title: Nanowire Heterostructures Comprising Germanium Stems and Silicon Branches as High-Capacity Li-Ion Anodes with Tunable Rate Capability.
abstract: Here we report the rational design of a high-capacity Li-ion anode material comprising Ge nanowires with Si branches. The unique structure provides an electrode material with tunable properties, allowing the performance to be tailored for either high capacity or high rate capability by controlling the mass ratio of Si to Ge. The binder free Si-Ge branched nanowire heterostructures are grown directly from the current collector and exhibit high capacities of up to ∼1800 mAh/g. Rate capability testing revealed that increasing the Ge content within the material boosted the performance of the anode at fast cycling rates, whereas a higher Si content was optimal at slower rates of charge and discharge. Using ex-situ electron microscopy, Raman spectroscopy and energy dispersive X-ray spectroscopy mapping, the composition of the material is shown to be transient in nature, transforming from a heterostructure to a Si-Ge alloy as a consequence of repeated lithiation and delithiation.
authors.affiliation: †Materials and Surface Science Institute, and ‡Department of Chemical and Environmental Sciences, University of Limerick, Limerick, Ireland.
authors.forename: Tadhg
authors.initials: T
authors.lastname: Kennedy
authors.affiliation: †Materials and Surface Science Institute, and ‡Department of Chemical and Environmental Sciences, University of Limerick, Limerick, Ireland.
authors.forename: Michael
authors.initials: M
authors.lastname: Bezuidenhout
authors.affiliation: †Materials and Surface Science Institute, and ‡Department of Chemical and Environmental Sciences, University of Limerick, Limerick, Ireland.
authors.forename: Kumaranand
authors.initials: K
authors.lastname: Palaniappan
authors.affiliation: †Materials and Surface Science Institute, and ‡Department of Chemical and Environmental Sciences, University of Limerick, Limerick, Ireland.
authors.forename: Killian
authors.initials: K
authors.lastname: Stokes
authors.affiliation: †Materials and Surface Science Institute, and ‡Department of Chemical and Environmental Sciences, University of Limerick, Limerick, Ireland.
authors.forename: Michael
authors.initials: M
authors.lastname: Brandon
authors.affiliation: †Materials and Surface Science Institute, and ‡Department of Chemical and Environmental Sciences, University of Limerick, Limerick, Ireland.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Ryan
keywords: branched nanowires; germanium; heterostructure; lithium-ion anode; silicon