WO2024082123A1 - 电解液、二次电池、电池模块、电池包和用电装置 - Google Patents

电解液、二次电池、电池模块、电池包和用电装置 Download PDF

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WO2024082123A1
WO2024082123A1 PCT/CN2022/125847 CN2022125847W WO2024082123A1 WO 2024082123 A1 WO2024082123 A1 WO 2024082123A1 CN 2022125847 W CN2022125847 W CN 2022125847W WO 2024082123 A1 WO2024082123 A1 WO 2024082123A1
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electrolyte
secondary battery
salt
alkali metal
positive electrode
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PCT/CN2022/125847
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English (en)
French (fr)
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傅寒立
李振华
李星
汤强强
牛少军
金海族
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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/CN2022/125847 priority Critical patent/WO2024082123A1/zh
Publication of WO2024082123A1 publication Critical patent/WO2024082123A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes

Definitions

  • the present application relates to the technical field of secondary batteries, and in particular to an electrolyte, a secondary battery, a battery module, a battery pack and an electrical device.
  • secondary batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • secondary batteries have made great progress, higher requirements are also put forward for the cycle life of secondary ions.
  • the electrolyte is an important component of the secondary battery.
  • the electrolyte determines the composition and structure of the SEI film, and has an important impact on the stability of the secondary battery electrode structure and the cycle life. Optimizing the design of the electrolyte is the main means to improve the cycle life of the secondary battery. Therefore, seeking an electrolyte that can better improve the cycle life of the secondary battery is one of the research directions that technicians in this field focus on.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide an electrolyte, a secondary battery, a battery module, a battery pack and an electrical device, which can make the secondary battery containing the electrolyte have a higher cycle life.
  • the first aspect of the present application provides an electrolyte, comprising an organic solvent and an electrolyte salt dissolved in the organic solvent;
  • the electrolyte salt comprises an alkali metal double salt, and the alkali metal double salt contains lithium ions and at least one other alkali metal ion other than lithium ions.
  • the other alkali metal ions in the alkali metal double salt include sodium ions and potassium ions.
  • the alkali metal double salt contains both sodium ions and potassium ions.
  • the alkali metal double salt includes one or more of Li a Na b K c PF 6 , Li a Na b K c BOB, Li a Na b K c ODFB, Li a Na b K c TFOP, Li a Na b K c PO 2 F 2 , Li a Na b K c TFSI, Li a Na b K c FSI and Li a Na b K c BODFP;
  • the electrolyte salt further contains a basic lithium salt
  • the basic lithium salt includes one or more of LiPF 6 , LiBOB, LiODFB, LiTFOP, LiPO 2 F 2 , LiTFSI, LiFSI and LiBODFP.
  • the mass ratio of the basic lithium salt to the alkali metal complex salt in the electrolyte salt is X:1;
  • the base lithium salt and the alkali metal double salt have the same anion type.
  • the molar concentration of the electrolyte salt in the electrolyte solution is 0.5 mol/L to 2 mol/L.
  • the organic solvent includes one or more of dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl formate, methyl acetate, methyl butyrate, ethyl propionate, ethylene carbonate, propylene carbonate and diethyl carbonate.
  • the second aspect of the present application also provides a secondary battery, comprising the electrolyte of the first aspect of the present application.
  • the positive electrode active material in the positive electrode sheet of the secondary battery is a layered structure positive electrode active material.
  • a third aspect of the present application further provides a battery module, comprising the secondary battery of the second aspect of the present application.
  • the fourth aspect of the present application also provides a battery pack, comprising the battery module of the third aspect of the present application.
  • the fifth aspect of the present application also provides an electrical device, comprising at least one of the secondary battery of the second aspect of the present application, the battery module of the third aspect of the present application, or the battery pack of the fourth aspect of the present application.
  • the electrolyte of the present application adopts an alkali metal complex salt including lithium ions and at least one alkali metal ion other than lithium ions in the electrolyte salt; on the one hand, the radius of the alkali metal ions other than lithium (such as sodium ions and potassium ions) in the alkali metal complex salt is larger than that of lithium, and can be embedded in part of the lithium sites of the layered positive electrode during the first discharge process, thereby improving the stability of the layered structure and preventing the Li/Ni mixed arrangement of the layered positive electrode, thereby improving the cycle performance of the secondary battery; on the other hand, the sodium ions, potassium ions, etc.
  • the radius of the alkali metal ions other than lithium (such as sodium ions and potassium ions) in the alkali metal complex salt is larger than that of lithium, and can be embedded in part of the lithium sites of the layered positive electrode during the first discharge process, thereby improving the stability of the layered structure and preventing the Li/Ni mixed arrangement of the layered positive
  • the alkali metal complex salt help to increase the organic lithium component in the SEI during the formation of the SEI film for the first charge and discharge, thereby effectively improving the co-embedding of solvent molecules, avoiding damage to the electrode material caused by the co-embedding of solvent molecules, and greatly improving the cycle performance of the electrode;
  • part of the lithium sites in the lithium salt are replaced by sodium salts, potassium salts, etc. with larger ionic radii, and the sodium ions and potassium ions can occupy the same spatial sites and energy levels as the lithium ions, and the structures of the sodium ions and potassium ions occupying the original lithium sites in the lithium salt are more stable, Lithium vacancies provide a stable space for storing sodium and potassium.
  • the failure rate of sodium and potassium ions detaching from and embedding into corresponding lithium sites is reduced, which is conducive to a longer-lasting effect of sodium and potassium ions.
  • the ions have the same movement trajectory when they are released during charging and discharging, which can quantitatively improve the cycle life of the battery cell without introducing additional impurities or causing side reactions.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.
  • range disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range.
  • the range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected.
  • the numerical range "a-b" represents an abbreviation of any real number combination between a and b, wherein a and b are both real numbers.
  • the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in this application are open-ended or closed-ended.
  • the “include” and “comprising” may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: 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).
  • ternary cathode materials With the increasing demand for energy density of secondary batteries, ternary cathode materials now mostly use high-nickel materials, but the overall life of high-nickel materials is generally poor. On the one hand, the increase in nickel content will inevitably cause more lithium-nickel mixing, thereby reducing the cycle life of the secondary battery; on the other hand, the organic lithium content in the SEI film formed by conventional lithium salt electrolyte is low, and solvent molecules are easily co-embedded, thereby destroying the electrode material, thereby reducing the cycle life of the secondary battery.
  • the inventor has discovered an electrolyte solution, in which an alkali metal complex salt is used as the electrolyte salt of the electrolyte solution, and the alkali metal complex salt contains lithium ions and other alkali metal ions (such as sodium, potassium, etc.) in addition to lithium ions.
  • the electrolyte solution can effectively improve the cycle performance of the secondary battery and increase the cycle life of the secondary battery.
  • the first aspect of the present application provides an electrolyte comprising an organic solvent and an electrolyte salt dissolved in the organic solvent; wherein the electrolyte salt comprises an alkali metal double salt, and the alkali metal double salt contains lithium ions and at least one other alkali metal ion other than lithium ions.
  • the electrolyte of the present application adopts an alkali metal complex salt containing lithium ions and at least one alkali metal ion other than lithium ions in the electrolyte salt; the radius of the alkali metal ions other than lithium in the alkali metal complex salt (such as sodium ions and potassium ions) is larger than that of lithium, and can be embedded in part of the lithium sites of the layered positive electrode during the first discharge process, thereby improving the stability of the layered structure, preventing Li/Ni mixing of the layered positive electrode, and thus improving the cycle performance of the secondary battery.
