Transmission Line Model for Description of the Impedance Response of Li Electrodes with Dendritic Growth

A general transmission line model that is able to describe accurately the measured impedance spectra of uncycled and cycled lithium electrodes is introduced. The model has all the essential features that are contained in analytical solutions for determining the impedance response of porous electrodes. In addition to that, it allows easy coupling between the various phenomena met in lithium anodes in contact with a separator: transport through a solid electrolyte interphase film, transport across “live lithium dendrites”, reaction inside “live lithium dendrites”, transport across “dead dendrites”, diffusion in a porous separator, and so forth. The model is used for quantitative analysis of measured impedance spectra collected at different C-rates and after different numbers of charge–discharge cycles. Further, combining impedance spectroscopy with scanning electron microscopy, several unique correlations between the morphological development of lithium anodes and development of impedance spectra are identified and discussed. Finally, several simplified schemes that allow identification of the main degradation or failure mechanism(s) occurring in cycled lithium anodes are presented.