An energetic K+-S aqueous battery with 96% sulfur redox utilization

Potassium-sulfur electrochemistry represents a compelling energy storage technology due to its cost-efficient chemicals and unparalleled capacity. However, achieving high sulfur redox utilization (SRU) remains a great challenge during K + storage due to K 2 S n kinetics inertia. Here, for the first time, we unveil an aqueous K + -S electrochemistry, leveraging boosted K 2 S n conversion kinetics in water. A stable two-electron charge transfer process is achieved via tuning K 2 S solubility. Spectroscopic evaluation and molecular dynamics simulations reveal a unique solid-liquid-solid conversion pathway (S ↔ K 2 S 4 ↔ K 2 S), which effectively avoids soluble K 2 S shuttling. Consequently, an unprecedented K + storage capacity of 1,619 mAh g −1 ( ca. 96% SRU) can be achieved with 95% initial Coulombic efficiency, appealing cyclability over 500 times, and a high-energy density of 392 Wh kg S+Zn −1 . These findings signify a paradigm shift and introduce transformative opportunities for the design of safe and high-energy aqueous batteries.