A research team in South Korea is building a battery that runs on seawater, and in the process makes freshwater and pulls carbon dioxide out of the air. The video from Undecided with Matt Ferrell walks through a system from Professor Kim Youngsik and colleagues at the Ulsan National Institute of Science and Technology, developed over more than a decade. The pitch is one device doing the job of three: energy storage, desalination and carbon capture. The most striking claim is on cost. Because the design does without the expensive cathode found in conventional batteries, the video reports a material cost of around 10 cents per kWh, against roughly 78 dollars per kWh for the cathode in a lithium-ion cell.
The technology it is really competing with is reverse osmosis, the method behind most large-scale desalination plants in the world today. Reverse osmosis works by forcing seawater through a membrane at high pressure, which is effective but energy-hungry, and that energy cost has long been the main barrier to desalinating at scale. The timing is notable because both halves of this system sit in growing markets. The video cites BloombergNEF projecting grid battery installations rising about 35 percent in 2025 and climbing toward 220 GW a year by 2035, while seawater desalination grows at roughly 7 percent a year as water scarcity spreads. According to the video, removing the same amount of salt took about 2.51 watt-hours in the lab versus 4.06 for reverse osmosis, roughly 40 percent less, because charging the battery and separating the salt are the same physical process rather than two separate steps. The catch, which the video is upfront about, is that the system only removes the sodium and chloride, around 80 percent of seawater's salts, so a reverse-osmosis polishing step is still needed to finish the job.
This is not a sodium-ion battery, the video is careful to note, even though it draws sodium from the sea. The mechanism hinges on a ceramic membrane called NASICON that lets sodium ions through while blocking other salts. As the battery charges, sodium passes into a sealed compartment and plates out as pure metal, while chloride is pushed the other way, and the water left in the middle comes out largely desalinated. On discharge, the process runs in reverse, and the alkaline water it produces absorbs carbon dioxide, locking it away as a solid carbonate. The cost advantage, the video explains, comes from skipping the conventional cathode, which can account for around 40 percent of a traditional battery's material cost. On carbon, it cites a researcher estimate that treating 150 cubic meters of seawater a day could capture between 640 and 1,280 kg of CO2, which the video likens to taking 50 to 100 cars off the road while supplying water for 1,000 to 1,500 people. It is careful about maturity: the battery itself is fairly proven and already powers marine buoys, while the desalination and carbon-capture functions sit at a much earlier, lab-stage level. Researchers are also working to make the NASICON membrane more durable, which the video frames as central to bringing costs down further.
Bottom line: A battery that stores energy, makes drinking water and captures carbon sounds too good to be true, and for now it partly is, because no single built system does all three at once. But the core idea, that desalination and energy storage can be the same process instead of two expensive ones, is genuinely clever, and the lab energy numbers are hard to ignore. The likeliest near-term payoff is not a magic three-in-one box but pairing these batteries with existing desalination plants. Worth watching, not yet worth betting the water supply on.
Commentary on a third-party video. Figures and claims are as presented in the source and have not been independently verified. Spotted an error? Tell us and we will correct it.