The synthesis of a new family of anion receptors and the studies of their effect on ion pair dissociation and conductivity of lithium salts in nonaqueous solutions

A new family of anion receptors, based on aza-ether compounds, has been synthesized. These compounds can have either cyclic or linear aza-ether structures in which the amine hydrogen is substituted with electron withdrawing groups such as CF3SO2-. When these compounds are added to Lithium salt nonaqueous electrolytes, such as LiCl/tetrahydrofuran (THF) or LiBr/THF solutions, the ionic conductivity can be dramatically increased. Near-edge x-ray absorption fine structure spectroscopy studies show that Cl- anions are complexed with the nitrogen groups in these compounds. The increase in ionic conductivity, the degree of complexation, and the stability of the complexes are related to the anion size and the structure of the aza compound. Unlike conventional anion complexing agents these compounds are not based on positively charged sites, Lewis acid metal centers, or hydrogen bonding, so they have the potential to be used as additives in lithium battery electrolytes. Details of the synthesis of several of these compounds are given. They can be synthesized with various geometries to accomodate polyatomic anions.