A high-energy potassium–sulfur battery enabled by facile and effective imidazole-solvated copper catalysts

Abstract

The potassium–sulfur (K–S) battery is a promising low-cost energy storage technology; however, its development is limited by a low achievable capacity (∼560 mAh g_S⁻¹) and a low average cell voltage (typically <1.5 V) owing to the formation of thermodynamic traps (K₂S₃) and sluggish reduction kinetics. In this study, we design a facile and effective homogeneous catalyst, 1-methylimidazole (Me-Im) solvated-copper, to promote the reduction kinetics of K₂S₃ to K₂S, achieving a high reversible sulfur capacity of 922 mAh g_S⁻¹ with a high average cell voltage of 1.93 V, corresponding to a gravimetric energy of 1779 Wh kg_S⁻¹. X-ray photoelectron spectroscopy, X-ray diffraction and density functional theory calculation elucidated the working mechanism of the Me-Im-solvated Cu catalyst toward weakening the S–S bond in K₂S₃ and promoting the formation of K₂S. This work provides a key strategy to achieve high-energy reversible potassium–sulfur batteries.