About the Impact of Lithium Plating on Electrochemical Impedance Spectra of Lithium Ion Batteries
Authors: Shafiei Sabet Pouyan , Witzenhausen Heiko , Ecker Madeleine , Sauer Dirk Uwe 
Published: February 2020

Lithium ion batteries are key to the development of electric vehicles. While on the one hand, their energy and power density needs to be increased, on the other hand their aging behavior needs to be understood as well.
Electrochemical Impedance Spectroscopy (EIS) is a mighty tool to investigate aging processes of batteries [1]. One advantage over e.g. post mortem analysis is its non-invasive character. By using battery models, curve fitting algorithms and also a separation process called ‘Distribution of Relaxation Times’ (DRT), it is possible to separate and track different battery processes throughout different aging states [2]. For example, it is possible to separate and track charge transfer resistances or double layer capacities of the two electrodes [3]. Furthermore, information about diffusion processes of the electrodes can be gathered [4].
Lithium plating is an aging mechanism that is induced by charging a lithium ion battery at relatively low temperatures and/or relatively high charging rates. Charging under these conditions leads to a quick capacity loss, since the intercalation rate of the lithium ions into the anode cannot follow the demanded electrical current [5]. Instead of intercalating into the anode, the active lithium is deposited in a metallic shape at or nearby the anode surface. While this process is theoretically reversible, in practice it is mostly not due to occurring passivation processes. Therefore, it is important to gain a better understanding of the effect.
In order to achieve this goal, several specimen of a lithium ion battery are cycled at conditions which will induce lithium plating. After each cycling process, a checkup including EIS measurements is performed. The impact of the different lithium plating conditions (e.g. different temperatures, different charge currents) on the impedance spectra is investigated. Thus, the impact on lithium plating on the different battery processes (e.g. charge transfer or diffusion) can be deduced. This gives new insight into this important aging mechanism. With the results of this work, improved models can be developed which might prevent lithium plating when used in battery management systems (BMS). Furthermore, a better understanding of lithium plating is gained which might lead to improved cells – resulting in better performance and longer lifetime.
[1] Stefan Käbitz: Untersuchung der Alterung von Lithium-Ionen-Batterien mittels Elektroanalytik und elektrochemischer Impedanzspektroskopie, Dissertation, Aachen, Germany 2016
[2] Heiko Witzenhausen: OpenSource FittingGUI, https://github.com/HWitz/FittingGUI
[3] Heiko Witzenhausen: Elektrische Batteriespeichermodelle: Modellbildung, Parameteridentifikation und Modellreduktion, Dissertation, Aachen, Germany 2017
[4] Madeleine Ecker et. al.: Parameterization of a Physico-Chemical Model of a Lithium-Ion Battery, Journal of The Electrochemical Society, 162 (9) A1836-A1848 (2015)
[5] Madeleine Ecker: Lithium Plating in Lithium-Ion Batteries - An Experimental and Simulation Approach, Dissertation, Aachen Germany, 2016