Just like solar, the whole Lithium Ion battery deal still isn't there yet. It is somewhat for common AA and AAA sizes for digital cameras and the like, albeit they're 5 to 6 times as expensive as Alkaline batteries of the same size. But in large, heavy draw situations, they get hot. Really HOT. Remember the laptop fires, along with the fires they had on board the Boeing 777 and 787 that grounded the whole fleet sometime back? All were Lithium Ion battery related. I believe the Chevy "Volt" went through much the same thing, bursting into flames without any warning.
Again, I think in time this sort of thing will improve, and costs drop because the technology will get cheaper over time, much like big screen TV's. Perhaps in 20 or 30 years these things will be common, and almost as cheap as dirt. But for now it's just not there yet. This in spite of Obama thinking he can legislate technology. As I said, remember Solyndra, and the whole Fuel Cell cars pie in the sky..