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Title: Elucidation of the Local and Long-Range Structural Changes that Occur in Germanium Anodes in Lithium-Ion Batteries

Abstract

Metallic germanium is a promising anode material in secondary lithium-ion batteries (LIBs) due to its high theoretical capacity (1623 mAh/g) and low operating voltage, coupled with the high lithium-ion diffusivity and electronic conductivity of lithiated Ge. Here, the lithiation mechanism of micron-sized Ge anodes has been investigated with X-ray diffraction (XRD), pair distribution function (PDF) analysis, and in-/ex-situ high-resolution Li-7 solid-state nuclear magnetic resonance (NMR), utilizing the structural information and spectroscopic fingerprints obtained by characterizing a series of relevant Li(x)Gey model compounds. In contrast to previous work, which postulated the formation of Li9Ge4 upon initial lithiation, we show that crystalline Ge first reacts to form a mixture of amorphous and crystalline Li7Ge3 (space group P32(1)2). Although Li7Ge3 was proposed to be stable in a recent theoretical study of the Li-Ge phase diagram (Morris, A. J.; Grey, C. P.; Pickard, C. J. Phys. Rev. B: Condens. Matter Mater. Phys. 2014, 90, 054111), it had not been identified in prior experimental studies. Further lithiation results in the transformation of Li7Ge3, via a series of disordered phases with related structural motifs, to form a phase that locally resembles Li7Ge2, a process that involves the gradual breakage of the Ge-Ge bonds in the Ge-Gemore » dimers (dumbbells) on lithiation. Crystalline Li15Ge4 then grows, with an overlithiated phase, Li15+delta Ge4, being formed at the end of discharge. This study provides comprehensive experimental evidence, by using techniques that probe short-, medium-, and long-range order, for the structural transformations that occur on electrochemical lithiation of Ge; the results are consistent with corresponding theoretical studies regarding stable lithiated LixGey phases.« less

Authors:
; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1391996
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemistry of Materials; Journal Volume: 27; Journal Issue: 3
Country of Publication:
United States
Language:
English

Citation Formats

Jung, Hyeyoung, Allan, Phoebe K., Hu, Yan-Yan, Borkiewicz, Olaf J., Wang, Xiao-Liang, Han, Wei-Qiang, Du, Lin-Shu, Pickard, Chris J., Chupas, Peter J., Chapman, Karena W., Morris, Andrew J., and Grey, Clare P. Elucidation of the Local and Long-Range Structural Changes that Occur in Germanium Anodes in Lithium-Ion Batteries. United States: N. p., 2015. Web. doi:10.1021/cm504312x.
Jung, Hyeyoung, Allan, Phoebe K., Hu, Yan-Yan, Borkiewicz, Olaf J., Wang, Xiao-Liang, Han, Wei-Qiang, Du, Lin-Shu, Pickard, Chris J., Chupas, Peter J., Chapman, Karena W., Morris, Andrew J., & Grey, Clare P. Elucidation of the Local and Long-Range Structural Changes that Occur in Germanium Anodes in Lithium-Ion Batteries. United States. doi:10.1021/cm504312x.
Jung, Hyeyoung, Allan, Phoebe K., Hu, Yan-Yan, Borkiewicz, Olaf J., Wang, Xiao-Liang, Han, Wei-Qiang, Du, Lin-Shu, Pickard, Chris J., Chupas, Peter J., Chapman, Karena W., Morris, Andrew J., and Grey, Clare P. Tue . "Elucidation of the Local and Long-Range Structural Changes that Occur in Germanium Anodes in Lithium-Ion Batteries". United States. doi:10.1021/cm504312x.
@article{osti_1391996,
title = {Elucidation of the Local and Long-Range Structural Changes that Occur in Germanium Anodes in Lithium-Ion Batteries},
author = {Jung, Hyeyoung and Allan, Phoebe K. and Hu, Yan-Yan and Borkiewicz, Olaf J. and Wang, Xiao-Liang and Han, Wei-Qiang and Du, Lin-Shu and Pickard, Chris J. and Chupas, Peter J. and Chapman, Karena W. and Morris, Andrew J. and Grey, Clare P.},
abstractNote = {Metallic germanium is a promising anode material in secondary lithium-ion batteries (LIBs) due to its high theoretical capacity (1623 mAh/g) and low operating voltage, coupled with the high lithium-ion diffusivity and electronic conductivity of lithiated Ge. Here, the lithiation mechanism of micron-sized Ge anodes has been investigated with X-ray diffraction (XRD), pair distribution function (PDF) analysis, and in-/ex-situ high-resolution Li-7 solid-state nuclear magnetic resonance (NMR), utilizing the structural information and spectroscopic fingerprints obtained by characterizing a series of relevant Li(x)Gey model compounds. In contrast to previous work, which postulated the formation of Li9Ge4 upon initial lithiation, we show that crystalline Ge first reacts to form a mixture of amorphous and crystalline Li7Ge3 (space group P32(1)2). Although Li7Ge3 was proposed to be stable in a recent theoretical study of the Li-Ge phase diagram (Morris, A. J.; Grey, C. P.; Pickard, C. J. Phys. Rev. B: Condens. Matter Mater. Phys. 2014, 90, 054111), it had not been identified in prior experimental studies. Further lithiation results in the transformation of Li7Ge3, via a series of disordered phases with related structural motifs, to form a phase that locally resembles Li7Ge2, a process that involves the gradual breakage of the Ge-Ge bonds in the Ge-Ge dimers (dumbbells) on lithiation. Crystalline Li15Ge4 then grows, with an overlithiated phase, Li15+delta Ge4, being formed at the end of discharge. This study provides comprehensive experimental evidence, by using techniques that probe short-, medium-, and long-range order, for the structural transformations that occur on electrochemical lithiation of Ge; the results are consistent with corresponding theoretical studies regarding stable lithiated LixGey phases.},
doi = {10.1021/cm504312x},
journal = {Chemistry of Materials},
number = 3,
volume = 27,
place = {United States},
year = {Tue Feb 10 00:00:00 EST 2015},
month = {Tue Feb 10 00:00:00 EST 2015}
}