The specific energy, specific power, fast-charge capability, low temperature operation, cycle-life and self-discharge of five energy storage devices was compared. The group included a conventional carbon–carbon supercapacitor, Li-ion battery and three types of asymmetric hybrid supercapacitors. Asymmetric hybrid supercapacitors use a nanostructured Li4Ti5O12 anode, and an acetonitrile electrolyte containing a lithium salt. Their cathode was activated carbon, LiCoO2, or LiMn2O4. All devices were built using common plastic Li-ion technology developed by Telcordia Technologies.