溶液中，负电荷逐渐聚集在纤维分子链上，产生静电斥力，将顶部的纤维分裂成平均为1-2μm的PPTA微纤维。随着去质子作用的增加，聚合物链之间的静电斥力越来越强，为破坏聚合物链之间的氢键提供了所需的能量，最终获得高宽长径比的纳米纤维。在静电斥力、范德华力和π-π叠层平衡下，纳米纤维能够稳定地分散。
S702，将核体材料加入到有机纤维溶液中，分散均匀。
核体材料即未经表面处理的电极材料，可以是正极材料，也可以是负极材料。其中，正极材料包括但不限于三元材料，如NCM811。负极材料包括但不限于硅基、锡基、硫基、金属锂等。可以理解的是，所采用的核体材料一般是体积膨胀严重的电极材料。
S703，对核体材料与有机纤维的混合液进行干燥处理，得到复合电极材料。
其中，可采用冷冻干燥、喷雾干燥、热风干燥的方式对核体材料与有机纤维的混合液进行干燥处理，并可以根据需求调整干燥参数。
值得注意的是，在进行干燥处理时，无需惰性气体氛围，无需热处理(半碳化)，从而保证包覆层的强度。
以下通过具体的实施例介绍复合电极材料的制备方法，并以在实施例中制备的复合电极材料样本制备锂离子电池，测试锂离子电池的性能及极片的膨胀情况。
实施例1
制备芳纶纳米纤维(ANFs)复合三元正极材料(NCM811)，复合比例为0.05％，以下简称为“ANFs-NCM811-0.05”，具体实施步骤如下。
S110，制备芳纶纳米纤维溶液。具体包括：
S111，将100mL N-甲基吡咯烷酮加入反应容器中，在氮气气氛下加热至100℃。
S112，在100℃条件下搅拌5min。
S113，加入CaCl2和甲醚，并在100℃下搅拌溶解30min。
S114，冷却至0℃，加入对苯二胺，搅拌直到对苯二胺完全溶解。
在上述步骤中，搅拌速度可以控制在400转/分。
S115，加入对苯二甲酰氯，搅拌，开始反应。其中，搅拌速度可以控制在2000转/分。
在上述反应体系中，对苯二甲酰氯和对苯二胺的浓度分别为0.21和0.20mol/L，甲醚占对苯二甲酰氯和对苯二胺总重量的3wt％。
S116，反应停止后，使用N-甲基吡咯烷酮稀释反应产物，加入一定量的去离子水。
S117，将稀释后的产物置于高剪切均质器中进行均质，得到浓度为0.1％的芳纶纳米纤维溶液。其中，均质器的速度为10000rpm，均质时间为5min
S120，将NCM811材料加入到上述芳纶纳米纤维溶液中，低速搅拌分散均匀，其中，NCM811材料与芳纶纳米纤维的质量比为0.05:99.95。
S130，将NCM811材料与芳纶纳米纤维的混合液转移到冷冻干燥机中，在-60℃左右的条件下冻干，收集产物，即为芳纶纳米纤维(ANFs)复合多晶三元正极材料(NCM811)。
实施例2
制备芳纶纳米纤维(ANFs)复合氧化亚硅，复合比例为0.1％，以下简称为“ANFs-SiO-0.1”，具体实施步骤如下。
S210，制备芳纶纳米纤维溶液。具体包括：
S211，将0.5g聚对苯二甲酰对苯二胺和1.0gKOH的混合物加入到300mL的二甲基亚砜中，在室温下磁搅拌7天，得到均匀透明的ANF/DMSO溶液。
S212，采用二甲基亚砜稀释反应产物，将ANF的浓度稀释到0.05％。
S220，将500g氧化亚硅粉末加入到上述ANF浓度为0.05％的ANF/DMSO溶液中，搅拌均匀后，转移到混匀机中，以1200rpm震动15min。
S230，将氧化亚硅与ANF/DMSO的混合液置于冷冻干燥机中，在-60℃左右的条件下冻干。
S240，将冻干产物加入到含有微量水的乙醇中。通过S240，以较慢的速度对ANF重新进行质子化，修复部分纳米纤维之间的连接，保证芳纶纳米纤维的强度和其在氧化亚硅颗粒的附着效果。
