Among various safety issues of the cells, internal short-circuits
are known to be one of the most critical threats that are difficult
to avoid. A separator (membrane) in the cell is considered a key
component to prevent the failures, because its primary function is
to maintain electrical isolation between cathode and anode [13e
25]. Another major role of a separator is to allow ionic transport
via its liquid electrolyte-filled pores. Ionic conductivity of a separator,
which strongly depends on its porous structure and polarity,
affects ohmic polarization (i.e., IR drop) of a cell. Notably, this in-
fluence on cell polarization becomes more pronounced at high
current density conditions needed for high-power applications