Facile Synthesis of Sheet Stacking Structure NiCo2S4@PPy with Enhanced Rate Capability and Cycling Performance for Aqueous Supercapacitors

A NiCo2S4@PPy series with sheet stacking structure and suitable pore size distribution is successfully synthesized through a one-step vulcanization process and polymerization process. Interestingly, the abundant sites and large electroactive surface area of NiCo2S4@PPy stacking structure are formed via the etching effect of S2- ions and ultrasonic oscillation effect, which render the morphology of NiCo2S4@PPy with a lamellar feature. In contrast, polypyrrole (PPy) with good conductivity provides favorable electron transport pathways for electrolyte ions. The as-prepared sheet stacking structure NiCo2S4@PPy (NCSP-3) electrode delivers good electrochemical properties with the highest specific capacitance of 1606.6 F g(-1) at 1 A g(-1) and excellent rate performance of 77.4% at high discharge rate of 10 A g(-1). Furthermore, the NCSP-3 electrode exhibits remarkable cycling stability, where the ultimate specific capacitance has no attenuation (retained at around 100%) compared with its incipient value after 20 000 cycles even at 20 A g(-1). These promising results can be put down to the unique structure and synergetic effect of NiCo2S4 and PPy, which ensure good conductivity, more redox reactions, as well as large specific surface area. This work has guiding significance for the general and low-cost route design of high-performance electrode materials for supercapacitor applications.