Microwave-assisted preparation and improvement mechanism of carbon nanotube@NiMn2O4 core-shell nanocomposite for high performance asymmetric supercapacitors

Abstract A carbon nanotube (CNT)@NiMn2O4 core-shell nanocomposite is successfully prepared by a facile microwave-assisted hydrothermal process. The as-obtained nanocomposite exhibits low charge transfer resistance (2.19 Ω), high specific capacitance (up to 915.6 F g−1 measured by charge-discharge at 1 A g−1) and excellent cycling stability (93.0% capacity retention after 5000 cycles at 5 A g−1). It is found that the weaker crystallinity induced by microwave treatment, synergism between CNTs and NiMn2O4 in the core-shell heterostructure and more defects and vacancies in CNTs caused by acidifying pretreatment can all devote to improving the electrochemical performance of the as-obtained nanocomposite. An asymmetric supercapacitor device using the as-obtained CNT@NiMn2O4 as positive electrode is also successfully fabricated, which exhibits the maximum energy density of 36.5 Wh kg−1 at a power density of 800 W kg−1 and outstanding cycling stability with 82.8% retains capacitance after 10000 cycles at 5 A g−1. The excellent performance indicates that as-fabricated CNT@NiMn2O4 is one of the competitive electrode materials for energy storage devices.