WO2024164532A1 - 钠二次电池用电解液、钠二次电池及用电装置 - Google Patents

钠二次电池用电解液、钠二次电池及用电装置 Download PDF

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WO2024164532A1
WO2024164532A1 PCT/CN2023/118202 CN2023118202W WO2024164532A1 WO 2024164532 A1 WO2024164532 A1 WO 2024164532A1 CN 2023118202 W CN2023118202 W CN 2023118202W WO 2024164532 A1 WO2024164532 A1 WO 2024164532A1
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sodium
solvent
electrolyte
secondary battery
sodium secondary
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French (fr)
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黄起森
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to JP2025524711A priority Critical patent/JP2026512688A/ja
Priority to EP23920724.4A priority patent/EP4641738A4/en
Publication of WO2024164532A1 publication Critical patent/WO2024164532A1/zh
Priority to US19/216,719 priority patent/US20250286147A1/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
    • H01M10/054—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
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • 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 the field of batteries, and in particular to an electrolyte for a sodium secondary battery, a sodium secondary battery and an electrical device.
  • electrolyte plays an important role as an ion carrier in electrochemical reactions.
  • the electrolyte currently used in commercial sodium secondary batteries increases in viscosity and is easy to solidify at low temperatures, which leads to problems such as low ionic conductivity, high electrochemical impedance and slow kinetic process, which seriously affects the service life and cycle stability of the battery, further limiting the practical application of sodium secondary batteries at low temperatures.
  • the present application provides an electrolyte for a sodium secondary battery, a sodium secondary battery and an electrical device, which can improve the reaction kinetics of the sodium secondary battery at low temperatures and improve the low-temperature performance of the sodium secondary battery.
  • the present application provides an electrolyte for a sodium secondary battery, comprising: a metallic sodium salt and a solvent; wherein the desolvation energy of a sodium ion-solvent complex formed by sodium ions of the metallic sodium salt and the solvent is less than or equal to 100 kJ/mol.
  • the desolvation energy of the complex (Na + -(solvent) x complex) formed by sodium ions and the solvent in the electrolyte can be regulated by regulating the solvent type of the electrolyte.
  • Such a design makes the desolvation process of the sodium ion-solvent complex have a low energy barrier at low temperature.
  • the affinity between sodium ions and solvent molecules is weak, which improves the difficulty of desolvation of solvated sodium ions at low temperatures, improves the reaction kinetics of sodium secondary batteries at low temperatures, and improves the low-temperature performance of sodium secondary batteries.
  • the molar concentration of the metal sodium salt is 0.1-1.2 mol/L; alternatively, the molar concentration of the metal sodium salt is 0.2-0.8 mol/L.
  • the solvent includes a first solvent and a second solvent; the first solvent includes a linear ether solvent; and the second solvent includes one or more of diethyl ether and cyclic ethers.
  • the first solvent can increase the solubility of the metal sodium salt and improve the conductivity of the electrolyte.
  • the second solvent can reduce the desolvation barrier of the sodium ion-solvent complex and enhance the desolvation process of the sodium ion-solvent complex. Through the mutual cooperation of the first solvent and the second solvent, the conductivity and reaction kinetics of the electrolyte can be improved, and the low-temperature electrochemical performance of the battery can be more effectively improved.
  • the first solvent includes one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dipropyl ether and dibutyl ether; and/or the second solvent includes one or more of diethyl ether, 1,3-dioxolane, tetrahydrofuran and methyltetrahydrofuran.
  • the volume ratio of the first solvent to the second solvent is greater than or equal to 1:1 and less than or equal to 10:1; optionally, the volume ratio of the first solvent to the second solvent is greater than or equal to 1.5:1 and less than or equal to 5:1.
  • the metal sodium salt includes one or more of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate, and sodium bis(trifluoromethylsulfonyl)imide.
  • the above metal sodium salts have high ionic conductivity and strong electrochemical stability, and are easy to improve the electrochemical performance of the battery at low temperatures.
  • the present application provides a sodium secondary battery, which includes the electrolyte for sodium secondary batteries in the above embodiment.
  • the desolvation energy of the sodium ion-solvent complex in the electrolyte of the sodium secondary battery is less than or equal to 100 kJ/mol.
  • the sodium secondary battery is a negative electrode-free sodium secondary battery.
  • the negative electrode structure of the negative electrode-free battery only includes a current collector in the initial state, and no negative electrode active material is arranged on the surface of the current collector.
  • the metallic sodium in the positive electrode material migrates to the negative electrode side and is deposited on the surface of the negative electrode current collector. Part of the metallic sodium will remain on the surface of the negative electrode current collector.
  • the metallic sodium is deposited and stripped on the surface of the negative electrode current collector to achieve circulation.
  • the desolvation energy barrier of the sodium ion-solvent complex in the electrolyte is low at low temperature, it is easier to achieve sodium deposition and stripping, and the low temperature reaction activity is higher.
  • the battery includes a negative electrode, the negative electrode includes a negative electrode current collector and a negative electrode active material; the negative electrode active material includes one or more of a silicon-based material, a silicon-carbon material, a carbon material, and a selenium-based material.
  • the desolvation energy barrier of the sodium ion-solvent complex in the electrolyte is low, and the sodium ions are easily embedded in the above-mentioned negative electrode active material, and are also easily de-embedded from the above-mentioned negative electrode active material, and have excellent low-temperature reaction activity.
  • the structure of the active material changes little, which is beneficial to prolonging the service life of the battery.
  • the battery includes a positive electrode, the positive electrode includes a positive electrode current collector and a positive electrode active material; the positive electrode active material includes one or more of a transition metal oxide, a polyanion compound, and a Prussian blue analog.
  • Sodium ions are easily embedded in the above-mentioned positive electrode active material, and are also easily de-embedded from the above-mentioned positive electrode active material, and have excellent low-temperature reaction activity.
  • the structure of the active material changes little, which is conducive to extending the service life of the battery.
  • the diaphragm resistance of the positive electrode is 0.1 ⁇ -50 ⁇ ; optionally, the diaphragm resistance of the positive electrode is 0.1 ⁇ -10 ⁇ .
  • the size of the diaphragm resistance will affect the desolvation process of the sodium ion-solvent complex to a certain extent. When the diaphragm resistance is small, the electrode polarization is small, and the concentration polarization at low temperature is small, which can promote desolvation. Setting the diaphragm resistance of the positive electrode sheet within this resistance range further optimizes the effect of the desolvation process and is more conducive to improving the low temperature performance of the battery.
  • the present application provides an electrical device, comprising the aforementioned sodium secondary battery, having excellent low temperature performance.
  • FIG1 is a schematic diagram of the structure of some embodiments of the sodium secondary battery of the present application.
  • FIG2 is a schematic diagram of the exploded structure of some embodiments of the sodium secondary battery of the present application.
  • FIG3 is a schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application.
  • FIG. 4 is a schematic diagram of the structure of a vehicle according to some embodiments of the present application.
  • the term "and/or" is only a description of the association relationship of associated objects, indicating that three relationships may exist.
  • a and/or B can represent: A exists alone, A and B exist at the same time, and B exists alone.
  • the character "/" in this article generally indicates that the associated objects before and after are in an "or" relationship.
  • multiple refers to more than two (including two).
  • multiple groups refers to more than two groups (including two groups), and “multiple pieces” refers to more than two pieces (including two pieces).
  • Power batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields.
  • energy storage power systems such as hydropower, thermal power, wind power and solar power stations
  • electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields.
  • the market demand is also constantly expanding, and its performance stability in different use environments, especially in low temperature environments (less than or equal to 0°C) has become a research hotspot.
  • the inventors have noticed that as the ambient temperature decreases, the viscosity of the conventional carbonate-based electrolyte gradually increases, and the reaction rate of the sodium secondary battery decreases, which is extremely unfavorable to the low-temperature performance stability of the sodium secondary battery.
  • linear carboxylates with lower viscosity can be added to the electrolyte system as co-solvents to reduce the viscosity of the system, the carboxylates are easily oxidized during the circulation of the sodium secondary battery, which in turn reduces the capacity of the sodium secondary battery.
  • the applicant has found that by reducing the desolvation energy of sodium ion-solvent complexes in the electrolyte, the barrier of the desolvation process of sodium ion-solvent complexes in the electrolyte can be reduced, so as to improve the chemical reaction activity of sodium secondary batteries at low temperatures and improve the low-temperature performance of sodium secondary batteries.
  • the electrolyte for sodium secondary batteries includes: a metal sodium salt and a solvent; wherein the desolvation energy of a sodium ion-solvent complex formed by sodium ions of the metal sodium salt and the solvent is less than or equal to 100 kJ/mol.
  • the electrolyte is used in sodium secondary batteries, which are batteries that can be charged after discharge.
  • a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte.
  • the separator is arranged between the positive electrode sheet and the negative electrode sheet to play a role of isolation.
  • the electrolyte plays a role of conducting ions between the positive electrode sheet and the negative electrode sheet.
  • the electrolyte includes an electrolyte salt and a solvent.
  • the electrolyte salt dissolves to form electrolyte ions, which conduct electricity through the movement of electrolyte ions in the electrolyte salt.
  • the negative electrode absorbs metal cations in the electrolyte and releases electrical energy.
  • the negative electrode releases metal cations into the electrolyte again.
  • the electrolyte ions need to be desolvated. Desolvation refers to the phenomenon that the metal electrolyte ions in the electrolyte are separated from the surrounding solvent molecules, which is the process of interfacial charge transfer.
  • the electrolyte of the sodium secondary battery includes sodium ions, and it mainly relies on the movement of sodium ions between the positive and negative electrodes to work.
  • the electrodeposition process of sodium ions on the negative electrode sheet includes:
  • the sodium ions dissolved in the electrolyte form a Na + -(solvent) x complex with the solvent molecules, and the solvated sodium ions are transferred from the electrolyte to the surface of the negative electrode.
  • the desolvation process usually exhibits a high potential barrier, and its kinetics is very sensitive to temperature. Therefore, it is generally believed that the desolvation process is the rate-determining step at low temperatures, especially in high-rate cycling processes.
  • the desolvation energy of the sodium ion-solvent complex by controlling the desolvation energy of the sodium ion-solvent complex to be less than or equal to 100 kJ/mol, the energy barrier of the desolvation of the sodium ion-solvent complex can be reduced, making it easy for the sodium ion-solvent complex to be desolvated. And as the desolvation energy decreases, sodium ions are more likely to pass through the SEI interface and combine with electrons, and the reaction activity inside the sodium secondary battery is stronger, which increases the chemical reaction rate inside the battery at low temperatures, thereby improving the low temperature performance of the sodium secondary battery.
  • the desolvation energy is less than or equal to 100 kJ/mol.
  • the desolvation energy test method is to use Na + -(solvent) x complex as an example, use multiple solvents, and use Vmp3 electrochemical workstation.
