Ionic buffer layer design for stabilizing Zn electrodes in aqueous Zn-based batteries

Aqueous Zn-based batteries (AZBs) are hindered by issues associated with the Zn electrodeposition process (ZEDP) on electrode surfaces, including passivation, dendrite formation, and hydrogen evolution. One of the important reasons is the drastic fluctuation in the concentration of Zn 2+ ions on the electrode surface during the charging and discharging process. In this work, an electrolyte with Zn 2+ ion buffer layer (EZIBL) is proposed to regulate the ZEDP. First, numerical simulations and corresponding experiments are conducted to assess the impact of different thicknesses of the Zn 2+ ion buffer layer (ZIBL) on the variation in Zn 2+ ion concentration, from which the optimal thickness of the ZIBL is determined. Then, the regulation role of EZIBL in the cycling process is demonstrated by a Zn-Cu half cell. Further, combined with the potential profile of the symmetric cell and the experimental phenomena, the regulation role of EZIBL in ZEDP is systematically explained at the mechanistic level through the analysis of key parameters. Finally, a full battery composed of Zn-LiMn 2 O 4 is assembled to evaluate the practical applicability of the EZIBL in real battery cycles, which shows great enhancement in capacity retention and coulombic efficiency. This work proposes the design of the EZIBL used to regulate the ZEDP and provides a simple, low-cost regulation method for the development of high-performance AZBs. • An electrolyte with an ion buffer layer is designed to achieve uniform Zn deposition. • The hydrogen evolution reaction is alleviated by this electrolyte design. • Regulation mechanism is illustrated by combining simulations and experiments. • This electrolyte design is a low cost and simple method to regulate Zn deposition. • The applicability of this electrolyte design in practical use is validated.