Optimizing carbon-nanotube-driven polyhedral Cu2Mn3O8 structures for hybrid supercapacitors: unveiling strategies for enhanced electrochemical efficiency

Abstract

Driven by the intensifying global energy crisis, significant efforts have been focused on designing advanced nanostructured electrode materials that are capable of delivering both energy and power output simultaneously while ensuring optimized diffusion dynamics. Herein, a rationally engineered Cu₂Mn₃O₈ (CMO) and its nanocomposites with 3%, 6%, and 9% carbon nanotubes (CNTs) (CMO-1, CMO-2, and CMO-3, respectively) were prepared via a cost-effective synthesis method. Quasi-rectangular, polyhedral structures were revealed via electron microscopy. A hybrid charge-storage mechanism was observed via voltammetric analysis combined with insights from Dunn's model. Galvanostatic charge–discharge testing revealed that CMO-2 delivered a specific capacity of 954.25 C g⁻¹ at 11.76 A g⁻¹, accompanied by an excellent energy density of 66.26 Wh kg⁻¹ and power density of 2941.17 W kg⁻¹. Notably, the electrode retained 99% of its initial capacity after 3000 cycles, confirming excellent durability. Galvanostatic intermittent titration technique measurements further estimated a diffusion coefficient of ∼4.96 × 10⁻¹⁵ m² s⁻¹ for the optimized sample, highlighting efficient ion transport through the electrode material. Electrochemical impedance spectroscopy revealed a low solution resistance of 0.91 Ω, high conductivity of 0.099 S cm⁻¹, and a short relaxation time of 0.082 s. The observed agglomeration of CNTs in CMO-3 reduced the ion diffusion coefficient, highlighting a critical consideration for future researchers in optimizing material design. Collectively, these results position CMO-2 as a highly attractive electrode material for future hybrid supercapacitors.