Electronic coupling effect optimized FeOOH nanosheets to enable high-performance Ni-Fe battery

Abstract

Aqueous rechargeable Ni-Fe batteries exhibit unique advantages in large-scale energy storage thanks to their affordability, safety, and reliability. However, their limited energy density and Coulombic efficiency stem from unfavorable OH⁻ adsorption capability and low electrochemical activity of Fe sites, result in electrode kinetic delays for Fe anodes. Here, we report Mn and S co-modified FeOOH (MSFF) nanosheets as an advanced anode in Ni-Fe batteries, synthesized from a facile one-step surface-redox-etching method at room temperature. Based on the strong electronic coupling effect between Mn and S atoms, such MSFF anode presents fast electron transport capability, enhanced OH⁻-adsorption capability, and redox reactivity. Specifically, the MSFF anode can achieve a high areal capacity of 2 mAh cm⁻² at 10 mA cm⁻², which retains a staggering 96% of the initial capacity after undergoing 9000 cycles at a higher current density of 30 mA cm⁻². In addition, the assembled Ni-Fe battery can provide a capacity of 0.85 mAh cm⁻² at 16 mA cm⁻², significantly outperforming most recently reported aqueous rechargeable batteries. This work may offer an innovative and feasible approach for modulating the local electronic structure of high-performance Ni-Fe battery electrode materials.