Electrochemical Performance in Alkaline Electrolyte of Aluminum Alloy 6061 As Anode in Aluminum-Air Battery Applications

Abstract

Climate change. Pollution endangering public health. Lasting damage to the environment. These are only several of the concerns about extracting fossil fuels from the earth and combusting them to supply energy for a myriad of human needs. Fossil fuels contributed 81% of global energy demand in 2017 1, and between 7%- 17% of energy consumption worldwide in 2050 is predicted to be expended in overcoming effects of climate change 2. Significant expansion of electrification in the energy sector, particularly in transportation, is expected to be required to meet the objective of limiting global temperature increase to 1.5°C compared with pre-industrial levels 3.Electric vehicles (EV) for road transport are present in the marketplace now, but vast expansion is necessary to impact global temperature goals. EV annual sales of 2 million in 2016 would need to grow to 1.8 billion annually by 2060 4. Lithium-ion (Li-ion) batteries are chiefly employed in EVs, but issues with supply and disposal 5 have already emerged. High-performance batteries - safe, economical, and widely available – will have great impact on reduction of fossil fuel consumption in meeting global transportation needs. Some metal-air battery designs have the potential to fulfill this role. In this talk, we will discuss the performance of aluminum-air battery anodes in aqueous alkaline electrolytes. In particular, the electrochemical behavior of commercial aluminum alloy 6061 will be compared to that for aluminum anodes of purity 99.95% and 99.999%. Aluminum alloy 6061 is a weldable Al–Mg–Si alloy within which super-saturated solid solutions can be formed by heat treatment 6. Alkaline corrosion of aluminum is a primary concern in aluminum-air cells, and the effect of two corrosion mitigation methods for each anode material is presented. One method, anode heat treatment, is intended to minimize cathodic behavior caused by precipitate phases of alloying materials. The second method employs corrosion inhibiting additives in the alkaline electrolyte. Inorganic additives, such as sodium stannate, can deposit a metal more noble than aluminum on the anode surface. The relatively higher hydrogen overpotential of these metals can increase corrosion resistance. Additives comprising surfactants, or “green” materials, such as linseed oil, can promote a measure of hydrophobicity, discouraging hydroxide ion transport, near the anode surface after adsorption. Hybrid additives are found to be even more effective, as the surfactant or organic additive can aid in stabilizing metal deposition from inorganic additive components. References Arroyo, F. & Miguel, L. J. Analysis of Energy Demand Scenarios in Ecuador: National Government Policy Perspectives and Global Trend to Reduce CO2 Emissions. International Journal of Energy Economics and Policy 9, 364–374 (2019).de Cian, E. & Sue Wing, I. Global Energy Consumption in a Warming Climate. Environmental and Resource Economics 72, 365–410 (2019).Méjean, A., Guivarch, C., Lefèvre, J. & Hamdi-Cherif, M. The transition in energy demand sectors to limit global warming to 1.5 °C. Energy Efficiency 12, 441–462 (2019).Cano, Z. P. et al. Batteries and fuel cells for emerging electric vehicle markets. Nature Energy 3, 279–289 (2018).Notter, D. A. et al. Contribution of Li-Ion Batteries to the Environmental Impact of Electric Vehicles. Environmental Science & Technology 44, 6550–6556 (2010).Maisonnette D. et al. Effects of heat treatments on the microstructure and mechanical properties of a 6061 aluminium alloy. Materials Science and Engineering: A 528, 2718–2724 (2011).