Carbon Nanotubes‐Integrated Nanoporous Architectures for Superior Electrochemical Storage Efficiency Mediated by Fast Ion Kinetics in Hybrid Supercapacitors

The pursuit of green energy solutions has provoked the quest for advanced electrode materials with remarkable electrochemical capabilities. In this context, spinel‐type FeCo 2 O 4 (FCO) porous structures were deliberately synthesized, showcasing potential to drive advancements in cutting‐edge supercapacitor systems. Composites labeled as FCO FCO‐3, FCO‐6, and FCO‐9 were prepared by incorporating carbon nanotubes (CNTs) at 3, 6, and 9 wt% into the FCO matrix. The X‐ray diffraction analysis showed a well‐defined crystalline cubic phase, while precisely controlled morphology was revealed by scanning and transmission electron microscopy. The emergence of distinct redox peaks in cyclic voltammograms across various sweep rates manifests the hybrid charge storage mechanism, which was validated using Dunn's model. FCO‐9 stands out as more promising among all composites, demonstrating an impressive specific capacity of 1681 C/g at 5.9 A/g, with 99.7% capacity retention after 7000 cycles. The subjected electrode achieved a remarkable energy density of 112.09 Wh/kg and a power density 1411.76 W/kg. Notably, the ionic conductivity and the diffusion coefficient for FCO‐9 were found to be 0.073 S/cm and 6.05 × 10 −10 cm 2 /s, respectively, indicating phenomenal ion transport and diffusion traits. Asymmetric supercapacitor device demonstrated a specific capacity of 345.23 C/g and an energy density of 57.54 Wh/kg at a power density of 1882.35 W/kg. Such outstanding capabilities of FCO‐9, stemming from the strong interaction between its constituents, make it a promising candidate for next‐generation supercapacitors.