Herein, we report, the fabrication of a mechanically stable, flexible graphene based all-solid-state supercapacitor with ionic liquid incorporated polyacrylonitrile (PAN/[BMIM][TFSI]) electrolyte for electric vehicles (EVs). The PAN/[BMIM][TFSI] electrolyte shows high ionic conductivity (2.42 mS/cm at 28 °C) with high thermal stability. Solid-like layered phase of ionic liquid is observed on the surface of pores of PAN membrane along with liquid phase which made it possible to hold 400 wt% of mobile phase. This phase formation is facilitated by the ionic interaction of C. N moieties with the electrolyte ions. A supercapacitor device, comprised PAN/[BMIM][TFSI] electrolyte and graphene as electrode, is fabricated and the performance is demonstrated. Several parameters of the device, like, energy storage and discharge capacity, internal power dissipation, operating temperature, safe operation and mechanical stability, meet the requirements of future EVs. In addition, a good cyclic stability is observed even after 1000 cycles. © 2012 Elsevier Ltd.