WO2023088247A1 - 富锂复合材料及其制备方法和应用 - Google Patents

富锂复合材料及其制备方法和应用 Download PDF

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WO2023088247A1
WO2023088247A1 PCT/CN2022/131989 CN2022131989W WO2023088247A1 WO 2023088247 A1 WO2023088247 A1 WO 2023088247A1 CN 2022131989 W CN2022131989 W CN 2022131989W WO 2023088247 A1 WO2023088247 A1 WO 2023088247A1
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lithium
rich
composite material
rich composite
precursor
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PCT/CN2022/131989
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English (en)
French (fr)
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钟泽钦
万远鑫
孔令涌
赵中可
钟文
朱成奔
裴现一男
张於财
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深圳市德方创域新能源科技有限公司
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Publication of WO2023088247A1 publication Critical patent/WO2023088247A1/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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the application belongs to the field of secondary batteries, and specifically relates to a lithium-rich composite material and its preparation method and application.
  • Lithium-ion batteries are considered to be the most promising due to their high working voltage and energy density, relatively small self-discharge level, no memory effect, no pollution from heavy metal elements such as lead and cadmium, and long cycle life. one of the energy sources.
  • the surface of the negative electrode is usually accompanied by the formation of a solid electrolyte film SEI film.
  • This process consumes a large amount of Li + , which means that the Li + part released from the positive electrode material is irreversibly consumed, corresponding to the reversible charge of the battery cell. Lower specific capacity.
  • Anode materials, especially silicon-based anode materials will further consume Li + , resulting in loss of lithium in cathode materials, reducing the first Coulombic efficiency and battery capacity of the battery. For example, in a lithium-ion battery system using a graphite negative electrode, about 10% of the lithium source will be consumed for the first charge.
  • anode materials with high specific capacity such as alloys (silicon, tin, etc.), oxides (silicon oxide, tin oxide), and amorphous carbon anodes
  • the consumption of lithium sources in the cathode will be further aggravated.
  • lithium-rich iron-based materials reported publicly is as high as 867mAh/g
  • the operating voltage window is consistent with conventional lithium-ion batteries, and basically does not participate in the electrochemical process in the later stage. It is a positive lithium supplement additive with broad prospects.
  • Li 5 FeO 4 it is prepared by a sol-gel method. This material is used as a lithium ion battery positive electrode lithium supplement material and has the characteristics of large charge capacity and small discharge capacity.
  • the carbon source is used for gas-phase coating to isolate the external environment, and the contact between lithium ferrite and water in the air is relieved to improve the stability of the material; however, the coating layer is always It is difficult to completely isolate the contact with water in the air, resulting in material deterioration and failure.
  • the electronic conductivity of the carbon-coated lithium ferrite material can be improved, the path of ion conduction is increased and the ion conductivity is affected, which leads to the lithium supplementation effect of the carbon-coated lithium ferrite material.
  • the carbon-coated lithium ferrite material still has residual alkali in the coating layer or between the interface with the lithium ferrite core body, which makes it difficult to process.
  • the interface activity between the surface and the electrolyte is high, so as to cause side reactions with the electrolyte, resulting in a decrease in the electrochemical performance of the battery.
  • the purpose of this application is to overcome the above-mentioned deficiencies in the prior art, provide a lithium-rich composite material and its preparation method, to solve the problems of unsatisfactory stability and high interfacial activity with the electrolyte in the existing coating structure of the positive electrode lithium supplement additive technical problem.
  • Another object of the present application is to provide a positive electrode sheet and a secondary battery containing the positive electrode sheet, so as to solve the technical problems of unsatisfactory first coulombic efficiency and battery capacity of existing secondary batteries.
  • the first aspect of the present application provides a lithium-rich composite material.
  • the lithium-rich composite material of the present application includes a core body and a dense hydrophobic layer coated on the core body, the core body includes a lithium-rich material, and the material of the dense hydrophobic layer includes a polyanion type electrochemically active material, and the polyanion type electrochemically active material
  • the material is a phosphate electrode active material.
  • the material of the dense hydrophobic layer also includes an electron-conducting agent, and the electron-conducting agent forms a mixture with the polyanionic electrochemically active material.
  • the electronic conductive agent includes at least one of conductive carbon materials, conductive oxides, and conductive organic substances.
  • the electron-conducting agent accounts for 1-6 wt% of the mass of the polyanionic electrochemically active material.
  • the conductive carbon material includes at least one of amorphous carbon, carbon nanotubes, graphite, carbon black, and graphene;
  • the conductive oxide includes at least one of In 2 O 3 , ZnO, and SnO 2 ;
  • the conductive organic compound includes Conductive polymers.
  • the dense hydrophobic layer includes an active material coating layer, the active material coating layer covers the core body, and the material of the active material coating layer is a polyanionic electrochemically active material.
  • the dense hydrophobic layer also includes an electronic conductor encapsulation layer, and the electronic conductor encapsulation layer covers the surface of the active material encapsulation layer away from the core body.
  • the material of the electronic conductor packaging layer includes at least one of carbon materials, conductive oxides, and conductive organics.
  • the electronic conductor encapsulation layer has a thickness of 1-100 nm.
  • the content of the polyanionic electrochemically active material in the lithium-rich composite material is 0.5-30 wt%.
  • the polyanionic electrochemically active material includes at least one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium nickel phosphate, and lithium cobalt phosphate.
  • the lithium-rich material includes at least one of lithium-rich iron, lithium-rich manganese, lithium-rich nickel, and lithium-rich cobalt.
  • the general chemical formula of lithium-rich iron-based materials is aLiFeO 2 ⁇ bLi 2 O ⁇ cM x O y ; wherein a, b, and c in the chemical general formula are moles, and a+b ⁇ 0.98 ; c ⁇ 0.02; 1.8 ⁇ b/a ⁇ 2.1; M is one or more of Si, Ni, Co, Mn, Ti, Al, Cu, V, Zr, Sn; 1 ⁇ y/x ⁇ 2.5, x is 1-3.
  • the particle size of the lithium-rich composite material satisfies: 1 ⁇ m ⁇ D50 ⁇ 10 ⁇ m.
  • the particle size of the lithium-rich composite material satisfies: 1 ⁇ m ⁇ D50 ⁇ 10 ⁇ m, D10/D50 ⁇ 0.3, D90/D50 ⁇ 2.
  • the BET specific surface of the lithium-rich composite material is 0.5-20 m 2 /g.
  • the resistivity of the lithium-rich composite material is 1.0-500 ⁇ /cm.
  • the second aspect of the present application provides a preparation method of the lithium-rich composite material of the present application.
  • the preparation method of the lithium-rich composite material of the present application comprises the following steps:
  • the lithium-rich material containing a polyanion-type electrochemically active material or its precursor material, coating the lithium-rich material to obtain a lithium-rich composite material; wherein the polyanion-type electrochemically active material is phosphate electrode active materials.
  • the method for forming a dense hydrophobic layer on the surface of the lithium-rich material with the precursor material containing the polyanionic electrochemically active material comprises the following steps:
  • the first lithium-rich composite material precursor is subjected to a first sintering treatment to obtain a lithium-rich composite material.
  • the method for forming a dense hydrophobic layer on the surface of the lithium-rich material with the precursor material containing the polyanionic electrochemically active material comprises the following steps:
  • the second lithium-rich composite material precursor is subjected to a second sintering treatment to obtain a lithium-rich composite material with an active material coating layer;
  • the third lithium-rich composite material precursor is subjected to a third sintering treatment to obtain a lithium-rich composite material.
  • the precursor materials of polyanionic electrochemically active materials include lithium iron phosphate precursors, lithium manganese phosphate precursors, lithium manganese iron phosphate precursors, lithium vanadium phosphate precursors, lithium nickel phosphate precursors, lithium cobalt phosphate precursors at least one of the
  • a positive electrode sheet in a third aspect of the present application, includes a positive electrode current collector and a positive electrode active layer bonded to the surface of the positive electrode current collector.
  • the positive electrode active layer contains the lithium-rich composite material of the present application or the lithium-rich composite material prepared by the preparation method of the lithium-rich composite material of the present application.
  • a secondary battery in a fourth aspect of the present application, includes a positive electrode sheet and a negative electrode sheet, and the positive electrode sheet is the positive electrode sheet of this application.
  • the lithium-rich composite material of the present application coats the core body containing the lithium-rich material through a dense hydrophobic layer.
  • the dense hydrophobic layer can effectively coat the lithium-rich material contained in the core body, so that the core body is isolated from the outside world and avoids moisture in the outside world.
  • the contact with carbon dioxide and the nuclei ensures the stability of the nuclei, thereby ensuring the lithium-replenishing effect and the stability of the lithium-rich composite material.
  • the dense hydrophobic layer at least in the dense hydrophobic layer, the residual alkali content is low, which endows the lithium-rich composite material of the present application with excellent processing performance.
  • the polyanionic electrochemically active material endows the dense hydrophobic layer with high chemical stability in contact with the electrolyte, reduces side reactions with the electrolyte, and improves the stability of the electrochemical performance of the battery.
  • the preparation method of the lithium-rich composite material of the present application can effectively prepare a lithium-rich composite material with a core-shell structure, and can make the dense hydrophobic layer contain polyanionic electrochemically active materials, effectively coat the core body containing lithium-rich materials, and at the same time make
  • the prepared lithium-rich composite material contains low residual alkali content, so as to ensure that the prepared lithium-rich composite material has stable electrochemical performance, has good processing performance, and endows the prepared lithium-rich composite material with high electrochemical stability at the contact interface with the electrolyte sex.
  • the preparation method of the lithium-rich composite material can ensure that the prepared lithium-rich composite material has a stable structure and electrochemical performance, and has high efficiency and saves production costs.
  • the positive electrode sheet of this application contains the lithium-rich composite material of this application, the components contained in the positive active layer of the positive electrode sheet of this application are uniformly dispersed, the film layer is of high quality, and the chemical properties of the contact interface with the electrolyte are stable, which endows the positive electrode sheet of this application with excellent performance.
  • the electrochemical performance of the battery improves the first effect and the overall electrochemical performance of the battery.
  • the secondary battery of the application contains the electrode sheet of the application, so the lithium ion battery of the application has excellent first coulombic efficiency, battery capacity and cycle performance, long life, and stable electrochemical performance.
  • Fig. 1 is the structural schematic diagram of the lithium-rich composite material of the embodiment of the present application.
  • Fig. 2 is a schematic structural view of the lithium-rich composite material of the embodiment of the present application shown in Fig. 1;
  • Fig. 3 is another schematic structural view of the lithium-rich composite material of the embodiment of the present application shown in Fig. 1;
  • Fig. 4 provides the SEM figure of lithium-rich composite material for embodiment 1;
  • Fig. 5 provides the SEM figure of lithium-rich material for comparative example 1;
  • Fig. 6 provides the XRD figure of lithium-rich composite material for embodiment 1;
  • FIG. 7 is the XRD pattern of the lithium-rich composite material provided by Example 5.
  • the term "and/or” describes the association relationship of associated objects, indicating that there may be three relationships, for example, A and/or B may mean: A exists alone, A and B exist simultaneously, and B exists alone Condition. Among them, A and B can be singular or plural.
  • the character "/" generally indicates that the contextual objects are an "or" relationship.
  • At least one means one or more, and “multiple” means two or more.
  • At least one of the following” or similar expressions refer to any combination of these items, including any combination of single or plural items.
  • at least one item (unit) of a, b, or c or “at least one item (unit) of a, b, and c” can mean: a, b, c, a-b( That is, a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.
  • sequence numbers of the above-mentioned processes do not mean the order of execution, and some or all steps may be executed in parallel or sequentially, and the execution order of each process shall be based on its functions and The internal logic is determined and should not constitute any limitation to the implementation process of the embodiment of the present application.
  • the weight of the relevant components mentioned in the description of the embodiments of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the various components.
  • the scaling up or down of the content of the fraction is within the scope disclosed in the description of the embodiments of the present application.
  • the mass described in the description of the embodiments of the present application may be ⁇ g, mg, g, kg and other well-known mass units in the chemical industry.
  • first and second are only used for descriptive purposes to distinguish objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features.
  • first XX can also be called the second XX
  • second XX can also be called the first XX.
  • a feature defined as “first” and “second” may explicitly or implicitly include one or more of these features.
  • the embodiment of the present application provides a lithium-rich composite material.
  • the lithium-rich composite material of the embodiment of the present application includes a core body and a dense hydrophobic layer coated on the core body, that is, the lithium-rich composite material of the embodiment of the present application has a core-shell structure, as in the embodiment, the lithium-rich composite material of the embodiment of the present application
  • the structure of the material is shown in FIGS. 1 to 5 , including a core body 10 and a dense hydrophobic layer 20 covering the core body 10 .
  • the core body 10 includes a lithium-rich material, that is, in the lithium-rich composite material of the embodiment of the present application, the core body 10 is a lithium source for providing lithium ions. Since the core body 10 is rich in lithium, it is ensured that the lithium-rich composite material of the embodiment of the present application can provide abundant lithium.
