WO2021008429A1 - 二次电池及其相关的电池模块、电池包和装置 - Google Patents

二次电池及其相关的电池模块、电池包和装置 Download PDF

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WO2021008429A1
WO2021008429A1 PCT/CN2020/100990 CN2020100990W WO2021008429A1 WO 2021008429 A1 WO2021008429 A1 WO 2021008429A1 CN 2020100990 W CN2020100990 W CN 2020100990W WO 2021008429 A1 WO2021008429 A1 WO 2021008429A1
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secondary battery
negative electrode
voltage
delithiation
battery
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PCT/CN2020/100990
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English (en)
French (fr)
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官英杰
赵玉珍
温严
黄起森
刘欣
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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 EP20827980.2A priority Critical patent/EP3800707B1/en
Publication of WO2021008429A1 publication Critical patent/WO2021008429A1/zh
Priority to US17/159,138 priority patent/US11316158B2/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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • This application belongs to the technical field of energy storage devices, and specifically relates to a secondary battery and its related battery modules, battery packs and devices.
  • silicon-based materials have a very high theoretical gram capacity, which is about ten times that of carbon-based materials. Therefore, silicon-based materials are widely studied.
  • the present application provides a secondary battery including a positive pole piece, a negative pole piece, a separator and an electrolyte.
  • the positive pole piece includes a positive electrode current collector and is arranged on at least one surface of the positive electrode current collector and includes A positive electrode membrane of a positive electrode active material, the negative electrode piece comprising a negative electrode current collector and a negative electrode membrane provided on at least one surface of the negative electrode current collector and comprising the negative electrode active material;
  • the positive electrode active material includes one or more of layered lithium nickel cobalt manganese oxide and layered lithium nickel cobalt aluminum oxide;
  • the negative electrode active material includes graphite and silicon oxide compound SiO x , where 0 ⁇ x ⁇ 2;
  • the button battery made of the negative pole piece and the lithium metal sheet is inserted with a constant current of lithium at a rate of 0.1C to a voltage of 0.005V, and then at a rate of 0.05C to insert lithium to a voltage of 0.005V, and then at a rate of 0.1C
  • the constant current delithiation voltage is 1.2V
  • the ratio of the total delithiation energy of the negative electrode membrane in the voltage range of 0.005V to 1.2V to the total capacity of delithiation is defined as the delithiation platform voltage
  • the negative electrode membrane is at 0.005V to the delithiation platform
  • the delithiation capacity of the voltage range of the voltage is defined as A
  • the delithiation capacity of the negative electrode membrane in the voltage range of the delithiation platform voltage to 1.2V is defined as B, and the relationship between A and B satisfies: 1 ⁇ A/B ⁇ 2;
  • the voltage U of the negative pole piece relative to the lithium metal reference electrode satisfies: 0.5V ⁇ U ⁇ 0.7V.
  • the positive electrode active material includes one or more of layered lithium nickel cobalt manganese oxide and layered lithium nickel cobalt aluminum oxide
  • the negative electrode active material includes silicon oxide.
  • 1.1 ⁇ A/B ⁇ 1.6, or 1.2 ⁇ A/B ⁇ 1.5 optionally, 1.1 ⁇ A/B ⁇ 1.6, or 1.2 ⁇ A/B ⁇ 1.5.
  • A/B value within the given range can better enable the battery to have both higher energy density, first coulombic efficiency and better cycle performance.
  • the voltage U of the negative pole piece relative to the lithium metal reference electrode may be 0.55V ⁇ U ⁇ 0.65V.
  • the value of the voltage U within the proper range can better enable the battery to have both higher energy density, first coulombic efficiency and better cycle performance.
  • the graphite can be selected from one or more of artificial graphite and natural graphite.
  • the graphite can improve the cycle performance and energy density of the secondary battery.
  • the mass percentage ⁇ of the silicon-oxygen compound in the negative electrode active material satisfies 5% ⁇ 40%; optionally, 15% ⁇ 35%. Within the given range, the energy density and cycle performance of the battery can be further improved.
  • the negative active material further satisfies one or more of the following:
  • the negative electrode active material average particle diameter D v 50 a is 5 ⁇ m ⁇ D v 50 a ⁇ 20 ⁇ m; Alternatively, 6 ⁇ m ⁇ D v 50 a ⁇ 15 ⁇ m;
  • the average particle diameter D v 50 b silicone compound is 3 ⁇ m ⁇ D v 50 b ⁇ 12 ⁇ m; Alternatively, 4 ⁇ m ⁇ D v 50 b ⁇ 10 ⁇ m;
  • the average particle diameter of graphite is a D v 50 c 5 ⁇ m ⁇ D v 50 c ⁇ 18 ⁇ m; Alternatively, 6 ⁇ m ⁇ D v 50 c ⁇ 15 ⁇ m.
  • D v 50 a , D v 50 b and D v 50 c is within the given range, the cycle performance of the secondary battery can be further improved, and the energy density of the secondary battery can also be improved.
  • the lithium nickel cobalt manganese oxide can be selected from one or more of the compounds represented by formula 1 and their surface coating modified compounds,
  • the lithium nickel cobalt aluminum oxide can be selected from one or more of the compounds represented by formula 2 and their surface coating modified compounds,
  • 0.8 ⁇ 1.2, 0.5 ⁇ 1, 0 ⁇ 1, 0 ⁇ 1, 0 ⁇ 0.1, 1 ⁇ 2, 0 ⁇ 1, M 2 It is selected from one or more of Zr, Mn, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and X is selected from one or more of N, F, S and Cl.
  • the lithium nickel cobalt manganese oxide and/or lithium nickel cobalt aluminum oxide may have a higher gram capacity, thereby improving the energy density of the secondary battery.
  • At least a part of the positive electrode active material has a single particle morphology.
  • the use of the positive electrode active material can improve the energy density and cycle performance of the secondary battery.
  • the capacity excess coefficient of the secondary battery may be 1.05 to 1.3, and optionally 1.1 to 1.2.
  • the capacity excess coefficient of the secondary battery is within the given range, which can increase the energy density of the secondary battery and help prevent the negative electrode membrane from being lithium-deposited during the cycle.
  • the areal density ⁇ of the negative electrode film satisfies: 7 mg/cm 2 ⁇ ⁇ ⁇ 10 mg/cm 2 ; optionally, 7 mg/cm 2 ⁇ ⁇ ⁇ 9 mg/cm 2 .
  • the secondary battery can take into account both higher energy density and better dynamic performance.
  • the application provides a battery module including the secondary battery according to the first aspect of the application.
  • the application provides a battery pack including the battery module according to the second aspect of the application.
  • the present application provides a device including the secondary battery according to the first aspect of the present application.
  • the battery module, battery pack, and device of the present application include the secondary battery described in the present application, and therefore have at least the same or similar technical effects.
  • Fig. 1 is a schematic diagram of an embodiment of a secondary battery.
  • Figure 2 is an exploded view of Figure 1.
  • Fig. 3 is a schematic diagram of an embodiment of a battery module.
  • Fig. 4 is a schematic diagram of an embodiment of a battery pack.
  • Fig. 5 is an exploded view of Fig. 4.
  • Fig. 6 is a schematic diagram of an embodiment of a device in which a secondary battery is used as a power source.
  • any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and any upper limit can 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 application provides a secondary battery, which includes a positive pole piece, a negative pole piece, a separator and an electrolyte.
  • the positive pole piece includes a positive electrode current collector and a positive electrode membrane provided on at least one surface of the positive electrode current collector.
  • the positive electrode current collector has two opposite surfaces in its thickness direction, and the positive electrode film is disposed on either or both of the two surfaces.
