Identification of LiNi0.5Mn1.5O4 spinel in layered manganese enriched electrode materials

We report the synthesis and characterization of the composite materials Li1 + x(Ni0.25Mn0.75)O2.25 + x/2 and Li1 + x(Ni0.25Co0.125Mn0.625)O2.19 + x/2 (x = 0.25, 0.375, 0.5, and 0.625) via a solid-state reaction. XRD patterns and electrochemical cycling of the materials in lithium cells revealed features consistent with the presence of the high voltage spinel LiNi0.5Mn1.5O4 phase within the materials, which diminished with increasing relative lithium compositions. The cobalt-containing materials had less evidence of a spinel phase than the cobalt-free materials of equivalent relative lithium to transition metal compositions. The results presented herein provide evidence that the additional XRD features were correlated with the presence of the LiNi0.5Mn1.5O4 phase within these materials.