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CN-122025797-A - Electrolyte applied to alkali metal secondary battery and having wide temperature range and high working voltage

CN122025797ACN 122025797 ACN122025797 ACN 122025797ACN-122025797-A

Abstract

The invention belongs to the field of batteries, and particularly discloses an electrolyte applied to an alkali metal secondary battery and having a wide temperature range and a high working voltage. The electrolyte comprises a first alkali metal salt, a second alkali metal salt, an ether solvent and a fluorine-containing diluent, wherein the molar ratio of the ether solvent to the fluorine-containing diluent is 1 (0.1-5), and the molar ratio of the first alkali metal salt to the second alkali metal salt is 1 (0.5-20). The battery assembled by the electrolyte has the capability of working under the condition of wide temperature range, keeps high working voltage, and realizes high energy density, and particularly, the working temperature can reach-70 ℃, and the working voltage is more than 4.4V.

Inventors

  • DENG WEI
  • LI XUEZHONG
  • LI WENQING
  • TANG YONGBING

Assignees

  • 中国科学院深圳先进技术研究院

Dates

Publication Date
20260512
Application Date
20260309

Claims (10)

  1. 1. An electrolyte is characterized by comprising a first alkali metal salt, a second alkali metal salt, an ether solvent and a fluorine-containing diluent, wherein the molar ratio of the ether solvent to the fluorine-containing diluent is 1 (0.1-5), and the molar ratio of the first alkali metal salt to the second alkali metal salt is 1 (0.5-20); the first alkali metal salt and the second alkali metal salt are lithium salts, or the first alkali metal salt and the second alkali metal salt are sodium salts.
  2. 2. The electrolyte of claim 1, wherein the first alkali metal salt comprises at least one of lithium bisoxalato borate, lithium difluorooxalato borate, lithium bisoxalato diphosphate, lithium difluorophosphate, lithium nitrate, lithium tetrafluoroborate, lithium bisfluorosulfonamide, or at least one of sodium bisoxalato borate, sodium difluorooxalato borate, sodium bisoxalato diphosphate, sodium difluorophosphate, sodium nitrate, sodium tetrafluoroborate, sodium bisfluorosulfonamide; And/or the molar concentration of the first alkali metal salt in the electrolyte is 0.1-2 mol/L.
  3. 3. The electrolyte of claim 1, wherein the second alkali metal salt comprises at least one of lithium difluorosulfonamide, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium difluorooxalato borate, lithium bisoxalato diphosphate, lithium bistrifluorosulfonimide, or at least one of sodium bisfluorosulfonamide, sodium hexafluoroarsenate, sodium hexafluorophosphate, sodium difluorooxalato borate, sodium bisoxalato diphosphate, and sodium bistrifluorosulfonimide; And/or the molar concentration of the second alkali metal salt in the electrolyte is 0.5-5 mol/L.
  4. 4. The electrolyte according to claim 1, wherein the fluorine-containing diluent comprises at least one of a fluoroether-type diluent and a fluorobenzene-type diluent; And/or the number of the groups of groups, the fluorine-containing diluent comprises 1, 2-tetrafluoroethyl methyl ether, 1, 2-tetrafluoroethyl ether, bis (2, 2-trifluoroethyl) ether 1, 2-tetrafluoroethyl-2, 2-trifluoroethyl ether, hexafluoroisopropyl ether, 2, 3-pentafluoropropyl methyl ether 1, 2-tetrafluoroethyl-2, 2-trifluoroethyl ether hexafluoroisopropyl ether, 2, 3-pentafluoropropyl methyl ether Bis (1, 2) Tetrafluoroethoxy) ethane, 3 At least one of fluorobenzene, m-fluorotoluene, m-fluorobenzotrifluoride and m-benzotrifluoride.
  5. 5. The electrolyte according to claim 1, wherein the ether solvent comprises at least one of a chain ether solvent and a cyclic ether solvent.
  6. 6. The electrolyte according to claim 5, wherein the chain ether solvent comprises at least one of dimethyl ether, diethyl ether, methylethyl ether, methylpropyl ether, methylisopropyl ether, methylbutyl ether, methylisobutyl ether, methyl t-butyl ether, dipropyl ether, isopropyl ether, dibutyl ether, diphenyl ether, anisole, phenetole, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol mono t-butyl ether, dipropylene glycol monoethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, dimethoxymethane, diethoxymethane, 1, 2-dimethoxypropane, 1-dimethoxypropane, diallyl ether, ethylvinyl ether, and methyl vinyl ether; And/or the cyclic ether solvent comprises ethylene oxide, propylene oxide, epichlorohydrin, cyclohexane oxide, phenethyl oxide, 2-methyl propylene oxide, 1, 2-butylene oxide, oxetane, 3-methyl oxetane, 3-dimethyl oxetane, tetrahydrofuran, 2-methyl tetrahydrofuran, 3-methyl tetrahydrofuran, 2, 5-dimethyl tetrahydrofuran, 1, 3-dioxolane, 4-methyl-1, 3-dioxolane, 2-methyl-1, 3-dioxolane, 4, 5-dimethyl-1, 3-dioxolane, furan, 2-methyl furan, tetrahydrofurfuryl alcohol, cyclopentyl methyl ether, 1, 4-dioxane, 1, 3-dioxane, 4-methyl-1, 4-dioxane, tetrahydropyran, 2-methyl tetrahydropyran, 4-methyl tetrahydropyran, 2, 6-dimethyl tetrahydropyran, 12-crown-4, 15-crown-5, 18-crown-6, dicyclohexyl-18-benzo-6, 3-crown-5 At least one of butylene oxide.
  7. 7. The electrolyte according to claim 5, wherein the ether solvent comprises a chain ether solvent and a cyclic ether solvent in a volume ratio of (0 to 10): 1.
  8. 8. The method for preparing the electrolyte according to any one of claims 1 to 7, which is characterized by comprising the following steps: the fluorine-containing aqueous dispersion is prepared by mixing materials comprising a first alkali metal salt, a second alkali metal salt, an ether solvent and a fluorine-containing diluent.
  9. 9. An alkali metal secondary battery comprising the electrolyte according to any one of claims 1 to 7.
  10. 10. An electric device is characterized by comprising the electrolyte according to any one of claims 1 to 7 or the alkali metal secondary battery according to claim 9.

