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ChemRXIV_Submission_Hatzell.pdf (9.33 MB)

In Situ Investigation of Interphase and Microstructure Effects on the Chemo-Mechanics of Thiophosphate Solid Electrolytes

preprint
submitted on 30.06.2020 and posted on 02.07.2020 by Marm Dixit, Nikhilendra Singh, James Horwath, Pavel Shevchenko, Eric Stach, Timothy S. Arthur, Kelsey Hatzell

Lithium thiophosphates (Li3PS4, LPS) are promising solid electrolytes for safe, energy dense solid-state batteries. However, chemo-mechanical transformations within the bulk solid electrolyte and at solidjsolid interfaces can lead to lithium filament formation and fracture-induced failure. The interdependent role of kinetically stable interphases and electrolyte microstructures on the onset and propagation of fracture is not clearly understood. Here, we investigate the effect of interphase chemistry and microstructure on the chemo-mechanical performance of LPS electrolytes. Kinetically metastable interphases are engineered with iodine doping and microstructural control is achieved using milling and annealing processing techniques. In situ transmission electron microscopy reveals how iodine diffuses to the interphase and upon electrochemical cycling pores are formed in the interphase region. Pores/voids formed in the interphase are chemo-mechanically driven via directed ion transport. In situ synchrotron tomography reveals that interphase pore formation drives edge fracture events which are the origin of through-plane fracture failure. Active Li metal has a tendency to fill the fracture region. Cycling lithium in fracture sites leads to localized stress within the solid electrolyte which accumulates and ultimately leads to catastrophic failure. Fractures in thiophosphate electrolytes actively grow toward regions of higher porosity and are impacted by heterogenity in solid electrolyte microstructure (e.g. porosity factor).

Funding

National science foundation 1847029.

History

Email Address of Submitting Author

kelsey.b.hatzell@vanderbilt.edu

Institution

Vanderbilt University

Country

United States

ORCID For Submitting Author

0000-0002-5222-7288

Declaration of Conflict of Interest

None

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