Oxygen and transition metal involvement in the charge compensation mechanism of LiNi1/3Mn1/3Co1/3O2 cathodes

Abstract

X-ray absorption spectroscopy at the Ni, Mn, and Co K-edges is used to investigate the charge compensation mechanism and its relationship to the magnetic moments in Li_1−xNi_1/3Mn_1/3Co_1/3O₂. Multiple analytical methods are compared to separate element-specific redox trends from collective effects. EXAFS is used not only for structural, but also for chemical information while XANES is used not only for chemical, but also for structural information. While Ni is found to be the only transition metal involved in the charge compensation reaction until half the Li is removed, the second half of the deintercalation reaction is not accompanied by transition-metal oxidation. It is deduced that over the second half of Li deintercalation, the oxidation of oxygen ions bonded to cobalt is responsible for charge compensation and for an increase in the magnetic moment.