title: Structure and Reactivity of Alucone-Coated Films on Si and Li(x)Si(y) Surfaces.
abstract: Coating silicon particles with a suitable thin film has appeared as a possible solution to accommodate the swelling of silicon upon lithiation and its posterior cracking and pulverization during cycling of Li-ion batteries. In particular, aluminum alkoxide (alucone) films have been recently deposited over Si anodes, and the lithiation and electrochemical behavior of the system have been characterized. However, some questions remain regarding the lithium molecular migration mechanisms through the film and the electronic properties of the alucone film. Here we use density functional theory, ab initio molecular dynamics simulations, and Green's function theory to examine the film formation, lithiation, and reactivity in contact with an electrolyte solution. It is found that the film is composed of Al-O complexes with 3-O or 4-O coordination. During lithiation, Li atoms bind very strongly to the O atoms in the most energetically favorable sites. After the film is irreversibly saturated with Li atoms, it becomes electronically conductive. The ethylene carbonate molecules in liquid phase are found to be reduced at the surface of the Li-saturated alucone film following similar electron transfer mechanisms as found previously for lithiated silicon anodes. The theoretical results are in agreement with those from morphology and electrochemical analyses.
authors.forename: Yuguang
authors.initials: Y
authors.lastname: Ma
authors.forename: Julibeth M
authors.initials: JM
authors.lastname: Martinez de la Hoz
authors.forename: Ivette
authors.initials: I
authors.lastname: Angarita
authors.forename: Jose M
authors.initials: JM
authors.lastname: Berrio-Sanchez
authors.forename: Laura
authors.initials: L
authors.lastname: Benitez
authors.forename: Jorge M
authors.initials: JM
authors.lastname: Seminario
authors.affiliation: ∥National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401, United States.
authors.forename: Seoung-Bum
authors.initials: SB
authors.lastname: Son
authors.affiliation: ⊥University of Colorado at Boulder, Boulder, Colorado 80309, United States.
authors.forename: Se-Hee
authors.initials: SH
authors.lastname: Lee
authors.affiliation: ⊥University of Colorado at Boulder, Boulder, Colorado 80309, United States.
authors.forename: Steven M
authors.initials: SM
authors.lastname: George
authors.affiliation: ∥National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401, United States.
authors.forename: Chunmei
authors.initials: C
authors.lastname: Ban
authors.forename: Perla B
authors.initials: PB
authors.lastname: Balbuena
keywords: alucone coating; density functional theory; lithium-ion batteries; silicon anodes; solid-electrolyte-interphase; structural changes from lithiation