  • the radius of the alkali metal ions other than lithium in the alkali metal complex salt such as sodium ions and potassium ions
  • the sodium ions, potassium ions, etc. in the alkali metal complex salt help to increase the organic lithium content in the SEI during the formation of the SEI film during the first charge and discharge, which can effectively improve the co-embedding of solvent molecules, avoid damage to the electrode material due to the co-embedding of solvent molecules, and greatly improve the cycle performance of the electrode.
  • sodium and potassium ions are not bound by ionic bonds, and the ions move irregularly, making it impossible to quantitatively control the improvement of the SEI film, and simply adding sodium salts and potassium salts will introduce additional anions; in the same solvent, the type of metal salt will change the thermodynamic stability and solvation structure of the electrolyte, thereby affecting the decomposition behavior of the electrolyte, and then changing the interface characteristics of the electrode
  • the present application replaces some lithium sites in lithium salts with alkali metal complex salts such as sodium salts and potassium salts with larger ionic radius; compared with the method of directly adding sodium salts and potassium salts to lithium salts, the sodium ions and potassium ions in the alkali metal complex salts can occupy the same spatial positions and have the same energy levels as lithium ions, the structure of sodium ions and potassium ions occupied by the original lithium sites in the lithium salts is more stable, the lithium holes provide a stable space for storing sodium and potassium, the failure rate of sodium ions and potassium ions detaching from and embedding into the corresponding lithium sites is reduced, which is conducive to a more lasting effect of sodium and potassium ions, and the ions have the same motion trajectory when they are released during charging and discharging, which can quantitatively improve the cycle life of the secondary battery, and will not introduce additional impurities or cause side reactions.
  • alkali metal complex salts such as sodium salts and potassium salts with larger ionic radius
  • alkali metal ions in the alkali metal double salt include sodium ions and potassium ions. It is understood that other alkali metal ions may also include alkali metal ions such as rubidium ions and cesium ions.
  • the alkali metal double salt contains both sodium ions and potassium ions, that is, the alkali metal double salt includes two or more other alkali metal ions, and the two or more other alkali metal ions include sodium ions and potassium ions.
  • the other alkali metal ions in the above-mentioned alkali metal double salt are sodium and potassium.
  • the electrolyte salt adopts the above-mentioned alkali metal double salt, which can effectively improve the cycle life of the secondary battery.
  • a, b, c respectively represent the number of atoms of lithium, sodium and potassium in the molecular formula of the above-mentioned alkali metal double salt.
  • the values include the minimum and maximum values of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values in the embodiment and: 0.6, 0.7, 0.8, 0.9.
  • the electrolyte salt further contains a basic lithium salt
  • the basic lithium salt includes one or more of LiPF 6 , LiBOB, LiODFB, LiTFOP, LiPO 2 F 2 , LiTFSI, LiFSI and LiBODFP.
  • the electrolyte salt contains both an alkali metal double salt and a basic lithium salt. It is understood that in some other embodiments, the electrolyte salt may only include an alkali metal double salt, but not the above-mentioned basic lithium salt.
  • the electrolyte salt contains both an alkali metal double salt and a basic lithium salt
  • the anions in the alkali metal double salt and the anions in the basic lithium salt are of the same type.
  • the mass ratio of the basic lithium salt to the alkali metal complex salt in the electrolyte salt is X:1, wherein 0.65 ⁇ X ⁇ 1. It is understood that the mass content of the basic lithium salt in the electrolyte salt is less than the mass content of the alkali metal complex salt.
  • the values include the minimum and maximum values of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values in the embodiments and: 0.68, 0.70, 0.72, 0.75, 0.78, 0.80, 0.82, 0.85, 0.88, 0.90, 0.92, 0.95, and 0.98.
  • the molar concentration of the electrolyte salt in the electrolyte solution is 0.5 mol/L to 2 mol/L.
  • the organic solvent includes one or more of dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl formate, methyl acetate, methyl butyrate, ethyl propionate, ethylene carbonate, propylene carbonate and diethyl carbonate. That is, the organic solvent in the electrolyte may include any one of the above organic solvents, or may include two or more of the above organic solvents at the same time.
  • the second aspect of the present application further provides a secondary battery, comprising the electrolyte of the first aspect of the present application.
  • the secondary battery has good cycle performance and a long cycle life.
  • the positive electrode active material in the positive electrode sheet of the secondary battery is a layered structure positive electrode active material.
  • a third aspect of the present application further provides a battery module, comprising the secondary battery of the second aspect of the present application.
  • the fourth aspect of the present application also provides a battery pack, comprising the battery module of the third aspect of the present application.
  • the fifth aspect of the present application also provides an electrical device, comprising at least one of the secondary battery of the second aspect of the present application, the battery module of the third aspect of the present application, or the battery pack of the fourth aspect of the present application.
  • a secondary battery is provided.
  • a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator.
  • active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet.
  • the electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet.
  • the separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.
  • 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, wherein the positive electrode film layer includes a positive electrode active material.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • aluminum foil may be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material on a polymer material substrate.
  • the metal material includes but is not limited to aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.
  • Polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the positive electrode active material may include a positive electrode active material for a battery known in the art.
  • the positive electrode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to , lithium cobalt oxide (such as LiCoO2 ), lithium nickel oxide (such as LiNiO2 ), lithium manganese oxide (such as LiMnO2 , LiMn2O4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi1 / 3Co1 / 3Mn1 / 3O2 (also referred to as NCM333 ), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523 ) , LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211 ) , LiNi0.6Co0.2Mn0.2O2 (also referred to as NCM622 ), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the weight ratio of the positive electrode active material in the positive electrode film layer is 80 to 100 weight %, based on the total weight of the positive electrode film layer.
  • the positive electrode film layer may also optionally include a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • the weight ratio of the binder in the positive electrode film layer is 0 to 20% by weight, based on the total weight of the positive electrode film layer.
  • the positive electrode film layer may further include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the weight ratio of the conductive agent in the positive electrode film layer is 0 to 20 weight %, based on the total weight of the positive electrode film layer.
  • the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, wherein the positive electrode slurry has a solid content of 40-80wt%, and the viscosity at room temperature is adjusted to 5000-25000mPa ⁇ s, the positive electrode slurry is coated on the surface of the positive electrode collector, and after drying, it is cold-pressed by a cold rolling mill to form a positive electrode sheet; the positive electrode powder coating unit area density is 150-350mg/ m2 , and the positive electrode sheet compaction density is 3.0-3.6g/ cm3 , and can be optionally 3.3-3.5g/ cm3 .
  • a solvent such as N-methylpyrrolidone
  • Compacted density coating surface density/(thickness of the electrode after extrusion - thickness of the current collector).
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other 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 electrode current collector may be a metal foil or a composite current collector.
  • copper foil may be used as the metal foil.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector may be formed by forming a metal material on a polymer material substrate.
  • the metal material includes but is not limited to copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.
  • the polymer material substrate includes but is not limited to polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) and other substrates.
  • the negative electrode active material may adopt the negative electrode active material for the battery known in the art.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for 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 may further include a binder.
  • the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • the negative electrode film layer may further include a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the weight ratio of the conductive agent in the negative electrode film layer is 0 to 20 weight %, based on the total weight of the negative electrode film layer.
