The capacity of current battery technology is about two orders of magnitude below the limits imposed by physics and materials science, which provides an opportunity for many creative ideas. But as always the development of new technologies opens up problems in fundamental physics and materials that have not been much studied. From Li-‐ion development, one is forced to consider the effects of strong electron correlations (Mott physics) on doping and intercalation. Oxide heterostructures offer the possibility of “modulation doping” by charged ionic species, ranging from ionic liquids to oxygen vacancies, and working with polar materials allows one to contemplate a battery where the working counterion is not an alkali ion but a positively charged “hole”. Whether or not such ideas ultimately prove practical, the impact of engineering problems in stimulating fundamental science should be explored.