WO2023078071A1 - 正极材料极片、制备方法、二次电池、电池模组、电池包及用电装置 - Google Patents

正极材料极片、制备方法、二次电池、电池模组、电池包及用电装置 Download PDF

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WO2023078071A1
WO2023078071A1 PCT/CN2022/125637 CN2022125637W WO2023078071A1 WO 2023078071 A1 WO2023078071 A1 WO 2023078071A1 CN 2022125637 W CN2022125637 W CN 2022125637W WO 2023078071 A1 WO2023078071 A1 WO 2023078071A1
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positive electrode
pole piece
electrode material
battery
lithium
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PCT/CN2022/125637
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English (en)
French (fr)
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高靖宇
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宁德时代新能源科技股份有限公司
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Priority to EP22889096.8A priority Critical patent/EP4418368A1/en
Publication of WO2023078071A1 publication Critical patent/WO2023078071A1/zh
Priority to US18/652,103 priority patent/US20240290988A1/en

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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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Nickelates
    • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
    • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese of the type [MnO2]n-, e.g. Li(NixMn1-x)O2, Li(MyNixMn1-x-y)O2
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/50—Solid solutions
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • H—ELECTRICITY
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    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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 lithium ion batteries, and relates to a positive electrode material pole piece, in particular to a high-nickel ternary positive electrode material piece, its preparation method, a secondary battery containing the positive electrode material pole piece, and a battery containing the secondary battery Battery modules, battery packs and electrical devices.
  • Lithium-ion batteries mainly use high-nickel ternary cathode materials.
  • there is too much residual lithium on the surface of the pole piece of the high-nickel ternary positive electrode material which leads to an increase in the side reaction of the pole piece and a large impedance.
  • the water and hydrofluoric acid in the electrolyte will decompose the solid electrolyte interface on the surface of the pole piece during charging and discharging. (SEI) film, causing the loss of active materials, resulting in a decrease in the cycle performance of the battery. Therefore, it is necessary to process the positive electrode material to improve the electrochemical performance of the battery.
  • the electrochemical performance of the battery is improved by treating the positive electrode material sheet of the battery with inorganic phosphoric acid.
  • inorganic phosphoric acid has weak activity and cannot form a continuous structure, which cannot guarantee the continuity and stability of the pole piece protective layer, and the treatment process requires high temperature heating.
  • the present application improves the electrochemical performance of the lithium-ion battery by using a specific content of phytic acid solution to treat the positive electrode material pole piece.
  • a positive electrode material pole piece is provided, and the positive electrode material pole piece comprises:
  • pole piece substrate and a cladding layer arranged on the surface of the pole piece substrate
  • the coating layer is a three-dimensional network lithium phosphate layer with a thickness of 10nm-20nm, wherein the content of lithium phosphate is 20%-30%.
  • the pole piece matrix includes a compound of formula I:
  • M is at least one of Mn, Al, Ti, Zr, Mg, W and Mo.
  • the cladding layer is a three-dimensional network lithium phosphate layer with a thickness of 12nm-13nm.
  • the cladding layer is a three-dimensional network lithium phosphate layer with a thickness of 12.4nm-12.8nm.
  • the lithium phosphate content is 22%-26%.
  • a three-dimensional network-like lithium phosphate protective layer is formed on the surface of the positive electrode material, which effectively protects the active material from side reactions with the electrolyte. Electrochemical performance of lithium-ion batteries.
  • a method for preparing a positive electrode material pole piece comprising:
  • a mixture of nickel source, cobalt source and metal M source is provided, wherein M is at least one of Mn, Al, Ti, Zr, Mg, W and Mo, the mixture is mixed with urea and deionized water and stirred, and then Precursor obtained after hydrothermal reaction;
  • the precursor is reacted with a lithium source, and the positive electrode material is obtained after sintering, and the positive electrode material has formula I:
  • M is at least one of Mn, Al, Ti, Zr, Mg, W and Mo;
  • the positive electrode material is coated on the positive electrode current collector, and processed to obtain the positive electrode material pole piece.
  • the processing steps include:
  • the coating layer is a three-dimensional network lithium phosphate layer with a thickness of 12nm to 13nm, The lithium phosphate content is 20% to 30%;
  • the ratio of the amount of the phytic acid solution to the area of the positive electrode sheet is 0.2mL/cm 2 -0.45mL/cm 2 .
  • phytic acid solution is used for treatment.
  • phytic acid can react with residual lithium on the surface of the pole piece to form a lithium phosphate protective layer, which can inhibit the dissolution of active materials and SEI layers.
  • the highly active phosphorus hydroxyl and The ester group can be cross-linked with lithium phosphate to form a spatial network protective film with high cross-link density, which is beneficial to the transmission of lithium ions on the surface of the pole piece.
  • the ratio of the amount of the phytic acid solution to the area of the positive electrode sheet is 0.2 mL/cm 2 -0.3 mL/cm 2 .
  • the ratio of the amount of the phytic acid solution to the area of the positive electrode sheet is 0.25 mL/cm 2 .
  • the use of an appropriate amount of phytic acid solution can produce a cross-linked lithium phosphate protective layer with an optimal thickness, effectively protect the active material and SEI layer on the surface of the pole piece, and also ensure the lithium ion on the surface of the pole piece. Fast transfer.
  • the treatment time for the surface of the positive electrode material pole piece is 20 minutes to 45 minutes.
  • the treatment time for the surface of the positive electrode material pole piece is 20 minutes to 30 minutes.
  • the treatment time for the surface of the positive electrode material pole piece is 25 minutes.
  • a cross-linked lithium phosphate protective layer with an optimal thickness can be produced, which can effectively protect the active material and SEI layer on the surface of the pole piece, and at the same time ensure that the lithium ions are Fast transfer of pole piece surface.
  • a secondary battery which includes the above-mentioned positive electrode material pole piece.
  • a battery module which includes the above-mentioned secondary battery.
  • a battery pack which includes the above-mentioned secondary battery or battery module.
  • an electric device which includes the above-mentioned secondary battery, or the above-mentioned battery module, or the above-mentioned battery pack, and the secondary battery or the battery module or the battery pack is used for Serve as the power source of the electric device or the energy storage unit of the electric device.
  • a three-dimensional network lithium phosphate protective layer is formed on the surface of the positive electrode material pole piece, which effectively protects the active material from side reactions with the electrolyte
  • the three-dimensional network structure can ensure the rapid transmission of lithium ions on the surface of the pole piece, and improve the electrochemical performance of lithium-ion batteries.
  • Fig. 1 shows the scanning electron microscope (SEM) image (A), the phosphorus scanning image (B) and the high-resolution spectrogram (C and D) of the cathode electrode sheet of Example 1 of the present application.
  • SEM scanning electron microscope
  • Fig. 2 is the phosphorus 2p X-ray photoelectron energy spectrum (P 2p XPS) figure of the cathode pole sheet of the embodiment 1 of the present application.
  • FIG. 3 is a schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 4 is an exploded view of the secondary battery shown in FIG. 3 .
  • FIG. 5 is a schematic diagram of an embodiment of a battery module of the present application.
  • Fig. 6 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 7 is an exploded view of the battery pack shown in FIG. 6 .
  • FIG. 8 is a schematic diagram of an embodiment of a device using the secondary battery of the present application as a power source.
  • ranges disclosed herein are defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range "a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • ⁇ 2 when a certain parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the "comprising” and “comprising” mentioned herein mean an open type or a closed type.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B.” More specifically, the condition “A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • the existing high-nickel ternary positive electrode material has too much residual lithium on the surface of the pole piece, which leads to increased side reactions and increased impedance of the pole piece.
  • water and hydrofluoric acid in the electrolyte will decompose the solid electrolyte on the surface of the pole piece during charging and discharging.
