Highly compressible 3-D hierarchical porous carbon nanotube/metal organic framework/polyaniline hybrid sponges supercapacitors

Abstract

Optimization of the transport behaviors of ions and electrons is the key for the property improvement of supercapacitor, which are essentially controlled by the design of hierarchical porous structure and electrical conductive backbone, from nanoscale to microscale, respectively. However, such design requirements are very difficult to be satisfied simultaneously, because the generation of porosity would result to the detrimental effects on the electrical conductivity of electrode. In this study, we propose to prepare a hierarchical porous supercapacitor electrode, with a novel 3-D highly porous (with pore size in the range of 50-100 nm) carbon nanotube sponges (CNTS) as a conductive substrate for the successively deposition of metal organic frameworks (MOF) and polyaniline. The porous structure of the sponge is beneficial for precursor penetration and uniform deposition of MOF and polyaniline (PANI) on to the nanotubes. The highly porous CNTS not only provides conductive highway for electrons, but also channels for ions quick diffusion. The coated MOF offers extra ion storage reservoir, while PANI further wire the insulating MOF together. In addition, the composite structure does not require any conductive additives or mechanical binders and delivers excellent capacitance coupled with flexible, compressive, and have relatively high specific capacitance.