Electrochemical Quantification of Lithium Plating: Challenges and Considerations

Low-level overlithiation (1.5 to 5.5% based on the theoretical capacity of graphite, 372 mAh^-1) behavior of graphite electrode is reported to illustrate the challenges of detecting Li plating via electrochemical methods such as voltage, incremental capacity (dQ.dV^-1), and coulombic efficiency. Low-level overlithiation is closely tied to multiple in-vehicle mild-abuse and aging-related conditions such as overcharge and fast-charge where early detection of plating is highly desirable. Here, the analysis following overlithiation includes the interplay between reversibly and irreversibly plated Li with and without rest after overlithiation, impacts on the electrode, and the feasibility of using reversible Li stripping as a detection method. Following overlithiation the capacity for graphite readily approaches theoretical values. Inspection of the lithiation voltage profile suggests that a portion of this capacity is associated with the chemical lithiation of graphite and effectively suppresses the dQ.dV^-1 signal related to Li stripping. Analysis of coulombic efficiency and the lithiation and delithiation profiles are used to quantify the capacity of graphite, irreversibly and reversibly plated lithium. It has been found that the extent of reversibility of lithium plating is distinctly impacted by rest with periods as short as one hour reducing the extent of reversibility and hence electrochemical detection. Authors: