Understanding the Influence of Polypyrrole Coating over V2O5 Nanofibers on Electrochemical Properties

As an example of hybrid electrode materials for electrochemical energy storage with potential to deliver high specific capacitance, rate capability and energy density in addition to low inner resistance, V2O5 nanofibers wrapped with polypyrrole (PPy) were synthesized. This study focused on the understanding of the synergistic effect of the V2O5@PPy nanocomposites as well as the individual role of each component on electrochemical properties. To explore the cooperative effects of individual functional materials, a classic model was applied to the V2O5@PPy nanocomposites for the first time to simulate and analyze the partitioned contributions from the electric double-layer capacitance and pseudocapacitance of the V2O5@PPy nanocomposites with various PPy coating amounts. The optimal ratio of PPy to V2O5 was determined to be ∼40% where the sum of the polymer's electric double-layer (EDL) capacitance and the layered oxide's subsurface Faradic capacitance could be maximized. It was also observed that overloading of PPy on V2O5 nanofibers could cause shear cracks in the nanocomposites due to localized condensation and thus cause internal stress between the electroactive materials and current collector. The resulting mechanical integration breakdown therefore restrained the overall performances of electrodes. This work lays the foundation for understanding synergistic effect and individual role of each component of hybrid electrode materials consisting of conductive polymer and transition metal oxide which can be applied in electrochemical energy storage devices, such as aqueous supercapacitors.