Post‐Synthetic Cerium Modification of Commercial NCM811 for Concurrent Cycling and Safety Upgrading

The widespread use of Ni‐rich LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathodes in high‐energy batteries remains limited by structural degradation, side reactions, and oxygen release, yet most modification strategies prove incompatible with commercial materials. This work presents a facile solid‐state method that achieves synergistic cerium ion (Ce 3+ ) doping and CeO 2 coating on commercial NCM811 by mixing with CeO 2 nanoparticles followed by calcination. Structural and morphological analyses confirm Ce incorporation into the near‐surface lattice and the formation of a nanoscale CeO 2 layer without disturbing the layered framework. Electrochemical tests demonstrate that the optimal 1 wt.% Ce‐modified sample exhibits superior rate capability and long‐term stability, retaining 82.04% of its initial capacity after 500 cycles at 1 C, compared to 74.10% for pristine, owing to suppressed cation mixing, enhanced structural stability, and improved Li + diffusion kinetics. Crucially, differential electrochemical mass spectrometry shows Ce modification curtails O 2 release and reduces H 2 and CO 2 generation across various rates, effectively mitigating gas evolution associated with safety degradation. Accelerating rate calorimetry further confirms delayed thermal runaway and improved adiabatic stability. Overall, this work establishes a scalable post‐treatment route to simultaneously boost the electrochemical performance and safety of commercial nickel‐rich cathodes, offering a practical solution for next‐generation lithium‐ion batteries.