WO2022198654A1 - 一种正极补锂材料、包含该材料的正极极片和电化学装置 - Google Patents

一种正极补锂材料、包含该材料的正极极片和电化学装置 Download PDF

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WO2022198654A1
WO2022198654A1 PCT/CN2021/083357 CN2021083357W WO2022198654A1 WO 2022198654 A1 WO2022198654 A1 WO 2022198654A1 CN 2021083357 W CN2021083357 W CN 2021083357W WO 2022198654 A1 WO2022198654 A1 WO 2022198654A1
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positive electrode
lithium
supplement material
present application
lithium supplement
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PCT/CN2021/083357
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English (en)
French (fr)
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周墨林
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宁德新能源科技有限公司
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Priority to CN202180004626.8A priority Critical patent/CN114175310B/zh
Priority to PCT/CN2021/083357 priority patent/WO2022198654A1/zh
Publication of WO2022198654A1 publication Critical patent/WO2022198654A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of electrochemistry, and in particular, to a positive electrode lithium supplement material, a positive electrode pole piece comprising the material, and an electrochemical device.
  • Lithium-ion secondary batteries have the advantages of high energy storage density, high open circuit voltage, low self-discharge rate, long cycle life, and good safety. They are widely used in various fields such as electrical energy storage, mobile electronic equipment, electric vehicles, and aerospace equipment. With the rapid development of mobile electronic devices and electric vehicles, the market has put forward higher and higher requirements for the energy density, cycle performance and kinetic performance of lithium-ion secondary batteries.
  • Solid Electrolyte Interphase Solid Electrolyte Interphase
  • SEI Solid Electrolyte Interphase
  • the active lithium source is consumed in the first cycle; when using anode materials with high specific capacity, such as alloys (silicon, tin, etc.), oxides (silicon oxide, tin oxide, etc.) and amorphous carbon anode, the consumption of active lithium source will be further exacerbated. Therefore, a suitable lithium replenishment method is particularly important to improve the energy density of lithium ion secondary batteries.
  • Li 2 NiO 2 lithium-rich transition metal oxide-based lithium-replenishing materials have high specific capacity and simple preparation methods, and can better improve the energy density of lithium-ion secondary batteries.
  • the surface free lithium content of such materials is extremely high, and it is easy to cause the gel of the slurry during the slurry mixing process, which seriously affects the processing performance.
  • the extremely high free lithium content will greatly deteriorate the high-temperature storage performance of the lithium-ion secondary battery, resulting in storage flatulence and performance degradation.
  • the purpose of the present application is to provide a positive electrode lithium supplement material, a positive electrode electrode sheet and an electrochemical device comprising the material, so as to improve the high temperature storage performance of the electrochemical device.
  • the present application is explained by taking a lithium ion secondary battery as an example of the electrochemical device, but the electrochemical device of the present application is not limited to the lithium ion secondary battery.
  • a first aspect of the present application provides a positive electrode lithium supplement material, which includes an inner core of a lithium-rich transition metal oxide Li 2 MO 2 , and a surface layer existing on the inner core, the surface layer including organic acid lithium Li w C x H y O z , wherein M includes at least one of Mn, Fe, Co, Ni or Cu, Li w C x H y O z includes at least one -COOLi group, 1 ⁇ w ⁇ 3, 1 ⁇ x ⁇ 6, 0 ⁇ y ⁇ 8, 2 ⁇ z ⁇ 7.
  • the surface layer existing on the inner core of the lithium-rich transition metal oxide Li 2 MO 2 may completely wrap the inner core surface or partially wrap the inner core surface, which is not particularly limited in this application. , as long as the purpose of this application can be achieved.
  • M includes at least one of Mn, Fe, Co, Ni or Cu, etc., which can be selected by those skilled in the art according to actual needs, for example, including but not It is limited to at least one of Li 2 NiO 2 , Li 2 CuO 2 or Li 2 Ni 0.5 Cu 0.5 O 2 and the like.
  • the organic acid lithium Li w C x H y O z includes at least one -COOLi group
  • the -COOLi group is an organic acid containing -COOH and a lithium-rich transition metal oxide Li 2 MO 2 surface free Lithium (LiOH or Li 2 CO 3 , mainly LiOH) is generated by the reaction, which can achieve the purpose of consuming free lithium impurities, reduce the content of "residual alkali", suppress the coagulation of the positive electrode slurry, and facilitate the positive electrode slurry
  • the preparation, storage, and coating on the positive electrode plate of the present invention improve the processing performance; and the organic acid lithium of the present application can cover the surface of the Li 2 MO 2 material particles, reducing the impact of the lithium-rich transition metal oxide on the Sensitivity to environmental moisture.
  • the positive electrode lithium supplement material provided by the present application includes an inner core of a lithium-rich transition metal oxide Li 2 MO 2 and a surface layer existing on the inner core, and the surface layer includes an organic acid lithium Li w C x H y Oz .
  • the free lithium content on the surface of the positive electrode lithium supplement material is low, which can not only improve the gel phenomenon during the slurry mixing process of the positive electrode, improve the processing performance, but also improve the high temperature storage performance of the lithium ion secondary battery.
  • the mass percentage content of the organic acid lithium LiwCxHyOz in the surface layer is 0.5% to 5%.
  • the lower limit of the mass percentage content of the organic acid lithium Liw C x H y O z in the surface layer may include the following values: 0.5% or 1%; the organic acid lithium Li w C x H in the surface layer
  • the upper limit of the mass percentage content of y O z may be included in the following values: 3% or 5%.
  • the mass percentage of organic acid lithium in the surface layer is too low (for example, less than 0.5%), and the organic acid lithium covered on the inner core of the lithium-rich transition metal oxide is too small, and it will not be able to effectively improve the enrichment.
  • the average particle size Dv50 of the positive electrode lithium supplement material is 3 ⁇ m to 25 ⁇ m.
  • the average particle size Dv50 of the positive electrode lithium supplement material is 5 ⁇ m to 20 ⁇ m.
  • the lower limit value of the average particle size Dv50 of the positive electrode lithium supplement material may include the following values: 3 ⁇ m, 5 ⁇ m, 9 ⁇ m or 14 ⁇ m; the upper limit value of the average particle size Dv50 of the positive electrode lithium supplement material may be included in the following values: 20 ⁇ m or 25 ⁇ m.
  • the flatness of the positive electrode active material layer can be improved; it is advisable that the positive electrode lithium supplement material does not exceed the thickness of the positive electrode active material layer, otherwise it will be easy to puncture during the cold pressing process The aluminum foil is damaged, forming concave and convex points beyond the thickness of the target cathode active material layer.
  • the use of the positive electrode lithium supplement material with the above particle size distribution range further improves the electron and ion transport performance of the positive electrode sheet, thereby improving the cycle performance and rate performance of the lithium ion secondary battery.
  • Dv50 represents the particle size at which the particle reaches 50% of the volume cumulatively from the small particle size side in the particle size distribution on a volume basis.
  • the specific surface area of the positive electrode lithium supplement material is 0.1 m 2 /g to 30 m 2 /g.
  • the specific surface area of the positive electrode lithium supplement material is 0.5 m 2 /g to 25 m 2 /g.
  • the lower limit value of the specific surface of the positive electrode lithium supplement material may include the following values: 0.1 m 2 /g, 0.5 m 2 /g, 5 m 2 /g, 10 m 2 /g or 15 m 2 /g; the positive electrode lithium supplement material
  • the upper limit value of the specific surface of the can be included in the following values: 20m 2 /g or 30m 2 /g.
  • the specific surface area of the positive electrode lithium supplement material is too small (for example, less than 0.1 m 2 /g), and the positive electrode lithium supplement material cannot be fully contacted with the electrolyte, so that more oxide active sites cannot be provided, which will affect the lithium The rate performance of ion batteries; the specific surface of the positive electrode lithium supplement material is too large (for example, more than 30m 2 /g), the slurry is not easy to disperse evenly, and it will cause too many active sites, increase side reactions and deteriorate the stability of lithium ion batteries, and It is necessary to consume a larger proportion of the binder, which is likely to cause a decrease in the binding force of the positive electrode active material layer and an increase in the growth rate of the internal resistance.
