Thermally doped polypyrrole nanotubes with sulfuric acid for flexible all-solid-state supercapacitors

We have synthesized a binder-free electrode on the basis of thermal acid doped polypyrrole nanotubes on carbon cloth (CC/PPy NTs-T), which can be used for flexible all-solid-state supercapacitors (FSSCs). PPy NTs on the CC substrate (CC/PPy NTs) with an interconnected network structure were prepared by a facile self-degradation template method. Then a unique acid doping process at high temperature was developed and used to fabricate the CC/PPy NTs-T composite electrodes, showing the better electrochemical performances than the CC/PPy NTs (without doping) and CC/PPy NTs-R (doping at room temperature) composite electrodes. The CC/PPy NTs-T FSSCs were assembled based on the prepared CC/PPy NTs-T composite electrodes, which showed good flexibility and excellent electrochemical performances with a high areal specific capacitance of 73.3 mF cm⁻² at the current density of 1 mA cm⁻², the highest energy density of 0.081 mW h cm⁻³, the highest power density of 25 mW cm⁻³, and the capacitance retention of 85.3% after 5000 cycles. The outstanding electrochemical performances can be attributed to the unique interconnected network structure of the composite electrodes and the thermal acid doping of PPy NTs, which proposes a new and feasible general pathway of flexible electrode configuration for energy storage devices. (paper)