WO2022021273A1 - 二次电池、其制备方法及含有该二次电池的电池模块、电池包和装置 - Google Patents

二次电池、其制备方法及含有该二次电池的电池模块、电池包和装置 Download PDF

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WO2022021273A1
WO2022021273A1 PCT/CN2020/106076 CN2020106076W WO2022021273A1 WO 2022021273 A1 WO2022021273 A1 WO 2022021273A1 CN 2020106076 W CN2020106076 W CN 2020106076W WO 2022021273 A1 WO2022021273 A1 WO 2022021273A1
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negative electrode
active material
electrode active
optionally
secondary battery
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PCT/CN2020/106076
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English (en)
French (fr)
Inventor
康蒙
董晓斌
王家政
何立兵
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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 PCT/CN2020/106076 priority Critical patent/WO2022021273A1/zh
Priority to CN202080095001.2A priority patent/CN115004418B9/zh
Priority to EP20947276.0A priority patent/EP4167324A4/en
Priority to KR1020227023445A priority patent/KR102599831B1/ko
Priority to JP2022542212A priority patent/JP7355942B2/ja
Publication of WO2022021273A1 publication Critical patent/WO2022021273A1/zh
Priority to US17/810,610 priority patent/US11658335B2/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
    • H01M10/04—Construction or manufacture in general
    • H01M10/0422—Cells or battery with cylindrical casing
    • H01M10/0427—Button cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—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
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application belongs to the technical field of secondary batteries, and specifically relates to a secondary battery, a preparation method thereof, and a battery module, battery pack and device containing the secondary battery.
  • a first aspect of the present application provides a secondary battery, which includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and containing a negative electrode active material, so
  • the negative electrode active material includes graphite
  • the negative electrode pole piece satisfies: when the negative electrode pole piece and the lithium metal piece are formed into a button battery, and the button battery is discharged at 0.05C to 5.0mV, its capacity increases
  • the curve V-dQ/dV has the third-order lithium intercalation phase transition peak of graphite at the position of 0.055V-0.085V.
  • the negative electrode active material of the negative electrode sheet includes graphite, and the negative electrode electrode sheet satisfies: when the negative electrode electrode sheet and the lithium metal sheet form a button battery, and the button battery is discharged at 0.05C to At 5.0mV, the obtained capacity increase curve V-dQ/dV has a phase transition peak from the fourth-order lithium intercalation compound of graphite to the third-order lithium intercalation compound at the position of 0.055V to 0.085V, which can make the negative electrode While the sheet has high reversible capacity, it also has a high ability to deintercalate active ions, which greatly improves the moving speed of active ions between the positive and negative electrodes, so that the secondary battery has a higher energy density under the premise. , significantly improving fast charging capability and cycle life.
  • the capacity increase curve V-dQ/dV has a third-order lithium intercalation phase transition peak of graphite at a position of 0.057V to 0.077V; optionally, the capacity increase curve V -dQ/dV has a third-order lithium intercalation phase transition peak of graphite at the position of 0.061V to 0.074V.
  • the negative pole piece satisfies the above conditions, the fast charging capability and cycle life of the battery can be further improved.
  • the peak intensity of the third-order lithium intercalation phase transition peak of the graphite is -3Ah/V/g to -15Ah/V/g.
  • the negative pole piece has a higher actual lithium intercalation capacity, which can further improve the energy density of the battery.
  • the volume average particle diameter D v 50 of the negative electrode active material satisfies: 8 ⁇ m ⁇ D v 50 ⁇ 16 ⁇ m; optionally, 9.5 ⁇ m ⁇ D v 50 ⁇ 14.5 ⁇ m.
  • the Dv50 of the negative active material is within the given range, which can further improve the fast charging capability of the battery. In addition, the cycle life of the battery can also be improved.
  • the areal density CW of the negative electrode film layer satisfies: 0.09kg/m 2 ⁇ CW ⁇ 0.117kg/m 2 ; optionally, the areal density CW of the negative electrode film layer satisfies: 0.094kg/m 2 ⁇ CW ⁇ 0.107kg/m 2 .
  • the energy density and fast charging capability of the battery can be improved.
  • the compaction density PD of the negative electrode film layer satisfies: 1.5g/m 3 ⁇ PD ⁇ 1.7g/m 3 ; optionally, the compaction density PD of the negative electrode film layer Satisfaction: 1.53 ⁇ PD ⁇ 1.68g/m 3 .
  • the compaction density of the negative film layer is within the above range, which can improve the fast charging capability and cycle performance of the battery.
  • the negative electrode active material includes artificial graphite; optionally, the mass ratio of the artificial graphite in the negative electrode active material is greater than or equal to 60%; optionally, the artificial graphite The mass ratio in the negative electrode active material is 80% to 100%.
  • the negative electrode active material satisfies the above-mentioned conditions, enabling the battery to obtain higher fast charging capability and longer cycle life.
  • the negative electrode active material includes natural graphite; optionally, the mass ratio of the natural graphite in the negative electrode active material is ⁇ 40%; optionally, the natural graphite The mass ratio in the negative electrode active material is 10% to 30%.
  • the negative electrode active material satisfies the above conditions and can further improve the fast charging capability of the battery.
  • the negative electrode active material includes secondary particles; optionally, the secondary particles account for ⁇ 60% of the negative electrode active material; optionally, the two The proportion of secondary particles in the negative electrode active material is 80% to 100%.
  • the negative electrode active material satisfies the above conditions, which can further improve the fast charging capability of the battery and further improve the cycle life of the battery.
  • the uniformity of particle size of the negative electrode active material is 0.3-0.4; optionally, the uniformity of particle size of the negative electrode active material is 0.31-0.36.
  • the uniformity of the particle size of the negative electrode active material is within the given range, which can further improve the fast charging capability of the battery, and further improve the cycle life and energy density of the battery.
  • the particle size span of the negative electrode active material (D v 90-D v 10)/D v 50 satisfies: 1.0 ⁇ (D v 90-D v 10)/D v 50 ⁇ 1.4 ; optional, 1.1 ⁇ (D v 90-D v 10)/D v 50 ⁇ 1.3.
  • the particle size span (D v 90-D v 10)/D v 50 of the negative active material is within the given range, which can further improve the fast charging capability of the battery.
  • the graphitization degree of the negative electrode active material is 93% to 95%; optionally, the graphitization degree of the negative electrode active material is 93.5% to 94.5%.
  • the graphitization degree of the negative electrode active material is within the given range, which can further improve the fast charging capability of the battery, and also improve the cycle life of the battery.
  • the powder OI value of the negative electrode active material is 2.5-4.5; optionally, the powder OI value of the negative electrode active material is 3-4.
  • the powder OI value of the negative electrode active material is within the given range, which can further improve the fast charging capability of the battery and improve the cycle life of the battery.
  • the tap density of the negative electrode active material is 0.8g/cm 3 to 1.2g/cm 3 ; optionally, the tap density of the negative electrode active material is 0.9g/cm 3 to 1.1 g/cm 3 .
  • the tap density of the negative electrode active material is within the given range, which enables the battery to obtain a higher energy density and further improves the fast charging capability of the battery.
  • the powder compaction density of the negative electrode active material under a pressure of 30kN is 1.65g/cm 3 to 1.85g/cm 3 ; optionally, the negative electrode active material has a pressure of 30kN
  • the compacted density of the lower powder is 1.7 g/cm 3 to 1.8 g/cm 3 .
  • the powder compaction density of the negative electrode active material under the pressure of 30kN is within the given range, which can improve the energy density of the battery.
  • the gram capacity of the negative electrode active material is 350mAh/g to 360mAh/g; optionally, the gram capacity of the negative electrode active material is 352mAh/g to 358mAh/g.
  • the use of negative electrode active materials in this capacity range can ensure that the battery has high energy density and fast charging capability.
  • the porosity P of the negative electrode film layer satisfies: 25% ⁇ P ⁇ 45%; optionally, the porosity P of the negative electrode film layer satisfies: 28% ⁇ P ⁇ 35 %.
  • the porosity of the negative electrode film layer is within the above range, which can improve the energy density and fast charging capability of the battery.
  • the adhesive force F between the negative electrode film layer and the negative electrode current collector satisfies: 4.5N/m ⁇ F ⁇ 15N/m; optionally, the negative electrode film layer
  • the bonding force F with the negative electrode current collector satisfies: 8N/m ⁇ F ⁇ 12N/m.
  • the bonding force between the negative electrode film layer and the negative electrode current collector is within the above range, which can improve the fast charging capability and cycle performance of the battery.
  • the secondary battery includes a positive electrode sheet including a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and containing a positive electrode active material
  • the positive active material includes one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, composite material of lithium iron phosphate and carbon, and their respective modified compounds.
  • a second aspect of the present application provides a method for manufacturing a secondary battery, which includes the steps of preparing a negative electrode pole piece by the following method: providing a negative electrode active material, the negative electrode active material includes graphite; and forming the negative electrode active material into a negative electrode slurry The negative electrode slurry is coated on at least one surface of the negative electrode current collector to form a negative electrode film layer to obtain a negative electrode pole piece; wherein, the negative electrode pole piece satisfies: when the negative electrode pole piece is combined with lithium metal
  • the coin-type battery is formed into a coin-type battery, and the coin-type battery is discharged at 0.05C to 5.0mV, its capacity increment curve V-dQ/dV has a third-order lithium intercalation phase transition peak of graphite at the position of 0.055V-0.085V.
  • the negative electrode active material of the negative electrode electrode sheet includes graphite, and the negative electrode electrode sheet satisfies: when the negative electrode electrode sheet and the lithium metal sheet are formed into a button battery, and the
  • the obtained capacity increase curve V-dQ/dV has the third-order lithium intercalation phase transition peak of graphite at the position of 0.055V to 0.085V, which can make the negative pole piece With high reversible capacity, it also has a high ability to deintercalate active ions, which greatly improves the moving speed of active ions between the positive and negative electrodes, so that the secondary battery has a higher energy density under the premise. Significantly improves fast charging capability and cycle life.
  • a third aspect of the present application provides a battery module comprising the secondary battery according to the first aspect of the present application, or the secondary battery obtained according to the manufacturing method of the second aspect of the present application.
  • a fourth aspect of the present application provides a battery pack including the battery module according to the third aspect of the present application.
  • a fifth aspect of the present application provides a device comprising the secondary battery according to the first aspect of the present application, the secondary battery obtained according to the manufacturing method of the second aspect of the present application, the battery module according to the third aspect of the present application, or the At least one of the battery packs of the fourth aspect of the present application.
  • the battery module, battery pack and device of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary battery.
  • FIG. 1 is a V-dQ/dV graph of the capacity increment curve V-dQ/dV of a coin-type battery composed of a negative pole piece and a lithium metal piece of a secondary battery provided in Example 2 of the present application when discharged from 0.05C to 5.0mV.
  • FIG. 2 is a V-dQ/dV graph of the capacity increment curve V-dQ/dV of a button battery composed of a negative pole piece and a lithium metal piece of a secondary battery provided in Comparative Example 2 of the present application when discharged from 0.05C to 5.0mV.
  • FIG. 3 is a schematic diagram of an embodiment of a secondary battery.
  • FIG. 4 is an exploded view of FIG. 3 .
  • FIG. 5 is a schematic diagram of an embodiment of a battery module.
  • FIG. 6 is a schematic diagram of an embodiment of a battery pack.
  • FIG. 7 is an exploded view of FIG. 6 .
  • FIG. 8 is a schematic diagram of one 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 any other lower limit to form an unspecified range, and likewise any upper limit can be combined with any other upper limit to form an unspecified range.
  • every point or single value between the endpoints of a range is included within the range, even if not expressly recited.
  • each point or single value may serve as its own lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.
  • Embodiments of the first aspect of the present application provide a secondary battery.
  • the secondary battery includes a positive electrode sheet, a negative electrode sheet and an electrolyte.
  • active ions are inserted and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the negative electrode plate of the present application includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material, the negative electrode active material includes graphite, and the negative electrode electrode plate satisfies: when the The negative pole piece and the lithium metal piece form a button battery, and the button battery is discharged at 0.05C to 5.0mV, and its capacity increment curve V-dQ/dV has a graphite-like characteristic at the position of 0.055V to 0.085V.
  • the third-order lithium intercalation phase transition peak is described in this specification, the third-order lithium intercalation phase transition peak.
  • the fourth-order lithium intercalation phase transition peak (4# peak) corresponds to the phase transition process of graphite (C) to the fourth-order graphite intercalation compound (LiC 36 );
  • the third-order lithium intercalation phase transition peak ( 3# peak) corresponds to the phase transition process of the fourth-order graphite intercalation compound (LiC 36 ) to the third-order graphite intercalation compound (LiC 27 ) (hereinafter referred to as the third-order lithium intercalation phase transition process);
  • the second-order lithium intercalation phase transition peak (2# peak) corresponds to the phase transition process of the third-order graphite intercalation compound (LiC 27 ) to the second-order graphite intercalation compound (LiC 12 );
  • the first-order lithium intercalation phase transition peak (1# peak) corresponds to the second-order graphite layer
  • the inventors have found through keen research for the first time that when the negative electrode active material of the negative electrode pole piece includes graphite, and the negative electrode pole piece satisfies: the negative electrode pole piece and the lithium metal piece are assembled into a button battery, and the button battery is heated to 0.05C Discharged to 5.0mV (that is, the negative pole piece was intercalated with lithium at 0.05C until the voltage of the coin cell was 5.0mV), and its capacity increment curve V-dQ/dV had a graphitic characteristic at the position of 0.055V to 0.085V.
