Highly Stable S ²⁻ ‐Doped‐rGO@Fe _2.57 Mn _0.43 O ₄ @C Hybrid Heterostructures by Sulfur‐ Doping of Graphene‐Coated 3D Fe _2.57 Mn _0.43 O ₄ Nanorods on rGO Nanosheets for High‐Performance Fast Charge/Discharge Ni/Fe Batteries

Abstract 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 ).