WO2023004819A1 - 二次电池与含有该二次电池的电池模块、电池包和用电装置 - Google Patents

二次电池与含有该二次电池的电池模块、电池包和用电装置 Download PDF

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WO2023004819A1
WO2023004819A1 PCT/CN2021/109903 CN2021109903W WO2023004819A1 WO 2023004819 A1 WO2023004819 A1 WO 2023004819A1 CN 2021109903 W CN2021109903 W CN 2021109903W WO 2023004819 A1 WO2023004819 A1 WO 2023004819A1
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secondary battery
solvent
positive electrode
battery
negative electrode
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PCT/CN2021/109903
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English (en)
French (fr)
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黄磊
韩昌隆
吴则利
张翠平
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2021/109903 priority Critical patent/WO2023004819A1/zh
Priority to KR1020237000405A priority patent/KR20230021096A/ko
Priority to CN202180006893.9A priority patent/CN115917825A/zh
Priority to EP21942135.1A priority patent/EP4345971A1/en
Priority to JP2023501536A priority patent/JP2023538720A/ja
Publication of WO2023004819A1 publication Critical patent/WO2023004819A1/zh
Priority to US18/317,094 priority patent/US20230387469A1/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
    • H01M10/0569—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
    • H01M10/05—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
    • 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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—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
    • H01M2300/004—Three solvents
    • 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 belongs to the technical field of secondary batteries, and in particular relates to a secondary battery, a battery module containing the secondary battery, a battery pack, and an electrical device.
  • Secondary batteries have the characteristics of good cycle performance, stable electrochemical performance, and low price, so they occupy a huge market share. As customers' requirements for battery energy density are getting higher and higher, it is very important to develop batteries with higher energy density and longer cycle life.
  • an effective way to increase the energy density of the battery is to increase the utilization of the internal space of the battery, for example, to increase the coating weight and compaction density of the pole piece, but the disadvantages of this are that the transmission path of the active ions becomes longer and the diffusion of the active ions The rate becomes slower, which makes it difficult for active ions to deintercalate between the positive and negative electrodes of the battery, and the kinetic performance of the battery deteriorates.
  • the purpose of this application is to provide a secondary battery and a battery module containing the secondary battery, a battery pack, and an electrical device, aiming to make the secondary battery have good kinetic performance and relatively high energy density while maintaining high energy density. High capacity retention and low volume expansion.
  • the first aspect of the present application provides a secondary battery, which includes a positive pole piece and an electrolyte.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes one or more of lithium-containing phosphates with an olivine structure and modified compounds thereof .
  • the electrolytic solution includes an organic solvent, and the organic solvent includes the first solvent shown in Formula 1.
  • R 11 and R 12 are each independently one of C1-C4 alkyl and C1-C4 haloalkyl.
  • the secondary battery of the present application satisfies: the mass of the first solvent/the rated capacity of the secondary battery ⁇ 0.7g/Ah, the mass of the electrolyte/the rated capacity of the secondary battery ⁇ 3.5g/Ah.
  • the secondary battery of the present application meets the quality of the first solvent/rated capacity of the secondary battery ⁇ 0.7g/Ah and the quality of the electrolyte/rated capacity of the secondary battery ⁇ 3.5g/Ah, the electrolyte inside the battery can The positive pole piece and the negative pole piece are well wetted, and the first solvent can fully exert the effect of improving the kinetic performance of the battery, and at the same time, the irreversible consumption of active ions inside the battery can also be controlled within a small range. Therefore, the secondary battery can have good kinetic performance, high capacity retention rate and low volume expansion rate while maintaining high energy density.
  • the mass of the first solvent/the rated capacity of the secondary battery is ⁇ 1.0 g/Ah.
  • the mass of the electrolyte/rated capacity of the secondary battery is 2.8g/Ah-3.3g/Ah.
  • the secondary battery further satisfies: content of the first solvent/(thickness of the positive electrode film layer ⁇ 3+0.008/porosity of the positive electrode film layer) ⁇ 1.
  • the content of the first solvent refers to the mass percentage of the first solvent based on the total mass of the organic solvent; the thickness of the positive electrode film layer indicates the thickness of the single-sided positive electrode film layer on the positive electrode current collector in mm.
  • the secondary battery further satisfies: content of the first solvent/(thickness of the positive electrode film layer ⁇ 3+0.008/porosity of the positive electrode film layer) ⁇ 1.5.
  • the electrolyte solution further includes additives.
  • the additive has a reduction potential > 0.8 V (vs Li + /Li).
  • the additive can participate in the formation of the SEI film on the surface of the negative electrode active material prior to the electrochemical reduction reaction of the organic solvent, and promote the formation of a stable SEI film on the surface of the negative electrode active material, preventing further reaction between the negative electrode active material and the electrolyte, reducing the first The degree of damage to the SEI film by protons generated by solvent reduction.
  • the additive includes an organic additive, and the organic additive includes one of vinylene carbonate, fluoroethylene carbonate, vinyl vinyl carbonate, vinyl sulfate, and 1,3-propane sultone or several.
  • the organic additive can preferentially undergo electrochemical reduction on the surface of the negative electrode active material to form an SEI film with excellent performance, and reduce the degree of damage to the SEI film by the protons generated by the reduction of the first solvent.
  • the reduction products of organic additives are mainly organic components, which can improve the mechanical stability of the SEI film and help improve the cycle performance of the battery.
  • the additives include inorganic additives, and the inorganic additives include tris(trimethylsilyl) phosphate, lithium bisoxalate borate, lithium difluorooxalate phosphate, lithium tetrafluorooxalate phosphate, difluorooxalic acid One or more of lithium borate and lithium difluorophosphate.
  • the inorganic additive can preferentially undergo electrochemical reduction on the surface of the negative electrode active material to form an SEI film with excellent performance, thereby reducing the degree of damage to the SEI film by the protons generated by the reduction of the first solvent.
  • the reduction products of inorganic additives are mainly inorganic components, which can improve the thermal stability of the SEI film and help improve the high-temperature performance of the battery.
  • the mass percentage of the organic additive is ⁇ 50%.
  • the mass percentage of the organic additive is 70%-100%.
  • the mass percentage of the inorganic additive is ⁇ 50%.
  • the mass percentage of the inorganic additive is 0%-30%.
  • the secondary battery further includes a negative electrode sheet, and the negative electrode sheet includes a negative electrode active material.
  • the secondary battery also satisfies: (liquid retention coefficient ⁇ content of additive)/(relative mass of negative electrode ⁇ specific surface area of negative electrode active material ⁇ 0.012+liquid retention coefficient ⁇ content of first solvent ⁇ 0.03) ⁇ 1.
  • the additive can effectively protect the negative electrode interface, suppress the aggravation of side reactions at the negative electrode interface caused by the instability of the first solvent, and the capacity retention rate during the use of the secondary battery is higher and the volume expansion rate is lower.
  • the liquid retention coefficient refers to the ratio of the mass of the electrolyte to the rated capacity of the secondary battery, in g/Ah; the content of the additive refers to the mass percentage of the additive based on the total mass of the electrolyte; the relative mass of the negative electrode refers to the negative electrode sheet
  • the ratio of the mass of the negative electrode active material to the rated capacity of the secondary battery is expressed in g/Ah; the specific surface area of the negative electrode active material is expressed in m 2 /g.
  • the secondary battery also satisfies: (liquid retention coefficient ⁇ additive content)/(negative electrode relative mass ⁇ negative electrode active material specific surface area ⁇ 0.012+liquid retention coefficient ⁇ first solvent content ⁇ 0.03) ⁇ 2 .
  • the thickness of the positive electrode film layer is ⁇ 0.07 mm.
  • the thickness of the positive electrode film layer is 0.07mm-0.14mm.
  • the thickness of the positive electrode film layer is moderate, and the transmission path of active ions in the positive electrode film layer is moderate, so that the battery can maintain good kinetic performance without excessively sacrificing the energy density of the battery.
  • the porosity of the positive electrode film layer is ⁇ 50%.
  • the porosity of the positive film layer is 5%-50%.
  • the porosity of the positive electrode film layer is moderate, the transmission resistance of active ions in the positive electrode film layer is moderate, and the battery can maintain good kinetic performance without excessively sacrificing the energy density of the battery.
  • the relative mass of the negative electrode is ⁇ 2.1 g/Ah.
  • the relative mass of the negative electrode is 1.2g/Ah-2.1g/Ah.
  • the specific surface area of the negative electrode active material is 0.5m 2 /g-6.0m 2 /g.
  • the specific surface area of the negative electrode active material is 1.0m 2 /g-3.2m 2 /g.
  • the content of the first solvent is ⁇ 10%.
  • the content of the first solvent is 10%-80%.
  • the content of the first solvent is moderate, on the one hand, it can fully play the role of improving the kinetic performance of the battery, and on the other hand, it can avoid excessive damage to the negative electrode interface.
  • the content of the additive is ⁇ 3%.
  • the content of the additive is 3%-9%.
  • the content of the additive is moderate, on the one hand, it can give full play to the protective effect on the negative electrode interface, on the other hand, it can avoid the formation of an overly thick SEI film on the surface of the negative electrode active material, and increase the resistance of the negative electrode film formation.
  • R 11 and R 12 are independently methyl, ethyl, propyl, butyl, fluoromethyl, fluoroethyl, fluoropropyl, fluorine One of the butyl groups.
  • R 11 and R 12 are selected from the above groups, the viscosity of the electrolyte can be kept in an appropriate range, and the electrolyte has higher conductivity.
  • the first solvent represented by formula 1 is selected from one or more of the following compounds:
  • the organic solvent also includes one or more of the second solvent shown in Formula 2 and the third solvent shown in Formula 3.
  • R 21 is H
  • R 31 and R 32 are independently one of methyl, ethyl, and propyl.
  • the mass percentage of the second solvent is ⁇ 10%.
  • the mass percentage of the second solvent is 10%-80%.
  • the dielectric constant of the second solvent is relatively high, which is beneficial to the dissociation of the lithium salt, and the addition of the second solvent in the electrolyte is beneficial to the increase of the conductivity of the electrolyte.
  • the mass percentage of the third solvent is ⁇ 0%.
  • the mass percentage of the third solvent is 5%-80%.
  • the dielectric constant of the third solvent is small, and the ability to dissociate lithium salts is weak, but the viscosity is small and the fluidity is good. After adding the third solvent to the electrolyte, it can increase the migration rate of active ions to increase the mobility of the electrolyte. conductivity.
  • the second solvent represented by formula 2 is selected from one or both of the following compounds:
  • the third solvent represented by formula 3 is selected from one or more of the following compounds:
  • the lithium-containing phosphate of the olivine structure includes lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, One or more of the composite materials of lithium manganese iron phosphate and carbon and their respective modified compounds.
  • the second aspect of the present application provides a battery module, which includes the secondary battery according to the first aspect of the present application.
  • the third aspect of the present application provides a battery pack, which includes one of the secondary battery of the first aspect of the present application and the battery module of the second aspect of the present application.
  • the fourth aspect of the present application provides a device, which includes at least one of the secondary battery of the first aspect of the present application, the battery module of the second aspect of the present application, and the battery pack of the third aspect of the present application.
  • the battery module, battery pack and electric device of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of an embodiment of a secondary battery of the present application.
  • FIG. 2 is an exploded schematic diagram of an embodiment of the secondary battery of the present application.
  • Fig. 3 is a schematic diagram of an embodiment of the battery module of the present application.
  • Fig. 4 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 5 is an exploded view of FIG. 4 .
  • FIG. 6 is a schematic diagram of an embodiment of an electrical device in which a secondary battery is used as a power source of the present application.
  • ranges disclosed herein are defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range "a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
  • steps (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and so on.
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • Secondary batteries also known as rechargeable batteries or accumulators, refer to batteries that can be activated by charging the active materials and continue to be used after the battery is discharged.
  • a secondary battery typically includes a positive pole piece, a negative pole piece, a separator, and an electrolyte.
  • active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows active ions to pass through.
  • the electrolyte plays the role of conducting active ions between the positive pole piece and the negative pole piece.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode current collector has two opposite surfaces in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material.
  • the positive electrode active material may include one or more of lithium transition metal oxides, olivine-structured lithium-containing phosphates and their respective modified compounds.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide One or more of lithium nickel cobalt aluminum oxide and its modified compounds.
  • olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, lithium manganese iron phosphate One or more of the composite materials with carbon and their respective modified compounds. These positive electrode active materials may be used alone or in combination of two or more.
  • the positive electrode active material may at least include one or more of olivine-structured lithium-containing phosphate and modified compounds thereof.
  • the positive electrode active material may be only one or more of olivine-structured lithium-containing phosphates and modified compounds thereof.
  • the modification compounds of the above-mentioned positive electrode active materials may be modified by doping, surface coating, or surface coating while doping.
  • the positive electrode film layer generally includes a positive electrode active material and an optional binder and an optional conductive agent.
  • the positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing.
  • the positive electrode slurry is usually formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder and any other components in a solvent and stirring them uniformly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the binder used for the positive film layer may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoro One or more of propylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • the conductive agent used in the positive film layer may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • a metal foil or a composite current collector can be used as the positive electrode current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base and a metal material layer formed on at least one surface of the polymer material base.
  • the metal material may be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector.
  • the negative electrode current collector has two opposite surfaces in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative active material known negative active materials for secondary batteries can be used in the art.
  • the negative electrode active material may include one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate.
  • the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials.
  • the tin-based material may include one or more of simple tin, tin oxide, and tin alloy materials. The present application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials for secondary batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode film layer generally includes negative electrode active materials, optional binders, optional conductive agents and other optional additives.
  • the negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing.
  • the negative electrode slurry coating is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring them evenly.
  • the solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.
  • the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, polyacrylate sodium PAAS), polyacrylamide ( One or more of PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • SR-1B water-soluble unsaturated resin
  • water-based acrylic resin for example, polyacrylic acid PAA, polymethacrylic acid PMAA, polyacrylate sodium PAAS), polyacrylamide ( One or more of PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS).
  • Other optional additives may include thickeners (eg, sodium carboxymethylcellulose CMC-Na), PTC thermistor materials, and the like.
  • a metal foil or a composite current collector can be used as the negative electrode current collector.
  • the metal foil copper foil can be used.
  • the composite current collector may include a polymer material base and a metal material layer formed on at least one surface of the polymer material base.
  • the metal material may be selected from one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the electrolyte can be selected from at least one of solid electrolyte, gel electrolyte, and liquid electrolyte (ie, electrolyte solution).
  • the secondary battery of the present application uses a liquid electrolyte, that is, an electrolytic solution.
  • the electrolytic solution may include an organic solvent and optional additives.
