Distinguished from commonly used Fe 2 O 3 and Fe 3 O 4 , a three-dimensional multilevel macromicro-mesoporous structure of FeC 2 O 4 /graphene composite has been prepared as binderfree electrode for supercapacitors. The as-prepared materials are composed of macroporous graphene and microporous/mesoporous ferrous oxalate. Generally, the decomposition voltage of water is 1.23 V and the practical voltage window limit is about 2 V for asymmetric supercapacitors in aqueous electrolytes. When FeC 2 O 4 /rGO hydrogel was used as the negative electrode and a pure rGO hydrogel was used as the positive electrode, the asymmetrical supercapacitor voltage window raised to 1.7 V in KOH (1.0 mol/L) electrolyte and reached up to 2.5 V in a neutral aqueous Na 2 SO 4 (1.0 mol/L) electrolyte. Correspondingly it also exhibits a high performance with an energy density of 59.7 Wh/kg. By means of combining a metal oxide that owns micro-mesoporous structure with graphene, this work provides a new opportunity for preparing high-voltage aqueous asymmetric supercapacitors without addition of conductive agent and binder.