Three-dimensional structures and lithium-ion conduction pathways of (Li2S)x(GeS2)100 − x superionic glasses

Abstract

The conduction pathways of Li ions in (7Li2S)x(GeS2)100−x glasses (x=40, 50, and 60) were predicted and visualized by combining reverse Monte Carlo (RMC) modeling and the bond valence sum (BVS) approach, using synchrotron X-ray and time-of-flight neutron diffraction data. The conduction pathways of the Li ions could be classified into four grades, according to the magnitude of |ΔV(Li)|: (I) |ΔV(Li)|<0.04 (i.e., relatively stable regions for the Li ions), (II) 0.04≤|ΔV(Li)|<0.07, (III) 0.07≤|ΔV(Li)|<0.10, and (IV) 0.10≤|ΔV(Li)|<0.13; here, |ΔV(Li)| is the mismatch of the BVS for Li ions, V(Li). These were used to obtain a clear understanding of the movement of the Li ions in the (7Li2S)x(GeS2)100−x glasses. It was also found that there is a definite relationship between the topology of the conduction pathways of the Li ions and the activation energy, Ea, of the electrical conduction.