Phase transitions in Li₂MnO₃ electrodes at various states-of-charge

We studied the structural transformations from the layered-type to spinel-type ordering upon galvanostatic charging (Li⁺ extraction) of Li₂MnO₃ electrodes. We have determined by X-ray, electron diffraction techniques and Raman spectroscopy analyses that these transformations partially occurred even at the initial states-of-charge, at potentials of 4.3-4.5 V, and in fully charged (4.7 V) and discharged (2.0 V) states as well. The above transformations are evident also from the analysis of the intrinsic magnetic properties of Li₂MnO₃ electrodes that indicate short-range spin correlations typical for the Li ₂Mn₂O₄ and LiMn₂O₄ spinel-type structures, depending on the state of charge and the C-rates used for the cycling.