WO2022205135A1 - 一种负极极片、包含该负极极片的锂金属电池和电子装置 - Google Patents

一种负极极片、包含该负极极片的锂金属电池和电子装置 Download PDF

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Publication number
WO2022205135A1
WO2022205135A1 PCT/CN2021/084577 CN2021084577W WO2022205135A1 WO 2022205135 A1 WO2022205135 A1 WO 2022205135A1 CN 2021084577 W CN2021084577 W CN 2021084577W WO 2022205135 A1 WO2022205135 A1 WO 2022205135A1
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Prior art keywords
piezoelectric
negative electrode
piezoelectric layer
lithium
layer
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PCT/CN2021/084577
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English (en)
French (fr)
Inventor
关文浩
陈茂华
谢远森
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to CN202180004984.9A priority Critical patent/CN114287071B/zh
Priority to PCT/CN2021/084577 priority patent/WO2022205135A1/zh
Priority to EP21867903.3A priority patent/EP4089758A4/en
Priority to US17/709,023 priority patent/US20220320522A1/en
Publication of WO2022205135A1 publication Critical patent/WO2022205135A1/zh
Anticipated expiration legal-status Critical
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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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/664—Ceramic materials
    • 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
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—Lithium
    • 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
    • H01M2004/027—Negative electrodes
    • 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
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of lithium metal batteries, and in particular, to a negative electrode pole piece, a lithium metal battery and an electronic device comprising the negative electrode pole piece.
  • Lithium metal is the metal with the smallest relative atomic mass (6.94) and the lowest standard electrode potential (-3.045V) among all metal elements, and its theoretical gram capacity can reach 3860mAh/g. Therefore, using lithium metal as the negative electrode of the battery, with some high energy density positive electrode materials, can greatly improve the energy density of the battery and the working voltage of the battery. However, if batteries with lithium metal as anode material are truly commercialized, the cycle life and safety issues must be improved: 1) During the charging process of lithium metal batteries, lithium deposits on the surface of the anode current collector.
  • lithium ions cannot nucleate uniformly and rapidly, resulting in uneven lithium ion concentration at the anode/electrolyte interface, resulting in uneven current density distribution at the interface, resulting in excessively fast deposition at the nucleation site.
  • the formation perpendicular to the surface of the anode is formed.
  • the inhomogeneous liquid electric convection caused by the deposition of Li metal in the direction perpendicular to the current collector is faster than that in the direction parallel to the current collector, which is also an important factor for the formation of Li dendrite structure; 3)
  • the consumption of Li ions The speed is far less than the mass transfer speed in the electrolyte, which leads to the accumulation of lithium ions on the dendrite surface, forming a huge space charge layer and deposition barrier, which hinders the deposition of lithium ions at the root of the dendrite and makes the lithium dendrite sharper.
  • Sharp Li dendrites may pierce the separator and directly contact the positive electrode to form a short circuit, causing serious safety problems.
  • the purpose of the present application is to provide a negative pole piece, a lithium metal battery including the negative pole piece, and an electronic device, so as to improve the cycle performance and safety performance of the lithium metal battery.
  • a first aspect of the present application provides a negative electrode piece, which includes a negative electrode current collector and a piezoelectric layer, the piezoelectric layer has a polarized electric field, and the direction of the polarized electric field is directed from the negative electrode current collector to an opposite direction.
  • the surface of the negative electrode, and the material of the piezoelectric layer includes at least one of piezoelectric polymers, piezoelectric ceramics, piezoelectric single crystals or inorganic piezoelectric materials.
  • the piezoelectric layer is polarized so that the direction of the polarized electric field is directed from the negative electrode current collector to the surface of the negative electrode.
  • the ordered polarized electric field constructed inside it is in the macroscopic
  • the surface of the negative electrode can be negatively charged, thereby increasing the deposition site of lithium metal, reducing the overpotential of lithium deposition, and making the distribution of lithium crystal nuclei more uniform; microscopically, the newly deposited lithium metal during charging will bring deformation to the piezoelectric layer , Li metal deposition brings strain while producing piezoelectric effect, reducing the polarization strength of piezoelectric layer material, increasing the potential at the deposition site, inducing subsequent lithium ions to preferentially deposit in the undeposited place, forming planar growth, thereby improving lithium ion Deposition morphology and inhibition of lithium dendrites.
  • strain refers to the local relative deformation of an object under the action of external force or non-uniform temperature field.
  • deposition overpotential refers to the overpotential that provides the thermodynamic energy for lithium metal nucleation deposition.
  • the material of the piezoelectric layer includes at least one of piezoelectric polymer, piezoelectric ceramic, piezoelectric single crystal or inorganic piezoelectric material.
  • a piezoelectric layer with piezoelectric effect is prepared by selecting the above-mentioned materials, so that a polarized electric field exists inside the piezoelectric layer, so as to induce orderly deposition of lithium metal in the direction of the electric field, thereby preventing the generation of lithium dendrites.
  • the material of the piezoelectric layer can be an elastic material, and the material of the elastic piezoelectric layer can buffer the volume change of the lithium metal negative electrode to a certain extent, thereby protecting the negative electrode.
  • the material of the piezoelectric layer includes any one of piezoelectric polymer, piezoelectric ceramic, piezoelectric single crystal or inorganic piezoelectric material, so that the material of the piezoelectric layer has consistency, and the electric field distribution inside the piezoelectric layer more uniform, so that the lithium deposition is more uniform, and the growth of lithium dendrites can be suppressed more effectively.
  • piezoelectric effect means that when some dielectrics are deformed by an external force in a certain direction, polarization will be generated inside them, and positive and negative will appear on its two opposite surfaces at the same time. opposite charge.
  • the negative electrode piece provided by the present application includes a negative electrode current collector and a piezoelectric layer, the piezoelectric layer has a polarized electric field, and the direction of the polarized electric field is from the negative electrode current collector to the surface of the negative electrode.
  • the material includes at least one of piezoelectric polymers, piezoelectric ceramics, piezoelectric single crystals, or inorganic piezoelectric materials.
  • the negative electrode plate can increase the deposition sites of lithium metal, improve the deposition morphology, effectively inhibit the growth of lithium dendrites, greatly improve the cycle performance of lithium metal batteries, and avoid the existence of sharp lithium dendrites to pierce the separator and directly connect with The positive contact forms a short circuit, which improves the safety performance of the lithium metal battery.
  • the intensity Ec of the coercive field at room temperature of the material of the piezoelectric layer satisfies: 0kV/mm ⁇ Ec ⁇ 100kV/mm.
  • the lower limit value of the strength Ec of the room temperature coercive field may be included in the following values: 1kV/mm, 10kV/mm, 20kV/mm, 30kV/mm or 40kV/mm;
  • the upper limit value of the strength Ec of the room temperature coercive field Can be included in the following values: 50kV/mm, 60kV/mm, 70kV/mm, 80kV/mm, 90kV/mm or 99kV/mm.
  • the room temperature coercive field strength Ec of the material of the piezoelectric layer is too high (for example, higher than 100kV/mm), the requirements for the piezoelectric material are too high, the available materials are few, and the material polarization voltage is high, which is difficult. large, and will not significantly further improve battery performance, it is not suitable for practical applications.
  • the term "room temperature coercive field” refers to the electric field strength at which the material is in an electric field at room temperature so that the polarization disappears.
  • the intensity of the polarization electric field is selected according to the intensity Ec of the room temperature coercive field of the material of the piezoelectric layer, and the intensity of the polarization electric field is preferably room temperature coercive field.
  • the strength of the coercive field is 0.1 to 6 times that of Ec.
  • the lower limit value of the intensity of the polarization electric field may include the following values: 0.1 times, 1 time, 2 times, 2.9 times or 3 times the intensity Ec of the coercive field at room temperature;
  • the upper limit value of the intensity of the polarization electric field may be Included in the following values: 4 times, 5 times or 6 times the intensity Ec of the coercive field at room temperature.
  • the intensity of the polarization electric field is too low (for example, lower than 0.1 times the intensity Ec of the coercive field at room temperature), the polarization electric field cannot be generated inside the piezoelectric layer; if the intensity of the polarization electric field is too high (for example, Higher than 6 times the strength Ec of the coercive field at room temperature), material breakdown of the piezoelectric layer will occur and cause it to fail.
