Failure Inducing Features at Lithium Battery Interfaces

2019-03-04T20:12:29Z (GMT) by Sarah Frisco
Next generation rechargeable lithium metal battery chemistries have the potential to revolutionize energy storage. However, they remain stymied by the same potentially catastrophic failure mechanisms that caused the lithium metal anode to be removed from commercial rechargeable batteries in the first place: the formation of the solid electrolyte interphase (SEI) and dendritic lithium growth. This document is concerned with characterizing the morphology of these failure modes and implementing new<br>strategies in their prevention. Here, we investigated a cycled graphite anode and found that the build-up of SEI could be seen not only clogging the surface of the electrode, but<br>also closing the internal pores. Additionally, lithium electrodes cycled at varying temperatures and current densities show significantly different internal void morphology, which affects the dendrite deposition volume. A challenge in characterizing lithium<br>failure in general and dendrites in particular is that there is no established set of conditions at which cells are meant to be tested in order to observe their growth or test prevention strategies. A proposed method of standardization was created in the form of a baseline of bare lithium performance at particular temperatures and current densities. Rather than test long term cycling, this baseline measured the extent of stable lithium deposition before signs of dendritic growth were observed. This metric has the advantage of being quick and accessible to any lab involved in electrochemical testing. Its viability as a means of predicting cell cyclability was tested by comparing the performance of different polymer coatings on the lithium electrodes. An increase in the extent of stable lithium deposition occurred in parallel to increased long term cycling performance.