LITHIUM-AIR BATTERY CATHODES: A STUDY ON THE EFFECTS OF FABRICATION METHOD AND ACTIVE MATERIAL PROPERTIES ON BATTERY PEFORMANCE
Lithium Air (Li-Air) batteries have received scientific interest due to their high gravimetric energy density, which is the largest of the well known battery systems; however, the reactive chemistry of these batteries, which is the source of their high energy density, is very taxing on the battery components, creating inefficiencies that limit the progress of these batteries to becoming the replacement for the burning of fossil fuels. Although many different research groups have studied many of the different facets of these challenges, in this thesis, the effects of fabrication methods on structural properties and electrochemical performance are studied. These considerations were limited to the carbon cathode system for multiple reasons. Carbon materials, like activated carbon, graphene, reduced graphene oxide (rGO), carbon nanotubes, etc., where considered due to their relative cheapness and are already considered within the battery industry for traditional battery electrodes for other battery systems and therefore may be more easily adopted by industry for the future production of Li-Air batteries. Additionally, the focus was placed entirely on the battery cathode, as it is normally on the cathode surface where reactions, both desired and parasitic, are taking place.Within this thesis, many different considerations and studies were performed for the Li-Air battery cathode. For experimental laboratory work, the pros and cons of dropcasting electrospraying, and electrospinning were considered for Li-Air battery cathode fabrication. The later two methods are highlighted for their scalability for industrial production line and for the ease at which electrocatalysts can be added into the carbon matrix during the fabrication process. Many different carbon materials, such as rGO, graphene nanoribbons (GNR), and graphenes, of which the latter was made through the industrially scalable Taylor Couette Reactor (TCR) system, and electrocatalysts, such as Molybdenum Carbide (Mo2C), were compared for their different properties as cathode active materials. These were tested both alone and in different morphological hierarchies such as stacked layers and within/on carbon fibers. Additionally, porous carbon cathodes were mathematically modeled via two different numerical model systems in an attempt to parse out the contributions and effects of the different physical and electrochemical characteristics of different Li-Air battery systems, with a level of control that would not be obtainable within traditional experimental battery methods. Altogether, this work seeks to prove the benefits of the air-controlled electrospray (ACES) technique over traditional battery fabrication methods, while still producing a wholistic understanding of both traditional and improved battery cathode systems through both physical and simulated testing of these varying carbon cathode systems.
Batteries; Carbon; Cathode; Electrospray; Li-Air; Li-O2
Joo, Yong L.
Suntivich, Jin; Hanrath, Tobias
Ph. D., Chemical Engineering
Doctor of Philosophy
dissertation or thesis