The demand of electrical energy system is increasing rapidly these days for diverse applications from portable electronics and electrical vehicles to grid-scale energy storage. Lithium-ion battery has been utilized for most of those applications, but due to high cost (about $600/ kWh) and lower energy density (0.38 kWh/kg) [1], the advent of low cost and high performing battery system is required. Metal-air system, which has metal as a reactant for the anode side and oxygen for the cathode side of the battery cell, is getting intense attention due to its benefits such as high energy density and low system cost. Especially, metals such as lithium, aluminum, magnesium, calcium, iron, and zinc whose reduction potential is substantially low are typically used for the negative electrode, while oxygen generally from air is used for the positive side.

The energy density of the metal-air battery systems is 3 to 10 times greater than that of the conventional lithium ion battery (i.e. specific energy of the metal-air system is in the range from 0.8 to 3.9 kWh/kg, while that of the conventional lithium ion battery is 0.38 kWh/kg) [2].

Especially, aluminum of which specific energy is roughly 10 times greater than lithium ion battery is abundant, low price, environmentally benign, and inertness to humid operating condition, preventing the catastrophic thermal failure which is the major safety issue of the conventional system. However those promising systems could not reach the commercialization stage due to the challenging issue associated with the redox reaction of metal electrode: self-corrosion reaction (i.e. hydrogen evolution)[3].

In this study, the effect of H₂ evolution due to aluminum corrosion on the cell performance will be investigated through combined research of experiment (cell-based and component-based tests) and physics-based computational model. Especially, the coverage of H₂ bubbles on the electrode surface, change of diffusion layer thickness affected by the H₂ bubble rise, and change in the electrolyte conductivity will be analyzed with respect to various pH conditions, flow rate conditions, and currents. The results will be utilized to understand the underlying physics of H₂ bubble issues and to define the key controlling parameters for the cell performance.

Reference

[1] P. G. Bruce, S. A. Freunberger, L. J. Hardwick, J.-M. Tarascon, Nat Mater 2012, 11, 19-29.

[2] Q. Li, N. J. Bjerrum, J. Power Sources 2002, 110, 1-10.

[3] D. R. Egan, C. Ponce de León, R. Stokes, F. C. Walsh, J. Power Sources 2013, 236, 293-310.