WO2020238628A1 - 负极极片、电芯、锂离子电池及其制备方法和包含锂离子电池的装置 - Google Patents

负极极片、电芯、锂离子电池及其制备方法和包含锂离子电池的装置 Download PDF

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WO2020238628A1
WO2020238628A1 PCT/CN2020/090018 CN2020090018W WO2020238628A1 WO 2020238628 A1 WO2020238628 A1 WO 2020238628A1 CN 2020090018 W CN2020090018 W CN 2020090018W WO 2020238628 A1 WO2020238628 A1 WO 2020238628A1
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negative electrode
inorganic dielectric
active material
negative
dielectric layer
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PCT/CN2020/090018
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English (en)
French (fr)
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盛长亮
王铈汶
黄起森
李铖
梁成都
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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 EP20814327.1A priority Critical patent/EP3951930B1/en
Publication of WO2020238628A1 publication Critical patent/WO2020238628A1/zh
Priority to US17/536,118 priority patent/US12119483B2/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0421—Methods of deposition of the material involving vapour deposition
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H01M4/133—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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • 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
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—Lithium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • H01M4/58—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
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • 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

  • This application belongs to the technical field of batteries, and specifically relates to a negative pole piece, a battery cell, a lithium ion battery, a preparation method thereof, and a device containing the lithium ion battery.
  • lithium ion battery mainly relies on the reciprocating movement of lithium ions between the positive electrode active material and the negative electrode active material for charging and discharging, and electrolyte is usually used as a carrier for lithium ion transmission.
  • electrolyte is usually used as a carrier for lithium ion transmission.
  • lithium-ion batteries can provide stable voltage and current, and the use process is green and environmentally friendly. They are widely used in various electronic products and electric vehicles, occupying the mainstream position in the battery field.
  • a first aspect of the application provides a negative electrode sheet, which includes: a negative electrode current collector; a negative electrode active material layer disposed on the negative electrode current collector; a binder-free inorganic dielectric layer disposed on the negative electrode active material layer away from the negative electrode
  • the inorganic dielectric layer includes an inorganic dielectric material
  • the inorganic dielectric layer includes at least a main body disposed on the surface of the negative active material layer, and the main body has a thickness of 30nm ⁇ 1000nm; the lithium metal layer is disposed on the inorganic dielectric The surface of the electric layer away from the negative active material layer.
  • a second aspect of the present application provides a negative electrode sheet, which includes: a negative electrode current collector; a negative electrode active material layer disposed on the negative electrode current collector, the negative electrode active material layer contains a negative electrode active material pre-inserted with lithium;
  • the dielectric layer is disposed on the side of the negative electrode active material layer away from the negative electrode current collector.
  • the inorganic dielectric layer includes an inorganic dielectric material.
  • the inorganic dielectric layer at least includes a main body disposed on the surface of the negative active material layer. The thickness of the main body It is 30nm ⁇ 1000nm.
  • the third aspect of the present application provides a battery cell, which includes a negative pole piece, a positive pole piece, and a separator.
  • the negative pole piece is the negative pole piece provided in the first aspect and/or the second aspect of the application.
  • the fourth aspect of the present application provides a battery cell, which includes a negative pole piece, a positive pole piece and a separator, and the negative pole piece is the negative pole piece provided in the first aspect of the application;
  • the weight ratio of the lithium metal layer to the negative electrode active material layer in every 2cm ⁇ 2cm unit area of the negative pole piece is 0.5% to 5%;
  • the ratio of the negative electrode capacity C 1 per unit area to the positive electrode capacity C 2 per unit area is 1.2 to 2.1;
  • the capacity of the negative electrode per unit area C 1 , the capacity of the positive electrode per unit area C 2 and the capacity C 3 of the lithium metal layer per unit area satisfy C 1 /(C 2 +C 3 ⁇ K) ⁇ 1.05, where K is the value of lithium metal in the lithium metal layer Utilization rate.
  • the fifth aspect of the present application provides a lithium ion battery, which includes a battery cell and an electrolyte, and the battery cell adopts the battery cell provided in the third aspect or the fourth aspect of the present application.
  • the lithium metal layer therein can spontaneously carry out the pre-insertion of lithium metal into the negative electrode active material layer under the action of the electrolyte, so that the negative electrode is active
  • the material layer forms a negative electrode active material pre-inserted with lithium.
  • a sixth aspect of the present application provides a device, which includes the lithium ion battery provided in the fifth aspect of the present application.
  • a seventh aspect of the present application provides a method for preparing a lithium ion battery, which includes preparing the negative pole piece of the lithium ion battery by the following steps:
  • the inorganic dielectric material is deposited on the side of the negative active material layer away from the negative current collector to form a binder-free inorganic dielectric layer.
  • the inorganic dielectric layer includes at least the negative active material
  • the main body part of the layer surface, the thickness of the main body part is 30nm ⁇ 1000nm;
  • the lithium metal layer is arranged on the surface of the inorganic dielectric layer away from the negative electrode active material layer to obtain a negative electrode pole piece.
  • the negative pole piece provided by the present application because it is provided with a lithium metal layer, can pre-insert lithium into the negative electrode active material to compensate for the consumption of active lithium ions in a lithium ion battery, thereby improving the first coulombic efficiency of the battery and increasing the cycle life of the battery. Storage life.
  • an inorganic dielectric layer is provided between the negative electrode active material layer and the lithium metal layer to play a physical isolation role.
  • the metal lithium of the lithium metal layer diffuses through the inorganic dielectric layer to the negative electrode active material layer for pre-insertion of lithium, and at the same time
  • the inorganic dielectric layer has dielectric properties, and has the effect of stabilizing the micro-current at the interface between the lithium metal layer and the negative electrode active material during the lithium pre-insertion process, effectively controlling the lithium pre-insertion rate in the negative electrode active material layer, and avoiding pre-insertion Lithium reacts too fast to generate a lot of heat, which can effectively prevent thermal runaway, improve the cycle life and safety performance of the battery, and prevent the negative active material layer from reducing the interlayer bonding force or film due to excessive volume expansion.
  • the layer falls off or the negative active material is broken, which further improves the cycle life of the battery.
  • FIG. 1 is a schematic diagram of the structure of a negative pole piece in an embodiment of the present application.
  • Fig. 2 is a schematic diagram of the structure of a negative pole piece in another embodiment of the present application.
  • FIG. 3 is a schematic diagram of the structure of the inorganic dielectric layer in the negative pole piece of an embodiment of the present application.
  • FIG. 4 is a schematic diagram of the structure of the inorganic dielectric layer in the negative pole piece of another embodiment of the present application.
  • FIG. 5 is a schematic diagram of the structure of a negative pole piece in another embodiment of the present application.
  • Fig. 6 is an enlarged view of part A in Fig. 5.
  • Fig. 7 is a schematic diagram of an embodiment of a lithium ion battery.
  • Fig. 8 is an exploded view of Fig. 7.
  • Fig. 9 is a schematic diagram of an embodiment of a battery module.
  • Fig. 10 is a schematic diagram of an embodiment of a battery pack.
  • Fig. 11 is an exploded view of Fig. 9.
  • FIG. 12 is a schematic diagram of an embodiment of a device in which a lithium ion battery is used as a power source.
  • any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and any upper limit may be combined with any other upper limit to form an unspecified range.
  • every point or single value between the end points of the range is included in the range. Therefore, each point or single numerical value can be used as its own lower limit or upper limit in combination with any other point or single numerical value or in combination with other lower or upper limits to form an unspecified range.
  • the embodiment of the present application provides a negative electrode sheet 10, which includes a negative electrode current collector 11, a negative electrode active material layer 12, an inorganic dielectric layer 13, and a lithium metal layer 14 which are stacked.
  • the negative electrode current collector 11 includes two opposite surfaces along its thickness direction.
  • the negative electrode active material layer 12 can be provided on either of the two surfaces (as shown in FIG. 1), or can be respectively provided on the two surfaces. (as shown in picture 2).
  • the negative active material layer 12 includes a first surface 121 and a second surface 122 opposite to each other in the thickness direction thereof, wherein the first surface 121 is disposed away from the negative current collector 11 and the second surface 122 is disposed toward the negative current collector 11.
  • the anode active material layer 12 includes an anode active material.
  • the inorganic dielectric layer 13 is disposed on the first surface 121 side of the negative active material layer 12.
  • the inorganic dielectric layer 13 at least includes a main body portion 131 disposed on the first surface 121, and the main body portion 131 has a thickness T of 30 nm to 1000 nm.
  • the inorganic dielectric layer 13 is a binder-free inorganic dielectric layer, which includes an inorganic dielectric material.
  • the lithium metal layer 14 is disposed on the surface of the inorganic dielectric layer 13 away from the negative electrode active material layer 12.
  • the negative pole piece 10 of the first aspect of the embodiments of the present application is a negative pole piece that has not been infiltrated by the electrolyte, and after the electrolyte is injected, there is a potential difference between the negative electrode active material layer 12 and the lithium metal layer 14, which can The lithium metal layer 14 is spontaneously pre-inserted into the negative electrode active material layer 12, and part or all of the metal lithium of the lithium metal layer 14 is pre-inserted into the negative electrode active material to form a lithium pre-inserted negative electrode active material.
  • the negative pole piece provided by the embodiment of the present application is provided with the lithium metal layer 14, which can pre-insert lithium into the negative electrode active material to compensate for the consumption of active lithium ions in the lithium ion battery, thereby improving the first coulombic efficiency of the battery and improving the battery Cycle life and storage life.
  • an inorganic dielectric layer 13 with a predetermined thickness is provided between the negative electrode active material layer 12 and the lithium metal layer 14 to act as a physical insulation. The metal lithium of the lithium metal layer 14 diffuses through the inorganic dielectric layer 13 to the negative electrode activity.
  • the material layer 12 is pre-inserted with lithium, and because the inorganic dielectric layer 13 has dielectric properties, it has the effect of stabilizing the micro-current at the interface between the lithium metal layer 14 and the negative electrode active material during the pre-insertion process, and can effectively control the presence of metal lithium
  • the lithium pre-insertion rate of the negative active material layer 12 avoids the excessively fast lithium pre-insertion reaction speed and generates a large amount of heat, which can effectively prevent thermal runaway, improve the cycle life and safety performance of the battery, and can also prevent the negative active material layer 12 Due to the rapid volume expansion, the interlayer bonding force decreases, or the film layer falls off, or the negative electrode active material ruptures, which further improves the cycle life of the battery.
  • the inorganic dielectric layer 13 also functions to stabilize the negative electrode interface, greatly reducing the side reaction of the electrolyte at the negative electrode interface, and avoiding the electrolyte on the negative electrode interface under high temperature and rapid charging. Side reactions occur, which effectively inhibit the decomposition of electrolyte to produce gas, reduce heat generation, and reduce the consumption of active lithium ions, thereby improving the safety performance, cycle performance and storage performance of the battery, which improves the cycle performance and storage performance of the battery at high temperatures
  • the aforementioned high temperature is, for example, 40°C to 80°C.
  • the use of the negative pole piece 10 of the embodiment of the present application reduces the increase in the DC internal resistance of the lithium ion battery during cycling and storage, thereby reducing thermal effects, reducing battery polarization, and improving battery cycle performance and rate performance.
  • the inorganic dielectric material is nano-scale particles, and the surface contains a large number of polar groups, which ensures that the inorganic dielectric layer 13 has good electrolyte wettability and can improve the electrolyte
  • the inorganic dielectric layer 13 does not contain a binder, the particles of the inorganic dielectric material are not bonded by the organic molecular chains of the binder, which can ensure the composition, thickness, film cohesion, and inorganic
  • the binding force between the dielectric layer 13 and the negative electrode active material layer 12 has high uniformity, which can effectively avoid the decrease in the adhesion of part of the inorganic dielectric layer 13 on the surface of the negative electrode active material layer 12 after the electrolyte is soaked. Falling off is beneficial to improve the uniformity of lithium insertion of the negative electrode active material layer 12 during the pre-lithium insertion process and the charging and discharging process, thereby increasing the cycle life of the battery.
  • the thickness of the inorganic dielectric layer 13 is very small and only nanometer level, the influence on the volume and weight of the negative electrode piece 10 is basically negligible. Therefore, it can ensure that the lithium ion battery has a high volume energy density and weight energy density.
  • the thickness T of the main body portion 131 of the inorganic dielectric layer 13 may be 1000 nm, 990 nm, 950 nm, 900 nm, 850 nm, 800 nm, 750 nm, 720 nm, 700 nm, 680 nm, 650 nm, 600 nm, 550 nm, 500 nm, 490 nm, 450nm, 430nm, 400nm, 380nm, 350nm, 300nm, 280nm, 250nm, 200nm, 190nm, 180nm, 170nm, 160nm, 150nm, 140nm, 130nm, 120nm, 110nm, 100nm, 95nm, 90nm, 85nm, 80nm, 75nm, 70nm, 65nm, 60nm, 55nm, 50nm, 45nm, 40nm, 35nm or 30nm etc.
  • the main body 131 may be a compact structure composed of inorganic dielectric material particles, and the micropores between the inorganic dielectric material particles may form a pore structure inside the inorganic dielectric layer 13 for the passage of lithium ions.
  • the coverage ⁇ of the inorganic dielectric layer 13 on the first surface 121 may be 50% ⁇ 100%, for example, 50%, 60%, 65%, 70%, 75%, 80%, 85%, 80%, 95%, 100%, etc.
  • the above-mentioned coverage ⁇ can be measured by the following test method: the first surface 121 of the negative pole piece 10 sample is subjected to scanning electron microscope (SEM) test, and the energy spectrum (EDS) element analysis method is used to test
  • SEM scanning electron microscope
  • EDS energy spectrum
  • the main body 131 may further have a channel 132 penetrating in the thickness direction of the main body 131. That is, the main body portion 131 is provided in a discontinuous state between the negative electrode active material layer 12 and the lithium metal layer 14.
  • an open channel can be provided to increase the retention of the negative pole piece 10 to the electrolyte and the ion permeability, and to increase the lithium ion
  • the dynamic performance and rate performance of the battery and when the negative electrode active material layer 12 and the inorganic dielectric layer 13 undergo different equal volume shrinkage or expansion under conditions such as overcooling or overheating, the stress of the inorganic dielectric layer 13 can also be effectively released .
  • it can also further reduce the weight of the inorganic dielectric layer 13, thereby increasing the volume energy density and weight energy density of the battery.
  • the embodiment of the present application does not specifically limit the shape, number, and arrangement of the channels 132 of the main body 131.
  • the channels 132 may be connected or disconnected.
  • the width of the channel 132 is 0.05 ⁇ m to 6 ⁇ m, such as 0.5 ⁇ m to 6 ⁇ m, and for example, 3 ⁇ m to 6 ⁇ m; furthermore, the aspect ratio of the channel 132 is greater than or equal to 50.
  • the coverage ⁇ of the inorganic dielectric layer 13 with the aforementioned channel 132 on the first surface 121 may be 50% ⁇ 100%, for example, 50% ⁇ 95%, and for example 60% ⁇ 80%.
  • the main body portion 131 may include a plurality of inorganic dielectric regions 133, and the plurality of inorganic dielectric regions 133 are independent of each other and spaced apart from each other on the first surface 121 of the negative active material layer 12.
  • the interval between the dielectric regions 133 forms the aforementioned channel 132.
  • the shape, number, and arrangement of the inorganic dielectric regions 133 are not specifically limited, and they may be circular, polygonal, or other shapes.
  • the interval between two adjacent inorganic dielectric regions 133 is, for example, 0.05 ⁇ m to 6 ⁇ m, for example, 0.5 ⁇ m to 6 ⁇ m, and for example, 3 ⁇ m to 6 ⁇ m.
  • the main body portion 131 is a sheet-shaped body provided on the first surface 121 of the negative active material layer 12, and the sheet-shaped body has an opening extending through the thickness direction of the sheet. This is the aforementioned channel 132.
  • the shape, number, and arrangement of the openings are not specifically limited, and they may be circular, polygonal, or other shapes, such as cracks formed in the main body 131.
  • the width of the crack is, for example, 0.05 ⁇ m to 6 ⁇ m, and further, for example, is 0.5 ⁇ m to 6 ⁇ m, or 3 ⁇ m to 6 ⁇ m. Further, the aspect ratio of the crack is ⁇ 50.
  • the cracks in FIG. 4 generally extend along the length direction of the inorganic dielectric layer 13, in other embodiments, the extending direction of the cracks on the inorganic dielectric layer 13 may be any direction.
  • the size of the inorganic dielectric layer 13 is preferably equal to or substantially equal to the size of the negative electrode active material layer 12. Specifically, the outer peripheral edge of the inorganic dielectric layer 13 and the outer peripheral edge of the negative electrode active material layer 12 are flush or substantially flush.
  • the inorganic dielectric layer 13 further includes an extension 134 connected to the surface of the main body 131 facing the negative active material layer 12, and the extension 134 runs along the negative active material layer 12.
  • the pore wall surface of the pore wall extends in a direction away from the main body portion 131 and is coated on the pore wall surface of the negative electrode active material layer 12 in a film shape. This can further improve the lithium pre-insertion rate of the negative pole piece 10 and the stabilizing effect on the negative interface, thereby further improving the safety performance, cycle performance, and storage performance of the lithium ion battery.
