Achieving Highly Reversible All-Solid-State Lithium-Sulfur Batteries through Metal–Sulfur Bonding Regulation

Single-atom catalysts (SACs) are extensively utilized as sulfur cathode promoters in liquid lithium–sulfur batteries owing to their remarkable catalytic efficacy. Nonetheless, their utilization in all-solid-state lithium–sulfur batteries (ASSLSBs) is largely constrained by the unclear metal–sulfur (M–S) interactions in the solid state. Herein, we suggest that the strength of the M–S bond formed between SACs and sulfur can be an indicator to evaluate the bidirectional catalytic ability of SACs. Single atomic sites that possess fewer occupied antibonding states bond the sulfur species robustly via enhanced d–p orbital hybridization, which effectively catalyze the redox reaction. However, the excessively strong M–S bond increases the risk of catalyst poisoning, owing to the solid-state interface characteristics. Among the prepared three SACs, CoNC featuring moderate M–S interactions displays superior rate and cycling performances. An initial capacity of 1151 mAh g–1 is achieved at 2C, with a capacity retention rate of up to 94.66% after 500 cycles.