Carbon\nNanotube/Reduced Graphene Oxide/Aramid Nanofiber\nStructural Supercapacitors

Abstract

Reduced\ngraphene oxide/aramid nanofiber (rGO/ANF) supercapacitor\nelectrodes have a good combination of energy storage and mechanical\nproperties, but ion transport remains an issue toward achieving higher\nenergy densities at high current because of the tightly packed electrode\nstructure. Herein, carbon nanotubes (CNTs) are introduced to prevent\nrGO flake stacking to improve the rate capability of the rGO/ANF structural\nsupercapacitor. The effect of CNTs on the rGO/ANF composite electrode’s\nmechanical and electrochemical properties is investigated by varying\nthe composition. The addition of 20 wt % CNTs led to an increase in\nYoung’s modulus up to 10.3 ± 1.8 GPa, while a maximum\nin ultimate strain and strength of 1.3 ± 0.14% and 55 ±\n6.8 MPa, respectively, was found at a loading of 2.5 wt % CNTs. At\nlow specific currents, the electrodes performed similarly (160–170\nF g^–1), but at high specific currents (5 A g^–1), the addition of 20 wt % CNTs led to a significantly\nhigher capacitance (76 F g^–1) as compared to that\nof rGO/ANF electrodes without CNTs (26 F g^–1). In\naddition, the energy density also improved significantly at high power\nfrom 1.4 to 5.1 W h L^–1 with the addition of CNTs.\nThe improvement in mechanical properties is attributed to the introduction\nof additional hydrogen-bonding and π–π interactions\nfrom the carboxylic acid-functionalized CNTs. The increase in capacitance\nat higher discharge rates is due to improved ion transport from the\nCNTs. Finally, <i>in situ</i> electrochemomechanical testing\nexamines how capacitance varies with strain in these structural electrodes\nfor the first time.