XAS and RIXS investigation of O2-type Li-rcih manganese oxides

O2-type Li0.75[Li0.25Mn0.75]O2 is a typical Li-rich cathode for lithium ion batteries, featuring reversible anionic redox and suppression of transition metal migration thanks to the unique stacking. Beyond previous knowledge, our recent investigation of this material reveals superior cycling stability at high temperature (55oC) compared to room temperature (25oC), which is particularly anomalous for manganese-based cathode materials that suffer from Mn dissolution problems. As shown by electrochemical analysis, this unconventional high-temperature stability is linked to the enhanced anionic-redox capacity during initial cycles and to the possible conversion from anionic redox to Mn-redox during subsequent cycling. In this case, we propose to monitor the lattice oxygen and Mn oxidation states during electrochemical cycling by synchrotron-based ex situ soft XAS and RIXS measurements in order to reveal the fundamental mechanism behind the unconventional electrochemistry.