Lithium dendrites in solid-state batteries - Where they come from and how to mitigate them

Abstract

A major contributor to global CO2 emissions is transportation and a transition to electric vehicles could lead to a significant reduction of those emissions. A roadblock in this transition are safety issues of electric vehicles. Namely that the batteries can burst into flames, be it in an accident or sometimes even without showing obvious signs during charging. This can be caused by filaments, also called dendrites growing within the battery causing a short circuit. By exchanging the flammable liquid electrolyte in the battery with a non-flammable solid one the safety aspect can be remedied. It also allows an increase of the battery capacity through the now viable use of lithium metal. This was deemed too dangerous with liquid electrolyte because lithium metal tends to form dendrites more easily which caused several accidents in the early advent of lithium-ion batteries. However, these dendrites can still form inside of solid electrolytes and while the consequences are less severe the possible lifetime of the battery is cut short. Therefore, this work concerned itself with understanding the growth of dendrites in solid electrolytes, more specifically in the oxide based garnet Li7La3Zr2O12, and how to mitigate it. Starting with the influence of the charging mode of the cell on dendritic growth with the use of current pulses, increasing the charge rate. Followed by investigating the effect of altered near surface properties of the garnet via ion implantation, on the path of the dendrite. Finally x-ray microscopy observations into the environment close to the dendrite deliver more information what happens microscopically when the dendrite grows. Thus, bringing us closer to functional solid-state batteries without failure by dendrites.