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CN-122025800-A - Electrolyte of lithium-carbon fluoride battery with high specific capacity, preparation method and application thereof

CN122025800ACN 122025800 ACN122025800 ACN 122025800ACN-122025800-A

Abstract

The invention discloses an electrolyte of a high specific capacity lithium-fluorocarbon battery and a preparation method and application thereof, wherein the electrolyte comprises double lithium salts and a multi-component solvent, the double lithium salts are lithium tetrafluoroborate (LiBF 4) and lithium difluorosulfimide (LiWSI), the multi-component solvent contains Tetrahydrofuran (THF) and 1, 3-Dioxolane (DOL), and at least one of Methyl Acetate (MA), N-diethyl-2, 2-trifluoroacetamide (DMTFA), ethylene Carbonate (EC) and m-fluorotoluene (m-FT) is not simultaneously contained with MA and DMTFA, the discharge specific capacity of the battery at normal temperature and low temperature is improved through the combined design of the differentiated lithium salts and the multi-component solvent, the synergistic requirements of wide temperature range, high interface stability and high safety are solved, and the electrolyte can be kept to operate efficiently in a wide temperature range.

Inventors

  • GAO JUN
  • ZHANG MEILAN
  • CAI YUEZONG
  • YANG YONG

Assignees

  • 厦门大学

Dates

Publication Date
20260512
Application Date
20260320

Claims (10)

  1. 1. An electrolyte of a lithium-fluorocarbon battery with high specific capacity is characterized by comprising a double lithium salt and a multicomponent solvent, wherein the double lithium salt is lithium tetrafluoroborate (LiBF 4 ) and lithium difluorosulfimide (LiFSI), the multicomponent solvent contains Tetrahydrofuran (THF) and 1, 3-Dioxolane (DOL) and at least one of Methyl Acetate (MA), N-diethyl-2, 2-trifluoroacetamide (DMTFA), ethylene Carbonate (EC) and m-fluorotoluene (m-FT), the multicomponent solvent does not contain MA and DMTFA at the same time, the THF has a ratio in the range of 10-80 vol%, the DOL has a ratio in the range of 10-30 vol%, when MA is contained, the ratio in the range of 10-30 vol%, when EC is contained, the ratio in the range of 10-20 vol% and when EC is contained, the ratio in the range of 10-30 vol% when M-FT is contained.
  2. 2. The electrolyte of a lithium-carbon fluoride battery with high specific capacity according to claim 1, wherein the concentration of LiBF 4 is 0.2-1.0 mol/L and the concentration of LiFSI is 0.2-1.0 mol/L.
  3. 3. The electrolyte of a high specific capacity lithium-fluorocarbon battery of claim 2, wherein the total concentration of the double lithium salt is 0.5-2.0 mol/L.
  4. 4. The electrolyte of a high specific capacity lithium-carbon fluoride battery according to claim 3, wherein the total concentration of the double lithium salts is 0.8 to 1.2 mol/L.
  5. 5. The electrolyte of a high specific capacity lithium-fluorocarbon battery according to claim 1, wherein the multicomponent solvent consists of 40 to 80 vol% THF, 10 to 30 vol% DOL and 10 to 30 vol% MA.
  6. 6. The electrolyte of a high specific capacity lithium-fluorocarbon battery of claim 1, wherein the multicomponent solvent consists of 40 to 80 vol% THF, 10 to 30 vol% DOL and 10 to 30 vol% DMTFA.
  7. 7. The electrolyte of a high specific capacity lithium-fluorocarbon battery of claim 1, wherein the multicomponent solvent consists of 10 to 30 vol% THF, 10 to 30 vol% DOL, 10 to 20 vol% EC, 10 to 30 vol% MA and 10 to 30 vol% m-FT.
  8. 8. A preparation method of the electrolyte of the lithium-carbon fluoride battery with high specific capacity is characterized by comprising the steps of uniformly mixing the components of the multi-component solvent according to claim 1 to obtain the multi-component solvent, and then adding two lithium salts of LiBF 4 and LiFSI to fully dissolve to obtain the electrolyte of the lithium-carbon fluoride battery with high specific capacity.
  9. 9. A high specific capacity lithium-fluorocarbon battery comprising the electrolyte of any one of claims 1 to 7.
  10. 10. The high specific capacity lithium-fluorocarbon battery of claim 9, comprising a positive electrode, a negative electrode, a diaphragm and the electrolyte, wherein the positive electrode is formed by mixing fluorocarbon powder, conductive agent and binder, the negative electrode is a lithium sheet or a lithium belt, the diaphragm is arranged between the positive electrode and the negative electrode, and the electrolyte is added to assemble the battery.