  • the negative electrode film layer may further include other additives, such as a thickener (such as sodium carboxymethyl cellulose (CMC-Na)), etc.
  • a thickener such as sodium carboxymethyl cellulose (CMC-Na)
  • the weight ratio of the other additives in the negative electrode film layer is 0 to 15 weight %, based on the total weight of the negative electrode film layer.
  • the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70wt%, and the viscosity at room temperature is adjusted to 2000-10000mPa ⁇ s; the obtained negative electrode slurry is coated on the negative electrode collector, and after a drying process, cold pressing such as rolling, a negative electrode sheet is obtained.
  • the negative electrode powder coating unit area density is 75-220mg/ m2
  • the negative electrode sheet compaction density is 1.2-2.0g/ m3 .
  • the electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate.
  • the electrolyte of the present application is used.
  • the electrolyte includes an electrolyte salt and an organic solvent; wherein the electrolyte salt includes an alkali metal complex salt, and the alkali metal complex salt includes lithium ions and at least one alkali metal ion other than lithium ions.
  • the electrolyte salt further includes a basic lithium salt
  • the basic lithium salt includes one or more of LiPF 6 , LiBOB, LiODFB, LiTFOP, LiPO 2 F 2 , LiTFSI, LiFSI, and LiBODFP.
  • the mass ratio of the basic lithium salt to the alkali metal complex salt in the electrolyte salt is X:1; wherein 0.65 ⁇ X ⁇ 1.
  • the organic solvent includes one or more of ethylene carbonate, propylene carbonate, and diethyl carbonate.
  • the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • additives such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the isolation film has a thickness of 6 to 40 ⁇ m, and may be 12 to 20 ⁇ m.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package that can be used to encapsulate the electrode assembly and the electrolyte.
  • the outer package of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer package of the secondary battery may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG1 is a secondary battery 5 of a square structure as an example.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 52.
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • the secondary batteries 5 may be assembled into a battery module 4 .
  • the number of the secondary batteries 5 included in the battery module 4 may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module 4 .
  • the plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a housing space, and the plurality of secondary batteries 5 are housed in the housing space.
  • the battery modules 4 described above may also be assembled into a battery pack 1 .
  • the number of battery modules 4 included in the battery pack 1 may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack 1 .
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3.
  • the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device 6, which includes at least one of the secondary battery 5, battery module 4, or battery pack 1 provided in the present application.
  • the secondary battery 5, battery module 4, or battery pack 1 can be used as a power source for the electric device 6, and can also be used as an energy storage unit for the electric device 6.
  • the electric device 6 may include mobile devices (such as mobile phones, laptops, 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., but are not limited thereto.
  • a secondary battery 5 As the power-consuming device 6 , a secondary battery 5 , a battery module 4 or a battery pack 1 may be selected according to its usage requirements.
  • Fig. 4 is an example of an electric device 6.
  • the electric device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack 1 or a battery module 4 may be used.
  • a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery 5 may be used as a power source.
  • Embodiment 1 is a diagrammatic representation of Embodiment 1:
  • the electrolyte salt in the electrolyte is Li 0.5 Na 0.3 K 0.2 PF 6.
  • the electrolyte is prepared to a concentration of 1M.
  • the electrolyte salt Li 0.5 Na 0.3 K 0.2 PF 6 can be prepared by the hydrogen fluoride solvent method, and its reaction process can be expressed as follows:
  • Preparation of secondary battery positive electrode sheet 1) Mix polyvinylidene fluoride (PVDF), layered positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O 2 and conductive agent carbon black Super P in a mass ratio of 90:5:5, use N-methyl-pyrrolidone (NMP) as solvent, adjust the amount of solvent added to control the viscosity of the slurry to 100mPa.s ⁇ 20000mPa.s. Use a coater or sprayer to coat the slurry on the positive electrode collector. After drying at 85°C, cold press, then trim, cut, and strip, and then dry at 85°C under vacuum for 4h, weld the tabs, and make a secondary battery positive electrode sheet that meets the requirements.
  • PVDF polyvinylidene fluoride
  • conductive agent carbon black Super P in a mass ratio of 90:5:5
  • NMP N-methyl-pyrrolidone
  • Preparation of negative electrode sheets for secondary batteries Add negative electrode active material graphite, conductive agent Super-P, thickener CMC, and adhesive SBR in a mass ratio of 96.5:1.0:1.0:1.5 into solvent deionized water and mix evenly to form negative electrode slurry; coat the negative electrode slurry on the current collector copper foil and dry it at 85°C, then trim, cut and strip it, and then dry it at 110°C under vacuum conditions for 4 hours, weld the pole ears, and make a secondary battery negative electrode sheet that meets the requirements.
  • Preparation of secondary batteries Using 12 ⁇ m polypropylene film as a separator, stack the positive electrode sheet, separator, and negative electrode sheet in order, so that the separator is between the positive and negative electrode sheets to play a role of isolation, and then wind them into a square bare cell.
  • the bare cell is wrapped in aluminum foil, injected with electrolyte and vacuum sealed, and repeatedly charged and discharged to complete the preparation of the secondary battery.
  • Embodiment 2 is a diagrammatic representation of Embodiment 1:
  • the electrolyte salt in the electrolyte is Li 0.5 Na 0.3 K 0.2 BOB.
  • the electrolyte is prepared to a concentration of 1M.
  • the electrolyte salt Li 0.5 Na 0.3 K 0.2 BOB can be prepared by a hydrogen fluoride solvent method.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 3 is a diagrammatic representation of Embodiment 3
  • the electrolyte salt in the electrolyte is Li 0.5 Na 0.3 K 0.2 ODFB.
  • the electrolyte is prepared to a concentration of 1M.
  • the electrolyte salt Li 0.5 Na 0.3 K 0.2 ODFB can be prepared by a hydrogen fluoride solvent method.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 4 is a diagrammatic representation of Embodiment 4:
  • the electrolyte salt in the electrolyte is Li 0.5 Na 0.3 K 0.2 TFOP.
  • the electrolyte is prepared to a concentration of 1M.
  • the electrolyte salt Li 0.5 Na 0.3 K 0.2 TFOP can be prepared by a hydrogen fluoride solvent method.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 5 is a diagrammatic representation of Embodiment 5:
  • the electrolyte salt in the electrolyte is Li 0.5 Na 0.3 K 0.2 PO 2 F 2.
  • the electrolyte is prepared to a concentration of 1M.
  • the electrolyte salt Li 0.5 Na 0.3 K 0.2 PO 2 F 2 can be prepared by a hydrogen fluoride solvent method.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 6 is a diagrammatic representation of Embodiment 6
  • the electrolyte salt in the electrolyte is Li 0.5 Na 0.3 K 0.2 TFSI.
  • the electrolyte is prepared to a concentration of 1M.
  • the electrolyte salt Li 0.5 Na 0.3 K 0.2 TFSI can be prepared by a hydrogen fluoride solvent method.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 7 is a diagrammatic representation of Embodiment 7:
  • the electrolyte salt in the electrolyte is Li 0.5 Na 0.3 K 0.2 FSI.
  • the electrolyte is prepared to a concentration of 1M.
  • the electrolyte salt Li 0.5 Na 0.3 K 0.2 FSI can be prepared by a hydrogen fluoride solvent method.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 8 is a diagrammatic representation of Embodiment 8
  • the electrolyte salt in the electrolyte is Li 0.5 Na 0.3 K 0.2 BODFP.
