The lithium ion batteries in your mobile devices are inherently limited by the "ion" part of their name; they can safely use lithium only in the part of the cell that supplies ions, wasting a lot of potential energy. It's good news, then, that researchers at Stanford have developed a new lithium battery that could last for much, much longer. The technique allows for denser, more efficient lithium in the battery's anode (which discharges electrons) by using a nanoscopic carbon shield that keeps the unstable chemical in check -- uncontrolled, it can quickly shorten the device's lifespan.