Pint-Sized Power Packs

I always seem to be suffering a personal energy crisis. I can drain my mobile-phone battery dry in a day, my PDA craves a charge after 48 hours and my notebook computer beeps plaintively during the shortest airplane flight. The situation isn't getting better. Portable devices continue to sprout power-hungry features such as color screens and wireless communications capabilities. Yet the humble, overtaxed batterywithout which no device would be portableis evolving too slowly to keep up.

To anyone hauling around spare AAs and an emergency power cord, it's obvious that energy-storage technology needs a rethink. Fortunately, one is...