Topic Metal-Air Batteries: Understanding the Nanoscale Redox-Behavior of Rechargeable Iron-Air Batteries

doi: 10.1016/j.nanoen.2017.10.023

Secondary iron-air cells provide a promising and resource-efficient alternative battery concept with superior area specific power density characteristics compared to state-of-the-art Li-air batteries and po-tentially superior energy density characteristics compared to present Li-ion battery technology. Understanding charge-transfer reactions at the anode electrolyte interface is the key to develop high-performance cells. By employing in-situ electrochemical atomic force microscopy (in-situ EC-AFM), in-depth insight into the electrochemi-cally induced surface reaction processes on iron in concentrated alkaline electrolyte is obtained. The results highlight the formation and growth of the redox-layer on iron over the course of several oxida-tion/reduction cycles. By this means, a direct correlation between topography changes and the corresponding electrochemical reactions at the nanoscale could unambiguously be established. Here, the two-fold character of the nano-particulate redox-layer in terms of its pas-sivating character and its contribution to the electrochemical reac-tions is elucidated. Furthermore, the evolution of single nanoparticles on the iron electrode surface is evaluated in unprecedented and artifact-free detail. Based on the dedicated topography analysis, a detailed structural model for the evolution of the redox-layer, which is likewise elementary for corrosion science and battery research, is derived.