Inert Group-Containing Electrolyte Additive Enabling Stable Aqueous Zinc-Ion Batteries

Aqueous zinc ion batteries (AZIBs) are considered promising energy storage devices because of their high theoretical energy density and cost-effectiveness. However, the ongoing side reactions and zinc dendrite growth during cycling limit their practical application. Herein, trisodium methylglycine diacetate (Na3MGDA) additive containing the additional inert group methyl is introduced for Zn anode protection, and the contribution of methyl as an inert group to the Zn anode stability is discussed. Experimental results reveal that the methyl group with various effects enhances the interaction between the polar groups in Na3MGDA and the Zn2+/Zn anode. Thus, the polar carboxylate negative ions in MGDA anions can more easily modify the solvation structure and adsorb on the anode surface in situ to establish a hydrophobic electrical double layer (EDL) layer with steric hindrance effects. Such the EDL layer exhibits a robust selectivity for Zn deposition and a significant inhibition of parasitic reactions. Consequently, the Zn||Zn symmetric battery presents 2375 h at 1 mA cm-2, 1 mAh cm-2, and the Zn||V6O13 full battery provides 91% capacity retention after 1300 cycles at 3 A g-1. This study emphasizes the significant role of inert groups of the additive on the interfacial stability during the plating/stripping of high-performance AZIBs. The methyl group in additive trisodium methylglycine diacetate (Na3MGDA) enables the MGDA anion more easily to replace the active water in the solvation structure and adsorb at the interface to form a hydrophobic EDL layer with spatial effect, thus significantly alleviating the water-induced side reactions during the deposition process and promoting the homogeneous Zn deposition.image