All-functionalized-graphene ribbon films for flexible asymmetric supercapacitors with ultrahigh energy and power densities

Abstract

Asymmetric (hybrid) supercapacitors (ASCs) based on different positive and negative pseudocapacitance materials can deliver more energy density than electric double layer capacitors (EDLCs). Yet, few pseudocapacitive materials can provide high energy and power density, simultaneously, due to their poor conductivity and unfavorable reaction kinetics under fast charge/discharge rates. Here, we graft sulphur- and oxygen- functionalized into interconnected graphene ribbons to improve the accessibility of ion and enhance redox-active sites. The prepared sulphur- and oxygen- functionalized interconnected graphene ribbon (S-IGR and O-IGR) films as positive electrode and negative electrode, respectively, for high energy density flexible ASCs. Benefiting from the more “active sites” for the graphene ribbons, the S-IGR and O-IGR films connect more sulphur and oxygen groups. As a result, the S-IGR and O-IGR films exhibit ultra-high specific capacitance of 1660 F g−1 (1.66 F cm−2) and 428 F g−1 (0.43 F cm−2), respectively. More importantly, the assembled O-IGR//S-IGR ASCs based on aqueous and gel electrolytes exhibit ultra-high energy densities of 106.6 Wh kg−1 and 35.6 Wh kg−1, respectively. With the ultrafast charging and discharging capability, the ASCs based on aqueous electrolytes can be charge/discharged within 0.53 s to deliver high energy density of 15.0 Wh kg−1 and ultrahigh-power density of 101.4 kW kg−1. Thus, this strategy could possibly be used as designing and fabricating new generation of all grphene-based ASCs with high energy and power densities.