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Title: Electrochemical testing of alkali metal-oxygen batteries
Author: Nogueira, F. B.
ISNI:       0000 0004 7428 6064
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2018
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The main focus of this thesis is the development of high specific energy alkali metal-oxygen batteries. Chapter 1 provides a general point of view of the energy storage field and the specific background knowledge of each alkali metaloxygen system. Chapter 2 discusses the experimental methods and techniques applied for the investigation of these battery devices. Chapter 3 investigates specific approaches for the development of the nonaqueous lithium-oxygen battery. An attempt to fabricate more suitable positive electrodes is made by utilising hypercrosslinked polymer carbons. The effect of nitrogen heteroatom doping and pore volume on the performance of lithium-oxygen cell is discussed. The effect of integrating a tertiary amine acting as a singlet oxygen quencher on the performance of the cell is evaluated. Analysis of the chemical nature and morphology of discharge products helped elucidate the processes occurring during galvanostatic cycling. Chapter 4 sets out an investigation into several aspects of the non-aqueous sodium-oxygen battery. The stability of various cells components, such as carbon, polymeric binder and electrolyte solvent, against superoxide radical attack is evaluated. The conditions in which the discharge of the cell undergoes different solution or surface mechanisms is determined as well as the conditions in which different reaction products are obtained. The stability of sodium superoxide, the desired discharge product, in the battery environment is discussed. Chapter 5 presents a comprehensive study into the non-aqueous potassiumoxygen battery. In ether based electrolytes, faster kinetics for the formation and decomposition of potassium superoxide are obtained. Electrolyte degradation products are detected to a lesser extent compared to other alkali metal-oxygen cells. The main factor hindering long cycling are instabilities associated with the metal anode. The condition in which a protective surface layer or a passivating surface layer are formed on the metal anode are determined. Attempts to enhance the stability of the protective surface layer are performed by utilising highly concentrated electrolytes and ionic liquid based electrolytes. An alternative antimony based anode material is investigated and stable cycling with capacities close to the theoretical value are obtained. Finally, the oxygen reduction/evolution reactions occurring at the positive electrode are analysed by looking into the stability of polymer binders, the performance of carbon cathodes and the stability of potassium superoxide in the cell environment.
Supervisor: Hardwick, Laurence Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral