WO2024152146A1 - 非水电解液及包含该电解液的钠离子电池和用电装置 - Google Patents

非水电解液及包含该电解液的钠离子电池和用电装置 Download PDF

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WO2024152146A1
WO2024152146A1 PCT/CN2023/072330 CN2023072330W WO2024152146A1 WO 2024152146 A1 WO2024152146 A1 WO 2024152146A1 CN 2023072330 W CN2023072330 W CN 2023072330W WO 2024152146 A1 WO2024152146 A1 WO 2024152146A1
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sodium
aqueous electrolyte
sodium salt
optionally
salt
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English (en)
French (fr)
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铁志伟
邹海林
陈培培
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to KR1020257009475A priority Critical patent/KR20250049423A/ko
Priority to JP2025517414A priority patent/JP2025531407A/ja
Priority to PCT/CN2023/072330 priority patent/WO2024152146A1/zh
Priority to EP23916639.0A priority patent/EP4611104A4/en
Priority to CN202380066616.6A priority patent/CN119895619A/zh
Publication of WO2024152146A1 publication Critical patent/WO2024152146A1/zh
Priority to US19/087,271 priority patent/US20250219149A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—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
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—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
    • 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 a non-aqueous electrolyte, which includes at least two sodium salts, wherein the first sodium salt includes at least one of sodium hexafluorophosphate, sodium hexafluoroarsenate, sodium perchlorate and sodium trifluoroacetate, and the second sodium salt includes one, two or more of sodium salts having sulfonate, sodium salt of oxalate, sodium salt of phosphate and sodium salt of borate.
  • the present application also relates to a sodium ion battery and an electrical device containing the non-aqueous electrolyte.
  • Lithium-ion batteries have shown good development prospects in the fields of mobile phones, computers, electric vehicles, portable electronic devices, etc. due to their high energy density.
  • lithium resources such as lithium carbonate
  • resource and cost issues will limit the large-scale and long-term use of lithium-ion batteries. Therefore, the further development of new battery systems with high performance and low cost is of great research significance.
  • sodium resources are more abundant in the earth's crust, and its abundance ranks sixth. Moreover, sodium resources are distributed evenly in the earth's crust and exist all over the world. Therefore, the utilization of sodium resources will not be severely restricted by reserves and regions. More importantly, the cost of sodium resources is low, which is suitable for large-scale and long-term use. Therefore, sodium-ion batteries have greater advantages than lithium-ion batteries in terms of resources and cost issues.
  • metallic sodium has similar physical and chemical properties to lithium, so sodium-ion batteries can learn from the development experience of lithium-ion batteries to a certain extent and use their production processes.
  • Sodium-ion batteries show good development prospects in the field of electrochemical energy storage, and the industrial development of sodium-ion batteries has great strategic significance and economic value.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide a non-aqueous electrolyte suitable for sodium ion batteries, which can improve the high-temperature cycle performance of sodium ion batteries and the capacity retention rate after high-temperature storage, and can reduce the battery volume expansion rate of sodium ion batteries after high-temperature storage, as well as a sodium ion battery and an electrical device comprising the non-aqueous electrolyte.
  • the first aspect of the present application provides a non-aqueous electrolyte, comprising:
  • a first sodium salt which includes at least one of sodium hexafluorophosphate (NaPF 6 ), sodium hexafluoroarsenate (NaAsF 6 ), sodium perchlorate (NaClO 4 ) and sodium trifluoroacetate (CF 3 COONa), and optionally, the first sodium salt is sodium hexafluorophosphate;
  • the second sodium salt includes one, two or more of a sodium salt with a sulfonate group, a sodium salt with an oxalate group, a sodium salt with a phosphate group and a sodium salt with a borate group; optionally, the second sodium salt includes a sodium salt with a sulfonate group, a sodium salt with an oxalate group, a sodium salt with a phosphate group and a sodium salt with a borate group.
  • the non-aqueous electrolyte is obtained by dissolving a sodium salt electrolyte containing electron-rich anions in a non-aqueous solvent.
  • a sodium salt electrolyte containing electron-rich anions in a non-aqueous solvent.
  • the solvation structure of the sodium ions in the electrolyte and the chemical environment of the solvent molecules can be regulated, thereby solving the gas generation problem caused by the continuous decomposition of the solvent in the sodium ion battery.
  • the molar concentration ratio of the first sodium salt to the second sodium salt is greater than 1/1, and can be greater than 3/1, and less than 40/1, and can be less than 15/1.
  • the molar concentration ratio of the first sodium salt to the second sodium salt is within the above range, which can reduce the risk of excessive film formation on the electrode surface and reduce the resistance to sodium ion transmission at the electrode/electrolyte interface, thereby having less impact on the kinetic process of the sodium ion battery.
  • the sodium salt having a sulfonate group includes sodium fluorosulfonate (FSO 3 Na), sodium trifluoromethylsulfonate (NaSO 3 CF 3 ), sodium bis(fluorosulfonyl)imide (Na[(FSO 2 ) 2 N]), sodium bis(trifluoromethylsulfonyl)imide (Na[(CF 3 SO 2 ) 2 N]), sodium methanesulfonate (CH 3 SO 3 Na), sodium vinylsulfonate (C 2 H 3 NaO 3 S), sodium methyl sulfate (CH 3 OSO 3 Na), sodium methylthiosulfonate (CH 3 NaO 2 S 2 ), sodium 1,2-ethanedisulfonate (NaO 3 SCH 2 CH 2 SO 3 Na), sodium ethyl sulfate (C 2 H 5 NaO 4 S), sodium propanesulfonate (C 3 H 7 NaO 3 S), sodium ethylthios
  • the concentration of the sodium salt having sulfonate groups in the non-aqueous electrolyte is in the range of 0.0005-1 mol/L, and optionally in the range of 0.01-0.3 mol/L.
  • the concentration of the second sodium salt containing sulfonate in the electrolyte is above 0.0005 mol/L, which can improve the stability of the first sodium salt in the electrolyte. Moreover, it enables the sodium ion battery to form a stable solid electrolyte interface film on the electrode surface during the electrochemical reaction, effectively inhibiting the dissolution of the electrolyte.
  • the decomposition and gas production of the agent on the electrode surface improves the electrochemical performance of the sodium ion battery (especially at high temperatures).
  • the concentration of the sodium salt containing sulfonate groups in the electrolyte may be above 0.01 mol/L.
  • the concentration of the sodium salt with sulfonate groups in the electrolyte is below 0.3 mol/L, which can more effectively reduce the risk of excessive film formation on the electrode, and thus will not have a significant impact on the electrochemical performance of the sodium ion battery at high temperatures.
  • the concentration may be below 0.15 mol/L.
  • the sodium salt having oxalate includes one or more of sodium oxalate (Na 2 C 2 O 4 ), sodium bis(oxalate)borate (C 4 BNaO 8 ), sodium difluoro(oxalate)borate (C 2 BF 2 NaO 4 ), sodium tetrafluoro(oxalate)phosphate (C 2 F 4 NaO 4 P), and sodium difluorobis(oxalate)phosphate (C 4 F 2 NaO 8 P).
  • sodium oxalate Na 2 C 2 O 4
  • sodium bis(oxalate)borate C 4 BNaO 8
  • sodium difluoro(oxalate)borate C 2 BF 2 NaO 4
  • sodium tetrafluoro(oxalate)phosphate C 2 F 4 NaO 4 P
  • sodium difluorobis(oxalate)phosphate C 4 F 2 NaO 8 P
  • the concentration of the sodium salt containing oxalate in the electrolyte is above 0.0005 mol/L, which can significantly improve the stability of the first sodium salt in the electrolyte, and has an improvement effect on the cycle performance of the sodium ion battery at high temperature and the improvement of the capacity retention rate after storage.
  • the concentration may be above 0.006 mol/L, and further may be above 0.01 mol/L.
  • the concentration is preferably below 0.08 mol/L, which can more effectively reduce the possibility of excessive film formation of the sodium salt with oxalate on the electrode, and thus will not have a significant impact on the kinetic process during the charge and discharge process of the sodium ion battery.
  • the sodium salt having a phosphate group includes one or more of sodium difluorophosphate (NaPO 2 F 2 ), sodium monofluorophosphate (Na 2 PO 3 F), sodium trimetaphosphate (Na 3 P 3 O 9 ), sodium hexametaphosphate (Na 6 P 6 O 18 ), sodium hydroxyethylidene diphosphonate (C 2 H 7 NaO 7 P 2 ), disodium clodronate (CH 2 Cl 2 Na 2 O 6 P 2 ), sodium olpadronate (C 5 H 15 NO 7 P 2 ), sodium diethylenetriamine pentamethylenephosphonate (C 9 H 18 N 3 Na 10 O 15 P 5 ), sodium tripolyphosphate (Na 5 P 3 O 10 ) and disodium phenyl phosphate (C 6 H 5 Na 2 O 4 P), and optionally includes sodium difluorophosphate (NaPO 2 F 2 ) and sodium fluorophosphate (Na 2 PO 3 F) one or more.
  • the concentration of the sodium salt having phosphate in the non-aqueous electrolyte is in the range of 0.0005-0.12, optionally in the range of 0.01-0.05 mol/L, and more optionally in the range of 0.01-0.03 mol/L.
  • the molar concentration of the sodium salt containing phosphate in the non-aqueous electrolyte is above 0.0005 mol/L, which can improve the stability of the first sodium salt in the electrolyte, and enable the sodium ion battery to form a thin and solid solid electrolyte film mainly composed of inorganic components on the electrode surface during the formation process, which can significantly suppress the gas production problem in the sodium ion battery.
  • the concentration is above 0.01 mol/L.
  • the concentration is below 0.12 mol/L, which can effectively reduce the possibility of excessive film formation of the sodium salt containing phosphate on the electrode surface, and thus will not have a significant impact on the kinetic process during the charge and discharge process of the sodium ion battery.
  • the sodium salt having a borate group includes sodium tetrafluoroborate (NaBF 4 ), sodium metaborate (BNaO 2 ), sodium tetraphenylborate ((C 6 H 5 ) 4 BNa), tetrakis[3,5-bis(trifluoromethyl)phenyl]borane, One or more of sodium tetrafluoroborate (C 32 H 12 BF 24 Na), optionally including one or more of sodium tetrafluoroborate, sodium metaborate and sodium tetraphenylborate, and further optionally including one or more of sodium tetrafluoroborate and sodium metaborate.
  • the concentration of the sodium salt having a borate group in the non-aqueous electrolyte is in the range of 0.0005-0.05 mol/L, and optionally in the range of 0.01-0.04 mol/L.
  • the molar concentration of the sodium salt containing borate in the non-aqueous electrolyte is above 0.0005 mol/L, which can have a certain effect on improving the stability of the first sodium salt in the electrolyte, and enable the sodium ion battery to form a thin and dense solid electrolyte interface film on the electrode surface, thereby inhibiting the continuous decomposition of the solvent in the electrolyte at the electrode/electrolyte interface, thereby significantly inhibiting the gas production problem in the sodium ion battery, and also improving the capacity retention rate after the circulation and high temperature storage of the sodium ion battery (especially at high temperature).
  • the concentration is below 0.05 mol/L, which can effectively reduce the possibility of excessive film formation of the sodium salt containing borate on the electrode surface, and thus will not have a significant impact on the kinetic process during the charge and discharge process of the sodium ion battery.
  • the concentration of other sodium salts except sodium hexafluorophosphate in the non-aqueous electrolyte is 0.001 mol/L or more, can be optionally 0.01 mol/L or more, further can be optionally 0.03 mol/L or more, and is 1 mol/L or less, can be optionally 0.5 mol/L or less.
  • the electrochemical performance of the sodium ion battery at high temperature is improved. If the concentration of other sodium salts in the non-aqueous solvent is below 1 mol/L, the solvation structure of sodium ions in the electrolyte and the chemical environment of the non-aqueous solvent molecules can be regulated to a certain extent, and the decomposition and gas production of the electrolyte under high temperature conditions can be inhibited, which has a promoting effect on the improvement of the electrochemical performance of the sodium ion battery at high temperature.
  • NaPF 6 sodium hexafluorophosphate
  • the combination of a sodium salt having a sulfonate group and a sodium salt having one or more of oxalate, phosphate and borate groups will produce a synergistic effect, synergistically participate in the solvation process of sodium ions in the electrolyte, provide partial electrons for the sodium ions, and effectively inhibit the strong electron-withdrawing property of sodium ions to non-aqueous solvent molecules, and can significantly inhibit the continuous decomposition and gas production of the electrolyte; in addition, the combination of a sodium salt having a sulfonate group and a sodium salt having one or more of oxalate, phosphate and borate groups can form a thin and dense solid electrolyte interface film rich in inorganic components at the electrode/electrolyte interface, which has a significant improvement effect on the electrochemical performance of sodium ion batteries (especially at high temperatures).
  • the second sodium salt comprises a sodium salt having a sulfonate group and a sodium salt having an oxalate group.
  • the molar ratio of the sodium salt having a sulfonate group to the sodium salt having an oxalate group is 0.03/1 to 70/1, and optionally 0.5/1 to 20/1.
  • the sodium salt with oxalate group, sodium salt with phosphate group and sodium salt with borate group can improve the inhibitory effect on electrolyte decomposition and gas generation.
  • the molar ratio of sodium salt with sulfonate group to sodium salt with oxalate group is 1/1 to 10/1, it is more likely that a thin solid electrolyte interface film mainly composed of inorganic components will be formed on the electrode surface during the charge and discharge process of the sodium ion battery.
  • the non-aqueous electrolyte contains cyclic carbonate, and the mass concentration of the cyclic carbonate in the non-aqueous electrolyte is greater than 10%, and may be greater than 15%, and less than 60%.
  • the stability of the electrode/electrolyte interface film of the sodium ion battery under high temperature conditions can be improved to a certain extent without substantially affecting the sodium ion migration rate.
  • the non-aqueous electrolyte contains linear carbonates and linear carboxylates, and the mass percentage of the sum of the linear carbonates and the linear carboxylates in the non-aqueous electrolyte is above 40%, optionally above 50%, more optionally above 60%, and below 90%, optionally below 85%, and further optionally below 80%.
  • the mass percentage of the linear carbonate and the linear carboxylic acid ester in the electrolyte is above 40%, and can be selected to be above 50%, and can be further selected to be above 60%, so that the viscosity of the electrolyte will not be too high; the upper limit of the content is below 90%, and can be selected to be below 85%, and can be further selected to be below 80%, so that the ionic conductivity does not decrease much, and the impact on the electrochemical performance of the sodium ion battery is small.
  • the non-aqueous electrolyte includes at least one cyclic carbonate and at least one chain ester, and the mass percentage of the at least one cyclic carbonate to the at least one chain ester is above 0.1:1 and below 1.5:1, optionally below 1:1, and more optionally, between 0.2:1 and 1:1.
  • the non-aqueous electrolyte contains one or more of the following combinations of substances: cyclic carbonates and chain carbonates; cyclic carbonates and chain carboxylates; cyclic carbonates and ethers; chain carbonates and chain carboxylates; chain carbonates and ethers; chain carboxylates and ethers; cyclic carbonates, chain carbonates and chain carboxylates; cyclic carbonates, chain carbonates and ethers; cyclic carbonates, chain carboxylates and ethers; chain carbonates, chain carboxylates and ethers.
  • the cyclic carbonate, chain carbonate, chain carboxylate, ether, etc. included in the non-aqueous electrolyte of the present application exist as non-aqueous solvents.
