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Electrochemical lithium alloying behavior of guest-free type II silicon clathrates

DOI: 10.1021/acs.jpcc.1c04020 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: The Journal Of Physical Chemistry C

State: Published (Approved)
Published: August 2021
Diamond Proposal Number(s): 22209

Open Access Open Access

Abstract: The guest-free type II Si clathrate (Si136) is an open framework polymorph of Si that displays unique electrochemical reactions with Li. Li ions are first topotactically inserted into the vacant clathrate cages, followed by an alloying reaction that forms an amorphous lithium silicide phase. The alloying reaction voltage is higher than those seen in other Si electrodes, suggesting that there are structural differences in the formed amorphous phases. Synchrotron X-ray total scattering measurements and pair distribution function analysis are employed to characterize the amorphous phases formed after lithiation. The results show that the clathrate becomes completely amorphous at an earlier stage of lithiation when compared to diamond cubic Si, forming a phase with comparatively larger amounts of Si–Si bonding. The initial insertion of Li into the clathrate cages establishes important Li diffusion paths that kinetically enable the formation of an amorphous phase with lower Li content than typically seen in other silicon-based electrodes. After the initial crystalline-to-amorphous conversion reaction, lithiation takes place via solid-solution alloying. These results demonstrate how the topotactic insertion of Li into an alloying host can kinetically enable modified reaction pathways leading to more homogeneous lithiation throughout the electrode, which is beneficial for Li-ion battery applications.

Journal Keywords: Crystal structure; Lithiation; Electrodes; Solvates; Chemical structure

Diamond Keywords: Batteries; Lithium-ion

Subject Areas: Materials, Chemistry, Energy

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

Other Facilities: P02.1 at Deutsches Elektronen-Synchrotron

Added On: 02/09/2021 08:40


Discipline Tags:

Energy Storage Energy Physical Chemistry Energy Materials Chemistry Materials Science

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Scattering Pair Distribution Function (PDF)