Chemical and Biomolecular Engineering Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2751
Browse
2 results
Search Results
Item NOVEL AQUEOUS-BASED ELECTROLYTES AND ELECTRODE SYSTEMS FOR THE NEXT GENERATION OF AQUEOUS LITHIUM-ION BATTERIES(2022) Eidson, Nicolas Thierry; Wang, Chunsheng; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Aqueous Li-ion batteries are a vital component for the future electrification of society. Their extreme safety and reduced manufacturing costs could enable them to fit into many niche markets. Current aqueous Li-ion battery systems suffer from many of the same form factor restrictions as organic Li-ion batteries and rely heavily on maximizing the amount of LiTFSI in the system at the cost of important properties such as electrolyte cost, viscosity, and ionic conductivity in order to maintain the highly concentrated electrolyte classification. They are also limited by the lack of suitable anodes to replace the dominant choice of LTO. Much of the advancement in recent years has been due to the focus on improving the SEI with less attention paid to other important concerns. The goal of this research is not only to continue advancing the limits of aqueous Li-ion batteries, but to shed light on some of the other areas that are often overlooked but of equal importance. Reported here are three key advancements in the development of a novel aqueous cell chemistry for form factor, electrolyte, and anode. First is the development of a gel polymer electrolyte and gel protection layer for the fabrication of a flexible 4V aqueous Li-ion battery employing a Graphite/LCO electrode pair, with focus given to the system’s feasibility to be transitioned to industry. Second, the development of a safer hybrid electrolyte and subsequent transition from the highly concentrated electrolyte regime to the first reported localized highly concentrated hybrid aqueous/non-aqueous electrolyte. Finally, the first incorporation of TNO as an anode replacement for LTO. With the combination of this novel electrolyte and aqueous anode chemistry, a TNO/LMO full cell using a 1,4-dioxane diluted water/TEP co-solvent electrolyte provided an initial discharge capacity of 187 mAh/g reaching a Coulombic efficiency of >99.5% and a capacity retention of 92% after 90 cycles at a cycling cutoff potential of 2.8V.Item NANOSTRUCTURED THIN FILM POLYMER ELECTROLYTES FOR FLEXIBLE BATTERY APPLICATIONS(2009) Ghosh, Ayan; Kofinas, Peter; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In recent years, the interest in polymeric batteries has increased dramatically. With the advent of lithium ion batteries being used in cell phones and laptop computers, the search for an all solid state battery has continued. Current configurations have a liquid or gel electrolyte along with a separator between the anode and cathode. This leads to problems with electrolyte loss and decreased performance over time. The highly reactive nature of these electrolytes necessitates the use of protective enclosures which add to the size and bulk of the battery. Polymer electrolytes are more compliant than conventional inorganic glass or ceramic electrolytes. The goal of this work was to design and investigate novel nanoscale polymer electrolyte flexible thin films based on the self-assembly of block copolymers. Block copolymers were synthesized, consisting of a larger PEO block and a smaller block consisting of random copolymer of methyl methacrylate (MMA) and the lithium salt of methacrylic acid (MAALi). The diblock copolymer [PEO-b-(PMMA-ran-PMAALi)] with added lithium bis(oxalato)borate, LiBC4O8 (LiBOB) salt (in the molar ratio ethylene oxide:LiBOB = 3:1) was used to form flexible translucent films which exhibited nearly two orders of magnitude greater conductivity than that shown by traditional high molecular weight PEO homopolymer electrolytes, in the absence of ceramic fillers and similar additives. The presence of the smaller second block and the plasticizing effect of the bulky lithium salt were shown to effectively reduce the crystallinity of the solid electrolyte, resulting in improved ion transporting behavior. The tailored solid self-assembled diblock copolymer electrolyte matrix also exhibits an exceptionally high lithium-ion transference number of 0.9, compared to a value between 0.2 and 0.5, shown by typical polymer-lithium salt materials. The electrolyte material also has a wide electrochemical stability window and excellent interfacial behavior with lithium metal electrode. The combination of these properties make electrolyte membranes composed of the diblock copolymer PEO-b-(PMMA-ran-PMAALi) and LiBOB salt, viable electrolyte candidates for flexible lithium ion based energy conversion/storage devices.