Interpreting the structural and electrochemical complexity of 0.5Li₂MnO₃·0.5LiMO₂electrodes for lithium batteries (M = Mn_0.5−xNi_0.5−xCo_2x, 0 ≤ x ≤ 0.5)

The structural and electrochemical features of layered 0.5Li2MnO3·0.5LiMO2 electrodes, in which M = Mn0.5−xNi0.5−xCo2x (0 ≤ x ≤ 0.5), have been studied by powder X-ray diffraction, electrochemical differential-capacity measurements, 7Li magic-angle-spinning nuclear magnetic resonance, and X-ray absorption near-edge spectroscopy. Li2MnO3-like regions in the as-prepared samples were observed for all values of x, with transition-metal cation disorder between the LiMO2 and Li2MnO3 components increasing with cobalt content (i.e., the value of x). The structural disorder and complexity of the electrochemical redox reactions increase when the Li2MnO3-like regions within the electrode are activated to 4.6 V in lithium cells; interpretations of structural and electrochemical phenomena are provided.