A Descriptor and Tool for Guiding Composition Design toward Developing Single- or Mixed/Hybrid-Phase “Layered” Transition Metal Oxide Cathode Materials for Na-Ion Batteries

Abstract

Abstract The structure type and phase assemblage of “layered” Na-transition metal (TM) oxides dictate their performance as cathode materials, resulting in an impetus toward developing biphasic or hybrid Na-TM-oxides. However, a fundamental understanding as to what drives the formation of such biphasic structures, instead of a single phase, remains unestablished. This also means that a coherent strategy to rationally design hybrid Na-TM-oxides and tune the relative contents of the constituent phases is missing. Against this backdrop, we report a simple strategy and an associated descriptor, that is based on the overall covalency of cation−oxygen bonds in the TMO2-“slab”, viz..