WO2021127997A1 - 二次电池及含有该二次电池的装置 - Google Patents

二次电池及含有该二次电池的装置 Download PDF

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Publication number
WO2021127997A1
WO2021127997A1 PCT/CN2019/127976 CN2019127976W WO2021127997A1 WO 2021127997 A1 WO2021127997 A1 WO 2021127997A1 CN 2019127976 W CN2019127976 W CN 2019127976W WO 2021127997 A1 WO2021127997 A1 WO 2021127997A1
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secondary battery
lithium
electrolyte
mol
battery according
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PCT/CN2019/127976
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English (en)
French (fr)
Inventor
梁成都
吴则利
陈培培
付成华
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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 CN201980098832.2A priority Critical patent/CN114175338A/zh
Priority to KR1020227012242A priority patent/KR102585596B1/ko
Priority to PCT/CN2019/127976 priority patent/WO2021127997A1/zh
Priority to JP2022522047A priority patent/JP7381737B2/ja
Priority to EP19958003.6A priority patent/EP3930067B1/en
Publication of WO2021127997A1 publication Critical patent/WO2021127997A1/zh
Priority to US17/550,934 priority patent/US20220109190A1/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
    • H01M10/056—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
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • 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
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • 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
    • 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application relates to the field of battery technology, and in particular to a secondary battery and a device containing the secondary battery.
  • the present application provides a secondary battery and a device containing the secondary battery.
  • the secondary battery can have both good high-temperature cycle performance and high-temperature cycle performance under the premise of higher energy density. High temperature storage performance.
  • the first aspect of the present application provides a secondary battery
  • the secondary battery includes an electrolyte
  • the electrolyte includes an electrolyte salt and an organic solvent
  • the electrolyte salt includes lithium bisfluorosulfonimide ( LiFSI) and lithium hexafluorophosphate (LiPF 6 );
  • the molar concentration of the lithium bisfluorosulfonimide (LiFSI) in the electrolyte is 0.8 mol/L to 1.2 mol/L;
  • the lithium hexafluorophosphate (LiPF 6 ) is The volume molar concentration in the electrolyte is 0.15 mol/L to 0.4 mol/L;
  • the organic solvent includes ethylene carbonate (EC), and the content of the ethylene carbonate (EC) in the organic solvent is The proportion is less than or equal to 20%. .
  • a device which includes the secondary battery described in the first aspect of the present application.
  • the electrolyte salt in the electrolyte includes both lithium bisfluorosulfonimide (LiFSI) and lithium hexafluorophosphate (LiPF 6 ) at a specific content, and the organic solvent includes a specific content of ethylene carbonate (EC).
  • LiFSI lithium bisfluorosulfonimide
  • LiPF 6 lithium hexafluorophosphate
  • EC ethylene carbonate
  • the secondary battery has both good high-temperature cycle performance and high-temperature storage performance at the same time.
  • the device of the present application includes the secondary battery and therefore has at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of an embodiment of a secondary battery.
  • Fig. 2 is a schematic diagram of an embodiment of a battery module.
  • Fig. 3 is a schematic diagram of an embodiment of a battery pack.
  • Fig. 4 is an exploded view of Fig. 3.
  • Fig. 5 is a schematic diagram of an embodiment of a device in which a secondary battery is used as a power source.
  • the secondary battery includes an electrolyte
  • the electrolyte includes an electrolyte salt and an organic solvent
  • the electrolyte salt includes lithium bisfluorosulfonimide (LiFSI) and lithium hexafluorophosphate (LiPF 6 )
  • the molar concentration of the lithium bisfluorosulfonimide (LiFSI) in the electrolyte is 0.8 mol/L to 1.2 mol/L
  • the lithium hexafluorophosphate (LiPF 6 ) is in the electrolyte
  • the volume molar concentration in the organic solvent is 0.15 mol/L to 0.4 mol/L
  • the organic solvent includes ethylene carbonate (EC)
  • the mass ratio of the ethylene carbonate (EC) in the organic solvent is less than or equal to 20%.
  • the inventors have discovered through a lot of research that when the electrolyte simultaneously satisfies the electrolyte salt including lithium bisfluorosulfonimide (LiFSI) and lithium hexafluorophosphate (LiPF 6 ), the double The molar concentration of lithium fluorosulfonimide (LiFSI) in the electrolyte is 0.8 mol/L to 1.2 mol/L, and the molar concentration of lithium hexafluorophosphate (LiPF 6 ) in the electrolyte is 0.1 mol /L ⁇ 0.4mol/L, and the organic solvent includes ethylene carbonate (EC), and the mass proportion of the ethylene carbonate (EC) in the organic solvent is ⁇ 20%, under the combined action of the above conditions, two The secondary battery has good high temperature cycle performance and high temperature storage performance.
  • LiFSI lithium bisfluorosulfonimide
  • LiPF 6 lithium hexafluorophosphate
  • the inventor guessed that the possible reason for the above-mentioned beneficial effects is that when LiFSI and LiPF 6 are combined as an electrolyte salt, and when the molar concentration of the two is controlled within a specific range, the advantages of the two complement each other and can effectively alleviate the oxidation of LiFSI on the positive electrode.
