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CN-122025768-A - Lithium battery electrolyte and preparation method and application thereof

CN122025768ACN 122025768 ACN122025768 ACN 122025768ACN-122025768-A

Abstract

The invention provides a lithium battery electrolyte, a preparation method and application thereof, and the raw materials for preparing the lithium battery electrolyte comprise: thionyl chloride, lithium tetrachloroaluminate, sulfur dioxide, and nitrogen trifluoride. According to the invention, nitrogen trifluoride is added into the electrolyte, and the nitrogen trifluoride reacts with the metal lithium negative electrode to generate a lithium fluoride enriched solid electrolyte interface with high ion conductivity on the surface of the electrode in situ, so that the lithium ion transmission efficiency is remarkably improved, and the voltage hysteresis phenomenon is effectively improved. The preparation method has simple process and obvious effect, and provides a new solution for the development of the high-performance lithium thionyl chloride battery.

Inventors

  • WANG SONGRU
  • XIANG XINYUAN
  • XU YANGMING
  • ZHANG ZHUORAN
  • Zhang Nuoxi

Assignees

  • 武汉中原长江科技发展有限公司

Dates

Publication Date
20260512
Application Date
20260113

Claims (10)

  1. 1. The lithium battery electrolyte is characterized by comprising thionyl chloride, lithium tetrachloroaluminate, sulfur dioxide and nitrogen trifluoride as raw materials for preparing the lithium battery electrolyte.
  2. 2. The lithium battery electrolyte according to claim 1, wherein the nitrogen trifluoride accounts for 2-8% of the total mass of the thionyl chloride and the lithium tetrachloroaluminate.
  3. 3. The lithium battery electrolyte according to claim 1, wherein the sulfur dioxide accounts for 5-7% of the total mass of the thionyl chloride and the lithium tetrachloroaluminate.
  4. 4. A method for preparing a lithium battery electrolyte according to any one of claims 1 to 3, comprising the steps of: S1, purifying thionyl chloride, drying lithium tetrachloroaluminate, sulfur dioxide and nitrogen trifluoride; S2, mixing thionyl chloride and lithium tetrachloroaluminate to obtain a premix; and S3, mixing the premix, sulfur dioxide and nitrogen trifluoride to obtain the lithium battery electrolyte.
  5. 5. The process according to claim 4, wherein in step S1, the thionyl chloride is purified by distillation in a fume hood and/or, In the step S1, the specific steps of drying the lithium tetrachloroaluminate are that the lithium tetrachloroaluminate is placed in a vacuum drying oven to be dried for 12 hours under the condition of 70 ℃, then the dried argon is introduced to replace three times and is continuously dried for 12 hours under the condition of 70 ℃, and/or, In step S1, the method for drying sulfur dioxide and nitrogen trifluoride comprises the steps of introducing sulfur dioxide and nitrogen trifluoride into a gas washing cylinder filled with molecular sieve to obtain dried sulfur dioxide and nitrogen trifluoride.
  6. 6. The process of claim 5 wherein sulfur dioxide and nitrogen trifluoride are dried in a gas wash cylinder containing molecular sieve, wherein the molecular sieve is type 3A molecular sieve.
  7. 7. The preparation method according to claim 4, wherein in the step S2, the thionyl chloride and the lithium tetrachloroaluminate are mixed in such a manner that the purified thionyl chloride is added to the dried lithium tetrachloroaluminate and stirred to obtain a premix, and/or, In step S2, the concentration of lithium tetrachloroaluminate in the premix is 1mol/L.
  8. 8. The preparation method according to claim 4, wherein in the step S2, the obtained premix is mixed with sulfur dioxide and nitrogen trifluoride after impurity removal, and the specific steps of impurity removal are that the lithium sheet is put into the premix, heated and refluxed at 60-70 ℃ until the lithium sheet becomes black, filtered, another lithium sheet is put into the filtered premix, reflux is continued for 1h, if the lithium sheet is not black, impurity removal is completed, and if the lithium sheet becomes black, the above operation is continued until the lithium sheet is not significantly black.
  9. 9. The method according to claim 4, wherein in step S3, the sulfur dioxide and nitrogen trifluoride are mixed by introducing sulfur dioxide into the premix and then introducing nitrogen trifluoride.
  10. 10. A lithium ion battery comprising the lithium battery electrolyte according to any one of claims 1 to 3 or the lithium battery electrolyte prepared by the preparation method according to any one of claims 4 to 9.

