WO2020133671A1 - 电极组件以及锂离子电池 - Google Patents

电极组件以及锂离子电池 Download PDF

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WO2020133671A1
WO2020133671A1 PCT/CN2019/076160 CN2019076160W WO2020133671A1 WO 2020133671 A1 WO2020133671 A1 WO 2020133671A1 CN 2019076160 W CN2019076160 W CN 2019076160W WO 2020133671 A1 WO2020133671 A1 WO 2020133671A1
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lithium
negative electrode
active material
layer
electrode active
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PCT/CN2019/076160
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English (en)
French (fr)
Inventor
杨龙飞
王国宝
刘晓梅
刘江
林永寿
赵丰刚
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宁德时代新能源科技股份有限公司
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Priority to EP19906550.9A priority Critical patent/EP3905396B1/en
Priority to US17/416,026 priority patent/US11996545B2/en
Publication of WO2020133671A1 publication Critical patent/WO2020133671A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. 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
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/04—Construction or manufacture in general
    • H01M10/049—Processes for forming or storing electrodes in the battery container
    • H—ELECTRICITY
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    • 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
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    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/04—Processes of manufacture in general
    • H01M4/0438—Processes of manufacture in general by electrochemical processing
    • H01M4/044—Activating, forming or electrochemical attack of the supporting material
    • H01M4/0445—Forming after manufacture of the electrode, e.g. first charge, cycling
    • H01M4/0447—Forming after manufacture of the electrode, e.g. first charge, cycling of complete cells or cells stacks
    • H—ELECTRICITY
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    • H01M4/049—Manufacturing of an active layer by chemical means
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—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
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/387—Tin or alloys based on tin
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • 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
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to the field of batteries, and more particularly to an electrode assembly and a lithium ion battery.
  • lithium ion batteries have a higher energy density advantage than other types of secondary batteries, which makes them occupy a mainstream position in the market.
  • lithium ion batteries using lithium iron phosphate as the positive electrode active material are widely used in electric bus power systems due to their high safety, low cost, and long life, and have broad application prospects in the field of large-scale energy storage.
  • the loss of active lithium caused by side reactions inside the lithium ion battery is an important reason for the capacity decay of the lithium ion battery.
  • An effective way to solve this problem is to add appropriate amount of lithium in advance in the design and manufacturing stage of lithium-ion batteries. These lithium can gradually release and compensate the active lithium caused by the side reactions inside the lithium-ion battery during the manufacture and use of the lithium-ion battery. Loss, thereby greatly avoiding the capacity decline of lithium ion batteries.
  • a proper amount of lithium is directly covered on the surface of the negative pole piece to form a metal lithium layer, but after covering the surface of the negative pole piece, part of the lithium will react with air, resulting in a low utilization rate of lithium in the metal lithium layer.
  • the battery life improvement effect is not as expected; at the same time, the products of lithium and air reaction, such as lithium oxide and lithium carbonate, accumulate on the surface of the negative pole piece, which will increase the negative electrode impedance after pre-intercalation of lithium and affect the DC resistance of the lithium ion battery.
  • the object of the present invention is to provide an electrode assembly and a lithium-ion battery, the lithium-ion battery has a higher lithium supplementation efficiency and a lower DC impedance, and the lithium-ion battery also has Long cycle life and storage life.
  • an electrode assembly which includes a positive electrode tab, a separator, and a negative electrode tab
  • the negative electrode tab includes a negative electrode current collector
  • the negative electrode current collector is provided at least A negative active material layer on one surface and including a negative active material.
  • the negative pole piece further includes a metal lithium layer disposed on a surface of the negative electrode active material layer away from the negative electrode current collector side, the metal lithium layer is formed by a plurality of regular or irregular strip-shaped lithium-rich regions , And the plurality of lithium-rich regions present a discontinuous shape with spaced distribution along the length direction of the negative pole piece.
  • a lithium ion battery including an electrode assembly, a battery case, and an electrolyte
  • the electrode assembly is the electrode assembly according to the first aspect of the present invention
  • the electrode assembly is After being inserted into the battery case and injecting the electrolyte, at least a part of lithium in the metal lithium layer on the surface of the negative electrode active material layer undergoes pre-intercalation of lithium under the action of the electrolyte, and is distributed in the negative electrode activity in the form of a first lithium intercalation compound In the material layer.
  • the negative electrode tab of the present invention is provided with a discontinuously distributed metal lithium layer on the surface of the negative electrode active material layer, which reduces the contact area of the metal lithium layer with air, reduces the probability of lithium being oxidized, and thus improves
  • the utilization rate of lithium in the lithium metal layer improves the efficiency of inserting lithium into the negative electrode active material layer during the liquid injection process, improves the stability and film forming quality of the SEI film on the surface of the negative electrode, and reduces the DC resistance of the lithium ion battery.
  • the negative electrode active material After the lithium ion battery of the present invention is fully charged during use, the negative electrode active material has sufficient vacancies to receive all the active lithium extracted from the positive electrode active material, and stores excess active lithium in the negative electrode after full discharge, and the lithium The rate of loss of active lithium during the decay of ion batteries is low, so it can effectively improve the cycle life and storage life of lithium ion batteries.
  • FIG. 1 is a schematic structural diagram of a negative pole piece of the present invention
  • FIG. 2 is a schematic structural view of a first embodiment of a negative pole piece of the present invention
  • FIG. 3 is a schematic structural view of a second embodiment of the negative pole piece of the present invention.
  • FIG. 4 is a schematic structural view of a third embodiment of the negative pole piece of the present invention.
  • FIG. 5 is a schematic structural view of a fourth embodiment of the negative pole piece of the present invention.
  • FIG. 6 is a schematic structural diagram of a fifth embodiment of the negative pole piece of the present invention.
  • the electrode assembly according to the first aspect of the present invention includes a negative electrode tab, a positive electrode tab, and a separator. It should be noted that the electrode assembly according to the first aspect of the present invention refers to an electrode assembly that has not been immersed in the electrolyte (that is, the structure before the electrolyte is injected). The electrode assembly according to the first aspect of the present invention can only be Including negative pole piece, positive pole piece and separator.
  • the negative electrode tab includes a negative electrode current collector 1 and a negative electrode active material layer 2 provided on at least one surface of the negative electrode current collector 1 and including a negative electrode active material.
  • the negative pole piece further includes a metal lithium layer 3 provided on the surface of the negative electrode active material layer 2 away from the negative electrode current collector 1.
  • the metal lithium layer 3 is formed of a plurality of regular or irregular strip-shaped lithium-rich regions 31.
  • the plurality of lithium-rich regions 31 have a discontinuous shape distributed at intervals along the longitudinal direction L of the negative electrode tab.
  • the negative pole piece according to the first aspect of the present invention refers to a negative pole piece that has not been immersed in electrolyte (that is, a pole piece structure before injection of electrolyte).
  • the plurality of lithium-rich regions 31 presents a discontinuously distributed form along the longitudinal direction L of the negative pole piece, that is, the metal lithium layer 3 is a discontinuous form of the distributed form, so that the metal lithium layer 3 is provided on the negative electrode
  • the contact area between the metal lithium layer 3 and the air is reduced, and the probability of lithium being oxidized is reduced, thereby improving the utilization rate of lithium in the metal lithium layer 3 and improving the activity of lithium intercalating into the negative electrode during the liquid injection process.
  • the efficiency of the material layer that is, the pre-intercalation lithium efficiency of the negative pole piece is improved), improves the stability and film formation quality of the SEI film on the negative electrode surface, and reduces the DC resistance of the lithium ion battery.
  • discontinuous channel structures can be formed between the discontinuous metal lithium layer 3 and the negative electrode active material layer 2 to increase the diffusion path of the electrolyte on the surface of the negative pole piece, greatly increase the rate of infiltration of the negative pole piece with the electrolyte, and thus increase lithium Liquid injection efficiency of ion batteries.
  • the non-continuous shape of the metal lithium layer 3 provided on the surface of the negative electrode active material layer 2 can also improve the efficiency of the active lithium intercalating into the negative electrode active material layer 2 during the decay of the battery after injection, and reduce the loss of active lithium during the decay of the lithium ion battery Rate, so the present invention can effectively increase the cycle life and storage life of lithium ion batteries.
  • each lithium-rich region 31 is in the form of regular or irregular strips, and its advantage lies in the ability to form regularly distributed or irregular strip-shaped grooves (that is, adjacent lithium-rich regions 31) on the entire surface of the negative pole piece.
  • the gap position of the gap constitutes a groove), increasing the specific surface area of the negative pole piece, which is beneficial to use the capillary effect to improve the negative pole piece to the electrolyte infiltration effect and the rate of infiltration.
  • the angle between the longitudinal direction of each lithium-rich region 31 and the longitudinal direction L of the negative electrode tab is 45° to 135°.
  • the negative electrode sheet of this structure is particularly suitable for forming a wound electrode assembly.
  • the wound electrode assembly uses the width direction of the electrode sheet as the central axis, and the long side of the electrode sheet is circumferentially wound around the central axis to form an electrode. Components.
  • the angle between the longitudinal direction of each lithium-rich region 31 and the longitudinal direction L of the negative pole piece is 45° to 135°
  • the longitudinal extension direction of each lithium-rich region 31 is substantially perpendicular to the winding direction of the negative pole piece.
  • each lithium-rich region 31 will not break or fall off the surface of the negative electrode active material layer 2 due to the tensile stress in the winding direction, thereby ensuring that each lithium-rich region 31 (or metal lithium layer 3 ) Stably adheres to the surface of the negative electrode active material layer 2.
  • the electrolyte gradually infiltrate the entire electrode assembly from the heads of both ends of the winding of the electrode assembly.
  • each lithium-rich region 31 When the length extension direction of each lithium-rich region 31 is substantially perpendicular to the winding direction of the negative electrode sheet, the surface of the negative electrode sheet The extending direction of the spaced-apart strip grooves formed is generally consistent with the electrolyte diffusion direction, which is also beneficial to use the capillary effect to improve the infiltration effect and infiltration rate of the anode pole piece on the electrolyte.
  • the angle between the longitudinal direction of each lithium-rich region and the longitudinal direction L of the negative electrode tab is 60° to 120°.
