Constructing optimized three-dimensional electrochemical interface in carbon nanofiber/carbon nanotube hierarchical composites for high-energy-density supercapacitors

It is demonstrated that the performances of supercapacitors are often affected by the electrochemical interface in their electrodes. In this work, the electrochemical interface in carbon nanofiber (CNF)/carbon nanotube (CNT) hierarchical composites was well optimized by tuning the diameters of electrospun CNF skeletons and the densities/lengths of CNT hierarchies. The optimized CNF/CNT composites decorated with MnO₂ exhibited high specific capacitance (∼631.0 F g⁻¹ at current density of 0.9 A g⁻¹) and excellent cycling stability (over 95% after 1500 cycles). Moreover, the assembled symmetric supercapacitors show a high flexibility and an excellent dynamic cycling stability, outputting the maximum energy density of 19.11 W h kg⁻¹ and the maximum power density reaching 25,000 W kg⁻¹. This research confirmed that the performances of the electrodes based on CNF/CNT hierarchical composites and their counterpart devices can be well tuned by tailoring their three-dimensional electrochemical interface.