Active carbon wrapped carbon nanotube buckypaper for the electrode of electrochemical supercapacitors

Active carbon (AC) is a widely used electrode material for electrochemical double layer capacitors (EDLCs). However, it often shows poor rate capability due to its low conductivity. Herein, we report a binder-free carbon nanomaterials hybrid structure formed by core-shell structural nanowire network, in which carbon nanotube (CNT) buckypaper serves as conductive scaffold and porous AC layer is coated on individual CNTs in the buckypapers as active component for capacitance contribution. Such hybrid structure shows a greatly enhanced rate performance compared to pure CNT and AC electrode with its electrochemical capacitance better than its two components at large charge/discharge current densities. The AC layer in this hybrid buckypaper, which is as the main component contributed to the electrochemical capacitance, shows good rate performance and enhanced electrochemical capacitance at large current density. The performance improvement arises from the integration of resultant highly porous AC layer, conducting network and good interfacial contact between AC coating and CNTs, favoring the efficient transport of ions and electrons over the electrode surface. Moreover, the assembled EDLC with such hybrid buckypaper electrode also present higher and more stable energy densities with the increase of power densities compared to AC based EDLC. (C) 2013 Elsevier B.V. All rights reserved.