  • each lithium-rich region 31 In the longitudinal direction of each lithium-rich region 31, the ratio of the length of the anode active material layer region covered with the metal lithium layer on the surface to the length of the anode active material layer region not covered with the metal lithium layer is not less than 20:1. Preferably, in the longitudinal direction of each lithium-rich region 31, each lithium-rich region 31 completely covers the negative electrode active material layer 2. Referring to FIGS. 2 to 4, in the longitudinal direction of each lithium-rich region 31, each lithium-rich region 31 almost completely covers the anode active material layer 2. 5 and 6, in the longitudinal direction of each lithium-rich region 31, each lithium-rich region 31 fails to completely cover the negative electrode active material layer 2.
  • each lithium-rich region 31 covers a relatively large area in the width direction W of the negative pole piece, which can ensure that the binding force between the metal lithium layer 3 and the negative electrode active material layer 2 is good, so that the negative electrode During the preparation and use of the pole piece, such as cold pressing or winding, the metal lithium layer 3 can be stably attached to the surface of the negative electrode active material layer 2 without falling off from the surface of the negative electrode active material layer 2.
  • each lithium-rich region 31 is 0.2 mm to 2 mm, and the distance between each two adjacent lithium-rich regions 31 is 0.25 times to 2 times the average width of the two adjacent lithium-rich regions 31.
  • the coverage area of each lithium-rich region 31 in the width direction W of the negative pole piece is relatively high and almost completely covered, while the coverage area in the longitudinal direction L of the negative pole piece is relatively low, showing a discontinuous form of interval distribution In this way, it can be ensured that the contact area of the metal lithium layer 3 with air is small, and the probability of occurrence of lithium oxidation is small, so that the utilization rate of lithium in the metal lithium layer 3 is high.
  • the diffusion rate of lithium in the lithium-rich region 31 to the lithium-depleted region is faster, thereby ensuring the negative electrode active material layer 2
  • the internal lithium insertion has good uniformity.
  • each lithium-rich region 31 may be a regular elongated strip, a regular strip or a regular wavy strip, or may be an irregular elongated strip or an irregular strip Shaped or irregular wavy strips.
  • each lithium-rich region 31 has a regular or irregular wavy strip shape.
  • each lithium-rich region 31 exhibits a discontinuous shape with a spaced distribution on the surface of the negative electrode active material layer 2, the lithium in each lithium-rich region 31 will first be deposited in the negative electrode active material covered with the lithium-rich region 31 during the negative electrode pre-intercalation process Longitudinal diffusion in the layer (that is, first diffuse in the thickness direction of the negative electrode active material layer covered with the lithium-rich region 31), and then laterally diffuse into the negative electrode active material layer region at the gap position on both sides of each lithium-rich region 31, and finally reach the pre-
  • the provided metal lithium layer 3 is combined with most of the anode active material in the anode active material layer 2 to form a pre-intercalated lithium compound.
  • each lithium-rich region 31 is a regular or irregular wavy strip
  • the diffusion path of lithium is shortened, which is more conducive to the rapid combination of lithium and the negative electrode active material at the gap position, thereby improving the lithium in the metal lithium layer 3 Utilization rate.
  • each lithium-rich region 31 is lithium foil, lithium mesh, or lithium powder.
  • Each lithium-rich region 31 may be provided on the surface of the negative electrode active material layer 2 away from the negative electrode current collector 1 by rolling, using the intermolecular force of lithium and the negative electrode active material (such as graphite) to make each The lithium-rich region 31 is stably attached to the surface of the negative electrode active material layer 2.
  • the mass of the lithium metal layer 3 is 0.5% to 5% of the total mass of the negative electrode active material layer 2; preferably, the mass of the lithium metal layer 3 is 1% to 5% of the total mass of the negative electrode active material layer 2.
  • the anode active material layer 2 may be provided on one surface of the anode current collector 1 or may be provided on both surfaces of the anode current collector 1.
  • the material of the negative electrode current collector 1 is not subject to specific restrictions, and can be selected according to actual needs.
  • the negative electrode active material is selected from materials that can accept and extract lithium ions.
  • the negative electrode active material is selected from graphite, soft carbon, hard carbon, mesophase carbon microspheres, nanocarbon, elemental silicon, silicon oxide, silicon carbon composite, silicon alloy, elemental tin, tin oxide, tin One or more of carbon composite, tin alloy, lithium titanate. More preferably, the negative electrode active material includes at least graphite.
  • the negative electrode active material layer 2 further includes a binder and an optional conductive agent.
  • the types of the binder and the conductive agent are not specifically limited, and can be selected according to actual needs.
  • the binder may be selected from one or more of styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC).
  • the conductive agent may be selected from one or more of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene, and carbon nanotubes.
  • the negative pole piece further includes a tab 4 provided on the negative electrode current collector 1.
  • the number of tabs 4 is not specifically limited, and may be one or more.
  • the tab 4 is obtained by die-cutting the negative electrode current collector 1.
  • the positive electrode tab includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector and including a positive electrode active material
  • the positive electrode active material layer may be It may be provided on one surface of the positive electrode current collector or on both surfaces of the positive electrode current collector.
  • the material of the positive electrode current collector is not subject to specific restrictions, and can be selected according to actual needs.
  • the positive electrode active material is selected from materials that can accept and extract lithium ions.
  • the positive electrode active material may be selected from one or more compounds selected from the group consisting of lithium transition metal oxides, lithium transition metal oxides and other transition metals or non-transition metals or non-metals.
  • the positive electrode active material may be selected from lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, olivine structure One or more of lithium-containing phosphates.
  • Olivine structure lithium-containing phosphate in the formula may be LiFe 1-xy Mn x M ' y PO 4, 0 ⁇ x ⁇ 1,0 ⁇ y ⁇ 0.1,0 ⁇ x + y ⁇ 1, M' is selected from other One or more of transition metal elements or non-transition metal elements other than Fe and Mn.
  • the olivine-structured lithium-containing phosphate may be lithium iron phosphate, lithium manganese phosphate and lithium manganese phosphate.
  • the olivine-structured lithium-containing phosphate itself has high structural stability, and it will not cause structural loss during cycling due to structural changes like other positive electrode active materials. Therefore, the olivine structure containing The capacity attenuation of the lithium phosphate electrode assembly is mainly due to the loss of active lithium that can shuttle between the positive and negative electrodes (for example, some active lithium participates in the repair process of the SEI film on the surface of the negative electrode), so it can effectively reduce the capacity loss of the electrode assembly Rate, greatly improve the cycle life and storage life of the electrode assembly.
  • the positive electrode active material of the present invention is not limited to lithium-containing phosphates having an olivine structure.
  • the positive electrode active material layer further includes a conductive agent and a binder.
  • the types of the binder and the conductive agent are not subject to specific restrictions, and can be selected according to actual needs.
  • the binder may be selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene One or more of meta-copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, and fluorine-containing acrylate resins.
  • the conductive agent may be selected from one or more of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene, and carbon nanotubes.
  • the capacity of the lithium metal layer ⁇ 80%) ⁇ 1.10.
  • the cycle life and storage life of the lithium ion battery can be effectively improved without reducing the energy density.
  • the negative electrode active material has the ability to accept lithium ions, and the vacancies provided need to accommodate the insertion of lithium from the metal lithium layer when the negative electrode is pre-intercalated with lithium, and accommodate the extraction of the active material from the positive electrode during the first charging process Of all active lithium.
  • the negative electrode capacity per unit area/positive electrode capacity per unit area 1.3 to 2.1.
  • Negative electrode capacity per unit area negative electrode coating mass per unit area ⁇ negative electrode active material coating mass fraction ⁇ reversible gram capacity of negative electrode active material.
  • Positive electrode capacity per unit area positive electrode coating mass per unit area ⁇ positive electrode active material coating mass fraction ⁇ reversible gram capacity of positive electrode active material.
  • the capacity of the metal lithium layer per unit area of the surface of the negative electrode active material layer the mass of the metal lithium layer per unit area of the surface of the negative electrode active material layer ⁇ the theoretical gram capacity of metal lithium is 3861.3 mAh/g. Since the lithium metal layer is in a discontinuous form with an interval distribution, the "mass of the lithium metal layer on the surface of the anode active material layer per unit area" means the ratio of the total mass of the lithium metal layer on the surface of the anode active material layer to the total area of the anode active material layer.
  • the separation membrane is provided between the positive pole piece and the negative pole piece to play a role of isolation.
  • the type of the isolation membrane is not specifically limited, and may be any isolation membrane material used in the prior art, such as polyethylene, polypropylene, polyvinylidene fluoride, and their multilayer composite membranes, but not limited to these.
  • the lithium ion battery according to the second aspect of the present invention includes an electrode assembly, a battery case, and an electrolyte, wherein the electrode assembly is the electrode assembly according to the first aspect of the present invention, and the electrode assembly is assembled into the battery case And after injecting the electrolyte, at least a part of lithium in the metal lithium layer on the surface of the negative electrode active material layer undergoes pre-intercalation of lithium under the action of the electrolyte, and is distributed in the negative electrode active material layer in the form of a first lithium intercalation compound.
  • the metal lithium layer provided on the surface of the negative electrode active material layer of the present invention is in a discontinuous form with a spaced distribution, there are regions not covered by the metal lithium layer between adjacent lithium-rich regions. After the electrolyte is injected, the negative electrode tab There is a potential difference on the surface. After a long enough infiltration and diffusion, the lithium in the lithium-rich region will diffuse to the lithium-poor region (the gap position of the lithium-rich region), and finally the lithium content in the negative electrode active material layer can still be uniform to achieve uniform lithium insertion .
  • the lithium ion battery of the second aspect of the present invention after the electrode assembly is inserted into the battery case and the electrolyte is injected, a part of lithium in the metal lithium layer on the surface of the negative electrode active material layer is formed under the action of the electrolyte.
  • the lithium-intercalation compound is present on the surface of the negative electrode active material layer, and the second lithium-intercalation compound exhibits a discontinuous shape with a spaced distribution on the surface of the negative electrode active material layer.
  • the electrode assembly After the electrode assembly is installed in the battery case and the electrolyte is injected, part of the lithium (about 80%) in the metal lithium layer on the surface of the negative electrode active material layer will be inserted into the negative electrode active material layer and exist in the negative electrode in the form of the first lithium intercalation compound Inside the active material layer, at the same time, the second lithium intercalation compound is formed at the original region where the metal lithium layer is provided on the surface of the negative electrode active material layer.