S250，将S240中的溶液置于冷冻干燥机中，在-60℃左右的条件下冻干，收集产物，即为芳纶纳米纤维(ANFs)复合氧化亚硅。
图8为实施例2制得的芳纶纳米纤维复合氧化亚硅电镜图。
实施例3
制备芳纶纳米纤维(ANFs)复合氧化亚硅，复合比例为0.5％，以下简称为 “ANFs-SiO-0.5”，具体实施步骤如下。
S310，制备芳纶纳米纤维溶液。具体包括：
S311，将0.5g聚对苯二甲酰对苯二胺和1.0gKOH的混合物加入到300mL的二甲基亚砜中，在室温下磁搅拌7天，得到均匀透明的ANF/DMSO溶液。
S312，采用二甲基亚砜稀释反应产物，将ANF的浓度稀释到0.05％。
S320，将100g氧化亚硅粉末加入到上述ANF浓度为0.05％的ANF/DMSO溶液中，搅拌均匀后，转移到混匀机中，以1200rpm震动15min。
S330，将氧化亚硅与ANF/DMSO的混合液置于冷冻干燥机中，在-60℃左右的条件下冻干。
S340，将冻干产物加入到含有微量水的乙醇中。通过S340，以较慢的速度对ANF重新进行质子化，修复部分纳米纤维之间的连接，保证芳纶纳米纤维的强度和其在氧化亚硅颗粒的附着效果。
S350，将S340中的溶液置于冷冻干燥机中，在-60℃左右的条件下冻干，收集产物，即为芳纶纳米纤维复合氧化亚硅。
实施例4
制备芳纶纳米纤维(ANFs)复合氧化亚硅，复合比例为1％，以下简称为“ANFs-SiO-1”，具体实施步骤如下。
S410，制备芳纶纳米纤维溶液。具体包括：
S411，将0.5g聚对苯二甲酰对苯二胺和1.0gKOH的混合物加入到300mL的二甲基亚砜中，在室温下磁搅拌7天，得到均匀透明的ANF/DMSO溶液。
S412，采用二甲基亚砜稀释反应产物，将ANF的浓度稀释到0.05％。
S420，将50g氧化亚硅粉末加入到上述ANF浓度为0.05％的ANF/DMSO溶液中，搅拌均匀后，转移到混匀机中，以1200rpm震动15min。
S430，将氧化亚硅与ANF/DMSO的混合液置于冷冻干燥机中，在-60℃左右的条件下冻干。
S440，将冻干产物加入到含有微量水的乙醇中。通过S340，以较慢的速度对ANF重新进行质子化，修复部分纳米纤维之间的连接，保证芳纶纳米纤维的强度和其在氧化亚硅颗粒的附着效果。
S450，将S440中的溶液置于冷冻干燥机中，在-60℃左右的条件下冻干，收集产物，即为芳纶纳米纤维复合氧化亚硅。
实施例5
制备芳砜纶纳米纤维(PSA)复合氧化亚硅二次复合颗粒，复合比例为0.5％，以下简称为“PSA-SiO-agg-0.5”，具体实施步骤如下。
S510，制备芳砜纶纳米纤维溶液。具体包括：
S511，将原纤PSA纤维和KOH按1:1质量配比，加入到N-甲基吡咯烷酮溶液中，搅拌30min。
S512，将搅拌后的溶液置于超声波细胞粉碎机中，在18kHz-21kHz条件下，对溶液中的芳砜纶纤维进行超声剥离处理，得到芳砜纶纳米纤维溶液。
S520，制备氧化亚硅与芳砜纶纳米纤维的混合液。
S521，将D50为5μm的氧化亚硅粉末加入到乙醇溶液中，得到氧化亚硅浆料；使用直径为3mm的氧化锆砂球磨珠，对该氧化亚硅浆料进行砂磨处理。其中，球料比为10:1，转速为3000rpm，砂磨时间为30min。通过S521对氧化亚硅粉末进行砂磨处理，可使氧化亚硅得D50降低到1μm以下，并使氧化亚硅的粒径分布更为均匀。
S522，将经砂磨处理的氧化亚硅浆料与芳砜纶纳米纤维溶液按复合配比混合均匀，复合配比为0.5％。
S530，将氧化亚硅与芳砜纶纳米纤维的混合液转移到闭式喷雾干燥容器中，在离心雾化盘的速度为15000rpm、雾化温度为150℃、干燥介质为N2的条件下，对混合液进行喷雾干燥处理，得到芳砜纶纳米纤维与氧化亚硅的二次复合颗粒。
