Distinct Nanoscale Interphases and Morphology of Lithium Metal Electrodes Operating at Low Temperatures

Abstract

While Li-ion batteries are known to fail at temperatures below −20 °C, very little is known regarding the low-temperature behavior of next-generation high-capacity electrode materials. The lithium metal anode is of particular interest for high-energy battery chemistries, but improved understanding of and control over its electrochemical and nanoscale interfacial behavior in diverse conditions is necessary. Here, we investigate lithium deposition/ stripping, morphology evolution, and solid-electrolyte interphase (SEI) structure and properties down to −80 °C using an etherbased electrolyte (DOL/DME). As temperature is reduced, we find that the morphology of deposited lithium is significantly altered. Furthermore, cryogenic transmission electron microscopy coupled with vacuum-transfer X-ray photoelectron spectroscopy reveal that the SEI exhibits different structure, chemistry, thickness, and conductive properties at lower temperatures. These results show that Li is promising for batteries operating under extreme conditions, and the distinct nanoscale evolution of Li electrodes at different temperatures must be considered when designing high-energy batteries.

Interface Engineering for Lithium Metal Anodes in Liquid Electrolyte

“…McDowell's group investigated the morphology evolution and SEI properties during Li plating/stripping process at different temperatures (from −80 to 20 °C) using cryo-TEM coupled with vacuum-transfer XPS (ether-based electrolyte: DOL/DME). [74] The reduced temperatures lead to the smaller Li particles deposited on the current collectors ( Figure 9e). The SEI formed at lower temperature is thinner, chemically and structurally distinct, and less resistive in comparison to the SEI formed at room temperature.…”

“…Reproduced with permission. [74] Copyright 2019, American Chemical Society. Cryo-TEM images and corresponding schematic illustrations of different SEI nanostructure formed at h) 20 °C and i) 60 °C, respectively.…”

Designing Advanced Lithium‐Based Batteries for Low‐Temperature Conditions

“…[45] Thus, engineering a more favorable SEI could potentially suppress the high surface area growth and dead-lithium formation characteristic to lithium-metal at sub-zero temperatures. [43] McDowell and co-workers recently demonstrated the degree to which cycling in ether versus cyclic carbonate electrolytes affects the subsequent morphology of lithium-metal deposition at low temperatures. [46] Interestingly, they demonstrated that lithium metal deposits cycled in a mixed ether-carbonate formulation tend to be larger on average than those cycled in a pure ether solvent, and subsequently demonstrated better cycling performance at low-temperature conditions.…”

“…The vast presence of supporting salt at such Reproduced with permission. [43] Copyright 2019, American Chemical Society.…”

“…As outlined in a recent study performed by McDowell and co‐workers, one primary difference at low temperatures is that lithium‐metal SEIs contain a much higher proportion of inorganic LiF components, with significantly diminished presence of organic polymeric decomposition products. [ 43 ] Furthermore, the formed layer is found to be much thinner and less resistive. Finally, the morphology of lithium‐metal deposits is found to be much more nanoscale with substantially increased surface area, as shown Figure 3 .…”