It is well recognized that electrification of road transportation would do much to minimize our consumption of fossil fuels, and thereby reduce CO2 emissions and consequent effects on climate change, as well as providing better energy security and lessening the economic drain of fossil fuel imports. Two possible routes to this electrification are using batteries or fuel cells in cars, both of which currently have high promise but technical and economic challenges for mass market adoption. The principal challenge with batteries is that the existing battery chemistries (e. g. Li-ion) do not seem able to provide affordable and safe transportation at a sufficient range (> 300 miles), and this is principally related to the limited battery energy density.