Interconnected three-dimensionally hierarchical heterostructures with homogeneously-dispersed V₂O₅ nanocrystals and carbon for high performance supercapacitor electrodes

In this article, a simple "liquid phase impregnation template" strategy has been developed to synthesize hierarchically porous V₂O₅/C (HPVC) nanocomposites by using commercial V₂O₅ and phenol-formaldehyde (PF) resol as precursors and polystyrene opal microspheres as template. The amount of vanadium sol in the vanadium-PF precursor has a significant effect on the morphology and microstructure of the resulting HPVC nanocomposites. Due to the intact interconnected hierarchical network framework and the homogeneous dispersion of constitutive V₂O₅ nanocrystals and carbon phases, the optimal sample HPVC2 with higher surface area (645 m² g⁻¹) and mesopore surface area (394 m² g⁻¹) and an appropriate content of V₂O₅ (38.7 wt.%), is found to be the most efficient one as supercapacitor electrode with a high specific capacitance up to 492.1F g⁻¹ at a scan rate of 5 mV s⁻¹ in the three-electrode system. When used as symmetric electrode, the HPVC2//HPVC2 supercapacitor exhibits a high energy density up to 87.6 Wh kg⁻¹ at a power density of 497 W kg⁻¹, which greatly surpasses those of pure single-component counterparts and others reported V₂O₅/C composites. The present work conceptually provides a facile way for integrating transition metal oxide with carbon in hierarchically porous nanostructure to synthesize hybrid electrode materials for advanced energy storage/conversion devices.