Bifunctional air electrodes for flexible rechargeable Zn-air batteries

Flexible rechargeable Zn-air batteries are considered as one of the most promising battery systems to drive flexible and wearable electronic devices owing to their high safety, high gravimetric energy density, low self-discharge and low cost. One of the key challenges is to develop air electrodes with high performance and high mechanical flexibility. This minireview discusses the recent progress in the design and fabrication of flexible air electrodes. It focuses on the latest innovations in bifunctional oxygen reduction reaction and oxygen evolution reaction electrocatalysts, mainly including carbon-based materials (e.g., heteroatom-doped carbon, metal-nitrogen moieties doped carbon), metal oxides (e.g., spinel oxides, perovskite oxides) and their composites. It aims to provide an insight into the structure-property relationship of bifunctional catalysts. We also discuss the challenges and future perspectives.