Innovating Rechargeable Zn-Air Batteries for Low Charging Voltage and High Energy Efficiency

The commercialization of rechargeable zinc-air batteries (ZABs) is significantly impeded by their high charging voltage and low energy efficiency. In this work, we apply soluble KI to ZABs as a reaction modifier to change the oxidation pathway in the charging process from oxygen evolution reaction to I– oxidation reaction (IOR), which enjoys lower oxidation potential and faster kinetics. In addition, we surprisingly find that commercial cost-effective XC72R carbon delivers satisfactory bifunctional IOR and oxygen reduction reaction activity. Density functional theory calculation is provided to demonstrate the IOR mechanism by XC72R carbon. Finally, the KI-modified ZABs with XC72R exhibit a low charging voltage of 1.79 V, improved energy efficiency of 65.3% (2.0 V and 60% for conventional ZABs with noble-metal catalysts), and long cycle life of over 120 h at 5 mA cm–2. Further characterizations have illuminated the reason behind the extended battery cycle life as well. This work can significantly facilitate the future use of rechargeable ZABs in energy storage.