title: Diffusion mechanism of lithium ion through basal plane of layered graphene.
abstract: Coexistence of both edge plane and basal plane in graphite often hinders the understanding of lithium ion diffusion mechanism. In this report, two types of graphene samples were prepared by chemical vapor deposition (CVD): (i) well-defined basal plane graphene grown on Cu foil and (ii) edge plane-enriched graphene layers grown on Ni film. Electrochemical performance of the graphene electrode can be split into two regimes depending on the number of graphene layers: (i) the corrosion-dominant regime and (ii) the lithiation-dominant regime. Li ion diffusion perpendicular to the basal plane of graphene is facilitated by defects, whereas diffusion parallel to the plane is limited by the steric hindrance that originates from aggregated Li ions adsorbed on the abundant defect sites. The critical layer thickness (l(c)) to effectively prohibit substrate reaction using CVD-grown graphene layers was predicted to be ∼6 layers, independent of defect population. Our density functional theory calculations demonstrate that divacancies and higher order defects have reasonable diffusion barrier heights allowing lithium diffusion through the basal plane but neither monovacancies nor Stone-Wales defect.
authors.affiliation: Department of Energy Science, BK21 Physics Division, Graphene Center, Sungkyunkwan Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon, Republic of South Korea.
authors.forename: Fei
authors.initials: F
authors.lastname: Yao
authors.forename: Fethullah
authors.initials: F
authors.lastname: Güneş
authors.forename: Huy Quang
authors.initials: HQ
authors.lastname: Ta
authors.forename: Seung Mi
authors.initials: SM
authors.lastname: Lee
authors.forename: Seung Jin
authors.initials: SJ
authors.lastname: Chae
authors.forename: Kyeu Yoon
authors.initials: KY
authors.lastname: Sheem
authors.forename: Costel Sorin
authors.initials: CS
authors.lastname: Cojocaru
authors.forename: Si Shen
authors.initials: SS
authors.lastname: Xie
authors.forename: Young Hee
authors.initials: YH
authors.lastname: Lee