Peeking inside lithium-ion batteries offers new ways to put a stop to deadly fires

Lithium-ion batteries are an indispensable part of the transition away from fossil fuels thanks to their high voltage output and long cycle life, but their tendency to overheat and catch fire is a serious problem. Now two different papers have tackled different aspects of the problem: in the first, researchers in the US have imaged working battery electrodes with unprecedented resolution to ascertain why lithium batteries sometimes ignite when not on charge. In the second, researchers in China have developed an optical sensor that could be placed inside batteries to detect the onset of thermal runaway before it becomes dangerous.

Intercalation electrodes were central to the development of functional, rechargeable lithium-ion batteries. ‘The gurus who came up with it gave the world a new kind of material … the fact that you can produce energy and release energy many thousands of times now is the miracle,’ says Nitash Balsara at the University of California, Berkeley. Simply plating the lithium onto an electrode causes significant capacity loss in every charge–discharge cycle. When the battery is charged rapidly, however, lithium may first plate onto the anode and subsequently intercalate into it owing to the flow of ionic currents that continue after the electric current has been switched off. ‘Between the lithium metal and the graphite you make a small battery,’ explains Balsara.