Investigation of oxide ( V 2 O 5 ) thin films as electrodes for rechargeable microbatteries using Li

V 2 O 5 thin films were prepared by reactive rf sputtering and used in the application as electrodes in rechargeable battery with Li as a counterelectrode. The V 2 O 5 films were deposited onto uncoated and SnO 2 coated glass by sputtering a V cathode using Ar + O 2 gas mixtures. The structural properties of the V 2 O 5 films were characterized by x-ray diffraction, infrared spectroscopy, and photoelectron spectroscopy (XPS: x-ray induced and UPS: UV induced photoelectron spectroscopy). Microbatteries were constructed using the V 2 O 5 thin films as cathode, LiClO 4 + propylene carbonate as the electrolyte and Li metal as the anode. The V 2 O 5 electrodes were characterized by there electrochemical behavior (current–voltage curves during charging and recharging). X-ray diffraction measurement demonstrated that unannealed V 2 O 5 films were amorphous with no sharp reflexes. Annealing to 350 ° C was sufficient to produce crystalline β- V 2 O 5 (monoclinic) on uncoated glass or orthorhombic V 2 O 5 on SnO 2 coated glass. XPS spectra revealed the expected V/O ratio and line positions. However, the O 1s peak was split into two components, one from the V 2 O 5 component (530.4 eV), the other at 532.9 eV is attributed to the uptake of water from the atmosphere. The charged microbattery resulted in a maximum voltage of 3.4 V for the currentless circuit and a capacity of 34.5 mC/cm 2 . With XPS we could demonstrate the migration of Sn (from the conductive coating of the glass substrate) into the V 2 O 5 layer for the Li intercalated electrodes. Further, UPS spectra from charged and uncharged V 2 O 5 indicate band-gap changes due to the Li uptake.