In situ small-angle X-ray scattering reveals solution phase discharge of Li-O batteries with weakly solvating electrolytes.

Electrodepositing insulating lithium peroxide (LiO) is the key process during discharge of aprotic Li-O batteries and determines rate, capacity, and reversibility. Current understanding states that the partition between surface adsorbed and dissolved lithium superoxide governs whether LiO grows as a conformal surface film or larger particles, leading to low or high capacities, respectively. However, better understanding governing factors for LiO packing density and capacity requires structural sensitive in situ metrologies.