  • the impact on the cycle performance of the secondary battery; at the same time, on the basis of the above-mentioned mixed electrolyte salt, the organic solvent also includes a specific content of ethylene carbonate (EC), which can dissociate the above-mentioned mixed electrolyte salt well, and The high-temperature storage performance of the battery can be further improved.
  • EC ethylene carbonate
  • the molar concentration of the lithium bisfluorosulfonimide (LiFSI) in the electrolyte is 0.9 mol/L to 1.2 mol/L.
  • the molar concentration of lithium bisfluorosulfonimide (LiFSI) in the electrolyte is within this range, the high-temperature storage performance of the battery can be further improved.
  • the molar concentration of the lithium hexafluorophosphate (LiPF 6 ) in the electrolyte is 0.15 mol/L to 0.3 mol/L.
  • the molar concentration of lithium hexafluorophosphate (LiPF 6 ) in the electrolyte is within this range, the high temperature cycle performance of the battery will be further improved.
  • the mass ratio of the ethylene carbonate (EC) in the organic solvent is ⁇ 15%. If the content of EC is too high, the SEI film formed by the decomposition products on the surface of the negative electrode will be too thick, which will deteriorate the DC resistance of the secondary battery to a certain extent. More preferably, the mass ratio of the ethylene carbonate (EC) in the organic solvent is ⁇ 10%.
  • the molar concentration ratio of the lithium bisfluorosulfonimide (LiFSI) to the lithium hexafluorophosphate (LiPF 6 ) is 3-7:1.
  • the two can better exert a synergistic effect, so that the high-temperature cycle performance and high-temperature storage performance of the secondary battery are better improved.
  • the ratio of the molar concentration of the lithium bisfluorosulfonimide (LiFSI) to the lithium hexafluorophosphate (LiPF 6) is 4-6:1.
  • the organic solvent further includes one of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) or Several kinds.
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • the organic solvent further includes ethyl methyl carbonate (EMC), and the mass ratio of the ethyl methyl carbonate (EMC) in the organic solvent is 60%-95%, more preferably 75%-95%.
  • EMC ethyl methyl carbonate
  • the electrolyte further includes additives.
  • the additives include fluoroethylene carbonate (FEC), vinyl sulfate (DTD), 1,3-propane sulfonate Lactone (PS), 1,3-propenyl-sultone (PST), succinic anhydride (SA), lithium difluorooxalate borate (LiDFOB), lithium difluorobisoxalate phosphate (LiDFOP), tris(tris) One or more of methylsilyl)phosphate (TMSP) and tris(trimethylsilyl)borate (TMSB).
  • FEC fluoroethylene carbonate
  • DTD vinyl sulfate
  • PS 1,3-propane sulfonate Lactone
  • PST 1,3-propenyl-sultone
  • SA succinic anhydride
  • LiDFOB lithium difluorooxalate borate
  • LiDFOP lithium difluorobisoxalate phosphate
  • TMSP methyl
  • the electrolytic solution has a conductivity of 6.5 mS/cm to 9.5 mS/cm at 25°C; more preferably, the electrolytic solution has a conductivity of 6.5 mS/cm to 9.5 mS/cm at 25°C.
  • the electrical conductivity is 7.0mS/cm ⁇ 9.0mS/cm.
  • the electrical conductivity of the electrolyte at 25° C. can be tested by a well-known method in the art, and the testing instrument used can be a lightning electrical conductivity device.
  • the molar concentration of the electrolyte salt in the electrolyte is 0.9 mol/L to 1.1 mol/L.
  • the secondary battery further includes a negative electrode piece including a negative electrode current collector and a negative electrode disposed on at least one surface of the negative electrode current collector and including a negative electrode active material Diaphragm.
  • the type of the negative electrode current collector is not particularly limited, and can be selected according to actual needs.
  • the negative electrode current collector can be selected from metal foils, such as copper foil.
  • the negative electrode active material includes one or more of a carbon material and a silicon-based material.
  • the carbon material may include one or more of graphite, soft carbon, and hard carbon; preferably, the carbon material includes graphite, and the graphite is selected from artificial One or more of graphite and natural graphite.
  • the silicon-based material may include one or more of silicon element, silicon alloy, silicon-oxygen compound, silicon-carbon composite, and silicon-nitrogen compound; preferably, the The silicon-based material includes silicon-oxygen compound.
  • the weight of the silicon-based material in the negative electrode active material is ⁇ 40%; more preferably Ground, the weight ratio of the silicon-based material in the negative electrode active material is 15%-30%.
  • the secondary battery further includes a positive pole piece including a positive electrode current collector and a positive electrode provided on at least one surface of the positive electrode current collector and including a positive electrode active material Diaphragm.
  • the type of the positive electrode current collector is not specifically limited, and can be selected according to actual needs.
  • the positive electrode current collector may be selected from metal foils, such as aluminum foil.
  • the positive electrode active material includes one or more of lithium nickel cobalt manganese oxide compound and lithium nickel cobalt aluminum oxide.