  • the lithium-rich material contained in the core body 10 may be a conventional lithium-replenishing material, or a newly developed lithium-replenishing material.
  • the lithium-rich material contained in the core body 10 may be a ternary lithium supplement material or a binary lithium supplement material.
  • the lithium-rich material may be at least one of lithium-rich iron, lithium-rich manganese, lithium-rich nickel, and lithium-rich cobalt.
  • the general chemical formula of the lithium-rich iron-based material may be aLiFeO 2 ⁇ bLi 2 O ⁇ cM x O y .
  • the a, b, and c in the general chemical formula are moles, and satisfy a+b ⁇ 0.98; c ⁇ 0.02; 1.8 ⁇ b/a ⁇ 2.1; M is Si, Ni, Co, Mn, Ti, Al, Cu
  • M is Si, Ni, Co, Mn, Ti, Al, Cu
  • One or more of , V, Zr, Sn; 1 ⁇ y/x ⁇ 2.5, x is 1-3.
  • the lithium-rich iron-based material may be LiFeO 2 ⁇ 1.99Li 2 O, LiFeO 2 ⁇ 1.99Li 2 O ⁇ 0.005Al 2 O 3 or the like. These lithium-rich materials are rich in lithium and can efficiently provide lithium ions.
  • the core 10 may be at least one of primary particles and secondary particles, specifically at least one of primary particles and secondary particles formed of lithium-rich materials contained in the core 10 .
  • the particle diameter of the core body 10 may be 0.5 ⁇ m-20 ⁇ m.
  • the particle size of the primary particle that is, the particle size distribution of the nucleus 10 is 0.5 ⁇ m-15 ⁇ m; when the nucleus 10 is a secondary particle, the particle size of the secondary particle is the nucleus The particle size distribution of 10 is 1 ⁇ m-20 ⁇ m.
  • secondary particles refer to agglomerated particles formed by aggregating more than one primary particle.
  • the processability of the lithium-rich composite material in the preparation of lithium battery slurry is also improved.
  • the smaller one Particle size can also extract more lithium.
  • the lithium-rich material contained in the core body 10 in the above-mentioned embodiments is rich in lithium, it is unstable when it encounters water and carbon dioxide, and it is easy to react with water and carbon dioxide, thus resulting in the lithium-rich material in the embodiments of the present application.
  • the lithium supplementation effect of the composite material is reduced.
  • lithium-rich materials are generally rich in residual alkali due to processing, and these residual alkalis will further reduce their processing performance. For example, the viscosity of the slurry containing the above lithium-rich materials will increase sharply, and the gel will lose fluidity rapidly. , so that subsequent processing cannot be performed.
  • lithium-rich materials especially lithium-supplementing materials
  • the primary difficulty of lithium-rich materials lies in the control of the interface of highly active materials and a large amount of residual alkali on the surface layer, which leads to the fact that the residual alkali is easily converted into lithium hydroxide and other products in an atmosphere with a certain humidity.
  • the highly active interface is very prone to complex side reactions with carbonate solvents, resulting in unstable or reduced electrochemical performance of lithium-rich materials.
  • the dense hydrophobic layer 20 contained in the lithium-rich composite material in the above-mentioned embodiments covers the core body 10 to form a complete coating layer, as shown in FIG. 1 .
  • the dense hydrophobic layer 20 can effectively cover the lithium-rich material contained in the core body 10, so that the core body 10 is isolated from the outside world, avoiding contact with the core body 10 such as moisture and carbon dioxide in the outside world, and ensuring the stability of the core body 10.
  • the dense hydrophobic layer 20 can effectively cover the lithium-rich material contained in the core body 10, so that the core body 10 is isolated from the outside world, avoiding contact with the core body 10 such as moisture and carbon dioxide in the outside world, and ensuring the stability of the core body 10.
  • the material of the dense hydrophobic layer 20 includes a polyanion type electrochemically active material, and the polyanion type electrochemically active material is a phosphate electrode active material.
  • a polyanionic electrochemically active material is added in the dense hydrophobic layer 20.
  • the existence of the polyanionic electrochemically active material enhances the compact performance of the dense hydrophobic layer 20 and enhances the isolation effect of the core body 10 from the outside world.
  • the polyanionic electrochemically active material can improve the conductivity of lithium ions, and is more conducive to the extraction and conduction of lithium ions in the core body 10 .
  • the lithium-rich material contained in the core body 10 is a lithium-replenishing material
  • the presence of polyanionic electrochemically active materials enhances the chemical stability of the contact interface between the dense hydrophobic layer 20 and the electrolyte, such as enhancing the chemical stability of the dense hydrophobic layer 20 in contact with carbonate solvents, reducing or even avoiding The side reaction of the electrolyte contact interface, thereby enhancing the chemical stability of the complex side reaction lithium-rich composite material in contact with the electrolyte.
  • the existence of the polyanionic electrochemically active material also makes the residual alkali content in the core body 10 and the dense hydrophobic layer 20 low, endowing the lithium-rich composite material of the embodiment of the present application with excellent processing performance.
  • the polyanionic electrochemically active material is selected as a phosphate electrode active material, which endows the dense hydrophobic layer 20 with excellent water resistance, low residual alkali on the surface, and is easier to process than ternary materials.
  • the conductive carbon layer attached to the phosphate-based material can effectively increase the overall conductive effect of the dense hydrophobic layer 20 .
  • the distribution of the polyanionic electrochemically active material added by the dense hydrophobic layer 20 in the dense hydrophobic layer 20 can be the following situations:
  • the polyanionic electrochemically active material forms a mixture with other materials, and forms a dense hydrophobic layer 20 to cover the core body 10 .
  • the other material may be an electronic conductive agent, that is, the material of the dense hydrophobic layer 20 also includes an electronic conductive agent, and the electronic conductive agent forms a mixture with the polyanionic electrochemically active material.
  • the polyanionic electrochemically active material and the electronic conductive agent material form a dense hydrophobic layer 20 together, so that the dense hydrophobic layer 20 has high density, and the two play a synergistic effect, enhancing lithium ion conduction while improving
  • the electronic conductivity of the dense hydrophobic layer 20 reduces the residual alkali content and enhances the chemical stability of the contact interface between the dense hydrophobic layer 20 and the electrolyte.
  • the content of the polyanionic electrochemically active material in the lithium-rich composite material is controlled to be 0.5-30wt% Specifically, it can be 0.5wt%, 1wt%, 3wt%, 5wt%, 8wt%, 10wt%, 13wt%, 15wt%, 17wt%, 20wt%, 23wt%, 25wt%, 27wt%, 30wt% and other contents.
  • the electronic conductive agent is controlled to account for 1-6 wt% of the mass of the polyanionic electrochemically active material, specifically 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%.
  • the compactness of the dense hydrophobic layer 20 is further improved, the ionic conductivity and electronic conductivity of the dense hydrophobic layer 20 are enhanced, and the residual alkali content in the lithium-rich composite material, especially the dense hydrophobic layer 20, is further reduced. And enhance the chemical stability of the contact interface between the dense hydrophobic layer 20 and the electrolyte.
  • the electronic conductive agent may include at least one of conductive carbon materials, conductive oxides, and conductive organic substances.
  • the conductive carbon material includes at least one of amorphous carbon, carbon nanotubes, graphite, carbon black, graphene and the like.
  • the conductive oxide may include at least one of In 2 O 3 , ZnO, and SnO 2 .
  • the conductive organic substance may be a conductive polymer or the like.
  • the structure of the dense hydrophobic layer 20 is as shown in FIG. 2 , including an active material coating layer 21 .
  • the active material coating layer 21 covers the core body 10, and the material of the active material coating layer 21 is a polyanionic electrochemically active material. That is, in the dense hydrophobic layer 20 shown in FIG. 2 , the polyanionic electrochemically active material forms a coating layer, that is, the formed active material coating layer 21 covers the core body 10 . Further, based on the structure shown in FIG. 2 , the content of the polyanionic electrochemically active material, that is, the active material coating layer 21 formed therefrom, in the lithium-rich composite material is 0.5-30 wt%. By controlling the thickness of the active material coating layer 21 to the content of the active material coating layer 21 , the active material coating layer 21 has high density and fully exerts the above-mentioned functions of the polyanionic electrochemical active material.
  • the dense hydrophobic layer 20 based on the structure of the dense hydrophobic layer 20 described in FIG. 2, as shown in FIG.
  • the surface of 21 facing away from the core body 10 that is, the electronic conductor packaging layer 22 is coated on the outer surface of the active material coating layer 21 .
  • the active material coating layer 21 and the electronic conductor packaging layer 22 together constitute a composite structure coating layer, and at this time, the dense hydrophobic layer 20 is a composite structure.
  • the active material coating layer 21 plays the role of the above active material coating layer 21
  • the electronic conductor packaging layer 22 plays the role of electronic conductivity
  • the compounding of the two film layers plays a synergistic effect.
  • the electronic conductor encapsulation layer 22 shown in FIG. 3 may have a thickness of 1-100 nm.
  • the material of the electronic conductor encapsulation layer 22 may include at least one of carbon materials, conductive oxides, and conductive organics.
  • the carbon material includes at least one of amorphous carbon, carbon nanotubes, graphite, carbon black, graphene, and the like.
  • the conductive oxide may include at least one of In 2 O 3 , ZnO, and SnO 2 .
  • the conductive organic substance may be a conductive polymer or the like.
  • the polyanionic electrochemically active material contained in the dense hydrophobic layer 20 in the above embodiments may include lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium nickel phosphate, and lithium cobalt phosphate. at least one of .
  • the above-mentioned effects of polyanionic electrochemically active materials can be improved, thereby improving the delithiation ability and ion conductivity of lithium-rich composite materials, and improving the dense hydrophobic layer.
  • the specific surface area of the lithium-rich composite material in the above embodiment is 0.2-20 m 2 /g, and the compactness is good.
  • the resistivity of the lithium-rich composite material is 1.0-500 ⁇ /cm, and the electronic conductivity is high.
  • the particle size of the lithium-rich composite material can be controlled and adjusted, such as controlling and adjusting the particle size of the lithium-rich composite material to meet: 1 ⁇ m ⁇ D50 ⁇ 10 ⁇ m; further, the particle size of the lithium-rich composite material satisfies: 1 ⁇ m ⁇ D50 ⁇ 10 ⁇ m, D10/D50 ⁇ 0.3, D90/D50 ⁇ 2. Therefore, the particle size of the lithium-rich composite material in the above embodiments is uniform and controllable.
  • the embodiment of the present application also provides the preparation method of the above lithium-rich composite material.
  • the preparation method of the lithium-rich composite material in the embodiment of the present application includes the following steps:
  • the lithium-rich material used in the preparation method of the lithium-rich composite material in the embodiment of the present application is the lithium-rich material that forms the core body 10 of the lithium-rich composite material above.
  • the polyanionic electrochemically active material is also the polyanionic electrochemically active material in the dense hydrophobic layer 20 of the above lithium-rich composite material. In order to save space, the lithium-rich materials and polyanionic electrochemically active materials will not be repeated here.
  • the lithium-rich material and the polyanionic electrochemically active material can be prepared respectively according to the preparation method of the corresponding lithium-rich material.
  • the preparation method of the lithium-rich composite material in the embodiment of the present application uses the electrochemically active material containing polyanion or its precursor material to form a dense hydrophobic layer. Therefore, polyanionic electrochemically active materials are contained in the formed dense hydrophobic layer, thereby generating the dense hydrophobic layer 20 of the embodiment of the above application.
  • the prepared lithium-rich composite material has a core-shell coating structure, and the dense hydrophobic layer formed has a high density, which enhances the isolation effect of the core body from the outside world, and has a good effect of isolating unfavorable factors such as water and carbon dioxide in the environment.
  • the residual alkali contained in the prepared lithium-rich composite material especially the dense hydrophobic layer, has low residual alkali content and high chemical stability in contact with the electrolyte, which makes the lithium-rich composite material excellent processing performance and reduces the contact with the electrolyte. side effects.
  • the preparation method of the lithium-rich composite material can ensure that the prepared lithium-rich composite material has a stable structure and electrochemical performance, and has high efficiency and saves production costs.
  • the method of treating the precursor material containing the polyanion-type electrochemically active material on the surface of the lithium-rich material to form a dense hydrophobic layer can be based on the specific polyanion-containing electrochemically active material.
  • the corresponding method is adopted to realize the coating of the lithium-rich material and form a dense hydrophobic layer.
  • at least the following methods can be used to coat lithium-rich materials and form a dense hydrophobic layer:
  • the method for forming a dense hydrophobic layer on the surface of a lithium-rich material with a precursor material containing a polyanion-type electrochemically active material comprises the following steps:
  • the first lithium-rich composite material precursor is subjected to a first sintering treatment to obtain a lithium-rich composite material.
  • step S11 after the mixture of the first electronic conductive agent or the precursor material of the first electronic conductive agent and the precursor material of the polyanionic electrochemically active material is mixed with the lithium-rich material, the mixture will be on the surface of the lithium-rich material A coating layer is formed to obtain the first lithium-rich composite material precursor.
  • the mixing process can be determined according to the form of the mixture, for example, it can be liquid mixing coating, or solid mixing coating, etc.
