Energetics and\nDynamics of Metal-Ion Coordination\nwith Ionic Liquid Electrolytes: A Combined DFT and AIMD Investigation\nfor Rechargeable Batteries

In\nthis work, we have employed density functional theory\ncalculations\nand <i>ab initio</i> molecular dynamics (AIMD) simulations\nto identify suitable ionic liquids (ILs) as better electrolytes for\nrechargeable lithium (Li<sup>+</sup>), sodium (Na<sup>+</sup>), potassium\n(K<sup>+</sup>), magnesium (Mg<sup>2+</sup>), and aluminum (Al<sup>3+</sup>) ion batteries. We have considered 12 different ILs which\ninclude imidazolium, pyridinium, pyrrolidinium, piperidinium cations,\nand [BF<sub>4</sub>], [Cl], [DCA], [FSI], and [TFSI] anions for the\ncalculations. Interaction studies were carried out between the ILs\nand Li<sup>+</sup>/Na<sup>+</sup>/K<sup>+</sup>/Mg<sup>2+</sup>/Al<sup>3+</sup> ions. In particular, we investigated the structural, electronic,\nand thermochemical properties to decode the binding and solvation\nproperties of Li<sup>+</sup>/Na<sup>+</sup>/K<sup>+</sup>/Mg<sup>2+</sup>/Al<sup>3+</sup> solvated by [FSI]/[TFSI]/[DCA] anions. Lastly, AIMD\nsimulations are carried out to investigate the structural and dynamical\nchanges in the solvation shell surrounding Li<sup>+</sup> in the ILs\nand anions environments. In the Li<sup>+</sup>-ILs systems, the Li<sup>+</sup> ions are mostly coordinated by the atoms present in the anions.\nIn Li<sup>+</sup>-[anion] systems, the oxygen atoms of [FSI] and [TFSI]\nare more coordinated around the Li<sup>+</sup> ions. The nitrogen\natoms are coordinated to Li<sup>+</sup> to form the aggregates in\nthe Li<sup>+</sup>-DCA system. The highest self-diffusion coefficient\n(<i>D</i><sub>s</sub>) of Li<sup>+</sup> is calculated to\nbe 5.61 × 10<sup>–10</sup> m<sup>2</sup>/s in [EMIM]-[FSI]\nwhen compared to [EMIM]-[DCA] and [EMIM]-[TFSI]. In an anion environment,\nLi<sup>+</sup>-[FSI] shows the highest <i>D</i><sub>s</sub> value of 3.69 × 10<sup>–10</sup> m<sup>2</sup>/s. Therefore,\nit can be concluded that the Li<sup>+</sup>-ion solvation shell formation\nand diffusion in ILs are primarily influenced by the nature of the\nanions. In summary, our work reveals the solvation properties of ILs\nand their stability which offers new guidelines for designing more\nreliable electrolytes for rechargeable batteries.