The next breakthrough smartphone, or maybe the one after that, might not have a traditional battery as its sole source of power. Instead, it could pull energy from the air or power itself through television, cellular or Wi-Fi signals.Engineers at Apple even tried for many years to build a smarter battery by adding solar charging to iPhones and iPods, a former Apple executive said. And they have continued to experiment with solar charging, two people who work at the company said.
http://www.nytimes.com/2014/02/03/technology/building-a-better-battery.html