  • Lithium nickel cobalt manganese oxide compound and lithium nickel cobalt aluminum oxide have the advantages of high specific capacity and long cycle life as the positive electrode active material of the secondary battery.
  • the positive electrode active material includes the general formula Li a Ni b Co c M d M'e O f A g or at least a part of the surface provided with a coating layer li a Ni b Co c M d M 'e O f a g of one or more materials, wherein, 0.8 ⁇ a ⁇ 1.2,0.5 ⁇ b ⁇ 1,0 ⁇ c ⁇ 1,0 ⁇ d ⁇ 1 , 0 ⁇ e ⁇ 0.1, 1 ⁇ f ⁇ 2, 0 ⁇ g ⁇ 1, M is selected from one or more of Mn and Al, M'is selected from Zr, Al, Zn, Cu, Cr, Mg, Fe One or more of, V, Ti, and B, and A is selected from one or more of N, F, S, and Cl.
  • the coating layer on the surface of the positive electrode active material may be a carbon layer, an oxide layer, an inorganic salt layer or a conductive polymer layer.
  • the cycle performance of the secondary battery can be further improved by coating and modifying the surface of the positive electrode active material.
  • the positive electrode active material may further include lithium nickel oxide (such as lithium nickelate), lithium manganese oxide (such as spinel lithium manganate, layer Lithium manganate), lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium cobaltate and modified compounds thereof.
  • lithium nickel oxide such as lithium nickelate
  • lithium manganese oxide such as spinel lithium manganate, layer Lithium manganate
  • lithium iron phosphate lithium manganese phosphate
  • lithium iron manganese phosphate lithium iron manganese phosphate
  • lithium cobaltate lithium cobaltate
  • the secondary battery further includes an isolation film
  • the type of the isolation film is not particularly limited, and it may be various isolation films suitable for lithium ion batteries in the field.
  • the isolation film can be selected from one or more of polyethylene film, polypropylene film, polyvinylidene fluoride film and their multilayer composite film.
  • the secondary battery may include an outer package for packaging the positive pole piece, the negative pole piece, and the electrolyte.
  • the positive pole piece, the negative pole piece and the separator can be laminated or wound to form an electrode assembly with a laminated structure or an electrode assembly with a wound structure, the electrode assembly is packaged in an outer package; the electrolyte is infiltrated in the electrode assembly .
  • the number of electrode assemblies in the secondary battery can be one or several, which can be adjusted according to requirements.
  • the outer packaging of the secondary battery may be a soft bag, such as a pouch-type soft bag.
  • the material of the soft bag can be plastic, for example, it can include one or more of polypropylene PP, polybutylene terephthalate PBT, polybutylene succinate PBS, and the like.
  • the outer packaging of the secondary battery may also be a hard case, such as an aluminum case.
  • Fig. 1 shows a secondary battery 5 with a square structure as an example.
  • the secondary battery 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. 2 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, it can also be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having an accommodating space, and a plurality of secondary batteries 5 are accommodated in the accommodating space.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • Figures 3 and 4 show the battery pack 1 as an example. 3 and 4, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3.
  • the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4.
  • a plurality of battery modules 4 can be arranged in the battery box in any manner.
  • a second aspect of the present application provides a device including the secondary battery according to the first aspect of the present application.
  • the secondary battery can be used as a power source of the device, and can also be used as an energy storage unit of the device.
  • the device includes, but is not limited to, 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 Vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the device can select a secondary battery, a battery module, or a battery pack according to its usage requirements.
  • Figure 5 is a device as an example.
  • the device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • battery packs or battery modules can be used.
  • the device may be a mobile phone, a tablet computer, a notebook 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 positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2
  • the binder polyvinylidene fluoride, and the conductive agent Super P are mixed in a weight ratio of 98:1:1, and N-methylpyrrolidone (NMP) is added.
  • NMP N-methylpyrrolidone
  • the negative active material artificial graphite is mixed with the conductive agent Super P and the binder SBR in a mass ratio of 96:2:2, and deionized water is added.
  • the negative electrode slurry is obtained under the action of a vacuum mixer; the negative electrode slurry is evenly coated on The negative electrode current collector is on the copper foil; the copper foil is dried at room temperature and then transferred to an oven for drying, and then cold pressed and slit to obtain a negative electrode piece.
  • a polyethylene film is used as the isolation film.
  • Example 2-24 and Comparative Example 1-7 adjust the ratio of electrolyte in the secondary battery (See Table 1 for details).
  • the secondary batteries of Examples 25-48 and Comparative Examples 8-14 were prepared according to the following methods
  • the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2
  • the binder polyvinylidene fluoride, and the conductive agent Super P are mixed in a weight ratio of 98:1:1, and N-methylpyrrolidone (NMP) is added.
  • NMP N-methylpyrrolidone
  • the negative electrode active material silicon oxide and artificial graphite After mixing the negative electrode active material silicon oxide and artificial graphite at a mass ratio of 2:8, then mix it with the conductive agent Super P and the binder acrylate at a mass ratio of 92:2:6, add deionized water, and place it in a vacuum mixer.
