Structural change during charge-discharge for iron substituted lithium manganese oxide

摘要

For this study, Fe-substituted Li2MnO3 (Li1+x(Fe0.25Mn0.75)(1-x)O-2, 0 < x < 1/3) was prepared using coprecipitation-calcination. The change in the cation distribution was examined after charge discharge using a monoclinic Li2MnO3 unit cell (C2/m). At the initial Li-extraction, Fe ion moved to the tetrahedral 8j site. At the end of charging, transition metals moved from 4g and 2b sites in (Mn, Fe)-Li layer to 2c and 4h sites in the Li-layer via 4i and 8j sites. The cation random distribution was maintained after the end of discharging. The stability of layered rock-salt phase after cycle testing depended on the mode of charging; although the positive electrode decomposed to a mixture of layered rock-salt and spinel phases by typical galvanostatic charging, the positive electrode remained a single phase with a layered rock-salt structure by application of stepwise charging. Careful control of the charging mode at the initial cycle is important for Fe-substituted Li2MnO3 positive electrode material. (C) 2016 Elsevier B.V. All rights reserved.