As our smartphones, watches, tablets and even cars have begun to make ever-increasing use of battery power, those batteries haven't quite managed to keep up. We're charging our smartphones at least once a day, and the new smartwatches on the market don't do much better. Cars need recharging at worryingly short intervals, and at this point it's arguable that we've been held back by the amount of juice we can give things. Something has to change.