ELECTROCHEMICAL STUDIES OF LITHIUM INSERTION IN MOO3 FILMS

MoO3 is one of the most interesting layered intercalation materials with orthorhombic symmetry because of its use in solid state batteries and display systems. In the present investigation thin films of MoO3 were prepared by the flash evaporation technique on silica glass substrates maintained in the temperature range 30-300-degrees-C. The films were systematically characterized by studying their optical, electrical and electrochemical properties. The bandgap for the films deposited at room temperature is evaluated at 3.15 eV. The bandgap decreases with increasing substrate temperature. The electrical conductivity is in the range 10(-3)-10(-5)S-1 cm-1 and further decreases to 10(-6)-10(-7) S-1 cm-1 by heat treatment at 350-degrees-C. Several electrochemical cells of configuration MoO3/LiClO4-PC/Li were fabricated with a capacity of 70 muA h and studied. EMF of 3.1 V is measured and 1.5 electron is transferred in the host. Cells are discharged with a current density of 100 muA cm-2 without strong polarization. The measured lithium diffusivity in MoO3 films is in the range 10(-11)-10(-12) cm2 s-1.