  • the electrolyte is prepared to a concentration of 1M.
  • the electrolyte salt Li 0.5 Na 0.3 K 0.2 BODFP can be prepared by a hydrogen fluoride solvent method.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 9 is a diagrammatic representation of Embodiment 9:
  • the electrolyte salt in the electrolyte is Li 0.7 Na 0.2 K 0.1 PF 6.
  • the electrolyte is prepared to a concentration of 1M.
  • the electrolyte salt Li 0.7 Na 0.2 K 0.1 PF 6 can be prepared by a hydrogen fluoride solvent method.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 10 is a diagrammatic representation of Embodiment 10:
  • the electrolyte salt in the electrolyte is Li 0.8 Na 0.1 K 0.1 PF 6.
  • the electrolyte is prepared to a concentration of 1M.
  • the electrolyte salt Li 0.8 Na 0.1 K 0.1 PF 6 can be prepared by a hydrogen fluoride solvent method.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 11 is a diagrammatic representation of Embodiment 11:
  • the electrolyte salt in the electrolyte is Li 0.9 Na 0.05 K 0.05 PF 6.
  • the electrolyte is prepared to a concentration of 1M.
  • the electrolyte salt Li 0.9 Na 0.05 K 0.05 PF 6 can be prepared by a hydrogen fluoride solvent method.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 12 is a diagrammatic representation of Embodiment 12
  • the electrolyte salts in the electrolyte are LiPF 6 and Li 0.5 Na 0.3 K 0.2 PF 6.
  • the mass ratio of LiPF 6 and Li 0.5 Na 0.3 K 0.2 PF 6 is 0.7:1, and the electrolyte concentration is 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 13 is a diagrammatic representation of Embodiment 13:
  • the electrolyte salts in the electrolyte were LiBOB and Li 0.5 Na 0.3 K 0.2 BOB.
  • the mass ratio of LiBOB to Li 0.5 Na 0.3 K 0.2 BOB was 0.8:1, and the electrolyte concentration was prepared to be 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 14 is a diagrammatic representation of Embodiment 14:
  • the electrolyte salts in the electrolyte were LiODFB and Li 0.5 Na 0.3 K 0.2 ODFB.
  • the mass ratio of LiODFB to Li 0.5 Na 0.3 K 0.2 ODFB was 0.9:1, and the electrolyte concentration was prepared to be 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 15 is a diagrammatic representation of Embodiment 15:
  • the electrolyte salt in the electrolyte is Li 0.5 Na 0.5 PF 6 .
  • the electrolyte is prepared to a concentration of 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 16 is a diagrammatic representation of Embodiment 16:
  • the electrolyte salt in the electrolyte is Li 0.5 K 0.5 BOB.
  • the electrolyte is prepared to have a concentration of 0.5M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 17 is a diagrammatic representation of Embodiment 17:
  • the electrolyte salt in the electrolyte is Li 0.5 Na 0.5 ODFB.
  • the electrolyte is prepared to a concentration of 1.5M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 18 is a diagrammatic representation of Embodiment 18:
  • the electrolyte salt in the electrolyte is Li 0.5 K 0.5 TFOP.
  • the electrolyte is prepared to a concentration of 2M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 19 is a diagrammatic representation of Embodiment 19:
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 20 is a diagrammatic representation of Embodiment 20.
  • the electrolyte salt in the electrolyte is Li 0.5 Na 0.5 TFSI.
  • the electrolyte is prepared to a concentration of 1.2M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 21 is a diagrammatic representation of Embodiment 21.
  • the electrolyte salt in the electrolyte is Li 0.5 K 0.5 FSI.
  • the electrolyte is prepared to a concentration of 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 22 is a diagrammatic representation of Embodiment 22.
  • the electrolyte salt in the electrolyte is Li 0.5 Na 0.5 BODFP.
  • the electrolyte is prepared to a concentration of 1.8M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 23 is a diagrammatic representation of Embodiment 23.
  • the electrolyte salt in the electrolyte is Li 0.7 K 0.3 PF 6 .
  • the electrolyte is prepared to a concentration of 0.9M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 24 is a diagrammatic representation of Embodiment 24.
  • the electrolyte salt in the electrolyte is Li 0.8 Na 0.2 PF 6 .
  • the electrolyte is prepared to a concentration of 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 25 is a diagrammatic representation of Embodiment 25.
  • the electrolyte salt in the electrolyte is Li 0.9 K 0.1 PF 6 .
  • the electrolyte is prepared to a concentration of 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 26 is a diagrammatic representation of Embodiment 26.
  • the electrolyte salts in the electrolyte are LiPF 6 and Li 0.5 Na 0.5 PF 6.
  • the mass ratio of LiPF 6 to Li 0.5 Na 0.5 PF 6 is 0.7:1.
  • the electrolyte is prepared to a concentration of 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • Embodiment 27 is a diagrammatic representation of Embodiment 27.
  • the electrolyte salts in the electrolyte are LiBOB and Li 0.5 K 0.5 BOB.
  • the mass ratio of LiBOB to Li 0.5 K 0.5 BOB is 0.8:1.
  • the electrolyte is prepared to a concentration of 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • the electrolyte salt in the electrolyte is LiBOB, and the electrolyte is prepared to a concentration of 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • the electrolyte salt in the electrolyte is LiODFB.
  • the electrolyte is prepared to a concentration of 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • the electrolyte salt in the electrolyte is LiTFOP.
  • the electrolyte is prepared to a concentration of 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • the electrolyte salt in the electrolyte is LiPO 2 F 2 .
  • the electrolyte is prepared to a concentration of 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • the electrolyte salt in the electrolyte is LiTFSI.
  • the electrolyte is prepared to a concentration of 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • the electrolyte salt in the electrolyte is LiFSI.
  • the electrolyte is prepared to a concentration of 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • the electrolyte salt in the electrolyte is LiBODFP.
  • the electrolyte is prepared to a concentration of 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • the electrolyte salt in the electrolyte is all Li 0.3 Na 0.3 K 0.4 PF 6 , and the electrolyte concentration is prepared to be 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • the electrolyte salts in the electrolyte are LiPF 6 and Li 0.5 Na 0.3 K 0.2 PF 6.
  • the mass ratio of LiPF 6 and Li 0.5 Na 0.3 K 0.2 PF 6 is 0.4:1, and the electrolyte concentration is 1M.
  • the preparation of the positive electrode sheet, the negative electrode sheet and the secondary battery is the same as that in Example 1.
  • the cycle performance test conditions of the secondary battery are: at 25°C and 45°C, the secondary battery is subjected to 1C/1C cycle charge and discharge test, the charge and discharge voltage range is 2.8V ⁇ 4.35V, and the test is stopped when the capacity decays to 80% of the initial discharge capacity (i.e. 80% SOH (state of health)).
  • SOH is the battery health life, which represents the percentage of the full charge capacity of the secondary battery relative to the rated capacity.
  • the SOH of a newly manufactured secondary battery is 100%.
  • sodium and potassium ions By replacing some lithium sites in lithium salts with sodium and potassium with larger ion radius, sodium and potassium ions occupy the same spatial positions as lithium ions, have the same energy levels, and have the same motion trajectories when charged and discharged.
  • the doped sodium or potassium ions can effectively prevent Li/Ni mixing in the layered positive electrode, thereby improving the cycle performance; on the other hand, the sodium ions and potassium ions in the alkali metal double salt help to increase the organic lithium component in the SEI during the formation of the SEI film during the first charge and discharge.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and the same effect as the technical solution of the present application are all included in the technical scope of the present application.
