Improved Electrochemical Performances of Surface-Modified Spinel LiMn[sub 2]O[sub 4] for Long Cycle Life Lithium-Ion Batteries

The surface of spinel was modified with inorganic salt by a sol-gel method to improve its electrochemical performance at elevated temperatures. Compared with pristine spinel surface-modification improved the cycling stability of the material at elevated temperatures. The capacity retention of -modified spinel was more than 94% after 500 cycles at room temperature and more than 90% after 200 cycles at 55°C at 1C charge-discharge rate. Thermogravimetry/differential scanning calorimetry studies showed that the formation process of on was different from that of pure Powder X-ray diffraction indicated that spinel was the only detected phase in -modified X-ray photoelectron spectroscopy showed that the Al content in the spinel decreased with the detection depth beneath the particle surface of the sample. Introduction of Al and Li into changed the electronic structures of its O and Mn atoms on the particle surface, but the electronic structure of Al remained unchanged. Therefore a surface solid solution of was formed on The thickness of the surface solid solution was estimated to be about 12 nm. The improved electrochemical performance of surface-modified spinel was attributed to the protection effect of the surface solid solution shell while the improved stability of crystalline structure was assigned to the entrance of and into the spinel crystalline structure. © 2003 The Electrochemical Society. All rights reserved.