  • the thickness of the negative electrode active material layer covered with the second lithium intercalation compound is greater than the thickness of the position not covered with the second lithium intercalation compound along the thickness direction of the negative pole piece, this can ensure that the negative pole piece still has a high level after pre-lithium intercalation
  • the specific surface area facilitates the active lithium to better intercalate into the negative electrode active material during the use of lithium-ion batteries.
  • the position of the second lithium intercalation compound on the surface of the negative electrode active material layer is the same as the position of the metal lithium layer, and the second lithium intercalation compound includes one of a lithium nitrogen compound, lithium carbonate, and lithium oxide Or several.
  • an SEI film is formed on the surface of the negative electrode, and the second lithium intercalation compound includes one or more of lithium nitrogen compounds, lithium carbonate, and lithium oxide.
  • the second lithium intercalation compound formed on the surface of the negative electrode active material layer can effectively improve the composition of the SEI film formed during the first charge of the battery, and reduce the impedance of the SEI film, thereby reducing the DC resistance of the lithium ion battery, Improve the cycle life of lithium ion batteries.
  • the SEI film formed by the above-mentioned materials has poor flexibility, and by providing a discontinuously distributed metal lithium layer on the surface of the negative electrode active material layer, the second lithium intercalation compound formed after pre-intercalation of the negative pole piece is also
  • the non-continuous form of the space distribution can reduce the relative content and coverage of the above substances in the SEI film, make better use of the above substances to improve the SEI film, and avoid excessively reducing the flexibility of the SEI film.
  • the ratio of the remaining active lithium capacity in the negative pole piece to the positive electrode capacity after the first week of the lithium ion battery is 5% to 97%, in other words, the lithium
  • the lithium-rich state of the ion battery after charge and discharge in the first week is 105% to 197% (relative to the positive electrode capacity).
  • the ratio is less than 5%, there is less active lithium remaining in the negative pole piece after the first week of charge and discharge, and the improvement effect on the cycle life and storage life of the lithium ion battery is not significant; the ratio is greater than 97%, the negative pole after the first week of charge and discharge Too much active lithium remains in the sheet, which may easily lead to lithium residue on the surface of the negative pole piece, which causes a high safety hazard for lithium ion batteries.
  • the ratio of the remaining active lithium capacity in the negative pole piece to the positive pole capacity of the lithium ion battery after the first week of charge and discharge is 5% to 50%.
  • the electrolyte includes a lithium salt and an organic solvent, and the specific composition of the lithium salt and the organic solvent is not subject to specific restrictions, and can be selected according to actual needs.
  • the organic solvent may include one or more of cyclic carbonate, chain carbonate, and carboxylic acid ester.
  • the cyclic carbonate may be selected from one or more of ethylene carbonate, propylene carbonate, 1,2-butene carbonate, and 2,3-butanediol carbonate; preferably,
  • the chain carbonate may be selected from ethyl methyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, ethyl propyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate ,
  • the carboxylic acid ester may be selected from methyl pivalate, ethyl pivalate, propyl pivalate, butyl pivalate, butyric acid Methyl ester, ethyl butyrate, propyl butyrate, butyl butyrate, methyl propionate, e
  • the lithium salt may be selected from one or more of LiPF 6 , LiBF 4 , LiClO 4 , LiPO 2 F 2 , Li 2 PO 3 F, LiSO 3 F, and LiBOB.
  • the electrolyte may further include additives, and the types of the additives are not particularly limited, and may be negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain performance of the battery.
  • additives to improve battery overcharge performance additives to improve battery high temperature performance, additives to improve battery low temperature performance, etc.
  • the battery case has a receiving cavity, and the electrode assembly is placed in the receiving cavity of the battery case.
  • the material of the battery case is not particularly limited, and may be plastic, metal, or aluminum-plastic film.
  • the positive electrode active material lithium iron phosphate (reversible gram capacity is 139mAh/g), the conductive agent acetylene black, and the binder PVDF are mixed at a mass ratio of 94:4:2, the solvent N-methylpyrrolidone is added, and the mixture is stirred and mixed to obtain
  • the positive electrode slurry is then coated on both surfaces of the positive electrode current collector aluminum foil, and then dried and cold-pressed to obtain a positive electrode sheet, wherein the coating mass of the positive electrode slurry is 0.198g/1540.25mm 2 (without containing a solvent Quality meter).
  • the negative electrode active material graphite (reversible gram capacity is 340mAh/g), conductive agent acetylene black, binder SBR+CMC according to the mass ratio of 95:1.5:3.1:0.4, add solvent deionized water, stir and mix well to obtain
  • the negative electrode slurry is then coated on both surfaces of the negative electrode current collector copper foil, and the negative electrode active material layer is obtained after drying and cold pressing, in which the coating quality of the negative electrode slurry is 0.120g/1540.25mm 2 (with no Mass meter containing solvent).
  • a plurality of wavy strip-shaped lithium foils are compounded on the surface of the negative electrode active material layer at equal intervals by rolling to form a discontinuously distributed metal lithium layer in a spaced-apart manner to obtain a negative electrode tab.
  • the mass of the lithium metal layer is 3.05mg/1540.25mm 2
  • the width of each wavy strip lithium foil is 0.5mm
  • the distance between two adjacent wavy strip lithium foils is 0.5mm
  • the wavy strip lithium The angle between the longitudinal direction of the foil and the longitudinal direction of the negative pole piece is about 80°, and along the longitudinal direction of each wavy strip-shaped lithium foil, the surface of the negative electrode active material layer is completely covered by the lithium foil.
  • an organic solvent is obtained, and then the lithium salt LiPF 6 that has been sufficiently dried is dissolved in the above organic solvent, and after stirring uniformly, an electrolyte is obtained, in which the concentration of LiPF 6 is 1 mol/L.
  • a porous polyethylene membrane was used as the separator.
  • the positive pole piece, the separator and the negative pole piece are stacked in order, so that the separator is placed in the middle of the positive and negative electrodes to play the role of isolation, and the electrode assembly is wound.
  • the electrode assembly is placed in the battery case, and the prepared electrolyte is injected and packaged to obtain a lithium ion battery.
  • the preparation process of the lithium-ion battery is the same as that in Example 1, except that in the preparation of the negative pole piece, a number of wavy strip-shaped lithium foils are replaced with elongated strip-shaped lithium foils and compounded at equal intervals by rolling A discontinuously distributed metallic lithium layer is formed on the surface of the negative electrode active material layer.
  • the mass of the metal lithium layer is 3.05mg/1540.25mm 2
  • the width of each elongated strip-shaped lithium foil is 0.5mm
  • the spacing between two adjacent elongated strip-shaped lithium foils is 0.5mm
  • the length of each elongated strip-shaped lithium foil The angle between the longitudinal direction of the foil and the longitudinal direction of the negative pole piece is about 85°, and along the longitudinal direction of each elongated strip-shaped lithium foil, the surface of the negative electrode active material layer is completely covered by the lithium foil.
  • the preparation process of the lithium-ion battery is the same as that in Example 1, except that in the preparation of the negative pole piece, several wavy strip-shaped lithium foils are replaced with strip-shaped lithium foils and compounded to the negative electrode at equal intervals by rolling A discontinuously distributed metallic lithium layer is formed on the surface of the active material layer.
  • the mass of the metal lithium layer is 3.05mg/1540.25mm 2
  • the width of each strip-shaped lithium foil is 0.5mm
  • the distance between two adjacent strip-shaped lithium foils is 0.5mm
  • the length of each strip-shaped lithium foil The angle between the direction and the longitudinal direction of the negative pole piece is about 92°, and along the longitudinal direction of each strip-shaped lithium foil, the surface of the negative electrode active material layer is completely covered by the lithium foil.
  • the preparation process of the lithium-ion battery is the same as that in Example 1, except that in the preparation of the negative pole piece, a number of wavy strip-shaped lithium foils are replaced with elongated strip-shaped lithium foils and compounded at equal intervals by rolling A discontinuously distributed metallic lithium layer is formed on the surface of the negative electrode active material layer.
  • the mass of the metal lithium layer is 3.05mg/1540.25mm 2
  • the width of each elongated strip-shaped lithium foil is 0.5mm
  • the distance between two adjacent elongated strip-shaped lithium foils is 0.2mm
  • the length of each elongated strip-shaped lithium foil The angle between the longitudinal direction of the foil and the longitudinal direction of the negative pole piece is about 100°, and along the longitudinal direction of each elongated strip-shaped lithium foil, the length and surface of the area of the negative electrode active material layer covered with the lithium foil are not covered
  • the ratio of the length of the region of the negative electrode active material layer with lithium foil is 20:1.
  • the preparation process of the lithium-ion battery is the same as that in Example 1, except that in the preparation of the negative pole piece, several wavy strip-shaped lithium foils are replaced with elongated strip-shaped lithium foils and compounded at regular intervals by rolling A discontinuously distributed metallic lithium layer is formed on the surface of the negative electrode active material layer.
  • the mass of the metal lithium layer is 3.05mg/1540.25mm 2
  • the width of each elongated strip-shaped lithium foil is 0.5mm
  • the spacing between two adjacent elongated strip-shaped lithium foils is 1mm
  • the length of each elongated strip-shaped lithium foil The angle between the longitudinal direction of the electrode and the longitudinal direction of the negative pole piece is about 95°, and along the longitudinal direction of each elongated strip-shaped lithium foil, the length and surface of the area of the negative electrode active material layer covered with lithium foil are not covered
  • the ratio of the length of the negative electrode active material layer region of the lithium foil is 40:1.
  • the preparation process of the lithium ion battery is the same as that in Example 1, except that the coating quality of the positive electrode slurry is 0.198 g/1540.25 mm 2 , the coating quality of the negative electrode slurry is 0.104 g/1540.25 mm 2 , and the surface of the negative electrode active material layer The mass of the lithium metal layer is 1.52 mg/1540.25 mm 2 .
  • the preparation process of the lithium ion battery is the same as that in Example 1, except that the coating quality of the positive electrode slurry is 0.259 g/1540.25 mm 2 , the coating quality of the negative electrode slurry is 0.136 g/1540.25 mm 2 , and the surface of the negative electrode active material layer The mass of the lithium metal layer is 1.99 mg/1540.25 mm 2 .
