Improving Ionic Conductivity and Lithium-Ion Transference Number in Lithium-Ion Battery Separators

The microstructure of lithium-ion battery separators plays an important role in separator performance; however, here we show that a geometrical analysis falls short in predicting the lithium-ion transport in the electrolyte-filled pore space. By systematically modifying the surface chemistry of a commercial polyethylene separator while keeping its microstructure unchanged, we demonstrate that surface chemistry, which alters separator–electrolyte interactions, influences ionic conductivity and lithium-ion transference number. Changes in separator surface chemistry, particularly those that increase lithium-ion transference numbers can reduce voltage drops across the separator and improve C-rate capability.