Batteries are something of a miracle — they power a huge part of our lives, yet the best ones work behind the scenes, quietly powering your phone and asking for little more than a few hours of charging a few times per week.

But now, they're so ubiquitous that they have us at their mercy. It's the reason you'll see crowds huddled around power outlets at airports, each person waiting for his or her turn to charge a phone, tablet or laptop. It only takes an hour or so, but what if you only have a minute?

It's time for a new battery. As gadgets shrink and energy demands grow, the challenge of fitting more power into tinier spaces — increasing the energy density, as it's called — becomes increasingly difficult.