Molecular Structure Engineering Enables Stable Zn Metal Interfaces and Fast Kinetics in Aqueous Zinc Batteries

ABSTRACT

Aqueous rechargeable zinc batteries are promising for large‐scale energy storage but suffer from water/proton‐induced parasitic reactions and unstable Zn deposition in conventional mildly acidic ZnSO ₄ electrolytes. However, suppressing parasitic reactions often comes at the expense of Zn ²⁺ transport kinetics. Here, we introduce 3‐methylglutaric acid (MGA) as a structurally tailored molecular additive to simultaneously regulate Zn ²⁺ solvation and interfacial chemistry. The tailored molecular configuration of MGA enables synergistic modulation of electrolyte acidity and interfacial steric environment, thereby suppressing water/proton‐induced side reactions and stabilizing Zn deposition, while maintaining favorable Zn ²⁺ desolvation and fast kinetics. With MGA, Zn//Zn symmetric cells operate stably for 7050 h at 1 mA cm ⁻² /0.5 mAh cm ⁻² and sustain continuous cycling for 200 h at a depth of discharge of 73%. Zn//Cu cells deliver 2000 cycles at 2 mA cm ⁻² /1 mAh cm ⁻² with an average Coulombic efficiency of 99.9%. Moreover, Zn//NH ₄ V ₄ O ₁₀ full cells achieve 12 000 highly stable cycles at 5 A g ⁻¹ . This work highlights molecular structure engineering as an effective strategy to concurrently stabilize Zn metal interfaces and maintain rapid reaction kinetics for high‐performance aqueous Zn batteries.