Atomistic Insights into the Role of Grain Boundary in Ionic Conductivity of Polycrystalline Solid-State Electrolytes
Kun Shen, Ruibin He, Yixuan Wang, Changchun Zhao, Hao Chen
Abstract
It is widely accepted that grain boundary (GB) in polycrystalline solid-state electrolytes (SSEs) can substantially reduce ionic conduction, which is regarded as the most essential property for SSEs. However, the physical origin of the GB-induced retardation effects remains unanswered. In this study, molecular dynamics simulations and first-principle calculations were combined to reveal the role of GBs in ionic conduction via the evaluation of the thermodynamic–kinetic interaction between GBs and vacancy in cubic Na3PS4. Our results suggest that the reduced ionic conduction in GBs is attributed to the segregation of Na vacancy in the GB core. The GB-blocking effects strongly depend on both vacancy segregation energy and the number of segregation sites in the GB core, which are determined by the GB structure. This study will shed new light on the future design of polycrystalline SSEs with a high ionic conductivity via grain boundary engineering.