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Dopilka A, Childs A, Ovchinnikov A, Zhao R, Bobev S, Peng X, Chan CK. Structural and Electrochemical Properties of Type VIII Ba 8Ga 16-δSn 30+δ Clathrate (δ ≈ 1) during Lithiation. ACS APPLIED MATERIALS & INTERFACES 2021; 13:42564-42578. [PMID: 34477361 PMCID: PMC8447186 DOI: 10.1021/acsami.1c07240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 08/04/2021] [Indexed: 06/13/2023]
Abstract
Clathrates of the tetrel (Tt = Si, Ge, Sn) elements are host-guest structures that can undergo Li alloying reactions with high capacities. However, little is known about how the cage structure affects the phase transformations that take place during lithiation. To further this understanding, the structural changes of the type VIII clathrate Ba8Ga16-δSn30+δ (δ ≈ 1) during lithiation are investigated and compared to those in β-Sn with ex situ X-ray total scattering measurements and pair distribution function (PDF) analysis. The results show that the type VIII clathrate undergoes an alloying reaction to form Li-rich amorphous phases (LixBa0.17Ga0.33Sn0.67, x = 2-3) with local structures similar to those in the crystalline binary Li-Sn phases that form during the lithiation of β-Sn. As a result of the amorphous phase transition, the type VIII clathrate reacts at a lower voltage (0.25 V vs Li/Li+) compared to β-Sn (0.45 V) and goes through a solid-solution reaction after the initial conversion of the crystalline clathrate phase. Cycling experiments suggest that the amorphous phase persists after the first lithiation and results in considerably better cycling than in β-Sn. Density functional theory (DFT) calculations suggest that topotactic Li insertion into the clathrate lattice is not favorable due to the high energy of the Li sites, which is consistent with the experimentally observed amorphous phase transformation. The local structure in the clathrate featuring Ba atoms surrounded by a cage of Ga and Sn atoms is hypothesized to kinetically circumvent the formation of Li-Sn or Li-Ga crystalline phases, which results in better cycling and a lower reaction voltage. Based on the improved electrochemical performance, clathrates could act as tunable precursors to form amorphous Li alloying phases with novel electrochemical properties.
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Affiliation(s)
- Andrew Dopilka
- Materials
Science and Engineering, School for Engineering of Matter, Transport
and Energy, Arizona State University, P.O. Box 876106, Tempe, Arizona 85827, United
States
| | - Amanda Childs
- Department
of Chemistry and Biochemistry, University
of Delaware, Newark, Delaware 19716, United States
| | - Alexander Ovchinnikov
- Department
of Chemistry and Biochemistry, University
of Delaware, Newark, Delaware 19716, United States
- Department
of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16 C, 10691 Stockholm, Sweden
| | - Ran Zhao
- School
of Molecular Sciences, Arizona State University, P.O. Box 871604, Tempe, Arizona 85287, United
States
| | - Svilen Bobev
- Department
of Chemistry and Biochemistry, University
of Delaware, Newark, Delaware 19716, United States
| | - Xihong Peng
- College
of Integrative Sciences and Arts, Arizona
State University Polytechnic Campus, Mesa, Arizona 85212, United States
| | - Candace K. Chan
- Materials
Science and Engineering, School for Engineering of Matter, Transport
and Energy, Arizona State University, P.O. Box 876106, Tempe, Arizona 85827, United
States
- Department
of Heterogenous Catalysis, Max-Planck-Institut
für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
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