Improved Ether-Based Battery Electrolytes

Improved Ether-Based Battery Electrolytes

Author: Angewandte Chemie International Edition

Ether-based electrolytes with high reduction stability are important in the development of batteries. However, their generally insufficient stability toward oxidation and high flammability restrict applications in high-voltage lithium-metal batteries.

Inspired by the flame-retarding mechanism of chlorine in fire-extinguishing agents, Xiaodi Ren, University of Science and Technology of China, Hefei, and colleagues have used a chloroether, i.e., 1,2-bis(2-chloroethoxy) ethane (Cl-DEE, pictured), as the base solvent in a localized high-concentration electrolyte (LHCE) system. The electrolyte system contained lithium bis(fluorosulfonyl)imide (LiFSI), Cl-DEE, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether (TTE). The additional chlorine groups improve the oxidation stability and turn the highly flammable parent molecule DEE (pictured) into a flame retardant, increasing the flashpoint from 35 °C to 126 °C

The team found that the formulated chloroether electrolyte allows for stable battery operation at an ultrahigh voltage of up to 4.7 V. LiF/LiCl-enriched interphases formed on the cathode and the anode effectively suppress undesired side reactions for better cycling life. The molecular design concept of chlorine substitution in this work could provide a useful approach to developing safe lithium-metal batteries with high energy density.


 

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