Achieving fast ionic conductivity and high electrochemical stability through polyhedral structure design

Abstract

All-solid-state batteries incorporating lithium metal anode can potentially resolve many intrinsic drawbacks of current lithium-ion batteries, such as flammability and leakage of organic electrolyte, and limited energy density. However, they face a large challenge in developing a high-performance solid electrolyte with simultaneously achieving fast ionic conductivity and high chemical/electrochemical stability specifically against active lithium metal anode. Here, we comparatively design a new compound Li10SiP2S12 with body-centered cubic-like anion framework, not only possessing higher ionic conductivity (20 mS/cm) than Li10GeP2S12 (12 mS/cm), but also exhibiting a wider electrochemical window (2.31 V) than Li10GeP2S12 (1.66 V) through calculating (de)lithiated reaction decomposing pathways. The wide electrochemical window of Li10SiP2S12 may be attributed to form a stronger Si-S covalent bond than Ge-S bond in Li10GeP2S12. Our structural analysis shows that high ionic conductivity is originated from suitable size of bottleneck between two neighboring tetrahedrons. The present study makes a new avenue to design high-performance solid electrolyte through polyhedron structure and bond strength.