IL-Based Electrolytes

As shown in Table 2.10, imidazolium-based ILs generally provide higher ionic conductivity whereas pyrrolidinium-based ILs exhibit larger electrochemical stability. It appears that a trade-off between the ionic conductivity and electrochemical stability of ILs exists. As mentioned previously, the operative cell voltages of commercial organic electrolyte-based EDLCs are generally restricted to 2.5-2.8 V, 

Electrochemical Stability and Conductivity Measured at Room Temperature for a Range of ILs [369,505] 

Source Reprinted from Journal of Power Sources, 173, Lewandowski, A., and M. Galinski, Practical and theoretical limits for electrochemical double-layer capacitors, 822-828, Copyright 2007, with permission from Elsevier. 

FIGURE 2.49 Basic types of ILs aprotic, protic, and zwitterionic types. (Reprinted by permission from Macmillan Publishers Ltd. Nature Materials Armand, M. et al. 2009. Ionic-liquid materials for the electrochemical challenges of the future. 8 621-629, copyright 2009.) 

Tetrafluoroborate Hexafluorophosphate Bis(Fluorosulfonyl)imide Bis(Trifluoromethanesulfonyl)imide [BF4]- [PF r [FSIJ- [TFSI]- 

---

The mechanism of lithium transport was also studied in [pyri3][TFSI] + 0.25 LiTFSI [86]. The LL cation transport was found to occur primarily by exchanging TFSF anions in the first coordination shell of a LL with a smaller ( 30%) contribution also due to Li" cations diffusing together with their first coordination shell. It is important to note that despite high conductivity of IL-based electrolytes ( 10 S/cm) the hthium contribution to the charge transport remains quite low. 

In conclusion, it is expected that both ethereal solutions and a variety of IL-based electrolyte systems may be suitable for reversible Mg electrochemistry. 

---