Unravelling the Polymorph Dependant Electrochemical Behaviour of VO2 for Advanced Supercapacitor Applications.

The development of sustainable, high-performance electrode materials is essential for scalable energy storage devices. A key challenge lies in developing cost-effective systems that combine high energy and power densities. Vanadium dioxide (VO2) with its remarkable pseudo-capacitive behaviour emerges as a promising candidate owing to its polymorphic forms, and unique phase transition property. Herein, VO2 polymorphs (A, B, D, and M) were hydrothermally synthesized and systematically investigated. Among them, VO2(M) micro-rods exhibited a superior electrochemical performance, delivering specific capacitance of 150 F g-1 at 1 A g-1 current density and demonstrating 99 % of capacitive contribution at 40mV/s, as confirmed by kinetic studies. Furthermore, an, asymmetric hybrid supercapacitor employing VO2(M) micro-rods as the positive electrode and Ti3C2Tx MXene as the negative electrode achieved remarkable energy storage performance, delivering specific capacitance of 92.8 F g-1 at 2 A g-1. The device delivered a maximum energy density of 68.18 Wh kg-1 and power density of 2298.2 W kg-1, while maintaining 100 % capacitive retention and coulombic efficiency over 5000 cycles. The high capacitive contribution observed in both pristine VO2(M) and the asymmetric VO2(M)//Ti3C2 system highlights their potential as promising electrode material for the next generation energy storage technologies.