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

Abstract 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.