Remarkably high capacity Li ion batteries with rf sputter deposited TiO2 thin film anodes on SS substrates

Abstract

TiO2 thin film electrodes have been prepared using radio-frequency magnetron sputtering technique on polished stainless-steel substrates. Films with amorphous, anatase and rutile phases have been obtained by varying the preparation conditions and coin cell type Lithium Ion Batteries (LIB’s) have been prepared with these samples as anodes. During the cycling test, all the samples show a gradual increase in capacity with increasing no. of charging/discharging cycles after an initial decrease with the cell containing the rutile phase TiO2 showing the highest specific capacity of around 1.217 mAh.cm-2.μm−1 after 1000 cycles at a high current density of 0.127 mA.cm−2, which is better than any reported value so far. Structural and morphological investigations of the samples by various techniques show that a synergy between the deposited TiO2 film and the Fe2O3 layers present on the SS substrate alongwith an increase in porosity in the films during the charge–discharge cycling gives rise to the remarkably high capacity of the cells which increases gradually with cycling. The present study shows that LIB’s with composite TiO2/Fe2O3 anode having advantage of structural stability of TiO2 and better diffusion kinetics of Fe2O3 can be obtained by a simple, easily scalable, reproducible rf magnetron sputtering technique and specific capacities of the present LIB’s are comparable to or better than that obtained through much more complicated and multi-step chemical processes and hence the results are important for large scale technological applications.