Mechanisms of Ion Transport in Lithium Salt-doped Block Copolymeric Ionic Liquid Electrolytes

We used multiscale simulations to study the mechanisms of ion transport in salt-doped block copolymeric ionic liquid electrolyte and compared with the homo polyIL and monomeric IL counterparts. Consistent with the experimental observations, our simulations indicate that lithium transference number is negative throughout the investigated lithium concentrations when using the polymer center of mass as the reference frame. Further, the mobility of all mobile ions decreases with increase in lithium salt concentration, regardless of the system. In contrast, the lithium transference number in block copolymeric IL and polyIL exhibits completely different trend in comparison with the monomeric system. Further, the Nernst-Einstein conductivities and the true conductivities, which were obtained through non-equilibrium simulations, are presented and compared. We rationalize the observations by presentation of the radial distribution functions, the ion pair associations, hopping frequency analyses. Together, our results demonstrate that the (co-)polymeric ionic liquid electrolytes exhibit different ion transport mechanisms in comparison with the monomeric ionic liquid electrolytes, and the reference frame should be chosen with caution when evaluating the lithium transference number.