In situ small-angle X-ray scattering reveals solution phase discharge of Li–O <sub>2</sub> batteries with weakly solvating electrolytes
Christian Prehal, Aleksej Samojlov, Manfred Nachtnebel, Ludek Lovicar, Manfred Kriechbaum, Heinz Amenitsch, Stefan A. Freunberger
Abstract
Significance Lithium–air batteries are promising next-generation energy storage devices and operate by electrodepositing insulating lithium peroxide (Li 2 O 2 ). Understanding how large amounts of Li 2 O 2 form, corresponding to large capacities, and what limits the amount is therefore paramount and requires following its structural evolution from atomic to micron scales. We demonstrate that in situ small- and wide-angle X-ray scattering together with sophisticated data evaluation provides access to these scales. This allows distinguishing the two reported competing reaction mechanisms, which are thought to be responsible for large and small capacities, respectively. We find that, surprisingly, only one pathway predominates at all conditions. On a wider perspective, we introduce a powerful tool to characterize transformations in complex multiphase materials.