Glycerophosphocholine‐Mediated Dual Regulation for Highly Stable Aqueous Iron‐Ion Batteries

ABSTRACT

Iron‐ion batteries (FeIB) offer the advantages of low cost and high capacity, demonstrating potential for large‐scale energy storage. However, severe hydrogen evolution reaction (HER) occurs during cycling, which significantly impacts battery lifespan. Herein, we propose glycerophosphocholine (GPC) as an electrolyte additive to enable dual regulation of the iron anode interface and the Fe ²⁺ solvation structure, thereby suppressing the hydrogen evolution reaction (HER) and enhancing battery stability and Coulombic efficiency (CE). Because of the negative electric field at the iron anode surface, positively charged choline ions adsorb preferentially, occupying active sites and thereby suppressing HER. The phosphate group and glycerol backbone interact strongly with Fe ²⁺ ions, thereby permeating their solvation structure. This reduces the coordination number and reactivity of water molecules, minimizing side reactions. Therefore, the modified electrolyte Fe||Fe symmetric cell exhibits ultra‐long cycling performance exceeding 2250 h with an average CE of 94%. Meanwhile, in the Fe|| Polyaniline (PANI) full cell, the capacity retention rate reached 81.8% after 300 cycles at 0.1 A g ⁻¹ . This study offers new solutions and relevant insights for the design of highly stable FeIB.