Toward Positive Electrode Materials with High-Energy Density: Electrochemical and Structural Studies on LiCo Mn O with 0 ≤ ≤ 1.

To obtain positive electrode materials with higher energy densities (s), we performed systematic structural and electrochemical analyses for LiCo Mn O (LCMO) with 0 ≤ ≤ 1. X-ray diffraction measurements and Raman spectroscopy clarified that the samples with ≤ 0.5 are in the single-phase of a spinel structure with the 3̅ space group, whereas the samples with ≥ 0.75 are in a mixture of the spinel-phase and LiMnO phase with the 2/ space group. The -dependence of the discharge capacity ( ) indicated a broad maximum at = 0.5, although the average operating voltage ( ) monotonically increased with . Thus, the value obtained by × reached the maximum (=627 mW h·g) at = 0.5, which is greater than that for Li[NiMn]O. Furthermore, the change in the lattice volume (Δ) during charge and discharge reactions approached 0%, that is, zero-strain, at = 1. Because Δ for = 0.5 was smaller than that for Li[NiMn]O, the = 0.5 sample is found to be an alternative positive electrode material for Li[NiMn]O with a high .