title: Nanoscale imaging of fundamental li battery chemistry: solid-electrolyte interphase formation and preferential growth of lithium metal nanoclusters.
abstract: The performance characteristics of Li-ion batteries are intrinsically linked to evolving nanoscale interfacial electrochemical reactions. To probe the mechanisms of solid electrolyte interphase (SEI) formation and to track Li nucleation and growth mechanisms from a standard organic battery electrolyte (LiPF6 in EC:DMC), we used in situ electrochemical scanning transmission electron microscopy (ec-S/TEM) to perform controlled electrochemical potential sweep measurements while simultaneously imaging site-specific structures resulting from electrochemical reactions. A combined quantitative electrochemical measurement and STEM imaging approach is used to demonstrate that chemically sensitive annular dark field STEM imaging can be used to estimate the density of the evolving SEI and to identify Li-containing phases formed in the liquid cell. We report that the SEI is approximately twice as dense as the electrolyte as determined from imaging and electron scattering theory. We also observe site-specific locations where Li nucleates and grows on the surface and edge of the glassy carbon electrode. Lastly, this report demonstrates the investigative power of quantitative nanoscale imaging combined with electrochemical measurements for studying fluid-solid interfaces and their evolving chemistries.
authors.affiliation: Materials Science and Technology Division and ‡Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Sacci
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Black
authors.forename: Nina
authors.initials: N
authors.lastname: Balke
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Dudney
authors.forename: Karren L
authors.initials: KL
authors.lastname: More
authors.forename: Raymond R
authors.initials: RR
authors.lastname: Unocic
mesh_terms: D003460:Crystallization / Q000379:methods; D011211:Electric Power Supplies; D004735:Energy Transfer; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008094:Lithium / Q000737:chemistry*; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D044367:Phase Transition
chemical_list: D008094:Lithium
keywords: In situ ec-S/TEM; Li dendrites; Li deposition; Li-ion batteries; electron microscopy; solid electrolyte interface