Description

Lithium battery electrolyte and preparation method and application thereof Technical Field The invention belongs to the technical field of lithium batteries, and particularly relates to a lithium battery electrolyte, a preparation method and application thereof. Background The lithium thionyl chloride battery is a typical nonaqueous inorganic electrolyte battery, the negative electrode is a metal lithium sheet, the positive electrode is porous carbon, the lithium thionyl chloride battery does not participate in electrode reaction, and a thionyl chloride solution of lithium tetrachloroaluminate is used as an electrolyte, wherein thionyl chloride is used as a solvent and an active substance to participate in the positive electrode reaction. The battery is a primary battery with highest specific energy in batteries used nowadays, has a wide working temperature range, high specific energy, low annual self-discharge rate and long storage life, and therefore has a very important role in series batteries for practical application. The total reaction of the lithium thionyl chloride battery is 4Li+2SOCl 2→4LiCl+S+SO2, so that a layer of LiCl film is firstly generated after the metal lithium is contacted with thionyl chloride and is attached to the surface of the metal lithium, the porous material is gradually thickened along with the time until the electrode is completely blocked from being contacted with electrolyte, the occurrence of side reaction is avoided, and the long-time storage of the battery is ensured. However, it has been studied that the passage of ions through a solid electrolyte membrane (SEI film, the main component of which is LiCl) is a step of determining the reaction inside a battery, and therefore, an LiCl film having relatively low ion conductivity and being too thick increases ion transport resistance, resulting in voltage hysteresis at discharge and deterioration of high-current discharge performance. Currently, few solutions to the above problems have been reported. Therefore, there is a need to develop a new method to alleviate the lithium thionyl chloride battery voltage hysteresis problem. Disclosure of Invention In view of the above, the invention provides a lithium battery electrolyte, a preparation method and application thereof, which remarkably improves lithium ion transmission efficiency and effectively improves voltage hysteresis. In order to achieve the above purpose, the invention adopts the following technical scheme: In a first aspect, the invention provides a lithium battery electrolyte, which is prepared from thionyl chloride, lithium tetrachloroaluminate, sulfur dioxide and nitrogen trifluoride. Preferably, the nitrogen trifluoride comprises 2-8% of the total mass of the thionyl chloride and the lithium tetrachloroaluminate. Preferably, the sulfur dioxide accounts for 5-7% of the total mass of the thionyl chloride and the lithium tetrachloroaluminate. In a second aspect, the invention provides a preparation method of the lithium battery electrolyte, which comprises the following steps: S1, purifying thionyl chloride, drying lithium tetrachloroaluminate, sulfur dioxide and nitrogen trifluoride; S2, mixing thionyl chloride and lithium tetrachloroaluminate to obtain a premix; and S3, mixing the premix, sulfur dioxide and nitrogen trifluoride to obtain the lithium battery electrolyte. Preferably, in step S1, the specific step of purifying thionyl chloride is distillation purification of thionyl chloride in a fume hood, and/or, In the step S1, the specific steps of drying the lithium tetrachloroaluminate are that the lithium tetrachloroaluminate is placed in a vacuum drying oven to be dried for 12 hours under the condition of 70 ℃, then the dried argon is introduced to replace three times and is continuously dried for 12 hours under the condition of 70 ℃, and/or, In step S1, the method for drying sulfur dioxide and nitrogen trifluoride comprises the steps of introducing sulfur dioxide and nitrogen trifluoride into a gas washing cylinder provided with a molecular sieve to remove water and obtain dried sulfur dioxide and nitrogen trifluoride. Preferably, sulfur dioxide and nitrogen trifluoride are dried by passing them into a gas wash cylinder containing a molecular sieve, wherein the molecular sieve is a type 3A molecular sieve. Preferably, in step S2, the specific steps of mixing thionyl chloride and lithium tetrachloroaluminate are that purified thionyl chloride is added into dry lithium tetrachloroaluminate, stirred to obtain a premix, and when purified thionyl chloride is added into dry lithium tetrachloroaluminate, slow addition is required to avoid rapid heat release leading to explosion of electrolyte, and/or, In step S2, the concentration of lithium tetrachloroaluminate in the premix is 1mol/L. Preferably, in the step S2, the obtained premix is required to be subjected to impurity removal, and then the obtained premix is mixed with sulfur dioxide and nitrogen trifluoride,