Date of Award
Master of Science (MS)
The explosive growth of electrochemistry and battery research has been fueled by two primary sources; the complexity of lithium-ion chemistries and the potential impact of high-performance energy storage markets. Superior energy storage aims to connect energy produced from clean, renewable sources with the grid fluctuations and transportation demands. Through electrochemical devices, the lithium-ion battery holds high potential to be that connection, and unlocking this potential starts with materials science and engineering. A lack of a singular, clear direction to higher energy dense batteries leaves many pathways open for investigation.
Since the commercialization of lithium-ion batteries, liquid electrolyte systems have dominated, but novel and niche approaches with the liquid electrolyte design space are needed to continue increasing energy density. Nickel manganese cobalt oxide cathodes (NMC) exemplify the next target for high energy materials but are plagued with material and system degradation. Implementing ionic liquid electrolytes with NMC cathodes results in a system with far superior cycle life and energy retention. Commonly, systems such as these would be paired with a graphite anode. Yet, with 10 times the theoretical capacity, silicon anodes have drawn the attention of battery research. Pure silicon and mixed silicon-graphite have been enabled through nano-scale surface treatments to overcome the traditional problems of silicon capacity fade. Ionic liquid/NMC systems and surface coated anodes will be explored in this work.
Solid-state electrolytes look to overtake liquid electrolyte systems and serve as another pathway to improve lithium-ion battery energy density. Lithium phosphorous sulfide electrolytes demonstrate relatively high conductivity for a solid-state material. Iron disulfide cathodes, when paired with this solid-state electrolyte and the mixed-conducting matrix of lithium titanium sulfide, demonstrate very high capacities and elevated rates. Lithium titanium sulfide itself proved to be a pseudocapacitor when prepared via solid-state methods and demonstrated exceptional rate capabilities and stability over long-term cycling. Lithium phosphorous sulfide, iron disulfide, and lithium titanium sulfide will all be discussed in this work.
Despite material science innovations, solid-state batteries are plagued by more than material science limitations; the processing and scaling of solid-state manufacturing techniques poses a significant challenge. Many solid-state electrolytes are not air stable, and common lab-scale methods that yield high performing solid-state batteries are not readily scalable. Within solid-state batteries themselves, thick electrolyte layers, high electrode-electrolyte interface resistance, and porous electrodes limit energy density. The process of synchronized electrospinning electrospraying attempts to both enable solid-state battery fabrication is a continuous roll-to-roll process while simultaneously addressing intrinsic solid-state problems through novel deposition methods.
Hafner, Simon Elnicki, "Enalbing Energy Dense Battery Materials and Paving the Way for Solid-State Batteries" (2019). Mechanical Engineering Graduate Theses & Dissertations. 192.
Available for download on Thursday, December 05, 2019