Influence of europium doping on the electrochemical performance of LiNi0.5Co0.2Mn0.3O2 cathode materials for lithium ion batteries

Abstract

Pristine LiNi0.5Co0.2Mn0.3O2 and a series of Eu-doped LiNi0.5Co0.2Mn0.3O2 cathode materials have been successfully synthesized by a solid-state route. The influence of Eu doping on the crystal structure and electrochemical properties of LiNi0.5Co0.2Mn0.3O2 was evaluated by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge tests. The results show that doping with Eu can expand the channels for diffusion of Li ion and reduce the charge transfer resistance. Furthermore, the 0.5mol% Eu-doped LiNi0.5Co0.2Mn0.3O2 exhibits an excellent rate capacity (122.00mAhg−1 at 3C) and cycling ability (139.99mAg−1 at 1C with a capacity retention of 96.93% after 50 cycles), which can be explained by the fact that doping with inactive Eu3+ ions may stabilize the crystal structure and expand the pathways for lithium ion diffusion.