WO2022198577A1 - 电化学装置和电子装置 - Google Patents

电化学装置和电子装置 Download PDF

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Publication number
WO2022198577A1
WO2022198577A1 PCT/CN2021/083042 CN2021083042W WO2022198577A1 WO 2022198577 A1 WO2022198577 A1 WO 2022198577A1 CN 2021083042 W CN2021083042 W CN 2021083042W WO 2022198577 A1 WO2022198577 A1 WO 2022198577A1
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active material
electrode active
negative electrode
positive electrode
electrochemical device
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PCT/CN2021/083042
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English (en)
French (fr)
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王强
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东莞新能源科技有限公司
宁德新能源科技有限公司
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Priority to CN202180001912.9A priority Critical patent/CN113366673B/zh
Priority to PCT/CN2021/083042 priority patent/WO2022198577A1/zh
Priority to EP21870477.3A priority patent/EP4089782A4/en
Priority to US17/709,010 priority patent/US20220320508A1/en
Publication of WO2022198577A1 publication Critical patent/WO2022198577A1/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
    • 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
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M4/386—Silicon or alloys based on silicon
    • 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
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • 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
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M2010/4292—Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode
    • 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 electrochemical energy storage, in particular to electrochemical devices and electronic devices.
  • anode active materials with high gram capacity (for example, silicon-based materials) are usually used.
  • high gram capacity anode active materials are accompanied by significant volume expansion with the progress of cycling, This causes problems such as de-coating and pulverization of the negative electrode active material layer, and reduces the cycle performance of the electrochemical device.
  • an electrochemical device which includes a positive electrode piece, a negative electrode piece, and a separator disposed between the positive electrode piece and the negative electrode piece.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes lithium cobalt oxide.
  • the negative electrode pole piece includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.
  • A is the percentage of the mass of the positive active material in the total mass of the positive active material layer
  • B is the gram capacity of the positive active material, in mAh/g
  • C is the mass per unit area of the positive active material layer, in mg/cm 2
  • A' is the percentage of the mass of the negative electrode active material to the total mass of the negative electrode active material layer
  • B' is the gram capacity of the negative electrode active material, in mAh/g
  • C' is the amount of the negative electrode active material layer
  • Mass per unit area unit is mg/cm 2
  • U is the charge cut-off voltage of the electrochemical device
  • unit is V.
  • the negative active material includes at least one of SiO x , a silicon alloy, or a silicon carbon composite, where 0.3 ⁇ x ⁇ 1.5.
  • the electrochemical device further includes a conductive layer disposed between the negative electrode current collector and the negative electrode active material layer, the conductive layer including a conductive agent and a binder.
  • the conductive agent includes at least one of carbon black, acetylene black, ketjen black, graphene, carbon nanotubes, carbon fibers, or carbon nanowires.
  • an electrochemical device which includes a positive pole piece, a negative pole piece, and a separator disposed between the positive pole piece and the negative pole piece.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes at least one of nickel cobalt lithium manganate or nickel cobalt lithium aluminate.
  • the negative electrode pole piece includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.
  • the electrochemical device satisfies the following relation:
  • A is the percentage of the mass of the positive active material in the total mass of the positive active material layer
  • B is the gram capacity of the positive active material, in mAh/g
  • C is the mass per unit area of the positive active material layer, in mg/cm 2
  • A' is the percentage of the mass of the negative electrode active material to the total mass of the negative electrode active material layer
  • B' is the gram capacity of the negative electrode active material, in mAh/g
  • C' is the amount of the negative electrode active material layer
  • Mass per unit area unit is mg/cm 2
  • U is the charge cut-off voltage of the electrochemical device
  • unit is V.
  • the negative active material includes at least one of SiO x , a silicon alloy, or a silicon carbon composite, where 0.3 ⁇ x ⁇ 1.5.
  • the electrochemical device further includes a conductive layer disposed between the negative electrode current collector and the negative electrode active material layer, the conductive layer including a conductive agent and a binder.
  • the conductive agent includes at least one of carbon black, acetylene black, ketjen black, graphene, carbon nanotubes, carbon fibers, or carbon nanowires.
  • Embodiments of the present application also provide an electronic device, including the above electrochemical device.
  • the electrochemical device includes an electrode assembly, and the electrode assembly includes a positive pole piece, a negative pole piece, and a separator disposed between the positive pole piece and the negative pole piece.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector.
  • the cathode active material layer may be disposed on one or both sides of the cathode current collector.
  • the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes lithium cobalt oxide.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.
  • the anode active material layer may be disposed on one or both sides of the anode current collector.
  • the anode active material layer includes an anode active material.
  • the electrochemical device satisfies the following relationship:
  • A is the percentage of the mass of the positive active material in the total mass of the positive active material layer
  • B is the gram capacity of the positive active material, in mAh/g
  • C is the mass per unit area of the positive active material layer, in mg/cm 2
  • A' is the percentage of the mass of the negative electrode active material to the total mass of the negative electrode active material layer
  • B' is the gram capacity of the negative electrode active material, in mAh/g
  • C' is the amount of the negative electrode active material layer
  • Mass per unit area unit is mg/cm 2
  • U is the charge cut-off voltage of the electrochemical device
  • unit is V.
  • CB refers to the ratio of the negative electrode discharge capacity per unit area to the positive electrode discharge capacity per unit area, and can be used to adjust CB by changing any of the parameters A, B, C, A', B' and C'. value.
  • 1.04 ⁇ CB ⁇ 2.0 If the CB is too small, lithium precipitation easily occurs on the surface of the negative electrode active material layer, while if the CB is too large, the negative electrode capacity is wasted and the energy density of the electrochemical device is reduced.
  • 1.04 ⁇ CB ⁇ 2.0 with the increase of CB, it is more conducive to suppress the volume expansion of the negative electrode active material during the cycle, alleviate the damage to the solid electrolyte interface (SEI) film due to the volume expansion, and improve the electrical conductivity. Cycling performance of chemical devices.
  • SEI solid electrolyte interface
  • the charge cut-off voltage of the electrochemical device is 4.3 ⁇ U ⁇ 4.5.
  • the CB value of the electrochemical device increases, the depth of lithium intercalation of the anode active material layer decreases in the fully charged state, and the absolute potential of the anode (to Li/Li + potential) inevitably increases, while the electrochemical device (such as a lithium-ion battery)
  • the full-cell voltage is the difference between the absolute potential of the positive electrode (to Li/Li + potential) and the absolute potential of the negative electrode. At this time, if the full-cell voltage remains unchanged, the full-cell potential should be kept unchanged when the absolute potential of the negative electrode increases.
