Structural investigations of Li(1.5+x)Na0.5MnO(2.85)I(0.12) electrodes by Mn X-ray absorption near edge spectroscopy

Mn K-edge X-ray absorption near edge spectroscopy (XANES) has been performe d on an amorphous, Mn-based oxide, Li1.5Na0.5MnO2.85I0.12, and on electrode s containing this material to determine the changes that occur in the local atomic and electronic structure with state of charge and with cycling. Com parison of the XANES data with those from lambda-MnO2, LiMn2O4, and Li2Mn2O 4 reveals that the Mn are octahedrally coordinated and reduced from Mn4+ to Mn3+ during discharge to 2 V. Additional ly, it was found that the amorpho us nature of Li1.5Na0.5MnO2.85I0.12 results in less dramatic changes upon i nserting Li+, leading to increased cycling stability and the potential for better rate capabilities within the 4-2 V range in comparison to LiMn2O4. ( C) 2000 The Electrochemical Society. S0013-4651(99)02-024-8. All rights res erved.