An Ultrastable Aqueous Iodine‐Hydrogen Gas Battery

Rechargeable hydrogen gas batteries are highly desirable for large‐scale energy storage because of their long life cycle, high round trip efficiency, fast reaction kinetics, and hydrogen gas profusion. Coupling advanced cathode chemistries with hydrogen gas anode is an emerging and exciting area of research. Here, a novel high‐performance aqueous iodine‐hydrogen gas (I2‐H2) battery using iodine as cathode and hydrogen gas as the electrocatalytic anode in environmentally benign aqueous electrolytes is reported. The working chemistry of the battery involves I2/I− solid‐liquid reactions occurring over the cathode along with H2/H2O gas‐liquid reactions at the anode, achieving a high rate performance of 100 C and long‐lasting stability of over 60 000 cycles. Additionally, the static aqueous I2‐H2 battery displays a volumetric capacity of 15.5 Ah L−1 along with good self‐healing capability towards cell overcharge. The current battery design exhibits robust electrochemical performance irrespective of acidic, neutral, and alkaline electrolyte systems. This study paves the way towards the industrialization of economically effective, high‐power density, and long‐term I2‐H2 batteries for large‐scale energy storage applications. A novel aqueous iodine‐hydrogen gas (I2‐H2) battery is proposed using iodine as the cathode and hydrogen gas as the electrocatalytic anode in eco‐friendly aqueous electrolytes. The battery is operated by solid‐liquid reactions of I2/I− in the cathode and gas‐liquid reactions of H2/H2O in the anode with a high rate, long cycling stability, and good self‐healing capability toward cell overcharge.