  • the organic solvent in the present application is a non-aqueous organic solvent, and the organic solvent may include the first solvent shown in Formula 1.
  • R 11 and R 12 are each independently one of C1-C4 alkyl and C1-C4 haloalkyl, and R 11 and R 12 may be the same or different.
  • Alkyl and haloalkyl substituents may be linear or branched.
  • the number of halogen atoms in the haloalkyl substituent may be one or more; when the haloalkyl substituent contains multiple halogen atoms, these halogen atoms may be the same or different.
  • the high energy density and good kinetic performance of the battery cannot be balanced.
  • Increasing the coating weight and compaction density of the positive electrode film layer can improve the energy density of the battery, but at the same time it will lead to poor kinetic performance of the battery.
  • Adding the first solvent shown in formula 1 to the electrolyte can improve the kinetic performance of the electrolyte and the kinetic performance of the battery, because the first solvent shown in formula 1 has the advantages of low viscosity and high dielectric constant , can greatly increase the conductivity of the electrolyte.
  • the inventors have found that when the positive pole piece includes lithium-containing phosphate with an olivine structure and its modified compound, within a certain range, the amount of electrolyte injection increases, the wettability of the electrolyte inside the battery becomes better, and the kinetics of the battery The performance also becomes better; however, continuing to increase the amount of electrolyte injection has little effect on the improvement of battery kinetic performance; and continuing to increase the amount of electrolyte injection, the content of organic solvents inside the battery will also increase, and some organic solvents will be consumed Active ions, the result is to accelerate the decay of battery capacity and increase the gas production of the battery.
  • the inventors have also found that, in a battery mainly using lithium-containing phosphate with an olivine structure and its modified compound as the positive electrode active material, when the quality of the first solvent/rated capacity of the secondary battery is ⁇ 0.7g/Ah and the electrolytic When the mass of liquid/rated capacity of the secondary battery is ⁇ 3.5g/Ah, the battery can maintain high energy density while having good dynamic performance, high capacity retention rate and low volume expansion rate.
  • the possible reason is that the energy density of batteries mainly using lithium-containing phosphates with olivine structure and their modified compounds as positive electrode active materials is low.
  • an effective way is to increase the utilization of internal space in batteries.
  • the electrolyte In order to improve the kinetic performance of the electrolyte and the kinetic performance of the battery, the electrolyte often uses the above-mentioned first solvent.
  • the first solvent has poor oxidation resistance and is easy to oxidize and decompose, resulting in an increase in gas production inside the battery. Therefore, for batteries that mainly use lithium-containing phosphate with olivine structure and its modified compounds as positive electrode active materials, the contents of the internal electrolyte and the first solvent must be strictly controlled.
  • the inventor found that when the battery satisfies the quality of the first solvent/rated capacity of the secondary battery ⁇ 0.7g/Ah and the quality of the electrolyte/rated capacity of the secondary battery ⁇ 3.5g/Ah, the internal The electrolyte can well infiltrate the positive pole piece and the negative pole piece, and give full play to the improvement effect of the first solvent on the kinetic performance of the battery.
  • the irreversible consumption of active ions inside the battery can also be controlled within a small range. Therefore, the secondary battery can have good kinetic performance, high capacity retention rate and low volume expansion rate while maintaining high energy density.
  • the positive electrode active material can be only lithium-containing phosphate with olivine structure and its modified compound, and the positive electrode active material can also be The composition of lithium-containing phosphate of olivine structure and its modified compound and other positive electrode active materials, that is, the positive electrode active material includes other positive electrode active materials in addition to lithium-containing phosphate of olivine structure and its modified compound, Examples include lithium transition metal oxides and their modified compounds.
  • the mass percentage of the olivine-structured lithium-containing phosphate and its modified compound is ⁇ 50%.
  • the mass percentage of lithium-containing phosphate with olivine structure and its modified compound is 80%-100%.
  • the quality of the electrolyte refers to the quality of the electrolyte inside the finished battery, not the quality of the electrolyte injected during the battery preparation process.
  • the rated capacity of the secondary battery refers to the capacity released when the fully charged battery at room temperature is discharged with a current of 1/3 ⁇ I 1 (A) and reaches the cut-off voltage, and I 1 means 1 hour rate discharge current.
  • I 1 means 1 hour rate discharge current.
  • the ratio of the mass of the electrolyte to the rated capacity of the secondary battery can also be called the liquid retention coefficient.
  • the mass of the first solvent/rated capacity of the secondary battery can be ⁇ 0.7g/Ah, ⁇ 0.8g/Ah, ⁇ 0.9g/Ah, ⁇ 1.0g/Ah, ⁇ 1.1g/Ah, ⁇ 1.2g/Ah, ⁇ 1.3g/Ah, ⁇ 1.4g/Ah, ⁇ 1.5g/Ah, ⁇ 1.6g/Ah, ⁇ 1.7g/Ah, ⁇ 1.8g/Ah, or ⁇ 1.9g/Ah.
  • the mass of the first solvent/rated capacity of the secondary battery can be 0.7g/Ah-2.0g/Ah, 0.8g/Ah-2.0g/Ah, 0.9g/Ah-2.0g/Ah, 1.0g/Ah-2.0g/Ah, 1.1g/Ah-2.0g/Ah, 1.2g/Ah-2.0g/Ah, 1.5g/Ah-2.0g/Ah, 0.7g/Ah-1.9g/Ah, 0.8g/Ah-1.9g/Ah, 0.9g/Ah-1.9g/Ah, 1.0g/Ah-1.9g/Ah, 1.1g/Ah-1.9g/Ah, 1.2g/Ah-1.9g/Ah, 1.5g/Ah-1.9g/Ah, 0.7g/Ah-1.6g/Ah, 0.8g/Ah-1.6g/Ah, 0.9g/Ah-1.6g/Ah, 1.0g/Ah-1.6g/Ah, 1.1g/Ah-
  • the mass of the electrolyte/rated capacity of the secondary battery may be ⁇ 3.5g/Ah, ⁇ 3.4g/Ah, ⁇ 3.3g/Ah, ⁇ 3.2g/Ah, ⁇ 3.1g/Ah, ⁇ 3.0 g/Ah, ⁇ 2.9g/Ah, ⁇ 2.8g/Ah, ⁇ 2.7g/Ah, ⁇ 2.6g/Ah, ⁇ 2.5g/Ah, ⁇ 2.4g/Ah, ⁇ 2.3g/Ah, ⁇ 2.2g/Ah Ah, ⁇ 2.1g/Ah, or ⁇ 2.0g/Ah.
  • the quality of the electrolyte/rated capacity of the secondary battery can be 2.4g/Ah-3.5g/Ah, 2.5g/Ah-3.5g/Ah, 2.6g/Ah-3.5g/Ah, 2.7 g/Ah-3.5g/Ah, 2.8g/Ah-3.5g/Ah, 2.9g/Ah-3.5g/Ah, 3.0g/Ah-3.5g/Ah, 3.1g/Ah-3.5g/Ah, 2.4 g/Ah-3.3g/Ah, 2.5g/Ah-3.3g/Ah, 2.6g/Ah-3.3g/Ah, 2.7g/Ah-3.3g/Ah, 2.8g/Ah-3.3g/Ah, 2.9 g/Ah-3.3g/Ah, 3.0g/Ah-3.3g/Ah, or 3.1g/Ah-3.3g/Ah.
  • R 11 and R 12 can be independently methyl, ethyl, propyl, butyl, fluoromethyl, fluoroethyl, fluoropropyl, fluoro One of butyl, R 11 and R 12 may be the same or different. Wherein, the number of fluorine atoms may be one or more. When R 11 and R 12 are selected from the above groups, the viscosity of the electrolyte can be kept in an appropriate range, and the electrolyte has higher conductivity.
  • the first solvent represented by Formula 1 may be selected from one or more of the following compounds:
  • the first solvent shown in Formula 1 has the advantages of low viscosity and high dielectric constant, which can improve the conductivity of the electrolyte, and then improve the battery power brought by the increase in the coating weight and compaction density of the positive electrode film layer to a certain extent.
  • the problem of poor academic performance the inventors also found that the first solvent represented by Formula 1 is unstable at the negative electrode and is easily reduced to generate protons and other products, which increases the gas production of the battery.
  • the protons produced by the reduction of the first solvent shown in Formula 1 will also decompose components such as lithium carbonate and lithium alkoxide in the SEI film, making the stability of the SEI film worse; like this, the SEI film needs to be continuously repaired during battery use.
  • this repair process will consume more active ions, increase the irreversible consumption of active ions, and rapidly decay the battery capacity.
  • the first solvent reduction product shown in formula 1 accumulates on the surface of the negative electrode active material, which will also prolong the transmission path of active ions and reduce the transmission speed of active ions, thus deteriorating the kinetic performance of the negative electrode sheet and The kinetic performance of the battery.
  • the inventor found a solution to the above problems through a lot of research work, which not only ensures high energy density and good kinetic performance of the battery, but also ensures that the battery has good cycle performance and storage performance.
  • the coating weight and compaction density of the positive electrode film layer are usually increased, which brings about a problem that the positive electrode film layer has higher and higher requirements on the kinetic properties of the electrolyte.
  • the inventor obtained the coefficients of these two mutually independent requirements through a lot of research and experiments, and used the sum of the two to represent the total requirement for the kinetic performance of the electrolyte.
  • the content of the first solvent is strongly related to the kinetic performance of the electrolyte. The higher the content of the first solvent, the better the kinetic performance of the electrolyte.
  • the inventor has found through a large number of studies that when the secondary battery also satisfies: the content of the first solvent/(the thickness of the positive electrode film * 3+0.008/the porosity of the positive film layer) ⁇ 1, the coating weight and pressure of the positive film layer The problem of poor battery kinetic performance caused by the increase of solid density can be effectively solved.
  • the secondary battery can satisfy: the content of the first solvent/(thickness of the positive electrode film layer ⁇ 3+0.008/porosity of the positive electrode film layer) ⁇ 1.1, the content of the first solvent/(positive electrode film Layer thickness ⁇ 3+0.008/porosity of the positive film layer) ⁇ 1.2, content of the first solvent/(thickness of the positive film layer ⁇ 3+0.008/porosity of the positive film layer) ⁇ 1.3, content of the first solvent /(thickness of positive electrode film ⁇ 3+0.008/porosity of positive electrode film) ⁇ 1.4, first solvent content/(thickness of positive electrode film ⁇ 3+0.008/porosity of positive electrode film) ⁇ 1.5, second Content of a solvent/(thickness of the positive film layer ⁇ 3+0.008/porosity of the positive film layer) ⁇ 1.6, content of the first solvent/(thickness of the positive film layer ⁇ 3+0.008/porosity of the positive film layer) ⁇ 1.7, or the content of the first solvent/
  • the content of the first solvent refers to the mass percentage of the first solvent based on the total mass of the organic solvent.
  • the thickness of the positive electrode film layer represents the thickness of the single-sided positive electrode film layer on the positive electrode current collector in mm.
  • a micrometer can be used for thickness measurement, for example, a micrometer with a model number of Mitutoyo293-100 and an accuracy of 0.1 ⁇ m can be used.
  • the thickness of the positive electrode film layer refers to the thickness of the single-sided positive electrode film layer
  • the total thickness of the positive electrode film layer means that when the positive electrode film layer is simultaneously arranged on the two opposite surfaces of the positive electrode current collector, each positive electrode The sum of the thicknesses of the film layers.
  • the porosity of the positive electrode film layer is represented by the ratio of the pore volume of the positive electrode sheet (ie the true volume of the positive electrode sheet) to the apparent volume of the positive electrode sheet.
  • the porosity of the positive film layer can be tested with reference to GB/T 24586-2009 Iron Ore Apparent Density, True Density and Porosity Determination Method.
  • the test method includes the following steps: cut 30 small discs with a diameter of 14mm from the positive pole piece, based on the principle of gas adsorption, use an inert gas (for example, helium or nitrogen) as a medium, and test the 30 discs with a diameter of 14mm.
  • the true volume of the small disc; the apparent volume of the positive electrode sheet calculated according to the area, thickness and quantity of the small disc, the ratio of the true volume to the apparent volume is the porosity of the positive electrode film.
  • Lithium-containing phosphate with olivine structure and its modified compounds contain polar functional groups on the surface and have a large specific surface area, which is very easy to absorb water, but the drying process before battery liquid injection cannot completely remove the water; during the use of the battery , this part of moisture will gradually diffuse into the electrolyte and react with the electrolyte; at the same time, the presence of moisture will also destroy the SEI film (Solid Electrolyte Interface Membrane) on the surface of the negative electrode active material, affecting the stability of the negative electrode interface.
  • SEI film Solid Electrolyte Interface Membrane
  • the thickness of the positive electrode film layer is reduced, the transmission path of active ions in it is shortened, and the kinetic performance of the secondary battery becomes better; at the same time, the moisture in the positive electrode film layer is easier to remove in the drying process, and the degree of damage of water to the negative interface get smaller.
  • the thickness of the positive electrode film layer is reduced, and the energy density of the secondary battery is also reduced.
  • the thickness of the positive electrode film layer may be ⁇ 0.07 mm.
  • the thickness of the positive film layer can be ⁇ 0.075mm, ⁇ 0.08mm, ⁇ 0.085mm, ⁇ 0.09mm, ⁇ 0.10mm, ⁇ 0.11mm, ⁇ 0.12mm, ⁇ 0.13mm, ⁇ 0.14mm, or ⁇ 0.15mm.
  • the thickness of the positive electrode film layer may be 0.07mm-0.14mm. More specifically, the thickness of the positive electrode film layer may be 0.09mm-0.12mm.
  • the porosity of the positive electrode film increases, the electrolyte is more likely to infiltrate the positive electrode film, the transmission resistance of active ions in the positive electrode film becomes smaller, and the kinetic performance of the secondary battery becomes better; at the same time, the moisture in the positive electrode film is easier to dry. The drying process is removed, and the damage degree of moisture to the negative electrode interface becomes smaller.
  • the porosity of the positive electrode film layer may be ⁇ 50%.
  • the porosity of the positive film layer may be ⁇ 48%, ⁇ 45%, ⁇ 42%, ⁇ 40%, ⁇ 38%, ⁇ 37%, ⁇ 35%, ⁇ 32%, or ⁇ 30%.
  • the porosity of the positive electrode film layer may be 5%-50%. More specifically, the porosity of the positive electrode film layer may be 20%-40%.
  • the coating weight of one side of the positive electrode film layer may be ⁇ 20 mg/cm 2 .
  • the coating weight of one side of the positive electrode film layer may be 23 mg/cm 2 -29 mg/cm 2 . More specifically, the coating weight of one side of the positive electrode film layer may be 25 mg/cm 2 -29 mg/cm 2 .
