Compressibility, diffusivity, and elasticity in relationship with ionic conduction: An atomic scale description of densified Li2S-SiS2 glasses

We examine the dynamic and ionic properties of a typical sulfide glass electrolyte 50 (Formula presented.) –50 (Formula presented.) using molecular dynamics simulations and a previously parameterized force-field able to describe both the crystalline (Formula presented.) phase and the corresponding glass. We especially focus on the effect of moderate pressures on the glassy and supercooled state since the design of all-solid state batteries use molding conditions at moderate pressures in order to achieve contact between the electrolyte and the electrodes. The behavior of the conductivity (Formula presented.) with pressure permits to define an activation volume and to infer the role of compressibility and diffusivity, the latter contributing dominantly to ionic conduction, whereas temperature does not seem to impact the structural properties. These features are linked with the underlying dynamics of the Li ions as studied here by computing the longitudinal and transversal atomic species current correlations. The resulting elasticity is found to be close to experimental values.