Fabrication of porous carbon nanofibril/MnO2 composite aerogels from TEMPO-oxidized cellulose nanofibrils for high-performance supercapacitors

Abstract Supercapacitors have played a key role in energy storage field due to their fast charge-discharge processes and long cycle life. Here, 2,2,6,6-tetramethylpiperidine-1-oxylradical (TEMPO)-oxidized cellulose nanofibrils were carbonized to fabricate carbon nanofibrils (CTOCN). CTOCN/manganese dioxide (MnO2) composite aerogels were then obtained via a simple hydrothermal method, through which MnO2 strongly attached to the surface of CTOCN, thus maintaining the highly porous 3-dimensional (3D) structure. CTOCN/MnO2 with MnO2 content of 20.8 wt% exhibited the most outstanding electrochemical performance. It possessed a maximum specific capacitance of 171.1 F g−1 at 0.5 A g−1 and could still remain 98.4% of the initial value after 5000 cycles at 3 A g−1. Moreover, an asymmetric supercapacitor using the CTOCN/MnO2 composite as positive electrode and activated carbon (AC) as negative electrode was assembled. The assembled supercapacitor delivered an energy density of 8.6 W h kg−1 at a power density of 619.2 W kg−1, and could still remain 4.13 W h kg−1 at a power density of 6.8 kW kg−1. Additionally, it possessed an excellent cycle life with 99.4% retention of the first cycle after 4500 cycles at 3 A g−1, suggesting an available method for designing a promising electrode material for supercapacitors.