Meaning
An imide-based lithium salt with the chemical formula LiN(SO2F)2 serves as a conductive solute and film-forming agent in advanced non-aqueous electrolytes. The compound lithium bis fluorosulfonyl imide enhances ionic conductivity and stabilizes electrode-electrolyte interfaces due to its weakly coordinating anion and high thermal stability compared to conventional lithium hexafluorophosphate. Its use requires specialized corrosion-resistant aluminum current collectors, stopping short of broad deployment in cells utilizing standard untreated cathode foils at high cell voltages.
Chemical Properties
The bis(fluorosulfonyl)imide anion features high charge delocalization across its nitrogen and sulfonyl groups, promoting rapid ion-pair dissociation in carbonate and ether solvents. This molecular configuration yields superior low-temperature ionic conductivity and lowers the activation energy of ion desolvation at active material interfaces. The salt generates a robust, inorganic-rich solid electrolyte interphase containing lithium fluoride and lithium sulfate, which suppresses transition metal dissolution and dendrite growth.
Corrosion Mitigation
Standard battery-grade aluminum current collectors suffer anodic dissolution above 3.8 volts when paired with pure imide electrolytes because the anion does not passivate aluminum surfaces as effectively as phosphate salts. Cell manufacturers resolve this corrosion vulnerability by utilizing dual-salt formulations that combine the imide salt with lithium hexafluorophosphate or lithium difluorophosphate additives. Specialized surface coatings on aluminum foils also provide an effective barrier against high-voltage pitting corrosion.
Purchasing Considerations
Procurement teams evaluate imide salt adoption when balancing extreme low-temperature power delivery against raw material costs. The synthesis of high-purity battery-grade salt requires stringent purification to eliminate residual chloride and water contaminants that accelerate cell degradation. Cell buyers mandate strict chemical purity certifications, requiring halogen and moisture impurities to remain below ten parts per million to qualify the electrolyte for high-reliability applications.
