High-voltage lithium–manganese-rich cathodes show loss of voltage and capacity under electrochemical cycling. Structural changes, including the migration of transition metals into the lithium layer, are believed to be primarily responsible for the voltage and capacity fading. Thus a detailed atomic scale understanding of the structural changes is essential for establishing correlations between structural and electrochemical properties. This works demonstrates that Ni antisite defects are the predominant disorder in the pristine material. Furthermore, open facets terminated by a mix of cation and anions show larger concentrations of defects compared to closed oxygen-terminated facets. Surprisingly, Ni favorably substitutes for Mn in the transition metal layers near the surface of open facets (but not at closed facets). Hence appropriate facets can be selected to minimize the surface segregation of the Ni atoms, which may have important implications for the cathode performance and stability.
Hemant Dixit, Wu Zhou, Juan-Carlos Idrobo, Jagjit Nanda, and Valentino R. Cooper, “Facet dependent disorder in the pristine high voltage lithium–manganese-rich composite cathode” ACS Nano (2014). DOI: 10.1021/nn505740v
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