| Summary: | <p>The lithium-oxygen (Li-O2) battery has the highest theoretical specific energy and energy density amongst modern energy storage technologies. If these can be realised in a practical device, the Li-O2 battery could transform energy storage. There are, however, significant challenges which must be overcome before the move towards a practical device can be considered. These include the improvement of the reversibility of the positive electrode reactions, the development of a high-performance positive Gas Diffusion Electrode (GDE) and the stabilisation of the Li metal negative electrode. The following thesis deals with the second of these challenges, namely the development of a GDE which allows for sufficient O2 mass transport to achieve high areal capacities at practical discharge rates.</p>
<p>In the first results chapter, a Gas Diffusion Polymer (GDP) is introduced into the GDE with the dual purpose of binding carbon together and transporting oxygen throughout the volume of the electrode. The GDP allows for areal capacities of 30 mAh cm-2 at discharge rates of 1 mA cm-2. A new technique is introduced to quantify the distribution of lithium peroxide at the end of discharge, presenting evidence of the oxygen mass transport capabilities of the GDE.</p>
<p>The second results chapter introduces oxygen diffusion channels into the newly developed GDE. Li2O2 depth profiling experiments on a 500 µm thick electrode provides insight into the ideal channel architecture. The channels are then fabricated with the aid of sub-micron scale 3D-printing.</p>
<p>Acknowledging the instability of the cell during discharge and charge, the final results chapter explores the cyclability of high energy density GDEs. The accumulation of lithium carbonate causes cell death after only 12 cycles. By removing the lithium carbonate, the cell is able to sustain cycling for a further 10 cycles.</p>
|
|---|