Tailored quantum dots as a multifunctional electrolyte additive for highly reversible zinc anodes in alkaline batteries

Abstract

Alkaline aqueous zinc batteries (AZBs) are promising for high safety and high-energy density, but are plagued by the poor reversibility of the zinc anode, manifesting as severe corrosion, hydrogen evolution, and passivation. While electrolyte additives can mitigate these issues, most of them fail to address the sluggish kinetics of the essential Zn/Zn(OH)₄²⁻/ZnO solid-liquid-solid conversion. Herein, we introduce cadmium selenide quantum dots (CdSe QDs) with tailored abundant Cd2+ dangling bonds as a multifunctional electrolyte additive. The QDs species form a uniform dispersion across the electrode interface, significantly suppressing corrosion and hydrogen evolution. Simultaneously, the positively charged Cd dangling bonds act as active sites that adsorb OH-, which lowers the activation energy for the conversion reaction and enhances ion transport. As a result, Zn||Zn symmetric batteries with the QDs additive exhibit longer cycle stability, lasting over 220,000 s at 5 mA cm-2, while that of KOH + ZnO is just around 30,000 s. This superiority is also validated in Zn-Ni full batteries, which demonstrate longer cycle life and higher capacity for the CdSe QDs system. This work presents a novel strategy of using functional QDs as electrolyte additives to simultaneously stabilize the interface and promote reaction dynamics, paving the way for high-performance alkaline zinc-based batteries.