Visualization of Lithium Plating Morphologies on Graphite Electrode By O perando X-Ray Tomography

Abstract

The plating of lithium metal on graphite electrodes in Li-ion batteries is a major factor limiting the fast charging of electric vehicles. Lithium metal plating leads to the growth of dendritic structures that can pierce through the battery’s separator resulting in an internal short circuit and catastrophic failure of the battery. Moreover, the plating of lithium metal on graphite is not reversible, manifesting in poor Coulombic efficiency, severe reduction of the battery’s life expectancy, and safety issues. Understanding how and when plating occurs in Li-ion batteries is crucial in the development of strategies to prevent plating under fast charging conditions. Thus, we have conducted an operando X-ray tomographic microscopy experiment to directly monitor the plating of lithium metal in a Li/Graphite cell when applying electrolytes with the additives vinylene carbonate (VC) and Lithium bis(fluorosulfonyl)imide (LiFSI). The experiment was performed at the ID19 beamline (ESRF, France) where tomographic scans, linked with the lithiation state of graphite, made it possible to gain a strong understanding of the mechanisms behind Li-deposition and stripping at high current rates in addition to understand the effect of the VC and LiFSI additives.