  • the extension 134 has a function of wetting and retaining the electrolyte, and therefore can also improve the capacity and rate performance of the lithium ion battery.
  • the ratio H/T of the dimension H of the extension portion 134 of the inorganic dielectric layer 13 in the thickness direction of the negative electrode active material layer 12 to the thickness T of the main body portion 131 is preferably 1/1000 to 1/10. This makes it possible to effectively exert the above-mentioned effects of the extension portion 134 while ensuring higher lithium ion and electron transport performance in the negative active material layer 12, so that the lithium ion battery has higher comprehensive electrochemical performance.
  • H/T can be 1/500, 1/120, 1/100, 1/80, 1/20, etc.
  • the coverage ⁇ of the inorganic dielectric layer 13 including the main portion 131 and the extension portion 134 on the first surface 121 of the negative electrode active material layer 12 may be 50% ⁇ 100%, for example, 50%, 60%, 65 %, 70%, 75%, 80%, 85%, 80%, 95%, 100%, etc., such as 60% to 80%.
  • the surface of the inorganic dielectric layer 13 away from the negative active material layer 12 is an uneven surface.
  • the lithium metal layer 14 is laminated on the inorganic dielectric layer 13, it is possible to form a capillary channel between the lithium metal layer 14 and the inorganic dielectric layer 13 for the electrolyte to penetrate, and the electrolyte can quickly fill the capillary channel by capillary action , It is more conducive to the solvation of the metal lithium in the lithium metal layer 14 under the action of the potential difference, and the diffusion distance of lithium ions is shorter, so that the lithium metal layer 14 has a higher lithium utilization rate during the pre-lithium insertion process.
  • the uneven structure of the uneven surface of the inorganic dielectric layer 13 is not particularly limited, as long as capillary channels can be formed between the lithium metal layer 14 and the inorganic dielectric layer 13 for electrolyte penetration.
  • the uneven surface of the inorganic dielectric layer 13 may be a rough surface, the rough surface has many nanometer-scale peaks and valleys with a small distance between each other; it may also be the inorganic dielectric layer 13 far away from the negative active material layer 12
  • the surface is processed to form a plurality of nano-scale grooves, forming the above-mentioned uneven surface.
  • the average size G of the capillary channels in the thickness direction of the inorganic dielectric layer 13 is preferably 0 ⁇ m ⁇ G ⁇ 3 ⁇ m, and more preferably 0 ⁇ m ⁇ G ⁇ 2 ⁇ m.
  • the capillary pores have the above-mentioned average size G in the thickness direction of the inorganic dielectric layer 13, so that the distance between the portion of the lithium metal layer 14 that is not in contact with the inorganic dielectric layer 13 and the inorganic dielectric layer 13 is small, and the capillary force of the electrolyte Under the action, the capillary pores can be filled quickly, and the diffusion distance of lithium ions is short, which can improve the lithium utilization rate of the lithium metal layer 14 in the pre-lithium insertion process, and improve the uniformity of lithium insertion of the negative electrode active material layer 12, thereby improving the battery Cycle life.
  • the inorganic dielectric material in the inorganic dielectric layer 13 has ion conductivity.
  • the lithium metal layer 14 can be embedded in the negative electrode active material layer 12 at a higher utilization rate and at a more controllable speed during the pre-lithium insertion stage; and during the subsequent charge and discharge cycles, the negative electrode piece 10 can be ensured
  • the impedance is small, so as to ensure that the lithium-ion battery has a high cycle life, and excellent dynamic performance and rate performance.
  • the average particle size D v 50 of the inorganic dielectric material may be 1 nm to 100 nm, for example, 3 nm to 50 nm, and further, for example, 5 nm to 30 nm.
  • the average particle size D v 50 of the inorganic dielectric material is within the above range, which better forms a channel for ion migration between the particles, and improves the ion-conducting performance of the inorganic dielectric layer 13.
  • the inorganic dielectric material may include one or more of oxides of element A, nitrides of element A, and halides of element A, where element A is Al, Si, Ti, Zn, Mg, Zr, Ca, and Ba One or more of.
  • the halide of element A includes one or more of fluoride of element A, chloride of element A, bromide of element A, and iodide of element A, and is preferably fluoride of element A.
  • the inorganic dielectric material is selected from Al oxides (such as Al 2 O 3 , AlO(OH), etc.), Al nitrides, Al fluorides, Si oxides, Si nitrides, and Si oxides.
  • Fluoride, Ti oxide, Ti nitride, Ti fluoride, Zn oxide, Zn nitride, Zn fluoride, Mg oxide, Mg nitride, Mg fluoride, Zr One or more of oxide, Zr nitride, Zr fluoride, Ca oxide, Ca nitride, Ca fluoride, Ba oxide, Ba nitride, and Ba fluoride.
  • the weight ratio of the lithium metal layer 14 to the inorganic dielectric layer 13 in the negative electrode sheet 10 of a unit area of 2 cm ⁇ 2 cm is preferably 2:1 to 200:1, and more preferably 5.5 to 101.7.
  • the weight ratio of the lithium metal layer 14 to the inorganic dielectric layer 13 is within the above range, which can better control the lithium pre-insertion rate of the negative pole piece 10, and improve the safety performance and service life of the lithium ion battery; and the inorganic dielectric layer 13
  • the weight is very small, which is beneficial to increase the volume energy density and weight energy density of lithium-ion batteries.
  • the weight ratio of the lithium metal layer 14 to the inorganic dielectric layer 13 may be 3.1, 5.5, 7.6, 10, 13.4, 15, 17.3, 20, 27.2, 30.5, 101.7, 120, 150 or 180 etc.
  • the weight ratio of the lithium metal layer 14 to the negative electrode active material layer 12 is preferably 0.5% to 5%, for example, 1% to 5%, in the negative electrode sheet 10 having a unit area of 2 cm ⁇ 2 cm.
  • the weight ratio of the lithium metal layer 14 to the negative electrode active material layer 12 is within the above range, which can effectively reduce the capacity loss during the cycle and storage of the lithium ion battery, and improve the cycle performance and storage performance of the battery.
  • the weight ratio of the lithium metal layer 14 to the negative electrode active material layer 12 for every 2cm ⁇ 2cm unit area of the negative electrode sheet 10 may be 1.5%, 2%, 2.54%, 3%, 3.5%, 4% or 4.5% Wait.
  • the binding force between the lithium metal layer 14 and the inorganic dielectric layer 13 is F 1
  • the binding force between the inorganic dielectric layer 13 and the negative active material layer 12 is F 2 , F 1 and F 2 Satisfy between: 0 ⁇ F 1 ⁇ F 2 .
  • the inorganic dielectric layer 13 can be effectively prevented from falling off under the action of external force during the process of setting the lithium metal layer 14 and the subsequent winding preparation of the battery, improving the stability of the processing technology of the negative pole piece 10, and improving the negative pole piece 10 and electricity
  • the preparation rate of the core and the reliability during use are beneficial to improve the performance of the lithium ion battery.
  • the relationship between F 1 and F 2 satisfies: F 1 ⁇ 0.8 ⁇ F 2 .
  • the binding force F 1 between the lithium metal layer 14 and the inorganic dielectric layer 13 is preferably 2N/m to 25N/m, for example, 5N/m to 20N/m, and for example, 8N/m to 15N/m .
  • the binding force F 2 between the inorganic dielectric layer 13 and the negative electrode active material layer 12 is preferably 10 N/m or more, for example, 10 N/m to 400 N/m, for example, 10 N/m to 300 N/m, and for example, 20 N /m ⁇ 150N/m.
  • the inorganic dielectric layer 14 Determination of the inorganic dielectric layer is 13 F bonding force between the inorganic dielectric layers. 1 and 13 F 12 and the binding force between the anode active material layer 2 is well known in the art methods and apparatus may be used lithium metal layers.
  • a lithium metal layer 14 and the method for measuring the bonding force between the inorganic dielectric layer 13 is F 1: less than 2% in humidity, temperature 25 °C thermostatic pressure drying room, to the negative electrode side current collector 11
  • the negative electrode active material layer 12, the inorganic dielectric layer 13 and the lithium metal layer 14 are arranged in sequence.
  • the negative electrode piece 10 without any coating on the other side is the sample to be tested, and the width of the sample to be tested is 0.02m; the 3M double-sided tape is uniform Stick it on a stainless steel plate, and then evenly stick the uncoated surface of the negative electrode current collector 11 of the sample to be tested on the double-sided tape; use a tensile testing machine (such as INSTRON3365) to combine the lithium metal layer 14 of the sample to be tested with the inorganic dielectric layer 13 Perform 180° continuous peeling at 50mm/min; read the maximum tensile force (in N) according to the data graph of tensile force and displacement, and calculate the bonding strength of the lithium metal layer 14 based on the ratio of the maximum tensile force to the width of the sample to be tested, namely The bonding force F 1 (N/m) between the lithium metal layer 14 and the inorganic dielectric layer 13.
  • a tensile testing machine such as INSTRON3365
  • the binding force F 2 between the inorganic dielectric layer 13 and the negative electrode active material layer 12 is measured as follows: in a constant temperature and normal pressure drying room with a humidity of less than 2% and a temperature of 25° C., the negative electrode current collector 11
  • the negative electrode active material layer 12 and the inorganic dielectric layer 13 are arranged in sequence on one side, and the negative electrode piece 10 without any coating on the other side is the sample to be tested.
  • the width of the sample to be tested is 0.02m; the 3M double-sided tape is evenly attached to the stainless steel plate Then, evenly stick the uncoated surface of the negative electrode current collector 11 of the sample to be tested on the double-sided tape; use a tensile testing machine (such as INSTRON3365) to measure the size of the inorganic dielectric layer 13 and the negative electrode active material layer 12 of the sample to be tested to 50 mm /min for continuous peeling at 180°; read the maximum tensile force (in N) according to the data graph of tensile force and displacement, and calculate the bonding firmness of the inorganic dielectric layer 13 according to the ratio of the maximum tensile force to the width of the sample to be tested, that is, inorganic dielectric
  • the bonding force between the layer 13 and the negative electrode active material layer 12 is F 2 (N/m).
  • the embodiment of the present application does not particularly limit the thickness of the negative active material layer 12, and those skilled in the art can adjust it according to actual needs.
  • the thickness of the negative active material layer 12 may be 90 ⁇ m to 200 ⁇ m, for example, 100 ⁇ m to 130 ⁇ m.
  • the embodiments of the present application have no particular limitation on the types of negative electrode active materials, and the negative electrode active materials known in the art that can insert/release lithium ions can be used.
  • the negative active material may be natural graphite, artificial graphite, soft carbon, hard carbon, mesocarbon microspheres, nano-carbon, elemental silicon, silicon-oxygen compound, silicon-carbon composite, silicon alloy, elemental tin, tin-oxygen compound One or more of, tin-carbon composite, tin alloy and lithium titanate.
  • silicon-oxygen compound its molecular formula may be SiO x , 0 ⁇ x ⁇ 2, such as silicon oxide.
  • silicon-carbon composite it may be one of carbon-coated silicon, carbon-coated silicon-oxygen compound, a mixture of silicon and carbon, a mixture of silicon-oxygen compound and carbon, and a mixture of silicon and silicon-oxygen compound and carbon.
  • the carbon can be one or more of graphite, soft carbon and hard carbon.
  • the average particle size D v 50 of the negative active material may be 6 ⁇ m to 10 ⁇ m.
  • the negative active material layer 12 may also optionally include a binder, a conductive agent and/or other auxiliary agents.
  • the types of the binder and the conductive agent are not specifically limited, and can be selected according to requirements.
  • the binder may be styrene butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polyvinyl butyral (PVB), polytetrafluoroethylene ( One or more of PTFE), ethylene-vinyl acetate copolymer (EVA) and polyvinyl alcohol (PVA).
  • the conductive agent may be one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • Other auxiliary agents are, for example, thickeners, such as sodium carboxymethyl cellulose (CMC-Na).
  • the compaction density of the negative pole piece 10 is preferably 1.2 g/cm 3 to 2.0 g/cm 3 .
  • the compaction density of the negative pole piece 10 is within an appropriate range, which enables the battery to have a higher energy density and cycle life.
  • the porosity of the negative pole piece 10 is preferably 25% to 60%, for example, 30% to 45%.
  • the porosity of the negative pole piece 10 is within an appropriate range, which enables the negative pole piece 10 to have higher lithium ion and electron transport performance, and a proper electrolyte infiltration capacity, which is beneficial to improve the cycle life and energy density of the lithium ion battery .
  • the porosity of the negative pole piece 10 has a meaning known in the art, and can be measured using methods and equipment known in the art. For example, it can be measured by a gas replacement method.
  • True density meter (such as AccuPyc II 1340) can be used for testing. The test can refer to the standard GB/T 24586-2009 determination of apparent density, true density and porosity of iron ore.
  • the type of the negative electrode current collector 11 is not specifically limited, and materials with good electrical conductivity and mechanical properties can be selected according to requirements.
  • a metal foil, a carbon-coated metal foil, or a porous metal plate can be used, such as copper foil.
  • the method includes the following steps:
  • the negative electrode active material, the binder, and the conductive agent are dispersed in a solvent.
  • the solvent can be deionized water or N-methylpyrrolidone (NMP) to form a uniform negative electrode slurry;
  • NMP N-methylpyrrolidone
  • the negative electrode slurry is coated on the surface of the negative electrode current collector 11, and after drying and other processes, the negative electrode active material layer 12 is formed on the surface of the negative electrode current collector 11.
  • the anode active material is deposited on the anode current collector 11 to obtain the anode active material layer 12.
  • a vapor deposition method is used to deposit the negative electrode active material on the negative electrode current collector 11.
  • the vapor deposition method may be one or more of Atomic Layer Deposition (ALD), Chemical Vapor Deposition (CVD) and Physical Vapor Deposition (PVD), for example, Thermal evaporation method (Thermal Evaporation Deposition), plasma assisted thermal evaporation (Plasma assisted Thermal Evaporation), electron beam evaporation method (EBEM), plasma assisted electron beam evaporation (Plasma assisted electron beam Evaporation), One or more of Reactive Ion-beam Sputtering (RIBS), Magnetron Sputtering (MS) and Arc Ion Plating (AIP).
  • ALD Atomic Layer Deposition
  • CVD Chemical Vapor Deposition
  • PVD Physical Vapor Deposition
  • Thermal evaporation method Thermal Evaporation Deposition
  • an inorganic dielectric material may be deposited on the first surface 121 of the negative electrode active material layer 12 by a vapor deposition method to obtain the inorganic dielectric layer 13.
  • the bonding force between the inorganic dielectric layer 13 and the negative electrode active material layer 12 formed by the vapor deposition method is stronger, and it is better to avoid the inorganic dielectric layer 13 from the negative electrode active material layer 12 during long-term battery cycling and mechanical abuse. The problem of surface peeling.
  • the inorganic dielectric material can not only be deposited on the first surface 121 of the negative active material layer 12 to form the main body portion 131 of the inorganic dielectric layer 13, but can also diffuse from the first surface 121 to the negative active material layer 12 In the internal pores and deposited on the wall surface of the pores, the extension 134 of the inorganic dielectric layer 13 is formed.
  • the thickness of the main body portion 131 of the inorganic dielectric layer 13 continues to increase, and the thickness of the extension portion 134 on the surface of the pore wall of the negative active material layer 12 adjacent to it also continues to increase.
  • the resistance to spreading and diffusion inside the active material layer 12 becomes larger and larger, and the thickness of the extension portion 134 decreases along the thickness direction of the anode active material layer 12.
  • the position of the anode active material layer 12 far from the anode current collector 11 has a smaller pore size and lower porosity, and the closer the anode active material layer 12 is to the anode current collector 11, the larger the pore size and the higher the porosity.
  • step S200 the vapor deposition method can be the vapor deposition method described above, and will not be repeated here.
  • step S200 may include the following steps:
  • the reactive gas a can be one or more of oxygen, ozone, carbon dioxide, water vapor, nitrogen, nitrogen monoxide, nitrogen dioxide, and ammonia.
  • the inorganic dielectric material precursor b may be one or more of elemental A-containing element, alloy, alkyl compound, nitrate, acetate, and sulfate.
  • step S200 may include the following steps:
  • the reactive gas a can be diluted by the inert gas. Under the action of the ICP source, the reactive gas a generates a plasma containing element B.
  • the element is one or more of O, N, F, Cl, Br, and I.
  • the reactive gas a may be as described above, and the inert gas may be one or more of argon, nitrogen, and helium.
  • the power of the ICP source can be 300W to 600W.
  • the flow rate of the reactive gas a may be 200 sccm to 1000 sccm.
  • the electron gun In the reaction chamber, the electron gun generates an electron beam.
  • the electron beam bombards the target material c containing element A to melt and evaporate.
  • the gaseous material chemically reacts with the plasma and deposits on the surface of the negative electrode active material layer 12 to form an inorganic material. Dielectric layer 13.
  • the target c containing the A element may be one or more of the simple substance and the alloy containing the A element.
  • the voltage of the electron beam can be 6kV-12kV, and the surface temperature of the negative active material layer 12 is preferably controlled to be ⁇ 100°C.
  • the surface temperature of the negative active material layer 12 is 20°C-100°C, such as 60°C-90°C.
