Hydrazide chemistry for durable, dendrite-free zinc anodes: Insights into solvation structures and electrolyte interfaces

The practical application of aqueous Zn-ion batteries (AZIBs) is impeded by intrinsic limitations of Zn metal anode. Herein, benzoyl hydrazine (BH), incorporating multiple functional groups, serves as an electrolyte additive to mitigate interfacial side reactions and thereby enhancing its cycling durability. Experimental characterizations incorporating with theoretical simulations reveal that the BH molecule can not only reconstruct the solvation configuration by replacing the coordinated water of hydrated Zn²⁺, but strengthen hydrogen-bond network by forming strong hydrogen bonds, thus suppressing proton transport and active water decomposition. Additionally, BH molecules adsorb onto the Zn anode surface, establishing a versatile protective interfacial layer: hydrophobic benzene ring ligand can impede the direct desolvation of [Zn(H₂O)₆]²⁺ on the anode surface; nucleophilic sites coordinate desolvated Zn²⁺, modulating its flux to promote uniform Zn deposition and stripping. Consequently, Zn//Zn cells with low dosage of BH display a extended cycle life of 1200 h, and Zn//Cu cells run stably for 600 h with maintaining a high coulombic efficiency of 99.55 %. Moreover, Zn//MnO₂ full cells with 10 mM BH exhibited superior capacity retention after 1400 cycles. This work proposes a practical strategy by harnessing hydrazide chemistry to facilitate the development of AZIBs.