Transparent and flexible high-power supercapacitors based on carbon nanotube fibre aerogels

In this work, we report the fabrication of continuous transparent and flexible supercapacitors by depositing a CNT network onto a polymer electrolyte membrane directly from an aerogel of ultra-long CNTs produced floating in the gas phase. The supercapacitors show a combination of a power density of 1370 kW kg-1 at high transmittance (ca. 70%), and high electrochemical stability during extended cycling (>94% capacitance retention over 20 000 cycles) and against repeated 180° flexural deformation. They represent a significant enhancement of 1-3 orders of magnitude compared to prior state-of-the-art transparent supercapacitors based on graphene, CNTs, and rGO. These features mainly arise from the exceptionally long length of CNTs, which makes the material behave as a bulk conductor instead of an aspect ratio-limited percolating network, even for electrodes with >90% transparency. The electrical and capacitive figures-of-merit for the transparent conductor are FoMe = 2.7, and FoMc = 0.46 F S-1 cm-2 respectively.