I've had a think and Shagohad's Dead Space theory seems to be something similar to what I was thinking. Capacitors: Their basically two wide plates of metal in a circuit seperated by a small space. The space can be occupied by air but the capacitor conducts more efficiently when the space is filled by a saturated spongy material (details are irrelevent). But really it's not the conductability that would be useful in this instance, but the insulation of the air. When an electric current is introduced to the circuit, electrons move out of one of the plates to continue the flow; they travel around the circuit and into the other plate. This means the second plate obtains a negative charge since it's obtaining more electrons coming in from the circuit. The first plate gains a positive charge due to the lack of electrons.
Normally, the instability in the plates would be equalised by a bolt of electricity jumping across the space between plates. The bigger the insulator, the more electrons will need to be transferred from one plate to the other, ergo, the process will take longer, and ergo, the bigger the charge will be.
Air is a fairly good insulator of electricity. So after it all, your left with two highly charged plates of metal.
That's all i've got. But maybe the charges could be manipulated? Similar principles to magnetism.
