**4. Conclusions**

Two di fferent electrolytes, (1 M LiPF6 in EC/DMC (1:1 *v*/*v*) and 1 M LiTFSI in 60% EMI-TFSI 40% EC/DMC (1:1 *v*/*v*) with 5 wt% SN), were synthesized, characterized electrochemically, and compared using lithium anode (or cathode) half-cells with either a SnO2/C anode or a LiCoO2 cathode. The SnO2/C composite-fiber electrode was prepared by forcespinning of a PAN/SnO2 precursor solution and subsequent thermal treatment. The electrochemical performance results showed that lithium

anode half-cells with a SnO2/C composite-fiber electrode in 1 M LiTFSI in 60% EMI-TFSI 40% EC/DMC (1:1 *v*/*v*) and 5 wt% SN perform better than that with commercial organic liquid electrolyte. The use of ionic liquid electrolyte with 5 wt% SN in lithium anode half-cells with a SnO2/C electrode demonstrated good cycling stability and capacity retention after 100 charge/discharge cycles. The results showed that 1 M LiTFSI in 60% EMI-TFSI 40% EC/DMC (1:1 *v*/*v*) with 5 wt% SN had a higher ionic conductivity than 1 M LiPF6 in EC/DMC (1:1 *v*/*v*) electrolyte. The electrochemical performance of a commercial LiCoO2 cathode was evaluated at 60 ◦C using lithium cathode half-cells with MOILEs, both without and with SN electrolytes. The commercial LiCoO2 cathode was evaluated electrochemically at 60 ◦C, cycled with 1 M LiTFSI in 60% EMI-TFSI 40% EC/DMC (1:1 *v*/*v*) and 5 wt% SN and had an excellent performance. The LiCoO2 cathode in 60% EMI-TFSI 40% EC/DMC (1:1 *v*/*v*) and 5 wt% SN showed good electrochemical performance at 60 ◦C, which was attributed to the high ionic conductivity of the MOILE/SN at elevated temperature.

**Author Contributions:** For research articles with several authors, a short paragraph specifying their individual contributions must be provided. The following statements should be used "Conceptualization, M.A.methodology, S.A.C. and J.V.; validation, J.V. and and S.A.C.; formal analysis, J.V.; investigation, J.V. and S.A.C.; data curation and analysis, J.V. and R.O.C.; writing J.V.; R.O.C. and M.A.—original draft preparation, J.V., and M.A.; writing—review and editing, M.A. and T.P.L.; supervision, M.A. and T.P.L.; funding acquisition, M.A. and T.P.L. All authors have read and agreed to the published version of the manuscript."

**Funding:** This research was supported by NSF PREM award under gran<sup>t</sup> No. DMR-1523577: UTRGV-UMN Partnership for Fostering Innovation by Bridging Excellence in Research and Student Success. Part of this work was carried out in the College of Science and Engineering Characterization Facility, University of Minnesota, which has received capital equipment funding from the NSF through the UMN MRSEC program under Award Number DMR-1420013.

**Acknowledgments:** This research was supported by NSF PREM award under gran<sup>t</sup> No. DMR-1523577: UTRGV-UMN Partnership for Fostering Innovation by Bridging Excellence in Research and Student Success. Part of this work was carried out in the College of Science and Engineering Characterization Facility, University of Minnesota, which has received capital equipment funding from the NSF through the UMN MRSEC program under Award Number DMR-1420013.

**Conflicts of Interest:** The authors declare no conflict of interest.