  • various modifications that can be thought of by those skilled in the art are applied to the embodiments, and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

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Abstract

本申请涉及一种电解液，所述电解液包括有机溶剂和溶解在所述有机溶剂中的电解质盐；其中，所述电解质盐中包括碱金属复盐，所述碱金属复盐中含有锂离子以及至少一种除锂离子之外的其他碱金属离子。并涉及相应的二次电池、电池模块、电池包和用电装置。该电解液由于在电解质盐中采用含有锂离子和至少一种除锂离子之外的其他碱金属离子的碱金属复盐，能够有效改善二次电池的循环性能，提高二次电池的循环寿命，且不会导入额外杂质，不会造成副反应。

Description

电解液、二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及二次电池技术领域，尤其涉及一种电解液、二次电池、电池模块、电池包和用电装置。
背景技术
近年来，随着二次离子电池的应用范围越来越广泛，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。由于二次电池取得了极大的发展，因此对二次离子的循环寿命也提出了更高的要求。
伴随能量密度需求的提升，三元正极的需求和设计使用由最早的低镍材料到如今的高镍材料，而高镍材料的整体寿命都较差。其原因在于，一方面，镍含量的增多势必造成更多锂镍混排进而降低电池循环寿命；另一方面，常规的锂盐电解液形成的电极表面固体电解质两相界面(SEI，solid electrolyte interphase)膜中有机锂含量少，有机锂含量少会发生溶剂分子共嵌入，从而破坏电极材料，进而降低二次电池的循环寿命。
电解液是二次电池的重要组成部分，电解液决定了SEI膜的成分和结构，对二次电池电极结构的稳定性及循环寿命有着重要影响。对电解液进行优化设计是改善二次电池循环寿命的主要手段。因此，寻求能够更好地提高二次电池循环寿命的电解液，是本领域技术人员重点关注的研究方向之一。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种电解液、二次电池、电池模块、电池包和用电装置，可以使包含该电解液的二次电池具有较高的循环寿命。
为了达到上述目的，本申请的第一方面提供一种电解液，包括有机溶剂和溶解在所述有机溶剂中的电解质盐；所述电解质盐中包括碱金属复盐，所述碱金属复盐中含有锂离子以及至少一种除锂离子之外的其他碱金属离子。
在任意实施方式中，所述碱金属复盐中所述其他碱金属离子包括钠离子和钾离子。
在任意实施方式中，所述碱金属复盐中同时含有钠离子和钾离子。
在任意实施方式中，所述碱金属复盐包括Li aNa bK cPF 6、Li aNa bK cBOB、Li aNa bK cODFB、Li aNa bK cTFOP、Li aNa bK cPO 2F 2、Li aNa bK cTFSI、Li aNa bK cFSI和Li aNa bK cBODFP中的一种或多种；
其中，a+b+c＝1，0.5≤a＜1。
在任意实施方式中，所述电解质盐中还含有基础锂盐，所述基础锂盐包括LiPF 6、LiBOB、LiODFB、LiTFOP、LiPO 2F 2、LiTFSI、LiFSI和LiBODFP中的一种或多种。
在任意实施方式中，所述电解质盐中所述基础锂盐与所述碱金属复盐的质量比为X：1；
其中，0.65≤X＜1。
在任意实施方式中，0.7≤X＜0.9。
在任意实施方式中，所述基础锂盐与所述碱金属复盐的阴离子种类相同。
在任意实施方式中，所述电解质盐在所述电解液中的物质的量浓度为 0.5mol/L～2mol/L。
在任意实施方式中，所述有机溶剂包括碳酸二甲酯、碳酸甲乙酯、碳酸甲丙酯、甲酸甲酯、乙酸甲酯、丁酸甲酯、丙酸乙酯、碳酸乙烯酯、碳酸丙烯酯和碳酸二乙酯中的一种或多种。
本申请的第二方面还提供一种二次电池，包括本申请第一方面的电解液。
在任意实施方式中，所述二次电池的正极极片中的正极活性材料为层状结构正极活性材料。
本申请的第三方面还提供一种电池模块，包括本申请的第二方面的二次电池。
本申请的第四方面还提供一种电池包，包括本申请的第三方面的电池模块。
本申请的第五方面还提供一种用电装置，包括本申请的第二方面的二次电池、本申请的第三方面的电池模块或本申请的第四方面的电池包中的至少一种。
本申请的电解液，通过在电解质盐中采用包括锂离子和至少一种除锂离子之外的碱金属离子的碱金属复盐；一方面，该碱金属复盐中除锂之外的碱金属离子(如钠离子、钾离子)的半径比锂大，可以在首次放电过程中嵌入层状正极的部分锂位，提高层状结构稳定性，防止层状正极的Li/Ni混排，进而提高二次电池的循环性能；另一方面，碱金属复盐中的钠离子、钾离子等有助于在首次充放电SEI膜形成过程中提高SEI中有机锂的成分，进而可有效改善溶剂分子的共嵌入，避免因溶剂分子共嵌入对电极材料造成破坏，大大提高电极的循环性能；再一方面，将锂盐中的部分锂位替换成离子半径更大的钠盐、钾盐等，钠离子、钾离子可以与锂离子占据相同空间位，能级相同，锂盐中原位锂位占据的钠离子和钾离子结构更稳定， 锂空穴提供了储钠和储钾的稳定空间，钠离子和钾离子脱离和嵌入相应锂位的失效率降低，有利于钠钾离子更持久的作用，且在充放电离子脱出时具有相同的运动轨迹，可以定量改善电芯的循环寿命，且不会导入额外杂质，不会造成副反应。
附图说明
图1是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是本申请一实施方式的电池模块的示意图。
图4是本申请一实施方式的电池包的示意图。
图5是图4所示的本申请一实施方式的电池包的分解图。
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53盖板；6用电装置。
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电解液、二次电池、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)。
目前，由于二次电池取得了极大的发展，对二次电池的循环性能也提出了更高的要求。循环性能优异的二次电池对电解液具有很高的要求。因此，寻求能够更好地提高二次电池的循环性能的电解液是本领域技术人员重点关注的研究方向之一。
随着对二次电池能量密度需求的提升，三元正极材料现多采用高镍材料,而高镍材料的整体寿命一般较差。一方面，镍含量的增多势必造成更多锂镍混排，进而降低二次电池的循环寿命；另一方面，常规的锂盐电解液形成的SEI膜中的有机锂含量少，容易发生溶剂分子共嵌入从而破坏电极材料，进而使二次电池的循环寿命下降。
发明人研究发现一种电解液，在电解液的电解质盐中使用碱金属复盐，该碱金属复盐中含有锂离子以及除锂离子之外的其他碱金属离子(如钠、钾等)。该电解液能够有效改善二次电池的循环性能，提高二次电池的循环寿命。
在一些实施方式中，本申请的第一方面提供了一种电解液，包括有机溶剂和溶解在所述有机溶剂中的电解质盐；其中，所述电解质盐中包括碱金属复盐，所述碱金属复盐中含有锂离子以及至少一种除锂离子之外的其他碱金属离子。
本申请的电解液，通过在电解质盐中采用含有锂离子和至少一种除锂离子之外的其他碱金属离子的碱金属复盐；该碱金属复盐中除锂之外的其他碱金属离子(如钠离子、钾离子)的半径比锂大，可以在首次放电过程中嵌入层状正极的部分锂位，提高层状结构稳定性，防止层状正极的Li/Ni混排，进而提高二次电池的循环性能。
另一方面，该碱金属复盐中的钠离子、钾离子等有助于在首次充放电 SEI膜形成过程中提高SEI中有机锂的成分，进而可有效改善溶剂分子的共嵌入，避免因溶剂分子共嵌入对电极材料造成破坏，大大提高电极的循环性能。
若将钠盐、钾盐等直接加入到锂盐中作为电解质盐；一方面，在电解液的生产工艺中，需要使用额外管道增加额外导入和提纯工序来引入钠盐、钾盐等，这一系列工艺都需要额外设备导入支持和增加生产成本；另一方面，简单的在锂盐中加入钠盐、钾盐，钠、钾离子会大量游离在电解液中，这些钠、钾离子未受离子键的束缚，离子无规律性运动较大，无法定量地控制对SEI膜的改善，且简单的添加钠盐、钾盐会引入额外阴离子；在相同溶剂中，金属盐的种类会改变电解液的热力学稳定性与溶剂化结构，从而影响电解液的分解行为，进而改变电极|电解液的界面特性与电极的电化学性能；不同阴离子间电负性不同，阴离子会进入溶剂化层，参与溶剂化结构反应，进而加速电解液的分解，造成不可逆损失。
本申请采用锂盐中的部分锂位替换为离子半径更大的钠盐、钾盐等的碱金属复盐；相比于直接在锂盐中添加钠盐、钾盐的方式，碱金属复盐中的钠离子、钾离子可以与锂离子占据相同的空间位，能级相同，锂盐中原位锂位占据的钠离子和钾离子结构更稳定，锂空穴提供了储钠和储钾的稳定空间，钠离子和钾离子脱离和嵌入相应锂位的失效率降低，有利于钠钾离子更持久的作用，且在充放电离子脱出时具有相同的运动轨迹，可以定量地改善二次电池的循环寿命，且不会导入额外杂质，不会造成副反应。
在一些实施方式中，碱金属复盐中的其他碱金属离子包括钠离子和钾离子。可以理解，其他碱金属离子还可以包括铷离子、铯离子等碱金属离子。
在一些实施方式中，碱金属复盐中同时含有钠离子和钾离子。即碱金属复盐中包括两种以上的其他碱金属离子，该两种以上的其他碱金属离子 包括钠离子和钾离子。
在一些实施方式中，碱金属复盐包括Li aNa bK cPF 6、Li aNa bK cBOB、Li aNa bK cODFB、Li aNa bK cTFOP、Li aNa bK cPO 2F 2、Li aNa bK cTFSI、Li aNa bK cFSI和Li aNa bK cBODFP中的一种或多种；其中，a+b+c＝1，0.5≤a＜1。由此，上述的碱金属复盐中的其他碱金属离子为钠和钾。电解质盐采用上述的碱金属复盐，可以有效地提高二次电池的循环寿命。其中a、b、c分别表示上述碱金属复盐分子式中锂、钠、钾的原子数。
