Homologous Fatty Acid Additives for Simultaneous Corrosion Suppression and Zn 2+ Transport Enhancement in Aqueous Zinc‐Ion Batteries

Aqueous zinc‐ion batteries represent a compelling pathway toward safe and low‐cost grid‐scale energy storage. Yet, the persistent instability of the zinc anode, given by dendrite formation, hydrogen evolution, and corrosion, remains an obstacle to their practical deployment. Here, we report on the use of medium‐chain fatty acids, namely lauric acid (C 12 ), tridecanoic acid (C 13 ), and myristic acid (C 14 ), as electrolyte additives in 1 M ZnSO 4 . They are used to mitigate side reactions at the zinc anode, combining a Zn 2+ ‐coordinating carboxylate head group with a self‐assembling hydrophobic alkyl tail. Dissolved as sodium salts to overcome the inherent aqueous solubility limitations of fatty acids, these additives suppress parasitic side reactions while maintaining facile Zn 2+ transport. Among the additives tested, C 12 provided the most stable symmetric‐cell cycling and lowest overpotential, while C 14 offered the best full‐cell capacity retention, underscoring that additive selection should be guided by the intended application and evaluation metric rather than by a single universal “best” additive. The poor performance of the odd‐chain C 13 system further indicates a proposed odd‐chain packing parity effect as a critical and previously overlooked design parameter. Our findings show that fatty acids are a well‐suited tunable additive for stabilizing zinc anodes.