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 cm2 at a technically relevant current density of 50 mA cm2 . 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.