Influence of microstructure on the chemical diffusion of lithium ions in amorphous lithiated tungsten oxide films

We describe how the chemical diffusion of lithium ions is affected by micro structural changes in amorphous lithiated tungsten oxide (a-LixWO3) films a s a function of lithium ion concentration. The chemical diffusion of lithiu m ions in a-LixWO3 films is investigated using ac impedance spectroscopy an d Raman scattering measurements. Two different a-WO3 films deposited by the rmal evaporation at different partial pressures of nitrogen are used for th ese measurements. Based on the results of ac impedance spectroscopy and Ram an scattering measurements, we conclude that the mechanism of these diffusi on phenomena is attributed to an increase or decrease of the W-6 + =O/O-W6 -O ratio with lithium ion insertion. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.