Self-assembled ultrathin carbon black/carbon nanotube films as electrodes for microsupercapacitors

The ability to control the morphology of composite thin films is essential to construct networks exhibiting the desired final properties. In this work, we report that the vortex-assisted assembly of dispersions containing carbon black and carbon nanotubes could generate structures with varying densities and electrical properties. The controlled aggregation of carbon black nanoparticles led to the formation of a porous framework, with the nanotubes percolating through the entire film. The use of dispersions containing 20 wt% of carbon nanotubes led to thin films with thickness of 129 nm and an electronic conductivity of 2.0 S cm −1 . This composite displayed good performance as electrode for micro in-plane supercapacitors (thickness also of 129 nm) with ionic liquid electrolyte, exhibiting capacitances as high as 41.0 F g −1 , and a power density of 7.6 Wh kg −1 at 4 A g −1 . Besides proposing a new route to produce thin-film electrodes for energy storage applications, we also demonstrate that dispersion composition can be successfully used to regulate the interactions in aggregating systems. Graphical abstract