Practical relevance of charge transfer resistance at the Li metal electrode|electrolyte interface in batteries?

The theoretically possible energy and power densities of rechargeable batteries are practically limited by resistances as these lead to overvoltages, particularly pronounced at kinetically harsher conditions, i.e., high currents and/or low temperature. Charge transfer resistance (R_ct), being a major type of resistance alongside with Ohmic (R_Ω) and mass transport (R_mt), is related with the activation hindrance of electrochemical reactions. Its practical relevance is discussed within this work via analyzing  \(\mathrm{Li}\mid \,\, \mid\mathrm{Li}\) $\mathrm{Li}\mid \mid \mathrm{Li}$  cells with the galvanostatic/constant current (CC) technique. R_ct at Li|electrolyte interfaces is shown to be relevantly impacted by electrode–electrolyte interphases; implying the electrolyte type, as well. While solid polymer electrolytes (SPEs), e.g., based on poly(ethylene) oxide (PEO), show negligible R_ct, it is evident for commercial liquid electrolytes and readily increase during storage. Given the asymptotic overvoltage vs. current behavior of R_ct, obeying Butler-Volmer equation, R_ct gets less relevant at enhanced currents, as experimentally validated, finally pointing to the dominance of R_Ω and (depending on system) R_mt in the overall resistance.