Electrolyte design or functional development is very effective at promoting the performance of sodium-ion batteries, which are attractive for electrochemical energy storage devices due to abundant sodium resources and low cost. This review discusses recent advances on electrolytes for sodium-ion batteries and comprehensive electrolyte design strategies for various materials systems as well as functional applications. The discussion is divided into three electrolyte types: liquid, solid state, and gel state. Liquid electrolytes are further divided into different solvent types, including organic carbonate ester, ether, ionic liquid, and water. Solid-state electrolytes also contain two types: solid polymer and glass–ceramic composite. The challenges and prospects of electrolytes for sodium-ion batteries are discussed as well.