  • the positive electrode film layer may have a compacted density ⁇ 2.1 g/cm 3 .
  • the positive electrode film layer may have a compacted density of 2.1 g/cm 3 -2.8 g/cm 3 .
  • the positive electrode film layer may have a compacted density of 2.3 g/cm 3 -2.6 g/cm 3 .
  • the mass percentage of the first solvent (ie, the content of the first solvent) may be ⁇ 10%.
  • the content of the first solvent can be ⁇ 15%, ⁇ 20%, ⁇ 25%, ⁇ 30%, ⁇ 35%, ⁇ 40%, ⁇ 45%, ⁇ 50%, ⁇ 55%, or ⁇ 60%.
  • the content of the first solvent can be 10%-80%, 15%-80%, 20%-80%, 25%-80%, 30%-80%, 35%-80%, 40% %-80%, 45%-80%, 50%-80%, 10%-75%, 15%-75%, 20%-75%, 25%-75%, 30%-75%, 35%- 75%, 40%-75%, 45%-75%, 50%-75%, 10%-70%, 15%-70%, 20%-70%, 25%-70%, 30%-70% , 35%-70%, 40%-70%, 45%-70%, 50%-70%, 10%-65%, 15%-65%, 20%-65%, 25%-65%, 30% %-65%, 35%-65%, 40%-65%, 45%-65%, 50%-65%, 10%-60%, 15%-60%, 20%-60%, 25%- 60%, 30%-60%, 35%-60%, 40%-60%, 45%-60%, 50%-60%, 10%-55%, 15%-55%, 20%-55% , 25%-55%, 30%-55%, 35%-55%, 40%-55%, 45%-55%, or 50%-55%.
  • the organic solvent may further include one or more of the second solvent shown in Formula 2 and the third solvent shown in Formula 3.
  • R 21 is one of H, methyl, and ethyl; in Formula 3, R 31 and R 32 are independently one of methyl, ethyl, and propyl, and R 31 and R 32 may be the same or different.
  • the organic solvent in addition to the first solvent shown in Formula 1, may also include the second solvent shown in Formula 2, or the third solvent shown in Formula 3, Alternatively, the second solvent represented by Formula 2 and the third solvent represented by Formula 3 may also be included at the same time. In some embodiments, the organic solvent further includes the second solvent shown in Formula 2 in addition to the first solvent shown in Formula 1.
  • the second solvent represented by Formula 2 may be selected from one or both of the following compounds:
  • the third solvent represented by formula 3 can be selected from one or more of the following compounds:
  • the dielectric constant of the second solvent is relatively high, which is beneficial to the dissociation of the lithium salt.
  • the mass percentage of the second solvent may be ⁇ 10%.
  • the mass percentage of the second solvent may be 10%-80%. More specifically, the mass percentage of the second solvent may be 20%-50%.
  • the third solvent has a small dielectric constant and a weak ability to dissociate lithium salts, but has low viscosity and good fluidity, which can increase the migration rate of active ions.
  • the mass percentage of the third solvent may be ⁇ 0%.
  • the mass percentage of the third solvent may be 5%-80%. More specifically, the mass percentage of the third solvent may be 5%-20%.
  • the electrolytic solution may further include an additive, and the additive may be a film-forming additive.
  • the reduction potential of the additive may satisfy ⁇ 0.8V (vs Li + /Li).
  • the SEI film on the surface of the negative electrode active material is electronically insulated, while allowing active ions to enter and exit freely, and it can also prevent further reaction between the negative electrode active material and the electrolyte. Therefore, the properties of the SEI film on the surface of the negative electrode active material will affect the performance of the negative electrode sheet and the battery. Performance, for example, battery cycle performance, storage performance, etc.
  • the reduction potential of the additive of the present application is ⁇ 0.8V (vs Li + /Li), which can preferentially occur in the electrochemical reduction reaction of organic solvents to participate in the formation of the SEI film on the surface of the negative electrode active material, and promote the formation of a stable SEI film on the surface of the negative electrode active material , to prevent further reaction between the negative electrode active material and the electrolyte, and reduce the degree of damage to the SEI film caused by the protons generated by the reduction of the first solvent.
  • the additive may include one or more of organic additives and inorganic additives.
  • the additives may also include only organic additives.
  • the organic additive may include vinylene carbonate (Vinylene carbonate, VC), fluoroethylene carbonate (FloroEthylene carbonate, FEC), vinyl ethylene carbonate (Vinylethylene carbonate, VEC) , Ethylene sulfate (DTD), 1,3-propane sultone (1,3-Propane sultone, PS) one or more.
  • the organic additive is an electrochemical reduction additive, and its reduction potential is higher than that of the organic solvent. Therefore, the electrochemical reduction can preferentially occur on the surface of the negative electrode active material to form an SEI film with excellent performance, thereby reducing the protons generated by the reduction of the first solvent. Damage to the SEI film degree.
  • the reduction products of organic additives are mainly organic components, and these organic components can improve the mechanical stability of the SEI film, which is conducive to improving the cycle performance of the battery.
  • the inorganic additives may include tris(trimethylsilyl)phosphate (tris(trimethylsilyl)phosphate, TMSP), bisoxalate lithium borate (Lithium bis(oxalate)borate, LiBOB), Lithium bis[ethanedioato(2-)- ⁇ O1, ⁇ O2]difluorophosphate(1-), LiDFOP), lithium tetrafluoro(oxalato)phosphate, LiTFOP, lithium difluorooxalate borate (Lithium difluoro(oxalato)borate, LiDFOB), lithium difluorophosphate (lithium difluorophosphate, LiPO 2 F 2 ) or one or more.
  • TMSP tris(trimethylsilyl)phosphate
  • TMSP bisoxalate lithium borate
  • the inorganic additive is an electrochemical reduction additive, and its reduction potential is higher than that of the organic solvent. Therefore, the electrochemical reduction can preferentially occur on the surface of the negative electrode active material to form an SEI film with excellent performance, thereby reducing the protons generated by the reduction of the first solvent. Damage to the SEI film degree.
  • the reduction products of inorganic additives are mainly inorganic components, and these inorganic components can improve the thermal stability of the SEI film, thereby helping to improve the high-temperature performance of the battery.
  • the additive includes vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, vinyl sulfate, lithium difluorophosphate, tris(trimethylsilyl )
  • the reduction products of vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, and vinyl sulfate can be used as organic components in the SEI film to improve the mechanical stability of the SEI film, and the SEI film has Tolerance of negative electrode active material volume change during battery cycling.
  • the reduction products of lithium difluorophosphate and tris(trimethylsilyl)phosphate can be used as inorganic components in the SEI film to improve the thermal stability of the SEI film, so that the SEI film is not easy to decompose even in high temperature environments.
  • the mass percentage of the organic additive may be ⁇ 50%.
  • the mass percentage of the organic additive can be ⁇ 55%, ⁇ 60%, ⁇ 65%, ⁇ 70%, ⁇ 75%, ⁇ 80%, ⁇ 85%, ⁇ 90%, ⁇ 95%, or 100% .
  • the mass percentage of the organic additive can be 50%-100%, 55%-100%, 60%-100%, 65%-100%, 70%-100%, 75%-100% , 80%-100%, 85%-100%, 90%-100%, or 95%-100%.
  • the mass percentage of the inorganic additive may be ⁇ 50%.
  • the mass percentage of the inorganic additive can be ⁇ 45%, ⁇ 40%, ⁇ 35%, ⁇ 30%, ⁇ 25%, ⁇ 20%, ⁇ 15%, ⁇ 10%, ⁇ 5%, or 0% .
  • the mass percentage of the inorganic additive can be 0%-50%, 0%-45%, 0%-40%, 0%-35%, 0%-30%, 0%-25% , 0%-20%, 0%-15%, 0%-10%, or 0%-5%.
  • the mass percentage of the additive ie, the content of the additive may be ⁇ 3%.
  • additive content can be ⁇ 3.5%, ⁇ 4%, ⁇ 4.5%, ⁇ 5%, ⁇ 5.5%, ⁇ 6%, ⁇ 6.5%, ⁇ 7%, ⁇ 7.5%, ⁇ 8%, ⁇ 9%, ⁇ 10%, ⁇ 11%, or ⁇ 12%.
  • the content of the additive refers to the sum of the content of the organic additive and the content of the inorganic additive.
  • the content of the additive may be 3%-9%. More specifically, the content of the additive may be 5%-8%.
  • the lithium salt may include LiPF 6 , LiBF 4 , LiAsF 6 , Li(FSO 2 ) 2 N, LiCF 3 SO 3 , LiClO 4 , LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ), where x and y are positive integers.
  • the potential of the negative electrode drops rapidly, and dendrites are easy to grow on the surface of the negative electrode, increasing the irreversible consumption of active ions; The continuous growth of dendrites may also pierce the separator, resulting in an internal short circuit between the positive and negative electrodes.
  • the smaller the mass percentage of the lithium salt the more free organic solvent (especially the first solvent) content in the electrolyte, which will also make the SEI film on the surface of the negative electrode active material unstable, and then the SEI film is easily decomposed by protons.
  • the mass percentage of the lithium salt may be ⁇ 10%.
  • the mass percentage of the lithium salt may be ⁇ 11%, ⁇ 12%, ⁇ 13%, ⁇ 14%, ⁇ 15%, ⁇ 16%, ⁇ 17%, or ⁇ 18%.
  • the conductivity of the electrolyte is affected by the total number of mobile active ions and the migration rate of active ions.
  • the mass percentage of lithium salt may be 10%-20%.
  • the mass percentage of the lithium salt may be 12%-17%.
  • the additives will promote the formation of a stable SEI film on the surface of the negative active material.
  • the inventor obtained the coefficients of the consumption behaviors of these two additives, and expressed the demand level of additives by the sum of the two consumption behaviors; while the retention level of additives can be expressed by liquid retention coefficient ⁇ content of additives. Only when the retention level of additives is greater than or equal to the required level of additives can a good negative electrode interface be guaranteed, thereby effectively suppressing side reactions at the negative electrode interface.
  • the additive can effectively protect the negative electrode interface and suppress the aggravation of side reactions at the negative electrode interface caused by the instability of the first solvent. Therefore, the capacity retention rate during the use of the secondary battery is higher and the volume expansion rate is lower.
  • the liquid retention coefficient refers to the ratio of the mass of the electrolyte to the rated capacity of the secondary battery, in g/Ah; the content of the additive refers to the mass percentage of the additive based on the total mass of the electrolyte; the relative mass of the negative electrode refers to the negative electrode sheet
  • the ratio of the mass of the negative electrode active material to the rated capacity of the secondary battery is expressed in g/Ah; the specific surface area of the negative electrode active material is expressed in m 2 /g.
  • the secondary battery can also satisfy: (liquid retention coefficient ⁇ additive content)/(negative electrode relative mass ⁇ specific surface area of negative electrode active material ⁇ 0.012+liquid retention coefficient ⁇ first solvent content ⁇ 0.03 ) ⁇ 1.2, (liquid retention coefficient ⁇ content of additive)/(negative electrode relative mass ⁇ specific surface area of negative electrode active material ⁇ 0.012+ liquid retention coefficient ⁇ content of the first solvent ⁇ 0.03) ⁇ 1.4, (liquid retention coefficient ⁇ additive content)/(negative electrode relative mass ⁇ specific surface area of negative electrode active material ⁇ 0.012+liquid retention coefficient ⁇ first solvent content ⁇ 0.03) ⁇ 1.6, (liquid retention coefficient ⁇ additive content)/(negative electrode relative mass ⁇ negative electrode active material Specific surface area ⁇ 0.012+ liquid retention coefficient ⁇ content of the first solvent ⁇ 0.03) ⁇ 1.8, (liquid retention coefficient ⁇ additive content)/(negative electrode relative mass ⁇ specific surface area of negative active material ⁇ 0.012+ liquid retention coefficient ⁇ second A solvent content ⁇ 0.03) ⁇ 2, (liquid retention coefficient ⁇ additive
  • the relative mass of the negative electrode may be ⁇ 2.1 g/Ah.
  • the relative mass of the negative electrode can be ⁇ 2.08g/Ah, ⁇ 2.05g/Ah, ⁇ 2.0g/Ah, ⁇ 1.95g/Ah, ⁇ 1.9g/Ah, ⁇ 1.85g/Ah, ⁇ 1.8g/Ah, ⁇ 1.75g/Ah, ⁇ 1.7g/Ah, ⁇ 1.65g/Ah, ⁇ 1.6g/Ah, ⁇ 1.55g/Ah, or ⁇ 1.5g/Ah.
  • the relative mass of the negative electrode may be 1.2 g/Ah-2.1 g/Ah. More specifically, the relative mass of the negative electrode may be 1.5g/Ah-1.8g/Ah.
  • the specific surface area of the negative electrode active material may be 0.5m 2 /g-6.0m 2 /g.
  • the specific surface area of the negative electrode active material may be 1.0m 2 /g-5.0m 2 /g, 1.0m 2 /g-4.0m 2 /g, 1.0m 2 /g-3.2m 2 /g, 1.0m 2 /g-2.8m 2 /g, 1.2m 2 /g-5.0m 2 /g, 1.2m 2 /g-4.0m 2 /g, 1.2m 2 /g-3.0m 2 /g, 1.2m 2 /g g-2.8m 2 /g, 1.5m 2 /g-5.0m 2 /g, 1.5m 2 /g-4.0m 2 /g, 1.5m 2 /g-3.0m 2 / g , 2.0m 2 /g- 5.0m 2 /g, 2.0m 2 /g-4.0m 2 /g, or 2.0m 2 /g/g
  • the secondary battery of the present application further includes a separator.
  • the separator is arranged between the positive pole piece and the negative pole piece to play the role of isolation.
  • 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 material of the isolation film can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film. When the separator is a multilayer composite film, the materials of each layer are the same or different.
  • a ceramic coating or a metal oxide coating may also be provided on the isolation membrane.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • the 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, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS) and the like.
  • FIG. 1 shows a secondary battery 5 with a square structure as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the receiving chamber, and the cover plate 53 is used to cover the opening to close the receiving chamber.
  • the positive pole piece, the negative pole piece and the separator can be formed into an 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 several, and can be adjusted according to requirements.
  • 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. 3 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 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 is used to cover the lower box body 3 and forms a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the preparation method of the secondary battery of the present application may include the following steps:
  • the secondary battery is detected, and the secondary battery that satisfies the quality of the first solvent/rated capacity of the secondary battery ⁇ 0.7g/Ah and the quality of the electrolyte/rated capacity of the secondary battery ⁇ 3.5g/Ah is screened out. Battery.
