Surface tailoring of polypropylene separators for lithium-ion batteries via N-hydroxyphthalimide catalysis

Abstract Surface modification of polyolefine separators for high performance lithium-ion batteries has been a worthwhile research topic. In this work, poly (poly (ethylene glycol) methacrylate) (PPEGMA) was firstly grafted onto polypropylene (PP) separator based on N-hydroxyphthalimide (NHPI) catalysis and activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP). Bis(2,2,2-trichloroethyl) azodicarboxylate (BTCEAD) was anchored on the surface of PP separators in the presence of NHPI. Then BTCEAD functionalized PP separator initiated the polymerization of PEGMA by ARGET-ATRP. Thus, structure controllable PPEGMA was grafted on the surface of PP separators. The results of contact angle and electrolyte uptake tests demonstrated that electrolyte wettability of PPEGMA functionalized PP separator has been significantly improved. Electrochemical measurements indicated that the ionic conductivity and discharge capacity retention of cells assembled with PPEGMA functionalized PP separators were distinctly higher than that of cells with pristine PP separator. Herein, we presented a new methodology with high efficiency to modify PP separators under mild condition, which was also applied to other polyolefine separator for high performance lithium-ion batteries. The proposed approach might have many other potential applications in membrane modification field.