WO2023050414A1 - 二次电池及包含其的电池模块、电池包和用电装置 - Google Patents

二次电池及包含其的电池模块、电池包和用电装置 Download PDF

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WO2023050414A1
WO2023050414A1 PCT/CN2021/122432 CN2021122432W WO2023050414A1 WO 2023050414 A1 WO2023050414 A1 WO 2023050414A1 CN 2021122432 W CN2021122432 W CN 2021122432W WO 2023050414 A1 WO2023050414 A1 WO 2023050414A1
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secondary battery
mass
active material
negative electrode
electrolyte
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PCT/CN2021/122432
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English (en)
French (fr)
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郭洁
韩昌隆
吴则利
姜彬
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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 EP21945367.7A priority Critical patent/EP4184650A1/en
Priority to CN202180088018.XA priority patent/CN116670844A/zh
Priority to PCT/CN2021/122432 priority patent/WO2023050414A1/zh
Priority to US18/155,059 priority patent/US20230216089A1/en
Publication of WO2023050414A1 publication Critical patent/WO2023050414A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
    • H01M50/207—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape
    • H01M50/209—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape adapted for prismatic or rectangular cells
    • 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
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/102—Primary casings; Jackets or wrappings characterised by their shape or physical structure
    • H01M50/103—Primary casings; Jackets or wrappings characterised by their shape or physical structure prismatic or rectangular
    • 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
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • H01M2300/004—Three solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of secondary batteries, in particular to secondary batteries and battery modules, battery packs and electrical devices containing them.
  • Patent document CN113097429A records: by adjusting the relationship between the terminal potential of the negative electrode active material of the electrochemical device and the excess coefficient of the electrochemical device (the ratio between the negative electrode capacity and the positive electrode capacity under the same area), the electrochemical device can be realized in the The effect of improving the rate performance of the battery without affecting the energy density of the battery.
  • Patent document CN113036298A records: by adjusting the OI value of the first negative electrode active material layer and the second negative electrode active material layer, the secondary battery has both better rate performance and long cycle life.
  • the patent document CN111653829A records that the rate performance and cycle performance of the battery can be improved by adding film-forming additives to the electrolyte.
  • Patent document CN108847489B records that battery performance such as rate performance is improved by improving the negative electrode.
  • the inventors of the present application found through in-depth research that by using a specific negative electrode and electrolyte and designing a specific relationship between the negative electrode and electrolyte of a secondary battery, the rate performance, cycle performance and storage performance of the battery can be improved.
  • a secondary battery includes an electrolyte and a negative electrode
  • the electrolyte comprises a low viscosity solvent, an electrolyte salt and a high dielectric constant solvent,
  • the viscosity of the low-viscosity solvent at 25°C is 0.3mPa ⁇ s ⁇ 0.6mPa ⁇ s,
  • the dielectric constant of the high dielectric constant solvent is 30F/m-100F/m, and the mass percentage of the high dielectric constant solvent to the total solvent in the electrolyte is more than 20% by mass,
  • the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and
  • the secondary battery satisfies the following relationship:
  • B is the mass percent that the low-viscosity solvent accounts for the total solvent in the electrolyte
  • C is the mass percent that the electrolyte salt accounts for the electrolyte
  • P is the porosity of the negative electrode active material layer
  • CW is The coating amount of the negative active material layer, in mg/cm 2
  • OI is the orientation index of the negative active material layer
  • C004 is the peak area of the 004 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode active material layer
  • C110 is the peak of the 110 characteristic diffraction peak in the X-ray diffraction pattern of the described negative electrode active material layer area.
  • the rate performance, cycle performance, and storage performance of the battery can be improved.
  • the low-viscosity solvent may include at least one selected from dimethyl carbonate (DMC), ethyl acetate (EA), methyl acetate (MA), and acetonitrile (ACN).
  • DMC dimethyl carbonate
  • EA ethyl acetate
  • MA methyl acetate
  • ACN acetonitrile
  • the mass percentage B of the low-viscosity solvent in the total solvent in the electrolyte may be 10 mass % to 80 mass %, optionally 20 mass % to 70 mass %. Thereby, the rate performance of the secondary battery can be improved.
  • the electrolyte salt may comprise LiPF 6 , LiBF 4 , LiN(SO 2 F) 2 (LiFSI), LiN(CF 3 SO 2 ) 2 (LiTFSI), LiClO 4 , LiAsF 6 , LiB(C 2 O 4 ) 2 (LiBOB), LiBF 2 C 2 O 4 (LiDFOB); or the electrolyte salt may comprise NaPF 6 , NaClO 4 , NaBCl 4 , NaSO 3 CF 3 and at least one of Na(CH 3 )C 6 H 4 SO 3 . Thereby, the performance such as the rate performance of the secondary battery can be improved.
  • the mass percentage C of the electrolyte salt in the electrolyte solution may be 10 mass % to 23 mass %, optionally 13 mass % to 20 mass %. Thereby, the performance such as the rate performance of the secondary battery can be improved.
  • the high dielectric constant solvent may comprise a cyclic carbonate, optionally, the cyclic carbonate comprises ethylene carbonate, propylene carbonate, 1,2-carbonic acid At least one of butylene, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and fluoroethylene carbonate.
  • the performance such as the rate performance of the secondary battery can be improved.
  • the mass percentage of the high dielectric constant solvent in the total solvent in the electrolyte may be 20% by mass to 40% by mass.
  • the mass percentage of the high dielectric constant solvent to the total solvent in the electrolyte is within the above range, it is beneficial to improve the rate performance, cycle performance and storage performance of the secondary battery.
  • the electrolytic solution may also contain a mixture selected from diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, methyl propionate, ethyl propionate at least one of esters.
  • a mixture selected from diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, methyl propionate, ethyl propionate at least one of esters.
  • the electrolytic solution may also include a film-forming additive comprising a film-forming additive selected from vinylene carbonate, fluoroethylene carbonate, lithium difluorobisoxalate phosphate, 1,3- At least one of propane sultone, lithium difluorophosphate, lithium difluorooxalate borate, nitrile compounds and cyclic sulfuric acid ester, optionally, the cyclic sulfuric acid ester is ethylene sulfate. Therefore, it can be beneficial to improve the rate performance, cycle performance, storage performance, flame retardancy and other performances of the secondary battery.
  • a film-forming additive comprising a film-forming additive selected from vinylene carbonate, fluoroethylene carbonate, lithium difluorobisoxalate phosphate, 1,3- At least one of propane sultone, lithium difluorophosphate, lithium difluorooxalate borate, nitrile compounds and cyclic sulfuric acid ester, optionally, the cyclic sulfuric acid ester is
  • the conductivity of the electrolyte at 25° C. may be 8 mS/cm ⁇ 16 mS/cm.
  • it can be beneficial to improve the rate performance, cycle performance and storage performance of the secondary battery.
  • the viscosity of the electrolytic solution at 25° C. may be 1 mPa ⁇ s ⁇ 7 mPa ⁇ s.
  • it can be beneficial to improve the rate performance, cycle performance and storage performance of the secondary battery.
  • the OI value of the negative electrode active material layer may be 3-24, optionally 8-24.
  • it can be beneficial to improve the rate performance, cycle performance and storage performance of the secondary battery.
  • the coating amount CW of the negative electrode active material layer may be 6.5 mg/cm 2 -19.5 mg/cm 2 , optionally 6.5 mg/cm 2 -13 mg/cm 2 .
  • it can be beneficial to improve the rate performance, cycle performance and storage performance of the secondary battery.
  • the porosity P of the negative electrode active material layer may be 20% ⁇ 60%.
  • it can be beneficial to improve the rate performance, cycle performance and storage performance of the secondary battery.
  • the negative electrode active material may include at least one selected from artificial graphite, natural graphite, soft carbon, hard carbon, and silicon-based materials.
  • the silicon-based material may include selected From at least one of silicon simple substance, silicon oxide, silicon-carbon composite and silicon-based alloy (when the secondary battery is a lithium-ion battery); or the negative electrode active material can comprise selected from natural graphite, modified graphite, Artificial graphite, graphene, carbon nanotubes, carbon nanofibers, porous carbon, tin, antimony, germanium, lead, ferric oxide, vanadium pentoxide, tin dioxide, titanium dioxide, molybdenum trioxide, elemental phosphorus, titanic acid At least one of sodium and sodium terephthalate (when the secondary battery is a sodium ion battery).
  • it can be beneficial to improve the rate performance, cycle performance and storage performance of the secondary battery.
  • the mass percentage of the silicon-based material in the total negative electrode active material may be 0 mass % to 30 mass %, optionally 0 mass % to 10 mass %.
  • it can be beneficial to improve the rate performance, cycle performance and storage performance of the secondary battery.
  • a positive electrode active material with the molecular formula LiNixCoyMnzM1 -xyzO2 , where 0 ⁇ x ⁇ 1 , 0 ⁇ y ⁇
  • a battery module which includes the above-mentioned secondary battery.
  • the battery module has excellent rate performance, cycle performance and storage performance.
  • a battery pack which includes the above-mentioned battery module.
  • the battery pack has excellent rate performance, cycle performance and storage performance.
  • an electric device which includes at least one of the above-mentioned secondary battery, battery module or battery pack.
  • the electric device has excellent rate performance, cycle performance and storage performance.
  • the present application provides a secondary battery having excellent rate performance, cycle performance, and storage performance by using a specific negative electrode and an electrolyte and designing a specific relationship between the negative electrode and the electrolyte.
  • the present application also provides a battery module, a battery pack, and an electrical device including the secondary battery.
  • the battery module, battery pack and electrical device also have excellent rate performance, cycle performance and storage performance.
  • FIG. 1 is a schematic diagram of a secondary battery according to one embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an electrical device in which a secondary battery is used as a power source according to an embodiment of the present application.
  • any lower limit can be combined with any upper limit to form an unexpressed range; and any lower limit can be combined with any other lower limit to form an unexpressed range, just as any upper limit can be combined with any other upper limit to form an unexpressed range.
  • every point or individual value between the endpoints of a range is included within that range, although not expressly stated herein. Thus, each point or individual value may serve as its own lower or upper limit in combination with any other point or individual value or with other lower or upper limits to form a range not expressly recited.
  • the first embodiment of the present application may provide a secondary battery including an electrolyte and a negative electrode,
  • the electrolyte comprises a low viscosity solvent, an electrolyte salt and a high dielectric constant solvent,
  • the viscosity of the low-viscosity solvent at 25°C is 0.3mPa ⁇ s ⁇ 0.6mPa ⁇ s,
  • the dielectric constant of the high dielectric constant solvent is 30F/m-100F/m, and the mass percentage of the high dielectric constant solvent to the total solvent in the electrolyte is more than 20% by mass,
  • the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and
  • the secondary battery satisfies the following relationship:
  • B is the mass percent that the low-viscosity solvent accounts for the total solvent in the electrolyte
  • C is the mass percent that the electrolyte salt accounts for the electrolyte
  • P is the porosity of the negative electrode active material layer
  • CW is The coating amount of the negative active material layer, in mg/cm 2
  • OI is the orientation index of the negative active material layer
  • C004 is the peak area of the 004 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode active material layer
  • C110 is the peak of the 110 characteristic diffraction peak in the X-ray diffraction pattern of the described negative electrode active material layer area.
  • the secondary battery As a complex electrochemical system, the secondary battery has many elements (such as the type of positive and negative active materials, the composition of the electrolyte, the internal structure of the battery, etc.) important influence.
  • the inventors of the present application have found through in-depth research that, among the components of the secondary battery, the design of the electrolyte and the negative electrode has a greater impact on the rate performance, cycle performance and storage performance of the secondary battery.
  • the content of high kinetic solvent such as low viscosity solvent
  • the content of high dielectric constant solvent such as cyclic carbonate
  • the electrolyte salt concentration the porosity of the negative electrode active material layer, the negative electrode active material layer in the secondary battery
  • the coating amount and the orientation index of the negative electrode active material have a very important impact on the rate performance, cycle performance and storage performance.
