WO2024197667A1 - 电解液、二次电池和用电装置 - Google Patents

电解液、二次电池和用电装置 Download PDF

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Publication number
WO2024197667A1
WO2024197667A1 PCT/CN2023/084866 CN2023084866W WO2024197667A1 WO 2024197667 A1 WO2024197667 A1 WO 2024197667A1 CN 2023084866 W CN2023084866 W CN 2023084866W WO 2024197667 A1 WO2024197667 A1 WO 2024197667A1
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Prior art keywords
sodium
ether
electrolyte
glycol dimethyl
dimethyl ether
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PCT/CN2023/084866
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English (en)
French (fr)
Inventor
官英杰
秦猛
赵玉珍
温严
黄起森
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to PCT/CN2023/084866 priority Critical patent/WO2024197667A1/zh
Priority to CN202380057212.0A priority patent/CN119631219A/zh
Priority to EP23929265.9A priority patent/EP4611101A4/en
Publication of WO2024197667A1 publication Critical patent/WO2024197667A1/zh
Priority to US19/273,151 priority patent/US20250343269A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • H01M10/0567—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
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—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
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0088—Composites
    • H01M2300/0091—Composites in the form of mixtures
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of secondary batteries, and in particular to an electrolyte, a secondary battery and an electrical device.
  • secondary batteries have been widely used in energy storage power systems such as hydropower, thermal, wind and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • electrolyte has a key impact on the performance of secondary batteries.
  • electrolyte has many defects and cannot meet the application needs of the new generation of electrochemical systems.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide an electrolyte that can effectively inhibit sodium dendrites, thereby helping to improve the cycle performance and high-temperature storage performance of the battery.
  • an electrolyte for a sodium secondary battery comprising a sodium salt and a metal ion having an ion radius larger than that of a sodium ion.
  • the ionic radius of metal ions is larger than that of sodium ions.
  • they can form a steric hindrance effect on sodium ions to prevent the growth of sodium dendrites.
  • metal ions can form a charge shielding effect, improve the current density of sodium ion deposition, promote the uniform deposition of sodium ions, and form a synergistic effect with the steric hindrance effect to inhibit the growth of sodium dendrites, avoid internal short circuits in the battery, and improve the battery's cycle performance and high-temperature storage performance.
  • the metal ions include one or more of K + , Ca 2+ , Sr 2+ , and Ba 2+ , and optionally include K + .
  • the above metal ions all satisfy that their ionic radius is larger than that of sodium ions, which can effectively inhibit the growth of sodium dendrites and improve the cycle performance and high-temperature storage performance of the battery. Moreover, when the reduced state of the above-mentioned metal ions is used as an electrode, its standard electrode potential is lower than the standard electrode potential of sodium, so that during the charging process of the battery, the metal ions are not reduced to metal atoms for deposition, thereby avoiding or reducing the impact on sodium ion deposition.
  • the electrolyte includes one or more of PF 6 ⁇ , NO 3 ⁇ , and ClO 3 ⁇ .
  • the electrolyte includes one or more of potassium hexafluorophosphate, calcium hexafluorophosphate, strontium hexafluorophosphate, barium hexafluorophosphate, potassium nitrate, calcium nitrate, strontium nitrate, barium nitrate, potassium perchlorate, calcium perchlorate, strontium perchlorate, and barium perchlorate, and optionally includes one or more of potassium hexafluorophosphate, potassium nitrate, and calcium hexafluorophosphate.
  • the above substances not only have steric hindrance effect and charge shielding effect, but are also compatible with sodium salt in the electrolyte, thus avoiding or reducing the negative effects caused by the addition of the above substances.
  • the concentration of the metal ions in the electrolyte is 0.005 mol/L to 0.3 mol/L, and can be optionally 0.01 mol/L to 0.1 mol/L.
  • Controlling the metal ion concentration in the electrolyte to have a suitable concentration can not only avoid or reduce the metal ion concentration being too low so that it cannot fully function, but also avoid or reduce the metal ion concentration being too high to affect the deposition of sodium ions, resulting in increased battery polarization, which is not conducive to improving battery performance.
  • the appropriate concentration of metal ions is conducive to the uniform deposition of sodium ions. Further controlling the concentration of metal ions in the electrolyte to 0.01mol/L to 0.1mol/L is conducive to further significantly improving the high-temperature storage performance of the battery.
  • the sodium salt includes one or more of sodium chloride, sodium bromide, sodium nitrate, sodium perchlorate, sodium hexafluorophosphate, sodium acetate, sodium trifluoroacetate, sodium trifluoromethylsulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, sodium tetrafluoroborate, and sodium tetraphenylborate, and optionally includes one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, and sodium tetrafluoroborate.
  • the electrolytes including the above sodium salts all have excellent battery cycle performance and high-temperature storage performance.
  • the concentration of the sodium salt in the electrolyte is 0.1 mol/L to 1.8 mol/L, and can be optionally 0.5 mol/L to 1.5 mol/L.
  • Controlling the appropriate concentration of sodium salt in the electrolyte avoids or reduces the concentration of sodium salt that is too low, resulting in the concentration of dissociated sodium ions in the electrolyte being too low, thereby causing the sodium ions to On the other hand, avoid or reduce the increase in electrolyte viscosity caused by excessive sodium salt concentration, which in turn leads to a decrease in sodium ion conductivity.
  • the appropriate concentration of sodium salt is conducive to the improvement of sodium ion conductivity. Further controlling the concentration of sodium salt in the electrolyte to 0.5mol/L to 1.5mol/L is conducive to further significantly improving the battery's cycle performance and high-temperature storage performance.
  • the electrolyte further includes an ether solvent
  • the ether solvent includes one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, tetrahydrofuran, methyltetrahydrofuran and 1,3-dioxolane, and optionally includes one or more of ethylene glycol diethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and diethylene glycol dibutyl ether.
  • the above-mentioned ether solvents have excellent anti-reduction properties, which can effectively reduce the side reactions between sodium metal and solvents, and further improve the high-temperature storage performance of the battery.
  • the ether solvent includes at least two of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, tetrahydrofuran, methyltetrahydrofuran and 1,3-dioxolane, and optionally includes at least two of ethylene glycol diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.
  • the ether solvents include at least two of the above-mentioned ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, tetrahydrofuran, methyltetrahydrofuran and 1,3-dioxolane, which is beneficial to further significantly improve the cycle performance and high temperature storage performance of the battery.
  • the electrolyte further includes a fluoroether compound, the fluoroether compound including 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), bis (2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl methyl ether (TME), 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (TFTFE), tris (trifluoroethoxy) methane (TFEO), methyl nonafluorobutyl ether (MFE), 1,1,1,3,3,3-hexafluoroisopropyl methyl ether (HFPM), 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether (OFE), optionally including one or more of 1,1,2,2-tetrafluoroethyl 2,2,3,3-t
  • the above-mentioned fluoroether compounds are inert fluoroether compounds, which are in the outermost layer of the sodium ion solvation structure. Moreover, the above-mentioned fluoroether compounds have low reactivity and are not easy to react with sodium metal, thereby improving the interface stability between the electrolyte and sodium metal, and improving the cycle performance and high-temperature storage performance of the battery.
  • the mass content of the fluoroether compound is 2% to 30%, and can be optionally 5% to 20%.
  • Controlling the mass content of the fluorinated ether compound within a suitable range is beneficial to improving the cycle performance and high temperature storage performance of the battery. Further controlling the mass content of the fluorinated ether compound to 5% to 20% is beneficial to further significantly improving the cycle performance and high temperature storage performance of the battery.
  • the sodium salt includes sodium hexafluorophosphate
  • the metal ion includes K +
  • the ether solvent includes ethylene glycol dimethyl ether
  • the fluoroether compound includes 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether.
  • the electrolyte containing sodium salt, metal ions, ether solvents and fluoroether compounds is beneficial to improving the cycle performance and high-temperature storage performance of the battery and improving the performance of the battery.
  • a second aspect of the present application provides a secondary battery, comprising the electrolyte of the first aspect.
  • the secondary battery is a negative electrode-free sodium secondary battery.
  • Anode-free sodium secondary batteries have high energy density.
  • the secondary battery further includes a negative electrode plate, the negative electrode plate includes a negative electrode collector and a primer layer disposed on at least one surface of the negative electrode collector, the primer layer includes one or more of carbon nanotubes, graphite, graphene, silver composite carbon nanoparticles, and tin composite carbon nanoparticles.
  • the above-mentioned base coating not only has excellent conductivity, but also facilitates the uniform deposition of metal ions on the surface of the current collector, thereby improving the coulombic efficiency and cycle performance of the battery.
  • the surface density of the primer layer is 0.5 g/m 2 to 35 g/m 2 .
  • the undercoat layer with a surface density of 0.5 g/m 2 to 35 g/m 2 is beneficial to the uniform distribution of nucleation sites in the negative electrode-free secondary battery, promotes the uniform deposition of metals, and does not affect the transmission behavior of electrons.
  • the primer layer has a thickness of 0.2 ⁇ m to 50 ⁇ m.
  • Controlling the thickness of the primer layer to 0.2 ⁇ m to 50 ⁇ m can provide anode-free secondary batteries. Providing sufficient nucleation sites is conducive to the uniform deposition of metal ions and inhibits dendrites.
  • a third aspect of the present application provides an electrical device, comprising the secondary battery of the second aspect of the present application.
  • FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG2 is an exploded view of the secondary battery of one embodiment of the present application shown in FIG1 ;
  • FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG4 ;
  • 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.
  • ranges are defined in the form of lower limits and upper limits.
  • 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 the particular range. Ranges defined in this way can be inclusive or exclusive of the end values and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if 60-120 and The range of 80-110 is understood to be that the range of 60-110 and 80-120 is also expected. In addition, 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 can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.
