Reversible Secondary‐Solvation‐Shell Regulation Enables Dendrite‐Free Zinc Anodes via a Polarizable Two‐Segment Additive

ABSTRACT Electrolyte additives are an effective approach to suppress dendrite growth and parasitic reactions on Zn anodes. However, additive‐enabled solvation regulation is often limited by poor reversibility during long‐term cycling. Here, we propose a screening strategy for electrolyte additives based on secondary‐solvation‐shell interactions, in which an ideal molecule combines high polarizability with a two‐segment architecture. Guided by these criteria, isopropyl β‐D‐1‐thiogalactopyranoside (IPTG) is identified as a representative additive. Experimental and theoretical analyses reveal that IPTG predominantly resides in the secondary solvation shell and reversibly modulates the Zn ²⁺ solvation environment. IPTG forms an interfacial electrostatic shield that homogenizes Zn ²⁺ transport, promotes (002)‐oriented growth, and enables the in situ formation of an ionically conductive IPTG‐ZnS hybrid solid‐electrolyte interphase. As a result, the Zn||Zn symmetric cell operates stably for 5377 h at 1 mA cm ⁻² and 1 mAh cm ⁻² , and the Zn||Cu cell delivers an average Coulombic efficiency of 99.94% over 10 000 cycles at 8 mA cm ⁻² and 1 mAh cm ⁻² . This work establishes generalizable screening criteria for rational electrolyte‐additive design toward practical aqueous zinc‐ion batteries.