  • the use of the positive electrode lithium supplement material with the above-mentioned specific surface area in the preferred range can more effectively improve the rate performance and cycle stability of the positive electrode sheet.
  • the first charge specific capacity of the positive electrode lithium supplement material is ⁇ 350 mAh/g. It shows that the specific capacity of the positive electrode lithium supplement material is high, and a large amount of lithium ions can be released during the first charge to make up for the loss of active lithium caused by the formation of SEI, and enough lithium ions are inserted back into the positive electrode active material during the first discharge, which effectively improves the The discharge specific capacity of the battery, thereby improving the energy density of the lithium-ion secondary battery.
  • the preparation method of the positive electrode lithium supplement material provided by the present application is not particularly limited, as long as the purpose of the present application can be achieved.
  • the following preparation method can be adopted: dispersing the lithium-rich transition metal oxide Li 2 MO 2 in an organic solvent, adding an organic acid, mixing uniformly, suction filtration and vacuum drying to obtain a positive electrode lithium supplementary material. It can be understood that, when the content of the transition metal oxide is constant, the mass percentage content of the organic acid lithium in the surface layer increases with the increase of the added amount (or concentration) of the organic acid.
  • the type of the organic solvent is not particularly limited, as long as the boiling point is 50°C to 300°C, the purpose of the present application can be achieved.
  • the organic solvent may include at least one of ethanol, decalin, diphenyl ether, and the like.
  • the type of organic acid is not particularly limited, as long as the molecular formula of the organic acid includes at least one carboxyl group, and the organic acid lithium in the surface layer of the positive electrode lithium supplement material includes at least one -COOLi group, the application can be realized.
  • the organic acid may include at least one of malonic acid, succinic acid, acrylic acid, pyruvic acid, citric acid, formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, lactic acid, maleic acid, fumaric acid, and the like.
  • the lithium-rich transition metal oxide Li 2 MO 2 is uniformly mixed with the organic acid, as long as the purpose of the present application can be achieved.
  • magnetic stirring, mechanical stirring, or sonication, etc. may be included.
  • a second aspect of the present application provides a positive electrode sheet, including a positive electrode lithium supplement material, and the positive electrode lithium supplement material is the positive electrode lithium supplement material described in any one of the above embodiments.
  • the application of the positive electrode lithium supplement material of the present application in the positive electrode plate can effectively supplement active lithium and improve the high temperature storage performance and energy density of the lithium ion secondary battery.
  • diffraction peak A appears at 36° to 38°
  • diffraction peak B appears at 42° to 44°
  • diffraction peak B appears at 62°
  • Diffraction peak C appears at 64°.
  • Diffraction peak A, diffraction peak B, and diffraction peak C correspond to the diffraction peaks of rock-salt NiO, indicating that there is nickel oxide in the positive pole piece of the present application after the first charge and discharge.
  • the positive electrode sheet in the present application is not particularly limited, as long as the purpose of the present application can be achieved.
  • a positive electrode sheet typically includes a positive current collector and a layer of positive material.
  • the positive electrode current collector is not particularly limited, as long as the purpose of the present application can be achieved, for example, it may include aluminum foil, aluminum alloy foil, or composite current collector.
  • the positive electrode material layer includes a positive electrode active material and a positive electrode lithium supplement material.
  • the positive electrode active material is not particularly limited, as long as it can achieve the purpose of the present application, for example, it can include nickel-cobalt lithium manganate (811, 622, 523, 111), nickel-cobalt lithium aluminate, lithium iron phosphate, lithium-rich manganese-based materials , at least one of lithium cobaltate, lithium manganate, lithium iron manganese phosphate or lithium titanate.
  • the positive electrode lithium supplement material is at least one of the positive electrode lithium supplement materials provided in this application.
  • the thicknesses of the positive electrode current collector and the positive electrode material layer are not particularly limited as long as the purpose of the present application can be achieved.
  • the thickness of the positive electrode current collector is 5 ⁇ m to 20 ⁇ m, preferably 6 ⁇ m to 18 ⁇ m, and more preferably 8 ⁇ m to 16 ⁇ m.
  • the thickness of the positive electrode material layer is 30 ⁇ m to 120 ⁇ m.
  • the positive electrode sheet may further comprise a conductive layer, and the conductive layer is located between the positive electrode current collector and the positive electrode material layer.
  • the composition of the conductive layer is not particularly limited, and may be a conductive layer commonly used in the art.
  • the conductive layer includes a conductive agent and a binder.
  • the positive electrode lithium supplement material can be directly added to the slurry when the positive electrode material is slurried to form a positive electrode slurry comprising the positive electrode lithium supplement material of the present application, which is coated on the surface of the positive electrode current collector.
  • the positive electrode lithium supplement material can also be slurried separately and coated on the surface of the positive electrode piece, or on the surface of the separator near the positive electrode side.
  • the positive electrode lithium supplement material, the conductive agent and the binder can also be mixed to prepare a sheet and attached to the separator on the side close to the positive electrode.
  • the above-mentioned "surface” may be the entire area of the positive electrode sheet/separator, or a partial area of the positive electrode electrode sheet/separator, which is not particularly limited in this application, as long as the purpose of the application can be achieved.
  • the negative electrode sheet of the present application may be a metallic lithium sheet, and may also include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector.
  • the present application does not specifically limit the negative electrode current collector as long as it can achieve the purpose of the present application.
  • it may contain copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, foam copper or composite current collector.
  • the anode active material layer in the present application includes an anode active material, a conductive agent, and a thickener.
  • the negative electrode active material of the present application may include natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO, Li-Sn alloy, Li-Sn-O alloy At least one of , Sn, SnO, SnO 2 , lithium titanate with spinel structure Li 4 Ti 5 O 12 , Li-Al alloy and metallic lithium.
  • the thickness of the negative electrode current collector and the negative electrode active material layer is not particularly limited, as long as the purpose of the present application can be achieved, for example, the thickness of the negative electrode current collector is 6 ⁇ m to 10 ⁇ m, and the thickness of the negative electrode active material layer is 30 ⁇ m to 10 ⁇ m. 120 ⁇ m.
  • the thickness of the negative electrode sheet is not particularly limited, as long as the purpose of the present application can be achieved, for example, the thickness of the negative electrode sheet is 50 ⁇ m to 150 ⁇ m.
  • the negative electrode sheet may further comprise a conductive layer, and the conductive layer is located between the negative electrode current collector and the negative electrode material layer.
  • the composition of the conductive layer is not particularly limited, and may be a conductive layer commonly used in the art.
  • the conductive layer includes a conductive agent and a binder.
  • the conductive agent is not particularly limited as long as the object of the present application can be achieved.
  • the conductive agent may include conductive carbon black (Super P), carbon nanotubes (CNTs), carbon nanofibers, flake graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, or graphene, among others. at least one.
  • the above-mentioned binder is not particularly limited, and any binder known in the art can be used as long as the purpose of the present application can be achieved.
  • the binder may include polyacryl alcohol, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyimide, polyamideimide, styrene butadiene rubber (SBR), polyvinyl alcohol ( PVA), polyvinylidene fluoride, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin, carboxymethyl cellulose (CMC) or carboxymethyl At least one of sodium cellulose (CMC-Na) and the like.
  • SBR styrene butadiene rubber
  • PVA polyvinyl alcohol
  • PVDF polyvinylidene fluoride
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PVB polyvinyl butyral
  • water-based acrylic resin carboxymethyl cellulose (CMC) or carboxymethyl At least one of sodium cellulose (CMC-Na)
  • the separator in the present application is not particularly limited as long as the purpose of the present application can be achieved.
