Highly stable and reversible Zn anodes enabled by an electrolyte additive of sucrose.

ABSTRACT

Aqueous zinc-ion batteries (ZIBs) are one of the most promising candidates for electric energy storage devices due to their merits of low cost and high safety. However, the notorious side reactions and dendrite formation on zinc anodes impede the commercialization of ZIBs. In this work, a cheap and edible electrolyte additive sucrose is applied to address the above issues. Sucrose with hydroxyl groups can react as zincophilic sites to adsorb Zn2+. As verified by Raman and FT-IR spectroscopy, the solvation structure of Zn2+ and the hydrogen bonds can be regulated by the sucrose molecule. The weakened solvated structure of Zn2+ and lowered coupling degree between Zn2+ and SO42- can inhibit the hydrogen evolution reaction (HER) and the generation of the sulfate by-product. Furthermore, a solid electrolyte interphase (SEI)-like ion buffer layer is formed because of the preferentially adsorbed sucrose, which can increase the nucleation overpotential and equalize the ion distribution. The enriched Zn nucleation sites and inhibited 2D diffusion of Zn2+ resulting from the sucrose additive enable uniform Zn deposition. Thus, improved performances of symmetric Zn||Zn, asymmetric Zn||Cu and Zn||VO2 cells are realized. The Zn||Zn cell exhibits a highly reversible cycling performance for 1200 h and 400 h at 5 mA cm-2/1 mA h cm-2 and 10 mA cm-2/5 mA h cm-2, respectively. This work provides a readily available and edible additive to improve the performance of ZIBs.