Titanium oxynitride thin films as high-capacity and high-rate anode materials for lithium-ion batteries

• Titanium oxynitride (TiOxNy) thin films as anode materials were studied.
• TiOxNy thin films with various amounts of nitrogen contents were studied.
• High rate capability of TiOxNy was studied.

Titanium oxynitride (TiOxNy) was synthesized by reactive magnetron sputtering in a mixed N2/O2/Ar gas at ambient temperature. TiOxNy thin films with various amounts of nitrogen contents were deposited by varying the N2/O2 ratios in the background gas. The synthesized TiOxNy films with different compositions (TiO1.837N0.060, TiO1.890N0.068, TiO1.865N0.073, and TiO1.882N0.163) all displayed anatase phase, except TiO1.882N0.163. The impedances and grain sizes showed obvious variations with the nitrogen contents. A wide potential window from 3.0 V to 0.05 V, high-rate charge–discharge testing, and long cycle testing were applied to investigate the performances of synthesized TiOxNy and pure TiO2 as anodes for lithium-ion batteries. These TiOxNy anodes can be cycled under high rates of 125 μA/cm2 (10 °C) because of the lower charge–transfer resistance compared with the TiO2 anode. At 10 °C the discharge capacity of the optimal TiOxNy composition is 1.5 times higher than that of pure TiO2. An unexpectedly large reversible capacity of ~ 300 μAh/cm2 μm (~ 800 mAh/g) between 1.0 V and 0.05 V was recorded for the TiOxNy anodes. The TiOxNy anode was cycled (3.0 V to 0.05 V) at 10 °C over 300 times without capacity fading while delivering a capacity of ~ 150 μAh/cm2 μm (~ 400 mAh/g).