MnO2/C composite electrodes free of conductive enhancer for supercapacitors

MnO2 nanostructures can be directly and conformably deposited on the highly conductive Ketjen Black (KB) substrate by an in situ redox reaction between KMnO4 and C. By controlling the MnO2 contents in KB-MnO2 composites, the use of extra conductive enhancers can be avoided. When the MnO2 content is 37 wt% (KB-MnO2-37), its specific capacity (Cg) is up to 252 F g−1 at 5 mV s−1 and the capacity retention is 50% as the scan rate increases 60 times to 300 mV s−1. Moreover, asymmetric supercapacitors based on KB-MnO2-37 can reversibly charge/discharge at a cell voltage of 2.0 V in 1 M Na2SO4 electrolyte solution. A sulfonated pitch porous carbon//KB-MnO2-37 asymmetric supercapacitor delivers an energy density of 31.1 Wh kg−1 and a power density of 150 W kg−1. KB-MnO2 composites have a great potential in large-scale energy storage applications.