Influence of amphiphilic additives on zinc ion transport in water-based electrolytes for aqueous zinc ion batteries

초록

The effects of oleic acid (OA) additives on Zn ion diffusivity in aqueous zinc-ion battery (AZIB) electrolytes are systematically investigated using molecular dynamics simulations. The amphiphilic nature of OA introduces competing influences on Zn ion transport. The hydrophilic head of OA forms strong interactions with Zn ions, which stabilizes the solvation shell and reduces diffusivity. In contrast, the hydrophobic tail disrupts the solvation structure by weakening Zn ion hydration, thereby enhancing mobility. Since the bulky hydrocarbon chains of OA tails exert a stronger influence than the OA head, Zn ion diffusivity increases at low OA concentrations. However, at higher concentrations, OA tails tend to aggregate and create dead spaces that inhibit Zn ion diffusion. As a result, the relationship between OA concentration and Zn ion diffusivity exhibits a non-monotonic trend, with an optimal concentration that maximizes ion transport. These findings provide fundamental insights into the role of amphiphilic additives in electrolyte performance and highlight the importance of precise concentration control in designing high-performance AZIB electrolytes.

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