  • the inventors of the present application improved the rate performance, cycle performance and storage performance of the secondary battery by using a specific negative electrode and electrolyte and designing a specific relationship between the negative electrode and the electrolyte of the secondary battery.
  • the viscosity of the low-viscosity solvent at 25° C. is 0.3 mPa ⁇ s ⁇ 0.6 mPa ⁇ s.
  • the use of such a solvent with a lower viscosity can better improve the conductivity of the electrolyte, thereby enabling the secondary battery to have a higher rate performance.
  • using the above-mentioned high dielectric constant solvent in the electrolyte can ensure the degree of solvation of the electrolyte salt, thereby increasing the conductivity of the electrolyte, which is beneficial to improving the rate performance of the secondary battery.
  • the content of high kinetic solvent (such as low viscosity solvent) in the secondary battery the content of high dielectric constant solvent (such as cyclic carbonate), electrolyte salt concentration, the porosity of negative electrode active material layer, Adjusting the coating amount of the negative electrode active material layer and the orientation index of the negative electrode active material so that the above parameters satisfy the above relational formula can improve the rate performance, cycle performance and storage performance of the secondary battery.
  • the polarization of the secondary battery at high rates is small, the internal resistance is low, and the battery temperature does not increase significantly.
  • the secondary battery of the present embodiment preferably uses the aforementioned low-viscosity solvent.
  • the type of low-viscosity solvent there is no particular limitation on the type of low-viscosity solvent, as long as it is less likely to cause side reactions in the secondary battery and can improve the rate performance of the secondary battery.
  • the low-viscosity solvent may contain at least one selected from dimethyl carbonate (DMC), ethyl acetate (EA), methyl acetate (MA), and acetonitrile (ACN).
  • the mass percentage B of the low-viscosity solvent in the secondary battery of the present embodiment in the total solvent in the electrolyte can be 10% by mass to 80% by mass, and can be selected as 20% by mass to 70% by mass.
  • the mass percentage B of the low-viscosity solvent in the total solvent in the electrolyte can be 10 mass % to 70 mass %, 10 mass % to 60 mass %, 10 mass % to 50 mass %, 20 mass % % to 50% by mass, 30% to 70% by mass, 30% to 60% by mass, and 30% to 40% by mass.
  • the mass percentage B of the low-viscosity solvent in the total solvent in the electrolyte can be 15 mass%, 25 mass%, 35 mass%, 45 mass%, 55 mass%, 65 mass% and 75 mass% %.
  • the above-mentioned low-viscosity solvent can improve the rate performance of the secondary battery.
  • the content of the low-viscosity solvent is too high, the content of the high dielectric constant solvent in the electrolyte may be too low, thereby affecting the dissociation of the electrolyte salt and deteriorating the ionic conductivity of the electrolyte, thereby deteriorating the performance of the secondary battery. rate performance.
  • the content of the low-viscosity solvent is too low, the effect of improving the rate performance of the secondary battery may not be significant.
  • the type of electrolyte salt in the present application is not particularly limited, and electrolyte salts commonly used in the art can be used.
  • the electrolyte salt in this embodiment may include LiPF 6 , LiBF 4 , LiN(SO 2 F) 2 (LiFSI), LiN(CF 3 SO 2 ) 2 ( At least one of LiTFSI), LiClO 4 , LiAsF 6 , LiB(C 2 O 4 ) 2 (LiBOB), LiBF 2 C 2 O 4 (LiDFOB); or the electrolyte salt may include NaPF 6 , NaClO 4 , NaBCl 4 , NaSO 3 CF 3 and Na(CH 3 )C 6 H 4 SO 3 at least one.
  • LiFSI and LiPF 6 are preferably used as lithium salts.
  • the mass percentage C of the electrolyte salt in the electrolyte solution of this embodiment may be 10 mass % to 23 mass %, and may be 13 mass % to 20 mass %.
  • the mass percentage B of the low-viscosity solvent in the total solvent in the electrolyte can be 10 mass % to 22 mass %, 10 mass % to 20 mass %, 10 mass % to 18 mass %, 10 mass % % to 16 mass %, 10 mass % to 14 mass %, 10 mass % to 15 mass %, 11 mass % to 20 mass %, 12 mass % to 18 mass %, 12 mass % to 17 mass %, 12 mass % to 15% by mass, 13% by mass to 20% by mass, 13% by mass to 18% by mass, and 13% by mass to 15% by mass.
  • the electrolyte salt can provide active ions such as lithium ions, and a larger concentration of active ions in the electrolyte can improve the concentration polarization during fast charging. However, if the concentration of the electrolyte salt is too high, the viscosity of the electrolyte is high, deteriorating the rate performance. When the concentration of the electrolyte salt in the electrolyte is within the above range, it is beneficial to improve the rate performance of the secondary battery.
  • the high dielectric constant solvent of the present embodiment may include a cyclic carbonate
  • the cyclic carbonate may include a cyclic carbonate selected from ethylene carbonate, propylene carbonate, At least one of 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and fluoroethylene carbonate.
  • the high dielectric constant solvent has better solvating ability, so a certain amount of high dielectric constant solvent in the electrolyte can better dissociate the electrolyte salt, achieve a higher ionic conductivity of the electrolyte, and improve the secondary The rate performance of the battery.
  • the mass percentage of the high dielectric constant solvent in the present embodiment to the total solvent in the electrolyte solution may be 20% by mass to 40% by mass.
  • the mass percentage of the high dielectric constant solvent in the total solvent in the electrolyte can be 20 mass % to 35 mass %, 20 mass % to 30 mass %, 20 mass % to 25 mass %, 25 mass % % by mass to 40% by mass, 25% to 36% by mass, 25% to 32% by mass, 25% to 28% by mass, 30% to 40% by mass, and 30% to 35% by mass.
  • the mass percentage of the high dielectric constant solvent in the total solvent in the electrolyte can be 21 mass%, 22 mass%, 23 mass%, 24 mass%, 27 mass%, 28 mass%, 29 mass% % by mass, 33% by mass, 34% by mass, 37% by mass, 38% by mass and 39% by mass.
  • the mass percentage of the high dielectric constant solvent in the total solvent in the electrolytic solution is too low, the electrolyte salt in the electrolytic solution may not be sufficiently dissociated, thereby deteriorating the ionic conductivity of the electrolytic solution.
  • the mass percentage of the high dielectric constant solvent in the total solvent in the electrolyte is too high, the viscosity of the electrolyte may become larger, which may cause the electrolyte to infiltrate the positive and negative electrodes degrade the performance of the secondary battery.
  • the mass percentage of the high dielectric constant solvent in the total solvent in the electrolyte is within the above range, it is beneficial to improve the rate performance, cycle performance and storage performance of the secondary battery.
  • the electrolytic solution of the present embodiment may further include diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethylene propyl carbonate , methyl butyl carbonate, methyl propionate, ethyl propionate at least one.
  • the electrolyte solution of the present embodiment may also include a film-forming additive.
  • the film-forming additive may comprise vinylene carbonate, fluoroethylene carbonate, lithium difluorobisoxalate phosphate, 1,3-propane sultone, lithium difluorophosphate, lithium difluorooxalate borate, nitrile At least one of compound and cyclic sulfate, optionally, the cyclic sulfate is ethylene sulfate.
  • the film-forming additive can form a low-impedance protective film on the surface of the positive electrode and/or negative electrode of the secondary battery to reduce side reactions in the battery, thereby improving the rate performance, cycle performance and storage performance of the secondary battery.
  • the conductivity of the electrolyte solution in this embodiment at 25° C. may be 8 mS/cm ⁇ 16 mS/cm.
  • the electrical conductivity can be 8mS/cm ⁇ 16mS/cm, 8mS/cm ⁇ 14mS/cm, 8mS/cm ⁇ 12mS/cm, 8mS/cm ⁇ 10mS/cm, 9mS/cm ⁇ 15mS/cm, 9mS/cm ⁇ 13mS/cm, 9mS/cm ⁇ 11mS/cm, 10mS/cm ⁇ 15mS/cm and 11mS/cm ⁇ 16mS/cm.
  • the viscosity of the electrolyte solution in this embodiment at 25° C. may be 1 mPa ⁇ s ⁇ 7 mPa ⁇ s.
  • the viscosity can be 1mPa ⁇ s ⁇ 7mPa ⁇ s, 1mPa ⁇ s ⁇ 6mPa ⁇ s, 1mPa ⁇ s ⁇ 5mPa ⁇ s, 1mPa ⁇ s ⁇ 4mPa ⁇ s, 2mPa ⁇ s ⁇ 7mPa ⁇ s, 2mPa ⁇ s ⁇ 5mPa s, 2mPa ⁇ s ⁇ 4mPa ⁇ s, 3mPa ⁇ s ⁇ 7mPa ⁇ s, 2mPa ⁇ s ⁇ 6mPa ⁇ s and 2mPa ⁇ s ⁇ 6.5mPa ⁇ s.
  • the OI value of the negative electrode active material layer in this embodiment may be 3-24, and may be 8-24.
  • the OI value of the negative electrode active material layer may be 3-20, 3-18, 3-15, 3-14, 3-10, 3-8, 3-6, 5-22, 5-20 , 5 ⁇ 18, 5 ⁇ 10, 5 ⁇ 8, 6 ⁇ 22, 6 ⁇ 18, 6 ⁇ 15, 6 ⁇ 10, 6 ⁇ 8, 7 ⁇ 18, 7 ⁇ 12, 7 ⁇ 10, 7 ⁇ 9, 8 ⁇ 18, 8 ⁇ 14 and 8 ⁇ 10.
  • the OI value of the negative electrode active material layer is within the above range, it is beneficial for the secondary battery to have excellent rate performance, cycle performance and storage performance.
  • the OI value of the negative electrode active material layer is used to represent the orientation index of the negative electrode active material layer, that is, the degree of anisotropy of grain arrangement in the negative electrode active material layer.
  • the OI value is defined as the area ratio of the (004) characteristic diffraction peak and the (110) characteristic diffraction peak of the negative electrode active material layer in the X-ray diffraction spectrum.
  • C004 is the peak area of the 004 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode active material layer
  • C110 is the area of the 110 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode active material layer Peak area.
  • the OI value of the negative electrode active material layer can be measured by methods known in the art, for example, by the methods described in the Examples of this application.
  • the OI value of the negative electrode active material layer can be controlled by adjusting the following parameters.
  • both the volume average particle diameter Dv50 of the negative active material and the OI value G OI of the active material powder have a certain influence on the OI value of the negative active material layer.
  • magnetic field induction technology can be introduced in the coating or drying process to artificially induce the arrangement of the negative active material in the negative electrode, thereby changing the OI value of the negative active material layer; it can also be used in the cold pressing process, By adjusting the compaction density of the negative electrode active material layer, the arrangement of the negative electrode active material is changed, thereby controlling the OI value of the negative electrode active material layer.
  • the coating amount CW of the negative electrode active material layer in this embodiment can be 6.5 mg/cm 2 to 19.5 mg/cm 2 , which can be selected as 6.5 mg/cm 2 -13 mg/cm 2 .
  • the coating amount CW of the negative electrode active material layer may be 6.5 mg/cm 2 to 18 mg/cm 2 , 6.5 mg/cm 2 to 16 mg/cm 2 , 6.5 mg/cm 2 to 14 mg/cm 2 , 6.5mg/cm 2 ⁇ 12mg/cm 2 , 6.5mg/cm 2 ⁇ 10mg/cm 2 , 7mg/cm 2 ⁇ 18mg/cm 2 , 7mg/cm 2 ⁇ 16mg/cm 2 , 7mg/cm 2 ⁇ 14mg/cm 2 , 7mg/cm 2 ⁇ 12mg/cm 2 , 7mg/cm 2 ⁇ 10mg/cm 2 , 8mg/cm 2 ⁇ 18mg/cm 2 , 8mg/cm 2 ⁇ 16mg/cm 2 , 8mg/cm 2 ⁇ 14mg/cm 2 , 8mg/cm 2 ⁇ 14
  • the coating amount CW of the negative electrode active material layer may be 9 mg/cm 2 , 11 mg/cm 2 , 13 mg/cm 2 , 15 mg/cm 2 , 17 mg/cm 2 and 19 mg/cm 2 .
