Rapid and Energy-Saving\nSynthesis of MnCo<sub>2</sub>O<sub>4</sub>/MWCNT Nanocomposites for\nHigh-Energy-Density Asymmetric\nSupercapacitors

Recent advancements in materials science have resulted\nin impressive\nelectrode materials; however, their practical implementation is often\nlimited by complex and resource-intensive synthesis processes including\nhigh-temperature requirements, long synthesis times, and low yield.\nTo advance the field of energy storage, it is crucial to develop synthesis\nmethods that minimize both energy and time consumption. In this study,\nwe employed a low-temperature, time-efficient, and cost-effective\nsynthesis technique for fabricating high-performance electrode materials.\nHerein, a MnCo<sub>2</sub>O<sub>4</sub>/multiwalled carbon nanotube\n(MWCNT) (MCOC) nanocomposite is synthesized via a low-temperature\ncoprecipitation approach. The effect of MWCNTs on the electrochemical\nproperties of the nanocomposites has been studied. The synthesized\nMCOC1 sample (0.99MnCo<sub>2</sub>O<sub>4</sub> + 0.01MWCNT) demonstrated\nenhanced electrochemical characteristics, exhibiting a specific capacitance\nof 540 Fg<sup>–</sup><sup>1</sup> at 0.5 Ag<sup>–</sup><sup>1</sup> and good cyclic stability with 87.91% capacitance retention\nover 5000 cycles at 8 Ag<sup>–</sup><sup>1</sup>, attributed\nto its higher surface area (113 m<sup>2</sup>/g) and mesoporous pore\nsize distribution. An asymmetric supercapacitor was constructed by\nusing MCOC1 as the cathode and activated carbon as the anode, demonstrating\nthe highest specific energy density and power density of 58 and 21\nkW kg<sup>–1</sup>, respectively. The device also exhibited\n80.5% capacitance retention and a Coulombic efficiency of 97.82% over\n5000 cycles at 3 Ag<sup>–</sup><sup>1</sup> in a PVA/KOH gel\nelectrolyte. Notably, when two devices were connected in series, they\nsuccessfully powered three green LEDs for over 4 min each. The facile\nlow-temperature synthesis and excellent electrochemical properties\nof the synthesized MnCo<sub>2</sub>O<sub>4</sub>/MWCNT nanocomposites\nmake them promising candidates for high-performance supercapacitors.