Dual‐Site Modulation of Mg ²⁺ Desolvation Beyond the Primary Solvation Shell in Magnesium Battery Electrolytes

Abstract

Abstract High overpotential and instability of Mg anode reactions limit the development of halide‐free Mg battery electrolytes. Here, we report 7‐aminoindole (7AID), a predominantly noncoordinating additive that modulates solvation via CH–π and hydrogen‐bonding interactions with both Mg 2+ ‐bound and free ether solvents. These outer‐shell and bulk‐phase interactions weaken Mg 2+ ···solvent binding, enhance solvent mobility, and lower the desolvation barrier. As a result, Mg plating/stripping overpotentials are significantly reduced and interfacial stability is improved. Compared to strongly coordinating additives, this approach suppresses parasitic reactions and enables more stable cycling. This work presents a solvation‐targeted additive design paradigm beyond the primary coordination shell for advancing multivalent battery electrolytes.