  • the absolute potential of the positive electrode will inevitably increase. Since the positive electrode active material is prone to irreversible phase transitions between the spinel phase and the rock salt phase under the high voltage state, it will deteriorate the structural stability of the surface phase and bulk phase of the positive electrode active material, and exacerbate the It has a side reaction with the electrolyte, thereby deteriorating the cycle performance of the electrochemical device. Therefore, the present application reduces the charge cut-off voltage of the electrochemical device in a fully charged state while increasing the CB value of the electrochemical device, so as to avoid the performance deterioration of the positive electrode active material under high voltage. Therefore, the charge cut-off voltage of the electrochemical device is set to be 4.3V or more and less than 4.5V.
  • the principle of reducing the charge cut-off voltage U of the electrochemical device is as follows: when the CB value of the electrochemical device is increased, the absolute potential of the negative electrode increases, and the charge cut-off voltage U is reduced at this time, so that the absolute potential of the positive electrode is not maintained like the charge cut-off voltage of the electrochemical device.
  • the absolute potential of the positive electrode remains unchanged, the absolute potential of the positive electrode increases so much or keeps the absolute potential of the positive electrode basically unchanged, thereby easing the stability of the positive electrode active material, and will not aggravate the side reaction with the electrolyte, eliminating the inconsistency of the charging cut-off voltage of the electrochemical device.
  • the increase in the absolute potential of the cathode when decreasing has an adverse effect on the cycling performance of the electrochemical device.
  • the cathode active material lithium cobalt oxide may be coated or doped.
  • 0.17 ⁇ CB/U ⁇ 0.48 By increasing the CB value of the electrochemical device and reducing the charge cut-off voltage U at the same time, 0.17 ⁇ CB/U ⁇ 0.48, the volume expansion of the negative electrode active material during the cycle can be suppressed, and at the same time, the positive electrode active material can be prevented from being caused by the high absolute potential of the positive electrode. The electrochemical performance deteriorates and the cycle performance of the electrochemical device is improved.
  • the negative active material may include at least one of SiO x , a silicon alloy, or a silicon carbon composite, where 0.3 ⁇ x ⁇ 1.5. Due to the high gram capacity of silicon, the energy density of electrochemical devices can be increased by using these silicon-containing materials.
  • a conductive agent and a binder may also be included in the anode active material layer.
  • the conductive agent in the negative active material layer may include at least one of conductive carbon black, Ketjen black, lamellar graphite, graphene, carbon nanotubes, or carbon fibers.
  • the binder in the negative active material layer may include carboxymethyl cellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyimide, polyamideimide, polysilicon At least one of oxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene.
  • the mass ratio of the anode active material, the conductive agent, and the binder in the anode active material layer may be (80 to 99):(0.1 to 10):(0.1 to 10). It should be understood that the above are only examples and any other suitable materials and mass ratios may be employed.
  • the current collector of the negative electrode sheet can be at least one of copper foil, nickel foil or carbon-based current collector.
  • the electrochemical device further includes a conductive layer disposed between the negative electrode current collector and the negative electrode active material layer, the conductive layer including a conductive agent and a binder.
  • a conductive layer between the negative electrode current collector and the negative electrode active material layer, it can be used to improve the bonding force between the negative electrode current collector and the negative electrode active material layer, and prevent the negative electrode from being caused by volume expansion of the negative electrode active material during cycling. Release of the active material layer.
  • the conductive agent in the conductive layer may include at least one of carbon black, ketjen black, acetylene black, graphene, carbon nanotubes, carbon fibers, or carbon nanowires.
  • the binder in the conductive layer may include polyacrylic acid, polyacrylate (sodium polyacrylate, calcium polyacrylate, etc.), polymethacrylic acid, polyacrylamide, polymethacrylamide, polymethyl At least one of acrylate, polyvinyl alcohol or sodium alginate.
  • the weight average molecular weight of the binder in the conductive layer is 1W to 50W.
  • the weight average molecular weight of the binder By making the weight average molecular weight of the binder from 1W to 50W, it can be ensured that the binder is anchored to the residual functional groups (for example, carboxyl group/hydroxyl group/phenol group, etc.) on the particle surface of the conductive agent with an anionic dispersant, thereby realizing the conductive agent effective dispersion. If the weight average molecular weight of the binder is too large, for example, greater than 50W, it is not conducive to the effective dispersion of the conductive agent. In some embodiments, the mass content of the binder is 10% to 48% based on the total mass of the conductive layer. If the mass content of the binder is too small, it is unfavorable to fully exert the adhesion performance of the conductive layer, and if the mass content of the binder is too large, the conductive performance of the conductive layer will be adversely affected.
  • the mass content of the binder is 10% to 48% based on the total mass of the conductive layer
  • the positive electrode active material layer may further include a conductive agent.
  • the conductive agent in the positive active material layer may include at least one of conductive carbon black, Ketjen black, lamellar graphite, graphene, carbon nanotubes, or carbon fibers.
  • the positive electrode active material layer may further include a binder, and the binder in the positive electrode active material layer may include carboxymethyl cellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyamide At least one of imine, polyamideimide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene.
  • CMC carboxymethyl cellulose
  • the mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode active material layer may be (80 to 99):(0.1 to 10):(0.1 to 10).
  • the thickness of the cathode active material layer may be 10 ⁇ m to 500 ⁇ m. It should be understood that the above descriptions are only examples, and any other suitable materials, thicknesses and mass ratios may be used for the positive electrode active material layer of the positive electrode sheet.
  • the current collector of the positive electrode sheet can be made of Al foil, of course, other current collectors commonly used in the art can also be used.
  • the thickness of the current collector of the positive electrode sheet may be 1 ⁇ m to 50 ⁇ m.
  • the positive active material layer may be coated only on a partial area of the positive current collector of the positive electrode sheet.
  • the cathode active material is lithium cobaltate
  • the positive active material includes at least one of nickel cobalt lithium manganate or nickel cobalt lithium aluminate.
  • Lithium nickel cobalt manganate and lithium nickel cobalt aluminate bring some changes to the applicable charge cut-off voltage U due to the different structures of the materials.
  • lithium nickel cobalt manganate or lithium nickel cobalt aluminate allows The range of U is wider, and only the differences brought about by the change of the positive electrode active material will be discussed below. For other parts, reference is made to the embodiment in which the positive electrode active material is lithium cobalt oxide.
  • the positive active material includes at least one of nickel cobalt lithium manganate or nickel cobalt lithium aluminate, 4 ⁇ 100 ⁇ (4.49-U)-10 ⁇ (CB-1) ⁇ 22.
