Valence Determination of Manganese in Battery Cathode Materials by High-Resolution Mn K_α1 Spectra

Abstract

High-resolution the Mn K_α1 X-ray fluorescence spectra (HRXRF) were measured for a variety of manganese compounds, the oxidation number (valence) of which was from II to VII. Plots of the valence against the full width at half maximum (FWHM) and the chemical shift of the K_α1 X-ray fluorescence spectra give a curve and a liniar relation, respectively. The coefficient of correlation (R²) for the latter plot was 0.989 between valency II and VII. More excellent linearlity from III to IV was obtained with R² = 0.995, which enabled us to determine the oxidation number of manganese atom in a nickel ion doped spinel structure, LiMn₂O₄ (LiNi_xMn_2-xO₄, with 0.2 < x < 0.42). From the valence of manganese ion obtained from HRXRF, the oxidation number of nickel ion is concluded to be divalent.