(577f) Detecting the Onset of Li Plating during Fast Charging of Li-Ion Batteries Using Operando Electrochemical Impedance Spectroscopy

To promote the continued growth of the electric vehicle (EV) market—as well as to improve the performance of other battery-powered technologies such as phones, laptops, and drones—Li-ion battery charging times need to be significantly reduced. At higher charging rates, Li metal may plate on the graphite anode, which is a possible safety concern and leads to decreased cycle life of the battery.¹ There is clearly a need to develop a consistently reliable electrochemical technique to detect the onset of Li plating during active battery operation..^1,2 Previous work has included techniques that interrogate Li plating after charging, including dV/dQ analysis of discharge profiles after fast charging,^3,4 impedance analysis after fast charging^5,6 and during pseudo-operando measurements,⁷ dV/dt analysis of voltage relaxation profiles after fast charging,^5,7 three electrode graphite potential monitoring,⁴ and simple optical inspection after many fast charging cycles, among other techniques.¹ Our group has also developed ex situ mass spectrometry titrations to detect and quantify electrically isolated Li deposits,⁸ as well as an improved dV/dt technique to detect the onset of Li plating after fast charging.⁹

In this work, we use impedance spectroscopy—and specifically the Distribution of Relaxation Times (DRT) analysis method¹⁰—to detect in operando the onset of Li plating during extreme fast charging. There is a change in the graphite interfacial impedance upon Li plating on the graphite surface. Coupled with both differential voltage relaxation and mass spectrometry titrations for cross-validation, we can reliably detect the Li plating onset graphite state of charge (SOC) for rates as high as 6C at room temperature and for different graphite loadings with <0.5% graphite capacity sensitivity. This study was primarily carried out using three-electrode cell measurements, but we will also show a proof-of-concept for the application of this technique to more commercially relevant two-electrode cells. We will also discuss possible physical explanations for the observed impedance behavior. This capability to detect the onset of Li plating allows for the safe implementation of fast charging protocols, and represents, to the best of our knowledge, the first operando electrochemical technique for Li plating detection.

References

1. P. P. Paul et al., Adv. Energy Mater., 2100372 (2021).

2. T. Waldmann, B.-I. Hogg, and M. Wohlfahrt-Mehrens, Journal of Power Sources, 384, 107–124 (2018).

3. K. G. Gallagher, D. W. Dees, A. N. Jansen, D. P. Abraham, and S.-H. Kang, J. Electrochem. Soc., 159, A2029–A2037 (2012).

4. C. Uhlmann, J. Illig, M. Ender, R. Schuster, and E. Ivers-Tiffée, Journal of Power Sources, 279, 428–438 (2015).

5. S. Schindler, M. Bauer, M. Petzl, and M. A. Danzer, Journal of Power Sources, 304, 170–180 (2016).

6. X. Chen, L. Li, M. Liu, T. Huang, and A. Yu, Journal of Power Sources, 496, 229867 (2021).

7. U. R. Koleti, T. Q. Dinh, and J. Marco, Journal of Power Sources, 451, 227798 (2020).

8. E. J. McShane et al., ACS Energy Lett., 5, 2045–2051 (2020).

9. Z. M. Konz, E. J. McShane, and B. D. McCloskey, ACS Energy Lett., 1750–1757 (2020).

10. E. Ivers-Tiffée and A. Weber, J. Ceram. Soc. Japan, 125, 193–201 (2017).