Chemistry Design Towards a Stable Sulfide-Based Superionic Conductor Li4Cu8Ge3S12

Sulfide-based superionic conductors with high ionic conductivity have been explored as candidates for solid-state Li batteries. However, moisture hypersensitivity has made their manufacture complicated and costly and also impeded applications in batteries. Now, a sulfide-based superionic conductor Li4Cu8Ge3S12 with superior stability was developed based on the hard/soft acid-base theory. The compound is stable in both moist air and aqueous LiOH aqueous solution. The electrochemical stability window was up to 1.5V. An ionic conductivity of 0.9x10(-4)Scm with low activation energy of 0.33eV was achieved without any optimization. The material features a rigid Cu-Ge-S open framework that increases its stability. Meanwhile, the weak bonding between Li+ and the framework promotes ionic conductivity. This work provides a structural configuration in which weak Li bonding in the rigid framework promotes an environment for highly conductive and stable solid-state electrolytes.