  • the secondary batteries obtained by the method of the present application can maintain high energy density and have good kinetic performance, high capacity retention rate and low volume expansion rate.
  • the positive electrode sheet, the separator, and the negative electrode sheet can be wound or stacked to form an electrode assembly, and the electrode assembly is placed in the outer packaging and dried
  • the electrolyte is injected, and the secondary battery is obtained through processes such as vacuum packaging, standing still, chemical formation, and shaping.
  • step S20 optionally, secondary batteries satisfying the mass of the first solvent/rated capacity of the secondary battery ⁇ 1.0 g/Ah are screened out.
  • step S20 optionally, secondary batteries satisfying the quality of the electrolyte/rated capacity of the secondary battery are 2.8 g/Ah-3.3 g/Ah are screened out.
  • the preparation method further includes a step: S30, screening secondary batteries satisfying the content of the first solvent/(thickness of the positive electrode film layer ⁇ 3+0.008/porosity of the positive electrode film layer) ⁇ 1. At this time, not only the high energy density and good kinetic performance of the battery are guaranteed, but also a good negative electrode interface is guaranteed, so that the battery of the present application can have good cycle performance and storage performance.
  • the preparation method further includes the step: S40, screening out the content of the first solvent/(thickness of the positive electrode film layer ⁇ 3+0.008/porosity of the positive electrode film layer) ⁇ 1 and (liquid retention coefficient) ⁇ content of additives)/(relative mass of negative electrode ⁇ specific surface area of negative electrode active material ⁇ 0.012 + liquid retention coefficient ⁇ content of the first solvent ⁇ 0.03) ⁇ 1 secondary battery.
  • S40 screening out the content of the first solvent/(thickness of the positive electrode film layer ⁇ 3+0.008/porosity of the positive electrode film layer) ⁇ 1 and (liquid retention coefficient) ⁇ content of additives)/(relative mass of negative electrode ⁇ specific surface area of negative electrode active material ⁇ 0.012 + liquid retention coefficient ⁇ content of the first solvent ⁇ 0.03) ⁇ 1 secondary battery.
  • the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack of 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 can be, but 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 carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the electric device can select a secondary battery, a battery module or a battery pack according to its usage 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 can be used.
  • the electric device may be a mobile phone, a tablet computer, a notebook computer, and the like.
  • the electrical device is usually required to be light and thin, and a secondary battery can be used as a power source.
  • the positive electrode active material lithium iron phosphate, the binder polyvinylidene fluoride, and the conductive agent acetylene black at a mass ratio of 96:2:2, and then add the solvent N-methylpyrrolidone (NMP) to adjust the viscosity, according to methods known in the art Stir fully to form a positive electrode slurry; apply the positive electrode slurry evenly on the aluminum foil of the positive electrode current collector, dry and cold press to obtain the positive electrode sheet.
  • NMP solvent N-methylpyrrolidone
  • Negative electrode active material graphite (specific surface area is 2m 2 /g), conductive agent acetylene black, binder styrene-butadiene rubber (SBR), thickener carboxymethylcellulose sodium (CMC-Na) in a mass ratio of 97:1 : 1:1 mixing, then add solvent deionized water, fully stir into negative electrode slurry according to known methods in the art; evenly coat the negative electrode slurry on the copper foil of the negative electrode current collector, dry and cold press to obtain the negative electrode sheet .
  • SBR binder styrene-butadiene rubber
  • CMC-Na thickener carboxymethylcellulose sodium
  • a polyethylene (PE) film coated with nano-alumina coating was used as the separator.
  • the rated capacity of the first solvent/secondary battery is 1.6g/Ah
  • the liquid retention coefficient of the secondary battery is 3.1g/Ah
  • the relative mass of the negative electrode is 1.7g/Ah.
  • Example 2 The preparation methods of Examples 2 to 30 and Comparative Examples 1 to 8 are similar to those of Example 1, except that the relevant parameters in the preparation of the positive pole piece, the negative pole piece and the electrolyte were adjusted, and the specific parameters are shown in Table 1 and Table 1. Table 2.
  • the formula I the content of the first solvent/(the thickness of the positive film layer ⁇ 3+0.008/the porosity of the positive film layer)
  • the formula II (the liquid retention coefficient ⁇ the content of the additive)/(the relative mass of the negative electrode ⁇ specific surface area of the negative electrode active material ⁇ 0.012+liquid retention coefficient ⁇ content of the first solvent ⁇ 0.03).
  • compound 1-1 has the worst stability on the negative electrode, and it is easier to destroy the stability of the negative electrode interface, resulting in continuous film formation on the surface of the negative electrode active material and the most irreversible consumption of lithium ions; compound 1-1
  • the products generated by the reduction decomposition of the negative electrode accumulate on the negative electrode interface, which also prolongs the lithium ion transmission path and slows down the lithium ion transmission rate;
  • the capacity decays the fastest, and the volume expansion rate of the battery is the largest when it is stored at high temperature.
  • the thickness of the positive electrode film layer is reduced, the initial DCR of the battery is reduced, the high-temperature cycle capacity retention rate is increased, and the high-temperature storage volume expansion rate is reduced.
  • the surface of lithium-containing phosphate with olivine structure used in the positive electrode film contains polar functional groups and has a large specific surface area, which is very easy to absorb water.
  • the drying process before battery injection cannot completely remove the water in the positive electrode film.
  • the moisture in the positive electrode film will gradually diffuse into the electrolyte and react with the electrolyte; at the same time, the presence of moisture will destroy the SEI film on the surface of the negative electrode active material, affecting the stability of the negative electrode interface. Therefore, when the thickness of the positive electrode film layer is reduced, the moisture in the positive electrode film layer is more easily removed in the drying process, and the degree of damage to the negative interface by the water is reduced, and the high-temperature cycle capacity of the battery decays slowly, and the high-temperature storage gas production decreases. .
  • the reduction in the battery’s demand for additives will also cause the battery’s internal additives to interfere.
  • the amount of additives available for consumption increases when the SEI film is formed on the surface of the negative electrode active material, and the formed SEI film is thicker. Therefore, the initial DCR of the battery will increase. .
  • the dynamic performance level of the electrolyte can meet the total demand of the positive film layer on the kinetic performance of the electrolyte, and the initial DCR of the battery is not large.
  • the retention level of the additive is lower than the required level of the additive, and the protection of the additive to the negative electrode interface is not sufficient, and the first solvent has a side reaction at the negative electrode interface, which will consume a certain amount of lithium ions. Therefore, the battery The high temperature cycle capacity decay will become faster.
  • the first solvent will also destroy the SEI film on the surface of the negative electrode active material, so that the SEI film needs to be repaired continuously during the use of the battery. A certain amount of gas will be generated during the repair of the SEI film. Therefore, the high-temperature storage volume expansion rate of the battery will increase. .
  • the specific surface area of the negative electrode active material increases, the amount of additives that need to be consumed to form the SEI film on the surface of the negative electrode active material increases. Due to a certain total amount of additives, the SEI film formed on the surface of the negative electrode active material will be relatively thinner. Therefore, the initial DCR of the battery will decrease.
  • the retention level of the additive is less than the required level of the additive, and the additive cannot fully form an SEI film on the surface of the negative electrode active material, and cannot fully protect the negative electrode interface. Therefore, the high temperature cycle capacity of the battery The attenuation is obviously faster, and the high-temperature storage volume expansion rate is obviously larger.
  • the amount of additives that can participate in the formation of an SEI film on the surface of the negative electrode active material is relatively reduced, and the film forming resistance of the negative electrode becomes lower. Therefore, the initial DCR of the battery also decreases.
  • the retention level of the additive is lower than the required level of the additive, and the additive cannot fully form an SEI film on the surface of the negative electrode active material, and cannot fully protect the negative electrode interface. Therefore, the high temperature cycle capacity of the battery is significantly reduced. Rapid and high temperature storage volume expansion rate becomes significantly larger.
  • the amount of additives that can participate in the formation of the SEI film on the surface of the negative electrode active material is relatively reduced, and the resistance of the negative electrode film formation becomes lower. Therefore, the initial DCR of the battery also decreases.
  • the retention level of the additive is lower than the required level of the additive. At this time, the additive cannot fully protect the negative electrode interface. Therefore, the high-temperature cycle capacity decay of the battery is obviously faster, and the high-temperature storage volume expansion rate is obvious. get bigger.
  • the SEI film formed on the surface of the negative electrode active material will be relatively thinner due to the constant total amount of additives, so the initial DCR of the battery will decrease.
  • the retention level of the additive is lower than the required level of the additive, and the additive cannot fully form an SEI film on the surface of the negative electrode active material, and cannot fully protect the negative electrode interface. Therefore, the high temperature cycle capacity of the battery is significantly reduced Rapid and high temperature storage volume expansion rate becomes significantly larger.
  • Example 26 due to the reduction of the content of the first solvent, the kinetic performance level of the electrolyte cannot reach the total demand for the kinetic performance of the electrolyte by the positive electrode film layer, and the kinetic performance of the electrolyte and the battery cannot be effectively improved.
  • the initial DCR of the battery will increase significantly.
  • the thickness of the positive electrode film layer increases, and the energy density of the battery increases.
  • Example 27 due to the increase in the thickness of the positive electrode film, the dynamic performance level of the electrolyte cannot reach the total demand of the positive electrode film for the dynamic performance of the electrolyte, and the transmission path of lithium ions in the positive electrode film becomes longer, and the battery life The initial DCR will increase significantly.
  • the porosity of the positive electrode film layer decreases, and the energy density of the battery increases.
  • Example 28 due to the reduction of the porosity of the positive electrode film, the dynamic performance level of the electrolyte cannot reach the total demand of the positive electrode film for the dynamic performance of the electrolyte, and it is difficult for the electrolyte to infiltrate the positive electrode film, and the lithium ions in the positive electrode
  • the transport resistance in the film layer becomes larger, therefore, the initial DCR of the battery will increase significantly.
  • the initial DCR of the battery is relatively high; on the other hand, the content of the electrolyte additive is low, so that the retention level of the additive is less than the demand level of the additive, and the additive cannot fully protect the negative electrode interface Therefore, the high-temperature cycle capacity decay of the battery becomes faster, and the high-temperature storage gas production increases.
  • the batteries of Examples 1-22 satisfy the mass of the first solvent/rated capacity of the secondary battery ⁇ 0.7g/Ah and the mass of the electrolyte/rated capacity of the secondary battery ⁇ 3.5g/Ah At the same time, it also satisfies formulas I and II, and the battery can simultaneously have a lower initial DCR, a higher high-temperature cycle capacity retention rate, and a lower high-temperature storage volume expansion rate.
  • the kinetic performance level of the electrolyte can meet the overall demand of the positive electrode film layer on the battery kinetic performance, so the battery has a lower initial DCR; on the other hand, the electrolyte additive can effectively protect the negative electrode interface and inhibit The side reaction at the negative electrode interface caused by instability is aggravated. Therefore, the high-temperature cycle capacity decay of the battery is slowed down, and the high-temperature storage gas production is reduced.
