High-performance free-standing capacitor electrodes of multilayered Co9S8 plates wrapped by carbonized poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/reduced graphene oxide

In this paper, a free-standing electrode structure composed of multilayered Co9S8 plates wrapped by carbonized poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/reduced graphene oxide (PEDOT:PSS/rGO) layers is introduced. Excellent supercapacitive behaviors, especially long cycling stability at high current densities are delivered owing to the synergetic effects of stable electrical contact between the active material and carbonized PEDOT:PSS/rGO due to the wrapped configuration, efficient charge exchange between the multilayered Co9S8 plates and electrolyte, improved electrical conductance by rGO, and plenty of voids for accommodating volume changes. For the optimized electrode (starting materials: 0.5 mL PEDOT:PSS, 1.0 mL GO (6.0 mg mL−1) and 10.0 mg Co(OH)2), a specific capacitance of about 788.9 F g−1 at 1.0 A g−1 and good cycling stability of over 100% of the initial capacitance (∼488.6 F g−1) after 10000 cycles at a current density of 15.0 A g−1 can be achieved. The assembled asymmetric supercapacitor based on the optimized electrode//active carbon exhibits an energy density of ∼19.6 Wh kg−1 at a power density of 400.9 W kg−1.