Batteries with metallic lithium anodes offer enhanced efficiency compared to conventional lithium-ion batteries because of their higher capacity. However, safety concerns and a short lifespan stand in the way. To better analyze the causes of malfunctions and premature failure of such batteries, researchers have developed a technique that visualizes the distribution of active lithium on the anode and differentiates between dendrites and “dead” lithium. As reported in the journal Angewandte Chemie, the technique makes use of a fluorescent dye.