  • the above-mentioned specific combination of non-aqueous solvents can not only improve the solubility and dispersion ability of the electrolyte sodium salt therein, but also participate in the formation of certain specific sodium ion solvation configurations, thereby Effectively inhibit the decomposition of solvents in the electrolyte and the accompanying gas production problems, and further improve the electrochemical performance of sodium-ion batteries (especially under high temperature conditions).
  • the non-aqueous solvent in the non-aqueous electrolyte includes one or more of propylene carbonate, ethyl methyl carbonate, ethyl acetate, diethyl carbonate, methyl propionate, ethyl propionate, diethylene glycol dimethyl ether, and fluoroethylene carbonate.
  • the non-aqueous electrolyte includes one or more of anhydride additives, fluorine-containing organic additives, nitrile additives, silicone additives, aldehyde additives, sulfur-containing additives, lithium salt additives, and potassium salt additives.
  • the total mass percentage of these additives in the non-aqueous electrolyte is greater than 0.001%, optionally greater than 0.2%, and less than 5%, optionally less than 4%.
  • the above-mentioned additive can be optionally added to the electrolyte.
  • the mass percentage of the additive in the non-aqueous electrolyte is 0.001% or more, and can be 0.2% or more, which has an effect of improving the stability of the film formed on the electrode surface; the upper limit is below 5%, and can be below 4%, which reduces the possibility of excessive film formation on the electrode surface.
  • the second aspect of the present application provides a sodium ion battery, which includes a positive electrode sheet, a negative electrode sheet and the non-aqueous electrolyte described in the first aspect of the present application.
  • the third aspect of the present application provides an electrical device, which includes the non-aqueous electrolyte described in the first aspect of the present application or the sodium ion battery described in the second aspect of the present application.
  • 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. 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.
  • “Scope” disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range.
  • the scope limited in this way can be including end values or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected.
  • 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 also include step (c), which means that step (c) can 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.
  • Sodium-ion batteries are mainly composed of positive and negative electrode materials that can embed/extract sodium ions, electrolytes containing sodium salts and non-aqueous solvents. Among them, the electrolyte plays an important role in the development of sodium-ion batteries. As a bridge for the transmission of sodium ions between the positive and negative electrodes, the electrolyte determines the capacity of the positive and negative electrode materials, thereby affecting the electrochemical performance of sodium-ion batteries. However, the electrolyte is also affected by the positive and negative electrode materials, the environment (such as temperature), and the electrolyte. The influence of factors such as temperature, test conditions (such as voltage), etc.
  • the electrolyte of sodium-ion batteries is greatly affected by the negative electrode materials.
  • the negative electrode materials of sodium-ion batteries include metallic sodium, carbon materials (such as hard carbon, graphite, etc.), metal compounds (such as metal oxides, alloys, etc.), etc.
  • the sodium insertion potential of these materials is often relatively low, which may cause the electrolyte to undergo reductive decomposition.
  • the problem of reductive decomposition of the solvent in the electrolyte on the surface of the negative electrode is more serious.
  • the continuous decomposition of the solvent will cause sodium-ion batteries to face serious gas production problems.
  • the large amount of gases produced (such as carbon dioxide, carbon monoxide, hydrogen, propylene, etc.) will accumulate in the sodium-ion battery, which will increase the risk of safe use of sodium-ion batteries.
  • the continuous decomposition of the solvent often forms a large amount of organic decomposition products.
  • These organic substances are deposited on the surface of the negative electrode to form a thick and uneven organic solid electrolyte (SEI) film, which will significantly slow down the transport dynamics of sodium ions at the negative electrode/electrolyte interface, and ultimately deteriorate the electrochemical performance (such as cycle and rate performance, etc.) of the sodium ion battery (especially at high temperatures); moreover, the continuous deposition of the organic SEI film will also cause the electrode to swell.
  • SEI organic solid electrolyte
  • the electrolyte of sodium-ion batteries is also affected by factors such as the working voltage and chemical composition of the positive electrode material.
  • the positive electrode materials of sodium-ion batteries mainly include transition metal oxides, polyanionic compounds, Prussian blue analogs, etc. These positive electrode materials often undergo sodium ion insertion/extraction reactions in the high voltage range. Under high voltage, the electrolyte will undergo oxidative decomposition at the positive electrode accompanied by a large amount of gas precipitation.
  • the transition metals such as iron, cobalt, nickel, etc.
  • the transition metals have strong catalytic properties and may catalyze the decomposition of solvents and electrolyte/positive electrode interface films.
  • the composition of metal salts plays a vital role in the chemical and electrochemical stability of batteries.
  • the type of metal salt determines the solvation structure and thermodynamic stability of the electrolyte, thereby affecting the decomposition behavior of the electrolyte, and then regulating the interface properties of the electrode/electrolyte and the electrochemical performance of the electrode.
  • Introducing electron-rich anions into the electrolyte system of sodium ion batteries can significantly inhibit the decomposition and gas production of solvents.
  • Electron-rich anions participate in the solvation structure of sodium ions, which can provide part of the electrons to sodium ions, weaken the strong electron-withdrawing properties of sodium ions to solvent molecules, and reduce the weakening of chemical bonds and the instability of the molecular structure of solvent molecules due to local electron loss.
  • our research found that the selection of anion types and radii can further regulate the solvation structure of sodium ions in the electrolyte and the chemical environment of solvent molecules. More importantly, some different types of anions also have synergistic effects in electrolytes. These anions act as electron "sponges" to provide electrons for the sodium ion solvation shell, synergistically improving the chemical stability, electrochemical stability and thermal stability of the electrolyte.
  • the purpose of the present application is to provide a sodium ion battery electrolyte and a sodium ion battery containing electron-rich anions by regulating the solvation structure of sodium ions in the electrolyte and the chemical environment of the solvent molecules, so as to solve the gas production problem caused by the continuous decomposition of the solvent in the sodium ion battery.
  • non-aqueous electrolyte which comprises:
  • a first sodium salt which includes at least one of sodium hexafluorophosphate (NaPF 6 ), sodium hexafluoroarsenate (NaAsF 6 ), sodium perchlorate (NaClO 4 ) and sodium trifluoroacetate (CF 3 COONa), and optionally, the first sodium salt is sodium hexafluorophosphate;
  • the second sodium salt includes one, two or more of a sodium salt with a sulfonate group, a sodium salt with an oxalate group, a sodium salt with a phosphate group and a sodium salt with a borate group; optionally, the second sodium salt includes a sodium salt with a sulfonate group, a sodium salt with an oxalate group, a sodium salt with a phosphate group and a sodium salt with a borate group.
  • the sulfonate group in the sodium salt having a sulfonate group includes, but is not limited to, for example, SO 3 2- , (SO 3 CF 3 ) - , [N(FSO 2 ) 2 ] - , etc.;
  • the oxalate group in the sodium salt having an oxalate group includes, but is not limited to, for example, C 2 O 4 2- , (C 2 O 4 BF 2 ) - , [(C 2 O 4 ) 2 B] -, etc.
  • the borate group in the sodium salt having a borate group includes, but is not limited to, for example, BF 4 - , BO 2 -, etc.;
  • the phosphate group in the sodium salt having a phosphate group includes, but is not limited to, for example, PO 4 3- , (PO 3 F) 2- , (PO 2 F 2 ) - , etc.
  • the non-aqueous electrolyte is obtained by dissolving a sodium salt electrolyte containing electron-rich anions in a non-aqueous solvent.
  • a sodium salt electrolyte containing electron-rich anions in a non-aqueous solvent.
  • the solvation structure of the sodium ions in the electrolyte and the chemical environment of the solvent molecules can be regulated, thereby solving the gas generation problem caused by the continuous decomposition of the solvent in the sodium ion battery.
  • the molar concentration ratio of the first sodium salt to the second sodium salt is above 1/1, can be above 2/1, more can be above 5/1, further can be above 10/1, and is below 1000/1, can be below 40/1, and more can be below 20/1.
  • the molar concentration ratio of the first sodium salt to the second sodium salt is greater than 1/1, and can be selected to be greater than 3/1, and less than 40/1, and can be selected to be less than 15/1.
  • the molar concentration ratio of the first sodium salt to the second sodium salt is within the above range, which can reduce the risk of excessive film formation on the electrode surface and reduce the resistance to sodium ion transmission at the electrode/electrolyte interface, thereby having less impact on the kinetic process of the sodium ion battery.
  • the sodium salt having a sulfonate group includes sodium fluorosulfonate (FSO 3 Na), sodium trifluoromethylsulfonate (NaSO 3 CF 3 ), sodium bis(fluorosulfonyl)imide (Na[(FSO 2 ) 2 N]), sodium bis(trifluoromethylsulfonyl)imide (Na[(CF 3 SO 2 ) 2 N]), sodium methanesulfonate (CH 3 SO 3 Na), sodium vinylsulfonate (C 2 H 3 NaO 3 S), sodium methyl sulfate (CH 3 OSO 3 Na), sodium methylthiosulfonate (CH 3 NaO 2 S 2 ), sodium 1,2-ethanedisulfonate (NaO 3 SCH 2 CH 2 SO 3 Na), sodium ethyl sulfate (C 2 H 5 NaO 4 S), sodium propanesulfonate (C 3 H 7 NaO 3 S), sodium ethylthio
  • the concentration of the sodium salt having a sulfonate group in the non-aqueous electrolyte is in the range of 0.0005-1 mol/L, and optionally in the range of 0.01-0.3 mol/L.
  • the concentration of the sodium salt having sulfonate groups in the non-aqueous electrolyte is greater than 0.001 mol/L, optionally greater than 0.01 mol/L, and less than 0.3 mol/L, optionally less than 0.15 mol/L.
  • the concentration of the second sodium salt containing sulfonate in the electrolyte is above 0.0005 mol/L, which can improve the stability of the first sodium salt in the electrolyte. Moreover, it enables the sodium ion battery to form a stable solid electrolyte interface film on the electrode surface during the electrochemical reaction, effectively inhibiting the dissolution of the electrolyte.
  • the decomposition and gas production of the agent on the electrode surface improves the electrochemical performance of the sodium ion battery (especially at high temperatures).
  • the concentration of the sodium salt containing sulfonate groups in the electrolyte may be above 0.01 mol/L.
  • the concentration of the sodium salt with sulfonate groups in the electrolyte is below 1 mol/L, which can more effectively reduce the risk of excessive film formation on the electrode, and thus will not have a significant impact on the electrochemical performance of the sodium ion battery at high temperatures.
  • the concentration may be below 0.15 mol/L.
  • the sodium salt having oxalate includes one or more of sodium oxalate (Na 2 C 2 O 4 ), sodium bis(oxalate)borate (C 4 BNaO 8 ), sodium difluoro(oxalate)borate (C 2 BF 2 NaO 4 ), sodium tetrafluoro(oxalate)phosphate (C 2 F 4 NaO 4 P), and sodium difluorobis(oxalate)phosphate (C 4 F 2 NaO 8 P).
  • sodium oxalate Na 2 C 2 O 4
  • sodium bis(oxalate)borate C 4 BNaO 8
  • sodium difluoro(oxalate)borate C 2 BF 2 NaO 4
  • sodium tetrafluoro(oxalate)phosphate C 2 F 4 NaO 4 P
  • sodium difluorobis(oxalate)phosphate C 4 F 2 NaO 8 P
  • Sodium bis(oxalato)borate and sodium difluoro(oxalato)borate contain both oxalate and borate, and can be classified as sodium salts with oxalate or sodium salts with borate, and are classified as sodium salts with oxalate here.
  • sodium tetrafluoro(oxalato)phosphate and sodium difluorobis(oxalato)phosphate can also be classified as sodium salts with phosphate, and are classified as sodium salts with oxalate here.
  • the concentration of the sodium salt having oxalate in the non-aqueous electrolyte is above 0.001 mol/L, optionally above 0.006 mol/L, further optionally above 0.01 mol/L and below 0.08 mol/L.
  • the concentration of the sodium salt having oxalate in the non-aqueous electrolyte is in the range of 0.0005-0.1 mol/L, optionally in the range of 0.006-0.08 mol/L, and further optionally in the range of 0.01-0.02 mol/L.
  • the concentration of the sodium salt containing oxalate in the electrolyte is above 0.0005 mol/L, which can significantly improve the stability of the first sodium salt in the electrolyte, and has an improvement effect on the cycle performance of the sodium ion battery at high temperature and the improvement of the capacity retention rate after storage.
  • the concentration may be above 0.006 mol/L, and further may be above 0.01 mol/L.
  • the concentration is preferably below 0.08 mol/L, which can more effectively reduce the possibility of excessive film formation of the sodium salt with oxalate on the electrode, and thus will not have a significant impact on the kinetic process during the charge and discharge process of the sodium ion battery.
  • the sodium salt having a phosphate group includes one or more of sodium difluorophosphate (NaPO 2 F 2 ), sodium monofluorophosphate (Na 2 PO 3 F), sodium trimetaphosphate (Na 3 P 3 O 9 ), sodium hexametaphosphate (Na 6 P 6 O 18 ), sodium hydroxyethylidene diphosphonate (C 2 H 7 NaO 7 P 2 ), disodium clodronate (CH 2 Cl 2 Na 2 O 6 P 2 ), sodium olpadronate (C 5 H 15 NO 7 P 2 ), sodium diethylenetriamine pentamethylenephosphonate (C 9 H 18 N 3 Na 10 O 15 P 5 ), sodium tripolyphosphate (Na 5 P 3 O 10 ) and disodium phenyl phosphate (C 6 H 5 Na 2 O 4 P), and optionally includes sodium difluorophosphate (NaPO 2 F 2 ) and sodium fluorophosphate (Na 2 PO 3 F) one or more.
  • the concentration of the sodium salt having phosphate in the non-aqueous electrolyte is above 0.001 mol/L, optionally above 0.01 mol/L, and below 0.12 mol/L.
  • the concentration of the sodium salt having phosphate in the non-aqueous electrolyte is in the range of 0.0005-0.12, optionally in the range of 0.01-0.05 mol/L, and more optionally in the range of 0.01-0.03 mol/L.
  • the molar concentration of the sodium salt containing phosphate in the non-aqueous electrolyte is above 0.0005 mol/L, which can improve the stability of the first sodium salt in the electrolyte, and enable the sodium ion battery to form a thin and solid solid electrolyte film mainly composed of inorganic components on the electrode surface during the formation process, which can significantly suppress the gas production problem in the sodium ion battery.
  • the concentration is above 0.01 mol/L.
  • the concentration is below 0.12 mol/L, which can effectively reduce the possibility of excessive film formation of the sodium salt containing phosphate on the electrode surface, and thus will not have a significant impact on the kinetic process during the charge and discharge process of the sodium ion battery.
  • the sodium salt having a borate group includes one or more of sodium tetrafluoroborate (NaBF 4 ), sodium metaborate (BNaO 2 ), sodium tetraphenylborate ((C 6 H 5 ) 4 BNa), and sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (C 32 H 12 BF 24 Na), and may optionally include one or more of sodium tetrafluoroborate, sodium metaborate, and sodium tetraphenylborate, and may further optionally include one or more of sodium tetrafluoroborate and sodium metaborate.
  • the concentration of the sodium salt having a borate group in the non-aqueous electrolyte is above 0.001 mol/L, optionally above 0.008 mol/L, and below 0.03 mol/L.
  • the concentration of the sodium salt having a borate group in the non-aqueous electrolyte is in the range of 0.0005-0.05 mol/L, and optionally in the range of 0.01-0.04 mol/L.
  • the molar concentration of the sodium salt containing borate in the non-aqueous electrolyte is above 0.0005mol/L, which can have a certain effect on improving the stability of the first sodium salt in the electrolyte, and enable the sodium ion battery to form a thin and dense solid electrolyte interface film on the electrode surface during the electrochemical reaction, thereby inhibiting the continuous decomposition of the solvent in the electrolyte at the electrode/electrolyte interface, thereby significantly inhibiting the gas production problem in the sodium ion battery, and also improving the capacity retention rate after the circulation and high temperature storage of the sodium ion battery (especially at high temperature).
