WO2020001561A1 - 锂离子电池正极材料及其制备方法、锂离子电池正极和全固态锂电池 - Google Patents

锂离子电池正极材料及其制备方法、锂离子电池正极和全固态锂电池 Download PDF

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WO2020001561A1
WO2020001561A1 PCT/CN2019/093382 CN2019093382W WO2020001561A1 WO 2020001561 A1 WO2020001561 A1 WO 2020001561A1 CN 2019093382 W CN2019093382 W CN 2019093382W WO 2020001561 A1 WO2020001561 A1 WO 2020001561A1
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positive electrode
core
active material
electrode active
lithium
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PCT/CN2019/093382
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English (en)
French (fr)
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历彪
郭姿珠
马永军
谢静
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比亚迪股份有限公司
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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
    • 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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • 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
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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 disclosure relates to the field of all-solid-state lithium batteries, and in particular, to a lithium-ion battery cathode material and a method for preparing the same, a lithium-ion battery anode, and an all-solid-state lithium battery.
  • All-solid-state lithium batteries are prone to element diffusion at the interface between the positive electrode material and the solid-state electrolyte, resulting in reduced battery performance.
  • the positive electrode material is mostly coated to improve the interface between the positive electrode material and the solid electrolyte.
  • Common coatings include Li 4 Ti 5 O 12 , Al 2 O 3 , LiNbO 3 and the like.
  • a single coating has limited performance improvement on the positive electrode material, and it cannot solve the interface diffusion problem between the positive electrode material and the coating.
  • the purpose of the present disclosure is to solve the problem that the existing oxide-coated positive electrode material has limited improvement in interface performance, and provides a lithium ion battery positive electrode material, which has a stable surface or less interface element diffusion phenomenon.
  • the inventors of the present disclosure have discovered through research that a composite material having a fluorine-containing fluorinated layer and a fluorine oxide layer in order to form a core-shell structure having a two-layer shell can be interposed between the positive electrode material and the solid electrolyte.
  • a composite material having a fluorine-containing fluorinated layer and a fluorine oxide layer in order to form a core-shell structure having a two-layer shell can be interposed between the positive electrode material and the solid electrolyte.
  • a first aspect of the present disclosure provides a lithium ion battery cathode material, the cathode material comprising a core-shell structure composite material, the core-shell structure composite material comprising a core material, an inner shell material and an outer shell material, the core material comprising a positive electrode active material
  • the inner case material is a positive electrode active material containing fluorine
  • the outer case material includes fluorine oxide.
  • a method for preparing a positive electrode material for a lithium ion battery includes the steps of: mixing a positive electrode active material, a fluorine oxide precursor, and hydrogen fluoride in a solvent to react at a reaction temperature of 100-250 ° C.
  • the pressure is 0.1 to 100 MPa.
  • a third aspect of the present disclosure provides a lithium ion battery cathode material prepared according to the method described in the second aspect of the present disclosure.
  • a fourth aspect of the present disclosure provides a lithium ion battery positive electrode, the positive electrode containing the lithium ion battery positive electrode material described in the first and third aspects of the present disclosure.
  • a fifth aspect of the present disclosure provides an all-solid-state lithium battery including the lithium ion battery positive electrode according to the fourth aspect of the present disclosure.
  • the lithium ion battery positive electrode material of the present disclosure has a fluorinated inner shell and a fluorinated oxide outer shell.
  • the formed two-layered shell-covered core-shell structure makes the material-clad structure stable, which can avoid the positive electrode material and The interface reaction or element diffusion occurs between the solid electrolytes, and the element diffusion between the positive electrode material and the coating is reduced, thereby greatly optimizing the interface of the positive electrode material.
  • the method for preparing a positive electrode material disclosed by the present disclosure can complete coating and fluorination in one step, has a low coating temperature, is simple and feasible to operate, reduces the situation of element interpenetration, and optimizes the interface between the positive electrode material and the solid electrolyte.
  • FIG. 1 is a schematic structural diagram of a specific embodiment of a lithium ion battery cathode material according to the present disclosure.
  • a first aspect of the present disclosure provides a cathode material for a lithium-ion battery.
  • the cathode material includes a core-shell structure composite material.
  • the core-shell structure composite material includes a core 1, an inner shell 2, and an outer shell 3 which are arranged in order from the inside to the outside.
  • the core 1 includes a positive electrode active material
  • the inner case 2 includes a positive electrode active material containing fluorine
  • the outer case 3 includes a fluorine oxide.
  • the inventor of the present disclosure has found that the core-shell structure of a lithium-ion battery anode material coating structure with a two-layer case having a fluorine-containing positive electrode active material inner shell (or fluorinated layer inner shell) and a fluorine oxide outer shell is stable , Can significantly improve the electrochemical performance of the cathode material.
  • the inner shell of the fluorinated layer stabilizes the surface of the positive electrode material, increases the stability of the positive electrode material, reduces the side reactions of the positive electrode material, and at the same time helps to alleviate the negative impact of interface element diffusion;
  • the ionic conductance of the fluorine oxide shell High rate, low electronic conductivity reduce the chemical potential of lithium after covering the shell, not only facilitate the transport of lithium ions, effectively reduce the surface voltage of the positive electrode material in contact with the solid electrolyte, and prevent the solid electrolyte from being oxidized by the positive electrode material.
  • the average particle diameter of the core-shell structure composite material may vary within a relatively large range.
  • the average particle diameter of the core-shell structure composite material may be 100 nm to 500 ⁇ m, such as 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 ⁇ m, 50 ⁇ m, 100 ⁇ m, 150 ⁇ m, 200 ⁇ m, 250 ⁇ m, 300 ⁇ m, 350 ⁇ m, 400 ⁇ m, 450 ⁇ m, 500 ⁇ m, etc .; in other specific embodiments, the core-shell structure The average particle diameter of the composite material may be 200 nm to 50 ⁇ m, such as 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 ⁇ m, 10 ⁇ m, 20
  • the average particle size of the core-shell structure composite material can be randomly observed by scanning electron microscope (SEM) 100 particles of the core-shell structure composite material, and the particle size value is measured separately, and the average particle size is the core-shell structure composite material. Average particle size.
  • the thickness of the inner shell and the outer shell of the core-shell structure composite material can be changed within a relatively large range.
  • the thickness of the inner shell may be 1 nm to 10 ⁇ m, such as 1 nm, 100 nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, etc .;
  • the thickness of the inner shell may be 1nm ⁇ 5 ⁇ m, specifically 1nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, etc .;
  • the thickness of the inner shell It can be 1 nm to 10 ⁇ m, such as 1 nm, 100 nm
  • the thickness of the shell may be 1 nm to 10 ⁇ m, such as 1 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, etc .; in other specific embodiments, the thickness of the shell may be 1 nm to 5 ⁇ m, such as 1 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, etc .; in still other specific embodiments, the thickness of the shell may be 100 nm to 1 nm, 100
  • the inner shell and the outer shell have a better coating and isolation effect on the positive electrode active material constituting the core, and can prevent the interface elements between the positive electrode material and the electrolyte from diffusing.
  • the thickness of the outer shell and the inner shell refers to the average thickness.
  • FIB Fluorine Beam
  • direct cross-section grinding can be used to expose the cross-section. Then, under the tool such as SEM, measure the inner shell of any 100 positive electrode material particles.
  • the thickness of the outer shell the average of the thickness of the inner shell and the outer shell is the average thickness of the inner shell and the outer shell, respectively.
  • the contents of the inner shell and the outer shell in the core-shell structure composite material can be varied within a relatively large range; in some specific embodiments, in order to obtain a core-shell structure composite material with an appropriate thickness of the inner shell and the outer shell, Based on the total mass of the positive electrode material, the content of the inner shell may be 0.1 to 50% by weight, such as 0.1% by weight, 0.5% by weight, 1% by weight, 3% by weight, 5% by weight, 6% by weight, 10% by weight, 15% by weight, 20% by weight , 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, etc .; in other specific embodiments, the content of the inner shell may be 0.2-20wt%, such as 0.2wt%, 0.3wt%, 0.4wt %, 0.5% by weight, 0.6% by weight, 0.7% by weight, 0.8% by weight, 0.9% by weight, 1% by weight, 2% by weight, 3% by weight
  • the shell may include metal oxyfluoride, and the metal in the metal oxyfluoride may be Fe, Ti, At least one of V, Bi, Zr, Nb, Ag, Cr, Mn, Co, Ni, and Zn, that is, the metal oxyfluoride may be selected from FeOF, TiOF 2 , VO 2 F, VOF 3 , BiOF, ZrOF 2 , At least one of NbO 2 F, NbOF 3 , AgOF, CrOF, MnOF 2 , CoOF, NiOF, and Zn 2 OF 2 .
  • the inner shell (that is, the positive electrode active material containing fluorine) and the core may be obtained by subjecting the surface of the positive electrode active material to a fluorination treatment, and the non-fluorinated positive electrode active material constitutes the The core and the fluorinated positive electrode active material constitute the inner shell. That is, the inner shell of the core-shell structure composite material may be a fluorine-containing film layer formed after the original surface of the positive electrode active material is fluorinated. In this case, the fluorine-containing film layer is not fluorinated.
  • the positive electrode active material is the core of the core-shell structure composite material.