  • the numerical range “ab” represents an abbreviation of any real number combination between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been fully listed in this article, 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 represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent 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).
  • the present application proposes an electrolyte for a sodium secondary battery, the electrolyte comprising a sodium salt and metal ions having an ion radius greater than that of sodium ions.
  • sodium salt refers to a salt composed of sodium ions and anions, which is liquid at room temperature or near room temperature. Room temperature refers to 25°C ⁇ 5°C. It includes but is not limited to one or more of sodium perchlorate, sodium hexafluorophosphate, sodium acetate, sodium trifluoroacetate, and sodium trifluoromethanesulfonate.
  • ionic radius refers to the average distance from the nucleus to the outermost electron.
  • the ionic radius generally increases with increasing atomic number.
  • the ionic radius of metal ions is larger than that of sodium ions.
  • they can form a steric hindrance effect on sodium ions to prevent the growth of sodium dendrites.
  • metal ions can form a charge shielding effect, improve the current density of sodium ion deposition, promote the uniform deposition of sodium ions, and form a synergistic effect with the steric hindrance effect to inhibit the growth of sodium dendrites, avoid internal short circuits in the battery, and improve the battery's cycle performance and high-temperature storage performance.
  • the metal ions include one or more of K + , Ca 2+ , Sr 2+ , Ba 2+ , and optionally K + .
  • the ionic radius of Na + is 0.097nm
  • the ionic radius of K + is 0.133nm
  • the ionic radius of Ca2 + is 0.099nm
  • the ionic radius of Sr2 + is 0.112nm
  • the ionic radius of Ba2 + is 0.134nm.
  • the reduced state of Na + is used as an electrode, and its standard electrode potential is -2.711V; the reduced state of potassium ion is used as an electrode, and its standard electrode potential is -2.923V; the reduced state of calcium ion is used as an electrode, and its standard electrode potential is -2.76V; the reduced state of Sr2 + is used as an electrode, and its standard electrode potential is -2.89V; the reduced state of Ba2 + is used as an electrode, and its standard electrode potential is -2.90V.
  • metal ion reduced state means that the metal ion is reduced to obtain a metal atom.
  • standard electrode potential refers to the standard potential of the electrode, that is, the electrode potential when all substances participating in the electrode reaction are in a standard state with an activity of 1.
  • the metal ion comprises K + . In some embodiments, the metal ion comprises Ca 2+ . In some embodiments, the metal ion comprises Ba 2+ . In some embodiments, the metal ion comprises Sr 2+ .
  • the above metal ions all satisfy that their ionic radius is larger than that of sodium ions, which can effectively inhibit the growth of sodium dendrites and improve the cycle performance and high-temperature storage performance of the battery.
  • their standard electrode potential is lower than the standard electrode potential of sodium, so that during the charging process of the battery, the metal ions are not reduced to metal atoms for deposition, avoiding or reducing the impact on the deposition of sodium ions.
  • the electrolyte includes one or more of PF 6 ⁇ , NO 3 ⁇ , and ClO 3 ⁇ .
  • the electrolyte comprises PF 6 ⁇ . In some embodiments, the electrolyte comprises NO 3 ⁇ . In some embodiments, the electrolyte comprises ClO 3 ⁇ .
  • the electrolyte includes one or more of potassium hexafluorophosphate, calcium hexafluorophosphate, strontium hexafluorophosphate, barium hexafluorophosphate, potassium nitrate, calcium nitrate, strontium nitrate, barium nitrate, potassium perchlorate, calcium perchlorate, strontium perchlorate, and barium perchlorate, and optionally includes one or more of potassium hexafluorophosphate, potassium nitrate, and calcium hexafluorophosphate.
  • the electrolyte comprises potassium hexafluorophosphate. In some embodiments, the electrolyte comprises calcium nitrate. In some embodiments, the electrolyte comprises strontium perchlorate. In some embodiments, the electrolyte comprises potassium hexafluorophosphate and calcium nitrate. In some embodiments, the electrolyte comprises potassium hexafluorophosphate and calcium hexafluorophosphate.
  • the above substances not only have steric hindrance effect and charge shielding effect, but are also compatible with sodium salt in the electrolyte, thus avoiding or reducing the negative effects caused by the addition of the above substances.
  • the concentration of metal ions in the electrolyte is 0.005 mol/L to 0.3 mol/L, and can be optionally 0.01 mol/L to 0.1 mol/L.
  • the concentration of metal ions in the electrolyte may be selected as 0.005mol/L, 0.01mol/L, 0.05mol/L, 0.1mol/L, 0.12mol/L, 0.15mol/L, 0.18mol/L, 0.2mol/L, 0.22mol/L, 0.25mol/L, 0.27mol/L, 0.3mol/L, or a value in the range formed by any two of the above points.
  • Controlling the appropriate concentration of metal ions in the electrolyte can not only avoid or reduce the metal ion concentration being too low so that it cannot fully function, but also avoid or reduce the metal ion Excessive ion concentration affects the deposition of sodium ions, resulting in increased battery polarization, which is not conducive to improving battery performance.
  • Appropriate concentration of metal ions is conducive to the uniform deposition of sodium ions. Further controlling the concentration of metal ions in the electrolyte to 0.01mol/L to 0.1mol/L is conducive to further significantly improving the high-temperature storage performance of the battery.
  • the sodium salt includes one or more of sodium chloride, sodium bromide, sodium nitrate, sodium perchlorate, sodium hexafluorophosphate, sodium acetate, sodium trifluoroacetate, sodium trifluoromethylsulfonate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, sodium tetrafluoroborate, and sodium tetraphenylborate, and optionally includes one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, and sodium tetrafluoroborate.
  • the sodium salt comprises sodium chloride. In some embodiments, the sodium salt comprises sodium tetrafluoroborate. In some embodiments, the sodium salt comprises sodium trifluoroacetate. In some embodiments, the sodium salt comprises sodium chloride. In some embodiments, the sodium salt comprises sodium tetrafluoroborate.
  • the electrolytes including the above sodium salts all have excellent battery cycle performance and high-temperature storage performance.
  • the concentration of the sodium salt in the electrolyte is 0.1 mol/L to 1.8 mol/L, and can be optionally 0.5 mol/L to 1.5 mol/L.
  • the concentration of sodium salt in the electrolyte is 0.1 mol/L, 0.2 mol/L, 0.4 mol/L, 0.5 mol/L, 0.6 mol/L, 0.8 mol/L, 1.0 mol/L, 1.2 mol/L, 1.4 mol/L, 1.5 mol/L, 1.6 mol/L, 1.8 mol/L, or a value in the range formed by any two of the above points.
  • Controlling the sodium salt to have a suitable concentration in the electrolyte can, on the one hand, avoid or reduce the low sodium salt concentration, which leads to a low concentration of dissociated sodium ions in the electrolyte, thereby causing a decrease in the conductivity of sodium ions; on the other hand, avoid or reduce the high sodium salt concentration, which leads to an increase in electrolyte viscosity, thereby causing a decrease in the sodium ion conductivity rate.
  • the appropriate concentration of sodium salt is conducive to the improvement of sodium ion conductivity. Further controlling the concentration of sodium salt in the electrolyte to 0.5mol/L to 1.5mol/L is conducive to further significantly improving the battery's cycle performance and high-temperature storage performance.
  • the electrolyte further comprises an ether solvent
  • the ether solvent comprises ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether,
  • polyethylene glycol dimethyl ether, ethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, tetrahydrofuran, methyltetrahydrofuran and 1,3-dioxolane optionally including one or more of ethylene glycol diethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and diethylene glycol dibutyl ether.
  • the ether solvent comprises ethylene glycol diethyl ether. In some embodiments, the ether solvent comprises diethylene glycol dimethyl ether. In some embodiments, the ether solvent comprises tetraethylene glycol dimethyl ether. In some embodiments, the ether solvent comprises ethylene glycol dimethyl ether. In some embodiments, the ether solvent comprises ethylene glycol dimethyl ether. In some embodiments, the ether solvent comprises tetrahydrofuran.
  • the above-mentioned ether solvents have excellent anti-reduction properties, which can effectively reduce the side reactions between sodium metal and solvents, and further improve the high-temperature storage performance of the battery.
  • the ether solvent includes at least two of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, tetrahydrofuran, methyltetrahydrofuran and 1,3-dioxolane, and optionally includes at least two of ethylene glycol diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.
  • the ether solvent includes ethylene glycol dimethyl ether and diethylene glycol dimethyl ether. In some embodiments, the ether solvent includes ethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether. In some embodiments, the ether solvent includes ethylene glycol dibutyl ether and diethylene glycol dimethyl ether. In some embodiments, the ether solvent includes ethylene glycol dimethyl ether and tetrahydrofuran.
  • the ether solvents include at least two of the above-mentioned ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, tetrahydrofuran, methyltetrahydrofuran and 1,3-dioxolane, which is beneficial to further significantly improve the cycle performance and high temperature storage performance of the battery.
  • the electrolyte further includes a fluorinated ether compound, the fluorinated ether compound including 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl methyl ether (TME), 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (TFTFE), tris(trifluoroethoxy)methane (TFEO), methyl nonafluorobutyl ether (MFE), 1,1,1,3,3,3-hexafluoroisopropyl methyl ether (HFPM), 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether (OFE), and optionally include one or more of 1,1,2,2-tetrafluoroe
  • TTE
  • the fluoroether compound includes 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether. In some embodiments, the fluoroether compound includes bis(2,2,2-trifluoroethyl) ether. In some embodiments, the fluoroether compound includes tris(trifluoroethoxy)methane. In some embodiments, the fluoroether compound includes 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether. In some embodiments, the fluoroether compound includes 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether and bis(2,2,2-trifluoroethyl) ether.
