Flexible graphene‐carbon nanotube electrochemical double layer capacitors with ultrahigh areal performance

The fabrication of electrochemical double layer capacitors (EDLCs) with high areal capacitance relies on the use of elevated mass loadings of highly porous active materials. Herein, we demonstrate a high‐throughput manufacturing of graphene/nanotubes hybrid EDLCs. Wet‐jet milling (WJM) method is exploited to exfoliate graphite into single/few‐layer graphene flakes (WJM–G) in industrial volume (production rate ~0.5 kg/day). Commercial single/double walled carbon nanotubes (SDWCNTs) are mixed with graphene flakes in order to act as spacers between the graphene flakes during their film formation. The latter is obtained by one‐step vacuum filtration, resulting in self‐standing, metal‐ and binder‐free flexible EDLC electrodes with high active material mass loadings up to ~30 mg cm‐2. The corresponding symmetric WJM–G/SDWCNTs EDLCs exhibit electrode energy densities of 539 μWh cm‐2 at 1.3 mW cm‐2 and operating power densities up to 532 mW cm‐2 (outperforming most of the EDLC technologies). The EDCLs show excellent cycling stability and outstanding flexibility even under highly folded states (up to 180°). The combination of industrial‐like production of active materials, simplified manufacturing of EDLC electrodes, and ultrahigh areal performance of the as‐produced EDLCs are promising for novel advanced EDLCs designs.