Microscopic mechanism of ion transport in iodide ionic liquid

 

Research Highlights : Investigate the microscopic mechamism of ion transport in iodide ionic liquid by first-principles calculations

 

Abstract : We investigated the microscopic mechanism of ion transport in iodide ionic liquid, using first-principles calculations. We show that the desorption barrier of polyiodides (I₃⁻or I₅⁻) from the cation is in a similar energy range as or higher than the barrier for the bond dissociation and ensued desorption of neutral iodine (I₂). This suggests that, instead of the physical diffusion of such a negatively charged multiatomic species, the exchange of neutral iodine (I₂) between the polyiodides can be an easier channel for the movement of polyiodide. For the transport of the monoiodide anion (I⁻), we suggest the contribution of the Grotthuss-type ion exchange through the intermediately formed even-member anion (I_2n⁻), in addition to drift and diffusion. As a result, we suggest that, instead of the commonly cited diffusion of the triiodide/iodide (I₃⁻/I⁻) redox couple, the exchange of neutral iodine (I₂) and the Grotthuss-type transport (I⁻) constitute the dominant ion transport mechanism