  • the positive electrode film includes a positive electrode active material, and the positive electrode active material includes one or more of layered lithium nickel cobalt manganese oxide and layered lithium nickel cobalt aluminum oxide.
  • the negative electrode piece includes a negative electrode current collector and a negative electrode membrane provided on at least one surface of the negative electrode current collector.
  • the negative electrode current collector has two opposite surfaces in its thickness direction, and the negative electrode film is disposed on either or both of the two surfaces.
  • the negative electrode film includes a negative electrode active material, and the negative electrode active material includes graphite and a silicon oxide compound SiO x , where 0 ⁇ x ⁇ 2.
  • the negative pole piece and the lithium metal piece are prepared into a button battery, and lithium is inserted at a constant current at a rate of 0.1C to a voltage of 0.005V, and then at a rate of 0.05C to a voltage of 0.005V, and then at a rate of 0.1C Constant current delithiation to a voltage of 1.2V, the ratio of the total delithiation energy of the negative electrode membrane in the voltage range of 0.005V to 1.2V to the total capacity of delithiation is defined as the delithiation platform voltage, and the negative electrode membrane is The delithiation capacity in the voltage range from 0.005V to the delithiation platform voltage is defined as A, and the delithiation capacity of the negative electrode film in the voltage range from the delithiation platform voltage to 1.2V is defined as B, between the A and B Meet: 1 ⁇ A/B ⁇ 2;
  • the voltage U of the negative pole piece relative to the lithium metal reference electrode satisfies: 0.5V ⁇ U ⁇ 0.7V.
  • the preparation process of the button battery can refer to national standards or industry specifications.
  • the negative electrode active material and the customary binder and conductive agent in the industry can be prepared into the above-mentioned electrode containing the negative electrode membrane, and then the lithium metal disc is used as the counter electrode, and the customary electrolyte in the industry can be added to prepare the button cell. .
  • a button battery can be prepared as follows:
  • the electrolyte may be a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an organic solvent.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the fully dried lithium The salt LiPF 6 is dissolved in an organic solvent, and then fluoroethylene carbonate (FEC) is added, and the electrolyte is obtained after mixing.
  • the concentration of LiPF 6 is 1 mol/L, and the mass percentage of FEC in the electrolyte is 6 %.
  • the voltage U of the negative pole piece can be tested using methods known in the art. For example, it can be measured by the following test method: when making a secondary battery, a lithium metal reference electrode is embedded to form a three-electrode structure secondary battery, and the voltage difference between the negative pole piece and the reference electrode is the negative pole piece The voltage U.
  • the lithium-embedded metal reference electrode As a specific example of the lithium-embedded metal reference electrode: during the preparation of the secondary battery, a diameter of 300 ⁇ m is placed between the positive pole piece and the negative pole piece (persons skilled in the art can adjust this according to actual needs. Diameter), and the copper wire uniformly plated with metallic lithium (or copper wire not plated with metallic lithium), after assembling into a secondary battery, connect the positive electrode and the copper wire electrode to charge, and the active lithium ion in the positive electrode Deposited on the surface of the copper wire; similarly, connect the negative electrode and the copper wire to discharge, the active lithium ions in the negative electrode can also be deposited on the surface of the copper wire, so that the surface of the copper wire is evenly plated with a layer of lithium metal), and at the same time, A layer of isolation film is placed between the positive pole piece and the copper wire, and between the negative pole piece and the copper wire to prevent short circuit between the positive pole piece or the negative pole piece and the copper wire coated with lithium metal.
  • the positive electrode active material includes one or more of layered lithium nickel cobalt manganese oxide and layered lithium nickel cobalt aluminum oxide
  • the negative electrode active material includes silicon oxygen compound and Graphite helps to make the secondary battery have a higher energy density.
  • SEI solid electrolyte interface
  • the ratio of the delithiation capacity A of the negative electrode film in the voltage range from 0.005V to the delithiation platform voltage to the delithiation capacity B in the voltage range from the delithiation platform voltage to 1.2V A/ B can be ⁇ 2, ⁇ 1.95, ⁇ 1.9, ⁇ 1.85, ⁇ 1.8, ⁇ 1.75, ⁇ 1.7, ⁇ 1.65, ⁇ 1.6, ⁇ 1.55, ⁇ 1.5, ⁇ 1.45, ⁇ 1.4, or ⁇ 1.35.
  • A/B can be ⁇ 1, ⁇ 1.1, ⁇ 1.15, ⁇ 1.2, ⁇ 1.25, ⁇ 1.28, or ⁇ 1.3. Further optionally, 1.1 ⁇ A/B ⁇ 1.6; or, 1.2 ⁇ A/B ⁇ 1.5.
  • A/B value within the given range can better enable the battery to have both higher energy density, first coulombic efficiency and better cycle performance.
  • the mass ratio of the silicon-oxygen compound in the negative electrode active material, the type and content of the binder, the type and content of the conductive agent, etc. so that A/B is described above In the range.
  • 0 ⁇ x ⁇ 2 in the silicon oxide compound SiO x 0 ⁇ x ⁇ 2 in the silicon oxide compound SiO x .
  • the silicon-oxygen compound satisfies x within an appropriate range, which enables the silicon-oxygen compound to have higher capacity performance and higher first-time coulombic efficiency, and can increase the cycle life of the silicon-oxygen compound, thereby improving the response of the secondary battery using it performance.
  • the powder volume resistivity of the silicon-oxygen compound under a pressure of 16 MPa may be 1000 ⁇ cm or less.
  • the average particle diameter of the negative electrode active material (that is, the average particle diameter of the silicon-oxygen compound and graphite after mixing) D v 50 a may be 5 ⁇ m ⁇ D v 50 a ⁇ 20 ⁇ m , Or 6 ⁇ m ⁇ D v 50 a ⁇ 15 ⁇ m.
  • an optional average particle diameter D v of the silicone compound 50 b may 3 ⁇ m ⁇ D v 50 b ⁇ 12 ⁇ m, or 4 ⁇ m ⁇ D v 50 b ⁇ 10 ⁇ m.
  • D v 50 b is 3 ⁇ m or more, which can reduce the film-forming consumption of active lithium ions on the negative electrode, and reduce the side reaction of the electrolyte on the negative electrode, thereby improving the cycle performance of the battery.
  • a proper D v 50 b can also reduce the amount of binder added in the negative electrode film, which is beneficial to increase the energy density of the battery.
  • D v 50 b ⁇ 4 ⁇ m.
  • D v 50 b is less than 12 ⁇ m, which can increase the migration rate of lithium ions and electrons in the silicon-oxygen compound, and also help prevent the silicon-oxygen compound from cracking during charging and discharging, and improve the cycle life of the silicon-oxygen compound, thereby increasing the battery cycle performance.
  • D v 50 b ⁇ 10 ⁇ m.
  • the average particle diameter D v 50 c of the graphite may be 5 ⁇ m ⁇ D v 50 c ⁇ 18 ⁇ m, or 6 ⁇ m ⁇ D v 50 c ⁇ 15 ⁇ m.
  • D v 50 c is 5 ⁇ m or more, which can reduce the film-forming consumption of active lithium ions on the negative electrode, and reduce the side reaction of the electrolyte on the negative electrode, thereby improving the cycle performance of the battery.
  • a proper D v 50 c can also reduce the amount of binder added in the negative pole piece, which is beneficial to increase the energy density of the battery.
  • D v 50 c ⁇ 6 ⁇ m.
  • D v 50 c is less than 18 ⁇ m, which can increase the migration rate of lithium ions and electrons in graphite, thereby improving the cycle performance of the battery.
  • D v 50 c ⁇ 15 ⁇ m.
