Ionic Current in Lithium-Ion Batteries during Rest after Fast Charging*

Reducing electric vehicles charging time is essential to alleviate range anxiety and expand mass market adoption. Fast charging of Li-ion batteries is hindered by lithium plating on the graphite electrode, which is detrimental to cell performance and safety. In addition, some Li-ion batteries can explode in an electric vehicle even the electric vehicle is not being charged or discharged. Lithium plating that occurs during fast charging can reintercalate into the graphite during rest. However, this process has not been studied in three dimensions.

In this work, we use synchrotron X-ray microtomography with a low-noise cell configuration to obtain high-contrast in situ 3D imaging of lithium plating in fast charged graphite half cells. We detect and quantify the capacity of plated lithium after fast charging and track changes during rest. Furthermore, we measure strains within the graphite electrode from lithiation using digital volume correlation to determine local state of charge over time. Since these measurements are in 3D over time, we determine ionic currents from the lithium plating and ionic currents into the graphite electrode.

We relate these observations to gain insight into the correlations between graphite lithiation and lithium plating during and after fast charging.