图9为实施例5制得的芳砜纶纳米纤维与氧化亚硅的二次复合颗粒的电镜图。
实施例6
制备聚芳噁二唑纳米纤维(POD)复合硅碳(Si/C)，复合比例为1％，以下简称为“POD-Si/C-1”，具体实施步骤如下。
S610，制备聚芳噁二唑纳米纤维溶液。具体包括：
S611，将原纤POD纤维和KOH按1:1质量配比，加入到300ml的N-甲基吡咯烷酮溶液中，搅拌7天，得到POD/DMSO悬浊液。
因为POD中苯环和杂环共轭作用较强，因此在经历强碱DMSO环境搅拌7天后仅能达到部分去质子化形成纳米纤维。
S612，将POD/DMSO悬浊液倒入离心管中，在10000rpm转速下，离心分离15min后取上层透明溶液部分，得到POD纳米纤维/DMSO分散液。
S620，按照复合比例，向POD纳米纤维/DMSO分散液加入硅碳(Si/C)粉末，在300rpm转速条件下，搅拌6h。
S630，将硅碳(Si/C)粉末与POD纳米纤维的混合液置于鼓风干燥箱中，在60℃条件下干燥完全，收集产物，得到聚芳噁二唑纳米纤维(POD)复合硅碳(Si/C)。
对比例1
以未经表面处理的氧化亚硅材料，作为对比例一中的负极材料，以下简称为“SiO空白”。
对比例2
制备聚氨酯(PUR)复合氧化亚硅负极材料，复合比例为0.1％，以下简称为“PUR-SiO-0.1”。
具体制备步骤包括：称取1g聚氨酯溶于水中，搅拌至聚氨酯完全溶解；称取1000gSiO加入聚氨酯溶液中，搅拌得到混合浆料；将混合浆料转移至喷雾干燥机中，通入N2，在130℃下进行喷雾干燥，得到聚氨酯(PUR)复合氧化亚硅粉料。
对比例3
制备聚苯胺(PANI)复合氧化亚硅负极材料，复合比例为0.5％，以下简称为“PANI-SiO-0.5”。
具体制备步骤包括：称取1g聚苯胺溶于NMP中，搅拌至聚苯胺完全溶解；称取200gSiO加入聚苯胺溶液中，搅拌得到混合浆料；将混合浆料转移至喷雾干燥机中，通入N2，在200℃下进行喷雾干燥，得到固体粉料。
对比例4
以未经表面处理的Si/C材料，作为对比例四中的负极材料，以下简称为“Si/C空白”。
对比例5
制备氧化亚硅聚合颗粒，以下简称为“SiO-agg空白”。
具体实施步骤如下：
将D50为5μm的氧化亚硅粉末加入到乙醇溶液中，得到氧化亚硅浆料；使用直径为3mm的氧化锆砂球磨珠，对该氧化亚硅浆料进行砂磨处理。其中，球料比为10:1，转速为3000rpm，砂磨时间为30min。将经砂磨处理的氧化亚硅浆料转移到闭式喷雾干燥容器中，在离心雾化盘的速度为15000rpm、雾化温度为150℃、干燥介质为N2的条件下进行喷雾干燥处理，得到氧化亚硅聚合颗粒。
材料性能测试
将实施例1中制备的复合正极材料“ANFs-NCM811-0.05”和对比例1中制备的正极材料“NCM811空白”分别与石墨负极搭配，组装成两组容量为4Ah的软包电池，该两组电池设计相同。具体的，负极面密度为12.8mg/cm2，压实密度为1.7g/cm3，正极面密度为20.7mg/cm2，压实密度为3.5g/cm3，N/P比为1.1。
在1C电流密度下，对上述两组电池进行循环充放电测试，1000cyls后，测试容量保持率，并拆解正极极片，测试正极极片膨胀率。测试结果如下表1所示：
表1
Figure PCTCN2022119412-appb-000005
如表1所示，相对于“NCM811空白”，“ANFs-NCM811-0.05”的1000次循环容量保持率提升6％，同时，正极极片的膨胀率改善2％。从上述结果来看，采用芳纶纳米纤维(ANFs)复合三元正极材料(NCM811)正极材料，可以限制正极极片的膨胀，同时提升电池电性能。这是因为，充电至4.3V时，多晶高镍材料脱出近80％的锂，晶粒收缩，微应力变化剧烈，放电时，多晶高镍材料嵌锂，晶粒体积又发生膨胀，晶粒反复的收缩和膨胀导致晶格坍塌和晶粒微裂缝，继而引起极片不可逆膨胀、厚度增加。同时，颗粒间失去接触，导电性下降，甚至失去导电网络，电性能随之下降。