可以理解，上述“0.5≤a＜1”中，取值包括该范围的最小值及最大值，以及这种最小值与最大值之间的每一个值，具体示例包括但不限于实施例中的点值以及：0.6、0.7、0.8、0.9。
在任意实施方式中，电解质盐中还含有基础锂盐，该基础锂盐包括LiPF 6、LiBOB、LiODFB、LiTFOP、LiPO 2F 2、LiTFSI、LiFSI和LiBODFP中的一种或多种。由此，电解质盐中同时包含有碱金属复盐和基础锂盐。可以理解，在其他一些实施方式中，电解质盐中可以仅包括碱金属复盐，而不包括上述的基础锂盐。
进一步地，当电解质盐中同时包含有碱金属复盐和基础锂盐时，碱金属复盐中的阴离子与基础锂盐中的阴离子种类相同。
在任意实施方式中，电解质盐中的基础锂盐与碱金属复盐的质量比为X：1；其中，0.65≤X＜1。可理解，电解质盐中基础锂盐的质量含量小于碱金属复盐的质量含量。
可以理解，上述“0.65≤X＜1”中，取值包括该范围的最小值及最大值，以及这种最小值与最大值之间的每一个值，具体示例包括但不限于实施例中的点值以及：0.68、0.70、0.72、0.75、0.78、0.80、0.82、0.85、0.88、0.90、0.92、0.95、0.98。
在任意实施方式中，0.7≤X＜0.9。
在任意实施方式中，电解质盐在电解液中的物质的量浓度为0.5mol/L～2mol/L。
在任意实施方式中，有机溶剂包括碳酸二甲酯、碳酸甲乙酯、碳酸甲丙酯、甲酸甲酯、乙酸甲酯、丁酸甲酯、丙酸乙酯、碳酸乙烯酯、碳酸丙烯酯和碳酸二乙酯中的一种或多种。即，电解液中的有机溶剂可以包括上述有机溶剂中的任意一种，也可以同时包括上述有机溶剂中的两种或两种以上。
本申请的第二方面还提供一种二次电池，包括本申请第一方面的电解液。由此，所述二次电池具有良好的循环性能，具有较长的循环寿命。
在任意实施方式中，所述二次电池的正极极片中的正极活性材料为层状结构正极活性材料。
本申请的第三方面还提供一种电池模块，包括本申请的第二方面的二次电池。
本申请的第四方面还提供一种电池包，包括本申请的第三方面的电池模块。
本申请的第五方面还提供一种用电装置，包括本申请的第二方面的二次电池、本申请的第三方面的电池模块或本申请的第四方面的电池包中的至少一种。
以下适当参照附图对本申请的二次电池、电池模块、电池包和用电装置进行说明。
本申请的一个实施方式中，提供一种二次电池。
通常情况下，二次电池包括正极极片、负极极片、电解液和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解液在正极极片和负极极片之间起到传导离子的作用。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 使离子通过。
[正极极片]
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，所述正极膜层包括正极活性材料。
作为示例，正极集流体具有在其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相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料形成在高分子材料基材上而形成。其中，金属材料包括但不限于铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等。高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)。
在一些实施方式中，正极活性材料可包含本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、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(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化 合物等中的至少一种。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(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
所述正极活性材料在正极膜层中的重量比为80～100重量％，基于正极膜层的总重量计。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(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-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。所述粘结剂在正极膜层中的重量比为0～20重量％，基于正极膜层的总重量计。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。所述导电剂在正极膜层中的重量比为0～20重量％，基于正极膜层的总重量计。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料，其中所述正极浆料固含量为40～80wt％，室温下的粘度调整到5000～25000mPa·s，将正极浆料涂覆在正极集流体的表面，烘干后经过冷轧机冷压后形成正极极片；正极粉末涂布单位面密度为150～350mg/m 2，正极极片压实密度为3.0～3.6g/cm 3，可选为3.3～3.5g/cm 3。
所述压实密度的计算公式为：
压实密度＝涂布面密度/(挤压后极片厚度-集流体厚度)。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其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相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料形成在高分子材料基材上而形成。其中，金属材料包括但不限于铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等，高分子材料基材包括但不限于聚丙烯(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)等基材。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。所述粘结剂在负极膜层中的重量比为0～30重量％，基于负极膜层的总重量计。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。所述导电剂在负极膜层中的重量比为0～20重量％，基于负极膜层的总重量计。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。所述其他助剂在负极膜层中的重量比为0～15重量％，基于负极膜层的总重量计。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料，其中所述负极浆料固含量为30～70wt％，室温下的粘度调整到2000～10000mPa·s；将所得到的负极浆料涂覆在负极集流体上，经过干燥工序，冷压例如对辊，得到负极极片。负极粉末涂布单位面密度为75～220mg/m 2，负极极片压实密度1.2～2.0g/m 3。
[电解液]
电解液在正极极片和负极极片之间起到传导离子的作用。本申请的二次电池中，采用本申请的电解液。该电解液包括电解质盐和有机溶剂；其中，所述电解质盐中包括碱金属复盐，所述碱金属复盐中包括锂离子以及至少一种除锂离子之外的碱金属离子。
在一些实施方式中，碱金属复盐包括Li aNa bK cPF 6、Li aNa bK cBOB、Li aNa bK cODFB、Li aNa bK cTFOP、Li aNa bK cPO 2F 2、Li aNa bK cTFSI、Li aNa bK cFSI和Li aNa bK cBODFP中的一种或多种；其中，a+b+c＝1，0.5≤a＜1。
在一些实施方式中，所述电解质盐中还包括基础锂盐，所述基础锂盐包括LiPF 6、LiBOB、LiODFB、LiTFOP、LiPO 2F 2、LiTFSI、LiFSI和 LiBODFP中的一种或多种。
在一些实施方式中，所述电解质盐中所述基础锂盐与所述碱金属复盐的质量比为X：1；其中，0.65≤X＜1。
在一些实施方式中，有机溶剂包括碳酸乙烯酯、碳酸丙烯酯和碳酸二乙酯中的一种或多种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。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，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，所述隔离膜的厚度为6～40μm，可选为12～20μm。
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，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，参照图3，二次电池5可以组装成电池模块4，电池模块4所含二次电池5的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块4的应用和容量进行选择。
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，参照图4和图5，上述电池模块4还可以组装成电池包1，电池包1所含电池模块4的数量可以为一个或多个，具体数量本领域技术人员可根据电池包1的应用和容量进行选择。
在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布 于电池箱中。
另外，本申请还提供一种用电装置6，所述用电装置6包括本申请提供的二次电池5、电池模块4、或电池包1中的至少一种。所述二次电池5、电池模块4、或电池包1可以用作所述用电装置6的电源，也可以用作所述用电装置6的能量存储单元。所述用电装置6可以包括移动设备(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，但不限于此。
