▎ 摘　　要

Activated graphene nanosheets (AGNs) are fabricated from graphene nanosheets (GNSs) by the facile KOH activation process. It displays that the obtained AGNs have a hierarchical porous structure, leading to the superhigh specific surface area of 2662 m(2) g(-1). The obtained AGNs electrode exhibited high specific capacitance (238 F g(-1) at 1 A g(-1)) and remarkable rate performance (79.41% at 10 A g(-1)), exhibiting higher rate performance than reported carbon materials. Furthermore, the AGNs also show exceptional cycling capacity (99% after 20,000 cycles at 5 A g(-1)) in 1.0 M TEA BF4/AN electrolyte with an ultra-high potential range from 0 to 3.5 V. The symmetric supercapacitor displays a high energy density of 42.78 Wh kg(-1) at a power density of 2071 W kg(-1) and excellent cycle stability. The superior electrochemical performance can be attributed to the high specific surface area that has a larger contact area with the electrolyte, and the porous structure which provides a richer ion transport channel.