Localized High‐Concentration Electrolyte with Water‐Miscible Diluent Enables Stable Zinc Deposition and Long‐Life Aqueous Zinc Metal Batteries

ABSTRACT Electrolyte engineering has emerged as a pivotal strategy to address critical challenges in aqueous zinc metal batteries (AZMBs), including zinc dendrite growth, parasitic side reactions, and anode corrosion. While conventional regular‐concentration electrolytes (≤2 mol L −1 ) fail to mitigate these issues, high‐concentration electrolytes (≥3 mol L −1 ) have demonstrated improved interfacial stability but suffer from high costs, limiting their practical applicability. Inspired by the concept of localized high‐concentration electrolytes (LHCEs) in non‐aqueous systems, we report a novel aqueous LHCE by introducing diisopropyl ether (DIPE) as a cost‐effective, inert diluent. This tailored electrolyte enables the simultaneous formation of robust solid electrolyte interphase and cathode electrolyte interphase on zinc anodes and NaV 3 O₈·1.5H 2 O cathodes, respectively, significantly enhancing interfacial stability and suppressing side reactions. Molecular dynamics simulations and spectroscopic analyses reveal that although DIPE is excluded from the Zn 2 ⁺ solvation sheath, it effectively modulates the solvation environment, suppresses water activity, and directs uniform Zn deposition along the (002) plane. Consequently, the DIPE‐based LHCE delivers a high coulombic efficiency of ∼99.7% over 700 cycles in Zn//Cu half‐cells (1 mA cm − 2 , 1 mAh cm − 2 ), demonstrating outstanding reversibility and long‐term cycling stability. Beyond demonstrating a practical electrolyte formulation, this work establishes a general design principle for aqueous LHCEs, using water‐miscible, weakly coordinating diluents to decouple bulk salt concentration from interfacial coordination, and provides mechanistic guidance for extending LHCE strategies to other zinc‐based and multivalent metal battery systems.