  • the interfacial film causes the loss of active materials, resulting in a decrease in the cycle performance of the battery.
  • the electrochemical performance of the battery is improved by treating the positive electrode material sheet of the battery with inorganic phosphoric acid.
  • inorganic phosphoric acid has weak activity and cannot form a continuous structure, which cannot guarantee the continuity and stability of the pole piece protective layer, and the treatment process requires high temperature heating.
  • this application chooses phytic acid solution to treat the high-nickel ternary material pole piece.
  • phytic acid can react with the residual lithium on the surface of the pole piece. Generate a lithium phosphate protective layer to inhibit the dissolution of active materials and SEI layers.
  • the highly active phosphorus hydroxyl and ester groups in phytic acid can be cross-linked with lithium phosphate to form a high cross-linking density spatial network protective film, which is beneficial to lithium ions. Transport on the pole piece surface.
  • the surface-modified high-nickel ternary material pole piece prepared by this application has a three-dimensional network lithium phosphate protective layer on the surface, which effectively protects the active material from side reactions with the electrolyte, and at the same time, the three-dimensional network structure can protect lithium ions. Rapid transport on the surface of the pole piece improves the electrochemical performance of the lithium-ion battery.
  • Phytic acid also known as phytic acid, cyclohexyl hexaphosphate, its molecular formula is C 6 H 18 O 24 P 6 , is an organophosphorus compound extracted from plant seeds.
  • the phytic acid solution used is a solution prepared by dissolving 25 mg of phytic acid powder in 100 mL of dimethyl sulfoxide.
  • the thickness of the three-dimensional network lithium phosphate layer is 10nm-20nm, and the lithium phosphate content is 20%-30%, calculated based on the area of the peak in the P 2p XPS spectrum.
  • (A) and (B) in Figure 1 show that the surface of the high-nickel ternary positive electrode sheet in the present application is treated with phytic acid to form a three-dimensional network crosslinked layer, which proves the effective doping of phosphorus in the surface crosslinked layer.
  • the thickness of the surface crosslinked layer can be seen to be about 12.6nm after the pole piece in the present application is processed, and the high-resolution spectrum analysis results show that the interplanar spacing of the surface corresponds to phosphoric acid
  • the (460) crystal face of lithium proves that the phytic acid treatment makes a lithium phosphate three-dimensional cross-linked layer with a thickness of about 12.6nm formed on the surface of the high-nickel ternary pole piece.
  • the XPS spectrogram peak of P 2p in the present application mainly corresponds to lithium phosphate, simultaneously by comparing the change of peak area, can draw the content of lithium phosphate layer in different embodiments and comparative examples.
  • the positive electrode material includes a high-nickel ternary material.
  • the positive electrode material pole piece includes a pole piece base body and a cladding layer arranged on the surface of the pole piece base body.
  • the pole piece matrix includes a compound of formula I:
  • the coating layer is a three-dimensional network lithium phosphate layer.
  • the thickness of the three-dimensional network lithium phosphate layer is 10nm-20nm.
  • the thickness of the three-dimensional network lithium phosphate layer is 12nm-13nm.
  • the thickness of the three-dimensional network lithium phosphate layer is 12.4nm-12.8nm.
  • the thickness of the three-dimensional network lithium phosphate layer is 12.6 nm.
  • the lithium phosphate content in the three-dimensional network lithium phosphate layer is 20% to 30%, which is calculated based on the area of the peak in the P 2p XPS spectrum.
  • the lithium phosphate content in the three-dimensional network lithium phosphate layer is 22% to 26%, calculated based on the area of the peak in the P 2p XPS spectrum.
  • the lithium phosphate content in the three-dimensional network lithium phosphate layer is 24.5%, calculated based on the area of the peak in the P 2p XPS spectrum.
  • the three-dimensional network lithium phosphate protective layer effectively protects the active material from side reactions with the electrolyte, and at the same time, the three-dimensional network structure can ensure the rapid transmission of lithium ions on the surface of the pole piece, improving the electrochemical performance of the lithium-ion battery. performance.
  • the positive electrode material of the present application is suitable for a secondary battery, which can be used as an energy storage unit of an electric device.
  • the electric devices include but are not limited to mobile digital devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the preparation method of the positive electrode material pole piece includes:
  • a mixture of nickel source, cobalt source and metal M source is provided, wherein M is at least one of Mn, Al, Ti, Zr, Mg, W and Mo, the mixture is mixed with urea and deionized water and stirred, and then Precursor obtained after hydrothermal reaction;
  • the precursor is reacted with a lithium source, and the positive electrode material is obtained after sintering, and the positive electrode material has formula I:
  • M is at least one of Mn, Al, Ti, Zr, Mg, W and Mo;
  • the positive electrode material is coated on the positive electrode current collector, and processed to obtain the positive electrode material pole piece.
  • the precursor has the general formula Ni x Co y M 1-xy CO 3 , where 0.6 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 0.2, M is Mn, Al, Ti, At least one of Zr, Mg, W and Mo.
  • the treatment step includes: dripping the phytic acid solution onto the surface of the positive electrode material pole piece drop by drop, forming a coating layer on the surface of the positive electrode material pole piece.
  • phytic acid can react with residual lithium on the surface of the pole piece to form a lithium phosphate protective layer, which can inhibit the dissolution of active materials and SEI layers; on the other hand, the highly active phosphorus hydroxyl and ester groups in phytic acid can cross-link with lithium phosphate A spatial network protective film with high crosslink density is formed, which is conducive to the transmission of lithium ions on the surface of the pole piece.
  • the ratio of the amount of the phytic acid solution to the area of the positive electrode material is 0.2mL/cm 2 -0.45mL/cm 2 .
  • the ratio of the amount of the phytic acid solution to the area of the positive electrode sheet is 0.2mL/cm 2 -0.3mL/cm 2 .
  • the ratio of the amount of the phytic acid solution to the area of the positive electrode sheet is 0.25 mL/cm 2 .
  • the use of an appropriate amount of phytic acid solution can produce a cross-linked lithium phosphate protective layer with an optimal thickness, effectively protect the active material and SEI layer on the surface of the pole piece, and at the same time ensure the rapid transmission of lithium ions on the surface of the pole piece.
  • the treatment time is 20 minutes to 45 minutes.
  • the treatment time is 20 minutes to 30 minutes.
  • the treatment time is 25 minutes.
  • the lithium phosphate layer generated on the surface will also be too thick, hindering the transmission of lithium ions on the surface of the pole piece; when the treatment time is too short, the lithium phosphate layer generated on the surface will A layer that is too thin reduces the effect of the phytic acid solution treatment. Therefore, when the phytic acid solution is treated with a suitable treatment time, a cross-linked lithium phosphate protective layer with an optimal thickness can be produced, which can effectively protect the active material and SEI layer on the surface of the pole piece, and at the same time ensure that the lithium ions remain on the surface of the pole piece. fast transfer.
  • a secondary battery in one embodiment of the present application, can be a lithium-ion secondary battery, a potassium-ion secondary battery, a sodium-ion secondary battery, a lithium-sulfur battery, etc., and is particularly preferably a lithium-ion secondary battery. ion secondary battery.
  • the secondary battery of the present application includes a positive electrode (pole sheet), a negative electrode (pole sheet), a separator, an electrolyte/liquid, and the like.
  • active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the positive electrode sheet includes a positive electrode collector and a positive electrode film layer (or called a positive electrode active material layer) disposed on at least one surface of the positive electrode collector and including a positive electrode active material.
  • the positive current collector has two opposite surfaces in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive current collector.
  • the positive current collector may be a metal foil or a composite current collector, for example, the metal foil may be an aluminum foil, and the composite current collector may include a polymer material base layer and a base layer formed on the high polymer material. A metallic layer on at least one surface of the molecular material base layer.
