In recent years, there has been an explosion of research into Li metal anodes for high-energy-density batteries. However, despite tremendous progress in the field, the reversible plating and stripping of Li has been hindered by the complex interplay between electrode morphology, surface chemistry, and mechanics. This has led to many empirical observations of improved performance, but our ability to rationally design solutions to solve the challenges of reversibility remain limited by our fundamental understanding of the complex electrodeposition and dissolution processes involved [1]. In an analogous example, Li plating on graphite anodes during fast-charging also plagues the Li-ion community [2], but fundamental studies of the complex nature of Li plating on intercalation electrodes is equally lacking.

To address these challenges, in situ/operando analyses are of paramount importance to the community. However, given the dynamic nature of Li plating and stripping, challenges arise with respect to tradeoffs in spatial and temporal resolution. To address these challenges, we have recently integrated our optical visualization cells with a digital microscope capable of focus variation microscopy. This enables 3-D visualization of the electrode morphology with high temporal resolution, allowing for video capture of Li plating and stripping [2-3].

In this talk, I will discuss the application of operando 3-D microscopy for visualization of both Li metal anodes and Li plating on graphite surfaces during fast-charging of Li-ion batteries. In the case of Li metal anodes, we observe significant anisotropy in the geometric shape of individual pits during stripping [3]. The nucleation density and anisotropy are shown to be strongly influenced by the surface microstructure and underlying crystallographic texture of the Li metal surface. As a results, pits can exhibit strong faceting, which influences the nature of nucleation at pit edges in subsequent cycles [4]. As a parallel example, we demonstrate 3-D visualization of Li plating on graphite electrodes during fast-charge, which illustrates the coupling between nucleation of Li plating and local heterogeneity in state-of-charge [2]. Overall, these results highlight the importance of both spatial and temporal heterogeneity in the nature of nucleation, growth, dissolution, pitting, and dead Li formation

References

[1] K. N. Wood, M. Noked, N. P. Dasgupta, ACS Energy Lett. 2, 664 (2017).

[2] Y. Chen, K.-H. Chen, A. J. Sanchez, E. Kazyak, V. Goel, Y. Gorlin, J. Christensen, K. Thornton, N. P. Dasgupta, J. Mater Chem. A 9, 23522 (2021).

[3] A. J. Sanchez, E. Kazyak, Y. Chen, J. Lasso, N. P. Dasgupta, J. Mater Chem. A. 9, 21013 (2021).

[4] A. J. Sanchez, E. Kazyak, Y. Chen, K.-H. Chen, E. R. Pattison, N. P. Dasgupta, ACS Energy Lett. 5, 994 (2020).