  • the volume expansion of the negative electrode active material layer during the charging and discharging process can be reduced, and then Improve the cycle performance of electrochemical devices.
  • the charge cut-off voltage of the electrochemical device in a fully charged state is reduced, so as to avoid the deterioration of the performance of the positive electrode active material under high voltage. Therefore, when the positive electrode active material is at least one of nickel cobalt lithium manganate or nickel cobalt aluminate, the charge cut-off voltage of the electrochemical device is set to be 4.1V or more and less than 4.49V.
  • the principle of reducing the charge cut-off voltage U of the electrochemical device is: when the CB value of the electrochemical device is increased, the absolute potential of the negative electrode increases, and at this time, the charge cut-off voltage U is reduced, so that the absolute potential of the positive electrode is not maintained like the charge cut-off voltage of the electrochemical device.
  • the absolute potential of the positive electrode remains unchanged, the absolute potential of the positive electrode increases so much or keeps the absolute potential of the positive electrode basically unchanged, thereby easing the stability of the positive electrode active material, and will not aggravate the side reaction with the electrolyte, eliminating the inconsistency of the charging cut-off voltage of the electrochemical device.
  • the increase in the absolute potential of the cathode when decreasing has an adverse effect on the cycling performance of the electrochemical device.
  • lithium nickel cobalt manganate and lithium nickel cobalt aluminate may be clad or doped.
  • the release membrane includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid.
  • polyethylene includes at least one of high density polyethylene, low density polyethylene or ultra-high molecular weight polyethylene.
  • the thickness of the isolation film is in the range of about 2 ⁇ m to 100 ⁇ m.
  • the surface of the separator may further include a porous layer, the porous layer is disposed on at least one surface of the substrate of the separator, the porous layer includes inorganic particles and a binder, and the inorganic particles include alumina (Al 2 O 3 ) .
  • the pores of the isolation membrane have diameters in the range of about 0.01 ⁇ m to 5 ⁇ m.
  • the binder of the porous layer is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyamide At least one of vinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • the porous layer on the surface of the separator can improve the heat resistance, oxidation resistance and electrolyte wettability of the separator, and enhance the adhesion between the separator and the pole piece.
  • the electrode assembly of the electrochemical device is a wound electrode assembly, a stacked electrode assembly, or a folded electrode assembly.
  • the positive pole piece and/or the negative pole piece of the electrochemical device may be a multi-layer structure formed by winding or stacking, or may be a single-layer positive pole piece, a separator, and a single-layer negative pole piece superimposed single-layer structure.
  • the electrochemical device may be a lithium-ion battery, although the application is not so limited.
  • the electrochemical device may also include an electrolyte.
  • the electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolytic solution, and the electrolytic solution includes a lithium salt and a non-aqueous solvent.
  • the lithium salt is selected from LiPF6, LiBF4 , LiAsF6, LiClO4 , LiB ( C6H5 ) 4 , LiCH3SO3 , LiCF3SO3 , LiN ( SO2CF3 ) 2 , LiC ( SO2CF3 ) 3 , LiSiF 6 , LiBOB or one or more of lithium difluoroborate.
  • LiPF 6 is chosen as the lithium salt because it has high ionic conductivity and can improve cycle characteristics.
  • the non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof.
  • the carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof.
  • chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl carbonate Ethyl esters (MEC) and combinations thereof.
  • chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl carbonate Ethyl esters (MEC) and combinations thereof.
  • Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), or a combination thereof.
  • fluorocarbonate compound examples include fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-carbonate -Difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, or a combination thereof.
  • FEC fluoroethylene carbonate
  • 1,2-difluoroethylene carbonate 1,1-difluoroethylene carbonate
  • 1,1,2-trifluoroethylene carbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-carbonate -Difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene
  • carboxylate compounds are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, decolactone, Valerolactone, mevalonolactone, caprolactone, methyl formate, or a combination thereof.
  • ether compounds are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxy Ethane, 2-methyltetrahydrofuran, tetrahydrofuran, or a combination thereof.
  • organic solvents examples include dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, methyl amide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, phosphate ester, or combinations thereof.
  • the positive electrode, separator, and negative electrode are sequentially wound or stacked to form electrode parts, which are then packaged in, for example, an aluminum-plastic film, and then injected into an electrolytic film. Liquid, chemical formation, packaging, that is, into a lithium-ion battery. Then, the performance test of the prepared lithium-ion battery was carried out.
  • electrochemical devices eg, lithium ion batteries
  • electrochemical devices eg, lithium ion batteries
  • Other methods commonly used in the art may be employed without departing from the disclosure of the present application.
  • Embodiments of the present application also provide electronic devices including the above electrochemical devices.
  • the electronic device in the embodiment of the present application is not particularly limited, and it may be used in 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.
  • the preparation of the positive electrode plate using aluminum foil as the positive electrode current collector, the positive electrode active material lithium cobalt oxide (g capacity is 176mAh/g), the conductive agent conductive carbon black, and the binder polyacrylic acid are in a weight ratio of 97.6: 1.1: 1.3 ratio Dissolved in N-methylpyrrolidone (NMP) solution to form a positive electrode slurry, the positive electrode slurry was coated on the positive electrode current collector, and after drying, cold pressing and cutting, the surface was provided with a mass per unit area of 19.865 mg. /cm 2 of the positive electrode sheet of the positive electrode active material layer. The compacted density of the positive electrode sheet in the cold pressing process was 4.15 g/cm 3 .
  • NMP N-methylpyrrolidone
  • negative pole piece silicon oxide (g capacity is 1545mAh/g), acrylic resin, conductive carbon black, single-walled carbon nanotubes and sodium carboxymethylcellulose in a weight ratio of 88.3:9:1.5:0.2:1.0
  • the proportion of ions is dissolved in deionization to form negative electrode slurry.
  • copper foil as the negative electrode current collector, coating the negative electrode slurry on the negative electrode current collector, drying, cold pressing, and cutting to obtain a negative electrode pole piece with a negative electrode active material layer having a mass per unit area of 3.252 mg/mm on the surface. .
  • the isolation film substrate is polyethylene (PE) with a thickness of 9 ⁇ m, and 2 ⁇ m alumina ceramic layers are coated on both sides of the isolation film substrate, and finally 2.5 ⁇ m of alumina ceramic layers are coated on both sides of the coated ceramic layer.
  • PE polyethylene
  • PVDF polyvinylidene fluoride
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • PC propylene carbonate
  • PP vinylene carbonate
  • VC vinylene carbonate
  • weight ratio weight ratio
  • Preparation of lithium ion battery stack the positive pole piece, the separator and the negative pole piece in order, so that the separator is in the middle of the positive pole piece and the negative pole piece to play a role of isolation, and coil to obtain the electrode assembly.