  • polyethylene (PE), polypropylene (PP)-based polyolefin (PO) separators polyester films (such as polyethylene terephthalate (PET) films), cellulose films, polyimide Amine film (PI), polyamide film (PA), spandex or aramid film, woven film, non-woven film (non-woven fabric), microporous film, composite film, diaphragm paper, rolled film, spinning film, etc. at least one of.
  • the release film may include a substrate layer and a surface treatment layer.
  • the substrate layer can be a non-woven fabric, film or composite film with a porous structure, and the material of the substrate layer can include at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, etc. kind.
  • polypropylene porous membranes, polyethylene porous membranes, polypropylene non-woven fabrics, polyethylene non-woven fabrics, or polypropylene-polyethylene-polypropylene porous composite membranes may be used.
  • at least one surface of the substrate layer is provided with a surface treatment layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance.
  • the inorganic layer includes inorganic particles and a binder
  • the inorganic particles are not particularly limited, and can be selected from aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, nickel oxide, for example , at least one of zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate.
  • the binder is not particularly limited, for example, it can be selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyethylene One or a combination of rolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
  • the polymer layer contains a polymer, and the material of the polymer includes polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly( At least one of vinylidene fluoride-hexafluoropropylene) and the like.
  • the lithium ion battery of the present application further includes an electrolyte, and the electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolyte, and the electrolyte includes a lithium salt and a non-aqueous solvent.
  • the lithium salt may include LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2. At least one of LiC(SO 2 CF 3 ) 3 , LiSiF 6 , LiBOB or lithium difluoroborate.
  • LiPF 6 may be chosen as the lithium salt because it gives high ionic conductivity and improves cycling characteristics.
  • the non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof.
  • the above-mentioned carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof.
  • Examples of the above-mentioned chain carbonate compounds are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), carbonic acid Methyl ethyl ester (MEC) and combinations thereof.
  • Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), and combinations thereof.
  • fluorocarbonate compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Ethyl carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-dicarbonate Fluoro-1-methylethylene, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof.
  • FEC fluoroethylene carbonate
  • 1,2-difluoroethylene carbonate 1,1-difluoroethylene carbonate
  • 1,1,2-trifluoroethylene carbonate Ethyl carbonate 1,1,2,2-tetrafluoroethylene carbonate
  • 1-fluoro-2-methylethylene carbonate 1-fluoro-1-methylethylene carbonate
  • 1,2-dicarbonate Fluoro-1-methylethylene 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethyl
  • carboxylate compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone , caprolactone, valerolactone, mevalonolactone, caprolactone, and combinations thereof.
  • ether compounds examples include dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethyl ether Oxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.
  • Examples of the above-mentioned other organic solvents are dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, Formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters and combinations thereof.
  • a third aspect of the present application provides an electrochemical device including the positive electrode plate provided by the present application, and the electrochemical device has good high-temperature storage performance and energy density.
  • the electrochemical device of the present application is not particularly limited, and it may include any device in which an electrochemical reaction occurs.
  • the electrochemical device may include, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery, or a lithium ion polymer secondary battery, and the like.
  • the present application also provides an electronic device comprising the electrochemical device described in the embodiments of the present application, and the electronic device has good high temperature storage performance and energy density.
  • the electronic device of the present application is not particularly limited, and it may be used for any electronic device known in the prior art.
  • electronic devices may include, but are not limited to, notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, assisted bicycles, bicycles, Lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large-scale household storage batteries and lithium-ion capacitors, etc.
  • an electrochemical device can be manufactured by the following process: overlapping the positive electrode and the negative electrode through a separator, wrapping them, folding them, etc., and putting them into the casing as needed, injecting the electrolyte into the casing and sealing it, wherein
  • the separator used is the aforementioned separator provided in this application.
  • an overcurrent preventing element, a guide plate, etc. may be placed in the case to prevent pressure rise and overcharge and discharge inside the electrochemical device.
  • the present application provides a positive electrode lithium supplement material, a positive electrode plate comprising the material, and an electrochemical device
  • the positive electrode lithium supplement material includes an inner core of a lithium-rich transition metal oxide Li 2 MO 2 , and a surface layer existing on the inner core , the surface layer includes organic acid lithium LiwCxHyOz , wherein, M includes at least one of Mn, Fe, Co, Ni or Cu , and LiwCxHyOz includes at least one -COOLi group group, 1 ⁇ w ⁇ 3, 1 ⁇ x ⁇ 6, 0 ⁇ y ⁇ 8, 2 ⁇ z ⁇ 7.
  • Applying the positive electrode lithium supplement material in the positive electrode plate can realize the effective supplement of active lithium and improve the energy density of the electrochemical device.
  • the free lithium content on the surface of the positive electrode lithium supplementing material is low, which can effectively suppress the gel phenomenon during the slurry mixing process, improve the processing performance, and effectively improve the high-temperature storage performance of the electrochemical device.
  • Fig. 1 is the XRD (X-ray diffraction) pattern of the positive pole piece of the button battery in Example 1 of the application after the first charge and discharge;
  • FIG. 2 is the XRD patterns of the Li 2 NiO 2 material in Example 1 of the application before and after treatment.
  • the present application is explained by taking a lithium ion battery as an example of an electrochemical device, but the electrochemical device of the present application is not limited to a lithium ion battery.
  • FIG. 1 shows the XRD diffraction pattern of the positive pole piece of the coin-type battery in Example 1 of the present application after the first charge and discharge.
  • (a) in FIG. 1 is the graph after the first charge and discharge of the positive pole piece
  • (b) in FIG. 1 is the NiO standard card.
  • diffraction peak A appears at 36° to 38°
  • diffraction peak B appears at 42° to 44°
  • diffraction peak C appears at 62° to 64°.
  • Diffraction peak A, diffraction peak B, and diffraction peak C correspond to the diffraction peaks of rock-salt NiO, indicating that there is nickel oxide in the positive pole piece of the present application after the first charge and discharge.
  • FIG. 2 shows the XRD patterns of the Li 2 NiO 2 material in Example 1 of the present application before and after treatment.
  • (c) in Fig. 2 is the spectrum of Li 2 NiO 2 treated with malonic acid
  • (d) in Fig. 2 is the spectrum of dilithium malonate
  • (e) in Fig. 2 is untreated The spectrum of Li 2 NiO 2 .
  • the XRD pattern of the obtained cathode lithium-supplementing material shows the peak position of dilithium malonate, indicating that the free lithium on the surface of malonic acid and Li 2 NiO 2 The impurities reacted in situ to form a protective layer of dilithium malonate.
  • Wuhan Blue Electric CT2001A system is used for charging specific capacity test.
  • the button-type battery to be tested containing the positive electrode lithium supplement material is allowed to stand for 30 minutes in the environment of 25 ⁇ 3°C, and the theoretical gram capacity is calculated as 400mAh/g at 0.1C. ) at a rate of constant current charging to a voltage of 4.4 V, followed by constant voltage charging to a current of 0.025 C, and the charging capacity was recorded.
  • the charging specific capacity of the positive electrode lithium supplement material charging capacity/mass of the lithium supplement material.
  • This application uses the TEMP 850 high and low temperature experimental box to test the high temperature storage performance of the battery. First, test and record the initial thickness d 0 after the battery is fully charged, and store the lithium ion battery in a high and low temperature box at 85°C for 24 hours. Test and record For the thickness d 1 of the battery, calculate (d 1 -d 0 )/d 0 and record.
  • NiO and Li 2 O were mixed in argon at a mass ratio of 1:1, and ball-milled for 24 h to obtain a mixture.
  • the mixture is compressed into pellets.
  • the pellets were put into a nickel tube filled with argon, and heated at 650° C. for 24 h to obtain a lithium-rich transition metal oxide Li 2 NiO 2 .
  • the average particle size Dv50 of the positive electrode lithium supplement material is 14 ⁇ m, the specific surface area is 0.5 m 2 /g, and the mass percentage of Li 2 C 3 H 2 O 4 in the surface layer is 3%.