Description

Electrolyte of lithium-carbon fluoride battery with high specific capacity, preparation method and application thereof Technical Field The invention relates to the technical field of batteries, in particular to electrolyte of a lithium-carbon fluoride battery with high specific capacity, and a preparation method and application thereof. Background Lithium-carbon fluoride (Li/CF x) batteries have high energy density, long shelf life, low self-discharge rate, and light weight, and have been receiving attention because of meeting the operational demands of extreme environments such as emergency power supplies, military fields, deep sea exploration, and the like. In lithium-carbon fluoride batteries, the electrolyte serves as a key ion transport medium, providing a thermodynamically stable environment for li+ cross-electrode migration, whose ionic conductivity directly affects the rate capability of the battery. However, as the ambient temperature decreases, the viscosity of the electrolyte increases and the ionic conductivity decreases, which causes slow kinetics and impedes the lithium ion desolvation process, resulting in a significant decrease in the discharge capacity of the Li/CF x cell. In addition, electrolyte is decomposed during storage, and the gas production of the battery bulges, resulting in degradation of battery performance and safety problems. Aiming at the problem of performance decay of a lithium-carbon fluoride battery in a complex environment, it is important to develop an electrolyte which has high discharge capacity at low temperature and good storage stability. In order to improve the performance of lithium-fluorocarbon batteries in complex environments, researchers are adopting various strategies such as adding potassium electrolyte and anion acceptor additive (CN 117525469 a) to the base electrolyte, with a maximum discharge capacity of 699 mAh/g at-40 ℃. In addition, the release paper of China science: chemistry, the university Wu Xinglong of northeast university in 2023 shows that the weak solvation structure of Tetrahydrofuran (THF) and 1, 3-Dioxolane (DOL) which are coordinated by the close anions and the separation solvent is introduced, so that the discharge capacity at-40 ℃ is up to 723 mAh/g, the boiling point of the two ether solvents is lower, the gas is easily generated after the ether solvents are stored, and the safety is greatly compromised. Disclosure of Invention Aiming at the problems, the invention provides a high-performance electrolyte which is matched with lithium tetrafluoroborate (LiBF 4) and lithium bis (fluorosulfonyl) imide (LiFSI) and has a synergistic function and is suitable for lithium-carbon fluoride batteries, in order to solve the problem of low-temperature ion migration dynamics blocking. The electrolyte not only ensures that the lithium-carbon fluoride battery has higher normal-temperature discharge capacity, but also has higher low-temperature discharge performance. In order to achieve the above object, the technical scheme of the present invention is as follows: An electrolyte of a high specific capacity lithium-fluorocarbon battery comprises a double lithium salt and a multi-component solvent, wherein the double lithium salt is lithium tetrafluoroborate (LiBF 4) and lithium difluorosulfimide (LiFSI), the multi-component solvent contains Tetrahydrofuran (THF) and 1, 3-Dioxolane (DOL) and comprises at least one of Methyl Acetate (MA), N-diethyl-2, 2-trifluoroacetamide (DMTFA), ethylene Carbonate (EC) and m-fluorotoluene (m-FT), the multi-component solvent does not contain MA and DMTFA at the same time, the THF has a ratio in the range of 10-80 vol%, the DOL has a ratio in the range of 10-30 vol%, when MA is contained, the ratio in the range of 10-30 vol%, when EC is contained, the ratio in the range of 10-30 vol% when EC is contained, and the ratio in the range of 10-20 vol% when M-FT is contained. Optionally, the concentration of LiBF 4 is 0.2-1.0 mol/L, and the concentration of LiFSI is 0.2-1.0 mol/L. Further preferably, the total concentration of the double lithium salt is 0.5-2.0 mol/L. Further preferably, the total concentration of the double lithium salt is 0.8-1.2 mol/L. Optionally, the multicomponent solvent is composed of 40 to 80 vol% THF, 10 to 30 vol% DOL, and 10 to 30 vol% MA. Optionally, the multicomponent solvent is composed of 40 to 80 vol% THF, 10 to 30 vol% DOL, and 10 to 30 vol% DMTFA. Optionally, the multicomponent solvent is composed of 10-30 vol% THF, 10-30 vol% DOL, 10-20 vol% EC, 10-30 vol% MA and 10-30 vol% m-FT. The electrolyte comprises the following components: The lithium salt system adopts a differential coordination double-salt design, combines LiBF 4 with strong binding capacity with LiFSI with strong dissociation capacity and high conductivity, and aims to realize functional complementation by the characteristics of different anions. LiBF 4 is helpful to form a stable interface and improve low-temperature ion transmis