Attenuating Water Activity Through Impeded Proton Transfer Resulting from Hydrogen Bond Enhancement Effect for Fast and Ultra-Stable Zn Metal Anode

The high activity of water molecules induces notorious side reactions that seriously impair the stability of the Zn metal anode. Inspired by the mechanism of proton transfer in an aqueous solution, ectoine (ET) with a kosmotropic effect is first introduced into the typical aqueous electrolyte of aqueous zinc-ion batteries (ZIBs). The hydrogen bond enhancement brought by the ET additive increases the energy barrier for the reconfiguration of hydrogen bonds, thereby impeding the hopping transport of protons based on the Grotthuss mechanism. The inhibited hydrogen evolution reaction (HER) by impeded proton transfer is strongly proved by in situ electrochemical gas chromatography (EC-GC). The distinctive hydrogen bond enhancement effect of ET results in remarkably improved Zn anode stability while maintaining fast reaction kinetics. Consequently, the Zn//Zn symmetric cell delivers an ultra-long cycle life of 5700 h 1 mA cm⁻²/1 mAh cm⁻² and 2000 h at 5 mA cm⁻²/5 mAh cm⁻² with lower voltage hysteresis, extending a cycling life by >27 and 24 times without sacrificing reaction kinetics.