Structural Characterization of Layered LiMnO₂ Electrodes by Electron Diffraction and Lattice Imaging

Electrode materials of the formula were prepared by an ion‐exchange process from and were examined by X‐ray diffraction and convergent‐beam electron diffraction to determine crystal structure and phase purity. Electron diffraction data showed that a typical parent sample consisted predominantly of layered with lithiated‐spinel present in minor concentration; orthorhombic (Pmmm) was detected in trace quantity. An orientation relationship between the monoclinic layered and tetragonal lithiated‐spinel was obtained from an analysis of single‐crystal electron diffraction data. Electron diffraction analyses of three electrochemically cycled (0 < < 1) samples showed that the parent compound was unstable to repeated lithium intercalation/deintercalation and transformed to a spinel‐type structure, consistent with previous reports. These electrodes, like those derived from , show greater stability compared to standard spinel electrodes, when cycled between 4.6 and 2.0 V. The unexpected stability of the electrodes (0.5 ≤ < 1.0) at 3 V is attributed to the presence of spinel domains (0 < < 0.33) in a composite electrode structure. © 1999 The Electrochemical Society. All rights reserved.