  • the above-mentioned fluoroether compounds are inert fluoroether compounds, which are in the outermost layer of the sodium ion solvation structure. Moreover, the above-mentioned fluoroether compounds have low reactivity and are not easy to react with sodium metal, thereby improving the interface stability between the electrolyte and sodium metal, and improving the cycle performance and high-temperature storage performance of the battery.
  • the mass content of the fluoroether compound is 2% to 30%, optionally 5% to 20%.
  • the mass content of the fluoroether compound is 2%, 4%, 5%, 8%, 10%, 12%, 14%, 15%, 16%, 18%, 20%, 22%, 24%, 25%, 26%, 28%, 30%, or a value in the range formed by any two of the above points.
  • Controlling the mass content of the fluorinated ether compound within a suitable range is beneficial to improving the cycle performance and high temperature storage performance of the battery. Further controlling the mass content of the fluorinated ether compound to 5% to 20% is beneficial to further significantly improving the cycle performance and high temperature storage performance of the battery.
  • the sodium salt includes sodium hexafluorophosphate
  • the metal ion includes K +
  • the ether solvent includes ethylene glycol dimethyl ether
  • the fluoroether compound includes 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether.
  • the electrolyte containing sodium salt, metal ions, ether solvents and fluoroether compounds is beneficial to improving the cycle performance and high-temperature storage performance of the battery and improving the performance of the battery.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode current collector formed on at least a portion of the surface
  • the positive electrode active material layer comprises a positive electrode active material, and the positive electrode active material may comprise at least one of a layered transition metal oxide, a polyanionic compound and a Prussian blue compound.
  • the transition metal in the layered transition metal oxide may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • the layered transition metal oxide is, for example, NaxMO2 , wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 ⁇ x ⁇ 1.
  • the polyanionic compound may be a compound having metal ions, transition metal ions and tetrahedral (YO 4 ) n- anion units.
  • the metal ions may be selected from sodium ions, lithium ions, potassium ions and zinc ions;
  • the transition metal may be selected from at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce;
  • Y may be selected from at least one of P, S and Si; and n represents the valence state of (YO 4 ) n- .
  • the Prussian blue compound may be a compound having sodium ions, transition metal ions and cyanide ions (CN-).
  • the transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • the Prussian blue compound is, for example, Na a Me b Me' c (CN) 6 , wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 ⁇ a ⁇ 2, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1.
  • the positive electrode active material layer may further include a conductive agent to improve the conductivity of the positive electrode.
  • the conductive agent may be selected from one or more of Super P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene and carbon nanofibers.
  • the positive electrode active material layer may further include a binder to firmly bind the positive electrode active material and the optional conductive agent to the positive electrode current collector.
  • the binder may be selected from at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA) and carboxymethyl chitosan (CMCS).
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PAA polyacrylic acid
  • PVA polyvinyl alcohol
  • EVA ethylene-vinyl acetate copolymer
  • SBR styrene-butadiene rubber
  • CMC carboxymethyl cellulose
  • SA sodium al
  • the positive electrode current collector can be a conductive carbon sheet, metal foil, carbon-coated metal foil, porous metal plate or composite current collector.
  • the conductive carbon material of the conductive carbon sheet can be selected from one or more of Super P, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene and carbon nanofibers.
  • the metal material of the metal foil, carbon-coated metal foil and porous metal plate can be selected from one or more of Super P, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene and carbon nanofibers.
  • the composite current collector is independently selected from at least one of copper, aluminum, nickel and stainless steel, and can be a composite current collector formed by a composite of a metal foil and a polymer base film.
  • the positive electrode sheet can be prepared in the following manner: 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; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N-methylpyrrolidone
  • the negative electrode sheet may only include a negative electrode current collector without including a negative electrode active material.
  • the negative electrode sheet may also be formed by pre-depositing a metal phase on the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • 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 (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode plate includes a negative electrode current collector and a primer layer disposed on at least one surface of the negative electrode current collector, and the primer layer includes one or more of carbon nanotubes, graphite, graphene, carbon black, aluminum oxide, silver composite carbon nanoparticles, and tin composite carbon nanoparticles.
  • carbon nanotube refers to a seamless hollow cylinder formed by rolling up a single or multiple layers of graphene, with a tube diameter of less than 100nm and a tube length of more than 100nm.
  • carbon nanotubes include but are not limited to single-walled carbon nanotubes and/or multi-walled carbon nanotubes.
  • the above-mentioned base coating layer not only has excellent conductivity, but also facilitates the uniform deposition of metal ions on the surface of the current collector, thereby improving the cycle performance and safety of the battery.
  • the surface density of the primer layer is 0.5 g/m 2 to 35 g/m 2 .
  • the surface density of the primer layer may be 0.5 g/ m2 , 1 g/ m2 , 5 g/ m2 , 10 g/ m2 , 15 g/ m2 , 20 g/ m2 , 25 g/ m2 , 30 g/ m2 , 35 g/ m2 , or a value in a range consisting of any two of the above.
  • the undercoat layer with an area density of 5 g/m 2 to 50 g/m 2 is conducive to the uniform distribution of nucleation sites and promotes the uniform deposition of metals, while not affecting the transmission behavior of electrons.
  • the thickness of the primer layer is 0.2 ⁇ m to 50 ⁇ m.
  • the thickness of the primer layer may be 0.2 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 2 ⁇ m, 5 ⁇ m, 10 ⁇ m, 15 ⁇ m, 20 ⁇ m, 25 ⁇ m, 30 ⁇ m, 35 ⁇ m, 40 ⁇ m, 45 ⁇ m, 50 ⁇ m, or a value in a range consisting of any two of the above points.
  • Controlling the thickness of the base coating to be 2 ⁇ m to 100 ⁇ m can provide enough nucleation sites to facilitate uniform deposition of metal ions and inhibit dendrites.
  • 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 polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fiber.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.
  • 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, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging 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.
  • a secondary battery includes an electrolyte in some embodiments.
  • FIG. 1 is a square-structured battery cell 5 as an example
  • FIG. 2 is an exploded view of the battery cell 5 .
  • the secondary battery further includes a positive electrode sheet, a negative electrode sheet, and a separator.
  • the secondary battery includes at least one of a lithium battery and a sodium battery.
  • the secondary battery includes at least one of a potassium battery, a magnesium battery, and a zinc battery.
  • the secondary battery is a negative electrode-free sodium battery.
  • a negative electrode-free sodium secondary battery refers to a battery that does not actively set a negative electrode active material layer on the negative electrode side during the manufacturing process of the battery.
  • a sodium metal or carbonaceous active material layer is not set at the negative electrode through coating or deposition to form a negative electrode active material layer during the manufacturing process of the battery.
  • the sodium ions obtain electrons on the anode side and metallic sodium is deposited on the surface of the current collector to form a sodium metal phase.
  • the metallic sodium can be converted into sodium ions and return to the positive electrode to achieve cyclic charge and discharge.
  • negative electrode-free sodium secondary batteries can achieve higher energy density due to the lack of a negative electrode active material layer.
  • the negative electrode side of the negative electrode-free sodium secondary battery may be provided with some conventional substances that can be used as negative electrode active materials, such as carbonaceous materials, metal oxides, alloys, etc. Although these materials have a certain capacity, due to the small amount of these materials, they are not used as the main negative electrode active materials in the battery, and therefore are not considered to form a negative electrode active material layer that plays a role in sodium insertion, and the sodium secondary battery thus constructed can still be considered as a negative electrode-free sodium secondary battery.
  • some conventional substances that can be used as negative electrode active materials such as carbonaceous materials, metal oxides, alloys, etc.
  • the CB value of the negative electrode-free sodium secondary battery is less than or equal to 0.1.
  • the CB value is the unit area capacity of the negative electrode plate in the secondary battery divided by the unit area capacity of the positive electrode plate. Since the negative electrode-free battery contains no or only a small amount of negative electrode active material, the unit area capacity of the negative electrode plate is small, and the CB value of the secondary battery is less than or equal to 0.1.
  • 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 are enclosed to form 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 be formed into an electrode assembly 52 by a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • Secondary electrode The number of electrode assemblies 52 contained in the cell 5 can be one or more, and those skilled in the art can select one according to specific practical needs.
  • secondary batteries may be assembled into a battery module.
  • the number of secondary batteries contained in the battery module 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.
  • FIG3 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, 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 receiving space, and the plurality of secondary batteries 5 are received in the receiving space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • FIG4 and FIG5 are battery packs 1 as an example.
  • 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, and the upper box body 2 can be covered on the lower box body 3 to 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.
  • an electric device comprising at least one of a secondary battery of any embodiment, a battery module of any embodiment, or a battery pack of any embodiment.
  • the electrical device includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device.
  • the electrical device 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, a battery module or a battery pack can be selected according to its usage requirements.
  • Fig. 6 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • the device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • a device is usually required to be light and thin, and a secondary battery may be used as a power source.
  • 10wt% polyvinylidene fluoride binder was fully dissolved in N-methylpyrrolidone, and then 10wt% carbon black conductive agent and 80wt% Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 positive electrode active material were added and stirred and mixed evenly to obtain positive electrode slurry.
  • the slurry was evenly coated on the surface of the current collector aluminum foil to prepare a positive electrode film layer, and then transferred to a vacuum drying oven for complete drying.
  • the dried pole piece was rolled and punched to obtain a positive electrode piece.
  • Polypropylene film is used as the isolation film.
  • the positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, the separator is placed between the positive and negative electrode sheets to play an isolating role, the bare cell is welded with a pole ear, and the bare cell is placed in an aluminum shell, and baked at 80°C to remove water, and then the above-mentioned electrolyte is injected and sealed to obtain an uncharged battery.
