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 Fe 2.57 Mn 0.43 O 4 heterostructure on the surface of the rGO nanosheets, followed by sulfur-doping and calcination processes to achieve S 2− -doped-rGO@Fe 2.57 Mn 0.43 O 4 @C heterostructure. Note that S 2− -doped Fe 2.57 Mn 0.43 O 4 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 S 2− -doping in heterostructures can build stabilized solid electrolyte interphase on or near the surface of the Fe 2.57 Mn 0.43 O 4 nanorods. Moreover, Mn heteroatomic doping can optimize the crystalline structure of the Fe 2.57 Mn 0.43 O 4 . The exposed active sites and kinetics of S 2− -doped-rGO@Fe 2.57 Mn 0.43 O 4 @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)//S 2− -doped-rGO@Fe 2.57 Mn 0.43 O 4 @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 ).