Ionic conductivity and ion transport mechanisms of solid-state lithium-ion battery electrolytes: A review

Abstract

This review article deals with the ionic conductivity of solid-state electrolytes for lithium batteries. It has discussed the mechanisms of ion conduction in ceramics, polymers, and ceramic-polymer composite electrolytes. In ceramic electrolytes, ion transport is accomplished with mobile point defects in a crystal. Li+ ions migrate mainly via the vacancy mechanism, interstitial mechanism, or interstitial-substitutional exchange mechanism. In solid polymer electrolytes, Li+ ions are transported mainly via the segment motion, ion hopping (Grotthuss mechanism), or vehicle mechanism (mass diffusion). This study has also introduced various electrolyte materials including perovskite oxides, garnet oxides, sodium superionic conductors, phosphates, sulfides, halides, cross-linked polymers, block-copolymers, metal-organic frameworks, covalent organic frameworks, as well as ceramic-polymer composites. In addition, it has highlighted some strategies to improve the ionic conductivity of solid-state electrolytes, such as doping, defect engineering, microstructure tuning, and interface modification.