New separator prepared by electron beam irradiation for high voltage lithium secondary batteries

Grafted separators, for which poly(ethylene glycol) borate acrylate (PEGBA) was grafted onto polyethylene (PE) separator, were newly prepared by electron beam irradiation. The grafted separators were characterized by FT-IR, energy dispersive X-ray spectrometer (EDS). The morphological changes of the grafted separators were investigated by scanning electron microscopy (SEM). The degree of grafting was increased with irradiation doses. The ionic conductivity of the grafted separator showed the highest value of 6.24 × 10−4 S cm−1 at 10 kGy. In addition, its lithium ion transference number and electrochemical stability were enhanced to 0.53 and 4.8 V, respectively owing to anion trapping effect of the grafted unit. The Li ion cells using the grafted separator showed better cycle performances than that using conventional PE separator at various C-rates and high voltage operation conditions. It is suggested that this grafted separator can be a promising candidate for high voltage operation of lithium secondary batteries.