  • the composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene PP, polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers).
  • a metal material aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.
  • a polymer material substrate such as polypropylene PP, polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers.
  • the compaction density of the first positive electrode active material layer and the second positive electrode active material layer of the secondary battery is controlled, which can reduce the ion transmission path to improve the cycle life of the secondary battery, while not Due to the high compaction density, the particles of the active material will be broken, and the specific surface area (BET) will increase, which will lead to side reactions and deteriorate the cycle life of the secondary battery to a certain extent.
  • the compacted density of the first positive electrode active material layer and the second positive electrode active material layer may be 2.0-3.6 g/cm 3 .
  • the compacted densities of the first positive electrode active material layer and the second positive electrode active material layer may be within a numerical range formed by any two of the following numerical values as endpoints: 2.0 , 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5.
  • the compacted density of the first positive electrode active material layer and the second positive electrode active material layer may be 2.3-3.5 g/cm 3 .
  • the positive electrode active material may be a positive electrode active material known in the art for secondary batteries.
  • the positive electrode active material may include one or more of the following: olivine-structured lithium-containing phosphate, lithium transition metal oxides, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for secondary batteries can also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811)), lithium nickel cobalt aluminum oxide (such as One or more of LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and its modified compounds.
  • lithium cobalt oxides such as LiCoO 2
  • lithium nickel oxides such as Li
  • olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon One or more of composite materials, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composite materials.
  • the second positive electrode active material and the third positive electrode active material are the same or different, and are selected from lithium iron phosphate (LFP), lithium manganese oxide (LMO), nickel cobalt lithium manganese oxide (NCM), Lithium cobalt oxide (LCO), lithium nickel cobalt aluminate (NCA) and oxides containing active sodium ions, polyanionic materials or Prussian blue-like materials.
  • LFP lithium iron phosphate
  • LMO lithium manganese oxide
  • NCM nickel cobalt lithium manganese oxide
  • LCO Lithium cobalt oxide
  • NCA lithium nickel cobalt aluminate
  • oxides containing active sodium ions polyanionic materials or Prussian blue-like materials.
  • the positive electrode film layer may further optionally include a binder.
  • the non-limiting example that can be used for the binding agent of anode film layer can include following one or more: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene meta-copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the first positive electrode active material layer and/or the second positive electrode active material layer each independently contain polyvinylidene fluoride, polyacrylic acid, polytetrafluoroethylene, polyimide and binders for their combination.
  • the positive electrode film layer may further optionally contain a conductive agent.
  • the conductive agent used in the positive film layer may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the first positive electrode active material layer and/or the second positive electrode active material layer independently contain conductive materials such as graphite, carbon black, acetylene black, graphene, carbon nanotubes, and combinations of the above materials. agent.
  • the positive electrode can be prepared in the following manner: the above-mentioned components for preparing the positive electrode, such as positive electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as N- Methylpyrrolidone) to form a uniform positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N- Methylpyrrolidone
  • the secondary battery of the present application includes a negative electrode sheet, and the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer (or called a negative electrode active material layer) arranged on at least one surface of the negative electrode current collector.
  • the first negative electrode active material and the second negative electrode active material are the same or different, each independently containing natural graphite, artificial graphite, graphene, carbon nanotubes, soft carbon, hard carbon and two or more of them combination of species.
  • the compacted density of the first negative electrode active material layer and the second negative electrode active material layer may be 0.5-2.0 g/cm 3 .
  • the compacted densities of the first negative electrode active material layer and the second negative electrode active material layer may be within a numerical range formed by any two of the following numerical values as end values: 0.5 , 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0.
  • the compacted density of the first positive electrode active material layer and the second positive electrode active material layer may be 1.0-1.8 g/cm 3 .
  • the negative electrode film layer can also include a certain amount of other commonly used negative electrode active materials, such as natural graphite, other artificial graphite, soft carbon, hard carbon, One or more of silicon-based materials, tin-based materials, and lithium titanate.
  • the silicon-based material can be selected from one or more of elemental silicon, silicon oxide, and silicon-carbon composites.
  • the tin-based material may be selected from one or more of simple tin, tin oxide compounds, and tin alloys.
  • the negative electrode membrane includes negative electrode active materials, optional binders, optional conductive agents and other optional additives, and is usually formed by coating and drying negative electrode slurry.
  • the negative electrode slurry coating is usually formed by dispersing the negative electrode active material and optional conductive agent and binder in a solvent and stirring them evenly.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water.
  • the conductive agent may include one or more of superconducting carbon, carbon black (such as acetylene black, ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • carbon black such as acetylene black, ketjen black
  • carbon dots carbon nanotubes, graphene, and carbon nanofibers.
  • the binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA) , sodium alginate (SA) and carboxymethyl chitosan (CMCS) in one or more.
  • the binder may include one of styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS) or several.
  • Other optional additives are, for example, thickeners (such as sodium carboxymethylcellulose CMC-Na), PTC thermistor materials, and the like.
  • the negative electrode sheet does not exclude other additional functional layers other than the negative electrode film layer.
  • the negative electrode sheet of the present application can also include a conductive primer layer (for example, made of a conductive agent and a bonding agent composition).
  • the negative electrode sheet of the present application may also include a covering protective layer covering the surface of the second negative electrode film layer.
  • the negative electrode current collector may be a metal foil or a composite current collector, for example, the metal foil may be copper foil, silver foil, iron foil, or a foil composed of an alloy of the above metals.
  • the composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer, and can be made by adding metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) ) formed on the base layer of polymer materials (such as polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers and other materials) Formed on the base layer).
  • polymer materials such as polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers and other materials
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the electrolyte may be selected from at least one of solid electrolytes and liquid electrolytes (ie, electrolytic solutions).
  • the electrolyte is an electrolytic solution.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiAsF 6 (lithium hexafluoroarsenate), LiFSI (difluorosulfonate Lithium imide), LiTFSI (lithium bistrifluoromethanesulfonyl imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dioxalate borate), LiPO 2 F 2 One or more of (lithium difluorophosphate), LiDFOP (lithium difluorooxalatephosphate) and LiTFOP (lithium tetrafluorooxalatephosphate).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • the solvent can be selected from one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), Dimethyl Carbonate (DMC), Dipropyl Carbonate (DPC), Methyl Propyl Carbonate (MPC), Ethyl Propyl Carbonate (EPC), Butylene Carbonate (BC), Fluoroethylene Carbonate (FEC ), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and two E
  • the content of the solvent is 60-99% by weight, such as 65-95% by weight, or 70-90% by weight, or 75- 89% by weight, or 80-85% by weight. In one embodiment of the present application, based on the total weight of the electrolyte, the content of the electrolyte is 1-40% by weight, such as 5-35% by weight, or 10-30% by weight, or 11- 25% by weight, or 15-20% by weight.
  • additives may optionally be included in the electrolyte.
  • additives can include one or more of the following: negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, Additives to improve low-temperature performance of batteries, etc.
  • the secondary battery further includes a separator, which separates the anode side and the cathode side of the secondary battery, and provides selective permeation for substances of different types, sizes and charges in the system.
  • a separator which separates the anode side and the cathode side of the secondary battery, and provides selective permeation for substances of different types, sizes and charges in the system.
  • barrier for example, the separator can insulate the electrons, physically separate the positive and negative active materials of the secondary battery, prevent internal short circuit and form an electric field in a certain direction, and at the same time allow the ions in the battery to pass through the separator to the positive and negative electrodes to move between.
  • the material used to prepare the isolation film may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film.
  • the materials of each layer may be the same or different.
  • the isolation film is selected from polyolefin isolation films, polyester isolation films, polyimide isolation films, polyamide isolation films and cellulose isolation films.
