Highly Reversible Positive‐Valence Conversion of Sulfur Chemistry for High‐Voltage Zinc–Sulfur Batteries

Sulfur is a promising conversion‐type cathode for zinc batteries (ZBs) due to its high discharge capacity and cost‐effectiveness. However, the redox conversion of multivalent S in ZBs is still limited, only having achieved S0/S2− redox conversion with low discharge voltage and poor reversibility. This study presents significant progress by demonstrating, for the first time, the reversible S2−/S4+ redox behavior in ZBs with up to six‐electron transfer (with an achieved discharge capacity of ≈1284 mAh g−1) using a highly concentrated ClO4−‐containing electrolyte. The developed succinonitrile–Zn(ClO4)2 eutectic electrolyte stabilizes the positive‐valence S compound and contributes to an ultra‐low polarization voltage. Notably, the achieved flat discharge plateaus demonstrate the highest operation voltage (1.54 V) achieved to date in Zn‖S batteries. Furthermore, the high‐voltage Zn‖S battery exhibits remarkable conversion dynamics, excellent cycling performance (85.7% capacity retention after 500 cycles), high efficiency (98.4%), and energy density (527 Wh kg S−1). This strategy of positive‐valence conversion of sulfur represents a significant advancement in understanding sulfur chemistry in batteries and holds promise for future high‐voltage sulfur‐based batteries. The highly reversible S2‐/S4+ redox behavior with up to six‐electron transfer is achieved in zinc batteries based on the highly concentrated ClO4−‐containing eutectic electrolyte, which can stabilize the positive‐valence S compound. Notably, the achieved conversion process demonstrates the highest operation voltage achieved to date in Zn‖S batteries and delivered remarkable electrochemical performance.