Hexamethylenetetramine additive with zincophilic head and hydrophobic tail for realizing ultra-stable Zn anode

Abstract

Aqueous zinc batteries are regarded as one of the promising next-generation energy storage batteries due to their high safety and low cost, however, one of the most important problems limiting their commercialization is the cyclic stability of the zinc anode. Therefore, in this work, we first employed hexamethylenetetramine (HMT) as the electrolyte additive to in-situ construct a Zn-HMT complex film to stabilize the zinc anode. After adding the HMT, its zincophilic head will be prior to adsorbing on the zinc foil to form Zn-HMT complex film and then introduce uniform zinc deposition, and simultaneously the formed Zn-HMT complex with hydrophobic alkyl tail will repel the H2O from combining with Zn2+ to form Zn4SO4(OH)6·nH2O by-product as well as the hydrogen evolution reaction (HER). As a result, the HMT-based electrolyte promotes ultra-stable zinc anode cycling for as long as 2000 h with extremely high average Coulombic efficiency (99.51 %). When applied in the Zn-V2O5 full cell, it also demonstrates outstanding electrochemical performances with a reversible capacity as high as 197.8 mAh/g after 500 cycles. This work provides a simple and effective method for the implementation of high-safety and high-stable aqueous zinc-ion batteries.