Reversible Li-Ion Conversion Reaction for a TixGe Alloy in a Ti/Ge Multilayer

Xiao Chen, Tim T. Fister, Jennifer Esbenshade, Bing Shi, Xianyi Hu, Jinsong Wu, Andrew A. Gewirth, Michael J. Bedzyk, Paul Fenter

Research output: Contribution to journalArticlepeer-review

Abstract

Group IV intermetallics electrochemically alloy with Li with stoichiometries as high as Li4.4M (M = Si, Ge, Sn, or Pb). This provides the second highest known specific capacity (after pure lithium metal) for lithium-ion batteries, but the dramatic volume change during cycling greatly limits their use as anodes in Li-ion batteries. We describe an approach to overcome this limitation by constructing electrodes using a Ge/Ti multilayer architecture. In operando X-ray reflectivity and ex situ transmission electron microscopy are used to characterize the heterolayer structure at various lithium stoichiometries along a lithiation/delithiation cycle. The as-deposited multilayer spontaneously forms a one-dimensional TixGe/Ti/TixGe core-shell planar structure embedded in a Ge matrix. The interfacial TixGe alloy is observed to be electrochemically active and exhibits reversible phase separation (i.e., a conversion reaction). Including the germanium components, the overall multilayer structure exhibits a 2.3-fold reversible vertical expansion and contraction and is shown to have improved capacity and capacity retention with respect to a Ge film with equivalent active material thickness.

Original languageEnglish (US)
Pages (from-to)8169-8176
Number of pages8
JournalACS Applied Materials and Interfaces
Volume9
Issue number9
DOIs
StatePublished - Mar 8 2017

Keywords

  • Ge/Ti alloy
  • Li-ion battery
  • Patterson function
  • X-ray reflectivity
  • germanium
  • multilayer
  • thin film

ASJC Scopus subject areas

  • Materials Science(all)

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