  • the above-mentioned positive pole piece, negative pole piece and separator can be made into an electrode assembly/bare cell through a winding process or a lamination process.
  • the secondary battery may include an outer package for encapsulating the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • the outer package of the secondary battery may be a soft bag, such as a pouch-type soft bag.
  • the material of the soft bag can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS) and the like.
  • FIG. 3 shows a secondary battery 5 having a square structure as an example.
  • FIG. 4 shows an exploded view of the secondary battery 5 of FIG. 3, the outer package may include a housing 51 and a cover plate 53, the housing 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and the side plates Enclosed to form an accommodation chamber.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece and the separator can form the electrode assembly 52 through a winding process or a lamination process.
  • the number of electrode assemblies 52 included in the secondary battery 5 may be one or more.
  • FIG. 5 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a case having an accommodation space in which a plurality of secondary batteries 5 are accommodated.
  • two or more of the above-mentioned battery modules can be assembled into a battery pack, and the number of battery modules contained in the battery pack depends on the application of the battery pack and the parameters of a single battery module.
  • the battery pack can include a battery box and a plurality of battery modules arranged in the battery box.
  • the battery box includes an upper box and a lower box.
  • the upper box can be covered on the lower box and well matched with it to form a battery for accommodating The enclosed space of the module.
  • Two or more battery modules can be arranged in the battery box in a desired manner.
  • the electric device of the present application includes at least one of the secondary battery, battery module, or battery pack of the present application, and the secondary battery, battery module, or battery pack can be used as The power source of the electrical device may also be used as an energy storage unit of the electrical device.
  • the electric devices include but are not limited to mobile digital devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • Figure 8 is an example device.
  • the device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • battery packs or battery modules can be employed.
  • a device may be a cell phone, tablet, laptop, or the like.
  • the device is generally required to be light and thin, and a secondary battery can be used as a power source.
  • the raw materials used in the present invention are analytically pure, and the water is deionized water.
  • a certain volume of phytic acid solution (25 mg of phytic acid powder dissolved in 100 mL of dimethyl sulfoxide) was dropped dropwise on the surface of the positive electrode sheet prepared above, and then left to stand for 25 minutes to dry the electrode sheet.
  • the ratio of the amount of the acid solution to the area of the pole piece is 0.25mL/cm 2 .
  • the high-nickel ternary positive pole piece was prepared as described in Example 1 and the surface of the pole piece was treated.
  • the high-nickel ternary positive pole piece was prepared as described in Example 1 and the surface of the pole piece was treated.
  • a high-nickel ternary positive electrode sheet was prepared as described in Example 1, but without phytic acid treatment.
  • the high-nickel ternary positive pole piece was prepared as described in Example 1 and the surface of the pole piece was treated.
  • the high-nickel ternary positive pole piece was prepared as described in Example 1 and the surface of the pole piece was treated.
  • the high-nickel ternary positive electrode prepared and processed in the above-mentioned Examples 1-5 and Comparative Examples 1-5, as well as the artificial graphite negative electrode and separator were assembled into a battery cell and injected with liquid (electrolyte) to obtain a lithium-ion battery product.
