Novel favorably interconnected N-doped porous carbon hybrid electrode materials for high energy density supercapacitors

Abstract

A strategy to prepare facile electrode materials for electrochemical capacitors with high conductivity, high surface area and hierarchical pore structure along with nitrogen functional groups to enhance the electrochemical performance, is presented in this work. Partially unravelled carbon nanotubes (PURNTs) are interconnected to the wrinkled few layered graphene nanosheets (WfG), which act as quick ion and charge transportation channels. Here, PURNTs acts as a spacer to the WfG to avoid the restacking. Though WfG-PURNTs exhibit good results, to further improve the electrochemical performance we developed an electrode material by designing nitrogen-doped porous carbon covered favorably interconnected WfG-PURNTs with interconnected pore structure. The WfG-PURNTs serve as the conductive matrix, which plays a key role in enhancing the N-PC (WfG-PURNTs) electrode material's electrochemical performance. And the nitrogen functional groups, through faradaic red-ox reactions, contribute to the pseudocapacitance in addition to the electric double layer capacitance, thereby enhancing overall supercapacitive performance. The developed N-PC (WfG-PURNTs)-700 shows a high nitrogen amount of 6.8 at %, with a high active surface area of 2418 m2 g−1. The synergistic effect of the WfG-PURNTs and N-doped porous carbon results in high supercapacitive performance and better cyclic stability. It shows an excellent specific capacitance (Cp) of 954 F g−1 at high current density of 2 A g−1. Also, the assembled symmetric supercapacitors show high energy densities of 61.1, 119.4, and 195.4 Wh kg−1 in acidic, neutral and ionic liquid electrolytes, respectively. We also designed asymmetric solid-state flexible supercapacitor which exhibits a high specific capacitance of 209.4 F g−1 at 2 A g−1 and an excellent energy density of 29.15 Wh kg−1. Furthermore, the assembled three such flexible supercapacitors in series connection, could able to light up red colored LED for 30 min once charged for 60 s.