Highly Stable S2−‐Doped‐rGO@Fe2.57Mn0.43O4@C Hybrid Heterostructures by Sulfur‐ Doping of Graphene‐Coated 3D Fe2.57Mn0.43O4 Nanorods on rGO Nanosheets for High‐Performance Fast Charge/Discharge Ni/Fe Batteries

Multicomponent transition metal heterostructures is constructed through a heteroatomic doping method sandwiched by the dual carbon layers. The promising strategy combines iron and manganese ions into a novel Fe2.57Mn0.43O4 heterostructure on the surface of the rGO nanosheets, followed by sulfur-doping and calcination processes to achieve S2--doped-rGO@Fe2.57Mn0.43O4@C heterostructure. Note that S2--doped Fe2.57Mn0.43O4 nanorods encapsulated by the carbon coating layers on the rGO nanosheets as the backbone are expected to restrict nanorods from collapsing during the charge-discharge processes. The S2--doping in heterostructures can build stabilized solid electrolyte interphase on or near the surface of the Fe2.57Mn0.43O4 nanorods. Moreover, Mn heteroatomic doping can optimize the crystalline structure of the Fe2.57Mn0.43O4. The exposed active sites and kinetics of S2--doped-rGO@Fe2.57Mn0.43O4@C heterostructure are significantly improved. As a result, the as-assembled batteries can achieve a high capacitance of 1410 F g-1 at 1 A g-1 with a high capacitance retention of 75% at 16 A g-1. Furthermore, the batteries are guaranteed a prolonged cycle life of 1000 cycles with 92.3% capacitance retention. The as-assembled NiAl-LDH (Ni-Al layered double hydroxide)//S2--doped-rGO@Fe2.57Mn0.43O4@C battery leads to excellent electrochemical properties (65.4 Wh kg-1 at 763.2 W kg-1, 9925.8 W kg-1 at a 43.9 Wh kg-1).