Electrochemical reaction of lithium with orthorhombic bismuth tungstate thin films fabricated by radio-frequency sputtering

Bi2WO6 thin films with fast deposition rate have been fabricated by radio-frequency (R.F.) sputtering deposition, and are used as positive electrodes in rechargeable thin film lithium batteries. An initial discharge capacity of 113 μAh/cm2-μm is obtainable for Bi2WO6 film electrode with good capacity reversibility. A multiple-center reactive mechanism associated with both Bi3+/Bi0 and W6+/Wx+(x < 6) is investigated by ex situ X-ray diffraction patterns, transmission electron microscopy and selected area electron diffraction techniques, apart from the direct comparison of Bi2WO6 electrochemical performance with those of Bi2O3 and WO3 thin films. A possible explanation about smooth capacity loss of Bi2WO6 after long-term cycling is suggested from the incomplete reaction of Bi component. The advantages of Bi2WO6 thin films over the singer-center Bi2O3 or WO3 thin films are shown in both the aspects of volumetric capacity and cycling life.