  • the secondary battery using the negative pole piece can significantly improve the fast charging capability and cycle life under the premise of higher energy density.
  • the inventors have discovered for the first time after extensive research that when the peak position of the third-order lithium intercalation peak is within the above-mentioned range, the negative pole piece is more likely to undergo a lithium intercalation reaction in the third-order lithium intercalation phase transition process, and the lithium ion
  • the moving speed between the positive and negative electrodes is greatly improved, thereby significantly improving the fast charging capability of the secondary battery.
  • the polarization of the battery during high-rate charging is small, resulting in a high capacity utilization rate and cycle capacity retention rate of the battery. Therefore, the battery using the negative pole piece can obtain better fast charging capability and longer cycle life under higher energy density.
  • the coin-type battery composed of the negative pole piece and the lithium metal piece is discharged from 0.05C to 5.0mV in the capacity increment curve V-dQ/dV
  • the peak of the third-order lithium intercalation peak Bit can be in 0.055V ⁇ 0.083V, 0.057V ⁇ 0.083V, 0.057V ⁇ 0.077V, 0.06V ⁇ 0.082V, 0.06V ⁇ 0.08V, 0.061V ⁇ 0.074V, 0.063V ⁇ 0.083V, 0.063V ⁇ 0.075V , 0.065V ⁇ 0.083V, 0.065V ⁇ 0.080V, 0.065V ⁇ 0.078V, or 0.068V ⁇ 0.075V, etc.
  • the peak position of the third-order lithium intercalation phase transition peak is within the given range, which can further improve the fast charging capability and cycle life of the secondary battery.
  • the peak intensity of the third-order lithium intercalation peak is -3Ah /V/g ⁇ -15Ah/V/g.
  • the negative electrode plate has a higher actual lithium intercalation capacity. Therefore, the battery using the negative pole piece can simultaneously take into account high fast charging capability and energy density.
  • the peak intensity of the third-order lithium intercalation phase transition peak may be -4 ⁇ -13Ah/V/g, -5 ⁇ -12Ah/V/g, -4 ⁇ -10Ah/V/g, -5 ⁇ - 10Ah/V/g, or -5 ⁇ -8Ah/V/g, etc.
  • the "button battery" described in this application is only to characterize the characteristics of the negative electrode plate of this application, and the preparation process thereof may refer to national standards or industry norms.
  • the negative pole piece can be made into a circular electrode piece, a small lithium metal disc is used as the counter electrode, and a conventional electrolyte solution in the industry is added to prepare a button battery.
  • ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed uniformly in a volume ratio of 1:1:1 to obtain an organic solvent, and the fully dried lithium salt LiPF 6 is uniformly dissolved.
  • an electrolyte solution is obtained, wherein the concentration of LiPF 6 can be 1 mol/L.
  • a separator is arranged between the negative pole piece and the lithium metal small disc to play a role of isolation.
  • the separator may be a separator commonly used in the industry, such as a polyethylene (PE) separator.
  • the coin cell battery can be a type commonly used in the industry, such as type CR2430. The assembly of the coin cell is carried out, for example, in an argon-protected glove box.
  • a button battery prepared from a negative pole piece and a lithium metal piece was discharged at 25°C at 0.05C to a voltage of 5.0mV, the voltage V and capacity Q of the battery were collected, and the capacity corresponding to a unit voltage change (dV) was calculated.
  • dQ/dV can be calculated by using the SLOPE function in EXCEL through the collected voltage V and capacity Q data.
  • the unit voltage change dV herein may be 0.2V ⁇ 0.5V (eg, 0.3V).
  • the negative pole piece used in the above-mentioned preparation of the button battery can be sampled during the preparation process of the negative pole piece, or the secondary battery can be disassembled and sampled.
  • the negative electrode film layer may be disposed on any one or both of the two surfaces of the negative electrode current collector that are opposite to each other in the thickness direction.
  • the types and structural parameters of the negative electrode active material such as the material structure parameters described herein
  • the structural parameters of the negative pole piece such as the pole piece structural parameters described herein
  • the negative electrode active material may include one or more of artificial graphite and natural graphite.
  • the negative active material includes artificial graphite.
  • the volume change of artificial graphite in the process of lithium intercalation is small, which is beneficial to the negative electrode pole piece to maintain a high electrolyte wettability and retention capacity, and the diffusion of lithium ions between the pores of the negative pole piece is easier, which is conducive to graphite intercalation of lithium
  • the progress of the reaction makes the peak position of the third-order lithium intercalation phase transition peak meet the demand.
  • the artificial graphite has high structural stability and fewer side reactions during the cycle, thereby enabling the battery to obtain a high cycle life.
  • the mass proportion of the artificial graphite in the negative electrode active material is ⁇ 60%.
  • the mass proportion of the artificial graphite in the negative electrode active material may be 70%-100%, 75%-100%, 80%-100%, or 90%-100%, etc.
  • the negative active material may further include natural graphite.
  • Natural graphite has more lithium intercalation sites on the surface and lower charge exchange resistance. At the same time, there are fewer defects in the graphite layer inside natural graphite, and the solid-phase diffusion capacity of lithium ions in it is higher. Therefore, an appropriate amount of natural graphite is included in the negative electrode active material. , which can further improve the lithium intercalation reaction performance of graphite and improve the fast charging ability of the battery.
  • the mass proportion of natural graphite in the negative electrode active material is ⁇ 40%.
  • the mass proportion of natural graphite in the negative electrode active material may be 10%-40%, 20%-40%, 10%-30%, or 15%-25%.
  • the mass proportion of natural graphite in the negative electrode active material is within an appropriate range, which can better balance the fast charging capability and cycle life of the secondary battery.
  • the negative electrode active material includes, in addition to the above-mentioned negative electrode active material of the present application, a certain amount of other commonly used negative electrode active materials, such as soft carbon, hard carbon, silicon-based materials, and tin-based materials. , one or more of lithium titanate.
  • the silicon-based material may be selected from one or more of elemental silicon, silicon-oxygen compound, silicon-carbon composite, and silicon alloy.
  • the tin-based material can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys.
  • the negative electrode active materials used in the present application can be obtained through commercial channels or prepared by methods known in the art.
  • the artificial graphite can be prepared as follows: the petroleum coke is pulverized, and the pulverized product may have a volume average particle diameter D v 50 of 5 ⁇ m to 10 ⁇ m, 5.5 ⁇ m to 7.5 ⁇ m, 6.5 ⁇ m to 8.5 ⁇ m, or 7.5 ⁇ m to 9.5 ⁇ m etc.; shape and classify the pulverized petroleum coke to obtain a precursor.
  • An optional step of granulating the precursor wherein the precursor can be granulated in the presence or absence of an organic carbon source to obtain a granulated precursor.
  • the precursor is subjected to graphitization treatment at a temperature of 2800° C. to 3200° C. to obtain artificial graphite.
  • an organic carbon source can also be used to coat the graphitized product, and after carbonization, a coated modified artificial graphite can be obtained.
  • the organic carbon source for granulation and coating can be independently selected from materials known in the art, such as pitch, polyacrylonitrile, epoxy resin, phenolic resin, and the like.
  • the volatile content of the graphite coke is 3% to 8% (mass percentage).
  • the petroleum coke includes petroleum green coke.
  • the volume average particle diameter D v 50 of the negative electrode active material satisfies 8 ⁇ m ⁇ D v 50 ⁇ 16 ⁇ m.
  • the Dv 50 of the negative active material may be 8 ⁇ m to 14 ⁇ m, 8 ⁇ m to 11 ⁇ m, 10 ⁇ m to 14 ⁇ m, 9 ⁇ m to 15 ⁇ m, 9.5 ⁇ m to 14.5 ⁇ m, or 13 ⁇ m to 16 ⁇ m, or the like.
  • the D v 50 of the negative electrode active material is in an appropriate range, which can make it have more rapid lithium intercalation channels, and make the migration path of lithium ions inside the particles shorter, and improve the lithium intercalation reaction performance of graphite.
  • the contact between the anode active material particles is good, and at the same time, a rich pore structure suitable for electrolyte infiltration can be formed, which can further improve the lithium intercalation performance of graphite. Therefore, by using a negative electrode active material with a suitable D v 50, it is beneficial to make the peak position of the third-order lithium intercalation phase transition peak in the V-dQ/dV curve meet the range given in this application.
  • the Dv50 of the negative active material is in an appropriate range, which can also reduce the side reaction of the electrolyte on the particle surface and reduce the polarization phenomenon, thereby improving the cycle life of the battery. Therefore, optionally, the D v 50 of the negative electrode active material may be 9.5 ⁇ m ⁇ 14.5 ⁇ m.
  • the anode active material optionally includes secondary particles.
  • the secondary particles account for ⁇ 60% of the negative electrode active material.
  • the proportion of secondary particles in the negative electrode active material may be 70%-100%, 75%-100%, 80%-100%, or 90%-100%, etc.
  • the particle size uniformity (Uniformity) of the negative electrode active material is 0.3-0.4.
  • the uniformity of particle size of the negative electrode active material may be 0.3-0.38, 0.31-0.36, 0.32-0.4, 0.32-0.37, 0.34-0.36, or 0.33-0.39, and the like.
  • the particles of the negative pole piece can have a large contact area to achieve close contact, so that the negative pole piece can obtain a higher compaction density and improve the energy density of the battery.
  • the particles and the current collector can also have a larger contact area, so that the negative pole piece can obtain better adhesion, which is conducive to the electron conduction in the negative pole piece, and improves the lithium intercalation reaction performance of the negative electrode active material.
  • the risk of film peeling and powder falling off of the negative pole piece can be further improved, so the fast charging ability and cycle life of the battery can be further improved.
  • the particle size span of the negative active material (D v 90-D v 10)/D v 50 may satisfy 1.0 ⁇ (D v 90-D v 10)/D v 50 ⁇ 1.4.
  • (D v 90-D v 10)/D v 50 of the negative electrode active material may be 1.0 to 1.3, 1.05 to 1.35, 1.1 to 1.4, 1.1 to 1.3, or 1.15 to 1.25, or the like.
  • the (D v 90-D v 10)/D v 50 of the negative active material reflects the degree to which the particle diameter of the larger particles and the particle diameter of the smaller particles deviate from the volume average particle diameter D v 50 in the negative active material.
  • the (D v 90-D v 10)/D v 50 of the negative electrode active material is appropriate, which is beneficial to make the negative electrode active material particles have high dispersion uniformity in the negative electrode film layer, which is beneficial to make the negative electrode film layer in different regions.
  • the anode active materials of the 2000-2000 exhibited high lithium intercalation reaction performance, thereby improving the fast charging capability of the battery.
  • the graphitization degree of the negative electrode active material may be 93%-95%.
  • the graphitization degree of the negative electrode active material may be 93.5% to 94.5% or the like.
  • the graphitization degree of the negative electrode active material is within the given range, which can enable the negative electrode active material to have a high reversible capacity and a large graphite interlayer spacing, thereby further improving the lithium intercalation performance of graphite and improving the fast charging capacity of the battery.
  • the negative electrode active material has good structural stability during charging and discharging, and can improve the cycle life of the battery.
  • the powder OI value of the negative electrode active material may be 2.5-4.5.
  • the powder OI value of the negative electrode active material may be 3 to 4.2, 3 to 4, or 3.2 to 3.8, or the like.
  • the powder OI value of the negative electrode active material characterizes the orientation index of the negative electrode active material.
  • the powder OI value of the negative electrode active material is appropriate, which can make it have more rapid intercalation channels of lithium ions, thereby improving the lithium intercalation performance.
  • the powder OI value of the negative electrode active material is in an appropriate range, which can also reduce the expansion effect of the negative electrode pole piece during the lithium intercalation process, and improve the cycle life of the battery.
  • the tap density of the negative electrode active material is 0.8 g/cm 3 to 1.2 g/cm 3 .
  • the tap density of the negative electrode active material may be 0.9 g/cm 3 to 1.1 g/cm 3 or the like.
  • the negative electrode film layer can have a high compaction density, thereby helping the battery to obtain a high energy density.
  • a smooth pore structure is also formed, which is beneficial to improve the lithium intercalation performance of the negative electrode active material, thereby improving the fast charging capability of the battery.
  • the powder compaction density of the negative electrode active material under a pressure of 30 kN may be 1.65 g/cm 3 to 1.85 g/cm 3 .
  • the powder compaction density of the negative electrode active material under a pressure of 30 kN may be 1.7 g/cm 3 to 1.8 g/cm 3 or the like.
  • the powder compaction density of the negative electrode active material under the pressure of 30kN is within the given range, which enables the negative electrode film layer to have a higher compaction density, thereby improving the energy density of the battery.
  • the gram capacity of the negative electrode active material is 350mAh/g ⁇ 360mAh/g.
  • the gram capacity of the negative electrode active material may be 352mAh/g ⁇ 358mAh/g, or 353mAh/g ⁇ 357mAh/g, or the like.
  • the use of negative electrode active materials in this capacity range can ensure that the battery has high energy density and fast charging capability.
  • At least a part of the surface of the negative electrode active material has a coating layer.