  • the vacuum degree of the reaction chamber can adjust the vacuum degree of the reaction chamber, the electron beam voltage, the composition and flow rate of the reactive gas a, and the composition of the target c containing element A according to the basic knowledge and principles of plasma-assisted electron beam evaporation deposition technology.
  • step S200 an inorganic dielectric layer 13 with a sheet-like structure can be obtained, and the aforementioned openings can be further formed in the inorganic dielectric layer 13 in any manner, for example, cold pressing the inorganic dielectric layer 13. It is also possible to use a template, such as a mask, to directly form the inorganic dielectric layer 13 with openings penetrating through its thickness.
  • the inorganic dielectric layer 13 including a plurality of inorganic dielectric regions 133 can also be formed in any manner, for example, a template such as a mask is used.
  • the raw material and form of the lithium metal layer 14 are not limited.
  • the raw material of the lithium metal layer 14 can be selected from one or more of lithium powder, lithium ingot, lithium flake, and lithium ribbon.
  • the lithium metal layer 14 may not be completely densely and uniformly distributed on the surface of the inorganic dielectric layer 13.
  • the raw material of the lithium metal layer 14 is lithium powder
  • the gap size can be controlled between 1 ⁇ m and 5000 ⁇ m
  • the raw material of the lithium metal layer 14 is lithium ingot
  • a plurality of lithium strips (or lithium strips) can also be formed on the surface of the inorganic dielectric layer 13 at intervals, and the distance between two adjacent lithium strips (or lithium strips) can be controlled between 1 ⁇ m and 5000 ⁇ m.
  • the lithium metal layer 14 pre-inserts lithium into the negative electrode active material layer 12, and finally the lithium content in the negative electrode active material layer 12 can still achieve a uniform distribution, achieving uniform lithium insertion.
  • the lithium metal layer 14 may be provided on the surface of the inorganic dielectric layer 13 by rolling.
  • the intermolecular force between the lithium metal and the inorganic dielectric layer 13 is used to stably fix the lithium metal layer 14 on the surface of the inorganic dielectric layer 13.
  • the negative active material layer 12 is obtained by coating the negative electrode slurry, and the inorganic dielectric layer 13 has a sheet-like structure with crack-like openings as described above.
  • the dried negative electrode active material coating may be cold pressed in step S100 to obtain the negative electrode active material layer 12 with a preset compaction density;
  • step S200 pressure is applied to the inorganic dielectric layer 13 obtained by the deposition of the inorganic dielectric material, such as cold pressing treatment, to form the aforementioned crack-like openings in the inorganic dielectric layer 13; then lithium metal is prepared on the surface of the inorganic dielectric layer 13 Layer 14.
  • the dried negative electrode active material coating is obtained in step S100, and then when the inorganic dielectric layer 13 is cold pressed in step S200, the cold pressing of the negative electrode active material coating is simultaneously realized to obtain a preset compaction.
  • the negative electrode active material layer 12 with a high density and the aforementioned crack-like openings are formed in the inorganic dielectric layer 13 at the same time; and then, a lithium metal layer 14 is formed on the surface of the inorganic dielectric layer 13.
  • the dried negative active material coating is obtained in step S100, and the inorganic dielectric layer 13 with a sheet-like structure is obtained in step S200, and then when the lithium metal layer 14 is prepared on the surface of the inorganic dielectric layer 13 by rolling, at the same time
  • the lithium metal layer 14 is prepared on the surface of the inorganic dielectric layer 13 by rolling, at the same time
  • To achieve cold pressing of the inorganic dielectric layer 13 and cold pressing of the negative electrode active material coating thereby obtaining the lithium metal layer 14 and the negative electrode active material layer 12 with a preset compaction density, while forming the foregoing on the inorganic dielectric layer 13
  • the crack-like opening is achieved.
  • the embodiment of the present application also provides a battery cell.
  • the battery core includes a positive pole piece, a negative pole piece and a separator.
  • the separator is interposed between the positive pole piece and the negative pole piece to isolate it.
  • the negative pole piece adopts the negative pole piece 10 provided in the embodiment of the application.
  • the battery cell in the embodiment of the present application refers to a battery cell that has not been infiltrated with electrolyte.
  • the battery cell of this application may only include a positive pole piece, a separator and a negative pole piece, but the cell of the present application may also include other structures in a broad sense, such as terminal components, protective shell components, etc.
  • the battery core of the embodiment of the present application also has corresponding beneficial effects, which will not be repeated here.
  • the weight ratio of the lithium metal layer 14 to the negative electrode active material layer 12 is 0.5% to 5%, and further 1% to 1% to the negative electrode sheet 10 of a unit area of 2 cm ⁇ 2 cm. 5%; the ratio of the negative electrode capacity C 1 per unit area to the positive electrode capacity C 2 per unit area is 1.2-2.1, further 1.3-2.1; the negative electrode capacity per unit area C 1 , the positive electrode capacity per unit area C 2 and the lithium metal layer capacity per unit area C C 1 /(C 2 +C 3 ⁇ K) ⁇ 1.05 is satisfied between 3 and C 1 /(C 2 +C 3 ⁇ K) ⁇ 1.10, where K is the utilization rate of metallic lithium in the lithium metal layer 14.
  • negative electrode capacity per unit area C 1 weight of negative electrode active material per unit area of negative electrode active material layer ⁇ reversible gram capacity of negative electrode active material.
  • Positive electrode capacity per unit area C 2 weight of the positive electrode active material per unit area of the positive electrode active material layer ⁇ reversible gram capacity of the positive electrode active material.
  • the capacity C 3 of the lithium metal layer per unit area refers to the theoretical capacity of the lithium metal layer per unit area.
  • Lithium metal layer capacity per unit area C 3 weight of metal lithium per unit area lithium metal layer x theoretical gram capacity of metal lithium. Due to the possible oxidation of some metallic lithium in the lithium metal layer 14 and the participation of some lithium ions in the negative electrode film formation, the utilization rate of metallic lithium in the lithium metal layer 14 is generally less than 100%. According to research experience, the lithium metal layer 14 The utilization rate of metallic lithium is generally 75%-85%, such as 78%-82%, and another example is 80%. Of course, by reducing the oxidation of lithium metal in the lithium metal layer 14 and reducing the participation of lithium ions from the lithium metal layer 14 in forming the negative electrode, the utilization rate can be improved.
  • the vacancy provided by the negative active material in the negative active material layer 12 can fully accommodate the insertion of all lithium ions from the lithium metal layer 12, and receive from the positive electrode during the first charge. For all lithium ions, avoid the accumulation of a large amount of lithium ions on the interface of the negative electrode to prevent lithium from the negative electrode.
  • the cycle life, safety performance and storage performance of the battery cell can be better improved.
  • the negative electrode lithium intercalation occurs inside the battery cell, and at least a part of the metal lithium of the lithium metal layer 14 is embedded in the negative electrode active material, and exists in the form of the negative electrode active material pre-inserted with lithium ,
  • the open circuit voltage of the cell is close to the voltage after the first week of charge and discharge.
  • the negative active material When the battery cell is fully charged, the negative active material has enough vacancies to receive all lithium ions from the positive active material and all lithium ions from the lithium metal layer 14, and store excess lithium ions in the negative electrode after full discharge, so that the discharge is cut off After that, the negative electrode still has 5%-97% (relative to the positive electrode capacity) of lithium ions that can shuttle between the positive and negative electrodes.
  • the negative electrode lithium-rich content after the first week of charging is 105% ⁇ 197% (Relative to the capacity of the positive electrode), so it can effectively reduce the capacity loss during the cycle of charging and discharging and storage of the battery, and improve the cycle life and storage performance of the battery.
  • the positive pole piece may include a positive current collector and a positive active material layer provided on at least one surface of the positive current collector.
  • the positive electrode current collector includes two opposite surfaces along its thickness direction, and the positive electrode active material layer may be provided on either of the two surfaces, or may be respectively provided on the two surfaces.
  • the embodiment of the present application does not particularly limit the thickness of the positive electrode active material layer, and those skilled in the art can adjust it according to actual needs.
  • the thickness of the positive active material layer may be 100 ⁇ m to 180 ⁇ m, for example, 110 ⁇ m to 130 ⁇ m.
  • the positive active material in the positive active material layer is a material that can reversibly accept and extract lithium ions, such as lithium transition metal composite oxide, lithium transition metal composite oxide and other transition metals or non-transition metals Or one or more of composite oxides obtained from non-metals.
  • the transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Ti, Zn, V, Al, Zr, Ce, and Mg.
  • 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, and lithium-containing olivine structure One or more of phosphates.
  • the molecular formula of the lithium-containing phosphate with olivine structure can be LiFe 1-xy Mn x M y PO 4 , 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 0.1, 0 ⁇ x+y ⁇ 1, and M is selected from other than Fe, One or more of transition metal elements other than Mn or non-transition metal elements.
  • the lithium-containing phosphate with an olivine structure is one or more of lithium iron phosphate, lithium manganese phosphate, and lithium iron manganese phosphate.
  • the positive active material layer may also include a binder and/or a conductive agent.
  • the types of the binder and the conductive agent are not limited in this application, and can be selected according to actual needs.
  • the binder may be polyvinylidene fluoride (PVDF), polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer One or more of tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin;
  • the conductive agent can be graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nano One or more of tube, graphene and carbon nanofiber.
  • the type of the positive electrode current collector is not subject to specific restrictions, and materials with good electrical conductivity and mechanical properties can be selected according to requirements.
  • the positive electrode current collector can be made of metal foil, carbon-coated metal foil or porous metal plate, such as aluminum foil.
  • the positive pole piece can be prepared according to conventional methods in the art. Generally, the positive electrode active material, conductive agent and binder are dispersed in a solvent (such as N-methylpyrrolidone) to form a uniform positive electrode slurry. The positive electrode slurry is coated on the positive electrode current collector and dried and cold pressed After the process, the positive pole piece is obtained.
  • a solvent such as N-methylpyrrolidone
  • isolation film in the battery cell can be any isolation film that can be used for lithium ion batteries, such as glass fiber isolation film, non-woven isolation film, polyethylene isolation film, polypropylene isolation film, Polyvinylidene fluoride isolation membranes and multilayer composite membranes formed by combining one or more of them, but not limited thereto.
  • the embodiment of the present application also provides a lithium ion battery.
  • the lithium ion battery includes a battery cell and an electrolyte, wherein the battery cell adopts the battery cell provided in the embodiment of the present application.
  • the battery core of the embodiment of the present application since the battery core of the embodiment of the present application is adopted, the battery core of the embodiment of the present application also has corresponding beneficial effects, which will not be repeated here.
  • the electrolyte includes an organic solvent and a lithium salt.
  • the embodiments of this application do not make specific restrictions on the types of organic solvents and lithium salts, and can be selected according to requirements.
  • the organic solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dicarbonate Propyl ester (DPC), methyl propyl carbonate (MPC), ethylene propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate ( MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), butyl One or more of ethyl sulfone (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl s
  • the lithium salt can be selected from LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiAsF 6 (lithium hexafluoroarsenate), LiFSI (lithium bisfluorosulfonimide), LiTFSI (lithium bistrifluoromethanesulfonimide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium bisoxalate borate), LiPO 2 F 2 (lithium difluorophosphate) One or more of LiDFOP (lithium difluorodioxalate phosphate) and LiTFOP (lithium tetrafluorooxalate phosphate).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiClO 4 lithium per
  • the electrolyte may also optionally include additives.
  • additives There are no specific restrictions on the types of additives, which can be selected according to needs, such as vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), succinonitrile (SN), One of adiponitrile (ADN), 1,3-propene sultone (PST), tris(trimethylsilane) phosphate (TMSP) and tris(trimethylsilane) borate (TMSB) Or multiple.
  • VC vinylene carbonate
  • VEC vinyl ethylene carbonate
  • FEC fluoroethylene carbonate
  • SN succinonitrile
  • ADN 1,3-propene sultone
  • PST 1,3-propene sultone
  • TMSP tris(trimethylsilane) phosphate
  • TMSB tris(trimethylsilane) borate
  • FIG. 7 shows a lithium ion battery 5 with a square structure as an example.
  • the lithium ion battery may include an outer package for encapsulating the battery cell and the electrolyte.
  • the outer packaging may be a hard shell, such as a hard plastic shell, aluminum shell, steel shell, etc.
  • the outer packaging of the lithium ion battery can also be a soft bag, such as a pouch type soft bag.
  • the material of the soft bag can be plastic, for example, it can include one or more of polypropylene PP, polybutylene terephthalate PBT, polybutylene succinate PBS, and the like.
  • the outer package may include a housing 51 and a cover 53.
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the housing 51 has an opening communicating with the containing cavity, and a cover plate 53 can cover the opening to close the containing cavity.
  • the positive pole piece, the negative pole piece and the isolation film may be formed into the cell 52 through a lamination process or a winding process.
  • the battery core 52 is encapsulated in the containing cavity.
  • the electrolyte is infiltrated in the cell 52.
  • the number of cells 52 contained in the lithium ion battery 5 can be one or several, which can be adjusted according to requirements.
  • lithium ion batteries can be assembled into battery modules, and the number of lithium ion batteries contained in the battery modules can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 9 is a battery module 4 as an example.
  • a plurality of lithium ion batteries 5 may be arranged in order along the length direction of the battery module 4. Of course, it can also be arranged in any other manner. Furthermore, the plurality of lithium ion batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having an accommodation space, and a plurality of lithium ion batteries 5 are accommodated in the accommodation space.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3.
  • the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4.
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the embodiment of the present application also provides a device including the lithium ion battery described in the present application.
  • the lithium ion battery can be used as a power source of the device, and can also be used as an energy storage unit of the device.
  • the device can be, but is not limited to, mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf Vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the device can select a lithium ion battery, battery module or battery pack according to its usage requirements.
  • Fig. 12 is a device as an example.
  • the device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • battery packs or battery modules can be used.
  • the device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • the device usually requires light and thin, and can use lithium-ion batteries as a power source.
  • the coating weight of the positive electrode slurry and the coating weight of the negative electrode slurry are calculated on a single side without solvent;
  • the unit area is calculated based on the area of 1540.25mm 2 .
  • the positive electrode active material lithium nickel cobalt manganate (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ), conductive agent acetylene black, and binder PVDF in the solvent NMP at a weight ratio of 94:4:2, and stir and mix well to obtain the positive electrode.
  • the reversible gram capacity of LiNi 0.8 Co 0.1 Mn 0.1 O 2 is 190 mAh/g.
  • the reversible gram capacity of artificial graphite is 340mAh/g.
  • the negative electrode slurry was coated on the two opposite surfaces of the negative electrode current collector copper foil, wherein the coating weight of the negative electrode slurry was 0.120g/1540.25mm 2 ; after drying and cold pressing, the negative electrode active material layer was obtained.
  • the thickness of the active material layer is 120 ⁇ m.
  • plasma-assisted thermal evaporation deposition technology is used to prepare an inorganic dielectric layer on the surface of the negative electrode active material layer facing away from the negative electrode current collector.
  • the heating source is electron beam
  • the heating target is aluminum simple substance.
  • the active gas of oxygen is used as the reaction gas to control the surface temperature of the negative electrode active material layer to 90°C ⁇ 110°C, and the width of the window during the manufacturing process It is equal to 80% of the width of the negative pole piece, the electron beam voltage is 10kV, the vacuum of the process chamber is 10-2 Pa, the oxygen flow rate is 800sccm, the power of the ICP source is 300W, and the process time is 1h.
  • the thickness of the main body part can be measured by using instruments and methods known in the art.
  • an ion polisher IB-19500CP
  • an ion polisher can be used to cut the negative pole piece to obtain a flat section of the negative pole piece; then place the pole piece under a scanning electron microscope (Sigma300) to observe the section of the negative pole piece and measure the thickness of the main body .
  • the measurement can refer to JY/T010-1996 analytical scanning electron microscope method general rule.
  • the coverage of the inorganic dielectric layer on the surface of the negative active material layer, the size of the extension in the thickness direction of the negative active material layer and the thickness ratio of the extension to the main body are all average values obtained by randomly scanning 6 regions.
  • the inorganic dielectric layer includes the main body and extension parts described above, and the main body is arranged in a lamellar structure.
  • the thickness T of the main body part is 200 nm, and the size of the extension part in the thickness direction of the negative electrode active material layer is 1/100 of the thickness of the main body part; the coverage rate of the inorganic dielectric layer on the surface of the negative electrode active material layer 80%.
  • the surface of the inorganic dielectric layer away from the negative active material layer is a rough surface.
  • the inorganic dielectric material in the inorganic dielectric layer is alumina.
  • the binding force F 2 between the inorganic dielectric layer and the negative electrode active material layer measured by the aforementioned measuring method was 35 N/m.
  • the lithium metal sheet is composited to the surface of the inorganic dielectric layer facing away from the negative electrode active material layer by a roll pressing method to obtain a lithium metal layer.
  • the size of the lithium metal layer is approximately equal to the size of the inorganic dielectric layer; the weight of the lithium metal layer is 3.05mg/1540.25mm 2 , and the theoretical gram capacity of metal lithium is 3861.3 mAh/g.
  • the weight ratio of the lithium metal layer per unit area to the inorganic dielectric layer per unit area is 15.3.
