Evidence of rutile to anatase phase transition of TiO2 thin film electrode during 1st discharging cycle of Li ion batteries

Abstract

TiO2 is a potential candidate for thin film electrode in Li ion batteries since it is abundant, cheap, has high theoretical specific capacity and can be produced in thin film form of desired crystallographic phase relatively easily by various physical vapor deposition techniques. Rutile phase TiO2 thin films have been prepared by radio frequency magnetron sputtering technique on stainless steel substrates at 450 °C substrate temperature, followed by post deposition annealing in air at 600 °C. These samples have been used as anode in Li ion batteries which are subjected to discharge/charge cycles. The electrodes have been extracted by de-crimping the batteries at various stages during the 1st discharge and 1st charge cycles and structural characterizations of these samples have been carried out by Grazing Incidence X-ray diffraction measurements with a laboratory X-ray source and Extended X-ray absorption fine structure measurements using synchrotron radiation. A clear signature of rutile to anatase phase transition has been observed in the samples during 1st discharge or Li ion insertion process, which is subsequently retained during the 1st charging cycle also. This is also verified by Raman spectroscopy measurements on few samples and is further corroborated by the constant voltage plateau observed in the galvanostatic cycle (potential versus capacitance plot) of the Li ion battery also during the 1st discharge cycle.