Polyetherimide (PEI) is an amorphous polymer with carboxyl
(C¼O) and oxy-ether bonds (—O—) in its molecular structure,
which possesses high chemical stability, good dimensional
stability and inherent flame resistance [29,30],thusitis
considered as a potential candidate for separator with heat
resistance and flame retardancy. Polyurethane (PU), a class of
thermoplastic polymer that contains two-phase microstructure
(soft segments and hard segments), is chosen as the polymer for
the preparation of separators with good ionic conductivity
because the soft segments didn't form ionic cluster after being
dissolved alkali metal[31]. To date, several efforts have been
devoted to the variables in electrospun PU-based nanofibrous
membranes[31]. However, no effort has been given to the
development of PEI-PU composite nanofibrous membranes
applying for separators of LIBs.