Quantification of Inactive Lithium, Solid Carbonate Species, and Lithium Acetylide on Graphite Electrodes after Fast Charging

Lithium plating on graphite anodes currently limits the fast charging performance of lithium-ion batteries because plated Li is prone to become electronically isolated from the electrode (referred to as 'inactive Li') or react with electrolyte, both of which contribute to rapid cell capacity fade. To understand the onset and extent of these detrimental processes, it is critical to quantify these sources of capacity loss. In this work, we demonstrate a titration technique to quantify both inactive Li and solid electrolyte interphase (SEI) species (solid carbonates and lithium acetylide, Li 2 C 2 ) that remain on the graphite electrode after fast charging. We additionally compare electrochemical modeling results with our experimental data to determine the Li plating exchange current density (10 A/m 2 ) and stripping efficiency (65%) of plated Li metal on graphite. Our techniques lay the groundwork for benchmarking proposed Li plating detection techniques and provide an avenue to pursue more comprehensive studies of Li plating on graphite surfaces.