  • the positive electrode active material lithium cobalt oxide (LiCoO 2 ), the above-prepared positive electrode lithium supplement material Li 2 NiO 2 ⁇ Li 2 C 3 H 2 O 4 , the conductive agent nano-conductive carbon black, and the binder PVDF are in a mass ratio of 92.5: Mix at 5.0:1.0:1.5, add NMP as a solvent, prepare a slurry with a solid content of 75%, and stir evenly. The slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10 ⁇ m, and dried at 130° C. to obtain a positive electrode sheet with a coating thickness of 110 ⁇ m. After the above steps are completed, the single-side coating of the positive electrode sheet is completed.
  • the above steps are repeated on the other surface of the positive electrode sheet to obtain a positive electrode sheet coated with positive active material on both sides.
  • the positive pole piece is cut into a size of 74mm ⁇ 867mm, and the tabs are welded for use.
  • the negative electrode active material graphite, nano-conductive carbon black, styrene-butadiene rubber and sodium carboxymethyl cellulose are mixed in a mass ratio of 95:2:2:1, and deionized water is added as a solvent to prepare a slurry with a solid content of 70%. ingredients and mix well.
  • the slurry was uniformly coated on the current collector copper foil, dried at 110° C., and cold-pressed to obtain a single-sided active material layer-coated negative pole piece with an active material layer thickness of 150 ⁇ m.
  • these steps are also completed on the back side of the negative electrode pole piece by the same method, that is, the negative pole piece with double-sided coating is obtained.
  • the negative pole piece is cut into a size of 76mm ⁇ 851mm and the tabs are welded for use.
  • a polypropylene (PP) film (supplied by Celgard) with a thickness of 14 ⁇ m was used.
  • the positive electrode, the separator and the negative electrode prepared above are stacked in sequence, so that the separator is placed between the positive and negative electrodes to play a role of isolation, and the electrode assembly is obtained by winding.
  • the electrode assembly is put into an aluminum-plastic film packaging bag, and the moisture is removed at 80 ° C, the prepared electrolyte is injected, and the lithium ion battery is obtained through vacuum packaging, standing, forming, and shaping.
  • the above-prepared positive electrode lithium supplement material Li 2 NiO 2 ⁇ Li 2 C 3 H 2 O 4 , conductive carbon black as a conductive agent and PVDF as a binder are mixed in a mass ratio of 90:5:5, and NMP is added as a solvent. Stir and prepare a slurry with a solid content of 40%. Use a scraper to coat the anode current collector aluminum foil with a thickness of 100 ⁇ m. After drying in a vacuum drying oven for 12 hours at 130 °C, use a punching machine to cut into diameters in a dry environment. It is a 1cm disc (that is, a positive pole piece), and a metal lithium piece is used as the counter electrode in the glove box.
  • the separator is selected from the separator prepared above, and the electrolyte solution prepared above is added to assemble to obtain a button battery.
  • Example 2 Example 3, Example 4, Example 5, Example 6, Example 7, Example 8, Example 9, Example 10, Example 11, Example 12, Example 13, Example 14.
  • Example 15 and Example 16 ⁇ preparation of positive electrode lithium supplement material>, ⁇ preparation of positive electrode pole piece>, ⁇ preparation of negative electrode pole piece>, ⁇ preparation of electrolyte>, ⁇ preparation of separator>, The preparation steps of ⁇ Preparation of Lithium Ion Battery> and ⁇ Preparation of Button Battery> are the same as those in Example 1, and the changes of relevant preparation parameters are shown in Table 1:
  • Comparative Example 1 Comparative Example 2, Comparative Example 3, Comparative Example 4 and Comparative Example 5, ⁇ Preparation of Positive Electrode Sheet>, ⁇ Preparation of Negative Electrode Sheet>, ⁇ Preparation of Electrolyte>, ⁇ Preparation of Separator
  • the preparation steps of > and ⁇ Preparation of lithium ion battery> are the same as in Example 1.
  • Comparative Example 4 and Comparative Example 5 ⁇ Preparation of positive electrode lithium supplement material> is the same as Example 1, and the changes of relevant preparation parameters are shown in the table. shown in 2:
  • Example 1 Example 2, Example 3, Example 4, Example 5, Example 6, Example 7, Example 8, Example 912, Example 13, Example 14, Example 15, Example 16. Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 3:
  • Example 2 From Example 1, Example 2, Example 3, Example 4, Example 5, Example 6, Example 7, Example 8, Example 9 and Comparative Example 1, Comparative Example 4, Comparative Example 5 It can be seen that the treatment of the same lithium-rich transition metal oxide with different organic acids and different organic solvents can effectively reduce the active lithium content on its surface, inhibit slurry coagulation, improve processing performance, and reduce high-temperature storage gas production. .
  • Example 1 Example 2, Example 3, Example 4 and Comparative Example 1, Comparative Example 4, Comparative Example 5, it can be seen that the active lithium ion content m(Li + ) on the surface of Li 2 NiO 2 varies with As the concentration of malonic acid changes, the higher concentration of malonic acid within the scope of the present application has a more significant reduction effect on the residual lithium content of Li 2 NiO 2 .
  • Comparative Example 1 the untreated Li 2 NiO 2 lithium-replenishing material was added to the positive electrode slurry, and the slurry particles agglomerated during the slurry mixing process. If the slurry waiting time is further extended, gelation will appear. lead to inability to coat.
  • Example 1 Example 2, Example 3, Example 4 and Comparative Example 4 and Comparative Example 5 that the mass percentage content of organic acid lithium in the surface layer is within the scope of the application, which can not only effectively improve the positive electrode compensation
  • the first charge specific capacity of lithium materials can effectively improve the thickness expansion ratio of lithium ion batteries under high temperature storage.
  • Example 1 From Example 1, Example 5, Example 6, Example 7, Example 8, and Example 9, it can be seen that if different organic acids are selected, the organic acid lithium in the surface layer changes accordingly, but all of them can effectively reduce The content of free lithium on the surface of the core material can effectively inhibit the gelation of the slurry, reduce the problem of gas production in high-temperature storage of lithium-ion batteries, and significantly reduce the thickness expansion ratio of lithium-ion batteries under high-temperature storage.
  • Example 10 From Example 1, Example 10, Example 11, Example 12, Example 13, Example 14, and Comparative Example 1, Comparative Example 2, and Comparative Example 3, it can be seen that the organic acid has a strong effect on different lithium-rich transition metals. After the oxide treatment, the content of free lithium on the surface of the lithium-rich transition metal oxide has been significantly reduced. After adding it to the positive electrode slurry, the slurry condition did not appear abnormal during the entire slurry mixing process, and it can also significantly improve the lithium-ion battery. Storage performance at high temperature.
  • Changes in the Dv50 and specific surface area of the positive electrode lithium supplement material usually also affect the content of free lithium on the surface of the positive electrode lithium supplement material of the present application. It can be seen from Example 1, Example 15 and Example 16 that as long as the Dv50 and specific surface area of the positive electrode lithium supplement material are within the scope of the present application, the content of free lithium on the surface of the core material can be further reduced, and the slurry gelation can be suppressed. .
  • the positive electrode lithium supplementary material provided by this application including the inner core of the lithium-rich transition metal oxide Li2MO2 , and the organic acid lithium LiwCxHyOz surface layer existing on the inner core, not only can
  • the supplement of active lithium can be realized, the energy density of the electrochemical device can be effectively improved, and the gel phenomenon in the slurry mixing process can be effectively suppressed, the processing performance can be improved, and the high-temperature storage performance of the electrochemical device can be effectively improved.

