Reduced
graphene oxide/aramid nanofiber (rGO/ANF) supercapacitor
electrodes have a good combination of energy storage and mechanical
properties, but ion transport remains an issue toward achieving higher
energy densities at high current because of the tightly packed electrode
structure. Herein, carbon nanotubes (CNTs) are introduced to prevent
rGO flake stacking to improve the rate capability of the rGO/ANF structural
supercapacitor. The effect of CNTs on the rGO/ANF composite electrode’s
mechanical and electrochemical properties is investigated by varying
the composition. The addition of 20 wt % CNTs led to an increase in
Young’s modulus up to 10.3 ± 1.8 GPa, while a maximum
in ultimate strain and strength of 1.3 ± 0.14% and 55 ±
6.8 MPa, respectively, was found at a loading of 2.5 wt % CNTs. At
low specific currents, the electrodes performed similarly (160–170
F g–1), but at high specific currents (5 A g–1), the addition of 20 wt % CNTs led to a significantly
higher capacitance (76 F g–1) as compared to that
of rGO/ANF electrodes without CNTs (26 F g–1). In
addition, the energy density also improved significantly at high power
from 1.4 to 5.1 W h L–1 with the addition of CNTs.
The improvement in mechanical properties is attributed to the introduction
of additional hydrogen-bonding and π–π interactions
from the carboxylic acid-functionalized CNTs. The increase in capacitance
at higher discharge rates is due to improved ion transport from the
CNTs. Finally, in situ electrochemomechanical testing
examines how capacitance varies with strain in these structural electrodes
for the first time.