  • the electrode assembly is placed in the outer packaging aluminum-plastic film, and after dehydration at 80°C, the above electrolyte is injected and packaged, and the lithium ion battery is obtained through the process of forming, degassing, and trimming.
  • the lithium-ion battery placed in a constant temperature box at 25°C ⁇ 2°C for 2 hours, charge it at a rate of 0.5C to 4.25V (the voltage value is the charging cut-off voltage of each embodiment), and then charge it at 4.25V (the voltage value is The charging cut-off voltage of each example) was charged to 0.05C under constant voltage and allowed to stand for 15 minutes. Then it was discharged to 3.0V at a rate of 0.5C and left for 5 minutes, which was a charge-discharge cycle process. Taking the capacity of the first discharge as 100%, the charge-discharge cycle process was repeated, and the ratio of the discharge capacity of each cycle to the first discharge capacity was used as an index to evaluate the cycle performance of the lithium-ion battery. Taking the initial thickness of the battery as 0%, the ratio of the fully charged thickness of the battery to the initial thickness of the battery after 500 cycles was used as an indicator of the cycle swelling of the lithium-ion battery.
  • Table 1 shows the respective parameters and evaluation results of Examples 1 to 5 and Comparative Example 1.
  • the mass per unit area and charge cut-off voltage of the negative electrode active material layers of Examples 1 to 5 were different from those of Comparative Example 1.
  • Table 2 shows the respective parameters and evaluation results of Examples 6 to 12.
  • the negative electrode active material is a mechanically mixed sample with a mass of 20% SiO and 80% graphite respectively, and the overall gram capacity is 593mAh/g; in Examples 8 to 9, the negative electrode active material is a mass of The mechanically mixed samples of 60% SiO and 40% graphite, respectively, have an overall gram capacity of 1069 mAh/g; in Examples 10 to 12, the negative active materials are mechanically mixed samples of 80% SiO and 20% graphite by mass, respectively. The gram capacity is 1307mAh/g.
  • Table 3 shows the respective parameters and evaluation results of Examples 13 to 15.
  • the negative electrode active material is a mechanically mixed sample with a mass of 80% SiC and 20% graphite respectively, the overall gram capacity is 1495mAh/g, and the unit area of the negative electrode active material layer of Examples 13 to 15 is The quality is different from Example 1, and the CB and U of Examples 13 and 15 are different from Example 1.
  • Table 4 shows the respective parameters and evaluation results of Examples 16 to 20.
  • the positive electrode active material in Examples 16 to 20 is nickel-cobalt-manganese material (the molar ratio of nickel: cobalt: manganese is 6:2:2), the gram capacity is 174mAh/g, and the negative electrode active material is 80% by mass.
  • the %SiO and 20% graphite mechanically mixed sample has a charge gram capacity of 1307 mAh/g.

Abstract

