The increasing demand for portable and wearable electronics requires lightweight, thin, and highly flexible power sources, for example, flexible zinc-air batteries (ZABs). The so-far reported flexible ZAB devices mostly remain bulky, with a design consisting of two relatively thick substrates (e.g., carbon cloths and/or metal foams) and a gel electrolyte-coated separator in between. Herein, an ultrathin (≈0.2 mm) solid-state ZAB with high flexibility and performance is introduced by directly forming self-standing active layers on each surface of an alkaline polymer membrane through an ink-casting/hot-pressing approach. A Fe/N-doped 3D carbon with hierarchic pores and an interconnected network structure is used as cathode electrocatalyst, so that the backing gas-diffusion layer (e.g., carbon cloth) can be abandoned. What is further, a microstructure-modulating method to significantly increase the FeN4 active sites for oxygen reduction reaction is developed, thus significantly boosting the performance of the ZAB. The assembled solid-state ZAB manifests remarkable peak power density of 250 mW cm⁻³ and high capacity of 150.4 mAh cm⁻³ at 8.3 mA cm⁻³, as well as excellent flexibility. The new design should provide valuable opportunity to the portable and wearable electronics.

    https://onlinelibrary.wiley.com/doi/10.1002/aenm.201803628