  • Negative electrode active material average particle diameter D v 50 a the average particle diameter
  • the average particle diameter D v D v silicone compounds Graphite 50 b and 50 c are well known meaning in the art, it may be known in the art instruments and methods Perform the measurement. For example, it can be easily measured with a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer of Malvern Instruments Co., Ltd., UK.
  • the graphite may be one or more of natural graphite and artificial graphite.
  • the weight ratio of the negative electrode active material in the negative electrode film is 90% to 98%, or 92% to 96%.
  • the mass ratio ⁇ of the silicon oxygen compound in the negative electrode active material satisfies 5% ⁇ 40%, or 15% ⁇ 35%.
  • the A/B value can be optimized, and the energy density and cycle performance of the battery can be further improved.
  • the negative electrode membrane may optionally contain other negative electrode active materials that can be used for the negative electrode of the secondary battery.
  • other negative electrode active materials may be one or more of elemental silicon, silicon-carbon composites, silicon alloys, mesophase carbon microspheres (MCMB), hard carbon, and soft carbon.
  • the negative electrode film may also optionally contain a binder and a conductive agent.
  • the binder in the negative electrode film can be selected from binders known in the art that can be used in secondary batteries.
  • the binder includes one or more of styrene-butadiene rubber (SBR), polyacrylic acid compounds and modified compounds thereof, polyacrylate compounds and modified compounds thereof.
  • SBR styrene-butadiene rubber
  • the weight ratio of the binder in the negative electrode film is 1%-9%, or 3%-7%.
  • the conductive agent in the negative electrode film may be selected from conductive agents known in the art that can be used in secondary batteries.
  • the conductive agent includes one or more of conductive carbon black (Super P, abbreviated as SP) and carbon nanotube (Carbon Nanotube, abbreviated as CNT). Further optionally, the conductive agent includes SP and CNT at the same time.
  • the mass proportion of the conductive agent in the negative electrode film is 1% to 5%, or 1% to 3%.
  • the voltage U of the negative pole piece relative to the lithium metal reference electrode may be ⁇ 0.7, ⁇ 0.68, ⁇ 0.65 , ⁇ 0.64, ⁇ 0.63, ⁇ 0.62, ⁇ 0.61, or ⁇ 0.6.
  • U can be ⁇ 0.59, ⁇ 0.58, ⁇ 0.57, ⁇ 0.56, ⁇ 0.55, ⁇ 0.54, ⁇ 0.53, ⁇ 0.52, ⁇ 0.51, or ⁇ 0.5.
  • the value of the voltage U within the proper range can better enable the battery to have both higher energy density, first coulombic efficiency and better cycle performance.
  • the capacity excess factor of the battery is the ratio of the capacity of the negative electrode membrane to the capacity of the positive electrode membrane in the same area.
  • the lithium pre-replenishing process for the negative electrode film can be a process known in the art.
  • one or more of lithium powder, lithium flakes, and lithium ingots can be used to pre-replenish lithium on the negative electrode membrane; or a silicon-oxygen compound pre-replenishing lithium can be directly used.
  • the capacity excess coefficient of the secondary battery can be selected from 1.05 to 1.3, or can be selected from 1.1 to 1.2.
  • the capacity excess coefficient of the secondary battery is within the above range, while optimizing the voltage U, it is also beneficial to the battery capacity, improving the energy density of the battery, and preventing the negative electrode membrane from lithium evolution during the cycle.
  • the areal density ⁇ of the negative electrode membrane may satisfy 7 mg/cm 2 ⁇ ⁇ ⁇ 10 mg/cm 2 .
  • 7mg/cm 2 ⁇ 9mg/cm 2 When the areal density of the negative electrode film is within the range, the secondary battery can take into account both higher energy density and better dynamic performance.
  • the areal density ⁇ mentioned here refers to the areal density of the negative electrode membrane on any side of the current collector.
  • the negative electrode current collector can be made of a material with good conductivity and mechanical strength, such as copper foil, but it is not limited thereto.
  • the layered lithium nickel cobalt manganese oxide can be selected from one or more of the compounds represented by formula 1 and their surface coating modification compounds:
  • M 1 is a cationic doping element, and M 1 can be selected from one or more of Zr, Al, Zn, Cu, Cr, Mg, Fe, V, Ti and B;
  • A is an anionic doping element, and A can be selected from one or more of N, F, S and Cl.
  • the layered lithium nickel cobalt aluminum oxide can be selected from one or more of the compounds represented by formula 2 and their surface coating modified compounds:
  • M 2 is a cationic doping element, and M 2 can be selected from one or more of Zr, Mn, Zn, Cu, Cr, Mg, Fe, V, Ti and B;
  • X is an anionic doping element, and X can be selected from one or more of N, F, S and Cl.
  • the surface coating modification compound may be provided with a coating layer on at least a part of the surface of the material particles, and the coating layer may be a carbon layer, an oxide layer, an inorganic salt layer or a conductive polymer layer.
  • Surface coating modification can further improve the cycle performance of the battery.
  • the carbon layer may include one or more of graphite, graphene, mesocarbon microbeads (MCMB), hydrocarbon pyrolysis carbon, hard carbon, and soft carbon.
  • MCMB mesocarbon microbeads
  • the oxide layer may include Al oxide, Ti oxide, Mn oxide, Zr oxide, Mg oxide, Zn oxide, Ba oxide, Mo oxide, and B oxide. One or more of the oxides.
  • the inorganic salt layer may include one or more of Li 2 ZrO 3 , LiNbO 3 , Li 4 Ti 5 O 12 , Li 2 TiO 3 , Li 3 VO 4 , LiSnO 3 , Li 2 SiO 3 and LiAlO 2 Kind.
  • the conductive polymer layer may include one or more of polypyrrole (PPy), poly 3,4-ethylenedioxythiophene (PEDOT), and polyamide (PI).
  • PPy polypyrrole
  • PEDOT poly 3,4-ethylenedioxythiophene
  • PI polyamide
  • the positive electrode active material may also optionally contain other positive electrode active materials that can be used in the positive electrode of the secondary battery.
  • other positive electrode active materials are, for example, one or more of lithium manganese oxide, lithium iron phosphate, lithium manganese phosphate, and lithium iron manganese phosphate.
  • the positive electrode active material has a single particle morphology (ie, a non-agglomerated particle morphology).
  • the single-particle morphology of the positive electrode active material can improve the overall compaction density and ductility of the positive electrode sheet, while reducing the contact area between the positive electrode active material and the electrolyte, reducing the occurrence of interface side reactions, reducing gas production, and further improving Cycle performance of lithium-ion batteries.
  • the positive electrode film may also optionally include a binder and a conductive agent.
  • the types of the binder and the conductive agent are not specifically limited, and those skilled in the art can perform according to actual needs. select.
  • the binder in the positive electrode film may be polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), carboxymethyl cellulose One or more of sodium (CMC), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the conductive agent in the positive electrode film can be one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode current collector can be made of a material with good conductivity and mechanical strength, such as aluminum foil, but it is not limited thereto.
  • the electrolyte includes an organic solvent and a lithium salt dispersed in the organic solvent.
  • organic solvents and lithium salts are not subject to specific restrictions, and can be selected according to actual needs.
  • the organic solvent may be ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), Dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethylene propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate Ester (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB) , Ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE) one or several Kind
  • the lithium salt may be selected from LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiTFSI (lithium bistrifluoromethanesulfonimide) and LiTFS (lithium trifluoromethanesulfonate) One or more.
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiTFSI lithium bistrifluoromethanesulfonimide
  • LiTFS lithium trifluoromethanesulfonate
  • the electrolyte may also optionally include additives, where there is no specific limitation on the type of additives, and can be selected according to requirements.