  • 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

本申请公开了一种二次电池与含有该二次电池的电池模块、电池包和用电装置，二次电池包括正极极片以及电解液。正极极片包括正极集流体以及设置在正极集流体至少一个表面上的正极膜层，正极膜层包括橄榄石结构的含锂磷酸盐及其改性化合物中的一种或几种。电解液包括有机溶剂，有机溶剂包括式1所示的第一溶剂。在式1中，R11和R12分别独立地为C1～C4的烷基、C1～C4的卤代烷基中的一种。二次电池满足：第一溶剂的质量/二次电池的额定容量≥0.7g/Ah，电解液的质量/二次电池的额定容量≤3.5g/Ah。本申请的二次电池能在保持高能量密度的同时，具有良好的动力学性能、较高的容量保持率以及较低的体积膨胀率。

Description

二次电池与含有该二次电池的电池模块、电池包和用电装置 技术领域
本申请属于二次电池技术领域，具体涉及一种二次电池与含有该二次电池的电池模块、电池包和用电装置。
背景技术
二次电池具有循环性能好、电化学性能稳定、价格低廉等特点，因此占据了极大的市场份额。随着客户对电池能量密度的要求越来越高，研发具有更高能量密度、更长循环寿命的电池至关重要。目前提高电池能量密度的一个有效途径是提升电池内部空间利用率，例如，提升极片的涂布重量和压实密度，但这带来的弊端就是活性离子的传输路径变长、活性离子的扩散速率变慢，从而使得活性离子在电池正极和负极之间的脱嵌变得困难，电池的动力学性能变差。
发明内容
本申请的目的在于提供一种二次电池与含有该二次电池的电池模块、电池包和用电装置，旨在使二次电池在保持高能量密度的同时，具有良好的动力学性能、较高的容量保持率以及较低的体积膨胀率。
本申请第一方面提供一种二次电池，其包括正极极片以及电解液。所述正极极片包括正极集流体以及设置在正极集流体至少一个表面上的正极膜层，所述正极膜层包括橄榄石结构的含锂磷酸盐及其改性化合物中的一种或几种。所述电解液包括有机溶剂，所述有机溶剂包括式1所示的第一溶剂。
Figure PCTCN2021109903-appb-000001
在式1中，R 11和R 12分别独立地为C1～C4的烷基、C1～C4的卤代烷基中的一种。
本申请的二次电池满足：第一溶剂的质量/二次电池的额定容量≥0.7g/Ah，电解液的质量/二次电池的额定容量≤3.5g/Ah。
当本申请的二次电池满足第一溶剂的质量/二次电池的额定容量≥0.7g/Ah以及电解液的质量/二次电池的额定容量≤3.5g/Ah时，电池内部的电解液能很好地浸润正极极片和负极极片，充分发挥第一溶剂对电池动力学性能的改善作用，同时电池内部活性离子的不可逆消耗也能控制在一个小范围内。因此，二次电池能在保持高能量密度的同时，具有良好的动力学性能、较高的容量保持率以及较低的体积膨胀率。
可选地，第一溶剂的质量/二次电池的额定容量≥1.0g/Ah。
可选地，电解液的质量/二次电池的额定容量为2.8g/Ah-3.3g/Ah。
在本申请任意实施方式中，所述二次电池还满足：第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)≥1。第一溶剂的含量是指基于有机溶剂的总质量，第一溶剂的质量百分数；正极膜层的厚度表示以mm计的正极集流体上的单面正极膜层的厚度。此时，正极膜层涂布重量和压实密度增加后带来的电池动力学性能欠佳的问题可以得到有效的解决。
可选地，所述二次电池还满足：第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)≥1.5。
在本申请任意实施方式中，所述电解液还包括添加剂。
可选地，添加剂的还原电位≥0.8V(vs Li +/Li)。此时，添加剂能优先于有机溶剂发生电化学还原反应参与负极活性材料表面SEI膜的形成，并促进在负极活性材料表面形成稳定的SEI膜，阻止负极活性材料与电解液进一步反应，降低第一溶剂还原产生的质子对SEI膜的破坏程度。
在本申请任意实施方式中，添加剂包括有机添加剂，所述有机添加剂包括碳酸亚乙烯酯、氟代碳酸乙烯酯、乙烯基碳酸乙烯酯、硫酸乙烯酯、1,3-丙烷磺内酯中一种或几种。有机添加剂可在负极活性材料表面优先发生电化学还原形成性能优良的SEI膜，降低第一溶剂还原产生的质子对SEI膜的破坏程度。有机添加剂的还原产物主要为有机组分，这些有机组分能提升SEI膜的机械稳定性，有利于提升电池的循环性能。
在本申请任意实施方式中，添加剂包括无机添加剂，所述无机添加剂包括三(三甲基硅基)磷酸酯、双草酸硼酸锂、二氟二草酸磷酸锂、四氟草酸磷酸锂、二氟草酸硼酸锂、二氟磷酸锂中一种或几种。无机添加剂可在负极活性材料表面优先发生电化学还原形成性能优良的SEI膜，从而降低第一溶剂还原产生的质子对SEI膜的破坏程度。无机添加剂的还原产物主要为无机组分，这些无机组分能提升SEI膜的热稳定性，有利于提升电池的高温性能。
在本申请任意实施方式中，基于添加剂的总质量，有机添加剂的质量百分数≥50％。可选地，有机添加剂的质量百分数为70％-100％。
在本申请任意实施方式中，基于添加剂的总质量，无机添加剂的质量百分数≤50％。可选地，无机添加剂的质量百分数为0％-30％。
在本申请任意实施方式中，所述二次电池还包括负极极片，所述负极极片包括负极活性材料。
在本申请任意实施方式中，所述二次电池还满足：(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)≥1。此时，添加剂能有效保护负极界面，抑制由于第一溶剂不稳定造成的负极界面副反应加剧问题，二次电池使用过程中的容量保持率更高、体积膨胀率更低。保液系数是指电解液的质量与二次电池的额定容量之比，以g/Ah计；添加剂的含量是指基于电解液的总质量，添加剂的质量百分数；负极相对质量是指负极极片中负极活性材料的质量与二次电池的额定容量之比，以g/Ah计；负极活性材料的比表面积以m 2/g计。
可选地，所述二次电池还满足：(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)≥2。
在本申请任意实施方式中，正极膜层的厚度≥0.07mm。可选地，正极膜层的厚度 为0.07mm-0.14mm。正极膜层的厚度适中，活性离子在正极膜层中的传输路径适中，电池能保持良好的动力学性能，同时又不过分牺牲电池的能量密度。
在本申请任意实施方式中，正极膜层的孔隙率≤50％。可选地，正极膜层的孔隙率为5％-50％。正极膜层的孔隙率适中，活性离子在正极膜层中的传输阻力适中，电池能保持良好的动力学性能，同时又不过分牺牲电池的能量密度。
在本申请任意实施方式中，负极相对质量≤2.1g/Ah。可选地，负极相对质量为1.2g/Ah-2.1g/Ah。
在本申请任意实施方式中，负极活性材料的比表面积为0.5m 2/g-6.0m 2/g。可选地，负极活性材料的比表面积为1.0m 2/g-3.2m 2/g。
在本申请任意实施方式中，第一溶剂的含量≥10％。可选地，第一溶剂的含量为10％-80％。第一溶剂的含量适中，一方面能充分发挥对电池动力学性能的改善作用，另一方面能避免对负极界面的过分破坏。
在本申请任意实施方式中，添加剂的含量≥3％。可选地，添加剂的含量为3％-9％。添加剂的含量适中，一方面能充分发挥对负极界面的保护作用，另一方面能避免在负极活性材料表面形成过厚的SEI膜，增加负极成膜阻抗。
在本申请任意实施方式中，在式1中，R 11和R 12分别独立地为甲基、乙基、丙基、丁基、氟代甲基、氟代乙基、氟代丙基、氟代丁基中的一种。R 11和R 12选自上述基团时，可以使电解液的粘度保持在合适的范围内，电解液具有更高的电导率。
在本申请任意实施方式中，式1所示的第一溶剂选自如下化合物中的一种或几种：
Figure PCTCN2021109903-appb-000002
在本申请任意实施方式中，所述有机溶剂还包括式2所示的第二溶剂、式3所示的第三溶剂中的一种或几种，在式2中，R 21为H、甲基、乙基中的一种，在式3，R 31、R 32分别独立地为甲基、乙基、丙基中的一种。
Figure PCTCN2021109903-appb-000003
在本申请任意实施方式中，基于有机溶剂的总质量，第二溶剂的质量百分数≥10％。可选地，第二溶剂的质量百分数为10％-80％。第二溶剂的介电常数较高，有利于锂盐的解离，在电解液中加入第二溶剂有利于电解液电导率的增加。
在本申请任意实施方式中，基于有机溶剂的总质量，第三溶剂的质量百分数≥0％。可选地，第三溶剂的质量百分数为5％-80％。第三溶剂的介电常数较小，解离锂盐的能力较弱，但黏度小、流动性好，在电解液中加入第三溶剂后能通过增加活性离子的迁移速率，来增加电解液的电导率。
在本申请任意实施方式中，式2所示的第二溶剂选自如下化合物中的一种或两种：
Figure PCTCN2021109903-appb-000004
在本申请任意实施方式中，式3所示的第三溶剂选自如下化合物中的一种或几种：
Figure PCTCN2021109903-appb-000005
在本申请任意实施方式中，所述橄榄石结构的含锂磷酸盐包括磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其各自的改性化合物中的一种或几种。
本申请第二方面提供一种电池模块，其包括本申请第一方面的二次电池。
本申请第三方面提供一种电池包，其包括本申请第一方面的二次电池、本申请第二方面的电池模块中的一种。
本申请第四方面提供一种装置，其包括本申请第一方面的二次电池、本申请第二方面的电池模块、本申请第三方面的电池包中的至少一种。
本申请的电池模块、电池包和用电装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使 用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请的二次电池的一实施方式的示意图。
图2是本申请的二次电池的一实施方式的分解示意图。
图3是本申请的电池模块的一实施方式的示意图。
图4是本申请的电池包的一实施方式的示意图。
图5是图4的分解图。
图6是本申请的二次电池用作电源的用电装置的一实施方式的示意图。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的二次电池与含有该二次电池的电池模块、电池包和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已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，附图及以下说明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。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
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形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
二次电池
二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。
通常情况下，二次电池包括正极极片、负极极片、隔离膜以及电解质。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。电解质在正极极片和负极极片之间起到传导活性离子的作用。
在本申请的二次电池中，正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层。例如，正极集流体具有在自身厚度方向相对的两个表面，正极膜层设置在正极集流体的两个相对表面中的任意一者或两者上。
在本申请的二次电池中，正极膜层包括正极活性材料。作为示例，正极活性材料可包括锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性化合物中的一种或几种。锂过渡金属氧化物的示例可包括但不限于锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其改性化合物中的一种或几种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其各自的改性化合物中的一种或几种。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，正极活性材料可至少包括橄榄石结构的含锂磷酸盐及其改性化合物中的一种或几种。
在一些实施方式中，正极活性材料可仅为橄榄石结构的含锂磷酸盐及其改性化合物中的一种或几种。
在本申请的二次电池中，上述各正极活性材料的改性化合物可以是对正极活性材料进行掺杂改性、表面包覆改性、或掺杂同时表面包覆改性。
在本申请的二次电池中，正极膜层通常包含正极活性材料以及可选的粘结剂和可选的导电剂。正极膜层通常是将正极浆料涂布在正极集流体上，经干燥、冷压而成的。正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。作为示例，用于正极膜层的粘结剂可包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物、含氟丙烯酸酯树脂中的一种或几种。作为示例，用于正极膜层的导电剂可包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中的一种或几种。
在本申请的二次电池中，正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铝箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层 至少一个表面上的金属材料层。作为示例，金属材料可选自铝、铝合金、镍、镍合金、钛、钛合金、银、银合金中的一种或几种。作为示例，高分子材料基层可选自聚丙烯(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。
在本申请的二次电池中，负极极片包括负极集流体以及设置在负极集流体至少一个表面的负极膜层。例如，负极集流体具有在自身厚度方向相对的两个表面，负极膜层设置在负极集流体的两个相对表面中的任意一者或两者上。
负极活性材料可采用本领域公知的用于二次电池的负极活性材料。作为示例，负极活性材料可包括天然石墨、人造石墨、软炭、硬炭、硅基材料、锡基材料、钛酸锂中的一种或几种。硅基材料可包括单质硅、硅氧化物、硅碳复合物、硅氮复合物、硅合金材料中的一种或几种。锡基材料可包括单质锡、锡氧化物、锡合金材料中的一种或几种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池负极活性材料的传统公知的材料。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。
本申请的二次电池中，负极膜层通常包含负极活性材料、可选的粘结剂、可选的导电剂以及其他可选的助剂。负极膜层通常是将负极浆料涂布在负极集流体上，经干燥、冷压而成的。负极浆料涂通常是将负极活性材料、可选的导电剂、可选地粘结剂、其他可选的助剂分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，但不限于此。作为示例，导电剂可包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中一种或几种。作为示例，粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、羧甲基壳聚糖(CMCS)中的一种或几种。其他可选的助剂可包括增稠剂(例如，羧甲基纤维素钠CMC-Na)、PTC热敏电阻材料等。
在本申请的二次电池中，负极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铜箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铜、铜合金、镍、镍合金、钛、钛合金、银、银合金中的一种或几种。作为示例，高分子材料基层可选自聚丙烯(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。
在电池领域，电解质可选自固态电解质、凝胶电解质、液态电解质(即电解液)中的至少一种。本申请的二次电池使用液态电解质，即电解液。
在本申请的二次电池中，所述电解液可包括有机溶剂以及可选的添加剂。本申请的有机溶剂为非水有机溶剂，所述有机溶剂可包括式1所示的第一溶剂。
Figure PCTCN2021109903-appb-000006
