Reaction Kinetics in Proton Batteries: An EIS/DRT-Based Case Study of Vanadium Pentoxide Electrodes

Re-emerging battery systems such as proton batteries are critical in mainstreaming green and renewable energy resources, mainly due to the scarcity and safety of lithium-based systems. However, the underlying electrochemical mechanisms governing charge transfer and mass transportation in electrode materials of these battery systems need a comprehensive breakdown. Electrochemical Impedance Spectroscopy (EIS) in combination with its simulation/computation facility offers valuable insights into these phenomena; nevertheless, its application in battery research is often underestimated. Using a V₂O₅ electrode in an aqueous proton electrolyte as a model, we intuitively address and quantify the individual contributions from charge transfer, diffusion, and interfacial phenomena to the total impedance. In general, EIS provides information on charge species dynamics, electrode-electrolyte interactions, and ionic conduction at grain boundaries, and when coupled with the distribution of relaxation time analysis (distinguishing processes with overlapping time constants) of relaxation processes and their corresponding relaxation frequencies renders EIS even more precise and accurate. Although the present study focuses on V₂O₅-based material, the EIS-DRT methodology and supplementary modeling recommendations are designed to be transferable to other proton-hosting electrodes, making the study diverse in its applications.