  • the preparation process of the lithium ion battery is the same as that in Example 1, except that the coating quality of the positive electrode slurry is 0.177 g/1540.25 mm 2 , the coating quality of the negative electrode slurry is 0.136 g/1540.25 mm 2 , and the metal on the surface of the negative electrode active material layer The mass of the lithium layer is 5.44 mg/1540.25 mm 2 .
  • the preparation process of the lithium ion battery is the same as that in Example 1, except that the coating quality of the positive electrode slurry is 0.160 g/1540.25 mm 2 , the coating quality of the negative electrode slurry is 0.136 g/1540.25 mm 2 , and the metal on the surface of the negative electrode active material layer The mass of the lithium layer is 6.16 mg/1540.25 mm 2 .
  • the preparation process of the lithium ion battery is the same as that in Example 1, except that the coating quality of the positive electrode slurry is 0.280 g/1540.25 mm 2 , the coating quality of the negative electrode slurry is 0.136 g/1540.25 mm 2 , and the surface of the negative electrode active material layer The mass of the lithium metal layer is 1.10 mg/1540.25 mm 2 .
  • a coating mass of the positive electrode slurry was 0.198g / 1540.25mm 2
  • the negative electrode slurry is applied mass of 0.120g / 1540.25mm 2
  • the surface of the negative electrode active material layer No metal lithium layer is provided.
  • a coating mass of the positive electrode slurry was 0.198g / 1540.25mm 2
  • the negative electrode slurry is applied mass of 0.094g / 1540.25mm 2
  • the surface of the negative electrode active material layer No metal lithium layer is provided.
  • a coating mass of the positive electrode slurry was 0.224g / 1540.25mm 2
  • the negative electrode slurry is applied mass of 0.136g / 1540.25mm 2
  • the surface of the negative electrode active material layer No metal lithium layer is provided.
  • the preparation process of the lithium ion battery is the same as that in Example 1, except that the coating quality of the positive electrode slurry is 0.287g/1540.25mm 2 , the coating quality of the negative electrode slurry is 0.136g/1540.25mm 2 , and the surface of the negative electrode active material layer No metal lithium layer is provided.
  • the preparation process of the lithium ion battery is the same as that in Example 1, except that the metal lithium layer on the surface of the negative electrode active material is continuous and the mass of the metal lithium layer is 3.05 mg/1540.25 mm 2 .
  • Formula 1 negative electrode capacity per unit area / positive electrode capacity per unit area
  • Formula 2 negative electrode capacity per unit area / (positive electrode capacity per unit area + capacity of lithium metal layer on the surface of the negative electrode active material layer per unit area ⁇ 80%)
  • the unit area is based on the area 1540.25mm 2 gauge.
  • C 0 is a reference to obtain a lithium ion battery of standard current I 0 1C.
  • the lithium ion battery During the DRC test, first charge the lithium ion battery at a constant current of 1I 0 to a voltage of 3.65V, then charge at a constant voltage of 3.65V to 0.05I 0 , and then discharge at 1I 0 for 30 minutes to 50% SOC; then test the ambient temperature After adjusting to 0°C and allowing it to stand for 3 hours, the lithium ion battery was discharged at 3I 0 for 30 seconds, and the voltage V 0 before discharge and the voltage V 1 after the end of the pulse were recorded.
  • Lithium ion battery discharge DCR (V 0 -V 1 )/3I 0 .
  • the capacity retention rate of the lithium ion battery after 500 cycles at 60°C (discharge capacity at the 500th cycle/discharge capacity at the first cycle) ⁇ 100%.
  • the capacity retention rate of a lithium ion battery after storage at 60°C for 90 days (discharge capacity after storage for 90 days/discharge capacity before storage) ⁇ 100%.
  • Example 1 and Comparative Example 5 the positive electrode pieces and the negative electrode pieces have the same capacity per unit area, and the mass percentage of the metal lithium layer relative to the negative electrode active material layer is also the same, but the metal lithium layer is distributed on the surface of the negative electrode active material layer
  • the morphology is different.
  • Example 1 is a discontinuous morphology distributed at intervals
  • Comparative Example 5 is a continuous morphology.
  • the lithium ion battery of the present invention can have more excellent cycle performance and storage performance.

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Abstract

本发明提供了一种电极组件以及锂离子电池。所述电极组件包括正极极片、隔离膜以及负极极片，所述负极极片包括负极集流体以及负极活性物质层，所述负极极片还包括金属锂层，所述金属锂层由多个规则或不规则的条状富锂区域形成，且所述多个富锂区域沿负极极片的长度方向呈现出间隔分布的非连续形态。所述电极组件还满足：单位面积负极容量/单位面积正极容量＝1.2～2.1且单位面积负极容量/(单位面积正极容量+单位面积负极活性物质层表面金属锂层容量×80％)≥1.10。本发明的锂离子电池具有较高的补锂效率以及较低的直流阻抗，同时所述锂离子电池还具有长的循环寿命和存储寿命。

