Mesoporous Co0.85Se nanosheets supported on Ni foam as a positive electrode material for asymmetric supercapacitor

Mesoporous Co 0.85 Se nanosheets on Ni foam for high-performance supercapacitors were prepared by a facile one-step hydrothermal method. The as-synthesized Co 0.85 Se electrodes possess high pseudocapacitive performance with large specific capacitance and excellent cycling stability. The specific capacitance can achieve a maximum of 1378   F   g −1 at a current density of 1   A   g −1 , which can still keep 95.5% of capacitance retention after 1000 cycles. Then, an asymmetric supercapacitor was fabricated by using Co 0.85 Se nanosheets as positive material and activated carbon (AC) as negative material. The asymmetric configuration can extend voltage window to 1.6   V, which lead to a significant increase in the energy density to 39.7   W   h   kg −1 at a power density of 789.6   W   kg −1 , couples with outstanding cycle stability. The results demonstrate that the mesoporous Co 0.85 Se nanosheets are promising electrode materials for supercapacitors.