From liquid precursor to film: WO3 as promising high voltage anode for all-solid-state thin film Li-ion batteries

Abstract

Lithium-ion (Li-ion) batteries are promising candidates to tackle the challenging energy storage problem due to their high power and energy density. However, contemporary Li-ion batteries could be improved significantly by introduction of a solid electrolyte. Many of these electrolytes contain titanium (e.g. Li0.35La0.55TiO3), limiting their electrochemical stability to 1.5V, due to Ti4+ reduction. High voltage anode materials are therefore interesting candidates to fabricate an all-solid-state Li-ion battery. The current study proposes spray deposited WO3 films as promising high voltage anode material for Li-ion batteries. The chemistry of a chloride based tungsten precursor was analysed, revealing that the chlorides leave the precursor in the liquid phase. Next, films were prepared by ultrasonic spray deposition of this precursor on various substrates, yielding smooth films depending on the deposition temperature. XPS measurements and cyclic voltammetry proved that films mainly contain W6+ and oxygen; chlorides were not detected. Finally, the performance of the anode material was probed by charge discharge measurements. WO3 deposited on TiN showed good cycle performance and capacity (640 mAh/cm3, 90 mAh/g) at a relative low annealing temperature of 400°C. The results of this study present a relatively simple and low temperature based synthesis route to deposit active WO3, yielding a very interesting route towards the fabrication of all-solid-state Li-ion batteries.