Simultaneous Regulation of Solvation Shell and Oriented Deposition toward a Highly Reversible Fe Anode for All-Iron Flow Batteries

Title: Simultaneous Regulation of Solvation Shell and Oriented Deposition toward a Highly Reversible Fe Anode for All-Iron Flow Batteries

Abstract: All-iron flow batteries (AIFBs) have gained significant attention as a promising energy storage solution due to their cost-effectiveness and environmental sustainability. However, the development of highly reversible iron anodes remains a challenge due to the irreversible Fe(II)/Fe(III) redox reaction and the formation of insulating Fe(III) precipitates. In this study, we propose a novel approach for simultaneous regulation of the solvation shell and oriented deposition of iron ions to achieve a highly reversible Fe anode for AIFBs.

By carefully selecting and optimizing the electrolyte composition, we control the solvation shell around Fe(II) ions, minimizing the formation of Fe(III) precipitates and enhancing the reversibility of the redox reaction. We demonstrate that the addition of a specific complexing agent significantly improves the solubility of Fe(II) species and prevents the precipitation of Fe(III) compounds. This leads to a more stable and reversible Fe(II)/Fe(III) redox couple.

Furthermore, we introduce a modified electrode design that promotes the oriented deposition of Fe(II) species on the anode surface. By incorporating a tailored surface coating and nanostructuring techniques, we achieve a highly ordered and compact Fe deposit, minimizing the formation of dendrites and enhancing the overall cycling stability of the anode.

The combination of solvation shell regulation and oriented deposition enables the development of a highly reversible Fe anode for AIFBs. Electrochemical studies reveal excellent cycling stability and Coulombic efficiency of the Fe anode, with minimal capacity decay over extended cycles. The proposed approach not only addresses the challenges associated with Fe anodes in AIFBs but also provides insights for the design of high-performance anode materials for other energy storage systems.

Keywords: all-iron flow batteries, iron anode, solvation shell regulation, oriented deposition, reversible redox reaction, nanostructuring, cycling stability, Coulombic efficiency