在式1中，R 11和R 12分别独立地为C1～C4的烷基、C1～C4的卤代烷基中的一种，R 11和R 12可相同或不同。烷基和卤代烷基取代基可以是直链结构，也可以是支链结构。卤代烷基取代基中的卤原子数目可以是一个，也可以是多个；当卤代烷基取代基含 有多个卤原子时，这些卤原子可以相同，也可以不同。
通常情况下，电池的高能量密度与良好的动力学性能不能兼顾，增加正极膜层的涂布重量和压实密度能提高电池的能量密度，但同时会导致电池动力学性能欠佳。在电解液中加入式1所示的第一溶剂可提升电解液的动力学性能以及电池的动力学性能，这是因为，式1所示的第一溶剂具有低粘度、高介电常数的优点，能极大地提升电解液的电导率。
通常情况下，电池中电解液的含量越高，电池的性能越好。但是发明人发现，当正极极片包括橄榄石结构的含锂磷酸盐及其改性化合物时，在一定范围内，电解液注液量增加，电池内部电解液浸润性变好，电池的动力学性能也变好；但之后继续增加电解液注液量，对电池动力学性能的改善效果不大；并且继续增加电解液注液量，电池内部有机溶剂的含量也会增加，部分有机溶剂会消耗活性离子，结果是加速电池容量的衰减、增加电池的产气量。
发明人还发现，在主要以橄榄石结构的含锂磷酸盐及其改性化合物为正极活性材料的电池中，当满足第一溶剂的质量/二次电池的额定容量≥0.7g/Ah以及电解液的质量/二次电池的额定容量≤3.5g/Ah时，电池可在保持高能量密度的同时，具有良好的动力学性能、较高的容量保持率以及较低的体积膨胀率。可能的原因在于，主要以橄榄石结构的含锂磷酸盐及其改性化合物为正极活性材料的电池的能量密度较低，为了进一步提高电池的能量密度，一个有效途径是提升电池内部空间利用率，例如，提升极片的涂布重量和压实密度，此时电池内部的残空间变得很小，当电解液的含量增加时，电池内部产气量也容易增加。因此，主要以橄榄石结构的含锂磷酸盐及其改性化合物为正极活性材料的电池对电解液的含量更敏感。同时，为了提升电解液的动力学性能以及电池的动力学性能，往往电解液会使用上述第一溶剂，但是，第一溶剂的耐氧化性较差、容易氧化分解，导致电池内部产气量增加。因此，主要以橄榄石结构的含锂磷酸盐及其改性化合物为正极活性材料的电池，要严格控制其内部电解液以及第一溶剂的含量。
发明人经过大量研究发现，当电池满足第一溶剂的质量/二次电池的额定容量≥0.7g/Ah以及电解液的质量/二次电池的额定容量≤3.5g/Ah时，电池的内部的电解液能很好地浸润正极极片和负极极片，充分发挥第一溶剂对电池动力学性能的改善作用，同时电池内部活性离子的不可逆消耗也能控制在一个小范围内。因此，二次电池能在保持高能量密度的同时，具有良好的动力学性能、较高的容量保持率以及较低的体积膨胀率。
“主要以橄榄石结构的含锂磷酸盐及其改性化合物为正极活性材料的电池”表示正极活性材料可仅为橄榄石结构的含锂磷酸盐及其改性化合物，正极活性材料也可为橄榄石结构的含锂磷酸盐及其改性化合物与其它正极活性材料的组合物，即正极活性材料除了包括橄榄石结构的含锂磷酸盐及其改性化合物外，还包括其它正极活性材料，例如锂过渡金属氧化物及其改性化合物。在一些实施方式中，基于正极活性材料的总质量，橄榄石结构的含锂磷酸盐及其改性化合物的质量百分数≥50％。可选地，橄榄石结构的含锂磷酸盐及其改性化合物的质量百分数为80％-100％。
在本申请的二次电池中，电解液的质量是指成品电池内部电解液的质量，而不是指电池制备过程中注入的电解液的质量。
在本申请的二次电池中，二次电池的额定容量是指室温下完全充电的电池以1/3× I 1(A)电流放电，达到终止电压时所放出的容量，I 1表示1小时率放电电流。具体可参考国标GB/T 31484-2015电动汽车用动力蓄电池循环性能要求及试验方法。
在本申请的二次电池中，电解液的质量与二次电池的额定容量之比又可称为保液系数。
在一些实施方式中，第一溶剂的质量/二次电池的额定容量可≥0.7g/Ah，≥0.8g/Ah，≥0.9g/Ah，≥1.0g/Ah，≥1.1g/Ah，≥1.2g/Ah，≥1.3g/Ah，≥1.4g/Ah，≥1.5g/Ah，≥1.6g/Ah，≥1.7g/Ah，≥1.8g/Ah，或≥1.9g/Ah。
在一些实施方式中，第一溶剂的质量/二次电池的额定容量可为0.7g/Ah-2.0g/Ah，0.8g/Ah-2.0g/Ah，0.9g/Ah-2.0g/Ah，1.0g/Ah-2.0g/Ah，1.1g/Ah-2.0g/Ah，1.2g/Ah-2.0g/Ah，1.5g/Ah-2.0g/Ah，0.7g/Ah-1.9g/Ah，0.8g/Ah-1.9g/Ah，0.9g/Ah-1.9g/Ah，1.0g/Ah-1.9g/Ah，1.1g/Ah-1.9g/Ah，1.2g/Ah-1.9g/Ah，1.5g/Ah-1.9g/Ah，0.7g/Ah-1.6g/Ah，0.8g/Ah-1.6g/Ah，0.9g/Ah-1.6g/Ah，1.0g/Ah-1.6g/Ah，1.1g/Ah-1.6g/Ah，1.2g/Ah-1.6g/Ah，或1.5g/Ah-1.6g/Ah。
在一些实施方式中，电解液的质量/二次电池的额定容量可≤3.5g/Ah，≤3.4g/Ah，≤3.3g/Ah，≤3.2g/Ah，≤3.1g/Ah，≤3.0g/Ah，≤2.9g/Ah，≤2.8g/Ah，≤2.7g/Ah，≤2.6g/Ah，≤2.5g/Ah，≤2.4g/Ah，≤2.3g/Ah，≤2.2g/Ah，≤2.1g/Ah，或≤2.0g/Ah。
在一些实施方式中，电解液的质量/二次电池的额定容量可为2.4g/Ah-3.5g/Ah，2.5g/Ah-3.5g/Ah，2.6g/Ah-3.5g/Ah，2.7g/Ah-3.5g/Ah，2.8g/Ah-3.5g/Ah，2.9g/Ah-3.5g/Ah，3.0g/Ah-3.5g/Ah，3.1g/Ah-3.5g/Ah，2.4g/Ah-3.3g/Ah，2.5g/Ah-3.3g/Ah，2.6g/Ah-3.3g/Ah，2.7g/Ah-3.3g/Ah，2.8g/Ah-3.3g/Ah，2.9g/Ah-3.3g/Ah，3.0g/Ah-3.3g/Ah，或3.1g/Ah-3.3g/Ah。
在一些实施方式中，在式1中，R 11和R 12可分别独立地为甲基、乙基、丙基、丁基、氟代甲基、氟代乙基、氟代丙基、氟代丁基中的一种，R 11和R 12可相同或不同。其中，氟原子数目可以是一个，也可以是多个。R 11和R 12选自上述基团时，可以使电解液的粘度保持在合适的范围内，电解液具有更高的电导率。
在一些实施方式中，作为示例，式1所示的第一溶剂可选自如下化合物中的一种或几种：
Figure PCTCN2021109903-appb-000007
Figure PCTCN2021109903-appb-000008
式1所示的第一溶剂具有低粘度、高介电常数的优点，可以提升电解液的电导率，进而在一定程度上改善正极膜层涂布重量和压实密度增加后带来的电池动力学性能欠佳的问题。但发明人还发现，式1所示的第一溶剂在负极不稳定，极易被还原生成质子及其它产物，增加电池产气量。式1所示的第一溶剂还原产生的质子还会分解SEI膜中的碳酸锂和烷氧基锂等组分，使SEI膜的稳定性变差；这样，电池使用过程中SEI膜需要不断进行修复，这一修复过程会消耗更多的活性离子，增加活性离子的不可逆消耗，使电池容量快速衰减。此外，式1所示的第一溶剂还原后的产物堆积于负极活性材料表面，还会延长活性离子的传输路径、降低活性离子的传输速度，由此还会恶化负极极片的动力学性能以及电池的动力学性能。
发明人通过大量的研究工作发现了针对上述问题的解决方案，不仅实现了保障电池高能量密度和良好动力学性能，还实现了保障电池具有良好的循环性能以及存储性能。
为了提高电池的能量密度，通常会增加正极膜层的涂布重量和压实密度，这带来的一问题是正极膜层对电解液的动力学性能的需求也越来越高。正极膜层越厚，活性离子的传输路径越长，对电解液的动力学性能的需求越高；正极膜层的孔隙率越小，活性离子传输过程中的阻力越大，对电解液动力学性能的需求也越高。因此，正极膜层的上述两种参数相互独立，且都对电解液的动力学性能有一定需求。发明人通过大量研究与实验得到这两种相互独立的需求的系数，并用两者之和来表示对电解液动力学性能的总需求。第一溶剂的含量与电解液动力学性能强相关，第一溶剂的含量越高，电解液动力学性能越好，发明人研究发现，使用第一溶剂的含量可表征电解液的动力学性能水平。且只有电解液动力学性能水平≥正极膜层对电解液动力学性能的总需求时，才能有效改善正极膜层涂布重量和压实密度增加后带来的电池动力学性能欠佳的问题。
发明人通过大量研究发现，当二次电池还满足：第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)≥1时，正极膜层涂布重量和压实密度增加后带来的电池动力学性能欠佳的问题可以得到有效的解决。
在一些实施方式中，所述二次电池可满足：第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)≥1.1，第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)≥1.2，第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)≥1.3，第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)≥1.4，第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)≥1.5，第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)≥1.6，第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)≥1.7，或第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)≥1.8。
第一溶剂的含量是指基于有机溶剂的总质量，第一溶剂的质量百分数。
正极膜层的厚度表示以mm计的正极集流体上的单面正极膜层的厚度。正极膜层设置在正极集流体的两个相对表面中的任意一者上时，正极膜层的厚度＝正极极片的厚度-正极集流体的厚度；正极膜层同时设置在正极集流体的两个相对表面上时，正极膜层的厚度＝(正极极片的厚度-正极集流体的厚度)/2。在本申请中，厚度测量可采用万分尺，例如可使用型号为Mitutoyo293-100、精度为0.1μm的万分尺。在本申请中，“正极膜层的厚度”均指单面正极膜层的厚度，“正极膜层的总厚度”表示当正极膜层同时设置在正极集流体的两个相对表面上时各正极膜层的厚度之和。
正极膜层的孔隙率用正极极片的孔隙体积(即正极极片的真体积)与正极极片的表观体积之比表示。正极膜层的孔隙率可参考GB/T 24586-2009铁矿石表观密度、真实密度和孔隙率的测定方法进行测试。该测试方法包括如下步骤：从正极极片上裁取30片直径为14mm的小圆片，基于气体吸附的原理，使用惰性气体(例如，氦气或者氮气)作为介质，测试这30片直径为14mm的小圆片的真体积；根据小圆片的面积、厚度和数量计算得到的正极极片的表观体积，真体积与表观体积之比即为正极膜层的孔隙率。
橄榄石结构的含锂磷酸盐及其改性化合物的表面含极性官能团且比表面积大，极易吸水，而电池注液前的烘干工序并不能完全除去其中的水分；在电池使用过程中，这部分水分会逐渐向电解液中扩散并与电解液反应；同时水分的存在还会破坏负极活性材料表面的SEI膜(Solid Electrolyte Interface Membrane)，影响负极界面的稳定性。
正极膜层的厚度降低，活性离子在其中的传输路径变短，二次电池的动力学性能变好；同时，正极膜层中的水分更容易在烘干工序除去，水分对负面界面的破坏程度变小。但是，正极膜层的厚度降低，二次电池的能量密度也会降低。在一些实施方式中，正极膜层的厚度可≥0.07mm。例如，正极膜层的厚度可≥0.075mm，≥0.08mm，≥0.085mm，≥0.09mm，≥0.10mm，≥0.11mm，≥0.12mm，≥0.13mm，≥0.14mm，或≥0.15mm。
在一些实施方式中，可选地，正极膜层的厚度可为0.07mm-0.14mm。更具体地，正极膜层的厚度可为0.09mm-0.12mm。
正极膜层的孔隙率增加，电解液更易浸润正极膜层，活性离子在正极膜层中传输阻力变小，二次电池的动力学性能变好；同时，正极膜层中的水分更容易在烘干工序除去，水分对负极界面的破坏程度变小。但是，正极膜层的孔隙率增加，二次电池的能量密度会降低。在一些实施方式中，所述正极膜层的孔隙率可≤50％。例如，所述正极膜层的孔隙率可≤48％，≤45％，≤42％，≤40％，≤38％，≤37％，≤35％，≤32％，或≤30％。
在一些实施方式中，可选地，所述正极膜层的孔隙率可为5％-50％。更具体地，所述正极膜层的孔隙率可为20％-40％。
在一些实施方式中，所述正极膜层的单面涂布重量可≥20mg/cm 2。可选地，所述正极膜层的单面涂布重量可为23mg/cm 2-29mg/cm 2。更具体地，所述正极膜层的单面涂布重量可为25mg/cm 2-29mg/cm 2。
在一些实施方式中，所述正极膜层的压实密度可≥2.1g/cm 3。可选地，所述正极膜层的压实密度可为2.1g/cm 3-2.8g/cm 3。更具体地，所述正极膜层的压实密度可为2.3g/cm 3-2.6g/cm 3。
在一些实施方式中，基于有机溶剂的总质量，第一溶剂的质量百分数(即第一溶剂的含量)可≥10％。例如，第一溶剂的含量可≥15％，≥20％，≥25％，≥30％，≥35％，≥40％，≥45％，≥50％，≥55％，或≥60％。
在一些实施方式中，第一溶剂的含量可为10％-80％，15％-80％，20％-80％，25％-80％，30％-80％，35％-80％，40％-80％，45％-80％，50％-80％，10％-75％，15％-75％，20％-75％，25％-75％，30％-75％，35％-75％，40％-75％，45％-75％，50％-75％，10％-70％，15％-70％，20％-70％，25％-70％，30％-70％，35％-70％，40％-70％，45％-70％，50％-70％，10％-65％，15％-65％，20％-65％，25％-65％，30％-65％，35％-65％，40％-65％，45％-65％，50％-65％，10％-60％，15％-60％，20％-60％，25％-60％，30％-60％，35％-60％，40％-60％，45％-60％，50％-60％，10％-55％，15％-55％，20％-55％，25％-55％，30％-55％，35％-55％，40％-55％，45％-55％，或50％-55％。
在一些实施方式中，所述有机溶剂还可包括式2所示的第二溶剂、式3所示的第三溶剂中的一种或几种。在式2中，R 21为H、甲基、乙基中的一种；在式3，R 31、R 32分别独立地为甲基、乙基、丙基中的一种，R 31和R 32可相同或不同。
Figure PCTCN2021109903-appb-000009
在本申请的二次电池中，所述有机溶剂除包括式1所示的第一溶剂外，还可包括式2所示的第二溶剂、或还可包括式3所示的第三溶剂、或还可同时包括式2所示的第二溶剂和式3所示的第三溶剂。在一些实施方式中，所述有机溶剂除包括式1所示的第一溶剂外，还包括式2所示的第二溶剂。
Figure PCTCN2021109903-appb-000010
在一些实施方式中，作为示例，式2所示的第二溶剂可选自如下化合物中的一种或两种：
Figure PCTCN2021109903-appb-000011
在一些实施方式中，作为示例，式3所示的第三溶剂可选自如下化合物中的一种或几种：
Figure PCTCN2021109903-appb-000012
Figure PCTCN2021109903-appb-000013
第二溶剂的介电常数较高，有利于锂盐的解离。在一些实施方式中，基于有机溶剂的总质量，所述第二溶剂的质量百分数可≥10％。可选地，所述第二溶剂的质量百分数可为10％-80％。更具体地，所述第二溶剂的质量百分数可为20％-50％。
第三溶剂的介电常数较小，解离锂盐的能力较弱，但黏度小、流动性好，可以增加活性离子的迁移速率。在一些实施方式中，基于有机溶剂的总质量，所述第三溶剂的质量百分数可≥0％。可选地，所述第三溶剂的质量百分数可为5％-80％。更具体地，所述第三溶剂的质量百分数可为5％-20％。
在本申请的二次电池中，所述电解液还可包括添加剂，所述添加剂可为成膜型添加剂。在一些实施方式中，所述添加剂的还原电位可满足≥0.8V(vs Li +/Li)。
