Deciphering the Ion Storage Mechanism in Vanadium Pentoxide Pseudocapacitive Behavior at the Single‐Particle Level

Understanding the ion storage mechanism and the influence of structural features on the pseudocapacitive behavior of electroactive materials is critical for enhancing energy and power density. In this study, the pseudocapacitive behavior of V₂O₅ at the single-particle level is investigated using scanning electrochemical cell microscopy (SECCM). This method allows simultaneous identification of structural features and electrochemical pseudocapacitive behavior in the same particle. Analysis of cyclic voltammetry at various scan rates for individual V₂O₅ particles reveals that the pseudocapacitive behavior, comprising surface redox reactions and (de)intercalation, dominates the energy storage process. The capacitive contribution ratio increases with particle diameter, highlighting the size-dependent kinetics. Furthermore, the effect of particle porosity is examined, demonstrating that 550 nm-diameter hollow-V₂O₅ particles exhibit a lower average capacitive contribution (82.5% at 0.5 V s^-1) compared to the solid-V₂O₅ particles with a similar size. This structural effect on the energy storage process can be attributed to the restricted diffusion-controlled faradaic (battery-like) process within the bulk V₂O₅ particles under fast charging/discharging conditions. This study presents a promising method for probing pseudocapacitive behavior at the single-particle level and provides insights into ion storage mechanisms.