  • the content of fluorine in the inner shell gradually decreases, that is, from the outer surface of the core-shell structure composite material to the inner direction (that is, from the outer shell to In the direction of the core), the content of fluorine in the positive electrode active material containing fluorine gradually decreases; in other words, the content of fluorine in the positive electrode active material containing fluorine decreases from the surface to the inside of the particles.
  • the inner shell of the core-shell structure composite material may completely isolate the core of the core-shell structure composite material from the outer shell.
  • complete isolation means that the inner shell completely covers the core and can prevent the diffusion of elements between the core and the outer shell.
  • the way to achieve the above complete isolation may include making the inner shell a suitable thickness and F / O atomic ratio.
  • the positive electrode active material may be a conventional kind in the art.
  • the positive electrode active material may include LiCoO 2 , LiNiO 2 , LiCo r Ni 1-r O 2 , LiCo x Ni 1- xy Al y O 2 , LiMn 2 O 4 , LiFe p Mn q X s O 4 , Li 1 + a L 1-b-c M b Q c O 2 , LiFePO 4 , Li 3 V 2 (PO 4 ) 3 , Li 3 V 3 (PO 4 ) 3 , LiVPO 4 F, Li 2 CuO 2 , Li 5 FeO 4 , TiS 2 , V 2 S 3 , FeS, FeS 2 , LiRS z , TiO 2 , Cr 3 O 8 , V 2 At least one of O 5 and MnO 2 ; wherein 0 ⁇ r ⁇ 1, 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ x + y ⁇ 1,
  • the disclosure has no special requirements on the particle size of the positive electrode active material particles (that is, the core), and can be changed within a relatively large range.
  • the average particle diameter of the positive electrode active material particles is 100 nm to 500 ⁇ m, such as 100 nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1 ⁇ m, 100 ⁇ m, 200 ⁇ m, 300 ⁇ m, 400 ⁇ m, 500 ⁇ m, etc .; in other specific embodiments, the average particle size of the positive electrode active material particles is 200nm-50 ⁇ m, specifically Such as 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1 ⁇ m, 10 ⁇ m, 20 ⁇ m, 30 ⁇ m, 40 ⁇ m, 50 ⁇ m, etc .; thus, it can promote the formation of the interface of the positive electrode material and improve the electrochemical performance.
  • a method for preparing a positive electrode material for a lithium ion battery includes the steps of: mixing a positive electrode active material, a fluorine oxide precursor, and hydrogen fluoride in a solvent, and the reaction temperature is 100-300 ° C.
  • the reaction pressure is 0.1 ⁇ 100MPa (specifically 0.1MPa, 1MPa, 10MPa, 15MPa, 20MPa, 25MPa, 30MPa, 35MPa, 40MPa, 45MPa, 50MPa, 55MPa, 60MPa, 65MPa, 70MPa, 75MPa, 80MPa, 85MPa, 90MPa, 95MPa, 100MPa, etc.).
  • the disclosed method uses a one-step reaction to prepare a double-layer core-shell structure positive electrode material with a fluorinated inner shell and a fluorinated oxide outer shell.
  • the method has low coating temperature, simple operation, and the prepared positive electrode material can reduce interface element diffusion. With a stable and good interface.
  • this method can be used to prepare the positive electrode material of the first aspect of the present disclosure, and it will not be repeated here.
  • the reaction temperature may be 100-250 ° C. and the reaction pressure may be 25-80 MPa to optimize the coating structure and surface performance of the positive electrode material.
  • the reaction can be performed in a conventional reaction container, such as a closed container or a semi-closed container (specifically, a container with a pressure reducing valve).
  • a conventional reaction container such as a closed container or a semi-closed container (specifically, a container with a pressure reducing valve).
  • the method may include, in a closed state Then, the positive electrode active material, the fluorooxide precursor, and hydrogen fluoride are mixed and reacted in a solvent.
  • the reaction pressure is 5 to 100 Mpa
  • the reaction is continued in a non-closed state and the reaction pressure is maintained at 25 to 100 Mpa.
  • the above reaction can be performed in a container with a pressure reducing valve. In the initial stage of the reaction, the pressure reducing valve can be closed.
  • the pressure reducing valve is opened to control the pressure in the container.
  • the pressure in each stage of the reaction process can be accurately controlled, so that the reactants can perform a uniform reaction on the surface of the positive electrode active material particles, and it is more helpful to form a positive electrode active material layer containing fluorine as the inner shell.
  • the outer shell is a positive electrode material with a double-layer core-shell structure with a fluorooxide coating layer.
  • the oxyfluoride precursor refers to a substance capable of generating a oxyfluoride after the above-mentioned mixed reaction (even if the positive electrode active material, the fluorooxide precursor, and hydrogen fluoride are mixed in a solvent), such as a fluoride
  • the fluorine oxide precursor may be a metal fluoride, and the metal in the metal fluoride may be At least one of Fe, Ti, V, Bi, Zr, Nb, Ag, Cr, Mn, Co, Ni, and Zn, such as FeF 3 , TiF 4 and the like.
  • a metal fluoride oxide coating can be obtained after the metal fluoride is mixed and reacted to effectively protect the positive electrode active material forming the core, and to prevent interface element diffusion between the positive electrode material and the electrolyte.
  • the solvent of the mixed reaction may be at least one of water and alcohol, such as methanol, ethanol, propanol, ethylene glycol, propylene glycol, cyclohexanol, glycerol, and stearyl alcohol. At least one.
  • alcohol such as methanol, ethanol, propanol, ethylene glycol, propylene glycol, cyclohexanol, glycerol, and stearyl alcohol. At least one.
  • the molar ratio of the amount of the positive electrode active material, the fluorooxide precursor, and the hydrogen fluoride may be 1: (0.0015 to 2): (0.001 to 1), and specifically may be 1: (0.003 to 0.8): ( 0.002 to 0.4), specifically, in terms of molar ratio, the amount of fluorine oxide precursor may be 0.003 times, 0.01 times, 0.0027 times, 0.003 times, 0.05 times, 0.006 times, 0.1 times, 0.15 times the amount of the positive electrode active material.
  • the amount of hydrogen fluoride can be the amount of positive electrode active material 0.002 times, 0.01 times, 0.05 times, 0.1 times, 0.15 times, 0.2 times, 0.25 times, 0.3 times, 0.35 times, 0.4 times and so on.
  • the fluorine in the fluorooxide precursor and hydrogen fluoride can be completely converted to form a core-shell structure composite material with an appropriate coating thickness; the amount of the solvent can be 0.1 to 1 part by weight of the positive electrode active material.
  • 10 parts by weight such as 0.1 parts by weight, 0.5 parts by weight, 0.8 parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, etc.
  • the amount of the solvent may be 0.5 to 2 parts by weight, such as 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1.0 parts by weight Parts, 1.1 parts by weight, 1.2 parts by weight, 1.3 parts by weight, 1.4 parts by weight, 1.5 parts by weight, 1.6 parts by weight, 1.7 parts by weight, 1.8 parts by weight, 1.9 parts by weight, 2.0 parts by weight, and the like.
  • the positive electrode active material may be a conventional type in the art, and specifically may be the types listed above (that is, the same as the positive electrode active material described above), and details are not described herein again.
  • hydrogen fluoride can be added in various forms.
  • an HF aqueous solution can be used to perform the reaction of the present disclosure.
  • the method can The method includes mixing and reacting an aqueous HF solution with a positive electrode active material and a fluorine oxide precursor in a solvent; a volume ratio of hydrogen fluoride to water in the aqueous HF solution may be 1: (0.1 to 100), and specifically may be 1: (5 to 20) , Such as 1: 5, 1: 6, 1: 7, 1: 8, 1: 9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, etc.
  • a third aspect of the present disclosure provides a lithium ion battery cathode material prepared according to the method of the second aspect of the present disclosure.
  • a fourth aspect of the present disclosure provides a lithium ion battery positive electrode, the positive electrode containing at least one of the lithium ion battery positive electrode materials of the first and third aspects of the present disclosure.
  • the positive electrode of a lithium ion battery may include a positive electrode current collector and a positive electrode material layer coated on the surface of the positive electrode current collector.
  • the positive electrode material layer may include the foregoing positive electrode material including the core-shell structure composite material, a conductive agent, and a binder.
  • the agent is a common binder for the positive electrode, for example, one or more of a fluorine-containing resin and a polyolefin compound such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and styrene-butadiene rubber (SBR).
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • SBR styrene-butadiene rubber
  • the conductive agent is a commonly used conductive agent for the positive electrode, such as acetylene black, carbon nanotubes, carbon fibers, carbon black, and the like.
  • the content of the binder is 0.01-10% by weight (wt%), and specifically may be 0.02-5wt% (such as 0.02wt%, 0.1wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, etc.); the content of the conductive agent is 0.1 to 20wt%, and specifically may be 1 to 10wt% (such as 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt% , 9wt%, 10wt%, etc.).
  • the solvent may be selected from one or more of N-methylpyrrolidone (NMP), water, ethanol, and acetone, and the amount of the solvent is generally 50-400 wt% (such as 50 wt%, 100 wt%, 150 wt%, 200 wt%). , 250wt%, 300wt%, 350wt%, 400wt%, etc.).
  • NMP N-methylpyrrolidone
  • a fifth aspect of the present disclosure provides an all-solid-state lithium battery including the lithium-ion battery positive electrode of the fourth aspect of the present disclosure.
  • the structure of an all-solid-state lithium battery may be conventional in the art, for example, it may include a positive electrode, a negative electrode, and a solid electrolyte layer.