  • the electrolyte systems with different solvents were subjected to AC impedance tests to obtain the impedance spectra of the Na + desolvation process; the desolvation energy of the Na + -(solvent) x complex in the electrolyte was obtained according to the Arrhenius equation.
  • the molar concentration of the metal sodium salt is 0.1-1.2 mol/L (for example, 0.1 mol/L, 0.2 mol/L, 0.3 mol/L, 0.4 mol/L, 0.5 mol/L, 0.6 mol/L, 0.7 mol/L, 0.8 mol/L, 0.9 mol/L, 1.0 mol/L, 1.1 mol/L and 1.2 mol/L, etc.); optionally, the molar concentration of the metal sodium salt is 0.2-0.8 mol/L (for example, 0.2 mol/L, 0.3 mol/L, 0.4 mol/L, 0.5 mol/L, 0.6 mol/L, 0.7 mol/L and 0.8 mol/L, etc.).
  • the molar concentration of the metal salt is 0.2-0.5 mol/L, 0.5-0.8 mol/L, 0.3-0.7 mol/L, 0.4-0.6 mol/L, 0.5-1.0 mol/L, etc.
  • the molar concentration of the metal sodium salt refers to the molar concentration of the metal sodium salt as a whole.
  • the metal sodium salt is sodium hexafluorophosphate
  • the molar concentration range of the sodium hexafluorophosphate is 0.1-1.2 mol/L.
  • the molar concentration range of the sodium hexafluorophosphate is 0.2-0.8 mol/L.
  • the concentration of the metal sodium salt decreases, the affinity between the sodium ions and the solvent molecules weakens, and the sodium ions and the solvent molecules are more easily separated, thereby accelerating the electrochemical reaction rate.
  • the molar concentration range of the metal sodium salt By setting the molar concentration range of the metal sodium salt to the above range, while having sufficient battery capacity, the sodium ions and the solvent can be easily separated at low temperatures, increasing the rate of sodium ion deposition or embedding on the negative electrode, which is beneficial to improving the low temperature performance of the sodium secondary battery.
  • the solvent includes a first solvent and a second solvent; the first solvent includes a chain ether solvent; and the second solvent includes one or more of diethyl ether and cyclic ethers.
  • Chain ether solvents have a low viscosity, generally less than 1.2 mPa ⁇ s, which helps to transport sodium ions at low temperatures. They have a strong complexing effect with sodium ions, which can increase the solubility of metallic sodium salts and increase the concentration of sodium ions. Using them as solvents in electrolytes can significantly increase the conductivity of the electrolyte and improve the reaction rate during battery charging and discharging.
  • Diethyl ether and cyclic ethers can weaken the solvation effect between sodium ions and solvents, which is beneficial to promote the desolvation process of solvated sodium ions, reduce the desolvation energy, and further improve the low-temperature performance of sodium secondary batteries.
  • the mutual cooperation of the first solvent and the second solvent enables the electrolyte to have a higher carrying rate for sodium ions and improves the conductivity of the electrolyte.
  • the formation of a weakly solvated electrolyte promotes the desolvation process of solvated sodium ions and improves the low-temperature performance of the sodium secondary battery.
  • the first solvent includes one or more of DME (ethylene glycol dimethyl ether), DEE (ethylene glycol diethyl ether), DEGDME (diethylene glycol dimethyl ether), TRGDME (triethylene glycol dimethyl ether), TEGDME (tetraethylene glycol dimethyl ether), dipropyl ether and dibutyl ether; and/or the second solvent includes one or more of diethyl ether, DOL (1,3-dioxolane), THF (tetrahydrofuran) and Me-THF (methyltetrahydrofuran).
  • DME ethylene glycol dimethyl ether
  • DEE ethylene glycol diethyl ether
  • DEGDME diethylene glycol dimethyl ether
  • TRGDME triethylene glycol dimethyl ether
  • TEGDME tetraethylene glycol dimethyl ether
  • dipropyl ether and dibutyl ether and/or the second solvent includes one or more of diethyl ether, DOL (1,3-
  • the above-mentioned ether solvent molecules can construct a stable electrode/electrolyte interface on the surface of the negative electrode plate, form a stable SEI interface, and reduce electrochemical polarization.
  • the above-mentioned ether solvents have good compatibility with metal negative electrode sheets. They can effectively passivate the metal negative electrode sheets, forming a thinner, uniform and dense SEI interface on the surface of the metal negative electrode sheets, further preventing the formation of dendrites, and preventing the SEI interface from further thickening due to the growth and evolution of dendrites, which is beneficial to promoting the smooth conduction of sodium ions.
  • the volume ratio of the first solvent to the second solvent is greater than or equal to 1:1, and less than or equal to 10:1 (for example, 1:1, 1.5:1, 2:1, 3:1, 4:1, 4.5:1, 5:1, 6:1, 7:1, 8:1, 9:1, 9.5:1, 10:1, etc.); optionally, the volume ratio of the first solvent to the second solvent is greater than or equal to 1.5:1, and less than or equal to 5:1 (for example, 1.5:1, 2:1, 3:1, 4:1, 4.5:1, 5:1, etc.). Or it is a range consisting of any two of the above values.
  • the volume ratio of the first solvent to the second solvent can be 2:1-4:1, 1.5:1-4.5:1, 3:1-5:1, 4:1-9:1, etc.
  • the volume ratio of the first solvent to the second solvent to be within the above range, the conductivity of the electrolyte can be improved and the solvation effect between the sodium ions and the solvent can be effectively weakened, which is beneficial to promoting the electrochemical reaction rate of the electrolyte.
  • the metal sodium salt includes one or more of NaPF 6 (sodium hexafluorophosphate), NaDFOB (sodium difluorooxalatoborate), NaBF 4 (sodium tetrafluoroborate), NaBOB (sodium bisoxalatoborate), NaClO 4 (sodium perchlorate), NaAsF 6 (sodium hexafluoroarsenate), NaFSI (sodium bis(fluorosulfonyl)imide), NaOTf (sodium trifluoromethylsulfonate) and NaTFSI (sodium bis(trifluoromethylsulfonyl)imide).
  • NaPF 6 sodium hexafluorophosphate
  • NaDFOB sodium difluorooxalatoborate
  • NaBF 4 sodium tetrafluoroborate
  • NaBOB sodium bisoxalatoborate
  • NaClO 4 sodium perchlorate
  • NaFSI sodium
  • the above sodium salt has high ionic conductivity and strong electrochemical stability, which can easily improve the electrochemical performance of batteries at low temperatures.
  • the electrolyte further includes additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, and additives that can improve battery performance. Additives, additives that improve the low temperature performance of batteries.
  • the present application also provides a sodium secondary battery, comprising the electrolyte for sodium secondary battery in the aforementioned embodiment.
  • the sodium secondary battery is a negative electrode-free sodium secondary battery.
  • negative electrode-free means that in the initial state, the negative electrode structure only includes a current collector without active materials.
  • the metal in the positive electrode material migrates to the surface of the negative electrode current collector, and a metal layer is formed on the negative electrode current collector.
  • the metal electrolyte ions in the electrolyte combine with electrons on the surface and/or in the pores of the negative electrode current collector, and deposition occurs.
  • the deposited layer on the surface of the negative electrode current collector peels off and dissolves to become metal electrolyte ions and electrons again, returning to the positive electrode, and so on.
  • the sodium secondary battery includes the electrolyte in the aforementioned embodiment, so the desolvation energy barrier of the solvated sodium ions in the electrolyte is low at low temperature, and it is easy to pass through the SEI interface and deposit on the surface of the negative electrode current collector. At the same time, the electrolyte has high conductivity and strong carrying capacity for sodium ions, so it has excellent low-temperature reaction activity.
  • the negative electrode of the sodium secondary battery may also be a traditional negative electrode structure, specifically including a negative electrode current collector and a negative electrode film layer arranged on the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector may be a conventional metal foil or a composite current collector (for example, a metal material may be disposed on a polymer substrate to form a composite current collector).
  • the negative electrode current collector may be a copper foil.
  • the negative electrode active material may include, but is not limited to, one or more of silicon-based materials, silicon-carbon materials, carbon materials, and selenium-based materials. Specifically include one or more of artificial graphite, natural graphite, hard carbon, soft carbon, silicon-based materials, and tin-based materials. Silicon-based materials can be selected from one or more of elemental silicon, silicon-oxygen compounds (such as silicon monoxide), silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Selenium-based materials can be selected from one or more of elemental selenium, selenium-oxygen compounds, and selenium alloys. These materials can all be obtained commercially.
  • the working principle of the sodium secondary battery is the embedding-deintercalation of metal cations in the metal sodium salt.
  • the sodium ions are deintercalated from the positive electrode, pass through the separator in the electrolyte, and embed into the negative electrode. active material, and at the same time, electrons flow from the positive electrode to the negative electrode in the external circuit;
  • sodium ions are deintercalated from the negative electrode active material, pass through the diaphragm in the electrolyte, and embed into the positive electrode, and at the same time, electrons flow from the negative electrode to the positive electrode in the external circuit.
  • the negative electrode active material can reduce the negative electrode impedance, increase the electrode capacity, and reduce the abnormal precipitation of metallic sodium.
  • Sodium metal is easily embedded in the above-mentioned negative electrode active material, and it is also easy to de-embed. When the battery is charged and discharged, the structure of the active material changes little, which is conducive to extending the service life of the battery.
  • the sodium secondary battery includes the electrolyte in the aforementioned embodiment, so the desolvation barrier of the solvated sodium ions in the electrolyte is low at low temperatures and is easily embedded in the negative electrode active material. At the same time, the electrolyte has high electrical conductivity and a strong carrying capacity for sodium ions, so it also has excellent low-temperature reaction activity.
  • the negative electrode active material may include a silicon-based material.
  • the negative electrode film layer usually optionally includes a binder, a conductive agent and other optional auxiliary agents.
  • the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the binder can be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB).
  • SBR styrene-butadiene rubber
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • EVA ethylene-vinyl acetate copolymer
  • PVA polyvinyl alcohol
  • PVB polyvinyl butyral
  • additives may be thickening and dispersing agents (eg sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials.
  • the sodium secondary battery includes a positive electrode plate, which generally includes a positive electrode current collector and a positive electrode film layer disposed on the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.
  • the positive electrode current collector may be a conventional metal foil or a composite current collector (a metal material may be disposed on a polymer substrate to form a composite current collector).
  • the positive electrode current collector may be an aluminum foil.
  • the positive electrode active material There is no limitation on the specific type of the positive electrode active material. Any active material known in the art that can be used for the positive electrode of a sodium secondary battery can be used. Those skilled in the art can select the material according to actual needs.
  • the positive electrode active material may include, but is not limited to, at least one of sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds.
  • the transition metal may be Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. At least one of.
  • the sodium transition metal oxide is, for example, Na x MO 2 , wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 ⁇ x ⁇ 1.