  • the coating layer can protect the negative electrode active material, greatly reduce the exfoliation of the graphite layer caused by the co-insertion of the solvent, and make the negative electrode active material have high structural stability, thereby enabling the secondary battery to obtain a high cycle. life.
  • 80% to 100% of the surface of the negative electrode active material may be covered with a coating layer. Further, 90% to 100% of the surface of the negative electrode active material can be covered with a coating layer.
  • the coating layer includes amorphous carbon.
  • the coating layer containing amorphous carbon enables faster diffusion of lithium ions in the particles, thereby improving the lithium intercalation performance of the negative electrode active material and enhancing the fast charging capability of the battery.
  • the amorphous carbon coating can be formed by carbonizing an organic carbon source.
  • the organic carbon source can be selected from high molecular polymers, such as coal pitch, petroleum pitch, phenolic resin, coconut shell and other materials.
  • the negative electrode film layer usually contains negative electrode active material and optional binder, optional conductive agent and other optional auxiliary agents, which is usually coated on the negative electrode current collector by negative electrode slurry, Dry and cold pressed.
  • the negative electrode slurry coating is usually formed by dispersing the negative electrode active material and optional conductive agent, optional binder, optional auxiliary agent, etc. in a solvent and stirring uniformly.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water.
  • the conductive agent may include one or more of superconducting carbon, carbon black (eg, Super P, acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • carbon black eg, Super P, acetylene black, Ketjen black
  • carbon dots carbon nanotubes, graphene, and carbon nanofibers.
  • the binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS) ) one or more of them.
  • SBR styrene-butadiene rubber
  • SR-1B water-soluble unsaturated resin
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • CMCS carboxymethyl chitosan
  • auxiliary agents are, for example, thickeners (such as sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, and the like.
  • the areal density CW of the negative electrode film layer satisfies 0.09kg/m 2 ⁇ CW ⁇ 0.117kg/m 2 .
  • the areal density CW of the negative electrode film layer is the weight of the negative electrode film layer per unit area.
  • CW is within the above range, it is helpful to control the peak position of the third-order lithium intercalation peak of graphite within the range given in the present application.
  • a suitable areal density can make the negative pole piece have a higher reversible capacity and reduce the migration distance of lithium ions in the pole piece, thereby further improving the energy density and fast charging capability of the battery.
  • the compaction density PD of the negative electrode film layer satisfies 1.5 g/m 3 ⁇ PD ⁇ 1.7 g/m 3 .
  • the compaction density PD of the negative electrode film layer is the weight of the negative electrode film layer per unit volume, which is equal to the areal density CW of the negative electrode film layer divided by the thickness of the negative electrode film layer.
  • a suitable compaction density can make the negative electrode film layer have high electronic conductivity and low liquid phase conduction impedance, thereby further improving the fast charging ability and cycle performance of the battery.
  • the inventor found that when the parameters of the negative electrode active material and the parameters of the negative electrode pole piece are reasonably designed, the battery can further improve the fast charging capability and cycle life of the battery under the premise of higher energy density.
  • the negative electrode film layer simultaneously satisfies: the D v 50 of the negative electrode active material is 8 ⁇ m to 11 ⁇ m, the CW of the negative electrode film layer is 0.105 kg/m 2 to 0.117 kg/m 2 , and the PD is 1.5g/m 3 ⁇ 1.6g/m 3 , and in the V-dQ/dV curve, the peak position of the third-order lithium intercalation phase transition peak of graphite is 0.07V ⁇ 0.085V; for example, the third-order intercalation phase of graphite The peak position of the lithium phase transition peak may be 0.07V to 0.08V, or 0.078V to 0.085V, and the like.
  • the negative electrode film layer simultaneously satisfies: the D v 50 of the negative electrode active material is 10 ⁇ m to 14 ⁇ m, the CW of the negative electrode film layer is 0.097 kg/m 2 to 0.110 kg/m 2 , and the PD is 1.55g/m 3 ⁇ 1.65g/m 3 , and in the V-dQ/dV curve, the peak position of the third-order lithium intercalation phase transition peak of graphite is 0.062V ⁇ 0.078V; for example, the third-order intercalation phase of graphite
  • the peak position of the lithium phase transition peak may be 0.062V to 0.072V, or 0.068V to 0.078V, and the like.
  • the negative electrode film layer simultaneously satisfies: the D v 50 of the negative electrode active material is 13 ⁇ m to 16 ⁇ m, the CW of the negative electrode film layer is 0.09 kg/m 2 to 0.097 kg/m 2 , and the The PD is 1.6g/m 3 ⁇ 1.7g/m 3 , and in the V-dQ/dV curve, the peak position of the third-order lithium intercalation phase transition peak of graphite is 0.055V ⁇ 0.067V; for example, the third-order intercalation phase of graphite
  • the peak position of the lithium phase transition peak may be 0.055V to 0.06V, or 0.059V to 0.067V, and the like.
  • the porosity P of the negative electrode film layer satisfies 25% ⁇ P ⁇ 45%.
  • the negative electrode sheet can have suitable electrolyte wettability and a good reaction interface, which reduces the liquid phase impedance of lithium ion conduction in the negative electrode sheet, thereby improving the lithium intercalation performance of the negative electrode active material and improving the The fast charging capability of the battery.
  • suitable P can also make the negative electrode film layer have a suitable amount of electrolyte retention, and at the same time make the battery have a lower weight and improve the energy density of the battery.
  • the adhesive force F between the negative electrode film layer and the negative electrode current collector satisfies 4.5N/m ⁇ F ⁇ 15N/m.
  • 4.5N/m ⁇ F ⁇ 15N/m For example, 5N/m ⁇ F ⁇ 14N/m, 7N/m ⁇ F ⁇ 15N/m, 6N/m ⁇ F ⁇ 13N/m, or 8N/m ⁇ F ⁇ 12N/m, etc.
  • the bonding force F between the negative electrode film layer and the negative electrode current collector is large, so that the negative electrode pole piece has good electron conductivity, which is beneficial to improve the lithium intercalation performance of the negative electrode active material.
  • F also reflects the ability of the negative pole piece to maintain the bonding reliability during the cycle process, which is beneficial to the battery's good electronic conductivity throughout the life cycle, thereby further improving the battery's cycle performance.
  • the negative electrode current collector can be made of a material with good electrical conductivity and mechanical strength, such as copper foil, but is not limited thereto.
  • the relevant parameters of the negative electrode film layer all refer to the parameters of the single-sided negative electrode film layer.
  • the parameters of the negative electrode film layer on any one of the surfaces meet the data range of the present application, that is, it is considered to fall within the protection scope of the present application.
  • the range of the peak position of the third-order lithium intercalation peak of graphite, the compaction density PD of the negative electrode film layer, the areal density CW, the porosity P, the cohesive force F, etc. of the graphite described in this application all refer to the combined use after cold compaction.
  • the film parameters of the negative pole piece of the assembled battery are used after cold compaction.
  • the negative electrode sheet of the present application does not exclude other additional functional layers other than the negative electrode film layer.
  • the negative electrode sheet further includes a conductive primer layer (eg, composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector.
  • the negative electrode plate described in the present application further includes a protective layer covering the surface of the negative electrode film layer.
  • the volume-average particle size D v 50, particle size uniformity (Uniformity), and particle size span (D v 90-D v 10)/D v 50 of the negative electrode active material are all meanings known in the art, and this
  • the assays are performed using instruments and methods known in the art. For example, it can refer to GB/T 19077-2016 particle size distribution laser diffraction method, and use a laser particle size analyzer (for example, Master Size 3000) to measure.
  • the particle size uniformity (Uniformity) of the negative electrode active material can characterize the degree of dispersion of the particle diameter of all particles in the negative electrode active material from the volume average particle diameter (D v 50) of the negative electrode active material, which reflects the particle size of the negative electrode active material. uniformity of distribution.
  • the particle size span of the negative active material (D v 90-D v 10)/D v 50 reflects the degree to which the particle size of the larger particles and the particle size of the smaller particles deviate from the volume-average particle size (Dv50) in the negative active material.
  • D v 10 represents the particle size corresponding to the cumulative volume distribution percentage of the negative electrode active material reaching 10%.
  • D v 50 represents the particle size corresponding to the cumulative volume distribution percentage of the negative active material reaching 50%.
  • D v 90 represents the particle size corresponding to the cumulative volume distribution percentage of the negative active material reaching 90%.
  • the graphitization degree of the negative electrode active material is a meaning known in the art, and can be measured by instruments and methods known in the art.
  • X-ray powder diffractometer such as Bruker D8 Discover
  • G the degree of graphitization G is calculated as 0.344-0.3354) x 100%, where d 002 is the interlayer spacing in the graphite crystal structure in nanometers (nm).
  • a copper target can be used as the anode target
  • CuK ⁇ rays are used as the radiation source
  • the ray wavelength The scanning 2 ⁇ angle range is 20° ⁇ 80°, and the scanning rate can be 4°/min.
  • the powder OI value of the negative electrode active material has a meaning known in the art, and can be measured by instruments and methods known in the art.
  • the powder OI value of the negative electrode active material was obtained.
  • C 004 is the peak area of the characteristic diffraction peak of the 004 crystal plane of graphite
  • C 110 is the peak area of the characteristic diffraction peak of the 110 crystal plane of the graphite.
  • the tap density CW of the negative electrode active material has a meaning well known in the art, and can be measured by instruments and methods known in the art. For example, refer to the standard GB/T 5162-2006, and use a powder tap density tester (such as Dandong Baxter BT-300 type) to conveniently measure.
  • a powder tap density tester such as Dandong Baxter BT-300 type
  • the powder compaction density PD of the negative electrode active material is a meaning known in the art, and can be measured by instruments and methods known in the art. For example, it can refer to the standard GB/T24533-2009, and it can be measured by an electronic pressure testing machine (such as UTM7305).
  • An exemplary test method is as follows: Weigh 1 g of negative active material, add it into a mold with a bottom area of 1.327 cm 2 , pressurize to 3000 kg (equivalent to 30 kN), hold the pressure for 30 s, then release the pressure for 10 s, then record and calculate Powder compaction density of negative active material under 30kN pressure.
  • primary particles refer to non-agglomerated particles
  • secondary particles refer to agglomerated particles formed by the aggregation of two or more primary particles.
  • the gram capacity of the negative electrode active material is a known meaning in the art, and can be tested by methods known in the art.
  • An exemplary test method for the gram capacity of the negative electrode active material is as follows: the negative electrode active material, the conductive agent carbon black (Super P), and the binder PVDF are mixed uniformly with the solvent NMP (N-methylpyrrolidone) in a mass ratio of 91.6:1.8:6.6 , make slurry; apply the prepared slurry on the copper foil current collector, and dry it in an oven for later use.
  • the metal lithium sheet is used as the counter electrode, and the polyethylene (PE) film is used as the separator.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the ratio of the charging capacity to the mass of the negative active material is the gram capacity of the negative active material.
  • the compaction density of the negative electrode film layer is a known meaning in the art, and can be tested by a method known in the art.
  • the compaction density of the negative electrode film layer area density of the negative electrode film layer/thickness of the negative electrode film layer.
  • the thickness of the negative electrode film layer has a meaning known in the art, and can be tested by a method known in the art. For example, a helical micrometer with 4-digit precision is used.
  • the porosity of the negative electrode film layer has a well-known meaning in the art, and can be measured by instruments and methods known in the art. For example, refer to GB/T24586-2009, and use the gas displacement method to measure.
  • An exemplary test method is as follows: take the negative pole piece coated on one side and after cold pressing (if it is a negative pole piece coated on both sides, the negative film layer on one side can be wiped off first), and punched into a 14mm diameter.
  • Small disc sample test the thickness of the negative electrode film (thickness of the negative electrode piece - the thickness of the negative current collector); calculate the apparent volume V1 of the negative film layer according to the calculation formula of the cylindrical volume; use an inactive gas such as helium or nitrogen As the medium, the gas displacement method is used to measure the real volume of the negative pole piece with a true density tester (such as Micromeritics AccuPyc II 1340).
  • the binding force between the negative electrode film layer and the negative electrode current collector is a well-known meaning in the art, and can be measured by instruments and methods known in the art. Cut the negative pole piece into a test sample with a length of 100mm and a width of 10mm. Take a stainless steel plate with a width of 25mm, paste it with double-sided tape (width 11mm), paste the test sample on the double-sided tape on the stainless steel plate, and roll it back and forth three times with a 2000g roller (300mm/min).
  • the positive electrode sheet may include a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector and containing a positive electrode active material.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer may be provided on either of the two surfaces, or may be provided on the two surfaces respectively.
  • the positive electrode active material may be a known positive electrode active material for secondary batteries in the art.
  • the positive active material may be selected from one or more of lithium transition metal oxides, olivine-structured lithium-containing phosphates and their respective modified materials.
  • the lithium transition metal oxide can 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 their One or more of the respective modified materials.
  • the lithium-containing phosphate of the olivine structure can be selected from lithium iron phosphate, composite material of lithium iron phosphate and carbon, lithium manganese phosphate, composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, manganese phosphate.
  • the modified material may be coating modification and/or doping modification of the material.
  • the positive active material may include one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, a composite of lithium iron phosphate and carbon, and their respective modified compounds or several.
  • the positive electrode active material may include one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.
  • the positive electrode film layer usually contains a positive electrode active material, an optional binder and an optional conductive agent, and is usually coated with a positive electrode slurry, dried and cold-pressed.
