Controlled Construction of Hierarchical Nanocomposites Consisting of MnO2 and PEDOT for High-Performance Supercapacitor Applications

The integration of hierarchical nanostructure design and encapsulation strategies using a combination of electrochemical deposition, hydrothermal, and insitu reaction methods has been recognized as one of the most effective strategies to realize practical applications of various supercapacitor materials. Herein, a facile and scalable method is developed to synthesize a core-shell-branch hierarchical MnO2@PEDOT@MnO2 composite by using a simple electrochemical deposition strategy. The proposed synthesis method facilitates the structural integration of three-dimensional nickel foam and the synergy of different electroactive materials, which offers several advantages including simplicity, efficiency, no binder, and low cost. The as-prepared, freestanding, hierarchical MnO2@PEDOT@MnO2 electrodes exhibit high specific capacitance and rate capability. An asymmetric supercapacitor is fabricated with the hierarchical MnO2@PEDOT@MnO2 nanocomposite as the positive electrode, activated carbon as the negative electrode, and Na2SO4 aqueous solution as the electrolyte. The asymmetric supercapacitor can be cycled reversibly in a high-voltage window of 0-1.8V and exhibits a high energy density of 47.8Whkg(-1) at a power density of 180 Wkg(-1), indicating remarkable rate capability as well as reasonable cycling performance with 91.3% retention after 5000 cycles.