Rare-earth oxide additives mitigate oxygen release and thermal runaway in Ni-rich NCM cathodes

Thermal runaway remains a critical barrier to the deployment of high-energy density lithium-ion batteries. While Ni-rich NCM cathodes offer exceptional capacity, their poor thermal stability, driven by early oxygen release, poses serious safety risks. Here, we propose a simple and scalable strategy that physically blended a trace amount of rare-earth (RE) oxide particles into the cathode as oxygen absorbers, capturing oxygen molecules released during heating and thereby suppressing oxygen-induced parasitic reactions at the anode. 5 wt% of CeO 2 , Gd 2 O 3 , Lu 2 O 3 , and Y 2 O 3 , were blended with single-crystal NCM-92 cathode material, separately. Differential scanning calorimetry (DSC) and online mass spectrometry (OMS) reveal that all RE oxide additives substantially suppress both heat generation and oxygen evolution during thermal ramping. Particularly, CeO 2 reduces early-stage oxygen release in the 220–240 °C range by up to ∼60% even in the presence of electrolyte, effectively interrupting the exothermic chain reaction. These results demonstrate a practical, coating-free approach to enhancing the thermal safety of high-nickel cathodes. A series of rare metal oxides was investigated as O 2 scavengers by simple physical mixture with Ni-Co-Mn oxide cathodes to suppress O 2 release and accumulation in Li-ion batteries.