INTERCALATION OF LITHIUM IN RF-SPUTTERED VANADIUM-OXIDE FILM AS AN ELECTRODE MATERIAL FOR LITHIUM-ION BATTERIES

Vanadium oxide films were prepared by r.f.-sputtering using an argon s putter gas and a V2O5 target. The films were characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ra y photoelectron spectroscopy and electrochemical techniques. The oxide film as deposited is amorphous; they are heat-treated in the range 30 0-700 degrees C in oxygen atmosphere and are composed of orthorhombic V2O5 crystals. At higher heat-treatment temperatures (600-700 degrees C) the crystallization of the oxide proceeded significantly with ab-di rection parallel to the substrate. The oxide film undergoes a reversib le lithium intercalation and deintercalation process. The kinetics of the intercalation process of lithium into amorphous V2O5 film was stud ied using an a.c. impedance method. Furthermore, a rocking-chair type V2O5 film/LixV2O5 film cell could be charge-discharge cycled over 300 times at a current of 10 mu A at 25 degrees C.