In this article, a facile method based on in-situ phase-separation was developed for the fabrication of ultrathin hybrid membranes for highly flexible supercapacitors. The structures and morphologies of the prepared electrodes were characterized by scanning electron microscopy (SEM), Fourier-transformed infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) measurements; and the electro-chemical behaviors were examined in 2 M KOH solution. SEM and FTIR characterizations reveal that activated carbon was imbedded into the polymer membrane of polyethersulfone to form a uniform and flexible hybrid membrane. When the thin polymer-carbon membrane (PCM) was used as an electrode material for supercapacitor, a high specific capacitance of 169.4 Fg(-1) was obtained at a current density of 0.5 Ag-1 along with good long-term cycle life of 94.6% capacity retention after 2000 charging discharging cycles. Benefiting from these merits, the as-fabricated PCM//PCM cell shows an excellent electrochemical property. These results suggest a promising route towards the fabrication of highly flexible electrodes for high-performance supercapacitors. (C) 2016 Elsevier B.V. All rights reserved.