  • the intensity of the polarization electric field within the above range, an ordered polarization electric field in a specific direction can be formed inside the piezoelectric layer, so that the surface of the negative electrode is negatively charged, and the lithiophilic property of the negative electrode is improved.
  • the electrical effect increases the potential of the deposition site, induces the deposition of lithium ions to the undeposited site, improves the lithium deposition morphology, and inhibits the growth of lithium dendrites.
  • piezoelectric polymers may include polyvinylidene fluoride (PVDF), vinylidene fluoride/trifluoroethylene copolymers, vinylidene fluoride/tetrafluoroethylene copolymers, vinylidene cyanide/vinyl acetate copolymers (P(VDCN) -VAC)), vinylidene cyanide/vinyl benzoate copolymer (P(VDCN-VBz)), vinylidene cyanide/vinyl propionate copolymer (P(VDCN-VPr)), vinylidene cyanide /Vinyl pivalate copolymer (P(VDCN-VPiv)), vinylidene cyanide/methyl methacrylate copolymer (P(VDCN-MMA)), vinylidene
  • PVDF polyvinylidene fluoride
  • PVDCN vinylidene fluoride/trifluoroethylene copolymers
  • piezoelectric ceramics are not particularly limited, as long as the purpose of the present application can be achieved.
  • piezoelectric ceramics may include barium titanate (BaTiO 3 ), lead titanate (PbTiO 3 ), lithium niobate (LiNbO 3 ), lithium tantalate (LiNbO 3 ), lead titanate zirconate PbZry Ti 1-y O 3.
  • the type of piezoelectric single crystal is not particularly limited, as long as the purpose of the present application can be achieved.
  • the piezoelectric single crystal may include quartz single crystal, tellurium oxide crystal, bismuth germanate single crystal (Bi 12 GeO 20 ), lithium iodate single crystal (LiIO 3 ), aluminum orthophosphate single crystal (AlPO 4 ), silicic acid Lanthanum gallium single crystal (La 3 Ga 5 SiO 14 ), barium titanate single crystal (BaTiO 3 ) or lead zirconate titanate single crystal PbZre Ti 1-e O 3 , etc., wherein 0 ⁇ e ⁇ 1.
  • the type of the inorganic piezoelectric material is not particularly limited, as long as the purpose of the present application can be achieved.
  • the inorganic piezoelectric material may include at least one of metal oxides, nitrides, carbides, or intermetallic compounds.
  • the inorganic piezoelectric material may include at least one of metal oxides, nitrides, carbides or intermetallic compounds having piezoelectric properties, for example, the metal oxides may include zinc oxide, bismuth oxide, cobalt oxide, oxide Lead, nickel oxide, chromium oxide or antimony oxide, etc.
  • Nitride may include aluminum nitride (AlN), aluminum gallium nitride (AlGaN), aluminum indium nitride (InAlN), gallium nitride (GaN), indium gallium nitride (InGaN) or indium nitride (InN), etc.
  • carbides include silicon carbide (SiC), etc.
  • intermetallic compounds include titanium trialuminum (Ti 3 Al) or titanium aluminum (TiAl) intermetallic compounds, and the like.
  • the piezoelectric layer includes a powder piezoelectric layer, and the powder piezoelectric layer has a thickness of 0.1 ⁇ m to 5 ⁇ m.
  • the lower limit value of the thickness of the powder piezoelectric layer may be included in the following values: 0.1 ⁇ m, 0.2 ⁇ m, 0.5 ⁇ m, 1 ⁇ m or 2 ⁇ m; the upper limit value of the thickness of the powder piezoelectric layer may be included in the following values: 3 ⁇ m, 4 ⁇ m , 4.5 ⁇ m, 4.8 ⁇ m or 5 ⁇ m.
  • the present application can improve the cycle performance and safety performance of the lithium metal battery by controlling the thickness of the powder piezoelectric layer within the above range.
  • the powder piezoelectric layer is composed of a powder piezoelectric material and a conductive material, the mass percentage of the powder piezoelectric material is 50 to 100%, and the mass percentage of the conductive material is 0 to 50%.
  • the piezoelectric materials in this application are mostly electronic insulators, which are not conducive to the uniform dispersion of the current on the surface of the current collector. Therefore, it is necessary to control the ratio of piezoelectric materials to conductive materials. And the mass percentage of the conductive material is controlled within the above range, which can disperse lithium ions and electrons at the same time, and achieve the purpose of inhibiting the growth of lithium dendrites.
  • the powder piezoelectric material includes at least one of the powder of the piezoelectric polymer, the powder of the piezoelectric ceramic, or the powder of the piezoelectric single crystal;
  • the conductive material includes at least one of conductive carbon powder or conductive metal powder.
  • the application does not limit the type of conductive material, as long as the purpose of the application can be achieved, for example, the conductive material may include at least one of acetylene black (AB), conductive carbon black (Super P) or Ketjen black .
  • the piezoelectric layer comprises a thin film piezoelectric layer; the thickness of the thin film piezoelectric layer is 5 ⁇ m to 200 ⁇ m, preferably 50 ⁇ m to 100 ⁇ m.
  • the lower limit value of the thickness of the thin film piezoelectric layer may be included in the following values: 5 ⁇ m, 10 ⁇ m, 20 ⁇ m, 50 ⁇ m or 100 ⁇ m; the upper limit value of the thickness of the thin film piezoelectric layer may be included in the following values: 110 ⁇ m, 130 ⁇ m, 150 ⁇ m, 180 ⁇ m or 200 ⁇ m.
  • the present application can improve the cycle performance and safety performance of the lithium metal battery by controlling the thickness of the thin film piezoelectric layer within the above range. Using the thin film piezoelectric layer with the thickness in the above preferred range has a better effect on improving the cycle performance and safety performance of the lithium metal battery.
  • the thin film piezoelectric layer includes a thin film piezoelectric material
  • the thin film piezoelectric material includes a piezoelectric polymer film, a piezoelectric ceramic film, a piezoelectric single crystal film, or an inorganic film. At least one of piezoelectric material films.
  • the inorganic piezoelectric material thin film may also include thin films or single crystal flakes prepared from the above piezoelectric ceramics.
  • PVDF powder and acetylene black can be dispersed in N-methylpyrrolidone (NMP), coated on the surface of the negative electrode current collector using a doctor blade, in a vacuum drying oven at 75 to 85°C
  • NMP N-methylpyrrolidone
  • the negative electrode pole piece obtained after drying includes a powder piezoelectric layer located on the surface of the negative electrode current collector.
  • the present application has no particular limitation on the preparation of the thin film piezoelectric layer.
  • the PVDF powder is put into 160 to 200 mL of anhydrous ethanol and 110 to 130 mL of a mixed solvent of NMP, stirred at 65 to 75° C. for 1.5 to 2.5 hours, and then placed in an ultrasonic cleaner, Connect the vacuum pump, pump ultrasonically for 8 to 12 minutes, and keep the temperature at 65 to 75 °C for 15 to 25 minutes to obtain a transparent and uniform solution.
  • the slit width is determined, and the prepared PVDF film is peeled off from the polyester film tape to obtain a film piezoelectric layer.
  • the piezoelectric layer is located on the surface of the negative electrode current collector; or between the negative electrode current collector and the negative electrode material layer, or on the outer surface of the negative electrode material layer; or the piezoelectric layer It is mixed with the negative electrode material layer and is located on the surface of the negative electrode current collector.
  • the negative electrode piece in this application may include a negative electrode material layer, or may not include a negative electrode material layer. It can be understood that when the negative electrode material layer is not included, the piezoelectric layer is located on the surface of the negative electrode current collector, and the piezoelectric layer can be uniformly Covered on the surface of the negative electrode current collector, the negative electrode current collector covered with the piezoelectric layer is directly used as the negative electrode pole piece.
  • the piezoelectric layer can evenly cover the surface of the negative electrode current collector, and is located between the negative electrode current collector and the negative electrode material layer; or the piezoelectric layer can evenly cover On the outer surface of the negative electrode material layer, located on the outer surface of the negative electrode material layer, between the negative electrode and the electrolyte; or the piezoelectric layer can be uniformly mixed with the negative electrode material layer, and then evenly covered on the surface of the negative electrode current collector, located at The surface of the negative current collector.
  • the negative electrode piece of the present application includes a negative electrode current collector and a piezoelectric layer.
  • the negative electrode current collector is not particularly limited as long as it can achieve the purpose of the present application.
  • it includes copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, foamed copper or composite current collector.