  • the positive electrode slurry is usually formed by dispersing the positive electrode active material and optional conductive agent and binder in a solvent and stirring uniformly.
  • the solvent may be N-methylpyrrolidone (NMP).
  • the binder for the positive electrode film layer may include polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoroethylene One or more of propylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • propylene-tetrafluoroethylene terpolymer tetrafluoroethylene-hexafluoropropylene copolymer
  • fluorine-containing acrylate resin fluorine-containing acrylate resin
  • the conductive agent used for the positive electrode film layer may include one or more of superconducting carbon, carbon black (such as Super P, acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers kind.
  • carbon black such as Super P, acetylene black, Ketjen black
  • carbon dots carbon nanotubes, graphene, and carbon nanofibers kind.
  • the positive electrode current collector can be made of a material with good electrical conductivity and mechanical strength.
  • a material with good electrical conductivity and mechanical strength for example, aluminum foil, but not limited to this.
  • the type of electrolyte is not specifically limited, and can be selected according to requirements.
  • the electrolyte may be selected from at least one of solid electrolyte and liquid electrolyte (ie, electrolyte).
  • the electrolyte is an electrolyte.
  • the electrolyte includes an electrolyte lithium salt and a solvent.
  • the lithium salt can be selected from LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiAsF 6 (lithium hexafluoroarsenate), LiFSI (bisfluorosulfonylidene) Lithium Amide), LiTFSI (Lithium Bistrifluoromethanesulfonimide), LiTFS (Lithium Trifluoromethanesulfonate), LiDFOB (Lithium Difluorooxalate Borate), LiBOB (Lithium Dioxalate Borate), LiPO 2 F 2 (Di One or more of LiDFOP (lithium difluorodioxalate phosphate) and LiTFOP (lithium tetrafluorooxalate phosphate).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • the solvent can be selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), carbonic acid Dipropyl (DPC), Methyl Propyl Carbonate (MPC), Ethyl 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), One or more of ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sul
  • additives are also optionally included in the electrolyte.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives to improve battery overcharge performance, additives to improve battery high temperature performance, and additives to improve battery low temperature performance. additives, etc.
  • a separator is further included in the secondary battery.
  • the separator is arranged between the positive pole piece and the negative pole piece, and plays the role of isolation.
  • the type of separator for the secondary battery of the present application is not particularly limited, and any well-known porous structure separator for secondary batteries can be selected.
  • the release film can be selected from glass fiber film, non-woven film, polyethylene film, polypropylene film, polyvinylidene fluoride film, and one or more multilayer composite films comprising one or more of them. species or several.
  • the secondary battery may include an outer package.
  • the outer packaging is used to encapsulate the positive pole piece, the negative pole piece and the electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, and the like.
  • the outer package of the secondary battery may also be a soft package, such as a pouch-type soft package.
  • the material of the soft bag may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), and the like.
  • the secondary battery can be prepared using methods known in the art.
  • the positive pole piece, the separator and the negative pole piece are formed into an electrode assembly by a winding process or a lamination process, wherein the separator is placed between the positive pole piece and the negative pole piece to isolate the electrode assembly; the electrode assembly is placed outside In the package, an electrolyte solution was injected and sealed to obtain a secondary battery.
  • FIG. 3 is a secondary battery 5 of a square structure as an example.
  • 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 are enclosed to form a accommodating cavity.
  • the housing 51 has an opening that communicates with the accommodating cavity, and a cover plate 53 can cover the opening to close the accommodating 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 solution is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 may be one or several, and may be adjusted according to requirements.
  • the secondary batteries can be assembled into a battery module, and 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. 5 shows the battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed with fasteners.
  • the battery module 4 may further include a housing having an accommodating space in which the plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules included 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 case and a plurality of battery modules 4 provided in the battery case.
  • the battery box includes an upper box body 2 and a lower box body 3 .
  • the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 .
  • the plurality of battery modules 4 may be arranged in the battery case in any manner.
  • a second aspect of the present application provides a device comprising at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery can be used as a power source for the device and also as an energy storage unit for the device.
  • the device may be, but is not limited to, mobile devices (eg, cell phones, laptops, etc.), electric vehicles (eg, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf balls) vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the device may select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • Figure 8 is an apparatus as an example.
  • the device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like.
  • a battery pack or a battery module can be employed.
  • the device may be a mobile phone, a tablet computer, a laptop computer, and the like.
  • the device is generally required to be thin and light, and a secondary battery can be used as a power source.
  • the negative electrode active materials of the embodiments of the present application can be obtained commercially or prepared by the following methods.
  • Artificial graphite A can be prepared as follows: using petroleum green coke, its volatile content is 10%, and pulverizing to obtain a petroleum green coke raw material with a volume-average particle diameter D v 50 of 6.5 ⁇ m; Shaping and grading treatment to obtain a precursor; the precursor is mixed with 5% pitch and then granulated at 600 ° C, and then graphitized at a temperature of 3000 ° C; the graphitized product is coated with pitch for carbonization treatment to obtain artificial graphite A.
  • the volume average particle size D v 50 of artificial graphite A is controlled at 9.5 ⁇ m, the particle size uniformity (Uniformity) is controlled at 0.36, and the gram capacity is controlled at 352 mAh/g.
  • Artificial graphite B can be prepared by the following method: using petroleum green coke, its volatile content is 8%, and pulverizing to obtain a petroleum green coke raw material with a volume average particle diameter D v 50 of 7.5 ⁇ m; shaping and grading treatment to obtain a precursor; the precursor is mixed with 8% pitch and then granulated at 600°C, and then graphitized at a temperature of 3000°C; the graphitized product is covered and carbonized with pitch to obtain artificial graphite B.
  • the volume average particle size D v 50 of artificial graphite B is controlled at 12 ⁇ m, the particle size uniformity (Uniformity) is controlled at 0.34, and the gram capacity is controlled at 355 mAh/g.
  • Artificial graphite C can be prepared as follows: using petroleum green coke, its volatile content is 6%, and pulverizing to obtain a petroleum green coke raw material with a volume average particle diameter D v 50 of 8.5 ⁇ m; Shaping and grading treatment to obtain a precursor; the precursor is mixed with 10% pitch, granulated at 600 ° C, and then graphitized at a temperature of 3000 ° C; the graphitized product is coated with pitch for carbonization treatment to obtain artificial graphite C.
  • the volume average particle size D v 50 of artificial graphite C is controlled at 14.5 ⁇ m, the particle size uniformity is controlled at 0.34, and the gram capacity is controlled at 358 mAh/g.
  • Natural graphite purchased from Bettray New Materials Group Co., Ltd., model AGP-8-3, the volume average particle size D v 50 is about 12.5 ⁇ m, the particle size uniformity (Uniformity) is about 0.41, and the gram capacity is 364mAh/ g.
  • the negative active material artificial graphite (A), the binder styrene-butadiene rubber (SBR), the thickener sodium carboxymethyl cellulose (CMC-Na) and the conductive agent carbon black (Super P) were prepared in a ratio of 96.2:1.8:1.2: The weight ratio of 0.8 is fully stirred and mixed in an appropriate amount of deionized water to form a uniform negative electrode slurry; the negative electrode slurry is coated on the surface of the negative electrode current collector copper foil, dried, cold pressed, slit and cut. , a negative electrode pole piece was obtained, the compaction density of the negative electrode pole piece was 1.53 g/cm 3 , and the areal density was 0.107 kg/m 2 .
  • the weight ratio of 1.1 is fully stirred and mixed in an appropriate amount of solvent NMP to form a uniform positive electrode slurry; the positive electrode slurry is coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, the positive electrode pole piece is obtained.
  • the areal density of the positive electrode film layer was 0.178 kg/m 2 , and the compaction density was 3.4 g/cm 3 .
  • PE film Polyethylene (PE) film is used.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the positive pole piece, the separator and the negative pole piece in order, and add a reference electrode between the separator and the negative pole piece (the reference electrode is used for the subsequent performance testing of the battery sample, and lithium pieces and lithium metal wires can be selected. etc., and the reference electrode should be separated by a separator to prevent contact with either side of the positive and negative electrodes), and the electrode assembly is obtained after winding; the electrode assembly is added to the outer package, and the above-mentioned electrolyte is added. , aging and other processes to obtain a secondary battery.
  • Examples 2 to 10 and Comparative Examples 1 to 4 are similar to the preparation methods of Example 1, but the design parameters of the negative pole piece and the positive pole piece are adjusted. See Table 2 for different product parameters.
  • Preparation of button battery Take the negative pole pieces in the above examples and comparative examples, respectively use metal lithium pieces as counter electrodes, and polyethylene (PE) films as separators. Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1, and then uniformly dissolve LiPF 6 in the above solution to obtain an electrolyte, where LiPF The concentration of 6 is 1 mol/L.
  • the CR2430 type coin cell was assembled in an argon gas-protected glove box.
  • the obtained button cell was discharged at a constant current of 0.05C to a voltage of 5.0mV, and the voltage and capacity data were collected; then the SLOPE function was used in EXCEL to calculate dQ/dV, where the unit The voltage change dV is 0.3V; the peak position of the corresponding phase change peak can be obtained by plotting the V-dQ/dV diagram of the capacity increment curve.
  • the secondary batteries prepared in the examples and comparative examples were charged with a constant current of 0.33C to a charge cut-off voltage of 4.4V, and then charged with a constant voltage to a current of 0.05C, left standing for 5 minutes, and then discharged with a constant current of 0.33C.
  • the discharge cut-off voltage of 2.8V record its actual capacity as C 0 .
  • the charging rate is the charging window in the SOC state, which are respectively denoted as C 10%SOC , C 20% SOC , C 30% SOC , C 40% SOC , C 50% SOC , C 60% SOC , C 70%
  • the secondary batteries prepared in the examples and comparative examples were charged with a constant current of 0.33C to a charge cut-off voltage of 4.4V, and then charged with a constant voltage to a current of 0.05C, left standing for 5 minutes, and then discharged with a constant current of 0.33C.
  • the initial capacity was recorded as C 0 .
  • charge according to the strategy described in Table 1 discharge at 0.33C, record the discharge capacity C n for each cycle, until the cycle capacity retention rate (C n /C 0 ⁇ 100%) is 80%, and record the number of cycles. The more cycles, the higher the cycle life of the battery.
  • V-dQ/dV curve has a third-order lithium intercalation peak of graphite at the position of 0.061V ⁇ 0.074V, the fast charging capability and cycle life of the battery are further improved.
  • Comparative Examples 1-4 do not meet the above conditions, it is difficult for the batteries to take into account both the fast charging capability and the cycle life.
  • the positive electrode active material of each embodiment of the present application only takes lithium nickel cobalt manganese oxide (NCM523) as an example, and those skilled in the art can select different positive electrode active materials according to the actual use environment of the battery.
  • CCM523 lithium nickel cobalt manganese oxide
  • other types of lithium nickel cobalt manganese oxides such as NCM622, NCM811, etc.
  • lithium nickel cobalt aluminum oxides lithium iron phosphate
  • composite materials of lithium iron phosphate and carbon and their respective modified compounds
  • the negative electrode plate described in the present application is used in combination with the above positive electrode active materials, similar improvement effects can be achieved. It will not be repeated here.

