The membrane is made from a polystyrene-based polymer, which is sandwiched between two metal plates. When charged by those plates, it can store the energy at a rate of 0.2 farads per square centimeter - standard capacitors, by contrast, can typically only manage an upper limit of 1 microfarad per square centimeter. Due in part to the membrane's low fabrication costs, the cost of storing energy in it reportedly works out to 72 cents US per farad. According to the researchers, the cost for standard liquid electrolyte-based batteries is more like US$7 per farad. This in turn translates to an energy cost of 2.5 watt-hours per US dollar for lithium-ion batteries, whereas the membrane comes in at 10-20 watt-hours per dollar. (more) (sing-a-long)
