In batteries, a metal reveals its dual personality
Battery researchers have been focusing on lithium metal electrodes as leading contenders for improving the amount of energy that batteries can store without increasing their weight. But lithium in this metallic form has a problem that has stymied much of this research effort: As the batteries are being charged, finger-like lithium deposits form on the metal surface, which can hamper performance and even lead to short-circuits that damage or disable the battery. Now, a team of researchers at MIT says it has carried out the most detailed analysis yet of exactly how these deposits form, and reports that there are two entirely different mechanisms at work. While both forms of deposits are composed of lithium filaments, the way they grow depends on the applied current. Clustered, “mossy” deposits, which form at low rates, turn out to grow from their roots and can be relatively easy to control. The much more sparse...