title: Solvation behavior of carbonate-based electrolytes in sodium ion batteries.
abstract: Sodium ion batteries are on the cusp of being a commercially available technology. Compared to lithium ion batteries, sodium ion batteries can potentially offer an attractive dollar-per-kilowatt-hour value, though at the penalty of reduced energy density. As a materials system, sodium ion batteries present a unique opportunity to apply lessons learned in the study of electrolytes for lithium ion batteries; specifically, the behavior of the sodium ion in an organic carbonate solution and the relationship of ion solvation with electrode surface passivation. In this work the Li+and Na+-based solvates were characterized using electrospray mass spectrometry, infrared and Raman spectroscopy,17O,23Na and pulse field gradient double-stimulated-echo pulse sequence nuclear magnetic resonance (NMR), and conductivity measurements. Spectroscopic evidence demonstrate that the Li+and Na+cations share a number of similar ion-solvent interaction trends, such as a preference in the gas and liquid phase for a solvation shell rich in cyclic carbonates over linear carbonates and fluorinated carbonates. However, quite different IR spectra due to the PF6-anion interactions with the Na+and Li+cations were observed and were rationalized with the help of density functional theory (DFT) calculations that were also used to examine the relative free energies of solvates using cluster - continuum models. Ion-solvent distances for Na+were longer than Li+, and Na+had a greater tendency towards forming contact pairs compared to Li+in linear carbonate solvents. In tests of hard carbon Na-ion batteries, performance was not well correlated to Na+solvent preference, leading to the possibility that Na+solvent preference may play a reduced role in the passivation of anode surfaces and overall Na-ion battery performance.
authors.affiliation: Electrochemistry Branch, Sensor and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, MD 20783, USA. arthur.v.cresce.civ@mail.mil.
authors.forename: Arthur V
authors.initials: AV
authors.lastname: Cresce
authors.affiliation: Electrochemistry Branch, Sensor and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, MD 20783, USA. arthur.v.cresce.civ@mail.mil.
authors.forename: Selena M
authors.identifier: http://orcid.org/0000-0001-7196-6409
authors.initials: SM
authors.lastname: Russell
authors.affiliation: Electrochemistry Branch, Sensor and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, MD 20783, USA. arthur.v.cresce.civ@mail.mil.
authors.forename: Oleg
authors.initials: O
authors.lastname: Borodin
authors.affiliation: Electrochemistry Branch, Sensor and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, MD 20783, USA. arthur.v.cresce.civ@mail.mil.
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Allen
authors.affiliation: Electrochemistry Branch, Sensor and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, MD 20783, USA. arthur.v.cresce.civ@mail.mil.
authors.forename: Marshall A
authors.initials: MA
authors.lastname: Schroeder
authors.affiliation: Electrochemistry Branch, Sensor and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, MD 20783, USA. arthur.v.cresce.civ@mail.mil.
authors.forename: Michael
authors.initials: M
authors.lastname: Dai
authors.affiliation: Department of Physics, Hunter College, City University of New York, New York, NY, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Peng
authors.affiliation: Department of Physics, Hunter College, City University of New York, New York, NY, USA.
authors.forename: Mallory P
authors.identifier: http://orcid.org/0000-0001-9735-0741
authors.initials: MP
authors.lastname: Gobet
authors.affiliation: Department of Physics, Hunter College, City University of New York, New York, NY, USA.
authors.forename: Steven G
authors.initials: SG
authors.lastname: Greenbaum
authors.affiliation: Department of Chemical Engineering, Rochester Institute of Technology, Rochester, NY, USA.
authors.forename: Reginald E
authors.initials: RE
authors.lastname: Rogers
authors.affiliation: Electrochemistry Branch, Sensor and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, MD 20783, USA. arthur.v.cresce.civ@mail.mil.
authors.forename: Kang
authors.initials: K
authors.lastname: Xu