Investigations of Bulk Li–Mn–Ni–O Samples to Confirm the Combinatorial Studies

Abstract

The key features in the Li–Mn–Ni–O pseudo-ternary phase diagrams, as determined using combinatorial samples, were confirmed with bulk samples synthesized under various conditions via two different synthesis routes. The four-phase equilibrium was observed and transformations were found to be reversible, thereby confirming that two three-phase regions exist and transform during slow cooling. The primary importance of this work is a better understanding of how the phase boundaries and coexisting regions transform when cooled at rates typically used commercially. It is also important to recognize that a small amount of transformation occurred even for samples quenched on a copper or steel plate. These changes cannot be avoided entirely without quenching in liquid nitrogen or avoiding the compositions where the transformations occur. Understanding the phase diagrams should have a significant impact on research focused on composite electrodes in the Li–Mn–Ni–O system, since this work identified the compositions and conditions required to obtain layered–layered nano-composites and layered–spinel composites.