Raquel Lizarraga

Rubbing a comb against wool creates a spark. A similar principle works in triboelectric nanogenerators — devices that convert mechanical touches into electricity. The problem is that ordinary materials produce a weak charge.

A lithium battery is like a sandwich: two slices of bread are the electrodes, and the filling between them is the electrolyte, through which lithium ions shuffle back and forth. In conventional batteries, the filling is liquid, like a sauce, and it can leak or catch fire.