  • the negative electrode sheet in the present application further includes a negative electrode material layer
  • the negative electrode material layer may include lithium metal or a composite material containing lithium metal.
  • the negative electrode sheet in the present application may further include 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 present application has no particular limitations on the conductive agent and the binder, as long as the purpose of the present application can be achieved.
  • the piezoelectric layer can uniformly cover the surface of the negative electrode current collector and be located between the negative electrode current collector and the conductive layer; or the piezoelectric layer can be interposed between the conductive layer between the negative electrode material layer and the negative electrode material layer; or the piezoelectric layer can be uniformly covered on the outer surface of the negative electrode material layer, located on the outer surface of the negative electrode material layer, between the negative electrode and the electrolyte; or the piezoelectric layer can be combined with The negative electrode material layer is uniformly mixed, and then uniformly covers the surface of the negative electrode current collector, and is located on the surface of the negative electrode current collector.
  • a second aspect of the present application provides a lithium metal battery, which includes the negative electrode plate provided in the first aspect of the present application.
  • the negative pole piece in the lithium metal battery of the present application adopts the negative pole piece provided by the present application, and other components, including the positive pole piece, the separator and the electrolyte, are not particularly limited, as long as the purpose of the present application can be achieved. Can.
  • 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.
  • 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 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 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 metal battery of the present application further includes an electrolyte, and the electrolyte may be at least one 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, LiTFSI or lithium difluoroborate.
  • LiTFSI can be chosen as a lithium salt because it can give high ionic conductivity and improve cycling characteristics.
  • the non-aqueous solvent may be at least one of carbonate compounds, carboxylate compounds, ether compounds or other organic solvents.
  • 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 compound 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, At least one of formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate or phosphate ester.
  • the preparation process of lithium metal batteries is well known to those skilled in the art, and there is no particular limitation in this application.
  • it can be manufactured by the following process: the positive electrode and the negative electrode are overlapped through the separator, and after being stacked, the four corners of the entire laminated structure are fixed with adhesive tape, and then placed in the aluminum plastic film. After encapsulation, a lithium metal laminated battery is finally obtained.
  • the negative electrode used therein is the negative electrode pole piece provided in this application.
  • a third aspect of the present application provides an electronic device comprising the lithium metal battery provided in the second aspect of the present application.
  • 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, video recorders , LCD TV, Portable Cleaner, Portable CD Player, Mini Disc, Transceiver, Electronic Notepad, Calculator, Memory Card, Portable Recorder, Radio, Backup Power, Motor, Automobile, motorcycle, Power-assisted Bicycle, Bicycle, Lighting Appliances, toys, game consoles, clocks, power tools, flashlights, cameras and large household batteries, etc.
  • the application provides a negative electrode piece, a lithium metal battery and an electronic device including the negative electrode piece, the negative electrode piece includes a negative electrode current collector and a piezoelectric layer, the piezoelectric layer has a polarization electric field, and the direction of the polarization electric field is From the negative electrode current collector to the surface of the negative electrode, the material of the piezoelectric layer includes at least one of piezoelectric polymers, piezoelectric ceramics, piezoelectric single crystals or inorganic piezoelectric materials.
  • the negative electrode plate can control the lithium deposition site, effectively inhibit the growth of lithium dendrites, and significantly improve the cycle performance and safety performance of the lithium metal battery.
  • a lithium metal battery is assembled with a lithium metal or current collector with a piezoelectric layer as the positive electrode and pure lithium metal as the negative electrode.
  • the separator and electrolyte are the same as the battery used for cycling.
  • the lithium metal battery was galvanostatic discharge at a current density of 0.3 mA/cm 2 at 25°C, and the voltage versus time curve was recorded. The absolute difference between the peak voltage and the stable voltage was the lithium metal deposition overpotential.
  • the lithium metal battery is turned into a circle with a charge rate of 0.1C and a discharge rate of 0.1C at 25°C. Then, at a test temperature of 25°C, it is charged to 4.3V with a constant current of 0.3C, and then charged to a constant voltage of 0.05C. Discharge to 2.8V at 1C after standing for 5 minutes. The capacity obtained in this step was taken as the initial capacity, and 0.3C charge/1C discharge was carried out for cycle test, and the capacity decay curve was obtained by taking the ratio of the capacity in each step to the initial capacity. The cycle performance of the lithium metal battery at room temperature was recorded as the number of cycles from 25°C until the capacity retention rate was 80%.
  • Disperse PVDF powder and acetylene black (AB) with a mass ratio of 95:5 in NMP prepare a slurry with a solid content of 12%, mix PVDF and AB evenly by stirring, and apply the slurry to a thickness of
  • the surface of the 10 ⁇ m negative electrode current collector copper foil was dried in a vacuum drying oven at 80° C. to obtain a negative electrode pole piece with a powder piezoelectric layer thickness of 3 ⁇ m.
  • the negative pole piece prepared above is placed in a parallel electric field for air polarization, the polarization electric field is 10kV/mm, the polarization time is 30min, the piezoelectric layer faces the negative voltage side, and the negative electrode current collector faces the positive voltage side. After the polarization is completed, cut the negative pole piece into a size of 40mm ⁇ 60mm for use. Among them, the intensity Ec of the coercive field at room temperature of PVDF is 50 kV/mm.
  • the positive active material lithium iron phosphate (LiFePO 4 ), the conductive agent conductive carbon black (Super P), and the binder PVDF are mixed according to the mass ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) is added as a solvent. It becomes a slurry with a solid content of 75%, and stirs it uniformly.
  • the slurry was uniformly coated on the positive electrode current collector aluminum foil with a thickness of 10 ⁇ m, and dried at 90° C. to obtain a positive electrode sheet with a positive electrode active material layer thickness of 100 ⁇ m coated on one side with a positive electrode active material layer. After the coating is completed, the positive pole piece is cut into a size of 38mm ⁇ 58mm for use.
  • LiTFSI lithium methanesulfonimide
  • Polyethylene (PE) with a thickness of 15 ⁇ m is selected as the separator, the above-prepared negative pole piece is placed in the middle, the upper and lower layers are respectively the positive pole piece coated on one side, and the separator between the positive pole piece and the negative pole piece is a separator. .
  • the four corners of the entire laminated structure are fixed with tape, and then placed in an aluminum-plastic film. After top-side sealing, liquid injection, and packaging, a lithium metal laminated battery is finally obtained.
  • PVDF powder into a round-bottomed flask containing 180 mL of anhydrous ethanol and 120 mL of NMP mixed solvent, and stir at 70 °C for 2 h. It was then placed in an ultrasonic cleaner, connected to a vacuum pump, ultrasonically pumped for 10 minutes, and kept at 70° C. for 20 minutes to obtain a transparent and uniform solution.
  • This solution was introduced into a casting machine equipped with a polyester film tape, and a PVDF film was prepared by casting, and the slit width of the doctor blade was adjusted, and the prepared PVDF film was peeled off from the polyester film tape with a thickness of 10 ⁇ m.
  • the above PVDF film was placed in a parallel electric field for air polarization, the polarization electric field was 10 kV/mm, the polarization time was 30 min, and the polarization electric field direction was constant.
  • the positive direction inside the PVDF film after polarization is attached to the copper foil side of the negative current collector to obtain a negative electrode piece with a film piezoelectric layer thickness of 10 ⁇ m, and the negative electrode piece is cut into 40mm ⁇ 60mm specifications for use.
  • Disperse PVDF powder and acetylene black (AB) with a mass ratio of 95:5 in NMP prepare a slurry with a solid content of 12%, mix PVDF and AB evenly by stirring, and use a scraper to coat the anode material layer lithium
  • the outer surface of the metal was dried in a vacuum drying oven at 80° C. for use, and a negative electrode pole piece with a powder piezoelectric layer thickness of 3 ⁇ m was obtained after drying.
  • the above-mentioned negative pole piece is placed in a parallel electric field for air polarization, the polarization electric field is 50kV/mm, the polarization time is 30min, and the piezoelectric layer faces the negative voltage side. After completion, cut the negative pole piece into 40mm ⁇ 60mm specifications for use.
  • Disperse PVDF powder and acetylene black (AB) with a mass ratio of 95:5 in NMP prepare a slurry with a solid content of 12%, mix PVDF and AB evenly by stirring, and use a scraper to coat the negative electrode current collector copper
  • the surface of the foil was dried at 80°C in a vacuum drying oven for use. After drying, a modified current collector with a powder piezoelectric layer thickness of 3 ⁇ m was obtained; Above the current collector, the pressure is 8t, and the negative pole piece is obtained.
