Elucidating Spatial Distribution of Electrochemical Reaction in a Porous Electrode by Electrochemical Impedance Spectra for Flow Batteries

A porous electrode is an essential component in a flow battery, and its structure determines the battery’s performance. The coupling of multi-temporal-spatial-scale processes (e.g., electrochemical reaction, mass transfer, charge transfer) makes recognition each process complicated. Herein, symmetric cell device developed, impedance measurement (two- or three-electrode configuration) realized to elucidate processes. First, effect rate concentration on spectra investigated identify Second, distributed resistance quantified describe spatial distribution reaction. It found that reaction occurs near membrane side at low polarization current, zones spatially extend from current collector with increase imposed polarization. Such evolution stems trade-off between transfer ion conduction electrode. This work provides experimental method nondestructively probe processes, result guidance for developing innovative structures batteries.