  • the mixture ratio of the first electron-conducting agent or the first electron-conducting agent precursor material and the polyanionic electrochemically active material precursor material can be determined according to the content of the electron-conducting agent in the dense hydrophobic layer formed, For example, the mixing ratio is controlled so that the electron-conducting agent accounts for 1-6 wt% of the mass of the polyanionic electrochemically active material. Or further control the mixing ratio of the mixture and the lithium-rich material, so that the content of the polyanionic electrochemically active material in the lithium-rich composite material is 0.5-30wt%.
  • the first electronic conductive agent such as the electronic conductive agent contained in the dense hydrophobic layer 20 above, may include at least one of a conductive carbon material and a conductive oxide.
  • the first electron-conducting agent precursor material is also a precursor material corresponding to the first electron-conducting agent.
  • the precursor material of the polyanionic electrochemically active material is also the precursor material corresponding to the above polyanionic electrochemically active material.
  • the polyanionic electrochemically active material is lithium iron phosphate
  • the precursor of the polyanionic electrochemically active material is a precursor for forming lithium iron phosphate, including a mixture of lithium source, iron source and phosphorus source.
  • the first sintering treatment in step S12 is to sinter the precursor of the polyanionic electrochemically active material or the first electron-conducting agent to form a mixture of the polyanion-type electrochemically active material and the first electron-conducting agent respectively, and in situ A dense hydrophobic layer is formed on the surface of lithium-rich materials.
  • the conditions of the first sintering treatment can be determined according to the sintering conditions of the polyanionic electrochemically active material precursor or the first electronic conductive agent precursor, such as when the polyanionic electrochemically active material precursor is a lithium iron phosphate precursor, the first When the electronic conductive agent precursor is an organic substance, the first sintering treatment may be carried out in a non-oxidizing atmosphere, heating at a rate of 100-500° C./h to 450° C.-900° C. for 0.5-10 hours.
  • the protective atmosphere in step S12 may be a chemically inert atmosphere formed by nitrogen or/and argon.
  • first electron-conducting agent or the precursor material of the first electron-conducting agent and the polyanion-type electrochemically active material or its precursor material to be deposited in situ on the surface of the lithium-rich material by vapor deposition to form a polyanion-containing A dense hydrophobic layer of a mixture of a type electrochemically active material and a first electron-conducting agent.
  • the method for forming a dense hydrophobic layer on the surface of the lithium-rich material with the precursor material containing the polyanionic electrochemically active material comprises the following steps:
  • the polyanionic electrochemically active material precursor material will form a coating layer on the surface of the lithium-rich material to obtain a second lithium-rich composite material precursor.
  • the mixing process can be determined according to the form of the precursor material of the polyanionic electrochemically active material, for example, it can be mixed coating in liquid state or mixed coating in solid state.
  • the mixing ratio of the lithium-rich material and the precursor material of the polyanionic electrochemical active material can be determined according to the content of the coating layer containing the active material, such as controlling the mixing ratio so that the polyanionic electrochemical active material
  • the content of the active material, that is, the coating layer containing the active material, in the lithium-rich composite material is 0.5-30 wt%.
  • step S22 during the second sintering process, the precursor material of the polyanionic electrochemically active material is sintered to form a polyanionic electrochemically active material, and a coating layer of the polyanionic electrochemically active material is formed to coat the lithium-rich
  • the surface of the material that is, the surface on which the active material coating layer is formed to cover the surface of the lithium-rich material.
  • the active material coating layer is the active material coating layer 21 contained in the lithium-rich material shown in FIG. 2 and FIG. 3 above. Therefore, the second sintering treatment can be determined according to the type of the precursor material of the polyanionic electrochemically active material.
  • the second sintering treatment can be carried out in a non-oxidizing atmosphere, at a temperature of 100-500°C/h to 450°C-900°C for 0.5-10h .
  • the protective atmosphere in step S22 may be a chemically inert atmosphere formed by nitrogen or/and argon.
  • step S23 the second electronic conductive agent or the precursor material of the second electronic conductive agent is mixed with the lithium-rich composite material of the active material coating layer prepared in step S22 to form a second electronic conductive agent on the outer surface of the active material coating layer.
  • the coating layer of the electronic conductive agent or the precursor material of the second electronic conductive agent is obtained to obtain the precursor of the third lithium-rich composite material.
  • the mixing process in step S23 can also be determined according to the form of the second electronic conductive agent or the precursor material of the second electronic conductive agent, for example, it can be mixed coating in liquid state or mixed coating in solid state.
  • the mixing ratio of the second electronic conductive agent or the precursor material of the second electronic conductive agent and the lithium-rich composite material of the active material coating layer can be determined according to the content of the second electronic conductive agent in the formed dense hydrophobic layer, such as The mixing ratio is controlled so that the second electron-conducting agent accounts for 1-6 wt% of the polyanionic electrochemically active material, that is, the mass of the coating layer containing the active material.
  • step S24 during the third sintering process, when it is the precursor material of the second electronic conductive agent, it is sintered and decomposed to form the second electronic conductive agent, and an electronic conductive coating layer is formed in situ on the surface of the coating layer containing the active material .
  • it is the second electron-conducting agent, it is sintered to form an electron-conducting cladding layer.
  • the electronically conductive coating layer The active material coating layer is the electronic conductor packaging layer 22 contained in the lithium-rich material shown in FIG. 3 above.
  • the electronically conductive coating layer and the active material coating layer formed in step S23 constitute a dense hydrophobic layer of a composite structure, such as the dense hydrophobic layer 20 contained in the lithium-rich material as shown in FIG. 3 .
  • the protective atmosphere in step S24 may be a chemically inert atmosphere formed by nitrogen or/and argon.
  • the third sintering treatment may be carried out according to the conditions for sintering and decomposition of the precursor material of the second electron conducting agent or the conditions for sintering the second electron conducting agent.
  • the third sintering treatment may be carried out in a non-oxidizing atmosphere, heating at a rate of 100-500° C./h to 450° C.-900° C. for 0.5-10 hours.
  • the dense hydrophobic layer with a composite structure as shown in Figure 3 is formed step by step, the polyanionic electrochemically active precursor material and the lithium-rich material in the above step S21 are mixed and coated and then sintered to form an active material.
  • other methods such as chemical deposition can also be used to directly deposit the precursor of the polyanionic electrochemically active material on the surface of the lithium-rich material in situ to form an active material coating layer.
  • the preparation method of the above-mentioned lithium-rich composite material can form a dense hydrophobic layer covering the lithium-rich material on the surface of the lithium-rich material to form the above-mentioned lithium-rich composite material with a core-shell structure, so that the electrochemical performance of the prepared lithium-rich composite material is stable. High electrochemical stability of the contact interface with the electrolyte. Moreover, the lithium-rich composite material contains low residual alkali content and has good processing performance.
  • the embodiment of the present application also provides a positive electrode sheet.
  • the positive electrode sheet of the embodiment of the present application includes a positive electrode current collector and a positive electrode active layer bonded to the surface of the positive electrode current collector.
  • the positive electrode active layer contains the lithium-rich composite material of the above application example.
  • the lithium-rich composite material can be used as a positive electrode material or as a positive electrode lithium supplement additive. Since the positive electrode sheet of the embodiment of the present application contains the above-mentioned lithium-rich composite material of the embodiment of the present application, the components contained in the positive electrode active layer of the positive electrode sheet of the embodiment of the present application are uniformly dispersed, and the quality of the film layer is high. Moreover, the chemical performance of the contact interface between the positive electrode sheet and the electrolyte is stable, endowing the electrode sheet with excellent electrochemical performance, and improving the first efficiency and overall electrochemical performance of the battery.
  • the mass content of the lithium-rich composite material of the above-mentioned application example contained in the positive electrode active layer may be 0.5-10 wt%.
  • the positive electrode active layer includes, in addition to the lithium-rich composite material, a binder and a conductive agent.
  • the content of binder can be 0.5-20wt%, and binder can be commonly used electrode binder, as comprises polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose , methylcellulose, carboxymethylcellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan and chitosan derivatives in one or more.
  • the content of the conductive agent can be 0.2-20wt%, and the conductive agent can also be a commonly used conductive agent, such as one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60 and carbon nanotube.
  • the lithium-rich composite material when used as a positive electrode lithium supplement additive, it also contains a positive electrode active material.
  • the positive electrode active material may include one of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium fluorovanadium phosphate, lithium titanate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate one or more species.
  • the preparation process of the positive electrode sheet can be as follows: the positive electrode lithium supplement additive, the conductive agent and the binder or further mixed with the positive electrode active material to obtain the electrode slurry, the positive electrode slurry is coated on the positive electrode current collector, and dried , roll pressing, die-cutting and other steps to prepare the positive electrode sheet.
  • the embodiment of the present application further provides a secondary battery.
  • the secondary battery of the embodiment of the present application includes necessary components such as a positive electrode sheet, a negative electrode sheet, a separator, and 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, that is, the positive electrode active layer contained in the positive electrode sheet contains the lithium-rich composite material of the above-mentioned application example.
  • the secondary battery of the embodiment of the present application contains the lithium-rich composite material of the above-mentioned application example, based on the excellent lithium-replenishing performance of the lithium-rich composite material of the above-mentioned application example or further has ion conductivity and/or electron conductivity, endows
  • the secondary battery of the embodiment of the present application has excellent first coulombic efficiency, battery capacity and cycle performance, long life, and stable electrochemical performance.
  • lithium-rich composite materials and preparation methods thereof:
  • the lithium-rich composite material includes a LiFeO 2 ⁇ 1.99Li 2 O core body and a dense hydrophobic layer covering the core body, and the material of the dense hydrophobic layer is a composite of LFP (lithium iron phosphate) and carbon.
  • LFP lithium iron phosphate
  • the core body is LiFeO 2 ⁇ 1.99Li 2 O
  • the cladding layer is a dense hydrophobic layer
  • the material of the dense hydrophobic layer is a composite of LFP (lithium iron phosphate) and carbon.
  • the mass of LFP is 3.9wt% of the total mass of lithium-rich composite material, and the mass of carbon is 15wt % of the mass of LFP;
  • the BET specific surface area is 4.1m 2 /g, and the measured resistivity is less than 450 ⁇ cm at 25°C.
  • the lithium-rich composite material includes LiFeO 2 ⁇ 1.99Li 2 O ⁇ 0.005Al 2 O 3 nuclei and a dense hydrophobic layer covering the nuclei, and the material of the dense hydrophobic layer is a composite of LMFP (lithium manganese iron phosphate) and carbon .
  • LMFP lithium manganese iron phosphate
  • the mass of LMFP is 3wt% of the total mass of the lithium-rich composite material , and the mass of carbon is 12wt % of the mass of LMFP;
  • the thickness of the dense hydrophobic layer is 80nm, the BET specific surface area is 7.3m 2 /g, and the measured resistivity is lower than 390 ⁇ cm at 25°C.
  • the lithium-rich composite material includes a LiFeO 2 ⁇ 2.025Li 2 O ⁇ 0.01CuO core body and a dense hydrophobic layer covering the core body, and the material of the dense hydrophobic layer is a composite of LVP (lithium vanadium phosphate) and carbon.
  • LVP lithium vanadium phosphate
  • the core body is LiFeO 2 ⁇ 2.025Li 2 O ⁇ 0.01CuO
  • the cladding layer is a dense hydrophobic layer
  • the material of the dense hydrophobic layer is a composite of LVP (lithium vanadium phosphate) and carbon.
  • the mass of LVP is 13wt% of the total mass of the lithium-rich composite material, and the mass of carbon is 4wt% of the mass of LVP;
  • the average particle size of the core body LiFeO 2 2.025Li 2 O 0.01CuO is 7.3 ⁇ m, dense and hydrophobic
  • the thickness of the layer is 130nm, the BET specific surface area is 5.9m 2 /g, and the measured resistivity is lower than 230 ⁇ cm at 25°C.
  • the lithium-rich composite material includes LiFeO 2 ⁇ 1.99Li 2 O ⁇ 0.005Al 2 O 3 nuclei and a dense hydrophobic layer covering the nuclei, and the material of the dense hydrophobic layer is a composite of LMP (lithium manganese phosphate) and carbon.
  • LMP lithium manganese phosphate
  • the mass of LMP is 12wt% of the total mass of the lithium-rich composite material, and the mass of carbon is 5wt% of the mass of LMP; the average particle size of the nuclei LiFeO 2 1.99Li 2 O 0.005Al 2 O 3 is 5.2 ⁇ m , the thickness of the dense hydrophobic layer is 75nm, the BET specific surface area is 11m 2 /g, and the measured resistivity is lower than 295 ⁇ cm at 25°C.
  • the lithium-rich composite material includes a LiFeO 2 ⁇ 2.025Li 2 O ⁇ 0.01CuO core body and a dense hydrophobic layer covering the core body, and the material of the dense hydrophobic layer is a composite of LFP (lithium iron phosphate) and carbon.