  • the cross-sectional SEM (Sigma300) test was performed on the above-mentioned negative pole piece, and a capillary channel for electrolyte penetration was formed between the lithium metal layer and the inorganic dielectric layer. 10 arbitrary positions were measured and calculated to obtain the thickness of the capillary channel in the inorganic dielectric layer.
  • the average size G in the direction is 1.0 ⁇ m.
  • the binding force F 1 between the lithium metal layer and the inorganic dielectric layer was determined to be 10 N/m using the measurement method described above.
  • ethylene carbonate (EC), propylene carbonate (PC) and dimethyl carbonate (DMC) are mixed uniformly in a weight ratio of 1:1:1 to obtain Organic solvent: Dissolve the lithium salt LiPF 6 in the above organic solvent and mix them uniformly to obtain an electrolyte, wherein the concentration of LiPF 6 is 1 mol/L.
  • the positive pole piece, the polyethylene porous separator, and the negative pole piece are laminated in order, and then wound to obtain a battery; the battery is placed in an outer package, electrolyte is injected and packaged to obtain a lithium ion battery.
  • Example 1 The difference from Example 1 is that the coating weight of the negative electrode slurry is 0.104g/1540.25mm 2 ; the size of the extension of the inorganic dielectric layer in the thickness direction of the negative electrode active material layer is 1/80 of the thickness of the main body; lithium The weight of the metal layer is 1.52mg/1540.25mm 2 ; the weight ratio of the lithium metal layer per unit area to the inorganic dielectric layer per unit area is 7.6; the average size G of the capillary channels in the thickness direction of the inorganic dielectric layer is 2.0 ⁇ m; lithium metal The bonding force F 1 between the layer and the inorganic dielectric layer is 15 N/m.
  • Example 2 The difference from Example 1 is that the coating weight of the positive electrode slurry is 0.164g/1540.25mm 2 , and the coating weight of the negative electrode slurry is 0.136g/1540.25mm 2 ; the extension of the inorganic dielectric layer is in the negative active material layer
  • the size in the thickness direction is 1/120 of the thickness of the main body; the weight of the lithium metal layer is 3.45mg/1540.25mm 2 ; the weight ratio of the lithium metal layer per unit area to the inorganic dielectric layer per unit area is 17.3; the capillary channels are in the inorganic medium
  • the average dimension G in the thickness direction of the electrical layer was 1.0 ⁇ m.
  • Example 1 The difference from Example 1 is that the coating weight of the positive electrode slurry is 0.189g/1540.25mm 2 , and the coating weight of the negative electrode slurry is 0.136g/1540.25mm 2 ; the extension of the inorganic dielectric layer is in the negative active material layer
  • the dimension in the thickness direction is 1/120 of the thickness of the main body; the weight of the lithium metal layer is 1.99mg/1540.25mm 2 ; the weight ratio of the lithium metal layer per unit area to the inorganic dielectric layer per unit area is 10; the capillary channels are in the inorganic medium
  • the average size G in the thickness direction of the electric layer is 1.5 ⁇ m; the bonding force F 1 between the lithium metal layer and the inorganic dielectric layer is 12 N/m.
  • Example 1 The difference from Example 1 is that the coating weight of the positive electrode slurry is 0.129g/1540.25mm 2 , and the coating weight of the negative electrode slurry is 0.136g/1540.25mm 2 ; the extension of the inorganic dielectric layer is at the thickness of the negative electrode active material layer.
  • the dimension in the direction is 1/120 of the thickness of the main body; the weight of the lithium metal layer is 5.44mg/1540.25mm 2 ; the weight ratio of the lithium metal layer per unit area to the inorganic dielectric layer per unit area is 27.2; the capillary channels are in the inorganic dielectric
  • the average size G in the layer thickness direction is 0.5 ⁇ m; the bonding force F 1 between the lithium metal layer and the inorganic dielectric layer is 9 N/m.
  • Example 1 The difference from Example 1 is that the coating weight of the positive electrode slurry is 0.117g/1540.25mm 2 , and the coating weight of the negative electrode slurry is 0.136g/1540.25mm 2 ; the extension of the inorganic dielectric layer is at the thickness of the negative active material layer.
  • the dimension in the direction is 1/120 of the thickness of the main body; the weight of the lithium metal layer is 6.16mg/1540.25mm 2 ; the weight ratio of the unit area of the lithium metal layer to the unit area of the inorganic dielectric layer is 30.8; the capillary channels are in the inorganic dielectric
  • the average size G in the layer thickness direction is 0.4 ⁇ m; the bonding force F 1 between the lithium metal layer and the inorganic dielectric layer is 8 N/m.
  • Example 1 The difference from Example 1 is that the coating weight of the positive electrode slurry is 0.204g/1540.25mm 2 , and the coating weight of the negative electrode slurry is 0.136g/1540.25mm 2 ; the extension of the inorganic dielectric layer is in the negative active material layer
  • the dimension in the thickness direction is 1/120 of the thickness of the main body; the weight of the lithium metal layer is 1.10mg/1540.25mm 2 ; the weight ratio of the lithium metal layer per unit area to the inorganic dielectric layer per unit area is 5.5; the capillary channels are in the inorganic medium
  • the average size G in the thickness direction of the electric layer is 2.5 ⁇ m; the bonding force F 1 between the lithium metal layer and the inorganic dielectric layer is 17 N/m.
  • Example 2 The difference from Example 1 is that in the preparation process of the inorganic dielectric layer, the control process time is 0.5h; the thickness T of the main part of the inorganic dielectric layer is 30nm, and the size of the extension part in the thickness direction of the negative electrode active material layer is 1/1000 of the thickness of the main body; the weight ratio of the lithium metal layer per unit area to the inorganic dielectric layer per unit area is 101.7; the average size G of the capillary channels in the thickness direction of the inorganic dielectric layer is 0.1 ⁇ m; the inorganic dielectric layer and the negative electrode The bonding force F 2 between the active material layers is 25 N/m.
  • Example 2 The difference from Example 1 is that in the preparation process of the inorganic dielectric layer, the process time is 0.7h; the thickness T of the main part of the inorganic dielectric layer is 100nm, and the size of the extension part in the thickness direction of the negative electrode active material layer is the main part
  • the weight ratio of the lithium metal layer per unit area to the inorganic dielectric layer per unit area is 30.5; the average size G of the capillary channels in the thickness direction of the inorganic dielectric layer is 1.0 ⁇ m; the inorganic dielectric layer and the negative electrode are active
  • the bonding force F 2 between the material layers is 30 N/m.
  • Example 1 The difference from Example 1 is that in the preparation process of the inorganic dielectric layer, the control process time is 1.5h; the thickness T of the main part of the inorganic dielectric layer is 500nm, and the size of the extension part in the thickness direction of the negative electrode active material layer is 1/20 of the thickness of the main body; the weight ratio of the lithium metal layer per unit area to the inorganic dielectric layer per unit area is 6.1; the binding force F 2 between the inorganic dielectric layer and the negative electrode active material layer is 40 N/m.
  • Example 1 The difference from Example 1 is that in the preparation process of the inorganic dielectric layer, the process time is 2.5h; the thickness T of the main body of the inorganic dielectric layer is 1000 nm, and the size of the extension in the thickness direction of the negative active material layer is the main body. 1/10 of the thickness; the weight ratio of the lithium metal layer per unit area to the inorganic dielectric layer per unit area is 3.1; the binding force F 2 between the inorganic dielectric layer and the negative electrode active material layer is 50 N/m.
  • Example 1 The difference from Example 1 is that the width of the window during the manufacturing process is changed to be equal to the width of the pole piece; the coverage rate of the inorganic dielectric layer on the surface of the negative electrode active material layer is 100%; the lithium metal layer per unit area and the inorganic dielectric layer per unit area The weight ratio is 19.1; the binding force F 2 between the inorganic dielectric layer and the negative electrode active material layer is 37 N/m.
  • the difference from Example 1 is that the width of the window during the manufacturing process is changed to be equal to the width of the pole piece, and the surface of the negative active material layer is covered with a mask.
  • the body of the obtained inorganic dielectric layer includes a plurality of inorganic dielectric regions. A plurality of inorganic dielectric regions are mutually independent and spaced apart on the surface of the negative electrode active material layer.
  • the coverage rate of the inorganic dielectric layer on the surface of the negative electrode active material layer is 50%; the unit area of the lithium metal layer and the unit area of the inorganic dielectric layer
  • the weight ratio is 9.6; the binding force F 2 between the inorganic dielectric layer and the negative electrode active material layer is 32 N/m.
  • the difference from Example 1 is that the width of the window during the manufacturing process is changed to be equal to the width of the pole piece.
  • the main body of the inorganic dielectric layer is a sheet-like body arranged on the surface of the negative electrode active material layer.
  • the sheet-like body has For the cracks arranged through the thickness direction, the coverage of the inorganic dielectric layer on the surface of the negative electrode active material layer is 70%; the weight ratio of the unit area lithium metal layer to the unit area inorganic dielectric layer is 13.4.
  • Example 1 The difference from Example 1 is that the width of the window during the manufacturing process is changed to be equal to the width of the pole piece, and the surface of the negative active material layer is covered with a mask.
  • the body of the obtained inorganic dielectric layer includes a plurality of inorganic dielectric regions. A plurality of inorganic dielectric regions are independently and spaced apart on the surface of the negative electrode active material layer. The coverage rate of the inorganic dielectric layer on the surface of the negative electrode active material layer is 90%; the difference between the unit area lithium metal layer and the unit area inorganic dielectric layer The weight ratio is 17.2.
  • the difference from Example 1 is that the width of the window during the manufacturing process is changed to be equal to the width of the pole piece.
  • the main body of the inorganic dielectric layer is a sheet-like body arranged on the surface of the negative electrode active material layer.
  • the sheet-like body has Cracks penetrated along its own thickness direction, and the coverage of the inorganic dielectric layer on the surface of the negative electrode active material layer is 80%; the lithium powder is composited to the surface of the inorganic dielectric layer facing away from the negative electrode active material layer by rolling ,
  • the lithium metal layer is prepared, there is no capillary channel between the lithium metal layer and the inorganic dielectric layer; the binding force F 2 between the inorganic dielectric layer and the negative electrode active material layer is 35N/m, and the lithium metal layer and the inorganic dielectric layer
  • the bonding force F 1 between the electrical layers is 7 N/m.
  • Example 1 The difference from Example 1 is that in the preparation process of the inorganic dielectric layer, the target material is titanium metal; the weight ratio of the lithium metal layer per unit area to the inorganic dielectric layer per unit area is 15; the inorganic dielectric layer and the negative electrode active material The bonding force F 2 between the layers is 100 N/m.
  • Example 1 The difference from Example 1 is that in the preparation process of the inorganic dielectric layer, the target material is tin metal; the weight ratio of the lithium metal layer per unit area to the inorganic dielectric layer per unit area is 20; the inorganic dielectric layer and the negative electrode active material The bonding force F 2 between the layers is 100 N/m.
  • Example 1 The difference from Example 1 is that in the preparation process of the inorganic dielectric layer, the target material is zinc metal; the weight ratio of the lithium metal layer per unit area to the inorganic dielectric layer per unit area is 16; the inorganic dielectric layer and the negative electrode active material The bonding force F 2 between the layers is 100 N/m.
  • Example 1 The difference from Example 1 is that no lithium metal layer is provided.
  • Example 2 The difference from Example 1 is that the coating weight of the negative electrode slurry is 0.094 g/1540.25 mm 2 .
  • the coating weight of the positive electrode slurry was 0.164g / 1540.25mm 2
  • a lithium metal layer is not provided.
  • Example 1 The difference from Example 1 is that the coating weight of the positive electrode slurry is 0.210 g/1540.25 mm 2 , and the coating weight of the negative electrode slurry is 0.136 g/1540.25 mm 2 , and the lithium metal layer is not provided.
  • the coating weight of the positive electrode slurry was 0.204g / 1540.25mm 2
  • the weight of the lithium metal layer 1.99mg / 1540.25mm 2
  • the weight ratio of the lithium metal layer per unit area to the inorganic dielectric layer per unit area is 10.0.
  • Example 1 The difference from Example 1 is that no inorganic dielectric layer is provided.
  • the lithium ion battery is charged to 4.2V at a constant current of 1C (that is, the current value of the theoretical capacity is completely discharged within 1h), and then charged at a constant voltage of 4.2V to a current of 0.05C, and then left for 5 minutes, then 1C constant current discharge to 2.8V, this is a charge-discharge cycle process, the discharge capacity this time is the discharge capacity of the first cycle.
  • the lithium ion battery is subjected to multiple cycles of charge and discharge tests according to the above method, and the discharge capacity of each cycle is recorded until the discharge capacity of the lithium ion battery decays to 80%, and the number of cycles of the lithium ion battery is recorded.
  • the lithium-ion battery At 60°C, charge the lithium-ion battery to 4.2V at a constant current of 1C, then charge at a constant voltage of 4.2V to a current of 0.05C, stand for 5 minutes, and then discharge at a constant current of 1C to 2.8V, which is a charge and discharge During the cycle, the discharge capacity this time is the discharge capacity of the first cycle.
  • the lithium ion battery was subjected to 500 cycles of charge-discharge test according to the above method, and the discharge capacity of the 500th cycle was recorded.
  • Lithium ion battery 60°C, 1C/1C, capacity retention rate (%) after 500 cycles discharge capacity at the 500th cycle/discharge capacity at the first cycle ⁇ 100%.
  • the capacity retention rate (%) of the lithium ion battery after storage at 60°C for 90 days discharge capacity after storage at 60°C for 90 days/discharge capacity before storage ⁇ 100%.
  • the initial DC internal resistance of the lithium ion battery DCR 0 (U 1 -U 2 )/I.
  • the DCR growth rate (%) of the lithium ion battery after 500 cycles of 1C/1C at 60°C (DCR 1 -DCR 0 )/DCR 0 ⁇ 100%.
  • the DCR growth rate (%) of a lithium-ion battery stored at 60°C for 90 days (DCR 2 -DCR 0 )/DCR 0 ⁇ 100%.
  • Disassemble the fully charged battery disassemble the negative pole piece, observe the state of lithium precipitation on the negative pole piece, and determine the degree of lithium precipitation.
  • the rules are as follows: A, no lithium precipitation; B, slight lithium precipitation; C, lithium formation in Partial area; D. Lithium remains in most areas; E. Lithium is severely separated.
  • Example 2 The difference from Example 1 is that the negative pole piece is not provided with an inorganic dielectric layer; the negative active material is made of artificial graphite coated with alumina, and the negative active material, conductive agent acetylene black, binder SBR and thickener CMC- Disperse Na in solvent deionized water, stir and mix uniformly to obtain negative electrode slurry.
  • the weight ratio of artificial graphite, acetylene black, SBR and CMC-Na is 95:1.5:3.1:0.4; the weight and unit of lithium metal layer per unit area
  • the weight ratio of alumina in the negative electrode active material layer by area was 15.3.
  • the reversible gram capacity of alumina-coated artificial graphite is 310 mAh/g.
  • the negative pole piece is not provided with an inorganic dielectric layer;
  • the negative active material is made of artificial graphite coated with titanium oxide, and the negative active material, conductive agent acetylene black, binder SBR and thickener CMC- Disperse Na in solvent deionized water, stir and mix uniformly to obtain negative electrode slurry.
  • the weight ratio of artificial graphite, acetylene black, SBR and CMC-Na is 95:1.5:3.1:0.4; the weight and unit of lithium metal layer per unit area
  • the weight ratio of titanium oxide in the area of the negative electrode active material layer was 15.
  • the reversible gram capacity of titanium oxide coated artificial graphite is 330 mAh/g.
  • the negative pole piece is not provided with an inorganic dielectric layer;
  • the negative electrode active material is made of artificial graphite coated with tin oxide, and the negative electrode active material, conductive agent acetylene black, binder SBR and thickener CMC- Disperse Na in solvent deionized water, stir and mix uniformly to obtain negative electrode slurry.
  • the weight ratio of artificial graphite, acetylene black, SBR and CMC-Na is 95:1.5:3.1:0.4; the weight and unit of lithium metal layer per unit area
  • the weight ratio of tin oxide in the negative electrode active material layer is 20 by area.
  • the reversible gram capacity of tin oxide-coated artificial graphite is 320 mAh/g.
  • the negative electrode is not provided with an inorganic dielectric layer;
  • the negative electrode active material is made of zinc oxide coated artificial graphite, and the negative electrode active material, conductive agent acetylene black, binder SBR and thickener CMC- Disperse Na in solvent deionized water, stir and mix uniformly to obtain negative electrode slurry.
  • the weight ratio of artificial graphite, acetylene black, SBR and CMC-Na is 95:1.5:3.1:0.4; the weight and unit of lithium metal layer per unit area
  • the weight ratio of zinc oxide in the negative electrode active material layer by area is 16.
  • the reversible gram capacity of zinc oxide-coated artificial graphite is 320mAh/g.
  • the test in Table 4 is the same as the test method described above.
  • the battery was disassembled and analyzed, and it was found that the inorganic dielectric layer of the negative pole piece and the negative electrode interface side reaction products were mixed to a higher degree , The thickness cannot be measured directly, and part of the inorganic dielectric material enters the negative electrode active material layer under the action of the potential difference.