  • the concentration is below 0.05mol/L, which can effectively reduce the possibility of excessive film formation of the sodium salt containing borate on the electrode surface, and thus will not have a greater impact on the kinetic process during the charge and discharge process of the sodium ion battery.
  • the concentration of the sodium salt with borate in the non-aqueous electrolyte is in the range of 0.01-0.02mol/L.
  • the concentration of other sodium salts except sodium hexafluorophosphate in the non-aqueous electrolyte is above 0.001 mol/L, can be selected as above 0.01 mol/L, can be further selected as above 0.03 mol/L, and can be below 1 mol/L, can be selected as below 0.5 mol/L.
  • the concentration of other sodium salts in the first sodium salt except sodium hexafluorophosphate (NaPF 6 ) in the non-aqueous solvent is preferably 0.005 mol/L or more, more preferably 0.01 mol/L or more, and further preferably 0.02 mol/L or more, and the upper limit of the concentration is preferably 0.7 mol/L or less, and further preferably 0.6 mol/L or less.
  • the concentration of sodium hexafluorophosphate in the non-aqueous electrolyte described in the present application may be any concentration or a conventional concentration.
  • the concentration of sodium hexafluorophosphate in the non-aqueous electrolyte described in the present application is 0.4-1.6 mol/L.
  • the electrochemical performance of the sodium ion battery at high temperature is improved. If the concentration of other sodium salts in the non-aqueous solvent is below 1 mol/L, the solvation structure of sodium ions in the electrolyte and the chemical environment of the non-aqueous solvent molecules can be regulated to a certain extent, and the decomposition and gas production of the electrolyte under high temperature conditions can be inhibited, which has a promoting effect on the improvement of the electrochemical performance of the sodium ion battery at high temperature.
  • NaPF 6 sodium hexafluorophosphate
  • the second sodium salt includes a sodium salt having a sulfonate group, and also includes one or more of a sodium salt having an oxalate group, a sodium salt having a phosphate group, and a sodium salt having a borate group.
  • the combination of a sodium salt having a sulfonate group and a sodium salt having one or more of oxalate, phosphate and borate groups will produce a synergistic effect, synergistically participate in the solvation process of sodium ions in the electrolyte, provide partial electrons for the sodium ions, and effectively inhibit the strong electron-withdrawing property of sodium ions to non-aqueous solvent molecules, and can significantly inhibit the continuous decomposition and gas production of the electrolyte; in addition, the combination of a sodium salt having a sulfonate group and a sodium salt having one or more of oxalate, phosphate and borate groups can form a thin and dense solid electrolyte interface film rich in inorganic components at the electrode/electrolyte interface, which has a significant improvement effect on the electrochemical performance of sodium ion batteries (especially at high temperatures).
  • the second sodium salt comprises a sodium salt having a sulfonate group and a sodium salt having an oxalate group
  • the molar ratio of the sodium salt having a sulfonate group to the sodium salt having an oxalate group is 0.03/1 to 70/1, and optionally 0.5/1 to 20/1.
  • the molar ratio of the sodium salt having a sulfonate group to the sodium salt having an oxalate group is 1/1 to 10/1.
  • the sodium salt with oxalate group, sodium salt with phosphate group and sodium salt with borate group can improve the inhibitory effect on electrolyte decomposition and gas generation.
  • the molar ratio of sodium salt with sulfonate group to sodium salt with oxalate group is 1/1 to 10/1, it is more likely that a thin solid electrolyte interface film mainly composed of inorganic components will be formed on the electrode surface during the charge and discharge process of the sodium ion battery.
  • the non-aqueous solvent in the non-aqueous electrolyte may contain cyclic carbonates, linear esters and/or ethers.
  • the non-aqueous solvent includes one or more of cyclic carbonates, linear carbonates, linear carboxylates and ethers.
  • the non-aqueous electrolyte contains cyclic carbonate, and the mass concentration of the cyclic carbonate in the non-aqueous electrolyte is greater than 10%, optionally greater than 15%, and less than 60%.
  • the cyclic carbonates are those commonly used as solvents in batteries, including, but not limited to, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl sulfite (ES), propylene sulfite (PS), vinyl ethylene carbonate (VEC), 4-ethynyl-1,3-dioxolane-2-one (EEC), cis-4,5-difluoro-1,3-dioxolane-2-one and trans-4,5-difluoro-1,3-dioxolane-2-one.
  • the above may further optionally include one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) and vinylene carbonate (VC).
  • the stability of the electrode/electrolyte interface film of the sodium ion battery under high temperature conditions can be improved to a certain extent without substantially affecting the sodium ion migration rate.
  • ethylene carbonate EC
  • propylene carbonate PC
  • butylene carbonate BC
  • vinylene carbonate VC
  • the non-aqueous electrolyte contains linear carbonates and linear carboxylates, and the mass percentage of the sum of the linear carbonates and the linear carboxylates in the non-aqueous electrolyte is above 40%, optionally above 50%, more optionally above 60%, and below 90%, optionally below 85%, and further optionally below 80%.
  • the chain carbonates are those that can be used as solvents in batteries, and may optionally include the following substances: one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate, ethyl propyl carbonate, dipropyl carbonate and dibutyl carbonate; among the chain carbonates, one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and methyl propyl carbonate (MPC) may be selected.
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • MPC methyl propyl carbonate
  • MIPC methyl isopropyl carbonate
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • EMC eth
  • the chain carboxylates are those that can be used as solvents in batteries, and may optionally include the following substances: one or more of methyl formate (MF), ethyl formate (EF), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), ethyl butyrate (EB), methyl acetate (MA), ethyl acetate (EA) and propyl acetate (PA); and one or more of methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl acetate (MA), ethyl acetate (EA) and propyl acetate (PA).
  • MF methyl formate
  • EF ethyl formate
  • MP methyl propionate
  • EP ethyl propionate
  • PP propyl propionate
  • EB methyl acetate
  • MA ethyl acetate
  • PA propyl
  • the mass percentage of the linear carbonate and the linear carboxylic acid ester in the electrolyte is above 40%, and can be selected to be above 50%, and can be further selected to be above 60%, so that the viscosity of the electrolyte will not be too high; the upper limit of the content is below 90%, and can be selected to be below 85%, and can be further selected to be below 80%, so that the ionic conductivity does not decrease much, and the impact on the electrochemical performance of the sodium ion battery is small.
  • the non-aqueous electrolyte includes at least one cyclic carbonate and at least one chain ester, and the mass percentage of the at least one cyclic carbonate to the at least one chain ester is above 0.1:1 and below 1.5:1, optionally below 1:1, and more optionally, between 0.2:1 and 1:1.
  • the cyclic carbonate is as described above.
  • the chain ester includes the chain carbonate and chain carboxylic acid ester as described above.
  • the total number of types of cyclic carbonates and chain esters in the non-aqueous electrolyte described in the present application is two or more.
  • the mass percentage of cyclic carbonate and chain ester in the non-aqueous electrolyte described in the present application will have a certain inhibitory effect on the decomposition and gas production of the electrolyte at high temperature of the sodium ion battery, and will have a certain promoting effect on the improvement of the electrochemical performance of the sodium ion battery.
  • the non-aqueous electrolyte contains one or more of the following combinations of substances: cyclic carbonates and chain carbonates; cyclic carbonates and chain carboxylates; cyclic carbonates and ethers; chain carbonates and chain carboxylates; chain carbonates and ethers; chain carboxylates and ethers; cyclic carbonates, chain carbonates and chain carboxylates; cyclic carbonates, chain carbonates and ethers; cyclic carbonates, chain carboxylates and ethers; chain carbonates, chain carboxylates and ethers.
  • the cyclic carbonate, chain carbonate, and chain carboxylic acid ester are as described above.
  • the ether is those that can be used as a solvent in a battery, and may optionally include the following substances: dioxolane (DOL), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2Me-THF), tetrahydropyran (THP), 1,2-dimethoxyethane (DME), diethylene glycol dimethyl ether (DG), 1,2-diethoxyethane, and 1,2-dibutoxyethane.
  • DOL dioxolane
  • THF tetrahydrofuran
  • 2Me-THF 2-methyltetrahydrofuran
  • TTP tetrahydropyran
  • DME 1,2-dimethoxyethane
  • DG diethylene glycol dimethyl ether
  • 1,2-diethoxyethane 1,2-diethoxyethane
  • 1,2-dibutoxyethane 1,2-di
  • the cyclic carbonate, chain carbonate, chain carboxylate, ether, etc. included in the non-aqueous electrolyte described in the present application exist as non-aqueous solvents.
  • the above-mentioned specific combination of non-aqueous solvents can not only improve the solubility and dispersion ability of the electrolyte sodium salt therein, but also participate in the formation of certain specific sodium ion solvation configurations, thereby effectively inhibiting the decomposition of the solvent in the electrolyte and the accompanying gas production problem, and further improving the electrochemical performance of the sodium ion battery (especially under high temperature conditions).
  • the non-aqueous solvent in the non-aqueous electrolyte includes one or more of propylene carbonate, ethyl methyl carbonate, ethyl acetate, diethyl carbonate, methyl propionate, ethyl propionate, diethylene glycol dimethyl ether, and fluoroethylene carbonate.
  • the non-aqueous electrolyte includes one or more of anhydride additives, fluorine-containing organic additives, nitrile additives, silicone additives, aldehyde additives, sulfur-containing additives, lithium salt additives, and potassium salt additives.
  • the total mass percentage of these additives in the non-aqueous electrolyte is greater than 0.001%, optionally greater than 0.2%, and less than 5%, optionally less than 4%.
  • additives can be optionally added to the electrolyte.
  • some additives can be added, which are specifically introduced as follows:
  • Anhydride additives are those that can be used in the electrolyte, and may include, but are not limited to, for example, one or more of succinic anhydride, maleic anhydride, caproic anhydride, maleic anhydride, succinic anhydride, butyric anhydride, crotonic anhydride, phthalic anhydride, pyromellitic anhydride, allyl succinic anhydride or 3-allyl succinic anhydride;
  • the fluorine-containing organic additive may include, but is not limited to, for example, one or more of fluoroethylene carbonate (FEC), bisfluoroethylene carbonate (DFEC), tris(2,2,2-trifluoroethyl) borate, tris(hexafluoroisopropyl) phosphate, and tris(2,2,2-trifluoroethyl) phosphite;
  • FEC fluoroethylene carbonate
  • DFEC bisfluoroethylene carbonate
  • tris(2,2,2-trifluoroethyl) borate tris(hexafluoroisopropyl) phosphate
  • tris(2,2,2-trifluoroethyl) phosphite tris(2,2,2-trifluoroethyl) phosphite
  • nitrile additives are those that can be used in the electrolyte, and may include, but are not limited to, for example, one or more of succinonitrile, malononitrile, isophthalonitrile, glutaronitrile, methoxypentafluorocyclotriphosphazene, acrylonitrile, cyclobutanenitrile, dimethylaminopropionitrile, ethoxypentafluorocyclotriphosphazene, dicyandiamide, phenoxypentafluorocyclotriphosphazene, ethyl cyanoacrylate, p-chlorophenylacetonitrile, 2-chloro-5-nitrobenzonitrile, p-toluenesulfonylmethyl isonitrile, adiponitrile and pimelonitrile;
  • the organosilicon additives are those that can be used in the electrolyte, and may include, but are not limited to, for example, one or more of silane, trimethylsilanol, trimethylchlorosilane, hexamethyldisiloxane, bis(diethylamino)silane, chloromethylsilane, octamethylcyclotetrasiloxane, N-methyl-N-trimethylsilanetrifluoroacetamide, diphenylsilanediol, phenyltrichlorosilane, chlorophenylsilane, tri(trimethylsilyl)phosphate, bromodifluoro(trimethylsilyl)methane or methyldichlorosilane;
  • Aldehyde additives may include, but are not limited to, for example, one or more of 2-imidazolecarboxaldehyde, 3-indolecarboxaldehyde, 2-pyrrolecarboxaldehyde, p-chlorobenzaldehyde, 6-chloronicotinaldehyde, 1-methylindole-3-carboxaldehyde, 2-formylthiazole, 5-chloro-2-furfural or oxazole-2-carboxaldehyde;
  • Sulfur-containing additives are those that can be used in the electrolyte, and may include, but are not limited to, for example, one or more of thiourea, sultone, 1,5-naphthalene disulfonic acid, dimethyl sulfone, cyclopentane, methylsulfonic anhydride, dimethyl sulfoxide, 2-mercapto-5-methyl-1,3,4-thiadiazole, dithiooxalamide, tert-butyldimethylsilyl trifluoromethanesulfonate, sodium 2,7-dihydroxynaphthalene-3,6-disulfonate, vinyl sulfate, propylene sulfate, butylene sulfate or vinyl sulfone;
  • the lithium salt additives are those that can be used in the electrolyte, and may include, but are not limited to, for example, one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoroacetate, lithium fluorosulfonate, lithium trifluoromethylsulfonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium methanesulfonate or lithium ethyl sulfate;
  • Potassium salt additives are those that can be used in the electrolyte, and may include, but are not limited to, for example, one or more of potassium hexafluorophosphate, potassium perchlorate, potassium tetrafluoroborate, potassium trifluoroacetate, potassium fluorosulfonate, potassium trifluoromethylsulfonate, potassium bis(fluorosulfonyl)imide, and potassium bis(trifluoromethylsulfonyl)imide;
  • the mass percentage of the additive in the non-aqueous electrolyte is above 0.001%, and can be optionally above 0.2%, the stability of the film formed on the electrode surface is improved; the upper limit is below 5%, and can be optionally below 4%, the possibility of excessive film formation on the electrode surface is reduced.
  • composition detection of the sodium ion battery electrolyte can refer to the sodium salt detection standard in the electrolyte: General Rules for Ion Chromatography Analysis Methods in the General Rules for Analysis Methods of Modern Analytical Instruments (JY/T 020-1996, issued on January 23, 1997, and implemented on April 1, 1997), and the sodium salt and anion in the electrolyte are tested and analyzed using the ion chromatography analysis method.
  • the second aspect of the present application provides a sodium ion battery, comprising a positive electrode sheet, a negative electrode sheet and the non-aqueous electrolyte described in the first aspect of the present application.
  • non-aqueous electrolyte are also applicable to the sodium ion battery described in the second aspect of the present application and the electrical device described in the third aspect of the present application.
  • the use of components such as the positive electrode sheet, the negative electrode sheet, and the separator other than the above-mentioned nonaqueous electrolyte is not particularly limited.
  • the positive electrode material used for the positive electrode sheet of the sodium ion battery in the present application is an electroactive material that can reversibly embed/extract sodium ions, which may include, but is not limited to, for example, any one of transition metal oxides, Prussian blue analogs, polyanion compounds and organic positive electrode materials, but the present application is not limited to these materials.
  • the negative electrode material used for the negative electrode sheet of the sodium ion battery in the present application is an electroactive material that can reversibly embed/extract sodium ions, and can be appropriately selected from any one of metallic sodium, hard carbon, graphite, metal oxides, metal sulfides, metal phosphides, and alloy negative electrodes, but the present application is not limited to these materials.
  • the positive electrode sheet and the negative electrode sheet may further include a conductive agent and a binder, the type and content of which are not specifically limited and can be selected and optimized according to actual needs.
  • the isolation membrane is often arranged between the positive electrode sheet and the negative electrode sheet to isolate the positive and negative electrode sheets.
