Intercalation property of PF6- into graphitic carbon was studied for a hybrid capacitor with different ratio of cathode and anode amount. Graphene sheet distance increased with increasing PF6- intercalation amount and it saturated at 0.4 nm at high applied potential, which is corresponded to stage 2 structure. On the other hand, it was found that nano size pore into graphene sheet was introduced at higher applied potential with 20 times larger anode carbon and this nano porous carbon shows a large capacity for intercalation capacity of 147 mAh g(-1). The estimated energy density of the hybrid capacitor using carbon with nano bubble structure was ca. 400 Wh kg(-1). (C) 2010 Elsevier B.V. All rights reserved.