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Abstract

一种负极极片（10）、电芯（52）、锂离子电池（5）及其制备方法和包含锂离子电池（5）的装置，所述负极极片（10）包括：负极集流体（11）；负极活性物质层（12），设置于负极集流体（11）；无粘结剂的无机介电层（13），设置于负极活性物质层（12）的远离负极集流体（11）的一侧，无机介电层（13）包括无机介电材料，无机介电层（13）至少包括设置于负极活性物质层（12）表面的主体部（131），主体部（131）的厚度为30nm～1000nm；锂金属层（14），设置于无机介电层（13）远离负极活性物质层（12）的表面。

Description

负极极片、电芯、锂离子电池及其制备方法和包含锂离子电池的装置
相关申请的交叉引用
本申请要求享有于2019年05月31日提交的名称为“负极极片、电芯及锂离子电池”的中国专利申请201910471884.1的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请属于电池技术领域，具体涉及一种负极极片、电芯、锂离子电池及其制备方法和包含锂离子电池的装置。
背景技术
锂离子电池作为一种二次电池，主要依靠锂离子在正极活性物质和负极活性物质之间的往返迁移来进行充电、放电，通常采用电解液作为锂离子传输的载体。在使用过程中，锂离子电池能够提供稳定的电压和电流，且使用过程绿色环保，而被广泛地应用于各类电子产品及电动车辆，占据电池领域的主流地位。
然而，现有锂离子电池的使用寿命亟待提高，以满足人们对电池寿命提出的越来越高的要求。
发明内容
本申请的第一方面提供一种负极极片，其包括：负极集流体；负极活性物质层，设置于负极集流体；无粘结剂的无机介电层，设置于负极活性物质层的远离负极集流体的一侧，无机介电层包括无机介电材料，无机介电层至少包括设置于负极活性物质层表面的主体部，主体部的厚度为30nm～1000nm；锂金属层，设置于无机介电层的远离负极活性物质层的表面。
本申请的第二方面提供一种负极极片，其包括：负极集流体；负极活性物质层，设置于负极集流体，负极活性物质层包含预嵌锂的负极活性物质；无粘结剂的无机介电层，设置于负极活性物质层的远离负极集流体的一侧，无机介电层包括无机介电材料，无机介电层至少包括设置于负极活性物质层表面的主体部，主体部的厚度为30nm～1000nm。
本申请第三方面提供一种电芯，其包括负极极片、正极极片及隔离膜，负极极片为本申请第一方面和/或第二方面提供的负极极片。
本申请第四方面提供一种电芯，其包括负极极片、正极极片及隔离膜，负极极片为本申请第一方面提供的负极极片；
每2cm×2cm单位面积的负极极片中，锂金属层与负极活性物质层的重量比为0.5％～5％；
单位面积负极容量C 1与单位面积正极容量C 2之比为1.2～2.1；
单位面积负极容量C 1、单位面积正极容量C 2与单位面积锂金属层容量C 3之间满足C 1/(C 2+C 3×K)≥1.05，其中K为锂金属层中金属锂的利用率。
本申请第五方面提供一种锂离子电池，其包括电芯及电解液，电芯采用本申请第三方面或第四方面提供的电芯。当锂离子电池的电芯为采用本申请第一方面提供的负极极片时，其中的锂金属层在电解液作用下，可自发进行金属锂对负极活性物质层预嵌锂，从而在负极活性物质层形成预嵌锂的负极活性物质。
本申请第六方面提供一种装置，其包括本申请第五方面提供的锂离子电池。
本申请第七方面提供一种锂离子电池的制备方法，其包括通过如下步骤制备所述锂离子电池的负极极片：
将负极活性物质层设置于负极集流体的至少一个表面；
将无机介电材料沉积在所述负极活性物质层的远离所述负极集流体的一侧，形成无粘结剂的无机介电层，所述无机介电层至少包括设置于所述负极活性物质层表面的主体部，所述主体部的厚度为30nm～1000nm；
将锂金属层设置于无机介电层的远离负极活性物质层的表面，得到负极极片。
与现有技术相比，本申请至少具有以下有益效果：
本申请提供的负极极片，由于设置有锂金属层，能够对负极活性物质预嵌锂，补偿锂离子电池中活性锂离子的消耗，从而提高电池的首次库伦效率，并提高电池的循环寿命及存储寿命。并且，在负极活性物质层与锂金属层之间设置有无机介电层，起到物理隔绝作用，锂金属层的金属锂经无机介电层扩散至负极活性物质层进行预嵌锂，同时由于该无机介电层具有介电性质，在预嵌锂过程中起到稳定锂金属层与负极活性物质界面微电流的效果，有效控制金属锂在负极活性物质层的预嵌锂速率，避免预嵌锂反应速度过快而产生大量热量，从而能够有效防止引发热失控，提高电池的循环寿命及安全性能，还能够防止负极活性物质层因体积膨胀过快而导致的层间结合力降低、或膜层脱落、或负极活性物质破裂，进一步提高电池的循环寿命。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。另外，附图中的结构件不一定是按照比例绘制的。例如，可能对于其他结构件或区域而放大了附图中的一些结构件或区域的尺寸，以帮助对本实用新型实施例的理解。
图1是本申请一个实施例中负极极片的结构示意图。
图2是本申请另一个实施例中负极极片的结构示意图。
图3是本申请一个实施例的负极极片中无机介电层的结构示意图。
图4是本申请另一个实施例的负极极片中无机介电层的结构示意图。
图5是本申请再一个实施例中负极极片的结构示意图。
图6为图5中A部放大图。
图7是锂离子电池的一实施方式的示意图。
图8是图7的分解图。
图9是电池模块的一实施方式的示意图。
图10是电池包的一实施方式的示意图。
图11是图9的分解图。
图12是锂离子电池用作电源的装置的一实施方式的示意图。
具体实施方式
为了使本申请的发明目的、技术方案和有益技术效果更加清晰，以下结合实施例对本申请进行进一步详细说明。应当理解的是，本说明书中描述的实施例仅仅是为了解释本申请，并非为了限定本申请。
为了简便，本文仅明确地公开了一些数值范围。然而，任意下限可以与任何上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，尽管未明确记载，但是范围端点间的每个点或单个数值都包含在该范围内。因而，每个点或单个数值可以作为自身的下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
在本文的描述中，需要说明的是，除非另有说明，“以上”、“以下”为包含本数，“一种或多种”中“多种”的含义是两种或两种以上。
本申请的上述发明内容并不意欲描述本申请中的每个公开的实施方式或每种实现方式。如下描述更具体地举例说明示例性实施方式。在整篇申请中的多处，通过一系列实施例提供了指导，这些实施例可以以各种组合形式使用。在各个实例中，列举仅作为代表性组，不应解释为穷举。
负极极片
请参照图1至图2，本申请的实施方式提供了一种负极极片10，其包括层叠设置的负极集流体11、负极活性物质层12、无机介电层13及锂金属层14。
负极集流体11沿自身厚度方向包括相对的两个表面，负极活性物质层12可以是设置于两个表面中的任意一者上(如图1所示)，也可以是分别设置于两个表面(如图2所示)。负极活性物质层12沿自身厚度方向包括相对的第一表面121和第二表面122，其中第一表面121背向负极集流体11设置，第二表面122朝向负极集流体11设置。负极活性物质层12包括负极活性物质。
无机介电层13设置于负极活性物质层12的第一表面121侧，无机介电层13至少包括设置于第一表面121的主体部131，该主体部131的厚度T为30nm～1000nm。无机介电层13为无粘结剂的无机介电层，其包括无机介电材料。
锂金属层14设置于无机介电层13的远离负极活性物质层12的表面。
需要说明的是，本申请实施例第一方面的负极极片10是尚未经过电解液浸润的负极极片，而注入电解液后，负极活性物质层12与锂金属层14之间存在电势差，可自发进行锂金属层14对负极活性物质层12的预嵌锂，锂金属层14的部分或全部金属锂预嵌入负极活性物质中，形成预嵌锂的负极活性物质。
本申请实施例提供的负极极片，由于设置有锂金属层14，能够对负极活性物质预嵌锂，补偿锂离子电池中活性锂离子的消耗，从而提高电池的首次库伦效率，并提高电池的循环寿命及存储寿命。并且，在负极活性物质层12与锂金属层14之间设置有预设厚度的无机介电层13，起到物理隔绝作用，锂金属层14的金属锂经无机介电层13扩散至负极活性物质层12进行预嵌锂，同时由于该无机介电层13具有介电性质，在预嵌锂过程中起到稳定锂金属层14与负极活性物质界面微电流的效果，能够有效控制金属锂在负极活性物质层12的预嵌锂速率，避免预嵌锂反应速度过快而产生大量的热量，从而能够有效防止引发热失控，提高电池的循环寿命及安全性能，还能够防止负极活性物质层12因体积膨胀过快而导致的层间结合力降低、或膜层脱落、或负极活性物质破裂，进一步提高电池的循环使用寿命。
本申请实施例提供的负极极片10，无机介电层13还起到稳定负极界面的作用，大幅度减少电解液在负极界面的副反应，避免在高温以及快速充电情况下电解液在负极 界面发生副反应，有效抑制电解液分解产气、减少产热量，以及降低活性锂离子的消耗，从而提高电池的安全性能、循环性能及存储性能，其中提高了电池在高温下的循环性能及存储性能，前述高温例如是40℃～80℃。
采用本申请实施例的负极极片10，使得锂离子电池在循环及存储过程中直流内阻的增长较小，从而降低热效应，减小电池极化，提高电池的循环性能及倍率性能。
本申请实施例的负极极片10中，无机介电材料为纳米级的颗粒，在其表面含有大量的极性基团，保证无机介电层13具有良好的电解液浸润性，能够提高电解液在无机介电层13与锂金属层14界面、以及无机介电层13与负极活性物质层12界面分布的均匀性，从而提高金属锂的利用率及负极极片10的嵌锂均匀性，提高电池的循环性能。
由于无机介电层13不含有粘结剂，无机介电材料颗粒之间并不是通过粘结剂有机分子链粘结，可保证无机介电层13的组分、厚度、膜层内聚力、以及无机介电层13与负极活性物质层12之间的结合力具有较高的均一性，可有效避免在电解液浸泡后部分无机介电层13在负极活性物质层12表面的附着力下降而导致的脱落，有利于提高负极活性物质层12在预嵌锂过程以及充放电过程中的嵌锂均匀性，从而提高电池的循环使用寿命。
由于无机介电层13厚度很小，仅为纳米级别，对负极极片10的体积及重量的影响基本可忽略不计，因此能保证锂离子电池具有较高的体积能量密度及重量能量密度。
在一些实施例中，无机介电层13的主体部131的厚度T可以为1000nm、990nm、950nm、900nm、850nm、800nm、750nm、720nm、700nm、680nm、650nm、600nm、550nm、500nm、490nm、450nm、430nm、400nm、380nm、350nm、300nm、280nm、250nm、200nm、190nm、180nm、170nm、160nm、150nm、140nm、130nm、120nm、110nm、100nm、95nm、90nm、85nm、80nm、75nm、70nm、65nm、60nm、55nm、50nm、45nm、40nm、35nm或30nm等。例如，主体部131的厚度T为50nm～600nm，再例如为100nm～500nm。
在一些实施例中，主体部131可以是无机介电材料颗粒构成的紧密结构，无机介电材料颗粒之间的微孔隙可形成无机介电层13内部的孔道结构以供锂离子通过。在这些实施例中，无机介电层13在第一表面121的覆盖率δ可以为50％≤δ≤100％，例如为50％、60％、65％、70％、75％、80％、85％、80％、95％、100％等。
在本说明书实施例中，上述覆盖率δ可以采用如下的测试方法进行测定：对负极极片10样品的第一表面121进行扫描电子显微镜(SEM)测试，利用能谱(EDS)元素分析法检测负极极片10表面无机介电材料的元素分布，无机介电材料的元素分布面积S 1与SEM图谱中负极活性物质层12第一表面121的面积S 2之比，即为无机介电层13 在负极活性物质层12第一表面121的覆盖率δ。
经发明人锐意研究发现，在另一些实施例中，也可以在主体部131进一步具有沿自身厚度方向贯穿设置的通道132。即主体部131以非连续状设置在负极活性物质层12与锂金属层14之间。在满足有效控制负极极片10的预嵌锂速率及对负极界面的稳定效果的前提下，能够提供开放性通道以提高负极极片10对电解液的保持量及离子透过率，提高锂离子电池的动力学性能及倍率性能；并使得在过冷或过热等条件下负极活性物质层12与无机介电层13发生不同等体积收缩或膨胀时，也能够有效释放无机介电层13的应力，保证无机介电层13与负极活性物质层12之间具有较高的结合力；还能够进一步降低无机介电层13的重量，从而提升电池的体积能量密度和重量能量密度。
可以理解的是，本申请实施例对主体部131的通道132的形状、数量及排列方式均没有特别的限制。通道132之间可以是连通的，也可以是不连通的。作为优选地，通道132的宽度为0.05μm～6μm，例如为0.5μm～6μm，再例如为3μm～6μm；再进一步地，通道132的长宽比大于或等于50。
进一步地，具有上述通道132的无机介电层13在第一表面121的覆盖率δ可以为50％≤δ<100％，例如为50％≤δ≤95％，再例如为60％≤δ≤80％。
请一并参照图3，作为一个示例，主体部131可以包括多个无机介电区133，多个无机介电区133相互独立且彼此间隔设置于负极活性物质层12的第一表面121，无机介电区133之间的间隔即形成上述通道132。在该示例中对无机介电区133的形状、数量及排列方式均不做具体限制，可以是圆形、多边形等形状。相邻两个无机介电区133之间的间隔例如为0.05μm～6μm，再例如为0.5μm～6μm，再例如为3μm～6μm。
请一并参照图4，作为另一个示例，主体部131为设置于负极活性物质层12的第一表面121的片状体，且在片状体具有沿自身厚度方向贯通设置的开口，该开口即为上述通道132。在该示例中对开口的形状、数量及排布方式均不做具体限制，可以是圆形、多边形等形状，例如是形成在主体部131的裂纹。所述裂纹的宽度例如为0.05μm～6μm，再例如为0.5μm～6μm，或3μm～6μm。进一步地，裂纹的长宽比≥50。
可以理解的是，尽管图4中裂纹大体是沿着无机介电层13的长度方向延伸，但在其他的实施例中，无机介电层13上裂纹的延伸方向可以是任意的方向。
在上述任一实施例中，无机介电层13的尺寸优选为等于或大体上等于负极活性物质层12的尺寸。具体的，无机介电层13的外周边缘与负极活性物质层12的外周边缘平齐或大体上平齐。
进一步地，请一并参照图5至图6，无机介电层13还包括延伸部134，延伸部134连接于主体部131朝向负极活性物质层12的表面，延伸部134沿负极活性物质层12的 孔隙壁表面向远离主体部131的方向延伸、并呈薄膜状覆设于负极活性物质层12的孔隙壁表面。这能够进一步改善负极极片10的预嵌锂速率及对负极界面的稳定效果，从而更加提高锂离子电池的安全性能、循环性能及存储性能。延伸部134对电解液具有浸润及保持作用，因此还能够提高锂离子电池的容量及倍率性能。
无机介电层13的延伸部134在负极活性物质层12的厚度方向上的尺寸H与主体部131的厚度T之比H/T优选为1/1000～1/10。这使得在有效发挥延伸部134上述效果的同时，保证负极活性物质层12中较高的锂离子和电子传输性能，从而使锂离子电池具有较高的综合电化学性能。例如，H/T可以为1/500、1/120、1/100、1/80或1/20等。
进一步地，包括主体部131和延伸部134的无机介电层13在负极活性物质层12第一表面121的覆盖率δ可以为50％≤δ≤100％，例如为50％、60％、65％、70％、75％、80％、85％、80％、95％、100％等，如60％～80％。
在一些实施例中，无机介电层13远离负极活性物质层12的表面为凹凸表面。当锂金属层14层叠设置于无机介电层13上时，能够使得锂金属层14与无机介电层13之间形成可供电解液渗透的毛细孔道，电解液可以通过毛细作用快速填充毛细孔道，更加有利于锂金属层14的金属锂在电势差作用下溶剂化，同时锂离子的扩散距离较短，使得锂金属层14在预嵌锂过程的锂利用率更高。
对无机介电层13凹凸表面的凹凸结构没有特别的限制，只要能够使锂金属层14与无机介电层13之间形成可供电解液渗透的毛细孔道即可。作为示例，可以是无机介电层13的凹凸表面为粗糙面，粗糙面具有许多纳米级且彼此之间间距较小的峰和谷；也可以是在无机介电层13远离负极活性物质层12的表面加工形成多个纳米级的沟槽，形成上述的凹凸表面。
进一步地，上述毛细孔道在无机介电层13厚度方向上的平均尺寸G优选为0μm<G≤3μm，更优选为0μm<G≤2μm。毛细孔道在无机介电层13厚度方向上具有上述平均尺寸G，使得未与无机介电层13接触的锂金属层14部分与无机介电层13之间的间距较小，电解液在毛细力作用下能够快速填充毛细孔道，且锂离子的扩散距离较短，能够提高锂金属层14在预嵌锂过程的锂利用率、以及提高负极活性物质层12的嵌锂均匀性，从而提高电池的循环使用寿命。
