Raman and X-Ray Absorption Spectroscopy Investigations of the Structure and Ru–Mn Valence States of Li2Mn0.9Ru0.1O3.

We report the effect of the sintering temperature on the structure and valence states of Ru–Mn in Li₂Mn_0.9Ru_0.1O₃. These effects are explored by synchrotron X-ray diffraction patterns, Raman and X-ray absorption spectroscopy spectra (analysis of the Ru–M₄, Mn–L_2,3, and O–K edges). Ru doping at the Mn site in Li₂MnO₃ changes the lattice parameters of the parent Li₂MnO₃. Li₂Mn_0.9Ru_0.1O₃ sintered at 950^oC shows two peaks of the Ru–M₄ absorption edge. These peaks confirm the presence of mixed valence states Ru⁺⁴ and Ru⁺⁵. The compound Li₂Mn_0.9Ru_0.1O₃ sintered at 1050^oC shows only one peak of the Ru–M₄ absorption edge, which reveals the presence of the Ru⁺⁴ valence state. The Mn–L₃ absorption edge of Li₂Mn_0.9Ru_0.1O₃ shifts towards lower energy in comparison to the absorption edge of Li₂MnO₃. The O–K absorption edge of Li₂Mn_0.9Ru_0.1O₃ shows the origin of a new peak in comparison to the absorption edge of Li₂MnO₃ due to the presence of Mn⁺³–O hybridization in Li₂Mn_0.9Ru_0.1O₃ sintered at 950^oC. The Raman spectrum of Li₂Mn_0.9Ru_0.1O₃ shows splitting and peak shifting with the change in the sintering conditions. The presence of mixed valences Mn⁺³, Mn⁺⁴, Ru⁺⁴, and Ru⁺⁵ in the lattice of Li₂Mn_0.9Ru_0.1O₃ sintered at 950^oC may affect the charge–discharge properties of the Li₂Mn_0.9Ru_0.1O₃ cathode. [ABSTRACT FROM AUTHOR]