Electrolyte and Interface Engineering for Solid-State Sodium Batteries

Sodium batteries are considered as promising candidates for large-scale energy-storage systems owing to the abundant and low-cost sodium resources. However, many reported sodium batteries are based on conventional organic liquid electrolyte, which would lead to potential safety issues. Developing solid-state electrolyte (SSE) for sodium batteries is an effective way to solve such problems. Nevertheless, how to develop high-performance SSE and compatible interface for constructing solid-state sodium batteries is still challenging. In this review, we mainly focus on the development and recent advances of SSE (including all-solid-state and quasi-solid-state electrolyte) and interface engineering for sodium batteries. The structure-property correlations and design principles of different inorganic and organic SSE are discussed in depth. The comprehensive performance of SSE depends on the structural characteristics such as defects, crystallinity, and stability of bonds. The design principles mainly include increasing the density of mobile Na+ ions, reducing the energy barrier, immobilizing anions, adjusting the stability of bonds, adding specific buffer layers, and increasing interfacial contact area. Moreover, we discuss the interface between SSE and electrode because a suitable interface is the key prerequisite for high-performance solid-state sodium batteries. This review provides fundamental insights and future perspectives to design advanced SSE and concomitant interface for next-generation rechargeable solid-state sodium batteries.