A comprehensive review of separator membranes in lithium-ion batteries

The widespread adaptation of lithium-ion batteries for consumer products, electrified vehicles and grid storage demands further enhancement in energy density, cycle life, and safety, all of which rely on the structural and physicochemical characteristics of cell components. The separator membrane is a key component in an electrochemical cell that is sandwiched between the positive and negative electrodes to prevent physical contact while permitting ionic conduction through the electrolyte. Though it is an inactive component in a cell, the separator has a profound impact on the ionic transport, performance, cell life, and safety of the batteries. Today there are numerous types of separators in use or being considered, including polyolefin separators, modified polyolefin separators, nonwoven separators, and ceramic composite separators. This review summarizes the state of practice and latest advancements in different classes of separator membranes, reviews the advantages and pitfalls of current separator technology, and outlines challenges in the development of advanced separators for future battery applications.