Ionogel Electrolytes through Sol-Gel Processing.
Horowitz, Ariel.
2015
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Abstract: Electrical energy needs have intensified due to the ubiquity of
personal electronics, the decarbonization of energy services through electrification, and
the use of intermittent renewable energy sources. Despite developments in mechanical and
thermal methods, electrochemical technologies are the most convenient and effective means
of storing electrical energy. These technologies incl... read moreude both electrochemical cells,
commonly called batteries, and electrochemical double-layer capacitors, or
"supercapacitors", which store energy electrostatically. Both device types require an
ion-conducting electrolyte. Current devices use solutions of complex salts in organic
solvents, leading to both toxicity and flammability concerns. These drawbacks can be
avoided by replacing conventional electrolytes with room-temperature molten salts, known as
ionic liquids (ILs). ILs are non-volatile, non-flammable, and offer high conductivity and
good electrochemical stability. Device mass can be reduced by combining ILs with a solid
scaffold material to form an "ionogel," further improving performance metrics. In this
work, sol-gel chemistry is explored as a means of forming ionogel electrolytes. Sol-gel
chemistry is a solution-based, industrially-relevant, well-studied technique by which
solids such as silica can be formed in situ. Previous works used a simple acid-catalyzed
sol-gel reaction to create brittle, glassy ionogels. Here, both the range of products that
can be accomplished through sol-gel processing and the understanding of interactions
between ILs and the sol-gel reaction network are greatly expanded. This work introduces
novel ionogel materials, including soft and compliant silica-supported ionogels and
PDMS-supported ionogels. The impacts of the reactive formulation, IL identity, and casting
time are detailed. It is demonstrated that variations in formulation can lead to rapid
gelation and open pore structures in the silica scaffold or slow gelation and more dense
silica morphologies. The IL identity is shown to have an impact on the apparent strength of
the acid catalyst, leading to significant shifts in gelation time. Delayed casting is
proven to be an optimal technique for avoiding pore blockage when combining ionogels with
high surface area electrodes for supercapacitor applications. Finally, a simple recycling
process is proposed, establishing that ILs can be easily reclaimed from silica-supported
ionogels and reused, thereby validating the reputation of ILs as "green"
materials.
Thesis (Ph.D.)--Tufts University, 2015.
Submitted to the Dept. of Chemical and Biological Engineering.
Advisor: Matthew Panzer.
Committee: William Moomaw, David Ofer, and Daniel Ryder.
Keywords: Chemical engineering, Materials Science, and Energy.read less - ID:
- wh247516t
- Component ID:
- tufts:21442
- To Cite:
- DCA Citation Guide EndNote