  • the above-mentioned negative pole piece is placed in a parallel electric field for air polarization, the polarization electric field is 50kV/mm, the polarization time is 30min, and the piezoelectric layer faces the negative voltage side. After completion, cut the negative pole piece into 40mm ⁇ 60mm specifications for use.
  • Disperse PVDF powder and acetylene black (AB) with a mass ratio of 95:5 in NMP prepare a slurry with a solid content of 12%, mix PVDF and AB evenly by stirring, and use a scraper to coat the negative electrode current collector copper
  • the surface of the foil was dried at 80° C. in a vacuum drying oven for use, and a modified current collector with a powder piezoelectric layer thickness of 3 ⁇ m was obtained after drying.
  • Lithium is pre-supplied by electrochemical lithium supplementation, and the lithium source is a lithium sheet with a thickness of 0.05mm.
  • a 15 ⁇ m PE diaphragm is selected, and the modified current collector and lithium metal are placed on both sides of the diaphragm, wherein the piezoelectric layer part and the lithium metal part are both facing the diaphragm, and assembled into a lithium-replenishing battery for electrochemical lithium replenishment.
  • the electrolyte is the same as ⁇ electrolyte Preparation of liquid > the electrolyte in the middle, the lithium replenishment equipment is a 5V, 5mA device (brand: Landian, model: CT2001A), the lithium replenishment current is 0.2mA/cm 2 , the discharge is 15.5h, and the lithium replenishment amount is 3.1mAh/cm 2 . After the pre-replenishment of lithium is completed, a negative electrode pole piece containing lithium metal is obtained.
  • the above-mentioned negative pole piece is placed in a parallel electric field for air polarization, the polarization electric field is 50kV/mm, the polarization time is 30min, and the piezoelectric layer faces the negative voltage side. After completion, cut the negative pole piece into 40mm ⁇ 60mm specifications for use.
  • the negative pole piece prepared above is placed in a parallel electric field for air polarization, the polarization electric field is 0.1kV/mm, the polarization time is 30min, and the piezoelectric layer faces the negative voltage side. After the polarization is completed, cut the negative pole piece into a size of 40mm ⁇ 60mm for use.
  • PbO, ZrO 2 , TiO 2 with a molar ratio of 5:3:2 were placed in a high-energy planetary ball mill, 100 ml of ethanol was added as a ball milling aid, and the ball milled at a speed of 250 r/min for 30 hours to obtain lead titanate zirconate PbZr 0.6 Ti 0.4 O3 powder.
  • the PbZr 0.6 Ti 0.4 O 3 powder was dispersed in NMP, and the PbZr 0.6 Ti 0.4 O 3 powder was uniformly dispersed by stirring to obtain a slurry with a solid content of 12%.
  • the slurry was applied to the negative electrode current collector copper foil using a doctor blade. The surface was dried in a vacuum drying oven at 80°C for use, to obtain a negative electrode pole piece with a powder piezoelectric layer thickness of 3 ⁇ m.
  • the negative pole piece prepared above is placed in a parallel electric field for air polarization, the polarization electric field is 3kV/mm, the polarization time is 30min, and the piezoelectric layer faces the negative voltage side. After the polarization is completed, cut the negative pole piece into a size of 40mm ⁇ 60mm for use.
  • the above - mentioned BaTiO3 single wafer was placed in a parallel electric field for air polarization, the polarization electric field was 0.1 kV/mm, the polarization time was 30 min, and the polarization electric field direction was parallel to the thickness direction of the single wafer and kept constant.
  • the polarized BaTiO 3 single wafer is attached to the copper foil side of the negative current collector in the positive direction to obtain a negative electrode piece with a film piezoelectric layer thickness of 10 ⁇ m, and the negative electrode piece is cut into 40mm ⁇ 60mm specifications for use .
  • a nylon 7 film with a thickness of 10 ⁇ m (brand: Taiwan Chemical Fiber Co., Ltd., brand: NP4000) was placed in a parallel electric field for air polarization, the polarization electric field was 280kV/mm, the polarization time was 30min, and the direction of the polarization electric field was Parallel to the film thickness direction and held constant.
  • the polarized nylon 7 film is attached to the copper foil side of the negative current collector with the positive direction of the polarized film to obtain a negative electrode piece with a film piezoelectric layer thickness of 10 ⁇ m, and the negative electrode piece is cut into 40mm ⁇ 60mm specifications for use.
  • a single tellurium oxide crystal wafer with a thickness of 10 ⁇ m (brand: Beijing Wuke Optoelectronics Technology Co., Ltd., brand: TEO2) was placed in a parallel electric field for air polarization, the polarization electric field was 3kV/mm, and the polarization time was 30min. The direction of the electric field is parallel to the thickness direction of the single wafer and remains constant.
  • the polarized tellurium oxide crystal single wafer is attached to the copper foil side of the negative current collector in the positive direction to obtain a negative electrode piece with a film piezoelectric layer thickness of 10 ⁇ m, and the negative electrode piece is cut into a size of 40mm ⁇ 60mm. use.
  • the negative pole piece is a negative current collector copper foil, and the preparation steps of ⁇ preparation of positive pole piece>, ⁇ preparation of electrolyte> and ⁇ preparation of lithium metal battery> are the same as those in Example 1.
  • the negative pole piece is lithium metal, and the preparation steps of ⁇ preparation of positive pole piece>, ⁇ preparation of electrolyte> and ⁇ preparation of lithium metal battery> are the same as those in Example 1.
  • the thickness of the piezoelectric layer also generally affects the deposition overpotential and cycling performance of Li metal batteries. From Examples 2, 5-7, 10, 13-15, 21, 23-25, 29, 31-33, it can be seen that the thickness of the piezoelectric layer is within the scope of the application, and the deposition overpotential is low and the cycle performance can be obtained. Good lithium metal battery.
  • the negative electrode piece provided by this application includes a negative electrode current collector and a piezoelectric layer with a polarized electric field inside, and the direction of the polarized electric field is from the negative electrode current collector to the surface of the negative electrode.
  • the negative electrode plate can control the lithium deposition site, effectively inhibit the growth of lithium dendrites, and significantly improve the cycle performance and safety performance of the lithium metal battery.