Description

电极组件以及锂离子电池 技术领域
本发明涉及电池领域，更具体而言涉及一种电极组件以及锂离子电池。
背景技术
在二次电池中，锂离子电池相对于其它种类的二次电池来说，其较高的能量密度优势使其在市场上占据主流地位。其中，以磷酸铁锂为正极活性物质的锂离子电池以其高安全性、低成本、长寿命的特点广泛应用于电动大巴动力系统，并在大规模储能领域拥有广泛的应用前景。
近年来，基于度电成本考虑，对锂离子电池寿命的要求越来越高。由于在石墨负极表面会发生固体-电解质液界面膜(SEI膜)的溶解-修复平衡，导致可用于正负极之间穿梭的活性锂不断减少，从而不可避免地发生容量损失。以钛酸锂为负极活性物质的锂离子电池由于不生成SEI膜，可以避免负极副反应导致的容量损失，但是负极较高的电压平台导致锂离子电池的放电电压平台较低，能量密度过低，且其昂贵的单价导致单位Wh成本过高，锂离子电池的实际应用价值大打折扣。
锂离子电池内部副反应导致的活性锂损失是锂离子电池容量衰减的重要原因。解决这一问题的有效途径是在锂离子电池设计和制造阶段预先加入适量锂，这些锂能在锂离子电池制造和全生命周期使用过程中逐步释放并补偿锂离子电池内部副反应导致的活性锂损失，从而极大的避免锂离子电池的容量下降。通常是将适量锂直接覆盖在负极极片表面形成金属锂层，但是将锂覆盖在负极极片表面后，部分锂会与空气反应，导致金属锂层中锂的利用率较低，对锂离子电池寿命提升效果不及预期；同时锂与空气反应的产物例如氧化锂、碳酸锂等在负极极片表面堆积，会造成预嵌锂后负极阻抗增大，影响锂离子电池的直流阻抗。
发明内容
鉴于背景技术中存在的问题，本发明的目的在于提供一种电极组件以及锂离子电池，所述锂离子电池具有较高的补锂效率以及较低的直流阻抗，同时所述锂离子电池还具有长 的循环寿命和存储寿命。
为了达到上述目的，在本发明的第一方面提供了一种电极组件，其包括正极极片、隔离膜以及负极极片，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面上且包括负极活性物质的负极活性物质层。所述负极极片还包括设置在所述负极活性物质层远离所述负极集流体一侧的表面上的金属锂层，所述金属锂层由多个规则或不规则的条状富锂区域形成，且所述多个富锂区域沿所述负极极片的长度方向呈现出间隔分布的非连续形态。所述电极组件还满足：单位面积负极容量/单位面积正极容量＝1.2～2.1且单位面积负极容量/(单位面积正极容量+单位面积负极活性物质层表面金属锂层容量×80％)≥1.10。
在本发明的第二方面提供了一种锂离子电池，其包括电极组件、电池壳体以及电解液，所述电极组件为根据本发明第一方面所述的电极组件，且所述电极组件在装入电池壳体以及注入电解液后，所述负极活性物质层表面金属锂层中至少一部分锂在电解液作用下发生预嵌锂，并以第一嵌锂化合物的形式分布在所述负极活性物质层中。
本发明的有益效果包括：
(1)本发明的负极极片将间隔分布的非连续形态的金属锂层设置在负极活性物质层表面，降低了金属锂层与空气的接触面积，降低了锂被氧化的概率，从而提高了金属锂层中锂的利用率，并提高了注液过程中锂嵌入负极活性物质层的效率，改善了负极表面SEI膜的稳定性和成膜质量，降低了锂离子电池的直流阻抗。
(2)本发明的锂离子电池在使用过程中满充后，负极活性物质有足够的空位接收来自正极活性物质脱出的所有活性锂，并在满放后于负极储存过量的活性锂，且锂离子电池在衰减过程中活性锂损失速率较低，因此能有效改善锂离子电池的循环寿命和存储寿命。
附图说明
图1为本发明的负极极片的一结构示意图；
图2为本发明的负极极片的第一实施例的结构示意图；
图3为本发明的负极极片的第二实施例的结构示意图；
图4为本发明的负极极片的第三实施例的结构示意图；
图5为本发明的负极极片的第四实施例的结构示意图；
图6为本发明的负极极片的第五实施例的结构示意图。
其中，附图标记说明如下：
1负极集流体
2负极活性物质层
3金属锂层
31富锂区域
4极耳
L负极极片的长度方向
H负极极片的厚度方向
W负极极片的宽度方向
具体实施方式
下面结合附图详细说明根据本发明的电极组件以及锂离子电池。
首先说明根据本发明第一方面的电极组件。
根据本发明第一方面的电极组件包括负极极片、正极极片以及隔离膜。需要说明的是，本发明第一方面所述的电极组件是指尚未经过电解液浸泡的电极组件(即注入电解液之前的结构)，本发明第一方面所述的电极组件在狭义上可仅包括负极极片、正极极片以及隔离膜。
在本发明第一方面的电极组件中，参考图1，所述负极极片包括负极集流体1以及设置在负极集流体1至少一个表面上且包括负极活性物质的负极活性物质层2。所述负极极片还包括设置在负极活性物质层2远离负极集流体1一侧的表面上的金属锂层3，金属锂层3由多个规则或不规则的条状富锂区域31形成，且所述多个富锂区域31沿负极极片的长度方向L呈现出间隔分布的非连续形态。需要说明的是，本发明第一方面所述的负极极片是指尚未经过电解液浸泡的负极极片(即为注入电解液之前的极片结构)。
其中，所述多个富锂区域31沿负极极片的长度方向L呈现出间隔分布的非连续形态，也即金属锂层3为间隔分布的非连续形态，这样将金属锂层3设置在负极活性物质层2表面后，降低了金属锂层3与空气的接触面积，降低了锂被氧化的概率，从而提高了金属锂层3中锂的利用率，提高了注液过程中锂嵌入负极活性物质层的效率(即提高了负极极片的预嵌锂效率)，改善了负极表面SEI膜的稳定性和成膜质量，降低了锂离子电池的直流阻抗。非连续形态的金属锂层3与负极活性物质层2之间可以形成若干个孔道结构，增加电解液在负极极片表面的扩散路径，大幅提高负极极片对电解液的浸润速率，进而提高 锂离子电池的注液效率。同时，非连续形态的金属锂层3设置在负极活性物质层2表面还可以提升注液后电池衰减过程中活性锂嵌入负极活性物质层2的效率，降低锂离子电池衰减过程中的活性锂损失速率，因此本发明能有效提升锂离子电池的循环寿命和存储寿命。
参考图1，各富锂区域31为规则或不规则的条状，其优势还在于能够在负极极片整体表面形成间隔分布的规则或不规则的条状凹槽(即相邻富锂区域31的间隙位置构成凹槽)，增加负极极片的比表面积，从而有利于利用毛细效应提高负极极片对电解液的浸润效果以及浸润速率。
参考图2至图6，各富锂区域31的长度方向与负极极片的长度方向L的夹角为45°～135°。这种结构的负极极片尤其适合形成卷绕式电极组件，通常，卷绕式电极组件是以极片的宽度方向为中心轴，将极片的长边围绕中心轴周向卷绕而形成电极组件。当各富锂区域31的长度方向与负极极片的长度方向L的夹角为45°～135°时，各富锂区域31的长度延伸方向与负极极片的卷绕方向基本垂直，在负极极片卷绕的过程中，各富锂区域31不会因受卷绕方向的拉应力而出现断裂或从负极活性物质层2表面脱落，由此保证各富锂区域31(或金属锂层3)稳定地附着在负极活性物质层2表面。同时，注液时，电解液从电极组件卷绕的两端头部逐渐浸润整个电极组件，当各富锂区域31的长度延伸方向与负极极片的卷绕方向基本垂直时，负极极片表面形成的间隔分布的条状凹槽的延伸方向与电解液扩散方向大体一致，从而还有利于利用毛细效应提高负极极片对电解液的浸润效果以及浸润速率。
优选地，各富锂区域的长度方向与负极极片的长度方向L的夹角为60°～120°。
在各富锂区域31的长度方向上，表面覆盖有金属锂层的负极活性物质层区域的长度与表面未覆盖有金属锂层的负极活性物质层区域的长度的比值不低于20:1。优选地，在各富锂区域31的长度方向上，各富锂区域31完全覆盖负极活性物质层2。参考图2至图4，在各富锂区域31的长度方向上，各富锂区域31几乎完全覆盖负极活性物质层2。参考图5和图6，在各富锂区域31的长度方向上，各富锂区域31未能完全覆盖负极活性物质层2。
参考图2至图6，各富锂区域31在负极极片的宽度方向W上的覆盖区域占比较高，可以保证金属锂层3与负极活性物质层2之间的结合力良好，从而在负极极片的制备以及使用过程中，例如冷压或卷绕等工序中，金属锂层3能稳定地附着在负极活性物质层2表面，不会从负极活性物质层2表面脱落。
各富锂区域31的宽度为0.2mm～2mm，每相邻两个富锂区域31的间距为该相邻两个 富锂区域31的平均宽度的0.25倍～2倍。各富锂区域31在负极极片的宽度方向W上的覆盖区域占比较高，几乎为完全覆盖，而在负极极片的长度方向L上的覆盖区域占比较低，呈现间隔分布的非连续形态，这样可以保证金属锂层3与空气的接触面积较少，出现锂被氧化的概率较小，从而金属锂层3中锂的利用率较高。
由于负极极片表面存在电势差，在一定扩散宽度内，富锂区域31中的锂向贫锂区(相邻富锂区域31的间隙位置)进行扩散速率较快，从而能够保证负极活性物质层2内部嵌锂均匀性良好。在负极极片补锂总量一定的情况下，相邻两个富锂区域31的间距越大，该局部位置处的富锂区域31中锂含量越高，越容易出现锂残留；相邻两个富锂区域31的间距越小，整个金属锂层3的表面积越大，与空气接触面积越大，出现锂被氧化的概率越大，从而金属锂层3中锂的利用率越低，对锂离子电池循环寿命和存储寿命的改善越不明显。
参考图2至图6，各富锂区域31可为规则的细长条状、规则的带条状或规则的波浪形条状，也可为不规则的细长条状、不规则的带条状或不规则的波浪形条状。优选地，各富锂区域31为规则或不规则的波浪形条状。由于各富锂区域31在负极活性物质层2表面呈现出间隔分布的非连续形态，因此负极预嵌锂过程中各富锂区域31中的锂会首先在覆盖有富锂区域31的负极活性物质层内纵向扩散(即首先沿覆盖有富锂区域31的负极活性物质层的厚度方向扩散)，再向各富锂区域31两侧的间隙位置处的负极活性物质层区域横向扩散，最终达到预先设置的金属锂层3与负极活性物质层2中的大部分负极活性物质结合形成预嵌锂化合物。当各富锂区域31为规则或不规则的波浪形条状时，缩短了锂的扩散路径，更有利于锂与间隙位置处的负极活性物质快速结合，由此提高了金属锂层3中锂的利用率。
各富锂区域31的材质为锂箔、锂网或锂粉。各富锂区域31可通过辊压的方式设置在负极活性物质层2远离负极集流体1一侧的表面上，辊压时利用锂与负极活性物质(诸如石墨等)的分子间作用力使各富锂区域31稳定地附着在负极活性物质层2的表面上。
金属锂层3的质量为负极活性物质层2的总质量的0.5％～5％；优选地，金属锂层3的质量为负极活性物质层2的总质量的1％～5％。
负极活性物质层2可设置在负极集流体1的其中一个表面上，也可以设置在负极集流体1的两个表面上。负极集流体1的材质不受到具体的限制，可以根据实际需求进行选择。
所述负极活性物质选自能接受、脱出锂离子的材料。优选地，所述负极活性物质选自石墨、软碳、硬碳、中间相碳微球、纳米碳、单质硅、硅氧化合物、硅碳复合物、硅合金、 单质锡、锡氧化合物、锡碳复合物、锡合金、钛酸锂中的一种或几种。更优选地，所述负极活性物质至少包括石墨。
负极活性物质层2还包括粘结剂以及可选的导电剂，所述粘结剂以及所述导电剂的种类均不受到具体的限制，可根据实际需求进行选择。优选地，所述粘结剂可选自丁苯橡胶(SBR)、羧甲基纤维素钠(CMC)中的一种或几种。优选地，所述导电剂可选自导电炭黑、超导炭黑、导电石墨、乙炔黑、科琴黑、石墨烯、碳纳米管中的一种或几种。
