Assembly of manganese dioxide/polypyrrole electrode//activated carbon flexible asymmetric supercapacitor with excellent electrochemical performances

Manganese dioxide (MnO 2 ) often suffers from a slow electron transport, and so improving the charge transport capability of MnO 2 is imminent. In here, crossed MnO 2 nanosheets grown on carbon cloth (CC) are fabricated firstly and subsequently coated with a layer of polypyrrole (PPy) to prepare CC/MnO 2 /PPy (CC/MP) electrode. At 1 A g −1 , the prepared electrode is able to deliver a specific capacitance of 328 F g −1 . The flexible asymmetric supercapacitor consists of CC/MP and CC/activated carbon (CC/AC) separately as positive and negative electrodes and PVA‐H 2 SO 4 as gel electrolyte. The assembled device exhibits a specific capacitance of 123.96 F g −1 at 10 mV s −1 , reaches a voltage window of 1.6 V, has a capacitance retention of 96.46% after 8000 cycles, and produces an energy density of 25.67 W h kg −1 at a power density of 401.79 W kg −1 , as well as an energy density of 8.78 W h kg −1 at a power density of 3902.22 W kg −1 . The two devices in series can illuminate 1.8 V red light‐emitting diode (LED) light. These excellent electrochemical properties are ascribed to the unique heterostructure of the electrode composite. The outcomes indicate that the prepared CC/MP electrode and the corresponding device have huge potential applications in next‐generation high‐performance supercapacitor devices.