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

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.