Stress-Free Pathway for Ion Transport in the Separator Membrane of Lithium Secondary Batteries

We evaluated the Coulombic interactions of the lithium cation in the separator membrane of lithium secondary batteries in terms of the morphological factors of the separator membrane and the solvation structure of the lithium cation carriers. The magnitudes of the cation/membrane and cation/anion interactions increased with the increasing tortuosity and decreasing width of the ion transport pathways comprising the linked-pore spaces in the membrane, which decreased cation mobility. Lithium cations strongly solvated by high-polarity solvents interacted weakly with the membrane and the anion due to the strong shielding by the solvent molecules coordinated to the lithium cation. In particular, we confirmed that the new membranes, which were tailored to have almost linear pathways across the membrane surface, showed no cation/membrane interaction, thereby indicating that the low-tortuosity aligned-pore pathways could be an ideal stress-free pathway for ion transport. Finally, DC resistance measurements of a l...