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Abstract

本申请提供了一种正极补锂材料、包含该材料的正极极片和电化学装置，该正极补锂材料包括富锂过渡金属氧化物Li 2MO 2的内核、及存在于该内核上的表层，该表层包括有机酸锂Li wC xH yO z，其中，M包括Mn、Fe、Co、Ni或Cu中的至少一种，Li wC xH yO z中包含至少一个-COOLi基团，1≤w≤3，1≤x≤6，0≤y≤8，2≤z≤7。将该正极补锂材料应用在正极极片中，不仅能实现活性锂地补充，有效提升电化学装置的能量密度。并且，该正极补锂材料表面的游离锂含量低，能够有效抑制调浆过程中的凝胶现象，改善加工性能，使电化学装置的高温存储性能得到有效改善。

Description

一种正极补锂材料、包含该材料的正极极片和电化学装置 技术领域
本申请涉及电化学领域，具体涉及一种正极补锂材料、包含该材料的正极极片和电化学装置。
背景技术
锂离子二次电池具有储能密度大、开路电压高、自放电率低、循环寿命长、安全性好等优点，广泛应用于电能储存、移动电子设备、电动汽车和航天航空设备等各个领域。随着移动电子设备和电动汽车进入高速发展阶段，市场对锂离子二次电池的能量密度、循环性能和动力学性能等都提出了越来越高的要求。
由于锂离子二次电池在首次充放电过程中，负极表面会产生大量的固体电解质界面膜(Solid Electrolyte Interphase，SEI)，消耗锂离子电池中有限的锂离子和电解液，造成不可逆容量损失，降低锂离子二次电池的能量密度。在使用石墨负极的电池中，首次循环会消耗大约10％的活性锂源；当采用高比容量的负极材料，如合金类(硅、锡等)、氧化物类(氧化硅、氧化锡等)和无定形碳负极时，活性锂源的消耗将进一步加剧。因此，一种合适的补锂方法对锂离子二次电池的能量密度的提高显得尤为重要。
针对上述问题，目前提出了相对安全和便于操作的正极补锂的方法。例如，Li 2NiO 2类富锂过渡金属氧化物补锂材料，这类材料的比容量高、制备方法简单，能较好地提升锂离子二次电池的能量密度。但这类材料的表面游离锂含量极高，在调浆过程极易造成浆料的凝胶，严重影响加工性能。而且，极高的游离锂含量，会极大恶化锂离子二次电池的高温存储性能，导致存储胀气、性能衰减。
发明内容
本申请的目的在于提供一种正极补锂材料、包含该材料的正极极片和电化学装置，以提高电化学装置的高温存储性能。
需要说明的是，本申请的内容中，以锂离子二次电池作为电化学装置的例子来解释本申请，但是本申请的电化学装置并不仅限于锂离子二次电池。
具体技术方案如下：
本申请的第一方面提供了一种正极补锂材料，其包括富锂的过渡金属氧化物Li 2MO 2 的内核、及存在于该内核上的表层，该表层包括有机酸锂Li wC xH yO z，其中，M包括Mn、Fe、Co、Ni或Cu中的至少一种，Li wC xH yO z中包括至少一个-COOLi基团，1≤w≤3，1≤x≤6，0≤y≤8，2≤z≤7。
在本申请中，本领域技术人员应当理解，存在于富锂的过渡金属氧化物Li 2MO 2内核上的表层，可以将内核表面全包裹，也可以将内核表面部分包裹，本申请没有特别限制，只要能实现本申请目的即可。
本申请的富锂的过渡金属氧化物Li 2MO 2中，M包括Mn、Fe、Co、Ni或Cu等中的至少一种，本领域技术人员可以根据实际需要进行选择，例如，包括但不限于Li 2NiO 2、Li 2CuO 2或Li 2Ni 0.5Cu 0.5O 2等中的至少一种。
在本申请中，有机酸锂Li wC xH yO z中包括至少一个-COOLi基团，-COOLi基团是含有-COOH的有机酸与富锂的过渡金属氧化物Li 2MO 2表面游离锂(LiOH或Li 2CO 3，主要是LiOH)反应所生成的，可以实现消耗游离锂杂质的目的，降低了“残碱”含量，使正极浆料凝浆现象得到抑制，而便于正极浆料的制备、存储及其在正极极片上的涂覆，从而改善了加工性能；并且，本申请的有机酸锂可覆盖在Li 2MO 2材料颗粒的表面，降低了富锂的过渡金属氧化物对环境水分的敏感性。
整体而言，本申请提供的正极补锂材料，包括富锂的过渡金属氧化物Li 2MO 2的内核、及存在于该内核上的表层，所述表层包括有机酸锂Li wC xH yO z。该正极补锂材料表面游离锂含量低，不仅能够改善正极浆料调浆过程中的凝胶现象，提高加工性能，还能提升锂离子二次电池的高温存储性能。
在本申请的一种实施方案中，基于正极补锂材料的总质量，其表层中的有机酸锂Li wC xH yO z的质量百分含量为0.5％至5％。例如，其表层中的有机酸锂Li wC xH yO z的质量百分含量的下限值可以包括以下数值中：0.5％或1％；其表层中的有机酸锂Li wC xH yO z的质量百分含量的上限值可以包括以下数值中：3％或5％。不限于任何理论，表层中的有机酸锂的质量百分含量过低(例如低于0.5％)，覆盖在富锂的过渡金属氧化物的内核上的有机酸锂过少，将无法有效改善富锂的过渡金属氧化物对环境水分的敏感性；表层中的有机酸锂的质量百分含量过高(例如高于5％)，使表层过厚，阻抗显著增加，极化随之增长，严重影响正极补锂材料的实际比容量，进而影响对锂离子二次电池能量密度的提升效果。通过将正极补锂材料的表层中的有机酸锂的质量百分比含量控制在上述范围内，能够有效降低富锂的过渡金属氧化物对环境水分的敏感性、提升锂离子二次电池的能量密度。
在本申请的一种实施方案中，正极补锂材料的平均粒径Dv50为3μm至25μm。优选地，正极补锂材料的平均粒径Dv50为5μm至20μm。例如，正极补锂材料的平均粒径Dv50的下限值可以包括以下数值中：3μm、5μm、9μm或14μm；正极补锂材料的平均粒径Dv50的上限值可以包括以下数值中：20μm或25μm。通过控制正极补锂材料的平均粒径Dv50在上述范围内，能够提高正极活性材料层的平整度；以正极补锂材料不超过正极活性材料层的厚度为宜，否则在冷压过程中易刺伤铝箔，形成凹凸点超出目标正极活性材料层的厚度。并且，采用具有上述粒径分布范围的正极补锂材料，进一步改善了正极极片的电子和离子传输性能，从而提高了锂离子二次电池的循环性能和倍率性能。采用具有上述粒径分布优选范围的正极补锂材料，对于改善正极极片的电子和离子传输性能，具有更优的效果。在本申请中，Dv50表示颗粒在体积基准的粒度分布中，从小粒径侧起，达到体积累积50％的粒径。
在本申请的一种实施方案中，正极补锂材料的比表面积为0.1m 2/g至30m 2/g。优选地，正极补锂材料的比表面积为0.5m 2/g至25m 2/g。例如，正极补锂材料的比表面的下限值可以包括以下数值中：0.1m 2/g、0.5m 2/g、5m 2/g、10m 2/g或15m 2/g；正极补锂材料的比表面的上限值可以包括以下数值中：20m 2/g或30m 2/g。不限于任何理论，正极补锂材料的比表面积过小(例如小于0.1m 2/g)，正极补锂材料与电解液无法充分接触，从而无法提供更多的氧化物活性位点，将影响锂离子电池的倍率性能；正极补锂材料的比表面过大(例如大于30m 2/g)，浆料不易分散均匀，且会造成活性位点过多，副反应增多恶化锂离子电池稳定性，且需要消耗更多比例的粘结剂，容易造成正极活性材料层的粘结力的降低，内阻增长率升高。采用具有上述比表面积优选范围内的正极补锂材料，可以更加有效地改善正极极片的倍率性能和循环稳定性。
在本申请的一种实施方案中，正极补锂材料的首次充电比容量≥350mAh/g。表明正极补锂材料的比容量高，在首次充电时可脱出大量的锂离子来弥补生成SEI造成的活性锂损失，首次放电时有足够的锂离子回嵌至正极活性材料中，有效地提升了电池的放电比容量，进而提升了锂离子二次电池的能量密度。
本申请提供的正极补锂材料的制备方法没有特别限制，只要能够实现本申请目的即可。例如，可以采用如下制备方法：将富锂的过渡金属氧化物Li 2MO 2分散于有机溶剂中，添加有机酸，混合均匀，抽滤并真空烘干，即得到正极补锂材料。可以理解的是，在过渡金属氧化物含量一定时，表层中有机酸锂的质量百分含量随有机酸的添加量(或浓度)增加而增加。