  • the coating amount of the negative electrode active material layer is the mass of the negative electrode active material layer coated on a unit area.
  • a negative electrode with a smaller coating amount has a smaller diffusion resistance, so that lithium ions can diffuse better in the negative electrode active material layer, thereby improving the rate performance of the secondary battery.
  • the amount of the negative electrode active material will directly affect the energy density of the secondary battery, so the coating amount of the negative electrode active material layer should not be too small.
  • the coating amount CW of the negative electrode active material layer is within the above range, it is beneficial to improve the rate performance, cycle performance and storage performance of the secondary battery.
  • the porosity P of the negative electrode active material layer in this embodiment may be 20%-60%.
  • the porosity P of the negative electrode active material layer may be 20% to 55%, 20% to 50%, 20% to 45%, 20% to 40%, 20% to 35%, 25% to 55% %, 25% ⁇ 50%, 25% ⁇ 45%, 25% ⁇ 40%, 25% ⁇ 35%, 30% ⁇ 55%, 30% ⁇ 45%, 30% ⁇ 43%, 30% ⁇ 41%, 30%-38%, 34%-55%, 34%-45%, 36%-43%, 36%-41% or 36%-48%.
  • the size of the porosity of the negative electrode active material layer will affect the diffusion of lithium ions in the negative electrode active material layer, thereby affecting the rate performance of the secondary battery.
  • the greater the porosity of the negative electrode active material layer the better the wettability of the electrolyte, and the better the rate performance of the secondary battery.
  • the porosity of the negative electrode active material layer is too large, there are disadvantages that an internal short circuit may occur or a self-discharge rate may be high.
  • the porosity of the negative electrode active material layer is too large, it may be unfavorable to maintain the mechanical strength of the negative electrode active material layer.
  • the porosity of the negative electrode active material layer is within the above range, it is beneficial to improve the rate performance, cycle performance and storage performance of the secondary battery, while maintaining the mechanical strength of the negative electrode active material layer and preventing internal short circuit or self-discharge.
  • the negative electrode active material of this embodiment may contain at least one selected from artificial graphite, natural graphite, soft carbon, hard carbon and silicon-based materials.
  • the negative electrode active material may comprise natural graphite, modified graphite, artificial graphite, graphene, carbon nanotubes, carbon nanofibers, porous carbon, tin, antimony, germanium, lead, ferric oxide, five At least one of vanadium oxide, tin dioxide, titanium dioxide, molybdenum trioxide, elemental phosphorus, sodium titanate and sodium terephthalate.
  • the silicon-based material may contain at least one selected from silicon simple substance, silicon oxide, silicon-carbon composite and silicon-based alloy.
  • the mass percentage of the silicon-based material in this embodiment to the total negative electrode active material can be 0 mass % to 30 mass %, and can be selected as 0% by mass to 10% by mass.
  • the mass percentage of the silicon-based material in the overall negative active material can be 0 mass % to 25 mass %, 0 mass % to 20 mass %, 0 mass % to 15 mass %, 0 mass % to 5 mass % % by mass, 4% to 20% by mass, 4% to 16% by mass, 4% to 12% by mass, 6% to 13% by mass, 6% to 26% by mass, 6% to 18% by mass , 7% to 13% by mass, 7% to 22% by mass or 7% to 19% by mass.
  • the positive electrode active material may be selected from LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ) and at least one of modified compounds thereof.
  • the positive electrode may comprise at least one positive active material selected from the following: layered transition metal oxides, polyanionic compounds, Prussian blue compounds, sulfides, nitrides , carbide, titanate.
  • a secondary battery is provided.
  • the secondary battery may be a lithium ion battery or a sodium ion battery.
  • the specific implementation manner of the present application will be described in detail below by taking a lithium-ion battery as an example.
  • a lithium-ion battery can contain a positive electrode, a negative electrode, an electrolyte, and a separator.
  • the electrolyte plays the role of conducting lithium ions between the positive electrode and the negative electrode.
  • the separator is arranged between the positive electrode and the negative electrode, mainly to prevent the short circuit of the positive and negative electrodes, and at the same time allow ions to pass through. In some cases, such as when a gel polymer electrolyte is used as the electrolyte, the electrolyte can simultaneously function as a separator.
  • the electrolyte is also regarded as the electrolyte solution described in this application.
  • the electrolyte solution of the present application is not limited to a liquid form.
  • the positive electrode may include a positive electrode collector and a positive electrode active material layer disposed on at least one surface of the positive electrode collector.
  • the positive active material layer may include a positive active material and optionally a binder and a conductive agent.
  • the positive electrode current collector has two surfaces opposing in its own thickness direction.
  • the positive electrode active material layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • aluminum foil can be used as the metal foil.
  • the composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate Formed on substrates such as polyethylene formate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.
  • PP polypropylene
  • PET polyethylene formate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries.
  • the positive active material may include at least one of the following materials: olivine-structured lithium-containing phosphate, lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials of lithium-ion batteries can also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • the positive electrode active material can be selected from LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ) and at least one of modified compounds thereof.
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ) , at least one of a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium manganese iron phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also abbreviated as LFP)
  • composite materials of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate
  • the positive electrode may comprise at least one positive active material selected from the following: layered transition metal oxides, polyanionic compounds, Prussian blue compounds, sulfides, nitrides , carbide, titanate.
  • the positive electrode active material includes, but is not limited to, selected from NaCrO 2 , Na 2 Fe 2 (SO 4 ) 3 , molybdenum disulfide, tungsten disulfide, vanadium disulfide, titanium disulfide, hexagonal boron nitride, carbon Doped with hexagonal boron nitride, titanium carbide, tantalum carbide, molybdenum carbide, silicon carbide, Na 2 Ti 3 O 7 , Na 2 Ti 6 O 13 , Na 4 Ti 5 O 12 , Li 4 Ti 5 O 12 , NaTi 2 ( At least one selected from the group consisting of PO 4 ) 3 .
  • the positive active material layer may further optionally contain a binder.
  • the binder may comprise polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexa At least one selected from the group consisting of fluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • the positive electrode active material layer may further optionally contain a conductive agent.
  • conductive agents generally used in the art can be used.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon nanotubes, carbon nanorods, graphene and carbon nanofibers.
  • the positive electrode can be prepared in the following manner: the above-mentioned components used to prepare the positive electrode, such as positive electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone ) to form a positive electrode slurry; the positive electrode slurry can be coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode can be obtained.
  • the positive electrode can be manufactured by casting the positive electrode slurry for forming the positive electrode active material layer on a separate carrier, and then putting the film layer obtained by peeling off from the carrier Pressed on the positive current collector.
  • the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode active material layer may contain negative electrode active materials and optional binders, conductive agents and other additives.
  • the anode current collector has two opposing surfaces in its own thickness direction, and the anode active material layer is disposed on either or both of the two opposing surfaces of the anode current collector.
  • the negative electrode current collector may use a metal foil or a composite current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate.
  • Composite current collectors can be formed by metal materials (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) Formed on substrates such as polyethylene formate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.
  • the negative electrode active material may be a known negative electrode active material for lithium ion batteries in the art.
  • the negative active material may contain at least one selected from artificial graphite, natural graphite, soft carbon, hard carbon, and silicon-based materials.
  • the silicon-based material includes at least one selected from silicon simple substance, silicon oxide, silicon-carbon composite and silicon-based alloy.
  • the mass percentage of the silicon-based material in the total negative electrode active material may be 0% to 30% by mass, optionally 0% to 10% by mass.
  • the present application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials of batteries can also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode active material may include natural graphite, modified graphite, artificial graphite, graphene, carbon nanotubes, carbon nanofibers, porous carbon, tin, antimony, germanium, At least one of lead, ferric oxide, vanadium pentoxide, tin dioxide, titanium dioxide, molybdenum trioxide, elemental phosphorus, sodium titanate and sodium terephthalate.
  • the negative electrode active material is at least one selected from natural graphite, modified graphite, artificial graphite and graphene.
  • the negative active material layer may further optionally contain a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative active material layer may further optionally contain a conductive agent.
  • the conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon nanotubes, carbon nanorods, graphene and carbon nanofibers.
  • the negative electrode active material layer may also optionally contain other additives, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode can be prepared in the following manner: the above-mentioned components for preparing the negative electrode, such as negative electrode active material, conductive agent, binder and any other components are dispersed in a solvent (such as deionized water), Form the negative electrode slurry; apply the negative electrode slurry on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode can be obtained.
  • the negative electrode can be manufactured by casting the negative electrode slurry for forming the negative electrode active material layer on a separate carrier, and then the film layer obtained by peeling off from the carrier on the negative electrode collector.
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • the electrolyte may be liquid or gel.
  • the electrolytic solution of the embodiment of the present application may contain additives.
  • the additives may include additives commonly used in this field.
  • the additives may include, for example, halogenated alkylene carbonate compounds (such as difluoroethylene carbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, (glyme) Ethers, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts , pyrrole, 2-methoxyethanol or aluminum trichloride.
  • the additive may be included in an amount of 0.1 wt% to 5 wt%, or the amount of the additive may be adjusted by those skilled in the art according to
  • the electrolytic solution may contain electrolyte salts and solvents.
  • the electrolyte salt may comprise a compound selected from LiPF 6 , LiBF 4 , LiN(SO 2 F) 2 (LiFSI), LiN(CF 3 SO 2 ) 2 (LiTFSI), At least one of LiClO 4 , LiAsF 6 , LiB(C 2 O 4 ) 2 (LiBOB), and LiBF 2 C 2 O 4 (LiDFOB).
  • the electrolyte salt may include at least one selected from NaPF 6 , NaClO 4 , NaBCl 4 , NaSO 3 CF 3 , and Na(CH 3 )C 6 H 4 SO 3 .
  • the electrolyte solution may also contain other solvents commonly used in the art such as selected from 1,4-butyrolactone, sulfolane, At least one of dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • a separator is further included in the secondary battery.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the separator preferably has excellent ion permeability and electrolyte moisturizing ability.
  • the material of the isolation film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the form of the separator is not particularly limited, and may be a single-layer film or a multi-layer composite film. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and there is no particular limitation.
  • the positive electrode, the negative electrode, and the separator can be fabricated into an electrode assembly through a winding process or a lamination process.
  • a secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag can be plastic. Examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG. 1 shows a square-shaped secondary battery 5 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 plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive electrode, the negative electrode and the separator can form the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the accommodating chamber. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to actual needs.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 3 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 are arranged in sequence along the length direction of the battery module 4 .
  • multiple secondary batteries 5 may also be arranged in any other manner.
  • the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may also include a case having a containing space in which a plurality of secondary batteries 5 are housed.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device.
  • the electric device may include mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, etc.) , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.
  • a secondary battery, a battery module or a battery pack can be selected according to its use requirements.
  • FIG. 6 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • a device may be a cell phone, tablet, laptop, or the like.
  • the device is usually required to be light and thin, and a secondary battery can be used as a power source.
  • Embodiments of the present application will be described in detail below.
  • the embodiments described below are exemplary and are only used for explaining the present application, and should not be construed as limiting the present application. If no specific technique or condition is indicated in the examples, it shall be carried out according to the technique or condition described in the literature in this field or according to the product specification. The reagents or instruments used were not indicated by the manufacturer, and they were all commercially available conventional products.
  • the embodiments of the present application will be described below by taking a lithium-ion battery as an example.
  • the preparation of the electrolyte is carried out in an argon atmosphere glove box with a water content of ⁇ 10 mass ppm.
  • dimethyl carbonate/ethylene carbonate/diethyl carbonate are mixed according to the ratio of 2/3/5 (mass ratio), and then 13wt% of LiPF 6 is added to the above mixed solvent to complete the electrolysis Liquid preparation.
  • the amount of the above-mentioned lithium salt is a percentage calculated based on the total weight of the electrolyte.
