Mn K-edge X-ray absorption near edge spectroscopy (XANES) has been performed on an amorphous, Mn-based oxide, Li1.5Na0.5MnO2.85I0.12, and on electrodes containing this material to determine the changes that occur in the local atomic and electronic structure with state of charge and with cycling. Comparison of the XANES data with those from lambda-MnO2, LiMn2O4, and Li2Mn2O4 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 amorphous nature of Li1.5Na0.5MnO2.85I0.12 results in less dramatic changes upon inserting Li+, leading to increased cycling stability and the potential for better rate capabilities within the 4-2 V range in comparison to LiMn2O4.