Mapping Lithium Plating Conditions for Fast Charging Using High-Throughput Coulombic Efficiency Techniques

Abstract

Long charge times and battery safety remain two of the largest hurdles for widespread adoption of electric vehicles. It is well known that the deposition of lithium metal on the graphite electrode, or ‘lithium plating’, can cause capacity fade and catastrophic cell shorting, so recent studies have focused on its detection and evolution throughout cycling. While many specialty lithium plating detection techniques have been reported, few are well suited for robust characterization of electrode and electrolyte materials for fast charging. We have developed cycling protocols that use coulombic efficiencies to estimate the evolving amount of irreversible Li plating during a single fast charge in graphite/lithium cells. The technique was applied to over 50 coin cells with varying electrode thicknesses (x), temperatures (T), and C-rates (C), and the results agree well with models developed a priori. Defining 0.1% of the graphite capacity of irreversible lithium plating as a threshold, we identify plating onset states-of-charge (SOC) for each condition and map the plating onsets as a function of x, T, and C. We contribute novel insights about the importance of these variables on the lithium plating onset and demonstrate this technique as one of the most sensitive, accessible, and reproducible methods for lithium plating detection.