  • the positive electrode may include a positive electrode current collector and a positive electrode material layer coated on the surface of the positive electrode current collector.
  • the negative electrode may include a negative electrode current collector and The negative electrode material layer coated on the surface of the negative electrode current collector.
  • the solid electrolyte layer may include a solid electrolyte material.
  • the solid electrolyte material may be conventional in the art, including but not limited to one or more of a NASICON-type solid electrolyte, an oxide solid electrolyte, and a sulfur-based solid electrolyte.
  • the NASICON-type solid electrolyte is one or more of LiM 2 (PO 4 ) 3 and its dopants, where M is Ti, Zr, Ge, Sn, or Pb.
  • the doping element used for the dopant is selected. From one or more of Mg, Ca, Sr, Ba, Sc, Al, Ga, In, Nb, Ta, V.
  • A is Li, At least one element of Na, J is at least one element of La, Ce, Pr, Y, Sc, Nd, Sm, Eu, Gd, Nd, Al, and G is Sr, Ca, Ba, Ir, Pt, At least one of Te and Zr elements, and D is at least one of Nb and Ta elements.
  • the negative electrode material layer may include a negative electrode active material commonly used by those skilled in the art, for example, various kinds of negative electrode active materials that can be inserted and removed lithium. Or more of silicon, tin, germanium, metal lithium, lithium-indium alloy, etc.
  • the carbon material may be one or more of non-graphitizable carbon, graphite, or pyrolytic carbon, coke, organic polymer sintered matter, and activated carbon obtained from polyacetylene-based polymer materials through high-temperature oxidation.
  • the negative electrode material layer further contains a conductive agent, and its role is well known to those skilled in the art, and is not repeated here.
  • the all-solid-state lithium battery of the present disclosure can be prepared by the following method:
  • the positive electrode current collector is coated with a positive electrode active material layer to form a positive electrode C, and then a solid electrolyte material layer E is coated on the positive electrode active material layer to form a CE layer, and the negative electrode current collector is coated with a negative electrode active material layer to form a negative electrode. A, and then pressing the A and CE layers together to form the all-solid-state battery of the present disclosure.
  • the positive electrode active material layer may include a positive electrode material including a core-shell structure composite material, a conductive agent, and a binder of the present disclosure.
  • the positive electrode active material layer is manufactured by an existing method: the core material includes the core-shell structure composite material of the present disclosure.
  • the slurry of the positive electrode material, the conductive agent, the binder, and the solvent is coated on a current collector. After drying, an active material layer is formed on the current collector, and then subjected to a rolling treatment of 0 to 5 MPa to obtain a pole piece C.
  • the binder is a commonly used binder for the positive electrode, for example, one of a fluorine-containing resin and a polyolefin compound such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and styrene-butadiene rubber (SBR).
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • SBR styrene-butadiene rubber
  • the conductive agent is a commonly used conductive agent for the positive electrode, such as acetylene black, carbon nanotubes, carbon fibers, carbon black, and the like.
  • the content of the binder is 0.01 to 10% by weight (wt%), and specifically may be 0.02 to 5wt% (such as 0.02wt%, 0.1wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, etc.); the content of the conductive agent is 0.1-20wt%, and specifically may be 1-10wt% (such as 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt% , 9wt%, 10wt%, etc.).
  • the solvent may be selected from one or more of N-methylpyrrolidone (NMP), water, ethanol, and acetone, and the amount of the solvent is generally 50 to 400% by weight.
  • NMP N-methylpyrrolidone
  • the ordinary positive electrode is prepared by mixing the positive electrode material, the conductive agent and the binder in a solvent at a certain ratio, and stirring to obtain the required positive electrode slurry, and then coating the slurry on an aluminum foil current collector, An ordinary positive electrode containing a positive electrode active material layer is obtained by drying and tableting.
  • the solid electrolyte material layer E may include a solid electrolyte material and a binder.
  • the solid electrolyte material layer E is produced by a coating method: a slurry containing the solid electrolyte material, a binder, and a solvent is coated on the positive electrode active material layer, and dried and rolled to form CE.
  • the solid electrolyte material is Li 10 GeP 2 S 12 sulfur-based solid electrolyte.
  • the binder is selected from the group consisting of polythiophene, polypyrrole, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polystyrene, polyacrylamide, ethylene-propylene-diene copolymer resin, and styrene butadiene Ethylene rubber, polybutadiene, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, carboxypropyl cellulose, ethyl cellulose, polymer One or more of ethylene oxide, sodium carboxymethyl cellulose (CMC), and styrene-butadiene latex (SBR).
  • CMC sodium carboxymethyl cellulose
  • SBR styrene-butadiene latex
  • the components of the negative electrode active material layer are well known to those skilled in the art, and include a negative electrode active material and a binder.
  • the negative electrode active material used may be various kinds of negative electrode active materials that can be intercalated and delithium commonly used by those skilled in the art, and may be selected from one of carbon materials, tin alloys, silicon alloys, silicon, tin, and germanium, or There are many kinds of metal lithium and lithium-indium alloy.
  • the carbon material may be one or more of non-graphitizable carbon, graphite, or pyrolytic carbon, coke, organic polymer sintered matter, and activated carbon obtained from polyacetylene-based polymer materials through high-temperature oxidation.
  • the negative electrode active material layer further contains a conductive agent, and its role is well known to those skilled in the art, and is not repeated here.
  • the binder is various anode binders known to those skilled in the art, and may be selected from, for example, polythiophene, polypyrrole, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polystyrene, polyacrylamide , Ethylene-propylene-diene copolymer resin, styrene butadiene rubber, polybutadiene, fluorine rubber, polyethylene epoxy, polyvinylpyrrolidone, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyethylene One or more of alcohol, carboxypropyl cellulose, ethyl cellulose, sodium carboxymethyl cellulose (CMC), and styrene-butadiene latex (CMC), and styrene-butadiene latex (CMC), and s
  • the content of the binder in the negative electrode active material layer is 0.01 to 10% by weight based on the weight of the negative electrode active material (such as 0.01% by weight, 0.05% by weight, 0.1% by weight, and 0.5% by weight). %, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, etc.).
  • the negative electrode active material layer is obtained by mixing a negative electrode active material, a binder, etc. in a solvent at a certain ratio, and stirring to obtain the required negative electrode slurry. The slurry is then coated on a copper foil current collector.
  • the ordinary negative electrode A containing the negative electrode active material layer is obtained by drying and tableting. When the negative electrode uses lithium or a lithium-indium alloy, a metal lithium belt or a lithium-indium alloy belt can be directly used.
  • the pressing method can be isostatic pressing.
  • This embodiment is used to describe the lithium-ion battery cathode material and the all-solid-state lithium battery CEA1 of the present disclosure, and their preparation methods.
  • a positive electrode material having a core-shell structure with a fluorinated inner shell and a fluorinated oxide outer shell is prepared.
  • the positive electrode active material as the core material is LiCoO 2 material.
  • the specific preparation method is to put 1000 g of LiCoO 2 and 30 g of FeF 3 into a half of a volume of 5 L.
  • the pressure reducing valve is opened to ensure that the pressure in the vessel is 8 ⁇ 10 6 Pa.
  • the fluorinated LiCoO 2 cathode material with core and shell structure of shell and FeOF outer shell 930 g of the above-mentioned LiCoO 2 cathode material (93%), 30 g of a binder PVDF (3%), 20 g of acetylene black (2%), and 20 g of a conductive agent carbon fiber (2%) were added to 1500 g of a solvent NMP (nitromethylpyrrolidone).
  • the positive electrode slurry was uniformly and intermittently coated on both sides of an aluminum foil (the size of the aluminum foil was 160 mm in width and 16 ⁇ m in thickness), and then dried at 393 K, and the positive electrode C was obtained after being pressed by a roller press.
  • the CE obtained in step 2 and the A obtained in step 3 were aligned and placed in a hot press, and 423K hot-pressed for 1 h. After vacuum sealing with an aluminum plastic film, the sample was taken out.
  • the all-solid-state lithium battery of this embodiment is obtained after the above-mentioned pressed sample is pressed in an isostatic press at 200 MPa and 300 seconds (s).
  • coated positive electrode material of this embodiment and the lithium ion battery CEA2 of this embodiment are prepared by using the same steps as in Example 1, except that:
  • step (1) the amount of FeF 3 is not 30 g, but 60 g.
  • the 100 mL of the diluted HF solution used is 22.2 mL: 77.85 L of anhydrous HF: deionized water.
  • the other steps and operations are the same.
  • coated positive electrode material of this embodiment and the lithium ion battery CEA3 of this embodiment are prepared by using the same steps as in Example 1, except that:
  • a LiCoO 2 cathode material that is simultaneously fluorinated and coated with TiOF 2 is prepared.
  • LiCoO 2 cathode material that is simultaneously fluorinated and coated with TiOF 2 , and then use the cathode directly Materials are used for the assembly of solid-state lithium batteries, and other steps and operations are the same.
  • Example 2 The same procedure as in Example 1 was used to prepare the lithium ion battery CEA4 of this comparative example, except that:
  • LiCoO 2 positive electrode material did not have an iron oxyfluoride FeOF outer shell, but only a fluorinated inner shell.
  • the preparation method was to put 1000 g of LiCoO 2 into a semi-closed reaction container with a volume of 5 L.
  • Example 2 The same procedure as in Example 1 was used to prepare the lithium battery CEA5 of this comparative example, except that:
  • the HF solution is not added during the preparation of the positive electrode material.
  • the obtained LiCoO 2 positive electrode material does not have a fluorinated inner shell and only has a FeOF outer shell.
  • the preparation method is that 1000 g of LiCoO 2 and 30 g of FeF 3 are placed in a semi-closed volume of 5 L. In the reaction container, add 100 mL of deionized water and 900 mL of ethanol, turn on the stirring, and then heat it to 180 ° C. after the reaction to obtain the LiCoO 2 cathode material coated with FeOF. Then use this cathode material directly for solid lithium batteries. Assembly, the remaining steps and operations remain unchanged.
  • Example 2 The same procedure as in Example 1 was used to prepare the lithium battery CEA6 of this comparative example, except that:
  • LiCoO 2 cathode material does not have a fluorinated inner shell and FeOF outer shell. It is only a cathode material prepared by blending LiCoO 2 cathode material with FeOF physical ball milling. The preparation method is to put 1000g LiCoO 2 and 29.5g FeOF into a ball mill tank together. Ball milling at a speed of 250 rpm for 2 h, the product of LiCoO 2 positive electrode material and FeOF physical ball milling can be obtained, and then the positive electrode material is directly used to assemble the solid lithium battery, and the remaining steps and operations are unchanged.
  • the same procedure as in Example 1 was used to prepare the lithium battery CEA7 of this comparative example.
  • the LiCoO 2 cathode material has a fluorinated inner shell, except that:
  • the positive electrode material is prepared by blending a fluorinated LiCoO 2 positive electrode material with a physical ball mill of FeOF.
  • a surface fluorinated LiCoO 2 positive electrode material can be obtained.
  • the surface fluorinated LiCoO 2 positive electrode material and 29.5 g FeOF are put into a ball mill tank together.
  • a product obtained by blending LiCoO 2 cathode material with FeOF physical ball milling on the surface can be obtained, and then the cathode material is directly used for assembly of solid lithium batteries, and the remaining steps and operations remain unchanged.
  • Example 2 The same procedure as in Example 1 was used to prepare the lithium battery CEA8 of this comparative example, except that:
  • the LiCoO 2 cathode material does not have a fluorinated inner shell or an iron oxyfluoride FeOF outer shell, but a LiCoO 2 cathode material coated with Li 4 Ti 5 O 12 on the surface.
  • the preparation method is as follows: 1000 g of LiCoO 2 and 73.4 mL of titanium Tetrabutyl acid acid, 12g lithium ethoxide, and 1000mL ethanol were put into the same container.
  • Example 2 The same procedure as in Example 1 was used to prepare the lithium battery CEA9 of this comparative example, except that:
  • the LiCoO 2 active material is directly used to assemble the solid lithium battery without any treatment, and the remaining steps and operations are unchanged.
  • the positive electrode materials obtained in Examples 1 to 3 and Comparative Examples 1 to 6 were subjected to SEM (JSM-7600F) and XPS (PHI5800) tests to obtain the surface fluorine oxide cation element content (atomic ratio) and surface F / O.
  • the data of the atomic ratio, the thickness of the coating (inner shell and outer shell) and the content of the inner and outer shells are listed in Table 1. Among them, the inner shell content is obtained by calculating the proportion of the fluorinated product, and the outer shell content is calculated by calculating the quality of the coated product. Method.
  • the positive electrode material with a double-shell core-shell structure can effectively increase the first discharge specific capacity and the number of rings of an all-solid-state lithium battery, and can significantly extend the battery life; and, compared with an inner shell without a fluorinated layer (Comparative Example 2)
  • the battery life of the positive electrode material of the present disclosure is also longer than that of a positive electrode material that does not have a fluorooxide casing (Comparative Example 1) or that is only combined with a positive electrode active material (Comparative Examples 3-4) in a blended form.

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Abstract

提供了锂离子电池正极材料及其制备方法、锂离子电池正极和全固态锂电池。该正极材料包括核壳结构复合材料，核壳结构复合材料包括由内向外依次设置的核、内壳和外壳材料，核包括正极活性物质，内壳包括含有氟的正极活性物质，外壳包括氟氧化物。

Description

锂离子电池正极材料及其制备方法、锂离子电池正极和全固态锂电池
优先权信息
本申请请求2018年6月29日向中国国家知识产权局提交的、专利申请号为201810715053.X的专利申请的优先权和权益，并且通过参照将其全文并入此处。
技术领域
本公开涉及全固态锂电池领域，具体地，涉及一种锂离子电池正极材料及其制备方法、锂离子电池正极和全固态锂电池。
背景技术
全固态锂电池的正极材料与固态电解质界面易发生元素扩散现象，导致电池性能降低。现有技术多是对正极材料进行包覆，从而改善正极材料与固态电解质之间的界面，常用的包覆物有Li 4Ti 5O 12、Al 2O 3、LiNbO 3等。但是单一包覆对正极材料带来的性能提升有限，也无法解决正极材料与包覆物之间的界面扩散问题。
发明内容
本公开的目的是为了解决现有的氧化物包覆正极材料对界面性能改善有限的问题，提供一种锂离子电池正极材料，该正极材料表面稳定或界面元素扩散现象少。
本公开的发明人通过研究发现，正极活性物质外依次包覆含有氟的氟化层和氟氧化物层，形成具有两层壳体的核壳结构的复合材料能够在正极材料与固体电解质之间提供一个有效的隔离层结构，有效避免正极材料与固体电解质之间的元素扩散，从而解决由于界面元素扩散带来的界面阻抗升高和电池寿命下降的问题。
本公开第一方面提供一种锂离子电池正极材料，该正极材料包括核壳结构复合材料，所述核壳结构复合材料包括核材料、内壳材料和外壳材料，所述核材料包括正极活性物质，所述内壳材料为含有氟的正极活性物质，所述外壳材料包括氟氧化物。
本公开第二方面提供一种制备锂离子电池正极材料的方法，该方法包括如下步骤：将正极活性物质、氟氧化物前体和氟化氢在溶剂中混合反应，反应温度为100～250℃，反应压力为0.1～100MPa。
本公开第三方面提供根据本公开第二方面所述的方法制备得到的锂离子电池正极材料。
本公开第四方面提供一种锂离子电池正极，该正极含有本公开第一方面和第三方面所述的锂离子电池正极材料。
本公开第五方面提供一种全固态锂电池，该全固态锂电池包括本公开第四方面所述的锂离子电池正极。
通过上述技术方案，本公开的锂离子电池正极材料具有氟化层内壳及氟氧化物外壳，形成的两层壳体包覆的核壳结构使得该材料包覆结构稳定，可以避免正极材料与固态电解质之间发生界面反应或元素扩散，同时减少了正极材料与包覆物之间的元素扩散，从而极大地优化了正极材料的界面。本公开的制备正极材料的方法能够一步完成包覆和氟化，包覆温度低，操作简单可行，降低了元素互渗的情况，优化了正极材料与固态电解质之间的界面。
本公开的其他特征和优点将在随后的具体实施方式部分予以详细说明。
附图说明
附图是用来提供对本公开的深入理解，并且构成说明书的一部分，与下面的具体实施方式一起用于解释本公开，但并不构成对本公开的限制。在附图中：
图1是本公开的锂离子电池正极材料的一种具体实施方式的结构示意图。
附图标记说明
1 核      2 内壳
3 外壳
具体实施方式
以下结合附图对本公开的具体实施方式进行详细说明。应当理解的是，此处所描述的具体实施方式仅用于说明和解释本公开，并不用于限制本公开。
本公开第一方面提供一种锂离子电池正极材料，该正极材料包括核壳结构复合材料，参照图1，该核壳结构复合材料包括由内向外依次设置的核1、内壳2和外壳3，核1包括正极活性物质，内壳2包括含有氟的正极活性物质，外壳3包括氟氧化物。
本公开的发明人发现，具有含有氟的正极活性物质内壳(或称氟化层内壳)及氟氧化物外壳的两层壳体包覆的核壳结构锂离子电池正极材料包覆结构稳定，能明显提升正极材料的电化学性能。其中，氟化层内壳稳定了正极材料的表面，增加了正极材料的稳定性，减少了正极材料的副反应，同时有利于缓解界面元素扩散带来的负面影响；氟氧化物外壳 的离子电导率较高、电子电导率低，包覆外壳后降低了锂的化学势，不仅有利于锂离子的传输，有效地降低与固态电解质接触的正极材料的表面电压，避免固态电解质被正极材料氧化，并且有效缓解了空间电荷层带来的锂离子传输阻碍问题，也有利于降低正极材料与固态电解质之间的元素扩散；氟化层内壳和氟氧化物外壳双层共同作用的结果为有效地减少了界面副反应，降低了界面阻抗，改善正极材料界面，使正极材料的循环稳定性和其他电化学性能得到了极大地优化。
根据本公开的实施例，核壳结构复合材料的平均粒径可以在较大范围内变化，在一些具体实施例中，核壳结构复合材料的平均粒径可以为100nm～500μm，具体如100nm、200nm、300nm、400nm、500nm、600nm、700nm、800nm、900nm、1μm、50μm、100μm、150μm、200μm、250μm、300μm、350μm、400μm、450μm、500μm等；在另一些具体实施例中，核壳结构复合材料的平均粒径可以为200nm～50μm，具体如200nm、300nm、400nm、500nm、600nm、700nm、800nm、900nm、1μm、10μm、20μm、30μm、40μm、50μm等，以提高正极材料的电化学性能。其中，核壳结构复合材料的平均粒径可以通过扫描电镜(SEM)随机观察100个核壳结构复合材料颗粒，并且分别量取其粒径值，粒径的平均值即为核壳结构复合材料的平均粒径。
根据本公开的实施例，核壳结构复合材料的内壳和外壳的厚度可以在较大范围内变化，在一些具体实施例中，内壳的厚度可以为1nm～10μm，具体如1nm、100nm、200nm、300nm、400nm、500nm、600nm、700nm、800nm、900nm、1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm、10μm等；在另一些具体实施例中，内壳的厚度可以为1nm～5μm，具体如1nm、100nm、200nm、300nm、400nm、500nm、600nm、700nm、800nm、900nm、1μm、2μm、3μm、4μm、5μm等；在又一些具体实施例中，内壳的厚度可以为100nm～1μm，具体如100nm、150nm、200nm、250nm、300nm、350nm、400nm、450nm、500nm、550nm、600nm、650nm、700nm、750nm、800nm、850nm、900nm、950nm、1μm等。在一些具体实施例中，外壳的厚度可以为1nm～10μm，具体如1nm、100nm、200nm、300nm、400nm、500nm、600nm、700nm、800nm、900nm、1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm、10μm等；在另一些具体实施例中，外壳的厚度可以为1nm～5μm，具体如1nm、100nm、200nm、300nm、400nm、500nm、600nm、700nm、800nm、900nm、1μm、2μm、3μm、4μm、5μm等；在又一些具体实施例中，外壳的厚度可以为100nm～1μm，具体如100nm、150nm、200nm、250nm、300nm、350nm、400nm、450nm、500nm、550nm、600nm、650nm、700nm、750nm、800nm、850nm、900nm、950nm、1μm等。在上述厚度范围内，内壳和外壳对构成核的正极活性物质具有更好的包覆和隔离作用，能 够阻止正极材料与电解质之间的界面元素扩散。其中，外壳和内壳的厚度是指平均厚度，可使用FIB(聚焦离子束)或者直接截面研磨的方法，使截面暴露，然后在SEM等工具下，量取任意100个正极材料颗粒的内壳和外壳的厚度值，内壳和外壳厚度的平均值即分别为内壳和外壳的平均厚度。
根据本公开的实施例，核壳结构复合材料中内壳和外壳的含量可以分别在较大范围内变化；在一些具体实施例中，为了得到内壳和外壳厚度适宜的核壳结构复合材料，以正极材料的总质量为基准，内壳的含量可以为0.1～50wt％，具体如0.1wt％、0.5wt％、1wt％、3wt％、5wt％、6wt％、10wt％、15wt％、20wt％、25wt％、30wt％、35wt％、40wt％、45wt％、50wt％等；另一些具体实施例中，内壳的含量可以为0.2～20wt％，具体如0.2wt％、0.3wt％、0.4wt％、0.5wt％、0.6wt％、0.7wt％、0.8wt％、0.9wt％、1wt％、2wt％、3wt％、4wt％、5wt％、6wt％、7wt％、8wt％、9wt％、10wt％、11wt％、12wt％、13wt％、14wt％、15wt％、16wt％、17wt％、18wt％、19wt％、20wt％等；一些具体实施例中，外壳的含量可以为0.1～50wt％，具体如0.1wt％、0.5wt％、1wt％、2.4wt％、4.6wt％、5wt％、10wt％、15wt％、20wt％、25wt％、30wt％、35wt％、40wt％、45wt％、50wt％等；另一些具体实施例中，外壳的含量可以为0.2～20wt％，具体如0.2wt％、0.3wt％、0.4wt％、0.5wt％、0.6wt％、0.7wt％、0.8wt％、0.9wt％、1wt％、2wt％、2.4wt％、3wt％、4wt％、4.6wt％、5wt％、6wt％、7wt％、8wt％、9wt％、10wt％、11wt％、12wt％、13wt％、14wt％、15wt％、16wt％、17wt％、18wt％、19wt％、20wt％等。
根据本公开的实施例，为了有效保护构成核的正极活性物质，避免正极材料与电解质之间发生界面元素扩散，外壳可以包括金属氟氧化物，金属氟氧化物中的金属可以为Fe、Ti、V、Bi、Zr、Nb、Ag、Cr、Mn、Co、Ni和Zn中的至少一种，即金属氟氧化物可以选自FeOF、TiOF 2、VO 2F、VOF 3、BiOF、ZrOF 2、NbO 2F、NbOF 3、AgOF、CrOF、MnOF 2、CoOF、NiOF和Zn 2OF 2中的至少一种。
根据本公开的实施例，为便于制备，内壳(即含有氟的正极活性物质)和核可以通过将正极活性物质的表面进行氟化处理得到，内部未被氟化的正极活性物质构成所述核，表面被氟化的正极活性物质构成所述内壳。也就是说，核壳结构复合材料的内壳可以为正极活性物质的原始表面经氟化后形成的含有氟的膜层，在这种情况下，该含有氟的膜层内部的未经氟化的正极活性物质即为核壳结构复合材料的核。在一些实施例中，在所述外壳向所述核的方向上，所述内壳中氟的含量逐渐减少，即在所述核壳结构复合材料的外表面向内部的方向上(即从外壳向核的方向上)，该含有氟的正极活性物质中氟的含量逐渐减少；换句话说所述含有氟的正极活性物质由表面向颗粒内部氟的含量减少。
根据本公开的实施例，为了防止正极材料和电解质之间的界面元素扩散，核壳结构复合材料的内壳可以将核壳结构复合材料的核与外壳完全隔离。其中，完全隔离是指内壳完全包覆核，并且能够阻止核与外壳之间的元素扩散。实现上述完全隔离的方式可以包括使内壳具有适宜的厚度和F/O原子比。
根据本公开的实施例，正极活性物质可以为本领域的常规种类，在一些具体实施例中，正极活性物质可以包括LiCoO 2、LiNiO 2、LiCo rNi 1-rO 2、LiCo xNi 1-x-yAl yO 2、LiMn 2O 4、LiFe pMn qX sO 4、Li 1+aL 1－b－cM bQ cO 2，LiFePO 4、Li 3V 2(PO 4) 3、Li 3V 3(PO 4) 3、LiVPO 4F、Li 2CuO 2、Li 5FeO 4、TiS 2、V 2S 3、FeS、FeS 2、LiRS z、TiO 2、Cr 3O 8、V 2O 5和MnO 2中的至少一种；其中，0≤r≤1，0≤x≤1，0≤y≤1，0≤x+y≤1，0≤p≤1，0≤q≤1，0≤s≤1，p+q+s＝1，-0.1≤a≤0.2，0≤b≤1，0≤c≤1，0≤b+c≤1，1≤z≤2.5；X为Al、Mg、Ga、Cr、Co、Ni、Cu、Zn和Mo的至少一种，L、M、Q为Li、Co、Mn、Ni、Fe、Al、Mg、Ga、Ti、Cr、Cu、Zn、Mo、F、I、S和B中的至少一种，R为Ti、Fe、Ni、Cu和Mo中的至少一种。本公开对正极活性物质颗粒(即核)的粒径没有特别要求，可以在较大范围内变化，在一些具体实施例中，正极活性物质颗粒的平均粒径为100nm～500μm，具体如100nm、200nm、300nm、400nm、500nm、600nm、700nm、800nm、900nm、1μm、100μm、200μm、300μm、400μm、500μm等；另一些具体实施例中，正极活性物质颗粒的平均粒径为200nm～50μm，具体如200nm、300nm、400nm、500nm、600nm、700nm、800nm、900nm、1μm、10μm、20μm、30μm、40μm、50μm等；由此，可以促进正极材料的界面形成和提高电化学性能。
本公开第二方面提供一种制备锂离子电池正极材料的方法，该方法包括如下步骤：将正极活性物质、氟氧化物前体和氟化氢在溶剂中混合反应，反应温度为100～300℃(具体如100℃、110℃、120℃、130℃、140℃、150℃、160℃、170℃、180℃、190℃、200℃、210℃、220℃、230℃、240℃、250℃、260℃、270℃、280℃、290℃、300℃等)，反应压力为0.1～100MPa(具体如0.1MPa、1MPa、10MPa、15MPa、20MPa、25MPa、30MPa、35MPa、40MPa、45MPa、50MPa、55MPa、60MPa、65MPa、70MPa、75MPa、80MPa、85MPa、90MPa、95MPa、100MPa等)。
本公开的方法通过一步反应制备具有氟化层内壳和氟氧化物外壳包覆的双层核壳结构正极材料，该方法包覆温度低、操作简便，制备的正极材料能够降低界面元素扩散现象，具有稳定良好的界面。本领域技术人员可以理解，该方法可以用于制备本公开第一方面的正极材料，在此不再过多赘述。
其中，在一些具体实施例中，反应温度可以为100～250℃，反应压力可以为25～80MPa，以优化正极材料的包覆结构和表面性能。
在本公开的方法中，可以在常规的反应容器中进行反应，例如密闭容器或半密闭容器(具体如带有减压阀的容器)，为了便于控制反应压力，该方法可以包括，在密闭状态下，使正极活性物质、氟氧化物前体和氟化氢在溶剂中混合反应，待反应压力为5～100Mpa时，在非密闭状态下继续进行反应且保持反应压力为25～100Mpa。具体地，例如可以在带有减压阀的容器中进行上述反应，在反应初始阶段，可以使减压阀处于关闭状态，待反应容器内压力达到25～80Mpa时打开减压阀控制容器内压力，在这种实施方式中，能够精确地控制反应过程各阶段的压力，以使反应物在正极活性物质颗粒表面进行均一的反应，并更有助于形成内壳为含有氟的正极活性物质层(或称氟化层)，外壳为氟氧化物包覆层的双层核壳结构的正极材料。
根据本公开的实施例，氟氧化物前体是指经上述混合反应(即使正极活性物质、氟氧化物前体和氟化氢在溶剂中混合反应)后能够生成氟氧化物的物质，例如氟化物，为了提高氟氧化物的包覆和隔离效果，阻止正极材料与电解质之间的界面元素扩散，在一些具体实施例中，氟氧化物前体可以为金属氟化物，金属氟化物中的金属可以为Fe、Ti、V、Bi、Zr、Nb、Ag、Cr、Mn、Co、Ni和Zn中的至少一种，具体的，如FeF 3、TiF 4等。在这种情况下，金属氟化物经混合反应后可以得到金属氟氧化物包覆层，以有效保护构成核的正极活性物质，避免正极材料与电解质之间发生界面元素扩散。
根据本公开的实施例，混合反应的溶剂可以为水和醇中的至少一种，例如为甲醇、乙醇、丙醇、乙二醇、丙二醇、环己醇、丙三醇和十八烯醇中的至少一种。
根据本公开的实施例，正极活性物质、氟氧化物前体和氟化氢的用量摩尔比可以为1：(0.0015～2)：(0.001～1)，具体可以为1：(0.003～0.8)：(0.002～0.4)，具体的，按照摩尔比计，氟氧化物前体的用量可以为正极活性物质用量的0.003倍、0.01倍、0.0027倍、0.003倍、0.05倍、0.006倍、0.1倍、0.15倍、0.2倍、0.25倍、0.3倍、0.35倍、0.4倍、0.45倍、0.5倍、0.55倍、0.6倍、0.65倍、0.7倍、0.75倍、0.8倍等，氟化氢的用量可以为正极活性物质用量的0.002倍、0.01倍、0.05倍、0.1倍、0.15倍、0.2倍、0.25倍、0.3倍、0.35倍、0.4倍等。上述用量范围内，氟氧化物前体和氟化氢中的氟分别可以完全转化，以形成包覆厚度适宜的核壳结构复合材料；相对于1重量份的正极活性物质，溶剂的用量可以为0.1～10重量份，具体如0.1重量份、0.5重量份、0.8重量份、1重量份、2重量份、3重量份、4重量份、5重量份、6重量份、7重量份、8重量份、9重量份、10重量份等，一些具体实施例中，溶剂的用量可以为0.5～2重量份，具体如0.5重量份、0.6重量份、0.7重量份、0.8重量份、0.9重量份、1.0重量份、1.1重量份、1.2重量份、1.3重量份、1.4重量份、1.5重量份、1.6重量份、1.7重量份、1.8重量份、1.9重量份、2.0重量份等。其中，正极 活性物质可以为本领域常规的种类，具体可以为上述所列出的种类(即与前文描述的正极活性物质一致)，此处不再赘述。
根据本公开的实施例，氟化氢可以以多种形式加入，为了便于操作且提高氟化效果，在一些具体实施例中，可以采用HF水溶液进行本公开的反应，在这种情况下，该方法可以包括，使HF水溶液与正极活性物质、氟氧化物前体在溶剂中混合反应；HF水溶液中氟化氢与水的体积比可以为1：(0.1～100)，具体可以为1：(5～20)，如1:5、1:6、1:7、1:8、1:9、1:10、1:11、1:12、1:13、1:14、1:15、1:16、1:17、1:18、1:19、1:20等。
本公开第三方面提供根据本公开第二方面的方法制备得到的锂离子电池正极材料。
本公开第四方面提供一种锂离子电池正极，该正极含有本公开第一方面和第三方面的锂离子电池正极材料中的至少一种。
锂离子电池正极可以包括正极集流体及涂覆于正极集流体表面上的正极材料层，正极材料层可以包括上述包括核壳结构复合材料的正极材料、导电剂及粘结剂，所述粘结剂为正极常用粘结剂，例如：含氟树脂和聚烯烃化合物如聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)和丁苯橡胶(SBR)中的一种或几种。所述导电剂为正极常用导电剂，例如乙炔黑、碳纳米管、碳纤维、碳黑等。以正极材料的重量为基准，粘结剂的含量为0.01-10重量％(wt％)，具体可以为0.02-5wt％(如0.02wt％、0.1wt％、1wt％、2wt％、3wt％、4wt％、5wt％等)；导电剂的含量为0.1～20wt％，具体可以为1～10wt％(如1wt％、2wt％、3wt％、4wt％、5wt％、6wt％、7wt％、8wt％、9wt％、10wt％等)。所述溶剂可选自N-甲基吡咯烷酮(NMP)、水、乙醇、丙酮中的一种或几种，溶剂的用量一般为50-400wt％(如50wt％、100wt％、150wt％、200wt％、250wt％、300wt％、350wt％、400wt％等)。
本公开第五方面提供一种全固态锂电池，该全固态锂电池包括本公开第四方面的锂离子电池正极。
