Achieving reversible precipitation-decomposition of reactive Li2S towards high-areal-capacity lithium-sulfur batteries with a wide-temperature range

Abstract Facilitating polysulfide conversion by electrocatalysis is a promising strategy to suppress shuttle effect in lithium-sulfur (Li-S) batteries, yet the active sites in electrocatalysts are gradually passivated by continuous formation of Li2S passivation layer over cycling, making it challenging to achieve steady conversion of sulfur species. Herein, a strategy of reactive Li2S collaborated with dual-directional Fe3C electrocatalyst is proposed to achieve fast and continuous conversion of sulfur species for drastically boosting the performance of Li-S batteries. During the reduction process, reactive Li2S with unique three-dimensional porous structure is precipitated on Fe3C surface, which not only shortens ion/electron diffusion path but also exposes and retains more active sites in Fe3C. While for the following oxidation process, Fe3C also promotes the decomposition of reactive Li2S to refresh electrocatalyst surface. Therefore, the high catalytic activity of Fe3C is well retained during the entire electrochemical process, as verified by comprehensive experimental and theoretical calculation results. Eventually, Fe3C enables stable operation of high-areal-capacity Li-S batteries (> 6.0 mAh cm−2) under a wide-temperature range (-10 to 40 °C). Our strategy of coupling reactive Li2S with a bidirectional electrocatalyst provides a new avenue for developing high-energy and wide-temperature Li-S batteries.