Hierarchically interconnected conducting polymer hybrid fiber with high specific capacitance for flexible fiber-shaped supercapacitor

Polypyrrole (PPy) based fiber-shaped supercapacitor (FSSC) is attracting increasing attention as energy storage devices of flexible and wearable electronic products in recent years. However, its application is limited by the low specific capacitance and poor rate capability, mainly suffering from inferior conductivity and inhibited ions channels of fiber electrode. Here, a high-performance flexible FSSC is constructed based on hierarchically interconnected porous poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)/PPy composite fiber prepared by in situ chemical polymerization of pyrrole on a novel highly-conductive PEDOT:PSS hydrogel support. The good electronic and ionic conductor properties, hierarchically porous structure and π-π interaction of conducting polymer hybrid fiber ensure fast electrons transfer/ions diffusion and the efficient utilization of whole electrode. Benefiting from the well-designed hybrid architecture and synergistic effect, the PEDOT:PSS/PPy hybrid fiber in FSSC exhibits superb volumetric/areal/length specific capacitance (393.8 F cm−3, 770.6 mF cm−2 and 18.9 mF cm−1 at 2.0 A cm−3) and excellent rate performance (52.8% capacitance retention even at ultrahigh current density of 50 A cm−3). The FSSC device displays record-high energy density (8.3 mWh cm−3 or 16.2 μWh cm−2 at such a high power density of 389.1 mW cm−3 or 761.5 μW cm−2) compared to other previously-reported PPy based FSSCs, as well as long-term cycle stability and exceptional flexibility. The outstanding electrochemical and flexural performances of our PPy based FSSC are competent for portable and wearable electronics.