Hydrated Eutectic Electrolytes Stabilizing Quasi‐Underpotential Mg Plating/Stripping for High‐Voltage Mg Batteries
Guigui Liu, Yongchao Tang, Hongqing Li, Jiangfeng He, Minghui Ye, Yufei Zhang, Zhipeng Wen, Xiaoqing Liu, Cheng Chao Li
Abstract
Abstract Aqueous rechargeable Mg batteries (ARMBs) usually fail from severe anode passivation, alternatively, executing quasi‐underpotential Mg plating/stripping chemistry (UPMC) on a proper heterogeneous metal substrate is a crucial remedy. Herein, a stable UPMC on Zn substrate is initially achieved in new hydrated eutectic electrolytes (HEEs), delivering an ultralow UPMC overpotential and high energy/voltage plateau of ARMBs. The unique eutectic property remarkably expands the lower limit of electrochemical stability window (ESW) of HEEs and undermines the competition between hydrogen evolution/corrosion reactions and UPMC, enabling a reversible UPMC. The UPMC is carefully revealed by multiple characterizations, which shows a low overpotential of 50 mV at 0.1 mA cm −2 over 550 h. With sulfonic acid‐doped polyaniline (SPANI) cathodes, UPMC‐based full cells show high energy/power densities of 168.6 Wh kg −1 /2.1 kWh kg −1 and voltage plateau of 1.3 V, far overwhelming conventional aqueous systems.