  • the surface of the high-nickel ternary positive electrode sheet in Example 1 is treated with phytic acid to form a three-dimensional network cross-linked layer, and the element scanning results in (B) also prove that the surface is cross-linked Effective doping of phosphorus in the layer.
  • the thickness of the surface crosslinked layer is about 12.6nm, and the high-resolution spectrum analysis results show that the interplanar spacing of the surface corresponds to that of phosphoric acid.
  • the (460) crystal face of lithium proves that the phytic acid treatment makes a lithium phosphate three-dimensional cross-linked layer with a thickness of about 12.6nm formed on the surface of the high-nickel ternary pole piece.
  • the XPS spectrogram peak of P 2p mainly corresponds to lithium phosphate among the embodiment 1, simultaneously by comparing the change of peak area, can draw the content of lithium phosphate layer in different embodiments and comparative examples.
  • Table 2 shows the first cycle coulombic efficiency data and battery capacity retention data corresponding to all the examples and comparative examples (the data measured after 200 cycles under the above test conditions, ie the value of P200).
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请涉及正极材料极片、制备方法、二次电池、电池模组、电池包及用电装置。所述正极材料极片包括：极片基体和在所述极片基体表面设置的包覆层，其中，所述极片基体包括具有式I的化合物：LiNi xCo yM 1-x-yO 2(式I)，式中，0.6≤x＜1，0≤y≤0.2，M为Mn、Al、Ti、Zr、Mg、W和Mo中的至少一种；所述包覆层为厚度在12nm～13nm的三维网络状磷酸锂层，其中磷酸锂含量为20％～30％。本申请的正极材料极片表面形成了三维网络状磷酸锂保护层，有效地保护活性材料不和电解液发生副反应，同时三维网络结构可以保障锂离子在极片表面进行快速传输，提高锂离子电池的电化学性能。

Description

正极材料极片、制备方法、二次电池、电池模组、电池包及用电装置
相关申请的交叉引用
本申请要求享有于2021年11月2日提交的名称为“正极材料极片、制备方法、二次电池、电池模组、电池包及用电装置”的中国专利申请202111290738.2的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请属于锂离子电池领域，涉及一种正极材料极片，具体涉及一种高镍三元正极材料片，其制备方法，以及包含该正极材料极片的二次电池、包含该二次电池的电池模组、电池包及用电装置。
背景技术
随着新能源汽车及储能业务发展，市场对锂离子电池的电化学性能的要求越来越高。锂离子电池主要采用高镍三元正极材料极片。但是，高镍三元正极材料极片表面残锂过多，导致极片副反应增多，阻抗变大，同时充放电过程中电解液中的水和氢氟酸会分解极片表面的固体电解质界面(SEI)膜，造成活性材料流失，导致电芯的循环性能下降。因此，需要对正极材料极片进行处理来提高电池的电化学性能。
目前，通过用无机磷酸处理电池正极材料片来提高电池的电化学性能。但是，无机磷酸活性弱而且形成不了连续结构，无法保证极片保护层的连续性和稳固性，并且处理过程需要高温加热。
因此，本领域亟需克服了上述现有技术缺陷的，对正极极片处理以提高电池电化学性能的改进方法。
发明内容
为了解决现有技术中存在的问题，本申请通过采用特定含量的植酸溶液来处理正极材料极片，提高了锂离子电池的电化学性能。
根据本申请的第一方面，提供一种正极材料极片，所述正极材料极片包括：
极片基体和在所述极片基体表面设置的包覆层，
其中，所述包覆层为厚度在10nm～20nm的三维网络状磷酸锂层，其中磷酸锂含量为20％～30％。
可选地，所述极片基体包括具有式I的化合物：
LiNi xCo yM 1-x-yO 2  式I
式中，0.6≤x＜1，0≤y≤0.2，M为Mn、Al、Ti、Zr、Mg、W和Mo中的至少一种。
可选地，所述包覆层为厚度在12nm～13nm的三维网络状磷酸锂层。
可选地，所述包覆层为厚度在12.4nm～12.8nm的三维网络状磷酸锂层。可选地，所述磷酸锂含量为22％～26％。
在本申请中，正极材料极片表面形成了三维网络状磷酸锂保护层，有效地保护活性材料不和电解液发生副反应，同时三维网络结构可以保障锂离子在极片表面进行快速传输，提高锂离子电池的电化学性能。
根据本申请的第二方面，提供一种正极材料极片的制备方法，该方法包括：
提供镍源、钴源与金属M源的混合物，其中M为Mn、Al、Ti、Zr、Mg、W和Mo中的至少一种，将所述混合物与尿素和去离子水混合后搅拌，再水热反应后得到前驱体；
将所述前驱体与锂源反应，烧结后得到正极材料，所述正极材料具有式I：
LiNi xCo yM 1-x-yO 2  式I
式中，0.6≤x＜1，0≤y≤0.2，M为Mn、Al、Ti、Zr、Mg、W和Mo中的至少一种；
将所述正极材料涂覆在正极集流体上，经处理，得到正极材料极片。可选地，所述处理步骤包括：
将植酸溶液逐滴滴到所述正极材料极片的表面，在所述正极材料极片的表面形成包覆层，所述包覆层为厚度在12nm～13nm的三维网络状磷酸锂层，其中磷酸锂含量为20％～30％；
其中，植酸溶液的用量与正极材料极片的面积比为0.2mL/cm 2～0.45mL/cm 2。
在本申请中，使用植酸溶液进行处理，一方面植酸可以与极片表面残余锂反应生成磷酸锂保护层，抑制活性材料及SEI层的溶解，另一方面植酸中高活性的磷羟基和酯基可与磷酸锂交联形成高交联密度的空间网状保护膜，有利于锂离子在 极片表面的传输。
在本申请的实施方式中，植酸溶液的用量与正极材料极片的面积比为0.2mL/cm 2～0.3mL/cm 2。可选地，植酸溶液的用量与正极材料极片的面积比为0.25mL/cm 2。
在本申请中，合适量植酸溶液的使用可以产生最佳厚度的交联网状磷酸锂保护层，有效地保护极片表面的活性物质及SEI层，同时也会保障锂离子在极片表面的快速传输。
在本申请的实施方式中，正极材料极片表面的处理时间为20分钟～45分钟。可选地，正极材料极片表面的处理时间为20分钟～30分钟。可选地，正极材料极片表面的处理时间为25分钟。
在本申请中，植酸溶液处理时采用合适的处理时间，可以产生最佳厚度的交联网状磷酸锂保护层，有效地保护极片表面的活性物质及SEI层，同时也会保障锂离子在极片表面的快速传输。
根据本申请的第三方面，提供一种二次电池，其包括上述正极材料极片。
根据本申请的第四方面，提供一种电池模组，其包括上述二次电池。
根据本申请的第五方面，提供一种电池包，其包括上述二次电池或电池模组。
根据本申请的第六方面，提供一种用电装置，其包括上述二次电池、或上述电池模组、或上述电池包，所述二次电池或所述电池模组或所述电池包用作所述用电装置的电源或所述用电装置的能量存储单元。
与现有技术相比，通过采用特定含量的植酸溶液来处理正极材料极片，在正极材料极片表面形成了三维网络状磷酸锂保护层，有效地保护活性材料不和电解液发生副反应，同时三维网络结构可以保障锂离子在极片表面进行快速传输，提高锂离子电池的电化学性能。
通过阅读下面的详细描述并参考相关联的附图，这些及其他特点和优点将变得显而易见。应该理解，前面的概括说明和下面的详细描述只是说明性的，不会对所要求保护的各方面形成限制。
附图说明
图1示出了本申请实施例1的阴极极片的扫描电子显微镜(SEM)图(A)，磷 元素扫描图(B)和高分辨率谱图(C和D)。
图2是本申请实施例1的阴极极片的磷2p X射线光电子能谱(P 2p XPS)图。
图3是本申请二次电池的一实施方式的示意图。
图4是图3所示二次电池的分解图。
图5是本申请电池模块的一实施方式的示意图。
图6是本申请电池包的一实施方式的示意图。
图7是图6所示电池包的分解图。
图8是使用本申请的二次电池用作电源的装置的一实施方式的示意图。
附图标记说明：
1、电池包
2、上箱体
3、下箱体
4、电池模块
5、二次电池
51、壳体
52、电极组件
53、盖板
具体实施方式
下面结合附图详细描述本申请，本申请的特点将在以下的具体描述中得到进一步的显现。
