Molecular Crowding Programs Trifluoroacetate-Solvation Nanoclusters for Stable Aqueous Zinc Metal Chemistry

Abstract Aqueous zinc metal batteries offer a safe and cost-effective platform for electrochemical energy storage, yet their practical operation remains limited by water-driven parasitic reactions and spatially heterogeneous Zn deposition. Here, we report a molecule-crowding strategy that programs zinc/sodium trifluoroacetate (Zn(TFA)2/NaTFA) aqueous electrolytes into an anion-rich nanoclustered solvation environment. The balanced affinity of TFA– toward Zn2+ and H2O promotes Zn2+–TFA– association and drives the evolution from water-rich local coordination toward abundant contact ion pairs, ion aggregates, and interconnected multi-ion nanoclusters. Spectroscopic characterization, X-ray scattering, and molecular dynamics simulations collectively reveal reconstructed Zn2+ coordination, extended ion-associated correlations, and reorganization of the water hydrogen-bonding environment, accompanied by reduced water activity. The nanocluster electrolyte suppresses hydrogen evolution and Zn corrosion and promotes more uniform Zn deposition. The optimized nanocluster electrolyte sustains Zn||Zn cycling for over 2100 h, enables Zn||Cu cells to operate for more than 3000 h with an average Coulombic efficiency of 99.4%, and affords Zn||Na2V6O16·3H2O full cells with 82.4% capacity retention after 30,000 cycles at 10 A g–1. These results show that balanced anion interactions and molecular crowding regulate ion association and the water hydrogen-bonding environment, contributing to improved Zn reversibility and cycling stability.