Synthesis of Ultrathin MnO2 Nanosheets/Bagasse Derived Porous Carbon Composite for Supercapacitor with High Performance

In this paper, activated porous carbon (AC) derived from bagasse was prepared by carbonization and activation using KOH. Then, a hydrothermal route was employed to fabricate ultrathin manganese oxide (MnO2) nanosheets/activated porous carbon (AC) composite (MnO2/AC). AC and MnO2/AC composite were employed as negative and positive electrode materials for a supercapacitor, respectively. An AC electrode delivers excellent electrochemical properties with a specific capacitance of 89 F g−1 at 1 A g−1 and super cycling stability of 89% capacitance retention after 5000 cycles. For a MnO2/AC composite, its specific capacitance can reach 492.5 F g−1 at 1 A g−1, but its cycle performance (78.4% capacitance retention after 5000 cycles) is lower than that of AC (89%). In view of the good electrochemical performance of AC and MnO2/AC composite, a MnO2/AC//AC all-solid-state asymmetric supercapacitor (ASC) was assembled. The constructed ASC exhibits high specific capacitance of 69.375 F g−1 at 1 A g−1 and delivers a high energy density of 24.67 Wh kg−1 at a power density of 814.8 W kg−1. Two ASCs in series can power one LED for more than 70 s. This work demonstrates that MnO2/AC//AC asymmetric supercapacitor shows good practical value.