High temperature electrochemical behaviors of ramsdellite Li2Ti3O7 and its Fe-doped derivatives for lithium ion batteries

The high temperature electrochemical cell performances of Li2Ti3O7 and its Fe-doped derivatives were studied. Pure Li2Ti3O7 gave higher charge/discharge capacities at 40 and 50 degrees C than at room temperature and featured good cycleabilities among the initial 40 cycles. However, the cell performance was terribly deteriorated at 70 degrees C. XRD measurement revealed its structure degradation into a rocksalt-type cubic structure phase with lower crystallinity in this high temperature of 70 degrees C. The XRD results from the electrodes experienced different cycles at 40 degrees C showed that the structure degradation is gradually developed as the cell is cycled. Meanwhile, Fe-doped Li2Ti3O7 ramsdellite samples afforded improved insertion/extraction properties of the lithium ions, even at 70 degrees C. The improved high temperature performance is presumedly considered from the stabilization of the foreign iron metal ions for ramsdellite structure. (c) 2006 Elsevier B.V. All rights reserved.