Ni2V2O7 thin films for negative electrode application of rechargeable microbatteries

Metallic thin films Ni / V / (Ni / V)(x) /Ni were deposited under vacuum with an electron beam on Pt sheet substrates. The thickness of the films was measured in situ by the vibrating quartz method in order to achieve the atomic ratio Ni/V=1. Samples were first annealed for 30 min under vacuum at 853 K in order to initiate the metals interdiffusion and annealed for another 30 min in room atmosphere at 863 K. The films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Results show that monoclinic homogeneous Ni2V2O7 thin films can be synthesized on Pt substrates by this simple technique. These Ni2V2O7 were tested for their Li insertion properties in standard laboratory Li batteries. It is shown that the cycling behavior of the films is much more favorable than that of the bulk powders. The hypothesis that this behavior is linked to improved grain size and film morphology is discussed (C) 2002 Elsevier Science B.V All rights reserved.