  • LFP lithium iron phosphate
  • the mass of LFP is 15wt% of the total mass of the lithium-rich composite material, and the mass of carbon is 3.0wt% of the mass of LFP;
  • the thickness of the hydrophobic layer is 130nm, the BET specific surface area is 2.5m 2 /g, and the measured resistivity is lower than 430 ⁇ cm at 25°C.
  • the lithium-rich composite material includes a LiFeO 2 ⁇ 2.025Li 2 O ⁇ 0.01MnO core body and a dense hydrophobic layer covering the core body, and the material of the dense hydrophobic layer is a composite of LMFP (lithium manganese iron phosphate) and carbon.
  • LMFP lithium manganese iron phosphate
  • the core body was LiFeO 2 ⁇ 2.025Li 2 O ⁇ 0.01MnO
  • the cladding layer was a dense hydrophobic layer
  • the material of the dense hydrophobic layer is a composite of LMFP and carbon.
  • the mass of LMFP is 4.6wt% of the total mass of the lithium-rich composite material, and the mass of carbon is 3.1wt% of the mass of LMFP;
  • the thickness of the dense hydrophobic layer is 45nm, the BET specific surface area is 5.9m 2 /g, and the measured resistivity is lower than 420 ⁇ cm at 25°C.
  • the lithium-rich composite material includes a LiFeO 2 ⁇ 2.025Li 2 O ⁇ 0.01MnO core body and a dense hydrophobic layer covering the core body, and the material of the dense hydrophobic layer is a composite of LMFP (lithium manganese iron phosphate) and carbon.
  • LMFP lithium manganese iron phosphate
  • step S2 Mix the composite material prepared in step S2 with the citric acid solution, dry and heat-treat in air at 300°C for 4 hours, add 7wt% of the powder mass ratio of LiFeO 2 1.99Li 2 O 0.01MnO 2 , then ball mill and mix evenly, place Pass N 2 protection in the rotary furnace, pass 1L/min ethanol and 20L/min N 2 , raise the temperature to 650°C at a heating rate of 200°C/h and keep it for 4 hours, then cool down to obtain a lithium-rich composite material, and its nucleus is LiFeO 2 ⁇ 2.025 Li 2 O ⁇ 0.01MnO, the first cladding layer is LMFP, and the first cladding layer is a composite dense hydrophobic layer of carbon layer.
  • This comparative example provides a lithium-rich material and a preparation method thereof.
  • the lithium-rich material of this comparative example is LiFeO 2 ⁇ 1.99Li 2 O.
  • the lithium-rich material of this comparative example does not contain a dense hydrophobic layer of LFP and carbon composite.
  • This comparative example provides a lithium-rich material and a preparation method thereof.
  • the lithium-rich material in this comparative example is LiFeO 2 ⁇ 2.025Li 2 O ⁇ 0.01CuO.
  • the lithium-rich material in this comparative example does not contain a dense hydrophobic layer of LVP and carbon composite.
  • This comparative example provides a lithium-rich composite material and a preparation method thereof.
  • the lithium-rich composite material of this comparative example includes LiFeO 2 ⁇ 1.99Li 2 O nuclei and a dense hydrophobic layer of carbon material covering the nuclei.
  • the difference is that there is no
  • the dense hydrophobic layer containing LFP is only the dense hydrophobic layer of the carbon material, and the thickness of the dense hydrophobic layer of the carbon material of the lithium-rich material in this comparative example is basically equal to the thickness of the dense hydrophobic layer of the lithium-rich composite material in Example 1.
  • This comparative example provides a lithium-rich composite material and a preparation method thereof.
  • the lithium-rich composite material of this comparative example includes a LiFeO 2 ⁇ 1.99Li 2 O core body and a dense hydrophobic layer of ternary materials covering the core body.
  • the difference lies in the dense hydrophobic layer material of the lithium-rich material of this comparative example
  • the dense hydrophobic layer formed by the ternary material was replaced, and the thickness of the dense hydrophobic layer of the lithium-rich material in this comparative example was controlled to be substantially equal to the thickness of the dense hydrophobic layer of the lithium-rich composite material in Example 1.
  • lithium-rich composite materials provided by the above-mentioned examples 1 to 7 and the lithium-rich materials provided by the comparative examples were assembled into positive electrodes and lithium-ion batteries according to the following methods:
  • Positive electrode under the same conditions, LFP, lithium supplement additive, polyvinylidene fluoride and SP-Li were mixed and ball-milled at a mass ratio of 90:5:2:3 to obtain positive electrode slurry, and the positive electrode slurry was coated on The surface of the aluminum foil was rolled and dried overnight at 110°C in vacuum to obtain the positive pole piece; wherein, the lithium-supplementing additives were the lithium-rich composite materials provided in the above-mentioned Examples 1 to 7 and the ones provided in Comparative Examples 1 to 3. Lithium-rich materials;
  • Negative electrode lithium metal sheet
  • Electrolyte Mix ethylene carbonate and ethyl methyl carbonate at a volume ratio of 3:7, and add LiPF 6 to form an electrolyte, the concentration of LiPF 6 is 1mol/L;
  • Diaphragm polypropylene microporous septum
  • Lithium-ion battery assembly The structure of lithium metal sheet-diaphragm-electrolyte-positive electrode sheet is assembled into a lithium-ion battery in an inert atmosphere glove box.
  • the lithium-rich composite materials provided in the above-mentioned Examples 1 to 7 and the lithium-rich materials provided in the comparative examples were analyzed by scanning electron microscopy, wherein, the SEM photos of the lithium-rich composite materials provided in Example 1 are shown in Figure 4.
  • the SEM photo of the lithium-rich material provided in Example 1 is shown in Figure 5.
  • the SEM photos of the lithium-rich composite material provided in other embodiments are similar to those shown in FIG. 4 .
  • the lithium-rich iron-based composite material with a coating structure and a dense hydrophobic layer provided in this example has many non-standard particles, and the interface is relatively rough and grainy.
  • the interface of the uncoated lithium-rich iron-based composite material in Comparative Example 1 is also relatively rough.
