Morphological, mechanical and electrochemical investigations into the solid electrolyte interphase
- Despite their importance to an array of technologies, many processes in lithium-ion batteries are incompletely understood, especially those involving air sensitive interfaces such as the solid electrolyte interphase (SEI). Motivated by a desire enable next generation lithium-ion battery chemistries, this thesis attempts to shed light on the SEI in its native environment by a combination of in-situ and operando techniques including atomic force microscopy (AFM), selected because its ability to take nanoscale measurements of the SEI in its native liquid environment. To further capture insights into the SEI's formation and evolution, electrochemical impedance spectroscopy (EIS) is leveraged since its quantitative and nondestructive capabilities are highly synergistic with AFM operando techniques. First this thesis explores the process by which the SEI self-passivates, combining data from AFM thickness measurements and electrochemical capacity to demonstrate to demonstrate that models assuming a single SEI phase cannot simultaneously describe capacity and thickness of the initially grown SEI. Second the nanomechanical capabilities of the AFM are leveraged to study SEI grown on lithium metal, a promising next-generation anode material. While the Young's modulus has of SEI has been previously reported, lack of replicates and poor reproducibility of experiments makes interpreting the relationship between mechanics and performance difficult. Further non-elastic mechanical properties are rarely reported, despite their key role in many types of solid electrolyte and protective coating. Combining a more complex indentation protocol with the use of replicates and careful statistics, this work demonstrates that although the elastic properties are uncorrelated to cell performance, the inelastic properties are and that SEI creep under load is correlated with poor cycling efficiency of lithium metal in the associated electrolyte. The final scientific question tackled by this work is how the impedance of the SEI varies during formation, both as a function of potential and time. The SEI resistance is shown to grow linearly with SEI capacity once past the very initial formation. Further, the low frequency portion of the EIS spectra, which is not frequently studied, is discussed and shown to relate both to blocking processes at the copper-SEI interface as well as electrolyte reactivity that gives rise to the formation of new SEI.
|Type of resource
|electronic resource; remote; computer; online resource
|1 online resource.
|Thaman, Henry Louis
|Degree committee member
|Degree committee member
|Stanford University, School of Engineering
|Stanford University, Department of Materials Science and Engineering
|Statement of responsibility
|Henry Louis Thaman.
|Submitted to the Department of Materials Science and Engineering.
|Thesis Ph.D. Stanford University 2023.
- © 2023 by Henry Louis Thaman
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