  • the positive electrode active material LiNi 5 Co 2 Mn 3 O 2 the binder polyvinylidene fluoride, and the conductive agent acetylene black in a weight ratio of 98:1:1 and disperse them in the solvent N-methylpyrrolidone (NMP)
  • NMP solvent N-methylpyrrolidone
  • Negative electrode active material artificial graphite (its OI value is shown in table 1; Same below), conductive agent carbon black, thickener CMC, binding agent styrene-butadiene rubber (SBR) according to weight ratio 96:2:1:1 Mix and disperse in the solvent deionized water, and stir with a vacuum mixer to obtain the negative electrode slurry; then apply the above negative electrode slurry on the copper foil of the current collector, and perform cold pressing, trimming, cutting, and slitting after drying etc., and a negative electrode having a coating weight of 8 mg/cm 2 and a porosity of 40% was produced.
  • the OI value of the negative electrode active material layer in this embodiment is 7 (the OI value is shown in Table 1; the same below).
  • the specific test method is: open the compression cylinder, adjust the pressure reducing valve to balance the pressure at 0.14MPa ⁇ 0.18MPa, punch the negative electrode into a relatively flat disc with an area of 1.5394cm2 , the number of samples is > 20, put the sample into the sample Cup, operate the true density tester (GB/T2790-1995) to test, and obtain the real volume V12 of the negative pole piece; V11 is obtained by 1.5394cm 2 *the thickness of the pole piece.
  • the OI value of the negative electrode active material layer is used to characterize the orientation index of the active material in the negative electrode active material layer.
  • a commercially available polypropylene film was used as the separator.
  • a lithium-ion battery was prepared in the same manner as in Example 1, except that dimethyl carbonate/ethylene carbonate/diethyl carbonate were mixed in a ratio of 4/3/3 (mass ratio).
  • a lithium-ion battery was prepared in the same manner as in Example 1, except that dimethyl carbonate/ethylene carbonate/diethyl carbonate were mixed in a ratio of 7/3/0 (mass ratio).
  • Lithium-ion batteries were prepared in the same manner as in Example 2, except that the contents of lithium salts were changed to 10 wt% and 23 wt%, respectively.
  • a lithium-ion battery was prepared in the same manner as in Example 2, except that the orientation index OI values of the negative electrode active material layer were changed to 3 and 24, respectively.
  • a lithium ion battery was prepared in the same manner as in Example 2, except that the coating amount of the prepared negative electrode was changed to 6.5 mg/cm 2 and 13 mg/cm 2 .
  • a lithium ion battery was prepared in the same manner as in Example 2, except that the porosity of the prepared negative electrode was changed to 20% and 60%.
  • a lithium ion battery was prepared in the same manner as in Example 2 except that dimethyl carbonate was replaced with ethyl acetate.
  • a lithium ion battery was prepared in the same manner as in Example 1, except that 1% by mass of ethylene sulfate based on the total mass of the electrolyte was additionally added in the preparation of the electrolyte.
  • a lithium ion battery was prepared in the same manner as in Example 2, except that the content of the solvent such as the high dielectric constant solvent in the electrolytic solution was adjusted as shown in Table 2 below.
  • a lithium-ion battery was prepared in the same manner as in Example 2, except that the surface of the artificial graphite used as the negative active material was coated with soft carbon accounting for 2 mass % of the total mass of the artificial graphite as the negative active material.
  • the OI value of the negative electrode active material layer prepared in this example was 4.
  • a lithium ion battery was prepared in the same manner as in Example 2, except that SiO was used in combination in an amount of 3% by mass based on the total mass of the artificial graphite as the negative electrode active material.
  • the OI value of the negative electrode active material layer prepared in this embodiment was 7.
  • a sodium ion battery was fabricated in the same manner as in Example 1, except that the positive electrode active material was replaced by NaCrO 2 and the electrolyte salt in the electrolyte solution was replaced by NaPF 6 .
  • the electrical conductivity of the finished electrolyte was tested using a Lei Magnetic (DDSJ-318) electrical conductivity meter. Control the ambient temperature at 25°C and the ambient humidity ⁇ 80%. Take 40mL of electrolyte, pour the sample into a dry and clean plastic centrifuge tube, place it in a constant temperature bath at 25°C for 30 minutes, and place the electrode that has absorbed moisture vertically. Into the uniform sample to be tested, start the instrument for testing, repeat the test 3 times, and take the average value of the 3 results.
  • DDSJ-318 Lei Magnetic
  • the shear force on the rotor when it continues to rotate at a constant speed in the sample causes the spring to generate a torque, and the torque is proportional to the viscosity, thereby obtaining the viscosity value.
  • a Brookfield (DV-2TLV) viscometer is used to test the viscosity of the finished electrolyte. Control the ambient temperature to 25°C and the ambient humidity to ⁇ 80%. Take 30mL of electrolyte and keep it in a water bath at 25°C for at least 30 minutes. Put the rotor into the sample cup and add the sample to a distance of about 0.3cm from the mouth of the cup. Start the connected viscometer, select the rotating speed of 70RPM to test, collect 10 data points, and calculate the average value of multiple points.
  • DV-2TLV Brookfield viscometer
  • Rate performance test (test for charging to 80% SOC): adjust the test temperature to 35°C, charge the lithium-ion battery at xC rate (x is 0.5, 0.8, 1, 1.2, 1.5, 2, 2.5, 3), Then discharge at 1C, the charging rate increases sequentially, with the anode potential 0V as the charging cut-off condition, 0-10% SOC, 10-20% SOC, 20-30% SOC, 30-40% SOC, 40-50% SOC are obtained , 50-60% SOC, 60-70% SOC, and 70-80% SOC, the maximum charging rate x 1 C, x 2 C , x 3 C, x 4 C, x 5 C, x 6 C, x 7 C, x 8 C, using the formula: Thus calculate the charging time (min) required for 0-80% SOC.
