The presence of structural water leads to a transition of energy storage mechanism in tungsten oxide from battery-type intercalation (bulk diffusion limited) to pseudocapacitance (interface kinetics limited). In this study, we demonstrate that the energy storage mechanisms are linked to the materials mechanical response to the intercalation process and present a method to study local electrochemical intercalation through mechanical coupling. We employed
operandoatomic force microscopy dilatometry ( operandoAFM dilatometry) to monitor the real-time mechanical response of WO3 and WO32H2O thin film electrodes during cyclic voltammetry in a 0.5 M H2SO4 electrolyte at sweep rates from 10 to 200 mV s-1 (80- to 4-second charge/discharge). This technique reveals that the deformation of WO32H2O is more facile and more gradual than that of WO3 during intercalation. We attribute the transition of energy storage mechanism to the more facile mechanical deformation of WO32H2O as compared to WO3. In addition, a mapping technique was developed to correlate local mechanical response from electrochemistry to the electrode nanostructure.