Nanostructured solid-state battery electrolytes

• Main Author: Ong, Jing Yi
• Other Authors: Tan Kwan Wee
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Materials
• Online Access: https://hdl.handle.net/10356/147986
• Institution: Nanyang Technological University

In this report, blends of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were prepared to investigate film morphology and its influences on ionic conductivity and mechanical properties for utilisation as solid-state polymer-based electrolyte. Films of different EO:Li+ compositions of the same thickness were prepared. From DSC and EIS measurements, we found that the solid electrolyte ionic conductivity was significantly improved due to a decrease in systematic crystallinity due to the addition of LiTFSI salt. However, the mechanical properties of the film were compromised, as seen from the DMA results. Further investigation was also conducted for different film thicknesses with the same composition. Surprisingly, the crystallinity of these films was maintained at 25%. This indicated that the change in crystallinity is primarily dependent on EO:Li+ ratio. More specifically, an increased amount of Li+ could potentially promote the mobility of PEO chains, ultimately providing more free conductive pathways for Li+ and resulting in an enhanced ionic conductivity. Therefore, further steps were taken to simultaneously improve the ionic conductivity and mechanical stability of the EO:Li+ film compositions.