  • the negative electrode slurry is obtained under the action; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil; the copper foil is dried at room temperature and then transferred to an oven for drying, and then cold pressed and slit to obtain a negative electrode pole piece.
  • a polyethylene film is used as the isolation film.
  • the capacity retention rate of the secondary battery after 800 cycles at 45°C (%) (discharge capacity after 800 cycles of the secondary battery/discharge capacity at the first cycle of the secondary battery) ⁇ 100%.
  • volume expansion rate of secondary battery after storage at 60°C for 30 days (%) [(V 2 -V 1 )/V 1 ] ⁇ 100%
  • the secondary battery of the present application can take into account both good high-temperature cycle performance and high-temperature storage performance.
  • comparative examples 1-7 are compared with examples 1-24
  • comparative examples 8-14 are compared with examples 25-48, which are relatively unable to take into account high-temperature cycle performance at the same time. And high temperature storage performance.

Abstract

本申请提供了一种二次电池及含有该二次电池的装置，所述二次电池包括电解液，所述电解液包括电解质盐和有机溶剂；所述电解质盐包括双氟磺酰亚胺锂(LiFSI)和六氟磷酸锂(LiPF 6)；所述双氟磺酰亚胺锂(LiFSI)在所述电解液中的体积摩尔浓度为0.8mol/L～1.2mol/L；所述六氟磷酸锂(LiPF 6)在所述电解液中的体积摩尔浓度为0.15mol/L～0.4mol/L；所述有机溶剂包括碳酸乙烯酯(EC)，所述碳酸乙烯酯(EC)的含量在所述有机溶剂中的质量占比≤20％。

Description

二次电池及含有该二次电池的装置 技术领域
本申请涉及电池技术领域，尤其涉及一种二次电池及含有该二次电池的装置。
背景技术
随着化石能源的日益枯竭及环境污染的压力越来越大，新能源汽车得到了前所未有的重视和发展。二次电池由于具有高能量密度、高工作电压、无记忆效应等特点从而被广泛应用。
对于应用于电动汽车的二次电池而言，客户对电池的长期可靠性以及续航里程提出了更高的要求。
因此为满足新能源汽车对动力能源的性能需要，有必要提供一种具有良好综合性能的二次电池。
发明内容
鉴于背景技术中存在的问题，本申请提供一种二次电池及含有该二次电池的装置，所述二次电池在较高能量密度的前提下，可同时兼具较好的高温循环性能及高温存储性能。
为了达到上述目的，本申请第一方面提供一种二次电池，所述二次电池包括电解液，所述电解液包括电解质盐和有机溶剂；所述电解质盐包括双氟磺酰亚胺锂(LiFSI)和六氟磷酸锂(LiPF 6)；所述双氟磺酰亚胺锂(LiFSI)在所述电解液中的体积摩尔浓度为0.8mol/L～1.2mol/L；所述六氟磷酸锂(LiPF 6)在所述电解液中的体积摩尔浓度为0.15mol/L～0.4mol/L；所述有机溶剂包括碳酸乙烯酯(EC)，所述碳酸乙烯酯(EC)的含量在所述有机溶剂中的质量占比≤20％。。
本申请的第二方面，提供一种装置，其包括本申请第一方面所述的二次电池。
本申请至少包括以下的有益效果：
本申请的二次电池，电解液中的电解质盐同时包括特定含量的双氟磺酰亚胺锂(LiFSI)和六氟磷酸锂(LiPF 6)、且有机溶剂包括特定含量的碳酸乙烯酯(EC)，可以使二次电池同时兼顾较好的高温循环性能及高温存储性能。本申请的装置包括所述二次电池，因而至少具有与所述二次电池相同的优势。
附图说明
图1是二次电池的一实施方式的示意图。
图2是电池模块的一实施方式的示意图。
图3是电池包的一实施方式的示意图。
图4是图3的分解图。
图5是二次电池用作电源的装置的一实施方式的示意图。