  • the uncharged battery is then subjected to the processes of static, hot and cold pressing, formation, shaping, and capacity testing in sequence to obtain the negative electrode-free sodium secondary battery product of Example 1.
  • Examples 2 to 3 are basically similar to those in Example 1, but the types of ether solvents or metal ions are adjusted. The specific parameters are shown in Table 1.
  • the battery preparation method in Example 4 is basically similar to that in Example 1, but a fluoroether compound is introduced into the electrolyte.
  • the preparation method of the electrolyte is specifically as follows:
  • sodium hexafluorophosphate sodium salt and potassium hexafluorophosphate containing metal ions potassium ions were added and dissolved in the mixed solvent, stirred uniformly, and the concentration of sodium hexafluorophosphate sodium salt was controlled to be 1 mol/L and the concentration of potassium ions was controlled to be 0.03 mol/L to prepare an electrolyte.
  • the battery preparation methods in Examples 5 to 31 are basically similar to those in Example 4, but the concentration of metal ions, the type of metal ions, the type of ether solvents, the type of fluoroether compounds, the concentration of fluoroether compounds, the type of sodium salts, and the concentration of sodium salts are adjusted.
  • the specific parameters are shown in Table 1.
  • Comparative Example 1 The battery preparation method in Comparative Example 1 is basically similar to that in Example 1, but there are no metal ions in the electrolyte. The specific parameters are shown in Table 1.
  • Comparative Example 2 The battery preparation method in Comparative Example 2 is basically similar to that in Comparative Example 1, but a fluoroether compound is added to the electrolyte.
  • the specific parameters are shown in Table 1.
  • Comparative Example 3 The battery preparation method in Comparative Example 3 is basically similar to that in Comparative Example 2, but the type of the electrolyte ether solvent is adjusted. The specific parameters are shown in Table 1.
  • the battery preparation method in Comparative Example 4 is basically similar to that in Example 1, but the metal ions are adjusted to magnesium ions (the ionic radius of Mg 2+ is 0.066nm, and the reduced state of Mg 2+ is used as an electrode, and its standard electrode potential is -2.375V).
  • the specific parameters are shown in Table 1.
  • the prepared battery was charged to 3.7V at a constant current of 0.2C, then charged at a constant voltage of 3.7V until the current dropped to 0.05C, and then discharged to 2.5V at a constant current of 0.2C to obtain the discharge capacity before storage (Cd1); then the battery was charged to 3.7V at a constant current of 0.2C again, and then charged at a constant voltage of 3.7V until the current dropped to 0.05C.
  • the battery was then stored in a 60°C constant temperature box for 30 days, and after being taken out, the battery was placed at 25°C and charged to 3.7V at a constant current of 0.2C, then charged at a constant voltage of 3.7V until the current dropped to 0.05C, and then discharged to 2.5V at a constant current of 0.2C to obtain the discharge capacity after storage (Cd2), and the battery capacity retention rate after storage at 60°C for 30 days was calculated according to the following formula:
  • Storage capacity retention rate discharge capacity after storage (Cd2)/discharge capacity before storage (Cd1).
  • the cycle performance test process is as follows: at 25°C, the prepared battery was left to stand for 30 minutes, then discharged at a constant current of 0.33C to 3.65V, then charged at a constant voltage of 3.65V until the current dropped to 0.05C, and after standing for 1 hour, discharged at a constant current of 0.33C to 2.5V to obtain the initial capacity (C0); after standing for 1 hour, charged at a constant current of 0.33C to 3.65V, and then Then charge at 3.65V constant voltage until the current drops to 0.05C, stand for 1h, and then discharge at 0.33C constant current to 2.5V to obtain process capacity (C1).
  • Cn process capacity of the battery after the 100th cycle.
  • the capacity retention rate after 100 cycles Cn/C1 ⁇ 100%.
  • the test process of the comparative example and other embodiments is the same as above.
  • the battery after the above cycle of n cycles was disassembled in an argon atmosphere glove box ( H2O ⁇ 0.1ppm, O2 ⁇ 0.1ppm), and the surface morphology of the negative electrode was visually observed to determine whether sodium dendrites were generated.
  • the negative electrode sheet without white spots was judged as no sodium dendrites
  • the negative electrode sheet with sporadic white spots was judged as slight sodium dendrites
  • the negative electrode sheet with dense white spots was judged as severe sodium dendrites.
  • the test process of the comparative example and other embodiments is the same as above.
  • the batteries of the embodiments and comparative examples were prepared according to the above method, and various performance parameters were measured. The results are shown in Tables 1 and 2 below.
  • the electrolytes in Examples 1 to 31 include sodium salt and metal ions whose ion radius is larger than that of sodium ions.
  • the electrolyte includes metal ions having an ion radius larger than that of sodium ions, which effectively inhibits the formation of sodium dendrites, and is beneficial to improving the battery's cycle capacity retention rate and the capacity retention rate after storage at 60°C for 30 days, thereby improving the battery's performance.
  • the electrolyte in the present application includes potassium hexafluorophosphate, calcium hexafluorophosphate, calcium nitrate or strontium nitrate, which effectively inhibits the formation of sodium dendrites, and is beneficial to improve the battery's cycle capacity retention rate and the capacity retention rate after storage at 60°C for 30 days, thereby improving the battery's performance.
  • the concentration of sodium salt in the electrolyte is controlled to be 0.1 mol/L to 1.8 mol/L, so that the battery has excellent cycle capacity retention and capacity retention after 30 days of storage at 60°C, and effectively inhibits sodium dendrites.
  • further controlling the concentration of sodium salt in the electrolyte to be 0.5 mol/L to 1.5 mol/L is conducive to further significantly improving the cycle capacity retention and capacity retention after 30 days of storage at 60°C of the battery.
  • the electrolyte includes one of potassium hexafluorophosphate, calcium hexafluorophosphate, calcium nitrate, and strontium nitrate, and the batteries thereof have excellent cycle capacity retention and capacity retention after storage at 60°C for 30 days, and effectively inhibit sodium dendrites.
  • controlling the ether solvent in the electrolyte to be selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether or diethylene glycol dimethyl ether is beneficial to improving the battery's cycle capacity retention rate and the capacity retention rate after storage at 60°C for 30 days, as well as inhibiting the sodium dendrite phenomenon of the battery.
  • controlling the ether solvent in the electrolyte to be selected from at least two of ethylene glycol dimethyl ether, ethylene glycol diethyl ether and diethylene glycol dimethyl ether is beneficial to further significantly improve the battery's cycle capacity retention rate and the capacity retention rate after storage at 60°C for 30 days.
  • the sodium salt includes one of sodium hexafluorophosphate, sodium perchlorate and sodium bis(fluorosulfonyl)imide, and the batteries thereof have excellent cycle capacity retention and capacity retention after storage at 60°C for 30 days, and effectively inhibit sodium dendrites.
  • metal ions including Ca 2+ metal ions including K + are beneficial to further improve the cycle capacity retention and capacity retention after storage at 60°C for 30 days of the battery.
  • the sodium salt includes one of 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, and 1,1,2,2-tetrafluoroethyl methyl ether, and the batteries thereof have excellent cycle capacity retention rate and capacity retention rate after storage at 60°C for 30 days, and effectively inhibit sodium dendrites.