  • the separator is provided between the positive pole piece and the negative pole piece to play a role of isolation.
  • This application has no special restrictions on the types of isolation membranes, and any well-known porous structure isolation membrane with good chemical and mechanical stability can be selected, such as glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene two One or more of vinyl fluoride.
  • the isolation film can be a single-layer film or a multilayer composite film. When the isolation film is a multilayer composite film, the materials of each layer may be the same or different.
  • the secondary battery of the present application can be prepared according to conventional methods in the art, for example, the negative electrode active material and optional conductive agent and binder are dispersed in a solvent (such as water) to form a uniform negative electrode slurry, and the negative electrode slurry Coated on the negative electrode current collector, after drying, cold pressing and other processes, the negative electrode piece is obtained; the positive electrode active material and optional conductive agent and binder are dispersed in a solvent (such as N-methylpyrrolidone, referred to as In NMP), a uniform positive electrode slurry is formed, and the positive electrode slurry is coated on the positive electrode current collector.
  • a solvent such as water
  • NMP N-methylpyrrolidone
  • the positive electrode piece After drying and cold pressing, the positive electrode piece is obtained; the positive electrode piece, separator, and negative electrode piece are pressed Sequentially winding (or lamination), so that the separator is placed between the positive pole piece and the negative pole piece to isolate the electrode assembly, the electrode assembly is placed in the outer package, and the electrolyte is injected to obtain the secondary battery.
  • Fig. 1 shows a secondary battery 5 having a square structure as an example.
  • the secondary battery may include an outer package.
  • the outer packaging is used to package the positive pole piece, the negative pole piece and the electrolyte.
  • 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 separator may be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the receiving cavity.
  • the electrolyte may be an electrolyte, and the electrolyte is infiltrated in the electrode assembly 52.
  • the number of electrode assemblies 52 included in the secondary battery 5 can be one or several, which can be adjusted according to requirements.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, or the like.
  • the outer packaging of the secondary battery may 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 secondary battery may be assembled into a battery module.
  • the number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 3 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, it can also be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having an accommodation space, and a plurality of secondary batteries 5 are accommodated in the accommodation space.
  • the above-mentioned battery module can also be assembled into a battery pack.
  • 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 application also provides a device including the secondary battery described in the application.
  • the secondary 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 secondary battery, battery module, or battery pack according to its usage requirements.
  • Figure 6 is a device as an example.
  • the device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module can be used.
  • the device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • the device is generally required to be thin and light, and a secondary battery can be used as a power source.
  • the positive electrode active material LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811), the conductive agent SP, and the binder PVDF are mixed in an appropriate amount of NMP at a weight ratio of 95:1.5:3.5 to form a uniform positive electrode slurry ; Coating the positive electrode slurry on the positive electrode current collector aluminum foil, drying and cold pressing, to obtain the positive electrode pole piece.
  • PAAS binder sodium polyacrylate
  • PE film is used as the isolation film.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the lithium salt LiPF 6 is dissolved in an organic solvent, then fluoroethylene carbonate (FEC) is added, and the electrolyte is obtained after uniform mixing.
  • the concentration of LiPF 6 is 1 mol/L, and the mass percentage of FEC in the electrolyte is 6%.
  • the above-mentioned negative pole piece satisfies: the above-mentioned negative pole piece, electrolyte (the electrolyte prepared in the above step 4), and the lithium metal counter electrode form a button cell, and the button cell is inserted with lithium to a constant current at a rate of 0.1C.
  • the voltage is 0.005V, and then the lithium is inserted at a constant current at a rate of 0.05C to a voltage of 0.005V, and then a constant current at a rate of 0.1C is delithified to a voltage of 1.2V, where the negative electrode diaphragm is in the voltage range from 0.005V to the voltage of the delithiation platform
  • the delithiation capacity of the negative electrode membrane is A
  • the delithiation capacity of the negative electrode membrane in the voltage range of the delithiation platform voltage to 1.2V is B.
  • Example 1 meets both 1 and 2:
  • the secondary batteries of Examples 1 to 23 and Comparative Examples 1 to 4 were charged to 4.25V at a constant current rate of 0.1C, then charged at a constant voltage to a current of 0.05C, and then left to stand for 5 minutes , Record the charge capacity at this time, which is the first charge capacity; then discharge to 2.5V at a constant current rate of 0.1C, and then stand for 5 minutes. This is a cyclic charge and discharge process. Record the discharge capacity at this time, which is the first discharge capacity.
  • the secondary battery was subjected to 300 cycles of charge-discharge test according to the above method, and the discharge capacity of each was recorded.
  • Battery weight energy density (Wh/kg) first discharge energy / battery weight
  • the first coulombic efficiency of the battery (%) first discharge capacity/first charge capacity ⁇ 100%
  • Battery capacity retention rate (%) 300th discharge capacity/first discharge capacity ⁇ 100%
  • ⁇ is the mass percentage of silicon oxide compound (ie SiO) in the negative electrode active material.
  • the positive electrode active material of the secondary battery includes one or more of layered lithium nickel cobalt manganese oxide and layered lithium nickel cobalt aluminum oxide, and the negative electrode active material includes silicon oxygen compound And graphite can make the battery have a higher energy density; by making the secondary battery meet both the A/B value of the negative electrode membrane and the voltage U value of the negative pole piece in a specific range, the battery's cycle capacity retention rate is obvious Increase, effectively improve the cycle performance of the battery, in particular, can further increase the energy density of the battery.

