A Universal Fluorinated Composite Interphase with Self-Healing Function Enabling Long-Cycling Rechargeable Magnesium Batteries

Abstract

Rechargeable magnesium batteries (RMBs) have significant advantages of high energy density, abundant resources and low dendrite tendency, positioning them as highly promising candidates for next-generation post-lithium-ion energy storage systems. However, poor reversibility and severe interfacial passivation at the Mg anode interface have hindered the viability and development of RMBs. In this work, a flexible multi-component fluoride-rich interface layer was constructed by coating organic polymers and inducing the reaction of Mg metal and organic magnesium salt. By adjusting the solvation structure of Mg²⁺ at the interface, rapid de-solvation and improved Mg²⁺ transport kinetics have been achieved. Additionally, ion-dipole interactions between-CF₃ functional groups of the polymer and ion group from organic magnesium salt contribute to the enhanced electrochemical stability and self-healing capability of the interface layer during electrochemical cycling in various electrolytes. In consequence, the symmetric cells with modified Mganode demonstrates superior cycling stability for over 3500 hours. Full cells assembled with the B-PC@Mg anode, paired with either a novel polyanthraquinonylimid e-based composite cathode or a conventional Mo_6S8 cathode, deliver significantly improved specific discharge capacities and enhanced capacity retention. This research provides a novel and straight forward strategy for designing Mg anode with high cycling stability in RMBs energy storage system.