其中，附图标记说明如下：
1电池包
2上箱体
3下箱体
4电池模块
5二次电池
具体实施方式
下面详细说明根据本申请的二次电池及含有该二次电池的装置。
根据本申请第一方面的二次电池，所述二次电池包括电解液，所述电解液包括电解质盐和有机溶剂，其中，所述电解质盐包括双氟磺酰亚胺锂(LiFSI)和六氟磷酸锂(LiPF 6)，所述双氟磺酰亚胺锂(LiFSI)在所述电解液中的体积摩尔浓度为0.8mol/L～1.2mol/L，所述六氟磷酸锂(LiPF 6)在所述电解液中的体积摩尔浓度为0.15mol/L～0.4mol/L，所述有机溶剂包括碳酸乙烯酯(EC)，所述碳酸乙烯酯(EC)在所述有机溶剂中的质量占比≤20％。
在根据本申请第一方面所述的二次电池中，发明人通过大量研究发现，当电解液同时满足电解质盐包括双氟磺酰亚胺锂(LiFSI)和六氟磷酸锂 (LiPF 6)，所述双氟磺酰亚胺锂(LiFSI)在所述电解液中的体积摩尔浓度为0.8mol/L～1.2mol/L，所述六氟磷酸锂(LiPF 6)在所述电解液中的体积摩尔浓度为0.1mol/L～0.4mol/L，且有机溶剂包括碳酸乙烯酯(EC)，所述碳酸乙烯酯(EC)在所述有机溶剂中的质量占比≤20％时，在上述条件共同作用下，二次电池具有较好的高温循环性能及高温存储性能。
发明人猜测产生上述有益效果的可能原因是因为将LiFSI和LiPF 6联合为电解质盐使用，且将两者的体积摩尔浓度控制在特定范围内时，两者优势互补，可以有效缓解LiFSI在正极氧化给二次电池循环性能带来的影响；同时，在上述混合电解质盐的基础上，有机溶剂中还包括特定含量的碳酸乙烯酯(EC)，既可以很好的解离上述混合电解质盐，又可以进一步改善电池的高温存储性能。
在根据本申请第一方面的二次电池中，优选地，所述双氟磺酰亚胺锂(LiFSI)在所述电解液中的体积摩尔浓度为0.9mol/L～1.2mol/L。当双氟磺酰亚胺锂(LiFSI)在所述电解液中的体积摩尔浓度在此范围内时，可以进一步改善电池的高温存储性能。
在根据本申请第一方面的二次电池中，优选地，所述六氟磷酸锂(LiPF 6)在所述电解液中的体积摩尔浓度为0.15mol/L～0.3mol/L。当六氟磷酸锂(LiPF 6)在所述电解液中的体积摩尔浓度在此范围内时，会进一步改善电池的高温循环性能。
在根据本申请第一方面的二次电池中，优选地，所述碳酸乙烯酯(EC)在所述有机溶剂中的质量占比≤15％。若EC的含量过高，则其分解产物在负极表面形成的SEI膜过厚，会在一定程度上恶化二次电池的直流阻抗。更优选地，所述碳酸乙烯酯(EC)在所述有机溶剂中的质量占比≤10％。
在根据本申请第一方面的二次电池中，优选地，所述双氟磺酰亚胺锂(LiFSI)与所述六氟磷酸锂(LiPF 6)的体积摩尔浓度的比值为3～7:1。当二者的体积摩尔浓度比值进一步控制在所给范围内时，二者之间可以更好地发挥协同作用，使二次电池的高温循环性能及高温存储性能得到更好的改善。更优选地，所述双氟磺酰亚胺锂(LiFSI)与所述六氟磷酸锂(LiPF 6)的体积摩尔浓度的比值为4～6:1。
在根据本申请第一方面的二次电池中，进一步地，所述有机溶剂还包括 碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)中的一种或几种。
在根据本申请第一方面的二次电池中，优选地，所述有机溶剂还包括碳酸甲乙酯(EMC)，所述碳酸甲乙酯(EMC)在所述有机溶剂中的质量占比为60％～95％，更优选为75％～95％。
在根据本申请第一方面的二次电池中，所述电解液还包括添加剂，优选地，所述添加剂包括氟代碳酸乙烯酯(FEC)、硫酸乙烯酯(DTD)、1,3-丙烷磺内酯(PS)、1,3-丙烯基-磺酸内酯(PST)、丁二酸酐(SA)、二氟草酸硼酸锂(LiDFOB)、二氟双草酸磷酸锂(LiDFOP)、三(三甲基甲硅烷)磷酸酯(TMSP)、三(三甲基甲硅烷)硼酸酯(TMSB)中的一种或几种。
在根据本申请第一方面的二次电池中，优选地，所述电解液在25℃时的电导率为6.5mS/cm～9.5mS/cm；更优选地，所述电解液在25℃时的电导率为7.0mS/cm～9.0mS/cm。
所述电解液在25℃时的电导率可以用本领域的公知方法进行测试，所采用的测试仪器可以是雷磁电导率设备仪。
在根据本申请第一方面的二次电池中，优选地，所述电解质盐在所述电解液中的体积摩尔浓度为0.9mol/L～1.1mol/L。
在根据本申请第一方面的二次电池中，所述二次电池还包括负极极片，所述负极极片包括负极集流体以及设置于负极集流体至少一个表面上且包括负极活性材料的负极膜片。
在根据本申请第一方面的二次电池中，所述负极集流体的种类没有特别的限制，可根据实际需求进行选择。具体地，所述负极集流体可选自金属箔，例如：铜箔。
在根据本申请第一方面的二次电池中，优选地，所述负极活性材料包括碳材料、硅基材料中的一种或几种。
在根据本申请第一方面的二次电池中，所述碳材料可包括石墨、软碳、硬碳中的一种或几种；优选地，所述碳材料包括石墨，所述石墨选自人造石墨、天然石墨中的一种或几种。