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Abstract

一种二次电池（5）及其相关的电池模块（4）、电池包（1）和装置。二次电池（5）包括正极极片、负极极片、隔离膜及电解液，所述二次电池（5）的正极活性材料包括锂镍钴锰氧化物及锂镍钴铝氧化物中的一种或几种，负极活性材料包括硅氧化合物和石墨；负极极片与锂金属片制成的扣式电池，以0.1C倍率恒流嵌锂至电压为0.005V，再以0.05C倍率恒流嵌锂至电压为0.005V，再以0.1C倍率恒流脱锂至电压为1.2V，负极膜片在0.005V至脱锂平台电压的电压区间的脱锂容量A与负极膜片在脱锂平台电压至1.2V的电压区间的脱锂容量B之间满足1≤A/B≤2；且当二次电池（5）放电至电压为2.5V时，负极极片相对于锂金属参比电极的电压U为0.5V≤U≤0.7V。

Description

二次电池及其相关的电池模块、电池包和装置
相关申请的交叉引用
本申请要求享有于2019年07月16日提交的名称为“二次电池”的中国专利申请201910638890.1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
本申请属于储能装置技术领域，具体涉及一种二次电池及其相关的电池模块、电池包和装置。
背景技术
随着环境保护问题日益受到重视，环境友好的二次电池逐渐被应用到消费类电子产品及电动汽车中。其中，电池的能量密度和循环寿命越来越受到终端消费者的重视。与传统的碳基材料相比，硅基材料具有极高的理论克容量，大约是碳基材料的十多倍，因此，硅基材料被广泛研究。
然而，硅基材料在使用过程中膨胀问题严重，从而导致电池的循环性能恶化，这大大限制了硅基材料在商业化产品中的应用。
发明内容
第一方面，本申请提供一种二次电池，其包括正极极片、负极极片、隔离膜及电解液，所述正极极片包括正极集流体以及设置在正极集流体至少一个表面上且包括正极活性材料的正极膜片，所述负极极片包括负极集流体以及设置在负极集流体至少一个表面上且包括负极活性材料的负极膜片；
所述正极活性材料包括层状锂镍钴锰氧化物及层状锂镍钴铝氧化物中的一种或几种；
所述负极活性材料包括石墨和硅氧化合物SiO x，其中0＜x＜2；
所述负极极片与锂金属片制成的扣式电池，以0.1C倍率恒流嵌锂至电压为0.005V，再以0.05C倍率恒流嵌锂至电压为0.005V，再以0.1C倍率恒流脱锂至电压为1.2V，负极膜片在0.005V至1.2V电压区间的脱锂总能量与脱锂总容量的比值定义为脱锂平台电压，负极膜片在0.005V至脱锂平台电压的电压区间的脱锂容量定义为A，负极膜片在脱锂平台电压至1.2V的电压区间的脱锂容量定义为B，A与B之间满足：1≤A/B≤2；
且当二次电池放电至电压为2.5V时，负极极片相对于锂金属参比电极的电压U满足：0.5V≤U≤0.7V。
令人惊奇地发现，本申请提供的二次电池中，正极活性材料包括层状锂镍钴锰氧化物及层状锂镍钴铝氧化物中的一种或几种，负极活性材料包括硅氧化合物和石墨，并且同时满足所述负极极片的A/B值及电池在放电至2.5V时负极极片的电压U值在特定的范围内，可以使电池同时兼顾较高的能量密度、首次库伦效率及较好的循环寿命。
在上述任意实施方式中，可选的，1.1≤A/B≤1.6，或者1.2≤A/B≤1.5。A/B值在所给范围内，能更好地使电池兼具较高的能量密度、首次库伦效率及较好的循环性能。
在上述任意实施方式中，当所述二次电池放电至电压为2.5V时，所述负极极片相对于锂金属参比电极的电压U可以为0.55V≤U≤0.65V。电压U的值在适当范围内，能更好地使电池兼具较高的能量密度、首次库伦效率及较好的循环性能。
在上述任意实施方式中，所述石墨可选自人造石墨及天然石墨中的一种或几种。所述石墨可以改善二次电池的循环性能和能量密度。
在上述任意实施方式中，所述负极活性材料中所述硅氧化合物的质量百分含量ω满足5％≤ω≤40％；可选的，15％≤ω≤35％。ω在所给范围内，能进一步改善电池的能量密度及循环性能。
在上述任意实施方式中，所述负极活性材料还满足如下中的一个或几个：
所述负极活性材料的平均粒径D v50 a为5μm≤D v50 a≤20μm；可选 的，6μm≤D v50 a≤15μm；
所述硅氧化合物的平均粒径D v50 b为3μm≤D v50 b≤12μm；可选的，4μm≤D v50 b≤10μm；
所述石墨的平均粒径D v50 c为5μm≤D v50 c≤18μm；可选的，6μm≤D v50 c≤15μm。
D v50 a、D v50 b和D v50 c中的一个或几个在所给范围内，能进一步改善二次电池的循环性能，并且还有利于提高二次电池的能量密度。
在上述任意实施方式中，所述锂镍钴锰氧化物可选自式1所示的化合物及其表面包覆改性化合物中的一种或几种，
Li aNi bCo cMn dM 1 eO fA g     式1，
所述式1中，0.8≤a≤1.2，0.5≤b＜1，0＜c＜1，0＜d＜1，0≤e≤0.1，1≤f≤2，0≤g≤1，M 1选自Zr、Al、Zn、Cu、Cr、Mg、Fe、V、Ti及B中的一种或几种，A选自N、F、S及Cl中的一种或几种；和/或，
所述锂镍钴铝氧化物可选自式2所示的化合物及其表面包覆改性化合物中的一种或几种，
Li αNi βCo γAl δM 2 εO νX σ    式2，
所述式2中，0.8≤α≤1.2，0.5≤β＜1，0＜γ＜1，0＜δ＜1，0≤ε≤0.1，1≤ν≤2，0≤σ≤1，M 2选自Zr、Mn、Zn、Cu、Cr、Mg、Fe、V、Ti及B中的一种或几种，X选自N、F、S及Cl中的一种或几种。
所述锂镍钴锰氧化物和/或锂镍钴铝氧化物可具有较高的克容量，由此能提高二次电池的能量密度。
在上述任意实施方式中，所述正极活性材料中的至少一部分为单颗粒形貌。采用该正极活性材料可以提高二次电池的能量密度和循环性能。
在上述任意实施方式中，所述二次电池的容量过量系数可以为1.05～1.3，可选的为1.1～1.2。二次电池的容量过量系数在所给范围内，可以提高二次电池的能量密度，并有利于防止负极膜片在循环过程中析锂。
在上述任意实施方式中，所述负极膜片的面密度ρ满足：7mg/cm 2≤ρ≤10mg/cm 2；可选的，7mg/cm 2≤ρ≤9mg/cm 2。负极膜片的面密度在所述范围内时，二次电池可同时兼顾较高的能量密度和较好的动力学性 能。
第二方面，本申请提供一种电池模块，其包括根据本申请第一方面的二次电池。
第三方面，本申请提供一种电池包，其包括根据本申请第二方面的电池模块。
第四方面，本申请提供一种装置，其包括根据本申请第一方面的二次电池。
本申请的电池模块、电池包和装置包括本申请所述二次电池，因而至少具有相同或类似的技术效果。
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，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，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，还可以根据附图获得其他的附图。
图1是二次电池的一实施方式的示意图。
图2是图1的分解图。
图3是电池模块的一实施方式的示意图。
图4是电池包的一实施方式的示意图。
图5是图4的分解图。
图6是二次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，以下结合具体实施例对本申请进行详细说明。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，“一种或几种”中“几种”的含义是两个或两个以上。
本申请的上述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。
本申请提供一种二次电池，其包括正极极片、负极极片、隔离膜及电解液。
所述正极极片包括正极集流体以及设置在正极集流体至少一个表面上的正极膜片。例如正极集流体在自身厚度方向具有相对的两个表面，正极膜片设置于该两个表面中的任意一者或两者上。
所述正极膜片包括正极活性材料，所述正极活性材料包括层状锂镍钴锰氧化物及层状锂镍钴铝氧化物中的一种或几种。
所述负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜片。例如负极集流体在自身厚度方向具有相对的两个表面，负极膜片设置于该两个表面中的任意一者或两者上。
