Three-dimensional porous polyacrylonitrile/polyaniline core-shell (PAN@PANI) nanofibers are fabricated by electrospinning technique combining in situ chemical polymerization of aniline monomers. The obtained PAN@PANI nanofibers possess unique continuous and homogeneous core-shell nanostructures and high mass loading of PANI (similar to 60 wt%) as active materials, which have greatly improved the electrochemical performance with a specific capacitance up to 577 F/g at a scan rate of 5 mV/s. Moreover, the porous networks of randomly arrayed PAN@PANI nanofibers provide binder-free and freestanding electrodes for flexible solid-state supercapacitors. The obtained devices based on PAN@PANI networks present excellent electrochemical properties with an energy density of 12.6 Wh/kg at a power density of 2.3 kW/kg and good cycling stability with retaining more than 98% of the initial capacitance after 1000 charge/discharge cycles, showing the possibility for practical applications in flexible electronics. (C) 2015 Published by Elsevier Ltd.