Rapid and Energy-Saving Synthesis of MnCo2O4/MWCNT Nanocomposites for High-Energy-Density Asymmetric Supercapacitors

Abstract

Recent advancements in materials science have resulted in impressive electrode materials; however, their practical implementation is often limited by complex and resource-intensive synthesis processes including high-temperature requirements, long synthesis times, and low yield. To advance the field of energy storage, it is crucial to develop synthesis methods that minimize both energy and time consumption. In this study, we employed a low-temperature, time-efficient, and cost-effective synthesis technique for fabricating high-performance electrode materials. Herein, a MnCo₂O₄/multiwalled carbon nanotube (MWCNT) (MCOC) nanocomposite is synthesized via a low-temperature coprecipitation approach. The effect of MWCNTs on the electrochemical properties of the nanocomposites has been studied. The synthesized MCOC1 sample (0.99MnCo₂O₄ + 0.01MWCNT) demonstrated enhanced electrochemical characteristics, exhibiting a specific capacitance of 540 Fg^–1 at 0.5 Ag^–1 and good cyclic stability with 87.91% capacitance retention over 5000 cycles at 8 Ag^–1, attributed to its higher surface area (113 m²/g) and mesoporous pore size distribution. An asymmetric supercapacitor was constructed by using MCOC1 as the cathode and activated carbon as the anode, demonstrating the highest specific energy density and power density of 58 and 21 kW kg^–1, respectively. The device also exhibited 80.5% capacitance retention and a Coulombic efficiency of 97.82% over 5000 cycles at 3 Ag^–1 in a PVA/KOH gel electrolyte. Notably, when two devices were connected in series, they successfully powered three green LEDs for over 4 min each. The facile low-temperature synthesis and excellent electrochemical properties of the synthesized MnCo₂O₄/MWCNT nanocomposites make them promising candidates for high-performance supercapacitors.