Development and characterisation of a lightweight alkaline aluminium-air cell

• Main Author: Egan, Derek
• Other Authors: Ponce De Leon Albarran, Carlos
• Published: University of Southampton 2015
• Subjects: 620; TP Chemical technology
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.675182

This experimental study examined the development of a lightweight aluminium-air cell. The novelty of this study was the characterisation of the behaviour of the lightweight aluminium-air cell, depending on the choice of aluminium anode and air-cathode. Development of the prototype aluminium-air cell involved three areas of study. For the first two high purity aluminium alloys, Al/0.5 Mg/0.07 Sn and Al/0.4 Mg/0.07 Sn/0.05 Ga, were evaluated as anodes in a half-cell in 4 mol dm-3 NaOH at 22 °C and 60 °C and compared against 99.999 %wt aluminium. Alloys were pre-treated by solution heat treating in a furnace at 600 °C for 8 hours followed by a water quench. Corrosion rates were quantified at open-circuit and under galvanostatic discharge via a hydrogen collection method. For the second method of study, the electrochemistry of a LaCaCo3/LaCaMnO3 air-electrode, known as KTH, supplied by a project collaborator, was compared against seven commercial gas diffusion electrodes. The catalysts on the commercial electrodes include Pt, MnOx, Ag2O and Co-based. Air-electrodes were compared structurally using scanning electron microscopy, mercury intrusion porosimetry and pycnometry. The KTH electrode outperformed the others with a limiting current density for oxygen reduction of −463 mA cm-2 at −0.49 V vs. Hg/HgO. In the final area of study three prototype aluminium-air cells were investigated with the third one being selected as the final design. Cell characterisation involved measurement of electrode potentials and cell temperature during variable loading and galvanostatic discharge experiments, and assessing their inter-relationship. The best performing prototype cell with a solution heat treated Al/Mg/Sn anode and KTH air-electrode had a peak power density of 174 mW cm-2 at 208 mA cm−2. Under galvanostatic discharge at 100 mA cm-2 over an hour duration, this cell had a specific power capability of 62 W kg-1 and a specific energy of 66 W h kg-1.