Electrochemical performances of surface modified CePO4-coated LiMn2O4 cathode materials for rechargeable lithium ion batteries.

Improved electrochemical performances of Spinel LiMn2O4 cathode was prepared by a sol-gel coating of CePO4 to the surface of the LiMn2O4 powder and subsequent heat treatment at 600 degrees C for 8 h in air. The surface modified LiMn2O4 cathode materials were characterized by using TG/DTA, X-ray diffraction, Scanning electron microscope, X-ray photoelectron spectroscope, cyclic voltammetry techniques and charge/discharge studies. XRD and SEM results show that no significant bulk structural differences are observed between the coated and pristine LiMn2O4. 2 wt.% CePO4 coated LiMn2O4 cathode materials was enhance the particle size compared to pristine due to small layer of CePO4 particle covered on the over the surface. XPS data illustrated that, the CePO4 was completely coated over the surface of the LiMn2O4 core materials. Galvanostatic charge/discharge studies of the uncoated and CePO4-coated LiMn2O4 cathode materials were carried out in the voltage range between 3.0 and 4.5 V at elevated temperature (50 degrees C). The composition of CePO4 coating was increased from 0.0 to 3.0 Wt.%, the initial capacity of the samples decreased slightly. But the cycling stability was increased remarkably between 3-4.5 V. 2.0 Wt.% CePO4-coated LiMn2O4 cathode has satisfied the structural stability, high reversible capacity and excellent electrochemical performances. This result indicates that, the surface treatment should be an effective way to improve the comprehensive properties of the cathode materials for lithium ion batteries.