The Battery That Rusts

Today, we examine how a process of nature can be harnessed to store energy in the modern world. The University of Houston presents this series about the machines that make our world work and the creative people who made them.

Today, a battery that does something we usually try to stop.

Leave a piece of iron outside long enough and something familiar happens. It rusts.  For thousands of years, people have fought rust. We paint bridges to stop it. We coat tools to protect them. We try to keep water away from cars, pipes, and machines.

“Solar panels, wind turbines, and an electricity pylon,” public domain, CC0 1.0, via Rawpixel/Wikimedia Commons.

Rust seems like an enemy of engineering.  But what if we could put rust to work?  That's the idea behind an iron-air battery.

A battery stores energy using a chemical reaction. When we use the battery, that reaction produces electricity. When we recharge it, electricity is used to push the chemical reaction backward.

An iron-air battery does something much like that, but with a material almost everyone knows: iron.

When the battery gives out electricity, oxygen from the air reacts with iron inside the battery. The iron changes into rust. In the process, electrons are released. Those moving electrons can become electricity that we use. When electricity is sent back into the battery, the process reverses. The rust changes back into iron.

The battery rusts. Then it "un-rusts."

And it can do this again and again.

The idea sounds strange because rust usually seems permanent. An old nail left in the rain certainly doesn't fix itself. But inside a battery, engineers carefully control the chemical reaction. Rust becomes part of a cycle instead of simply being the end of a piece of metal.

Why bother?

Think about a wind turbine on a windy night. It may produce more electricity than people need at that moment. Or think about solar panels on a bright afternoon. They make electricity while the Sun shines, but people still need electricity after sunset.

“Solar panels, wind turbines, and an electricity pylon,” public domain, CC0 1.0, via Rawpixel/Wikimedia Commons.

If we can store some of that extra energy, we can save it for later.

Lithium-ion batteries already do this. They power our phones, laptops, and electric cars. They can also help electric grids. But engineers are looking for other kinds of batteries that can store very large amounts of energy for longer periods.

Iron offers an interesting choice.

It is a familiar material, and an iron-air battery can be designed for long-term energy storage. One modern design uses what its maker calls "reversible rusting." During discharge, oxygen changes iron into rust. During charging, electricity changes the rust back into iron. 

There's something wonderful about the idea.

For centuries, engineers have worked to defeat rust. They invented paints, coatings, and new metals to hold it back. Rust meant damage. Rust meant waste.

Then someone asked a different question.

Instead of asking, "How do we stop rust?"

What if we asked, "What can rust do for us?"

And that's often how engineering moves forward. The thing that looks like the problem may turn out to be part of the solution.

I'm Andy Moon, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

Technology Review article.

This Episode first aired October 21, 2026.