Observing the Effect of Architecture on Spiral and Bobbin Lithium Thionyl Chloride (Li/SOCl 2 ) Batteries with Temperature-Dependent Electrochemical Impedance Spectroscopy (EIS)

Abstract

Electrochemical Impedance Spectroscopy (EIS) has been utilized as an in situ, non-destructive diagnostic tool for the comprehensive electrochemical characterization of lithium thionyl chloride (Li/SOCl 2 ) batteries. Li/SOCl 2 batteries come in various geometries or architectures tailored for the application area and required specifications. In this study, detailed EIS studies of spiral and bobbin-type Li/SOCl 2 batteries are performed at different temperatures to investigate the impedance response, calculate the activation energy of various processes, and observe the effect of geometry. An extensive comparison between the two geometries reveals that the processes can be differentiated by their time constants and capacitances. It was observed that the current collector impedance masks the high-frequency response of bobbin-type at elevated temperatures with similar Li redox processes in the middle-frequency region. Additionally, transmission line fit is performed on the bobbin type to investigate diffusion-related cathodic processes. Spiral geometry demonstrates lower impedance response than bobbin geometry. The current collector in bobbin-type dominates the solid-electrolyte interface (SEI) process, whereas spiral-type has no current collector effect. Li oxidation process is observed with similar properties in both geometries. Diffusion-limited cathodic processes are observed in the bobbin case but not in the spiral due to the difference in cell architecture.