负极活性材料表面的SEI膜对电子绝缘，同时允许活性离子自由进出，并且还能阻止负极活性材料与电解液进一步反应，因此，负极活性材料表面SEI膜的性质会影响负极极片的性能以及电池的性能，例如，电池的循环性能、存储性能等。本申请的添加剂的还原电位≥0.8V(vs Li +/Li)，能优先于有机溶剂发生电化学还原反应参与负极活性材料表面SEI膜的形成，并促进在负极活性材料表面形成稳定的SEI膜，阻止负极活性材料与电解液进一步反应，降低第一溶剂还原产生的质子对SEI膜的破坏程度。
在一些实施方式中，所述添加剂可包括有机添加剂、无机添加剂中的一种或几种。
在本申请的二次电池中，所述添加剂也可仅包括有机添加剂。
在一些实施方式中，作为示例，所述有机添加剂可包括碳酸亚乙烯酯(Vinylene carbonate，VC)、氟代碳酸乙烯酯(FloroEthylene carbonate，FEC)、乙烯基碳酸乙烯酯(Vinyl ethylene carbonate，VEC)、硫酸乙烯酯(Ethylene sulfate，DTD)、1,3-丙烷磺内酯(1,3-Propane sultone，PS)中一种或几种。有机添加剂为电化学还原型添加剂，其还原电位比有机溶剂高，因此可在负极活性材料表面优先发生电化学还原形成性能优良的SEI膜，从而降低第一溶剂还原产生的质子对SEI膜的破坏程度。有机添加剂的还原产物主要为有机组分，这些有机组分能提升SEI膜的机械稳定性，从而有利于提升电池的循环性能。
在一些实施方式中，作为示例，所述无机添加剂可包括三(三甲基硅基)磷酸酯(tris(trimethylsilyl)phosphate，TMSP)、双草酸硼酸锂(Lithium bis(oxalate)borate，LiBOB)、二氟二草酸磷酸锂(Lithium bis[ethanedioato(2-)-κO1,κO2]difluorophosphate(1-)，LiDFOP)、四氟草酸磷酸锂(Lithium tetrafluoro(oxalato)phosphate，LiTFOP)、二氟草酸硼酸锂(Lithium difluoro(oxalato)borate，LiDFOB)、二氟磷酸锂(lithium difluorophosphate，LiPO 2F 2)中一种或几种。无机添加剂为电化学还原型添加剂，其还原电位比有机溶剂高，因此可在负极活性材料表面优先发生电化学还原形成性能优良的SEI膜，从而降低第一溶剂还原产生的质子对SEI膜的破坏程度。无机添加剂的还原产物主要为无机组分，这些无机组分能提升SEI膜的热稳定性，从而有利于提升电池的高温性能。
在一些实施方式中，可选地，所述添加剂包括碳酸亚乙烯酯、氟代碳酸乙烯酯、1,3-丙烷磺内酯、硫酸乙烯酯、二氟磷酸锂、三(三甲基硅基)磷酸酯中的一种或几 种。其中，碳酸亚乙烯酯、氟代碳酸乙烯酯、1,3-丙烷磺内酯、硫酸乙烯酯的还原产物可作为SEI膜中的有机组分，提升SEI膜的机械稳定性，以及SEI膜对电池循环过程中负极活性材料体积变化的耐受度。二氟磷酸锂、三(三甲基硅基)磷酸酯的还原产物可作为SEI膜中的无机组分，提升SEI膜的热稳定性，使SEI膜即使在高温环境下也不容易分解。
在一些实施方式中，基于所述添加剂的总质量，所述有机添加剂的质量百分数可≥50％。例如，所述有机添加剂的质量百分数可≥55％，≥60％，≥65％，≥70％，≥75％，≥80％，≥85％，≥90％，≥95％，或为100％。
在一些实施方式中，所述有机添加剂的质量百分数可为50％-100％，55％-100％，60％-100％，65％-100％，70％-100％，75％-100％，80％-100％，85％-100％，90％-100％，或95％-100％。
在一些实施方式中，基于所述添加剂的总质量，所述无机添加剂的质量百分数可≤50％。例如，所述无机添加剂的质量百分数可≤45％，≤40％，≤35％，≤30％，≤25％，≤20％，≤15％，≤10％，≤5％，或为0％。
在一些实施方式中，所述无机添加剂的质量百分数可为0％-50％，0％-45％，0％-40％，0％-35％，0％-30％，0％-25％，0％-20％，0％-15％，0％-10％，或0％-5％。
添加剂的含量增加，二次电池化成过程可供消耗的添加剂数量增加，负极活性材料表面形成的SEI膜会变厚，负极成膜阻抗会增加；但是，SEI膜变厚对负极活性材料的保护作用会变强，负极界面的稳定性变好，SEI膜对第一溶剂所引起的副作用的耐受度变高。在一些实施方式中，基于电解液的总质量，所述添加剂的质量百分数(即添加剂的含量)可≥3％。例如，添加剂含量可≥3.5％，≥4％，≥4.5％，≥5％，≥5.5％，≥6％，≥6.5％，≥7％，≥7.5％，≥8％，≥9％，≥10％，≥11％，或≥12％。
在本申请的二次电池中，“添加剂的含量”是指有机添加剂的含量与无机添加剂的含量之和。
在一些实施方式中，可选地，所述添加剂的含量可为3％-9％。更具体地，所述添加剂的含量可为5％-8％。
本申请对锂盐的种类没有具体的限制，可根据实际需求进行选择。在一些实施方式中，作为示例，所述锂盐可包括LiPF 6、LiBF 4、LiAsF 6、Li(FSO 2) 2N、LiCF 3SO 3、LiClO 4、LiN(C xF 2x+1SO 2)(C yF 2y+1SO 2)中的一种或几种，其中，x、y为正整数。
锂盐的质量百分数越小(例如，小于10％)，电池内部活性离子传递单元越少，大倍率充电时，负极电位快速下降，进而负极表面容易长出枝晶，增加活性离子的不可逆消耗；枝晶不断生长还有可能会刺穿隔离膜，导致正负极发生内短路。锂盐的质量百分数越小，电解液中游离的有机溶剂(尤其是第一溶剂)含量相对越多，还会使负极活性材料表面的SEI膜不稳定，进而SEI膜容易被质子分解。在一些实施方式中，基于电解液的总质量，所述锂盐的质量百分数可≥10％。例如，所述锂盐的质量百分数可≥11％，≥12％，≥13％，≥14％，≥15％，≥16％，≥17％，或≥18％。
电解液的电导率受可迁移活性离子总数和活性离子迁移速率影响。锂盐的质量百分数增加，可迁移活性离子总数增加，但同时电解液粘度也增加，活性离子迁移速率反而减慢。因此，锂盐的质量百分数会出现一个最佳值。在一些实施方式中，所述锂盐的 质量百分数可为10％-20％。可选地，所述锂盐的质量百分数可为12％-17％。
添加剂会促进在负极活性材料表面形成稳定的SEI膜。负极活性材料的比表面积越大，对添加剂的需求量也越大；第一溶剂也会额外消耗添加剂。发明人经过大量研究与实验，得到这两种添加剂消耗行为的系数，并用这两种消耗行为之和表示添加剂的需求水平；而添加剂的保有水平则可以用保液系数×添加剂的含量表示。只有添加剂的保有水平≥添加剂的需求水平时，才能保证良好的负极界面，从而有效抑制负极界面处的副反应。
发明人通过大量研究发现，当二次电池还满足：(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)≥1时，添加剂能有效保护负极界面，抑制由于第一溶剂不稳定造成的负极界面副反应加剧问题，因此，二次电池使用过程中的容量保持率更高、体积膨胀率更低。
保液系数是指电解液的质量与二次电池的额定容量之比，以g/Ah计；添加剂的含量是指基于电解液的总质量，添加剂的质量百分数；负极相对质量是指负极极片中负极活性材料的质量与二次电池的额定容量之比，以g/Ah计；负极活性材料的比表面积以m 2/g计。
在一些实施方式中，所述二次电池还可满足：(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)≥1.2，(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)≥1.4，(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)≥1.6，(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)≥1.8，(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)≥2，(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)≥2.2，(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)≥2.4，(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)≥2.8，或(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)≥3.2。
在一些实施方式中，所述负极相对质量可≤2.1g/Ah。例如，所述负极相对质量可≤2.08g/Ah，≤2.05g/Ah，≤2.0g/Ah，≤1.95g/Ah，≤1.9g/Ah，≤1.85g/Ah，≤1.8g/Ah，≤1.75g/Ah，≤1.7g/Ah，≤1.65g/Ah，≤1.6g/Ah，≤1.55g/Ah，或≤1.5g/Ah。
在一些实施方式中，可选地，所述负极相对质量可为1.2g/Ah-2.1g/Ah。更具体地，所述负极相对质量可为1.5g/Ah-1.8g/Ah。
在本申请的二次电池中，所述负极活性材料的比表面积可为0.5m 2/g-6.0m 2/g。例如，所述负极活性材料的比表面积可为1.0m 2/g-5.0m 2/g，1.0m 2/g-4.0m 2/g，1.0m 2/g-3.2m 2/g，1.0m 2/g-2.8m 2/g，1.2m 2/g-5.0m 2/g，1.2m 2/g-4.0m 2/g，1.2m 2/g-3.0m 2/g，1.2m 2/g-2.8m 2/g，1.5m 2/g-5.0m 2/g，1.5m 2/g-4.0m 2/g，1.5m 2/g-3.0m 2/g，2.0m 2/g-5.0m 2/g，2.0m 2/g-4.0m 2/g，或2.0m 2/g-3.0m 2/g。
本申请的二次电池还包括隔离膜。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。本申请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。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一种或几种。隔离膜可以是单层薄膜，也可以是多层复合薄膜。隔离膜为多层复合薄膜时，各层的材料相同或不同。在一些实施方式中，隔离膜上还可以设置陶瓷涂层、金属氧化物涂层。
在一些实施方式中，正极极片、负极极片和隔离膜可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，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或几种。
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。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53用于盖设所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或几个，可根据需求来调节。
在一些实施方式中，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多个，具体数量可根据电池模块的应用和容量来调节。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，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根据电池包的应用和容量进行调节。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2用于盖设下箱体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。
二次电池的制备方法
在一些实施方式中，本申请的二次电池的制备方法可包括如下步骤：
S10，将正极极片、隔离膜、负极极片和电解液组装形成二次电池；
S20，对二次电池进行检测，从中筛选出满足第一溶剂的质量/二次电池的额定容量≥ 0.7g/Ah以及电解液的质量/二次电池的额定容量≤3.5g/Ah的二次电池。
通过本申请的方法得到的二次电池，均能在保持高能量密度的同时，具有良好的动力学性能、较高的容量保持率以及较低的体积膨胀率。
在一些实施方式中，在步骤S10中，作为示例，可将正极极片、隔离膜、负极极片经卷绕工艺或叠片工艺形成电极组件，将电极组件置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
在一些实施方式中，在步骤S20中，可选地，筛选出满足第一溶剂的质量/二次电池的额定容量≥1.0g/Ah的二次电池。
在一些实施方式中，在步骤S20中，可选地，筛选出满足电解液的质量/二次电池的额定容量为2.8g/Ah-3.3g/Ah的二次电池。
在一些实施方式中，所述制备方法还包括步骤：S30，筛选出满足第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)≥1的二次电池。此时，不仅实现了保障电池高能量密度和良好动力学性能，还实现了保障良好负极界面，使本申请的电池能具有良好的循环性能以及存储性能。
在一些实施方式中，所述制备方法还包括步骤：S40，筛选出满足第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)≥1以及(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)≥1的二次电池。此时，正极膜层涂布重量和压实密度增加后带来的电池动力学性能欠佳以及第一溶剂带来的负极界面破坏的问题可以得到有效的解决。
用电装置
本申请还提供一种用电装置，所述用电装置包括本申请的二次电池、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。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于重量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
正极极片的制备
将正极活性材料磷酸铁锂、粘结剂聚偏氟乙烯、导电剂乙炔黑按质量比96:2:2进行混合，之后加入溶剂N-甲基吡咯烷酮(NMP)调节粘度，按照本领域公知方法充分搅拌成正极浆料；将正极浆料均匀涂布在正极集流体铝箔上，经干燥、冷压，得到正极极片。其中，正极膜层的孔隙率为30％，正极膜层的厚度为0.1mm。
负极极片的制备
将负极活性材料石墨(比表面积为2m 2/g)、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按质量比97:1:1:1混合，之后加入溶剂去离子水，按照本领域公知方法充分搅拌成负极浆料；将负极浆料均匀涂布在负极集流体铜箔上，经干燥、冷压，得到负极极片。
电解液的制备
在含水量<10ppm的氩气气氛手套箱中，将第一溶剂化合物1-1、第二溶剂化合物2-1、第三溶剂化合物3-1按质量比50:30:20混合均匀得到有机溶剂；缓慢加入质量百分数为15％的六氟磷酸锂(LiPF 6)作为锂盐，充分搅拌至其完全溶解；待混合液恢复常温后，依次加入3％的碳酸亚乙烯酯(VC)、2％的氟代碳酸乙烯酯(FEC)、0.5％的1,3-丙烷磺内酯(PS)、0.5％的二氟二草酸磷酸锂(LiDFOP)，得到电解液。
隔离膜的制备
使用涂覆纳米氧化铝涂层的聚乙烯(PE)膜作为隔离膜。
二次电池的制备
将正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件加入外包装铝塑膜，烘干后注入电解液，经封装、静置、化成、老化、二次封装、容量等工序，得到二次电池。第一溶剂/二次电池的额定容量为1.6g/Ah，二次电池的保液系数为3.1g/Ah，负极相对质量为1.7g/Ah。
实施例2～30及对比例1～8
实施例2～30及对比例1～8的制备方法与实施例1类似，不同之处在于：调整了正极极片、负极极片以及电解液制备中的相关参数，具体参数详见表1和表2。
表1
Figure PCTCN2021109903-appb-000014
Figure PCTCN2021109903-appb-000015
表2
Figure PCTCN2021109903-appb-000016
测试部分
(1)初始直流内阻(DC internal resistance，DCR)测试
