Carbon nanotube mediated nanoporous electrodes for electrolyte-dependent interfacial ion transport in hybrid supercapacitors

Abstract

Understanding ion transport at the electrode–electrolyte interfaces is crucial for optimizing charge storage devices. In this work, Co3O4, NiMn2O4, and Co3O4/NiMn2O4 electrodes were synthesized via a combined hydrothermal-solvothermal approach and further engineered into a ternary nanocomposite with 9% carbon nanotubes to create a controlled Co3O4/NiMn2O4/CNTs (CO-II) interfacial architecture. Phase investigation displayed a cubic crystal structure for both phases, while the scanning electron microscopy revealed a well-developed three-dimensional interconnected architecture. Voltametric study demonstrated the hybrid charge storage mechanism, which was further validated via Dunn's analysis. Moreover, the CO-II achieved a superior specific capacity (Qs) of 1112.70 C g−1, accompanied by an energy density (ED) of 77.27 Wh kg−1 at 1470.58 W kg−1. Furthermore, CO-II preserved 98.89% of its initial capacity after 7500 cycles. Importantly, superior interfacial kinetic parameters of CO-II indicate rapid ion migration of the ternary composite. Additionally, the electrolyte-dependent diffusion behavior and the galvanostatic intermittent titration technique demonstrated the highest diffusion coefficients in both KOH and NaOH electrolytes of 6.6 × 10−11 cm2 s−1 and 5.9 × 10−11 cm2 s−1. Moreover, the CO-II-based asymmetric supercapacitor device delivered outstanding Qs of 443.58 C g−1 and ED of 73.93 at a power density of 1764.71 W kg−1. These findings demonstrate that engineered oxide-carbon interfaces effectively enhance interfacial kinetics and diffusion-controlled charge storage, making the proposed hybrid electrode promising for advanced energy storage applications.