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Issue 22, 2017
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Electrochemical synthesis of the allotrope allo-Ge and investigations on its use as an anode material

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Abstract

Due to the high lithium-ion mobility and high theoretical capacity, elemental germanium is an interesting candidate for anode materials. The layered Ge modification allo-Ge just recently obtained as a microcrystalline powder by topochemical oxidation of Li7Ge12 with ethanol has now for the first time been observed by electrochemical delithiation of Li7Ge12. The investigation of the Li-ion battery performance of allo-Ge is reported with operando PXRD phase monitoring compared to α-Ge. In addition, an alternative synthesis of Li7Ge12 by reaction of LiGe and α-Ge is presented. Cycling experiments of coin half-cells containing allo-Ge and α-Ge electrodes, respectively, show that the cycling stability of allo-Ge is inferior to common α-Ge. After an initial amorphization step, all Ge half-cells shuttle between the following phases: crystalline Li15Ge4 ↔ amorphous phase (most likely Li13Ge4) ↔ crystalline Li7Ge3 ↔ amorphous Ge. According to operando PXRD, allo-Ge capacity losses during cycling seem to be characterized by electronically disconnected Li7Ge3. The inferior cycling stability of allo-Ge, which consists of stacked Ge sheets, is therefore attributed to a morphological predisposition towards aging for consistency and contact loss in LIBs.

Graphical abstract: Electrochemical synthesis of the allotrope allo-Ge and investigations on its use as an anode material

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Publication details

The article was received on 11 Apr 2017, accepted on 13 May 2017 and first published on 17 May 2017


Article type: Paper
DOI: 10.1039/C7TA03164E
Citation: J. Mater. Chem. A, 2017,5, 11179-11187
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    Electrochemical synthesis of the allotrope allo-Ge and investigations on its use as an anode material

    L. M. Scherf, J. Hattendorff, I. Buchberger, S. Geier, H. A. Gasteiger and T. F. Fässler, J. Mater. Chem. A, 2017, 5, 11179
    DOI: 10.1039/C7TA03164E

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