title: Tailoring lithiation behavior by interface and bandgap engineering at the nanoscale.
abstract: Controlling the transport of lithium (Li) ions and their reaction with electrodes is central in the design of Li-ion batteries for achieving high capacity, high rate, and long lifetime. The flexibility in composition and structure enabled by tailoring electrodes at the nanoscale could drastically change the ionic transport and help meet new levels of Li-ion battery performance. Here, we demonstrate that radial heterostructuring can completely suppress the commonly observed surface insertion of Li ions in all reported nanoscale systems to date and to exclusively induce axial lithiation along the [111] direction in a layer-by-layer fashion. The new lithiation behavior is achieved through the deposition of a conformal, epitaxial, and ultrathin silicon (Si) shell on germanium (Ge) nanowires, which creates an effective chemical potential barrier for Li ion diffusion through and reaction at the nanowire surface, allowing only axial lithiation and volume expansion. These results demonstrate for the first time that interface and bandgap engineering of electrochemical reactions can be utilized to control the nanoscale ionic transport/insertion paths and thus may be a new tool to define the electrochemical reactions in Li-ion batteries.
authors.affiliation: Center for Integrated Nanotechnologies, Sandia National Laboratories , Albuquerque, New Mexico 87185, United States.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.forename: Xiao Hua
authors.initials: XH
authors.lastname: Liu
authors.forename: Binh-Minh
authors.initials: BM
authors.lastname: Nguyen
authors.forename: Jinkyoung
authors.initials: J
authors.lastname: Yoo
authors.forename: John P
authors.initials: JP
authors.lastname: Sullivan
authors.forename: S Tom
authors.initials: ST
authors.lastname: Picraux
authors.forename: Jian Yu
authors.initials: JY
authors.lastname: Huang
authors.forename: Shadi A
authors.initials: SA
authors.lastname: Dayeh
mesh_terms: D011211:Electric Power Supplies; D004563:Electrochemistry; D005857:Germanium / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D008094:Lithium / Q000737:chemistry*; D008968:Molecular Conformation; D053770:Nanowires / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*
chemical_list: D007477:Ions; D005857:Germanium; D008094:Lithium; D012825:Silicon