Study on Performance Enhancement of Lithium-Oxygen Batteries
thesisposted on 08.02.2018 by Chengji Zhang
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
The electrification of transportation is well-recognized as alternative strategies to minimize the dependence on fossil fuels and eventually address the effects on Climate change. Among all strong candidate for the next generation energy storage technology, the lithium-air battery has attracted exclusively attention in terms of its high theoretical energy density, which is even comparable to gasoline combustion. And as a result, makes it promise for powering the fully battery powered Electric Vehicles (EVs). However, the high overpotential while redox reaction happens between charge and discharge is the enormous challenges obstructed the way to success. On the other hand, electrolyte and electrode decomposition was almost inevitable as the battery keeps cycling and eventually leads to cathode clogging which is in responsible for poor energy efficiency as well as limited cyclability after testing. In this research, in order to achieve highly desirable battery developments, we first introduce Ir3Li, a lithium intermetallic, as new catalyst material that helps stabilize the formation of LiO2, a meta-stable intermediate product instead of the commonly reported Li2O2 after discharge, and as a result mechanically reducing the energy barrier. In addition, the way to fabricate improved carbon black cathode and other performance perfection technique were also investigated. Different characterization techniques including SEM, Raman, and titration will be employed to investigate the morphology as well as the distribution of redox products. Along with battery cycling test, which helps better understand the two-step mechanism of the Li-Oxygen battery system. With the help of all these characterization and justification, an improved Li-O2 cell will be presented with an energy efficiency of 70% for more than 70 cycles with only moderate capacity loss. At the same time, the discharge products are believed to be Lithium superoxide as wanted instead of Lithium peroxide. As a result, the improved Li-O2 battery has been successfully explored that could keep running continuously for more than eight weeks.