Electrolyte Engineering for Long-Life Li-SPAN Batteries

Sulfurized polyacrylonitrile, or SPAN, has been studied as an alternative to elemental sulfur as a cathode in lithium–sulfur batteries. Unlike elemental S, the material features a solid-phase conversion reaction during charge and discharge, which shows promise in providing long cycle life under lean electrolyte conditions. However, this altered mechanism also imposes a unique set of electrolyte design requirements. In this Review, we outline the key advancements in electrolyte engineering and discuss the design principles of these electrolytes with a focus on the solvation structures and their ability to control the interphasial chemistry on both the Li and the SPAN surfaces. We then argue for the need to develop electrolytes with improved transport properties while preserving their high stabilities in order to realize Li-SPAN batteries with practical energy densities.