## 3 Results
### Ftir  
To evaluate the solvation of the Li\({}^{+}\) and B\({}_{12}\)H\({}_{12}\)\({}^{-2}\) ions in the different solvents, FTIR was utilized to monitor the changes in the vibrational modes of selected functional groups responsible for the solvation. Figure 6a shows the FTIR of pure PC (black) and the PC-Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\) electrolyte (red) with selected vibrational modes identified. The formation of new vibrational modes is evident in the presence of the salt. The differences are highlighted in the \(\Delta\) Transmittance plot (green) in the bottom frame of the figure. The \(\Delta\) Transmittance plot is obtained by subtracting the normalized spectrum of pure PC from PC-Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\) (red spectrum-black spectrum). The negative peaks in this portion of the figure highlight the formation of new peaks formed by the interaction of PC with the dissolved salt. It is known that the shift in the carbonyl resonance (C=O) to lower wavenumbers and the shift of the carbonate ring structure (O-CH\({}_{2}\), O-C-O, and C-O) to higher wavenumbers is consistent with the solvation of a Li\({}^{+}\) with 4 PC molecules as previously shown for LiClO\({}_{4}\) in PC [54]. The B-H stretching mode of Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\) powder (blue) and PC-Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\) electrolyte (red) is shown in Figure 6b. A dual peak is shown for the B\({}_{12}\)H\({}_{12}\)\({}^{-2}\) due to the unsymmetrical Li\({}^{+}\) environment around the cage in the solid state. Upon dissolution in PC, the peak coalesces into one peak and is consistent with a symmetrical solvation environment around the B\({}_{12}\)H\({}_{12}\)\({}^{-2}\). Similar behavior has been observed for a Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\).7 NH\({}_{3}\) complex in which the Li\({}^{+}\) are displaced from the B\({}_{12}\)H\({}_{12}\)\({}^{-2}\) and solvated by NH\({}_{3}\)[55]. It is likely that a similar process is occurring when Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\) is dissolved in PC. The solvation of the B\({}_{12}\)H\({}_{12}\)\({}^{-2}\) is likely achieved by interacting with the electropositive portion of the PC ring (-CH\({}_{2}\)-CH\({}_{2}\)-CH(CH\({}_{3}\))-) rather than the electronegative carbonate portion which favors Li\({}^{+}\) solvation. Figure 6: Selected FTIR regions for PC and the PC-Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\) electrolyte at 20 \({}^{\circ}\)C, (**a**) PC liquid (black), PC with Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\) (red), the difference between the transmittance of the PC solvent with and without the added Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\) (green). The dashed lines indicate selected modes of PC (**b**) B-H stretching region of the B\({}_{12}\)H\({}_{12}\)\({}^{-2}\), Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\) dry powder (blue), (1:1) PC with Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\) (red). Figure 7a shows the FTIR of a pure (1:1) EC-DMC mixture (black) and the EC-DMC -Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\) electrolyte (red) with the corresponding peaks of the two carbonates labeled. It is clear that the addition of Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\) interacts with both EC and DMC based on the changes in peak intensity and formation of new peaks. The \(\Delta\) Transmittance plot (green) in the bottom panel highlights the formation of new peaks (negative) and is consistent with EC and DMC facilitating the solvation of Li\({}^{+}\) as previously shown in a EC-DMC-LiClO\({}_{4}\) electrolyte [56]. It is likely that this creates a relatively dynamic solvation environment in this system with multiple energetically similar solvation environments unlike the single component PC solvate. These multiple environments could lead to more disorder in the system and help to create a more mobile Li\({}^{+}\), leading to the observed higher ionic conductivity for this electrolyte system. Figure 7b shows a result similar to what was observed for PC-Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\) in the B-H stretching region.