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

• We visualized the local structures of the Li2S–GeS2 glasses using RMC modeling.
• We visualized the conduction pathways of Li ions in the Li2S–GeS2 glasses.
• We directly compared topology of the conduction pathways using activation energy.

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.