Review—Recent Developments in Safety-Enhancing Separators for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) dominate an important power position in most fields because of high storage energy, superior service lifetime, low self-discharge, and high voltage output, but safety concerns are a recurring theme. How to solve the safety problem has become an urgent hotspot in the field and in our daily life. Separator, an indispensable composition in LIBs, isolates cathodes from anodes and provides channels for lithium ion migration. Polyolefin microporous separators with excellent chemical stability, mechanical strength, and low price are widely used in LIBs. However, several shortcomings exist, such as poor thermal stability and low wetness, causing such hazards under some abuse as overcharging, external short circuiting, crushing, and other types of mechanical damage. In this review, recent developments toward potential-sensitive separator and heat-resistant separator for safer LIBs are summarized, including their induced materials, working mechanisms, modified ways and improved properties.