Reinforce the interface of Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode material for lithium-ion batteries under high operating voltage through Ce.

Nickel-rich cathode material is one of the most promising cathode materials for high-energy lithium-ion batteries. However, the structure stability, thermodynamic stability, cycle and rate performances of Ni-rich materials still need to be further improved. In this research, rare earth element Ce is employed to reinforce the interface of Ni-rich cathode material both internally and externally. It has been determined that high valence state Ce4+ can easily cause the oxidization of Ni2+ to Ni3+ when being doped into the material due to its strong oxidation performance, thus reducing Li+/Ni2+ mixing degree. Besides, the inert Ce3+-ions in transition metal slabs with the strong Ce-O bond can maintain the layered structure at high delithiation state. Further, when the calcination temperature during synthesis is above 500℃, a CeO2 coating layer will form, which can protect the electrode from the erosion of electrolyte and alleviate the increasing resistance during cycling. The modified Ni-rich materials fabricated with an erosion-resisting CeO2 layer outside and stronger Ce-O bond inside with reduced Li+/Ni2+ mixing degree exhibit excellent electrochemical properties, especially under high operating voltage, i.e., the 50th capacity retention at 0.2 C within 2.75-4.5V has been improved from 89.8% to 99.2% after the modification.