Enhancing Zn-Ion Battery Performance with Thioacetamide Electrolyte Additive

Zn-ion batteries (ZIBs) are emerging as a next-generation energy storage solution, characterized by enhanced safety, cost-effectiveness, and a more abundant resource base compared to their flammable, naturally occurring counterparts. Distinctively, ZIBs employ a Zn-metal anode and a Zn-ion (Zn²⁺) storage cathode, resulting in a substantial theoretical capacity (820 mAh g^-1 or 5850 mAh cm^-3) and a low redox potential of −0.76 V versus the Standard Hydrogen Electrode (SHE). Nevertheless, ZIBs confront several challenges, including limited charge-discharge reversibility attributed to the formation of Zn dendrites via the hydrogen evolution reaction (HER), uneven Zn electrodeposition, and the presence of electrochemically inert by-products such as ZnO, Zn(OH)₂, and ZnSO₄[Zn(OH)₂]₃-<i>x</i>H₂O. To resolve these issues, a range of methodologies has been explored, encompassing innovations in Zn electrode design, separator development, and the exploration of electrolyte additives.<br/>In this study, the electrochemical characteristics and transformations on the Zn-metal surface were investigated by employing Thioacetamide (TAA) as an electrolyte additive within the aqueous liquid electrolyte of Zn-ion batteries. The primary objective of this research is to reduce the formation of the aforementioned Zn dendrites and byproducts while aiming to achieve a uniform Zn-metal surface deposition. TAA, characterized by primary amine functional groups, is recognized for its electrochemical activity, primarily attributable to the sulfur (S) present in the thioamide species, which tends to actively participate in electrochemical reactions. Furthermore, TAA undergoes hydrolysis within the electrolyte, resulting in the generation of weak acid by-products such as hydrofluoric acid and acetic acid, thereby facilitating the removal of impurities and contributing to a smooth deposition process. Consequently, TAA emerges as a promising functional additive capable of controlling the Zn electrodeposition process.