Chemically Coupled Fe₂O₃/Graphene Hydrogel as Binder‐Free Anode Material for Stable Ni‐Fe Battery with High Energy and Power Density

Abstract Aqueous nickel‐iron (Ni−Fe) batteries provide a sustainable solution for large‐scale power sources, but their practical applications are still restrained by the nonstable Fe anodes. A simple, inexpensive and mass‐manufacturable one‐pot strategy is used to in situ grow Fe₂O₃ nanoparticles on graphene sheets for preparing a chemically coupled Fe₂O₃/graphene hydrogel (Fe₂O₃@GH), of which the pore structure can be well rationally tuned by the ratio of graphene to Fe₂O₃. In contrast to the conventional iron oxide/carbon anodes (FeO_x/C), Fe₂O₃@GH anode in Ni−Fe batteries delivers much higher specific capacity (287.2 mAh g⁻¹ vs. 159.5 mAh g⁻¹ at 2 A g⁻¹), better stability (capacity retention of 95 % vs. 61.2 % after 1000 charge/discharge cycles) and superior power density comparable with supercapacitors. More remarkably, the assembled full rechargeable Ni−Fe battery made from Ni(OH)₂ microspheres growing on Ni foam (Ni(OH)₂ MSs@NF) (+)//Fe₂O₃@GH (−) achieves excellent cycling stability (retention of 82 % of specific capacity after 500 cycles) at a large operating potential of 1.6 V, while delivering the largest energy density of 203 Wh kg⁻¹ and also a highest power density of 6.4 kW kg⁻¹ among the reported full Ni−Fe batteries. This work holds great promises to fabricate alternative safer high‐performance vehicle batteries.