First-cycle evolution of local structure in electrochemically activated Li₂MnO₃

X-ray absorption spectroscopy is utilized to determine changes in the local structure of Li₂MnO₃ resulting from electrochemical extraction and insertion of lithium. Specially prepared electrodes allow for a first-cycle charge close to 100% of theoretical, even in crystalline Li₂MnO₃ prepared at 850 °C. After full delithiation to ∼5 V, the local Mn environments are similar to those of the freshly prepared Li₂MnO₃ electrodes but with increased disorder. On discharge, significant reduction of Mn is observed accompanied by rearrangement of Mn resulting in Jahn-Teller distorted, Mn³⁺ local environments. It is also shown, as expected, that the electrochemical and structural behavior of pure Li₂MnO₃ is markedly different than that observed for the structurally similar Li₂MnO₃ component of lithium- and manganese-rich composite cathodes.