Selenium-Anchored Chlorine Redox Chemistry in Aqueous Zinc Dual-Ion Batteries.

Chlorine-based batteries with Cl to Cl redox reaction (ClRR) are promising for high-performance energystorage due to their high redox potential and large theoretical capacity. However, the inherent gas-liquid conversion feature of ClRR together with poor Cl fixation can cause Cl leakage, reducing battery reversibility. Herein, we utilize a Se-based organic molecule, diphenyl diselenide (di-Ph-Se), as the Cl anchoring agent and realize an atomic level-Cl fixation through chalcogen-halogencoordinating chemistry. The promoted Cl fixation, with two oxidized Cl anchoring on a single Ph-Se, and the multivalence conversion of Se contributeto a six-electron conversion process with up to 507 mAh g and an average voltage of 1.51 V, as well as a high energy density of 665 Wh Kg . Based on the superior reversibility of thedeveloped di-Ph-Se electrode with ClRR, a remarkable rate performance (205 mAh g at 5 A g ) and cycling performance (capacity retention of 77.3 % after 500cycles) are achieved. Significantly, the pouch cell delivers a record arealcapacity of up to 6.87 mAh cm and extraordinary self-discharge performance. This chalcogen-halogen coordination chemistry between the Se electrode and Cl provides a new insight for developing reversible and efficientbatteries with halogen redox reactions.