Nowadays, hierarchical porosity of electrode materials has attracted numerous attentions due to allowing the smooth mass transportation and capability of improving the rate performance of electrochemical applications. In this study, hierarchically porous N-doped carbon (HPDC) materials were fabricated in a facile and scalable way via the dehalogenation of polyvinyl dichloride and applied as electrode materials for assembling symmetric aqueous supercapacitors. The resulted supercapacitors were found having a very high specific energy of 21.5 Wh kg(-1) in 1.0 M Li2SO4 with a safe operating voltage of 1.8 V. The enhanced capacitive performance was ascribed to both the HPDC's abundant pore hierarchy with a large accessible surface area and also the applicable neutral electrolyte with a wide stable potential. Besides the potentially scalable production of hierarchically porous carbon materials with high capacitive performance, our work may also envision that other halogenated polymers such as polyvinyl chloride and its wastes can be easily converted into useful carbon materials via our developed dehalogenation strategy.