First-Cycle Evolution of Local Structure in Electrochemically Activated Li₂MnO₃

X-ray absorption spectroscopy is utilized to determine changes in the local structure of Li 2 MnO 3 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 Li 2 MnO 3 prepared at 850 °C. After full delithiation to ∼5 V, the local Mn environments are similar to those of the freshly prepared Li 2 MnO 3 electrodes but with increased disorder. On discharge, significant reduction of Mn is observed accompanied by rearrangement of Mn resulting in Jahn–Teller distorted, Mn 3+ local environments. It is also shown, as expected, that the electrochemical and structural behavior of pure Li 2 MnO 3 is markedly different than that observed for the structurally similar Li 2 MnO 3 component of lithium- and manganese-rich composite cathodes.