title: The Impact of Li Grain Size on Coulombic Efficiency in Li Batteries.
abstract: One of the most promising means to increase the energy density of state-of-the-art lithium Li-ion batteries is to replace the graphite anode with a Li metal anode. While the direct use of Li metal may be highly advantageous, at present its practical application is limited by issues related to dendrite growth and low Coulombic efficiency, CE. Here operando electrochemical scanning transmission electron microscopy (STEM) is used to directly image the deposition/stripping of Li at the anode-electrolyte interface in a Li-based battery. A non-aqueous electrolyte containing small amounts of H2O as an additive results in remarkably different deposition/stripping properties as compared to the "dry" electrolyte when operated under identical electrochemical conditions. The electrolyte with the additive deposits more Li during the first cycle, with the grain sizes of the Li deposits being significantly larger and more variable. The stripping of the Li upon discharge is also more complete, i.e., there is a higher cycling CE. This suggests that larger grain sizes are indicative of better performance by leading to more uniform Li deposition and an overall decrease in the formation of Li dendrites and side reactions with electrolyte components, thus potentially paving the way for the direct use of Li metal in battery technologies.
authors.affiliation: Joint Center for Energy Storage Research (JCESR), Pacific Northwest National Laboratory (PNNL), Richland, WA 99352, USA.|Physical and Computational Science Directorate, PNNL, Richland, WA 99352, USA.
authors.forename: B Layla
authors.initials: BL
authors.lastname: Mehdi
authors.affiliation: National Security Directorate, PNNL, Richland, WA 99352, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Stevens
authors.affiliation: Joint Center for Energy Storage Research (JCESR), Pacific Northwest National Laboratory (PNNL), Richland, WA 99352, USA.|Energy and Environmental Directorate, PNNL, Richland, WA 99352, USA.
authors.forename: Jiangfeng
authors.initials: J
authors.lastname: Qian
authors.affiliation: Industrial and Manufacturing Engineering, Florida State University, Tallahassee, FL 32306, USA.
authors.forename: Chiwoo
authors.initials: C
authors.lastname: Park
authors.affiliation: Joint Center for Energy Storage Research (JCESR), Pacific Northwest National Laboratory (PNNL), Richland, WA 99352, USA.|Energy and Environmental Directorate, PNNL, Richland, WA 99352, USA.
authors.forename: Wu
authors.initials: W
authors.lastname: Xu
authors.affiliation: Energy and Environmental Directorate, PNNL, Richland, WA 99352, USA.
authors.forename: Wesley A
authors.initials: WA
authors.lastname: Henderson
authors.affiliation: Joint Center for Energy Storage Research (JCESR), Pacific Northwest National Laboratory (PNNL), Richland, WA 99352, USA.|Energy and Environmental Directorate, PNNL, Richland, WA 99352, USA.
authors.forename: Ji-Guang
authors.initials: JG
authors.lastname: Zhang
authors.affiliation: Joint Center for Energy Storage Research (JCESR), Pacific Northwest National Laboratory (PNNL), Richland, WA 99352, USA.|Environmental Molecular Sciences Laboratory, PNNL, Richland, WA 99352, USA.|Department of Chemistry, Penn State University, University Park, PA, 16802, USA.
authors.forename: Karl T
authors.initials: KT
authors.lastname: Mueller
authors.affiliation: Joint Center for Energy Storage Research (JCESR), Pacific Northwest National Laboratory (PNNL), Richland, WA 99352, USA.|Physical and Computational Science Directorate, PNNL, Richland, WA 99352, USA.|Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA.
authors.forename: Nigel D
authors.initials: ND
authors.lastname: Browning