High-capacity and high-rate Ni-Fe batteries based on mesostructured quaternary carbon/Fe/FeO/Fe₃O₄ hybrid material

The Ni-Fe battery is a promising alternative to lithium ion batteries due to its long life, high reliability, and eco-friendly characteristics. However, passivation and self-discharge of the iron anode are the two main issues. Here, we demonstrate that controlling the valence state of the iron and coupling with carbon can solve these problems. We develop a mesostructured carbon/Fe/FeO/Fe₃O₄ hybrid by a one-step solid-state reaction. Experimental evidence reveals that the optimized system with three valence states of iron facilitates the redox kinetics, while the carbon layers can effectively enhance the charge transfer and suppress self-discharge. The hybrid anode exhibits high specific capacity of 604 mAh⋅g^-1 at 1 A⋅g^-1 and high cyclic stability. A Ni-Fe button battery is fabricated using the hybrid anode exhibits specific device energy of 127 Wh⋅kg^-1 at a power density of 0.58 kW⋅kg^-1 and maintains good capacity retention (90%) and coulombic efficiency (98.5%).