参照图2至图6，所述负极极片还包括设置在负极集流体1上的极耳4，极耳4的数量不受到具体的限制，可以为一个也可以为多个。优选地，极耳4通过模切负极集流体1得到。
在本发明第一方面的电极组件中，所述正极极片包括正极集流体以及设置在所述正极集流体至少一个表面上且包括正极活性物质的正极活性物质层，所述正极活性物质层可设置在所述正极集流体的其中一个表面上，也可以设置在所述正极集流体的两个表面上。所述正极集流体的材质不受到具体的限制，可以根据实际需求进行选择。
其中，所述正极活性物质选自能接受、脱出锂离子的材料。优选地，所述正极活性物质可选自锂过渡金属氧化物、锂过渡金属氧化物添加其它过渡金属或非过渡金属或非金属得到的化合物中的一种或几种。具体地，所述正极活性物质可选自锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物、橄榄石结构的含锂磷酸盐中的一种或几种。
橄榄石结构的含锂磷酸盐的通式可为LiFe 1-x-yMn xM’ yPO 4，0≤x≤1，0≤y≤0.1，0≤x+y≤1，M’选自除Fe、Mn外的其它过渡金属元素或非过渡金属元素中的一种或几种。优选地，橄榄石结构的含锂磷酸盐可为磷酸铁锂、磷酸锰锂以及磷酸锰铁锂。
在上述正极活性物质中，橄榄石结构的含锂磷酸盐本身具有较高的结构稳定性，不会像其它正极活性物质在循环过程中出现结构变化而导致容量损失，因此使用橄榄石结构的含锂磷酸盐的电极组件的容量衰减主要源自可穿梭于正负极之间的活性锂损失(例如部分活性锂在负极表面参与了SEI膜的修复过程)，因此可以有效降低电极组件的容量损失速率，大幅提升电极组件的循环寿命和存储寿命。但本发明的正极活性物质并不仅限于橄榄石结构的含锂磷酸盐。
所述正极活性物质层还包括导电剂以及粘结剂，所述粘结剂以及所述导电剂的种类均不受到具体的限制，可根据实际需求进行选择。优选地，所述粘结剂可选自聚偏氟乙烯(PVDF)、聚四氟乙烯、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟 乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物、含氟丙烯酸酯树脂中的一种或几种。优选地，所述导电剂可选自导电炭黑、超导炭黑、导电石墨、乙炔黑、科琴黑、石墨烯、碳纳米管中的一种或几种。
在本发明第一方面的电极组件中，所述电极组件还满足：单位面积负极容量/单位面积正极容量＝1.2～2.1且单位面积负极容量/(单位面积正极容量+单位面积负极活性物质层表面金属锂层容量×80％)≥1.10，此时可在不降低能量密度的前提下有效提升锂离子电池的循环寿命和存储寿命。这是由于，所述负极活性物质具有接受锂离子的能力，且其提供的空位需要在负极预嵌锂时容纳来自金属锂层中锂的嵌入，并在首次充电过程中容纳来自正极活性物质脱出的所有活性锂。如果金属锂层和正极活性物质的含量之和过高、负极活性物质含量过少，电极组件满充过程中易发生负极析锂，从而影响锂离子电池的循环寿命和存储寿命。
由于负极活性物质层表面的金属锂层的容量难以被完全发挥出来，因此在进行电极组件设计时，按金属锂层容量的80％设计不同的正负极容量，即能够得到循环寿命和存储寿命均较优的锂离子电池。
优选地，单位面积负极容量/单位面积正极容量＝1.3～2.1。
其中：
单位面积负极容量＝单位面积的负极涂布质量×负极活性物质涂布质量分数×负极活性物质的可逆克容量。
单位面积正极容量＝单位面积的正极涂布质量×正极活性物质涂布质量分数×正极活性物质的可逆克容量。
单位面积负极活性物质层表面金属锂层容量＝单位面积负极活性物质层表面金属锂层质量×金属锂的理论克容量3861.3mAh/g。由于金属锂层为间隔分布的非连续形态，这里“单位面积负极活性物质层表面金属锂层质量”表示负极活性物质层表面金属锂层的总质量与负极活性物质层总面积的比值。
在本发明第一方面的电极组件中，所述隔离膜设置在正极极片和负极极片之间，起到隔离作用。所述隔离膜的种类并不受到具体的限制，可以是现有技术中使用的任何隔离膜材料，例如聚乙烯、聚丙烯、聚偏氟乙烯以及它们的多层复合膜，但不仅限于这些。
其次说明根据本发明第二方面的锂离子电池。
根据本发明第二方面的锂离子电池包括电极组件、电池壳体以及电解液，其中所述电 极组件为根据本发明第一方面所述的电极组件，且所述电极组件在装入电池壳体以及注入电解液后，所述负极活性物质层表面金属锂层中至少一部分锂在电解液作用下发生预嵌锂，并以第一嵌锂化合物的形式分布在所述负极活性物质层中。
在本发明第二方面的锂离子电池中，所述第一嵌锂化合物包括LiC x，x＝12～120。本发明中负极活性物质层表面设置的金属锂层虽然为间隔分布的非连续形态，在相邻的富锂区域之间存在未被金属锂层覆盖的区域，注入电解液后，由于负极极片表面存在电势差，经过足够长时间的浸润扩散，富锂区域的锂会向贫锂区(富锂区域的间隙位置)扩散，最终负极活性物质层内部的锂含量仍可达到均匀，实现均匀嵌锂。
在本发明第二方面的锂离子电池中，所述电极组件在装入电池壳体以及注入电解液后，所述负极活性物质层表面金属锂层中还有部分锂在电解液作用下形成第二嵌锂化合物并存在于所述负极活性物质层表面，且所述第二嵌锂化合物在所述负极活性物质层表面呈现出间隔分布的非连续形态。
电极组件在装入电池壳体以及注入电解液后，负极活性物质层表面金属锂层中的部分锂(80％左右)会嵌入负极活性物质层中并以第一嵌锂化合物的形式存在于负极活性物质层内部，同时，负极活性物质层表面设置有金属锂层的原区域位置会形成第二嵌锂化合物。由于沿负极极片的厚度方向，负极活性物质层覆盖有第二嵌锂化合物位置的厚度大于未覆盖有第二嵌锂化合物位置的厚度，这样能够保证负极极片在预嵌锂后仍具有高的比表面积，进而有利于活性锂在锂离子电池使用过程中更好地嵌入负极活性物质中。
其中，所述第二嵌锂化合物在所述负极活性物质层表面的位置与所述金属锂层的位置相同，所述第二嵌锂化合物包括锂氮化合物、碳酸锂、氧化锂中的一种或几种。锂离子电池在首次充电过程中，负极极片表面会形成SEI膜，而第二嵌锂化合物包括锂氮化合物、碳酸锂、氧化锂中的一种或几种，上述物质是构成SEI膜的主要成分，因此在负极活性物质层表面形成的第二嵌锂化合物能够有效地改善电池首次充电过程中形成的SEI膜的组分、并降低SEI膜的阻抗，从而起到降低锂离子电池直流阻抗、提升锂离子电池循环寿命的作用。但是上述物质参与形成的SEI膜柔韧性较差，而通过在负极活性物质层表面设置间隔分布的非连续形态的金属锂层，负极极片在预嵌锂后形成的第二嵌锂化合物也为间隔分布的非连续形态，由此可以降低SEI膜中上述物质的相对含量以及覆盖率，更好地发挥上述物质对SEI膜的改善作用，避免过分降低SEI膜的柔韧性。
在本发明第二方面的锂离子电池中，所述锂离子电池首周充放电后负极极片中剩余活性锂容量相对于正极容量的比值为5％～97％，换句话说，所述锂离子电池首周充放电后的 富锂状态为105％～197％(相对于正极容量)。这样能保证锂离子电池使用过程中满充后，负极活性物质有足够的空位容纳活性锂，并在满放后于负极储存过量的活性锂，从而能有效降低锂离子电池容量损失速率，提升锂离子电池的循环寿命和存储寿命。该比值小于5％，首周充放电后负极极片中剩余活性锂较少，对锂离子电池的循环寿命和存储寿命的改善效果不显著；该比值大于97％，首周充放电后负极极片中剩余活性锂太多，容易导致负极极片表面发生锂残留，使锂离子电池存在较高的安全隐患。
优选地，所述锂离子电池首周充放电后负极极片中剩余活性锂容量相对于正极容量的比值为5％～50％。
在本发明第二方面的锂离子电池中，所述电解液包括锂盐以及有机溶剂，其中锂盐和有机溶剂的具体组成均不受到具体的限制，可根据实际需求进行选择。
其中，所述有机溶剂可包括环状碳酸酯、链状碳酸酯、羧酸酯中的一种或几种。优选地，所述环状碳酸酯可选自碳酸乙烯酯、碳酸丙烯酯、碳酸1,2-丁烯酯、碳酸-2,3-丁二醇酯中的一种或几种；优选地，所述链状碳酸酯可选自碳酸甲乙酯、碳酸甲丙酯、碳酸甲基异丙酯、碳酸甲丁酯、碳酸乙丙酯、碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸二丁酯中的一种或几种；优选地，所述羧酸酯可选自新戊酸甲酯、新戊酸乙酯、新戊酸丙酯、新戊酸丁酯、丁酸甲酯、丁酸乙酯、丁酸丙酯、丁酸丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丙酸丁酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、乙酸丁酯中的一种或几种。
优选地，所述锂盐可选自LiPF 6、LiBF 4、LiClO 4、LiPO 2F 2、Li 2PO 3F、LiSO 3F、LiBOB中的一种或几种。
优选地，所述电解液还可包括添加剂，所述添加剂的种类也没有特别的限制，可以为负极成膜添加剂，也可为正极成膜添加剂，也可以为能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温性能的添加剂等。
在本发明第二方面的锂离子电池中，所述电池壳体具有容纳腔，而所述电极组件放置于所述电池壳体的容纳腔内。其中，所述电池壳体的材质没有特别的限制，可以为塑料、金属或铝塑膜。
下面结合实施例，进一步阐述本申请。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。
实施例1
(1)正极极片的制备
将正极活性物质磷酸铁锂(可逆克容量为139mAh/g)、导电剂乙炔黑、粘结剂PVDF按质量比94:4:2进行混合，加入溶剂N-甲基吡咯烷酮，充分搅拌混合均匀得到正极浆料，然后涂覆于正极集流体铝箔的两个表面上，然后烘干、冷压，得到正极极片，其中正极浆料的涂布质量为0.198g/1540.25mm 2(以不包含溶剂的质量计)。
(2)负极极片的制备
将负极活性物质石墨(可逆克容量为340mAh/g)、导电剂乙炔黑、粘结剂SBR+CMC按照质量比95:1.5:3.1:0.4进行混合，加入溶剂去离子水，充分搅拌混合均匀得到负极浆料，然后涂覆于负极集流体铜箔的两个表面上，经烘干、冷压后得到负极活性物质层，其中负极浆料的涂布质量为0.120g/1540.25mm 2(以不包含溶剂的质量计)。
然后将若干个波浪形条状的锂箔采用辊压的方式等间距地复合到负极活性物质层的表面形成间隔分布的非连续形态的金属锂层，得到负极极片。
其中，金属锂层的质量为3.05mg/1540.25mm 2，各波浪形条状锂箔的宽度为0.5mm，相邻两个波浪形条状锂箔的间距为0.5mm，各波浪形条状锂箔的长度方向与负极极片的长度方向的夹角均约为80°，且沿各波浪形条状锂箔的长度方向，负极活性物质层表面均被锂箔完全覆盖。
(3)电解液制备
在含水量<10ppm的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二甲酯(DMC)按照质量比为EC:PC:DMC＝3:3:3进行混合后，得到有机溶剂，再将充分干燥的锂盐LiPF 6溶解于上述有机溶剂中，搅拌均匀后，获得电解液，其中LiPF 6的浓度为1mol/L。
