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23 January 2021 | New Scientist | 39

out with almost no resistance, giving it

a long life. “There’s basically no wear out

mechanism,” says Jack Pouchet at Natron.

“We have shown 37,000 cycles with no end

in sight.” The company is selling its wares

mostly to data centres, servers that support

the internet. These need extra battery power

during periods of peak energy demand

and as an insurance against mains power

outages. For applications like this, a heavy

battery isn’t a problem.

More conventional sodium battery

technology is set to improve quickly,

according to forecasts from Stefano Passerini

at the Karlsruhe Institute of Technology in

Germany and his colleagues. The researchers

totted up the materials needed to make

lithium-ion and sodium-ion batteries with a

capacity of 11.5 kilowatt hours, about a third

of what is required in a small electric car.

Then they repeated the exercise considering

advanced prototype batteries and expected

future developments. The results suggest

that we can shave 32 kilograms off a lithium

battery and 42 kilograms off a sodium battery

Katharine Sanderson is a

science journalist based in

Cornwall, UK

of this capacity. The price of sodium

batteries is set to come down quickly too.

They will be competitive with lithium

batteries by about 2025, estimates Passerini.

We shouldn’t necessarily expect

sodium batteries to directly replace lithium

ones. Instead, it might make sense to use

sodium cells in certain applications and

so, hopefully, take pressure off our lithium

reserves. What is important is that we can

store electricity from renewable sources

without wrecking the planet in the process.

If they are to aid in that goal, batteries will,

one way or another, need a total recharge. ❚

batteries can short circuit, overheat and catch

fire when disconnected. This is especially a

risk when lots of batteries are being shipped

around together. Sodium batteries can use

aluminium at both cathode and anode,

which eliminates this problem at a stroke.

On your bike

Sodium-ion batteries might be heavier

than lithium ones, but with advantages

at almost every other turn, that is starting

to look like a worthy compromise.

That’s certainly the attitude of Faradion,

a company based in Sheffield, UK. It

produces a 1-kilogram sodium-ion battery

that it says has a similar performance to a

lithium cell. In 2015, the firm demonstrated

an electric bike powered by its product.

“You can certainly see them competing

with lithium-ion,” says Armstrong.

Perhaps the most original approach

to sodium batteries comes from a firm

called Natron Energy. The company’s

founder Colin Wessells developed an

electrode material based on the pigment

Prussian blue. This iron-based molecule

has pores that are much bigger than a

sodium ion and so it can let them in and

The battery-making Tesla

Gigafactory in Nevada is one

of the world’s largest buildings

Numbers of electric cars are

shooting up. These ones are

charging in Shanghai, China

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