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Abstract

本申请提供了一种负极极片、包含该负极极片的锂金属电池和电子装置，该负极极片包括负极集流体和压电层，压电层存在极化电场，极化电场的方向为从负极集流体指向负极的表面，压电层的材料包括压电聚合物、压电陶瓷、压电单晶或无机压电材料中的至少一种。该负极极片能够控制锂沉积位点，有效抑制锂枝晶的生长，使锂金属电池的循环性能和安全性能均得到明显提升。

Description

一种负极极片、包含该负极极片的锂金属电池和电子装置 技术领域
本申请涉及锂金属电池技术领域，具体涉及一种负极极片、包含该负极极片的锂金属电池和电子装置。
背景技术
锂金属是所有金属元素中相对原子质量最小(6.94)、标准电极电位(-3.045V)最低的金属，其理论克容量可达到3860mAh/g。因此，使用锂金属作为电池的负极，配合一些高能量密度的正极材料，可以大大提高电池的能量密度以及电池的工作电压。然而，如果锂金属作为负极材料的电池真正实现商业化，循环寿命和安全问题必须得到改善：1)锂金属电池在充电过程中，锂沉积在负极集流体表面。由于集流体亲锂性质弱，锂离子无法均匀、快速形核，导致负极/电解液界面处锂离子浓度不均匀，使得界面处电流密度分布不均匀，造成形核位点处沉积速度过快的现象，形成枝晶结构，严重限制了锂金属电池的效率、循环寿命和能量密度；2)在锂金属负极与电解液界面处，由于施加电场与锂离子流产生相互作用，形成垂直于负极表面的不均匀液体电对流，导致锂金属在垂直于集流体方向的沉积比平行于集流体方向更快，这也是锂枝晶结构形成的重要因素；3)在液态电解质体系中，锂离子的消耗速度远不及电解液中的传质速度，导致锂离子在枝晶表面堆积，形成巨大的空间电荷层和沉积势垒，阻碍锂离子在枝晶根部沉积，使锂枝晶更加尖锐。尖锐的锂枝晶可能会刺穿隔膜直接与正极接触形成短路，引发严重的安全问题。
基于上述问题，亟需寻找一种能够提高负极集流体亲锂性质、均匀化负极/电解液界面电流密度分布、抑制沉积锂表面空间电荷层产生的方法，抑制锂枝晶生长，以改善锂金属电池循环性能和安全性能。
发明内容
本申请的目的在于提供一种负极极片、包含该负极极片的锂金属电池及电子装置，以改善锂金属电池循环性能和安全性能。
本申请的第一方面提供了一种负极极片，其包括负极集流体和压电层，所述压电层存在极化电场，所述极化电场的方向为从所述负极集流体指向所述负极的表面，所述压电层的材料包括压电聚合物、压电陶瓷、压电单晶或无机压电材料中的至少一种。
在本申请中，对压电层进行极化，使极化电场的方向从负极集流体指向负极的表面， 经过定向极化处理的压电层，其内部构建的有序极化电场，在宏观上，可以使负极表面带负电，从而增加锂金属沉积位点，降低锂沉积过电位，使锂晶核分布更加均匀；在微观上，充电时新沉积的锂金属会给压电层带来形变，锂金属沉积带来应变的同时产生压电效应，降低压电层材料的极化强度，提高沉积位点处的电势，诱导后续锂离子优先沉积在未沉积处，形成平面生长，从而改善锂沉积形貌，抑制锂枝晶。本申请中，术语“应变”是指在外力或非均匀温度场等因素作用下物体局部的相对变形。本申请中，“沉积过电位”是指为锂金属形核沉积提供热力学能量的过电位。
在本申请中，压电层的材料包括压电聚合物、压电陶瓷、压电单晶或无机压电材料中的至少一种。通过选用上述材料制备出具有压电效应的压电层，使压电层内部存在极化电场，以利用电场方向诱导锂金属进行有序沉积，从而防止锂枝晶的产生。该压电层的材料可以为弹性材料，弹性的压电层的材料可以在一定程度上缓冲锂金属负极的体积变化，从而对负极起到保护作用。优选地，压电层的材料包括压电聚合物、压电陶瓷、压电单晶或无机压电材料中的任一种，使压电层的材料具有一致性，压电层内部的电场分布更加均匀，从而使锂沉积更加均匀，以更加有效地抑制锂枝晶的生长。在本申请中，术语“压电效应”是指，某些电介质在沿一定方向上受到外力的作用而变形时，其内部会产生极化现象，同时在它的两个相对表面上出现正负相反的电荷。
整体而言，本申请提供的负极极片，包括负极集流体和压电层，所述压电层存在极化电场，极化电场的方向为从负极集流体指向负极的表面，压电层的材料包括压电聚合物、压电陶瓷、压电单晶或无机压电材料中的至少一种。该负极极片能够增加锂金属沉积位点，改善沉积形貌，有效抑制锂枝晶的生长，大大提高锂金属电池的循环性能，并能避免存在尖锐的锂枝晶来刺穿隔离膜直接与正极接触形成短路，使锂金属电池的安全性能得到提升。
在本申请第一方面的一些实施方式中，所述压电层的材料的室温矫顽场的强度Ec满足：0kV/mm＜Ec＜100kV/mm。例如，室温矫顽场的强度Ec的下限值可以包括以下数值中：1kV/mm、10kV/mm、20kV/mm、30kV/mm或40kV/mm；室温矫顽场的强度Ec的上限值可以包括以下数值中：50kV/mm、60kV/mm、70kV/mm、80kV/mm、90kV/mm或99kV/mm。不限于任何理论，压电层的材料的室温矫顽场的强度Ec过高(例如高于100kV/mm)，对压电材料要求太高，可用的材料少，且材料极化电压高，难度大，并且不会明显进一步改善电池性能，不适用于实际应用。本申请中，术语“室温矫顽场”是指室温下材料在电场中使得极化消失的电场强度。
在本申请第一方面的一些实施方式中，本领域技术人员可以理解，极化电场的强度依据压电层的材料的室温矫顽场的强度Ec进行选择，极化电场的强度优选为室温矫顽场的强度Ec的0.1倍至6倍。例如，极化电场的强度的下限值可以包括以下数值中：室温矫顽场的强度Ec的0.1倍、1倍、2倍、2.9倍或3倍；极化电场的强度的上限值可以包括以下数值中：室温矫顽场的强度Ec的4倍、5倍或6倍。不限于任何理论，极化电场的强度过低(例如低于室温矫顽场的强度Ec的0.1倍)，将无法使压电层的内部产生极化电场；极化电场的强度过高(例如高于室温矫顽场的强度Ec的6倍)，将发生压电层的材料击穿使其失效。通过将极化电场的强度控制在上述范围内，能够使压电层的内部形成特定方向的有序极化电场，使负极表面带负电荷，提高负极亲锂性质，同时利用压电层的压电效应提升沉积处电势，诱导锂离子向未沉积处沉积，改善锂沉积形貌，抑制锂枝晶生长。
在本申请第一方面的一些实施方式中，对压电聚合物的种类没有特别限制，只要能实现本申请目的即可。例如，压电聚合物可以包括聚偏氟乙烯(PVDF)、偏氟乙烯/三氟乙烯共聚物、偏氟乙烯/四氟乙烯共聚物、亚乙烯基二氰/醋酸乙烯共聚物(P(VDCN-VAC))、亚乙烯基二氰/苯甲酸乙烯共聚物(P(VDCN-VBz))、亚乙烯基二氰/丙酸乙烯共聚物(P(VDCN-VPr))、亚乙烯基二氰/新戊酸乙烯共聚物(P(VDCN-VPiv))、亚乙烯基二氰/甲基丙烯酸甲酯共聚物(P(VDCN-MMA))、亚乙烯基二氰/异丁烯共聚物(P(VDCN-IB))或奇数尼龙系压电聚合物-(HN-(CH 2) x-CO-) n-等，其中，x为2至10中的偶数、n为90至400中的整数，当n大于400时，-(HN-(CH 2) x-CO-) n-的分子量过大，将使其加工难度急剧增大。在本申请中，对压电聚合物的重均分子量没有特别限制，本领域技术人员可以根据实际情况进行选择，只要能实现本申请目的即可。
在本申请第一方面的一些实施方式中，对压电陶瓷的种类没有特别限制，只要能实现本申请目的即可。例如，压电陶瓷可以包括钛酸钡(BaTiO 3)、钛酸铅(PbTiO 3)、铌酸锂(LiNbO 3)、钽酸锂(LiNbO 3)、钛锆酸铅PbZr yTi 1-yO 3、铌镁酸铅PbMg zNb 1-zO 3、铌锌酸铅PbZn vNb 1-vO 3、锰锑酸铅PbMn wSb 1-wO 3或Pb 1-sM m(Zr tTi 1-t) 1-(s/4)O 3等中的至少一种，其中，0＜y＜1，0＜z＜1，0＜v＜1，0＜w＜1，0＜s＜1，0＜m＜1，0＜t＜1，M选自稀土元素的任一种，所述稀土元素包括Y、La、Ce、Nd、Sm、Eu、Gd或Dy等。
在本申请第一方面的一些实施方式中，对压电单晶的种类没有特别限制，只要能实现本申请目的即可。例如，压电单晶可以包括石英单晶、氧化碲晶体、锗酸铋单晶(Bi 12GeO 20)、碘酸锂单晶(LiIO 3)、正磷酸铝单晶(AlPO 4)、硅酸镓镧单晶(La 3Ga 5SiO 14)、钛酸钡单晶(BaTiO 3) 或锆钛酸铅单晶PbZr eTi 1-eO 3等，其中，0＜e＜1。
