Due to the high chemical reactivity of metallic lithium, safety and life-time of Lithium-ion cells are closely related to the aging phenomenon of lithium plating [1–5]. Lithium plating on graphite anodes can occur during charging at low temperatures, high C-rates, and high states-of-charge [1,3,4]. However, lithium deposition depends also on the combination of these parameters and can emerge in cases where it might not have been expected. For instance, lithium deposition can occur in commercial cells [3,4]. For safe and long-life operation of Lithium-ion batteries, lithium plating should therefore be prevented.

Lithium plating is caused by negative anode potentials vs. Li/Li⁺ and can be determined in measurements with a reference electrode (see Figure 1). Furthermore, lithium plating is related to the activity of lithium ions in the electrolyte [5]. For example, it was recently found in our lab that the activity of lithium ions in the electrolyte is changing during the charging process [5]. This is in agreement with the change of the anode potential during charging (see Figure 1).

In the present study, we present results from cells with and without lithium plating. The results are based on accelerated rate calorimetry (ARC) tests, measurements of lithium ion activity and of anode potentials in full cells vs. Li/Li⁺, as well as Post-Mortem results with a variety of physico-chemical analysis methods.

A model is developed to explain the interplay between the main operational parameters influencing lithium plating. This model allows to prevent lithium deposition in commercial cells and therefore to increase safety and life-time significantly.

[1]        N. Ghanbari, T. Waldmann, M. Kasper, P. Axmann, M. Wohlfahrt-Mehrens, Detection of Li Deposition by Glow Discharge Optical Emission Spectroscopy in Post-Mortem Analysis, ECS Electrochem. Lett. 4 (2015) A100–A102. doi:10.1149/2.0041509eel.

[2]        M. Fleischhammer, T. Waldmann, G. Bisle, B.-I. Hogg, M. Wohlfahrt-Mehrens, Interaction of cyclic ageing at high-rate and low temperatures and safety in lithium-ion batteries, J. Power Sources. 274 (2015) 432–439. doi:10.1016/j.jpowsour.2014.08.135.

[3]        J.C. Burns, D.A. Stevens, J.R. Dahn, In-Situ Detection of Lithium Plating Using High Precision Coulometry, J. Electrochem. Soc. 162 (2015) A959–A964. doi:10.1149/2.0621506jes.

[4]        T. Waldmann, M. Kasper, M. Wohlfahrt-Mehrens, Optimization of Charging Strategy by Prevention of Lithium Deposition on Anodes in high-energy Lithium-ion Batteries – Electrochemical Experiments, Electrochimica Acta. 178 (2015) 525–532. doi:10.1016/j.electacta.2015.08.056.

[5]        B.-I. Hogg, M. Wohlfahrt-Mehrens, In Operando Li+-Activity Measurements in Lithium Ion Batteries-a Method to Develop and Optimize Safe Operating Strategies Even at Unfavourable Conditions, in: Meet. Abstr., The Electrochemical Society, 2015: pp. 343–343.

Part of the research leading to these results has been performed within the MAT4BAT project (http://mat4bat.eu/) and received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement n°608931.

Figure 1 Measurement of anode potential vs. Li/Li⁺ for different temperatures in a full cell.