Does Cell Polarization Matter in Single-Ion Conducting Electrolytes?

Abstract

Single-ion conducting polymer electrolytes (SIPE) are particularly promising electrolyte materials in lithium metal-based batteries since theoretical considerations suggest that the immobilization of anions avoids polarization phenomena at electrode|electrolyte interfaces. SIPE in principle could allow for fast charging while preventing cell failure induced by short circuits arising from the growth of inhomogeneous Li depositions provided that SIPE membranes possess sufficient mechanical stability. To date, different chemical structures are developed for SIPE, where new compounds are often reported through electrochemical characterization at low current rates. Experimental counterparts to model-based assumptions and determination of system limitations by correlating both models and experiments are rare in the literature. Herein, Chazalviel's model, which is derived from ion concentration gradients, is applied to theoretically determine the limiting current density (JLim) of a SIPE. Comparison with the experimentally obtained JLim reveals a large deviation between the theoretical and practical values. Beyond that, charge-discharge profiles show a distinct arcing behavior at moderate current densities (0.5 to 1 mA cm-2), indicating polarization of the cell, which is not so far reported for SIPE. In this context, by application of various electrochemical and physiochemical methods, the details of cell polarization and the role of the solid electrolyte interphase in producing arcing behavior in the voltage profiles in stripping/plating experiments are revealed, which eventually also elucidate the inconsistency of JLim.