Hierarchical VOx@Wood Aerogel Electrodes with Tunable Valence States for Enhanced Energy Storage

Vanadium-based electrode materials are limited in practical applications, due to their low energy density, cycling instability, and poor electrochemical stability. To address these limitations, a wood-derived vanadium oxide (VO<i>_x</i>) electrode was developed through sol-gel assembly followed by thermal annealing, in which VO<i>_x</i> aerogel formed within the vertically aligned wood channels, resulting in a continuous porous network to mitigate particle aggregation and enhance ion diffusion. After thermal annealing at 800 °C, V⁵⁺ partially converts to V⁴⁺, forming a mixed-valence heterostructure that significantly increases the density of redox-active sites and facilitates efficient charge transfer. The optimized VO<i>_x</i>@Wood-800 °C (VOW-800) electrode exhibits a high specific capacitance of 317.8 F g^-1 at 2 mA cm^-2 and a specific surface area of 111.22 m^-2 g^-1, attributed to the synergistic effects of the mixed-valence structure and the enhanced ion accessibility provided by the wood-derived porous framework. This approach offers a promising pathway for developing vanadium-based electrodes with improved charge storage capacity and interface stability.