Complete Electrochemical Characterization and Limiting Current of Polyacetal Electrolytes

We investigate a polyacetal-based electrolyte, poly(1,3,6-Trioxocane) (P(2EO-MO)) mixed with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt, and report full electrochemical characterization of the transport parameters and a thermodynamic property in comparison to the previously reported poly(ethylene oxide) (PEO) electrolyte data [D. Gribble et al., J. Electrochem. Soc., 166, A3228 (2019)]. While the steady-state current fraction (?+) of P(2EO-MO) electrolyte is greater than that of PEO electrolyte in the entire salt concentration window we explored, the rigorously defined transference number using Newman s concentrated solution theory ( + t 0) appears to be similar to that of PEO electrolyte. On the basis of full electrochemical characterization, we calculate the salt concentration profile as a function of position in the cell and predict limiting current density (iLL) as a function of salt concentration. Experimental data were compared to the predicted values. The non-monotonic behaviors were observed both in prediction and experimental results with offset peak positions. We find that the limiting current density of P (2EO-MO) electrolyte is systematically lower than that of PEO electrolyte in most of the salt concentrations with the exception of rav = 0.05. It is noteworthy that even though one measure of electrolyte efficacy (?+) is superior in P(2EO-MO) electrolyte, the limiting current density, which is another metric of electrolyte efficacy at high currents, is not greater in P(2EO-MO)