  • the polyanionic compound may be a class of compounds having sodium ions, transition metal ions and tetrahedral (YO 4 ) n- anion units.
  • the transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y may be at least one of P, S and Si; n represents the valence state of (YO 4 ) n- .
  • the polyanionic compound may also be a class of compounds having sodium ions, transition metal ions, tetrahedral (YO 4 ) n- anion units and halogen anions.
  • the transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y may be at least one of P, S and Si, and n represents the valence state of (YO 4 ) n- ; the halogen may be at least one of F, Cl and Br.
  • the polyanionic compound may also be a class of compounds having sodium ions, tetrahedral (YO 4 ) n- anion units, polyhedral units (ZO y ) m+ and optional halogen anions.
  • Y may be at least one of P, S and Si, and n represents the valence state of (YO 4 ) n- ; Z represents a transition metal, and may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents the valence state of (ZO y ) m+ ; the halogen may be at least one of F, Cl and Br.
  • the polyanionic compound is, for example, at least one of NaFePO 4 , Na 3 V 2 (PO 4 ) 3 , NaM'PO 4 F (M' is one or more of V, Fe, Mn and Ni) and Na 3 (VO y ) 2 (PO 4 ) 2 F 3-2y (0 ⁇ y ⁇ 1).
  • the Prussian blue compound may be a compound having sodium ions, transition metal ions and cyanide ions (CN - ).
  • the transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • the Prussian blue compound is, for example, Na a Me b Me' c (CN) 6 , wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 ⁇ a ⁇ 2, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1. These materials can be obtained through commercial channels.
  • the modified compounds of the above materials may be doping-modified and/or surface-coated modified materials.
  • the positive electrode film layer usually optionally includes a binder, a conductive agent and other optional auxiliary agents.
  • the conductive agent can be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene and carbon nanofibers.
  • the binder can be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB).
  • SBR styrene-butadiene rubber
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • EVA ethylene-vinyl acetate copolymer
  • PAA polyacrylic acid
  • CMC carboxymethyl cellulose
  • PVA polyvinyl alcohol
  • PVB polyvinyl butyral
  • auxiliary agents may be thickening and dispersing agents (such as sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials.
  • sodium metal is easily embedded in the positive electrode active material or deposited or embedded in the positive electrode active material, and is also easily de-embedded or stripped from the positive electrode active material.
  • the structure of the active material changes little, which is conducive to extending the service life of the battery.
  • transition metal oxides are easy to synthesize and have high energy density; Prussian blue analogs and polyanions have good positive electrode stability.
  • the diaphragm resistance of the positive electrode is greater than or equal to 0.1 ⁇ and less than or equal to 50 ⁇ ; optionally, the diaphragm resistance of the positive electrode is greater than or equal to 0.1 ⁇ and less than or equal to 10 ⁇ .
  • the diaphragm resistance can be measured by any known method, such as a single-probe method, a four-probe method, or a DC two-probe method, and the contact area between the probe and the positive electrode sheet is set to 49 ⁇ mm 2 .
  • the diaphragm resistance R of the positive electrode sheet is tested using a Hioki BT23562 internal resistance tester, and the upper and lower sides of the positive electrode sheet are clamped between two conductive terminals of the tester, and pressure is applied to fix them.
  • the diameter of the conductive terminals is 14 mm, and the applied pressure is 15 MPa to 27 MPa, and the diaphragm resistance of the positive electrode sheet is measured.
  • the size of the membrane resistance will affect the desolvation process of the sodium ion-solvent complex to a certain extent.
  • the electrode polarization is small, and the concentration polarization at low temperature is small, which can promote desolvation. Setting the membrane resistance of the positive electrode within this resistance range further optimizes the effect of the desolvation process and is more conducive to improving the low-temperature performance of sodium secondary batteries.
  • Sodium secondary batteries also include a separator, which is arranged between the positive electrode and the negative electrode. As an insulating layer, it can effectively prevent the positive electrode and the negative electrode from contacting each other and causing an internal short circuit, while allowing sodium ions to pass through.
  • the performance of the separator determines the interface structure and internal resistance of the sodium secondary battery, and directly affects the mechanical strength and safety performance of the battery.
  • the specific type of the material of the separator is not limited, and materials known in the art that can be used for sodium secondary battery separators can be used, and those skilled in the art can select according to needs.
  • the material of the separator may include, but is not limited to, one or more of polyolefins, fluorinated polymers, cellulose, and glass fibers.
  • Polyolefins may include, but are not limited to, one or more of polypropylene and polyethylene. These materials can all be obtained through commercial channels.
  • the isolation film includes a base film and a coating located on one side/both sides of the base film, and the coating includes a filler.
  • the filler may include an inorganic material, a polymer adhesive, Agent, dispersant, inorganic materials include one or more of boehmite and silica, polymer adhesive materials include one or more of PVDF (polyvinylidene fluoride) and polystyrene-acrylate; dispersant materials include polyvinyl alcohol and the like.
  • a filler with heat insulation and heat resistance can be added to improve the heat resistance of the isolation membrane.
  • the specific type of the base film material is not limited, and can include, but is not limited to, one or more of polyethylene, polypropylene and glass fiber. These materials can all be obtained through commercial channels.
  • the embodiment of the present application has no particular limitation on the shape of the sodium secondary battery, which can be cylindrical, square or any other shape.
  • a square-structured sodium secondary battery 100 is used as an example.
  • FIG1 is a schematic diagram of the structure of some embodiments of the sodium secondary battery 100 of the present application.
  • the sodium secondary battery 100 of the present application includes a housing 10 and a battery cell 20, and the battery cell 20 is contained in the housing 10.
  • FIG. 2 is a schematic diagram of the exploded structure of some embodiments of the sodium secondary battery 100 of the present application.
  • the housing 10 is used to provide a storage space for the battery cell 20, and the housing 10 can adopt a variety of structures.
  • the housing 10 may include a first part 11 and a second part 12, and the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 jointly define a storage space for accommodating the battery cell 20.
  • the second part 12 may be a hollow structure with one end open, and the first part 11 may be a plate-like structure, and the first part 11 covers the open side of the second part 12, so that the first part 11 and the second part 12 jointly define a storage space; the first part 11 and the second part 12 may also be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12.
  • the box body 10 formed by the first part 11 and the second part 12 can be in various shapes, such as a cylinder, a cuboid, etc.
  • the sodium secondary battery 100 there may be a plurality of battery cells 20, and the plurality of battery cells 20 may be connected in series, in parallel, or in a hybrid connection.
  • a hybrid connection means that the plurality of battery cells 20 are both connected in series and in parallel.
  • the plurality of battery cells 20 may be directly connected in series, in parallel, or in a hybrid connection, and then the whole formed by the plurality of battery cells 20 is accommodated in the box 10; of course, the sodium secondary battery 100 may also be a battery module formed by first connecting the plurality of battery cells 20 in series, in parallel, or in a hybrid connection, and then the plurality of battery modules are connected in series, in parallel, or in a hybrid connection to form a whole, and then accommodated in the box 10.
  • the sodium secondary battery 100 may also include other structures, for example, the sodium secondary battery 100 may also include a busbar component for realizing electrical connection between the plurality of battery cells 20.
  • Each battery cell 20 may be a sodium secondary battery and may be cylindrical, flat, rectangular or in other shapes.
  • Battery manufacturing methods include stacking and winding, that is, batteries are divided into stacking batteries and winding batteries.
  • Stacking batteries have uniform current collection effect, small battery internal resistance, and large specific power, but in order to ensure accuracy, the mold accuracy requirements are extremely high, the equipment investment is high, and the process is relatively complex, and the production efficiency is low.
  • Winding batteries are simple to make, and the production and assembly processes have general requirements for equipment accuracy, high production efficiency, and low cost. In terms of performance, wound batteries have excellent high and low temperature performance, very fast charging, ultra-long life, stable high output voltage, strong structure, and strong shock resistance.
  • FIG3 is a schematic diagram of the exploded structure of a battery cell 20 in some embodiments of the present application.
  • a battery cell 20 is the smallest unit that constitutes a battery. As shown in FIG3 , a battery cell 20 includes an end cap 21 , a housing 22 , an electrode assembly 23 and other functional components.
  • the end cap 21 refers to a component that covers the opening of the shell 22 to isolate the internal environment of the battery cell 20 from the external environment.
  • the shape of the end cap 21 can be adapted to the shape of the shell 22 to match the shell 22.
  • the end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 21 is not easily deformed when squeezed and collided, so that the battery cell 20 can have a higher structural strength and the safety performance can also be improved.
  • Functional components such as electrode terminals 21a can be provided on the end cap 21.
  • the electrode terminal 21a can be used to electrically connect to the electrode assembly 23 for outputting or inputting electrical energy of the battery cell 20.
  • the end cap 21 can also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold.
  • the material of the end cap 21 can also be a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose special restrictions on this.
  • an insulating member may be provided inside the end cap 21, and the insulating member may be used to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit.
  • the insulating member may be plastic, rubber, or the like.
  • the shell 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the electrode assembly 23, electrolyte and other components.
  • the shell 22 and the end cap 21 can be independent components, and an opening can be set on the shell 22, and the end cap 21 is made to cover the opening to form the internal environment of the battery cell 20.
  • the end cap 21 and the shell 22 can also be integrated.
  • the end cap 21 and the shell 22 can form a common connection surface before other components are put into the shell, and when it is necessary to encapsulate the interior of the shell 22, the end cap 21 can be made to cover the opening.
  • the cover 21 covers the housing 22.
  • the housing 22 can be in various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the electrode assembly 23.
  • the housing 22 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions on this.
  • the electrode assembly 23 is a component in the battery cell 20 where electrochemical reactions occur.
  • One or more electrode assemblies 23 may be included in the housing 22.
  • the electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets.
  • the parts of the positive and negative electrode sheets with active materials constitute the main body of the electrode assembly, and the parts of the positive and negative electrode sheets without active materials each constitute a tab 23a.
  • the positive tab and the negative tab may be located together at one end of the main body or respectively at both ends of the main body.
  • the positive active material and the negative active material react with the electrolyte, and the tab 23a connects the electrode terminals to form a current loop.
  • the electrolyte and sodium secondary battery disclosed in the embodiments of the present application can be used in electrical devices that use sodium secondary batteries as power sources or various energy storage systems that use sodium secondary batteries as energy storage elements.
  • Electrical devices can be, but are not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, etc.
  • electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc.
  • spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.
  • the energy storage system can be a hydropower, thermal, wind power, solar power station or other energy storage power supply system.
  • FIG. 4 is a schematic diagram of the structure of a vehicle 1000 according to some embodiments of the present application.
  • the vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc.
  • a sodium secondary battery 100 is arranged inside the vehicle 1000, and the sodium secondary battery 100 may be arranged at the bottom, head or tail of the vehicle 1000.
