Stretchable and compressible conductive foam based on Cu nanowire/MWCNT/ethylene-vinyl acetate composites for high-mass-loading supercapacitor electrode

Abstract

Stretchable and compressible conductor with a 3D structure has received widespread attention in smart robotics and deformable electronics, because of its special mechano-electrical properties. However, the poor mechanical properties, low electrical conductivity and unstable performance during deformation process are still the biggest technical bottlenecks. In this work, a stretchable and compressible conductive foam with stable mechano-electrical properties was comprised of copper nanowires (Cu NWs) and multi-walled carbon nanotubes (MWCNTs) that were wrapped firmly on flame-retardant ethylene-vinyl acetate (FR-EVA) skeleton. The 3D porous FR-EVA matrix with sufficient internal space provided a remarkable mechanicaldeformability for the composites foam. Additionally, the excellent conductivity of composites foam was mainly derived from the well-connected Cu NW networks, which were welded by chemical steam reduction method. Finally, the MWCNTs not only significantly improved the adhesion between the Cu NWs and FR-EVA skeleton but also effectively overcame the Cu NWs oxidation. Consequently, the 3D conductive composites foam possessed an excellent electrical conductivity (R = 2.40 Ω), mechanical stability (R/R0 < 1.6, after 100 cycles) and environmental stability (R/R0 < 1.3, exposed 33 days in air). When applied to supercapacitors, the composites foam as an excellent conductive carrier can effectively improve both mass loading and electrochemical performance of active materials. In a three-electrode cell, ~5.6 mg cm−2 of high-mass loading of activated carbon on the composites foam exhibited high specific capacitance, excellent cycle performance and remarkable compressing stability (85.97% of capacitance retention after 500 cycles), which is much better than that of commercialized Ni foam.