  • Example 2 and Example 14 and Comparative Example 8 By the comparison of Example 2 and Example 14 and Comparative Example 8, it can be seen that when the content of high dielectric constant solvent was lower than the scope of the present application, the rate performance and cycle performance (especially cycle performance) of lithium-ion batteries were reduced obvious.
  • the high dielectric constant solvent can improve the battery rate performance, when the content of the high dielectric constant solvent is greater than the preferred range of the present application (20% by mass to 40% by mass) , compared with Example 2 in which the content of the high dielectric constant solvent is within the preferred range of the present application, the rate performance, cycle performance and high-temperature storage performance of the lithium-ion battery of Example 14 are slightly worse.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请涉及一种二次电池及包含其的电池模块、电池包和用电装置。所述二次电池包含具有特定的低粘度溶剂和特定的含量的高介电常数溶剂的电解液和具有负极活性材料层的负极，并且所述二次电池满足关系式：1x10-4≤（BxCxP）/（OIxCW）≤1x10-3其中B为所述低粘度溶剂占所述电解液中的总溶剂的质量百分比；C为所述电解质盐占所述电解液的质量百分比；P为所述负极活性材料层的孔隙率；CW为所述负极活性材料层的涂布量，单位为mg/cm 2；且OI为所述负极活性材料层的取向指数，其中OI＝C004/C110，C004为所述负极活性材料层的X射线衍射图谱中004特征衍射峰的峰面积，且C110为所述负极活性材料层的X射线衍射图谱中110特征衍射峰的峰面积。

Description

二次电池及包含其的电池模块、电池包和用电装置 技术领域
本申请涉及二次电池领域，尤其涉及二次电池及包含其的电池模块、电池包和用电装置。
背景技术
近年来，随着人们对清洁能源的需求日益递增，二次电池已广泛应用于水力、火力、风力和太阳能电站等储能电源***，以及电动工具、电动交通工具、军用设备、航空航天等多个领域。由于二次电池的应用领域得到了极大的扩展，因此对其倍率性能、能量密度和存储性能(尤其是高温存储性能)等也提出了更高的要求。
为了改善电池性能如倍率性能，已经提出了如下技术。专利文献CN113097429A记载了：通过调节电化学装置的负极活性材料的末端电位与电化学装置的过量系数(相同面积下负极容量与正极容量之间的比值)之间的关系，实现电化学装置能够在不影响电池的能量密度的前提下提高电池的倍率性能的效果。专利文献CN113036298A记载了：通过调节第一负极活性材料层和第二负极活性材料层的OI值使得二次电池兼具较好的倍率性能和长的循环寿命。专利文献CN111653829A记载了：通过在电解液中添加成膜添加剂来改善电池的倍率性能和循环性能。专利文献CN108847489B记载了：通过对负极进行改进来改善电池性能如倍率性能。
发明内容
技术问题
尽管上述文献已经记载了通过各种技术手段改善了电池性能如倍率性能，但是上述技术的改进仅在于正、负极和电解液本身，而没有考虑通过设计电极如负极与电解液之间的关系来改善电池的倍率性能且同时改善循环性能和存储性能。此外，上述现有技术仍未明显改善(或未改善)由于大电流充电时导致的电池内部的极化较大、电池内部温度较高(由此导致例如电池膨胀等问题)的问题。
技术方案
本申请的发明人通过深入研究发现，通过使用特定的负极和电解液并设计二次电池的负极与电解液之间的特定关系，可以改善电池的倍率性能、循环性能和存储性能。
根据本申请的第一方面，提供一种二次电池，所述二次电池包含电解液和负极，
所述电解液包含低粘度溶剂、电解质盐和高介电常数溶剂，
所述低粘度溶剂在25℃下的粘度为0.3mPa·s～0.6mPa·s，
所述高介电常数溶剂的介电常数为30F/m～100F/m，且所述高介电常数溶剂占所述电解液中的总溶剂的质量百分比为20质量％以上，
所述负极包含负极集流体和设置于所述负极集流体的至少一个表面上的负极活性材料层，并且
所述二次电池满足如下关系式：
Figure PCTCN2021122432-appb-000001
其中B为所述低粘度溶剂占所述电解液中的总溶剂的质量百分比；C为所述电解质盐占所述电解液的质量百分比；P为所述负极活性材料层的孔隙率；CW为所述负极活性材料层的涂布量，单位为mg/cm 2；且OI为所述负极活性材料层的取向指数，并且
其中OI＝C004/C110，C004为所述负极活性材料层的X射线衍射图谱中004特征衍射峰的峰面积，且C110为所述负极活性材料层的X射线衍射图谱中110特征衍射峰的峰面积。
在本方面，通过使用特定的负极和电解液并设计二次电池的负极与电解液之间的特定关系，可以改善电池的倍率性能、循环性能和存储性能。
根据本申请的任一方面，所述低粘度溶剂可以包含选自碳酸二甲酯(DMC)、乙酸乙酯(EA)、乙酸甲酯(MA)、乙腈(ACN)中的至少一种。由此，可以改善二次电池的倍率性能。
根据本申请的任一方面，所述低粘度溶剂占所述电解液中的总溶剂的质量百分比B可以为10质量％～80质量％，可选为20质量％～70质量％。由此，可以改善二次电池的倍率性能。
根据本申请的任一方面，所述电解质盐可以包含选自LiPF 6、LiBF 4、LiN(SO 2F) 2(LiFSI)、LiN(CF 3SO 2) 2(LiTFSI)、LiClO 4、LiAsF 6、LiB(C 2O 4) 2(LiBOB)、LiBF 2C 2O 4(LiDFOB)中的至少一种；或者所述电解质盐可以包含选自NaPF 6、NaClO 4、NaBCl 4、NaSO 3CF 3及Na(CH 3)C 6H 4SO 3中的至少一种。由此，可以改善二次电池的倍率性能等性能。
根据本申请的任一方面，所述电解质盐占所述电解液的质量百分比C可以为10质量％～23质量％，可选为13质量％～20质量％。由此，可以改善二次电池的倍率性能等性能。
根据本申请的任一方面，所述高介电常数溶剂可以包含环状碳酸酯，可选地，所述环状碳酸酯包含选自碳酸亚乙酯、碳酸亚丙酯、碳酸1,2-亚丁酯、碳酸2,3-亚丁酯、碳酸1,2-亚戊酯、碳酸2,3-亚戊酯、氟代碳酸亚乙酯中的至少一种。由此，可以改善二次电池的倍率性能等性能。
根据本申请的任一方面，所述高介电常数溶剂占所述电解液中的总溶剂的质量百分比可以为20质量％～40质量％。当高介电常数溶剂占所述电解液中的总溶剂的质量百分比在上述范围内时，有利于改善二次电池的倍率性能、循环性能和存储性能。
根据本申请的任一方面，所述电解液还可以包含选自碳酸二乙酯、碳酸甲乙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸甲丁酯、丙酸甲酯、丙酸乙酯中的至少一种。由此，可以有利于改善二次电池的倍率性能、循环性能和存储性能。
根据本申请的任一方面，所述电解液还可以包含成膜添加剂，所述成膜添加剂包含选自碳酸亚乙烯酯、氟代碳酸亚乙酯、二氟双草酸磷酸锂、1,3-丙烷磺酸内酯、二氟磷酸锂、双氟草酸硼酸锂、腈类化合物和环状硫酸酯中的至少一种，可选地，所述环状硫酸酯为硫酸亚乙酯。由此，可以有利于改善二次电池的倍率性能、循环性能、存储性能和阻燃性能等性能。
根据本申请的任一方面，所述电解液在25℃下的电导率可以为8mS/cm～16mS/cm。由此，可以有利于改善二次电池的倍率性能、循环性能和存储性能。
根据本申请的任一方面，所述电解液在25℃下的粘度可以为1mPa·s～7mPa·s。由此，可以有利于改善二次电池的倍率性能、循环性能和存储性能。
根据本申请的任一方面，所述负极活性材料层的OI值可以为3～24，可选为8～24。由此，可以有利于改善二次电池的倍率性能、循环性能和存储性能。
根据本申请的任一方面，所述负极活性材料层的涂布量CW可以为6.5mg/cm 2～19.5mg/cm 2，可选为6.5mg/cm 2～13mg/cm 2。由此，可以有利于改善二次电池的倍率性能、循环性能和存储性能。
根据本申请的任一方面，所述负极活性材料层的孔隙率P可以为20％～60％。由此，可以有利于改善二次电池的倍率性能、循环性能和存储性能。
根据本申请的任一方面，所述负极活性材料可以包含选自人造石墨、天然石墨、软碳、硬碳和硅基材料中的至少一种，可选地，所述硅基材料可以包含选自硅单质、硅氧化物、硅碳复合物和硅基合金中的至少一种(当二次电池为锂离子电池时)；或者所述负极活性材料可以包含选自天然石墨、改性石墨、人造石墨、石墨烯、碳纳米管、碳纳米纤维、多孔碳、锡、锑、锗、铅、三氧化二铁、五氧化二钒、二氧化锡、二氧化钛、三氧化钼、单质磷、钛酸钠和对苯二甲酸钠中的至少一种(当二次电池为钠离子电池时)。由此，可以有利于改善二次电池的倍率性能、循环性能和存储性能。
根据本申请的任一方面，所述硅基材料占所述负极活性材料总体的质量百分比可以为0质量％～30质量％，可选为0质量％～10质量％。由此，可以有利于改善二次电池的倍率性能、循环性能和存储性能。
根据本申请的任一方面，所述二次电池还可以包含正极，所述正极包含分子式为LiNi xCo yMn zM 1-x-y-zO 2的正极活性材料，其中0≤x≤1，0≤y≤0.5，0≤z≤0.5，且x+y+z＝1，可选地，0.5≤x≤0.9，0≤y≤0.3，且0≤z≤0.3，并且M为选自Zr、Al、Mg、Sb、Fe、Cu、W中的至少一种(当二次电池为锂离子电池时)；或者所述正极包含选自如下中的至 少一种正极活性材料：层状过渡金属氧化物、聚阴离子化合物、普鲁士蓝类化合物、硫化物、氮化物、碳化物、钛酸盐(当二次电池为钠离子电池时)。由此，可以有利于改善二次电池的倍率性能、循环性能和存储性能。
根据本申请的第二方面，提供一种电池模块，其包含上述的二次电池。所述电池模块具有优异的倍率性能、循环性能和存储性能。
根据本申请的第三方面，提供一种电池包，其包含上述的电池模块。所述电池包具有优异的倍率性能、循环性能和存储性能。
根据本申请的第四方面，提供一种用电装置，其包含上述的二次电池、电池模块或电池包中的至少一种。所述用电装置具有优异的倍率性能、循环性能和存储性能。
有益效果
本申请提供一种二次电池，所述二次电池通过使用特定的负极和电解液并设计负极与电解液之间的特定关系而具有优异的倍率性能、循环性能和存储性能。本申请还提供包含所述二次电池的电池模块、电池包和用电装置。所述电池模块、电池包和用电装置同样具有优异的倍率性能、循环性能和存储性能。
附图说明
图1是本申请的一个实施方式的二次电池的示意图。
图2是图1所示的本申请的一个实施方式的二次电池的分解图。
图3是本申请的一个实施方式的电池模块的示意图。
图4是本申请的一个实施方式的电池包的示意图。
图5是图4所示的本申请的一个实施方式的电池包的分解图。
图6是本申请的一个实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件。
具体实施方式
以下，对本申请的二次电池进行详细说明，但是会存在省略不必要的详细说明的情况。例如，存在省略对众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，以下说明及实施例是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合而形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合而形成新的技术方案。
为了简便，本申请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。
在本申请的描述中，需要说明的是，除非另有说明，“以上”、“以下”包含本数，“一种或几种”中“几种”的含义是两种或两种以上。
本申请的第一实施方式可以提供一种二次电池，所述二次电池包含电解液和负极，
所述电解液包含低粘度溶剂、电解质盐和高介电常数溶剂，
所述低粘度溶剂在25℃下的粘度为0.3mPa·s～0.6mPa·s，
所述高介电常数溶剂的介电常数为30F/m～100F/m，且所述高介电常数溶剂占所述电解液中的总溶剂的质量百分比为20质量％以上，
所述负极包含负极集流体和设置于所述负极集流体的至少一个表面上的负极活性材料层，并且
所述二次电池满足如下关系式：
Figure PCTCN2021122432-appb-000002
其中B为所述低粘度溶剂占所述电解液中的总溶剂的质量百分比；C为所述电解质盐占所述电解液的质量百分比；P为所述负极活性材料层的孔隙率；CW为所述负极活性材料层的涂布量，单位为mg/cm 2；且OI为所述负极活性材料层的取向指数，并且
其中OI＝C004/C110，C004为所述负极活性材料层的X射线衍射图谱中004特征衍射峰的峰面积，且C110为所述负极活性材料层的X射线衍射图谱中110特征衍射峰的峰面积。
