Investigation on the role of different conductive polymers in supercapacitors based on a zinc sulfide/reduced graphene oxide/conductive polymer ternary composite electrode

Conductive polymers, such as polyaniline (PANI), polypyrrole (PPy), polythiophene (PTh) and poly 3,4-ethylenedioxythiophene (PEDOT), play an important role in the application of pseudocapacitors. It is necessary to explore the effects of different conductive polymers in electrode composites. Herein, we prepare zinc sulfide/reduced graphene oxide (ZnS/RGO) by the hydrothermal method, and conductive polymers (PANI, PPy, PTh and PEDOT) doped with the same mass ratio (polymer to 70 wt%) via in situ polymerization on the surface of ZnS/RGO composite. For the supercapacitor application, the ZnS/RGO/PANI ternary electrode composite possesses the best capacitance performance and cycle stability out of all of the polymer-coated ZnS/RGO composites. In the three-electrode system, the discharge specific capacitance and cycle stability of ZnS/RGO/PANI are 1045.3 F g−1 and 160% at 1 A g−1 after 1000 loops. In a two-electrode symmetric system, the discharge specific capacitance and cycle stability of ZnS/RGO/PANI are 722.0 F g−1 and 76.1% at 1 A g−1 after 1000 loops, and the greatest energy and power density of the ZnS/RGO/PANI electrode are 349.7 W h kg−1 and 18.0 kW kg−1. In addition, conductive polymers can effectively improve the voltage range of the electrode composites in 6 M KOH electrolyte for the two-electrode system. The discharge voltage ∼1.6 V makes them promising electrode materials for supercapacitors.