Publication Date
Summer 2026
Degree Type
Thesis
Degree Name
Master of Science (MS)
Department
Mechanical Engineering
Advisor
Sang-Joon (John) Lee; Dahyun Oh; Min Hwan Lee
Abstract
Polymer-based solid state batteries are strong candidates for meeting the increasing demand in small form-factor energy storage due to their broad temperature range for conductivity and compliant mechanical behavior. However, polymer electrolytes are hindered by high crystallinity, which reduces ionic conductivity, so developing techniques that alter polymer morphology (an indicator of crystallinity) is important. The hypothesis of this proposed investigation is that spin coating conditions, such as spin time and substrate type, can affect the morphology of PEO-LiTFSI. This investigation was conducted by quantifying the morphological differences between PEO-LiTFSI (18:1 EO:Li molar ratio) spin-coated on different substrates and for different spin times using optical microscopy. In addition, the differences in ionic conductivity between electrolytes with different morphologies were compared. The polymer exhibited different morphologies when spin-coated on indium tin oxide (ITO), sputtered aluminum, and stainless steel. Image analysis showed significant differences in morphology between electrolytes spin-coated for 30 s and 300 s. Most notably, electrolytes spin-coated for shorter spin time on average had 16% lower area percentage of crystalline regions than those spin-coated for longer spin time. Despite significant morphological differences, ionic conductivity did not differ among the electrolytes, which may be attributed to measurement uncertainty and substrate nonuniformity.
Recommended Citation
Cao, Dang Khoa M., "Influence of Spin Coating Conditions on Semicrystalline Morphology of Thin-Film Peo-Litfsi as a Solid Polymer Electrolyte" (2026). Master's Theses. 5821.
DOI: https://doi.org/10.31979/etd.fqj6-9k9x
https://scholarworks.sjsu.edu/etd_theses/5821