在本申请第一方面的一些实施方式中，对无机压电材料的种类没有特别限制，只要能实现本申请目的即可。例如，无机压电材料可以包括金属氧化物、氮化物、碳化物或金属间化合物中的至少一种。具体地，无机压电材料可以包括具有压电性质的金属氧化物、氮化物、碳化物或金属间化合物中的至少一种，例如，金属氧化物可以包括氧化锌、氧化铋、氧化钴、氧化铅、氧化镍、氧化铬或氧化锑等，氮化物可以包括氮化铝(AlN)、氮化镓铝(AlGaN)、氮化铝铟(InAlN)、氮化镓(GaN)、氮化镓铟(InGaN)或氮化铟(InN)等，碳化物包括碳化硅(SiC)等，金属间化合物包括钛三铝基(Ti 3Al)或钛铝基(TiAl)金属间化合物等。
在本申请第一方面的一些实施方式中，所述压电层包括粉末压电层，所述粉末压电层的厚度为0.1μm至5μm。例如，粉末压电层的厚度的下限值可以包括以下数值中：0.1μm、0.2μm、0.5μm、1μm或2μm；粉末压电层的厚度的上限值可以包括以下数值中：3μm、4μm、4.5μm、4.8μm或5μm。发明人发现，当粉末压电层的厚度过小，粉末压电层过薄，其强度不够，易发生破裂，锂金属电池的安全性能受到影响；当粉末压电层的厚度过大，会降低锂金属电池的能量密度。本申请通过将粉末压电层的厚度控制在上述范围内，能够提高锂金属电池的循环性能和安全性能。
在本申请第一方面的一些实施方式中，所述粉末压电层由粉末压电材料和导电材料组成，粉末压电材料质量百分数为50至100％，导电材料质量百分数为0至50％。本申请中的压电材料，多为电子绝缘体，不利于集流体表面的电流均匀分散，因此需要控制好压电材料与导电材料的比例，本申请通过将粉末压电层中的粉末压电材料和导电材料的质量百分数控制在上述范围内，能够同时分散锂离子和电子，达到抑制锂枝晶生长的目的。
在本申请第一方面的一些实施方式中，所述粉末压电材料包括所述压电聚合物的粉末、所述压电陶瓷的粉末或所述压电单晶的粉末中的至少一种；所述导电材料包括导电碳粉末或导电金属粉末中的至少一种。本申请对导电材料的种类不做限定，只要能够实现本申请的目的即可，例如所述导电材料可以包括乙炔黑(AB)、导电炭黑(Super P)或科琴黑中的至少一种。
在本申请第一方面的另一些实施方式中，所述压电层包括薄膜压电层；所述薄膜压电层的厚度为5μm至200μm，优选为50μm至100μm。例如，薄膜压电层的厚度的下限值可以包括以下数值中：5μm、10μm、20μm、50μm或100μm；薄膜压电层的厚度的上限值可以包括以下数值中：110μm、130μm、150μm、180μm或200μm。发明人发现，当薄膜压 电层的厚度过小，薄膜压电层过薄，其强度不够，易发生破裂，锂金属电池的安全性能受到影响；当薄膜压电层的厚度过大，会降低锂金属电池的能量密度。本申请通过将薄膜压电层的厚度控制在上述范围内，能够提高锂金属电池的循环性能和安全性能。采用上述优选范围的厚度的薄膜压电层，对于改善锂金属电池的循环性能和安全性能，具有更优的效果。
在本申请第一方面的另一些实施方式中，所述薄膜压电层包括薄膜压电材料，所述薄膜压电材料包括压电聚合物薄膜、压电陶瓷薄膜、压电单晶薄膜或无机压电材料薄膜中的至少一种。其中，无机压电材料薄膜还可以包括上述压电陶瓷制备的薄膜或单晶薄片等。
在本申请中，对于锂金属电池中压电层的种类，本申请没有特别限制，本领域技术人员可以根据实际情况选择使用粉末压电层或薄膜压电层，只要能实现本申请目的即可。
本申请对粉末压电层的制备没有特别限制。在一种实施方式中，示例性地，可以将PVDF粉末与乙炔黑分散于N-甲基吡咯烷酮(NMP)中，使用刮刀涂覆于负极集流体的表面，在真空干燥箱中75至85℃烘干后得到的负极极片，其包括位于负极集流体表面的粉末压电层。
本申请对薄膜压电层的制备没有特别限制。在一种实施方式中，示例性地，将PVDF粉末投入160至200mL无水乙醇和110至130mL NMP混合溶剂中，在65至75℃下搅拌1.5至2.5h，再放置于超声波清洗器中，连接真空泵，超声抽气8至12min，在65至75℃下保温15至25min，得到透明均匀的溶液，将溶液引入装有聚酯膜带的流延机上，流延制备PVDF薄膜，调整刮刀狭缝宽度，从聚酯膜带上剥离制备好的PVDF薄膜，得到薄膜压电层。
在本申请第一方面的一些实施方式中，所述压电层位于负极集流体表面；或者位于负极集流体与负极材料层之间，或者位于负极材料层的外表面；或者所述压电层与负极材料层混合，位于负极集流体表面。
本申请中的负极极片可以包括负极材料层，也可以不包括负极材料层，可以理解为，当不包括负极材料层时，所述压电层位于负极集流体表面，压电层可以均匀地覆盖在负极集流体的表面，采用覆盖着压电层的负极集流体直接作为负极极片。本申请中的负极极片包括负极材料层时，所述压电层可以均匀地覆盖在负极集流体的表面，位于负极集流体与负极材料层之间；或者所述压电层可以均匀地覆盖在负极材料层的外表面，位于负极材料层的外表面，介于负极与电解液之间；或者所述压电层可以与负极材料层均匀混合，然后 均匀地覆盖在负极集流体表面，位于负极集流体表面。
本申请的负极极片包括负极集流体和压电层。其中，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，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。本申请中的负极极片还包括负极材料层时，所述负极材料层，可以包括锂金属或含有锂金属的复合材料。本申请中的负极极片还可以包括导电层，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。本申请对导电剂和粘结剂没有特别限制，只要能够实现本申请目的即可。当本申请的负极极片包含导电层时，所述压电层可以均匀地覆盖在负极集流体的表面，位于负极集流体与导电层之间；或者所述压电层介于所述导电层与负极材料层之间；或者所述压电层可以均匀地覆盖在负极材料层的外表面，位于负极材料层的外表面，介于负极与电解液之间；或者所述压电层可以与负极材料层均匀混合，然后均匀地覆盖在负极集流体表面，位于负极集流体表面。
本申请的第二方面提供了一种锂金属电池，其包含本申请第一方面所提供的负极极片。
本申请的锂金属电池中的负极极片采用本申请提供的负极极片，而其它的组成部分，包括正极极片、隔离膜及电解液等，没有特别的限制，只要能够实现本申请目的即可。
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。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。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。
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。
本申请的锂金属电池还包括电解质，电解质可以是凝胶电解质、固态电解质和电解液中的至少一种，电解液包括锂盐和非水溶剂。在本申请一些实施方式中，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、LiTFSI或二氟硼酸锂中的至少一种。举例来说，锂盐可以选用LiTFSI，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、醚化合物或其它有机溶剂中的至少一种。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、磷酸三辛酯或磷酸酯中的至少一种。
锂金属电池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。例如可以通过以下过程制造：将正极和负极经由隔离膜重叠，叠好后，用胶带将整个叠片结构的四个角固定好后，置入铝塑膜中，经顶侧封、注液、封装后，最终得到锂金属叠片电池。其中所用的负极为本申请提供的负极极片。
本申请的第三方面提供了一种电子装置，其包含本申请第二方面提供的锂金属电池。
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、照相机和家庭用大型蓄电池等。
