Elucidating Relaxation Phenomena in Lithium Metal Batteries with Odd-Random Phase Electrochemical Impedance Spectroscopy

Abstract

The high reactivity of lithium metal is central to the challenges posed in lithium batteries with solid electrolyte interphase (SEI) and dendrite formation playing a major role in the performance and lifetime of batteries [1]. A wide variety of surface analysis, spectrometric, and spectroscopic techniques have already been deployed to investigate the deposition characteristics and time evolution, but it still remains a big challenge to access the interface region from an in-situ and operando perspective, not to mention the transparency of lithium metal to X-rays which excludes the effective use of many X-ray based techniques.Odd-Random Phase Electrochemical Impedance Spectroscopy (ORP-EIS) is a non-invasive, in-situ and operando technique developed at the Electrochemistry and Surface Engineering (SURF) research group at the Vrije Universiteit Brussel [2].ORP-EIS is a multisine technique which is able to produce instantaneous EIS spectra and also quantifies the noise level, non-linearities and non-stationarities through a selective frequency excitation mechanism. This is especially important in lithium metal systems in which the high reactivity means that the system is continuously evolving after deposition and where if conventional single-sine EIS were to be used, the principle of stationarity would not be respected due to the measurement time being considerably slower than the evolution of the system itself [3].In this presentation we discuss the findings of the first ever ORP-EIS analysis of lithium metal batteries and the behavior observed in the short timespan immediately after lithium deposition onto a copper current collector and how this technique can help to elucidate more of the dynamics with a much greater accuracy and confidence than conventional single-sine EIS measurements.