Next generation high-energy-density battery systems need alternatives to graphite-based intercalation anodes that have insufficient energy density for wide-spread vehicle electrification. The lithium metal anode is an attractive alternative, however it is plagued with dendrite growth, and poor Coulombic efficiency. Significant improvements have been made in safety and electrochemical performance of the lithium anodes recently through modified electrolyte chemistry and protective layers. Despite the apparent improvements in the electrochemical performance, postmortem/ ex-situ analyses bring limited understanding of the underlying mechanisms that generate the deposition morphology and growth patterns.

Here, we will present on an X-ray transparent coin cell configuration we have developed for operando imaging and 3D imaging in nano-scale resolution X-ray microscopes. We use nano-resolution x-ray computed tomography (nano-CT) and the X-ray transparent coin cell to directly observe the electrochemical deposition on lithium anodes as a function of time. Lithium electrodepositions in different electrolyte formulations reveal drastically different nucleation and deposition growth mechanisms that could not be revealed by inspecting post-mortem structures. We will present and discuss operando 2D & in-situ 3D images of lithium electrodeposition under varying parameters and electrolyte chemistry.

This material is based upon work supported by the US Office of Naval Research for the battery safety studies under grant N00173-17-1-G009. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Office of Naval Research.