Recent developments in pliable electrode materials for lithium ion batteries (LIBs) have attracted much attention. However, flexible and robust separator with high ionic conductivity and thermal stability is also eagerly anticipated for advanced secondary batteries. Here porous polyurethane@graphene oxide (PU@GO) membranes prepared by electrospun technique have been developed as ideal separator candidates for high-performance LIBs. Electrolyte-uptake capacity and ionic conductivity of the flexible PU@GO separators are superior to those of commercial Celgard separators at 733% and 3.73 mS cm(-1), respectively, resulting in better battery performances in terms of impedance, specific discharge capacity and cycle life.