Impact of Negative Charge Delocalization on the Properties of Solid Polymer Electrolytes.

The nature of salt anion is of particular relevance in determining the features of solid polymer electrolytes (SPEs). Here, lithium salt containing an extremely delocalized anion (Li[CF3SO- (=NSO₂CF₃)₂], LisTFSI) is introduced into SPEs utilizing poly (ethylene oxide) (PEO) as a matrix, aiming to elucidate the role of negative charge delocalization on the properties of SPEs. In comparison with the reference Li[N(SO₂CF₃)₂] (LiTFSI)/PEO electrolyte, LisTFSI/PEO shows higher lithium-ion transference number and lithium-ion-only conductivity (i. e., the ionic conductivity contributed only by the lithium ions), owing to the improved flexibility and super-delocalized negative charge of the - SO₂N(-)- SO(=NSO₂CF₃)- structure in sTFSI- (vs. TFSI-). Moreover, the interphases of lithium metal electrode j SPE formed in LisTFSI/PEO show superior stability upon storage. These interesting properties of the LisTFSI/PEO system suggest that extending negative charge delocalization in sulfonimide anions is a powerful tool to improve the properties of SPEs. [ABSTRACT FROM AUTHOR]