Highly porous honeycomb manganese oxide@carbon fibers core–shell nanocables for flexible supercapacitors

Core–shell electrodes composed of highly porous honeycomb manganese oxide@carbon fibers (HMO@CFs) are synthesized by a facile hydrothermal approach involving an in situ redox replacement reaction between potassium permanganate (KMnO₄) and carbon fibers. In this reaction, the carbon fibers serve as not only a sacrificial reductant, but also the substrate. The porous HMO@CFs core–shell nanocables deliver remarkable electrochemical performance with a high capacitance (295.24 F g⁻¹ at 100 mA g⁻¹), high good rate capability, and superior cycling stability (about 96.4% specific capacitance retained after 3000 cycles). The maximum energy density of 22.2 W h kg⁻¹ (at a power density of 400 W kg⁻¹) and power density of 12,000 W kg⁻¹ (at an energy density of 10 W h kg⁻¹) can be achieved at an operating voltage of 1.6 V. The fabrication method is simple, cost-effective, and readily scalable thereby having large commercial potential.