所述负极膜片包括负极活性材料，所述负极活性材料包括石墨和硅氧化合物SiO x，其中0＜x＜2。
将所述负极极片与锂金属片制备成扣式电池，以0.1C倍率恒流嵌锂至电压为0.005V，再以0.05C倍率恒流嵌锂至电压为0.005V，再以0.1C倍率恒流脱锂至电压为1.2V，将所述负极膜片在0.005V至1.2V电压区间的脱锂总能量与脱锂总容量的比值定义为脱锂平台电压，将所述负极膜片在0.005V至脱锂平台电压的电压区间的脱锂容量定义为A，将所述负极膜片在脱锂平台电压至1.2V的电压区间的脱锂容量定义为B，所述A与B之间 满足：1≤A/B≤2；
且将所述二次电池放电至电压为2.5V时，所述负极极片相对于锂金属参比电极的电压U满足：0.5V≤U≤0.7V。
需要说明的是，上述扣式电池制备过程可参考国家标准或行业规范。例如可将负极活性材料与行业内惯用的粘结剂和导电剂制备成上述包含负极膜片的电极，然后以锂金属小圆片为对电极，加入行业内惯用的电解液制备成扣式电池。
作为具体的示例，扣式电池可以按如下步骤制备：
将所选用的负极活性材料与导电剂、粘结剂按一定质量比分散于溶剂(例如水)中制成负极浆料，之后涂布在铜箔上，烘干除去溶剂、裁片、压制后制成包含上述负极膜片的圆形电极片，之后以锂金属小圆片为对电极，并加入电解液，在手套箱中组装成扣式电池。所述电解液可以是将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照体积比为1:1:1混合均匀得到有机溶剂，将充分干燥的锂盐LiPF 6溶解于有机溶剂中，之后加入氟代碳酸亚乙酯(FEC)，混合均匀后获得电解液，其中LiPF 6的浓度为1mol/L，FEC在电解液中的质量百分含量为6％。
将二次电池放电至电压为2.5V时，负极极片的电压U可以采用本领域已知的方法进行测试。例如通过以下测试方法测得：在制作二次电池时，内嵌一个锂金属参比电极，即制成三电极结构的二次电池，负极极片与参比电极的电压差即为负极极片的电压U。
作为内嵌锂金属参比电极的一个具体示例为：在二次电池制备过程中，在正极极片与负极极片之间放置一根直径为300μm(本领域技术人员可以根据实际需求进行调整该直径)、且表面均匀镀有金属锂的铜丝(或者未镀有金属锂的铜丝，则在组装成二次电池后，连接正极与铜丝电极，进行充电，将正极中的活性锂离子沉积到铜丝表面；类似的，连接负极与铜丝，进行放电，同样可以将负极中的活性锂离子沉积到铜丝表面，使铜丝表面均匀镀上一层锂金属)，同时，分别在正极极片与铜丝之间、负极极片与铜丝之间各放置一层隔离膜以防止正极极片或者负极极片与表面镀有金属锂的铜丝发生短路。
在本申请的二次电池中，所述正极活性材料包括层状锂镍钴锰氧化物及层状锂镍钴铝氧化物中的一种或几种，所述负极活性材料包括硅氧化合物和石墨，有利于使二次电池具有较高的能量密度。
经申请人的锐意研究发现，当二次电池同时满足负极膜片的A/B值及负极极片的电压U值在适当范围内时，能够有效提升负极膜片中可存储的活性锂离子的数量，而且有利于保持硅氧化合物表面SEI(solid electrolyte interface，固体电解质界面)膜的稳定性及负极膜片中导电网络的稳定性，同时能够保证正极活性材料的容量得到充分利用，从而大幅度提升了二次电池的能量密度、首次库伦效率和循环性能。
在本申请的二次电池中，所述负极膜片在0.005V至脱锂平台电压的电压区间的脱锂容量A与脱锂平台电压至1.2V的电压区间的脱锂容量B之比A/B可以≤2、≤1.95、≤1.9、≤1.85、≤1.8、≤1.75、≤1.7、≤1.65、≤1.6、≤1.55、≤1.5、≤1.45、≤1.4、或≤1.35。可选的，A/B可以≥1、≥1.1、≥1.15、≥1.2、≥1.25、≥1.28、或≥1.3。进一步可选的，1.1≤A/B≤1.6；或者，1.2≤A/B≤1.5。
A/B值在所给范围内，能更好地使电池兼具较高的能量密度、首次库伦效率及较好的循环性能。
在本申请的二次电池中，可以通过调整硅氧化合物在负极活性材料中的质量占比、粘结剂的种类及含量、导电剂的种类及含量等，以使得A/B在前文所述的范围内。
在本申请的二次电池中，硅氧化合物SiO x中0＜x＜2。可选的，0.6≤x≤1.5，或者，0.9≤x≤1.2。
硅氧化合物满足x在适当范围内，能使硅氧化合物具有较高的容量性能及较高的首次库伦效率，并且能提高硅氧化合物的循环寿命，从而可以改善采用其的二次电池的相应性能。
在本申请的二次电池中，可选的，所述硅氧化合物在16MPa压力下的粉体体积电阻率可以为1000Ω·cm以下。
在本申请的二次电池中，可选的，所述负极活性材料的平均粒径(即硅氧化合物与石墨混合后的平均粒径)D v50 a可以为5μm≤D v50 a≤ 20μm，或者6μm≤D v50 a≤15μm。
在本申请的二次电池中，可选的，所述硅氧化合物的平均粒径D v50 b可以为3μm≤D v50 b≤12μm，或者4μm≤D v50 b≤10μm。
D v50 b为3μm以上，能减少活性锂离子在负极的成膜消耗，以及减少电解液在负极的副反应，从而提高电池的循环性能。另外，适当的D v50 b还能减少负极膜片中粘结剂的添加量，这有利于提高电池的能量密度。可选的，D v50 b≥4μm。
D v50 b为12μm以下，能提高硅氧化合物中锂离子和电子的迁移速率，还有利于防止硅氧化合物在充放电过程中发生破裂，提高硅氧化合物的循环寿命，进而提高电池的循环性能。可选的，D v50 b≤10μm。
在本申请的二次电池中，可选的，所述石墨的平均粒径D v50 c可以为5μm≤D v50 c≤18μm，或者6μm≤D v50 c≤15μm。
D v50 c为5μm以上，能减少活性锂离子在负极的成膜消耗，以及减少电解液在负极的副反应，从而提高电池的循环性能。另外，适当的D v50 c还能减少负极极片中粘结剂的添加量，这有利于提高电池的能量密度。可选的，D v50 c≥6μm。
D v50 c为18μm以下，能提高石墨中锂离子和电子的迁移速率，从而提高电池的循环性能。可选的，D v50 c≤15μm。
负极活性材料的平均粒径D v50 a、硅氧化合物的平均粒径D v50 b及石墨的平均粒径D v50 c均为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以用激光粒度分析仪方便地测定，如英国马尔文仪器有限公司的Mastersizer3000型激光粒度分析仪。
在本申请的二次电池中，所述石墨可以是天然石墨及人造石墨中的一种或几种。
在本申请的二次电池中，可选的，所述负极活性材料在所述负极膜片中的质量占比为90％～98％，或者92％～96％。
在本申请的二次电池中，可选的，所述硅氧化合物在所述负极活性材料中的质量占比ω满足5％≤ω≤40％，或者15％≤ω≤35％。ω在上述范围内，能优化A/B值，还能进一步改善电池的能量密度及循环性能。
在本申请的二次电池中，所述负极膜片中还可选地含有可用于二次电池负极的其他负极活性材料。作为示例，其他负极活性材料可以是单质硅、硅碳复合物、硅合金、中间相微碳球(MCMB)、硬碳及软碳中的一种或几种。
在本申请的二次电池中，所述负极膜片中还可选地含有粘结剂和导电剂。
所述负极膜片中的粘结剂可以选自本领域公知的能够用于二次电池的粘结剂。可选的，所述粘结剂包括丁苯橡胶(SBR)、聚丙烯酸类化合物及其改性化合物、聚丙烯酸盐类化合物及其改性化合物中的一种或几种。
可选的，所述粘结剂在负极膜片中的质量占比为1％～9％，或者3％～7％。
所述负极膜片中的导电剂可以选自本领域公知的能够用于二次电池的导电剂。可选的，所述导电剂包括导电炭黑(Super P，简写为SP)及碳纳米管(Carbon Nanotube，简写为CNT)中的一种或几种。进一步可选的，所述导电剂同时包括SP与CNT。
可选的，所述导电剂在负极膜片中的质量占比为1％～5％，或者1％～3％。
在本申请的二次电池中，可选的，所述二次电池放电至电压为2.5V时，所述负极极片相对于锂金属参比电极的电压U可以≤0.7、≤0.68、≤0.65、≤0.64、≤0.63、≤0.62、≤0.61、或者≤0.6。可选的，U可以≥0.59、≥0.58、≥0.57、≥0.56、≥0.55、≥0.54、≥0.53、≥0.52、≥0.51、或≥0.5。可选的，0.55V≤U≤0.65V。
电压U的值在适当范围内，能更好地使电池兼具较高的能量密度、首次库伦效率及较好的循环性能。