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Abstract

本申请公开了一种二次电池、其制备方法及含有该二次电池的电池模块、电池包和装置。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含负极活性材料的负极膜层，所述负极活性材料包括石墨，且所述负极极片满足：当将所述负极极片与锂金属片组成扣式电池，并将所述扣式电池以0.05C放电至5.0mV时，其容量增量曲线V-dQ/dV在0.055V～0.085V的位置具有石墨的三阶嵌锂相变峰。

Description

二次电池、其制备方法及含有该二次电池的电池模块、电池包和装置 技术领域
本申请属于二次电池技术领域，具体涉及一种二次电池、其制备方法及含有该二次电池的电池模块、电池包和装置。
背景技术
近年来，世界各国均在大力推动新能源汽车的发展与应用。二次电池因具有能量密度高、循环寿命长、且无污染、无记忆效应等优点，已被广泛应用于作为新能源汽车代表的电动汽车中。但与传统燃油车进行补充燃油的便捷性和高效性相比，二次电池一般是以很小的倍率充电，充电时间长达10小时以上。这严重加剧了用户的里程焦虑，影响了消费者的体验，从而限制了电动汽车的快速普及。因此，如何提高二次电池的快速充电能力成为研究的热点问题。
发明内容
本申请第一方面提供一种二次电池，其包括负极极片，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面上且包含负极活性材料的负极膜层，所述负极活性材料包括石墨，且所述负极极片满足：当将所述负极极片与锂金属片组成扣式电池，并将所述扣式电池以0.05C放电至5.0mV，其容量增量曲线V-dQ/dV在0.055V～0.085V的位置具有石墨的三阶嵌锂相变峰。
本申请的二次电池中，负极极片的负极活性材料包括石墨，且所述负极极片满足：当将负极极片与锂金属片组成扣式电池，并将扣式电池以0.05C放电至5.0mV时，所得到的容量增量曲线V-dQ/dV在0.055V～0.085V的位置具有石墨的四阶嵌锂化合物向三阶嵌锂化合物转变的相变峰，由此可以使得负极极片具有较高的可逆容量的同时，还具有较高的脱嵌活性离子能力，大幅度提升活性离子在正负极之间的移动速度，从而使得二次电池在具有较高能量密度的前提下，显著提高快速充电能力和循环寿命。
在本申请的一些实施方式中，所述容量增量曲线V-dQ/dV在0.057V～0.077V的位置具有石墨的三阶嵌锂相变峰；可选的，所述容量增量曲线V-dQ/dV在0.061V～0.074V的 位置具有石墨的三阶嵌锂相变峰。当负极极片满足上述条件时，可以进一步改善电池的快速充电能力和循环寿命。
在本申请的上述任意实施方式中，所述石墨的三阶嵌锂相变峰的峰强度为-3Ah/V/g～-15Ah/V/g。当该峰强度在适当范围内时，负极极片具有较高的实际嵌锂容量，可进一步改善电池的能量密度。
在本申请的上述任意实施方式中，所述负极活性材料的体积平均粒径D v50满足：8μm≤D v50≤16μm；可选的，9.5μm≤D v50≤14.5μm。负极活性材料的D v50在所给范围内，能进一步提高电池的快速充电能力。此外，电池的循环寿命也能得到提升。
在本申请的上述任意实施方式中，所述负极膜层的面密度CW满足：0.09kg/m 2≤CW≤0.117kg/m 2；可选的，所述负极膜层的面密度CW满足：0.094kg/m 2≤CW≤0.107kg/m 2。负极膜层的面密度在上述范围内，可提高电池的能量密度和快速充电能力。
在本申请的上述任意实施方式中，所述负极膜层的压实密度PD满足：1.5g/m 3≤PD≤1.7g/m 3；可选的，所述负极膜层的压实密度PD满足：1.53≤PD≤1.68g/m 3。负极膜层的压实密度在上述范围内，可提高电池的快速充电能力和循环性能。
在本申请的上述任意实施方式中，所述负极活性材料包括人造石墨；可选的，所述人造石墨在所述负极活性材料中的质量占比≥60％；可选的，所述人造石墨在所述负极活性材料中的质量占比为80％～100％。负极活性材料满足上述条件，能使电池获得更高的快速充电能力和更长的循环寿命。
在本申请的上述任意实施方式中，所述负极活性材料包括天然石墨；可选的，所述天然石墨在所述负极活性材料中的质量占比≤40％；可选的，所述天然石墨在所述负极活性材料中的质量占比为10％～30％。负极活性材料满足上述条件，能进一步提高电池的快速充电能力。
在本申请的上述任意实施方式中，所述负极活性材料包括二次颗粒；可选的，所述二次颗粒在所述负极活性材料的数量占比≥60％；可选的，所述二次颗粒在所述负极活性材料的数量占比为80％～100％。负极活性材料满足上述条件，能进一步提升电池的快速充电能力，还能进一步改善电池的循环寿命。
在本申请的上述任意实施方式中，所述负极活性材料的粒度一致性(Uniformity)为0.3～0.4；可选的，所述负极活性材料的粒度一致性(Uniformity)为0.31～0.36。负极活性材料的粒度一致性(Uniformity)在所给范围内，能进一步提升电池的快速充电能力，还能进一步改善电池的循环寿命和能量密度。
在本申请的上述任意实施方式中，所述负极活性材料的粒度跨度(D v90-D v10)/D v50满 足：1.0≤(D v90-D v10)/D v50≤1.4；可选的，1.1≤(D v90-D v10)/D v50≤1.3。负极活性材料的粒度跨度(D v90-D v10)/D v50在所给范围内，能进一步改善电池的快速充电能力。
在本申请的上述任意实施方式中，所述负极活性材料的石墨化度为93％～95％；可选的，所述负极活性材料的石墨化度为93.5％～94.5％。负极活性材料的石墨化度在所给范围内，能进一步提高电池的快速充电能力，还能提高电池的循环寿命。
在本申请的上述任意实施方式中，所述负极活性材料的粉体OI值为2.5～4.5；可选的，所述负极活性材料的粉体OI值为3～4。负极活性材料的粉体OI值在所给范围内，能进一步提高电池的快速充电能力，还能提高电池的循环寿命。
在本申请的上述任意实施方式中，所述负极活性材料的振实密度为0.8g/cm 3～1.2g/cm 3；可选的，所述负极活性材料的振实密度为0.9g/cm 3～1.1g/cm 3。负极活性材料的振实密度在所给范围内，能使电池获得更高的能量密度，还能进一步改善电池的快速充电能力。
在本申请的上述任意实施方式中，所述负极活性材料在30kN压力下的粉体压实密度为1.65g/cm 3～1.85g/cm 3；可选的，所述负极活性材料在30kN压力下的粉体压实密度为1.7g/cm 3～1.8g/cm 3。负极活性材料在30kN压力下的粉体压实密度在所给范围内，可提升电池的能量密度。
在本申请的上述任意实施方式中，所述负极活性材料的克容量为350mAh/g～360mAh/g；可选的，所述负极活性材料的克容量为352mAh/g～358mAh/g。采用该容量区间的负极活性材料可保证电池具有较高的能量密度和快速充电能力。
在本申请的上述任意实施方式中，所述负极膜层的孔隙率P满足：25％≤P≤45％；可选的，所述负极膜层的孔隙率P满足：28％≤P≤35％。负极膜层的孔隙率在上述范围内，可提高电池的能量密度和快速充电能力。
在本申请的上述任意实施方式中，所述负极膜层与所述负极集流体之间的粘结力F满足：4.5N/m≤F≤15N/m；可选的，所述负极膜层与所述负极集流体之间的粘结力F满足：8N/m≤F≤12N/m。负极膜层与负极集流体之间的粘结力在上述范围内，可提高电池的快速充电能力和循环性能。
在本申请的上述任意实施方式中，所述二次电池包括正极极片，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含正极活性材料的正极膜层，所述正极活性材料包括锂镍钴锰氧化物、锂镍钴铝氧化物、磷酸铁锂、磷酸铁锂与碳的复合材料、以及它们各自的改性化合物中的一种或几种。
本申请第二方面提供一种二次电池的制造方法，其包括采用如下的方法制备负极极 片的步骤：提供负极活性材料，所述负极活性材料包括石墨；使所述负极活性材料形成负极浆料；将所述负极浆料涂覆于负极集流体的至少一个表面，使其形成负极膜层，得到负极极片；其中，所述负极极片满足：当将所述负极极片与锂金属片组成扣式电池，并将扣式电池以0.05C放电至5.0mV时，其容量增量曲线V-dQ/dV在0.055V～0.085V的位置具有石墨的三阶嵌锂相变峰。
本申请提供的制造方法所得到的二次电池中，负极极片的负极活性材料包括石墨，且所述负极极片满足：当将负极极片与锂金属片组成扣式电池，并将所述扣式电池以0.05C放电至5.0mV时，所得到的容量增量曲线V-dQ/dV在0.055V～0.085V的位置具有石墨的三阶嵌锂相变峰，由此可以使得负极极片具有较高的可逆容量的同时，还具有较高的脱嵌活性离子能力，大幅度提升活性离子在正负极之间的移动速度，从而使得二次电池在具有较高能量密度的前提下，显著提高快速充电能力和循环寿命。
本申请第三方面提供一种电池模块，其包括根据本申请第一方面的二次电池、或根据本申请第二方面的制造方法得到的二次电池。
本申请第四方面提供一种电池包，其包括根据本申请第三方面的电池模块。
本申请第五方面提供一种装置，其包括根据本申请第一方面的二次电池、根据本申请第二方面的制造方法得到的二次电池、根据本申请第三方面的电池模块、或根据本申请第四方面的电池包中的至少一种。
本申请的电池模块、电池包和装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
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为本申请实施例2提供的一种二次电池的负极极片与锂金属片组成的扣式电池以0.05C放电至5.0mV的容量增量曲线V-dQ/dV图。
图2为本申请对比例2提供的一种二次电池的负极极片与锂金属片组成的扣式电池以0.05C放电至5.0mV的容量增量曲线V-dQ/dV图。
图3是二次电池的一实施方式的示意图。
图4是图3的分解图。
图5是电池模块的一实施方式的示意图。
图6是电池包的一实施方式的示意图。
图7是图6的分解图。
图8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，“一种或几种”中“几种”的含义是两种及两种以上。
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。
二次电池
本申请第一方面的实施方式提供一种二次电池。该二次电池包括正极极片、负极极片和电解质。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。
[负极极片]
本申请的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层，所述负极活性材料包括石墨，且所述负极极片满足：当将所述负极极片与锂金属片组成扣式电池，并将所述扣式电池以0.05C放电至5.0mV，其容量增量曲线V-dQ/dV在0.055V～0.085V的位置具有石墨的三阶嵌锂相变峰。
本领域的技术人员应该知晓，当石墨在嵌锂反应过程中，其在容量增量曲线V-dQ/dV 中有4个嵌锂相变峰(一阶、二阶、三阶和四阶)，分别对应石墨在嵌锂过程中的4个不同相变阶段。也就是说，4个嵌锂相变峰是石墨嵌锂特性的外在表现。具体来说，参照图1，四阶嵌锂相变峰(4#峰)对应石墨(C)向四阶石墨层间化合物(LiC 36)转变的相变过程；三阶嵌锂相变峰(3#峰)对应四阶石墨层间化合物(LiC 36)向三阶石墨层间化合物(LiC 27)转变的相变过程(以下简称三阶嵌锂相变过程)；二阶嵌锂相变峰(2#峰)对应三阶石墨层间化合物(LiC 27)向二阶石墨层间化合物(LiC 12)转变的相变过程；一阶嵌锂相变峰(1#峰)对应二阶石墨层间化合物(LiC 12)向一阶石墨层间化合物(LiC 6)转变的相变过程。其中，石墨的各阶嵌锂相变峰的峰位以该相变峰的峰值(在本申请中峰值是指该相变峰的最低点)对应的电压计。
本发明人经锐意研究首次发现，当负极极片的负极活性材料包括石墨，且负极极片满足：将该负极极片与锂金属片组装成扣式电池，并将该扣式电池以0.05C放电至5.0mV(即，以0.05C对负极极片进行嵌锂，直至扣式电池的电压为5.0mV)，其容量增量曲线V-dQ/dV在0.055V～0.085V的位置具有石墨的三阶嵌锂相变峰时，采用该负极极片的二次电池可以在较高能量密度的前提下，显著提高快速充电能力和循环寿命。
不希望限于任何理论，本发明人经过大量研究首次发现，当三阶嵌锂峰的峰位在上述范围内时，负极极片更容易发生三阶嵌锂相变过程的嵌锂反应，锂离子在正负极之间的移动速度得到大幅度提升，从而能显著提高二次电池的快速充电能力。同时，电池在大倍率充电时的极化较小，使得电池的容量利用率和循环容量保持率较高。因此，采用该负极极片的电池能在较高能量密度下，获得更好的快速充电能力和更长的循环寿命。
在一些实施方式中，可选的，所述负极极片与锂金属片组成的扣式电池以0.05C放电至5.0mV的容量增量曲线V-dQ/dV中，三阶嵌锂峰的峰位可以在0.055V～0.083V，0.057V～0.083V，0.057V～0.077V，0.06V～0.082V，0.06V～0.08V，0.061V～0.074V，0.063V～0.083V，0.063V～0.075V，0.065V～0.083V，0.065V～0.080V，0.065V～0.078V，或0.068V～0.075V等。三阶嵌锂相变峰的峰位在所给范围内，能进一步改善二次电池的快速充电能力和循环寿命。
在一些实施方式中，所述负极极片与锂金属片组成的扣式电池以0.05C放电至5.0mV的容量增量曲线V-dQ/dV中，三阶嵌锂峰的峰强度为-3Ah/V/g～-15Ah/V/g。当三阶嵌锂相变峰的峰强度在适当范围内时，负极极片具有较高的实际嵌锂容量。因此，采用该负极极片的电池能同时兼顾较高的快速充电能力和能量密度。可选的，三阶嵌锂相变峰的峰强度可以为-4～-13Ah/V/g，-5～-12Ah/V/g，-4～-10Ah/V/g，-5～-10Ah/V/g，或-5～-8Ah/V/g等。
