## 3 Results
### Electrochemical Properties
The synergistic effect of the high \(\varepsilon\) component (EC) and the low \(\eta\) component (DMC) helps to dissolve the Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\) and allows the least restriction to ion migration. PC has moderate \(\varepsilon\) and \(\eta\) values relative to the series leading to the intermediate ionic conductivity. The BMIM has an extremely high \(\eta\) and a relatively low \(\varepsilon\) value leading to the observed lower ionic conductivity for this electrolyte. To evaluate the stability and compatibility of the electrolytes with a lithium metal electrode, symmetrical cells (Li/electrolyte/Li) were assembled and cycled at different current densities (Figure 2). The EC-DMC electrolyte showed the lowest voltage hysteresis followed by PC and BMIM-TFSI which is consistent with the ionic conductivity measurements. In all three of the tested solvents, they showed compatibility with the metallic lithium electrodes and there was no obvious indication of shorting due to dendrite formation for the constant current cycling tested at the indicated current densities. However, it will be necessary to perform additional extended cycling and characterization of the 3 electrolyte systems to confirm this finding (Figure S1). Figure 1: (**a**) Ionic conductivity in EC-DMC as a function of the weight % of Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\) suspended in EC-DMC liquid. (**b**) Ionic conductivity as a function of temperature (25 to 60 \({}^{\circ}\)C) for the three different solvents containing 0.5 M Li\({}_{2}\)B\({}_{12}\)H\({}_{12}\). Demonstrating compatibility with lithium metal anodes is essential for the development of new electrolyte systems and salts. The lithium metal anode has an extremely high theoretical specific gravimetric and volumetric capacities (3860 mAh/g and 2061 mAh/cm\({}^{3}\)) and the lowest negative electrochemical potential (\(-\)3.04 V vs. SHE) [49]. This would allow a significant enhancement in the gravimetric and volumetric capacity of commercial LIB if it replaced the graphite anode (350 mAh/g and 760 mAh/cm\({}^{3}\)). However, a major hurdle to overcome is the formation of lithium dendrites during the deposition of lithium from the cathode onto the lithium metal anode [50]. This requires the uniform deposition of lithium and minimization of \"hotspots\" that facilitate dendrite growth upon subsequent cycles. The evaluation of in-situ and ex-situ monitoring of the lithium deposition on the surface of the metallic lithium anode is currently under investigation for this series of electrolytes to confirm. Figures 3-5 show the galvanostatic cycling data for the three different solvent systems with LTO, TiS\({}_{2}\), and PTCDI respectively at the indicated cycling rates. For the anode LTO (Figure 3) the two carbonate-based electrolytes (PC and EC-DMC) display a relatively small loss in capacity as the cycle rate is increased from 0.1 C (10 h charge or discharge) up to 10 C (6 min charge or discharge). Both of these electrolytes show excellent and stable capacity retention up to 300 cycles at a rate of 2 C. The difference in capacity between the two carbonate electrolytes after 300 cycles is less than 4%. The BMIM-TFSI electrolyte shows a significant capacity loss as the cycling rate is increased and has zero capacity at 10 C. The behavior of the cells prepared with the BMIM-TFSI also show very erratic and unstable cycling profile. The profile shown in Figure 3 is a typical example of the behavior observed for this electrolyte. The cycle stability of the TiS\({}_{2}\) cathode is shown in Figure 4 for the solvent systems. The EC-DMC electrolyte clearly showed a higher capacity retention over the PC electrolyte up to 5 C. However, both of the carbonate electrolytes do not show any capacity at the high cycling rate at 10 C. During extended cycling at 2 C up to 300 cycles the EC-DMC electrolyte clearly outperforms the PC electrolyte by maintaining a 178 mAh/g capacity versus 154 mAh/g.