This paper reports the fabrication of an electrochemical supercapacitor (ES) with high gravimetric and areal capacitances, achieved at a high mass ratio of active material to current collector. The active material, polypyrrole, is in situ polymerized in an aerogel-based current collector composed of crosslinked cellulose nanocrystals (CNCs) and multiwalled carbon nanotubes (MWCNTs). Mechanical robustness, flexibility, and low impedance of the current collectors are achieved by the chemical crosslinking of CNC aerogels and efficient dispersion of MWCNTs through the use of bile acid as a dispersant. Furthermore, the advanced electrode design results in low contact resistance. A single-electrode areal capacitance of 2.1 F cm(-2) is obtained at an active mass loading of 17.8 mg cm(-2) and an active material to current collector mass ratio of 0.57. Large area ES electrodes and devices show flexibility, excellent compression stability at 80% compression, and electrochemical cyclic stability over 5000 cycles. Moreover, good retention of capacitive properties is achieved at high charge-discharge rates and during compression cycling. The results of this investigation pave the way for the fabrication of advanced lightweight ES, which can be used for energy storage in wearable electronic devices and other applications.