Interplay of Thermal Gradients and C-Rate on Lithium Plating

Extreme fast charging (XFC) of lithium-ion batteries is crucial for solving range anxiety and rapid adoption of electric vehicles by significantly reducing charging time [1]. However, one of the key challenges in achieving this goal is lithium plating at the anode during the charging process [2]. Moreover, XFC will induce spatial temperature variations within the battery pack which will translate into thermal gradients inside a cell [3]. Interelectrode thermal gradients were previously found to induce accelerated lithium plating, degrading the battery life drastically [4], [5]. Therefore, it is critical to understand the complex interplay between C-rate and thermal gradients on lithium plating and its governing mechanisms. In this work, we investigate lithium plating under various thermal gradients and C-rates in single-layer NMC/graphite instrumented pouch cells. Thermistors were placed inside the cell at each electrode to precisely measure the magnitude of the thermal gradient conditions being applied. Galvanostatic cycling was performed at different C-rates and interelectrode thermal gradients. A comprehensive analysis was performed, including incremental capacity analysis. Three-electrode cells were utilized to isolate graphite-specific electrochemical processes and decipher the governing mechanisms. Post-mortem analysis was also performed to corroborate the electrochemical behavior. Acknowledgments The authors thank Dr. Michele Anderson (Office of Naval Research, grant N00014-22-1-2411) for financial support of this work. The authors also acknowledge Dr. Rachel Carter (U.S. Naval Research Laboratory) for technical discussion of this work. References [1] X. G. Yang, T. Liu, Y. Gao, S. Ge, Y. Leng, D. Wang, and C.Y. Wang , “Asymmetric Temperature Modulation for Extreme Fast Charging of Lithium-Ion Batteries,” Joule , vol. 3, no. 12, pp. 3002–3019, 2019, doi: 10.1016/j.joule.2019.09.021. [2] C. Fear, M. Parmananda, V. Kabra, R. Carter, C. T. Love, and P. P. Mukherjee, “Mechanistic underpinnings of thermal gradient induced inhomogeneity in lithium plating,” Energy Storage Mater. , vol. 35, no. July 2020, pp. 500–511, 2021, doi: 10.1016/j.ensm.2020.11.029. [3] I. A. Hunt, Y. Zhao, Y. Patel, and J. Offer, “Surface Cooling Causes Accelerated Degradation Compared to Tab Cooling for Lithium-Ion Pouch Cells,” J. Electrochem. Soc. , vol. 163, no. 9, pp. A1846–A1852, 2016, doi: 10.1149/2.0361609jes. [4] R. Carter, T.A. Kingston, R.W. Atkinson, M. Parmananda, M. D