二次电池作为一个复杂的电化学体系，其中的很多要素(如正极和负极活性材料的类型、电解液的组成、电池内部结构等)均对其性能如倍率性能、循环性能和存储性能有非常重要的影响。本申请的发明人通过深入研究发现，在二次电池的各构成要素之中，电解液与负极的设计对二次电池的倍率性能、循环性能和存储性能影响较大。具体地，二次电池中高动力学溶剂(如低粘度溶剂)的含量、高介电常数溶剂(如环状碳酸脂)的含量、电解质盐浓度、负极活性材料层的孔隙率、负极活性材料层的涂布量及负极活性材料的取向指数对倍率性能、循环性能和存储性能有非常重要的影响。
基于此，本申请的发明人通过使用特定的负极和电解液并设计二次电池的负极与电解液之间的特定关系，改善了二次电池的倍率性能、循环性能和存储性能。
在本实施方式中，所述低粘度溶剂在25℃下的粘度为0.3mPa·s～0.6mPa·s。使用这样的粘度较低的溶剂可较好地提升电解液的电导率，由此可以使得二次电池具有较高的倍率性能。此外，在电解液中使用上述含量的高介电常数溶剂可以保证电解质盐的溶剂化程度，由此提高电解液的电导率，从而有利于提高二次电池的倍率性能。在此基础上，通过对二次电池中高动力学溶剂(如低粘度溶剂)的含量、高介电常数溶剂(如环状碳酸脂)的含量、电解质盐浓度、负极活性材料层的孔隙率、负极活性材料层的涂布量及负极活性材料的取向指数进行调节以使得以上参数满足上述关系式，可以改善二次电池的倍率性能、循环性能和存储性能。此时，二次电池在高倍率下(如快速充电时)的极化较小、内阻较低并且电池温度不会明显升高。
从改善二次电池的倍率性能方面考虑，本实施方式的二次电池优选使用上述低粘度溶剂。在本申请中，对低粘度溶剂的类型没有特别限制，只要其在二次电池中不易引起副反 应并且能够提高二次电池的倍率性能即可。例如，所述低粘度溶剂可以包含选自碳酸二甲酯(DMC)、乙酸乙酯(EA)、乙酸甲酯(MA)、乙腈(ACN)中的至少一种。
从改善二次电池的倍率性能方面考虑，本实施方式的二次电池中所述低粘度溶剂占所述电解液中的总溶剂的质量百分比B可以为10质量％～80质量％，可选为20质量％～70质量％。可选地，所述低粘度溶剂占所述电解液中的总溶剂的质量百分比B可以为10质量％～70质量％，10质量％～60质量％，10质量％～50质量％，20质量％～50质量％，30质量％～70质量％，30质量％～60质量％，30质量％～40质量％。可选地，所述低粘度溶剂占所述电解液中的总溶剂的质量百分比B可以为15质量％、25质量％、35质量％、45质量％、55质量％、65质量％和75质量％。如上所述，上述低粘度溶剂能够改善二次电池的倍率性能。但是，当低粘度溶剂的含量过高时，高介电常数溶剂在电解液中的含量可能过低，从而影响电解质盐的解离而劣化电解液的离子电导率，由此劣化二次电池的倍率性能。另一方面，当低粘度溶剂的含量过低时，提高二次电池的倍率性能的效果可能不显著。
本申请中电解质盐的类型没有特别限制，可以使用本领域常用的电解质盐。从改善二次电池的倍率性能等方面考虑，本实施方式的所述电解质盐可以包含选自LiPF 6、LiBF 4、LiN(SO 2F) 2(LiFSI)、LiN(CF 3SO 2) 2(LiTFSI)、LiClO 4、LiAsF 6、LiB(C 2O 4) 2(LiBOB)、LiBF 2C 2O 4(LiDFOB)中的至少一种；或者所述电解质盐可以包含选自NaPF 6、NaClO 4、NaBCl 4、NaSO 3CF 3及Na(CH 3)C 6H 4SO 3中的至少一种。其中，锂盐优选使用LiFSI和LiPF 6。
从改善二次电池的倍率性能等方面考虑，本实施方式的所述电解质盐占所述电解液的质量百分比C可以为10质量％～23质量％，可选为13质量％～20质量％。可选地，所述低粘度溶剂占所述电解液中的总溶剂的质量百分比B可以为10质量％～22质量％，10质量％～20质量％，10质量％～18质量％，10质量％～16质量％，10质量％～14质量％，10质量％～15质量％，11质量％～20质量％，12质量％～18质量％，12质量％～17质量％，12质量％～15质量％，13质量％～20质量％，13质量％～18质量％和13质量％～15质量％。
电解质盐可以提供活性离子如锂离子，并且电解液中较大的活性离子浓度能够改善快速充电过程中的浓差极化。但是，如果电解质盐浓度过高，则电解液粘度较大，从而会劣 化倍率性能。当电解液中电解质盐的浓度在上述范围内时，有利于改善二次电池的倍率性能。
从改善二次电池的倍率性能等方面考虑，本实施方式的所述高介电常数溶剂可以包含环状碳酸酯，所述环状碳酸酯可以包含选自碳酸亚乙酯、碳酸亚丙酯、碳酸1,2-亚丁酯、碳酸2,3-亚丁酯、碳酸1,2-亚戊酯、碳酸2,3-亚戊酯、氟代碳酸亚乙酯中的至少一种。
高介电常数溶剂具有较好的溶剂化能力，因此在电解液中含有一定量的高介电常数溶剂能够较好地解离电解质盐，实现较高的电解液离子电导率，从而改善二次电池的倍率性能。
从改善二次电池的倍率性能等方面考虑，本实施方式的所述高介电常数溶剂占所述电解液中的总溶剂的质量百分比可以为20质量％～40质量％。可选地，所述高介电常数溶剂占所述电解液中的总溶剂的质量百分比可以为20质量％～35质量％，20质量％～30质量％，20质量％～25质量％，25质量％～40质量％，25质量％～36质量％，25质量％～32质量％，25质量％～28质量％，30质量％～40质量％和30质量％～35质量％。可选地，所述高介电常数溶剂占所述电解液中的总溶剂的质量百分比可以为21质量％，22质量％，23质量％，24质量％，27质量％，28质量％，29质量％，33质量％，34质量％，37质量％，38质量％和39质量％。当所述高介电常数溶剂占所述电解液中的总溶剂的质量百分比过低时，电解液中的电解质盐可能不会被充分地解离，从而劣化电解液的离子电导率。另一方面，当所述高介电常数溶剂占所述电解液中的总溶剂的质量百分比过高时，电解液的粘度可能变得较大，由此可能导致电解液对正负极的浸润性变差而劣化二次电池的性能。当高介电常数溶剂占电解液中的总溶剂的质量百分比在上述范围内时，有利于改善二次电池的倍率性能、循环性能和存储性能。
从改善二次电池的倍率性能、循环性能和存储性能等方面考虑，本实施方式的所述电解液可以还包含选自碳酸二乙酯、碳酸甲乙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸甲丁酯、丙酸甲酯、丙酸乙酯中的至少一种。
从改善二次电池的倍率性能、循环性能和存储性能等方面考虑，本实施方式的所述电 解液可以还包含成膜添加剂。所述成膜添加剂可以包含选自碳酸亚乙烯酯、氟代碳酸亚乙酯、二氟双草酸磷酸锂、1,3-丙烷磺酸内酯、二氟磷酸锂、双氟草酸硼酸锂、腈类化合物和环状硫酸酯中的至少一种，可选地，所述环状硫酸酯为硫酸亚乙酯。所述成膜添加剂可以在二次电池正极和/或负极的表面上形成低阻抗的保护膜而减少电池内的副反应，从而提高二次电池的倍率性能、循环性能和存储性能等。
从改善二次电池的倍率性能、循环性能和存储性能等方面考虑，本实施方式的所述电解液在25℃下的电导率可以为8mS/cm～16mS/cm。所述电导率可以为8mS/cm～16mS/cm，8mS/cm～14mS/cm，8mS/cm～12mS/cm，8mS/cm～10mS/cm，9mS/cm～15mS/cm，9mS/cm～13mS/cm，9mS/cm～11mS/cm，10mS/cm～15mS/cm和11mS/cm～16mS/cm。
从改善二次电池的倍率性能、循环性能和存储性能等方面考虑，本实施方式的所述电解液在25℃下的粘度可以为1mPa·s～7mPa·s。所述粘度可以为1mPa·s～7mPa·s，1mPa·s～6mPa·s，1mPa·s～5mPa·s，1mPa·s～4mPa·s，2mPa·s～7mPa·s，2mPa·s～5mPa·s，2mPa·s～4mPa·s，3mPa·s～7mPa·s，2mPa·s～6mPa·s和2mPa·s～6.5mPa·s。
从改善二次电池的倍率性能、循环性能和存储性能等方面考虑，本实施方式的所述负极活性材料层的OI值可以为3～24，可选为8～24。可选地，所述负极活性材料层的OI值可以为3～20，3～18，3～15，3～14，3～10，3～8，3～6，5～22，5～20，5～18，5～10，5～8，6～22，6～18，6～15，6～10，6～8，7～18，7～12，7～10，7～9，8～18，8～14和8～10。
OI值越小越有利于锂离子较快地嵌入负极中。当负极活性材料层的OI值在上述范围内时，有利于使二次电池具有优异的倍率性能、循环性能和存储性能。
本领域技术人员理解：负极活性材料层的OI值用于表示负极活性材料层的取向指数，即负极活性材料层中晶粒排列的各向异性程度。在本申请中，OI值被定义为负极活性材料层在X射线衍射谱图中(004)特征衍射峰和(110)特征衍射峰的面积比。即，OI＝C004/C110，C004为所述负极活性材料层的X射线衍射图谱中004特征衍射峰的峰面积，且C110为所述负极活性材料层的X射线衍射图谱中110特征衍射峰的峰面积。
负极活性材料层的OI值可以用本领域公知的方法进行测定，例如用本申请实施例部分所述的方法进行测定。
在负极的制备过程中，负极活性材料层的OI值可通过调节以下参数来控制。
首先，负极活性材料的体积平均粒径Dv50和活性材料粉体OI值G OI对负极活性材料层OI值均有一定影响。通常，负极活性材料的Dv50越大，负极活性材料层的OI值越大，负极活性材料的粉体OI值越大，负极活性材料层的OI值越大。
其次，在电池制备过程中，可在涂布或干燥工序引入磁场诱导技术，人为诱导负极活性材料在负极中的排布，从而改变负极活性材料层OI值的大小；也可在冷压工序，通过调节负极活性材料层的压实密度，改变负极活性材料的排布，进而控制负极活性材料层的OI值。
从改善二次电池的倍率性能、循环性能和存储性能等方面考虑，本实施方式的所述负极活性材料层的涂布量CW可以为6.5mg/cm 2～19.5mg/cm 2，可选为6.5mg/cm 2～13mg/cm 2。可选地，所述负极活性材料层的涂布量CW可以为6.5mg/cm 2～18mg/cm 2，6.5mg/cm 2～16mg/cm 2，6.5mg/cm 2～14mg/cm 2，6.5mg/cm 2～12mg/cm 2，6.5mg/cm 2～10mg/cm 2，7mg/cm 2～18mg/cm 2，7mg/cm 2～16mg/cm 2，7mg/cm 2～14mg/cm 2，7mg/cm 2～12mg/cm 2，7mg/cm 2～10mg/cm 2，8mg/cm 2～18mg/cm 2，8mg/cm 2～16mg/cm 2，8mg/cm 2～14mg/cm 2，8mg/cm 2～12mg/cm 2，8mg/cm 2～10mg/cm 2，8.5mg/cm 2～18mg/cm 2，8.5mg/cm 2～16mg/cm 2，8.5mg/cm 2～14mg/cm 2，8.5mg/cm 2～12mg/cm 2，8.5mg/cm 2～10mg/cm 2。进一步可选地，所述负极活性材料层的涂布量CW可以为9mg/cm 2，11mg/cm 2，13mg/cm 2，15mg/cm 2，17mg/cm 2和19mg/cm 2。
负极活性材料层的涂布量为单位面积上涂覆的负极活性材料层的质量。具有较小涂布量的负极具有较小的扩散阻抗，使得锂离子能够在负极活性材料层中较好地扩散，由此改善二次电池的倍率性能。但是，负极活性材料的用量会直接影响二次电池的能量密度，因此负极活性材料层的涂布量不宜过小。当负极活性材料层的涂布量CW在上述范围内时，有利于改善二次电池的倍率性能、循环性能和存储性能。
从改善二次电池的倍率性能、循环性能和存储性能等方面考虑，本实施方式的所述负极活性材料层的孔隙率P可以为20％～60％。可选地，所述负极活性材料层的孔隙率P可以为20％～55％，20％～50％，20％～45％，20％～40％，20％～35％，25％～55％，25％～50％，25％～45％，25％～40％，25％～35％，30％～55％，30％～45％，30％～43％，30％～41％，30％～38％，34％～55％，34％～45％，36％～43％，36％～41％或36％～48％。
负极活性材料层的孔隙率P可以如下进行测量：利用小分子直径的惰性气体如氦气或氮气，通过置换法精确测量得到待测样品的真实体积，并且结合玻尔定律(PV＝nRT)得到待测样品的孔隙率。孔隙率P＝(V11-V12)/V11×100％，其中V11表示负极活性材料层的表观体积，V12表示负极活性材料层的真实体积。
负极活性材料层的孔隙率的大小会影响锂离子在负极活性材料层中的扩散，从而影响二次电池的倍率性能。通常，负极活性材料层的孔隙率越大，电解液的浸润性越好，二次电池的倍率性能越好。但是，孔隙率过大则存在可能发生内部短路或者自放电率大的缺点。此外，负极活性材料层的孔隙率过大，有可能不利于保持负极活性材料层的机械强度。当负极活性材料层的孔隙率在上述范围内时，有利于改善二次电池的倍率性能、循环性能和存储性能，同时又能保持负极活性材料层的机械强度、防止发生内部短路或者自放电。
从改善二次电池的倍率性能、循环性能和存储性能等方面考虑，本实施方式的所述负极活性材料可以包含选自人造石墨、天然石墨、软碳、硬碳和硅基材料中的至少一种；或者所述负极活性材料可以包含选自天然石墨、改性石墨、人造石墨、石墨烯、碳纳米管、碳纳米纤维、多孔碳、锡、锑、锗、铅、三氧化二铁、五氧化二钒、二氧化锡、二氧化钛、三氧化钼、单质磷、钛酸钠和对苯二甲酸钠中的至少一种。可选地，所述硅基材料可以包含选自硅单质、硅氧化物、硅碳复合物和硅基合金中的至少一种。
从改善二次电池的倍率性能、循环性能和存储性能等方面考虑，本实施方式的所述硅基材料占所述负极活性材料总体的质量百分比可以为0质量％～30质量％，可选为0质量％～10质量％。可选地，所述硅基材料占所述负极活性材料总体的质量百分比可以为0质量％～25质量％，0质量％～20质量％，0质量％～15质量％，0质量％～5质量％，4质量％～20质量％，4质量％～16质量％，4质量％～12质量％，6质量％～13质量％，6质 量％～26质量％，6质量％～18质量％，7质量％～13质量％，7质量％～22质量％或7质量％～19质量％。