在本申请中，对有机溶剂的种类没有特别限制，只要沸点为50℃至300℃，能实现本申请目的即可。例如，有机溶剂可以包括乙醇、十氢化萘或二苯醚等中的至少一种。
在本申请中，对有机酸的种类没有特别限制，只要有机酸的分子式中包括至少一个羧基，使正极补锂材料的表层中的有机酸锂中包括至少一个-COOLi基团，能实现本申请目的即可。例如，有机酸可以包括丙二酸、丁二酸、丙烯酸、丙酮酸、柠檬酸、甲酸、乙酸、丙酸、丁酸、草酸、乳酸、马来酸或富马酸等中的至少一种。
在本申请中，对富锂的过渡金属氧化物Li 2MO 2与有机酸混合均匀的方式没有特别限制，只要能够实现本申请目的即可。例如，可以包括磁力搅拌、机械搅拌或超声处理等。
本申请的第二方面提供了一种正极极片，包括正极补锂材料，该正极补锂材料为上述任一实施方案所述的正极补锂材料。将本申请的正极补锂材料应用在正极极片中，能够实现活性锂地有效补充，提升锂离子二次电池的高温存储性能和能量密度。
在本申请的一种实施方案中，正极极片首次充放电后的XRD衍射图谱中，在36°至38°处出现衍射峰A，在42°至44°处出现衍射峰B，在62°至64°处出现衍射峰C。衍射峰A、衍射峰B、衍射峰C对应岩盐相NiO的衍射峰，表明本申请的正极极片在首次充放电后存在氧化镍。
本申请中的正极极片没有特别限制，只要能够实现本申请目的即可。例如，正极极片通常包含正极集流体和正极材料层。其中，正极集流体没有特别限制，只要能够实现本申请目的即可，例如，可以包含铝箔、铝合金箔或复合集流体等。正极材料层包括正极活性材料和正极补锂材料。正极活性材料没有特别限制，只要能够实现本申请目的即可，例如，可以包含镍钴锰酸锂(811、622、523、111)、镍钴铝酸锂、磷酸铁锂、富锂锰基材料、钴酸锂、锰酸锂、磷酸锰铁锂或钛酸锂中的至少一种。正极补锂材料为本申请提供的正极补锂材料中的至少一种。在本申请中，正极集流体和正极材料层的厚度没有特别限制，只要能够实现本申请目的即可。例如，正极集流体的厚度为5μm至20μm，优选为6μm至18μm，更优选为8μm至16μm。正极材料层的厚度为30μm至120μm。任选地，所述正极极片还可以包含导电层，所述导电层位于正极集流体和正极材料层之间。所述导电层的组成没有特别限制，可以是本领域常用的导电层。所述导电层包括导电剂和粘结剂。
本申请对正极补锂材料的使用方式没有特别限制，本领域技术人员可以根据实际需要进行选择，只要能实现本申请目的即可。例如，可以在正极材料调浆时直接向浆料中添加 正极补锂材料，形成包含本申请正极补锂材料的正极浆料，涂覆于正极集流体表面。也可以将正极补锂材料单独调浆，涂覆在正极极片表面，或涂覆在靠近正极一侧的隔膜表面。还可以将正极补锂材料、导电剂、粘结剂混合制备成片，贴在靠近正极一侧的隔膜上。需要说明的是，上述的“表面”可以是正极极片/隔膜的全部区域，也可以是正极极片/隔膜的部分区域，本申请没有特别限制，只要能实现本申请目的即可。
本申请的负极极片可以是金属锂片，也可以包含负极集流体及设置于负极集流体的至少一个表面上的负极活性材料层。本申请对负极集流体没有特别限制，只要能够实现本申请目的即可，例如，可以包含铜箔、铜合金箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜或复合集流体等。本申请中的负极活性材料层包括负极活性物质、导电剂和增稠剂。本申请的负极活性物质可以包括天然石墨、人造石墨、中间相微碳球(MCMB)、硬碳、软碳、硅、硅-碳复合物、SiO、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的钛酸锂Li 4Ti 5O 12，Li-Al合金及金属锂等中的至少一种。在本申请中，对负极集流体和负极活性材料层的厚度没有特别限制，只要能够实现本申请目的即可，例如，负极集流体的厚度为6μm至10μm，负极活性材料层的厚度为30μm至120μm。本申请中，负极极片的厚度没有特别限制，只要能够实现本申请目的即可，例如，负极极片的厚度为50μm至150μm。任选地，所述负极极片还可以包含导电层，所述导电层位于负极集流体和负极材料层之间。所述导电层的组成没有特别限制，可以是本领域常用的导电层。所述导电层包括导电剂和粘结剂。
上述导电剂没有特别限制，只要能够实现本申请目的即可。例如，导电剂可以包括导电炭黑(Super P)、碳纳米管(CNTs)、碳纳米纤维、鳞片石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管或石墨烯等中的至少一种。上述所述粘结剂没有特别限制，可以使用本领域公知的任何粘结剂，只要能够实现本申请目的即可。例如，粘结剂可以包括聚丙烯醇、聚丙烯酸钠、聚丙烯酸钾、聚丙烯酸锂、聚酰亚胺、聚酰亚胺、聚酰胺酰亚胺、丁苯橡胶(SBR)、聚乙烯醇(PVA)、聚偏氟乙烯、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚乙烯醇缩丁醛(PVB)、水性丙烯酸树脂、羧甲基纤维素(CMC)或羧甲基纤维素钠(CMC-Na)等中的至少一种。
在本申请中的隔离膜没有特别限制，只要能够实现本申请目的即可。例如，聚乙烯(PE)、聚丙烯(PP)为主的聚烯烃(PO)类隔膜，聚酯膜(例如聚对苯二甲酸二乙酯(PET)膜)、纤维素膜、聚酰亚胺膜(PI)、聚酰胺膜(PA)，氨纶或芳纶膜、织造膜、非织造膜(无纺布)、微孔膜、复合膜、隔膜纸、碾压膜、纺丝膜等中的至少一种。例如，隔离膜可以包括基材 层和表面处理层。基材层可以为具有多孔结构的无纺布、膜或复合膜，基材层的材料可以包括聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯和聚酰亚胺等中的至少一种。任选地，可以使用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。任选地，基材层的至少一个表面上设置有表面处理层，表面处理层可以是聚合物层或无机物层，也可以是混合聚合物与无机物所形成的层。例如，无机物层包括无机颗粒和粘结剂，所述无机颗粒没有特别限制，例如可以选自氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙和硫酸钡等中的至少一种。所述粘结剂没有特别限制，例如可以选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯和聚六氟丙烯中的一种或几种的组合。聚合物层中包含聚合物，聚合物的材料包括聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚偏氟乙烯或聚(偏氟乙烯-六氟丙烯)等中的至少一种。
本申请的锂离子电池还包括电解质，电解质可以是凝胶电解质、固态电解质和电解液中的一种或多种，电解液包括锂盐和非水溶剂。在本申请一些实施方案中，锂盐可以包括LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB或二氟硼酸锂中的至少一种。举例来说，锂盐可以选用LiPF 6，因为它可以给出高的离子导电率并改善循环特性。非水溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物、其它有机溶剂或它们的组合。上述碳酸酯化合物可为链状碳酸酯化合物、环状碳酸酯化合物、氟代碳酸酯化合物或其组合。上述链状碳酸酯化合物的实例为碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸甲乙酯(MEC)及其组合。环状碳酸酯化合物的实例为碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)、碳酸乙烯基亚乙酯(VEC)及其组合。氟代碳酸酯化合物的实例为碳酸氟代亚乙酯(FEC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯、碳酸三氟甲基亚乙酯及其组合。上述羧酸酯化合物的实例为甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯、甲瓦龙酸内酯、己内酯及其组合。上述醚化合物的实例为二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基乙烷、2-甲基四氢呋喃、四氢呋喃及其组合。上 述其它有机溶剂的实例为二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯和磷酸酯及其组合。
