Large-Scale Conductive Yarns Based on Twistable Korean Traditional Paper (Hanji) for Supercapacitor Applications: Toward High-Performance Paper Supercapacitors

A simple and scalable method to fabricate a yarn-type supercapacitor with a large specific capacitance without the aid of traditional pseudocapacitive electrode materials such as conducting polymers and metal oxides is reported. The yarn-type supercapacitors are made from twisting reduced graphene oxide (rGO) or/and single-walled carbon nanotubes (SWNTs)-coated Korean traditional paper (KTP). The yarn-type paper supercapacitor displays surprisingly enhanced electrochemical capacitance values, showing synergistic effect between rGO and SWNTs (500 times larger than performance of yarn-type rGO-coated paper supercapacitors). Coating rGO or/and SWNTs on KTP gives good morphology to the composite film, in which porosity increases and mean pore diameter decreases. The yarn-type rGO/SWNT paper supercapacitor shows good mechanical strength, high flexibility, excellent electrochemical performance, and long-life operation. The yarn-type supercapacitor has an excellent electrochemical performance with a specific capacitance of 366 F g⁻¹ at scan rate of 25 mV s⁻¹ and high stability without any degradation in electrical performance up to 10 000 charge–discharge cycles. The average capacitance of rGO/SWNT@KTP yarn-type supercapacitors is seven times higher than that of sheet-type supercapacitors at scan rate of 500 mV s⁻¹. The lighting of a red light-emitting diode (LED) is demonstrated by the yarn-type paper supercapacitor without connecting supercapacitors in series.