在根据本申请第一方面的二次电池中，所述硅基材料可包括硅单质、硅合金、硅氧化合物、硅碳复合物、硅氮化合物中的一种或几种；优选地，所 述硅基材料包括硅氧化合物。
在根据本申请第一方面的二次电池中，当所述负极活性材料包括硅基材料时，优选地，所述硅基材料在所述负极活性材料中的重量占比≤40％；更优选地，所述硅基材料在所述负极活性材料中的重量占比为15％～30％。
在根据本申请第一方面的二次电池中，所述二次电池还包括正极极片，所述正极极片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括正极活性材料的正极膜片。
在根据本申请第一方面的二次电池中，所述正极集流体的种类没有具体的限制，可根据实际需求进行选择。具体地，所述正极集流体可选自金属箔，例如：铝箔。
在根据本申请第一方面的二次电池中，优选地，所述正极活性材料包括锂镍钴锰氧化合物、锂镍钴铝氧化物中的一种或几种。锂镍钴锰氧化合物、锂镍钴铝氧化物作为二次电池的正极活性材料具有比容量高、循环寿命长等优点。
在根据本申请第一方面的二次电池中，优选地，所述正极活性材料包括通式为Li aNi bCo cM dM’ eO fA g或表面至少一部分设置有包覆层的Li aNi bCo cM dM’ eO fA g的材料中的一种或几种，其中，0.8≤a≤1.2，0.5≤b＜1，0＜c＜1，0＜d＜1，0≤e≤0.1，1≤f≤2，0≤g≤1，M选自Mn、Al中的一种或几种，M’选自Zr、Al、Zn、Cu、Cr、Mg、Fe、V、Ti、B中的一种或几种，A选自N、F、S、Cl中的一种或几种。
上述正极活性材料表面的包覆层可以是碳层、氧化物层、无机盐层或导电高分子层。通过对正极活性材料表面包覆改性能够进一步改善二次电池的循环性能。
在根据本申请第一方面的二次电池中，进一步地，所述正极活性材料还可以包括锂镍氧化物(例如镍酸锂)、锂锰氧化物(例如尖晶石型锰酸锂、层状结构锰酸锂)、磷酸铁锂、磷酸锰锂、磷酸锰铁锂、钴酸锂及其改性化合物中的一种或几种。
在根据本申请第一方面的二次电池中，所述二次电池还包括隔离膜，所述隔离膜的种类没有特别的限制，其可以是本领域中各种适用于锂离子电池的隔离膜。具体地，所述隔离膜可选自聚乙烯膜、聚丙烯膜、聚偏氟乙烯膜 以及它们的多层复合膜中的一种或几种。
在一些实施例中，二次电池可以包括外包装，用于封装正极极片、负极极片和电解液。作为一个示例，正极极片、负极极片和隔离膜可经叠片或卷绕形成叠片结构的电极组件或卷绕结构的电极组件，电极组件封装在外包装内；电解液浸润于电极组件中。二次电池中电极组件的数量可以为一个或几个，可以根据需求来调节。
在一些实施例中，二次电池的外包装可以是软包，例如袋式软包。软包的材质可以是塑料，如可包括聚丙烯PP、聚对苯二甲酸丁二醇酯PBT、聚丁二酸丁二醇酯PBS等中的一种或几种。二次电池的外包装也可以是硬壳，例如铝壳等。
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。如图1是作为一个示例的方形结构的二次电池5。
在一些实施例中，二次电池可以组装成电池模块，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2是作为一个示例的电池模块4。参照图2，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壳体，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3和图4是作为一个示例的电池包1。参照图3和图4，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。
本申请的第二方面提供一种装置，其包括本申请第一方面所述二次电池。所述二次电池可以用作所述装置的电源，也可以作为所述装置的能量存储单元。所述装置包括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5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。
下面结合实施例，进一步阐述本申请。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。
实施例1-24和对比例1-7的二次电池均按照下述方法制备
(1)正极极片的制备
将正极活性材料(LiNi 0.8Co 0.1Mn 0.1O 2)、粘结剂聚偏氟乙烯、导电剂Super P按照重量比98:1:1进行混合，加入N-甲基吡咯烷酮(NMP)，在真空搅拌机作用下搅拌至体系成均一透明状，获得正极浆料；将正极浆料均匀涂覆于铝箔上；将铝箔在室温晾干后转移至烘箱干燥，然后经过冷压、分切得到正极极片。
(2)负极极片的制备
将负极活性材料人造石墨与导电剂Super P、粘结剂SBR按照质量比96:2:2进行混合，加入去离子水，在真空搅拌机作用下获得负极浆料；将负极浆料均匀涂覆在负极集流体铜箔上；将铜箔在室温晾干后转移至烘箱干燥，然后经过冷压、分切得到负极极片。
(3)电解液的制备
