An intrinsic safe siloxane ether-based electrolyte for lithium-sulfur batteries at high temperatures

Abstract

As the next candidate of secondary batteries, lithium-sulfur (Li-S) batteries are hampered by short cycle life and safety issues caused by combustion of electrolytes and unstable cycling performance generated by Li dendrites growth, which become more serious when Li-S batteries are operated at high temperatures. To solve these problems, an intrinsic flame-retardant siloxane ether-based electrolyte, 2.5 M LiFSI/tetrapropoxysilane (TPOS), is innovatively investigated in Li-S batteries with sulfurized pyrolyzed poly(acrylonitrile) (SPAN) cathode at 80 ℃. This electrolyte exhibits desirable flame retardancy, unique solvation structure and excellent interfacial stability. Particularly, this electrolyte performs outstandingly in cathode protection derived from the robust and flexible electrolyte/electrode interphases simultaneously for Li metal anode and SPAN cathode. Li-S batteries delivered a reversible capacity of 760 mAh gSPAN−1 (1535 mAh gsulfur−1) and a capacity retention of 98.4 % after 85 cycles at 1C and 80 ℃. This work provides the concept and paves the way to develop high temperature Li-S batteries.