Date of Award
Elizabeth J. Biddinger
Robert J. Messinger
Battery, Safety, Switchable Electrolyte
Modern Li-ion batteries employ flammable electrolytes that pose safety concerns. Battery safety has become important as several incidents involving Li-ion battery fires have been observed. This issue could be addressed through a switchable battery electrolyte. Reversible ionic liquids (RevILs) could be used in such an electrolyte that would cease operation in the event of rapid temperature elevation because they can switch between states of drastically different properties upon the application of an external stimulus, such as temperature or CO2 addition. Silylamines, in particular, are a class of thermally responsive RevILs that are conducting in its ionic liquid (RevIL) state and non-conducting in its molecular liquid (ML) state. Thus, silylamines could serve as model compounds for the thermally switchable battery electrolyte concept. However, the temperature dynamics and ion-ion interactions within the silylamine system need to be understood before implementation.
This thesis explores the viability of the (3-aminopropyl)tripropylsilylamine (TPSA) system based on its thermal responses and salt interactions. Because neat TPSA (RevIL) is viscous and non-conductive, TPSA was also studied as a solvent mixture with DMSO. Variable temperature (VT) FT-IR studies showed that the RevIL to ML switch was maintained in the TPSA/DMSO system. VT conductivity studies showed a conductivity maximum at 90°C. The thermal dependence of conductivity makes TPSA a potential candidate for the thermal switch. HOESY and PGSE NMR experiments were also performed to understand the issue of salt solubility, which correlate the ion-ion interactions within the electrolyte mixture. These experiments revealed that the alkyl groups may participate in interactions upon addition of lithium hexafluorophosphate salt, which results in inhibited diffusion. This signals a possible route for tuning the TPSA structure to improving the conductivity and salt solubility for eventual use as an electrolyte solvent.
Chen, Josephine, "Understanding of Molecular Interactions and Reversibility in Silylamines" (2018). CUNY Academic Works.