MnOx nanosheets anchored on a bio-derived porous carbon framework for high-performance asymmetric supercapacitors

Abstract

MnO2 is regarded as one of the most promising electrode materials for supercapacitors due to its high theoretical capacitance and low cost; however, it suffers from poor electronic and ionic conductivity. Herein, nanostructured manganese oxides (MnOx) are anchored on a lotus seedpod-derived carbon framework (LSCF) in situ using a one-step hydrothermal-based redox synthesis strategy. The as-prepared MnOx@LSCF hybrid features a 3D conductive network and ultrathin MnOx nanosheets with oxygen vacancies, which can enhance both electrons and ions transfer intrinsically and facilitate sufficient surface Faradaic redox reactions. Benefitting from the synergistic effect of the nanostructured MnOx and the conductive LSCF, the optimized MnOx@LSCF hybrid exhibits a high specific capacitance (406 F g−1 at 0.5 A g−1) and a remarkable discharging rate capability (270 F g−1 at 10 A g−1). Moreover, an asymmetric supercapacitor fabricated by using MnOx@LSCF as the positive electrode and LSCF as the negative electrode achieves a high energy density of 48.1 Wh kg−1 at 500 W kg−1 (which still retains 22.2 Wh kg−1 at 10 kW kg−1), and a considerable cyclic stability of 90.1% after 5000 cycles. These properties demonstrate the MnOx@LSCF hybrid would have a valuable commercial application prospects in high-performance supercapacitors.