Title:
Understanding the Role Mechanical Properties of Lithium Metal and Reacted Interphases Play in Solid-Solid Interfacial Chemo-Mechanics of Batteries
Understanding the Role Mechanical Properties of Lithium Metal and Reacted Interphases Play in Solid-Solid Interfacial Chemo-Mechanics of Batteries
Author(s)
Marchese, Thomas S.
Advisor(s)
McDowell, Matthew T.
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Abstract
Batteries are being incorporated into many technologies around us in the age of the ‘smart home’ and wearable technology. This, along with the electrification of vehicles, is creating exponential growth in the demand for high energy density batteries. Commercialization of lithium metal anode solid-state batteries would increase the energy density and safety by replacing the flammable liquid electrolyte with a solid-state electrolyte. Understanding the mechanical properties of lithium metal foil for battery anodes is imperative to forming and maintaining the solid-solid interfaces in these systems. Alkali metals have low yield strength (~1 MPa or lower) and are sensitive to creep; such deformation behavior needs to be understood under realistic multi-contact conditions prior to commercial implementation. Here, we demonstrate a new constant loading indentation mechanical deformation technique that employs indenter arrays of different sizes and spacings dropped into contact by force of gravity. The indenters probe the average material response to an array of contacting points, which is directly applicable to the conditions realized in bench-scale solid-state battery production. Testing across three different stainless steel indenter array sizes and a stainless-steel single pillar indenter of equivalent cumulative contact surface area at a single loading value demonstrated size effects of lithium metal foil. Examining the average total deformation observed over 12 minutes, the single pillar indenter averaged a total displacement of 99.40 ± 36.67 μm and the large indenter array averaged 99.16 ± 17.98 μm. Less deformation was seen by the medium indenter array which averaged 29.93 ± 9.06 μm, and by the small indenter array which averaged 45.00 ± 6.41 μm in total displacement. The smaller indenters are seen to penetrate to a lower depth due to increased frictional resistance by greater total surface area in contact and earlier horizontal interaction of neighboring indenters deformation volumes. This indentation array technique provides important knowledge for analyzing realistic deformation behavior of lithium and will provide insight into the action of creep in “healing” voids at the alkali anode/SSE interface. The importance of conformal component contact cannot be overstated in the creation of stable and reproducible electrochemical performance for lithium metal solid-state batteries.
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Date Issued
2023-06-02
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Undergraduate Thesis