Recent progress of self-supported air electrodes for flexible Zn-air batteries

Smart wearable devices are regarded to be the next prevailing technology product after smartphones and smart homes, and thus there has recently been rapid development in flexible electronic energy storage devices. Among them, flexible solid-state zinc-air batteries have received widespread attention because of their high energy density, good safety, and stability. Efficient bifunctional oxygen electrocatalysts are the primary consideration in the development of flexible solid-state zinc-air batteries, and self-supported air cathodes are strong candidates because of their advantages including simplified fabrication process, reduced interfacial resistance, accelerated electron transfer, and good flexibility. This review outlines the research progress in the design and construction of nanoarray bifunctional oxygen electrocatalysts. Starting from the configuration and basic principles of zinc-air batteries and the strategies for the design of bifunctional oxygen electrocatalysts, a detailed discussion of self-supported air cathodes on carbon and metal substrates and their uses in flexible zinc-air batteries will follow. Finally, the challenges and opportunities in the development of flexible zinc-air batteries will be discussed.