Unweaving dendrite formation through in operando synchrotron X-ray diffraction study of individual lithium crystallites

Abstract

In the search for renewable energy storage materials, lithium metal has been considered the ideal electrode material for decades, due to its high specific capacity. However, dendrite formation leading to poor cycling behaviour has seemed an insurmountable problem ever since. In recent years, advancements in observational- and nanotechnologies have allowed for the identification of many of the factors that influence dendrite formation, as well as many suggestions to overcome them.
Obtaining further understanding of the fundamental processes at play in dendrite formation is crucial in developing the next generation lithium batteries.
In order to investigate dendrite formation at the nanoscale, in operando synchrotron X-ray diffraction experiments were conducted. A pouch cell with a Li-Li symmetric cell using a LiPF6 1:1 EC:DMC electrolyte was used to perform the experiments.
The growth rate of individual crystallites was determined, as well as the consumption of lithium crystallites by the electrolyte to form solid-electrolyte interphase (SEI).
By determining the volume of individual crystallites over time, their formation and decay rate could be determined. Three categories were put forward to classify the types of behavior of individual crystallites during plating and relaxation. It was found that a significant part of dendrites show behaviour that is independent of the macroscopic current density.