Hybrid-ion strategy enables ultra-long life aqueous iron-organic batteries

Among aqueous batteries, the research on the battery employing metal as the anode is still mainly focused on the aqueous zinc-ion battery. Compared with zinc, iron has better stability for reversible deposition, lower cost, and higher specific capacity, which is suitable for aqueous batteries. In this study, an aqueous iron-organic battery is constructed by employing polyaniline as the cathode, Fe plate as the anode, and Fe(CF3SO3)2 as the electrolyte, which demonstrates the hybrid storage mechanism of iron plating/stripping in the anode and transmission of CF3SO3− in the cathode. The polyaniline-Fe battery delivers a specific capacity of 105.8 mAh g−1 at a current density of 0.05 A g−1 and a stable cycle performance over 5,000 cycles with almost no capacity fading at a current density of 0.2 A g−1, which provides a new direction for the development of aqueous iron-ion batteries.