Lithium difluorophosphate (LiDFP, CAS 24389-25-1) is an inorganic lithium salt with the chemical formula LiPO_F_. It is a white crystalline powder that is highly soluble in polar aprotic solvents commonly used in lithium-ion battery electrolytes. Structurally, it features a central phosphorus atom bonded to two oxygen atoms and two fluorine atoms, forming the difluorophosphate anion. LiDFP is primarily utilized as a functional electrolyte additive or co-salt in advanced lithium-ion batteries. Its key application is to improve the electrochemical performance and stability of the cathode-electrolyte interphase (CEI) and the solid-electrolyte interphase (SEI). By forming a thin, stable, and conductive protective layer on both the cathode (e.g., NMC, LCO) and anode (e.g., graphite) surfaces, LiDFP effectively suppresses transition metal dissolution, reduces gas generation, and enhances cycling stability, especially at high voltages and elevated temperatures. It is also explored as a precursor for synthesizing other lithium-ion conducting materials. Due to its hygroscopic nature, LiDFP must be handled and stored in a dry, inert atmosphere. It is a critical material in the development of next-generation high-energy-density and long-life lithium-ion batteries for electric vehicles and energy storage systems.