全固态锂电池的结构可以为本领域常规的，例如可以包括正极、负极和固态电解质层，正极可以包括正极集流体和涂覆于正极集流体表面的正极材料层，负极可以包括负极集流体和涂覆于负极集流体表面的负极材料层，固态电解质层可以包括固态电解质材料。固态电解质材料可以为本领域常规的，包括但不限于NASICON型固态电解质、氧化物固态电解质、硫系固态电解质中的一种或者多种。其中NASICON型固态电解质为LiM 2(PO 4) 3及其掺杂物中的一种或多种，其中M为Ti、Zr、Ge、Sn或Pb，所述掺杂物采用的掺杂元素选自Mg、Ca、Sr、Ba、Sc、Al、Ga、In、Nb、Ta、V中的一种或多种。氧化物型固态电解质的化学式为A x1J y1TiO 3、A x1J y1Ta 2O 6、A x1J y1Nb 2O 6、A hG kD nTi wO 3或A 3J 2(GO 4) 3，其中x1+3y1＝2，h+2k+5n+4w＝6，0＜x1＜2，0＜y1＜2/3，h、k、n、w均大于0；A为Li、 Na元素中的至少一种，J为La、Ce、Pr、Y、Sc、Nd、Sm、Eu、Gd、Nd、Al元素中的至少一种，G为Sr、Ca、Ba、Ir、Pt、Te、Zr元素中的至少一种，D为Nb、Ta元素中的至少一种。硫系固态电解质为结晶态的Li x2H y2P z2S w2(H为Si、Ge、Sn中的一种或多种，其中x2+4y2+5z2＝2w2，0≤y2≤1.5，0≤x2≤15，0≤z2≤3，0≤w2≤18)、玻璃态Li 2S-P 2S 5(包括Li 7P 3S 11、70Li 2S-30P 2S 5等)或玻璃陶瓷态Li 2S-P 2S 5及其掺杂物中的一种或多种。
本公开的全固态锂离子电池中，负极材料层可以包括本领域技术人员常用的负极活性物质，例如为各种可嵌脱锂的负极活性物质，例如可以选自碳材料、锡合金、硅合金、硅、锡、锗中的一种或多种，同时也可以采用金属锂、锂-铟合金等。其中所述碳材料可以采用非石墨化炭、石墨或由多炔类高分子材料通过高温氧化得到的炭或热解炭、焦炭、有机高分子烧结物、活性炭中的一种或多种。作为本领域技术人员的公知常识，当负极活性物质采用硅类材料时，所述负极材料层中还含有导电剂，其作用为本领域技术人员所公知，此处不再赘述。
本公开的全固态锂电池可以采用如下方法制备：
正极集流体上涂覆正极活性材料层，形成正极C，然后在正极活性材料层上面涂覆一层固态电解质材料层E，形成CE层，在负极集流体上涂覆负极活性材料层，形成负极A，然后将A与CE层压制在一起形成本公开的全固态电池。
所述正极活性材料层可以包括本公开的包括核壳结构复合材料的正极材料、导电剂和粘结剂，正极活性材料层通过现有的方法进行制作：将本公开的包括核壳结构复合材料的正极材料、导电剂、粘结剂和溶剂的浆料涂覆于集流体上，干燥后在集流体上形成活性材料层，然后经过0～5MPa的辊压处理，得到极片C。所述粘结剂为正极常用粘结剂，例如：含氟树脂和聚烯烃化合物如聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)和丁苯橡胶(SBR)中的一种或几种。所述导电剂为正极常用导电剂，例如乙炔黑、碳纳米管、碳纤维、碳黑等。以正极材料的重量为基准，粘结剂的含量为0.01～10重量％(wt％)，具体可以为0.02-5wt％(如0.02wt％、0.1wt％、1wt％、2wt％、3wt％、4wt％、5wt％等)；导电剂的含量为0.1-20wt％，具体可以为1～10wt％(如1wt％、2wt％、3wt％、4wt％、5wt％、6wt％、7wt％、8wt％、9wt％、10wt％等)。所述溶剂可选自N-甲基吡咯烷酮(NMP)、水、乙醇、丙酮中的一种或几种，溶剂的用量一般为50～400wt％。普通正电极的制备工艺是将正极材料、导电剂、粘结剂按一定比例混合在溶剂中，搅拌均匀后得到所需的正极浆料，然后将该浆料涂敷在铝箔集流体上，经过干燥、压片处理即得含有正极活性材料层的普通正电极。
所述固态电解质材料层E可以包含固态电解质材料和粘结剂。固态电解质材料层E由涂覆方法进行制作：将含有固态电解质材料、粘结剂和溶剂的浆料涂覆上述正极活性材料 层上，干燥、辊压后形成CE。其中固态电解质材料为Li 10GeP 2S 12硫系固态电解质。所述粘结剂选自聚噻吩、聚吡咯、聚四氟乙烯、聚偏氟乙烯、聚乙烯、聚丙烯、聚苯乙烯、聚丙烯酰胺、乙烯-丙烯-二烯共聚树脂、苯乙烯丁二烯橡胶、聚丁二烯、氟橡胶、聚环氧乙烯、聚乙烯吡咯烷酮、聚酯树脂、丙烯酸树脂、酚醛树脂、环氧树脂、聚乙烯醇、羧丙基纤维素、乙基纤维素、聚氧化乙烯、羧甲基纤维素钠(CMC)、丁苯胶乳(SBR)中的一种或多种。
所述负极活性材料层的组分为本领域技术人员所公知，包括负极活性物质和粘结剂。其中，所采用的负极活性物质可以为本领域技术人员常用的各种可嵌脱锂的负极活性物质，例如可以选自碳材料、锡合金、硅合金、硅、锡、锗中的一种或多种，同时也可以采用金属锂、锂-铟合金等。其中所述碳材料可以采用非石墨化炭、石墨或由多炔类高分子材料通过高温氧化得到的炭或热解炭、焦炭、有机高分子烧结物、活性炭中的一种或多种。作为本领域技术人员的公知常识，当负极活性物质采用硅类材料时，所述负极活性材料层中还含有导电剂，其作用为本领域技术人员所公知，此处不再赘述。粘结剂为本领域技术人员公知的各种负极粘结剂，例如可以选自聚噻吩、聚吡咯、聚四氟乙烯、聚偏氟乙烯、聚乙烯、聚丙烯、聚苯乙烯、聚丙烯酰胺、乙烯-丙烯-二烯共聚树脂、苯乙烯丁二烯橡胶、聚丁二烯、氟橡胶、聚环氧乙烯、聚乙烯吡咯烷酮、聚酯树脂、丙烯酸树脂、酚醛树脂、环氧树脂、聚乙烯醇、羧丙基纤维素、乙基纤维素、羧甲基纤维素钠(CMC)、丁苯胶乳(SBR)中的一种或多种。在一些具体实施例中，所述负极活性材料层中，以负极活性物质的重量为基准，粘结剂的含量为0.01～10wt％(如0.01wt％、0.05wt％、0.1wt％、0.5wt％、1wt％、2wt％、3wt％、4wt％、5wt％、6wt％、7wt％、8wt％、9wt％、10wt％等)。负极活性材料层的获得是将负极活性物质、粘结剂等按一定比例混合在溶剂中，搅拌均匀后得到所需的负极浆料，然后将该浆料涂敷在铜箔集流体上，经过干燥、压片处理即得含有负极活性材料层的普通负电极A。当负极采用锂或锂-铟合金时可以直接采用金属锂带或锂-铟合金带。
最后将A与CE压制在一起形成CEA，即可得本公开的全固态电池，压制方式具体可以为等静压。
下面通过实施例描述本公开，但是本公开并不因此而受到任何限制。
实施例1
本实施例用于说明本公开的锂离子电池正极材料及全固态锂电池CEA1，以及它们的制备方法。
(1)正极C的制作
首先制备具有氟化内壳和氟氧化物外壳的核壳结构的正极材料，作为核材料的正极活性物质为LiCoO 2材料，具体制备方法为，将1000gLiCoO 2与30gFeF 3放入体积为5L的半密闭反应容器中，加入100mL的去离子水、100mL经过稀释的HF溶液(无水HF：去离子水＝11.1mL：88.9mL)和800mL乙醇，开启搅拌，密闭后加热至170℃，进行反应，待反应容器中压力达到8×10 6Pa(即80个大气压)后，开启减压阀，保证容器中压力为8×10 6Pa，直至反应完成，即可得到本实施例的具有氟化内壳和氟氧化铁FeOF外壳的核壳结构的LiCoO 2正极材料。而后，将930g上述LiCoO 2正极材料(93％)、30g粘结剂PVDF(3％)、20g乙炔黑(2％)、20g导电剂碳纤维(2％)加入到1500g溶剂NMP(氮甲基吡咯烷酮)中，然后在真空搅拌机中搅拌，形成稳定均一的正极浆料。将该正极浆料均匀地间歇涂布在铝箔(铝箔尺寸为：宽度160mm，厚度16μm)的两面上，然后393K烘干，经过辊压机压片后得到正极C。
(2)CE的制作
在手套箱中，将600g的Li 10GeP 2S 12置入1200g的甲苯溶液中，其中甲苯溶液中含有30g丁二烯橡胶粘结剂，然后加热搅拌至稳定、均一的溶液。将该溶液连续涂布在步骤2得到的C上，然后333K烘干，剪裁为尺寸为485mm(长)×46mm(宽)的CE。
(3)负极A的制作
将940g负极活性材料人造石墨(94％)、30g粘接剂CMC(3％)和30g粘接剂SBR(3％)加入到1200g去离子水中，然后在真空搅拌机中搅拌，形成稳定均一的负极浆料。将该浆料均匀地间歇涂布在铜箔(铜箔尺寸为：宽度160mm，厚度16μm)的两面上，然后393K烘干，经过辊压机压片后，剪裁为尺寸为480mm(长)×45mm(宽)的负极片A。
(4)CEA的制作
在手套箱中，将步骤2得到的CE和步骤3得到的A剪裁后对齐放置在热压机中，进行423K热压1h，使用铝塑膜抽真空密封后，取出样品。
将上述压制后的样品在等静压机中200MPa、300秒(s)压制后即得本实施例的全固态锂电池。
实施例2
采用与实施例1相同的步骤制备本实施例的包覆后正极材料及锂离子电池CEA2，不同之处在于：
步骤(1)中，FeF 3的用量不是30g，而是60g，所使用的100mL经过稀释的HF溶液， 其无水HF：去离子水为22.2mL：77.85L，其它步骤与操作均相同。
实施例3
采用与实施例1相同的步骤制备本实施例的包覆后正极材料及锂离子电池CEA3，不同之处在于：
步骤(1)中，制备同时氟化和TiOF 2包覆的LiCoO 2正极材料，其制备方法为，将1000gLiCoO 2与30gTiF 4放入体积为5L的半密闭反应容器中，加入100mL的去离子水、100mL经过稀释的HF溶液(无水HF：去离子水＝11.1mL：88.9mL)和800mL乙醇，开启搅拌，密闭后加热至200℃，进行反应，待反应容器中压力达到1×10 7Pa(即100个大气压)后，开启减压阀，保证容器中压力为1×10 7Pa，直至反应完成，即可得到同时氟化和TiOF 2包覆的LiCoO 2正极材料，而后直接使用该正极材料进行固态锂电池的装配，其它步骤与操作均相同。
对比例1
采用与实施例1相同的步骤制备本对比例的锂离子电池CEA4，不同之处在于：
制备正极材料过程中不加入FeF 3，所得的LiCoO 2正极材料不具有氟氧化铁FeOF外壳，仅具有氟化内壳，其制备方法为将1000gLiCoO 2放入体积为5L的半密闭反应容器中，加入100mL经过稀释的HF溶液(无水HF：去离子水＝11.1mL：88.9mL)和900mL乙醇，开启搅拌，密闭后加热至150℃，进行反应，待反应容器中压力达到8×10 6Pa(即80个大气压)后，开启减压阀，保证容器中压力为8×10 6Pa，直至反应完成，即可得到表面氟化的LiCoO 2正极材料，然后直接使用该正极材料进行固态锂电池的组装，其余步骤与操作不变。
对比例2
采用与实施例1相同的步骤制备本对比例的锂电池CEA5，不同之处在于：
