title: Emergence of Metallic Properties at LiFePO4 Surfaces and LiFePO4/Li2S Interfaces: An Ab Initio Study.
abstract: The atomic and electronic structures of the LiFePO4 (LFP) surface, both bare and reconstructed upon possible oxygenation, are theoretically studied by ab initio methods. On the basis of total energy calculations, the atomic structure of the oxygenated surface is proposed, and the effect of surface reconstruction on the electronic properties of the surface is clarified. While bare LFP(010) surface is insulating, adsorption of oxygen leads to the emergence of semimetallic behavior by inducing the conducting states in the band gap of the system. The physical origin of these conducting states is investigated. We further demonstrate that deposition of Li2S layers on top of oxygenated LFP(010) surface leads to the formation of additional conducting hole states in the first layer of Li2S surface because of the charge transfer from sulfur p-states to the gap states of LFP surface. This demonstrates that oxygenated LFP surface not only provides conducting layers itself, but also induces conducting channels in the top layer of Li2S. These results help to achieve further understanding of potential role of LFP particles in improving the performance of Li-S batteries through emergent interface conductivity.
authors.affiliation: Institut de recherche d'Hydro-Québec (IREQ) , 1800, boul. Lionel-Boulet, Varennes, Québec Canada J3X 1S1.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Timoshevskii
authors.affiliation: Institut de recherche d'Hydro-Québec (IREQ) , 1800, boul. Lionel-Boulet, Varennes, Québec Canada J3X 1S1.
authors.forename: Zimin
authors.initials: Z
authors.lastname: Feng
authors.affiliation: Département de génie des mines et matériaux, Division de génie des matériaux, McGill University , Montréal, Québec, Canada H3A 0C5.
authors.forename: Kirk H
authors.initials: KH
authors.lastname: Bevan
authors.affiliation: Institut de recherche d'Hydro-Québec (IREQ) , 1800, boul. Lionel-Boulet, Varennes, Québec Canada J3X 1S1.
authors.forename: Karim
authors.initials: K
authors.lastname: Zaghib
keywords: Li2S; LiFePO4; density functional theory; electronic structure; gap states; interface; lithium−sulfur batteries