  • the type and thickness of the isolation membrane are not subject to specific restrictions and can be any isolation membrane material used in existing batteries, such as polyethylene, polypropylene, polyvinylidene fluoride or its multilayer composite film, but the present application is not limited to these materials.
  • the sodium ion battery includes a positive electrode sheet and a negative electrode sheet, and the capacity ratio of the positive electrode sheet to the negative electrode sheet is 1:(1-1.3).
  • the capacity ratio of the positive electrode sheet to the negative electrode sheet is within the above range, the possibility of excessive film formation of the electrolyte on the electrode surface is reduced, and the continuous decomposition of the electrolyte and the accompanying gas production rate can be appropriately slowed down, thereby promoting the improvement of the electrochemical performance of the sodium ion battery (especially at high temperatures).
  • test method for the capacity ratio of the positive electrode sheet to the negative electrode sheet is as follows:
  • Positive electrode sheet capacity test The positive electrode sheet was punched into small discs with a diameter of 14 mm, and a metal sodium sheet was used as the negative electrode. A polypropylene film was used as the isolation film to assemble a button battery. The positive electrode charge specific capacity Q1 was obtained by constant current charge and discharge test at a voltage range of 1.5-4.2 V at a rate of 0.1C.
  • Negative electrode sheet capacity test The negative electrode sheet was punched into a small disc with a diameter of 14mm, and a metal sodium sheet was used as the negative electrode. A polypropylene film was used as the isolation film to assemble a button battery. A constant current charge and discharge test was performed in the voltage range of 0.005-2V. The discharge process was performed at a constant current of 0.05C, 40 ⁇ A and 10 ⁇ A to 0.005V. The charging process was performed at a constant current of 0.05C to 2V, and the charging specific capacity was recorded as Q2.
  • 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.
  • FIG1 is a secondary battery 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.
  • Secondary batteries include battery cells, battery modules, and battery packs.
  • battery cells can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG3 is a battery module 4 as an example.
  • a plurality of battery cells 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 battery cells 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.
  • the battery cells can be assembled into a battery pack.
  • the battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • 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.
  • the present application also provides an electrical device, the electrical device comprising the secondary battery provided in the second aspect of the present application.
  • the secondary battery can be used as a power source for the electrical device, and can also be used 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 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.
  • Example 1 In an argon atmosphere glove box (H 2 O ⁇ 0.1ppm, O 2 ⁇ 0.1ppm), non-aqueous organic solvents (see Table 1 below) were mixed uniformly according to the mass ratio in Table 1, and the following sodium salts were slowly added thereto: the first sodium salt, the second sodium salt and the additive in Table 1, and stirred uniformly to obtain the corresponding electrolyte;
  • Example 2 Other examples and comparative examples are similar to Example 1, using the respective non-aqueous solvents, the first sodium salt, the second sodium salt and the additives in Table 1 to prepare the corresponding non-aqueous electrolytes;
  • the positive electrode active material NaCu 1/9 Ni 2/9 Fe 1/3 Mn 1/3 O 2 , the conductive agent acetylene black, and the binder polyvinylidene fluoride are dissolved in a solvent N-methylpyrrolidone at a mass ratio of 94:3:3, and the mixture is fully stirred and mixed to obtain a positive electrode slurry; the positive electrode slurry is then evenly coated on the positive electrode current collector, and then dried, cold pressed, and cut to obtain a positive electrode sheet;
  • the active material hard carbon, the conductive agent acetylene black, the binder styrene butadiene rubber and the thickener sodium carboxymethyl cellulose are dissolved in the solvent deionized water at a weight ratio of 95:2:2:1, and the mixture is uniformly mixed with the solvent deionized water to prepare a negative electrode slurry; the negative electrode slurry is then uniformly coated on the negative electrode current collector copper foil, and then dried, cold pressed and cut to obtain a negative electrode sheet;
  • the isolation film uses polypropylene film
  • the positive electrode sheet, the separator, and the negative electrode sheet are stacked in order so that the separator is between the positive and negative electrode sheets to play an isolating role. Then they are wound and packaged to obtain a soft-pack battery. After vacuum drying, the electrolyte is injected. After formation and standing, a sodium ion soft-pack battery with a capacity of 2Ah is obtained.
  • PC propylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • EP ethyl propionate
  • DG diethylene glycol dimethyl ether
  • Sodium salt abbreviations are: NaPF 6 : sodium hexafluorophosphate, NaAsF 6 : sodium hexafluoroarsenate, NaClO 4 : sodium perchlorate, C 2 F 3 NaO 2 : sodium trifluoroacetate, Na(FSO 2 ) 2 N: sodium bis(fluorosulfonyl)imide, CF 3 NaO 3 S: sodium trifluoromethanesulfonate, C 2 BF 2 NaO 4 : sodium difluoro(oxalato)borate, C 4 BNaO 8 : sodium bis(oxalato)borate, NaPO 2 F 2 : sodium difluorophosphate, Na 2 PO 3 F: sodium monofluorophosphate, NaBF 4 : sodium tetrafluoroborate, BNaO 2 : sodium metaborate;
  • FEC fluoroethylene carbonate
  • the sodium ion battery is charged to 4.2V at a constant current of 1C, then charged at a constant voltage of 4.2V until the current is less than 0.05C, then discharged to 1.5V at a constant current of 1C, and then discharged to 1.5V at a constant current of 0.04C.
  • This is a charge and discharge process. Repeat the charge and discharge in this way, and calculate the capacity retention rate of the sodium ion battery after 500 cycles.
  • the specific calculation formula is as follows:
  • Capacity retention rate (%) of the sodium ion battery after 500 cycles at 25° C. (discharge capacity at the 500th cycle/discharge capacity at the first cycle) ⁇ 100%.
  • the sodium ion battery is charged to 4.2V at a constant current of 1C, then charged at a constant voltage of 4.2V until the current is less than 0.05C, then discharged to 1.5V at a constant current of 1C, and then discharged to 1.5V at a constant current of 0.04C.
  • This is a charge and discharge process. Repeat the charge and discharge in this way, and calculate the capacity retention rate of the sodium ion battery after 500 cycles.
  • the specific calculation formula is as follows:
  • Capacity retention rate (%) of the sodium ion battery after 500 cycles at 45° C. (discharge capacity at the 500th cycle/discharge capacity at the first cycle) ⁇ 100%.
