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

Abstract

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.

Electrochemical impedance spectroscopy study of lithium–sulfur batteries: Useful technique to reveal the Li/S electrochemical mechanism

“…On the other side, the characteristic frequency of the MF semicircles in complete (Li/S) and symmetric Li||Li cells are almost identical, with the same amplitude. Therefore, the loop in the MF range can be attributed univocally to the lithium negative electrode, with a main contribution coming from the passivation layer on the lithium surface [20][21][22].…”

“…The LF loop could rather originate from a diffusion processes through passivation layer(s) on Li surface, i.e. thin compact SEI sublayer and porous thicker SEI layer and, at lower frequencies (the tails of the loop at frequencies <10 mHz), from the diffusion process into the electrolyte through the porous separator [22]. This observation is in a good agreement with the report of Woo et al [23] who studied symmetrical Li||Li cell degradation, with the study of J. Fang et al in the four-electrode cell configuration [6], and with the transmission line model used for the investigation of Li dendritic growth in lithium electrode [22].…”

“…Almost identical trend of MF semicircle evolution is observed (Figure 3d). This suggests that the increase of the resistance of that MF loop is due to the increase of the passivation layer on the lithium metal, caused by decomposition of the electrolyte when in contact with Li [11,22].…”

Advances in understanding Li battery mechanisms using impedance spectroscopy - Review

“…results from the study published in ref. [23] The electrolyte used was 20 µL of 1 M LiTFSI in TEGDME:DOL 1:1 (v:v). The electrochemical experiments on the cells were done with a combination of impedance spectroscopy measurements and stripping and deposition cycles on Li||Li symmetrical cells.…”

“…In order to check the validity of such measurements (that potentially include some uncompensated dynamics and additionally is carried out to very low frequencies), we carried out a couple of standard testings such as (i) measurements at different values of excitation signal (testing the linearity of response), (ii) repetition of measurements at given steady state conditions (checking the time invariance of the system) and (iii) Kramers-Kronig analysis (for details see ref. [23]).…”