Dual-atom pairs with electron buffering enable ultrastable-cycling all-solid-state lithium–sulfur batteries

ABSTRACT All-solid-state lithium–sulfur batteries (ASSLSBs) show promise in balancing high energy density and safety, but face the bottleneck of sluggish sulfur conversion kinetics. Single-atom catalysts (SACs) could alleviate this by maximizing active-site utilization and intimate contact with sulfur. However, the metal centers often undergo irreversible electronic reconstruction, causing fast degradation and capacity fading. Here, we report an atomic-scale electron buffering strategy with electronegativity-matched dual-metal atom sites, which strengthen interfacial bonding with sulfur species while maintaining stability. The dual-metal Cu and Ni atoms are anchored on the polymeric carbon nitride (Cu1Ni1–PCN) to form spatial proximity (∼3.4 Å) single-atom pairs with similar electronegativity. This pair mediates electron buffering between the metals, enabling dynamic valence modulation that suppresses deactivation and enhances interfacial d–p orbital hybridization with sulfur. Consequently, the catalyst enables consistently low activation energy during long cycling, retaining a high capacity of 948 mAh g−1 after 2500 cycles at 1 mA cm−2 and exhibiting almost no capacity decay over 7000 cycles at 2 mA cm−2. This work establishes electron buffering as a robust approach to stabilize atomic-scale catalysts and offers a general design framework for high-performance sulfur electrocatalysis in ASSLSBs.