How Much Mn Is Needed To Inhibit Molecular Oxygen and Improve the Thermal Stability of High-Ni LiNi x Mn 1– x O 2 Cathodes?

High-nickel (Ni) cathodes exhibit promising potential for the development of high-energy density batteries. While increasing the nickel content improves the cathode capacity, it also increases the risk of molecular oxygen release and degrades the thermal stability. In this work, the critical manganese content required to stabilize high-nickel LiNixMn1–xO2 systems and suppress molecular oxygen formation is systematically investigated. Using electron paramagnetic resonance (EPR) and thermogravimetric analysis (TGA), the optimal Mn content is determined to be larger than 8.33%, which effectively inhibits molecular oxygen formation and enhances the thermal stability of the material. A Mn content higher than 25% can completely suppress molecular oxygen formation. This phenomenon can be rationalized by a simple two-shell-layer-control model. It is further proposed that during the oxygen release stage, strong magnetic frustration acts as the driving force for the generation of molecular oxygen.