Evolution of Dead Lithium Growth in Lithium Metal Batteries: Experimentally Validated Model of the Apparent Capacity Loss

In this work, a physics-based model has been developed to understand how dead lithium (Li) affects the apparent capacity loss in Li metal battery cells. Specifically, the dead Li layer is modeled as a secondary layer which restricts ion transport similar to the separator. The measured dead Li thickness is used as an input to the model, and both the effective diffusion coefficient and ionic conductivity of the dead Li layer have been tuned to match the terminal voltage response of a Li-NMC 532 coin cell under galvanostatic cycling. The model captures the changes in terminal voltage and apparent cell capacity as the dead Li layer builds up. This model can be inverted to estimate the thickness and effective transport properties of the dead Li layer from the observed terminal voltage for enhanced diagnostics of the apparent capacity degradation of Li metal battery cells as well as fast-charging Li ion battery systems with graphite anodes.