Lithium insertion into amorphous WO3 films prepared by the electron beam evaporation technique was investigated by measurements of voltage-composition curve and chemical diffusion coefficient. The extraction of equilibrium and kinetic parameters allows the determination of the jump diffusion coefficient dependence on composition. In addition, first-principles calculations combining a pseudopotential plane wave scheme have been performed with the aim of providing a better understanding of the dependence of the potential barrier height for the hopping pathway with the insertion level for crystalline compounds. Our results predict a lowering of the barrier height for less doped systems and both experiments and simulations exhibit a relation of the type Delta E proportional to ck(B)T ln x for the composition range x < 0.3. (c) 2005 The Electrochemical Society.