Electronic state of sulfide-based lithium ion conducting glasses

Electronic states of the sulfide-based lithium ion conducting glasses were calculated by the DV-Xα cluster method. The cluster models were constructed by the coordination number reported by experimental methods and the bond length estimated from the ionic radii of each ion. The movement of the Li ion was simulated by several model clusters with different positions of the moving ion. The relationship between ionic conductivity and the differential total bond overlap population (DBOP) was discussed for the sulfide-based glasses in the systems Li2S–SiS2–Al2S3 and Li2S–SiS2–P2S5. In these glasses, the DBOP with the movement of the lithium ion had good negative correlations with the ionic conductivities and positive correlations with the activation energies obtained by the experimental measurements. In any cases, the smaller change of the total bond overlap population of the moving cations played an important role for the fast ion movement in the superionic conducting glasses. This bonding state of the moving cations is one of the characteristics of the electronic state in the sulfide-based lithium ion conducting glasses.