本申请提供了一种负极极片、包含该负极极片的锂金属电池和电子装置，该负极极片包括负极集流体和压电层，压电层存在极化电场，极化电场的方向为从负极集流体指向负极的表面，压电层的材料包括压电聚合物、压电陶瓷、压电单晶或无机压电材料中的至少一种。该负极极片能够控制锂沉积位点，有效抑制锂枝晶的生长，使锂金属电池的循环性能和安全性能均得到明显提升。
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，以下举实施例，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中的实施例所获得的所有其他实施例，都属于本申请保护的范围。
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。
测试方法和设备：
沉积过电位测试：
以带有压电层的锂金属或集流体为正极，纯锂金属为负极组装锂金属电池，隔膜与电解液与用于循环的电池一致。在25℃下以0.3mA/cm 2的电流密度对锂金属电池进行恒电流放电，记录电压随时间变化的曲线，峰值电压与稳定电压的绝对值差值即为锂金属沉积过电位。
循环性能测试：
将锂金属电池在25℃下以0.1C的充电倍率和放电倍率化成一圈，然后，在测试温度为25℃条件下，以0.3C恒流充电到4.3V，再恒压充电到0.05C，静置5分钟后以1C放电到2.8V。以此步得到的容量为初始容量，进行0.3C充电/1C放电进行循环测试，以每一步的容量与初始容量做比值，得到容量衰减曲线。以25℃循环截至到容量保持率为80％的圈数记为锂金属电池的室温循环性能。
实施例1
<负极极片的制备>
将质量比为95:5的PVDF粉末与乙炔黑(AB)分散于NMP中，调配成为固含量为12％的浆料，通过搅拌使PVDF和AB混合均匀，使用刮刀将浆料涂覆于厚度为10μm的负极集流体铜箔的表面，在真空干燥箱中80℃烘干，得到粉末压电层厚度为3μm的负极极片。
将上述制备得到的负极极片放置于平行电场中进行空气极化，极化电场为10kV/mm，极化时间为30min，压电层面对负电压侧，负极集流体面对正电压侧。极化完成后，将负极极片裁切成40mm×60mm的规格待用。其中，PVDF的室温矫顽场的强度Ec为50kV/mm。
<正极极片的制备>
将正极活性材料磷酸铁锂(LiFePO 4)、导电剂导电炭黑(Super P)、粘结剂PVDF按照质量比97.5:1.0:1.5进行混合，加入N-甲基吡咯烷酮(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的正极集流体铝箔上，90℃条件下烘干，得到正极活性材料层厚度为100μm的单面涂覆正极活性材料层的正极极片。涂布完成后，将正极极片裁切成38mm×58mm的规格待用。
<电解液的制备>
在干燥氩气气氛中，将二氧环戊烷(DOL)、二甲醚(DME)以体积比DOL:DME＝1:1混合，得到混合溶剂，然后向混合溶剂中加入锂盐双三氟甲磺酰亚胺锂(LiTFSI)溶解并混合均匀，得到锂盐的浓度为1mol/L的电解液。
<锂金属电池的制备>
选用厚度15μm的聚乙烯(PE)作为隔离膜，将上述制备的负极极片置于中间，上下两层分别为单面涂布的正极极片，正极极片与负极极片之间为隔离膜。叠好后，用胶带将整个叠片结构的四个角固定好后，置入铝塑膜中，经顶侧封、注液、封装后，最终得到锂金属叠片电池。
实施例2-8
<负极极片的制备>、<正极极片的制备>、<电解液的制备>及<锂金属电池的制备>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。
实施例9
<负极极片的制备>
将80g PVDF粉末投入装有180mL无水乙醇和120mL NMP混合溶剂的圆底烧瓶中，在70℃下搅拌2h。再放置于超声波清洗器中，连接真空泵，超声抽气10min，在70℃下保温20min，得到透明均匀的溶液。将此溶液引入装有聚酯膜带的流延机上，流延制备PVDF薄膜，调整刮刀狭缝宽度，从聚酯膜带上剥离制备好的PVDF薄膜，厚度为10μm。
将上述PVDF薄膜放置于平行电场中进行空气极化，极化电场为10kV/mm，极化时间为30min，极化电场方向恒定。完成后，极化后PVDF薄膜内部带正电方向贴在负极集流体铜箔侧，得到薄膜压电层厚度为10μm的负极极片，将负极极片裁切成40mm×60mm的规格待用。
<正极极片的制备>、<电解液的制备>、<锂金属电池的制备>与实施例1相同。
实施例10-15
<负极极片的制备>、<正极极片的制备>、<电解液的制备>及<锂金属电池的制备>的制备步骤均与实施例9相同，相关制备参数的变化如表1中所示。
实施例16
<负极极片的制备>
将质量比为95:5的PVDF粉末与乙炔黑(AB)分散于NMP中，调配成为固含量为12％的浆料，通过搅拌使PVDF和AB混合均匀，使用刮刀涂覆于负极材料层锂金属的外表面，在真空干燥箱中80℃烘干待用，烘干后得到粉末压电层厚度为3μm的负极极片。
将上述负极极片放置于平行电场中进行空气极化，极化电场为50kV/mm，极化时间为30min，压电层面对负电压侧。完成后，将负极极片裁切成40mm×60mm的规格待用。
<正极极片的制备>、<电解液的制备>、<锂金属电池的制备>与实施例1相同。
实施例17
<负极极片的制备>
将质量比为95:5的PVDF粉末与乙炔黑(AB)分散于NMP中，调配成为固含量为12％的浆料，通过搅拌使PVDF和AB混合均匀，使用刮刀涂覆于负极集流体铜箔的表面，在真空干燥箱中80℃烘干待用，烘干后得到粉末压电层厚度为3μm的改性集流体；再将负极材料层的锂金属使用辊压机辊压于改性集流体上方，压力为8t，得到负极极片。
将上述负极极片放置于平行电场中进行空气极化，极化电场为50kV/mm，极化时间为30min，压电层面对负电压侧。完成后，将负极极片裁切成40mm×60mm的规格待用。
<正极极片的制备>、<电解液的制备>、<锂金属电池的制备>与实施例1相同。
实施例18
<负极极片的制备>
将质量比为95:5的PVDF粉末与乙炔黑(AB)分散于NMP中，调配成为固含量为12％的浆料，通过搅拌使PVDF和AB混合均匀，使用刮刀涂覆于负极集流体铜箔的表面，在真空干燥箱中80℃烘干待用，烘干后得到粉末压电层厚度为3μm的改性集流体。利用电化学补锂方式进行预补锂，锂源采用厚度0.05mm的锂片。选用15μm的PE隔膜，将改性集流体和锂金属放置在隔膜两侧，其中压电层部分和锂金属部分均正对隔膜，组装成补锂电池进行电化学补锂，电解液同<电解液的制备>中的电解液，补锂设备为5V、5mA的设备(品牌：蓝电，型号：CT2001A)，补锂电流为0.2mA/cm 2，放电15.5h，补锂量3.1mAh/cm 2。预补锂完成后，得到含有锂金属的负极极片。
将上述负极极片放置于平行电场中进行空气极化，极化电场为50kV/mm，极化时间为30min，压电层面对负电压侧。完成后，将负极极片裁切成40mm×60mm的规格待用。
<正极极片的制备>、<电解液的制备>、<锂金属电池的制备>与实施例1相同。
实施例16-18的相关制备参数见表1。
实施例19
<负极极片的制备>
将质量比为95:5的BaTiO 3压电陶瓷粉末与导电炭黑(SP)分散于NMP中，调配成为固含量为12％的浆料，通过搅拌使BaTiO 3和SP混合均匀，使用刮刀涂覆于负极集流体铜箔的表面，在真空干燥箱中80℃烘干待用，得到粉末压电层厚度为3μm的负极极片。
将上述制备得到的负极极片放置于平行电场中进行空气极化，极化电场为0.1kV/mm，极化时间为30min，压电层面对负电压侧。极化完成后，将负极极片裁切成40mm×60mm的规格待用。
<正极极片的制备>、<电解液的制备>、<锂金属电池的制备>与实施例1相同。
实施例20-25
<负极极片的制备>、<正极极片的制备>、<电解液的制备>及<锂金属电池的制备>的制备步骤均与实施例19相同，相关制备参数的变化如表1中所示。
实施例26
<负极极片的制备>
将摩尔比为5:3:2的PbO、ZrO 2、TiO 2置于高能行星球磨机中，加入100ml乙醇作为球磨助剂，以250r/min的转速球磨30h，得到钛锆酸铅PbZr 0.6Ti 0.4O 3粉末。将PbZr 0.6Ti 0.4O 3粉末分散于NMP中，通过搅拌使PbZr 0.6Ti 0.4O 3粉末分散均匀，得到固含量为12％的浆料，使用刮刀将浆料涂覆于负极集流体铜箔的表面，在真空干燥箱中80℃烘干待用，得到粉末压电层厚度为3μm的负极极片。
