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Understanding the amorphous lithiation pathway of the type I Ba8Ge43 clathrate with synchrotron X-ray characterization

DOI: 10.1021/acs.chemmater.0c03641 DOI Help

Authors: Andrew Dopilka (Arizona State University) , Amanda Childs (University of Delaware) , Svilen Bobev (University of Delaware) , Candace Chan (Arizona State University; Max-Planck-Institut für Kohlenforschung)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemistry Of Materials

State: Published (Approved)
Published: October 2020
Diamond Proposal Number(s): 21467 , 22209

Open Access Open Access

Abstract: Tetrel (Tt = Si, Ge, and Sn) clathrates have highly tunable host–guest structures and have been investigated as novel electrode materials for Li-ion batteries. However, there is little understanding of how the clathrate structure affects the lithiation processes and phase evolution. Herein, the electrochemical lithiation pathway of type I clathrate Ba8Ge43 is investigated with synchrotron X-ray diffraction (XRD) and pair distribution function (PDF) analyses and compared to the lithiation of germanium with a diamond cubic structure (α-Ge). The results confirm previous laboratory XRD studies showing that Ba8Ge43 goes through a solely amorphous phase transformation, which contrasts with the crystalline phase transformations that take place during lithiation of micrometer-sized α-Ge particles. The local structure of framework-substituted clathrate Ba8Al16Ge30 after lithiation is found to proceed through an amorphous phase transformation similar to that in Ba8Ge43. In situ PDF and XRD during heating show that the amorphous phases derived from lithiation of Ba8Ge43 are structurally related to various Li–Ge phases and crystallize at low temperatures (350–420 K). We conclude that the Ba atoms inside the clathrate structure act to break up the long-range ordering of Li–Ge clusters and kinetically prevent the nucleation and growth of bulk crystalline phases. The amorphous phase evolution of the clathrate structure during lithiation results in electrochemical properties distinct from those in α-Ge, such as a single-phase reaction mechanism and lower voltage, suggesting possible advantages of clathrates over elemental phases for use as anodes in Li-ion batteries.

Journal Keywords: Crystal structure; Lithiation; Solvate; Physical and chemical processes; Phase transitions

Subject Areas: Materials, Chemistry, Energy

Instruments: I15-1-X-ray Pair Distribution Function (XPDF)

Other Facilities: Beamline P02.1 at DESY


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