TFEC is a critical electrolyte additive designed for high-voltage lithium-ion batteries, particularly in Li-metal and Si-anode systems. Its unique fluorinated structure enhances cell safety by significantly reducing electrolyte flammability. TFEC preferentially decomposes to form a durable, LiF-rich Solid Electrolyte Interphase (SEI), suppressing parasitic reactions and greatly improving long-term cycling performance.