This review discusses the design of nonflammable liquid electrolytes for safe lithium-ion (Li-ion) batteries. Li-ion batteries are essential for electronic devices due to their high energy density, long cycle life, and cost-effectiveness. However, their safety is compromised by the flammable nature of traditional liquid electrolytes, which can lead to thermal runaway and fires. Nonflammable electrolytes are critical for improving battery safety without sacrificing electrochemical performance. The review covers the mechanisms of thermal runaway in Li-ion batteries, including exothermic reactions that can lead to rapid temperature increases and combustion. It discusses the design strategies for nonflammable electrolytes based on molecular structure, solvation, and battery compatibility. Key factors include radical quenching, intermolecular interactions, intrinsic nonflammability, and salt design. Fluorinated and phosphorus-based compounds are highlighted for their flame-retardant properties, while ionic liquids and eutectic electrolytes are considered for their low volatility and thermal stability. The review also addresses the challenges of balancing safety, cost, and performance in nonflammable electrolytes. It emphasizes the importance of comprehensive safety tests, including flammability, calorimetric, and abuse tests, to evaluate the thermal stability and safety of electrolytes. The study concludes that further research is needed to develop more effective nonflammable electrolytes that enhance the safety and stability of Li-ion batteries for practical applications.This review discusses the design of nonflammable liquid electrolytes for safe lithium-ion (Li-ion) batteries. Li-ion batteries are essential for electronic devices due to their high energy density, long cycle life, and cost-effectiveness. However, their safety is compromised by the flammable nature of traditional liquid electrolytes, which can lead to thermal runaway and fires. Nonflammable electrolytes are critical for improving battery safety without sacrificing electrochemical performance. The review covers the mechanisms of thermal runaway in Li-ion batteries, including exothermic reactions that can lead to rapid temperature increases and combustion. It discusses the design strategies for nonflammable electrolytes based on molecular structure, solvation, and battery compatibility. Key factors include radical quenching, intermolecular interactions, intrinsic nonflammability, and salt design. Fluorinated and phosphorus-based compounds are highlighted for their flame-retardant properties, while ionic liquids and eutectic electrolytes are considered for their low volatility and thermal stability. The review also addresses the challenges of balancing safety, cost, and performance in nonflammable electrolytes. It emphasizes the importance of comprehensive safety tests, including flammability, calorimetric, and abuse tests, to evaluate the thermal stability and safety of electrolytes. The study concludes that further research is needed to develop more effective nonflammable electrolytes that enhance the safety and stability of Li-ion batteries for practical applications.