  • the sodium ion battery was discharged at a constant current of 1/3C to 1.5V, then charged at a constant current of 1/3C to 4.2V, and charged at a constant voltage of 4.2V to a current less than 0.05C, and then placed in a thermostat at 60°C. After 2 months of storage, the sodium-ion battery after high-temperature storage was cooled to 25°C and discharged at a constant current of 1/3C to 1.5V.
  • the capacity retention rate of the sodium-ion battery after storage at 4.2V at 60°C was calculated as follows:
  • Capacity retention rate (%) of sodium ion battery after 60°C high temperature storage (discharge capacity at 25°C after high temperature storage/first discharge capacity at 25°C) ⁇ 100%.
  • the volume expansion ratio (%) of the sodium ion battery after being stored at 60°C for 2 months (V2-V1)/V1 ⁇ 100%.
  • test results of each embodiment and comparative example are as follows.
  • Example 1-43 significantly reduces the battery volume expansion rate after high-temperature storage while ensuring that the battery internal resistance is equivalent, and improves the capacity retention rate after room temperature, high-temperature cycling and high-temperature storage.
  • Comparative Examples 2-5 It can be seen from Comparative Examples 2-5 that by adding a second sodium salt containing electron-rich anions (having sulfonate/oxalate/phosphate/borate) to the electrolyte of Comparative Example 1, the capacity retention rate of the sodium ion battery after 500 cycles at 25°C and 45°C, and the capacity retention rate after high temperature (60°C) storage will both increase, and the volume expansion rate of the battery will decrease. This shows that the addition of a second sodium salt containing electron-rich anions can inhibit the decomposition of the electrolyte and the accompanying gas production problems to a certain extent.
  • a second sodium salt containing electron-rich anions having sulfonate/oxalate/phosphate/borate
  • Example 5 when 0.01M and 0.03M of the second sodium salt (Na(FSO 2 ) 2 N) are added (Examples 3-4), the electrochemical performance of the sodium ion battery is further improved, and various performance improvements are obvious compared with Comparative Examples 1-6. It can be concluded from Example 5 that when the addition amount of the second sodium salt (Na(FSO 2 ) 2 N) is 1 M, the resistance of the sodium ion battery is increased. This is because adding an excessive amount of the second sodium salt will cause excessive film formation and deteriorate the interface resistance, thereby affecting the kinetic process of the sodium ion battery.
  • the second sodium salt with oxalate also has a certain effect on the electrochemical performance of the sodium ion battery. From Examples 6-11, it can be concluded that after adding 0.0005M of the second sodium salt with oxalate (C 2 BF 2 NaO 4 ), the electrochemical performance of the sodium ion battery can be improved to a certain extent. When the addition amount exceeds 0.015M, the electrochemical performance of the corresponding battery deteriorates, indicating that excessive addition may affect the interface impedance and kinetic process of the sodium ion battery.
  • Example 43 it can be seen from Example 43 that after removing the additive FEC from the electrolyte, the electrochemical performance of the sodium ion battery deteriorates, indicating that the additive in the electrolyte will participate in the formation of the electrode/electrolyte interface film in the sodium ion battery, and also plays an important role in improving the electrochemical performance of the sodium ion battery.
  • the sodium ion battery non-aqueous electrolyte and sodium ion battery of the present application are targeted at solving the problems of electrolyte decomposition and gas production in the actual application of sodium ion batteries, and have good applicability in the industrialization process.

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Abstract

本申请提供一种非水电解液，其包含：第一钠盐，所述第一钠盐包括六氟磷酸钠、六氟砷酸钠、高氯酸钠及三氟乙酸钠中的至少一种；第二钠盐，所述第二钠盐包括具有磺酸根的钠盐、草酸根的钠盐、磷酸根的钠盐和硼酸根的钠盐中的一种、两种或更多种。本申请提供的非水电解液适用于钠离子电池，能够改善钠离子电池的常温及高温循环性能和高温储存后的容量保持率，并且能够显著降低钠离子电池在高温存储后的电池体积膨胀率。

Description

非水电解液及包含该电解液的钠离子电池和用电装置 技术领域
本申请涉及一种非水电解液，其包括至少两种钠盐，其中第一钠盐包括六氟磷酸钠、六氟砷酸钠、高氯酸钠及三氟乙酸钠中的至少一种，第二钠盐包括具有磺酸根的钠盐、草酸根的钠盐、磷酸根的钠盐和硼酸根的钠盐中的一种、两种或者更多种。此外，本申请还涉及包含所述非水电解液的钠离子电池和用电装置。
背景技术
为了实现国家“双碳”战略目标，新能源资源的利用变得尤为重要。锂离子电池由于具有较高的能量密度，因此在手机、电脑、电动汽车、便携式电子设备等领域展现出较好的发展前景。然而，由于锂资源有限且在全球的分布不均匀，并且近年来锂资源(如碳酸锂)的价格飞速增长，因此资源问题和成本问题将会限制锂离子电池的大规模长期使用。由此，进一步开发高性能和低成本的新电池体系具有重要的研究意义。
与锂资源相比，钠资源在地壳中的储量更为丰富，其丰度位于第6。而且，钠资源在地壳的分布比较均匀，在全球各地都存在。因此，钠资源的利用将不受储量和地域的严重限制。更重要的是，钠资源的成本较低，适合大规模和长期使用。因此，在资源和成本问题上，钠离子电池比锂离子电池具有更大的优势。此外，金属钠与锂具有相似的物理化学性质，因此，钠离子电池可以在一定程度上借鉴锂离子电池的开发经验并沿用其生产工序。
钠离子电池在电化学储能领域展现出较好的发展前景，钠离子电池的产业化开发具有重大的战略意义和经济价值。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种适用于钠离子电池，能够改善钠离子电池的高温循环性能和高温储存后的容量保持率，并且能够降低钠离子电池在高温存储后的电池体积膨胀率的非水电解液，以及包括该非水电解液的钠离子电池和用电装置。
为了实现上述目的，本申请第一方面提供一种非水电解液，其包含：
第一钠盐，其包括六氟磷酸钠(NaPF6)、六氟砷酸钠(NaAsF6)、高氯酸钠(NaClO4)及三氟乙酸钠(CF3COONa)中的至少一种，可选地，所述第一钠盐为六氟磷酸钠；
第二钠盐，其包括具有磺酸根的钠盐、草酸根的钠盐、磷酸根的钠盐和硼酸根的钠盐中的一种、两种或更多种；可选地，所述第二钠盐包括具有磺酸根的钠盐、具有草酸根的钠盐、具有磷酸根的钠盐和具有硼酸根的钠盐。
非水电解液是通过将含有富电子阴离子的钠盐电解质等溶于非水溶剂中得到。如上所述，通过选择地添加上述第一钠盐和第二钠盐，能够调控电解液中钠离子的溶剂化结构和溶剂分子的化学环境，从而能够解决钠离子电池中溶剂持续分解导致的产气问题。
在任意实施方式中，所述非水电解液中，第一钠盐与第二钠盐的摩尔浓度比在1/1以上，可选为3/1以上，且在40/1以下，更可选为15/1以下。
在整个电解液中，第一钠盐与第二钠盐的摩尔浓度比在上述范围内，能够降低在电极表面过度成膜的风险，减小钠离子在电极/电解液界面传输的阻力，从而对钠离子电池动力学过程的影响较小。
在任意实施方式中，所述具有磺酸根的钠盐包括氟磺酸钠(FSO3Na)、三氟甲基磺酸钠(NaSO3CF3)、双(氟磺酰)亚胺钠(Na[(FSO2)2N])、双(三氟甲基磺酰)亚胺钠(Na[(CF3SO2)2N])、甲基磺酸钠(CH3SO3Na)、乙烯基磺酸钠(C2H3NaO3S)、甲基硫酸钠(CH3OSO3Na)、甲基硫代磺酸钠(CH3NaO2S2)、1,2-乙烷基二磺酸钠(NaO3SCH2CH2SO3Na)、乙基硫酸钠(C2H5NaO4S)、丙烷磺酸钠(C3H7NaO3S)、乙硫代磺酸钠(C2H5NaO2S2)、2-碘苯磺酸钠(C6H4INaO3S)、4-硝基苯甲磺酸钠(C7H6NNaO5S)、苯乙烯磺酸钠(C8H7NaO3S)、4-异丙苯磺酸钠(C9H11NaO3S)、苯酚磺酸钠(C6H5NaO4S)、β-苯乙烯磺酸钠(C8H7NaO3S)、环己烷磺酸钠(C6H11NaO3S)、2-环己胺基乙磺酸钠(C8H16NNaO3S)、4-氨基-N-甲基苯磺酰胺(C7H10N2O2S)、聚二硫二丙烷磺酸钠(C6H12Na2O6S4)、吡啶-3-亚磺酸钠(C5H4NNaO2S)、哌嗪-1,4-二乙磺酸单钠盐(C8H17N2NaO6S2)中的一种及以上，可选地包括氟磺酸钠、三氟甲基磺酸钠、双(氟磺酰)亚胺钠、双(三氟甲基磺酰)亚胺钠、甲基磺酸钠、甲基硫酸钠中的一种及以上。
在任意实施方式中，所述具有磺酸根的钠盐在所述非水电解液中的浓度在0.0005-1mol/L范围内，可选地在0.01-0.3mol/L范围内。
第二钠盐中，含有磺酸根的钠盐在电解液中的浓度在0.0005mol/L以上，可具有提高第一钠盐在电解液中稳定性的效果，而且，其使得钠离子电池能够在电化学反应过程中在电极表面形成稳定的固态电解质界面膜，有效抑制电解液中溶 剂在电极表面的分解和产气现象，提高钠离子电池(尤其在高温下)的电化学性能。可选地，含有磺酸根的钠盐在电解液中的浓度可为0.01mol/L以上。此外，具有磺酸根的钠盐在电解液中的浓度在0.3mol/L以下，能够更有效地减小在电极上过度成膜的风险，因而不会对钠离子电池高温下电化学性能产生较大的影响。可选地，该浓度可为0.15mol/L以下。
在任意实施方式中，所述具有草酸根的钠盐包括草酸钠(Na2C2O4)、双(草酸根)硼酸钠(C4BNaO8)、二氟(草酸根)硼酸钠(C2BF2NaO4)、四氟(草酸根)磷酸钠(C2F4NaO4P)、二氟双(草酸根)磷酸钠(C4F2NaO8P)中的一种及以上。
在任意实施方式中，所述具有草酸根的钠盐在所述非水电解液中的浓度在0.0005-0.1mol/L范围内，可选地在0.006-0.08mol/L范围内，进一步可选地在0.01-0.02mol/L范围内。
第二钠盐中，含有草酸根的钠盐在电解液中的浓度在0.0005mol/L以上，能够明显提高电解液中第一钠盐稳定性，且对钠离子电池高温下的循环性能及存储后容量保持率的提升具有改善效果。可选地，该浓度可为0.006mol/L以上，进一步可选为0.01mol/L以上。此外，该浓度最好在0.08mol/L以下，这样能够更有效地降低该具有草酸根的钠盐在电极上过度成膜的可能性，因而不会对钠离子电池充放电过程中动力学过程的产生较大影响。
在任意实施方式中，所述具有磷酸根的钠盐包括二氟磷酸钠(NaPO2F2)、单氟磷酸钠(Na2PO3F)、三偏磷酸钠(Na3P3O9)、六偏磷酸钠(Na6P6O18)、羟基乙叉二膦酸钠(C2H7NaO7P2)、氯屈膦酸二钠(CH2Cl2Na2O6P2)、奥帕膦酸钠(C5H15NO7P2)、二乙烯三胺五亚甲基膦酸钠(C9H18N3Na10O15P5)、三聚磷酸钠(Na5P3O10)及磷酸苯基二钠(C6H5Na2O4P)中的一种及以上，可选地包括二氟磷酸钠(NaPO2F2)及氟磷酸钠(Na2PO3F)中的一种及以上。
在任意实施方式中，所述具有磷酸根的钠盐在所述非水电解液中的浓度在0.0005-0.12范围内、可选在0.01-0.05mol/L范围内，更可选在0.01-0.03mol/范围内。
第二钠盐中，含有磷酸根的钠盐在非水电解液中的摩尔浓度在0.0005mol/L以上，可以提高电解液中第一钠盐的稳定性，并且使得钠离子电池能够在化成过程中在电极表面形成以无机成分为主的薄而坚实的固态电解质膜，其可以显著抑制钠离子电池中的产气问题。可选地，该浓度为0.01mol/L以上。此外，该浓度在0.12mol/L以下，能够有效地降低含有磷酸根的钠盐在电极表面过度成膜的可能性，因而不会对钠离子电池充放电过程中的动力学过程产生较大的影响。
在任意实施方式中，所述具有硼酸根的钠盐包括四氟硼酸钠(NaBF4)、偏硼酸钠(BNaO2)、四苯基硼酸钠((C6H5)4BNa)、四[3,5-双(三氟甲基)苯基]硼 酸钠(C32H12BF24Na)中的一种及以上，可选地包括四氟硼酸钠、偏硼酸钠及四苯基硼酸钠中的一种及以上，进一步可选地包括四氟硼酸钠及偏硼酸钠中的一种及以上。
在任意实施方式中，所述具有硼酸根的钠盐在所述非水电解液中的浓度在0.0005-0.05mol/L范围内，可选地在0.01-0.04mol/L范围内。