Description

Electrolyte applied to alkali metal secondary battery and having wide temperature range and high working voltage Technical Field The invention belongs to the field of batteries, and particularly relates to an electrolyte applied to an alkali metal secondary battery and having a wide temperature range and a high working voltage. Background The lithium metal battery is used as a battery with high energy density and has wide application in the fields of electric automobiles, energy storage systems and the like. However, the lithium metal battery has various problems in the cycle process, such as short cycle life caused by growth of lithium dendrite, low ionic conductivity of electrolyte at low temperature, poor low-temperature performance, short storage time at high temperature, decomposition of electrolyte and the like, which severely limit the large-scale commercial application of the lithium metal battery. In the traditional carbonate electrolyteBelow 20 ℃ a significant performance drop is exhibited, which is mainly caused by the increased viscosity of the carbonate solvent at low temperatures and the rapid decrease in conductivity. At present, the design of low-temperature lithium battery electrolyte is not limited by the mixing of multi-carbonic acid esters, but is designed towards modified ester and ether electrolyte, electrolyte based on carboxylic ester base solvent or fluorinated carboxylic ester, local high-concentration electrolyte (LHCEs) and the like, wherein the ester base solvent is unstable to a lithium cathode, the fluorinated carboxylic ester solvent and LHCEs have higher cost, and the problems of corrosion of a current collector by the used lithium salt and the like further aggravate the cost. In addition, lithium ions have high desolventizing energy barrier in high-polarity solvents such as conventional esters and ethers, and the formed interfacial film has low ion transmission rate and poor stability, so that the problem that the charging is difficult due to overlarge polarization of the negative electrode side during low-temperature charging, electrolyte is decomposed at high temperature, and transition metal on the positive electrode side is dissolved out is solved. Disclosure of Invention In order to overcome at least one technical problem of the prior art, one of the purposes of the present invention is to provide an electrolyte. The second purpose of the invention is to provide a preparation method of the electrolyte. It is a third object of the present invention to provide an alkali metal secondary battery. The fourth object of the invention is to provide an electric device. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: The first aspect of the invention provides an electrolyte, which comprises a first alkali metal salt, a second alkali metal salt, an ether solvent and a fluorine-containing diluent, wherein the molar ratio of the ether solvent to the fluorine-containing diluent is 1 (0.1-5), and the molar ratio of the first alkali metal salt to the second alkali metal salt is 1 (0.5-20); the first alkali metal salt and the second alkali metal salt are lithium salts, or the first alkali metal salt and the second alkali metal salt are sodium salts. In the invention, anions, ether solvents and fluorine-containing diluents in the first alkali metal salt and the second alkali metal salt are weakly coordinated with alkali metal ions, so that solvation structure and interface behavior are regulated and controlled, the stability of an electrode/electrolyte interface of a battery assembled by an electrolyte is improved, the performance of an alkali metal secondary battery under a high-low temperature working condition is obviously improved, the oxidation stability of the electrolyte is further improved through the fluorine-containing diluents, the viscosity and solidifying point of the electrolyte are reduced, and the ion transmission rate, the interface stability and the oxidation potential of the electrolyte are improved, so that the electrolyte disclosed by the invention has excellent electrochemical performance under a wide-temperature-range and high-voltage condition and excellent high-low temperature resistance. In addition, the first alkali metal salt and the second alkali metal salt have competitive effects in ether solvents and fluorine-containing diluents to balance the binding capacity between cation-anion-solvents in the electrolyte, thereby constructing a wide-temperature-range and high-voltage electrolyte. In some embodiments of the invention, the molar ratio of the first alkali metal salt to the ether solvent is 1 (5-15), and in some embodiments of the invention, the molar ratio of the first alkali metal salt to the ether solvent is any one or any two of the values 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15. In some embodiments of the invention, the molar ratio of the ether solvent to the fluorine-containing