Inhibiting Li Plating on Graphite Electrodes during 4C Fast-Charging with Atomic Layer Deposition

Abstract

The ability to increase the charging rate of lithium-ion batteries (LIBs) is of critical importance to the widespread commercialization of electric vehicles (EVs).1 One of the primary factors limiting the fast-charge ability of state-of-the-art LIBs is the tendency for plating out of metallic Li on the graphite electrode during charging.2 This phenomenon leads to rapid capacity fading of the cell, consumption of the electrolyte (cell drying), and the potential for short-circuit from dendrites penetrating the separator.To prevent/mitigate these effects, we implement a surface coating on post-calendared graphite anodes. To date, the vast majority of atomic layer deposition (ALD) coatings that have been investigated as electrode coatings are simple binary metal oxides that have very low ionic conductivity. This has limited the maximum usable thickness due to high impedance. In contrast, the ALD coating used in this work is a lithium borate-carbonate (LBCO) solid electrolyte film. The film has previously been shown to exhibit ionic conductivities above 2*10-6 S/cm and excellent electrochemical stability, including with Li metal.3 Full graphite-NMC 532 cells with ALD-coated graphite electrodes exhibit dramatic improvements in performance during 4C fast-charging, enabling fast-charging of high loading (>3 mAh/cm2) electrodes in 15 minutes with minimal Li plating. This resulted in >40x improvement in the cycle life to 80% capacity retention in 7x10 cm pouch cells.The cells with LBCO-coated electrodes demonstrated improved Coulombic efficiency, decreased interfacial impedance, decreased cell polarization, improved rate capability, improved cycle life, and dramatically reduced Li plating during fast charging. The properties and performance of the coating will be examined using electrochemical impedance spectroscopy (EIS), x-ray photoelectron spectroscopy (XPS), differential voltage analysis, and electron microscopy. This work represents a significant advance in the state-of-the art of electrode coatings for fast-charging of LIBs with high electrode loadings. It also demonstrates the critical role of the SEI in fast-charging, and the opportunity it presents for achieving enhanced performance. References (1) Zeng, X.; Li, M.; Abd El‐Hady, D.; Alshitari, W.; Al‐Bogami, A. S.; Lu, J.; Amine, K. Commercialization of Lithium Battery Technologies for Electric Vehicles. Adv. Energy Mater. 2019, 9 (27), 1900161. https://doi.org/10.1002/aenm.201900161.(2) Gallagher, K. G.; Trask, S. E.; Bauer, C.; Woehrle, T.; Lux, S. F.; Tschech, M.; Lamp, P.; Polzin, B. J.; Ha, S.; Long, B.; Wu, Q.; Lu, W.; Dees, D. W.; Jansen, A. N. Optimizing Areal Capacities through Understanding the Limitations of Lithium-Ion Electrodes. J. Electrochem. Soc. 2016, 163 (2), A138–A149. https://doi.org/10.1149/2.0321602jes.(3) Kazyak, E.; Chen, K. H.; Davis, A. L.; Yu, S.; Sanchez, A. J.; Lasso, J.; Bielinski, A. R.; Thompson, T.; Sakamoto, J.; Siegel, D. J.; Dasgupta, N. P. Atomic Layer Deposition and First Principles Modeling of Glassy Li3BO3-Li2CO3 Electrolytes for Solid-State Li Metal Batteries. J. Mater. Chem. A 2018, 6 (40), 19425–19437. https://doi.org/10.1039/c8ta08761j.