Performance Enhancement and Corrosion Studies of Metal-Air Batteries

Metal-air batteries (MABs) are an attractive and promising alternative energy storage system to existing batteries due to their high energy density, cost efficiency, and intrinsic safety. They have potential applications in both the electromobility sector and stationary energy storage. This thesis examines the possible uses of MABs, in specific silicon, aluminum, zinc and their alloys, and proposes strategies for performance improvement. One of the main focusses in this research is the potential applications of alkaline and non-aqueous Si-air batteries in low-power electronics. As a proof–of–concept, the use of a Si–air battery with an integrated circuit (IC) on the anode to power an LED is demonstrated. Additionally, the self–destructive capability of the Si–IC is also examined. The study also surveys the potential improvement of Si electrodes through alloying with Al, which show a slight increase in the anodic current densities without passivating the electrode. This work further extends the investigations from the primary Si–air battery to secondary Zn-air batteries (ZABs). ZABs have the advantage that the zinc electrodes can be cycled in several types of electrolytes, including neutral solutions. By doing so, the prejudicial high corrosion of Zn in the alkaline electrolytes is avoided. However, the potentials of zinc in neutral electrolytes are relatively low in comparison to alkaline solutions. To increase the discharge potential of Zn, alloying it with more electronegative materials is proposed, such as Zn–Al alloy. The tested Zn–10 wt.%Al electrodes require, however, an initial cathodic pulse to reveal the more negative potential, which is also limited over time. This study finds that the potential enhancement can be further improved and prolonged by the introduction of the chelating agent ethylenediaminetetraacetic acid (EDTA). Such beneficial effect is present under discharge conditions even after applying relatively high anodic current densities on Zn electrodes. The cycling of the ZABs was possible in both electrolyte formulations but could be slightly extended in presence of EDTA, which also showed higher discharge voltages in comparison to the neat 2M NaCl electrolyte.