Lithium is one of the most favorable materials for next-generation secondary energy storage devices due to its low redox potential, high gravimetric/volumetric capacities, and fast reaction kinetics [1]. However, the use of metallic lithium as the anode has been largely limited by the inherent safety concerns with lithium dendrite growth - causing short-circuits, leading to thermal runaway reactions, and fires/explosions [2]. Many efforts have been devoted to understanding dendrite morphologies with the influencing factors - temperature, electrolyte composition, current density and over-potentials [3]. However, the studies are limited to the nucleation and growth of Li dendrite at early stages [1,2]. At present, the growth mechanism and morphological changes taking place in Li dendrite formation near/after short-circuit condition, which presumably form the basis for its improved performance and safety, are not well understood.

Recent advances in in situ electrochemical transmission X-ray microscopy (EC-TXM), with its unique ability to provide simultaneous temporally and spatially resolved information as well as electrochemical parameters, enable exploration of the underlying physics of the electrochemical reactions that occur at the surface and inside of secondary energy storage devices during cycling [4,5]. Here, we focus the direct visualization of the propagation of Li dendrites at short-circuit condition using in situ EC-TXM. After the short-circuit, we follow three-dimensional morphological and microstructural changes of Li dendrites to explore relationships between electrochemical parameters and failure mechanisms during cycling. We further characterize the structural evolution of Li dendrites using in situ X-ray diffraction.

References:

[1] D. Lin, Y. Liu, & Y. Cui. Nat. Nanotechnol. 12, 194−206 (2017).

[2] W. Xu, J. Wang, F. Ding, X. Chen, E. Nasybulin, Y. Zhang, & J.-G. Zhang. Energy Environ. Sci. 7, 513−537 (2014).

[3] D. X. Liu, S. Frisco, P. Mandal, J. Whitacre, S. Litster, C. T. Love, & K. Swider-Lyons. ECS Meeting Abstracts MA2016-01 213.

[4] P. R. Shearing, D. S. Eastwood, R. S. Bradley, J. Gelb, S. J. Cooper, F. Tariq, D. J. L. Brett, N. P. Brandon, P. J. Withers, & P. D. Lee. Microsc. Microanal. 27, 19−22 (2013).

[5] J. Nelson, S. Misra, Y. Yang, A. Jackson, Y. Liu, H. Wang, H. Dai, J. C. Andrews, Y. Cui, & M. F. Toney. J. Am. Chem. Soc. 134, 6337−6343 (2012).

[6] We gratefully acknowledge funding supports from the BP Carbon Mitigation Initiative.