Chloride battery: reversing chemistry with seawater

A team of US researchers has shown you can make a battery with chloride ions, one of the most abundant ions in seawater.

Their prototype battery, made mostly from iron, is based on a new chemical reaction that taps into chloride ions to help the battery work.

The research is published in Chemistry of Materials.

In their paper, the researchers say that their discovery could lead to water-based batteries made from scrap iron rust (or iron oxide).

These batteries, while likely too bulky to work in things like cars, could be used for cheaper and safer electricity grid storage.

Iron oxide could be a major source of battery material – the US alone sends over 10 million tonnes of iron scrap to landfill each year, much of which is rusted.

But rechargeable batteries need materials in them that can do reversible chemical reactions – that’s how batteries charge and discharge – and chemists have struggled to make iron oxides do this.

This study has shown how chloride ions, which could come straight from seawater, can help the iron to do its job.

The chloride forms a green rust on the iron, which prompts it to charge and discharge properly.

So far, the battery has only been shown to work at the very small scale, in a lab.

But the results at this small scale are promising: it can discharge effectively, and still performed well after 400 cycles.

Senior author Professor Xiaowei Teng, a chemist at Worcester Polytechnic Institute, says that while the team hasn’t calculated the cost of their batteries, the battery’s composition of abundant materials will make it quite cheap.