where C is the capacitance of the device and V is the operatingvoltage window for the cell. On the basis of this expression, a 2-fold increase in voltage could result in a 4-fold increase in energydensity for the same value of capacitance. Thus, a properlydesigned asymmetric supercapacitor offers the prospect ofincreasing the energy density for applications where energyneeds to be stored and delivered with high power.