Mesoporous Co0.85Se nanowire arrays for flexible asymmetric supercapacitors with high energy and power densities

Transition metal selenides have attracted particular interest in the energy storage field due to their high conductivity, but their low specific capacitances limit their development. Herein, we design the Co0.85Se with an orderly aligned nanowire-arrayed (NWA) structure, which has great micromorphological stability and fast electronic/ionic transport rate, achieving a high specific capacitance of 1800 F g−1 at 1 mV s−1. The asymmetric supercapacitors (ASCs) are built to widen the voltage window to 0– 1.6 V and then increase the energy density, which reaches 71.3 Wh kg−1 at a power density of 800 W kg−1 in the liquid-state electrolyte, and 3.03 mWh cm−3 at the power density of 8.0 W cm−3 in the solid-state electrolyte. It also shows excellent cycling stability of 86 % retention after 10,000 charge/discharge cycles, fast rate capability of 79 % retention at the 15-fold increased current density and little performance degradation even under severe bent deformation. As shown, the Co0.85Se NWAs-based ASCs own high energy and power densities, long cycle life, fast rate capability and stable flexibilities simultaneously, which have significant potential in high-performance wearable energy storage systems.