  • the sodium secondary battery 100 may be used to power the vehicle 1000, for example, the sodium secondary battery 100 may be used as an operating power source for the vehicle 1000.
  • the vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the sodium secondary battery 100 to power the motor 300, for example, for the starting, navigation and working power requirements of the vehicle 1000 during driving.
  • the sodium secondary battery 100 can be used not only as an operating power source for the vehicle 1000 , but also as a driving power source for the vehicle 1000 , replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000 .
  • the desolvation energy of the sodium ion-solvent complex formed by the sodium ions of the metal sodium salt and the solvent in the electrolyte of the sodium secondary battery of the present application is less than or equal to 100 kJ/mol. This makes the desolvation process of the metal sodium salt have a low barrier at low temperatures, and the sodium ions have a weak affinity with the solvent molecules, which improves the problem of insufficient battery capacity caused by the difficulty of desolvation of the solvated sodium ions at low temperatures, thereby making the sodium secondary battery have excellent low-temperature performance, and also making the above-mentioned electrical device and energy storage system have excellent low-temperature performance.
  • 10wt% polyvinylidene fluoride binder was fully dissolved in N-methylpyrrolidone, and 10wt% carbon black conductive agent and 80wt% positive electrode active material Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 were added to prepare a uniformly dispersed slurry.
  • the slurry was evenly coated on the surface of aluminum foil and then transferred to a vacuum drying oven for complete drying. The obtained pole piece was rolled and then punched to obtain a positive pole piece.
  • sodium hexafluorophosphate NaPF6 was dissolved in diethylene glycol dimethyl ether DEGDME (first solvent) and tetrahydrofuran THF (second solvent), and stirred evenly to obtain an electrolyte with a sodium salt concentration of 0.5 mol/L, i.e., the electrolyte of Example 1.
  • Polypropylene film is used as the isolation 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 a role of isolation, and the electrolyte is added to assemble into a laminated battery.
  • Example 19 The hard carbon in Example 19 is replaced with soft carbon, and the other steps are the same as Example 19.
  • the prepared sodium secondary battery was charged to 3.7V at a constant current of 1/3C at 0°C, and then charged at a constant voltage of 3.7V until the current dropped to 0.05C to obtain the first charging capacity (Cc1); then discharged to 1.5V at a constant current of 1/3C to obtain the first discharge capacity (Cd1), and the coulombic efficiency of the sodium secondary battery was calculated according to the following formula.
  • Sodium secondary battery coulombic efficiency first discharge capacity (Cd1) / first charge capacity (Cc1).
  • the sodium secondary battery is charged to 3.7V at a constant current of 1C at 0°C, then charged at a constant voltage of 3.7V until the current drops to 0.05C, and then discharged to 1.5V at a constant current of 1C to obtain the first cycle discharge capacity (Cd1); this charging and discharging is repeated until the nth cycle, and the discharge capacity of the sodium secondary battery after n cycles is obtained, which is recorded as Cdn, and the capacity retention rate of the sodium secondary battery is calculated according to the following formula:
  • Capacity retention rate discharge capacity after n cycles (Cdn) / first cycle discharge capacity (Cd1).
  • DCR refers to the resistance of the current in the battery cell. After the battery discharge process is completed, due to the existence of polarization, the battery voltage will rebound.
  • DC impedance technology uses the difference between the voltage before the end of the discharge and the voltage after the discharge is stabilized during the intermittent discharge process of the battery. Calculate the internal resistance of the battery.
  • the sodium secondary battery was charged to 3.7V at a constant current of 1C at 0°C, then charged at a constant voltage of 3.7V until the current dropped to 0.05C, and then discharged to 1.5V at a constant current of 1C, and then left for 5 minutes (stabilization time) before continuing the next cycle.
  • the sodium secondary battery after 100 cycles was disassembled in an argon atmosphere glove box ( H2O ⁇ 0.1ppm, O2 ⁇ 0.1ppm), and the surface morphology of the negative electrode was visually observed to determine whether sodium dendrites were generated. If there were no white spots on the negative electrode, it was determined that there were no sodium dendrites; if there were sporadic white spots on the negative electrode, it was determined that the sodium dendrites were slight; if there were dense white spots on the negative electrode, it was determined that the sodium dendrites were severe.
  • the sodium secondary batteries in each embodiment and each comparative example were tested by AC impedance using a Vmp3 electrochemical workstation to obtain impedance spectra of the desolvation process of the Na + -(solvent) x complex.
  • the desolvation energy of the Na + -(solvent) x complex in each embodiment and each comparative example can be obtained according to the Arrhenius equation.
