An ester electrolyte for lithium–sulfur batteries capable of ultra-low temperature cycling

A novel lithium bis(fluorosulfonyl)imide in a methyl propionate/fluoroethylene carbonate (LiFSI MP/FEC) electrolyte was designed for high compatibility with the Li metal and sulfurized polyacrylonitrile (SPAN). The resulting Li||SPAN cells can charge and discharge at -20 °C and -40 °C with over 91% and 78% room temperature capacity retention.