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 g_S ^-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.