Ellen Phiddian
Cheaper, more environmentally sustainable, and safer to ship, sodium-ion batteries could one day replace lithium-ion in a range of places.
While not as energy dense, sodium is much more abundant than lithium, so could remove much of the strain on precious metals as we keep electrifying.
Cosmos is in Cairns in Far North Queensland attending the First Australian Conference on Green and Sustainable Chemistry and Engineering, and sat with Professor Maria Forsyth, a researcher at Deakin University in Melbourne, to discuss the future of sodium-ion batteries.
How similar are sodium-ion and lithium-ion batteries?
“Sodium is in the same column in the periodic table, one below lithium,” says Forsyth.
“It’s got similar properties, but its [atoms are] much bigger and heavier and there are also some really clear chemical differences.
“Manufacturing-wise, it’s a drop-in technology. If you can have a manufacturing plant that can make lithium-ion batteries, you can swap in sodium-ion batteries.
“But actual chemistry-wise, to optimise the batteries and make them as efficient as our current lithium-ion batteries are, we have a little way to go.”
Can we make them more environmentally friendly?
Battery components like the cathode, the anode, the current collectors and the electrolytes all need to be made from different materials to work better with sodium.
Read more: How do batteries work?
Forsyth and her colleagues’ research has shown many of these components can be more environmentally friendly. Take the anode, for example, which in lithium-ion batteries tends to work best with layers of carbon-based graphite.
“Lithium goes between those layers. If you are trying the same with sodium, because it’s bigger, it pushes those layers apart and destroys the anode. So the graphite that we currently use for lithium, you can’t use that for sodium,” says Forsyth.
But other types of carbon can be swapped in. One of these options is hard carbon, which was one of the first substances used in early lithium-ion batteries.
“Hard carbon doesn’t work as well for lithium, but it works really well for sodium. And the beauty about hard carbon is we can derive that from any number of biomasses, preferably from waste biomass,” says Forsyth.
Forsyth and colleagues are currently working on sodium battery anodes made with carbon from burning green waste.
“The residual carbon that’s formed can then be optimised and tailored to be used in sodium-ion batteries,” says Forsyth.
They’re also trying to get useful carbon out of biochar and waste textiles.
Another point in the battery where things can be swapped is at the battery current collector. Lithium-ion batteries need to use different metals at each end as current collectors – copper at the anode and aluminium at the cathode – while sodium-ion can use aluminium everywhere.
This makes the batteries safer to ship, because they can’t discharge themselves if there’s a short circuit.
Aluminium is also a cheaper and more sustainable metal to use, and lighter – which can account for some of the energy density that sodium-ion batteries lose.
Then there’s the liquid electrolyte, which in lithium-ion batteries is often dissolved in volatile carbon-based liquids. While good at their jobs, these liquids can form flammable gases during manufacturing, so the process has to be slowed down to de-gas.
Sodium-ion batteries can use solid electrolytes, according to Forsyth, which can be applied much faster because they don’t have the same safety risks.
So when can I get my sodium car?
Because sodium is a heavier atom, lithium-ion batteries will probably always be more energy-dense.
“You probably are not going to drive a high model Tesla using a sodium-ion battery anytime soon. Because you’re not going to get as many kilometres from the car,” says Forsyth.
The same goes for planes, and other uses where every gram of weight makes a difference.
“But if you’re looking at stationary storage, power tools, home storage, community batteries, anything where basically a little bit of extra weight for a given amount of energy doesn’t really bother you, then sodium is a better option,” says Forsyth.
“It’s more sustainable, it will ultimately be cheaper.”
Forsyth thinks we’re about five years away from full commercialisation, but says some companies have already been making sodium batteries for several years – including Chinese companies HiNa and CATL, French company Tiamat, and UK company Faradion.
And lithium-based non-ion batteries, like lithium iron phosphate or lithium vanadium phosphate, could also have their lithium switched out for cheaper and more abundant sodium.
“Everything we’ve learned from lithium is helping us with sodium,” says Forsyth.
“We’re not starting from scratch.”
Ellen Phiddian’s airfare to Cairns was paid by the Royal Australian Chemical Institute, which is managing the First Australian Conference on Green and Sustainable Chemistry and Engineering.
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