Ionic Transport in Solid Electrolytes: Conductivity, Interfacial Challenges, and Optimization Strategies

Solid-state batteries are different from traditional liquid lithium-ion batteries because they do not use flammable organic liquids for the electrolyte, and are therefore safer, with high energy density and a long cycle life. They are the main development directions for the next generation of energy storage systems and power sources. The ionic conductivity of the solid electrolyte affects the speed of charging and discharging for a cell, changes in internal resistance during operation, etc.; now, it has become one of the main technical bottlenecks preventing its industrial application. First, the whole structure and functions of solid-state batteries will be introduced in this paper. Then, it will gather the current methods for evaluating ionic conductivity and the present situation of research on ion transport paths. Finally, the technical attributes and applications of the four fundamental kinds of solid electrolytes will be introduced: polymer-based, oxide-based, sulfide-based and halide-based. Based on the systematic comparison of the strengths and weaknesses of all these links, this paper presents the current development stage of each link and points out problems that need to be solved to promote progress in the exploration and construction of high-performance solid-state batteries.