从改善二次电池的倍率性能、循环性能和存储性能等方面考虑，本实施方式的所述二次电池还包含正极，所述正极可以包含分子式为LiNi xCo yMn zM 1-x-y-zO 2的正极活性材料，其中0≤x≤1，0≤y≤0.5，0≤z≤0.5，且x+y+z＝1，可选地，0.5≤x≤0.9，0≤y≤0.3，且0≤z≤0.3，并且M为选自Zr、Al、Mg、Sb、Fe、Cu、W中的至少一种。可选地，所述正极活性材料可以选自LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)及其改性化合物中的至少一种。当二次电池为钠离子二次电池时，所述正极可以包含选自如下中的至少一种正极活性材料：层状过渡金属氧化物、聚阴离子化合物、普鲁士蓝类化合物、硫化物、氮化物、碳化物、钛酸盐。
本申请的实施方式的详细说明
以下适当地参照附图对本申请的二次电池、电池模块、电池包和用电装置进行详细说明。
在本申请的一个实施方式中，提供一种二次电池。所述二次电池可以为锂离子电池和钠离子电池。以下以锂离子电池为例对本申请的具体实施方式进行详细说明。
通常情况下，锂离子电池可以包含正极、负极、电解液和隔离膜。在电池充放电过程中，锂离子在正极和负极之间往返嵌入和脱出。电解液在正极和负极之间起到传导锂离子的作用。隔离膜设置在正极和负极之间，主要起到防止正负极短路的作用，同时可以使离子通过。在某些情况下，例如在采用凝胶聚合物电解质作为电解液的情况下，所述电解质可以同时起到隔离膜的作用。此时，所述电解质也视为本申请中所述的电解液。换而言之，本申请的电解液不限于液态形式。以下对锂离子电池的各构成要素进行详细说明。
[正极]
正极可以包含正极集流体以及设置在正极集流体的至少一个表面上的正极活性材料 层。所述正极活性材料层可以包含正极活性材料以及可选的粘结剂和导电剂。
作为示例，正极集流体具有在其自身厚度方向上相对的两个表面。正极活性材料层设置在正极集流体的相对的两个表面中的任一者或两者上。
在一些实施方式中，所述正极集流体可以采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铝箔。复合集流体可以包含高分子材料基材和形成于高分子材料基材的至少一个表面上的金属层。复合集流体可以通过将金属材料(如铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可以采用本领域公知的用于锂离子电池的正极活性材料。作为示例，正极活性材料可以包含以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可以被用作锂离子电池正极活性材料的传统材料。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。例如，可以使用分子式为LiNi xCo yMn zM 1-x-y-zO 2的正极活性材料，其中0≤x≤1，0≤y≤0.5，0≤z≤0.5，且x+y+z＝1，可选地，0.5≤x≤0.9，0≤y≤0.3，且0≤z≤0.3，并且M为选自Zr、Al、Mg、Sb、Fe、Cu、W中的至少一种。可选地，所述正极活性材料可以选自LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)及其改性化合物中的至少一种。此外，橄榄石结构的含锂磷酸盐的示例可以包含但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、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中的至少一种。
当所述二次电池为钠离子电池时，所述正极可以包含选自如下中的至少一种正极活性材料：层状过渡金属氧化物、聚阴离子化合物、普鲁士蓝类化合物、硫化物、氮化物、碳化物、钛酸盐。可选地，所述正极活性材料包括但不限于选自由NaCrO 2、Na 2Fe 2(SO 4) 3、 二硫化钼、二硫化钨、二硫化钒、二硫化钛、六方氮化硼、碳掺杂六方氮化硼、碳化钛、碳化钽、碳化钼、碳化硅、Na 2Ti 3O 7、Na 2Ti 6O 13、Na 4Ti 5O 12、Li 4Ti 5O 12、NaTi 2(PO 4) 3构成的组中的至少一种。
在一些实施方式中，正极活性材料层还可以选择性地包含粘结剂。作为示例，所述粘结剂可以包含选自由聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏二氟乙烯-四氟乙烯-丙烯三元共聚物、偏二氟乙烯-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构成的组中的至少一种。
在一些实施方式中，正极活性材料层还可以选择性地包含导电剂。作为示例，可以使用本领域通常使用的导电剂。所述导电剂可以包含超导碳、乙炔黑、炭黑、科琴黑、碳纳米管、碳纳米棒、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极：将上述用于制备正极的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可以得到正极。可替代地，在另一个实施方式中，可以通过如下方式来制造正极：将用于形成正极活性材料层的正极浆料流延在单独的载体上，然后将通过从载体剥离而获得的膜层压在正极集流体上。
[负极]
负极包含负极集流体以及设置在负极集流体的至少一个表面上的负极活性材料层。所述负极活性材料层可以包含负极活性材料以及可选的粘结剂、导电剂和其他助剂。
作为示例，负极集流体具有在其自身厚度方向上相对的两个表面，负极活性材料层设置在负极集流体的相对的两个表面中的任一者或两者上。
在一些实施方式中，所述负极集流体可以采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可以包含高分子材料基材和形成于高分子材料基材的至少一个表面上的金属层。复合集流体可以通过将金属材料(如铜、铜合金、镍、镍合金、 钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在二次电池为锂离子电池的实施方式中，负极活性材料可以采用本领域公知的用于锂离子电池的负极活性材料。作为示例，负极活性材料可以包含选自人造石墨、天然石墨、软碳、硬碳和硅基材料中的至少一种。所述硅基材料包含选自硅单质、硅氧化物、硅碳复合物和硅基合金中的至少一种。在负极活性材料包含硅基材料时，所述硅基材料占所述负极活性材料总体的质量百分比可以为0质量％～30质量％，可选为0质量％～10质量％。但本申请并不限定于这些材料，还可以使用其他可以被用作电池负极活性材料的传统材料。这些负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。
在二次电池为钠离子电池的实施方式中，负极活性材料可以包括选自天然石墨、改性石墨、人造石墨、石墨烯、碳纳米管、碳纳米纤维、多孔碳、锡、锑、锗、铅、三氧化二铁、五氧化二钒、二氧化锡、二氧化钛、三氧化钼、单质磷、钛酸钠和对苯二甲酸钠中的至少一种。可选地，所述负极活性材料为选自天然石墨、改性石墨、人造石墨和石墨烯中的至少一种。
在一些实施方式中，负极活性材料层还可以选择性地包含粘结剂。所述粘结剂可以选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极活性材料层还可以选择性地包含导电剂。导电剂可以选自超导碳、乙炔黑、炭黑、科琴黑、碳纳米管、碳纳米棒、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极活性材料层还可以选择性地包含其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极：将上述用于制备负极的组分，例如 负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可以得到负极。可替代地，在另一个实施方式中，可以通过如下方式来制造负极：将用于形成负极活性材料层的负极浆料流延在单独的载体上，然后将通过从载体剥离而获得的膜层压在负极集流体上。
[电解液]
电解液在正极和负极之间起到传导离子的作用。本申请对电解液的种类没有具体的限制，可以根据需求进行选择。例如，电解液可以是液态的或凝胶态的。
此外，本申请的实施方式的电解液可以包含添加剂。所述添加剂可以包含本领域中常用的添加剂。所述添加剂可以包含例如卤代碳酸亚烷基酯类化合物(如二氟碳酸亚乙酯)、吡啶、亚磷酸三乙酯、三乙醇胺、环醚、乙二胺、(缩)甘醇二甲醚类、六甲基磷酸三酰胺、硝基苯衍生物、硫、醌亚胺染料、N-取代的唑烷酮、N,N-取代的咪唑烷、乙二醇二烷基醚、铵盐、吡咯、2-甲氧基乙醇或三氯化铝。此时，基于电解液的总重量，可以以0.1重量％至5重量％的量包含添加剂或者由本领域技术人员根据实际需要调整添加剂的用量。
一般而言，电解液可以包含电解质盐和溶剂。
在二次电池为锂离子电池的实施方式中，所述电解质盐可以包含选自LiPF 6、LiBF 4、LiN(SO 2F) 2(LiFSI)、LiN(CF 3SO 2) 2(LiTFSI)、LiClO 4、LiAsF 6、LiB(C 2O 4) 2(LiBOB)、LiBF 2C 2O 4(LiDFOB)中的至少一种。
在二次电池为钠离子电池的实施方式中，电解质盐可以包含选自NaPF 6、NaClO 4、NaBCl 4、NaSO 3CF 3及Na(CH 3)C 6H 4SO 3中的至少一种。
在一些实施方式中，除了上述提及的低粘度溶剂和高介电常数溶剂等溶剂以外，电解液还可以根据需要包含本领域常用的其他溶剂如选自1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜等中的至少一种。
[隔离膜]
在一些实施方式中，二次电池中还包含隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。此外，所述隔离膜优选具有优异的离子透过能力和电解液保湿能力。
在一些实施方式中，隔离膜的材质可以选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜的形式没有特别限制，可以是单层薄膜，也可以是多层复合薄膜。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极、负极和隔离膜可以通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可以包含外包装。该外包装可以用于封装上述电极组件及电解液。
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。作为塑料，可以列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
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。例如，图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，外包装可以包含壳体51和盖板53。其中，壳体51可以包含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、负极和隔离膜可以经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。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多个，本领域技术人员可以根据实际需求进行选择。
在一些实施方式中，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一个或多个，具体数量本领域技术人员可以根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池5沿电池模块4的长度方向依次排列设置。当然，多个二次电池5也可以按照其他任意的方式进行排布。进一步地，可以通过紧固件将所述多个二次电池5进行固定。
可选地，电池模块4还可以包含具有容纳空间的外壳，多个二次电池5容纳于该容纳空间内。
在一些实施方式中，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为一个或多个，具体数量本领域技术人员可以根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包含电池箱和设置于电池箱中的多个电池模块4。电池箱包含上箱体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。
另外，本申请还提供一种用电装置，所述用电装置包含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、电池模块或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包含移动设备(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***等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电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
以下详细说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商的，均为可以通过市购获得的常规产品。以下以锂离子电池为例对本申请的实施例进行说明。
实施例1
锂离子电池的制备
1、电解液的制备
电解液的制备在含水量<10质量ppm的氩气气氛手套箱中进行。首先，将碳酸二甲酯/碳酸亚乙酯/碳酸二乙酯按照2/3/5(质量比)的比例进行混合，然后将13wt％的LiPF 6加入到上述混合溶剂中，由此完成电解液的配制。上述锂盐的量为基于电解液的总重量计算得到的百分数。
2、正极的制备
将正极活性材料LiNi 5Co 2Mn 3O 2、粘结剂聚偏二氟乙烯、导电剂乙炔黑按照重量比98:1:1的比例进行混合并分散于溶剂N-甲基吡咯烷酮(NMP)中制成正极浆料，然后将上述浆料涂布在集流体铝箔上，干燥后进行冷压、切边、裁片、分条等，制成锂离子电池的正极。
3、负极的制备
