Regulated dual-network hydrogel with interfacial engineering effect of alkaline zinc surface for flexible zinc-air battery

Abstract

Flexible zinc-air battery (FZAB) has been developed for wearable electronics with various merits, including high energy density, environmental friendliness, low cost and inherent safety. However, the instability of zinc surface contact to alkaline hydrogel electrolyte, including excess ZnO formation after cycles and parasitic side reaction, is a substantial hurdle to broad usage, and is less explored. Another challenge is the limited ionic conductivity, which is especially important under low-temperature conditions. Therefore, we develop the regulated dual-network hydrogel with addition of histidine, which tailors the hydrogel with amino and carboxyl groups, leading to high ionic conductivity, efficient ion transfer channels and anti-freezing property. The imidazole group employs the effect of interfacial engineering to regulate the adsorption of Zn2+ on alkaline zinc surfaces, resulting in homogeneous deposition and reduction of ZnO during cycles and longer lifetime of FZAB. Both simulation and experimental analyses confirm the superiority of regulated hydrogel. The as-fabricated FZAB achieves a maximum power density of 117.8 mW cm−2 and can run 627 cycles, reaching 209 h. Meantime, the FZAB can reserve 76.8 % working voltage at −20 °C.