THE SYNTHESIS OF A NEW FAMILY OF BORON-BASED ANION RECEPTORS AND THE STUDY OF THEIR EFFECT ON ION-PAIR DISSOCIATION AND CONDUCTIVITY OF LITHIUM-SALTS IN NONAQUEOUS SOLUTIONS

A new family of anion receptors based on boron compounds has been synt hesized. These compounds can be used as anion receptors in lithium bat tery electrolytes. This family includes various borane and berate comp ounds with different fluorinated aryl and fluorinated alkyl groups. Wh en these anion receptors are used as additives in 1,2-dimethoxyethane (DME) solutions containing various lithium salts, the ionic conductivi ties of these solutions are greatly increased. The electrolytes tested in this study were DME solutions containing the following lithium sal ts: LiF, LiCl, LiBr, LiI, CF3COOLi, and C2F5COOLi. Without the additiv e, the solubility of LiF in DME land all other nonaqueous solvents) is very low With some of these boron compounds as additives, LiF solutio ns in DME with concentration as high as 1 M were obtained. The solubil ities of the other salts were also increased by these additives. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy studies sho w that Cl- and I- anions are complexed with these compounds in DME sol utions containing LiCl or LiI salts. The degree of complexation is als o closely related to the structures of the fluorinated aryl and alkyl groups, which act as electron-withdrawing groups. The NEXAFS results a re in good agreement with ionic conductivity studies.