需要说明的是，本申请所记载的“扣式电池”仅为了表征本申请的负极极片的特征，其制备过程可参考国家标准或行业规范。作为示例，可以将负极极片制成圆形电极片，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。例如将碳酸亚乙酯(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均匀溶解于有机溶剂中，得到电解液，其中LiPF 6的浓度可以为1mol/L。在负极极片与锂金属小圆片之间设置隔离膜以起到隔离的作用。隔离膜可以是行业内惯用的隔离膜，例如聚乙烯(PE)隔离膜。扣式电池可以是行业内惯用的型号，例如CR2430型。扣式电池的组装例如在氩气保护的手套箱中进行。
将负极极片与锂金属片制备成的扣式电池，在25℃下，以0.05C放电至电压为5.0mV，采集电池的电压V和容量Q；计算一个单位电压变化(dV)对应的容量增量dQ/dV；然后绘制出容量增量曲线V-dQ/dV。可以通过采集的电压V和容量Q数据，在EXCEL中利用SLOPE函数计算得到dQ/dV。本文中的单位电压变化dV可以为0.2V～0.5V(例如0.3V)。在此，用扣式电池测试负极极片的容量以及容量增量是本领域公知的方法。
上述制备扣式电池所用的负极极片可以在负极极片的制备工序中取样，也可以将二次电池拆解后取样。
可以理解的是，负极膜层可以是设置在负极集流体自身厚度方向相对的两个表面中的任意一者或两者上。
在本申请的负极极片中，可以通过调整负极活性材料的种类、结构参数(例如本文所描述的材料结构参数)，以及负极极片的结构参数(例如本文所描述的极片结构参数)中的一种或几种，来将所述V-dQ/dV曲线中石墨的三阶嵌锂相变峰的峰位控制在本申请所给的范围内。
在本申请的负极极片中，负极活性材料可包括人造石墨和天然石墨中的一种或几种。
在一些实施方式中，可选的，负极活性材料包括人造石墨。人造石墨在嵌锂过程中的体积变化较小，有利于负极极片保持较高的电解液浸润性和保持量，锂离子在负极极片孔隙间的扩散更加容易，由此有利于石墨嵌锂反应的进行，使三阶嵌锂相变峰的峰位满足需求。并且，人造石墨的结构稳定性较高，循环过程中的副反应较少，由此能使电池获得较高的循环寿命。
在一些实施方式中，可选的，所述人造石墨在所述负极活性材料中的质量占比≥60％。例如，所述人造石墨在所述负极活性材料中的质量占比可以为70％～100％，75％～ 100％，80％～100％，或90％～100％等。
在一些实施方式中，负极活性材料还可包括天然石墨。天然石墨的表面嵌锂位点较多，电荷交换阻抗较小，同时天然石墨内部石墨层缺陷较少，锂离子在其中的固相扩散能力更高，因此在负极活性材料中包含适量的天然石墨，能进一步改善石墨的嵌锂反应性能，提高电池的快速充电能力。
在一些实施方式中，可选的，天然石墨在负极活性材料中的质量占比≤40％。例如，天然石墨在负极活性材料中的质量占比可以为10％～40％，20％～40％，10％～30％，或15％～25％等。天然石墨在负极活性材料中的质量占比在适当范围内，能更好地平衡二次电池的快速充电能力和循环寿命。
本申请的负极极片中，负极活性材料除了包括本申请上述的负极活性材料外，还可选地包括一定量的其它常用负极活性材料，例如软炭、硬炭、硅基材料、锡基材料、钛酸锂中的一种或几种。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅合金中的一种或几种。所述锡基材料可选自单质锡、锡氧化合物、锡合金中的一种或几种。
本申请所使用的负极活性材料均可以通过商业途径获得或采用本领域公知的方法制备得到。作为示例，人造石墨可按如下方法制备：将石油焦粉碎，粉碎产物的体积平均粒径D v50可以为5μm～10μm，5.5μm～7.5μm，6.5μm～8.5μm，或7.5μm～9.5μm等；对粉碎后的石油焦进行整形、分级处理，得到前驱体。可选的对前驱体进行造粒的步骤，其中可以在有机碳源存在或不存在的条件下对前驱体进行造粒，得到造粒型的前驱体。对前驱体在2800℃～3200℃的温度下进行石墨化处理，得到人造石墨。可选的，还可以采用有机碳源对石墨化处理产物进行包覆，经炭化处理后，得到包覆改性的人造石墨。造粒及包覆用有机碳源可独立地选自本领域公知的材料，例如沥青、聚丙烯腈、环氧树脂、酚醛树脂等。可选的，所述石墨焦的挥发份含量为3％～8％(质量百分含量)。可选的，所述石油焦包括石油生焦。
在一些实施方式中，可选的，负极活性材料的体积平均粒径D v50满足8μm≤D v50≤16μm。例如，负极活性材料的D v50可以为8μm～14μm，8μm～11μm，10μm～14μm，9μm～15μm，9.5μm～14.5μm，或13μm～16μm等。负极活性材料的D v50在适当范围内，能使其具有较多的快速嵌锂通道，并且使锂离子在颗粒内部的迁移路径较短，提高石墨的嵌锂反应性能。此外，负极活性材料颗粒之间的接触良好，同时可形成适于电解液浸润的丰富孔道结构，能进一步改善石墨的嵌锂性能。因此，通过采用具有合适D v50的负极活性材料，有利于使V-dQ/dV曲线中三阶嵌锂相变峰的峰位满足本申请所给的范围。
负极活性材料的D v50在适当范围内，还能减少电解液在颗粒表面的副反应，并减小 极化现象，从而能提高电池的循环寿命。因此可选的，负极活性材料的D v50可以为9.5μm～14.5μm。
在一些实施方式中，可选的，负极活性材料包括二次颗粒。发明人研究发现，当负极活性材料中含有一定量的二次颗粒时，其可提供的嵌锂通道增多，可进一步改善负极活性材料的嵌锂反应性能，有利于提升电池的快速充电能力。同时还能减小负极极片在嵌锂过程中的膨胀效应，这有利于改善电池的循环寿命。可选的，二次颗粒在负极活性材料的数量占比≥60％。例如，二次颗粒在负极活性材料的数量占比可以为70％～100％，75％～100％，80％～100％，或90％～100％等。
在一些实施方式中，可选的，负极活性材料的粒度一致性(Uniformity)为0.3～0.4。例如，所述负极活性材料的粒度一致性(Uniformity)可以为0.3～0.38，0.31～0.36，0.32～0.4，0.32～0.37，0.34～0.36，或0.33～0.39等。采用该负极活性材料的负极极片，易于形成较短的液相传输路径，由此能进一步改善石墨的嵌锂反应性能，提升电池的快速充电能力。并且，负极极片的颗粒之间能具有较大的接触面积，实现紧密接触，使负极极片获得较高的压实密度，提升电池的能量密度。颗粒与集流体之间也能具有较大的接触面积，使负极极片获得较好的粘结性，有利于负极极片中的电子传导，改善负极活性材料的嵌锂反应性能，同时还降低了负极极片发生脱膜、掉粉的风险，因此能进一步提升电池的快速充电能力和循环寿命。
在一些实施方式中，可选的，负极活性材料的粒度跨度(D v90-D v10)/D v50可满足1.0≤(D v90-D v10)/D v50≤1.4。例如，负极活性材料的(D v90-D v10)/D v50可以为1.0～1.3，1.05～1.35，1.1～1.4，1.1～1.3，或1.15～1.25等。
负极活性材料的(D v90-D v10)/D v50反应了负极活性材料中较大颗粒的粒径和较小颗粒的粒径偏离体积平均粒径D v50的程度。负极活性材料的(D v90-D v10)/D v50适当，有利于使负极活性材料颗粒在负极膜层中具有较高的分散均匀性，由此有利于使负极膜层不同区域处的负极活性材料均表现出较高的嵌锂反应性能，从而改善电池的快速充电能力。
在一些实施方式中，可选的，负极活性材料的石墨化度可以为93％～95％。例如，负极活性材料的石墨化度可以为93.5％～94.5％等。负极活性材料的石墨化度在所给范围内，能使负极活性材料具有较高的可逆容量，同时兼具较大的石墨层间距，从而进一步改善石墨的嵌锂性能，提高电池的快速充电能力。并且，该负极活性材料在充放电过程中的结构稳定性较好，能提高电池的循环寿命。
在一些实施方式中，可选的，负极活性材料的粉体OI值可以为2.5～4.5。例如，负极活性材料的粉体OI值可以为3～4.2，3～4，或3.2～3.8等。负极活性材料的粉体OI值 表征负极活性材料的取向指数。负极活性材料的粉体OI值适当，能使其具有较多的锂离子快速嵌入通道，从而能提高嵌锂性能。并且，负极活性材料的粉体OI值在适当范围内，还能减小负极极片在嵌锂过程中的膨胀效应，改善电池的循环寿命。
在一些实施方式中，可选的，负极活性材料的振实密度为0.8g/cm 3～1.2g/cm 3。例如，负极活性材料的振实密度可以为0.9g/cm 3～1.1g/cm 3等。负极活性材料的振实密度在所给范围内，能使负极膜层具有较高的压实密度，从而有利于使电池获得较高的能量密度。并且，负极膜层中的负极活性材料颗粒之间形成良好接触的同时，还形成通畅的孔道结构，有利于改善负极活性材料的嵌锂性能，从而能改善电池的快速充电能力。
在一些实施方式中，可选的，负极活性材料在30kN压力下的粉体压实密度可以为1.65g/cm 3～1.85g/cm 3。例如，负极活性材料在30kN压力下的粉体压实密度可以为1.7g/cm 3～1.8g/cm 3等。负极活性材料在30kN压力下的粉体压实密度在所给范围内，能使负极膜层具有较高的压实密度，从而可提升电池的能量密度。
在一些实施方式中，可选的，负极活性材料的克容量为350mAh/g～360mAh/g。例如，负极活性材料的克容量可以为352mAh/g～358mAh/g，或353mAh/g～357mAh/g等。采用该容量区间的负极活性材料可保证电池具有较高的能量密度和快速充电能力。
在一些实施方式中，可选的，负极活性材料的至少一部分表面具有包覆层。包覆层能对负极活性材料起到保护作用，大大减少因溶剂共嵌入而造成的石墨层剥离，使负极活性材料具有较高的结构稳定性，由此能使二次电池获得较高的循环寿命。
可选的，可以在负极活性材料80％～100％的表面覆盖包覆层。进一步的，可以在负极活性材料的90％～100％的表面覆盖包覆层。
可选的，所述包覆层包括无定形碳。包含无定形碳的包覆层能使锂离子在颗粒中较快地扩散，从而能改善负极活性材料的嵌锂性能，提升电池的快速充电能力。无定形碳包覆层可以是有机碳源经炭化形成的。例如，有机碳源可选自高分子聚合物，如煤沥青、石油沥青、酚醛树脂、椰壳等材料。
本申请的负极极片中，负极膜层通常包含负极活性材料以及可选的粘结剂、可选的导电剂和其他可选助剂，通常是由负极浆料涂布在负极集流体上，经干燥、冷压而成的。负极浆料涂通常是将负极活性材料以及可选的导电剂、可选的粘结剂、可选助剂等分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水。
作为示例，导电剂可包括超导碳、炭黑(例如Super P、乙炔黑、科琴黑)、碳点、碳纳米管、石墨烯及碳纳米纤维中一种或几种。
作为示例，粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸 树脂、聚乙烯醇(PVA)、海藻酸钠(SA)及羧甲基壳聚糖(CMCS)中的一种或几种。
其他可选助剂例如是增稠剂(如羧甲基纤维素钠CMC-Na)、PTC热敏电阻材料等。
在一些实施方式中，可选的，负极膜层的面密度CW满足0.09kg/m 2≤CW≤0.117kg/m 2。例如，0.09kg/m 2≤CW≤0.105kg/m 2，0.09kg/m 2≤CW≤0.097kg/m 2，0.09kg/m 2≤CW≤0.095kg/m 2，0.094kg/m 2≤CW≤0.107kg/m 2，0.095kg/m 2≤CW≤0.110kg/m 2，0.095kg/m 2≤CW≤0.105kg/m 2，0.097kg/m 2≤CW≤0.110kg/m 2，或0.105kg/m 2≤CW≤0.117kg/m 2等。
负极膜层的面密度CW是单位面积负极膜层的重量。CW在上述范围内，有助于将石墨的三阶嵌锂峰的峰位控制在本申请所给的范围内。同时，合适的面密度可以使负极极片具有较高的可逆容量，并减小锂离子在极片中的迁移距离，从而进一步改善电池的能量密度和快速充电能力。
在一些实施方式中，可选的，负极膜层的压实密度PD满足1.5g/m 3≤PD≤1.7g/m 3。例如，1.5g/m 3≤PD≤1.65g/m 3，1.5g/m 3≤PD≤1.6g/m 3，1.53g/m 3≤PD≤1.68g/m 3，1.55g/m 3≤PD≤1.65g/m 3，1.55g/m 3≤PD≤1.63g/m 3，1.58g/m 3≤PD≤1.63g/m 3，或1.6g/m 3≤PD≤1.7g/m 3等。
负极膜层的压实密度PD是单位体积负极膜层的重量，其等于负极膜层的面密度CW除以负极膜层的厚度。PD在上述范围内，有助于将石墨的三阶嵌锂相变峰的峰位控制在本申请所给的范围内。同时，合适的压实密度可以使负极膜层具有较高的电子电导能力和较低的液相传导阻抗，从而进一步改善电池的快速充电能力和循环性能。
发明人经过深入研究发现，当负极活性材料的参数与负极极片的参数合理设计时，能使电池在具有较高能量密度的前提下，进一步提升电池的快速充电能力和循环寿命。
在一些实施方式中，可选的，负极膜层同时满足：负极活性材料的D v50为8μm～11μm，负极膜层的CW为0.105kg/m 2～0.117kg/m 2，负极膜层的PD为1.5g/m 3～1.6g/m 3，且在V-dQ/dV曲线中，石墨的三阶嵌锂相变峰的峰位在0.07V～0.085V；例如，石墨的三阶嵌锂相变峰的峰位可以在0.07V～0.08V，或0.078V～0.085V等。
在一些实施方式中，可选的，负极膜层同时满足：负极活性材料的D v50为10μm～14μm，负极膜层的CW为0.097kg/m 2～0.110kg/m 2，负极膜层的PD为1.55g/m 3～1.65g/m 3，且在V-dQ/dV曲线中，石墨的三阶嵌锂相变峰的峰位在0.062V～0.078V；例如，石墨的三阶嵌锂相变峰的峰位可以在0.062V～0.072V，或0.068V～0.078V等。
在一些实施方式中，可选的，负极膜层同时满足：负极活性材料的D v50为13μm～ 16μm，负极膜层的CW为0.09kg/m 2～0.097kg/m 2，负极膜层的PD为1.6g/m 3～1.7g/m 3，且在V-dQ/dV曲线中，石墨的三阶嵌锂相变峰的峰位在0.055V～0.067V；例如，石墨的三阶嵌锂相变峰的峰位可以在0.055V～0.06V，或0.059V～0.067V等。