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Abstract

本申请提供了一种电解液、二次电池和用电装置。该电解液包括钠盐和离子半径大于钠离子的金属离子。该电解液能够有效地抑制钠枝晶，有利于提升电池的循环性能和高温存储性能。

Description

电解液、二次电池和用电装置 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、二次电池和用电装置。
背景技术
近年来，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。
电解液的性能对二次电池的性能有关键性影响。目前，电解液存在诸多缺陷，无法满足新一代电化学体系的应用需要。
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，该电解液能够有效地抑制钠枝晶，有利于提升电池的循环性能和高温存储性能。
本申请的第一方面，提供了一种用于钠二次电池的电解液，所述电解液包括钠盐和离子半径大于钠离子的金属离子。
金属离子的离子半径大于钠离子的离子半径，一方面，可以对钠离子形成空间位阻效应，避免钠枝晶的生长。另一方面，金属离子能够形成电荷屏蔽作用，改善钠离子沉积的电流密度，促使钠离子均匀沉积，且与空间位阻效应形成协同作用，抑制钠枝晶的生长，避免电池内部短路，提升电池的循环性能和高温存储性能。
在任意实施方式中，所述金属离子包括K+、Ca2+、Sr2+、Ba2+中的一种或多种，可选地包括K+。
上述金属离子均满足其离子半径大于钠离子的离子半径，可有效地抑制钠枝晶的生长，提升电池的循环性能和高温存储性能。并 且，以上述金属离子还原态作为电极，其标准电极电势低于钠的标准电极电势，使得在电池的充电过程中，金属离子不被还原成金属原子进行沉积，避免或减少对钠离子沉积的影响。
在任意实施方式中，所述电解液包括PF6 -、NO3 -、ClO3 -中的一种或多种。
在任意实施方式中，所述电解液包括六氟磷酸钾、六氟磷酸钙、六氟磷酸锶、六氟磷酸钡、硝酸钾、硝酸钙、硝酸锶、硝酸钡、高氯酸钾、高氯酸钙、高氯酸锶、高氯酸钡中的一种或多种，可选地包括六氟磷酸钾、硝酸钾、六氟磷酸钙中的一种或多种。
上述物质不仅具有位阻效应和电荷屏蔽作用，还能与电解液中的钠盐兼容，避免或减少上述物质的加入所带来的负面影响。
在任意实施方式中，所述金属离子在所述电解液中的浓度为0.005mol/L～0.3mol/L，可选为0.01mol/L～0.1mol/L。
控制金属离子在电解液中具有合适的浓度，既能避免或较少金属离子浓度过小导致其无法充分发挥作用，又能避免或减少金属离子浓度过大影响钠离子的沉积，导致电池极化增大，不利于电池性能的改进。合适浓度的金属离子有利于钠离子的均匀沉积。进一步控制金属离子在电解液中的浓度为0.01mol/L～0.1mol/L，有利于进一步大幅提升电池的高温存储性能。
在任意实施方式中，所述钠盐包括氯化钠、溴化钠、硝酸钠、高氯酸钠、六氟磷酸钠、乙酸钠、三氟乙酸钠、三氟甲基磺酸钠、双(氟磺酰)亚胺钠、双(三氟甲基磺酰)亚胺钠、四氟硼酸钠、四苯硼酸钠中的一种或多种，可选地包含六氟磷酸钠、高氯酸钠、双(氟磺酰)亚胺钠、双(三氟甲基磺酰)亚胺钠、四氟硼酸钠中的一种或多种。
包括上述钠盐的电解液均具有优异的电池循环性能和高温存储性能。
在任意实施方式中，所述钠盐在所述电解液中的浓度为0.1mol/L～1.8mol/L，可选为0.5mol/L～1.5mol/L。
控制钠盐在电解液中具有合适的浓度，一方面，避免或减少钠盐浓度过低导致电解液中解离的钠离子浓度过低，从而造成钠离子的 传导率下降；另一方面，避免或减少钠盐浓度过高导致电解液粘度的升高，进而导致钠离子传导速率的下降。合适浓度的钠盐有利于钠离子传导率的提升。进一步控制钠盐在电解液中的浓度为0.5mol/L～1.5mol/L，有利于进一步大幅提升电池的循环性能和高温存储性能。
在任意实施方式中，所述电解液还包括醚类溶剂，所述醚类溶剂包括乙二醇二甲醚、二乙二醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、聚乙二醇二甲醚、乙醚、乙二醇二乙醚、乙二醇二丁醚、二乙二醇二乙醚、二乙二醇二丁醚、四氢呋喃、甲基四氢呋喃和1,3-二氧五环中的一种或多种，可选地包括乙二醇二乙醚、乙二醇二甲醚、乙二醇二乙醚、二乙二醇二甲醚、四乙二醇二甲醚、二乙二醇二丁醚中的一种或多种。
上述醚类溶剂具有优异的抗还原性能，可以有效地减少钠金属与溶剂发生副反应，进一步提升电池的高温存储性能。
在任意实施方式中，所述醚类溶剂包括乙二醇二甲醚、二乙二醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、聚乙二醇二甲醚、乙二醇二乙醚、乙二醇二丁醚、四氢呋喃、甲基四氢呋喃和1,3-二氧五环中的至少两种，可选地包括乙二醇二乙醚、乙二醇二甲醚、二乙二醇二甲醚、三乙二醇二甲醚和四乙二醇二甲醚中的至少两种。
醚类溶剂包括上述乙二醇二甲醚、二乙二醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、聚乙二醇二甲醚、乙二醇二乙醚、乙二醇二丁醚、四氢呋喃、甲基四氢呋喃和1,3-二氧五环中的至少两种，有利于进一步大幅提升电池的循环性能和高温存储性能。
在任意实施方式中，所述电解液还包括氟醚化合物，所述氟醚化合物包括1,1,2,2-四氟乙基2,2,3,3-四氟丙醚(TTE)、双(2,2,2-三氟乙基)醚、1,1,2,2-四氟乙基甲基醚(TME)、1,1,2,2-四氟乙基-2,2,2-三氟乙基醚(TFTFE)、三(三氟乙氧基)甲烷(TFEO)、甲基九氟丁醚(MFE)、1,1,1,3,3,3-六氟异丙基甲基醚(HFPM)、1H,1H,5H-八氟戊基-1,1,2,2-四氟乙醚(OFE)中的一种或多种，可选地包括1,1,2,2-四氟乙基2,2,3,3-四氟丙醚、双(2,2,2-三氟乙基)醚中 的一种或多种。
上述氟醚化合物属于惰性氟醚化合物，在钠离子溶剂化结构的最外层，且上述氟醚化合物具有较低的反应活性，不易与钠金属进行反应，进而提升电解液与钠金属的界面稳定性，提升电池的循环性能和高温存储性能。
在任意实施方式中，基于所述醚类溶剂和所述氟醚化合物的总质量计，所述氟醚化合物的质量含量为2％～30％，可选为5％～20％。
控制氟醚化合物的质量含量在合适的范围内，有利于提升电池的循环性能和高温存储性能。进一步控制氟醚化合物的质量含量为5％～20％，有利于进一步大幅提升电池的循环性能和高温存储性能。
在任意实施方式中，所述钠盐包括六氟磷酸钠，所述金属离子包括K+，所述醚类溶剂包括乙二醇二甲醚，所述氟醚化合物包括1,1,2,2-四氟乙基2,2,3,3-四氟丙醚。
上述包含钠盐、金属离子、醚类溶剂和氟醚化合物的电解液，有利于提高电池的循环性能和高温存储性能，改善电池的性能。
本申请的第二方面提供一种二次电池，包括第一方面的电解液。
在任意实施方式中，所述二次电池是无负极钠二次电池。
无负极钠二次电池具有高能量密度。
在任意实施方式中，所述二次电池还包括负极极片，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面的底涂层，所述底涂层包括碳纳米管、石墨、石墨烯、银复合碳纳米颗粒、锡复合碳纳米颗粒中的一种或多种。
上述底涂层不仅具有优异的导电性，还有利于金属离子在集流体表面的均匀沉积，提升电池的库伦效率和循环性能。
在任意实施方式中，所述底涂层的面密度为0.5g/m2～35g/m2。
面密度为0.5g/m2～35g/m2的底涂层有利于无负极二次电池中成核位点的均匀分布，促进金属的均匀沉积，同时也不影响电子的传输行为。
在任意实施方式中，所述底涂层的厚度为0.2μm～50μm。
控制底涂层的厚度为0.2μm～50μm，可以为无负极二次电池提 供足够多的成核位点有利于金属离子的均匀沉积，抑制枝晶。
本申请的第三方面提供一种用电装置，包括本申请第二方面的二次电池。
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。
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)。
电池中枝晶的生长不仅容易引起安全隐患，也会严重影响电池的性能。以钠电池为例，通常，电流分布不均匀会导致钠枝晶的生 长，电解液不具有机械强度，无法阻挡钠枝晶的生长。因此，我们需要设计一种新的电解液，以满足新一代电化学的需求。
[电解液]
基于此，本申请提出了一种用于钠二次电池的电解液，电解液包括钠盐和离子半径大于钠离子的金属离子。
在本文中，术语“钠盐”是指由钠离子和阴离子组成、在室温或室温附近温度条件下呈现液态的盐。室温是指25℃±5℃。包括但不限于高氯酸钠、六氟磷酸钠、乙酸钠、三氟乙酸钠、三氟甲基磺酸钠中的一种或多种。
在本文中，术语“离子半径”是指核到最外层电子的平均距离。离子半径一般随原子序数的递增而增大。
金属离子的离子半径大于钠离子的离子半径，一方面，可以对钠离子形成空间位阻效应，避免钠枝晶的生长。另一方面，金属离子能够形成电荷屏蔽作用，改善钠离子沉积的电流密度，促使钠离子均匀沉积，且与空间位阻效应形成协同作用，抑制钠枝晶的生长，避免电池内部短路，提升电池的循环性能和高温存储性能。
在一些实施方式中，金属离子包括K+、Ca2+、Sr2+、Ba2+中的一种或多种，可选地包括K+。
在本文中，Na+的离子半径为0.097nm，K+的离子半径为0.133nm，Ca2+的离子半径为0.099nm，Sr2+的离子半径为0.112nm，Ba2+的离子半径为0.134nm。
在本文中，Na+的还原态作为电极，其标准电极电势为-2.711V；钾离子的还原态作为电极，其标准电极电势为-2.923V；钙离子的还原态作为电极，其标准电极电势为-2.76V；Sr2+的还原态作为电极，其标准电极电势为-2.89V；Ba2+的还原态作为电极，其标准电极电势为-2.90V。
在本文中，术语“金属离子还原态”是指金属离子被还原得到金属原子。
