Publication Date
Spring 2024
Degree Type
Thesis
Degree Name
Master of Science (MS)
Department
Mechanical Engineering
Advisor
Sang-Joon Lee; Dahyun Oh; Min Hwan Lee
Abstract
In a semi-crystalline polymer which consists of rigid, highly ordered (crystalline) and soft, randomly entangled (amorphous) regions, ion transport is promoted by lithium-ion mobility, primarily through the amorphous regions. Mechanical compression can alter ionic conductivity for polymer-based solid electrolytes by limiting polymer chain motion apart from inhibiting dendrite formation. The hypothesis of this investigation is that compressive stress lowers through-plane ionic conductivity as the applied stress densifies the amorphous regions, inhibiting ion transport. The research study experimentally tests how compressive stress can affect ionic conductivity of solution-casted PEO-LiTFSI with and Mw = 600,000 g/mol PEO and 18:1 EO:Li ratio, utilizing simultaneous compression testing and electrochemical impedance spectroscopy, as well as image analysis. It was found that compression in the axial direction after 3 compression cycles decreased ionic conductivity by as much as 34%. The hypothesis was supported, where there were no changes in the semi-crystalline structure upon cyclic compression and that ionic conductivity decreased due to increasing the density of the polymer, reducing possibly free volume within the system. Since mechanical strain reduces ionic conductivity, polymer-based battery electrolytes can be improved by improving elastic modulus of the polymer to limit mechanical strain.
Recommended Citation
Baltazar, Jericko Jay, "EFFECT OF COMPRESSIVE STRAIN ON BULK RESISTANCE AND IONIC CONDUCTIVITY OF PEO-LITFSI SOLID POLYMER ELECTROLYTES" (2024). Master's Theses. 5492.
DOI: https://doi.org/10.31979/etd.ut3b-j495
https://scholarworks.sjsu.edu/etd_theses/5492
