Supramolecular Regulation of Anions Enhances Conductivity and Transference Number of Lithium in Liquid Electrolytes.

Achieving high ionic conductivity in lithium-ion battery (LIB) electrolytes requires dissociation of Li-salts; however, though the generation of free Li+ from salt dissociation is advantageous, the presence of freely diffusing anions may reduce the Li+ transference number. The use of supramolecular anion recognition to regulate and modify ion-pairing and diffusion of anions in battery electrolytes is yet to be deeply understood. Herein, we demonstrate that addition of a selective and strong PF6--binding macrocycle to a solution of LiPF6 in low dielectric media leads to enhanced ion pair dissociation and an increased Li+ transference number. This work provides a well-defined model system to study the effects of anion binding in battery electrolytes.