第二钠盐中，含有硼酸根的钠盐在非水电解液中的摩尔浓度在0.0005mol/L以上，能够对提高电解液中第一钠盐稳定性有一定效果，并且使得钠离子电池可以在电极表面形成薄而致密的固态电解质界面膜，从而抑制电解液中的溶剂在电极/电解液界面的持续分解，由此对钠离子电池中的产气问题有明显地抑制效果，对钠离子电池(尤其在高温下)的循环和高温存储后的容量保持率也有提升作用。此外，该浓度在0.05mol/L以下，能够有效地降低含硼酸根的钠盐在电极表面过度成膜的可能性，因而不会对钠离子电池充放电过程中动力学过程产生较大的影响。
在任意实施方式中，第一钠盐中，在六氟磷酸钠与六氟砷酸钠、高氯酸钠及三氟乙酸钠中的至少一种联用时，除六氟磷酸钠以外的其他钠盐在非水电解液中的浓度为0.001mol/L以上，可选为0.01mol/L以上，进一步可选为0.03mol/L以上，且为1mol/L以下，可选为0.5mol/L以下。
第一钠盐中，若除六氟磷酸钠(NaPF6)以外的其他钠盐在非水溶剂中的浓度为0.001mol/L以上，则对钠离子电池高温下的电化学性能具有提高效果。若其他钠盐在非水溶剂中的浓度占比在1mol/L以下，可以在一定程度上调控电解液中钠离子的溶剂化结构和非水溶剂分子的化学环境，对高温条件下电解液分解和产气问题存在抑制效果，对钠离子电池高温下电化学性能的提升具有促进效果。
在任意实施方式中，所述第二钠盐包括具有磺酸根的钠盐，还包括具有草酸根的钠盐、具有磷酸根的钠盐及具有硼酸根的钠盐中的一种及以上。
第二钠盐中，具有磺酸根的钠盐与具有草酸根、磷酸根和硼酸根中的一种及以上钠盐的联用会产生协同作用，协同参与电解液中钠离子的溶剂化过程，为钠离子提供部分电子，可以有效抑制钠离子对非水溶剂分子的强吸电子性，能够显著抑制电解液的持续分解和产气；此外，具有磺酸根的钠盐与具有草酸根、磷酸根和硼酸根中的一种及以上钠盐的联用可以在电极/电解液界面形成富含无机成分的较薄且致密的固态电解质界面膜，对钠离子电池(尤其在高温下)的电化学性能具有明显的提升效果。
在任意实施方式中，所述第二钠盐包括具有磺酸根的钠盐和具有草酸根的钠盐，可选地，具有磺酸根的钠盐和具有草酸根的钠盐的摩尔比为0.03/1至70/1，可选为0.5/1至20/1。
具有草酸根的钠盐与具有磷酸根的钠盐和硼酸根的钠盐联用对电解液分解和产气的抑制效果有改善作用。当具有磺酸根的钠盐与具有草酸根的钠盐的摩尔比为1/1至10/1时，钠离子电池充放电过程中在电极表面形成以无机成分为主的较薄的固态电解质界面膜的可能性较大。
在任意实施方式中，所述非水电解液包含环状碳酸酯，所述环状碳酸酯在非水电解液中的质量浓度占比在10％以上，可选为15％以上，且在60％以下。
环状碳酸酯在非水电解液中的质量浓度占比在上述范围内，则可以在基本不影响钠离子迁移速率的情况下，在一定程度上能够提高钠离子电池在高温条件下电极/电解液界面膜的稳定性。
在任意实施方式中，所述非水电解液包含链状碳酸酯和链状羧酸酯，所述链状碳酸酯和链状羧酸酯之和在所述非水电解液中的质量百分比在40％以上，可选为50％以上，更可选为60％以上，且在90％以下，可选在85％以下，进一步可选在80％以下。
所述链状碳酸酯和链状羧酸酯在电解液中的质量百分比在40％以上，可选为50％以上，更可选为60％以上，则使得电解液的粘度不会过高；其含量上限为90％以下，可选为85％以下，进一步可选为80％以下，则离子电导率下降幅度不大，对钠离子电池电化学性能的影响较小。
在任意实施方式中，所述非水电解液包括至少一种环状碳酸酯与至少一种链状酯，所述至少一种环状碳酸酯与所述至少一种链状酯的质量百分比在0.1:1以上，且在1.5:1以下，可选地在1:1以下，更可选地，在0.2:1至1:1之间。
本申请所述的非水电解液中环状碳酸酯与链状酯的质量百分比在上述范围内，则对钠离子电池高温下的电解液分解和产气现象会有一定的抑制效果，并对钠离子电池电化学性能的提高具有一定的促进作用。
在任意实施方式中，所述非水电解液包含以下物质组合中的一种及以上：环状碳酸酯与链状碳酸酯；环状碳酸酯与链状羧酸酯；环状碳酸酯与醚；链状碳酸酯与链状羧酸酯；链状碳酸酯与醚；链状羧酸酯与醚；环状碳酸酯、链状碳酸酯与链状羧酸酯；环状碳酸酯、链状碳酸酯与醚；环状碳酸酯、链状羧酸酯与醚；链状碳酸酯、链状羧酸酯与醚。
本申请所述非水电解液中包括的环状碳酸酯、链状碳酸酯、链状羧酸酯、醚等作为非水溶剂而存在。上述这些特定组合的非水溶剂不仅可以提高电解质钠盐在其中的溶解和分散能力，还可以参与形成某些特定的钠离子溶剂化构型，从而 有效抑制电解液中溶剂的分解和伴随的产气问题，进一步提高钠离子电池(尤其在高温条件下)的电化学性能。
在任意实施方式中，所述非水电解液中的非水溶剂包括碳酸丙烯酯、碳酸甲乙酯、乙酸乙酯、碳酸二乙酯、丙酸甲酯、丙酸乙酯、二乙二醇二甲醚、氟代碳酸乙烯酯中的一种及以上。
在任意实施方式中，所述非水电解液包括酸酐类添加剂、含氟有机添加剂、腈类添加剂、有机硅类添加剂、醛类添加剂、含硫类添加剂、锂盐类添加剂、钾盐类添加剂中的一种或两种以上，可选地，这些添加剂总和在非水电解液中的质量百分比为0.001％以上，可选为0.2％以上，且为5％以下，可选为4％以下。
为了进一步优化钠离子电池充放电过程中在电极表面形成膜的稳定性，并得到以无机成分为主的薄而致密的电极/电解液界面膜，可选在电解液中加入上述添加剂。所述添加剂在非水电解液中的质量百分比为0.001％以上、可选为0.2％以上，则对电极表面形成膜的稳定性有提升效果；其上限在5％以下、可选为4％以下，则在电极表面过度成膜的可能性下降。
本申请第二方面提供一种钠离子电池，其包括正极片、负极片和本申请第一方面所述的非水电解液。
本申请的第三方面提供一种用电装置，其包括本申请第一方面所述的非水电解液或本申请第二方面所述的钠离子电池。
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顶盖组件
具体实施方式
以下，适当地参照附图详细说明具体公开了非水电解液和钠离子电池的实施方式。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2-6。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，可选是顺序进行的。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)。
钠离子电池主要由可嵌入/脱出钠离子的正负极材料、含有钠盐和非水溶剂的电解液共同组成。其中，电解液在钠离子电池开发过程中起着重要的作用。电解液作为正负极之间钠离子传输的桥梁，决定着正负极材料的容量发挥，从而影响着钠离子电池的电化学性能。然而，电解液也会受到正负极材料、环境(如温 度)、测试条件(如电压)等因素的影响。
通常，钠离子电池电解液受负极材料的影响比较大。钠离子电池的负极材料包括金属钠、碳材料(如硬碳、石墨等)、金属化合物(如金属氧化物、合金等)等。这些材料的嵌钠电位往往比较低，这可能会导致电解液发生还原分解。尤其在高温下，电解液中的溶剂在负极表面还原分解的问题更为严重。溶剂的持续分解将使得钠离子电池面临严重的产气问题，产生的大量气体(如二氧化碳、一氧化碳、氢气、丙烯等)在钠离子电池内积聚，将增加钠离子电池的安全使用风险。此外，溶剂的持续分解往往会形成大量有机类分解产物，这些有机物沉积在负极表面形成厚且不均匀的有机固态电解质(SEI)膜，会显著减缓钠离子在负极/电解液界面的传输动力学，最终恶化钠离子电池(尤其在高温下)的电化学性能(如循环及倍率性能等)；而且，有机类SEI膜的不断沉积还会使电极发生膨胀，电极的膨胀和大量的产气导致钠离子电池发生体积膨胀，这会使得钠离子电池在使用过程中存在一定的安全隐患。
钠离子电池电解液还会受到正极材料的工作电压、化学组成等因素的影响。目前，钠离子电池的正极材料主要有过渡金属氧化物、聚阴离子化合物、普鲁士蓝类似物等。这些正极材料往往在高电压区间发生钠离子的嵌入/脱出反应。在高压状态时，电解液会在正极发生氧化分解并伴随着大量的气体析出。而且，一些金属氧化物正极材料中的过渡金属(如铁、钴、镍等)具有较强的催化性能，可能催化溶剂和电解液/正极界面膜的分解。这会使得钠离子电池在使用过程中需要持续消耗电解液成膜，从而损耗大量的可逆活性钠和溶剂，最终导致钠离子电池的使用寿命显著降低。在高温条件下，电解液的分解速率往往会显著加快，产气问题更加严重。而且，持续的溶剂分解会产生大量的有机类分解产物沉积在正极表面，形成厚且不均匀的电解液/正极界面膜，严重地增加钠离子在电解液/正极界面的传输阻力，最终影响着钠离子电池的电化学性能。
在钠离子电池的实际使用过程中，伴随着电化学反应的进行，电池会持续放热升温。在高温条件下，电解液分解导致的产气问题更加严重，这将影响到钠离子电池的产业化发展。因此，通过合理的电解液设计来满足钠离子电池在高温下的使用需求，提高钠离子电池的安全和电化学性能具有重要的研究意义。
我们研究发现，钠离子电池的产气问题主要源于溶剂在电极/电解液界面的持续分解，这跟溶剂在电解液中的化学环境密切相关。通常，在钠离子电池电解液中，由于钠离子和溶剂分子静电势的差异，钠离子会通过静电相互作用吸引溶剂分子分布在其周围形成溶剂化的钠离子壳层结构。然而，由于钠离子的强吸电子性，一部分溶剂分子中的电子会转移到钠离子中，使得壳层结构中溶剂分子内的化学键强变弱，导致这些溶剂分子的化学稳定性变差。同时，跟纯溶剂分子相 比，溶剂化钠离子的最低未占有轨道(LUMO)的能量进一步降低，这将使得钠离子溶剂化外壳结构中的溶剂分子更容易在负极表面得到电子发生还原分解反应，导致电解液相对于纯溶剂更容易发生还原分解。因此，调控溶剂分子在钠离子电池电解液中的化学环境是抑制溶剂分解产气的关键。
根据现有的报道和我们系统的研究发现，金属盐的组成(尤其是金属盐中的阴离子)对电池的化学及电化学稳定性起着至关重要的作用。在相同溶剂中，金属盐的种类决定着电解液的溶剂化结构与热力学稳定性，从而影响电解液的分解行为，进而调控着电极/电解液的界面性质与电极的电化学性能。将富电子的阴离子引入钠离子电池电解液体系可以显著抑制溶剂的分解和产气问题。富电子的阴离子参与到钠离子的溶剂化结构中，可以给钠离子提供一部分电子，削弱钠离子对溶剂分子的强吸电子性能，减少溶剂分子由于局部电子缺失导致的化学键变弱和分子结构的不稳定性。而且，我们研究发现，阴离子种类和半径的选择可以进一步调控电解液中钠离子的溶剂化结构和溶剂分子的化学环境。更重要的是，一些不同种类的阴离子在电解液中还具有协同作用。这些阴离子作为电子“海绵”为钠离子溶剂化壳层提供电子，协同提高电解液的化学稳定性、电化学稳定性及热稳定性。此外，我们研究发现，有些含氟阴离子中的部分电子转移到钠离子中会使其离子结构中局部化学键变弱，在钠离子电池的电化学反应过程中优先分解形成富含无机成分的薄而致密的电极/电解液界面膜，显著抑制电解液中溶剂的持续分解和产气现象，可以有效提高钠离子电池(尤其在高温下)的电化学性能。
因此，本申请的目的在于通过调控电解液中钠离子的溶剂化结构和溶剂分子的化学环境，提供一种含富电子阴离子的钠离子电池电解液及钠离子电池，以解决钠离子电池中溶剂持续分解导致的产气问题。
基于上述内容，本申请第一方面提供一种非水电解液，其包含：
第一钠盐，其包括六氟磷酸钠(NaPF6)、六氟砷酸钠(NaAsF6)、高氯酸钠(NaClO4)及三氟乙酸钠(CF3COONa)中的至少一种，可选地，所述第一钠盐为六氟磷酸钠；
第二钠盐，其包括具有磺酸根的钠盐、草酸根的钠盐、磷酸根的钠盐和硼酸根的钠盐中的一种、两种或者更多种；可选地，所述第二钠盐包括具有磺酸根的钠盐、具有草酸根的钠盐、具有磷酸根的钠盐和具有硼酸根的钠盐。
本申请中，具有磺酸根的钠盐中所述磺酸根包括，但不限于，例如SO3 2-、(SO3CF3)-、[N(FSO2)2]-等；具有草酸根的钠盐中所述草酸根包括，但不限于，例如C2O4 2-、(C2O4BF2)-、[(C2O4)2B]-等；具有硼酸根的钠盐中所述硼酸根包括，但不限于，例如BF4 -、BO2 -等；具有磷酸根的钠盐中所述磷酸根包括，但不限于，例如PO4 3-、(PO3F)2-、(PO2F2)-等。
非水电解液是通过将含有富电子阴离子的钠盐电解质等溶于非水溶剂中得到。如上所述，通过选择地添加上述第一钠盐和第二钠盐，能够调控电解液中钠离子的溶剂化结构和溶剂分子的化学环境，从而能够解决钠离子电池中溶剂持续分解导致的产气问题。
在一些可选实施方式中，所述非水电解液中，第一钠盐与第二钠盐的摩尔浓度比在1/1以上，可选为2/1以上，更可选为5/1以上，进一步可选为10/1以上，且在1000/1以下，可选为40/1以下，更可选为20/1以下。
在一些实施方式中，所述非水电解液中，第一钠盐与第二钠盐的摩尔浓度比在1/1以上，可选为3/1以上，且在40/1以下，更可选为15/1以下。
在整个电解液中，第一钠盐与第二钠盐的摩尔浓度比在上述范围内，能够降低在电极表面过度成膜的风险，减小钠离子在电极/电解液界面传输的阻力，从而对钠离子电池动力学过程的影响较小。
在一些实施方式中，所述具有磺酸根的钠盐包括氟磺酸钠(FSO3Na)、三氟甲基磺酸钠(NaSO3CF3)、双(氟磺酰)亚胺钠(Na[(FSO2)2N])、双(三氟甲基磺酰)亚胺钠(Na[(CF3SO2)2N])、甲基磺酸钠(CH3SO3Na)、乙烯基磺酸钠(C2H3NaO3S)、甲基硫酸钠(CH3OSO3Na)、甲基硫代磺酸钠(CH3NaO2S2)、1,2-乙烷基二磺酸钠(NaO3SCH2CH2SO3Na)、乙基硫酸钠(C2H5NaO4S)、丙烷磺酸钠(C3H7NaO3S)、乙硫代磺酸钠(C2H5NaO2S2)、2-碘苯磺酸钠(C6H4INaO3S)、4-硝基苯甲磺酸钠(C7H6NNaO5S)、苯乙烯磺酸钠(C8H7NaO3S)、4-异丙苯磺酸钠(C9H11NaO3S)、苯酚磺酸钠(C6H5NaO4S)、β-苯乙烯磺酸钠(C8H7NaO3S)、环己烷磺酸钠(C6H11NaO3S)、2-环己胺基乙磺酸钠(C8H16NNaO3S)、4-氨基-N-甲基苯磺酰胺(C7H10N2O2S)、聚二硫二丙烷磺酸钠(C6H12Na2O6S4)、吡啶-3-亚磺酸钠(C5H4NNaO2S)、哌嗪-1,4-二乙磺酸单钠盐(C8H17N2NaO6S2)中的一种及以上，可选地包括氟磺酸钠、三氟甲基磺酸钠、双(氟磺酰)亚胺钠、双(三氟甲基磺酰)亚胺钠、甲基磺酸钠、甲基硫酸钠中的一种及以上。
在一些实施方式中，所述具有磺酸根的钠盐在所述非水电解液中的浓度在0.0005-1mol/L范围内，可选地在0.01-0.3mol/L范围内。
在一些可选实施方式中，所述具有磺酸根的钠盐在所述非水电解液中的浓度为0.001mol/L以上，可选为0.01mol/L以上，且为0.3mol/L以下，可选为0.15mol/L以下。
第二钠盐中，含有磺酸根的钠盐在电解液中的浓度在0.0005mol/L以上，可具有提高第一钠盐在电解液中稳定性的效果，而且，其使得钠离子电池能够在电化学反应过程中在电极表面形成稳定的固态电解质界面膜，有效抑制电解液中溶 剂在电极表面的分解和产气现象，提高钠离子电池(尤其在高温下)的电化学性能。可选地，含有磺酸根的钠盐在电解液中的浓度可为0.01mol/L以上。此外，具有磺酸根的钠盐在电解液中的浓度在1mol/L以下，能够更有效地减小在电极上过度成膜的风险，因而不会对钠离子电池高温下电化学性能产生较大的影响。可选地，该浓度可为0.15mol/L以下。
在一些实施方式中，所述具有草酸根的钠盐包括草酸钠(Na2C2O4)、双(草酸根)硼酸钠(C4BNaO8)、二氟(草酸根)硼酸钠(C2BF2NaO4)、四氟(草酸根)磷酸钠(C2F4NaO4P)、二氟双(草酸根)磷酸钠(C4F2NaO8P)中的一种及以上。
双(草酸根)硼酸钠和二氟(草酸根)硼酸钠中既有草酸根又有硼酸根，其可归类于具有草酸根的钠盐也可归类于具有硼酸根的钠盐，此处归类于具有草酸根的钠盐。类似地，四氟(草酸根)磷酸钠、二氟双(草酸根)磷酸钠也可归类于具有磷酸根的钠盐，本文中将其归类于具有草酸根的钠盐。
在一些可选实施方式中，所述具有草酸根的钠盐在所述非水电解液中的浓度在0.001mol/L以上，可选地在0.006mol/L以上，进一步可选地在0.01mol/L以上，且在0.08mol/L以下。
在一些实施方式中，所述具有草酸根的钠盐在所述非水电解液中的浓度在0.0005-0.1mol/L范围内，可选地在0.006-0.08mol/L范围内，进一步可选地在0.01-0.02mol/L范围内。
第二钠盐中，含有草酸根的钠盐在电解液中的浓度在0.0005mol/L以上，能够明显提高电解液中第一钠盐稳定性，且对钠离子电池高温下的循环性能及存储后容量保持率的提升具有改善效果。可选地，该浓度可为0.006mol/L以上，进一步可选为0.01mol/L以上。此外，该浓度最好在0.08mol/L以下，这样能够更有效地降低该具有草酸根的钠盐在电极上过度成膜的可能性，因而不会对钠离子电池充放电过程中动力学过程的产生较大影响。
在一些实施方式中，所述具有磷酸根的钠盐包括二氟磷酸钠(NaPO2F2)、单氟磷酸钠(Na2PO3F)、三偏磷酸钠(Na3P3O9)、六偏磷酸钠(Na6P6O18)、羟基乙叉二膦酸钠(C2H7NaO7P2)、氯屈膦酸二钠(CH2Cl2Na2O6P2)、奥帕膦酸钠(C5H15NO7P2)、二乙烯三胺五亚甲基膦酸钠(C9H18N3Na10O15P5)、三聚磷酸钠(Na5P3O10)及磷酸苯基二钠(C6H5Na2O4P)中的一种及以上，可选地包括二氟磷酸钠(NaPO2F2)及氟磷酸钠(Na2PO3F)中的一种及以上。
