Near-neutral flexible zinc-air batteries with high power densities and long cycle life using chloride-based gel polymer electrolytes

In this work, to get improved battery performance via changing electrolyte formulations, a bifunctional catalyst, Ru0.6Sn0.4O2, and a polyvinyl alcohol gel polymer electrolyte (GPE) with a high water content (70%) are employed to fabricate flexible zinc-air batteries (FZABs). The optimal FZAB with a GPE containing 0.6 M ZnCl2 and 2.8 M NH4Cl reveals excellent power density of 12 mW cm−2 and prolonged cycle life over 100 h. Additionally, it can be charged and discharged under a bending angle of 90° at a large current density of 10 mA cm−2, 10 times higher than the best one reported, for more than 30 h, indicating excellent stability and flexibility. With a further increase or decrease in the ZnCl2 concentration in GPEs, the power performance or long-term cycling stability of FZABs declined, attributable to the low water content of GPEs and the degradation of zinc, respectively. We also, for the first time, report the origin of the decayed charge/discharge behavior of near-neutral FZABs, which can be ascribed to the precipitates of Zn(NH3)2Cl2 and Zn5(OH)8Cl2H2O on the zinc electrode to form a passivation layer. This study paves an avenue to further improve near-neutral FZABs.