The guarantee of large-scale energy storage: Non-flammable organic liquid electrolytes for high-safety sodium ion batteries

Rechargeable stationary batteries with economy and high-capacity are indispensable for the integrated electrical power grid reliant on renewable energy. Hence, sodium ion batteries have stood out as an appealing candidate for the ‘beyond-lithium’ electrochemical storage technology for their high resource abundance and favorable economic/environmental sustainability. In which, electrolyte is an important factor for enhancing the electrochemical performance. Traditional carbonate and ether electrolytes have been widely used, while they pose significant safety hazards, such as thermal abuse, dendrite growth, parasitic reactions and short-circuit, have aroused concerns and attention to the exploration of non-flammable electrolytes. This review firstly systematically summarizes the advantages of non-flammable organic liquid electrolytes (NFOLEs) and deeply analyzes the quenching mechanism of flame-retardant electrolyte. Additionally, the challenges, available solutions and strategies of compatibility issues between non-flammable electrolytes and battery systems are highlighted. Drawing from a comprehensive overview of current research progress, valuable proposals have been put forth focusing on flame-retardant mechanisms, sodium salts, solvents, solvation structures, and additives. These insights and guidance offer valuable direction for the future development and design of non-flammable electrolytes in the practical application of SIBs.