在含水量<10ppm的氩气气氛手套箱中，将各有机溶剂进行混合，接着将充分干燥的电解质盐溶解于有机溶剂中，然后在有机溶剂中加入添加剂(0.5％的FEC，1％的DTD)，混合均匀，获得电解液。其中，各电解质盐的体积摩尔浓度、各有机溶剂的重量比如表1所示。在表1中，各电解质盐 的体积摩尔浓度为基于电解液的总体积计算得到的体积摩尔浓度；各有机溶剂的含量为基于有机溶剂的总重量计算得到的重量百分数。上述添加剂的含量为基于电解液的总重量计算得到的重量百分数。
(4)隔离膜的制备
以聚乙烯膜作为隔离膜。
(5)二次电池的制备：
将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，然后卷绕得到电极组件；将电极组件置于外包装中，将上述制备好的电解液注入到干燥后的电池中，经过真空封装、静置、化成、整形等工序，得到二次电池。
实施例2-24和对比例1-7的二次电池的制备方法与实施例1类似，不同点在于：实施例2-24和对比例1-7调整了二次电池中电解液的配比(具体详见表1)。
实施例25-48和对比例8-14的二次电池均按照下述方法制备
(1)正极极片的制备
将正极活性材料(LiNi 0.8Co 0.1Mn 0.1O 2)、粘结剂聚偏氟乙烯、导电剂Super P按照重量比98:1:1进行混合，加入N-甲基吡咯烷酮(NMP)，在真空搅拌机作用下搅拌至体系成均一透明状，获得正极浆料；将正极浆料均匀涂覆于铝箔上；将铝箔在室温晾干后转移至烘箱干燥，然后经过冷压、分切得到正极极片。
(2)负极极片的制备
将负极活性材料氧化亚硅与人造石墨按质量比2:8混合后，再与导电剂Super P、粘结剂丙烯酸酯按照质量比92:2:6进行混合，加入去离子水，在真空搅拌机作用下获得负极浆料；将负极浆料均匀涂覆在负极集流体铜箔上；将铜箔在室温晾干后转移至烘箱干燥，然后经过冷压、分切得到负极极片。
(3)电解液的制备
在含水量<10ppm的氩气气氛手套箱中，将各有机溶剂进行混合，接着将充分干燥的电解质盐溶解于有机溶剂中，然后在有机溶剂中加入添加剂(8％的FEC，1％的SA，0.8％的TMSP)，混合均匀，获得电解液。其中， 各电解质盐的体积摩尔浓度、各有机溶剂的重量比如表1所示。在表2中，各电解质盐的体积摩尔浓度为基于电解液的总体积计算得到的体积摩尔浓度；各有机溶剂的含量为基于有机溶剂的总重量计算得到的重量百分数。上述添加剂的含量为基于电解液的总重量计算得到的重量百分数。
(4)隔离膜的制备
以聚乙烯膜作为隔离膜。
(5)二次电池的制备：
将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，然后卷绕得到电极组件；将电极组件置于外包装中，将上述制备好的电解液注入到干燥后的电池中，经过真空封装、静置、化成、整形等工序，得到二次电池。
实施例26-48和对比例8-14的二次电池的制备方法与实施例25类似，不同点在于：实施例26-48和对比例8-14调整了二次电池中电解液的配比(具体详见表2)。
表1实施例1-24和对比例1-7的参数
Figure PCTCN2019127976-appb-000001
Figure PCTCN2019127976-appb-000002
表2实施例25-48和对比例8-14的参数
Figure PCTCN2019127976-appb-000003
Figure PCTCN2019127976-appb-000004
接下来说明二次电池的测试过程
(1)高温循环性能测试
在45℃下，将二次电池以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，再用1C恒流放电至截止电压下限(表1中各实施例及对比例取2.8V；表2中各实施例及对比例取2.5V)，此为二次电池的首次充电/放电循环，此次的放电容量记为二次电池首次循环的放电容量，按照上述方法将二次电池进行800次循环充电/放电，得到二次电池循环800次后的放电容量。
二次电池45℃循环800次后的容量保持率(％)＝(二次电池循环800次后的放电容量/二次电池首次循环的放电容量)×100％。
(2)高温存储性能测试
在60℃下，将二次电池以0.5C恒流充电至4.25V，再以4.25V恒压充电至电流为0.05C，用排水法测试此时锂离子电池的体积并记为V 1；之后将二次电池放入60℃的恒温箱，储存30天后取出，测试此时二次电池的体积并记为V 2。
二次电池60℃存储30天后的体积膨胀率(％)＝[(V 2-V 1)/V 1]×100％
表3实施例1-24和对比例1-7的性能测试结果
Figure PCTCN2019127976-appb-000005
Figure PCTCN2019127976-appb-000006
表4实施例25-48和对比例8-14的性能测试结果
Figure PCTCN2019127976-appb-000007
Figure PCTCN2019127976-appb-000008
