ELECTROSPINNING AND AIR-CONTROLLED ELECTROSPRAYING OF POLYMER/PRECURSOR SOLUTIONS TO PRODUCE NANOMATERIALS FOR ENERGY STORAGE APPLICATIONS
Carlin, Joseph Michael
Electrochemical energy storage is increasingly used in applications ranging from portable electronics to electric vehicles to grid-sized storage installations and the next generation of energy storage requires increased capacity, performance, and safety. To meet these demands, energy storage will rely more heavily on the use of nanostructured materials to improve performance. However, there are few ways to produce nanomaterials scalably while keeping them from being cost prohibitive. This work focuses on using electrospinning and air-controlled electrospraying techniques to prepare electrodes and separators for energy storage. These processes have the advantage of using inexpensive precursors, scalable production, and direct application of fiber mats and films and can overcome many of the shortcomings of conventional processes. First, electrospinning is used to prepare free-standing, binder-free electrodes. Utilizing the natural non-woven mat formed by electrospinning, both carbon and carbon composite fiber sheets are prepared from polymer and precursor solutions and used directly as electrodes after heat treatment. These electrodes are used in supercapacitor, Li-ion, and Li-air energy storage applications. Second, a combination of electrospinning and air-controlled electrospraying is used to prepare silicon fiber/RGO, direct-deposit anodes for Li-ion batteries. Silicon fibers are prepared by magnesiothermic reduction of electrospun silica fibers. Anodes are then prepared using a binder-free, water-based, direct-deposition method of electrospraying fibers with graphene sheets. After thermal treatment, reduced graphene oxide and silicon fiber anodes show high cycling capacity and rate capability. The system shows stability in accommodating silicon expansion, and the use of large diameter silicon fibers increased first coulombic efficiencies above 80%. Finally, Li-ion battery separators are made using a combination of polymer and ceramic precursor. Electrospun separators have always shown excellent performance, but their large pore sizes can lead to short circuits and many of the common polymers used, such as PAN and PVDF, do not mitigate the risk of fire and other safety hazards. Through combinations of electrospinning and air-controlled electrospraying, as well as use of thermally resistant polymers with ceramic precursors, this work achieves thermally robust, flame-resistant separators with improved pore size distribution for safer, high rate Li-ion batteries.
Battery Separator; Ceramic Precursor; Electrospinning; Electrospraying; Lithium Ion Battery; Polyimide
Joo, Yong L.
Frey, Margaret W.; Daniel, Susan
Ph. D., Chemical Engineering
Doctor of Philosophy
dissertation or thesis