title: Nanostructured Si(₁-x)Gex for tunable thin film lithium-ion battery anodes.
abstract: Both silicon and germanium are leading candidates to replace the carbon anode of lithium ions batteries. Silicon is attractive because of its high lithium storage capacity while germanium, a superior electronic and ionic conductor, can support much higher charge/discharge rates. Here we investigate the electronic, electrochemical and optical properties of Si(1-x)Gex thin films with x = 0, 0.25, 0.5, 0.75, and 1. Glancing angle deposition provided amorphous films of reproducible nanostructure and porosity. The film's composition and physical properties were investigated by X-ray photoelectron spectroscopy, four-point probe conductivity, Raman, and UV-vis absorption spectroscopy. The films were assembled into coin cells to test their electrochemical properties as a lithium-ion battery anode material. The cells were cycled at various C-rates to determine the upper limits for high rate performance. Adjusting the composition in the Si(1-x)Gex system demonstrates a trade-off between rate capability and specific capacity. We show that high-capacity silicon anodes and high-rate germanium anodes are merely the two extremes; the composition of Si(1-x)Gex alloys provides a new parameter to use in electrode optimization.
authors: Department of Chemical Engineering, University of Texas at Austin, 200 E Dean Keeton Street C0400, Austin, Texas 78712, United States.
authors: Paul R
authors: PR
authors: Abel
authors: Aaron M
authors: AM
authors: Chockla
authors: Yong-Mao
authors: YM
authors: Lin
authors: Vincent C
authors: VC
authors: Holmberg
authors: Justin T
authors: JT
authors: Harris
authors: Brian A
authors: BA
authors: Korgel
authors: Adam
authors: A
authors: Heller
authors: C Buddie
authors: CB
authors: Mullins