在本申请的二次电池中，可以采用对负极膜片进行预补锂、采用预嵌锂的硅氧化合物、及调整电池的容量过量系数(即CB值)中的一种或几种方式，来控制上述电压U在本申请所给的范围内。其中，电池的容量过量系数为相同面积的负极膜片容量与正极膜片容量之比。
在本申请的二次电池中，对负极膜片的预补锂工艺可以采用本领域已 知的工艺。例如，可以采用锂粉、锂片及锂锭中的一种或多种在负极膜片上进行预补锂；也可以直接采用预补锂的硅氧化合物。
在本申请的二次电池中，二次电池的容量过量系数可选为1.05～1.3，或者可选为1.1～1.2。二次电池的容量过量系数在上述范围内，在优化电压U的同时，还有利于电池容量发挥，提高电池的能量密度，并且有利于防止负极膜片在循环过程中析锂。
在本申请的二次电池中，可选的，所述负极膜片的面密度ρ可满足7mg/cm 2≤ρ≤10mg/cm 2。可选的，7mg/cm 2≤ρ≤9mg/cm 2。所述负极膜片的面密度在所述范围内时，所述二次电池可同时兼顾较高的能量密度和较好的动力学性能。需要说明的是，此处所述的面密度ρ是指集流体上任意一面的负极膜片的面密度。
在本申请的二次电池中，所述负极集流体可采用具有良好导电性及机械强度的材质，例如铜箔，但并不限于此。
在本申请的二次电池中，可选的，所述层状锂镍钴锰氧化物可选自式1所示的化合物及其表面包覆改性化合物中的一种或几种：
Li aNi bCo cMn dM 1 eO fA g     式1
式1中，0.8≤a≤1.2，0.5≤b＜1，0＜c＜1，0＜d＜1，0≤e≤0.1，1≤f≤2，0≤g≤1；
M 1为阳离子掺杂元素，M 1可选自Zr、Al、Zn、Cu、Cr、Mg、Fe、V、Ti及B中的一种或几种；
A为阴离子掺杂元素，A可选自N、F、S及Cl中的一种或几种。
在本申请的二次电池中，可选的，所述层状锂镍钴铝氧化物可选自式2所示的化合物及其表面包覆改性化合物中的一种或几种：
Li αNi βCo γAl δM 2 εO νX σ    式2
式2中，0.8≤α≤1.2，0.5≤β＜1，0＜γ＜1，0＜δ＜1，0≤ε≤0.1，1≤ν≤2，0≤σ≤1；
M 2为阳离子掺杂元素，M 2可选自Zr、Mn、Zn、Cu、Cr、Mg、Fe、V、Ti及B中的一种或几种；
X为阴离子掺杂元素，X可选自N、F、S及Cl中的一种或几种。
上述表面包覆改性化合物可以在材料颗粒的至少一部分表面设置有包覆层，所述包覆层可以是碳层、氧化物层、无机盐层或导电高分子层。通过表面包覆改性能够进一步改善电池的循环性能。
可选地，碳层可以包括石墨、石墨烯、中间相微碳球(MCMB)、烃类化合物热解碳、硬碳及软碳中的一种或多种。
可选地，氧化物层可以包括Al的氧化物、Ti的氧化物、Mn的氧化物、Zr的氧化物、Mg的氧化物、Zn的氧化物、Ba的氧化物、Mo的氧化物及B的氧化物中的一种或几种。
可选地，无机盐层可以包括Li 2ZrO 3、LiNbO 3、Li 4Ti 5O 12、Li 2TiO 3、Li 3VO 4、LiSnO 3、Li 2SiO 3及LiAlO 2中的一种或几种。
可选地，导电高分子层可以包括聚吡咯(PPy)、聚3,4-亚乙二氧基噻吩(PEDOT)及聚酰胺(PI)中的一种或几种。
在本申请的二次电池中，所述正极活性材料还可选地含有可用于二次电池正极的其他正极活性材料。作为示例，其他正极活性材料例如是锂锰氧化物、磷酸铁锂、磷酸锰锂及磷酸锰铁锂中的一种或几种。
在本申请的二次电池中，可选的，所述正极活性材料中的至少一部分为单颗粒形貌(即非团聚颗粒形貌)。单颗粒形貌的正极活性材料可以提高正极极片整体的压实密度和延展性，同时降低正极活性材料与电解液之间的接触面积，减少界面副反应的发生，降低产气量，可进一步改善锂离子电池的循环性能。
在本申请的二次电池中，所述正极膜片中还可选地包括粘结剂和导电剂，对粘结剂、导电剂的种类不做具体限制，本领域技术人员可以根据实际需求进行选择。
可选地，所述正极膜片中的粘结剂可以是聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚丙烯酸(PAA)、聚乙烯醇(PVA)、羧甲基纤维素钠(CMC)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的一种或几种。所述正极膜片中的导电剂可以是石墨、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几种。
在本申请的二次电池中，所述正极集流体可采用具有良好导电性及机械强度的材质，例如铝箔，但并不限于此。
在本申请的二次电池中，所述电解液包含有机溶剂及分散于有机溶剂中的锂盐。其中有机溶剂和锂盐的具体种类及组成均不受到具体的限制，可根据实际需求进行选择。
可选地，所述有机溶剂可以是碳酸亚乙酯(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)及二乙砜(ESE)中的一种或几种。
可选地，所述锂盐可以选自LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiTFSI(双三氟甲磺酰亚胺锂)及LiTFS(三氟甲磺酸锂)中的一种或几种。
在本申请的二次电池中，所述电解液中还可选地包括添加剂，其中对添加剂的种类没有具体的限制，可根据需求进行选择。
在本申请的二次电池中，所述隔离膜设置在正极极片和负极极片之间起到隔离的作用。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜，例如玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或多种。隔离膜可以是单层薄膜，也可以是多层复合薄膜。隔离膜为多层复合薄膜时，各层的材料可以相同，也可以不同。
可以按照本领域常规方法制备本申请的二次电池，例如，将负极活性材料及可选的导电剂和粘结剂分散于溶剂(例如水)中，形成均匀的负极浆料，将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，得到负极极片；将正极活性材料及可选的导电剂和粘结剂分散于溶剂(例如N-甲基吡咯烷酮，简称为NMP)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，得到正极极片；将正极极片、隔离膜、负极极片按顺序卷绕(或叠片)，使隔离膜处于正极极片与负极极片之间起到隔离的作用，得到电极组件，将电极组件置于外包装中，注入电解液，得到二次电池。
本申请对二次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1是作为一个示例的方形结构的二次电池5。
在一些实施例中，二次电池可包括外包装。该外包装用于封装正极极片、负极极片和电解质。
在一些实施例中，参照图2，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卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔。电解质可采用电解液，电解液浸润于电极组件52中。二次电池5所含电极组件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，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次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，二次电池可以组装成电池模块。电池模块所含二次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3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池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二次电池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，多个二次电池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4和图5是作为一个示例的电池包1。参照图4和图5，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