在本文中，术语“标准电极电势”是指该电极的标准电势，即参与电极反应的所有物质都处于活度为1标准状态时的电极电势。
在一些实施方式中，金属离子包括K+。在一些实施方式中，金属离子包括Ca2+。在一些实施方式中，金属离子包括Ba2+。在一些实施方式中，金属离子包括Sr2+。
上述金属离子均满足其离子半径大于钠离子的离子半径，可有效地抑制钠枝晶的生长，提升电池的循环性能和高温存储性能。并且，以上述金属离子还原态作为电极，其标准电极电势低于钠的标准电极电势，使得在电池的充电过程中，金属离子不被还原成金属原子进行沉积，避免或减少对钠离子沉积的影响。
在一些实施方式中，电解液包括PF6 -、NO3 -、ClO3 -中的一种或多种。
在一些实施方式中，电解液包括PF6 -。在一些实施方式中，电解液包括NO3 -。在一些实施方式中，电解液包括ClO3 -。
在一些实施方式中，电解液包括六氟磷酸钾、六氟磷酸钙、六氟磷酸锶、六氟磷酸钡、硝酸钾、硝酸钙、硝酸锶、硝酸钡、高氯酸钾、高氯酸钙、高氯酸锶、高氯酸钡中的一种或多种，可选地包括六氟磷酸钾、硝酸钾、六氟磷酸钙中的一种或多种。
在一些实施方式中，电解液包括六氟磷酸钾。在一些实施方式中，电解液包括硝酸钙。在一些实施方式中，电解液包括高氯酸锶。在一些实施方式中，电解液包括六氟磷酸钾和硝酸钙。在一些实施方式中，电解液包括六氟磷酸钾和六氟磷酸钙。
上述物质不仅具有位阻效应和电荷屏蔽作用，还能与电解液中的钠盐兼容，避免或减少上述物质的加入所带来的负面影响。
在一些实施方式中，金属离子在电解液中的浓度为0.005mol/L～0.3mol/L，可选为0.01mol/L～0.1mol/L。
在一些实施方式中，金属离子在电解液中的浓度可选为0.005mol/L、0.01mol/L、0.05mol/L、0.1mol/L、0.12mol/L、0.15mol/L、0.18mol/L、0.2mol/L、0.22mol/L、0.25mol/L、0.27mol/L、0.3mol/L、或由上述任意两点构成的范围中的数值。
控制金属离子在电解液中具有合适的浓度，既能避免或较少金属离子浓度过小导致其无法充分发挥作用，又能避免或减少金属离 子浓度过大影响钠离子的沉积，导致电池极化增大，不利于电池性能的改进。合适浓度的金属离子有利于钠离子的均匀沉积。进一步控制金属离子在电解液中的浓度为0.01mol/L～0.1mol/L，有利于进一步大幅提升电池的高温存储性能。
在一些实施方式中，钠盐包括氯化钠、溴化钠、硝酸钠、高氯酸钠、六氟磷酸钠、乙酸钠、三氟乙酸钠、三氟甲基磺酸钠、双(氟磺酰)亚胺钠、双(三氟甲基磺酰)亚胺钠、四氟硼酸钠、四苯硼酸钠中的一种或多种，可选地包含六氟磷酸钠、高氯酸钠、双(氟磺酰)亚胺钠、双(三氟甲基磺酰)亚胺钠、四氟硼酸钠中的一种或多种。
在一些实施方式中，钠盐包括氯化钠。在一些实施方式中，钠盐包括四氟硼酸钠。在一些实施方式中，钠盐包括三氟乙酸钠。在一些实施方式中，钠盐包括氯化钠。在一些实施方式中，钠盐包括四氟硼酸钠。
包括上述钠盐的电解液均具有优异的电池循环性能和高温存储性能。
在一些实施方式中，钠盐在电解液中的浓度为0.1mol/L～1.8mol/L，可选为0.5mol/L～1.5mol/L。
在一些实施方式中，钠盐在电解液中的浓度为0.1mol/L、0.2mol/L、0.4mol/L、0.5mol/L、0.6mol/L、0.8mol/L、1.0mol/L、1.2mol/L、1.4mol/L、1.5mol/L、1.6mol/L、1.8mol/L、或由上述任意两点构成的范围中的数值。
控制钠盐在电解液中具有合适的浓度，一方面，避免或减少钠盐浓度过低导致电解液中解离的钠离子浓度过低，从而造成钠离子的传导率下降；另一方面，避免或减少钠盐浓度过高导致电解液粘度的升高，进而导致钠离子传导速率的下降。合适浓度的钠盐有利于钠离子传导率的提升。进一步控制钠盐在电解液中的浓度为0.5mol/L～1.5mol/L，有利于进一步大幅提升电池的循环性能和高温存储性能。
在一些实施方式中，电解液还包括醚类溶剂，醚类溶剂包括乙二醇二甲醚、二乙二醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、 聚乙二醇二甲醚、乙醚、乙二醇二乙醚、乙二醇二丁醚、二乙二醇二乙醚、二乙二醇二丁醚、四氢呋喃、甲基四氢呋喃和1,3-二氧五环中的一种或多种，可选地包括乙二醇二乙醚、乙二醇二甲醚、乙二醇二乙醚、二乙二醇二甲醚、四乙二醇二甲醚、二乙二醇二丁醚中的一种或多种。
在一些实施方式中，醚类溶剂包括乙二醇二乙醚。在一些实施方式中，醚类溶剂包括二乙二醇二甲醚。在一些实施方式中，醚类溶剂包括四乙二醇二甲醚。在一些实施方式中，醚类溶剂包括乙二醇二甲醚。在一些实施方式中，醚类溶剂包括乙二醇二甲醚。在一些实施方式中，醚类溶剂包括四氢呋喃。
上述醚类溶剂具有优异的抗还原性能，可以有效地减少钠金属与溶剂发生副反应，进一步提升电池的高温存储性能。
在一些实施方式中，醚类溶剂包括乙二醇二甲醚、二乙二醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、聚乙二醇二甲醚、乙二醇二乙醚、乙二醇二丁醚、四氢呋喃、甲基四氢呋喃和1,3-二氧五环中的至少两种，可选地包括乙二醇二乙醚、乙二醇二甲醚、二乙二醇二甲醚、三乙二醇二甲醚和四乙二醇二甲醚中的至少两种。
在一些实施方式中，醚类溶剂包括乙二醇二甲醚和二乙二醇二甲醚。在一些实施方式中，醚类溶剂包括乙二醇二甲醚和四乙二醇二甲醚。在一些实施方式中，醚类溶剂包括乙二醇二丁醚和二乙二醇二甲醚。在一些实施方式中，醚类溶剂包括乙二醇二甲醚和四氢呋喃。
醚类溶剂包括上述乙二醇二甲醚、二乙二醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、聚乙二醇二甲醚、乙二醇二乙醚、乙二醇二丁醚、四氢呋喃、甲基四氢呋喃和1,3-二氧五环中的至少两种，有利于进一步大幅提升电池的循环性能和高温存储性能。
在一些实施方式中，电解液还包括氟醚化合物，氟醚化合物包括1,1,2,2-四氟乙基2,2,3,3-四氟丙醚(TTE)、双(2,2,2-三氟乙基)醚、1,1,2,2-四氟乙基甲基醚(TME)、1,1,2,2-四氟乙基-2,2,2-三氟乙基醚(TFTFE)、三(三氟乙氧基)甲烷(TFEO)、甲基九氟丁醚 (MFE)、1,1,1,3,3,3-六氟异丙基甲基醚(HFPM)、1H,1H,5H-八氟戊基-1,1,2,2-四氟乙醚(OFE)中的一种或多种，可选地包括1,1,2,2-四氟乙基2,2,3,3-四氟丙醚、双(2,2,2-三氟乙基)醚中的一种或多种。
在一些实施方式中，氟醚化合物包括1,1,2,2-四氟乙基2,2,3,3-四氟丙醚。在一些实施方式中，氟醚化合物包括双(2,2,2-三氟乙基)醚。在一些实施方式中，氟醚化合物包括三(三氟乙氧基)甲烷。在一些实施方式中，氟醚化合物包括1H,1H,5H-八氟戊基-1,1,2,2-四氟乙醚。在一些实施方式中，氟醚化合物包括1,1,2,2-四氟乙基2,2,3,3-四氟丙醚和双(2,2,2-三氟乙基)醚。
上述氟醚化合物属于惰性氟醚化合物，在钠离子溶剂化结构的最外层，且上述氟醚化合物具有较低的反应活性，不易与钠金属进行反应，进而提升电解液与钠金属的界面稳定性，提升电池的循环性能和高温存储性能。
在一些实施方式中，基于醚类溶剂和氟醚化合物的总质量计，氟醚化合物的质量含量为2％～30％，可选为5％～20％。
在一些实施方式中，基于醚类溶剂和氟醚化合物的总质量计，氟醚化合物的质量含量为2％、4％、5％、8％、10％、12％、14％、15％、16％、18％、20％、22％、24％、25％、26％、28％、30％、或由上述任意两点构成的范围中的数值。
控制氟醚化合物的质量含量在合适的范围内，有利于提升电池的循环性能和高温存储性能。进一步控制氟醚化合物的质量含量为5％～20％，有利于进一步大幅提升电池的循环性能和高温存储性能。
在一些实施方式中，钠盐包括六氟磷酸钠，金属离子包括K+，醚类溶剂包括乙二醇二甲醚，氟醚化合物包括1,1,2,2-四氟乙基2,2,3,3-四氟丙醚。
上述包含钠盐、金属离子、醚类溶剂和氟醚化合物的电解液，有利于提高电池的循环性能和高温存储性能，改善电池的性能。
[正极极片]
正极极片包括正极集流体及形成于正极集流体的至少部分表面 上的正极活性物质层，正极活性物质层包括正极活性物质，正极活性物质可以包括层状过渡金属氧化物、聚阴离子型化合物和普鲁士蓝类化合物中的至少一种。
层状过渡金属氧化物中的过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种。可选的，层状过渡金属氧化物例如为NaxMO2，其中M为Ti、V、Mn、Co、Ni、Fe、Cr及Cu中的一种或几种，0＜x≤1。
聚阴离子型化合物可以是具有金属离子、过渡金属离子及四面体型(YO4)n-阴离子单元的一类化合物。金属离子可选为钠离子、锂离子、钾离子、锌离子的一种；过渡金属可选为Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种；Y可选为P、S及Si中的至少一种；n表示(YO4)n-的价态。
普鲁士蓝类化合物可以是具有钠离子、过渡金属离子及氰根离子(CN-)的一类化合物。过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种。普鲁士蓝类化合物例如为NaaMebMe’c(CN)6，其中Me及Me’各自独立地为Ni、Cu、Fe、Mn、Co及Zn中的至少一种，0＜a≤2，0＜b＜1，0＜c＜1。
正极活性物质层还可以包括导电剂，以改善正极的导电性能。导电剂可选为Super P、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨、石墨烯及碳纳米纤维中的一种或几种。
正极活性物质层还可以包括粘结剂，以将正极活性物质和可选的导电剂牢固地粘结在正极集流体上。粘结剂可选为聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚丙烯酸(PAA)、聚乙烯醇(PVA)、乙烯-醋酸乙烯酯共聚物(EVA)、丁苯橡胶(SBR)、羧甲基纤维素(CMC)、海藻酸钠(SA)、聚甲基丙烯酸(PMA)及羧甲基壳聚糖(CMCS)中的至少一种。
