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

Chlorine-based batteries with Cl 0 to Cl - redox reaction (ClRR) are promising for high-performance energy storage 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 2 leakage, reducing battery reversibility and raising the safety concern. 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-halogen coordinating chemistry, achieving a highly reversible ClRR with extra low Cl 2 emission and a notably high discharge voltage (1.87 V versus Zn 2+ /Zn). The promoted Cl fixation, with two oxidized Cl 0 anchoring on a single Ph-Se, and the multivalence conversion of Se contribute to a six-electron conversion process, resulting in a significantly high discharge capacity of up to 507 mAh g -1 with an average voltage of 1.51 V and a high Coulombic efficiency of 99.3%, as well as a high energy density of 665 Wh Kg -1 . Based on the superior reversibility of the developed di-Ph-Se electrode with ClRR, a remarkable rate performance (205 mAh g -1 at 5 A g -1 ) and cycling performance (with a capacity retention of 77.3% after 500 cycles) are achieved. Significantly, the pouch cell delivers a record areal capacity of up to 6.87 mAh cm -2 and extraordinary self-discharge performance, demonstrating great potential for practical applications. This chalcogen-halogen coordination chemistry between the Se electrode and Cl provides a new insight for developing reversible and efficient batteries with halogen redox reactions. This article is protected by copyright. All rights reserved.