Exploiting deep sulfur conversion by tandem catalysis for all-solid-state lithium–sulfur batteries

All-solid-state lithium–sulfur batteries (ASSLSBs) promise high theoretical energy density and inherent safety, but their full capacity delivery is seriously hindered by incomplete sulfur conversion. Here, we propose to exploit deep conversion of S8 to Li2S via intermediate Li2S2 by using tandem catalysis for high-capacity ASSLSBs, which we demonstrate by cobalt single-atom catalysts anchored on a conductive MXene substrate. In contrast to commonly believed one-step S8 reduction to Li2S in ASSLSBs, our results show that tandem catalysis achieves stepwise S8 reduction to Li2S via Li2S2, during which atomically dispersed Co sites break S–S bonds and the polar MXene surface facilitates Li+ diffusion, significantly reducing the sulfur conversion energy barriers. Consequently, the Co@MX-based ASSLSB reserves a high capacity of 1329 mAh gS−1 after 2000 cycles at 2.8 mA cm−2 at room temperature. This work demonstrates the promise of tandem catalysis for tailoring an all-solid-state sulfur conversion path and exploiting deep sulfur conversion capacity for high-performance ASSLSBs.