The effect of nanolayer AlF3 coating on LiMn2O4 cycle life in high temperature for lithium secondary batteries

Abstract

The surface of the spinel LiMn2O4 was coated with AlF3 by a chemical process to improve its electrochemical performance at high temperatures. The morphology and structure of the original and AlF3-coated LiMn2O4 samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM). All the samples exhibited a pure cubic spinel structure without any impurities in the XRD patterns. It was found that the surfaces of the original LiMn2O4 samples were covered with a nanolayer AlF3 after the treatment. The charge/discharge of the materials were carried at 220 mA/g in the range of 3.0 and 4.4 V at 55°C. While the original LiMn2O4 showed 17.8% capacity loss in 50 cycles at 55°C, the AlF3-coated LiMn2O4 (118.1 mA h/g) showed only 3.4% loss of the initial capacity (122.3 mA h/g) at 55°C. It is obvious that the improvement in cycling performance of the coated-LiMn2O4 electrode at 55°C is attributed to the presence of AlF3 on the surface of LiMn2O4.