将上述制备得到的负极极片放置于平行电场中进行空气极化，极化电场为3kV/mm，极化时间为30min，压电层面对负电压侧。极化完成后，将负极极片裁切成40mm×60mm的规格待用。
<正极极片的制备>、<电解液的制备>、<锂金属电池的制备>与实施例1相同。
实施例27
<负极极片的制备>
利用助溶剂法生长BaTiO 3单晶片，将BaTiO 3粉末与助溶剂KF和补氧剂Fe 2O 3混合均匀，放入铂金坩埚中，在高温炉中升温至1175℃，保温8小时，缓慢冷却至875℃，然后将熔融的KF倒出，再以10℃/小时的速度冷却至室温，在用热水将坩埚中剩余的KF熔化，得到BaTiO 3单晶片。
将上述BaTiO 3单晶片放置于平行电场中进行空气极化，极化电场为0.1kV/mm，极化时间为30min，极化电场方向平行于单晶片厚度方向且保持恒定。完成后，极化后BaTiO 3单晶片带正电方向贴在负极集流体铜箔侧，得到薄膜压电层厚度为10μm的负极极片，将负极极片裁切成40mm×60mm的规格待用。
<正极极片的制备>、<电解液的制备>、<锂金属电池的制备>与实施例1相同。
实施例28-33
<负极极片的制备>、<正极极片的制备>、<电解液的制备>及<锂金属电池的制备>的制备步骤均与实施例32相同，相关制备参数的变化如表1中所示。
实施例34
<负极极片的制备>
将厚度为10μm的尼龙7薄膜(品牌：台湾化学纤维股份有限公司，牌号：NP4000)放置于平行电场中进行空气极化，极化电场为280kV/mm，极化时间为30min，极化电场方向平行于薄膜厚度方向且保持恒定。完成后，极化后尼龙7薄膜带正电方向贴在负极集流体铜箔侧，得到薄膜压电层厚度为10μm的负极极片，将负极极片裁切成40mm×60mm的规格待用。
<正极极片的制备>、<电解液的制备>、<锂金属电池的制备>与实施例1相同。
实施例35
<负极极片的制备>
将厚度为10μm的氧化碲晶体单晶片(品牌：北京物科光电技术有限公司，牌号：TEO2)放置于平行电场中进行空气极化，极化电场为3kV/mm，极化时间为30min，极化电场方向平行于单晶片厚度方向且保持恒定。完成后，极化后氧化碲晶体单晶片带正电方向贴在负极集流体铜箔侧，得到薄膜压电层厚度为10μm的负极极片，将负极极片裁切成40mm×60mm的规格待用。
<正极极片的制备>、<电解液的制备>、<锂金属电池的制备>与实施例1相同。
对比例1
负极极片为负极集流体铜箔，<正极极片的制备>、<电解液的制备>及<锂金属电池的制备>的制备步骤均与实施例1相同。
对比例2-5
<负极极片的制备>、<正极极片的制备>、<电解液的制备>及<锂金属电池的制备>的制备步骤均与实施例1相同。
对比例6-7
<负极极片的制备>、<正极极片的制备>、<电解液的制备>及<锂金属电池的制备>的制备步骤均与实施例9相同。
对比例8-9
<负极极片的制备>、<正极极片的制备>、<电解液的制备>及<锂金属电池的制备>的制备步骤均与实施例19相同。
对比例10-11
<负极极片的制备>、<正极极片的制备>、<电解液的制备>及<锂金属电池的制备>的制备步骤均与实施例32相同。
对比例12
负极极片为锂金属，<正极极片的制备>、<电解液的制备>及<锂金属电池的制备>的制备步骤均与实施例1相同。
上述各对比例中相关制备参数的变化如表1中所示。
Figure PCTCN2021084577-appb-000001
Figure PCTCN2021084577-appb-000002
Figure PCTCN2021084577-appb-000003
从实施例1-4、9-12、19-22、27-30可以看出，选用同一种类的压电层的锂金属电池时，随着极化电场强度的变化，其沉积过电位和循环性能随之变化。其中，利用本申请范围内的极化电场强度及方向对负极极片进行极化后，可以有效降低沉积过电位，提升锂金属电池的循环性能。
压电层的厚度通常也会对锂金属电池的沉积过电位和循环性能产生影响。从实施例2、5-7、10、13-15、21、23-25、29、31-33可以看出，压电层的厚度在本申请范围内，可以得到沉积过电位低、循环性能好的锂金属电池。
从实施例1-15、19-25、27-33和对比例1可以看出，包括本申请所提供的压电层的锂金属电池，其循环性能明显优于未设置压电层的锂金属电池。从实施例16-18和对比例12可以看出，当负极极片还包括负极材料层时，包括本申请所提供的压电层的锂金属电池，其循环性能也明显优于未设置压电层的锂金属电池。在负极极片中设置本申请范围内的压电层，能够明显提高锂金属电池的循环性能。
综合上述分析可知，本申请提供的负极极片，包括负极集流体和内部存在极化电场的压电层，极化电场的方向为从负极集流体指向负极的表面，压电层的材料包括压电聚合物、压电陶瓷、压电单晶或无机压电材料中的至少一种。该负极极片能够控制锂沉积位点，有效抑制锂枝晶的生长，使锂金属电池的循环性能和安全性能均得到明显提升。
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 (12)

  1. 一种负极极片，其包括负极集流体和压电层，所述压电层存在极化电场，所述极化电场的方向为从所述负极集流体指向所述负极的表面，所述压电层的材料包括压电聚合物、压电陶瓷、压电单晶或无机压电材料中的至少一种。
  2. 根据权利要求1所述的负极极片，其中，所述压电层的材料的室温矫顽场的强度Ec满足：0kV/mm＜Ec＜100kV/mm。
  3. 根据权利要求2所述的负极极片，其中，所述极化电场的强度为所述室温矫顽场的强度Ec的0.1倍至6倍。
  4. 根据权利要求1所述的负极极片，其中，所述压电聚合物包括聚偏氟乙烯、偏氟乙烯/三氟乙烯共聚物、偏氟乙烯/四氟乙烯共聚物、亚乙烯基二氰/醋酸乙烯共聚物、亚乙烯基二氰/苯甲酸乙烯共聚物、亚乙烯基二氰/丙酸乙烯共聚物、亚乙烯基二氰/新戊酸乙烯共聚物、亚乙烯基二氰/甲基丙烯酸甲酯共聚物、亚乙烯基二氰/异丁烯共聚物或奇数尼龙系压电聚合物-(HN-(CH 2) x-CO-) n-，其中，x为2至10中的偶数，n为90至400中的正整数；所述压电陶瓷包括钛酸钡、钛酸铅、铌酸锂、钽酸锂、锆钛酸铅PbZr yTi 1-yO 3、铌镁酸铅PbMg zNb 1-zO 3、铌锌酸铅PbZn vNb 1-vO 3、锰锑酸铅PbMn wSb 1-wO 3或Pb 1-sM m(Zr tTi 1-t) 1-(s/4)O 3中的至少一种，其中，0＜y＜1，0＜z＜1，0＜v＜1，0＜w＜1，0＜s＜1，0＜m＜1，0＜t＜1，M选自稀土元素的任一种；所述压电单晶包括石英单晶、氧化碲晶体、锗酸铋单晶、碘酸锂单晶、正磷酸铝单晶、硅酸镓镧单晶、钛酸钡单晶或锆钛酸铅单晶PbZr eTi 1-eO 3，其中，0＜e＜1；所述无机压电材料包括氧化锌、氧化铋、氧化钴、氧化铅、氧化镍、氧化铬、氧化锑、氮化铝、氮化镓铝、氮化铝铟、氮化镓、氮化镓铟、氮化铟、碳化硅、钛三铝基或钛铝基金属间化合物中的至少一种。
  5. 根据权利要求1所述的负极极片，其中，所述压电层包括粉末压电层，所述粉末压电层的厚度为0.1μm至5μm。
  6. 根据权利要求5所述的负极极片，其中，所述粉末压电层由粉末压电材料和导电材料组成，粉末压电材料质量百分数为50％至100％，导电材料质量百分数为0％至50％。
  7. 根据权利要求6所述的负极极片，其中，所述粉末压电材料包括所述压电聚合物的粉末、所述压电陶瓷的粉末或所述压电单晶的粉末中的至少一种；所 述导电材料包括导电碳粉末或导电金属粉末中的至少一种。
  8. 根据权利要求1所述的负极极片，其中，所述压电层包括薄膜压电层；所述薄膜压电层的厚度为5μm至200μm。
  9. 根据权利要求8所述的负极极片，其中，所述薄膜压电层包括薄膜压电材料，所述薄膜压电材料包括压电聚合物薄膜、压电陶瓷薄膜、压电单晶薄膜或无机压电材料薄膜中的至少一种。
  10. 根据权利要求1所述的负极极片，其中，所述压电层位于负极集流体表面；或者位于负极集流体与负极材料层之间，或者位于负极材料层的外表面；或者所述压电层与负极材料层混合，位于负极集流体表面。
  11. 一种锂金属电池，其包含权利要求1-10中任一项所述的负极极片。
  12. 一种电子装置，其包含权利要求11所述的锂金属电池。
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