  • the lithium-rich composite materials provided in the above-mentioned Examples 1 to 7 were respectively subjected to X-ray diffraction analysis, wherein, the XRD photo of the lithium-rich composite material provided in Example 1 is shown in Figure 6, and the lithium-rich material provided in Example 5 The SEM photographs are shown in Figure 7.
  • the lithium-rich composite material in Example 1 has a diffraction peak with a small amount of LiFePO 4 in addition to the main peak being Li 5 FeO 4 ; it can be seen from Figure 7 that the lithium-rich iron-based composite material is mainly Li 5 The diffraction peaks of FeO 4 and LiFePO 4 are more obvious.
  • Inductively coupled plasma (Inductively Coupled Plasma: ICP) emission spectrometry was used to analyze the content of the doping element M in the lithium-rich iron-based nuclei contained in the lithium-rich composite materials of Examples 1-6.
  • ICP Inductively Coupled Plasma
  • the y value of the doping element M in Table 1 is the content of the doping element M in the lithium-rich iron-based nuclei.
  • the charge-discharge voltage is 2.7V-4.3V. Please refer to Table 1 for the electrochemical properties of the lithium secondary batteries of Examples 1-6 and Comparative Examples 1-2. .
  • the lithium-rich composite material of the embodiment of the present application is provided with a dense hydrophobic layer, and the positive electrode slurry used for its preparation does not appear jelly phenomenon and is easy to coat, and when it is added to a lithium secondary battery,
  • the positive electrode can be made to have higher first-time gram capacity and lower first-time efficiency, thereby compensating for the decrease in energy density caused by the irreversible lithium loss of the first negative electrode.
  • the lithium-rich iron-based materials in Comparative Example 1 and Comparative Example 2 were not coated, and jelly was formed due to water absorption during the preparation of the positive electrode slurry, which was not conducive to the coating of the positive electrode slurry.
  • Comparative Example 3 contains a carbon coating, it still absorbs water and forms a jelly-like shape.
  • Comparative Example 4 contains a ternary material coating and does not cause a jelly-like appearance during processing, it directly leads to slurry The rise of viscosity still leads to the reduction and instability of its processing performance.

Abstract

本申请公开了一种富锂复合材料及其制备方法和应用。本申请富锂复合材料包括核体和包覆于核体的致密疏水层，核体包括富锂材料，致密疏水层的材料包括聚阴离子型电化学活性材料。本申请富锂复合材料含有致密疏水层，具有高的致密性，且残碱含量低，与电解液接触的化学稳定性高。另外，富锂复合材料的制备方法能够保证制备的富锂复合材料结构和电化学性能稳定，而且效率高，节约生产成本。

Description

富锂复合材料及其制备方法和应用
本申请要求于2021年11月22日提交中国专利局，申请号为202111390217.4，申请名称为“富锂复合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，具体涉及一种富锂复合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。
锂离子电池在首次充电过程中，负极表面通常伴随着固态电解质膜SEI膜的形成，这个过程会消耗大量的Li +，意味着从正极材料脱出的Li +部分被不可逆消耗，对应电芯的可逆比容量降低。负极材料特别是硅基负极材料则会进一步消耗Li +，造成正极材料的锂损失，降低电池的首次库伦效率和电池容量。如在使用石墨负极的锂离子电池体系中，首次充电会消耗约10％的锂源。当采用高比容量的负极材料，例如合金类(硅、锡等)、氧化物类(氧化硅、氧化锡)和无定形碳负极时，正极锂源的消耗将进一步加剧。
为改善由于负极不可逆损耗引起的低库伦效率问题，除在负极材料、极片预锂化外，对正极进行补锂同样可以达到高能量密度的要求。如目前公开报道的富锂铁系材料理论容量高达867mAh/g，工作电压窗口与常规锂离子电池一致，且在后期基本不参与电化学过程，是一种具有广阔前景的正极补锂添加剂。在公开的另一份正极补锂材料Li 5FeO 4中，其采用溶胶凝胶法制备，该材料用作锂离子电池正极补锂材料具有充电容量大，放电容量小特点，然而该材料对环境适应性苛刻，表层残碱大不易加工。在公开的另一份碳包覆铁酸锂材料中，通过采用碳源进行气相包覆隔绝外界环境，缓解铁酸锂和空气中的水接触从而提高材料稳定性；尽管如此，包覆层始终难以彻底隔绝与空气中的水接触，导致材料变质失效。而且采用碳包覆后，虽然可以改善碳包覆铁酸锂材料的电子导率，但是增加了离子传导的路径和影响了离子导率，从而导致碳包覆铁酸锂材料补锂效果。同时碳包覆铁酸锂材料在包覆层中或与铁酸锂核体界面之间依然存在残碱，导致其不易加工。而且表面与电解液界面活性高，以与电解液发生副反应，从而导致电池电化学性能降低。
技术问题
本申请的目的在于克服现有技术的上述不足，提供一种富锂复合材料及其制备方法，以解决现有包覆结构的正极补锂添加剂存在稳定性不理想和与电解液界面活性高的技术问题。
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，以解决现有二次电池首次库伦效率和电池容量不理想的技术问题。
技术解决方案
为了实现上述申请目的，本申请的第一方面，提供了一种富锂复合材料。本申请富锂复 合材料，包括核体和包覆于核体的致密疏水层，核体包括富锂材料，致密疏水层的材料包括聚阴离子型电化学活性材料，所述聚阴离子型电化学活性材料为磷酸盐类电极活性材料。
进一步地，致密疏水层的材料还包括电子导电剂，电子导电剂与聚阴离子型电化学活性材料形成混合物。
更进一步地，电子导电剂包括导电碳材料、导电氧化物、导电有机物中的至少一种。
更进一步地，在致密疏水层中，电子导电剂占聚阴离子型电化学活性材料质量的1-6wt％。
具体地，导电碳材料包括无定形碳、碳纳米管、石墨、炭黑、石墨烯中的至少一种；导电氧化物包括In 2O 3、ZnO、SnO 2中的至少一种；导电有机物包括导电聚合物。
进一步地，致密疏水层包括活性材料包覆层，活性材料包覆层包覆核体，且活性材料包覆层的材料为聚阴离子型电化学活性材料。
更进一步地，致密疏水层还包括电子导体封装层，电子导体封装层包覆在活性材料包覆层的背离核体的表面。
具体地，电子导体封装层的材料包括碳材料、导电氧化物、导电有机物中的至少一种。
具体地，电子导体封装层的厚度为1-100nm。
进一步地，聚阴离子型电化学活性材料在富锂复合材料中的含量为0.5-30wt％。
进一步地，聚阴离子型电化学活性材料包括磷酸铁锂、磷酸锰锂、磷酸锰铁锂、磷酸钒锂、磷酸镍锂、磷酸钴锂中的至少一种。
进一步地，富锂材料包括富锂铁系、富锂锰系、富锂镍系，富锂钴系中的至少一种。
具体地，富锂铁系材料的化学通式为aLiFeO 2·bLi 2O·cM xO y；其中，所述化学通式中的a、b、c为摩尔数，且满足a+b≥0.98；c≤0.02；1.8≤b/a≤2.1；M为Si、Ni、Co、Mn、Ti、Al、Cu、V、Zr、Sn中的一种或多种；1≤y/x≤2.5，x为1-3。
进一步地，富锂复合材料的粒径满足：1μm≤D50≤10μm。
进一步地，富锂复合材料的粒径满足：1μm≤D50≤10μm，D10/D50≥0.3，D90/D50≤2。
进一步地，富锂复合材料的BET比表面为0.5-20m 2/g。
进一步地，富锂复合材料的电阻率为1.0-500Ω/cm。
本申请的第二方面，提供了本申请富锂复合材料的制备方法。本申请富锂复合材料的制备方法包括如下步骤：
将含聚阴离子型电化学活性材料或其前驱体材料在富锂材料表面形成致密疏水层，包覆富锂材料，得到富锂复合材料；其中，所述聚阴离子型电化学活性材料为磷酸盐类电极活性材料。
进一步地，将含聚阴离子型电化学活性材料前驱体材料在富锂材料表面形成致密疏水层的方法包括如下步骤：
将包括第一电子导电剂或第一电子导电剂前驱体材料与聚阴离子型电化学活性材料前驱体材料的混合物与富锂材料进行混合处理，在富锂材料表面形成第一包覆层，得到第一富锂复合材料前驱体；
于保护气氛中，将第一富锂复合材料前驱体进行第一烧结处理，得到富锂复合材料。
进一步地，将含聚阴离子型电化学活性材料前驱体材料在富锂材料表面形成致密疏水层的方法包括如下步骤：
将聚阴离子型电化学活性材料前驱体与富锂材料进行混合处理，在富锂材料表面形成第二包覆层，得到第二富锂复合材料前驱体；
于保护气氛中，将第二富锂复合材料前驱体进行第二烧结处理，得到活性材料包覆层的富锂复合材料；
将第二电子导电剂或第二电子导电剂前驱体材料与活性材料包覆层的富锂复合材料进行混合处理，在活性材料包覆层的富锂复合材料表面形成第三包覆层，得到第三富锂复合材料前驱体；
于保护气氛中，第三富锂复合材料前驱体进行第三烧结处理，得到富锂复合材料。
进一步地，聚阴离子型电化学活性材料前驱体材料包括磷酸铁锂前驱体、磷酸锰锂前驱体、磷酸锰铁锂前驱体、磷酸钒锂前驱体、磷酸镍锂前驱体、磷酸钴锂前驱体中的至少一种。
本申请的第三方面，提供了一种正极片。本申请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，正极活性层中含有本申请富锂复合材料或由本申请富锂复合材料制备方法制备的富锂复合材料。
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：
本申请富锂复合材料通过致密疏水层包覆含富锂材料的核体，这样，致密疏水层能够有效包覆核体所含的富锂材料，使得核体与外界隔离，避免外界中如水分和二氧化碳与核体的接触，保证核体的稳定性从而保证富锂复合材料的补锂效果和补锂的稳定性。致密疏水层所含的聚阴离子型电化学活性材料，具体是磷酸盐类电极活性材料，这样该聚阴离子型电化学活性材料一方面有效增强了致密疏水层的致密性能，增强了核体与外界隔离效果；另一方面，至少在致密疏水层中残碱含量低，赋予本申请富锂复合材料优异的加工性能。另外，聚阴离子型电化学活性材料赋予致密疏水层与电解液接触的化学稳定性高，降低了与电解液之间的副反应，提高了电池电化学性能的稳定性。
本申请富锂复合材料的制备方法能够有效制备具有核壳结构的富锂复合材料，而且能够使得致密疏水层含有聚阴离子型电化学活性材料，有效包覆含富锂材料的核体，同时使得制备的富锂复合材料所含残碱含量低，从而保证制备的富锂复合材料电化学性能稳定，具有良好的加工性能，而且赋予制备的富锂复合材料与电解液接触界面高的电化学稳定性。另外，富锂复合材料的制备方法能够保证制备的富锂复合材料结构和电化学性能稳定，而且效率高，节约生产成本。
本申请正极片由于含有本申请富锂复合材料，因此，本申请正极片的正极活性层所含成分分散均匀，膜层质量高，与电解液接触界面的化学性能稳定，赋予本申请正极片优异的电化学性能，提高了电池首效和整体电化学性能。
本申请二次电池由于含有本申请电极片，因此，本申请锂离子电池具有优异的首次库伦 效率和电池容量以及循环性能，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为本申请实施例富锂复合材料的结构示意图；
图2为图1所示本申请实施例富锂复合材料的一种结构示意图；
图3为图1所示本申请实施例富锂复合材料的另一种结构示意图；
图4为实施例1提供富锂复合材料的SEM图；
图5为对比例1提供富锂材料的SEM图；
图6为实施例1提供富锂复合材料的XRD图；
