Design and fabrication of high performance flexible supercapacitor with polypyrrole@carbon fiber yarn electrode and redox active dopants

The flexible fiber-shaped electrodes that polypyrrole (PPy) and hydroquinone (HQ) derivatives coated on the surface of carbon fiber yarn (CFY) were synthesized by a simple one-step electrosynthesis. Besides, the effects of the size and structure of the HQ derivatives on the electrochemical performance of the doped PPy@CFY electrodes were analyzed. The study suggested that sodium lignosulfonate doped PPy@CFY (LS-PPy@CFY) exhibited a high specific capacitance of 245.89 F cm −3 at 0.26 A cm −3 . The all-solid-state flexible fiber-shaped supercapacitor (AFFSC) based on two parallel LS-PPy@CFY electrodes showed a high specific capacitance of 50.08 F cm −3 and an excellent energy density of 4.45 mW h cm −3 . Moreover, the AFFSC achieved prominent cyclic stability, maintaining 92.7% capacitance retention after 25,000 cycles, as well as excellent flexibility and mechanical stability which kept 89% capacitance retention after 5000 bending cycles. In addition, the AFFSC also exhibited good voltage and current scalability and potentiality in its practical application.