Temperature‐Assisted Surface Modified Nanostructured V ₂ O ₅ for High‐Performance Li‐Ion Supercapacitors

The electrochemical performance of V 2 O 5 as an electrode material for Li‐ion supercapacitors is limited by low electronic conductivity and sluggish kinetics. Here, the influence of annealing temperature on the electrochemical properties of surface‐modified V 2 O 5 nanoparticles, synthesized from commercial V 2 O 5 via oxalic acid treatment is systematically investigated. Temperature‐assisted surface modification tunes the oxidation states and defect structure of V 2 O 5 , without introducing any external, additives providing a simple, yet effective route to optimize the electrochemical kinetics. The samples are annealed at varying temperatures, and their performance is evaluated to determine the optimal conditions. The sample annealed at 400 °C exhibited the highest specific capacitance of 432 F g −1 at a scan rate of 5 mV s −1 and capacitance retention of 41.5% after 1000 cycles. The improved performance is attributed to the optimal creation of surface defects and increased surface area (28.87 m 2 g −1 ), which enhances electronic conductivity and facilitates the movement of electrolyte ions. The assembled asymmetric device showed energy density of 20.8 Wh kg −1 at a power density of 480 W kg −1 , with 37.5% capacitance retention after 3000 galvanostatic charge–discharge cycles. These findings highlight the critical role of annealing temperature in tuning the structure and electrochemical behavior of V 2 O 5 nanomaterials, positioning them as promising candidates for advanced Li‐ion supercapacitor applications.