Intercalation of lithium in r.f.-sputtered vanadium oxide film as an electrode material for lithium-ion batteries

Abstract

Vanadium oxide films were prepared by r.f.-sputtering using an argon sputter gas and a V 2 O 5 target. The films were characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical techniques. The oxide film as deposited is amorphous; they are heat-treated in the range 300-700 °C in oxygen atmosphere and are composed of orthorhombic V 2 O 5 crystals. At higher heat-treatment temperatures (600-700°C) the crystallization of the oxide proceeded significantly with ab-direction parallel to the substrate. The oxide film undergoes a reversible lithium intercalation and deintercalation process. The kinetics of the intercalation process of lithium into amorphous V 2 O 5 film was studied using an a.c. impedance method. Furthermore, a rocking-chair type V 2 O 5 film/Li x V 2 O 5 film cell could be charge-discharge cycled over 300 times at a current of 10 μA at 25 °C.