图7为实施例5提供富锂复合材料的XRD图。
本发明的实施方式
为了使本申请要解决的技术问题、技术方案及有益效果更加清楚明白，以下结合实施例，对本申请进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本申请，并不用于限定本申请。
本申请中，术语“和/或”，描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B的情况。其中A，B可以是单数或者复数。字符“/”一般表示前后关联对象是一种“或”的关系。
本申请中，“至少一个”是指一个或者多个，“多个”是指两个或两个以上。“以下至少一项(个)”或其类似表达，是指的这些项中的任意组合，包括单项(个)或复数项(个)的任意组合。例如，“a,b,或c中的至少一项(个)”，或，“a,b,和c中的至少一项(个)”，均可以表示：a,b,c,a-b(即a和b),a-c,b-c,或a-b-c，其中a,b,c分别可以是单个，也可以是多个。
应理解，在本申请的各种实施例中，上述各过程的序号的大小并不意味着执行顺序的先后，部分或全部步骤可以并行执行或先后执行，各过程的执行顺序应以其功能和内在逻辑确定，而不应对本申请实施例的实施过程构成任何限定。
在本申请实施例中使用的术语是仅仅出于描述特定实施例的目的，而非旨在限制本申请。在本申请实施例和所附权利要求书中所使用的单数形式的“一种”、“所述”和“该”也旨在包括多数形式，除非上下文清楚地表示其他含义。
本申请实施例说明书中所提到的相关成分的重量不仅仅可以指代各组分的具体含量，也可以表示各组分间重量的比例关系，因此，只要是按照本申请实施例说明书相关组分的含量按比例放大或缩小均在本申请实施例说明书公开的范围之内。具体地，本申请实施例说明书中所述的质量可以是μg、mg、g、kg等化工领域公知的质量单位。
术语“第一”、“第二”仅用于描述目的，用来将目的如物质彼此区分开，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。例如，在不脱离本申请实施例范围的情况下，第一XX也可以被称为第二XX，类似地，第二XX也可以被称为第一XX。 由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括一个或者更多个该特征。
第一方面，本申请实施例提供了一种富锂复合材料。本申请实施例富锂复合材料包括核体和包覆于核体的致密疏水层，也即是本申请实施例富锂复合材料为核壳结构，如实施例中，本申请实施例富锂复合材料的结构如图1至图5所示，包括核体10和包覆于核体10的致密疏水层20。
其中，核体10包括富锂材料，也即是在本申请实施例富锂复合材料中，核体10是为用于提供锂离子的锂源。由于核体10富含锂，从而保证本申请实施例富锂复合材料能够提供丰富的锂。
同时，核体10所含的富锂材料可以是常规的补锂材料，也可以是新研发的补锂材料。基于本申请实施例富锂复合材料的作用，实施例中，核体10所含的富锂材料可以是三元补锂材料或二元补锂材料。如该富锂材料可以是包括富锂铁系、富锂锰系、富锂镍系，富锂钴系中的至少一种。如当富锂材料为富锂铁系材料时，富锂铁系材料的化学通式可以是aLiFeO 2·bLi 2O·cM xO y。该化学通式中的a、b、c为摩尔数，且满足a+b≥0.98；c≤0.02；1.8≤b/a≤2.1；M为Si、Ni、Co、Mn、Ti、Al、Cu、V、Zr、Sn中的一种或多种；1≤y/x≤2.5，x为1-3。因此，具体实施例中，该富锂铁系材料可以是LiFeO 2·1.99Li 2O、LiFeO 2·1.99Li 2O·0.005Al 2O 3等。该些富锂材料富含锂，能够高效的提供锂离子。
实施例中，核体10可以是一次颗粒、二次颗粒中的至少一种，具体的核体10所含富锂材料形成的一次颗粒、二次颗粒中的至少一种。实施例中，核体10的粒径可以为0.5μm-20μm。如当核体10为一次颗粒时，一次颗粒粒径也即是核体10的粒径分布为0.5μm-15μm；当核体10为二次颗粒时，二次颗粒粒径也即是核体10的粒径分布为1μm-20μm。其中，二次颗粒是指由一颗以上的一次颗粒聚集而成的团聚颗粒。通过对核体10粒径形态和粒径控制，在其能够提供丰富的锂离子的基础上，还提高了富锂复合材料在锂电池浆料制备中的可加工性，其中，较小的一次粒径也可以脱出更多的锂。
另外，上述各实施例中的核体10所含的富锂材料虽然富含锂，但是其遇水和二氧化碳具有不稳定性，其易与水和二氧化碳发生反应，从而导致本申请实施例富锂复合材料的补锂效果降低。同时富锂材料一般还富含由于加工形成的残碱，该些残碱会进一步导致其加工性能的降低，如会导致含有上文富锂材料如浆料粘度剧增，迅速凝胶失去流动性，从而无法进行后续加工处理。如相关研究表明富锂材料特别是补锂材料的首要难点在于高活性材料界面以及表层大量残碱的控制，导致其在具有一定湿度的氛围中，残碱极易转化为氢氧化锂等产物，对后续浆料加工造成诸多麻烦。而且高活性界面极易与碳酸酯类溶剂发生复杂的副反应，从而导致富锂材料的电化学性能不稳定或降低。因此，在上述各实施例中的核体10的基础上，上述各实施例中富锂复合材料所含的致密疏水层20包覆于核体10，形成完整的包覆层，如图1所示。这样，致密疏水层20能够有效包覆核体10所含的富锂材料，使得核体10与外界隔离，避免外界中如水分和二氧化碳与核体10的接触，保证核体10的稳定性从而保证富锂复合材料电化学性能的稳定性。
其中，致密疏水层20的材料包括聚阴离子型电化学活性材料，而且聚阴离子型电化学活性材料为磷酸盐类电极活性材料。这样，在致密疏水层20中增设聚阴离子型电化学活性 材料，该聚阴离子型电化学活性材料的存在增强了致密疏水层20的致密性能，增强了核体10与外界隔离效果。而且该聚阴离子型电化学活性材料能够提高锂离子的导率，更有利于核体10中锂离子的脱出和传导。如当核体10内所含的富锂材料为补锂材料时，有利于该富锂材料所含锂离子的脱出和传导，提高该富锂材料的补锂效果。另外，聚阴离子型电化学活性材料的存在，增强了致密疏水层20与电解液接触界面的化学稳定性，如增强了致密疏水层20与碳酸酯类溶剂接触的化学稳定性，降低甚至避免了电解液接触界面的副反应，从而增强了发生复杂的副反应富锂复合材料与电解液接触的化学稳定性。与此同时，聚阴离子型电化学活性材料的存在，还使得核体10和致密疏水层20中残碱含量低，赋予本申请实施例富锂复合材料优异的加工性能。而且该聚阴离子型电化学活性材料选定为磷酸盐类电极活性材料，赋予致密疏水层20优异的耐水性，表面残碱低，相对三元材料更易于加工。与此同时，磷酸盐类材料附带导电性碳层，有效增加致密疏水层20整体导电效果。
基于致密疏水层20的上述作用，致密疏水层20增设的聚阴离子型电化学活性材料在致密疏水层20中的分布可以是如下几种情况：
实施例中，聚阴离子型电化学活性材料与其他材料形成混合物，并形成致密疏水层20以包覆核体10。如实施例中，其他材料可以是电子导电剂，也即是致密疏水层20的材料还包括电子导电剂，该电子导电剂与该聚阴离子型电化学活性材料形成混合物。其中，该聚阴离子型电化学活性材料与电子导电剂材料共同形成致密疏水层20，使得致密疏水层20具有高致密性的基础上，两者起到增效作用，增强锂离子传导的同时提高致密疏水层20的电子电导率，降低残碱含量和增强致密疏水层20与电解液接触界面的化学稳定性。
进一步实施例中，当致密疏水层20的材料为电子导电剂与该聚阴离子型电化学活性材料形成混合物时，控制聚阴离子型电化学活性材料在富锂复合材料中的含量为0.5-30wt％，具体可以是0.5wt％、1wt％、3wt％、5wt％、8wt％、10wt％、13wt％、15wt％、17wt％、20wt％、23wt％、25wt％、27wt％、30wt％等含量。另些实施例中，控制该电子导电剂占聚阴离子型电化学活性材料质量的1-6wt％，具体可以是1wt％、2wt％、3wt％、4wt％、5wt％、6wt％。通过控制两者混合复配的比例，进一步提高致密疏水层20的致密性，增强致密疏水层20的离子导率和电子导率，进一步降低富锂复合材料特别是致密疏水层20中残碱含量和增强致密疏水层20与电解液接触界面的化学稳定性。
具体实施例中，电子导电剂可以包括导电碳材料、导电氧化物、导电有机物中的至少一种。当为导电碳材料时，导电碳材料包括无定形碳、碳纳米管、石墨、炭黑、石墨烯等中的至少一种。当为导电氧化物时，导电氧化物可以包括In 2O 3、ZnO、SnO 2中的至少一种。导电有机物可以是导电聚合物等。该些电子导电剂具有高的电子导率，且与聚阴离子型电化学活性材料一起提高致密疏水层20的致密性或进一步提高与电解液接触界面的化学稳定性和降低残碱的含量。
另些实施例中，致密疏水层20的结构如图2所示，包括活性材料包覆层21。该活性材料包覆层21包覆核体10，且活性材料包覆层21的材料为聚阴离子型电化学活性材料。也即是，在如图2所示的致密疏水层20中，聚阴离子型电化学活性材料形成包覆层，也即是形成的该活性材料包覆层21包覆核体10。进一步地，基于图2所示的结构，聚阴离子型电化 学活性材料也即是其形成的活性材料包覆层21在富锂复合材料中的含量为0.5-30wt％。通过对活性材料包覆层21的含量控制活性材料包覆层21的厚度，使得活性材料包覆层21具有高的致密性，并充分发挥聚阴离子型电化学活性材料上文所述的作用。
在进一步实施例中，基于图2所述的致密疏水层20结构，如图3所示，致密疏水层20还包括电子导体封装层22，该电子导体封装层22包覆在活性材料包覆层21的背离核体10的表面，也即是该电子导体封装层22包覆在活性材料包覆层21的外表面上。这样，活性材料包覆层21与电子导体封装层22一起构成复合结构包覆层，此时，致密疏水层20为复合结构。在该复合结构中，该活性材料包覆层21在发挥上文活性材料包覆层21的作用，电子导体封装层22发挥电子导率作用的基础上，两膜层复配起到增效作用，进一步提高致密疏水层20的致密性，进一步增强致密疏水层20的离子导率和电子导率以及与电解液接触界面的化学稳定性，进一步降低富锂复合材料特别是密疏水层20的残碱含量。
实施例中，图3所示的电子导体封装层22的厚度可以是1-100nm。另些实施例中，电子导体封装层22的材料可以包括碳材料、导电氧化物、导电有机物中的至少一种。具体实施例中，电子导体封装层22的材料为碳材料时，碳材料包括无定形碳、碳纳米管、石墨、炭黑、石墨烯等中的至少一种。当电子导体封装层22的材料为导电氧化物时，导电氧化物可以包括In 2O 3、ZnO、SnO 2中的至少一种。导电有机物可以是导电聚合物等。通过调节电子导体封装层22的含量和材料，进一步提高其上述的作用。
另外，在基于图1至图3所示的结构基础上，还可以根据需要在图1所示的致密疏水层20外表面包覆其他功能层，或在图2所示的活性材料包覆层21外表面包覆其他功能层，或在图3所示的电子导体封装层22外表面包覆其他功能层。其他功能层的种类可以根据需要进行灵活选择。
实施例中，上述各实施例中致密疏水层20所含的聚阴离子型电化学活性材料可以包括磷酸铁锂、磷酸锰锂、磷酸锰铁锂、磷酸钒锂、磷酸镍锂、磷酸钴锂中的至少一种。通过对该聚阴离子型电化学活性材料种类的控制和选择，提高聚阴离子型电化学活性材料上文所述的作用，从而提高富锂复合材料脱锂能力和离子传导性能，而且提高致密疏水层20致密性和与电解液接触界面的化学稳定性，降低残碱含量，从而提高富锂复合材料的电化学性能和电化学性能的稳定性以及加工性能。经测得，上述实施例富锂复合材料的比表面积为0.2-20m 2/g，致密性好。富锂复合材料的电阻率为1.0-500Ω/cm，电子导率高。
另外，通过控制富锂复合材料核体10的粒径和致密疏水层20的厚度范围，可以控制和调节富锂复合材料的粒径，如控制和调节富锂复合材料的粒径满足：1μm≤D50≤10μm；进一步地，富锂复合材料的粒径满足：1μm≤D50≤10μm，D10/D50≥0.3，D90/D50≤2。因此，上述实施例富锂复合材料的粒径均匀，且可控。
第二方面，本申请实施例还提供了上文富锂复合材料的制备方法。实施例中，本申请实施例富锂复合材料的制备方法包括以下步骤：
将含聚阴离子型电化学活性材料或其前驱体材料在富锂材料表面形成致密疏水层，包覆富锂材料，得到富锂复合材料。
其中，本申请实施例富锂复合材料的制备方法中所用的富锂材料是形成上文富锂复合材 料的核体10中的富锂材料。聚阴离子型电化学活性材料也为上文富锂复合材料的致密疏水层20中的聚阴离子型电化学活性材料。为了节约篇幅，在此不再对富锂材料和聚阴离子型电化学活性材料做赘述。其中，富锂材料和聚阴离子型电化学活性材料可以分别按照对应富锂材料的制备方法进行制备获得。
由于本申请实施例富锂复合材料的制备方法采用了含聚阴离子型电化学活性材料或其前驱体材料形成致密疏水层。因此，在形成的致密疏水层中含有聚阴离子型电化学活性材料，从而生成上文本申请实施例的致密疏水层20。这样，制备的富锂复合材料所具有核壳包覆结构，而且形成的致密疏水层致密性高，增强了核体与外界隔离效果，隔绝环境中的水、二氧化等不利因素效果好。而且使得制备的富锂复合材料所含残碱特别是致密疏水层残碱含量低和与电解液接触的高化学稳定性，使得富锂复合材料优异的加工性能，降低了与电解液之间的副反应。另外，富锂复合材料的制备方法能够保证制备的富锂复合材料结构和电化学性能稳定，而且效率高，节约生产成本。
上述本申请实施例富锂复合材料的制备方法中，将含聚阴离子型电化学活性材料前驱体材料在富锂材料表面形成致密疏水层处理的方法可以根据具体的含聚阴离子型电化学活性材料或其前驱体材料的种类和性能而采用相应方法实现对富锂材料的包覆并形成致密疏水层。如至少可以是如下方法对富锂材料的包覆并形成致密疏水层：
一实施例中，将含聚阴离子型电化学活性材料前驱体材料在富锂材料表面形成致密疏水层的方法包括如下步骤：
S11：将包括第一电子导电剂或第一电子导电剂前驱体材料与聚阴离子型电化学活性材料前驱体材料的混合物与富锂材料进行混合处理，在富锂材料表面形成第一包覆层，得到第一富锂复合材料前驱体；
S12：于保护气氛中，将第一富锂复合材料前驱体进行第一烧结处理，得到富锂复合材料。
其中，步骤S11中，将第一电子导电剂或第一电子导电剂前驱体材料与聚阴离子型电化学活性材料前驱体材料的混合物与富锂材料混合处理后，该混合物会在富锂材料表面形成包覆膜层，得到第一富锂复合材料前驱体。该混合处理可以根据该混合物的形态而定，如可以是液态混合包覆，也可以是固态混合包覆等。另外，该混合物中，第一电子导电剂或第一电子导电剂前驱体材料与聚阴离子型电化学活性材料前驱体材料的混合物比例可以根据在形成的致密疏水层中电子导电剂含量而定，如控制混合比例，使得电子导电剂占聚阴离子型电化学活性材料质量的1-6wt％。或进一步控制混合物与富锂材料的混合比例，使得聚阴离子型电化学活性材料在富锂复合材料中的含量为0.5-30wt％。