(4)隔离膜的制备
以聚乙烯多孔膜作为隔离膜。
(5)锂离子电池的制备
将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到电极组件。将电极组件置于电池壳体中，注入配好的电解液并封装，获得锂离子电池。
其中，
负极活性物质层表面的金属锂层的质量百分含量＝(3.05mg/1540.25mm 2)/ (0.120g/1540.25mm 2)×100％＝2.54％。
单位面积(以面积为1540.25mm 2计，以下实施例类似)负极容量＝0.120g×95％×340mAh/g＝38.76mAh。
单位面积(以面积为1540.25mm 2计，以下实施例类似)正极容量＝0.198g×94％×139mAh/g＝25.87mAh。
单位面积(以面积为1540.25mm 2计，以下实施例类似)负极活性物质层表面金属锂层容量＝3.05mg×3861.3mAh/g＝11.78mAh。
单位面积负极容量/单位面积正极容量＝38.76mAh/25.87mAh＝1.50。
单位面积负极容量/(单位面积正极容量+单位面积负极活性物质层表面金属锂层容量×80％)＝38.76mAh/(25.87mAh+11.78mAh×80％)＝1.10。
锂离子电池首周充放电后的富锂状态＝[25.87mAh+11.78mAh-38.76mAh×8％]/25.87mAh×100％＝133.5％。
实施例2
锂离子电池的制备过程同实施例1，区别在于：负极极片制备中，将若干个波浪形条状的锂箔替换为细长条状的锂箔并采用辊压的方式等间距地复合到负极活性物质层的表面形成间隔分布的非连续形态的金属锂层。
其中，金属锂层的质量为3.05mg/1540.25mm 2，各细长条状锂箔的宽度为0.5mm，相邻两个细长条状锂箔的间距为0.5mm，各细长条状锂箔的长度方向与负极极片的长度方向的夹角均约为85°，且沿各细长条状锂箔的长度方向，负极活性物质层表面均被锂箔完全覆盖。
实施例3
锂离子电池的制备过程同实施例1，区别在于：负极极片制备中，将若干个波浪形条状的锂箔替换为带条状的锂箔并采用辊压的方式等间距地复合到负极活性物质层的表面形成间隔分布的非连续形态的金属锂层。
其中，金属锂层的质量为3.05mg/1540.25mm 2，各带条状锂箔的宽度为0.5mm，相邻两个带条状锂箔的间距为0.5mm，各带条状锂箔的长度方向与负极极片的长度方向的夹角均约为92°，且沿各带条状锂箔的长度方向，负极活性物质层表面均被锂箔完全覆盖。
实施例4
锂离子电池的制备过程同实施例1，区别在于：负极极片制备中，将若干个波浪形条状的锂箔替换为细长条状的锂箔并采用辊压的方式等间距地复合到负极活性物质层的表面形成间隔分布的非连续形态的金属锂层。
其中，金属锂层的质量为3.05mg/1540.25mm 2，各细长条状锂箔的宽度为0.5mm，相邻两个细长条状锂箔的间距为0.2mm，各细长条状锂箔的长度方向与负极极片的长度方向的夹角均约为100°，且沿各细长条状锂箔的长度方向，表面覆盖有锂箔的负极活性物质层区域的长度与表面未覆盖有锂箔的负极活性物质层区域的长度的比值为20:1。
实施例5
锂离子电池的制备过程同实施例1，区别在于：负极极片制备中，将若干个波浪形条状的锂箔替换为细长条状的锂箔并采用辊压的方式等间距地复合到负极活性物质层的表面形成间隔分布的非连续形态的金属锂层。
其中，金属锂层的质量为3.05mg/1540.25mm 2，各细长条状锂箔的宽度为0.5mm，相邻两个细长条状锂箔的间距为1mm，各细长条状锂箔的长度方向与负极极片的长度方向的夹角均约为95°，且沿各细长条状锂箔的长度方向，表面覆盖有锂箔的负极活性物质层区域的长度与表面未覆盖有锂箔的负极活性物质层区域的长度的比值为40:1。
实施例6
锂离子电池的制备过程同实施例1，区别在于：正极浆料的涂布质量为0.198g/1540.25mm 2，负极浆料的涂布质量为0.104g/1540.25mm 2，负极活性物质层表面的金属锂层的质量为1.52mg/1540.25mm 2。
负极活性物质层表面的金属锂层的质量百分含量＝(1.52mg/1540.25mm 2)/(0.104g/1540.25mm 2)×100％＝1.46％。
单位面积负极容量＝0.104g×95％×340mAh/g＝33.59mAh。
单位面积正极容量＝0.198g×94％×139mAh/g＝25.87mAh。
单位面积负极活性物质层表面金属锂层容量＝1.52mg×3861.3mAh/g＝5.87mAh。
单位面积负极容量/单位面积正极容量＝33.59mAh/25.87mAh＝1.30。
单位面积负极容量/(单位面积正极容量+单位面积负极活性物质层表面金属锂层容量×80％)＝33.59mAh/(25.87mAh+5.87mAh×80％)＝1.10。
锂离子电池首周充放电后的富锂状态＝[25.87mAh+5.87mAh-33.59mAh×8％]/25.87mAh×100％＝112.3％。
实施例7
锂离子电池的制备过程同实施例1，区别在于：正极浆料的涂布质量0.224g/1540.25mm 2，负极浆料的涂布质量0.136g/1540.25mm 2，负极活性物质层表面的金属锂层的质量为3.45mg/1540.25mm 2。
负极活性物质层表面的金属锂层的质量百分含量＝(3.45mg/1540.25mm 2)/(0.136g/1540.25mm 2)×100％＝2.54％。
单位面积负极容量＝0.136g×95％×340mAh/g＝43.93mAh。
单位面积正极容量＝0.224g×94％×139mAh/g＝29.27mAh。
单位面积负极活性物质层表面金属锂层容量＝3.45mg×3861.3mAh/g＝13.32mAh。
单位面积负极容量/单位面积正极容量＝43.93mAh/29.27mAh＝1.50。
单位面积负极容量/(单位面积正极容量+单位面积负极活性物质层表面金属锂层容量×80％)＝43.93mAh/(29.27mAh+13.32mAh×80％)＝1.10。
锂离子电池首周充放电后的富锂状态＝[29.27mAh+13.32mAh-43.93mAh×8％]/29.27mAh×100％＝133.5％。
实施例8
锂离子电池的制备过程同实施例1，区别在于：正极浆料的涂布质量为0.259g/1540.25mm 2，负极浆料的涂布质量为0.136g/1540.25mm 2，负极活性物质层表面的金属锂层的质量为1.99mg/1540.25mm 2。
负极活性物质层表面的金属锂层的质量百分含量＝(1.99mg/1540.25mm 2)/(0.136g/1540.25mm 2)×100％＝1.46％。
单位面积负极容量＝0.136g×95％×340mAh/g＝43.93mAh。
单位面积正极容量＝0.259g×94％×139mAh/g＝33.84mAh。
单位面积负极活性物质层表面金属锂层容量＝1.99mg×3861.3mAh/g＝7.68mAh。
单位面积负极容量/单位面积正极容量＝43.93mAh/33.84mAh＝1.30。
单位面积负极容量/(单位面积正极容量+单位面积负极活性物质层表面金属锂层容量×80％)＝43.93mAh/(33.84mAh+7.68mAh×80％)＝1.10。
锂离子电池首周充放电后的富锂状态＝[33.84mAh+7.68mAh-43.93mAh×8％]/33.84mAh×100％＝112.3％。
实施例9
锂离子电池的制备过程同实施例1，区别在于：正极浆料的涂布质量为0.177g/1540.25mm 2，负极浆料的涂布质量0.136g/1540.25mm 2，负极活性物质层表面的金属锂层的质量为5.44mg/1540.25mm 2。
负极活性物质层表面的金属锂层的质量百分含量＝(5.44mg/1540.25mm 2)/(0.136g/1540.25mm 2)×100％＝4.0％。
单位面积负极容量＝0.136g×95％×340mAh/g＝43.93mAh。
单位面积正极容量＝0.177×94％×139mAh/g＝23.13mAh。
单位面积负极活性物质层表面金属锂层容量＝5.44mg×3861.3mAh/g＝21.01mAh。
单位面积负极容量/单位面积正极容量＝43.93mAh/23.13mAh＝1.90。
单位面积负极容量/(单位面积正极容量+单位面积负极活性物质层表面金属锂层容量×80％)＝43.93mAh/(23.13mAh+21.01mAh×80％)＝1.10。
锂离子电池首周充放电后的富锂状态＝[23.13mAh+21.01mAh-43.93mAh×8％]/23.13mAh×100％＝175.6％。
实施例10
锂离子电池的制备过程同实施例1，区别在于：正极浆料的涂布质量为0.160g/1540.25mm 2，负极浆料的涂布质量0.136g/1540.25mm 2，负极活性物质层表面的金属锂层的质量为6.16mg/1540.25mm 2。
负极活性物质层表面的金属锂层的质量百分含量＝(6.16mg/1540.25mm 2)/(0.136g/1540.25mm 2)×100％＝4.53％。
单位面积负极容量＝0.136g×95％×340mAh/g＝43.93mAh。
单位面积正极容量＝0.160g×94％×139mAh/g＝20.91mAh。
单位面积负极活性物质层表面金属锂层容量＝6.16mg×3861.3mAh/g＝23.79mAh。
单位面积负极容量/单位面积正极容量＝43.93mAh/20.91mAh＝2.10。
单位面积负极容量/(单位面积正极容量+单位面积负极活性物质层表面金属锂层容量×80％)＝43.93mAh/(20.91mAh+23.79mAh×80％)＝1.10。
锂离子电池首周充放电后的富锂状态＝[20.91mAh+23.79mAh-43.93mAh×8％]/20.91mAh×100％＝196.9％。
实施例11
锂离子电池的制备过程同实施例1，区别在于：正极浆料的涂布质量为0.280g/1540.25mm 2，负极浆料的涂布质量为0.136g/1540.25mm 2，负极活性物质层表面的金属锂层的质量为1.10mg/1540.25mm 2。
负极活性物质层表面的金属锂层的质量百分含量＝(1.10mg/1540.25mm 2)/(0.136g/1540.25mm 2)×100％＝0.81％。
单位面积负极容量＝0.136g×95％×340mAh/g＝43.93mAh。
单位面积正极容量＝0.280g×94％×139mAh/g＝36.58mAh。
单位面积负极活性物质层表面金属锂层容量＝1.10mg×3861.3mAh/g＝4.25mAh。
单位面积负极容量/单位面积正极容量＝43.93mAh/36.58mAh＝1.20。
单位面积负极容量/(单位面积正极容量+单位面积负极活性物质层表面金属锂层容量×80％)＝43.93mAh/(36.58mAh+4.25mAh×80％)＝1.10。
锂离子电池首周充放电后的富锂状态＝[36.58mAh+4.25mAh-43.93mAh×8％]/36.58mAh×100％＝102.0％。
对比例1