将实施例2-6中制备的“ANFs-SiO-0.1”、“ANFs-SiO-0.5”、“ANFs-SiO-1”、“PSA-SiO-agg-0.5”、“POD-Si/C-1”，以及对比例1-5中制备的“PUR-SiO-0.1”、“PANI-SiO-0.5”、“Si/C空白”及“SiO-agg空白”，分别按照复合电极材料：导电剂(SP)：粘结剂＝75％：15％：10％的比例，制备浆料及负极极片，并与金属锂对正极搭配制备扣式电池。
对上述制备的十组扣式电池进行测试，包括可逆克容量、首次效率、倍率性能、50cyls循环容量保持率以及负极极片膨胀情况，测试结果如下表2所示：
表2
Figure PCTCN2022119412-appb-000006
如表2所示，相对于未经表面处理的电极材料，复合电极材料的克容量、首次效率和倍率性能基本保持不变。换句话说，负极核体材料表面的有机纤维包覆层，不会影响核体材料的基础电化学性能。值得注意的是，相对于未经表面处理的负极材料而言，电池循环50cyls后，复合负极极片的膨胀率明显改善。可见，本申请实施例提供的表面具有有机纤维包覆层的复合负极材料具有显著的降低极片膨胀的效果。
应理解，本申请实施例提供的复合电极材料不仅限于上述列举的几种，基于在核体材料表面包覆具有骨架结构的有机纤维包覆层的核心思路，核体材料及有机纤维的选择还可以包括其他多种，本申请对此并不限定。
由以上实施例可以看出，本申请提供一种复合电极材料，包括电极材料内核和具有骨架结构的有机纤维包覆层，该有机纤维包覆层通过键合作用复合在电极材料内核表面；该有机纤维含有-CO-NH-和-C＝N-中的至少一种，以及苯环结构。其中，有机纤维所含有的-CO-NH-或者-C＝N-可以与电极材料内核表面的-OH形成丰富的氢键，使得有机纤维相互缠绕地复合在电极材料内核表面上，从而在电极材料内核表面形成牢固的且具有骨架结构的包覆层。该有机纤维包覆层的高强度特性和较小的拉伸应变可以限制电极材料的体积膨胀，同时保证包覆层本身不易发生塑性变形。
此外，本申请实施例还提供一种锂电池，包括正极材料、电解液、隔膜和负极材料，其特征在于，正极材料或者负极材料采用上述复合电极材料。
本申请实施例还提供一种电子设备，包括充放电电路以及用电元件，还包括上述锂电池，锂电池与充放电电路连接，通过充放电电路进行充电或者为用电元件供电。
通过本申请实施例提供的复合电极材料及其制备方法，可以获得包括该复合电极材料锂电池，以及包括该锂电池的电子设备。该复合电极材料包括电极材料内核和具有骨架结构的有机纤维包覆层，该有机纤维包覆层通过键合作用复合在电极材料内核表面。其中，有机纤维所含有的-CO-NH-或者-C＝N-可以与电极材料内核表面的-OH形成丰富的氢键，使得有机纤维相互缠绕地复合在电极材料内核表面上，从而在电极材料内核表面形成牢固的 且具有骨架结构的包覆层。该有机纤维包覆层的高强度特性和较小的拉伸应变可以限制电极材料的体积膨胀，同时保证包覆层本身不易发生塑性变形。进而，可以提高电池循环稳定性，减小电池在电子设备内部腔体中的占比，提高电子设备中芯片、电路板等关键器件的可用腔体空间，避免长循环后出现的电池鼓包、后盖翘起等问题，提高电子产品的寿命和安全性。
本说明书中各个实施例之间相同相似的部分互相参见即可。尤其，对于实施例而言，由于其基本相似于方法实施例，所以描述的比较简单，相关之处参见方法实施例中的说明即可。
以上所述的本发明实施方式并不构成对本发明保护范围的限定。