具体实施例中，第一电子导电剂如上文致密疏水层20所含的电子导电剂，可以包括导电碳材料、导电氧化物中的至少一种。那么第一电子导电剂前驱体材料也是对应第一电子导电剂的前驱体材料。同样，聚阴离子型电化学活性材料前驱体材料也是形成上文聚阴离子型电化学活性材料对应的前驱体材料。如当聚阴离子型电化学活性材料为磷酸铁锂时，那么聚阴离子型电化学活性材料前驱体为形成磷酸铁锂的前驱体，包括锂源、铁源和磷源的混合物。
步骤S12中的第一烧结处理是使得聚阴离子型电化学活性材料前驱体或第一电子导电 剂前驱体烧结分别形成聚阴离子型电化学活性材料和第一电子导电剂的混合物，并原位在富锂材料表面形成致密疏水层。第一烧结处理的条件可以根据聚阴离子型电化学活性材料前驱体或第一电子导电剂前驱体的烧结条件而定，如当聚阴离子型电化学活性材料前驱体为磷酸铁锂前驱体，第一电子导电剂前驱体为有机物时，该第一烧结处理可以是于非氧化气氛中，以100-500℃/h升温至450℃-900℃下保温0.5-10h。
步骤S12中保护气氛可以是氮气或/和氩气形成的化学惰性气氛环境。
当然，也可以直接利用第一电子导电剂或第一电子导电剂前驱体材料和聚阴离子型电化学活性材料或其前驱体材料采用气相沉积的方式在富锂材料表面原位沉积形成含聚阴离子型电化学活性材料与第一电子导电剂混合物的致密疏水层。
另一实施例中，将含聚阴离子型电化学活性材料前驱体材料在富锂材料表面形成致密疏水层的方法包括如下步骤：
S21：将聚阴离子型电化学活性材料前驱体材料与富锂材料进行混合处理，在富锂材料表面形成第二包覆层，得到第二富锂复合材料前驱体；
S22：于保护气氛中，将第二富锂复合材料前驱体进行第二烧结处理，得到含活性材料包覆层的富锂复合材料；
S23：将包括第二电子导电剂或第二电子导电剂前驱体材料与含活性材料包覆层的富锂复合材料进行混合处理，在含活性材料包覆层的富锂复合材料表面形成第三包覆层，得到第三富锂复合材料前驱体；
S24：于保护气氛中，第三富锂复合材料前驱体进行第三烧结处理，得到富锂复合材料。
其中，步骤S21中的混合处理后，该聚阴离子型电化学活性材料前驱体材料会在富锂材料表面形成包覆膜层，得到第二富锂复合材料前驱体。该混合处理可以根据该聚阴离子型电化学活性材料前驱体材料的形态而定，如可以是液态混合包覆，也可以是固态混合包覆等。另外，在该混合处理中，富锂材料与聚阴离子型电化学活性材料前驱体材料的混合比例可以根据在形成含活性材料包覆层含量而定，如控制混合比例，使得聚阴离子型电化学活性材料也即是含活性材料包覆层在富锂复合材料中的含量为0.5-30wt％。
步骤S22中，第二烧结处理过程中，聚阴离子型电化学活性材料前驱体材料烧结形成聚阴离子型电化学活性材料，并形成聚阴离子型电化学活性材料包覆层原位包覆在富锂材料表面，也即是形成活性材料包覆层包覆在富锂材料表面的表面。该活性材料包覆层为上文图2和图3所示富锂材料所含的活性材料包覆层21。因此，该第二烧结处理可以根据聚阴离子型电化学活性材料前驱体材料种类而定。如当聚阴离子型电化学活性材料前驱体为磷酸铁锂前驱体，该第二烧结处理可以是于非氧化气氛中，以100-500℃/h升温至450℃-900℃下保温0.5-10h。步骤S22中保护气氛可以是氮气或/和氩气形成的化学惰性气氛环境。
步骤S23中，第二电子导电剂或第二电子导电剂前驱体材料与步骤S22中制备的活性材料包覆层的富锂复合材料进行混合处理，在活性材料包覆层的外表面形成第二电子导电剂或第二电子导电剂前驱体材料的包覆层，得到第三富锂复合材料前驱体。步骤S23中的该混合处理也可以根据该第二电子导电剂或第二电子导电剂前驱体材料的形态而定，如可以是液态混合包覆，也可以是固态混合包覆等。另外，第二电子导电剂或第二电子导电剂前驱体材料 与活性材料包覆层的富锂复合材料的混合比例可以根据第二电子导电剂在形成的致密疏水层中的含量而定，如控制混合比例，使得第二电子导电剂占聚阴离子型电化学活性材料也即是占含活性材料包覆层质量的1-6wt％。
步骤S24中，第三烧结处理过程中，当为第二电子导电剂前驱体材料时，其被烧结分解形成第二电子导电剂并在含活性材料包覆层表面原位形成电子导电包覆层。当为第二电子导电剂时，其烧结形成电子导电包覆层。该电子导电包覆层该活性材料包覆层为上文图3所示富锂材料所含的电子导体封装层22。该电子导电包覆层与步骤S23中形成的活性材料包覆层一起构成了复合结构致密疏水层，如图3所示富锂材料所含致密疏水层20。步骤S24中保护气氛可以是氮气或/和氩气形成的化学惰性气氛环境。
因此，该第三烧结处理可以根据第二电子导电剂前驱体材料烧结分解的条件或第二电子导电剂烧结的条件进行烧结处理。如当第二电子导电剂前驱体为碳源时，该第三烧结处理可以是于非氧化气氛中，以100-500℃/h升温至450℃-900℃下保温0.5-10h。
当然，在上述采用分步形成如图3所示的复合结构致密疏水层时，除上述步骤S21中的聚阴离子型电化学活性前驱体材料与富锂材料进行混合包覆后烧结处理形成活性材料包覆层之外，还可以采用其他方式如化学沉积等方法将聚阴离子型电化学活性材料前驱体直接在富锂材料表面原位沉积形成活性材料包覆层。还可以直接利用聚阴离子型电化学活性材料采用其他方式如气相沉积或磁控溅射等方式在富锂材料表面形成活性材料包覆层。
同理，还可以采用其他方式如化学沉积等方法将第二电子导电剂前驱体材料直接在活性材料包覆层表面原位沉积形成电子导电包覆层。还可以直接利用第二电子导电剂采用其他方式如气相沉积或磁控溅射等方式在电子导电包覆层形成电子导电包覆层。
因此，上述富锂复合材料的制备方法能够在富锂材料表面形成包覆富锂材料的致密疏水层形成上文核壳结构的富锂复合材料，使得制备的富锂复合材料电化学性能稳定，与电解液接触界面高的电化学稳定性。而且富锂复合材料所含残碱含量低，具有良好的加工性能。
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富锂复合材料。在本申请实施例正极片中，该富锂复合材料可以是作为正极材料也可以是作为正极补锂添加剂。由于本申请实施例正极片含有上述本申请实施例富锂复合材料，因此，本申请实施例正极片的正极活性层所含成分分散均匀，膜层质量高。而且正极片与电解液接触界面的化学性能稳定，赋予极片优异的电化学性能，提高了电池首效和整体电化学性能。
在一实施例中，正极活性层中所含上文本申请实施例富锂复合材料的质量含量可以为0.5-10wt％。正极活性层包括除了该富锂复合材料之外，还包括粘结剂和导电剂。其中，粘结剂的含量可以是0.5-20wt％，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。导电剂的含量可以是0.2-20wt％，导电剂也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。当该富锂复合材料作为正极补锂添加剂时，还含有正极活性材料。正极活性材料可以包括钴酸锂、锰酸锂、磷酸铁锂、磷酸钒锂，磷酸钒氧锂、氟代 磷酸钒锂、钛酸锂、镍钴锰酸锂、镍钴铝酸锂中的一种或多种。
实施例中，正极片制备过程可以为：将该正极补锂添加剂、导电剂与粘结剂或进一步与正极活性材料混合得到电极浆料，将正极浆料涂布在正极集流体上，经干燥、辊压、模切等步骤制备得到正极片。
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，也即是正极片所含的正极活性层中含有上文本申请实施例富锂复合材料。
由于本申请实施例二次电池中含有上文本申请实施例富锂复合材料，基于上文本申请实施例富锂复合材料所具有优异补锂性能或进一步具有离子传导性和/或电子传导性，赋予本申请实施例二次电池优异的首次库伦效率和电池容量以及循环性能，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富锂复合材料及其制备方法和应用等。
1.富锂复合材料及其制备方法实施例：
实施例1
本实施例提供一种富锂复合材料及其制备方法。该富锂复合材料包括LiFeO 2·1.99Li 2O核体和包覆核体的致密疏水层，且致密疏水层的材料为LFP(磷酸铁锂)和碳的复合物。
本实施例富锂复合材料的制备方法包括如下步骤：
S1.LiFeO 2·1.99Li 2O的制备：
将Fe(NO 3) 3·9H 2O、LiNO 3以1：4.98的摩尔比水溶液中充分混合均匀，于280℃下喷雾干燥后破碎；在空气气氛中，以300℃/h的速率升温至850℃并保温15h，冷却后对产物进行机械破碎分级得到内核LiFeO 2·1.99Li 2O粉体；
S2.LFP与碳复合材料的致密疏水层的制备：
将柠檬酸、Fe(NO 3) 3·9H 2O、LiNO 3和磷酸二氢铵按照摩尔比为1:1:1:1水溶液中充分混合均匀后，于300℃下空气中干燥热处理4h，按照LiFeO 2·1.99Li 2O粉体质量比的15wt％添加后一起球磨混合均匀，放置回转炉中通N 2保护，以200℃/h升温速率升温至650℃保温4h，降温冷却得到富锂复合材料，其核体为LiFeO 2·1.99Li 2O，包覆层为致密疏水层，且致密疏水层的材料为LFP(磷酸铁锂)与碳的复合物。
经测得，LFP的质量为富锂复合材料总质量的3.9wt％，碳的质量为LFP质量的15wt％；核体LiFeO 2·1.99Li 2O的平均粒径为8μm，致密疏水层的厚度为35nm，BET比表面积为4.1m 2/g，测得电阻率为25℃低于450Ω·cm。
实施例2
本实施例提供一种富锂复合材料及其制备方法。该富锂复合材料包括LiFeO 2·1.99Li 2O·0.005Al 2O 3核体和包覆核体的致密疏水层，且致密疏水层的材料为LMFP(磷酸锰铁锂)和碳的复合物。
本实施例富锂复合材料的制备方法包括如下步骤：
S1.LiFeO 2·1.99Li 2O·0.005Al 2O 3的制备：
将Fe(NO 3) 3·9H 2O、LiNO 3、Al(NO 3) 3以1：4.98：0.01的摩尔比加入到15wt％柠檬酸水溶液中充分混合均匀，于280℃下喷雾干燥后破碎，得到LiFeO 2·1.99Li 2O·0.005Al 2O 3粉体；
S2.LMFP与碳复合材料的致密疏水层的制备：
将柠檬酸、Fe(NO 3) 3·9H 2O、Mn(NO 3) 2、LiNO 3和磷酸二氢铵按照摩尔比为1:0.6:0.4:1水溶液中充分混合均匀后，于300℃下空气中干燥热处理4h，按照LiFeO 2·1.99Li 2O·0.005Al 2O 3粉体质量比的10wt％添加后一起球磨混合均匀，放置回转炉中通N 2保护，以200℃/h升温速率升温至650℃保温4h，降温冷却得到富锂复合材料，其核体为LiFeO 2·1.99Li 2O·0.005Al 2O 3，包覆层为致密疏水层，且致密疏水层的材料为LMFP(磷酸铁锂)与碳的复合物。
经测得，LMFP的质量为富锂复合材料总质量的3wt％，碳的质量为LMFP质量的12wt％；核体LiFeO 2·1.99Li 2O·0.005Al 2O 3的平均粒径为12μm，致密疏水层的厚度为80nm，BET比表面积为7.3m 2/g，测得电阻率为25℃低于390Ω·cm。
实施例3
本实施例提供一种富锂复合材料及其制备方法。该富锂复合材料包括LiFeO 2·2.025Li 2O·0.01CuO核体和包覆核体的致密疏水层，且致密疏水层的材料为LVP(磷酸钒锂)和碳的复合物。
本实施例富锂复合材料的制备方法包括如下步骤：
S1.LiFeO 2·2.025Li 2O·0.01CuO的制备：
将Fe 2O 3、LiOH、CuO以1：10.1：0.01的摩尔比充分混合均匀。在氮气气氛中，以300℃/h的速率升温至900℃并保温20h，冷却后对产物进行机械破碎分级，得到LiFeO 2·2.025Li 2O·0.01CuO粉体；
S2.LVP与碳复合材料的致密疏水层的制备：
将PVP、NH 4VO 3、LiNO 3和磷酸二氢铵按照摩尔比为1：2：3：3水溶液中充分混合均匀后，于300℃下空气中干燥热处理4h，按照LiFeO 2·2.025Li 2O·0.01CuO粉体质量比的20wt％添加后一起球磨混合均匀，放置回转炉中通N 2保护，以200℃/h升温速率升温至750℃保温4h，降温冷却得到富锂复合材料，其核体为LiFeO 2·2.025Li 2O·0.01CuO，包覆层为致密疏水层，且致密疏水层的材料为LVP(磷酸钒锂)与碳的复合物。
经测得，LVP的质量为富锂复合材料总质量的13wt％，碳的质量为LVP质量的4wt％；核体LiFeO 2·2.025Li 2O·0.01CuO的平均粒径为7.3μm，致密疏水层的厚度为130nm，BET比表面积为5.9m 2/g，测得电阻率为25℃低于230Ω·cm。
实施例4
本实施例提供一种富锂复合材料及其制备方法。该富锂复合材料包括LiFeO 2·1.99Li 2O·0.005Al 2O 3核体和包覆核体的致密疏水层，且致密疏水层的材料为LMP(磷酸锰锂)和碳的复合物。
本实施例富锂复合材料的制备方法包括如下步骤：
S1.LiFeO 2·1.99Li 2O·0.005Al 2O 3的制备：
将Fe(NO 3) 3·9H 2O、LiNO 3、Al(NO 3) 3以1：4.98：0.01的摩尔比在水溶液中充分混合均匀，于280℃下喷雾干燥后破碎；在空气气氛中，以300℃/h的速率升温至850℃并保温15h，冷却后对产物进行机械破碎分级得到LiFeO 2·1.99Li 2O·0.005Al 2O 3粉体；
S2.LMP与碳复合材料的致密疏水层的制备：
将聚乙二醇、Mn(NO 3) 2、LiNO 3和磷酸二氢铵按照摩尔比为0.5：1：1：1水溶液中充分混合均匀后，于300℃下惰性气氛中干燥热处理4h，按照LiFeO 2·1.99Li 2O·0.005Al 2O 3粉体质量比的20wt％添加后一起球磨混合均匀，放置回转炉中通N 2保护，以200℃/h升温速率升温至750℃保温4h，降温冷却得到富锂复合材料，其核体为LiFeO 2·1.99Li 2O·0.005Al 2O 3，包覆层为致密疏水层，且致密疏水层的材料为LMP与碳的复合物。
经测得，LMP的质量为富锂复合材料总质量的12wt％，碳的质量为LMP质量的5wt％；核体LiFeO 2·1.99Li 2O·0.005Al 2O 3的平均粒径为5.2μm，致密疏水层的厚度为75nm，BET比表面积为11m 2/g，测得电阻率为25℃低于295Ω·cm。
实施例5
本实施例提供一种富锂复合材料及其制备方法。该富锂复合材料包括LiFeO 2·2.025Li 2O·0.01CuO核体和包覆核体的致密疏水层，且致密疏水层的材料为LFP(磷酸铁锂)和碳的复合物。
本实施例富锂复合材料的制备方法包括如下步骤：
S1.LiFeO 2·2.025Li 2O·0.01CuO的制备：