在常温下，将电池以0.5C恒流充电到3.65V，再恒压充电至电流为0.05C；将电池 以0.5C恒流放电30分钟，以调整电池至50％SOC，此时电池的电压记为U 1；将电池以4C恒流放电30秒，采用0.1秒采点，放电末期电压记为U 2。用电池50％SOC时的放电DCR表示电池的初始DCR，电池的初始DCR＝(U 1-U 2)/4C。
(2)60℃循环性能测试
在60℃下，将电池以0.5C恒流充电至3.65V，再恒压充电至电流为0.05C；将电池静置5分钟，以1/3C恒流放电至2.5V；此为电池的首次充电放电循环过程，此次的放电容量记为电池首次循环的放电容量。按照上述方法对电池进行1000次循环充电放电过程，记录电池循环1000次后的放电容量。电池60℃循环1000次后的容量保持率(％)＝(电池循环1000次后的放电容量/电池首次循环的放电容量)×100％。
(3)60℃体积膨胀率测试
在60℃下，将电池以0.5C恒流充电至3.65V，再恒压充电至电流为0.05C，此时用排水法测试电池的体积并记为V 0；将电池放入60℃的恒温箱，存储30天后取出，此时用排水法测试电池的体积并记为V 1。电池60℃存储30天后的体积膨胀率＝[(V 1-V 0)/V 0]×100％。
实施例1-30及对比例1-8的具体参数详见表1和表2，测试结果详见表3。
在表3中，公式Ⅰ＝第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)，公式Ⅱ＝(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)。
表3
Figure PCTCN2021109903-appb-000017
Figure PCTCN2021109903-appb-000018
通过对比实施例1-30和对比例1-8可以发现，只有当电池同时满足第一溶剂的质量/二次电池的额定容量≥0.7g/Ah以及电解液的质量/二次电池的额定容量≤3.5g/Ah时，二次电池能在保持高能量密度的同时，具有较低的初始DCR、较高的高温循环容量保持率以及较低的高温存储体积膨胀率。当第一溶剂的质量/二次电池的额定容量不满足≥0.7g/Ah时，电池内部第一溶剂的含量过少，不能有效提高电池的动力学性能，电池的初始DCR较高。当电解液的质量/二次电池的额定容量不满足≤3.5g/Ah时，电解液中的部分有机溶剂会持续消耗活性离子，活性离子的不可逆消耗持续增加，电池不能同时具有较低的初始DCR、较高的高温循环容量保持率以及较低的高温存储体积膨胀率。
通过对比实施例1-7可以发现，电池的初始DCR均较低、高温循环容量保持率均较高、高温存储体积膨胀率均较低。并且，电解液中第一溶剂种类不同，电池的上述性能会有轻微变化，这是由于不同第一溶剂自身的特性造成的。在这些第一溶剂中，化合物1-1的粘度最低、介电常数最高，因此制备的电池的初始DCR也最低。但是，在这些第一溶剂中，化合物1-1在负极的稳定性最差，更容易破坏负极界面的稳定性，造成负极活性材料表面持续成膜，锂离子的不可逆消耗最多；化合物1-1在负极还原分解所生成的产物堆积于负极界面，还延长锂离子传输路径、减慢锂离子传输速率；因此，在实施例1-7中，实施例1的负极界面状况最差、电池高温循环容量衰减最快、电池高温存储体积膨胀率最大。
通过对比实施例8-9可以发现，第一溶剂的含量越低，对负极界面破坏程度越小，电池的高温循环容量保持率越高、高温存储体积膨胀率越小，但同时，第一溶剂的含量越低，对电池的动力学性能的改善越弱，电池的初始DCR越大。
通过对比实施例10-11可以发现，正极膜层的厚度降低，电池的初始DCR降低、高温循环容量保持率增加、高温存储体积膨胀率变小。这主要是因为，正极膜层的厚度降低后，锂离子在其中的传输路径变短，电池的动力学性能变好、初始DCR降低。正极膜层中使用的橄榄石结构的含锂磷酸盐的表面含极性官能团且比表面积大，极易吸水，而电池注液前的烘干工序并不能完全除去正极膜层中的水分。在电池使用过程中，正极膜层中的水分会逐渐向电解液中扩散并与电解液反应；同时水分的存在还会破坏负 极活性材料表面的SEI膜，影响负极界面的稳定性。因此，当正极膜层的厚度降低后，正极膜层中的水分更容易在烘干工序除去，水分对负面界面的破坏程度减小，进而电池的高温循环容量衰减变慢、高温存储产气量降低。
通过对比实施例12-13可以发现，正极膜层的孔隙率增加，电池的初始DCR降低、高温循环容量保持率增加、高温存储体积膨胀率变小。正极膜层的孔隙率提高后，电解液更易浸润正极膜层，锂离子在正极膜层中传输阻力变小，因此，电池的动力学性能变好、初始DCR降低。正极膜层的孔隙率提高后，正极膜层中的水分更容易在烘干工序除去，水分对负极界面的破坏程度减小，因此，电池的高温循环容量衰减变慢、高温存储产气量降低。
通过对比实施例16-17可以发现，提高添加剂的含量，电池的初始DCR升高、高温循环容量保持率增加、高温存储体积膨胀率变小。这主要是因为，电池中添加剂的含量增加后，化成过程消耗的添加剂数量增加，负极活性材料表面形成的SEI膜更厚，负极成膜阻抗增加，因此，电池的初始DCR升高。相应的，电池中添加剂的含量增加后，SEI膜对负极活性材料的保护作用更强，负极界面稳定性更好，对第一溶剂所引起的副作用的耐受度也越高，因此，电池的高温循环容量衰减变慢、高温存储产气量降低。
通过对比实施例18-21可以发现，降低负极相对质量、降低负极活性材料的比表面积，电池的初始DCR升高、高温循环容量保持率增加、高温存储体积膨胀率变小。这主要是因为，电池中负极相对质量减少、负极活性材料的比表面积减少后，在负极活性材料表面形成SEI膜所需要消耗的添加剂数量减少，电池对添加剂的需求量会大幅降低，进而电池内部添加剂数量更充足，因此，电池的高温循环容量衰减变慢、高温存储产气量降低。电池对添加剂的需求量降低还会使电池内部添加剂过盈，化成过程中负极活性材料表面形成SEI膜时可供消耗的添加剂数量增加，形成的SEI膜更厚，因此，电池的初始DCR会增加。
通过对比实施例22-25可以发现，电解液动力学性能水平均能满足正极膜层对电解液动力学性能的总需求，电池的初始DCR都不大。但是，当某些参数发生变化，使添加剂的保有水平小于添加剂的需求水平，添加剂对负极界面的保护不够充分，第一溶剂在负极界面发生副反应，会消耗一定数量的锂离子，因此，电池的高温循环容量衰减会变快。第一溶剂还会破坏负极活性材料表面的SEI膜，使得电池使用过程中SEI膜需要不断被修复，SEI膜修复过程中会产生一定量的气体，因此，电池的高温存储体积膨胀率会变大。
负极活性材料的比表面积增加后，在负极活性材料表面形成SEI膜需要消耗的添加剂数量变多，由于添加剂总量一定，负极活性材料表面形成的SEI膜会相对变薄，因此，电池的初始DCR会降低。但是，实施例22中由于负极活性材料的比表面积增加使得添加剂的保有水平小于添加剂的需求水平，添加剂不能充分在负极活性材料表面形成SEI膜，不能充分保护负极界面，因此，电池的高温循环容量衰减明显变快、高温存储体积膨胀率明显变大。
添加剂的含量降低后，能够参与在负极活性材料表面形成SEI膜的添加剂数量相对减少，负极成膜阻抗变低，因此，电池的初始DCR也降低。但是，实施例23中由于添加剂的含量降低使得添加剂的保有水平小于添加剂的需求水平，添加剂不能充分在负 极活性材料表面形成SEI膜，不能充分保护负极界面，因此，电池的高温循环容量衰减明显变快、高温存储体积膨胀率明显变大。
电池保液系数降低后，能够参与在负极活性材料表面形成SEI膜的添加剂数量相对减少，负极成膜阻抗变低，因此，电池的初始DCR也降低。但是，实施例24中由于保液系数降低使得添加剂的保有水平小于添加剂的需求水平，此时添加剂已经不能充分保护负极界面，因此，电池的高温循环容量衰减明显变快、高温存储体积膨胀率明显变大。
负极相对质量增加后，由于添加剂总量一定，在负极活性材料表面形成的SEI膜会相对变薄，因此，电池的初始DCR会降低。但是，实施例25中由于负极相对质量增加使得添加剂的保有水平小于添加剂的需求水平，添加剂不能充分在负极活性材料表面形成SEI膜，不能充分保护负极界面，因此，电池的高温循环容量衰减明显变快、高温存储体积膨胀率明显变大。
通过对比实施例26-28可以发现，添加剂的保有水平均大于添加剂的需求水平时，即使电解液中含有第一溶剂，负极界面依然能得到有效保护，因此，电池仍具有较高的高温循环容量保持率和较低的高温存储体积膨胀率。但是，当某些参数发生变化，使得电解液动力学性能水平达不到正极膜层对电解液动力学性能的总需求时，电池的初始DCR会明显增加。
实施例26中由于第一溶剂的含量降低使得电解液动力学性能水平达不到正极膜层对电解液动力学性能的总需求，无法有效提升电解液以及电池的动力学性能，电池的初始DCR会明显增加。
正极膜层的厚度增加，电池的能量密度增加。但是，实施例27中由于正极膜层厚度增加使得电解液动力学性能水平达不到正极膜层对电解液动力学性能的总需求，锂离子在正极膜层中的传输路径变长，电池的初始DCR会明显增加。
正极膜层的孔隙率降低，电池的能量密度增加。但是，实施例28中由于正极膜层的孔隙率降低使得电解液动力学性能水平达不到正极膜层对电解液动力学性能的总需求，电解液较难浸润正极膜层，锂离子在正极膜层中的传输阻力变大，因此，电池的初始DCR会明显增加。
通过对比实施例29-30可以发现，电池的初始DCR较高、高温循环容量保持率较低、高温存储体积膨胀率较高。这主要是因为，一方面，正极膜层的厚度增加、孔隙率降低，电解液较难浸润正极膜层，锂离子传输路径变长、传输阻力变大，电解液动力学性能水平达不到正极膜层对电解液动力学性能的总需求，因此，电池的初始DCR较高；另一方面，电解液添加剂的含量较低，使得添加剂的保有水平小于添加剂的需求水平，添加剂无法充分保护负极界面，因此，电池的高温循环容量衰减变快、高温存储产气量增加。
通过对比实施例14-15还可以发现，锂盐质量百分数增加，电池的初始DCR先下降后上升，这主要是由于电解液的电导率发生变化所导致的。电解液的电导率受可迁移锂离子总数和锂离子迁移速率影响，锂盐质量百分数增加，可迁移锂离子总数增加，但同时电解液粘度也增加，锂离子迁移速率反而变慢。因此，锂盐质量百分数会有一个最佳值，此时电池的初始DCR最低。而锂盐质量百分数越高，电解液中游离的有机溶剂 含量越少，在负极界面发生副反应的第一溶剂的含量也越少，因此，电池的高温循环容量衰减变慢、高温存储产气量降低。
由表3的数据可知，实施例1-22的电池在满足第一溶剂的质量/二次电池的额定容量≥0.7g/Ah以及电解液的质量/二次电池的额定容量≤3.5g/Ah的同时还满足公式Ⅰ和公式Ⅱ，电池能同时具有较低的初始DCR、较高的高温循环容量保持率以及较低的高温存储体积膨胀率。一方面，电解液动力学性能水平能满足正极膜层对电池动力学性能的总需求，电池因而具有较低的初始DCR；另一方面，电解液添加剂能有效保护负极界面，抑制由于第一溶剂不稳定造成的负极界面副反应加剧问题，因此，电池的高温循环容量衰减变慢、高温存储产气量降低。
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 (19)

  1. 一种二次电池，包括正极极片以及电解液；
    所述正极极片包括正极集流体以及设置在正极集流体至少一个表面上的正极膜层，所述正极膜层包括橄榄石结构的含锂磷酸盐及其改性化合物中的一种或几种；
    所述电解液包括有机溶剂，所述有机溶剂包括式1所示的第一溶剂；
    Figure PCTCN2021109903-appb-100001
    在式1中，R 11和R 12分别独立地为C1～C4的烷基、C1～C4的卤代烷基中的一种；
    且所述二次电池满足：
    第一溶剂的质量/二次电池的额定容量≥0.7g/Ah，可选地为≥1.0g/Ah；
    电解液的质量/二次电池的额定容量≤3.5g/Ah，可选地为2.8g/Ah-3.3g/Ah。
  2. 根据权利要求1所述的二次电池，其中，所述二次电池还满足：第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)≥1，可选地，第一溶剂的含量/(正极膜层的厚度×3+0.008/正极膜层的孔隙率)≥1.5，
    第一溶剂的含量是指基于有机溶剂的总质量，第一溶剂的质量百分数，
    正极膜层的厚度表示以mm计的正极集流体上的单面正极膜层的厚度。
  3. 根据权利要求1-2任一项所述的二次电池，其中，所述电解液还包括添加剂，所述添加剂的还原电位≥0.8V，vs Li +/Li。
  4. 根据权利要求3所述的二次电池，其中，所述添加剂包括有机添加剂，所述有机添加剂包括碳酸亚乙烯酯、氟代碳酸乙烯酯、乙烯基碳酸乙烯酯、硫酸乙烯酯、1,3-丙烷磺内酯中一种或几种。
  5. 根据权利要求3-4任一项所述的二次电池，其中，所述添加剂包括无机添加剂，所述无机添加剂包括三(三甲基硅基)磷酸酯、双草酸硼酸锂、二氟二草酸磷酸锂、四氟草酸磷酸锂、二氟草酸硼酸锂、二氟磷酸锂中一种或几种。
  6. 根据权利要求4-5任一项所述的二次电池，其中，基于添加剂的总质量，有机添加剂的质量百分数≥50％，可选地为70％-100％。
  7. 根据权利要求4-6任一项所述的二次电池，其中，基于添加剂的总质量，无机添加剂的质量百分数≤50％，可选地为0％-30％。
  8. 根据权利要求1-7任一项所述的二次电池，其中，
    所述二次电池还包括负极极片，所述负极极片包括负极活性材料，且所述二次电池还满足：(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)≥1，可选地，(保液系数×添加剂的含量)/(负极相对质量×负极活性材料的比表面积×0.012+保液系数×第一溶剂的含量×0.03)≥2；
    保液系数是指电解液的质量与二次电池的额定容量之比，以g/Ah计；
    添加剂的含量是指基于电解液的总质量，添加剂的质量百分数；
    负极相对质量是指负极极片中负极活性材料的质量与二次电池的额定容量之比，以g/Ah计；
    负极活性材料的比表面积以m 2/g计。
  9. 根据权利要求1-8任一项所述的二次电池，其中，正极膜层的厚度≥0.07mm，可选地为0.07mm-0.14mm；和/或
    正极膜层的孔隙率≤50％，可选地为5％-50％。
  10. 根据权利要求1-9任一项所述的二次电池，其中，负极相对质量≤2.1g/Ah，可选地为1.2g/Ah-2.1g/Ah；和/或
    负极活性材料的比表面积为0.5m 2/g-6.0m 2/g，可选地为1.0m 2/g-3.2m 2/g；和/或
    添加剂的含量≥3％，可选地为3％-9％。
  11. 根据权利要求1-10任一项所述的二次电池，其中，第一溶剂的含量≥10％，可选地为10％-80％。
  12. 根据权利要求1-11任一项所述的二次电池，其中，在式1中，R 11和R 12分别独立地为甲基、乙基、丙基、丁基、氟代甲基、氟代乙基、氟代丙基、氟代丁基中的一种。
  13. 根据权利要求1-12任一项所述的二次电池，其中，式1所示的第一溶剂选自如下化合物中的一种或几种：
    Figure PCTCN2021109903-appb-100002
  14. 根据权利要求1-13任一项所述的二次电池，其中，所述有机溶剂还包括式2所示的第二溶剂、式3所示的第三溶剂中的一种或几种，在式2中，R 21为H、甲基、乙基中的一种，在式3，R 31、R 32分别独立地为甲基、乙基、丙基中的一种；
    Figure PCTCN2021109903-appb-100003
    可选地，式2所示的第二溶剂选自如下化合物中的一种或两种：
    Figure PCTCN2021109903-appb-100004
    可选地，式3所示的第三溶剂选自如下化合物中的一种或几种：
    Figure PCTCN2021109903-appb-100005
  15. 根据权利要求14所述的二次电池，其中，基于有机溶剂的总质量，第二溶剂的质量百分数≥10％，可选地为10％～80％；和/或
    基于有机溶剂的总质量，第三溶剂的质量百分数≥0％，可选地为5％～80％。
  16. 根据权利要求1-15任一项所述的二次电池，其中，所述橄榄石结构的含锂磷酸盐包括磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其各自的改性化合物中的一种或几种。
  17. 一种电池模块，包括根据权利要求1-16任一项所述的二次电池。
  18. 一种电池包，包括根据权利要求1-16任一项所述的二次电池、根据权利要求17所述的电池模块中的一种。
  19. 一种用电装置，包括根据权利要求1-16任一项所述的二次电池、根据权利要求17所述的电池模块、根据权利要求18所述的电池包中的至少一种。
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