将负极活性材料人造石墨(其OI值示于表1中；下同)、导电剂碳黑、增稠剂CMC、粘结剂丁苯橡胶(SBR)按照重量比96:2:1:1的比例进行混合并分散于溶剂去离子水中，通过真空搅拌机搅拌而获得负极浆料；然后将上述负极浆料涂布在集流体铜箔上，干燥后进行冷压、切边、裁片、分条等，制成涂布重量为8mg/cm 2，孔隙率为40％的负极。本实施例中的负极活性材料层的OI值为7(其OI值示于表1中；下同)。
负极活性材料层的孔隙率P的测定
负极活性材料层的孔隙率P可以如下进行测量：利用小分子直径的惰性气体如氦气或氮气，通过置换法精确测量得到待测样品的真实体积，并且结合玻尔定律(PV＝nRT)得到待测样品的孔隙率。孔隙率P＝(V11-V12)/V11×100％，其中V11表示负极极片的表观体积，通过计算极片的长*宽*厚获得；V12表示负极极片的真实体积。具体测试方法为：打开压缩钢瓶，调节减压阀使压力平衡在0.14MPa～0.18MPa，将负极冲压成面积为1.5394cm 2的相对平整无缺的圆片，样品数量＞20，将样品放入样品杯，操控真密度测试仪(GB/T2790-1995)进行测试，获得负极极片的真实体积V12；V11通过1.5394cm 2*极片厚度获得。通过根据公式孔隙率P＝(V11-V12)/V11×100％获得待测样品的孔隙率。
负极活性材料层OI值的测定
负极活性材料层的OI值用于表征负极活性材料层中活性材料的取向指数。负极活性材料层的OI值可以通过使用X射线粉末衍射仪测量得到的X射线衍射谱图进行计算得到。即OI＝C004/C110，其中，C004为负极活性活性材料层004特征衍射峰的峰面积，且C110为负极活性活性材料层110特征衍射峰的峰面积。具体测试方法：控制环境温度为15-25℃，环境湿度为20％-80％，取极片样品面积不小于30mm*30mm的极片，用双面胶将极片小心贴在干净的载玻片的一端，置于Bruker D8Discover X射线粉末衍射仪中，设定扫描角度范围为50-80°，步长0.01°，每步时长0.9S，启动设备获得负极活性材料层的X射线衍射谱，利用软件DIFFRAC.EVA V4.2.2获得负极活性材料层004晶面衍射峰的峰面积及110晶面衍射峰的峰面积，从而利用公式OI＝C004/C110得到负极活性材料层的OI值。
4、隔离膜
以市售聚丙烯膜作为隔离膜。
5、电池的组装
将上述的正极、隔离膜、负极按顺序卷绕或叠好，使隔离膜处于正、负极中间，得到裸电芯，将裸电芯置于铝塑壳外包装中，将上述制备的电解液注入到干燥后的电芯中，经过静置、化成、整形等工序，获得锂离子电池。
实施例2
除了以碳酸二甲酯/碳酸亚乙酯/碳酸二乙酯按照4/3/3(质量比)的比例进行混合以外，以与实施例1相同的方式制备了锂离子电池。
实施例3
除了以碳酸二甲酯/碳酸亚乙酯/碳酸二乙酯按照7/3/0(质量比)的比例进行混合以外，以与实施例1相同的方式制备了锂离子电池。
实施例4和5
除了锂盐的含量分别改为10wt％和23wt％以外，以与实施例2相同的方式制备了锂离子电池。
实施例6和7
除了将负极活性材料层的取向指数OI值分别改为3和24以外，以与实施例2相同的方式制备了锂离子电池。
实施例8和9
除了将所制备的负极的涂布量改为6.5mg/cm 2和13mg/cm 2以外，以与实施例2相同的方式制备了锂离子电池。
实施例10和11
除了将所制备的负极的孔隙率改为20％和60％以外，以与实施例2相同的方式制备了锂离子电池。
实施例12
除了将碳酸二甲酯换成乙酸乙酯以外，以与实施例2相同的方式制备了锂离子电池。
实施例13
除了在电解液的制备中额外添加占电解液的总质量的1质量％的硫酸亚乙酯以外，以与实施例1相同的方式制备了锂离子电池。
实施例14
除了按照下表2中所示调节电解液中高介电常数溶剂等溶剂的含量以外，以与实施例2相同的方式制备了锂离子电池。
实施例15
除了所用负极活性材料人造石墨表面包覆有占负极活性材料人造石墨的总质量的2质量％的软碳以外，以与实施例2相同的方式制备了锂离子电池。本实施例中制得的负极活性材料层的OI值为4。
实施例16
除了以占负极活性材料人造石墨的总质量为3质量％的量组合使用SiO以外，以与实施例2相同的方式制备了锂离子电池。本实施例中制得的负极活性材料层的OI值为7。
实施例17
除了将正极活性材料替换为NaCrO 2并且将电解液中的电解质盐替换为NaPF 6以外，以与实施例1相同的方式制备了钠离子电池。
对比例1～8
除了按照下表1和2中所示调节电解液中溶剂的比例、负极活性材料层的OI值、锂盐浓度、负极活性材料层的孔隙率和负极活性材料层的涂布量以外，以与实施例2相同的方式制备了锂离子电池。
接下来，说明锂离子电池的测试过程。
1.电解液的电导率测试
在相互平行的两个铂黑极板间施加1KHz的交流电压，电解质溶液中的带电离子在电场的影响下将产生移动而传递电子，传递电子的能力转化为电信号输出，即得到电导率。
具体地，采用雷磁(DDSJ-318)电导率仪对成品电解液的电导率进行测试。控制环境温度为25℃，环境湿度＜80％，取量40mL的电解液，将样品倒入干燥洁净的塑料离心管 中置于25℃的恒温槽中恒温30min，将吸干水分的电极垂直放入均匀的待测样品中启动仪器进行测试，重复测试3次，取3次结果的平均值。
2.电解液的粘度测试
在一定温度下，转子在样品中以恒定转速持续旋转时受到的剪切力使弹簧产生扭矩，扭矩与粘度成正比，由此得到粘度值。
具体地，采用博勒飞(DV-2TLV)粘度计对成品电解液的粘度进行测试。控制环境温度为25℃，环境湿度＜80％，取30mL的电解液，将其恒温在25℃的水浴锅中至少30min，将转子装入样品杯，加入样品至离杯口约0.3cm处，启动连接着的粘度计，选择70RPM的转速进行测试，采集10个数据点，求取多点平均值。
3.倍率性能测试
倍率性能测试(充电至80％SOC的测试)：调节测试温度至35℃，对锂离子电池进行xC倍率(x为0.5、0.8、1、1.2、1.5、2、2.5、3)下的充电，然后在1C下放电，充电倍率依次增高，以阳极电位0V为充电截止条件，获得0～10％SOC、10～20％SOC、20～30％SOC、30～40％SOC、40～50％SOC、50～60％SOC、60～70％SOC、70～80％SOC区间内能够实现的最大充电倍率x 1C、x 2C、x 3C、x 4C、x 5C、x 6C、x 7C、x 8C，利用公式：
Figure PCTCN2021122432-appb-000003
Figure PCTCN2021122432-appb-000004
从而计算出0～80％SOC所需的充电时间(min)。
4.循环寿命
在45℃下，将锂离子电池以1C恒流充电至4.25V，再以4.25V恒压充电至电流为0.05C，静置5min，再以1C恒流放电至截止电压下限2.8V，此为二次电池的首次充电/放电循环。将本次的放电容量记为锂离子电池首次循环的放电容量。然后，在45℃下，将上述锂离子电池以1C恒流充电至4.25V，再以4.25V恒压充电至电流为0.05C，静置5min，再以1C恒流放电至截止电压下限2.8V。以上述充放电条件进行循环充放电直至锂离子电池到达80％容量保持率为截止条件，得到80％容量保持率的条件下二次电池的循环圈数。
5.高温存储性能测试
在60℃下，将锂离子电池以1C恒流充电至4.25V，再以4.25V恒压充电至电流为0.05C，用排水法测定此时锂离子电池的体积并记为V21；之后将锂离子电池放入60℃的恒温箱中，储存30天后取出。测定此时锂离子电池的体积并记为V22。二次电池60℃存储100天后的体积膨胀率(％)＝[(V22-V21)/V21]×100。
表1
Figure PCTCN2021122432-appb-000005
Figure PCTCN2021122432-appb-000006
由上述表2中的实施例1～17与对比例1～8的比较可以看出，在锂离子电池满足上述关系式的情况下，锂离子电池具有优异的倍率性能，并且同时还具有优异的循环性能和良好的高温存储性能。
由实施例2和实施例14与对比例8的比较可以看出，当高介电常数溶剂的含量低于本申请的范围时，锂离子电池的倍率性能和循环性能(尤其是循环性能)降低明显。由实施例2与实施例14的比较可以看出，虽然高介电常数溶剂能够提高电池倍率性能，但是当高介电常数溶剂的含量大于本申请的优选范围(20质量％～40质量％)时，与高介电常数溶剂的含量在本申请的优选范围内的实施例2相比，实施例14的锂离子电池的倍率性能、循环性能和高温存储性能略差。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (21)

  1. 一种二次电池，包含电解液和负极，
    所述电解液包含低粘度溶剂、电解质盐和高介电常数溶剂，
    所述低粘度溶剂在25℃下的粘度为0.3mPa·s～0.6mPa·s，
    所述高介电常数溶剂的介电常数为30F/m～100F/m，且所述高介电常数溶剂占所述电解液中的总溶剂的质量百分比为20质量％以上，
    所述负极包含负极集流体和设置于所述负极集流体的至少一个表面上的负极活性材料层，并且
    所述二次电池满足如下关系式：
    Figure PCTCN2021122432-appb-100001
    其中B为所述低粘度溶剂占所述电解液中的总溶剂的质量百分比；C为所述电解质盐占所述电解液的质量百分比；P为所述负极活性材料层的孔隙率；CW为所述负极活性材料层的涂布量，单位为mg/cm 2；且OI为所述负极活性材料层的取向指数，并且
    其中OI＝C004/C110，C004为所述负极活性材料层的X射线衍射图谱中004特征衍射峰的峰面积，且C110为所述负极活性材料层的X射线衍射图谱中110特征衍射峰的峰面积。
  2. 根据权利要求1所述的二次电池，其中，所述低粘度溶剂包含选自碳酸二甲酯(DMC)、乙酸乙酯(EA)、乙酸甲酯(MA)、乙腈(ACN)中的至少一种。
  3. 根据权利要求1或2所述的二次电池，其中，所述低粘度溶剂占所述电解液中的总溶剂的质量百分比B为10质量％～80质量％，可选地为20质量％～70质量％。
  4. 根据权利要求1～3中任一项所述的二次电池，其中，所述电解质盐占所述电解液的质量百分比C为10质量％～23质量％，可选为13质量％～20质量％。
  5. 根据权利要求1～4中任一项所述的二次电池，其中，所述高介电常数溶剂包含环状碳酸酯，可选地，所述环状碳酸酯包含选自碳酸亚乙酯、碳酸亚丙酯、碳酸1,2-亚丁酯、 碳酸2,3-亚丁酯、碳酸1,2-亚戊酯、碳酸2,3-亚戊酯、氟代碳酸亚乙酯中的至少一种。
  6. 根据权利要求1～5中任一项所述的二次电池，其中，所述高介电常数溶剂占所述电解液中的总溶剂的质量百分比为20质量％～40质量％。
  7. 根据权利要求1～6中任一项所述的二次电池，其中，所述电解液还包含选自碳酸二乙酯、碳酸甲乙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸甲丁酯、丙酸甲酯、丙酸乙酯中的至少一种。
  8. 根据权利要求1～7中任一项所述的二次电池，其中，所述电解液还包含成膜添加剂，
    所述成膜添加剂包含选自碳酸亚乙烯酯、氟代碳酸亚乙酯、二氟双草酸磷酸锂、1,3-丙烷磺酸内酯、二氟磷酸锂、双氟草酸硼酸锂、腈类化合物和环状硫酸酯中的至少一种，可选地，所述环状硫酸酯为硫酸亚乙酯。
  9. 根据权利要求1～8中任一项所述的二次电池，其中，所述电解液在25℃下的电导率为8mS/cm～16mS/cm。
  10. 根据权利要求1～9中任一项所述的二次电池，其中，所述电解液在25℃下的粘度为1mPa·s～7mPa·s。
  11. 根据权利要求1～10中任一项所述的二次电池，其中，所述负极活性材料层的OI值为3～24，可选为8～24。
  12. 根据权利要求1～11中任一项所述的二次电池，其中所述负极活性材料层的涂布量CW为6.5mg/cm 2～19.5mg/cm 2，可选为6.5mg/cm 2～13mg/cm 2。
  13. 根据权利要求1～12中任一项所述的二次电池，其中，所述负极活性材料层的孔隙率P为20％～60％。
  14. 根据权利要求1～13中任一项所述的二次电池，其中，所述电解质盐包含选自LiPF 6、 LiBF 4、LiN(SO 2F) 2(LiFSI)、LiN(CF 3SO 2) 2(LiTFSI)、LiClO 4、LiAsF 6、LiB(C 2O 4) 2(LiBOB)、LiBF 2C 2O 4(LiDFOB)中的至少一种。
  15. 根据权利要求1～13中任一项所述的二次电池，其中，所述电解质盐包含选自NaPF 6、NaClO 4、NaBCl 4、NaSO 3CF 3及Na(CH 3)C 6H 4SO 3中的至少一种。
  16. 根据权利要求1～14中任一项所述的二次电池，其中，所述负极活性材料包含选自人造石墨、天然石墨、软碳、硬碳和硅基材料中的至少一种，可选地，所述硅基材料包含选自硅单质、硅氧化物、硅碳复合物和硅基合金中的至少一种。
  17. 根据权利要求15所述的二次电池，其中，所述负极活性材料包含选自天然石墨、改性石墨、人造石墨、石墨烯、碳纳米管、碳纳米纤维、多孔碳、锡、锑、锗、铅、三氧化二铁、五氧化二钒、二氧化锡、二氧化钛、三氧化钼、单质磷、钛酸钠和对苯二甲酸钠中的至少一种。
  18. 根据权利要求16所述的二次电池，其中，所述硅基材料占所述负极活性材料总体的质量百分比为0质量％～30质量％，可选为0质量％～10质量％。
  19. 根据权利要求1～14、16或18中任一项所述的二次电池，其中，所述二次电池还包含正极，
    所述正极包含分子式为LiNi xCo yMn zM 1-x-y-zO 2的正极活性材料，其中0≤x≤1，0≤y≤0.5，0≤z≤0.5，且x+y+z＝1，可选地，0.5≤x≤0.9，0≤y≤0.3，且0≤z≤0.3，并且M为选自Zr、Al、Mg、Sb、Fe、Cu、W中的至少一种。
  20. 根据权利要求1～13、15或17所述的二次电池，其中，所述二次电池还包含正极，
    所述正极包含选自如下中的至少一种正极活性材料：层状过渡金属氧化物、聚阴离子化合物、普鲁士蓝类化合物、硫化物、氮化物、碳化物、钛酸盐。
  21. 一种用电装置，其包含根据权利要求1至20中任一项所述的二次电池。
PCT/CN2021/122432 2021-09-30 2021-09-30 二次电池及包含其的电池模块、电池包和用电装置 WO2023050414A1 (zh)

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