  • V1:V2 is the volume ratio of the first solvent to the second solvent
  • Coulomb efficiency/% is after the battery is cycled 100 times
  • DCR is after the battery is cycled 100 times
  • the desolvation energy is that of the Na + -(solvent) x complex.
  • Comparative Example 2 Comparative Example 3 and Example 1 that the desolvation energy of the Na + (solvent) x complex of Comparative Example 2 using DEGDME alone and Comparative Example 3 using THF alone is greater than 100KJ/mol, while the desolvation energy of Example 1 using a combination of DEGDME and THF is reduced to less than 100KJ/mol, and the low-temperature performance of the battery of Example 1 is significantly better than that of Comparative Examples 2 and Comparative Example 3. It is proved that the combination of the first solvent and the second solvent can improve the low-temperature performance of the battery.
  • Example 1 By comparing Example 1 with Examples 6-9, it can be found that when the volume ratio of the first solvent to the second solvent is 1:1-10:1, both have higher coulombic efficiency and capacity retention after 100 cycles, lower battery DCR, no sodium dendrites, and excellent low-temperature performance. In particular, when the volume ratio of the first solvent to the second solvent is 1.5:1-5:1, the battery DCR is below 3000m ⁇ after 100 cycles.
  • Example 1 Comparing Example 1 with Examples 10-13, it can be found that the types of sodium salts are different The low temperature performance of the battery is also different. The best performance is NaPF6 in Example 1, followed by NaOTf, NaFSI, NaTFSI and NaDFOB.
  • Example 1 By comparing Example 1 and Examples 14-18, it can be seen that the types of the first solvent and the second solvent also affect the low temperature performance of the battery.
  • the performance of the sample Example 1 using DEGDME is the best, followed by TEGDME and DME.
  • the performance of the sample Example 1 using THF is better than that of the sample using DOL.
  • Comparison of Examples 18-20 shows that both the "sodium battery without negative electrode” without negative electrode active material and the traditional sodium battery with negative electrode active material have excellent low temperature performance.
  • the performance of Sample Example 18 without negative electrode active material is better than that of Examples 19 and 20 with negative electrode active material
  • the performance of Sample Example 19 with hard carbon as negative electrode active material is better than that of Sample Example 20 with soft carbon as negative electrode active material.
  • the present application provides an electrolyte for a sodium secondary battery, a sodium secondary battery, and an electrical device.
  • the electrolyte for a sodium secondary battery includes: a metal sodium salt and a solvent; wherein the desolvation energy of a sodium ion-solvent complex formed by the sodium ions of the metal sodium salt and the solvent is less than or equal to 100 kJ/mol.

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Abstract

一种钠二次电池用电解液、钠二次电池及用电装置。钠二次电池用电解液包括：金属钠盐以及溶剂；其中，金属钠盐的钠离子与溶剂形成的钠离子-溶剂配合物的去溶剂化能小于或等于100kJ/mol。通过上述方式，能够提升钠二次电池在低温下的反应动力学，提升钠二次电池的低温性能。

Description

钠二次电池用电解液、钠二次电池及用电装
相关申请的交叉引用
本申请要求以下专利申请的优先权和权益，其全部内容通过引用结合在本申请中：2023年02月06日提交至中国国家知识产权局的、申请号为202310065507.4、名称为“一种钠二次电池用电解液、钠二次电池及用电装置”的中国专利申请。
技术领域
本申请涉及电池领域，具体涉及一种钠二次电池用电解液、钠二次电池及用电装置。
背景技术
节能减排是可持续发展的关键，也就促进了能源结构的调整，推动了电池技术的发展与应用。电解液作为二次电池的重要组成部分，在电化学反应中起着离子载体的重要作用。而目前商用的用于钠二次电池的电解液在低温下粘度增大且易凝固，进而导致低的离子电导率、高的电化学阻抗和缓慢的动力学过程等问题，严重影响电池的使用寿命和循环稳定性，进一步限制了钠二次电池在低温下的实际应用。
发明内容
鉴于上述问题，本申请提供一种钠二次电池用电解液、钠二次电池及用电装置，能够提升钠二次电池在低温下的反应动力学，提升钠二次电池的低温性能。
第一方面，本申请提供了一种钠二次电池用电解液，包括：金属钠盐以及溶剂；其中，金属钠盐的钠离子与溶剂形成的钠离子-溶剂配合物的去溶剂化能小于或等于100kJ/mol。
本申请实施例的技术方案中，通过调控电解液的溶剂类型，能够调控钠离子与电解液中溶剂形成的配合物(Na+-(溶剂)x配合物)的去溶剂化能，这样的设计使得在低温时钠离子-溶剂配合物的去溶剂化过程具有低能垒， 钠离子与溶剂分子之间亲和力弱，从而改善低温时溶剂化的钠离子去溶剂化困难的问题，提升钠二次电池在低温下的反应动力学，提升钠二次电池的低温性能。
在一些实施例中，金属钠盐的摩尔浓度为0.1-1.2mol/L；可选地，金属钠盐的摩尔浓度为0.2-0.8mol/L。
通过将金属钠盐控制在较低浓度，可以减弱钠离子与溶剂分子之间的亲和力，更有效地提升电池在低温下的反应动力学。
在一些实施例中，溶剂包括第一溶剂和第二溶剂；第一溶剂包括链状醚类溶剂；第二溶剂包括二乙醚、环状醚类中的一种或多种。
其中，第一溶剂可以提高金属钠盐的溶解度，提高电解液的电导率，第二溶剂可以降低钠离子-溶剂配合物的去溶剂化势垒，提升钠离子-溶剂配合物的去溶剂化过程，通过第一溶剂和第二溶剂的相互配合，可以提高电解液的电导率和反应动力学，更有效地提升电池的低温电化学性能。
在一些实施例中，第一溶剂包括乙二醇二甲醚、乙二醇二乙醚、二乙二醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、二丙基醚以及二丁醚中的一种或多种；和/或第二溶剂包括二乙醚、1，3-二氧戊环、四氢呋喃以及甲基四氢呋喃中的一种或多种。
在一些实施例中，第一溶剂与第二溶剂的体积比大于或等于1∶1，且小于或等于10∶1；可选地，第一溶剂与第二溶剂的体积比大于或等于1.5∶1，且小于或等于5∶1。通过将第一溶剂与第二溶剂的体积比控制在上述范围内，可以提升溶剂对于金属钠盐的溶解度，进而调控金属钠盐的浓度；也能够降低钠离子-溶剂配合物的去溶剂化能，更有效地提升电池的低温电化学性能。
在一些实施例中，金属钠盐包括六氟磷酸钠、二氟草酸硼酸钠、四氟硼酸钠、双草酸硼酸钠、高氯酸钠、六氟砷酸钠、双(氟磺酰)亚胺钠、三氟甲基磺酸钠以及双(三氟甲基磺酰)亚胺钠中的一种或多种。上述金属钠盐的离子电导率较高，且电化学稳定性较强，易于提升低温下电池的电化学性能。
第二方面，本申请提供了一种钠二次电池，其包括上述实施例中的钠二次电池用电解液。
本申请实施例的技术方案中，钠二次电池的电解液中钠离子-溶剂配合物的去溶剂化能小于或等于100kJ/mol，这样的设计使得钠二次电池在低温时钠离子-溶剂配合物的去溶剂化过程具有较低势垒，钠离子与溶剂分子之间具有较弱亲和力，改善低温时溶剂化的钠离子去溶剂化困难的问题，提升钠二次电池在低温下的反应动力学，从而提升钠二次电池的低温性能。
在一些实施例中，钠二次电池为无负极钠二次电池。无负极电池的负极结构在初始状态只包括集流体，集流体表面不设置负极活性材料。无负极钠二次电池首次充电后正极材料中的金属钠迁移至负极侧，并沉积在负极集流体表面。部分金属钠会残留在负极集流体表面，再次充放电时，金属钠在负极集流体表面沉积-剥离，实现循环。该实施方式中，在低温下电解液中的钠离子-溶剂配合物的去溶剂化能垒较低，更容易实现钠的沉积与剥离，低温反应活性较高。
在一些实施例中，电池包括负极，负极包括负极集流体和负极活性材料；负极活性材料包括硅基材料、硅碳材料、碳材料、硒基材料中的一种或多种。电解液中的钠离子-溶剂配合物的去溶剂化能垒低，钠离子容易嵌入上述负极活性材料，同时也容易从上述负极活性材料上脱嵌，具有优异的低温反应活性。且电池进行充放循环时，活性材料的结构变化小，有利于延长电池的使用寿命。
在一些实施例中，电池包括正极，正极包括正极集流体以及正极活性材料；正极活性材料包括过渡金属氧化物、聚阴离子化合物以及普鲁士蓝类似物中的一种或多种。钠离子容易嵌入上述正极活性材料，同时也容易从上述正极活性材料上脱嵌，具有优异的低温反应活性。且电池进行充放循环时，活性材料的结构变化小，有利于延长电池的使用寿命。
在一些实施例中，正极的膜片电阻为0.1Ω-50Ω；可选地，正极的膜片电阻为0.1Ω-10Ω。膜片电阻的大小一定程度上会影响钠离子-溶剂配合物的去溶剂化过程，膜片电阻小时电极极化较小，低温下的浓差极化小，能够促进去溶剂化。设置正极极片的膜片电阻在该阻值范围内，进一步优化了去溶剂化过程的效果，更有利于提高电池的低温性能。
