Flow Cell Stack for Aluminum-Air Battery Testing, CAABTFCS

Testing an Aluminum-Air (Al-air) battery presents a different set of challenges compared to hydrogen fuel cells, primarily because you are managing a solid consumable anode (Aluminum) and a liquid electrolyte (typically KOH or NaOH) rather than just gases. A flow cell stack for Al-air testing is designed to circulate the electrolyte to remove reaction byproducts—specifically aluminum hydroxide Al(OH)3—which can otherwise precipitate and "passivate" the anode, killing the battery's performance.

Unlike a standard fuel cell, the Al-air stack must be designed for easy disassembly or "mechanical recharging" since the aluminum plates are physically consumed during discharge.

Anode Compartments: (1) High-purity Aluminum (99.99%) or specific alloys (e.g., Al-Sn, Al-Ga) to reduce self-corrosion. (2) Current Collection: A brass or nickel-plated copper "feeder" plate presses against the back of the aluminum slab. (3) Variable Gap: Advanced test cells use a spring-loaded mechanism to push the aluminum plate forward as it thins, maintaining a constant inter-electrode distance for stable internal resistance.

Electrolyte Flow Field: (1) Manifolding: Electrolyte enters from the bottom and exits at the top to ensure gas bubbles (hydrogen from parasitic corrosion) are flushed out. (2) Turbulence Promoters: Small plastic spacers or "mesh" are often placed in the flow channel to increase ionic mass transfer and prevent the buildup of a stagnant boundary layer.

Air Cathode (Gas Diffusion Electrode): (1) Structure: A multi-layered GDE consisting of a catalyst layer (often Carbon/MnO₂ or Silver), a nickel mesh current collector, and a hydrophobic PTFE layer. (2) Air Breathing vs. Forced Air: In a stack, the "air side" is usually a separate chamber where compressed air is lightly pressurized or fanned across the back of the cathode.

References:

1. H. Wen, et al., High energy efficiency and high power density aluminum-air flow battery, Int. J. Energy Res., 2020, DOI: 10.1002/er.5485. 

2. Maham Dilshad, et al. Next-Generation Aluminum-Air Batteries: Integrating New Materials and Technologies for Superior Performance, ACS Appl. Energy Mater. 2025, 8, 6, 3248–3275.