A variety of solvents, electrolytes, and additives are tested to optimize the electrolyte. Several different solvents were tested: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dimethoxyethane (DME), and dioxolane. These solvents were tested in different combinations with three electrolytes: sodium perchlorate (NaClO4), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), and sodium hexafluorophosphate (NaPF6). Lastly additives were tested in combination with above cases to test how they improve the electrolyte. The ionic liquid, 1-Butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI) and lithium nitrate (LiNO3) were tested as additives.
We look at the overpotential to gauge the effectiveness of the electrolytes by cycling symmetrical Na/Na cells. An example of the cycling with EC/PC/DEC and NaClO4 electrolyte is shown in the below Figure 1.
1. L. Xin, X. Huang, H. Xu, Y. Zhang, J. Lam, J. Cheng and J. A. Rogers, Adv Mater 26, 3879-3884 (2014).
2. A. Ponrouch, D. Monti, A. Boschin, B. Steen, P. Johansson and M. R. Palacin, J. Mater. Chem. A, 3, 22 (2015).