在一些可选的实施方式中，所述具有磷酸根的钠盐在所述非水电解液中的浓度在0.001mol/L以上，可选为0.01mol/L以上，且在0.12mol/L以下。
在一些实施方式中，所述具有磷酸根的钠盐在所述非水电解液中的浓度在0.0005-0.12范围内、可选在0.01-0.05mol/L范围内，更可选在0.01-0.03mol/范围内
第二钠盐中，含有磷酸根的钠盐在非水电解液中的摩尔浓度在0.0005mol/L以上，可以提高电解液中第一钠盐的稳定性，并且使得钠离子电池能够在化成过程中在电极表面形成以无机成分为主的薄而坚实的固态电解质膜，其可以显著抑制钠离子电池中的产气问题。可选地，该浓度为0.01mol/L以上。此外，该浓度在0.12mol/L以下，能够有效地降低含有磷酸根的钠盐在电极表面过度成膜的可能性，因而不会对钠离子电池充放电过程中的动力学过程产生较大的影响。
在一些实施方式中，所述具有硼酸根的钠盐包括四氟硼酸钠(NaBF4)、偏硼酸钠(BNaO2)、四苯基硼酸钠((C6H5)4BNa)、四[3,5-双(三氟甲基)苯基]硼酸钠(C32H12BF24Na)中的一种及以上，可选地包括四氟硼酸钠、偏硼酸钠及四苯基硼酸钠中的一种及以上，进一步可选地包括四氟硼酸钠及偏硼酸钠中的一种及以上。
在一些可选的实施方式中，所述具有硼酸根的钠盐在所述非水电解液中的浓度在0.001mol/L以上，可选为0.008mol/L以上，且在0.03mol/L以下。
在一些实施方式中，所述具有硼酸根的钠盐在所述非水电解液中的浓度在0.0005-0.05mol/L范围内，可选地在0.01-0.04mol/L范围内。
第二钠盐中，含有硼酸根的钠盐在非水电解液中的摩尔浓度在0.0005mol/L以上，能够对提高电解液中第一钠盐稳定性有一定效果，并且使得钠离子电池在电化学反应过程中能够在电极表面形成薄而致密的固态电解质界面膜，从而抑制电解液中的溶剂在电极/电解液界面的持续分解，由此对钠离子电池中的产气问题有明显地抑制效果，对钠离子电池(尤其在高温下)的循环和高温存储后的容量保持率也有提升作用。此外，该浓度在0.05mol/L以下，能够有效地降低含硼酸根的钠盐在电极表面过度成膜的可能性，因而不会对钠离子电池充放电过程中动力学过程产生较大的影响。还可选地，所述具有硼酸根的钠盐在所述非水电解液中的浓度在0.01-0.02mol/L范围内。
在一些实施方式中，第一钠盐中，在六氟磷酸钠与六氟砷酸钠、高氯酸钠及三氟乙酸钠中的至少一种联用时，除六氟磷酸钠以外的其他钠盐在非水电解液中的浓度为0.001mol/L以上，可选为0.01mol/L以上，进一步可选为0.03mol/L以上，且为1mol/L以下，可选为0.5mol/L以下。
可选地，第一钠盐中，除六氟磷酸钠(NaPF6)以外的其他钠盐在非水溶剂中的浓度优选为0.005mol/L以上，更优选为0.01mol/L以上，进一步优选为0.02mol/L以上，其浓度上限优选0.7mol/L以下，进一步优选为0.6mol/L以下。
六氟磷酸钠在本申请所述的非水电解液中的浓度可为任何浓度或常规浓度，可选地，六氟磷酸钠在本申请所述的非水电解液中的浓度为0.4-1.6mol/L。
第一钠盐中，若除六氟磷酸钠(NaPF6)以外的其他钠盐在非水溶剂中的浓度为0.001mol/L以上，则对钠离子电池高温下的电化学性能具有提高效果。若其他钠盐在非水溶剂中的浓度占比在1mol/L以下，可以在一定程度上调控电解液中钠离子的溶剂化结构和非水溶剂分子的化学环境，对高温条件下电解液分解和产气问题存在抑制效果，对钠离子电池高温下电化学性能的提升具有促进效果。
在一些实施方式中，所述第二钠盐包括具有磺酸根的钠盐，还包括具有草酸根的钠盐、具有磷酸根的钠盐及具有硼酸根的钠盐中的一种及以上。
第二钠盐中，具有磺酸根的钠盐与具有草酸根、磷酸根和硼酸根中的一种及以上钠盐的联用会产生协同作用，协同参与电解液中钠离子的溶剂化过程，为钠离子提供部分电子，可以有效抑制钠离子对非水溶剂分子的强吸电子性，能够显著抑制电解液的持续分解和产气；此外，具有磺酸根的钠盐与具有草酸根、磷酸根和硼酸根中的一种及以上钠盐的联用可以在电极/电解液界面形成富含无机成分的较薄且致密的固态电解质界面膜，对钠离子电池(尤其在高温下)的电化学性能具有明显的提升效果。
在一些实施方式中，所述第二钠盐包括具有磺酸根的钠盐和具有草酸根的钠盐，可选地，具有磺酸根的钠盐和具有草酸根的钠盐的摩尔比为0.03/1至70/1，可选为0.5/1至20/1。还可选地，具有磺酸根的钠盐和具有草酸根的钠盐的摩尔比为1/1至10/1。
具有草酸根的钠盐与具有磷酸根的钠盐和硼酸根的钠盐联用对电解液分解和产气的抑制效果有改善作用。当具有磺酸根的钠盐与具有草酸根的钠盐的摩尔比为1/1至10/1时，钠离子电池充放电过程中在电极表面形成以无机成分为主的较薄的固态电解质界面膜的可能性较大。
所述非水电解液中的非水溶剂可包含环状碳酸酯、线状酯和/或醚，可选地，所述非水溶剂包括环状碳酸酯、链状碳酸酯、链状羧酸酯和醚中的一种及以上。
在一些实施方式中，所述非水电解液包含环状碳酸酯，所述环状碳酸酯在非水电解液中的质量浓度占比在10％以上，可选为15％以上，且在60％以下。
所述环状碳酸酯为常在电池中用作溶剂的那些，包括、但不限于，例如，碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸丁烯酯(BC)、碳酸亚乙烯酯(VC)、氟代碳酸乙烯酯(FEC)、亚硫酸乙烯酯(ES)、亚硫酸丙烯酯(PS)、碳酸乙烯基亚乙酯(VEC)、4-乙炔基-1,3-二氧杂环戊烷-2-酮(EEC)、顺式-4,5-二氟-1,3-二氧杂环戊烷-2-酮及反式-4,5-二氟-1,3-二氧杂环戊烷-2-酮中的一种或两种 以上，更可选地包括碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸丁烯酯(BC)和碳酸亚乙烯酯(VC)中的一种或两种以上。
环状碳酸酯在非水电解液中的质量浓度占比在上述范围内，则可以在基本不影响钠离子迁移速率的情况下，在一定程度上能够提高钠离子电池在高温条件下电极/电解液界面膜的稳定性。
在环状碳酸酯中，使用碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸丁烯酯(BC)和碳酸亚乙烯酯(VC)，则对钠离子电池高温下的动力学过程具有一定的提升作用。
在一些实施方式中，所述非水电解液包含链状碳酸酯和链状羧酸酯，所述链状碳酸酯和链状羧酸酯之和在所述非水电解液中的质量百分比在40％以上，可选为50％以上，更可选为60％以上，且在90％以下，可选在85％以下，进一步可选在80％以下。
所述链状碳酸酯为可在电池中用作溶剂的那些，可选地包括以下物质：碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸甲丙酯(MPC)、碳酸甲基异丙酯(MIPC)、碳酸甲丁酯、碳酸乙丙酯、碳酸二丙酯及碳酸二丁酯中的一种及以上；在链状碳酸酯中，可选碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸甲丙酯(MPC)中的一种或两种以上。
所述链状羧酸酯为可在电池中用作溶剂的那些，可选地包括以下物质：甲酸甲酯(MF)、甲酸乙酯(EF)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸乙酯(EB)、乙酸甲酯(MA)、乙酸乙酯(EA)及乙酸丙酯(PA)中的一种及以上；可选丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、乙酸甲酯(MA)、乙酸乙酯(EA)及乙酸丙酯(PA)中的一种及以上。
所述链状碳酸酯和链状羧酸酯在电解液中的质量百分比在40％以上，可选为50％以上，更可选为60％以上，则使得电解液的粘度不会过高；其含量上限为90％以下，可选为85％以下，进一步可选为80％以下，则离子电导率下降幅度不大，对钠离子电池电化学性能的影响较小。
在一些实施方式中，所述非水电解液包括至少一种环状碳酸酯与至少一种链状酯，所述至少一种环状碳酸酯与所述至少一种链状酯的质量百分比在0.1:1以上，且在1.5:1以下，可选地在1:1以下，更可选地，在0.2:1至1:1之间。
所述环状碳酸酯如上所述。所述链状酯包括如上所述的链状碳酸酯和链状羧酸酯。
可选地，本申请所述的非水电解液中环状碳酸酯与链状酯的种类总和在两种及以上。
本申请所述的非水电解液中环状碳酸酯与链状酯的质量百分比在上述范围内，则对钠离子电池高温下的电解液分解和产气现象会有一定的抑制效果，并对钠离子电池电化学性能的提高具有一定的促进作用。
在一些实施方式中，所述非水电解液包含以下物质组合中的一种及以上：环状碳酸酯与链状碳酸酯；环状碳酸酯与链状羧酸酯；环状碳酸酯与醚；链状碳酸酯与链状羧酸酯；链状碳酸酯与醚；链状羧酸酯与醚；环状碳酸酯、链状碳酸酯与链状羧酸酯；环状碳酸酯、链状碳酸酯与醚；环状碳酸酯、链状羧酸酯与醚；链状碳酸酯、链状羧酸酯与醚。
所述环状碳酸酯、链状碳酸酯、链状羧酸酯如上所述。所述醚为可在电池中用作溶剂的那些，可选地包括以下物质：二氧戊环(DOL)、四氢呋喃(THF)、2-甲基四氢呋喃(2Me-THF)、四氢吡喃(THP)、1,2-二甲氧基乙烷(DME)、二乙二醇二甲醚(DG)、1,2-二乙氧基乙烷及1,2-二丁氧基乙烷中的一种及以上。
本申请所述非水电解液中包括的环状碳酸酯、链状碳酸酯、链状羧酸酯、醚等作为非水溶剂而存在。上述这些特定组合的非水溶剂不仅可以提高电解质钠盐在其中的溶解和分散能力，还可以参与形成某些特定的钠离子溶剂化构型，从而有效抑制电解液中溶剂的分解和伴随的产气问题，进一步提高钠离子电池(尤其在高温条件下)的电化学性能。
在一些实施方式中，所述非水电解液中的非水溶剂包括碳酸丙烯酯、碳酸甲乙酯、乙酸乙酯、碳酸二乙酯、丙酸甲酯、丙酸乙酯、二乙二醇二甲醚、氟代碳酸乙烯酯中的一种及以上。
在一些实施方式中，所述非水电解液包括酸酐类添加剂、含氟有机添加剂、腈类添加剂、有机硅类添加剂、醛类添加剂、含硫类添加剂、锂盐类添加剂、钾盐类添加剂中的一种或两种以上，可选地，这些添加剂总和在非水电解液中的质量百分比为0.001％以上，可选为0.2％以上，且为5％以下，可选为4％以下。
为了进一步优化钠离子电池充放电过程中在电极表面形成膜的稳定性，并得到以无机成分为主的薄而致密的电极/电解液界面膜，可选在电解液中加入一些添加剂，例如，可添加一些添加剂，现具体介绍如下：
酸酐类添加剂为可用于电解液中的那些，可包括、但不限于，例如，琥珀酸酐、马来酸酐、己酸酐、顺酐、丁二酸酐、丁酸酐、巴豆酸酐、苯酐、均苯四甲酸二酐、烯丙基琥珀酸酐或3-烯丙基琥珀酸酐中的一种或两种以上；
含氟有机添加剂，可包括、但不限于，例如，氟代碳酸乙烯酯(FEC)、双氟代碳酸乙烯酯(DFEC)、硼酸三(2,2,2-三氟乙基)酯、三(六氟异丙基)磷酸酯、三(2,2,2-三氟乙基)亚磷酸酯中的一种或两种以上；
腈类添加剂为可用于电解液中的那些，可包括、但不限于，例如，丁二腈、丙二腈、间苯二甲腈、戊二腈、甲氧基五氟环三磷腈、丙烯腈、环丁腈、二甲氨基丙腈、乙氧基五氟环三磷腈、双氰胺、苯氧基五氟环三磷腈、氰基丙烯酸乙酯、对氯苯乙腈、2-氯-5-硝基苯腈、对甲基苯磺酰甲基异腈、己二腈及庚二腈中的一种及以上；
有机硅类添加剂为可用于电解液中的那些，可包括、但不限于，例如，硅烷、三甲基硅醇、三甲基氯硅烷、六甲基二硅氧烷、双(二乙氨基)硅烷、氯甲基硅烷、八甲基环四硅氧烷、N-甲基-N-三甲基硅烷三氟乙酰胺、二苯基硅二醇、苯基三氯硅烷、氯苯基硅烷、三(三甲基硅烷)磷酸酯、溴二氟(三甲基硅基)甲烷或甲基二氯硅烷中的一种或两种以上；
醛类添加剂，可包括、但不限于，例如，2-咪唑甲醛、3-吲哚甲醛、2-吡咯甲醛、对氯苯甲醛、6-氯烟醛、1-甲基吲哚-3-甲醛、2-醛基噻唑、5-氯-2-糠醛或唑-2-甲醛中的一种及以上；
含硫类添加剂为可用于电解液中的那些，可包括、但不限于，例如，硫脲、磺内酯、1,5-萘二磺酸、二甲基砜、环丁砜、甲基磺酸酐、二甲基亚砜、2-巯基-5-甲基-1,3,4-噻二唑、二硫代草酰氨、叔丁基二甲基硅基三氟甲磺酸酯、2,7-二羟基萘-3,6-二磺酸钠、硫酸乙烯酯、硫酸丙烯酯、硫酸丁烯酯或乙烯基砜中的一种或两种以上；
锂盐类添加剂为可用于电解液中的那些，可包括、但不限于，例如，六氟磷酸锂、六氟砷酸锂、高氯酸锂、四氟硼酸锂、三氟乙酸锂、氟磺酸锂、三氟甲基磺酸锂、双(氟磺酰)亚胺锂、双(三氟甲基磺酰)亚胺锂、甲基磺酸锂或乙基硫酸锂中的一种或两种以上；
钾盐类添加剂为可用于电解液中的那些，可包括、但不限于，例如，六氟磷酸钾、高氯酸钾、四氟硼酸钾、三氟乙酸钾、氟磺酸钾、三氟甲基磺酸钾、双(氟磺酰)亚胺钾、双(三氟甲基磺酰)亚胺钾中的一种或两种以上；
所述添加剂在非水电解液中的质量百分比为0.001％以上、可选为0.2％以上，则对电极表面形成膜的稳定性有提升效果；其上限在5％以下、可选为4％以下，则在电极表面过度成膜的可能性下降。
本申请中钠离子电池电解液的成分检测可参照电解液中的钠盐检测标准：现代分析仪器分析方法通则中的离子色谱分析方法通则(JY/T 020-1996，1997年1月23日发布，1997年4月1日实施)来进行，采用离子色谱分析方法对电解液中钠盐及阴离子进行测试分析。
本申请第二方面提供一种钠离子电池，包括正极片、负极片和本申请第一方面所述的非水电解液。
上述针对非水电解液的所有描述也适用于本申请第二方面所述的钠离子电池以及本申请第三方面所述的用电装置。
在钠离子电池中，除了上述非水电解液以外的正极片、负极片、隔离膜等部件的使用没有特别地限制。
本申请中用于钠离子电池正极片的正极材料是能够可逆地嵌入/脱出钠离子的电活性材料，其可包括、但不限于，例如，过渡金属氧化物、普鲁士蓝类似物、聚阴离子化合物和有机正极材料中的任意一种，但本申请不限定于这些材料。
本申请中用于钠离子电池负极片的负极材料是能够可逆地嵌入/脱出钠离子的电活性材料，可适当选自金属钠、硬碳、石墨、金属氧化物、金属硫化物、金属磷化物、合金负极中的任意一种，但本申请不限定于这些材料。
在本申请所述的钠离子电池中，所述正极片和负极片还可包括导电剂和粘结剂，其种类和含量不受具体的限制，可根据实际需求进行选择和优化。
在本申请所述的钠离子电池中，所述隔离膜往往设置在正极片和负极片之间，起到隔离正负极片的作用，所述隔离膜的种类和厚度并不受到具体的限制，可以是现有电池中使用的任意一种隔离膜材料，例如聚乙烯、聚丙烯、聚偏氟乙烯或其多层复合膜，但本申请不限定于这些材料。
在一些可选实施方式中，所述钠离子电池包括正极片和负极片，所述正极片与所述负极片的容量比为1:(1-1.3)。
本申请的钠离子电池中，正极片与负极片的容量比在上述范围内时，电解液在电极表面过度成膜的可能性减小，且电解液持续分解和伴随的产气速率可适当减缓，因此对钠离子电池(尤其在高温下)电化学性能的提升具有促进作用。
例如，正极片与负极片的容量比的测试方法如下：
正极片容量测试：将正极片冲切成直径为14mm的小圆片，并使用金属钠片作为负极，聚丙烯膜为隔离膜组装纽扣电池，在1.5-4.2V电压区间以0.1C倍率恒流充放电测试得到正极充电比容量Q1；
负极片容量测试：将负极片冲切成直径为14mm的小圆片，并使用金属钠片作为负极，聚丙烯膜作为隔离膜组装纽扣电池，在0.005-2V电压区间进行恒流充放电测试，放电过程依次按0.05C、40μA和10μA的倍率进行恒流放电到0.005V，充电过程按0.05C倍率恒流充电到2V，并将充电比容量记为Q2；
正负极容量比＝Q1/Q2。
在一些实施方式中，正极片、负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。
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。正极片、负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。
二次电池包括电池单体形式、电池模块形式、电池包形式。在一些实施方式中，电池单体可以组装成电池模块，电池模块所含电池单体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，多个电池单体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电池单体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，多个电池单体5容纳于该容纳空间。
在一些实施方式中，上述电池单体可以组装成电池包。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。
另外，本申请还提供一种用电装置，所述用电装置包括本申请第二方面提供的二次电池。所述二次电池可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(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，可以根据其使用需求来选择二次电池。
