Ultrathin manganese oxide nanosheets uniformly coating on carbon nanocoils as high-performance asymmetric supercapacitor electrodes.

Two key limitations affecting supercapacitor application of manganese oxide (MO) are the poor electric conductivity and low accessible surface area. In this work, we reported an effective method to fabricate lamellar MO coating on carbon nanocoil (CNC) and investigated its supercapacitive properties. The elegant MO/CNC core shell structure enabled synergistic effects from both MO nanosheets and CNC by using nanosheets to provide a large interaction area for ion transport and CNC to improve the electric conductivity of composites. The investigation of electrochemistry showed that the specific capacitance of MO could reach 435 F g-1 at current density of 1 A g-1. Moreover, the composites presented an excellent rate capability and cycling performance with 92.7% capacitance retention at current density of 2 A g-1 after 5000 cycles. In addition, the asymmetric supercapacitor fabricated with MO/CNC as the positive electrode and CNC as the negative electrode demonstrated excellent energy density of 21.58 Wh kg-1 at a power density of 100 W kg-1. And the asymmetric supercapacitor exhibited an excellent electrochemical cycling stability with 96.3% initial capacitance remained after 1000 cycles.