▎ 摘　　要

Asymmetric electrochemical capacitors (ECs) consisting of composites of reduced graphene oxide (RGO) and CoAl layered double hydroxide (LDH) as positive electrode, activated carbon (AC) as negative electrode (RGO/LDH//AC)and 6 M KOH solution as electrolyte were achieved. RGO/LDH was synthesized by a facile solution method in one step under mild conditions. Owing to its wide operating voltage window of 0-1.75 V and the utilization of RGO, the RGO/LDH//AC capacitor exhibited excellent electrochemical properties with a maximum energy density of 35.5 W h kg(-1), much higher than those of LDH//AC (25.1 W h kg(-1)) and AC//AC (6.3 W h kg(-1)) electrochemical capacitors. Moreover, the devices also showed a high power density of 8.75 kW kg(-1) and long cycle life of similar to 90% retention after 6000 cycles at the current density of 4 A g(-1). Such high-performance asymmetric electrochemical capacitors offer great promise in the application of energy storage systems.