Iodine-steam functionalized reduced graphene oxide/oxidized carbon yarn electrodes for knittable fibriform supercapacitor

Fibriform supercapacitor (FSC) is considered as a promising energy storage component for future wearable electronics. The modification and fabrication of reduced graphene oxide (rGO) based FSC are recent research focus. Enhancing electrical conductivity of rGO is an important factor to improve the electrochemical performance of FSC. Hence, we fabricated iodine-functionalized reduced graphene oxide (I-rGO) on oxidized carbon yarn (OCY) by a simple iodine steam functionalization method. The I-rGO displays enhanced electrical conductivity which facilitates the ion and electron transport and increases the utilization of rGO. The I-rGO combined with the OCY which processes good hydrophilicity and high electrochemical activity very well, endowing the FSCs with high performance. The all-solid state FSC, assembled by using two intertwined I-rGO/OCY electrodes and KOH-polyvinyl alcohol gel electrolyte, shows high specific capacitance of 1.7 mF cm(-1) at scan rate of 5 mV s(-1) and the capacitance almost increases linearly with device length increasing. Meanwhile, the FSC exhibits well cycling performance of 88% capacitance retention after 5000 cycles, considerable mechanical flexibility and stability of 94% capacitance retention after 1000 continuous bending cycles, fascinating series-parallel performance and knittability. Therefore, the FSC based on I-rGO/OCY has great potential to be applied to wearable electronics in the future.