Hexagonal Boron Nitride-Coated Polyimide Ion Track Etched Separator with Enhanced Thermal Conductivity and High-Temperature Stability for Lithium-Ion Batteries

The separator plays a vital role in preventing thermal runaway in lithium-ion batteries (LIBs). Herein, a PI/hBN (polyimide/hexagonal boron nitride) separator with excellent thermal stability and enhanced thermal conductivity is successfully prepared by ion track etching and doctor blade coating to achieve highly safe LIBs. The PI/hBN separator displays good electrolyte wettability, high mechanical strength, excellent thermal stability, and enhanced in-plane thermal conductivity, as well as good electrochemical performance when applied in LIBs. Specifically, PI track-etched membranes have been used to prepare separators with rigid structures and functional groups in polymer chains, thereby enabling the separators to be stable at temperatures as high as 500 degrees C. Moreover, hBN-coated nanoplates enhance the in-plane thermal conductivity of the separator to reduce the local heat accumulation in the battery while also promoting interfacial compatibility to facilitate the conduction of lithium ions. Lithium iron phosphate/lithium cells with the PI/hBN separator deliver better rate capability and superior capacity retention. The PI/hBN separator is a promising candidate for achieving highly safe LIBs, and this work paves the way for engineering roll-to-roll techniques to suppress thermal runaway and improve battery safety.