Solid Composite Electrolytes for Solid-State Alkali Metal Batteries

Solid composite electrolytes (SCEs) are considered promising candidates in solid-state alkali metal batteries for next-generation energy storage systems. Using solid-state ion conductors to replace liquid electrolytes is a promising strategy to achieve solid-state alkali metal batteries with higher energy density and enhanced safety. Solid ionic conductors can be divided into ceramics, polymers, and composites. Ceramic conductors (e.g., oxides, sulfides) exhibit superior room-temperature ionic conductivity, high mechanical strength, and a wide electrochemical window but suffer from poor interfacial issues toward electrodes. Solid polymer electrolytes display outstanding flexibility and great compatibility with electrodes, although they show low ionic conductivity at room temperature. To overcome the drawbacks of inorganic and polymer electrolytes, SCEs that integrate ceramic with polymer electrolytes provide an attractive solution to achieve desirable properties such as great flexibility, intimate contact with electrodes, and fast ion transport at room temperature. This chapter introduces the compositions and ion transport mechanisms of SCEs, as well as the interface between SCEs and electrodes (anodes and cathodes) in solid-state alkali metal batteries.