Many experimental studies are thus performed on the sulfur phase though research suggests that the Se phase performs with improved capacity and kinetics, even a partial substitution of Mo 6 S 8-x Se x . This is because the triclinic distortion in selenide enlarges the distance between inner sites and shortens the distance between inner and outer site, thus opening possibilities for tailoring the ionic conductivity of the system. There are some theoretical reports on the diffusion of cations other than Mg, which showed a direct correlation between ionic radius and the diffusion barrier as a descriptor for the ion mobility in the CP specifically, 5 as illustrated in Figure . This has been attributed