将Fe 2O 3、LiOH、CuO以1：10.1：0.01的摩尔比充分混合均匀。在氮气气氛中，以300℃/h的速率升温至900℃并保温20h，冷却后对产物进行机械破碎分级得到LiFeO 2·2.025Li 2O·0.01CuO粉体；
S2.LFP与碳复合材料的致密疏水层的制备：
将柠檬酸、Fe(NO 3) 3·9H 2O、LiNO 3和磷酸二氢铵按照摩尔比为0.2:1:1:1水溶液中充分混合均匀后，于300℃下空气中干燥热处理4h，按照LiFeO 2·2.025Li 2O·0.01CuO粉体质量比的30wt％添加后一起球磨混合均匀，放置回转炉中通N 2保护，通1L/min丙酮和20L/min N 2，以200℃/h升温速率升温至700℃保温4h，降温冷却得到富锂复合材料，其核体为LiFeO 2·2.025Li 2O·0.01CuO，包覆层为致密疏水层，且致密疏水层的材料为LFP与碳的复合物。
经测得，LFP的质量为富锂复合材料总质量的15wt％，碳的质量为LFP质量的3.0wt％；核体LiFeO 2·2.025Li 2O·0.01CuO的平均粒径为9.2μm，致密疏水层的厚度为130nm，BET比表面积为2.5m 2/g，测得电阻率为25℃低于430Ω·cm。
实施例6
本实施例提供一种富锂复合材料及其制备方法。该富锂复合材料包括LiFeO 2·2.025Li 2O·0.01MnO核体和包覆核体的致密疏水层，且致密疏水层的材料为LMFP(磷 酸锰铁锂)和碳的复合物。
本实施例富锂复合材料的制备方法包括如下步骤：
S1.LiFeO 2·2.025Li 2O·0.01MnO的制备：
将Fe 2O 3、LiOH、MnO 2以1：10.1：0.01的摩尔比充分混合均匀。在氮气气氛中，以300℃/h的速率升温至900℃并保温20h，冷却后对产物进行机械破碎分级得到LiFeO 2·2.025Li 2O·0.01MnO粉体；
S2.LMFP与碳复合材料的致密疏水层的制备：
将柠檬酸、Fe(NO 3) 3·9H 2O、Mn(NO 3) 2、LiNO 3和磷酸二氢铵按照摩尔比为0.2:0.6:0.4:1水溶液中充分混合均匀后，于300℃下空气中干燥热处理4h，按照LiFeO 2·1.99Li 2O·0.01MnO 2粉体质量比的7wt％添加后一起球磨混合均匀，放置回转炉中通N 2保护，通1L/min乙醇和20L/min N 2，以200℃/h升温速率升温至650℃保温4h，降温冷却得到富锂复合材料，其核体为LiFeO 2·2.025Li 2O·0.01MnO，包覆层为致密疏水层，且致密疏水层的材料为LMFP与碳的复合物。
经测得，LMFP的质量为富锂复合材料总质量的4.6wt％，碳的质量为LMFP质量的3.1wt％；核体LiFeO 2·2.025Li 2O·0.01MnO的平均粒径为3.9μm，致密疏水层的厚度为45nm，BET比表面积为5.9m 2/g，测得电阻率为25℃低于420Ω·cm。
实施例7
本实施例提供一种富锂复合材料及其制备方法。该富锂复合材料包括LiFeO 2·2.025Li 2O·0.01MnO核体和包覆核体的致密疏水层，且致密疏水层的材料为LMFP(磷酸锰铁锂)和碳的复合物。
本实施例富锂复合材料的制备方法包括如下步骤：
S1.LiFeO 2·2.025Li 2O·0.01MnO的制备：
将Fe 2O 3、LiOH、MnO 2以1：10.1：0.01的摩尔比充分混合均匀。在氮气气氛中，以300℃/h的速率升温至900℃并保温20h，冷却后对产物进行机械破碎分级得到LiFeO 2·2.025Li 2O·0.01MnO粉体；
S2.LMFP致密疏水层的制备：
将Fe(NO 3) 3·9H 2O、Mn(NO 3) 2、LiNO 3和磷酸二氢铵按照摩尔比为0.6:0.4:1水溶液中充分混合均匀后，于300℃下空气中干燥热处理4h，按照LiFeO 2·1.99Li 2O·0.01MnO 2粉体质量比的7wt％添加后一起球磨混合均匀，放置回转炉中通N 2保护，通1L/min甲醇和20L/min N 2，以200℃/h升温速率升温至650℃保温4h，降温冷却得到富锂复合材料，其核体为LiFeO 2·2.025Li 2O·0.01MnO，包覆层为LMFP致密疏水层，且致密疏水层的材料为LMFP。
S3.碳致密疏水层的制备：
将步骤S2制备的复合材料与柠檬酸溶液混合，于300℃下空气中干燥热处理4h，按照LiFeO 2·1.99Li 2O·0.01MnO 2粉体质量比的7wt％添加后一起球磨混合均匀，放置回转炉中通N 2保护，通1L/min乙醇和20L/min N 2，以200℃/h升温速率升温至650℃保温4h，降温冷却得到富锂复合材料，其核体为LiFeO 2·2.025Li 2O·0.01MnO，第一包覆层为LMFP，第一包覆层为 碳层的复合致密疏水层。
对比例1
本对比例提供一种富锂材料及其制备方法。本对比例富锂材料为LiFeO 2·1.99Li 2O，与实施例1相比，不同在于本对比例富锂材料不含LFP与碳的复合物致密疏水层。
对比例2
本对比例提供一种富锂材料及其制备方法。本对比例富锂材料为LiFeO 2·2.025Li 2O·0.01CuO，与实施例3相比，不同在于本对比例富锂材料不含LVP与碳的复合物致密疏水层。
对比例3
本对比例提供一种富锂复合材料及其制备方法。本对比例富锂复合材料包括LiFeO 2·1.99Li 2O核体和包覆核体的碳材料致密疏水层，与实施例1相比，不同在于本对比例富锂材料的致密疏水层中不含LFP只为碳材料的致密疏水层，且控制本对比例富锂材料的碳材料致密疏水层的厚度与实施例1富锂复合材料的致密疏水层厚度基本相等。
对比例4
本对比例提供一种富锂复合材料及其制备方法。本对比例富锂复合材料包括LiFeO 2·1.99Li 2O核体和包覆核体的三元材料致密疏水层，与实施例1相比，不同在于本对比例富锂材料的致密疏水层材料替换为三元材料形成的致密疏水层，且控制本对比例富锂材料的三元材料致密疏水层的厚度与实施例1富锂复合材料的致密疏水层厚度基本相等。
2.锂离子电池实施例：
将上述实施例1至实施例7提供的富锂复合材料和对比例提供的富锂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，将LFP，补锂添加剂、聚偏氟乙烯和SP-Li以90∶5：2∶3的质量比混合球磨搅拌得到正极浆料，将正极浆料涂覆在铝箔表面，辊压后，110℃下真空干燥过夜，得到正极极片；其中，补锂添加剂分别为上述实施例1至实施例7提供的富锂复合材料和对比例1至对比例3提供的富锂材料；
负电极：锂金属片；
电解液：将碳酸乙烯酯和碳酸甲乙酯以3:7的体积比混合，并加入LiPF 6，形成电解液，LiPF 6的浓度为1mol/L；
隔膜：聚丙烯微孔隔；
锂离子电池组装：锂金属片-隔膜-电解液-正极片的结构在惰性气氛手套箱内组装成锂离子电池。
3.相关性能测试
1.富锂复合材料的相关测试
1.1富锂复合材料的电镜分析(SEM)：
将上述实施例1至实施例7提供的富锂复合材料和对比例提供的富锂材料分别进行扫描电镜分析，其中，实施例1提供的富锂复合材料的SEM照片如图4所示，对比例1提供的富锂材料的SEM照片如图5所示。其他实施例提供的富锂复合材料SEM照片与图4近似。
由SEM照片可以看出，本实施例提供的含有致密疏水层的包覆结构富锂铁系复合材料具有较多无规格颗粒，界面比较粗糙有颗粒感。对比例1中未包覆的富锂铁系复合材料界面同样比较粗糙。
1.2富锂复合材料的X射线衍射分析(XRD)：
将上述实施例1至实施例7提供的富锂复合材料分别进行X射线衍射分析，其中，实施例1提供的富锂复合材料的XRD照片如图6所示，实施例5提供的富锂材料的SEM照片如图7所示。
由图6可以看出，实施例1中富锂复合材料具有除了主峰为Li 5FeO 4外，附带有少量LiFePO 4的衍射峰；由图7可以看出，富锂铁系复合材料主要为Li 5FeO 4，LiFePO 4的衍射峰较为明显。
1.2富锂复合材料的所含富锂铁系核体(通式aLiFeO 2·bLi 2O·cM xO y)中掺杂元素M含量的测定；
采用电感耦合等离子体(Inductively Coupled Plasma：ICP)发光分光法对各实施例1-6富锂复合材料所含富锂铁系核体中掺杂元素M的含量进行分析，测试结果请参阅表1，表1中掺杂元素M的y值即为富锂铁系核体中掺杂元素M的含量。
2.锂离子电池实施例：
将上述锂离子电池实施例中组装的各锂离子电池电化学性能进行测试，测试条件为：
将装配好的电池在室温下放置24h后进行充放电测试，充放电电压为2.7V-4.3V，实施例1-6和对比例1-2的锂二次电池的电化学性能请参阅表1。
表1
Figure PCTCN2022131989-appb-000001
Figure PCTCN2022131989-appb-000002
从表1中可以看出，本申请实施例富锂复合材料设有致密疏水层，用于其配制的正极浆料不出现果冻现象，容易涂覆，并且将其添加到锂二次电池时，可以使正极具有更高的首次克容量发挥和更低的首次效率，从而补偿由于首次负极不可逆锂损耗导致的能量密度降低。而对比例1和对比例2的富锂铁系材料未进行包覆，在正极浆料的制备过程中吸水导致形成果冻，不利于正极浆料的涂覆。对比例3虽然含有碳包覆层，但是其依然存在吸水导致形成果冻状，对比文件4虽然含有三元材料包覆层，且在加工过程中没有导致出现果冻状，但是其直接导致了浆料粘度的上升，依然导致其加工性能的降低和不稳定性。
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 (16)

  1. 一种富锂复合材料，包括核体和包覆于所述核体的致密疏水层，其特征在于：所述核体包括富锂材料，所述致密疏水层的材料包括聚阴离子型电化学活性材料，所述聚阴离子型电化学活性材料为磷酸盐类电极活性材料。
  2. 根据权利要求1所述的富锂复合材料，其特征在于：所述致密疏水层的材料还包括电子导电剂，所述电子导电剂与所述聚阴离子型电化学活性材料形成混合物。
  3. 根据权利要求2所述的富锂复合材料，其特征在于：所述电子导电剂包括导电碳材料、导电氧化物、导电有机物中的至少一种；或/和
    在所述致密疏水层中，所述电子导电剂占所述聚阴离子型电化学活性材料质量的1-6wt％。
  4. 根据权利要求3所述的富锂复合材料，其特征在于：所述导电碳材料包括无定形碳、碳纳米管、石墨、炭黑、石墨烯中的至少一种；
    所述导电氧化物包括In 2O 3、ZnO、SnO 2中的至少一种；
    所述导电有机物包括导电聚合物。
  5. 根据权利要求1所述的富锂复合材料，其特征在于：所述致密疏水层包括活性材料包覆层，所述活性材料包覆层包覆所述核体，且所述活性材料包覆层的材料为所述聚阴离子型电化学活性材料。
  6. 根据权利要求5所述的富锂复合材料，其特征在于：所述致密疏水层还包括电子导体封装层，所述电子导体封装层包覆在活性材料包覆层的背离所述核体的表面。
  7. 根据权利要求6所述的富锂复合材料，其特征在于：所述电子导体封装层的材料包括碳材料、导电氧化物、导电有机物中的至少一种；和/或
    所述电子导体封装层的厚度为1-100nm。
  8. 根据权利要求1-7任一项所述的富锂复合材料，其特征在于：所述聚阴离子型电化学活性材料在所述富锂复合材料中的含量为0.5-30wt％；或/和
    所述聚阴离子型电化学活性材料包括磷酸铁锂、磷酸锰锂、磷酸锰铁锂、磷酸钒锂、磷酸镍锂、磷酸钴锂中的至少一种；或/和
    所述富锂材料包括富锂铁系、富锂锰系、富锂镍系，富锂钴系中的至少一种。
  9. 根据权利要求8所述的富锂复合材料，其特征在于：所述富锂铁系材料的化学通式为aLiFeO 2·bLi 2O·cM xO y；其中，所述化学通式中的a、b、c为摩尔数，且满足a+b≥0.98；c≤0.02；1.8≤b/a≤2.1；M为Si、Ni、Co、Mn、Ti、Al、Cu、V、Zr、Sn中的一种或多种；1≤y/x≤2.5，x为1-3。
  10. 根据权利要求1-9任一项所述的富锂复合材料，其特征在于：所述富锂复合材料的粒径满足：1μm≤D50≤10μm；和/或
    所述富锂复合材料的粒径满足：1μm≤D50≤10μm，D10/D50≥0.3，D90/D50≤2；和/或
    所述富锂复合材料的BET比表面为0.5-20m 2/g；和/或
    所述富锂复合材料的电阻率为1.0-500Ω/cm。
  11. 一种富锂复合材料的制备方法，其特征在于，包括如下步骤：
    将含聚阴离子型电化学活性材料或其前驱体材料在富锂材料表面形成致密疏水层，包覆所述富锂材料，得到富锂复合材料；其中，所述聚阴离子型电化学活性材料为磷酸盐类电极活性材料。
  12. 根据权利要求11所述的制备方法，其特征在于：将含聚阴离子型电化学活性材料前驱体材料在富锂材料表面形成致密疏水层的方法包括如下步骤：
    将包括第一电子导电剂或第一电子导电剂前驱体材料与所述聚阴离子型电化学活性材料前驱体材料的混合物与所述富锂材料进行混合处理，在所述富锂材料表面形成第一包覆层，得到第一富锂复合材料前驱体；
    于保护气氛中，将所述第一富锂复合材料前驱体进行第一烧结处理，得到所述富锂复合材料。
  13. 根据权利要求11所述的制备方法，其特征在于：将含聚阴离子型电化学活性材料前驱体材料在富锂材料表面形成致密疏水层的方法包括如下步骤：
    将所述聚阴离子型电化学活性材料前驱体与所述富锂材料进行混合处理，在所述富锂材料表面形成第二包覆层，得到第二富锂复合材料前驱体；
    于保护气氛中，将所述第二富锂复合材料前驱体进行第二烧结处理，得到活性材料包覆层的富锂复合材料；
    将第二电子导电剂或第二电子导电剂前驱体材料与所述活性材料包覆层的富锂复合材料进行混合处理，在所述活性材料包覆层的富锂复合材料表面形成第三包覆层，得到第三富锂复合材料前驱体；
    于保护气氛中，所述第三富锂复合材料前驱体进行第三烧结处理，得到所述富锂复合材料。
  14. 根据权利要求11-13任一项所述的制备方法，其特征在于，所述聚阴离子型电化学活性材料前驱体材料包括磷酸铁锂前驱体、磷酸锰锂前驱体、磷酸锰铁锂前驱体、磷酸钒锂前驱体、磷酸镍锂前驱体、磷酸钴锂前驱体中的至少一种。
  15. 一种正极片，包括正极集流体和结合在正极集流体表面的正极活性层，其特征在于：所述正极活性层中含有权利要求1-10任一项所述的富锂复合材料或由权利要求11-14任一项所述的制备方法制备的富锂复合材料。
  16. 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15所述的正极片。
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