作为所述用电装置6，可以根据其使用需求来选择二次电池5、电池模块4或电池包1。
图4是作为一个示例的用电装置6。该用电装置6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6对二次电池5的高功率和高能量密度的需求，可以采用电池包1或电池模块4。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池5作为电源。
实施例
为了使本申请所解决的技术问题、技术方案及有益效果更加清楚，以下将结合实施例和附图对本申请进行进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。以下对至少一个示例性实施例的描述实际上仅仅是说明性的，决不作为对本申请及其应用的任何限制。基于本申请中的实施例，本领域普通技术人员在没有付出创造性劳动前提下所获得的所有其他实施例都属于本申请保护的范围。
实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.5Na 0.3K 0.2PF 6。配制成浓度为1M的电解液。其中，电解质盐Li 0.5Na 0.3K 0.2PF 6可通过氟化氢溶剂法制备得到，其反应过程可表示如下：
(0.5LiF+0.3NaF+0.2KF)+PF 5+CH 3CN→Li 0.5Na 0.3K 0.2(CH 3CN) 4PF 6→Li 0.5Na 0.3K 0.2PF 6
二次电池正极极片的制备：1)将聚偏氟乙烯(PVDF)、层状结构正极活性材料LiNi 0.6Co 0.2Mn 0.2O 2、导电剂炭黑Super P按质量比90:5:5混合，以N甲基-吡咯烷酮(NMP)为溶剂，调节溶剂的加入量，使浆料粘度控制在100mPa.s～20000mPa.s。使用涂布机或喷涂机将该浆料涂布在正极集流体上。在85℃下烘干后进行冷压，然后切边、裁片、分条，再在85℃真空条件下烘干4h，焊接极耳，制成满足要求的二次电池正极极片。
二次电池负极极片的制备：将负极活性材料石墨、导电剂Super-P、增稠剂CMC、粘接剂SBR按质量比96.5:1.0:1.0:1.5加入到溶剂去离子水中混合均匀制成负极浆料；将负极浆料涂布在集流体铜箔上并在85℃下烘干，然后进行切边、裁片、分条，再在110℃真空条件下烘干4h，焊接极耳，制成满足要求的二次电池负极极片。
二次电池的制备：以12μm的聚丙烯薄膜作为隔离膜，将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极极片中间起到隔离的作用，然后卷绕成方形裸电芯。将裸电芯进行铝箔包装，注入电解液后真空封装，重复进行多次充放电，完成二次电池的制备。
实施例2：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.5Na 0.3K 0.2BOB。配制成浓度为1M的电解液。电解质盐Li 0.5Na 0.3K 0.2BOB可通过氟化氢溶剂法制备得到。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例3：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.5Na 0.3K 0.2ODFB。配制成浓度为1M的电解液。电解质盐Li 0.5Na 0.3K 0.2ODFB可通过氟化氢溶剂法制备得到。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例4：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.5Na 0.3K 0.2TFOP。配制成浓度为1M的电解液。电解质盐Li 0.5Na 0.3K 0.2TFOP可通过氟化氢溶剂法制备得到。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例5：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以 及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.5Na 0.3K 0.2PO 2F 2。配制成浓度为1M的电解液。电解质盐Li 0.5Na 0.3K 0.2PO 2F 2可通过氟化氢溶剂法制备得到。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例6：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.5Na 0.3K 0.2TFSI。配制成浓度为1M的电解液。电解质盐Li 0.5Na 0.3K 0.2TFSI可通过氟化氢溶剂法制备得到。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例7：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.5Na 0.3K 0.2FSI。配制成浓度为1M的电解液。电解质盐Li 0.5Na 0.3K 0.2FSI可通过氟化氢溶剂法制备得到。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例8：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为 EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.5Na 0.3K 0.2BODFP。配制成浓度为1M的电解液。电解质盐Li 0.5Na 0.3K 0.2BODFP可通过氟化氢溶剂法制备得到。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例9：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.7Na 0.2K 0.1PF 6。配制成浓度为1M的电解液。其中，电解质盐Li 0.7Na 0.2K 0.1PF 6可通过氟化氢溶剂法制备得到。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例10：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.8Na 0.1K 0.1PF 6。配制成浓度为1M的电解液。其中，电解质盐Li 0.8Na 0.1K 0.1PF 6可通过氟化氢溶剂法制备得到。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例11：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.9Na 0.05K 0.05PF 6。配制成 浓度为1M的电解液。其中，电解质盐Li 0.9Na 0.05K 0.05PF 6可通过氟化氢溶剂法制备得到。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例12：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为LiPF 6和Li 0.5Na 0.3K 0.2PF 6。LiPF 6和Li 0.5Na 0.3K 0.2PF 6的质量比为0.7：1，配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例13：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为LiBOB和Li 0.5Na 0.3K 0.2BOB。LiBOB和Li 0.5Na 0.3K 0.2BOB的质量比为0.8：1，配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例14：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为LiODFB和Li 0.5Na 0.3K 0.2ODFB。LiODFB和Li 0.5Na 0.3K 0.2ODFB的质量比为0.9:1，配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例15：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.5Na 0.5PF 6。配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例16：
二次电池电解液的制备：以碳酸二甲酯、碳酸甲乙酯以及碳酸甲丙酯的混合物为有机溶剂，其中各组分的质量比为碳酸二甲酯：碳酸甲乙酯：碳酸甲丙酯＝20:30:40。电解液中的电解质盐为Li 0.5K 0.5BOB。配制成浓度为0.5M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例17：
二次电池电解液的制备：以甲酸甲酯、乙酸甲酯以及丁酸甲酯的混合物为有机溶剂，其中各组分的质量比为甲酸甲酯：乙酸甲酯：丁酸甲酯＝30:20:30。电解液中的电解质盐为Li 0.5Na 0.5ODFB。配制成浓度为1.5M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例18：
