The idea of charging to a safer medium than a battery, or even gasoline, appeals to my imagination. Sugar, for instance, doesn't burn exothermically unless you add the right catalyst. My chemistry teacher never told me what it was, but his explosive demonstration left this imprint in my mind!

I just checked. A sugar bio-battery is demonstrated with 10x the energy density of the Li-Ion battery. I'm getting Popular Science vibes here, though, where an idea is demonstrated but somehow never goes commercial.