Strategies to Improve the Electrochemical Performance of Aluminum Anodes in Primary Alkaline Aluminum-Air Batteries
Passivation layers and self-corrosion developed on the Aluminum anodes in alkaline Aluminum-air batteries can significantly reduce the widespread application and capacity density of the batteries. Most corrosion prevention techniques focus on changing the electrode and electrolyte, including electrode alloying, additives for the electrolyte, and nonaqueous electrolytes. This thesis concentrates on some novel approaches like application of ultrasonic waves, as well as cold working to prevent the formation of passivation layers and hydrogen evolution. Furthermore, a conventional strategy of adding different inhibitors, including cerium chloride, a hybrid inhibitor of sodium vanadate and nanoclay is investigated.
Experimental analyses were performed using ultrasonication generators, and a frequency range of 28 - 50 kHz and a power range of 20 - 120 W were provided. These variables were combined and examined to determine how ultrasonic frequency and power affected the performance of the Al anode. For the OCP measurements, the ultrasonic irradiation was continually turned on and off to evaluate the impact of ultrasonication with non-ultrasonic circumstances on the potential change. In addition, it was confirmed that the potential shifts toward more adverse values when ultrasonication was used. According to the findings, the anode exposed to ultrasonic waves exhibited greater corrosion resistance, a lower current density of corrosion, and more negative corrosion potential than the anode not exposed to them. Furthermore, the use of ultrasonic waves increased anodic efficiency and decreased hydrogen development on the Al anode surface.
Another strategy was employed for commercially AA1100 and AA7050 to reduce the thickness of the samples by 10%, 25%, 50%, 90%, and 95%, using cold working on a rolling machine. It was found that cold-worked anodes had a more negative corrosion potential and a lower corrosion current density, which suggested a higher level of electrochemical activity and improved anti-corrosion behaviour. When the amount of cold working increased, the rate of self-corrosion decreased. The amount of the drop was greater for the alloy AA7050 than for AA1100, demonstrating the inhibitory impact of the MgO and ZnO layers formed on the surface of AA7050 after immersion in KOH solution.
Electrolyte additives such as cerium chloride, sodium vanadate and nanoclay at different concentrations were used to examine the anticorrosion inhibitory effect of the additives on the prevention of self-corrosion of Al anodes. It was figured out that the efficiency of the Al anode increased from 43.8% to 76.1% as the cerium chloride concentration rose, and the capacity density rose from 1294 to 2244 mAh.g-1 . The outcomes demonstrated that the addition of vanadate, nanoclay, or a blend of the two significantly decreased Al anode corrosion. However, compared to 57.6% for vanadium and 69.8% for nanoclay, the hybrid additive's 72.6% inhibitory efficiency was the highest. With the help of a hybrid inhibitor, the anode's anodic efficiency and capacity density were increased to 81.4% and 2426 mAh.g-1, respectively.