One of the major
hurdles in the utilization of metallic lithium
anodes is understanding the Li+ transfer kinetics through
the solid electrolyte interface (SEI) in addition to Li oxidation.
Electrochemical impedance spectroscopy (EIS) combined with temperature
variation provides deeper comprehension and reveals kinetic parameters
of individual processes separately. In this study, we report temperature-dependent
EIS analysis of metallic Li anodes to shed light on the kinetics of
anodic/interfacial processes at different states of charge and wide
temperature ranges (−25 to 75 °C), utilizing lithium thionyl
chloride (Li/SOCl2) and lithium manganese dioxide (Li/MnO2) primary batteries as model systems. We found in both batteries
that the impedance of the SEI processes is highly temperature-dependent
with non-Arrhenius behavior at temperatures greater than 35 °C.
Conversely, the kinetics of the anodic process showed small temperature
dependence that is explained by the Arrhenius equation throughout
the temperature range studied. The results provide a deeper understanding
of the underlying processes separately in metallic Li anodes under
operando and real-time conditions.
Non-linear EIS analysis is gaining wider attention and interest due to the deeper understanding that is provided especially when combined with linear EIS. The nonlinear part of the data can get corrupted due to a number of effects. One of these is the initial transient, which is the response right after excitation signal is applied before a steady-state is reached. In this study, we demonstrate this phenomenon through analyzing simplified Randles’ cells via Kirchoff’s laws. To get rid of the effects of the initial transient, instrument manufacturers typically discard some fraction of the response, the effectiveness of which, as demonstrated here has to be checked.
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