An all-solid state asymmetric supercapacitor has been fabricated using carbon aerogel (CA) microspheres as the negative electrode and CO3O4 nanowires on nickel foam (Co3O4-NF) as the positive electrode separated by PVA-KOH membrane as the electrolyte. For the desirable porous structure, high specific capacitance and rate capability of CA and Co3O4-NF, broader potential window of the two electrodes, no binder and conductive agent added, the asymmetric supercapacitor can be cycled reversibly in a wide potential window of 0-1.5 V with an energy density of 17.9 Wh kg(-1) at a power density of 750 W The energy density of the asymmetric supercapacitor is significantly improved in comparison with those of the symmetric supercapacitors based on CA (6.28 Wh kg(-1)) and Co3O4 NF (2.42 Wh kg(-1)). The asymmetric supercapacitor can also deliver a high energy density of 10.44 Wh kg(-1), even at a high power density of 7.5 kW kg(-1). In addition, the asymmetric device shows good stability with approximately 85% of its initial capacitance after 1000 cycles. (C) 2015 Elsevier B.V. All rights reserved.