本申请提供了电化学装置和电子装置。电化学装置包括正极极片、负极极片和设置于正极极片和负极极片之间的隔离膜。正极极片包括正极集流体和设置在正极集流体上的正极活性材料层，正极活性材料层包括正极活性材料，正极活性材料包括钴酸锂。负极极片包括负极集流体和设置在负极集流体上的负极活性材料层，负极活性材料层包括负极活性材料。电化学装置满足如下关系式：3≤100×(4.5-U)-10×(CB-1)≤10，CB＝(A'×B'×C')/(A×B×C)。本申请的实施例通过提升电化学装置的CB并且减小充电截止电压U，减小负极活性材料层在充放电过程中的体积膨胀，防止正极电位的提升给正极活性材料带来不利影响，进而提升电化学装置的循环性能。

Description

电化学装置和电子装置 技术领域
本申请涉及电化学储能领域，尤其涉及电化学装置和电子装置。
背景技术
随着电化学装置(例如，锂离子电池)的发展和进步，对其循环性能和能量密度提出了越来越高的要求。目前，为了提升电化学装置的能量密度，通常采用一些高克容量的负极活性材料(例如，硅基材料)，然而，高克容量的负极活性材料随着循环的进行伴随着显著的体积膨胀，造成负极活性材料层的脱膜和粉化等问题，降低电化学装置的循环性能。
因此，如何在确保电化学装置的能量密度的同时，改善电化学装置的循环性能，仍是丞待解决的问题。
发明内容
本申请的一些实施例提供了一种电化学装置，电化学装置包括正极极片、负极极片和设置于正极极片和负极极片之间的隔离膜。正极极片包括正极集流体和设置在正极集流体上的正极活性材料层，正极活性材料层包括正极活性材料，正极活性材料包括钴酸锂。负极极片包括负极集流体和设置在负极集流体上的负极活性材料层，负极活性材料层包括负极活性材料。电化学装置满足如下关系式：
3≤100×(4.5-U)-10×(CB-1)≤10，
CB＝(A’×B’×C’)/(A×B×C)，
其中，A为正极活性材料的质量占正极活性材料层的总质量的百分含量，B为正极活性材料的克容量，单位为mAh/g，C为正极活性材料层的单位面积质量，单位为mg/cm 2，A’为负极活性材料的质量占负极活性材料层的总质量的百分含量，B’为负极活性材料的克容量，单位为mAh/g，C’为负极活性 材料层的单位面积质量，单位为mg/cm 2，U为电化学装置的充电截止电压，单位为V。
在一些实施例中，3.5≤100×(4.5-U)-10×(CB-1)≤6。在一些实施例中，1.04≤CB≤2.0，4.3≤U<4.5。在一些实施例中，0.17＜CB/U＜0.48。在一些实施例中，负极活性材料包括SiO x、硅合金或硅碳复合物中的至少一种，其中0.3≤x≤1.5。在一些实施例中，电化学装置还包括设置在负极集流体和负极活性材料层之间的导电层，导电层包括导电剂和粘结剂。在一些实施例中，导电剂包括炭黑、乙炔黑、科琴黑、石墨烯、碳纳米管、碳纤维或碳纳米线中的至少一种。
本申请的另一实施例提供了一种电化学装置，电化学装置包括正极极片、负极极片和设置于正极极片和负极极片之间的隔离膜。正极极片包括正极集流体和设置在正极集流体上的正极活性材料层，正极活性材料层包括正极活性材料，正极活性材料包括镍钴锰酸锂或镍钴铝酸锂中的至少一种。负极极片包括负极集流体和设置在负极集流体上的负极活性材料层，负极活性材料层包括负极活性材料。电化学装置满足如下关系式：
4≤100×(4.49-U)-10×(CB-1)≤22，
CB＝(A’×B’×C’)/(A×B×C)，
其中，A为正极活性材料的质量占正极活性材料层的总质量的百分含量，B为正极活性材料的克容量，单位为mAh/g，C为正极活性材料层的单位面积质量，单位为mg/cm 2，A’为负极活性材料的质量占负极活性材料层的总质量的百分含量，B’为负极活性材料的克容量，单位为mAh/g，C’为负极活性材料层的单位面积质量，单位为mg/cm 2，U为电化学装置的充电截止电压，单位为V。
在一些实施例中，5≤100×(4.49-U)-10×(CB-1)≤13。在一些实施例中，1.04≤CB≤2.0，4.1≤U<4.49。在一些实施例中，0.17＜CB/U＜0.48。在一些实施例中，负极活性材料包括SiO x、硅合金或硅碳复合物中的至少一种，其中0.3≤x≤1.5。在一些实施例中，电化学装置还包括设置在负极集流体和负极活性材料层之间的导电层，导电层包括导电剂和粘结剂。在一些实施例中，导电剂包括炭黑、乙炔黑、科琴黑、石墨烯、碳纳米管、碳纤维或碳纳米线中的至少一种。
本申请的实施例还提供了一种电子装置，包括上述电化学装置。
本申请的实施例通过满足3≤100×(4.5-U)-10×(CB-1)≤10，其中CB＝(A’×B’×C’)/(A×B×C)，一方面增大电化学装置的CB值，另一方面减小电化学装置的充电截止电压U，如此可以减小负极活性材料层在充放电过程中的体积膨胀，防止正极电位的提升给正极活性材料带来不利影响，进而提升电化学装置的循环性能。
具体实施方式
下面的实施例可以使本领域技术人员更全面地理解本申请，但不以任何方式限制本申请。
本申请的一些实施例提供了一种电化学装置，电化学装置包括电极组件，电极组件包括正极极片、负极极片以及设置在正极极片和负极极片之间的隔离膜。在一些实施例中，正极极片包括正极集流体和设置在正极集流体上的正极活性材料层。在一些实施例中，正极活性材料层可以设置在正极集流体的一侧或两侧上。在一些实施例中，正极活性材料层包括正极活性材料，正极活性材料包括钴酸锂。在一些实施例中，负极极片包括负极集流体和设置在负极集流体上的负极活性材料层。在一些实施例中，负极活性材料层可以设置在负极集流体的一侧或两侧上。在一些实施例中，负极活性材料层包括负极活性材料。
在一些实施例中，电化学装置满足如下关系式：
3≤100×(4.5-U)-10×(CB-1)≤10，
CB＝(A’×B’×C’)/(A×B×C)，
其中，A为正极活性材料的质量占正极活性材料层的总质量的百分含量，B为正极活性材料的克容量，单位为mAh/g，C为正极活性材料层的单位面积质量，单位为mg/cm 2，A’为负极活性材料的质量占负极活性材料层的总质量的百分含量，B’为负极活性材料的克容量，单位为mAh/g，C’为负极活性材料层的单位面积质量，单位为mg/cm 2，U为电化学装置的充电截止电压，单位为V。由上可知，CB指的是单位面积的负极放电容量与单位面积的正极放电容量的比值，通过改变A、B、C、A’、B’和C’中任一个参数均可以用于调节CB值。
在一些实施例中，通过控制电化学装置的充电截止电压U和单位面积的负极放电容量与单位面积的正极放电容量的比值CB，使得3≤100×(4.5-U)-10×(CB-1)≤10，可以减小负极活性材料层在充放电过程中的体积膨胀，进而提升电化学装置的循环性能。在一些实施例中，3.5≤100×(4.5-U)-10×(CB-1)≤6。
在一些实施例中，1.04≤CB≤2.0。如果CB太小，容易在负极活性材料层表面发生析锂，而如果CB太大，则浪费了负极容量，降低了电化学装置的能量密度。另外，在1.04≤CB≤2.0时，随着CB的增大，更有利于抑制负极活性材料在循环过程中的体积膨胀，缓解由于体积膨胀对固体电解质界面(SEI)膜的破坏，进而改善电化学装置的循环性能。
