Non-woven polyaramid porous membranes as separators for Li-ion batteries?

Abstract

Macroporous separators play a crucial role regarding safety in current Li-ion batteries. Most separators used in battery applications are based on polyolefin and present shrinkage and a decrease in mechanical properties when used at high temperatures, both detrimental in the battery performance. In search of more suitable alternatives that render to more stable and safer batteries, in this work, non-woven separators based on polyacrylonitrile blended with cellulose and para-aramid fibers are systematically investigated. This study has been carried out in terms of microstructure, mechanical properties, ionic conductivity and thermal and electrochemical stability (using Li4Ti5O12/LiCoO2 full cells with a nominal potential of ≈2.5 V). Although conductivity values of separators are somewhat modest, the electrochemical performance developed when used in Li4Ti5O12/LiCoO2 cells are, at moderate C rates, comparable to commercial Celgard©2400 separator. At high C rates, in particular at 2C, DwG40 exhibits much higher capacities than the whole of the separators, including Celgard®2400. This study responds to the continuous need reflected not only by the scientific community but also by the industrial one when new materials for electrolytes and electrodes should be tested, since there is a lack of reports characterizing such elements in the literature.