在一些实施例中，无机介电层13中的无机介电材料具有导离子性。由此在预嵌锂阶段能够实现锂金属层14以更高的利用率、同时更加可控的速度嵌入负极活性物质层12中；并且在后续的充放电循环过程中，保证负极极片10的阻抗较小，从而保证锂离子电池具有较高的循环使用寿命、以及优良的动力学性能及倍率性能。
无机介电材料的平均粒径D v50可以为1nm～100nm，例如为3nm～50nm，再例 如为5nm～30nm。无机介电材料的平均粒径D v50在上述范围内，更好地在颗粒之间形成供离子迁移的通道，提高无机介电层13的导离子性能。
无机介电材料可以包括A元素的氧化物、A元素的氮化物及A元素的卤化物中的一种或多种，其中A元素为Al、Si、Ti、Zn、Mg、Zr、Ca及Ba中的一种或多种。A元素的卤化物包括A元素的氟化物、A元素的氯化物、A元素的溴化物及A元素的碘化物中的一种或多种，优选为A元素的氟化物。
作为示例，无机介电材料为选自Al的氧化物(如Al 2O 3、AlO(OH)等)、Al的氮化物、Al的氟化物、Si的氧化物、Si的氮化物、Si的氟化物、Ti的氧化物、Ti的氮化物、Ti的氟化物、Zn的氧化物、Zn的氮化物、Zn的氟化物、Mg的氧化物、Mg的氮化物、Mg的氟化物、Zr的氧化物、Zr的氮化物、Zr的氟化物、Ca的氧化物、Ca的氮化物、Ca的氟化物、Ba的氧化物、Ba的氮化物及Ba的氟化物中的一种或多种。
在一些实施例中，每2cm×2cm单位面积的负极极片10中，锂金属层14与无机介电层13的重量比优选为2:1～200:1，更优选为5.5～101.7。锂金属层14与无机介电层13的重量比在上述范围内，能够更好地控制负极极片10的预嵌锂速率，提高锂离子电池的安全性能及使用寿命；并且无机介电层13的重量很小，有利于提高锂离子电池的体积能量密度和重量能量密度。例如，每2cm×2cm单位面积的负极极片10中，锂金属层14与无机介电层13的重量比可以为3.1、5.5、7.6、10、13.4、15、17.3、20、27.2、30.5、101.7、120、150或180等。
在一些实施例中，每2cm×2cm单位面积的负极极片10中，锂金属层14与负极活性物质层12的重量比优选为0.5％～5％，例如为1％～5％。锂金属层14与负极活性物质层12的重量比在上述范围内，能够有效降低锂离子电池循环及存储过程中的容量损失，提高电池的循环性能和存储性能。例如，每2cm×2cm单位面积的负极极片10中，锂金属层14与负极活性物质层12的重量比可以为1.5％、2％、2.54％、3％、3.5％、4％或4.5％等。
在一些实施例中，锂金属层14与无机介电层13之间的结合力为F 1，无机介电层13与负极活性物质层12之间的结合力为F 2，F 1与F 2之间满足：0<F 1<F 2。由此可以有效避免无机介电层13在设置锂金属层14以及后续电芯卷绕制备过程中的外力作用下发生脱落，提高负极极片10加工工艺的稳定性，提高负极极片10和电芯的制备优率及在使用过程中的可靠性，从而有利于提高锂离子电池的性能。
作为优选地，F 1与F 2之间满足：F 1≤0.8×F 2。
进一步地，锂金属层14与无机介电层13之间的结合力F 1优选为2N/m～25N/m，例如为5N/m～20N/m，再例如为8N/m～15N/m。
无机介电层13与负极活性物质层12之间的结合力F 2优选为10N/m以上，例如为10N/m～400N/m，再例如为10N/m～300N/m，再例如为20N/m～150N/m。
锂金属层14与无机介电层13之间的结合力F 1以及无机介电层13与负极活性物质层12之间的结合力F 2可以采用本领域公知的方法和设备进行测定。作为示例，锂金属层14与无机介电层13之间的结合力F 1的测定方法为：在湿度低于2％、温度为25℃的恒温常压干燥房中，以负极集流体11一面依次设置负极活性物质层12、无机介电层13以及锂金属层14，另一面未设置任何涂层的负极极片10为待测样品，待测样品宽度为0.02m；将3M双面胶均匀贴于不锈钢板上，再将待测样品的负极集流体11未涂敷面均匀贴于双面胶上；使用拉力试验机(如INSTRON3365)将待测样品的锂金属层14与无机介电层13以50mm/min进行180°连续剥离；根据拉力和位移的数据图，读取最大拉力(单位N)，根据最大拉力与待测样品宽度的比值计算得到锂金属层14的结合牢固度，即锂金属层14与无机介电层13之间的结合力F 1(N/m)。
同理，无机介电层13与负极活性物质层12之间的结合力F 2的测定方法为：在湿度低于2％、温度为25℃的恒温常压干燥房中，以负极集流体11一面依次设置负极活性物质层12、无机介电层13，另一面未设置任何涂层的负极极片10为待测样品，待测样品宽度为0.02m；将3M双面胶均匀贴于不锈钢板上，再将待测样品的负极集流体11未涂敷面均匀贴于双面胶上；使用拉力试验机(如INSTRON3365)将待测样品的无机介电层13与负极活性物质层12以50mm/min进行180°连续剥离；根据拉力和位移的数据图，读取最大拉力(单位N)，根据最大拉力与待测样品宽度的比值计算得到无机介电层13结合牢固度，即无机介电层13和负极活性物质层12之间的结合力F 2(N/m)。
本申请实施例对负极活性物质层12的厚度没有特别地限制，本领域技术人员可以根据实际需求进行调整。在一些实施例中，负极活性物质层12的厚度可以为90μm～200μm，例如为100μm～130μm。
本申请实施例对负极活性物质的种类没有特别限制，可以使用本领域已知的可嵌入/释出锂离子的负极活性物质。作为示例，负极活性物质可以是天然石墨、人造石墨、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、锡合金及钛酸锂中的一种或多种。
作为上述硅氧化合物，其分子式可以为SiO x，0<x<2，例如氧化亚硅等。
作为上述硅碳复合物，可以是碳包覆的硅、碳包覆的硅氧化合物、硅与碳的混合物、硅氧化合物与碳的混合物、以及硅和硅氧化合物与碳的混合物中的一种或多种，其中碳可以是石墨、软碳及硬碳中的一种或多种。
作为示例，上述锡合金可选自Li-Sn合金、Li-Sn-O合金；上述锡氧化合物可选自SnO、SnO 2；上述钛酸锂例如为尖晶石结构的Li 4Ti 5O 12。
在一些实施例中，负极活性物质的平均粒径D v50可以为6μm～10μm。
负极活性物质层12还可选地包括粘结剂、导电剂和/或其它助剂，粘结剂和导电剂的种类均不受到具体的限制，可根据需求进行选择。作为示例，粘结剂可以是丁苯橡胶(SBR)、水性丙烯酸树脂(water-based acrylic resin)、聚偏二氟乙烯(PVDF)、聚乙烯醇缩丁醛(PVB)、聚四氟乙烯(PTFE)、乙烯-醋酸乙烯酯共聚物(EVA)及聚乙烯醇(PVA)中的一种或多种。导电剂可以是石墨、超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种或多种。其它助剂例如是增稠剂，如羧甲基纤维素钠(CMC-Na)。
本申请实施例中，负极极片10的压实密度优选为1.2g/cm 3～2.0g/cm 3。负极极片10的压实密度在适当范围内，能使电池具有较高能量密度和循环寿命。
负极极片10的压实密度C为本领域公知的含义，可采用本领域已知的方法和设备进行测定。例如可以通过公式C＝(m×w)/(s×D)计算，式中m为负极活性物质层12的质量，w为负极活性物质层12中负极活性物质的质量分数，s为负极活性物质层12的面积，D为负极活性物质层12的厚度。
本申请实施例中，负极极片10的孔隙率优选为25％～60％，例如为30％～45％。负极极片10的孔隙率在适当范围内，能使负极极片10具有较高的锂离子和电子的传输性能，以及合适的电解液浸润量，有利于提高锂离子电池的循环寿命和能量密度。
负极极片10的孔隙率为本领域公知的含义，可以采用本领域已知的方法和设备进行测定。例如可以通过气体置换法测定。测试可采用真密度仪(如AccuPycⅡ1340)。测试可参考标准GB/T 24586-2009铁矿石表观密度、真密度和孔隙率的测定。
本申请实施例中，负极集流体11的种类不受到具体的限制，可根据需求进行选择具有良好导电性能及机械性能的材料。例如可以使用金属箔材、涂炭金属箔材或多孔金属板等，如使用铜箔。
接下来提供一种负极极片10的制备方法，方法包括以下步骤：
S100、将负极活性物质层12设置于负极集流体11的至少一个表面。
S200、将无机介电材料沉积在负极活性物质层12背向负极集流体11设置的第一表面121，得到无机介电层13。
S300、将锂金属层14设置于无机介电层13的背向负极活性物质层12的表面，得到负极极片10。
在一些实施例中，在步骤S100，将负极活性物质、粘结剂和导电剂分散于溶剂 中，溶剂可以是去离子水或N-甲基吡咯烷酮(NMP)，形成均匀的负极浆料；将负极浆料涂覆于负极集流体11表面，经烘干等工序后，在负极集流体11的表面制得负极活性物质层12。
在另一些实施例中，在步骤S100，将负极活性物质沉积于负极集流体11上，得到负极活性物质层12。例如采用气相沉积法将负极活性物质沉积于负极集流体11上。气相沉积法可以是原子层沉积法(Atomic Layer Deposition，ALD)、化学气相沉积法(Chemical Vapor Deposition，CVD)及物理气相沉积法(Physical Vapor Deposition，PVD)中的一种或多种，例如为热蒸发法(Thermal Evaporation Deposition)、等离子体辅助热蒸发法(Plasma assisted Thermal Evaporation)、电子束蒸发法(electron beam evaporation method，EBEM)、等离子体辅助电子束蒸发法(Plasma assisted electron beam Evaporation)、反应离子束溅射法(Reactive Ion-beam Sputtering，RIBS)、磁控溅射法(Magnetron Sputtering，MS)及电弧离子镀法(Arc Ion Plating，AIP)中的一种或多种。
在步骤S200，可以采用气相沉积法将无机介电材料沉积在负极活性物质层12的第一表面121，得到无机介电层13。采用气相沉积法形成的无机介电层13与负极活性物质层12之间的结合力更强，更好地避免电池长期循环过程中以及遭受机械滥用时无机介电层13从负极活性物质层12表面脱落的问题。
在气相沉积过程中，无机介电材料不仅可以沉积在负极活性物质层12的第一表面121形成无机介电层13的主体部131，还可以由第一表面121扩散至负极活性物质层12的内部孔隙中，并沉积在孔隙的壁表面，形成无机介电层13的延伸部134。
随着沉积过程的进行，无机介电层13的主体部131的厚度不断增加，与之紧邻的负极活性物质层12孔隙壁表面上的延伸部134的厚度也不断增加，无机介电材料向负极活性物质层12内部蔓延扩散的阻力越来越大，进而延伸部134的厚度沿负极活性物质层12的厚度方向递减。这样，负极活性物质层12远离负极集流体11的位置孔径较小、孔隙率较低，且负极活性物质层12越靠近负极集流体11的位置，孔径越大、孔隙率越高。
在步骤S200，气相沉积法可以采用前文所述的气相沉积法，在此不再赘述。
作为一个示例，采用热蒸发法制备无机介电层，步骤S200可以包括以下步骤：
S210、将沉积腔抽真空至气压为0.1Pa以下，如0.001Pa以下。
S220、在沉积腔中，通入反应活性气体a。反应活性气体a可以是氧气、臭氧、二氧化碳、水蒸汽、氮气、一氧化氮、二氧化氮及氨气中的一种或多种。
S230、在加热腔中将无机介电材料前驱体b加热成气态，通入沉积腔。无机介电 材料前驱体b可以是含有A元素的单质、合金、烷基化合物、硝酸盐、醋酸盐及硫酸盐中的一种或多种。
S240、在沉积腔中，调节气态无机介电材料前驱体b的浓度、腔内温度、沉积距离及沉积时间等参数，反应活性气体a与气态无机介电材料前驱体b发生化学反应，在负极活性物质层12表面形成无机介电层13。
作为另一个示例，采用等离子体辅助电子束蒸发法制备无机介电层，步骤S200可以包括以下步骤：
S210′、将反应室抽真空至气压为0.1Pa以下，如0.001Pa以下。
S220′、在电感耦合等离子体(ICP)源中通入反应活性气体a，反应活性气体a可以通过惰性气体稀释，在ICP源的作用下，反应活性气体a产生含有B元素的等离子体，B元素为O、N、F、Cl、Br及I中的一种或多种。
作为示例，反应活性气体a可以如前文所述，惰性气体可以是氩气、氮气及氦气中的一种或多种。
ICP源的功率可以是300W～600W。
反应活性气体a的流量可以是200sccm～1000sccm。
S230′、在反应室中，电子枪产生电子束，电子束轰击含有A元素的靶材c以使其融化蒸发，气态的材料与等离子体发生化学反应并在负极活性物质层12表面沉积，形成无机介电层13。
作为示例，含有A元素的靶材c可以是含有A元素的单质及合金的一种或多种。
电子束的电压可以是6kV～12kV，并优选地控制负极活性物质层12的表面温度≤100℃，例如负极活性物质层12的表面温度为20℃～100℃，如60℃～90℃。
本领域技术人员可以根据等离子体辅助电子束蒸发沉积技术的基本知识和原理，通过调节反应室真空度、电子束电压、反应活性气体a的组成与流量、含有A元素的靶材c的组分、ICP源、负极活性物质层12的表面温度及工艺时间等参数中的一种或多种，以调节无机介电层13的组分、厚度、形态、以及无机介电层13中无机介电材料的粒径等参数。
在步骤S200，可以得到片状结构的无机介电层13，并可进一步采用任意的方式在无机介电层13形成前文所述的开口，例如对无机介电层13进行冷压处理。也可以采用模板，例如掩模版，直接形成具有贯通自身厚度方向的开口的无机介电层13。
在步骤S200，也可以采用任意的方式形成包括多个无机介电区133的无机介电层13，例如采用模板，如掩模版。
在步骤S300，对锂金属层14的原料及形式不受限制，锂金属层14的原料可选自 锂粉、锂锭、锂片、锂带中的一种或几种。锂金属层14也可以不完全密集均匀分布在无机介电层13的表面。例如当锂金属层14的原料是锂粉时，锂金属层14中锂粉颗粒之间可以存在一定的间隙，间隙大小可控制在1μm～5000μm；当锂金属层14的原料是锂锭、锂带或锂片时，也可以形成多个锂片(或锂带)彼此间隔设置在无机介电层13表面，相邻两个锂片(或锂带)之间的间距可控制在1μm～5000μm。注入电解液后，锂金属层14对负极活性物质层12预嵌锂，最终负极活性物质层12中的锂含量仍可达到均匀分布，实现均匀嵌锂。
在步骤S300，可采用辊压的方式在无机介电层13的表面设置锂金属层14。利用锂金属与无机介电层13之间的分子间作用力，将锂金属层14稳定地固定在无机介电层13的表面。
在一些实施例中，负极活性物质层12是采用负极浆料涂覆获得，无机介电层13为具有前文所述裂纹状开口的片状结构。在这些实施例中，在负极极片10的制备过程中，可以先在步骤S100对干燥后的负极活性物质涂层进行冷压，获得具有预设压实密度的负极活性物质层12；之后在步骤S200对无机介电材料沉积得到的无机介电层13施加压力，如进行冷压处理，以在无机介电层13形成前文所述裂纹状开口；之后在无机介电层13表面制备锂金属层14。
还可以是先在步骤S100得到干燥后的负极活性物质涂层，之后在步骤S200对无机介电层13进行冷压时，同时实现对负极活性物质涂层的冷压，获得具有预设压实密度的负极活性物质层12，同时在无机介电层13形成前文所述裂纹状开口；之后在无机介电层13表面制备锂金属层14。
还可以是先在步骤S100得到干燥后的负极活性物质涂层，在步骤S200得到片状结构的无机介电层13，之后通过辊压在无机介电层13表面制备锂金属层14时，同时实现对无机介电层13冷压，以及对负极活性物质涂层冷压，从而获得锂金属层14，以及具有预设压实密度的负极活性物质层12，同时在无机介电层13形成前文所述裂纹状开口。
通过本申请实施方式所描述的负极极片10的制备方法，能够实现本申请上述的负极极片10。
电芯
本申请的实施方式还提供一种电芯。电芯包括正极极片、负极极片及隔离膜，隔离膜介于正极极片和负极极片之间起到隔离的作用，其中负极极片采用本申请实施方式所提供的负极极片10。
需要说明的是，本申请实施例的电芯是指尚未经过电解液浸润的电芯。本申请的 电芯在狭义上可仅包括正极极片、隔离膜和负极极片，但是本申请的电芯在广义上还可包括其它的结构，例如端子组件、保护壳组件等。
由于采用了本申请实施方式的负极极片10，本申请实施例的电芯也具有相应的有益效果，在此不再赘述。
进一步地，本申请实施例的电芯中，每2cm×2cm单位面积的负极极片10中，锂金属层14与负极活性物质层12的重量比为0.5％～5％，进一步为1％～5％；单位面积负极容量C 1与单位面积正极容量C 2之比为1.2～2.1，进一步为1.3～2.1；单位面积负极容量C 1、单位面积正极容量C 2与单位面积锂金属层容量C 3之间满足C 1/(C 2+C 3×K)≥1.05，进一步为C 1/(C 2+C 3×K)≥1.10，其中K为锂金属层14中金属锂的利用率。
其中，单位面积负极容量C 1＝单位面积负极活性物质层中负极活性物质的重量×负极活性物质的可逆克容量。
单位面积正极容量C 2＝单位面积正极活性物质层中正极活性物质的重量×正极活性物质的可逆克容量。