在一些实施例中，当电化学装置的正极活性材料为钴酸锂时，电化学装置的充电截止电压4.3≤U<4.5。随着电化学装置的CB值提高，在满充状态下负极活性材料层的嵌锂深度降低，负极绝对电位(对Li/Li +电位)必然升高，而电化学装置(例如锂离子电池)的全电池电压为正极绝对电位(对Li/Li +电位)与负极绝对电位的差，此时如果全电池电压不变，在负极绝对电位升高的情况下，要保持全电池电位不变，那意味着正极绝对电位必然升高，由于正极活性材料在高电压状态下，容易发生尖晶石相和岩盐相的不可逆相变，恶化正极活性材料的表相与体相的结构稳定性，加剧其和电解液的副反应，从而恶化电化学装置的循环性能。因此，本申请在提高电化学装置的CB值的同时，降低电化学装置在满充状态下的充电截止电压，以避免正极活性材料在高电压下的性能恶化。因此，将电化学装置的充电截止电压设置为大于等于4.3V且小于4.5V。降低电化学装置的充电截止电压U的原理为：在提升电化学装置的CB值时，负极绝对电位提升，此时降低充电截止电压U，使得正极绝对电位不像电化学装置的充电截止电压保持不变时正极绝对电位提升得那么大或保持正极绝对电位基本不变，从而缓解了正极活性材料的稳定性，并且不会加剧与电解液的副反应，消除了电化学装置的充电截止电压不降低时的正极绝对电位的提升对电化学装置的循环性能的不利影响。然而，如果电化学装置的充电截止电压U过低，例如，小于4.3V，则不利地影响电化学装置的能量密度。在一些实施例中，正极活性材料钴酸锂可以经过包覆或掺杂。
在一些实施例中，0.17＜CB/U＜0.48。通过提升电化学装置的CB值，同时降低充电截止电压U，使得0.17＜CB/U＜0.48，能够抑制负极活性材料在循环过程中的体积膨胀，同时避免正极活性材料由于正极绝对电位过高引发的电化学性能恶化，提升了电化学装置的循环性能。
在一些实施例中，负极活性材料可以包括SiO x、硅合金或硅碳复合物中的至少一种，其中0.3≤x≤1.5。由于硅的克容量高，通过采用这些含硅材料，能够提升电化学装置的能量密度。在一些实施例中，负极活性材料层中还可以包括导电剂和粘结剂。在一些实施例中，负极活性材料层中的导电剂可以包括导电炭黑、科琴黑、片层石墨、石墨烯、碳纳米管或碳纤维中的至少一种。在一些实施例中，负极活性材料层中的粘结剂可以包括羧甲基纤维素(CMC)、聚丙烯酸、聚乙烯基吡咯烷酮、聚苯胺、聚酰亚胺、聚酰胺酰亚胺、聚硅氧烷、丁苯橡胶、环氧树脂、聚酯树脂、聚氨酯树脂或聚芴中的至少一种。在一些实施例中，负极活性材料层中的负极活性材料、导电剂和粘结剂的质量比可以为(80至99)：(0.1至10)：(0.1至10)。应该理解，以上所述仅是示例，可以采用任何其他合适的材料和质量比。在一些实施例中，负极极片的集流体可以采用铜箔、镍箔或碳基集流体中的至少一种。
在一些实施例中，电化学装置还包括设置在负极集流体和负极活性材料层之间的导电层，导电层包括导电剂和粘结剂。通过在负极集流体和负极活性材料层之间设置导电层，可以用于改善负极集流体和负极活性材料层之间的粘结力，防止由于循环过程中的负极活性材料的体积膨胀引起的负极活性材料层的脱膜。
在一些实施例中，导电层中的导电剂可以包括炭黑、科琴黑、乙炔黑、石墨烯、碳纳米管、碳纤维或碳纳米线中的至少一种。在一些实施例中，导电层中的粘结剂可以包括聚丙烯酸、聚丙烯酸盐(聚丙烯酸钠、聚丙烯酸钙等)、聚甲基丙烯酸、聚丙烯酰胺、聚甲基丙烯酰胺、聚甲基丙烯酸盐、聚乙烯醇或海藻酸钠中的至少一种。在一些实施例中，导电层中的粘结剂的重均分子量为1W至50W。通过使粘结剂的重均分子量为1W至50W，可以保证粘结剂以阴离子分散剂锚定于导电剂的颗粒表面的残余官能团(例如，羧基/羟基/酚基等)，从而实现导电剂的有效分散。如果粘结剂的重均分子量太大，例如，大于50W，则不利于导电剂的有效分散。在一些实施例中，基于 导电层的总质量，粘结剂的质量含量为10％至48％。如果粘结剂的质量含量太小，则不利于导电层的粘结性能的充分发挥，如果粘结剂的质量含量太大，则导电层的导电性能会受到不利的影响。
在一些实施例中，正极活性材料层还可以包括导电剂。在一些实施例中，正极活性材料层中的导电剂可以包括导电炭黑、科琴黑、片层石墨、石墨烯、碳纳米管或碳纤维中的至少一种。在一些实施例中，正极活性材料层还可以包括粘结剂，正极活性材料层中的粘结剂可以包括羧甲基纤维素(CMC)、聚丙烯酸、聚乙烯基吡咯烷酮、聚苯胺、聚酰亚胺、聚酰胺酰亚胺、聚硅氧烷、丁苯橡胶、环氧树脂、聚酯树脂、聚氨酯树脂或聚芴中的至少一种。在一些实施例中，正极活性材料层中的正极活性材料、导电剂和粘结剂的质量比可以为(80至99)：(0.1至10)：(0.1至10)。在一些实施例中，正极活性材料层的厚度可以为10μm至500μm。应该理解，以上所述仅是示例，正极极片的正极活性材料层可以采用任何其他合适的材料、厚度和质量比。
在一些实施例中，正极极片的集流体可以采用Al箔，当然，也可以采用本领域常用的其他集流体。在一些实施例中，正极极片的集流体的厚度可以为1μm至50μm。在一些实施例中，正极活性材料层可以仅涂覆在正极极片的正极集流体的部分区域上。
上面讨论了正极活性材料为钴酸锂的实施例。在其他一些实施例中，正极活性材料包括镍钴锰酸锂或镍钴铝酸锂中的至少一种。镍钴锰酸锂和镍钴铝酸锂由于材料自身结构的不同，由此给适用的充电截止电压U带来一些变化，作为三元材料的镍钴锰酸锂或镍钴铝酸锂，允许的U的范围更宽，下面仅讨论正极活性材料的变化带来的不同之处，其他部分参考正极活性材料为钴酸锂的实施例。
在一些实施例中，正极活性材料包括镍钴锰酸锂或镍钴铝酸锂中的至少一种，4≤100×(4.49-U)-10×(CB-1)≤22。与正极活性材料采用钴酸锂时相同，通过使4≤100×(4.49-U)-10×(CB-1)≤22，可以减小负极活性材料层在充放电过程中的体积膨胀，进而提升电化学装置的循环性能。在一些实施例中，5≤100×(4.49-U)-10×(CB-1)≤13。在一些实施例中，4.1≤U<4.49。本申请在提高电化学装置的CB值的同时，降低电化学装置在满充状态下的充电截止 电压，以避免正极活性材料在高电压下的性能恶化。因此，在正极活性材料为镍钴锰酸锂或镍钴铝酸锂中的至少一种时，将电化学装置的充电截止电压设置为大于等于4.1V且小于4.49V。降低电化学装置的充电截止电压U的原理为：在提升电化学装置的CB值时，负极绝对电位提升，此时降低充电截止电压U，使得正极绝对电位不像电化学装置的充电截止电压保持不变时正极绝对电位提升得那么大或保持正极绝对电位基本不变，从而缓解了正极活性材料的稳定性，并且不会加剧与电解液的副反应，消除了电化学装置的充电截止电压不降低时的正极绝对电位的提升对电化学装置的循环性能的不利影响。然而，如果电化学装置的充电截止电压U过低，例如，小于4.1V，则不利地影响电化学装置的能量密度。在一些实施例中，镍钴锰酸锂和镍钴铝酸锂可以经过包覆或掺杂。
在一些实施例中，隔离膜包括聚乙烯、聚丙烯、聚偏氟乙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺或芳纶中的至少一种。例如，聚乙烯包括高密度聚乙烯、低密度聚乙烯或超高分子量聚乙烯中的至少一种。尤其是聚乙烯和聚丙烯，它们对防止短路具有良好的作用，并可以通过关断效应改善电池的稳定性。在一些实施例中，隔离膜的厚度在约2μm至100μm的范围内。