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。
下面结合实施例，进一步阐述本申请，这些实施例仅用于说明本申请而不用于限制本申请的范围。
各实施例和对比例的二次电池均按照下述方法制备：
(1)电解液的制备
实施例1：在氩气气氛手套箱中(H2O<0.1ppm，O2<0.1ppm)，将非水有机溶剂(参见下表1)按照表1中的质量比混合均匀，向其中缓慢加入如下钠盐：表1中的第一钠盐、第二钠盐和添加剂，搅拌均匀，得到相应的电解液；
其他实施例和对比例均类似于实施例1采用表1中各自的非水溶剂、第一钠盐、第二钠盐和添加剂制备得到相应的非水电解液；
(2)正极片的制备
将正极活性材料NaCu1/9Ni2/9Fe1/3Mn1/3O2、导电剂乙炔黑、粘结剂聚偏二氟乙烯按质量比为94:3:3溶于溶剂N-甲基吡咯烷酮中，充分搅拌混合均匀后得到正极浆料；然后将正极浆料均匀涂覆于正极集流体上，之后经过烘干、冷压、分切，得到正极片；
(3)负极片的制备
将活性物质硬碳、导电剂乙炔黑、粘结剂丁苯橡胶和增稠剂羧甲基纤维素钠按照重量比为95:2:2:1溶于溶剂去离子水中，并与溶剂去离子水均匀混合后制备成负极浆料；然后将负极浆料均匀地涂覆在负极集流体铜箔上，之后经过烘干、冷压、分切，得到负极片；
(4)隔离膜的制备
隔离膜使用聚丙烯膜；
(5)钠离子电池(电芯)的制备
将正极片、隔离膜、负极片按顺序叠好，使隔离膜处于正、负极片之间起到隔离的作用，然后卷绕封装得到软包电池，真空干燥后注入电解液，再经过化成、静置等工序制得容量为2Ah的钠离子软包电池。



表1中缩写的含义如下所述：
溶剂缩写为：PC：碳酸丙烯酯，EMC：碳酸甲乙酯，DEC：碳酸二乙酯，EP：丙酸乙酯，DG：二乙二醇二甲醚；
钠盐缩写为：NaPF6：六氟磷酸钠，NaAsF6：六氟砷酸钠，NaClO4：高氯酸钠，C2F3NaO2：三氟乙酸钠，Na(FSO2)2N：双(氟磺酰)亚胺钠，CF3NaO3S：三氟甲磺酸钠，C2BF2NaO4：二氟(草酸根)硼酸钠，C4BNaO8：双(草酸根)硼酸钠，NaPO2F2：二氟磷酸钠，Na2PO3F：单氟磷酸钠，NaBF4：四氟硼酸钠，BNaO2：偏硼酸钠；
添加剂缩写为：FEC：氟代碳酸乙烯酯。
表格中涉及的物质均为化学纯，可商购获得。
以下为相关参数的测试过程：
1.钠离子电池内阻mΩ测试
在25℃下，将钠离子电池以1C恒流充电至4.2V，然后以4.2V恒压充电至电流小于0.05C，然后再以1C放电30min，即将电芯的电量调整到50％SOC。然后将TH2523A交流内阻测试仪的正负表笔分别接触电池的正负极，通过内阻测试仪读取电池的内阻值。
2.25℃循环500次容量保持率测试
在25℃下，将钠离子电池以1C倍率恒流充电至4.2V，然后在4.2V恒压充电至电流小于0.05C，随后以1C倍率恒流放电至1.5V，然后以0.04C恒流放电至1.5V，此为一个充放电过程。如此反复进行充放电，计算钠离子电池循环500次后的容量保持率，具体计算公式如下：
钠离子电池25℃循环500次后的容量保持率(％)＝(第500次循环的放电容量/首次循环的放电容量)×100％。
3.45℃循环500次容量保持率测试
在45℃下，将钠离子电池以1C倍率恒流充电至4.2V，然后在4.2V恒压充电至电流小于0.05C，随后以1C倍率恒流放电至1.5V，然后以0.04C恒流放电至1.5V，此为一个充放电过程。如此反复进行充放电，计算钠离子电池循环500次后的容量保持率，具体计算公式如下：
钠离子电池45℃循环500次后的容量保持率(％)＝(第500次循环的放电容量/首次循环的放电容量)×100％。
4.高温存储后的容量保持率测试
在25℃下，将钠离子电池以1/3C恒流放电至1.5V，再以1/3C倍率恒流充电至4.2V，在4.2V恒压充电至电流小于0.05C，然后将其在恒温箱中60℃高温 存储2个月，之后将高温存储后的钠离子电池降温到25℃，并以1/3C恒流放电至1.5V。计算钠离子电池60℃下4.2V存储后的容量保持率，具体计算公式如下：
钠离子电池60℃高温存储后的容量保持率(％)＝(高温存储后25℃的放电容量/首次25℃的放电容量)×100％。
5.高温存储后的体积膨胀测试
在25℃下，以1C恒流充电至电压为4.2V，然后以4.2V恒压充电至电流为0.05C，此时测试钠离子电池的体积并记为V1；然后将满充的钠离子电池放入60℃恒温箱中，存储2个月，采用排水法测试体积并记为V2。
钠离子电池60℃存储2月后的体积膨胀率(％)＝(V2-V1)/V1×100％。
各实施例和对比例测试结果如下。
表2实施例和对比例钠离子电池性能

从表1-2的数据可以看出，与对比例1-6相比，实施例1-43在保证电池内阻相当的情况下明显降低了高温存储后电池体积膨胀率并且提高了室温、高温循环及高温存储后的容量保持率。
根据对比例1的实验结果可以看出，即使存在成膜添加剂FEC，基于酯类电解液的钠离子电池在25℃的循环性能仍然比较差。当温度升高到45℃，钠离子电池循环500次后的容量保持率显著降低。更为严重的是，钠离子电池在高温存储2个月后的体积膨胀率比较高，这是由于在钠离子电池充放电过程中，电解液面临着严重的分解并伴随着大量的气体产生，这将导致钠离子电池在使用过程中存在严重的安全隐患。
从对比例2-5可以看出，通过向对比例1电解液中添加一种含有富电子阴离子(具有磺酸根/草酸根/磷酸根/硼酸根)的第二钠盐后，钠离子电池在25℃及45℃循环500次后的容量保持率、高温(60℃)存储后的容量保持率均会提高且电池的体积膨胀率有所降低。这说明含有富电子阴离子的第二钠盐的加入可以在一定程度上抑制电解液的分解和伴随的产气问题，这是由于含有富电子的阴离子参与钠离子的溶剂化结构会给钠离子提供部分电子，从而削弱钠离子对电解液中溶剂分子的强吸电子作用，使得溶剂分子内化学键强降低的幅度减小，从而抑制了溶剂分子的分解和伴随的产气问题。然而，单一的含有富电子阴离子钠盐的添 加不能起到明显的抑制效果，这可能跟阴离子的数量、大小、供电子能力及成膜情况等有关。
从对比例6可以看出，当电解液中去除第一钠盐(NaPF6)后，钠离子电池在25℃及45℃循环性能以及60℃下的高温储存后的容量保持率显著变差，这说明第一钠盐对钠离子电池的整体电化学性能起到了不可或缺的作用，第一钠盐与第二钠盐的复配使用才能协同提升钠离子电池的电化学性能。另外，第二钠盐的含量对钠离子电池的电化学性能也有一定的影响。
从实施例1-5可以看出，当电解液中添加0.0005M、0.001M的具有磺酸根的第二钠盐(Na(FSO2)2N)后(实施例1-2)，对电池的25℃及45℃循环性能有所提升，对60℃下的高温储存后的容量保持率的提升较明显，并且显著降低了高温存储后的电池体积膨胀率，但如此低含量的第二钠盐(Na(FSO2)2N)对电解液的调控作用较差。值得注意的是，当添加0.01M、0.03M的第二钠盐(Na(FSO2)2N)后(实施例3-4)，钠离子电池的电化学性能产生了进一步的提升，与对比例1-6相比各项性能改善明显。从实施例5可以得出，第二钠盐(Na(FSO2)2N)的添加量为1M时，钠离子电池的电阻有所提升，这是由于添加过量的第二钠盐会造成过度成膜并恶化界面电阻，从而影响钠离子电池的动力学过程。
除了具有磺酸根的第二钠盐，具有草酸根的第二钠盐对钠离子电池电化学性能也有一定的影响。从实施例6-11可以得出，添加0.0005M的具有草酸根的第二钠盐(C2BF2NaO4)后，钠离子电池的电化学性能就能产生一定的提升作用。其添加量超过0.015M后，对应电池的电化学性能有所恶化，说明过量的添加可能会影响钠离子电池的界面阻抗和动力学过程。
此外，从实施例12-23可以看出，含有富电子阴离子(具有磷酸根/硼酸根)的第二钠盐的添加同样会提升钠离子电池的电化学性能。
另外，从实施例24-29可以得出，具有磺酸根、草酸根、磷酸根和硼酸根的第二钠盐之间的复配会对钠离子电池在25℃/45℃循环性能、高温存储性能及高温下的体积膨胀率均有一定的改善效果。
从实施例30-33可以得出，改变具有磺酸根、草酸根、磷酸根和硼酸根的第二钠盐的种类对钠离子电池的电化学性能也有类似的提升作用。
从实施例34-39可以看出，除了碳酸酯类溶剂，在含有羧酸酯和醚类溶剂的电解液中添加含有富电子阴离子(具有磺酸根、草酸根、磷酸根和硼酸根)的第二钠盐后，对钠离子电池电解液的分解和产气也具有类似的抑制效果，对钠离子电池(尤其在高温下)电化学性能的提升具有促进作用。这说明第二钠盐的添加对电解液中钠离子的溶剂化过程及溶剂分子在电解液中的化学环境可以起到较 好的调控作用，且容易形成无机成分为主的薄而致密的固态电解质界面膜，从而可以有效抑制电解液中溶剂的分解及伴随的产气问题，并改善钠离子电池的电化学性能。另外，即使向电解液中同时添加四种含有富电子阴离子(具有磺酸根、草酸根、磷酸根和硼酸根)的第二钠盐后，钠离子电池的阻抗值变化也不大，说明含有富电子阴离子钠盐的同时使用对钠离子电池阻抗影响的可能性是比较小的。
从实施例40-42可以看出，第二钠盐与其他种类的第一钠盐的复配使用也会对钠离子电池的电化学性能产生一定的改善效果。同时，我们发现电解液中使用不同种类的第一钠盐后，钠离子电池的电化学性能存在一定的差异。
此外，从实施例43可以看出，在电解液中去除添加剂FEC后，钠离子电池的电化学性能发生恶化，说明电解液中的添加剂会参与钠离子电池中电极/电解液界面膜的形成，对钠离子电池电化学性能的提升也具有重要的作用。
本申请的钠离子电池非水电解液及钠离子电池对解决钠离子电池实际应用过程中存在的电解液分解和产气问题具有一定的针对性，在产业化过程中具有较好的可利用性。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (21)

  1. 一种非水电解液，其包含：第一钠盐，其包括六氟磷酸钠、六氟砷酸钠、高氯酸钠及三氟乙酸钠中的至少一种，可选地，所述第一钠盐为六氟磷酸钠；第二钠盐，其包括具有磺酸根的钠盐、草酸根的钠盐、磷酸根的钠盐和硼酸根的钠盐中的一种、两种或更多种；可选地，所述第二钠盐包括具有磺酸根的钠盐、具有草酸根的钠盐、具有磷酸根的钠盐和具有硼酸根的钠盐。
  2. 根据权利要求1所述的非水电解液，其特征在于，所述非水电解液中，第一钠盐与第二钠盐的摩尔浓度比在1/1以上，可选为3/1以上，且在40/1以下，更可选为15/1以下。
  3. 根据权利要求1或2所述的非水电解液，其特征在于，所述具有磺酸根的钠盐包括氟磺酸钠、三氟甲基磺酸钠、双(氟磺酰)亚胺钠、双(三氟甲基磺酰)亚胺钠、甲基磺酸钠、乙烯基磺酸钠、甲基硫酸钠、甲基硫代磺酸钠、1,2-乙烷基二磺酸钠、乙基硫酸钠、丙烷磺酸钠、乙硫代磺酸钠、2-碘苯磺酸钠、4-硝基苯甲磺酸钠、苯乙烯磺酸钠、4-异丙苯磺酸钠、苯酚磺酸钠、β-苯乙烯磺酸钠、环己烷磺酸钠、2-环己胺基乙磺酸钠、4-氨基-N-甲基苯磺酰胺、聚二硫二丙烷磺酸钠、吡啶-3-亚磺酸钠、哌嗪-1,4-二乙磺酸单钠盐中的一种及以上，可选地包括氟磺酸钠、三氟甲基磺酸钠、双(氟磺酰)亚胺钠、双(三氟甲基磺酰)亚胺钠、甲基磺酸钠、甲基硫酸钠中的一种及以上。
  4. 根据权利要求1-3中任一项所述的非水电解液，其特征在于，所述具有磺酸根的钠盐在所述非水电解液中的浓度在0.0005-1mol/L范围内，可选地在0.01-0.3mol/L范围内。
  5. 根据权利要求1-4中任一项所述的非水电解液，其特征在于，所述具有草酸根的钠盐包括草酸钠、双(草酸根)硼酸钠、二氟(草酸根)硼酸钠、四氟(草酸根)磷酸钠、二氟双(草酸根)磷酸钠中的一种及以上，可选地包括草酸钠、双(草酸根)硼酸钠、二氟(草酸根)硼酸钠、四氟(草酸根)磷酸钠、二氟双(草酸根)磷酸钠中的一种及以上。
  6. 根据权利要求1-5中任一项所述的非水电解液，其特征在于，所述具有草酸根的钠盐在所述非水电解液中的浓度在0.0005-0.1mol/L范围内，可选地在0.006-0.08mol/L范围内，进一步可选地在0.01-0.02mol/L范围内。
  7. 根据权利要求1-6中任一项所述的非水电解液，其特征在于，所述具有磷酸根的钠盐包括二氟磷酸钠、单氟磷酸钠、三偏磷酸钠、六偏磷酸钠、羟基乙叉二膦酸钠、氯屈膦酸二钠、奥帕膦酸钠、二乙烯三胺五亚甲基膦酸钠、三聚磷酸钠及磷酸苯基二钠中的一种及以上，可选地包括二氟磷酸钠及氟磷酸钠中的一种及以上。
  8. 根据权利要求1-7中任一项所述的非水电解液，其特征在于，所述具有磷酸根的钠盐在所述非水电解液中的浓度在0.0005-0.12范围内、可选在0.01-0.05mol/L范围内，更可选在0.01-0.03mol/范围内。
  9. 根据权利要求1-8中任一项所述的非水电解液，其特征在于，所述具有硼酸根的钠盐包括四氟硼酸钠、偏硼酸钠、四苯基硼酸钠、四[3,5-双(三氟甲基)苯基]硼酸钠中的一种及以上，可选地包括四氟硼酸钠、偏硼酸钠及四苯基硼酸钠中的一种及以上，进一步可选为四氟硼酸钠及偏硼酸钠中的一种及以上。
  10. 根据权利要求1-9中任一项所述的非水电解液，其特征在于，所述具有硼酸根的钠盐在所述非水电解液中的浓度在0.0005-0.05mol/L范围内，可选地在0.01-0.04mol/L范围内。
  11. 根据权利要求1-10中任一项所述的非水电解液，其特征在于，第一钠盐中，在六氟磷酸钠与六氟砷酸钠、高氯酸钠及三氟乙酸钠中的至少一种联用时，除六氟磷酸钠以外的其他钠盐在非水电解液中的浓度为0.001mol/L以上，可选为0.01mol/L以上，进一步可选为0.03mol/L以上，且为1mol/L以下，可选为0.5mol/L以下。
  12. 根据权利要求1-11中任一项所述的非水电解液，其特征在于，所述第二钠盐包括具有磺酸根的钠盐，还包括具有草酸根的钠盐、具有磷酸根的钠盐及具有硼酸根的钠盐中的一种及以上。
  13. 根据权利要求1-12中任一项所述的非水电解液，其特征在于，所述第二钠盐包括具有磺酸根的钠盐和具有草酸根的钠盐，可选地，具有磺酸根的钠盐和具有草酸根的钠盐的摩尔比为0.03/1至70/1，可选为0.5/1至20/1。
  14. 根据权利要求1-13中任一项所述的非水电解液，其特征在于，所述非水电解液包含环状碳酸酯，所述环状碳酸酯在非水电解液中的质量浓度占比在10％以上，可选为15％以上，且在60％以下。
  15. 根据权利要求1-14中任一项所述的非水电解液，其特征在于，所述非水电解液包含链状碳酸酯和链状羧酸酯，所述链状碳酸酯和链状羧酸酯之和在所述非水电解液中的质量百分比在40％以上，可选为50％以上，更可选为60％以上，且在90％以下，可选在85％以下，进一步可选在80％以下。
  16. 根据权利要求1-15中任一项所述的非水电解液，其特征在于，所述非水电解液包括至少一种环状碳酸酯与至少一种链状酯，所述至少一种环状碳酸酯与所述至少一种链状酯的质量百分比在0.1:1以上，且在1.5:1以下，可选地在1:1以下，更可选地，在0.2:1至1:1之间。
  17. 根据权利要求1-16中任一项所述的非水电解液，其特征在于，所述非水电解液包含以下物质组合中的一种及以上：环状碳酸酯与链状碳酸酯；环状碳酸酯与链状羧酸酯；环状碳酸酯与醚；链状碳酸酯与链状羧酸酯；链状碳酸酯与醚；链状 羧酸酯与醚；环状碳酸酯、链状碳酸酯与链状羧酸酯；环状碳酸酯、链状碳酸酯与醚；环状碳酸酯、链状羧酸酯与醚；链状碳酸酯、链状羧酸酯与醚。
  18. 根据权利要求1-17中任一项所述的非水电解液，其特征在于，所述非水电解液中的非水溶剂包括碳酸丙烯酯、碳酸甲乙酯、乙酸乙酯、碳酸二乙酯、丙酸甲酯、丙酸乙酯、二乙二醇二甲醚、氟代碳酸乙烯酯中的一种及以上。
  19. 根据权利要求1-18中任一项所述的非水电解液，其特征在于，所述非水电解液包括酸酐类添加剂、含氟有机添加剂、腈类添加剂、有机硅类添加剂、醛类添加剂、含硫类添加剂、锂盐类添加剂、钾盐类添加剂中的一种或两种以上，可选地，这些添加剂总和在非水电解液中的质量百分比为0.001％以上，可选为0.2％以上，且为5％以下，可选为4％以下。
  20. 一种钠离子电池，包括正极片、负极片和权利要求1-19中任一项所述的非水电解液。
  21. 一种用电装置，其包括权利要求1-19中任一项所述的非水电解液或权利要求20所述的钠离子电池。
PCT/CN2023/072330 2023-01-16 2023-01-16 非水电解液及包含该电解液的钠离子电池和用电装置 Ceased WO2024152146A1 (zh)

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JP2025517414A JP2025531407A (ja) 2023-01-16 2023-01-16 非水電解液及びこの電解液を含むナトリウムイオン電池と電力消費装置
PCT/CN2023/072330 WO2024152146A1 (zh) 2023-01-16 2023-01-16 非水电解液及包含该电解液的钠离子电池和用电装置
EP23916639.0A EP4611104A4 (en) 2023-01-16 2023-01-16 Non-aqueous electrolyte, sodium-ion battery containing same, and electrical apparatus
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