Preparation and cycling performance of Al3+ and F- co-substituted compounds Li4AlxTi5-xFyO12-y

Li4AlxTi5-xFyO12-y compounds were prepared by a solid-state reaction method. Phase analyses demonstrated that both Al3+ and F- ions entered the structure of spinel-type Li4Ti5O12. Charge-discharge cycling results at a constant current density of 0.15 mA cm(-2) between the cutoff voltages of 2.5 and 0.5 V showed that the Al3+ and F- substitutions improved the first total discharge capacity of Li4Ti5O12. However, Al3+ substitution greatly increased the reversible capacity and cycling stability of Li4Ti5O12.While F-substitution decreased its reversible capacity and cycling stability slightly. The electrochemical performance of the Al3+-F--co-substituted specimen was better than the F--substituted one but worse than the Al3+-substituted one. (c) 2005 Elsevier Ltd. All rights reserved.