Dual redox-active bi-metallic oxide/nanoporous carbon nanotubes hybrid architectures: Probing diffusion dynamics and ionic conductivity for advanced supercapacitors

Abstract

Growing demand for sustainable energy storage drives advanced materials and porous structures. Here, CrCo2O4 (CCO) and its composites with varying carbon-nanotube (CNTs) content (3, 6, and 9%) are synthesized, termed as CCO-3%, CCO-6% and CCO-9%. X-ray diffraction confirms the spinel phase of CCO, while morphology reveals higher CNTs content, enhancing surface porosity. Cyclic voltammetry study demonstrates a battery-type hybrid charge storage mechanism, as evident by Dunn’s model. Among these composites, CCO-9% exhibits the highest performance, achieving an impressive specific capacity (Qsp) of 817.30 C g-1 at 1.3 A g-1. It delivers an energy density (Ed) of 56.75 Wh kg-1 along with a power density (Pd) of 338.98 W kg-1. The galvanostatic intermittent titration technique reveals the highest value of diffusion coefficient, ⁓2.65×10-10 cm2 s-1, while electrochemical impedance spectroscopy reveals a reduced charge transfer resistance and improved ionic conductivity of 4.02×10-4 S cm-1. The electrode is utilized in an asymmetric device, where testing reveals a Qsp of 129.48 C g-1, corresponding to an Ed of 21.58 Wh kg-1 at Pd of 1016.94 W kg-1. The electrode displays remarkable cyclic stability, sustaining 98% of its initial capacity after 10k cycles. These results highlight CCO-9% as a viable contender for hybrid capacitors, portable electronic devices and regenerative braking systems.