Operando x-ray imaging of zinc-air flow battery anode

Abstract

Zinc-air batteries are widely considered as the next-generation rechargeable batteries due to their high energy density, low cost, and high safety. However, internal short circuits caused by zinc dendrite growth and bubble generation by side reaction during high-speed charging can deteriorate battery performance. To address this issue, a zinc-air flow battery with an electrolyte flow has been proposed for high-speed charging, and previous studies have shown improved cycle performance. Optimization of operating conditions for practical use requires elucidation of the behavior of the zinc electrode and bubble with electrolyte flow during battery operation, but this remains unclear. This study utilized operando X-ray imaging to investigate the zinc electrode and bubble behavior of a zinc-air flow battery during charging. The results revealed that when charging without electrolyte flow, zinc was deposited in a dendrite structure, and the dendrite growth rate increased with the charging speed. In contrast, it was observed that dendrite growth was suppressed, and dense zinc deposition was achieved even under high current density conditions when charged with a flowing electrolyte. Furthermore, the voltage fluctuation due to a decrease in the reaction area caused by the bubbles generated by water reduction was successfully suppressed when the flow was present. This was achieved by removing the bubbles through convection, which prevented the increase in overvoltage. Overall, it can be said that the flow of electrolytes has a positive effect on battery performance, as it helps to achieve a more uniform deposition of zinc and to prevent voltage fluctuation.