Six-electron-conversion selenium cathodes stabilized by dead-selenium revitalizer for aqueous zinc batteries
Jingwei Du, Jiaxu Zhang, Xingyuan Chu, Hao Xu, Yirong Zhao, Markus Löffler, Gang Wang, Dongqi Li, Quanquan Guo, Ahiud Morag, Jie Du, Jianxin Zou, Daria Mikhailova, Vlastimil Mazánek, Zdeněk Sofer, Xinliang Feng, Minghao Yu
Abstract
Abstract Aqueous zinc batteries are attractive for large-scale energy storage due to their inherent safety and sustainability. However, their widespread application has been constrained by limited energy density, underscoring a high demand of advanced cathodes with large capacity and high redox potential. Here, we report a reversible high-capacity six-electron-conversion Se cathode undergoing a ZnSe↔Se↔SeCl 4 reaction, with Br − /Br n − redox couple effectively stabilizes the Zn | |Se cell. This Se conversion, initiated in a ZnCl 2 -based hydrogel electrolyte, presents rapid capacity decay (from 1937.3 to 394.1 mAh g Se −1 after only 50 cycles at 0.5 A g Se −1 ) primarily due to the dissolution of SeCl 4 and its subsequent migration to the Zn anode, resulting in dead Se passivation. To address this, we incorporate the Br − /Br n − redox couple into the Zn | |Se cell by introducing bromide salt as an electrolyte additive. The generated Br n − species acts as a dead-Se revitalizer by reacting with Se passivation on the Zn anode and regenerating active Se for the cathode reaction. Consequently, the cycling stability of the Zn | |Se cell is improved, maintaining 1246.8 mAh g Se −1 after 50 cycles. Moreover, the Zn | |Se cell exhibits a specific capacity of 2077.6 mAh g Se −1 and specific energy of 404.2 Wh kg −1 based on the overall cell reaction.