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

The surface of the spinel LiMn2O4 was modified with zinc oxide by a chemical process to improve its electrochemical performance at high temperatures. The physical properties of the prepared products have been investigated by thermogravimetry (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-rays analysis (EDAX). The charge/discharge of the materials was carried at 1 mA/cm(2) in the range of 3.0 and 4.4 V at 55 degrees C. The discharge capacity of ZnO-coated LiMn2O4 (117 mAh/g) showed only 3% loss of the initial capacity (121 mAh/g) over 60 cycles. The cycle ability improvement of the spinel LiMn2O4 coated with ZnO is demonstrated at high temperatures. From the analysis of electrochemical impedance spectroscopy (EIS), the improvement of cycle ability may be attributed to the suppression on the formation of the passivation film and the reduction of Mn dissolution, which result from the modifying the surface of the spinet LiMn,04 with zinc oxide. (c) 2006 Elsevier B.V. All rights reserved.