A new tapered flow channel design for electrodes improves the efficiency of battery-based seawater desalination, potentially reducing energy use compared to reverse osmosis. This breakthrough may benefit other electrochemical devices, but manufacturing challenges need to be addressed.
Engineers have developed a solution to eliminate fluid flow “dead zones” in electrodes used for battery-based seawater desalination. This breakthrough involves a physics-driven tapered flow channel design within the electrodes, enabling faster and more efficient fluid movement. This design has the potential to consume less energy compared to conventional reverse osmosis techniques.
Desalination technology has faced significant challenges preventing widespread adoption. The most common method, reverse osmosis, filters salt from water by forcing it through a membrane, which is both energy-intensive and expensive. In contrast, the battery desalination method uses electricity to remove charged salt ions from the water. However, this approach also requires energy to push water through electrodes with tiny, irregular pore spaces, which has been a limiting factor—until now.
A New Approach: Structured Flow Channels
“Traditional electrodes still require energy to pump fluids through because they do not contain any inherently structured flow channels,” said University of Illinois Urbana-Champaign mechanical science and engineering professor Kyle Smith, who led the study. “However, by creating channels within the electrodes, the technique could require less energy to push the water through and eventually become more efficient than what is commonly used in the reverse-osmosis process.”
Smith’s battery-based desalination technique builds from years of modeling and experiments by his research group at Illinois, culminating in a recent study demonstrating the first use of electrodes containing tiny microchannels called interdigitated flow fields.
The group’s new study also incorporates IDFFs in electrodes, but this time the channel shape is tapered, not straight. Using electrodes with tapered channels improved fluid flow — or permeability —two to three times over straight channels. The findings are published in the journal Electrochimica Acta.
“Our initial work on straight channels in electrodes led us to discover dead zones within the electrodes where we saw pressure drops and nonuniform flow distribution,” said Illinois graduate student Habib Rahman. “To overcome this challenge, we created a library of 28 different straight channels to experiment with and understand conductance and flow variation, and eventually implemented this channel-tapering technique.”
Challenges and Future Applications
While performing the experiments, Smith and Rahman said they faced some manufacturing challenges, particularly with the time it takes to mill the channels into the electrodes, which would be problematic in any scaled-up production scenario. However, Smith said they are confident this challenge can be overcome.
“Beyond its impact toward electrochemical desalination, our channel-tapering theory and associated design principles can be applied directly to any other electrochemical device that uses flowing fluids, including those for energy storage conversion and environmental sustainability like fuel cells, electrolysis cells, flow batteries, carbon capture devices, and lithium recovery devices,” Smith said. “Unlike prior channel-tapering strategies that used impromptu designs, our approach here provides physics-based design guidelines to create uniform flow and minimize pressure drops simultaneously.”
Reference: “Tapered, interdigitated channels for uniform, low-pressure flow through porous electrodes for desalination and beyond” by Md Habibur Rahman, Irwin C. Loud IV, Vu Q. Do, Md Abdul Hamid and Kyle C. Smith, 1 January 2025, Electrochimica Acta.
DOI: 10.1016/j.electacta.2024.145632
The Office of Naval Research supported this study. Smith, Rahman and study coauthors Irwin Loud IV, Vu Do and Abdul Hamid have patents pending under the U.S. patent applications 17/980,017, 17/980,023, and 63/743,995.
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