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 °C than at room temperature and featured good cycleabilities among the initial 40 cycles. However, the cell performance was terribly deteriorated at 70 °C. XRD measurement revealed its structure degradation into a rocksalt-type cubic structure phase with lower crystallinity in this high temperature of 70 °C. The XRD results from the electrodes experienced different cycles at 40 °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 °C. The improved high temperature performance is presumedly considered from the stabilization of the foreign iron metal ions for ramsdellite structure.