Mechanically Strong Graphene/Aramid Nanofiber Composite Electrodes for Structural Energy and Power

Abstract

Structural energy and power systems offer both mechanical and electrochemical performance in a single multifunctional platform. These are of growing interest because they potentially offer reduction in mass and/or volume for aircraft, satellites, and ground transportation. To this end, flexible graphene-based supercapacitors have attracted much attention due to their extraordinary mechanical and electrical properties, yet they suffer from poor strength. This problem may be exacerbated with the inclusion of functional guest materials, often yielding strengths of <15 MPa. Here, we show that graphene paper supercapacitor electrodes containing aramid nanofibers as guest materials exhibit extraordinarily high tensile strength (100.6 MPa) and excellent electrochemical stability. This is achieved by extensive hydrogen bonding and π-π interactions between the graphene sheets and aramid nanofibers. The trade-off between capacitance and mechanical properties is evaluated as a function of aramid nanofiber loading, where it is shown that these electrodes exhibit multifunctionality superior to that of other graphene-based supercapacitors, nearly rivaling those of graphene-based pseudocapacitors. We anticipate these composite electrodes to be a starting point for structural energy and power systems that harness the mechanical properties of aramid nanofibers.

Interfacial Engineering of Reduced Graphene Oxide for Aramid Nanofiber‐Enabled Structural Supercapacitors

“…The enhancement of the mechanical properties is attributed to the increased hydrogen bonding and the π ‐ π interactions that facilitate load transfer between the reduced graphene oxide sheets and the 2D randomly oriented ANFs (Figure S4 and Figure S6). The reported values are comparatively lower from our previous studies since the previous tests were conducted at higher strain rates . As shown in Figure S7, f‐rGO/ANF films exhibited strong strain rate dependency.…”

“…For rGO−COOH/10 wt % ANF, the deconvolution of the C 1s peak was necessary to determine the ratio of the carboxylic acid (−COOH) groups after reduction. The C 1s peak was deconvoluted to C−C (284.5 eV), C−N/C−O (286.1 eV), N−C=O (287.8 eV), O=C−OH (289 eV), and π ‐ π interactions (291 eV) . It was found that the amount of carboxylic acid (−COOH) groups for rGO−COOH/10 wt % ANF (5.6 %) was higher than rGO/10 wt % ANF (3.4 %) (Figure S4 and Table S2).…”

“…ultimate strength of our results compared against other free‐standing structural electrodes from the literature was constructed, Figure a and Table S7. The plot includes rGO aerogels, multi‐ and single‐ walled carbon nanotube (MWCNT and SWCNT) buckypapers, rGO/MnO 2 , rGO/MnO 2 /CNTs, polypyrrole (Ppy)/rGO, rGO‐cellulose, rGO‐polyaniline (PANI), SWCNT‐Ppy‐cyanate ester (CE), and rGO/CNT wire shaped composites ,. It can be observed that f‐rGO/ANF electrodes exhibit a good combination of mechanical and electrochemical properties compared to other carbon‐based structural electrodes.…”

“…Here, the multifunctional efficiency was calculated using carbon aerogel (specific energy 12.5 Wh/kg) as the monofunctional energy storage material . The structural efficiency was calculated for four different monofunctional structural materials: carbon fiber reinforced epoxy (specific Young's modulus of 44 GPa cm 3 /g and specific tensile strength of 375 MPa cm 3 /g), aluminum (specific Young's modulus of 25.5 GPa cm 3 /g and specific tensile strength of 153.7 MPa cm 3 /g), steel (specific Young's modulus of 26.5 GPa cm 3 /g and specific tensile strength of 88.5 MPa cm 3 /g), and epoxy (specific Young's modulus of 2.8 GPa cm 3 /g and specific tensile strength of 60 MPa cm 3 /g) . All four materials are currently used in automobile and aerospace applications.…”

Graphene‐Based Nanomaterials for Flexible and Wearable Supercapacitors

“…By increasing the ANF content, the rGO/ANF films showed enhanced mechanical properties, though their specific capacitances decreased. Even so, SCs based on the rGO/ANF films (25 wt% ANF) still exhibited a high volumetric capacitance up to 108 F cm −3 . Structural SCs have recently attracted growing attention as they, when used as structural parts in an electric car or aircraft, can potentially reduce the mass/volume and save energy .…”