Quantification of Lithium Plating and Sources of Capacity Loss during Fast Charging of Graphite Electrodes

Fast charging of lithium-ion batteries is often hindered by rapid capacity fade, which is spurred by Li metal deposition, or 'Li plating,' on the graphite anode. Plated Li is problematic for multiple reasons, including the low reversibility of the Li plating/stripping process and the highly reactive nature of Li metal with electrolyte. Understanding when Li plating occurs and how much Li has plated is therefore crucial for improving battery lifetime. To this end, we demonstrate a titration technique which is used to quantify inactive Li and solid electrolyte interphase (SEI) species (solid carbonates and lithium acetylide, Li₂C₂) that remain on the graphite electrode after fast charging. We also employ electrochemical modeling in conjunction with experimental data to determine the Li plating exchange current density (10 A/m²) and stripping efficiency (65%) of plated Li metal on graphite. In this work, we provide quantitative insights into the limitations of fast charging and determine valuable kinetic parameters for the Li plating process.