本申请的第三方面提供了一种电化学装置，包括本申请提供的正极极片，该电化学装置具有良好的高温存储性能和能量密度。
本申请的电化学装置没有特别限制，其可以包括发生电化学反应的任何装置。在一些实施例中，电化学装置可以包括但不限于：锂金属二次电池、锂离子二次电池(锂离子电池)、锂聚合物二次电池或锂离子聚合物二次电池等。
本申请还提供了一种电子装置，包含本申请实施方案中所述的电化学装置，该电子装置具有良好的高温存储性能和能量密度。
本申请的电子装置没有特别限制，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，电子装置可以包括，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
电化学装置的制备过程为本领域技术人员所熟知的，本申请没有特别的限制。例如电化学装置可以通过以下过程制造：将正极极片和负极极片经由隔离膜重叠，并根据需要将其卷绕、折叠等操作后放入壳体内，将电解液注入壳体并封口，其中所用的隔离膜为本申请提供的上述隔离膜。此外，也可以根据需要将防过电流元件、导板等置于壳体中，从而防止电化学装置内部的压力上升、过充放电。
本申请提供了一种正极补锂材料、包含该材料的正极极片和电化学装置，该正极补锂材料包括富锂过渡金属氧化物Li 2MO 2的内核、及存在于该内核上的表层，该表层包括有机酸锂Li wC xH yO z，其中，M包括Mn、Fe、Co、Ni或Cu中的至少一种，Li wC xH yO z中包含至少一个-COOLi基团，1≤w≤3，1≤x≤6，0≤y≤8，2≤z≤7。将该正极补锂材料应用在正极极片中，能实现活性锂地有效补充，提升电化学装置的能量密度。并且，该正极补锂材料表面的游离锂含量低，能够有效抑制调浆过程中的凝胶现象，改善加工性能，使 电化学装置的高温存储性能得到有效改善。
附图说明
为了更清楚地说明本申请和现有技术的技术方案，下面对实施例和现有技术中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例。
图1为本申请实施例1中扣式电池的正极极片在首次充放电后的XRD(X射线衍射)图谱；
图2为本申请的实施例1中Li 2NiO 2材料在处理前和处理后的XRD图谱。
具体实施方式
为使本申请的目的、技术方案、及优点更加清楚明白，以下参照附图和实施例，对本申请进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。本领域普通技术人员基于本申请所获得的所有其他实施例，都属于本申请保护的范围。
需要说明的是，本申请的具体实施方式中，以锂离子电池作为电化学装置的例子来解释本申请，但是本申请的电化学装置并不仅限于锂离子电池。
图1示出了本申请实施例1中扣式电池的正极极片在首次充放电后的XRD衍射图谱。其中，图1中的(a)为正极极片首次充放电后的图谱，图1中的(b)为NiO标准卡片。如图1所示，在36°至38°处出现衍射峰A，在42°至44°处出现衍射峰B，在62°至64°处出现衍射峰C。衍射峰A、衍射峰B、衍射峰C对应岩盐相NiO的衍射峰，表明本申请的正极极片在首次充放电后存在氧化镍。
图2示出了本申请的实施例1中Li 2NiO 2材料在处理前和处理后的XRD图谱。其中，图2中的(c)为利用丙二酸对Li 2NiO 2处理后的图谱；图2中的(d)为丙二酸二锂的图谱；图2中的(e)为未处理的Li 2NiO 2的图谱。可以看出，利用丙二酸处理Li 2NiO 2后，所得到的正极补锂材料的XRD图谱中出现了丙二酸二锂的峰位，说明丙二酸与Li 2NiO 2表面的游离锂杂质原位反应生成了一层丙二酸二锂保护层。
实施例
以下，举出实施例及对比例来对本申请的实施方式进行更具体地说明。各种的试验及评价按照下述的方法进行。另外，只要无特别说明，“份”、“％”为质量基准。
测试方法和设备：
正极补锂材料Dv50测试：
使用激光粒度仪测试正极补锂材料的Dv50。
比表面积测试：
在恒温低温(-199℃至-193℃)下，测定不同相对压力时的气体在固体表面的吸附量后，基于布朗诺尔-埃特-泰勒吸附理论及其公式(BET公式)求得试样单分子层吸附量，从而计算出正极补锂材料的比表面积。
BET公式：
Figure PCTCN2021083357-appb-000001
其中：W---相对压力(P/P0)下固体样品所吸附的气体的质量，单位cm 3/g；
Wm---铺满一单分子层的气体饱和吸附量，单位cm 3/g；
C---与第一层吸附热和凝聚热有关的常数；
斜率：(C-1)/(WmC)，截距：1/WmC，总表面积：St＝(Wm×N×Acs/M)；
比表面积：S＝St/m，其中m为样品质量，Acs：每个N 2分子的所占据的平均面积16.2A 2。
称取1.5g至3.5g粉末样品装入比表面积和孔隙度分析仪(型号TriStar II 3020)的测试测试样品管中，于200℃脱气120min后进行测试。
充电比容量测试：
本申请采用武汉蓝电CT2001A系统进行充电比容量测试，将含有正极补锂材料的待测扣式电池在25±3℃环境中静置30分钟，以0.1C(理论克容量以400mAh/g计)的倍率恒流充电至电压为4.4V，随后恒压充电至电流为0.025C，记录充电容量。
正极补锂材料的充电比容量＝充电容量/补锂材料的质量。
游离锂测试：
采用GB/T 9725-2007化学试剂电位滴定法通则，对材料中的游离碳酸根和游离氢氧根进行测定，其百分质量含量分别记录为m(Li 2CO 3)和m(LiOH)。
总游离锂含量m(Li +)＝[2×m(Li 2CO 3)/73.89+m(LiOH)/23.95]×6.94。
高温存储性能测试：
本申请采用TEMP 850高低温实验箱对电池进行高温存储性能测试，首先测试并记录电池满充后的初始厚度d 0，将锂离子电池放置在85℃的高低温箱中存储24h，测试并记录电池的厚度d 1，计算(d 1-d 0)/d 0并记录。
实施例1
<正极补锂材料的制备>
将NiO和Li 2O按照质量比1:1在氩气中混合，球磨24h，得到混合物。将混合物压制成粒料。将粒料放入填充有氩气的镍管中，在650℃下加热24h，得到富锂的过渡金属氧化物Li 2NiO 2。
将Li 2NiO 2分散于无水乙醇中，基于100wt％Li 2NiO 2的质量，然后添加3.1wt％丙二酸，磁力搅拌使其混合均匀，抽滤并烘干，得到正极补锂材料Li 2NiO 2·Li 2C 3H 2O 4。其中，正极补锂材料的平均粒径Dv50为14μm、比表面积为0.5m 2/g，表层中Li 2C 3H 2O 4的质量百分含量为3％。
<正极极片的制备>
将正极活性材料钴酸锂(LiCoO 2)、上述制备得到的正极补锂材料Li 2NiO 2·Li 2C 3H 2O 4、导电剂纳米导电炭黑、粘结剂PVDF按照质量比92.5:5.0:1.0:1.5进行混合，加入NMP作为溶剂，调配成为固含量为75％的浆料，并搅拌均匀。将浆料均匀涂覆在厚度为10μm的正极集流体铝箔的一个表面上，130℃条件下烘干，得到涂层厚度为110μm的正极极片。以上步骤完成后，即完成正极极片的单面涂布。之后，在该正极极片的另一个表面上重复以上步骤，即得到双面涂布正极活性材料的正极极片。涂布完成后，将正极极片裁切成74mm×867mm的规格并焊接极耳待用。
