Oxygen Involvement in the Charge Compensation of LiMO2 Compounds and the Consequences for Battery Safety and Unprecedented Electrical Magnetic Properties

An intimate view of the operando electronic and atomic structure local to oxygen and transition metals in LiMO₂ cathodes has been developed. We present here a combination of in-situ and operando measurements of structure, resistivity and magnetic susceptibility to expose the direct role of oxygen in charge compensation reactions. The formation of electron holes at oxygen sites, as detected by X-ray absorption spectroscopy (XAS), is a prerequisite for oxygen evolution reactions that can lead to battery fires. However, the same reaction, if managed well can lead to beneficial switching behavior of their magnetic and electrical properties. The magnetic susceptibility of LixCoO₂ has been studied in composition range of 0.94 ≤ x ≤ 0.75. A consistent and linear increase in susceptibility with respect to decreasing lithium content has been observed with the notable exception of a sharp decrease in susceptibility at x = 0.94. This sharp change in molar magnetic susceptibility as well as the associated change in resistivity has potential use in neuromorphic memory applications.