锂离子电池的制备过程同实施例1，区别在于：正极浆料的涂布质量为0.198g/1540.25mm 2，负极浆料的涂布质量为0.120g/1540.25mm 2，负极活性物质层的表面不设置金属锂层。
单位面积负极容量＝0.120g×95％×340mAh/g＝38.76mAh。
单位面积正极容量＝0.198g×94％×139mAh/g＝25.87mAh。
单位面积负极容量/单位面积正极容量＝38.76mAh/25.87mAh＝1.50。
锂离子电池首周充放电后的富锂状态＝[25.87mAh-38.76mAh×8％]/25.87mAh×100％＝88.0％。
对比例2
锂离子电池的制备过程同实施例1，区别在于：正极浆料的涂布质量为 0.198g/1540.25mm 2，负极浆料的涂布质量为0.094g/1540.25mm 2，负极活性物质层的表面不设置金属锂层。
单位面积负极容量＝0.094g×95％×340mAh/g＝30.36mAh。
单位面积正极容量＝0.198g×94％×139mAh/g＝25.87mAh。
单位面积负极容量/单位面积正极容量＝30.36mAh/25.87mAh＝1.17。
锂离子电池首周充放电后的富锂状态＝[25.87mAh-30.36mAh×8％]/25.87mAh×100％＝90.6％。
对比例3
锂离子电池的制备过程同实施例1，区别在于：正极浆料的涂布质量为0.224g/1540.25mm 2，负极浆料的涂布质量为0.136g/1540.25mm 2，负极活性物质层的表面不设置金属锂层。
单位面积负极容量＝0.136g×95％×340mAh/g＝43.93mAh。
单位面积正极容量＝0.224g×94％×139mAh/g＝29.27mAh。
单位面积负极容量/单位面积正极容量＝43.93mAh/29.27mAh＝1.50。
锂离子电池首周充放电后的富锂状态＝[29.27mAh-43.93mAh×8％]/29.27mAh×100％＝88.0％。
对比例4
锂离子电池的制备过程同实施例1，区别在于：正极浆料的涂布质量为0.287g/1540.25mm 2，负极浆料的涂布质量为0.136g/1540.25mm 2，负极活性物质层的表面不设置金属锂层。
单位面积负极容量＝0.136g×95％×340mAh/g＝43.93mAh。
单位面积正极容量＝0.287g×94％×139mAh/g＝37.50mAh。
单位面积负极容量/单位面积正极容量＝43.93mAh/37.50mAh＝1.17。
锂离子电池首周充放电后的富锂状态＝[37.50mAh-43.93mAh×8％]/37.50mAh×100％＝90.6％。
对比例5
锂离子电池的制备过程同实施例1，区别在于：负极活性物质表面的金属锂层为连续 形态且金属锂层的质量为3.05mg/1540.25mm 2。
表1实施例1-11和对比例1-5的参数
Figure PCTCN2019076160-appb-000001
注：公式1＝单位面积负极容量/单位面积正极容量，公式2＝单位面积负极容量/(单位面积正极容量+单位面积负极活性物质层表面金属锂层容量×80％)，单位面积以面积为1540.25mm 2计。
接下来说明锂离子电池的测试过程。
(1)锂离子电池的直流阻抗(DCR)测试
首先，在25℃下将锂离子电池放电至2.5V，然后以1C恒流充电至电压为3.65V，然后以3.65V恒压充电至电流为0.05C，静置5分钟后，再将锂离子电池以1C恒流放电至电压为2.5V，此时的放电容量记为C 0，以C 0为基准获得锂离子电池1C的标准电流I 0。
DRC测试时，首先将锂离子电池以1I 0恒流充电至电压为3.65V，然后以3.65V恒压充电至0.05I 0，然后以1I 0放电30分钟至50％SOC；接着将测试环境温度调整为0℃，静置3h后，将锂离子电池以3I 0放电30秒，记录放电前电压V 0以及脉冲结束后电压V 1。
锂离子电池的放电DCR＝(V 0-V 1)/3I 0。
(2)锂离子电池的高温循环性能测试
在60℃下，将制备好的锂离子电池先以1C恒流充电至电压为3.65V，然后以3.65V恒压充电至电流为0.05C，静置5分钟后，将锂离子电池以1C恒流放电至电压为2.5V，此为一个充放电循环过程，此次的放电容量为首次循环的放电容量。将锂离子电池按上述方法进行多次循环充放电测试，检测得到第500次循环的放电容量。
锂离子电池60℃循环500次后的容量保持率＝(第500次循环的放电容量/首次循环的放电容量)×100％。
(3)锂离子电池的存储性能测试
首先，在25℃下，将制备好的锂离子电池以0.5C恒流充电至电压为3.65V，然后以3.65V恒压充电至电流为0.05C，静置5分钟后，将锂离子电池以0.5C恒流放电至电压为2.5V，此次的放电容量为存储前的放电容量；而后以0.5C的充电电流将锂离子电池满充，并于60℃下静置90天，之后取出并置于25℃下静置2小时，再以0.5C恒流放电至电压为2.5V，静置5分钟后，以0.5C恒流充电至电压为3.65V，然后以3.65V恒压充电至电流为0.05C，静置5分钟后，将锂离子电池以0.5C恒流放电至电压为2.5V，此时的放电容量为存储90天后的放电容量。
锂离子电池60℃存储90天后的容量保持率＝(存储90天后的放电容量/存储前的放电容量)×100％。
表2实施例1-11以及对比例1-5的性能测试结果
Figure PCTCN2019076160-appb-000002
Figure PCTCN2019076160-appb-000003
在实施例1与对比例5中，正极极片、负极极片的单位面积容量相同，金属锂层相对负极活性物质层的质量百分含量也相同，但是金属锂层在负极活性物质层表面分布的形态不同，实施例1为间隔分布的非连续形态，对比例5为连续形态。结合表2中锂离子电池的电化学性能测试结果可以发现：当负极活性物质表面的金属锂层的分布形态为间隔分布的非连续形态时，金属锂层与空气的接触面积较小，锂被氧化的概率较低，金属锂层中锂的利用率较高，由此提高了注液过程中锂嵌入负极活性物质层的效率，改善了负极表面SEI膜的稳定性和成膜质量，降低了锂离子电池的直流阻抗，同时锂离子电池衰减过程中的活性锂损失速率较低。因此本发明的锂离子电池能具有更优异的循环性能和存储性能。
从对比例1-2的比较可以得知，在正极容量一定的条件下，增加负极容量对锂离子电池的循环寿命和存储寿命影响不大。从实施例1和实施例6的比较可以得知，在负极活性物质层表面设置间隔分布的非连续形态的金属锂层后，当增加负极容量时，锂离子电池的循环寿命和存储寿命显著提升，并且随着金属锂层质量百分含量的增加，锂离子电池的循环寿命和存储寿命能得到进一步延长，因此通过调控负极容量和金属锂层的含量可以实现锂离子电池循环寿命和存储寿命的定制化。
从对比例3-4的比较可以得知，在负极容量一定的条件下，减少正极容量对锂离子电池的循环寿命和存储寿命影响不大。从实施例7-11的比较可以得知，在负极活性物质层表面设置间隔分布的非连续形态的金属锂层后，当降低正极容量时，锂离子电池的循环寿命和存储寿命显著提升，并且随着金属锂层质量百分含量的增加，锂离子电池的循环寿命和存储寿命能得到进一步延长，因此通过调控正极容量和金属锂层的含量也可以实现锂离子电池循环寿命和存储寿命的定制化。
根据上述说明书的揭示和教导，本申请所属领域的技术人员还可以对上述实施方式进行适当的变更和修改。因此，本申请并不局限于上面揭示和描述的具体实施方式，对本申请的一些修改和变更也应当落入本申请的权利要求的保护范围内。此外，尽管本说明书中使用了一些特定的术语，但这些术语只是为了方便说明，并不对本申请构成任何限制。

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  1. 一种电极组件，包括正极极片、隔离膜以及负极极片，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面上且包括负极活性物质的负极活性物质层；
    其特征在于，
    所述负极极片还包括设置在所述负极活性物质层远离所述负极集流体一侧的表面上的金属锂层，所述金属锂层由多个规则或不规则的条状富锂区域形成，且所述多个富锂区域沿负极极片的长度方向呈现出间隔分布的非连续形态；
    所述电极组件还满足：单位面积负极容量/单位面积正极容量＝1.2～2.1且单位面积负极容量/(单位面积正极容量+单位面积负极活性物质层表面金属锂层容量×80％)≥1.10。
  2. 根据权利要求1所述的电极组件，其特征在于，各富锂区域的长度方向与所述负极极片的长度方向的夹角为45°～135°。
  3. 根据权利要求2所述的电极组件，其特征在于，各富锂区域的长度方向与所述负极极片的长度方向的夹角为60°～120°。
  4. 根据权利要求1所述的电极组件，其特征在于，在各富锂区域的长度方向上，表面覆盖有金属锂层的负极活性物质层区域的长度与表面未覆盖有金属锂层的负极活性物质层区域的长度的比值不低于20:1。
  5. 根据权利要求4所述的电极组件，其特征在于，在各富锂区域的长度方向上，各富锂区域完全覆盖负极活性物质层。
  6. 根据权利要求1至5中任一项所述的电极组件，其特征在于，各富锂区域的宽度为0.2mm～2mm，每相邻两个富锂区域之间的间距为所述相邻两个富锂区域的平均宽度的0.25倍～2倍。
  7. 根据权利要求1所述的电极组件，其特征在于，所述金属锂层的质量为所述负极活性物质层的总质量的0.5％～5％。
  8. 根据权利要求7所述的电极组件，其特征在于，所述金属锂层的质量为所述负极活性物质层的总质量的1％～5％。
  9. 根据权利要求1所述的电极组件，其特征在于，各富锂区域的材质为锂箔、锂网或锂粉。
  10. 根据权利要求1所述的电极组件，其特征在于，所述负极活性物质选自石墨、软碳、硬碳、中间相碳微球、纳米碳、单质硅、硅氧化合物、硅碳复合物、硅合金、单质锡、锡氧化合物、锡碳复合物、锡合金、钛酸锂中的一种或几种。
  11. 根据权利要求10所述的电极组件，其特征在于，所述负极活性物质至少包括石墨。
  12. 一种锂离子电池，包括电极组件、电池壳体以及电解液，其特征在于，所述电极组件为根据权利要求1至11中任一项所述的电极组件，且所述电极组件在装入电池壳体以及注入电解液后，所述负极活性物质层表面金属锂层中至少一部分锂在电解液作用下发生预嵌锂，并以第一嵌锂化合物的形式分布在所述负极活性物质层中。
  13. 根据权利要求12所述的锂离子电池，其特征在于，所述第一嵌锂化合物包括LiC x，x＝12～120。
  14. 根据权利要求12所述的锂离子电池，其特征在于，所述电极组件在装入电池壳体以及注入电解液后，所述负极活性物质层表面金属锂层中还有部分锂在电解液作用下形成第二嵌锂化合物并存在于所述负极活性物质层表面，且所述第二嵌锂化合物在所述负极活性物质层表面呈现出间隔分布的非连续形态。
  15. 根据权利要求14所述的锂离子电池，其特征在于，所述第二嵌锂化合物在所述负极活性物质层表面的位置与所述金属锂层的位置相同。
  16. 根据权利要求14至15中任一项所述的锂离子电池，其特征在于，所述第二嵌锂化合物包括锂氮化合物、碳酸锂、氧化锂中的一种或几种。
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