制备正极材料过程中不加入HF溶液，所得的LiCoO 2正极材料不具有氟化内壳，仅具有氟氧化铁FeOF外壳，其制备方法为，将1000gLiCoO 2、30gFeF 3放入体积为5L的半密闭反应容器中，加入100mL去离子水和900mL乙醇，开启搅拌，密闭后加热至180℃，进行反应，即可得到经过FeOF包覆的LiCoO 2正极材料，然后直接使用该正极材料进行固态锂电池的组装，其余步骤与操作不变。
对比例3
采用与实施例1相同的步骤制备本对比例的锂电池CEA6，不同之处在于：
LiCoO 2正极材料不具有氟化内壳及FeOF外壳，仅为LiCoO 2正极材料与FeOF物理球磨共混制备的正极材料，其制备方法为，将1000gLiCoO 2与29.5g FeOF共同放入球磨罐中，以转速250rpm球磨2h，即可得LiCoO 2正极材料与FeOF物理球磨共混的产物，然后直接使用该正极材料进行固态锂电池的组装，其余步骤与操作不变。
对比例4
采用与实施例1相同的步骤制备本对比例的锂电池CEA7，LiCoO 2正极材料具有氟化内壳，不同之处在于：
该正极材料是表面经过氟化的LiCoO 2正极材料与FeOF物理球磨共混制备的，其制备方法为，将1000gLiCoO 2放入体积为5L的半密闭反应容器中，加入100mL经过稀释的HF溶液(无水HF：去离子水＝11.1mL：88.9mL)和900mL乙醇，开启搅拌，密闭后加热至150℃，进行反应，待反应容器中压力达到8×10 6Pa(即80个大气压)后，开启减压阀，保证容器中压力为8×10 6Pa，直至反应完成，即可得到表面氟化的LiCoO 2正极材料，将该表面氟化的LiCoO 2正极材料与29.5gFeOF共同放入球磨罐中，以转速250rpm球磨2h，即可得到表面经过氟化的LiCoO 2正极材料与FeOF物理球磨共混的产物，然后直接使用该正极材料进行固态锂电池的组装，其余步骤与操作不变。
对比例5
采用与实施例1相同的步骤制备本对比例的锂电池CEA8，不同之处在于：
LiCoO 2正极材料不具有氟化内壳，也不具有氟氧化铁FeOF外壳，而是表面经过Li 4Ti 5O 12包覆的LiCoO 2正极材料，其制备方法为，将1000gLiCoO 2、73.4mL钛酸四丁酯、12g乙醇锂、1000mL乙醇放入同一容器中，开启搅拌，逐渐加入稀氨水，调整pH范围至9-10，将所得沉淀物离心，在空气中加热至800℃，即可得表面经过Li 4Ti 5O 12包覆的LiCoO 2正极材料，然后直接使用该正极材料进行固态锂电池的组装，其余步骤与操作不变。
对比例6
采用与实施例1相同的步骤制备本对比例的锂电池CEA9，不同之处在于：
直接使用未经任何处理的LiCoO 2活性物质进行固态锂电池的组装，其余步骤与操作不变。
测试实施例1
对实施例1～3和对比例1～6中得到的正极材料进行SEM(JSM-7600F)和XPS(PHI5800)测试，得到含有其表面氟氧化物阳离子元素含量(原子比)、表面F/O的原子比、包覆层(内壳和外壳)厚度及内外壳含量的数据列于表1，其中，内壳含量采用计算氟化产物所占比例的方法得到，外壳含量采用计算包覆产物质量的方法得到。
将实施例1～3和对比例1～6中得到的正极材料进行Ar +离子蚀刻后，测试其表面元素含量和F/O的原子比，数据同样列于表1，其中Ar +离子蚀刻的步长为2min，所使用离子束能量为2keV。
表1
Figure PCTCN2019093382-appb-000001
Figure PCTCN2019093382-appb-000002
Figure PCTCN2019093382-appb-000003
测试实施例2
对实施例1～3和对比例1～6中得到的全固态锂电池CEA1-CEA9进行电池的循环寿命测试，所得数据列于表2。测试方法如下：
将各实施例和对比例制备得到的电池各取20支，在LAND CT 2001C二次电池性能检测装置上，298±1K条件下，将电池以0.1C进行充放电循环测试。步骤如下：搁置10min；恒压充电至4.2V/0.05C截止；搁置10min；恒流放电至3.0V，即为1次循环。重复该步骤，循环过程中当电池容量低于首次放电容量的80％时，循环终止，该循环次数即为电池的循环寿命，每组取平均值，该参数与电池平均首次放电容量的数据如表2所示。
表2
Figure PCTCN2019093382-appb-000004
由表1和表2数据可知，与一般氧化物包覆的正极材料(对比例5)或未经任何处理的正极材料(对比例6)相比，本公开的含有氟化内壳和氟氧化物外壳双层包覆核壳结构的正极材料能够有效提高全固态锂电池的首次放电比容量和环次数，并能明显延长电池寿命；并且，与不具有氟化层内壳(对比例2)或不具有氟氧化物外壳(对比例1)或氟氧化物仅以共混的形式与正极活性物质结合(对比例3-4)的正极材料相比，本公开的正极材料的电池寿命也更有优势，这说明同时具有氟化层内壳和氟氧化物外壳的电池材料提高了正极物质的界面性能，减少了元素扩散，更有利于延长电池的寿命。
以上结合附图详细描述了本公开的优选实施方式，但是，本公开并不限于上述实施方 式中的具体细节，在本公开的技术构思范围内，可以对本公开的技术方案进行多种简单变型，这些简单变型均属于本公开的保护范围。
另外需要说明的是，在上述具体实施方式中所描述的各个具体技术特征，在不矛盾的情况下，可以通过任何合适的方式进行组合。为了避免不必要的重复，本公开对各种可能的组合方式不再另行说明。
此外，本公开的各种不同的实施方式之间也可以进行任意组合，只要其不违背本公开的思想，其同样应当视为本公开所公开的内容。

Claims (18)

  1. 一种锂离子电池正极材料，其特征在于，该正极材料包括核壳结构复合材料，所述核壳结构复合材料包括由内向外依次设置的核、内壳和外壳，所述核包括正极活性物质，所述内壳包括含有氟的正极活性物质，所述外壳包括氟氧化物。
  2. 根据权利要求1所述的正极材料，其中，所述核壳结构复合材料的平均粒径为100nm～500μm。
  3. 根据权利要求1或2所述的正极材料，其中，所述内壳的厚度为1nm～5μm，所述外壳的厚度为1nm～5μm。
  4. 根据权利要求1～3中任意一项所述的正极材料，其中，以所述正极材料的总质量为基准，所述内壳的含量为0.1wt.％～50wt.％；所述外壳的含量为0.1wt.％～50wt.％。
  5. 根据权利要求1～4中任意一项所述的正极材料，其中，所述氟氧化物选自金属氟氧化物，所述金属氟氧化物中的金属为Fe、Ti、V、Bi、Zr、Nb、Ag、Cr、Mn、Co、Ni和Zn中的至少一种。
  6. 根据权利要求1～5中任意一项所述的正极材料，其中，所述内壳和所述核是对正极活性物质的表面进行氟化处理得到的，其中，内部未被氟化的正极活性物质构成所述核，表面被氟化的正极活性物质构成所述内壳。
  7. 根据权利要求1～6中任意一项所述的正极材料，其中，在所述外壳向所述核的方向上，所述内壳中氟的含量逐渐减少。
  8. 根据权利要求1～7中任意一项所述的正极材料，其中，所述内壳将所述核与所述外壳完全隔离。
  9. 根据权利要求1～8中任意一项所述的正极材料，其中，所述正极活性物质包括LiCoO 2、LiNiO 2、LiCo rNi 1-rO 2、LiCo xNi 1-x-yAl yO 2、LiMn 2O 4、LiFe pMn qX sO 4、Li 1+aL 1－b－ cM bQ cO 2，LiFePO 4、Li 3V 2(PO 4) 3、Li 3V 3(PO 4) 3、LiVPO 4F、Li 2CuO 2、Li 5FeO 4、TiS 2、V 2S 3、 FeS、FeS 2、LiRS z、TiO 2、Cr 3O 8、V 2O 5和MnO 2中的至少一种；
    其中，0≤r≤1，0≤x≤1，0≤y≤1，0≤x+y≤1，0≤p≤1，0≤q≤1，0≤s≤1，p+q+s＝1，-0.1≤a≤0.2，0≤b≤1，0≤c≤1，0≤b+c≤1，1≤z≤2.5；
    X为Al、Mg、Ga、Cr、Co、Ni、Cu、Zn和Mo的至少一种，L、M、Q为Li、Co、Mn、Ni、Fe、Al、Mg、Ga、Ti、Cr、Cu、Zn、Mo、F、I、S和B中的至少一种，R为Ti、Fe、Ni、Cu和Mo中的至少一种。
  10. 一种制备锂离子电池正极材料的方法，其特征在于，该方法包括如下步骤：
    将正极活性物质、氟氧化物前体和氟化氢在溶剂中混合反应，反应温度为100～300℃，反应压力为0.1～100MPa。
  11. 根据权利要求10所述的方法，其中，所述氟氧化物前体为金属氟化物，所述金属氟化物中的金属为Fe、Ti、V、Bi、Zr、Nb、Ag、Cr、Mn、Co、Ni和Zn中的至少一种。
  12. 根据权利要求10或11所述的方法，其中，所述溶剂为水和醇中的至少一种。
  13. 根据权利要求10～12中任意一项所述的方法，其中，所述正极活性物质、所述氟氧化物前体和所述氟化氢的用量摩尔比为1：(0.0015～2)：(0.001～1)；相对于1重量份的所述正极活性物质，所述溶剂的用量为0.1～10重量份。
  14. 根据权利要求10～13中任意一项所述的方法，其中，该方法包括，使HF水溶液与所述正极活性物质、所述氟氧化物前体在所述溶剂混合反应；所述HF水溶液中氟化氢与水的体积比为1：(0.1～100)。
  15. 根据权利要求10～14中任意一项所述的方法，其中，该方法包括，在密闭状态下，使所述正极活性物质、所述氟氧化物前体和所述氟化氢在所述溶剂中混合反应，待反应压力为5～100Mpa时，在非密闭状态下继续进行所述反应且保持反应压力为25～100Mpa。
  16. 根据权利要求10～15中任意一项所述的方法制备得到的锂离子电池正极材料。
  17. 一种锂离子电池正极，该正极含有权利要求1～9和权利要求16中任意一项所述的 锂离子电池正极材料。
  18. 一种全固态锂电池，该全固态锂电池包括权利要求17所述的锂离子电池正极。
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