Long‐Term Performance of a Zinc–Silver/Air Hybrid Flow Battery with a Bifunctional Gas‐Diffusion Electrode at High Current Density

Abstract

This work demonstrates an improved cell design of a zinc–silver/air hybrid flow battery with a two‐electrode configuration intended to extend the cycling lifetime with high specific capacities up to 66.7 mAh cm−2 at a technically relevant current density of 50 mA cm−2. A hybrid approach combines the advantages of both zinc–air and zinc–silver batteries enabling enhanced energy efficiency while maintaining high battery capacity. A pulsed charging protocol is applied to maintain compact zinc deposits on a porous copper foam, which extends capacity compared to a planar surface. The single‐cell battery is successfully operated for 216 cycles (t = 756.10 h) after an interruption after 47 cycles (t = 163.20 h), which reveals that the gas‐diffusion electrode aging is the first cycling lifetime limitation. At the end of operation, an accumulation of zinc in the inlet zone of the cell sets a second‐lifetime limitation driven by progressively shorter discharge associated again with the aging of the gas‐diffusion electrode. Despite zincate ion depletion and the final irregular deposition, postmortem analysis shows no dendrites, only the compact zinc structure, confirming the benefits of a pulsed current. Developments within this path can further raise the technological prospects of the zinc–silver/air battery.