Can graphite oxide active material achieve commercial supercapacitor level energy and power densities? Binder free coating and WIS electrolyte strategies

Unlike carbon materials such as graphene, reduced graphite/graphene oxide, activated carbon, etc., graphite oxide (GO) is not considered to be a potent active material for energy storage applications. This study proposes a sustainable approach for developing high energy and power density supercapacitors using graphite oxide (GO) active material, viz., binder free coating and water in salt (WIS) electrolyte. The use of 17 m NaClO4 WIS electrolyte ensures an electrochemical stability window of 2.5 V, which surpasses the thermodynamic limit of water electrolysis. In three electrode configuration, the binder free Ni@GO electrode achieved an energy density of 31.2 Wh/kg and a power density of 625 W/kg, with excellent cycle stability of 133.3 % after 1000 chargedischarge cycles. Energy and power densities of Ni@GO electrodes in aqueous electrolytes viz., 6 M KOH (1.5 Wh/kg and 137 W/kg) and 1 M Na2SO4 (12.6 Wh/kg and 349 W/kg) were significantly lower than those in WIS electrolytes. The GO/17 m NaClO4 WIS symmetric supercapacitor achieved energy and power density values of 24 Wh/kg and 1250 W/kg at 0.5 A/g, with 100 % retention of cycle stability after 10,000 charge-discharge cycles. The energy density values achieved through this strategy of binder-free GO/WIS based supercapacitors are consistent with the range reported for other carbon materials, including activated carbon, carbon nanotubes, and reduced graphene oxide. This suggests that the approach has significant potential for developing highenergy-density supercapacitors using GO, which could have practical applications in a variety of fields.