The "shuttle effect" induced by the dissolution and diffusion of the Li2Sx (4 <= x <= 8) into the electrolyte is a crucial problem of a LieS battery. Anatase or Al2O3 can be used as an additive to suppress the "shuttle effect". First-principles approach coupled with van der Waals (vdW) interaction is used to calculate the adsorption energies of Li2Sx (x = 4, 6, 8) molecules on an anatase (1 0 1) or an alpha-Al2O3 (0 0 0 1) surface. The results show that the adsorption of the molecules on an alpha-Al2O3 (0 0 0 1) is stronger than that on an anatase (1 0 1) surface. Furthermore, owing to the existence of an electric field inside the battery during the charge-discharge process, the external electric field effects on the adsorption are investigated. As a result, the adsorption energy (absolute value) almost linearly increases with the increase of electric field intensity in the range from -0. 16 to 0.16 V/A. In addition, the responses of different Li2Sx molecules on an anatase (1 0 1) surface or an alpha-Al2O3 (0 0 0 1) surface to the external electric fields are different.