单位面积锂金属层容量C 3是指单位面积锂金属层的理论容量。单位面积锂金属层容量C 3＝单位面积锂金属层中金属锂的重量×金属锂的理论克容量。由于锂金属层14中可能存在的部分金属锂的氧化问题，以及部分锂离子参与负极成膜，导致锂金属层14中金属锂的利用率通常小于100％，根据研究经验，锂金属层14中金属锂的利用率一般为75％～85％，例如78％～82％，再例如80％。当然，通过减少锂金属层14中金属锂的氧化，以及减少来自锂金属层14的锂离子参与负极成膜，可以提高其利用率。
使本申请实施例的电芯满足上述关系，负极活性物质层12中的负极活性物质提供的空位能够充分容纳来自锂金属层12中所有锂离子的嵌入，并在首次充电过程中接收来自正极的所有锂离子，避免在负极界面堆积大量锂离子，防止负极析锂。
使本申请实施例的电芯满足上述关系，能够更好地改善电芯的循环寿命、安全性能和存储性能。
在本申请实施例的电芯中，注入电解液液后，电芯内部发生负极嵌锂，锂金属层14的至少一部分金属锂嵌入负极活性物质中，以预嵌锂的负极活性物质的形式存在，电芯的开路电压与首周充放电后的电压接近。当电芯满充后，负极活性物质有足够的空位接收来自正极活性物质的所有锂离子以及来自锂金属层14的所有锂离子，并在满放后于负极储存过量的锂离子，使得放电截止后，负极依然有5％～97％(相对于正极容量)可在正负极之间穿梭的锂离子，换句话说，电芯首周充电后的负极富锂量为105％～197％(相对于正极容量)，因此能有效降低电芯循环充放电及存储过程中的容量损失，提高电芯的循环寿命和存储性能。
本申请实施例的电芯中，正极极片可以包括正极集流体以及设置于正极集流体至少一个表面上的正极活性物质层。
例如，正极集流体沿自身厚度方向包括相对的两个表面，正极活性物质层可以是设置于两个表面中的任意一者上，也可以是分别设置于两个表面。
本申请实施例对正极活性物质层的厚度没有特别地限制，本领域技术人员可以根据实际需求进行调整。在一些实施例中，正极活性物质层的厚度可以为100μm～180μm，例如110μm～130μm。
对正极活性物质层中的正极活性物质没有特别地限制，只要是能够可逆地接受、脱出锂离子的物质，例如锂过渡金属复合氧化物、锂过渡金属复合氧化物添加其它过渡金属或非过渡金属或非金属得到的复合氧化物中的一种或多种。其中过渡金属可以是Mn、Fe、Ni、Co、Cr、Ti、Zn、V、Al、Zr、Ce及Mg中的一种或多种。
作为示例，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多种。其中橄榄石结构的含锂磷酸盐的分子式可为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多种。可选地，橄榄石结构的含锂磷酸盐为磷酸铁锂、磷酸锰锂及磷酸锰铁锂中的一种或多种。
正极活性物质层还可以包括粘结剂和/或导电剂，本申请对粘结剂和导电剂的种类不做限制，可以根据实际需求进行选择。作为示例，粘结剂可以为聚偏二氟乙烯(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-六氟丙烯共聚物及含氟丙烯酸酯树脂中的一种或多种；导电剂可以为石墨、超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中一种或多种。
正极集流体的种类不受到具体的限制，可根据需求进行选择具有良好导电性能及机械性能的材料。例如正极集流体可以采用金属箔材、涂炭金属箔材或多孔金属板，如采用铝箔。
正极极片可以按照本领域常规方法制备。通常将正极活性材料及导电剂和粘结剂分散于溶剂(例如N-甲基吡咯烷酮)中，形成均匀的正极浆料，将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后即得到正极极片。
对电芯中隔离膜的种类不做具体的限制，可以是能够被用于锂离子电池的任意隔离膜，例如玻璃纤维隔离膜、无纺布隔离膜、聚乙烯隔离膜、聚丙烯隔离膜、聚偏二氟乙烯隔离膜、以及它们中的一种或多种复合形成的多层复合膜，但不限于此。
锂离子电池
本申请的实施方式还提供一种锂离子电池。锂离子电池包括电芯和电解液，其中电芯采用本申请实施方式所提供的电芯。
由于采用了本申请实施方式的电芯，本申请实施例的电芯也具有相应的有益效果，在此不再赘述。
电解液包括有机溶剂和锂盐。本申请实施例对有机溶剂及锂盐的种类均不做具体的限制，可根据需求进行选择。
作为示例，有机溶剂可以选自碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)、二乙砜(ESE)中的一种或多种，优选为两种以上。
锂盐可以选自LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、LiAsF 6(六氟砷酸锂)、LiFSI(双氟磺酰亚胺锂)、LiTFSI(双三氟甲磺酰亚胺锂)、LiTFS(三氟甲磺酸锂)、LiDFOB(二氟草酸硼酸锂)、LiBOB(二草酸硼酸锂)、LiPO 2F 2(二氟磷酸锂)、LiDFOP(二氟二草酸磷酸锂)及LiTFOP(四氟草酸磷酸锂)中的一种或多种。
电解液中还可选地包括添加剂。对添加剂的种类没有具体的限制，可根据需求进行选择，例如碳酸亚乙烯酯(VC)、碳酸乙烯亚乙酯(VEC)、氟代碳酸亚乙酯(FEC)、丁二腈(SN)、己二腈(ADN)、1,3-丙烯磺酸内酯(PST)、三(三甲基硅烷)磷酸酯(TMSP)及三(三甲基硅烷)硼酸酯(TMSB)中的一种或多种。
将上述正极极片、隔离膜及负极极片按顺序层叠好，使隔离膜处于正极极片与负极极片之间起到隔离的作用，得到电芯，也可以是经卷绕后得到电芯；将电芯置于包装外壳中，注入电解液并封口，得到锂离子电池。
本申请对锂离子电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图7是作为一个示例的方形结构的锂离子电池5。
在一些实施例中，锂离子电池可包括外包装，用于封装电芯和电解液。
在一些实施例中，外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。锂离子电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，如可包括聚丙烯PP、聚对苯二甲酸丁二醇酯PBT、聚丁二酸丁二醇酯PBS等中的一种或几种。
在一些实施例中，参照图8，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经叠片工艺或卷绕工艺形成电芯52。电芯52封装于所述容纳腔。电解液浸润于电芯52中。
锂离子电池5所含电芯52的数量可以为一个或几个，可根据需求来调节。
在一些实施例中，锂离子电池可以组装成电池模块，电池模块所含锂离子电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图9作为一个示例的电池模块4。参照图9，在电池模块4中，多个锂离子电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个锂离子电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个锂离子电池5容纳于该容纳空间。
在一些实施例中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图10和图11作为一个示例的电池包1。参照图10和图11，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
装置
本申请的实施方式还提供一种装置，所述装置包括本申请所述的锂离子电池。所述锂离子电池可用作所述装置的电源，也可以作为所述装置的能量存储单元。所述装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
所述装置可以根据其使用需求来选择锂离子电池、电池模块或电池包。
图12是作为一个示例的装置。该装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该装置对锂离子电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用锂离子电池作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于重量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
在以下实施例中，
正极浆料的涂布重量及负极浆料的涂布重量均是以单面且不含溶剂计；
单位面积均是以面积为1540.25mm 2计。
实施例1
正极极片的制备
将正极活性物质锂镍钴锰酸锂(LiNi 0.8Co 0.1Mn 0.1O 2)、导电剂乙炔黑、粘结剂PVDF按照重量比94:4:2分散于溶剂NMP中，充分搅拌混合均匀得到正极浆料；将正极浆料涂覆于正极集流体铝箔相对的两个表面，其中正极浆料的涂布重量为0.145g/1540.25mm 2；经烘干、冷压后，得到正极极片。LiNi 0.8Co 0.1Mn 0.1O 2的可逆克容量为190mAh/g。
负极极片的制备
将负极活性物质人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶SBR及增稠剂羧甲基纤维素钠(CMC-Na)按照重量比95:1.5:3.1:0.4分散于溶剂去离子水中，搅拌混合均匀后得到负极浆料。人造石墨的可逆克容量为340mAh/g。
之后将负极浆料涂覆在负极集流体铜箔相对的两个表面，其中负极浆料的涂布重量为0.120g/1540.25mm 2；经烘干、冷压后，得到负极活性物质层，负极活性物质层的厚度为120μm。
之后采用等离子体辅助热蒸发沉积技术，在负极活性物质层的背向负极集流体的表面制得无机介电层。其中加热源为电子束，加热靶材为铝单质，在真空条件下，以氧气的活化气体为反应气体，控制负极活性物质层的表面温度为90℃～110℃，制成过程中的窗口宽度等于负极极片宽度的80％，电子束电压为10kV、工艺腔真空度10 -2Pa、氧流量800sccm、ICP源的功率300W、以及工艺时间为1h。
可以用本领域公知的仪器及方法进行测定主体部的厚度。例如，可以采用离子抛光仪(IB-19500CP)切割负极极片，从而得到平整的负极极片截面；随后将极片放入 扫描电子显微镜(Sigma300)下观测负极极片截面并测量主体部的厚度。测量可以参考JY/T010-1996分析型扫描电子显微镜方法通则。无机介电层在负极活性物质层表面的覆盖率、延伸部在负极活性物质层厚度方向上的尺寸及其与主体部的厚度比均是随机扫描6个区域取得的平均值。
结合表面及截面的扫描电子显微镜(SEM)图谱、以及X射线能谱仪(EDS)元素分析发现，无机介电层包括前文所述的主体部及延伸部，主体部呈片层状结构设置于负极活性物质层的表面，主体部的厚度T为200nm，延伸部在负极活性物质层厚度方向上的尺寸为主体部厚度的1/100；无机介电层在负极活性物质层表面的覆盖率为80％。无机介电层远离负极活性物质层的表面为粗糙表面。无机介电层中无机介电材料为氧化铝。采用前文所述的测定方法测定无机介电层与负极活性物质层之间的结合力F 2为35N/m。
之后采用辊压的方式将锂金属片复合到无机介电层的背向负极活性物质层的表面，制得锂金属层。其中，在负极极片的长度及宽度方向上，锂金属层的尺寸均与无机介电层的尺寸大致相等；锂金属层的重量为3.05mg/1540.25mm 2，金属锂的理论克容量为3861.3mAh/g。
单位面积锂金属层与单位面积无机介电层的重量比为15.3。
对上述负极极片进行截面SEM(Sigma300)测试，锂金属层与无机介电层之间形成可供电解液渗透的毛细孔道，任意取10个位置测量并计算得到毛细孔道在无机介电层厚度方向上的平均尺寸G为1.0μm。
采用前文所述的测定方法测定锂金属层与无机介电层之间的结合力F 1为10N/m。
电解液的制备
在含水量小于10ppm的氩气气氛手套箱中，将碳酸亚乙酯(EC)、碳酸亚丙酯(PC)及碳酸二甲酯(DMC)按照重量比为1:1:1混合均匀，得到有机溶剂；再将锂盐LiPF 6溶解于上述有机溶剂中，混合均匀，得到电解液，其中LiPF 6的浓度为1mol/L。
锂离子电池的制备
将正极极片、聚乙烯多孔隔离膜、负极极片按顺序层叠好，然后卷绕得到电芯；将电芯装入外包装中，注入电解液并封装，得到锂离子电池。
其中，
单位面积锂金属层与单位面积负极活性物质层的重量比＝(3.05mg/1540.25mm 2)/(0.120g/1540.25mm 2)×100％＝2.54％
单位面积负极容量C 1＝0.120g×95％×340mAh/g＝38.76mAh
单位面积正极容量C 2＝0.145g×94％×190mAh/g＝25.90mAh
CB值＝单位面积负极容量C 1/单位面积正极容量C 2＝38.76mAh/25.90mAh＝1.50
CBL值＝单位面积负极容量C 1/(单位面积正极容量C 2+单位面积锂金属层容量C 3×K)＝38.76mAh/(25.90mAh+3.05mg×3861.3mAh/g×80％)＝1.10
实施例2
与实施例1不同的是，负极浆料的涂布重量为0.104g/1540.25mm 2；无机介电层的延伸部在负极活性物质层厚度方向上的尺寸为主体部厚度的1/80；锂金属层的重量为1.52mg/1540.25mm 2；单位面积锂金属层与单位面积无机介电层的重量比为7.6；毛细孔道在无机介电层厚度方向上的平均尺寸G为2.0μm；锂金属层与无机介电层之间的结合力F 1为15N/m。
实施例3
与实施例1不同的是，正极浆料的涂布重量为0.164g/1540.25mm 2，负极浆料的涂布重量为0.136g/1540.25mm 2；无机介电层的延伸部在负极活性物质层厚度方向上的尺寸为主体部厚度的1/120；锂金属层的重量为3.45mg/1540.25mm 2；单位面积锂金属层与单位面积无机介电层的重量比为17.3；毛细孔道在无机介电层厚度方向上的平均尺寸G为1.0μm。
实施例4
与实施例1不同的是，正极浆料的涂布重量为0.189g/1540.25mm 2，负极浆料的涂布重量为0.136g/1540.25mm 2；无机介电层的延伸部在负极活性物质层厚度方向上的尺寸为主体部厚度的1/120；锂金属层的重量为1.99mg/1540.25mm 2；单位面积锂金属层与单位面积无机介电层的重量比为10；毛细孔道在无机介电层厚度方向上的平均尺寸G为1.5μm；锂金属层与无机介电层之间的结合力F 1为12N/m。
实施例5
与实施例1不同的是，正极浆料的涂布重量为0.129g/1540.25mm 2，负极浆料的涂布重量0.136g/1540.25mm 2；无机介电层的延伸部在负极活性物质层厚度方向上的尺寸为主体部厚度的1/120；锂金属层的重量为5.44mg/1540.25mm 2；单位面积锂金属层与单位面积无机介电层的重量比为27.2；毛细孔道在无机介电层厚度方向上的平均尺寸G为0.5μm；锂金属层与无机介电层之间的结合力F 1为9N/m。
实施例6
与实施例1不同的是，正极浆料的涂布重量为0.117g/1540.25mm 2，负极浆料的涂布重量0.136g/1540.25mm 2；无机介电层的延伸部在负极活性物质层厚度方向上的尺寸 为主体部厚度的1/120；锂金属层的重量为6.16mg/1540.25mm 2；单位面积锂金属层与单位面积无机介电层的重量比为30.8；毛细孔道在无机介电层厚度方向上的平均尺寸G为0.4μm；锂金属层与无机介电层之间的结合力F 1为8N/m。
实施例7
与实施例1不同的是，正极浆料的涂布重量为0.204g/1540.25mm 2，负极浆料的涂布重量为0.136g/1540.25mm 2；无机介电层的延伸部在负极活性物质层厚度方向上的尺寸为主体部厚度的1/120；锂金属层的重量为1.10mg/1540.25mm 2；单位面积锂金属层与单位面积无机介电层的重量比为5.5；毛细孔道在无机介电层厚度方向上的平均尺寸G为2.5μm；锂金属层与无机介电层之间的结合力F 1为17N/m。
实施例8
与实施例1不同的是：无机介电层的制备工艺中，控制工艺时间为0.5h；无机介电层的主体部的厚度T为30nm，延伸部在负极活性物质层厚度方向上的尺寸为主体部厚度的1/1000；单位面积锂金属层与单位面积无机介电层的重量比为101.7；毛细孔道在无机介电层厚度方向上的平均尺寸G为0.1μm；无机介电层与负极活性物质层之间的结合力F 2为25N/m。
实施例9
与实施例1不同的是：无机介电层的制备工艺中，工艺时间为0.7h；无机介电层的主体部的厚度T为100nm，延伸部在负极活性物质层厚度方向上的尺寸为主体部厚度的1/500；单位面积锂金属层与单位面积无机介电层的重量比为30.5；毛细孔道在无机介电层厚度方向上的平均尺寸G为1.0μm；无机介电层与负极活性物质层之间的结合力F 2为30N/m。
实施例10
与实施例1不同的是：无机介电层的制备工艺中，控制工艺时间为1.5h；无机介电层的主体部的厚度T为500nm，延伸部在负极活性物质层厚度方向上的尺寸为主体部厚度的1/20；单位面积锂金属层与单位面积无机介电层的重量比为6.1；无机介电层与负极活性物质层之间的结合力F 2为40N/m。