<负极极片的制备>
将负极活性材料石墨、纳米导电炭黑、丁苯橡胶和羧甲基纤维素钠按照质量比95︰2︰2︰1进行混合，加入去离子水作为溶剂，调配成为固含量为70％的浆料，并搅拌均匀。将浆料均匀涂覆在集流体铜箔上，110℃条件下烘干，冷压后得到活性材料层厚度为150μm的单面涂覆活性材料层的负极极片。以上步骤完成后，采用同样的方法在该负极极片背面也完成这些步骤，即得到双面涂布完成的负极极片。涂布完成后，将负极极片裁切成 76mm×851mm的规格并焊接极耳待用。
<电解液的制备>
在干燥氩气气氛中，将有机溶剂碳酸乙烯酯、碳酸甲乙酯和碳酸二乙酯以质量比EC︰EMC︰DEC＝30︰50︰20混合得到有机溶液，然后向有机溶剂中加入锂盐六氟磷酸锂溶解并混合均匀，得到锂盐的浓度为1.15mol/L的电解液。
<隔离膜的制备>
采用厚度为14μm的聚丙烯(PP)薄膜(Celgard公司提供)。
<锂离子电池的制备>
将上述制备的正极、隔离膜、负极按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到电极组件。将电极组件装入铝塑膜包装袋中，并在80℃下脱去水分，注入配好的电解液，经过真空封装、静置、化成、整形等工序得到锂离子电池。
<扣式电池的制备>
将上述制备得到的正极补锂材料Li 2NiO 2·Li 2C 3H 2O 4、导电剂导电炭黑和粘结剂PVDF按照质量比90:5:5进行混合，加入NMP作为溶剂，经过搅拌调配成为固含量为40％的浆料，利用刮刀在正极集流体铝箔上涂覆100μm厚度的涂层，130℃下经过12h真空干燥箱烘干后，利用冲压机在干燥环境中切成直径为1cm的圆片(即正极极片)，在手套箱中以金属锂片作为对电极，隔离膜选择上述制备得到的隔离膜，加入上述制备得到的电解液组装得到扣式电池。
实施例2、实施例3、实施例4、实施例5、实施例6、实施例7、实施例8、实施例9、实施例10、实施例11、实施例12、实施例13、实施例14、实施例15和实施例16中，<正极补锂材料的制备>、<正极极片的制备>、<负极极片的制备>、<电解液的制备>、<隔离膜的制备>、<锂离子电池的制备>及<扣式电池的制备>的制备步骤均与实施例1相同，相关制备参数的变化如表1中所示：
表1
Figure PCTCN2021083357-appb-000002
在对比例1、对比例2、对比例3、对比例4和对比例5中，<正极极片的制备>、<负极极片的制备>、<电解液的制备>、<隔离膜的制备>及<锂离子电池的制备>的制备步骤均与实施例1相同，在对比例4和对比例5中，<正极补锂材料的制备>与实施例1相同，相关制备参数的变化如表2中所示：
表2
Figure PCTCN2021083357-appb-000003
Figure PCTCN2021083357-appb-000004
注：表2中的“/”表示不存在该对应制备参数。
实施例1、实施例2、实施例3、实施例4、实施例5、实施例6、实施例7、实施例8、实施例912、实施例13、实施例14、实施例15、实施例16、对比例1、对比例2、对比例3、对比例4、对3所示：
表3
Figure PCTCN2021083357-appb-000005
Figure PCTCN2021083357-appb-000006
注：表3中的“/”表示不存在该对应制备参数。
从实施例1、实施例2、实施例3、实施例4、实施例5、实施例6、实施例7、实施例8、实施例9和对比例1、对比例4、对比例5可以看出，利用不同的有机酸和不同的有机溶剂对相同富锂的过渡金属氧化物进行处理，都可以有效降低其表面的活性锂含量，抑制浆料凝浆，改善加工性能，降低高温存储产气。其中，从实施例1、实施例2、实施例3、实施例4和对比例1、对比例4、对比例5可以看出，Li 2NiO 2表面的活性锂离子含量m(Li +)随着丙二酸浓度的变化而变化，在本申请范围内的较高浓度的丙二酸对Li 2NiO 2的残锂含量的降低效果更为显著。并且，对比例1中将未经处理的Li 2NiO 2补锂材料加入正极浆料中，在调浆过程中浆料颗粒发生了团聚，如果浆料待料时间进一步延长，则会出现凝胶导致无法涂布。从实施例1、实施例2、实施例3、实施例4和对比例4、对比例5可以看出，表层中有机酸锂的质量百分含量在本申请范围内，不仅能够有效提升正极补锂材料材料的首次充电比容量，而且可以有效改善锂离子电池在高温存储下的厚度膨胀比例。
从实施例1、实施例5、实施例6、实施例7、实施例8、实施例9可以看出，选择不同的有机酸，则表层的有机酸锂随之变化，但其均能有效降低内核材料表面游离锂的含量，能够有效抑制浆料凝胶，能够降低锂离子电池高温存储产气的问题，使锂离子电池在高温存储下厚度膨胀比例明显降低。
从实施例1、实施例10、实施例11、实施例12、实施例13、实施例14和对比例1、对比例2、对比例3可以看出，有机酸对不同的富锂的过渡金属氧化物处理后，富锂的过渡金属氧化物表面游离锂的含量得到了显著降低，将其加入正极浆料后，在整个调浆过程中浆料状况未出现异常，还能够明显改善锂离子电池在高温下的存储性能。
正极补锂材料的Dv50和比表面积的变化通常也会影响本申请的正极补锂材料表面游离锂的含量。从实施例1、实施例15、实施例16可以看出，只要使得正极补锂材料的Dv50和比表面积在本申请范围内，就能够进一步降低内核材料表面游离锂的含量，抑制浆料凝胶。
综合上述分析可知，本申请提供的正极补锂材料，包括富锂过渡金属氧化物Li 2MO 2的内核、及存在于该内核上的有机酸锂Li wC xH yO z表层，不仅能实现活性锂地补充，有效提升电化学装置的能量密度，而且能够有效抑制调浆过程中的凝胶现象，改善加工性能，使电化学装置的高温存储性能得到有效改善。
以上所述仅为本申请的较佳实施例，并不用以限制本申请，凡在本申请的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本申请保护的范围之内。

Claims (10)

  1. 一种正极补锂材料，其包括富锂的过渡金属氧化物Li 2MO 2的内核、及存在于所述内核上的表层，所述表层包括有机酸锂Li wC xH yO z，其中，M包括Mn、Fe、Co、Ni或Cu中的至少一种，Li wC xH yO z中包括至少一个-COOLi基团，1≤w≤3，1≤x≤6，0≤y≤8，2≤z≤7。
  2. 根据权利要求1所述的正极补锂材料，其中，基于所述正极补锂材料的总质量，所述表层中的有机酸锂Li wC xH yO z的质量百分含量为0.5％至5％。
  3. 根据权利要求1所述的正极补锂材料，其中，所述正极补锂材料的平均粒径Dv50为3μm至25μm。
  4. 根据权利要求1所述的正极补锂材料，其中，所述正极补锂材料的比表面积为0.1m 2/g至30m 2/g。
  5. 根据权利要求1所述的正极补锂材料，其中，所述正极补锂材料的首次充电比容量≥350mAh/g。
  6. 根据权利要求1所述的正极补锂材料，其中，所述富锂的过渡金属氧化物包括Li 2NiO 2、Li 2CuO 2或Li 2Ni 0.5Cu 0.5O 2中的至少一种。
  7. 一种正极极片，其包括权利要求1至6中任一项所述的正极补锂材料。
  8. 根据权利要求7所述的正极极片，其中，所述正极极片首次充放电后的XRD衍射图谱中，在36°至38°处出现衍射峰A，在42°至44°处出现衍射峰B，在62°至64°处出现衍射峰C。
  9. 一种电化学装置，其包括权利要求7或8所述的正极极片。
  10. 一种电子装置，其包括权利要求9所述的电化学装置。
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