从表3和表4的测试结果分析可知，实施例1-24与对比例1-7相比、实施例25-48与对比例8-14相比，本申请实施例1-48的电解质盐包括双氟磺酰亚胺锂(LiFSI)和六氟磷酸锂(LiPF 6)，所述双氟磺酰亚胺锂(LiFSI)在所述电解液中的体积摩尔浓度为0.8mol/L～1.2mol/L，所述六氟磷酸锂(LiPF 6)在所述电解液中的体积摩尔浓度为0.15mol/L～0.4mol/L，且有机溶剂包括碳酸乙烯酯(EC)，所述碳酸乙烯酯(EC)在所述有机溶剂中的质量占比≤20％，在上述电解质盐和有机溶剂的共同作用下，本申请的二次电池可以同时兼顾较好的高温循环性能及高温存储性能。而当二次电池不满足本申请的上述条件时，对比例1-7与实施例1-24相比、对比例8-14与实施例25-48相比，相对地无法同时兼顾高温循环性能和高温存储性能。

Claims (15)

  1. 一种二次电池，包括电解液，所述电解液包括电解质盐和有机溶剂；其中，
    所述电解质盐包括双氟磺酰亚胺锂(LiFSI)和六氟磷酸锂(LiPF 6)；
    所述双氟磺酰亚胺锂(LiFSI)在所述电解液中的体积摩尔浓度为0.8mol/L～1.2mol/L；
    所述六氟磷酸锂(LiPF 6)在所述电解液中的体积摩尔浓度为0.15mol/L～0.4mol/L；
    所述有机溶剂包括碳酸乙烯酯(EC)，所述碳酸乙烯酯(EC)的含量在所述有机溶剂中的质量占比≤20％。
  2. 根据权利要求1所述的二次电池，其中，所述双氟磺酰亚胺锂(LiFSI)在所述电解液中的体积摩尔浓度为0.9mol/L～1.2mol/L。
  3. 根据权利要求1或2所述的二次电池，其中，所述六氟磷酸锂(LiPF 6)在所述电解液中的体积摩尔浓度为0.15mol/L～0.3mol/L。
  4. 根据权利要求1-3任一项所述的二次电池，其中，所述双氟磺酰亚胺锂(LiFSI)与所述六氟磷酸锂(LiPF 6)的体积摩尔浓度的比值为3～7:1，优选为4～6:1。
  5. 根据权利要求1-4任一项所述的二次电池，其中，所述碳酸乙烯酯(EC)在所述有机溶剂中的质量占比≤15％；优选地，所述碳酸乙烯酯(EC)在所述有机溶剂中的质量占比≤10％。
  6. 根据权利要求1-5任一项所述的二次电池，其中，所述有机溶剂还包括碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)中的一种或几种。
  7. 根据权利要求1-6任一项所述的二次电池，其中，所述有机溶剂还包括碳酸甲乙酯(EMC)，所述碳酸甲乙酯(EMC)在所述有机溶剂中的质量占比为60％～95％，优选为75％～95％。
  8. 根据权利要求1-7任一项所述的二次电池，其中，所述电解液还包括添加剂，所述添加剂包括氟代碳酸乙烯酯(FEC)、硫酸乙烯酯(DTD)、1,3-丙烷磺内酯(PS)、1,3-丙烯基-磺酸内酯(PST)、丁二酸酐(SA)、二氟草酸硼酸锂(LiDFOB)、二氟双草酸磷酸锂(LiDFOP)、三(三甲基甲硅烷)磷酸酯(TMSP)、三(三甲基甲硅烷)硼酸酯(TMSB)中的一种或几种。
  9. 根据权利要求1-8任一项所述的二次电池，其中，所述电解液在25℃时的电导率为6.5mS/cm～9.5mS/cm；优选地，所述电解液在25℃时的电导率为7.0mS/cm～9.0mS/cm。
  10. 根据权利要求1-9任一项所述的二次电池，其中，所述电解质盐在所述电解液中的体积摩尔浓度为1.0mol/L～1.4mol/L，优选为1.1mol/L～1.3mol/L。
  11. 根据权利要求1-10任一项所述的二次电池，其中，所述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于负极集流体至少一个表面上且包括负极活性材料的负极膜片，所述负极活性材料包括碳材料、硅基材料中的一种或几种。
  12. 根据权利要求11所述的二次电池，其中，所述负极活性材料包括硅基材料，且所述硅基材料在所述负极活性材料中的重量占比≤40％；优选地，所述硅基材料在所述负极活性材料中的重量占比为15％～30％。
  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于正极集流体至少一个表面上且包括正极活性材料的正极膜片，所述正极活性材料包括锂镍钴锰氧 化物、锂镍钴铝氧化物中的一种或几种；
    优选地，所述正极活性材料包括通式为Li aNi bCo cM dM’ eO fA g或表面至少一部分设置有包覆层的Li aNi bCo cM dM’ eO fA g中的一种或几种，其中，0.8≤a≤1.2，0.5≤b＜1，0＜c＜1，0＜d＜1，0≤e≤0.1，1≤f≤2，0≤g≤1，M选自Mn、Al中的一种或几种，M’选自Zr、Al、Zn、Cu、Cr、Mg、Fe、V、Ti、B中的一种或几种，A选自N、F、S、Cl中的一种或几种。
  14. 根据权利要求13所述的二次电池，其中，所述正极活性材料还包括锂镍氧化物、锂锰氧化物、磷酸铁锂、磷酸锰锂、磷酸锰铁锂、钴酸锂及其改性化合物中的一种或几种。
  15. 一种装置，其中，所述装置包括根据权利要求1-14任一项所述的二次电池。
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