Impact of Formation Rate on the Performance of Anode-Free Lithium Metal Batteries

Anode-free lithium metal batteries (AFBs) hold significant promise for high-energy-density storage applications. However, their practical deployment is hindered by a limited cycle life, primarily due to heterogeneous lithium deposition and dendrite formation. These issues lead to rapid capacity fade as lithium inventory is consumed in side reactions, compounded by the lack of a lithium reservoir that conventional Li-metal anodes possess. To enhance AFB stability, various strategies have been proposed, including innovative current collector designs, optimized electrolytes, tailored cycling protocols, and increased stack pressure, all of which have shown notable improvements in lithium plating/stripping behavior.[1-4]<br/><br/>Our proposed talk will focus on elucidating the interaction between lithium and copper surfaces under varying charge conditions, utilizing classical molecular dynamics simulations of 1M LiPF₆ in EC/DEC at the copper interface, complemented by XPS and SEM analyses. Our findings indicate that PF₆^- ions begin to integrate into the lithium solvation shell near the interface as voltage increases, corroborated by XPS data showing elevated LiF formation at higher current densities. The resultant LiF-rich solid electrolyte interphase (SEI) is crucial for enhancing stability in subsequent cycles. We demonstrate that the initial formation protocol significantly influences the long-term cycling stability of AFBs. Therefore, optimizing the current density during the formation cycle is a critical factor in improving the performance and durability of anode-free lithium metal batteries.<br/><br/><br/><br/>[1] Xie, Z.; Wu, Z.; An, X.; Yue, X.; Wang, J.; Abudula, A.; Guan, G. Anode-free rechargeable lithium metal batteries: Progress and prospects. Energy Storage Mater. 2020, 32, 386-401. DOI: <u>https://doi.org/10.1016/j.ensm.2020.07.004</u>.<br/>[2] Weber, R.; Genovese, M.; Louli, A. J.; Hames, S.; Martin, C.; Hill, I. G.; Dahn, J. R. Long cycle life and dendrite-free lithium morphology in anode-free lithium pouch cells enabled by a dual-salt liquid electrolyte. Nat. Energy 2019, 4 (8), 683-689. DOI: https://doi.org/10.1038/s41560-019-0428-9.<br/>[3] Tong, Z.; Bazri, B.; Hu, S.-F.; Liu, R.-S. Interfacial chemistry in anode-free batteries: challenges and strategies. J. Mater. Chem. A 2021, 9 (12), 7396-7406, DOI:https://doi.org/10.1039/D1TA00419K.<br/>[4] Lin, L.; Suo, L.; Hu, Y.-s.; Li, H.; Huang, X.; Chen, L. Epitaxial Induced Plating Current-Collector Lasting Lifespan of Anode-Free Lithium Metal Battery. Adv. Energy Mater. 2021, 11 (9), 2003709. DOI: https://doi.org/10.1002/aenm.202003709.