Constructing β-FeOOH scaffold for enhancing conductance and capacitances of coaxial polypyrrole/nylon fibers

Polypyrrole-based fabrics are of rapid development owing to their favorable flexibility, potential pseudocapacitances and easy integration into garments. To further improve the mass loading of polypyrrole on nylon strip, acicular β-FeOOH scaffold that provides more space for polypyrrole growing is constructed through hydrolysis of Fe3+. With the assistance of β-FeOOH, the prepared PFNS-10 obtains lower surface resistance (0.43 kΩ) and higher areal capacitances (433.3–222.2 mF cm−2 at 1–10 mA cm−2) than PNS-10 (without β-FeOOH, 0.80 kΩ and 275.9–171.3 mF cm−2). The symmetric supercapacitor based on PFNS-10 maintains 52.2% capacitance after 10000 galvanostatic charge-discharge cycles. Besides, an equivalent series circuit of supercapacitor consisting of a pure capacitor and an internal resistance is employed to analyze the charging/discharging process, which reveals potential occupied by internal resistance is equal to 0.5IRdrop. The equation E=0.5Itd(U-1.5IRdrop) is put forward for calculating energy that the assembled PFNS-10 supercapacitor supplies to the external circuit, producing similar results to E = I∫U(t)dt based on discharging curve integral. [Display omitted] •A new modification way is proposed for nylon fibers.•β-FeOOH serves as scaffold to improve conductance and capacitance of fiber electrode.•It is demonstrated more rational to calculate capacitance using whole voltage window.•E=0.5Itd(U-1.5IRdrop) is proposed for the energy with closer results to E = I∫U(t)dt.