Claims (20)

  1. 一种复合电极材料，其特征在于，包括电极材料内核和有机纤维包覆层，所述有机纤维包覆层通过键合作用复合在所述电极材料内核表面；
    所述有机纤维含有-CO-NH-和-C＝N-中的至少一种，以及苯环结构。
  2. 根据权利要求1所述的复合电极材料，其特征在于，所述有机纤维还含有-COOH和/或-NH 2。
  3. 根据权利要求2所述的复合电极材料，其特征在于，所述有机纤维在所述复合电极材料中的质量占比为0.05％-1％。
  4. 根据权利要求1所述的复合电极材料，其特征在于，所述苯环结构位于所述有机纤维的大分子链中。
  5. 根据权利要求4所述的复合电极材料，其特征在于，所述有机纤维的断裂强度大于3cN·dtex -1，所述有机纤维的初始模量大于50cN·dtex -1。
  6. 根据权利要4所述的复合电极材料，其特征在于，所述有机纤维包覆层的厚度为10nm-200nm。
  7. 根据权利要求6所述的复合电极材料，其特征在于，所述有机纤维的直径为5nm-60nm，长度为1μm-20μm。
  8. 根据权利要求1所述的复合电极材料，其特征在于，所述有机纤维为芳纶纤维、聚芳噁二唑纤维或芳砜纶纤维。
  9. 根据权利要求8所述的复合电极材料，其特征在于，所述芳纶纤维中芳酰胺链节含量大于85％，所述芳纶纤维的直径为5nm-40nm，长度为2μm-20μm。
  10. 根据权利要求1所述的复合电极材料，其特征在于，所述复合电极材料包括复合颗粒和/或聚合颗粒，所述复合颗粒包括所述电极材料内核和通过键合作用复合在所述电极材料内核表面上的有机纤维包覆层，所述聚合颗粒由所述复合颗粒聚合形成。
  11. 根据权利要10所述的复合电极材料，其特征在于，所述复合颗粒包括一次复合颗粒和二次复合颗粒，所述一次复合颗粒的内核为所述电极材料内核，所述二次复合颗粒的内核为所述一次复合颗粒聚合形成的所述聚合颗粒。
  12. 根据权利要求10所述的复合电极材料，其特征在于，还包括导电剂和/或离子导体。
  13. 根据权利要求12所述的复合电极材料，其特征在于，所述导电剂和/或离子导体包覆在所述复合颗粒和/或聚合颗粒的表面，或者混合在所述复合颗粒和/或聚合颗粒之 间。
  14. 根据权利要求10所述的复合电极材料，其特征在于，所述导电剂包括无定形碳、软碳、硬碳、石墨、碳纳米管、石墨烯、金属颗粒中的一种或多种的组合。
  15. 根据权利要求1所述的复合电极材料，其特征在于，所述电极材料包括三元正极材料，硅基、锡基、硫基、金属锂负极材料。
  16. 一种复合电极材料的制备方法，其特征在于，所述方法包括：
    制备有机纤维溶液，有机纤维的分子结构中含有-CO-NH-和-C＝N-中的至少一种，以及苯环结构；
    按照预定复合比例，将电极材料添加到所述有机纤维溶液中，搅拌至分散均匀；
    对电极材料与有机纤维的混合液进行干燥处理，得到如权利要求1所述的复合电极材料。
  17. 一种复合电极材料，其特征在于，采用如权利要求16所述的制备方法制备得到。
  18. 权利要求1所述的复合电极材料在制备锂电池的领域中的应用。
  19. 一种锂电池，其特征在于，包括正极材料、电解液、隔膜和负极材料，其特征在于，所述正极材料或者负极材料采用权利要求1-15任一项所述的复合电极材料。
  20. 一种电子设备，包括充放电电路以及用电元件，其特征在于，还包括权利要求19所述的锂电池，所述锂电池与所述充放电电路连接，通过所述充放电电路进行充电或者为所述用电元件供电。
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