Uniform Fe₂ O₃ Nanospheres Anchored on Multilayer Graphene as Anode Materials for High-Rate Ni-Fe Batteries

Ni-Fe battery is one of prospective aqueous alkaline batteries due to its high safety, eco-friendliness and cost-effectiveness. However, the electrochemical performance of Fe-based anodes is limited due to the particle aggregation and low electric conductivity. In this work, iron powder is used as a precursor in a chemical bath deposition method. By optimizing the concentration of HNO₃ , a balanced dissolution-crystallization process is achieved to obtain uniform Fe₂ O₃ nanospheres in size between 60 and 90 nm, which are separately anchored on ultrasonically prepared multilayer graphene (MLG). This composite delivers specific discharge capacities of 191.1 and 160.8 mAh g^-1 at the current densities of 2 and 10 A g^-1 , respectively. A Ni-Fe battery with the as-prepared Fe₂ O₃ /MLG as anode and Ni(OH)₂ /MLG as cathode exhibits an energy density of 69.5 Wh kg^-1 at a high power density of 3931.6 W kg^-1 .