Diminishing Soluble Tetrasulfide to Stabilize Li‐S Chemistry

ABSTRACT The understanding of Li‐S chemistry is evolving beyond the solely classical stepwise reaction mechanism toward intricate multiple reaction pathways. The coexistent liquid polysulfides in electrolytes necessitate role differentiation and pathway manipulation to restrain the shuttling effect. As discharge deepens in Li‐S system, Li 2 S 4 accumulates to high abundance and is prone to shuttling adversely between electrodes driven by the electric field and concentration diffusion. Herein, we propose diminishing Li 2 S 4 to stabilize Li‐S chemistry by simultaneously promoting the relative speed of its consumption and generation and circumventing the Li 2 S 4 ‐generation pathway. The Mg 4 C 60 catalyst with all‐catalytic‐active sites accelerates Li 2 S 4 ‐to‐Li 2 S reduction and facilitates the direct Li 2 S 6 ‐to‐Li 2 S conversion. LiOTF/MPE‐based electrolyte, featuring low polysulfides solubility and high donor number, decelerates Li 2 S 6 ‐to‐Li 2 S 4 reduction and expedites the dissociation of Li 2 S 6 into S 3 · − radicals. Accordingly, Li‐S batteries deliver a high capacity of 1331.3 mAh g −1 at 0.2 C and maintain 75.9% of the capacity after 1200 cycles at 5 C. A stable 0.8 Ah Li‐S pouch cell is achieved, corresponding to the cell‐level‐energy density of 509.7 Wh kg −1 . This work establishes a systematic framework for reaction pathway manipulation to eliminate soluble tetrasulfide and stabilize Li‐S batteries.