在一些实施方式中，可选的，负极膜层的孔隙率P满足25％≤P≤45％。例如，25％≤P≤42％，28％≤P≤40％，28％≤P≤38％，28％≤P≤35％，30％≤P≤43％，30％≤P≤40％，或30％≤P≤38％等。P在上述范围内，能使负极极片具有适宜的电解液浸润性能和良好的反应界面，降低了锂离子在负极极片传导的液相阻抗，从而能改善负极活性材料的嵌锂性能，提高电池的快速充电能力。此外，合适的P还能使负极膜层具有适宜的电解液保持量的同时，使得电池具有较低的重量，提升电池的能量密度。
在一些实施方式中，可选的，负极膜层与负极集流体之间的粘结力F满足4.5N/m≤F≤15N/m。例如，5N/m≤F≤14N/m，7N/m≤F≤15N/m，6N/m≤F≤13N/m，或8N/m≤F≤12N/m等。负极膜层与负极集流体之间的粘结力F较大，使得负极极片具有良好的电子传导能力，这有利于改善负极活性材料的嵌锂性能。并且，F还体现了负极极片在循环过程中维持粘接可靠性的能力，有利于电池在全生命周期保持良好的电子传导能力，从而能进一步改善电池的循环性能。
在本申请的负极极片中，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。
在本申请的负极极片中，负极膜层的相关参数均指的是单面负极膜层的参数。当负极膜层设置在负极集流体两个表面上时，其中任意一个表面上的负极膜层的参数满足本申请的数据范围，即认为落入本申请的保护范围内。且本申请所述的石墨的三阶嵌锂峰的峰位、负极膜层的压实密度PD、面密度CW、孔隙率P、粘结力F等范围均是指经冷压压实后并用于组装电池的负极极片的膜层参数。
另外，本申请的负极极片并不排除除了负极膜层之外的其他附加功能层。例如在某些实施方式中，负极极片还包括夹在负极集流体和负极膜层之间、设置于负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施方式中，本申请所述的负极极片还包括覆盖在负极膜层表面的保护层。
在本申请中，负极活性材料的体积平均粒径D v50、粒度一致性(Uniformity)、粒度跨度(D v90-D v10)/D v50均为本领域公知的含义，可采用本领域已知的仪器及方法进行测定。例如可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪(例如Master Size 3000)测定。
其中，负极活性材料的粒度一致性(Uniformity)可以表征负极活性材料中所有颗粒 的粒径偏离负极活性材料的体积平均粒径(D v50)的离散程度，其反映了负极活性材料的粒径分布均匀性。
负极活性材料的粒度跨度(D v90-D v10)/D v50反应了负极活性材料中较大颗粒的粒径和较小颗粒的粒径偏离体积平均粒径(Dv50)的程度。
D v10表示负极活性材料累计体积分布百分数达到10％时所对应的粒径。
D v50表示负极活性材料累计体积分布百分数达到50％时所对应的粒径。
D v90表示负极活性材料累计体积分布百分数达到90％时所对应的粒径。
负极活性材料的石墨化度为本领域公知的含义，可以用本领域已知的仪器及方法测定。例如可使用X射线粉末衍射仪(例如Bruker D8 Discover)测出d 002的大小，测试可参考JIS K 0131-1996、JB/T 4220-2011；然后根据公式G＝(0.344-d 002)/(0.344-0.3354)×100％计算得出石墨化度G，其中d 002是以纳米(nm)计的石墨晶体结构中的层间距。
在本申请的X射线衍射分析测试中，可以采用铜靶作为阳极靶，以CuKα射线为辐射源，射线波长
Figure PCTCN2020106076-appb-000001
扫描2θ角范围为20°～80°，扫描速率可以为4°/min。
负极活性材料的粉体OI值为本领域公知的含义，可以用本领域已知的仪器及方法测定。例如可使用X射线粉末衍射仪(例如Bruker D8 Discover)，依据JIS K 0131-1996、JB/T4220-2011，得到负极活性材料的X射线衍射谱图；然后根据OI值＝C 004/C 110计算得到负极活性材料的粉体OI值。其中，C 004为石墨004晶面的特征衍射峰的峰面积，C 110为石墨110晶面的特征衍射峰的峰面积。
负极活性材料的振实密度CW为本领域公知的含义，可以用本领域已知的仪器及方法测定。例如可参照标准GB/T 5162-2006，使用粉体振实密度测定仪(例如丹东百特BT-300型)方便地测定。
负极活性材料的粉体压实密度PD为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。例如可以参照标准GB/T24533-2009，通过电子压力试验机(例如UTM7305型)测定。示例性测试方法如下：称取1g负极活性材料，加入底面积为1.327cm 2的模具中，加压至3000kg(相当于30kN)，保压30s，然后卸压，保持10s，然后记录并计算得到负极活性材料在30kN压力下的粉体压实密度。
在本申请中，一次颗粒和二次颗粒均为本领域公知的含义。其中，一次颗粒是指非团聚态颗粒；二次颗粒是指由两个或两个以上一次颗粒聚集而成的团聚态的颗粒。
二次颗粒在负极活性材料中的数量占比可采用本领域已知的方法测试。示例性测试方法如下：将负极活性材料铺设并粘于导电胶上，制成长×宽＝6cm×1.1cm的待测样品；使用扫描电子显微镜(例如ZEISS Sigma 300)对颗粒形貌进行测试。测试可参考 JY/T010-1996。为了确保测试结果的准确性，可在待测样品中随机选取多个(例如20个)不同区域进行扫描测试，并在一定放大倍率(例如1000倍)下，计算各区域中二次颗粒数量占总颗粒数量的百分比，即为该区域中二次颗粒的数量占比，取多个测试区域的测试结果的平均值作为二次颗粒在负极活性材料中的数量占比。
负极活性材料的克容量为本领域公知的含义，可采用本领域已知的方法测试。负极活性材料克容量的示例性测试方法如下：将负极活性材料、导电剂炭黑(Super P)、粘结剂PVDF按质量比91.6:1.8:6.6与溶剂NMP(N-甲基吡咯烷酮)混合均匀，制成浆料；将制备好的浆料涂覆于铜箔集流体上，于烘箱中干燥后备用。以金属锂片为对电极，聚乙烯(PE)薄膜作为隔离膜。将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按体积比1:1:1混合，然后将LiPF 6均匀溶解在上述溶液中得到电解液，其中LiPF 6的浓度为1mol/L。在氩气保护的手套箱组装成CR2430型扣式电池。将所得扣式电池静置12小时后，以0.05C的电流恒流放电至0.005V，静置10分钟，以50μA的电流再恒流放电至0.005V，静置10分钟，以10μA的电流再恒流放电至0.005V；然后以0.1C的电流恒流充电至2V，记录充电容量。充电容量与负极活性材料质量的比值即为负极活性材料的克容量。
负极膜层的面密度为本领域公知的含义，可采用本领域已知的方法测试。例如取单面涂布且经冷压后的负极极片(若是双面涂布的负极极片，可先擦拭掉其中一面的负极膜层)，冲切成面积为S1的小圆片，称其重量，记录为M1。然后将上述称重后的负极极片的负极膜层擦拭掉，称量负极集流体的重量，记录为M0，负极膜层面密度＝(负极极片的重量M1-负极集流体的重量M0)/S1。
负极膜层的压实密度为本领域公知的含义，可采用本领域已知的方法测试。负极膜层的压实密度＝负极膜层的面密度/负极膜层的厚度。
负极膜层的厚度为本领域公知的含义，可采用本领域已知的方法测试。例如采用4位精度的螺旋测微仪。
负极膜层的孔隙率为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。例如可参考GB/T24586-2009，采用气体置换法测量。示例性测试方法如下：取单面涂布且经冷压后的负极极片(若是双面涂布的负极极片，可先擦拭掉其中一面的负极膜层)，冲切成直径为14mm的小圆片样品；测试负极膜层的厚度(负极极片的厚度-负极集流体的厚度)；按照圆柱体积计算公式，计算负极膜层的表观体积V1；使用非活性气体如氦气或氮气作为介质，采用气体置换法，利用真密度测试仪(例如Micromeritics AccuPyc II 1340型)测得负极极片的真实体积，测试可参考GB/T 24586-2009；负极极片 的真实体积减去负极集流体的体积，得到负极膜层的真实体积V2；负极膜层的孔隙率＝(V1-V2)/V1×100％。可取多片(如30片)极片样品进行测试，结果取平均值，可提高测试结果的准确性。
负极膜层与负极集流体之间的粘结力为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。将负极极片裁成长100mm、宽10mm的测试样品。取一条宽度25mm的不锈钢板，贴双面胶(宽度11mm)，将测试样品粘贴在不锈钢板上的双面胶上，用2000g压辊在其表面来回滚压三次(300mm/min)。将测试样品180度弯折，手动将测试样品的负极膜片与集流体剥开25mm，将该测试样品固定在试验机(例如INSTRON 336)上，使剥离面与试验机力线保持一致，试验机以30mm/min连续剥离，得到的剥离力曲线，取平稳断的均值作为剥离力F0，则测试样品中负极膜层与集流体之间的粘结力F＝F0/测试样品的宽度(F的计量单位：N/m)。
[正极极片]
在本申请的二次电池中，正极极片可包括正极集流体以及设置于正极集流体至少一个表面上且包含正极活性材料的正极膜层。例如，正极集流体具有在自身厚度方向相对的两个表面，正极膜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。
本申请的二次电池中，所述正极活性材料可采用本领域公知的用于二次电池的正极活性材料。可选的，正极活性材料可以选自锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及它们各自的改性材料中的一种或几种。可选的，所述锂过渡金属氧化物可选自锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及它们各自的改性材料中的一种或几种。可选的，所述橄榄石结构的含锂磷酸盐可选自磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及它们各自的改性材料中的一种或几种。所述改性材料可以是对材料进行包覆改性和/或掺杂改性。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，正极活性材料可包括锂镍钴锰氧化物、锂镍钴铝氧化物、磷酸铁锂、磷酸铁锂与碳的复合材料、以及它们各自的改性化合物中的一种或几种。例如，正极活性材料可包括锂镍钴锰氧化物、锂镍钴铝氧化物、以及它们各自的改性化合物中的一种或几种。
本申请的二次电池中，所述正极膜层通常包含正极活性材料以及可选的粘结剂和可选的导电剂，通常是由正极浆料涂布，并经干燥、冷压而成的。正极浆料通常是将正极 活性材料以及可选的导电剂和粘结剂等分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)。
作为示例，用于正极膜层的粘结剂可以包括聚偏氟乙烯(PVDF)和聚四氟乙烯(PTFE)、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几种。
作为示例，用于正极膜层的导电剂可以包括超导碳、炭黑(如Super P、乙炔黑、科琴黑)、碳点、碳纳米管、石墨烯及碳纳米纤维中一种或几种。
本申请的二次电池中，所述正极集流体可采用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。
[电解质]
在本申请的二次电池中，对电解质的种类没有具体的限制，可根据需求进行选择。所述电解质可以选自固态电解质、液态电解质(即电解液)中的至少一种。
在一些实施方式中，电解质采用电解液。所述电解液包括电解质锂盐和溶剂。
可选的，锂盐可选自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)中的一种或几种。
可选的，溶剂可选自碳酸亚乙酯(EC)、碳酸亚丙基酯(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。
在一些实施方式中，电解液中还可选地包括添加剂。例如添加剂可包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。隔离膜设置在正极极片和负极极片 之间，起到隔离的作用。本申请的二次电池对隔离膜的种类没有特别的限制，可以选用任意公知的用于二次电池的多孔结构隔离膜。例如，隔离膜可选自玻璃纤维薄膜、无纺布薄膜、聚乙烯薄膜、聚丙烯薄膜、聚偏二氟乙烯薄膜、以及包含它们中的一种或两种以上的多层复合薄膜中的一种或几种。
在一些实施方式中，二次电池可包括外包装。外包装用于封装正极极片、负极极片和电解质。
在一些实施方式中，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。
可以采用本领域公知的方法制备二次电池。例如，将正极极片、隔离膜及负极极片经卷绕工艺或叠片工艺形成电极组件，其中隔离膜处于正极极片与负极极片之间起到隔离的作用；将电极组件置于外包装中，注入电解液并封口，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3是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图4，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5是作为一个示例的电池模块4。参照图5，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6和图7是作为一个示例的电池包1。参照图6和图7，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
