| Summary: | High-energy density supercapacitors have attracted extensive attention due to their electrode structure design. A synergistic effect related to core–shell structure can improve the energy storage capacity and power density of electrode materials. The Ni-foam (NF) substrate coupled with polypyrrole (PPy) conductive coating can serve as an internal/external bicontinuous conductive network. In this work, the distinctive PPy@FeNi<sub>2</sub>S<sub>4</sub>@NF and PPy@NiCo<sub>2</sub>S<sub>4</sub>@NF materials were prepared by a simple two-step hydrothermal synthesis with a subsequent in situ polymerization method. PPy@FeNi<sub>2</sub>S<sub>4</sub>@NF and PPy@NiCo<sub>2</sub>S<sub>4</sub>@NF could deliver ultrahigh specific capacitances of 3870.3 and 5771.4 F·g<sup>−1</sup> at 1 A·g<sup>−1</sup> and marvelous cycling capability performances of 81.39% and 93.02% after 5000 cycles. The asymmetric supercapacitors composed of the prepared materials provided a high-energy density of over 47.2 Wh·kg<sup>−1</sup> at 699.9 W·kg<sup>−1</sup> power density and 67.11 Wh·kg<sup>−1</sup> at 800 W·kg<sup>−1</sup> power density. Therefore, the self-assembled core–shell structure can effectively improve the electrochemical performance and will have an effective service in advanced energy-storage devices.
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