正极集流体可以采用导电碳片、金属箔材、涂炭金属箔材、多孔金属板或复合集流体。导电碳片的导电碳材质可选为Super P、炭黑、科琴黑、碳点、碳纳米管、石墨、石墨烯及碳纳米纤维中的一种或几种，金属箔材、涂炭金属箔材和多孔金属板的金属材质各自 独立地选自铜、铝、镍及不锈钢中的至少一种，复合集流体可以为金属箔材与高分子基膜复合形成的复合集流体。
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；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片可以仅包括负极集流体，不包含负极活性材料。负极极片也可以在负极集流体上预沉积金属相。
在一些实施方式中，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，可以采用铝箔或铜箔。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(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，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底涂层，底涂层包括碳纳米管、石墨、石墨烯、炭黑、氧化铝、银复合碳纳米颗粒、锡复合碳纳米颗粒中的一种或多种。
在本文中，术语“碳纳米管”是指单层或多层石墨烯卷起来形成的无缝空心圆柱体，管径低于100nm，管长超过100nm。作为示例，碳纳米管包括但不限于单壁碳纳米管和/或多壁碳纳米管。
上述底涂层不仅具有优异的导电性，还有利于金属离子在集流体表面的均匀沉积，提升电池的循环性能和安全性。
在一些实施方式中，底涂层的面密度为0.5g/m2～35g/m2。
在一些实施方式中，底涂层的面密度可选为0.5g/m2、1g/m2、5g/m2、10g/m2、15g/m2、20g/m2、25g/m2、30g/m2、35g/m2、或由上述任意两点构成的范围中的数值。
面密度为5g/m2～50g/m2的底涂层有利于成核位点的均匀分布，促进金属的均匀沉积，同时也不影响电子的传输行为。
在一些实施方式中，底涂层的厚度为0.2μm～50μm。
在一些实施方式中，底涂层的厚度可选为0.2μm、0.5μm、1μm、2μm、5μm、10μm、15μm、20μm、25μm、30μm、35μm、40μm、45μm、50μm、或由上述任意两点构成的范围中的数值。
控制底涂层的厚度为2μm～100μm，可以提供足够多的成核位点有利于金属离子的均匀沉积，抑制枝晶。
[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聚乙烯、聚丙烯、聚偏氟乙烯、芳纶、聚对苯二甲酸乙二醇酯、聚四氟乙烯、聚丙烯腈、聚酰亚胺，聚酰胺、聚酯和天然纤维中的至少一种。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，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。
[二次电池]
二次电池，包括一些实施方式中的电解液。
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电池单体5，图2是电池单体5的分解图。
在一些实施方式中，二次电池还包括正极极片、负极极片和隔离膜。
在一些实施方式中，二次电池包括锂电池、钠电池中的至少一种。
在一些实施方式中，二次电池包括钾电池、镁电池、锌电池中的至少一种。
在一些实施方式中，二次电池为无负极钠电池。
无负极钠二次电池是指在电池的制造过程中，在负极侧不主动设置负极活性材料层而构成的电池，例如在电池的制造过程中不在负极处通过涂敷或沉积等工序设置钠金属或碳质活性材料层而形成负极活性材料层。首次充电时，钠离子在阳极侧得到电子以金属钠在集流体表面沉积形成钠金属相，放电时，金属钠能够转变为钠离子回到正极，实现循环充放。相比于其他钠二次电池，无负极钠二次电池由于没有负极活性材料层，可以获得更高的能量密度。
在一些实施方式中，为了改善电池性能，无负极钠二次电池的负极侧可以设置一些常规可作为负极活性材料的物质，如碳质材料、金属氧化物、合金等。虽然这些材料具有一定容量，但是由于这些材料的量较少，其在电池中不是作为主要的负极活性材料使用，因此不被视为形成起到嵌钠作用的负极活性材料层，这样构成的钠二次电池仍然可被视为无负极钠二次电池。
在一些实施方式中，无负极钠二次电池的CB值小于等于0.1。
CB值为二次电池中负极极片的单位面积容量除以正极极片的单位面积容量。由于无负极电池中，不包含或者仅包含少量的负极活性材料，因此负极极片的单位面积容量较小，二次电池的CB值小于等于0.1。
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能够盖设于开口，以封闭容纳腔。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封装于容纳腔内。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，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池5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为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包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。
[用电装置]
本申请的一个实施方式中，提供一种用电装置，包括任意实施方式的二次电池、任意实施方式的电池模块或任意实施方式的电池包中的至少一种。
用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。二次电池、电池模块、或电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以包括移动设备(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。
作为用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
一、制备方法
实施例1
1)电解液
在氩气气氛手套箱中(H2O<0.1ppm，O2<0.1ppm)，将22.2％的乙二醇二甲醚(DME)与77.8％的乙二醇二乙醚混合均匀，得到混合溶剂。然后加入钠盐六氟磷酸钠和包含金属离子钾离子的六氟磷酸钾溶解于上述混合溶剂中，搅拌均匀，控制钠盐六氟磷酸钠的浓度为1mol/L，金属离子钾离子的浓度为0.03mol/L，制备电解液。
2)正极极片的制备
将10wt％聚偏二氟乙烯粘结剂充分溶解于N-甲基吡咯烷酮中，再加入10wt％炭黑导电剂与80wt％Na4Fe3(PO4)2P2O7正极活性材料搅拌混合均匀，得到正极浆料。将浆料均匀涂敷在集流体铝箔表面以制备正极膜层，然后转移到真空干燥箱中完全干燥。将干燥后的极片进行辊压、冲切，得到正极极片。
3)负极极片的制备
取5g CMC溶解于1000mL去离子水中，然后加入5g单壁碳纳米管，经超声分散后制备成浆料，再将浆料涂布在铜箔表面。最后转移到真空干燥箱中完全干燥，之后分切、模切，制备无负极结构的负极极片。
4)隔离膜
以聚丙烯膜作为隔离膜。
5)电池的制备
将正极极片、隔离膜、负极极片按顺序叠好，隔离膜处于正、负极片之间起到隔离的作用，给裸电芯焊接极耳，并将裸电芯装入铝壳中，并在80℃下烘烤除水，随即注入上述电解液并封口，得到不带电的电池。不带电的电池再依次经过静置、热冷压、化成、整形、容量测试等工序，获得实施例1的无负极钠二次电池产品。
实施例2～3
实施例2～3中的电池制备方法与实施例1基本相似，但是调整了醚类溶剂的种类或者金属离子的种类，具体参数如表1所示。
实施例4
实施例4中的电池制备方法与实施例1基本相似，但是电解液中引入了氟醚化合物，电解液的制备方法具体如下：
在氩气气氛手套箱中(H2O<0.1ppm，O2<0.1ppm)，将20％的乙二醇二甲醚(DME)、70％的乙二醇二乙醚与10％的1,1,2,2-四氟乙基2,2,3,3-四氟丙醚(TTE)混合均匀，得到混合溶剂。然后加入钠盐六氟磷酸钠和包含金属离子钾离子的六氟磷酸钾溶解于上述混合溶剂中，搅拌均匀，控制钠盐六氟磷酸钠的浓度为1mol/L，钾离子的浓度为0.03mol/L，制备电解液。
实施例5～31
实施例5～31中的电池制备方法与实施例4基本相似，但是调整了金属离子的浓度、金属离子的种类、醚类溶剂的种类、氟醚化合物的种类、氟醚化合物的浓度、钠盐的种类以及钠盐的浓度，具体参数如表1所示。
对比例1
对比例1中的电池制备方法与实施例1基本相似，但是电解液中没有金属离子，具体参数如表1所示。
对比例2
对比例2中的电池制备方法与对比例1基本相似，但是电解液中加入了氟醚化合物，具体参数如表1所示。
对比例3
对比例3中的电池制备方法与对比例2基本相似，但是调整了电解液醚类溶剂的种类，具体参数如表1所示。
对比例4
对比例4中的电池制备方法与实施例1基本相似，但是将金属离子调整为镁离子(Mg2+的离子半径为0.066nm，Mg2+的还原态作为电极，其标准电极电势为-2.375V)，具体参数如表1所示。
二、性能测试
1、电池性能测试
1)存储容量保持率测试
在25℃下，将制备的电池以0.2C的恒定电流充电至3.7V，之后以3.7V恒压充电至电流降到0.05C，再以0.2C的恒定电流放电至2.5V，得到存储前放电容量(Cd1)；然后将此电池再次以0.2C的恒定电流充电至3.7V，之后以3.7V恒压充电至电流降到0.05C。然后将电池至于60℃恒温箱中存储30天，取出后将电池放在25℃下以0.2C的恒定电流充电至3.7V，之后以3.7V恒压充电至电流降到0.05C，再以0.2C的恒定电流放电至2.5V，得到存储后放电容量(Cd2)，并按照下式计算60℃储存30天后的电池容量保持率：
