Bryan McCloskey1
University of California-Berkeley1
Bryan McCloskey1
University of California-Berkeley1
Li-ion battery fast charge is limited due to challenges posed by lithium plating on the graphite anode, whereby the large overvoltage necessary to drive high Li<sup>+</sup> insertion rates instead results in favorable thermodynamic conditions for Li metal deposition on the graphite surface. Li plating is difficult to detect, particularly in small quantities, and results in safety risks and capacity fade due to lithium metal’s high reactivity with conventional electrolytes. Here, we present our efforts to develop both chemical and electrochemical methods to precisely quantify Li plating and detect the state-of-charge (SOC) onset of lithium plating on graphite electrodes during constant current fast charging. We will discuss titration mass spectrometry (TiMS), a highly sensitive (~20 nmol resolution, or 0.5 mAh of plated Li) chemical analysis where gases evolved from harvested graphite electrodes immersed in acid are used to quantify various solid electrolyte interphase species, including electrically isolated (inactive) Li metal.<sup>1</sup> TiMS is then used to determine the precise onset of Li plating and to distinguish between the various capacity fade mechanisms that arise during fast charge.<sup>2</sup> We then will discuss the use of simple electrochemical cycling techniques to quantify irreversible Li plating in Li|Graphite half-cells as a function of energy density (electrode thickness), charge rate, temperature, and SOC.<sup>3</sup> Similar methods are developed to quantify in-situ Li plating for commercially relevant Graphite|LiNi<sub>0.5</sub>Mn<sub>0.3</sub>Co<sub>0.2</sub>O<sub>2</sub> (NMC) cells. In combination, all of these techniques provide a highly accurate measure of the onset of Li plating and quantitative insight into capacity losses during fast charging.<br/><br/>1. McShane, E. J.; Colclasure, A. M.; Brown, D. E.; Konz, Z. M.; Smith, K.; McCloskey, B. D., Quantification of inactive lithium and solid–electrolyte interphase species on graphite electrodes after fast charging. <i>ACS Energy Lett. </i><b>2020,</b> <i>5</i> (6), 2045-2051.<br/>2. McShane, E. J.; Bergstrom, H. K.; Weddle, P. J.; Brown, D. E.; Colclasure, A. M.; McCloskey, B. D., Quantifying graphite solid-electrolyte interphase chemistry and its impact on fast charging. <i>ACS Energy Lett. </i><b>2022,</b> <i>7</i> (8), 2734-2744.<br/>3. Konz, Z. M.; Wirtz, B. M.; Verma, A.; Huang, T.-Y.; Bergstrom, H. K.; Crafton, M. J.; Brown, D. E.; McShane, E. J.; Colclasure, A. M.; McCloskey, B. D., High-throughput Li plating quantification for fast-charging battery design. <i>Nature Energy </i><b>2023,</b> <i>8</i> (5), 450-461.