Structure and electrochemical performance of surface modified LaPO4 coated LiMn2O4 cathode materials for rechargeable lithium batteries

LiMn2O4 spinel cathode materials were coated with 1.0, 2.0 and 3.0 wt% of LaPO4 by the polymeric process, followed by calcinations at 800 °C for 6 h in air. The structure and electrochemical properties of the surface modified LiMn2O4 materials were characterized by XRD, SEM, XPS, cyclic voltammetry and charge–discharge techniques. XRD patterns of LaPO4 coated LiMn2O4 revealed that the coating did not affect the crystal structure and space group Fd3m of the powder materials, compared to the uncoated LiMn2O4. XPS data illustrate that the LaPO4 was completely coated over the surface of the LiMn2O4 core materials. 2 wt% of LaPO4 coated LiMn2O4 cathode material exhibits specific capacity of 103 mAh/g (versus lithium metal) and excellent capacity retention (82% of its initial capacity) between 4.5 and 3 V after 100 cycles at elevated temperature (50 °C). LiMn2O4 coated with 0.0–3.0 wt% of LaPO4 has slightly decreased the initial capacity, but the cycling stability increased remarkably over 3–4.5 V. This result indicates that the surface treatment should be an effective way to improve the overall properties of the cathode materials for lithium ion batteries. Among them, 2 wt% of LaPO4 coated spinel LiMn2O4 cathode material has improved the structural stability, high reversible capacity at elevated temperature and excellent electrochemical performances of the rechargeable lithium batteries.