Electrolyte and interface engineering for solid-state sodium batteries

Solid-state sodium (Na) batteries (SSSBs) effectively address traditional organic liquid battery safety concerns such as leakage, inadequate thermal stability, and high susceptibility to fire and explosion. However, there are two critical issues for the development of SSSBs: (i) low ionic conductivity of the solid-state electrolyte (SSE) and (ii) interfacial challenge between the electrode and electrolyte. Although extensive work has been reported in these areas, there is a lack of systematic review to consider high ionic conductivity of SSEs and reasonable electrode–electrolyte interfaces simultaneously. Hence, we have reviewed the structural characteristics and conductivity mechanisms of various SSEs in detail, and recent advancements in electrolyte engineering to enhance their ionic conductivity were summarized. Additionally, interfacial challenges were thoroughly analyzed, and techniques for interface engineering were rigorously assessed. This review highlights the key obstacles and opportunities in designing effective SSSBs.