Flower-like MnO2 on layered carbon derived from sisal hemp for asymmetric supercapacitor with enhanced energy density

MnO2 has been considered as a very promising positive electrode candidate for high energy density asymmetric supercapacitors (ASCs) because of high theoretical capacitance. However, the electrochemical performance of pure MnO2 for ASCs has still been severely limited by poor electronic conductivity, volume expansion and dissolution problem. Herein, we report flower-like MnO2-carbon composite (MnO2/SHAC) as positive electrode and layered Sisal Hemp Active Carbon (SHAC) as negative electrode for high-energy ASCs. The flower-like MnO2/SHAC positive electrode comprised a number of interconnected thin nano-flakes with a length of about 50–100 nm and a thickness of about 10 nm and exhibited a large specific surface area of 189.6 m2 g−1 and good conductivity. The SHAC negative electrode showed multi-layered graphene-like structure and a high BET surface area of 1303.5 m2 g−1. Moreover, the assembled MnO2/SHAC//SHAC ASC exhibits a maximum energy density of 46.2 Wh kg−1 at 0.1 A g−1 and a maximum power density of 3679.5 W kg−1 at 6 A g−1, suggesting that MnO2/SHAC composite has promising potential for practical supercapacitors with enhanced energy.