Theflame retarding ability of separators is a critical factor for
the safety of LIBs, but it has been rarely mentioned because most
separators are combustible. The combustion tests of the Celgard
and SiO2/PEI-PU composite membranes are shown inFig. 7,when
Celgard was ignited, it was on fire immediately and was
completely engulfed in flame. However, the PEI-PU and SiO2/
PEI-PU composite membranes exhibit excellentflame retarding
ability because of the introduction offlame retarded PEI although
they shrank, which may play an important role in reducing the
danger of explosive burning, and thus improving the safety of
LIBs