A flame retarding separator with improved thermal stability for safe lithium-ion batteries

• A flame retarding separator (FRS) reduced the flammability of liquid electrolyte.
• The conductivity of FRS was 2.9 times higher than that of the PE/PP separator.
• The Li/LiFePO4 cell using the FRS showed stable cycling performance.

This study demonstrates a new flame retarding separator (FRS) based on brominated poly(phenylene oxide) (BPPO) which remarkably reduces the flammability of the liquid electrolyte without decrease in electrochemical performances such as ionic conductivity and cycle life of a lithium-ion battery. The FRS showed improved thermal stability, higher ionic conductivity and stable cycling performance of the Li/LiFePO4 cell compared with the PE/PP separator.