Enhancing the Electrochemical Performance of Nickel-Rich Layered Cathode Material (NMC 622) for Lithium-Ion Batteries by Ultrathin Conductive Ceria-Surface Coating

Abstract

Layered LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622) has been lauded as robust and fitting candidates for the development of the next generation lithium-ion batteries for electric vehicles and other high energy demanding applications. However, widespread commercialization of NMC622 cathode material has been frustrated by its poor cycling performance which is due to structural instability. This work shows that the electrochemical performance of the NMC622 can be greatly enhanced by surface-coating with CeO₂. A commercial NMC622 is chemically modified with a very low amount of CeO₂ (~2 %) to form an ultrathin CeO₂-coated NMC622 surface (NMC622-c). The coated electrode material exhibits enhanced electrochemical performance compared to its pristine counterpart, especially in terms of Li-ion diffusion kinetics and capacity retention. This enhancement has been made possible by the NMC622-c overcoming the destructive H2/H3 phase transition, reduced Ni/Li mixing, and improved ordered hexagonal structure. Improved Li diffusion rate has also been improved for long battery life. This work provides excellent insight to researchers and entrepreneurs working hard to overcome the inherent challenges of the NMC622 and related NMC layered cathode materials.