第三方面，本申请提供了一种用电装置，包括前述钠二次电池。具有优异的低温性能。
上述说明仅是本申请技术方案的概述，为了能够更清楚了解本申请的技术手段，而可依照说明书的内容予以实施，并且为了让本申请的上述和其它目的、特征和优点能够更明显易懂，以下特举本申请的具体实施方式。
附图说明
通过阅读对下文优选实施方式的详细描述，各种其他的优点和益处对于本领域普通技术人员将变得清楚明了。附图仅用于示出优选实施方式的目的，而并不认为是对本申请的限制。而且在全部附图中，用相同的附图标号表示相同的部件。在附图中：
图1是本申请钠二次电池一些实施例的结构示意图；
图2是本申请钠二次电池一些实施例的分解结构示意图；
图3是本申请一些实施例的电池单体的分解结构示意图；
图4是本申请一些实施例的车辆的结构示意图。
具体实施方式
下面将对本申请技术方案的实施例进行详细的描述。以下实施例仅用于更加清楚地说明本申请的技术方案，因此只作为示例，而不能以此来限制本申请的保护范围。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同；本文中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请；本申请的说明书和权利要求书及上述附图说明中的术语“包括”和“具有”以及它们的任何变形，意图在于覆盖不排他的包含。
在本申请实施例的描述中，技术术语“第一”“第二”等仅用于区别不同对象，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量、特定顺序或主次关系。在本申请实施例的描述中，“多个”的含义是两个以上，除非另有明确具体的限定。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的 或备选的实施例。本领域技术人员显式地和隐式地理解的是，本文所描述的实施例可以与其它实施例相结合。
在本申请实施例的描述中，术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
在本申请实施例的描述中，术语“多个”指的是两个以上(包括两个)，同理，“多组”指的是两组以上(包括两组)，“多片”指的是两片以上(包括两片)。
目前，从市场形势的发展来看，动力电池的应用越加广泛。动力电池不仅被应用于水力、火力、风力和太阳能电站等储能电源系统，而且还被广泛应用于电动自行车、电动摩托车、电动汽车等电动交通工具，以及军事装备和航空航天等多个领域。随着动力电池应用领域的不断扩大，其市场的需求量也在不断地扩增，其在不同使用环境下，尤其是低温环境(小于或等于0℃)下的性能稳定性成为研究热点。
本发明人注意到，随着环境温度的降低，传统碳酸酯基电解液的粘度逐渐增大，钠二次电池反应速率下降，对钠二次电池的低温性能稳定性是极其不利的。具有较低粘度的线性羧酸酯虽然可以作为共溶剂加入到电解液体系中降低体系粘度，但是在钠二次电池循环过程中羧酸酯易被氧化，反而会降低钠二次电池容量。
为了改善钠二次电池低温性能不佳的问题，申请人研究发现，通过降低电解液中钠离子-溶剂配合物的去溶剂化能，能够降低电解液中钠离子-溶剂配合物的去溶剂化过程的势垒，以提高钠二次电池低温下的化学反应活性，提高钠二次电池的低温性能。
基于以上考虑，为了解决钠二次电池低温性能不佳的问题，发明人经过深入研究，设计了一种钠二次电池用电解液，钠二次电池用电解液包括：金属钠盐以及溶剂；其中，金属钠盐的钠离子与溶剂形成的钠离子-溶剂配合物的去溶剂化能小于或等于100kJ/mol，通过上述方式，能够降低钠离子-溶剂配合物的去溶剂化过程的势垒，改善钠二次电池的低温性能。
该电解液应用于钠二次电池中，二次电池是指在电池放电后可通过充 电的方式使活性材料激活而继续使用的电池。利用化学反应的可逆性，实现化学能和电能的相互转化，以实现多次的充电和放电。
通常情况下，二次电池包括正极极片、负极极片、隔离膜及电解质。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。电解质在正极极片和负极极片之间起到传导离子的作用。
具体地，电解液包括电解质盐和溶剂，电解质盐溶解后形成电解质离子，通过电解质盐中电解质离子的移动来导电，当电池放电时，负极吸收电解液中的金属阳离子并释放电能。当电池充电时，负极重新向电解液中释放金属阳离子。其中，在充放电过程中，电解质离子需要去溶剂化，去溶剂化是指电解液中的金属电解质离子脱离溶剂分子包围的现象，是界面电荷转移的过程。钠二次电池的电解液中包括钠离子，主要依靠钠离子在正极和负极之间移动来工作。
对于钠二次电池，钠离子在负极极片上的电沉积过程包括：
(1)溶解在电解液中的钠离子与溶剂分子形成Na+-(溶剂)x配合物，溶剂化的钠离子从电解液转移到负极极片表面。
(2)溶剂化的钠离子在负极极片表面去溶剂化，由Na+-(溶剂)x配合物去溶剂形成游离的钠离子。
(3)去溶剂化的钠离子穿过SEI界面(Solid Electrolyte Interface，固体电解质相界面)。
(4)钠离子与负极极片中的电子结合，还原为钠原子。
其中，去溶剂化过程通常表现出较高的势垒，且其动力学过程对温度很敏感，因此，通常认为，去溶剂化过程是低温下，特别是在高倍率循环过程中的速率决定步骤。
该实施方式中，通过控制钠离子-溶剂配合物的去溶剂化能小于或等于100kJ/mol，能够降低钠离子-溶剂配合物去溶剂化的能垒，使得钠离子-溶剂配合物易于实现去溶剂化。且随着去溶剂化能的降低，钠离子更容易穿过SEI界面与电子结合，钠二次电池内部的反应活性越强，提高了低温下电池内部的化学反应速率，从而提升了钠二次电池的低温性能。
其中，去溶剂化能小于或等于100kJ/mol。去溶剂化能的测试方法，以Na+-(溶剂)x配合物为例，使用多溶剂种类，利用Vmp3电化学工作站， 分别对不同溶剂的电解液体系进行交流阻抗测试，即得到Na+去溶剂化过程的阻抗谱；根据阿仑尼乌斯方程可获得该电解液中Na+-(溶剂)x配合物的去溶剂化能。
根据本申请的一些实施例，金属钠盐的摩尔浓度为0.1-1.2mol/L(例如，0.1mol/L、0.2mol/L、0.3mol/L、0.4mol/L、0.5mol/L、0.6mol/L、0.7mol/L、0.8mol/L、0.9mol/L、1.0mol/L、1.1mol/L以及1.2mol/L等)；可选地，金属钠盐的摩尔浓度为0.2-0.8mol/L(例如，0.2mol/L、0.3mol/L、0.4mol/L、0.5mol/L、0.6mol/L、0.7mol/L以及0.8mol/L等)。或是上述任意两个数值组成的范围，例如，金属盐的摩尔浓度为0.2-0.5mol/L、0.5-0.8mol/L、0.3-0.7mol/L、0.4-0.6mol/L、0.5-1.0mol/L等。
金属钠盐的摩尔浓度是指金属钠盐整体的摩尔浓度，例如，金属钠盐为六氟磷酸钠时，六氟磷酸钠的摩尔浓度范围为0.1-1.2mol/L，可选的，六氟磷酸钠的摩尔浓度范围为0.2-0.8mol/L。
随着金属钠盐浓度的降低，钠离子与溶剂分子之间的亲和力减弱，钠离子与溶剂分子更容易分离，从而加速电化学反应速率。通过将金属钠盐的摩尔浓度范围设置为上述范围，在有足够的电池容量的同时，也可以使得在低温下钠离子与溶剂容易分离，提高钠离子在负极上沉积或嵌入的速率，从而有利于提升钠二次电池的低温性能。
根据本申请的一些实施例，溶剂包括第一溶剂和第二溶剂；第一溶剂包括链状醚类溶剂；第二溶剂包括二乙醚、环状醚类中的一种或多种。
链状醚类溶剂具有较低的粘度，一般小于1.2mPa·s，有助于低温下运载钠离子进行移动，且其与钠离子具有较强的络合作用，可以增加金属钠盐的溶解度，提高钠离子的浓度，将其作为电解液中的溶剂可以明显提高电解液的电导率，提高电池充电和放电过程中的反应速率。
二乙醚以及环状醚类均可以弱化钠离子与溶剂的溶剂化作用，有利于促进溶剂化钠离子的去溶剂化过程，降低去溶剂化能，进一步提高钠二次电池的低温性能。
第一溶剂和第二溶剂的相互配合，一方面使得电解液对钠离子具有较高的运载速率，提高电解液的电导率，另一方面形成弱溶剂化电解液促进了溶剂化钠离子的去溶剂化过程，提升了钠二次电池的低温性能。
根据本申请的一些实施例，第一溶剂包括DME(乙二醇二甲醚)、DEE(乙二醇二乙醚)、DEGDME(二乙二醇二甲醚)、TRGDME(三乙二醇二甲醚)、TEGDME(四乙二醇二甲醚)、二丙基醚以及二丁醚中的一种或多种；和/或第二溶剂包括二乙醚、DOL(1，3-二氧戊环)、THF(四氢呋喃)以及Me-THF(甲基四氢呋喃)中的一种或多种。
上述醚类溶剂分子可以在负极极片表面构建稳定的电极/电解液界面，形成稳定的SEI界面，减小电化学极化。
此外，上述醚类溶剂对金属负极极片兼容性较好，其能有效钝化金属负极极片，在金属负极极片表面形成较薄的、均一且致密的SEI界面，进一步阻止枝晶的形成，防止SEI界面因为枝晶的生长和演变进一步增厚，有利于促进钠离子的顺利传导。
根据本申请的一些实施例，第一溶剂与第二溶剂的体积比大于或等于1∶1，且小于或等于10∶1(例如，1∶1、1.5∶1、2∶1、3∶1、4∶1、4.5∶1、5∶1、6∶1、7∶1、8∶1、9∶1、9.5∶1、10∶1等)；可选地，第一溶剂与第二溶剂的体积比大于或等于1.5∶1，且小于或等于5∶1(例如，1.5∶1、2∶1、3∶1、4∶1、4.5∶1、5∶1等)。或是上述任意两个数值组成的范围。例如，第一溶剂与第二溶剂的体积比可以为2∶1-4∶1、1.5∶1-4.5∶1、3∶1-5∶1、4∶1-9∶1等。
通过将第一溶剂与第二溶剂的体积比设计为上述范围，既可以提高电解液的电导率，也可以有效弱化钠离子与溶剂的溶剂化作用，有利于促进电解液的电化学反应速率。
根据本申请的一些实施例，金属钠盐包括NaPF6(六氟磷酸钠)、NaDFOB(二氟草酸硼酸钠)、NaBF4(四氟硼酸钠)、NaBOB(双草酸硼酸钠)、NaClO4(高氯酸钠)、NaAsF6(六氟砷酸钠)、NaFSI(双(氟磺酰)亚胺钠)、NaOTf(三氟甲基磺酸钠)以及NaTFSI(双(三氟甲基磺酰)亚胺钠)中的一种或多种。
上述钠盐的离子电导率较高，且电化学稳定性较强，易于提升低温下电池的电化学性能。
在一些实施方式中，电解液中还包括添加剂。例如添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的 添加剂、改善电池低温性能的添加剂。
本申请还提供一种钠二次电池，包括前述实施例中的钠二次电池用电解液。
在一实施方式中，钠二次电池为无负极钠二次电池。其中，无负极是指在初始状态，负极结构仅包括集流体而没有活性材料。在首次充电完成后，正极材料中的金属迁移到负极集流体的表面，负极集流体上形成金属层。在充电过程中，电解液中的金属电解质离子在负极集流体表面和/或孔隙内与电子结合，发生沉积行为。在放电过程中，负极集流体表面的沉积层剥离溶解重新变为金属电解质离子和电子，回到正极，如此反复。相比传统的二次电池，无负极二次电池的能量密度进一步提升，安全性和稳定性也更高，重量和体积更小。该钠二次电池包括前述实施例中的电解液，因此在低温下电解液中的溶剂化钠离子的去溶剂化能垒低，容易穿过SEI界面并沉积在负极集流体表面，同时电解液电导率高，对钠离子的运载能力强，因此具有优异的低温反应活性。
根据本申请的一些实施例，钠二次电池的负极也可以是传统的负极结构，具体包括负极集流体及设置在负极集流体上的负极膜层，负极膜层包括负极活性材料。
负极集流体可以采用常规金属箔片或复合集流体(例如可以将金属材料设置在高分子基材上形成复合集流体)。作为示例，负极集流体可以采用铜箔。
负极活性材料的具体种类不做限制，可以采用本领域已知的能够用于钠二次电池负极的活性材料，本领域技术人员可以根据实际需求进行选择。作为示例，负极活性材料可以包括，但不限于，硅基材料、硅碳材料、碳材料、硒基材料中的一种或多种。具体包括人造石墨、天然石墨、硬碳、软碳、硅基材料和锡基材料中的一种或几种。硅基材料可选自单质硅、硅氧化合物(例如氧化亚硅)、硅碳复合物、硅氮复合物、硅合金中的一种或几种。硒基材料可选自单质硒、硒氧化合物、硒合金中的一种或几种。这些材料均可以通过商业途径获得。
该钠二次电池的工作原理为金属钠盐中的金属阳离子的嵌入-脱嵌。当电池充电的时候，钠离子从正极脱嵌，在电解液中穿过隔膜，嵌入负极活 性材料，同时，电子在外部电路从正极流向负极；当电池放电的时候，钠离子从负极活性材料脱嵌，在电解液中穿过隔膜，嵌入正极，同时，电子在外部电路中从负极流向正极。
负极活性材料可以降低负极电极阻抗，增加电极容量，减少金属钠的非正常析出。钠金属容易嵌入上述负极活性材料，同时也容易脱嵌，电池进行充放循环时，活性材料的结构变化小，有利于延长电池的使用寿命。
