Fabrication and characterization analysis of flexible porous nitrogen-doped carbon-based supercapacitor electrodes

Supercapacitor as a new-type energy storage device has attracted increasing interests, because it can provide substantially higher specific/volumetric energy density compared to conventional capacitors, and higher power density and longer cycling lifetime compared to Li-ion batteries. Therefore, it shows great promise as green energy storage device for back-up energy systems and electronic vehicles. Among all kinds of supercapacitors, flexible solid-state supercapacitor, which consists of flexible electrodes, solid-state electrolyte and separator, has attracted much attention due to its potential abilities in wearable electronics and flexible devices. Numerous efforts have been devoted to fabricate flexible electrodes because the fundamental limit of energy storage capability is largely determined by the electrode material. Therefore, how to fabricate suitable flexible electrodes alerts significant influence on supercapacitors' performance. Compared to pseudocapacitive materials, carbon-based materials have been widely investigated for flexible electrodes due to their good electrical conductivity, excellent cycling stability, high power density and outstanding mechanical properties. In this work, an effective and feasible method to fabricate carbon-based electrode for the fabrication of flexible and high-performance supercapacitors has been proposed. In order to find the relatively suitable electrode, samples under different experimental conditions have been tested and analyzed systematically. Through the simultaneous activation and carbonization process of the biomass-derived natural silk, all of these carbon-based electrodes have a few features, like hierarchical porous, rich N-doped and carbon nanosheet structure. The as-obtained electrodes show favorable capabilities for electrochemical energy storage. The specific/mass capacitor of the best carbon-based electrode can achieve 226 mF/cm² and 26 F/g, respectively, and the equivalent series resistance of it is only 4 Ω, thus showing satisfactory electrochemical performance. In conclusion, the excellent capacitance performance of the ultralight and flexible nanomaterials makes them promising candidates as electrode materials. Attributed to the good flexibility and ultralight weight, this proposed electrodes can be directly fabricated into flexible solid-state supercapacitor without any binder and conductive agents. © 2016, Science Press. All right reserved.