A medicine-inspired hydroxyl-rich equimolar ZnSO4/d-mannitol electrolyte enables horizontally stacked Zn deposition for long-cycling aqueous batteries

Abstract

Dendrite growth and adverse side reactions at the Zn anode often compromise the cycling stability and lifespan of aqueous Zn-metal batteries (AZMBs). Inspired by the high osmotic dehydration effect in medicine, this study introduces an equimolar ZnSO₄/D-mannitol (MNT) electrolyte to stabilize the Zn anodes. Comprehensive spectrochemical characterization and theoretical calculations, coupled with rigorous electrochemical and electroanalytical tests, show that the hydroxyl-rich MNT strongly interacts with water, reducing hydrogen bonds and reshaping solvation structures of hydrated Zn²⁺, thereby effectively suppressing corrosion and side reactions. Furthermore, the preferential adsorption of MNT at the Zn anode surface regulates the interfacial reaction environment, enabling dendrite-free, orderly-stacked and corrosion-less Zn deposition. This is confirmed by backscattered-electron scanning electron microscopy observations on cycled electrodes prepared using a cross-section polisher. As a result, the use of a D-mannitol-enriched ZnSO₄ electrolyte extends the cycle life of Zn||Zn symmetric cells to over 2980 hours and significantly enhances the long-term cycling performance of Zn||PANI (polypyrrole–polyaniline) full cells at a low N/P ratio of 22.48.