在一些实施例中，隔离膜表面还可以包括多孔层，多孔层设置在隔离膜的基材的至少一个表面上，多孔层包括无机颗粒和粘结剂，无机颗粒包括氧化铝(Al 2O 3)、氧化硅(SiO 2)、氧化镁(MgO)、氧化钛(TiO 2)、二氧化铪(HfO 2)、氧化锡(SnO 2)、二氧化铈(CeO 2)、氧化镍(NiO)、氧化锌(ZnO)、氧化钙(CaO)、氧化锆(ZrO 2)、氧化钇(Y 2O 3)、碳化硅(SiC)、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙或硫酸钡中的至少一种。在一些实施例中，隔离膜的孔具有在约0.01μm至5μm的范围的直径。多孔层的粘结剂选自聚偏氟乙烯、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、羧甲基纤维素钠、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯或聚六氟丙烯中的至少一种。隔离膜表面的多孔层可以提升隔离膜的耐热性能、抗氧化性能和电解质浸润性能，增强隔离膜与极片之间的粘结性。
在本申请的一些实施例中，电化学装置的电极组件为卷绕式电极组件、堆叠式电极组件或折叠式电极组件。在一些实施例中，电化学装置的正极极片和/或负极极片可以是卷绕或堆叠式形成的多层结构，也可以是单层正极极片、隔离膜、单层负极极片叠加的单层结构。
在一些实施例中，电化学装置可以是锂离子电池，但是本申请不限于此。在一些实施例中，电化学装置还可以包括电解质。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。锂盐选自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或者二氟硼酸锂中的一种或多种。例如，锂盐选用LiPF 6，因为它具有高的离子导电率并可以改善循环特性。
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。
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。
链状碳酸酯化合物的实例为碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸甲乙酯(MEC)及其组合。所述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)或者其组合。所述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或者其组合。
羧酸酯化合物的实例为乙酸甲酯、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、甲酸甲酯或者其组合。
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 氢呋喃或者其组合。
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、磷酸酯或者其组合。
在本申请的一些实施例中，以锂离子电池为例，将正极极片、隔离膜、负极极片按顺序卷绕或堆叠成电极件，之后装入例如铝塑膜中进行封装，注入电解液，化成、封装，即制成锂离子电池。然后，对制备的锂离子电池进行性能测试。
本领域的技术人员将理解，以上描述的电化学装置(例如，锂离子电池)的制备方法仅是实施例。在不背离本申请公开的内容的基础上，可以采用本领域常用的其他方法。
本申请的实施例还提供了包括上述电化学装置的电子装置。本申请实施例的电子装置没有特别限定，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。
下面列举了一些具体实施例和对比例以更好地对本申请进行说明，其中，采用锂离子电池作为示例。
实施例1
正极极片的制备：采用铝箔作为正极集流体，将正极活性材料钴酸锂(克容量为176mAh/g)、导电剂导电炭黑、粘结剂聚丙烯酸按重量比97.6：1.1：1.3的比例溶于N-甲基吡咯烷酮(NMP)溶液中，形成正极浆料，将该正极浆料涂覆于正极集流体上，经过干燥、冷压、裁切后得到表面设置有单位面积质量为19.865mg/cm 2的正极活性材料层的正极极片。冷压过程的正极极片的压实密度为4.15g/cm 3。
负极极片的制备：将氧化亚硅(克容量为1545mAh/g)、丙烯酸树脂、导电碳黑、单壁碳纳米管和羧甲基纤维素钠按重量比88.3：9：1.5：0.2：1.0的比例溶于去离子中，形成负极浆料。采用铜箔作为负极集流体，将负极浆料涂覆于负极集流体上，干燥，冷压，裁切后得到表面设置有单位面积质量为3.252mg/mm 2的负极活性材料层的负极极片。
隔离膜的制备：隔离膜基材为9μm厚的聚乙烯(PE)，在隔离膜基材的两侧各涂覆2μm氧化铝陶瓷层，最后在涂布了陶瓷层的两侧各涂覆2.5mg/cm 2的粘结剂聚偏氟乙烯(PVDF)，烘干。
电解液的制备：在含水量小于10ppm的环境下，将LiPF 6加入非水有机溶剂(碳酸乙烯酯(EC)：碳酸二乙酯(DEC)：碳酸亚丙酯(PC)：丙酸丙酯(PP)：碳酸亚乙烯酯(VC)＝20：30：20：28：2，重量比)，混合均匀，得到电解液。电解液中的LiPF 6的质量百分含量为8％。
锂离子电池的制备：将正极极片、隔离膜、负极极片按顺序依次叠好，使隔离膜处于正极极片和负极极片中间起到隔离的作用，并卷绕得到电极组件。将电极组件置于外包装铝塑膜中，在80℃下脱去水分后，注入上述电解液并封装，经过化成，脱气，切边等工艺流程得到锂离子电池。
其他实施例和对比例是在实施例1的步骤的基础上进行参数变更，具体变更的参数如下面的表格所示。
下面描述本申请的各个参数的测试方法。
循环性能测试：
将锂离子电池置于25℃±2℃的恒温箱中静置2小时，以0.5C倍率进行充电至4.25V(电压值为各实施例的充电截止电压)，然后在4.25V(电压值为各实施例的充电截止电压)下恒压充电至0.05C并且静置15分钟。随后以0.5C倍率放电至3.0V，静置5分钟，此为一次充放电循环过程。以首次放电的容量为100％，反复进行充放电循环过程，以每个循环的放电容量和首次放电容量的比值作为评价锂离子电池的循环性能的指标。以电池的初始厚度为0％，以500次循环的电池满充厚度与电池的初始厚度的比值作为锂离子电池的循环膨胀的指标。
表1示出了实施例1至5和对比例1的各个参数和评估结果。实施例1至5的负极活性材料层的单位面积质量和充电截止电压与对比例1不同。
表1
Figure PCTCN2021083042-appb-000001
通过比较实施例1至5和对比例1可知，在3≤100×(4.5-U)-10×(CB-1)≤10时，相比于100×(4.5-U)-10×(CB-1)＝22的情况，锂离子电池的循环容量保持率显著增大，而锂离子电池的循环膨胀率明显减小。另外，随着100×(4.5-U)-10×(CB-1)的增大或者随着充电截止电压的减小，锂离子电池的循环容量保持率有增大的趋势，而锂离子电池的循环膨胀率有减小的趋势。