实施例11
与实施例1不同的是：无机介电层的制备工艺中，工艺时间2.5h；无机介电层的主体部的厚度T为1000nm，延伸部在负极活性物质层厚度方向上的尺寸为主体部厚度的1/10；单位面积锂金属层与单位面积无机介电层的重量比为3.1；无机介电层与负极活性物质层之间的结合力F 2为50N/m。
实施例12
与实施例1不同的是，改变制成过程中的窗口宽度等于极片宽度；无机介电层在负极活性物质层表面的覆盖率为100％；单位面积锂金属层与单位面积无机介电层的重量比为19.1；无机介电层与负极活性物质层之间的结合力F 2为37N/m。
实施例13
与实施例1不同的是，改变制成过程中的窗口宽度等于极片宽度，在负极活性物质层的表面覆盖掩模版，得到的无机介电层的主体部包括多个无机介电区，该多个无机介电区相互独立且彼此间隔设置于负极活性物质层的表面，无机介电层在负极活性物质层表面的覆盖率为50％；单位面积锂金属层与单位面积无机介电层的重量比为9.6；无机介电层与负极活性物质层之间的结合力F 2为32N/m。
实施例14
与实施例1不同的是，改变制成过程中的窗口宽度等于极片宽度，无机介电层的主体部为设置于负极活性物质层表面的片状体，通过冷压处理使得片状体具有沿自身厚度方向贯通设置的裂纹，无机介电层在负极活性物质层表面的覆盖率为70％；单位面积锂金属层与单位面积无机介电层的重量比为13.4。
实施例15
与实施例1不同的是，改变制成过程中的窗口宽度等于极片宽度，在负极活性物质层的表面覆盖掩模版，得到的无机介电层的主体部包括多个无机介电区，该多个无机介电区相互独立且彼此间隔设置于负极活性物质层的表面，无机介电层在负极活性物质层表面的覆盖率为90％；单位面积锂金属层与单位面积无机介电层的重量比为17.2。
实施例16
与实施例1不同的是，改变制成过程中的窗口宽度等于极片宽度，无机介电层的主体部为设置于负极活性物质层表面的片状体，通过冷压处理使得片状体具有沿自身厚度方向贯通设置的裂纹，且无机介电层在负极活性物质层表面的覆盖率为80％；采用辊压的方式将锂粉复合到无机介电层的背向负极活性物质层的表面，制得锂金属层，锂金属层与无机介电层之间无上述的毛细孔道；无机介电层与负极活性物质层之间的结合力F 2为35N/m，锂金属层与无机介电层之间的结合力F 1为7N/m。
实施例17
与实施例1不同的是，无机介电层的制备工艺中，靶材为钛金属单质；单位面积锂金属层与单位面积无机介电层的重量比为15；无机介电层与负极活性物质层之间的结合力F 2为100N/m。
实施例18
与实施例1不同的是，无机介电层的制备工艺中，靶材为锡金属单质；单位面积锂金属层与单位面积无机介电层的重量比为20；无机介电层与负极活性物质层之间的结合力F 2为100N/m。
实施例19
与实施例1不同的是，无机介电层的制备工艺中，靶材为锌金属单质；单位面积锂金属层与单位面积无机介电层的重量比为16；无机介电层与负极活性物质层之间的结合力F 2为100N/m。
对比例1
与实施例1不同的是，未设置锂金属层。
对比例2
与实施例1不同的是，负极浆料的涂布重量为0.094g/1540.25mm 2。
对比例3
与实施例1不同的是，正极浆料的涂布重量为0.164g/1540.25mm 2，负极浆料的涂布重量为0.136g/1540.25mm 2，未设置锂金属层。
对比例4
与实施例1不同的是，正极浆料的涂布重量为0.210g/1540.25mm 2，负极浆料的涂布重量为0.136g/1540.25mm 2，未设置锂金属层。
对比例5
与实施例1不同的是，正极浆料的涂布重量为0.204g/1540.25mm 2，负极浆料的涂布重量为0.136g/1540.25mm 2，锂金属层的重量为1.99mg/1540.25mm 2，单位面积锂金属层与单位面积无机介电层的重量比为10.0。
对比例6
与实施例1不同的是，未设置无机介电层。
测试部分
(1)锂离子电池的常温循环性能测试
在25℃下，将锂离子电池以1C(即1h内完全放掉理论容量的电流值)恒流充电至4.2V，之后以4.2V恒压充电至电流为0.05C，静置5min，然后以1C恒流放电至2.8V，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。将锂离子电池按照上述方法进行多次循环充放电测试，记录每一次循环的放电容量，直至锂离子电池的放电容量衰减至80％，记录锂离子电池的循环次数。
(2)锂离子电池的高温循环性能测试
在60℃下，将锂离子电池以1C恒流充电至4.2V，之后以4.2V恒压充电至电流 为0.05C，静置5min，然后以1C恒流放电至2.8V，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。将锂离子电池按照上述方法进行500次循环充放电测试，记录第500次循环的放电容量。
锂离子电池60℃、1C/1C、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，将锂离子电池以0.5C(即2h内完全放掉理论容量的电流值)恒流充电至4.2V，之后以4.2V恒压充电至电流为0.05C，静置5min，然后以0.5C恒流放电至电压为2.8V，此次的放电容量记为存储前的放电容量。而后将锂离子电池以0.5C恒流充电至4.2V，之后以4.2V恒压充电至电流为0.05C，静置5min，然后将满充后的锂离子电池于60℃下静置90天；之后取出并置于25℃下静置2h，再以0.5C恒流充电至4.2V，之后以4.2V恒压充电至电流为0.05C，静置5min，之后以0.5C恒流放电至2.8V，此次的放电容量记为60℃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(％)＝60℃存储90天后的放电容量/存储前的放电容量×100％。
(4)锂离子电池高温循环500次及高温存储90天后的直流内阻(DCR)增长率测试
在25℃下，首先将锂离子电池以1C恒流充电至电压为4.2V，之后以4.2V恒压充电至电流为0.05C，静置5min，然后以1C恒流放电至2.8V，记录实际放电容量，并以实际放电容量将锂离子电池的荷电状态(SOC)调整至满充容量的20％，调整完成后，测试此时锂离子电池的电压并记为U 1，然后以0.3C的倍率放电10s，测试锂离子电池放电后的电压并记为U 2。
锂离子电池的初始直流内阻DCR 0＝(U 1-U 2)/I。
按照上述方法测试锂离子电池60℃、1C/1C、循环500次后的直流内阻DCR 1，并计算锂离子电池的DCR增长率。
锂离子电池60℃、1C/1C循环500次后的DCR增长率(％)＝(DCR 1-DCR 0)/DCR 0×100％。
同样地，按照上述方法测试锂离子电池60℃存储90天后的直流内阻DCR 2，并计算锂离子二次电池的DCR增长率。
锂离子电池60℃存储90天后的DCR增长率(％)＝(DCR 2-DCR 0)/DCR 0×100％。
(5)锂离子电池大电流充电下负极表面析锂测试
在25℃下，将锂离子电池以2C即0.5h内完全放掉理论容量的电流值)恒流充电至4.2V，之后以4.2V恒压充电至电流为0.05C，静置5min，然后以2C恒流放电至2.8V，此为一个充放电循环过程。将锂离子电池按照上述方法进行10次大电流充放电循环，然后以2C恒流充电至4.2V，之后以4.2V恒压充电至电流为0.05C。
将满充后的电池进行拆解，拆解出负极极片，观察负极极片上锂的析出状态，判定析锂程度规则如下：A、无析锂；B、轻微析锂；C、锂形成于局部区域；D、大部分区域存在锂残留；E、严重析锂。
实施例1～19和对比例1～6的测试结果示于下面的表2。
表1
Figure PCTCN2020090018-appb-000001
表2
Figure PCTCN2020090018-appb-000002
从实施例1-19和对比例1、3、4、6的比较可以得知，通过在负极极片设置上述的无机介电层和锂金属层，能够显著提高锂离子二次电池的循环寿命，可以满足长寿命电动大巴及大规模储能系统的使用需求。另外，还能够降低锂离子二次电池在高温循环及高温存储过程中的直流电阻增长率，有利于提高电池的性能。
从实施例1-19和对比例2、4、5的比较可以得知，通过使单位面积负极容量C 1与单位面积正极容量C 2之比为1.2～2.1，单位面积负极容量C 1、单位面积正极容量C 2与单位面积锂金属层容量C 3之间满足C 1/(C 2+C 3×K)≥1.05，有利于提高锂离子二次电池 的循环寿命，以及降低锂离子二次电池在高温循环及高温存储过程中的直流电阻增长率，从而提高电池的性能。
对比例2-1
与实施例1不同的是，负极极片未设置无机介电层；负极活性物质采用氧化铝包覆的人造石墨，将负极活性物质、导电剂乙炔黑、粘结剂SBR及增稠剂CMC-Na分散于溶剂去离子水中，搅拌混合均匀后得到负极浆料，其中人造石墨、乙炔黑、SBR及CMC-Na的重量比为95:1.5:3.1:0.4；单位面积锂金属层的重量与单位面积负极活性物质层中氧化铝的重量之比为15.3。氧化铝包覆的人造石墨的可逆克容量为310mAh/g。
对比例2-2
与实施例17不同的是，负极极片未设置无机介电层；负极活性物质采用氧化钛包覆的人造石墨，将负极活性物质、导电剂乙炔黑、粘结剂SBR及增稠剂CMC-Na分散于溶剂去离子水中，搅拌混合均匀后得到负极浆料，其中人造石墨、乙炔黑、SBR及CMC-Na的重量比为95:1.5:3.1:0.4；单位面积锂金属层的重量与单位面积负极活性物质层中氧化钛的重量之比为15。氧化钛包覆的人造石墨的可逆克容量为330mAh/g。
对比例2-3
与实施例18不同的是，负极极片未设置无机介电层；负极活性物质采用氧化锡包覆的人造石墨，将负极活性物质、导电剂乙炔黑、粘结剂SBR及增稠剂CMC-Na分散于溶剂去离子水中，搅拌混合均匀后得到负极浆料，其中人造石墨、乙炔黑、SBR及CMC-Na的重量比为95:1.5:3.1:0.4；单位面积锂金属层的重量与单位面积负极活性物质层中氧化锡的重量之比为20。氧化锡包覆的人造石墨的可逆克容量为320mAh/g。
对比例2-4
与实施例19不同的是，负极极片未设置无机介电层；负极活性物质采用氧化锌包覆的人造石墨，将负极活性物质、导电剂乙炔黑、粘结剂SBR及增稠剂CMC-Na分散于溶剂去离子水中，搅拌混合均匀后得到负极浆料，其中人造石墨、乙炔黑、SBR及CMC-Na的重量比为95:1.5:3.1:0.4；单位面积锂金属层的重量与单位面积负极活性物质层中氧化锌的重量之比为16。氧化锌包覆的人造石墨的可逆克容量为320mAh/g。
表3
Figure PCTCN2020090018-appb-000003
表4
Figure PCTCN2020090018-appb-000004
表4中的测试与前文所述的测试方法相同。
将实施例1、17、18、19的锂离子电池分别高温循环500次和高温存储90天后，将电池拆解分析发现，负极极片的无机介电层与负极界面副反应产物混合程度较高，无法直接测量厚度，部分无机介电材料在电势差作用下进入负极活性物质层。通过实施例1、17、18、19与对比例2-1～2-4的测试结果可以看到，相较于对比例中采用表面包覆的负极活性物质，本申请实施例的无机介电材料进入负极活性物质层中后，电池的直流电阻增长率也明显较小，电池的循环容量保持率明显较高。这是由于负极活性物质层已形成连续的导电网络，无机介电材料进入负极活性物质层中，也能使负极保持较高的锂离子和电子的传输性能，从而提高电池的循环使用寿命。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到各种等效的修改或替换，这些修改或替换都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。

Claims (18)

  1. 一种负极极片，包括：
    负极集流体；
    负极活性物质层，设置于所述负极集流体；
    无粘结剂的无机介电层，设置于所述负极活性物质层的远离所述负极集流体的一侧，所述无机介电层包括无机介电材料，所述无机介电层至少包括设置于所述负极活性物质层表面的主体部，所述主体部的厚度为30nm～1000nm；
    锂金属层，设置于所述无机介电层的远离所述负极活性物质层的表面。
  2. 根据权利要求1所述的负极极片，其中，每2cm×2cm单位面积的所述负极极片中，所述锂金属层与所述无机介电层的重量比为2:1～200:1；和/或，
    每2cm×2cm单位面积的所述负极极片中，所述锂金属层与所述负极活性物质层的重量比为0.5％～5％。
  3. 根据权利要求1或2所述的负极极片，其中，所述无机介电层在所述负极活性物质层表面的覆盖率δ为50％≤δ≤100％。
  4. 根据权利要求1至3任一项所述的负极极片，其中，所述主体部包括多个无机介电区，多个所述无机介电区设置于所述负极活性物质层的表面，且相邻所述无机介电区之间彼此间隔设置；或者，
    所述主体部为设置于所述负极活性物质层表面的片状体，所述片状体具有沿自身厚度方向贯通设置的开口。
  5. 根据权利要求1至4任一项所述的负极极片，其中，所述无机介电层还包括连接于所述主体部朝向所述负极活性物质层的表面的延伸部，所述延伸部沿所述负极活性物质层的孔隙壁表面向远离所述主体部的方向延伸、并呈薄膜状覆设于所述孔隙壁表面；
    所述延伸部在所述负极活性物质层厚度方向上的尺寸为所述主体部厚度的1/1000～1/10。
  6. 根据权利要求1至5任一项所述的负极极片，其中，所述无机介电材料具有导离子性。
  7. 根据权利要求1至6任一项所述的负极极片，其中，
    所述无机介电材料包括A元素的氧化物、A元素的氮化物及A元素的卤化物中的一种或多种，所述A元素的卤化物优选为A元素的氟化物，其中A元素为Al、Si、Ti、Zn、Mg、Zr、Ca及Ba中的一种或多种；和/或，
    所述无机介电材料的平均粒径D v50为1nm～100nm。
  8. 根据权利要求1至7任一项所述的负极极片，其中，所述无机介电层为通过气相沉积法设置于所述负极活性物质层表面的无机介电层。
  9. 根据权利要求1至8任一项所述的负极极片，其中，所述无机介电层远离所述负极活性物质层的表面为凹凸表面，以使所述锂金属层与所述无机介电层之间形成可供电解液渗透的毛细孔道；
    优选地，所述毛细孔道在所述无机介电层厚度方向上的平均尺寸G为0μm<G≤3μm。
  10. 根据权利要求1至9任一项所述的负极极片，其中，所述锂金属层与所述无机介电层之间的结合力为F 1，所述无机介电层与所述负极活性物质层之间的结合力为F 2，所述F 1与F 2之间满足：0<F 1<F 2；
    优选地，所述F 1与F 2之间满足：F 1≤0.8×F 2。
  11. 根据权利要求1至10任一项所述的负极极片，其中，
    所述负极极片的压实密度为1.2g/cm 3～2.0g/cm 3；和/或，
    所述负极极片的孔隙率为25％～60％。
  12. 根据权利要求1至11任一项所述的负极极片，其中，所述负极活性物质层的负极活性物质选自天然石墨、人造石墨、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、锡合金及钛酸锂中的一种或多种。
  13. 一种负极极片，包括：
    负极集流体；
    负极活性物质层，设置于所述负极集流体，所述负极活性物质层包含预嵌锂的负极活性物质；
    无粘结剂的无机介电层，设置于所述负极活性物质层的远离所述负极集流体的一侧，所述无机介电层包括无机介电材料，所述无机介电层至少包括由设置于所述负极活性物质层表面的主体部，所述主体部的厚度为30nm～1000nm。
  14. 一种电芯，包括负极极片、正极极片及隔离膜，所述负极极片为权利要求1至13任一项所述的负极极片。
  15. 一种电芯，包括负极极片、正极极片及隔离膜，所述负极极片为权利要求1至12任一项所述的负极极片；
    每2cm×2cm单位面积的所述负极极片中，所述锂金属层与所述负极活性物质层的重量比为0.5％～5％；
    单位面积负极容量C 1与单位面积正极容量C 2之比为1.2～2.1；
    单位面积负极容量C 1、单位面积正极容量C 2与单位面积锂金属层容量C 3之间满足C 1/(C 2+C 3×K)≥1.05，其中K为所述锂金属层中金属锂的利用率。
  16. 一种锂离子电池，包括电芯及电解液，所述电芯采用根据权利要求14或15所述的电芯。
  17. 一种装置，包括根据权利要求16所述的锂离子电池。
  18. 一种锂离子电池的制备方法，包括通过如下步骤制备所述锂离子电池的负极极片：
    将负极活性物质层设置于负极集流体的至少一个表面；
    将无机介电材料沉积在所述负极活性物质层的远离所述负极集流体的一侧，形成无粘结剂的无机介电层，所述无机介电层至少包括设置于所述负极活性物质层表面的主体部，所述主体部的厚度为30nm～1000nm；
    将锂金属层设置于无机介电层的远离负极活性物质层的表面，得到负极极片。
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