Surface-driven charge storage materials based on both electrochemical double layer (EDL) formation and pseudocapacitive behavior can deliver high energy and power capabilities with long-lasting cycling performance. On the other hand, the electrochemical performance is strongly dependent on the material properties, requiring sophisticated electrode design with a high active surface area and a large number of redox-active sites. In this study, hierarchically nanoporous pyropolymer nanofibers (HN-PNFs) were fabricated from electrospun polyacrylonitrile nanofibers by simple heating with KOH. The HN-PNFs have a hierarchically nanoporous structure and an exceptionally high specific surface area of 3,950.7m(2)g(-1) as well as numerous redox-active heteroatoms (C/O and C/N ratio of 10.6 and 16.8, respectively). These unique material properties of HN-PNFs resulted in high reversible Na-ion capacity of similar to 292mAhg(-1) as well as rapid kinetics and stable cycling performance in the cathodic potential range (1-4.5V vs. Na+/Na). Furthermore, energy storage devices based on HN-PNFs showed a remarkably high specific energy of similar to 258 Wh kg(-1) at similar to 245Wkg(-1) as well as a high specific power of similar to 21,500Wkg(-1) at similar to 78 Wh kg(-1), with long and stable cycling behaviors over 2,000 cycles. (C) 2017 Elsevier Ltd. All rights reserved.