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Title: Reversible Li-ion conversion reaction for a Ti xGe alloy in a Ti/Ge multilayer

Group IV inter-metallics electrochemically alloy with Li with stoichiometries as high as Li 4.4M (M=Si, Ge, Sn or Pb). Furthermore, 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 hetero-layer structure at various lithium stoichiometries along a lithiation/delithiation cycle. The as-deposited multilayer spontaneously forms a one-dimensional Ti xGe/Ti/Ti xGe core-shell planar structure embedded in a Ge matrix. The interfacial Ti xGe 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.
 [1] ;  [2] ;  [3] ;  [2] ;  [4] ;  [4] ; ORCiD logo [3] ; ORCiD logo [4] ; ORCiD logo [2]
  1. Argonne National Lab. (ANL), Lemont, IL (United States); Northwestern Univ., Evanston, IL (United States)
  2. Argonne National Lab. (ANL), Lemont, IL (United States)
  3. Univ. of Illinois Urbana-Champaign, Champaign, IL (United States)
  4. Northwestern Univ., Evanston, IL (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
ACS Applied Materials and Interfaces
Additional Journal Information:
Journal Volume: 9; Journal Issue: 9; Journal ID: ISSN 1944-8244
American Chemical Society (ACS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
36 MATERIALS SCIENCE; 25 ENERGY STORAGE; Ge/Ti alloy; germanium; Li-ion battery; Patterson function; X-ray reflectivity; multilayer; thin film
OSTI Identifier: