Interpreting the structural and electrochemical complexity of 0.5Li2MnO3·0.5LiMO2 electrodes for lithium batteries (M = Mn0.5−xNi0.5−xCo2x, 0 ≤ x ≤ 0.5)

Abstract

The structural and electrochemical features of layered 0.5Li₂MnO₃·0.5LiMO₂ electrodes, in which M = Mn_0.5−xNi_0.5−xCo_2x (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.