Reducing Overpotential of Solid‐State Sulfide Conversion in Potassium‐Sulfur Batteries

To achieve a superior potassium-sulfur battery performance, we elucidate the solid-state K₂S₃−K₂S conversion pathway via meta-stable intermediates on a range of transition metal single-atom catalytic sulfur hosts. It is demonstrated that the host with Cu single atom exhibits a relatively weak Cu-S bonding, resulting in low overpotential of K₂S₃−K₂S conversion. The resultant catalytic sulfur host demonstrates high discharge capacities of 1595 and 1226 mAh g⁻¹ under 335 and 1675 mA g⁻¹, respectively.

Abstract

Improving kinetics of solid-state sulfide conversion in sulfur cathodes can enhance sulfur utilization of metal-sulfur batteries. However, fundamental understanding of the solid-state conversion remains to be achieved. Here, taking potassium-sulfur batteries as a model system, we for the first time report the reducing overpotential of solid-state sulfide conversion via the meta-stable S₃ ²⁻ intermediates on transition metal single-atom sulfur hosts. The catalytic sulfur host containing Cu single atoms demonstrates high capacities of 1595 and 1226 mAh g⁻¹ at current densities of 335 and 1675 mA g⁻¹, respectively, with stable Coulombic efficiency of ≈100 %. Combined spectroscopic characterizations and theoretical computations reveal that the relatively weak Cu-S bonding results in low overpotential of solid-state sulfide conversion and high sulfur utilization. The elucidation of solid-state sulfide conversion mechanism can direct the exploration of highly efficient metal-sulfur batteries.

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