I₃⁻ : mediated oxygen evolution activities to boost rechargeable zinc-air battery performance with low charging voltage and long cycling life

Abstract

An effective strategy to facilitate oxygen redox chemistry in metal-air batteries is to introduce a redox mediator into the liquid electrolyte. The rational utilization of redox mediators to accelerate the charging kinetics while ensuring the long lifetime of alkaline Zn-air batteries is challenging. Here, we apply commercial acetylene black catalysts to achieve an I3−-mediated Zn-air battery by using ZnI2 additives that provide I3− to accelerate the cathodic redox chemistry and regulate the uniform deposition of Zn2+ on the anode. The Zn-air battery performs an ultra-long cycle life of over 600 h at 5 mA cm−2 with a final charge voltage of 1.87 V. We demonstrate that I− mainly generates I3− on the surface of carbon catalysts during the electrochemically charging process, which can further chemically react with OH− to generate oxygen and further revert to I−, thus obtaining a stable electrochemical system. This work offers a strategy to simultaneously improve the cycling life and reduce the charging voltage of Zn-air batteries through redox mediator methods. Graphical abstract: [Figure not available: see fulltext.]