Mechanistic investigation of the charge storage process of pseudocapacitive Fe3O4 nanorod film

This work presents the quantitative analysis of different mechanistic contribution to charge storage process of Fe3O4 in Li2SO4 aqueous electrolyte using nanorod film electrode as the ideal platform. “Capacity (stored charge)-charging time” relationship and “current-sweep rate” power law relationship, etc. are investigated. In addition to capacitive charge storage process, diffusion-controlled process is also found to occur in Fe3O4 nanorod film. This diffusion-controlled contribution dominates at low rates (78.4% at 0.5 mV s−1) and cannot be ignored even at relatively high rates (22.8% at 100 mV s−1). Our finding clearly uncovers that nanostructured Fe3O4 stores charges not merely on the surface/near-surface like typical pseudocapacitive materials, but rather through the intercalation of Li+ in the bulk.