二次电池电解液的制备：以丙酸乙酯、碳酸乙烯酯以及碳酸丙烯酯的混合物为有机溶剂，其中各组分的质量比为丙酸乙酯：碳酸乙烯酯：碳酸 丙烯酯＝30:20:50。电解液中的电解质盐为Li 0.5K 0.5TFOP。配制成浓度为2M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例19：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.5Na 0.5PO 2F 2。配制成浓度为0.8M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例20：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.5Na 0.5TFSI。配制成浓度为1.2M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例21：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝20:20:40。电解液中的电解质盐为Li 0.5K 0.5FSI。配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例22：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝20:20:40。电解液中的电解质盐为Li 0.5Na 0.5BODFP。配制成浓度为1.8M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例23：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝20:20:40。电解液中的电解质盐为Li 0.7K 0.3PF 6。配制成浓度为0.9M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例24：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.8Na 0.2PF 6。配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例25：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.9K 0.1PF 6。配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例26：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为LiPF 6和Li 0.5Na 0.5PF 6。LiPF 6和Li 0.5Na 0.5PF 6的质量比为0.7：1。配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
实施例27：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为LiBOB和Li 0.5K 0.5BOB。LiBOB和Li 0.5K 0.5BOB的质量比为0.8：1。配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
对比例1：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为LiPF 6，配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
对比例2：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为 EC:PC:DEC＝30:30:40。电解液中的电解质盐为LiBOB，配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
对比例3：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为LiODFB。配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
对比例4：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为LiTFOP。配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
对比例5：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为LiPO 2F 2。配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
对比例6：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为LiTFSI。配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
对比例7：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为LiFSI。配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
对比例8：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为LiBODFP。配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
对比例9：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为Li 0.4Na 0.5K 0.1PF 6，配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
对比例10：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐全为Li 0.3Na 0.3K 0.4PF 6，配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
对比例11：
二次电池电解液的制备：以碳酸乙烯酯(EC)、碳酸丙烯酯(PC)以及碳酸二乙酯(DEC)的混合物为有机溶剂，其中各组分的质量比为EC:PC:DEC＝30:30:40。电解液中的电解质盐为LiPF 6和Li 0.5Na 0.3K 0.2PF 6。LiPF 6和Li 0.5Na 0.3K 0.2PF 6的质量比为0.4：1，配制成浓度为1M的电解液。
正极极片、负极极片以及二次电池的制备均与实施例1相同。
循环性能测试：
二次电池的循环性能测试条件为：在25℃和45℃下，将二次电池进行1C/1C循环充放电测试，充放电电压范围为2.8V～4.35V，容量衰减至首次放电比容量的80％(即80％SOH(state of health))时停止测试。其中，SOH为电池健康寿命，表征二次电池满充容量相对额定容量的百分比。新出厂二次电池的SOH为100％。
对以上各实施例和对比例的二次电池进行循环性能测试，测试结果如表1所示。
表1各实施例和对比例的二次电池的循环性能测试数据
Figure PCTCN2022125847-appb-000001
Figure PCTCN2022125847-appb-000002
通过上述实施例和对比例的循环性能测试数据可知：不同锂盐的电解液中，锂位原位掺杂合理比例的钠或钾离子，均可以有效改善电池的循环寿命，当锂盐中的掺杂离子比例总和大于0.5系数时，由于锂盐中的掺杂离子较多，Li量保有量不足，会导致循环中后期锂耗不足进而降低电池循环寿命。
通过将锂盐中部分锂位替换成离子半径更大的钠和钾，钠、钾离子与锂离子占据相同空间位，能级相同，充放电离子脱出时具有相同的运动轨迹，掺杂的钠或钾离子可有效防止层状正极的Li/Ni混排，进而提高循环性能；另一方面，碱金属复盐中的钠离子、钾离子有助于首次充放电SEI膜形成过程中提高SEI中有机锂成分。
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 (15)

  1. 一种电解液，包括有机溶剂和溶解在所述有机溶剂中的电解质盐；
    所述电解质盐包括碱金属复盐，所述碱金属复盐含有锂离子以及至少一种除锂离子之外的其他碱金属离子。
  2. 根据权利要求1所述的电解液，其特征在于，所述碱金属复盐中所述其他碱金属离子包括钠离子和钾离子。
  3. 根据权利要求1或2所述的电解液，其特征在于，所述碱金属复盐中同时含有钠离子和钾离子。
  4. 根据权利要求1至3中任一项所述的电解液，其特征在于，所述碱金属复盐包括Li aNa bK cPF 6、Li aNa bK cBOB、Li aNa bK cODFB、Li aNa bK cTFOP、Li aNa bK cPO 2F 2、Li aNa bK cTFSI、Li aNa bK cFSI和Li aNa bK cBODFP中的一种或多种；
    其中，a+b+c＝1，0.5≤a＜1。
  5. 根据权利要求1至4中任一项所述的电解液，其特征在于，所述电解质盐中还含有基础锂盐，所述基础锂盐包括LiPF 6、LiBOB、LiODFB、LiTFOP、LiPO 2F 2、LiTFSI、LiFSI和LiBODFP中的一种或多种。
  6. 根据权利要求5所述的电解液，其特征在于，所述电解质盐中所述基础锂盐与所述碱金属复盐的质量比为X：1；
    其中，0.65≤X＜1。
  7. 根据权利要求6所述的电解液，其特征在于，0.7≤X＜0.9。
  8. 根据权利要求5至7中任一项所述的电解液，其特征在于，所述基础锂盐与所述碱金属复盐的阴离子种类相同。
  9. 根据权利要求1至8中任一项所述的电解液，其特征在于，所述电解质盐在所述电解液中的浓度为0.5mol/L～2mol/L。
  10. 根据权利要求1至9中任一项所述的电解液，其特征在于，所述有 机溶剂包括碳酸二甲酯、碳酸甲乙酯、碳酸甲丙酯、甲酸甲酯、乙酸甲酯、丁酸甲酯、丙酸乙酯、碳酸乙烯酯、碳酸丙烯酯和碳酸二乙酯中的一种或多种。
  11. 一种二次电池，其特征在于，包括权利要求1至10中任一项所述的电解液。
  12. 根据权利要求11所述的二次电池，其特征在于，所述二次电池的正极极片中的正极活性材料为层状结构正极活性材料。
  13. 一种电池模块，其特征在于，包括权利要求11或12所述的二次电池。
  14. 一种电池包，其特征在于，包括权利要求13所述的电池模块。
  15. 一种用电装置，其特征在于，包括权利要求11或12所述的二次电池、权利要求13所述的电池模块或权利要求14所述的电池包中的至少一种。
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