本申请还提供一种装置，所述装置包括本申请所述的二次电池。所述二次电池可以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二次电池、电池模块或电池包。
图6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。为了满足该装置对二次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，可以采用二次电池作为电源。
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。
实施例1
1)正极极片的制备
将正极活性材料LiNi 0.8Mn 0.1Co 0.1O 2(NMC811)、导电剂SP、粘结剂PVDF按95:1.5:3.5的重量比在适量的NMP中充分搅拌混合，使其形成均匀的正极浆料；将正极浆料涂覆于正极集流体铝箔上，经干燥、冷压后，得到正极极片。
2)负极极片的制备
将表1所示的负极活性材料、导电剂SP和CNT、粘结剂聚丙烯酸钠(PAAS)按一定重量比(详见表1)在适量的去离子水中充分搅拌混合，形成均匀的负极浆料；将负极浆料涂覆于负极集流体铜箔上，经干燥、冷压后，得到负极极片。同时，通过极片预补锂的方式调整电压U的值。
3)隔离膜采用聚乙烯(PE)薄膜。
4)电解液的制备
将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照体积比为EC:EMC:DEC＝1:1:1进行混合，得到有机溶剂，将充分干燥的锂盐LiPF 6溶解于有机溶剂中，之后加入氟代碳酸亚乙酯(FEC)，混合均匀后获得电解液，其中LiPF 6的浓度为1mol/L，FEC在电解液中的质量百分含量为6％。
5)将上述正极极片、隔离膜、锂金属参比电极、隔离膜、负极极片按顺序叠好，经卷绕后得到电极组件，将电极组件装入外包装中，加入上述电解液并封口，得到二次电池。
其中，上述负极极片满足：将上述负极极片与电解液(同上述步骤4)制备的电解液)、锂金属对电极组成扣式电池，对扣式电池以0.1C倍率恒流嵌锂至电压为0.005V，再以0.05C倍率恒流嵌锂至电压为0.005V，再以0.1C倍率恒流脱锂至电压为1.2V，其中负极膜片在0.005V至脱锂平台电压的电压区间的脱锂容量为A，负极膜片在脱锂平台电压至1.2V的电压区间的脱锂容量为B。
实施例1的电池同时满足①和②：
①A/B＝1.0；
②将电池放电至电压为2.5V时，所述负极极片相对于锂金属参比电极的电压U＝0.6V。
实施例2～23和对比例1～4与实施例1的制备方法相似，不同的产品参数详见表1。
二次电池的首次库伦效率及循环性能测试
在25℃、常压环境下，将实施例1～23及对比例1～4的二次电池以0.1C倍率恒流充电至4.25V，之后恒压充电至电流为0.05C，之后静置5min，记录此时的充电容量，即为首次充电容量；再以0.1C倍率恒流放电至2.5V，再静置5min，此为一个循环充放电过程，记录此时的放电容量，即为首次放电容量。将二次电池按照上述方法进行300次循环充放电测试，记录每次的放电容量。
电池的重量能量密度(Wh/kg)＝首次放电能量/电池重量
电池的首次库伦效率(％)＝首次放电容量/首次充电容量×100％
电池的容量保持率(％)＝第300次的放电容量/首次放电容量×100％
表1
Figure PCTCN2020100990-appb-000001
表1中，ω是硅氧化合物(即SiO)在负极活性材料中的质量百分含量。
表2
Figure PCTCN2020100990-appb-000002
由表2的测试结果可以看出，二次电池的正极活性材料包括层状锂镍钴锰氧化物及层状锂镍钴铝氧化物中的一种或几种，负极活性材料包括硅氧化合物和石墨，能够使电池具有较高的能量密度；通过使二次电池同时 满足负极膜片的A/B值及负极极片的电压U值在特定的范围内，电池的循环容量保持率得到明显提高，有效改善了电池的循环性能，特别地，还能进一步提高电池的能量密度。
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 (13)

  1. 一种二次电池，包括正极极片、负极极片、隔离膜及电解液，所述正极极片包括正极集流体以及设置在所述正极集流体至少一个表面上且包括正极活性材料的正极膜片，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面上且包括负极活性材料的负极膜片，其中，
    所述正极活性材料包括层状锂镍钴锰氧化物及层状锂镍钴铝氧化物中的一种或几种；
    所述负极活性材料包括石墨和硅氧化合物SiO x，其中0＜x＜2；
    所述负极极片与锂金属片制成的扣式电池，以0.1C倍率恒流嵌锂至电压为0.005V，再以0.05C倍率恒流嵌锂至电压为0.005V，再以0.1C倍率恒流脱锂至电压为1.2V，所述负极膜片在0.005V至1.2V电压区间的脱锂总能量与脱锂总容量的比值定义为脱锂平台电压，所述负极膜片在0.005V至脱锂平台电压的电压区间的脱锂容量定义为A，所述负极膜片在脱锂平台电压至1.2V的电压区间的脱锂容量定义为B，所述A与B之间满足：1≤A/B≤2；
    且当所述二次电池放电至电压为2.5V时，所述负极极片相对于锂金属参比电极的电压U满足：0.5V≤U≤0.7V。
  2. 根据权利要求1所述的二次电池，其中，所述A与B之间满足：1.1≤A/B≤1.6；可选的，1.2≤A/B≤1.5。
  3. 根据权利要求1或2所述的二次电池，其中，当所述二次电池放电至电压为2.5V时，所述负极极片相对于锂金属参比电极的电压U为0.55V≤U≤0.65V。
  4. 根据权利要求1至3任一项所述的二次电池，其中，所述石墨选自人造石墨及天然石墨中的一种或几种。
  5. 根据权利要求1至4任一项所述的二次电池，其中，所述负极活性材料中所述硅氧化合物的质量百分含量ω满足5％≤ω≤40％；可选的，15％≤ω≤35％。
  6. 根据权利要求1至5任一项所述的二次电池，其中，所述负极活性 材料还满足如下中的一个或几个：
    所述负极活性材料的平均粒径D v50 a为5μm≤D v50 a≤20μm；可选的，6μm≤D v50 a≤15μm；
    所述硅氧化合物的平均粒径D v50 b为3μm≤D v50 b≤12μm；可选的，4μm≤D v50 b≤10μm；
    所述石墨的平均粒径D v50 c为5μm≤D v50 c≤18μm；可选的，6μm≤D v50 c≤15μm。
  7. 根据权利要求1至6任一项所述的二次电池，其中，
    所述锂镍钴锰氧化物选自式1所示的化合物及其表面包覆改性化合物中的一种或几种，
    Li aNi bCo cMn dM 1 eO fA g    式1，
    所述式1中，0.8≤a≤1.2，0.5≤b＜1，0＜c＜1，0＜d＜1，0≤e≤0.1，1≤f≤2，0≤g≤1，M 1选自Zr、Al、Zn、Cu、Cr、Mg、Fe、V、Ti及B中的一种或几种，A选自N、F、S及Cl中的一种或几种；
    和/或，
    所述锂镍钴铝氧化物选自式2所示的化合物及其表面包覆改性化合物中的一种或几种，
    Li αNi βCo γAl δM 2 εO νX σ    式2，
    所述式2中，0.8≤α≤1.2，0.5≤β＜1，0＜γ＜1，0＜δ＜1，0≤ε≤0.1，1≤ν≤2，0≤σ≤1，M 2选自Zr、Mn、Zn、Cu、Cr、Mg、Fe、V、Ti及B中的一种或几种，X选自N、F、S及Cl中的一种或几种。
  8. 根据权利要求1至7任一项所述的二次电池，其中，所述正极活性材料中的至少一部分为单颗粒形貌。
  9. 根据权利要求1至8任一项所述的二次电池，其中，所述二次电池的容量过量系数为1.05～1.3；可选的，所述二次电池的容量过量系数为1.1～1.2。
  10. 根据权利要求1至9任一项所述的二次电池，其中，所述负极膜片的面密度ρ满足：7mg/cm 2≤ρ≤10mg/cm 2；可选的，7mg/cm 2≤ρ≤9mg/cm 2。
  11. 一种电池模块，包括根据权利要求1至10任一项所述的二次电池。
  12. 一种电池包，包括根据权利要求11所述的电池模块。
  13. 一种装置，包括根据权利要求1至10任一项所述的二次电池。
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