本文所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表 述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
在本申请中，如果没有特别的说明，本文所提到的所有实施方式以及优选实施方式可以相互组合形成新的技术方案。在本申请中，如果没有特别的说明，本文所提到的所有技术特征以及优选特征可以相互组合形成新的技术方案。
在本申请中，如果没有特别的说明，本文所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
在本文的描述中，除非另有说明，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
现有的高镍三元正极材料极片表面残锂过多，导致极片副反应增多，阻抗变大，同时充放电过程中电解液中的水和氢氟酸会分解极片表面的固体电解质界面膜，造成活性材料流失，导致电芯的循环性能下降。目前，通过用无机磷酸处理电池正极材料片来提高电池的电化学性能。但是，无机磷酸活性弱而且形成不了连续结构，无法保证极片保护层的连续性和稳固性，并且处理过程需要高温加热。
为了解决现有技术中用无机磷酸处理高镍三元正极材料极片存在的上述缺陷，本申请选取植酸溶液处理高镍三元材料极片，一方面植酸可以与极片表面残余锂反应生成磷酸锂保护层，抑制活性材料及SEI层的溶解，另一方面植酸中高活性的磷羟基和酯基可与磷酸锂交联形成高交联密度的空间网状保护膜，有利于锂离子在极片表面的传输。
本申请制备得到的表面修饰后的高镍三元材料极片，其表面形成了三维网络状磷酸锂保护层，有效地保护活性材料不和电解液发生副反应，同时三维网络结构可以保障锂离子在极片表面进行快速传输，提高锂离子电池的电化学性能。
植酸，又名肌醇六磷酸、环己六醇六磷酸，其分子式为C 6H 18O 24P 6，是从植物种籽中提取的一种有机磷类化合物。在本申请中，使用的植酸溶液是将25mg植酸粉末溶解在100mL二甲基亚砜中制得的溶液。
在本申请中，三维网络状磷酸锂层的厚度为10nm～20nm，其中磷酸锂含量为20％～30％，基于P 2p XPS谱图中峰的面积计算得到。图1中(A)和(B)示出了， 本申请中高镍三元正极极片经过植酸处理后表面生成三维网络交联层，证明了表面交联层中磷元素的有效掺杂。图1中(C)和(D)示出了，本申请中的极片经过处理后可以看到表面交联层厚度约12.6nm，同时高分辨谱图分析结果显示表面的晶面间距对应磷酸锂的(460)晶面，证明植酸处理使高镍三元极片表面生成厚度约12.6nm的磷酸锂三维交联层。图2中示出了，本申请中P 2p的XPS谱图峰主要对应磷酸锂，同时通过对比峰面积的变化，可以得出不同实施例和对比例中磷酸锂层的含量。
正极材料极片
在本申请中，正极材料包括高镍三元材料。正极材料极片包括极片基体和在所述极片基体表面设置的包覆层。所述极片基体包括具有式I的化合物：
LiNi xCo yM 1-x-yO 2  式I
式中，0.6≤x＜1，0≤y≤0.2，M为Mn、Al、Ti、Zr、Mg、W和Mo中的至少一种。所述包覆层为三维网络状磷酸锂层。
在本申请中，所述三维网络状磷酸锂层的厚度为10nm～20nm。可选地，所述三维网络状磷酸锂层的厚度为12nm～13nm。可选地，所述三维网络状磷酸锂层的厚度为12.4nm～12.8nm。可选地，所述三维网络状磷酸锂层的厚度为12.6nm。
在本申请中，所述三维网络状磷酸锂层中磷酸锂含量为20％～30％，基于P 2p XPS谱图中峰的面积计算得到。可选地，所述三维网络状磷酸锂层中磷酸锂含量为22％～26％，基于P 2p XPS谱图中峰的面积计算得到。可选地，所述三维网络状磷酸锂层中磷酸锂含量为24.5％，基于P 2p XPS谱图中峰的面积计算得到。
在本申请中，所述三维网络状磷酸锂保护层有效地保护活性材料不和电解液发生副反应，同时三维网络结构可以保障锂离子在极片表面进行快速传输，提高锂离子电池的电化学性能。
本申请的正极材料适用于二次电池，该二次电池可以用作用电装置的能量存储单元。所述用电装置包括但不限于移动数字装置(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
正极材料极片的制备方法
在本申请中，正极材料极片的制备方法包括：
提供镍源、钴源与金属M源的混合物，其中M为Mn、Al、Ti、Zr、Mg、W和Mo中的至少一种，将所述混合物与尿素和去离子水混合后搅拌，再水热反应后得到前驱体；
将所述前驱体与锂源反应，烧结后得到正极材料，所述正极材料具有式I：
LiNi xCo yM 1-x-yO 2  式I
式中，0.6≤x＜1，0≤y≤0.2，M为Mn、Al、Ti、Zr、Mg、W和Mo中的至少一种；
将所述正极材料涂覆在正极集流体上，经处理，得到正极材料极片。
在本申请的一个实施方式中，所述前驱体具有通式Ni xCo yM 1-x-yCO 3，式中，0.6≤x＜1，0≤y≤0.2，M为Mn、Al、Ti、Zr、Mg、W和Mo中的至少一种。
在本申请中，所述处理步骤包括：将植酸溶液逐滴滴到所述正极材料极片的表面，在所述正极材料极片的表面形成包覆层。
在本申请中，植酸可以与极片表面残余锂反应生成磷酸锂保护层，抑制活性材料及SEI层的溶解；另一方面，植酸中高活性的磷羟基和酯基可与磷酸锂交联形成高交联密度的空间网状保护膜，有利于锂离子在极片表面的传输。
在本申请中，植酸溶液的用量与正极材料极片的面积比为0.2mL/cm 2～0.45mL/cm 2。可选地，植酸溶液的用量与正极材料极片的面积比为0.2mL/cm 2～0.3mL/cm 2。可选地，植酸溶液的用量与正极材料极片的面积比为0.25mL/cm 2。
在本申请中，当植酸溶液用量过多时，极片表面生成的磷酸锂层太厚，阻碍锂离子在极片表面的传输；当植酸溶液用量过少时，极片表面生成的磷酸锂层太薄，造成植酸溶液处理效果降低。因此，合适量植酸溶液的使用可以产生最佳厚度的交联网状磷酸锂保护层，有效地保护极片表面的活性物质及SEI层，同时也会保障锂离子在极片表面的快速传输。
在本申请中，处理时间为20分钟～45分钟。可选地，处理时间为20分钟～30分钟。可选地，处理时间为25分钟。
在本申请中，当使用植酸处理的时间过长时，也会导致表面生成的磷酸锂层太厚，阻碍锂离子在极片表面的传输；当处理时间过短时，表面生成的磷酸锂层太薄，降低植酸溶液处理的效果。因此，植酸溶液处理时采用合适的处理时间，可以产生最佳厚度的交联网状磷酸锂保护层，有效地保护极片表面的活性物质及SEI层，同时也会保 障锂离子在极片表面的快速传输。
二次电池
在本申请的一个实施方式中，提供了一种二次电池，该二次电池可以是锂离子二次电池、钾离子二次电池、钠离子二次电池、锂硫电池等，特别优选是锂离子二次电池。本申请的二次电池包括正极(极片)、负极(极片)、隔离膜、电解质/液等。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。
[正极极片]
本申请的二次电池中，正极极片包括正极集流体以及设置在正极集流体至少一个表面且包括正极活性材料的正极膜层(或称为正极活性物质层)。例如，正极集流体具有在自身厚度方向相背的两个表面，正极膜层设置于正极集流体的两个相背表面中的任意一者或两者上。本申请的二次电池中，所述正极集流体可以是金属箔片或复合集流体，例如所述金属箔片可以是铝箔，而所述复合集流体可包括高分子材料基层和形成于该高分子材料基层至少一个表面上的金属层。所述复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯PP、聚对苯二甲酸乙二醇酯PET、聚对苯二甲酸丁二醇酯PBT、聚苯乙烯PS、聚乙烯PE及其共聚物等的基材)上而形成。
在本申请中，所述二次电池的第一正极活性物质层和第二正极活性物质层的压实密度进行控制，可以减小离子传输路径，以提高二次电池的循环寿命，同时又不会因为压实密度过高而导致活性物质的颗粒破碎，出现比表面积(BET)增大的情况，导致出线副反应而在一定程度上恶化二次电池的循环寿命。通常，第一正极活性物质层和第二正极活性物质层的压实密度可以为2.0-3.6g/cm 3。在本申请的一个实施方式中，所述第一正极活性物质层和第二正极活性物质层的压实密度可以在以下所列数值中任意两个作为端值而构成的数值范围之内：2.0、2.1、2.2、2.3、2.4、2.5、2.6、2.7、2.8、2.9、3.0、3.1、3.2、3.3、3.4、3.5。在本申请可选的实施方式中，所述第一正极活性物质层和第二正极活性物质层的压实密度可以为2.3-3.5g/cm 3。
在本申请的二次电池中，所述正极活性材料(物质)可采用本领域公知的用于二次电池的正极活性材料。例如，该正极活性材料可包括以下的一种或多种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些 材料，还可以使用其他可被用作二次电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(NCM523)、LiNi 0.5Co 0.25Mn 0.25O 2(NCM211)、LiNi 0.6Co 0.2Mn 0.2O 2(NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(NCM811))、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的一种或几种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的一种或几种。在本申请的实施方式中，所述第二正极活性物质和第三正极活性物质相同或不同，选自磷酸铁锂(LFP)、锰酸锂(LMO)、镍钴锰酸锂(NCM)、钴酸锂(LCO)、镍钴铝酸锂(NCA)以及包含活性钠离子的氧化物、聚阴离子材料或普鲁士蓝类材料。
