High-entropy sulfides enhancing adsorption and catalytic conversion of lithium polysulfides for lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) batteries with high energy density suffer from the soluble lithium polysulfide species. Traditional metal sulfides containing a single metal element used as electrocatalysts for Li-S batteries commonly have limited catalytic abilities to improve battery performance. Herein, based on the Hume-Rothery rule and solvothermal method, the high-entropy sulfide NiCoCuTiVS_x derived from Co₉S₈ was designed and synthesized, to realize the combination of small local strain and excellent catalytic performance. With all five metal elements (Ni, Co, Cu, Ti, and V) capable of chemical interactions with soluble polysulfides, NiCoCuTiVS_x exhibited strong chemical confinement of polysulfides and promoted fast kinetics for polysulfides conversion. Consequently, the S/NiCoCuTiVS_x cathode can maintain a high discharge capacity of 968.9 mA h g⁻¹ after 200 cycles at 0.5 C and its capacity retention is 1.3 times higher than that of S/Co₉S₈. The improved cycle stability can be attributed to the synergistic effect originating from the multiple metal elements, coupled with the reduced nucleation and activation barriers of Li₂S. The present work opens a path to explore novel electrocatalyst materials based on high entropy materials for the achievement of advanced Li-S batteries.