title: Liquid Sulfur Impregnation of Microporous Carbon Accelerated by Nanoscale Interfacial Effects.
abstract: Impregnation of porous carbon matrices with liquid sulfur has been exploited to fabricate composite cathodes for lithium-sulfur batteries, aimed at confining soluble sulfur species near conducting carbon to prevent both loss of active material into the electrolyte and parasitic reactions at the lithium metal anode. Here, through extensive computer simulations, we uncover the strongly favorable interfacial free energy between liquid sulfur and graphitic surfaces that underlies this phenomenon. Previously unexplored curvature-dependent enhancements are shown to favor the filling of smaller pores first and effect a quasi-liquid sulfur phase in microporous domains (diameters <2 nm) that persists ∼30° below the expected freezing point. Evidence of interfacial sulfur on carbon is shown to be a 0.3 eV red shift in the simulated and measured interfacial X-ray absorption spectra. Our results elucidate the critical morphology and thermodynamic properties necessary for future cathode design and highlight the importance of molecular-scale details in defining emergent properties of functional nanoscale interfaces.
authors.affiliation: Molecular Foundry, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Tod A
authors.identifier: 0000-0003-2096-1143
authors.initials: TA
authors.lastname: Pascal
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California , Berkeley, California 94720, United States.|Energy Technologies Area, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Irune
authors.identifier: 0000-0002-1299-2479
authors.initials: I
authors.lastname: Villaluenga
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Kevin H
authors.initials: KH
authors.lastname: Wujcik
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California , Berkeley, California 94720, United States.|Energy Technologies Area, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Didier
authors.initials: D
authors.lastname: Devaux
authors.affiliation: Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Xi
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Department of Materials Science and Engineering, University of California , Berkeley, California 94720, United States.
authors.forename: Dunyang Rita
authors.initials: DR
authors.lastname: Wang
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California , Berkeley, California 94720, United States.|Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Energy Technologies Area, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Nitash
authors.identifier: 0000-0002-0106-5565
authors.initials: N
authors.lastname: Balsara
authors.affiliation: Molecular Foundry, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: David
authors.initials: D
authors.lastname: Prendergast
keywords: Battery; computer simulation; energy storage; entropy; free energy; molecular dynamics; nanoscale; spectroscopy; sulfur