Stabilizing Metallic Iron Nanoparticles by Conformal Graphitic Carbon Coating for High-Rate Anode in Ni-Fe Batteries.

Nickel-iron (Ni-Fe) batteries are promising candidates for large-scale energy storage due to their high safety and low cost. However, their power density and cycling efficiency remain limited by the poor kinetics of the Fe anode. Herein, we report high-performance Fe anodes based on active Fe nanoparticles conformally coated with carbon shells, which were synthesized from low-cost precursors using a scalable process. Such core-shell structured C-Fe anodes offer high electrochemical activity and stability. Specifically, a high specific capacity of 208 mAh g at a current density of 1 A g (based on the total weight of Fe and C) and a capacity retention of 93% after 2000 cycles at 4 A g can be achieved. When coupled with a Ni cathode, such a full cell battery can deliver a high energy density of 101.0 Wh kg at power density of 0.81 kW kg and 51.6 Wh kg at 8.2 kW kg (based on the mass of the electrode materials), among the best energy and power performance among Ni-Fe batteries reported results. Thus, this work may provide an effective and scalable route toward high-performance anodes for high-power and long-life Ni-Fe batteries.