Hierarchical FeS/RGO/FeS@Fe foil as high-performance negative electrode for asymmetric supercapacitors

Abstract

A hierarchical FeS/RGO/FeS composite in situ grown on Fe foil was designed and prepared via an Fe foil-involved one-step hydrothermal route, in which Fe foil acted as the Fe source for the lower FeS layer, reductant of GO and subsequent current collector. The as-prepared FeS/RGO/FeS@Fe showed a high specific capacity of 247.5 C g⁻¹ (206.25 F g⁻¹) and good cyclability with 118% capacity retention after 5000 cycles when directly used as an electrode. Additionally, an asymmetric supercapacitor (ASC) was assembled using Ni(OH)₂ and FeS/RGO/FeS@Fe as the positive electrode and negative electrode, respectively. This ASC exhibited maximum power density and energy density of 20 000 W kg⁻¹ and 34.07 W h kg⁻¹, respectively, suggesting that FeS/RGO/FeS is a promising negative electrode material.