在一些实施方式中，正极膜层还可选地包括粘结剂。可用于正极膜层的粘结剂的非限制性例子可以包括以下的一种或多种：聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂。在本申请的实施方式中，所述第一正极活性物质层和/或第二正极活性物质层中各自独立的含有选自聚偏氟乙烯、聚丙烯酸、聚四氟乙烯、聚酰亚胺和它们组合的粘结剂。
在一些实施方式中，正极膜层还可任选地包含导电剂。用于正极膜层的导电剂的例子可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种或几种。在本申请的实施方式中，所述第一正极活性物质层和/或第二正极活性物质层中各自独立的含有石墨、炭黑、乙炔黑、石墨烯、碳纳米管和上述物质组合的导电剂。
在本申请的一个实施方式中，可以通过以下方式制备正极：将上述用于制备正极的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成均匀的正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
本申请的二次电池中包括负极极片，所述负极极片包括负极集流体以及设置在所 述负极集流体至少一个表面上的负极膜层(或称为负极活性物质层)，在本申请的实施方式中，所述第一负极活性物质和第二负极活性物质相同或不同，各自独立地含有天然石墨、人造石墨、石墨烯、碳纳米管、软碳、硬碳和它们两种或多种的组合。
在本申请的实施方式中，所述第一负极活性物质层和第二负极活性物质层的压实密度可以为0.5-2.0g/cm 3。在本申请的一个实施方式中，所述第一负极活性物质层和第二负极活性物质层的压实密度可以在以下所列数值中任意两个作为端值而构成的数值范围之内：0.5、0.6、0.7、0.8、0.9、1.0、1.1、1.2、1.3、1.4、1.5、1.6、1.7、1.8、1.9、2.0。在本申请可选的实施方式中，所述第一正极活性物质层和第二正极活性物质层的压实密度可以为1.0-1.8g/cm 3。
在本申请的一个实施方式中，负极膜层除了包括本申请上述的负极活性材料外，还可以包括一定量的其它常用负极活性材料，例如，天然石墨、其它人造石墨、软炭、硬炭、硅基材料、锡基材料、钛酸锂中的一种或几种。所述硅基材料可选自单质硅、硅氧化物、硅碳复合物中的一种或几种。所述锡基材料可选自单质锡、锡氧化合物、锡合金中的一种或几种。
本申请的二次电池中，所述负极膜片包含负极活性材料以及可选的粘结剂、可选的导电剂和其他可选助剂，通常是由负极浆料涂布干燥而成的。负极浆料涂通常是将负极活性材料以及可选的导电剂和粘结剂等分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水。
作为示例，导电剂可包括超导碳、炭黑(例如乙炔黑、科琴黑)、碳点、碳纳米管、石墨烯及碳纳米纤维中一种或几种。
作为示例，粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)和羧甲基壳聚糖(CMCS)中的一种或几种。作为示例，粘结剂可包括丁苯橡胶(SBR)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的一种或几种。其他可选助剂例如是增稠剂(如羧甲基纤维素钠CMC-Na)、PTC热敏电阻材料等。
另外，本申请的二次电池中，负极极片并不排除除了负极膜层之外的其他附加功能层。例如在某些实施方式中，本申请的负极极片还可包括夹在负极集流体和第一负极膜层之间、设置于负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施方式中，本申请的负极极片还可包括覆盖在第二负极膜层表面的覆盖 保护层。
本申请的二次电池中，所述负极集流体可以是金属箔片或复合集流体，例如金属箔片可以是铜箔、银箔、铁箔、或者上述金属的合金构成的箔片。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层，可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基层(如聚丙烯PP、聚对苯二甲酸乙二醇酯PET、聚对苯二甲酸丁二醇酯PBT、聚苯乙烯PS、聚乙烯PE及其共聚物等材料制成的基层)上而形成。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。电解质可以选自固态电解质及液态电解质(即电解液)中的至少一种。在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。在一些实施方式中，电解质盐可选自LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、LiAsF 6(六氟砷酸锂)、LiFSI(双氟磺酰亚胺锂)、LiTFSI(双三氟甲磺酰亚胺锂)、LiTFS(三氟甲磺酸锂)、LiDFOB(二氟草酸硼酸锂)、LiBOB(二草酸硼酸锂)、LiPO 2F 2(二氟磷酸锂)、LiDFOP(二氟二草酸磷酸锂)及LiTFOP(四氟草酸磷酸锂)中的一种或几种。在本申请的一个实施方式中，溶剂可选自以下的一种或多种：碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)。在本申请的一个实施方式中，以所述电解液的总重量为基准计，所述溶剂的含量为60-99重量％，例如65-95重量％，或者70-90重量％，或者75-89重量％，或者80-85重量％。在本申请的一个实施方式中，以所述电解液的总重量为基准计，所述电解质的含量为1-40重量％，例如5-35重量％，或者10-30重量％，或者11-25重量％，或者15-20重量％。
在本申请的一个实施方式中，所述电解液中还可任选地包含添加剂。例如添加剂可以包括以下的一种或多种：负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温性能的添加剂等。
[隔离膜]
在本申请的一个实施方式中，所述二次电池还包括隔离膜，隔离膜将二次电池的阳极侧与阴极侧隔开，对体系内不同种类、尺寸和电荷的物质提供选择性透过或阻隔，例如隔离膜可以对电子绝缘，将二次电池的正负极活性物质物理隔离，防止内部发生短路并形成一定方向的电场，同时使得电池中的离子能够穿过隔离膜在正负极之间移动。在本申请的一个实施方式中，用来制备隔离膜的材料可包括玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或几种。隔离膜可以是单层薄膜，也可以是多层复合薄膜。隔离膜为多层复合薄膜时，各层的材料可以相同或不同。在本申请的实施方式中，所述隔离膜选自聚烯烃类隔离膜、聚酯隔离膜、聚酰亚胺隔离膜、聚酰胺隔离膜和纤维素隔离膜。
在本申请的一个实施方式中，上述正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件/裸电芯。在本申请的一个实施方式中，二次电池可包括外包装，该外包装可用于封装上述电极组件及电解质。在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。在另一些实施方式中，所述二次电池的外包装可以是软包，例如袋式软包。软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或几种。
本申请二次电池的形状可以是圆柱形、方形或其他任意的形状。图3是作为一个示例的方形结构的二次电池5。图4显示了图3的二次电池5的分解图，所述外包装可包括壳体51和盖板53，壳体51可包括底板和连接于底板上的侧板，所述底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52，该电极组件封装于所述容纳腔中，所述电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个。
在本申请的一个实施方式中，可以将若干个二次电池组装在一起以构成电池模块，电池模块中包含两个或更多个二次电池，具体数量取决于电池模块的应用和单个电池模块的参数。
图5是作为一个示例的电池模块4。参照图5，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该 容纳空间。
在本申请的一个实施方式中，可以将两个或更多个上述电池模块组装成电池包，电池包所含电池模块的数量取决于电池包的应用和单个电池模块的参数。电池包可以包括电池箱和设置于电池箱中的多个电池模块，该电池箱包括上箱体和下箱体，上箱体能够盖在下箱体上并与之良好匹配，形成用于容纳电池模块的封闭空间。两个或更多个电池模块可以按照所需的方式排布于该电池箱中。
图6和图7是作为一个示例的电池包1。参照图6和图7，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2用于盖设下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
用电装置
在本申请的一个实施方式中，本申请的用电装置包括本申请的二次电池、电池模块、或电池包中的至少一种，所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置包括但不限于移动数字装置(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
