Pursuing the smaller and multi-functional portable electronic devices, it is necessary to develop the rechargeable lithium batteries with higher energy density. However, the graphite that has been adopted as the anode material in commercial rechargeable lithium battery can’t fulfill such a demand any more because its specific capacity almost reached the maximum theoretical
value. Therefore, the anode materials with higher gravimetric and volumetric capacities than those of the graphite have long been desired. To replace the graphite, a lot of transition metal oxides MxOy (M=Co, Fe, Ni, Mo, etc.) have been studied as the anode materials for lithium batteries. As a promising candidate of the next-generation anode material with high volumetric capacity, tungsten oxide (WO3) has long been noted because its theoretical capacity is very large, as compared to that of graphite. Accordingly, the tungsten oxides with a variety of shapes have been investigated, as a form of composites onsisting of tungsten oxide particles, binder and conducting additives, to explore the feasibility of using them as the anode materials. But, the works on the binder-free ungsten oxide thin film as the anode in rechargeable lithium micro-battery are absent as far as we know. In this work, tungsten oxide thin films were fabricated by an electrochemical deposition process for the use as the anode in rechargeable lithium battery. Continuous potentiostatic deposition of the film resulted in a lot of cracks of the deposits. Whereas, the pulsed deposition dramatically suppressed the crack generation and the delamination of the deposits. Especially, crack-free tungsten oxide film with a thickness of about 210 nm was successfully prepared with 50% duty cycle. From the compositional and structural analyses, it proved that the as-prepared electro-deposit is amorphous tungsten oxide and the heat treatment changes it into crystalline (triclinic) tungsten oxide. Both the as-prepared and heat-treated samples reacted reversibly with lithium as the anode for rechargeable lithium battery. In particular, the heat-treated sample was much more stable with cycling, as compared to the as-prepared one. The results in this work shows that
the electrolytic tungsten oxides can be a promising option as the thin film anode in lithium battery. But, further works are still needed to make the dense film with higher thickness and improved cycling stability for its commercial use.