A Water Battery That Could Last 300 Years

Ruminations
Written By William Bayne

A Water Battery That Could Last 300 Years

No toxic metals, no fire risk, and an electrolyte safe enough to pour out.

Saw something this week that made me stop and think for a minute. Researchers out of City University of Hong Kong and Southern University of Science and Technology built a water-based battery that ran for 120,000 charge cycles in lab testing. If you charged it once a day, that's about 300 years before it gave out.

A few things that caught my attention:

  • No toxic metals.
  • Non-flammable.
  • The electrolyte is basically tofu brine. Neutral pH. Safe enough that you could pour it out and not hurt anything.

The trick is they swapped the usual metal negative electrode for something they engineered out of covalent organic polymers, and paired it with a Prussian blue analog on the positive side. The whole thing runs on magnesium and calcium salts in water. No acid, no alkaline, no fire risk.

Now, I want to be straight about it — this is still lab work. The energy density is lower than what's in your phone or your car, so the first place you'd actually see this show up is grid-scale storage. The kind of big batteries that hold solar and wind power until you need it. That's a real problem worth solving. Right now those batteries wear out and have to be replaced, and the replacements are expensive, hazardous to dispose of, and built from materials we have to mine and ship from across the world.

I love the kinds of discoveries that are happening right now. Just about every week there's something new being worked on that could genuinely change the trajectory of things — energy, medicine, food, computing. We hear so much about what's going wrong in the world. It's worth pausing on what's going right too. There are smart people in labs all over the place quietly figuring out how to make hard problems smaller.

If something like this scales, the downstream effects are big. Cleaner storage for renewables. Less battery waste in landfills. Fewer fires. Maybe even backup power for remote infrastructure that today nobody can keep batteries serviced at.

The trickier question — and the one the tweet I read raised — is what happens to the industries built around batteries wearing out. Replacement cycles drive a lot of revenue. If a battery lasts a hundred years instead of ten, that changes the math for a lot of companies. I don't have a strong take on that yet. New tech tends to break old business models and build new ones in their place. We'll see.

For now I'm just glad people are working on it. Hopeful it scales.

Sources
William Bayne
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