Synergistic effects of Fe and Mn dual-doping in CoS ultrathin nanosheets for high-performance hybrid supercapacitors.

Dopant engineering in nanostructured materials is an effective strategy to enhance electrochemical performances via regulating the electronic structures and achieving more active sites. In this work, a robust electrode based on Fe and Mn co-doped CoS (FM-CoS) ultrathin nanosheet arrays (NSAs) on the Ni foam substrate is prepared through a facile hydrothermal method followed by a subsequent sulfurization reaction. It has been found that the incorporation of Fe ions is beneficial to higher specific capacity of the final electrode and Mn ions contribute to the excellent rate capability in the reversible redox processes. Density functional theory (DFT) calculations further verify that the Mn doping in the CoS obviously shorten the energy gap of CoS, which favors the electrochemical performances. Due to the synergetic effects of different transition metal ions, the as-prepared FM-CoS ultrathin NSAs exhibit a high specific capacity of 390 mAh g at 5 A g, as well as superior rate capability and excellent cycling stability. Moreover, the corresponding quasi-solid-state hybrid supercapacitors constructed with the FM-CoS ultrathin NSAs and active carbon exhibit a high energy density of 55 Wh kg at the power density of 752 W kg. These findings demonstrate a new platform for developing high-performance electrodes for energy storage applications.