Plate Nº 69 · recorded November 15, 2026
Chemistry & MaterialsReported finding
Four Electrons Instead of Two: UCL Chemistry Boosts Water Battery Hopes
UCL scientists doubled the electrons iodine shuttles in water-based batteries, keeping nearly full capacity over thousands of cycles — but larger real-world tests remain.
By James Calloway3 min read656 words
In brief
- UCL-led design transfers 4 electrons per iodine atom instead of the usual 2, boosting potential energy storage.
- Zinc-iodine batteries retained almost all capacity after thousands of charge-discharge cycles.
- The findings were published in Nature.
- The design avoids the corrosive, concentrated halogen liquids used in earlier iodine batteries.
- Larger batteries must still be tested under realistic conditions before commercial viability is known.
A battery chemistry that moves four electrons per iodine atom instead of the usual two could push water-based batteries — a safer cousin of lithium-ion — toward meaningful energy storage. Scientists led by University College London published the design in Nature, and the results deserve attention. They also deserve skepticism.
Here's the promise: safer grid storage for wind and solar power, without the flammable liquids that make some lithium-ion installations a fire risk. Here's the catch: the tests so far ran on small cells, not the building-sized systems the technology is meant to serve.
Why does anyone want a water-based battery?
Lithium-ion works well. Your phone, your neighbor's electric car and most utility-scale storage facilities run on it. But some lithium designs catch fire, and their materials can be costly or environmentally punishing to mine.
Batteries built around water-based liquids cut those risks substantially. Their weakness is stubborn: low energy density, meaning they store less juice per kilo or per liter. For a grid battery that sits in a warehouse, weight matters less than cost and safety — so aqueous chemistry looks attractive there, if engineers can squeeze more energy out of it.
What did the UCL team actually do?
They targeted iodine, an element that participates in the reactions that store and release electricity. Conventional iodine chemistry transfers two electrons during charge and discharge. The new design doubles that to four. More electrons means more stored charge from the same amount of active material — without simply building a bigger battery.
One obstacle nearly killed the idea. A highly reactive form of iodine reacts with water and breaks down. Earlier fixes used heavily concentrated, halogen-containing liquids to shield the iodine. Those liquids work, but they're corrosive and expensive. Corrosive and expensive is a bad combination for anything you want to manufacture at scale.
The UCL group took a different route. They redesigned the chemical environment surrounding the iodine:
- Some molecules physically block water from reaching the reactive iodine.
- Others bind to the iodine and stabilize it.
The result: no reliance on harsh, corrosive electrolytes.
How well did it perform?
The team tested the chemistry in several battery formats, including small coin cells and pouch cells — the flat, sealed packages you find inside portable electronics. In zinc-iodine batteries, the design held onto almost all of its storage capacity after thousands of charge-discharge cycles. The researchers also see a path to aluminum-iodine systems.
That cycling figure is the strongest number in the paper. Thousands of cycles with minimal degradation is exactly what a grid battery needs, since stationary storage systems charge and drain daily for a decade or more.
What's not in the study?
Plenty, and the researchers say so themselves. A promising reaction is one component of a useful battery, not the whole machine. Engineers still need to check:
- How fast the battery charges.
- How it performs across different temperatures.
- How long it survives in real conditions, not lab coin cells.
- Whether the ingredients can be produced affordably at volume.
None of that has been settled. The next step, per the team, is testing larger batteries under realistic operating conditions — the point where many promising chemistries quietly stall.
What does this change for renewable energy?
Right now, not much. Wind and solar farm operators will keep buying lithium-ion, because it's proven and getting cheaper. What this research changes is the roadmap: it removes the corrosive-electrolyte problem that made high-energy aqueous batteries look impractical, and it does so with a clean mechanism that other labs can now build on.
If larger cells hold up — and that's a genuine if — utilities gain a storage option that doesn't burn. Until those tests report, treat this as elegant chemistry awaiting its engineering trial. The gap between a Nature paper and a shipping product is where most battery breakthroughs go to rest.
via knowridge.com (Source)
More from James Calloway
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Staff writer covering regulation, policy and their impact on general science news at SciBeat.
392 articles
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