Monitoring Lithium Metal Plating in Battery Modules: Insights from NMR and Electrochemical Analysis

Abstract

Current interest in and projected demands for large-scale batteries are constantly expanding. In particular, envisioning batteries as power source for electric vehicles, it is important to move scientific research beyond individual cells to much larger units such as battery pack level. Marginal differences inside a battery pack may have strong impact on the achievable battery performance and cycle life. Hence, safer and more efficient management of battery modules and packs is emphasized. This talk highlights aspects of undesirable lithium metal plating in lithium-ion batteries and the importance of detecting such deposits based on electrochemical methods. The study involved cycling of model battery modules comprised of up to four cells and monitoring the evolution of lithium metal deposits by 7Li NMR, where various operational conditions to induce lithium metal plating were applied to individual cells. After deposition, the cells were continuously cycled within a battery pack to evaluate the effects of the lithium metal deposits on the achievable performance. Electrochemical methods, such as impedance measurements, were invoked to detect faulty cells, and corresponding fractions of lithium metal deposits were quantified by NMR and GC-MS measurements. Malfunctioning cells exhibited unfavourable impact on all the surroundings cells, as monitored by electrochemical methods without disassembly of considered modules. The insights of this study are significant for designing strategies for better safety and overall efficiency of large-scale battery packs.