The effect of separator and electrolyte solution on cross-talk phenomena in sodium metal batteries with propylene carbonate based electrolyte solutions

In this work we studied the effects of the separators’ nature and the composition of electrolyte solutions based on propylene carbonate (PC) on the initial irreversible capacity, cycling performance of Na|Ni 0.33 Fe 0.33 Mn 0.33 O 2 (NFM) and Hard Carbon (HC)|NFM cells with practical loading of the electrodes. Parasitic cross-talk processes which develops during the initial charging of Na|NFM cells hamper the surface passivation of the electrodes and interfere badly with the cathodes’ charging processes. Through X-ray photoelectron spectroscopy (XPS) we established a crucial effect of the separators’ type on the passivation efficiency of Na metal anodes during the initial charging. We also discuss the effect of the linear carbonate, ethyl methyl carbonate (EMC), on the development of cross talk processes with PC-based electrolyte solutions and the composition of the surface films formed on Na metal anodes and NFM cathodes.