Water-attracting adsorbates for enhancing the cyclability of Zn anodes in aqueous Zn-ion batteries

Abstract

Aqueous Zn-ion batteries (AZIBs) are promising candidates for large-scale energy storage systems (ESSs) due to their inherent safety. However, several challenges, including limited cyclability, hinder their commercialization. A key challenge in AZIBs is the non-uniform Zn growth on the anode, which induces dendrite formation and ultimately short circuits. Additionally, side reactions such as hydrogen evolution and Zn corrosion further deteriorate the cyclability of AZIBs. Modifying electrolytes with additives is a promising approach to overcoming these challenges. Additives adsorb onto the Zn surface, regulating Zn deposition and suppressing side reactions. Conventional explanations, such as facet-dependent capping and electrostatic shielding, have been widely used to describe how additives inhibit dendrite growth. However, these mechanisms alone do not fully explain additive behavior, limiting the rational design of effective additives. To gain deeper insights into additive design, this study elucidates the role of hydroxyl functional groups in promoting uniform Zn growth. Phloroglucinol, a benzene derivative with three hydroxyl groups, uniformly adsorbs onto the Zn surface, where its hydroxyl groups attract water molecules in hydrated Zn ions. This interaction facilitates uniform Zn nucleation and lowers water activity, mitigating side reactions. Consequently, Zn symmetric cells with phloroglucinol exhibited markedly enhanced cyclability over additive-free cells.