Quantitative Investigation of Lithium Metal Plating via Operando 7Li NMR Spectroscopy of a Unique Three Electrode Lithium-Ion Battery

This work represents the first investigation that simultaneously uses both 7Li NMR chemical analysis and three-electrode (3E) electrochemical analysis in real time to observe SiO-graphite anodes experiencing lithium plating during fast charge. NMR has the unparalleled ability to distinguish lithium in various forms, such as plated metal, alloyed lithium-silicon, or intercalated lithium-graphite compounds. This permits a detailed accounting of the whereabouts of lithium in an anode undergoing high-rate charge. This highly specialized technique comes at a high cost, however, in terms of time, equip-ment, and expertise. Establishing correlation between NMR and the more common and readily implemented 3E tech-nique for detecting the onset of plating allows the latter to be applied with confidence to the type of extensive testing required to build fast charge tables. NMR provides additional insight into the disposition of lithium after plating has occurred, allowing a clear analysis of the fraction of lithium metal that is spontaneously re-dissolved and taken up by the anode (reversible lithium plating).