Turning conductive carbon nanospheres into nanosheets for high-performance supercapacitors of MnO2 nanorods.

Oxidized carbon nanosheets (OCNs), produced from black carbon nanospheres and used as a conductive additive in the supercapacitor electrodes of MnO2 nanorods, can significantly improve the charge-storage performance of the symmetric MnO2-nanorod supercapacitors with a maximum specific energy of 64 W h kg(-1) and power of 3870 W kg(-1). An optimum material composition of the supercapacitor electrode finely tuned is 60 : 30 : 10 wt% of MnO2 : OCN : PVDF, respectively. Interestingly, after 5000 charge/discharge cycles, the oxidation numbers of Mn at the positive and negative electrodes of the as-fabricated supercapacitor are +3.22 and +3.04, respectively.