该钠二次电池包括前述实施例中的电解液，因此在低温下电解液中的溶剂化钠离子的去溶剂化能垒低，容易嵌入负极活性材料中，同时电解液电导率高，对钠离子的运载能力强，因此也具有优异的低温反应活性。
在一些实施方式中，为了进一步提高电池的能量密度，负极活性材料可以包括硅基材料。
负极膜层通常更可选地包括粘结剂、导电剂和其他可选助剂。
作为示例，导电剂可以为超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中一种或几种。
作为示例，粘结剂可以为丁苯橡胶(SBR)、水性丙烯酸树脂(water-based acrylic resin)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、乙烯-醋酸乙烯酯共聚物(EVA)、聚乙烯醇(PVA)及聚乙烯醇缩丁醛(PVB)中的一种或几种。
作为示例，其他可选助剂可以是增稠及分散剂(例如羧甲基纤维素钠CMC-Na)、PTC热敏电阻材料。
钠二次电池包括正极极片，正极极片通常包括正极集流体及设置在正极集流体上的正极膜层，正极膜层包括正极活性材料。
正极集流体可以采用常规金属箔片或复合集流体(可以将金属材料设置在高分子基材上形成复合集流体)。作为示例，正极集流体可以采用铝箔。
正极活性材料的具体种类不做限制，可以采用本领域已知的能够用于钠二次电池正极的活性材料，本领域技术人员可以根据实际需求进行选择。
作为示例，正极活性材料可以包括，但不限于，钠过渡金属氧化物、聚阴离子型化合物和普鲁士蓝类化合物中的至少一种。钠过渡金属氧化物中，过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce 中的至少一种。钠过渡金属氧化物例如为NaxMO2，其中M为Ti、V、Mn、Co、Ni、Fe、Cr及Cu中的一种或几种，0＜x≤1。聚阴离子型化合物可以是具有钠离子、过渡金属离子及四面体型(YO4)n-阴离子单元的一类化合物。过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种；Y可以是P、S及Si中的至少一种；n表示(YO4)n-的价态。聚阴离子型化合物还可以是具有钠离子、过渡金属离子、四面体型(YO4)n-阴离子单元及卤素阴离子的一类化合物。过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种；Y可以是P、S及Si中的至少一种，n表示(YO4)n-的价态；卤素可以是F、Cl及Br中的至少一种。聚阴离子型化合物还可以是具有钠离子、四面体型(YO4)n-阴离子单元、多面体单元(ZOy)m+及可选的卤素阴离子的一类化合物。Y可以是P、S及Si中的至少一种，n表示(YO4)n-的价态；Z表示过渡金属，可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种，m表示(ZOy)m+的价态；卤素可以是F、Cl及Br中的至少一种。聚阴离子型化合物例如是NaFePO4、Na3V2(PO4)3、NaM’PO4F(M’为V、Fe、Mn及Ni中的一种或几种)及Na3(VOy)2(PO4)2F3-2y(0≤y≤1)中的至少一种。普鲁士蓝类化合物可以是具有钠离子、过渡金属离子及氰根离子(CN-)的一类化合物。过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种。普鲁士蓝类化合物例如为NaaMebMe’c(CN)6，其中Me及Me’各自独立地为Ni、Cu、Fe、Mn、Co及Zn中的至少一种，0＜a≤2，0＜b＜1，0＜c＜1。这些材料均可以通过商业途径获得。
上述各材料的改性化合物可以是对材料进行掺杂改性和/或表面包覆改性。
正极膜层通常更可选地包括粘结剂、导电剂和其他可选助剂。
作为示例，导电剂可以为超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、Super P(SP)、石墨烯及碳纳米纤维中一种或几种。
作为示例，粘结剂可以为丁苯橡胶(SBR)、水性丙烯酸树脂(water-based acrylic resin)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、乙烯-醋酸乙烯酯共聚物(EVA)、聚丙烯酸(PAA)、羧甲基纤维素(CMC)、聚乙烯醇(PVA)及聚乙烯醇缩丁醛(PVB)中的一种或几种。
作为示例，其他可选助剂可以是增稠及分散剂(例如羧甲基纤维素钠CMC-Na)、PTC热敏电阻材料。
与负极活性材料相似，钠金属容易嵌入上述正极活性材料或者在上述正极活性材料行沉积或嵌入，同时也容易从上述正极活性材料上脱嵌或者剥离，电池进行充放循环时，活性材料的结构变化小，有利于延长电池的使用寿命。此外，过渡金属氧化物合成方便，能量密度高；普鲁士蓝类似物以及聚阴离子均具有较好的正极稳定性。
根据本申请的一些实施例，正极的膜片电阻大于或等于0.1Ω，且小于或等于50Ω；可选地，正极的膜片电阻大于或等于0.1Ω，且小于或等于10Ω。
膜片电阻可以通过任意公知的方式进行测量，例如单探针法、四探针法、直流两探针法，探针与正极极片的接触面积设置为49πmm2。本实施例，采用日置BT23562型内阻测试仪测试正极极片的膜片电阻R，将正极极片的上下侧夹持于该测试仪的两个导电端子之间，并施加压力以固定，导电端子的直径为14mm，施加压力为15MPa～27MPa，即测得正极极片的膜片电阻。
膜片电阻的大小一定程度上会影响钠离子-溶剂配合物去溶剂化过程，膜片电阻小时电极极化小，低温下的浓差极化小，能够促进去溶剂化。设置正极极片的膜片电阻在该阻值范围内，进一步优化了去溶剂化过程的效果，更有利于提高钠二次电池的低温性能。
钠二次电池还包括隔离膜，隔离膜设置在正极极片和负极极片之间，作为绝缘层可以有效防止正极极片和负极极片相接触而导致内部短路，同时使钠离子通过。隔离膜的性能决定着钠二次电池的界面结构、内阻等，直接影响着此电池的机械强度以及安全性能。
隔离膜的材料的具体种类不做限制，可以采用本领域已知的能够用于钠二次电池隔离膜的材料，本领域技术人员可以根据需求进行选择。作为示例，隔离膜的材料可以包括，但不限于，聚烯烃、含氟聚合物、纤维素、玻璃纤维中的一种或几种。聚烯烃可以包括，但不限于聚丙烯、聚乙烯中的一种或几种。这些材料均可以通过商业途径获得。
在一些实施方式中，在一些实施方式中，隔离膜包括基膜以及位于基膜一侧/两侧的涂层，涂层包括填料。填料可以包含无机材料、聚合物粘接 剂、分散剂，无机材料包括勃母石、二氧化硅中的一种或多种，聚合物粘接剂材料包括PVDF(聚偏二氟乙烯)、聚苯乙烯-丙烯酸酯中的一种或多种；分散剂材料包括聚乙烯醇等。通过在隔离膜一侧/两侧设置涂层，能够改善调控隔离膜的性能。可以通过调控填料的类型，调控隔离膜的性能。例如，可以添加具有隔热耐热性的填料，来提高隔离膜的耐热性。基膜的材料的具体种类不做限制，可以包括，但不限于，聚乙烯、聚丙烯以及玻璃纤维中的一种或几种。这些材料均可以通过商业途径获得。
本申请实施例对钠二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图1是作为一个示例的方形结构的钠二次电池100，图1为本申请钠二次电池100一些实施例的结构示意图。
在一些实施方式中，本申请的钠二次电池100包括箱体10和电池单体20，电池单体20容纳于箱体10内，请参照图2，图2为本申请钠二次电池100一些实施例的分解结构示意图。箱体10用于为电池单体20提供容纳空间，箱体10可以采用多种结构。在一些实施例中，箱体10可以包括第一部分11和第二部分12，第一部分11与第二部分12相互盖合，第一部分11和第二部分12共同限定出用于容纳电池单体20的容纳空间。第二部分12可以为一端开口的空心结构，第一部分11可以为板状结构，第一部分11盖合于第二部分12的开口侧，以使第一部分11与第二部分12共同限定出容纳空间；第一部分11和第二部分12也可以是均为一侧开口的空心结构，第一部分11的开口侧盖合于第二部分12的开口侧。当然，第一部分11和第二部分12形成的箱体10可以是多种形状，比如，圆柱体、长方体等。
在钠二次电池100中，电池单体20可以是多个，多个电池单体20之间可串联或并联或混联，混联是指多个电池单体20中既有串联又有并联。多个电池单体20之间可直接串联或并联或混联在一起，再将多个电池单体20构成的整体容纳于箱体10内；当然，钠二次电池100也可以是多个电池单体20先串联或并联或混联组成电池模块形式，多个电池模块再串联或并联或混联形成一个整体，并容纳于箱体10内。钠二次电池100还可以包括其他结构，例如，该钠二次电池100还可以包括汇流部件，用于实现多个电池单体20之间的电连接。
其中，每个电池单体20可以为钠二次电池。电池单体20可呈圆柱体、扁平体、长方体或其它形状等。
电池制作方式包括叠片式和卷绕式，即电池分为叠片电池和卷绕电池两种。叠片电池集流效果均匀，电池内阻较小，比功率大，但为了保证精度，对模具精度要求极高，设备投入高，而且工艺较为复杂，生产效率低下。卷绕电池制作简单，制片、装配过程对设备精度要求一般，生产效率高，成本较低。在性能方面，卷绕电池拥有卓越的高低温性能，充电非常迅速，拥有超长寿命，平稳的高输出电压，结构坚固、抗震性强。
请参照图3，图3为本申请一些实施例的电池单体20的分解结构示意图。电池单体20是指组成电池的最小单元。如图3，电池单体20包括有端盖21、壳体22、电极组件23以及其他的功能性部件。
端盖21是指盖合于壳体22的开口处以将电池单体20的内部环境隔绝于外部环境的部件。不限地，端盖21的形状可以与壳体22的形状相适应以配合壳体22。可选地，端盖21可以由具有一定硬度和强度的材质(如铝合金)制成，这样，端盖21在受挤压碰撞时就不易发生形变，使电池单体20能够具备更高的结构强度，安全性能也可以有所提高。端盖21上可以设置有如电极端子21a等的功能性部件。电极端子21a可以用于与电极组件23电连接，以用于输出或输入电池单体20的电能。在一些实施例中，端盖21上还可以设置有用于在电池单体20的内部压力或温度达到阈值时泄放内部压力的泄压机构。端盖21的材质也可以是多种的，比如，铜、铁、铝、不锈钢、铝合金、塑胶等，本申请实施例对此不作特殊限制。在一些实施例中，在端盖21的内侧还可以设置有绝缘件，绝缘件可以用于隔离壳体22内的电连接部件与端盖21，以降低短路的风险。示例性的，绝缘件可以是塑料、橡胶等。
壳体22是用于配合端盖21以形成电池单体20的内部环境的组件，其中，形成的内部环境可以用于容纳电极组件23、电解液以及其他部件。壳体22和端盖21可以是独立的部件，可以于壳体22上设置开口，通过在开口处使端盖21盖合开口以形成电池单体20的内部环境。不限地，也可以使端盖21和壳体22一体化，具体地，端盖21和壳体22可以在其他部件入壳前先形成一个共同的连接面，当需要封装壳体22的内部时，再使端 盖21盖合壳体22。壳体22可以是多种形状和多种尺寸的，例如长方体形、圆柱体形、六棱柱形等。具体地，壳体22的形状可以根据电极组件23的具体形状和尺寸大小来确定。壳体22的材质可以是多种，比如，铜、铁、铝、不锈钢、铝合金、塑胶等，本申请实施例对此不作特殊限制。
电极组件23是电池单体20中发生电化学反应的部件。壳体22内可以包含一个或更多个电极组件23。电极组件23主要由正极片和负极片卷绕或层叠放置形成，并且通常在正极片与负极片之间设有隔膜。正极片和负极片具有活性物质的部分构成电极组件的主体部，正极片和负极片不具有活性物质的部分各自构成极耳23a。正极极耳和负极极耳可以共同位于主体部的一端或是分别位于主体部的两端。在电池的充放电过程中，正极活性物质和负极活性物质与电解液发生反应，极耳23a连接电极端子以形成电流回路。
本申请实施例公开的电解液以及钠二次电池可以用于使用钠二次电池作为电源的用电装置或者使用钠二次电池作为储能元件的各种储能系统。用电装置可以为但不限于手机、平板、笔记本电脑、电动玩具、电动工具、电瓶车、电动汽车、轮船、航天器等等。其中，电动玩具可以包括固定式或移动式的电动玩具，例如，游戏机、电动汽车玩具、电动轮船玩具和电动飞机玩具等等，航天器可以包括飞机、火箭、航天飞机和宇宙飞船等等。
储能系统可以为水力、火力、风力和太阳能电站等储能电源系统。
以下实施例为了方便说明，以本申请一实施例的一种用电装置为车辆1000为例进行说明。
请参照图4，图4为本申请一些实施例的车辆1000的结构示意图。车辆1000可以为燃油汽车、燃气汽车或新能源汽车，新能源汽车可以是纯电动汽车、混合动力汽车或增程式汽车等。车辆1000的内部设置有钠二次电池100，钠二次电池100可以设置在车辆1000的底部或头部或尾部。钠二次电池100可以用于车辆1000的供电，例如，钠二次电池100可以作为车辆1000的操作电源。车辆1000还可以包括控制器200和马达300，控制器200用来控制钠二次电池100为马达300供电，例如，用于车辆1000的启动、导航和行驶时的工作用电需求。