表2示出了实施例6至12的各个参数和评估结果。其中，在实施例6至7中，负极活性材料为质量分别为20％SiO和80％石墨的机械混合样品，整体克容量为593mAh/g；在实施例8至9中，负极活性材料为质量分别为60％SiO和40％石墨的机械混合样品，整体克容量为1069mAh/g；在实施例10至12中，负极活性材料为质量分别为80％SiO和20％石墨的机械混合样品，整体克容量为1307mAh/g。
表2
Figure PCTCN2021083042-appb-000002
Figure PCTCN2021083042-appb-000003
通过比较实施例6至12可知，通过改变负极活性材料层的单位面积质量和负极活性材料的克容量调节了CB值。通过比较实施例6和7可知，在增大CB和减小充电截止电压U时，锂离子电池的循环容量保持率提高，并且循环膨胀率降低。通过比较实施例7和8以及比较实施例9至12，可以得到同样的结果。
另外，通过比较实施例6、9和12可知，虽然负极活性材料中的硅材料的质量含量提高，但是由于增大了CB和减小了充电截止电压U，锂离子电池的循环膨胀率反而减小，并且锂离子电池的循环容量保持率也有一定的提升。
表3示出了实施例13至15的各个参数和评估结果。其中，在实施例13至15中，负极活性材料为质量分别为80％SiC和20％石墨的机械混合样品，整体克容量为1495mAh/g，实施例13至15的负极活性材料层的单位面积质量与实施例1不同，实施例13和15的CB和U与实施例1不同。
表3
Figure PCTCN2021083042-appb-000004
通过比较实施例13至15可知，通过改变负极活性材料层的单位面积质量调节了CB值，随着CB的增大和充电截止电压U的减小，针对同样的负 极活性材料SiC+石墨，锂离子电池的循环容量保持率有增大的趋势，而循环膨胀率有减小的趋势。
表4示出了实施例16至20的各个参数和评估结果。其中，实施例16至20中的正极活性材料为镍钴锰材料(镍：钴：锰的摩尔比为6：2：2)，克容量为174mAh/g，负极活性材料以质量百分数计为80％SiO和20％石墨机械混合样品，充电克容量为1307mAh/g。
表4
Figure PCTCN2021083042-appb-000005
通过比较实施例16至20可知，在三元材料(镍钴锰)体系中，在4≤100×(4.5-U)-10×(CB-1)≤22时，相比于100×(4.5-U)-10×(CB-1)＝1时，通过改变负极活性材料层的单位面积质量调节了CB值，在增大CB同时降低充电截止电压U，即，CB/U增大，针对同样的负极活性材料SiO，锂离子电池的循环容量保持率逐渐提升，而循环膨胀率逐渐降低。
以上描述仅为本申请的较佳实施例以及对所运用技术原理的说明。本领域技术人员应当理解，本申请中所涉及的公开范围，并不限于上述技术特征的特定组合而成的技术方案，同时也应涵盖由上述技术特征或其等同特征进行任意组合而形成的其它技术方案。例如上述特征与本申请中公开的具有类似功能的技术特征进行互相替换而形成的技术方案。

Claims (15)

  1. 一种电化学装置，其包括：
    正极极片，包括正极集流体和设置在所述正极集流体上的正极活性材料层，所述正极活性材料层包括正极活性材料，所述正极活性材料包括钴酸锂；
    负极极片，包括负极集流体和设置在所述负极集流体上的负极活性材料层，所述负极活性材料层包括负极活性材料；
    隔离膜，设置在所述正极极片和所述负极极片之间；
    其中，所述电化学装置满足如下关系式：
    3≤100×(4.5-U)-10×(CB-1)≤10，
    CB＝(A’×B’×C’)/(A×B×C)，
    其中，A为所述正极活性材料的质量占所述正极活性材料层的总质量的百分含量，B为所述正极活性材料的克容量，单位为mAh/g，C为所述正极活性材料层的单位面积质量，单位为mg/cm 2，A’为所述负极活性材料的质量占所述负极活性材料层的总质量的百分含量，B’为所述负极活性材料的克容量，单位为mAh/g，C’为所述负极活性材料层的单位面积质量，单位为mg/cm 2，U为所述电化学装置的充电截止电压，单位为V。
  2. 根据权利要求1所述的电化学装置，其中，3.5≤100×(4.5-U)-10×(CB-1)≤6。
  3. 根据权利要求1或2所述的电化学装置，其中，1.04≤CB≤2.0，4.3≤U<4.5。
  4. 根据权利要求1所述的电化学装置，其中，0.17＜CB/U＜0.48。
  5. 根据权利要求1所述的电化学装置，其中，所述负极活性材料包括SiO x、硅合金或硅碳复合物中的至少一种，其中0.3≤x≤1.5。
  6. 根据权利要求1所述的电化学装置，其中，所述电化学装置还包括设置在所述负极集流体和所述负极活性材料层之间的导电层，所述导电层包括导电剂和粘结剂。
  7. 根据权利要求6所述的电化学装置，其中，所述导电剂包括炭黑、乙炔黑、科琴黑、石墨烯、碳纳米管、碳纤维或碳纳米线中的至少一种。
  8. 一种电化学装置，其包括：
    正极极片，包括正极集流体和设置在所述正极集流体上的正极活性材料层，所述正极活性材料层包括正极活性材料，所述正极活性材料包括镍钴锰酸锂或镍钴铝酸锂中的至少一种；
    负极极片，包括负极集流体和设置在所述负极集流体上的负极活性材料层，所述负极活性材料层包括负极活性材料；
    隔离膜，设置在所述正极极片和所述负极极片之间；
    其中，所述电化学装置满足如下关系式：
    4≤100×(4.49-U)-10×(CB-1)≤22，
    CB＝(A’×B’×C’)/(A×B×C)，
    其中，A为所述正极活性材料的质量占所述正极活性材料层的总质量的百分含量，B为所述正极活性材料的克容量，单位为mAh/g，C为所述正极活性材料层的单位面积质量，单位为mg/cm 2，A’为所述负极活性材料的质量占所述负极活性材料层的总质量的百分含量，B’为所述负极活性材料的克容量，单位为mAh/g，C’为所述负极活性材料层的单位面积质量，单位为mg/cm 2，U为所述电化学装置的充电截止电压，单位为V。
  9. 根据权利要求8所述的电化学装置，其中，5≤100×(4.49-U)-10×(CB-1)≤13。
  10. 根据权利要求8或9所述的电化学装置，其中，1.04≤CB≤2.0，4.1≤U<4.49。
  11. 根据权利要求8所述的电化学装置，其中，0.17＜CB/U＜0.48。
  12. 根据权利要求8所述的电化学装置，其中，所述负极活性材料包括SiO x、硅合金或硅碳复合物中的至少一种，其中0.3≤x≤1.5。
  13. 根据权利要求8所述的电化学装置，其中，所述电化学装置还包括设置在所述负极集流体和所述负极活性材料层之间的导电层，所述导电层包括导电剂和粘结剂。
  14. 根据权利要求13所述的电化学装置，其中，所述导电剂包括炭黑、乙炔黑、科琴黑、石墨烯、碳纳米管、碳纤维或碳纳米线中的至少一种。
  15. 一种电子装置，包括根据权利要求1至14中任一项所述的电化学装置。
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