In this study, polyethylene separators were modified by dip coating of polyethylene (PE) separators in poly(vinylidene fluoride-co-hexafluoropropylene)/poly(ethylene glycol) dimethacrylate (PVDF-HFP/PEGDMA) mixtures at different humidity levels (0–50%), followed by electron beam irradiation. Micro-porous structures of the coating layer were generated by performing dip-coating process at high humidity levels (i.e. phase inversion process) and were found to be affected by the PEGDMA content and humidity level. The thermal shrinkage of the prepared separators significantly decreased with increasing EB absorption dose due to the formation of crosslinked networks of the PVDF-HFP/PEGDMA-coated PE separators. It was also observed that the separators prepared under high humidity condition showed a higher liquid electrolyte uptake and the ionic conductivity than the original PE separators.