Ion transport in novel lithium-ion battery electrolytes
Harnessing polymerization-induced phase separation for hybrid systems
Time: Fri 2024-11-01 10.00
Location: F3 (Flodis), Lindstedtsvägen 26
Video link: https://kth-se.zoom.us/j/61354274681
Language: English
Subject area: Fibre and Polymer Science
Doctoral student: Samuel Emilsson , Ytbehandlingsteknik
Opponent: Professor Claudio Gerbaldi, Politecnico di Torino, Italien
Supervisor: Professor Mats Johansson, Fiber- och polymerteknologi, Ytbehandlingsteknik, Wallenberg Wood Science Center, Polymerteknologi, Wallenberg Wood Science Center, Ytbehandlingsteknik; Professor Göran Lindbergh, Tillämpad elektrokemi, Kemiteknik, Wallenberg Wood Science Center, Tillämpad elektrokemi
QC 20241008
Abstract
Lithium-ion batteries have enabled the rapid adoption of consumer electronics and electromobility. In many next-generation lithium-based batteries, the development of high-performing and safe electrolytes is key. Although liquid electrolytes have high ionic conductivity, they suffer from stability and safety issues. Conversely, solid polymer electrolytes offer a safer and more stable alternative, but exhibit inherently low ionic conductivity. This thesis has focused on developing new hybrid liquid and polymer electrolyte systems.
The first part focuses on understanding the ion transport in new liquid electrolytes and oligomers. Dicarbonate structures with varying spacer and end group were investigated and compared to traditional linear carbonate electrolytes. The dicarbonate electrolytes exhibit high thermal stabilities but simultaneously a non-ideal ion transport with extensive ion pairing. The effect of molecular weight (Mn) and end group on the ion transport in two polymers with different backbones were also investigated. The investigation elucidated the effect of coordination strength on the partial lithium ion transport. It also showed that when changing the molecular weight (Mn), distinct ion transport mechanism regimes did not exist.
The second part focuses on the development of hybrid polymer-liquid electrolytes (HEs) using polymerization-induced phase separation (PIPS). It was shown that both the monomer and porogen structure has a significant effect on thermomechanical and electrochemical properties of the HEs. Finally, the use of UV-initiated PIPS was investigated as an efficient technique to manufacture porous thermoset membranes as battery separators. A membrane with low ionic resistance and promising battery cycling performance was developed. Overall, this thesis shows that hybrid systems have a role to play in systems where multiple properties need to be fulfilled simultaneously and that PIPS is a promising tool to fabricate such materials.