在本申请一些实施例中，钠二次电池100不仅可以作为车辆1000的操作电源，还可以作为车辆1000的驱动电源，代替或部分地代替燃油或天然气为车辆1000提供驱动动力。
本申请的钠二次电池的电解液中金属钠盐的钠离子与溶剂形成的钠离子-溶剂配合物的去溶剂化能小于或等于100kJ/mol。这样使得在低温时金属钠盐的去溶剂化过程具有低势垒，钠离子与溶剂分子之间具有弱亲和力，改善低温时溶剂化的钠离子去溶剂化困难而导致的电池容量不足的问题，从而使得钠二次电池具有优异的低温性能，也使得上述用电装置和储能系统具有优异的低温性能。
下面结合具体的实施例说明钠二次电池用电解液以及钠二次电池的制备方法以及性能测试结果，本领域的技术人员将理解，本申请中描述的钠二次电池用电解液以及钠二次电池的制备方法仅是示例，其他任何合适的制备方法均在本申请的范围内。
实施例1
1.正极极片的制备：
将10wt％聚偏氟乙烯粘结剂充分溶解于N-甲基吡咯烷酮中，加入10wt％炭黑导电剂与80wt％正极活性材料Na4Fe3(PO4)2P2O7制成分散均匀的浆料。将浆料均匀涂敷在铝箔表面，然后转移到真空干燥箱中完全干燥。将得到的极片进行辊压，然后进行冲切，得到正极极片。
2.负极极片的制备：
将4wt％碳纳米管材料和1.6wt％聚合物粘结剂羧甲基纤维素钠加到水中搅拌成均匀的浆料，将浆料涂覆在铜箔表面上，然后转移到真空干燥箱中完全干燥，然后进行冲切，得到负极极片。
3.电解液的制备：
在氩气气氛手套箱中(H2O＜0.1ppm，O2＜0.1ppm)，将钠盐六氟磷酸钠NaPF6溶解于二乙二醇二甲醚DEGDME(第一溶剂)和四氢呋喃THF(第二溶剂)中，搅拌均匀，得到钠盐浓度0.5mol/L的电解液，即实施例1的电解液。
4.隔离膜：
以聚丙烯膜作为隔离膜。
5.钠二次电池的制备：
将上述正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间，起到隔离的作用，加入上述电解液组装成叠片电池。
除电解液配方不同以外，实施例2-18、对比例1-3的其他步骤与实施例1相同。
实施例19-20
除负极极片的制备不同以外，其他步骤与实施例1相同。
实施例19负极极片的制备：
将90wt％硬碳、5wt％乙炔黑、4％粘结剂苯乙烯-丁二烯橡胶和1wt％粘结剂羧甲基纤维素钠加到水中搅拌成均匀的浆料，将浆料涂覆在铜箔表面上，然后转移到真空干燥箱中完全干燥，然后进行冲切，得到负极极片。实施例20负极极片的制备：
将实施例19中的硬碳更换为软碳，其他步骤与实施例19相同。
性能测试方法
1.库伦效率：
将制得的钠二次电池在0℃下以1/3C的恒定电流充电至3.7V，之后以3.7V恒压充电至电流降到0.05C，得到首次充电容量(Cc1)；再以1/3C的恒定电流放电至1.5V，得到首次放电容量(Cd1)，并按照下式计算钠二次电池库伦效率。
钠二次电池库伦效率＝首次放电容量(Cd1)/首次充电容量(Cc1)。
2.容量保持率：
将钠二次电池在0℃下以1C的恒定电流充电至3.7V，之后以3.7V恒压充电至电流降到0.05C，再以1C的恒定电流放电至1.5V，得到首圈放电容量(Cd1)；如此反复充放电至第n圈，得钠二次电池循环n圈后的放电容量，记为Cdn，并按照下式计算钠二次电池容量保持率：
容量保持率＝循环n圈后的放电容量(Cdn)/首圈放电容量(Cd1)。
3.DCR(Directive Current Resistance，直流电阻)：
DCR是指电流在电芯内部受到的阻力，电池在放电过程结束后，由于极化的存在，电池电压会出现反弹的现象。直流阻抗技术就是利用电池在间歇放电过程中，放电结束前一瞬间的电压与放电结束稳定后的电压差来 计算电池内阻的。
将钠二次电池在0℃下以1C的恒定电流充电至3.7V，之后以3.7V恒压充电至电流降到0.05C，再以1C的恒定电流放电至1.5V，后搁置5min(稳定时间)，继续下一个循环，每个循环记录放电中止前的电池电压和电池电压稳定后的电池电压，然后利用以下公式计算直流阻抗R＝ΔU/I(其中：ΔU为电压差，R为直流电阻，I为放电电流)。
4.钠枝晶：
将上述循环100圈后的钠二次电池在氩气气氛手套箱(H2O＜0.1ppm，O2＜0.1ppm)进行拆解，目视观察负极极片表面形貌，确定是否有钠枝晶生成。负极极片无白点判定为钠枝晶情况无、负极极片有零星白点判定为钠枝晶情况轻微、负极极片有密密麻麻白点判定为钠枝晶情况严重。
各实施例和各对比例的成分及性能测试结果请参考表1。
5.去溶剂化能
利用Vmp3电化学工作站，分别对各实施例和各对比例中的钠二次电池进行交流阻抗测试，得到Na+-(溶剂)x配合物去溶剂化过程的阻抗谱。根据阿仑尼乌斯方程可获得各实施例和各对比例中Na+-(溶剂)x配合物的去溶剂化能。
表1：各实施例和各对比例的成分及性能测试结果

注：V1∶V2为第一溶剂与第二溶剂的体积比；库伦效率/％为电池循环100圈后的；DCR为电池循环100圈后的，去溶剂化能为Na+-(溶剂)x配合物的。
结果分析
1.将实施例1-20与对比例1-3进行对比，可以看出，实施例1-20中Na+(溶剂)x配合物的去溶剂化能均小于100KJ/mol，其库伦效率以及循环100圈后的容量保持率高均较对比例1-3高，循环100圈后电池DCR均较对比例1-3低，且无钠枝晶，具有更好的低温性能。而对比例1-3的去溶剂化能大于100KJ/mol，其低温性能明显低于实施例1-20，由此可以看出去溶剂化能小于或等于100KJ/mol能有效提升钠二次电池的低温性能。
2.将实施例1-20、对比例1与对比例2-3进行对比，可以看出，因为实施例1-20以及对比例1中的溶剂为第一溶剂和第二溶剂的组合，因此其库伦效率以及循环100圈后的容量保持率高均较对比例2-3高，循环100圈后电池DCR均较对比例2-3低，除了对比例1有轻微的枝晶外，实施例1-20均没有枝晶。此外，从对比例2、对比例3和实施例1可以看出，单独使用DEGDME的对比例2和单独使用THF的对比例3的Na+(溶剂)x配合物的去溶剂化能均大于100KJ/mol，而将DEGDME和THF组合使用的实施例1，去溶剂化能则降低到100KJ/mol以下，实施例1的电池低温性能明显优于对比例2和对比例3。证明了第一溶剂和第二溶剂的组合可以提高电池的低温性能。
3.将实施例1-5以及对比例1对比，可以看出，当钠盐浓度在0.1-1.2mol/L之间时，库伦效率和循环100圈后的容量保持率较高，且无钠枝晶，具有较好的电池性能。尤其是当钠盐浓度在0.2-0.8mol/L时，电池性能进一步提升。但是对于钠盐浓度超过0.1-1.2mol/L的对比例1，虽然溶剂包括第一溶剂和第二溶剂，但是由于钠盐浓度过高，Na+(溶剂)x配合物的去溶剂化能大于100KJ/mol，出现了轻微的枝晶，电池性能不如实施例1-5，证明了使用0.1-1.2mol/L钠盐浓度的电解液，可以提高电池的低温性能。
4.将实施例1以及实施例6-9进行对比，可以发现当第一溶剂和第二溶剂的体积比为1∶1-10∶1时，均有较高的库伦效率以及循环100圈后的容量保持率，均有较低的电池DCR，且均无钠枝晶，有优异的低温性能。尤其是当第一溶剂和第二溶剂的体积比为1.5∶1-5∶1时，循环100圈后电池DCR均在3000mΩ以下。
5.将实施例1以及实施例10-13进行对比，可以发现钠盐的种类不同 时，电池的低温性能也有所差异，性能最好的为实施例1的NaPF6，其次依次为NaOTf、NaFSI、NaTFSI以及NaDFOB。
6.将实施例1以及实施例14-18进行对比，可以看到，第一溶剂和第二溶剂的种类对于电池的低温性能也有影响。在表1中的实施例中，对于第一溶剂来说，使用DEGDME的样品实施例1的性能最为优异，TEGDME和DME次之，对于第二溶剂来说，使用THF的样品实施例1比使用DOL的样品的性能更为优异。
7.对比实施例18-20可以得知，无论是负极无活性材料的“无负极钠电池”还是负极有活性材料的传统钠电池都具有优异的低温性能。此外，无负极活性材料的样品实施例18的性能要优于具有负极活性材料的实施例19和20，且负极活性材料为硬碳的样品实施例19的性能要优于负极活性材料为软碳的样品实施例20。
综上所述，本申请提供了一种钠二次电池用电解液、钠二次电池及用电装置。其中，钠二次电池用电解液包括：包括金属钠盐以及溶剂；其中，金属钠盐的钠离子与溶剂形成的钠离子-溶剂配合物的去溶剂化能小于或等于100kJ/mol。通过上述方式，能够提升钠二次电池在低温下的反应动力学，提升钠二次电池的低温性能。
最后应说明的是：以上各实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述各实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围，其均应涵盖在本申请的权利要求和说明书的范围当中。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (15)

  1. 一种钠二次电池用电解液，其特征在于，
    包括金属钠盐以及溶剂；
    其中，所述金属钠盐的钠离子与所述溶剂形成的钠离子-溶剂配合物的去溶剂化能小于或等于100kJ/mol。
  2. 根据权利要求1所述的钠二次电池用电解液，其特征在于，
    所述金属钠盐的摩尔浓度为0.1-1.2mol/L。
  3. 根据权利要求2所述的钠二次电池用电解液，其特征在于，
    所述金属钠盐的摩尔浓度为0.2-0.8mol/L。
  4. 根据权利要求1所述的钠二次电池用电解液，其特征在于，
    所述溶剂包括第一溶剂和第二溶剂；
    所述第一溶剂包括链状醚类溶剂；
    所述第二溶剂包括二乙醚、环状醚类中的一种或多种。
  5. 根据权利要求4所述的钠二次电池用电解液，其特征在于，
    所述第一溶剂包括乙二醇二甲醚、乙二醇二乙醚、二乙二醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、二丙基醚以及二丁醚中的一种或多种；和/或
    所述第二溶剂包括二乙醚、1，3-二氧戊环、四氢呋喃以及甲基四氢呋喃中的一种或多种。
  6. 根据权利要求4所述的钠二次电池用电解液，其特征在于，
    所述第一溶剂与所述第二溶剂的体积比大于或等于1∶1，且小于或等于10∶1。
  7. 根据权利要求6所述的钠二次电池用电解液，其特征在于，
    所述第一溶剂与所述第二溶剂的体积比大于或等于1.5∶1，且小于或等于5∶1。
  8. 根据权利要求1-7任一项所述的钠二次电池用电解液，其特征在于，
    所述金属钠盐包括六氟磷酸钠、二氟草酸硼酸钠、四氟硼酸钠、双草酸硼酸钠、高氯酸钠、六氟砷酸钠、双(氟磺酰)亚胺钠、三氟甲基磺酸钠以及双(三氟甲基磺酰)亚胺钠中的一种或多种。
  9. 一种钠二次电池，其特征在于，包括如权利要求1-8任一项所述的 钠二次电池用电解液。
  10. 根据权利要求9所述的钠二次电池，其特征在于，
    所述电池为无负极钠二次电池。
  11. 根据权利要求9所述的钠二次电池，其特征在于，
    所述电池包括负极，所述负极包括负极集流体和负极活性材料；
    所述负极活性材料包括硅基材料、硅碳材料、碳材料、硒基材料中的一种或多种。
  12. 根据权利要求9-11任一项所述的钠二次电池，其特征在于，
    所述电池包括正极，所述正极包括正极集流体以及正极活性材料；
    所述正极活性材料包括过渡金属氧化物、聚阴离子化合物以及普鲁士蓝类似物中的一种或多种。
  13. 根据权利要求12所述的钠二次电池，其特征在于，
    所述正极的膜片电阻为0.1Ω-50Ω。
  14. 根据权利要求13所述的钠二次电池，其特征在于，
    所述正极的膜片电阻为0.1Ω-10Ω。
  15. 一种用电装置，其特征在于，包括如权利要求9-14任一项所述的钠二次电池。
PCT/CN2023/118202 2023-02-06 2023-09-12 钠二次电池用电解液、钠二次电池及用电装置 Ceased WO2024164532A1 (zh)

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EP23920724.4A EP4641738A4 (en) 2023-02-06 2023-09-12 SODIUM-ION SECONDARY BATTERY ELECTROLYTE, SODIUM-ION SECONDARY BATTERY AND ELECTRICAL APPLIANCE
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