Lithium Plating Detection and Characterization Utilizing Impedance Changes During the Lithium Deposition

Summary:

Lithium plating is one of the most damaging ageing mechanisms in Lithium Ion Batteries that also poses a safety risk due to dendrite growth. It is very challenging to detect the onset of lithium plating in operando before the plating even occurs to prevent plating during battery operation as well as very time consuming to characterize a cell regarding to its plating behavior to better determine the safe operation limits. Changes of the cell impedance during the lithium plating deposition can be used to solve both problems. In operando the deviation of the measured charging voltage curve can be compared in real time with a synthetic plating free reference curve to detect the plating onset and tell the battery management system to stop the charging process or adjust the charging parameters. For the creation of this reference curve the cell is characterized under different conditions and a plating free cell model is built based on this data. For the characterization of the plating behavior of a cell a forced constant voltage phase under plating conditions can be utilized. This creates a distinctly shaped current curve that can be fitted using the Johnson–Mehl–Avrami–Kolmogorov equation for the electrochemical deposition of metals on a surface. The fitting of this curve yields parameters that can show the morphology of the plating process and if extended over multiple plating cycles can be used to predict the cell ageing under plating conditions as well as the safety risk of the cell under plating conditions. In this presentation both approaches, in-situ plating detection and prevention, and plating behaviors prediction are introduced, explained and shown on example measurements of round and pouch cells.