We've been spoiled by Moore's Law in technology. In comparison, all the "battery breakthroughs" of the past decade are pretty feeble. If someone could double or triple the energy density of a battery, that would be a breakthrough.

Unfortunately, there's another discipline where energy density is important: explosives. The critical difference is in how quickly the energy is released, and as Li-Ion batteries show it isn't always as controllable as we'd like.