图8是作为一个示例的装置。该装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该装置对高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
在下文中，基于具体的实施例表征了按照本申请实施方式制造的二次电池对电化学装置性能的影响，但是需要特别指出的是，本申请的保护范围由权利要求书限定，而不仅限于以上的具体实施方式。
实施例
除非另外说明本发明使用的原料均为分析纯，水均为去离子水。
实施例1
高镍三元正极极片的制备
将高镍三元材料(LiNi 0.6Co 0.2Mn 0.2O 2)、导电碳黑和粘结剂聚偏二氟乙烯(PVDF)按重量比为95.0：2.3：2.7在N-甲基吡咯烷酮中搅拌混合均匀，得到正极浆料；然后将得到的正极浆料均匀涂覆于正极集流体(铝箔)上，之后经过烘干、冷压、分切(即对极片进行裁减、切割成所需要大小的尺寸)，得到正极极片。
极片表面处理
将一定体积的植酸溶液(25mg植酸粉末溶解在100mL二甲基亚砜中制得)逐滴滴到上述制备的正极极片表面，然后静置25分钟后烘干极片，其中，植酸溶液的用量与极片面积比为0.25mL/cm 2。
实施例2
除了植酸溶液的用量与极片面积比为0.35mL/cm 2，按照实施例1所述制备高镍三元正极极片并处理极片表面。
实施例3
除了植酸溶液的用量与极片面积比为0.45mL/cm 2，按照实施例1所述制备高镍三元正极极片并处理极片表面。
实施例4
除了静置时间为35分钟，按照实施例1所述制备高镍三元正极极片并处理极片表面。
实施例5
除了静置时间为45分钟，按照实施例1所述制备高镍三元正极极片并处理极片表面。
对比例1
按照实施例1所述制备高镍三元正极极片，但是未经植酸处理。
对比例2
除了植酸溶液的用量与极片面积比为0.05mL/cm 2，按照实施例1所述制备高镍三元正极极片并处理极片表面。
对比例3
除了植酸溶液的用量与极片面积比为0.15mL/cm 2，按照实施例1所述制备高镍三元正极极片并处理极片表面。
对比例4
除了静置时间为5分钟，按照实施例1所述制备高镍三元正极极片并处理极片表面。
对比例5
除了静置时间为15分钟，按照实施例1所述制备高镍三元正极极片并处理极片表面。
锂离子电池的制备
将上述实施例1-5和对比例1-5中制备和处理得到的高镍三元正极，以及人造石墨负极和隔离膜组装成电芯并注液(电解液)，获得锂离子电池产品。
高镍三元正极极片相关参数测试
1.极片表面形貌测试
将所有实施例和对比例的正极极片用ZEISS sigma 300扫描电子显微镜(SEM)(德国卡尔蔡司)参照标准JY/T010-1996进行测试，测试内容包括极片表面，并对表面做磷元素面扫描分析。结果示于图1中(A)和(B)。
如图1中(A)和(B)所示，实施例1中高镍三元正极极片经过植酸处理后表面生成三维网络交联层，(B)中的元素扫描结果也证明表面交联层中磷元素的有效掺杂。
2.磷酸锂层厚度测试
对所有实施例和对比例正极极片用Tecnai F30型号场发射透射电子显微镜(TEM)(荷兰Philips-FEI公司)进行高分辨测试，确定其高镍三元基体和磷酸锂包覆层的结构及厚度。结果示于图1中(C)和(D)以及下表1。
如图1中(C)和(D)所示，实施例1的极片经过处理后可以看到表面交联层厚度约12.6nm，同时高分辨谱图分析结果显示表面的晶面间距对应磷酸锂的(460)晶面，证明植酸处理使高镍三元极片表面生成厚度约12.6nm的磷酸锂三维交联层。
3.磷酸锂含量计算
对所有实施例和对比例正极极片用Thermo Scientific ESCALAB 250Xi型号X射线光电子能谱仪(XPS)(美国赛默飞)进行测试，通过对比P 2p的谱图来评估所有实施例和对比例中磷酸锂的含量。结果示于图2以及下表1。
如图2所示，实施例1中P 2p的XPS谱图峰主要对应磷酸锂，同时通过对比峰面积的变化，可以得出不同实施例和对比例中磷酸锂层的含量。
表1
Figure PCTCN2022125637-appb-000001
从上表1可以看出，在本申请中，当植酸处理用量与正极材料极片的面积比为0.25mL/cm 2～0.45mL/cm 2，且正极材料极片表面的处理时间为25分钟～45分钟时，可以获得所需的磷酸锂层厚度(12.0nm～12.6nm)和磷酸锂含量(21.9％～24.5％)，其中，当植酸处理用量与正极材料极片的面积比为0.25mL/cm 2，且正极材料极片表面的处理时间为25分钟时，可以获得最佳磷酸锂层厚度(12.6nm)和磷酸锂含量(24.5％)。
电池性能测试
1.电池首圈库伦效率测试及计算
在25℃下，得到的电池以1/3C恒流充电至4.2V，再以4.2V恒定电压充电至电流为0.05C，所得充电容量记为首圈充电容量C1，搁置5min，再以1/3C放电至2.8V，所得放电容量记为首圈放电容量D1，则首圈库伦效率E1＝D1/C1*100％。
2.电池容量保持率测试
在25℃下，将实施例1对应的电池，以1/3C恒流充电至4.2V，再以4.2V恒定电压充电至电流为0.05C，搁置5min，再以1/3C放电至2.8V，所得容量记为初始容量C0。对上述同一个电池重复以上步骤，并同时记录循环第n次后电池的放电容量Cn，则每次循环后电池容量保持率Pn＝Cn/C0*100％。
该测试过程中，第一次循环对应n＝1、第二次循环对应n＝2、……第200次循环对应n＝200。
下表2中示出了所有实施例和对比例对应的电池首圈库伦效率数据和电池容量保持率数据(在上述测试条件下循环200次之后测得的数据，即P200的值)。
表2
Figure PCTCN2022125637-appb-000002
从上表2可以看出，在本申请中，当植酸处理用量与正极材料极片的面积比为0.25mL/cm 2～0.45mL/cm 2，且正极材料极片表面的处理时间为25分钟～45分钟时，可以获得所需的首圈库伦效率(87.5％～88.4％)和200圈容量保持率(85.8％～86.9％)，其中，当植酸处理用量与正极材料极片的面积比为0.25mL/cm 2，且正极材料极片表面的处理时间为25分钟时，可以获得最佳首圈库伦效率(88.4％)和200圈容量保持率(86.9％)。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (16)

  1. 一种正极材料极片，其特征在于，所述正极材料极片包括：
    极片基体和在所述极片基体表面设置的包覆层，
    其中，所述包覆层为厚度在10nm～20nm的三维网络状磷酸锂层，其中磷酸锂含量为20％～30％。
  2. 根据权利要求1所述的正极材料极片，其特征在于，所述包覆层为厚度在12nm～13nm的三维网络状磷酸锂层。
  3. 根据权利要求1所述的正极材料极片，其特征在于，所述包覆层为厚度在12.4nm～12.8nm的三维网络状磷酸锂层。
  4. 根据权利要求1～3任一项所述的正极材料极片，其特征在于，所述磷酸锂含量为22％～26％。
  5. 根据权利要求1～4任一项所述的正极材料极片，其特征在于，所述极片基体包括具有式I的化合物：
    LiNi xCo yM 1-x-yO 2  式I
    式中，0.6≤x＜1，0≤y≤0.2，M为Mn、Al、Ti、Zr、Mg、W和Mo中的至少一种。
  6. 一种正极材料极片的制备方法，该方法包括：
    提供镍源、钴源与金属M源的混合物，其中M为Mn、Al、Ti、Zr、Mg、W和Mo中的至少一种，将所述混合物与尿素和去离子水混合后搅拌，再水热反应后得到前驱体；
    将所述前驱体与锂源反应，烧结后得到正极材料，所述正极材料具有式I：
    LiNi xCo yM 1-x-yO 2  式I
    式中，0.6≤x＜1，0≤y≤0.2，M为Mn、Al、Ti、Zr、Mg、W和Mo中的至少一种；
    将所述正极材料涂覆在正极集流体上，经处理，得到正极材料极片。
  7. 根据权利要求6所述的方法，其特征在于，所述处理步骤包括：
    将植酸溶液逐滴滴到所述正极材料极片的表面，在所述正极材料极片的表面形成包覆层，所述包覆层为厚度在12nm～13nm的三维网络状磷酸锂层，其中磷酸锂含量为20％～30％；
    其中，植酸溶液的用量与正极材料极片的面积比为0.2mL/cm 2～0.45mL/cm 2。
  8. 根据权利要求7所述的方法，其特征在于，植酸溶液的用量与正极材料极片的面积比为0.2mL/cm 2～0.3mL/cm 2。
  9. 根据权利要求8所述的方法，其特征在于，植酸溶液的用量与正极材料极片的面积比为0.25mL/cm 2。
  10. 根据权利要求7-9中任一项所述的方法，其特征在于，正极材料极片表面的处理时间为20分钟～45分钟。
  11. 根据权利要求10所述的方法，其特征在于，正极材料极片表面的处理时间为20分钟～30分钟。
  12. 根据权利要求11所述的方法，其特征在于，正极材料极片表面的处理时间为25分钟。
  13. 一种二次电池，其特征在于，包括根据权利要求1-5中任一项所述的正极材料极片。
  14. 一种电池模组，其特征在于，包括根据权利要求13所述的二次电池。
  15. 一种电池包，其特征在于，包括根据权利要求13所述的二次电池或根据权利要求14所述的电池模组。
  16. 一种用电装置，其特征在于，包括根据权利要求13所述的二次电池、或根据权利要求14所述的电池模组、或根据权利要求15所述的电池包，所述二次电池或所述电池模组或所述电池包用作所述用电装置的电源或所述用电装置的能量存储单元。
PCT/CN2022/125637 2021-11-02 2022-10-17 正极材料极片、制备方法、二次电池、电池模组、电池包及用电装置 WO2023078071A1 (zh)

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