存储容量保持率＝存储后的放电容量(Cd2)/存储前的放电容量(Cd1)。
2)循环性能测试
循环性能测试过程如下：在25℃下，将制备的电池静置30min，随后以0.33C恒定电流放电至3.65V，之后以3.65V恒压充电至电流降到0.05C，静置1h后，以0.33C恒定电流放电至2.5V，得到初始容量(C0)；静置1h后，再以0.33C恒定电流充电至3.65V，之 后以3.65V恒压充电至电流降到0.05C，静置1h后，以0.33C恒定电流放电至2.5V，得到过程容量(C1)，对上述同一个电池重复以上步骤，并同时记录循环第100次后电池的过程容量(Cn)，循环100圈后的容量保持率＝Cn/C1×100％。对比例以及其他实施例的测试过程同上。
3)钠枝晶测试
将上述循环n圈后的电池在氩气气氛手套箱中(H2O<0.1ppm，O2<0.1ppm)进行拆解，目视观察负极极片表面形貌，确定是否有钠枝晶生成。负极极片无白点判定为钠枝晶情况无、负极极片有零星白点判定为钠枝晶情况轻微、负极极片有密密麻麻白点判定为钠枝晶情况严重。对比例以及其他实施例的测试过程同上。
三、各实施例、对比例测试结果分析
按照上述方法分别制备各实施例和对比例的电池，并测量各项性能参数，结果见下表1和表2。
表1

表2
根据上述结果可知，实施例1～31中的电解液包括钠盐和离子半径大于钠离子的金属离子。
从实施例1～31与对比例1～3的对比可见，电解液包括离子半径大于钠离子的金属离子，有效地抑制了钠枝晶的生成，同时有利于提升电池的循环容量保持率和60℃存储30天的容量保持率，改善了电池的性能。
从实施例1～31与对比例1～4的对比可见，相比于电解液包括六氟磷酸镁，本申请中电解液包括六氟磷酸钾、六氟磷酸钙、硝酸钙或硝酸锶，有效地抑制了钠枝晶的生成，同时有利于提升电池的循环容量保持率和60℃存储30天的容量保持率，改善了电池的性能。
从实施例4～8与实施例9的对比可见，控制金属离子在电解液中的浓度为0.005mol/L～0.3mol/L，有利于提升电池的循环容量保持率和60℃存储30天的容量保持率。从实施例4、6～7与实施例5、8的对比可见，进一步控制金属离子在电解液中的浓度为0.01mol/L～0.1mol/L，有利于进一步大幅提升电池60℃存储30天的容量保持率。
从实施例4、10～13与实施例1的对比可见，氟醚化合物的加入有利于提升电池的循环容量保持率和60℃存储30天的容量保持率，抑制电池的钠枝晶。从实施例4、10～13中可见，基于醚类溶剂和氟醚化合物的总质量计，控制氟醚化合物的质量含量为2％～30％，其电池具有优异的循环容量保持率和60℃存储30天的容量保持率，以及有效的抑制了钠枝晶。从实施例4、11～12与实施例5、13的对比可见，基于醚类溶剂和氟醚化合物的总质量计，进一步控制氟醚化合物的质量含量为5％～20％，有利于进一步大幅提升电池的循环容量保持率和60℃存储30天的容量保持率。
从实施例4、14～18中可见，控制钠盐在电解液中的浓度为0.1mol/L～1.8mol/L，以使其电池具有优异的循环容量保持率和60℃存储30天的容量保持率，以及有效的抑制了钠枝晶。从实施例4、14～16与实施例17～18的对比可见，进一步控制钠盐在电解液中的浓度为0.5mol/L～1.5mol/L，有利于进一步大幅提升电池的循环容量保持率和60℃存储30天的容量保持率。
从实施例4、19～21中可见，电解液包括六氟磷酸钾、六氟磷酸钙、硝酸钙、硝酸锶中的一种，其电池均具有优异的循环容量保持率和60℃存储30天的容量保持率，以及有效的抑制了钠枝晶。
从实施例1～2、4、22～26与实施例27的对比可见，控制电解液中的醚类溶剂选自乙二醇二甲醚、乙二醇二乙醚或二乙二醇二甲醚，有利于提升电池的循环容量保持率和60℃存储30天的容量保持率、以及抑制电池的钠枝晶现象。
从实施例4与实施例24、26，实施例22与实施例24～25的对比可见，控制电解液中的醚类溶剂选自乙二醇二甲醚、乙二醇二乙醚和二乙二醇二甲醚中的至少两种，有利于进一步大幅提升电池的循环容量保持率和60℃存储30天的容量保持率。
从实施例4、28～29中可见，钠盐包括六氟磷酸钠、高氯酸钠和双(氟磺酰)亚胺钠中的一种，其电池均具有优异的循环容量保持率和60℃存储30天的容量保持率，以及有效的抑制了钠枝晶。从实施例1与实施例3，实施例4与实施例19的对比可见，相比于包括Ca2+的金属离子，包括K+的金属离子有利于进一步提升电池的循环容量保持率和60℃存储30天的容量保持率。
从实施例4、30～31中可见，钠盐包括1,1,2,2-四氟乙基2,2,3,3-四氟丙醚、双(2,2,2-三氟乙基)醚、1,1,2,2-四氟乙基甲基醚中的一种，其电池均具有优异的循环容量保持率和60℃存储30天的容量保持率，以及有效的抑制了钠枝晶。
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 (18)

  1. 一种用于钠二次电池的电解液，其特征在于，所述电解液包括钠盐和离子半径大于钠离子的金属离子。
  2. 根据权利要求1所述的电解液，其特征在于，所述金属离子包括K+、Ca2+、Sr2+、Ba2+中的一种或多种，可选地包括K+。
  3. 根据权利要求1或2所述的电解液，其特征在于，所述电解液包括PF6 -、NO3 -、ClO3 -中的一种或多种。
  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，所述电解液包括六氟磷酸钾、六氟磷酸钙、六氟磷酸锶、六氟磷酸钡、硝酸钾、硝酸钙、硝酸锶、硝酸钡、高氯酸钾、高氯酸钙、高氯酸锶、高氯酸钡中的一种或多种，可选地包括六氟磷酸钾、硝酸钾、六氟磷酸钙中的一种或多种。
  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，所述金属离子在所述电解液中的浓度为0.005mol/L～0.3mol/L，可选为0.01mol/L～0.1mol/L。
  6. 根据权利要求1至5中任一项所述的电解液，其特征在于，所述钠盐包括氯化钠、溴化钠、硝酸钠、高氯酸钠、六氟磷酸钠、乙酸钠、三氟乙酸钠、三氟甲基磺酸钠、双(氟磺酰)亚胺钠、双(三氟甲基磺酰)亚胺钠、四氟硼酸钠、四苯硼酸钠中的一种或多种，可选地包含六氟磷酸钠、高氯酸钠、双(氟磺酰)亚胺钠、双(三氟甲基磺酰)亚胺钠、四氟硼酸钠中的一种或多种。
  7. 根据权利要求1至6中任一项所述的电解液，其特征在于，所述钠盐在所述电解液中的浓度为0.1mol/L～1.8mol/L，可选为0.5 mol/L～1.5mol/L。
  8. 根据权利要求1至7中任一项所述的电解液，其特征在于，所述电解液还包括醚类溶剂，所述醚类溶剂包括乙二醇二甲醚、二乙二醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、聚乙二醇二甲醚、乙醚、乙二醇二乙醚、乙二醇二丁醚、二乙二醇二乙醚、二乙二醇二丁醚、四氢呋喃、甲基四氢呋喃和1,3-二氧五环中的一种或多种，可选地包括乙二醇二乙醚、乙二醇二甲醚、乙二醇二乙醚、二乙二醇二甲醚、四乙二醇二甲醚、二乙二醇二丁醚中的一种或多种。
  9. 根据权利要求8所述的电解液，其特征在于，所述醚类溶剂包括乙二醇二甲醚、二乙二醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、聚乙二醇二甲醚、乙二醇二乙醚、乙二醇二丁醚、四氢呋喃、甲基四氢呋喃和1,3-二氧五环中的至少两种，可选地包括乙二醇二乙醚、乙二醇二甲醚、二乙二醇二甲醚、三乙二醇二甲醚和四乙二醇二甲醚中的至少两种。
  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，所述电解液还包括氟醚化合物，所述氟醚化合物包括1,1,2,2-四氟乙基2,2,3,3-四氟丙醚、双(2,2,2-三氟乙基)醚、1,1,2,2-四氟乙基甲基醚、1,1,2,2-四氟乙基-2,2,2-三氟乙基醚、三(三氟乙氧基)甲烷、甲基九氟丁醚、1,1,1,3,3,3-六氟异丙基甲基醚、1H,1H,5H-八氟戊基-1,1,2,2-四氟乙醚中的一种或多种，可选地包括1,1,2,2-四氟乙基2,2,3,3-四氟丙醚、双(2,2,2-三氟乙基)醚中的一种或多种。
  11. 根据权利要求10所述的电解液，其特征在于，基于所述醚类溶剂和所述氟醚化合物的总质量计，所述氟醚化合物的质量含量为2％～30％，可选为5％～20％。
  12. 根据权利要求10或11所述的电解液，其特征在于，所述钠盐包括六氟磷酸钠，所述金属离子包括K+，所述醚类溶剂包括乙二醇二甲醚，所述氟醚化合物包括1,1,2,2-四氟乙基2,2,3,3-四氟丙醚。
  13. 一种二次电池，其特征在于，包括权利要求1至12中任一项所述的电解液。
  14. 根据权利要求13所述的二次电池，其特征在于，所述二次电池是无负极钠二次电池。
  15. 根据权利要求13或14所述的二次电池，其特征在于，所述二次电池还包括负极极片，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面的底涂层，所述底涂层包括碳纳米管、石墨、石墨烯、银复合碳纳米颗粒、锡复合碳纳米颗粒中的一种或多种。
  16. 根据权利要求15所述的二次电池，其特征在于，所述底涂层的面密度为0.5g/m2～35g/m2。
  17. 根据权利要求15或16所述的二次电池，其特征在于，所述底涂层的厚度为0.2μm～50μm。
  18. 一种用电装置，其特征在于，包括权利要求15至17中任一项所述的二次电池。
PCT/CN2023/084866 2023-03-29 2023-03-29 电解液、二次电池和用电装置 Ceased WO2024197667A1 (zh)

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