Revealing the effect of grain boundary segregation on Li ion transport in polycrystalline anti-perovskite Li3ClO: a phase field study
Lithium ion transport in the polycrystalline solid-state electrolyte (SSE) is directly linked to the properties of lithium ion bat-teries. Grain boundaries (GBs), as essential defects in SSE, were found to play a significant role in the overall kinetics of Lithi-um ion transport, while the mechanism is not well understood due to the complex role of GBs. GBs could affect the overall kinetics of ionic transport in SSEs from two aspects: (i) Li/Na diffusivities inside GBs could be different from those in bulk; (ii) Point defects segregation at GBs. The first aspect was well recognized, while the second one has been rarely studied. In this study, a combination of first principles and phase field calculations, in which the interaction between point defects and grain boundaries were considered at different scales, were performed to reveal the role of grain boundaries in the overall ionic conduction of solid-state electrolyte anti-perovskite Li3ClO. The results shows that the defect segregation which varies significantly with the GB orientation, reinforces the negative contribution of GBs on the overall ionic diffusivity by approximately one-order magnititude. This study could help improve the fundamental understanding of ionic transport in polycrystalline solid-state electrolytes, and provide guidance for designing new solid-state electrolytes with excellent ionic conductivity.