Breaking the Additive Paradox in Aqueous Aluminum‐Ion Batteries via Weak‐Coordination Asymmetric Electrolyte Chemistry

ABSTRACT Aqueous aluminum‐ion batteries (AAIBs) are compelling for sustainable storage, yet the strong hydrolysis of Al 3+ acidifies the electrolyte, causing corrosion and passivation that necessitate modification. Additives designed to break the rigid Al 3+ solvation shell face a paradox: they often compromise reversibility via either dielectric collapse or kinetic deadlocks. Here, we break this paradox by establishing a weak‐coordination asymmetric electrolyte based on aluminum trifluoromethanesulfonate (Al(OTF) 3 ), dimethyl sulfoxide (DMSO), and fluoroethylene carbonate (FEC). DMSO coordinates to Al 3+ , displacing coordinated water to suppress water activity, but cannot preserve the dielectric environment. FEC compensates via three synergistic functions: high dielectric constant for electrostatic screening, weak hydrogen bonding for solvation asymmetry reinforcement, and reductive decomposition for solid electrolyte interphase(SEI) formation. The sequential coupling of DMSO‐mediated solvation disruption with FEC‐enables dielectric/interfacial compensation accelerates desolvation and stabilizes electrode: a fluorinated SEI enables 2000 h reversible Al plating/stripping, while a spinel‐to‐layer transformation creates a fluorinated interface on vanadium oxide with asymmetric channels, mitigating dissolution. The full cell retains 90.8% capacity after 2000 cycles at 4 A g −1 . By showing that resolving one bottleneck can expose another, this work reframes additive optimization as sequential processes of identifying and compensating coupled failure mechanisms, generalizing a design principle for multivalent aqueous electrolytes.