This review focuses on the safety hazards of sodium-ion batteries (SIBs). By systematically decoupling the thermal runaway mechanisms, advances and future directions in high-safety electrolytes are evaluated through four strategic dimensions: flame-retardant components, solvation structure regulation, sodium salt optimization, and safety-enhancing additives. Structured around the “prevention–delay–suppression” principle, this analysis establishes a comprehensive framework for developing safe SIBs.

The pursuit of intrinsically safe sodium-ion batteries (SIBs) with high energy density has spurred significant research into developing nonflammable organic liquid electrolytes, given their wide electrochemical stability window and excellent compatibility with electrodes. As safety requirements grow increasingly stringent, electrolyte design must comprehensively address both internal risks such as dendrite growth, parasitic reactions, and high flammability, and external abuses including overcharging and short circuits. In this review, the critical role of electrolytes in suppressing thermal runaway in SIBs is systematically elucidated, and contemporary methodologies for electrolyte safety assessment are summarized. Based on these insights, targeted strategies are further outlined to enhance the safety of each electrolyte component, including solvent systems, sodium salt selection, and functional additive design. Finally, the remaining challenges are discussed, and perspectives on future high-safety electrolyte design strategies are presented, aiming to accelerate the practical deployment of SIBs.