本申请的第二方面提供一种装置，所述装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。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8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。
一、负极活性材料的制备
本申请实施例的负极活性材料可以通过商购获得，也可以通过如下方法制备获得。
1、人造石墨A可以按如下方法制备：采用石油生焦，其挥发份含量为10％，粉碎得到体积平均粒径D v50为6.5μm的石油生焦原料；对所述石油生焦原料进行整形、分级处理，得到前驱体；前驱体混合5％沥青后在600℃进行造粒，然后在3000℃的温度下进行石墨化处理；对石墨化产物用沥青进行包覆炭化处理，得到人造石墨A。人造石墨A的体积平均粒径D v50控制在9.5μm，粒度一致性(Uniformity)控制在0.36，克容量控制在352mAh/g。
2、人造石墨B可以按如下方法制备：采用石油生焦，其挥发份含量为8％，粉碎得到体积平均粒径D v50为7.5μm的石油生焦原料；对所述石油生焦原料进行整形、分级处理， 得到前驱体；前驱体混合8％沥青后在600℃进行造粒，然后在3000℃的温度下进行石墨化处理；对石墨化产物用沥青进行包覆炭化处理，得到人造石墨B。人造石墨B的体积平均粒径D v50控制在12μm，粒度一致性(Uniformity)控制在0.34，克容量控制在355mAh/g。
3、人造石墨C可以按如下方法制备：采用石油生焦，其挥发份含量为6％，粉碎得到体积平均粒径D v50为8.5μm的石油生焦原料；对所述石油生焦原料进行整形、分级处理，得到前驱体；前驱体混合10％沥青后在600℃进行造粒，然后在3000℃的温度下进行石墨化处理；对石墨化产物用沥青进行包覆炭化处理，得到人造石墨C。人造石墨C的体积平均粒径D v50控制在14.5μm，粒度一致性(Uniformity)控制在0.34，克容量控制在358mAh/g。
4、天然石墨：购于贝特瑞新材料集团股份有限公司，型号AGP-8-3，体积平均粒径D v50约为12.5μm，粒度一致性(Uniformity)约为0.41，克容量364mAh/g。
二、电池的制备
实施例1
负极极片的制备
将负极活性材料人造石墨(A)、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)以及导电剂炭黑(Super P)以96.2:1.8:1.2:0.8的重量比在适量的去离子水中充分搅拌混合，使其形成均匀的负极浆料；将负极浆料涂覆于负极集流体铜箔的表面上，经干燥、冷压、分条、裁切，得到负极极片，所述负极极片的压实密度为1.53g/cm 3，面密度为0.107kg/m 2。
正极极片的制备
将正极活性材料锂镍钴锰氧化物LiNi0.5Co0.2Mn0.3O2(NCM523)、导电剂碳纳米管(CNT)和导电剂炭黑(Super P)、粘结剂PVDF按97.5:0.5:0.9:1.1的重量比在适量的溶剂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的表面上，经干燥、冷压后，得到正极极片。其中，正极膜层的面密度为0.178kg/m 2，压实密度为3.4g/cm 3。
隔离膜
采用聚乙烯(PE)薄膜。
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)体积比1:1:1混合，然后将LiPF 6均匀溶解在上述溶液中得到电解液，其中LiPF 6的浓度为1mol/L。
二次电池的制备
将正极极片、隔离膜、负极极片按顺序堆叠，并在隔离膜和负极极片之间增加参比电极(参比电极用于电池样品后续的性能检测，可选择锂片、锂金属丝等，且参比电极应通过隔离膜隔开，防止和正负极任一侧接触)，经卷绕后得到电极组件；将电极组件加入外包装中，加入上述电解液，经封装、静置、化成、老化等工序，得到二次电池。
实施例2～10和对比例1～4与实施例1的制备方法相似，但是调整了负极极片和正极极片的设计参数，不同的产品参数详见表2。
测试部分
(1)石墨相变峰的峰位测试
扣式电池的制备：取上述各实施例及对比例中的负极极片，分别以金属锂片为对电极，聚乙烯(PE)薄膜作为隔离膜。将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按体积比1:1:1混合，然后将LiPF 6均匀溶解在上述溶液中得到电解液，其中LiPF 6的浓度为1mol/L。在氩气保护的手套箱组装成CR2430型扣式电池。
在25℃下，将所得扣式电池静置8小时后，以0.05C恒流放电至电压为5.0mV，收集电压和容量数据；然后在EXCEL中利用SLOPE函数，计算得到dQ/dV，其中单位电压变化dV为0.3V；绘制出容量增量曲线V-dQ/dV图，即可得到对应相变峰的峰位。
(2)快速充电能力测试
25℃下，将实施例和对比例制备得到的二次电池以0.33C恒流充电至充电截止电压4.4V，之后恒压充电至电流为0.05C，静置5min，再以0.33C恒流放电至放电截止电压2.8V，记录其实际容量为C 0。
然后将电池依次以0.5C 0、1C 0、1.5C 0、2C 0、2.5C 0、3C 0、3.5C 0、4C 0、4.5C 0恒流充电至全电池充电截止电压4.4V或者0V负极截止电位(以先达到者为准)，每次充电完成后需以1C 0放电至全电池放电截止电压2.8V，记录不同充电倍率下充电至10％、20％、30％……80％SOC(State of Charge，荷电状态)时所对应的负极电位，绘制出不同SOC态下的倍率-负极电位曲线，线性拟合后得出不同SOC态下负极电位为0V时所对应的充电倍率，该充电倍率即为该SOC态下的充电窗口，分别记为C 10％SOC、C 20％SOC、C 30％SOC、C 40％SOC、C 50％SOC、C 60％SOC、C 70％SOC、C 80％SOC，根据公式(60/C 20％SOC+60/C 30％SOC+60/C 40％SOC+60/C 50％SOC+60/C 60％SOC+60/C 70％SOC+60/C 80％SOC)×10％计算得到该电池从10％SOC充电至80％SOC的充电时间T(min)。该时间越短，则代表电池的快速充电能力越优秀。
(3)循环寿命测试
25℃下，将实施例和对比例制备得到的二次电池以0.33C恒流充电至充电截止电压4.4V，之后恒压充电至电流为0.05C，静置5min，再以0.33C恒流放电至放电截止电压2.8V，记录其初始容量为C 0。然后按照表1所述策略进行充电，0.33C放电，记录每次循环的放电容量C n，直至循环容量保持率(C n/C 0×100％)为80％，记录循环圈数。循环圈数越多，则代表电池的循环寿命越高。
表1
电池的荷电状态SOC 充电倍率(C)
0～10％ 0.33
10％～20％ 6.5
20％～30％ 5
30％～40％ 4.5
40％～50％ 3.5
50％～60％ 3
60％～70％ 2.5
70％～80％ 2
80％～100％ 0.33
各实施例和对比例的测试结果示于表2。
表2
Figure PCTCN2020106076-appb-000002
由表2的结果可知，当负极极片的负极活性材料包括石墨，且负极极片满足：当将负极极片与锂金属片组成的扣式电池，以0.05C放电至5.0mV，其容量增量曲线V-dQ/dV在0.055V～0.085V的位置具有石墨的三阶嵌锂峰时，二次电池可以同时兼顾较好的快速充电能力和较高的循环寿命。
特别是，当V-dQ/dV曲线在0.061V～0.074V的位置具有石墨的三阶嵌锂峰时，电池的快速充电能力和循环寿命均得到进一步改善。
对比例1-4由于不满足上述条件，导致电池难以同时兼顾快速充电能力和循环寿命。
本申请的各实施例的正极活性材料仅以锂镍钴锰氧化物(NCM523)为例，本领域的技术人员可以根据电池的实际使用环境选择不同的正极活性材料。例如，可以选择其它种类的锂镍钴锰氧化物(如NCM622、NCM811等)、锂镍钴铝氧化物、磷酸铁锂、磷酸铁锂与碳的复合材料、以及它们各自的改性化合物等中的一种或几种。本申请所述的负极极片与上述各正极活性材料搭配使用时，可以起到类似的改善效果。此处不再赘述。
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 (17)

  1. 一种二次电池，包括负极极片，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面上且包含负极活性材料的负极膜层，所述负极活性材料包括石墨，且所述负极极片满足：当将所述负极极片与锂金属片组成扣式电池，并将所述扣式电池以0.05C放电至5.0mV时，其容量增量曲线V-dQ/dV在0.055V～0.085V的位置具有石墨的三阶嵌锂相变峰。
  2. 根据权利要求1所述的二次电池，其中，所述容量增量曲线V-dQ/dV在0.057V～0.077V的位置具有石墨的三阶嵌锂相变峰；可选的，所述容量增量曲线V-dQ/dV在0.061V～0.074V的位置具有石墨的三阶嵌锂相变峰。
  3. 根据权利要求1-2任一项所述的二次电池，其中，所述石墨的三阶嵌锂相变峰的峰强度为-3Ah/V/g～-15Ah/V/g。
  4. 根据权利要求1-3任一项所述的二次电池，其中，所述负极活性材料的体积平均粒径D v50满足：8μm≤D v50≤16μm；可选的，9.5μm≤D v50≤14.5μm。
  5. 根据权利要求1-4任一项所述的二次电池，其中，所述负极膜层的面密度CW满足：0.09kg/m 2≤CW≤0.117kg/m 2；可选的，所述负极膜层的面密度CW满足：0.094kg/m 2≤CW≤0.107kg/m 2。
  6. 根据权利要求1-5任一项所述的二次电池，其中，所述负极膜层的压实密度PD满足：1.5g/m 3≤PD≤1.7g/m 3；可选的，所述负极膜层的压实密度PD满足：1.53g/m 3≤PD≤1.68g/m 3。
  7. 根据权利要求1-6任一项所述的二次电池，其中，所述负极活性材料包括人造石墨；可选的，所述人造石墨在所述负极活性材料中的质量占比≥60％；可选的，所述人造石墨在所述负极活性材料中的质量占比为80％～100％。
  8. 根据权利要求1-7任一项所述的二次电池，其中，所述负极活性材料包括天然石墨；可选的，所述天然石墨在所述负极活性材料中的质量占比≤40％；可选的，所述天然石墨在所述负极活性材料中的质量占比为10％～30％。
  9. 根据权利要求1-8任一项所述的二次电池，其中，所述负极活性材料包括二次颗粒；可选的，所述二次颗粒在所述负极活性材料的数量占比≥60％；可选的，所述二次颗粒在所述负极活性材料的数量占比为80％～100％。
  10. 根据权利要求1-9任一项所述的二次电池，其中，所述负极活性材料的粒度一致 性(Uniformity)为0.3～0.4；可选的，所述负极活性材料的粒度一致性(Uniformity)为0.31～0.36。
  11. 根据权利要求1-10任一项所述的二次电池，其中，所述负极活性材料还满足下述(1)～(6)中的一个或几个：
    (1)所述负极活性材料的粒度跨度(D v90-D v10)/D v50满足：1.0≤(D v90-D v10)/D v50≤1.4；可选的，1.1≤(D v90-D v10)/D v50≤1.3；
    (2)所述负极活性材料的石墨化度为93％～95％；可选的，所述负极活性材料的石墨化度为93.5％～94.5％；
    (3)所述负极活性材料的粉体OI值为2.5～4.5；可选的，所述负极活性材料的粉体OI值为3～4；
    (4)所述负极活性材料的振实密度为0.8g/cm 3～1.2g/cm 3；可选的，所述负极活性材料的振实密度为0.9g/cm 3～1.1g/cm 3；
    (5)所述负极活性材料在30kN压力下的粉体压实密度为1.65g/cm 3～1.85g/cm 3；可选的，所述负极活性材料在30kN压力下的粉体压实密度为1.7g/cm 3～1.8g/cm 3；
    (6)所述负极活性材料的克容量为350mAh/g～360mAh/g；可选的，所述负极活性材料的克容量为352mAh/g～358mAh/g。
  12. 根据权利要求1-11任一项所述的二次电池，其中，所述负极膜层满足下述(1)～(2)中的一个或几个：
    (1)所述负极膜层的孔隙率P满足：25％≤P≤45％；可选的，所述负极膜层的孔隙率P满足：28％≤P≤35％；
    (2)所述负极膜层与所述负极集流体之间的粘结力F满足：4.5N/m≤F≤15N/m；可选的，所述负极膜层与所述负极集流体之间的粘结力F满足：8N/m≤F≤12N/m。
  13. 根据权利要求1-12任一项所述的二次电池，其中，所述二次电池包括正极极片，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含正极活性材料的正极膜层，所述正极活性材料包括锂镍钴锰氧化物、锂镍钴铝氧化物、磷酸铁锂、磷酸铁锂与碳的复合材料、以及它们各自的改性化合物中的一种或几种。
  14. 一种二次电池的制造方法，包括采用如下的方法制备负极极片的步骤：
    提供负极活性材料，所述负极活性材料包括石墨；
    使所述负极活性材料形成负极浆料；
    将所述负极浆料涂覆于负极集流体的至少一个表面，使其形成负极膜层，得到负极极片；
    其中，所述负极极片满足：当将所述负极极片与锂金属片组成扣式电池，并将所述扣式电池以0.05C放电至5.0mV时，其容量增量曲线V-dQ/dV在0.055V～0.085V的位置具有石墨的三阶嵌锂相变峰。
  15. 一种电池模块，包括根据权利要求1-13任一项所述的二次电池、或根据权利要求14所述制造方法得到的二次电池。
  16. 一种电池包，包括根据权利要求15所述的电池模块。
  17. 一种装置，包括根据权利要求1-13任一项所述的二次电池、根据权利要求14所述制造方法得到的二次电池、根据权利要求15所述的电池模块、或根据权利要求16所述的电池包中的至少一种。
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